Room: Exhibit Hall | Forum 2
Purpose: Due to procedural challenges (patient positioning and repeated scans acquired over the same body area), CT fluoroscopy-guided (CTF) biopsies can lead to high peak skin doses. This study was to enhance dose awareness by estimating the number of CTF scans for patients of various body sizes that could potentially cause the onset of skin erythema.
Methods: All investigated biopsy procedures were performed on a GE LightSpeed 16 CT scanner. A typical scan sequence includes: AP/Lateral scout scan, helical planning scan, CTF scans in helical mode (300 mA, 0.937 pitch, 20 mm collimation) and/or CTF scans in axial mode (60 mA, 10 mm collimation) at 120 kVp. CTF scan is repeated over the same region until a viable tissue sample is successfully extracted. The percentage of directly irradiated skin surface area (PDIS) was estimated using the Lund and Browder chart (LB). The peak skin dose (PSD) per scan for adult patients, who ranged from normal-weight to obese, was estimated with VirtualDoseáµ€á´¹ CT and the LB. The number of CTF scans required to reach an early skin erythema dose threshold of 2 Gy was calculated. Since tumor accessibility can result in unconventional patient positioning, the PSD from off-centered positions was also investigated.
Results: For PDIS of 0.51% for male and assuming all CTF scans were axial, the number of CTF scans decreased as patient size increased (normal-weight to obese): 188 to 148. A 6-cm off-centering increased PSD to obese patient by 49% and could reduce the number of scans by the same amount if scan technique were not modified.
Conclusion: A PSD awareness threshold has been investigated for a range of patient sizes found in the clinic. A notable increase in PSD from off-centered patient positions highlights the need to incorporate realistic scan conditions into any organ dose estimate.
Funding Support, Disclosures, and Conflict of Interest: This research was funded in part through the NIH/NCI Cancer Center Support Grant P30 CA008748. Dr. X. George Xu is the CEO of VirtualPhantoms, Inc.
Not Applicable / None Entered.