Using thoracic helical CT to assess iodine concentration in a small volume of nonionic contrast medium during vascular opacification: A prospective study

OBJECTIVE. The goal of the study was to assess whether, using thoracic helical CT, diagnostic mediastinal and hilar vascular enhancement can be obtained with a small amount of nonionic contrast material (80 ml) injected at a relatively slow rate (2 ml/sec). SUBJECTS AND METHODS. One hundred twenty patients (60 in their fourth decade of hfe and 60 in their seventh decade of life) referred for contrast-enhanced thoracic CT for malignancies or infections prospectively entered the study. They were randomly assigned to be given one of three iodine concentrations of a nonionic contrast material: 250 mg/ml (I250), 300 mg/ml (I300), and 350 mg/ml (I350). Two radiologists independently graded perivenous artifacts and arterial enhancement of mediastinal and hilar vessels on a 4-point scale: 1, poor; 2, fair; 3, good; and 4. excellent. Measurements of arterial attenuation values (quantitative assessment) were obtained on the aorta and pulmonary artery. RESULTS. Mean scares were equal to or greater than 3 for all vessels only using I350. The higher the iodine concentration was, the higher the mean score, but there was a statistically significant difference only between scores obtained with I350 and those obtained with I300 or I250. Mean scores were higher for the patients in their seventh decade of life than those in their fourth decade; however, there was no statistically significant difference between scores of the two decade groups. We found a highly significant statistical relationship between scores and arterial attenuation values, CONCLUSION. During contrast-enhanced helical CT examinations for general thoracic evaluations, good opacification of central vascular structures is obtained with a low volume of high iodine concentration nonionic contrast medium.