Program Information
Characterizing Needle Applicator Displacement for Gynecological High-Dose-Rate Interstitial Treatment
W Taylor*, M Carlson , A Quick , N Gupta , Ohio State Univ, Columbus, OH
Presentations
SU-E-205-5 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: 205
Purpose: The purpose of this study is to determine if applicator displacement can be identified for patients receiving high-dose-rate interstitial brachytherapy (HDR-ISBT) by characterizing the position and motion of the individual needle applicators, pubic symphysis, and implanted gold seed markers throughout the course of treatment.
Methods: This study retrospectively evaluates 12 patients with a gynecologic malignancy who underwent HDR-ISBT at our institution. Prior to applicator placement, at least two gold seed markers were placed in 11 of the 12 patients to mark superior and inferior extent of disease. Post-implant CT and MRI were performed following applicator placement. Treatments were delivered for 5 fractions BID over 3 days. CT scans were performed on fractions 2 and 4 and were registered to the original CT dataset using three reference objects: template (including the vaginal obturator), pubic symphysis, and gold seed markers.
Results: The average inter-needle superior/inferior displacement from day 1 to 2 and day 1 to 3 was 0.99 ± 1.88 mm and 0.82 ± 1.24 mm. The average gold seed displacements, with respect to their centroid, from day 1 to 2 and day 1 to 3 was 1.16 ± 0.69 mm and 1.51 ± 1.11 mm. For 4 of the 12 patients, there were displacements of the gold seed marker centroids of at least 10 mm with respect to the obturator/template. For 5 of the 12 patients, needle centroid displacements were observed of at least 10 mm with respect to the pubic symphysis, largely in the inferior direction.
Conclusion: These results show that inter-needle displacement is minimal. The large displacements of the needles with respect to gold seed markers and the pubic symphysis signify the entire applicator apparatus is moving out of the patient. The gold seed marker registration could be utilized to monitor and assess current applicator position.
Contact Email: