Estimation of patient dose with standard and low-dose MDCT fluoroscopy protocols for lung biopsy

Purpose: This study aimed at assessing patient dose with standard and low-dose MDCT fluoroscopy protocols for lung biopsy. Materials and Methods: The low-dose protocol used lower tube potential (80 kV) respect to the standard protocol (120 kV); all other scanning parameters were left unchanged. Data from sixty-nine (69) CT fluoroscopy (CTF) lung interventions were prospectively collected and included in the study. Nineteen (19) procedures where performed using the standard protocol (120 kV), while the remaining 50 where performed with the low-dose protocol ( 80 kV). Effective patient dose was calculated using the dose-length product information, while peak entrance skin dose was measured with EBT2 gafchromic films. Lesion size, total fluoroscopy time, success rate and complication rate were also recorded. The Mann-Whitney U test was used to assess statistical significant difference in terms of lesion size and fluoroscopy time, between the two study groups. Fisher's test was used to assess significant difference in terms of success and conclusiveness. Results: The median effective patient dose was 5.4 mSv (minimum 2.4 mSv, maximum 18.8 mSv; 19 procedures) for the standard protocol and 1.1 mSv (minimum 0.4 mSv, maximum 4.5 mSv; 50 procedures) for the low-dose protocol (p<0.01). The median peak entrance skin dose was 268 mGy (95-899 mGy) and 141 mGy (38-410 mGy) for the standard and low-dose protocol respectively (p<0.01). There was no significant difference (p=0.95) in mean lesion size between the two groups: standard protocol 2.7 cm (min 0.9 cm, max 10.7 cm); lowdose protocol 2.6 cm (min 1.0 cm, max 7.9 cm). Average fluoroscopy time was 1.4 min (range 0.6-5.0 min) and 1.3 min (range 0.4-4.5 min), respectively for the standard and low-dose protocol (p-value=0.36). Biopsy performed using the low-dose protocol was technically successful in 98% of the cases and complication rate was 18%, compared to 100% and 10% for the standard protocol. No statistical significant difference was found between the two groups ( p> 0.05). Conclusions: High patient entrance skin dose (up to 899 mGy) and high effective patient dose (up to 18.8 mSv) can occur for standard CTF lung biopsy protocol. Simple means, like lowering the kV, allow reducing patient dose significantly, with skin doses now far below the 2 Gy level of deterministic effects. Occupational doses, occasionally of concern in high work load regimes, are expected to follow the same trend. © 2013 SPIE.

ISBN:978-0-8194-9442-9

Publication year:2013

BOF-keylabel:yes

IOF-keylabel:yes

Authors from:Higher Education