ABDOMINAL AORTIC-ANEURYSMS - EVALUATION WITH VARIABLE-COLLIMATION HELICAL CT AND OVERLAPPING RECONSTRUCTION

PURPOSE: To determine the value of variable collimation and overlappin g reconstruction in helical computed tomography (CT) to evaluate abdom inal aortic aneurysm. MATERIALS AND METHODS: Twenty-three patients (15 men and eight women, aged 59-85 years) underwent helical CT scanning, nine with fixed 5-mm collimation and 14 with 3- and 7-mm collimation combined. The ability to visualize main and accessary renal arteries, detect stenoses, and determine aneurysm extent were evaluated. RESULTS : Extent of aneurysm was accurately determined in 17 of 23 cases witho ut overlapping sections; failure to detect ancillary findings such as accessory arteries or stenosis occurred in nine of these cases. With o verlapping sections, determination of aneurysm extent improved to 19 o f 23 cases and ancillary errors were reduced to four. Five errors occu rred with fixed collimation and three errors with variable collimation . CONCLUSION: Overlapping, variable-collimation helical CT allows for a more complete evaluation of abdominal aortic aneurysms than does non overlapping, fixed-collimation CT.