M. Remy-jardin et al., Thoracic helical CT: influence of subsecond scan time and thin collimationon evaluation of peripheral pulmonary arteries, EUR RADIOL, 10(8), 2000, pp. 1297-1303
The objective of this study was to analyze the influence of collimation on
the identification of peripheral pulmonary arteries on helical CT scans. Th
ree hundred sixty of 370 consecutive helical CT angiograms of the pulmonary
circulation obtained during an 18-month investigation period were consider
ed as technically acceptable for the detection of acute pulmonary embolism
and were retrospectively analyzed. Patients in group A (n = 274) underwent
CT with 2-mm collimation and pitch of 2; those in group B (n = 86) underwen
t CT with 3-mm collimation and pitch 1.7; a 0.75-s rotation time was system
atically used. A total of 2160 segmental (six arterial zones per patient) a
nd 2160 subsegmental (sii arterial zones per patient) arterial zones were a
ssessed. Whereas the percentage of segmental arteries was not significantly
different between group A (86 %) and group B (89 %), the percentage of ana
lyzable subsegmental arteries was greater in group A (65 %) than in group B
(43 %) (P < 0.001). The causes of inadequately depicted subsegmental arter
ial zones were partial-volume effects (group A, n = 302; 52 %; group B, n =
197; 67 %; P < 0.001), suboptimal enhancement (group A, n = 145; 25 %; gro
up B, n = 43; 15 %; P < 0.05), motion artifacts (group A, n = 113; 20 %; gr
oup B, n = 30; 10 %), and unincluded arteries (group A, n = 20, 3 %; group
B, n = 25; 8 %). Helical CT with 3-mm collimation at 0.75 s per revolution
enables marked improvement in the analysis of subsegmental arteries in rout
ine clinical practice.