Optimal contrast dose determined for spotting liver lesions

For the assessment of hypervascular hepatocellular carcinoma (HCC), the optimal iodine dose of contrast material for hepatic arterial-dominant phase (HAP) imaging has been shown to be between 567-647 mgl/kg, according to a study published in the September issue of Academic Radiology.

Authors Tomoaki Ichikawa, MD, of the University of Yamanashi, Japan, and colleagues also found the recommended iodine dose for hepatic parenchymal phase (HPP) imaging to be 572 mgl/kg.

“[B]ased on such results, radiologists should recognize that the optimal dose of contrast material required for HAP and HPP imaging may differ and HAP imaging may require more dose of contrast material than HPP imaging,” wrote the authors. “Specifically, the optimal dose of contrast material for HPP imaging may be insufficient and may correspond to the only minimally accepted dose of contrast material for HAP imaging.”

The study was the first large-scale, multicenter, prospective trial to determine optimal contrast dose for evaluating hypervascular HCC with multiphasic contrast-enhanced CT imaging of the liver. Ichikawa and colleagues included 348 patients with hypervascular HCC from 77 hospitals. The tumor-to-liver contrast (TLC) of HAP images was assessed qualitatively and quantitatively.

There was good correlation between the qualitative and quantitative assessments of TLC, with the recommended iodine dose for HAP imaging in the range of 567-647 mgl/kg, according to the authors. Ichikawa and colleagues pegged the minimal and sufficient quantitative TLC as the CT values corresponding to the median and 75 percentile of the images qualitatively rated “good,” respectively. The recommended dose was estimated by the relationship between iodine and quantitative TLC.

“It is only natural that the optimal dose of contrast material may be different for HAP and HPP imaging because target lesions to be evaluated and mechanisms to obtain required lesion-to-liver image contrasts are quite different,” wrote the authors.

The authors added that their study design was particularly well-suited to minimize bias by including a large number of nonacademic general hospitals with a small number of patients enrolled from each.