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

OBJECTIVE. The goal of the study was to assess whether, using thoracic heli cal CT, diagnostic mediastinal and hilar vascular enhancement can be obtain ed 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 decad e of hfe and 60 in their seventh decade of life) referred for contrast-enha nced thoracic CT for malignancies or infections prospectively entered the s tudy. They were randomly assigned to be given one of three iodine concentra tions of a nonionic contrast material: 250 mg/ml (I250), 300 mg/ml (I300), and 350 mg/ml (I350). Two radiologists independently graded perivenous arti facts and arterial enhancement of mediastinal and hilar vessels on a 4-poin t scale: 1, poor; 2, fair; 3, good; and 4. excellent. Measurements of arter ial 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 u sing I350. The higher the iodine concentration was, the higher the mean sco re, but there was a statistically significant difference only between score s 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 thei r fourth decade; however, there was no statistically significant difference between scores of the two decade groups. We found a highly significant sta tistical relationship between scores and arterial attenuation values, CONCLUSION. During contrast-enhanced helical CT examinations for general th oracic evaluations, good opacification of central vascular structures is ob tained with a low volume of high iodine concentration nonionic contrast med ium.