Approximation and Reconstruction from Attenuated Radon Projections

Attenuated Radon projections with respect to the weight function $W_\mu(x,y) = (1-x^2-y^2)^{\mu-1/2}$ are shown to be closely related to the orthogonal expansion in two variables with respect to $W_\mu$. This leads to an algorithm for reconstructing two dimensional functions (images) from attenuated Radon projections. Similar results are established for reconstructing functions on the sphere from projections described by integrals over circles on the sphere, and for reconstructing functions on the three-dimensional ball and cylinder domains.Comment: 25 pages, 3 figure

Preliminary study on phase-contrast digital tomosynthesis: development and evaluation of experimental system

ABSTRACT The advantage of X-ray phase imaging is its ability to obtain information on soft tissues, which is difficult using conventional X-ray imaging. Moreover, a sharp X-ray image can be obtained from the edge effect resulting from phase contrast. Digital tomosynthesis is an imaging technique used to reconstruct multiple planes in a single scan. In this study, we developed an experimental system that combines the phase-contrast and digital tomosynthesis techniques. Our experimental system consists of a transmission-type micro-focus X-ray source (minimum focus size: 1 μm). We also introduced an indirect conversion-type flat panel detector (pixel pitch: 50 μm, matrix size: 2366 × 2368) as an imaging device. The sample is placed on a computer-controlled rotation table, and projection images are captured from various angles. The images are then reconstructed using the filtered back projection method. In the experiments, a tomosynthesis image of an acrylic phantom was obtained at a tube voltage of 40 kV and at a maximum projection angle of ±20°. To evaluate the edge enhancement effect by phase contrast, the resolution, degree of edge enhancement, and image contrast were measured using the acrylic phantom. A good edge enhancement effect was confirmed under the specified conditions. Furthermore, we compared to the shape between the projection image and the tomosynthesis image and found that the tomosynthesis image showed high shape reproducibility compared to the conventional projection image. These results indicate that phase-contrast digital tomosynthesis may be useful for the three-dimensional imaging of low-contrast material

Medical applications of ionizing radiation and radiation protection for European patients, population and environment

Medical applications of ionising radiation (IR) represent a key component of the diagnosis and treatment of many diseases, guaranteeing efficient health care. The use of IR in medicine, the largest source of general population radiation exposure, is potentially associated with increased risk of cancer and non-cancer diseases, which needs to be evaluated to provide evidence-based input for risk-benefit considerations. Efforts are also needed to improve the safety and efficacy of medical applications through optimisation. The EC Euratom programme enhances research in medical radiation protection. The four complementary multidisciplinary projects presented here contribute to (1) improving knowledge on exposure and effects of diagnostic and therapeutic applications and (2) transferring results into clinical practice. The common aim is to optimise use for individual patients, enhance education and training, ensuring adherence to ethical standards, particularly related to technologies based on artificial intelligence. MEDIRAD, SINFONIA and HARMONIC focus on improving exposure estimation and studying the detrimental effects of diagnostic and therapeutic medical exposures in patients and staff using different endpoints. EURAMED rocc-n-roll brings together the results of the projects and the recommendations generated by them to build, in collaboration with the EU Radiation Protection research platforms, a strategic research agenda and a roadmap for research priorities

Breathomics profiling of metabolic pathways affected by major depression: Possibilities and limitations

BackgroundMajor depressive disorder (MDD) is one of the most common psychiatric disorders with multifactorial etiologies. Metabolomics has recently emerged as a particularly potential quantitative tool that provides a multi-parametric signature specific to several mechanisms underlying the heterogeneous pathophysiology of MDD. The main purpose of the present study was to investigate possibilities and limitations of breath-based metabolomics, breathomics patterns to discriminate MDD patients from healthy controls (HCs) and identify the altered metabolic pathways in MDD.MethodsBreath samples were collected in Tedlar bags at awakening, 30 and 60 min after awakening from 26 patients with MDD and 25 HCs. The non-targeted breathomics analysis was carried out by proton transfer reaction mass spectrometry. The univariate analysis was first performed by T-test to rank potential biomarkers. The metabolomic pathway analysis and hierarchical clustering analysis (HCA) were performed to group the significant metabolites involved in the same metabolic pathways or networks. Moreover, a support vector machine (SVM) predictive model was built to identify the potential metabolites in the altered pathways and clusters. The accuracy of the SVM model was evaluated by receiver operating characteristics (ROC) analysis.ResultsA total of 23 differential exhaled breath metabolites were significantly altered in patients with MDD compared with HCs and mapped in five significant metabolic pathways including aminoacyl-tRNA biosynthesis (p = 0.0055), branched chain amino acids valine, leucine and isoleucine biosynthesis (p = 0.0060), glycolysis and gluconeogenesis (p = 0.0067), nicotinate and nicotinamide metabolism (p = 0.0213) and pyruvate metabolism (p = 0.0440). Moreover, the SVM predictive model showed that butylamine (p = 0.0005, pFDR=0.0006), 3-methylpyridine (p = 0.0002, pFDR = 0.0012), endogenous aliphatic ethanol isotope (p = 0.0073, pFDR = 0.0174), valeric acid (p = 0.005, pFDR = 0.0162) and isoprene (p = 0.038, pFDR = 0.045) were potential metabolites within identified clusters with HCA and altered pathways, and discriminated between patients with MDD and non-depressed ones with high sensitivity (0.88), specificity (0.96) and area under curve of ROC (0.96).ConclusionAccording to the results of this study, the non-targeted breathomics analysis with high-throughput sensitive analytical technologies coupled to advanced computational tools approaches offer completely new insights into peripheral biochemical changes in MDD

Estimation of central blood pressure waveform from femoral blood pressure waveform by blind sources separation

BackgroundCentral blood pressure (cBP) is a better indicator of cardiovascular morbidity and mortality than peripheral BP (pBP). However, direct cBP measurement requires invasive techniques and indirect cBP measurement is based on rigid and empirical transfer functions applied to pBP. Thus, development of a personalized and well-validated method for non-invasive derivation of cBP from pBP is necessary to facilitate the clinical routine. The purpose of the present study was to develop a novel blind source separation tool to separate a single recording of pBP into their pressure waveforms composing its dynamics, to identify the compounds that lead to pressure waveform distortion at the periphery, and to estimate the cBP. The approach is patient-specific and extracts the underlying blind pressure waveforms in pBP without additional brachial cuff calibration or any a priori assumption on the arterial model.MethodsThe intra-arterial femoral BPfe and intra-aortic pressure BPao were anonymized digital recordings from previous routine cardiac catheterizations of eight patients at the German Heart Centre Berlin. The underlying pressure waveforms in BPfe were extracted by the single-channel independent component analysis (SCICA). The accuracy of the SCICA model to estimate the whole cBP waveform was evaluated by the mean absolute error (MAE), the root mean square error (RMSE), the relative RMSE (RRMSE), and the intraclass correlation coefficient (ICC). The agreement between the intra-aortic and estimated parameters including systolic (SBP), diastolic (DBP), mean arterial pressure (MAP), and pulse pressure (PP) was evaluated by the regression and Bland–Altman analyses.ResultsThe SCICA tool estimated the cBP waveform non-invasively from the intra-arterial BPfe with an MAE of 0.159 ± 1.629, an RMSE of 5.153 ± 0.957 mmHg, an RRMSE of 5.424 ± 1.304%, and an ICC of 0.94, as well as two waveforms contributing to morphological distortion at the femoral artery. The regression analysis showed a strong linear trend between the estimated and intra-aortic SBP, DBP, MAP, and PP with high coefficient of determination R2 of 0.98, 0.99, 0.99, and 0.97 respectively. The Bland–Altman plots demonstrated good agreement between estimated and intra-aortic parameters with a mean error and a standard deviation of difference of −0.54 ± 2.42 mmHg [95% confidence interval (CI): −5.28 to 4.20] for SBP, −1.97 ± 1.62 mmHg (95% CI: −5.14 to 1.20) for DBP, −1.49 ± 1.40 mmHg (95% CI: −4.25 to 1.26) for MAP, and 1.43 ± 2.79 mmHg (95% CI: −4.03 to 6.90) for PP.ConclusionsThe SCICA approach is a powerful tool that identifies sources contributing to morphological distortion at peripheral arteries and estimates cBP

Education and training in radiation protection in Europe: an analysis from the EURAMED rocc-n-roll project

Background: A Strengths, weaknesses, opportunities and threats analysis was performed to understand the status quo of education and training in radiation protection (RP) and to develop a coordinated European approach to RP training needs based on stakeholder consensus and existing activities in the field. Fourteen team members represented six European professional societies, one European voluntary organisation, two international healthcare organisations and five professions, namely: Medical Physicists; Nuclear Medicine Physicians; Radiologists; Radiation Oncologists and Radiographers. Four subgroups analysed the “Strengths”, “Weaknesses”, “Opportunities” and “Threats” related to E&T in RP developed under previous European Union (EU) programmes and on the Guidelines on Radiation Protection Education and Training of Medical Professionals in the EU. Results: Consensus agreement identified four themes for strengths and opportunities, namely: (1) existing structures and training recommendations; (2) RP training needs assessment and education & training (E&T) model(s) development; (3) E&T dissemination, harmonisation, and accreditation; (4) financial supports. Weaknesses and Threats analysis identified two themes: (1) awareness and prioritisation at a national/global level and (2) awareness and prioritisation by healthcare professional groups and researchers. Conclusions: A lack of effective implementation of RP principles in daily practice was identified. EuRnR strategic planning needs to consider processes at European, national and local levels. Success is dependent upon efficient governance structures and expert leadership. Financial support is required to allow the stakeholder professional agencies to have sufficient resources to achieve a pan European radiation protection training network which is sustainable and accredited across multiple national domains.info:eu-repo/semantics/publishedVersio

Simulation study of the effect of the geometrical parameters on the performance of a beta probe

An intraoperative probe is a small tool used to identify, locate, and dissect pathological lesions during surgery and confirm their removal. The most common type of probe is the gamma probe, which detects gamma-emitting sources. Despite the successful use of gamma probes in clinics, their application can be limited when the background radiation from healthy tissue nearby or the injection site is high. In these cases, the use of beta probes that detect beta-emitting radiotracers would be beneficial. The shorter range of beta radiation compared to gamma radiation would result in improved detection efficacy when background radiation is significant. In this simulation study, we examined how geometrical parameters may impact the performance of a beta probe. Our results showed that the source depth inside the phantom and detector size affected the performance of the beta probe. We also proposed and evaluated two designs of beta probes capable of adjusting their performance

Imaging in nuclear medicine

This volume addresses a wide range of issues in the field of nuclear medicine imaging, with an emphasis on the latest research findings. Initial chapters set the scene by considering the role of imaging in nuclear medicine from the medical perspective and discussing the implications of novel agents and applications for imaging. The physics at the basis of the most modern imaging systems is described, and the reader is introduced to the latest advances in image reconstruction and noise correction. Various novel concepts are then discussed, including those developed within the framework of the EURATOM FP7 MADEIRA research project on the optimization of imaging procedures in order to permit a reduction in the radiation dose to healthy tissues. Advances in quality control and quality assurance are covered, and the book concludes by listing rules of thumb for imaging that will be of use to both beginners and experienced researchers

The potential role of 3D-printed phantoms in quality control of artificial intelligence-based algorithms in medical imaging

To ensure accurate and consistent imaging of patients, medical imaging systems are controlled and tested using phantoms. Despite the availability of commercial standard phantoms for decades, 3D printing technology has gained special attention as a tool for producing accurate and costeffective tissue-mimicking phantoms. As artificial intelligence (AI) becomes increasingly prevalent in medical imaging, dedicated phantoms are needed for testing their reliability, robustness, and quality before they are implemented in clinical settings. In this context, 3D-printed imaging phantoms, which have specific requirements relevant to AI models, can play a crucial role. Due to its unique ability to create phantoms of almost any complexity, 3D printing technology seems a suitable approach for the quality control of AI models in medical imaging. The following reviews some of the works that used 3D-printed technology to create custom-built phantoms for use in Computed Tomography (CT), nuclear imaging, Magnetic Resonance Imaging (MRI), and ultrasound imaging. The focus of this short review is on the accuracy of 3D-printed technology in creating imaging phantoms. In the end, the potential of the 3D-printed phantoms in testing and quality control of AI-based algorithms in radiology is discussed

Radiation physics for nuclear medicine

The field of nuclear medicine is expanding rapidly, with the development of exciting new diagnostic methods and treatments relevant to a variety of diseases. This growth is closely associated with significant advances in radiation physics. In this book, acknowledged experts explain the basic principles of radiation physics in relation to nuclear medicine and examine important novel approaches in the field. The first section is devoted to what might be termed the "building blocks" of nuclear medicine, including the mechanisms of interaction between radiation and matter and Monte Carlo codes. In subsequent sections, radiation sources for medical applications, radiopharmaceutical development and production, and radiation detectors are discussed in detail. New frontiers are then explored, including the PET magnifying probe, improved algorithms for image reconstruction, biokinetic models, and voxel phantoms for internal dosimetry. Both trainees and experienced practitioners and researchers will find this book to be an invaluable source of up-to-date information