OPTIMIZATION OF PARAMETERS FOR THE DETECTION OF CEREBRAL ANEURYSMS - CT ANGIOGRAPHY OF A MODEL

PURPOSE: To optimize parameters with computed tomographic angiography for the detection of cerebral aneurysms. MATERIALS AND METHODS: Model aneurysms were placed randomly at various branch points and scanned mu ltiple times with spiral technique. The final analysis included 63 bra nch points and 22 aneurysms. Each spiral scan used a different paramet er combination. Collimation ranged from 1.5 to 4.0 mm and pitch ranged from 1:1 to 1.5:1. Images were constructed with shaded surface displa y (SSD) and maximum intensity projection (MIP) algorithms and were int erpreted by three readers for the presence or absence of aneurysm. RES ULTS: The receiver operating area for 1.5-mm collimation was greater t han those of 3- or 4-mm collimation (P < .01 and P < .001, respectivel y). There was no statistically significant difference in the ROC curve areas between 3- and 4-mm collimation (P = .37). There was no statist ically significant decrease in ROC curve area when increasing pitch fr om 1:1 to 1.5:1 for any value of collimation (P = .96). For all parame ter combinations the ROC curve areas for SSD images was greater than t hat of MIP images (P < .0001). CONCLUSION: For cerebral aneurysm detec tion, narrow collimation is superior to wider collimation. Mild increa ses in pitch do not substantially degrade diagnostic accuracy. SSD off ers improved diagnostic accuracy over MIP display in this model.