A new approach to the solution of Maxwell's equations for low frequency and high-resolution biomedical problems

High spatial resolution studies of the interaction of the human body with electromagnetic waves of low frequency presents a difficult computational problem. As these studies typically require at least $10^4$ points per wavelength, a huge number of time steps would be needed to be able to use the finite difference time domain method (FDTD). In this paper, a new technique is described, which allows the FDTD method to be efficiently applied over a very large frequency range, including low frequencies. In the method, no alterations to the properties of either the source or the transmission media are required. The method is essentially frequency independent and has been verified against analytical solutions within the frequency range 50 Hertz to 1 Gigahertz. As an example of the lower frequency range, the method has been applied to the simulation of electromagnetic field behavior in the human body exposed to the pulsed magnetic field gradients of a magnetic resonance image (MRI) system

Improved l1-SPIRiT using 3D walsh transform-based sparsity basis

l1-SPIRiT is a fast magnetic resonance imaging (MRI) method which combines parallel imaging (PI) with compressed sensing (CS) by performing a joint l1-norm and l2-norm optimization procedure. The original l1-SPIRiT method uses two-dimensional (2D) Wavelet transform to exploit the intra-coil data redundancies and a joint sparsity model to exploit the inter-coil data redundancies. In this work, we propose to stack all the coil images into a three-dimensional (3D) matrix, and then a novel 3D Walsh transform-based sparsity basis is applied to simultaneously reduce the intra-coil and inter-coil data redundancies. Both the 2D Wavelet transform-based and the proposed 3D Walsh transform-based sparsity bases were investigated in the l1-SPIRiT method. The experimental results show that the proposed 3D Walsh transform-based l1-SPIRiT method outperformed the original l1-SPIRiT in terms of image quality and computational efficiency

FDTD Investigations into UWB Radar Technique of Breast Tumor Detection and Location

In this paper, a finite difference time domain (FDTD) method is applied to investigate capabilities of an ultra-wide band (UWB) radar system to detect and locate a breast tumor. The investigations are divided into three parts. The first part concerns an EM field analysis of a phantom formed by a plastic container with liquid and a small highly reflecting target. In the second part, a three-dimensional numerical breast model is used to perform more advanced studies. In the carried out 3D FDTD simulations, a quasi-plane wave is used as an incident wave. Various time snap shots of the electromagnetic field are recorded to learn about the physical phenomenon of reflection and scattering in different layers of the phantoms. The third part of the investigations concerns a two dimensional (cylindrical) image reconstruction, which is performed by means of 2D FDTD. The obtained results should form the ground for working out suitable guidelines for designing an optimal microwave breast imaging apparatus based on the UWB radar technique

Перспективы развития рынка еврокапитала в современных условиях

Clinical and research staff who work around magnetic resonance imaging (MRI) scanners are exposed to the static magnetic stray fields of these scanners. Although the past decade has seen strong developments in the assessment of occupational exposure to electromagnetic fields from MRI scanners, there is insufficient insight into the exposure variability that characterizes routine MRI work practice. However, this is an essential component of risk assessment and epidemiological studies. This paper describes the results of a measurement survey of shift-based personal exposure to static magnetic fields (SMF) (B) and motion-induced time-varying magnetic fields (dB/dt) among workers at 15 MRI facilities in the Netherlands. With the use of portable magnetic field dosimeters, >400 full-shift and partial shift exposure measurements were collected among various jobs involved in clinical and research MRI. Various full-shift exposure metrics for B and motion-induced dB/dt exposure were calculated from the measurements, including instantaneous peak exposure and time-weighted average (TWA) exposures. We found strong correlations between levels of static (B) and time-varying (dB/dt) exposure (r = 0.88–0.92) and between different metrics (i.e. peak exposure, TWA exposure) to express full-shift exposure (r = 0.69–0.78). On average, participants were exposed to MRI-related SMFs during only 3.7% of their work shift. Average and peak B and dB/dt exposure levels during the work inside the MRI scanner room were highest among technical staff, research staff, and radiographers. Average and peak B exposure levels were lowest among cleaners, while dB/dt levels were lowest among anaesthesiology staff. Although modest exposure variability between workplaces and occupations was observed, variation between individuals of the same occupation was substantial, especially among research staff. This relatively large variability between workers with the same job suggests that exposure classification based solely on job title may not be an optimal grouping strategy for epidemiological purposes

Automated 3D quantitative assessment and measurement of alpha angles from the femoral head-neck junction using MR imaging

To develop an automated approach for 3D quantitative assessment and measurement of alpha angles from the femoral head-neck (FHN) junction using bone models derived from magnetic resonance (MR) images of the hip joint

Validity and reliability of computerized measurement of lumbar intervertebral disc height and volume from magnetic resonance images

BACKGROUND CONTEXT: Magnetic resonance (MR) examinations of morphologic characteristics of intervertebral discs (IVDs) have been used extensively for biomechanical studies and clinical investigations of the lumbar spine. Traditionally, the morphologic measurements have been performed using time- and expertise-intensive manual segmentation techniques not well suited for analyses of large-scale studies.

Mutual information-based binarisation of multiple images of an object: an application in medical imaging

A new method for image thresholding of two or more images that are acquired in different modalities or acquisition protocols is proposed. The method is based on measures from information theory and has no underlying free parameters nor does it require training or calibration. The method is based on finding an optimal set of global thresholds, one for each image, by maximising the mutual information above the thresholds while minimising the mutual information below the thresholds. Although some assumptions on the nature of images are made, no assumptions are made by the method on the intensity distributions or on the shape of the image histograms. The effectiveness of the method is demonstrated both on synthetic images and medical images from clinical practice. It is then compared against three other thresholding method

Метод преобразования обычной разводки печатных плат в полигональную

Описан метод преобразования традиционной разводки печатной платы в полигональную с предварительным рассмотрением вопросов построения триангуляции Делоне, диаграммы Вороного и эквидистанты к контуру.Описаний метод дозволяє автоматизувати процес полігонального розведення друкованих плат, що потрібен при проектуванні потужних радіопередавачів, а також багатошарових друкованих плат, коли на опорному шарі є присутними декілька різних кіл живлення.The described method allows to automate the polygonal interconnection process, which is essential for powerful radio transmitters designing, and also for multi-layer printed circuit boards designing, when the reference layer includes several different circuits

A Novel, non-invasive Test Enabling Bladder Cancer Detection in Urine Sediment of Patients Presenting with Haematuria:A Prospective Multicentre Performance Evaluation of ADXBLADDER

Bladder cancer is the sixth most commonly diagnosed cancer in the European Union. Here, we evaluate the performance of a novel, commercially available enzyme-linked immunosorbent assay utilising MCM5 antibodies (ADXBLADDER; Arquer Diagnostics Ltd, Sunderland, UK) for the detection of bladder cancer, in a blinded, prospective study of 856 patients, across seven centres, presenting with haematuria. The results were compared with the patients’ clinical data and final diagnosis as defined by the results of the imaging and cystoscopy, with a prevalence of bladder cancer of 8.6%. ADXBLADDER detected bladder tumours in 54/74 cancers, giving overall sensitivity of 73.0% and an overall negative predictive value (NPV) of 96.4%. Sensitivity and NPV of ADXBLADDER were highest in muscle-invasive bladder cancer, both at 100%, and on analysis of non-pTa (pT1 and above) tumours, the sensitivity for detection was 97% with an NPV of 99.8%. A subset of 173 patients had matching cytology data; of these patients, 18 were positive for bladder cancer. ADXBLADDER detected 16/18 of these cancers, whilst cytology was positive in only four of 18, providing evidence that ADXBLADDER may be a more sensitive test for bladder cancer than standard urine cytology. Patient summary: We conducted a large clinical study of a novel, simple urine test (ADXBLADDER), which measures a protein (MCM5) in urine and can be used to detect bladder cancer in patients. We recruited 856 patients and demonstrated that the new urine test can detect bladder cancer with a high degree of accuracy, performing better than the most commonly used urine test—urine cytology. In conclusion, this novel ADXBLADDER urine test can be used to help detect bladder cancers and it can replace the current, standard urine test. The ADXBLADDER test measures the novel biomarker MCM5. Outperforming cytology, and achieving one of the highest sensitivities and negative predictive values of any urine test for bladder cancer diagnosis, it has the potential to improve the bladder cancer diagnostic pathway.</p