Pancreatic ductal adenocarcinoma is associated with dismal prognosis. The detection of small pancreatic tumors which are still resectable is still a challenging problem.
The aim of this study was to investigate the effect of decreasing the tube voltage from 120 to 80kV on the detection of pancreatic tumors.
Three scanning protocols was used; one using the standard tube voltage (120kV) and current (160mA) and two using 80kV but with different tube currents (500 and 675mA) to achieve equivalent dose (15mGy) and noise (15 HU) as that of the standard protocol.
Tumors were simulated into collected CT phantom images. The attenuation in normal parenchyma at 120kV was set at 130 HU, as measured previously in clinical examinations, and the tumor attenuation was assumed to differ 20 HU and was set at 110HU. By scanning and measuring of iodine solution with different concentrations the corresponding tumor and parenchyma attenuation at 80kV was found to be 185 and 219 HU, respectively.
To objectively evaluate the differences between the three protocols, a multi-reader multi-case receiver operating characteristic study was conducted, using three readers and 100 cases, each containing 0–3 lesions.
The highest reader averaged figure-of-merit (FOM) was achieved for 80kV and 675mA (FOM=0,850), and the lowest for 120kV (FOM=0,709). There was a significant difference between the three protocols (p<0,0001), when making an analysis of variance (ANOVA). Post-hoc analysis (students t-test) shows that there was a significant difference between 120 and 80kV, but not between the two levels of tube currents at 80kV.
We conclude that when decreasing the tube voltage there is a significant improvement in tumor conspicuity.
Keywords: Pancreatic adenocarcinoma, CT, Low tube voltage, Phantom