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Background: In Vietnam and other global settings, men who have sex with men (MSM) have become the population at greatest risk of HIV infection. Although HIV pre-exposure prophylaxis (PrEP) has been implemented as a prevention strategy, PrEP outcomes may be affected by low persistence and adherence among MSM with unhealthy alcohol use. MSM have a high prevalence of unhealthy alcohol use in Vietnam, which may affect PrEP outcomes. Methods: Design: We will conduct a two-arm hybrid type 1 effectiveness-implementation randomized controlled trial of a brief alcohol intervention (BAI) compared to the standard of care (SOC) at the Sexual Health Promotion (SHP) clinic Hanoi, Vietnam. Participants: Sexually active MSM (n=564) who are newly initiating PrEP or re-initiating PrEP and have unhealthy alcohol use will be recruited and randomized 1:1 to the SOC or BAI arm. A subgroup of participants (n=20) in each arm will be selected for longitudinal qualitative interviews; an additional subset (n=48) in the BAI arm will complete brief quantitative and qualitative interviews after completion of the BAI to assess the acceptability of the intervention. Additional implementation outcomes will be assessed through interviews with clinic staff and stakeholders (n=35). Intervention: Study participants in both arms will receive standard care for PrEP clients. In the BAI arm, each participant will receive two face-to-face intervention sessions and two brief booster phone sessions, based on cognitive behavioral therapy and delivered in motivational interviewing informed style, to address their unhealthy alcohol use. Outcomes: Effectiveness (PrEP and alcohol use) and cost-effectiveness outcomes will be compared between the two arms. Intervention implementation outcomes (acceptability, feasibility, adoption) will be assessed among MSM participants, clinic staff, and stakeholders. Discussion: This proposed trial will assess an alcohol intervention for MSM with unhealthy alcohol use who initiate or re-initiate PrEP, while simultaneously preparing for subsequent implementation. The study will measure the effectiveness of the BAI for increasing PrEP persistence through reducing unhealthy alcohol use in a setting where excessive alcohol consumption is a normative behavior. If effective, implementation-focused results will inform future scale-up of the BAI in similar settings. Trial registration: NCT06094634 on clinicaltrials.gov. Registered 16 October 2023. [ABSTRACT FROM AUTHOR]

Background: Evidence-based interventions (EBIs) often address normative behaviors. If a behavior is also common among clinicians, they may be skeptical about the necessity or effectiveness of an EBI. Alternatively, clinicians' attitudes and behaviors may be misaligned, or they may lack the knowledge and self-efficacy to deliver the EBI. Several EBIs address unhealthy alcohol use, a common and often culturally acceptable behavior. But unhealthy alcohol use may be particularly harmful to people with HIV (PWH). Here, we present an implementation trial using an experiential implementation strategy to address clinicians' knowledge, attitudes, and behaviors. Clinicians receive the experiential intervention before they begin delivering an evidence-based brief alcohol intervention (BAI) to PWH with unhealthy alcohol use. Methods: Design: In this hybrid type 3 implementation-effectiveness cluster randomized controlled trial, ART clinics (n = 30) will be randomized 1:1 to facilitation, a flexible strategy to address implementation barriers, or facilitation plus the experiential brief alcohol intervention (EBAI). In the EBAI arm, clinicians, irrespective of their alcohol use, will be offered the BAI as experiential learning. EBAI will address clinicians' alcohol-related attitudes and behaviors and increase their knowledge and confidence to deliver the BAI. Participants: ART clinic staff will be enrolled and assessed at pre-BAI training, post-BAI training, 3, 12, and 24 months. All PWH at the ART clinics who screen positive for unhealthy alcohol use will be offered the BAI. A subset of PWH (n = 810) will be enrolled and assessed at baseline, 3, and 12 months. Outcomes: We will compare implementation outcomes (acceptability, fidelity, penetration, costs, and sustainability) and effectiveness outcomes (viral suppression and alcohol use) between the two arms. We will assess the impact of site-level characteristics on scaling-up the BAI. We will also evaluate how experiencing the BAI affected clinical staff's alcohol use and clinic-level alcohol expectations in the EBAI arm. Discussion: This trial contributes to implementation science by testing a novel strategy to implement a behavior change intervention in a setting in which clinicians themselves may engage in the behavior. Experiential learning may be useful to address normative and difficult to change lifestyle behaviors that contribute to chronic diseases. Trial Registration: NCT06358885 (04/10/2024), https://clinicaltrials.gov/study/NCT06358885. [ABSTRACT FROM AUTHOR]

Young men who have sex with men (YMSM) and young transgender women (YTGW) have unique challenges to HIV care. We conducted a systematic review to summarize behavioral and structural interventions exclusively targeting YMSM and YTGW living with HIV. We screened 6546 records published through August 19th, 2022 from six databases. For eligibility, studies needed to involve structural or behavioral interventions exclusively targeting YMSM and/or YTGW living with HIV or presenting disaggregated data in this group. Quality assessment was performed using the ICROMS checklist. Twenty studies from 18 interventions were included in the review. There was considerable heterogeneity in intervention characteristics, including population, location, content and format of the interventions and targeted outcomes. Half of the interventions were described as pilot studies, and all but one study was conducted in the United States. The most common outcomes included the HIV care continuum, followed by HIV knowledge and self-efficacy, HIV-risk behaviors and mental health. The evidence base remained sparse, and the results on effectiveness were inconsistent, with some interventions reporting improved outcomes among participants after receiving treatment and others not reporting any meaningful changes. Although there has been some progress in the development of interventions targeting this group, we highlighted several directions for future research. Interventions expanding to low-resource settings, addressing structural barriers, and targeting different aspects of health among participants are warranted. Rigorous studies with larger sample sizes that follow participants over longer periods are necessary to increase the strength of the evidence. [ABSTRACT FROM AUTHOR]

Social events and stressful settings can be catalysts for alcohol consumption. Motivational enhancement therapy (MET) and cognitive behavioral therapy (CBT) are widely used in alcohol interventions. We assessed how alcohol consumption varied across three types of days (positive/social, negative/stressful, and neutral) among hazardous alcohol users living with HIV in Vietnam. We further evaluated how those consumption patterns changed after two MET/CBT alcohol reduction interventions versus the standard of care (SOC). The 'combined' intervention offered 6 individual sessions and 3 group sessions; the 'brief' intervention offered 2 individual sessions and 2 phone calls. A 30-day timeline follow-back was administered at study visits, detailing daily drinks and events. Days were categorized as neutral, positive/social, or negative/stressful; negative binomial models and generalized estimating equations were used to estimate drinks consumed by type of day at baseline and 12 months. Prior to intervention, more drinks were consumed on positive/social days (5.2 drinks; 95% Confidence Interval [CI]:4.8, 5.7) than negative/stressful (1.5; 95% CI:1.3, 1.9) and neutral days (2.2; 95% CI: 1.9, 2.5). After the brief intervention, drinks consumed decreased on neutral days (ratio: 0.5: 95% CI: 0.4, 0.7). After the combined intervention, drinks consumed decreased on neutral days (ratio: 0.4; 95% CI: 0.3, 0.6), positive/social days (ratio: 0.6; 95% CI: 0.5, 0.7) and negative/stressful days (ratio: 0.3; 95% CI: 0.2, 0.6). No reductions in consumption were observed in the SOC group. Social/positive days had the highest alcohol consumption prior to intervention, and the combined intervention showed the greatest decrease in consumption on those days. Clinical Trial Registration: The study is registered at clinicaltrials.gov (NCT02720237). [ABSTRACT FROM AUTHOR]

Background: Stigma around human immunodeficiency virus (HIV), injection drug use (IDU), and mental health disorders can be co-occurring and have different impacts on the well-being of people living with HIV (PWH) who use drugs and have mental health disorders. This stigma can come from society, health professionals, and internalized stigma. A person who has more than one health condition can experience overlapping health-related stigma and levels of stigma which can prevent them from receiving necessary support and healthcare, serving to intensify their experience with stigma. This study investigates HIV, drug use, and mental health stigmas in three dimensions (social, internalized, and professional) around PWH on methadone maintenance treatment (MMT) who have common mental disorders (CMDs) including depression, anxiety, and stress-related disorders in Hanoi, Vietnam.Please check and confirm whether corresponding author's email id is correctly identified.The cooresponding author's email is correct Methods: We conducted semi-structured, in-depth interviews (IDIs) (n = 21) and two focus group discussions (FGDs) (n = 10) with PWH receiving MMT who have CMD symptoms, their family members, clinic health care providers, and clinic directors. We applied thematic analysis using NVIVO software version 12.0, with themes based on IDI and FGD guides and emergent themes from interview transcripts. Results: The study found evidence of different stigmas towards HIV, IDU, and CMDs from the community, family, health care providers, and participants themselves. Community and family members were physically and emotionally distant from patients due to societal stigma around illicit drug use and fears of acquiring HIV. Participants often conflated stigmas around drug use and HIV, referring to these stigmas interchangeably. The internalized stigma around having HIV and injecting drugs made PWH on MMT hesitant to seek support for CMDs. These stigmas compounded to negatively impact participants' health. Conclusions: Strategies to reduce stigma affecting PWH on MMT should concurrently address stigmas around HIV, drug addiction, and mental health. Future studies could explore approaches to address internalized stigma to improve self-esteem, mental health, and capacities to cope with stigma for PWH on MMT. Trial registration: NCT04790201, available at clinicaltrials.gov. [ABSTRACT FROM AUTHOR]

Background: The prevalence of common mental disorders (CMDs) among people living with HIV and people who inject drugs is high worldwide and in Vietnam. However, few evidence-informed CMD programs for people living with HIV who inject drugs have been adapted for use in Vietnam. We adapted the Friendship Bench (FB), a problem-solving therapy (PST)-based program that was successfully implemented among patients with CMDs in primary health settings in Zimbabwe and Malawi for use among people living with HIV on methadone maintenance treatment (MMT) with CMDs in Hanoi, Vietnam. Objective: This study aimed to describe the adaptation process with a detailed presentation of 4 phases from the third (adaptation) to the sixth (integration) of the Assessment-Decision-Adaptation-Production-Topical Experts-Integration-Training-Testing (ADAPT-ITT) framework. Methods: The adaptation phase followed a qualitative study design to explore symptoms of CMDs, facilitators, and barriers to conducting FB for people living with HIV on MMT in Vietnam, and patient, provider, and caretaker concerns about FB. In the production phase, we revised the original program manual and developed illustrated PST cases. In the topical expert and integration phases, 2 investigators (BNG and BWP) and 3 subject matter experts (RV, DC, and GML) reviewed the manual, with reviewer comments incorporated in the final, revised manual to be used in the training. The draft program will be used in the training and testing phases. Results: The study was methodologically aligned with the ADAPT-ITT goals as we chose a proven, effective program for adaptation. Insights from the adaptation phase addressed the who, where, when, and how of FB program implementation in the MMT clinics. The ADAPT-ITT framework guided the appropriate adaptation of the program manual while maintaining the core components of the PST of the original program throughout counseling techniques in all program sessions. The deliverable of this study was an adapted FB manual to be used for training and piloting to make a final program manual. Conclusions: This study successfully illustrated the process of operationalizing the ADAPT-ITT framework to adapt a mental health program in Vietnam. This study selected and culturally adapted an evidence-informed PST program to improve CMDs among people living with HIV on MMT in Vietnam. This adapted program has the potential to effectively address CMDs among people living with HIV on MMT in Vietnam. [ABSTRACT FROM AUTHOR]

Implementation strategies are systematic approaches to improve the uptake and sustainability of evidence-based interventions. They frequently focus on changing provider behavior through the provision of interventions such as training, coaching, and audit-and-feedback. Implementation strategies often impact intermediate behavioral outcomes like provider guideline adherence, in turn improving patient outcomes. Fidelity of implementation strategy delivery is defined as the extent to which an implementation strategy is carried out as it was designed. Implementation strategy fidelity measurement is under-developed and under-reported, with the quality of reporting decreasing over time. Benefits of fidelity measurement include the exploration of the extent to which observed effects are moderated by fidelity, and critical information about Type-III research errors, or the likelihood that null findings result from implementation strategy fidelity failure. Reviews of implementation strategy efficacy often report wide variation across studies, commonly calling for increased implementation strategy fidelity measurement to help explain variations. Despite the methodological benefits of rigorous fidelity measurement, implementation researchers face multi-level challenges and complexities. Challenges include the measurement of a complex variable, multiple data collection modalities with varying precision and costs, and the need for fidelity measurement to change in-step with adaptations. In this position paper, we weigh these costs and benefits and ultimately contend that implementation strategy fidelity measurement and reporting should be improved in trials of implementation strategies. We offer pragmatic solutions for researchers to make immediate improvements like the use of mixed methods or innovative data collection and analysis techniques, the inclusion of implementation strategy fidelity assessment in reporting guidelines, and the staged development of fidelity tools across the evolution of an implementation strategy. We also call for additional research into the barriers and facilitators of implementation strategy fidelity measurement to further clarify the best path forward. [ABSTRACT FROM AUTHOR]

Implementation strategies are systematic approaches to improve the uptake and sustainability of evidence-based interventions. They frequently focus on changing provider behavior through the provision of interventions such as training, coaching, and audit-and-feedback. Implementation strategies often impact intermediate behavioral outcomes like provider guideline adherence, in turn improving patient outcomes. Fidelity of implementation strategy delivery is defined as the extent to which an implementation strategy is carried out as it was designed. Implementation strategy fidelity measurement is under-developed and under-reported, with the quality of reporting decreasing over time. Benefits of fidelity measurement include the exploration of the extent to which observed effects are moderated by fidelity, and critical information about Type-III research errors, or the likelihood that null findings result from implementation strategy fidelity failure. Reviews of implementation strategy efficacy often report wide variation across studies, commonly calling for increased implementation strategy fidelity measurement to help explain variations. Despite the methodological benefits of rigorous fidelity measurement, implementation researchers face multi-level challenges and complexities. Challenges include the measurement of a complex variable, multiple data collection modalities with varying precision and costs, and the need for fidelity measurement to change in-step with adaptations. In this position paper, we weigh these costs and benefits and ultimately contend that implementation strategy fidelity measurement and reporting should be improved in trials of implementation strategies. We offer pragmatic solutions for researchers to make immediate improvements like the use of mixed methods or innovative data collection and analysis techniques, the inclusion of implementation strategy fidelity assessment in reporting guidelines, and the staged development of fidelity tools across the evolution of an implementation strategy. We also call for additional research into the barriers and facilitators of implementation strategy fidelity measurement to further clarify the best path forward. [ABSTRACT FROM AUTHOR]

Introduction: Mental health disorders may negatively impact HIV outcomes, such as viral suppression (VS) and antiretroviral (ART) adherence among people with HIV (PWH) with hazardous alcohol use. This study evaluates the longitudinal association between depression, anxiety symptoms, VS and complete ART adherence among ART clients with hazardous alcohol use in Vietnam; and examines alcohol dependence as a modifier in this association. Methods: This was a secondary data analysis of a trial for hazardous drinking ART clients in Thai Nguyen, Vietnam. From March 2016 to May 2018, 440 ART clients with an Alcohol Use Disorders Identification Test‐Concise (AUDIT‐C) score ≥4 for men and ≥3 for women were enrolled. Individuals were randomized to either a combined intervention, a brief intervention or a standard of care. Data on sociodemographics, depression, anxiety symptoms, alcohol use, VS and ART adherence were collected at baseline, three, six, and twelve months. Generalized estimating equation models controlling for intervention exposure were used to estimate time‐lagged associations. Risk ratios were estimated using Poisson regression with robust variance estimation. Results: The mean age of participants was 40.2. The majority was male (96.8%), had at least some secondary school education (85.0%) and had a history of injection drug use (80.9%). No overall effect of depression and anxiety symptoms on VS was observed. When stratified by time, increased anxiety symptoms at six months were associated with VS at 12 months (adjusted risk ratio (aRR) = 1.09; 95% CI 1.02 to 1.17). An increase in depression or anxiety symptoms was associated with a decreased probability of complete ART adherence (depression symptoms: aRR = 0.95; 95% CI: 0.91 to 0.99; anxiety symptoms: aRR = 0.93; 85% CI: 0.88 to 0.99). The negative effects of anxiety symptoms on ART adherence were stronger among participants with alcohol dependence, compared to those without. Conclusions: Depression and anxiety symptoms had no overall effect on VS, although they were associated with a lower probability of complete ART adherence. Interventions focusing on mental healthcare for PWH with hazardous alcohol use are needed, and integration of mental healthcare and alcohol reduction should be implemented in HIV primary care settings. [ABSTRACT FROM AUTHOR]

Introduction: Mental health disorders may negatively impact HIV outcomes, such as viral suppression (VS) and antiretroviral (ART) adherence among people with HIV (PWH) with hazardous alcohol use. This study evaluates the longitudinal association between depression, anxiety symptoms, VS and complete ART adherence among ART clients with hazardous alcohol use in Vietnam; and examines alcohol dependence as a modifier in this association. Methods: This was a secondary data analysis of a trial for hazardous drinking ART clients in Thai Nguyen, Vietnam. From March 2016 to May 2018, 440 ART clients with an Alcohol Use Disorders Identification Test‐Concise (AUDIT‐C) score ≥4 for men and ≥3 for women were enrolled. Individuals were randomized to either a combined intervention, a brief intervention or a standard of care. Data on sociodemographics, depression, anxiety symptoms, alcohol use, VS and ART adherence were collected at baseline, three, six, and twelve months. Generalized estimating equation models controlling for intervention exposure were used to estimate time‐lagged associations. Risk ratios were estimated using Poisson regression with robust variance estimation. Results: The mean age of participants was 40.2. The majority was male (96.8%), had at least some secondary school education (85.0%) and had a history of injection drug use (80.9%). No overall effect of depression and anxiety symptoms on VS was observed. When stratified by time, increased anxiety symptoms at six months were associated with VS at 12 months (adjusted risk ratio (aRR) = 1.09; 95% CI 1.02 to 1.17). An increase in depression or anxiety symptoms was associated with a decreased probability of complete ART adherence (depression symptoms: aRR = 0.95; 95% CI: 0.91 to 0.99; anxiety symptoms: aRR = 0.93; 85% CI: 0.88 to 0.99). The negative effects of anxiety symptoms on ART adherence were stronger among participants with alcohol dependence, compared to those without. Conclusions: Depression and anxiety symptoms had no overall effect on VS, although they were associated with a lower probability of complete ART adherence. Interventions focusing on mental healthcare for PWH with hazardous alcohol use are needed, and integration of mental healthcare and alcohol reduction should be implemented in HIV primary care settings. [ABSTRACT FROM AUTHOR]

Background: People who inject drugs (PWID) bear a disproportionate burden of HIV infection and experience poor outcomes. A randomized trial demonstrated the efficacy of an integrated System Navigation and Psychosocial Counseling (SNaP) intervention in improving HIV outcomes, including antiretroviral therapy (ART) and medications for opioid use disorder (MOUD) uptake, viral suppression, and mortality. There is limited evidence about how to effectively scale such intervention. This protocol presents a hybrid type III effectiveness-implementation trial comparing two approaches for scaling-up SNaP. We will evaluate the effectiveness of SNaP implementation approaches as well as cost and the characteristics of HIV testing sites achieving successful or unsuccessful implementation of SNaP in Vietnam.Methods: Design: In this cluster randomized controlled trial, two approaches to scaling-up SNaP for PWID in Vietnam will be compared. HIV testing sites (n = 42) were randomized 1:1 to the standard approach or the tailored approach. Intervention mapping was used to develop implementation strategies for both arms. The standard arm will receive a uniform package of these strategies, while implementation strategies for the tailored arm will be designed to address site-specific needs.Participants: HIV-positive PWID participants (n = 6200) will be recruited for medical record assessment at baseline; of those, 1500 will be enrolled for detailed assessments at baseline, 12, and 24 months. Site directors and staff at each of the 42 HIV testing sites will complete surveys at baseline, 12, and 24 months.Outcomes: Implementation outcomes (fidelity, penetration, acceptability) and effectiveness outcomes (ART, MOUD uptake, viral suppression) will be compared between the arms. To measure incremental costs, we will conduct an empirical costing study of each arm and the actual process of implementation from a societal perspective. Qualitative and quantitative site-level data will be used to explore key characteristics of HIV testing sites that successfully or unsuccessfully implement the intervention for each arm.Discussion: Scaling up evidence-based interventions poses substantial challenges. The proposed trial contributes to the field of implementation science by applying a systematic approach to designing and tailoring implementation strategies, conducting a rigorous comparison of two promising implementation approaches, and assessing their incremental costs. Our study will provide critical guidance to Ministries of Health worldwide regarding the most effective, cost-efficient approach to SNaP implementation.Trial Registration: NCT03952520 on Clinialtrials.gov. Registered 16 May 2019. [ABSTRACT FROM AUTHOR]

Background Neisseria gonorrhoeae (NG) infections are a global health burden. NG resistance to cephalosporins, which is increasingly reported, is an imminent threat to public health. Many hypothesize that commensal Neisseria species are an important reservoir for genetic material conferring antimicrobial resistance in NG; however, clinical data are lacking. Methods Men who have sex with men (MSM) in Hanoi, Vietnam, completed a questionnaire regarding antibiotic use. We collected pharyngeal specimens, cultured Neisseria species, and measured minimum inhibitory concentrations (MICs) to ciprofloxacin, cefixime, ceftriaxone, and cefpodoxime. Using MIC criteria for antimicrobial susceptibility in NG, we categorized the Neisseria species and compared mean MIC levels between different antibiotic user groups. Results Of 207 participants, 38% used at least 1 antibiotic in the past 6 months; 52% without a prescription. A median of 1 Neisseria species was cultured from each participant (range, 1–4) with 10 different Neisseria species identified overall. The proportion of Neisseria with reduced susceptibility to ciprofloxacin was 93%, cefpodoxime 84%, cefixime 31%, and ceftriaxone 28%. Antibiotic use within the past month was strongly associated with Neisseria species having increased MICs to cefixime, ceftriaxone, and cefpodoxime (mean MIC ratios of 6.27, 4.11, and 7.70, respectively), compared with those who used antibiotics between 1 and 6 months prior (P <.05, all comparisons). Conclusions MSM in our study often used antibiotics without a prescription. At least 1 commensal Neisseria species colonized all men. Recent use of any antibiotics may select for oropharyngeal Neisseria species with antimicrobial resistance. The normal flora of the oropharynx may be an important source of antimicrobial resistance in Neisseria gonorrhoeae. [ABSTRACT FROM AUTHOR]

Background: The HIV epidemic in Vietnam has been primarily driven by injection drug use. HIV-infected people who inject drugs (PWID) in Vietnam have very high rates of mental health problems, which can accelerate progression to AIDS and increase mortality rates. No research has explored the barriers and facilitators of mental health care for HIV-infected PWID in Vietnam. Methods: We conducted 28 in-depth interviews among HIV-infected PWID (n = 16), HIV and MMT (methadone maintenance treatment) providers (n = 8), and health officials (n = 4) in Hanoi. We explored participants' perceptions of mental health disorders, and barriers and facilitators to seeking and receiving mental health care. Results: HIV-infected PWID were perceived by both PWID, HIV/MMT providers, and health officials to be vulnerable to mental health problems and to have great need for mental health care. Perceived social, physical, and economical barriers included stigma towards HIV, injection drug use, and mental illnesses; lack of awareness around mental health issues; lack of human resources, facilities and information on mental health services; and limited affordability of mental health services. Social support from family and healthcare providers was a perceived facilitator of mental health care. Conclusions: Interventions should raise self-awareness of HIV-infected PWID about common mental health problems; address social, physical, economic barriers to seeking mental health services; and increase social support for patients. [ABSTRACT FROM AUTHOR]

In an era where mobile phones and computers are ubiquitous, technology-based interventions to reduce HIV and other sexually transmitted infections (STIs) have great potential to reach high-risk groups, including men who have sex with men (MSM). This study aimed to examine technology usage to find sexual health information online among MSM in Hanoi, Vietnam. A cross-sectional study of 205 MSM in Hanoi was conducted from February to May 2016. Overall, 50.7% of participants reported having used a smartphone, computer, or tablet to find HIV/STI testing locations in the past year, and 75.1% reported having used such devices to find other HIV/STI information online. Unemployment (adjusted prevalence ratio [aPR]: 1.13, 95%CI: 1.00-1.28) and having been tested for HIV (aPR: 1.27, 95%CI: 1.07-1.51) were significantly associated with using technology to find online sexual health information. MSM who had ever exchanged sex for money or drugs (aPR: 0.80; 95%CI: 0.68-0.94) were less likely to use technology to find sexual health information online. Technology is a promising platform for HIV/STI prevention programs among MSM, with the potential to reach different subgroups. Further efforts to develop technology-based interventions tailored to the needs of the MSM communities in Hanoi and to encourage MSM who were not currently seeking sexual health information and testing services online to do so are necessary. [ABSTRACT FROM AUTHOR]

In this paper, we present an interactive high dynamic range volume visualization framework (HDR VolVis) for visualizing volumetric data with both high spatial and intensity resolutions. Volumes with high dynamic range values require high precision computing during the rendering process to preserve data precision. Furthermore, it is desirable to render high resolution volumes with low opacity values to reveal detailed internal structures, which also requires high precision compositing. High precision rendering will result in a high precision intermediate image (also known as high dynamic range image). Simply rounding up pixel values to regular display scales will result in loss of computed details. Our method performs high precision compositing followed by dynamic tone mapping to preserve details on regular display devices. Rendering high precision volume data requires corresponding resolution in the transfer function. To assist the users in designing a high resolution transfer function on a limited resolution display device, we propose a novel transfer function specification interface with nonlinear magnification of the density range and logarithmic scaling of the colon opacity range. By leveraging modern commodity graphics hardware, multiresolution rendering techniques and out-of-core acceleration, our system can effectively produce an interactive visualization of large volume data, such as 2,048³. [ABSTRACT FROM AUTHOR]