Search

Background Few data exist on the long-term risk prediction of elevated left ventricular (LV) mass quantified by MRI for cardiovascular (CV) events in a contemporary, ethnically diverse cohort. Purpose To assess the long-term impact of elevated LV mass on CV events in a prospective cohort study of a multiethnic population in relationship to risk factors and coronary artery calcium (CAC) score. Materials and Methods The Multi-Ethnic Study of Atherosclerosis, or MESA ( ClinicalTrials.gov : NCT00005487), is an ongoing prospective multicenter population-based study in the United States. A total of 6814 participants (age range, 45-84 years) free of clinical CV disease at baseline were enrolled between 2000 and 2002. In 4988 participants (2613 [52.4%] women; mean age, 62 years ± 10.1 [standard deviation]) followed over 15 years for CV events, LV mass was derived from cardiac MRI at baseline enrollment by using semiautomated software at a central core laboratory. Cox proportional hazard models, Kaplan-Meier curves, and z scores were applied to assess the impact of LV hypertrophy. Results A total of 290 participants had hard coronary heart disease (CHD) events (207 myocardial infarctions [MIs], 95 CHD deaths), 57 had other CV disease-related deaths, and 215 had heart failure (HF). LV hypertrophy was an independent predictor of hard CHD events (hazard ratio [HR]: 2.7; 95% confidence interval [CI]: 1.9, 3.8), MI (HR: 2.8; 95% CI: 1.8, 4.0), CHD death (HR: 4.3; 95% CI: 2.5, 7.3), other CV death (HR: 7.5; 95% CI: 4.2, 13.5), and HF (HR: 5.4; 95% CI: 3.8, 7.5) ( P < .001 for all end points). LV hypertrophy was a stronger predictor than CAC for CHD death, other CV death, and HF ( z scores: 5.4 vs 3.4, 6.8 vs 2.4, and 9.7 vs 3.2 for LV hypertrophy vs CAC, respectively). Kaplan-Meier analysis demonstrated an increased risk of CV events in participants with LV hypertrophy, particularly after 5 years. Conclusion Elevated left ventricular mass was strongly associated with hard coronary heart disease events, other cardiovascular death, and heart failure over 15 years of follow-up, independent of traditional risk factors and coronary artery calcium score. © RSNA, 2019 See also the editorial by Hanneman in this issue.

Purpose To investigate the diagnostic performance of three-dimensional (3D) MRI for depicting meniscal injuries of the knee by using surgery as the standard of reference. Materials and Methods A literature search was performed to identify original studies published between 1985 and 2017. Summary receiver operating characteristic curve and sensitivity analyses were performed to compare the diagnostic performance of 3D versus two-dimensional (2D) MRI for the assessment of knee meniscal injuries and to evaluate the impact of relevant covariates on the diagnostic performance for assessment of knee meniscal injuries. Results Of identified records, 31 studies (1743 3D knee MRI examinations) were included (23 studies also reported the results of 2D MRI). All studies before 2008 used gradient-echo (GRE) sequences, whereas all studies after 2011 used fast spin-echo (FSE) sequences. By comparing FSE and GRE sequences with 2D MRI, pooled estimate of sensitivity (90.0%; P = .2 and 90.1%; P = .2 vs 88.5%) and pooled estimate of specificity (91%; P = .3 and 89.8% vs 90.1%; P = .7) were comparable. The 3D FSE sequences demonstrated similar diagnostic performance as 3D GRE sequences, except for slightly improved sensitivity for depicting lateral meniscal injuries (FSE, 84.6%; GRE, 75%; P = .01). The specificity of 3D sequences improved when multiplanar reformatting was performed (P = .02). Conclusion Both three-dimensional (3D) fast spin-echo (FSE) and 3D gradient-echo (GRE) sequences had similar diagnostic performance as two-dimensional sequences, with slight superior sensitivity of 3D FSE sequences compared with 3D GRE sequences for depicting lateral meniscal injuries of the knee. © RSNA, 2018 Online supplemental material is available for this article.

Purpose To determine the diagnostic performance of three-dimensional (3D) MRI for the depiction and characterization of cartilage defects within the knee joint by using arthroscopy and/or open surgery as the standard of reference. Materials and Methods A systematic literature search was performed to extract diagnostic studies published between January 1985 and October 2017. Two independent investigators assessed the methodologic quality of each study by using Quality Assessment of Diagnostic Accuracy Studies 2. Bivariate random-effects model was used to compare the diagnostic odds ratio (DOR) of 3D and two-dimensional (2D) MRI for helping to detect knee cartilage defects and to assess the effect of relevant covariates on diagnostic performance of 3D MRI. Meta-regression analysis was performed to assess DOR of 3D MRI during the last 3 decades. Results Twenty-seven studies (composed of 1710 MRI examinations) were included. Of those, 16 (59%) studies compared the diagnostic performance of 3D and 2D MRI. The diagnostic performance of 3D MRI statistically significantly improved over the last 3 decades (P = .003). Three-dimensional MRI obtained by using 3.0-T field strength had higher DOR relative to 1.5-T or lower field strength (relative DOR, 4.05; P = .01). Three-dimensional multiplanar reformation was associated with higher specificity (P = .001) compared with conventional axial, sagittal, and coronal 2D MRI planes. Three-dimensional fast-spin-echo sequences provided higher sensitivity and specificity (P < .05) than did 2D MRI. Conclusion Three-dimensional MRI currently provides comparable diagnostic performance to two-dimensional MRI, with improvement in diagnostic performance achieved by using 3.0-T field strength, three-dimensional fast-spin-echo sequences, and multiplanar reformation. © RSNA, 2018 Online supplemental material is available for this article.

Objective: The purpose of this study is to determine the diagnostic performance of MRI and MR arthrography for depicting ligamentum teres lesions., Materials and Methods: A literature search was performed. Original studies reporting the diagnostic accuracy of MRI examinations for the depiction of ligamentum teres lesions were included., Results: Eight studies entailing 1456 MRI examinations were included (frequency of median ligamentum teres injury, 25.9%; interquartile range, 14.1-45.3%). Two studies reported the results of unenhanced MRI examinations, and their diagnostic performance could not be estimated. Sensitivity, specificity, and diagnostic odds ratio (DOR) of all MRI examinations were 64.7%, 86.9%, and 12.2, respectively, whereas the sensitivity, specificity, and DOR of MR arthrography examinations were 82.2%, 88.6%, and 35.9, respectively. The heterogeneity (I 2 ) for all MRI and MR arthrography examinations was 92.3% and 88.2%, respectively. Five blinded MR arthrography studies with 643 MR arthrography examinations found an appropriate threshold effect for summary ROC construction (AUC, 0.95). The summary estimate of these studies yielded a sensitivity of 87.8%, a specificity of 91%, and DOR of 73.1. The heterogeneity (I 2 ) for this group was 64.3%. In patients with low pretest probability (25%), MR arthrography enabled the exclusion of ligamentum teres lesion (postprobability for a negative result, 4%; negative likelihood ratio, 0.13)., Conclusion: MR arthrography can depict ligamentum teres lesions with high accuracy. However, its diagnostic performance for differentiating various types of ligamentum teres lesions (partial, complete ligamentum teres tears, and hypertrophic ligamentum teres), as well as the diagnostic performance of unenhanced MRI for the depiction of ligamentum teres lesions, is yet to be determined because of the paucity of reported data in the literature.

Rationale and Objectives: The study aimed to perform a systematic review and meta-analysis for evaluating the diagnostic accuracy of 1.5 Tesla and 3.0 Tesla magnetic resonance imaging (MRI), and magnetic resonance arthrography (MRA), in the detection of scapholunate interosseous ligament (SLIL) injury., Materials and Methods: A literature search was performed (until July 2015) using the PubMed (MEDLINE), Embase, ISI Web of Science, Scopus, and conference proceedings. Original studies evaluating the diagnostic accuracy of MRI or MRA in the detection of SLIL injuries using arthroscopy or open surgery as the reference standard were included., Results: Of the initial 930 published records and 103 conference proceedings, 24 studies (1902 MRI examinations) were included (median SLIL injury prevalence: 33% [interquartile range: 25-42]). Heterogeneity was detected for 1.5 T MRI (chi-square: 47.93, P < 0.001) but not for 3.0 T MRI (chi-square: 8.00, P value: 0.09) and MRA (chi-square: 14.54, P value: 0.34) studies. The sensitivities of 1.5 T MRI, 3.0 T MRI, and MRA for detection of SLIL injury were 45.7% (95% confidence interval: 40.1-51.4), 75.7% (66.8-83.2), and 82.1% (76.1-87.2), respectively. The specificities of 1.5 T MRI, 3.0 T MRI, and MRA for detection of SLIL injury were 80.5% (77.3-83.4), 97.1% (89.8-99.6), and 92.8% (90.2-94.9), respectively. The diagnostic odds ratios of 1.5 T MRI, 3.0 T MRI, and MRA for detection of SLIL injury were 5.56 (2.71-11.39), 23.23 (3.16-171.00), and 65.04 (32.89-128.62) (P value < 0.001), respectively. The results were consistent after addressing publication bias and sensitivity analyses., Conclusions: MRA is superior to 3.0 T MRI, and 3.0 T MRI is superior to 1.5 T MRI in terms of diagnostic performance. 3.0 T MRI has the highest specificity for the detection of SLIL injuries., (Copyright © 2016 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.)

Purpose: To test the inter-observer and inter-method reliability among the measures suggesting patellofemoral joint disorder on both CT and MRI in the same subject and find possible association with internal derangements of the patellofemoral joint on MRI., Methods: Institutional review board approval was obtained with waiver of the informed consent in this HIPPA-compliant study. CT and MRI were evaluated in 32 knees in 32 respective subjects (10 men/22 women, mean age 38 ± 19 years). Three trained observers assessed tibial tuberosity-trochlear groove (TT-TG) distance, trochlear angle and trochlear depth on both CT and MRI. Intra-class correlation coefficient (ICC) was used to evaluate inter-observer and inter-method reliability. Two radiologists' consensus reading was used to evaluate their association with soft tissue abnormalities of the patellofemoral joint. Chi-square test was used to assess the statistical significance of the qualitative variables., Results: There was an excellent inter-observer reliability (ICC for CT >0.89 and for MRI >0.90) and inter-method reliability (ICC >0.86) for all the quantitative measurements. There was a significant association between increased TT-TG distance value on MR imaging and lateral facet patellar cartilage abnormality and joint effusion (p < 0.05)., Conclusion: Quantitative trochlear parameters can be reliably calculated on MRI, and an abnormal TT-TG distance is the most useful measurement among various static MR imaging parameters to correlate with patellar chondrosis and joint effusion. TT-TG distance should be reported in patellofemoral pain syndrome patients., Level of Evidence: IV.

Purpose: To evaluate age-related left ventricular (LV) remodeling during longitudinal observation of a large cohort of asymptomatic individuals who were free of clinical cardiovascular disease at baseline., Materials and Methods: The applicable institutional review boards approved this study, and all participants gave informed consent. Cardiac magnetic resonance (MR) imaging was used to identify longitudinal changes in LV structure and function in 2935 participants who underwent baseline and follow-up cardiac MR imaging in the Multi-Ethnic Study of Atherosclerosis. Participants were free of clinical cardiovascular disease at baseline. Participants who experienced an incident coronary heart disease event were excluded. Data were analyzed with multivariable mixed-effects regression models in which the outcome was cardiac MR imaging measurement, and the covariates included follow-up time and cardiac risk factors., Results: Participants were aged 54-94 years at follow-up, and 53% of the participants were women. Median time between baseline and follow-up cardiac MR imaging was 9.4 years. Over this period, LV mass increased in men and decreased slightly in women (8.0 and -1.6 g per decade, respectively; P < .001). In both men and women, LV end-diastolic volume decreased (-9.8 and -13.3 mL per decade, respectively; P < .001), stroke volume decreased (-8.8 and -8.6 mL per decade, respectively; P < .001), and mass-to-volume ratio increased (0.14 and 0.11 g/mL per decade, respectively; P < .001). Change in LV mass was positively associated with systolic blood pressure and body mass index and negatively associated with treated hypertension and high-density lipoprotein cholesterol level. In men, the longitudinal LV mass increase was in contrast to a cross-sectional pattern of LV mass decrease., Conclusion: As patients age, the LV responds differently in its mass and volume between men and women, although both men and women experience increased concentric LV remodeling with age. In men, the opposition of longitudinal and cross-sectional changes in LV mass highlights the importance of longitudinal study.

Purpose: To evaluate, in a confirmatory fashion, whether baseline and change from baseline to 24-month follow-up in cartilage damage, bone marrow lesions and meniscal damage are predictors of knee replacement (KR) in subjects with a high risk of osteoarthritis (OA), independent of the level of physical activity, symptom severity and radiographic abnormalities., Methods: Data from the Osteoarthritis Initiative's (OAI) baseline and 24-month follow-up knee MRIs of 115 patients (age range: 45-78 years; 48 % female; BMI: 20.9-48.7) were analyzed. Cartilage, bone marrow and menisci were semi-quantitatively scored according to the Whole-Organ Magnetic Resonance Imaging Score (WORMS) and Boston-Leeds Osteoarthritis Knee Score (BLOKS) systems in all compartments. Baseline and 24-month interval changes in structural tissue damage assessed by BLOKS and WORMS were used as predictors of KR independent of clinical and radiographic parameters using Cox hazard analysis. Adjustments were performed for age, gender, BMI and physical activity (Physical Activity Scale for the Elderly: PASE), Western Ontario and McMaster Questionnaire (WOMAC) total score and radiographic Kellgren-Lawrence (KL) score., Results: BLOKS and WORMS baseline cartilage scores were predictors of KR independent of the PASE, WOMAC and KL score. One score increase in the average baseline BLOKS full-thickness cartilage defect score was associated with a [hazard ratio (95 % CI)] 13.55 (3.61-50.89) times greater risk of KR independent of the PASE, WOMAC and KL score. Net reclassification improvements (NRIs) of the additional evaluation of 24-month follow-up MRI scores and assessment of changes were not significant for prediction of KR (NRI range: - 7.23 - 24.8 %)., Conclusions: The BLOKS cartilage score for full-thickness cartilage defects had the highest hazard for KR. Follow-up MRI changes in structural tissue damage, detected by BLOKS and WORMS cartilage, bone marrow or meniscus scores (up to 24 months) had no significant predictive value in addition to the baseline MRI.

Background and Purpose: To determine whether lesion to activation distance (LAD) on presurgical blood-oxygen-level-dependent functional magnetic resonance imaging (fMRI) and degree of white matter involvement by primary or metastatic brain lesions predict perioperative motor and language deficits., Methods: We retrospectively evaluated 76 patients with intra-axial brain lesions referred for presurgical fMRI and diffusion tensor imaging (DTI). We measured expressive, receptive, global language and motor LAD and assessed degree of involvement of the corticospinal tract (CST) and the superior longitudinal fasciculus (SLF). We performed a Wilcoxon rank-sum test to determine whether the LAD and the degree of CST/SLF involvement were statistically significantly different between patients with and without preoperative or postoperative neurological deficits., Results: In preoperatively symptomatic patients, motor and expressive language LAD were significantly lower (z = -3.78, P = .0002, and z = -2.51, P = .01, respectively) than in asymptomatic patients. No significant difference was noted in LAD between postoperative symptomatic and asymptomatic patients, except for a trend level effect for motor LAD (P = .07). The degree of CST involvement was significantly different between symptomatic and asymptomatic patients (z = 3.40, P = .0007 and z = 2.97, P = .003, respectively, for pre- and postoperative motor deficits).The degree of SLF involvement was significantly different between preoperatively (but not postoperatively) symptomatic and asymptomatic patients (z = 2.85, P = .004)., Conclusion: Presurgical motor and expressive language LAD as well as degree of tract involvement on DTI are predictive of preoperative but not postoperative deficits, except for CST DTI and (trend level) motor LAD; inability of language LAD to predict postoperative deficits suggests that preoperative fMRI is valuable to neurosurgeons in avoiding resection of eloquent cortex., (Copyright © 2015 by the American Society of Neuroimaging.)

Morphological and functional parameters such as chamber size and function, aortic diameters and distensibility, flow and T1 and T2* relaxation time can be assessed and quantified by cardiovascular magnetic resonance (CMR). Knowledge of normal values for quantitative CMR is crucial to interpretation of results and to distinguish normal from disease. In this review, we present normal reference values for morphological and functional CMR parameters of the cardiovascular system based on the peer-reviewed literature and current CMR techniques and sequences.

Objective: The aim of this study was to evaluate response of the targeted tumor burden by functional magnetic resonance imaging (MRI) including volumetric diffusion-weighted imaging and volumetric contrast-enhanced MRI (CE-MRI) and its impact on survival in patients with hepatocellular carcinoma treated with intra-arterial therapy (IAT)., Materials and Methods: This institutional review board-approved, Health Insurance Portability and Accountability Act-compliant retrospective study included 157 hepatocellular carcinoma lesions in 97 patients (78 men and 19 women; mean age, 64 years) treated with IAT. All patients had pretreatment and 3- to 4-week follow-up MRI with diffusion-weighted imaging and CE-MRI. All lesions 2 cm or larger that were targeted during the first session of IAT were segmented using research software (MR-Oncotreat) to determine targeted tumor burden relative to liver volume (%). Targeted tumor burden was stratified into low (≤10%) or high (>10%). Response using volumetric functional apparent diffusion coefficient (ADC; increase by ≥25%) and CE-MRI (decrease by ≥50% and ≥65% in arterial and venous enhancement [VE], respectively) was assessed in all targeted tumors (range, 1-11) using paired t tests. Kaplan-Meier survival analysis was performed and log-rank test was used to compare pairs of survival curves. Multivariate Cox regression analysis was performed to determine the simultaneous effect of treatment response and tumor burden on survival after adjusting for age, sex, and Child Pugh status., Results: There was a significant increase in volumetric ADC (median, 15%; P < 0.001) and a decrease in volumetric arterial enhancement (AE) and VE (median AE, -43% and portal venous phase (PVP), -29%, respectively; P < 0.001) 3 to 4 weeks after treatment in the targeted tumor burden. Multivariable Cox regression demonstrated that both ADC response and low tumor burden were independently associated with greater survival (hazard ratios, 0.53 and 0.55; P values, 0.025 and 0.016, respectively) after adjustment for age, sex, and Child Pugh status. Multivariable Cox regression models demonstrated no statistically significant relationship between AE response and survival after adjusting for tumor burden. However, multivariable Cox regression demonstrated that VE response was associated with greater survival only in those with low tumor burden (hazard ratio, 0.10; P = 0.001), indicating a strong interaction between VE response and tumor burden., Conclusion: Quantifying targeted tumor burden is important in predicting patient survival when using functional MRI metrics in assessing treatment response.

Background: Although left ventricular cardiac geometric indices such as size and sphericity characterize adverse remodeling and have prognostic value in symptomatic patients, little is known of shape distributions in subclinical populations. We sought to quantify shape variation across a large number of asymptomatic volunteers, and examine differences among sub-cohorts., Methods: An atlas was constructed comprising 1,991 cardiovascular magnetic resonance (CMR) cases contributed from the Multi-Ethnic Study of Atherosclerosis baseline examination. A mathematical model describing regional wall motion and shape was used to establish a coordinate map registered to the cardiac anatomy. The model was automatically customized to left ventricular contours and anatomical landmarks, corrected for breath-hold mis-registration between image slices. Mathematical techniques were used to characterize global shape distributions, after removal of translations, rotations, and scale due to height. Differences were quantified among ethnicity, sex, smoking, hypertension and diabetes sub-cohorts., Results: The atlas construction process yielded accurate representations of global shape (errors between manual and automatic surface points in 244 validation cases were less than the image pixel size). After correction for height, the dominant shape component was associated with heart size, explaining 32% of the total shape variance at end-diastole and 29% at end-systole. After size, the second dominant shape component was sphericity at end-diastole (13%), and concentricity at end-systole (10%). The resulting shape components distinguished differences due to ethnicity and risk factors with greater statistical power than traditional mass and volume indices., Conclusions: We have quantified the dominant components of global shape variation in the adult asymptomatic population. The data and results are available at cardiacatlas.org. Shape distributions were principally explained by size, sphericity and concentricity, which are known correlates of adverse outcomes. Atlas-based global shape analysis provides a powerful method for quantifying left ventricular shape differences in asymptomatic populations., Trial Registration: ClinicalTrials.gov NCT00005487.

Purpose: To assess the interobserver agreement in 50 patients with hepatocellular carcinoma (HCC) before and 1 month after intra-arterial therapy (IAT) using two semi-automated methods and a manual approach for the following functional, volumetric and morphologic parameters: (1) apparent diffusion coefficient (ADC), (2) arterial phase enhancement (AE), (3) portal venous phase enhancement (VE), (4) tumor volume, and assessment according to (5) the Response Evaluation Criteria in Solid Tumors (RECIST), and (6) the European Association for the Study of the Liver (EASL)., Materials and Methods: This HIPAA-compliant retrospective study had institutional review board approval. The requirement for patient informed consent was waived. Tumor ADC, AE, VE, volume, RECIST, and EASL in 50 index lesions was measured by three observers. Interobserver reproducibility was evaluated using intraclass correlation coefficients (ICC). P<0.05 was considered to indicate a significant difference., Results: Semi-automated volumetric measurements of functional parameters (ADC, AE, and VE) before and after IAT as well as change in tumor ADC, AE, or VE had better interobserver agreement (ICC=0.830-0.974) compared with manual ROI-based axial measurements (ICC=0.157-0.799). Semi-automated measurements of tumor volume and size in the axial plane before and after IAT had better interobserver agreement (ICC=0.854-0.996) compared with manual size measurements (ICC=0.543-0.596), and interobserver agreement for change in tumor RECIST size was also higher using semi-automated measurements (ICC=0.655) compared with manual measurements (ICC=0.169). EASL measurements of tumor enhancement in the axial plane before and after IAT ((ICC=0.758-0.809), and changes in EASL after IAT (ICC=0.653) had good interobserver agreement., Conclusion: Semi-automated measurements of functional changes assessed by ADC and VE based on whole-lesion segmentation demonstrated better reproducibility than ROI-based axial measurements, or RECIST or EASL measurements., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Magnetic resonance neurography (MRN) is a specialized technique that is rapidly becoming part of the diagnostic algorithm of peripheral nerve pathology. However, in order for this modality to be considered appropriate, its value compared with current methods of diagnosis should be established. Therefore, radiologists involved in MRN research should use appropriate methodology to evaluate MRN's effectiveness with a multidisciplinary approach. This article reviews the various tiers of research available to assess the clinical value of a diagnostic modality with an emphasis on how to evaluate the impact of MRN on diagnostic thinking and therapeutic decisions., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Purpose: To identify and validate the optimal thresholds for volumetric functional MR imaging response criteria to predict overall survival after intraarterial treatment (IAT) in patients with unresectable hepatocellular carcinoma (HCC)., Materials and Methods: Institutional review board approval and waiver of informed consent were obtained. A total of 143 patients who had undergone MR imaging before and 3-4 weeks after the first cycle of IAT were included. MR imaging analysis of one representative HCC index lesion was performed with proprietary software after initial treatment. Subjects were randomly divided into training (n = 114 [79.7%]) and validation (n = 29 [20.3%]) data sets. Uni- and multivariate Cox models were used to determine the best cutoffs, as well as survival differences, between response groups in the validation data set., Results: Optimal cutoffs in the training data set were 23% increase in apparent diffusion coefficient (ADC) and 65% decrease in volumetric enhancement in the portal venous phase (VE). Subsequently, 25% increase in ADC and 65% decrease in VE were used to stratify patients in the validation data set. Comparison of ADC responders (n = 12 [58.6%]) with nonresponders (n = 17 [34.5%]) showed significant differences in survival (25th percentile survival, 11.2 vs 4.9 months, respectively; P = .008), as did VE responders (n = 9 [31.0%]) compared with nonresponders (n = 20 [69.0%]; 25th percentile survival, 11.5 vs 5.1 months, respectively; P = .01). Stratification of patients with a combination of the criteria resulted in significant differences in survival between patients with lesions that fulfilled both criteria (n = 6 [20.7%]; too few cases to determine 25th percentile), one criterion (n = 9 [31.0%]; 25th percentile survival, 6.0 months), and neither criterion (n = 14 [48.3%]; 25th percentile survival, 5.1 months; P = .01). The association between the two criteria and overall survival remained significant in a multivariate analysis that included age, sex, Barcelona Clinic for Liver Cancer stage, and number of follow-up treatments., Conclusion: After IAT for unresectable HCC, patients can be stratified into significantly different survival categories based on responder versus nonresponder status according to MR imaging ADC and VE cutoffs.

Purpose: To assess whether volumetric functional magnetic resonance (MR) results 3-4 weeks after initial intraarterial therapy can aid accurate distinction between responders and nonresponders, to determine whether overall survival (OS) is improved, and to compare volumetric functional MR response with anatomic response criteria (Response Evaluation Criteria in Solid Tumors [RECIST], modified RECIST [mRECIST], European Association for the Study of the Liver [EASL]), as well as α1-fetoprotein [AFP] level., Materials and Methods: In this single-institution HIPAA-compliant retrospective, institutional review board-approved study, informed consent was waived; 143 patients with hepatocellular carcinoma underwent intraarterial therapy between October 2005 and February 2011. Volumetric functional MR response (25% or more increase in apparent diffusion coefficient, 65% or more decrease in enhancement) was stratified as follows: Dual-parameter responders fulfilled both criteria, single-parameter responders fulfilled one criterion, and those with stable disease (SD) fulfilled neither. RECIST, mRECIST, EASL, and AFP response criteria were determined. Kaplan-Meier technique, log-rank tests, and the Cox proportional hazards model were used to test whether OS was different per response., Results: OS differed significantly between single-parameter responders and dual-parameter responders (P = .01) and between single-parameter responders and those with SD (P = .001). Dual-parameter responders' response improved OS compared with single-parameter responders; risk of death decreased (hazard ratio [HR] = 0.28, P = .01). In those with SD compared with single-parameter responders, risk of death increased (HR = 2.09, P = .001). RECIST, mRECIST, and EASL stratification was short of significant; most lesions were classified as SD. Baseline AFP level increased in 55 patients; AFP responders versus AFP nonresponders had decreased risk of death (HR = 0.36, P = .002). Agreement between anatomic response criteria and volumetric functional MR findings (κ = 0.06-0.12) and between AFP response and imaging criteria (κ = -0.04 to 0.14) was low., Conclusion: Volumetric functional MR response 3-4 weeks after initial intraarterial therapy showed improved OS. Volumetric functional MR was superior to current imaging (RECIST, mRECIST, and EASL) and biochemical (AFP level) response criteria.

Objective: To assess the diagnostic accuracy and observer performance of 3-Tesla magnetic resonance neurography (MRN) in the evaluation of meralgia paresthetica (MP)., Materials and Methods: Two independent readers were blinded to the clinical diagnosis and evaluated the MRN studies of the pelvis of 11 patients with MP and 28 control participants. In each study, the lateral femoral cutaneous nerves were assessed for signal alteration and/or neuroma formation, indicating lateral femoral cutaneous neuropathy, at various levels along their course. Intra- and inter-observer reliability was evaluated., Results: Both readers exhibited substantial intraobserver agreement in detecting signal alterations and neuroma formation of the lateral femoral cutaneous nerve (LFCN). The readers demonstrated moderate interobserver agreement in detecting signal alteration of the LFCN and poor interobserver agreement in diagnosing neuroma formation. Sensitivity, specificity, positive predictive value, and negative predictive value of LFCN neuropathy diagnosis were ≥ 71 % and ≥ 94 % for both readers respectively. The diagnostic test accuracy was ≥ 90 % for both readers., Conclusion: 3-Tesla MRN provides reliable and accurate diagnostic evaluation of meralgia paresthetica.

Background and Purpose: A number of benign and malignant peripheral nerve tumor and tumorlike conditions produce similar imaging features on conventional anatomic MR imaging. Functional MR imaging using DTI can increment the diagnostic performance in differentiation of these lesions. Our aim was to evaluate the role of 3T anatomic MR imaging and DTI in the characterization of peripheral nerve tumor and tumorlike conditions., Materials and Methods: Twenty-nine patients (13 men, 16 women; mean age, 41±18 years; range, 11-83 years) with a nerve tumor or tumorlike condition (25 benign, 5 malignant) underwent 3T MR imaging by using anatomic (n=29), functional diffusion, DWI (n=21), and DTI (n=24) techniques. Images were evaluated for image quality (3-point scale), ADC of the lesion, tractography, and fractional anisotropy of nerves with interobserver reliability in ADC and FA measurements., Results: No significant differences were observed in age (benign, 40±18 versus malignant, 45±19 years) and sex (benign, male/female=12:12 versus malignant, male/female=3:2) (P>.05). All anatomic (29/29, 100%) MR imaging studies received "good" quality; 20/21 (95%) DWI and 21/24 (79%) DTI studies received "good" quality. ADC of benign lesions (1.848±0.40×10(-3) mm2/s) differed from that of malignant lesions (0.900±0.25×10(-3) mm2/s, P<.001) with excellent interobserver reliability (ICC=0.988 [95% CI, 0.976-0.994]). There were no FA or ADC differences between men and women (P>.05). FA of involved nerves was lower than that in contralateral healthy nerves (P<.001) with excellent interobserver reliability (ICC=0.970 [95% CI, 0.946-0.991]). ADC on DTI and DWI was not statistically different (P>.05), with excellent intermethod reliability (ICC=0.943 [95% CI, 0.836-0.980]). Tractography differences were observed in benign and malignant lesions., Conclusions: 3T MR imaging and DTI are valuable methods for anatomic and functional evaluation of peripheral nerve lesions with excellent interobserver reliability. While tractography and low FA provide insight into neural integrity, low diffusivity values indicate malignancy in neural masses.

Diagnosis of tibial neuropathy has been traditionally based on clinical examination and electrodiagnostic studies; however, cross-sectional imaging modalities have been used to increase the diagnostic accuracy and provide anatomic mapping of the abnormalities. In this context, magnetic resonance neurography (MRN) offers high-resolution imaging of the tibial nerve (TN), its branches and the adjacent soft tissues, and provides an objective assessment of the neuromuscular anatomy, abnormality, and the surrounding pathology. This review describes the pathologies affecting the TN and illustrates their respective 3 Tesla (T) MRN appearances with relevant case examples., (Copyright © 2012 by the American Society of Neuroimaging.)

Purpose: To investigate whether the universally accepted range of normal patellar height ratios derived from radiography for the Insall-Salvati (IS) and Blackburne-Peel (BP) methods could be similarly applied to both CT and MRI., Materials and Methods: Institutional review board approval was obtained with waiver of informed consent for this HIPPA-compliant study. A total of 45 knees in 42 patients (15 men, 27 women; age range 11 to 75 years, mean age 39 ± 20 years) who underwent tri-modality (radiograph, CT, and MRI) examinations were selected. All patients had knee imaging obtained for a variety of reasons and measurements were performed by two independent readers who were blinded to each other's measurements or the respective measurements derived from each of the methods. Paired t test was used to compare the mean values among the modalities. Inter-observer and inter-method agreements were assessed using intra-class correlation coefficients., Results: Statistically significant, but small quantitative differences are noted between tri-modality patellar height ratios. For comparable results, the small addition of 0.13 and 0.10 are needed for the Insall-Salvati measurements on MRI and CT respectively, compared with radiographs. For the Blackburne-Peel ratio, an additional adjustment of 0.09 is needed between radiographs and MRI, but not between radiographs and CT. These adjustments are independent of gender. The interobserver reproducibility was excellent (ICC ≥ 0.94) for both the Insall-Salvati and Blackburne-Peel methods for all modalities., Conclusion: The results indicate that cut-off values for patella alta and baja derived from radiographs should not be directly transposed to CT and MRI; however, the adjustments are relatively minor. These measurements show excellent reproducibility for all modalities currently used for patellar height measurements.

Purpose: To evaluate volumetric changes in apparent diffusion coefficient (ADC) and contrast material enhancement on contrast-enhanced (CE) magnetic resonance (MR) images in hepatic arterial and portal venous phases for assessing early response in cholangiocarcinoma treated with transcatheter arterial chemoembolization (TACE)., Materials and Methods: Twenty-nine patients with unresectable cholangiocarcinoma, including 11 men (mean age, 60 years; standard deviation, 16.8) and 18 women (mean age, 63 years; standard deviation, 11.5) were included in this retrospective institutional review board-approved, HIPAA-compliant study; informed consent was waived. Sixty-nine TACE procedures were performed during the observational time (range, one to five TACE sessions). No patients received another form of therapy after treatment with TACE. MR Imaging was performed before and 3-4 weeks after TACE, and images were analyzed with a semiautomatic volumetric software package. Patients were stratified as responders and nonresponders on the basis of overall survival (OS) as the primary end point. Differences between responders and nonresponders were analyzed with paired t tests, and OS was calculated with the Kaplan-Meier method. Significant differences were analyzed with the log-rank test., Results: Mean volumetric ADC increased from 1.54×10(-3) mm2/sec to 1.92×10(-3) mm2/sec (P<.0001), with no significant decrease in mean volumetric enhancement in hepatic arterial (40.6% vs 37.5%, P=.546) and portal venous (79.0% vs 70.0%, P=.105) phases. Patients who demonstrated improved survival of 10 months or more had a significant increase in mean volumetric ADC and volumetric ADC above the threshold level of 1.60×10(-3) mm2/sec (P<.002). Patients with 45% or greater (n=21; log-rank test, P<.02) and 60% or greater (n=12; log-rank test, P<.009) ADC changes for the whole tumor volume demonstrated better OS compared with patients in whom these ADC changes were not achieved., Conclusion: Patients with percentage tumor volume increase in ADC of 45% or greater and 60% or greater above the threshold level of 1.60×10(-3) mm2/sec had favorable response to therapy and improved survival., (© RSNA, 2012.)

Objective: To examine diagnostic accuracy of semiquantitative and qualitative magnetic resonance neurography criteria in common peroneal nerve (CPN) neuropathy., Materials and Methods: Institutional review board approval was obtained with a waiver of informed consent for this Health Insurance Portability and Accountability Act-compliant retrospective study. A review of 28 knees in 28 subjects (12 males and 16 females; age range, 13-84 years; mean [SD] age, 42 [20] years) who had undergone magnetic resonance neurography of the knee was performed. Thirteen patients who had a final diagnosis of CPN were classified as cases, and 15 patients who lacked a final diagnosis of CPN neuropathy were classified as controls. Morphological characteristics of the CPN, including nerve T2 signal intensity, nerve size, nerve course, fascicles morphology, regional muscle edema, and fatty infiltration, and an overall assessment of the CPN as being normal or abnormal were evaluated by 2 independent radiologists blinded to the clinical history. Overall sensitivity, specificity, and accuracy compared against our reference standards were expressed as percentages. Interobserver agreements were assessed using linear weighted κ statistics., Results: Common peroneal nerve T2 signal abnormality had the highest sensitivity (77%) in identifying CPN neuropathy. Except for T2 signal abnormality, overall specificity for the nerve morphological parameters and muscle denervation change assessed was fairly high, ranging from 94% to 100%. The consensus accuracy ranged from 68% to 79% for the morphological characteristics assessed. The interobserver reproducibility was very good (k = 0.90 to 0.91) for assessment of regional muscle denervation changes and moderate (k = 0.46 to 0.59) for morphological CPN characteristics., Conclusion: Magnetic resonance neurography is a useful modality in supplementing the diagnosis of CPN. Using predefined classification criteria helps standardize the morphological criteria of CPN neuropathy diagnosis.

This review provides magnetic resonance neurography (MRN) imaging appearances of median neuropathy proximal to the carpal tunnel. Carpal tunnel syndrome (CTS) and its imaging have been extensively described in the literature; however, there is a relative paucity of information on the MR imaging appearances of different pathologies of the median nerve proximal to the carpal tunnel.

Study Design: This study is a research synthesis of the published literature evaluating the performance of magnetic resonance imaging (MRI) for differentiation of malignant from benign vertebral compression fractures (VCFs)., Objective: Perform a systematic review and meta-analysis to summarize and combine the published data on MRI for discriminating malignant from benign VCFs., Summary of Background Data: The differentiation between benign and malignant VCFs in the spine is a challenging problem confronting spine practitioners., Methods: MEDLINE, EMBASE, and other databases were searched by 2 independent reviewers to identify studies that reported the performance of MRI for discriminating malignant from benign VCF. Included studies were assessed for described MRI features and study quality. The sensitivity, specificity, and diagnostic odds ratio (OR) of each feature were pooled with a random-effects model weighted by the inverse of the variance of each individual estimate., Results: A total of 31 studies with 1685 subjects met the selection criteria. All the studies focused on describing specific features rather than overall diagnostic performance. Signal intensity ratio on opposed phase (chemical shift) imaging 0.8 or more (OR = 164), apparent diffusion coefficient on echo planar diffusion-weighted images 1.5 × 10(-3) mm2/s or less with b value 500 s/mm2 (OR = 130), presence of other noncharacteristic vertebral lesions (OR = 55), presence of paraspinal mass (OR = 33), involvement of posterior element (OR = 28), involvement of pedicle (OR = 24), complete replacement of normal bone marrow in VCF (OR = 19), presence of epidural mass (OR = 13), and diffuse convexity of posterior vertebral border (OR = 10) were associated with malignant VCFs, whereas coexisting healed benign VCF (OR = 0.006), presence of "fluid sign" (OR = 0.08), presence of focal posterior vertebral border convexity/retropulsion (OR = 0.08), and band-like shape of abnormal signal (OR = 0.07) were associated with benign VCFs., Conclusion: Several specific MRI features using signal intensity characteristics, morphological characteristics, quantitative techniques, and findings at other levels can be useful for distinguishing benign from malignant VCFs and can serve as inputs for a prediction model. Observer performance reliability has not been adequately assessed.

Rationale and Objectives: The aims of this study were to determine agreement between clinical examination and magnetic resonance imaging (MRI) (rectal contrast and noncontrast MRI) for pelvic organ prolapse using both the pubococcygeal line (PCL) and the midpubic line (MPL) and to assess the relationship between measurements performed relative to each line., Materials and Methods: Dynamic MRI exams in 88 women (with rectal contrast, n = 39; noncontrast, n = 49) were evaluated, followed by review of clinical exam notes. Agreement between clinical exam and MRI and the difference between PCL and MPL measurements were evaluated., Results: Agreement of rectal contrast MRI with clinical exam was 79% for PCL and 85% for MPL (P = .17) for cystoceles, 50% for PCL and 59% for MPL (P = .20) for vaginal prolapse, 56% for PCL for enteroceles, and 61% for rectoceles. Agreement of noncontrast MRI with clinical exam was 67% for PCL and 78% for MPL (P = .19) for cystoceles, 58% for PCL and 71% for MPL (P = .10) for vaginal prolapse, 65% for enteroceles, and 40% for rectoceles. The average difference between the PCL and the MPL was 3.12 ± 0.24 cm at the bladder base and 4.88 ± 0.37 cm at the vaginal apex., Conclusions: Agreement of MRI with clinical exam was highest for cystoceles. There was no significant difference in agreement using the MPL or PCL, suggesting that either line can be used on MRI. The average differences between the PCL and MPL at the bladder base and vaginal apex were approximately 3 and 5 cm, respectively., (Copyright © 2011 AUR. Published by Elsevier Inc. All rights reserved.)

Purpose: To verify iliolumbar ligament (ILL) location, to evaluate magnetic resonance (MR) imaging morphologic features for detecting lumbosacral transitional vertebrae (TVs) (LSTVs), and to determine whether transitional situations are associated with anomalous vertebral numbering., Materials and Methods: Investigational review board approval was obtained for this HIPAA-compliant retrospective study. A review of 147 subjects was performed by using spine radiography as the reference standard to determine total and segmental vertebral count and transitional anatomy. Thoracolumbar TVs (TLTVs) and LSTVs were identified. The lumbosacral intervertebral disk angle (LSIVDA), defined as the angle between the endplates, was measured, S1-2 disk morphology was rated according to the classification by O'Driscoll et al, and the ILL level was determined from MR images. Statistical analysis was performed by using χ(2) tests for dichotomous and ordinal variables and the t test for continuous variables., Results: An anomalous total number of vertebrae were present in 12 (8.2%) of 147 subjects. The ILL was identified in 126 (85.7%) of 147 subjects and was present at L5 in 122 (96.8%) subjects; the remaining four (3.2%) subjects had an anomalous total number of vertebrae. A complete S1-2 intervertebral disk was associated with LSTVs (P = .004); however, LSIVDA was not (P = .2). TLTVs were present in six (4.1%) and LSTVs were present in 22 (15.0%) of 147 subjects. Both were present in four (2.7%) subjects. The presence of a TLTV was associated with a higher incidence of a concomitant LSTV and vice versa (P < .001; odds ratio [OR], 13.7; 95% confidence interval [CI]: 2.7, 68.4]). A TLTV was not associated with an anomalous total number of vertebrae (P = .46), but an LSTV was (P < .001; OR, 7.4; 95% CI: 2.2, 24.8)., Conclusion: The ILL denotes the lowest lumbar vertebra, which does not always represent L5. A well-formed, complete S1-2 intervertebral disk is associated with LSTVs, but alteration in LSIVDA is not. LSTVs are associated with anomalous vertebral numbering., (© RSNA, 2011.)

Objective: Nonelderly patients presenting with knee pain often have patellofemoral maltracking or impingement abnormalities. There is a relative paucity of literature on the incidence and significance of impingement-related edema of the superolateral aspect of Hoffa's (infrapatellar) fat pad in these cases. Our study was designed to systematically evaluate the correlation of superolateral Hoffa's fat pad edema with various anatomic parameters of trochlear morphology and patellar alignment., Materials and Methods: We evaluated 50 knee MRI examinations in 47 patients for the presence of edema in superolateral Hoffa's fat pad and associated anatomic abnormalities of the patellofemoral joint., Results: Of the 50 examinations, 25 (50%) showed superolateral Hoffa's fat pad edema, and statistically significant differences were seen between those with and without edema with respect to sex (6/22 men vs 19/28 women) and patellar tendon patellar-length ratio (1.3 ± 0.16 and 1.1 ± 0.12 for those with and without edema, respectively)., Conclusion: The findings in our study suggest that edema in superolateral Hoffa's fat pad may be an important indicator of underlying patellofemoral maltracking or impingement in younger, symptomatic patients.

Purpose: To compare supine magnetic resonance imaging (MRI), with and without rectal contrast, with fluoroscopic cystocolpoproctography (CCP) for the diagnosis of pelvic organ prolapse., Materials and Methods: Supine MRI and CCP studies were reviewed in 82 patients. All patients were women with an average age of 58.8 years, and the studies were done a mean of 25 days apart. Magnetic resonance imaging was performed with rectal contrast (n = 35) and without rectal contrast (n = 47). Fluoroscopic cystocolpoproctography was performed with rectal (n = 82), vaginal (n = 82), small bowel (n = 81), and bladder (n = 78) contrast, and images were corrected for magnification. Each study was independently reviewed by 2 readers, and outcome variables were presence/absence of cystocele, vaginal prolapse, enterocele, sigmoidocele, and anterior rectocele. Sigmoidoceles were included with enteroceles for data analysis., Results: For the entire patient group, the prevalence of cystoceles was 89% on CCP and 80% on MRI; vaginal prolapse was 81% on CCP and 56% on MRI; enteroceles, 38% on CCP and 24% on MRI; and anterior rectoceles, 45% on CCP and 37% on MRI. There were significantly more cystoceles (odds ratio [OR] 4.7, P = 0.003), vaginal prolapses (OR 5.2, P < 0.0005), and enteroceles (OR 3.8, P< 0.0005) on CCP than on MRI. For MRI with rectal contrast versus CCP, the prevalence of cystoceles was 94% on CCP and 91% on MRI; vaginal prolapse, 74% on CCP and 70% on MRI; enteroceles, 36% on CCP and 19% on MRI; and anterior rectoceles, 51% on CCP and 59% on MRI. There was statistical significance only for enteroceles, more of which were found on CCP (OR 7.4, P = 0.003). For MRI without rectal contrast versus CCP, the prevalence of cystoceles was 85% on CCP and 72% on MRI; vaginal prolapse, 86% on CCP and 46% on MRI; enteroceles, 40% on CCP and 28% on MRI; and anterior rectoceles, 39% on CCP and 21% on MRI. There were significantly more cystoceles (OR 6.6, P = 0.003), vaginal prolapses (OR 20.8, P < 0.0005), enteroceles (OR 2.9, P = 0.015), and rectoceles (OR 4.9, P = 0.001) on CCP than on noncontrast MRI., Conclusions: Magnetic resonance imaging without rectal contrast showed statistically fewer pelvic floor abnormalities than CCP. Except for enteroceles, MRI with rectal contrast showed statistically similar frequency of pelvic organ prolapse as CCP.

Purpose: To assess treatment response of hepatocellular carcinoma (HCC) after transarterial chemoembolization (TACE) with use of diffusion and dynamic contrast medium-enhanced magnetic resonance (MR) imaging., Materials and Methods: MR imaging studies before and after TACE in 38 patients with HCC (33 male patients and five female patients) were evaluated. Diffusion and dynamic contrast medium-enhanced MR imaging was performed on a 1.5-T unit. The imaging protocol included T2-weighted fast spin-echo, breath-hold diffusion-weighted echoplanar, and breath-hold unenhanced and contrast medium-enhanced T1-weighted three-dimensional fat-saturation gradient-recalled echo imaging in the arterial and portal venous phases. Tumor size, percent enhancement, and apparent diffusion coefficient (ADC) values were recorded before and after treatment. Survival analysis was also performed., Results: The study included 38 lesions with a mean diameter of 8.0 cm. Mean reduction in tumor diameter was 8 mm after treatment (t test; P = .0005), which did not fulfill Response Evaluation Criteria in Solid Tumors for complete or partial response. Reduction in tumor enhancement in the arterial (30%) and venous (47%) phases was statistically significant (signed-rank test; P = .0003 and P < 0.00005, respectively). Tumor ADC value increased from 0.0015 mm(2)/sec to 0.0018 mm(2)/sec after treatment (t test; P = .026), whereas the ADC values for the liver, spleen, and muscle remained unchanged. Median patient survival was 19 months., Conclusions: After TACE, tumors demonstrated decreased size and enhancement with increases in ADC values. In this cohort, diffusion and dynamic contrast medium-enhanced MR imaging parameters were significantly altered after TACE, and these could be useful tools in the assessment of tumor response.

Purpose: To determine the accuracy of breath-hold magnetic resonance (MR) imaging for preoperative staging of patients with organ-confined (stage I) renal cell carcinoma., Materials and Methods: Preoperative MR examinations of 43 patients (50 lesions) who underwent nephrectomy were reviewed. The MR examination consisted entirely of breath-hold sequences, and images were retrospectively evaluated by 2 blinded radiologists. Reviewers independently evaluated each case for findings that could affect the radiologic staging, particularly those that distinguish between organ-confined (stage I) and non-organ-confined (>stage II) disease. Each reviewer assigned a stage, and results were correlated with findings at surgery and pathologic examination., Results: The difference between both reviewers and pathologic findings in evaluating an intact renal capsule (stage I) was statistically significant (P < 0.05) and resulted in a statistically significant difference between radiologic and pathologic staging (Wilcoxon test, P < 0.05). The kappa test demonstrated moderate agreement between radiologic and pathologic staging (82% and 80% for reviewers 1 and 2, kappa = 0.54 and 0.80, respectively) and substantial agreement (90%, kappa = 0.80) between the 2 reviewers in assigning a radiologic stage., Conclusion: Breath-hold MR imaging has an accuracy ranging between 80% and 82% in staging patients with organ-confined renal cell carcinoma, with substantial (90%) agreement between readers.

Java is a relatively new programming language that has been used to develop a World Wide Web-based tool for estimating magnetic resonance (MR) imaging relaxation times, thereby demonstrating how Java may be used for Web-based radiology applications beyond improving the user interface of teaching files. A standard processing algorithm coded with Java is downloaded along with the hypertext markup language (HTML) document. The user (client) selects the desired pulse sequence and inputs data obtained from a region of interest on the MR images. The algorithm is used to modify selected MR imaging parameters in an equation that models the phenomenon being evaluated. MR imaging relaxation times are estimated, and confidence intervals and a P value expressing the accuracy of the final results are calculated. Design features such as simplicity, object-oriented programming, and security restrictions allow Java to expand the capabilities of HTML by offering a more versatile user interface that includes dynamic annotations and graphics. Java also allows the client to perform more sophisticated information processing and computation than is usually associated with Web applications. Java is likely to become a standard programming option, and the development of stand-alone Java applications may become more common as Java is integrated into future versions of computer operating systems.

A method that improves contrast in gradient-recalled-echo magnetic resonance images is described. The increase in contrast is produced by applying low-power radio-frequency irradiation 5-10 kHz from the main water proton resonance frequency to excite macromolecular hydrogen-1 nuclei as part of a conventional gradient-recalled-echo sequence. The contrast so obtained is theoretically different from T1 or T2 contrast and has been termed magnetization transfer contrast. Cat head images were acquired in vivo with this method at 4.7 and 1.5 T. Compared with conventional gradient-recalled-echo images, the magnetization transfer images demonstrate increased contrast between many tissue pairs, such as between white matter and blood and between gray matter and cerebrospinal fluid. The dependence of the magnetization transfer effect on repetition time and preirradiation power were also studied.

Trimethylamines are required as substrates in the biosynthesis of a number of important molecules in the cell. Herein, we describe the use of choline, deuterated in its 9 methyl positions, as an NMR label for following the distribution and metabolism of methyl groups after intravenous choline infusion. Deuterium (2H) NMR spectroscopy of the rabbit kidney in vivo revealed a linear uptake of infused choline that was directly proportional to the rate of infusion. The sensitivity limit for the spectroscopic studies in vivo was in the order of 100 microM for a 2 min data collection. After the infusion, 2H NMR imaging of the kidney in vivo demonstrated high trimethylamine concentrations in both the cortex and inner medulla but not in the outer medulla. The inner medullary fraction, however, was more labile to diuresis induced by furosemide. Companion high resolution 2H NMR studies of extracts revealed a cortex betaine/choline concentration ratio of 0.69 +/- 0.05 (mean +/- SEM, n = 3) before furosemide administration. Following furosemide infusion, the cortex betaine/choline concentration ratio was 3 +/- 1 (n = 6). Thus, 2H renal images following furosemide treatment can be interpreted as metabolic maps of betaine distribution. In addition, extraction studies revealed high concentrations of labelled choline and betaine in the liver. These data demonstrate that 2H-labelled choline is an effective marker of choline methyl metabolism in vivo and should provide a unique tool for the investigation of this important substrate.

The mechanism by which the mammalian kidney generates a concentration gradient of sodium from cortex to papilla is still not entirely understood. Studies of how the kidney as an organ generates this gradient have been hampered by the lack of a noninvasive method for monitoring the intrarenal sodium distribution. Herein, we demonstrate the value of sodium-23 nuclear magnetic resonance (23Na-NMR) imaging to nondestructively assess the intrarenal sodium distribution. 23Na-NMR images were obtained from a surgically exposed kidney preparation that showed the two-dimensional distribution of sodium in the rabbit kidney. In the antidiuretic kidney this gradient resulted in papillary sodium concentrations that were approximately threefold higher than cortical values. Serial 23Na-NMR images obtained during saline infusion demonstrated the kinetics by which the sodium gradient increases with diuresis. The half-time for 23Na washout of the medulla of the kidney was approximately 6 min with this protocol. In addition, a three-dimensional data set of the sodium distribution of the kidney was obtained with voxel dimensions of 1.5 mm3 by use of a three-dimensional 23Na-NMR imaging technique. Without surgical exposure, 23Na-NMR images of the rabbit kidney were collected under completely noninvasive conditions by use of a surface coil. The 23Na-NMR signal from the kidney was easily detected; however, to obtain images of comparable signal-to-noise ratio to the surgically exposed kidney, spatial and temporal resolution were significantly reduced.