Biomedical subjects

W Heindel

Publications and source records attributed to W Heindel.

At least 73 records · Page 4Linked to original sources

PubMed2001

[MRI and MR spectroscopy after silicone breast implants in the female breast].

This paper reviews the evaluation of the breast of women by MR-techniques after implantation with silicon gel protheses. The main topics are the diagnosis of implant defects such as extensive "gel bleed" and intra- and extracapsular ruptures. Moreover, the MR-detection of siliconomas (encapsulated silicone) and differentiation from malignomas as well as MR-features of chronic foreign body reactions are presented. "Gel bleed" is difficult to diagnose unambiguously by MRI alone. The "linguini" sign is the only reliable mans to diagnose intracapsular ruptures. The presence of silicone outside the implant capsule indicates extracapsular rupture. The MR-spectroscopic detection of silicone in the liver suggests after short implantation times and a normal MR scan the diagnosis "gel bleed", and after longer implantation times of more than 10 years and missing "linguini" sign the diagnosis of ruptures due to a dissolved shell of the implant. MRI, in comparison to other imaging modalities, has the highest specificity and sensitivity in the diagnosis of implant defects. Due to its high costs, however, MR is not suitable as a screening tool and should only be used in cases of sonographic suspected rupture or after radical mastectomy. In these cases MRI is the method of choice.

Breast↗

PubMed2001

[Radiologic screening for lung cancer: present status and future perspectives].

Radiologic screening for lung cancer: present status and future perspectives. Lung cancer is the most common cause of death from malignancy. This is predominantly due to the poor prognosis of the mostly advanced tumor stages at the time of presentation. Prognosis of early, usually asymptomatic stages is more favourable, particularly in non-small-cell histologic types. Therefore, early detection using diagnostic tests promises reduction of mortality from lung cancer. Due to its high sensitivity for small pulmonary nodules - the most common manifestation of early lung cancer - computed tomography appears suitable as a screening test particularly as the high radiation exposure associated with standard examination protocols can be significantly reduced for this purpose. Due to the high prevalence of benign small pulmonary nodules diagnostic algorithms are required for non-invasive classification of detected nodules. Preliminary studies of low-dose CT using algorithms based on size and density of detected nodules revealed a high proportion of asymptomatic lung cancers and early resectable tumor stages with a small number of invasive procedures for benign nodules. Prior to a wide application of this technique in clinical routine more data is required as to appropriate inclusion criteria, screening intervals and most importantly the effect of screening on reduction of mortality from lung cancer.

Adult↗

PubMed2001

Colorectal polyps: Detection with multi-slice CT colonography.

PURPOSE: To compare the performance of virtual and conventional colonoscopy for the detection of colorectal polyps using a multislice spiral CT scanner (MSCT). MATERIALS AND METHODS: 48 patients (20 women, 28 men, mean age 61.5 years) with clinical indication for conventional colonoscopy were prospectively studied using a MSCT (Somatom Volume Zoom, Siemens, Forchheim). Examination was performed after standard oral preparation for colonoscopy and colonic distension with room air and i. v. butylscopolamin. Images were obtained in prone and supine position using a detector configuration of 4 x 1 mm, a table feed of 5 mm/rotation at 140 mAs and 120 kV. Slice thickness and reconstruction increment were 3 and 1.5 mm, respectively. CT data were assessed by two blinded radiologists on a Vitrea workstation (Vital Images, USA) using a software with multiplanar and volume-rendering capabilities. RESULTS: 33 patients had normal findings on conventional colonoscopy. In 15 patients a total of 30 polyps and one carcinoma with stenosis were identified. MSCT-colonography identified the carcinoma and 23 polyps (77 %). 3 of 3 polyps were 10 mm or more (100 %), 6 of 7 were 5.1 to 9.9 mm (86 %) and 14 of 20 were 5 mm or smaller (70 %). There were 13 false positive findings for polyps (10 lesions < 6 mm in 5 patients) and no false positive finding of carcinoma. CONCLUSIONS: MSCT colonography allows accurate detection of polyps larger than 10 mm. Compared to published results of single-slice CT, multislice CT colonography increases the rate of detection of small colorectal polyps in particular. However, false positive results still remain a problem.

Colonic Diseases↗

PubMed2001

Does the trabecular bone structure depicted by high-resolution MRI of the calcaneus reflect the true bone structure?

RATIONALE AND OBJECTIVES: The purpose of this study was to compare trabecular bone structure parameters assessed with high-resolution magnetic resonance imaging (HR-MRI) with those determined in specimen sections. METHODS: High-resolution MR images were obtained for 30 calcaneus specimens with a three-dimensional, T1-weighted spin-echo sequence (spatial in-plane resolution 0.195 mm, slice thicknesses of 0.3 and 0.9 mm). Thirty-eight sections were obtained from the specimens, and contact radiography was performed. In the corresponding sections, structural parameters analogous to bone histomorphometry were determined. RESULTS: Significant correlations between MRI-derived structural parameters and those derived from macro pathological sections were found: r values of up to 0.75 were obtained (P < 0.01). The highest correlations were found for apparent bone volume/total volume and trabecular thickness. Image thresholding techniques showed a significant impact on these correlations (P < 0.01). The thinner MR sections were less susceptible to the different thresholding algorithms. CONCLUSIONS: Trabecular bone structure depicted by HR-MR images is significantly correlated with that shown in macro sections (P < 0.01); however, a number of limitations have to be considered, including the substantial impact of thresholding techniques and slice thickness.

Aged↗

PubMed2001

Multislice CT angiography of the iliac arteries in the presence of various stents: in vitro evaluation of artifacts and lumen visibility.

RATIONALE AND OBJECTIVES: To evaluate the imaging characteristics of various iliac artery stents and stent-grafts in a multislice, computed tomography angiography (MSCTA) phantom study. METHODS: Twelve types of stents and three stent-grafts made of different materials (steel, nitinol, tantalum, cobalt-based alloy) were implanted in plastic tubes with an 8-mm inner diameter filled with iodinated contrast medium diluted to 200 HU. To evaluate the influence of scan parameters on artifacts, the Palmaz stent (as one example) was scanned with a four-slice scanner (Siemens VolumeZoom) with different detector collimations and pitches. All other stents were examined with a collimation of 4 x 1 mm and a table feed of 4 mm/rotation. Axial images and multiplanar reformations were evaluated regarding artifact size, lumen visibility, and intraluminal attenuation values. RESULTS: Higher pitch values caused more pronounced artifacts. Image quality and delineation of the stent struts improved with thinner detector collimation. The size of the stent-related artifacts and the visibility of the stent lumen depended on the underlying stent material and design. Pronounced artifacts, resulting in an insufficient delineation of the stent lumen, were caused by the Strecker tantalum stent and the Zenith stent. Moderate artifacts were caused by the Wallgraft, Passager, Palmaz P 395 and P 424, Bridge, Perflex, and ZA stents. Some artificial lumen narrowing but good lumen delineation was seen with the Strecker nitinol, Symphony, Memotherm, SMART, Corinthian, and Wallstent stents. CONCLUSIONS: Scanning parameters, stent material, and stent design influence lumen assessability and image quality in MSCTA. Detailed lumen assessment is impossible in the Strecker tantalum and Zenith stents and limited in the Wallgraft, Passager, Palmaz P 395 and PS 424, Bridge, Perflex, and ZA-stent stent-grafts but feasible in all other examined products.

Angiography↗

PubMed2001

Renal tolerance of a neutral gadolinium chelate (gadobutrol) in patients with chronic renal failure: results of a randomized study.

PURPOSE: To assess the renal tolerance of 1.0 mol/L gadobutrol as an electrically neutral contrast agent at magnetic resonance (MR) imaging in patients with impaired renal function. MATERIALS AND METHODS: Twenty-one patients with impaired renal function were enrolled in this prospective randomized study and classified into two subgroups according to their creatinine clearance: group 1 (n = 12), less than 80 mL/min (<1.33 mL/sec) and greater than 30 mL/min (>0.50 mL/sec); group 2 (n = 9), less than 30 mL/min (<0.50 mL/sec) and not requiring dialysis. Gadobutrol (1.0 mol/L) was injected intravenously at randomly assigned doses of either 0.1 or 0.3 mmol per kilogram of body weight. Changes in vital signs, clinical chemistry, and urinalysis results, including creatinine clearance, were monitored before, at 6 hours, and then every 24 hours until 72 hours (group 1) or 120 hours (group 2) after intravenous injection of gadobutrol. Hematologic results were checked every other day. RESULTS: No serious adverse event occurred, and no clinically relevant changes in vital signs, hematologic results, clinical chemistry, or urinalysis results were detected in the observation period. Markers for glomerular filtration (creatinine, cystatin C, beta2-microglobulin, creatinine clearance) and tubular function (N-acetyl-beta-D-glucosaminidase, alpha1-microglobulin) were unaffected by gadobutrol in both groups. CONCLUSION: Gadobutrol did not affect renal function and, therefore, proved to be a safe MR contrast agent in patients with impaired renal function. Even in patients with marginal excretory function (creatinine clearance, <30 mL/min [<0.50 mL/sec]), prehydration or treatment with diuretics or hemodialysis are not required after the administration of gadobutrol.

Adult↗

PubMed2001

Three-dimensional contrast-enhanced MR angiography of endovascular covered stents in patients with peripheral arterial occlusive disease.

OBJECTIVE: Three-dimensional contrast-enhanced MR angiography was performed to study MR characteristics of Hemobahn devices. MATERIALS AND METHODS: Changes in endoluminal signal intensities and the precision of the endoluminal diameter measurement were investigated in phantom studies for different concentrations of gadopentetate dimeglumine. Before and after the Hemobahn devices had been implanted, 10 patients with peripheral arterial occlusive disease were examined on MR imaging and three-dimensional contrast-enhanced MR angiography. RESULTS: Phantom experiments using three-dimensional MR angiography showed stent-related signal void as a dark ring in the axial image orientation, providing a precise delineation of the stent--vessel border (mean endoluminal diameter, 8.2 mm; SD, 0.6 mm). Changes in endoluminal signal intensity were evaluated quantitatively. Stent-related artifacts did not compromise diagnostic imaging quality. All Hemobahn devices were found to be patent without migration of an implanted graft. In one patient, an extensive perigraft reaction (edema and contrast-enhanced perivascular tissue) was postinterventionally detected on MR imaging and corresponded to clinically evident postimplantation symptoms. CONCLUSION: Three-dimensional contrast-enhanced MR angiography is a suitable tool to follow up the implantation of Hemobahn devices and to detect intra- and extraluminal abnormalities.

Aged↗

PubMed2001

Relation between 1H MR spectroscopic imaging and regional cerebral glucose metabolism in Alzheimer's disease.

1 H Magnetic resonance spectroscopic imaging (MRSI) and positron emission tomography (PET) of (18) F-2-fluoro-2-deoxy-D-glucose (FDG) were performed in 18 patients with probable Alzheimer's disease (AD) and 3 normal controls. We measured the distribution and relative signal intensities of N-acetyl aspartate (NAA; a presumed neuronal marker), choline residues (Cho) representing cellular membrane compounds and of creatine-containing metabolites (Cr), and correlated these to regional cerebral glucose metabolism (rCMRGI) after coregistration of both imaging-techniques. The pattern of choline was significantly different between AD and normals (p < 0.01). RCMRGI was significantly related to Cho/Cr (r=-0.21, p<.05) and NAA/Cho quotients (r=0.35, p<.001). Our results suggest that in AD reduced neuronal energy performance and membrane abnormalities contribute to metabolic deterioration.

Adult↗

PubMed2001

Central nervous system involvement in hemolytic uremic syndrome (HUS)--a retrospective analysis of cerebral CT and MRI studies.

PURPOSE: To evaluate the morphological changes of cerebral involvement in children with HUS utilizing CT and MRI. METHOD AND PATIENTS: We retrospectively analyzed 13 cranial CTs (CCT) and 3 cranial MRI studies of 5 out of 93 patients with clinically proven HUS and severe CNS involvement (seizures and coma and dysregulation of breathing) referred to the department of pediatric nephrology (aged 1.5-15 years, median 2 years, 2 girls, 3 boys) between 1987-2000. RESULTS: Three of 5 patients had CT and MRI studies, 2 patients had CT scans only. One of 2 patients with isolated basal ganglia ischemia and normal first CCT developed a secondary hemorrhagic infarction. Another patient with an initially normal MRI developed an infarction of the right cerebral arteries with mass effects. One of 2 patients with basal ganglia involvement showed additional infarction of thalami and external and internal capsules whereas the other had only minimal involvement of adjacent white matter, but consecutive hemorrhagic infarction. Four of 5 children died (3 of them with varying extents of basal ganglia and adjacent white matter involvement, 1 with right cerebral artery infarction). Basal ganglia involvement was found in the majority of cases as well as in all lethal cases. The surviving patient with isolated basal ganglia involvement now suffers from tetraspastic disorder and convulsions. CONCLUSION: Cerebral involvement is one of the major complications of HUS. According to the literature, basal ganglia involvement in HUS is common and quite often associated with other cerebral pathologies. First imaging findings may not show pathologies. Contradictory to previous reports, even children with isolated basal ganglia pathology and/or less involvement of white matter and coma may either die from the underlying disease or their clinical outcome may be poor.

Adolescent↗

PubMed2000

[Diagnosis and therapy of renovascular hypertension].

BACKGROUND: Renovascular hypertension as a secondary form of hypertension can be improved or cured in many cases by interventional radiology or vascular surgery. BASIS: The renin-angiotensin-aldosterone system and the development of hypertension are linked in renovascular hypertension. CLINICAL APPEARANCE: Early clinical symptoms are of special interest in diagnosing renovascular hypertension. DIAGNOSIS AND THERAPY: Nowadays, angioplasty or stenting have mostly replaced surgery in view of treatment of renovascular hypertension. CONCLUSION: Renovascular hypertension, if diagnosed early, can be improved or cured in many cases regarding hypertension and/or renal insufficiency.

Angioplasty, Balloon↗

PubMed2000

[Proton-MR spectroscopy of the spinal bone marrow. An analysis of physiological signal behavior].

BACKGROUND: Magnetic resonance imaging has shown to be a sensitive method for diagnostics of the red bone marrow, the composition of which changes physiologically and during pathological processes. However, the interpretation of MRI in patients with disorders of the red bone marrow is very difficult. The aim of this study was the characterization of the proton spectrum of healthy bone marrow and its age- and sex-dependent changes to obtain a data basis for measurements in patients. METHODS: 154 healthy volunteers have been examined. After imaging, a spectroscopic measurement was performed to determine the relative intensities of fat and water, and their respective T2 times. RESULTS: While T2 (water: 46.9 ms and fat: 75.4 ms) does not depend on age or sex, the relative signal intensity of fat increases by about 6% per decade. In the age groups between 31 and 50 years it diverges significantly between men (43.5%) and woman (32.5%) (p < or = 0.01, Mann-Whitney-Test. CONCLUSIONS: Proton spectroscopy can increase the reliability of diagnosis by offering information on composition of the marrow. The analysis of spectroscopic measurements requires exact knowledge about normal physiological values.

Adolescent↗

PubMed2000

Spiral CT of pulmonary nodules: interobserver variation in assessment of lesion size.

The aim of this study was to assess interobserver variability in size determination of pulmonary nodules at spiral CT. Twenty-three patients with known pulmonary nodules (diameter 2-40 mm, mean diameter 7 mm) underwent spiral chest CT (collimation 5 mm, pitch 1). Images were reconstructed at 3- and 5-mm intervals (RI). Hard copies were analyzed by two radiologists who recorded every nodule with regard to location, diagnostic confidence ("definite," "probable") and nodule size in increments of 1 mm with specific attention to correct classification into one of three size classes (< or = 5 mm, 6-10 mm, > 10 mm). Interobserver variability was determined with Pearson's correlation coefficient and kappa measure. Of a total of 286 nodules, 103 nodules were found accordingly by both readers at 3 mm RI, and 96 at 5 mm RI. There was a good correlation of measurements (in millimeters) between both readers (Pearson's correlation coefficient: 0.89-0.95). Interobserver variability in categories was good at both reconstruction intervals (kappa: 0.61 at 3 mm, 0.74 at 5 mm RI) and very good (0.81) at 5 mm RI when uncertain nodules were excluded. Spiral CT allows reproducible size determination of pulmonary nodules as shown by good interobserver agreement in exact size measurement and categorization into three size classes.

Calibration↗

PubMed2000

Osteochondroma: MR imaging of tumor-related complications.

Osteochondromas can be complicated by mechanical irritation, compression or injury of adjacent structures, fracture, malignant transformation, and postoperative recurrence. Magnetic resonance imaging represents the most valuable imaging modality in symptomatic cases, because it can demonstrate typical features of associated soft tissue pathology, which can be differentiated from malignant transformation. Reactive bursae formation presents as an overlying fluid collection with peripheral contrast enhancement. Dislocation, deformation, and signal alterations of adjacent soft tissue structures can be observed in different impingement syndromes caused by osteochondromas. Magnetic resonance imaging provides excellent demonstration of arterial and venous compromise and represents the method of choice in cases with compression of spinal cord, nerve roots, or peripheral nerves, depicting changes in size, position, and signal intensity of the affected neural structures. Malignant transformation as the most worrisome complication occurs in approximately 1% of solitary and 5-25% of multiple osteochondromas. Magnetic resonance imaging is the most accurate method in measuring cartilage cap thickness, which represents an important criterion for differentiation of osteochondromas and exostotic (low-grade) chondrosarcomas. Cartilage cap thickness exceeding 2 cm in adults and 3 cm in children should raise the suspicion for malignant transformation. Finally, MR imaging can detect postoperative recurrence by depiction of a recurrent mass presenting typical morphological features of a cartilage-forming lesion.

Adolescent↗

PubMed2000

Assessing permeability alterations of the blood-bone marrow barrier due to total body irradiation: in vivo quantification with contrast enhanced magnetic resonance imaging.

Our aim was to quantify irradiation-induced permeability alterations of the blood-bone marrow barrier (BMB) with dynamic contrast enhanced magnetic resonance imaging (MRI). The standard small molecular contrast agent, gadoterate meglumine, and a new macromolecular contrast agent, carboxymethyldextran-Gd-DOTA (CMD-Gd-DOTA), were compared. Twenty New Zealand white rabbits underwent MRI of the bone marrow before and 1-2 days after total body irradiation (TBI). Dynamic, repetitive T1-weighted MRI was performed before and after injection of either 0.05 mmol/kg BW CMD-Gd-DOTA (n = 10) or 0.5 mmol/kg BW gadoterate (n = 10). Bone marrow contrast enhancement was quantified as delta signal intensity: DeltaSI = |(SIpost - SIpre) / SIpre| * 100%. All MRI data were compared with the histopathologic BMB ultrastructure. Dynamic bone marrow DeltaSI data steadily increased after CMD-Gd-DOTA injection, while blood DeltaSI data slightly decreased. This bone marrow contrast enhancement, indicative of contrast agent extravasation, was significantly higher and prolonged in the irradiated group as compared to non-irradiated controls (P < 0.05) and corresponded to irradiation-induced alterations of the BMB ultrastructure seen on electron microscopy. By contrast, DeltaSI data of non-irradiated and irradiated marrow were not significantly different following gadoterate injection (P > 0.05). We conclude that irradiation-induced alterations in BMB permeability could be reliably assessed with dynamic MRI, using the new macromolecular contrast agent CMD-Gd-DOTA. Bone Marrow Transplantation (2000) 25, 71-78.

Animals↗

PubMed2000

[The sacral perineural system--are there radiological criteria for an indication for surgery? First results and literature survey].

PURPOSE: To establish recommendations for diagnostic imaging of cystic lesions of the sacral region and to evaluate for potential predictors of therapeutic outcome. METHODS: Conventional imaging of the lumbar spine, conventional CT, myelography, post myelo-CT and MRI were performed in 7 symptomatic [corrected] patients. All patients underwent operative decompression and histological examination. The radiographic examinations were reevaluated retrospectively and correlated with the postoperative outcome. RESULTS: In one patient the differential diagnosis of a neurinoma could not be excluded with CT and CT-myelography alone. In all 7 patients MRI provided a definite diagnosis and a precise presentation of the cyst extension. A complete postoperative remission of symptoms was noticed in 4, a partial remission in three cases. The correlation of cyst extension, cyst shape, and the communication with the subarachnoid space did not provide predictive information concerning operative outcome. CONCLUSION: MR can be used as the sole imaging tool for demonstration of cystic lesions. Relevant disadvantages in comparison to myelography and myelo-CT were not evident. No imaging modality could predict the value of surgical intervention.

Decompression, Surgical↗

PubMed2000

[MR morphology of primary aneurysmal bone cysts: a retrospective analysis of 38 cases].

PURPOSE: To define MR imaging characteristics of primary aneurysmal bone cyst. MATERIALS AND METHODS: MR imaging studies of 38 patients with histologically proven primary aneurysmal bone cyst were reviewed with reference to morphological features, signal characteristics, and patterns of contrast-enhancement. RESULT: Most lesions were well marginated towards bone and soft tissues (95%), either surrounded by a complete (84%) or incomplete (16%) rim of low signal intensity on images of all pulse sequences. Frequent features were polycyclic margins (84%), cortical expansion (87%), cystic spaces (100%), contrast-enhancing cyst walls (100%), internal septations (89%), fluid levels (71%) and diverticula-like projections of cyst walls (68%). Solid tissue components could be identified by MR imaging in all lesions which, on pathological examination, contained larger portions of solid material (18%). Edema of surrounding soft-tissues was observed in 29% of the cases. CONCLUSIONS: Primary aneurysmal bone cysts demonstrate a relatively uniform MR imaging appearance, which reflects the patho-anatomic composition of the lesion.

Adolescent↗

PubMed2000

[Detection and quantification of coronary calcification: an update].

The demonstration of calcification of the coronary arterial wall indicates the presence of coronary heart disease (CHD). The prevalence of coronary calcifications increases with age. The extent of the calcifications correlates with the total coronary plaque burden and with the probability of a future myocardial infarction in symptomatic patients. In asymptomatic subjects with risk factors for a myocardial event demonstration of coronary calcifications is diagnostic for coronary atherosclerotic disease before clinical manifestation of the disease. Exact quantification of coronary arterial calcifications (calcium scoring) has become possible with electron beam computed tomography (EBCT) or ECG triggered subsecond CT scanners. Further improvements in the detection of coronary calcifications can be expected with the introduction of multi-slice CT. The prognostic relevance of coronary calcium scoring in asymptomatic high-risk patients is not yet clearly defined. It remains to be clarified whether newer, volume based methods of calcium quantification will be superior to the classic calcium score (Agatston-Score) for risk assessment and follow-up in this patient group.

Calcinosis↗

PubMed2000

Non-invasive determination of metabolite concentrations in human transplanted kidney in vivo by 31P MR spectroscopy.

PURPOSE: To investigate concentrations of phosphorus-containing metabolites in human transplanted kidney in vivo by quantitative 31P MR spectroscopy (MRS) using surface coils and to compare the obtained values with previous data. MATERIAL AND METHODS: In 5 patients with well-functioning transplanted kidneys, 31P spectra were obtained with the three-dimensional localization image-selected in vivo spectroscopy technique applying a protocol for quantitative spectroscopy using surface coils. Relaxation corrected signal intensities determined by time domain fitting were used to derive absolute molar concentrations for phosphate-containing metabolites. RESULTS: Little or no phosphocreatine in all spectra verified the absence of muscle contamination, confirming proper volume localization. The mean concentrations in the transplanted kidneys were as follows: ATP 1.60 +/- 0.26 mmol/ 1, PDE 2.14 +/- 0.91 mmol/l, Pi 0.66 +/- 0.25 mmol/l, PME 2.32+ /- 0.50 mmol/l. These values are consistent with previously reported values determined by other techniques. CONCLUSION: The non-invasive determination of absolute metabolite concentrations in human kidney using MRS supplements the use of signal intensity ratios to detect pathologic changes in the energy metabolism of transplanted kidneys.

Adenosine Triphosphate↗