Original Article
Spiral CT Angiography: Applications in Neurovascular Imaging Wg Cdr A Alam*, Gp Capt BN Chander+ Abstract Background : The advent of Spiral Computed Tomographic (CT) angiography has provided the patients a non-invasive, accurate and fast modality of imaging the vasculature. Methods : Spiral CT angiography was performed in 30 patients to evaluate intracranial circulation using standard protocols of data acquisition. The images were processed and reconstructed in 3-dimension to delineate anatomy and pathology accurately. Results : The study established that CT angiography is an accurate modality for evaluating the intracranial circulation in a variety of abnormalities. It is safe both in terms of being non-invasive and exposure to radiation. It has a distinct advantage over other non-invasive modalities of imaging like MRI in the evaluation of patients with metallic stents and clips. Conclusion : CT angiography has tremendous potential in imaging the intracranial vasculature. It is unquestionably safer than catheter angiography as it avoids arterial puncture and intra-arterial catheter manipulation. It is fast and capable of producing excellent 3-dimensional images of the intracranial vasculature. MJAFI 2006; 62 : 16-19 Key Words : Neurovascular imaging; Spiral CT; CT Angiography
Introduction atheter angiography has been the gold standard in imaging the neurovasculature. However it is expensive and invasive with an associated risk of 1.5 to 2% morbidity and mortality [1]. In addition, the results of catheter angiography are negative in 5-15% of patients with SAH as a result of a thrombosed aneurysm, vasospasm, poor vascular opacification or inadequate angiographic views [2]. These disadvantages of catheter angiography have lead to the development of alternative imaging techniques like Colour Flow Doppler Sonography and Magnetic Resonance Angiography (MRA). Colour Flow Doppler Sonography has been used in evaluation of extracranial carotid arteries; showing 92% accuracy [3]. This modality is operator dependent and cannot be used in the evaluation of the intracranial vasculature. MRA has disadvantages like longer imaging time leading to motion and pulsation artefacts, exaggeration of stenosis with inability to depict true lumen of vessels in areas of turbulence and poor demonstration of calcium. MRA requires the patient to be motion free for long periods of time, which may not be possible in patients with neurovascular disorders. Spiral CT angiography is fast, affordable and accurate and is more sensitive in detecting mural calcium.
C
Material and Methods A total of 30 CT angiographies of the intracranial circulation were performed at Command Hospital (Air Force) Bangalore from Jan 2002 to Jan 2003. The investigations were carried out on a Philips Tomoscan AV Spiral CT scanner with a gantry rotation period of one second. The procedure was explained to the patient and an informed consent obtained. A preliminary non-contrast axial CT scan with 10 mm collimation was done to study the brain parenchyma as well to localize the region of interest. After localization of the scan coverage, 90 ml of non-ionic contrast containing 300 mg of Iodine per ml was injected at a rate of 3 ml per second using a power injector. Subsequently volume scanning with a collimation of 1.5 mm and table speed of 2 mm/sec was started after a time delay of 14 to 16 seconds depending on the area being examined. For the circle of Willis a 16 sec delay was given whereas for the carotid bifurcation 14 sec delay was necessary. The axial images obtained were reconstructed at 1 mm intervals with segmented interpolation and a field of view of 18–20 cm. This yielded 180–200 images, which were then sent to a workstation where 3-dimensional reconstruction and vascular mapping was done using Shaded Surface Display (SSD) and Maximum Intensity Projection (MIP) protocols. Indications for performing CT angiography of the neurovascular tree are depicted in Table 1. Results The results of CT angiograms of 30 patients under study,
* Associate Professor (Radiodiagnosis & Imaging) Armed Forces Medical College Pune-411040, +Sr Adv (Radiodiagnosis & Imaging), Command Hospital (Air Force), Bangalore-560 007.
Received : 20.09.2003; Accepted : 16.05.2005
CT Angiography in Neurovascular Imaging
17
18 males and 12 females, were analysed and the abnormalities detected in various vascular territories are recorded in Table 2. A total of 30 CT angiograms of the intracranial circulation were performed out of which 9 were normal and 21 had various abnormalities. Subarachnoid haemorrhage and intracranial aneurysms comprised the largest group of patients who underwent CT angiography. Out of this group 7 patients had aneurysms in various parts like the Middle cerebral (Fig 1), Basilar, Posterior Communicating and Anterior Communicating arteries. 2 patients of arteriovenous malformation underwent CT angiography which confirmed a deep-seated right frontal arteriovenous malformation (Fig 2) in one and a left parietal arteriovenous malformation in the other. Vertebrobasilar dolichoectasia with fusiform aneurysm of the left vertebral artery and an intraluminal thrombus was seen in one patient who presented with features of vertebro-basilar insufficiency. 4 patients suspected of having Cerebral Venous Thrombosis were subjected to CT venography of the brain, of which 1 patient had thrombosis of the posterior aspect of the Superior Sagittal Sinus. Post-operative CT angiography was performed in 4 patients who had undergone clipping, 2 with aneurysms of the Middle Cerebral Artery and 2 with aneurysms of the Anterior Communicating Artery and the study revealed normal postoperative appearance in all (Fig 3). Pre operative CT angiography was performed in 4 patients
Fig. 1 : CT Angiography (MIP) showing a multilobulated aneurysm of the Lt Middle Cerebral artery.
Table 1 Clinical Indications for CT angiography (N=30) Indication Subarachnoid Haemorrhage Evaluation of intracranial aneurysms Evaluation of post clipping status of aneurysm Vertebro-basilar Dolichoectasia Post Embolisation follow up of AVM CT venography for Cerebral Venous thrombosis Vascularity of Intracranial tumours Evaluation of Arterio-venous malformations
No. of patients 5 6 4 1 4 4 4 2
Table 2 Analysis of results of CT Angiographic studies (N=30) Abnormality detected Aneurysm of Middle Cerebral Artery Basilar tip aneurysm Posterior Communicating Artery Aneurysm Anterior Communicating Aneurysm Normal post clipping status of aneurysm Vertebro-basilar Dolichoectasia Arterio-venous malformations Post Embolisation follow up of AVM Thrombosis of Superior Sagittal Sinus Highly vascular glioma Low grade vascular glioma Normal Cerebral CT venogram Normal Intracranial arteriogram MJAFI, Vol. 62, No. 1, 2006
No. of patients 2 1 2 2 4 1 2 2 1 2 2 3 6
Fig. 2 : CT Angiography (MIP) showing a deep seated Rt Frontal arterio-venous malformation.
with supratentorial gliomas to assess the vascularity of the tumour so as to determine grade of malignancy as well as map the arterial supply prior to surgery. Out of these 4 patients 2 had highly vascular parietal gliomas (Fig . 4) whereas the vascularity in the other 2 cases were of lesser grade.
Discussion Although catheter angiography is considered the gold standard in the evaluation of subarachnoid haemorrhage, it carries 1 % risk of complication and 0.5 % risk of persistent neurological deficit [4] and if performed within the first six hours of the initial bleed it carries an increased risk of rebleeding [5]. MR angiography is non invasive and accurate but is time consuming and not appropriate in an acute setting and presence of intramural calcium leads to creation of magnetic field in homogeneties with
18
Alam and Chander
Fig. 3 : CT angiography showing normal post clipped status of Rt Middle Cerebral Aneurysm.
resultant overestimation of stenosis. In subarachnoid haemorrhage, CT angiography has a sensitivity ranging from 87 to 100% and specificity of 50 to 100% in the detection of intracranial aneurysms [6]. Studies have revealed that CT angiography is equal to or even superior to catheter angiography in 83% of cases. In 74% of cases surgery is based on CT angiography findings alone without the need for catheter angiography [7]. CT angiography has a sensitivity of 87 to 97% in detecting aneurysm more than 5 mm in size [8] and provides a detailed analysis of the dome, neck, vessel of origin and the surrounding anatomy which is helpful in determining appropriate treatment option whether surgical or endovascular [9]. If endovascular treatment is contemplated it is mandatory that the precise anatomy of the aneurysm sac, information of presence of calcium, parent vessel calibre and their inter-relationship is also necessary as it directly influences the selection of embolisation material [10]. CT angiography is the best suited for evaluation of post clipping status of the aneurysms as it accurately depicts residual aneurysm filling, vascular patency of the artery and position of the clip relative to the desired placement site [11]. MR angiography is contraindicated in imaging of such cases due to the presence of metallic clips. The present study included 4 patients with aneurysm clips which revealed normal post op appearance with no filling of the aneurysm sac and aneurysm clips in situ. Intracranial arterio-venous malformations are being imaged with CT angiography although the role is limited as compared to catheter angiography [12]. Imaging of AVM’s need high temporal resolution of the arterial and
Fig. 4 : CT angiography showing a highly vascular Lt Parietal glioma.
venous phases to depict the feeding arteries, nidus and early draining veins. Such high degree of temporal resolution is lacking in CT angiography but is provided by catheter angiography. Today CT angiography is being used in the evaluation of the AVM nidus prior to radiosurgery planning and in follow- up of patients after surgical treatment [13]. In the present study 4 cases of AVM’s underwent CT angiography and in all the patients the feeding arteries with the early draining veins could be identified. Though CT angiography displays arterial feeders, nidus and draining veins together and it may be difficult to separate the nidus from the tangle of feeding arteries and early draining veins. Thus catheter angiography remains the gold standard in evaluation of AVM’s. Dural sinus thrombosis carries a high morbidity and hence requires early and accurate diagnosis. MR venography is the imaging modality of choice for diagnostic evaluation and follow up of dural venous thrombosis. However recent studies have shown that cerebral CT venography can be used in the identification of cerebral veins and dural sinuses and is comparable to MR venography in the diagnosis of dural sinus thrombosis [14]. In the present study 4 patients suspected of having Sinus thrombosis were subjected to CT venography and thrombosis of Superior Sagittal Sinus was confirmed in 1. Assessment of the vascularity of tumours is preferred prior to surgery so as to map the arterial feeders, evaluate MJAFI, Vol. 62, No. 1, 2006
CT Angiography in Neurovascular Imaging
the degree of vascularity to get an indication of the grade of malignancy and to assess the vascular encasement of skull base tumours. CT angiography with its advanced 3-dimensional images provides excellent pre-operative assessment of the bony and vascular anatomy and helps the surgeon to plan his surgical approach leading to considerable reduction in intra-operative time. CT angiography has proved to be an efficient and rapid method for evaluation of intracranial and the extracranial carotids in patients with stroke. A negative CT angiography may obivate catheter angiography. Intraarterial thrombolysis in acute ischaemic stroke has improved patient outcome and prognosis significantly [15]. To achieve this, the thrombus must be first identified and the involved arterial segment accurately mapped with CT angiography, which provides important information about the site of arterial occlusion, pattern of collaterals, location of the unenhanced/poorly perfused brain tissue and also the condition of the extracranial carotids. With continuing technological advancements like multislice technology, tube heads with greater heat storage capacity and enhanced- radiologist friendly post processing reconstruction techniques the potentials of CT angiography will expand further. However time will tell whether CT angiography would compete with contrast enhanced MR angiography, which is emerging as gold standard in vascular imaging. References 1. Waugh JR, Sacharia N. Arteriographic complications in the DSA era. Radiology 1992; 182: 243-6. 2. Villablanca JP, Jahan R, Hooshi P, et al. Detection and characterization of very small cerebral aneurysms by using 2D and 3D helical CT angiography. AJNR Am J Neuroradiol. 2002; 23:1187-98. 3. Dinkel HP, Moll R, Debus S. Colour flow Doppler ultrasound of the carotid bifurcation: Can it replace routine angiography
MJAFI, Vol. 62, No. 1, 2006
19 before carotid endarterectomy? Br J Radiol 2001; 74:590-4. 4. Heiserman JE, Dean BL, Hodak JA, Flom RA, Bird CR, Drayer BP et al. Neurologic complications of cerebral angiography. AJNR1994; 14:1401-7. 5. Saitoh H, Hayakawa K, Nishimura K, Okuno Y, Teraura T, Yumitori K et al. Re-rupture of cerebral aneurysms during angiography. AJNR1995; 16:539-42. 6. Alberico RA, Patel M, Casey S, Jacobs B, Maguire W, Decker R. Evaluation of the circle of Willis with three-dimensional CT angiography in patients with suspected intracranial aneurysms. AJNR 1995; 16:1571-8. 7. Velthuis BK, Rinkel GJ, Ramos LM, Witkamp TD, Van der Sprenkel JW, Vandertop WP et al. Subarachnoid haemorrhage. Aneurysm detection and preoperative evaluation with CT angiography. Radiology 1998; 208: 423-30. 8. Ogawa T, Okudera T, Noguchi K, Sasaki N, Inugami A, Uemura K et al. Cerebral aneurysms: evaluation with three-dimensional CT angiography. AJNR1996; 17:447-54. 9. Brown JH, Lustrin ES, Lev MH, Egilvy CS, Yaveras JM. Characterization of intracranial aneurysms using CT angiography. AJR 1997; 169: 889-93. 10. Congard C, Pierot L, Boulin A, Weill A, Tori M, Castings L et al. Intracranial aneurysms: endovascular treatment with mechanical detachable spirals in 60 aneurysms. Radiology1997; 202:783-92. 11. Vieco PT, Marin EE, Gross CE. CT angiography in the examination of patients with aneurysm clips. AJNR1996; 17:455-7. 12. Reiger J, Hoston N, Neuman K. Initial clinical experience with spiral CT and 3 D arterial reconstruction in intracranial aneurysm and arteriovenous malformations. Neuroradiology1996; 36: 245-51. 13. Schwartz RB. Helical CT in neuroradiologic diagnosis. Radiol Clin North Am1995; 33: 981-95. 14. Ozsvath RR, Casey SO, Lustrin ES, Alberico RA, Hassankhani A, Patel M. Cerebral venography: Comparison of CT & MR projection venography. AJR1997; 169: 1699-707. 15. Lanzieri CF, Tarr RW, Landis D, Selman WR, Lewin JS, Adler LP et al. Cost-effectiveness of emergency intra-arterial intracerebral thrombolysis: a pilot study. AJNR 1995; 16: 198793.
Spiral CT Angiography: Applications in Neurovascular Imaging Wg Cdr A Alam*, Gp Capt BN Chander+ Abstract Background : The advent of Spiral Computed Tomographic (CT) angiography has provided the patients a non-invasive, accurate and fast modality of imaging the vasculature. Methods : Spiral CT angiography was performed in 30 patients to evaluate intracranial circulation using standard protocols of data acquisition. The images were processed and reconstructed in 3-dimension to delineate anatomy and pathology accurately. Results : The study established that CT angiography is an accurate modality for evaluating the intracranial circulation in a variety of abnormalities. It is safe both in terms of being non-invasive and exposure to radiation. It has a distinct advantage over other non-invasive modalities of imaging like MRI in the evaluation of patients with metallic stents and clips. Conclusion : CT angiography has tremendous potential in imaging the intracranial vasculature. It is unquestionably safer than catheter angiography as it avoids arterial puncture and intra-arterial catheter manipulation. It is fast and capable of producing excellent 3-dimensional images of the intracranial vasculature. MJAFI 2006; 62 : 16-19 Key Words : Neurovascular imaging; Spiral CT; CT Angiography
Introduction atheter angiography has been the gold standard in imaging the neurovasculature. However it is expensive and invasive with an associated risk of 1.5 to 2% morbidity and mortality [1]. In addition, the results of catheter angiography are negative in 5-15% of patients with SAH as a result of a thrombosed aneurysm, vasospasm, poor vascular opacification or inadequate angiographic views [2]. These disadvantages of catheter angiography have lead to the development of alternative imaging techniques like Colour Flow Doppler Sonography and Magnetic Resonance Angiography (MRA). Colour Flow Doppler Sonography has been used in evaluation of extracranial carotid arteries; showing 92% accuracy [3]. This modality is operator dependent and cannot be used in the evaluation of the intracranial vasculature. MRA has disadvantages like longer imaging time leading to motion and pulsation artefacts, exaggeration of stenosis with inability to depict true lumen of vessels in areas of turbulence and poor demonstration of calcium. MRA requires the patient to be motion free for long periods of time, which may not be possible in patients with neurovascular disorders. Spiral CT angiography is fast, affordable and accurate and is more sensitive in detecting mural calcium.
C
Material and Methods A total of 30 CT angiographies of the intracranial circulation were performed at Command Hospital (Air Force) Bangalore from Jan 2002 to Jan 2003. The investigations were carried out on a Philips Tomoscan AV Spiral CT scanner with a gantry rotation period of one second. The procedure was explained to the patient and an informed consent obtained. A preliminary non-contrast axial CT scan with 10 mm collimation was done to study the brain parenchyma as well to localize the region of interest. After localization of the scan coverage, 90 ml of non-ionic contrast containing 300 mg of Iodine per ml was injected at a rate of 3 ml per second using a power injector. Subsequently volume scanning with a collimation of 1.5 mm and table speed of 2 mm/sec was started after a time delay of 14 to 16 seconds depending on the area being examined. For the circle of Willis a 16 sec delay was given whereas for the carotid bifurcation 14 sec delay was necessary. The axial images obtained were reconstructed at 1 mm intervals with segmented interpolation and a field of view of 18–20 cm. This yielded 180–200 images, which were then sent to a workstation where 3-dimensional reconstruction and vascular mapping was done using Shaded Surface Display (SSD) and Maximum Intensity Projection (MIP) protocols. Indications for performing CT angiography of the neurovascular tree are depicted in Table 1. Results The results of CT angiograms of 30 patients under study,
* Associate Professor (Radiodiagnosis & Imaging) Armed Forces Medical College Pune-411040, +Sr Adv (Radiodiagnosis & Imaging), Command Hospital (Air Force), Bangalore-560 007.
Received : 20.09.2003; Accepted : 16.05.2005
CT Angiography in Neurovascular Imaging
17
18 males and 12 females, were analysed and the abnormalities detected in various vascular territories are recorded in Table 2. A total of 30 CT angiograms of the intracranial circulation were performed out of which 9 were normal and 21 had various abnormalities. Subarachnoid haemorrhage and intracranial aneurysms comprised the largest group of patients who underwent CT angiography. Out of this group 7 patients had aneurysms in various parts like the Middle cerebral (Fig 1), Basilar, Posterior Communicating and Anterior Communicating arteries. 2 patients of arteriovenous malformation underwent CT angiography which confirmed a deep-seated right frontal arteriovenous malformation (Fig 2) in one and a left parietal arteriovenous malformation in the other. Vertebrobasilar dolichoectasia with fusiform aneurysm of the left vertebral artery and an intraluminal thrombus was seen in one patient who presented with features of vertebro-basilar insufficiency. 4 patients suspected of having Cerebral Venous Thrombosis were subjected to CT venography of the brain, of which 1 patient had thrombosis of the posterior aspect of the Superior Sagittal Sinus. Post-operative CT angiography was performed in 4 patients who had undergone clipping, 2 with aneurysms of the Middle Cerebral Artery and 2 with aneurysms of the Anterior Communicating Artery and the study revealed normal postoperative appearance in all (Fig 3). Pre operative CT angiography was performed in 4 patients
Fig. 1 : CT Angiography (MIP) showing a multilobulated aneurysm of the Lt Middle Cerebral artery.
Table 1 Clinical Indications for CT angiography (N=30) Indication Subarachnoid Haemorrhage Evaluation of intracranial aneurysms Evaluation of post clipping status of aneurysm Vertebro-basilar Dolichoectasia Post Embolisation follow up of AVM CT venography for Cerebral Venous thrombosis Vascularity of Intracranial tumours Evaluation of Arterio-venous malformations
No. of patients 5 6 4 1 4 4 4 2
Table 2 Analysis of results of CT Angiographic studies (N=30) Abnormality detected Aneurysm of Middle Cerebral Artery Basilar tip aneurysm Posterior Communicating Artery Aneurysm Anterior Communicating Aneurysm Normal post clipping status of aneurysm Vertebro-basilar Dolichoectasia Arterio-venous malformations Post Embolisation follow up of AVM Thrombosis of Superior Sagittal Sinus Highly vascular glioma Low grade vascular glioma Normal Cerebral CT venogram Normal Intracranial arteriogram MJAFI, Vol. 62, No. 1, 2006
No. of patients 2 1 2 2 4 1 2 2 1 2 2 3 6
Fig. 2 : CT Angiography (MIP) showing a deep seated Rt Frontal arterio-venous malformation.
with supratentorial gliomas to assess the vascularity of the tumour so as to determine grade of malignancy as well as map the arterial supply prior to surgery. Out of these 4 patients 2 had highly vascular parietal gliomas (Fig . 4) whereas the vascularity in the other 2 cases were of lesser grade.
Discussion Although catheter angiography is considered the gold standard in the evaluation of subarachnoid haemorrhage, it carries 1 % risk of complication and 0.5 % risk of persistent neurological deficit [4] and if performed within the first six hours of the initial bleed it carries an increased risk of rebleeding [5]. MR angiography is non invasive and accurate but is time consuming and not appropriate in an acute setting and presence of intramural calcium leads to creation of magnetic field in homogeneties with
18
Alam and Chander
Fig. 3 : CT angiography showing normal post clipped status of Rt Middle Cerebral Aneurysm.
resultant overestimation of stenosis. In subarachnoid haemorrhage, CT angiography has a sensitivity ranging from 87 to 100% and specificity of 50 to 100% in the detection of intracranial aneurysms [6]. Studies have revealed that CT angiography is equal to or even superior to catheter angiography in 83% of cases. In 74% of cases surgery is based on CT angiography findings alone without the need for catheter angiography [7]. CT angiography has a sensitivity of 87 to 97% in detecting aneurysm more than 5 mm in size [8] and provides a detailed analysis of the dome, neck, vessel of origin and the surrounding anatomy which is helpful in determining appropriate treatment option whether surgical or endovascular [9]. If endovascular treatment is contemplated it is mandatory that the precise anatomy of the aneurysm sac, information of presence of calcium, parent vessel calibre and their inter-relationship is also necessary as it directly influences the selection of embolisation material [10]. CT angiography is the best suited for evaluation of post clipping status of the aneurysms as it accurately depicts residual aneurysm filling, vascular patency of the artery and position of the clip relative to the desired placement site [11]. MR angiography is contraindicated in imaging of such cases due to the presence of metallic clips. The present study included 4 patients with aneurysm clips which revealed normal post op appearance with no filling of the aneurysm sac and aneurysm clips in situ. Intracranial arterio-venous malformations are being imaged with CT angiography although the role is limited as compared to catheter angiography [12]. Imaging of AVM’s need high temporal resolution of the arterial and
Fig. 4 : CT angiography showing a highly vascular Lt Parietal glioma.
venous phases to depict the feeding arteries, nidus and early draining veins. Such high degree of temporal resolution is lacking in CT angiography but is provided by catheter angiography. Today CT angiography is being used in the evaluation of the AVM nidus prior to radiosurgery planning and in follow- up of patients after surgical treatment [13]. In the present study 4 cases of AVM’s underwent CT angiography and in all the patients the feeding arteries with the early draining veins could be identified. Though CT angiography displays arterial feeders, nidus and draining veins together and it may be difficult to separate the nidus from the tangle of feeding arteries and early draining veins. Thus catheter angiography remains the gold standard in evaluation of AVM’s. Dural sinus thrombosis carries a high morbidity and hence requires early and accurate diagnosis. MR venography is the imaging modality of choice for diagnostic evaluation and follow up of dural venous thrombosis. However recent studies have shown that cerebral CT venography can be used in the identification of cerebral veins and dural sinuses and is comparable to MR venography in the diagnosis of dural sinus thrombosis [14]. In the present study 4 patients suspected of having Sinus thrombosis were subjected to CT venography and thrombosis of Superior Sagittal Sinus was confirmed in 1. Assessment of the vascularity of tumours is preferred prior to surgery so as to map the arterial feeders, evaluate MJAFI, Vol. 62, No. 1, 2006
CT Angiography in Neurovascular Imaging
the degree of vascularity to get an indication of the grade of malignancy and to assess the vascular encasement of skull base tumours. CT angiography with its advanced 3-dimensional images provides excellent pre-operative assessment of the bony and vascular anatomy and helps the surgeon to plan his surgical approach leading to considerable reduction in intra-operative time. CT angiography has proved to be an efficient and rapid method for evaluation of intracranial and the extracranial carotids in patients with stroke. A negative CT angiography may obivate catheter angiography. Intraarterial thrombolysis in acute ischaemic stroke has improved patient outcome and prognosis significantly [15]. To achieve this, the thrombus must be first identified and the involved arterial segment accurately mapped with CT angiography, which provides important information about the site of arterial occlusion, pattern of collaterals, location of the unenhanced/poorly perfused brain tissue and also the condition of the extracranial carotids. With continuing technological advancements like multislice technology, tube heads with greater heat storage capacity and enhanced- radiologist friendly post processing reconstruction techniques the potentials of CT angiography will expand further. However time will tell whether CT angiography would compete with contrast enhanced MR angiography, which is emerging as gold standard in vascular imaging. References 1. Waugh JR, Sacharia N. Arteriographic complications in the DSA era. Radiology 1992; 182: 243-6. 2. Villablanca JP, Jahan R, Hooshi P, et al. Detection and characterization of very small cerebral aneurysms by using 2D and 3D helical CT angiography. AJNR Am J Neuroradiol. 2002; 23:1187-98. 3. Dinkel HP, Moll R, Debus S. Colour flow Doppler ultrasound of the carotid bifurcation: Can it replace routine angiography
MJAFI, Vol. 62, No. 1, 2006
19 before carotid endarterectomy? Br J Radiol 2001; 74:590-4. 4. Heiserman JE, Dean BL, Hodak JA, Flom RA, Bird CR, Drayer BP et al. Neurologic complications of cerebral angiography. AJNR1994; 14:1401-7. 5. Saitoh H, Hayakawa K, Nishimura K, Okuno Y, Teraura T, Yumitori K et al. Re-rupture of cerebral aneurysms during angiography. AJNR1995; 16:539-42. 6. Alberico RA, Patel M, Casey S, Jacobs B, Maguire W, Decker R. Evaluation of the circle of Willis with three-dimensional CT angiography in patients with suspected intracranial aneurysms. AJNR 1995; 16:1571-8. 7. Velthuis BK, Rinkel GJ, Ramos LM, Witkamp TD, Van der Sprenkel JW, Vandertop WP et al. Subarachnoid haemorrhage. Aneurysm detection and preoperative evaluation with CT angiography. Radiology 1998; 208: 423-30. 8. Ogawa T, Okudera T, Noguchi K, Sasaki N, Inugami A, Uemura K et al. Cerebral aneurysms: evaluation with three-dimensional CT angiography. AJNR1996; 17:447-54. 9. Brown JH, Lustrin ES, Lev MH, Egilvy CS, Yaveras JM. Characterization of intracranial aneurysms using CT angiography. AJR 1997; 169: 889-93. 10. Congard C, Pierot L, Boulin A, Weill A, Tori M, Castings L et al. Intracranial aneurysms: endovascular treatment with mechanical detachable spirals in 60 aneurysms. Radiology1997; 202:783-92. 11. Vieco PT, Marin EE, Gross CE. CT angiography in the examination of patients with aneurysm clips. AJNR1996; 17:455-7. 12. Reiger J, Hoston N, Neuman K. Initial clinical experience with spiral CT and 3 D arterial reconstruction in intracranial aneurysm and arteriovenous malformations. Neuroradiology1996; 36: 245-51. 13. Schwartz RB. Helical CT in neuroradiologic diagnosis. Radiol Clin North Am1995; 33: 981-95. 14. Ozsvath RR, Casey SO, Lustrin ES, Alberico RA, Hassankhani A, Patel M. Cerebral venography: Comparison of CT & MR projection venography. AJR1997; 169: 1699-707. 15. Lanzieri CF, Tarr RW, Landis D, Selman WR, Lewin JS, Adler LP et al. Cost-effectiveness of emergency intra-arterial intracerebral thrombolysis: a pilot study. AJNR 1995; 16: 198793.
