LARP4 is an RNA-binding protein that binds nuclear-encoded mitochondrial mRNAs to promote mitochondrial function.

Mitochondria-associated RNA-binding proteins (RBPs) have emerged as key contributors to mitochondrial biogenesis and homeostasis. With few examples known, we set out to identify RBPs that regulate nuclear-encoded mitochondrial mRNAs (NEMmRNAs). Our systematic analysis of RNA targets of 150 RBPs identified RBPs with a preference for binding NEMmRNAs, including LARP4, a La RBP family member. We show that LARP4's targets are particularly enriched in mRNAs that encode respiratory chain complex proteins (RCCPs) and mitochondrial ribosome proteins (MRPs) across multiple human cell lines. Through quantitative proteomics, we demonstrate that depletion of LARP4 leads to a significant reduction in RCCP and MRP protein levels. Furthermore, we show that LARP4 depletion reduces mitochondrial function, and that LARP4 re-expression rescues this phenotype. Our findings shed light on a novel function for LARP4 as an RBP that binds to and positively regulates NEMmRNAs to promote mitochondrial respiratory function.

Survey of National Health Service (NHS) orthodontic practitioners in Wales, UK. Part 2: job satisfaction perceptions of the workforce 2021-2022.

OBJECTIVE: To ascertain the perceptions of the Welsh NHS orthodontic workforce regarding their job satisfaction and work life balance. DESIGN: Descriptive cross-sectional survey. PARTICIPANTS AND SETTING: Clinicians providing NHS orthodontic treatment in Wales. METHODS: An anonymised, email-distributed, electronic, two-part survey (onlinesurveys.ac.uk) of the Welsh NHS orthodontic workforce working within Wales was undertaken. The survey consisted of three sections: (1) demographic information (part 1); (2) respondents' working pattern (part 1); and (3) perceptions of professional job satisfaction and work/life balance (part 2). The responses received were exported into an Excel spreadsheet for descriptive analysis. The free-text comments were collated for each question and subsequently underwent a content analysis to identify any common themes. RESULTS: Part 2 of the survey yielded an overall response rate of 69.6% (n = 78). Over 96% (n = 75) of respondents felt that they had 'made the right career choice, including 100% of orthodontic trainees, orthodontic specialists and orthodontic consultants. Of the respondents, 88.5% (n = 69) said they 'enjoyed going to work', with the remaining being mostly neutral in their opinion. Of the respondents, 79.5% (n = 62) felt they were able to 'provide their patients the optimum care' and 64.1% (n = 50) felt that more demands were being placed upon them by patients and parents. Overall, 52.6% (n = 41) of survey respondents believed it was becoming increasingly difficult to achieve an effective work/life balance, and this was more prevalent among male respondents (61.5%, n = 16) than female respondents (48.1%, n = 25), although this difference was not statistically significant (P >0.05). CONCLUSIONS: Over 96% of respondents felt they have chosen the right career and that flexibility and a good working environment are important to job satisfaction. Respondents felt that there are increasing demands being placed upon them by patients/parents, employers, the Regulators, the Government and Health Boards. This is leading to increased difficulty in achieving a satisfactory work/life balance, especially among male respondents.

Survey of National Health Service (NHS) orthodontic practitioners in Wales, UK. Part 1: working patterns 2021-2022.

OBJECTIVE: To ascertain the working patterns of the NHS orthodontic workforce in Wales and any possible future changes. DESIGN: Descriptive cross-sectional survey. PARTICIPANTS: NHS orthodontic practitioners in Wales. METHODS: An anonymised email distributed an electronic two-part survey of the Welsh NHS orthodontic workforce. The survey consisted of three sections: (1) demographic information; (2) respondents' working pattern (part 1); and (3) perceptions of professional satisfaction (part 2). RESULTS: Part 1 of the survey yielded a 70.5% response rate (n = 79); 65.8% of the respondents were women. Of the respondents, 45.6% (n = 36) worked full time (F/T), 39.2% (n = 31) worked less than F/T and 15.2% (n = 12) worked more than F/T. Of the male respondents, 81.5% (n = 22) worked 10 sessions or more compared to 50% (n = 26) of women. The respondents undertook 508.5 orthodontic clinical sessions per week within Wales; of these sessions, 87.6% (n = 445.5) delivered NHS orthodontic care. Of the respondents, 8.4% (n = 7) were planning to increase their orthodontic clinical time within the next 2 years, 24.1% (n = 19) were planning to decrease it and 20.3% (n = 16) were unsure. One-quarter of respondents indicated that they were planning to stop clinical orthodontic activity within the next 5 years, including 53.3% (n = 8) of DwSIs, 37% (n = 10) of primary care specialists and 13.3% (n = 2) of consultants. The pandemic was an influencing factor for 80% of these clinicians. CONCLUSIONS: Part 1 of the survey suggested that the majority of the orthodontic workforce was female, were working full time or more, and spent most sessions delivering NHS care. One-quarter of respondents were planning to cease undertaking orthodontic activity within the next 5 years.

Chromatographic Phospholipid Trapping for Automated H/D Exchange Mass Spectrometry of Membrane Protein-Lipid Assemblies.

Lipid interactions modulate the function, folding, structure, and organization of membrane proteins. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) has emerged as a useful tool to understand the structural dynamics of these proteins within lipid environments. Lipids, however, have proven problematic for HDX-MS analysis of membrane-embedded proteins due to their presence of impairing proteolytic digestion, causing liquid chromatography column fouling, ion suppression, and/or mass spectral overlap. Herein, we describe the integration of a chromatographic phospholipid trap column into the HDX-MS apparatus to enable online sample delipidation prior to protease digestion of deuterium-labeled protein-lipid assemblies. We demonstrate the utility of this method on membrane scaffold protein-lipid nanodisc─both empty and loaded with the ∼115 kDa transmembrane protein AcrB─proving efficient and automated phospholipid capture with minimal D-to-H back-exchange, peptide carry-over, and protein loss. Our results provide insights into the efficiency of phospholipid capture by ZrO2-coated and TiO2 beads and describe how solution conditions can be optimized to maximize not only the performance of our online but also the existing offline, delipidation workflows for HDX-MS. We envision that this HDX-MS method will significantly ease membrane protein analysis, allowing to better interrogate their dynamics in artificial lipid bilayers or even native cell membranes.

Epistemic injustice and the psychiatrist.

BACKGROUND: Psychiatrists depend on their patients for clinical information and are obligated to regard them as trustworthy, except in special circumstances. Nevertheless, some critics of psychiatry have argued that psychiatrists frequently perpetrate epistemic injustice against patients. Epistemic injustice is a moral wrong that involves unfairly discriminating against a person with respect to their ability to know things because of personal characteristics like gender or psychiatric diagnosis. METHODS: We review the concept of epistemic injustice and several claims that psychiatric practice is epistemically unjust. RESULTS: While acknowledging the risk of epistemic injustice in psychiatry and other medical fields, we argue that most concerns that psychiatric practice is epistemically unjust are unfounded. CONCLUSIONS: The concept of epistemic injustice does not add significantly to existing standards of good clinical practice, and that it could produce changes in practice that would be deleterious. Psychiatrists should resist calls for changes to clinical practice based on this type of criticism.

Evaluating motion of pancreatic tumors and anatomical surrogates using cine MRI in 0.35T MRgRT under free breathing conditions.

Treatment tolerability is a significant limitation to pancreatic cancer treatment with radiotherapy due to proximity to highly radiosensitive organs and respiratory motion necessitating expanded target margins. Further, pancreatic tumors are difficult to visualize on conventional radiotherapy systems. Surrogates are often used to locate the tumor but are often inconsistent and do not provide strong positional relations throughout the respiratory cycle. This work utilizes a retrospective dataset of 45 pancreatic cancer patients treated on an MR-Linac system with cine MRI acquired for real-time target tracking. We investigated intra-fraction motion of tumors and two abdominal surrogates, leading to prediction models between the tumor and surrogate. Patient specific motion evaluation and prediction models were generated from 225 cine MRI series acquired during treatment. Tumor contours were used to evaluate the pancreatic tumor motion. Linear regression and principal component analysis (PCA) based models were used to predict tumor position from the anterior-posterior (AP) motion of the abdominal surface, the superior-inferior (SI) motion of the diaphragm, or a combination. Models were evaluated using mean squared error (MSE) and mean absolute error (MAE). Contour analysis showed the average pancreatic tumor motion range was 7.4 ± 2.7 mm and 14.9 ± 5.8 mm in the AP and SI directions, respectively. The PCA model had MSE of 1.4 mm2 and 0.6 mm2 , for the SI and AP directions, respectively, with both surrogates as inputs for the models. When only the abdomen surrogate was used, MSE was 1.3 mm2 and 0.4 mm2 in the SI and AP directions, while it was 0.4 mm2 and 1.3 mm2 when only the diaphragm surrogate was used. We evaluated intra-fraction pancreatic tumor motion and demonstrated prediction models between the tumor and surrogate. The models calculated the pancreatic tumor position from diaphragm, abdominal, or both contours within standard pancreatic cancer target margin, and the process could be applied to other disease sites in the abdominothoracic cavity.

Assessment of Various Multimodal Fusion Approaches Using Synthetic Aperture Radar (SAR) and Electro-Optical (EO) Imagery for Vehicle Classification via Neural Networks.

Multimodal fusion approaches that combine data from dissimilar sensors can better exploit human-like reasoning and strategies for situational awareness. The performance of a six-layer convolutional neural network (CNN) and an 18-layer ResNet architecture are compared for a variety of fusion methods using synthetic aperture radar (SAR) and electro-optical (EO) imagery to classify military targets. The dataset used is the Synthetic and Measured Paired Labeled Experiment (SAMPLE) dataset, using both original measured SAR data and synthetic EO data. We compare the classification performance of both networks using the data modalities individually, feature level fusion, decision level fusion, and using a novel fusion method based on the three RGB-input channels of a residual neural network (ResNet). In the proposed input channel fusion method, the SAR and the EO imagery are separately fed to each of the three input channels, while the third channel is fed a zero vector. It is found that the input channel fusion method using ResNet was able to consistently perform to a higher classification accuracy in every equivalent scenario.

Assessment of a novel commercial large field of view phantom for comprehensive MR imaging quality assurance of a 0.35T MRgRT system.

Consistent quality assurance (QA) programs are vital to MR-guided radiotherapy (MRgRT), for ensuring treatment is delivered accurately and the onboard MRI system is providing the expected image quality. However, daily imaging QA with a dedicated phantom is not common at many MRgRT centers, especially with large phantoms that cover a field of view (FOV), similar to the human torso. This work presents the first clinical experience with a purpose-built phantom for large FOV daily and periodic comprehensive quality assurance (QUASAR™ MRgRT Insight Phantom (beta)) from Modus Medical Devices Inc. (Modus QA) on an MRgRT system. A monthly American College of Radiology (ACR) QA phantom was also imaged for reference. Both phantoms were imaged on a 0.35T MR-Linac, a 1.5T Philips wide bore MRI, and a 3.0T Siemens MRI, with T1-weighted and T2-weighted acquisitions. The Insight phantom was imaged in axial and sagittal orientations. Image quality tests including geometric accuracy, spatial resolution accuracy, slice thickness accuracy, slice position accuracy, and image intensity uniformity were performed on each phantom, following their respective instruction manuals. The geometric distortion test showed similar distortions of -1.7 mm and -1.9 mm across a 190 mm and a 283 mm lengths for the ACR and MRgRT Insight phantoms, respectively. The MRgRT Insight phantom utilized a modulation transform function (MTF) for spatial resolution evaluation, which showed decreased performance on the lower B0 strength MRIs, as expected, and could provide a good daily indicator of machine performance. Both the Insight and ACR phantoms showed a match with scan parameters for slice thickness analysis. During the imaging and analysis of this novel MRgRT Insight phantom the authors found setup to be straightforward allowing for easy acquisition each day, and useful image analysis parameters for tracking MRI performance.

Visually guided respiratory motion management for Ethos adaptive radiotherapy.

PURPOSE: Ethos adaptive radiotherapy (ART) is emerging with AI-enhanced adaptive planning and high-quality cone-beam computed tomography (CBCT). Although a respiratory motion management solution is critical for reducing motion artifacts on abdominothoracic CBCT and improving tumor motion control during beam delivery, our institutional Ethos system has not incorporated a commercial solution. Here we developed an institutional visually guided respiratory motion management system to coach patients in regular breathing or breath hold during intrafractional CBCT scans and beam delivery with Ethos ART. METHODS: The institutional visual-guidance respiratory motion management system has three components: (1) a respiratory motion detection system, (2) an in-room display system, and (3) a respiratory motion trace management software. Each component has been developed and implemented in the clinical Ethos ART workflow. The applicability of the solution was demonstrated in installation, routine QA, and clinical workflow. RESULTS: An air pressure sensor has been utilized to detect patient respiratory motion in real time. Either a commercial or in-house software handled respiratory motion trace display, collection and visualization for operators, and visual guidance for patients. An extended screen and a projector on an adjustable stand were installed as the in-room visual guidance solution for the closed-bore ring gantry medical linear accelerator utilized by Ethos. Consistent respiratory motion traces and organ positions on intrafractional CBCTs demonstrated the clinical suitability of the proposed solution in Ethos ART. CONCLUSION: The study demonstrated the utilization of an institutional visually guided respiratory motion management system for Ethos ART. The proposed solution can be easily applied for Ethos ART and adapted for use with any closed bore-type system, such as computed tomography and magnetic resonance imaging, through incorporation with appropriate respiratory motion sensors.

Don't Turn Off the Tap! The Importance of Discovery Science to the Australian Cardiovascular Sector and Improving Clinical Outcomes Into the Future.

Despite significant advances in interventional and therapeutic approaches, cardiovascular disease (CVD) remains the leading cause of death and mortality. To lower this health burden, cardiovascular discovery scientists need to play an integral part in the solution. Successful clinical translation is achieved when built upon a strong foundational understanding of the disease mechanisms involved. Changes in the Australian funding landscape, to place greater emphasis on translation, however, have increased job insecurity for discovery science researchers and especially early-mid career researchers. To highlight the importance of discovery science in cardiovascular research, this review compiles six science stories in which fundamental discoveries, often involving Australian researchers, has led to or is advancing to clinical translation. These stories demonstrate the importance of the role of discovery scientists and the need for their work to be prioritised now and in the future. Australia needs to keep discovery scientists supported and fully engaged within the broader cardiovascular research ecosystem so they can help realise the next game-changing therapy or diagnostic approach that diminishes the burden of CVD on society.

The COVID-19 experience of orthodontists in the UK.

OBJECTIVE: To understand and compare the perceived impact and ongoing effects of the COVID-19 pandemic on orthodontic clinical services in the UK. DESIGN: Descriptive cross-sectional survey. SETTING: Online electronic questionnaire. PARTICIPANTS: Members of the British Orthodontic Society (BOS). METHODS: Electronic questionnaires were circulated between March and June 2021. The UK survey was distributed via emails from the BOS, Orthodontic Managed Clinical Networks and WhatsApp groups. RESULTS: A total of 560 unique responses were received. There were more respondents who were aged over 50 years (52%) then respondents who were aged below 50 years (48%) with the median age range being 50-54 years (20%). The main causes of disruption to clinical practice were felt to be national restrictions (85%), increased cross-infection measures (84%), social distancing (80%) and professional guidance (80%). Respondents felt more negatively in their opinions regarding dentistry's preparedness for the pandemic (5%) and how dentistry coped in the crisis (35%), when compared to orthodontic services specifically (8% and 58%, respectively). The respondents were not confident about the potential beneficial effects of a vaccination programme on orthodontic clinical service provision (21%). Telephone consultations (84%) and video consultations (61%) were the main adaptations used by the respondents during the pandemic. CONCLUSIONS: Respondents felt that COVID-19 will have long-term societal, clinical and professional implications. The majority of our respondents supported the vaccination and weekly testing of the orthodontic team. Respondents felt that during the pandemic there had been a deterioration in care provision and were not optimistic about a vaccination programme restoring services to pre-pandemic levels of activity. During the pandemic, patients in active orthodontic treatment have been prioritised but at the expense of new and review patients, and as services recover respondents were concerned about the difficulty of arranging dental extractions.

Assessing The Key Photophysical Properties of Triangulenium Dyes for DNA Binding by Alteration of the Fluorescent Core.

Four-stranded G-quadruplex (G4) DNA is a non-canonical DNA topology that has been proposed to form in cells and play key roles in how the genome is read and used by the cellular machinery. Previously, a fluorescent triangulenium probe (DAOTA-M2) was used to visualise G4s in cellulo, thanks to its distinct fluorescence lifetimes when bound to different DNA topologies. Herein, the library of available triangulenium probes is expanded to explore how modifications to the fluorescent core of the molecule affect its photophysical characteristics, interaction with DNA and cellular localisation. The benzo-bridged and isopropyl-bridged diazatriangulenium dyes, BDATA-M2 and CDATA-M2 respectively, featuring ethyl-morpholino substituents, were synthesised and characterised. The interactions of these molecules with different DNA topologies were studied to determine their binding affinity, fluorescence enhancement and fluorescence lifetime response. Finally, the cellular uptake and localisation of these optical probes were investigated. Whilst structural modifications to the triangulenium core only slightly alter the binding affinity to DNA, BDATA-M2 and CDATA-M2 cannot distinguish between DNA topologies through their fluorescence lifetime. It is argued theoretically and experimentally that this is due to reduced effectiveness of photoinduced electron transfer (PET) quenching. This work presents valuable new evidence into the critical role of PET quenching when using the fluorescence lifetime of triangulenium dyes to discriminate G4 DNA from duplex DNA, highlighting the importance of fine tuning redox and spectral properties when developing new triangulenium-based G4 probes.

Aetiologies and factors associated with poor clinical outcomes in rhabdomyolysis: a retrospective cohort study in an Australian trauma centre.

Rhabdomyolysis is a clinical syndrome with significant morbidity and mortality that occurs as a result of traumatic and non-traumatic aetiologies. Acute kidney injury, the need for dialysis, and death, can occur due to rhabdomyolysis. This study explores the aetiologies, clinical outcomes and associated factors for poor outcomes in a cohort of patients with rhabdomyolysis in a tertiary trauma centre in Australia.

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 MRI4D QUASAR motion phantom for latency measurements on a 0.35-T magnetic resonance-linear accelerator (MR-LINAC) with two imaging speeds and four tracking algorithms was studied. 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 MRI4D QUASAR motion phantom in a 0.35-T MR-LINAC. The latency measurements include time delay related to MR imaging method, target tracking algorithm and system delay. The gating uncertainty was estimated based on the beam-off latency measurements and the target motion.

First clinical experience of correcting phantom-based image distortion related to gantry position on a 0.35T MR-Linac.

MR-guided radiotherapy requires strong imaging spatial integrity to deliver high quality plans and provide accurate dose calculation. The MRI system, however, can be compromised by the integrated linear accelerator (Linac), resulting in inaccurate imaging isocenter position and geometric distortion. Dependence on gantry position further complicates the correction of distortions. This work presents a new clinical application of a commercial phantom and software system that quantifies isocenter alignment and geometric distortion, as well as providing a deformation vector field (DVF). A large distortion phantom and a smaller grid phantom were imaged at multiple gantry angles from 0 to 330° on a 0.35 T integrated MR-Linac. The software package was used to assess geometric distortion and generate DVFs to correct distortions within the phantom volume. The DVFs were applied to the grid phantom with resampling software then evaluated using structural similarity index measure (SSIM). Scans were also performed with a ferromagnetic clip near the phantom to investigate the correction of more severe artifacts. The mean magnitude isocenter shift was 0.67 mm, ranging from 0.25 to 1.04 mm across all angles. The DVF had a mean component value of 0.27 ± 0.02, 0.24 ± 0.01, and 0.19 ± 0.01 mm in the right-left (RL), anterior-posterior (AP), and superior-inferior (SI) directions. The ferromagnetic clip increased isocenter position error from 1.98 mm to 2.20 mm and increased mean DVF component values in the RL and AP directions. The resampled grid phantom had an increased SSIM for all gantry angles compared to original images, increasing from 0.26 ± 0.001 to 0.70 ± 0.004. Through this clinical assessment, we were able to correct geometric distortion and isocenter shift related to gantry position on a 0.35 T MR-Linac using the distortion phantom and software package. This provides encouragement that it could be used for quality assurance and clinically to correct systematic distortion caused by imaging at different gantry angles.

Evaluation of diffusion-weighted MRI and geometric distortion on a 0.35T MR-LINAC at multiple gantry angles.

Diffusion-weighted imaging (DWI) provides a valuable diagnostic tool for tumor evaluation. Yet, it is difficult to acquire daily MRI data sets in the traditional radiotherapy clinical setting due to patient burden and limited resources. However, integrated MRI radiotherapy treatment systems facilitate daily functional MRI acquisitions like DWI during treatment exams. Before ADC values from MR-RT systems can be used clinically their reproducibility and accuracy must be quantified. This study used a NIST traceable DWI phantom to verify ADC values acquired on a 0.35 T MR-LINAC system at multiple gantry angles. A diffusion-weighted echo planar imaging sequence was used for all image acquisitions, with b-values of 0, 500, 900, 2000 s/mm2 for the 1.5 T and 3.0 T systems and 0, 200, 500, 800 s/mm2 for the 0.35 T system. Images were acquired at multiple gantry angles on the MR-LINAC system from 0° to 330° in 30° increments to assess the impact of gantry angle on geometric distortion and ADC values. CT images, and three fiducial markers were used as ground truth for geometric distortion measurements. The distance between fiducial markers increased by as much as 7.2 mm on the MR-LINAC at gantry angle 60°. ADC values of deionized water vials from the 1.5 T and 3.0 T systems were 8.30 × 10-6  mm2 /s and -0.85 × 10-6  mm2 /s off, respectively, from the expected value of 1127 × 10-6  mm2 /s. The MR-LINAC system provided an ADC value of the pure water vials that was -116.63 × 10-6  mm2 /s off from the expected value of 1127 × 10-6  mm2 /s. The MR-LINAC also showed a variation in ADC across all gantry angles of 33.72 × 10-6  mm2 /s and 20.41 × 10-6  mm2 /s for the vials with expected values of 1127 × 10-6  mm2 /s and 248 × 10-6  mm2 /s, respectively. This study showed that variation of the ADC values and geometric information on the 0.35 T MR-LINAC system was dependent on the gantry angle at acquisition.

Selective Detection of Cu+ Ions in Live Cells via Fluorescence Lifetime Imaging Microscopy.

Copper is an essential trace element in living organisms with its levels and localisation being carefully managed by the cellular machinery. However, if misregulated, deficiency or excess of copper ions can lead to several diseases. Therefore, it is important to have reliable methods to detect, monitor and visualise this metal in cells. Herein we report a new optical probe based on BODIPY, which shows a switch-on in its fluorescence intensity upon binding to copper(I), but not in the presence of high concentration of other physiologically relevant metal ions. More interestingly, binding to copper(I) leads to significant changes in the fluorescence lifetime of the new probe, which can be used to visualize copper(I) pools in lysosomes of live cells via fluorescence lifetime imaging microscopy (FLIM).

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.

Direct tumor visual feedback during free breathing in 0.35T MRgRT.

To present a tumor motion control system during free breathing using direct tumor visual feedback to patients in 0.35 T magnetic resonance-guided radiotherapy (MRgRT). We present direct tumor visualization to patients by projecting real-time cine MR images on an MR-compatible display system inside a 0.35 T MRgRT bore. The direct tumor visualization included anatomical images with a target contour and an auto-segmented gating contour. In addition, a beam-status sign was added for patient guidance. The feasibility was investigated with a six-patient clinical evaluation of the system in terms of tumor motion range and beam-on time. Seven patients without visual guidance were used for comparison. Positions of the tumor and the auto-segmented gating contour from the cine MR images were used in probability analysis to evaluate tumor motion control. In addition, beam-on time was recorded to assess the efficacy of the visual feedback system. The direct tumor visualization system was developed and implemented in our clinic. The target contour extended 3 mm outside of the gating contour for 33.6 ± 24.9% of the time without visual guidance, and 37.2 ± 26.4% of the time with visual guidance. The average maximum motion outside of the gating contour was 14.4 ± 11.1 mm without and 13.0 ± 7.9 mm with visual guidance. Beam-on time as a percentage was 43.9 ± 15.3% without visual guidance, and 48.0 ± 21.2% with visual guidance, but was not significantly different (P = 0.34). We demonstrated the clinical feasibility and potential benefits of presenting direct tumor visual feedback to patients in MRgRT. The visual feedback allows patients to visualize and attempt to minimize tumor motion in free breathing. The proposed system and associated clinical workflow can be easily adapted for any type of MRgRT.

Drug and Chemical Glucosidation by Control Supersomes and Membranes from Spodoptera frugiperda (Sf) 9 Cells: Implications for the Apparent Glucuronidation of Xenobiotics by UDP-glucuronosyltransferase 1A5.

Accumulating evidence indicates that several human UDP-glucuronosyltransferase (UGT) enzymes catalyze both glucuronidation and glucosidation reactions. Baculovirus-infected insect cells [Trichoplusia ni and Spodoptera frugiperda (Sf9)] are used widely for the expression of recombinant human UGT enzymes. Following the observation that control Supersomes (c-SUP) express a native enzyme capable of glucosidating morphine, we characterized the glucosidation of a series of aglycones with a hydroxyl (aliphatic or phenolic), carboxylic acid, or amine functional group by c-SUP and membranes from uninfected Sf9 cells. Although both enzyme sources glucosidated the phenolic substrates investigated, albeit with differing activities, differences were observed in the selectivities of the native UDP-glucosyltransferases toward aliphatic alcohols, carboxylic acids, and amines. For example, zidovudine was solely glucosidated by c-SUP. By contrast, c-SUP lacked activity toward the amines lamotrigine and trifluoperazine and did not form the acyl glucoside of mycophenolic acid, reactions all catalyzed by uninfected Sf9 membranes. Glucosidation intrinsic clearances were high for several substrates, notably 1-hydroxypyrene (∼1400-1900 µl/min⋅mg). The results underscore the importance of including control cell membranes in the investigation of drug and chemical glucosidation by UGT enzymes expressed in T. ni (High-Five) and Sf9 cells. In a coincident study, we observed that UGT1A5 expressed in Sf9, human embryonic kidney 293T, and COS7 cells lacked glucuronidation activity toward prototypic phenolic substrates. However, Sf9 cells expressing UGT1A5 glucosidated 1-hydroxypyrene with UDP-glucuronic acid as the cofactor, presumably due to the presence of UDP-glucose as an impurity. Artifactual glucosidation may explain, at least in part, a previous report of phenolic glucuronidation by UGT1A5.