Pre-exposure prophylaxis and telemedicine during coronavirus (COVID-19): a qualitative study of the experiences of health care professionals in Mexico.

Background Telemedicine, which involves utilising technologies for remote health care delivery, proved useful to continue offering certain health services during the coronavirus disease 2019 (COVID-19) lockdown. However, the extent of its effectiveness in delivering pre-exposure prophylaxis services for HIV prevention remains underexplored from the viewpoint of health care providers. Therefore, this study aimed to assess the experiences of health care professionals in Mexico who utilised telemedicine for delivering pre-exposure prophylaxis services during the COVID-19 contingency. Methods A qualitative study was performed: 15 virtual interviews with health care professionals were conducted, transcribed and coded in ATLAS.ti. Results The results indicate that telemedicine effectively mitigated COVID-19 exposure, facilitated users' access to pre-exposure prophylaxis counselling, minimised waiting times and enhanced health care professionals' perceived control during sessions. While implementing remote services, certain organisational challenges, which were somewhat latent before the pandemic, became more apparent: colleagues recognised the necessity for more formal communication channels to disseminate information effectively. Additionally, there was a recognised need for electronic patient files to streamline data-sharing processes. An optimal approach would involve a blend of face-to-face and virtual services, contingent upon the availability of essential infrastructure, well-defined implementation protocols and comprehensive training programs. Conclusions Telemedicine streamlined certain processes, garnered positive acceptance from healthcare professionals and holds promise as a valuable post-pandemic tool for improving retention among pre-exposure prophylaxis users.

Macrovascular and microvascular type 2 diabetes complications are interrelated in a mouse model.

AIM: Evaluate the development of multiple complications, their interactions, and common mechanisms in the same individual with T2D. MATERIAL AND METHODS: 4-week-old male C57BL/6J mice were divided into: control (n = 6) and T2D (n = 6). T2D was induced through a high-carbohydrate-diet and low doses of streptozotocin. T2D was validated by metabolic parameters. Diabetic neuropathy was evaluated by mechanical and thermal sensitivity tests. We performed a histopathological analysis of the heart, kidney, liver, and parotid salivary glands and changes in bone microarchitecture by µCT. We calculated the relative risk (RR), odd ratios (OR) and Pearson correlation coefficients between the different complications and metabolic features. RESULTS: T2D mice have cardiomyopathy, neuropathy, nephropathy, liver steatosis and fibrosis, structural damage in parotid salivary glands, and bone porosity. RR analysis shows that all complications are interrelated by hyperglycaemia, insulin resistance, obesity, and systemic inflammation. CONCLUSIONS: T2D mice develop multiple complications simultaneously, which are related to each other, and this is associated with metabolic alterations. Our findings open up new approaches for the study and new therapeutic approaches of the pathophysiology of T2D and its complications.

CD4+ T-cell activation of bone marrow causes bone fragility and insulin resistance in type 2 diabetes.

Type 2 diabetes mellitus (T2DM) causes an increased risk of bone fractures. However, the pathophysiology of diabetic bone fragility is not completely understood. It has been proposed that an inflammatory microenvironment in bone could be a major mechanism by inducing uncontrolled bone resorption, inadequate bone formation and consequently more porous bones. We propose that activated T-cells in the bone marrow cause a pro-inflammatory microenvironment in bone, and cause bone fragility in T2DM. We induced T2DM in C57BL/6 male mice through a hypercaloric diet rich in carbohydrates and low doses of streptozocin. In T2DM mice we inhibited systemic activation of T-cells with a fusion protein between the extracellular domain of Cytotoxic T-Lymphocyte Antigen 4 and the Fc domain of human immunoglobulin G (CTLA4-Ig). We analysed the effects of T2DM or CTLA4-Ig in lymphocyte cell subsets and antigen-presenting cells in peripheral blood and femoral bone marrow; and their effect on the metabolic phenotype, blood and bone cytokine concentration, femoral bone microarchitecture and biomechanical properties, and the number of osteoblast-like cells in the femoral endosteum. We performed a Pearson multiple correlation analysis between all variables in order to understand the global mechanism. Results demonstrated that CTLA4-Ig decreased the number of activated CD4+ T-cells in the femoral bone marrow and consequently decreased TNF-α and RANK-L concentration in bone, notably improved femoral bone microarchitecture and biomechanical properties, increased the number of osteoblast-like cells, and reduces osteoclastic activity compared to T2DM mice that did not receive the inhibitor. Interestingly, we observed that blood glucose levels and insulin resistance may be related to the increase in activated CD4+ T-cells in the bone marrow. We conclude that bone marrow activated CD4+ T-cells cause poor bone quality and insulin resistance in T2DM.

Positron range effects of 66Ga in small-animal PET imaging.

PURPOSE: Gallium-66 is a non-conventional positron emitter that stands out not only for its high potential to label peptides, proteins and antibodies, but also because it can provide spatio-temporal information of relatively slow physiological processes in the body due to its conveniently long half-life of 9.5 h. However, 66Ga emits the most energetic positrons for PET imaging. The lack of information of the positron range effect on spatial resolution for this positron emitter is an issue, particularly in preclinical imaging. METHODS: The line spread function (LSF) in tissue-equivalent materials with densities between 0.2 and 1.93 g/cm3 was obtained with 66Ga and 18F. A complementary study with the NEMA NU 4-2008 image quality phantom is also included. RESULTS: High-energy positrons moving in lower density materials produce far-reaching activity distributions. The LSFs were characterized with Lorentzian-Gaussian fits, with spatial resolution (FWHM) in the 2.14-3.2 mm range, and long tails extending a few tens of mm depending on the material type and density. A narrowing of the LSF was observed for lung-equivalent materials, indicating the lack of enough material for the positron annihilation to take place. The NEMA NU 4-2008 image quality phantom produced blurred images, notoriously observed in the hot and cold cylinders used for evaluation of recovery coefficients (RC) and spill-over ratios (SOR), producing very low RC and very large SOR. CONCLUSIONS: Quantitative PET imaging with the non-conventional 66Ga is hampered due to the large range of its high-energy positrons affecting both spatial resolution and activity concentration quantification.

Interprofessional training for the delivery of community health services in Mexico: the experience of Partners in Health.

Interprofessional training in health is scarce in Mexico. Partners in Health (CES in Spanish), is the branch of an international civil society organization that provides health services to poor and rural populations. CES runs a set of ten health centers in Chiapas, Mexico, in partnership with the local Ministry of Health. A key component of the provision strategy is to train healthcare providers, mainly medical and nursing students in their final year of training, to create healthcare teams that work together while fostering their individual capacities. CES offers a diploma on Global Health and Social Medicine, where medical and nursing students -also called pasantes- interact to discuss jointly the effects of global and social determinants of health in local communities, as well as specific clinical topics. A qualitative study including interviews and nonparticipant observations was undertaken to identify initial achievements and challenges of the experience. CES has achieved important benefits related to teamwork as well as clinical capacities of individuals as healthcare providers. However, challenges have emerged: differences in social origin, personal development expectations, professional identity and institutional roles hinder team cohesion. Consequently, CES has introduced adjustments to reduce the negative impact of these differences. Although the training model needs further development, the possibility of transferring some of its good practices to non-CES scenarios should be seriously considered by health authorities.

Understanding the intrinsic radioactivity energy spectrum from 176Lu in LYSO/LSO scintillation crystals.

Lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) are the scintillator materials most widely used today in PET detectors due to their convenient physical properties for the detection of 511 keV annihilation photons. Natural lutetium contains 2.6% of 176Lu which decays beta to excited states of 176Hf producing a constant background signal. Although previous works have studied the background activity from LSO/LYSO, the shape of the spectrum, resulting from ß-particle and γ radiation self-detection, has not been fully explained. The present work examines the contribution of the different ß-particle and γ-ray interactions to provide a fuller comprehension of this background spectrum and to explain the differences observed when using crystals of different sizes. To this purpose we have shifted the continuous ß-particle energy spectrum of 176Lu from zero to the corresponding energy value for all combinations of the isomeric transitions of 176Hf (γ-rays/internal conversion). The area of each shifted ß-spectrum was normalized to reflect the probability of occurrence. To account for the probability of the γ-rays escaping from the crystal, Monte Carlo simulations using PENELOPE were performed in which point-like sources of monoenergetic photons were generated, inside LYSO square base prisms (all 1 cm thick) of different sizes: 1.0 cm to 5.74 cm. The analytic distributions were convolved using a varying Gaussian function to account for the measured energy resolution. The calculated spectra were compared to those obtained experimentally using monolithic crystals of the same dimensions coupled to SiPM arrays. Our results are in very good agreement with the experiment, and even explain the differences observed due to crystal size. This work may prove useful to calibrate and assess detector performance, and to measure energy resolution at different energy values.

Optimization of a large-area detector-block based on SiPM and pixelated LYSO crystal arrays.

We present the performance evaluation of a large-area detector module based on the ArrayC-60035-64P, an 8×8 array of tileable, 7.2mm pitch, silicon photomultipliers (SiPM) by SensL, covering a total area of 57.4mm×57.4mm. We characterized the ArrayC-60035-64P, operating at room temperature, using LYSO pixelated crystal arrays of different pitch sizes (1.075, 1.430, 1.683, 2.080 and 2.280mm) to determine the resolvable crystal size. After an optimization process, a 7mm thick coupling light guide was used for all crystal pitches. To identify the interaction position a 16-channel (8 columns, 8 rows) symmetric charge division (SCD) readout board together with a center-of-gravity algorithm was used. Based on this, we assembled the detector modules using a 40×40 LYSO, 1.43mm pitch array, covering the total detector area. Calibration was performed using a 137Cs source resulting in excellent crystal maps with minor geometric distortion, a mean 4.1 peak-to-valley ratio and 9.6% mean energy resolution for 662keV photons in the central region. The resolvability index was calculated in the x and y directions with values under 0.42 in all cases. We show that these large area SiPM arrays, combined with a 16-channel SCD readout board, can offer high spatial resolution, without processing a big number of signals, attaining excellent energy resolution and detector uniformity.

Positron range in tissue-equivalent materials: experimental microPET studies.

In this work an experimental investigation was carried out to study the effect that positron range has over positron emission tomography (PET) scans through measurements of the line spread function (LSF) in tissue-equivalent materials. Line-sources consisted of thin capillary tubes filled with (18)F, (13)N or (68)Ga water-solution inserted along the axis of symmetry of cylindrical phantoms constructed with the tissue-equivalent materials: lung (inhale and exhale), adipose tissue, solid water, trabecular and cortical bone. PET scans were performed with a commercial small-animal PET scanner and image reconstruction was carried out with filtered-backprojection. Line-source distributions were analyzed using radial profiles taken on axial slices from which the spatial resolution was determined through the full-width at half-maximum, tenth-maximum, twentieth-maximum and fiftieth-maximum. A double-Gaussian model of the LSFs was used to fit experimental data which can be incorporated into iterative reconstruction methods. In addition, the maximum activity concentration in the line-sources was determined from reconstructed images and compared to the known values for each case. The experimental data indicates that positron range in different materials has a strong effect on both spatial resolution and activity concentration quantification in PET scans. Consequently, extra care should be taken when computing standard-uptake values in PET scans, in particular when the radiopharmaceutical is taken up by different tissues in the body, and more even so with high-energy positron emitters.

Effect of correction methods of radiochromic EBT2 films on the accuracy of IMRT QA.

Radiochromic films are dosimeters with more favorable characteristics than other two-dimensional (2D) radiation detectors. Transmission film scanners using a linear charge-coupled device (CCD) array have a drawback of variation in response along the detector array, which may result in a nonuniform transmission of signal over the scanned image. This study uses 2D gamma index analysis to compare two methods for correcting the nonuniform response of EBT2: the first method was based on the new red:blue method proposed by the manufacturer (to compensate for small nonuniformities in the film coating) and the second method, proposed by Menegotti et al. (2008), was based on dose-dependent matrix correction factors. The gamma index analysis shows that both the methods are comparably accurate for all the criteria values used for evaluation (1 mm/1%, 2 mm/2%, 3 mm/3%). Centers around the world use both the methods to correct EBT2 local heterogeneities, but it is important to note that the former method has several advantages such as less time consumption and easy implementation.

Radiochromic dye film studies for brachytherapy applications.

Commercial radiochromic dye films have been used in recent years to quantify absorbed dose in several medical applications. In this study we present the characterisation of the GafChromic MD-55-2 dye film, a double sensitive layer film suitable for photon irradiation in brachytherapy applications. Dose measurements were carried out with a low dose rate 137Cs brachytherapy source, which produces very steep dose gradients in its vicinity, and therefore requires the capability of producing high spatial resolution isodose curves. Quantification of the dose rate in water per unit air kerma strength was obtained using a high-resolution transmission commercial scanner (Agfa DuoScan T1200 with the capability of digitising up to 600 x 1200 pixels per inch using 36 bits per pixel, together with optical density measurements. The Monte Carlo calculations and experimental measurements compared well in the 0-50 Gy dose interval used in this study.

Coalescence of liquid drops by surface tension.

The merging of two mercury drops at very low kinetic energy is observed using fast, digital, and analog imaging techniques. Sequences showing the time evolution of the overall-surface shape as well as an amplified view of the contact region are shown. Qualitative and quantitative comparisons with computations of the Navier-Stokes equation with a free surface are made. In the model, the surface is tracked by a marker-chain method.

A CCD based focal spot camera.

Rapid, quantative assessment of x-radiation source intensity distributions would be useful in several areas of radiation physics. A simple x-ray sensitive CCD based camera for the measurement of focal spot and radiation beam intensity profiles has been constructed. Focal spot images recorded with the CCD camera and radiographic emulsion are compared and the advantage of the CCD camera in rapidly recording true radiation intensity distributions is demonstrated.