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OCTOBER 1838 (pg. 310-301). NOVEMBER 1838 (pg. 310-301). DECEMBER 1838 (pg. 310-313). JANUARY (pg. 313-322). FEBRUARY (pg. 322-328). MARCH (pg. 328-331). APRIL (pg. 331-337). MAY (pg. 337-343). JUNE (pg. 343-349). JULY (pg. 350-357). AUGUST (pg. 357-362). SEPTEMBER (pg. 362-367). OCTOBER (pg. 367-371). NOVEMBER (pg. 371-374). DECEMBER (pg. 374-381).

The most investigated semiconductor photosensor for MRI-compatible PET detectors is the avalanche photodiode (APD). However, the silicon photomultiplier (SiPM), also called the Geiger-mode APD, is gaining attention in the development of the next generation of PET/MRI systems because the SiPM has much better performance than the APD. We have developed an MRI-compatible PET system based on multichannel SiPM arrays to allow simultaneous PET/MRI. The SiPM PET scanner consists of 12 detector modules with a ring diameter of 13.6 cm and an axial extent of 3.2 cm. In each detector module, 4 multichannel SiPM arrays (with 4 × 4 channels arranged in a 2 × 2 array to yield 8 × 8 channels) were coupled with 20 × 18 Lu(1.9)Gd(0.1)SiO(5):Ce crystals (each crystal is 1.5 × 1.5 × 7 mm) and mounted on a charge division network for multiplexing 64 signals into 4 position signals. Each detector module was enclosed in a shielding box to reduce interference between the PET and MRI scanners, and the temperature inside the box was monitored for correction of the temperature-dependent gain variation of the SiPM. The PET detector signal was routed to the outside of the MRI room and processed with a field programmable gate array-based data acquisition system. MRI compatibility tests and simultaneous PET/MRI acquisitions were performed inside a 3-T clinical MRI system with 4-cm loop receiver coils that were built into the SiPM PET scanner. Interference between the imaging systems was investigated, and phantom and mouse experiments were performed. No radiofrequency interference on the PET signal or degradation in the energy spectrum and flood map was shown during simultaneous PET/MRI. The quality of the MRI scans acquired with and without the operating PET showed only slight degradation. The results of phantom and mouse experiments confirmed the feasibility of this system for simultaneous PET/MRI. Simultaneous PET/MRI was possible with a multichannel SiPM-based PET scanner, with no radiofrequency interference on PET signals or images and only slight degradation of the MRI scans.

G-ratio weighted imaging is a non-invasive, in-vivo MRI-based technique that aims at estimating an aggregated measure of relative myelination of axons across the entire brain white matter. The MR g-ratio and its constituents (axonal and myelin volume fraction) are more specific to the tissue microstructure than conventional MRI metrics targeting either the myelin or axonal compartment. To calculate the MR g-ratio, an MRI-based myelin-mapping technique is combined with an axon-sensitive MR technique (such as diffusion MRI). Correction for radio-frequency transmit (B1+) field inhomogeneities is crucial for myelin mapping techniques such as magnetization transfer saturation. Here we assessed the effect of B1+ correction on g-ratio weighted imaging. To this end, the B1+ field was measured and the B1+ corrected MR g-ratio was used as the reference in a Bland-Altman analysis. We found a substantial bias (≈-89%) and error (≈37%) relative to the dynamic range of g-ratio values in the white matter if the B1+ correction was not applied. Moreover, we tested the efficiency of a data-driven B1+ correction approach that was applied retrospectively without additional reference measurements. We found that it reduced the bias and error in the MR g-ratio by a factor of three. The data-driven correction is readily available in the open-source hMRI toolbox ( www.hmri.info ) which is embedded in the statistical parameter mapping (SPM) framework.

The authors present a novel 16/32/64/128-point single-path delay feedback pipeline fast Fourier transform (FFT) architecture targeting the multi-rate and multi-regional orthogonal frequency division multiplexing (MR-OFDM) physical layer of IEEE 802.15.4-g. The proposed FFT architecture employs a mixed-radix algorithm to significantly reduce the number of complex multipliers. It utilises a configurable complex constant multiplier structure instead of a fixed constant multiplier to efficiently conduct $W_{32}$W32, $W_{64}$W64, and $W_{128}$W128 twiddle factor multiplication. A hardware-sharing mechanism has also been formulated to reduce the memory space requirements of the proposed 16/32/64/128-point FFT computation scheme. The proposed design is implemented in Xilinx Virtex-5 and Altera's field-programmable gate array devices. For the computation of 128-point FFT, the proposed mixed-radix FFT architecture significantly reduces the hardware cost in comparison with existing FFT architecture. The proposed FFT architecture is also implemented by adopting the 90 nm complementary metal-oxide-semiconductor technology with a supply voltage of 1 V. Post-synthesis results reveal that the design is efficient in terms of gate count and power consumption, compared to earlier reported designs. The proposed variable-length FFT architecture gate count is 22.3K and consumes 3.832 mW, while the word-length is 12-bits and can be efficiently useful for the IEEE 802.15.4-g standard.

CHAPTER I (pg. 106-113). CHAPTER II. CANADA (pg. 114-126). CHAPTER III. AUSTRALASIA (pg. 126-151). CHAPTER IV. SOUTH AFRICA (pg. 151-163). THE UNION OF SOUTH AFRICA [by G. V. Taylor] (pg. 151-160). CHAPTER V (pg. 163-174).

Continued optimism (pg. 24-25). H.M.S. Amethyst (pg. 25-26). visit of Commonwealth Prime Ministers (pg. 26). Western Union (pg. 26-27). lifting of Berlin blockade (pg. 27). Foreign Ministers' conference (pg. 27-28). parliamentary debates (pg. 28-30). Church questions (pg. 30). Eire's independence (pg. 30-33). progress of nationalised industries (pg. 33-34). Labour Believes in Britain (pg. 34-36). local elections (pg. 36-37). Blackpool conference of Labour Party (pg. 37-40). dock strikes (pg. 40-42). new economic crisis (pg. 42-43). the dollar problem reviewed (pg. 43). Sir S. Cripps' statement, 6 July (pg. 43-46). The Right Road for Britain (pg. 46-48).