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T Ehrenstein

Publications and source records attributed to T Ehrenstein.

16 recordsLinked to original sources
PubMed2001

Quantification of morphologic and hemodynamic severity of coarctation of the aorta by magnetic resonance imaging.

OBJECTIVE: As the morpholgic severity of coarctation of the aorta is difficult to assess, especially after previous repair, the value of the technique of multiplanar reconstruction of magnetic resonance imaging data to achieve a 3-dimensional reconstruction of the aortic arch was evaluated and compared to hemodynamic measurements. METHODS AND RESULTS: We performed 30 examinations in 27 patients aged from 6 to 54 years, with a mean of 21 years, by magnetic resonance imaging using a 1.5Tesla scanner with a standard body coil. Measurements of flow across the coarctation were performed using phase shift velocity mapping, and peak velocity was calculated at the site of stenosis. Aortic cross-sectional area before, at, and beyond the stenosis was reconstructed 3-dimensionally to calculate a percentage degree of stenosis. Morphologic severity of stenosis was correlated to invasively assessed hemodynamic gradients and morphologic data from biplane angiography in 23 patients. Among the 30 examinations, 24 patients had been previously treated by either surgery, in 17 patients, or balloon dilation, while 6 had native coarctation. 3-dimensional reconstruction was possible in all and better delineated the anatomy concerning the hemodynamic relevance of stenoses even as compared with biplane angiography. The correlation between severity of narrowing assessed by diameter measurements in the biplane angiography and 2-dimensional magnetic resonance imaging was r = 0.94, and multiplanar reformation with 2-dimensional magnetic resonance imaging was r = 0.87 with a tendency of higher grading with the 3-dimensional technique (p = 0.0001). The correlation of 2-dimensional magnetic resonance imaging with invasively measured hemodynamic gradients was r = 0.67 versus r = 0.74 for the areas assessed by multiplanar reformation, indicating that the hemodynamic relevance of a morphological approach to evaluate the degree of a stenosis should better be assessed 3-dimensionally. CONCLUSIONS: The 3-dimensional reconstruction of the morphologic severity of coarctation offers additional information over conventional imaging especially in patients with kinking, complex geometry, or collaterals, in whom hemodynamic measurements can become unreliable.

Adolescent↗
PubMed2000

[The T2-weighted half-Fourier acquired single-shot turbo-spin-echo technic compared to the conventional T2-weighted turbo-spin-echo technic for cerebral magnetic resonance tomography. A sequence comparison].

PURPOSE: To compare a T2-weighted half-fourier acquired single-shot turbo spin-echo (HF-TSE) sequence (HA-STE-sequence) for cerebral MRI with a standard T2-weighted fast spin-echo (TSE) sequence. MATERIALS AND METHODS: Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) for different cerebral structures, and intracerebral lesions as well as the detectability of intracerebral lesions depending on size and relaxation properties were evaluated on cranial MR examinations of 46 patients with both a TSE and a HF-TSE sequence. RESULTS: SNR and CNR were found to be significantly higher with the TSE sequence for all normal structures and lesions except CSF, and lesions with short relaxation time T2 (p < 0.001). The number of detected lesions larger than 10 mm was similar with both sequences. Thirty-six (TSE) and 34 (HF-TSE) hyperintense, and 7 (TSE) and 2 (HF-TSE) hypointense lesions of at least 5 mm but less than 10 mm in size were detected. Thirty-three (TSE) and 10 (HF-TSE) hyperintense, and 2 (TSE) and no (HF-TSE) hypointense lesions smaller than 5 mm were detected. CONCLUSION: Due to its short acquisition time, the HF-TSE sequence is an alternative for MR examinations of non-compliant or claustrophobic patients. The low SNR and CNR relative to the TSE-technique are limiting factors as to the detectability of small lesions or lesions with low contrast to surrounding structures, with the risk of an increasing number of false negative results in lesions with short T2 relaxation time smaller than 10 mm.

Artifacts↗
PubMed2000

Arterial switch procedure for D-transposition of the great arteries: quantitative midterm evaluation of hemodynamic changes with cine MR imaging and phase-shift velocity mapping-initial experience.

PURPOSE: To evaluate cine magnetic resonance (MR) imaging and phase-shift velocity mapping for assessment of the hemodynamic relevance of stenotic segments or specific hemodynamic changes in the great vessels after an arterial switch procedure for correction of D-transposition of the great arteries. MATERIALS AND METHODS: Twenty consecutive patients (age range, 2-17 years) with an acoustic window that was insufficient for Doppler transthoracic echocardiography were included in the study. Flow and diameter measurements of the pulmonary arterial trunk and its primary branches were performed with phase-shift velocity mapping and cine MR imaging. RESULTS: There were good correlations between pressure gradients in the pulmonary arteries estimated with MR imaging and those measured with Doppler echocardiography (r = 0.83, n = 15) and cardiac catheterization (r = 0.90, n = 13). Cine MR imaging revealed that the diameters of the right and left pulmonary arteries decreased with the expansion of the aorta during systole, which increased the peak velocity. This temporary stenosis was more severe in the right than in the left pulmonary artery and was accompanied by a significantly (P <.05) lower volume flow in the right artery. CONCLUSION: The anatomic situation after arterial switch repair tended to produce temporary stenoses in the primary pulmonary arterial branches, with significant changes in hemodynamics. These changes may affect the long-term outcome and go undetected with other imaging modalities.

Adolescent↗
PubMed2000

A windows based viewing application for image postprocessing in DICOM format.

OBJECTIVE: To design, implement and evaluate a PC-based medical viewing application including image postprocessing for DICOM images for use within an existing hospital infrastructure. MATERIAL AND METHODS: A user-friendly DICOM compliant viewing application including image postprocessing (spatial frequency and contrast enhancement) and HL7 communication ability was designed and implemented on PC basis to run under Windows OS. To assess its quality compared to high-end workstations, an ROC analysis was performed. RESULTS: The use of image postprocessing on a PC significantly improved the perception of low-contrast details in computed radiographs. Review at a radiological workstation was superior to review at a PC with image postprocessing.

Computer Communication Networks↗
PubMed1999

A new ultrasound-based method for the assessment of torsional differences following closed intramedullary nailing of femoral fractures.

OBJECTIVE: A torsional difference of more than 15 degrees is found in up to 30% of patients following closed intramedullary nailing of femoral fractures. The diagnosis is usually established postoperatively by computed tomography. A torsional deformity of more than 15 degrees should be corrected by early derotation. In order to enable an intraoperative control and possible correction to avoid a second operation for the patient, a new ultrasound-based method suitable for the intraoperative setting has been developed, using the anterior condylar line as a distal reference line. DESIGN AND PATIENTS: In a prospective study the torsional difference after closed intramedullary nailing of femoral fractures was measured postoperatively by ultrasound in 32 patients and compared with standard CT readings. RESULTS: Torsional differences measured by ultrasound and CT showed a high correlation (r = 0.8) and a median difference of less than +/-3 degrees. CONCLUSIONS: By the introduction of the anterior condylar line as a distal reference line femoral torsion can accurately be assessed by ultrasound in a position required for intraoperative control and possible correction.

Adolescent↗
PubMed1999

[Automated speech recognition for the generation of medical records in computed tomography].

PURPOSE: A study was performed to compare the performance of automatic speech recognition (ASR) with conventional transcription. MATERIALS AND METHODS: 100 CT reports were generated by using ASR and 100 CT reports were dictated and written by medical transcriptionists. The time for dictation and correction of errors by the radiologist was assessed and the type of mistakes was analysed. The text recognition rate was calculated in both groups and the average time between completion of the imaging study by the technologist and generation of the written report was assessed. A commercially available speech recognition technology (ASKA Software, IBM ViaVoice) running on a personal computer was used. RESULTS: The time for the dictation using digital voice recognition was 9.4 +/- 2.3 min compared to 4.5 +/- 3.6 min with an ordinary Dictaphone. The text recognition rate was 97% with digital voice recognition and 99% with medical transcriptionists. The average time from imaging completion to written report finalization was reduced from 47.3 hours with medical transcriptionists to 12.7 hours with ASR. The analysis of misspellings demonstrated (ASR vs. medical transcriptionists): 3 vs. 4 for syntax errors, 0 vs. 37 orthographic mistakes, 16 vs. 22 mistakes in substance and 47 vs. erroneously applied terms. CONCLUSIONS: The use of digital voice recognition as a replacement for medical transcription is recommendable when an immediate availability of written reports is necessary.

Algorithms↗
PubMed1999

[The value of magnetic resonance tomography (MRT) for evaluating ventricular and anastomotic functions in patients with an extra- or intracardiac total cavopulmonary connection (TCPC)-modified Fontan operation].

PURPOSE: To evaluate different MR methods (ventricle and flow measurements) for the postoperative follow-up of hemodynamics in patients with extra- or intracardial TCPC. MATERIALS AND METHODS: Twenty-eight consecutive patients (14 female, 14 male) within the ages of two to thirty-eight years were examined using a 1.5 T Gyroscan ACS-NT scanner (Philips, Best, Netherlands). 7 patients had an extracardial (eTCPC), and 21 an intracardial (iTCPC) tunnel. The calculation of the ventricular function and muscle mass was performed using "multislice-multiphase" technique by summing up the end-diastolic and end-systolic areas; the flow measurements were evaluated by phase shift velocity mapping in the superior vena cava (SVC), inferior vena cava (IVC), right (RPA) and left (LPA) pulmonary artery. Besides peak and mean velocity, the mean and maximal flow volumes (ml/min) were calculated. RESULTS: Ejection fraction (EF) of the functionally single ventricle was within the normal range (mean 57%) in 22/28 patients while mean muscle mass was elevated in the group with eTCPC (mean 121 g/m2). The mean flow volumes and the peak velocities in all vessels were higher in the group with iTCPC as compared to the one with eTCPC. Clinically relevant retrograde flows in the IVC were only found in the group with iTCPC (7/21), as well as a significant predominant flow distribution towards the RPA (p < 0.05; Wilcoxon signed-rank test); in the group with eTCPC towards the LPA (n.s.). CONCLUSIONS: MRI is a useful method for the assessment of ventricular function and muscle mass in the follow-up after the modified Fontan operation. MRI flow measurements additionally provided clinically relevant information about the hemodynamics in Fontan patients.

Adolescent↗
PubMed1999

Muscle metabolism of professional athletes using 31P-spectroscopy.

PURPOSE: The aim of the study was to examine muscle metabolism in athletes by 31P-spectroscopy (MRS) and to evaluate to what degree the respective resonance spectrum correlates with the kind of muscle exercise. MATERIAL AND METHODS: Twelve runners and 12 young ice skaters were studied by 31P-spectroscopy of the gastrocnemic medialis muscle and the vastus medialis muscle using a surface coil at 1.5 T. RESULTS: Sprinters displayed a higher phosphocreatinine/inorganic phosphate (PCr/Pi) and PCr/beta-ATP ratios than marathon runners. The respective parameters for middle distance runners were in between. Ice skaters could prospectively be divided into sprint- and long-distance runners by our results which correlated with the athletes' training performance. CONCLUSION: 31P-spectroscopy can evaluate the distribution of muscle fiber types. Thus, the athlete's potential for sprint- or long-distance running can be determined. Additional studies will have to demonstrate to what extent training may change muscle fiber distribution.

Adenosine Triphosphate↗
PubMed1998

[Blood flow quantification in hemodialysis shunts by phase contrast magnetic resonance angiography (PC-MRA) compared with duplex sonography].

PURPOSE: Aim of this study was to evaluate whether phase contrast MR angiography (PC-MRA) could provide additional functional information besides morphology in the assessment of haemodialysis fistulae. MATERIAL AND METHOD: Twenty-two patients (11 male, 11 female), aged 22-77 years, were examined. MR images were obtained with a 1.5 T Gyroscan ACS-NT (Philips, Best, Netherlands) using a high-resolution wrap-around coil. In addition to MRA blood-flow measurements were performed with a gradient-echo sequence (TR 14 ms, TE 5-5.5 ms, flip-angle 15 degrees, 6 mm slice thickness, retrospective gating, matrix 96:128) in the venous and arterial section of the fistulae. Doppler flow measurements were performed at the same position with a Sonoline Elegra (Siemens AG, Erlangen) using a 7.5 MHz transducer. RESULTS: Both methods of flow-volume measurements showed a good correlation (r = 0.94 in the arterial section, r = 0.90 in the venous section, p < 0.001). The average calculated blood flow was measured 11% (arterial section) and 12.8% (venous section) higher with Pulsed Waved Doppler as compared to PC-MRA. CONCLUSION: PC-MRA with a high-resolution wrap-around coil is a reliable method for measuring functional parameters like flow-volume and flow velocity in haemodialysis fistulae and a useful complement to the visualisation capabilities of MRA.

Adult↗
PubMed1998

[The diagnosis and imaging of the a. hepatica after orthoptic liver transplantation--a comparison of frequency-modulated and amplitude-modulated color Doppler sonography].

PURPOSE: We examined whether amplitude-modulated color Doppler (power Doppler) sonography provides a better anatomic imaging of the vascular course of the hepatic artery after liver transplantation. PATIENTS AND METHODS: 82 patients were examined with Doppler sonography after liver transplantation. The distal section of the hepatic artery was imaged both with frequency-modulated color Doppler (color Doppler) and power Doppler and a Doppler spectrum derived from each mode for determination of the flow velocity. RESULTS: Native imaging of the hepatic artery was possible in 78/82 patients, in 2/82 patients only after administration of Levovist, and in 2/82 patients it could not be seen. In these two patients the diagnosis of hepatic artery occlusion was confirmed by angiography. The anatomic course was demonstrated more longitudinally by power Doppler than by color Doppler (p < 0.001; chi 2 test) which made the angle correction easier. A disadvantage of power Doppler was the lack of image contrast to the portal veins; thus evaluation of the vascular course in this section was better possible with color Doppler by means of a specifically generated aliasing in the flow of the hepatic artery (p < 0.001; chi 2 test). Determination of the flow velocity showed no significant differences between color and power Doppler supported duplex sonography. CONCLUSIONS: The combined use of color Doppler and power Doppler improves visualization of the hepatic artery after liver transplantation. The lack of visualization of the vessel after administration of Levovist is diagnostic for occlusion of the vessel.

Adult↗
PubMed1998

[Optimal use of MRI mammography from the economic viewpoint].

With the introduction of the contrast agent gadolinum DTPA there were hopes that "MRM" would prove to be the investigatory technique that would largely solve the problems of breast diagnostics. However, after the early years of acceptance, the new method of investigation became a subject of controversy. Nonetheless, MRM today occupies a recognized place in diagnostics for certain indications. It is still true, however, that reliable use of this procedure requires a great deal of experience, since there is a relatively large area of overlap between benign and malignant tumors. Further, the costs are significantly higher than those for conventional methods of investigation. New studies that have been conducted at the Charité, Campus Virchow Medical Center in Berlin, suggest that, if one takes the relevant indications into account, MRM can be economic and contribute significantly to cost reduction. Application of a newly developed software package has shown that the good discrimination in a suspect area resulting from contrast agent enhancement makes possible a reliable differentiation between malignant and benign tissue changes. A further result was that, when certain boundary conditions are satisfied, a contrast agent bolus of 0.1 mmol/kg BW is sufficient, making a double dose (0.2 mmol/kg BW) unnecessary.

Breast Neoplasms↗
PubMed1997

[Contrast agent enhanced duplex ultrasonography: visualization of the hepatic artery after orthotopic liver transplantation].

PURPOSE: A prospective study was carried out to determine whether an improved assessment of the anatomy and flow velocity in the hepatic artery could be achieved by the administration of a capillary transversing contrast agent (Levovist) in patients after orthotopic liver transplantation. METHODS: In 21 (62%) of 34 patients after liver transplantation, only an insufficient visualisation of the hepatic artery was achieved. Therefore, a capillary transversing contrast agent was administered intravenously. Pre- and post-contrast peak velocity and Doppler frequency shift in the proper hepatic artery were measured and image quality of colour and spectral Doppler was assessed by a qualitative scale. RESULTS: Image quality, with complete visualisation of hepatic artery in 79% (precontrast 38%) of all cases, was significantly improved (p < 0.01 (Wilcoxon test)) by the administration of a contrast agent. CONCLUSIONS: Visualisation of the hepatic artery after orthotopic liver transplantation can be improved by the administration of Levovist. It allows a reliable measurement of peak velocity and Doppler frequency shift and helps to avoid further imaging.

Adult↗
PubMed1997

[Dynamic computerized tomography of the bone marrow of normal and pathologic vertebrae].

PURPOSE: The contrast medium dynamics of normal and abnormal bone marrow was examined by CT. MATERIAL AND METHOD: Standardised sections of lumbar vertebrae were obtained after intravenous injection of 80 ml Ultravist 370 and time-density curves of the marrow spaces were calculated in 38 patients. RESULTS: Time-density curves of patients with normal bone marrow differed significantly from those with proliferative bone marrow diseases in respect of maximal density and uptake at 120 and 240 seconds. Patients treated by radiation showed reduced uptake. CONCLUSION: Variations in the time-density curves between normal and abnormal bone marrow provided evidence of different perfusion and uptake of the contrast medium in the extracellular space of the bone marrow. Further investigation will be necessary to determine whether dynamic CT is able to document the effect of radiotherapy or chemotherapy on malignant bone marrow infiltration.

Adenocarcinoma↗
PubMed1995

The role of perforin-expression by granular metrial gland cells in pregnancy.

The pregnant uterus of humans and rodents contains a population of granulated lymphoid cells, which, in the mouse, are called granular metrial gland (GMG) cells and have been described to express high levels of perforin. Since there is evidence for cytolytic activity of these cells and since perforin is a crucial effector molecule for the lytic action of cytotoxic T cells and natural killer cells, we evaluated the function of perforin in the pregnant uterus by using perforin-deficient mice. Perforin-deficient female mice were found to reproduce as efficiently as normal control females when bred either with syngeneic or allogeneic males. However, perforin-deficient mice differed from normal mice in that the frequency of GMG cells was significantly higher within maternal blood spaces and within several compartments of the feto-maternal interface. Proliferating GMG cells, identified by [3H] thymidine incorporation, were observed during more advanced stages of pregnancy when compared to normal controls. In contrast to normal mice, perforin-deficient mice did not display GMG cells attached to degenerating trophoblasts; instead perforin-deficient GMG cells were often observed in association with small maternal lymphocytes. In addition, the lack of transmission of lymphocytic choriomeningitis virus from infected pregnant perforin-deficient mice to the fetuses argued against a role of perforin expression by GMG cells in prevention of virus transmission from the mother to the fetus. Our data indicate that functional perforin is not necessary for successful pregnancies. The morphological changes in the pregnant uterus of perforin-deficient mice might, however, point to a certain, as-yet undefined function of perforin in the uterus of pregnant normal mice, which is functionally compensated in perforin-deficient mice.

Animals↗