Thomas Beyer

Medical University of Vienna | MedUni Vienna · Center for Medical Physics and Biomedical Engineering

PurposeRisk classification of primary prostate cancer in clinical routine is mainly based on prostate-specific antigen (PSA) levels, Gleason scores from biopsy samples, and tumor-nodes-metastasis (TNM) staging. This study aimed to investigate the diagnostic performance of positron emission tomography/magnetic resonance imaging (PET/MRI) in vivo mod...

In the present paper, a method of local statistical regularization is studied for solving image reconstruction problems in emission tomography with Poisson data. A priori model based on the properties of the object under study is developed. A new reconstruction algorithm MAP-KL based on the Bayesian Maximum a Posteriori (MAP) approach with the a pr...

Background: Hybrid PET/CT and PET/MRI are increasingly important technologies in the evaluation of malignancy and require cooperation between radiologists and specialists in molecular imaging. The aim of our study was to probe the mindsets of radiological and nuclear medicine professionals in regard to current hybrid imaging practice and to assess...

Absolute quantification of PET brain imaging requires the measurement of an arterial input function (AIF), typically obtained invasively via an arterial cannulation. We present an approach to automatically calculate an image-derived input function (IDIF) and cerebral metabolic rates of glucose (CMRGlc) from the [18F]FDG PET data using an integrated...

State-of-the-art patient management frequently requires the use of non-invasive imaging methods to assess the anatomy, function or molecular-biological conditions of patients or study subjects. Such imaging methods can be singular, providing either anatomical or molecular information, or they can be combined, thus, providing “anato-metabolic” infor...

Recent studies have suggested that ¹⁸F-NaF-PET enables visualization and quantification of plaque micro-calcification in the coronary tree. However, PET imaging of plaque calcification in the coronary arteries is challenging because of the respiratory and cardiac motion as well as partial volume effects. The objective of this work is to...

Gliomas are the most common types of tumors in the brain. While the definite diagnosis is routinely made ex vivo by histopathologic and molecular examination, diagnostic work-up of patients with suspected glioma is mainly done by using magnetic resonance imaging (MRI). Nevertheless, L-S-methyl-11C-methionine (11C-MET) Positron Emission Tomography (...

Objective: To evaluate the frequency of artifacts in MR-based attenuation correction (AC) maps and their impact on the quantitative accuracy of PET-based flow and metabolism measurements in a cohort of consecutive heart failure patients undergoing combined PET/MR imaging. Methods: Myocardial viability studies were performed in 20 patients follow...

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both...

Objectives To evaluate and compare the effect of reduced acquisition time, as a surrogate of injected activity, on the PET quantification accuracy in PET/CT and PET/MR imaging. Methods Twenty min ¹⁸F-FDG phantom measurements and 10 min ¹⁸F-FET brain scans were acquired in a Biograph-True-Point-True-View PET/CT (n = 8) and a Biograph mMR PET/MR (n...

Since 2010 the portfolio of PET-based imaging has been expanded by industry with the introduction of combined whole-body PET/MRI systems with the intent of merging PET-based molecular imaging with the strengths of MRI. PET/MRI has created a lot of hype in the scientific community but comparatively little traction in the clinic. The first years of w...

The purpose of this study was to test the feasibility of migrating a quantitative brain imaging protocol from a positron emission tomography (PET)-only system to an integrated PET/MR system. Potential differences in both absolute radiotracer concentration as well as in the derived kinetic parameters as a function of PET system choice have been inve...

This paper highlights the origins of combined positron emission tomography (PET) and magnetic resonance imaging (MRI) whole-body systems that were first introduced for applications in humans in 2010. This text first covers basic aspects of each imaging modality before describing the technical and methodological challenges of combining PET and MRI w...

Aim: To compare attenuation correction (AC) approaches for positron emission tomography/magnetic resonance imaging (PET/MRI) in clinical neuro-oncology. Methods: Forty-nine PET/MRI brain scans were included: brain tumor studies using (18)F-FET (n = 31) and 68-Ga-DOTANOC (n = 7) and studies of healthy subjects using (18)F-FDG (n = 11). For each sub...

Background and Aim:(18)F-fluorodeoxyglucose ((18)F-FDG) is the most widely validated positron emission tomography (PET) tracer for the evaluation of atherosclerotic inflammation. (18)F-sodium fluoride ((18)F-NaF) has also been recently considered a potential novel biomarker of osteogenesis in atherosclerosis. We aimed to analyze the association bet...

Background Accurate quantification of plaque imaging using 18F-NaF PET requires partial volume correction (PVC). MethodsPVC of PET data was implemented by the use of a local projection (LP) method. LP-based PVC was evaluated with an image quality (NEMA) and with a thorax phantom with “plaque-type” lesions of 18-36 mL. The validated PVC method was t...

Purpose: Inspection and quantitative validation of tomographic imaging properties of SPECT systems, i.e. spatial resolution, contrast and inhomogeneity must be performed in regular intervals. Typically, the modular Jaszczak phantom is used for that purpose, since it offers the possibility to investigate all three system properties with a single me...

A 24 channel head and neck coil for PET/MR with an integrated moving radioactive source is presented to enable transmission measurements for accurate attenuation mapping. Purpose Multimodal imaging has shown to bring additional and valuable information for medical diagnostic imaging [1]. The combination of diferent modalities is always associated w...

Over the past decades, imaging in oncology has been undergoing a "quiet" revolution to treat images as data, not as pictures. This revolution has been sparked by technological advances that enable capture of images that reflect not only anatomy, but also of tissue metabolism and physiology in situ Important advances along this path have been the in...

Combined PET and MR systems provide added value for diagnostic imaging [1]. Attenuation correction (AC) is a challenge in PET/MRI and currently implemented MR-based AC methods are of limited accuracy [2]. We present a set-up combining - a PET-optimized [3] MRI head coil and - a radioactive point source moved hydraulically with heavy water in a hel...

This article provides a collaborative perspective of the discussions and conclusions from the fifth international workshop of combined positron emission tomorgraphy (PET)/magnetic resonance imaging (MRI) that was held in Tübingen, Germany, from February 15 to 19, 2016. Specifically, we summarise the second part of the workshop made up of invited pr...

Methods: A web-based survey of PET/MRI users was conducted from June to October 2015. The survey was composed of 26 questions related to the PET/MRI center, present use and imaging protocols, and perspectives on key applications. Results: Responses were collected from 39 international sites that operated PET/MRI for a median of 30 mo (range, 2-6...

Purpose PET with 18F-FDG has the potential to assess vascular macrophage metabolism. 18F-FDG is most often used in combination with contrast-enhanced CT to localize increased metabolism to specific arterial lesions. Novel 18F-FDG PET/MRI hybrid imaging shows high potential for the combined evaluation of atherosclerotic plaques, due to the superior...

Aims: To assess incremental and total patient exposure from clinical SPECT/CT imaging by means of effective dose estimations with regards to different protocols and SPECT/CT systems. Materials and methods: Consecutive patient exposure levels were documented prospectively from SPECT/CT operations at three European imaging centers. Documentation i...

Objectives: Hybrid positron emission tomography and magnetic resonance imaging (PET/MRI) using dual-tracer N13-NH3/18F-FDG PET and simultaneous late gadolinium enhancement (LGE) MRI enables quantification of myocardial viability and scar tissue. The goal of this study was an intra-individual comparison of perfusion defect size, scar size and hibern...

Objectives: Combined PET/MR is a promising imaging modality for cardiac applications currently under evaluation for clinical use. The aim of this observational study was an intra-individual comparison of left ventricular function and left ventricular volumes obtained through integrated PET/MR imaging following a dual-tracer protocol. Methods: Card...

Since its introduction in 2000, PET/CT has become a widespread and effective imaging tool for the diagnosis and management of patients with cancer. Today, over 5,000 combined PET/CT systems are in clinical operation worldwide. As a core component of PET/CT, PET is a highly sensitive imaging technique capable of detecting as few as one million cance...

Table of contents: A1 68Ga-PSMA PET/CT in staging and restaging of Prostate Cancer Patients: comparative study with 18F-Choline PET/CTW Langsteger, A Rezaee, W Loidl, HS Geinitz, F Fitz, M Steinmair, G Broinger, L Pallwien-Prettner, M BeheshtiA2 F18 Choline PET - CT: an accurate diagnostic tool for the detection of parathyroid adenoma?L Imamovic,...

Aim: To assess the reproducibility of standard, Dixon-based attenuation correction (MR-AC) in positron emission tomography/magnetic resonance (PET/MR) imaging. Further, to estimate a patient-specific lean body mass (LBM) from these MR-AC data. Methods: Ten subjects were positioned in a fully-integrated PET/MR system and three consecutive multi-b...

Objective: We assess inter- and intra-subject variability of magnetic resonance (MR)-based attenuation maps (MRμMaps) of human subjects for state-of-the-art positron emission tomography (PET)/MR imaging systems. Materials and methods: Four healthy male subjects underwent repeated MR imaging with a Siemens Biograph mMR, Philips Ingenuity TF and G...

Die Positronenemissionstomographie (PET) ist eine quantitative 4-dimensionale Bildgebungsmethode, die darauf beruht, die Verteilung von radioaktiv markierten Biomolekülen im lebenden Körper über geeignete Messmethoden nicht-invasiv zu bestimmen. Konkret werden zur Markierung der Biomoleküle instabile Radioisotope verwendet, die über einen beta+ (Po...

Background: The purpose of the study is to evaluate the physical performance of a Biograph mCT Flow 64-4R PET/CT system (Siemens Healthcare, Germany) and to compare clinical image quality in step-and-shoot (SS) and continuous table motion (CTM) acquisitions. Methods: The spatial resolution, sensitivity, count rate curves, and Image Quality (IQ)...

Purpose: Integrated positron emission tomography/magnetic resonance (PET/MR) systems derive the PET attenuation correction (AC) from dedicated MR sequences. While MR-AC performs reasonably well in clinical patient imaging, it may fail for phantom-based quality control (QC). The authors assess the applicability of different protocols for PET QC in...

This paper summarises key themes and discussions from the 4th international workshop dedicated to the advancement of the technical, scientific and clinical applications of combined positron emission tomography (PET)/magnetic resonance imaging (MRI) systems that was held in Tübingen, Germany, from February 23 to 27, 2015. Specifically, we summarise...

A challenge when using current magnetic resonance (MR)-based attenuation correction in positron emission tomography/MR imaging (PET/MRI) is that the MRIs can have a signal void around the dental fillings that is segmented as artificial air-regions in the attenuation map. For artifacts connected to the background, we propose an extension to an exist...

Accurate quantification of the activity distribution in positron emission tomography (PET) mandates attenuation correction (AC). Unlike in PET/CT, AC in PET/MR is, however, challenging, since information about the attenuation properties of the patient tissue distribution is not available directly. Standard MR-based AC (MRAC) does not account for th...

In the absence of CT or traditional transmission sources in combined clinical positron emission tomography/magnetic resonance (PET/MR) systems, MR images are used for MR-based attenuation correction (MR-AC). The susceptibility effects due to metal implants challenge MR-AC in the neck region of patients with dental implants. The purpose of this stud...

This paper summarises the proceedings and discussions at the third annual workshop held in Tübingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited...

Background CT-based attenuation correction (CT-AC) using contrast-enhancement CT impacts 111In-SPECT image quality and quantification. In this study we assessed and evaluated the effect. Methods A phantom (5.15 L) was filled with an aqueous solution of In-111. Three SPECT/CT scans were performed: (A) no IV contrast, (B) with 100-mL IV contrast, an...

The purpose of these guidelines is to assist physicians in recommending, performing, interpreting and reporting the results of FDG PET/CT for oncological imaging of adult patients. PET is a quantitative imaging technique and therefore requires a common quality control (QC)/quality assurance (QA) procedure to maintain the accuracy and precision of q...

The current MR-based attenuation correction (AC) used in combined PET/MR systems computes a Dixon attenuation map (MR-ACDixon) based on fat and water images derived from in- and opposed-phase MRI. We observed an occasional fat/water inversion in MR-ACDixon. The aim of our study was to estimate the prevalence of this phenomenon in a large patient co...

Nuclear medicine is an integral part of modern healthcare. It uses biomolecules tagged with radioactive isotopes that can recognize different molecular targets in the body or seek out hallmarks of malignant and benign conditions. The distribution of trace amounts of a radioactively labelled molecule, known as a radiotracer, can be mapped and follow...

Aim: To gather information on clinical operations, quality control (QC) standards and adoption of guidelines for FDG-PET/CT imaging in Austrian PET/CT centres. Methods: A written survey composed of 68 questions related to A) PET/CT centre and installation, B) standard protocol parameters for FDG-PET/CT imaging of oncology patients, and C) standa...

The combination of PET with Diffusion Weighted Imaging (DWI) is a promising application of PET/MR. DWI geometric accuracy can be compromised in body regions with complex anatomy. Here, we assess DWI head/neck image quality following optimization of acquisition and post-processing. Preliminary data from 10 patients with cancer of the tonsil or base...

Purpose: In combined PET/MRI standard PET attenuation correction (AC) is based on tissue segmentation following dedicated MR sequencing and, typically, bone tissue is not represented. We evaluate PET quantification in whole-body (WB)-PET/MRI following MR-AC without considering bone attenuation and then investigate different strategies to account f...

This workshop was held a year after the initial positron emission tomography/magnetic resonance (PET/MR) workshop in Tübingen, which was recently reported in this journal. The discussions at the 2013 workshop, however, differed substantially from those of the initial workshop, attesting to the progress of combined PET/MR as an innovative imaging mo...

In combined PET/MR, attenuation correction (AC) is performed indirectly based on the available MR image information. Metal implant-induced susceptibility artifacts and subsequent signal voids challenge MR-based AC. Several papers acknowledge the problem in PET attenuation correction when dental artifacts are ignored, but none of them attempts to so...

Because scintigraphic images lack anatomical information, single photon emission tomography (SPECT) and positron emission tomography systems (PET) are combined physically with CTs to compensate for this drawback. In our work, we present a method where the CT is replaced by a 3D ultrasound device. Because in this case a mechanical linkage is not pos...

At the 2013 Annual Meeting of the European Nuclear Medi-cine Association (EANM) in Lyon, Springer launched a newcompanion journal to the European Journal of Nuclear Med-icine and Molecular Imaging (EJNMMI):the EJNMMI Phys-ics journal. EJNMMI Physics will be a partner journal ofEJNMMI Research, of which Angelika Bischof Delaloye hasbeentheeditor-in-...

Aim: Combined PET/MR systems have now become available for clinical use. Given the lack of integrated standard transmission (TX) sources in these systems, attenuation and scatter correction (AC) must be performed using the available MR-images. Since bone tissue cannot easily be accounted for during MR-AC, PET quantification can be biased, in parti...

Most people require diagnostic tests during their lifetime in order to detect a suspected malignancy, plan a therapy and follow-up on a treatment. In almost all of these cases diagnostic tests entail a single imaging examination or a series of complementary imaging exams. Non-invasive imaging is central to personalized disease management and includ...

We report from the First International Workshop on positron emission tomography/magnetic resonance imaging (PET/MRI) that was organized by the University of Tübingen in March 2012. Approximately 100 imaging experts in MRI, PET and PET/computed tomography (CT), among them early adopters of pre-clinical and clinical PET/MRI technology, gathered from...

After the very successful clinical introduction of combined PET/CT imaging a decade ago, a hardware combination of PET and MR is following suit. Today, three different approaches towards integrated PET/MR have been proposed: (1) a triple-modality system with a 3T MRI and a time-of-flight PET/CT installed in adjacent rooms, (2) a tandem system with...