Robert Hunter

2D/3D registration algorithm for lung brachytherapy

PURPOSE A 2D∕3D registration algorithm is proposed for registering orthogonal x-ray images with a diagnostic CT volume for high dose rate (HDR) lung brachytherapy. METHODS The algorithm utilizes a rigid registration model based on a pixel∕voxel intensity matching approach. To achieve accurate registration, a robust similarity measure combining normalized mutual information, image gradient, and intensity difference was developed. The algorithm was validated using a simple body and anthropomorphic phantoms. Transfer catheters were placed inside the phantoms to simulate the unique image features observed during treatment. The algorithm sensitivity to various degrees of initial misregistration and to the presence of foreign objects, such as ECG leads, was evaluated. RESULTS The mean registration error was 2.2 and 1.9 mm for the simple body and anthropomorphic phantoms, respectively. The error was comparable to the interoperator catheter digitization error of 1.6 mm. Preliminary analysis of data acquired from four patients indicated a mean registration error of 4.2 mm. CONCLUSIONS Results obtained using the proposed algorithm are clinically acceptable especially considering the complications normally encountered when imaging during lung HDR brachytherapy.

Endotracheal brachytherapy alone: An effective palliative treatment for tracheal tumors

BACKGROUND Tracheal tumors are rare. They are usually unresectable and treated primarily with external beam radiation. The use of palliative endotracheal brachytherapy (ETBT) alone in treating patients with tracheal tumors has not been reported. METHODS Using a prospective database, demographic, treatment, and outcome data of patients with tracheal tumors treated palliatively with ETBT from 2006 to 2014 were analyzed. Tumor and symptom responses were evaluated based on response evaluation criteria in solid tumors criteria. Survival, in-field disease control, symptom response, and duration of symptom responses were evaluated using descriptive analyses. RESULTS Sixteen ETBT (median, 2) treatments were delivered to 8 patients. Median age was 63.4 years old. Common symptoms were hemoptysis, cough, and dyspnea. Tracheal lengths of 3.5-11 cm were treated with 5-7 Gy/fraction, using 1-3 fractions. The mean overall survival was 5 months and symptom-free survival was 6.8 months, respectively. After ETBT, 88% of patients experienced symptomatic improvement (hemoptysis [n = 3/3], cough [n = 6/7], and dyspnea [n = 4/4]). One patient developed Grade 1 stenosis that did not require intervention. CONCLUSIONS This is among the largest series of tracheal tumors treated palliatively with ETBT alone. ETBT provided effective palliation with symptom improvement and minimal toxicity.

146: Current Practice of External Beam Radiotherapy and Brachytherapy for Management of Endometrial Cancer in Ontario, Canada

CARO 2016 _________________________________________________________________________________________________________ excluded. The query identified 142 patients who received treatment for clinical Stage II disease. Median age was 38 years (range: 19 – 68), 33 had Stage IIA, 47 IIB, and 62 had IIC disease. Fifty-nine patients were treated with radiation therapy (RT) while 83 received chemotherapy (CT). Only three patients with Stage IIA got CT, and only five with IIC got RT. Median RT dose was 30 Gy. Most common CT regimens used were EP (n = 68) and BEP (n = 13). Results: After a median follow up of 18 years, 24 patients had died, and there were 16 recurrences (three in the contra-lateral testis). Patients were more likely to die of second cancers (n = 7) and myocardial infarctions (n = 6), than from progressive Seminoma (n = 3). Two patients died during treatment (neutropenia and sepsis). The 10and 15-year overall survival (OS) was, IIA: 93.8% and 93.8%; IIB: 91.4% and 88.3%; IIC: 83.2% and 76.0%. The 10-year cumulative incidence of relapse (CIR) for Stage IIA patients treated with RT was 3.4%. Stage IIC patients treated with CT had a 10-yr CIR of 10.6%. The 10-year CIR for Stage IIB patients treated with RT (n = 24) versus CT (n = 23) was 29.8% versus 0% (p = 0.005). Seventeen patients developed a second malignancy (SM); non-melanoma skin cancers were excluded. The 15-year cumulative incidence of SM was 7.3% for patients treated with RT, versus 9.7% for those treated with CT (p = 0.321). Conclusions: Long-term outcomes for patients with Stage II Seminoma continue to be excellent. Patients are more likely to die of second cancers and cardiovascular disease than from progressive seminoma.

Poster — Thurs Eve‐38: CT Imaging in high dose rate brachytherapy for treatment of cervical cancer: Estimation of dose to bowel

Treatment of cervical cancer often involves intracavitary high dose rate (HDR) brachytherapy. Dose delivered to the bladder and rectum are typically estimated using the ICRU reference points. Dose to the sigmoid and small bowel are not estimated, yet these organs typically exhibit significant complication rates. The objective of this study was to estimate dose to the small bowel and sigmoid using CT images. Bladder and rectum dose estimates obtained from the reference point method were also compared to those obtained from CT images. Eighteen CT scans taken before or after treatment of women treated with HDR using ring and tandem applicators were included in this study. The small bowel, sigmoid, bladder and rectum were contoured and the ICRU points were digitized. The minimum dose to 2cc (D2cc ) of each organ was calculated and normalized to % prescribed to Point A. Average D2cc bowel dose was 70%. D2cc bowel dose was significantly higher than both D2cc rectal (27%) and D2cc sigmoid (31%) doses. The average D2cc bladder and rectal doses were 68% (p=NS) and 27% (p<0.001) of prescribed Point A dose. D2cc bowel dose, although significantly higher than rectum and sigmoid, is within an acceptable limit. D2cc bladder and rectum values are either not significantly different from or are significantly lower than ICRU reference values. The results of this study suggest that CT imaging is not necessary for determination of dose to organs at risk. However, image guidance is of value for identifying perforations prior to commencing treatment.