Double Boundary Trench Isolation Effects on a Stacked Gradient Homojunction Photodiode Array

The effect of the width of inter-pixel double boundary trench isolation on the response resolution of a two dimensional CMOS compatible stacked gradient homojunction photodiode array was simulated. Insulation and P-doped double boundary trench isolation were compared. Both geometries showed improved crosstalk suppression and enhanced sensitivity compared to photodiode geometries previously investigated, combined with a reduction in fabrication complexity for the insulation DBTI configuration

A micro-photonic stationary optical delay line for fibre optic time domain OCT

We present results for the characterisation of a micro-photonic stationary optical delay line. The delay line is intended to generate true time delays for a fibre optic based optical coherence tomography system

Effect of a Polywell geometry on a CMOS Photodiode Array

The effect of a polywell geometry hybridized with a stacked gradient poly-homojunction architecture, on the response of a CMOs compatible photodiode array was simulated. Crosstalk and sensitivity improved compared to the polywell geometry alone, for both back and front illuminatio

Low-Cost Educational Optical Coherence Tomography System for Thickness MeasurmentsTomography System for Thickness Measurments

We have developed an inexpensive rudimentary low coherence interferometer that can be used to measure sample thickness in the micron to mm range, and for exploring educational aspects of interferometry and optical coherence tomography

Double boundary trench isolation effects on a stacked gradient homojunction photodiode array

The effect of the width of inter-pixel double boundary trench isolation on the response resolution of a two dimensional CMOS compatible stacked gradient homojunction photodiode array was simulated. Insulation and P-doped double boundary trench isolation were compared. Both geometries showed improved crosstalk suppression and enhanced sensitivity compared to photodiode geometries previously investigated, combined with a reduction in fabrication complexity for the insulation DBTI configuration

Development and Validation of a Risk Score for Chronic Kidney Disease in HIV Infection Using Prospective Cohort Data from the D:A:D Study

Ristola M. on työryhmien DAD Study Grp ; Royal Free Hosp Clin Cohort ; INSIGHT Study Grp ; SMART Study Grp ; ESPRIT Study Grp jäsen.Background Chronic kidney disease (CKD) is a major health issue for HIV-positive individuals, associated with increased morbidity and mortality. Development and implementation of a risk score model for CKD would allow comparison of the risks and benefits of adding potentially nephrotoxic antiretrovirals to a treatment regimen and would identify those at greatest risk of CKD. The aims of this study were to develop a simple, externally validated, and widely applicable long-term risk score model for CKD in HIV-positive individuals that can guide decision making in clinical practice. Methods and Findings A total of 17,954 HIV-positive individuals from the Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D) study with >= 3 estimated glomerular filtration rate (eGFR) values after 1 January 2004 were included. Baseline was defined as the first eGFR > 60 ml/min/1.73 m2 after 1 January 2004; individuals with exposure to tenofovir, atazanavir, atazanavir/ritonavir, lopinavir/ritonavir, other boosted protease inhibitors before baseline were excluded. CKD was defined as confirmed (>3 mo apart) eGFR In the D:A:D study, 641 individuals developed CKD during 103,185 person-years of follow-up (PYFU; incidence 6.2/1,000 PYFU, 95% CI 5.7-6.7; median follow-up 6.1 y, range 0.3-9.1 y). Older age, intravenous drug use, hepatitis C coinfection, lower baseline eGFR, female gender, lower CD4 count nadir, hypertension, diabetes, and cardiovascular disease (CVD) predicted CKD. The adjusted incidence rate ratios of these nine categorical variables were scaled and summed to create the risk score. The median risk score at baseline was -2 (interquartile range -4 to 2). There was a 1: 393 chance of developing CKD in the next 5 y in the low risk group (risk score = 5, 505 events), respectively. Number needed to harm (NNTH) at 5 y when starting unboosted atazanavir or lopinavir/ritonavir among those with a low risk score was 1,702 (95% CI 1,166-3,367); NNTH was 202 (95% CI 159-278) and 21 (95% CI 19-23), respectively, for those with a medium and high risk score. NNTH was 739 (95% CI 506-1462), 88 (95% CI 69-121), and 9 (95% CI 8-10) for those with a low, medium, and high risk score, respectively, starting tenofovir, atazanavir/ritonavir, or another boosted protease inhibitor. The Royal Free Hospital Clinic Cohort included 2,548 individuals, of whom 94 individuals developed CKD (3.7%) during 18,376 PYFU (median follow-up 7.4 y, range 0.3-12.7 y). Of 2,013 individuals included from the SMART/ESPRIT control arms, 32 individuals developed CKD (1.6%) during 8,452 PYFU (median follow-up 4.1 y, range 0.6-8.1 y). External validation showed that the risk score predicted well in these cohorts. Limitations of this study included limited data on race and no information on proteinuria. Conclusions Both traditional and HIV-related risk factors were predictive of CKD. These factors were used to develop a risk score for CKD in HIV infection, externally validated, that has direct clinical relevance for patients and clinicians to weigh the benefits of certain antiretrovirals against the risk of CKD and to identify those at greatest risk of CKD.Peer reviewe

Characterising the effect of a novel optical delay line and light sources on the resolvability of time domain optical coherence tomography

Optical coherence tomography (OCT) is a reflection based imaging technique, with numerous applications, initially in medical diagnostics. Unlike ultrasound, another reflection imaging technique, OCT relies on light scattering in samples, low coherence near- infrared interferometry, and graphical image construction, to acquire 2D and 3D reflectogram images. OCT has resolution an order of magnitude greater than ultrasound, but its depth penetration is less than a few millimetres. Axial resolution is a critical parameter in determining whether OCT can be used to resolve specific features in a sample image. Typically, measures of resolution have been attributed only to the light source’s characteristics, including its coherence length and the FWHM of its frequency spectrum’s inverse FT, or auto-correlogram. The need to cost effectively visualize the OCT-system-generated auto-correlograms, and OCT cross-correlograms (A-scan) (produced using many different OCT light sources), has necessitated the extrinsic-evolution of an OCT simulation model, presented in this thesis. This research indicated that empirical resolution in vivo is also strongly dependent on the optical characteristics of the tissue, including surface reflection. When the surface reflection is removed from the A-scan, the minimum stratum depth that can be resolved for the sub-surface strata, is significantly enhanced. Furthermore, this subtraction enhances the stratum depth resolution, so that it approaches more closely the light source’s resolution limit, compared to A-scans without the subtraction. The time domain OCT’s optical delay line (ODL) and light source components were also reviewed to determine their affordability and functionality for engineering a portable, high resolution, but simple OCT modality. To this end, a stationary ODL, using a transmissive optical light valve array and a stepped mirrored structure (SMS), was characterised in ‘proof of principle’ experiments. Unfortunately, fabrication of the SMS, using four affordable techniques, proved unsuccessful; however, more promising techniques, based on the theoretical developments in this thesis, are envisaged. A stochastic pseudo-genetic algorithm (GAM), similar, but not exactly analogous to theoretical genetic intrinsic-evolution, was characterised and used to backwards-fit the solution set of strata depths and reflectivities of a selected OCT A-scan. Unfortunately, its speed in Matlab was not timely enough for e-medical application – though in c this GAM could run faster. This slowness is due to the GAM’s stochastic nature, prompting future investigation of other GAMs, which will eliminate the stochastic element so that more timely results can be achieved