Biomedical subjects

G Layer

Publications and source records attributed to G Layer.

79 records · Page 5Linked to original sources

PubMed1989

[Oleothorax 40 years later].

Between 1930 and 1950 the induction of an oleothorax was widely accepted as treatment of patients with progressive tuberculosis. Now, the late complications of this therapeutic approach can occasionally be observed. A patient with an oleothorax induced forty years ago and extensive x-ray exposure through frequent fluoroscopie follow-up is presented. In addition, he has a carcinoma of the lung infiltrating the chest wall. The late complications of oleothorax and the possibility of a radiation-induced malignancy are discussed.

Carcinoma, Bronchogenic↗

PubMedDate not supplied

Determination of 1H relaxation times of water in human bone marrow by fat-suppressed turbo spin echo in comparison to MR spectroscopic methods.

Relaxation times of water were measured in human vertebral bodies by a fat-suppressed dual-echo turbo spin echo/turbo inversion recovery MRI sequence. Comparison was made with T1 and T2 values obtained by localized 1H-MR spectroscopy. The accuracy of the results and the diagnostic potential of the fast quantitative MRI technique were evaluated in 20 volunteers, 11 patients with osteoporosis, 6 patients with lymphoma, and 6 patients with bone marrow metastasis. No significant alterations of T1 and T2 relaxation times of water and fat were found in osteoporosis. With both methods, an increase in the T1 values of the water resonance by 16% was observed in lymphomas, which was highly significant (P < .001) in the MRS measurements, and an elevation by the same amount was obtained by the MRI sequence for the metastases (P = .040). A strong reduction of fat fraction was quantified by MRS in the tumorous cases. T2 of the water resonance increased by more than 30% (P < .003) in metastases. Water T2 values obtained by the MRI sequence showed systematic deviations from the MRS results, especially at short echo spacings.

Adipose Tissue↗

PubMedDate not supplied

In vivo 1H, 31P-[1H] and 13C-[1H] magnetic resonance spectroscopy of malignant histiocytoma and skeletal muscle tissue in man.

Human tumor and skeletal muscle tissue was studied by means of in vivo 1H, 31P, and 13C MRS. The examinations were performed with a 1.5 T whole-body MR scanner equipped with a second RF system. Localized 1H and broadband proton-decoupled 31P and 13C MR spectra were obtained in measurement times of 5, 10 and 33 min, respectively, from a malignant fibrous histiocytoma in a patient and from gastrocnemius muscle tissue in healthy volunteers. Proton decoupling enhanced the sensitivity (via the nuclear Overhauser effect) and the information available from in vivo 31P and 13C MR spectra significantly. The most information was obtained from 1H-decoupled 31P spectra. Observation of more than one spin species allows peak assignments to be verified mutually. The spectral data of the histiocytoma differ largely from that of muscle tissue and show a tumor with elevated pH value, normal level of nucleoside 5'-triphosphates, and high level of compounds involved in phospholipid turnover. The multinuclear in vivo MRS experiment may allow the non-invasive observation of almost the complete pathway of phospholipid synthesis and degradation in intact human tissue.

Histiocytoma, Benign Fibrous↗

PubMedDate not supplied

Clinical applications of MR angiography in intrathoracic masses.

This is a prospective evaluation of the use of MR angiography (MRA) at 1.5 T in the assessment of intrathoracic masses. Two-dimensional (2D) MRA was obtained sequentially by means of a fast low angle shot (FLASH) technique (repetition time 30 ms, echo time 10 ms, flip angle 30 degrees) one slice per breath-holding. An automated control procedure and instantaneous image reconstruction permitted constant monitoring of the image quality and tailoring of the timing of the scans to each patient's breathing capacity; MRA was successfully completed in all patients. Two-dimensional FLASH angiography was postprocessed into three-dimensional (3D) MR angiography (projections) by a maximum-intensity-projection algorithm; a 3D spatial impression of the MRA was achieved by obtaining 3D MRAs from different viewing angles and by viewing these in a cine-loop. Superimposition of vessels was avoided by creating angiograms of interest of a specific anatomic region. Fifteen patients with malignant or benign intrathoracic tumor were evaluated; their MR findings were correlated with chest radiography, conventional angiography, bolus enhanced CT, and/or perfusion scintigraphy. Magnetic resonance angiography revealed stenosis, distortion, and displacement of vessels by tumors as well as distal perfusion defects caused by proximal tumors. The MRA findings were readily accepted by our clinical colleagues and incorporated into their surgical planning. We believe MRA to be a promising complement to MR imaging in the assessment of intrathoracic masses.

Adult↗

PubMedDate not supplied

Pharmacokinetic parameters in CNS Gd-DTPA enhanced MR imaging.

Dynamic MR imaging can be used to study tissue perfusion and vascular permeability. In the present article a procedure for dynamic MR is presented, which (a) accurately resolves the fast kinetics of tissue response during and after intravenous infusion of the paramagnetic contrast medium Gd-DTPA and (b) yields a linear relationship between the measured MR signal and the Gd-DTPA concentration in the tissue. According to these features, the measured signal-time curves can be analyzed within the framework of pharmacokinetic modeling. Tissue response has been parameterized using a linear two-compartment open model, with only negligible effects of the peripheral compartment on the central compartment. The three model parameters were fitted to the signal-time data pixel by pixel, based on a set of 64 rapid SE images (SE 100/10 ms, image scan time 13 s, interscan intervals 11 s). This makes it possible to construct parameter images, whereby structures become visible that cannot be distinguished in conventional Gd-DTPA enhanced MR. As a clinical example, the approach is discussed in a case of glioblastoma.

Brain Neoplasms↗

PubMedDate not supplied

MRI and MRA in treatment planning of subdiaphragmatic radiation therapy.

Radiotherapy treatment planning needs optimum definition of target volume in its relative position to normal tissue. The aim of our study was to achieve individual field definition in subdiaphragmatic radiotherapy by visualization of the target volume using fast, breath-held MRI and MR angiography. A modified rapid acquisition SE technique (SE 150/10) was used to obtain a coronal image within a 14 s breath-holding period, displaying kidneys, spleen, and lumbar spine on one slice. Coronal MR angiography acquisition in breath-hold technique was performed using a sequential FLASH-2D sequence (FLASH-2D 30/10/30 degrees). For reconstruction of the MR angiogram in coronal view, we used a maximum intensity projection algorithm. A computer program superimposed the MR angiogram onto the MR image. Correct magnification of the superposition image allowed direct projection onto the simulation film. Problems of distortion and different projection techniques were taken into account and quantified by phantom measurements. The localization error measured in a reference plane was less than 5 mm within a radius of 140 mm. Fourteen cases of Hodgkin disease and non-Hodgkin lymphomas were treated employing the novel technique. By superposition of the MR image and the MR angiogram, demarcation of vascular architecture from parenchymatous organs was achieved. Projection of the MR superposition onto the simulation film yielded accurate and convenient field definition using noninvasive imaging techniques.

Abdomen↗

PubMedDate not supplied

3D TOF MR angiography of cerebral arteriovenous malformations after radiosurgery.

To investigate the potential of three-dimensional time-of-flight MR angiography (MRA) to complement SE imaging, 18 patients with intracerebral arteriovenous malformations were prospectively followed after undergoing radiosurgery. Vessel occlusion after stereotaxic single high dose radiotherapy develops slowly. The MRA detected signs of nidus obliteration earlier and with a higher sensitivity than did SE imaging. Six months after radiosurgery, MRA showed a reduction of the nidus flow signals in nine patients and after 1 year it showed reduction in 15 of the 18 patients. As shown by MRA, the loss of flow signals was related to a reduction of the nidus size in 4 patients after 6 months and in 11 after 1 year. The SE imaging revealed a reduction of the nidus size in only two patients after 6 months and in eight after 1 year. The signal intensity of the feeding arteries was reduced in nine patients and that of the draining veins was reduced in six. The T2-weighted images exhibited white matter lesions in eight patients after 1 year. For complete follow-up, SE imaging should be performed together with MRA.

Adolescent↗