Magnetic Resonance Imaging Signal Intensity Changes Research Articles

Effect of Early Postoperative Resolution of MRI Signal Intensity Changes on the Outcomes of Degenerative Cervical Myelopathy.

A retrospective cohort study. To investigate whether the timing of postoperative resolution of increased signal intensity (ISI) in the spinal cord is associated with surgical outcomes. It remains unclear whether changes in ISI in the early postoperative period influence surgical outcomes. This retrospective cohort study evaluated consecutive patients undergoing surgery for degenerative cervical myelopathy at a single academic hospital between January 2012 and September 2019. These patients underwent magnetic resonance imaging (MRI) preoperatively, within two weeks postoperatively (early MRI) and after six months postoperatively (late MRI). ISI was classified as follows: grade 0, none; grade 1, light (obscure); and grade 2, intense (bright). Patients were categorized into the following three groups: those with postoperative ISI resolution at early MRI (group E) or only at the late MRI (group L) stage and those whose ISI was persistent (group P). The surgical outcomes were compared between these three groups. We included 204 patients with complete data eligible for the analysis, and 163 of them had preoperative ISI. Postoperative ISI regression was observed in 49 (30.1%) patients. Of these 49 patients, 25 showed ISI resolution at early MRI (group E) and 24 only at late MRI (group L). All 49 were grade 1 on preoperative MRI, and this was not found to significantly impact surgical outcomes. In comparing surgical outcomes between the groups, group E had better postoperative Japanese Orthopedic Association scores and Japanese Orthopedic Association recovery rates than groups L and P. No significant differences were observed between groups L and P. Early resolution of preoperative grade 1 ISI on postoperative T2-weighted MRI may be associated with better surgical outcomes in patients with degenerative cervical myelopathy undergoing cervical spinal surgery.

Gadolinium Presence in the Brain After Administration of the Liver-Specific Gadolinium-Based Contrast Agent Gadoxetate: A Systematic Comparison to Multipurpose Agents in Rats.

Clinical studies have reported different results regarding the signal intensity (SI) increase in the dentate nucleus on unenhanced T1-weighted magnetic resonance imaging (MRI) after repeated administrations of gadolinium-based contrast agents (GBCAs). The aim of this study was to evaluate MRI SI changes and gadolinium (Gd) brain concentrations in an animal model after repeated administration of liver-specific linear gadoxetate in comparison to multipurpose linear and macrocyclic GBCAs. Recently, it was demonstrated that small amounts of GBCAs are able to cross the blood-cerebrospinal fluid (CSF) barrier. Therefore, a secondary aim was to test if the administration of these GBCAs directly into the CSF results in a similar MRI pattern and brain Gd concentration than after systemic intravenous injection. Forty-eight Han-Wistar rats were equally divided into the following 4 groups: gadoxetate (liver-specific linear), gadodiamide (multipurpose linear), gadobutrol (multipurpose macrocyclic), and control (saline, artificial CSF). For systemic application, 6 animals per group received 8 intravenous injections on 4 consecutive days per week over 2 weeks using a dose of 0.15 mmol/kg for gadoxetate and 0.6 mmol/kg for multipurpose GBCAs per injection, which corresponds to the recommended clinical dose in humans. For CSF application, 6 animals per group received one intracisternal administration of 0.31 μmol Gd (gadoxetate) and 1.25 μmol Gd (multipurpose GBCAs) or an equal volume of artificial CSF. Brain MRI was performed after a period of 5 weeks to evaluate the SI in deep cerebellar nuclei (DCN) and brain stem. Subsequently, animals were euthanized and their brains were dissected for Gd quantification by inductively coupled plasma-mass spectrometry. Visually evident increased SIs in the DCN were observed in blinded image review only after administration of gadodiamide. The respective SI ratios between DCN and brain stem were significantly higher compared with the control groups (P = 0.009 and P = 0.002 for intravenous and intracisternal application, respectively), whereas no difference was found for gadoxetate and gadobutrol (P ≥ 0.9). Inductively coupled plasma-mass spectrometry revealed the lowest Gd content in the brain tissue after administration for gadoxetate. The mean Gd concentrations in the cerebellum were 0.08 nmol/g (gadoxetate), 2.66 nmol/g (gadodiamide), and 0.26 nmol/g (gadobutrol) after intravenous administration, and 0.28 nmol/g (gadoxetate), 3.23 nmol/g (gadodiamide), and 0.69 nmol/g (gadobutrol) after intracisternal application. This rat study demonstrates distinct differences in the presence of gadolinium in the brain between the liver-specific linear gadoxetate and the multipurpose linear GBCA gadodiamide. No MRI signal alterations were observed after 8 dose-adapted intravenous or a single intracisternal administrations of gadoxetate and multipurpose macrocyclic gadobutrol. The Gd concentrations in the brain 5 weeks after intravenous administration of gadoxetate were an order of magnitude lower compared with gadodiamide and slightly lower than for gadobutrol. Likely reasons for these differences are the 4-fold lower dose, the dual excretion pathway, and the higher complex stability of gadoxetate compared with multipurpose linear GBCAs. The similar findings for both routes of GBCA administration underlines the assumption that the very small amount of GBCAs that cross the blood-CSF barrier is further transported into the brain tissue.

MRI response of obturator internus muscle to carbon-ion dose in prostate cancer treatment.

It is important to confirm the dose distribution and its biophysiological response in patients subjected to carbon-ion radiotherapy (CIRT) by using medical imaging methods. In this study, the correlation between the signal intensity changes of muscles observed in magnetic resonance imaging (MRI) after CIRT and planned dose distribution was evaluated. Seven patients were arbitrarily selected from among localized prostate cancer patients on whom CIRT was performed in our facilities in 2010. All subjects received the same dose of CIRT, namely, 57.6 Gy relative biological effectiveness (RBE) in 16 fractions. The following two types of images were acquired for each subject: planning computed tomography (CT) images overlaying the dose distribution of CIRT and MRI T2-weighted images (T2WI) taken 1 year after CIRT. The fusion image of the planning CT and MRI images was registered by using a treatment-planning system, and the CIRT dose distribution was compared with changes observed in the MRI of the obturator internus muscles located near the prostate. The signal changes in the axial image passing through the isocenter of the planning target volume were digitized, and a scatter diagram was created showing the relationship between the radiation dose and digitized signal changes. A strong correlation between the radiation dose and the MRI signal intensity changes was observed, and a quadratic function was found to have the best fit. However, estimating the dose distribution from the normalized MRI signal intensity is difficult at this point, owing to the wide variation. Therefore, further investigation is required.

Relationship of preoperative intramedullary MRI signal intensity and dynamic factors with surgical outcomes of laminoplasty for cervical ossification of the posterior longitudinal ligament

ObjectiveWe aimed to analyze the relationship of preoperative signal intensity on magnetic resonance imaging (MRI) and dynamic factor with surgical outcomes of laminoplasty for cervical ossification of the posterior longitudinal ligament (OPLL). Patients and methodsWe retrospectively reviewed the records of 29 patients (20 males and 9 females) who underwent double-door laminoplasty for cervical OPLL. T2-weighted MRI was performed preoperatively. To assess the high-signal changes of the spinal cord, signal intensity was classified as grade 0 (low signal, no changes), grade 1 (medium signal, mild changes), and grade 2 (bright signal, pronounced changes). The following factors were analyzed for their relationship with surgical outcome, expressed as the Japanese Orthopedic Association (JOA) score recovery rate: pre- and postoperative C2-C7 range of motion (ROM), segmental ROM, C2-C7 lordotic angle, and spinal cord occupying ratio, as well as disease duration. ResultsDisease duration was significantly longer in patients with pronounced high-signal changes on preoperative MRI (P < 0.05 for grade 2 vs. grade 1 or 0). The mean preoperative JOA score and JOA score recovery rate were significantly lower in patients with pronounced high-signal changes on preoperative MRI (P < 0.05 for grade 2 vs. grade 1 or 0). Preoperatively, segmental ROM was significantly smaller in patients with no MRI signal intensity changes (P < 0.05 for grade 0 vs. grade 1 or 2). Additionally, preoperative segmental ROM was negatively correlated with JOA score recovery rate (R=-0.470, P = 0.01) and positively correlated with high-signal changes on preoperative MRI (R = 0.460, P = 0.012). On multivariate analysis, preoperative segmental ROM was negatively associated with JOA score recovery rate (odds ratio, - 0.407; P = 0.046). ConclusionGiven its negative correlation with JOA score recovery rate and positive correlation with high-signal changes on preoperative MRI, higher preoperative segmental ROM may be associated with spinal cord damage due to repeated minor trauma, predicting poor surgical outcome of laminoplasty in cervical OPLL.

Iliopsoas Disorder in Athletes with Groin Pain: Prevalence in 638 Consecutive Patients Assessed with MRI and Clinical Results in 134 Patients with Signal Intensity Changes in the Iliopsoas.

Background:Although iliopsoas disorder is one of the most frequent causes of groin pain in athletes, little is known about its prevalence and clinical impact.Methods:We retrospectively reviewed the cases of 638 consecutive athletes who had groin pain. Each athlete was assessed with magnetic resonance imaging (MRI). First, we identified the prevalence of changes in signal intensity in the iliopsoas. Then we classified the changes in signal intensity in the iliopsoas, as visualized on short tau inversion recovery MRI, into 2 types: the muscle-strain type (characterized by a massive high-signal area in the muscle belly, with a clear border) and the peritendinitis type (characterized by a long and thin high-signal area extending proximally along the iliopsoas tendon from the lesser trochanter, without a clear border). Finally, we compared the time to return to play for the athletes who had these signal intensity changes.Results:Changes in signal intensity in the iliopsoas were detected in 134 (21.0%) of the 638 athletes. According to our MRI classification, 66 athletes had peritendinitis changes and 68 had muscle-strain changes. The time from the onset of groin pain to return to play was significantly shorter for the patients with muscle-strain changes on MRI than for those with peritendinitis changes (8.6 ± 8.3 versus 20.1 ± 13.9 weeks, respectively; p < 0.0001).Conclusions:Changes in MRI signal intensity in the iliopsoas were observed in 21.0% of 638 athletes who had groin pain. Distinguishing between muscle-strain changes and peritendinitis changes could help to determine the time to return to play.

Correlation between Preoperative Magnetic Resonance Imaging Signal Intensity Changes and Clinical Outcomes in Patients Surgically Treated for Cervical Myeloradiculopathy.

Study DesignThis was a single surgeon, single center-based retrospective study with prospective data collection.PurposeTo assess the correlation between T2-weighted magnetic resonance imaging (MRI) signal intensity (SI) changes and factors such as age, duration of symptoms, baseline modified Japanese Orthopedic Association (mJOA) score and to determine its prognostic value in predicting recovery after surgery.Overview of LiteratureWhether intramedullary cord T2-weighted MRI SI changes can predict operative outcomes of cervical myeloradiculopathy remains debatable, with only a few prospective studies analyzing the same.MethodsForty-six consecutive patients who underwent cervical myeloradiculopathy were included and were followed up for an average of 1 year. Preoperative T2-weighted MRI SI grading was performed for all patients. The correlation between MRI SI changes and age, duration of symptoms, preoperative mJOA score, and mJOA score at 1-year follow-up were analyzed.ResultsFifteen patients had single-level (21.73%) or double-level (10.86%) prolapsed discs; 54.34% had degenerative cervical spondylosis with canal stenosis or multilevel disc prolapse and 13.07% had ossified posterior longitudinal ligaments. The mean age was 56.17±9.53 years (range, 35–81 years). The mean baseline mJOA score was 10.83±2.58 (range, 6–16), which postoperatively improved to 13.59±2.28 (range, 8–17; p<0.001). There was a statistically significant correlation between mJOA score at 1 year and MRI T2 SI grading (p=0.017).ConclusionsPatients with longer symptom durations had high grades of intramedullary cord T2-weighted MRI SI changes. Age and preoperative neurological status were not significantly correlated with the existence of intramedullary cord SI changes. However, patients without or with mild and diffuse intramedullary cord T2-weighted MRI SI changes had better postoperative neurological recovery than those with sharp and focal SI changes.

Case Scenario: Postoperative Brachial Plexopathy Associated with Infraclavicular Brachial Plexus Blockade

Case Scenario: Postoperative Brachial Plexopathy Associated with Infraclavicular Brachial Plexus Blockade

Transplantation of Activated Nucleus Pulposus Cells after Cryopreservation: Efficacy Study in Canine Disc Degeneration Model

IntroductionTissue disruption and altered function of the intervertebral disc (IVD) leads to progression of degenerative disc disease. Transplantation of viable cells that can function to maintain ...

High-Resolution Magnetic Resonance Imaging and 18FDG-PET Findings of the Cervical Spinal Cord Before and After Decompressive Surgery in Patients With Compressive Myelopathy

Evaluation of cervical spinal cord (CSC) of patients with compressive myelopathy by magnetic resonance imaging (MRI) and high-resolution (18F)fluoro-deoxyglucose (18FDG) positron emission tomography (PET). To determine changes in morphology, intramedullary signal intensity, and glucose metabolic rate in CSC after decompression, and to assess the utility of 18FDG-PET in evaluation of patients with cervical myelopathy. The significance of CSC enlargement after decompression and signal intensity changes within the cord remain elusive. No data are available on metabolic activity of the compressed CSC. Only a few studies have examined correlation between high-resolution MRI and 18FDG-PET neuroimaging in cervical myelopathy. We studied 24 patients who underwent cervical decompressive surgery in terms of postoperative neurologic improvement and changes in MRI and 18FDG-PET. Neurologic status was assessed by the Japanese Orthopedic Association scoring system (17-point scale). Signal intensity change in the cord was qualitatively assessed on both T1- and T2-weighted images. The transverse area of the CSC on MRIs and glucose metabolic rate (standardized uptake value [SUV]) from 18FDG-PET were measured digitally. Neurologic improvement correlated with preoperative CSC transverse area at maximal compression (P < 0.01) and at follow-up (P < 0.001) and with mean SUV before surgery (P < 0.01) and at follow-up (P < 0.05). Preoperative signal intensity change on MRIs (low intramedullary signal intensity abnormality on T1-weighted image and high intramedullary on T2-weighted image) correlated negatively with neurologic improvement rate (P < 0.05). The transverse area of the CSC was significantly smaller after surgery in patients with preoperative MRI signal intensity changes (P < 0.05). The SUV at follow-up tended to normalize in association with neurologic improvement. Our results showed that postoperative neurologic improvement in patients with cervical compressive myelopathy correlated with increased transverse area of the spinal cord, signal intensity change on both T1- and T2-weighted image, and the mean SUV.

The effects of MRI signal intensity changes and clinical manifestations on prognosis after surgical intervention for cervical spondylotic myelopathy

To investigate whether the magnetic resonance (MR) T2 image signal intensity ratio and clinical manifestations can predict the prognosis in patients with cervical spondylotic myelopathy (CSM). A total of 73 patients treated with anterior, posterior, or posterior-anterior combined surgery for compressive cervical myelopathy were enrolled retrospectively in this study. 1.5 T magnetic resonance imaging (MRI) was performed on all patients before surgery. T2-weighted images (T2WI) of sagittal signal intensity were obtained of the cervical spinal cord, and the regions of interest (ROI) were taken by 0.05 cm(2). MR T2WI of sagittal normal cord signal at the C7-T1 disc level were also obtained, and the ROI were taken by 0.3 cm(2). Signal value was measured by computer and the signal ratio between regions 0.05 cm(2) and 0.3 cm(2) calculated. Where no intramedullary high signal intensity was noted on MR T2WI, the ROI were taken by 0.05 cm(2) of the region of most severe spinal cord compression. The 73 patients were divided into three groups by hierarchical clustering analysis with signal intensity ratio (group 1: low signal intensity ratio; group 2: middle signal intensity ratio; group 3: high signal intensity ratio). Statistical analyses were performed with SPSS 11.0. There were significant differences between the three groups according to the recovery rate (P < 0.001), age (P= 0.003), duration of disease (P= 0.001), Babinski sign (P < 0.001), pre- and postoperative Japanese Orthopaedic Association (JOA) score (P= 0.006). With increases in both signal intensity ratio grade and age, the recovery rate and pre- and postoperative JOA scores gradually decreased, and the incidence of Babinski sign increased. There was no significant difference in sex among the three groups (P= 0.387). Multiple comparison tests further supported the above-mentioned results. Patients with light or no intramedullary signal changes on T2WI had a good surgical outcome. However, increase of signal intensity ratio and occurrence of the pyramidal sign were associated with a poor prognosis after surgery.

Detection of Leukemia in MLL-AF9 Transgenic Mice Using Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy

Standard methods to assess tumor progression and treatment response for leukemia patients rely on repeat sampling of bone marrow. These methods evaluate overall disease status, but are not sensitive to early biochemical or cellular responses to therapies. Identification and validation of additional pharmacodynamic endpoints that are useful for accurate prediction of therapeutic efficacy would allow for earlier assessment of clinical response and thereby facilitate the development of effective individualized treatment regimens. Ideally, these markers would be assessed using non-invasive methods. Toward this end, we used in vivo magnetic resonance imaging (MRI) and ex vivo magnetic resonance spectroscopy (MRS) to investigate changes in the bone marrow, spleen, and/or blood of leukemic MLL-AF9 transgenic (Tg) mice relative to wild-type littermates.MLL-AF9 Tg mice with leukemia exhibited a statistically significant 1.5-fold increase in bone marrow T1-weighted MRI signal intensity. Increased signal intensity preceded development of leukemia and is therefore likely to be due, at least in part, to increased bone marrow cellularity, initially as a result of pre-neoplastic myeloproliferation and later as a result of marrow infiltration with leukemic blasts. We are currently determining microvessel density in the bone marrow of leukemic MLL-AF9 Tg mice and littermate controls to determine whether an increase in blood supply may also contribute to changes in MRI signal intensity in leukemic mice. These studies suggest that T1-weighted MRI signal intensity may be useful as an indicator of bone marrow tumor burden.Leukemic MLL-AF9 Tg mice also exhibited statistically significant changes in metabolite levels in spleen, blood, and bone marrow. The Warburg effect, whereby cancer cells utilize aerobic glycolysis to meet their increased energy demands, was evident in all tissues examined as indicated by increased glycolysis rates, increased glucose utilization, and increased levels of lactate and alanine, the end-products of glycolysis. Additional changes in metabolite levels were observed in the bone marrow and/or spleen of leukemic mice. Absolute levels of glutathione were increased. Glutathione reduces reactive oxygen species that are generated as a result of increased glycolysis and high levels of glutathione are associated with chemoresistance and poor prognosis in patients with acute leukemia (Maung et al., 1994, Leukemia 8:1487–91; Kearns et al., 2001, Blood 97:393–8). Increased glycine levels were also observed and may be associated with increased pyridine and DNA synthesis in leukemia cells. Decreased glutamate and glutamine levels may reflect a decrease in utilization of the mitochondrial Krebs cycle in tumor cells. Decreased levels of myo-inositol and taurine, which function as osmoregulators, may occur as a result of osmotic stress due to increased cellularity in leukemic organs. Levels of aromatic acids, lysine and arginine, and creatine and phosphocreatine were also decreased. Many of these changes in metabolism are recapitulated in immunocompetent mice orthotopically transplanted with MLL-AF9 Tg leukemias.This study represents the first description of a comprehensive analysis of the “metabolomic” profile associated with development of acute leukemia and is, to our knowledge, the first description of changes in metabolism in an animal model of acute leukemia. The data presented here suggest novel metabolic targets for therapeutic intervention. In addition, because metabolic changes often precede detectable changes in tumor burden, they may be particularly useful as early indicators of therapeutic efficacy and may thereby allow for more rapid determination of clinical response, decreased exposure to toxic therapies in resistant patients, and more expedient conversion to effective therapies. Because changes in glucose metabolism are a central feature of tumorigenesis and changes in glutathione levels have been associated with clinical outcome in patients with acute leukemia, these metabolites are of particular interest. Future studies will use MLL-AF9 transgenic mice to investigate the roles of metabolic changes during de novo development of leukemia. Mice transplanted with MLL-AF9 Tg leukemias will also be used for studies investigating the utility of metabolic changes as indicators of therapeutic efficacy.

Using MRI to Determine Painful Vertebrae to be Treated by Kyphoplasty in Multiple-Level Vertebral Compression Fractures: A Prospective Study

A prospective study in 35 osteoporotic patients with 120 multiple-level vertebral compression fractures (VCFs) assessed the use of magnetic resonance imaging (MRI) to determine painful vertebrae for treatment with kyphoplasty (KP). A total of 51 vertebrae were identified as painful and selected for KP based on changes in MRI signal intensity between T1-weighted, T2-weighted and short tau inversion recovery MRI. Efficacy was assessed by the mean change in anterior/middle vertebral body height, Cobb's angle, a visual analogue pain scale and the Oswestry Disability Index at pre-operative, post-operative and final follow-up assessments. Significant improvements in all efficacy measures were observed at the postoperative versus pre-operative assessments; no significant differences were observed between post-operative and final follow-up assessments. It is concluded that painful vertebrae can be determined by MRI signal intensity changes and their selection for KP can improve outcomes in patients with multiple-level VCFs.

Magnetic resonance imaging of neuronal and glial swelling as an indicator of function in cerebral tissue slices

Here we demonstrate a new basis of signal change in magnetic resonance imaging (MRI) related to neuronal function, independent of blood oxygenation or flow. Time series MRI data acquired from living, superfused brain slices of adult rats revealed that the signal intensity reversibly increased with depolarization evoked by briefly elevating extracellular K(+). This was presumably a consequence of increased tissue water in the intracellular compartment. Reversible increases in light transmittance (LT) demonstrating a similar time course in response to K(+) elevation supported cellular swelling as generating the MRI signal intensity changes. This was confirmed by reversibly swelling cells in the slice under hypoosmotic challenge, which increased both MRI and LT signals with an identical time course. Conversely, shrinking cells under hyperosmotic challenge reversibly decreased the MRI and LT signals. We propose that specific MRI of neuronal function (fMRI) signals detected under identical parameters during predominantly proton-density-weighted fMRI of the spinal cord can now be explained by neuronal and glial swelling in activated central nervous system (CNS) regions. These observations demonstrate the biophysical basis of the fMRI contrast mechanism that has been termed "signal enhancement by extravascular water protons," or SEEP.

Predicting Outcome of Patients with High-grade Gliomas After Radiotherapy using Quantitative Analysis of T1-weighted Magnetic Resonance Imaging

The aim of this study was to test the hypothesis that measuring quantitative changes in signal intensity early after radiotherapy (RT) in the contrast-enhancing tumor rim and nonenhancing core may be a noninvasive marker of early treatment response in patients with high-grade gliomas. Twenty patients with high-grade gliomas had magnetic resonance imaging (MRI) performed 1 week before RT, during Weeks 1 and 3 of RT, and every 1 to 3 months after RT as part of a clinical prospective study. Regions of interest (ROI) including contrast-enhancing rim, and the nonenhancing core were defined automatically based on a calculated image of post- to precontrast T1-weighted MRI. Pretreatment T1-weighted MRI signal intensity changes were compared with Weeks 1 and 3 RT and 1 and 3 months post-RT MRI. Clinical and MRI parameters were then tested for prediction of overall survival. Regional T1-weighted signal intensity changes in both the contrast-enhancing rim and the nonenhancing core were observed in all patients during Week 1 and Week 3 of RT. Imaging parameters including signal intensity change within the nonenhancing core after Weeks 1 to 2 RT (p = 0.004), Weeks 3 to 4 RT (p = 0.002) and 1 month after completion of RT (p = 0.002) were predictive of overall survival. Using multivariate analysis including RTOG recursive partitioning analysis (RPA) and signal intensity change, only the signal intensity change in the nonenhancing core at 1 month after RT (p = 0.01) retained significance. Quantitative measurements of T1-weighted MRI signal intensity changes in the nonenhancing tumor core (using ratios of pre-post values) may provide valuable information regarding early response during treatment and improve our ability to predict posttreatment outcome.

Brain T1 intensity changes after levodopa administration in healthy subjects: a voxel‐based morphometry study

To test T1 intensity variations induced by levodopa administration in the regional fixation area in the human brain. Using non-invasive magnetic resonance imaging (MRI) technique [T1-weighted sequence MPRAGE; TE/TR/TI = 5/25/800 ms; impulsion angle = 15 degrees; field of view = 256 x 230 x 180 mm3; acquisition matrix = 256 x 192 x 104; reconstruction matrix = 256 x 256 x 128), we tested changes in the T1 MRI signal intensity resulting in changes in the grey matter automatic classification after administration of a single dose of 100 mg of levodopa by a voxel-based morphometry method (VBM) in 12 healthy subjects. The VBM analysis demonstrated an increased number of voxels attributed to grey matter after levodopa administration in an anatomical cluster which included substantia nigra, tegmental ventral area and subthalamic nucleus bilaterally, the principal origin and first relay nuclei of projections in brain dopaminergic systems (t = 8.61; corrected for all grey matter volume P < 0.001). Our results suggest that levodopa administration could induce an MRI T1 signal intensity variation that is not evident to the naked eye, but is detectable by measuring local signal intensities. Possible clinical applications are discussed.

Work above shoulder level and degenerative alterations of the rotator cuff tendons: a magnetic resonance imaging study.

To determine whether work performed with the arms in a highly elevated position is associated with alterations in the rotator cuff tendons as assessed by magnetic resonance imaging (MRI). A cross-sectional study was performed in a historical cohort of male machinists, car mechanics, and house painters. The participants were right-handed, ages 40-50 years, and had been employed in their trades for not less than 10 years. Seventy-one percent of invited subjects participated (136 of 192). Lifetime upper arm elevation was assessed by direct measurements combined with individual work histories obtained by questionnaire and from registry data. Supraspinatus tendinopathy was evidenced by MRI signal intensity changes and morphologic alterations. Infraspinatus and subscapularis tendinopathy were also assessed. Additional outcomes were acromioclavicular joint degeneration and humeral head cysts. The MRI findings were evaluated by radiologists who were blinded to exposure status and symptoms. An exposure-response relationship was found between lifetime upper arm elevation and supraspinatus tendinopathy, with an age-adjusted odds ratio of 1.27 (95% confidence interval 1.02-1.60) for a 5-month increase in the total number of full-time working months spent with the arm elevated >90 degrees . Work with the arms in a highly elevated position is associated with MRI-diagnosed alterations in the supraspinatus tendon. By demonstrating the first part of a possible biologic pathway, the study corroborates the work-relatedness of rotator cuff disorders.

Comparing genomic and histologic correlations to radiographic changes in tumors: a murine SCC VII model Study 1

Rationale and Objectives. To investigate the correlation between the temporal changes in T1- and T2-weighted contrast-enhanced magnetic resonance imaging (MRI), histologic evaluation, and genomic analysis using oligonucleotide microarrays in a murine squamous cell carcinoma tumor models Materials and Methods. The squamous cell carcinoma (SCC VII) cell line was used to initiate subcutaneous tumors in mice. This mouse model has been used as a model for human head and neck carcinomas. Animals were imaged using contrast enhanced MRI (CE-MRI). Different stages of tumor growth were defined based on changes in the T1- and T2-weighted MRI patterns. The contrast enhancing (CE) and nonenhancing (NE) regions of the tumors were marked and biopsied for oligonucleotide microarray and histologic analysis. Tumors with no differential contrast enhancement were used as controls. Results. Distinct temporal stages of tumor progression can be defined using both T1- and T2-weighted CE-MRI and microarray analysis. The early stage tumors show a homogeneous contrast enhancement pattern in the T1- and T2-weighted images with no significant differential gene expression from the center and periphery of the tumor. The more advanced tumors that show discrete regions of contrast enhancement in the post-contrast T1-weighted MRIs and tissues from the CE and NE regions show distinctly differential gene expression profiles. Histologic analysis (hematoxylin-eosin stain) showed that the samples obtained from the periphery and center of the early stage tumors and the CE and NE regions from these more advanced tumors were similar. The gene expression profiles of late-stage tumors that showed changes in T2-weighted MRI signal intensity were consistent with tissue degradation in the NE region, which also showed characteristic signs of tissue necrosis in histologic analysis. Conclusion. These results show that temporal changes in T1- and T2-weighted CE-MRI are related to distinct gene expression profiles, and histologic analysis may not be sufficient to detect these detailed changes. As tumors progress, discrete regions of post-contrast T1 enhancement are identified; these regions have distinct gene expression patterns despite similar histologic features. In late-stage tumors, regions of T2 signal changes are observed which correspond with tissue necrosis.

MRI guided focused ultrasound opening of blood brain barrier

Previously, we demonstrated that focused ultrasound can focally open the blood brain barrier (BBB) reversibly without damage to the neurons. In this study, we varied the ultrasound pulse parameters to investigate their influence on BBB opening and any resulting tissue damage. Under magnetic resonance imaging (MRI) guidance, a series of targeted ultrasound bursts (1.5 MHz, burst duration: 5 cycles to 100 ms, repetition frequency: 1 Hz–1 kHz) were delivered into rabbit brains at low pressure levels (up to approximately 5 MPa) after intravenous administration of a commercially available ultrasound contrast agent containing preformed gas bubbles. Focal MRI signal intensity changes were observed during the deposition of acoustic energy. BBB opening at the correct target was confirmed by detecting the localized uptake of an MRI contrast agent. In some animals Trypan Blue was injected intravenously after the sonications. The animals were sacrificed at time intervals ranging from 2 h to 7 days. Light and electron microscopy evaluation was performed. No neuronal damage was observed at the lowest power levels that produced BBB opening. No neuronal damage was observed at the lowest power levels that produced BBB opening. Correlation of focal MRI signal changes to the uptake of a large molecular size contrast agent was observed demonstrating the potential of image guided drug delivery.

Noninvasive MR imaging-guided focal opening of the blood-brain barrier in rabbits.

To determine if focused ultrasound beams can be used to locally open the blood-brain barrier without damage to surrounding brain tissue and if magnetic resonance (MR) imaging can be used to monitor this procedure. The brains of 18 rabbits were sonicated (pulsed sonication) in four to six locations, with temporal peak acoustic power ranging from 0.2 to 11.5 W. Prior to each sonication, a bolus of ultrasonographic (US) contrast agent was injected into the ear vein of the rabbit. A series of fast or spoiled gradient-echo MR images were obtained during the sonications to monitor the temperature elevation and potential tissue changes. Contrast material-enhanced MR images obtained minutes after sonications and repeated 1-48 hours later were used to depict blood-brain barrier opening. Whole brain histologic evaluation was performed. Opening of the blood-brain barrier was confirmed with detection of MR imaging contrast agent at the targeted locations. The lowest power levels used produced blood-brain barrier opening without damage to the surrounding neurons. Contrast enhancement correlated with the focal signal intensity changes in the magnitude fast spoiled gradient-echo MR images. The blood-brain barrier can be consistently opened with focused ultrasound exposures in the presence of a US contrast agent. MR imaging signal intensity changes may be useful in the detection of blood-brain barrier opening during sonication.

The effects of eccentric velocity on activation of elbow flexors: evaluation by magnetic resonance imaging.

To compare magnetic resonance imaging (MRI) signal intensity changes in the primary elbow flexors during two isotonic exercise protocols varying in eccentric velocity and the ratio of eccentric to concentric activity. Twelve men performed two exercise protocols. The right and left arms were randomly assigned to one of two protocols that had the same workload (60% 1RM) and same total time of exercise (144 s) but differed in the velocity and ratio of eccentric to concentric activity (1:1 and 5:1 for the fast and slow protocols, respectively). MRI signal intensity changes were quantified pre- and post-exercises using an inversion recovery sequence with a 1.5T MRI system (TR = 2500 ms, TE = 90 ms, TI = 140 ms). Percent change in MRI signal intensity, rate of perceived exertion (RPE), and delayed onset muscle soreness (DOMS) were recorded and analyzed. The biceps brachii was found to be preferentially recruited during the fast protocol compared with the brachialis, whereas the brachialis was found to be preferentially recruited during the slow protocol (P < 0.05). The fast exercise protocol was perceived as being more strenuous (RPE = 8.3 +/- 2.1) than the slow (RPE = 5.4 +/- 1.5, P < 0.05) and produced DOMS in 58% of the tested subjects. These results suggest that agonists respond to various loading conditions nonhomogeneously. These findings may have implications with respect to exercise prescriptions for specific muscles.