The determination of patient effective dose in transarterial oily chemo embolization (TOCE) procedure using digital flat-panel system

Abstract

Transarterial Oily Chemo Embolization (TOCE) is the procedure producing high dose to both patient and staff. Radiation skin injury to patient was reported by this interventional procedure. Therefore, the avoidance of skin injury during the procedure is needed. The objective of this study is to determine patient effective dose at the skin during TOCE procedure for Hepatocellular Carcinoma (HCC) using a new angiographic unit with a digital flat-panel system and the relationship between the patient effective doses measured by Unfors PSD and the dose area product (DAP) values. The patient effective doses (ED) were determined during TOCE procedure using the digital Flat-panel system, Philips Allura FD 20 at Vascular and Interventional Radiology Unit, King Chulalongkorn Memorial Hospital. The system is equipped with the dose-area-product (DAP) and used to determine the average entrance surface dose (ESD) for each procedure. The peak ESD were evaluated by the solid state dosemeter; Unfors Patient Skin Dosemeters (PSD) placed on patient back at three regions at left, middle, and right portions of the liver. The patients ED were calculated in sixty-nine patients in May-November 2009. The average + SD (range) fluoroscopic time was 16.06+ 11.26 (3.38-59.13) min, average number of frames from DSA (Digital Subtraction Angiography) was 180.81+94.59 ( 75-618), the number of frames from x-per CT with the range was 224 -1114. The average ESD determined by DAP was 222.6+114.6 (22.58-537.43) Gycm2. The average ESD determined by Unfors PSD was 1004.2+565.11 (192.6-3145.29) mGy. The average ED determined by DAP was 9.70+5.27 (1.11 - 23.6) mSv. The peak ED at the skin above the liver determined by Unfors PSD was 10.04+5.65 (1.93-31.45) mSv. The average of ED at left lobe of liver was 9.68+5.5 (1.75- 31.4) mSv, the middle lobe was 8.48+5.13 (1.21 - 28.78) mSv and the right lobe was 5.72+3.55 (0.64 -16.31) mSv. The DAP-to–effective dose conversion factors were 0.043 mSv.Gy-1cm-2. Discussion and Conclusion: The solid state dosemeter is most suitable for entrance surface dose measurement for the small size of detector and easily use. There was no need to estimate the surface area exposed as in DAP method. Two from sixty-nine patients received the entrance surface dose from TOCE procedure using Digital flat-panel system exceeding the threshold for radiation skin injuries which confirmed by both dosemeters.