Single-energy low-voltage arterial phase scanning increases conspicuity of hypervascular lesions of the liver: an intra-patient study

Purpose: To compare intra-patient a single-energy low-voltage arterial phase protocol and a 120 kv protocol for detecting hypervascular focal liver lesions (hFLL).Methods and Materials: 27 patients with chronic liver disease and ≥1 hFLL underwent abdominal MDCT with 80 kV arterial phase (test group) on a 64-row scanner. This was compared to a previous 120 kV scan. The mean interscan interval was 139 days; lesions were not treated between exams. Scans were compared for attenuation and standard deviation in the liver, aorta and largest hFLL, image noise, CNR, CTDI and DLP, (paired t-test). Effective dose was calculated with TLD measurements.Results: All scans were of diagnostic quality, according to thereporting radiologist. Mean attenuation was significantly higher inthe test group than in the control group in the aorta (501.7±148.3 vs 273.6±82.9HU), liver (78.5±14.3 vs 60.9±11.9HU) and hFLL (160.0±32.2 vs 107.9±23.2HU) (all p<0.0001). CTDI and DLP were significantly lower in the test group (6.4±0.4 vs 12.96±4.3mGy and 194.3±27.5 vs 405.4±117.4mGy x cm, respectively; all p<0.0001). Lesion conspicuity (HUnodule -HUliver), was significantly higher in the test group (83.8±35.5 vs48.8±21.5HU; p= 0.0008). Mean image noise was significantly higher in the test group than in control group (12.3±3.6vs 8.5±2.4HU; p<0.0001).Lesion CNR was not significantly different between the two protocols.TLD effective dose was significantly lower for the test protocol (0.158 vs 0.202mSv; p=0.0083).Conclusion: The use of a 80 kVp arterial phase protocol for abdominal CT increases conspicuity of hFLL, possibly improving identification, while allowing significant dose reduction.