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M Taupitz

Publications and source records attributed to M Taupitz.

At least 37 records · Page 2Linked to original sources
PubMed2003

Visualization of the pulmonary valve using cine MR imaging.

PURPOSE: To evaluate the capability of bright-blood cine MR to directly visualize the leaflets of the valve replacement in pulmonary position following Ross operation. MATERIAL AND METHODS: Long and short axis views of the pulmonary valve were obtained in 10 normal subjects and 14 patients after Ross operation. Valve morphology and function were analyzed and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. Flow measurements were performed in the pulmonary trunk to assess pulmonary regurgitation. RESULTS: In all subjects, tricuspid morphology of the pulmonary valve was visualized. SNR of the leaflets in normal subjects (9.8 +/- 3.0) and in patients after Ross operation (7.5 +/- 2.2) differed significantly from blood (12.6 +/- 3.2 and 11.3 +/- 2.5, respectively, p < 0.05). Valvular regurgitation was seen in 5 patients as an insufficient closure of the valve which was confirmed by flow measurements. CONCLUSION: Cine MR enables in-plane visualization of the pulmonary valve and allows for functional and morphological evaluation in patients after pulmonary valve surgery.

Adult↗
PubMed2002

Bounded-depth threshold circuits for computer-assisted CT image classification.

We present a stochastic algorithm that computes threshold circuits designed to discriminate between two classes of computed tomography (CT) images. The algorithm employs a partition of training examples into several classes according to the average grey scale value of images. For each class, a sub-circuit is computed, where the first layer of the sub-circuit is calculated by a new combination of the Perceptron algorithm with a special type of simulated annealing. The algorithm is evaluated for the case of liver tissue classification. A depth-five threshold circuit (with pre-processing: depth-seven) is calculated from 400 positive (abnormal findings) and 400 negative (normal liver tissue) examples. The examples are of size n=14,161 (119 x 119) with an 8 bit grey scale. On test sets of 100 positive and 100 negative examples (all different from the learning set) we obtain a correct classification close to 99%. The total sequential run-time to compute a depth-five circuit is about 75h up to 230h on a SUN Ultra 5/360 workstation, depending on the width of the threshold circuit at depth-three. In our computational experiments, the depth-five circuits were calculated from three simultaneous runs for depth-four circuits. The classification of a single image is performed within a few seconds.

Algorithms↗
PubMed2002

[Image quality and detection of pathology by ultrasound: comparison of B-mode ultrasound with photopic imaging and tissue harmonic imaging alone and in combination].

PURPOSE: To determine the accuracy of photopic imaging (PI) in detecting pathology by ultrasound (US) and to assess the image quality in direct comparison with conventional B-mode ultrasound and tissue harmonic imaging (THI). MATERIAL AND METHODS: Fifty-two patients underwent US examination, among them 29 patients for abdominal assessment and 23 for otolaryngological assessment. A total of 208 freeze frames, 52 B-mode scans each with and without THI and 52 B-mode scans each with and without PI, were assessed by three readers, who determined the presence of pathology on a scale of 1 (definitely abnormal) to 5 (definitely normal). All 52 patients underwent US follow-up within six weeks. The results were confirmed by CT in 30 patients and by histology in five cases. Image quality and different color encodings of each technique were rated on a ranking scale of 1 (optimal) to 4 (poor). The different US techniques were compared in terms of image quality, diagnostic accuracy, and color encoding using McNemar's test and ROC analysis. RESULTS: The results for image quality were as follows: B-scan 3.9; THI 1.9; PI 2.8; and THI plus PI 1.5 (each p < 0.05). The following AUCs (Area under Curve, presence of pathology) were calculated: 0.925, 0.990, and 0.990 for B-mode US, THI, and PI, respectively (not significant), and 0.994 for THI plus PI (significant compared to B-mode scan). The different color encodings were rated as follows: reddish brown 1.6, gray 1.9, blue 3.1, and green 3.6 (each p < 0.05). CONCLUSION: For ultrasound examinations, PI in combination with THI improves the image quality and conspicuity of pathology.

Abdomen↗
PubMed2002

Iron-oxide-enhanced magnetic resonance imaging of atherosclerotic plaques: postmortem analysis of accuracy, inter-observer agreement, and pitfalls.

INTRODUCTION: Contrast-enhanced magnetic resonance (MR) imaging using ultra small superparamagnetic iron oxide (USPIO) particles is a new noninvasive modality for imaging inflammatory atherosclerotic plaques. We determined the accuracy, interobserver agreement, and potential sources of error of this technique by means of postmortem MR imaging of aortic preparations. MATERIAL AND METHODS: Anesthetized atherosclerotic Watanabe heritable hyperlipidemic (WHHL) rabbits were studied after administration of different dosages of intravenous USPIO (DDM 43/34, IDF Berlin, Germany) and different postcontrast time intervals. A (n = 5) received 0 micromol Fe/kg. B (n = 5) received 50 micromol Fe/kg, 8-hour postcontrast interval. C (n = 5) received 50 micromol, 24 hours. D received 200 micromol, 48 hours. The aortas were removed and 3-mm segments prepared for postmortem examination by MR imaging using a T2-weighted gradient-echo sequence (TR/TE/FA; 41 milliseconds/11 milliseconds/15 degrees ), radiography (mammography), and histology (iron staining). USPIO accumulation was defined as the presence of 20 iron-positive cells per microscopic view (x100 magnification). Two independent readers analyzed the MR images and rated their confidence level for a positive MRI finding, defined as a focal signal loss, on a 5-point scale. The results were evaluated by receiver-operator characteristic (ROC) analysis. RESULTS: Of a total of 621 vessel segments technically acceptable for evaluation, 534 were histologically negative and 87 positive. Accuracy, expressed as the area under the ROC curve, was 0.85 for reader 1 and 0.88 for reader 2. Interobserver agreement was 0.67. False-positive findings were established by at least one reader for 121 of the 621 segments, false-negative findings for only 15 segments. Calcifications and mural thrombi were identified as potential sources of error of the method. CONCLUSION: Postmortem USPIO-enhanced MR imaging of atherosclerotic plaques showed a high accuracy and good interobserver agreement in the animal model used here. Further optimization of the method should aim at reducing the rather high percentage of false-positive results.

Animals↗
PubMed2001

Magnetic resonance imaging of atherosclerotic plaques using superparamagnetic iron oxide particles.

Experimental data show accumulation of superparamagnetic iron oxide (SPIO) particles in atherosclerotic plaques. SPIO uptake occurred in plaques, suggesting an increased endothelial permeability and macrophage infiltrates as signs of inflammatory plaque activity. We incidentally observed SPIO uptake in aortic and arterial wall segments in patients who had originally received the magnetic resonance (MR) contrast agent for staging lymph node metastases. Twenty patients (19 male, 1 female; mean age, 64; range, 41-78 years) with bladder or prostate cancer underwent MR imaging (MRI) using a T2*-weighted high-resolution gradient-echo sequence prior to and 24-36 hours after intravenous injection of 2.6 mg of Fe/kg of SPIO (Sinerem). The aorta, both common external and internal iliac, as well as both superficial femoral arteries, were retrospectively analyzed for atherosclerotic wall changes. One patient was excluded. A positive finding was defined as an area of pronounced signal loss on postcontrast images clearly confined to the arterial wall, which was absent in the precontrast examination or increased in size. Such a finding was observed in one to three arteries in 7 of the 19 patients. The pronounced signal loss in the wall of the aorta and pelvic arteries seen in part of an elderly patient population after intravenous SPIO administration strongly suggests that this contrast agent accumulates in human atherosclerotic plaques.

Adult↗
PubMed2001

Coronary magnetic resonance angiography: experimental evaluation of the new rapid clearance blood pool contrast medium P792.

The signal-enhancing characteristics of a new monodisperse monogadolinated macromolecular MR contrast medium (P792) were evaluated for magnetic resonance angiography (MRA) of the coronary arteries. A total of 15 cardiac examinations were performed in pigs at 1.5 T using a 3D gradient-echo sequence. Images were acquired during breath-hold before and up to 35 min after IV injection of Gd-DTPA (0.3 mmol Gd/kg), Gd-BOPTA (0.2 mmol Gd/kg), and P792 (13 micromol Gd/kg). An increase in the signal-to-noise ratio (SNR) of 97% +/- 17%, 108% +/- 37%, and 109% +/- 31% in coronary arteries and of 82% +/- 19%, 82% +/- 24%, and 28% +/- 18% in myocardium, respectively, was measured during the first postcontrast acquisition. The blood-to-myocardium signal-difference-to-noise ratio (SDNR) was significantly higher for P792 than for the other Gd compounds (P <.05) for up to 15 min after injection. Qualitative assessment showed that visualization of the coronary arteries and their branches was significantly better for P792 compared to the low-molecular Gd compounds (P <.05). The blood pool contrast medium P792 is well suited for MRA of the coronary arteries.

Animals↗
PubMed2001

Patent ductus venosus: diagnosis by MR angiography.

We report a 15-year-old boy with patent ductus venosus in whom the diagnosis was made by MR angiography. A patent ductus venosus Arantii is a rare form of portosystemic shunt. Only a few cases have been reported in adults and children. The diagnosis is usually made by US and digital subtraction angiography. In our patient, the diagnosis was first made by MR angiography. This demonstrates the excellent diagnostic potential of the method in paediatric patients.

Adolescent↗
PubMed2001

Sectional depiction of the pelvic floor by CT, MR imaging and sheet plastination: computer-aided correlation and 3D model.

The structures of the pelvic floor are clinically important but difficult to assess. To facilitate the understanding of the complicated pelvic floor anatomy on sectional images obtained by CT and MR imaging, and to make the representation more vivid, a computer-aided 3D model was created from a male and a female torso to develop a teaching tool. A male and a female cadaver torso were investigated by means of CT, MR imaging, and serial-section sheet plastination. A 3D reconstruction of the pelvic floor and adjacent structures was performed by fusion of CT and MR imaging data sets with sheet plastination sections. Corresponding sections from all three methods could be compared and visualized in their 3D context. Sheet plastination allows distinction of connective tissue, muscles, and pelvic organs down to a microscopic level. In combination with CT, MR imaging, and sheet plastination a 3D model of the pelvic floor offers a better understanding of the complex pelvic anatomy. This knowledge may be applied in the diagnostic imaging of urinary incontinence or prolapse and prior to prostate surgery.

Anatomy, Cross-Sectional↗
PubMed2001

Gadolinium-enhanced MR angiography of the breast: is breast cancer associated with ipsilateral higher vascularity?

The aim of this study was to assess a possible association between breast malignancy and ipsilateral higher vascularity on gadolinium-enhanced MR angiography. One hundred six patients were examined by dynamic gadolinium-enhanced 3D MR imaging. Magnetic resonance angiographic views were generated by image subtraction and maximum intensity projection. The study included 85 patients with unilateral malignant breast neoplasms and 21 with unilateral benign lesions. Three blinded readers independently reviewed the MR angiograms after masking the lesions and the corresponding contralateral sites. The readers were asked to determine whether vascularity was higher on the right side, higher on the left side, or equal on both sides. The results were analyzed by the Kappa statistic and Pearson's chi-square test. The blood vessels of the breasts were clearly seen in all cases. There was good agreement among the observers (kappa > 0.54) in assessing vascularity on both sides. Breasts harboring malignant neoplasms were found to have a higher vascularity than the contralateral breasts (p < 0.005). This sign of malignancy had a sensitivity of 76.5%, a specificity of 57%, and an accuracy of 72.6%. Blood vessels of the breast can be depicted by MR angiography. Unilateral malignant neoplasms are associated with a higher ipsilateral vascularity. In conjunction with other indications of malignancy on gadolinium-enhanced MR images, a higher ipsilateral vascularity may serve as an additional sign of malignancy.

Adult↗
PubMed2001

Diagnostic difficulties before definitive treatment of an extragonadal retroperitoneal germ cell tumor.

A primary extragonadal germ cell tumor of the retroperitoneum was diagnosed in a 47-year-old man without elevated serum alpha-fetoprotein, human chorionic gonadotropin, or lactate dehydrogenase levels. The diagnosis was made by histologic analysis after resection. The patient responded well to a combination of cisplatin, etoposide, and ifosfamide, achieving a partial response with four cycles. Residual tumor resection revealed necrotic tissue only. The patient was alive and disease free 24 months after diagnosis. The diagnostic difficulties of this particular situation are discussed.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Logarithmic simulated annealing for X-ray diagnosis.

We present a new stochastic learning algorithm and first results of computational experiments on fragments of liver CT images. The algorithm is designed to compute a depth-three threshold circuit, where the first layer is calculated by an extension of the Perceptron algorithm by a special type of simulated annealing. The fragments of CT images are of size 119x119 with eight bit grey levels. From 348 positive (focal liver tumours) and 348 negative examples a number of hypotheses of the type w(1)x(1)+. . .;+w(n)x(n)>/=theta were calculated for n=14161. The threshold functions at levels two and three were determined by computational experiments. The circuit was tested on various sets of 50+50 additional positive and negative examples. For depth-three circuits, we obtained a correct classification of about 97%. The input to the algorithm is derived from the DICOM standard representation of CT images. The simulated annealing procedure employs a logarithmic cooling schedule c(k)=Gamma/ln(k+2), where Gamma is a parameter that depends on the underlying configuration space. In our experiments, the parameter Gamma is chosen according to estimations of the maximum escape depth from local minima of the associated energy landscape.

Algorithms↗
PubMed2001

[Contribution of MRI in diagnosis of urinary stress incontinence without concomitant urogenital prolapse].

PURPOSE: To detect pathomorphological changes of the pelvic floor, the vagina, and the urethra by MR imaging in patients with stress urinary incontinence in the absence of organ descent compared with findings in 10 healthy controls. MATERIALS AND METHODS: The study included 10 healthy controls and 38 patients with stage II urinary incontinence showing no urge symptoms but a pathological stress profile on urodynamic testing. The subjects underwent MR imaging with a phased-array coil at 1.5 T in addition to urodynamic testing and gynecological examination. The following sequences were used: axial and coronal PD-weighted TSE sequences with a FOV of 20 cm and a section thickness of 4 mm; axial STIR sequence. Sagittal T2-weighted HASTE sequences were acquired during pelvic floor contraction, relaxation, and straining maneuvers. RESULTS: In 22/38 cases pathomorphological changes were found by MR imaging. The pathomorphological changes were classified as lateral defects (n = 14) if the musculofascial connection between the levator muscle and the lateral vaginal wall or the butterfly shape of the vagina was absent and as central (n = 16) if changes were detected in the urethral wall. Defects of the pelvic floor muscles were detected in 8 cases. No underlying changes were identified in 16/38 cases. CONCLUSION: In cases of female urinary incontinence, MR imaging of the pelvic floor can detect pathomorphological changes, which are difficult to identify by clinical examination. MR imaging currently does not allow the detection of morphological changes in all forms of female urinary stress incontinence.

Adult↗
PubMed2001

The active magnetic resonance imaging stent (AMRIS): initial experimental in vivo results with locally amplified MR angiography and flow measurements.

RATIONALE AND OBJECTIVES: Magnetic resonance (MR) is limited by artifacts in vessels after stenting. An active MR imaging stent (AMRIS) allows for artifact-free imaging with local improvement in signal-to-noise ratio (SNR). In a rabbit model, we evaluated the imaging properties by MR angiography (MRA) and flow measurements. METHODS: The AMRIS was placed in the abdominal aorta of five rabbits. At 1.5 T, MRA (three-dimensional fast low-angle shot) was performed before and after intravenous injection of an iron oxide-based, blood-pool contrast medium (dose, 50 micromol Fe/kg), and flow measurements were performed (electrocardiographically triggered phase-contrast cine gradient-echo sequence). Mean SNRs were calculated and flow volume curves were generated. RESULTS: The SNR was 6.0 +/- 0.6 (outside the stent) versus 12.3 +/- 1.1 (inside the stent, P < 0.05) for plain MRA, 21.2 +/- 0.6 versus 40.6 +/- 5.2 (P < 0.05) for contrast-enhanced MRA, and 5.4 +/- 0.4 versus 13.7 +/- 2.1 (P < 0.05) for the magnitude images of flow measurements. Flow volume curves within and distal to the stent were comparable. CONCLUSIONS: By using the AMRIS as a vascular stent, the stented vessel segment can be examined with enhanced signal intensity on MRI.

Animals↗
PubMed2001

Three-dimensional gadolinium-enhanced magnetic resonance venography in suspected thrombo-occlusive disease of the central chest veins.

STUDY OBJECTIVE: To determine the usefulness of high-resolution three-dimensional (3D) gadolinium-enhanced magnetic resonance venography (MRV) in the evaluation of central venous thrombo-occlusive disease of the chest. DESIGN: Prospective study. SETTING: University hospital. PATIENTS: Sixteen consecutive patients with clinically suspected thrombosis of the superior vena cava, subclavian, brachiocephalic/innominate, internal jugular, or axillary veins. Thirteen patients had a neoplasm, two patients had a connective tissue disease, and one patient had a history of strenuous exercise. Twelve of 16 patients had prior central venous catheter placement. MRI was correlated with color-coded duplex sonography (CCDS) in 7 of 16 patients, digital subtraction angiography (DSA) in 3 of 16 patients, and CT in 2 of 16 patients. INTERVENTION: Contrast-enhanced MRV was performed in a total of 20 examinations. A 3D data set (gradient echo; time to repeat, 4.6 ms; time to echo, 1.8 ms; flip angle, 30 degrees; time of acquisition, 23 s; 512 matrix/64 partitions; slice thickness, 1.5 mm) was acquired in the arterial and venous phase. Overall image quality was assessed on a 5-point scale. The presence, site, and extent of thrombus, as well as presence of an intravascular device, were determined. MEASUREMENTS AND RESULTS: Overall image quality was rated very good (1 point) in 7 of 16 cases (44%) and good (2 points) in 9 of 16 cases (56%). Thrombus was detected in 16 of 16 patients, and complete extent of disease could be determined in 15 of 16 patients (94%). MRV did not miss any finding obtained by CCDS, DSA, or CT, and provided additional information in 6 of 16 examinations (38%). CONCLUSION: Contrast-enhanced MRV is a fast and reliable noninvasive procedure with excellent results regarding detection and determination of the extent of thrombo-occlusive disease of the chest veins.

Adult↗
PubMed2000

Age-related blood half-life of particulate contrast material: experimental results with a USPIO in rats.

It has been well established in the literature that phagocytic activity in animals and humans changes with age, but this phenomenon has not yet been investigated for particulate contrast agents. The present study was therefore performed to determine the effect of age on blood half-life of a superparamagnetic iron oxide blood pool contrast agent and on the velocity of its uptake in the liver and spleen of the rat by means of magnetic resonance (MR) imaging. A total of 18 rats (group A: 214-255 g, age: 45-50 days; group B: 432-563 g, age: 100-120 days) were imaged at 1.5 T using a 3D gradient-recalled echo (GRE) sequence (TR/TE 6.6/2.3 msec; alpha 25 degrees, frontal). Images were acquired before and every 3-5 minutes for up to 30 minutes after i.v. injection of 30 micromol Fe/kg of a citrate-coated superparamagnetic iron oxide-based contrast agent (VSOP-C43). Intravenous injection of VSOP-C43 resulted in a pronounced initial signal enhancement in vessels, which decreased with a half-life of 8.4 +/- 0.9 minutes in group A and of 15.9 +/- 2. 4 minutes in group B (P < 0.01). The half-life of signal decrease was 11.6 +/- 2 minutes and 19.9 +/- 4.4 minutes in the liver (P < 0. 01) and 19.6 +/- 3.1 minutes and 26.7 +/- 5.2 minutes in the spleen (not significant). The results show that the age-related phagocytic activity has a significant effect on the circulation time and velocity of uptake of a particulate MR imaging contrast agent. This fact must be taken into consideration in both the preclinical and clinical development of particulate contrast material and in the clinical application of such agents.

Age Factors↗
PubMed2000

New generation of monomer-stabilized very small superparamagnetic iron oxide particles (VSOP) as contrast medium for MR angiography: preclinical results in rats and rabbits.

The purpose of this study was to evaluate the signal enhancement characteristics of very small superparamagnetic iron oxide particles (VSOP)-C63, a new monomer-coated, iron oxide-based magnetic resonance (MR) blood pool contrast medium with a very small particle size and optimized physical properties. Equilibrium MR angiography (MRA) of rats (thoracic and abdominal vessels) was performed at 1.5 T with a three-dimensional gradient-recalled echo (3D GRE) technique (TR/TE 6.6/2.3 msec, flip angle 25 degrees ) before and after (every 3-5 minutes up to 50 minutes) i.v. injection of VSOP-C63 [dosages: 15, 30, 45, 60, 75, and 90 micromol Fe/kg; diameter: 8 nm; relaxivities at 0.47 T: R1 = 30 l/(mmol * s); R2 = 39 l/(mmol * s)]. First-pass MRA images (3D-GRE, TR/TE 4.5/1.7 msec, flip angle 25 degrees ) were obtained with 45 micromol Fe/kg VSOP-C63 in comparison with 0.2 mmol Gd/kg of gadolinium diethylene triamine pentaacetic acid (Gd DTPA; before and every 5 seconds p.i.). MRA (3D GRE, TR/TE 4.5/1.7 msec, flip angle 25 degrees) of coronary vessels in rabbits was performed after i.v. injection of 45 micromol Fe/kg of VSOP-C63. In rats maximal S/N ratio in thoracic and abdominal arteries directly after i.v. injection of VSOP-C63 was 25 +/- 1, 43 +/- 2, 49 +/- 4, 57 +/- 3, 64 +/- 3, and 63 +/- 3 for the different dosages. Blood half-life was dose dependent (15 +/- 2, 20 +/- 3, 29 +/- 6, 37 +/- 5, 61 +/- 16, and 86 +/- 21 minutes). At a dose of 30 micromol Fe/kg even small intrarenal arteries were sharply delineated. First-pass MRA showed no significant difference in the S/N ratio between Gd-DTPA (71.5 +/- 11.5) and VSOP-C63 (65.1 +/- 18. 3). The proximal segments of the coronary arteries in rabbits were clearly depicted at a dose of 45 micromol Fe/kg. The monomer-coated, iron oxide-based contrast medium VSOP-C63 exhibits favorable properties as a blood pool agent for both equilibrium and first-pass MRA. J. Magn. Reson. Imaging 2000;12:905-911.

Animals↗
PubMed2000

MR imaging in posthysterectomy vaginal prolapse.

In the diagnostic work-up of vaginal prolapse after hysterectomy cystoceles can be identified by sonography, whereas enteroceles and rectoceles can only be suspected in a routine clinical setting. The present pilot study was undertaken to investigate the diagnostic role of magnetic resonance imaging (MRI) in the differentiation of cysto-, entero- and rectoceles in women with posthysterectomy vaginal prolapse. Thirteen women (mean age 61, SD +/- 7 years) with posthysterectomy vaginal prolapse underwent MRI (Gyroscan S 15, Philips). A median sagittal image series was obtained with a gradient-echo sequence, fast field echo, both at rest and during Valsalva maneuvers. MRI allowed the identification of cysto-, entero- and rectoceles, and differentiation between entero- and rectoceles in cases with inconclusive clinical findings. These findings make dissection more reliable and improve the outcome of hernia repair. No additional diagnostic information is obtained with MRI compared to ultrasound in the assessment of cystoceles.

Aged↗