Assessment of radicular dentin permeability after irradiation with CO2 laser and endodontic irrigation treatments with thermal imaging.

Previous studies have demonstrated that the permeability changes due to the surface modification of dentin can be quantified via thermal imaging during dehydration. The CO2 laser has been shown to remove the smear layer and disinfect root canals. Moreover, thermal modification via CO2 laser irradiation can be used to convert dentin into a highly mineralized enamel-like mineral. The purpose of this study is to evaluate the radicular dentin surface modification after CO2 laser irradiation by measuring the permeability with thermal imaging. Human molar specimens (n=12) were sectioned into 4 axial walls of the pulp chamber and treated with either 10% NaClO for 1 minute, 5% EDTA for 1 minute, CO2 laser or none. The CO2 laser was operated at 9.4 µm with a pulse duration of 26 µs, pulse repetition rate of 300 Hz and a fluence of 13 J/cm2. The samples were dehydrated using an air spray for 60 seconds and imaged using a thermal camera. The resulting surface morphological changes were assessed using 3D digital microscopy. The images from digital microscopy confirmed melting of the mineral phase of dentin. The area enclosed by the time-temperature curve during dehydration, ΔQ, measured with thermal imaging increased significantly with treatments with EDTA and the CO2 laser (P<0.05). These results indicate that the surface modification due to CO2 laser treatment increases permeability of radicular dentin.

Activity assessment of root caries lesions with thermal and near-IR imaging methods.

The purpose of this study was to evaluate thermal and near-infrared (NIR) reflectance imaging methods for the assessment of the activity of root caries lesions. In addition, changes in the lesion structure were monitored with polarization sensitive optical coherence tomography (PS-OCT). Artificial bovine and natural root caries lesions were imaged with PS-OCT, and their dehydration rate was measured with thermal and NIR cameras. The lesion activity of the natural root caries samples was also assessed by two clinicians by conventional means according to ICDAS II guidelines. The thickness of the highly mineralized transparent surface layer measured using PS-OCT increased and the area enclosed by the time-temperature curve, ΔQ, measured with thermal imaging decreased significantly with longer periods of remineralization in simulated dentin lesions, but the NIR reflectance intensity differences, ΔI, failed to show any significant relationship with the degree of remineralization. The PS-OCT algorithm for the automated assessment of remineralization successfully detected the highly mineralized surface layer on both natural and simulated lesions. Thermal imaging provided the most accurate diagnosis of root caries lesion activity. These results demonstrate that thermal imaging and PS-OCT may be ideally suited for the nondestructive root caries lesion activity during a clinical examination.

Infrared Methods for Assessment of the Activity of Natural Enamel Caries Lesions.

New diagnostic methods are needed for the accurate assessment of caries lesion activity to establish the need for surgical treatment. Detection of the highly mineralized surface layer that forms near the surface of the lesions as a result of remineralization is important for diagnosis of the lesion activity. Previous studies have demonstrated that novel imaging methods can be used to detect remineralization of artificial enamel caries lesions. In this paper, the activity of natural enamel caries lesions was assessed in-vitro via detection of the surface layer with PS-OCT and dehydration rate measurements with NIR reflectance and thermal imaging modalities. An automated approach for detecting the surface layer with PS-OCT yielded high sensitivity (= 0.79) and high specificity (= 0.93) with moderate correlation (R2 = 0.5920) with histology. Significant differences in dehydration rate measurements were found between the active and the arrested lesions using both the NIR reflectance and thermal imaging modalities. These results demonstrate that these novel imaging methods are ideally suited for nondestructive, noninvasive and quantitative measurement of lesion activity during a single clinical examination in real-time.

Assessment of simulated lesions on primary teeth with near-infrared imaging.

Previous studies have demonstrated that the structural changes on enamel due to demineralization and remineralization can be exploited through optical imaging methods such as QLF, thermal and NIR imaging. The purpose of this study is to investigate whether PS-OCT and NIR reflectance imaging can be utilized to assess lesion structure in artificial enamel lesions on the smooth surfaces of primary teeth exposed to fluoride. The smooth coronal surfaces of primary teeth (n=25) were divided into 4 windows: sound, demineralization, demineralization with remineralization and APF with demineralization. Windows were treated with either acidulated phosphate fluoride (APF) for 1 minute, a demineralization solution for 4 days, and/or an acidic remineralization solution for 12 days. The samples were imaged using PS-OCT, QLF and NIR reflectance at 1400-1700 nm wavelengths. This study demonstrated that both PS-OCT and NIR reflectance imaging were suitable for assessing lesion structure in the smooth surfaces of primary dentition.

Assessment of remineralized dentin lesions with thermal and near-infrared reflectance imaging.

Accurate detection and measurement of the highly mineralized surface layer that forms on caries lesions is important for the diagnosis of lesion activity. Previous studies have demonstrated that optical imaging methods can be used to measure the degree of remineralization on enamel lesions. The purpose of this study was to determine if thermal and near-IR reflectance imaging could be used to assess the remineralization process in simulated dentin lesions. Artificial bovine (n=15) dentin lesions were prepared by immersion in a demineralization solution for 24 hours and they were subsequently placed in an acidic remineralization solution for up to 12 days. The samples were dehydrated using an air spray for 30 seconds and imaged using thermal and InGaAs cameras. The area enclosed by the time-temperature curve, ΔQ, from thermal imaging decreased significantly with longer periods of remineralization. However, near-IR reflectance intensity differences, ΔI, before and after dehydration failed to show any significant relationship with the degree of remineralization. This study shows that thermal imaging can be used for the assessment of the remineralization of dentin lesions.

Assessment of remineralization via measurement of dehydration rates with thermal and near-IR reflectance imaging.

OBJECTIVES: Previous studies have demonstrated that the optical changes due to the loss of water from porous lesions can be exploited to assess lesion severity with QLF, thermal and near-IR imaging. Since arrested lesions are less permeable to water due to the highly mineralized surface layer, changes in the rate of water loss can be related to changes in lesion structure. The purpose of this study was to investigate whether the rate of water loss correlates with the degree of remineralization and whether that rate can be measured using thermal and near-IR reflectance imaging. METHODS: Artificial bovine enamel lesions (n=30) were prepared by immersion in a demineralization solution for either 8 and 24 h and they were subsequently placed in an acidic remineralization solution for different periods. The samples were dehydrated using an air spray for 30s and surfaces were imaged using a thermal camera and an InGaAs camera at 1300-1700 nm wavelengths. RESULTS: The area enclosed by the time-temperature curve, ΔQ, from thermal imaging showed significant differences (P<0.05) between the lesion window and other windows. Near-IR reflectance intensity differences, ΔI, before and after dehydration decreased with longer periods of remineralization. Only near-IR reflectance imaging was capable of detecting significant differences (P<0.05) between the different periods of remineralization. CONCLUSIONS: This study demonstrated that both thermal and near-IR reflectance imaging were suitable for the detection of remineralization in simulated caries lesions and near-IR wavelengths longer than 1400 nm are well suited for the assessment of remineralization.

Assessment of remineralization in simulated enamel lesions via dehydration with near-IR reflectance imaging.

Previous studies have demonstrated that near-IR imaging can be used to nondestructively monitor the severity of enamel lesions. Arrested lesions typically have a highly mineralized surface layer that reduces permeability and limits diffusion into the lesion. The purpose of this study was to investigate whether the rate of water loss correlates with the degree of remineralization using near-IR reflectance imaging. Artificial bovine (n=15) enamel lesions were prepared by immersion in a demineralization solution for 24 hours and they were subsequently placed in an acidic remineralization solution for different periods. The samples were dehydrated using an air spray for 30 seconds and surfaces were imaged using an InGaAs camera at 1300-1700 nm wavelengths. Near-IR reflectance intensity differences before and after dehydration decreased with longer periods of remineralization. This study demonstrated that near-IR reflectance imaging was suitable for the detection of remineralization in simulated caries lesions and near-IR wavelengths longer than 1400 nm are well suited for the assessment of remineralization.

Automated assessment of the remineralization of artificial enamel lesions with polarization-sensitive optical coherence tomography.

Accurate measurement of the highly mineralized transparent surface layer that forms on caries lesions is important for diagnosis of the lesion activity because chemical intervention can slow or reverse the caries process via remineralization. Previous in-vitro and in-vivo studies have demonstrated that polarization-sensitive optical coherence tomography (PS-OCT) can nondestructively image the subsurface lesion structure and the highly mineralized transparent surface zone of caries lesions. The purpose of this study was to develop an approach to automatically process 3-dimensional PS-OCT images and to accurately assess the remineralization process in simulated enamel lesions. Artificial enamel lesions were prepared on twenty bovine enamel blocks using two models to produce varying degree of demineralization and remineralization. The thickness of the transparent surface layer and the integrated reflectivity of the subsurface lesion were measured using PS-OCT. The automated transparent surface layer detection algorithm was able to successfully detect the transparent surface layers with high sensitivity ( = 0.92) and high specificity ( = 0.97). The estimated thickness of the transparent surface layer showed a strong correlation with polarized light microscopy (PLM) measurements of all regions (R(2) = 0.90). The integrated reflectivity, ΔR, and the integrated mineral loss, ΔZ, showed a moderate correlation (R(2) = 0.32). This study demonstrates that PS-OCT can automatically measure the changes in artificial enamel lesion structure and severity upon exposure to remineralization solutions.

Traumatic childhood experiences in the 21st century: broadening and building on the ACE studies with data from the National Child Traumatic Stress Network.

The study objectives were to (a) examine the association between total number of trauma types experienced and child/adolescent behavioral problems and (b) determine whether the number of trauma types experienced predicted youth behavioral problems above and beyond demographic characteristics, using a diverse set of 20 types of trauma. Data came from the National Child Traumatic Stress Network's (NCTSN) Core Data Set (CDS), which includes youth assessed and treated for trauma across the United States. Participants who experienced at least one type of trauma were included in the sample (N = 11,028; age = 1½-18 years; 52.3% girls). Random effects models were used to account for possible intraclass correlations given treatment services were provided at different NCTSN centers. Logistic regression analyses were used to investigate associations among demographic characteristics, trauma, and emotional and behavioral problems as measured by the Child Behavior Checklist (CBCL). Significant dose-response relations were found between total number of trauma types and behavior problems for all CBCL scales, except Sleep, one of the subscales only administered to 1½- to 5-year-olds. Thus, each additional trauma type endorsed significantly increased the odds for scoring above the clinical threshold. Results provide further evidence of strong associations between diverse traumatic childhood experiences and a diverse range of behavior problems, and underscore the need for a trauma-informed public health and social welfare approach to prevention, risk reduction, and early intervention for traumatized youth.

Non-destructive clinical assessment of occlusal caries lesions using near-IR imaging methods.

OBJECTIVE: Enamel is highly transparent in the near-IR (NIR) at wavelengths near 1,300 nm, and stains are not visible. The purpose of this study was to use NIR transillumination and optical coherence tomography (OCT) to estimate the severity of caries lesions on occlusal surfaces both in vivo and on extracted teeth. METHODS: Extracted molars with suspected occlusal lesions were examined with OCT and polarization sensitive OCT (PS-OCT), and subsequently sectioned and examined with polarized light microscopy (PLM) and transverse microradiography (TMR). Teeth in test subjects with occlusal caries lesions that were not cavitated or visible on radiographs were examined using NIR transillumination at 1,310 nm using a custom built probe attached to an indium gallium arsenide (InGaAs) camera and a linear OCT scanner. After imaging, cavities were prepared using dye staining to guide caries removal and physical impressions of the cavities were taken. RESULTS: The lesion severity determined from OCT and PS-OCT scans in vitro correlated with the depth determined using PLM and TMR. Occlusal caries lesions appeared in NIR images with high contrast in vivo. OCT scans showed that most of the lesions penetrated to dentin and spread laterally below the sound enamel. CONCLUSION: This study demonstrates that both NIR transillumination and OCT are promising new methods for the clinical diagnosis of occlusal caries.

Taxonometric applications in radiotherapy incident analysis.

Recent publications in both the scientific and the popular press have highlighted the risks to which patients expose themselves when entering a healthcare system. Patient safety issues are forcing us to, not only acknowledge that incidents do occur, but also actively develop the means for assessing and managing the risks of such incidents. To do this, we ideally need to know the probability of an incident's occurrence, the consequences or severity for the patient should it occur, and the basic causes of the incident. A structured approach to the description of failure modes is helpful in terms of communication, avoidance of ambiguity, and, ultimately, decision making for resource allocation. In this report, several classification schemes or taxonomies for use in risk assessment and management are discussed. In particular, a recently developed approach that reflects the activity domains through which the patient passes and that can be used as a basis for quantifying incident severity is described. The estimation of incident severity, which is based on the concept of the equivalent uniform dose, is presented in some detail. We conclude with a brief discussion on the use of a defined basic-causes table and how adding such a table to the reports of incidents can facilitate the allocation of resources.

Costs associated with diffuse large B-cell lymphoma patient treatment in a Canadian integrated cancer care center.

OBJECTIVE: The objective of this study was to provide a detailed comparative microcosting analysis for two cancer treatment pathways to contribute evidence for resource allocation and operational decision-making in a Canadian cancer care context. METHODS: We estimated direct medical costs (in 2004 CAN$) of the entire pathway of care for diffuse large B-cell lymphoma (DLBCL) patients in a large Canadian cancer treatment center. Patient samples were defined as those who received R-CHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone; n = 85) or CHOP (i.e., without rituximab; n = 86) as first-line treatment. All subsequent treatments including palliative care for these patient samples were assessed. Hospitalization costs and unit costs of medical resources were collected from integrated medical organizations. Individual patient resource consumption was assessed via medical chart review. RESULTS: For first-line treatment, drug cost was the largest contributor to total cost, followed by hospitalization cost. Rituximab was the largest contributor to mean cost differences between R-CHOP and CHOP treatments. For treatments subsequent to first-line treatment, no significant cost differences were found. Hospitalization and transplantation costs were the two largest constituents of total costs subsequent to first-line treatment, followed by drug cost. Patients with advanced stage disease cost significantly more than patients with limited stage disease. CONCLUSION: This is the first detailed microcosting study that has employed consistent local data to estimate total medical costs for DLBCL patients in Canada. This information is useful for resource allocation planning and operational decisions, because it provides more substantive, relevant evidence as compared to aggregated, literature or extrapolated information.

Probabilistic fault tree analysis of a radiation treatment system.

Inappropriate administration of radiation for cancer treatment can result in severe consequences such as premature death or appreciably impaired quality of life. There has been little study of vulnerable treatment process components and their contribution to the risk of radiation treatment (RT). In this article, we describe the application of probabilistic fault tree methods to assess the probability of radiation misadministration to patients at a large cancer treatment center. We conducted a systematic analysis of the RT process that identified four process domains: Assessment, Preparation, Treatment, and Follow-up. For the Preparation domain, we analyzed possible incident scenarios via fault trees. For each task, we also identified existing quality control measures. To populate the fault trees we used subjective probabilities from experts and compared results with incident report data. Both the fault tree and the incident report analysis revealed simulation tasks to be most prone to incidents, and the treatment prescription task to be least prone to incidents. The probability of a Preparation domain incident was estimated to be in the range of 0.1-0.7% based on incident reports, which is comparable to the mean value of 0.4% from the fault tree analysis using probabilities from the expert elicitation exercise. In conclusion, an analysis of part of the RT system using a fault tree populated with subjective probabilities from experts was useful in identifying vulnerable components of the system, and provided quantitative data for risk management.

Using a survey of incident reporting and learning practices to improve organisational learning at a cancer care centre.

OBJECTIVES: To motivate improvements in an organisational system by measuring staff perceptions of the organisation's ability to learn from incidents and by analysing their personal experience of incidents. METHODS: Respondents were questioned on the components of the incident learning system from both a personal and an organisational perspective. The respondents (n = 125) were radiotherapists, nurses, dosimetrists, doctors, and other staff at a major academic cancer centre. Responses were analysed in terms of per cent positive responses and response rate, differences between "frontline" and "support" staff, and the respondent's experience with incidents. RESULTS: Respondents were more familiar with and more positive about incident identification and reporting--the first two stages of incident learning. Their overall perception of incident learning was most influenced by the investigation and learning components of the system. Respondents in frontline positions were more positive than those in support positions about responding to, identifying and reporting incidents. Respondents reported having experienced a mean of three incidents per year, of which two were reported and two out of three of the reported incidents were investigated, and a median of two incidents being experienced and reported, but none investigated. Most incidents experienced were not captured by the organisation's existing incident reporting system. CONCLUSION: The survey tool was effective in measuring the ability of the organisation to learn from incidents. Implications of the survey results for improving organisational learning are discussed.

Risk analysis in radiation treatment: application of a new taxonomic structure.

BACKGROUND AND PURPOSE: Radiation treatment (RT) for cancer is susceptible to clinical incidents resulting from human errors and equipment failures. A systematic approach to collecting and processing incidents is required to manage patient risks. We describe the application of a new taxonomic structure for RT that supports risk analysis and organizational learning. MATERIALS AND METHODS: A systematic analysis of the RT process identified five process domains. Within each domain we defined incident type groups. We then constructed a database reflecting this taxonomic structure and populated it with incidents from publicly available sources. Querying this database provides insights into the nature and relative frequency of incidents in RT. RESULTS: There are relatively few reports of incidents in the Prescription domain compared with the Preparation and Treatment domains. There are also fewer reports of systematic and infrastructure incidents in comparison to sporadic and process incidents. Infrastructure incidents are mainly systematic in nature, while process incidents are more likely to be sporadic. CONCLUSIONS: The lack of a standard, systems-oriented framework for incident reporting makes it difficult to learn from existing incident report sources. A clear understanding of the potential consequences and relationships between different incident types will guide incident reporting, resource allocation, and risk management efforts.

Describing the longitudinal course of major depression using Markov models: data integration across three national surveys.

BACKGROUND: Most epidemiological studies of major depression report period prevalence estimates. These are of limited utility in characterizing the longitudinal epidemiology of this condition. Markov models provide a methodological framework for increasing the utility of epidemiological data. Markov models relating incidence and recovery to major depression prevalence have been described in a series of prior papers. In this paper, the models are extended to describe the longitudinal course of the disorder. METHODS: Data from three national surveys conducted by the Canadian national statistical agency (Statistics Canada) were used in this analysis. These data were integrated using a Markov model. Incidence, recurrence and recovery were represented as weekly transition probabilities. Model parameters were calibrated to the survey estimates. RESULTS: The population was divided into three categories: low, moderate and high recurrence groups. The size of each category was approximated using lifetime data from a study using the WHO Mental Health Composite International Diagnostic Interview (WMH-CIDI). Consistent with previous work, transition probabilities reflecting recovery were high in the initial weeks of the episodes, and declined by a fixed proportion with each passing week. CONCLUSION: Markov models provide a framework for integrating psychiatric epidemiological data. Previous studies have illustrated the utility of Markov models for decomposing prevalence into its various determinants: incidence, recovery and mortality. This study extends the Markov approach by distinguishing several recurrence categories.

Risk assessment for inherited susceptibility to cancer: a review of the psychosocial and ethical dimensions.

The objective of this study was to conduct a broad-based systematic review of social, ethical, and legal considerations associated with genetic cancer risk assessment technologies (CaRATs). This paper focuses on psychosocial and ethical issues. Search results were limited to papers published in English, French, or German from January, 1990, to May, 2003. A quality assessment tool was developed and applied to retrieved papers. Application of the quality assessment tool resulted in 77 of 247 qualitative and quantitative primary research papers being reviewed and synthesized. A broad range of issues were addressed and grouped into content areas. Despite a large literature addressing psychosocial and ethical issues associated with CaRATs, many existing studies are not adequate to inform decision-makers and stakeholders. Careful policy analysis, as in some of the economic analyses reviewed here, is important to bridge this gap.

Epidemiological theory, decision theory and mental health services research.

BACKGROUND: Mathematical models describing the epidemiology of major depression are potentially useful for epidemiological analyses, as decision support tools and in economic analyses. The objective of this project was to develop a Markov model based on epidemiological theory that may be useful for decision analysis and health services research. METHODS: Longitudinal data from a Canadian national survey, the National Population Health Survey (NPHS), were used. The NPHS has collected longitudinal data on a cohort of 17,262 subjects since 1994. The analysis employed a Markov tunnel in order to model the dependence of recovery probabilities on episode duration. RESULTS: Episode incidence ranged between 6.2 % per year in women under 35 to 0.26 % in men over the age of 65.A greater proportion of subjects over 35 years old reported episodes lasting more than 26 weeks. The probability of recovery declined with increasing episode duration, independently of sex. Under steady-state assumptions, a Markov model integrating these parameters predicted a point prevalence of approximately 2% in women and 1% in men under the age of 55. In older age groups, the predicted point prevalence declined in both sexes. CONCLUSIONS: These models support the hypothesis that sex differences in major depression prevalence are due primarily to differences in incidence rather than episode length. These results also indicate that there is no meaningful "central tendency" describing the distribution of episode length in major depression episode. Estimates of mean episode duration represent an intermixing of frequent brief episodes with infrequent protracted episodes. This finding may have important policy implications.

Towards a dynamic description of major depression epidemiology.

AIMS: The substantial impact of major depression on population health is widely acknowledged. To date, health system responses to this condition have been largely shaped by observational findings. In the future, health policy decisions will benefit from an increasingly integrated and dynamic understanding of the epidemiology of this condition. Policy decisions can also be supported by the development of decision-support tools that can simulate the impact of alternative policy decisions on population health. Markov models are useful both in epidemiological modelling and in decision analysis. METHODS: In this project, a Markov model describing major depression epidemiology was developed. The model employed a Markov Tunnel in order to depict the dependence of recovery probabilities on episode duration. Transition probabilities, including incidence, recovery and mortality were estimated from Canadian national survey data. RESULTS: Episode incidence was approximately 3% per year. Recovery rates declined exponentially over time. The model predicted point prevalence at slightly less than 1%, agreeing closely with observed prevalence data. CONCLUSIONS: Epidemiological models describing the dynamic relationships between major depression incidence, prevalence, recovery and mortality can help to integrate available epidemiological data. Such models offer an attractive option for support of health policy decisions.