Comparison of computerized tomography with magnetic resonance imaging (MRI) in the evaluation of encephalic ventricular volume

Summary The volume of the encephalic ventricles was determined from computerized tomographic (CT) and magnetic resonance imaging (MRI) scans of seven subjects without apparent pathology and three subjects with enlarged ventricles. Since there are many conditions in which the encephalic ventricles become enlarged such as Alzheimer's disease and hydrocephalus, accurate measurement of these structures provides (1) a valuable and safe means of aiding in the diagnosis of such conditions and (2) important follow-up information on affected patients. This paper presents the data obtained from the second phase of a three phase study. The first phase demonstrated the possibility of measuring fluid filled spaces by MRI in three phantom preparations (small, medium, and large ventricles). The results were compared with those obtained from the computerized tomography (CT) scans of the same preparations. This phase of the study compares the volumes obtained from CT scans with those obtained from MRI scans of the same individuals. The volumetric calculations were done with the aid of a Calcomp 9000 digital analyser programmed to compensate for the scale factor and slice thickness of the images. The results obtained from the MRI scans correlated closely with those obtained from the CT scans of the same subjects. The third and final phase of the project is the development of an MRI volumetric data base for the encephalic ventricles using a larger number of subjects.

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Etude comparée en TDM et en IRM de l'évaluation du volume des ventricules cérébraux

Résumé Le volume des ventricules cérébraux a été déterminé d'après des données tomodensitométriques et de résonance magnétique chez 7 sujets sans pathologie apparente et chez 3 malades présentant des ventricules élargis. De nombreuses conditions pathologiques sont susceptibles d'entraîner un tel élargissement ventriculaire, telles la maladie d'Alzheimer et l'hydrocéphalie; aussi la mesure précise de ces structures permet: une aide valable et sûre pour l'établissement du diagnostic de ces maladies et une information importante lors du follow-up de ces patients. Ce travail présente les résultats obtenus au cours de la deuxième phase d'une étude à 3 étapes. La première phase avait démontré la possibilité de mesurer des espaces liquidiens par résonance magnétique, à l'aide de 3 préparations fantômes («ventricules» petits, moyens et larges). Les résultats furent comparés avec ceux obtenus par examen tomodensitométrique des mêmes préparations [4]. La phase actuelle de cette étude compare les volumes obtenus par TDM avec ceux obtenus par IRM chez les mêmes individus. Les calculs volumétriques ont été réalisés à l'aide d'un ordinateur Calcomp 9000 programmé pour compenser les facteurs d'agrandissement et d'épaisseur de coupe des images. Les résultats obtenus d'après les données de l'IRM peuvent être corrélés étroitement avec ceux obtenus par TDM avec ces mêmes patients. La troisième et dernière étape du projet est le développement des données volumétriques obtenues par IRM concernant les ventricules cérébraux chez un plus grand nombre de sujets.

     

Volume determinations of the encephalic ventricles with CT and MRI

Summary The volume of the encephalic ventricles was determined from magnetic resonance imaging (MRI) scans. Since there are many conditions in which the encephalic ventricles become enlarged such as Alzheimer's disease and hydrocephalus, accurate measurement of the ventricles provides a valuable and safe means of aiding the diagnosis of such conditions and also provides important follow-up information in affected patients. The objective was pursued in a three phase study. This paper presents the data obtained from the first phase. This first phase demonstrated the possibility of measuring fluid filled spaces by MRI in three phantom preparations (small, medium, and large ventricles). The results were compared with those obtained from computerized tomography (CT) scans of the same preparations. These volumetric calculations were done with the aid of a Calcomp 9,000 digital analyzer programmed to compensate for the scale factor and slice thickness of the images. The phantom study showed that the results obtained from the MRI scans were better than those obtained from the CT scans in measuring the volume of water-filled cavities (ventricles) in gelatin phantoms. The average percent difference between volumes obtained by an imaging procedure compared to the actual volume as determined by water displacement was 15.8% for CT scanning and a more impressive 8.3% for MRI.

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Mesure du volume des ventricules cérébraux

Résumé Le volume des ventricules cérébraux a été mesuré à partir d'explorations en résonance magnétique. Il existe de nombreuses conditions pathologiques qui peuvent provoquer un élargissement ventriculaire, telles que la maladie d'Alzheimer et l'hydrocéphalie. La mesure précise de la taille des ventricules peut être d'importance pour le diagnostic de ces affections. Elle fournit également d'excellents critères de surveillance des patients porteurs de telles maladies. Notre objectif a été poursuivi au cours d'études séparées en 3 parties. Ce travail rapporte les résultats obtenus durant la première phase de cette étude. Celle-ci démontre qu'il est possible de mesurer les espaces liquidiens en IRM sur 3 fantômes ventriculaires (cavités petites, moyennes et larges). Les résultats ont été comparés avec ceux obtenus en examen tomodensitométrique des mêmes préparations. Des calculs volumétriques ont été obtenus à l'aide d'un analyseur numérique Calcomp 9 000 programmé pour corriger les facteurs d'agrandissement et les épaisseurs de coupe. L'étude des résultats des mesures de volume des cavités ventriculaires obtenus sur ces fantômes démontre que ceux-ci sont plus précis en coupes IRM qu'en coupes tomodensitométriques. La différence moyenne entre ces volumes obtenus en imagerie et les volumes réels calculés par mesure d'espaces liquidiens était de 15,8 % pour les coupes scanographiques et 8,3 % pour l'IRM.

     

Spinal cerebrospinal fluid leaks detected by radionuclide cisternography and magnetic resonance imaging in patients suspected of intracranial hypotension

PurposeAlthough many studies have described various features of neuroimaging tests associated with intracranial hypotension, few have examined their validity and reliability. We evaluated the association between CSF leaks detected by radionuclide cisternography and abnormal MRI findings in the accurate diagnosis of intracranial hypotension.Patients/methodsWe retrospectively assessed 250 patients who were suspected of intracranial hypotension and underwent subsequent radionuclide cisternography. We obtained 159 sagittal and 153 coronal T2-weighted MRI images and 101 gadolinium-enhanced T1-weighted MRI images. We assessed the CSF leaks in relation to a sagging brain, the maximum subdural space in sagittal and coronal images, and dural enhancement.ResultsOverall, 186 (74%) patients showed CSF leaks on radionuclide cisternography. A sagging brain was observed in 21 (13%) of the 159 patients with sagittal MRIs. A sagging brain was not associated with CSF leaks (14% vs. 10%; p = 0.49). Compared to patients without CSF leaks, those with CSF leaks tended to have a larger maximum subdural space in both the sagittal (3.7 vs. 4.1 mm) and coronal (2.5 vs. 2.8 mm) images; however, the differences were not significant (p = 0.18 and p = 0.53, respectively). Dural enhancement was observed only in one patient, who presented with CSF leaks on radionuclide cisternography.ConclusionsOur study, which included a relatively large population, did not find any association between the findings of radionuclide cisternography and MRI. Future research should focus on identifying more valid neuroimaging findings to diagnose intracranial hypotension accurately.     

Comparison of point counting and planimetry methods for the assessment of cerebellar volume in human using magnetic resonance imaging: a stereological study

The cerebellum is involved in motor learning and cognitive function in human. Many studies have been conducted to assess the cerebellar volume. To the best of our knowledge, there is no cerebellar volume study evaluating the efficiency and the accuracy of point-counting and planimetry methods of the Cavalieri principle in the literature. In this study, the volume of cerebellum was estimated in 53 Turkish young volunteers (26 males and 27 females), aged between 20 and 25 who are free of any neurological symptoms and signs, using serial magnetic resonance (MR) images. The cerebellar volumes of subjects were determined on MR images using the point-counting and planimetry methods. The mean results of planimetry method were 116.69 +/- 10.1 and 114.41 +/- 9.3 cm(3 )in males and females, respectively. The mean results of point-counting method were 116.34 +/- 10.6 and 113.48 +/- 8.8 cm(3 )in males and females, respectively. Our results revealed that female subjects had less cerebellar volumes compared with males, although there was no statistical significant difference between genders (P > 0.05). Total cerebellar volumes obtained by two different methods were not statistically different (P = 0.189) and they were correlated well to each other (r = 0.935). We found that the point-counting method takes less time than the planimetric method (mean 8 +/- 3.6 vs. 15 +/- 5.5 min). Thus, while planimetric and stereological approaches yield very similar results, the stereological method has the advantage of greater speed and, therefore, efficiency.     

Predictors of panic symptoms during magnetic resonance imaging scans

This study examined the usefulness of a score derived from nine items of Wolpe and Lang’s (1964) Fear Survey Schedule (FSS) in predicting the number of symptoms consistent with panic reported by a large outpatient sample undertaking magnetic resonance imaging (MRI) scans. The items were those identified by Lukins, Davan, and Drummond (1997) as likely to reflect fears associated with the aversive characteristics of the MRI procedure (i.e., noise, confinement, and isolation) and were taken 1 week before the scan. The MRI-related FSS score was a better predictorof symptoms consistent with panic attack during the scan than (a) Rachman and Taylor’s (1993) Claustrophobia Questionnaire, (b) a score derived from nine FSS items reflecting common community fears, or (c) a measure of state anxiety. It is suggested that the brief MRI-related FSS scale can provide information important for planning patient management during MRI scans at a time when the information can be most useful.     

小脑深部核团薄层横断面解剖与MRI的对照研究

目的 研究薄层断面上小脑深部核团的位置、分布和形态,为小脑功能影像学研究、电刺激核团疗法的功能相关性研究以及核团立体定向手术提供其中解剖学依据.方法 选择3具成年男性尸体标本,以CT与1.5T MRI经前后连合间线扫描,排除器质性病变.选取其中1例成年尸体头部标本,经明胶包埋和深低温冷冻后,采用铣削精度为0.001mm的SKC500型数控铣床,同样经连合间线制成层厚为0.1mm的连续薄层横断面,对获取的图像进行解剖学观察并择取与齿状核相关的典型断面与相应的活体3.0T MRI图像对照. 结果 共获得与小脑相关的薄层断面图像620幅,其中齿状核、顶核、球状核以及栓状核出现的层面数分别为145、12、25、20幅.在连续横断面上观察到齿状核最大且最先出现,位于最外侧,形似一个向内侧开口的折叠口袋状结构;顶核最靠内侧,紧邻第四脑室顶的外侧和上蚓前部的内侧面,在中线两侧对称分布;栓状核位于齿状核内侧,不易与其区分,核团部分遮盖齿状核门;球状核由多个散在分布的灰质团块组成,呈前后向伸展,出现于栓状核与顶核之间. 结论 连续薄层横断面上能较好地显示小脑深部核团的位置、形态以及与周围小脑结构的毗邻关系,对小脑深部核团的功能影像学研究和临床治疗有重要的参考价值.     

Course of cerebral lesions in a patient with periarteritis nodosa studied by magnetic resonance imaging

Summary The course is reported of a patient with periarteritis nodosa who initially presented with neurological symptoms. Multiple cerebral lesions were documented by the first magnetic resonance imaging (MRI) investigation. The majority of these had disappeared completely in the follow-up MRI studies. In contrast to neurological improvement the patient eventually died due to multiorgan failure. Postmortem histological examination revealed no pathological findings in the brain except one single necrotic area already known from MRI. Remissions of histological and angiographic alterations in periarteritis nodosa have been described as local healing leading to fibrosis and scarring. Our findings suggest that restitutio ad integrum may occur, at least in cerebral lesions.Abbreviations PAN panarteritis nodosa - MRI magnetic resonance imaging - CT computerized tomography - CNS central nervous system     

酪氨酸酶基因在HEK293细胞表达的MRI评价

目的:以酪氨酸酶基因作为报告基因转染HEK293细胞, 利用其合成大量黑色素而能被MRI检测的特性来反映基因表达的情况, 以探索磁共振成像(MRI)评价体外细胞基因表达的方法。方法:以脂质体将含酪氨酸酶基因完全cDNA的pcDNA3tyr质粒转染到HEK293细胞, 以MRIT₁WI、T₁WI/SPIR、T₂WI序列扫描转染细胞, 观察表达的黑色素的MRI信号。应用Fontana染色检测黑色素的合成, RT-PCR检测酪氨酸酶基因的cDNA片段, 以进一步验证酪氨酸酶基因的转染与表达。结果:(1)pcDNA3tyr质粒转染进入HEK293细胞并在其中表达生成黑色素, 转染5μg、10μg、20μg质粒的10⁶个细胞内生成的黑色素能够被MRI检测到并在MRIT₁WI、T₁WI/SPIR、T₂WI检查呈高信号, MRI信号强度与转染质粒量成正相关。(2)Fontana染色法检测到HEK293细胞内的黑色素颗粒;(3)采用RT-PCR方法检测到转染的HEK293细胞含酪氨酸酶基因的cDNA片段。结论:MRI能够检测到HEK293细胞内由外源基因表达合成的黑色素, 说明影像学与分子生物学技术结合可以评价体外细胞基因表达的情况。     

Anatomic correlation of cadaver cryomicrotomy with magnetic resonance imaging

Summary The performance of frozen sections of a thickness varying between 5 and 50 m in fresh undecalcified cadaveric human specimens was perfected in Sweden by one of the authors in 1983. This technique makes it possible to obtain anatomic images of high definition which were correlated with MRI sections made at intervals of 20 m.

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Corrélations anatomiques entre la cryomicrotomie sur cadavre et l'IRM

Résumé La réalisation de coupes congelées dont l'épaisseur varie entre 5 et 50 m, sur prélèvements cadavériques humains frais et non décalcifiés a été mise au point en Suède par l'un des auteurs en 1983. Cette technique permet d'obtenir des images anatomiques de haute définition qui ont été corrélées avec des coupes en IRM réalisées à des intervalles de 20 m.

     

Probing renal blood volume with magnetic resonance imaging

Damage to the kidney substantially reduces life expectancy. Renal tissue hypoperfusion and hypoxia are key elements in the pathophysiology of acute kidney injury and its progression to chronic kidney disease. In vivo assessment of renal haemodynamics and tissue oxygenation remains a challenge. Blood oxygenation level–dependent (BOLD) magnetic resonance imaging (MRI) is sensitive to changes in the effective transversal relaxation time (T₂*) in vivo, and is non‐invasive and indicative of renal tissue oxygenation. However, the renal T₂* to tissue pO₂ relationship is not governed exclusively by renal blood oxygenation, but is affected by physiological confounders with alterations in renal blood volume fraction (BVf) being of particular relevance. To decipher this interference probing renal BVf is essential for the pursuit of renal MR oximetry. Superparamagnetic iron oxide nanoparticle (USPIO) preparations can be used as MRI visible blood pool markers for detailing alterations in BVf. This review promotes the opportunities of MRI‐based assessment of renal BVf. Following an outline on the specifics of renal oxygenation and perfusion, changes in renal BVf upon interventions and their potential impact on renal T₂* are discussed. We also describe the basic principles of renal BVf assessment using ferumoxytol‐enhanced MRI in the equilibrium concentration regimen. We demonstrate that ferumoxytol does not alter control of renal haemodynamics and oxygenation. Preclinical applications of ferumoxytol enhanced renal MRI as well as considerations for its clinical implementation for examining renal BVf changes are provided alongside practical considerations. Finally, we explore the future directions of MRI‐based assessment of renal BVf.     

Program for generation of three-dimensional finite element mesh from magnetic resonance imaging scans of human limbs

A PC-AT based program for conversion of magnetic resonance imaging (MRI) scans into coordinate input for finite element mesh generation is presented. The program is written in Borland C + +3.1 and is compatible with every general-use personal computer, permitting the use of MS-DOS 3.0 or higher with a Microsoft mouse. The program is menu driven and does not demand specialised knowledge from the user. The system and memory requirements are minimal -- 640 kB RAM -- and it runs as a stand-alone program. A second program allows the construction of a three-dimensional representation of the limb sub-structure and generation of the FE mesh from the converted cross-sectional scans. The capabilities of the program are demonstrated using cross-sectional scans of the upper arm; the fat, muscle and bone contours were obtained to a very high level of precision (0.4 mm).     

Inertial properties of the human trunk of males determined from magnetic resonance imaging

The purpose of this study was to evaluate the segmental parameters of the human trunk of malesin vivo using magnetic resonance imaging (MRI). In addition, the efficacy of volumetric estimation and existing prediction formulas to produce segmental properties similar to those produced by MRI was evaluated. As opposed to finding one representative normal value for these parameters, a range of normal values was defined. For instance, the average trunk mass was 42.2%±3.5% (x±SD) of body mass, but values ranged from 35.8% to 48.0%. To account for segment parameters more accurately, specific anthropometric measures need to be considered in addition to overall measures of body height and mass. These specific measures included segment length, circumference, width, and depth. Studies reporting general percentages based on height and/or mass were found to be inadequate predictors of segmental parameters of the trunk compared with MRI estimates. Volumebased estimates, which assume a uniform density distribution within a segment, were found to correspond closely to MRI values except for the thorax. However, the use of density values reflective of the livingin vivo state would likely alleviate this disparity, thus indicating that the volumetric technique may be effective for deriving segmental parameters for large segments of the trunk. Future research should adopt noninvasive techniques such as MRI and/or volumetric estimation to enhance the predictability of segmental parameters of the body for specific population groups characterized by gender, developmental age, body type, and fitness level. Further efforts should be made to establish standardized boundary definitions for trunk segments to avoid unnecessary confusion, from which substantial errors may be introduced into biomechanical linked-segment analyses of human movement.     

Three-dimensional quantification of susceptibility artifacts from various metals in magnetic resonance images

Susceptibility artifacts generated in magnetic resonance (MR) images were quantitatively evaluated for various metals using a three-dimensional (3-D) artifact rendering to demonstrate the correlation between magnetic susceptibility and artifact volume. Ten metals (stainless steel, Co–Cr alloy, Nb, Ti, Zr, Mo, Al, Sn, Cu and Ag) were prepared, and their magnetic susceptibilities measured using a magnetic balance. Each metal was embedded in a Ni-doped agarose gel phantom and the MR images of the metal-containing phantoms were taken using 1.5 and 3.0 T MR scanners under both fast spin echo and gradient echo conditions. 3-D renderings of the artifacts were constructed from the images and the artifact volumes were calculated for each metal. The artifact volumes of metals decreased with decreasing magnetic susceptibility, with the exception of Ag. Although Sn possesses the lowest absolute magnetic susceptibility (1.8 × 10^?6), the artifact volume from Cu (?7.8 × 10^?6) was smaller than that of Sn. This is because the magnetic susceptibility of Cu was close to that of the agarose gel phantom (?7.3 × 10^?6). Since the difference in magnetic susceptibility between the agarose and Sn is close to that between the agarose and Ag (?17.5 × 10^?6), their artifact volumes were almost the same, although they formed artifacts that were reversed in all three dimensions.     

咀嚼时局部脑活动的功能性核磁共振成像

目的：应用功能性核磁共振成像（fMRI）探测人吸嚼时的大脑功能活动。方法：要求人在无任何其它躯体活动条件下咀嚼肌以10s运动20s休息的频率进行。选用8例成人冠状切面和横轴面的头部磁共振片,观察脑功能活动情况。结果：①在咀嚼时脑的广泛区域是激活的;②在相对应的咀嚼活动中有优势半球的激活区;③第I躯体感觉区激活的方式远较第I躯体运动区多样化;④在额叶中4例年轻观察对象出现了广泛的神经元激活区,但在老年人很少出现这样的激活区。结论：咀嚼活动除了它本身的功能运动外,在维持脑的活动方面具有重要的作用。同时也说明fMRI在研究活体人脑功能活动方面是一个相当有效的方法。     

Non-invasive temperature imaging of muscles with magnetic resonance imaging using spin-echo sequences

The application of spin-echo magnetic resonance imaging sequences on non-invasive temperature imaging for temperature mapping of human limbs is investigated. In an in vitro expriment performed on a meat sample, the equilibrium magnetisation P and the spin-lattice relaxation time T₁ are calculated from the values for the repetition time TR and the signal intensities obtained by a spin-echo sequence at different tissue temperatures tures as measured by a fibre-optic probe. T₁ is linearly correlated to the tissue temperature, and P is linearly correlated to the reciprocal value of the absolute temperature. Both effects, taken together, lead to a non-linear dependency of the signal intensity on temperature. Therefore a TR leading to maximum temperature dependency of the signal intensity is calculated and used in the futher experiments. In the in vivo experiments, the lower legs of two volunteers are cooled from outside. Images are acquired with a spin-echo sequence (1.5T, TR=1200 ms, TE=10 ms). A rise in signal intensity in the muscle with falling skin temperature is observed, particularly in more peripheral muscle layers. This study shows that spin-echo sequences can be used to monitor temperature changes and temperature differences in living muscle tissue.     

A comparison of the early development of ischemic brain damage in normoglycemic and hyperglycemic rats using magnetic resonance imaging

The early evolution of ischemic brain injury under normoglycemic and streptozotocin-induced hyperglycemic plasma conditions was studied using magnetic resonance imaging (MRI). Male Sprague-Dawley rats were subjected to either permanent middle cerebral artery occlusion (MCAO), or 1-h MCAO followed by reperfusion using the intraluminal suture insertion method. The animals were divided into four groups each with eight rats: normoglycemia with permanent MCAO, normoglycemia with 1-h MCAO, hyperglycemia with permanent MCAO, and hyperglycemia with 1-h MCAO. Diffusion-weighted images (DWIs) and T2-weighted images (T2WIs) were aquired every l h from 20 min until 6 h after MCAO, at which time cerebral plasma volume images (PVIs) were acquired. Tissue infarction was determined by triphenyltetrazolium chloride staining at 7 h after MCAO. The ischemic damage, measured as the area of DWI and T2WI hyperintensity and tissue infarction, increased significantly in hyperglycemic rats in both permanent and transient MCAO models. In the permanent MCAO model, the maximal apparent water diffusion coefficient (ADC) decline under either normoor hyperglycemia was about 40%, but the speed of ADC drop was faster in hyperlgycemic rats than in normoglycemic rats. Reperfusion after l h of MCAO in normoglycemic rats partly reversed the decline in ADC, whereas the low ADC area continued to expand after reperfusion in the hyperlgycemic group. Between the two hyperglycemic groups with either permanent MCAO or reperfusion, no significant difference was found in the infarct volume measured at 7 h after MCAO. However, reperfusion dramatically increased the extent and accelerated the development rate of vasogenic edema. ADC in the hyperglycemic reperfusion group also dropped to a lower level. A large no-reflow zone was found in the ischemic hemisphere in the hyperglycemic reperfusion group. This study provides strong evidence to support that preischemic hyperglycemia exacerbates ischemic damage in both transient and permanent MCAO models and demonstrates, using MRI, that reperfusion under preischemic hyperglycemia accelerates the evolution of early ischemic injury.     

磁共振弥散张量成像联合纤维束成像在脑梗死中的应用研究

目的 分析脑梗死患者磁共振弥散张量成像(DTI)和纤维束成像(DTT)的特点,探讨DTI、DTT在对不同时期脑梗死患者诊断的价值。方法分别对58例不同时期脑梗死患者和25名健康志愿者行MRI检查,包括T1WI、T2WI成像、FLAIR及DTI成像,重建部分各向异性(FA)图,对梗死区、健侧相应部位及正常对照组相应部位进...     

Sexual dimorphism and handedness in the human corpus callosum based on magnetic resonance imaging

The corpus callosum (CC) is a major anatomical and functional commissure linking the two cerebral hemispheres. With MR imaging in the sagittal plane, the corpus callosum can be depicted in great detail. Mid-sagittal magnetic resonance images of 80 normal individuals were analyzed to assess whether or not the morphology of the corpus callosum and its parts are related to sex and handedness. The subjects were 40 males (20 right-handers and 20 left-handers) and 40 females (20 right-handers and 20 left-handers). The midsagittal area of the corpus callosum was divided into seven sub-areas using Witelsons method. The most striking morphological changes concerned left-handers, who had larger areas of the anterior body, posterior body and isthmus than right-handers. In addition, right-handed males had larger rostrums and isthmuses than right-handed females. These significantly increased areas were related to handedness in right-handed males. However, left-handed males had larger anterior and posterior bodies than right-handed males. In contrast, there was no significant difference between left-handers and right-handers in females. The areas of the rostrum and posterior body of the corpus callosum increased significantly with sex in males. Moreover, there were no significant age-related changes in the total corpus callosum and sub-areas of the corpus callosum. In conclusion, these anatomical changes in corpus callosum morphology require taking the sexual definition and dominant handedness into consideration.     

Temporal evolution of focal cerebral ischemia in the rat assessed by T2-weighted and diffusion-weighted magnetic resonance imaging

Summary The present study was undertaken to characterize the formation of ischemic brain edema using diffusion-weighted and T₂-weighted magnetic resonance imaging in a rat model of focal ischemia. The extent of edema formation was measured from multislice diffusion-weighted and T₂-weighted spin-echo images acquired at various times after ischemia. The spin-spin relaxation time (T₂) and the apparent diffusion coefficient in normal and ischemic tissue were also determined. The results show that on the diffusion-weighted images the lesion was clearly visible at 30 minutes after ischemia, while on the T₂-weighted images it became increasingly evident after 2–3 hours. On both types of images the hyperintense area increased in size over the first 48 hours. After 1 week the hyperintensity on the diffusion-weighted images rapidly disappeared and evolved as a hypointense lesion in the chronic phase. These results confirm the high sensitivity of diffusion-weighted MRI for the detection of early ischemia. The temporal course of the edema observed on T₂W-images is in agreement with the reported increase of total water content occurring in this model. The increase of the lesion observed on the diffusion-weighted images during the first 2 days points to an aggravation of cytotoxic edema that parallels the changes in free water shown by the T₂-weighted images. It is shown that the highly elevated T₂'s of the infarcted area several days after ischemia can substantially contaminate the diffusion-weighted images.Part of this research was carried out at the Netherlandsin vivo NMR facility at the Bijvoet Center for Biomolecular Research, which is supported by the Netherlands Organization for Scientific Research (NWO).