Dual source abdominal computed tomography: the effect of reduced X-ray tube voltage and intravenous contrast media dosage in patients with reduced renal function.

ABSTRACT

BACKGROUND: X-ray tube voltage (kVp) reduction increases intravenous contrast medium (CM) attenuation at computed tomography (CT), but tube output limits its use in large patients. PURPOSE: To evaluate the feasibility and image quality of reducing CM dose by low kVp and using dual X-ray source at liver CT. MATERIAL AND METHODS: Patients with estimated glomerular filtration rate (eGFR) < 45 mL/min (n = 43) aged 60-91 years (75 ± 7.7), weighing 42-114 kg (75 ± 15) were prospectively scanned using a reduced CM dose of 0.25 or 0.3 g iodine (I)/kg with 70 or 80 kVp respectively, using either single-source or dual-source CT depending on patient size. Liver contrast-to-noise ratio (CNR), liver noise, and muscle noise were quantitatively compared with those of 43 consecutive patients aged > 65 years with eGFR > 45 mL/min scanned using a standard abdominal protocol at 120 kVp after receiving 0.5 gI/kg. RESULTS: There was no statistically significant difference in CNR, liver noise, or muscle noise at reduced CM protocols compared to the standard protocol CNR was 4.6 (95% CI = 4.2-5.0) vs. 5.0 (95% CI = 4.5-5.5), liver noise was 11.1 (95% CI = 10.7-11.6) vs. 11.0 (95% CI = 10.5-11.6), muscle noise was 11.7 (95% CI = 11.2-12.1) vs. 10.8 (95% CI = 10.1-11.4). The mean SSDE was 70% higher with the reduced CM protocol. CONCLUSION: CM dosage can be reduced by 40-50% with maintained measured noise and CNR in patients with BMIs of 15-36 kg/m2 by lowering the tube voltage and dual-source CT scanning of the liver.