Comparison of multidetector CT angiography and MR imaging of cervical artery dissection

BACKGROUND AND PURPOSE: Conventional angiography has been historically considered the gold standard for the diagnosis of cervical artery dissection, but MR imaging/MR angiography (MRA) and CT/CT angiography (CTA) are commonly used noninvasive alternatives. The goal of this study was to compare the ability of multidetector CT/CTA and MR imaging/MRA to detect common imaging findings of dissection.MATERIALS AND METHODS: Patients in the data base of our Stroke Center between 2003 and 2007 with dissections who had CT/CTA and MR imaging/MRA on initial work-up were reviewed retrospectively. Two neuroradiologists evaluated the images for associated findings of dissection, including acute ischemic stroke, luminal narrowing, vessel irregularity, wall thickening/hematoma, pseudoaneurysm, and intimal flap. The readers also subjectively rated each vessel on the basis of whether the imaging findings were more clearly displayed with CT/CTA or MR imaging/MRA or were equally apparent.RESULTS: Eighteen patients with 25 dissected vessels (15 internal carotid arteries [ICA] and 10 vertebral arteries [VA]) met the inclusion criteria. CT/CTA identified more intimal flaps, pseudoaneurysms, and high-grade stenoses than MR imaging/MRA. CT/CTA was preferred for diagnosis in 13 vessels (5 ICA, 8 VA), whereas MR imaging/MRA was preferred in 1 vessel (ICA). The 2 techniques were deemed equal in the remaining 11 vessels (9 ICA, 2 VA). A significant preference for CT/CTA was noted for VA dissections (P < .05), but not for ICA dissections.CONCLUSION: Multidetector CT/CTA visualized more features of cervical artery dissection than MR imaging/MRA. CT/CTA was subjectively favored for vertebral dissection, whereas there was no technique preference for ICA dissection. In many cases, MR imaging/MRA provided complementary or confirmatory information, particularly given its better depiction of ischemic complications.

Dissection of the extracranial arteries accounts for 10%–25% of strokes in young and middle-aged patients.¹ It may be spontaneous or traumatic and can cause a variety of clinical presentations, including stroke, headache, neck pain, tinnitus, Horner syndrome, and cranial neuropathies.^1-4 Dissections are typically diagnosed on the basis of a combination of the clinical presentation, imaging studies (conventional angiography, CT/CT angiography [CTA], MR imaging/MR angiography [MRA], and sonography), and exclusion of other arterial disease, particularly atherosclerosis.^1,2,5 In patients with mild or atypical symptoms, noninvasive imaging may facilitate earlier diagnosis and prevent embolic ischemic complications with the use of antithrombotic therapy.^3,6Conventional angiography has historically been considered the gold standard for dissection diagnosis, but it has limitations, which include its cost and invasiveness.^1,7,8 Although the angiographic appearance of dissection is often characteristic, it does not assess the vessel wall for intramural hematoma; because of this feature, dissections in unusual locations or with atypical morphology may be misclassified or attributed to other processes. MR imaging/MRA and CT/CTA have emerged as viable alternatives for both diagnosis and follow-up of dissection.^9-15 In general, the 2 techniques have different strengths and weaknesses. Diffusion-weighted MR imaging is a powerful technique for detecting acute stroke,¹⁶ which may then lead to increased scrutiny of the upstream arterial tree. Axial T1-weighted fat-suppressed images can detect the methemoglobin of the intramural hematoma within the false lumen, a finding referred to as a crescent sign.^9,13 Multidetector CT/CTA has enabled routine acquisition of thinner sections with rapid imaging times, facilitating multiplanar and volume reconstructions. Additionally, it is more widely available (especially at night), has fewer contraindications, and provides greater spatial resolution than MR imaging/MRA. However, the use of ionizing radiation in the relatively young population of patients with dissection is potentially concerning, especially given the often frequent follow-up studies in these patients.Only 1 study to date has compared CT/CTA with MR imaging/MRA for evaluation of dissection, retrospectively reviewing 7 internal carotid dissections and showing CTA to be marginally more effective in the identification of the dissected vessel.¹¹ To our knowledge, this current study is the largest comparative series of cervical artery dissection imaged with both tomographic techniques. Given the higher spatial resolution of CT/CTA, we hypothesized that CT/CTA may be particularly suited to visualize dissections within the smaller vertebral arteries. Additionally, we hypothesized that in a series of known dissections, CT/CTA would be more sensitive to identify specific imaging features associated with dissections.     

An In Vivo,MRI-Integrated Real-Time Model of Active Contrast Extravasation in Acute Intracerebral Hemorrhage

BACKGROUND AND PURPOSE:The “spot sign” or contrast extravasation is strongly associated with hematoma formation and growth. An animal model of contrast extravasation is important to test existing and novel therapeutic interventions to inform present and future clinical studies. The purpose of this study was to create an animal model of contrast extravasation in acute intracerebral hemorrhage.MATERIALS AND METHODS:Twenty-eight hemispheres of Yorkshire male swine were insonated with an MR imaging–guided focused sonography system following lipid microsphere infusion and mean arterial pressure elevation. The rate of contrast leakage was quantified by using dynamic contrast-enhanced MR imaging and was classified as contrast extravasation or postcontrast leakage by using postcontrast T1. Hematoma volume was measured on gradient recalled-echo MR imaging performed 2 hours postprocedure. Following this procedure, sacrificed brain was subjected to histopathologic examination. Power level, burst length, and blood pressure elevation were correlated with leakage rate, hematoma size, and vessel abnormality extent.RESULTS:Median (intracerebral hemorrhage) contrast extravasation leakage was higher than postcontrast leakage (11.3; 6.3–23.2 versus 2.4; 1.1–3.1 mL/min/100 g; P < .001). Increasing burst length, gradient recalled-echo hematoma (ρ = 0.54; 95% CI, 0.2–0.8; P = .007), and permeability were correlated (ρ = 0.55; 95% CI, 0.1–0.8; P = .02). Median permeability (P = .02), gradient recalled-echo hematoma (P = .02), and dynamic contrast-enhanced volumes (P = .02) were greater at 1000 ms than at 10 ms. Within each burst-length subgroup, incremental contrast leakage was seen with mean arterial pressure elevation (ρ = 0.2–0.8).CONCLUSIONS:We describe a novel MR imaging–integrated real-time swine intracerebral hemorrhage model of acute hematoma growth and contrast extravasation.

Intracerebral hemorrhage (ICH) accounts for 10%–30% of strokes and is the most deadly and disabling stroke type with little improvement in mortality seen during the past 20 years.¹ These characteristics underscore the importance of developing a better understanding of the pathophysiology of ICH formation and growth to facilitate the development of improved therapeutic agents or interventions.² The causative lesion in primary ICH is yet to be elucidated, though pathologic studies demonstrate focal vessel integrity loss in association with blood extravasation into the brain parenchyma.³ Following initial ICH formation, continuous^4,5 or delayed⁶ extravasation results in hematoma expansion,⁷ which is associated with early neurologic deterioration and significant mortality.⁸Several recent studies have shown an association between contrast extravasation (CE) detected on CTA, coined the CTA “spot sign,” and hematoma growth.^9–14 Prospective studies have demonstrated that contrast extravasation independently predicts a larger hematoma size and a poorer clinical outcome.^13,14 These are the first clinical studies to suggest a robust “real-time” imaging marker of hematoma expansion. Three clinical studies are presently enrolling patients dichotomized by the CTA spot sign to validate the prior study findings and to determine the therapeutic efficacy of recombinant factor VIIa or tranexamic acid.^15–17 A more recent study using dynamic spot sign imaging with a biphasic CT perfusion protocol¹⁸ has confirmed 2 patterns of contrast extravasation associated with significantly different rates of leakage. These patterns, comprising a brisker active extravasation (spot sign) and slower postcontrast leakage (PCL),¹⁹ are also demonstrated with early and late structural imaging,^10,19 dynamic CTA/CTP,¹⁸ and biphasic or repeat delayed CTA acquisitions.¹²Morphologic patterns and more recent studies illustrate that the spot sign is not an all-or-none phenomenon but constitutes a spectrum of extravasation.^18,19 The extravasation rate likely significantly impacts timely and clinically meaningful hemostasis.²⁰ A bleeding threshold likely exists beyond which prothrombotic treatment is futile, exposing patients to harmful adverse effects without hope of therapeutic benefit.²¹ Increasingly, new innovative surgical techniques are being developed to address contrast extravasation.²² Knowledge of the impact of the extravasation rate on therapeutic response is critical to stratify patients to the most appropriate therapies. An animal model of acute contrast extravasation in ICH could potentially inform the patient-selection process. We describe a novel MR imaging–integrated real-time swine model of acute hematoma growth and contrast extravasation.     

Fellows' Journal Club: Contrast Extravasation on CT Angiography Predicts Hematoma Expansion and Mortality in Acute Traumatic Subdural Hemorrhage

BACKGROUND AND PURPOSE:The presence of active contrast extravasation at CTA predicts hematoma expansion and in-hospital mortality in patients with nontraumatic intracerebral hemorrhage. This study aims to determine the frequency and predictive value of the contrast extravasation in patients with aSDH.MATERIALS AND METHODS:We retrospectively reviewed 157 consecutive patients who presented to our emergency department over a 9-year period with aSDH and underwent CTA at admission and a follow-up NCCT within 48 hours. Two experienced readers, blinded to clinical data, reviewed the CTAs to assess for the presence of contrast extravasation. Medical records were reviewed for baseline clinical characteristics and in-hospital mortality. aSDH maximum width in the axial plane was measured on both baseline and follow-up NCCTs, with hematoma expansion defined as >20% increase from baseline.RESULTS:Active contrast extravasation was identified in 30 of 199 discrete aSDHs (15.1%), with excellent interobserver agreement (κ = 0.80; 95% CI, 0.7–0.9). The presence of contrast extravasation indicated a significantly increased risk of hematoma expansion (odds ratio, 4.5; 95% CI, 2.0–10.1; P = .0001) and in-hospital mortality (odds ratio, 7.6; 95% CI, 2.6–22.3; P = 0.0004). In a multivariate analysis controlled for standard risk factors, the presence of contrast extravasation was an independent predictor of aSDH expansion (P = .001) and in-hospital mortality (P = .0003).CONCLUSIONS:Contrast extravasation stratifies patients with aSDH into those at high risk and those at low risk of hematoma expansion and in-hospital mortality. This distinction could affect patient treatment, clinical trial selection, and possible surgical intervention.

Acute traumatic subdural hemorrhage carries a mortality rate of 68% in patients who are in a coma at the time of presentation.^1–4 The incidence of aSDH is approximately 21% in patients with severe TBI⁴ and decreases to 11% in patients with mild and moderate TBI.⁵ Mortality secondary to aSDH has been related to initial hematoma size, the presence of additional brain injury, midline shift, comatose state, and delay in hematoma evacuation >2 hours after arrival to the emergency department.^6,7 The decision to undertake surgical intervention versus expectant management of aSDH is based on hematoma size, the presence of midline shift, admission GCS score, and hematoma growth.⁸ Early hematoma evacuation (<4 hours) has been shown to improve intracranial pressure and therefore brain perfusion, with a decrease in mortality compared with delayed surgical intervention in comatose patients with severe TBI.⁴ Although a significant proportion of patients are treated nonoperatively (noncomatose patients and comatose patients with aSDH <10 mm in width and/or <5 mm of midline shift), a subset of these aSDHs will expand, necessitating delayed operative intervention. The strong relationship between mass effect and mortality suggests that hematoma expansion is probably deleterious for brain perfusion and clinical outcome.⁹ However, to date, no reliable predictors of aSDHs expansion in the initial 48 hours have been identified. Identifying such a predictor may be helpful in the clinical decision to triage patients to early surgical intervention versus expectant management.Prior studies have found that the presence of active contrast extravasation at CTA, defined as the spot sign, is a powerful predictor of hematoma expansion and in-hospital mortality in patients with primary intracerebral hemorrhage.^9–15 However, to date, no studies have assessed the frequency and predictive value of this important finding in patients with aSDH.In our emergency department, CTA of the head and neck is frequently performed in patients who present with craniocervical trauma to detect vascular injury.^15,16 Subsets of these patients also have an associated aSDH. This study aims to determine the frequency and predictive value for hematoma expansion and in-hospital mortality of the CTA contrast extravasation in patients with aSDH.     

Renal safety of CT angiography and perfusion imaging in the emergency evaluation of acute stroke

BACKGROUND AND PURPOSE: Multimodal CT imaging with contrast-enhanced CT angiography (CTA) and CT perfusion (CTP) is increasingly being used to guide emergency management of acute stroke. However, little has been reported about the safety of intravenous contrast administration associated with these studies in the acute stroke population, including cases in which baseline creatinine values are unknown. We investigated the incidence of contrast-induced nephropathy (CIN), defined as a 25% or more increase in baseline creatinine levels within 72 hours of contrast administration and chronic kidney disease in patients receiving CTA±CTP at our regional stroke center.MATERIALS AND METHODS: We analyzed 198 patients who underwent contrast CT studies for evaluation of acute ischemic or hemorrhagic stroke at our center (2003–2007). Through retrospective chart abstraction, we analyzed serial creatinine levels (baseline to day 3) and later values (≥day 4) where available. The incidences of CIN and/or chronic kidney disease were documented. After power analysis, CIN and non-CIN groups were compared by using the unpaired t test, Wilcoxon rank sum test, or Fisher exact test.RESULTS: None of the 198 patients developed chronic kidney disease or required dialysis. Of 175 patients with serial creatinine measurements between baseline and day 3, 5 (2.9%) developed CIN. The incidence of CIN was 2% in patients who were scanned before a baseline creatinine level was available.CONCLUSION: The incidence of renal sequelae is relatively low in acute stroke patients undergoing emergent multimodal CT scanning. Prompt CTA/CTP imaging of acute stroke, if indicated, need not be delayed in those with no history of renal impairment.

Multimodal CT scanning is increasingly being used to aid acute stroke diagnosis and management. Dynamic CT perfusion (CTP) differentiates thresholds of reversible and irreversible ischemia and, thus, helps to identify “tissue at risk” that is potentially salvageable with thrombolytic therapy.^1–4 CT angiography (CTA) allows for rapid noninvasive assessment of the intracranial and extracranial vasculature and identifies vessel occlusions or stenoses that may be amenable to acute treatment.^1–4 For intracerebral hemorrhage, CTA can identify secondary causes of hemorrhage, and, in the acute phase, the CTA “spot sign” can predict which hemorrhages are likely to expand.^5–7 Advantages of multimodal CT over MR imaging include its rapid accessibility, lower costs, shorter scanning time intervals, better patient tolerability, and higher spatial resolution.^8,9 Although it is not yet clear whether the information provided by multimodal CT improves stroke outcomes, the increasing use of these imaging methods warrants more thorough assessment of their safety profiles.Little has been reported regarding the safety of multimodal CT imaging in the acute setting. Because “time is brain” for acute stroke patients,¹⁰ some stroke centers perform such imaging immediately on patient arrival to the emergency department, often before the results of blood work (eg, creatinine) are available. The primary safety concern regarding contrast-enhanced CT is the potential development of contrast-induced nephropathy (CIN), defined as a 25% or more increase in baseline creatinine levels within 72 hours of contrast administration.^11,12 Some clinicians feel uneasy about ordering contrast studies given the potential for CIN and the difficulty in obtaining a reliable history of renal disease in acute stroke patients who are frequently incapacitated or unable to communicate. In patients with CIN, creatinine levels usually peak around days 2–3 and normalize within 2 weeks, but a small proportion go on to chronic renal failure and dialysis.^11,13 CIN has been associated with prolonged hospital stay, increased resource use, and a fivefold increase in mortality.^12,14,15This purpose of this study was to assess the renal safety of emergency multimodal CT scanning in acute stroke patients at a large regional stroke center, including those patients for whom the baseline creatinine level was not known.     

Thrombus volume comparison between patients with and without hyperattenuated artery sign on CT

BACKGROUND AND PURPOSE: Although the hyperattenuated middle cerebral artery sign is known to be related to acute infarction, the volume of clot associated with it is not known. We investigated whether the presence or absence of hyperattenuated artery sign (HAS) on noncontrast CT (NCCT) can predict the thrombus volume.MATERIALS AND METHODS: We enrolled 90 consecutive patients with acute infarction who underwent both 5- and 1.25-mm NCCT and CT angiography (CTA). HAS was determined on 5-mm NCCT retrospectively. According to the location of thrombi, the patients were classified into ICA (ICA terminus/ICA and others), M1 (M1/both M1 and M2), and M2 (M2) groups. Thrombus volumes were measured by 1.25-mm NCCT and were compared between patients with and without HAS.RESULTS: Occlusion of major arteries was seen on CTA in 78 patients. HAS was found in 46 patients (59.0%). The mean thrombus volume was significantly larger in patients with HAS than in those without except for the M2 group (ICA group: [n = 14], 188.7 ± 122.5 mm³ versus 39.4 ± 12.1 mm³ [P = .022]; M1 group: [n = 42], 128.1 ± 119.2 versus 56.8 ± 32.5 [P = .005]; M2 group: [n = 22], 34.7 ± 32.2 versus 20.0 ± 20.0 [P = .18]). Thrombus volumes determined by receiver operating characteristic curve analysis were 52.36 mm³ in the ICA group (sensitivity, 90.9%; specificity, 100%) and 53.96 mm³ in the M1 group (sensitivity, 88.0%; specificity, 58.8%).CONCLUSION: Thrombus volumes were significantly larger in patients with HAS than in those without in ICA and M1 occlusions. The detection of HAS may provide an idea concerning rapid and dichotomized estimation of thrombus volume, which may be helpful for treatment decisions in potential candidates for thrombolysis.

Although hyperattenuated artery sign (HAS) on noncontrast CT (NCCT) represents the presence of the thrombus in acute ischemic stroke,^1,2 many patients with the thrombus do not show the HAS. In previous studies using NCCT with ≥5-mm thickness, it has been reported that the HAS presents in 5%–50% of patients with the thrombus in the M1 segment of the middle cerebral artery (MCA)^3–5 and in approximately 15% with the thrombus in the M2 segment.^5,6 The volume of the thrombus may affect outcomes. Patients with HAS in the M1 segment had more severe ischemia and poorer outcome than those without.^5,7 In addition, rapid estimation of the thrombus volume and its location may be helpful in determining treatment techniques, particularly in candidates for thrombolytic treatment.⁸ The volume of the thrombus, as well as its location, can be one of the factors determining the presence of HAS. However, the relationship between the thrombus volume and the presence of HAS is unknown. This may be partly due to difficulty in estimation of thrombus volume.Recently, more sensitive detection of thrombus and measurement of its volume in patients with acute ischemic stroke became feasible by using thin-section NCCT.^9,10 Therefore, we hypothesized that the relationship between the thrombus volume and the presence of HAS on conventional 5-mm CT could be determined with measurement of thrombus volume by using thin-section NCCT, and also the best threshold of thrombus volume for predicting the presence of HAS could be determined. The purpose of this study was to investigate whether the presence or absence of HAS can be used in the prediction of thrombus volume.     

Diagnostic accuracy of CT angiography with matched mask bone elimination for detection of intracranial aneurysms: comparison with digital subtraction angiography and 3D rotational angiography

BACKGROUND AND PURPOSE: Our aim was to determine the diagnostic accuracy of multisection CT angiography combined with matched mask bone elimination (CTA-MMBE) for detection of intracranial aneurysms compared with digital subtraction angiography (DSA) and 3D rotational angiography (3DRA).MATERIALS AND METHODS: Between January 2004 and February 2006, 108 patients who presented with clinically suspected subarachnoid hemorrhage underwent both CTA-MMBE and DSA for diagnosis of an intracranial aneurysm. Two neuroradiologists, independently, evaluated 27 predefined vessel locations in the CTA-MMBE images for the presence of an aneurysm. After consensus, diagnostic accuracy of CTA was calculated per predefined location and per patient. Interobserver agreement was calculated with κ statistics.RESULTS: In 88 patients (81%), 117 aneurysms (82 ruptured, 35 unruptured) were present on DSA. CTA-MMBE detected all ruptured aneurysms except 1. Overall specificity, sensitivity, positive predictive value, and negative predictive value of CTA-MMBE were 0.99, 0.90, 0.98, and 0.95 per patient and 0.91, 1.00, 0.97, and 0.99 per location, respectively. Sensitivity was 0.99 for aneurysms ≥3 mm and 0.38 for aneurysms <3 mm. Interobserver agreement for aneurysm detection was excellent (κ value of 0.92 per location and 0.80 per patient).CONCLUSION: CTA-MMBE is accurate in detecting intracranial aneurysms in any projection without overprojecting bone. CTA-MMBE has limited sensitivity in detecting very small aneurysms. Our data suggest that DSA and 3DRA can be limited to the vessel harboring the ruptured aneurysm before endovascular treatment, after detection of a ruptured aneurysm with CTA.

In current clinical practice, CT angiography (CTA) is the most frequently used noninvasive diagnostic tool for detection of intracranial aneurysms in the acute setting.^1–8 However, detection of intracranial aneurysms by CTA is limited because axial source section evaluation is tedious and 3D visualization is hampered by overprojecting bone, especially in the region of the skull base.^2,9–13 Several methods to remove bone, such as subtraction and manual or automated bone editing, have been developed.^7,8,14–19 Drawbacks of these methods are the complexity of use, dependence on the user, or high dose of radiation.Matched mask bone elimination (MMBE) is a relatively new technique to remove bone from CTA source images (CTA-MMBE) in an automatic and user-independent way with little additional radiation dose.^20–22 In CTA-MMBE, a second nonenhanced low-dose scan (about a quarter of the radiation dose of a regular CTA) is used to identify bony structures that can subsequently be masked in the CTA scan.Digital subtraction angiography (DSA) is the gold standard for detection of intracranial aneurysms. Extension of DSA with 3D rotational angiography (3DRA) can further improve detection of intracranial aneurysms that may be obscured by overprojecting vessels.^23–25 The advantages of DSA over CTA are superior spatial and contrast resolution, no interference of bony structures, and the possibility to perform direct endovascular interventions.^26,27 However, DSA is an invasive technique with a small but significant risk of neurologic complications, estimated to occur in 0.3%–1.8% of patients.^28,29The purpose of this study was to determine the diagnostic accuracy of CTA-MMBE for detection of intracranial aneurysms in a large patient population with clinically suspected subarachnoid hemorrhage (SAH) with DSA and 3DRA as reference standards.     

Whole-Body CT Trauma Imaging with Adapted and Optimized CT Angiography of the Craniocervical Vessels: Do We Need an Extra Screening Examination?

BACKGROUND AND PURPOSE: Blunt carotid and vertebral artery injury (BCVI) is rare but potentially devastating. The objective of our study was to prospectively evaluate the usefulness of a dedicated and optimized CT angiography (CTA) protocol of the craniocervical vessels as part of a whole-body CT work-up of patients with multiple trauma in a population of patients with blunt trauma.MATERIAL AND METHODS: From February 2006 to July 2007, a total of 368 consecutive patients with trauma were evaluated. All examinations were performed on a 16-row multisection CT (MSCT) scanner. CTA was performed from the level of the T2 vertebra to the roof of the lateral ventricles with 40 mL of iodinated contrast agent. Images were reconstructed with use of the angiography and bone window settings to evaluate vessels and bones.RESULTS: Of all eligible patients imaged, 100 had injuries to the head and neck including 35 skull base fractures (9.5%), 24 maxillofacial (6.5%), and 11 cervical spine fractures (3%). CTA was diagnostic in all patients. BCVI was diagnosed in 6 cases (6 lesions of the internal carotid artery, 3 lesions of the vertebral artery); among them were 2 who did not meet the screening criteria. No patient with negative results on CTA subsequently had development of neurologic deficits suspicious for BCVI.CONCLUSION: This study confirms that optimized craniocervical CTA can be easily integrated into a whole-body CT protocol for patients with multiple trauma. No additional screening technique is necessary to identify clinically relevant vascular injuries. Earlier recognition enables earlier treatment and may decrease mortality and morbidity rates of these rare but potentially devastating injuries.

Blunt carotid and vertebral artery injury (BCVI) is a rare event. The diagnosis is quite challenging because of the relatively low incidence of BCVI and delayed onset of clinical manifestations.^1,2 Although early series reported an incidence of carotid dissections of less than 0.1% of patients with blunt trauma,^3,4 recent studies have found BCVI in up to 1.6% of patients admitted for trauma.^5–8 In the light of the potential devastating consequences of BCVI, much effort has focused on improving detection and treatment during the past decade.^9,10 Initially, neurologic deficits were thought to be inevitable in these patients, but prompt systemic anticoagulation before the onset of stroke has significantly reduced ischemic neurologic events in such patients.^8,11 On the basis of these insights and increased awareness of BCVI, subsequent efforts have been directed toward the identification of injuries before the onset of stroke, resulting in screening protocols^7,12,13 according to mechanism of injury and specific injury patterns^9,10,14,15 6,16 and of how to screen patients at risk.¹Table 1.Findings that are suspicious for BCVI and should trigger screening

Association between cerebral microbleeds on T2*-weighted MR images and recurrent hemorrhagic stroke in patients treated with warfarin following ischemic stroke

BACKGROUND AND PURPOSE: Although accumulating evidence suggests the presence of microbleeds as a risk factor for intracerebral hemorrhage (ICH), little is known about its significance in anticoagulated patients. The aim of this study was to determine whether the presence of microbleeds is associated with recurrent hemorrhagic stroke in patients who had received warfarin following atrial fibrillation–associated cardioembolic infarction.MATERIALS AND METHODS: A total of 87 consecutive patients with acute recurrent stroke, including 15 patients with ICH and 72 patients with cerebral infarction, were enrolled in this study. International normalized ratios (INRs), vascular risk factors, and imaging characteristics, including microbleeds on T2*-weighted MR images and white matter hyperintensity (WMH) on T2-weighted MR images, were compared in the 2 groups.RESULTS: Microbleeds were noted more frequently in patients with ICH than in patients with cerebral infarction (86.7% versus 38.9%, P = .0007). The number of microbleeds was larger in patients with ICH than in patients with cerebral infarction (mean, 8.4 versus 2.1; P = .0001). INR was higher in patients with ICH than in patients with cerebral infarction (mean, 2.2 versus 1.4; P < .0001). The frequency of hypertension was higher in patients with ICH than in patients with cerebral infarction (86.7% versus 45.8%, P = .0039). Multivariate analysis revealed that the presence of cerebral microbleeds (odds ratio, 7.383; 95% confidence interval, 1.052–51.830) was associated with ICH independent of increased INR and hypertension.CONCLUSION: The presence of cerebral microbleeds may be an independent risk factor for warfarin-related ICH, but more study is needed because of strong confounding associations with elevated INR and hypertension.

One of the major complications of warfarin treatment following atrial fibrillation–related cardioembolic infarction is the occurrence of intracerebral hemorrhage (ICH). With advancing age, the incidence of both atrial fibrillation–related cardioembolic infarction and warfarin-related ICH increases.Cerebral microbleeds detected by gradient-echo T2*-weighted MR imaging, which are shown as signal-intensity loss, represent hemosiderin deposit^1,2 and are associated with occurrence of ICH.^3–19 Although accumulating evidence suggests that the presence of microbleeds is a risk factor for ICH in patients treated by antiplatelet therapy^13,20 and hemorrhagic complications of anticoagulation in patients with prior ICH and atrial fibrillation have been reported,²¹ little is known about the significance of microbleeds in anticoagulated patients because, to our knowledge, no studies have focused on the association between cerebral microbleeds and anticoagulation therapy in a large number of patients. On the other hand, previous studies focusing on radiographic characteristics have shown that the presence of microangiopathy (leukoaraiosis) detected by CT is a risk factor for warfarin-related ICH.²² However, considering the close association between cerebral microbleeds and leukoaraiosis (white matter hyperintensity [WMH]),^{7,8,11,14–16,19,23,24} one could hypothesize that cerebral microbleeds, which represent bleeding from small vessels, may be more closely associated with ICH than WMH is. Therefore, the present study was performed to determine whether the presence of microbleeds is associated with recurrent hemorrhagic stroke in patients who have received warfarin treatment following atrial fibrillation–associated cardioembolic infarction.     

Nontraumatic skull base defects with spontaneous CSF rhinorrhea and arachnoid herniation: imaging findings and correlation with endoscopic sinus surgery in 27 patients

BACKGROUND AND PURPOSE: Defects at the skull base leading to spontaneous CSF rhinorrhea are rare lesions. The purpose of our study was to correlate CT and MR findings regarding the location and content of CSF leaks in 27 patients with endoscopic sinus surgery observations.MATERIALS AND METHODS: Imaging studies in 27 patients with intermittent CSF rhinorrhea (CT in every patient including 10 examinations with intrathecal contrast, plain CT in 2 patients, and MR in 15 patients) were analyzed and were retrospectively blinded to intraoperative findings.RESULTS: CT depicted a small endoscopy-confirmed osseous defect in 3 different locations: 1) within the ethmoid in 15 instances (53.6% of defects) most commonly at the level of the anterior ethmoid artery (8/15); 2) adjacent to the inferolateral recess of the sphenoid sinus in 7 patients including one patient with bilateral lesions (8/28 defects, 28.6%); 3) within the midline sphenoid sinus in 5 of 28 instances (17.9%). Lateral sphenoid defects (3.5 ± 0.80 mm) were larger than those in ethmoid (2.7 ± 0.77 mm, P ≤ 0.029) or midsphenoid location (2.4 ± 0.65 mm, P ≤ 0.026). With endoscopy proven arachnoid herniation in 24 instances as reference, MR was correct in 14 of 15 instances (93.3%), CT cisternography in 5 of 8 instances (62.5%). Plain CT in 1 patient was negative.CONCLUSION: In patients with a history of spontaneous CSF rhinorrhea, CT was required to detect osseous defects at specific sites of predilection. MR enabled differentiating the contents of herniated tissue and allowed identification of arachnoid tissue as a previously hardly recognized imaging finding.

The term “spontaneous” CSF rhinorrhea has been applied to describe nasal discharge of CSF unrelated to trauma, surgery, malformation, tumor, or previous radiation therapy.^1–4 Spontaneous CSF rhinorrhea is uncommon. Estimates of the spontaneous cause among all causes of CSF rhinorrhea are subject to variation ranging from only 6%,⁵ 11.4%,⁶ 14%,³ 21%,⁷ to 23%.⁸ Periodic release of CSF from the nose was first described by Galen in 200 B.C. and was considered a physiologic phenomenon until Thomson, in 1899, assembled 21 patients in a monograph reporting spontaneous CSF rhinorrhea as a pathologic clinical entity.^9,10Spontaneous CSF rhinorrhea has been recognized as a distinct entity with respect to clinical presentation,^2,11,12 treatment,^13–15 and propensity for recurrence.^8,16,17 As early as 1968, Ommaya et al⁹ postulated the existence of “high-pressure leaks” related to intracranial tumors and of “normal pressure leaks” occasionally associated with empty sella. The role of empty sella as an indicator of raised intracranial pressure as well was supported by the observation of elevated CSF pressure in individual patients¹¹ and in a series of 10 patients who underwent lumbar puncture after sealing of the defect.¹⁸ In addition to the presence of an empty sella as a radiologic sign,¹⁹ a common clinical constellation in patients with spontaneous CSF rhinorrhea is female sex, middle age, and obesity.^{8,14,15,18–22}Spontaneous CSF leaks have been postulated to represent a manifestation of benign intracranial hypertension²² or pseudotumor cerebri.²³ Pulsatile-increased hydrostatic pressure is capable of bone erosion during the course of many years.^2,24 To become effective as a CSF leak, bone erosion and creation of an osteodural defect is required to occur at pneumatized parts of the skull base leading to communication of the subarachnoid space with the sinonasal spaces or temporal bone cavity. Related to CSF rhinorrhea, a review of the literature up to 1972¹⁰ identified the cribriform plate, craniopharyngeal canal, sella, and spheno-occipital synchondrosis as possible sites of predilection. Arachnoid granulations in proximity to the ethmoid and sphenoid sinus have been implicated as precursors of osteodural leaks.² Accordingly, arachnoid granulations causing erosion of the temporal bone may present with CSF otorrhea.^2,25,26Among the imaging techniques used to localize the site of the fistula, radionuclide isotope cisternography and CT cisternography were of limited sensitivity in 66% of patients only.³ When active leaks were present, CT cisternography provided positive results in 85% of patients.²⁷ However, in cases of inactive fistulas, CT cisternography failed to recognize the site of leakage in 27.7%²⁸ and in 19% of patients.²⁹ Advances in CT and MR imaging techniques have improved sensitivity, which amounted to 88.25%³⁰ and 93%³¹ for high-resolution CT and for MR cisternography to 89%,^6,31 93.6%,²⁸ and 100%^32,33 even in patients with inactive leaks. Therefore, high-resolution CT, MR cisternography, or a combination of both techniques have replaced the previously used invasive procedures.A confounding nomenclature exists regarding the contents of osteodural defects such as meningocele,^10,14 meningoencephalocele,⁴ encephalocele,^11,34 meningeal or arachnoid hernia,^24,35 arachnoid diverticulum,³⁶ or arachnoid cyst.³⁷ These differing designations reflect variable contents of herniation and occasional inaccuracy because of the limited ability to visualize the lesions by imaging^24,29 and during transcranial surgery.^1,10 Knowledge of the contents of herniation may modify the grafting technique and therefore facilitates preoperative planning.¹⁶ The endoscopic skull base approach has rendered direct visualization of the defect and its contents feasible.^38–40 Therefore, endoscopy was chosen as a standard of reference in this study. CT and MR findings in this series of patients with spontaneous CSF rhinorrhea were particularly assessed regarding the contents of herniation and location and correlated with endoscopy. Predisposing factors (arachnoid granulation, empty sella) and the size of the osseous defect were assessed on CT images.     

Sinonasal organized hematoma: CT and MR imaging findings

BACKGROUND AND PURPOSE: Sinonasal organized hematoma (OH) is an uncommon, nonneoplastic benign condition that can be locally aggressive. The purpose of this work was to characterize the CT and MR imaging findings of sinonasal OH.MATERIALS AND METHODS: CT (n = 11) and MR (n = 10) images of 12 patients (9 men and 3 women; mean age, 41 years; range, 12–76 years) with pathologically proved sinonasal OH were retrospectively reviewed. Particular attention was put on the location, shape, size, extent, internal architecture, and enhancement pattern of the lesion and associated sinus wall change.RESULTS: The lesions were seen as an expansile (n = 9) or nonexpansile (n = 3) mass, ranging in size from 2.2 to 6.0 cm (mean, 4.2 cm), primarily involving the maxillary sinus (n = 11) or nasal cavity (n = 1) unilaterally. The ipsilateral nasal cavity was also involved in 9 of 11 maxillary sinus lesions. Smooth sinus wall erosion other than the medial maxillary sinus wall was noted in 8 lesions. The internal architecture was best displayed on T2-weighted MR images on which all of the lesions were seen as a mixture of marked heterogeneous hypointensity and isointensity, surrounded by a hypointense peripheral rim, reflecting histologic heterogeneity of the lesion composed of hemorrhage, fibrosis, and neovascularization. Marked irregular nodular, papillary, or frondlike enhancement at the areas of neovascularization was also a typical finding seen in all of the lesions.CONCLUSION: An expansile soft tissue mass, smooth sinus wall erosion, marked heterogeneous signal intensity with a hypointense peripheral rim on T2-weighted MR images, and marked irregular nodular, papillary, or frondlike enhancement are characteristic CT and MR imaging findings of sinonasal OH.

Sinonasal organized hematoma (OH) is an uncommon, nonneoplastic benign condition that can be locally aggressive. Without careful evaluation of all of the imaging features, this may be mistaken for a malignant lesion both clinically and radiologically. It most commonly affects the maxillary sinus and can result from various causes of hemorrhage with chronic hematoma formation, followed by the process of organization through fibrosis and neovascularization.^1,2 Since the first report by Ozhan et al³ in a patient with von Willebrand disease, only fewer than 40 cases have been reported in the English literature under various names, including pseudotumor,^3,4 hematoma,⁵ organized or organizing hematoma,^1,2,6–8 and hematoma-like mass of the maxillary sinus.⁹Correct preoperative diagnosis of sinonasal OH is important to avoid unnecessary extensive surgery, because this condition is curative with a simple, conservative surgical approach and rarely recurs. Although there have been a few reports on the CT findings of sinonasal OH,^1–3,5–9 which are reported to be rather nonspecific, to our knowledge, the MR imaging features have not systematically been analyzed previously. Only 2 studies had briefly mentioned the MR imaging features.^8,9 Yagisawa et al⁹ reported that masses were well demarcated from the surrounding structures and heterogeneous in signal intensity on both T1- and T2-weighted MR images. Song et al⁸ reported that the lesions appeared as isosignal intensity with a margin that had a slightly higher signal intensity on T1-weighted images and a mosaic of various signal intensities and a low signal intensity rim on T2-weighted images. The purpose of this study was to report the CT and MR imaging findings, which are believed to be characteristic for sinonasal OH.     

CT Angiography ASPECTS Predicts Outcome Much Better Than Noncontrast CT in Patients with Stroke Treated Endovascularly

BACKGROUND AND PURPOSE:Noncontrast CT ASPECTS has been investigated as a predictor of outcome in patients with acute ischemic stroke. Our purpose was to investigate whether CTA source images are a better predictor of clinical and radiologic outcomes than NCCT ASPECTS in candidates for endovascular stroke therapy.MATERIALS AND METHODS:CT scans of patients (n = 124) were independently evaluated by 2 readers for baseline NCCT and CTA source image ASPECTS and for follow-up ASPECTS. An mRS of ≤2 at 3 months was considered a favorable outcome. Receiver operating characteristic curve analysis was used to assess the ability of NCCT and CTA source image ASPECTS to identify patients with favorable outcomes. A stepwise multiple regression analysis was performed to find independent predictors of outcome.RESULTS:Baseline CTA source image ASPECTS correlated better than NCCT ASPECTS with follow-up ASPECTS (r = 0.76 versus r = 0.51; P for comparison of the 2 coefficients < .001). Receiver operating characteristic curve analysis showed that baseline CTA source image ASPECTS compared with NCCT ASPECTS can better identify patients with favorable outcome (CTA source image area under the curve = 0.83; 95% CI, 0.76–0.91; NCCT area under the curve = 0.67; 95% CI, 0.58–0.77; P < .001). Finally, the stepwise regression analysis showed that lower age, good recanalization, lower time to recanalization, and good baseline CTA source image ASPECTS, not NCCT ASPECTS, were independent predictors of favorable outcome.CONCLUSIONS:CTA source image ASPECTS predicts outcome better than NCCT ASPECTS; this finding suggests CTA rather than NCCT as a main step in the decision-making process for patients with acute ischemic stroke.

The Alberta Stroke Program Early CT Score merges the ability of quantifying and describing the topography of brain tissue damage produced by acute ischemic stroke in a semiquantitative way.¹ ASPECTS on noncontrast CT is widely used for the assessment of early ischemic changes, and its prognostic value has already been established,² though with poor NCCT sensitivity.³ Recent randomized controlled trials on endovascular stroke therapy (ET) have been based on strict inclusion criteria, leading to treatment of only those patients with high CT ASPECTS indicating smaller infarct burden.^4–6Many attempts have been made to understand which patients are likely to undergo futile reperfusion.⁷ For instance, it has been recently demonstrated that patients with poor collaterals and longer time to reperfusion do not achieve good outcomes after ET.⁸ Thus, a careful patient selection for ET should be desirable and should be based on a multimodal neuroimaging approach in addition to onset time and stroke severity. Although not as commonly available as NCCT in the acute ischemic stroke setting, CT angiography is useful for confirmation of vessel occlusion in candidates for ET, and hypodensity on CTA source images (CTA-SI) has been shown to reliably correlate with ischemic lesion volume on diffusion-weighted imaging⁹ and final infarct size.¹⁰ The superiority of CTA-SI on NCCT in the detection of infarcted areas has been demonstrated for readers of all levels of experience.¹¹ Few data exist on the value of CTA-SI ASPECTS in patients undergoing ET for acute ischemic stroke,^12,13 and this lack of data may explain why only ASPECTS NCCT is currently considered in the guidelines for eligibility for ET. Our purpose was to investigate whether CTA-SI ASPECTS correlate better than NCCT ASPECTS with clinical and radiologic outcome measures in patients with acute ischemic stroke undergoing ET.     

No increased risk for contrast-induced nephropathy after multiple CT perfusion studies of the brain with a nonionic, dimeric, iso-osmolal contrast medium

BACKGROUND AND PURPOSE: Contrast-induced nephropathy (CIN) is one of the most common causes of in-hospital acute renal failure. The aim of this study was to assess the risk for CIN after repeated administration of the nonionic, dimeric, iso-osmolal contrast agent iodixanol regardless of pre-existing renal function. Changes in serum creatinine (SCr) levels were compared with those of control subjects who did not receive iodinated contrast media (CM).MATERIALS AND METHODS: Between January 2005 and March 2007, a total of 100 consecutive patients were prospectively included. Patients underwent a CT perfusion (CTP) study of the brain from clinical signs of acute cerebral infarction. CTP was performed with an intravenous bolus of 60 mL of iodixanol-270. Precontrast and postcontrast SCr levels were obtained, and the CTP study was repeated within 32 hours and postcontrast SCR was assessed. The control group consisted of 100 patients scheduled for plain cranial CT examination, who were not exposed to iodinated CM.RESULTS: Mean baseline SCr level was 0.96 ± 0.35 mg/dL in the contrast group and 1.14 ± 0.74 mg/dL in the control group. After repeated administration of CM, a total of 7 patients had a relative increase of greater than or equal to 25% compared with baseline. In the control group, a relative increase of 25% or more was seen in 12 patients. The difference in the incidence of the rise in SCr of >25% was not significantly different (P = .094).CONCLUSION: Multiple contrast-enhanced studies with intravenously administered iodixanol are not associated with a higher risk for CIN compared with a control group receiving no CM.

With increased use of contrast media (CM), interest in contrast-induced nephropathy (CIN) has risen considerably in recent years. CIN continues to be one of the most common causes of hospital-acquired acute renal failure¹ and is associated with increased morbidity and mortality, especially when hemodialysis is required.² The effects of CM are compounded by increased comorbidities in patients receiving them, including pre-existing renal impairment with or without concurrent diabetes, the use of drugs that affect renal function, advanced age, and the use of large volumes of CM.³CIN is an acute decline in renal function occurring after intravascular contrast administration and the absence of an alternative cause.^4,5 CIN has been variably defined: a postcontrast increase in serum creatinine (SCr) levels of at least 0.5 mg/dL or of more than 25% above precontrast values.^6,7 In most cases, the increase in SCr levels occurs within 24 to 48 hours of the administration of the iodinated contrast agent and normally returns to or near the baseline value within 7 days.^4,6,8 The pathophysiology of CIN is not completely understood, but the literature indicates that a reduction in renal perfusion from a direct effect of CM on the kidney and toxic effects on the tubular cells are the main cause.⁵ Mechanisms responsible for the reduction in renal perfusion involve vascular and tubular effects (eg, increase in intratubular pressure and tubular obstruction).⁹ Characteristics of CM, such as osmolality^10,11 or chemical composition,¹² might influence the risk for CIN. The route of administration may also contribute to the pathogenesis of CIN.¹³The Nephrotoxic Effects in High-Risk Patients Undergoing Angiography (NEPHRIC) study documented that iso-osmolal CM (IOCM) may have better renal tolerance than low-osmolar CM (LOCM) in high-risk patients undergoing angiography.¹⁴ This has influenced several guideline recommendations that a high risk for the development of CIN be considered one of the indications for the use of LOCM or IOCM.^5,15 Many studies have evaluated the renal safety of the nonionic IOCM iodixanol or that of the other nonionic LOCM in patients with impaired renal function^16–22 but only after intra-arterial contrast injection. Only 3 studies have compared the nephrotoxicity of the dimeric IOCM iodixanol with monomeric CM after intravenous injection.^23-25 These studies indicate a very low risk for CIN after intravenous injection of iodixanol. Petrik et al²⁶ reported no detectable nephrotoxic adverse effect after a single administration of a maximal of 80 mL of iodixanol regardless of pre-existing renal function.In a review of published guidelines, Thomsen and Morcos²⁷ in 2006 reported that most authors advocate the use of the IOCM iodixanol for patients with renal insufficiency. Most guidelines recommend avoiding multiple examinations with iodinated CM in a short period.²⁷ No published study in the literature evaluates the renal safety of a double administration of iodixanol in patients undergoing contrast-enhanced CT examinations regardless of the pre-existing renal function.We compared changes in SCr levels on days 3 and 7 in 100 consecutive patients after a double administration of 60 mL of iodixanol for CT perfusion studies of the brain within 48 hours with changes in SCr levels of in-hospital patients who were not exposed to an iodinated contrast agent.     

Transcranial Duplex Sonography Predicts Outcome following an Intracerebral Hemorrhage

BACKGROUND AND PURPOSE:Several radiologic features such as hematoma volume are related to poor outcome following an intracerebral hemorrhage and can be measured with transcranial duplex sonography. We sought to determine the prognostic value of transcranial duplex sonography in patients with intracerebral hemorrhage.MATERIALS AND METHODS:We conducted a prospective study of patients diagnosed with spontaneous intracerebral hemorrhage. Transcranial duplex sonography examinations were performed within 2 hours of baseline CT, and we recorded the following variables: hematoma volume, midline shift, third ventricle and lateral ventricle diameters, and the pulsatility index in both MCAs. We correlated these data with the CT scans and assessed the prognostic value of the transcranial duplex sonography measurements. We assessed early neurologic deterioration during hospitalization and mortality at 1-month follow-up.RESULTS:We included 35 patients with a mean age of 72.2 ± 12.8 years. Median baseline hematoma volume was 9.85 mL (interquartile range, 2.74–68.29 mL). We found good agreement and excellent correlation between transcranial duplex sonography and CT when measuring hematoma volume (r = 0.791; P < .001) and midline shift (r = 0.827; P < .001). The logistic regression analysis with transcranial duplex sonography measurements showed that hematoma volume was an independent predictor of early neurologic deterioration (OR, 1.078; 95% CI, 1.023–1.135) and mortality (OR, 1.089; 95% CI, 1.020–1.160). A second regression analysis with CT variables also demonstrated that hematoma volume was associated with early neurologic deterioration and mortality. When we compared the rating operation curves of both models, their predictive power was similar.CONCLUSIONS:Transcranial duplex sonography showed an excellent correlation with CT in assessing hematoma volume and midline shift in patients with intracerebral hemorrhage. Hematoma volume measured with transcranial duplex sonography was an independent predictor of poor outcome.

Spontaneous intracerebral hemorrhage (ICH) is a major cause of morbidity and mortality,¹ with half of the events related to case fatality occurring within the first 48 hours.² Thus, identifying variables that contribute to early neurologic deterioration (END) and mortality is of enormous importance. An early estimation of the prognosis is crucial for deciding on a treatment plan. Several neuroimaging prognostic factors include hematoma volume (HV), hematoma enlargement, midline shift (MLS), and intraventricular hemorrhage,^3–9 and CT is the technique most frequently used to assess them. However, in the early stages, it can be difficult to monitor these radiologic features with repeat CT due to the clinical and/or hemodynamic state of the patient and the risk of radiation overexposure.Transcranial duplex sonography (TDS) is a noninvasive technique that provides simultaneous 2D imaging of brain parenchyma and hemodynamic information from the main cerebral arteries. The role of TDS is well-established in the assessment of ischemic stroke, but its usefulness in acute ICH has been reported in only a few studies.^10–15Visualization of acute ICH with TDS is feasible: The ICH can be identified as a hyperechoic mass.^10–12 Additionally, TDS allows the assessment of the third ventricle (IIIV), the lateral ventricles (LVs), MLS, and the presence of intraventricular hemorrhage.^13–16 TDS may have some potential advantages over CT, including the feasibility of performance at the bedside as many times as necessary and regardless of the hemodynamic situation of the patient. Despite a good correlation between TDS and CT having been previously reported,^10–15 the prognostic value of this technique in ICH is yet to be established.The question of whether TDS may reliably measure ICH characteristics and predict END and mortality following ICH has important implications for clinical practice and research. In the current study, we sought to determine the prognostic value of TDS in patients with acute ICH.     

Preoperative visualization of the artery of Adamkiewicz by intra-arterial CT angiography

BACKGROUND AND PURPOSE: CT and MR angiographies have been reported to visualize the artery of Adamkiewicz (AKA) noninvasively to prevent spinal cord ischemia in surgery of thoracic descending aortic aneurysms. The purpose of this work was to compare the usefulness of CT angiography (CTA) with intra-arterial contrast injection (IACTA) with that of conventional CTA with intravenous contrast injection (IVCTA).MATERIALS AND METHODS: We enrolled 32 consecutive patients with thoracic or thoracoabdominal aortic aneurysms who were scheduled for surgical repair or endovascular stent-graft treatment. All of the CTA images were obtained using a 16-detector row CT scanner and 100 mL of contrast material (370 mg/mL) injected at a rate of 5 mL/s. Contrast was injected via the antecubital veins of 15 patients and via a pig-tail catheter placed at the proximal portion of the descending aorta in 17 patients who underwent IVCTA and IACTA, respectively. Two datasets were reconstructed from 2 consecutive scans. The AKA was identified as a characteristic hairpin curved vessel in the anterior midsagittal surface of the spine and by the absence of further enhancement in the second rather than in the first phase. Continuity between the AKA and aorta was confirmed when the vessel could be traced continuously by paging the oblique coronal multiplanar reconstruction or original axial images.RESULTS: Intra-arterial contrast injection was significantly more sensitive in identifying the AKA than IVCTA: 16 (94.1%) of 17 versus 9 (60.0%) of 15 (P = .033). Continuity between the AKA and aorta through intercostal or lumbar artery was confirmed in 14 (87.5%) of 16 and 5 (55.6%) of 9 of the IACTA and IVCTA groups, respectively.CONCLUSION: Intra-arterial contrast injection detected the AKA at a high rate and verified continuity from the aorta to the AKA.

Paraplegia and paraplesis secondary to spinal cord ischemia remain serious complications of surgical repair or of endovascular treatment for descending thoracic aortic aneurysm (TAA) or thoracoabdominal aortic aneurysm (TAAA). The incidence ranges between 5% and 11% of thoracoabdominal surgeries.^1–4 The great anterior radiculomedullary artery (the artery of Adamkiewicz [AKA]) is the dominant feeder of the spinal cord. One possible cause of spinal cord ischemia during surgery is failure to reestablish the spinal cord blood supply, and many reports have stressed the importance of reattaching the intercostal or lumbar arteries related to the AKA.^5,6 Preoperative AKA identification and display of intercostal and lumbar arteries help surgeons to determine the appropriate range of aortic lesions that require graft replacement and intercostal or lumbar arteries requiring reconstruction.⁷The most reliable way to visualize the AKA is selective intercostal arterial angiography, the detection rate of which is 43%–86%.^8–12 However, selective angiography is time consuming, and complications including spinal cord injury can develop.^10,11 Recently, MR angiography (MRA)^13–18 and CT angiography (CTA)^17–21 have been used to visualize the AKA less invasively with reported detection rates of 67%–93% and 68%–90%, respectively. However, these rates could be further improved.The AKA is a small vessel with a diameter of 0.5–1.5 mm^22,23 that is surrounded by osseous structures. In addition, intercostal or lumbar arteries and dorsal branches run very close to the osseous structures (Fig 1). Due to these anatomic features, the contrast-to-noise ratio (CNR) in the spinal canal is decreased, and the AKA and its continuity with the aorta can be obscured. Robust aortic contrast enhancement is necessary to detect small vessels, but CTA with intravenous contrast injection (IVCTA) has limitations with respect to elevating aortic enhancement, because contrast material is diluted in the circulation of the right side of the heart. Nojiri et al²⁴ showed that CTA with intra-arterial contrast injection (IACTA) could track the AKA to the aorta because of high contrast. The present study compares the abilities of IACTA and IVCTA to detect the AKA.Open in a separate windowFig 1.Anatomic course of the AKA. Right anterosuperior view of a 3D volume-rendered CT image of IACTA with semitransparent skeletal system. Intercostal and lumbar arteries (1) originate from the aorta, and divide into posterior (2) and anterior (3) branches. Anterior branches run through the intercostal groove. Posterior branches subdivide into the radiculomedullary artery (4) and muscular branch (5). Radiculomedullary artery courses to the spine and enters the vertebral foramen. The AKA (6) is the largest anterior radiculomedullary artery and joins the anterior spinal artery (7) in a characteristic hairpin curve.     

Neuroradiologic applications with routine C-arm flat panel detector CT: evaluation of patient dose measurements

BACKGROUND AND PURPOSE: Since the introduction of flat panel detector–equipped C-arms, the use of flat panel detector CT (FPCT) in the neuroradiologic angiography suite has become more frequent. This examination implicates its own specific radiation exposure. We used the CT dose index (CTDI) concept and adapted it to the special FPCT geometry to provide a consistent comparison with multisection head CT (cCT).MATERIALS AND METHODS: Exposure data obtained for routine scanning during a period of 1 year were used to assess a specific dose of a total of 217 rotational scans performed in 105 patients. One hundred seventy-two scans were 3D digital subtraction angiography (DSA) scans. There were 45 scans that were performed to achieve high-quality, soft-tissue resolution. Dose measurements in cylindrical polymethylmethacrylate (PMMA) phantoms were used to determine the CTDI value and to compare it with the reference values for cCT. In addition, the dose-area product (DAP) was registered and correlated with the CTDI and corresponding dose-length product (DLP) values. Exposure data and dose values were compared with cCT.RESULTS: Mean-weighted CTDI value of 3D-DSA was approximately 9 mGy per scan. High-quality, soft-tissue resolution FPCT scans, comparable with cCT, revealed a mean dose value of 75 mGy (reference value for cCT, CTDI_w ∼ 60 mGy).CONCLUSION: The high-speed scans used for 3D-DSA revealed a significantly lower CTDI_w and DLP compared with clinical CT. The high-quality FPCT protocol resulted in a higher dose and should therefore be limited to acute cases, when patient transfer to a CT scanner is considered to be a disadvantage for patient management.

Flat panel detectors (FPD) mounted on dedicated gantry systems or interventional C-arms are currently used for CT scanning. These scanners are used for interventional radiology and angiography or image-guided radiation therapy units and offer large coverage of up to 200 mm.^1-6 Volumetric imaging provided in the operating room has proved to be valuable for intraoperative procedures and is available for navigation and fusion with other preoperative or postoperative imaging modalities.^6-8Neuroradiology may benefit from the dual capabilities of such scanners.^8-12 Conventional digital subtraction angiography (DSA) can be combined with rotational digital subtraction angiography (3D-DSA). Furthermore, rotational datasets can also be used to reconstruct native or contrast CT datasets of the brain and skull. The image quality of modern C-arm scanners has improved, especially with respect to low-contrast detectability.^4-6 The first C-arms with use of CT functionality were equipped with image intensifier tubes and had their application, especially in the very-high-contrast angiographic imaging, working with contrast differences of more than 1000 HU. Current systems are equipped with FPDs and offer a significant improvement in low-contrast resolution. Contrast differences of down to 10 HU can be detected, which is a qualitative highlight.^1,4 Imaging of cerebral bleeding, which was only detectable on conventional CT, now is possible within the angiography suite with use of FPCT. Nevertheless, low-contrast image quality is inferior compared with clinical CT.^3,5,6 On the other hand, imaging of small, high-contrast targets, like intracranial microstents, seems to be superior compared with conventional multisection CT.⁹ Bone imaging with FPCT, a high-contrast target again, at least is equal to multisection CT, which is published for lumbar myelography and postmyelographic FPCT.¹⁰The frequent use of FPCT is associated with an increase of radiation dose to the patient when FPCT is performed as an additional examination. It is not surprising that this concern has led to increased scrutiny with regard to the accuracy of radiation dose assessment to patients who undergo CT examinations. C-arm FPCT again has substantial changes in geometry, providing collimations by far higher than the 100-mm recommended integration length of the CT dose index (CTDI) standard.^13-19 In addition, the systems use partial rotation scanning, which is expected to result in inhomogeneous dose distributions in the patient.^6,20 It is also questionable if the common phantoms are sufficient for dosimetry with use of wide-beam fields.^15,19 Although these scanners perform CT scanning, there is no consensus yet on estimating the patient dose for FPCT imaging. Because the systems emerged from radiography and angiography, many manufacturers provide the dose-area product (DAP) omitting any CT-specific terminology.²¹ Still, it is important for intermodality comparison reasons to adapt dose metrics used for FPCT to provide an accurate and flexible dose assessment.In this study, we used the CTDI concepts as they are defined for standard CT and adapted them to the special C-arm geometry to provide a consistent comparison between clinical CT and C-arm CT. The exposure data are provided for routine scanning for 1 year with use of automatic exposure control for the acquisition of 105 patients with C-arm FPCT.     

Multiphase CT angiography versus single-phase CT angiography: comparison of image quality and radiation dose

BACKGROUND AND PURPOSE: Conventional CT angiography (CTA) is acquired during only a short interval in the arterial phase, which limits its ability to evaluate the cerebral circulation. Our aim was to compare the image quality and radiation dose of conventional single-phase CTA (SP-CTA) with a multiphase CTA (MP-CTA) algorithm reconstructed from a perfusion CT (PCT) dataset.MATERIALS AND METHODS: Fifty consecutive patients undergoing head CTA and PCT in 1 examination were enrolled. The PCT dataset was obtained with 40.0-mm-detector coverage, 5.0-mm axial thickness, 80 kilovolt peak (kVp), 180 mA, and 30 mL of contrast medium. MP-CTA was reconstructed from the same PCT dataset with an axial thickness of 0.625 mm by using a new axial reconstruction algorithm. A conventional SP-CTA dataset was obtained with 0.625-mm axial thickness, 120 kVp, 350 mA, and 60 mL of contrast medium. We compared image quality, vascular enhancement, and radiation dose.RESULTS: SP-CTA and MP-CTA of 50 patients (male/female ratio, 31/19; mean age, 59.25 years) were analyzed. MP-CTA was significantly better than SP-CTA in vascular enhancement (P = .002), in the absence of venous contamination (P = .006), and was significantly higher in image noise (P < .001). MP-CTA used less contrast medium than SP-CTA and could demonstrate hemodynamic information. The effective dose of MP-CTA was 5.73 mSv, which was equal to that in conventional PCT, and it was 3.57 mSv in SP-CTA.CONCLUSION: It is feasible that MP-CTA may provide both CTA and PCT results. Compared with SP-CTA, MP-CTA provides comparable image quality, better vascular enhancement, hemodynamic information, and more noise with less detail visibility with a lower tube voltage. The radiation dose of MP-CTA is higher than that of SP-CTA, but the dose can be reduced by altering the sampling interval.

Cerebral CT angiography (CTA) is a well-established minimally invasive diagnostic procedure used to detect cerebral aneurysms, acute vascular occlusions, or vasospasms and even predicts hematoma expansion in acute intracerebral hemorrhage.^1–6 Cerebral perfusion CT (PCT) is an important tool to evaluate cerebral ischemia, infarction, cerebral vascular reserve, and microvascular permeability of intracranial neoplasms.⁷ With PCT, the linear relationship between contrast concentration and pixel intensity lends itself more readily to quantification of blood flow values, compared with bolus contrast MR perfusion imaging.^8,9 PCT generates parametric maps of blood flow, including cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT), by using complex deconvolution algorithms.⁷ In a systematic review, the authors concluded that the most accurate assessment of the site of occlusion, infarct core, salvageable brain tissue, and collateral circulation in patients suspected of acute stroke is by a combination of PCT and CTA.¹⁰ Compared with the dose used for single-detector-row CT, thin-section, multidetector CT (MDCT) requires an increased radiation dose for both CTA and PCT examinations.^11–13 To attain an “as low as reasonably achievable radiation dose,” many techniques have been tried to optimize radiation-dose levels in MDCT CTA.Currently, most commercialized CT scanners provide axial scanning in maximum z-axis coverage of 40-mm (2.5 mm × 16) sections; thin-thickness reconstruction modes can be scanned in 20-mm (0.625 mm × 32) sections. During acquisition of conventional CTA, only a short interval in the arterial phase is taken for reconstruction. We call this “single-phase CTA” (SP-CTA). During PCT examinations, to evaluate the area of attenuation change, we acquired axial scans of sequential images at the same level in a fixed or variable time interval (ie, multiphase mode). With the increasing scanning speed of CT, the time interval can be reduced to 0.5 second in state-of-the-art MDCT. Scanning coverage is still a problem because of the cone beam geometry in current MDCT. The fully sampled region, the region covered by every view in the scanning, is less than the cylinder, with a height equal to the detector isocenter coverage.^14,15 To overcome this problem, we used extrapolation during the back projection process. The cone beam effect increases farther away from the isocenter and becomes more prominent with a larger FOV. Under such conditions, a novel vendor reconstruction algorithm has been developed to solve the cone beam effect, conducting a 40-mm beam of 64i × 0.625 mm in an axial scanning. We can then obtain raw data of thin-section PCT and perform postprocessing to reconstruct CTA from this thin-section PCT. Because such CTA images contain data from different time points, we call the technique “multiphase CTA” (MP-CTA), in contrast to conventional single-phase (SP-CTA). This study was designed to compare the image quality and radiation dose of MP-CTA by using the novel thin-reconstruction algorithm from the PCT dataset with the SP-CTA data from the same patient.     

Subtraction 3D CT angiography with the orbital synchronized helical scan technique for the evaluation of postoperative cerebral aneurysms treated with cobalt-alloy clips

BACKGROUND AND PURPOSE: CT angiography (CTA) has been used for the evaluation of intracranial aneurysms and recently has been applied to assess postoperative aneurysms treated with titanium-alloy clips. We investigated the clinical usefulness of subtraction CTA by using the orbital synchronized helical scan technique (OSHST) for evaluating intracranial aneurysms surgically treated with cobalt-alloy clips.MATERIALS AND METHODS: We scanned an agar gel phantom with a cobalt-alloy clip mounted in the center by using subtraction CT with and without OSHST. Eighteen patients (20 aneurysms) who underwent surgery with cobalt-alloy clips were postoperatively evaluated with subtraction CTA with OSHST, and the results were compared with those from digital subtraction angiography. Two neuroradiologists independently evaluated the 3D CTA images and source images with and without subtraction for the presence of residual flow in the aneurysm and stenotic change in parent or neighboring arteries.RESULTS: For the phantom study, significantly fewer artifacts from clips were noted on images obtained by using subtraction CT with OSHST than on those obtained without OSHST. For the clinical study, subtraction CTA with OSHST also showed fewer clip artifacts than did conventional CTA. Image quality was poor, and we were unable to diagnose residual neck for 5% (1/20) with subtraction CTA with OSHST and 75% (15/20) with conventional CTA. For evaluation of adjacent vessels, image quality was poor for none (0/20) with subtraction CTA with OSHST and for 55% (11/20) with conventional CTA. For subtraction CTA with OSHST, sensitivity in detecting residual neck was 1.0, and specificity was 0.94. For conventional CTA, sensitivity and specificity were both 0.25.CONCLUSIONS: OSHST is a useful technique for subtracting cobalt-alloy clips, and subtraction CTA with OSHST is available for evaluating aneurysms after clipping with cobalt-alloy clips.

Subtraction CT angiography (CTA), which eliminates bone structures by using a precontrast scan, has become a useful and noninvasive technique to evaluate intracranial aneurysms, especially those adjacent to bone.^1–3 The orbital synchronized helical scan technique (OSHST) was developed to permit 2 consecutive acquisitions along the same helical path, thereby reducing the misregistration between the 2 scans to enable acquisition of accurate subtraction images.⁴CTA of the brain has recently been applied to assess aneurysms surgically occluded by the use of titanium-alloy clips.^5–7 However, the strong artifacts from cobalt-alloy clips complicated assessment of the aneurysm neck and adjacent vessels^8,9; it was thought that postoperative evaluation by using CTA was difficult for patients treated with cobalt-alloy clips.To elucidate the clinical usefulness of subtraction CTA with OSHST for evaluating intracranial aneurysms surgically treated with cobalt-alloy clips, we examined the difference in subtraction images with or without OSHST in a phantom and compared findings from subtraction CTA with OSHST, conventional CTA, and digital subtraction angiography (DSA) in patients who had undergone cobalt-clip occlusion.     

Intra-arterial nimodipine for severe cerebral vasospasm after aneurysmal subarachnoid hemorrhage: influence on clinical course and cerebral perfusion

BACKGROUND AND PURPOSE: The efficacy of intra-arterial administration of nimodipine (IAN) in patients with severe vasospasm after aneurysmal subarachnoid hemorrhage (SAH) remains unproved. The goal of the present study was to investigate the clinical effect and cerebral perfusion after IAN in patients with severe vasospasm refractory to hemodynamic treatment.MATERIALS AND METHODS: Twenty-six of 214 patients with aneurysmal SAH were included in the prospective study, approved by the local ethics committee. All patients met the criteria of medically refractory cerebral vasospasm. Effectiveness was monitored angiographically by digital subtraction angiography and by transcranial Doppler (TCD), perfusion CT (PCT), and neurologic examination during treatment course and follow-up.RESULTS: No angiographic effect was observed in 8 patients. The pooled PCT values revealed a reduction of time to peak (P = .03) and mean transit time (P = .17) 1 day after intervention. This effect did not persist during the following days. The pooled TCD analysis demonstrated a transient increase in flow 1 day after intervention (P = .03). No trend was evident during the next 7 days after intervention. Additional infarction was experienced by 61.1% of patients.CONCLUSIONS: IAN in a selective patient group resulted in a positive response with reduction of angiographic vasospasm and increase in cerebral perfusion as detected by PCT after 24 hours. Therefore, IAN appears more effective than intra-arterial papaverine. Nevertheless the efficacy of IAN is temporary. Therefore, the search for more effective treatment strategies to reduce critical vasospasm and to improve cerebral perfusion must be continued.

Severe cerebral vasospasm constitutes the dominant factor of secondary morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH).^1-4 The current strategies for preventing vasospasm comprise the systemic administration of the calcium channel blocker nimodipine.^5-7 Moreover, the use of intracisternal thrombolysis⁸ and the intracisternal application of nicardipine-prolonged implants^9,10 demonstrated effectiveness in preventing cerebral vasospasm. Despite these treatment methods,^6,11 the rate of vasospasm-related permanent disability is estimated as totaling 10%–20%.^12,13 Meta-analyses on the efficacy of hemodynamic therapy are partially contradictory but usually recommend hemodynamic optimization for symptomatic vasospasm.^6,13-15For symptomatic vasospasm refractory to hemodynamic therapy, endovascular strategies such as balloon angioplasty¹⁶ and intra-arterial spasmolysis with papaverine¹⁷ or nimodipine¹⁸ have been recommended. Balloon angioplasty was found effective, but the procedure is limited to proximal vessel segments. In addition, it demands an experienced endovascular surgeon and is associated with significant risk.^19,20 Intra-arterial papaverine has been shown to reverse angiographic vasospasm and to reduce the velocities as detected by transcranial Doppler (TCD).^17,21 However, clinical trials have failed to demonstrate the effectiveness of intra-arterial papaverine on outcome.²² The most likely reason for this failure is the short duration of effect that has been documented: it is limited to a mere few hours.²³ Intra-arterial nimodipine (IAN) in patients with severe vasospasm has been reported by several authors.^24-26 Data from a larger series by Biondi et al¹⁸ suggested that IAN is effective and safe for the treatment of vasospasm after SAH. However, no information regarding the influence of IAN on cerebral perfusion is available. Moreover, there is a lack of information about the duration of effect.The objective of the present study was to investigate the effect and duration of the action of IAN by repeated assessment of the clinical condition with TCD, digital subtraction angiography (DSA), and perfusion measurements by means of perfusion CT (PCT).     

Accuracy of the Alberta Stroke Program Early CT Score during the first 3 hours of middle cerebral artery stroke: comparison of noncontrast CT, CT angiography source images, and CT perfusion

BACKGROUND AND PURPOSE: The Alberta Stroke Program Early CT Score (ASPECTS) is a reliable method of delineating the extent of middle cerebral artery (MCA) stroke. Our aim was to retrospectively compare the accuracy of ASPECTS on noncontrast CT, CT angiography (CTA) source images, and CT perfusion maps of cerebral blood volume (CBV) during the first 3 hours of middle cerebral artery (MCA) stroke.MATERIALS AND METHODS: First-time patients with MCA stroke who presented <3 hours from symptom onset and were evaluated by noncontrast CT/CTA/CT perfusion, had confirmed acute nonlacunar MCA infarct on diffusion-weighted MR imaging (DWI) within 7 days, and had follow-up angiography were included. Patients were excluded for persistent MCA occlusion or stenosis. Two raters through consensus assigned an ASPECTS on the noncontrast CT, CTA source images, and the section-selective (2 × 12 mm coverage) CT perfusion CBV maps. ASPECTS on follow-up DWI served as the reference standard. For each CT technique, the detection rates of regional infarction, the mean ASPECTS, and the linear correlation to final ASPECTS were determined and compared. P values <.05 were considered significant.RESULTS: Twenty-eight patients satisfied the criteria with DWI performed at a mean of 50.3 hours (range, 22–125 hours) post-CT imaging. Of 280 ASPECTS regions, 100 were infarcted on DWI. The accuracy of noncontrast CT, CTA source images, and CT perfusion CBV for detecting regional infarct was 80.0%, 84.3%, and 96.8%, respectively (P < .0001). The mean ASPECTSs of noncontrast CT, CTA source images, CT perfusion CBV, and DWI were 8.4 ± 1.8, 8.0 ± 1.8, 6.8 ± 1.9, and 6.5 ± 1.8, respectively. The mean noncontrast CT and CTA source image ASPECTS was different from that of DWI (P < .05). Correlation of noncontrast CT, CTA source images, and CT perfusion CBV ASPECTS with final ASPECTS was r² = 0.34, r² = 0.42, and r² = 0.91, respectively.CONCLUSION: In a retrospective cohort of MCA infarcts imaged <3 hours from stroke onset, ASPECTS was most accurately determined on CT perfusion CBV maps.

The Alberta Stroke Program Early CT Score (ASPECTS) is a semiquantitative method of defining infarct extent in the middle cerebral artery (MCA) territory that is more reliable than the “1/3 MCA” rule^1,2 and is highly predictive of outcome.^3-6 ASPECTS was designed for conventional noncontrast CT, the ubiquitously performed imaging technique for triaging acute stroke. However, several recent studies have reported application of ASPECTS to CT angiography (CTA) source images^7-9 and CT perfusion parametric color maps,^10-12 with data to suggest that the acute ASPECTS is more accurately determined on these advanced CT techniques. Our aim was to retrospectively compare the accuracy and strength of the correlation of the acute ASPECTSs obtained on noncontrast CT, CTA source images, and CT perfusion mapping of cerebral blood volume (CBV) for nonlacunar MCA territory strokes imaged during the initial 3 hours of symptom onset. We hypothesized that with arterial recanalization, the CT perfusion CBV map is the best predictor of the final ASPECTS.