cerebral aneurysms accuracy of 320detector row nonsubtracted and subtracted volumetric ct angiography for diagnosis purpose to assess the accuracy of 320detector row nonsubtracted and subtracted volumetric computed tomographic ct angiography for detection of cerebral aneurysmsmaterials and methods after institutional review board approval and informed written consent were obtained 282 consecutive patients suspected of having cerebral aneurysms underwent ct angiography with a 320detector row volumetric ct scanner and threedimensional 3d rotational digital subtraction angiography dsa the sensitivity specificity and accuracy of nonsubtracted and subtracted volumetric ct angiography for depiction of aneurysms were analyzed with 3d dsa as the reference standard p values less than 05 were considered to indicate a significant differenceresults among the 282 patients 198 702 had 239 cerebral aneurysms that were detected on the basis of 3d dsa nonsubtracted volumetric ct angiography showed 231 of the 239 967 aneurysms the primary reason for missed aneurysms was close proximity to bone tissue sensitivity specificity and accuracy of nonsubtracted volumetric ct angiography for depicting aneurysms were 967 100 and 975 respectively on a peraneurysm basis subtracted volumetric ct angiography showed 237 of 239 992 aneurysms sensitivity specificity and accuracy of subtracted volumetric ct angiography for depicting aneurysms were 992 100 and 994 respectively on a peraneurysm basis there was no statistically significant difference in accuracy between subtracted volumetric ct angiography and 3d dsa p 500 however nonsubtracted volumetric ct angiography was significantly less sensitive than 3d dsa and subtracted volumetric ct angiography p 031 and 008 respectivelyconclusion subtracted 320detector row volumetric ct angiography provides excellent sensitivity for detection of cerebral aneurysms and should be the firstline imaging technique for the noninvasive evaluation of aneurysms the accuracy of nonsubtracted volumetric ct angiography was lower than that for subtracted volumetric ct angiography especially for aneurysms adjacent to bone tissue