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M Deimling

Publications and source records attributed to M Deimling.

At least 55 records · Page 3Linked to original sources
PubMed1988

A new steady-state imaging sequence for simultaneous acquisition of two MR images with clearly different contrasts.

We present a new steady-state imaging sequence, which simultaneously allows in a single acquisition the formation of two MR images with clearly different contrasts. The contrast of the first image is FISP-like, whereas the second image is strongly T2-weighted. In principle the T2 values in the image can be calculated from the combination of the first and second images. We also show calculated T2 images.

Head↗
PubMed1988

[Clinical use of gradient echo sequences of longer repetition times].

Studies designed to optimise image contrasts of gradient echo sequences showed, that especially repetition times between 250 and 500 ms in combination with adequate echo times and flip angles provide new image contrasts. The clinical purpose of gradient echo sequences with longer TR was systematically evaluated in 450 patients. A major advantage of GE sequences was the low signal intensity of fat and bone tissue. On the other hand different pathologic changes showed a high signal intensity in comparison to T2 weighted spin echo sequences as well. With the possibility of multiple slices GE sequences were of outstanding diagnostic value especially in MR of soft tissue and of the musculoskeletal system. T2 weighted SE sequences provided no additional informations and could therefore be omitted in a great number of examinations.

Abdomen↗
PubMed1987

ECG-triggered arterial FLASH-MR flow measurement using an external standard.

In ECG-triggered FLASH-MR images, the inflow of unsaturated spins into the imaging plane results in the reproducible delineation of time variant flow in the arterial system. With the additional acquisition of an external reference image upstream the arterial vessel under investigation, the quantification of flow is possible with the FLASH-MR sequence in one measurement. The method allows the rapid measurement of arterial flow at least in great vessels.

Aorta, Abdominal↗
PubMed1987

[Rapid nuclear magnetic resonance tomography. Initial results of studies using the new gradient echo sequence].

In 60 patients with intracerebral lesions, examined by MRI, a new gradient-echo sequence was employed. This imaging technique uses excitation pulse angles smaller than 90 degrees and echoes are produced by an inversion of the read gradient. Since no 180 degrees pulse between successive excitations is necessary, very short repetition times can be used. Depending on matrix-size and signal averaging, MR imaging time can be reduced to approximately 5 to 40 seconds for single slice scan. For comparison, conventional T1- and T2-weighted spin-echo images were performed. Diagnostic results of the T1-weighted fast gradient-echo images corresponded with T1-weighted spin-echo images in 30% of cases. Diagnostic information was lower in 40% of cases. In the remainder of cases (30%) lesions were not detected with the gradient-echo technique. This especially applied to multiple sclerosis, infarctions and low-grade gliomas. Due to image artefacts and low contrast, visualization of small pathologic lesions was limited. Significant improvement of tumor visualization on gradient-echo scans was observed after injection of Gd-DTPA (0.1 mmol/kg).

Brain Diseases↗
PubMed1987

[MR tomographic demonstration of liquor pulsation].

With ECG-gated FLASH-sequences motion of cerebrospinal fluid (CSF) is demonstrated in axial slices of the zervikal vertebral column. The course of the movement is dissolved by signal enhancement of flowing structures in magnitude images and by velocity-dependent phases. It is shown with both methods, that the oscillation of the CSF within the cardiac cycle is superimposed by a directed movement, with is cranial directed in the lateral cervical subarachnoidal spaces and caudal in the ventral subarachnoidal spaces.

Cerebrospinal Fluid↗
PubMed1987

Cartilage disorders: comparison of spin-echo, CHESS, and FLASH sequence MR images.

Magnetic resonance (MR) imaging is known to be a suitable modality for the visualization of the hyaline cartilage and the fibrocartilage joint structures. To compare standard spin-echo (SE) images with water images obtained with the chemical shift selective (CHESS) sequence and with the fast low angle shot (FLASH) sequence, examinations were performed with all three sequences in eight volunteers and 28 patients with inflammatory degenerative and traumatic alterations of the knee, hip, and sacroiliac joints. Arthroscopic and/or surgical correlation were available in 16 patients; bone scanning and computed tomography of the sacroiliac joints were performed in four patients. CHESS-water and FLASH images proved superior to SE images in demonstrating hyaline cartilage disorders. There was no difference between SE, CHESS, and FLASH in the detection of fibrocartilage disorders. Short imaging times and satisfactory depiction of cartilage alterations make FLASH a promising method.

Adult↗
PubMed1986

[Importance of rapid gradient echo sequences for nuclear magnetic tomographic diagnosis of joint diseases].

The possibilities and limitations of rapid echo acquisition methods in various posttraumatic, degenerative and inflammatory diseases of the joints are demonstrated and discussed on the basis of a pilot study. It is evident that specific information important for clarifying effusions and meniscopathies is supplied especially by "water"-like images. Limitations of spatial resolution are at present still a limiting factor.

Humans↗
PubMed1986

Description of flow phenomena in magnetic resonance imaging.

The magnetic resonance (MR) signal from the hydrogen nuclei of blood is not only determined by the MR parameters T1, T2 and proton density, but is strongly dependent on the movement of the protons. Magnetic resonance imaging (MRI) offers therefore the possibility to visualize the distribution of moving spins, especially blood flow, noninvasively and without contrast agents; moreover, the velocity of the moving spins can be quantified. Flow phenomena in MRI are a pretentious field because the complicated hydrodynamics of the living system is coded in the MR signal; therefore, an understanding of the underlying physical principle of the MR signal is required to interpret and extract flow information from the image. However, rather simple theoretical and experimental models of fluid transport in vessels allow to explain the main features of various effects observed in images.

Blood Circulation↗
PubMed1985

[Nuclear spin tomography of the male pelvis. Methods, anatomy and initial clinical results].

A pilot study of MRI was carried out on three normal male volunteers and 15 patients with tumours in the prostate or bladder. One advantage of the method is the ability to obtain images in three planes, without moving the patient. It is therefore possible for the first time to demonstrate lesions in the base of the bladder in their cranio-caudal extent. Tissue contrast of MRI, using long sequences with suitable proton or T2-weighted images is better than with CT and provides more accurate diagnosis. Even non-expansive tumours within the gland can be differentiated from normal glandular tissue. It has been noted that carcinoma of the prostate in the T2-mode provides an increased signal, whereas tumours of the bladder look dark. Up to a point, tissue characterisation may be possible.

Aged↗
PubMed1985

The effects of fluid-mechanical factors on MR imaging in the arterial model.

Blood flow is a significant factor in MR imaging. The purpose of this investigation was to study fluid-mechanical effects on MR imaging. MR images generated by the pulsatile flow of bovine blood in an elastic model of the aorta with both renal arteries were studied. The high-frequency pulse sequence was synchronized to an ECG trigger signal. It was demonstrated that different flow velocities, laminar and turbulent flow, and backward flow can be visualized with MR imaging.

Aorta↗
PubMed1983

Nuclear magnetic resonance (NMR) tomography of the central nervous system: comparison of two imaging sequences.

A brief description of a nuclear magnetic resonance (NMR) imaging system and preliminary results from its clinical evaluation in the study of various central nervous system diseases are presented. Particular attention is paid to NMR capabilities for soft tissue discrimination, topographical demarcation, and specificity of diagnosis. Two imaging sequences were used: (a) Spin echo measurements with four sets of imaging parameters revealed the different appearances of normal and pathological structures. (b) Inversion recovery images showed marked gray-white matter contrast and clear depiction of pathological lesions. Finally, a number of measurements of longitudinal (T1) and transverse (T2) relaxation times of normal and pathological tissues were carried out.

Adult↗
PubMedDate not supplied

Detection of BOLD changes by means of a frequency-sensitive trueFISP technique: preliminary results.

A new method is introduced to detect magnetic field modulation arising from brain activation-induced BOLD effects. This approach uses a two-dimensional high-bandwidth, high-resolution conventional gradient-echo steady-state imaging sequence known as TrueFISP. The ability to visualize changes in oxygen saturation comes from the fact that the method is sensitive to the local field. As is well known, as the oxygen saturation changes so does the local field associated with the venous blood. We demonstrate that it is possible to visualize not only venous blood with this approach on a macroscopic level for major veins, but also to measure conventional oscillatory like signal changes during activated and resting states. Unfortunately, the method has two major drawbacks. First, a long TR is needed to maximize signal changes and, second, the field must be very well shimmed or numerous experiments need to be run to find the activation, as the signal response is sensitive to the starting frequency in the resting state. Nevertheless, these images can be compared directly with anatomical images collected with the same method without the need for distortion correction.

Brain↗
PubMedDate not supplied

MR imaging of the pancreas at high field strength: comparison of six sequences.

The authors compared six MR sequences comprising conventional breath-hold [rapid spin echo (RASE) repetition time (TR) 240 ms/echo time (TE) 8 ms/90 degrees, fast low angle shot (FLASH) 130/4.5/80 degrees, TurboFLASH 6.5/3.5/8 degrees], fat suppressed regular spin echo (FS SE 330/15/90 degrees), and two combined fat suppressed breath-hold sequences (FS FLASH 130/8/80 degrees, FS RASE 240/10/90 degrees) for studying the normal pancreas. Sequences were selected on the basis of features desirable for demonstrating the pancreas, particularly absence or decrease in artifacts and improved dynamic range of intraabdominal tissue signal intensities. Ten normal volunteers were studied, six at 1.5 T and four at 1.0 T, and comparison was made to regular short TR/TE SE. Quantitative pancreas signal-to-noise (S/N) and pancreas fat-to-noise (SD/N) measurements and qualitative evaluation of overall resolution and artifacts were determined. Fat suppressed FLASH had the highest S/N (44.1 +/- 10.8, p less than 0.0001) and SD/N (35.0 +/- 11.9, p less than 0.0001), and seven studies were considered good or very good. Fat suppressed SE had good S/N (32.6 +/- 7.7) and SD/N (19.0 +/- 3.6), and eight FS SE studies were considered good or very good. Among the nonsuppressed sequences, FLASH had the best combination of quantitative and qualitative measurements. Our results suggest that fat suppression may be important for studying the pancreas and that nonsuppressed FLASH may be a reasonable alternative.

Adult↗
PubMedDate not supplied

Assessment of cerebral blood volume with dynamic susceptibility contrast enhanced gradient-echo imaging.

OBJECTIVE: Dynamic susceptibility contrast (DSC) enhanced MRI was used to study relative cerebral blood volume (rCBV). MATERIALS AND METHODS: We examined 15 healthy subjects and 47 patients with vascular stenosis or occlusion, with brain infarctions, and with cerebral neoplasms. During bolus injection of Gd-diethylenetriamine pentaacetic acid, a series of rapid T2*-weighted fast low angle shot two-dimensional images were recorded from the same slice. From these images, changes in signal intensity during bolus passage were computed pixel-by-pixel and converted into contrast agent concentration curves. Applying the principles of indicator dilution theory, images of rCBV were calculated. RESULTS AND CONCLUSION: Regions of infarctions show almost zero rCBV. In patients with high-grade vascular stenosis or occlusion a bolus delay in comparison to the unaffected side and an increased mean transit time can be observed. Some of the affected areas show an increased rCBV, which is a well-known physiological mechanism that takes place to compensate for the reduced cerebral blood pressure. In brain tumors, rCBV imaging reveals focal or homogeneous areas of increased blood volume. This can even be observed in low-grade astrocytomas with unaffected blood-brain barrier. In CBV imaging, the effects of radiotherapy on tumor tissue can be monitored as a significant decrease of rCBV in tumor tissue after therapy.

Adult↗
PubMedDate not supplied

Misleading changes of the signal intensity on opposed-phase MRI after injection of contrast medium.

OBJECTIVE: The effect of opposed-phase imaging on the interpretation of MR contrast studies is highlighted. MATERIALS AND METHODS: A model calculation is performed. It demonstrates the change of signal intensity of an average tumor before and after application of Gd-DTPA on an in-phase and an opposed-phase image, depending on the percentage of fat within the voxels. The effect is then demonstrated, using a small cotton stick soaked with water or a solution of contrast agent representing a tumor before and after i.v. application of Gd-DTPA. RESULTS: If an average enhancing tumor, which is surrounded by fat, occupies less than 50-60% of the slice thickness, it becomes undetectable on opposed-phase images. The reason is that due to signal cancellation on the opposed image, no signal change or even signal decrease results, while signal increase is visible on the in-phase image. CONCLUSION: In those areas of the body where significant partial volume of a tumor with fat may occur (such as for breast tumors growing along ducts, which are surrounded by fat), severe errors can result. Therefore we explicitly warn from using opposed-image sequences for MR contrast studies.

Contrast Media↗