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KMID : 1164220130250010015
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Journal of Korean Society for Radiotherapeutic Technology
2013 Volume.25 No. 1 p.15 ~ p.24
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Feasibility Study of Isodose Structure Based Field-in-Field Technique for Total Body Irradiation
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Lee Yoon-Hee
Ban Tae-Joon
Lee Woo-Suk
Kang Tae-Young
Back Geum-Mun
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Abstract
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Purpose: In Asan Medical Center, Two parallel opposite beams are employed for total body irradiation. Patients are
required to be in supine position where two arms are attached to mid axillary line. Normally, physical compensators
are required to compensate the large dose difference for different parts of body due to the different thicknesses
compared to the umbilicus separation. There was the maximum dose difference up to 30% in lung and chest wall
compared to the prescription dose. In order to resolve the dose discrepancy occurring on different body regions,
the feasibility of using Fieid-in-Field Technique is investigated in this study.
Materials and Methods: CT scan was performed to The RANDO Phantom with fabricated two arms and sent to
Eclipse treatment planning system (version 10.0, Varian, USA). Conventional plan with physical lead compensator
and new plan using Field-in-Field Technique were established on TPS. AAA (Anisotropic Analytical Algorithm) dose
calculation algorithm was employed for two parallel opposite beams attenuation.
Results: The dose difference between two methods was compared with the prescription dose. The dose
distribution of chest and anterior chest wall uncovered by patient arms was 114∼124% for physical lead compensator
while Field-in-Field Technique gave 106∼107% of the dose distribution. In-vivo dosimetry result using TLD
showed that the dose distribution to the same region was 110∼117% for conventional physical compensator and
104∼107% for Field-in-Field Technique.
Conclusion: In this study, the feasibility of using FIF technique has been investigated with fabricated arms attached
Rando phantom. The dose difference was up to 17% due to the attached arms. It is shown that the dose
homogeneity is within ±10% with the CT based 3-dimensional 4 step FIF technique. The in-vivo dosimetry result
using TLD was showed that 95∼107% dose distribution compared to prescription dose. It is considered that CT
based 3-dimensional Field-in-Field Technique for the total body irradiation gives much homogeneous dose
distribution for different body parts than the conventional physical compensator method and might be useful to
evaluate the dose on each part of patient body.
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KEYWORD
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total body irradiation, Field-in-Field Technique, TLD
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