Biomedical subjects

W A Kaiser

Publications and source records attributed to W A Kaiser.

At least 55 records · Page 3Linked to original sources

PubMed2002

Electrical impedance scanning of lymph nodes: initial clinical and technical findings.

PURPOSE: The sonographic differentiation between inflammatory and malignant lymph node enlargement remains imprecise. Electrical impedance scanning (EIS) is of more value in malignant breast lesions, and this study was undertaken to determine if it was of use in differentiating nodal enlargement. MATERIALS AND METHODS: Two hundred and thirty-six sonographically suspicious lymph nodes (146 patients) of mean size 18 x 11 x 11 mm mean depth 9 mm were examined using a commercially available electrical impedance imaging system. The following locations of lymph nodes were included in the study: cervical, axillary, inguinal, supraclavicular and chest/abdominal wall. The EIS results were compared to histopathological, serological or follow up findings. RESULTS: Using EIS 105/115 malignant nodes were correctly diagnosed, while 70/121 inflammatory or benign lymph nodes were correctly identified as benign by EIS (10 false-negative, 51 false-positive). Sensitivity (91.3%) and specificity (57.9%) were obtained. Corresponding negative and positive predictive values were 87.5% and 67.3%, respectively. CONCLUSIONS: Results from this initial study suggest potential value for EIS as an imaging adjunct in the differentiation of sonographically equivocal lesions. Best accuracy was achieved at chest/abdominal wall and inguinal locations. Due to technical restrictions with the present system, the examination of inframandibular and para-aortal lymph nodes should be limited to special cases.

Diagnosis, Differential↗

PubMed2002

[Reduction of radiation exposure by using storage phosphor radiography on pelvis and lumbar spine].

PURPOSE: To examine the reduction of radiation dose for radiography of the pelvis and lumbar spine (LS) by using storage phosphor radiography (SPR)? MATERIAL AND METHODS: Each pelvis and LS of 2 phantoms (3 M) and 2 corpses were X-raxed digitally in an anterior-posterior orientation using SPR (ADC compact, Agfa). The tube current time product (mAs) was diminished gradually while keeping the voltage constant. The surface entrance dose was measured by a Dosimax (Wellhöfer) sensor. Five investigators evaluated the images for characteristics and critical features and pathological findings. RESULTS: The images of the 4 various pelvises/LS could be evaluated sufficiently down to an average dose of 34 to 40 %/18 to 35 %. For the assessment of hip joint, region typical corticalis and calcifications (pelvis/LS) 9 to 18 %/8 to 23 % of the initial dose (initial dose is equivalent to a conventional screen film system with a speed class of 400) are enough, spongiosa typical for the region and the sacrum 30 to 56 %/19 to 36 % on average among the readers. CONCLUSION: For the sufficient exclusion of a fracture the dose can be reduced on pelvis/LS to at least 39 %/28 % ( 23 %/17 %), for the assessment of sacroiliitis/osteolyses/demineralisation to at least 78 %/44 % ( 34 to 36 %/22 to 26 %), to position check after fracture to at least 15 %/25 % ( 9 %/10 %). Question-related tube current time products of the pelvis and LS can be deduced for various objects.

Aged↗

PubMed2002

[In vitro imaging of magnetite particles].

PURPOSE: To find an optimal imaging modality for the assessment of magnetite agglomerations used as the heating sources during magnetic thermoablation of tumors. METHODS: 1 to 107 mg of coated (starch) magnetite particles were directly administered to an in vitro tumor model (swine lymph nodes) and investigated immediately (radiography) or after being embedded within a 4 % agar-phantom (sonography). T1-weighted MR images (TR = 400 ms, TE = 14 ms) were acquired from lymph nodes containing 0.5 to 25 mg magnetite. RESULTS: All investigated magnetite masses were qualitatively detectable by radiography. Sonographically, only mass agglomerations containing 107 mg magnetite were appropriately discernible. MRT images revealed distinct susceptibility artifacts. CONCLUSIONS: Based on the investigated imaging modalities, radiography is the method of choice for assessment of magnetite agglomerations using relevant dosages for magnetic thermoablation of tumors.

Animals↗

PubMed2002

Electrical impedance scanning used in addition to ultrasound for the verification of submandibular and parotid lesions: initial results.

OBJECTIVES: Different dielectric properties of cancerous tissues are correlated with increased conductance potentially measurable using Electrical Impedance Scanning (EIS). Sonographically based differentiation of lesions in the salivary glands remains difficult. The clinical value of EIS used additionally to Ultrasound was investigated. METHODS: Sonographically suspicious lesions of parotid (n = 25) and submandibular (n = 16) glands were examined using TransScan TS2000 (TransScan Medical, Israel; distributed by Siemens, Sweden). Bright focal spots representing areas of high conductance were read as positive; absence of a focal spot (ie, homogeneous gray) was read as negative. All lesions were histopathologically proved. RESULTS: 14/15 malignant (93.3%) and 13/26 benign lesions (50.0%) were correctly detected using EIS, NPV 93%, PPV 52%. All cases of squamous cell carcinoma were correctly identified. Lymph node relapse of T-cell lymphoma, lymph node relapse of malignant melanoma, malignant hemangioendothelioma and 2/3 adenocystic carcinoma (primary metastases) were correctly detected. CONCLUSIONS: Our initial results suggest EIS to be of interest when used adjunctively to ultrasound for the identification of malignant lesions of the salivary glands. However, low specificity induced in part by current technical restrictions (bone interference, skin alterations, contact artifacts, prominence of the lesions) limit this clinical application.

Electric Impedance↗

PubMed2002

ROBITOM-robot for biopsy and therapy of the mamma.

MR-Mammography reaches a high sensitivity in detecting breast carcinomas of 3 mm in size at least. In cooperation with the Institute of Diagnostic and Interventional Radiology of the Friedrich-Schiller-University of Jena, a manipulator has been developed by the IMB, which combines the advantages of MRM imaging with a minimal invasive biopsy and a possible subsequent therapy. Referring to this ROBITOM I was introduced in November 1999 as worldwide first, precise operating manipulator system in the ISO center of a closed MR, at RSNA in Chicago. Clinical trials started at 22. November 2000. The experiences and results of these tests were brought into the following prototype ROBITOM II, that is currently developed at the IMB. The completion of this Prototype is planned at the end of 2002.

Biopsy↗

PubMed2002

Automatic image matching for breast cancer diagnostics by a 3D deformation model of the mamma.

X-ray mammograms and MR volumes provide complementary information for early breast cancer diagnosis. The breast is deformed during mammography, therefore the images can not be compared directly. A registration algorithm is investigated to fuse the images automatically. A finite element simulation was applied to a MR image of an underformed breast and compared to a compressed breast using different tissue models and boundary conditions. Based on the results a set of patient data was registered. To archive the requested accuracy distinguishing between the different tissue types of the breast was not necessary. A linear elastic model was sufficient. It was possible to simulate the deformation with an average deviation of approximately of the size of a voxel in the MRI data and retrieve the position of a lesion with an error of 3.8 mm in the patient data.

Breast↗

PubMed2001

Tumour detection rate of a new commercially available computer-aided detection system.

The aim of this study was to determine the tumour detection rate and false positive rate of a new mammographic computer-aided detection system (CAD) in order to assess its clinical usefulness. The craniocaudal and oblique images of 150 suspicious mammograms from 150 patients that were histologically proven to be malignant were analysed using the Second Look CAD (CADx Medical Systems, Quebec, Canada). Cases were selected randomly using the clinic's internal tumour case sampler. Correct marking of the malignant lesion in at least one view was scored as a true positive. Marks not at the location of the malignant lesion were scored as false positives. In addition, mammograms with histologically proven benign masses ( n=50) and microcalcifications ( n=50), as well as 100 non-suspicious mammograms, were scanned in order to determine the value of false-positive marks per image. The 150 mammograms included 94 lesions that were suspicious due to masses, 26 due to microcalcifications and 30 showed both signs of malignancy. The overall sensitivity was 90.0% (135 of 150). Sensitivity on subsets of the data was 88.7% (110 of 124) for suspicious masses (MA) and 98.2% (55 of 56) for microcalcifications. Eight of 14 false-negative cases were large lesions. The overall false-positive rate was observed as 0.28 and 0.97 marks per image of microcalcifications and masses, respectively. The lowest false-positive rates for microcalcifications and MA were observed in the cancer subgroup, whereas the highest false-positive rates were scored in the benign but mammographically suspicious subgroups, respectively. The new CAD system shows a high tumour detection rate, with approximately 1.3 false positive marks per image. These results suggest that this system might be clinically useful as a second reader of mammograms. The system performance was particularly useful for detecting microcalcifications.

Adenocarcinoma↗

PubMed2001

Development, standardization, and testing of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging studies.

The purpose of this study was to develop, standardize, and test reproducibility of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging (MRI) examinations. To standardize breast MRI lesion description and reporting, seven radiologists with extensive breast MRI experience developed consensus on technical detail, clinical history, and terminology reporting to describe kinetic and architectural features of lesions detected on contrast-enhanced breast MR images. This lexicon adapted American College of Radiology Breast Imaging and Data Reporting System terminology for breast MRI reporting, including recommendations for reporting clinical history, technical parameters for breast MRI, descriptions for general breast composition, morphologic and kinetic characteristics of mass lesions or regions of abnormal enhancement, and overall impression and management recommendations. To test morphology reproducibility, seven radiologists assessed morphology characteristics of 85 contrast-enhanced breast MRI studies. Data from each independent reader were used to compute weighted and unweighted kappa (kappa) statistics for interobserver agreement among readers. The MR lexicon differentiates two lesion types, mass and non-mass-like enhancement based on morphology and geographical distribution, with descriptors of shape, margin, and internal enhancement. Lexicon testing showed substantial agreement for breast density (kappa = 0.63) and moderate agreement for lesion type (kappa = 0.57), mass margins (kappa = 0.55), and mass shape (kappa = 0.42). Agreement was fair for internal enhancement characteristics. Unweighted kappa statistics showed highest agreement for the terms dense in the breast composition category, mass in lesion type, spiculated and smooth in mass margins, irregular in mass shape, and both dark septations and rim enhancement for internal enhancement characteristics within a mass. The newly developed breast MR lexicon demonstrated moderate interobserver agreement. While breast density and lesion type appear reproducible, other terms require further refinement and testing to lead to a uniform standard language and reporting system for breast MRI. J. Magn. Reson. Imaging 2001;13:889-895.

Breast↗

PubMed2001

Pitfalls in the clustering of neuroimage data and improvements by global optimization strategies.

In this paper, we examined three vector quantization (VQ) methods used for the unsupervised classification (clustering) of functional magnetic resonance imaging (fMRI) data. Classification means that each brain volume element (voxel), according to a given scanning raster, was assigned to one group of voxels based on similarity of the fMRI signal patterns. It was investigated how the VQ methods can isolate a cluster that describes the region involved in a particular brain function. As an example, word processing was stimulated by a word comparison task. VQ analysis methodology was verified using simulated fMRI response patterns. It was demonstrated in detail that VQ based on global rather than local optimization of the objective function yielded a higher performance. Performance was measured in statistically relevant series of VQ attempts using several indices for goodness, reliability and efficiency of VQ solutions. Furthermore, it was shown that a poor local optimization caused either an underestimation or an overestimation of the stimulus-induced brain activation. However, this was not observed if the cluster analysis was based upon a global optimization strategy.

Adult↗

PubMed2001

Elastic registration of x-ray mammograms and three-dimensional magnetic resonance imaging data.

Major problems in treating breast cancer are the early detection of tumors and accurate biopsy of small volumes of breast (mamma) tissue. This report presents an elastic registration algorithm of two x-ray mammograms and a corresponding magnetic resonance imaging (MRI) volume. To cope with the soft tissue deformation of the breast during mammography, a two-dimensional model of breast deformation behavior is used as an elastic transformation. Normalized mutual information is employed as a measure of similarity. Regions of interest in the uncompressed x-ray mammograms are projected into the MRI volume to determine their three-dimensional origin.

Algorithms↗

PubMed2001

[High resolution MR-venography of cerebral arteriovenous malformations].

PURPOSE: The purpose of this study was to evaluate the diagnostic potential of a high resolution MR venography technique in patients with cerebral arteriovenous malformations (AVM). A high-resolution 3D gradient echo sequence was used with a long echo time TE to obtain venous information down to sub-pixel sized vessel diameters of several hundred microns. The method is based on the paramagnetic property of deoxyhemoglobin and the resulting developing phase difference between veins and brain parenchyma at long echo times which leads to signal cancellation. The reconstructed venograms were compared with TOF-MR angiography using qualitative and quantitative criteria with the conventional DSA serving as the reference gold standard. METHODS: In 17 patients with angiographically proven cerebral AVM the method indicates its potential in clinical applications. Venography was able to detect all AVM whereas TOF-MRA failed in three patients. In the delineation of venous drainage patterns MR venography was superior to TOF-MRA, however, as expected the method detected only about half of the main feeding arteries. Due to susceptibility artifacts at air/tissue boundaries or interference with paramagnetic hemosiderin, MR venography was limited with respect to the delineation of the exact nidus sizes and shapes in ten patients with AVM located close to the skull base or in patients having suffered from previous bleeding. RESULTS: Although the visualization of draining veins represents an important prerequisite in the surgical and radiosurgical treatment planning of cerebral AVM, there exist limitations of the technique in regions where strong induced static field inhomogeneities are present. CONCLUSIONS: Due to its high sensitivity the method may be of special importance in the early detection and assessment of small AVM which are difficult to diagnose with other MR methods.

Adolescent↗

PubMed2001

[Imaging of coronary vascular abnormality with aneurysm and arteriovenous fistula using MRI bolus tracking].

Coronary arteriovenous fistulas are very rare findings and predominantly drain into the right atrium or the right ventricle. Echocardiography and x-ray coronary angiography are established methods in the detection of this anomalies. It is reported on a patient, in whom an anomaly with dilatation of the circumflex coronary artery, aneurysma and drainage over an arteriovenous fistula in the right ventricle was observed. By means of magnetic resonance tomography with bolustracking technique the vessel course and the dynamics of perfusion are noninvasive shown beside the imaging using TSE-sequence. The method of multiple injections of 2 ml Gd-DTPA makes the bolustracking technique to an ideal tool for the determination of the individual vessel course, the haemodynamics and draining direction of an coronary anomaly with fistula.

Adult↗

PubMed2001

High-resolution blood oxygen-level dependent MR venography (HRBV): a new technique.

Our purpose of this study was to demonstrate the clinical potential and spatial resolution of a new MRI technique: high-resolution blood oxygen-level dependent venography (HRBV), in well-known intracranial vascular lesions, such as cavernous and venous angiomas, and venous sinus thrombosis. HRBV provides unique high-resolution information on veins without administration of contrast medium. The data are independent of conventional findings on MRI and potentially useful in characterising and demonstrating the architecture of vascular lesions of the brain.

Adult↗

PubMed2001

Two cases of metastases to the breast on MR mammography.

We report appearance of two cases of metastases to the breast on MR mammography. Metastasis from cervical cancer displayed a hypointense tumor with a central area of high signal intensity on T2-weighted images and rapid annular enhancement with persistent central contrast enhancement. The metastases from rhabdomyosarcoma were characterized by multiple tumors with high signal intensity on T2-weighted images and fast annular contrast enhancement. We show unusual malignant breast lesions for possible identification in dynamic MR mammography.

Breast Neoplasms↗

PubMed2001

Additional value of electrical impedance scanning: experience of 240 histologically-proven breast lesions.

The aim of this study was to quantify the clinical value of using electrical impedance scanning (EIS) as an adjunct to other diagnostic techniques in order to identify cancerous tissue based upon its inherent altered local dielectric properties. 210 consecutive women with 240 sonographically and/or mammographically suspicious findings were examined using EIS. All lesions were histologically-proven. 86/103 malignant and 91/137 benign lesions were correctly identified using EIS (87.8% sensitivity, 66.4% specificity). NPV and PPV of 84.3% and 65.2% were observed, respectively. Excluding cases as defined by a priori criteria, i.e. lesions located deeper than 35 mm, lesions larger than 35 mm, and retroareolar lesions, a sensitivity of 85.5% was observed, and for invasive cancers, 91.7%. The detection rate for ductal carcinoma in situ (DCIS) was poor (57.1%, n=14). By adding EIS to mammography and ultrasound, the sensitivity rose from 86.4 to 95.1%, whereas the accuracy decreased from 82.3 to 75.7%. EIS appears to be of interest as an adjunct to breast diagnostic techniques, performing with a reasonable sensitivity. Further investigations on histomorphological characteristics and the reasons for false-negative findings are essential to gain further knowledge about the bioelectricity of breast lesions, and prove the value of this new technology.

Breast Neoplasms↗

PubMed2001

Vacuum-assisted resection of malignant tumors with and without subsequent radiofrequency ablation: feasibility of complete tumor treatment tested in an animal model.

PURPOSE: To evaluate the feasibility of vacuum-assisted tumor excision with and without RF ablation for the minimally invasive treatment of small tumors. MATERIALS AND METHODS: Twenty VX2 tumors were implanted bilaterally into the spine muscle of 10 rabbits. Tumor excision was performed after tumor sizes reached 10 mm (12-27 d incubation) with use of a vacuum-assisted biopsy device. Three or four directed vacuum-assisted biopsies were performed in angle steps of 30 degrees. In 10 tumors, ultrasound (US)-guided radiofrequency (RF) ablation (8 min, 60 W) was subsequently performed with use of a cooled-tip electrode system. Follow-up US was performed at 3-4-day intervals for as long as 3 weeks after excision/RF ablation. Autopsy and histopathologic analysis were performed. RESULTS: The duration of vacuum excision ranged from 12 to 45 minutes (25 min +/- 7). Histologically tumor-free margins in the outer round of the core biopsy specimens were found in only four of 20 cases (20%). Maximum lesion sizes during RF ablation ranged from 18 to 25 mm (20 mm +/- 2.6). Histologic examination of the excision specimens documented tumor-free margins in only three tumors (30%) among the excision-only group and only one (10%) among the combined excision/ablation group. Local recurrences occurred in eight of 10 cases (80%) after vacuum excision alone, whereas recurrence after combined excision and RF ablation occurred only in two of 10 cases (20%; P <.05). CONCLUSIONS: Local tumor resection with use of vacuum-assisted biopsy is feasible and promising as a minimally invasive therapy for the treatment of small focal breast neoplasms. Combined excision and RF ablation techniques may reduce the rate of local recurrence considerably.

Animals↗

PubMed2001

Differentiation of mammographically suspicious lesions: evaluation of breast ultrasound, MRI mammography and electrical impedance scanning as adjunctive technologies in breast cancer detection.

AIM: Various modalities are used as an adjunct to mammography for differentiation of potentially suspicious breast lesions. Electrical impedance scanning (EIS) is a new technique based upon the principle that cancer cells exhibit altered local dielectric properties and thus show measurably higher conductivity values. The accuracy of differentiation of benign and malignant breast lesions was evaluated to determine whether EIS duplicates or supplements the results obtainable from ultrasound (US) or magnetic resonance imaging (MRI). MATERIALS AND METHODS: One hundred mammographically suspicious lesions were examined using US, MRI and EIS. Definitive histology was acquired through either lesion biopsy or surgical excision. RESULTS: Fifty of 62 malignant lesions were correctly identified using EIS (81% overall sensitivity), 24/38 benign lesions were correctly identified as benign (63% specificity). Negative predictive value and positive predictive value of 67 and 78% were observed, respectively. kappa-factor evaluation revealed a value of 0.82 between MRI and EIS and 0.62 between US and EIS. CONCLUSIONS: EIS may be a valuable adjunct for differentiation of suspicious mammographic lesions. Based upon the calculated kappa-factor, EIS results supplement US examinations. Artifacts (superficial skin lesions, poor contact, air bubbles) currently result in the high false-positive rate of EIS.

Breast Neoplasms↗

PubMed2001

False-negative findings of malignant breast lesions on preoperative magnetic resonance mammography.

The aim of this study was to evaluate causes and percentages of false negative diagnoses of malignant breast lesions on preoperative dynamic magnetic resonance mammography (MRM). MRM was performed in 223 patients with 234 histopathologically proven malignant breast lesions (193 invasive carcinoma, 41 CIS) which were analyzed prospectively by routine analysis prior to surgery and re-analyzed by specialists, retrospectively. False negative findings were re-evaluated with respect to contrast enhancement, size and shape of lesions, reading errors, and technical problems. Preoperative analysis missed 27 of 234 malignant breast lesions (sensitivity 88.5%) including 15 of 193 invasive cancers (sensitivity 92%) and 12 of 41 CIS (sensitivity 71%). Five of 193 invasive cancers (four invasive lobular, one invasive tubular carcinoma) and five of 41 CIS lesions were missed due to delayed or no contrast enhancement. The remaining 17 false negative diagnoses were due to reading errors (n=8), previous core biopsies (n=3), metal induced artefacts (n=3), localization outside the field of view (n=1), incorrect injection (n=1) or movement artefacts (n=1). Using dynamic MR mammography, there were 4.3% slow contrast enhancing malignant breast lesions and a maximum sensitivity of 95.7% for detection of all malignant breast lesions (97.4% for invasive breast cancer, 87.8% for carcinoma in situ) can be achieved in a preselected preoperative population.

Journal Article↗