Bhabhatron: An Indigenous Telecobalt Machine For Cancer Treatment

BHABHATRON: AN INDIGENOUS TELECOBALT MACHINE FOR CANCER TREATMENT K. Jayarajan, D.C. Kar, R. Sahu and Manjit Singh Division of Remote Handling and Robotics

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Mr. K. Jayarajan is the recipient of the Homi Bhabha Science and Technology Award for the year 2006

)*564)+6 Cancer is a major health problem in India. Most of the cancer patients need radiation therapy during the course of their treatment. However, there is an acute shortage of radiotherapy facilities in the country, due to the high cost of radiotherapy machines. To meet the demand for affordable machines, Bhabha Atomic Research Centre has developed a telecobalt machine, called Bhabhatron. Compared to any imported telecobalt machines, the indigenous machine is cheaper and superior in features. Now, Bhabhatrons are installed in many cancer hospitals in the country.

Introduction In India, there are about 20-25 lakh cancer patients. The number will nearly double by the year 2015. Every year, about eight lakh new cancer cases are detected and over five lakh patients die due to this dreaded disease. Established methods of cancer treatment are radiotherapy, surgery and chemotherapy. A majority of the patients need radiotherapy during the course of treatment. In a developing country like India, teletherapy using cobalt-60 is the most cost-effective and relevant method of treatment.

one million. Therefore, India has to increase the number of machines four-fold. Many of the operating telecobalt machines are old and need immediate replacement. Most of the existing cancer treatment facilities are located in urban areas, while the vast rural areas remain untouched. More than 80 % of the districts in the country do not have any teletherapy machine. Non-availability of affordable telecobalt machines is the cause of this alarming shortage and urban-centric distribution of the machines.

Although, telecobalt machine is one of the essential equipment needed in a cancer hospital, the number of machines available in the country is only about 260. As per WHO, a developing country should have at least one teletherapy machine for a population of

Considering the growing demand for affordable cobalt60 teletherapy machines, BARC has taken up indigenization of telecobalt technology. It has resulted in Bhabhatron, a high performance telecobalt machine at a much lower price. The first unit of Bhabhatron

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was installed at the Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Navi Mumbai. Later, BARC developed an improved version of the machine, Bhabhatron-II. Bhabhatrons are installed in many cancer hospitals in India. Bhabhatron is an isocentric, external-beam radiation therapy machine, using cobalt-60 isotope as radiation source. High-energy gamma rays emitted from the source are directed to the cancer site to destroy cancerous cells. Normal cells are also affected by radiation, but they recover faster from the radiation effects than the cancerous cells. Bhabhatron has a high capacity of 250 RMM (Roentgen per minute at one metre). The challenge in Bhabhatron development is to make a system that delivers required high radiation dose to the cancerous site, while protecting adjacent parts of the body from harmful radiation. In addition to the safety of the patient, safety of hospital staff and the public is also a concern during design.

Fig. 1: A patient being treated on Bhabhatron at ACTREC

Fig. 2: Parts of Bhabhatron

Parts of Bhabhatron Bhabhatron houses a Cobalt-60 source of high activity in a well-shielded containment. For treatment, the source is moved from shielded position to treatment position and the radiation beam is directed to the cancerous site, after controlling the beam to desired size, shape and differential attenuation. Major

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components of the machine are radioactive source, source drawer, source head, collimator, gantry, base housing, patient support system and control console. Cobalt-60 Source Cobalt-60 isotope of high specific activity is used as a gamma source in Bhabhatron. Cobalt-60 emits

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high-energy gamma rays of 1.17 MeV and 1.33 MeV. Bhabhatron has the capacity to load a 15 kilocurie source. Source Drawer The source is assembled in a source drawer. The pneumatically driven drawer moves the source between shielded (beam-off) position and treatment (beam-on) position. The cylinder will withdraw the source automatically to beam-off position, in case of any emergency. In beam-off position, the shape, size and location of the radiation beam can be visualized using a light beam. Source Head Source head is a heavily shielded container, housing the source drawer. Depleted uranium and lead are used as shielding materials in the source head. Low

source-to-skin distance of 80 cm is achieved, by compact design of the source head and the collimator. Collimator The collimator assembly controls the size, shape and orientation of the radiation beam exposed to the patient. One of the unique features of Bhabhatron is it’s fully closable collimator. During any emergency, the collimator closes fully, protecting the patient from over-exposure. Two sets of trimmers are provided to reduce the penumbra of the beam. Beam Shaping and Modifying Devices The system has accessories like wedge filters, breast cone and shielding blocks, to modify the beam shape or beam attenuation. They are placed on the machine between the collimator and the patient. Shielding blocks protect vital organs in the path or near the

Fig. 3: Radiation head, Shielding, Source drawer, Source, etc.

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keypads attached on either side of the couch body. Salient features of the couch are high stability, noisefree motions and high precision. The couch top is made of lightweight, radio transparent carbon-fibre sheet. Patient restraining straps and universal metal clamps are provided for immobilization of the patient.

Fig. 4: Collimator

Fig. 6: Couch of Bhabhatron-II

Controls and Indicators Fig. 5: Shielding blocks

radiation field. Wedge filters generate ramped dose distribution of radiation field. Gantry, Mainframe and Base Gantry holds the source head and counter weight. It can rotate around the patient on a horizontal axis by ±180°, allowing source positioning at any point on a circle of 80 cm radius. The gantry is mounted on the mainframe. The entire unit is mounted on a steel base below floor level. The base supports the mainframe and the couch. Patient Support System The patient positioning table or couch consists of a turntable mounted eccentrically with the isocentre. The couch has four motorized motions: isocentric rotation and translations in longitudinal, lateral and vertical directions. The motions are controlled through

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Bhabhatron controller is fully computerized. Data of treatment session registered on hard disk can be retrieved for control and analysis. Many safety interlocks are provided, to prevent the patient from over-exposure to radiation. For example, treatment room door interlock prevents or terminates treatment when the room door is open; gantry fault interlock terminates treatment in case of any error in gantry motion; and source drawer movement interlock prevents treatment when the drawer fails to move in the desired manner. Controls and indicators are installed in mainframe, gantry, door, power panel, operator’s panel, couch and on the wall of the operational room. To provide additional security, access to modification of patient data and treatment data is limited to authorized staff, by password protection. Operator’s Panel Main interaction between the operator and the machine is through computer monitor, keyboard and mouse.

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Fig. 7: Control station of Bhabhatron

Fig. 8: Couch control panel

A key switch and an emergency switch are also provided near the operator’s panel.

a light beam along the passage of the source drawer. Optical Distance Indicator (ODI) displays the distance between the source and the patients’ skin. The scale of the ODI is projected on the patient’s skin.

Control console displays the status of AC power, battery charge level, emergency switch, door closure, correctness of wedge, presence of key and air pressure. Treatment can start, only when all of the above parameters are within the acceptable range. The console also displays collimator opening, collimator orientation, gantry orientation and couch configuration. Source position, whether it is in shielded, transit or exposed position, is also displayed. During treatment, it displays set time, exposed time and remaining time. Couch Control Panel Keypads and emergency switches are mounted on either side of the couch. An operator can quickly position the patient on the couch using the keypads. He can also control the motions of the gantry and collimator using the keypads. Patient positioning lasers, optical distance indicator, field light and room lights can be controlled, using the buttons on the keypads. Field Light and Optical Distance Indicator Field light is used to visualise the collimated radiation field in the beam-off position of the source. The field light system consists of an external projector employing a quartz halogen bulb and a concave mirror to direct

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Patient Positioning Lasers Patient Positioning Lasers are used, for accurate patient positioning. Two cross lasers and one sagittal laser are mounted on the wall of the treatment room. The intersection of these three laser beams represents the isocentre, which is the key reference of the machine. CCTV Camera System Using two CCTV cameras mounted in the treatment room, the operator at the control console can continuously monitor the patient, during treatment. Wall Mounted Display A unit parameter display in the treatment room displays the configurations of the gantry, collimator and couch. Other Controls and Indicators Many emergency switches are provided at main frame, couch, door and operator’s panel, to terminate treatment in case of any emergency. A mandatory T- rod is provided, for withdrawing the source manually to the fully shielded position, in the unlikely event of the failure of automatic source return system. Status

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lights to indicate the source position are provided on the gantry and access door.

Important Features Important features of Bhabhatron are listed in Table 1. Many of them are unique to Bhabhatron. Status of the Technology Bhabhatron - I The first unit of Bhabhatron was installed at ACTREC in March 2005. More than 50 patients were treated daily on the machine for various anatomic sites, such as head and neck, cervix, brain, pelvis and chest wall. The Cancer Research Institute used the machine for basic research in cancer. Blood banks were also using the machine, for blood irradiation in leuko-depletion.

Fig. 9: Wall mounted display inside the treatment room

Quality Assurance The main objective of quality assurance is to ensure consistency and accuracy in dose delivery as prescribed by the radiation oncologist, minimal dose to normal tissue, minimal exposure to occupational workers and adequate patient monitoring. In addition to radiological safety, the machine has to meet stringent regulatory requirements for mechanical safety and electrical safety. Electronics Regional Test Laboratory (South), Thiruvananthapuram, conducted the regulatory evaluation of the machine as per IEC standards for the Safety of Medical Electrical Equipment and certified the machine for electrical safety. AERB, with assistance from RP&AD and RSSD of BARC, evaluated the machine for radiological safety and conformity of the machine to IEC standards, IEC 6011 and IEC 60601-2-11. Parameters verified include radiation leakage at various locations in different conditions; accuracy of beam parameters and various components; and functionality of safety interlocks and other sub-systems.

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Bhabhatron - II Based on the operating experience of Bhabhatron at ACTREC, an advanced version of the machine, called Bhabhatron-II was developed. Bhabhatron-II has battery backup for six-hour operation, for use in rural areas, where there is power shortage. Other major enhancements include optimization of uranium shielding, reduction of source to skin distance and improvements in user interface. In December 2006, Honourable President of India, Dr A. P. J. Abdul Kalam dedicated the Bhabhatron-II to the cancer patients of the country at the Indian Red Cross Society Cancer (IRCS) Hospital, Nellore.

Fig. 10: Bhabhatron-II installed at the IRCS Hospital, Nellore

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Table 1: Important features of the Bhabhatron 1. High Capacity 2. Motorized motion 3. Computer controlled

4. Improved radiation

5. Enhanced security 6. Battery backup 7. User friendly

8. More spacious

Bhabhatron is designed to house 15 kilo curie cobalt-60 source. All the motions of the main unit and treatment couch are motorised to reduce the patient setup time. The computer continuously monitors all the vital system parameters. It terminates treatment, if any parameter exceeds the acceptable limits. Patient and treatment database are maintained. During power failure or other emergency conditions, the source automatically Safety gets withdrawn to beam-off position. In addition, the collimator closes fully to reduce unwanted exposure to the patient. Many safety interlocks are provided to protect the patient and the operator from unwanted exposure. Through password protection, access to operation of the machine, machine parameters, patent data and treatment data are limited only to authorised staff. The machine consumes only 1.5 kW power. A battery backup for six hours of continuous operation is provided to make it suitable for rural Indian conditions. All vital parameters are displayed in the computer screen. The operator can interact with the machine, using mouse and keyboard. Two ergonomic backlit keypads on the patient couch enable faster patient setup. Machine parameters and patient specific notes are displayed on a wall-mounted display in treatment room. Heavy counter weight of the gantry is located on the rear side of the machine, operator behind a wall to enhance safety. It also provides more space for the operator to setup the machine.

6ransport Container BARC has recently developed a container for transporting high capacity telecobalt sources of Bhabhatron and other telecobalt machines. After the drop test, fire test, radiological tests and necessary analysis, AERB awarded type B(U) approval to the container, for international transportation of Cobalt 60 sources. Machine Installations Eight machines are installed in various cancer hospitals in the country. More machines are under fabrication, based on orders from cancer hospitals. Conclusion Development of indigenous cobalt-60 teletherapy machine, Bhabhatron is completed. The machine has

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superior features in terms of safety, user-interface and security. Moreover, the cost of Bhabhatron is significantly lower than imported machines of similar capacity. The technology for this machine is already transferred for mass production. Bhabhatron development is improving the access of cancer patients to treatment facilities and reducing treatment cost. Acknowledgement The authors wish to thank all DRHR staff, Mr. B. C. Pal (retd.) and Mr. M. G. Radke (retd.) for their involvement in the development. We also thank Dr. Anil Kakodkar, Chairman AEC; Dr. S. Banerjee, Director, BARC; Mr. R. K. Sinha, Director, RDDG and DMAG; and Dr. K. A. Dinshaw, Director, Tata Memorial Centre for their guidance, support and encouragement.

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About the Authors Mr. K. Jayarajan joined the Division of Remote Handling and Robotics, after completion of training from the 28th Batch of BARC Training School. Mr. Jayarajan has developed and installed many mechanical master slave manipulators, servo manipulators, automation systems and special purpose remote handling tools for radioactive material handling. The first sets of servo manipulators installed in Indian hotcells were developed by him. He has also developed and supplied many remote handling systems to defence sector for handling hazardous materials. Another successful area of his work is development of Bhabhatron, the first indigenous teletherapy machine for cancer treatment. Dr. D.C. Kar after graduating from BARC Training School in 1990 joined the Division of Remote Handling and Robotics. He is working on design and development of robots, telemanipulator systems and specialized remote handling equipment for nuclear and other hazardous applications. Dr. Kar was actively associated with the development of the Indigenous Cobalt Teletherapy Machine Bhabhatron. He has successfully developed the Teletherapy Source Transportation Flask for transporting cobalt teletherapy source capsules. Presently he is working for the development of Radiotherapy Simulator, a remotelyoperated diagnostic machine, useful for localization of cancer-affected regions prior the radiation therapy. He is also involved with the development of Robotic Assistant for Minimally Invasive Surgery.

Mr. Ramakant Sahu after training from the 38th Batch of BARC Training School, joined the Division of Remote Handling and Robotics of BARC in 1995. His broad area of work includes development of remote handling tools and teletherapy machine. He has been involved in development of servo manipulators, cooperative servo robot, Bhabhatron couch and laser welding system for FBTR fuel pin.

Mr. Manjit Singh graduated from BARC Training School, where he got the Homi Bhabha Award for securing first rank. He is the Associate Director of Design, Manufacturing & Automation Group and Head of the Division of Remote Handling and Robotics of BARC. Mr. Manjit Singh has developed a large number of equipment and systems related to Nuclear Reactor Control, Remote Handling, Automation and Cancer Treatment. He has developed and delivered a large number of remote handling tools and automation systems to DAE establishments, Indian Navy and Ordnance Factories. Bhabhatron, the first indigenous Teletherapy Machine was developed under the leadership of Mr. Manjit Singh.

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