1	Effectiveness of multidetector computed tomographic angiography (CTA) in detecting cerebral aneurysms Gregory Christoforidis¹J, H. Wayne Slone¹, Kurt Husum¹, Ed Kim¹, Ming Yang¹, John McGregor² Departments of ¹Radiology and ²Neurosurgery
2	Overview Introduction Aneurysm detection with CTA Detection rate of aneurysms using CTA Evaluation of aneurysm using CTA Advantages and Disadvantages of DSA and CTA Example cases Survey of physicians who treat aneurysms Conclusion
3	Introduction Aneurysms are reported to have a 3-6% prevalence in the general population. Because they are the most common cause of spontaneous subarachnoid hemorrhage, which has a 60% mortality rate, their detection is in as least invasive a fashion. In addition, imaging information may help direct and optimize treatment
4	Examples of two multidetector techniques published in the literature and OSU.
5	Detection rate of Aneurysms using CTA The detection of aneurysms using CTA has been reviewed in the literature the next slide contains a table listing various studies and the sensitivity and specificity for the detection of aneurysms. The studies vary in the techniques used including bolus injection techniques, postprocessing, and methods of review. More recent studies by enlarge use multidetector CT to visualize aneurysms. It becomes apparent reviewing this table that CTA is a useful means for the detection of aneurysms with few false negatives and positives. Some of the authors indicate that review of CTAs with false negatives, retrospectively the aneurysm could be identified.
6	Detection rate of Aneurysms using CTA Reasons given for false negatives and positives Reviewer inexperience Small aneurysm size (<4mm) Technical issues patient motion poor contrast injection parameters used
7	Detection rate of Aneurysms using CTA
8	Review of 2D source images 3D CTA and DSA in 75 patients with 68 aneurysm by 2 reviewers at our institution indicate that review of 2D images in all 3 planes may help in the detection of aneurysms. (Average interpretation time in seconds is in parentheses)
9	Detection rate of Aneurysms using CTA Methods which may help identify aneurysms on CTA include Scrutiny of the expected locations for aneurysm Meticulous review of the 3D CTA as well as 2D reconstructions in multiple planes. Although time consuming this review helps reduce false negatives If a study is technically poor the interpreting physician may have to repeat the study or perform DSA.
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11	Evaluation of aneurysms on CTA CTA has also been touted to allow delineate aneurysm neck, shape, orientation, relationship to the parent vessel, and relationship to adjacent bony structures. This information is useful for treatment planning. DSA can provide useful information regarding origins of small vessels in relation to an aneurysm such as the relationship of the anterior choroidal artery as it relates to an aneurysm along the communicating segment of the internal carotid artery. CTA is not as sensitive to small vessel.
12	Expected aneurysm locations
13	CTA Advantages Disadvantages Ability to visualize vessels relative to adjacent structure Aneurysm to parent vessel relationship Low risk procedure Images can be obtained rapidly Spatial resolution limited Review of study requires careful analysis of both 3D images and 2D images which prolongs interpretation time Can’t repeat exam rapidly if technique is poor Susceptible to bone and metal artifacts
14	DSA Advantages Disadvantages Aneurysm to parent vessel relationship Able to repeat image acquisition Higher resolution allows for better visualization of small vessels that may affect treatment approach Gives information on circulation time Not as limited by metal artifact as CTA Study requires more skill to acquire Higher complication rate than CTA Does no visualize adjacent structures as readily
15	Example cases displaying advantages and disadvantages of CTA and DSA
16	Right internal carotid arteriogram arterial (A) and venous (B) phases demonstrating a mycotic aneurysm (arrow) off the posterior temporal branch of the posterior cerebral artery. The persistant stagnation of contrast within the aneurysm cannot be realized on CTA.
17	CTA with 3D (A) and axial source image (B) of mycotic aneurysm (arrows) off the posterior temporal artery. Note the halo of edema surrounding the aneurysm. While the aneurysm and its parent vessel are identified, its exact relationship to the parent vessel is better appreciated on DSA
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24	Survey We surveyed a neurosurgeon who performs aneurysm treatment using craniotomy and an interventional neuroradiologist with regards to CTA. The answers to three questions are in the the slides that follow.
25	Survey results: Did the CTA give you a better, equal or lesser appreciation of the relationship of the parent vessel to the aneurysm? Neurosurgery: Equal to DSA in most but not all cases. I prefer DSA Interventional Neuroradiologist: It simplified angiographic visualization, Now with 3D DSA it is becoming a moot point. I rely on angiography for this purpose.
26	Survey results: Did the CTA give you a better, equal or lesser appreciation of the relationship of the bony landmarks to the aneurysm? Neurosurgery: Much better Interventional Neuroradiologist: No question CTA is better
27	Survey results: Do you feel that CTA provided additional information? Neurosurgery: yes Interventional Neuroradiologist: yes
28	Conclusion When imaging cerebral aneurysms, CTA provides complimentary information relative to conventional angiography. Although CTA can be used as an initial screen for aneurysms and thus may help guide initial treatment, ultimately DSA answers additional quesitons that the treating physician may have.