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Biomedical subjects

G Bongartz

Publications and source records attributed to G Bongartz.

At least 91 records · Page 5Linked to original sources
PubMed1990

[The use of rapid sequences in craniocerebral MR diagnosis].

MRI of the head is routinely performed with spin-echo sequences whereas gradient-echo sequences are still uncommon. Certain features of fast imaging sequences make them a promising tool for clinical investigations. The relative high signal-to-noise ratio/unit time demonstrates the usefulness of GE imaging as localising images. The extremely high contrast-flexibility is sometimes superior to SE imaging and may help to characterise structures and lesions. Flow dynamics are more clearly depicted than with SE sequences and lead to the dynamic evaluation of intracranial motion (CSF flow, blood flow). This information may be used in a special mode to achieve MR angiograms. Due to the very short repetition times, GE sequences are excellently suited to 3D application. This enables to reduce slice thickness to less than 1 mm with optional reconstructions in any virtual direction. In view of present developments in MR, GE imaging will be accepted in clinical diagnostic imaging in the near future.

Brain↗
PubMed1990

[The MR tomographic findings in cranial manifestations of neurofibromatosis].

Twelve patients with central neurofibromatosis underwent MR examination of the head. Among these, chiasma glioma was the most common CNS tumour (6/12). Seven patients had multifocal areas of increased T2-signal without mass effect predominantly involving the region of the basal ganglia. No corresponding CT abnormalities were present. These lesions may represent multifocal dysplasia and seem to be characteristic of central neurofibromatosis.

Adolescent↗
PubMed1990

[Magnetic resonance angiography of the arteries supplying the brain].

In a prospective study involving 52 patients, magnetic resonance angiography (MRA) was compared with arterial digital subtraction angiography (IA-DSA). MRA was performed within three days of the IA-DSA. It was carried out without knowledge of the findings on IA-DSA. Of 38 stenoses of the carotid arteries or their branches, demonstrated by IA-DSA, 33 could be seen on MRA; in four cases the stenosis was outside the imaging area of the coil. Sixteen out of 17 carotid occlusions were diagnosed by MRA. There was one false positive. In the vertebral artery territory, eleven out of 13 stenoses and three out of four occlusions were diagnosed by MRA. In evaluating the degree of stenosis, there was agreement in only 16 out of 33 cases. MRA over-estimated the severity of stenoses in 15 cases and under-estimated it in two. MRA is a new non-invasive method in the diagnosis of cerebro-vascular disease which must be evaluated by further studies.

Angiography, Digital Subtraction↗
PubMed1990

Musculoskeletal neoplasms: fast low-angle shot MR imaging with and without Gd-DTPA.

In 121 patients, image contrast and contrast-to-noise ratios (C/Ns) obtained with gadolinium diethylene-triaminepentaacetic acid (DTPA)-enhanced and nonenhanced fast low-angle shot (FLASH) sequences were compared with those achieved with spin-echo (SE) sequences. Among FLASH sequences, contrast between neoplasms and muscle was sufficient with a flip angle of 90 degrees following administration of Gd-DTPA but was 61% lower than that with the T2-weighted SE sequence. High contrast levels were obtained between tumors and bone marrow or fat in sclerotic, calcified, and fibrotic lesions with the use of a flip angle of 90 degrees and in lytic lesions with a flip angle of 10 degrees, reaching 66% of the contrast level obtained with the T1-weighted SE sequence. C/N between tumor and surrounding tissue was always significantly lower with FLASH sequences than with the ideal SE sequences usually used for tumor delineation. Thus, a replacement of the T2-weighted SE sequences by FLASH sequences cannot be recommended. A replacement of the T1-weighted SE sequences by FLASH sequences seems possible but does not significantly reduce examination time.

Adolescent↗
PubMed1989

[A simplified technic in high-resolution MR tomography of the shoulder: ZEPRA (Zoom of Eccentric Positioned Regions by active Aliasing)].

A fairly easy method for high-resolution MR imaging of the shoulder is described. The combination of a defined arrangement of the gradients with a small-volume Helmholtz coil provides the possibility of a high zoom of structures apart from the magnet's centre. The maximal achievable zoom factor depends on the ratio of FOV/sensitive coil volume. The ZEPRA method acts by phase-encoded aliasing only. With this technique all interesting soft tissue of the shoulder may readily be visualized in every direction and with every type of sequence.

Humans↗
PubMed1989

[Magnetic resonance tomography: a patient-connected system for artificial respiration and monitoring].

Physical phenomena that occur during magnetic resonance imaging (MRI) and the position of the patient inside the scanning tube necessitate adaptations of anesthetic techniques and devices. An anesthesia unit is presented that operates in close proximity to the patient without interfering with the imaging process. This unit enables the anesthesiologist to be close to the patient and his equipment, and minimizes the length of necessary tubing between patient and anesthesia apparatus. The unit consists of commonly used, commercially available devices with only minor modifications.

Anesthesia↗
PubMed1989

[Early signs of arthrosis of the hip joint in MRT].

The hips of 8 young volunteers were investigated with high resolution MRI. The purpose of this study was to establish an imaging protocol to visualize hyaline cartilage, synovial fluid, and subchondral bone with optimized contrast. Spin Echo (SE) and Gradient Echo (GE) sequences were compared. FISP with a flip angle of 70 degrees was superior to the other techniques. The same sequences were applied on 45 volunteers aged 65-93 years. Early signs of degenerative arthritis of the hip were demonstrated as thinning, variable signal intensities within the cartilage layer, and cartilage loss. MRI of the hip may be a useful tool for the detection of early degenerative cartilage damage which cannot be documented with conventional x-rays.

Adult↗
PubMed1988

Magnetic resonance in cartilaginous lesions of the knee joint with three-dimensional gradient-echo imaging.

Diagnosis of chondromalacia of the patellofemoral joint using three-dimensional gradient-echo sequences was investigated in 41 patients, with arthroscopic verification in 25 patients. In vitro examinations in human cadaveric patellae were performed in order to determine optimal imaging parameters. FLASH (TR = 40 ms, TE = 10 ms, flip angle = 30 degrees) and FISP (TR = 40 ms, TE = 10 ms, flip angle = 40 degrees) were used in clinical studies. Advanced stages of chrondromalacia could be visualized with high sensitivity. In less advanced disease, overstaging was observed. The therapeutically relevant differentiation of major and minor degrees of chondromalacia seems to be possible. 30 degrees FLASH-images in the axial plane proved to be the most efficacious technique for the diagnosis of chondromalacia.

Arthroscopy↗
PubMed1988

[Sensitivity and specificity of sonographic diagnosis of the lymph nodes in malignant melanoma].

A total of 213 melanoma patients were checked perioperatively with a 5-MHz sonographic scanner in order to detect lymph-node metastases; they were also checked in the scope of tumor follow-up. Of the 415 sonographic results, the method yielded a 97% accuracy. The soundness of lymph-node sonography has been proved histologically and/or through clinical observation. Compared to the other diagnostic techniques available for checking surface and subsurface lymph-node groups, lymph-node sonography is an advantageous combination of diagnostic practicability, accuracy, economic feasibility, and patient acceptance. The possible therapeutic implications are also discussed in this paper.

Follow-Up Studies↗
PubMed1988

[Computerized tomography imaging of shoulder joint injuries].

In addition to conventional radiography using standard and special projections, CT offers valuable information in selected cases. Native CT allows detection of minimal bony lesions, which may cause severe pain that is resistant to therapy. Small amounts of joint effusion as well as the Hill-Sachs impression fracture of the humeral head can be detected with a high degree of accuracy. Following intra-articular injection of contrast medium, CT-arthrography enables visualization of capsular and ligamentous injuries of the shoulder joint. Lesions of the glenoid labrum following shoulder dislocation can be detected and classified by this method.

Arthrography↗
PubMed1988

[Possibilities of magnetic resonance tomography in diagnostic imaging of the shoulder joint].

By virtue of its multiplanar representation, magnetic resonance imaging (MRI) allows clear visualization of the complex anatomical relationships of the shoulder joint. In addition to axial planes, slices perpendicular and parallel to the glenoid cavity are used to good advantage. In tears of the rotator cuff an increase in signal intensity within the cuff is recognized in T2- and proton-density-weighted images. Lesions of the glenoid labrum following luxations of the glenohumeral joint can be detected and classified using MRI. The diagnostic value of MRI as compared with other imaging modalities will have to be evaluated in larger series with operative verification.

Arthrography↗
PubMed1987

[Clinical staging of malignant lymphoma].

The clinical staging of malignant lymphomas not only includes histopathological classification but also non-invasive methods for assessing the stage and prognosis. In contrast to the TNM system of staging malignant epithelial tumors, in lymphomas the size is unimportant. Comparison is made between the invasive methods of staging Hodgkin's disease and Non-Hodgkin's lymphomas (splenectomy, laparotomy) and the non-invasive clinical radiological investigations (conventional X-rays, lymphography, sonography, CT, MR) and their statistical reliability. Whereas positive results in clinical staging are diagnostic, a negative result requires further correlation. A phased program for clinical staging is offered.

Diagnostic Imaging↗
PubMed1987

[Intrahepatic collateral veins in obliteration of the inferior vena cava].

Occlusion of the inferior vena cava (IVC) can be either congenital or acquired. Tumors at the porta hepatis are the most common cause of acquired occlusion. Various pathways of venous collateralization are described. The development of a transhepatic venous shunt depends on the isolated inflow of the liver veins into the IVC at different levels, with flow reversal in the most inferior hepatic vein. The case of a 46-year-old female patient with an intrahepatic venous shunt is presented. Ultrasound, computed tomography, magnetic resonance imaging and angiography were performed. Their relative diagnostic values are discussed.

Collateral Circulation↗
PubMedDate not supplied

Is there a hazard to health by mercury exposure from amalgam due to MRI?

The local magnetic fields from computer monitors are well known. Recently a hypothesis was published that these magnetic fields may lead to a 400% increase of mercury dissolution from dental amalgam fillings. In MRI the exposure to the magnetic field exceeds by far the exposure from computer monitors. Therefore, this study examined the amalgam-related mercury release for typical MRI conditions, separated for both the static and the variable magnetic fields in a 1.5 T MR-unit. First, 20 dental cavities were filled with a non-gamma-2 amalgam, and the mercury release was measured for 14 days in a non-magnetic environment. Second, one half of the specimens were exposed to a static magnetic field for 24 hours (group A), while the other specimens were exposed to a repetitive gradient echo sequence for 60 minutes (group B). In both experiments there was no significant increase in mercury release due to MRI. This in vitro study demonstrated no evidence of an elevated mercury dissolution from a non-gamma-2 amalgam during magnetic field exposure by MRI; therefore, there is no increased risk to health.

Dental Amalgam↗
PubMedDate not supplied

Hydro-MRI for the visualization of gastric wall motility using RARE magnetic resonance imaging sequences.

BACKGROUND: Although different imaging techniques such as conventional X-ray, ultrasonography, and hydro-computed tomography are available for the imaging of the stomach, none can depict this organ in full size without radiation. Therefore, the study of the entire gastric wall motility of the stomach is difficult and in principle only performable with rapid magnetic resonance imaging (MRI) techniques. T1-weighted imaging sequences have been used for the dynamic study of gastric wall motility. This technique was combined with the oral intake of para- or superparamagnetic contrast agents to achieve sufficient intraluminal contrast. The technique described in the present study is based on a different contrast mechanism. METHODS: The stomach was filled with 500 mL of 10% of aqueous dextrose solution, and a strongly T2-weighted fast rapid acquisition with relaxation enhancement (RARE) type imaging sequence was used for data acquisition. No other contrast agents were applied. An ultrafast RARE imaging sequence with an asymmetric phase-encoding scheme was developed to achieve a high temporal and spatial resolution. The scanning time per image was approximately 1 s. RESULTS: The stomach was imaged in full size. The concentric constrictor rings moved from the proximal part of the body toward the antrum. The mean duration for one contraction cycle was approximately 17.9 +/- 2.5 s, the mean contractile frequency was 3.4 +/- 0.5 s, and the mean spreading velocity was 65.5 +/- 3.6 cm/min. CONCLUSIONS: The purpose of this study was to demonstrate a new technical approach for a noninvasive dynamic study of gastric motor function with hydro-MRI. This robust method may have clinical application, e.g., in the diagnosis of gastroparesis, and may be extended to the rest of the gastrointestinal tract.

Administration, Oral↗