Comparison of modeling accuracy between Radixact®and CyberKnife®Synchrony®respiratory tracking system.

Synchrony Respiratory Tracking system adapted from CyberKnife has been introduced in Radixact to compensate the tumor motion caused by respiration. This study aims to compare the modeling accuracy of the Synchrony system between Radixact and CyberKnife. Two Synchrony plans based on fiducial phantoms were created for CyberKnife and Radixact, respectively. Different respiratory motion traces were used to drive a motion platform to move along the superoinferior and left-right direction. The cycle time and the amplitude of target/surrogate motion of one selected motion trace were scaled to investigate the dependence of modeling accuracy on the motion characteristic. The predicted target position, the correlation error, potential difference (Radixact only) and standard error (CyberKnife only) were extracted from raw data or log files of the two systems. The modeling accuracy was evaluated by calculating the root-mean-square (RMS) error between the predicted target positions and the input motion trace. A threshold T95 within which 95% of the potential difference or the standard error lay was defined and evaluated. Except for the motion trace with a small amplitude and a good (linear) correlation between target and surrogate motion, Radixact showed smaller RMS errors than CyberKnife. The RMS error of both systems increased with the motion amplitude and showed a decreasing trend with the increasing cycle time. No correlation was found between the RMS error and the amplitude of surrogate motion. T95 could be a good estimator of modeling accuracy for CyberKnife rather than Radixact. The correlation error defined in Radixact were largely affected by the number of fiducial markers and the setup error. In general, the modeling accuracy of the Radixact Synchrony system is better than that of the CyberKnife Synchrony system under unfavorable conditions.

Feasibility of using a single MRI acquisition for fiducial marker localization and synthetic CT generation towards MRI-only prostate radiation therapy treatment planning.

Purpose.To investigate the feasibility of using a single MRI acquisition for fiducial marker identification and synthetic CT (sCT) generation towards MRI-only treatment planning for prostate external beam radiation therapy (EBRT).Methods.Seven prostate cancer patients undergoing EBRT, each with three implanted gold fiducial markers, participated in this study. In addition to the planning CT scan, all patients were scanned on a 3 T MR scanner with a 3D double-echo gradient echo (GRE) sequence. Quantitative susceptibility mapping (QSM) was performed for marker localization. QSM-derived marker positions were compared to those from CT. The bulk density assignment technique for sCT generation was adopted. The magnitude GRE images were segmented into muscle, bone, fat, and air using a combination of unsupervised intensity-based classification of soft tissue and convolutional neural networks (CNN) for bone segmentation.Results.All implanted markers were visualized and accurately identified (average error: 0.7 ± 0.5 mm). QSM generated distinctive contrast for hemorrhage, calcifications, and gold fiducial markers. The estimated susceptibility/HU values on QSM/CT for gold and calcifications were 31.5 ± 2.9 ppm/1220 ± 100 HU and 14.6 ± 0.9 ppm/440 ± 100 HU, respectively. The intensity-based soft tissue classification resulted in an average Dice score of 0.97 ± 0.02; bone segmentation using CNN resulted in an average Dice score of 0.93 ± 0.03.Conclusion.This work indicates the feasibility of simultaneous fiducial marker identification and sCT generation using a single MRI acquisition. Future works includes evaluation of the proposed method in a large cohort of patients with optimized acquisition parameters as well as dosimetric evaluations.

Initial clinical experience of patient-specific QA of treatment delivery in online adaptive radiotherapy using a 1.5 T MR-Linac.

Purpose. This study aims to evaluate the performance of a commercial 1.5 T MR-Linac by analyzing its patient-specific quality assurance (QA) data collected during one full year of clinical operation.Methods and Materials. The patient-specific QA system consisted of offline delivery QA (DQA) and online calculation-based QA. Offline DQA was based on ArcCHECK-MR combined with an ionization chamber. Online QA was performed using RadCalc that calculated and compared the point dose calculation with the treatment planning system (TPS). A total of 24 patients with 189 treatment fractions were enrolled in this study. Gamma analysis was performed and the threshold that encompassed 95% of QA results (T95) was reported. The plan complexity metric was calculated for each plan and compared with the dose measurements to determine whether any correlation existed.Results. All point dose measurements were within 5% deviation. The mean gamma passing rates of the group data were found to be 96.8 ± 4.0% and 99.6 ± 0.7% with criteria of 2%/2mm and 3%/3mm, respectively. T95 of 87.4% and 98.2% was reported for the overall group with the two passing criteria, respectively. No statistically significant difference was found between adaptive treatments with adapt-to-position (ATP) and adapt-to-shape (ATS), whilst the category of pelvis data showed a better passing rate than other sites. Online QA gave a mean deviation of 0.2 ± 2.2%. The plan complexity metric was positively correlated with the mean dose difference whilst the complexity of the ATS cohort had larger variations than the ATP cohort.Conclusions. A patient-specific QA system based on ArcCHECK-MR, solid phantom and ionization chamber has been well established and implemented for validation of treatment delivery of a 1.5 T MR-Linac. Our QA data obtained over one year confirms that good agreement between TPS calculation and treatment delivery was achieved.

Alcohol Consumption and Depression Among University Students and Their Perception of Alcohol Use.

OBJECTIVES: To investigate the association between alcohol use and depression among university students in Hong Kong, their stress-coping methods, and their knowledge and perception of the effects of alcohol on health. METHODS: 345 full-time undergraduate students from The University of Hong Kong were invited to complete a questionnaire to assess their alcohol consumption (Alcohol Use Disorders Identification Test, CAGE questionnaire), depressive symptoms (Patient Health Questionnaire-9), and stress-coping methods (Coping Orientation to Problems Experienced Inventory), as well as knowledge and perception of alcohol consumption on health. Multiple linear regression was used to determine significant variables associated with depressive symptoms. Multinominal logistic regression was used to determine the effect of such variables on depressive symptom caseness and AUDIT drinking risk groups. RESULTS: 43.2% of respondents were moderate- to high-risk drinkers, but only 23.2% were self-reported as moderate- to high-level drinkers. 57.9% of respondents had mild to severe depressive symptoms. Probable depression was more likely to occur in female students, those with higher general stress, those who do not use social support for stress-coping, and those who smoke. High-risk drinkers were more likely to occur in older students, smokers, those with higher household income, and those with higher general stress levels. Students with higher levels of depressive symptoms and higher risk of alcohol consumption were more likely to use avoidance for stress-coping. 89.5% of students considered alcohol consumption moderately to very harmful to health, but students demonstrated only moderate knowledge levels of alcohol consumption on health. CONCLUSION: Alcohol consumption and depressive symptoms are prevalent among university students in Hong Kong. The use of avoidance for stress-coping is common in those with higher levels of depressive symptoms and higher-risk drinkers. Students tend to avoid seeking help for depressive symptoms and potentially take up drinking as a coping strategy. Context-specific approaches should be used when providing counselling services for student wellbeing in university settings. Further education of university students on knowledge and perception of alcohol consumption on health should be provided.

Parental perspectives on hand, foot, and mouth disease among children in Hong Kong: a longitudinal study.

Hand, foot, and mouth disease (HFMD), usually a self-limiting illness for young children, could cause a significant burden for parents because it can take up to 1-2 weeks for a sick child to recover. We conducted a two-wave longitudinal study over one summer peak season (May-July 2014) of HFMD to examine parents' HFMD-related risk perceptions and protective responses. In total, 618 parents with at least one child aged ⩽12 years, recruited using randomly-dialled household telephone calls completed the baseline survey interview, 452 of whom subsequently completed the follow-up survey. Around two-thirds of participants perceived the chance of their child being infected by HFMD was 'zero/very small/small' but the likelihood of being hospitalized once infected was 'somewhat likely/likely/very likely'. At follow-up, 82% reported washing child's hands frequently (Hygiene), 16% would keep their child away from school if HFMD cases were identified in school (Distancing) and 23% were 'very likely/certainly' to take the child for HFMD vaccination if available (Vaccination). Anticipated regret was consistently the strongest predictor for Hygiene (OR 3.34), and intention of Distancing (OR 2.58) and Vaccination (OR 3.16). Interventions focusing on anticipated regret may be effective to promote protective behaviour against HFMD among parents for their children.

A randomised controlled trial of oral chloral hydrate vs. intranasal dexmedetomidine before computerised tomography in children.

Chloral hydrate is commonly used to sedate children for painless procedures. Children may recover more quickly after sedation with dexmedetomidine, which has a shorter half-life. We randomly allocated 196 children to chloral hydrate syrup 50 mg.kg-1 and intranasal saline spray, or placebo syrup and intranasal dexmedetomidine spray 3 µg.kg-1 , 30 min before computerised tomography studies. More children resisted or cried after drinking chloral hydrate syrup than placebo syrup, 72 of 107 (67%) vs. 42 of 87 (48%), p = 0.009, but there was no difference after intranasal saline vs. dexmedetomidine, 49 of 107 (46%) vs. 40 of 87 (46%), p = 0.98. Sedation was satisfactory in 81 of 107 (76%) children after chloral hydrate and 64 of 87 (74%) children after dexmedetomidine, p = 0.74. Of the 173 children followed up for at least 4 h after discharge, 38 of 97 (39%) had recovered normal function after chloral hydrate and 32 of 76 (42%) after dexmedetomidine, p = 0.76. Six children vomited after chloral hydrate syrup and placebo spray vs. none after placebo syrup and dexmedetomidine spray, p = 0.03.

Underage drinking, group identity and access to alcohol: a qualitative study of Chinese youths.

Despite substantial research into underage youth's source of alcohol, few studies have examined how they go about obtaining alcohol through various means. This study explored the nature of alcohol access by Chinese adolescents and how their own perceptions around alcohol availability influence them to source alcohol in particular ways. This research involved focus groups with 111 young people aged 14-17 in Hong Kong, China. A grounded theory analysis was conducted using NVivo 10. While participants perceived ease of obtaining alcohol from retail outlets, proxy purchasing through friendship group members was reported as routine experience primarily to avoid potential embarrassment of being turned away. Convincing vendors that they were of legal drinking age was the convention used most commonly by Chinese teen drinkers. Participants expressed resentment toward adults who were willing to supply minors with alcohol. Nevertheless, this feeling of disappointment did not alter the ways they sourced alcohol. Access activities embodied a symbol of group identity in the collectivist Chinese culture. Results suggest that greater consideration should be given to understanding the complex interplay between alcohol access and community experience within peers. The perceived importance of face saving in Chinese culture may provide avenues for preventing youth access to alcohol.

Filmless methods for quality assurance of Tomotherapy using ArcCHECK.

PURPOSE: Tomotherapy delivers an intensity-modulated radiation therapy (IMRT) treatment by the synchronization of gantry rotation, multileaf collimator (MLC), and couch movement. This dynamic nature makes the quality assurance (QA) important and challenging. The purpose of this study is to develop some methodologies using an ArcCHECK for accurate QA measurements of the gantry angle and speed, MLC synchronization and leaf open time, couch translation per gantry rotation, couch speed and uniformity, and constancy of longitudinal beam profile for a Tomotherapy unit. METHODS: Four test plans recommended by AAPM Task Group 148 (TG148) and the manufacturer were chosen for this study. Helical and static star shot tests are used for checking the leaves opened at the expected gantry angles. Another helical test is to verify the couch traveled the expected distance per gantry rotation. The final test is for checking the couch speed constancy with a static gantry. ArcCHECK can record the detector signal every 50 ms as a movie file, and has a virtual inclinometer for gantry angle measurement. These features made the measurement of gantry angle and speed, MLC synchronization and leaf open time, and longitudinal beam profile possible. A shaping parameter was defined for facilitating the location of the beam center during the plan delivery, which was thereafter used to calculate the couch translation per gantry rotation and couch speed. The full width at half maximum (FWHM) was calculated for each measured longitudinal beam profile and then used to evaluate the couch speed uniformity. Furthermore, a mean longitudinal profile was obtained for constancy check of field width. The machine trajectory log data were also collected for comparison. Inhouse programs were developed in MATLAB to process both the ArcCHECK and machine log data. RESULTS: The deviation of our measurement results from the log data for gantry angle was calculated to be less than 0.4°. The percentage differences between measured and planned leaf open time were found to be within 0.5% in all the tests. Our results showed mean values of MLC synchronization of 0.982, 0.983, and 0.995 at static gantry angle 0°, 45°, and 135°, respectively. The mean value of measured couch translation and couch speed by ArcCHECK had less than 0.1% deviation from the planned values. The variation in the value of FWHM suggested the couch speed uniformity was better than 1%. The mean of measured longitudinal profiles was suitable for constancy check of field width. CONCLUSION: Precise and efficient methods for measuring the gantry angle and speed, leaf open time, couch translation per gantry rotation, couch speed and uniformity, and constancy of longitudinal beam profile of Tomotherapy using ArcCHECK have been developed and proven to be accurate compared with machine log data. Estimation of the Tomotherapy binary MLC leaf open time is proven to be precise enough to verify the leaf open time as small as 277.8 ms. Our method also makes the observation and quantification of the synchronization of leaves possible.

Comparing the meanings of living with advanced breast cancer between women resilient to distress and women with persistent distress: a qualitative study.

BACKGROUND: Most women with advanced breast cancer (ABC) show little distress, but about one in ten show persistent distress over time. It remains unclear if meanings ascribed by patients to ABC differentiate these distress trajectories. STUDY AIMS: This qualitative study (a) compared illness meanings of ABC between women with persistent psychological distress and those with low/transient distress, and (b) examined how illness meanings might influence coping strategies. METHODS: The sample was drawn from a prior quantitative study exploring psychological distress trajectories following ABC diagnosis. Overall, 42 Cantonese- or Mandarin-speaking Chinese women diagnosed with locally advanced or metastatic ABC were recruited based on their distress trajectory status (low-stable, transient, or persistent distress). Interviews were recorded, transcribed, and analyzed following grounded theory approach using simultaneous analysis. RESULTS: Women with persistent distress viewed their diagnosis as another blow in life, the illness was global, permeating every aspect of their life. Maladaptive rumination and thought suppression were common responses to illness demands. These women had poor social support. A sense of demoralization stood out in their narratives. In contrast, women with transient/low-stable distress encapsulated the illness, with minimum impacts of their life. They did not evidence dysfunctional repetitive thoughts. Living in a supportive environment, they were able to accept and/or live in the present-moment. CONCLUSIONS: Rumination, thought suppression, social constraints, and pre-existing exposure to life stress may be potential risks for chronic distress in response to advanced breast cancer. Persistent and transient distress responses to cancer may have different underpinnings. Copyright © 2016 John Wiley & Sons, Ltd.

Individual Differences in the Alignment of Structural and Functional Markers of the V5/MT Complex in Primates.

Extrastriate visual area V5/MT in primates is defined both structurally by myeloarchitecture and functionally by distinct responses to visual motion. Myelination is directly identifiable from postmortem histology but also indirectly by image contrast with structural magnetic resonance imaging (sMRI). First, we compared the identification of V5/MT using both sMRI and histology in Rhesus macaques. A section-by-section comparison of histological slices with in vivo and postmortem sMRI for the same block of cortical tissue showed precise correspondence in localizing heavy myelination for V5/MT and neighboring MST. Thus, sMRI in macaques accurately locates histologically defined myelin within areas known to be motion selective. Second, we investigated the functionally homologous human motion complex (hMT+) using high-resolution in vivo imaging. Humans showed considerable intersubject variability in hMT+ location, when defined with myelin-weighted sMRI signals to reveal structure. When comparing sMRI markers to functional MRI in response to moving stimuli, a region of high myelin signal was generally located within the hMT+ complex. However, there were considerable differences in the alignment of structural and functional markers between individuals. Our results suggest that variation in area identification for hMT+ based on structural and functional markers reflects individual differences in human regional brain architecture.

Unusual mediastinal lymph node uptake and peritoneopleural fistula demonstrated on Technetium-99m macro-aggregated human serum albumin (Tc-99m MAA) peritoneal scintigraphy in a patient with portal hypertension.

Peritoneal radionuclide scan is an established imaging modality for evaluating peritoneopleural communications. In this case report, unusual mediastinal lymph node radiotracer uptake is seen in a patient with portal hypertension on peritoneal scintigraphy. This was suspected to be due to marked lymphatic enlargement from longstanding portal hypertension since childhood, permitting passage of the large Tc-99m MAA particle. The nodes were morphologically benign on CT. Mediastinal lymph node uptake on peritoneal scintigraphy is rare but should not raise undue clinical concern, particularly in a patient with chronic portal hypertension. Anatomic correlation with SPECT-CT can provide reassurance.

Middle East respiratory syndrome in South Korea during 2015: Risk-related perceptions and quarantine attitudes.

A telephone survey involving 200 household members in and around Seoul, South Korea, was completed during the maturity stage of the outbreak of Middle East respiratory syndrome (MERS) in Korea during June 2015. The study found that respondents perceived low risk from contracting MERS, had low trust in government in controlling MERS, and generally held unfavorable attitudes toward quarantine.

Uptake of breast screening and associated factors among Hong Kong women aged ≥50 years: a population-based survey.

OBJECTIVE: To examine the uptake of breast screening and its associated factors among Hong Kong Chinese women aged ≥50 years. STUDY DESIGN: Cross-sectional population-based survey. METHODS: A sample of Hong Kong Chinese women was recruited through telephone random-digit dialling. The survey consisted of six sections: perceived health status, use of complementary medicine, uptake of breast screening, perceived susceptibility to cancer, family history of cancer and demographic data. The factors associated with uptake of breast screening were analysed using logistic regression analysis. RESULTS: In total, 1002 women completed the (anonymous) telephone survey. The mean age was 63.5 (standard deviation 10.6) years. The uptake rate of breast screening among Hong Kong Chinese women aged ≥50 years was 34%. The primary reasons for undertaking breast screening were as part of a regular medical check-up (74%), prompted by local signs and symptoms (11%) and a physician's recommendation (7%). Higher educational level, married or cohabiting, family history of cancer, frequent use of complementary therapies, regular visits to a doctor or Chinese herbalist, and the recommendation of a health professional were all independently and significantly associated with increased odds of having had a mammogram. CONCLUSIONS: This study provides community-based evidence of the need for public health policy to promote broader use of mammography services among this target population, with emphasis on the active involvement of health care professionals, through the development and implementation of appropriate evidence-based and resource-sensitive strategies.