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Biomedical subjects

S Flacke

Publications and source records attributed to S Flacke.

At least 19 recordsLinked to original sources
PubMed2005

[Budd-Chiari syndrome in a patient with paroxysmal nocturnal haemoglobinuria].

HISTORY AND CLINICAL FINDINGS: A 61-year-old man with dyspnea and diffuse abdominal pain due to increasing ascites caused by liver cirrhosis of unknown etiology was admitted for consideration of transjugular intrahepatic portosystemic stent-shunting (TIPSS). The patient's medical history included paroxysmal nocturnal hemoglobinuria (PNH), presenting as slight hemolysis diagnosed 24 years previously. One year before the patient underwent radical retropubic prostatectomy for a localized prostate cancer. Shortly after this intervention he developed ascites. INVESTIGATIONS: Color Doppler ultrasonography revealed an abnormal flow in the major hepatic veins. Transjugular liver biopsy indicated hepatic a circulatory disorder. Hepatic venography revealed the so-called "spider web" pattern characteristic for the Budd-Chiari syndrome. The hypercoagulable state due to paroxysmal nocturnal hemoglobinuria was accentuated by manipulation on the prostate during prostatectomy and presumably resulted in a thrombotic obstruction of the hepatic veins. TREATMENT AND CLINICAL COURSE: After exclusion of contraindications a transjugular intrahepatic portosystemic stent shunt (TIPSS) was performed, which led to a decrease of portal pressure. Signs of portal hypertension such as esophageal varices and ascites resolved completely. The patient has been free of complaints for one year. CONCLUSION: We assume that a hypercoagulopathy due to asymptomatic paroxysmal nocturnal hemoglobinuria resulted in Budd-Chiari syndrome when boosted by postoperative release of procoagulation factors in the thrombokinase-rich prostate. TIPSS is a therapeutic option in these patients.

Ascites↗
PubMed2005

[Combined FDG PET/CT imaging for restaging of colorectal cancer patients: impact of image fusion on staging accuracy].

PURPOSE: To evaluate the diagnostic impact of positron emission tomography (PET) with fluorine-18-labeled deoxy-D-glucose (FDG) combined with non-contrast computed tomography (CT) as PET-CT modality in restaging colorectal cancer patients. MATERIAL AND METHODS: In this retrospective study, 29 consecutive patients with histologically proven colorectal cancer (17 female, 12 male, aged 51-76 years) underwent whole body scans in one session on a dual modality PET-CT system (Siemens Biograph) 90 min. after i.v. administration of 370 MBq 18F-FDG. The CT imaging was performed with 40 mAs, 130 kV, slice-thickness 5 mm and without i.v. contrast administration. PET and CT images were reconstructed with a slice-thickness of 5 mm in coronal, sagittal and transverse planes. During a first step of analysis, PET and CT images were scored blinded and independently by a group of two nuclear medicine physicians and a group of two radiologists, respectively. For this purpose, a five-point-scale was used. The second step of data-analysis consisted of a consensus reading by both groups. During the consensus reading, first a virtual (meaning mental) fusion of PET and CT images and afterwards the "real" fusion (meaning coregistered) PET-CT images were also scored with the same scale. The imaging results were compared with histopathology findings and the course of disease during further follow-up. RESULTS: The total number of malignant lesions detected with the combined PET/CT were 86. For FDG-PET alone it was n = 68, and for CT alone n = 65. Comparing PET-CT and PET, concordance was found in 81 of 104 lesions. Discrepancies predominantly occurred in the lung, where PET alone often showed true positive results in lymph nodes and soft tissue masses, where CT often was false negative. Comparing mental fusion and "real" co-registered images, concordance was found in 94 of 104 lesions. In 13 lesions or, respectively, in 7 of 29 patients, a relevant information was gathered using fused images. CONCLUSION: Combined PET/CT leads to greater accuracy in the interpretation of data and is a valuable tool for diagnosis and anatomic localization of metastases in colorectal cancer patients.

Aged↗
PubMed2005

[CT coronary angiography in patients with atrial fibrillation].

PURPOSE: Reliable visualization of the coronary arteries with multislice spiral CT angiography (MSCTA) in patients with atrial fibrillation (AF) remains a challenge despite retrospective ECG gating. A recently developed new algorithm automatically compensates dynamic changes in the heart rate during the scan, thus reducing misregistration and motion artifacts. The HeartBeat-RT algorithm combines a fixed-percent delay determined from the first R wave and the fixed offset delay based on the second R wave in the ECG cycle. The purpose of this study was to find out the optimal reconstruction window in MSCTA in patients with AF for each of the three major coronary arteries during the cardiac cycle. MATERIALS AND METHODS: 20 patients with permanent AF were imaged on a 16-slice scanner (slice collimation: 16 x 0.75 mm; rotation time 0.42 s; 140 kV; 380 mAs; 120 ml Ultravist 370 (R) i.v.). The patients had not received any previous drugs for heart frequency regulation. Acquisition was started after bolus tracking of a biphasic bolus of 120 ml Ultravist 370 injected intravenously. Each coronary segment was reconstructed at 0 % - 90 % of the cardiac cycle in increments of 10 %. For image analysis we used coronary segments as defined by the American Heart Association. Two blinded independent readers assessed the image quality in terms of visibility and artifacts (five-point rating scale 1 = very poor, 2 = poor, 3 = fair, 4 = good and 5 = excellent) and the degree of stenosis (five-point rating scale 1 = 0 %, 2 = 1 % - 49 %, 3 = 50 % - 74 %, 4 = 75 % - 99 %, 5 = 100 %) on axial slices, multiplanar reconstructions and three-dimensional volume-rendered images. RESULTS: The heart rate during examination ranged between 42 and 156 beats per minute, the average heart rate was 78 +/- 23. Each of the two readers evaluated 300 segments in 20 patients. Visualization of all coronary artery segments was superior at 40 % (mean score of the image quality 2.79) as compared to the standard diastolic reconstruction window at 80 % (image quality 2.33). The second best image quality (2.57) was acquired at 0 % of the cardiac cycle. CONCLUSION: The use of a frequency adapted delay algorithm with the choice of an end-systolic reconstruction window provided diagnostically valuable images in patients with AF.

Aged↗
PubMed2005

[Radiologic features of inflammatory pseudotumors].

Inflammatory pseudotumor is a rare benign tumor entity. Because inflammatory pseudotumors mimic malignant tumors both clinically and radiologically, the radiologist should be familiar with this entity. Inflammatory pseudotumor most commonly involves the lung and the orbit, but it has been reported to occur in nearly every site in the body. For making a definite diagnosis a biopsy is often essential. The treatment options are varied and consist of surgery, high-dose steroids, irradiation, and chemotherapeutics.

Adult↗
PubMed2004

[The value of applying nitroglycerin in 3D coronary MR angiographie with real-time navigation technique].

PURPOSE: Nitroglycerin administration results in dilation of epicardial coronary vessels and in an increase in coronary blood flow, and has been suggested to improve MR coronary angiography. This study evaluates systematically whether administration of nitroglycerin improves the visualization of coronary arteries and, as a result, the detection of coronary artery stenosis during free breathing 3D coronary MR angiography. MATERIALS AND METHODS: Coronary MR angiography was performed in 44 patients with suspected coronary artery disease at a 1.5 Tesla System (Intera, Philips Medical Systems) (a) with and (b) without continuous administration of intravenous nitroglycerin at a dose rate of 2.5 mg/h, using an ECG gated gradient echo sequence with real-time navigator correction (turbo field echo, in-plane resolution 0.70 x 0.79 mm(2), acquisition window 80 ms). Equivalent segments of the coronary arteries in the sequences with and without nitroglycerin were evaluated for visualized vessel length and diameter, qualitative assessment of visualization using a four point grading scale and detection of stenoses > 50 %. Catheter coronary angiography was used as a gold-standard. RESULTS: No significant differences were found between scans with and without nitroglycerin as to average length of the contiguously visualized vessel length (p > 0.05) and diameter (p > 0.05). There was also no significant difference in the coronary MR angiography with and without nitroglycerin in the average qualitative assessment score of the visualization of LM, proximal LAD, proximal CX, and proximal and distal RCA (2.1 +/- 0.8 and 2.2 +/- 0.7; p > 0.05). Sensitivity (77 % [17/22] vs. 82 % [18/22] p > 0.05) and specificity (72 % [13/18] vs. 72 % [13/18] p > 0.05) for the detection of coronary artery stenosis also did not differ significantly between scans with and without intravenous administration of nitroglycerin. CONCLUSION: Administration of nitroglycerin does not improve visualization of the coronary arteries and detection of coronary artery stenosis in free breathing 3D coronary MR angiography.

Coronary Angiography↗
PubMed2004

[Diagnostic imaging of vascular leiomyosarcomas].

Primary vascular leiomyosarcomas are very rare tumors, with the venous variety most often arising from the inferior caval vein and the arterial variety from the pulmonary artery. The tumors show either an exclusive intra- or extravascular pattern or a mixed growth pattern. The clinical symptoms depend on tumor location, with intraluminal tumors of the inferior caval vein causing edema or a Budd-Chiari syndrome. Leiomyosarcomas of the pulmonary artery can mimic chronic central or recurrent peripheral pulmonary embolism. Contrast enhanced spiral CT with multiplanar reconstruction is the diagnostic method of choice when a vascular leiomyosarcoma is suspected. MRI with MR-angiography can be added. If a tumor of undetermined origin shows a broad contact with a vessel and/or an intraluminal component, possible primary vascular leiomyosarcoma should be included in the differential diagnosis.

Budd-Chiari Syndrome↗
PubMed2002

Local intra-arterial thrombolysis in the carotid territory: does recanalization depend on the thromboembolus type?

Little is known about whether recanalization of carotid territory occlusions by local intra-arterial thrombolysis (LIT) depends on the type of the occluding thromboembolus. We retrospectively analysed the records of 62 patients with thromboembolic occlusions of the intracranial internal carotid artery (ICA) bifurcation or the middle cerebral artery who were undergoing LIT with urokinase within 6 h of symptom onset. We determined the influence of thromboembolus type (according to the TOAST criteria), thromboembolus location, leptomeningeal collaterals, time interval from onset of symptoms to onset of thrombolysis, and patient's age on recanalization. The thromboembolus type was atherosclerotic in six patients, cardioembolic in 29, of other determined etiology in four, and of undetermined etiology in 23 patients. Thirty-three (53%) thromboembolic occlusions were recanalized. The thromboembolus location but not the TOAST stroke type nor other parameters affected recanalization. In the TOAST group of patients with cardioembolic occlusions recanalization occurred significantly less frequently when transoesophageal echocardiography showed cardiac thrombus. The present study underlines the thromboembolus location as being the most important parameter affecting recanalization. The fact that thromboembolic occlusions originating from cardiac thrombi had a lower likelihood of being resolved by thrombolysis indicates the thromboembolus type as another parameter affecting recanalization.

Carotid Artery Thrombosis↗
PubMed2002

Perfusion and molecular diffusion-weighted MR imaging of the brain: in vivo assessment of tissue alteration in cerebral ischemia.

The combined use of perfusion imaging (PI) and diffusion-weighted imaging (DWI) is opening a new window into the processes that occur during the first hours of ischemia. DWI detects changes in molecular diffusion associated with cytotoxic edema. PI characterizes the degree of regional hypoperfusion. Regions showing mismatches between DWI and PI, i.e. hypoperfused areas with normal diffusion behavior are considered potentially salvageable. We present results of 11 patients with an occlusion of the middle cerebral artery stem and spontaneous stroke evolution. Whereas the infarct was clearly visible on initial DWI and PI, surrounding tissue at risk of infarction was marked in all patients by an increased blood volume and transit time, but only in a subgroup (n = 3) where alteration were more pronounced this tissue at risk was progressively infarcted. These human DWI and PI data show alterations in the area of tissue at risk which correlates with infarct progression.

Adolescent↗
PubMed2002

In-vivo proton MR-spectroscopy of the human brain: assessment of N-acetylaspartate (NAA) reduction as a marker for neurodegeneration.

Proton magnetic resonance spectroscopy ((1)H-MRS) is a non-invasive method to investigate changes in brain metabolite composition in different cerebral diseases. We performed proton spectroscopy in patients with dementia of the Alzheimer's type (AD) and in patients with motor neuron disease (MND) with the aim to detect the specific metabolic pattern for these neurodegenerative disorders. In the MND group we found a significant reduction of NAA/tCr metabolite ratios in the motor cortex, which correlates with the disease severity and the clinical lateralization of neurological symptoms and further decreases in the time course of the disease. In AD patients a reduction of NAA/tCr was observed in the medial temporal lobe. Since NAA is exclusively expressed in neurons as shown by immunohistochemical studies, reduced NAA levels suggest neuronal loss or dysfunction in the observed regions. The observed regional metabolic alterations reflect the neuronal basis of the characteristic neurological symptoms in AD (dementia) and MND (muscular palsy) and mirrors the disease progress over time.

Aged↗
PubMed2002

[1H-MR Spectroscopy of brain tumors in the course of radiation therapy: Use of fast spectroscopic imaging and single-voxel spectroscopy for diagnosing recurrence].

PURPOSE: To improve differential diagnosis of residual or recurrent tumor vs. tissue necrosis in the course of radiation therapy of neurosurgically-treated brain tumors by application of fast (1)H-MR spectroscopic imaging in combination with single-voxel spectroscopy (SVS). METHODS: 54 patients after with malignant brain tumor (44 cases of glioblastoma, 10 other high-grade gliomas) were examined post-surgically in a total of 140 proton MRS examinations in the course of radiotherapy and in follow-up controls. Fast SI acquisition was performed as single-slice or double-slice TSI sequence with 32 x 32 phase encodings within 11 or 15 minutes, respectively. SVS with TR/TE 2000/272 ms yielded relative metabolite ratios, and in 15 patients the time courses of the absolute concentrations of brain metabolites were also determined. RESULTS: In the group of 44 patients that could be tracked by MRS until therapy completion, TSI localized in 23 patients a persistent or newly arisen distinct choline accumulation indicating residual or recurrent tumor after radiation therapy. In all these cases MRS diagnosis was confirmed histologically or by short-term follow-up. However, in 6 of 15 patients showing a normal choline pattern in the TSI acquisition, tumor recurrence appeared within three months. SVS provided early recognition of recurrent tumor when detecting characteristic alterations of metabolite concentrations oin therapy follow-up. CONCLUSION: TSI and SVS represent complementary MRS techniques and are able to diagnose tumor recurrence early and unambiguously in cases where focal choline accumulation is detected.

Adult↗
PubMed2002

[Is a dynamic MRI examination of the pancreas still necessary?].

PURPOSE: Evaluation of the diagnostic potential of a dynamic MR examination of the pancreas. MATERIAL AND METHODS: Retrospective study on 49 patients who underwent MRI of the pancreas (2 insulinomas, 2 cystadenomas, 19 pancreatic carcinomas, 26 patients with chronic pancreatitis). Interpretation was done in two steps: Initial evaluation of T2-weighted TSE-sequences, T1-weighted gradient echo sequences before and after injection of Gadolinium-DTPA i. v. Afterwards, additional evaluation of a dynamic contrast-enhanced MRI series of the pancreas with four dynamic scans. RESULT: Dynamic MR examination of the pancreas is useful in case of insulinomas. However, in case of pancreatic cancer an additional dynamic MR examination of the pancreas does not provide further clinically relevant information. CONCLUSION: In patients with a suspicion of pancreatic cancer, the injection of contrast material should preferably be used for the performance of a contrast-enhanced MR angiography at the expense of a dynamic MR examination.

Carcinoma↗
PubMed2002

[Submillimeter 3D coronary MR angiography with real-time navigator correction in 107 patients with suspected coronary artery disease].

PURPOSE: To evaluate the clinical value of high-resolution coronary MR angiography (coronary MRA) in a large group of patients with suspected coronary artery disease. METHODS AND MATERIAL: 107 patients with suspected coronary artery disease underwent free-breathing coronary MRA (Intera, 1.5 T, Philips Medical Systems). To compensate for artefacts due to respiratory motion, a right hemidiaphragmatic navigator with real time-time slice correction was used. An ECG-gated, fat-suppressed, 3D segmented-k-space gradient echo sequence (in plane resolution 0.70 x 0.79 mm(2)) was used. Cardiac catheterization with selective coronary angiography was performed in all patients. Visualization of the coronary arteries (CA) was qualitatively assessed using a four-point grading scale. RESULTS: Image quality of grade 1 was achieved in 24 %, grade 2 in 48 %, grade 3 in 24 % and grade in in 4 % of patients. Based on an evaluation of the coronary MRAs of all patients (n = 107) sensitivity and specificity for the detection of stenoses > 60 % in the proximal and middle main coronary arteries were 74 % and 63 %, respectively. In coronary MRAs with good quality [grade 1 and 2, n = 77/107 (72 %)] sensitivity and specificity for the detection of coronary stenoses were 88 % and 91 %, respectively. CONCLUSION: Submillimeter 3D coronary MRA with real-time navigator correction allows high quality imaging of the proximal and middle main coronary arteries with good sensitivity and specificity for detection of stenoses > 50 % in selected patients. However, in about 28 % of patients image quality is severely impaired.

Adult↗
PubMed2002

Three-dimensional magnetic resonance cholangiopancreatography with respiratory triggering in the diagnosis of primary sclerosing cholangitis: comparison with endoscopic retrograde cholangiography.

BACKGROUND AND STUDY AIMS: The purpose of this study was to evaluate the accuracy of respiratory-triggered three-dimensional magnetic resonance cholangiopancreatography (3D-MRCP) for the detection of primary sclerosing cholangitis (PSC) and to compare the specific findings of magnetic resonance cholangiography and endoscopic retrograde cholangiography in patients with PSC. PATIENTS AND METHODS: The MRCP findings were evaluated in 150 patients with clinical symptoms (progressive fatigue, pruritus followed by icterus) and/or elevated values for alkaline phosphatase and serum aspartate transaminase, and occasionally an elevated serum concentration of bilirubin as a sign of cholestasis, who were consecutively referred for magnetic resonance imaging. Two observers independently classified bile duct abnormalities and established the MRCP diagnosis in a consensus reading. The results of MRCP were compared with the definitive diagnosis, which was based on the clinical history and laboratory and histological data, as well as on endoscopic retrograde cholangio-pancreatography (ERCP) findings. In a second step, the observers compared the delineation of the biliary system and morphological findings using MRCP and ERCP in patients with confirmed PSC. RESULTS: Diagnostic examinations were obtained in 146 of the 150 MRCPs (97 %). The diagnosis of PSC was confirmed by clinical data and ERCP in 34 of these 150 patients (23 %). The sensitivity and specificity of MRCP for diagnosing PSC were 88 % (29 of 33) and 99 % (108 of 109), respectively. MRCP and ERCP yielded similar scores for the delineation of the biliary system (P = 0.2) in patients with PSC. However, different bile duct abnormalities leading to the diagnosis of PSC were depicted by MRCP and ERCP; more bile duct stenoses and pruning were seen with ERCP and more skip dilatation with MRCP (P < 10(-4)). CONCLUSION: In patients with PSC, MRCP is a highly sensitive method and its diagnostic accuracy is comparable to that of ERCP.

Adolescent↗
PubMed2001

Novel MRI contrast agent for molecular imaging of fibrin: implications for detecting vulnerable plaques.

BACKGROUND: Molecular imaging of thrombus within fissures of vulnerable atherosclerotic plaques requires sensitive detection of a robust thrombus-specific contrast agent. In this study, we report the development and characterization of a novel ligand-targeted paramagnetic molecular imaging agent with high avidity for fibrin and the potential to sensitively detect active vulnerable plaques. METHODS AND RESULTS: The nanoparticles were formulated with 2.5 to 50 mol% Gd-DTPA-BOA, which corresponds to >50 000 Gd(3+) atoms/particle. Paramagnetic nanoparticles were characterized in vitro and evaluated in vivo. In contradistinction to traditional blood-pool agents, T1 relaxation rate as a function of paramagnetic nanoparticle number was increased monotonically with Gd-DTPA concentration from 0.18 mL. s(-1). pmol(-1) (10% Gd-DTPA nanoparticles) to 0.54 mL. s(-1). pmol(-1) for the 40 mol% Gd-DTPA formulations. Fibrin clots targeted in vitro with paramagnetic nanoparticles presented a highly detectable, homogeneous T1-weighted contrast enhancement that improved with increasing gadolinium level (0, 2.5, and 20 mol% Gd). Higher-resolution scans and scanning electron microscopy revealed that the nanoparticles were present as a thin layer over the clot surface. In vivo contrast enhancement under open-circulation conditions was assessed in dogs. The contrast-to-noise ratio between the targeted clot (20 mol% Gd-DTPA nanoparticles) and blood was approximately 118+/-21, and that between the targeted clot and the control clot was 131+/-37. CONCLUSIONS: These results suggest that molecular imaging of fibrin-targeted paramagnetic nanoparticles can provide sensitive detection and localization of fibrin and may allow early, direct identification of vulnerable plaques, leading to early therapeutic decisions.

Animals↗