Urinary System Nuclear Medicine: Renal Imaging

Urinary System Nuclear Medicine Part 2

Renal Imaging

Introduction Most patients with suspects renal problemes will have a conventional radiogaphic intravenous pyelogram ( IVP ) as an initial procedure . When coupled with nephrotomography , ultrasound , and computed tomography,nuclear renal imaging is a poor choice for the determination of anatomic integrity.

2

• Nuclear imaging is useful for measuring the relative function of each kidney , and for detecting dynamic alterations in function , such as in patients with hydronephrosis with no clearcut obstruction . using this method we can get anatomic and functional information of the patient with some renal disease.

3

In patients with compromised renal function , the contrast agents used for the IVP examination can cause acute loss of the remaining renal function . In these patients , the nuclear renal examination can be safely substituted for the conventional X-ray procedure.

4

Methods Sorting: • Renal imaging can be done with two methods: • 1.The dynamic renal imaging. It includes renal blood flow imaging and functional imaging; • 2.The static renal imaging. 5

Two methods use different Radiopharmaceuticals. Dynamic methods use rapidly passing radiolabeled tracer but the static method must use the

slow transit

radiopharmaceuticals. 6

Rapid Transit radiolabeled Tracer: • 1. 99mTc-DTPA (Diethylenetriamine-

pentacetic acid)

•

DTPA is cleared entirely by glomerular filtration . The agent can be used to evaluate renal glomerular filtration, and for renal and urinary tract imaging. The typical dose of 99mTc -DTPA in adults is 10-20 mCi . For children the dose is 0.1 mCi/ kg. 7

•

Unfortunately, DTPA renal extraction efficiency is low (20%) and this results in a low target-to-background ratio . On the imaging liver and spleen sometimes may be seen also, and the two latter can disturb the imaging analysis. So some other new tracers is studied.

8

• 2. 131I-Hippuran (Orthoiodohippurate 131 I-OIH) •

Hippuran is used for evaluation of tubular secretion (excretory function) . 80% is eliminated by tubular secretion, and 20% by glomerular filtration. There is 90% first-pass clearance which leads to a high kidney to background ratio. 9

• The typical dose used in adults is 150300 uCi . For children the dose is 3 uCi/kg . • The renal imaging with the radiopharmaceuticals 131I-OIH is more clearer then the imaging with 99mTcDTPA . But because the energy of 131I is very high so it is rarely used in clinics. 10

Because it has a higher renal extraction efficiency than DTPA, hippuran provides better visualization of the kidneys in patients with markedly impaired renal function. In acute renal failure, non-visualization of the kidneys with hippuran is a poor prognostic indicator. 11

• 3.99mTc- MAG3: (Mercaptoacetyltriglycine) •

Tc- MAG3 is cleared almost exclusively by tubular secretion,98% is secreted in the proximal tubule and only 2% of the agent is filtered at the glomerulus. A small amount of liver activity is often noted . Increased liver activity is seen in patients with underlying renal failure and gallbladder activity may also be seen in these patients. 99m

12

The typical dose of MAG3 in adults is 10 mCi (370 MBq). For children the dose is 0.1 mCi/ kg, minimum dose 0.5 mCi. • Image quality with MAG3 is also superior to DTPA, particularly in patients with impaired renal function , because MAG3 has a higher renal clearance , resulting in good kidney to background ratios . The relatively high extraction efficiency and the small distribution space of MAG3 result in fast accumulation of high intensity activity in the cortex and subsequently the collecting system. •

13

Slow Transit radiopharmaceuticals: • 1. 99mTc-DMSA (2,3-dimercaptosuccinic acid) •

DMSA is used for high resolution imaging of the renal cortex. The agent is slowly cleared from the blood as a result of its high protein binding. Only about 4% is extracted per pass. Peak renal activity is seen 4 to 6 hours post injection, but images are usually acquired before this time. 14

•

The typical dose in adults is 5 mCi (Minimum dose 300 to 350 uCi). For children the dose is 0.05 mCi/ kg, minimum dose .3 mCi.

15

• 2. 99mTc-Glucoheptonate •

Glucoheptonate has both cortical uptake and glomerular filtration . A large portion is cleared by glomerular filtration and rapidly excreted ( 80-90% cleared via urine), but a significant amount remains in the proximal tubular cells which permits cortical imaging. The typical dose in adults is 15 mCi. For children the dose is 0.1 mCi/ kg.

16

Indications: • Dynamic imaging: • 1.Measuring relative function of each kidney; • 2. Deternining urinary system fistula. • 3.Evaluating remaining renal function in patients with severe kidney damage; • 4.Differentiating the renal space occupying lesion. (renal blood flow imaging.) ; • 5.Diagnosing renal obstructive disease; • 6.Diagnosing Renovascular disease; • 7. Monitoring renal transplantation. 17

Indications : • Static renal imging: • 1. Diagnosing congenital anatomic abnormalities; • 2.Diagnosing renal position abnormalities; • 3.Determining renal space occupying lesions ； • 4.Differentiating upper abdomen masses being in or out of kidneys. 18

Exam Procedure 1.Renal blood flow: •

Patient lying down on the examing table , The probe of  camera or SPECT is located to the back area of kicneys. A bolus radiolabeled tracer (usualy 99mTcDTPA) is intravenously injected quikly to the patient’s vein and immediately we collect the imaging data at a speed 1 frame/s for 30s and get a series imaging of 30 frames.

19

Exam Procedure • Dynamic renal imaging: •

After or with out the renal blood flow imaging procedure we take the renal images at the speed 1frame/30s for 1170s or 1200s and get a series of images of 59 frames or 60 frames . with the determined computer programmes we can process the imaging data to get the quality or quantity results. 20

Exam Procedure • Static renal imaging: • Postinjection of radiotracer the delayed planar imaging can be taken after 1-2h. If there is a renal dysfunction the imaging can be taken later after 2h . Tomographic imaging is used for smaller lesions of the kicneys. 21

Normal Appearance: Renal Blood Flow Imaging

•

Flow activity should reach the kidneys about 1-3 sec after the bolus in the abdominal aorta passes the renal arteries. Two kidneys must visualized at same time. One should not delayed another above 1 second .When using DTPA the slope of the renal flow curve should be similar to that of the aorta.

22

•

After reaching a peak value, the renal curve decreases, reflecting the low extraction efficiency of the agent. With MAG3, the renal flow curve will reach a certain peak level, but not decline. Instead, it continues to slowly increase, reflecting the excellent extraction efficiency of MAG3.

23

Normal Appearance: Renal Blood Flow Imaging:

24

Normal Appearance: Renal Blood Flow Imaging:

25

Normal appearance: Dynamic renal imaging Both kidneys are seen at the first imaging,Parenchymal activity should peak by 3-5 minutes （ imaging procedure ), and then rapidly decline ( image fading procedure ). The bladder is now appeared and it’s radioactivity is higher and higher up during the examing time.

26

•

At the end of 20min, the renal imaging can being seen faintly discernible . During the exam the ureter reveals blurred imaging . Activity should appear symmetric from side to side. Parenchymal MAG3 activity falls quickly and at 20 minutes there is usually less than 20% of the peak activity remaining in the kidney.

27

Dehydrated patients will demonstrate peak parenchymal activity slightly later and may have delayed clearance of the tracer. The differential or relative renal function of each kidney can be calculated by determining the accumulation of tracer in each kidney between 2 and 3 minutes for DTPA. 28

•

Activity should clear rapidly from the intrarenal collecting system to the bladder. • Out side of the urinary system there must not be any abnormal radioactive accumulation.

29

•

Renogram curves from each kidney should be nearly identical with regard to shape and slope. Slight differences in height of the curves may be due to normal variation in renal size or depth , patient positioning, or differences in region of interest placement.

30

Normal appearance: Dynamic renal imaging

31

Normal appearance: Dynamic renal imaging

32

Static renal imaging Using the slow transit radioactive tracer we can take the planar or tomographic imaging of the kicneys with γ camera or SPECT 1-2h after injection of the radiopharmaceuticals.

33

Normal static renal imaging •

Double kidneys shape ellipse; outline clearly and margin tidily. Radioactivity diffuse uniformly except for some sparseness of radioactivity on renal gates.

34

• Two kidneys are symmetrical locating at the double side of the vertebral column.The up top close to the vertebral column like a chinese word 八 . • Usually left kidney is longer than the right one. And right kidney is wider than the left one.

35

Normal static renal imaging

Abnormal imaging and Clinical application • Renal artery stenosis: •

Renal vascular hypertension (RVH) is believed to be the etiology of hypertension in only 1 to 4% of hypertensive patients. It is the cause of about 5% of all cases of childhood hypertension. A slowlydeveloping renal artery stenosis allows the opening of collaterals and may result in a severely ischemic kidney with poor function that survives on this collateral flow , but produces large quantities of renin to sustain renovascular hypertension. 37

• On renal blood flow imaging the two kidneys doesn’t appear at the same time. Two renal imaging time after abdominal aort appear is discrepant above 1s (1 frame)and the blood perfusion of the lesion side is poor.The size of the lesion kidney is smaller than the normal one. • On the renal dynamic imaging lesion kidney is also smaller.If the renal failure occurs it can also imaging or imaging fading delay.

38

Renal artery stenosis:

39

Renal artery stenosis:

40

Renal artery stenosis:

41

Renal artery stenosis:

42

Renal artery stenosis:

43

• Scintigraphic Findings in Renal Failure: •

Acute renal failure is characterized by relative preservation of renal blood flow and extraction of tubular agents with a rising renogram curve (Retained cortical activity at 20 minutes will be almost 100% ). Extraction of glomerular agents in acute renal failure is low. The kidneys are usually of normal size. 44

•

In chronic renal failure there is severely and proportionately reduced renal blood flow and tracer extraction of both tubular and glomerular agents. The kidneys are often small in size. The renogram curve is typically flat with a low count plateau. In end-stage renal failure the kidneys are only faintly discernible from blood pool activity.

45

Renal Failure:

46

Renal Failure:

47

Renal Failure:

48

Renal Failure

Urinary tract system obstruction •

Causes of hydronephrosis and hydroureteronephrosis include :

• • • • •

Obstruction Vesicoureteral Reflux Recent urinary tract infection Congenital malformations Noncompliant bladder

50

Urinary tract system obstruction: Imaging findings •

The renal imaging appearance of obstruction depend upon the degree and stage of the disease:

• Acute obstruction: •

In the early stage the renal function is not damaged so the kidneys can uptake tracer well , the imaging procedure is normal but there is no fading procedure because there is no urine pass through the site. 51

•

If the cause does not release the renal dysfunction will occurs , it can also influence the imaging procedure.

• Chronic obstruction: • There is obstruction and renal dysfunction,so we can find features of the obstruction site and hydronephrosis and/or hydroureter above the obstruction on renal dynamic imaging . The imaging procedure and fading procedure are also delayed. 52

• The degree of the obstruction : •

When the obstruction is complete , the renal parenchyma atrophies completely and renal size decreases . In partial obstruction , the degree of parenchymal thinning is directly proportional to the severity of obstruction. Glomerular function (evaluated with Tc-DTPA) is more sensitive to ureteral obstruction than is tubular secretion ( evaluated with MAG3 ) , although once tubular changes occur, they take longer to reverse. 53

Renal calculus and hydronephrosis • Left up :blood flow imaging. • Right up:5min dynamic imaging. • Left lower: • 15min dynamic imaging. • Right lower : • 1h delayed imaging. 54

Hydronephrosis and hydroureter

55

Renal calculus and hydronephrosis

56

Hydronephrosis delayed imging

57

Left ureter calculus and obstruction

Congenital malformations

:

clevis kidney

Position abnormal: renal ptosis

60

Static renal imaging right kidney space occupying lesion

61

Renal transplantation normal imaging （ kidney in pelvis ， iliac pit ）

Renal transplantation normal imaging

Renal transplatation: ureter obstruction

Renal transplantation and urine fistula

Static renal imaging multiple space occupying lesion(cyst)

The The End End 67

68