Only strongly enhanced residual FDG uptake in early response PET (Deauville 5 or qPET ≥ 2) is prognostic in pediatric Hodgkin lymphoma: Results of the GPOH-HD2002 trial.

Purpose: In 2014, we published the qPET method to quantify fluorodeoxyglucose positron emission tomography (FDG-PET) responses. Analysis of the distribution of the quantified signals suggested that a clearly abnormal FDG-PET response corresponds to a visual Deauville score (vDS) of 5 and high qPET values ≥ 2. Evaluation in long-term outcome data is still pending.

MR-tomography on patients with heart pacemakers-a numerical study.

Patients having a heart pacemaker are not allowed to go to MR tomography (MRT). One of the most dangerous effects is the heating of the tissue around the electrode caused by the coupling to the RF field of the MR system. Experiments have been carried out using tanks filled with saline water and large heating has sometimes been observed.

Improvement of patient return electrodes in electrosurgery by experimental investigations and numerical field calculations.

Numerical field calculations and experimental investigations were performed to examine the heating of the surface of human skin during the application of a new electrode design for the patient return electrode. The new electrode is characterised by an equipotential ring around the central electrode pads. A multi-layer thigh model was used, to which the patient return electrode and the active electrode were connected.

Development and characterisation of a ceramic HF-resonator for the MR-tomography.

Future trends in magnetic resonance imaging (MRI) lead to higher magnetic field strengths of the static magnetic fields and as an implication of that to much higher frequencies. Nowadays a common model of a send-receive coil is the birdcage resonator. However it is very difficult to find an optimal L/C-relation for the capacities and inductivities at frequencies above 300 MHz.

Simulation of a birdcage and a ceramic cavity HF-resonator for high magnetic fields in magnetic resonance imaging.

The aim of this work was the 3D-simulation of a dielectric resonator for high-field-MRI. A 12-rod-bird-cage-resonator was simulated in a first step, in order to verify the capability of the commercial simulation software MAFIA to simulate homogeneous, transversal B-fields in resonators. The second step was the simulation of frequency-independent dielectric ceramic resonators for static magnetic field strengths of 7 T and 12 T (294 MHz and 504 MHz respectively).

Thermal heating of human tissue induced by electromagnetic fields of magnetic resonance imaging.

The paper presents a simulation of the transient temperature distribution in the human body caused by induced eddy currents during magnetic resonance imaging (MRI). In a first simulation the validity of the used heat conduction equation was proven using a simple example of a cool-down-process of a sphere. Thereafter the heating of a phantom model with an implanted electrode placed in a MRI-System (active body coil) was examined.

Numerical calculations of switched magnetic field gradients during magnetic resonance imaging.

During magnetic resonance imaging (MRI) pulse-sequences the human body is exposed to switched magnetic gradient fields. These gradients become stronger and are switched faster for fast imaging. Effects resulting from these fields with trapezoidal waveforms are on the one hand sensory perception of induced currents and on the other hand muscular and cardiac stimulation.

Development of a cost-effective and MRI compatible temperature measurement system.

A reliable temperature measurement system working inside a MRI-system is required in order to determine the amount of local temperature rise during application of radiofrequency fields on medical implants and thus to ensure patient safety. Hence the aim of this study was to develop a cost-effective temperature measurement system suitable for use in a MRI system to investigate this heating having mainly phantom experiments in mind. Three active temperature measurement systems were set up, the first using a PTC as the temperature sensor, the other two with platinum resistors of 100 omega and 1000 omega.

Magnetic resonance imaging with implanted neurostimulators: numerical calculation of the induced heating.

Magnetic resonance imaging (MRI) is still contraindicated in patients with implanted active medical devices, as the applied radiofrequency (RF) fields can lead to significant heating of the implants and the electrodes. A head model with an implanted deep brain stimulation electrode (DBS) was exposed to a continuous RF-field similar to the excitational field used in MRI at a frequency of 64 MHz. In this study a two-step procedure for the accurate estimation of electrode-heating during MRI is presented.

Numerical field calculation of patient return electrodes in electrosurgery.

In order to examine the warming up characteristics during application of a new electrode design for a patient return electrode of an electrosurgical system numerical field calculations were performed in this study. A multi-layer thigh model was provided for this purpose, to which the patient return electrode and the active electrode were connected. The simulation geometry as well as the dielectric tissue parameters were set according to the current frequency.

Simulation of non-contact measurement of the electrical impedance using an anatomical model.

The measurement of the impedance of biological tissue can be a non-invasive method to find new data of diagnostic relevance. A system for a non-contact measurement of the electrical impedance of biological tissue is presented. The system consists of an excitation coil and two sensing coils, an upper and a lower coil.

Calculation of the dielectric properties of biological tissue using simple models of cell patches.

The measurement of the dielectric properties of biological tissue is of increasing scientific relevance. Models for the comprehension of the dielectric properties at various frequencies have been successfully set up. However, students often have problems in understanding the effects taking place on cellular level which lead to the observed dispersion.

On the production of radioactive stents.

In the last few years, radioactive stents has been proved to inhibit neointima formation. This paper describes the actual status of producing such radioactive stents. After a short discussion of the different radioisotopes suitable for radioactive stents, potential production methods are discussed.