Rationale and Objectives
To determine the recommended iodine dose of contrast material (CM) for hepatic arterial–dominant phase (HAP) and hepatic parenchymal phase (HPP) imaging to assess hypervascular hepatocellular carcinoma (HCC).
Materials and Methods
This was a prospective study including 348 patients with hypervascular HCC in 77 hospitals as a postmarketing surveillance to investigate the effects of body weight–tailored dose of CM (300 mgI/mL of iohexol) for hepatic multiphasic contrast-enhanced multidetector-row computed tomography imaging. Informed consent was obtained from all patients who were enrolled. The tumor-to-liver contrast (TLC) of HAP images was assessed qualitatively (QL-TLC) and quantitatively (QT-TLC [HU]; computed tomography [CT] value of tumor–CT value of hepatic parenchyma). Minimal and sufficient QT-TLC were defined as CT values corresponding to the median and 75% of QL-TLC assigned with “good,” respectively. The recommended iodine dose was estimated by the relationship between iodine dose (mgI/kg) and QT-TLC.
Results
There was a good correlation between QL-TLC and QT-TLC. The recommended iodine dose of CM for HAP imaging was considered to be in the range of 567–647 mgI/kg based on minimal (33.7 HU) and sufficient QT-TLC (40.9 HU). Meanwhile, the recommended dose of CM for HPP imaging was 572 mgI/kg as a dose that gives hepatic enhancement more than 50 HU during HPP imaging.
Conclusions
The recommended iodine dose of CM for HAP and HPP imaging may be different, being 567–647 mgI/kg and 572 mgI/kg, respectively, in assessing hypervascular HCC.
There has been a recent trend for the dose of contrast material used in multiphasic contrast-enhanced computed tomography (CT) imaging of the liver that the dose of contrast material should be tailored according to the patients’ body weight to achieve adequate contrast enhancement. By introducing such a concept of body weight–tailored dose of contrast material, variation among patients with different body weights in the degree of contrast enhancement in the aorta and liver can be canceled .
Some investigators have attempted to determine the optimal dose of contrast material for multiphasic contrast-enhanced CT of the liver. In their studies, the optimal dose of contrast material has been determined based on a definition of the dose that can give adequate hepatic enhancement (>50 HU increase from unenhanced baseline HU of the liver) during hepatic parenchymal phase (HPP; identical to portal venous phase) . Summing up their reports, the optimal dose of contrast material for HPP imaging remains unclear because it ranges widely from 1.7 mL/kg to 2.5 mL/kg with 300 mgI/mL (520–750 mgI/kg). Such considerable discrepancy between their conclusions in the optimal dose might depend on the outdated methods including prolonged scan time throughout the entire liver with single-detector helical CT scanners and the limited, self-approving hepatic CT protocols.
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Materials and methods
Patients
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Table 1
Patients’ Characteristics
Overall ( n = 348) Gender Male 255 (73.3 ∗ ) Female 93 (26.7) Age 72.6 ± 8.78 † Body weight 58.3 ± 11.25 Iodine dose per weight (mgI/kg) 584.5 ± 61.93 Injection flow rate (mL/s) 3.65 ± 0.65 Injection duration (s) 31.0 ± 3.23
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CT Imaging
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Statistical Analysis
Imaging evaluation: Qualitative analysis
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Imaging evaluation: Quantitative analysis
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Estimation of recommended iodine dose
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Results
Relationship between QL-TLC and QT-TLC for HAP Imaging
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Estimation of the Recommended Iodine Dose for HAP Imaging
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Y(HU)=−17.17+0.0897X(mgI/kg) Y
(
HU
)
=
−
17.17
+
0.0897
X
(
mgI
/
kg
)
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Estimation of the Recommended Iodine Dose for HPP Imaging
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Y(HU)=−6.28+0.0984X(mgI/kg) Y
(
HU
)
=
−
6.28
+
0.0984
X
(
mgI
/
kg
)
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Table 2
A Quick Reference Table Showing Relationship between Recommended Volume of Contrast Material with 300 mgI/mL and Patient’s Body Weight
40 kg 45 kg 50 kg 55 kg 60 kg 65 kg 70 kg 80 kg 570 mgI/kg † 76 ∗ 86 95 105 114 124 133 152 600 mgI/kg 80 90 100 110 120 130 140 160 650 mgI/kg 87 98 108 119 130 141 152 173
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Discussion
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Acknowledgments
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