Patient’s skin dose estimation and investigation of factors for dose reduction in fluoroscopy guided procedures

The purpose of this study was to assess patient dose and investigate the parameters affecting patient’s dose during fluoroscopy guided procedures at a hospital for possible dose reduction.

Standard quality control tests were performed prior to the data collection. Twelve (12) thermoluminescent dosimeters TLDs were arranged on a Perspex phantom for skin dose measurement. Skin dose (SD) and Kerma Area Product (KAP) were recorded for varying radiation field size at fix phantom thickness and vice versa. Doses were assessed on one-hundred and one (101) patients undergoing barium swallow (BaS), retrograde (Rtr) and hysterosalpingoraphy (HSG).

The mean fluoroscopy time (FT) for Rtr, BaS and HSG procedures were 1 ± 0.67 min, 2.12 ± 1.30 min and 0.66 ± 0.5 min respectively. The mean KAP values were 8.21 ± 6.05 Gy.cm², 87.33 ± 31.2 Gy.cm² and 6.01 ± 3.25 Gy.cm² for Rtr, BaS and HSG. The mean skin dose (SD) values for the cited procedures were 11.64 ± 1.25 mGy, 121.80 ± 40.87 mGy and 7.55 ± 2.58 mGy. It was found that patient skin dose increase rapidly with the phantom thickness (factor ≈ 2) as compared with the field size (factor ≈ 1). The SD variation with field size for the same thickness was negligible but the KAP values increase considerably with field size. The mean KAP value obtained was found to be higher with average factors of 2 and 2.5 for Rtr and HSG respectively. The regression analysis shows that there is a poor correlation (R² =0.33) between ESD and KAP but a significant statistical significance (P-value = 0.003). It also shows that the SD in this study can be predictable with known fluoroscopy time for HSG and retrograde procedures at 77% and 52% accuracy respectively.

The main contributor of patient’s dose (i.e. SD) was patient thickness which cannot be regulated by the staff. Other factors that can be regulated by the staff to reduce patient’s dose were the fluoroscopy time for HSG and Rtr procedures and the use of smaller field size as possible without compromising the clinical outcome.