Objective Pretreatment imaging plays a crucial role in determining geometric positional uncertainty of the patient during radiotherapy. Our purpose is to investigate the effect of frequent pretreatment imaging protocol (scenario) on actual dose delivery in radiotherapy. This paper presents a critical analysis of frequent imaging protocol with respect to Idealized daily imaging protocol (IDIP). Methods and materials Retrospective patients of Ca-carcinoma cervix, Ca-buccal mucosa, Ca-tongue treated with intensity-modulated radiation therapy (IMRT) undergoing daily cone beam computed tomography (CBCT) imaging protocol was selected for this study. Every treated fraction of these patients was simulated considering its daily geometrical setup uncertainties occurred. Indirect evaluation of virtual treatment plans was conducted in the treatment planning system (TPS) for 3 days a week, 2 days a week, and 1 day a week frequency imaging protocols. Results obtained from these frequent imaging protocols were compared with IDIP. Result Deviation between predicted and delivered dose found increasing with decreasing frequency of imaging. Significant deviations were observed in all the estimated plan quality parameters for patients treated with frequent imaging protocols and IDIP. Deviations were found more in case of pelvis sites than head and neck sites. Conclusion This study plays a vital role in establishing optimum pretreatment imaging protocols in busy clinics. Three days a week imaging protocol is the best suit protocol found with minimal deviation and ample implementation feasibility. This study proposed an opinion pertaining to the revision of setup margin formula in order to accommodate variation due to imaging techniques and frequency of imaging attempted during radiotherapy.
Objectives Early-stage breast cancer patients survive longer so a radiotherapy technique which can reduce late toxicity is important. In this study, we made a dosimetric comparison of supine and prone breast irradiation techniques in patients with left breast cancer. Methods Ten patients scheduled for whole-breast radiotherapy after lumpectomy were included in this study. The patients underwent computed tomography scans in both supine and prone positions on a breast board. The breast was contoured as per standard guidelines. Treatment planning was done for both the positions. A dose of 40 Gy/15#/3 weeks was prescribed. Mean dose to the heart and left lung was calculated for each patient in the supine and prone positions. Dose-volume histograms were generated and compared between the two sets. Paired t test was applied to test the significance of difference between the mean doses received by the heart and left lung for the two techniques. The difference was considered statistically significant if p value was < 0.05. Results The heart and left lung were better spared in the prone position compared to supine. Mean heart dose in the supine and prone positions was 4.5558 Gy and 2.063 Gy (p = 0.02), respectively. Mean lung dose in the supine and prone positions was 6.5797 Gy and 0.8491 Gy (p = 0.001), respectively. Rotational setup error was noted in 3 and 1 patient in the prone position and supine position, respectively. Conclusion The prone position for the radiotherapy treatment of left breast cancer was dosimetrically better than the supine position in terms of mean dose to the heart and left lung.
Gamma-ray stereotactic radiosurgery systems available commercially contain either stationary or rotational source configuration. Rotational systems reduce the number of sources utilized and can also provide beneficial dosimetric properties. In this study, we explore the dosimetric advantage of a novel rotating gamma-ray design for stereotactic body radiotherapy (SBRT) as compared to the well-established CyberKnife system. CybeRay (OUR United Corp., Xian, China) is a rotating gamma-ray system (RGS). Its treatment head can rotate 360° in the axial plane and swing 35° in the superior direction. It includes 13 Co-60 sources focusing on the isocenter. The RT Pro planning system (Prowess, Concord, CA) was used for CybeRay treatment planning, while the Multiplan software (Accuray, Sunnyvale, CA) was used for CyberKnife treatment planning. Twelve SBRT patients previously treated with CyberKnife were re-planned for CybeRay, and their treatment plans were compared based on isodose distributions, dose volume histograms, conformity index (CI), and the estimated treatment time. The planning target volume ranged from 4.4 to 124.2 cc. Both treatment systems provided excellent SBRT plans that meet our clinical acceptance criteria. The mean value of CI was 1.25 for both CyberKnife and CybeRay (p = 0.03). The estimated treatment delivery time for the CyberKnife plans ranged from 13 to 53 min as compared to 6 to 54 min with CybeRay (p = 0.02). CybeRay was superior concerning peripheral doses appearing as excessive isodose lines extending to distal normal tissues. The new CybeRay machine showed promising dosimetric capabilities for stereotactic radiosurgery and radiotherapy of extra- and intra-cranial lesions.
Objective Many cancer patients are treated at treatment centers staffed by community radiation oncologists (CRO). Patients choose these facilities for location convenience and anticipate equivalent care to "high volume" centers despite contrary literature. Local CROs hypothesized that a two-step quality assurance (QA) program that added early contour and case review would improve confidence in radiation treatment plan quality and reduce variability across facilities. Methods Five physicians at five academic satellites participated in the pilot two-step QA program. This program established an efficient, secure, HIPPA compliant workflow to review case details and contours on CT simulation after uploading to a remote access server on a commercially available platform. Results Over 12 months, 148 patient contours were reviewed by at least one CRO with an average of 2 reviewers per case. Reviewers approved 67% without change, requested clarification or change in 28%, and would not approve 4% of cases unless revised. The most common reasons cited for change request were "review GTV-volume increase" and "review CTV-volume increase." Eighty-eight percent of treated cases that were not approved initially subsequently completed recommended modifications. Published literature was shared for 29% cases and sub-specialist consulted for 19% of cases. Conclusion A two-step QA program was considered highly valuable by all participants allowing easily implanted mechanisms for standardization, higher case volume, and shared educational resources for small academic satellite CROs who are faced with the challenge of caring for a diverse community cancer population. Feasibility suggests the model could serve as a model for other CRO.
