Objective: to evaluate whether there are difference among different thickness of CTPA imagings for detection of emboli in peripheral pulmonary arteries.
Methods: CTPA Images of 97 patients with acute pulmonary embolism were divided into four series for each patient: 0.625 mm thick original transaxial soure images and 3 series of reconstructed images using the MIP technique with slab thicknesses of 1.25 mm, 2.5 mm, and 5.0 mm. The difference was compared among 4 series of CTPA images for detection of emboli in peripheral pulmonary arteries, and the agreement of 2 observers for detection of emboli in peripheral pulmonary arteries in different thickness images was tested. Chi-Square test was taken for comparison of 4 series of CTPA images for detection of emboli in peripheral pulmonary arteries. Kappa test was taken for the agreement of 2 observers for detection of emboli in peripheral pulmonary arteries.
Results: the average images number of 0.625 mm, 1.25 mm, 2.5 mm, 5.0 mm thickness imaging was 403, 201, 101, and 53, respectively. For detecting clots in segmental pulmonary arteries, there was statistically significant difference between 5.0 mm thick imaging and other 3 series imagings (chi(2) = 60.099, P < 0.01), but agreement of 2 observers in each series imaging was excellent (value of κ from 0.751 to 0.973).For clots in sub-segment pulmonary arteries, no statistical significant difference was observed between 0.625 mm and 1.25 mm thick imagings (chi(2) = 1.051, P > 0.05), and superior to 2.5 mm and 5.0 mm thick images (chi(2) = 151.892, 204.553, respectively, P < 0.01), but agreement of two observers in each series imaging was good (value of kappa from 0.611 to 0.935).
Conclusion: compared with 0.625 mm thick transaxial imaging, 1.25 mm thick MIP imaging is equally sensitive for detecting emboli in peripheral pulmonary arteries, but needs fewer images and less time for image reading.