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| Year : 2005 | Volume
: 30
| Issue : 2 | Page : 41-59 |
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Performance Characteristics Of Indigenously Developed Bhabhatron-Telecobalt Unit
Rajesh Kumar, S D Sharma, Reena Phurailapam, D D Despande, S Kannan
Correspondence Address:
Rajesh Kumar
 Source of Support: None, Conflict of Interest: None  | Check |
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A new model of the telecobalt unit, Bhabhatron-I, was designed and developed by Bhabha
Atornic Research Centre. Fully software controlled operation which also keeps record of vital operational
history of the unit; availability of field sizes smaller than 5 x 5 cm2; automatic closure of collimator to 0 x 0 cm2
field in case of any functional abnormality; software controlled collimator, couch and gantry movement and
calibration facilities; and option of remote repairlservicing are the unique features of Bhabhatron-I. Thorough
evaluation of this telecobalt unit was carried out to verify its compliance with national and international standards
as well as to compare its performance with commercial telecobait units. Source head of Bhabhatron-l consists
of a stainless steel shell filled with lead and natural uranium and is designed to load a 60Co source of maximum
capacity 250 RMM. Source movement is controlled by pneumatic drive system. Field limiting devices contain
fixed opening primary as well as variable opening secondary collimators. Secondary collimator of this unit
includes two pairs of collimating jaws made up of natural uranium. All safety switches and interlocks as
required for a telecobalt unit are provided and are functional. lsocentre of this unit was always within 2 mm dia
sphere with respect to collimator, couch and gantry rotation. Field flatness and symmetry are within 3%, while
penumbra for 10 x 10 crn2 field is 11.3 mm. Percentage depth dose (PDD) data of this telecobalt unit are
comparable to BJR supplement 25 data (BJR, 1996) for telecobalt units. Percentage surface dose for 1 Ox1 0
crn2 field relative to maximum depth dose is 20.6%. Head leakage in source OFF and ON conditions as well
as collimator trsnsmission are well within the specified limits. Mechanical and dosimetry parameters of this
unit are also comparable to commercial telecobalt units. Bhabhatron-l can therafore be used safely for tho
clinical application in beam therapy. |
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