Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Keywords: DOPPLER ; Germany ; IN-VIVO ; MODEL ; MODELS ; CT ; VOLUME ; NEW-YORK ; ACCURACY ; computed tomography ; HEART ; INTEROBSERVER VARIABILITY ; PIGS ; RESOLUTION ; SURGERY ; validation
    Abstract: Background. Cardiac functional assessment represents the basis for diagnostics and cardiac operation planning. Spiral computed tomography (CT) combines the advantages of three-dimensional imaging and high temporal resolution when using gating techniques. However, in vivo validation data of this novel imaging technology are lacking. The purpose of this study was to validate in vivo the new imaging method using retrospective gating and to evaluate the clinical usefulness of the achieved temporal resolution. Methods. In domestic pigs (n = 10, weight 35 to 40 kg) a flowmeter was placed surgically on the ascending aorta. Flow velocity integrated over systole served as the gold standard for left ventricular (LV) stroke volume (LVSV-FM). CT signal, projection data, pacemaker signal, and flow velocity were recorded simultaneously at constant heart rate (pacemaker, 90 beats per minute). End-systolic and end-diastolic frames were calculated by retrospective gating. LV volumes were traced, the difference representing CT stroke volume (LVSV-CT). Image data were three-dimensionally reconstructed using ray- tracing. Results. Temporal resolution was 170 ms. Correlation of stroke volumes was high (r = 0.94, mean difference 1.75 mL). Intraobserver (0.49 mL, for LVEDV, 0.31 for LVESV) and interobserver variability (p = 0.21 and p = 0.06, respectively) were low. Postprocessing resulted in four-dimensional beating- heart models useful for operation planning. Conclusions. Spiral CT using retrospective gating was validated in vivo. Clinically acceptable temporal resolution and accuracy in determining cardiac stroke volumes were found. As a true volumetric imaging modality the method may now play an important role in computer- assisted diagnostics and surgery. (C) 2003 by The Society of Thoracic Surgeons
    Type of Publication: Journal article published
    PubMed ID: 12645712
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Keywords: Germany ; MODEL ; IMAGES ; MAGNETIC-RESONANCE ; AGE ; REPRODUCIBILITY ; active contour ; DISTENSIBILITY ; NMR MEASUREMENT ; VASCULAR COMPLIANCE ; VELOCITY-MEASUREMENT
    Type of Publication: Journal article published
    PubMed ID: 12953905
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    Keywords: Germany ; MODEL ; PERFUSION ; PHASE-I ; IMAGES ; imaging ; QUANTIFICATION ; HEPATOCELLULAR-CARCINOMA ; liver ; BLOOD-FLOW ; MICROCIRCULATION ; REPERFUSION ; TRANSPLANTATION ; CONTRAST ; CONTRAST AGENT ; MR ; SEQUENCE ; SEQUENCES ; magnetic resonance ; MAGNETIC-RESONANCE ; magnetic resonance imaging ; DISPLAY ; MORPHOLOGY ; HEAD ; ISCHEMIA ; dynamic MRI ; HEPATIC PERFUSION ; development ; PHASE ; COIL ; Phase I ; CIRCULATION ; MEDICINE ; MEDIA ; RESONANCE ; German ; PHARMACOKINETIC ANALYSIS ; CONTRAST-MEDIA ; SCANNER ; isolated organs
    Abstract: The investigation of reperfusion of organs after an ischaemic phase is of great interest in transplantation medicine. This work presents an experimental organ model for the examination of isolated canine livers by means of magnetic resonance imaging in reperfusion experiments. The perfusion of the organs inside a perfusate container in the scanner's head coil was performed with approximately physiological conditions for 1.5 hours. The pumps for the perfusate circulation were installed outside the scanner's room, where oxygenation and heating of the perfusate was also performed. In the MR examinations, T1- and T2-weighted sequences could be used to display the morphology of the organs and the spatial perfusion distribution after administration of contrast media. The images revealed oedema development during reperfusion and an inhomogenous perfusion distribution. Thus, the model allows for the non-invasive investigation of morphology and perfusion distribution in isolated reperfused organs
    Type of Publication: Journal article published
    PubMed ID: 17879818
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Keywords: Germany ; segmentation ; TISSUE ; ACCURACY ; TIME ; REDUCTION ; CONTRAST ; MR ; SEQUENCE ; SIGNAL ; magnetic resonance ; MAGNETIC-RESONANCE ; BREAST-CANCER ; LESIONS ; NUMBER ; REGION ; MUSCLE ; PARAMETERS ; NORMAL TISSUE ; sensitivity ; DEFORMATION ; RECONSTRUCTION ; focused ultrasound surgery ; ultrasound ; STATES ; ABLATION ; INVERSION ; development ; LONG ; LOSSES ; ELASTICITY ; phantom ; RESONANCE ; German ; ERROR ; ERRORS ; HIFU ; DISPLACEMENT ; focused ultrasound ; magnetic resonance elastography ; MR ELASTOGRAPHY ; STEAM ; STRAIN IMAGES ; strain imaging ; WAVES
    Abstract: In static magnetic resonance elastography, the elasticity of an object is determined by measuring the internal displacement between two compression states. To reduce signal loss during the long time delay between application of external deformation and the static compression state, a STEAM sequence with a long mixing time is used. This results in long scan times. The aim of this work was the development of a STEAM sequence with a multi-echo-readout, which allows the reduction of scan time and number of necessary external deformations. This new sequence was compared to the standard STEAM sequence on an agarose gel phantom with a hard inclusion. In addition, the elasticity of thermal tissue lesions was investigated, which were induced using high-intensity focused ultrasound (HIFU). During a given measurement time, more acquisitions per image can be taken using the multi-echo-readout. As a result the signal-to-noise ratio is increased and errors in the data become clearly smaller. Drawbacks of the new sequence are its higher signal loss due to T-2-decay and its greater sensitivity against ghosting artefacts caused by k-space segmentation. During the investigation of the thermally-induced lesions, a clear contrast in elasticity between normal tissue and the treated region was observed. Taking advantage of the greater accuracy of the new STEAM sequence, it was shown, that this contrast is significantly larger than the one in conventional MR parameters
    Type of Publication: Journal article published
    PubMed ID: 17665734
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    Keywords: Germany ; MODEL ; CT ; DIAGNOSIS ; computed tomography ; RESOLUTION ; kidney ; renal ; DIFFERENCE ; arteries ; tomography ; COMPUTED-TOMOGRAPHY ; DIGITAL SUBTRACTION ANGIOGRAPHY ; DIGITAL-SUBTRACTION-ANGIOGRAPHY ; maximum intensity projection ; MAXIMUM-INTENSITY-PROJECTION ; ARTERY ; VESSELS ; angiography,kidney,multislice computed tomography (MS-CT),resolution digital subtraction angiography ; HELICAL CT ANGIOGRAPHY
    Abstract: Objective: To compare maximum spatial resolution in multislice computed tomography (MS-CT) and digital subtraction angiography (DSA) using an arterial tree model for canine kidney specimens.Methods: Twenty-three isolated fox terrier kidneys were catheterized with a 4F catheter and underwent contrast-enhanced MS-CT with a maximum spatial resolution of 0.23-mm isotropic voxel size in an early arterial phase. In addition, a digital subtraction angiogram was performed on all kidneys. The kidneys were segmented semiautomatically, and each parenchymal vessel that was identified in the kidney was marked. The maximum intensity projections of arterial vessels in the CT datasets were evaluated in a comparison with the DSA datasets.Results: No significant difference in vessel delineation and count was found at any level up to the fourth level of intrarenal branching.Conclusion: MS-CT has the potential of replacing DSA in the diagnosis of intrarenal arteries
    Type of Publication: Journal article published
    PubMed ID: 14600451
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    Keywords: Germany ; ALGORITHM ; CT ; QUANTIFICATION ; DISEASE ; DISEASES ; computed tomography ; RESOLUTION ; validation ; TIME ; PATIENT ; REDUCTION ; CYCLE ; REPRODUCIBILITY ; LENGTH ; tomography ; COMPUTED-TOMOGRAPHY ; CT ANGIOGRAPHY ; ANGIOGRAPHY ; DISSECTION ; IMAGE-RECONSTRUCTION ; ENHANCEMENT ; development ; TESTS ; aortic distensibility ; aortic elasticity ; functional imaging of vessel wall ; multidetector-row computed tomography ; ROW CT ANGIOGRAPHY ; STIFFNESS ; TEMPORAL RESOLUTION ; ULTRASONIC MEASUREMENT ; WAVE VELOCITY-MEASUREMENT
    Abstract: Aortic distensibility depending on aortic cross-sectional area changes is an important parameter for the grading of vascular diseases. This study measured aortic area changes by multidetector computed tomography. An image reconstruction algorithm was developed to assess aorta diameter and area as a function of the cardiac cycle with sufficient time resolution along the entire length of the aorta by four-detector row computed tomography. The algorithm was tested on porcine aortic specimens and compared with an optical reference method. The error of the relative vessel area change comparing the two methods was found to be about 3%. Initial tests on patient datasets indicate that clinical application is feasible. The proposed method has the advantage that it can easily be integrated into a modified routine CT angiography study and allows the measurement of aortic cross-sectional area changes
    Type of Publication: Journal article published
    PubMed ID: 16044295
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...