Abstract: In this review article we describe the development of grating-based X-ray phase-contrast imaging, with particular emphasis on potential biomedical applications of the technology. We review the basics of image formation in grating-based phase-contrast and dark-field radiography and present some exemplary multimodal radiography results obtained with laboratory X-ray sources. Furthermore, we discuss the theoretical concepts to extend grating-based multimodal radiography to quantitative transmission, phase-contrast, and dark-field scattering computed tomography.

Abstract: We developed an X-ray phase imaging system based on Talbot-Lau interferometry and studied its feasibility for clinical diagnoses of joint diseases. The system consists of three X-ray gratings, a conventional X-ray tube, an object holder, an X-ray image sensor, and a computer for image processing. The joints of human cadavers and healthy volunteers were imaged, and the results indicated sufficient sensitivity to cartilage, suggesting medical significance.

Abstract: Inaccurate conversion of CT data to water-equivalent path length (WEPL) is one of the most important uncertainty sources in ion treatment planning. Dual energy CT (DECT) imaging might help to reduce CT number ambiguities with the additional information. In our study we scanned a series of materials (tissue substitutes, aluminum, PMMA, and other polymers) in the dual source scanner (Siemens Somatom Definition Flash). Based on the 80 kVp/140Sn kVp dual energy images, the electron densities ϱe and effective atomic numbers Zeff were calculated. We introduced a new lookup table that translates the ϱe to the WEPL. The WEPL residuals from the calibration were significantly reduced for the investigated tissue surrogates compared to the empirical Hounsfield-look-up table (single energy CT imaging) from (−1.0 ± 1.8)% to (0.1 ± 0.7)% and for non-tissue equivalent PMMA from −7.8% to −1.0%. To assess the benefit of the new DECT calibration, we conducted a treatment planning study for three different idealized cases based on tissue surrogates and PMMA. The DECT calibration yielded a significantly higher target coverage in tissue surrogates and phantom material (i.e. PMMA cylinder, mean target coverage improved from 62% to 98%). To verify the DECT calibration for real tissue, ion ranges through a frozen pig head were measured and compared to predictions calculated by the standard single energy CT calibration and the novel DECT calibration. By using this method, an improvement of ion range estimation from −2.1% water-equivalent thickness deviation (single energy CT) to 0.3% (DECT) was achieved. If one excludes raypaths located on the edge of the sample accompanied with high uncertainties, no significant difference could be observed.

Abstract: In molecular radiotherapy a radionuclide or a radioactively labelled pharmaceutical is administered to the patient. Treatment planning therefore comprises the determination of activity to administer. This administered activity should maximize tumour cell sterilization while minimizing normal tissue damage. In this work we present different approaches that are frequently used for determining the suitable activity. These approaches may be cohort- based as in chemotherapy, or patient-specific using dosimetry based on individual biokinetics. The approaches are different with respect to the input complexity, the corresponding costs and - in consequence - the quality of the therapy. In addition, a general scheme for data collection and analysis is proposed. To develop an effective and safe treatment, elaborate data need to be obtained. The main challenges, however, are collecting these complex data and analyse them properly.

Abstract: This study is concerned with the spatial resolution of air-filled ionization chambers in photon-beam dosimetry, i.e. with their dose response functions. These act as convolution kernels K(x,y), transforming true dose profiles D(x,y) into the measured signal profiles M(x,y). One-dimensional dose response functions have been experimentally determined for nine types of cylindrical ionization chambers both in their lateral and longitudinal directions, as well as across two plane-parallel chambers and for the single chambers of two 2D arrays. All these 1D dose response functions are closely described by Gaussian functions. The associated energy-dependent values of the standard deviations σ have been measured for 6 and 15 MV photons with an uncertainty of 0.02mm. At depths beyond secondary electron fluence build-up, there was no detectable depth dependence of the σ values. The general occurrence of Gaussian dose response functions, their extension beyond the geometrical boundaries of the chambers, and the energy dependence of their standard deviations can be understood by considering the underlying system of convolutions, which is the origin of the influences of secondary electron transport. Monte-Carlo simulations of the convolution kernels for a cylindrical, a square, and a flat ionization chamber and their Fourier analysis have been employed to show that the Gaussian convolution kernels are approximations to the true dose response functions, valid in the clinically relevant domain of the spatial frequency. This paper is conceived as the starting point for the deconvolution methods to be described in a further publication.

Abstract: Background Grating-based phase contrast computed tomography (PC-CT) at synchrotron radiation sources has been shown to provide improved visualization of breast tumors. However, broad clinical application of phase-contrast imaging will likely depend on transferring the technology to standard polychromatic X-ray sources. On the basis of selected findings, we demonstrate the potential of grating-based PC-CT using a conventional X-ray source. Materials and Methods Grating-based PC-CT of two ex-vivo formalin fixed breast specimens containing lobular carcinoma was conducted using a Talbot Lau interferometer run at a polychromatic X-ray source of 40 kVp. Phase-contrast and absorption-based 3D-datasets of both specimens were simultaneously recorded. Radiological images were manually matched with corresponding histological sections. The visualization of selected histological findings in phase contrast was compared to absorption contrast. Results Grating-based PC-CT was able to depict the 3-dimensional structure of dilated ducts and high phase contrast was found as a correlate to thickened fibrous ductal walls. Differences in contrast between fibrous and less fibrous breast tissue were observed in phase- but not in absorption-contrast images. Furthermore, regions of low phase contrast correlated with the extension of compact tumor components. Conclusions On the basis of selected findings, we show that grating-based PC-CT at a polychromatic X-ray source provides complementary information to conventional absorption contrast; albeit at lower spatial resolution than synchrotron-based imaging.

Abstract: Iterative reconstruction has a wide spectrum of proven advantages in the field of conventional X-ray absorption-based computed tomography (CT) In this paper, we report on an algebraic iterative reconstruction technique for grating-based differential phase-contrast CT (DPC-CT) Due to the differential nature of DPC-CT projections, a differential operator and a smoothing operator are added to the iterative reconstruction, compared to the one commonly used for absorption-based CT data This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured at a two-grating interferometer setup Since the algorithm is easy to implement and allows for the extension to various regularization possibilities, we expect a significant impact of the method for improving future medical and industrial DPC-CT applications

Abstract: Purpose: An experimental comparison of the contrast-to-noise ratio (CNR) between transmission and dark-field signals in grating-based X-ray imaging for ex-vivo murine lung tissue. Materials and Methods: Lungs from three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Background noise of transmission and dark-field signal was quantified by measuring the standard deviation in a region of interest (ROI) placed in a homogeneous area outside the specimen. Image contrast was quantified by measuring the signal range in rectangular ROIs placed in central and peripheral lung parenchyma. The relative contrast gain (RCG) of dark-field over transmission images was calculated as CNRDF /CNRT. Results: In all images, there was a trend for contrast-to-noise ratios of dark-field images (CNRDF) to be higher than for transmission images (CNRT) for all ROIs (median 61 vs. 38, p = 0.10), but the difference was statistically significant only for peripheral ROIs (61 vs. 32, p = 0.03). Median RCG was >1 for all Rats (1.84). RCG values were significantly smaller for central ROIs than for peripheral ROIs (1.34 vs. 2.43, p = 0.03). Conclusion: The contrast-to-noise ratio of dark-field images compares more favorably to the contrast-to-noise ratio of transmission images for peripheral lung regions as compared to central regions. For any specific specimen, a calculation of the RCG allows comparing which X-ray modality (dark-field or transmission imaging) produces better contrast-to-noise characteristics in a well-defined ROI. (Less)

Abstract: A method to evaluate the dosimetric accuracy of volumetric modulated arc therapy (VMAT) treatment plans, generated with the MONACO™ (version 3.0) treatment planning system in realistic CT-data with an independent Geant4 based dose calculation algorithm is presented. Therefore a model of an Elekta Synergy linear accelerator treatment head with an MLCi2 multileaf collimator was implemented in Geant4. The time dependent linear accelerator components were modeled by importing either logfiles of an actual plan delivery or a DICOM-RT plan sequence. Absolute dose calibration, depending on a reference measurement, was applied. The MONACO as well as the Geant4 treatment head model was commissioned with lateral profiles and depth dose curves of square fields in water and with film measurements in inhomogeneous phantoms. A VMAT treatment plan for a patient with a thoracic tumor and a VMAT treatment plan of a patient, who received treatment in the thoracic spine region including metallic implants, were used for evaluation. MONACO, as well as Geant4, depth dose curves and lateral profiles of square fields had a mean local gamma (2%, 2mm) tolerance criteria agreement of more than 95% for all fields. Film measurements in inhomogeneous phantoms with a global gamma of (3%, 3mm) showed a pass rate above 95% in all voxels receiving more than 25% of the maximum dose. A dose-volume-histogram comparison of the VMAT patient treatment plans showed mean deviations between Geant4 and MONACO of -0.2% (first patient) and 2.0% (second patient) for the PTVs and (0.5±1.0)% and (1.4±1.1)% for the organs at risk in relation to the prescription dose. The presented method can be used to validate VMAT dose distributions generated by a large number of small segments in regions with high electron density gradients. The MONACO dose distributions showed good agreement with Geant4 and film measurements within the simulation and measurement errors.

Abstract: Poster: "ECR 2013 / C-2565 / Grating-based X-ray phase-contrast tomography of atherosclerotic plaque at high photon energies" by: "S. Fill1, H. Hetterich1, J. Herzen2, M. S. Willner3, T. Weitkamp4, U. Schuller1, F. Pfeiffer3, F. Bamberg5, T. Saam5; 1Munich/DE, 2Geesthacht/DE, 3Garching/DE, 4Gif-sur-Yvette/FR, 5Munchen/DE"

Abstract: Although theoretical approaches to tracheobronchial (TB) clearance have been continuously refined during the past decades, questions concerning the exact course of particle removal from the TB tree have been largely remained unsolved. In order to clarify this problem, three-dimensional patterns of mucociliary particle clearance have to be generated at pre-defined time points after particle exposure. Here, we present a mathematical method for the generation of respective clearance patterns. Three-dimensional transport paths of inhaled particles as well as spatial deposition patterns were generated by determining spatial information of all airway tubes passed by the particles and the particle deposition sites. Three-dimensional data were converted to a coordinate system, within which the trachea represented the z-axis. Visualization of stored data was realized with the help of a freely available program code that is specialized in processing huge data sets. Mucociliary clearance of deposited particular mass was computed by assuming (1) an interrelationship between mucus velocity and airway caliber and (2) an average tracheal mucus velocity of 5.5mm min(-1). Position of cleared particles within the spatial TB tree was determined at t=0 h (immediately after exposure), t=12 h and t=24 h. Spatial patterns of mucociliary clearance were computed for particles with a uniform geometric diameter of 5μm and a density of 1g cm(-3). Inhalation of the aerosol loaded with those particles took place under sitting breathing conditions (breathing frequency: 15min(-1), tidal volume: 750 ml). As demonstrated by the generated clearance patterns, mucociliary transport of 5μm particles is completed after 30 h. Within the first 12 h following aerosol exposure, about 75% of the initially deposited particular mass is removed from the TB tree. After 24 h, 95% of the particles have been cleared. Clearance patterns are characterized by a successive transition of maximal particle concentrations towards more proximal airway generations. For 0.1μm particles and 1μm particles clearance times are significantly prolonged, whilst 10μm particles are even faster removed from the TB tree than the 5μm particles. Based on the results of this study the time span between initial deposition of particular matter and complete evacuation of deposited particles ranges from several hours to some days and depends on (1) the preferential deposition site of the inhaled material and (2) the mean mucus velocities in the bronchial airway generations.

Abstract: Purpose Phase-contrast X-ray computed tomography (PCCT) is currently investigated and developed as a potentially very interesting extension of conventional CT, and can offer several advantages for specific indications in diagnostic imaging. Current absorption-based computed tomography (CT) without the application of contrast material is limited in the detection of minor density differences in soft-tissue. The purpose of this study is to test whether PCCT can improve soft tissue contrast in healthy and tumorous human liver specimens. Materials and Methods Two specimens of human liver (one healthy and one metastasized liver sample) were imaged with brilliant X-ray beam at the synchrotron radiation source ESRF in Grenoble, France. For correlation the same specimens were imaged with a magnetic resonance imaging system at 1.5 T. The histopathology confirmed our findings in the corresponding sections of the specimens. Results In the phase-contrast CT images we observed a significantly enhanced soft-tissue contrast when compared to simultaneously recorded standard absorption CT measurements. Further, we found that the pathological and morphological information in the PCCT reconstructions show significant improvement when compared to those performed on MRI. Based on matching of prominent features, a good correlation between PCCT and the histological section is demonstrated; especially the tumor capsule and the surrounding vascular structures are visible in PCCT. In addition, our study revealed the ability of PCCT to visualize the blood vessels structure in the tumorous liver without the need of any contrast agents. Conclusion Grating-based PCCT significantly improves the soft-tissue contrast in ex-vivo liver specimens and holds the potential to overcome the need of contrast materials for visualization of the tumor vascularization.

Abstract: Background In stereotactic radiosurgery, sharp beam edges have clear advantages to spare normal tissues. In general, the dose gradient is a limiting factor in minimizing dose to nearby critical structures for clinical cases. Therefore the penumbral width should be diminished. Methods A Varian Clinac 2100 linear accelerator equipped with in-house designed radiosurgical collimator was modeled using the EGSnrc/BEAMnrc Monte Carlo code and compared with the measurements. The 0.015 cm3 PinPoint chamber was used to measure the 6 MV photon beam characteristics and to validate Monte Carlo calculations. Additional to the standard (STD) linac, a flattening filter free (FFF) linac was simulated. Percent depth doses, beam profiles and output factors were calculated for small field sizes with diameter of 5, 10, 20 and 30 mm with DOSXYZnrc. The mean energy and photon fluence at the water surface were calculated with BEAMDP for both FFF linac and STD linacs. Results The penumbra width (80%-20%) was decreased by 0.5, 0.3, 0.2 and 0.2 mm for field sizes of 5, 10, 20 and 30 mm respectively when removing the FF. The fluence of photons at the surface increased up to 3.6 times and the mean energy decreased by a factor of 0.69 when removing the FF. The penumbra width (80%-20%) decreased by 17% when a 2 MeV monoenergetic electron pencil beam incident on the target is used instead of 6.2 MeV. Conclusions It was found that the penumbra of small field sizes is decreased by removing the FF. Likewise using low megavoltage photons reduced the beam penumbra maintaining adequate penetration and skin sparing.

Abstract: During a helical tomotherapy a binary MLC is used for fluence modulation. The 64 pneumatically driven leaves of the MLC are either completely open or closed. The fast and frequent leaf movements result in a high demand of accuracy and stability of the MLC. This article is based on the analytical investigation of the accuracy and the stability of the MLC. Different patterns of MLC movements were generated to investigate the characteristics of the MLC. One of the considered aspects contains the friction between the leaves. The influence of variations of the compressed air on the MLC was also explored. The integrated MVCT detector of the tomotherapy system deposits the treatment data in a matrix. The detector is triggered with the linear accelerator, which is pulsed by 300Hz. The data matrix is available after the treatment. An IDL (Interactive Data Language) routine was programmed in order to analyse the matrix. The points of time, at which the leaves open (POT), and the period, in which the leaves stay open (LOT), were measured and compared with the desired values. That procedure has been repeated several times a week for approximately 6 months to investigate the stability of the MLC. Relative deviations of the LOT from -0.4% to -5.4% were measured. The friction between the leaves had no significant influence on the LOT. The available compressed air, that is used to move the leaves, depends on the number of moving leaves and also on the previous movements of the MLC. Variations of the compressed air resulted in deviations of the LOT from -1.8% to -3.7%. The measured POT deviates from the programmed POT up to -18.4ms ± 0.7ms. This maximal deviation correlates with a shift of the gantry angle of 0.52 which is negligible. The MLC has shown a stable behaviour over the 6 months. A separate consideration of the leaves showed no higher standard deviation of the LOT than ±0.7ms during the investigated time. The variation between the different leaves is much higher than the deviations of LOT caused by friction and changes of compressed air. The deviations of the LOT vary between -2.6ms and -11.0ms. The developed method is feasible in order to recognize a deterioration of the MLC performance.

Abstract: We present a biomechanical eye model to induce pseudophakic accommodative movement for evaluation of the focal shift of accommodative intraocular lenses. Therefore, an accommodative intraocular lens (IOL) was implanted into freshly enucleated porcine eyes. The eyes were glued into a mechanical apparatus to expand the ciliar body effectuating mechanical accommodation. An optical coherence tomographer was used to measure positional and geometrical changes of the IOL for different levels of expansion. The expansion unit allowed stretching of the globe of several millimeters. With the biomechanical eye model we were able to simulate the mechanical functionality of accommodation as well as to measure the lens vault and change in geometry. Accommodative vault could only be measured with an intact vitreous, indicating that the vitreous plays an important role for the functionality of accommodative IOLs.

Abstract: Introduction Protectional eyewear has to fulfill both mechanical and optical stress tests. To pass those optical tests the surfaces of safety spectacles have to be optimized to minimize optical aberrations. Material and Methods Starting with the surface data of three measured safety spectacles, a theoretical spectacle model (four spherical surfaces) is recalculated first and then optimized while keeping the front surface unchanged. Next to spherical power, astigmatic power and prism imbalance we used the wavefront error (five different viewing directions) to simulate the optical performance and to optimize the safety spectacle geometries. Results All surfaces were spherical (maximum global deviation ‘peak-to-valley’ between the measured surface and the best-fit sphere: 0.132 mm). Except the spherical power of the model Axcont (−0.07 m −1 ) all simulated optical performance before optimization was better than the limits defined by standards. The optimization reduced the wavefront error by 1% to 0.150 λ (Windor/Infield), by 63% to 0.194 λ (Axcont/Bolle) and by 55% to 0.199 λ (2720/3 M) without dropping below the measured thickness. Conclusion The simulated optical performance of spectacle designs could be improved when using a smart optimization. A good optical design counteracts degradation by parameter variation throughout the manufacturing process.

Abstract: EduGATE is a collection of basic examples to introduce students to the fundamental physical aspects of medical imaging devices. It is based on the GATE platform, which has received a wide acceptance in the field of simulating medical imaging devices including SPECT, PET, CT and also applications in radiation therapy. GATE can be configured by commands, which are, for the sake of simplicity, listed in a collection of one or more macro files to set up phantoms, multiple types of sources, detection device, and acquisition parameters. The aim of the EduGATE is to use all these helpful features of GATE to provide insights into the physics of medical imaging by means of a collection of very basic and simple GATE macros in connection with analysis programs based on ROOT, a framework for data processing. A graphical user interface to define a configuration is also included.

Abstract: Purpose Whenever treating a patient with percutaneous radiotherapy, a certain amount of dose is inevitably delivered to healthy tissue. This is mainly due to beam's entry and exit in the region of the target volume. In regions distant from the target volume, dose is delivered by leakage from the MLC and head scatter from the accelerator head and phantom scatter from the target volume (peripheral dose). Helical tomotherapy is a form of radiation therapy with a uniquely designed machine and delivery pattern which influence the peripheral dose. The goal of this work was to investigate peripheral dose in helical tomotherapy. The experiments were used to establish a complex characterization of the peripheral dose. Materials and methods A 30*30*60cm3 slab phantom and TLD-100 (Lithium fluoride) were used for the experiments. Treatment procedures were generated with the tomotherapy planning system (TPS). Additionally, procedures were created on the Operator Station of the tomotherapy system without a calculation of the dose distribution. The peripheral dose which was produced by a typical tomotherapy treatment plan was measured. Furthermore, these procedures were used to differentiate the parts of the peripheral dose in phantom scatter dose and head scatter and leakage dose. Additionally, the relation between peripheral dose and treatment time and between peripheral dose and delivered dose was investigated. Additionally, the peripheral dose was measured in an Alderson phantom. Results Distances of 30cm or more resulted in a decrease of the peripheral dose to less than 0.1% of the target dose. The measured doses have an offset of approximately 1cGy in comparison to the calculated doses from the TPS. The separated head scatter and leakage dose was measured in the range of 1cGy for typical treatments. Furthermore, the investigations show a linear correlation between head scatter leakage dose and treatment time and between scatter dose parts and delivered dose. A peripheral dose of 0.28% of the target dose was measured in the Alderson phantom at a distance of 17.5cm from the edge of the target volume. Conclusions The peripheral dose delivered by a tomotherapy treatment is clinically unobjectionable. The measurements confirmed a linear correlation between head scatter and leakage and treatment time and between scatter dose and delivered dose.

Abstract: Early recognition of and differential diagnosis between pancreatic cancer and chronic pancreatitis is an important step in successful therapy. Parameters of the IVIM (intra-voxel incoherent motion) theory can be used to differentiate between those lesions. The objective of this work is to evaluate the effects of rigid image registration on IVIM derived parameters for differentiation of pancreatic lesions such as pancreatic cancer and solid mass forming pancreatitis. The effects of linear image registration methods on reproducibility and accuracy of IVIM derived parameters were quantified on MR images of ten volunteers. For this purpose, they were evaluated statistically by comparison of registered and unregistered parameter data. Further, the perfusion fraction f was used to differentiate pancreatic lesions on eleven previously diagnosed patient data sets. Its diagnostic power with and without rigid registration was evaluated using receiver operating curves (ROC) analysis. The pancreas was segmented manually on MR data sets of healthy volunteers as well as the patients showing solid pancreatic lesions. Diffusion weighted imaging was performed in 10 blocks of breath-hold phases. Linear registration of the weighted image stack leads to a 3.7% decrease in variability of the IVIM derived parameter f due to an improved anatomical overlap of 5%. Consequently, after registration the area under the curve in the ROC-analysis for the differentiation approach increased by 2.7%. In conclusion, rigid registration improves the differentiation process based on f -values.

Abstract: For LDR-brachytherapy, a limited number of implant geometries and materials are available. To avoid wound healing related hyper-proliferation (stenosis, keloids) a novel radioactive foil system was developed based on beta emitting (32)P, which can be easily integrated in existing implants such as urethral catheters or bile duct stents. As substrate material for these foils PEEK (polyetherethercetone) was chosen because of its radiation hardness during neutron activation of (32)P. The activity was determined by liquid scintillation counting and gamma spectroscopy, dose distributions were measured with scintillation detectors and radiochromic films. The correlation between activity and dose was checked by Monte-Carlo-simulations (Geant4). Prototypes of the (32)P-implants have shown in wash-out tests the required tightness for sealed radioactive sources. In animal tests on urethra and bile duct, the uncomplicated and save application of (32)P-foils mounted on standard implants has been demonstrated, which is almost unchanged due to the simple radiation protection with plexiglass. This concept of radioactive implants with integrated (32)P-foils could extend essentially the application possibilities of LDR-brachytherapy.

Abstract: INTRODUCTION: Work in hazardous zones with the risk of mechanical injuries requires protection with safety spectacles. Mechanical eye injuries with metal foreign bodies are often caused by rotational material machining or production processes with high pressure or high velocity moving parts. Normative regulations restrict to tests with small and fast flying objects (e.g. 6mm ball). The literature does not provide any information about protection capabilities against larger objects with high mass and arbitrary shape. The purpose of this study was to test the protection efficiency of safety spectacles against flying objects. The scope of this paper is to present a new test setup for mechanical impact resistance testing of personal protective eyewear against objects with arbitrary shape and mass. MATERIAL AND METHODS: The setup is based on a catapult platform, accelerating a sliding carriage on a rail. A pull rope system allows velocities up to 62±2 m·s(-1). A photo sensor was used for velocity measurement. The carriage can be loaded with projectiles of up to 30mm×30mm×40mm in size with arbitrary orientation, depending on the carriage insert. Testing and validation was done with projectiles such as 7g metal chips and fragments with approximate dimensions of 10mm×15mm. Samples were standard occupational safety spectacles mounted on a test head. The projectile impact was captured with a monochrome high speed camera. RESULTS: The aiming accuracy test showed deviations of approximately 1mm of two impacts on the same spectacle surface with a free flight distance of 150mm. All tests with slow, medium and high speed projectiles showed no contact with the eye medium. Objects with velocities from 10 m·s(-1) to 62 m·s(-1) fired the spectacle off from the test head. The medium speed test cut off one side of the spectacle frame. The high speed test with 62±2 m·s(-1) cracked the polycarbonate shield. DISCUSSION: We describe a method for accelerating arbitrary objects up to 62 m·s(-1) and for aiming these objects on safety eyewear, mounted on a test head. The setup allows a variety of projectile shapes, orientations and velocities. The accuracy of velocity measurement is ± 2 m·s(-1) for high velocity ( Language: en

Abstract: There is a worldwide trend to expand the morphologic imaging of diseases by the assessment of tissue function and metabolism. Functional evaluation of normal and pathologic tissue is a classical domain of radiological imaging techniques such as time-resolved CT and functional magnetic resonance imaging (MRI) as well as contrast-enhanced ultrasound. Beyond this, molecular imaging aims at detection of processes at the cellular level by probes binding to specific structures. Positron Emission Tomography (PET) allows detecting disease-specific processes on the basis of nanomolar concentrations of radioactively-labeled tracers. The great challenge for the coming years is to translate this additional diagnostic information into a more effective, less invasive therapy for the patient with fewer side effects and at the same time higher cost-effectiveness rendering it more affordable for the general health care system. This implies that imaging is specific for the mechanism of the disease and the target of the therapy on one hand and provides a complete picture of the systemic spread and thus the stage of the disease on the other hand. For this, the critical gap between modern molecular histopathology, molecular imaging and image-guided, minimally-invasive therapy has to be bridged and the results transferred from basic science into clinical routine. This challenge cannot be comprehensively addressed by a single research group, but requires the close interaction of scientists from multiple disciplines of medical imaging and from different types of academic institutions as well as industry in close proximity on a medical university campus. Currently, industry on campus (IOC) initiatives such as the one from the German Federal Ministry of Research in Germany are specifically designed to facilitate this type of interdisciplinary, patient-focused research on a single campus in a long-term private-public partnership [1]. As an example, the initiative “Mannheim Molecular Intervention Environment (M2OLIE)” aims at developing a closed-loop treatment process in oligometastatic patients spanning from personalized molecular imaging to target-specific minimally-invasive multimodal therapy [2]. Patients with a previously treated oncologic disease and de novo development of a few metastases are the fastest growing group of cancer patients. With dedicated multimodal minimally-invasive therapies a stabilization of the disease can be potentially achieved with survival times almost similar to those in cured patients. The key to a precise elimination of these metastases is the in detail tumor characterization as current studies have shown that the

Abstract: One of the factors which influence the spatial resolution of a 2D detector array is the size of the single detector, another the transport of the secondary electrons from the walls into the measuring volume. In this study, the single ion chamber dose response function of an I’mRT MatriXX array was determined by comparison between slit beam dose profiles measured with the array and with EBT2 radiochromic film in a solid water-equivalent phantom at a shallow depth of 0.5 cm and at a depth of 5 cm beyond the depth dose maximum for a 6 MV photon beam. The dose response functions were obtained using two methods, the best fit method and the deconvolution method. At the shallow depth, a Lorentz function and at 5 cm depth a Gaussian function, both with the same FWHM of 7.4 mm within limits of uncertainty, were identified as the best suited dose response functions of the 4.5 mm diameter single array chamber. These dose response functions were then tested on various dose profiles whose true shape had been determined with EBT2 film and with the IC03 ionization chamber. By convolving these with the Lorentz kernel (at shallow depth) and the Gaussian kernel (at 5 cm depth) the signal profiles measured with the I’mRT MatriXX array were closely approximated. Thus, the convolution of TPS-calculated dose profiles with these dose response functions can minimize the differences between calculation and measurement which occur due to the limited spatial resolution of the I’mRT MatriXX detector.

Abstract: The purpose of this study was to investigate the effects of ultrasonic instrument gain, transducer frequency, and depth on the color variety and color filling of radiofrequency ultrasonic local estimators (RULES) images which indicated specific physical representation of liquid-containing lesions in order to find the optimal settings for the clinical application of RULES in liquid-containing lesions. Changing the ultrasonic instrument gain, transducer frequency, and depth affected the color filling and color variety of 21 pathologically-confirmed liquid-containing lesion images analyzed by RULES. Blue colored fill dominated the RULES images to represent the liquid-containing lesions. A frequency of 12.5 MHz led to red and green colors along the inner edges of the liquid-containing lesions. Changing the gain resulted in significantly different blue colored filling that was highest when the gain was 90 to 100. Changing the frequency also significantly changed the blue color filling, with the highest filling occurring at 12.5 MHz. Changing the depth did not affect the blue color filling. The liquid components of the lesions may be identified by their characteristic manifestations in RULES, where color variety is affected by transducer frequency and blue color filling which represent liquid-containing lesions in RULES images is affected by frequency and gain.

Abstract: Purpose Most of the protective eye wear devices currently on the market are manufactured on simple polycarbonate shields, produced by injection molding techniques. Despite high importance of optical quality , injection molds are rarely inspected for surface quality before or during the manufacturing process. Quality degradation is mainly monitored by optical testing of the molded parts . The purpose of this work was to validate a non-contact deflectometric measurement technique for surface and shape analysis of injection molds to facilitate deterministic surface quality control and to monitor minor conformity of the injection mold with the design data. Material and Methods The system is based on phase-measuring deflectometry with a operating measurement field of 80 × 80 mm2 (±18° slope), a lateral resolution of 60 μm and a local sensitivity of some nanometers . The calibration was tested with a calibration normal and a reference sphere. The results were crosschecked against a measurement of the same object with a tactile coordinate measuring machine . Eight injection molds for production of safety goggles with radii of +58 mm (convex) and -60 mm (concave) were measured in this study. The molds were separated into two groups (cavity 1 and 2 of the tool with different polishing techniques) and measured to test whether the measurement tool could extract differences. The analysis was performed on difference height between the measured surface and the spherical model. Results The device could derive the surface change due to polishing and discriminate between both polishing techniques, on the basis of the measured data. The concave nozzle sides of the first group (cavity 1) showed good shape conformity. In comparison, the nozzle sides of the second group (cavity 2) showed local deviations from design data up to 14.4 μm. Local form variations of about 5 μm occurred in the field of view. All convex ejector sides of both groups (cavity 1 and 2) showed rotational symmetric errors and the molds were measured in general flatter than design data. Conclusion We applied a deflectometric system for measuring and evaluating specular reflective injection molding tools to optimize the production process of occupational eye wear. The surface quality could be inline monitored in the production processes for actual spectacle models.

Abstract: Zusammenfassung Trotz zunehmender IMRT-Bestrahlungstechniken gibt es im klinischen Alltag der Strahlentherapie immer noch in Einzelfallen die Notwendigkeit zum Anschluss von Photonenfeldern an Photonen- oder Elektronenfelder. Derartige Feldanschlusse werden in dieser Arbeit untersucht, indem in mehreren Tiefen gemessene Dosisquerverteilungen durch systematische relative Verschiebungen zueinander rechnerisch uberlagert werden und die dabei entstehenden Dosisuberhohungen und Dosiseinbruche dargestellt werden. Es zeigt sich, dass „optimale“ Feldanschlusse nur in seltenen Fallen zu erreichen sind. Aber die Ergebnisse konnen dazu dienen, die Grosenordnung der zu erwartenden Dosisanderungen abzuschatzen.

Abstract: We describe the characterization of a chip-based platform (3D-KITChip) for the three-dimensional cultivation of cells under perfusion conditions via magnetic resonance imaging (MRI). Besides the chip, the microfluidic system is comprised of a bioreactor housing, a medium supply, a pump for generating active flow conditions as well as a gas mixing station. The closed circulation loop is ideally suited for a characterization via MRI since the small bioreactor setup with active perfusion, driven by the pump from outside the coils, not only is completely MRI-compatible but also can be transferred into the magnetic coil of an experimental animal scanner. We have found that the two halves of the chip inside the bioreactor are homogeneously perfused with cell culture medium both with and without cells inside the 3D-KITChip. In addition, the homogeneity of perfusion is nearly independent from the flow rates investigated in this study, and furthermore, the setup shows excellent washout characteristics after spiking with Gadolinium-DOTA which makes it an ideal candidate for drug screening purposes. We, therefore, conclude that the 3D-KITChip is well suited as a platform for high-density three-dimensional cell cultures, especially those requiring a defined medium flow and/or gas supply in a precisely controllable three dimensional environment, like stem cells.