科研之友
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摘要
Contrast-enhanced radiotherapy makes use of a kilovoltage X-ray beam, either from a diagnostic X-ray tube or modified megavoltage linear accelerator, in conjunction with a high-Z contrast medium deposited into the target volume to enhance the absorption of radiation In this work, using the Monte Carlo code PENELOPE and the voxelized Zubal phantom to model a prostate radiotherapy treatment, a comparison between the physical absorbed dose distributions rendered by three different enhancing agents namely bismuth, gadolinium, and iodine is performed It is assumed that there exists a concentration of 10 mg of enhancing agent per 1 g of tissue in the target volume while in the background a concentration of 1 5 mg per 1 g of tissue is present The X-ray beam energy spectrum was obtained by means of Monte Carlo simulation of a tungsten target upon which a 220 key mono-energetic electron pencil beam is made to impinge, and the resultant photon beam is heavily filtrated by 0 2 cm of copper The treatment delivery is simulated as a 360 arc collimated to conform to the target from every direction Cumulative dose-volume histograms and isodose curves are presented for the target as well as five organs-at-risk, namely rectal wall, bladder. femoral heads, skin, and bone marrow It is shown that under these conditions clinically acceptable treatment plans are obtained for all three contrast agents A 72 Gy dose to 100% of the target volume results in maximum absorbed doses to the above mentioned organs-at-risk of 65, 56, 44, 32 and 65 Gy respectively when bismuth is used as the contrast agent, but the results obtained with gadolinium follow closely
- 出版日期2010-6
