Search PubMed⌕ Search

Biomedical subjects

G Friedmann

Publications and source records attributed to G Friedmann.

173 records · Page 10Linked to original sources
PubMedDate not supplied

MR imaging of poststenotic flow phenomena: experimental studies.

Poststenotic flow patterns were analyzed in a flow phantom with a 1.5-T magnetic resonance (MR) imager, with use of different MR imaging and MR angiographic pulse sequences. Spin-echo, fast field-echo, two-dimensional inflow (multiple single-section technique), and flow-adjusted-gradient sequences were applied. For the spin-echo sequences, modulus and phase images were reconstructed from each data set. The length of the region of poststenotic changes in signal amplitude and phase measured at a constant flow rate increased with stenosis grade. Likewise, the length of the region of poststenotic changes measured at a constant stenosis grade increased with flow rate. Moreover, the results depended on the alignment of the flow direction with the readout gradient. Comparison of modulus and phase images allowed discrimination of turbulent and nonturbulent flow, which yields additional information on stenosis grade in clinical MR angiography.

Arterial Occlusive Diseases↗
PubMedDate not supplied

[Computerized tomography in lumbar compression syndrome].

Computertomography has been shown to be a reliable method for evaluation of lumbar compression syndromes. Excellent apparative equipment and differentiated examination techniques are required. As compared with myelography CT offers the advantages of a non-invasive procedure. Due to simultaneous axial visualisation of bone and soft tissue all components contributing to lumbar compression syndromes are included. This so far cannot be achieved by conventional radiographic methods. CT is superior to myelography concerning specificity and sensitivity of the diagnosis of primary and surgically treated herniated discs. It demonstrates extreme lateral dislocation of disc tissue as well as centrally located disc material at the L5/S1 level. Furthermore, compressing structures such like monosegmental osseous stenosis and stenosis of the spinal canal are well to be recognized. Tumors may be ruled out. Verification of postoperative hematoma and scar formation is of high clinical value. Myelography, however, remains being the method of choice when clinical symptoms are not to be appointed to a certain segment.

Diagnosis, Differential↗
PubMedDate not supplied

Artifacts in MR imaging after surgical intervention.

Artifacts are encountered repeatedly in magnetic resonance (MR) imaging after neurological orthopedic surgery, although there is no evidence of metallic foreign bodies on radiography and CT. Experiments demonstrated that surgical filling materials, such as bone cement and bone transplants are not the cause of the artifacts. On the other hand, we have been able to show that short-term contact between a diamond drill and untempered operating instruments can cause abrasions and set free minute metallic fragments. Those particles are missed by X-ray procedures including CT but cause MR artifacts by local disturbance of the homogeneity of the magnetic field. Therefore, MR represents a highly sensitive method to trace extremely small amounts of magnetic substances. Postsurgical MR, however, may be of limited value because of the disturbing artifacts.

Animals↗
PubMedDate not supplied

PET, CT, and MR imaging in cerebrovascular disease.

Forty-five patients with cerebrovascular disease (single and multiple infarcts, intracerebral hemorrhages) were examined with X-ray CT, magnetic resonance (MR) imaging, and positron emission tomography (PET). In six patients with acute infarcts repeat measurements with all techniques were performed after 2 weeks. Magnetic resonance and PET were more sensitive in the detection of ischemic lesions than X-ray CT. With PET, functional disturbances could be demonstrated even in two cases where CT and MR were normal, while the latter techniques were superior in exactly localizing a lesion. Changes in lesion appearance with time were observed with all techniques, and the pathophysiologically important phenomena of hyperperfusion or hypermetabolism were documented in four infarcts with PET.

Brain↗