A modified 60C teletherapy unit for total body irradiation.
OBJECTIVE
A modified teletherapy unit to achieve total body irradiation with a vertical beam in a conventional treatment room.


METHODS
A standard 60C teletherapy unit has been modified to achieve total body irradiation with a vertical beam in a conventional treatment room. Patients are treated in prone and supine positions. Removal of the adjustable collimator assembly of this standard machine provides a circular field of 196 cm in diameter at 167 cm from the source. Second, the machine has been elevated by about 50 cm on a metallic base to enlarge irradiation field to obtain 248 cm in diameter at 210 cm from the source, and to encompass tall patients under better conditions. A special lead conical beam flattening filter, 10-mm thick at the center, was designed to compensate the spatial inhomogeneity of the beam. An instantaneous dose rate of 6.10(-2) Gy/min is attained at the L4 level (midplane) in an average 20-cm thick patient with a source activity of 5099 RHM (air kerma rate of 44.8 Gy.h-1.m2). Between February 2, 1984 and December 27, 1990, 244 total body irradiations were performed either by single dose (n = 69, 10 Gy were given to midplane at L4 level in about 6 to 8 h, 8 Gy to the lungs), or by fractionated dose (n = 175, 12 Gy were given in 6 fractions over 3 consecutive days to midplane at L4 level, 9 Gy to the lungs).


RESULTS
The dose distribution is similar than the ones obtained by a linear accelerator with patients lying on their sides.


CONCLUSIONS
Patients were treated in a comfortable and highly reproductible position. Organ shielding was easily achievable. This could be a less expensive and reasonable alternative to linear accelerator.
Dominique
C
C
Department of Radiation Oncology, Hôpital Tenon, Paris, France.
Schwartz
L H
LH
Lescrainier
J
J
Keraudy
K
K
Belkacemi
Y
Y
Foulquier
J N
JN
Ozsahin
M
M
Lefkopoulos
D
D
Pene
F
F
D003037:Cobalt Radioisotopes / Q000627:therapeutic use*; D004867:Equipment Design; D006801:Humans; D011835:Radiation Protection; D011867:Radioisotope Teletherapy / Q000295:instrumentation* / Q000379:methods; D014916:Whole-Body Irradiation / Q000295:instrumentation* / Q000379:methods
D003037:Cobalt Radioisotopes