Comparison of planning techniques when air/fluid is present using the strut‐adjusted volume implant (SAVI) for HDR‐based accelerated partial breast irradiation

• Published in: Journal of applied clinical medical physics Vol. 14; no. 6; pp. 264 - 273
• Main Authors: Harmon, Joseph F., Rice, Brandon K.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 04.11.2013; John Wiley and Sons Inc
• Subjects: Air; APBI; brachytherapy; Brachytherapy - instrumentation; Breast cancer; Breast Neoplasms - radiotherapy; Dosimetry; Female; HDR; Humans; Patients; Planning; Prosthesis Implantation - instrumentation; Radiation Oncology Physics; Radiation therapy; Radiometry; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Retrospective Studies; SAVI; Skin
• ISSN: 1526-9914; 1526-9914
• DOI: 10.1120/jacmp.v14i6.4442

The presence of air/fluid surrounding implantable devices used for partial breast irradiation may significantly impact dose coverage to at‐risk tissue. Of the 67 total patients retrospectively evaluated for this study, 32 (48%) had greater than 1 cc volume of air/fluid extending outside of the strut‐adjusted volume implant (SAVI) device surface and were selected for comparison of planning approaches. The planning approaches utilized two different definitions of PTV_EVAL. One definition of a PTV_EVAL (PTV_EVALSAVI) was based on expanding 1 cm beyond the SAVI device only while accounting for the air/fluid using the NSABP Protocol B‐39/RTOG Protocol 0413. The second PTV_EVAL definition (PTV_EVALCAV) was based on expanding 1 cm beyond the cavity (SAVI device plus air/fluid volume). The results indicate use of the B‐39 formalism to account for air/fluid displacing the PTV_EVAL may overestimate the dose coverage to the at‐risk tissue, especially for large contiguous volumes of air/fluid. Using the SAVI device to optimize dose covering the PTV_EVALCAV volume surrounding the cavity improves dosimetric coverage to at‐risk tissue by 11.3% and 8.7% for V100 and V90, respectively, while the average V150 and V200 indices for PTV_EVALCAV increased by 9.1 cc and 5.0 cc, respectively, and the average maximum rib and skin doses increased by 11. 1% and 6.1%, respectively. The maximum skin dose, rib dose, V150, and V200 all met the planning objectives despite any increase in these parameters. PACS number: 87.55.kh