Radiation therapy is used for the management of localized cancers. Telecobalt units are preferred due to low cost, simplicity, predictive nature of the radiation dose and low maintenance/downtime. As of now, the radiation field openings defined by any telecobalt unit, are limited to rectangular fields only. Multi Leaf Collimator (MLC) System can provide complex and irregular radiation fields required for far better conformity to irregular tumour boundaries, leading to superior clinical performances.

BARC has developed MLC system which serves as secondary collimator. Here, thin divergent leaves made of tungsten alloys with tongue and groove arrangement are grouped in two banks. Each of these leaves projects one centimeter at patient plane and driven independently by individual electric motor. The system has been demonstrated after integrating with our indigenous telecobalt machine with source to axis distance at 80cm. Features like collimator rotation, motorized wedge filter, field light arrangement, optical distance indicator etc are arranged without compromising the patient clearance. This new version has been approved by AERB for clinical applications. Irregular radiation fields now can be generated conforming to the complex tumour geometries, allowing higher tumour dose while limiting unwanted dose to surrounding healthy tissues resulting in superior treatment outcome.

Indigenous telecobalt units can be upgraded with this MLC by replacing the existing collimator systems. However, the design modifications in mechanical, electronics, control and software essential for integration of this MLC design with the indigenous telecobalt machine is the responsibility of the manufacturers of the teletherapy machine.

1. Design is compatible with Cobalt Teletherapy Machine Bhabhatron with Source to Axis Distance at 800mm.
2. The movements of all the leaves are motorized and independent.
3. Dedicated software for generating field geometry conforming to the irregular field boundaries.
4. Field openings can be controlled from remote computer.
5. Back-up jaws for limiting inter-leaf leakage radiations.
6. Full closure of leaves as well as back-up jaws ensure radiation safety during emergency conditions, power failure etc.
7. Patient scans can be imported through DICOM.
8. Motorized Wedge Filter implemented within the collimator.

SPECIFICATIONS

Sr. No.	Specification	Value
1	Source to axis distance (SAD)	800 mm
2	Source to Diaphragm Distance (SDD)	465 mm
3	Leaf Design	Divergent, with tongue and groove
4	Collimator Type	Secondary
5	Collimator Rotation	motorized, ±90 deg
6	Max. Field Size (at isocentre)	250 mm x 250 mm
7	Min. Field Size	0 x 0 (completely closed)
8	Leaf Projection at isocentre	10 mm
9	Collimator Auto Set-up	Yes
10	Back-up Jaws	Yes, both axes
11	Motorized Wedge Filter	Yes (upto 60deg.)
12	Regulatory Approval	Atomic Energy Regulatory Board, INDIA

The job involves high precision fabrication, assembly, extensive QA testing as per AERB requirements. For those having facilities for manufacturing Teletherapy machines, additional infrastructure requirement will be insignificant Manufacturing processes involved:

Machine Tools/ Equipments needed for Manufacture

1. Lathe, milling machine, drilling machine.
2. Precision tool room machines: lathe, milling machine.
3. Universal grinding machine.
4. Crane: 2 T Capacity.
5. Inspection tools: Digital vernier caliper, Micrometer, digital Inclinometer, Digital height gauge, bevel protractor, multimeter, oscilloscope, water phantom, solid water phantom, radiation area monitor, radiation survey meter, pocket dosimeter, secondary standard dosimeter, radiation field analyzer and other commonly used inspection and measurement tools.
   

Space Required

1. An assembly room (approx. 5mx6m), in addition to the space required for manufacturing of a Telecobalt unit. For testing, AERB approved shielded bunker will be required

Electricity Supply

1. 230V, AC, 50Hz. (during assembly, performance evaluation and regular operations.)

MANPOWER

1. Manpower consisting of 3 engineers (1 - mechanical, 1 - electronics/ control, 1 - computer) and 6 technicians for fabrication, assembly and testing of the components, sub-assemblies, the complete unit and its performance are required. Additionally, medical physicist/radiation safety officer are required for ensuring conformity to clinical requirement and radiation safety to the working personnel respectively. Experience in Quality Assurance Requirements, Testing, Certification and Regulatory Framework for this type of Medical Electrical Equipments is essential.