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Biomedical subjects

D Matthaei

Publications and source records attributed to D Matthaei.

At least 19 recordsLinked to original sources
PubMed1992

Fast inversion recovery T1 contrast and chemical shift contrast in high-resolution snapshot FLASH MR images.

Fast MR imaging attracts the interest of both clinicians and physicists because new diagnostic information arises with reduced artifacts due to short investigational times. With the acceleration of the Snapshot FLASH MR sequence, the measurement of high-resolution images with 256 x 256 matrix is reported, together with contrasting prepulses that are applied to attain contrast in combination with higher in-plane resolution. Measuring times are in the range of a second. For whole-body imaging, a TR = 5.2 msec and a TE = 2.6 msec could be attained measuring omit 256 x 256 matrix images. Artifact-free images demonstrating T1 contrast and contrast from chemical shift are performed on moving organs (heart, intestine) in different experiments. These applications can easily be performed in a couple of minutes for clinical use. Especially in the lung, short TE and high resolution result in a new imaging quality of pulmonary and mediastinal vessels.

Abdomen↗
PubMed1992

[Case reports on the importance of the locoregional radiotherapy of Merkel cell tumor].

The Merkel cell tumor is becoming an increasingly diagnosed primary neoplasm of the skin. This subepidermal tumor is commonly located on the head and neck or extremities of elderly patients. Occasionally misinterpreted as cutaneous metastases, they show a high rate of local recurrence (27 to 52%) and distant metastatic spread (18 to 52%). The definitive diagnosis can be made with immunohistochemistry. Wide surgical excision with postoperative irradiation to the local site and regional lymphatics is the therapy of choice. In seven patients we describe management strategies and discuss their clinical results.

Adult↗
PubMed1992

A skin MR-marker for radiation treatment planning.

After experiences with fluid filled tubes a gel fitted with an adhesive has been developed, to reproducibly markate treatment ports on the patient's skin. A gel is chosen, that hinders loss of the fluid and smoothly fits to the skin surface due to the adhesive. The clinical use of the gel hopefully will help with the use of NMR image information in radiotherapy treatment planning.

Equipment Design↗
PubMed1991

[The intracavity radiotherapy of cervical carcinoma with flexible applicators following the vesicovaginal interposition of the uterus].

Advantages of new flexible intracervical applicators treating cervical cancer with high dose rate afterloading brachytherapy are reported: The insertion of the flexible applicator is usually possible without anesthesia and dilation of the cervix. Therefore the treatment can be performed on an outpatient basis. The risks of perforation and infection are minimal. Dosimetry and documentation of the applicator geometry are possible, if the planning system allows the definition of individual curves of an individual applicator. We now prefer flexible applicators instead of rigid steel applicators treating cervix carcinoma.

Brachytherapy↗
PubMed1990

3D-snapshot flash NMR imaging of the human heart.

SNAPSHOT-FLASH is a recently developed, ultrafast imaging technique, based on conventional FLASH imaging. The application of this new variant to 3D imaging allows the acquisition of a 128 x 128 x 32 data set in 12.5 seconds without triggering, or for cardiac imaging with gating within 32 heartbeats. Compared to standard 3D-FLASH this is 128 times faster, because triggering is only required when the 3D phase-encoding gradient is incremented. The method depicts for the first time fast three-dimensional views of the human heart without motional artifacts. The images are spin-density weighted. Using suitable prepulses any desired T1- or T2-contrast may be achieved. The generation of 3D movies is possible without an increase of the total scan time.

Heart↗
PubMed1990

Cardiac and vascular imaging with an MR snapshot technique.

Real-time vascular and cardiac magnetic resonance (MR) imaging has been reported only with echo-planar imaging. In this study, the fast low-angle shot (FLASH) MR imaging sequence was reduced to repetition times of 3 msec and echo times of less than 1.3 msec with use of an improved MR imaging system. The resulting 200-msec MR images (64 X 128 pixels) are called snapshot FLASH images. They allow measurements from dynamic series of MR images depicting processes such as relaxation behavior and the cardiac cycle in the absence of motion and flow artifacts. In animal studies (at 4.7 T) and in studies of human volunteers (at 2.0 T), vascular and cardiac snapshot FLASH images were obtained as a single shot, as reconstructed motion, and as real-time movies. The arbitrary and fast T1 contrast of these images and the reduction of motion artifacts result in favorable applications for the depiction of myocardial and great-vessel anatomy. These clinical applications can be performed on conventional MR imagers with minor technical modifications.

Animals↗
PubMed1990

[Diagnosis of oropharyngeal function with FLASH-MR tomography].

Magnetic resonance imaging (MRI) has several advantages over conventional X-ray methods: the patient is not exposed to radiation; images of any chosen level can be taken without changing the position of the patient; soft tissues are well differentiated; and artefacts due to dental materials are avoided. Thus, in certain fields of ENT diagnosis MRI is superior to computed tomography, for example, in the imaging of acoustic neuromas, glomus tumours and tumours of the parotids, oropharynx and orbit. The measuring time per slice image, which was previously measured in minutes, has been reduced by a factor up to 1000 by the FLASH (fast low angle shot) technique. Thus, it is now possible to follow human physiological processes on an MRI film with a frame speed of 5 pictures using a whole-body magnet. Films of speech, tongue movements and the act of swallowing reveal the value of this technique for the functional diagnosis of disease of the oropharynx. Precise imaging of the anatomical and functional situation, especially of soft tissues, is superior to that of previous methods such as ultrasound, X-ray, and endoscopy.

Deglutition↗
PubMed1987

SYS-FLASH. Systemic saturation in FLASH MR imaging.

A simple modification of FLASH (Fast Low Angle SHot) MR imaging, which results in a variable reduction of the intensity of flowing blood and flow artifacts in transaxial tomograms, is reported. Here a nonselective radiofrequency pulse of variable flip angle is used before the acquisition of each projection in FLASH imaging to saturate flowing blood within the whole volume (SYstemic Saturation = SYS-FLASH).

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

Biophysica and medical aspects of fast NMR-imaging.

Nuclear magnetic resonance (NMR) imaging is a promising new technique for non-invasive medical diagnosis. Following a decade of technical improvements and preliminary medical experiences, the measuring time of several minutes remained the major drawback of the method. The recent development of a fast NMR-imaging technique, the so-called FLASH (Fast Low Angle SHot) method, opens a new field of medical applications. This article deals with a few applications and aspects of FLASH imaging. Using the technique cross-sectional images can be taken within a few seconds without loss in spatial resolution. Therefore dynamic investigations of the function of internal organs and images of blood vessels become possible. Furthermore three-dimensional volume imaging of the whole object provides the full anatomical information. FLASH imaging is also applicable in combination with localized NMR-spectroscopy. Thus, biochemical information from NMR-spectroscopy and structural and functional information from NMR-tomography can easily be combined.

Fourier Analysis↗
PubMed1986

Nuclear magnetic resonance imaging of mummified corpses.

Clinical applications of nuclear magnetic resonance (NMR) imaging have demonstrated its great potential for noninvasive examinations of soft tissues. Here preliminary experiments are reported on mummified human tissue by means of NMR cross-sectional and transmission imaging. For this purpose the natural viscosity of the tissues has been lowered by rehydration with an aqueous solution of 20% acetone.

Acetone↗
PubMed1986

Rapid NMR imaging of dynamic processes using the FLASH technique.

FLASH (Fast Low-Angle SHot) imaging is a new method for rapid NMR imaging which has been demonstrated to provide abdominal images without artifacts due to respiratory or peristaltic motions. The sequence typically employs 15 degrees radiofrequency excitation pulses and acquires a free induction decay signal in the form of a gradient echo. Here FLASH images are recorded in the presence of dynamic processes with time constants even smaller than the measuring time of about 2 s for an image with a 128 X 128-pixel resolution. Experiments are carried out on flow phantoms and on rabbits yielding heart images without gating of the cardiac motion.

Animals↗
PubMed1986

Multipurpose NMR imaging using stimulated echoes.

STEAM (stimulated-echo acquisition mode) imaging techniques recently introduced by the authors are demonstrated to provide a versatile tool for improving the parametric specificity in NMR imaging. Stimulated echoes can be excited by a sequence of at least three rf pulses with flip angles of 90 degrees or less. The main characteristics of the STEAM method are based on the great functional flexibility of an imaging sequence comprising three rf pulses unequal to 180 degrees and three intervals prior to acquisition of the data. Major advantages are the easy access to contiguous multiplanar images, to CHESS (chemical-shift-selective) images, and to T1 information. Moreover, the rf power deposition is considerably reduced as compared to spin-echo NMR imaging sequences. Here first in vivo results on human extremities are presented including contiguous multislice images, multiple CHESS images, and spin-lattice relaxation time images calculated from a series of simultaneously recorded T1-weighted STEAM images.

Biophysical Phenomena↗
PubMed1986

Dynamic digital subtraction imaging using fast low-angle shot MR movie sequence.

High-quality magnetic resonance (MR) images can be recorded within seconds with the use of fast low-angle shot (FLASH) MR imaging. This technique also gives new access to the time evolution of both periodic functions, such as cardiac motion, and nonperiodic physiologic processes, such as flow within internal organs. The time course and regional distribution of dynamic processes detectable by FLASH MR movies are often demonstrated best within series of difference images obtained by digital subtraction of the original data, especially after the use of MR contrast agents. In addition, quantitative information is provided by the analysis of time-intensity profiles for selected regions of interest. Dynamic digital subtraction MR imaging was evaluated in rabbit brain and kidney using a 2.3-T, 40-cm-bore magnet. The time resolution was 1.5 seconds for brain studies and 28 seconds for kidney studies. The total examination times were 1.5 and 30 minutes, respectively.

Angiography↗
PubMed1986

MR imaging using stimulated echoes (STEAM).

The introduction of STEAM (stimulated echo acquisition mode) magnetic resonance (MR) sequences provides access to a variety of MR parameters. T1-weighted and calculated T1 proton MR images of the head of healthy volunteers and a patient with an astrocytoma are presented. MR examinations were performed with a 2.0-T whole-body system. The STEAM T1 method can be used to characterize multiexponential relaxation behavior, to evaluate T1 relaxation times, and to improve the T1 contrast within MR images. Both the measuring time and the spatial resolution are the same as for a conventional image.

Astrocytoma↗