Sebastia Sabater1, Ignacio Andres2, Esther Jimenez-Jimenez3, Roberto Berenguer2, Marimar Sevillano2, Veronica Lopez-Honrubia2, Angeles Rovirosa4, Ricardo Sanchez-Prieto5, Meritxell Arenas6. 1. Department of Radiation Oncology, Complejo Hospitalario Universitario de Albacete (CHUA), Albacete, Spain. Electronic address: ssabaterm@gmail.com. 2. Department of Radiation Oncology, Complejo Hospitalario Universitario de Albacete (CHUA), Albacete, Spain. 3. Department of Radiation Oncology, Hospital Son Espases, Palma de Mallorca, Spain. 4. Gynecological Cancer Unit, Radiation Oncology Department, ICMHO, Hospital Clinic, University of Barcelona, IDIBAPS, Barcelona, Spain. 5. Unidad de Medicina Molecular, Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, Albacete, Spain; Unidad asociada de Biomedicina, UCLM-CSIC, Albacete, Spain. 6. Department of Radiation Oncology, Hospital Universitari Sant Joan, Reus, Spain.
Abstract
PURPOSE: To evaluate the impact of rectal dose on rectal contrast use during vaginal cuff brachytherapy (VCB). METHODS AND MATERIALS: A retrospective review of gynecology patients who received some brachytherapy fractions with and without rectal contrast was carried out. Rectal contrast was instilled at the clinician's discretion to increase rectal visibility. Thirty-six pairs of CT scans in preparation for brachytherapy were analyzed. Pairs of CTs were segmented and planned using the same parameters. The rectum was always defined from 1 cm above the cylinder tip up to 1.5 cm below the last activated dwell source position. An individual plan was computed at every VCB fraction. A set of values (Dmax, D(0.1cc), D(1cc), and D(2cc)) derived from dose-volume histograms were extracted and compared according to the rectal status. RESULTS: Rectal volume was 26.7% larger in the fractions with rectal contrast. Such an increase in volume represented a significant increase from 7.7% to 10.4% in all parameters analyzed except Dmax dose-volume histogram. CONCLUSIONS: Avoiding rectal contrast is a simple way of decreasing the rectal dose parameters of VCB, which would mean a better therapeutic ratio. Results also suggest that action directed at maintaining the rectum empty might have the same effect.
PURPOSE: To evaluate the impact of rectal dose on rectal contrast use during vaginal cuff brachytherapy (VCB). METHODS AND MATERIALS: A retrospective review of gynecology patients who received some brachytherapy fractions with and without rectal contrast was carried out. Rectal contrast was instilled at the clinician's discretion to increase rectal visibility. Thirty-six pairs of CT scans in preparation for brachytherapy were analyzed. Pairs of CTs were segmented and planned using the same parameters. The rectum was always defined from 1 cm above the cylinder tip up to 1.5 cm below the last activated dwell source position. An individual plan was computed at every VCB fraction. A set of values (Dmax, D(0.1cc), D(1cc), and D(2cc)) derived from dose-volume histograms were extracted and compared according to the rectal status. RESULTS: Rectal volume was 26.7% larger in the fractions with rectal contrast. Such an increase in volume represented a significant increase from 7.7% to 10.4% in all parameters analyzed except Dmax dose-volume histogram. CONCLUSIONS: Avoiding rectal contrast is a simple way of decreasing the rectal dose parameters of VCB, which would mean a better therapeutic ratio. Results also suggest that action directed at maintaining the rectum empty might have the same effect.