Kallmes DF, Evans AJ, Woodcock RJ, Omary RA, Dix JE, McNulty BC, Holder
CA, Dion JE
Department of Radiology, University of Virginia Health Sciences Center,
Charlottesville 22908, USA.
Title
Optimization of parameters for the detection of cerebral
aneurysms: CT angiography of a model.
Source
Radiology 1996 Aug;200(2):403-405
Abstract
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 multiple
times with spiral technique. The final analysis included 63 branch points and 22
aneurysms. Each spiral scan used a different parameter 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 display (SSD) and maximum intensity projection
(MIP) algorithms and were interpreted by three readers for the presence or absence
of aneurysm. RESULTS: The receiver operating characteristic (ROC) curve area for
1.5-mm collimation was greater than those of 3- or 4-mm collimation (P < .01
and P < .001, respectively). There was no statistically significant difference in the
ROC curve areas between 3- and 4-mm collimation (P = .37). There was no
statistically significant decrease in ROC curve area when increasing pitch from 1:1
to 1.5:1 for any value of collimation (P = .96). For all parameter combinations the
ROC curve areas for SSD images was greater than that of MIP images (P < .0001).
CONCLUSION: For cerebral aneurysm detection, narrow collimation is superior to
wider collimation. Mild increases in pitch do not substantially degrade diagnostic
accuracy. SSD offers improved diagnostic accuracy over MIP display in this model.