Spatial orientation of coronary arteries and its implication for breast and thoracic radiotherapy-proposing "coronary strip" as a new organ at risk.

OBJECTIVES: Radiotherapy for breast cancer has been associated with various side effects including cardiac sequelae. Our study aimed to define the spatial arc of spread of coronary vessels in a radian angle. MATERIALS AND METHODS: We analysed the records of 51 CT coronary angiographies done in our hospital from January 2016 to July 2016. Left anterior descending (LAD) and right coronary (RC) were contoured for each patient. In each axial section, the radial spread of each artery was noted. A 5 mm brush tool was used to join the start and stop angles for making the summated "coronary strips". RESULTS: Start and end angle of LAD with 95% confidence interval (CI) (in clockwise direction) were 23.9 ± 4° and 79.0 ± 6.6°, respectively. Mean LAD arc length ± SD (standard deviation) noted was 55.1°â€¯± 7.7° (95% CI). For RC the smallest start angle and the largest end angle in all patients was 297.6° and 322.6°, respectively. RC start angle, end angle and arc length for 95% confidence interval were 322.2 ± 6.1°, 292.4 ± 11.6° and 29.8 ± 13.1°, respectively. CONCLUSIONS: Our study provides a measure of the radial spread of the coronary arteries, especially from the perspective of breast radiotherapy. We have proposed a new organ at risk (OAR) of coronary strip. This should provide an easy and cost-effective way to delineate the coronary vasculature in breast cancer patients undergoing radiotherapy.

Perfusion magnetic resonance imaging in contouring of glioblastoma patients: Preliminary experience from a single institution.

PURPOSE: T1-contrast and T2-flair images of magnetic resonance imaging (MRI) are commonly fused with computed tomography (CT) and used for delineation of postoperative residual tumor and bed after surgery in patients with glioblastoma multiforme (GBM). Our prospective study was aimed to see the feasibility of incorporating perfusion MRI in delineation of brain tumor for radiotherapy planning and its implication on treatment volumes. METHODS: Twenty-four patients with histopathologically proven GBM were included in the study. All patients underwent radiotherapy planning with a contrast CT scan. In addition to radiotherapy (RT) planning protocol, T1-perfusion MRI was also done in all patients in the same sitting. Perfusion imaging was processed on the in-house-developed JAVA-based software. The images of CT and MRI were sent to the iPlan planning system (Brainlab AG, GmbH) using a Digital Imaging and Communications in Medicine - Radiation Therapy (DICOM-RT) protocol. A structure of gross tumor volume (GTV)-perfusion (GTV-P) was delineated based only on the MRI perfusion images. Subsequently, GTV-P and GTV were fused together to make GTV-summated (GTV-S). Using existing guidelines, GTV-S was expanded to form clinical target volume-summated (CTV-S) and planning target volume-summated (PTV-S). The increment in each of the summated volumes as compared to baseline volume was noted. The common overlap volume (GTVO) between GTV and GTV-P was calculated using intersection theory (GTV n GTV-P = GTVO [Overlap]). RESULTS: Mean ± standard deviation (cc) for GTV, GTV-P, and GTVO was 46.3 ± 33.4 cc (range: 5.2 cc-108.0 cc), 26.0 ± 26.2 (range: 6.6 cc-10.3.0 cc), and 17.5 ± 22.3 cc (range: 10.0 cc-92 cc), respectively. Median volume (cc) for GTV, GTV-P, and GTVO was 40.8 cc, 17.2 cc, and 8.0 cc, respectively. Mean absolute and relative increments from GTV to that of GTV-S were 8.5 ± 8.2 cc and 27.2 ± 30.9%, respectively. Average CTV volume (cc) was 230.4 ± 115.3 (range: 80.8 cc-442.0 cc). Mean and median CTV-S volumes were 262.0 ± 126.3 cc (range: 80.8 cc-483.0 cc) and 221.0 cc, respectively. The increment in the mean CTV volume (with respect to CTV created from GTV-S) was 15.2 ± 15.9%. Mean and median PTV volumes created on the summated CTV were 287.1 ± 134.0 cc (range: 118.9 cc-576.0 cc) and 258.0 cc, respectively. Absolute and relative increments in PTV volume, while incorporating the perfusion volume, were 31.3 ± 28.9 cc and 12.5 ± 13.3%, respectively. Out of the total of 24 patients, perfusion scanning did not do any increment in GTV in five patients. CONCLUSIONS: Our study is the first to present the feasibility and the outcome of contouring on perfusion imaging and its overlay on regular MRI images. The implications of this on long-term outcome and control rates of glioblastoma patients need to be seen in future studies.