A longitudinal study of patients with cirrhosis treated with L-ornithine L-aspartate, examined with magnetization transfer, diffusion-weighted imaging and magnetic resonance spectroscopy

The presence of overt hepatic encephalopathy (HE) is associated with structural, metabolic and functional changes in the brain discernible by use of a variety of magnetic resonance (MR) techniques. The changes in patients with minimal HE are less well documented. Twenty-two patients with well-compensated cirrhosis, seven of whom had minimal HE, were examined with cerebral 3 Tesla MR techniques, including T1- and T2-weighted, magnetization transfer and diffusion-weighted imaging and proton magnetic resonance spectroscopy sequences. Studies were repeated after a 4-week course of oral L-ornithine L-aspartate (LOLA). Results were compared with data obtained from 22 aged-matched healthy controls. There was no difference in mean total brain volume between patients and controls at baseline. Mean cerebral magnetization transfer ratios were significantly reduced in the globus pallidus and thalamus in the patients with cirrhosis irrespective of neuropsychiatric status; the mean ratio was significantly reduced in the frontal white matter in patients with minimal HE compared with healthy controls but not when compared with their unimpaired counterparts. There were no significant differences in either the median apparent diffusion coefficients or the mean fractional anisotropy, calculated from the diffusion-weighted imaging, or in the mean basal ganglia metabolite ratios between patients and controls. Psychometric performance improved in 50% of patients with minimal HE following LOLA, but no significant changes were observed in brain volumes, cerebral magnetization transfer ratios, the diffusion weighted imaging variables or the cerebral metabolite ratios. MR variables, as applied in this study, do not identify patients with minimal HE, nor do they reflect changes in psychometric performance following LOLA

Time-resolved projection angiography after bolus injection of contrast agent

A method for MR angiography after bolus injection of a normal dose (0.1 mmol/kg) of contrast agent is presented. Projection angiograms are acquired with a non-slice selective Snapshot FLASH sequence with a time resolution of 1 s per image or better. Typically 40 to 60 images are acquired consecutively after bolus injection of a contrast agent. The signal from vessels can be separated from background by postprocessing based on the observed temporal evolution of the signal intensities during bolus passage. The subsecond projection MR-DSA is a reliable and robust technique to produce high resolution anatomical images of the vascular system avoiding the necessity of exact timing of the contrast agent bolus. It also supplies functional information about the hemodynamics in the observed region including perfusion

Novel variant of reversed midgut rotation – retro-arterial proximal jejunum and transverse colon: a case report and review of the literature

Abstract Background Reversed rotation of the midgut is the rarest variation of midgut malrotations, which are congenital disorders that result from aberrant rotation and fixation of the midgut during embryological development. Common complications of these disorders are small bowel obstruction by volvulus or peritoneal bands, usually occurring in early infancy. Case presentation A 23-year-old Caucasian woman presented with recurrent abdominal pain. A contrast-enhanced multidetector computed tomography study revealed a novel variant of reversed rotation of the midgut. Besides the specific finding of a retro-arterial transverse colon, we also found the proximal jejunum to cross posterior to the mesenteric root, a variation that has not been reported in the literature so far. In this case, substantial symptomatic relief was achieved with conservative management. Conclusions The hypothesis of a double reversed rotation of the pre-arterial segment of the umbilical loop around the superior mesenteric artery axis provides a possible explanation for this anomaly. There is no evidence-based consensus on the management of patients presenting with non-symptomatic or mildly symptomatic intestinal malrotations. In this case, radiologic and clinical presentations excluded acute small bowel obstruction, and surgical intervention was avoided

Fast functional MRA using time-resolved projection MR angiography with correlation analysis

Most recently, time-resolved 2D MRA after injection of a contrast agent bolus for various applications has been proposed. Similar to conventional digital subtraction angiography (DSA), 2D MR DSA offers the ability to observe the dilution of the bolus in the vascular system during the passage with a temporal resolution considerably below 1 sec. The purpose of this paper is to present strategies to improve the inherent low signal-to-noise ratio of 2D angiograms while retaining some temporal resolution. This can be achieved by applying algorithms for time series analysis as used in functional MRI. The significantly improved image quality is demonstrated on examples from clinical studies from bronchial MRA as well as cardiovascular MRA. In addition to the increased signal-to-noise ratio, correlation analysis leads to suppression of background signals and to a better discrimination of overlapping vessels. Further improvements in the temporal discrimination of vessels is afforded by the use of consecutive multiple contrast agent boli as demonstrated by numerical simulations and experiments. Magn Reson Med 43:303–309, 2000. © 2000 Wiley-Liss, Inc. In the last three years, the development of gradient systems for ultra fast imaging has made time-resolved projection angiography after administration of a bolus of contrast agent (c.a.) feasible (1, 2). Similar to conventional x-ray DSA, a thick slab or a non-slice selective projection through the volume is imaged consecutively with a temporal resolution below 1 sec, using an ultra-rapid T1-weighted gradient echo sequence. This offers the possibility to directly observe the dynamics of c.a. propagation. Due to the short image acquisition times, projection angiography is very insensitive to any kind of motion. This allows vascular imaging of the thorax without breathhold and even without synchronization of data acquisition to the ECG-signal. Moreover, the method avoids the requirements for exact bolus timing as in 3D MRA in which venous overlap obscure the delineation of the arteries when sampling of central k-space lines does not hit the peak concentration of the contrast agent in the arteries (3). Background signal that mainly arises from fatty tissue due to short T1 can be eliminated by (complex) subtraction of an image acquired before the c.a.-injection. Additional depth information can be obtained by acquiring images alternatively under different projection angles. Several clinical application of 2D MR DSA have already been reported, demonstrating the diagnostic feasibility of the method especially for vessel segments of the vascular system with short arterial transit and strong venous return like the carotid arteries, intracranial vessels or the pulmonary vessels (4–8). The major drawback of acquiring the 2D samples with a high temporal resolution is the low signal-to-noise ratio (SNR) of the projection images. The SNR can, of course, be improved by averaging over n consecutive projection images, which, however, will lead to a loss of functional information in the time resolved scan. The purpose of this paper is to propose and discuss the use of correlation analysis (9) as a post-processing strategy to improve the SNR in projection angiographic images while maintaining the functional information about the propagation of the c.a. bolus

Contrast-Enhanced Subtraction MR Angiography in Occlusive Disease of the Pelvic and Lower Limb Arteries: Results of a Prospective Intraindividual Comparative Study with Digital Subtraction Angiography in 76 Patients

Purpose: The purpose of this work was to evaluate the feasibility and clinical use of MR angiography (MRA) for examining the pelvic and lower limb arteries in patients with arterial occlusive disease. Method: Seventy-six patients with clinical signs of peripheral arterial occlusive disease were included in the study. MRA was performed using a fast contrast-enhanced high-resolution 3D technique that covered the area from the distal abdominal aorta to the distal lower limbs in two examination steps. Results: In all patients, diagnostic images comparable with those of conventional intraarterial digital subtraction angiography (DSA) could be obtained. No false-negative findings were seen in the iliac, femoral, or popliteal arteries. Ten to 16 of the mild stenoses and 6-14 of the severe stenoses, mainly in the crural vessels, were overgraded compared with intraarterial DSA. Particularly in patients with proximal severe obstructions or occlusions, the crural segments could be depicted more clearly due to decreased arterial runoff in conventional angiography. Conclusion: The consistency of the excellent depiction of the vascular territories of the distal aorta and the pelvic and lower limb arteries in a standardized setting suggests great potential for the use of MRA in the primary diagnosis of peripheral arterial occlusive disease