Innovative CT acquisition technique for the detection of hepatic nodules: What is the dose delivered to the patient?

Abstract

Introduction A Fast-kVp Switching (FKS) dual-energy and a routine adaptative iterative reconstruction (Adaptative Statistical Iterative Reconstruction, ASIR, GE Healthcare®) single-energy abdominal Computed Tomography (CT) protocols have been designed for hepatocellular carcinomas detection. Previous studies have shown that FKS exams can deliver a higher dose than standard exam with comparable image quality. This study aims to evaluate the dose delivered to patient exposed to these CT protocols. Material and methods Ten patients with 31 hepatocellular carcinomas underwent FKS dual-energy (80–140 kV; 630 mA, rotation time: 0.5 s pitch: 1.375) and single-energy abdominal contrast materialenhanced (120 kV, 150–650 mA, rotation time: 0.7 s pitch: 1.375, ASIR 50%, FBP 50%) CT exams with liver-arterial and portal venous phases. For each exam, image quality was judged qualitatively and quantitatively on arterial phase by radiologists. Radiation dose, based on Volume CT Index (CTDIVOL) and Dose Length Product (DLP) was reported using a Dose Archiving and Communication System (DACS) (DoseWatch, GE HealthCare®). Since only single energy abdominal protocol uses Automatic Exposure Control (AEC), all the results were classified according to patients Body Mass Index (BMI). Results Image quality, allowed the identification of 94% (29/31) of HCC nodules with adaptative iterative reconstruction single-energy exam and 97% (30/31) with FKS dual-energy protocol. A CTDIVOL of 13 mGy and a mean DLP of 393 mGy.cm were determined for the dual energy protocol whathever BMI. Whereas, for the routine exam, mean CTDIVOL and DLP were 7 mGy, 215 mGy cm; 14 mGy, 454 mGy cm and 18 mGy, 783 mGy cm for BMIs less than 20, of 20–25 and greater than 25 BMI, respectively. Conclusion FKS dual-energy and adaptative iterative reconstruction single-energy abdominal CT protocols can be optimized so as to deliver a radiation dose lower than swiss dose reference level (15 mGy, 500 mGy cm) without neglecting image quality. Current FKS dual energy protocol could be optimized since it now uses adaptive iterative reconstruction. Moreover, it could be adapted to low BMI patients.