Verification of segmented beam delivery using a commercial electronic portal imaging device

被引:45
作者
Curtin-Savard, AJ [1 ]
Podgorsak, EB [1 ]
机构
[1] McGill Univ, Montreal Gen Hosp, Med Phys Unit, Montreal, PQ H3G 1A4, Canada
关键词
conformal therapy; portal dosimetry; intensity modulation; electronic portal imaging device;
D O I
10.1118/1.598581
中图分类号
R8 [特种医学]; R445 [影像诊断学];
学科分类号
1002 ; 100207 ; 1009 ;
摘要
In modern radiotherapy, three-dimensional conformal dose distributions are achieved through the delivery of beam ports having precalculated planar distributions of photon beam intensity. Although sophisticated means to calculate and deliver these spatially modulated beams have been developed, means to verify their actual delivery are relatively cumbersome, making equipment and treatment quality assurance difficult to enforce. An electronic portal imaging device of the scanning liquid ionization chamber type yields images which, once calibrated from a previously determined calibration curve, provide highly precise planar maps of the incident dose rate. For verification of an intensity-modulated beam delivered in the segmented approach with a multileaf collimator, a portal image is acquired for each subfield of the leaf sequence. Subsequent to their calibration, the images are multiplied by their respective associated monitor unit settings, and summed to produce a planar dose distribution at the measurement depth in phantom. The excellent agreement of our portal imager measurements with calculations of our treatment planning system and measurements with a one-dimensional beam profiler attests to the usefulness of this method for the planar verification of intensity-modulated fields produced in the segmented approach on a computerized linear accelerator equipped with a multileaf collimator. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)02505-5].
引用
收藏
页码:737 / 742
页数:6
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