Rk. Zeman et al., ABDOMINAL AORTIC-ANEURYSMS - EVALUATION WITH VARIABLE-COLLIMATION HELICAL CT AND OVERLAPPING RECONSTRUCTION, Radiology, 193(2), 1994, pp. 555-560
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.