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Abstract
The aim of this work was to assess the role of multi-detector computerized tomographic angiography (CTA) and magnetic resonance angiography (MRA) in cases of aneurysmal subarachnoid hemorrhage
All Patients were subjected to complete history taking, thorough clinical assessment, CT axial scans and CT angiography, using multi-slice reconstruction, maximum intensity projection (MIP) and/or three dimensional (3D) rendering volume techniques to gather with MRI Axial T2 Flair and MR angiography. The CT and CTA images were analyzed separately by two expert neuro-radiologists blinded to any other angiographic data. The same was applied to MRI and MRA images by same expert neuro-radiologist. Finally the CT, CTA, MRI and MRA were analyzed together supported by angiographic and surgical data.
The fifty patients included in this study harbored sixty three aneurysms by the consensus of accumulated data of the performed CT, CTA, MRI and MRA and compared by the available angiographic techniques combined together as well as the available surgical data as a gold standard. The anterior communicating artery was the most frequent site involved by aneurysms, followed by middle cerebral artery and its branches, the internal carotid artery and its segment, posterior communicating artery, basilar artery and pericallosal artery.
The CTA correctly detected 61 aneurysms out of those 63 aneurysms while MRA by correctly detected 55 aneurysms out of those 63 aneurysms, during combined reading sessions, on retrograde basis, two additional aneurysms were detected on MRA reaching 57 aneurysms out of 63 aneurysms
MRA could not detect 8 aneurysms, this was attributed to small size of aneurysm, small sized aneurysms in cases harboring multiple aneurysms, small sized aneurysm combined with AVM in same case, late subacute SAH and intracerebral hematoma masking aneurysm, technical factors including patient instability due to bad general condition as well as peripheral location of aneurysms out of MRI field of interst.
MRI axial images were appreciated when combined with MRA images for increasing detectability of aneurysms, MRI was superior to MRA in detecting two aneurysms, not detected by MRA (3.2%) including: 2 Acom aneurysms detected only at T2WI as signal void, due to the effect of late subacute hematoma masked its adequate detection at MRA sequences, and the other Acom aneurysm its small size and cerebral hematoma masked its adequate detection at MRA sequences. MRI was superior to MRA in four aneurysms (6.3%), detected by MRI and MRA, however MRI sequences were superior to MRA in adequate aneurysms characterization, detection of aneurysmal thrombosis , their size as well as assessment of their relation with surrounding cerebral structures, these aneurysms were, giant Pcom aneurysm , MRI sequences delineate actual aneurysmal size better than MRA sequences, Basilar artery fusiform aneurysm of partially thrombosed lumen, Basilar trunk aneurysm measures 21.3 mm, and Cavernous portion giant ICA aneurysm.
Sensitivity of CTA was (96.8%) higher than that of MRA (87.3%) in aneurysmal detection, but both modalities showed lower sensitivity for detection of aneurysms below or equal 3 mm, while diagnostic performance of CTA and MRA for detection of aneurysms larger than 5 mm was excellent in patients with acute SAH.
CTA was superior to MRA in adequate characterization of detected aneurysms, and in fulfilling the pre-requisites for surgical planning including detection of aneurysmal partial thrombosis, aneurysmal calcifications, delineation of aneurysmal neck and shape as well as 3D-CT angiography was superior than MRA in understand the configurations of the aneurysm and its relationship to the skull which was helpful for making decisions on the most appropriate surgical approach and aneurysmal orientation during operation aided by 3D-CT angiography alone without conventional angiography. MRA on the contrary was better than CTA in detection of small aneurysms located near skull base.
Considering the clinical point of view as well as patient respect, we found that combining the two non invasive imaging techniques included in our study cannot yet replace IADSA in the detection of small and very small aneurysms as well as combining both non invasive modalities will not significantly increases sensitivity for aneurysmal detection, but this was factor for time consumption in patient considered to be in acute medical or surgical condition.
So we concluded that Intra-arterial digital subtraction angiography is still the golden standard for diagnosis of aneurysmal subarachnoid hemorrhage but it is invasive technique and of high detectability for aneurysmal size less than 3 mm.
CTA and MRA provide several advantages over digital subtraction angiography. These include availability, reduced cost, avoidance of arterial injury and stroke, rapid acquisition and retrospective manipulation of data.
CTA and MRA are two non invasive imaging modalities for detection of cerebral aneurysms, but their sensitivity is low for aneurysms less than 3 mm. putting in consideration, that aneurysms less than 3 mm are not commonly liable to rupture. CTA is better than MRA in detectability of small aneurysms more than 3 mm and less than 5 mm however both had good detectability for aneurysms above 5 mm
In emergency cases which require immediate operation, CTA can provide the adequate information needed for surgical treatment.
Although CTA or MRA are good positive (sensitive) modalities in detection of aneurysms in cases of subarachnoid hemorrhage, yet these modalities are not good negative (specific), so that at negative CTA or MRA studies in cases of aneurysmal subarachnoid hemorrhage, may raise the need to a second step procedure , which is digital subtraction angiography.