Exposure study on UV-induced degradation of PTFE and ceramic optical diffusers.

We report on a study of the ultraviolet (UV)-induced degradation on optical grade polytetrafluoroethylene (PTFE) and ceramic diffuser samples. Long-term UV exposure may significantly alter the reflectance and lead to an error in the calibration of optical instruments. A large integrating sphere was used to irradiate the samples for 334.7 days at an irradiance level of 194.9 W/m2. Samples were qualified and measured for reflectance factor, bidirectional reflectance distribution function, and fluorescence, before and after the exposure, and at 12-week intervals during the exposure. This study revealed significant differences between the aging behavior of ceramic and PTFE samples.

Fabrication of a multilayer tissue-mimicking phantom with tunable optical properties to simulate vascular oxygenation and perfusion for optical imaging technology.

Vast research has been carried out to fabricate tissue-mimicking phantoms, due to their convenient use and ease of storage, to assess and validate the performance of optical imaging devices. However, to the best of our knowledge, there has been little research on the use of multilayer tissue phantoms for optical imaging technology, although their structure is closer to that of real skin tissue. In this work, we design, fabricate, and characterize multilayer tissue-mimicking phantoms, with a morphological mouse ear blood vessel, that contain an epidermis, a dermis, and a hypodermis. Each tissue-mimicking phantom layer is characterized individually to match specific skin tissue layer characteristics. The thickness, optical properties (absorption coefficient and reduced scattering coefficient), oxygenation, and perfusion of skin are the most critical parameters for disease diagnosis and for some medical equipment. These phantoms can be used as calibration artifacts and help to evaluate optical imaging technologies.

Antigen retrieval prior to on-tissue digestion of formalin-fixed paraffin-embedded tumour tissue sections yields oxidation of proline residues.

MALDI-mass spectrometry imaging (MALDI-MSI) has been shown to allow the study of protein distribution and identification directly within formalin-fixed paraffin-embedded (FFPE) tissue sections. However, direct protein identification from tissue sections remains challenging due to signal interferences and/or existing post-translational or other chemical modifications. The use of antigen retrieval (AR) has been demonstrated for unlocking proteins prior to in situ enzymatic digestion and MALDI-MSI analysis of FFPE tissue sections. In the work reported here, the identification of proline oxidation, which may occur when performing the AR protocol, is described. This facilitated and considerably increased the number of identified peptides when adding proline oxidation as a variable modification to the MASCOT search criteria. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann.

Development of traceable measurement of the diffuse optical properties of solid reference standards for biomedical optics at National Institute of Standards and Technology.

The development of a national reference instrument dedicated to the measurement of the scattering and absorption properties of solid tissue-mimicking phantoms used as reference standards is presented. The optical properties of the phantoms are measured with a double-integrating sphere setup in the steady-state domain, coupled with an inversion routine of the adding-doubling procedure that allows for the computation of the uncertainty budget for the measurements. The results are compared to the phantom manufacturer's values obtained by a time-resolved approach. The results suggest that the agreement between these two independent methods is within the estimated uncertainties. This new reference instrument will provide optical biomedical research laboratories with reference values for absolute diffuse optical properties of phantom materials.

Establishment and application of the 0/45 reflectance factor scale over the shortwave infrared.

This paper describes the establishment and application of the 0/45 reflectance factor scale in the shortwave infrared (SWIR) from 1100 to 2500 nm. Design, characterization, and the demonstration of a four-stage, extended indium-gallium-arsenide radiometer to perform reflectance measurements in the SWIR have been previously discussed. Here, we focus on the incorporation of the radiometer into the national reference reflectometer, its validation through comparison measurements, and the uncertainty budget. Next, this capability is applied to the measurement of three different diffuser materials. The 0/45 spectral reflectance factors for these materials are reported and compared to their respective 6/di spectral reflectance factors.

Pasteurella species peritoneal dialysis-associated peritonitis: Household pets as a risk factor.

BACKGROUND: Pasteurella species are Gram-negative coccobacilli that are a part of the normal oropharyngeal flora of numerous domestic animals. They have been recognized as a rare but significant cause of peritonitis in patients undergoing peritoneal dialysis (PD). A consensus about management strategies for PD-associated peritonitis caused by Pasteurella species currently does not exist. METHODS: The microbiological database serving the Manitoba Renal Program was searched from 1997 to 2013 for cases of Pasteurella species PD-associated peritonitis, and charts were reviewed. PubMed was searched for case reports and data were abstracted. RESULTS: Seven new local cases and 30 previously reported cases were analyzed. This infection is clinically similar to other forms of PD peritonitis, with household pet exposure appearing to be the strongest risk factor. Cats are the most commonly implicated pet. Direct contact between the pet and the equipment was commonly reported (25 of 37 patients) but was not necessary for infection to develop. The mean duration of treatment was 15 days. Complication rates were low, with only 11% of patients requiring PD catheter removal. There was no mortality reported. CONCLUSION: Pasteurella species are a rare cause of PD-associated peritonitis that can be successfully treated with a two-week course of intraperitoneal antibiotics with a high likelihood of catheter salvage.

HISTORIQUE: Les espèces de Pasteurella sont des coccobacilles à Gram négatif qui font partie de la flore oropharyngée normale de nombreux animaux domestiques. Ils constituent une cause de péritonite rare, mais importante, chez les patients sous dialyse péritonéale (DP). Il n'y a pas de consensus quant aux stratégies de prise en charge de la péritonite associée à la dialyse péritonéale causée par les espèces de Pasteurella. MÉTHODOLOGIE: Les chercheurs ont exploré la base de données microbiologiques du Programme de lutte contre la maladie du rein du Manitoba de 1997 à 2013 pour déceler les cas de péritonite associée à la DP causée par les espèces de Pasteurella et ont examiné leur dossier. Ils ont fouillé PubMed pour trouver des rapports de cas et en ont extrait des données. RÉSULTATS: Les chercheurs ont analysé sept nouveaux cas locaux et 30 anciens cas. Cette infection est similaire sur le plan clinique à d'autres formes de péritonite associée à la DP, dont le principal facteur de risque semble être l'exposition à un animal domestique. Les chats sont les plus en cause. On signale souvent un contact direct entre l'animal et le matériel (25 patients sur 37), mais il n'est pas nécessaire pour provoquer l'infection. Le traitement durait en moyenne 15 jours. Le taux de complications était faible, puisque seulement 11 % des patients ont dû faire retirer leur cathéter de DP. Aucun décès n'a été signalé. CONCLUSION: Les espèces de Pasteurella sont de rares causes de péritonite associée à la DP qu'on peut soigner par un traitement de deux semaines aux antibiotiques intrapéritonéaux. Ce traitement s'associe à une forte probabilité de sauvegarder le cathéter.

Hyperspectral dark-field microscopy of human breast lumpectomy samples for tumor margin detection in breast-conserving surgery.

Significance: Hyperspectral dark-field microscopy (HSDFM) and data cube analysis algorithms demonstrate successful detection and classification of various tissue types, including carcinoma regions in human post-lumpectomy breast tissues excised during breast-conserving surgeries. Aim: We expand the application of HSDFM to the classification of tissue types and tumor subtypes in pre-histopathology human breast lumpectomy samples. Approach: Breast tissues excised during breast-conserving surgeries were imaged by the HSDFM and analyzed. The performance of the HSDFM is evaluated by comparing the backscattering intensity spectra of polystyrene microbead solutions with the Monte Carlo simulation of the experimental data. For classification algorithms, two analysis approaches, a supervised technique based on the spectral angle mapper (SAM) algorithm and an unsupervised technique based on the K-means algorithm are applied to classify various tissue types including carcinoma subtypes. In the supervised technique, the SAM algorithm with manually extracted endmembers guided by H&E annotations is used as reference spectra, allowing for segmentation maps with classified tissue types including carcinoma subtypes. Results: The manually extracted endmembers of known tissue types and their corresponding threshold spectral correlation angles for classification make a good reference library that validates endmembers computed by the unsupervised K-means algorithm. The unsupervised K-means algorithm, with no a priori information, produces abundance maps with dominant endmembers of various tissue types, including carcinoma subtypes of invasive ductal carcinoma and invasive mucinous carcinoma. The two carcinomas' unique endmembers produced by the two methods agree with each other within <2% residual error margin. Conclusions: Our report demonstrates a robust procedure for the validation of an unsupervised algorithm with the essential set of parameters based on the ground truth, histopathological information. We have demonstrated that a trained library of the histopathology-guided endmembers and associated threshold spectral correlation angles computed against well-defined reference data cubes serve such parameters. Two classification algorithms, supervised and unsupervised algorithms, are employed to identify regions with carcinoma subtypes of invasive ductal carcinoma and invasive mucinous carcinoma present in the tissues. The two carcinomas' unique endmembers used by the two methods agree to <2% residual error margin. This library of high quality and collected under an environment with no ambient background may be instrumental to develop or validate more advanced unsupervised data cube analysis algorithms, such as effective neural networks for efficient subtype classification.

Calibration and validation scheme for in vivo spectroscopic imaging of tissue oxygenation.

The determination of the level of oxygenation in optically accessible tissues using multispectral or hyperspectral imaging (HSI) of oxy- and deoxyhemoglobin has special appeal in clinical work due to its noninvasiveness, ease of use, and capability of providing molecular and anatomical information at near video rates during surgery. In this paper we refer to an example of the use of HSI in monitoring oxygenation of kidneys during partial nephrectomy. In a study using porcine models, it was found that artery-only clamping left the kidney better oxygenated, as opposed to simultaneously clamping the artery and the vein. A subsequent study correlates gradations in blood flow by partial clamping during the surgical procedure with postoperative renal function via assessment of creatinine level. We discuss the various contributions to the uncertainty of the oxygen saturation measured by this remote-sensing imaging technique in medical application.

2010 topical meeting on optical interference coatings: manufacturing problem.

For the 2010 Manufacturing Problem, the participants were required to produce a filter that had normal incidence transmittances of 0.001, 0.01, 0.1, and 0.96, respectively, in four separate 60 nm wide bands in the 400 to 700 nm wavelength region. The problem is not unlike those that need to be routinely solved in the telecommunication industry. Nine groups submitted a total of 11 different filters for the contest. The number of layers in the filters received ranged from 28 to 678, and the total metric thicknesses varied between 4,038 and 22,513 nm. The transmittances of the filters were measured at two independent laboratories. Some of the performances were quite close to the specifications.

When rotational atherectomy is not enough.

Extreme coronary calcification may require rotational atherectomy to create a navigable intravascular lumen followed by intravascular lithotripsy to fracture areas of deep calcification to allow for successful percutaneous coronary intervention.

Polydimethylsiloxane tissue-mimicking phantoms with tunable optical properties.

SIGNIFICANCE: The polymer, polydimethylsiloxane (PDMS), has been increasingly used to make tissue simulating phantoms due to its excellent processability, durability, flexibility, and limited tunability of optical, mechanical, and thermal properties. We report on a robust technique to fabricate PDMS-based tissue-mimicking phantoms where the broad range of scattering and absorption properties are independently adjustable in the visible- to near-infrared wavelength range from 500 to 850 nm. We also report on an analysis method to concisely quantify the phantoms' broadband characteristics with four parameters. AIM: We report on techniques to manufacture and characterize solid tissue-mimicking phantoms of PDMS polymers. Tunability of the absorption (µa ( λ ) ) and reduced scattering coefficient spectra (µs'(λ)) in the wavelength range of 500 to 850 nm is demonstrated by adjusting the concentrations of light absorbing carbon black powder (CBP) and light scattering titanium dioxide powder (TDP) added into the PDMS base material. APPROACH: The µa ( λ ) and µs'(λ) of the phantoms were obtained through measurements with a broadband integrating sphere system and by applying an inverse adding doubling algorithm. Analyses of µa ( λ ) and µs'(λ) of the phantoms, by fitting them to linear and power law functions, respectively, demonstrate that independent control of µa ( λ ) and µs'(λ) is possible by systematically varying the concentrations of CBP and TDP. RESULTS: Our technique quantifies the phantoms with four simple fitting parameters enabling a concise tabulation of their broadband optical properties as well as comparisons to the optical properties of biological tissues. We demonstrate that, to a limited extent, the scattering properties of our phantoms mimic those of human tissues of various types. A possible way to overcome this limitation is demonstrated with phantoms that incorporate polystyrene microbead scatterers. CONCLUSIONS: Our manufacturing and analysis techniques may further promote the application of PDMS-based tissue-mimicking phantoms and may enable robust quality control and quality checks of the phantoms.

Reducing Delay to Treatment of ST-Elevation Myocardial Infarction With Software Electrocardiographic Interpretation and Transmission (SCINET).

BACKGROUND: Prehospital diagnosis of ST-elevation myocardial infarction (STEMI) has resulted in improved outcomes. However, many patients still walk in to the emergency department (ED) with STEMI, experiencing delays and worse outcomes. Software electrocardiogram (ECG) diagnosis of STEMI and electronic transmission to a cardiologist may result in improved door-to-device (D2D) times. METHODS: We retrospectively identified all patients presenting with STEMI from January 2015 to September 2016. Components of delay in D2D, ED variables, and the patients' ECGs were extracted from our regional database. All ECGs performed for suspected myocardial infarction in the region were extracted over the study period. We assessed the accuracy of the software 12SL in diagnosing STEMI, ED contributors to delays in D2D, and the potential reduction in D2D if software diagnosis of STEMI resulted in activation of the cardiac catheterization laboratory. RESULTS: A total of 379 patients presented to an ED in our region and received primary percutaneous coronary intervention over the study period. In the 143,574 ECGs performed over the study period for suspected STEMI, the overall sensitivity and specificity of 12SL were 90.5% and 99.98%, respectively. We estimated a potential 17-minute reduction in D2D in the 90.5% of patients correctly identified as having STEMI, with a false activation rate of 4%. Female patients and older patients experienced an even larger potential benefit, with 24- and 25-minute reductions in D2D, respectively. CONCLUSIONS: Patients who walk in to an ED with STEMI experience significant system-related delays in recognition and treatment. Automated software diagnosis of STEMI is accurate and could result in significant improvements in D2D times.

CONTEXTE: Le diagnostic préhospitalier de l'infarctus du myocarde avec élévation du segment ST (STEMI) contribue à améliorer les résultats pour les patients. Toutefois, de nombreux patients subissant un STEMI se présentent encore d'eux-mêmes au service des urgences, ce qui retarde leur traitement et entraîne des conséquences plus graves. Le diagnostic de STEMI au moyen d'un logiciel de prise d'électrocardiogramme (ECG) qui est ensuite transmis à un cardiologue par voie électronique pourrait réduire le délai entre l'arrivée à l'hôpital et la pose d'un dispositif (délai avant l'intervention). MÉTHODOLOGIE: Nous avons rétrospectivement recensé tous les patients ayant subi un STEMI entre janvier 2015 et septembre 2016. Les facteurs entraînant l'augmentation du délai avant l'intervention, les variables relatives au service des urgences et les ECG des patients ont été extraits d'une base de données régionale. Tous les ECG réalisés dans les cas d'infarctus du myocarde suspectés dans la région pendant la période visée ont été extraits. Nous avons évalué l'exactitude des diagnostics de STEMI obtenus à l'aide du logiciel 12SL, les facteurs contribuant au délai avant l'intervention et la réduction potentielle de ce délai lorsque le diagnostic de STEMI obtenu par logiciel a permis au laboratoire de cathétérisme cardiaque de se préparer avant l'arrivée du patient. RÉSULTATS: Au total, 379 patients se sont présentés au service des urgences d'un hôpital de la région et ont subi une intervention coronarienne percutanée primaire durant la période visée par l'étude. Sur les 143 574 ECG réalisés dans les cas de STEMI suspectés durant la période étudiée, la sensibilité et la spécificité globales du logiciel 12SL s'établissaient respectivement à 90,5 % et à 99,98 %. Nous avons estimé que le délai avant l'intervention avait été potentiellement réduit de 17 minutes chez les patients ayant reçu un diagnostic de STEMI correct (90,5 %), le taux d'activation inutile du laboratoire de cathétérisme s'établissant à 4 %. Les femmes et les patients plus âgés sont ceux qui semblent avoir bénéficié le plus de cette stratégie, la réduction potentielle du délai avant l'intervention s'établissant dans leurs cas à 24 et à 25 minutes, respectivement. CONCLUSIONS: Les patients subissant un STEMI qui se présentent eux-mêmes au service des urgences doivent passer par toutes les étapes du processus d'admission avant que leur état soit reconnu et traité. Les outils de diagnostic automatisé du STEMI donnent des résultats justes, et leur utilisation pourrait réduire considérablement le délai entre l'arrivée à l'hôpital et l'intervention.

Atherectomy and Specialty Balloons in Percutaneous Coronary Intervention.

PURPOSE OF REVIEW: Interventional cardiologists are increasingly being called upon to perform complex revascularization in patients who are deemed not to be candidates for surgical revascularization and, until recently, many of these patients would have only been offered medical management. Further, changing demographics have resulted in an increasingly elderly and frail population with diabetes and chronic kidney disease being referred for revascularization. Owing to the increasing prevalence of coronary artery calcification and the importance of achieving complete revascularization, advanced tools and techniques are required to safely revascularize this patient population. RECENT FINDINGS: Coronary artery calcification is a marker for increased periprocedural complications and worse long-term outcomes in percutaneous intervention. Its presence may mandate advanced revascularization strategies to facilitate safe revascularization. Several studies have highlighted the importance of intracoronary imaging and there have been iterative changes and new devices that have been developed that can facilitate revascularization in the setting of significant coronary artery calcification. Successful coronary revascularization is increasingly dependent on the rational use of intraavascular imaging, specialized balloons and atherectomy to overcome complex coronary artery disease and calcification. A rational strategy for the safe use of advanced techniques and tools is presented here.

Comparative Performance of Prediction Models for Contrast-Associated Acute Kidney Injury After Percutaneous Coronary Intervention.

BACKGROUND: Identifying patients at increased risk of contrast-associated acute kidney injury (CA-AKI) can help target risk mitigation strategies toward these individuals during percutaneous coronary intervention. Illuminating which risk models best stratify risk is an important foundation for such quality improvement efforts. METHODS AND RESULTS: Seven previously published risk prediction models for CA-AKI and 3 models for kidney injury requiring dialysis were validated using 2 definitions for CA-AKI (the Kidney Disease: Improving Global Outcomes definition of ≥0.3 mg/dL within 48 hours or ≥50% increase in serum creatinine from baseline within 7 days and the historical definition of ≥0.5 mg/dL or ≥25% increase in serum creatinine from baseline within 48 hours), and AKI requiring dialysis within 30 days of percutaneous coronary intervention. Model performance was compared based on discrimination, calibration, and categorical net reclassification index before and after model recalibration. Among 7888 patients who underwent percutaneous coronary intervention in Alberta Canada, CA-AKI occurred in 330 patients (4.2%) when CA-AKI was defined using the Kidney Disease: Improving Global Outcomes definition and 571 (7.3%) when using the historical definition. CA-AKI requiring dialysis occurred in 42 (0.6%) patients. When validated using the Kidney Disease: Improving Global Outcomes definition for CA-AKI, the 2 most recently published models for CA-AKI showed better discrimination (C statistics, 0.75-0.76) than older models (C statistics, 0.61-0.68). C statistics of models for kidney injury requiring dialysis ranged from 0.70 to 0.86. The calibration of all models for CA-AKI deviated from ideal, and the proportion of patients classified into different risk categories for CA-AKI differed substantially for the 2 most recent models. Recalibration significantly improved risk stratification of patients into clinical risk categories for some models. CONCLUSIONS: Recent prediction models for CA-AKI show better discrimination compared with older models; however, model recalibration should be examined in external cohorts to improve the accuracy of predictions, particularly if predicted risk strata are used to guide management approaches.

Clinical Decision Support to Reduce Contrast-Induced Kidney Injury During Cardiac Catheterization: Design of a Randomized Stepped-Wedge Trial.

BACKGROUND: Contrast-induced acute kidney injury (CI-AKI) is a common and serious complication of invasive cardiac procedures. Quality improvement programs have been associated with a lower incidence of CI-AKI over time, but there is a lack of high-quality evidence on clinical decision support for prevention of CI-AKI and its impact on processes of care and clinical outcomes. METHODS: The Contrast-Reducing Injury Sustained by Kidneys (Contrast RISK) study will implement an evidence-based multifaceted intervention designed to reduce the incidence of CI-AKI, encompassing automated identification of patients at increased risk for CI-AKI, point-of-care information on safe contrast volume targets, personalized recommendations for hemodynamic optimization of intravenous fluids, and follow-up information for patients at risk. Implementation will use cardiologist academic detailing, computerized clinical decision support, and audit and feedback. All 31 physicians practicing in all 3 of Alberta's cardiac catheterization laboratories will participate using a cluster-randomized stepped-wedge design. The order in which they are introduced to this intervention will be randomized within 8 clusters. The primary outcome is CI-AKI incidence, with secondary outcomes of CI-AKI avoidance strategies and downstream adverse major kidney and cardiovascular events. An economic evaluation will accompany the main trial. CONCLUSIONS: The Contrast RISK study leverages information technology systems to identify patient risk combined with evidence-based protocols, audit, and feedback to reduce CI-AKI in cardiac catheterization laboratories across Alberta. If effective, this intervention can be broadly scaled and sustained to improve the safety of cardiac catheterization.

Light scattering of semitransparent sintered polytetrafluoroethylene films.

Polytetrafluoroethylene (PTFE) is a strongly scattering material and has been regarded to have optical properties similar to biological tissues. In the present study, the bidirectional reflectance distribution function (BRDF) and the bidirectional transmittance distribution function (BTDF) of several PTFE films, with thicknesses from 0.11 to 10 mm, are measured using a laser scatterometer at the wavelength of 635 nm. The directional-hemispherical reflectance (R) and transmittance (T) were obtained by integrating BRDF and BTDF for normal incidence. Comparison of the ratio of the measured R and T with that calculated from the adding-doubling method allows the determination of the reduced scattering coefficient. Furthermore, the effect of surface scattering is investigated by measuring the polarization-dependent BRDF and BTDF at oblique incidence. By analyzing the measurement uncertainty of BTDF in the near-normal observation angles at normal incidence, the present authors found that the scattering coefficient of PTFE should exceed 1200 cm(-1), which is much greater than that of biological tissues. On the other hand, the absorption coefficient of PTFE must be less than 0.01 cm(-1), much smaller than that of biological tissues, a necessary condition to achieve R > or =0.98 with a 10-mm-thick slab.

Correction of an adding-doubling inversion algorithm for the measurement of the optical parameters of turbid media.

We present broadband measurements of the optical properties of tissue-mimicking solid phantoms using a single integrating sphere to measure the hemispherical reflectance and transmittance under a direct illumination at the normal incident angle. These measurements are traceable to reflectance and transmittance scales. An inversion routine using the output of the adding-doubling algorithm restricted to the reflectance and transmittance under a direct illumination was developed to produce the optical parameters of the sample along with an uncertainty budget at each wavelength. The results for two types of phantoms are compared to measurements by time-resolved approaches. The results between our method and these independent measurements agree within the estimated measurement uncertainties.