Automatic segmentation of tumour and organs at risk in 3D MRI for cervical cancer radiation therapy with anatomical variations.

Cervical cancer is a common cancer in women globally, with treatment usually involving radiation therapy (RT). Accurate segmentation for the tumour site and organ-at-risks (OARs) could assist in the reduction of treatment side effects and improve treatment planning efficiency. Cervical cancer Magnetic Resonance Imaging (MRI) segmentation is challenging due to a limited amount of training data available and large inter- and intra- patient shape variation for OARs. The proposed Masked-Net consists of a masked encoder within the 3D U-Net to account for the large shape variation within the dataset, with additional dilated layers added to improve segmentation performance. A new loss function was introduced to consider the bounding box loss during training with the proposed Masked-Net. Transfer learning from a male pelvis MRI data with a similar field of view was included. The approaches were compared to the 3D U-Net which was widely used in MRI image segmentation. The data used consisted of 52 volumes obtained from 23 patients with stage IB to IVB cervical cancer across a maximum of 7 weeks of RT with manually contoured labels including the bladder, cervix, gross tumour volume, uterus and rectum. The model was trained and tested with a 5-fold cross validation. Outcomes were evaluated based on the Dice Similarity Coefficients (DSC), the Hausdorff Distance (HD) and the Mean Surface Distance (MSD). The proposed method accounted for the small dataset, large variations in OAR shape and tumour sizes with an average DSC, HD and MSD for all anatomical structures of 0.790, 30.19mm and 3.15mm respectively.

Assessment of interfraction dose variation in pancreas SBRT using daily simulation MR images.

Pancreatic Cancer is associated with poor treatment outcomes compared to other cancers. High local control rates have been achieved by using hypofractionated stereotactic body radiotherapy (SBRT) to treat pancreatic cancer. Challenges in delivering SBRT include close proximity of several organs at risk (OARs) and target volume inter and intra fraction positional variations. Magnetic resonance image (MRI) guided radiotherapy has shown potential for online adaptive radiotherapy for pancreatic cancer, with superior soft tissue contrast compared to CT. The aim of this study was to investigate the variability of target and OAR volumes for different treatment approaches for pancreatic cancer, and to assess the suitability of utilizing a treatment-day MRI for treatment planning purposes. Ten healthy volunteers were scanned on a Siemens Skyra 3 T MRI scanner over two sessions (approximately 3 h apart), per day over 5 days to simulate an SBRT daily simulation scan for treatment planning. A pretreatment scan was also done to simulate patient setup and treatment. A 4D MRI scan was taken at each session for internal target volume (ITV) generation and assessment. For each volunteer a treatment plan was generated in the Raystation treatment planning system (TPS) following departmental protocols on the day one, first session dataset (D1S1), with bulk density overrides applied to enable dose calculation. This treatment plan was propagated through other imaging sessions, and the dose calculated. An additional treatment plan was generated on each first session of each day (S1) to simulate a daily replan process, with this plan propagated to the second session of the day. These accumulated mock treatment doses were assessed against the original treatment plan through DVH comparison of the PTV and OAR volumes. The generated ITV showed large variations when compared to both the first session ITV and daily ITV, with an average magnitude of 22.44% ± 13.28% and 25.83% ± 37.48% respectively. The PTV D95 was reduced by approximately 23.3% for both plan comparisons considered. Surrounding OARs had large variations in dose, with the small bowel V30 increasing by 128.87% when compared to the D1S1 plan, and 43.11% when compared to each daily S1 plan. Daily online adaptive radiotherapy is required for accurate dose delivery for pancreas cancer in the absence of additional motion management and tumour tracking techniques.

Assessment of intrafraction motion and its dosimetric impact on prostate radiotherapy using an in-house developed position monitoring system.

Purpose: To implement an in-house developed position monitoring software, SeedTracker, for conventional fractionation prostate radiotherapy, and study the effect on dosimetric impact and intrafraction motion. Methods: Thirty definitive prostate radiotherapy patients with implanted fiducial markers were included in the study. All patients were treated with VMAT technique and plans were generated using the Pinnacle planning system using the 6MV beam model for Elekta linear accelerator. The target dose of 60 Gy in 20 fractions was prescribed for 29 of 30 patients, and one patient was treated with the target dose of 78 Gy in 39 fractions. The SeedTracker position monitoring system, which uses the x-ray images acquired during treatment delivery in the Elekta linear accelerator and associated XVI system, was used for online prostate position monitoring. The position tolerance for online verification was progressively reduced from 5 mm, 4 mm, and to 3 mm in 10 patient cohorts to effectively manage the treatment interruptions resulting from intrafraction motion in routine clinical practice. The delivered dose to target volumes and organs at risk in each of the treatment fractions was assessed by incorporating the observed target positions into the original treatment plan. Results: In 27 of 30 patients, at least one gating event was observed, with a total of 177 occurrences of position deviation detected in 146 of 619 treatment fractions. In 5 mm, 4 mm, and 3 mm position tolerance cohorts, the position deviations were observed in 13%, 24%, and 33% of treatment fractions, respectively. Overall, the mean (range) deviation of -0.4 (-7.2 to 5.3) mm, -0.9 (-6.1 to 15.6) mm, and -1.7 (-7.0 to 6.1) mm was observed in Left-Right, Anterior-Posterior, and Superior-Inferior directions, respectively. The prostate CTV D99 would have been reduced by a maximum value of 1.3 Gy compared to the planned dose if position deviations were uncorrected, but with corrections, it was 0.3 Gy. Similarly, PTV D98 would have been reduced by a maximum value of 7.6 Gy uncorrected, with this difference reduced to 2.2 Gy with correction. The V60 to the rectum increased by a maximum of 1.0% uncorrected, which was reduced to 0.5%. Conclusion: Online target position monitoring for conventional fractionation prostate radiotherapy was successfully implemented on a standard Linear accelerator using an in-house developed position monitoring software, with an improvement in resultant dose to prostate target volume.

Clinical validation of MR imaging time reduction for substitute/synthetic CT generation for prostate MRI-only treatment planning.

Radiotherapy treatment planning based only on magnetic resonance imaging (MRI) has become clinically achievable. Though computed tomography (CT) is the gold standard for radiotherapy imaging, directly providing the electron density values needed for planning calculations, MRI has superior soft tissue visualisation to guide treatment planning decisions and optimisation. MRI-only planning removes the need for the CT scan, but requires generation of a substitute/synthetic/pseudo CT (sCT) for electron density information. Shortening the MRI imaging time would improve patient comfort and reduce the likelihood of motion artefacts. A volunteer study was previously carried out to investigate and optimise faster MRI sequences for a hybrid atlas-voxel conversion to sCT for prostate treatment planning. The aim of this follow-on study was to clinically validate the performance of the new optimised sequence for sCT generation in a treated MRI-only prostate patient cohort. 10 patients undergoing MRI-only treatment were scanned on a Siemens Skyra 3T MRI as part of the MRI-only sub-study of the NINJA clinical trial (ACTRN12618001806257). Two sequences were used, the standard 3D T2-weighted SPACE sequence used for sCT conversion which has been previously validated against CT, and a modified fast SPACE sequence, selected based on the volunteer study. Both were used to generate sCT scans. These were then compared to evaluate the fast sequence conversion for anatomical and dosimetric accuracy against the clinically approved treatment plans. The average Mean Absolute Error (MAE) for the body was 14.98 ± 2.35 HU, and for bone was 40.77 ± 5.51 HU. The external volume contour comparison produced a Dice Similarity Coefficient (DSC) of at least 0.976, and an average of 0.985 ± 0.004, and the bony anatomy contour comparison a DSC of at least 0.907, and an average of 0.950 ± 0.018. The fast SPACE sCT agreed with the gold standard sCT within an isocentre dose of -0.28% ± 0.16% and an average gamma pass rate of 99.66% ± 0.41% for a 1%/1 mm gamma tolerance. In this clinical validation study, the fast sequence, which reduced the required imaging time by approximately a factor of 4, produced an sCT with similar clinical dosimetric results compared to the standard sCT, demonstrating its potential for clinical use for treatment planning.

Implementing online position monitoring for prostate radiotherapy using an in-house position monitoring system: User experience and impact on workforce.

INTRODUCTION: To evaluate the feasibility of prostate intrafraction motion monitoring using the SeedTracker real-time image guidance system in order to improve targeting accuracy in prostate radiotherapy. METHODS: SeedTracker was used to monitor prostate gold fiducial seeds with kV x-ray imaging during radiotherapy in 30 patients. Feedback from radiation therapists was collected via the use of a user evaluation form. The impact on treatment time was established by using a record and verify system. The effective dose and a risk of exposure-induced cancer death (REID) were estimated for a 60-year-old patient when using the SeedTracker system. RESULTS: A total of 22 radiation therapists completed user evaluation forms. The time taken to prepare a reference data set for one patient varied with three (13.6%) radiation therapists taking less than 2 min, 10 (45.5%) between 2 and 4 min, eight (36.4%) between 4 and 6 min and one (4.5%) between 6 and 8 min. The useability of the SeedTracker system was reported as 'easy' by 21 (95.5%) radiation therapists and 'hard' by 1 (4.5%) radiation therapist. Mean treatment time changed from 6 to 7 min with prostate-only radiotherapy treatment and from 6.9 to 10.2 min with prostate and whole pelvis radiotherapy treatments. The maximum effective dose with the SeedTracker was 1.6276 mSv, and increase in REID was 0.007%. CONCLUSION: The SeedTracker real-time image guidance system is a feasible tool to use in radiotherapy departments to monitor and correct for prostate intrafraction motion.

Intercultural adjustment of internationally mobile academics working in Thailand.

Non-nationals constitute up to a quarter of the academic staff workforce of Higher Education Institutions (HEIs) worldwide. Their motivations to 'work abroad', and their experiences of doing so, are, however, under-researched, especially where migration is to or within the global South. We report a study conducted among internationally mobile academics from a variety of countries working in Thailand. At policy level, Thailand aspires to increase the numbers of international staff and students in its HEIs, but with mixed success in terms of recruitment levels and the reported quality of the experience among these migrants. Conceptually, our study drew on a framework of intercultural adjustment defined as a multidimensional construct comprising psychological, sociocultural and professional/work aspects of the experience. Semi-structured focus groups were conducted to explore experiences of working in Thailand. Thematic analysis of findings showed that reported experiences mainly fell under the category of professional/work aspects of intercultural adjustment, although sociocultural issues were also important. The reported quality of experiences was mixed and generally more negative than positive in the key areas of professional and work adjustment. Specific challenges highlighted by participants related to issues with the work environment, most especially lingual-cultural problems and, crucially, a lack of secure status. We detail and discuss these findings and present recommendations for policy makers and HEIs, aspirant academic migrants, and for future research into global academic migration, particular as it relates to Thailand and other destinations for academic migration.

The delivered dose assessment in pancreas SBRT with the target position determined using an in-house position monitoring system.

Purpose: This study assessed the delivered dose accuracy in pancreas SBRT by incorporating the real-time target position determined using an in-house position monitoring system. Methods and materials: An online image-based position monitoring system, SeedTracker, was developed to monitor radiopaque marker positions using monoscopic x-ray images, available from the Elekta XVI imaging system. This system was applied to patients receiving SBRT for pancreatic cancer on the MASTERPLAN Pilot trial (ACTRN 12617001642370). All patients were implanted pre-treatment with at least three peri-tumoral radiopaque markers for target localisation. During treatment delivery, marker positions were compared to expected positions delineated from the planning CT. The position tolerance of ±3mm from the expected position of the markers was set to trigger a gating event (GE) during treatment. The dosimetric impact of position deviations and actual dose delivered with position corrections was assessed by convolving the plan control point dose matrices with temporal target positions determined during treatment. Results: Eight patients were treated within this study. At least one GE was observed in 38% of the treatment fractions and more than one GE was observed in 10% of the fractions. The position deviations resulted in the mean(range) difference of -0.1(-1.1 - 0.4)Gy in minimum dose to tumour and 1.9(-0.1- 4.6)Gy increase to Dmax to duodenum compared to planned dose. In actual treatment delivery with the patient realignment, the mean difference of tumour min dose and duodenal Dmax was reduced to 0.1(-1.0 - 1.1)Gy and 1.1 (-0.7 - 3.3)Gy respectively compared to the planned dose. Conclusions: The in-house real-time position monitoring system improved the treatment accuracy of pancreatic SBRT in a general-purpose linac and enabled assessment of delivered dose by incorporating the temporal target position during delivery. The intrafraction motion impacts the dose to tumour even if target position is maintained within a 3mm position tolerance.

Effects of MR imaging time reduction on substitute CT generation for prostate MRI-only treatment planning.

The introduction of MRI linear accelerators (MR-linacs) and the increased use of MR imaging in radiotherapy, requires improved approaches to MRI-only radiotherapy. MRI provides excellent soft tissue visualisation but does not provide any electron density information required for radiotherapy dose calculation, instead MRI is registered to CT images to enable dose calculations. MRI-only radiotherapy eliminates registration errors and reduces patient discomfort, workload and cost. Electron density requirements may be addressed in different ways, from manually applying bulk density corrections, to more computationally intensive methods to produce substitute CT datasets (sCT), requiring additional sequences, increasing overall imaging time. Reducing MR imaging time would reduce potential artefacts from intrafraction motion and patient discomfort. The aim of this study was to assess the impact of reducing MR imaging time on a hybrid atlas-voxel sCT conversion for prostate MRI-only treatment planning, considering both anatomical and dosimetric parameters. 10 volunteers were scanned on a Siemens Skyra 3T MRI. Sequences included the 3D T2-weighted (T2-w) SPACE sequence used for sCT conversion as previously validated against CT, along with variations to this sequence in repetition time (TR), turbo factor, and combinations of these to reduce the imaging time. All scans were converted to sCT and were compared to the sCT from the original SPACE sequence, evaluating for anatomical changes and dosimetric differences for a standard prostate VMAT plan. Compared to the previously validated T2-w SPACE sequence, scan times were reduced by up to 80%. The external volume and bony anatomy were compared, with all but one sequence meeting a DICE coefficient of 0.9 or better, with the largest variations occurring at the edges of the external body volume. The generated sCT agreed with the gold standard sCT within an isocentre dose of 1% and a gamma pass rate of 99% for a 1%/1 mm gamma tolerance for all but one sequence. This study demonstrates that the MR imaging sequence time was able to be reduced by approximately 80% with similar dosimetric results.

Comparison of posterior-stabilized, cruciate-retaining, and medial-stabilized knee implant motion during gait.

Accurate knowledge of knee joint motion is needed to evaluate the effects of implant design on functional performance and component wear. We conducted a randomized controlled trial to measure and compare 6-degree-of-freedom (6-DOF) kinematics and femoral condylar motion of posterior-stabilized (PS), cruciate-retaining (CR), and medial-stabilized (MS) knee implant designs for one cycle of walking. A mobile biplane X-ray imaging system was used to accurately measure 6-DOF tibiofemoral motion as patients implanted with PS (n = 23), CR (n = 25), or MS (n = 26) knees walked over ground at their self-selected speeds. Knee flexion angle did not differ significantly between the three designs. Relative movements of the femoral and tibial components were generally similar for PS and CR with significant differences observed only for anterior tibial drawer. Knee kinematic profiles measured for MS were appreciably different: external rotation and abduction of the tibia were increased while peak-to-peak anterior drawer was significantly reduced for MS compared with PS and CR. Anterior-posterior drawer and medial-lateral shift of the tibia were strongly coupled to internal-external rotation for MS, as was anterior-posterior translation of the contact center in the lateral compartment. MS exhibited the least amount of paradoxical anterior translation of the femur relative to the tibia during knee flexion. The joint center of rotation in the transverse plane was located in the lateral compartment for PS and CR and in the medial compartment for MS. Substantial differences were evident in 6-DOF knee kinematics between the healthy knee and all three prosthetic designs. Overall, knee kinematic profiles observed for MS resemble those of the healthy joint more closely than PS and CR.

A Multi-center Prospective Study for Implementation of an MRI-Only Prostate Treatment Planning Workflow.

Purpose: This project investigates the feasibility of implementation of MRI-only prostate planning in a prospective multi-center study. Method and Materials: A two-phase implementation model was utilized where centers performed retrospective analysis of MRI-only plans for five patients followed by prospective MRI-only planning for subsequent patients. Feasibility was assessed if at least 23/25 patients recruited to phase 2 received MRI-only treatment workflow. Whole-pelvic MRI scans (T2 weighted, isotropic 1.6 mm voxel 3D sequence) were converted to pseudo-CT using an established atlas-based method. Dose plans were generated using MRI contoured anatomy with pseudo-CT for dose calculation. A conventional CT scan was acquired subsequent to MRI-only plan approval for quality assurance purposes (QA-CT). 3D Gamma evaluation was performed between pseudo-CT calculated plan dose and recalculation on QA-CT. Criteria was 2%, 2 mm criteria with 20% low dose threshold. Gold fiducial marker positions for image guidance were compared between pseudo-CT and QA-CT scan prior to treatment. Results: All 25 patients recruited to phase 2 were treated using the MRI-only workflow. Isocenter dose differences between pseudo-CT and QA-CT were -0.04 ± 0.93% (mean ± SD). 3D Gamma dose comparison pass-rates were 99.7% ± 0.5% with mean gamma 0.22 ± 0.07. Results were similar for the two centers using two different scanners. All gamma comparisons exceeded the 90% pass-rate tolerance with a minimum gamma pass-rate of 98.0%. In all cases the gold fiducial markers were correctly identified on MRI and the distances of all seeds to centroid were within the tolerance of 1.0 mm of the distances on QA-CT (0.07 ± 0.41 mm), with a root-mean-square difference of 0.42 mm. Conclusion: The results support the hypothesis that an MRI-only prostate workflow can be implemented safely and accurately with appropriate quality assurance methods.

Assessment of electron density effects on dose calculation and optimisation accuracy for nasopharynx, for MRI only treatment planning.

Computed tomography (CT) is the gold standard for radiotherapy simulation and treatment planning, providing spatial accuracy, bony anatomy definition and electron density information for dose calculations. Magnetic resonance imaging (MRI) has been introduced in radiotherapy to improve visualisation of anatomy for accurate target definition and contouring, however lacks electron density information required for dose calculations, with various methods used to overcome this. The aim of this work is to assess the impact on dose calculation accuracy and optimisation results of different approaches to determine electron density, as could be used in MRI only treatment planning for nasopharyngeal datasets with VMAT treatment plans. Volumetric modulated arc therapy (VMAT) plans were created for 10 retrospective head and neck (H&N) nasopharyngeal patients. The VMAT plans were generated on the gold standard dataset, the original CT scan. Data sets with no density correction (water equivalent) and two different sets of bulk density correction for bone/air/tissue applied separately were generated for these patients and the VMAT plans were recalculated for each case. Plans were also reoptimised on these data sets, and recalculated. Optimisation error was assessed through equivalent uniform dose (EUD) differences. Additionally, point dose comparison, dose volume histogram (DVH) analysis and gamma analysis of dose were used to assess dose calculation error. The dose calculation error on average was an increase in EUD whereas the optimisation error on average was a reduction in EUD compared to the original plan for all datasets aside from the bone only override dataset where bone was set to 1.61 g/cm3. For the optimisation error, the largest mean absolute error (MAE) was 1.88 Gy EUD for the PTV, and 2.21 Gy EUD for the brainstem, for the reoptimisation completed on the air only overridden dataset, and recalculated on the original. Bulk density corrections for bone and air provide dose calculations within 3% of the original treatment plans. Optimisation errors have the potential to be greater than dose calculation errors if incorrect density corrections are utilized. Electron density correction using a bulk density approach achieves dose calculation uncertainties within 3%, however more advanced approaches, such as a voxel based approach, may improve accuracy and should be considered.

A Systematic Review of Clinical Functional Outcomes After Medial Stabilized Versus Non-Medial Stabilized Total Knee Joint Replacement.

BACKGROUND: Medial stabilized total knee joint replacement (TKJR) construct is designed to closely replicate the kinematics of the knee. Little is known regarding comparison of clinical functional outcomes of patients utilising validated patient reported outcome measures (PROM) after medial stabilized TKJR and other construct designs. PURPOSE: To perform a systematic review of the available literature related to the assessment of clinical functional outcomes following a TKJR employing a medial stabilized construct design. METHODS: The review was performed with a Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) algorithm. The literature search was performed using variouscombinations of keywords. The statistical analysis was completed using Review Manager (RevMan), Version 5.3. RESULTS: In the nineteen unique studies identified, there were 2,448 medial stabilized TKJRs implanted in 2,195 participants, there were 1,777 TKJRs with non-medial stabilized design constructs implanted in 1,734 subjects. The final mean Knee Society Score (KSS) value in the medial stabilized group was 89.92 compared to 90.76 in the non-medial stabilized group, with the final KSS mean value difference between the two groups was statistically significant and favored the non-medial stabilized group (SMD 0.21; 95% CI: 0.01 to 0.41; p = 004). The mean difference in the final WOMAC values between the two groups was also statistically significant and favored the medial stabilized group (SMD: -0.27; 95% CI: -0.47 to -0.07; p = 0.009). Moderate to high values (I2 ) of heterogeneity were observed during the statistical comparison of these functional outcomes. CONCLUSION: Based on the small number of studies with appropriate statistical analysis, we are unable to reach a clear conclusion in the clinical performance of medial stabilized knee replacement construct. LEVEL OF EVIDENCE: Level II.

Medical students' views about person-centred communication in dementia care.

Adopting principles of person-centred communication has been highlighted as one strategy to improve care of people living with dementia (PLWD) in health and social care settings. However, person-centred communication is interpreted and applied variably in different settings, and healthcare professionals' views about communicating with PLWD are under-explored. This study aimed to investigate medical students' views about the principles and applicability of a model of person centred communication - the Dementia Model of Effective Communication (DeMEC) - to clinical practice. Quantitative and qualitative data was collected using questionnaires ( n = 531), focus groups ( n = 21) and interviews ( n = 10). Students generally endorsed the person-centred approach to communication, but two aspects were highlighted as complex and divisive - the acceptability or otherwise of lying, and of communicating with family in advance of the PLWD. We discuss the nature of these communicative dilemmas, implications for the education and training of medical students, and future directions for research.

Comparison of three commercial dosimetric systems in detecting clinically significant VMAT delivery errors.

AIM: To study the sensitivity of three commercial dosimetric systems, Delta4, Multicube and Octavius4D, in detecting Volumetric Modulated Arc Therapy (VMAT) delivery errors. METHODS: Fourteen prostate and head and neck (H&N) VMAT plans were considered for this study. Three types of errors were introduced into the original plans: gantry angle independent and dependent MLC errors, and gantry angle dependent dose errors. The dose matrix measured by each detector system for the no-error and error introduced delivery were compared with the reference Treatment Planning System (TPS) calculated dose matrix for no-error plans using gamma (γ) analysis with 2%/2mm tolerance criteria. The ability of the detector system in identifying the minimum error in each scenario was assessed by analysing the gamma pass rates of no error delivery and error delivery using a Wilcoxon signed-rank test. The relative sensitivity of the system was assessed by determining the slope of the gamma pass line for studied error magnitude in each error scenario. RESULTS: In the gantry angle independent and dependent MLC error scenario the Delta4, Multicube and Octavius4D systems detected a minimum 2mm error. In the gantry angle dependent dose error scenario all studied systems detected a minimum 3% and 2% error in prostate and H&N plans respectively. In the studied detector systems Multicube showed relatively less sensitivity to the errors in the majority of error scenarios. CONCLUSION: The studied systems identified the same magnitude of minimum errors in all considered error scenarios.

Sensitivity of a helical diode array dosimeter to Volumetric Modulated Arc Therapy delivery errors.

PURPOSE: To study the sensitivity of an ArcCHECK dosimeter in detecting delivery errors during the delivery of Volumetric Modulated Arc Therapy (VMAT). METHODS: Three types of errors in Multi Leaf Collimator (MLC) position and dose delivery were simulated separately in the delivery of five prostate and five head and neck (H&N) VMAT plans: (i) Gantry independent: a systematic shift in MLC position and variation in output to the whole arc; (ii) Gantry dependent: sag in MLC position and output variation as a function of gantry angle; (iii) Control point specific MLC and output errors introduced to only a specific number of Control Points (CP). The difference in local and global gamma (γ) pass rate between the no-error and error-simulated measurements with 2%/2 mm and 3%/3 mm tolerances was calculated to assess the sensitivity of ArcCHECK. The clinical impact of these errors was also calculated. RESULTS: ArcCHECK was able to detect a minimum 3 mm MLC error and 3% output error for Gantry independent errors using either local or global gamma with 2%/2 mm tolerance. For the Gantry dependent error scenario a minimum 3 mm MLC error and 3% dose error was identifiable by ArcCHECK using either global or local gamma with 2%/2 mm tolerance. In errors introduced to specific CPs a MLC error of 10 mm and dose error of 100% introduced to 4CPs were detected by ArcCHECK. CONCLUSION: ArcCHECK used with either local or global gamma analysis and 2%/2 mm criteria can be confidently used in the clinic to detect errors above the stated error values.

Novel probiotics and prebiotics: road to the market.

Novel probiotics and prebiotics designed to manipulate the gut microbiota for improving health outcomes are in demand as the importance of the gut microbiota in human health is revealed. The regulations governing introduction of novel probiotics and prebiotics vary by geographical region. Novel foods and foods with health claims fall under specific regulations in several countries. The paper reviews the main requirements of the regulations in the EU, USA, Canada and Japan. We propose a number of areas that need to be addressed in any safety assessment of novel probiotics and prebiotics. These include publication of the genomic sequence, antibiotic resistance profiling, selection of appropriate in vivo model, toxicological studies (including toxin production) and definition of target population.

Medical students' attitudes toward people with dementia: an international investigation.

BACKGROUND: The changing demographics of societies mean that medical students worldwide must be sufficiently prepared to care competently for patients with dementia through development of appropriate knowledge, skills, and attitudes. No previous research had explored undergraduate medical students' attitudes toward people with dementia. METHODS: An adapted version of the Approaches to Dementia Questionnaire (ADQ) was completed by 501 medical undergraduates in years 1, 3, and 5 of their degree programs in the UK and Malaysia. Non-parametric statistical analysis focused on any differences between year groups and geographical locations. RESULTS: The mean ADQ response indicated a generally positive attitude across the sample, comparable with other healthcare professionals previously surveyed. Year 3 and year 5 students expressed significantly more positive attitudes than year 1 students. Year 1 students based in the UK expressed significantly more positive attitudes than year 1 student based in Malaysia, but there were no significant differences between year 3 students based in different locations. CONCLUSION: The more positive attitudes found amongst year 3 and year 5 students compared to year 1 may be a result of teaching emphasizing a person-centered approach. The differences between entry-level students from Malaysia and the UK may reflect variance in cultural norms and expectations, or the ADQ's "Western" origin. Medical schools aiming to equip students with dementia-specific skills and knowledge can draw on the generally positive attitudes found in this study.

An investigation into positron emission tomography contouring methods across two treatment planning systems.

Positron emission tomography (PET) imaging has been used to provide additional information regarding patient tumor location, size, and staging for radiotherapy treatment planning purposes. This additional information reduces interobserver variability and produces more consistent contouring. It is well recognized that different contouring methodology for PET data results in different contoured volumes. The goal of this study was to compare the difference in PET contouring methods for 2 different treatment planning systems using a phantom dataset and a series of patient datasets. Contouring methodology was compared on the ADAC Pinnacle Treatment Planning System and the CMS XiO Treatment Planning System. Contours were completed on the phantom and patient datasets using a number of PET contouring methods-the standardized uptake value 2.5 method, 30%, 40%, and 50% of the maximum uptake method and the signal to background ratio method. Differences of >15% were observed for PET-contoured volumes between the different treatment planning systems for the same data and the same PET contouring methodology. Contoured volume differences between treatment planning systems were caused by differences in data formatting and display and the different contouring tools available. Differences in treatment planning system as well as contouring methodology should be considered carefully in dose-volume contouring and reporting, especially between centers that may use different treatment planning systems or those that have several different treatment planning systems.