Richard I Aviv

The University of Calgary, Calgary, Alberta, Canada

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Publications (163)687.11 Total impact

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    ABSTRACT: To evaluate the impact of rejecting intermediate cerebral blood flow (CBF) images that are adversely affected by head motion during an arterial spin labeling (ASL) acquisition. Eighty participants were recruited, representing a wide age range (14-90 years) and heterogeneous cerebrovascular health conditions including bipolar disorder, chronic stroke, and moderate to severe white matter hyperintensities of presumed vascular origin. Pseudocontinuous ASL and T1 -weigthed anatomical images were acquired on a 3T scanner. ASL intermediate CBF images were included based on their contribution to the mean estimate, with the goal to maximize CBF detectability in gray matter (GM). Simulations were conducted to evaluate the performance of the proposed optimization procedure relative to other ASL postprocessing approaches. Clinical CBF images were also assessed visually by two experienced neuroradiologists. Optimized CBF images (CBFopt ) had significantly greater agreement with a synthetic ground truth CBF image and greater CBF detectability relative to the other ASL analysis methods (P < 0.05). Moreover, empirical CBFopt images showed a significantly improved signal-to-noise ratio relative to CBF images obtained from other postprocessing approaches (mean: 12.6%; range 1% to 56%; P < 0.001), and this improvement was age-dependent (P = 0.03). Differences between CBF images from different analysis procedures were not perceptible by visual inspection, while there was a moderate agreement between the ratings (κ = 0.44, P < 0.001). This study developed an automated head motion threshold-free procedure to improve the detection of CBF in GM. The improvement in CBF image quality was larger when considering older participants. J. Magn. Reson. Imaging 2015. © 2015 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 04/2015; DOI:10.1002/jmri.24918 · 2.79 Impact Factor
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    ABSTRACT: In a porcine ischemic stroke model, we sought to compare the acute predicted infarct core volume (PIV) defined by CT perfusion (CTP)-hemodynamic parameters and MR-diffusion-weighted imaging (MR-DWI)/apparent diffusion coefficient (ADC), with the true infarct core volume (TIV) as defined by histology. Ten Duroc-cross pigs had a CTP scan prior to injection of endothelin-1 (ET-1) into the left striatum. CTP scans were used to monitor ischemic progression. A second dose of ET-1 was injected 2 h from the first injection. The animal was moved to a 3-T MRI scanner where DWI was performed. CTP imaging was acquired immediately after the MR imaging. Next, the brain was removed and stained with tetrazolium chloride (TTC). Linear regression and Bland-Altman plots were used to correlate the PIV measured by each imaging modality to that of the TIV from the histological gold standard. The CTP-cerebral blood flow (CBF) parameter had the highest R (2) value and slope closest to unity, while the CTP-cerebral blood volume (CBV) had the lowest R (2) value and slope furthest away from unity. The CTP-CBF•CBV product parameter had a higher R (2) value but lower slope than both MR parameters. The best Bland-Altman agreement was observed with the CTP-CBF parameter. PIV from MR-DWI, ADC, and CTP-CBF overestimated the TIV defined with histology. We show that the PIV defined with absolute gray and white matter CT-CBF thresholds correlates best with the TIV and is similar to both MR-DWI and ADC-defined PIVs. Further, the acute CBF•CBV mismatch may not indicate penumbral tissue in the acute stroke setting.
    Translational Stroke Research 04/2015; 6(3). DOI:10.1007/s12975-015-0394-x · 1.94 Impact Factor
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    ABSTRACT: Lacunar infarcts account for approximately 25% of acute ischemic strokes. Compared with NCCT alone, the addition of CTP improves sensitivity for detection of infarcts overall. Our aim was to systematically evaluate the diagnostic benefit and interobserver reliability of an incremental CT protocol in lacunar infarction. Institutional review board approval and patient consent were obtained. One hundred sixty-three patients presenting with a lacunar syndrome ≤4.5 hours from symptom onset were enrolled. Images were reviewed incrementally by 2 blinded readers in 3 separate sessions (NCCT only, NCCT/CTA, and NCCT/CTA/CTP). Diagnostic confidence was recorded on a 6-point scale with DWI/ADC as a reference. Logistic regression analysis calculated differences between actual and observed diagnoses, adjusted for confidence. Predictive effects of observed diagnostic accuracy and confidence score were quantified with the entropy r(2) value. Sensitivity, specificity, and confidence intervals were calculated accounting for multiple readers. Receiver operating characteristic analyses were compared among diagnostic strategies. Interobserver agreement was established with Cohen κ statistic. The final study cohort comprised 88 patients (50% male). DWI/ADC-confirmed lacunar infarction occurred in 59/88 (67%) with 36/59 (61%) demonstrating a concordant abnormal finding on CTP. Sensitivity for definite or probable presence of lacunar infarct increased significantly from 9.3% to 42.4% with incremental protocol use, though specificity was unchanged (range, 91.9%-95.3%). The observed diagnosis was significantly related to the actual diagnosis after adjusting for CTP confidence level (P = .04) and was 5.1 and 2.4 times more likely to confirm lacunar infarct than NCCT or CTA source images. CTP area under the curve (0.77) was significantly higher than that of CTA source images (0.68, P = .006) or NCCT (0.55, P < .001). CTP offers an improved diagnostic benefit over NCCT and CTA for the diagnosis of lacunar infarction. © 2015 American Society of Neuroradiology.
    American Journal of Neuroradiology 02/2015; DOI:10.3174/ajnr.A4255 · 3.68 Impact Factor
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    ABSTRACT: Stroke Prognostication by Using Age and NIHSS score (SPAN-100 index) facilitates stroke outcomes. We assessed imaging markers associated with the SPAN-100 index and their additional impact on outcome determination. Of 273 consecutive patients with acute ischemic stroke (<4.5 hours), 55 were characterized as SPAN-100-positive (age +NIHSS score ≥ 100). A comprehensive imaging review evaluated differences, using the presence of the hyperattenuated vessel sign, ASPECTS, clot burden score, collateral score, CBV, CBF, and MTT. The primary outcome assessed was favorable outcome (mRS ≤ 2). Secondary outcomes included recanalization, lack of neurologic improvement, and hemorrhagic transformation. Uni- and multivariate analyses assessed factors associated with favorable outcome. Area under the curve evaluated predictors of favorable clinical outcome. Compared with the SPAN-100-negative group, the SPAN-100-positive group (55/273; 20%) demonstrated larger CBVs (<0.001), poorer collaterals (P < .001), and increased hemorrhagic transformation rates (56.0% versus 36%, P = .02) despite earlier time to rtPA (P = .03). Favorable outcome was less common among patients with SPAN-100-positive compared with SPAN-100-negative (10.9% versus 42.2%; P < .001). Multivariate regression revealed poorer outcome for SPAN-100-positive (OR = 0.17; 95% CI, 0.06-0.38; P = .001), clot burden score (OR = 1.14; 95% CI, 1.05-1.25; P < .001), and CBV (OR = 0.58; 95% CI, 0.46-0.72; P = .001). The addition of the clot burden score and CBV improved the predictive value of SPAN-100 alone for favorable outcome from 60% to 68% and 74%, respectively. SPAN-100-positivity predicts a lower likelihood of favorable outcome and increased hemorrhagic transformation. CBV and clot burden score contribute to poorer outcomes among high-risk patients and improve stroke-outcome prediction. © 2015 American Society of Neuroradiology.
    American Journal of Neuroradiology 01/2015; 36(4). DOI:10.3174/ajnr.A4195 · 3.68 Impact Factor
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    ABSTRACT: Purpose To investigate whether early relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF) and permeability (Ktrans2) measurements may serve as magnetic resonance imaging (MRI) biomarkers of radiation response or progression for brain metastases. Materials and methods Seventy brain metastases in 44 patients treated with either stereotactic radiosurgery or whole brain radiotherapy were imaged with dynamic susceptibility and dynamic contrast enhancement MRI at baseline, 1 week and 1 month after treatment. The final response status was determined according to volume criteria derived from a 1 year post-treatment MRI or last available follow-up MRI. Tumours were characterised as responders, non-responders, progressors and non-progressors and compared for Ktrans2, rCBF and rCBV differences. Uni- and multivariate analysis evaluated factors associated with tumour response and progression at 1 week and 1 month. A generalised estimating equations (GEE) model accounted for multiple tumours per subject. Receiver operator characteristic (ROC) analysis identified optimal cut-off values, sensitivity and specificity for response or progression. Results Tumour responders showed lower Ktrans2 and reduced rCBF at 1 week (P < 0.05 each). Progressive disease showed lower rCBF and reduced rCBV at 1 month (P < 0.05 each). GEE and multivariate analysis revealed lower Ktrans2 at 1 week, an absence of prior radiation predicted response. At 1 month only lower rCBV predicted progressive disease on GEE and multivariate analysis. Optimal cut-off points for Ktrans2 and rCBV were 1.37 and 2.03 with sensitivity and specificity of 61.5 and 81.1% and 73.9 and 81.8%, respectively. Conclusion Lower Ktrans2 at 1 week and rCBV at 1 month discriminated responders and progressive disease, respectively.
    Clinical Oncology 11/2014; DOI:10.1016/j.clon.2014.06.010 · 2.83 Impact Factor
  • International Journal of Stroke 10/2014; 9:44-45. · 4.03 Impact Factor
  • International Journal of Stroke 10/2014; 9:205-205. · 4.03 Impact Factor
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    ABSTRACT: Background Contrast extravasation (CE) in spontaneous intracerebral hemorrhage (ICH), coined the spot sign, predicts hematoma expansion (HE) and poor clinical outcome. The dynamic relationship between CE and the mode of ICH growth are poorly understood. We characterized the in vivo pattern and rate of HE using a novel animal model of acute ICH. Methods Basal ganglia ICH was created in 14 Yorkshire swine utilizing a novel MRI integrated model, permitting real-time CE observation using dynamic contrast-enhanced (DCE) MRI. Computerized planimetry measured CE volume at each time point. Spatial vector analysis along three orthogonal axes determined distance vectors. Maximizing and minimizing the coefficient of determination defined the temporal phases of growth and stability, respectively. CE rate was calculated using a Patlak model. Results Asymmetric growth and variable rates of expansion characterized HE defining three distinct growth phases and patterns. A primary growth phase (duration 160 s; IQR 50–130) demonstrated rapid linear growth (0.04 mm/s IQR 0.01–0.10) accounting for 85 ± 15 % of total HE. The stationary phase demonstrated stability (duration 145 s; IQR 0–655). A secondary growth phase (duration 300; 130–600 s) accounted for 23 ± 8 % of total HE. In the primary and secondary growth phase, asymmetric growth occurred in the anterior–posterior (AP) planes (0.056 mm/s; p = 0.026 and 0.0112 mm/s; p = 0.03). Monophasic 2 (14 %), biphasic 4 (35 %) (primary followed by secondary growth), and triphasic 8 (56 %) patterns (primary, stationary, and secondary growth phase) were observed. Conclusions A novel model of ICH provides real-time study of the dynamics and rate of CE. This data facilitates the understanding of pattern and rate of ICH formation.
    Neurocritical Care 09/2014; 22(2). DOI:10.1007/s12028-014-0071-z · 2.60 Impact Factor
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    ABSTRACT: The purpose of this investigation is to determine if CT perfusion (CTP) measurements at low doses (LD = 20 or 50 mAs) are similar to those obtained at regular doses (RD = 100 mAs), with and without the addition of adaptive statistical iterative reconstruction (ASIR).
    Neuroradiology 09/2014; DOI:10.1007/s00234-014-1434-z · 2.37 Impact Factor
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    ABSTRACT: Purpose To determine rates of death, disability, and symptomatic intracranial hemorrhage (SICH) among patients with acute ischemic stroke selected for thrombolytic therapy by using perfusion computed tomography (CT) by conducting a systematic review and meta-analysis. Materials and Methods A search of the literature up to July 2012 was performed by using MEDLINE, EMBASE, the Cochrane Library, PubMed, and Google Scholar on terms including "brain ischemia" and "perfusion imaging." The search was unrestricted by language of publication. Two reviewers extracted study data and independently assessed the risk of study bias. Outcomes of patients selected by using perfusion CT, including case-fatality rate, favorable outcome (modified Rankin Scale [mRS] score, ≤2), and rates of SICH, were estimated. Results Thirteen experimental or observational studies that included patients who received intravenous thrombolytic treatment after perfusion CT were identified. The methodologic quality of the small studies was generally good. Overall, 90-day mortality was 10.0% (95% confidence interval [CI]: 5.4%, 15.9%). Among patients treated within 3 hours of symptom onset, mortality was 12.5% (95% CI: 6.7%, 19.7%), a favorable outcome (mRS score, ≤2) was seen in 42.5% of patients (95% CI: 16.6%, 70.9%), and the SICH rate was 3.3% (95% CI: 0.7%, 7.7%). Among patients treated more than 3 hours after symptom onset, mortality was 2.9% (95% CI: 0.0%, 12.7%), 69.9% of patients (95% CI: 0%, 83.5%) had a favorable outcome, and the SICH rate was 3.9% (95% CI: 0.8%, 9.2%). Conclusion The outcomes (mortality, morbidity, and SICH rates) for patients selected with perfusion CT to receive intravenous thrombolytic treatment more than 3 hours after symptom onset appear favorable. © RSNA, 2014 Online supplemental material is available for this article.
    Radiology 09/2014; 274(1):140728. DOI:10.1148/radiol.14140728 · 6.21 Impact Factor
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    ABSTRACT: Background Atrial fibrillation is a leading preventable cause of recurrent stroke for which early detection and treatment are critical. However, paroxysmal atrial fibrillation is often asymptomatic and likely to go undetected and untreated in the routine care of patients with ischemic stroke or transient ischemic attack (TIA). Methods We randomly assigned 572 patients 55 years of age or older, without known atrial fibrillation, who had had a cryptogenic ischemic stroke or TIA within the previous 6 months (cause undetermined after standard tests, including 24-hour electrocardiography [ECG]), to undergo additional noninvasive ambulatory ECG monitoring with either a 30-day event-triggered recorder (intervention group) or a conventional 24-hour monitor (control group). The primary outcome was newly detected atrial fibrillation lasting 30 seconds or longer within 90 days after randomization. Secondary outcomes included episodes of atrial fibrillation lasting 2.5 minutes or longer and anticoagulation status at 90 days. Results Atrial fibrillation lasting 30 seconds or longer was detected in 45 of 280 patients (16.1%) in the intervention group, as compared with 9 of 277 (3.2%) in the control group (absolute difference, 12.9 percentage points; 95% confidence interval [CI], 8.0 to 17.6; P<0.001; number needed to screen, 8). Atrial fibrillation lasting 2.5 minutes or longer was present in 28 of 284 patients (9.9%) in the intervention group, as compared with 7 of 277 (2.5%) in the control group (absolute difference, 7.4 percentage points; 95% CI, 3.4 to 11.3; P<0.001). By 90 days, oral anticoagulant therapy had been prescribed for more patients in the intervention group than in the control group (52 of 280 patients [18.6%] vs. 31 of 279 [11.1%]; absolute difference, 7.5 percentage points; 95% CI, 1.6 to 13.3; P=0.01). Conclusions Among patients with a recent cryptogenic stroke or TIA who were 55 years of age or older, paroxysmal atrial fibrillation was common. Noninvasive ambulatory ECG monitoring for a target of 30 days significantly improved the detection of atrial fibrillation by a factor of more than five and nearly doubled the rate of anticoagulant treatment, as compared with the standard practice of short-duration ECG monitoring. (Funded by the Canadian Stroke Network and others; EMBRACE number, NCT00846924 .).
    New England Journal of Medicine 06/2014; 370:2467. DOI:10.1056/NEJMoa1311376 · 54.42 Impact Factor
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    ABSTRACT: RationaleIn acute stroke, time is brain: faster tissue plasminogen activator treatment improves patient outcomes. Published guidelines for door-to-scanner time are <25 minutes, and for door-to-needle time <60 minutes. These benchmarks are rarely met. Paradoxically, the earlier a stroke patient arrives to hospital, the longer treatment takes. There is an urgent need to shift focus away from the 4·5 hour time window, towards treatment times <60 minutes.AimsThe objective of the Countdown Lights to Optimize Quality in acute Stroke (CLOQS) trial is to determine whether a simple, low-cost organizational behavior intervention, a large, red stopwatch timer attached to the stretcher upon arrival, will decrease door-to-scanner and door-to-needle treatment times for tissue plasminogen activator-treated patients.DesignA multicenter, time-clustered randomized control trial. The stopwatch timers will be used in Emergency Departments for all acute stroke patients across the University of Toronto Stroke Program. The order of intervention (ON) and control (OFF) blocks will be randomly assigned in a 1:1 ratio over an 18 month period. Blocks will be weighted in a 2:1 ratio of ON/OFF using a permuted block design (ON blocks last two weeks; OFF blocks last one week).Study OutcomesThe primary end-point is percentage of patients achieving best-practice guidelines (door-to-needle treatment time <60 minutes). Secondary end-points are median time intervals for 1) door-to-scanner and 2) door-to-needle times during ON versus OFF blocks. Tertiary end-points are in-hospital mortality and time series analysis to determine change in treatment times from prior to study onset through study completion.
    International Journal of Stroke 06/2014; 9(4). DOI:10.1111/ijs.12066 · 4.03 Impact Factor
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    ABSTRACT: Cognitive impairment is a common, disabling symptom of MS. We investigated the association between cognitive impairment and WM dysfunction in secondary-progressive multiple sclerosis using DTI. Cognitive performance was assessed with a standard neuropsychological battery, the Minimal Assessment of Cognitive Function in Multiple Sclerosis. Cognitive impairment was defined as scoring >1.5 standard deviations below healthy controls on ≥2 subtests. Fractional anisotropy maps were compared against cognitive status using tract-based spatial statistics with threshold-free cluster enhancement. Forty-five patients with secondary-progressive multiple sclerosis (median age: 55 years, female/male: 27/18, median Expanded Disability Status Scale Score: 6.5) were prospectively recruited. Cognitively impaired patients (25/45) displayed significantly less normalized global GM and WM volumes (P = .001, P = .024), more normalized T2-weighted and T1-weighted WM lesion volumes (P = .002, P = .006), and lower WM skeleton fractional anisotropy (P < .001) than non-impaired patients. Impaired patients also had significantly lower fractional anisotropy (pcorr < .05) in over 50% of voxels within every major WM tract. The most extensively impinged tracts were the left posterior thalamic radiation (100.0%), corpus callosum (97.8%), and right sagittal stratum (97.5%). No WM voxels had significantly higher fractional anisotropy in patients with cognitive impairment compared with their non-impaired counterparts (pcorr > .05). After the inclusion of confounders in a multivariate logistic regression, only fractional anisotropy remained a significant predictor of cognitive status. Cognitively impaired patients with secondary-progressive multiple sclerosis exhibited extensive WM dysfunction, though preferential involvement of WM tracts associated with cognition, such as the corpus callosum, was apparent. Multivariate analysis revealed that only WM skeleton fractional anisotropy was a significant predictor of cognitive status.
    American Journal of Neuroradiology 05/2014; 35(10). DOI:10.3174/ajnr.A3974 · 3.68 Impact Factor
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    ABSTRACT: To determine the optimal imaging strategy for ICH incorporating CTA or DSA with and without a NCCT risk stratification algorithm. A Markov model included costs, outcomes, prevalence of a vascular lesion, and the sensitivity and specificity of a risk stratification algorithm from the literature. The four imaging strategies were: (a) CTA screening of the entire cohort; (b) CTA only in those where NCCT suggested a high or indeterminate likelihood of a lesion; (c) DSA screening of the entire cohort and (d) DSA only for those with a high or indeterminate suspicion of a lesion following NCCT. Branch d was the comparator. Age of the cohort and the probability of an underlying lesion influenced the choice of optimal imaging strategy. With a low suspicion for a lesion (<12%), branch (a) was the optimal strategy for a willingness-to-pay of $100,000/QALY. Branch (a) remained the optimal strategy in younger people (<35 years) with a risk below 15%. If the probability of a lesion was >15%, branch (b) became preferred strategy. The probabilistic sensitivity analysis showed that branch (b) was the optimal choice 70-72% of the time over varying willingness-to-pay values. CTA has a clear role in the evaluation of people presenting with ICH, though the choice of CTA everyone or CTA using risk stratification depends on age and likelihood of finding a lesion.
    PLoS ONE 05/2014; 9(5):e96496. DOI:10.1371/journal.pone.0096496 · 3.53 Impact Factor
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    ABSTRACT: 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. 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. 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). We describe a novel MR imaging-integrated real-time swine intracerebral hemorrhage model of acute hematoma growth and contrast extravasation.
    American Journal of Neuroradiology 04/2014; 35(9). DOI:10.3174/ajnr.A3939 · 3.68 Impact Factor
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    ABSTRACT: Purpose: To evaluate early perfusion changes in normal tissue following stereotactic radiosurgery (SRS). Methods: Nineteen patients harboring twenty-two brain metastases treated with SRS were imaged with dynamic susceptibility magnetic resonance imaging (DSC MRI) at baseline, 1 week and 1 month post SRS. Relative cerebral blood volume and flow (rCBV and rCBF) ratios were evaluated outside of tumor within a combined region of interest (ROI) and separately within gray matter (GM) and white matter (WM) ROIs. Three-dimensional dose distribution from each SRS plan was divided into six regions: (1) <2 Gy; (2) 2-5 Gy; (3) 5-10 Gy; (4) 10-12 Gy; (5) 12-16 Gy; and (6) >16 Gy. rCBV and rCBF ratio differences between baseline, 1 week and 1 month were compared. Best linear fit plots quantified normal tissue dose-dependency. Results: Significant rCBV ratio increases were present between baseline and 1 month for all ROIs and dose ranges except for WM ROI receiving <2 Gy. rCBV ratio for all ROIs was maximally increased from baseline to 1 month with the greatest changes occurring within the 5-10 Gy dose range (53.1%). rCBF ratio was maximally increased from baseline to 1 month for all ROIs within the 5-10 Gy dose range (33.9-45.0%). Both rCBV and rCBF ratios were most elevated within GM ROIs. A weak, positive but not significant association between dose, rCBV and rCBF ratio was demonstrated. Progressive rCBV and rCBF ratio increased with dose up to 10 Gy at 1 month. Conclusion: Normal tissue response following SRS can be characterized by dose, tissue, and time specific increases in rCBV and rCBF ratio.
    Technology in cancer research & treatment 04/2014; DOI:10.7785/tcrtexpress.2013.600279 · 1.94 Impact Factor
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    ABSTRACT: Standard (static) CT angiography is used to identify the intracerebral hemorrhage (ICH) spot sign. We used dynamic CT-angiography to describe spot sign characteristics and measurement parameters over 60-seconds of image acquisition. We prospectively identified consecutive patients presenting with acute ICH within 4.5 hours of symptom onset, and collected whole brain dynamic CT-angiography (dCTA). Spot parameters (earliest appearance, duration, maximum Hounsfield unit (HU), time to maximum HU, time to spot diagnostic definition, spot volume and hematoma volumes) were measured using volumetric analysis software. We enrolled 34 patients: three were excluded due to secondary causes of ICH. Of the remaining 31 patients there were 18 females (58%) with median age 70 (range 47-86) and baseline hematoma volume 33 ml (range 0.7-103 ml). Positive dCTA spot sign was present in 13 patients (42%) visualized as an expanding 3-dimensional structure temporally evolving its morphology over the scan period. Median time to spot appearance was 21 s (range 15-35 seconds). This method allowed tracking of spots evolution until the end of venous phase (active extravasation) with median duration of 39 s (range 25-45 seconds). The average density and time to maximum density was 204HU and 30.8 s (range 23-31 s) respectively. Median time to spot diagnosis was 20.8 s using either 100 or 120HU definitions. Dynamic CTA allows a 3-dimensional assessment of spot sign formation during acute ICH, and captured higher spot sign prevalence than previously reported. This is the first study to describe and quantify spot sign characteristics using dCTA; these can be used in ongoing and upcoming ICH studies.
    PLoS ONE 03/2014; 9(3):e90431. DOI:10.1371/journal.pone.0090431 · 3.53 Impact Factor
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    ABSTRACT: This study reviews the quality of economic evaluations of imaging after acute stroke and identifies areas for improvement. We performed full-text searches of electronic databases that included Medline, Econlit, the National Health Service Economic Evaluation Database, and the Tufts Cost Effectiveness Analysis Registry through July 2012. Search strategy terms included the following: stroke*; cost*; or cost-benefit analysis*; and imag*. Inclusion criteria were empirical studies published in any language that reported the results of economic evaluations of imaging interventions for patients with stroke symptoms. Study quality was assessed by a commonly used checklist (with a score range of 0% to 100%). Of 568 unique potential articles identified, 5 were included in the review. Four of 5 articles were explicit in their analysis perspectives, which included healthcare system payers, hospitals, and stroke services. Two studies reported results during a 5-year time horizon, and 3 studies reported lifetime results. All included the modified Rankin Scale score as an outcome measure. The median quality score was 84.4% (range=71.9%-93.5%). Most studies did not consider the possibility that patients could not tolerate contrast media or could incur contrast-induced nephropathy. Three studies compared perfusion computed tomography with unenhanced computed tomography but assumed that outcomes guided by the results of perfusion computed tomography were equivalent to outcomes guided by the results of magnetic resonance imaging or noncontrast computed tomography. Economic evaluations of imaging modalities after acute ischemic stroke were generally of high methodological quality. However, important radiology-specific clinical components were missing from all of these analyses.
    Stroke 02/2014; 45(3). DOI:10.1161/STROKEAHA.113.004027 · 6.02 Impact Factor
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    ABSTRACT: Variability in computed tomography angiography (CTA) acquisitions may be one explanation for the modest accuracy of the spot sign for predicting intracerebral hemorrhage expansion detected in the multicenter Predicting Hematoma Growth and Outcome in Intracerebral Hemorrhage Using Contrast Bolus CT (PREDICT) study. This study aimed to determine the frequency of the spot sign in intracerebral hemorrhage and its relationship with hematoma expansion depending on the phase of image acquisition. PREDICT study was a prospective observational cohort study of patients with intracerebral hemorrhage presenting within 6 hours from onset. A post hoc analysis of the Hounsfield units of an artery and venous structure were measured on CTA source images of the entire PREDICT cohort in a core laboratory. Each CTA study was classified into arterial or venous phase and into 1 of 5 specific image acquisition phases. Significant hematoma expansion and total hematoma enlargement were recorded at 24 hours. Overall (n=371), 77.9% of CTA were acquired in arterial phase. The spot sign, present in 29.9% of patients, was more frequently seen in venous phase as compared with arterial phase (39% versus 27.3%; P=0.041) and the later the phase of image acquisition (P=0.095). Significant hematoma expansion (P=0.253) and higher total hematoma enlargement (P=0.019) were observed more frequently among spot sign-positive patients with earlier phases of image acquisition. Later image acquisition of CTA improves the frequency of spot sign detection. However, spot signs identified in earlier phases may be associated with greater absolute enlargement. A multiphase CTA including arterial and venous acquisitions could be optimal in patients with intracerebral hemorrhage.
    Stroke 01/2014; 45(3):734-9. DOI:10.1161/STROKEAHA.113.003007 · 6.02 Impact Factor
  • Matylda H. Machnowska, Richard I. Aviv
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    ABSTRACT: This chapter discusses a variety of inflammatory, infectious, and not otherwise easily categorized diseases that can affect the intracranial vessels. These include diseases with known genetic mutations such as Fabry’s disease, cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL); those arising as a result of genetic and environmental factors such as moyamoya; and those with yet unknown etiologies such as Takayasu’s, posterior reversible encephalopathy syndrome (PRES) and Behcet’s disease. In each case, the preferred imaging methods and characteristic imaging findings are discussed. We concentrate on the standard imaging methods of MRI, cerebral angiography, and noninterventional angiography. Where applicable, advanced imaging techniques including cerebrovascular reactivity, vessel wall imaging, perfusion imaging, and MR spectroscopy are discussed.
    Neurovascular Imaging, 01/2014: pages 1-34; , ISBN: 978-1-4614-9212-2

Publication Stats

2k Citations
687.11 Total Impact Points


  • 2015
    • The University of Calgary
      Calgary, Alberta, Canada
  • 2007–2015
    • University of Toronto
      • • Department of Medical Imaging
      • • Sunnybrook Health Sciences Centre
      • • Division of Neuroradiology
      Toronto, Ontario, Canada
  • 2007–2014
    • Sunnybrook Health Sciences Centre
      • • Department of Medical Imaging
      • • Division of Neurology
      • • Department of Radiation Oncology
      Toronto, Ontario, Canada
  • 2006–2011
    • The University of Western Ontario
      London, Ontario, Canada
  • 2005–2007
    • SickKids
      • Division of Neurology
      Toronto, Ontario, Canada
    • Women's College Hospital
      Toronto, Ontario, Canada