Techniques for and uncertainties of MRI-based reconstruction of titanium tandem and ring brachytherapy applicators.

PURPOSE: Eliminating patient computed tomography (CT) scans for tandem and ring (T&R) brachytherapy can reduce overall procedure time and eliminates imaging dose. However, reconstructing titanium applicators in magnetic resonance imaging (MRI) is challenging. We evaluated the uncertainty of different applicator reconstruction workflows in MR-guided brachytherapy, and assessed the clinical impact of reconstruction uncertainties. METHODS AND MATERIALS: Titanium MRI-compatible T&Rs with aqueous gel in the buildup cap were reconstructed on CTs and MRIs to assess the uncertainties of four different workflows. Reconstruction was performed using (1) proton density-weighted MRIs with solid applicator from a library, (2) applicator-only reference CT fused with MRIs, (3) T2-weighted (T2W) MRIs following GEC-ESTRO guidelines, and (4) patient CTs fused with patient MRIs with in situ applicators. We evaluated dwell positions and plan quality differences using high-risk clinical target volume coverage, and EQD2 D2cc of rectum, sigmoid, bladder, and small bowel. RESULTS: The 2σ uncertainty for dwell positions for each workflow were (1) 2.7 mm for both ring and tandem, (2) 1.4 mm ring and 0.8 mm tandem, (3) 0.2 mm ring and 0.8 mm tandem, and (4) 1.9 mm ring and 0.4 mm tandem. Reconstruction uncertainties resulted in dose variations within acceptable levels (below 10%) except for (1) which resulted in larger dose to the rectum (20%). Dose uncertainties were similar between reference CT and patient CT. CONCLUSIONS: Reconstruction with a reference CT results in similar uncertainty to a patient CT. T2W MRI plans have acceptable uncertainty levels for the applicator reconstruction and resulting dose distributions.

Palliative Radiotherapy: Inpatients, Outpatients, and the Changing Role of Supportive Care in Radiation Oncology.

Palliative radiotherapy is an effective treatment in alleviating many symptoms of advanced cancer. Short courses of radiotherapy provide rapid symptom relief and minimize impact on patients. Patients referred for palliative radiotherapy have many concerns beyond radiotherapy; often, these concerns are not fully addressed in traditional radiotherapy clinics. Discussions of prognosis, patient goals, and concerns are areas for improved collaboration. Innovative, dedicated palliative radiotherapy programs have developed over the past 20 years to provide holistic care to patients referred for palliative radiotherapy and have improved patient-focused outcomes. Advanced radiotherapy techniques may provide opportunities to further improve palliative radiotherapy outcomes.