CT DONE 4-6-HR AFTER CT ARTERIAL PORTOGRAPHY - VALUE IN DETECTING HEPATIC-TUMORS AND DIFFERENTIATING FROM OTHER HEPATIC PERFUSION DEFECTS

OBJECTIVE. Nontumorous perfusion defects occur during CT arterial port ography (CTAP) as normal variants or in cirrhosis, focal fatty infiltr ation, and portal vein obstruction. The purpose of this study was to d etermine whether delayed CT 4-6 hr after CTAP improves sensitivity to hepatic tumors and differentiates them from other hepatic perfusion de fects. SUBJECTS AND METHODS. CTAP was done at I-cm increments on 26 pa tients for evaluation of hepatic tumors. Delayed CT scans were obtaine d 4-6 hr later in all patients. Two observers retrospectively reviewed the CT scans obtained during CTAP and recorded size, shape, and locat ion of suspected hepatic tumors. Confidence levels were assigned for e ach tumor. The delayed CT scan was then interpreted in conjunction wit h the CT scans obtained during CTAP, and confidence levels were reassi gned. Surgical correlation was obtained for all patients. In the 26 pa tients, 86 masses were found at surgery. The sensitivity and number of false-positives for both CTAP alone and CTAP combined with delayed CT were compared with a two-tailed Student t-test. Receiver-operating-ch aracteristic analysis also was performed. RESULTS. CTAP detected 73 (8 5%) of the 86 hepatic masses. Delayed CT had no effect on the sensitiv ity of CTAP. However, adding delayed CT decreased the total number of false-positives by Il,a statistically significant difference (p < .05) . Receiver-operating-characteristic analysis revealed a significantly greater (p < .05) area under the curve (A, index) of 0.927 +/- 0.025 f or CTAP combined with delayed CT compared with 0.886 +/- 0.032 for CTA P alone. Delayed CT was most useful for larger (>1 cm) wedge-shaped pe rfusion defects and least useful for smaller(<1 cm) round defects. CON CLUSION. Delayed CT has no effect in detecting tumors but may be usefu l for differentiating tumors from other hepatic perfusion defects seen on CTAP. The greatest benefit of delayed CT is in evaluating regions obscured by large wedge-shaped perfusion defects on CT scans obtained during CTAP.