Uncovering prostate cancer aggressiveness signal in T2-weighted MRI through a three-reference tissues normalization technique.

Quantitative T2-weighted MRI (T2W) interpretation is impeded by the variability of acquisition-related features, such as field strength, coil type, signal amplification, and pulse sequence parameters. The main purpose of this work is to develop an automated method for prostate T2W intensity normalization. The procedure includes the following: (i) a deep learning-based network utilizing MASK R-CNN for automatic segmentation of three reference tissues: gluteus maximus muscle, femur, and bladder; (ii) fitting a spline function between average intensities in these structures and reference values; and (iii) using the function to transform all T2W intensities. The T2W distributions in the prostate cancer regions of interest (ROIs) and normal appearing prostate tissue (NAT) were compared before and after normalization using Student's t-test. The ROIs' T2W associations with the Gleason Score (GS), Decipher genomic score, and a three-tier prostate cancer risk were evaluated with Spearman's correlation coefficient (rS ). T2W differences in indolent and aggressive prostate cancer lesions were also assessed. The MASK R-CNN was trained with manual contours from 32 patients. The normalization procedure was applied to an independent MRI dataset from 83 patients. T2W differences between ROIs and NAT significantly increased after normalization. T2W intensities in 231 biopsy ROIs were significantly negatively correlated with GS (rS = -0.21, p = 0.001), Decipher (rS = -0.193, p = 0.003), and three-tier risk (rS = -0.235, p < 0.001). The average T2W intensities in the aggressive ROIs were significantly lower than in the indolent ROIs after normalization. In conclusion, the automated triple-reference tissue normalization method significantly improved the discrimination between prostate cancer and normal prostate tissue. In addition, the normalized T2W intensities of cancer exhibited a significant association with tumor aggressiveness. By improving the quantitative utilization of the T2W in the assessment of prostate cancer on MRI, the new normalization method represents an important advance over clinical protocols that do not include sequences for the measurement of T2 relaxation times.

Power estimation for non-standardized multisite studies.

A concern for researchers planning multisite studies is that scanner and T1-weighted sequence-related biases on regional volumes could overshadow true effects, especially for studies with a heterogeneous set of scanners and sequences. Current approaches attempt to harmonize data by standardizing hardware, pulse sequences, and protocols, or by calibrating across sites using phantom-based corrections to ensure the same raw image intensities. We propose to avoid harmonization and phantom-based correction entirely. We hypothesized that the bias of estimated regional volumes is scaled between sites due to the contrast and gradient distortion differences between scanners and sequences. Given this assumption, we provide a new statistical framework and derive a power equation to define inclusion criteria for a set of sites based on the variability of their scaling factors. We estimated the scaling factors of 20 scanners with heterogeneous hardware and sequence parameters by scanning a single set of 12 subjects at sites across the United States and Europe. Regional volumes and their scaling factors were estimated for each site using Freesurfer's segmentation algorithm and ordinary least squares, respectively. The scaling factors were validated by comparing the theoretical and simulated power curves, performing a leave-one-out calibration of regional volumes, and evaluating the absolute agreement of all regional volumes between sites before and after calibration. Using our derived power equation, we were able to define the conditions under which harmonization is not necessary to achieve 80% power. This approach can inform choice of processing pipelines and outcome metrics for multisite studies based on scaling factor variability across sites, enabling collaboration between clinical and research institutions.

FL-41 Tint Reduces Activation of Neural Pathways of Photophobia in Patients with Chronic Ocular Pain.

PURPOSE: To assess the therapeutic effect of tinted lenses (FL-41) on photophobia and light-evoked brain activity using functional magnetic resonance imaging (fMRI) in individuals with chronic ocular surface pain. DESIGN: Prospective case series. METHODS: 25 subjects from the Miami veterans affairs (VA) eye clinic were recruited based on the presence of chronic ocular pain, dry eye symptoms, and photophobia. Using a 3T MRI scanner, subjects underwent 2 fMRI scans using an event-related design based on light stimuli: one scan while wearing FL-41 lenses and one without. Unpleasantness ratings evoked by the light stimuli were collected after each scan. RESULTS: With FL-41 lenses, subjects reported decreased (n = 19), maintained (n = 2), or increased (n = 4) light-evoked unpleasantness ratings. Group analysis at baseline (no lens) revealed significant light evoked responses in bilateral primary somatosensory (S1), bilateral secondary somatosensory (S2), bilateral insula, bilateral frontal pole, visual, precuneus, paracingulate, and anterior cingulate cortices (ACC) as well as cerebellar vermis, bilateral cerebellar hemispheric lobule VI, and bilateral cerebellar crus I and II. With FL-41 lenses, light-evoked responses were significantly decreased in bilateral S1, bilateral S2, bilateral insular, right temporal pole, precuneus, ACC, and paracingulate cortices as well as bilateral cerebellar hemispheric lobule VI. CONCLUSION: FL-41 lenses modulated photophobia symptoms in some individuals with chronic ocular pain. In conjunction, FL-41 lenses decreased activation in cortical areas involved in processing affective and sensory-discriminative dimensions of pain. Further research into these relationships will advance the ability to provide precision therapy for individuals with ocular pain.

Intramyocardial stem cell injection in patients with ischemic cardiomyopathy: functional recovery and reverse remodeling.

RATIONALE: Transcatheter, intramyocardial injections of bone marrow-derived cell therapy produces reverse remodeling in large animal models of ischemic cardiomyopathy. OBJECTIVE: We used cardiac MRI (CMR) in patients with left ventricular (LV) dysfunction related to remote myocardial infarction (MI) to test the hypothesis that bone marrow progenitor cell injection causes functional recovery of scarred myocardium and reverse remodeling. METHODS AND RESULTS: Eight patients (aged 57.2±13.3 years) received transendocardial, intramyocardial injection of autologous bone marrow progenitor cells (mononuclear or mesenchymal stem cells) in LV scar and border zone. All patients tolerated the procedure with no serious adverse events. CMR at 1 year demonstrated a decrease in end diastolic volume (208.7±20.4 versus 167.4±7.32 mL; P=0.03), a trend toward decreased end systolic volume (142.4±16.5 versus 107.6±7.4 mL; P=0.06), decreased infarct size (P<0.05), and improved regional LV function by peak Eulerian circumferential strain in the treated infarct zone (-8.1±1.0 versus -11.4±1.3; P=0.04). Improvements in regional function were evident at 3 months, whereas the changes in chamber dimensions were not significant until 6 months. Improved regional function in the infarct zone strongly correlated with reduction of end diastolic volume (r(2)=0.69, P=0.04) and end systolic volume (r(2)=0.83, P=0.01). CONCLUSIONS: These data suggest that transcatheter, intramyocardial injections of autologous bone marrow progenitor cells improve regional contractility of a chronic myocardial scar, and these changes predict subsequent reverse remodeling. The findings support the potential clinical benefits of this new treatment strategy and ongoing randomized clinical trials.

Disentangling the neurological basis of chronic ocular pain using clinical, self-report, and brain imaging data: use of K-means clustering to explore patient phenotypes.

Introduction: The factors that mediate the expression of ocular pain and the mechanisms that promote chronic ocular pain symptoms are poorly understood. Central nervous system involvement has been postulated based on observations of pain out of proportion to nociceptive stimuli in some individuals. This investigation focused on understanding functional connectivity between brain regions implicated in chronic pain in persons reporting ocular pain symptoms. Methods: We recruited a total of 53 persons divided into two cohorts: persons who reported no ocular pain, and persons who reported chronic ocular pain, irrespective of ocular surface findings. We performed a resting state fMRI investigation that was focused on subcortical brain structures including the trigeminal nucleus and performed a brief battery of ophthalmological examinations. Results: Persons in the pain cohort reported higher levels of pain symptoms relating to neuropathic pain and ocular surface disease, as well as more abnormal tear metrics (stability and tear production). Functional connectivity analysis between groups evinced multiple connections exemplifying both increases and decreases in connectivity including regions such as the trigeminal nucleus, amygdala, and sub-regions of the thalamus. Exploratory analysis of the pain cohort integrating clinical and brain function metrics highlighted subpopulations that showed unique phenotypes providing insight into pain mechanisms. Discussion: Study findings support centralized involvement in those reporting ocular-based pain and allude to mechanisms through which pain treatment services may be directed in future research.

Botulinum toxin A decreases neural activity in pain-related brain regions in individuals with chronic ocular pain and photophobia.

Introduction: To examine the effect of botulinum toxin A (BoNT-A) on neural mechanisms underlying pain and photophobia using functional magnetic resonance imaging (fMRI) in individuals with chronic ocular pain. Methods: Twelve subjects with chronic ocular pain and light sensitivity were recruited from the Miami Veterans Affairs eye clinic. Inclusion criteria were: (1) chronic ocular pain; (2) presence of ocular pain over 1 week recall; and (3) presence of photophobia. All individuals underwent an ocular surface examination to capture tear parameters before and 4-6 weeks after BoNT-A injections. Using an event-related fMRI design, subjects were presented with light stimuli during two fMRI scans, once before and 4-6 weeks after BoNT-A injection. Light evoked unpleasantness ratings were reported by subjects after each scan. Whole brain blood oxygen level dependent (BOLD) responses to light stimuli were analyzed. Results: At baseline, all subjects reported unpleasantness with light stimulation (average: 70.8 ± 32.0). Four to six weeks after BoNT-A injection, unpleasantness scores decreased (48.1 ± 33.6), but the change was not significant. On an individual level, 50% of subjects had decreased unpleasantness ratings in response to light stimulation compared to baseline ("responders," n = 6), while 50% had equivalent (n = 3) or increased (n = 3) unpleasantness ("non-responders"). At baseline, several differences were noted between responders and non-responders; responders had higher baseline unpleasantness ratings to light, higher symptoms of depression, and more frequent use of antidepressants and anxiolytics, compared to non-responders. Group analysis at baseline displayed light-evoked BOLD responses in bilateral primary somatosensory (S1), bilateral secondary somatosensory (S2), bilateral anterior insula, paracingulate gyrus, midcingulate cortex (MCC), bilateral frontal pole, bilateral cerebellar hemispheric lobule VI, vermis, bilateral cerebellar crus I and II, and visual cortices. BoNT-A injections significantly decreased light evoked BOLD responses in bilateral S1, S2 cortices, cerebellar hemispheric lobule VI, cerebellar crus I, and left cerebellar crus II. BoNT-A responders displayed activation of the spinal trigeminal nucleus at baseline where non-responders did not. Discussion: BoNT-A injections modulate light-evoked activation of pain-related brain systems and photophobia symptoms in some individuals with chronic ocular pain. These effects are associated with decreased activation in areas responsible for processing the sensory-discriminative, affective, dimensions, and motor responses to pain.

Bone marrow mesenchymal stem cells stimulate cardiac stem cell proliferation and differentiation.

RATIONALE: The regenerative potential of the heart is insufficient to fully restore functioning myocardium after injury, motivating the quest for a cell-based replacement strategy. Bone marrow-derived mesenchymal stem cells (MSCs) have the capacity for cardiac repair that appears to exceed their capacity for differentiation into cardiac myocytes. OBJECTIVE: Here, we test the hypothesis that bone marrow derived MSCs stimulate the proliferation and differentiation of endogenous cardiac stem cells (CSCs) as part of their regenerative repertoire. METHODS AND RESULTS: Female Yorkshire pigs (n=31) underwent experimental myocardial infarction (MI), and 3 days later, received transendocardial injections of allogeneic male bone marrow-derived MSCs, MSC concentrated conditioned medium (CCM), or placebo (Plasmalyte). A no-injection control group was also studied. MSCs engrafted and differentiated into cardiomyocytes and vascular structures. In addition, endogenous c-kit(+) CSCs increased 20-fold in MSC-treated animals versus controls (P<0.001), there was a 6-fold increase in GATA-4(+) CSCs in MSC versus control (P<0.001), and mitotic myocytes increased 4-fold (P=0.005). Porcine endomyocardial biopsies were harvested and plated as organotypic cultures in the presence or absence of MSC feeder layers. In vitro, MSCs stimulated c-kit(+) CSCs proliferation into enriched populations of adult cardioblasts that expressed Nkx2-5 and troponin I. CONCLUSIONS: MSCs stimulate host CSCs, a new mechanism of action underlying successful cell-based therapeutics.

Allogeneic mesenchymal stem cells restore cardiac function in chronic ischemic cardiomyopathy via trilineage differentiating capacity.

The mechanism(s) underlying cardiac reparative effects of bone marrow-derived mesenchymal stem cells (MSC) remain highly controversial. Here we tested the hypothesis that MSCs regenerate chronically infarcted myocardium through mechanisms comprising long-term engraftment and trilineage differentiation. Twelve weeks after myocardial infarction, female swine received catheter-based transendocardial injections of either placebo (n = 4) or male allogeneic MSCs (200 million; n = 6). Animals underwent serial cardiac magnetic resonance imaging, and in vivo cell fate was determined by co-localization of Y-chromosome (Y(pos)) cells with markers of cardiac, vascular muscle, and endothelial lineages. MSCs engrafted in infarct and border zones and differentiated into cardiomyocytes as ascertained by co-localization with GATA-4, Nkx2.5, and alpha-sarcomeric actin. In addition, Y(pos) MSCs exhibited vascular smooth muscle and endothelial cell differentiation, contributing to large and small vessel formation. Infarct size was reduced from 19.3 +/- 1.7% to 13.9 +/- 2.0% (P < 0.001), and ejection fraction (EF) increased from 35.0 +/- 1.7% to 41.3 +/- 2.7% (P < 0.05) in MSC but not placebo pigs over 12 weeks. This was accompanied by increases in regional contractility and myocardial blood flow (MBF), particularly in the infarct border zone. Importantly, MSC engraftment correlated with functional recovery in contractility (R = 0.85, P < 0.05) and MBF (R = 0.76, P < 0.01). Together these findings demonstrate long-term MSC survival, engraftment, and trilineage differentiation following transplantation into chronically scarred myocardium. MSCs are an adult stem cell with the capacity for cardiomyogenesis and vasculogenesis which contribute, at least in part, to their ability to repair chronically scarred myocardium.

Multi-Center Repeatability of Macular Capillary Perfusion Density Using Optical Coherence Tomography Angiography.

Background/Aims: This study was to determine the test-retest repeatability in quantifying macular capillary perfusion density (CPD, expressed as fractal dimension) using optical coherence tomography angiography (OCTA) in a multi-center setting. Methods: OCTA data were obtained in self-reported healthy subjects from Bascom Palmer Eye Institute at the University of Miami (UM, N = 18) and the University of Pennsylvania (UPenn, N = 22). The right eye of each subject was imaged twice at the first visit and then again at an interval of one week to assess intra-visit and inter-visit repeatability. The macular area of the OCTA-derived capillary perfusion density (OCTA-CPD) was analyzed by custom-made image processing and fractal analysis software. Fractal analysis was performed on the skeletonized microvascular network to yield OCTA-CPD by box-counting to the fractal dimension (Dbox) in the superficial vascular plexus (SVP). Repeatability was assessed by three measures: within-subject standard deviation (Sw), coefficient of variation (CoV) of repeated measures, and intraclass correlation coefficient (ICC). Results: OCTA-CPD from both sites (UM and UPENN) showed good to excellent intra-visit repeatability, as demonstrated by the Sw ≤0.004, CoVs ≤0.23%, and ICCs ≥0.61. Similarly, both sites had good to excellent inter-visit repeatability, as shown by the Sw ≤0.005, CoVs ≤0.28%, and ICCs ≥0.61. The Bland-Altman plots of the intra-visit and inter-visit measurements showed excellent agreements between the paired measurements with minimal biases. Conclusion: Our data showed that comparable high repeatability of OCTA-CPD can be achieved in both research sites using the same device, scan protocol, and image analysis.

Volumetric segmentation of ADC maps and utility of standard deviation as measure of tumor heterogeneity in soft tissue tumors.

PURPOSE: Determine interobserver concordance of semiautomated three-dimensional volumetric and two-dimensional manual measurements of apparent diffusion coefficient (ADC) values in soft tissue masses (STMs) and explore standard deviation (SD) as a measure of tumor ADC heterogeneity. RESULTS: Concordance correlation coefficients for mean ADC increased with more extensive sampling. Agreement on the SD of tumor ADC values was better for large regions of interest and multislice methods. Correlation between mean and SD ADC was low, suggesting that these parameters are relatively independent. CONCLUSION: Mean ADC of STMs can be determined by volumetric quantification with high interobserver agreement. STM heterogeneity merits further investigation as a potential imaging biomarker that complements other functional magnetic resonance imaging parameters.

Numerical simulation of PRESS localized MR spectroscopy.

Numerical simulations of NMR spectra can provide a rapid and convenient method for optimizing acquisition sequence parameters and generating prior spectral information required for parametric spectral analysis. For spatially resolved spectroscopy, spatially dependent variables affect the resultant spectral amplitudes and phases, which must therefore be taken into account in any spectral simulation model. In this study, methods for numerical simulation of spectra obtained using the PRESS localization pulse sequence are examined. A comparison is made between three different simulation models that include different levels of detail regarding the spatial distributions of the excitation functions, and spin evolution during application of the pulses. These methods were evaluated for measurement of spectra from J-coupled spin systems that are of interest for in vivo proton spectroscopy and results compared with experimental data. It is demonstrated that for optimized refocusing pulses it is sufficient to account for chemical shift effects only, although there is some advantage to implementing a more general numerical simulation approach that includes information on RF pulse excitation profiles, which provides sufficient accuracy while maintaining moderate computational requirements and flexibility to handle different spin systems.

Somatosensory phenotype is associated with thalamic metabolites and pain intensity after spinal cord injury.

Neuropathic pain is one of the most difficult consequences of spinal cord injury (SCI). The clinical correlates of the underlying mechanisms responsible for neuropathic pain are not well understood, although methods such as quantitative somatosensory testing (QST) or brain imaging have been used to further a mechanism-based understanding of pain. Our previous SCI study demonstrated a significantly lower glutamate-glutamine/myo-inositol ratio (Glx/Ins) in the anterior cingulate cortex in persons with severe neuropathic pain compared with those with less severe neuropathic pain or pain-free, able-bodied controls, suggesting that a combination of decreased glutamatergic metabolism and glial activation may contribute to the development of severe neuropathic pain after SCI. The present study aimed to determine the relationships between somatosensory function below the level of injury and low thalamic Glx/Ins in persons with intense neuropathic pain after SCI. Participants underwent QST and a 3 Tesla proton magnetic resonance spectroscopy. A cluster analysis including SCI participants resulted in 1 group (n = 19) with significantly (P < 0.001) greater pain intensity (6.43 ± 1.63; high neuropathic pain [HNP], and lower Glx/Ins [1.22 ± 0.16]) and another group (n = 35) with lower pain intensity ratings (1.59 ± 1.52, low neuropathic pain [LNP], and higher Glx/Ins [1.47 ± 0.26]). After correcting for age, QST indicated significantly greater somatosensory function in the HNP group compared with the LNP group. Our results are consistent with research suggesting that damage to, but not abolition of, the spinothalamic tract contributes to development of neuropathic pain after SCI and that secondary inflammatory processes may amplify residual spinothalamic tract signals by facilitation, disinhibition, or sensitization.

Proton magnetic resonance spectroscopy of the thalamus in patients with chronic neuropathic pain after spinal cord injury.

BACKGROUND AND PURPOSE: Spinal cord injury (SCI) results in a number of consequences; one of the most difficult to manage is chronic neuropathic pain. Thus, defining the potential neural and biochemical changes associated with chronic pain after SCI is important because this may lead to development of new treatment strategies. Prior studies have looked at the thalamus, because it is a major sensory relay station. The purpose of our study was to define alterations in metabolites due to injury-induced functional changes in thalamic nuclei by using single-voxel stimulated echo acquisition mode MR spectroscopy. METHODS: Twenty-six men were recruited: 16 patients with SCI and paraplegia (seven with pain, nine without pain) and 10 healthy control subjects. Pain was evaluated in an interview, which included the collection of information concerning the location, quality, and intensity of pain, carefully identifing the dysesthetic neuropathic pain often seen in SCI. Localized single-voxel (8-cm(3) volume) proton spectra were acquired from the left and right thalami. RESULTS: The concentration of N-acetyl (NA) was negatively correlated with pain intensity (r = -0.678), and the t test showed that NA was significantly different between patients with pain and patients without pain (P =.006). Myo-inositol was positively correlated with pain intensity (r = 0.520); difference between patients with pain and those without pain was almost significant (P =.06). CONCLUSION: The observed differences in metabolites in SCI patients with and pain and in those without pain suggest anatomic, functional, and biochemical changes in the thalamic region.

Proton MR spectroscopy of gliomatosis cerebri: case report of elevated myoinositol with normal choline levels.

A 69-year-old woman presented with clinical and imaging findings suspicious for gliomatosis cerebri, later confirmed by biopsy (moderately cellular, infiltrating glioma). Single voxel proton MR spectroscopy (TE 20 and TE 135) and spectroscopic imaging (TE 135) performed at admission showed normal choline, decreased N-acetyl, and elevated myo-inositol levels relative to creatine. The primary conclusion is that in suspected cases of gliomatosis cerebri, myo-inositol/creatine and myo-inositol/N-acetyl should be determined because they may provide evidence of tumor, even though choline/creatine is normal. A corollary to this conclusion is that choline/creatine may be misleading if used to demarcate infiltrating glioma from edema.

Effects of physiologic human brain motion on proton spectroscopy: quantitative analysis and correction with cardiac gating.

SUMMARY: Proton MR spectroscopy is a powerful noninvasive method that enables measurement of certain brain metabolites in healthy subjects and patients with diseases. A major difficulty with clinical and research applications of in vivo proton MR spectroscopy is the variability of metabolite concentrations, especially in regions with substantial physiologic motion. In our preliminary evaluation, we tested the hypothesis that physiologic brain motion leads to lower mean metabolite concentrations and higher SDs for the measured metabolite concentrations.

MR angiography of the spine and spinal cord.

OBJECTIVES: This review has three objectives: 1) to describe spinal vascular anatomy, focusing on thoracolumbar intradural vessels detectable by both magnetic resonance angiography (MRA) and digital subtraction x-ray angiography (DSA), 2) to compare the MRA techniques that have been used to detect the major intradural vessels, and 3) to illustrate the clinical application of these MRA techniques, especially their efficacy in characterizing spinal dural arteriovenous fistulae (AVF). METHODS: MRA is an adjunct to conventional magnetic resonance imaging. MRA is usually implemented as a three-dimensional (3D) contrast-enhanced (CE) gradient-echo technique, with two approaches to data acquisition: 1) "standard" 3D CE MRA, requiring approximately 10 minutes per 3D volume, and 2) "fast" (bolus/dynamic) 3D CE MRA, requiring approximately 0.5 to 2 minutes per 3D volume depending on k-space sampling schemes. Vessels are displayed on targeted maximum intensity projection images. RESULTS: Normal intradural vessels detected on standard CE MRA are primarily veins (medullary and median), whereas both arteries and veins are detected on fast CE MRA. Identification of arteries (artery of Adamkiewicz, anterior spinal artery) is limited, and their differentiation from veins can be incomplete. Intradural vessels in patients with dural fistulae have abnormal features on MRI (length of flow voids and postcontrast serpentine enhancement) and standard 3D CE MRA (length, tortuosity, and qualitative size of dominant perimedullary vessel), which differ significantly from those of normal vessels. Standard MRA added to a conventional MRI study significantly (P=0.016) increased the rate of detection of the spinal level of a dural fistula. The correct level +/- one vertebral segment was identified in 73% of true-positive patients. CONCLUSIONS: Application of spinal MRA requires knowledge of vascular anatomy, specifically the major intradural vessels, and careful implementation of 3D CE MRA techniques. The standard technique allows for more effective noninvasive screening for vascular lesions, particularly dural AVF, than magnetic resonance imaging alone. Preliminary results indicate that the fast technique may further improve characterization of normal and abnormal intradural vessels, especially if continued technical advances yield greater temporal resolution while maintaining adequate spatial resolution.

The brachial plexus: normal anatomy, pathology, and MR imaging.

The brachial plexus is the most technically and anatomically challenging area of the peripheral nervous system for diagnostic imaging. Marked improvements in spatial and contrast resolution of plexus images have resulted from the use of phased-array technology and newer MR pulse sequence designs. This article presents case material incorporating these improvements and discusses the primary factors that continue to limit MR image quality, such as inhomogenous fat suppression, motion artifacts, and small vessels that mimic or obscure plexus components, and potential solutions and imaging alternatives. Brachial plexus anatomy and its appearance on multiplanar MR images are reviewed. The morphologic features and MR signal characteristics that have been found useful in distinguishing between normal and abnormal plexus components,and in detecting neuropathic lesions, are addressed in the context of clinical indications for plexus imaging as follows: mass involving the plexus, traumatic injury, entrapment syndrome, posttreatment evaluation, and miscellaneous conditions.

MR angiography of the spine: update.

The role of MRA, as an adjunct to conventional MR imaging of the spine and spinal cord, is evolving. The older MRA methods that have been applied to spinal vascular imaging include 2D and 3D phase contrast techniques and a derivative of 3D time-of-flight techniques with data acquired for about several minutes after gadolinium contrast injection (standard 3D CE MRA). Newer 3D gradient-echo techniques, which allow the acquisition of each volume of data in tens of seconds as a contrast bolus traverses the region of interest (fast 3D CE MRA), offer the possibility of temporally resolving intradural arteries and veins. The appearance of normal and abnormal intradural vessels, primarily veins, on the standard 3D CE MRA method has been described for the thoracolumbar region. Normal intradural arteries have been more difficult to detect, although preliminary results with the fast 3D CE MRA method, are promising. Only by establishing the MRA appearance of normal arteries and veins, can one begin to define "abnormal" with greater confidence (presuming that the variability in the appearance of normal vessels is not so great as to preclude differentiation). In striving for this goal, MRA has already encountered competition from CT angiography. In the characterization of spinal vascular lesions, the value of MRA has been demonstrated most convincingly for dural AVF. This lesion is more accurately localized and more sensitively detected (by neuroradiolologists and others experienced in spine imaging) with combined MR imaging and standard 3D CE MRA than with MR imaging alone. Preliminary results suggest that sensitivity and specificity may be further improved if fast 3D CE MRA is combined with conventional MR imaging. Although less well documented, the value of MRA in characterizing other lesions, such as AVMs and vascular tumors, has been reported in recent publications. In the future, the role of MRA will depend on technical advances, such as parallel acquisition techniques and possibly implantable RF coils, which permit improved detection of, and differentiation between, intradural arteries and veins. With these improvements, MRA may play an expanded role in the characterization of spinal vascular abnormalities, encompassing trauma and degenerative spine disease and vascular malformations and tumors.

Metabolite concentrations in the anterior cingulate cortex predict high neuropathic pain impact after spinal cord injury.

Persistent pain is a common reason for reduced quality of life after a spinal cord injury (SCI). Biomarkers of neuropathic pain may facilitate translational research and the understanding of underlying mechanisms. Research suggests that pain and affective distress are anatomically and functionally integrated in the anterior cingulate cortex and can modulate sensory and affective aspects of pain. We hypothesized that severe neuropathic pain with a significant psychosocial impact would be associated with metabolite concentrations (obtained by magnetic resonance spectroscopy) in the anterior cingulate cortex, indicating neuronal and/or glial dysfunction. Participants with SCI and severe, high-impact neuropathic pain (SCI-HPI; n=16), SCI and moderate, low-impact neuropathic pain (SCI-LPI; n=24), SCI without neuropathic pain (SCI-noNP; n=14), and able-bodied, pain-free control subjects (A-B; n=22) underwent a 3-T magnetic resonance imaging brain scan. Analyses revealed that the SCI-HPI group had significantly higher levels of myoinositol (Ins) (P<.000), creatine (P=.007), and choline (P=.014), and significantly lower levels of N-acetyl aspartate/Ins (P=.024) and glutamate-glutamine (Glx)/Ins (P=.003) ratios than the SCI-LPI group. The lower Glx/Ins ratio significantly discriminated between SCI-HPI and the A-B (P=.006) and SCI-noNP (P=.026) groups, displayed excellent test-retest reliability, and was significantly related to greater pain severity, interference, and affective distress. This suggests that the combination of lower glutamatergic metabolism and proliferation of glia and glial activation are underlying mechanisms contributing to the maintenance of severe neuropathic pain with significant psychosocial impact in chronic SCI. These findings indicate that the Glx/Ins ratio may be a useful biomarker for severe SCI-related neuropathic pain with significant psychosocial impact.

Safety of serial MRI in patients with implantable cardioverter defibrillators.

OBJECTIVE: While patients with cardiac implantable electronic devices could benefit from magnetic resonance (MR) imaging, the presence of such devices has been designated as an absolute contraindication to MR. Although scanning algorithms are proposed for cardiac implantable electronic devices, their safety remains uncertain. To address this issue, the safety of serial cardiac MR scans was evaluated in patients with implantable cardioverter defibrillators (ICDs). METHODS: Three serial cardiac MR scans were prospectively performed at 1.5 T on 10 patients (9 men) of median age 56 years (range 51-68) with ICDs. ICD interrogation was performed before and after the MR scan and at a follow-up of median 370 days (range 274-723). Image quality was also assessed. RESULTS: In all patients MR scanning occurred without complications. There were no differences between pre- and post-MR pacing capture threshold, pacing lead or high voltage lead impedance, or battery voltage values. During follow-up there were no occurrences of ICD dysfunction. Although most patients had image artifacts, the studies were generally diagnostic regarding left ventricular function and wall motion. Delayed enhancement imaging was of good quality for inferior wall and inferolateral infarcts, but ICD artifacts often affected the imaging of anterior wall infarcts. CONCLUSION: Serial MR scans at 1.5 T in patients with ICDs, when carefully performed in a monitored setting, have no adverse effects on either patient or device. When required, single or multiple MR scans at 1.5 T may therefore be considered for clinical diagnostic purposes in these patients.