Biomedical subjects

J R Reichenbach

Publications and source records attributed to J R Reichenbach.

At least 19 recordsLinked to original sources

PubMed2003

[31P-MR spectroscopy of the brain in patients with anorexia nervosa: characteristic differences in the spectra between patients and healthy control subjects].

PURPOSE: To investigate whether 31 P-MR spectroscopy can detect reduced concentrations of high-energy phosphates, like PCr and NTP, caused by decreased metabolic activity in the brain of patients with anorexia nervosa (AN) and, furthermore, whether any impairment of the cerebral membrane metabolism can be derived from the spectra. MATERIAL AND METHODS: 10 female patients, age range 12 - 20 years and mean BMI (body mass index) of 14.8 +/- 1.6 kg/m 2, with clinically diagnosed AN (ICD-10, F50.0) and 10 healthy control subjects, age range 12 - 21 years and mean BMI 19.0 +/- 2.1 kg/m 2, without nutritional disturbances: were investigated. 31P-MR spectroscopy was performed with a 1.5 T MRI unit using single volume selection in the frontal/prefrontal region of brain. Relative metabolic concentrations were quantified by normalizing the peak areas of the metabolites with the total area of the complete phosphorous spectrum, P tot, as well as with the peak area of beta-NTP. RESULTS: Significant differences between the two groups were observed for the metabolic ratios PDE/P tot, PDE/beta-NTP and alpha-NTP/P tot which were lower in the patient group except for alpha-NTP/P tot. These ratios also revealed a statistically significant correlation with the BMI (r PDE/Ptot = 0.747, r PDE/beta-NTP = 0.57, r alpha-NTP/Ptot = -0.56; p </= 0.1). Reduced relative concentrations of PCr/P tot, beta-NTP/P tot or Pi/P tot were not encountered. CONCLUSION: The lowered PDE/P tot ratio for patients with AN and its correlation with BMI suggests that decreased BMI induces compositional changes of the phospholipids in the brain, which decrease the fraction of mobile phospholipids.

Adolescent↗

PubMed2002

31P-MR spectroscopy in children and adolescents with a familial risk of schizophrenia.

Based on a previous report [9] on alterations of membrane phosphorus metabolism in asymptomatic family members of schizophrenic patients, the aim of the present study was to extend and improve the evaluation and data processing of (31)P spectroscopic data obtained from a larger study population by including an analysis of the broad spectral component (BC) of membrane phospholipids (PL). Eighteen children and siblings of patients with schizophrenia and a gender- and age-matched control group of 18 healthy subjects without familial schizophrenia were investigated with phosphorus magnetic resonance spectroscopy ((31)P-MRS) by using image selected in vivo spectroscopy (ISIS) in the dorsolateral prefrontal regions (DLPFR) of the brain. Spectral analysis was performed by using both the full and truncated FID to estimate metabolic peak ratios of different (31)P metabolites and the intensity and linewidth of the broad component. A significantly higher PDE level (p<0.01) and increased linewidth of the PDE components were observed for the high-risk group compared with the control group (p=0.02). No significant differences were observed for PME as well as for other (31)P-metabolites. No differences were observed between the left and right hemispheres for different normalised (31)P-metabolic levels. Decreased intensities (p=0.03) and smaller linewidths (p=0.01) were obtained for the broad component in the high-risk group. Impairments of membrane metabolism that are typical for schizophrenic patients are partially observed in adolescent asymptomatic family members of schizophrenics, including increased levels of low molecular PDE compounds indicating increased membrane degradation processes, no changes for PME, and decreased intensities and linewidths of the BC indicating changes in the composition and fluidity of membrane phospholipids. Despite limitations to completely suppress fast-relaxing components by dismissing initial FID data points, the spectroscopic results indicate additional changes in the membrane metabolism of high-risk subjects beyond changes of synthesis and degradation.

Adolescent↗

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

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

DTI measurements of isotropic and anisotropic media.

The ability to measure different rates of diffusion along different directions is one of the features that distinguish DTI from other imaging methods. It allows to extract and visualize information on tissue microstructure and microdynamics. However, to correctly determine the full diffusion tensor, the so-called b-matrix has to be calculated by taking into account the non-negligible influences of image gradients and cross-terms between imaging and diffusion gradients. In this work validation of this b-matrix correction was investigated by determining self-diffusion coefficients of several isotropic media on a 1.5 T clinical whole-body scanner. To investigate these influences on the measurements of anisotropic media the same experiments were performed with a carrot.

1-Propanol↗

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

Quantitative differentiation between BOLD models in fMRI.

Several gradient-echo fMRI blood oxygenation level-dependent (BOLD) effects are described in the literature: extravascular spin dephasing around capillaries and veins, intravascular phase changes, and transverse relaxation changes of blood. This work considers a series of tissue compartmentalized models incorporating each of these effects, and tries to determine the model which is most consistent with the data. To isolate the different tissue contributions, a series of multi-echo inversion recovery (IR) fMRI scans were performed. Visual stimulation experiments were performed at 1.5 T, one interleaved six-echo and two IR six-echo EPI scans (the latter to suppress gray matter (GM) and cerebrospinal fluid (CSF)). The tissue and vascular composition of activated areas was analyzed using independent spin-echo IR MRI experiments and MR venography, respectively. This information was used to fit the multi-echo fMRI data to the BOLD models. The activated areas almost always included a venous vessel visible on the venogram and consisted of GM and CSF. The fMRI signal changes were best described by extravascular dephasing effects in both GM and CSF around a venous vessel, in combination with intravascular effects. The role of spin dephasing around capillaries in GM appears to be insignificant. Magn Reson Med 45:233-246, 2001.

Body Fluid Compartments↗

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

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

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

Percutaneous radiofrequency (RF) thermal ablation of rabbit tumors embedded in fat: a model for RF ablation of breast tumors.

RATIONALE AND OBJECTIVES: To develop an experimental tumor model for RF ablation of breast tumors surrounded by fat and to investigate the minimally invasive treatment of such tumors by saline-enhanced RF ablation monitored by ultrasound (US). METHODS: Twenty-eight VX2 tumors were implanted into the retroperitoneum of 14 rabbits and monitored by B-mode US at regular intervals of 2 to 3 days. Saline-enhanced RF ablation (25-mm tip length) was performed 16 days after tumor implantation (10-minute treatment time, 28 W, 15 mL/h infusion of 0.9% NaCl, which was increased to 30 mL/h in cases of an impedance increase). Thermal lesion growth was monitored by B-mode US. Treatment was considered complete if no relapse was detectable histopathologically after a follow-up period of up to 3 weeks. RESULTS: All tumor implantations were successful, reaching sizes from 5 to 38 mm 16 days after implantation. Tumors >20 mm showed central necrosis on US. Smaller tumors without signs of necrosis required greater needle perfusion to maintain constant needle-to-tissue impedance. Local relapses occurred in 14 of 27 tumors (51.8%), all with tumors >20 mm. In 12 cases, they were already detected sonographically. In 2 cases, "islands" of vital tumor were detected only during histopathological assessment. CONCLUSIONS: VX2 tumors are implantable into hypovascular adipose tissue with a high success rate and may be used as a model for RF ablation of breast tumors. B-mode US is not suitable for guiding RF ablation of tumors embedded in fat. The method appears to be more successful with smaller tumors.

Adipose Tissue↗

PubMed2001

Contrast-enhanced near-infrared laser mammography with a prototype breast scanner: feasibility study with tissue phantoms and preliminary results of imaging experimental tumors.

RATIONALE AND OBJECTIVES: Near-infrared (NIR) optical mammography without contrast has a low specificity. The application of optical contrast medium may improve the performance. The concentration-dependent detectability of a new NIR contrast medium was determined with a prototype optical breast scanner. In vivo imaging of experimental tumors was performed. METHODS: The NIR contrast agent NIR96010 is a newly synthesized, hydrophilic contrast agent for NIR mammography. A concentration-dependent contrast resolution was determined for tissue phantoms consisting of whole milk powder and gelatin. A central part of the phantoms measuring 2 x 2 cm2 without contrast was replaced with phantom material containing 1 micromol/L to 25 nmol/L NIR96010. The composite phantoms were measured with a prototype NIR breast scanner with lasers of lambda1 = 785 nm and lambda2 = 850 nm wavelength. Intensity profiles and standard deviations of the transmission signal in areas with and without contrast were determined by linear fit procedures. Signal-to-noise ratios and spatial resolution as a function of contrast concentration were determined. Near-infrared imaging of five tumor-bearing SCID mice (MX1 breast adenocarcinoma, tumor diameter 5-10 mm) was performed before and after intravenous application of 2 micromol/kg NIR96010. RESULTS: Spectrometry showed an absorption maximum of the contrast agent at 755 nm. No spectral shifts occurred in protein-containing solution. Signal-to-noise ratio in the transmission intensity profiles ranged from 1.1 at 25 nmol/L contrast to 28 at 1 micromol/L. At concentrations <40 nmol/L, no differentiation from the background was possible. The transitional area between the contrast-free edge of the phantom and the central contrast-containing part appeared in the profiles as a steep increase with a width of 4.2 +/- 1.8 mm. The experimental tumors were detectable in nonenhanced images as well as contrast-enhanced images, with better delineation after contrast administration. In postcontrast absorption profiles, a 44.1% +/- 11.3% greater absorption increase was seen in tumor tissue compared with normal tissue. CONCLUSIONS: The laser wavelength lambda1 of the prototype laser mammography device was not situated at maximum absorption of the contrast agent NIR96010 but on the descending shoulder of the absorption spectrum. This implies a 20% signal loss for contrast detection. Despite the nonideal measurement conditions, concentrations as low as 40 nmol/L were detectable in vitro. In vivo, all tumors were detectable in color-coded nonenhanced scans as well as in contrast-enhanced scans, with better delineation after contrast administration.

Alkenes↗

PubMed2001

Apparent diffusion coefficient decreases and magnetic resonance imaging perfusion parameters are associated in ischemic tissue of acute stroke patients.

Perfusion-and diffusion-weighted magnetic resonance imaging scans are thought to allow the characterization of tissue at risk of infarction. The authors tested the hypothesis that the apparent diffusion coefficient (ADC) decrease should be associated with the severity of the perfusion deficit in ischemic tissue of acute stroke patients. Perfusion-and diffusion-weighted scans were performed in 11 patients with sudden onset of neurologic deficits within the last 6 hours and T2-weighted magnetic resonance imaging scans were obtained after 6 days. Parameter images of the maximum of the contrast agent concentration, time to peak, relative cerebral blood volume, relative cerebral blood flow, and relative mean transit time were computed from the perfusion-weighted data. A threshold function was used to identify tissue volumes with stepwise ADC decreases. An onionlike distribution of successively decreasing ADC values was found, with the lowest ADC in the center of the ischemic region. Correspondingly, tissue perfusion decreased progressively from the periphery toward the ischemic core. This effect was most pronounced in the time-to-peak maps, with a linear association between ADC decrease and time-to-peak increase. Apparent diffusion coefficient values decreased from the periphery toward the ischemic core, and this distribution of ADC values was strongly associated with the severity of the perfusion deficit.

Adult↗

PubMed2000

Hemodynamic assessment of acute stroke using dynamic single-slice computed tomographic perfusion imaging.

BACKGROUND: Stroke management would benefit from a broadly available imaging tool that detects perfusion deficits in patients with acute stroke. OBJECTIVE: To determine the role of dynamic, single-slice computed tomographic (CT) perfusion imaging (CTP) in the assessment of acute middle cerebral artery stroke. DESIGN AND PATIENTS: Imaging with CTP and CT within the first 6 hours of symptom onset and before the start of treatment in a consecutive clinical series of 22 patients (mean age, 68.3 years; 14 women; studied within 143 +/- 96 minutes of stroke onset). SETTING: A stroke unit in a university hospital. MAIN OUTCOME MEASURES: Area of the perfusion deficit (nAP(0)) from time-to-peak maps, hemispheric lesion area from follow-up CT (HLA(F)), final infarct volume, and stroke recovery (National Institutes of Health Stroke Scale scores). RESULTS: Eighteen patients had perfusion deficits in the middle cerebral artery territory and corresponding hypoattenuation in follow-up CT. Three patients with normal CTP findings showed lacunar infarctions or normal findings on follow-up CT. In 1 patient, CTP did not reveal a territorial deficit above the imaging slice. The overall sensitivity and specificity of CTP for the detection of perfusion deficits in patients with proven territorial infarction (n = 18) on follow-up CT were 95% and 100%, respectively. The nAP(0) was significantly correlated with the National Institutes of Health Stroke Scale score at admission (P<.003) and the HLA(F) (P<.001). Different stroke patterns were identified in patients with follow-up CTP (n = 10): (1) initial perfusion deficit and partial nutritional reperfusion (nAP(0)>HLA(F); n = 6), (2) initial perfusion deficit and nonnutritional reperfusion (nAP( 0)>/=HLA(F); n = 2), and (3) initial perfusion deficit without reperfusion (nAP(0)>/=HLA(F); n = 2). CONCLUSIONS: Computed tomographic perfusion imaging detects major perfusion deficits in the middle cerebral artery territory. Because CTP is broadly available, it may play a role in acute stroke management. Arch Neurol. 2000;57:1161-1166

Acute Disease↗

PubMed2000

Comparison of artifacts produced from carbon fiber and titanium alloy needles at 1.5 T MR imaging.

A novel coaxial carbon fiber-based biopsy needle set was investigated in phantom experiments and compared with a commercially available, magnetic resonance (MR)-compatible titanium alloy set using MR imaging at 1.5 T. Image artifacts observed with different MR sequences were assessed. It was found that the carbon fibers produced distinctly smaller image artifacts compared with the titanium needle. Depending on the type of MR sequence, the relative range of artifact size ratios between the carbon and titanium needles was between 0.7 (spin-echo sequence) and 0.4 (gradient-echo sequence) with the needles oriented perpendicular to the main magnetic field. Carbon fiber composites are promising materials for the design and construction of MR-compatible instruments.

Artifacts↗

PubMed2000

31P magnetic resonance spectroscopy in fibromyalgic muscle.

OBJECTIVE: To measure inorganic phosphate (Pi), phosphocreatine (PCr), ATP and phosphodiesters (PDE) in fibromyalgic muscle tissue by (31)P magnetic resonance spectroscopy. METHODS: A 1.5 Tesla scanner with a P 100 surface coil was used to examine 15 patients (mean age 49.9+/-14.3 yr) with fibromyalgia, according to the American College of Rheumatology criteria, and 17 healthy controls (mean age 30.2+/-5.8 yr). RESULTS: Compared with the controls, there were increases in the levels of PDE (+22%, P = 0.032) and Pi (+19%, P = 0.019) in the spectra of fibromyalgia patients, but there was no difference in pH. CONCLUSION: The metabolic differences we found may have been related to weakness and fatigue in the fibromyalgia patients, but they do not fully explain the fibromyalgia symptoms.

Adenosine Triphosphate↗

PubMed2000

Saline-enhanced radiofrequency ablation of breast tissue: an in vitro feasibility study.

RATIONALE AND OBJECTIVES: The feasibility of radiofrequency (RF) ablation for the treatment of breast tumors was investigated in vitro. The best parameters for ablation of breast tissue were chosen. METHODS: Saline-enhanced RF ablation was performed in human breast tissue specimens and cow udder tissue. Temperature profiles were measured depending on RF power (20, 28, 36 W) and NaCl infusion rate (15, 30, 60 mL/h) using eight thermocouples. Lesion development was monitored by ultrasound. Thermolysis efficiency was measured by tissue weight determinations before and after ablation. RESULTS: After RF ablation of tissue samples, 73.6% turned into a fat/saline emulsion. Ultrasound monitoring showed a cone-shaped hyperechoic area during the first 2 minutes of RF ablation, followed by an irregular expansion of the area. Time-dependent spatial temperature curves were more homogeneous at low infusion rates (15 mL/h). Peak temperatures up to 160 degrees C were measured. CONCLUSIONS: Controlled RF ablation of breast tissue is feasible. The irregular expansion of RF lesions in fatty breast tissue is due to liquefied fat. Low saline interstitial infusion rates result in better control of lesioning.

Animals↗

PubMed1999

Sub-millimeter fMRI at 1.5 Tesla: correlation of high resolution with low resolution measurements.

Functional magnetic resonance imaging of the visual cortex with an in-plane resolution of 0.4 x 0.4 mm2 was performed using a simple visual stimulus resulting in clear maps of activation. A collapsing filter was used to compare these high-resolution images with low-resolution images collected during the same session. A good correspondence between the high- and low-resolution functional maps was found with respect to the center of localization of activation. However, only 20% of the size of activated areas in the low-resolution experiment was observed at high resolution, which was partly caused by the difference in signal-to-noise ratio. The high-resolution images produce signal changes much higher than the low-resolution images due to reduced partial volume effects. Additionally, the high-resolution functional maps were compared with detailed anatomical and venous information. The activated areas were predominantly observed at venous vessels within the sulci with a diameter on the order of the pixel size.

Adult↗