Characterization of radiotherapy component impact on MR imaging quality for an MRgRT system

Radiotherapy components of an magnetic resonnace-guided radiotherapy (MRgRT) system can alter the magnetic fields, causing spatial distortion and image deformation, altering imaging and radiation isocenter coincidence and the accuracy of dose calculations. This work presents a characterization of radiotherapy component impact on MR imaging quality in terms of imaging isocenter variation and spatial integrity changes on a 0.35T MRgRT system, pre- and postupgrade of the system. The impact of gantry position, MLC field size, and treatment table power state on imaging isocenter and spatial integrity were investigated. A spatial integrity phantom was used for all tests. Images were acquired for gantry angles 0-330° at 30° increments to assess the impact of gantry position. For MLC and table power state tests all images were acquired at the home gantry position (330°). MLC field sizes ranged from 1.66 to 27.4 cm edge length square fields. Imaging isocenter shift caused by gantry position was reduced from 1.7 mm at gantry 150° preupgrade to 0.9 mm at gantry 120° postupgrade. Maximum spatial integrity errors were 0.5 mm or less pre- and postupgrade for all gantry angles, MLC field sizes, and treatment table power states. However, when the treatment table was powered on, there was significant reduction in SNR. This study showed that gantry position can impact imaging isocenter, but spatial integrity errors were not dependent on gantry position, MLC field size, or treatment table power state. Significant isocenter variation, while reduced postupgrade, is cause for further investigation

Clinical experience of MRI4D QUASAR motion phantom for latency measurements in 0.35T MR‐LINAC

PURPOSE: In MRgRT, accuracy of treatment depends on the gating latency, when real-time targeting and gating is enabled. Gating latency is dependent on image acquisition, processing time, accuracy, efficacy of target tracking algorithms, and radiation beam delivery latency. In this report, clinical experience of the MRI MATERIALS/METHODS: Beam-control latency was measured on a 0.35-T MR-LINAC system with four target tracking algorithms and two real-time cine imaging sequences [four and eight frames per second (FPS)]. Using an MR-compatible motion phantom, the delays between phantom beam triggering signal and linac radiation beam control signal were evaluated for three motion periods with a rigid target. The gating point was set to be 8 mm above the full exhalation position. The beam-off latency was measured for a total of 24 combinations of tracking algorithm, imaging FPS, and motion periods. The corresponding gating target margins were determined using the target motion speed multiplied by the beam-off latency. RESULTS: The largest measured beam-off latency was 302 ± 20 ms with the Large Deforming Targets (LDT) algorithm and 4 s motion period imaged with 8-FPS cine MRI. The corresponding gating uncertainty based on target motion speed was 3.0 mm. The range of the average beam-off latency was 128-243 ms in 4-FPS imaging and 47-302 ms in 8-FPS imaging. CONCLUSIONS: The gating latency was measured using an MR

Simple top-down preparation of magnetic Bi0.9_{0.9}Gd0.1_{0.1}Fe1−x_{1-x}Tix_xO3_3 nanoparticles by ultrasonication of multiferroic bulk material

We present a simple technique to synthesize ultrafine nanoparticles directly from bulk multiferroic perovskite powder. The starting materials, which were ceramic pellets of the nominal compositions of Bi$_{0.9}$Gd$_{0.1}$Fe$_{1-x}$Ti$_x$O$_3$ (x = 0.00-0.20), were prepared initially by a solid state reaction technique, then ground into micrometer-sized powders and mixed with isopropanol or water in an ultrasonic bath. The particle size was studied as a function of sonication time with transmission electron microscopic imaging and electron diffraction that confirmed the formation of a large fraction of single-crystalline nanoparticles with a mean size of 11-13 nm. A significant improvement in the magnetic behavior of Bi$_{0.9}$Gd$_{0.1}$Fe$_{1-x}$Ti$_x$O$_3$ nanoparticles compared to their bulk counterparts was observed at room temperature. This sonication technique may be considered as a simple and promising route to prepare ultrafine nanoparticles for functional applications.Comment: 7 pages, 5 figure

The role of ethnic group and gender on beliefs about sexual problems : an experimental study with South Asians in the UK.

South Asians have been neglected from studies exploring help-seeking related to sexual problems. This experimental case vignette study aimed to explore the role of ethnic group and gender on the beliefs held about the causes, consequences and possible solutions to sexual problems. The study examined the impact of ethnic group (South Asian versus White British), gender of the person in a fictitious case vignette (male versus female), and participant gender (male versus female) on beliefs about sexual problems and coherence between beliefs. 291 participants randomly received a single sentence case vignette depicting either a male or female with a sexual problem and completed measures online concerning their beliefs about causes, consequences and solutions to sexual problems. South Asian and White British participants equally endorsed a psychological causal model, however South Asians showed greater endorsement for biological and social factors for the causes, consequences and solutions to sexual problems. Participants considering the male case vignette perceived greater psychological consequences and biological solutions compared to those who received the female case vignette. Female participants showed greater endorsement for biological, psychological and social causes, and biological and social consequences. Both ethnic groups showed a coherent model between beliefs about the causes and the solutions to sexual problems. The findings provide theoretical support to cognitive models of help-seeking and offer clinical implications to improve help-seeking behaviour and management of sexual problems

The role of ethnic group and gender on beliefs about sexual problems : an experimental study with South Asians in the UK.

South Asians have been neglected from studies exploring help-seeking related to sexual problems. This experimental case vignette study aimed to explore the role of ethnic group and gender on the beliefs held about the causes, consequences and possible solutions to sexual problems. The study examined the impact of ethnic group (South Asian versus White British), gender of the person in a fictitious case vignette (male versus female), and participant gender (male versus female) on beliefs about sexual problems and coherence between beliefs. 291 participants randomly received a single sentence case vignette depicting either a male or female with a sexual problem and completed measures online concerning their beliefs about causes, consequences and solutions to sexual problems. South Asian and White British participants equally endorsed a psychological causal model, however South Asians showed greater endorsement for biological and social factors for the causes, consequences and solutions to sexual problems. Participants considering the male case vignette perceived greater psychological consequences and biological solutions compared to those who received the female case vignette. Female participants showed greater endorsement for biological, psychological and social causes, and biological and social consequences. Both ethnic groups showed a coherent model between beliefs about the causes and the solutions to sexual problems. The findings provide theoretical support to cognitive models of help-seeking and offer clinical implications to improve help-seeking behaviour and management of sexual problems

Enhanced exoinulinase production from Kluyveromyces marxianus YS-1 using response surface methodology

Optimization of critical medium components for exoinulinase production by Kluyveromyces marxianus YS-1 at shake-flask was investigated using response surface methodology (RSM) based on a central composite rotatable design (CCRD). A five-level with five factors CCRD was used to evaluate the influence of related factors including concentration of inulin, meat extract, calcium chloride, sodium dodecyl sulphate and medium pH. Optimum values obtained by RSM were 2% inulin, 2.17% meat extract, 0.65 mM calcium chloride, 0.10 mM sodium dodecyl sulphate and pH 5.5. Optimized medium projected a theoretical exoinulinase production of 63.61 IU/mL and biomass yield of 0.965 (OD600/10). Multiple correlation coefficient R was 0.9976 and 0.9605 for exoinulinase production and biomass yield, respectively, which being close to one, justified an excellent correlation between the predicted and experimental values. Maximum productivity of exoinulinase (64.05 IU/mL) obtained experimentally by RSM was more than double in comparison to earlier findings using classical one-variable-at-a-time technique