Abstract # 2441 Left Anterior Descending Coronary Artery Motion in Deep Inspiration Breath-Hold and Free Breathing using 4D-CT Scanning: Potential Impact on Left-Sided Breast Cancer Radiotherapy

Presenter: Jarvis, Lesley

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Six patients treated with radiotherapy for breast cancer following mastectomy (1), bilateral mastectomy with tissue expanders (1), and breast-conserving surgery (4) were coached in free-breathing (FB) and deep inspiration breath-hold (DIBH) techniques. For treatment planning, static DIBH scans as well as 4-D CT scans during FB were acquired at 3.75 mm spacing using a GE Discovery ST hybrid PET-CT scanner with multi-detector CT. Respiratory cycles were tracked using the Varian Real-time Position Management (RPM) system, and 4-D images were reconstructed using a GE Advantage Workstation. End-inspiration (phase 0%) and end-expiration (phase 50%) scans were confirmed based on the position of the dome of the diaphragm. The DIBH and extracted 3-D CT image sets at end-inspiration and end­expiration were selected for further analysis. The LAD was contoured at each of these three respiratory phases from its origin off the left main coronary artery and extending 4.5 cm along the length of the vessel. The vertical (anterior-posterior) distance between the LAD and the chest wall was measured by a single observer on 13 consecutive CT slices per phase and per patient. Treatment plans were generated and dosimetric analysis performed using the Varian Eclipse treatment planning system with prescribed dose (PD) of 5040cGy in 28 fractions.

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