Accelerated partial breast irradiation (APBI) with high dose rate (HDR) brachytherapy offers an excellent compact course of radiation due to its limited number of fractions for early-stage carcinoma of breast. One of the recent devices is SAVI (strut-adjusted volume implant), which has 6, 8 or 10 peripheral source channels with one center channel. Each channel can be differentially loaded. This paper focuses on the treatment planning, dosimetry and quality assurance aspects of HDR brachytherapy implant with GammaMed Plus HDR afterloader unit. The accelerated PBI balloon devices normally inflate above 35 cc range, and hence these balloon type devices cannot be accommodated in small lumpectomy cavity sizes. CT images were obtained and 3-D dosimetric plans were done with Brachyvision planning system. The 3-D treatment planning and dosimetric data were evaluated with planning target volume (PTV)_eval V90, V95, V150, V200 skin dose and minimum distance to skin. With the use of the SAVI 6-1 mini device, we were able to accomplish an excellent coverage — V90, V95, V150 and V200 to 98%, 95%, 37 cc (<50 cc volume) and 16 cc (<20 cc volume), respectively. Maximum skin dose was between 73% and 90%, much below the prescribed dose of 34 Gy. The minimum skin distance achieved was 5 to 11 mm. The volume that received 50% of the prescribed radiation dose was found to be lower with SAVI. The multi-channel SAVI-based implants reduced the maximum skin dose to markedly lower levels as compared to other modalities, simultaneously achieving best dose coverage to target volume. Differential-source dwell-loading allows modulation of the radiation dose distribution in symmetric or asymmetric opening of the catheter shapes and is also advantageous in cavities close to chest wall.

Classical and anaplastic seminoma are traditionally treated with radiation therapy and are said to have the same prognosis. A retrospective study was undertaken of 90 seminoma patients treated with radiation therapy between 1961 and 1985. The classical group consisted of 71 patients of whom 50 had stage I and 21 had stage II disease. The anaplastic group consisted of 19 patients of whom ten had stage I and nine had stage II disease. The median follow-up time was 64 months for the entire group. The 10-year relapse-free survival rate for the classical group was 94% and for the anaplastic group was 70% (P less than .05). For patients with classical stage I disease, the relapse-free actuarial survival rate was 98%; for patients with anaplastic stage I disease, it was 64% (P less than .02). For the classical stage II disease group, the relapse-free actuarial survival rate was 84% and for the anaplastic stage II disease group, 75% (P less than .70). Four patients in the classical group (6%) had relapses; of these, one patient had local recurrence of tumor, and three had distant metastases. In the anaplastic group, four patients (21%) had relapses; two patients had local recurrence of tumor, and two had distant metastases. Therefore the data suggest a difference in survival and relapse rates between classical and anaplastic seminoma.

No abstract

Purpose: This presentation details commissioning and clinical implementation of IMRT with the Elekta MLC and Corvus inverse treatment planning system. Particular attention is paid to features unique to this hardware and software that are not addressed in general IMRT guidance literature. Method and Materials: An Elekta Precise accelerator, equipped with 6 and 15MV photon beams and 80 leaf MLC, was commissioned for clinical usage IMRT with Corvus version 5.0. Data required by the planning system was collected using equipment and techniques consistent with current recommendations. A series of user defined intensity shapes, were used for initial testing of both energies by comparing calculated and film measured dose distributions. Five multifield clinical plans for each energy were compared to film in axial, coronal and sagittal planes, with an additional ionization chamber measurement at the intersection point of the three film planes. Results: When a dual off axis segment is defined by Corvus, a common occurrence in IMRT plans, the segment boundaries may be delineated by up to five different penumbra forming hardware combinations, 1) curved end MLC alone, 2) curved end MLC with backup jaw, 3) backup jaw alone, 4) divergent MLC side face alone and 5) divergent main jaw alone. This implies that both sets of jaws, in addition to the MLCs, must be calibrated to a relative accuracy of 0.2mm. When penumbra 1 and 5 were used in the Corvus pencil beam model, optimum agreement was found between plan and measurements. Conclusion: The physicist must be aware of leaf and jaw motion constraints that are unique to the Elekta Accelerator and how they are used in IMRT segment delineation by Corvus. When these factors are considered in hardware calibration and beam modeling, dose accuracy of 3% or 2mm is achievable over a range of stringent tests and clinical plans.

No abstract