Differentiation of cocaine from heroine body packs by computed tomography: Impact of different tube voltages and the dual-energy index

ObjectivesTo investigate the computed tomography (CT) attenuation values and the dual-energy index (DEI) of cocaine and heroin at different tube voltage settings in a phantom study.Materials and methodsThirty-three hand-wrapped bodypacks prepared of heroin (n=17) and cocaine (n=16) at varying concentrations were submerged in a 28-cm water tank and imaged four times with a dual-source 64-detector row CT at peak tube voltage levels of 80 kVp, 100 kVp, 120 kVp, and 140 kVp. Tube current in each protocol was adjusted for a similar CT volume dose index of 8.0 mGy. Image noise and the CT attenuation values were measured in each drug container three times at each tube voltage level by two independent observers, and the DEI was calculated from measurements at 80 kVp and 140 kVp.ResultsImage noise at the four tube voltage levels was similar (p=0.32). Intra- and interobserver agreement was good (r=0.89 to.93; p<0.001). CT attenuation values were different between cocaine and heroin at any tube voltage and in the DEI (p<0.01) with the smallest overlap of attenuation values between both drugs at 80 kVp and the DEI. The drug concentration had a strong negative relationship with the DEI for heroin (r=−0.67; p<0.01) but not for cocaine (r=−0.15; p=0.23).ConclusionsCT attenuation values measured at low tube voltage level and using the DEI improve the differentiation of cocaine and heroin-containing bodypacks compared to measurements at higher tube voltage settings.