T2-FLAIR Mismatch: An Imaging Biomarker for Children's MYB/MYBL1-Altered Diffuse Astrocytoma or Angiocentric Glioma.

BACKGROUND AND PURPOSE: T2-FLAIR mismatch is a highly specific imaging biomarker of IDH-mutant diffuse astrocytoma in adults. It has however also been described in MYB/MYBL1-altered low grade tumors. Our aim was to assess the diagnostic power of the T2-FLAIR mismatch in IDH-mutant astrocytoma and MYB/MYBL1-altered low-grade tumors in children and correlate this mismatch with histology. MATERIALS AND METHODS: We evaluated MR imaging examinations of all pediatric patients, performed at the Princess Máxima Center for Pediatric Oncology and the University Medical Center Utrecht between January 2012 and January 2023, with the histomolecular diagnosis of IDH-mutant astrocytoma, diffuse astrocytoma MYB/MYBL1-altered, or angiocentric glioma, and the presence of T2-FLAIR mismatch was assessed. Histologically, the presence of microcysts in the tumor (a phenomenon suggested to be correlated with T2-FLAIR mismatch in IDH-mutant astrocytomas in adults) was evaluated. RESULTS: Nineteen pediatric patients were diagnosed with either IDH-mutant astrocytoma (n = 8) or MYB/MYBL1-altered tumor (n = 11: diffuse astrocytoma, MYB- or MYBL1-altered n = 8; or angiocentric glioma n = 3). T2-FLAIR mismatch was present in 11 patients, 3 (38%) in the IDH-mutant group and 8 (73%) in the MYB/MYBL1 group. No correlation was found between T2-FLAIR mismatch and the presence of microcysts or an enlarged intercellular space in either IDH-mutant astrocytoma (P = .38 and P = .56, respectively) or MYB/MYBL1-altered tumors (P = .36 and P = .90, respectively). CONCLUSIONS: In our pediatric population, T2-FLAIR mismatch was more often found in MYB/MYBL1-altered tumors than in IDH-mutant astrocytomas. In contrast to what has been reported for IDH-mutant astrocytomas in adults, no correlation was found with microcystic changes in the tumor tissue. This finding challenges the hypothesis that such microcystic changes and/or enlarged intercellular spaces in the tissue of these tumors are an important part of explaining the occurrence of the T2-FLAIR mismatch.

MR Imaging and Clinical Characteristics of Diffuse Glioneuronal Tumor with Oligodendroglioma-like Features and Nuclear Clusters.

BACKGROUND AND PURPOSE: Diffuse glioneuronal tumor with oligodendroglioma-like features and nuclear clusters (DGONC) is a new, molecularly defined glioneuronal CNS tumor type. The objective of the present study was to describe MR imaging and clinical characteristics of patients with DGONC. MATERIALS AND METHODS: Preoperative MR images of 9 patients with DGONC (median age at diagnosis, 9.9 years; range, 4.2-21.8 years) were reviewed. RESULTS: All tumors were located superficially in the frontal/temporal lobes and sharply delineated, displaying little mass effect. Near the circle of Willis, the tumors encompassed the arteries. All except one demonstrated characteristics of low-to-intermediate aggressiveness with high-to-intermediate T2WI and ADC signals and bone remodeling. Most tumors (n = 7) showed a homogeneous ground-glass aspect on T2-weighted and FLAIR images. On the basis of the original histopathologic diagnosis, 6 patients received postsurgical chemo-/radiotherapy, 2 were irradiated after surgery, and 1 patient underwent tumor resection only. At a median follow-up of 61 months (range, 10-154 months), 6 patients were alive in a first complete remission and 2 with stable disease 10 and 21 months after diagnosis. The only patient with progressive disease was lost to follow-up. Five-year overall and event-free survival was 100% and 86±13%, respectively. CONCLUSIONS: This case series presents radiomorphologic characteristics highly predictive of DGONC that contrast with the typical aspects of the original histopathologic diagnoses. This presentation underlines the definition of DGONC as a separate entity, from a clinical perspective. Complete resection may be favorable for long-term disease control in patients with DGONC. The efficacy of nonsurgical treatment modalities should be evaluated in larger series.

Detection of Early Ischemic Changes with Virtual Noncontrast Dual-Energy CT in Acute Ischemic Stroke: A Noninferiority Analysis.

BACKGROUND AND PURPOSE: Dual-energy virtual NCCT has the potential to replace conventional NCCT to detect early ischemic changes in acute ischemic stroke. In this study, we evaluated whether virtual NCCT is noninferior compared with standard linearly blended NCCT, a surrogate of conventional NCCT, regarding the detection of early ischemic changes with ASPECTS. MATERIALS AND METHODS: Adult patients who presented with suspected acute ischemic stroke and who underwent dual-energy NCCT and CTA and brain MR imaging within 48 hours were included. Standard linearly blended images were reconstructed to match a conventional NCCT. Virtual NCCT images were reconstructed from CTA. ASPECTS was evaluated on conventional NCCT, virtual NCCT, and DWI, which served as the reference standard. Agreement between CT assessments and the reference standard was evaluated with the Lin concordance correlation coefficient. Noninferiority was assessed with bootstrapped estimates of the differences in ASPECTS between conventional and virtual NCCT with 95% CIs. RESULTS: Of the 193 included patients, 100 patients (52%) had ischemia on DWI. Compared with the reference standard, the ASPECTS concordance correlation coefficient for conventional and virtual NCCT was 0.23 (95% CI, 0.15-0.32) and 0.44 (95% CI, 0.33-0.53), respectively. The difference in the concordance correlation coefficient between virtual and conventional NCCT was 0.20 (95% CI, 0.01-0.39) and did not cross the prespecified noninferiority margin of -0.10. CONCLUSIONS: Dual-energy virtual NCCT is noninferior compared with conventional NCCT for the detection of early ischemic changes with ASPECTS.

Evaluate the safety and efficacy of dura sealant patch in reducing cerebrospinal fluid leakage following elective cranial surgery (ENCASE II): study protocol for a randomized, two-arm, multicenter trial.

BACKGROUND: Cerebrospinal fluid (CSF) leakage is a frequent and challenging complication in neurosurgery, especially in the posterior fossa, with a prevalence of 8%. It is associated with substantial morbidity and increased healthcare costs. A novel dural sealant patch (LIQOSEAL) was developed for watertight dural closure. The objective of this study is to clinically assess the safety and effectiveness of LIQOSEAL as a means of reducing intra- as well as postoperative CSF leakage in patients undergoing elective posterior fossa intradural surgery with a dural closure procedure compared to the best currently available dural sealants. METHODS: We will conduct a two-arm, randomized controlled, multicenter study with a 90-day follow-up. A total of 228 patients will be enrolled in 19 sites, of which 114 will receive LIQOSEAL and 114 an FDA-approved PEG sealant. The composite primary endpoint is defined as intraoperative CSF leakage at PEEP 20 cm H2O, percutaneous CSF leakage within 90 days of, wound infection within 90 days of or pseudomeningocele of more than 20cc on MRI or requiring intervention. We hypothesize that the primary endpoint will not be reached by more than 10 patients (9%) in the investigational arm, which will demonstrate non-inferiority of LIQOSEAL compared to control. DISCUSSION: This trial will evaluate whether LIQOSEAL is non-inferior to control as a means of reducing CSF leakage and safety TRIAL REGISTRATION: ClinicalTrials.gov NCT04086550 . Registered on 11 September 2019.

Brain retraction injury after elective aneurysm clipping: a retrospective single-center cohort study.

BACKGROUND: BRI is estimated to occur in 10% of skull-base surgery and 5% of aneurysm surgery. These estimates are based on a few studies with unclear methodology. The purpose of this study is to assess the rate of BRI occurrence, its risk factors, and the association between BRI and postoperative focal neurological deficit in patients that underwent elective aneurysm surgery in a single institution. METHODS: All patients that underwent elective aneurysm surgery in a single tertiary center in the Netherlands were included. BRI was defined as cortical hypodensities in the surgical trajectory not matching areas of large arterial infarction. Risk ratios were calculated between BRI and (a) the use of temporary parent artery occlusion during clipping, (b) anterior communicating artery (ACom), and (c) middle cerebral artery (MCA) location of the aneurysm, (d) presence of mentioned CVA risk factors, (e) the clipping of > 1 aneurysm during the same procedure, and (f) new focal neurological deficit. Statistical analysis further included t-tests and binary logistical regression analysis on the correlation between age and BRI. RESULTS: BRI was identified postoperatively in 42 of the 94 patients included in this study. A new focal neurological deficit was found in 7 patients in the BRI group. A total of 5 patients had persisting symptoms at 3-month follow-up, of which 2 were caused by BRI. Increasing age is a risk factor for developing BRI. CONCLUSIONS: The high rate of BRI and significant risk of new postoperative focal neurological deficit in our patients should be considered when counseling patients for elective aneurysm surgery.

[Posture-dependent headache caused by spontaneous intracranial hypotension]. / Houdingsafhankelijke hoofdpijn door spontane intracraniële hypotensie.

A 36-year-old woman presented with a 3-4 month history of severe, progressive headache. The headache was characterized by postural variation, with excruciating headache in the upright position and near-immediate relief upon recumbence. There was no history of trauma or lumbar puncture. Gadolineum-enhanced brain MRI revealed abnormalities characteristic intracranial hypotension. Spinal MRI showed a longitudinal extradural fluid collection; a localization of the dural defect was not found. The patient was treated with caffeine, bed rest and lumbar epidural blood patches; she recovered completely. Severe orthostatic headache which aggravates upon standing and is relieved by recumbence, can be caused by spontaneous intracranial hypotension. Recognition of its characteristic symptoms is needed for timely referral. Treatment is usually successful and can prevent life-threatening complications.

Dose of CT protocols acquired in clinical routine using a dual-layer detector CT scanner: A preliminary report.

PURPOSE: To assess the radiation dose associated with always-on dual-energy acquisitions in clinical practice over a broad range of clinical protocols using a dual-layer detector CT (DLCT; IQon spectral CT, Philips Healthcare) as compared to an otherwise technically equivalent single-layer detector CT (SLCT; Brilliance iCT, Philips healthcare). MATERIALS AND METHODS: Dose-length-product data for consecutive examinations over a six-month period acquired with DLCT were retrospectively collected and compared to consecutive examinations from an SLCT. Imaging protocols were optimized for diagnostic image quality for each system prior to data collection. Dose reports of CT protocols that were used at least 50 times on both systems were collected. After exclusion of statistical outliers, protocols were evaluated with regard to reported dose levels. RESULTS: In total, 4536 dose reports for DLCT and 5783 reports for SLCT were collected. All DLCT examinations were acquired at 120 kVp, enabling dual-energy analysis. With SLCT, 79% of examinations were acquired at 120 kVp, and 21% at 100/80 kVp. Protocols for 15 indications were used more than 50 times on both scanners. For seven protocols there was no significant difference between the two scanners (p > 0.05), whereas seven protocols were acquired with higher dose levels on SLCT compared to the DLCT (p < 0.03). For one protocol, the DLCT dose was significantly higher (p < 0.005) compared to the SLCT. CONCLUSION: Dual-layer detector CT enables acquisition of dual-energy information over a broad range of clinical indications without increasing radiation dose when compared to a conventional single-layer detector CT.

Outcome in Patients with Isolated Moderate to Severe Traumatic Brain Injury.

INTRODUCTION: Traumatic brain injury (TBI) remains a major cause of death. Withdrawal of life-sustaining treatment (WLST) can be initiated if there is little anticipated chance of recovery to an acceptable quality of life. The aim of this study was firstly to investigate WLST rates in patients with moderate to severe isolated TBI and secondly to assess outcome data in the survivor group. MATERIAL AND METHODS: A retrospective cohort study was performed. Patients aged ≥ 18 years with moderate or severe isolated TBI admitted to the ICU of a single academic hospital between 2011 and 2015 were included. Exclusion criteria were isolated spinal cord injury and referrals to and from other hospitals. Gathered data included demographics, mortality, cause of death, WLST, and Glasgow Outcome Scale (GOS) score after three months. Good functional outcome was defined as GOS > 3. RESULTS: Of 367 patients, 179 patients were included after applying inclusion and exclusion criteria. 55 died during admission (33%), of whom 45 (82%) after WLST. Patients undergoing WLST were older, had worse neurological performance at presentation, and had more radiological abnormalities than patients without WLST. The decision to withdraw life-sustaining treatment was made on the day of admission in 40% of patients. In 33% of these patients, this decision was made while the patient was in the Emergency Department. 71% of survivors had a good functional outcome after three months. No patient left hospital with an unresponsive wakefulness syndrome (UWS) or suffered from UWS after three months. One patient died within three months of discharge. CONCLUSION: In-hospital mortality in isolated brain injured patients was 33%. The vast majority died after a decision to withdraw life-sustaining treatment. None of the patients were discharged with an unresponsive wakefulness syndrome.

Assessment of Collateral Status by Dynamic CT Angiography in Acute MCA Stroke: Timing of Acquisition and Relationship with Final Infarct Volume.

BACKGROUND AND PURPOSE: Dynamic CTA is a promising technique for visualization of collateral filling in patients with acute ischemic stroke. Our aim was to describe collateral filling with dynamic CTA and assess the relationship with infarct volume at follow-up. MATERIALS AND METHODS: We selected patients with acute ischemic stroke due to proximal MCA occlusion. Patients underwent NCCT, single-phase CTA, and whole-brain CT perfusion/dynamic CTA within 9 hours after stroke onset. For each patient, a detailed assessment of the extent and velocity of arterial filling was obtained. Poor radiologic outcome was defined as an infarct volume of ≥70 mL. The association between collateral score and follow-up infarct volume was analyzed with Poisson regression. RESULTS: Sixty-one patients with a mean age of 67 years were included. For all patients combined, the interval that contained the peak of arterial filling in both hemispheres was between 11 and 21 seconds after ICA contrast entry. Poor collateral status as assessed with dynamic CTA was more strongly associated with infarct volume of ≥70 mL (risk ratio, 1.9; 95% CI, 1.3-2.9) than with single-phase CTA (risk ratio, 1.4; 95% CI, 0.8-2.5). Four subgroups (good-versus-poor and fast-versus-slow collaterals) were analyzed separately; the results showed that compared with good and fast collaterals, a similar risk ratio was found for patients with good-but-slow collaterals (risk ratio, 1.3; 95% CI, 0.7-2.4). CONCLUSIONS: Dynamic CTA provides a more detailed assessment of collaterals than single-phase CTA and has a stronger relationship with infarct volume at follow-up. The extent of collateral flow is more important in determining tissue fate than the velocity of collateral filling. The timing of dynamic CTA acquisition in relation to intravenous contrast administration is critical for the optimal assessment of the extent of collaterals.

Imaging Findings Associated with Space-Occupying Edema in Patients with Large Middle Cerebral Artery Infarcts.

BACKGROUND AND PURPOSE: Prominent space-occupying cerebral edema is a devastating complication occurring in some but not all patients with large MCA infarcts. It is unclear why differences in the extent of edema exist. Better knowledge of factors related to prominent edema formation could aid treatment strategies. This study aimed to identify variables associated with the development of prominent edema in patients with large MCA infarcts. MATERIALS AND METHODS: From the Dutch Acute Stroke Study (DUST), 137 patients were selected with large MCA infarcts on follow-up NCCT (3 ± 2 days after stroke onset), defined as ASPECTS ≤4. Prominent edema was defined as a midline shift of ≥5 mm on follow-up. Admission patient and treatment characteristics were collected. Admission CT parameters used were ASPECTS on NCCT and CBV and MTT maps, and occlusion site, clot burden, and collaterals on CTA. Permeability on admission CTP, and day 3 recanalization and reperfusion statuses were obtained if available. Unadjusted and adjusted (age and NIHSS) odds ratios were calculated for all variables in relation to prominent edema. RESULTS: Prominent edema developed in 51 patients (37%). Adjusted odds ratios for prominent edema were higher with lower ASPECTS on NCCT (adjusted odds ratio, 1.32; 95% CI, 1.13-1.55) and CBV (adjusted odds ratio, 1.26; 95% CI, 1.07-1.49), higher permeability (adjusted odds ratio, 2.35; 95% CI, 1.30-4.24), more proximal thrombus location (adjusted odds ratio, 3.40; 95% CI, 1.57-7.37), higher clot burden (adjusted odds ratio, 2.88; 95% CI, 1.11-7.45), and poor collaterals (adjusted odds ratio, 3.93; 95% CI, 1.78-8.69). CONCLUSIONS: Extensive proximal occlusion, poor collaterals, and larger ischemic deficits with higher permeability play a role in the development of prominent edema in large MCA infarcts.

The use of (18)F-FDG PET to differentiate progressive disease from treatment induced necrosis in high grade glioma.

In the follow-up of patients treated for high grade glioma, differentiation between progressive disease (PD) and treatment-induced necrosis (TIN) is challenging. The purpose of this study is to evaluate the diagnostic accuracy of FDG PET for the differentiation between TIN and PD after high grade glioma treatment. We retrospectively identified patients between January 2011 and July 2013 that met the following criteria: age >18; glioma grade 3 or 4; treatment with radiotherapy or chemoradiotherapy; new or progressive enhancement on post treatment MRI; FDG PET within 4 weeks of MRI. Absolute and relative (to contralateral white matter) values of SUVmax and SUVpeak were determined in new enhancing lesions on MRI. The outcome of PD or TIN was determined by neurosurgical biopsy/resection, follow-up MRI, or clinical deterioration. The association between FDG PET and outcome was analyzed with univariate logistic regression and ROC analysis for: all lesions, lesions >10, >15, and >20 mm. We included 30 patients (5 grade 3 and 25 grade 4), with 39 enhancing lesions on MRI. Twenty-nine lesions represented PD and 10 TIN. Absolute and relative values of SUVmax and SUVpeak showed no significant differences between PD and TIN. ROC analysis showed highest AUCs for relative SUVpeak in all lesion sizes. Relative SUVpeak for lesions >20 mm showed reasonable discriminative properties [AUC 0.69 (0.41-0.96)]. FDG PET has reasonable discriminative properties for differentiation of PD from TIN in high grade gliomas larger than 20 mm. Overall diagnostic performance is insufficient to guide clinical decision-making.

Imaging findings of the orbital and intracranial complications of acute bacterial rhinosinusitis.

UNLABELLED: In patients with acute bacterial rhinosinusitis severe orbital and intracranial complications can occur. This review will illustrate the anatomic relationship between the paranasal sinuses and the orbital and intracranial compartments. Subsequently, the spectrum of orbital and intracranial complications of rhinosinusitis and related imaging findings will be discussed and illustrated by case material from daily practice. TEACHING POINTS: • Acute bacterial rhinosinusitis can cause severe orbital and intracranial complications. • If orbital or intracranial complications are suspected, cross-sectional imaging is mandatory. • Infection can spread from the ethmoid sinus to the orbit through the lamina papyracea. • Frontal sinusitis can spread intracranially through dehiscences or osteomyelitis. • Radiologists must recognize imaging findings of complications of acute bacterial rhinosinusitis.

Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study.

BACKGROUND AND PURPOSE: Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic stroke, to examine whether standard CTA can be omitted. MATERIALS AND METHODS: Patients with suspected ischemic stroke were prospectively enrolled and underwent CTA and CTP imaging at admission. Timing-invariant CTA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CTA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using κ statistics. RESULTS: We included 108 patients with 47 vessel occlusions. Overall, standard CTA and timing-invariant CTA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% CI, 90%-100%) and a specificity of 100% (99%-100%) for standard CTA and a sensitivity of 98% (95% CI, 94%-100%) and a specificity of 100% (95% CI, 100%-100%) for timing-invariant CTA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% CI, 100%-100%) for both techniques. Interrater agreement was good for both techniques (mean κ value, 0.75 and 0.76). CONCLUSIONS: Timing-invariant CTA derived from CTP data provides diagnostic accuracy similar to that of standard CTA for the detection of artery occlusions in acute stroke.

Predictors of reperfusion in patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: Ischemic stroke studies emphasize a difference between reperfusion and recanalization, but predictors of reperfusion have not been elucidated. The aim of this study was to evaluate the relationship between reperfusion and recanalization and identify predictors of reperfusion. MATERIALS AND METHODS: From the Dutch Acute Stroke Study, 178 patients were selected with an MCA territory deficit on admission CTP and day 3 follow-up CTP and CTA. Reperfusion was evaluated on CTP, and recanalization on CTA, follow-up imaging. Reperfusion percentages were calculated in patients with and without recanalization. Patient admission and treatment characteristics and admission CT imaging parameters were collected. Their association with complete reperfusion was analyzed by using univariate and multivariate logistic regression. RESULTS: Sixty percent of patients with complete recanalization showed complete reperfusion (relative risk, 2.60; 95% CI, 1.63-4.13). Approximately one-third of patients showed some discrepancy between recanalization and reperfusion status. Lower NIHSS score (OR, 1.06; 95% CI, 1.01-1.11), smaller infarct core size (OR, 3.11; 95% CI, 1.46-6.66; and OR, 2.40; 95% CI, 1.14-5.02), smaller total ischemic area (OR, 4.20; 95% CI, 1.91-9.22; and OR, 2.35; 95% CI, 1.12-4.91), lower clot burden (OR, 1.35; 95% CI, 1.14-1.58), distal thrombus location (OR, 3.02; 95% CI, 1.76-5.20), and good collateral score (OR, 2.84; 95% CI, 1.34-6.02) significantly increased the odds of complete reperfusion. In multivariate analysis, only total ischemic area (OR, 6.12; 95% CI, 2.69-13.93; and OR, 1.91; 95% CI, 0.91-4.02) was an independent predictor of complete reperfusion. CONCLUSIONS: Recanalization and reperfusion are strongly associated but not always equivalent in ischemic stroke. A smaller total ischemic area is the only independent predictor of complete reperfusion.

Vocal cord paralysis: anatomy, imaging and pathology.

UNLABELLED: Vocal cord paralysis (VCP) can be caused by any process that interferes with the normal function of the vagal nerves or recurrent laryngeal nerves. It may be a first sign of extensive and severe pathology. Radiologists must therefore be able to recognise the imaging findings of VCP and know the course of the vagal and recurrent laryngeal nerves. This review focuses on the anatomy and imaging evaluation of these nerves and thereby the possible sites for pathology causing VCP. The imaging characteristics and imaging mimics of VCP are discussed and cases from daily practice illustrating causes of VCP are presented. TEACHING POINTS: • Vocal cord paralysis may be the first presentation of severe pathology. • Radiologists must be aware of imaging characteristics and mimics of vocal cord paralysis. • Lesions along the vagal nerves and recurrent laryngeal nerves can cause vocal cord paralysis.

Predictive value of thrombus attenuation on thin-slice non-contrast CT for persistent occlusion after intravenous thrombolysis.

BACKGROUND: In stroke erythrocyte-rich thrombi are more sensitive to intravenous thrombolysis with recombinant tissue plasminogen activator (IV-rtPA) and have higher density on non-contrast CT (NCCT). We investigated the relationship between thrombus density and recanalization and whether persistent occlusions can be predicted by Hounsfield unit (HU) measurements. METHODS: In 88 IV-rtPA-treated patients with intracranial ICA or MCA occluding thrombus and follow-up imaging, thrombus and contralateral vessel attenuation measurements were performed on thin-slice NCCT. Mean absolute and relative HU were compared between patients with persistent occlusion (modified Thrombolysis in Cerebral Infarction system, grade 0/1/2a) and recanalization (grade 2b/3). Univariate and multivariate (adjusted for stroke subtype, clot burden score, occlusion site and time to thrombolysis) odds ratios for persistent occlusion were calculated. Additional prognostic value for persistent occlusion was estimated by adding HU measurements to the area under the curve (AUC) of known determinants and calculating optimal cut-off values. RESULTS: Patients with persistent occlusion (n = 19) had significant lower mean HU (absolute 52.2 ± 9.5, relative 1.29 ± 0.20) compared to recanalization (absolute 63.1 ± 10.7, relative 1.54 ± 0.23, both p < 0.0001). Odds ratios for persistent occlusion were 3.1 (95% confidence interval, CI 1.6-6.0) univariate and 3.1 (95% CI 1.7-5.7) multivariate per 10 absolute HU decrease and 3.2 (95% CI 1.6-6.5) univariate and 4.1 (95% CI 1.8-9.1) multivariate per 0.20 relative HU decrease. Attenuation measurements significantly increased the AUC (0.67) of the known determinants to 0.84 (absolute HU) and 0.86 (relative HU). Cut-off values of <56.5 absolute HU and <1.38 relative HU showed optimal predictive values for persistent occlusion. CONCLUSIONS: Thrombus density is related to recanalization rate. Lower absolute and relative HU are independently related to persistent occlusion and HU measurements significantly increase discriminative performances of known recanalization determinants.

Diagnostic accuracy of CT perfusion imaging for detecting acute ischemic stroke: a systematic review and meta-analysis.

BACKGROUND: The aim of the current study was to determine the sensitivity and specificity of CT perfusion (CTP) for the detection of ischemic stroke by performing a systematic review and meta-analysis of published reports. METHODS: We searched PubMed, Embase and the Cochrane library using the terms 'perfusion computed tomography', 'ischemic stroke' and synonyms. We included studies that: (1) reported original data, (2) studied the diagnostic value of CTP for detecting ischemic stroke, (3) used MRI-DWI, follow-up MRI or follow-up CT as the reference standard, (4) included at least 10 patients who were suspected of ischemic stroke, and (5) reported the number of true positives, true negatives, false positives and false negatives for the diagnosis of ischemic stroke. RESULTS: Fifteen studies were finally included in the current review with a total of 1,107 patients. A pooled analysis resulted in a sensitivity of 80% (95% confidence interval, CI: 72-86%) and a specificity of 95% (95% CI: 86-98%). Almost two thirds of the false negatives were due to small lacunar infarcts; the remaining false negatives were mostly due to limited coverage. CONCLUSIONS: The current systematic review shows that CTP has a high sensitivity and a very high specificity for detecting infarcts.

CT brain perfusion protocol to eliminate the need for selecting a venous output function.

BACKGROUND AND PURPOSE: In CTP, an arterial input function is used for cerebral blood volume measurement. AIFs are often influenced by partial volume effects resulting in overestimated CBV. A venous output function is manually selected to correct for partial volume. This can introduce variability. Our goal was to develop a CTP protocol that enables AIF selection unaffected by partial volume. MATERIALS AND METHODS: First, the effects of partial volume on artery sizes/types including the MCA were estimated by using a CTP phantom with 9 protocols (section thicknesses of 1, 1.8, and 5 mm and image resolutions of 0.5, 1, and 1.5 mm). Next, these protocols were applied to clinical CTP studies from 6 patients. The influence of the partial volume effect was measured by comparison of the time-attenuation curves from different artery locations with reference veins. RESULTS: AIFs from MCAs were unaffected by partial volume effects when using high image resolution (1 mm) and medium section thickness (1.8 mm). For the clinical data, a total of 104 arteries and 60 veins was selected. The data confirmed that high image resolution and thin section thickness enable selection of MCAs for AIFs free of partial volume influences. In addition, we found that large veins were not insusceptible to partial volume effects relative to large arteries, questioning the use of veins for partial volume correction. CONCLUSIONS: A CTP protocol with 1.8-mm section thickness and 1-mm image resolution allows AIF selection unaffected by partial volume effects in MCAs.

Changes in cerebral perfusion around the time of delayed cerebral ischemia in subarachnoid hemorrhage patients.

BACKGROUND: Because the pathogenesis of delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH) is unclear, we studied cerebral perfusion at different time points around the occurrence of DCI. METHODS: We prospectively enrolled 53 patients admitted to the University Medical Center Utrecht who underwent CT perfusion (CTP) scans on admission, and within 2 weeks after hemorrhage on 2 scheduled time points or during clinical deterioration. The occurrence of DCI was assessed according to predefined criteria by 2 neurological observers blinded to perfusion results. Clinically stable patients (no-DCI) served as reference, and patients with other causes of deterioration (n = 11) were excluded. In DCI patients, the day of DCI onset and in no-DCI patients the median day of DCI onset was taken as t = 0. Scans made before and after DCI were clustered into 5 additional time points. At each time point, cerebral blood volume (CBV) and flow (CBF), and mean transit time (MTT) were measured, and absolute and relative (interhemispheric asymmetry) values were compared between DCI and no-DCI patients. RESULTS: Absolute CBF was lower and MTT was higher in the 18 DCI patients than in the 24 no-DCI patients before, during and after DCI. MTT asymmetry increased during DCI and partially recovered afterwards in DCI patients while it remained constant in no-DCI patients. Absolute and relative CBV remained constant in both groups. CONCLUSIONS: Our findings suggest that DCI patients already have diffusely worse perfusion (absolute values) than no-DCI patients before focal worsening (increased asymmetry) occurs and becomes symptomatic. The partial recovery in the measured areas suggests that DCI can be partly reversible.