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Aad Van Der Lugt - One of the best experts on this subject based on the ideXlab platform.
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Associations of Ischemic Lesion Volume With Functional Outcome in Patients With Acute Ischemic Stroke 24-Hour Versus 1-Week Imaging
Stroke, 2017Co-Authors: Amber Bucker, Aad Van Der Lugt, Anna M. M. Boers, Joseph C J Bot, Olvert A. Berkhemer, Hester F. Lingsma, Albert J. Yoo, Wim H. Van Zwam, Robert J. Van Oostenbrugge, Diederik W.j. DippelAbstract:Background and Purpose—Ischemic Lesion Volume (ILV) on noncontrast computed tomography at 1 week can be used as a secondary outcome measure in patients with acute ischemic stroke. Twenty-four–hour ...
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Automated measurement of local white matter Lesion Volume
NeuroImage, 2011Co-Authors: Fedde Van Der Lijn, Benjamin F.j. Verhaaren, M. Arfan Ikram, Stefan Klein, Marleen De Bruijne, Henri A. Vrooman, Meike W. Vernooij, Alexander Hammers, Daniel Rueckert, Aad Van Der LugtAbstract:It has been hypothesized that white matter Lesions at different locations may have different etiology and clinical consequences. Several approaches for the quantification of local white matter Lesion load have been proposed in the literature, most of which rely on a distinction between Lesions in a periventricular region close to the ventricles and a subcortical zone further away. In this work we present a novel automated method for local white matter Lesion Volume quantification in magnetic resonance images. The method segments and measures the white matter Lesion Volume in 43 regions defined by orientation and distance to the ventricles, which allows a more spatially detailed study of Lesion load. The potential of the method was demonstrated by analyzing the effect of blood pressure on the regional white matter Lesion Volume in 490 elderly subjects taken from a longitudinal population study. The method was also compared to two commonly used techniques to assess the periventricular and subcortical Lesion load. The main finding was that high blood pressure was primarily associated with Lesion load in the vascular watershed area that forms the border between the periventricular and subcortical regions. It explains the associations found for both the periventricular and subcortical load computed for the same data, and that were reported in the literature. But the proposed method can localize the region of association with greater precision than techniques that distinguish between periventricular and subcortical Lesions only.
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Replication Study of Chr17q25 With Cerebral White Matter Lesion Volume
Stroke, 2011Co-Authors: Benjamin F.j. Verhaaren, Meike W. Vernooij, Aad Van Der Lugt, Renske De Boer, Fernando Rivadeneira, André G. Uitterlinden, Albert Hofman, Gabriel P. Krestin, Wiro J. Niessen, Monique M.b. BretelerAbstract:Background and Purpose—Recently, the first genomewide association study on cerebral white matter Lesion burden identified chr17q25 to be significantly associated with white matter Lesions. We report on the first independent replication study of this genetic association. Methods—In a population-based cohort study, we investigated the association between the 6 genomewide significant single nucleotide polymorphisms at that locus and cerebral white matter Lesion Volume on MRI, measured quantitatively, adjusted for age, sex, and intracranial Volume. Adjustments for ApoE4 carriership and cardiovascular risk factors were evaluated separately. Finally, we performed a meta-analysis of all published data for the single most significant single nucleotide polymorphism, rs3744028. Results—The risk alleles of all the 6 single nucleotide polymorphisms were significantly associated with white matter Lesion Volume with P=1.1*10−3 for rs3744028, adjusted for age, sex, and intracranial Volume. Additional adjustments only ha...
Soren Christensen - One of the best experts on this subject based on the ideXlab platform.
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validity of acute stroke Lesion Volume estimation by diffusion weighted imaging alberta stroke program early computed tomographic score depends on Lesion location in 496 patients with middle cerebral artery stroke
Stroke, 2014Co-Authors: Julian Schröder, Dong-wha Kang, Soren Christensen, Bastian Cheng, Martin Ebinger, Martin Köhrmann, David S. Liebeskind, Thomas Tourdias, Oliver C. Singer, Bruce C V CampbellAbstract:Background and Purpose—Alberta Stroke Program Early Computed Tomographic Score (ASPECTS) has been used to estimate diffusion-weighted imaging (DWI) Lesion Volume in acute stroke. We aimed to assess correlations of DWI-ASPECTS with Lesion Volume in different middle cerebral artery (MCA) subregions and reproduce existing ASPECTS thresholds of a malignant profile defined by Lesion Volume ≥100 mL. Methods—We analyzed data of patients with MCA stroke from a prospective observational study of DWI and fluid-attenuated inversion recovery in acute stroke. DWI-ASPECTS and Lesion Volume were calculated. The population was divided into subgroups based on Lesion localization (superficial MCA territory, deep MCA territory, or both). Correlation of ASPECTS and infarct Volume was calculated, and receiver-operating characteristics curve analysis was performed to identify the optimal ASPECTS threshold for ≥100-mL Lesion Volume. Results—A total of 496 patients were included. There was a significant negative correlation betw...
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Validity of Acute Stroke Lesion Volume Estimation by Diffusion-Weighted Imaging–Alberta Stroke Program Early Computed Tomographic Score Depends on Lesion Location in 496 Patients With Middle Cerebral Artery Stroke
Stroke, 2014Co-Authors: Julian Schröder, Dong-wha Kang, Bastian Cheng, Martin Ebinger, Martin Köhrmann, David S. Liebeskind, Thomas Tourdias, Oliver C. Singer, Soren ChristensenAbstract:Background and Purpose—Alberta Stroke Program Early Computed Tomographic Score (ASPECTS) has been used to estimate diffusion-weighted imaging (DWI) Lesion Volume in acute stroke. We aimed to assess correlations of DWI-ASPECTS with Lesion Volume in different middle cerebral artery (MCA) subregions and reproduce existing ASPECTS thresholds of a malignant profile defined by Lesion Volume ≥100 mL. Methods—We analyzed data of patients with MCA stroke from a prospective observational study of DWI and fluid-attenuated inversion recovery in acute stroke. DWI-ASPECTS and Lesion Volume were calculated. The population was divided into subgroups based on Lesion localization (superficial MCA territory, deep MCA territory, or both). Correlation of ASPECTS and infarct Volume was calculated, and receiver-operating characteristics curve analysis was performed to identify the optimal ASPECTS threshold for ≥100-mL Lesion Volume. Results—A total of 496 patients were included. There was a significant negative correlation betw...
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abstract w p28 precision of tmax and cbf Lesion Volume estimates in ct perfusion imaging
Stroke, 2014Co-Authors: Soren Christensen, Matus Straka, Roland Bammer, Nishant K Mishra, Dominik Fleischmann, Greg Zaharchuck, Mark W Parsons, Christopher R Levi, Greg Albers, Maarten LandsbergAbstract:Objective: CT perfusion (CTP) imaging is increasingly used to select patients for acute stroke trials. Patient selection criteria are typically based on the Volumes of reversibly and irreversibly injured tissue. Modern software allows for automated and quantitative assessment of these Lesion Volumes. There is a push towards reducing the radiation dose used in CTP protocols which may adversely affect the reproducibility of Lesion Volume assessments. The aim of this study was to assess the effect of radiation dose dependent image noise on the precision of Lesion Volume estimates. Methods: We generated 6 synthetic noise-less datasets based on a brain atlas of gray matter, white matter and CSF and integrated co-registered perfusion Lesions from 6 acute stroke patients. For each pixel, concentration time curves were simulated using standard tracer kinetic models to obtain CTP source data based on the Lesions of the 6 patients. To simulate a CTP protocol with standard radiation dose, we added CT textured noise (“Standard noise”) with a SD of 10 Hounsfield Units (HU) to the dynamic datasets and to simulate a low-dose (“high noise”) CTP protocol we added noise with a SD of 14 HU. This step was repeated 50 times per noise level and for each iteration we determined, using automated perfusion software, the Volumes of the ischemic core (rCBF based) and of critically hypoperfused tissue (Tmax>6s). Results: With standard noise, mean CBF Volume was 5.6 ml (SD 2.1) and mean Tmax>6s Volume was 38.2 ml (SD 1.3). In the high noise condition, the Tmax>6s Lesion Volume was on average 13% (5 ml) larger (p<0.0001) than in the standard noise condition. The SD of the Tmax Volumes increased from 1.3 mL to 1.8 mL with higher noise. Conversely, with high noise there was an average 5 mL (range 0-16 mL) absolute reduction in CBF Lesion Volume as compared to the low noise condition (p<0.0001). The CBF Lesion became in many cases undetectable (estimated as 0 ml) in the high noise setting. Conclusions: Noise in CTP data influences the precision of Lesion Volume estimates. The estimate of the infarcted core seems particularly sensitive to noise. This knowledge should be used to develop guidelines that specify the maximum amount of noise (ie minimum amount of radiation) that is acceptable in a given CTP protocol.
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Abstract W P28: Precision of Tmax and CBF Lesion Volume Estimates in CT Perfusion Imaging
Stroke, 2014Co-Authors: Soren Christensen, Matus Straka, Roland Bammer, Nishant K Mishra, Dominik Fleischmann, Greg Zaharchuck, Mark W Parsons, Christopher R Levi, Greg Albers, Maarten LandsbergAbstract:Objective: CT perfusion (CTP) imaging is increasingly used to select patients for acute stroke trials. Patient selection criteria are typically based on the Volumes of reversibly and irreversibly injured tissue. Modern software allows for automated and quantitative assessment of these Lesion Volumes. There is a push towards reducing the radiation dose used in CTP protocols which may adversely affect the reproducibility of Lesion Volume assessments. The aim of this study was to assess the effect of radiation dose dependent image noise on the precision of Lesion Volume estimates. Methods: We generated 6 synthetic noise-less datasets based on a brain atlas of gray matter, white matter and CSF and integrated co-registered perfusion Lesions from 6 acute stroke patients. For each pixel, concentration time curves were simulated using standard tracer kinetic models to obtain CTP source data based on the Lesions of the 6 patients. To simulate a CTP protocol with standard radiation dose, we added CT textured noise (“Standard noise”) with a SD of 10 Hounsfield Units (HU) to the dynamic datasets and to simulate a low-dose (“high noise”) CTP protocol we added noise with a SD of 14 HU. This step was repeated 50 times per noise level and for each iteration we determined, using automated perfusion software, the Volumes of the ischemic core (rCBF based) and of critically hypoperfused tissue (Tmax>6s). Results: With standard noise, mean CBF Volume was 5.6 ml (SD 2.1) and mean Tmax>6s Volume was 38.2 ml (SD 1.3). In the high noise condition, the Tmax>6s Lesion Volume was on average 13% (5 ml) larger (p
Susan White - One of the best experts on this subject based on the ideXlab platform.
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size doesn t matter cortical stroke Lesion Volume is not associated with upper extremity motor impairment and function in mild chronic hemiparesis
Archives of Physical Medicine and Rehabilitation, 2013Co-Authors: Stephen J. Page, Lynne V. Gauthier, Susan WhiteAbstract:Abstract Objectives To determine (1) the relationship between Lesion Volume and upper extremity (UE) motor impairment using the UE section of the Fugl-Meyer (FM) assessment; and (2) the relationship between Lesion Volume and UE functional outcomes using the Arm Motor Ability Test (AMAT) Functional Ability (FA) and Time scales. Design Secondary retrospective analysis of randomized controlled trial data. Setting Outpatient rehabilitation clinic. Participants Subjects with chronic stroke (N=139, 83 men; mean age ± SD of all subjects, 56.7±11.2y; mean time ± SD since stroke onset, 59.6±65.6mo; 90 subjects with right hemiparesis) and stable, active, distal UE movement. Intervention Data were collected related to subjects' Lesion Volume and UE movement before their participation in a multicenter, randomized controlled trial. Main Outcome Measures FM and AMAT. Results Neither age nor Lesion Volume was related to FM performance. The P value for the regression coefficient of Lesion Volume was .045 in the AMAT FA model and .016 in the AMAT Time model. Lesion Volume accounted for only an additional 1.7% (AMAT FA) to 3.1% (AMAT Time) of the variability in motor function and was not clinically meaningful. Conclusions Data suggest no relationship between Lesion Volume and UE impairment, and a small, clinically insignificant relationship between Lesion Volume and UE motor function. Stroke causes metabolic changes in intact regions and diffuse structural loss in anatomically remote regions from the infarction. These other factors may account for variance in motor outcomes after stroke.
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Size Doesn’t Matter: Cortical Stroke Lesion Volume is Not Associated with Upper Extremity Motor Impairment and Function in Mild, Chronic, Hemiparesis
Archives of physical medicine and rehabilitation, 2013Co-Authors: Stephen J. Page, Lynne V. Gauthier, Susan WhiteAbstract:Abstract Objectives To determine (1) the relationship between Lesion Volume and upper extremity (UE) motor impairment using the UE section of the Fugl-Meyer (FM) assessment; and (2) the relationship between Lesion Volume and UE functional outcomes using the Arm Motor Ability Test (AMAT) Functional Ability (FA) and Time scales. Design Secondary retrospective analysis of randomized controlled trial data. Setting Outpatient rehabilitation clinic. Participants Subjects with chronic stroke (N=139, 83 men; mean age ± SD of all subjects, 56.7±11.2y; mean time ± SD since stroke onset, 59.6±65.6mo; 90 subjects with right hemiparesis) and stable, active, distal UE movement. Intervention Data were collected related to subjects' Lesion Volume and UE movement before their participation in a multicenter, randomized controlled trial. Main Outcome Measures FM and AMAT. Results Neither age nor Lesion Volume was related to FM performance. The P value for the regression coefficient of Lesion Volume was .045 in the AMAT FA model and .016 in the AMAT Time model. Lesion Volume accounted for only an additional 1.7% (AMAT FA) to 3.1% (AMAT Time) of the variability in motor function and was not clinically meaningful. Conclusions Data suggest no relationship between Lesion Volume and UE impairment, and a small, clinically insignificant relationship between Lesion Volume and UE motor function. Stroke causes metabolic changes in intact regions and diffuse structural loss in anatomically remote regions from the infarction. These other factors may account for variance in motor outcomes after stroke.
Tracy K. Mcintosh - One of the best experts on this subject based on the ideXlab platform.
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Infusion of prostacyclin following experimental brain injury in the rat reduces cortical Lesion Volume.
Journal of neurotrauma, 2001Co-Authors: Peter Bentzer, Tracy K. Mcintosh, Gustav Mattiasson, Tadeusz Wieloch, Per-olof GrändeAbstract:Endothelial-derived prostacyclin is an important regulator of microvascular function, and its main actions are inhibition of platelet/leukocyte aggregation and adhesion, and vasodilation. Disturbances in endothelial integrity following traumatic brain injury (TBI) may result in insufficient prostacyclin production and participate in the pathophysiological sequelae of brain injury. The objective of this study was to evaluate the potential therapeutic effects of a low-dose prostacyclin infusion on cortical Lesion Volume, CA3 neuron survival and functional outcome following TBI in the rat. Anesthetized animals (sodium pentobarbital, 60 mg/kg, i.p.) were subjected to a lateral fluid percussion brain injury (2.5 atm) or sham injury. Following TBI, animals were randomized to receive a constant infusion of either prostacyclin (1 ng/kg x min(-1) i.v.) or vehicle over 48 h. All sham animals received vehicle (n = 6). Evaluation of neuromotor function, Lesion Volume, and CA3 neuronal loss was performed blindly. By 7 days postinjury, cortical Lesion Volume was significantly reduced by 43% in the prostacyclin-treated group as compared to the vehicle treated group (p < 0.01; n = 12 prostacyclin, n = 12 vehicle). No differences were observed in neuromotor function (48 h and 7 days following TBI), or in hippocampal cell loss (7 days following TBI) between the prostacyclin- and vehicle-treated groups. We conclude that prostacyclin in a low dose reduces loss of neocortical neurons following TBI and may be a potential clinical therapeutic agent to reduce neuronal cell death associated with brain trauma.
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Remacemide hydrochloride reduces cortical Lesion Volume following brain trauma in the rat
Neuroscience letters, 1997Co-Authors: Douglas H. Smith, Brian R. Perri, Ramesh Raghupathi, Kathryn E. Saatman, Tracy K. McintoshAbstract:We evaluated the therapeutic effects of remacemide hydrochloride, an N-methyl-D-aspartate (NMDA) receptor-associated ionophore blocker with sodium channel blocking activity, on cortical Lesion Volume and memory dysfunction following parasagittal fluid-percussion brain injury in the anesthetized rat. We found that intravenous (i.v.) administration 15 min following injury of remacemide hydrochloride at both 25 and 10 mg/kg significantly reduced posttraumatic cortical Lesion Volume (P < 0.05), measured at 48 h postinjury using a tetrazolium salt tissue staining technique. However, neither of these doses nor the dosing regimen of 25 mg/kg i.v. 15 min postinjury plus a subcutaneous infusion over 24 h of 20 mg/kg remacemide hydrochloride improved posttraumatic memory function determined by a Morris water maze paradigm.
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Metabolic quantification of Lesion Volume following experimental traumatic brain injury in the rat.
Journal of neurotrauma, 1997Co-Authors: Brian R. Perri, Douglas H. Smith, Ramesh Raghupathi, Kathryn E. Saatman, Hisayuki Murai, Grant Sinson, Raymond T. Bartus, Tracy K. McintoshAbstract:ABSTRACT A reliable and rapid method for quantifying Lesion Volume following traumatic brain injury (TBI) has vast potential in brain injury research. Staining with 2,3,5-triphenyltetrazolium chloride (TTC) provides for demarcation of damaged or infarcted tissue from normal, viable cerebral tissue, in which a red formazan product is formed by reduction during cellular respiration of mitochondrial dehydrogenase enzymes. The present study evaluated the use of TTC staining to quantify the cortical Lesion Volume in rats undergoing fluid-percussion (FP) brain injury. Male Sprague–Dawley rats (350–450 g, n = 27) were anesthetized (sodium pentobarbital, 60 mg/kg, ip) and subjected to lateral FP brain injury of mild (1.1–1.3 atm, n = 5), moderate (2.0–2.3 atm, n = 9), or high (2.4–2.6 atm, n = 8) severity, while sham (noninjured) animals (n = 5) were anesthetized and surgically prepared without injury. Forty-eight hours after injury animals were sacrificed, brains were stained with TTC, and Lesion Volumes were ca...
Massimo Filippi - One of the best experts on this subject based on the ideXlab platform.
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Estimating Brain Lesion Volume Change in Multiple Sclerosis by Subtraction of Magnetic Resonance Images.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 2016Co-Authors: Mark A. Horsfield, Maria A. Rocca, Elisabetta Pagani, Loredana Storelli, Paolo Preziosa, Roberta Messina, Fabiano Camesasca, Massimiliano Copetti, Massimo FilippiAbstract:BACKGROUND Change in Lesion Volume over time, measured on brain magnetic resonance imaging (MRI) scans, is an important outcome measure for natural history studies and clinical trials in multiple sclerosis (MS). PURPOSE To develop and test image analysis methods for quantification of Lesion Volume change in order to improve reliability. METHODS The technique is based on registration and subtraction, and was evaluated in a cohort of 20 MS patients with dual-echo images acquired annually over a period of four years. The study protocol was approved by the local ethics review boards of participating centers, and all subjects gave written informed consent. The repeatability was compared to that obtained by the standard method for obtaining Lesion Volume change by evaluating the total Volume at each time point, and then subtracting the Volumes to obtain the difference. RESULTS Compared to the standard method, the subtraction method had improved intrarater correlation (0.95 and 0.72 for the subtraction method and the standard method, respectively) and interrater correlation (0.51 and 0.28, respectively). Furthermore, the mean time required to analyze the scans from one patient was 41 minutes for the subtraction method compared to 125 minutes for the standard method. CONCLUSION Use of the subtraction algorithm leads to improved reliability and lower operator fatigue in clinical trials and studies of the natural history of MS.
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The precision of T1 hypointense Lesion Volume quantification in multiple sclerosis treatment trials: a multicenter study.
Multiple sclerosis (Houndmills Basingstoke England), 2000Co-Authors: Paul Molyneux, Massimo Filippi, Maria Pia Sormani, Peter A Brex, Caroline Fogg, Sara Lewis, Claire Middleditch, Frederik Barkhof, David H. MillerAbstract:The Volume of hypointense Lesions on T1 weighted brain MRI represents an increasingly used MR endpoint in phase III MS treatment trials. In this study we evaluated the reproducibility of hypointense T1 Lesion Volume quantification in a cohort of Multiple Sclerosis (MS) patients. The gadolinium enhanced T1 weighted brain MR images of 33 MS patients from three European centers were used in this study. These images were acquired as part of a phase III trial of interferon beta-1b in secondary progressive MS. The MRI machine manufacturers and imaging parameters varied according to the MRI acquisition center. Three experienced observers used a semi-automated local thresholding technique to quantify the hypointense T1 Lesion Volume on two occasions, separated by a delay. The intra and inter observer coefficients of variation were 3.7% and 4.9% respectively, with similar values derived for images obtained at all three sites. There was a generally high level of agreement between the Lesion Volumes obtained by the three raters. However, a modest but significant measurement drift was identified between the first and second sessions for one of the three raters, highlighting the very real possibility of measurement drift even for experienced observers. Our results support the increasing role for T1 hypointense Lesion Volume as an outcome measure in multicenter phase III MS treatment trials. Multiple Sclerosis (2000) 6 237 - 240
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How does brain MRI Lesion Volume change on serial scans in patients with multiple sclerosis
Magnetic resonance imaging, 1998Co-Authors: Massimo Filippi, Maria Pia Sormani, Marco Rovaris, G. ComiAbstract:Although Lesion load changes on conventional T2-weighted brain magnetic resonance imaging (MRI) scans from patients with multiple sclerosis (MS) are used to monitor the effect of treatment, there is no clear definition of how Lesion load changes over years according to the Lesion load present at a baseline evaluation. In the present study, we evaluated the relationship between Lesion load changes over time and Lesion load at a baseline evaluation in a group of untreated patients with MS. We scanned nineteen patients on two separate occasions with a mean interval 16.4 months between the two examinations. In each scanning session, a scan with forty contiguous 3-mm-thick axial slices was acquired. We assessed MRI Lesion loads using a semi-automated local thresholding technique. Both a linear (p < 0.0001) and a quadratic component (p = 0.0008) of the baseline Volume were significant in describing the follow-up Volume. The equation to model this finding was as follows: Vf = β0 Vb + β1 (Vb)2, where Vf is the Lesion Volume at follow-up, Vb is the Lesion Volume at baseline, β0 = 0.834 (SE = 0.098), and β1 = 0.014 (SE = 0.003) (mL)−1. Our data indicate that Lesion Volume changes detectable on serial brain MRI studies from patients with MS are dependent on the extent of Lesion burden present on the baseline MRI scans. This finding has to be considered when planning phase III trials.
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Intraobserver and interobserver variability in measuring changes in Lesion Volume on serial brain MR images in multiple sclerosis.
AJNR. American journal of neuroradiology, 1998Co-Authors: Massimo Filippi, Mark A. Horsfield, Maria A. Rocca, Maria Pia Sormani, Marco Rovaris, Ruggero Capra, F. Prandini, G. ComiAbstract:PURPOSE We evaluated the intraobserver and interobserver variability in measuring long-term changes in the Volume of brain Lesions on 5- and 3-mm-thick MR sections in patients with multiple sclerosis. METHODS Eighteen 18 patients were scanned on two separate occasions with a mean interval of 16.4 months between the two examinations. In each session, a scan with 24 contiguous 5-mm-thick axial sections and another with 40 contiguous 3-mm-thick axial sections was acquired consecutively without moving the patient. We assessed MR Lesion load by using a semiautomated local thresholding technique. RESULTS Lesion Volume was significantly higher on images with 3-mm-thick sections than on those with 5-mm-thick sections both at baseline and at follow up. Significant increases in total Lesion Volume were observed during the follow-up period on images obtained with both 5- and 3-mm-thick sections. The intra- and interobserver variability in measurements of changes in Lesion Volume was significantly higher on images with 5-mm-thick sections than on those with 3-mm-thick sections. CONCLUSION Our data indicate that the acquisition of thinner sections increases the reliability of the assessment of changes in brain Lesion load on MR images in patients with multiple sclerosis.
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The effect of imprecise repositioning on Lesion Volume measurements in patients with multiple sclerosis
Neurology, 1997Co-Authors: Massimo Filippi, Mark A. Horsfield, Maria A. Rocca, Ruggero Capra, F. Prandini, N Marcianò, Roberto Gasparotti, G. ComiAbstract:In this study, we evaluated the effect of imprecision in patient repositioning encountered in real life on multiple sclerosis (MS) Lesion Volumes measured from MRIs. We also evaluated two putative methods for reducing the variability in these Lesion Volume measurements: first, a reduction of slice thickness (from the conventional 5 mm to 3 mm) and second, the application of a new repositioning technique based on the use of head immobilization shells. We evaluated the errors in Lesion Volume by scanning 10 patients a total of four times using the two slice thicknesses and two repositioning methods (conventional and using a head immobilization shell). The mean absolute percentage difference between two corresponding scans was 6.8% (range, 1.24 to 11%) using conventional slice thickness and repositioning, 4.1% (range, 0.7 to 5.56%) using conventional slice thickness and head immobilization shells, 2.6% (range, 0.8 to 6.66%) using the conventional repositioning technique and 3-mm slice thickness, and 1.4%(range, 0.2 to 6.14%) using slice thickness of 3 mm and head immobilization shells. These mean absolute differences were significantly different( p = 0.0008). Our results indicate that the effect of repositioning errors of the order of those that can be encountered in the daily life situation of clinical trials affects significantly Lesion load measurements in MS and that the combined use of thinner slices and more accurate repositioning techniques can markedly improve the reproducibility of such measurements.