Part 2 Main Text

1. INTRODUCTION

The larynx or ‘voice box’ has a complicated anatomy with small structural components like cartilages, folds & ligaments. Earlier imaging in larynx was confined to plain radiography, multidirectional tomography and contrast laryngography. With the advent of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), imaging of larynx has been revolutionized. The imaging modalities for evaluation of larynx are plain radiographs, multidirectional tomography, contrast laryngography , CT and MRI. Plain X-ray is an inexpensive method to study temporal bone, but results in an inaccurate diagnosis. Multidirectional tomography allows visualization of the airway anatomy in the frontal view without the problems of superimposition of the spine , however there is increased radiation exposure. Contrast laryngography was developed to better define mucosal irregularities but the information derived from the laryngogram is now routinely obtainable by endoscopy. Moreover laryngography is poorly tolerated by patient. MRI has excellent soft tissue resolution, more sensitivity to effects of gadolinium as contrast agent, better spatial resolution and no exposure to radiation. However, MRI is expensive, requires patient’s cooperativeness & is prone to motion artefacts. MRI and CT can be complimentary to each other in some cases. Hence in a developing country like ours, computed radiography has become the most accurate radiological technique for evaluating patients with laryngeal

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carcinoma. In most of the cases CT demonstrate more extensive abnormalities than are initially appreciated by the other radiological modalities, including laryngography and plain film radiography. The cross-sectional display provided by CT allows evaluation of the entire larynx including cartilaginous structures and paralaryngeal soft tissues. Before advent of CT accurate assessment of these structures could be only achieved by surgical exploration. In patients with carcinoma of the larynx, CT supplements the findings detected by the indirect or direct laryngoscopy. Although laryngoscopy accurately demonstrates mucosal abnormalities, deep extension of the tumour into the pharyngeal and pre-epiglottic space or adjacent cartilaginous skeleton is not directly visualized and may be difficult to document even with deep biopsy. CT plays a complementary role to laryngoscopy by assessing the parapharyngeal soft tissues and the supporting cartilaginous structures better than was previously possible using contrast laryngography. Interpretation of CT of larynx is difficult.

Detailed knowledge of laryngeal

anatomy and its appearance in various planes is essential. Detection and characterization of pathological processes in the larynx require careful observation and experience.

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2. AIM AND OBJECTIVES

To demonstrate the role of multislice computed tomography in 1.

Morphological evaluation of the malignancy of larynx.

2.

Evaluation of the extent and spread of the malignant lesion and determine the staging. Then combine these findings to detect the operability.

3.

Follow up of post-operative, post-radiotherapy and post-laser ablated cases of carcinoma larynx.

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3. MATERIAL AND METHODS

The study comprises of 100 patients who were subjected to Multislice Computed Tomography in Radiology department during the time period of 24 months from November 2007 to November 2009.

3.1 SELECTION CRITERIA : Patients referred from clinical faculties with complaints and clinical findings pertaining to laryngeal carcinoma for evaluation by multislice CT. The patients were referred for 1.

Hoarseness of voice, odynophagia, dysphagia.

2.

Mass lesion suspected on indirect laryngoscopy.

3.

Palpable neck mass.

4.

Abnormal barium swallow study in a patient with mass lesion in larynx.

5.

Biopsy proven cases of carcinoma larynx.

3.2 EXCLUSION CRITERIA : Pregnant women were excluded from this study. 3.3 METHOD : •

All patients are called with at least 4 hours fasting before the scan.

•

Detailed history is taken & clinical findings are reviewed.

•

Plain soft tissue roentgenogram if available was reviewed.

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•

Informed consent was taken.

•

Pre-medication was given in case of intravenous contrast administration was to be needed.

3.4 TECHNIQUES OF EXAMINATION : Patients were scanned using “SIEMENS SOMATOM VOLUME ZOOM MULTISLICE (4 SLICE) MULTIDETECTOR SPIRAL CT SCANNER”. The CT images thus generated were printed on 14 x 17”, single emulsion and dry silver film using a laser camera. Scanning was done in supine position with a pad between shoulders to straighten the upper thorax. The arms were pulled down along the side of the body to avoid streak artifacts from shoulder girdle. The long axis of the larynx was kept perpendicular to the plane of the image. A lateral scout view was obtained followed by plain and contrast enhanced scan. The region covered extended from the base of skull upto upper mediastinum (arch of aorta). A Medrad Vistron CT pressure injector was used for IV contrast injection at the rate of 2.5 ml/sec. A bolus of 50 ml of 75% ionic contrast medium containing a combination of sodium diatriazoate and meglumine diatriazoate (each ml containing 370 mg. of iodine) was used in patients who did not have any history of allergy. Nonionic contrast medium containing iohexol (each ml containing 300 mg iodine) was used wherever indicated. Retrospective reconstruction of overlapping slices, coronal, sagittal multiplanar reconstruction images and curved planar reformations were obtained using the raw data

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3.5 SCANNING PARAMETERS Position: Supine Scanner Setting – kvp: 120 (however may vary according to patient age and size), mAS: 150 Phase of respiration - Breath hold or slow respiration Slice thickness - 5 mm (Thin 1mm sections of larynx in some cases) Feed / Rotation - 12.5 mm Slice collimation - 5 x 2.5 mm Rotation time - 0.5 sec. Kernel - B 30s Increment - 5 mm. Reconstruction interval - 2.5 sec Superior extent – Base of skull Inferior extent – Arch of aorta. IV contrast - Ionic or nonionic contrast medium. Rate - 2.5 ml/sec Total volume - 50ml. (may vary as per patient age & size) Scan delay - 30 sec for CECT Scout film - Lateral Display FOV - Approximately 512 and varying according to patient.

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3.6 MULTIDETECTOR ROW CT Multidetector computed tomography (CT) was introduced in 1992 with the advent of dual-section capable scanners and was improved in 1998 following the development of quad-section technology. With a recent increase in gantry speed from one to two revolutions per second, multidetector CT scanners are now up to eight times faster than conventional single-section helical CT scanners. The benefits of quad-section CT relative to single-section helical CT are considerable. Multidetector CT is superior to single-section helical CT for nearly all clinical applications. 3.6.1. Technical Principles The conventional single-section helical CT scanner has one x-ray tube and a single row of detectors. This detector row contains 500–900 detector elements, which describe an arc in the transverse (axial or x-y) plane, providing one channel of spatial data. The quad-section multidetector CT scanner has one xray tube and multiple rows of detectors along the longitudinal (z) axis of the patient. Each row has 500–900 elements, and many rows together create a twodimensional curved array containing thousands of detector elements, which are connected to four data acquisition systems that generate four channels of spatial data.

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(a)

(b)

CT gantry with an x-ray tube, an x-ray fan, and detectors for a single section scanner (a) and a multidetector scanner (b) (four section system) 3.6.2. Advantages in Neck Imaging  Scanning Speed A key advantage of multidetector CT is its speed. Combining a multirow detector array and a reduced gantry rotation time, multidetector CT can be five to eight times faster than single-row spiral CT. This, of course, allows scanning of a very large volume very quickly and therefore opens to CT to many applications in the abdomen that were not possible with spiral CT.  Improved Temporal Resolution Faster scanning results in fewer motion artifacts due to voluntary and involuntary movement. Breath-holding times are reduced.  Improved Spatial Resolution in the Z Axis

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Thinner sections improve resolution in the z axis (along the table), reducing partial volume artifacts, and increase diagnostic accuracy.  Increased Concentration of Intravascular Contrast Material Because scanning is done more quickly, contrast material can be administered at a faster rate, improving the conspicuity of arteries, veins, and pathologic conditions rich in blood flow (e.g., aneurysms, hypervascular tumors).  Decreased Image Noise For multidetector systems, more patient length is scanned per rotation; thus, for extended-length studies, the x-ray tube current can be higher than for single section units. The higher current reduces image noise and improves image quality, which is critical for thin-section studies.  Efficient X-ray Tube Use A shorter scanning time leads to diminished x-ray tube heating, decreasing or eliminating delays for x-ray tube cooling between scans; reducing such delays is critical in multiphase examinations. More images are produced during the lifetime of a tube, decreasing operating costs.  Longer Anatomic Coverage A great advantage of multidetector CT over single-section helical CT is the opportunity for longer anatomic coverage. The longer coverage is due to the simultaneous registration of four sections during each rotation and the increased gantry rotation speed. The coverage can be up to eight times longer than that of single-section helical CT with the same scanning time.  Reconstructions

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One clear advantage of multidetector CT over single-slice helical CT is its ability to scan large regions with very thin collimation. This technique generates numerous axial images, particularly when overlapping reconstructions are obtained. With a breath-held acquisition, volumetric data sets are obtained that may be used to create high-quality multiplanar reformations. 3.6.3. Disadvantages Some of the disadvantages are related to the basic physical principles of multidetector CT. Since the x rays are tilted in the outer rows of the detector array, a cone angle is created. In addition, since the x rays will wobble like a top in the circumferential rotation, cone artifacts are formed. Another drawback is the large data sets, typically between 500 and 1,000 images. This of course makes mandatory the use of workstations rather than film to analyze abdominal multisection CT data. Finally, with much higher speed, the timing of enhancement is crucial.

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4. REVIEW OF LITERATURE

Soujanen J.N., Mukherji S. K et al (1992) used spiral CT in the evaluation of 21 patients with head and neck lesions. Scanning time ranged from 24-36 sec. and quality diagnostic scans with excellent anatomic resolution and minimum motion artifact were produced. Vascular opacification was optimized and much less contrast was required as compared to conventional CT. Five of patients also underwent conventional CT for clinical reasons from this preliminary study, authors concluded that spiral CT was better than conventional CT in evaluation of head and neck.

Hopper DK (1996) reviewed the requirements of contrast material for spiral CT. The author stresses that since contrast is to be administered by power injector a 20-4 venocath should be used. Ionic contrast may be used safely in adults at low risk of reaction, in whom injection rate would be 2.5ml/sec.

Yoon DY, Chang KH et al (1997) evaluated the optimal dose of contrast medium for vascular enhancement in CT of head and neck. Adequate contrast enhancement of head and neck vessels is more important than that of tumor itself because of differentiation of neck node metastasis. The authors reevaluated the dosage of contrast medium for adequate vascular enhancement in

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CT of head and neck. These results suggest that 0.75 ml/kg of contrast medium appears sufficient for vascular opacification for head and neck lesions.

Keberle at el (2001) studied the best time for neck malignancies in contrast enhanced CT. The CT was done in 20 patients with squamous cell carcinoma using a standard protocol (100 ml contrast agent at 2ml/s). Using the examined single bolus technique, spiral CT allows a combination of perfect tumor contrast with good contrast between lymph nodes and neck vessels between 50 and 75s after starting injection.

Keberle et al (2003) assessed the diagnostic value of multiplanar reformations (MPR) in multislice CT by comparing relevant anatomic structures of larynx and hypo pharynx. Besides axial slices, coronal and sagittal MPR can improve the topographical visualization of laryngopharyngeal tumors and are recommended for preoperative evaluation of laryngeal and/or hypo pharyngeal carcinomas.

Scott M et al (1981) studied 19 patients with carcinoma larynx who underwent laryngoscopy and CT. CT with sagittal and coronal reconstruction was done. The study confirmed the accuracy and value of transaxial CT and direct laryngoscopy and indicated that coronal and sagittal reconstruction added significant information.

Sagel SS et al (1981) studied role of high resolution CT in staging of Ca larynx.

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The authors illustrated the normal CT anatomy of larynx and recommended CT as the first investigation when additional information is sought to supplement the findings of laryngoscopy. CT provided information regarding deep penetration of tumor, cartilage invasion and about inferior extension of neoplasm including subglottic areas. This knowledge help to determine whether conservative surgery as opposed to total laryngactomy is possible.

Mafee et al (1983) studied correlation of CT & histopathology in cases of laryngeal carcinoma The results indicate that CT scanning accurately demonstrates the anatomic location and gross size of laryngeal tumor, although early invasion of the laryngeal cartilages may be difficult to diagnose with CT. It is concluded that preoperative CT scanning of the larynx is the radiologic procedure of choice for evaluating carcinoma of the larynx

Silvermann, Bossen et al (1984) studied CT & histopathologic correlations in carcinoma of the larynx and hypopharynx. 20 consecutive patients underwent computed tomography (CT) prior to total laryngectomy in order to assess the accuracy of CT scanning in the evaluation of carcinoma of the larynx and hypopharynx.. The results were compared to assess the ability of CT to identify tumor extent accurately. Despite good correlation of gross tumor extent between histologic specimens and CT scanning, specific pitfalls in CT diagnosis were identified. Overestimation of tumor extent was caused by edematous changes in 6 patients and tumor-associated inflammatory changes in 3 patients. In 7

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patients, mass effect from adjacent bulky tumor significantly distorted normal structures, mimicking tumor involvement. Small foci of mucosal tumor in 3 patients and microscopic cartilage involvement in 2 patients were not identified on CT scanning, causing underestimation of tumor extent.

Larsson et al (1981) studied differentiation of pyriform sinus cancer from supraglottic laryngeal cancer by computed tomography. Nine pyriform sinus tumors and 16 supraglottic laryngeal lesions were studied by computed tomography. The pyriform sinus tumors had a much higher incidence of thyroid cartilage invasion (five of nine patients) and involved the posterolateral margins of the cartilage. Only two of 16 supraglottic tumors reached the thyroid cartilage, involving the midline or more inferior margins. The supraglottic tumors grew in a circumferential pattern, and when the pre-epiglottic space was involved, extension was bilateral. Lesions of the pyriform sinus more frequently showed unilateral involvement. Lymph node metastases were seen in an approximately equal proportion of patients in the two groups, and they correlated more with the size of the primary tumor than with its site of origin. Posteroinferior invasion of the space between the thyroid and cricoid cartilage was seen only with pyriform sinus lesions

Archer CT (1983) studied the role of CT Vs histology of Ca larynx in predicting laryngeal cartilage invasion. 27 cases of Ca larynx were examined preoperatively by CT and post operatively by transaxial anatomical section.

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The study provided a new radiological classification based on the relation of the plane of maximal tumor size to the apex, body or vocal process of arytenoids cartilage. Unlike those tumors whose maximal size lies at or above the apex of the arytenoids cartilage, those below have a very high association with cartilage invasion (8% Vs 86%). At these sites the collagen fibers pass through the perichondrium and attach directly to cartilage.

Isaacs J H, Manuso AA et al (1988) studied the deep spread patterns of Ca larynx in CT staging. 30 patients with T2-T4 Ca larynx were studied with CT larynx to identify findings on CT scans that might predict the likelihood of radiation therapy alone controlling the primary disease without significant irradiation related complications. The unfavorable factors which emerged at the end of the study were •

> 25% pre-epiglottic space involvement.

•

Extensive PPS spread and cartilage invasion.

Becker et al (1997) evaluated eight different diagnostic criteria to help detect neoplastic invasion of laryngeal cartilage at computed tomography (CT). 111 patients with carcinoma of the larynx or hypopharynx underwent CT before total or partial laryngectomy. The following CT criteria were evaluated: extralaryngeal tumor, sclerosis, tumor adjacent to nonossified cartilage, serpiginous contour, erosion or lysis, obliteration of marrow space, cartilaginous

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blowout, and bowing. Histologic findings were correlated with findings on CT scans obtained at each level. Depending on the diagnostic criteria and each specific cartilage, there was great variation in sensitivity (7%-83%) and specificity (40%-100%). Sclerosis was the most sensitive criteria in all cartilages but often corresponded to reactive inflammation in the thyroid cartilage. Extralaryngeal tumor and erosion or lysis yielded the highest specificity. Tumor adjacent to nonossified cartilage, serpiginous contour, and obliteration of marrow space were specific although not sensitive signs of invasion in the arytenoid and cricoid cartilage and were nonspecific in the thyroid cartilage. Blowout and bowing were not useful. Selection of the appropriate combination of criteria enabled an overall sensitivity of 91% (associated specificity, 68%) or an overall specificity of 79% (associated sensitivity, 82%). They concluded that detection of neoplastic cartilage invasion with CT greatly depended on the appropriate use of individual and combined CT criteria.

Munnoz A et al (1993) studied 75 patients of Ca larynx prospectively to assess the significance of sclerotic appearing cricoid and arytenoids cartilages and correlated the CT findings with pathological findings. Laryngeal CT obtained in 50 patients without Ca larynx were retrospectively reviewed. The positive predictive value of sclerotic appearing cartilage for invasion was 46%.

Munoz et al (1993) assessed the significance of sclerotic appearing cricoid and arytenoid cartilages with CT in patients with carcinoma larynx. They concluded 16

that although it is not a reliable sign of cartilage invasion, sclerotic-appearing cricoid and arytenoid cartilage in patients with laryngeal carcinoma is predictive of tumor to this cartilage (positive predictive value of 46%).

Becker et al (1995) studied comparison of MR imaging and CT in neoplastic invasion of the laryngeal cartilage with histopathologic correlation. In a prospective study, 53 patients with carcinoma of the larynx or piriform sinus underwent CT and MR imaging before total or partial laryngectomy. The findings at imaging and pathologic examination were compared. RESULTS: At histologic examination, neoplastic invasion of cartilage was present in 34 patients and absent in 19. MR imaging was more sensitive than CT (89% vs 66%; P = .001). Inflammatory changes and fibrosis, however, were indistinguishable from tumor on MR images, resulting in overestimation of neoplastic invasion in a large number of patients. Therefore, MR imaging was less specific than CT (84% vs 94%; P = .004). CONCLUSION: MR imaging is more sensitive than CT in detecting neoplastic invasion of cartilage, but the inability to differentiate between nonneoplastic inflammatory changes and tumor with MR imaging leads to overestimation of neoplastic invasion

Mukherji ; Tart et al (1994) studied whether laryngeal cartilage sclerosis was a predictor of poor outcome in patients with stage T3 glottic cancer treated with

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radiation therapy. 33 patients with stage T3 glottic cancer underwent CT before radiation therapy. 22 patients underwent post treatment CT. The presence of cartilage sclerosis, cartilage erosion, marrow invasion, and cartilage necrosis was determined. 19 of the 33 patients had cartilage sclerosis at CT. Of the 17 patients with cartilage sclerosis, disease was controlled with radiation therapy alone in 15 and with salvage laryngectomy in two. The remaining two patients out of 19 with cartilage sclerosis died of their original cancer despite undergoing early salvage laryngectomy. Of the 14 patients without sclerosis, eight had no evidence of disease, two died of their disease, and four died of intercurrent disease. They concluded that T3 glottic cancer with isolated laryngeal cartilage sclerosis can be cured with radiation therapy

Mukherji SK et al (1998) discussed the roles of CT and MRI for the examination of laryngeal and hypopharyngeal cancers. The author recommends MRI as imaging modality of choice for laryngeal and hypopharyngeal cancers and also for cartilage invasion. Spiral CT with sagittal and coronal reformations also provides excellent anatomic resolution and information about spread of disease.

J.A. Castellinjs, G.J Gerristen et al (1998) compared CT and MR imaging in depiction of invasion of laryngeal cartilage by cancer. Calcified cartilage that has been invaded by cancer is frequently seen on CT scans as having an intact contour. Tumor approaching nonossified cartilage may simulate cartilage invasion. On T1-weighted MR images, invaded marrow of ossified

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cartilage is of intermediate signal intensity, allowing it to be differentiated from normal bone marrow. On proton-density images, tumor is of increased signal intensity, which allows it to be differentiated from nonossified cartilage. They concluded that the specificities of CT and MR imaging were approximately equal (91% and 88%, respectively), but CT had a considerably lower sensitivity than MR (46% vs. 89%). Gross movement artifacts, which resulted in nondiagnostic images, occurred in 16% of the MR examinations. MR imaging is recommended as the modality of choice in the diagnosis of cartilage invasion.

Mancuso et al (1977) studied the role of computed tomography in the management of cancer of the larynx. Computed tomography (CT) offers a unique method of displaying the anatomy of laryngeal cancer. Asymmetrical contours of the thyroid cartilages have been found as a normal variant. Marked asymmetry may indicate buckling of the cartilage which could contribute to acute airway obstruction following radiation therapy. A low-density, soft-tissue plane medial to the thyroid cartilages may prove valuable in evaluating cartilaginous involvement with tumor. They concluded that Computed tomography should make a significant contribution to more accurate planning of radiation therapy portals by showing the relationship of lymphatic spread to the primary tumors

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Mukherji, Mancuso et al (1994) presented the expected appearance of the irradiated larynx and neck as seen at computed tomography (CT). Expected changes include symmetric thickening of the epiglottis, aryepiglottic folds, and false cords and increased attenuation of the paralaryngeal fat. The posterior pharyngeal wall tends to thicken and its mucosa enhances; retropharyngeal space edema is common. Glottic changes include increased attenuation of the paraglottic fat planes and thickening of the anterior and posterior commissures. Subglottic changes include thickening of the mucosa and submucosa. Soft-tissue changes include skin and platysmal thickening, as well as reticulation and increased attenuation of the subcutaneous and deeper fat. Familiarization with expected radiologic changes is essential for interpretation of CT images of the irradiated larynx so that such changes are not mistaken for signs of persistent or recurrent tumor.

Mukherji, Mancuso et al (1994) evaluated the CT appearance of laryngeal tumors treated with radiation therapy and the ability of CT to depict persistent or residual tumor. They concluded that lesions that are reduced by 50% or less at 4month follow-up CT are highly suspicious for treatment failure. Repeat CT studies every 4 months is recommended in addition to careful clinical follow-up.

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Hermans et al (1999) studied whether follow-up computed tomography (CT) after definitive radiation therapy for laryngeal carcinoma allows the detection of local failure earlier than clinical examination alone. MATERIALS AND METHODS: Pre– and post–radiation therapy follow-up CT scans in 66 patients were reviewed retrospectively. All patients underwent definitive hyperfractionated radiation therapy and were followed up clinically for at least 2 years after its completion. Post–radiation therapy CT scans (N = 153) were evaluated for posttreatment changes with a three-point score: A score of 1 represented expected posttreatment changes; 2, focal mass with a maximal diameter of less than 1 cm and/or asymmetric obliteration of laryngeal tissue planes; or 3, focal mass with a maximal diameter equal to or greater than 1 cm or estimated tumor volume reduction of less than 50%. All patients underwent the first posttreatment CT study 1–6 months after therapy. New or progressive laryngeal cartilage changes were noted. The clinical impression of the larynx at the time of each follow-up CT scan was also recorded. RESULTS: In 12 of 29 (41%) patients with treatment failure at the primary site, follow-up CT scans were definite for local failure (score, 3) a mean of 5.5 months (median, 3.5 months; range, 1–17 months) before clinical examination results. CONCLUSION: In many patients, follow-up CT shows local failure earlier than does clinical examination alone.

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Arguelles et al (2008) studied CT after laryngectomy. They said that familiarity with the typical imaging appearance of the larynx after each procedure is crucial for differentiating normal postsurgical changes from persistent or recurrent disease as well as for diagnosing associated second primary malignancies. Since computed tomography (CT) is often used for follow-up evaluations, an ability to interpret the characteristic CT features is particularly important.

Curtin et al (1998) studied Comparison of CT and MR imaging in staging of neck metastases. CT performed slightly better than MR imaging for all interpretative criteria. However, a high negative predictive value was achieved only when a low size criterion was used and was therefore associated with a relatively low positive predictive value.

Steinkamp HJ et al (1994) evaluated the criteria for differentiation between malignant and reactive lymph nodes in the H and N on basis of findings of helical CT. Helical CT scans evaluation of 70 consecutive patients (46 males and 24 female of aged between 40-70 yr) with known H & N tumors and cervical lymph node enlargement was performed. The ratio of maximal longitudinal to maximal axial dia. was calculated for nodes > 8mm in diameter. At histopathological examination 96 of 144 nodes were malignant. Of these, 96 had L/T ratio < 2 (sensitivity 97%, specificity 97%, accuracy 97% for malignancy), minimum dia. was > 8mm in 83 of 93 nodes (sensitivity 78%,

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specificity 100% and accuracy 86% for malignancy). Authors concluded that the L/T ratios at helical CT provides an accurate assessment of reactive Vs malignant nodes in head and neck.

Kaji, Arun, Vikram et al (1997) discussed the imaging of cervical lymhadenopathy and reviewed the anatomy and nomenclature of cervical lymph nodes. The regional (level) nomenclature for lymph nodes was discussed and emphasized. The criteria for diagnosing metastatic lymphadenopathy were discussed: •

Size – Axial dia > 1.5 cm for JD nodes and > 1 cm for all other nodes.

•

Minimal axial diameter (Perpendicular to maximal axial dia) 1.1 for JD and 1cm for other nodes.

•

Shape Round – Metastasis more likely Oval – Benign more likely

•

L/T ratio - < 2 with maximum axial dia. >8mm

•

Central necrosis – which appears as central area of hypoattenuation surrounded by rim of irregular enhancement is thought be most specific sign of metastatic involvement with specificity of 95-100%.

•

Extra nodal neoplastic spread : Amorphous, indistinct margins, irregular nodal capsular enhancement and infiltration of surrounding fat.

•

Invasion of adjacent structures: If there are clear fat planes surrounding vessels, it is unlikely that the carotid is invaded. Loss of

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fat plane with >270 degree circumferential involvement is highly suggestive of carotid involvement.

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5. RADIOLOGICAL ANATOMY

The larynx lies in anterior midline of neck, extending from the root of tongue to the trachea. In adults males it lies in front of 3rd to 6th cervical vertebrae. In children & adult females it lies at a higher level. The length varies from 44 mm in males to 36 mm in females. The larynx consists of 3 unpaired ( thyroid, Cricoid, epiglottis) and 3 paired cartilages ( arytenoid, corniculate, cuneiform). 5.1 The hyoid Bone and Laryngeal Cartilages: The laryngeal skeleton provides the framework for the larynx ands include the hyoid bone and the laryngeal cartilage. The hyoid bone is a U shaped structure that is anatomically considered part of lingual apparatus but provides a scaffold for muscles that suspend the larynx. The hyoid bone consists of central body and paired lateral greater and lesser horns. Positioned caudal to the hyoid bone, the thyroid cartilage is the largest laryngeal cartilage. The two ala of thyroid cartilage fuse anteriorly to form a V shaped shield. The naturally occurring notch in the superior portion of the laryngeal prominence should not be misinterpreted as cancer related cartilage destruction on transaxial imaging studies. The superior and inferior cornua project from the posterior free edges of the thyroid cartilage. The imaging appearance of thyroid cartilage varies considerably because of its hyaline composition and potential for minerialization. Calcification occurs by 8 to 10 years of age and most commonly begins within the posterior portion of the cartilage. Normal mineralization may be quite irregular, is often asymmetric, generally progresses at a variable rate

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through out the life. The irregular mineralization should not be confused with tumor invasion. The Cricoid cartilage is only cartilage that forms a complete. Calcification of Cricoid cartilage is usually more symmetric than that of the thyroid cartilage. The cricoid cartilage attaches to the inferior cornua of the thyroid cartilage by synovial joints that effect an approx 1.5mm separation between two cartilages. The paired pyramid-shaped arytenoid cartilage perch atop the posterosuperior rim of the cricoid cartilage and are affixed by synovial joints. The base of each arytenoid cartilage has an anterior vocal cords attached to the vocal processes. The epiglottis is leaf like cartilage that hovers over the glottic inlet forming the anterior wall of the laryngeal vestibule. The epiglottis consists primarily of elastic cartilage and seldom calcifies. The trans-axial plane of the hyoid bone divides the epiglottis into the suprahyoid and infrahyoid region. The tiny corniculate cartilages crown the apices of the arytenoid cartilages and articulate by synovial joints. The cuneiform cartilages form bulges in the posterolateral rims of the aryepiglottic folds and are a source of support. 5.2 The laryngeal ligaments and membranes: Binding the cartilages is a system of ligaments and membranes that provide much of structural and functional integrity of the larynx. These soft tissues form the true vocal cords, false vocal cords and aryepiglottic folds. One of the most important of these membranes is the conus elasticus; also know as the triangular membrane. The conus elasticus resembles an inverted funnel. The thickened

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superior edges form the vocal ligaments. The vocal ligaments together with the thyroarytenoid and vocalis muscle form the true vocal cords. The vocal ligament attach anteriorly to the inner surface of the thyroid cartilage prominence, forming the anterior commissure. The soft tissue posterior to the thyroid cartilage at the anterior commissure should measure no more than 1 mm in thickness. Unusual thickness of the tissue in this area may signify cancer of the anterior true cords and contralateral spread. The posterior vocal ligament attaches to the vocal processes of the arytenoid cartilages. The paired quadrangular membranes attach to the lateral free edges of the epiglottis and to the arytenoid cartilage. The superior free margin runs obliquely from the epiglottis to arytenoid and are thickened to form aryepiglottic folds. The thickened inferior margin stretches from the base of the epiglottis to the superior portion of the arytenoid and forms false vocal cords. Separating the true and the false vocal choirs is transversely oriented diverticulum known as the laryngeal ventricle. The lateral and upward extension of the ventricle is known as the saccule. 5.3 Laryngeal muscles: The muscles are divided into the extrinsic and intrinsic group. The extrinsic muscles are found external to the larynx proper and in turn, are divided in to suprahyoid and infrahyoid groups. The suprahyoid muscles originate from the base of the skull and insert on the hyoid bone. These muscles suspend the larynx and includes the stylohyoid, both

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bellies of the digastrics and the genihyoid. The infrahyoid muscle originates primarily from the sternum and other infrahyoid structures and insert on hyoid bone and thyroid cartilage. Intrinsic muscles are found within larynx proper and can be subdivided into vocal cords abductors/ adductors, tensors and protectors. The paired posterior cricoarytenoid muscles arise from the posterior cricoid cartilage and insert on the muscular process of the arytenoid cartilage. During contraction the muscular processes pivot and open the glottis. These muscles are only abductors of vocal folds. The adductor group closes the glottic aperture and consists of lateral cricoarytenoid, transverse arytenoid, oblique arytenoid and thyroarytenoid muscles. The thyroarytenoid muscle joins the arytenoid cartilage to the thyroid cartilage. The medical fiber insert on the vocal processes of the arytenoids and are termed the vocalis muscles. The paired cricothyriod muscles arise laterally from the thyroid cartilage and insert on cricoid cartilage. These muscles lengthen, stretch, and tense the vocal chords by tilting the anterior cricoid cartilage upwards and the posterior cricoid downwards. Decreased tension on vocal chords is accomplished by the thyroarytenoid muscle. 5.4 Spaces within larynx: Padding the cartilage membranes and the muscles are several fibrofatty spaces that lie concealed from the view of the laryngoscopist, but are important in spread of cancer. The paraglottic spaces are paired lateral spaces bordered medially by the quadrangular membrane, laterally by the thyrohyoid membrane and thyroid cartilage, posteriorly by the pyriform sinuses and inferiorly by the conus elasticus.

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The paraglottic spaces are primarily fat filled and therefore are easily recognized on CT and MR images. The midline anterior pre-epiglottic space is bordered superiorly by the vallecuale, anterosuperiorly by the base of the tongue, anteriorly by the hyoid bone, inferiorly by the epiglottis and laterally by the paraglottic space, thyrohyoid membrane and the thyroid cartilage. Within this space are the hyoepiglottic ligaments and glands. The pre epiglottic space is primarily fat filled and well depicted on CT & MR images. 5.5 Hypopharynx: The Hypopharynx is the portion of the foregut that lies between the oropharynx and the larynx, extending from the hyoid bone to the cricopharyngeus muscle. The Hypopharynx consists of three regions: The paired pyriform sinuses, the postcricoid

region

(pharyngoesophageal

junction)

and

the

posterior

hypopharyngeal wall. The pyriform sinuses are shaped like inverted cones with the apices directed inferiorly. The apex of each pyriform sinus lies lateral to the cricoarytenoid joint and above the cricothyriod space. The pyriform sinuses end in the postcricoid region where the hypopharynx empties into the cervical esophagus. The postcricoid region extends from the level of the arytenoid cartilages till the inferior border of the cricoid cartilage and is notoriously difficult to adequately asses by the indirect or direct endoscopy.

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5.6 Lymphatic drainage: Supraglottic larynx above the vocal cords is drained by lymphatics which pierce thyrohyoid membrane and go to upper deep cervical lymph nodes. Infraglottic larynx below the vocal cords is drained by lymphatics which pierce cricothyroid membrane and go to lower deep cervical and mediastinal lymph nodes. There are no lymphatics in vocal cords hence carcinoma of this site rarely shows lymphatic metastasis.

IMAGING-BASED LEVEL NODAL CLASSIFICATION

Level I: The submental (level IA) and submandibular (level IB) nodes. They lie above the hyoid bone, below the mylohyoid muscle and anterior to the back of the submandibular gland.

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Level II: The upper internal jugular nodes. They extend from the skull base to the level of the bottom of the body of the hyoid bone. They are posterior to the back of the submandibular gland and anterior to the back of the sternocleidomastoid muscle. Level III: The midjugular nodes. They extend from the level of the bottom of the body of the hyoid bone to the level of the bottom of the cricoid arch. They lie anterior to the back of the sternocleidomastoid muscle. Level IV: The low jugular nodes. They extend from the level of the bottom of the cricoid arch to the level of the clavicle. They lie anterior to a line connecting the back of the sternocleidomastoid muscle and the posterior-lateral margin of the anterior scalene muscle. They are also lateral to the carotid arteries. Level V: The nodes in the posterior triangle. They lie posterior to the back of the sternocleidomastoid muscle from the skull base to the level of the clavicle. They also lie anterior to the anterior edge of the trapezius muscle. Level VA (Upper level V nodes): Upto the level of the bottom of the cricoid arch. Level VB (Lower level V nodes): From the level of the bottom of the cricoid arch to the level of the clavicle. Level VI :The upper visceral nodes. They lie between the carotid arteries from the level of the bottom of the body of the hyoid bone to the level of the top of the manubrium. Level VII: The superior mediastinal nodes. They lie between the carotid arteries below the level of the top of the manubrium and above the level of the innominate vein.

31

5.7 Nerve supply of larynx: Motor nerve supply – All muscles of larynx are supplied by recurrent laryngeal nerve except cricothyriod which is supplied by external laryngeal nerve which is a branch of superior laryngeal nerve. Sensory nerve supply-

Above vocal cords, larynx is supplied by internal

laryngeal nerve which is a branch of superior laryngeal nerve and below vocal cords by recurrent laryngeal nerve.

32

6. PATHOLOGY AND GENERAL IMAGING FINDINGS

Laryngeal cancer accounts for 2 to 5 percent of all malignant neoplasms. The disease is more common in males than females by a ratio of 10 to 1 and its peak incidence is in 6th & 7th decades. Squamous cell carcinoma, originating from the mucosal lining, is the most common malignant tumor in the larynx. These tumors have the tendency to spread submucosally, and this extension into the deeply lying tissue planes may be difficult to evaluate by clinical examination or endoscopy alone. About 65%– 70% of laryngeal cancers originate at the glottic level, and about 30% at the supraglottic level; laryngeal cancer originating from the subglottic region is rare. The clinical criteria used for giving a tumor a particular T-classification are sitedependent; in the larynx involvement of different laryngeal subsites and reduced vocal cord mobility are important criteria. The local staging criteria for glottic, supraglottic and subglottic cancer are summarized as follows. 6.1 TNM STAGING ( by AJCC 2002) TUMOUR STAGING (T) Glottic cancer T1- Tumor limited to vocal cord(s) with normal mobility (may involve anterior or posterior commissure) T1a: limited to one vocal cord T1b: involving both vocal cords

33

T2 - Extension into supra- and/or subglottis, and/or with impaired vocal cord mobility T3 - Vocal cord fixation and/or invasion of paraglottic space, and/or minor thyroid cartilage erosion T4 - Extralaryngeal tumor spread T4a: tumor invading through thyroid cartilage, or tissues beyond the larynx (e.g. trachea, soft tissues of the neck, strap muscles, thyroid gland, esophagus) T4b: tumor invading prevertebral space, mediastinum, or encasing carotid artery Supraglottic cancer T1- Tumor limited to one subsite of supraglottis with normal vocal cord mobility T2 - Tumor invades mucosa of more than one adjacent subsite of supraglottis, glottis or region outside of supraglottis, without fixation of the larynx T3 - Vocal cord fixation or invasion of postcricoid area, preepiglottic and/or paraglottic space, and/or minor thyroid cartilage erosion T4 - Extralaryngeal tumor spread T4a: tumor invading through thyroid cartilage, or tissues beyond the larynx (e.g. trachea, soft tissues of the neck, strap muscles, thyroid gland, esophagus) T4b: tumor invading prevertebral space, mediastinum, or encasing carotid artery Subglottic cancer T1 - Tumor limited to subglottis

34

T2 - Tumor extends to vocal cord(s) with normal or impaired mobility T3 - Vocal cord fixation T4 - Extralaryngeal tumor spread T4a: tumor invading through cricoid or thyroid cartilage, and/or invades tissues beyond the larynx (e.g. trachea, soft tissues of the neck, strap muscles, thyroid gland, esophagus) T4b: tumor invading prevertebral space, mediastinum, or encasing carotid artery

REGIONAL LYMPH NODES (N) NX - Regional lymph nodes cannot be assessed N0 - No regional lymph node metastasis N1 - Metastasis in a single ipsilateral lymph node, 3cm or less in greatest dimension N2 - Metastasis in a single ipsilateral lymph node, more than 3 cm but not more than 6 cm in greatest dimension, or in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension, or in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension N3 - Metastasis in a lymph node, more than 6 cm in greatest dimension

35

DISTANT METASTASIS (M) MX - Distant metastasis cannot be assessed M0 - No distant metastasis M1 - Distant metastasis

STAGING Stage 0

T is

No

Mo

Stage I

T1

No

Mo

Stage II

T2

No

Mo

Stage III

T1

N1

Mo

T2

N1

Mo

T3

No, N1

Mo

T4

No, N1

Mo

IVB

Any T

No, N1

Mo

IVC

Any T

Any N

M1

Stage IVA

6.2 GENERAL IMAGING FINDINGS: Criteria used for tumor involvement are abnormal contrast enhancement, soft tissue thickening, presence of a bulky mass, infiltration of fatty tissue (even without distortion of surrounding soft tissues), or a combination of these. Any tissue thickening between the airway and the cricoid arch is considered to represent subglottic tumor.

36

Several studies have compared the CT findings with the results of whole organ sectioning after total or partial laryngectomy, showing that CT techniques is accurate methods to visualize laryngeal pathology (Zbären et al. 1996). Gross cartilage invasion can be detected with CT. Due to the large variability in the ossification pattern of the laryngeal cartilages, CT often fails to detect early cartilage invasion. Demonstration of tumor on the extralaryngeal side of the cartilage is a reliable, but late sign of cartilage invasion. Asymmetrical sclerosis, defined as thickening of the cortical margin and/ or increased medullary density, comparing one arytenoid to the other, or one side of the cricoid or thyroid cartilage to the other side, is a sensitive but non-specific finding on CT (Becker et al. 1995). Erosion or lysis has been found to be a specific criterion for neoplastic invasion in all cartilages. Other signs, such as cartilaginous blow-out or bowing, a serpiginous contour or obliteration of the medullary space are not very reliable for cartilage invasion. The combination of several diagnostic CTcriteria for neoplastic invasion of the laryngeal cartilages seems to constitute a reasonable compromise: when extralaryngeal tumor and erosion or lysis in the thyroid, cricoid and arytenoid cartilages was combined with sclerosis in the cricoid and arytenoid (but not the thyroid) cartilages, an overall sensitivity of 82%, an overall specificity of 79% and an overall negative predictive value of 91% was obtained (Becker et al. 1995). The controversy on which modality should be preferred to image the larynx dealt for a great part with the accuracy to detect cartilage invasion. MRI was recommended to be the best method to determine a laryngeal tumor (Becker et al. 1997a). MRI is a more sensitive technique than

37

CT to detect cartilage abnormalities. Areas of cartilage abnormality will result in an increase in signal intensity on T2-weighted images and contrast-enhanced T1-weighted

MRI

images.

However,

due

to

its

high

sensitivity

for

intracartilaginous alterations MRI will yield in a considerable number of cases a false positive result, as distinction between true cartilage invasion and reactive inflammation, edema, fibrosis or ectopic red bone marrow is not possible (Becker et al. 1995). NEOPLASTIC EXTENSION PATTERNS OF LARYNGEAL CANCER: 6.2.1. Glottic Cancer Local Tumor Spread The most common site of involvement is the anterior portion of the vocal cord, usually at the free margin or upper surface. Involvement of the anterior commissure is commonly present and such lesions may extend over the midline in the contralateral vocal cord. As the amount of normal soft tissue visible at the level of the anterior commissure is somewhat variable (Kallmes and Phillips 1997), radiological detection of subtle tumor spread into this structure by imaging can be challenging; however, usually the anterior commissure can be well evaluated during endoscopic examination. When the tumor arises from the posterior side of the vocal cord, posterior extension over the medial facet of the arytenoid cartilage, eventually involving the posterior commissure may occur . The redundant mucosa at the level of the posterior commissure should not be misinterpreted as evidence for tumor spread.

38

Extension into the subglottis may occur along the mucosal surface, or submucosally after penetration of the conus elasticus. When soft tissue thickening is seen adjacent to a glottic neoplasm along the inner side of the cricoid, the lesion is extending into subglottis. Coronal images or coronally reformatted CT images, may be helpful to evaluate more subtle subglottic tumor extension. Lateral spread of the cancer causes infiltration of the vocal ligament and muscle. In a more advanced stage, the paraglottic space is infiltrated and the perichondrium of the thyroid cartilage is reached. With extralaryngeal growth, tumor extension into non-fatty soft tissue structures surrounding the larynx may be present. Neoplastic invasion of the thyroid gland mostly occurs in glottic cancer showing subglottic extension or invading the thyroid cartilage (Dadas et al. 2001). Invasion of the subcutaneous layers and eventually skin may be seen in anteriorly spreading cancer. Posterior spread to the retrocricoid hypopharynx and eventually esophagus may occur. Cancer involving the glottic and supraglottic region is also called transglottic cancer. However, the definition of transglottic cancer varies from author to author. Usually, tumors crossing the laryngeal ventricle involving both the false and true vocal cord are called transglottic cancer; most agree that the use of this term also implies extension into subglottic region (Mancuso et al. 1989). Lymphatic Spread Usually, glottic cancer only metastasizes to the neck lymph nodes when growing beyond the glottic region. Level III is the most commonly affected level. Neck

39

adenopathies are very uncommonly encountered in small (T1) lesions, but the risk increases to about 8% and 30% in respectively T2 and T3 lesions. Imaging studies may detect these adenopathies at an earlier stage than clinical examination alone. 6.2.2. Supraglottic Cancer Essentially, the radiological signs are similar to those in glottic cancer, but supraglottic cancers often show a larger tumor volume at first presentation. Clinically visible tumor extension and radiological tumor volume are not always correlated, due to submucosal spread in the preepiglottic space and/or paraglottic space. Laryngeal cartilage invasion is rarely seen in supraglottic cancer. Suprahyoid Epiglottis Lesions of the suprahyoid epiglottis may grow exophytically. Others invade the epiglottic tip and spread to adjacent structures, such as the valleculae, tongue base and preepiglottic space; soft tissue ulceration and amputation of the epiglottic tip may be present. Infrahyoid Epiglottis As the infrahyoid epiglottis contains tiny perforations, such lesions easily infiltrate the preepiglottic space; from this space, they may spread upwards towards the valleculae and tongue base, or downwards to the epiglottic petiolus. Invasion of the anterior commissure or subglottic spread are rare, but may be seen in advanced cases. Extension into the aryepiglottic folds and false vocal cords may be seen; extension to the true vocal cords mostly occurs in advanced cases

40

Aryepiglottic Fold and Arytenoid Aryepiglottic fold tumors may present as exophytic lesions, or infiltrative masses invading the paraglottic space. Along the paraglottic space, they may spread towards the false and eventually true vocal cords. Invasion of the cricoarytenoid joint may be seen. Extension towards the piriform sinus commonly occurs, and it may be difficult to distinguish between a primary piriform sinus cancer and supraglottic cancer. False Vocal Cords Submucosal tumor spread is commonly present in these lesions with involvement of the paraglottic space. Subglottic tumor spread is seen in advanced cases. Lymphatic Spread As the supraglottic region has a rich network of lymphatic channels, lymphadenopathy is frequently present in supraglottic cancer. At presentation, about 50%–60% of patients with supraglottic cancer have clinically manifest lymphadenopathy. The incidence of neck metastasis is about 30% in T1 and T2 lesions, and about 70% in T3 and T4 lesions. Neck level II is most commonly affected, to a lesser extent level III. 6.2.3. Subglottic Cancer Subglottic cancer is a rare malignant lesion. At the time of diagnosis, subglottic cancer has usually invaded the true vocal cords, and it may be difficult to distinguish between a cancer originating in the glottis or subglottis. Subglottic cancer is commonly bilateral or even circumferential at presentation. Cricoid cartilage invasion occurs early; extralaryngeal extension, or anteriorly through the

41

cricothyroid membrane is often present. Lymphatic dissemination is seen in about 10% of cases; among the lymph nodes which may become involved are the Delphian node and paratracheal lymph nodes. Imaging shows a subglottic soft tissue mass (normally no soft tissue is seen between the subglottic air column and the cricoid cartilage), more or less with circumferential extension along the cricoid cartilage. The findings may include cricoid cartilage alterations (sclerosis, lysis), intratracheal soft tissue thickening, and infiltration of the glottic and prelaryngeal soft tissues.

6.3. TREATMENT OPTIONS Depending on site of lesion, extent of lesion, presence or absence of nodal and distant metastasis, treatment consists of :1) Radiotherapy 2) Sugery

a) Conservative laryngeal surgeries b) Radical sugery

3) Combined therapy

RADIOTHERAPY:- Curative radiotherapy is reserved for early lesions which neither impair cord immobility nor invade cartilage or cervical nodes. Radiotherapy does not give good results in lesions with fixed cords, subglottic extensions, cartilage invasion & nodal metastasis. These lesions require surgery. SURGERY:Conservative procedures

42

Endoscopic laser excision and cordectomy Vertical partial laryngectomy Frontolateral laryngectomy Hemilaryngectomy Horizontal laryngectomy Supraglottic Extended supraglottic Three-quarters Supracricoid With cricohyoidopexy With cricohyoidoepiglottopexy Near total laryngectomy Radical procedure Total laryngectomy. COMBINED THERAPY:Surgery may be combined with pre or postoperative radiation to decrease the incidence of recurrence.

Region wise treatment options:Glottic Cancer Carcinoma in situ can often be controlled by stripping the cord or laser treatment; radiotherapy is used after recurrences of such superficial cancer (Million 1992).

43

In T1 tumors radiation treatment is usually preferred, as the voice quality is better than after partial laryngectomy, and fewer complications are encountered. Patients with well defined lesions, suitable for transoral laser excision with a good functional outcome, can be treated with either laser or radiotherapy (Mendenhall et al. 2004). In T2 tumours vertical partial laryngectomy (frontolateral laryngectomy or vertical hemilaryngectomy) is done to preserve voice. In case of recurrence , total laryngectomy is done. T3 and T4 tumors are treated either with radiotherapy or total laryngectomy with possible postoperative irradiation. Patients with advanced disease are in the unfavorable group for radiotherapy and are advised to undergo total laryngectomy (Million 1992). Supraglottic Cancer Patients with a T1, T2 or a ‘favorable’ T3 lesion can be treated with either irradiation or supraglottic laryngectomy (Robbins et al. 1987; Lee et al. 1990). The selection is at the preference of the patient and the physician in charge. A ‘favorable’ T3 tumor is classified as T3 due to preepiglottic space involvement (visible on CT). considered

Unfavourable bulky T3 lesions and most T4 lesions are

unfavorable

for

radiotherapy.

Partial

(if

feasible)

or

total

laryngectomy, with or without postoperative radiotherapy, is often recommended in these patients, as the local control rates are better for the surgically treated patients (Weems et al. 1987). Patients who are medically unfit for total

44

laryngectomy or refuse this procedure are treated with radiotherapy (Mendenhall et al. 1996). Subglottic cancer Patients with a T1 tumour can be treated with hemilaryngectomy. More extensive tumours(T2, T3 & T4) require total laryngectomy.

6.4. POST TREATMENT IMAGING IN LARYNGEAL CANCER After treatment of a head and neck cancer, a number of tissue changes become visible on CT images of the neck. These expected alterations should be known, so that they are not misinterpreted as evidence of persistent or recurrent tumor. Imaging may be used to detect recurrent or persistent disease before it becomes clinically evident, possibly with a better chance for successful salvage. Treatment complications, such as soft tissue or cartilage/bone necrosis, are less frequent than tumor recurrences and definitive distinction between necrosis and recurrent tumor is difficult although imaging findings may be helpful.

6.4.1. Expected Tissue Changes After Radiotherapy:The changes visible on post-radiotherapy CT images depend on the radiation dose and rate, the irradiated tissue volume, and the time elapsed since the end of radiation therapy (Mukherji et al. 1994a; Nömayr et al. 2001). Changes which may be seen include : • Thickening of the skin and platysma muscles • Reticulation of the subcutaneous fat and the deep tissue fat layers

45

• Edema in the retropharyngeal space • Increased enhancement of the major salivary glands, followed by size reduction of these glands: postirradiation sialadenitis • Atrophy of lymphatic tissue, in both the lymph nodes and Waldeyer’s ring • Thickening and increased enhancement of the pharyngeal walls • Thickening of the laryngeal structures, with increased density of the fat in the preepiglottic and paraglottic spaces. These tissue changes are most pronounced during the first few months after the end of radiation therapy, and diminish or even resolve with time. It is important to note that the expected tissue changes after radiation therapy appear symmetrical, unless the neck was irradiated using asymmetric radiation portals. The laryngeal cartilages do not show changes after irradiation. Reduction in the degree of cartilage sclerosis in the neighborhood of the tumor has been described, and this appears to correlate with local control (Pameijer et al. 1999).

6.4.2. Expected Findings After Laryngeal Surgery:Laser Resection The expected findings after transoral laser excision of a laryngeal cancer depend on the amount of tissue resected. The laryngeal soft tissues may appear normal, or show a focal tissue defect . After a more extensive resection, the laryngeal soft tissue may be replaced by scar, appearing as homogenous but relatively dense tissue with a straighter inner border (Maroldi et al. 2001); in such cases,

46

differentiation with recurrent tumor may be difficult and correlation with endoscopic findings is necessary. In case of doubt, biopsy is warranted. Partial Laryngectomy The aim of partial laryngectomy is to combine radical tumor resection with preservation of laryngeal function. This requires continuity and patency of the airway, separation of the airway and digestive tract,and sparing or reconstruction of the glottic phonation function. Traditional partial laryngectomies include horizontal supraglottic laryngectomy and vertical hemilaryngectomy, but more complex surgical techniques are also being employed (Maroldi et al. 1997; Maroldi et al. 2001; Delaere and Hermans 2003). The postoperative radiological findings depend on the technique employed. The postoperative soft tissue changes are less predictable, depending on individual differences in healing, and variations in amount of edema and scarring (Maroldi et al. 2001). The differentiation between redundant or hypertrophic mucosa, as well as scar tissue, from recurrent cancer, may be difficult. Total Laryngectomy Complete removal of the larynx may be required as primary treatment of extensive laryngeal cancer or for salvage of tumor recurrence after radiation treatment or failed partial laryngectomy. When the larynx is removed, the airway and upper digestive tract become completely separated. The airway will then end at a tracheostomy in the base of the neck. If, following the laryngectomy, not sufficient hypopharyngeal tissue is left for creating a neopharyngeal lumen of acceptable diameter, a soft tissue flap is used to create a wider lumen.

47

6.4.3. Persistent or Recurrent Cancer:Post-treatment imaging is useful to confirm the presence of clinically suspected tumor recurrence. On CT, tumor recurrence appears after radiation therapy as a soft tissue mass at the primary site and/or as an enlarged (and/or centrally liquefied) neck adenopathy. After surgical treatment, the most reliable imaging finding in recurrent tumor is an enhancing soft tissue mass; after partial laryngectomy, destruction of residual laryngeal cartilage may be seen. Early tumor recurrence may be difficult to distinguish from tissue changes induced by therapy. Therefore, it is recommended to obtain a follow-up CT study after surgical, radiation or combined treatment for a laryngeal neoplasm with high-risk profile (Hermans et al. 2000a; Schwartz et al. 2003). Probably the best time to obtain such a baseline study is about 3–6 months after the end of treatment. Such a baseline study allows treatment-caused changes in the head and neck tissues to be documented. By comparing subsequent studies with the baseline study, it becomes possible to detect with more confidence tumor recurrences or treatment complications.

6.5 Treatment Complications 6.5.1 Complications After Surgery:Most surgical complications occur early after treatment, and are dealt with on a clinical basis. Imaging may be required in the detection and follow-up of a fistula after partial or total laryngectomy. Many of these fistulas will close

48

spontaneously, but some may need reintervention. Imaging may also be of use in the confirmation of flap failure due to necrosis.

6.5.2. Complications After Radiotherapy:Laryngeal Necrosis Persisting severe edema and radionecrosis of the larynx are uncommon treatment complications, with an incidence of about 1%. The occurrence of laryngeal necrosis peaks during the 12 months following treatment, which is more or less contemporaneous with the peak incidence of tumor recurrence. However, cases of laryngeal necrosis more than 10 years after radiation treatment do occur (O’Brien 1996). Cartilage itself is resistant to the effect of irradiation. Cartilage changes usually occur when the perichondrium is broached by

trauma

or

tumor,

exposing

the

underlying

irradiated

cartilage

to

microorganisms in the airway (Keene et al. 1982); this may lead to infectious perichondritis, possibly resulting in necrosis and laryngeal collapse. Patients with laryngeal necrosis often have hoarseness, dyspnea, neck and/or ear pain, some degree of dysphagia, and anterior neck swelling. On imaging studies, a variable degree of laryngeal soft-tissue swelling is seen (Hermans et al. 1998). These soft tissue changes surrounding the necrotic cartilage can be very pronounced and may be the only visible abnormality, making the differentiation with recurrent tumor very difficult. Furthermore, laryngeal necrosis and tumor recurrence may occur simultaneously.

49

In laryngeal necrosis, some fluid may be seen surrounding the cartilages. Necrosis of the thyroid cartilage may cause fragmentation and collapse of this cartilage with or without gas bubbles visible adjacent to or in it. Patients with arytenoid cartilage necrosis may show anterior dislocation of this cartilage; this could be due to crico-arytenoidal joint effusion, secondary to inflammation or infection. Progressive lysis of the arytenoid is possible, showing a crumbly aspect evolving to complete disappearance (De Vuysere et al. 1999). Also, sloughing of the arytenoid cartilage into the airway has been described (Hermans et al. 1998). The adjacent part of the cricoid cartilage may appear sclerotic. Cricoidal sclerosis or destruction may be also seen in association with lysis of the thyroid cartilage.

50

7. RESULTS

The current study is comprised of 100 patients. Table 7.1 Tabular and figurative distribution of patients according to age is as follows:

Sr.No

Age

(Yrs)

No. of Patients

%

1

0-20

0

0

2

20-40

2

2

3

40-60

34

34

4

>60

64

64

100

100

Total

COMMENTS: The commonest age group affected was >60 years.

70 60

Percentage (%)

50 40 30 20 10 0 0-20

20-40

40-60

A g e (in yr s )

51

>60

Table 7.2: Tabular and figurative distribution according to sex of the patient is as follows:

Sr.No

Sex

No. of Cases

%

1

MALE

91

91

2

FEMALE

9

9

100

100

Total

COMMENTS: Carcinoma larynx is much more common in males than in females

M A LE FEM A LE

52

Table 7.3: Tabular and figurative distribution according to region of involvement by ca. larynx is as follows:

Sr.No

Region of involvement

No. of Cases

%

1

Glottic

54

54

2

Supraglottic

24

24

3

Subglottic

4

4

4

Transglottic

6

6

5

Pyriform fossa

12

12

100

100

Total

COMMENTS: Carcinoma larynx most commonly involves glottic region.

60

Percentage (%)

50 40 30 20 10 0 Glottic

Supraglottic Subglottic Transglottic Pyriform fossa Region of involvem ent

53

Table 7.4: Tabular and figurative distribution of cartilage involvement by ca. larynx is as follows:

Sr.No

Cartilage involvement

No. of Cases

%

1

No cartilage involvement

38

38

2

Thyroid cartilage

34

34

3

Cricoid cartilage

18

18

4

Arytenoid cartilage

10

10

100

100

Total

COMMENTS: Most commonly involved cartilage was thyroid cartilage.

40 35

Percentage (%)

30 25 20 15 10 5 0 No c artilage inv olvement

Thyroid cartilage Cricoid c artilage Car tilage involve m e nt

54

A rytenoid c artilage

Table 7.5: Tabular distribution of signs of cartilage involvement by ca. larynx on MDCT are as follows:

Sr.No

No. of cases

SIGNS

%

1

Cartilage sclerosis

22

35

2

Erosion or Lysis

14

22

3

12

19

4

Extralaryngeal spread Tumour adjacent to nonossified cartilage

8

12

5

Obliteration of marrow space

4

8

6

Serpiginous contour/Bowing/Blowout

2

4

TOTAL

62

COMMENTS: Most common sign of cartilage involvement was cartilage sclerosis

Cartilage sclerosis Erosion or Lysis Extralaryngeal spread Tumour adjacent to nonossif ied cartilage Obliteration of marrow space Serpiginous contour/Bow ing/Blow out

55

Table 7.6: Tabular distribution of cases of ca. larynx presenting with metastatic lymphadenopthy on MDCT are as follows:

Glottic Ca.

Supra Glottic Ca

Sub Glottic Ca

Trans Glottic Ca

Ca Pyriform Fossa

TOTAL

No LNpathy

30

2

0

0

0

32

Level 1

0

2

0

1

0

3

Level 2

6

12

1

2

2

23

Level 3

14

6

2

3

4

29

Level 4

4

2

1

0

4

11

Level 5

0

0

0

0

2

2

TOTAL

54

24

4

6

12

100

COMMENTS: Level III was the most commonly affected level in glottic Ca Level II was most common level affected in supraglottic Ca. Overall most commonly affected level in carcinoma larynx was level III.

56

Table 7.7: Tabular and figurative distribution of signs of metastatic lymphadenopathy on MDCT are as follows:

Sr.No

SIGNS

No. of cases

%

1

Enlarged size

68

100

2

Round shape

48

70

3

Central Necrosis

36

53

4

Presence of clusters

22

32

5

Extracapsular spread

24

35

TOTAL

68

COMMENT: Enlarged size is the most common sign of metastatic LNpathy

70 60 50 Number

Enlarged size 40

Round shape Central Necrosis

30

Presence of clusters Extracapsular spread

20 10 0 Signs of metastatic LNpathy

57

Table 7.8: Tabular and figurative distribution according to T-staging of ca. larynx are as follows:

T1

T2

T3

T4

TOTAL

Glottic Ca. Supra Glottic Ca Sub Glottic Ca Trans Glottic Ca Ca Pyriform Fossa

2

36

12

4

54

4

4

10

6

24

0

2

1

1

4

0

0

0

6

6

0

2

2

8

12

TOTAL

6

44

25

25

100

60 50

No. of cas es

40 T4

30

T3 20

T2 T1

10 0 Glottic Ca.

Supra Sub Glottic Trans Ca Py rif orm Glottic Ca Ca Glottic Ca Fos s a Re g io n o f in vo ve m e n t

58

8. DISCUSSION A total of 100 patients suspected or diagnosed cases of laryngeal malignancy were studied using spiral multislice multidetector CT scanner. 91 patients were male and 9 patients were female. The higher number of males in this study could be attributed to cigarette smoking and tobacco chewing habits which were the most common risk factors associated with carcinoma larynx. We used 50ml of ionic water soluble contrast medium and were able to obtain good and consistent opacification of neck vessels and enhancement of lesions. We limited the use of non-ionic contrast medium (omnipaque, ultravist) for those at risk of contrast reactions or with compromised renal function. We decreased the contrast load and administered the contrast medium through a power injector at a rate of 2.5ml/sec, using a delay time of 30 seconds. The method of contrast administration and use of ionic contrast correlated with the recommendations of Hopper et al. The use of lesser volume of contrast was justified as discussed by Yoon DY et al. In our study, 15 patients developed minor reactions to contrast like nausea, flushing, itching etc, which were treated by injection metoclopromide, avil and hydrocortisone. None of our patients experienced a major reaction and there was no morbidity or mortality from contrast reaction. The use of much lesser volume of contrast agent proved safe in our study. We obtained images with patient lying supine and with breath hold. Reformatted sagittal and coronal images were obtained which were found to be extremely useful especially for knowing cranio-caudal extent of the lesion and also for

59

communicating with clinical colleagues. Our findings correlated with those of Mukherji et al and Silverman et al who discussed the importance of coronal & sagittal reformation. In our study of 100 patients of carcinoma larynx, it was found more commonly in males. This was comparable with the findings of Sasaki et al who found laryngeal carcinoma to be 15 times more common in male. In this study the peak age was in 7th decade. In our study, the most common region of involvement was Glottis (54%) followed by supraglottis (24%), pyriform fossa (12%), transglottic (6%) and subglottic (4%). These observations were consistent with findings of Zbaren et al, who found glottis harbouring more than 60% of all laryngeal tumours. In our study, CT helped in evaluation of extent of spread of malignant lesion and hence helped to detect its operability. It helped to determine T staging of the tumours. Out of 54 cases of glottic carcinoma, 2 cases were limited to vocal cords (T1 stage), 36 cases had extension into supra or subglottis (T2 stages), 12 had invasion of paraglottic space or thyroid cartilage erosion (T3 stage) and 4 had extralaryngeal spread (T4 stage). Similar T-staging was performed for supraglottic and subglottic tumours using AJCC (1999) classification of tumor staging as discussed earlier. CT also helped in choice of treatment due to its capability to stage the tumour. In our study, the cases with ‘favourable’ lesions (i.e. T1, T2 and few T3) were treated with voice conservation surgeries as discussed earlier. Other

60

‘unfavourable’ lesions were treated with radical surgeries or radiotherapy. These findings were very consistent with study performed by Mancuso et al. Cartilage invasion was observed in 62 out of 100 patients (62%). Out of 62 cases, 34 were glottic Ca, 16 were supraglottic Ca, 3 were subglottic Ca, 3 were transglottic Ca and 6 were pyriform fossa cancers. The cartilage most commonly involved was thyroid (34 cases), followed by cricoid (18 cases) and arytenoid cartilage (10 cases). The epiglottis was excluded from analysis because clinical significance of tumor invading this yellow fibrocartilage is not considered to be same as that of invasion of hyaline cartilages. We used the following diagnostic criterias to detect cartilage invasion: 1.

Cartilage sclerosis – was seen in 22 cases (35%).

2.

Erosion or lysis – was seen in 14 cases (22%).

3.

Extralaryngeal spread – 12 cases (19%).

4.

Tumour adjacent to nonossified cartilage – was seen in 8 cases (12%).

5.

Obliteration of marrow space – 4 cases (8%).

6.

Serpiginous contour / bowing or cartilage blowout -was seen in 2 cases (4%).

Cartilage sclerosis was seen in maximum number of cases, hence was considered as main CT findings of cartilage invasion. The above distribution of CT findings was very much consistent with that of Becker et al who concluded that detection of cartilage invasion with CT depends on appropriate use of individual and combined CT criteria.

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We studied 24 cases of supraglottic ca. & 12 cases of pyriform sinus carcinoma. CT helped in differentiation of pyriform sinus cancer from supraglottic laryngeal cancer. The supraglottic tumors grew in a circumferential pattern, and when the pre-epiglottic space was involved, extension was bilateral. Lesions of the pyriform sinus more frequently showed unilateral involvement. . The pyriform sinus tumors had a much higher incidence of thyroid cartilage invasion as compared to supraglottic carcinoma. Widening of cricothyriod space was seen only with pyriform sinus lesions. These findings were very much consistent with those of Larsson et al. Out of 100 patients in our study, 68 patients presented with metastatic lymphadenopathy (68%), of these, 24 were glottic carcinoma (35%), 22 were supraglottic Ca (32%), 4 were subglottic Ca. (5%), 6 were transglottic Ca, and 12 were pyriform carcinoma (17%). Glottic carcinoma metastasize to neck lymph nodes only when growing beyond glottic region. Level III was the most commonly affected level in glottic Ca (14 cases), level II was most common affected in supraglottic Ca (12 cases). Overall most commonly affected level in carcinoma larynx was level III (29 cases). These findings are in accordance with anatomic pathways of spread of laryngeal and hypopharyngeal cancers discussed by Kirabner JA, Wippold II, Pfreunder et al. We used the following criteria to diagnose metastatic lymphadenopathy. 1. Enlarged lymphnodes with transaxial diameter > 1.5cm (for level I and II) and > 1 cm (for level III to VI).

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2. Rounded shape. 3. Presence of central necrosis. 4. Presence of clusters (3 or more contiguous ill-defined nodes within some level). 5. Extra capsular spread (ill-defined indistinct margins, infiltration of surrounding fat or adherence to carotid vessels). All the findings correlated with various reports which described the criteria of benign (reactive) from metastatic adenopathy like those of Kaji., Steinkamp, Mancuso and Curtin et al. We also studied 10 cases treated with radiotherapy for carcinoma larynx who were subjected to a repeat CT scan after 6 months of treatment, to detect presence of clinically suspected tumor recurrence. Out of these 10 cases, 7 cases revealed expected tissue changes after radiotherapy with no evidence of tumour recurrence. The changes observed were in accordance with the study of Mukherji et al and Mancuso et al. 2 cases (out of 10) had evidence of tumour recurrence in form of enhancing soft tissue mass at primary site and enlarged necrotic lymphadenopathy. These findings correlated quite well with those of Kotzur et al and Mendenhall et al who emphasized not to get confused between post-radiotherapy changes and tumour recurrence in their study. 1 case (out of 10) was diagnosed as cartilage radionecrosis. Fragmented and collapse of cartilage was noted with gas bubbles and fluid adjacent to it. These findings were comparable with those of Hermans et al, Keene et al and Obrein et al.

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We also studied 6 post surgical cases who were treated with voice conservative surgery, to detect tumour recurrence. 5 out of these 6 cases had no evidence of recurrent tumour and showed expected changes after surgery. These findings correlated well with those of Maroldi et al and Delaere et al. 1 case showed enhancing soft tissue mass and was diagnosed as tumour recurrence.

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9. SUMMARY AND CONCLUSION

Despite developments in magnetic resonance imaging , CT remains the modality used most frequently for evaluation of laryngeal lesions. The benefits of MDCT relative to single – section helical CT are significant. The examination can be performed with thinner sections leading to high spatial resolution. Faster scanning improves temporal resolution and reduces motion artifact.

With introduction of voice conservation therapies for carcinoma larynx ( like partial laryngectomies, laser excision & radiotherapy ), it became essential to determine true extent of tumour to decide the exact modality of treatment. Direct examination via endoscopy allows only for visualization of mucosal & superficial submucosal lesions. However with advent of Multidetector CT scanners (MDCT), detailed evaluation of deeper laryngeal soft tissues & cartilage framework has become a practical reality. MDCT clearly demonstrates the true extent & local spread of the laryngeal tumour and hence determines the management of the patient. It also shows structural alterations in laryngeal framework due to tumour thus aiding substantially in preoperative planning and enabling the surgeon to operate without any surprises. MDCT can detect early cartilage involvement by the tumour, although MRI is considered slightly more sensitive in this regard. But MRI has got longer

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acquisition time & hence can only be performed in co-operative patients. Moreover images in MRI are frequently degraded secondary to motion artefacts from swallowing, breathing, coughing & carotid artery pulsations. MDCT offers distinct advantages in these aspects due to faster scanning, larger anatomic coverage & decreased motion artefacts. It also allows for various two & three dimensional reformation which are especially useful to understand complex anatomic relationship & disease extent. MDCT due to its larger anatomic coverage, easily detects early nodal metastasis & hence helps in TNM staging of tumours. MDCT also plays an important role in follow up of post radiotherapy & post surgical cases of carcinoma larynx. It clearly demonstrates various expected changes in such patients & also helps to detect early tumor recurrence. It is also modality of choice to demonstrate complications arising from treatment e.g. radionecrosis from radiotherapy , flap necrosis &

fistula formation from

surgeries. In a nutshell, we can conclude the MDCT is a highly efficacious modality for accurate delineation of anatomy & true extent of disease in carcinoma larynx & has a very important role to play in evaluation, management & follow up of these cases.

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11. ANNEXURE 11.1 CASE RECORD FORM Date: Name: Age :

Sex:

Indoor/Outdoor Reg. No:

Address:

Chief complaints: Clinical Examinations: Past History: Family History: Investigations: Routine investigations (like CBC, Hb, ESR, Sr. Electrolytes etc.) X-ray neck IDL findings: Clinical diagnosis:

CT findings:

Treatment: Follow – up:

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11.2 INFORMED CONSENT (For Contrast and Sedation)

I hereby give my consent for injection of contrast / sedation / anaesthesia for CT examination. I have been explained the benefits, risks and complications involved in this procedure in a language I understand the best.

Date:

Patient’s / Relative’s Signature / thumb impression

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