A prototype 1.5 T receive-only 3-element multi-directional MSK phased array wrist coil that is capable to maintain its performance even when it is angulated from +/-55° to B0 was constructed and successfully tested. The ability to angulate the coil through a wide range of angles, allows positioning the coil in the center of the DSV with the possibility for relaxed overhead positioning of the wrist through “horizontal flexion” of the elbow. With this setup, high quality wrist images can be acquired and patient comfort can be achieved.

Introduction: Previous studies have shown that the approach of sensitivity encoding using a mechanically rotating radiofrequency coil (RRFC) is capable of emulating a large number of decoupled coil elements [1, 2]. Recently, the RRFC concept has been successfully combined with phased-array coil (PACs) techniques to further improve the sensitivity encoding capability, using a naturally-decoupled RF coil array. A novel 4-element RRFC array (RRFCA) has shown to have better imaging acceleration capability than PACs with twice as many coil elements at 3T [3]. An enhanced acceleration capability of RRFCA is expected at higher fields as two advantages of the RRFCA can be strengthened: (1) the mutual coupling between RRFCA elements is dramatically reduced due to the shorter RF wavelength and (2) the B1 field (sensitivity profiles) become more inhomogeneous, which has the potential to improve encoding capability. In this novel study, the potential of RRFCA to accelerate imaging at 7T was investigated. A 4-element RRFCA in different operating modes was compared with an 8-element stationary PACs at various reduction factors. Method: The RRFCA consists of 4 identical coil elements evenly distributed around the cylindrical coil former of 280 mm in diameter. The length of each coil is 170 mm (longitudinal) with a subtended angle of 35 ̊. This arrangement naturally endows the excellent electromagnetic isolation between any two coil elements. After loading a 250 mm diameter homogeneous spherical phantom with εr=50.5 and σ=0.65 S/m (average of brain tissue at 300 MHz), all the mutual couplings are under 31dB without using any decoupling circuitry. This is much improved compared with -15dB mutual coupling of RRFCA elements at 3T. The RRFCA and phantom geometry are shown in Fig.1. The modelling and electromagnetic solutions were performed with the commercially available software package FEKO (EMSS, SA). The circular polarization of steady-state RF magnetic field (B1) was calculated according to [4]. In previous works [1-3], the RRFC was actuated pneumatically and rotated about the subject with constant velocity in fast-mode (typically over 1500rpm). Since the acquisition time (TACQ) is comparable to the rotational period, within the time of sampling each kspace line, acquisition experiences time-varying sensitivity profiles as shown in Fig. 2 from point A to B and C to D. However, fast rotating may bring multiple practical issues, which can be avoided by actuating RRFCA with a non-magnetic motor. In this way, the RRFCA sample at certain points (φ=0) in a stepped fashion with precise position-control, such as at point A and C. Compared with conventional PACs, the RRFCA provides the ability of encoding with much larger number of sensitivity profiles, in both fastand steppingmodes. The fast-mode provides us additional capability of optimising the sensitivity encoding performance, by adjusting the rotating speed (ω) in relation to the imaging parameters, such as repetition time (TR) and TACQ. The optimal speed of revolution can be obtained as following functions in Fast Low Angle Shot (FLASH) imaging sequence:

A prototype 3-element open phased array knee coil for dynamic musculoskeletal (MSK) MR imaging of the knee was constructed and tested in a 1.5T Siemens Espree system. The acquired MR images of the knee joint, flexed to a variety of angles and also at the normal relaxed position, show that the open design concept is feasible and can facilitate diagnostic and functional assessment of knee injuries and pathology.

This chapter discusses the regulatory aspects of the Islamic Banking business in Malaysia with reference to the various legislation promulgated by the Malaysian Parliament and other subsidiary legislation enforced on the said topic.

Introduction: Compressed sensing (CS) has been applied to MRI [1,2] so as to exploit the data redundancy, based on the theory that compressible signals can be reconstructed from randomly under-sampled frequency information [3,4]. Thus, the imaging acceleration can be achieved. A number of CS variants, especially those employing the parallel imaging techniques, have been proposed with the aim to reduce the scan time and ameliorate various image artefacts [5]. Recently, Time-Division-Multiplexed Sensitivity Encoding (TDM-SENSE) scheme was proposed to perform fast data acquisition and image reconstruction using a physically rotating RF coil (RRFC) [6], with its freedom to encode with spatial and temporal changing sensitivity profiles. In this work, we applied CS with the TDM-SENSE concept to further reduce artefacts and evaluated the imaging performance of this method.

Diffusion weighted (DW) MRI—and in particular the apparent diffusion coefficient (ADC)—shows potential for improving the characterization and classification of enhancing breast lesions identified using dynamic contrast-enhanced (DCE) MRI. Nevertheless, to date there does not exist a well defined and objective method for computing a representative ADC value for such lesions. Typically an average ADC is computed for a manually selected region of interest (ROI) [1]. This is problematic for two reasons. Firstly the choice of ROI is subjective. Differences in ROI selection between individuals, as well as the reproducibility of selection for a given individual, can lead to variation in the mean ADC. In addition ROIs are often defined to be circular or elliptical which imposes an arbitrary geometry on the ROI [2]. Secondly, given the heterogeneity in breast lesions, an ensemble average of ADC may not provide a truly representative value. It is assumed that a representative ADC will be present in the area of neovascularisation, as indicated by rapid contrast enhancement. In order to improve the objectivity, reproducibility and efficiency of representative ADC computation, we propose an automated method based on the selection of hypo-intense areas on the ADC map corresponding to regions of greatest initial contrast enhancement identified in the DCE-MRI data. We also present an evaluation of the method using routine clinical data.

This paper presents an investigation of the apparent diffusion coefficient (ADC) for improving the discrimination of benign and malignant lesions in breast magnetic resonance imaging (MRI). In particular a method is presented for automatically selecting hyper intense tumour voxels in dynamic contrast enhanced (DCE) MRI data and evaluating their average ADC in the corresponding diffusion-weighted (DW) MRI data. The method was applied to ten breast MRI datasets obtained from routine clinical practice. The results demonstrate that the combination of the relative signal increase (DCE-MRI) with the apparent diffusion coefficient (DW-MRI) leads to better discrimination than with either feature alone. The results also suggest that it is important to acquire the DWMRI data in a consistent fashion, i.e. either before or after the acquisition of the DCE-MRI data.

Introduction: Recent studies [1-2] have shown that rotating an RF transceive coil (RRFC) provides a uniform coverage of the object, requires only one RF channel, averts coil-coil coupling interactions and facilitates large-scale multi-nuclear imaging. When images are reconstructed in the conventional FFT manner, motion of the coil sensitivity profile can lead to ghosting artifacts. This work presents Time Division Multiplexed Sensitivity Encoding (TDM-SENSE) scheme, as a new image reconstruction method that facilitates ghost-free image reconstructions and reductions in image acquisition time. The TDM-SENSE experiments were performed using an in-house developed RRFC system for head imaging. In one of the presented applications, alias-free head images were obtained in half the usual scan time.

In this work, we presented a complete technological solution for tailoring uniform RF fields and minimizing tissue heating for high field MRI. The success of the new B1 shimming technique is largely facilitated by a mechanically rotating RF coil (RRFC) configuration. The proposed method is explained with a biologically loaded, one-element rotating coil operating at 400 MHz. The coil is modelled using the method of moment (MoM) and tissue-equivalent sphere phantom is loaded and modelled using the Green’s function method. A sensitivity matrix is constructed based on the pre-characterized B1 and electric field profiles of a large number of angular positions around the imaged phantom, an optimization procedure is then employed for the determination of optimal driving configuration by solving the ill-posed linear system equation. Test simulations show that, compared with conventional bird-cage mode driving scheme, the proposed excitation scheme is capable of significant improvement of the B1 -field homogeneity and reduction of the local and global SAR values. This primary study indicates that the proposed RF excitation technology can effectively perform field-tailoring and might hold the potential of solving the high frequency RF problem.

Studies have shown that blood-flow-induced change in electrical conductivity is of equal importance in assessment of the impedance cardiogram (ICG) as are volumetric changes attributed to the motion of heart, lungs and blood vessels. To better understand the sole effect of time-varying blood conductivity on the spatiotemporal distribution of trans-thoracic electric fields (i.e. ICG), this paper presents a segmented high-resolution (1 mm3) thoracic cardiovascular system, in which the time-varying pressures, flows and electrical conductivities of blood in different vessels are evaluated using a set of coupled nonlinear differential equations, red blood cell orientation and cardiac cycle functions. Electric field and voltage simulations are performed using two and four electrode configurations delivering a small alternating electric current to an anatomically realistic and electrically accurate model of modelled human torso. The simulations provide a three-dimensional electric field distribution and show that the time-varying blood conductivity alters the voltage potential difference between the electrodes by a maximum of 0.28% for a cardiac output of about 5 L min−1. As part of a larger study, it is hoped that this initial model will be useful in providing improved insights into blood-flow-related spatiotemporal electric field variations and assist in the optimal placement of electrodes in impedance cardiography experiments.

A new method for designing a ultra high field bilateral transceive breast coil is presented. The design method does not require any discrete capacitors (hence the name “Capless Transceive Breast Coil”) and can be driven by a single RF port for simultaneous bilateral breast imaging. A prototype breast coil using this design method was constructed and tested in a 7T Philips whole-body MRI system. Phantom images acquired using the prototype show high homogeneity and excellent RF penetration.

A conformal RF coil array design for use in a MRI system is proposed. In particular, the coil array is designed without the use of any cumbersome mutual decoupling schemes. Coil elements are designed based on orthogonality, which will naturally minimise the problematic mutual coupling effects that inherently exist in most MRI phased-array systems [1]. A prototype of a knee coil constructed with the proposed orthogonality design is shown to have consistent imaging quality invariant to coil orientation with respect to B0 and application for “magic angle” imaging of soft-tissues.

MRI requires rapidly switched magnetic field gradients. This time-dependent magnetic fields induce eddy currents in nearby conducting structures. These currents generate detrimental transient magnetic fields in the region of interest (ROI) and hence, current compensation is required to minimize the consequential image distortion. In order to apply successfully current compensation techniques, it is required that the primary and the secondary magnetic fields possess a similar spatial form in the ROI. In this work we present two approaches for gradient coil design that produces gradient fields with characteristics similar to those produced by the eddy currents.