N Patrik Brodin1, Keyur J Mehta2, Amar Basavatia3, Lee C Goddard3, Jana L Fox3, Sheldon M Feldman4, Maureen P McEvoy4, Wolfgang A Tomé5. 1. Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY; Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY. 2. Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY; Department of Urology, Montefiore Medical Center, Bronx, NY. 3. Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY. 4. Department of Surgery, Montefiore Medical Center, Bronx, NY. 5. Institute for Onco-Physics, Albert Einstein College of Medicine, Bronx, NY; Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY; Department of Neurology, Albert Einstein College of Medicine, Bronx, NY. Electronic address: wolfgang.tome@einstein.yu.edu.
Abstract
PURPOSE: Using in vivo measurements from optically stimulated luminescence dosimeters (OSLDs) to develop and validate a prediction model for estimating the skin dose received by patients undergoing breast intraoperative radiation therapy (IORT). METHODS AND MATERIALS: IORT was performed using INTRABEAM-600 with spherical applicators placed in the lumpectomy cavity. Ultrasound skin bridge measurements were used to determine the applicator-to-skin distance, with OSLDs placed to measure the skin surface dose at the corresponding points. The OSLD response was calibrated for the 50 kVp INTRABEAM-600 output. Models were fit to describe the dose fall-off with increasing applicator-to-skin distance and the best fitting model was chosen for estimating skin dose. RESULTS: Twenty four patients with 25 lumpectomy cavities were included, and the average skin dose recorded was 1.18 Gy ± 0.88 Gy, ranging from 0.17 Gy to 4.77 Gy, with an average applicator-to-skin distance of 19.9 mm ± 5.1 mm. An exponential-plateau model was found to best describe the dose fall-off with a root-mean-square error of 0.73. This model was then validated prospectively using skin dose measurements from five consecutive patients. Validation measurements were well within the 95% prediction limits of the model, with a root-mean-square error of 0.52, showing that the prediction model accurately estimates skin dose using ultrasound skin bridge measurements. CONCLUSIONS: This prediction model constitutes a useful tool for estimating the skin dose received during breast lumpectomy IORT. The model and accompanying 95% confidence intervals can be used to establish a minimum allowable skin bridge distance, effectively limiting the maximum allowable skin dose.
PURPOSE: Using in vivo measurements from optically stimulated luminescence dosimeters (OSLDs) to develop and validate a prediction model for estimating the skin dose received by patients undergoing breast intraoperative radiation therapy (IORT). METHODS AND MATERIALS: IORT was performed using INTRABEAM-600 with spherical applicators placed in the lumpectomy cavity. Ultrasound skin bridge measurements were used to determine the applicator-to-skin distance, with OSLDs placed to measure the skin surface dose at the corresponding points. The OSLD response was calibrated for the 50 kVp INTRABEAM-600 output. Models were fit to describe the dose fall-off with increasing applicator-to-skin distance and the best fitting model was chosen for estimating skin dose. RESULTS: Twenty four patients with 25 lumpectomy cavities were included, and the average skin dose recorded was 1.18 Gy ± 0.88 Gy, ranging from 0.17 Gy to 4.77 Gy, with an average applicator-to-skin distance of 19.9 mm ± 5.1 mm. An exponential-plateau model was found to best describe the dose fall-off with a root-mean-square error of 0.73. This model was then validated prospectively using skin dose measurements from five consecutive patients. Validation measurements were well within the 95% prediction limits of the model, with a root-mean-square error of 0.52, showing that the prediction model accurately estimates skin dose using ultrasound skin bridge measurements. CONCLUSIONS: This prediction model constitutes a useful tool for estimating the skin dose received during breast lumpectomy IORT. The model and accompanying 95% confidence intervals can be used to establish a minimum allowable skin bridge distance, effectively limiting the maximum allowable skin dose.
Authors: Fardeen Bhimani; Kelly Johnson; N Patrik Brodin; Wolfgang A Tomé; Jana Fox; Keyur Mehta; Maureen McEvoy; Sheldon Feldman Journal: Front Oncol Date: 2022-07-12 Impact factor: 5.738