Browsing Clinical Oncology by Subjects
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Assessing the effect of a contouring protocol on postprostatectomy radiotherapy clinical target volumes and interphysician variation.PURPOSE: To compare postprostatectomy clinical target volume (CTV) delineation before and after the introduction of a contouring protocol and to investigate its effect on interphysician variability METHODS AND MATERIALS: Six site-specialized radiation oncologists independently delineated a CTV on the computed tomography (CT) scans of 3 patients who had received postprostatectomy radiotherapy. At least 3 weeks later this was repeated, but with the physicians adhering to the contouring protocol from the Medical Research Council's Radiotherapy and Androgen Deprivation In Combination After Local Surgery (RADICALS) trial. The volumes obtained before and after the protocol were compared and the effect of the protocol on interphysician variability assessed. RESULTS: An increase in mean CTV for all patients of 40.7 to 53.9 cm(3) was noted as a result of observing the protocol, with individual increases in the mean CTV of 65%, 15%, and 24% for Patients 1, 2, and 3 respectively. A reduction in interphysician variability was noted when the protocol was used. CONCLUSIONS: Substantial interphysician variation in target volume delineation for postprostatectomy radiotherapy exists, which can be reduced by the use of a contouring protocol. The RADICALS contouring protocol increases the target volumes when compared with those volumes typically applied at our center. The effect of treating larger volumes on the therapeutic ratio and resultant toxicity should be carefully monitored, particularly if the same dose-response as documented in radical prostate radiotherapy applies to the adjuvant and salvage setting. Prostate cancer, Postprostatectomy, Radiotherapy, Target volume.
A novel imaging technique for fusion of high-quality immobilised MR images of the head and neck with CT scans for radiotherapy target delineation.Uncertainty and inconsistency are observed in target volume delineation in the head and neck for radiotherapy treatment planning based only on CT imaging. Alternative modalities such as MRI have previously been incorporated into the delineation process to provide additional anatomical information. This work aims to improve on previous studies by combining good image quality with precise patient immobilisation in order to maintain patient position between scans. MR images were acquired using quadrature coils placed over the head and neck while the patient was immobilised in the treatment position using a five-point thermoplastic shell. The MR image and CT images were automatically fused in the Pinnacle treatment planning system using Syntegra software. Image quality, distortion and accuracy of the image registration using patient anatomy were evaluated. Image quality was found to be superior to that acquired using the body coil, while distortion was < 1.0 mm to a radius of 8.7 cm from the scan centre. Image registration accuracy was found to be 2.2 mm (+/- 0.9 mm) and < 3.0 degrees (n = 6). A novel MRI technique that combines good image quality with patient immobilization has been developed and is now in clinical use. The scan duration of approximately 15 min has been well tolerated by all patients.