Wireless power transmission in endoscopy capsules.

The operating life of endoscopy capsules is limited by the batteries needed for use. The capacity of corresponding batteries, however, is too short to cover the total period of gastrointestinal transit. To overcome this limitation, a novel kind of wireless power transmission was used.

Bioelectric and biomagnetic measurements are differentially sensitive to spiral currents.

Observations indicate that different information is contained in electrocardiograms and magnetocardiograms in both patients and healthy volunteers. Closed loop currents could explain this phenomenon. We hypothesized that open loops, such as the spirally shaped currents in the heart, also contribute to these differences.

Pilot multi-reader study demonstrating potential for dose reduction in dual energy hepatic CT using non-linear blending of mixed kV image datasets.

Objective: To determine the potential for radiation dose reduction using sigmoidally-blended mixed-kV images from dual energy (DE) hepatic CT.

Methods: Multiple contrast-enhanced, DE (80 kV/140 kV) datasets were reconstructed from 34 patients undergoing clinically-indicated examinations using routine CTDI(vol). Noise was inserted in projection-space to simulate six dose levels reflecting 25-100% of the original dose.

[Magnetic resonance imaging of stents: quantitative in vitro examination at 3 Tesla].

Purpose: The aim of this study was to qualitatively and quantitatively study MR artifacts of various stents on the basis of in vitro experiments. We were particularly interested whether sequence type and orientation of the stent with respect to the static magnetic field influences the artifact.

Material And Methods: We examined 18 stents of different material (nitinol, stainless steel, cobalt alloy), different design of the stent meshes (AccuLink, OmniLink, DynaLink, Xact, Protoge, Wallstent Monorail), different diameter (5-10mm) and different length (18-58 mm) with a turbo spin echo (TSE), a 2D-fast low angle shot (FLASH) and a 3D-FLASH sequence.

Magnetic field distribution in the presence of paramagnetic plates in magnetic resonance imaging: a combined numerical and experimental study.

The amount and geometric distribution of paramagnetic components in tissue is considered as the basis of T2*-weighted magnetic resonance imaging (MRI). Such techniques are routinely applied for assessment of iron in parenchymal organs such as the liver (hemosiderosis). Furthermore, susceptibility sensitive MRI is discussed as an alternative method to x-ray techniques for quantitative assessment of paramagnetic spongy bone components in patients with osteoporosis.

Static magnetic fields induce blood flow decrease and platelet adherence in tumor microvessels.

Red blood cell flow in capillaries is reduced during exposure to strong static magnetic fields (SMFs). Intratumoral microcirculation is characterized by tortuous microvessels with chaotic architecture and by irregular, sluggish blood flow with unstable rheology. It was the aim of this study to analyze SMF exposure effects on tumor microcirculation with regard to interactions of corpuscular blood components with tumor microvessel walls.

Static magnetic fields affect capillary flow of red blood cells in striated skin muscle.

Blood flowing in microvessels is one possible site of action of static magnetic fields (SMFs). We evaluated SMF effects on capillary flow of red blood cells (RBCs) in unanesthetized hamsters, using a skinfold chamber technique for intravital fluorescence microscopy. By this approach, capillary RBC velocities (v(RBC)), capillary diameters (D), arteriolar diameters (D(art)), and functional vessel densities (FVD) were measured in striated skin muscle at different magnetic flux densities.

Quantitative diffusion tensor MR imaging of the brain: field strength related variance of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) scalars.

The objectives were to study the "impact" of the magnetic field strength on diffusion tensor imaging (DTI) metrics and also to determine whether magnetic-field-related differences in T2-relaxation times of brain tissue influence DTI measurements. DTI was performed on 12 healthy volunteers at 1.5 and 3.

Passive vortex currents in magneto- and electrocardiography: comparison of magnetic and electric signal strengths.

Vortex currents may be of importance in the early diagnosis of myocardial infarction caused by an occlusion of a coronary artery. We investigated the influence of a passive vortex current distribution, modelled by different conductivities in a hollow cylinder, on the localization error and on the signal strength in both the magnetocardiogram and the electrocardiogram. The hollow cylinder was mounted in a realistically shaped physical torso phantom.

Biodistribution and pharmacokinetics of the (19)F-labeled radiosensitizer 3-aminobenzamide: assessment by (19)F MR imaging.

3-Aminobenzamide (3-ABA) is a potent radiosensitizer that inhibits the repair of DNA strand breaks. The aim of this study was to monitor the biodistribution and pharmacokinetics of a fluorinated 3-ABA derivative in tumor-bearing rats by magnetic resonance imaging (MRI). To this end, 3-ABA was labeled with fluorine-19 by trifluoroethylation [3-amino-N-2,2,2-trifluoroethylbenzamide (3-ABA-TFE)], which only slightly increased the cytotoxicity of the compound as demonstrated by colony-forming assays.

A novel magnetic method for examination of bowel motility.

In contrast to the well-developed methods for morphological diagnosis of the gastrointestinal tract, there is no comparatively satisfying technique for functional disorders. One important example is irritable bowel syndrome (IBS), a disorder that affects a high percentage of all individuals. It can only be diagnosed by excluding organic diseases and by considering symptom criteria.

[Validation of an entropy-based algorithm for registration of serial 3D MR mammography data].

The aim of this study was to develop and implement an algorithm for the co-registration of 3D breast MRI sets acquired at two slightly different patient positions (repetitive examination). Combined translation and rotation with locally varying parameters were applied for the purpose of coordinate transformation. A phantom allowing selective changes of the volume of the glandular tissue model was developed, in order to prove the robustness of the proposed matcher against local changes.

[A software tool for analysis and quantification of regional pulmonary ventilation using dynamic hyperpolarised-(3)He-MRI].

Purpose: (3)He-MRI is able to visualize the regional distribution of lung ventilation with a temporal and spatial resolution so far unmatched by any other technique. The aim of the study was the development of a new software tool for quantification of dynamic ventilation parameters in absolute physical units.

Materials And Methods: During continuous breathing, a bolus of hyperpolarized (3)He (300 ml) was applied at inspiration and a series of 168 coronal projection images simultaneously acquired using a 2D FLASH-sequence.

ROC analysis for assessment of lesion detection performance in 3D PET: influence of reconstruction algorithms.

Image quality in positron emission tomography (PET) can be assessed with physical parameters, as spatial resolution and signal-to-noise ratio, or using psychophysical approaches, which include the observer performance and the considered task (ROC analysis). For PET in oncology, such a task is the detection of hot lesions. The aim of the present study was to assess the lesion detection performance due to adequate modeling of the scanner and the measurement process in the image reconstruction process.

Inductively coupled rf coils for examinations of small animals and objects in standard whole-body MR scanners.

Inductively coupled solenoid coils fitting to objects in the size of mice or rats were developed to adapt modem whole-body MR scanners featuring sufficient gradient strength for animal examinations with high spatial resolution. Homogenous receiver characteristics is achievable over almost the whole inner region of the solenoid coils. The SNR can be increased by a factor 2 to 6 with the adapting coils for examinations using the head coil as connected receiver.

VERIDOS: a new tool for quality assurance for intensity modulated radiotherapy.

Background: The use of intensity modulated radiation fields needs an extended quality assurance concept. This consists of a linac related part and a case related part. Case related means the verification of an individual treatment plan, optimized on a CT data set of an individual patient and prepared for the treatment of this patient.

An automated method for volumetric quantification of magnetization transfer of the brain.

Cerebral white matter damages can be detected and characterized using magnetization transfer (MT) imaging. In this study a fully automated method of measuring and analyzing the MT of the whole human brain is presented and assessed. A 3D-FLASH sequence with off-resonance RF pulse was optimized for fast, volumetric MT measurements.

[Assessment of radiation exposure caused by transmission scans in SPECT: an anthropomorphic dosimetry study].

Transmission measurements are performed in SPECT to correct for attenuation of the gamma quanta in the body. In this study, we measured the additional radiation dose caused by transmission scans using a field of collimated 153Gd rod sources. Two measurement series were performed with an anthropomorphic phantom and thermoluminescence dosimeters.

[Quantitative evaluation of cavitation bubble fields induced by lithotripter shock waves].

Extracorporeal shock wave lithotripsy is the world-wide standard therapy for renal stones. The rare-faction phase of the shock wave can induce cavitation within the body. Cavitation contributes to stone disintegration but also to medical side effects.

[Remote controlled drug release in the alimentary tract by local power deposition in alternating magnetic fields].

Remote controlled release of agents in the alimentary tract is an important task of gastroenterology and pharmacy. We investigated two different methods of drug release by heating locally restricted parts in medical capsules: hysteresis losses of magnetite powder and eddy current losses of metals in alternating magnetic fields. The comparison of our experimental results with theoretically derived expectations show that both methods are suitable techniques if special technical conditions are met.

[Assessment of radiation exposure caused by transmission scans in SPECT: an anthropomorphic dosimetry study].

Transmission measurements are performed in SPECT to correct for attenuation of the gamma quanta in the body. In this study, we measured the additional radiation dose caused by transmission scans using a field of collimated 153Gd rod sources. Two measurement series were performed with a anthropomorphic phantom and thermoluminescence dosimeters.

[Development of a laser-optical tomograph for demonstration of CT imaging without ionizing radiation].

Computed X-ray tomography (CT) is one of the most powerful diagnostic procedures in medicine. In this study, we developed a laser-optical CT scanner for the use by students as part of their curriculum in biomedical engineering. Our CT set-up employs a linear-scan technique where the measurement objects (light absorbing phantoms embedded in immersion oil), the light emitter (modulated laserdiode), and the detector (photodiode) are moved by linear-step motors.

[Assessment of image reconstruction parameters in PET using physical and statistical figures of merit].

The aim of this study was to analyze the recommended OSEM image reconstruction parameters in positron emission tomography (PET). Spatial resolution, signal-to-noise ratio, and contrast were used as physical figures of merit (FOM). For statistical FOMs, the t-value and the area under the receiver operating characteristic (ROC) were employed.

[Implementation of a measurement protocol to evaluate system parameters in positron emission tomography].

To evaluate system parameters in PET measurements, several different activity ratios of the investigated phantom must be analyzed. The aim of this study was to develop a measurement protocol which requires just one filling of the phantom to measure adequate image contrasts and count ranges. We used 11C for the hollow spheres and 18F for the background of the whole-body PET phantom.

[Quantification and visualization of oxygen partial pressure in vivo by 19F NMR imaging of perfluorocarbons].

Due to the high solubility of molecular oxygen in perfluorocabons (PFC), this class of fluorinated compounds has gained wide-spread interest for its biomedical application as temporary blood substitutes and as radiosensitizers. Since the observation that the NMR spin-lattice relaxation times (T1) of some 19F PFC resonances are sensitive to oxygen tension (pO2), this paramagnetic effect has been used to non-invasively probe pO2 in vivo. In this study, combined 19F/1H NMR image data of Copenhagen rats after PFC application were evaluated with the software package MATLAB.