COMPARISON OF HELICAL AND CONVENTIONAL COMPUTED-TOMOGRAPHY OF THE LIVER

OBJECTIVE: To compare helical and conventional computed tomography (CT ) of the liver in terms of enhancement (with different contrast media) and image quality, using optimal technique for each type of acquisiti on. PATIENTS AND METHODS: Of 218 consecutive patients referred to a te rtiary-care hospital for CT of the liver, 166 were randomly assigned t o undergo helical (79 patients) or conventional (87) CT. Fifty patient s were excluded from the study because they were unable to hold their breath or were unable to cooperate or because they weighed more than 1 20 kg. Two other patients were excluded at the time of scanning becaus e of a technical problem. Monophasic injections of contrast agent at 3 mL/second were given to patients undergoing helical CT and biphasic i njections at 2 and 0.7 mL/second to patients undergoing conventional C T. The contrast media used were iothalamate meglumine, ioversol, iopam idol and iohexol. For each patient, liver enhancement over baseline at tenuation was calculated for every slice, and time to peak enhancement was calculated. In addition, visualization of anatomic landmarks and image quality were scored by two independent reviewers. RESULTS: Minim um, maximum and mean liver enhancement were significantly greater in t he group that underwent helical imaging (49, 62 and 55 Hounsfield unit s [HU] respectively) than in the group that underwent conventional ima ging (36, 51 and 44 HU respectively) (Student's t-test, p < 0.0001). S imilar differences were obtained when the results were analysed separa tely for each contrast medium. Image quality was not significantly dif ferent between the two acquisition modes. CONCLUSIONS: For computed to mography of the liver, monophasic injection of contrast medium at a hi gh rate and helical acquisition (rather than biphasic injection and co nventional acquisition) resulted in significantly better enhancement, without compromising image quality.