USE OF ULTRASOUND TO GUIDE RADIATION BOOST PLANNING FOLLOWING LUMPECTOMY FOR CARCINOMA OF THE BREAST

Purpose: To determine if sonographic localization of the breast lumpectomy site is feasible and useful in boost planning. Methods and Materials: The operative beds following lumpectomy were localized by ultrasound in 22 patients (15-infiltrating ductal, 7-ductal carcinoma in situ; size: .4-2.0 cm). Twelve patients had two ultrasound examinations on different days for a total of 34 examinations. Twenty-one patients had their course of boost electron therapy planned using ultrasound to guide field placement. While the patient was in the treatment position, the surgical scar was placed at the machine's isocenter. With the electron cone in place, the ultrasound transducer was placed within the cone on top of the surgical scar. The biopsy site was localized and the light field maneuvered so that it's central axis would follow the axis of the transducer, transecting both the scar and biopsy site. Results: The operative bed was highly visible in 26 ultrasound examinations, visible in 7, and subtly visible in 1. Every biopsy site showed some hypoechoic area but most appeared as the mixed hypoechoic pattern. Ultrasound appearances were mixed or mostly hypoechoic (28), anechoic with irregular walls (4), and echoic (hypoechoic compared to parenchyma) (2). In two cases the surgeon placed surgical clips in the operative bed, and in both cases several of these clips could be identified at the margins of the operative bed as hyperechoic foci with shadowing. The mean depth of the operative bed was 21 mm (range 17-36 mm). In 12 patients, two ultrasound examinations were performed on different days, and the mean depth difference between these scans was 2 mm with a range of 0-5 mm. Among patients with two scans we found that both the location and appearance of the operative bed was highly reproducible. Conclusion: Ultrasound can successfully be used to localize the biopsy site and facilitate boost field placement in patients treated with lumpectomy and radiation.