Magnetic Resonance Signal Changes Research Articles

The Effect of Movement Rate and Complexity on Functional Magnetic Resonance Signal Change During Pedaling

We used functional magnetic resonance imaging (fMRI) to record human brain activity during slow (30 RPM), fast (60 RPM), passive (30 RPM), and variable rate pedaling. Ten healthy adults participated. After identifying regions of interest, the intensity and volume of brain activation in each region was calculated and compared across conditions (p < .05). Results showed that the primary sensory and motor cortices (S1, M1), supplementary motor area (SMA), and cerebellum (Cb) were active during pedaling. The intensity of activity in these areas increased with increasing pedaling rate and complexity. The Cb was the only brain region that showed significantly lower activity during passive as compared with active pedaling. We conclude that M1, S1, SMA, and Cb have a role in modifying continuous, bilateral, multijoint lower extremity movements. Much of this brain activity may be driven by sensory signals from the moving limbs.

Reversible Parainfectious Bilateral “Striatal Necrosis”

Bilateral striatal necrosis is usually associated with either endogenous or exogenous toxins, and with poor neurodevelopmental outcomes. We describe two patients with acute bilateral striatal clinical syndrome and magnetic resonance signal changes who made a complete clinical and radiologic recovery within 3 months. After an uneventful pregnancy, normal birth, and normal development, both boys presented at ages 3 and 5 years, respectively, after a viral illness with slurring of speech, bradykinesia, and an extrapyramidal movement disorder. On examination, both manifested bilateral cog wheel rigidity, with a broad-based gait and flexor plantar response. Cranial magnetic resonance imaging in both children indicated bilateral, symmetric, high signal changes in the lentiform nucleus, predominately in the putamen, with sparing of the globus pallidi bilaterally. The brain parenchyma was otherwise normal. Neurometabolic investigations produced normal results in both patients. The pathogenesis is uncertain, but could be immune-mediated. Both children, at 3-year and 1-year follow-ups, respectively, are doing well neurologically and academically. Our patients demonstrate that abnormal imaging findings during acute stages do not preclude good clinical and radiologic recovery.

MRI of Tumor-Associated Macrophages with Clinically Applicable Iron Oxide Nanoparticles

The presence of tumor-associated macrophages (TAM) in breast cancer correlates strongly with poor outcome. The purpose of this study was to develop a clinically applicable, noninvasive diagnostic assay for selective targeting and visualization of TAMs in breast cancer, based on magnetic resonanceI and clinically applicable iron oxide nanoparticles. F4/80-negative mammary carcinoma cells and F4/80-positive TAMs were incubated with iron oxide nanoparticles and were compared with respect to magnetic resonance signal changes and iron uptake. MMTV-PyMT transgenic mice harboring mammary carcinomas underwent nanoparticle-enhanced magnetic resonance imaging (MRI) up to 1 hour and 24 hours after injection. The tumor enhancement on MRIs was correlated with the presence and location of TAMs and nanoparticles by confocal microscopy. In vitro studies revealed that iron oxide nanoparticles are preferentially phagocytosed by TAMs but not by malignant tumor cells. In vivo, all tumors showed an initial contrast agent perfusion on immediate postcontrast MRIs with gradual transendothelial leakage into the tumor interstitium. Twenty-four hours after injection, all tumors showed a persistent signal decline on MRIs. TAM depletion via αCSF1 monoclonal antibodies led to significant inhibition of tumor nanoparticle enhancement. Detection of iron using 3,3'-diaminobenzidine-enhanced Prussian Blue staining, combined with immunodetection of CD68, localized iron oxide nanoparticles to TAMs, showing that the signal effects on delayed MRIs were largely due to TAM-mediated uptake of contrast agent. These data indicate that tumor enhancement with clinically applicable iron oxide nanoparticles may serve as a new biomarker for long-term prognosis, related treatment decisions, and the evaluation of new immune-targeted therapies.

MR signal change in venous thrombus relates organizing process and thrombolytic response in rabbit

Venous thrombus is subsequently organized and replaced by fibrous connective tissue. However, the sequential changes in venous thrombi are not reliably detected by current noninvasive diagnostic techniques. The purpose of this study is to reveal whether magnetic resonance (MR) can detect venous thrombus, define thrombus age and predict thrombolytic responses. Thrombus in the rabbit jugular vein was imaged with a 1.5-T MR system at 4 h and at 1, 2 and 4 weeks using three-dimensional (3D) fast asymmetric spin echo T2-weighted (T2W) and 3D-gradient echo T1-weighted (T1W) sequences. The jugular veins were histologically assessed at each time point. Magnetic resonance imaging (MRI) was also performed in vivo before and 30 min after tissue plasminogen activator (t-PA) administration. The thrombi in MRI were comparable in size to histological sections. The signal intensity (SI) of thrombi at 4 h was heterogeneously high or low on T2W or T1W images, respectively. The SI of thrombi on T2W images decreased time-dependently, but increased on T1W images at 1 and 2 weeks. Morphological analysis showed time-dependent decreases in erythrocyte, platelet and fibrin areas and time-dependent increases in smooth muscle cell, macrophage, collagen and iron areas. The t-PA administration significantly decreased thrombus volume at 4 h but not at 1, 2 and 4 weeks. Venous thrombosis can be reliably and noninvasively detected by MRI. Measurement of SI might support assessments of thrombus age and thrombolytic response.

Rotavirus encephalitis and cerebellitis with reversible magnetic resonance signal changes

Pediatrics InternationalVolume 53, Issue 2 p. 252-255 Rotavirus encephalitis and cerebellitis with reversible magnetic resonance signal changes Toshihiko Mori, Corresponding Author Toshihiko Mori Department of Pediatrics, NTT East Sapporo HospitalToshihiko Mori, MD PhD, Department of Pediatrics, NTT East Sapporo Hospital, South-1, West-15, Chuo-ku, Sapporo 060-0061, Japan. Email: [email protected]Search for more papers by this authorMayuko Morii, Mayuko Morii Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorYuki Kuroiwa, Yuki Kuroiwa Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorTomoyuki Hotsubo, Tomoyuki Hotsubo Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorShigeto Fuse, Shigeto Fuse Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorHiroyuki Tsustumi, Hiroyuki Tsustumi Department of Pediatrics, Sapporo Medical University School of Medicine, Sapporo, JapanSearch for more papers by this author Toshihiko Mori, Corresponding Author Toshihiko Mori Department of Pediatrics, NTT East Sapporo HospitalToshihiko Mori, MD PhD, Department of Pediatrics, NTT East Sapporo Hospital, South-1, West-15, Chuo-ku, Sapporo 060-0061, Japan. Email: [email protected]Search for more papers by this authorMayuko Morii, Mayuko Morii Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorYuki Kuroiwa, Yuki Kuroiwa Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorTomoyuki Hotsubo, Tomoyuki Hotsubo Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorShigeto Fuse, Shigeto Fuse Department of Pediatrics, NTT East Sapporo HospitalSearch for more papers by this authorHiroyuki Tsustumi, Hiroyuki Tsustumi Department of Pediatrics, Sapporo Medical University School of Medicine, Sapporo, JapanSearch for more papers by this author First published: 19 April 2011 https://doi.org/10.1111/j.1442-200X.2010.03221.xCitations: 16Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume53, Issue2April 2011Pages 252-255 RelatedInformation

Gastric distention induced functional magnetic resonance signal changes in the rodent brain

Investigating the localization of gastric sensation within the brain is important for understanding the neural correlates of satiety. Previous rodent studies have identified the brain-stem and hypothalamus as key mediators of gastric distention-induced satiation. Although, recent blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) studies in humans have identified a role for higher cortico-limbic structures in mediating the satiation effects of gastric distention, the role of these regions in rodents remains to be characterized. We determined the effects of gastric distention on global spatio-temporal BOLD fMRI signal changes in the rodent brain. Brain images were acquired with a high resolution 9.4 T magnet during gastric distention with continuous monitoring of blood pressure in adult male Sprague Dawley rats ( n=8–10). Distention of the stomach with an intragastric balloon, at rates which mimicked the rate of consumption and emptying of a mixed nutrient liquid meal, resulted in robust reduction in food intake and increase in blood pressure. Gastric distention increased BOLD fMRI activity within homeostatic regions such as the hypothalamus and nucleus tractus solitarius, as well as non homeostatic regions including the hippocampus, amygdala, thalamus, cerebellum and the cortex (cingulate, insular, motor and sensory cortices). Further, the increase in BOLD fMRI activity following distention was strongly correlated to an increase in blood pressure. These results indicate that gastric distention, mimicking the rate of intake and emptying of a liquid meal, increases BOLD fMRI activity in both homeostatic and non homeostatic brain circuits which regulate food intake, and that these BOLD fMRI signal changes may in part be attributable to transient increases in blood pressure.

Magnetic resonance signal detection of superparamagnetic iron oxide nanoparticles and its biological effects on endothelial cells

To investigate the magnetic resonance (MR) signal changes of superparamagnetic iron oxide (SPIO) and its biological effects on endothelial cells. The citric-acid coated SPIO was synthesized by co-precipitation method. The human umbilical vein endothelial cells (HUVECs) were incubated with SPIO for 24 h in culture medium at iron concentration of 0.01, 0.05, 0.10, 0.15 mg/ml (experimental groups), and the cells incubated without SPIO served as control groups. The uptake efficiency of intracellular iron was measured by Prussian blue staining, and the cell viability was monitored by Calcein-AM method. The cell cytoskeleton (F-actin and tubulin), adherence and migration capacity were measured by immunofluorescence staining. The iron oxide nanoparticles distribution and the cellular organelle change were monitored by transmission electron microscopy (TEM). Quantification of particle uptake was measured by atomic absorption spectrometry. The MR signal of endothelial cells after labeling was monitored by Philips 3.0 T MR scanner. SPIO was uptaken by HUVECs in a concentration-dependence manner. Compared with the control group, cell viability was decreased along with the increase of iron concentration. Compared with the control group, the cell cytoskeleton was markedly disorganized and the FAK spot was bigger and sparser.The nanoparticles were mainly existed in lysosomes, and the higher concentration of SPIO, the more lysosomes and vacuoles presented in the cells. The iron content per cell was (55.86 +/-9.935) pg when the SPIO concentration was 0.15 mg/ml. The MR image showed that the cells labeled with SPIO resulted in the decrease of MR signal. The cells labeled with SPIO can be detected by MR. The cell viability, cytoskeleton, adherence and migration capacity of HUVECs are affected by citric-acid coated SPIO in a concentration-dependent manner.

Transient splenial lesion of the corpus callosum in a case of benign convulsion associated with rotaviral gastroenteritis

Transient magnetic resonance (MR) signal changes in the splenium of the corpus callosum (SCC) arise from many different conditions, including encephalopathy or encephalitis caused by infection, seizures, metabolic derangements, and asphyxia. Few case reports exist on reversible SCC lesions associated with rotavirus infection. A benign convulsion with mild gastroenteritis (CwG) is frequently associated with rotaviral infections. This entity is characterized by normal laboratory findings, electroencephalogram, neuroimaging, and good prognosis. We report a case of a 2.5-year-old Korean girl with rotavirus-associated CwG demonstrating a reversible SCC lesion on diffusion-weighted MR images. She developed 2 episodes of brief generalized tonic-clonic seizure with mild acute gastroenteritis without any other neurologic abnormality. Stool test for rotavirus antigen was positive. Brain MRI done on the day of admission showed a linear high signal intensity and decreased apparent diffusion coefficient values on the SCC. The lesion completely disappeared on follow-up MRI 6 days later. The patient fully recovered without any sequelae.

Regional fMRI brain activation does correlate with global brain volume

In healthy elderly participants, there has been little correlation found between measures of global brain atrophy and functional magnetic resonance imaging activated voxel counts and mean percent magnetic resonance signal change. We used a validated passive viewing task to calculate the fMRI activated voxel counts and mean percent MR signal change from the striate and ventral extrastriate cortices of 24 healthy control subjects (age range = 33–89, mean age = 66). We correlated these data with three measures of atrophy – percent brain volume, normalised brain volume and grey matter volume – to evaluate the relationship between global brain atrophy and regional fMRI activation. There was a strong positive correlation ( r > 0.90) between regional activation volume in striate and ventral extrastriate cortex and decreasing total brain volume when results were averaged by decade. Correlation with percent brain volume was particularly strong. In addition, we found a strong negative correlation between mean percent MR signal change and brain volume measures. Within-subject individual correlation was less strong, highlighting the problem of individual variability in brain volume and regional activation measures.

Serial Functional Imaging Poststroke Reveals Visual Cortex Reorganization

Purpose. Visual cortical reorganization following injury remains poorly understood. The authors performed serial functional magnetic resonance imaging (fMRI) on patients with visual cortex infarction to evaluate early and late striate, ventral, and dorsal extrastriate cortical activation. Methods. Patients were studied with fMRI within 10 days and at 6 months. The authors used a high-level visual activation task designed to activate the ventral extrastriate cortex. These data were compared to those of age-appropriate healthy control participants. Results. The results from 24 healthy control individuals (mean age 65.7 ± SE 3.6 years, range 32-89) were compared to those from 5 stroke patients (mean age 73.8 ± SE 7 years, range 49-86). Patients had infarcts involving the striate and ventral extrastriate cortex. Patient activation patterns were markedly different to controls. Bilateral striate and ventral extrastriate activation was reduced at both sessions, but dorsal extrastriate activated voxel counts remained comparable to controls. Conversely, mean percent magnetic resonance signal change increased in dorsal sites. Conclusions. These data provide strong evidence of bilateral poststroke functional depression of striate and ventral extrastriate cortices. Possible utilization or surrogacy of the dorsal visual system was demonstrated following stroke. This activity could provide a target for novel visual rehabilitation therapies.

Calcific discitis in children: vertebral body involvement (possible insight into etiology)

The aim of the study was to present our cases of calcific discitis, analyze the imaging findings, and review the literature in an attempt to formulate a possible etiology. We reviewed the imaging and clinical findings in nine patients with calcific discitis and accomplished a literature review of the condition. There were nine patients, five males and four females. Age range was 5-13 years with a mean of 9.7 years. Twenty-three discs were involved, nine cervical and fourteen thoracic. Four cervical discs were not calcified but merely swollen. One patient presented with abnormal magnetic resonance (MR) signal changes within a vertebral body. Our literature search revealed another such patient and brought up the possibility that the insult to the disc might be secondary to vertebral body involvement and disruption of the tenuous vascular/nutritional support of the intervertebral disc from the adjacent vertebral body. In the early stages of calcific discitis, only swelling and expansion of the disc are seen. More recently, with MR imaging, vertebral body involvement has been demonstrated to also occur. As a result, it may be that the initial insult (vascular compromise) is to the vertebral body (nutritional support for the disc) rather than to the disc.

Differential recovery of behavioral status and brain function assessed with functional magnetic resonance imaging after mild traumatic brain injury in the rat*

The relationship between cerebral integrity, recovery of brain function, and neurologic status after mild traumatic brain injury is incompletely characterized. Prospective and randomized study in rodents. University laboratory. Male Wistar rats (290-310 g). In rats, quantitative diffusion weighted imaging (DWI), perfusion weighted imaging (PWI), T2-weighted imaging (T2WI), and functional magnetic resonance imaging (fMRI) were performed up to 21 days after weight-induced, closed-head, mild traumatic brain injury (MTBI, n = 6) or sham operation (n = 6). Pixel-by-pixel analysis and region of interest analysis were used to evaluate structural (apparent diffusion coefficient [ADC] and basal cerebral blood flow [bCBF]) and functional magnetic resonance signal changes within the brain, respectively. Quantitative fMRI signal changes were correlated with behavioral measures. Despite normal appearing DWI and T2WI findings following MTBI, persistent hypoperfusion developed that was not associated with cytotoxic edema. In contrast, the ADC was significantly increased by approximately 5% at 1 and 7 days post-MTBI. Post-MTBI fMRI responses to hypercapnia and forepaw stimulation were significantly impaired and showed a differential recovery rate between and within investigated region of interests. Significant dysfunction in forepaw placement test persisted up to day 1 and correlated significantly with fMRI signal changes in the primary somatosensory and motor cortices. MTBI produced distinct changes on multimodal MRI and behavioral variables acutely and chronically. Following MTBI, fMRI and ADC-bCBF pixel-by-pixel analysis identified subtle structural and functional alterations in the brain that appeared completely normal on conventional DWI and T2WI after concussion injury. The former techniques may therefore provide great potential for understanding mild traumatic brain injury, identifying mechanisms underlying recovery, and investigating specific interventions to enhance functional outcome.

Realistic simulations of neuronal activity: A contribution to the debate on direct detection of neuronal currents by MRI

Many efforts have been done in order to preview the properties of the magnetic resonance (MR) signals produced by the neuronal currents using simulations. In this paper, starting with a detailed calculation of the magnetic field produced by the neuronal currents propagating over single hippocampal CA1 pyramidal neurons placed inside a cubic MR voxel of length 1.2 mm, we proceeded on the estimation of the phase and magnitude MR signals. We then extended the results to layers of parallel and synchronous similar neurons and to ensembles of layers, considering different echo times, voxel volumes and neuronal densities. The descriptions of the neurons and of their electrical activity took into account the real neuronal morphologies and the physiology of the neuronal events. Our results concern: (a) the expected time course of the MR signals produced by the neuronal currents in the brain, based on physiological and anatomical properties; (b) the different contributions of post-synaptic potentials and of action potentials to the MR signals; (c) the estimation of the equivalent current dipole and the influence of its orientation with respect to the external magnetic field on the observable MR signal variations; (d) the size of the estimated neuronal current induced phase and magnitude MR signal changes with respect to the echo time, voxel-size and neuronal density. The inclusion of realistic neuronal properties into the simulation introduces new information that can be helpful for the design of MR sequences for the direct detection of neuronal current effects and the testing of bio-electromagnetic models.

Usefulness of combined fractional anisotropy and apparent diffusion coefficient values for detection of involvement in multiple system atrophy

Objective: To determine whether apparent diffusion coefficient (ADC) values and fractional anisotropy (FA) values can detect early pathological involvement in multiple system atrophy (MSA), and be used to differentiate MSA-P...

Extensive Cortical Magnetic Resonance Signal Change in Proximal Urea Cycle Disorder

The authors report a 3-year 8-month-old girl presenting with episodic hyperammonemic encephalopathy probably due to a proximal urea cycle disorder. The magnetic resonance imaging (MRI) of the brain performed during the third episode revealed extensive and diffuse cerebral cortical signal changes with sparing of occipital cortex. It is believed that intracerebral accumulation of glutamine mainly in astrocytes is the major cause of the encephalopathy. This results in astrocyte swelling, brain edema, intracranial hypertension, and cerebral hypoperfusion.

Three-dimensional fluid pressure mapping in porous media using magnetic resonance imaging with gas-filled liposomes

This paper presents and demonstrates a method for using magnetic resonance imaging to measure local pressure of a fluid saturating a porous medium. The method is tested both in a static system of packed silica gel and in saturated sintered glass cylinders experiencing fluid flow. The fluid used contains 3% gas in the form of 3-mum average diameter gas filled 1,2-distearoyl-sn-glycero-3-phosphocholine (C18:0, MW: 790.16) liposomes suspended in 5% glycerol and 0.5% Methyl cellulose with water. Preliminary studies at 2.35 T demonstrate relative magnetic resonance signal changes of 20% per bar in bulk fluid for an echo time T(E)=40 ms, and 6-10% in consolidated porous media for T(E)=10 ms, over the range 0.8-1.8 bar for a spatial resolution of 0.1 mm(3) and a temporal resolution of 30 s. The stability of this solution with relation to applied pressure and methods for improving sensitivity are discussed.

Salvage Operation for Persistent Low Back Pain and Sciatica Induced by Percutaneous Laser Disc Decompression Performed at Outside Institution: Correlation of Magnetic Resonance Imaging and Intraoperative and Pathological Findings

We identified several problems associated with percutaneous lumbar disc decompression (PLDD) based on a study of patients who required salvage operations for complications after undergoing PLDD at an outside institution. PLDD has been performed as a new treatment for intervertebral disc herniation in recent years, and its safety and effectiveness are in the process of being established. Because the procedure is simple to perform under local anesthesia, inappropriate irradiation and application to patients for whom it is not indicated have sometimes resulted in a poor outcome and serious complications. The patients comprised 10 with lumbar disc herniation and three with lumbar spondylolisthesis. We analyzed the magnetic resonance (MR) imaging and operative findings as well as the pathological features of surgically obtained disc specimens and studied their relationships with the clinical outcomes of the operations. Initial examination of all patients at our hospital showed that PLDD had no effect on low back pain or sciatica. In patients who showed MR signal changes in the end-plate, the pathological examination revealed extensive necrosis of cartilage and bone. During salvage operations, severe adhesion of herniated masses to nerve roots was often observed, with carbonized disc tissue surrounding the nerve roots and might have their nerve root injured thermally. PLDD is associated with significant risk of disc, end-plate, and nerve root injuries, contrary to the general belief that the procedure is minimally invasive. Our findings highlight the need for careful diagnosis and sufficient technical skill when selecting PLDD as a treatment option.

The functional anatomy of the iliotibial band during flexion and extension of the knee: implications for understanding iliotibial band syndrome

Iliotibial band (ITB) syndrome is a common overuse injury in runners and cyclists. It is regarded as a friction syndrome where the ITB rubs against (and 'rolls over') the lateral femoral epicondyle. Here, we re-evaluate the clinical anatomy of the region to challenge the view that the ITB moves antero-posteriorly over the epicondyle. Gross anatomical and microscopical studies were conducted on the distal portion of the ITB in 15 cadavers. This was complemented by magnetic resonance (MR) imaging of six asymptomatic volunteers and studies of two athletes with acute ITB syndrome. In all cadavers, the ITB was anchored to the distal femur by fibrous strands, associated with a layer of richly innervated and vascularized fat. In no cadaver, volunteer or patient was a bursa seen. The MR scans showed that the ITB was compressed against the epicondyle at 30 degrees of knee flexion as a consequence of tibial internal rotation, but moved laterally in extension. MR signal changes in the patients with ITB syndrome were present in the region occupied by fat, deep to the ITB. The ITB is prevented from rolling over the epicondyle by its femoral anchorage and because it is a part of the fascia lata. We suggest that it creates the illusion of movement, because of changing tension in its anterior and posterior fibres during knee flexion. Thus, on anatomical grounds, ITB overuse injuries may be more likely to be associated with fat compression beneath the tract, rather than with repetitive friction as the knee flexes and extends.

MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF THE FOOT IN HORSES WITH PALMAR FOOT PAIN AND CONTROL HORSES

Palmar foot pain is a common cause of lameness. Magnetic resonance imaging (MRI) has the potential to detect damage in all tissues of the equine foot, but an understanding of the differences in magnetic resonance (MR) images between feet from horses with and without palmar foot pain is required. This study aimed to describe MR findings in feet from horses with no history of foot-related lameness, and to compare these with MR findings in horses with lameness improved by palmar digital local analgesia. Thirty-four limbs from horses euthanized with a clinical diagnosis of navicular syndrome (ameness >2 months duration, positive response to palmar digital nerve blocks and absence of other forelimb problems) (Group L), and 25 feet from age-matched horses with no history of foot pain (Group N) were examined. For each anatomic structure, MR signal intensity and homogeneity, size, definition of margins, and relationships with other structures were described. Alterations in MR signal intensity and homogeneity were graded as mild, moderate, or severe and compared between Groups L and N. Results revealed that there were significant differences in MR images between Groups N and L. Multiple moderate-severe MR signal changes were present in 91% of limbs from Group L and moderate (none were graded severe) in 27% of limbs from Group N. In most Group L limbs, more than three structures and frequently six to eight structures were abnormal. Concomitant abnormalities involved most frequently the deep digital flexor tendon, distal sesamoidean impar ligament, navicular bone, collateral sesamoidean ligament, and navicular bursa (with significant associations in severity grade between these structures), sometimes with involvement of the distal interphalangeal joint and/or its collateral ligaments. It was concluded that findings on MR images were different between horses with and without foot pain, and that pain localized to the foot was associated with MR changes in a variety of structures, indicating that damage to several structures may occur concurrently and that MR imaging was useful for evaluation of foot pain.

Preoperative and postoperative mapping of cerebrovascular reactivity in moyamoya disease by using blood oxygen level—dependent magnetic resonance imaging

The ability to map cerebrovascular reactivity (CVR) at the tissue level in patients with moyamoya disease could have considerable impact on patient management, especially in guiding surgical intervention and assessing the effectiveness of surgical revascularization. This paper introduces a new noninvasive magnetic resonance (MR) imaging-based method to map CVR. Preoperative and postoperative results are reported in three cases to demonstrate the efficacy of this technique in assessing vascular reserve at the microvascular level. Three patients with angiographically confirmed moyamoya disease were evaluated before and after surgical revascularization. Measurements of CVR were obtained by rapidly manipulating end-tidal PCO2 between hypercapnic and hypocapnic states during MR imaging. The CVR maps were then calculated by comparing the percentage of changes in MR signal with changes in end-tidal PCO2. Presurgical CVR maps showed distinct regions of positive and negative reactivity that correlated precisely with the vascular territories supplied by severely narrowed vessels. Postsurgical reactivity maps demonstrated improvement in the two patients with positive clinical outcome and no change in the patient in whom a failed superficial temporal artery-middle cerebral artery bypass was performed. Magnetic imaging-based CVR mapping during rapid manipulation of end-tidal PCO2 is an exciting new method for determining the location and extent of abnormal vascular reactivity secondary to proximal large-vessel stenoses in moyamoya disease. Although the study group is small, there seems to be considerable potential for guiding preoperative decisions and monitoring efficacy of surgical revascularization.