Elsevier

Academic Radiology

Volume 18, Issue 7, July 2011, Pages 822-827
Academic Radiology

Original Investigation
Low-dose Unenhanced CT for IV Contrast Bolus Timing:: Is It Reliable to Assess Hepatic Steatosis?

https://doi.org/10.1016/j.acra.2011.02.013Get rights and content

Rationale and Objectives

To determine whether an unenhanced low-dose image acquired during automated contrast bolus timing can be used to assess hepatic steatosis.

Materials and Methods

Fifty subjects (29 male, 21 female; 26–92 years; mean body mass index (BMI; 26.9) with abdominal multiphasic computed tomography were included. Abdominal diameters and circumferences were derived from anteroposterior and lateral scout radiographs. Hepatic attenuation (HA) was measured on unenhanced low-dose images (120 kV; 40 mA; 0.5 seconds' rotation time) and corresponding unenhanced standard-dose images (120 kV, z-axis automatic tube current modulation, noise index 11.5). Noise estimates were measured in surrounding air. Pearson correlation was calculated between abdominal circumference and BMI. Mean HA assessed on low-dose images and standard-dose images was compared using a paired Student's t-test and Bland Altman plots.

Results

Abdominal circumference (mean, 142.8cm) correlated well with BMI (r = 0.83). No significant difference was found for HA on low-dose images (mean +57.7 HU) compared to HA on standard-dose images (+56.0 HU) (P = .077). Image noise (+11.5 HU) was significantly higher on low-dose images compared to image noise (+8.1 HU) on standard-dose images (P < .05). For HA mean difference comparing low- and standard-dose images was −1.7 HU (limits of agreement: −14.6, 11.2).

Conclusion

In all subjects, hepatic attenuation can be correctly assessed on unenhanced low-dose images.

Section snippets

Patient Population

Institutional review board approval was obtained for this Health Insurance Portability and Accountability Act–compliant retrospective study. A study population of 50 patients, comprising of 21 women and 29 men, was included in this study. Indications for multiphasic MDCT were as follows: abdominal aortic aneurysm (n = 16), living related renal donor candidate (n = 5), and pancreatic mass (n = 29). Patients with focal liver lesions and patients with ascites were not included in this study. The

Quantification of Body Habitus

Abdominal circumference at the level of the pedicle of L1 ranged from 103.0 to 203.6 cm with a mean of 142.8 cm ± 22.6 cm. Pearson correlation showed a good correlation between abdominal circumference and the BMI (r = 0.83, P < .05).

Attenuation Value Assessment

Mean hepatic attenuation on unenhanced low-dose images was 57.7 HU with a range from 5.7 to 73.9 HU and mean hepatic attenuation on unenhanced standard-dose images was 56.0 HU with a range from 7.3 to 76.7 HU. Hepatic attenuation did not differ significantly between

Discussion

Percutaneous liver biopsy is considered the gold standard for diagnosis of hepatic steatosis, and although it is a relatively safe procedure, the risk of significant bleeding is 1% 13, 14, 15, 16. Many research groups have investigated the role of CT as a noninvasive tool for the assessment of steatosis 1, 2, 3, 4, 5, 6, 7, 8. The most common biomarkers for steatosis are hepatic attenuation, the liver-to-spleen attenuation ratio, the difference between hepatic and splenic attenuation, and the

Conclusion

In summary, hepatic attenuation can be reliably assessed on unenhanced low radiation dose images to estimate steatosis. This is especially helpful in cases in which no unenhanced standard radiation dose phase is acquired and a contrast bolus monitoring scan covers parts of the liver.

Acknowledgements

This investigation was supported by the Swiss National Science Foundation.

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