Characterization of Objective Skin Color Changes during and after Breast and Chest Wall Radiotherapy and Correlation with Radiation-Induced Skin Toxicity in Breast Cancer Patients, Including Patients with Skin of Color

PURPOSE/OBJECTIVE(S)

Radiation dermatitis (RD) is common among women undergoing breast and chest wall radiotherapy (RT); however, existing scales to assess the severity of RD are subjective and do not account for variability in skin of color (SOC). For instance, the Common Terminology Criteria for Adverse Events (CTCAE) criteria do not include hyperpigmentation in the grading scale. There is data indicating worse RD in African American and Hispanic patients; however, the rate and severity in SOC remains unknown given the lack of data using objective measures of RD. Spectrophotometry is one method to quantify the appearance of color by measuring spectral characteristics without the bias associated with subjective clinical scoring. We present a phase I prospective non-therapeutic clinical trial to objectively define SOC at baseline and evaluate spectrophotometric skin changes during and after breast or chest wall RT in parallel with physician-graded RD using CTCAE criteria. We hypothesize that there will be greater discrepancy between physician graded RD and objective measures of RD in patients with SOC in whom hyperpigmentation will be undercaptured by physician-grading. This is the first study intending to correlate SOC with objective changes after RT as a reliable indicator of RD. We offer a novel system for evaluating RD that is applicable to SOC.

MATERIALS/METHODS

A total of 60 patients with localized breast cancer (stage 0-III) undergoing conventional whole breast or chest wall RT (50Gy/ 25 fx), hypofractionated whole breast RT (40.5Gy/15 fx) or ultrahypofractionated partial breast RT (6Gy x5), with or without regional nodal RT were enrolled. 3 skin color readouts using the Commission International de l'Eclairage 3D color system (l*, a*, b*) were measured within the radiation field using a spectrophotometer at baseline, once weekly during RT, 10 days post RT, 4 weeks and 12 months post RT. The spectrophotometer is a non-invasive, hand-held device that is used in the clinic room with no additional equipment or setup requirements. Data is automatically exported to a spreadsheet organized by timepoint and patient. The l* axis is a gray scale (0 = black, 100 = white) correlating with skin pigmentation and the a* axis describes red and green values correlating with erythema. The primary objective is to evaluate the changes from baseline in skin color readouts in the quadrant of tumor location during and after RT based on fractionation. The secondary objective is to evaluate changes within and across groups defined by baseline skin color. Exploratory objectives include evaluating the association of baseline color readouts and changes after RT with acute and late grade > 2 clinician-rated skin and subcutaneous tissue effects according to the CTCAE, v5.0, physician graded cosmesis and clinical interventions to treat RD, such as use of topical steroids and oral analgesics. As of January 2023, we have enrolled 100% of the planned patients.

RESULTS

To be determined.

CONCLUSION

To be determined. Clinical Study Identifier: S22-00192.

Anti-Asian racism related stigma, racial discrimination, and protective factors against stigma: a repeated cross-sectional survey among university students during the COVID-19 pandemic

Background

Since the onset of the COVID-19 pandemic in March 2020, reports of anti-Asian American or Pacific Islander (AAPI) hate have increased in the United States. Institutions of higher education provide a unique opportunity to examine COVID-19 related stigma and protective factors in AAPI young adults enrolled in college.

Objective

The goal of this research was to examine COVID-19 related stigma among a diverse college student population. We posited that AAPI students experience more racial discrimination, internalized stigma, and/or anticipated racial discrimination than other students. We also sought to identify protective behavioral factors against stigma.

Methods

This study includes data from a repeated cross-sectional survey that was administered among college students at a large public university in the United States in April (n = 1,359) and November 2020 (n = 1,196). All university enrolled students with an active email account were eligible to participate in the online survey, which included questions about COVID-19 stigma (anticipated, enacted, internalized), stigma resistance, sources of COVID-19 information, lifestyle behaviors, and sociodemographic information. Binary logistic regression models were utilized to assess differences in stigma between race and ethnic groups and to identify factors associated with stigma.

Results

AAPI students were more likely to experience all three types of stigma compared to other race and ethnic groups. AAPI students in both waves were at least 2 times more likely to experience enacted stigma and 7.3 times more likely to experience anticipated stigma in the earlier wave compared to non-Hispanic White students. Students who had experienced enacted stigma were more likely to experience anticipated stigma, and those who experienced enacted and anticipated stigma were more likely to experience internalized stigma. Higher education level, living with neighbors/roommates, maintaining a healthy lifestyle, and thinking positively about oneself may act as protective factors against different types of stigma.

Conclusion

AAPI students have a greater risk of experiencing COVID-19 stigma compared to those from other race and ethnic groups. Universities should combat anti-AAPI sentiments and COVID-19 stigma and promote public health efforts to build resistance against the negative effects of stigma.

Use of Community-Engaged Research Approaches in Clinical Interventions for Neurologic Disorders in the United States: A Scoping Review and Future Directions for Improving Health Equity Research

BACKGROUND AND OBJECTIVES

Evidence suggests a significant prevalence of race and ethnic disparities in the United States among people with neurologic conditions including stroke, Alzheimer disease and related dementia (ADRD), Parkinson disease (PD), epilepsy, spinal cord injury (SCI), and traumatic brain injury (TBI). Recent neurologic research has begun the paradigm shift from observational health disparities research to intervention research in an effort to narrow the disparities gap. There is an evidence base that suggests that community engagement is a necessary component of health equity. While the increase in disparities focused neurologic interventions is encouraging, it remains unclear whether and how community-engaged practices are integrated into intervention design and implementation. The purpose of this scoping review was to identify and synthesize intervention studies that have actively engaged with the community in the design and implementation of interventions to reduce disparities in neurologic conditions and to describe the common community engagement processes used.

METHODS

Two databases, PubMed and CINAHL, were searched to identify eligible empirical studies within the United States whose focus was on neurologic interventions addressing disparities and using community engagement practices.

RESULTS

We identified 392 disparity-focused interventions in stroke, ADRD, PD, epilepsy, SCI, and TBI, of which 53 studies incorporated community engagement practices: 32 stroke studies, 15 ADRD, 2 epilepsy studies, 2 PD studies, 1 SCI study, and 1 TBI study. Most of the interventions were designed as randomized controlled trials and were programmatic in nature. The interventions used a variety of community engagement practices: community partners (42%), culturally tailored materials and mobile health (40%), community health workers (32%), faith-based organizations and local businesses (28%), focus groups/health need assessments (25%), community advisory boards (19%), personnel recruited from the community/champions (19%), and caregiver/social support (15%).

DISCUSSION

Our scoping review reports that the proportion of neurologic intervention studies incorporating community engagement practices is limited and that the practices used within those studies are varied. The major practices used included collaboration with community partners and utilization of culturally tailored materials. We also found inconsistent reporting and dissemination of results from studies that implemented community engagement measures in their interventions. Future directions include involving the community in research early and continuously, building curricula that address challenges to community engagement, prioritizing the inclusion of community engagement reporting in peer-reviewed journals, and prioritizing and incentivizing research of subpopulations that experience disparities in neurologic conditions.

Abstract WP183: Social Activities Are Positively Associated With Medication Adherence In Stroke Survivors

Introduction: Social support may influence illness incidence or recovery through effects on health-related behaviors, and one aspect is emotional support, which includes the offering of empathy, friendship, care, and trust along with information. While we have previously reported on the positive relationship of family and friend networks in risk reduction, our objective was to examine whether participation in formalized group activities was related to medication adherence post-stroke.

Methods: Using Discharge Educational Strategies for Reduction of Vascular Events (DESERVE) data, information regarding religious and nonreligious social activities was collected at baseline. The outcome variable was measured by the self-reported 8-item Morisky Medication Adherence Scale (MMAS-8; score 0-8). Medium/high adherence (MMAS-8≥6) at 6- and 12-months post-discharge was modeled against social activities separately using logistic regression adjusting for age, gender, race/ethnicity, education, family and friend networks, NIH stroke scale at admission, and the intervention.

Results: Of the 541 participants who completed the baseline questionnaire, 286 and 344 had valid MMAS-8 scores for post 6-months and 12-months follow-up data collection. Medication adherence was poor among the participants. Only 44% for 6-months and 46% for 12-months had medium or high medication adherence. Participants going to nonreligious social events (n = 67, 21%) had higher odds of having medium/high medication adherence (OR = 3.08, 95% CI: 1.15-8.25) at 12-months.

Discussion: Nonreligious social activities, including meetings of social clubs or other non-religious groups not relevant to work, were shown to be positively related to 12-months post-discharge medication adherence among stroke patients. Social activities may play an important role in emotional support and may be an opportunity for targeted secondary stroke prevention.

Abstract WP186: Fewer Self-reported Memory Problems Are Associated With Better Blood Pressure Control Post-stroke

Introduction: Memory problems, a common cognitive issue, can have a negative influence on one’s ability to function and contributes to increased risk of secondary stroke.

Objective: To examine the association between self-reported memory problems at 6 months and blood pressure control at 12 months post-stroke.

Methods: This study utilized follow-up data from the Discharge Educational Strategies for Reduction of Vascular Events (DESERVE) stroke risk factor reduction trial (n=226). Sample size was restricted to those who answered memory questions and had a 12-month blood pressure (BP) reading. Exclusion criteria for DESERVE included any significant memory disorder prior to the baseline stroke. Seven memory domain questions (Table 1) from the Stroke Impact Scale were used separately to assess the association with systolic BP, with control defined as ≤120mmHg, at 12 months in logistic regression models adjusted for race, gender, education, age, and intervention status. Models were additionally adjusted for 6-month BP control as a mediator.

Results: Participants were almost equally white (28%), Black (33%), or Hispanic (34%) and 52% were female with a mean age of 65 (SD=13). About 25% had BP control at 6 or 12 months. Memory measures were not significantly associated with BP control prior to adjusting for BP control at 6 months. After adjusting for 6-month BP control, participants with less difficulty remembering things that people just told them (OR=1.69, 95% CI: 1.09, 2.63) or remembering to do things (OR=1.76, 95% CI:1.09, 2.86) had better odds of having their BP controlled at 12 months. Memory items 2 and 4-7 did not show an association with better BP control.

Discussion: Stroke survivors who were better at remembering what people told them and remembering to do things were more likely to achieve blood pressure control 1-year post-stroke. Evaluating early memory post-stroke may be an important target for secondary prevention strategies and should be further researched.

Abstract WP81: The Association Between Health-related Locus Of Control And Post-stroke Disability, Quality Of Life, And Depression

Introduction: Beliefs regarding ones’ control over their health can lie internally, influenced by their own actions, or externally, controlled by others or due to chance.

Objective: To examine the association between health-related locus of control (HRLC) type and post-stroke disability, quality of life, and depression.

Methods: This study utilized data from the Discharge Educational Strategies for Reduction of Vascular Events (DESERVE) trial (n=552). Participants were categorized into three groups based on their highest Multidimensional Health Locus of Control (MHLC) score. The Stroke Impact Scale (SIS) was used to assess post-stroke disability and quality of life. Linear regression was used to identify differences in each SIS domain score between the three groups while adjusting for the intervention. Depression was defined as a Center for Epidemiological Studies Depression (CESD) score ≥16. Logistic regression was used to examine differences in depression between the three groups while adjusting for the intervention.

Results: Of the 529 participants who completed the MHLC questionnaire at baseline, 179 (33.3%) were categorized into the internal group , 163 (30.8%) into the powerful others group, and 190 (35.9%) into the chance group. Of the 297 participants who completed the CESD questionnaires at 12 months, 163 (54.8%) scored ≥ 16. Participant’s mean scores for each SIS domain are reported in Table 1. For the SIS communication domain, the chance group’s mean score was 3.03 points lower than the powerful others group’s score (SE=1.39, p=.029). There were no statistically significant differences in scores for the other seven SIS domains or for depression between groups (Table 1).

Discussion: External HRLC based on chance may be a predictor of communication difficulties in patients post-stroke. However, mean communication scores are skewed. Control beliefs are important in post-stroke recovery. More research is needed to validate these findings.

Abstract P723: Adaptation of Stroke Prevention Interventions for Low- and Middle-Income Countries: A Scoping Review

Introduction: Stroke is a leading cause of mortality globally, with 85% of stroke death occurring in low- and middle-income countries (LMICs). Translation of evidence-based stroke prevention interventions from their original setting to the novel context in which they will be implemented is often unreported; especially in LMICs where it has been severely understudied. Thus, our objective was to investigate how adaptation has been examined within research on stroke prevention interventions in LMICs through a scoping review of the available literature in order to highlight benefits and best-practices, identify gaps, and develop a greater understanding of these efforts that will ultimately support attempts to address the global burden of stroke.

Methods: This review was conducted in accordance with PRISMA-ScR guidelines. Five databases were searched (PubMed, PsycINFO, CINAHL, EMBASE, and Web of Science), for eligible studies using a search strategy developed in consultation with a research librarian. Two reviewers independently assessed the retrieved articles for selection based on the inclusion criteria (peer-reviewed empirical papers or protocols, reported on adaptation of stroke prevention interventions, and occurred in at least one LMIC) through a two phase process consisting of (1) title and abstract screening and (2) full-text screening. Discrepancies were resolved through discussion until consensus was reached. Data were charted and a narrative synthesis, guided by the FRAME framework, was used to analyze and interpret the findings.

Results: Of 380 articles retrieved, a total of six articles reporting adaptation of primary (n=4) or secondary (n=2) stroke prevention interventions in LMICs were identified. Types of interventions included use of community health workers (n = 2), use of mHealth tools (n=2), and interventions aimed at risk factor modification (n = 2). Adaptations were proactively planned, with multiple adaptation goals reported.

Conclusions: This is the first review of its kind to focus on adaptation of evidence-based stroke prevention interventions in LMICs. Through our systematic investigation, we highlight the need for additional research to assess the processes and outcomes of stroke prevention interventions.

Abstract P681: Implementation of Stroke Prevention Interventions in Low- and Middle-Income Countries: A Scoping Review

Background: Stroke is the second leading cause of death globally and an increasing concern in low- and middle-income countries (LMIC) where, due to limited capacity to treat stroke, preventative efforts are critically important. Although some research on evidence-based interventions for stroke prevention in LMIC exists, there remains a significant gap in understanding of their implementation across various contexts in LMIC.

Objectives: In this scoping review, our objective was to identify and synthesize the implementation outcomes (using Proctor et al.’s taxonomy, 2011) for stroke prevention interventions, as well as to describe the diverse interventions employed.

Methods: Eligible studies were empirical, focused on implementation of stroke prevention programs or policies, and occurred in at least one LMIC. Five databases were searched, including PubMed, PsycINFO, CINAHL, EMBASE, and Web of Science. Two reviewers independently assessed studies for selection and charted data; discrepancies were resolved through discussion with a third reviewer until consensus was reached. Narrative synthesis was used to analyze and interpret the findings.

Results: Studies were predominantly focused in Asia, targeting primary or secondary prevention, and facility-based. Interventions were conducted at the level of individual (n=11), system (n=12), or both (n=4). Various implementation outcomes were reported, most commonly cost (n=10), acceptability (n=7), fidelity (n=7), and feasibility (n=6), but also adoption (n=4), penetration (n=3), appropriateness (n=1), and sustainability (n=1).

Conclusions: Findings highlight the breadth of evidence-based interventions for stroke prevention available to implement in LMIC settings, including culturally acceptable education interventions, cost-effective medications, and community-based interventions implemented by community health workers. Implementation outcomes remain under-reported, and more rigorous research is needed to better plan and evaluate the implementation of these interventions to prevent stroke.

Effects of an Exoskeleton-Assisted Gait Motor Imagery Training in Functional Brain Connectivity

Lower-limb exoskeletons have been used in gait rehabilitation to facilitate the restoration of motor skills. These robotics systems could be complemented by Brain-Computer Interfaces (BCIs) to assist or rehabilitate people with walking disabilities. In this preliminary study, electroencephalography-based brain functional connectivity is analyzed during exoskeleton-assisted gait motor imagery (MI) training. Partial Directed Coherence (PDC) analysis was employed to assess the exchange of information flow between EEG signals during gait MI in four healthy subjects, two using an exoskeleton and two without using it. Besides, in order to explore the functional connectivity, an outflow index based on the number of significant directed connectivities revealed by the PDC analysis is proposed. We found that the outflow index increases in the central zone (C2, C3, C4) while decreases in the central-parietal (CP1, CP2) and fronto-central (FC1) zones when the training was assisted by an exoskeleton. The results obtained can be useful to obtain informative features for BCI applications as well as in motor rehabilitation.

First operation in SPIDER and the path to complete MITICA

The requirements of ITER neutral beam injectors (1 MeV, 40 A negative deuterium ion current for 1 h) have never been simultaneously attained; therefore, a dedicated Neutral Beam Test Facility (NBTF) was set up at Consorzio RFX (Padova, Italy). The NBTF includes two experiments: SPIDER (Source for the Production of Ions of Deuterium Extracted from Rf plasma), the full-scale prototype of the source of ITER injectors, with a 100 keV accelerator, to investigate and optimize the properties of the ion source; and MITICA, the full-scale prototype of the entire injector, devoted to the issues related to the accelerator, including voltage holding at low gas pressure. The present paper gives an account of the status of the procurements, of the timeline, and of the voltage holding tests and experiments for MITICA. As for SPIDER, the first year of operation is described, regarding the solution of some issues connected with the radiofrequency power, the source operation, and the characterization of the first negative ion beam.

A Magnetometer Based on a Spin Wave Interferometer

We describe a magnetic field sensor based on a spin wave interferometer. Its sensing element consists of a magnetic cross junction with four micro-antennas fabricated at the edges. Two of these antennas are used for spin wave excitation while two other antennas are used for detection of the inductive voltage produced by the interfering spin waves. Two waves propagating in the orthogonal arms of the cross may accumulate significantly different phase shifts depending on the magnitude and direction of the external magnetic field. This phenomenon is utilized for magnetic field sensing. The sensitivity attains its maximum under the destructive interference condition, where a small change in the external magnetic field results in a drastic increase of the inductive voltage, as well as in the change of the output phase. We report experimental data obtained for a micrometer scale Y₃Fe₂(FeO₄)₃ cross structure. The change of the inductive voltage near the destructive interference point exceeds 40 dB per 1 Oe. The phase of the output signal exhibits a π-phase shift within 1 Oe. The data are collected at room temperature. Taking into account the low thermal noise in ferrite structures, we estimate that the maximum sensitivity of the spin wave magnetometer may exceed attotesla.

Electroencephalography in ellipsoidal geometry with fourth-order harmonics

We present a solution to the electroencephalographs (EEG) forward problem of computing the scalp electric potentials for the case when the head's geometry is modeled using a four-shell ellipsoidal geometry and the brain sources with an equivalent current dipole (ECD). The proposed solution includes terms up to the fourth-order ellipsoidal harmonics and we compare this new approximation against those that only considered up to second- and third-order harmonics. Our comparisons use as reference a solution in which a tessellated volume approximates the head and the forward problem is solved through the boundary element method (BEM). We also assess the solution to the inverse problem of estimating the magnitude of an ECD through different harmonic approximations. Our results show that the fourth-order solution provides a better estimate of the ECD in comparison to lesser order ones.

Evaluation of whole-body MR to CT deformable image registration

Multimodality image registration plays a crucial role in various clinical and research applications. The aim of this study is to present an optimized MR to CT whole‐body deformable image registration algorithm and its validation using clinical studies. A 3D intermodality registration technique based on B‐spline transformation was performed using optimized parameters of the elastix package based on the Insight Toolkit (ITK) framework. Twenty‐eight (17 male and 11 female) clinical studies were used in this work. The registration was evaluated using anatomical landmarks and segmented organs. In addition to 16 anatomical landmarks, three key organs (brain, lungs, and kidneys) and the entire body volume were segmented for evaluation. Several parameters — such as the Euclidean distance between anatomical landmarks, target overlap, Dice and Jaccard coefficients, false positives and false negatives, volume similarity, distance error, and Hausdorff distance — were calculated to quantify the quality of the registration algorithm. Dice coefficients for the majority of patients (>75%) were in the 0.8–1 range for the whole body, brain, and lungs, which satisfies the criteria to achieve excellent alignment. On the other hand, for kidneys, Dice coefficients for volumes of 25% of the patients meet excellent volume agreement requirement, while the majority of patients satisfy good agreement criteria (>0.6). For all patients, the distance error was in 0–10 mm range for all segmented organs. In summary, we optimized and evaluated the accuracy of an MR to CT deformable registration algorithm. The registered images constitute a useful 3D whole‐body MR‐CT atlas suitable for the development and evaluation of novel MR‐guided attenuation correction procedures on hybrid PET‐MR systems.

PACS number: 07.05.Pj

Large mitochondrial DNA deletion in an infant with addison disease

BACKGROUND

Mitochondrial diseases are a group of disorders caused by mutations in nuclear DNA or mitochondrial DNA, usually involving multiple organ systems. Primary adrenal insufficiency due to mitochondrial disease is extremely infrequent and has been reported in association with mitochondrial DNA deletion syndromes such as Kearns-Sayre syndrome.

AIM

To report a 3-year-old boy with Addison disease, congenital glaucoma, chronic pancreatitis, and mitochondrial myopathy due to large mitochondrial DNA deletion.

METHOD

Molecular analysis of mitochondrial DNA samples obtained from peripheral blood, oral mucosa, and muscle tissue.

RESULTS

A novel large mitochondrial DNA deletion of 7,372bp was identified involving almost all genes on the big arch of mtDNA.

CONCLUSIONS

This case reaffirms the association of adrenal insufficiency and mitochondrial DNA deletions and presents new evidence that glaucoma is another manifestation of mitochondrial diseases. Due to the genetic and clinical heterogeneity of mitochondrial disorders, molecular analysis is crucial to confirm diagnosis and to allow accurate genetic counseling.

[Cochlear implants in elderly: performance outcomes in the long term]

OBJECTIVES

To study and compare the evolving capacities of speech discrimination with cochlear implants in older patients compared to patients implanted at a younger age.

METHODOLOGY

A retrospective study comparing a group of 52 patients aged over 65 with a control group of 58 patients aged between 30 and 50 years, followed for 5 years after implantation. We analyzed and compared the evolution of speech discrimination in silence (disyllabic words, sentences) and noise (sentences, S/N ratio: +10 dB) after implantation.

RESULTS

In the group of elderly patients, the speech discrimination in silence remains stable over time (for disyllabic words, score at 6 months: 72.8 +/- 20.2%; score at 5 years: 73.7% +/- 19.7). Discrimination in noise tends to improve (mean score at 6 months: 70.5% +/- 21.5; score at 5 years: 76.9% +/- 16.9). The results obtained are in silence are comparable to the results of the group of patients aged between 30 and 50. In noise, their performance remains lower than the control group (mean differences between scores: -10.8; confidence interval at 95%: -17.9, -5.3).

CONCLUSION

The cochlear implant is effective over the long term in elderly patients, for speech discrimination in quiet and in noise. In silence, their performance is comparable to younger patients with implants.

Is High-Pressure Air Injection (HPAI) Simply a Flue-Gas Flood?

Abstract

High-pressure air injection (HPAI) is an enhanced oil recovery (EOR) process in which compressed air is injected into a deep, light-oil reservoir, with the expectation that the oxygen in the injected air will react with a fraction of the reservoir oil at an elevated temperature to produce carbon dioxide.

Over the years, HPAI has been considered a simple flue-gas flood, giving little credit to the thermal drive as a production mechanism. The truth is that, although early production during a HPAI process is mainly due to re-pressurization and gasflood effects, once a pore volume of air has been injected the combustion front becomes the main driving mechanism.

This paper presents laboratory and field evidence of the presence of a thermal front during HPAI operations, and of its beneficial impact on oil production. Production and injection data from the Buffalo Field, which comprises the oldest HPAI projects currently in operation, were gathered and analyzed for this purpose. These HPAI projects definitely do not behave as simple immiscible gasfloods.

This study shows that a HPAI project has the potential to yield higher recoveries than a simple immiscible gasflood. Furthermore, it gives recommendations about how to operate the process to take advantage of its full capabilities.

Introduction

High-Pressure Air Injection (HPAI) is an emerging technology for the enhanced oil recovery (EOR) of light oils that has proven to be a valuable process, especially in deep, thin, low-permeability reservoirs(1-7).

A number of successful high-pressure air injection projects in light oil reservoirs have been documented in the literature(8-10). Most of these projects have been operating for many years, attesting to their technical and economic success.

The improvement in recovery of light oil by HPAI involves a combination of complex processes, each contributing to the overall recovery. These processes include flue gas sweeping, field re-pressurization, oil swelling, viscosity reduction, stripping of the lighter components of the oil, and thermal effects. Early production during the HPAI process is related to re-pressurization and gasflood effects; hence, the influence of the thermal zone is secondary during the early life of an injector. The oil displaced directly by the thermal front will depend on the effectiveness of the generated flue gas on oil displacement from outside the thermal region.

The Challenge of Predicting Field Performance of Air Injection Projects Based on Laboratory and Numerical Modelling

Abstract

Air injection-based enhanced oil recovery processes are receiving increased interest because of their high recovery potentials and applicability to a wide range of reservoirs. However, most operators require a certain level of confidence in the potential recoveries from these (or any) processes prior to committing resources. This paper addresses the challenges of predicting field performance of air injection projects using laboratory and numerical modelling.

Laboratory testing, including combustion tube tests, ramped temperature oxidation and accelerating rate calorimeters can supply data for simple analytical models, as well as providing important insights into potential recovery-related behaviours. These tests are less suited to providing detailed kinetic data for direct and reliable use in numerical simulators. Indeed, the oxidation reactions are sufficiently complex that, regardless of how powerful the thermal reservoir simulator is, its predicting capability will strongly depend on the engineer's understanding of the process and ability to model the most relevant oxidation behaviours of the particular oil reservoir under study.

It is proposed that the optimum design cycle for air injection-based processes is to perform laboratory testing that would aid in the understanding of the process and in the design and monitoring of a pilot-scale field operation. Analytical models and simplified, semi-quantitative reservoir simulation models would be employed at this stage. If this evaluation stage is successful, a pilot operation would be initiated and the data gathered during the pilot, as well as laboratory oil property and compositional data, would then be used to history match and tune a model for predictions of the full field operation.

Introduction

This paper has been written in response to questions which many reservoir engineers express when evaluating the feasibility of air injection as an enhanced oil recovery process for their fields. Questions such as, "What laboratory tests are available? What type of data is provided by each test? How do we use the lab results to predict field performance?" are not uncommon, and, although there are not straightforward answers, a discussion on the usefulness of different lab tests is presented to clarify some of the related concepts.

This document has also been written in response to the concerns and comments expressed by many reservoir simulation practitioners when matching combustion tube tests and other supporting oxidation experiments, and trying to predict field performance of an air injection project based on kinetic parameters obtained from such tests. Questions such as, "How do we use the lab data in the reservoir simulator? What are the limitations of thermal reservoir simulation when predicting field performance of air injection projects?" are addressed to provide additional feedback and promote further discussion.

Additionally, this manuscript describes some of the combustion behaviours which have been observed by the In Situ Combustion Research Group (ISCRG) at the University of Calgary while performing combustion tube tests and supporting cracking/oxidation experiments, and gives some recommendations to improve the modelling of the combustion process using thermal reservoir simulators.

A comparison of the performance of digital mammography systems

An objective analysis of image quality parameters was performed for six digital mammography systems. The presampled modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) for the systems were determined at different doses, for 28 kVp with a Mo/Mo or W/Al target/filter combination and 2 mm of additional aluminium filtration. The flat-panel units have higher MTF and DQE in the mid to high frequency range than standard CR systems. The highest DQE, over the whole dose range, is for the slit-scanning direct photon counting system. Dual-side read CR can overcome the inherent x-ray absorption and signal collection limitations of standard CR mammography, improving the low-frequency DQE by 40%, to the same level as full-field systems, but it does not improve the poor spatial resolution of phosphor.

Real-time access of magnetoencephalographic / -cardiographic data: technical realization & application to online fetal heart rate recording

Current standard magnetoencephalographic and -cardiographic systems do not allow real-time access to the measured data. We developed a software solution for real-time access and used it to create an online fetal heart rate monitor.

A comparison of the imaging characteristics of the new Kodak Hyper Speed G film with the current T-MAT G/RA film and the CR 9000 system

Three standard radiation qualities (RQA 3, RQA 5 and RQA 9) and two screens, Kodak Lanex Regular and Insight Skeletal, were used to compare the imaging performance and dose requirements of the new Kodak Hyper Speed G and the current Kodak T-MAT G/RA medical x-ray films. The noise equivalent quanta (NEQ) and detective quantum efficiencies (DQE) of the four screen-film combinations were measured at three gross optical densities and compared with the characteristics for the Kodak CR 9000 system with GP (general purpose) and HR (high resolution) phosphor plates. The new Hyper Speed G film has double the intrinsic sensitivity of the T-MAT G/RA film and a higher contrast in the high optical density range for comparable exposure latitude. By providing both high sensitivity and high spatial resolution, the new film significantly improves the compromise between dose and image quality. As expected, the new film has a higher noise level and a lower signal-to-noise ratio than the standard film, although in the high frequency range this is compensated for by a better resolution, giving better DQE results--especially at high optical density. Both screen-film systems outperform the phosphor plates in terms of MTF and DQE for standard imaging conditions (Regular screen at RQA 5 and RQA 9 beam qualities). At low energy (RQA 3), the CR system has a comparable low-frequency DQE to screen-film systems when used with a fine screen at low and middle optical densities, and a superior low-frequency DQE at high optical density.

A comparison of the performance of modern screen-film and digital mammography systems

This work compares the detector performance and image quality of the new Kodak Min-R EV mammography screen-film system with the Fuji CR Profect detector and with other current mammography screen-film systems from Agfa, Fuji and Kodak. Basic image quality parameters (MTF, NPS, NEQ and DQE) were evaluated for a 28 kV Mo/Mo (HVL = 0.646 mm Al) beam using different mAs exposure settings. Compared with other screen-film systems, the new Kodak Min-R EV detector has the highest contrast and a low intrinsic noise level, giving better NEQ and DQE results, especially at high optical density. Thus, the properties of the new mammography film approach those of a fine mammography detector, especially at low frequency range. Screen-film systems provide the best resolution. The presampling MTF of the digital detector has a value of 15% at the Nyquist frequency and, due to the spread size of the laser beam, the use of a smaller pixel size would not permit a significant improvement of the detector resolution. The dual collection reading technology increases significantly the low frequency DQE of the Fuji CR system that can at present compete with the most efficient mammography screen-film systems.

Performance comparison of an active matrix flat panel imager, computed radiography system, and a screen-film system at four standard radiation qualities

Four standard radiation qualities (from RQA 3 to RQA 9) were used to compare the imaging performance of a computed radiography (CR) system (general purpose and high resolution phosphor plates of a Kodak CR 9000 system), a selenium-based direct flat panel detector (Kodak Direct View DR 9000), and a conventional screen-film system (Kodak T-MAT L/RA film with a 3M Trimax Regular screen of speed 400) in conventional radiography. Reference exposure levels were chosen according to the manufacturer's recommendations to be representative of clinical practice (exposure index of 1700 for digital systems and a film optical density of 1.4). With the exception of the RQA 3 beam quality, the exposure levels needed to produce a mean digital signal of 1700 were higher than those needed to obtain a mean film optical density of 1.4. In spite of intense developments in the field of digital detectors, screen-film systems are still very efficient detectors for most of the beam qualities used in radiology. An important outcome of this study is the behavior of the detective quantum efficiency of the digital radiography (DR) system as a function of beam energy. The practice of users to increase beam energy when switching from a screen-film system to a CR system, in order to improve the compromise between patient dose and image quality, might not be appropriate when switching from screen-film to selenium-based DR systems.

A strategy to qualify the performance of radiographic monitors

The purpose of this work was to compare standard desktop display systems with dedicated medical display systems. The set of image tests proposed by the American Association of Physicists in Medicine (AAPM TG18) was used to assess a Philips 107S desktop display system and a Siemens medical display. Three observers performed the subjective assessment, in a non-concerted manner. The objective assessment was performed using a CCD camera according to the AAPM TG18 procedure. The results clearly demonstrate the inadequacy of standard desktop display systems in the framework of diagnostic radiology. Moreover, a good correlation between the subjective and objective assessment methods was obtained.

End-to-end performance measurement of Internet based medical applications

We present a method to obtain an end-to-end characterization of the performance of an application over a network. This method is not dependent on any specific application or type of network. The method requires characterization of network parameters, such as latency and packet loss, between the expected server or client endpoints, as well as characterization of the application's constraints on these parameters. A subjective metric is presented that integrates these characterizations and that operates over a wide range of applications and networks. We believe that this method may be of wide applicability as research and educational applications increasingly make use of computation and data servers that are distributed over the Internet.

Patterns of avian seroprevalence to western equine encephalomyelitis and Saint Louis encephalitis viruses in California, USA

Temporal and spatial changes in the enzootic activity of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses were monitored at representative wetland study sites in the Coachella, San Joaquin, and Sacramento valleys of California from 1996 to 1998 using three methods: (1) virus isolation from pools of 50 host-seeking Culex tarsalis Coquillett females, (2) seroconversions in flocks of 10 sentinel chickens, and (3) seroprevalence in wild birds collected by mist nets and grain baited traps. Overall, 74 WEE and one SLE isolates were obtained from 222,455 Cx. tarsalis females tested in 4,988 pools. In addition, 133 and 40 seroconversions were detected in 28 chicken flocks, and 143 and 27 of 20,192 sera tested from 149 species of wild birds were positive for antibodies to WEE and SLE, respectively. WEE was active in all three valleys, whereas SLE only was detected in Coachella Valley. Seroconversions in sentinel chickens provided the most sensitive indication of enzootic activity and were correlated with seroprevalence rates in wild birds. Avian seroprevalence rates did not provide an early warning of pending enzootic activity in chickens, because positive sera from after hatching year birds collected during spring most probably were the result of infections acquired during the previous season. Few seroconversions were detected among banded recaptured birds collected during spring and early summer. Age and resident status, but not sex, were significant risk factors for wild bird infection, with the highest seroprevalence rates among after hatching year individuals of permanent resident species. Migrants (with the exception of mourning doves) and winter resident species rarely were positive. House finches, house sparrows, Gambel's quail, California quail, common ground doves, and mourning doves were most frequently positive for antibodies. The initial detection of enzootic activity each summer coincided closely with the appearance of hatching year birds of these species in our study areas, perhaps indicating their role in virus amplification. Bird species most frequently positive roosted or nested in elevated upland vegetation, sites where Cx. tarsalis host-seeking females hunt most frequently. These serosurveys provided important background information for planned host competence and chronic infection studies.

Characterization of the maitotoxin-induced calcium influx pathway from human skin fibroblasts

Maitotoxin (MTX), a water-soluble polyether obtained from the marine dinoflagellate Gambierdiscus toxicus increased intracellular calcium in a concentration-dependent manner in fibroblasts obtained from human skin. The effect of this toxin was both saturable and of high affinity, showing an apparent half activation constant of 450 fM. The toxin did not release intracellular calcium storage compartments nor did the release of these compartments with thapsigargin or ionomycin affect the toxin response. The toxin effect was reduced significantly by pre-incubating the cells with 0.1% trypsin for 30 min, strongly suggesting that the toxin receptor is a plasmalemmal protein. The effect of MTX was partially inhibited by diphenoxylate.

Cloning, expression and toxicity of a mosquitocidal toxin gene of Bacillus thuringiensis subsp. medellin

Bacillus thuringiensis (Bt) subsp. medellin (Btmed) produces parasporal crystalline inclusions which are toxic to mosquito larvae. It has been shown that the inclusions of this bacterium contain mainly proteins of 94, 68 and 28-30 kDa. EcoRI partially digested total DNA of Btmed was cloned by using the Lambda Zap II cloning kit. Recombinant plaques were screened with a mouse polyclonal antibody raised against the 94 kDa crystal protein of Btmed. One of the positive plaques was selected, and by in vivo excision, a recombinant pBluescript SK(-) was obtained. The gene encoding the 94 kDa toxin of Btmed DNA was cloned in a 4.4 kb DNA fragment. Btmed DNA was then subcloned as a EcoRI/EcoRI fragment into the shuttle vector pBU4 producing the recombinant plasmid pBTM3 and used to transform by electroporation Bt subsp. israelensis (Bti) crystal negative strain 4Q2-81. Toxicity to mosquito larvae was estimated by using first instar laboratory reared Aedes aegypti, and Culex quinquefasciatus larvae challenged with whole crystals. Toxicity results indicate that the purified inclusions from the recombinant Bti strain were toxic to all mosquito species tested, although the toxicity was not as high as the one produced by the crystal of the Btmed wild type strain. Polyacrylamide gel electrophoresis indicate that the inclusions produced by the recombinant strain Bti (pBTM3) were mainly composed of the 94 kDa protein of Btmed, as it was determined by Western blot.