Low D A, Gerber R L, Mutic S, Purdy J A
Mallinckrodt Institute of Radiology, Division of Radiation Oncology, St. Louis, MO 63110, USA.
Int J Radiat Oncol Biol Phys. 1998 Mar 15;40(5):1231-5. doi: 10.1016/s0360-3016(97)00910-3.
The verification of intensity-modulated radiation therapy (IMRT) patient treatment dose distributions is currently based on custom-built or modified dose measurement phantoms. The only commercially available IMRT treatment planning and delivery system (Peacock, NOMOS Corp.) is supplied with a film phantom that allows accurate spatial localization of the dose distribution using radiographic film. However, measurements using other dosimeters are necessary for the thorough verification of IMRT.
We have developed a phantom to enable dose measurements using a cylindrical ionization chamber and the localization of prescription isodose curves using a matrix of thermoluminescent dosimetry (TLD) chips. The external phantom cross-section is identical to that of the commercial phantom, to allow direct comparisons of measurements. A supplementary phantom has been fabricated to verify the IMRT dose distributions for pelvis treatments.
To date, this phantom has been used for the verification of IMRT dose distributions for head and neck and prostate cancer treatments. Designs are also presented for a phantom insert to be used with polymerizing gels (e.g., BANG-2) to obtain volumetric dose distribution measurements.
The phantoms have proven useful in the quantitative evaluation of IMRT treatments.
