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Biomedical subjects

T Krahe

Publications and source records attributed to T Krahe.

At least 55 records · Page 3Linked to original sources
PubMed1991

Quantification of vascular stenosis with color Doppler flow imaging: in vitro investigations.

The accuracy of quantifying the degree of vascular stenosis with color Doppler flow imaging (7.5-MHz, linear array system) was determined in an experimental study carried out on six concentric and five eccentric model stenoses (cross-sectional area reduction, 13.4%-93.8%). The measurements were made with use of pulsatile flow at four different flow rates (70.8-339.0 mL/min). The degree of stenosis was calculated from the ratio of prestenotic to intrastenotic flow velocity. The most exact measurement of the degree of stenosis could be achieved with Doppler spectral analysis by determining the maximum peak systolic velocity (r = .994, y = 0.98x - 3.2). With the velocity values derived only from the color-coded image, it was also possible to find the most exact degree of stenosis (r = .995, y = 0.99x - 2.9). For quantification of stenosis, pre- and intrastenotic Doppler spectral analysis is no longer necessary if the stenosis can be imaged sufficiently with color Doppler.

Blood Flow Velocity↗
PubMed1991

[A ROC analysis for comparing contrast perception in grey scale reversal of digital images].

Based on ROC (receiver operating characteristic) analysis, contrast perception by eight physicians engaged in x-ray diagnostics for different lengths of time was examined in respect of inversion of grey scale values of digital x-ray film images. The ROC analysis showed a significantly superior contrast perception for imaging by the negative mode (bones white) than by the positive mode (bones black). With r* = + 0.61 a positive correlation was obtained between the period of the physicians' activity in x-ray diagnostics and the difference between the areas below the ROC curves for both imaging modes. Hence, the negative mode is to be preferred for diagnostic work based on digital x-ray film images.

Humans↗
PubMed1991

[Experimental and clinical possibilities of MR spectroscopy of the heart].

MR-spectroscopy of the heart is a relatively new technique for the study of various aspects of cardiac metabolism. The majority of results has so far been obtained with the isolated perfused heart. Here, 31P-MR spectroscopy can be employed to measure high-energy phosphate metabolism and intracellular pH repeatedly and non-invasively. Using a technique called saturation transfer, velocities of enzymatic reactions, such as the creatine kinase reaction, can be measured. Intra- and extracellular Na+ and K+ concentrations can be registered with 23Na- and 39K-MR in conjunction with shift reagent. 13C-MR can be used to tackle carbohydrate metabolism. In-situ-R-spectroscopy allows determination of high-energy phosphates in intact large mammals. Clinical applications of MR-spectroscopy remain to be defined; preliminary results indicate high diagnostic and prognostic potential for patients with coronary artery disease and congestive heart failure.

Animals↗
PubMed1990

[Computed tomography in orbital trauma].

The results of CT in 104 patients with traumatic lesions of the orbits have been analysed retrospectively. Eighty-four fractures of the orbital skeleton were diagnosed in 58 patients; in 18 cases there was peri-orbital, retrobulbar or intrabulbar bleeding and two patients had a ruptured globe. A foreign body was demonstrated in 20 cases. Additional fractures of neighbouring paranasal sinuses were present in 22 cases. Mucosal swelling or bleeding in the sinus was found in 59 cases and orbital emphysema in 22 patients. The particular value of CT in the diagnosis of orbital trauma lies in the certainty with which bony injury of the orbit and peri-orbital structures can be demonstrated.

Adolescent↗
PubMed1990

[Gadolinium-DTPA as an oral contrast medium for MR tomography of the abdomen].

150 MR examinations of the upper abdomen were carried out after the oral administration of 5 ml/kg body weight of a gadolinium DTPA formulation (1.0 mmol/l, 15 g/l mannitol), with reference to the delineation of the pancrease, the liver and intra-abdominal fat. For comparison, 100 MR examinations without oral opacification of the G.I. tract were evaluated. Contrast administration resulted in a signal-intensive demonstration of the G.I. tract for all measurement sequences. The intraluminal contrast improved the distinction between normal and abnormal structures. T1 and T2 sequences and the demonstration of fat on T2-weighted series. T1-weighted series showed the best diagnostic results. In 25% there was meteorism and diarrhoea within 24 hours of the administration of the oral contrast.

Abdomen↗
PubMed1990

[Magnetic resonance tomography (MRT) of the hand in chronic polyarthritis].

Forty hands of 39 patients with rheumatic joint disease were examined by MRT. The method differentiates between inflammatory exudative and proliferative processes in soft tissues and bone. T2-weighted images provided criteria for judging the activity of the disease. MRT provided better demonstration of the soft tissues than just conventional radiography. The methods were of equal value for showing bone lesions. MRT is suitable as a means of diagnosing rheumatoid changes in the hand.

Adult↗
PubMed1990

[Indications for cardio-MRT].

Cardio-MRT provides complex diagnostic information (morphology, function, biochemistry) with little stress for the patient and is therefore used increasingly for clinical diagnosis. There is great need for interdisciplinary studies concerning function, the use of contrast media and spectroscopy.

Animals↗
PubMed1990

[Qualitative control over quantitative MR tomography: in vitro and in vivo checks on relaxation time measurements].

In-vivo and in-vitro checks on measurements of relaxation times in MRI have been carried out as part of quality control. For the in-vitro experiments we used 13 reagents consisting of varying concentrations of copper sulphate manganese sulphate, gadolinium solutions and various oils as well as water. For in-vivo measurements we used liver parenchyma and fat in three subjects. Eight different sequences were performed; intra- and interindividual variations and comparison of three similar MRI units showed average variations of 2-3% for T1 and 3-4% variations for T2 relaxation times. This margin of error makes quantitative MRI acceptable for clinical use.

Adolescent↗
PubMed1989

Tc-99m-HMPAO labelled human platelets: in vitro and in vivo results.

The lipophilic 99mTc-HMPAO complex can be used for labelling platelets as well as granulocytes. Platelets were isolated according to standard isolation procedures for the evaluation of the optimal labelling parameters. The labelling efficiency (%) depends on incubation temperature (22 degrees C: 40%: 37 degrees C: 50%), incubation time (3 min: 20%, 25 min: 55%) and the incubation medium (plasma: 40%; saline 50%). The 60 min 99mTc elution out of the platelets ranged around 8%. The platelet recovery used as a quality control parameter is around 25% +/- 4% and is stable for at least 240 min. The high elution rate out of the platelets leads to renal excretion of the label and hence to significant kidney and bladder activity. Intestinal excretion of the label can also be frequently demonstrated. Fresh thrombotic lesions can normally be detected 4 h after reinjection of the labelled platelets, and in some patients as early as 1 h after reinjection. In conclusion, 99mTc-HMPAO seems to be a promising platelet label for imaging thrombotic lesions but not for platelet survival studies, because of the short physical half life of 99mTc.

Blood Platelets↗
PubMed1989

[Diagnostic evaluation of full x-ray pictures and computed tomography of bone tumors of the spine].

The conventional radiographs and CT examinations of 112 patients with primary and secondary bone tumours of the spine have been compared. Two hundred and sixty-eight vertebrae were shown to be involved, using CT; conventional radiographs showed correctly in 88% an involvement of the vertebral bone and in 66% of the different parts of the vertebrae. Of the intraspinal and paravertebral tumour extensions shown by CT, only 23% and 33% respectively were correctly diagnosed by plain radiography. Only 51% of the vertebrae showing a reduction in height on conventional radiographs could be diagnosed on horizontal CT cuts. The type of lesion could be diagnosed in only very few cases by either method.

Evaluation Studies as Topic↗
PubMed1989

[Imaging properties of digital image-intensifier radiography compared to the conventional x-ray technic for chest pictures].

Projection properties of a digital fluorographic system for chest examinations are examined using varying test phantoms. A maximal geometric distortion of +14% between the centre and the periphery of the image intensifier and a maximal spatial resolution of 2.6 LP/mm is found. Contrast detail diagrams are used to show the combination of spatial and contrast resolution of the system. Compared with diagrams for conventional radiographic systems there is a significant loss of resolution.

Adolescent↗
PubMed1989

[High-resolution MR tomography of the hand: normal anatomy].

By using surface coils and a high resolution matrix, the images from MR tomography of small objects can be greatly improved. Normal subjects have been examined in order to demonstrate the usefulness of MR tomography for the examination of bones and soft tissues in the normal hand.

Adolescent↗
PubMed1989

[Digital image intensifier radiography and film-screen combinations in pulmonary nodules].

30 patients with known or suspected pulmonary nodules were examined using a digital image intensifier radiography system, a conventional radiography system and a tomography of the whole lung. 73.8% of the pulmonary nodules detected with tomography were also detected with the digital system, 69.1% with the conventional system. There was no significant difference between the two systems comparing false positive and false negative diagnoses. Regarding the dose reduction to nearly 25% of that of a conventional examination the digital technique should be preferred to the conventional technique, if pulmonary nodules are suspected.

Humans↗
PubMed1989

[Magnetic resonance tomography of children with surgically treated anal and rectal atresia].

MRI of the pelvis was performed in 17 children following surgical correction of anal and rectal atresias and in five children without ano-rectal malformations. A muscle score was used to characterize the muscles of the pelvic floor and their relationship to the rectum. There was close agreement between the MRI muscle score and clinical continence. MRI provided additional information that should improve continence following conservative and surgical treatment.

Adolescent↗
PubMed1989

[Computed tomographic volumetry of the orbit in endocrine orbitopathy].

The volumes of the four recti muscles and the orbital fat was measured by CT in 40 normal persons and in 60 patients with clinically confirmed Graves' disease. Compared with normal persons, 42 patients (70%) showed an increase in muscle volume and 28 patients (46.7%) an increase in the amount of fat. In nine patients (15%) muscle volume was normal, but the fat was increased. By using volumetric measurements, the amount of fat in the orbits in patients with Graves' disease could be determined.

Adipose Tissue↗
PubMed1989

[Effect of magnetic resonance tomography on therapy planning in incontinence after anal atresia].

Five healthy children and 16 children, ages 6-17 years, who had been operated on for anorectal atresia underwent magnetic resonance (MR) imaging of the pelvis. The development of sphincter muscles and the location of the pulled-through intestine in relation to the sphincter muscles were evaluated by a muscle score. There was good correlation between MR muscle score and clinical continence score. MR imaging provides additional information for therapeutic management and surgical procedures to improve continence.

Adolescent↗