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Title of the article: DIAGNOSIS OF A RUPTURED CEREBRAL ANEURYSM ON 128 SLICE
CT CEREBRAL ANGIOGRAPHY
Abstract:Conventional angiography is the gold standard for detecting cerebral aneurysm but
multisclice CT cerebral angiography has gained significant role in diagnosing cerebral
aneurysms because of its non invasive nature and increasing sensitivity to detect aneurysms
owing to latest technological advances.We report a case of ruptured cerebral aneurysm
diagnosed on 128 slice CT cerebral angiography with intraoperative correlation.
Key-words:128 slice CT cerebral angiography , aneurysms.
Text
Introduction: Digital subtraction angiography (DSA) has been the standard of reference for
the detection and characterization of intracranial aneurysms because of its high spatial
resolution and large field of view, but it has the disadvantage of being invasive and operator
dependent. As a result of recent innovations in CT scanner and workstation technology,
Computed Tomographic Angiography(CTA) has become a useful, noninvasive imaging
technique for evaluating cerebrovascular disease and can be first line investigation where
CTA is available. We report a case of ruptured intracranial aneurysm detected on 128 slice
CT cerebral Angiography with intraoperative correlation.
Case History:
A sixty four year old female with a acute history of severe headache and diagnosed as
suffering from acute subarachnoid haemorrhage on plain CT, was referred for CT cerebral
angiography for detection of ruptured cerebral aneurysms if any. CT cerebral angiography
was performed on our 128 slice CT scanner. 60 ml of non-ionic contrast
(OMNIPAQUE,350mg/ml) and 25 ml of saline was infused through antecubital vein with
power injector and bolus tracking was used to initiate scanning. Both arterial and venous
phase were taken. Acquired images were analysed at PHILIPS BRILLIANCE Workstation.
Images were viewed in multiple views and 3D reconstruction. A diagnosis of ruptured
aneurysm arising from supraclinoid portion of left internal carotid artery was made(Figures 1
& 2). These findings were confirmed and intraoperatively an aneurysm clip was positioned
at the site of aneurysm. Postoperative CT cerebral angiography was performed to know
status of the clip and aneurysm(Figure 3 & 4). There were no complications after surgery.
Discussion: One of the most important causes of subarachnoid haemorrhage is ruptured
cerebral aneurysm .Cerebral digital subtraction angiography has been used as the gold
standard for aneurysm detection.[7,10,11,14] However, DSA has the disadvantage of being an
invasive study. The risk of acquiring a permanent neurologic deficit with cerebral
angiography in patients with subarachnoid haemorrhage is around 0.1%.[1,2,3]. Computed
tomographic cerebral angiography is a noninvasive imaging modality that is being
increasingly used for the evaluation of suspected intracranial aneurysms. The introduction of
64 slice and 128 slice CT scanners has greatly advanced the role of CT angiography in
neurovascular imaging[4,5,6].
The technique of CT angiography entails fast thin section
volumetric spiral CT examination performed with a time optimized bolus of contrast
medium.[13] The examination usually includes the region from the first vertebral body up to
the vertex. Patient stabilisation on gantry couch is of utmost importance. A bolus tracking
method is used routinely to achieve optimal synchronization of contrast medium flow and
scanning. Once the injection is started, the bolus tracking software measures attenuation
values within one internal carotid artery and the spiral scan is automatically started as soon
as a the desired threshold is exceeded. If bolus tracking is not available, the test bolus
technique can be applied. Usually 70-80 ml of non-ionic contrast material is administered
followed by a saline chase. Once the source images are acquired, CT angiography data
can be evaluated by variety of techniques .The most widely used techniques are multiplanar
reformation (MPR), thin-slab maximum intensity projection(MIP) and volume rendering.
Sophisticated segmentation algorithms, vessel analysis tools and automatic lumen boundary
definition are established techniques. Bone removal with thresholding or subtraction
algorithms is available. Direct volume rendering (dVR) is the most sophisticated method for
3D visualization.
Aneurysm if identified is characterised according to shape as
saccular, lobulated or fusiform. Signs of aneurysmal rupture like lobulated appearance, tit
sign or contrast extravasation are documented. Imaging after surgical aneurysm clipping has
traditionally been achieved with conventional catheter-based angiography. CT angiography
may provide an acceptable alternative in many cases[17].It can often effectively depict
aneurysm remnants, demonstrate patency, stenosis, or vasospasm in the adjacent parent
vessels. . Accurate detection and characterization of intracranial aneurysms is an essential
prerequisite for surgical treatment planning.
Pitfalls of CT angiography include lack of visibility of small arteries, difficulty in
differentiating the infundibular dilatation at the origin of an artery from an aneurysm, the
kissing vessel artifact, demonstration of venous structures that can simulate aneurysms,
inability to identify thrombosis and calcification on three-dimensional images, and beam
hardening artifacts produced by aneurysm clips. When performing CT angiography for the
detection and therapy planning of intracranial aneurysms, knowledge about several potential
pitfalls is essential. Small perforating arteries with a diameter below 0.5 mm are not visible on
CT angiograms[13,15].
Recent studies found higher overall detection rates of up to 97%, and some
authors already solely rely on the findings of CT angiography in patients with subarachnoid
haemorrhage.[13] Imaging after surgical aneurysm clipping has traditionally been achieved
with conventional catheter-based angiography, CT angiography (CTA) may provide an
acceptable alternative in many cases[8,9]
Digital subtraction CT angiography can be the preferred noninvasive
modality for the evaluation of intracranial aneurysms in patients with acute subarachnoid
haemorrhage because of its high diagnostic accuracy, short scan time and
noninvasiveness[14,15,16]. Negative CT angiography findings in a patient with SAH must
always be corroborated with DSA. In conclusion CTA is an accurate imaging technique for
detection and characterization of intracranial aneurysms and has the potential to substitute,
in most cases, for DSA.
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