Task Group 101 of the AAPM has prepared this report for medical physicists, clinicians, and therapists in order to outline the best practice guidelines for the external-beam radiation therapy technique referred to as stereotactic body radiation therapy (SBRT). The task group report includes a review of the literature to identify reported clinical findings and expected outcomes for this treatment modality. Information is provided for establishing a SBRT program, including protocols, equipment, resources, and QA procedures. Additionally, suggestions for developing consistent documentation for prescribing, reporting, and recording SBRT treatment delivery is provided.

The Australian magnetic resonance imaging (MRI)-Linac program is a $16-million government-funded project to advance the science and clinical practice of exquisite real-time anatomical and physiological adaptive cancer therapy. The centerpiece of the program is a specifically designed 1-T open-bore MRI/6-MV linac system that is planned for delivery and completion of installation in 2014. Current scientific endeavors include engineering discovery in MRI component design, quantifying MRI and linac interactions, and developing image guidance and adaptation strategies.

Purpose-To quantify the type, frequency and magnitude of artifacts in four-dimensional (4D) CT images acquired using a multislice cine method.Methods and Materials-Fifty consecutive patients, who underwent 4D-CT scanning and radiotherapy for thoracic or abdominal cancers, were included in this study. All the 4D-CT scans were performed on the GE multislice PET/CT scanner with the Varian RPM system in cine mode. The GE Advantage 4D software was used to create 4D-CT data sets. The artifacts were then visually and quantitatively analyzed. We further performed statistical analyses to evaluate the relationships between patient-or breathing pattern-related parameters and the occurrence as well as magnitude of artifacts.Results-It was found that 45 of 50 patients (90%) had at least one artifact (other than blurring) with a mean magnitude of 11.6 mm (range, 4.4 -56.0 mm) in the diaphragm or heart. We also observed at least one artifact in 6 of 20 lung or mediastinal tumors (30%). Statistical analysis revealed that there were significant differences between several breathing pattern-related parameters, including abdominal displacement (p < 0.01), for the subgroups of patients with and without artifacts. The magnitude of an artifact was found to be significantly but weakly correlated with the abdominal displacement difference between two adjacent couch positions (R = 0.34, p < 0.01).Conclusions-This study has identified that the frequency and magnitude of artifacts in 4D-CT is alarmingly high. Significant improvement is needed in 4D-CT imaging.

An analysis of thoracic and abdominal tumour motion for stereotactic body radiotherapy patients was performed using more than 70 h of tumour motion estimated from the correlation between the external and internal motion for 143 treatment fractions in 42 patients. The tumour sites included lungs (30 patients) and retroperitoneum (12 patients). The overall mean respiratory-induced peak-to-trough distance was 0.48 cm, with individual treatment fraction means ranging from 0.02 to 1.44 cm. The overall mean respiratory period was 3.8 s, with individual treatment fraction means ranging from 2.2 to 6.4 s. In 57 treatment fractions (40%), the mean respiratory-induced peak-to-trough distance was greater than 0.5 cm. In general, tumour motion was predominantly superior-inferior (60% of all the treatment fractions), while anterior-posterior and left-right motion were 22% and 18%, respectively. The motion was predominantly linear, and the overall mean of the first principal component was 94%. However, for motion magnitude, direction and linearity, large variations were observed from patient to patient, fraction to fraction and cycle to cycle.