PURPOSE
In certain circumstance when MR is not available, CT could be a useful diagnostic tool for evaluation of complications in patients who underwent Fontan operation. However, due to its unique hemodynamics, inhomogenous enhancement of the Fontan tract was inevitable, restricting diagnostic abilities to detect major postoperative complications. Our purpose was to find an adequate contrast media injection protocol for Fontan patients to reduce needless repeated dynamic scans and decrease radiation exposure.
METHOD AND MATERIALS
CT angiography was done in 27 patients who received Fontan operation. A total of 42 image series was obtained in 34 CT scans. We divided into four groups; Group 1: Bolus-tracking method with either antecubital or foot vein route of contrast media(CM) injection, (n=20), Group 2: fixed 1 minute delay scan with antecubital route (n=11), Group 3: fixed 1 minute delay scan with foot vein route(n=3), and Grout 4: fixed 1 minute delay scan with simultaneous infusion via both antecubital and foot vein route (n=8). Bolus tracking were determined by measuring contrast transit time to ventricle. For each patient, attenuation was measured at three different anatomic levels, right main pulmonary artery(RPA), left main pulmonary artery(LPA), and Fontan tract and lower threshold of 160 H was considered optimal. Mean attenuation values and standard deviation(SD) were calculated. The attenuation uniformity of RPA, LPA, and Fontan tract were visually graded and analyzed.
RESULTS
The mean attenuation values and SD of Group 1, 2, 3, 4 was 281.3HU±75.7HU, 172.4HU±16.7HU, 242.6HU±65.3HU, 255.3HU±49.6HU respectively. The uniformity of enhancement was observed in 22% in group 1, 75.4% in group 2, 67% in group 3, and 75% in group 4. Maximum enhancement was gained by bolus tracking, however, it also showed large standard deviation value, meaning severe inhomogenousity. Minimum standard deviation value was gained in group 2, with adaquate contrast enhancement.
CONCLUSIONS
Uniform contrast enhancement of Fontan tract and pulmonary trunk, desirable for detection of postoperative complication, can be achieved by 1 minute delayed scan with antecubital route.
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