Contrast agents: innovations and potential applications for body MR angiography.
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Contrast Media↗
Biomedical subjects
Maureen N Hood
Publications and source records attributed to Maureen N Hood.
Major vascular anomalies in Turner syndrome: prevalence and magnetic resonance angiographic features.
BACKGROUND: Turner syndrome (TS) is associated with aortic coarctation and dissection; hence, echocardiographic evaluation of all patients is currently recommended. X-ray angiography in clinically symptomatic patients has suggested a range of other vascular anomalies, but the true prevalence of such lesions in TS is unknown. To better understand the prevalence and pathogenesis of cardiovascular defects in TS, we prospectively evaluated a group of asymptomatic adult volunteers with TS using magnetic resonance (MR) angiography. METHODS AND RESULTS: A total of 85 adults with TS and 27 normal female adult volunteers underwent gadolinium-enhanced 3D MR angiography. A high prevalence of aortic anomalies was seen in women with TS, including elongation of the transverse arch (49%), aortic coarctation (12%), and aberrant right subclavian artery (8%). Venous anomalies were also prominent, including persistent left superior vena cava (13%) and partial anomalous pulmonary venous return (13%). None of these anomalies were found in healthy female controls. The constellation of elongation of the transverse arch, aortic coarctation, and persistent left superior vena cava was significantly associated with women with TS. Neck webbing and increased thoracic anterior-to-posterior dimension diameters were strong predictors for arterial and venous anomalies. CONCLUSIONS: Thoracic vascular anomalies are common in TS, occurring in approximately 50% of a group not preselected for cardiovascular disease. The highly significant association between neck webbing, increased chest diameter, and these vascular anomalies suggests that in utero, centrally localized lymphatic obstruction may contribute to these cardiovascular deformities in TS. Improved recognition of these often-undetected vascular lesions may be important for identification of patients in need of closer cardiovascular monitoring.
Adult↗
MRA of the thoracic vessels.
Magnetic resonance imaging (MRI) is well suited for the noninvasive evaluation of the thoracic vasculature, and with improvements in scanner technology, the ability of MR to illustrate the thoracic vessels has significantly improved. Dedicated vascular software and pulse sequences have become commercially available, and fast imaging, in particular, has facilitated the time-efficient and comprehensive MR evaluation of most thoracic vascular lesions. Over the years, a host of black and bright blood MRI methods have evolved into practical tools for illustration of the thoracic vessels. As with other MR applications, successful vascular depiction relies significantly on the proper selection and prescription of imaging pulse sequences. In this article, these methods with their specific technical and practical pitfalls for thoracic magnetic resonance angiography (MRA) will be discussed. Current clinical indications for thoracic MRA will also be illustrated.
Aortic Diseases↗
MR angiography using steady-state free precession.
Contrast-enhanced MR angiography (CE-MRA) using steady-state free precession (SSFP) pulse sequences is described. Using SSFP, vascular structures can be visualized with high signal-to-noise ratio (SNR) at a substantial (delay) time after the initial arterial pass of contrast media. The peak blood SSFP signal was diminished by <20% 30 min after the initial administration of 0.2 mmol/kg of Gd-chelate. The proposed method allows a second opportunity to study arterial or venous structures with high image SNR and high spatial resolution. A mask subtraction scheme using spin echo SSFP-S(-) acquisition is also described to reduce stationary background signal from the delayed SSFP angiography images.
Adult↗
High-resolution gadolinium-enhanced 3D MRA of the infrapopliteal arteries. Lessons for improving bolus-chase peripheral MRA.
Peripheral magnetic resonance angiography (MRA) is growing in use. However, methods of performing peripheral MRA vary widely and continue to be optimized, especially for improvement in illustration of infrapopliteal arteries. The main purpose of this project was to identify imaging factors that can improve arterial visualization in the lower leg using bolus chase peripheral MRA. Eighteen healthy adults were imaged on a 1.5T MR scanner. The calf was imaged using conventional three-station bolus chase three-dimensional (3D) MRA, two dimensional (2D) time-of-flight (TOF) MRA and single-station Gadolinium (Gd)-enhanced 3D MRA. Observer comparisons of vessel visualization, signal to noise ratios (SNR), contrast to noise ratios (CNR) and spatial resolution comparisons were performed. Arterial SNR and CNR were similar for all three techniques. However, arterial visualization was dramatically improved on dedicated, arterial-phase Gd-enhanced 3D MRA compared with the multi-station bolus chase MRA and 2D TOF MRA. This improvement was related to optimization of Gd-enhanced 3D MRA parameters (fast injection rate of 2 mL/sec, high spatial resolution imaging, the use of dedicated phased array coils, elliptical centric k-space sampling and accurate arterial phase timing for image acquisition). The visualization of the infrapopliteal arteries can be substantially improved in bolus chase peripheral MRA if voxel size, contrast delivery, and central k-space data acquisition for arterial enhancement are optimized. Improvements in peripheral MRA should be directed at these parameters.
Adult↗
Renal masses: quantitative assessment of enhancement with dynamic MR imaging.
PURPOSE: To establish a quantitative magnetic resonance (MR) imaging contrast enhancement criterion for distinguishing cysts from solid renal lesions. MATERIALS AND METHODS: Regions of interest were measured in 74 patients with renal lesions evaluated by means of dynamic contrast material-enhanced MR imaging with serial breath-hold spoiled gradient-echo acquisitions. Sensitivity for renal tumors and specificity for renal cysts were established by using percentage of enhancement thresholds that varied between 5% and 35%. RESULTS: The mean percentage of enhancement at MR imaging for the 50 renal cysts was less than 5%; for the 50 renal tumors, it was 97% or higher. With use of a threshold percentage of enhancement of 15% and results obtained between 2 and 4 minutes after administration of contrast material, all malignancies (sensitivity for tumor, 100%) were diagnosed, and there were 6% or fewer false-positive tumor diagnoses. Lower thresholds resulted in unacceptably high false-positive rates (ie, cysts that appeared to enhance-pseudoenhancement), whereas higher threshold values (>20%) resulted in an unacceptably lower sensitivity for tumors. CONCLUSION: The optimal percentage of enhancement threshold for distinguishing cysts from malignancies with the imaging technique prescribed was 15%, and the optimal timing for measurement was 2-4 minutes after administration of contrast material.
Adult↗
Three-dimensional phase-contrast magnetic resonance angiography: a useful clinical adjunct to gadolinium-enhanced three-dimensional renal magnetic resonance angiography?
OBJECTIVE: To assess the value of three-dimensional (3D) phase-contrast (PC) magnetic resonance angiography (MRA) after gadolinium (Gd)-enhanced 3D MRA for renal artery imaging. METHODS: Twenty-one patients with suspected renal artery hypertension were reviewed. All studies included Gd-enhanced 3D MRA and 3D PC MRA. Blinded interpretation of the images was performed for each technique independently and in combination. Conventional X-ray angiography was used for diagnostic correlation when available. RESULTS: Renal artery stenosis was present in 7 (16.3%) of 43 renal arteries, confirmed by X-ray angiography. MRA images demonstrated 100% sensitivity and 74% specificity for Gd-enhanced 3D MRA and 100% sensitivity and 94% specificity for 3D PC MRA. All vessels were diagnosed correctly when both image sets were viewed. CONCLUSION: 3D PC MRA can improve the specificity of renal MRA by decreasing the number of false-positive Gd-enhanced 3D MRA interpretations.
Female↗
Computerized information management for institutional review boards.
The use of human subjects for medical research in most industrialized nations requires the scientific and ethical scrutiny of research proposals by a governing institutional review board (IRB) or its equivalent. As part of their primary charge to protect human subjects, IRBs are responsible for the regulatory oversight of not only the research protocol itself but also the research conduct of the investigators and, if applicable, the funding sponsor. This article will discuss the regulatory requirements for an accurate account of IRB protocols and investigators and present an overview of the general flow of information for an IRB protocol. The current and potential uses of information management systems by IRBs will also be reviewed and accompanied by a discussion of the potential advantages and disadvantages of various computerized information systems for management of clinical research.
Ethics Committees, Research↗