Philip A. Hodnett

Evaluation of Peripheral Arterial Disease with Nonenhanced Quiescent-Interval Single-Shot MR Angiography

PURPOSE To assess the diagnostic performance of quiescent-interval single-shot (QISS) magnetic resonance (MR) angiography, a nonenhanced two-dimensional electrocardiographically gated single-shot balanced steady-state free precession examination for the evaluation of symptomatic chronic lower limb ischemia. MATERIALS AND METHODS For this prospective institutional review board-approved, HIPAA-compliant study, the institutional review board waived the requirement for informed patient consent. The QISS nonenhanced MR angiography technique was evaluated in a two-center trial involving 53 patients referred for lower extremity MR angiography for suspected or known chronic peripheral arterial disease (PAD), with contrast material-enhanced MR angiography serving as the noninvasive reference standard. The accuracy of stenosis assessments performed with the nonenhanced MR angiography sequence was evaluated relative to the reference standard. Per-segment, per-region, and per-limb sensitivities and specificities were calculated, and assessments were considered correct only if they were in exact agreement with the reference standard-derived assessments. Generalized estimating equation (GEE) modeling with use of an unstructured binomial logit analysis was used to account for clustering of multiple measurements per case. The sensitivity and specificity of QISS MR angiography for the determination of nonsignificant (<50%) versus significant (50%-100%) stenosis were compared with the sensitivity and specificity of the reference standard. RESULTS The diagnostic performance of nonenhanced MR angiography was found to be nearly equivalent to the diagnostic performances of contrast-enhanced MR angiography and digital subtraction angiography. Non-GEE segment-based analysis revealed that for the two reviewers, nonenhanced MR angiography had sensitivities of 89.7% (436 of 486 segments) and 87.0% (423 of 486 segments) and specificities of 96.5% (994 of 1030 segments) and 94.6% (973 of 1028 segments). CONCLUSION QISS nonenhanced MR angiography offers an alternative to currently used imaging tests for symptomatic chronic lower limb ischemia, for which the administration of iodinated or gadolinium-based contrast agents is contraindicated.

Peripheral arterial disease in a symptomatic diabetic population: prospective comparison of rapid unenhanced MR angiography (MRA) with contrast-enhanced MRA.

OBJECTIVE The joint guidelines of the American College of Cardiology and American Heart Association support the use of contrast-enhanced MR angiography (CEMRA) to diagnose the location and degree of stenosis in patients with known or suspected peripheral arterial disease (PAD). The high prevalence of chronic renal impairment in diabetic patients with PAD and the need for high doses of gadolinium-based contrast agents place them at risk for nephrogenic systemic fibrosis. The purpose of our study was to evaluate the accuracy of the rapid technique of quiescent-interval single-shot (QISS) unenhanced MR angiography (MRA) compared with CEMRA for the diagnosis in diabetic patients referred with symptomatic chronic PAD. SUBJECTS AND METHODS This prospective two-center study evaluated 25 consecutive diabetic patients with documented or suspected symptomatic PAD. Both centers used identical imaging protocols. Images were independently analyzed by two radiologists. A subgroup analysis was performed of patients who were also assessed with digital subtraction angiography (DSA) as part of the standard-of-care protocol before revascularization. RESULTS For this study, 775 segments were analyzed. On a per-segment basis, the mean values of the diagnostic accuracy of unenhanced MRA compared with reference CEMRA for two reviewers, reviewers 1 and 2, were as follows: sensitivity, 87.4% and 92.1%; specificity, 96.8% and 96.0%; positive predictive value, 90.8% and 94.0%; and negative predictive value, 95.5% and 94.6%. Substantial agreement was found when overall DSA results were compared with QISS unenhanced MRA (κ = 0.68) and CEMRA (κ = 0.63) in the subgroup of patients who also underwent DSA. There was almost perfect agreement between the two readers for stenosis scores, with Cohens kappa values being greater than 0.80 for both MRA techniques. CONCLUSION The results of our study indicate that QISS unenhanced MRA is an accurate noncontrast alternative to CEMRA for showing clinically significant arterial disease in patients with diabetes with symptomatic PAD.

Stimulated echo diffusion tensor imaging and SPAIR T2 -weighted imaging in chronic exertional compartment syndrome of the lower leg muscles.

To evaluate the performance of diffusion tensor imaging (DTI) in the evaluation of chronic exertional compartment syndrome (CECS) as compared to T2‐weighted (T2w) imaging.

MR Imaging of Muscle Injury

Although most muscle injuries in the athlete are diagnosed clinically, MR imaging is an excellent noninvasive diagnostic adjunct to clinical examination, which allows the site and severity of muscle injury to be assessed accurately, influencing therapy and overall outcome. There has been a rapid expansion in the clinical use of MR imaging during the past decade. MR imaging conveys unparalleled anatomic resolution and high sensitivity in the detection of acute and chronic muscle abnormalities. This article discusses the spectrum of muscle injuries, emphasizing the important role of MR imaging in their diagnosis and management.

PRES (posterior reversible encephalopathy syndrome), a rare complication of tacrolimus therapy

With increasing numbers of solid organ and hematopoietic stem cell transplantations being performed, there have been significant increases in the use of immunosuppressive agents such as cyclosporine and tacrolimus. Posterior reversible encephalopathy syndrome (PRES) is a serious complication of immunosuppressive therapy use following solid organ or stem cell transplants. Clinical findings including headache, mental status changes, focal neurological deficits, and/or visual disturbances. Associated with these are characteristic imaging features of subcortical white matter lesions on computed tomography (CT) or magnetic resonance imaging (MRI). The changes in the subcortical white matter are secondary to potentially reversible vasogenic edema, although conversion to irreversible cytotoxic edema has been described. These imaging findings predominate in the territory of the posterior cerebral artery. Many studies have shown that the neurotoxicity associated with tacrolimus may occur at therapeutic levels. In most cases of PRES, the symptom complex is reversible by reducing the dosage or withholding the drug for a few days. While PRES is an uncommon complication, it is associated with significant morbidity and mortality if it is not expeditiously recognized. MRI represents the most sensitive imaging technique for recognizing PRES. This report highlights the value of MRI in prompt recognition of this entity, which offers the best chance of avoiding long-term sequelae.

Overuse ankle injuries in professional Irish dancers

BACKGROUND Overuse ankle injuries have been described in elite athletes and professional ballet dancers however the spectrum of injuries experienced by professional Irish dancers has not been defined. METHODS A troupe of actively performing dancers from an Irish-dance show were recruited (eight male, ten female; mean age, 26 years). The prevalence of overuse injuries in the right ankle was determined from magnetic resonance imaging. Foot and ankle self-report questionnaires were also completed (AOFAS and FAOS). RESULTS Only three ankles were considered radiologically normal. Achilles tendinopathy, usually insertional, was the most frequent observation (n=14) followed by plantar fasciitis (n=7), bone oedema (n=2) and calcaneocuboid joint degeneration (n=2). There were limited correlations between MRI patterns and clinical scores indicating that many conditions are sub-clinical. Dancers with ankle pain had poor low (p=0.004) and high (p=0.013) level function. CONCLUSIONS Overuse ankle injuries are common in Irish dancers. Incorporating eccentric exercises and plantar fascia stretching into a regular training program may benefit this population.

MR Imaging of Overuse Injuries of the Hip

The aim of this article is to emphasize the importance of MR imaging in the evaluation of chronic hip pain and overuse injuries. Image interpretation of the hip can be difficult because of the complex anatomy and the varied pathology that athletes can present with, such as labral and cartilaginous injuries, surrounding soft tissue derangement involving muscles or tendons, and osseous abnormalities. The differential diagnosis in adults is diverse and includes such common entities as stress fracture, avulsive injuries, snapping-hip syndrome, iliopsoas bursitis, femoroacetabular impingement syndrome, tendinosis, and tears of the gluteal musculature.

Nonenhanced MR Angiography of the Hand with Flow-Sensitive Dephasing–prepared Balanced SSFP Sequence: Initial Experience with Systemic Sclerosis

PURPOSE To compare the image quality and degree of vessel narrowing at flow-sensitive dephasing (FSD) magnetic resonance (MR) angiography of the hands with those at contrast material-enhanced MR angiography of the hands in patients with systemic sclerosis. MATERIALS AND METHODS In a single-center study with institutional review board approval and HIPAA compliance, six healthy volunteers and six patients with systemic sclerosis were imaged at 1.5-T nonenhanced FSD MR angiography followed by contrast-enhanced MR angiography. Sixteen vascular segments in four vessel groups were evaluated for image quality and assessed semiquantitatively for stenosis degree by using Likert scales. The nonparametric Wilcoxon signed rank test was used to perform pairwise comparisons of the MR angiographic techniques. P < .05 indicated statistical significance. RESULTS Performing FSD MR angiography, as compared with time-resolved MR angiography and high-spatial-resolution MR angiography, improved the image quality for all arterial segments combined in the control (mean score, 2.9 [FSD] vs 3.7 [time-resolved technique] and 3.1 [high-spatial-resolution technique]) and patient (mean score, 4.0 [FSD] vs 4.2 [time-resolved technique] and 4.3 [high-spatial-resolution technique]) groups. In the control subjects, FSD angiography depicted proper digital artery stenosis that was less severe (mean grade, 0.7) than that seen with the time-resolved (mean grade, 1.6) and high-spatial-resolution (mean grade, 1.0) techniques. In the patient group, FSD angiography depicted lower degrees of stenosis, with a lower mean grade for all segments combined (1.3) compared with the corresponding mean grades for time-resolved (1.5) and high-spatial-resolution (1.8) MR angiography. CONCLUSION Preliminary data indicate that the proposed nonenhanced FSD MR angiographic technique is an improvement over existing contrast-enhanced techniques for evaluation of the hand vasculature in vasospastic disorders of the hand. Further technical improvements and a systematic clinical study are warranted.

MDCT bolus tracking data as an adjunct for predicting the diagnosis of pulmonary hypertension and concomitant right-heart failure.

OBJECTIVE The purpose of this study was to investigate the utility of bolus-triggering data from pulmonary CT angiography for predicting the diagnosis of pulmonary hypertension (PH) and right ventricular dysfunction (RVD) and to test its performance against previously established CT signs of PH. MATERIALS AND METHODS Automated bolus-triggering data from pulmonary CT angiograms of 101 patients were correlated with echocardiographic findings and a variety of CT-derived indexes of PH and RVD, including right and left ventricular minor axis diameter; pulmonary artery (PA), aortic, and superior vena caval diameters; right ventricular thickness; contrast reflux; and configuration of the interventricular septum. For bolus triggering, a region of interest was placed in the main PA. Time to threshold, defined as the time from the beginning of contrast injection to the time attenuation exceeded the threshold (100 HU), was measured. On the basis of results of two consecutive echocardiographic studies, subjects were divided into control and PH groups. The latter group was subdivided into PH without RVD and PH with RVD. Time to threshold values were compared between groups and correlated with standard CT-derived parameters. RESULTS Significant differences between groups were found in time to threshold, PA and right ventricular diameters, and PA-to-aorta and right ventricular-to-left ventricular ratios. Time to threshold had an incremental pattern from the control group (6.6 ± 1.0 seconds) to PH without RVD (9.2 ± 2.4 seconds) and PH with RVD (12.1 ± 3.4 seconds) (p < 0.001). The optimal diagnostic performance of time to threshold for revealing the presence of PH and RVD was at cutoff values of 7.75 and 8.75 seconds, respectively. Time to threshold had a strong direct correlation with PA diameter. In multivariable analyses, time to threshold was identified as a significant predictor of PH and RVD. The specificity of time to threshold and PA diameter together was higher than that of PA diameter alone. CONCLUSION Measurement of time to threshold of contrast enhancement derived from bolus-timing data at MDCT may be a useful adjunctive tool for diagnosing PH and consequent RVD.

Nonenhanced methods for lower-extremity MRA: a phantom study examining the effects of stenosis and pathologic flow waveforms at 1.5T.

To evaluate the signal properties of 2D time of flight (TOF), quiescent‐interval single‐shot (QISS), ECG‐gated 3D fast spin‐echo (FBI), and ungated 3D fast spin‐echo ghost (Ghost) magnetic resonance angiography (MRA) over a range of flow velocities in a pulsatile flow phantom with a 50% diameter stenosis at 1.5T.