Hypervascular liver tumors: low tube voltage, high tube current multidetector CT during late hepatic arterial phase for detection--initial clinical experience.

PURPOSE

To intraindividually compare a low tube voltage (80 kVp), high tube current computed tomographic (CT) technique with a standard CT protocol (140 kVp) in terms of image quality, radiation dose, and detection of malignant hypervascular liver tumors during the late hepatic arterial phase.

MATERIALS AND METHODS

This prospective single-center HIPAA-compliant study had institutional review board approval, and written informed consent was obtained. Forty-eight patients (31 men, 17 women; age range, 35-77 years) with 60 malignant hypervascular liver tumors (mean diameter, 20.1 mm +/- 16.4 [standard deviation]) were enrolled. Pathologic proof of focal lesions was obtained with histopathologic analysis for 33 nodules and imaging follow-up after a minimum of 12 months for 27 nodules. Patients underwent dual-energy 64-section multi-detector row CT. By using vendor-specific software, two imaging protocols-140 kVp and 385 mA (protocol A) and 80 kVp and 675 mA (protocol B)-were compared during the late hepatic arterial phase of contrast enhancement. Paired t tests were used to compare tumor-to-liver contrast-to-noise ratio (CNR) for each lesion, mean image noise, and effective dose between the two data sets. Three readers qualitatively assessed the two data sets in a blinded and independent fashion. Lesion detection and characterization and reader confidence were recorded, as well as readers' subjective evaluations of image quality. Wilcoxon-Mann-Whitney statistical analysis was performed on this assessment.

RESULTS

Image noise increased from 5.7 to 11.4 HU as the tube voltage decreased from 140 to 80 kVp (P < .0001), resulting in a significantly lower image quality score (4.0 vs 3.0, respectively) with protocol B according to all readers (P < .001). At the same time, protocol B yielded significantly higher CNR (8.2 vs 6.4) and lesion conspicuity scores (4.6 vs 4.1) than protocol A, along with a lower effective dose (5.1 vs 17.5 mSv) (P < .001 for all).

CONCLUSION

By substantially increasing the tumor-to-liver CNR, a low tube voltage, high tube current CT technique improves the conspicuity of malignant hypervascular liver tumors during the late hepatic arterial phase while significantly reducing patient radiation dose.