Magnetic resonance imaging with computed tomography of a renal leiomyoma

Renal leiomyoma are rare, benign tumors of the kidney. There is little information about the imaging of these tumors with modern modalities. We present a case of computed tomographic (CT) and magnetic resonance (MR) imaging of a large renal leiomyoma.     

Magnetic resonance tomography of the heart in healthy persons

Potentialities of MR-tomography of the heart were studied in 20 healthy persons. Synchronization with the cardiac cycle on ECG was used in 15 cases. The VMT-1100 MR-tomograph (Brucker, FRG) was employed. The spinecho technique was used. MR-tomography of the heart was performed in axial, sagittal, frontal and oblique planes with relation to the anatomical heart axes. All major heart structures and mediastinal vascular bundles were clearly visualized on MR-images obtained by means of synchronization with the cardiac cycle. In some cases pericardial zones and fragments of coronary arteries were seen. MR-tomography permitted imaging of the heart in a desired phase of the cardiac cycle. This method was shown to be highly informative, providing quality images of the cardiac chambers and walls in different planes, permitting their quantitative and qualitative assessment. Further improvement of the method and programs for it will permit raising its diagnostic potentialities in studies on the heart.     

Magnetic resonance tomography of the heart in hypertrophic cardiomyopathy

The authors provide the results of the use of magnetic resonance tomography (MRT) in examining 20 patients suffering from hypertrophic cardiomyopathy (HCMP). MRT was made using an apparatus with a field force of 0.23 synchronized with the ECG. The MR-sections were performed both in transverse and inclined planes oriented along the long axis of the left ventricle. MRT made it possible to identify and to assess with a high accuracy asymmetric hypertrophy of the left ventricle myocardium including the cases with apical localization of hypertrophy. Analysis of the data showed a certain decrease of the left ventricle cavity in the systole, dilatation of the left atrium and pronounced hypertrophy of the myocardium (mainly of the interventricular septum). The asymmetry coefficient amounted to 2.1. Correlation of the MRT data and two-dimensional ultrasound cardiography readings demonstrated good comparability of the results obtained with the use of both methods. MRT can be applied in the diagnosis of HCMP in cases where it is difficult to carry out ultrasound cardiography as well as for diagnosis verification provided the results derived with the use of other research methods are inconclusive.     

Magnetic resonance tomography of the heart in dilated cardiomyopathy

NMR-tomography using a spin-echo technique, ECG synchronization in exposure to 0.23 T magnetic field was performed in 13 patients with dilated cardiomyopathy (DCMP). The results were correlated with echocardiography findings. NMR-tomography provided a good image of cardiac chambers dilatation, their size being in agreement with that shown by echocardiography. No significant differences in myocardial relaxation time T2 was recorded in DCMP patients compared to normal subjects. NMR-tomography can be successfully employed in cardiac investigations in case of complicated echocardiography.     

Magnetic resonance imaging vs. ultrafast computed tomography for cardiac diagnosis

Ultrafast computed tomography (CT) and magnetic resonance imaging (MRI) generate high resolution tomographic cardiac images. Ultrafast CT requires intravenous injection of x-ray contrast combined with an image acquisition time of 50 msec. MRI requires no contrast injection, but has relatively long acquisition times due to gating. Both technologies can be used to evaluate cardiac chamber and great vessel dimensions, intracardiac and extracardiac masses, ventricular hypertrophy, left ventricular mass, congenital heart disease, regional and global left ventricular function, right ventricular function and pericardium. MRI is highly useful for detection and semi-quantitation of valvular regurgitation while ultrafast CT is not. Aortic and mitral valve stenosis can be detected by both, but MRI is the preferred study. Though both techniques can be used to assess coronary artery bypass graft status, ultrafast CT is the preferred method. It is concluded that ultrafast CT and MRI have broad applications for cardiac diagnosis.     

Magnetic resonance imaging as a diagnostic adjunct to Wernicke encephalopathy in the ED

This report describes usefulness of magnetic resonance imaging (MRI) for the evaluation of the patient suspected of Wernicke encephalopathy (WE). Magnetic resonance imaging shows characteristic findings of symmetric hyperintense lesions predominantly located in the bilateral medial thalami, the periaqueductal regions, and the mamillary bodies. The diagnosis of Wernicke encephalopathy has been based generally on history and clinical symptoms. We now believe that MRI could be used as a diagnostic adjunct in the patient suspected of WE.     

Gadolinium-DTPA as an oral contrast medium in magnetic resonance tomography

80 patients with tumorous or inflammatory abdominal diseases were investigated with the paramagnetic MRT contrast medium Gadolinium-DTPA (Gd-DTPA, 1 mM, 15 g/l mannitol, 6-16 ml per kg body weight) at 0.5 Tesla with T1-, proton density and T2-weighted SE- and gradient-echo sequences. 53 patients were investigated also before the contrast medium was given. Gd-DTPA showed hyperintense labelling of the intestinal loops that was detectable with all excitation sequences and was constant over all phases of the passage. In 35 of the 53 patients investigated before and after application of Gd-DTPA lesions were better imaged while diagnostic improvements, especially for smaller lesions, were achieved in 5 of 80 patients. One third of the patients reported slight meteorism and diarrhoea after the mannitol-containing suspension.     

Magnetic resonance electrical impedance tomography (MREIT) for high-resolution conductivity imaging

Cross-sectional imaging of an electrical conductivity distribution inside the human body has been an active research goal in impedance imaging. By injecting current into an electrically conducting object through surface electrodes, we induce current density and voltage distributions. Based on the fact that these are determined by the conductivity distribution as well as the geometry of the object and the adopted electrode configuration, electrical impedance tomography (EIT) reconstructs cross-sectional conductivity images using measured current-voltage data on the surface. Unfortunately, there exist inherent technical difficulties in EIT. First, the relationship between the boundary current-voltage data and the internal conductivity distribution bears a nonlinearity and low sensitivity, and hence the inverse problem of recovering the conductivity distribution is ill posed. Second, it is difficult to obtain accurate information on the boundary geometry and electrode positions in practice, and the inverse problem is sensitive to these modeling errors as well as measurement artifacts and noise. These result in EIT images with a poor spatial resolution. In order to produce high-resolution conductivity images, magnetic resonance electrical impedance tomography (MREIT) has been lately developed. Noting that injection current produces a magnetic as well as electric field inside the imaging object, we can measure the induced internal magnetic flux density data using an MRI scanner. Utilization of the internal magnetic flux density is the key idea of MREIT to overcome the technical difficulties in EIT. Following original ideas on MREIT in early 1990s, there has been a rapid progress in its theory, algorithm and experimental techniques. The technique has now advanced to the stage of human experiments. Though it is still a few steps away from routine clinical use, its potential is high as a new impedance imaging modality providing conductivity images with a spatial resolution of a few millimeters or less. This paper reviews MREIT from the basics to the most recent research outcomes. Focusing on measurement techniques and experimental methods rather than mathematical issues, we summarize what has been done and what needs to be done. Suggestions for future research directions, possible applications in biomedicine, biology, chemistry and material science are discussed.     

Magnetic resonance enteroclysis compared with conventional enteroclysis and computed tomography enteroclysis: a critically appraised topic

Recent advances in CT and MR technology, particularly the advent of multidetector CT (MDCT), the advent of rapidly changing gradients in industry standard MRI scanners, enabling ultrafast sequences, have led to an expansion in the role of cross sectional imaging in the investigation of small bowel disorders. We conducted an evidence-based review of MR enteroclysis (MRE) and how it performs in comparison to CT enteroclysis (CTE) and the gold standard of conventional enteroclysis (CE) for diagnosis of small bowel Crohn’s disease and small bowel neoplasia. We used the standard 5 step evidence-based medicine method of ask, search, appraise, apply and evaluate. We found 3 relevant level 1B studies, and one level 3B study. No studies evaluating MRE in small bowel neoplasia were found. MRE does not perform as well as CE in evaluation of fine mucosal detail, but the additional extraluminal detail, and absence of ionising radiation enhances its overall performance. It was not possible to establish the relative diagnostic performances of MRE and CTE from existing literature. CTE does involve patient irradiation. For patients in whom jejunal intubation and enteroclysis is considered to evaluate the small bowel, MRE should be considered the first-line investigation, local resources and expertise permitting.     

Magnetic resonance imaging identifies occult hip fractures missed by 64-slice computed tomography

Background

Citing the enhanced resolution of 64-slice computed tomography (CT), some clinicians now use CT instead of magnetic resonance imaging (MRI) to detect occult hip fracture.

Objective

Our objective was to determine the incidence of occult hip fractures missed by 64-slice CT but detected by MRI.

Methods

We reviewed the medical records and radiology reports of patients over age 60 years with a hip fracture (acetabular, intertrochanteric, trochanteric, femoral neck, and femoral head) during a 3-year period, January 1, 2007 through December 31, 2009. We also reviewed all hip CT and MRI scans ordered during that period. Occult fractures were those visualized on CT or MRI but with negative plain films. We compared CT and MRI findings, and calculated percentages and 95% confidence intervals (CIs).

Results

Of 235 hip fractures, 211 were visible on initial plain films (90%, 95% CI 85–93%) and 24 (10%, 95% CI 6–15%) were occult. Eighteen occult fractures (7.6%, 95% CI 4.6–11.8%) were identified by CT (MRI not done), one (0.4%, 95% CI 0–2%) by MRI (CT not done), one (0.4%, 95% CI 0–2%) by both CT and MRI, and 4 patients (1.7%, 95% CI 0.5–4.3%) had a positive MRI but negative CT scan.

Conclusion

Although 64-slice CT detected the majority of occult fractures, it missed four (2%) significant fractures detected by MRI. CT scan is helpful in the diagnosis of occult hip fracture, but one should not completely exclude the diagnosis based on a negative 64-slice CT scan in a patient with persistent, localized hip pain who cannot bear weight.     

Magnetic resonance imaging in a routine clinical setting

The results of magnetic resonance imaging (MRI) examinations in the first 1,000 consecutive patients who were studied by this technique at our institution were reviewed to determine the disease states encountered, the sensitivity and accuracy of results, and the value of the examination as compared with computed tomography and other imaging procedures. The MRI device was a 0.15-tesla resistive magnet that used a variety of saturation recovery, spin echo, and inversion recovery pulse sequences to produce images. MRI was found equal to or superior to other imaging techniques in most cases. Exceptions included organs or body regions that are prone to excessive respiratory or vascular motion, lesions that necessitate exquisite spatial resolution for diagnosis, and lesions in which angulation of the viewing plane is necessary for optimal depiction. Fresh blood and calcification within a lesion were also difficult to detect with use of MRI.     

Magnetic resonance (MR) imaging as a marker for multiple sclerosis.

Since the diagnosis of multiple sclerosis (MS) may not be clear on clinical grounds or from other paraclinical tests, and due to the necessary assessment of new pharmacological therapeutical agents which demand objective outcome parameters for relatively short trials, magnetic resonance imaging (MRI) is not only used to diagnose MS, but is also broadly used to monitor disease progression. In exploratory trials, where MRI is used as a primary outcome measure, serial scans are used to detect disease activity as the number of active lesions showing signal enhancement after gadolinium administration. When the results is positive, the drug has to be tested further in a phase III study, using clinical endpoints as primary outcome measurements. MRI can be used as a secondary outcome measure. Given the uncertain relation between MRI and clinical findings, MR findings provide only supportive evidence. Serial scans (usually yearly) are used to monitor disease progression as an increase in total lesion load. Consequently, reproducibility of the lesions and therefore spatial resolution, should be maximized. Several putative treatments have been assessed using MR monitoring in phase II and phase III trials. A multitude of phase II trials have shown that it is indeed possible to demonstrate that MR is capable of showing, even in small groups, whether new drugs have any effect on the development of lesions.     

Magnetic resonance imaging appropriate for construction of subject-specific head models for diffuse optical tomography

Subject-specific head models of which their geometry is based on structural magnetic resonance images are essential to accurately estimate the spatial sensitivity profiles for image reconstruction in diffuse optical tomography. T1-weighted magnetic resonance images, which are commonly used for structural imaging, are not sufficient for the threshold-based segmentation of the superficial tissues. Two types of pulse sequences, which provide a high contrast among the superficial tissues, are introduced to complement the segmentation to construct the subject-specific head models. The magnetic resonance images acquired by the proposed pulse sequences are robust to the threshold level and adequate for the threshold-based segmentation of the superficial tissues compared to the T1- and T2-weighted images. The total scan time of the proposed pulse sequences is less than one-fourth of that for the T2-weighted pulse sequence.OCIS codes: (170.2655) Functional monitoring and imaging, (170.3660) Light propagation in tissues     

Anesthesia in magnetic resonance tomography

Sixty patients were anesthesized for MRI. Intravenous and/or intramuscular anesthesia with ketamine, diazepam, pipolphen (promethazine) was supplemented by aminazine (chlorpromazine) or tisercin for adult patients. Spontaneous respiration was maintained, which helped avoid problems with endotracheal intubation and assisted ventilation. The method is safe, economic, and its side effects are negligible. Main features of MRI and specific anesthesiological problems associated with this method are discussed.