Optimization of clinical target volume delineation using magnetic resonance spectroscopic imaging [MRSI] in 3D conformal radiotherapy of prostate cancer

For the purpose of individual clinical target volume assessment in radiotherapy of prostate cancer, MRSI was used as a molecular imaging modality with MRI and CT images. The images of 20 prostate cancer patients were used in this study. The MR and MRSI images were registered with CT ones using non-rigid registration technique. The CT based planning [BP], CT/MRI BP and CT/MRSI BP was performed for each patient. For plan evaluation, Dose Volume Histograms [DVHs] data were used. A paired sample T-test was used for the analysis of the obtained data. The percentage of variation of CTVMRI to CTVCT and PTVMRI to PTVCT were 12.83% and 8.97%, respectively. CTVMRSI and PTVMRSI were 21% and 27.41% more than their corresponding values of CT volumes. The mean percentage of variation in rectum volume that received 60% of the prescribe dose [V60R] in MRSI/CT BP relative to CT BP was 14.66%. The use of MRSI in detecting of prostate adenocarcinoma could provide some decisive information to determine optimum volume and safe margin for target definition to improve adaptive radiotherapy in prostate cancer

Comparing the results of 3D treatment planning and practical dosimetry in craniospinal radiotherapy using Rando phantom

Craniospinal radiotherapy faces technical challenges which are due to the sensitivity of the location in which the gross tumor is, and to organs at risk around planning target volume. Using modern treatment planning systems causes a reduction in the complexities of the treatment techniques. The most effective method to assess the dosimetric accuracy and the validity of the software used for treatment planning is to investigate the radiotherapy and treatment planning by means of a anthropomorphic Rando phantom which was used here for treatment planning and practical dosimetry for craniospinal radiotherapy. Studying the absorbed dose by the organs at risk was the secondary objective discussed in this paper. Treatment planning in craniospinal radiotherapy was done using CorePlan 3D treatment planning software. Radiotherapy was administered on a anthropomorphic Rando phantom and practical dosimetry was done using GR-200 TLDs. Varian Clinac 2100C/D was used for radiotherapy. The absorbed dose by regions of interest was separately calculated for treatment planning and radiotherapy. Except the conjunction areas of the cranial and spinal radiation fields, the difference among the results was not more than 5%. Full comparison of the results for each part has been presented. The comparison the results of practical dosimetry and treatment planning software supports the validity of CorePlan treatment planning system. Also analysis of the absorbed dose through organs at risk showed that the absorbed dose by organs at risk have an acceptable value with respect to tolerance dose of these organs. The only unacceptable result was related to thyroid