Radiotherapy Research Today is a free monthly online journal that collates and summarizes the latest research about Radiotherapy, including details on cancer treatment, side effects. | ||||||||
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MR and CT image fusion for postimplant analysis in permanent prostate seed implants.Polo A, Cattani F, Vavassori A, Origgi D, Villa G, Marsiglia H, Bellomi M, Tosi G, De Cobelli O, Orecchia R Division of Radiation Oncology, European Institute of Oncology, Milan, Italy. apolo@csub.scs.es PURPOSE: To compare the outcome of two different image-based postimplant dosimetry methods in permanent seed implantation. METHODS AND MATERIALS: Between October 1999 and October 2002, 150 patients with low-risk prostate carcinoma were treated with (125)I and (103)Pd in our institution. A CT-MRI image fusion protocol was used in 21 consecutive patients treated with exclusive brachytherapy. The accuracy and reproducibility of the method was calculated, and then the CT-based dosimetry was compared with the CT-MRI-based dosimetry using the dose-volume histogram (DVH) related parameters recommended by the American Brachytherapy Society and the American Association of Physicists in Medicine. RESULTS: Our method for CT-MRI image fusion was accurate and reproducible (median shift <1 mm). Differences in prostate volume were found, depending on the image modality used. Quality assurance DVH-related parameters strongly depended on the image modality (CT vs. CT-MRI): V(100) = 82% vs. 88%, p < 0.05. D(90) = 96% vs. 115%, p < 0.05. Those results depend on the institutional implant technique and reflect the importance of lowering inter- and intraobserver discrepancies when outlining prostate and organs at risk for postimplant dosimetry. CONCLUSIONS: Computed tomography-MRI fused images allow accurate determination of prostate size, significantly improving the dosimetric evaluation based on DVH analysis. This provides a consistent method to judge a prostate seed implant's quality. Published 13 December 2004 in Int J Radiat Oncol Biol Phys, 60(5): 1572-9.
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