Introduction 1 2 3 4 6 4 7 8 9 14 Materials and methods Subjects Between April 2003 and January 2006 all patients presenting with a SAH to the University Medical Centre Groningen consecutively underwent CTA as the first diagnostic study. Based on the CTA findings, patients were selected for surgical clipping or endovascular coiling of a ruptured intracranial aneurysm. SAH was suspected on clinical grounds and confirmed by unenhanced CT or by blood pigments on lumbar puncture. Imaging protocols The CT examinations were performed on a 16- or 64-multidetector row spiral CT machine (Somatom Sensation 16 or 64; Siemens Medical Systems, Erlangen, Germany), based on a standard protocol. The 64-multisclice CT was implemented in the Emergency Department in December 2004. Parameters for 16-slice CT for diagnosis of aneurysm Parameters for 16-slice CT for diagnosis of SAH Parameters for 64-slice CTA for diagnosis of aneurysm Parameters for 64-slice CT for diagnosis of SAH Postprocessing of CTA Source images were transferred to a remote computer workstation (Odelft Benelux diagnostic imaging) for viewing. Initial careful review of axial images was considered imperative. During this review any areas of concern could be noted. Two-dimensional maximum intensity projection (MIP) views and three-dimensional (3-D) surface-rendered and volume-rendered reconstructions were reformatted from the raw image date on a Vitrea computer workstation by one of the neuroradiologists. Parameters for IA-DSA and postprocessing From April 2003 until April 2004 the IA-DSA studies were produced on a digital angiographic unit (Siemens Multiskop with InfiMed image processing) with a 512×512 pixel matrix. From April 2004 onwards the studies were performed on a Siemens Axiom Artis angiographic unit with a 1024×1024 pixel matrix. Selective four- or six-vessel angiography using a standard projection format was performed initially and additional views were obtained if required to identify the parent vessel and aneurysm neck more clearly. The amount of contrast medium (Visipaque 270) used was 8 ml for the internal carotid artery and 6 ml for the external carotid artery, and the injection rate was 6 ml/s when the tip of the catheter was in the internal carotid artery and 3–4 ml/s when the tip of the catheter was in the external carotid artery. The rate of injection into the vertebrobasilar system was 6–8 ml/s to a total amount of 8 ml. In certain situations, rotational 3-D angiography was performed to better delineate the anatomic details of an aneurysm. Rotational 3-D angiography was performed on a Siemens Axiom Artis angiographic unit. The C-arm rotates in a continuous 200° arc around the patient’s head during a prolonged intraarterial catheter injection of contrast medium (28 ml Visipaque, injection rate 4 ml/s). The raw date images were transferred to a Leonardo workstation (AX Applications) from which 3-D volume-rendered reconstructions were reformatted. Image review and data analysis The presence of an aneurysm, its size and morphology, its parent and feeding vessels and the collateral circulation at the circle of Willis were determined by one of the diagnostic or interventional neuroradiologists. If multiple aneurysms were detected, the usual criteria were applied to decide which aneurysm was responsible for the haemorrhage. These criteria included the unenhanced CT findings (distribution of blood) and the size and irregularity of the aneurysm. All diagnostic findings were discussed with the neurosurgeons. The CTA results were categorized into proven ruptured aneurysm, inconclusive or negative. Patients with a proven ruptured aneurysm were selected subsequently for coiling or clipping. The surgical and endovascular findings were compared to the CTA findings. In general, ruptured aneurysms in the anterior circulation were selected for either coiling or clipping. Ruptured aneurysms located in the posterior circulation were preferably coiled. Giant intracranial aneurysms were preferably treated surgically. A ruptured aneurysm in association with an intraparenchymatous haemorrhage was most often selected for clipping of the aneurysm and surgical evacuation of the haematoma. Patients categorized as inconclusive or negative underwent IA-DSA. In patients with a perimesencephalic blood distribution, one IA-DSA examination was performed. In patients with a nonperimesencephalic blood distribution a second IA-DSA was performed if the first one was negative. IA-DSA was considered the gold standard. CTA was considered false-negative when IA-DSA revealed a ruptured aneurysm or when rebleeding occurred. P The IA-DSA findings in patients in the inconclusive category were compared with the CTA findings to assess whether IA-DSA actually provided any additional information. Results Patient population n n n 15 Detection of intracranial aneurysms Of the 224 patients, 140 underwent 16-slice CTA and 84 underwent 64-slice CTA. The CTA results were categorized as proven ruptured intracranial aneurysm (133 patients, 59%), inconclusive (31 patients, 14%), or negative for aneurysm (60 patients, 27%). Positive CTA result 1 2 3 4 1 Table 1 Location of symptomatic intracranial aneurysms in 224 patients Aneurysm location n n a n b n n n n Anterior circulation Anterior communicating artery 34 25 5 5 1 Pericallosal artery 2 2    Middle cerebral artery 3 18 1 6 1 Internal carotid artery 3 1 1  1 Posterior communicating artery 17 8  1  Anterior choroideal artery 1     Posterior circulation Basilar tip 11     Vertebral junction 1     Posterior cerebral artery     1 Posterior inferior cerebellar artery 5 1 1   Superior cerebellar artery 1     a b Table 2 Size distribution of symptomatic intracranial aneurysms in 224 patients Size (mm) n n a n b  < 5 47 12 4 5–9 70 4  10–14 14 3  15–24 1 1  ≥25 1   a b Table 3 Location of asymptomatic intracranial aneurysms in 224 patients Aneurysm location CTA-positive CTA inconclusive Anterior circulation Anterior communicating artery a 3 Pericallosal artery 2  Middle cerebral artery b 4 Internal carotid artery a  Posterior communicating artery a  Posterior circulation Basilar tip 1  Junction of vertebral artery 1  Posterior inferior cerebellar artery 1  a b Table 4 Size distribution of asymptomatic intracranial aneurysms in 224 patients  Size (mm) CTA-positive CTA-inconclusive  < 5 a 4 5–9 6 3 10–14 1  a Fig. 1 Flow chart of CTA results  n 2 Fig. 2 a b c d e f red arrow yellow arrow black arrow blue arrow  All ruptured intracranial aneurysms were confirmed by surgery or endovascular treatment. In two patients IA-DSA was performed after surgical treatment for evaluation of coiling of asymptomatic aneurysms. 2 The presence of CT-diagnosed additional asymptomatic aneurysms was checked in 22 patients. These patients had 29 aneurysms. Five aneurysms were confirmed at surgery and subsequently clipped, 5 aneurysms were checked with IA-DSA and subsequently coiled and 19 aneurysms were confirmed with IA-DSA. Three aneurysms in three patients were not verified. In four patients five asymptomatic aneurysms were false-negative on CTA. All were smaller than 5 mm. Four aneurysms were diagnosed with IA-DSA during an embolization session, one of them was also embolized. Another aneurysm was considered a vessel loop of the middle cerebral artery on CTA. However, an aneurysm of the middle cerebral artery was seen during surgery of a ruptured aneurysm of the anterior communicating artery. Clipping of the aneurysm of the middle cerebral artery was also performed. Inconclusive CTA result 5 1 Table 5 Indications for IA-DSA examination in 31 patients Indication No. of patients More information required regarding location and orientation Symptomatic aneurysm 10 Asymptomatic aneurysm 2 More information required regarding presence of intraaneurysmal thrombus in symptomatic giant aneurysm 2 Differentiation between asymptomatic and symptomatic aneurysm 1 Differentiation between infundibulum, vessel loop and aneurysm 5 Fisher grade IV SAH 1 Arterial vasospasm 3 Discrepancy between diagnosed intracranial aneurysm and distribution of blood 1 Incomplete angiography of circle of Willis 3 Overprojection of venous structures 1 Variance of normal intracranial vessel anatomy 1 Amalgam artefacts 1 In 11 patients (35%) IA-DSA confirmed the results of CTA. In 17 patients (55%) IA-DSA was able to give further diagnostic information required for a correct patient selection for therapy. In two patients (6%) no additional diagnostic information could was obtained from IA-DSA. In both patients vasospasm of a vertebral artery resulted in an inconclusive CTA, but also excluded selective catheterization with IA-DSA. A second CTA was negative in both patients. In one patient (3%) treatment selection was based on a false-positive IA-DSA. CTA was inconclusive because of amalgam artefacts in the region of the right posterior inferior cerebellar artery (PICA). An aneurysm of the right PICA was diagnosed on the first IA-DSA. A second IA-DSA was performed with the intention of coiling. However, with additional views the aneurysm turned out to be a vessel loop. 1 2 3 4 Negative CTA result 1 16 In 21 patients (70%) with perimesencephalic SAH, IA-DSA was performed once, and in one of them CTA was repeated once and in one CTA was repeated twice. In eight patients IA-DSA was repeated once and in one patient IA-DSA was repeated twice. In this category CTA was true-negative in all these patients. No rebleedings occurred. 1 2 Statistical analysis 6 7 8 Table 6 Diagnostic value of CTA in ruptured aneurysms Diagnostic value  True positive 132 patients False positive 1 patient True negative 55 patients False negative 6 patients Positive predictive value 99% Negative predictive value 90% Sensitivity 96% Specificity 98% Accuracy 96% Table 7 Diagnostic value of CTA in additional aneurysms Diagnostic value  Total number detected with CTA 25 patients (32 aneurysms) Presence checked 22 patients (29 aneurysms) True positive 22 patients (29 aneurysms) False positive 0 True negative a False negative 4 patients (5 aneurysms) Positive predictive value 100% Negative predictive value 97% Sensitivity 85% Specificity 100% Accuracy 97% a Table 8 Comparison of results of 16- and 64-slice CTA for detection of intracranial aneurysms    n n CTA result Positive 74 59 Negative 45 15 a 21 10 Ruptured aneurysms True positive 73 59 False positive 1 0 True negative 42 13 False negative b 2 Positive predictive value (%) 99 100 Negative predictive value (%) 91 87 Sensitivity (%) 95 97 Specificity (%) 98 100 Accuracy (%) 96 97 Unruptured aneurysms Total number on CTA 12 (15 aneurysms) 13 (17 aneurysms) Presence checked 11 (14 aneurysms) 11 (15 aneurysms) True positive 11 (14 aneurysms) 11 (15 aneurysms) False positive 0 0 True negative c d False negative 1 (1 aneurysm) 3 (4 aneurysms) Positive predictive value (%) 100 100 Negative predictive value (%) 99 94 Sensitivity (%) 92 79 Specificity (%) 100 100 Accuracy (%) 99 95 a b c d Discussion Our primary aim was to assess whether CTA is useful clinically in planning and performing clipping or coiling, especially in the acute phase in ruptured intracranial aneurysms, without recourse to IA-DSA. We demonstrated that it was possible to treat more than half of all patients with a ruptured intracranial aneurysm using only CTA. By avoiding conventional angiography, it was possible to streamline the management of ruptured aneurysm during the acute phase. Further, 3D-CTA was able to help in deciding whether to clip or to coil; in only two patients was treatment conversion needed due to incorrect treatment selection based on CTA. 17 17 26 9 22 23 25 17 20 27 Table 9 Presentation of previous studies and present study Study No. of patients CTA-positive CTA-negative CTA inconclusive or no CTA-based treatment Total patients CTA-based treatment True-positive CTA Total patients True-negative CTA Total patients 21 87 46 (55%) 44 (96%) 44 (100%) 15 (17%) 6 (60%) 26 (30%) 22 109 88 (81%) 87 (99%) 87 (100%) 5 (5%) 5 (100%) 16 (15%) 23 84 62 (74%) 62 (100%) 62 (100%) 7 (8%) 0 (0%) 15 (18%) 19 90 45 (100%) 45 (100%) 45 (100%) – – 45 (50%) 18 150 61 (41%) 61 (100%) a 24 (16%) 24 (100%) 65 (43%) 25 120 40 (27%) 40 (100%) 40 (100%) 13 (11%) 13 (100%) 67 (56%) 24 78 27 (35%) 27 (100%) 27 (100%) 20 (26%) b 31 (40%) 17 100 93 (93%) 93 (100%) 93 (100%) – – 7 (7%) 20 96 87 (91%) 87 (100%) 2 – – 9 (9%) 26 61 44 (72%) 44 (100%) 44 (100%) 15 (25%) 14 (93%) 2 (3%) Present study 224 133 (59%) 133 (100%) 2 60 (27%) 55 (92%) 31 (14%) a b In the present study CTA was false-negative in 8% of patients. The risk of rebleeding after a negative initial CTA was 7%. All false-negatives were in patients with a nonperimesencephalic blood distribution, giving a false-negative rate of 29% and a risk of rebleeding of 24%. It seems unlikely that the false-negative rate of initial CTA and the risk of rebleeding despite a negative initial CTA in patients with a nonperimesencephalic SAH might be influenced negatively by the use of CTA as the first diagnostic tool. Firstly, in all patients with a rebleeding, repeat IA-DSA was also false-negative. Secondly, repeat angiography with CTA performed after a rebleeding still demonstrated an aneurysm. 28 29 30 13 31 34 23 34 35 34 33 32 34 36 38 9 39 40 41 9 13 42 43 44 40 12 40 45 12 40 46 47 In conclusion, in this evaluation of the use of 16-row and 64-row multislice CTA in the management of ruptured intracranial aneurysms, we demonstrated that CTA can be used as the first-line diagnostic modality for the management of SAH patients. In CTA-negative patients IA-DSA provided no or marginal added value. IA-DSA is not needed in patients with negative CTA and classic perimesencephalic SAH. Repeat IA-DSA or CTA should still be performed in patients with a nonperimesencephalic SAH, due to false-negative CTAs and IA-DSAs in this patient group. The remaining true indication for IA-DSA was in patients with an inconclusive CTA result. In more than half of those IA-DSA provided relevant new diagnostic information.