Indigenous Cobalt- 60 teletherapy technology- 4 years experience Dr. Arun Chougule Pro Vice Chancellor RUHS Senior Professor and Head Department of Radiological Physics, SMS Medical College & Hospitals Jaipur, Rajasthan arunchougule11@gmail.com

Cancer Incidence- Indian scenario The reported cancer incidence in India is expected to increase from an estimated 1.1 million to 1.8 million by 2020 driven by a narrowing diagnosis gap. As per the assessment by WHO & IAEA, developing countries like India need minimum one radiation therapy machine per million of population. Accordingly, India needs at least 1300 – 1400 therapy machines for cancer treatment but has only about 400 units The slow growth of radiotherapy facility is primarily attributed to the high cost of imported machines, combined with lack of indigenous technology in our country. The present availability of teletherapy machine in India is only about 0.3 per one million population, whereas, in developed nations like USA and UK, the availability is 8.2 and 3.4 per million respectively There is a wide gap between the requirement and availability due to exorbitant cost of purchase (typically Rs 7-8 crore) and maintenance of imported machines. 

Scenario of Teletherapy units in India Being the most cost-effective, teletherapy cobalt-60 unit is the most relevant method of cancer treatment in a developing country like India. The Cobalt-60 teletherapy unit is the workhorse of radiotherapy and cancer treatment Many states and most of the districts in the country do not have any teletherapy machine. Although, more than two-third of cancer patients need radiation therapy, only about one-third of them receive the therapy, due to the shortage of therapy units and urban-centric distribution of radiotherapy centers. In view of the situation in India, Department of Atomic Energy, took up the development of radiotherapy machine indigenously for treatment of cancer patients under the name ‘Bhabhatron’. Currently Bhabhatron-II is most successful telecobalt unit of India, which is writing its success stories in India and outside India also.  

Inception of Bhabhatron by DAE, Govt of India Bhabhatron, a high performance telecobalt machine at a much lower price, was developed to meet the growing demand for affordable high-performance telecobalt machine. The first unit of Bhabhatron was installed at the Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Navi Mumbai in March 2005. Later, BARC developed an improved version of the machine, Bhabhatron-II. More than 60 Bhabhatron telecobalt units are installed in many cancer hospitals in India and India donated the unit to many countries- Vietnam, Magnolia, Kenya…..

Installation Details We are using Bhabhatron Co-60 teletherapy machine for over 4.5 years and treating more than 140 cancer patients daily. The machine is operated for about 14 hours daily and has uptime of 95% in last 4 years. Model No.- Bhabhatron II TAW & 31 Performance tests performed as per AERB RPAD/Telecobalt/QA protocol All components and parameters are found within acceptable limits Activity @loading:7741.44 Ci [ 168 RMM]

Bhabhatron-II Cobalt-60 Teletherapy Unit The first indigenous Telecobalt machine designed and developed by D.A.E & B.A.R.C to manage the increasing cancer incidence in the country It has many advanced features over other imported Telecobalt machines. Specifically designed for rural areas; Can provide 8 hrs battery backup even in case of of the power failure Majority of the motions are computer controlled The facility of 0 x 0 filed size and asymmetric Jaws differs this machine from other imported machines.

Recent Advancements of Bhabhatron II Source Head Interlocks /Indicator Gantry Software Collimator Functionality Keypad Couch Aesthetic Counter weight

BHABHATRON –II-TAW The first indigenous Telecobalt machine designed and developed by DAE & BARC to manage the increasing cancer incidence in the country Shielding vault composed of Tungsten alloy Carbon Fiber Couch Top maximum source capacity of 555 TBq (15000Ci) or 250 RMM of Co-60 Introducing asymmetric motion of collimator jaws & motorized wedge The facility of 0 X 0 cm2 filed size and asymmetric Jaws differs this machine from other imported machines. It can provide 8 hrs battery backup even in the absence of power failure Majority of the motions are computer controlled Potential to be attached with multileaf collimator (MLC) for 3D conformal treatment technique.

Accuracy of Field Sizes A calibrated graph sheet paper was utilized to measure the field size accuracy. After setting the jaw for X and Y the field light was checked at 80cm, SSD. The graph paper was placed on the COUCH at 80 cm. Tolerance :- within ± 2mm

ACCURACY OPTICAL DISTANCE INDICATOR Plastic slab phantom on table surface put 100 cm SSD on its surface isocentre by adding blocks verified by reduction in ODI values and checked that should be in line with slab thickness and additional We cross verify it by mechanical front pointer.

ALIGNMENT BETWEEN OPPOSING FIELDS: ROTATIONAL CHECKS OF GANTRY laser alignment test tool was used PATIENT TREATMENT TABLE AXIS OF ROTATION Gantry positioning with the collimator axis of rotation pointed vertically downwards. Millimeter graph paper is attached to the treatment table and the image of the cross-hair marked on this graph paper. The cross-hair image should trace an arc with a radius of less than 1 mm.

RADIATION CHECKS CONGRUENCE Between LIGHT AND RADIATION FIELD Checked by placing radiographic film perpendicularly to the collimator axis of rotation. The edges of the light field are marked with radio-opaque objects (lead marker) and by pricking holes with a pin through the ready pack film at the corners of the light field. A plastic slab phantom of .5mm is placed on the film to positioned film near zmax to yield an OD of between 1 and 2. The light field edge should correspond to the radiation field edge within 2 mm. RADIATION ISOCENTRE three type of isocentre are verified i. Collimator Rotation ii. Gantry Angles iii. Couch Position Tolerance of ± 2.0 mm dia . SSD 80 on Treatment Couch Field Size 3cm X 30 cm . the exposures was made by Rotating Collimator

S. No Wedge Filter Wedge Factor, WF Angle Field Size cm x cm Measured   S. No Wedge Filter Wedge Factor, WF Angle   Field Size cm x cm Measured Specified by Manufacturer 1 15 15WX20 0.662 0.674 2 30 10WX16 0.572 0.580 0.584 3 45 0.498 0.499 0.444 4 60 0.405 0.365 0.340 0.331

COUCH TRANSMISSION FACTOR  The average transmission factor of the treatment couch table is 96.67%. Linearity Check The linearity in time and dose is required for the delivery of prescription dose (Rx) to the patient.

RADIATION PROTECTION SURVEY Head Leakage in Source OFF position The sources OFF position leakage were measured at a distance of 5cm from the surface of the source Head and 1m from the center of the source. The OFF position leakage should not exceed 20mR/hr at 5cm from the outer surface of the source Head and should be less than 2mR/hr at 1m from the center of the source the maximum radiation leakage levels at 1 m from the source and at 5 cm from any accessible head surface was found to be 0.061875 mR/hr and 0.54375 mR/hr, respectively. It is for maximum rated capacity of the source head. Thus the values are within the permissible limits of ≤2mR/hr at 1m from the source and ≤20mR/hr.

Collimator Transmission Transmission of X JAWS The X JAWS are completely closed and the Y Jaws are completely opened for maximum field size. Points of measurement to check Collimator Transmission

Collimator Transmission : X JAWS The transmission of collimators are measured as per the diagram shown. The maximum field size 35 * 35 cm is considered. The hypotenuse R = 24.75 cm was found by Pithogerous formula. Keeping this as a Radius(24.75 cm) the outer circle is formed. Other two inner circles are formed from 1/3 & 2/3 of the major radius which gives 16cm & 8cm radiuses respectively and the two circles are formed. The transmission measurements done in the above points will give an overall detail of the Transmission of each Jaws . Prior to that Average readings of 10 x 10 field size was measured to find the transmission factor.

Collimator Transmission : Y JAWS & Combined Jaws   Collimator Transmission Y Jaw Points pC/min nC/min % of Transmission Tolerance 1 10.12 0.01012 0.026082474 < 2 % of RMM of the loaded source 2 9.25 0.00925 0.023840206 3 9.53 0.00953 0.024561856 4 9.34 0.00934 0.024072165 5 9.71 0.00971 0.025025773 6 9.7 0.0097 0.025 7 9.68 0.00968 0.024948454 8 9.81 0.00981 0.025283505 9 10.38 0.01038 0.026752577 10 9.67 0.00967 0.02492268 11 9.85 0.00985 0.025386598 12 10.37 0.01037 0.026726804 13 14 10.05 0.01005 0.025902062 15 0.01 0.025773196 16 10.43 0.01043 0.026881443 Average Transmission 0.022561481 Combined Jaws Transmission Points pC/min nC/min % of Transmission Tolerance 1 18.4 0.0184 0.045110091   < 2 % of RMM of the loaded source 2 1.12 0.0011 0.002745832 3 14.58 0.0145 0.035744844 4 5.95 0.0059 0.014587230 5 26.86 0.0268 0.065850926 6 19.43 0.0194 0.047635275 7 26 0.0260 0.063742519 8 14.48 0.0144 0.035499680 9 1.4194 0.0014 0.003479851 10 0.36 0.00036 0.000882589 11 1.2835 0.0013 0.003146674 12 0.45 0.0004 0.001103236 13 5.3 0.0053 0.012993667 14 3.5 0.0035 0.008580724 15 2.8691 0.0028 0.007033987 16 5.24 0.0052 0.012846569 Average Transmission 0.022561481

CONCLUSION All the Quality Assurances were under the recommended Tolerance limit. Bhabhatron-II being a computer controlled machine satisfies the necessary and basic safety requirements for Clinical usage The plan parameters such as Field size, Collimator, Gantry and Couch parameters can be loaded for individual patients along with the Treatment time. The source stays in ON Position till the programmed time and returns to OFF Position after delivering the Treatment. This ensures that the patient receives accurate Treatment when the patient setup is maintained. Configuring this machine in the TPS and executing the Treatment through 3-D Planning will give a huge benefit to the patient. Implementation of Multi leaf collimator in this advanced machine is expected. The Bhabhatron II head can accommodate nearly 250RMM [15000Ci] source strength. This unit has keypad attached at both sides of the couch that also has digital display. The patient treatment is computer controlled. This machine has advanced features such as asymmetric collimators, motorized wedge & integrated MLC etc. Superior features in terms of safety, user-interface and security. Implementation of computer controlled Treatment Delivery, Asymmetric Jaws, motorized wedge, Record of Patient History, Battery backup of Eight hours etc. has remarkably enhanced the Quality of treatment in the field of Radiotherapy.

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