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Biomedical subjects

W Semmler

Publications and source records attributed to W Semmler.

At least 91 records · Page 5Linked to original sources
PubMed1988

Monitoring human tumor response to therapy by means of P-31 MR spectroscopy.

Tumors in 23 patients were studied by means of in vivo phosphorus-31 magnetic resonance (MR) spectroscopy. In five patients, the response to chemotherapy and radiation therapy was monitored in a long-term follow-up study. In one patient, the P-31 MR spectra were recorded during the infusion of chemotherapeutic drugs. In comparison with healthy muscle tissue of patients, the tumors showed elevated inorganic phosphate, phosphomonoester, and phosphodiester peaks and reduced creatine phosphate peaks, whereas the nucleoside 5'-triphosphate levels remained nearly unchanged. Tumor treatment resulted in changes in the ratio of the signal intensity value of creatine phosphate to that of inorganic phosphate and in the sum of these values. In an osteosarcoma, an initial response followed by renewed tumor growth was clearly indicated by changes in these parameters. In the short-term follow-up examination, slight spectral changes were observed during the infusion of chemotherapeutic drugs. Changes in the concentrations of phosphorus metabolites during therapy can therefore be monitored in human tumors by means of P-31 MR spectroscopy.

Antineoplastic Agents↗
PubMed1988

[Nuclear magnetic resonance tomography in diseases of the parotid gland].

The clinical experience with Magnetic Resonance Imaging in parotid gland diseases of 13 patients in discussed. An excellent visualization of the surrounding anatomy, the intrinsic structures of the gland. such as the facial nerve and the lesion, which can be achieved by MRI only, will provide more detailed information for the surgeon and thus for the prognosis. On the other hand, the differentiation of the diseases is not yet improved and MRI will certainly not replace the clinical examination including aspiration cytology.

Diagnosis, Differential↗
PubMed1987

NMR relaxation times T1 and T2 of water in plasma from patients with lung carcinoma: correlation of T2 with blood sedimentation rate.

The T1 and T2 NMR relaxation times of water protons in plasma, obtained from patients with lung carcinoma, healthy volunteers, and patients with nontumor diseases were measured at a resonance frequency of 20 MHz. Additionally hematologic parameters were determined. In tumor patients the mean plasma T2 was shortened by about 20%, and an increase in the blood sedimentation rate (BSR) was noted. Similar but less pronounced results were found for the nontumor group of patients, indicating that the shortening of T2 in plasma is a secondary host response. However, a plot of plasma 1/T2 versus BSR from tumor patients showed a significant correlation between these two parameters. No such correlation could be detected in the nontumor group of patients. The correlation of 1/T2 with BSR, found solely in the tumor patient group, increased the diagnostic sensitivity of T2 measurements and may help to differentiate between malignant and nonmalignant disease. No significant variation in the T1 spin-lattice relaxation time was observed.

Adult↗
PubMed1987

[Oral contrast media for magnetic resonance tomography of the abdomen. 1. Comparative animal studies of positive and negative contrast media].

Beagle dogs were investigated by MRI (Siemens Magnetom, 0.35 T) after oral administration of aqueous solutions of Gd-DTPA (n = 4), ferric ammonium citrate (n = 1), and magnetite dextran (n = 2). High signal intensity of the GI-tract versus adjacent structures was obtained with Gd-DTPA and ferric ammonium citrate. Magnetite showed negative contrast versus adjacent structures. However, magnetite displayed lower contrast relative to liver, muscle and gut wall compared to Gd-DTPA and ferric ammonium citrate. In relatively T2-weighted sequences labeling of poorly filled bowel loops was significantly better with Gd-DTPA and ferric ammonium citrate. For GI-tract contrast enhancement we conclude that positive contrast media are of higher diagnostic value compared to negative contrast agents.

Abdomen↗
PubMed1987

[MR tomography of the breast. Supplemental information in select cases].

Magnetic resonance tomography (MRT), as the newest imaging procedure in breast diagnosis, has to be compared with the combined use of conventional imaging methods. Many advantages of MRT, which have been emphasized in comparison with mammography, are not superior to the complementary use of mammography and sonography. Additional diagnostic information through MRT is yielded only in the following cases: differentiation between fibrous fibroadenoma of the elderly woman and circumscribed carcinoma with similar mammographic and sonographic appearances; distinction of stellated fibrous scar tissue from the scirrhotic configuration of the more vascular tumour fibrosis around a carcinoma by using contrast medium MRT; differentiation of periductal fibrosis from inflammatory or carcinomatous ductal and periductal infiltration; better delineation of fat or silicon implants. Finally, a significant advantage of mammography over all other imaging methods should be pointed out: the detailed visualization of microcalcifications for the early diagnosis of breast carcinoma.

Breast Diseases↗
PubMed1987

[Intracranial manifestation of lymphomatoid granulomatosis (Liebow's disease)].

An intracranial manifestation of lymphomatoid granulomatosis occurs in 20% of patients. In the case of a 56-year-old patient it is shown that a relative long period can pass from the first neurological symptoms to histological diagnosis by stereotactic brain puncture. Over 15 months, follow-up studies were performed using computed tomography and magnetic resonance.

Brain Diseases↗
PubMed1986

Some aspects of the use of contrast agents in magnetic resonance imaging.

The parameters for signal intensity in magnetic resonance imaging (MRI) are classified and shortly described. Proton density, T1 and T2 are discussed as tissue parameters to be influenced in different ways by different types of contrast agents. Conclusions for the development of contrast agents for MRI are drawn. The influence of the concentration of paramagnetic substances on signal intensity is shortly described. The good tolerance of Gd-DTPA as a contrast agent for MRI is reported. Its favorable use is shown in three examples of brain tumors.

Adult↗
PubMed1985

[Effect of the contrast medium on the gray shading in magnetic resonance tomography].

Contrast media can significantly improve the diagnostic value of MR tomography. The basis of using contrast material for MR depends on totally different physical principles from those employed in conventional radiological diagnosis. The physical factors underlying the use of these contrast media are described, various suitable substances are discussed, and experience so far gained with some contrast agents is outlined.

Contrast Media↗
PubMed1985

[Contrast media in magnetic resonance tomography. A review. 1. Physicochemical and pharmacological bases of MR contrast media using gadolinium-DTPA as an example].

The principles underlying contrast media for MR tomography are totally different from those for conventional contrast media. Substances suitable for MR tomography are paramagnetic complexes which alter the relaxation times of the tissues. Signal intensity on the MR images are influenced correspondingly. The mode of action of MR contrast media is explained. Gadolinium-DTPA, the first MR contrast medium in clinical use by means of intravenous injection, is described. Its tolerance has been investigated by animal experiments and its effectiveness as an contrast agent has been studied in normal individuals. In the second part of the paper, early results from the use of gadolinium DTPA are given. The additional information which can be obtained by using MR contrast media is discussed.

Animals↗
PubMed1985

[Contrast media in magnetic resonance tomography. A review. 2. Biological basis, research technic and clinical application of gadolinium-DTPA in the diagnosis of intracranial tumors].

The early results of the use of the MR specific contrast medium gadolinium-DTPA in 40 patients with intracranial tumours are reported. Optimal pulse sequences, contrast dose and timing are discussed. The relationship between the blood-brain barrier and contrast distribution within tumour tissue is elaborated. The clinical significance of the application of contrast agents in the diagnosis of brain tumours is evaluated.

Adult↗
PubMed1984

[Contrast in nuclear magnetic resonance imaging].

It has been shown that signal strength from nuclear resonance and grey scale in NMR depend on pulse sequence, pulse repetition interval, delay time, tissue-dependent parameters, such as relaxation times T1 and T2, proton density, and flow movements. The relative grey scales for tissues using varying pulse sequences can be predicted mathematically. These relationships are shown graphically to indicate to the user the effect of pulse repetition, processing time and T1 and T2.

Adipose Tissue↗
PubMed1983

[Emission computed tomography of the left ventricle. Multiplanar ECG-triggered radionuclide ventriculography with a 7-pinhole collimator].

Tomographic studies and time-dependent tomograms on phantoms and patients were carried out using a 7-pinhole collimator in order to study the clinical value of ECG-triggered tomographic radionuclid ventriculography. A suitable computer programme has been developed. The results have shown that it is possible to evaluate local contraction abnormalities by this method. Using a left oblique position of the collimator (LAO [45 degrees]-cranial [15 degrees] ), emission computer tomography is aligned with the longitudinal axis of the heart. In this way, a single projection is sufficient to show the motility of the anterior and posterior walls and of the septum. Hypokinesis, akinesis or dyskinesis can be recognised visually. The localisation and extent of the defect can be determined through the 7-pinhole collimator. Reconstructed images of the triggered radionuclid scintigrams show excellent marginal definition. In the RAO projection, the left ventricle can be seen without superimposition and images obtained which equal those of a first-pass technique.

Cardiomyopathies↗
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

Liver and spleen enhancement after intravenous injection of carboxydextran magnetite: effect of dose, delay of imaging, and field strength in an ex vivo model.

It has been predicted that liver and spleen enhancement after administration of superparamagnetic contrast agents may be different, depending on the strength of the main magnetic field. With the use of an ex vivo model, we investigated at 0.3, 0.5, and 1.5 T the effects on liver and spleen signal intensity of 5, 15, and 45 mumol/kg body weight of dextran magnetite (SHU 555A) in 54 rats. Nine rats served as controls. At different time delays since injection, the animals were killed, and after perfusion with saline, the liver, brain, and spleen were fixed in formalin. The specimens were embedded in an agar gel matrix and imaged with inversion recovery T1-weighted, proton density spin echo, and T2*-weighted gradient recalled echo (GRE) sequences. At each magnetic field strength, peak liver and spleen signal loss increased with increasing dose of the contrast medium. Signal loss was significantly more conspicuous after a dose of 15 than 5 mumol/kg body weight, but not after a dose of 45 compared with 15 mumol/kg. No signal change was observed in the brain. GRE images showed higher enhancement than proton density-weighted spin echo and inversion recovery images but were noisier. The enhancement showed a plateau between 30 min and 24 hours. Only the signal decrease of the liver after a low dose of contrast medium on GRE images was significantly higher (p < 0.01) at 1.5 than at 0.5 and 0.3 T. Other differences in respect to the field strength were less significant (p < 0.05) or nonsignificant. Differences in the spleen enhancement were nonsignificant. SHU 555A at a dose of 15 mumol/kg is an efficient intracellular contrast agent for liver and spleen at low, mid, and high field strength. Proton density spin echo images are probably the sequence of choice to exploit SHU 555A contrast effects and a wide time window for imaging after its intravenous injection does exist.

Animals↗
PubMedDate not supplied

Impact of hyperthermic regional perfusion therapy on cell metabolism of malignant melanoma monitored by 31P MR spectroscopy.

For the first time, the influence of hyperthermic regional perfusion therapy on tumor cell metabolism has been monitored by means of 31P MR spectroscopy. Shortly after treatment, a complete depletion of high energy phosphates, a significant increase of inorganic phosphate, phosphomono- and phosphodiester resonances and a decrease of pH have been observed. Healthy muscle tissue showed only minor effects caused by this aggressive therapy. The time course of the transient variation of phosphate metabolite concentrations is explained in the framework of a simple pathophysiological model. The results demonstrate that the imediate effect of chemotherapy on tumor tissue can be detected by 31P MRS before any clinical signs of tumor response are visible.

Antineoplastic Agents↗