Evaluation of Compton gamma camera prototype based on pixelated CdTe detectors.

A proposed Compton camera prototype based on pixelated CdTe is simulated and evaluated in order to establish its feasibility and expected performance in real laboratory tests. The system is based on module units containing a 2×4 array of square CdTe detectors of 10×10 mm2 area and 2 mm thickness. The detectors are pixelated and stacked forming a 3D detector with voxel sizes of 2 × 1 × 2 mm3. The camera performance is simulated with Geant4-based Architecture for Medicine-Oriented Simulations(GAMOS) and the Origin Ensemble(OE) algorithm is used for the image reconstruction. The simulation shows that the camera can operate with up to 104 Bq source activities with equal efficiency and is completely saturated at 109 Bq. The efficiency of the system is evaluated using a simulated 18F point source phantom in the center of the Field-of-View (FOV) achieving an intrinsic efficiency of 0.4 counts per second per kilobecquerel. The spatial resolution measured from the point spread function (PSF) shows a FWHM of 1.5 mm along the direction perpendicular to the scatterer, making it possible to distinguish two points at 3 mm separation with a peak-to-valley ratio of 8.

Acceptability, feasibility and costs of universal offer of rapid point of care testing for HIV in an acute admissions unit: results of the RAPID project.

OBJECTIVES: UK guidance recommends that acute medical admissions are offered an HIV test. Our aim was to determine whether a dedicated staff member using a multimedia tool, a model found effective in the USA, is an acceptable, feasible, and cost-effective model when translated to a UK setting. METHODS: Over 4 months in 2010, a health advisor (HA) approached 19-65-year-olds at a central London acute medical admissions unit and offered a rapid HIV point of care test (POCT) with the aid of an educational video. Feasibility and acceptability were assessed through surveys and uptake rates. Costs per case of HIV infection identified were established. RESULTS: Of the 606 eligible people admitted during the pilot, 324 (53.5%) could not be approached or were individuals for whom testing was deemed inappropriate. In total, 23.0% of eligible admissions had an HIV POCT. Of the patients who watched the video and had not recently been tested for HIV, 93.6% (131 of 140) agreed to an HIV test; four further patients had an HIV test but did not watch the video. Three tests (2.2%; three of 135) were reactive and all were confirmed HIV positive on laboratory testing. HIV testing in this setting was felt to be appropriate by 97.5% of individuals. The cost per patient was £21, and the cost per case of HIV identified was £1083. CONCLUSIONS: Universal POCT HIV testing in an acute medical setting, facilitated by an educational video and dedicated staff, appears acceptable, feasible, effective, and low cost. These findings support the recommendation of HIV testing for all medical admissions in high-prevalence settings, although with this model a significant proportion remained untested.

Evaluation of Origin Ensemble algorithm for image reconstruction for pixelated solid-state detectors with large number of channels.

The Voxel Imaging PET (VIP) Pathfinder project intends to show the advantages of using pixelated solid-state technology for nuclear medicine applications. It proposes designs for Positron Emission Tomography (PET), Positron Emission Mammography (PEM) and Compton gamma camera detectors with a large number of signal channels (of the order of 106). For PET scanners, conventional algorithms like Filtered Back-Projection (FBP) and Ordered Subset Expectation Maximization (OSEM) are straightforward to use and give good results. However, FBP presents difficulties for detectors with limited angular coverage like PEM and Compton gamma cameras, whereas OSEM has an impractically large time and memory consumption for a Compton gamma camera with a large number of channels. In this article, the Origin Ensemble (OE) algorithm is evaluated as an alternative algorithm for image reconstruction. Monte Carlo simulations of the PET design are used to compare the performance of OE, FBP and OSEM in terms of the bias, variance and average mean squared error (MSE) image quality metrics. For the PEM and Compton camera designs, results obtained with OE are presented.

Energy and coincidence time resolution measurements of CdTe detectors for PET.

We report on the characterization of 2 mm thick CdTe diode detector with Schottky contacts to be employed in a novel conceptual design of PET scanner. Results at -8°C with an applied bias voltage of -1000 V/mm show a 1.2% FWHM energy resolution at 511 keV. Coincidence time resolution has been measured by triggering on the preamplifier output signal to improve the timing resolution of the detector. Results at the same bias and temperature conditions show a FWHM of 6 ns with a minimum acceptance energy of 500 keV. These results show that pixelated CdTe Schottky diode is an excellent candidate for the development of next generation nuclear medical imaging devices such as PET, Compton gamma cameras, and especially PET-MRI hybrid systems when used in a magnetic field immune configuration.

Pixelated CdTe detectors to overcome intrinsic limitations of crystal based positron emission mammographs.

A positron emission mammograph (PEM) is an organ dedicated positron emission tomography (PET) scanner for breast cancer detection. State-of-the-art PEMs employing scintillating crystals as detection medium can provide metabolic images of the breast with significantly higher sensitivity and specificity with respect to standard whole body PET scanners. Over the past few years, crystal PEMs have dramatically increased their importance in the diagnosis and treatment of early stage breast cancer. Nevertheless, designs based on scintillators are characterized by an intrinsic deficiency of the depth of interaction (DOI) information from relatively thick crystals constraining the size of the smallest detectable tumor. This work shows how to overcome such intrinsic limitation by substituting scintillating crystals with pixelated CdTe detectors. The proposed novel design is developed within the Voxel Imaging PET (VIP) Pathfinder project and evaluated via Monte Carlo simulation. The volumetric spatial resolution of the VIP-PEM is expected to be up to 6 times better than standard commercial devices with a point spread function of 1 mm full width at half maximum (FWHM) in all directions. Pixelated CdTe detectors can also provide an energy resolution as low as 1.5% FWHM at 511 keV for a virtually pure signal with negligible contribution from scattered events.

Metástasis rectal de carcinoma lobulillar mamario / No disponible

No disponible

Graduate medical education downsizing: perceived effects of participating in the HCFA demonstration project in New York State.

OBJECTIVE: Financial support for graduate medical education (GME) is shrinking nationally as Medicare cuts GME funds. Thirty-nine hospitals in New York State (NYS) voluntarily participated in a Health Care Financing Administration demonstration project (HCFADP)-the goal of which was to reduce total residency training positions by 4-5%/year over a five-year period, while increasing primary care positions. The objective of this study was to determine the effect of downsizing on emergency department (ED) staffing and emergency medicine (EM) residency training. METHODS: Structured interviews and surveys of NYS program directors (PDs) were conducted in October-December 1999. Simple frequencies are reported. RESULTS: One hundred percent of 17 PDs completed the interviews and seven of 12 participants in the HCFADP returned surveys. Twelve of 17 programs participated in HCFADP and two programs downsized outside HCFADP. Seven of 12 participants lost EM positions. Six of 12 programs were forced to exclude outside residents from rotating in their ED, leading to a need for one participating program and one non-participating program to find alternative sites for trauma. Five of 12 institutions provided resident staffing data, reporting a reduction in ED resident coverage in year 1 of the project of 9-40%. Programs compensated by increasing the number of shifts worked (4/12), increasing shift length (1/12), decreasing pediatric ED shifts (1/12), decreasing elective or research time (2/12), and decreasing off-service rotations (4/12). Six departments hired physician assistants or nurse practitioners, two hired faculty, and two hired resident moonlighters. Six of 12 programs withdrew from HCFADP and returned to previous resident numbers. Eight of 12 PDs thought that they had decreased time for clinical teaching. CONCLUSIONS: A 4-5% reduction in residency positions was associated with a marked reduction in ED resident staffing and EM residency curriculum changes.

Acute cyanide poisoning: a case report.

A case of attempted homicide by cyanide ingestion is reported. The victim, a 19-year-old woman, unknowingly ingested cyanide and presented to the Emergency Department unresponsive, in shock, and in profound metabolic acidosis. The differential diagnosis of this presentation and the patient's successful treatment are reviewed. The important management issues surrounding the treatment of cyanide poisoning are discussed.

Manometría, defecografía y ecografía endoanal en el estudio de los trastornos ano-rectales / Role of manometry, defecography and anal endosonography in the evaluation of colorectal disorders

INTRODUCCIÓN: la alteración de la motilidad o la, anatomía del recto, ano y piso perineal puede causar una sintomatología resistente a las actuaciones terapéuticas habituales. Estos trastornos suelen presentar estreñimiento y/o incontinencia. Se han desarrollado en las últimas dos décadas estudios para la valoración ano-rectal y perineal que han permitido comprender mejor estos problemas. OBJETIVO: valoración de la rentabilidad diagnóstica de la manometría ano-rectal, defecografía y ecografía endoanal combinadas en el estudio de trastornos ano-rectales. PACIENTES Y MÉTODO: se estudian 25 niños afectos de estreñimiento con o sin ensuciamiento, incontinencia y/o prolapso; grupos: A (n = 9) incontinencia; 13 (n = 10) estreñimiento con ensuciamiento; C (n = 6) estreñimiento aislado. Se les practicó manometría, defecografía y ecografía endoanal. RESULTADOS: en el grupo A destaca la asociación de incontinencia en reposo con hipotonía del esfínter anal externo (4/9), y en dos de ellos se evidencia un esfínter anal interno adelgazado. En el grupo B se observa la asociación de incontinencia en reposo e hipotonía del esfínter anal externo (8/10), con adelgazamiento de esfínter anal interno en s is de ellos. En el grupo C no se aprecian estas asociaciones. CONCLUSIONES: 1) el enema opaco no es suficiente para llegar al diagnóstico de las disfunciones ano-rectales. 2) Una sola exploración por sí misma no es capaz de diagnosticar el tipo de alteración. Estudios como manometría, defecografía y ecografía endoanal se complementan en el estudio de este grupo de afecciones, 3) Este nuevo enfoque hará que la patogenia de estos trastornos sea cada vez más conocida en Pediatría. 4) Nuevos estudios son necesarios para poder llegar a conclusiones definitivas (AU)

Bacterial sulfate production by biodesulfurization of aromatic hydrocarbons, determined by ion chromatography.

The use of bacteria to remove sulfur from crude oil or petroleum distillates is a novel concept that presents an alternative biotechnology to the current technology of hydrodesulfurization (HDS). Sulfur must be removed from crude oils prior use. The burning of fossil fuels containing sulfur releases sulfur dioxide into the atmosphere causing acid rain. The aim of this work is to determine the sulfate concentration by ion chromatography (IC), and calculate the percentage of transformation of organic bound sulfur, that is converted to sulfate, and estimate the efficiency of bacteria in desulfurization. IC is a suitable method for sulfate concentration determination. However, when chloride concentrations are significantly high, interference of the sulfate signal does occur. In this case, it could be avoided by diluting samples. A Dionex Model 2000i/SP IC system, with an anionic pre-column (Dionex AG4A), an anion separator column (Dionex AS4A), a suppressor column (Dionex AMMS-II), and a conductivity detector was used. The eluent (21 mM NaOH) and regenerant (electrolyzed 18 M omega/cm water) flow-rates were 1.0 and 2.0 ml/min, respectively. The sample loop volume was 10 microliters and the conductivity sensitivity was 30 muS. The diluted samples were filtered through a 0.45-micron filter before injection. The highest sulfate concentration detected was 24.10 mg/l, corresponding to a maximal conversion rate of 10% in a month. Sulfate ions were not detected in control samples. The correlation coefficient for a linear least squares fit was 0.99 (p < 0.001). The minimal concentration that we can read was 0.02 mg/l and this concentration corresponded to the limit of detection obtained under the conditions employed in this study. IC is an economical, sensitive and accurate way to estimate the sulfate concentrations in microbiological samples.

The effect of dental alloys on mouse lymphocyte subpopulations.

The aim of the present study was to determine the effect of nickel-containing alloys on lymphocyte subsets in an experimental setting. Plates of alloys containing nickel (Ceramalloy, Talladium, Cerillium, Rexillium) or gold (Orion) were implanted subcutaneously into mice. The levels of CD4+ and CD8+ T-lymphocyte subpopulations and of Smig+ B lymphocytes were determined at various intervals following implantation, using monoclonal antibodies and flow cytometry. No changes were detected in the proportion of the lymphocyte subsets tested. One month after implantation, the mean fluorescence intensity of CD4, CD8 or Smig, in the peripheral blood lymphocytes (PBL) of the nickel alloy-implanted animals, was significantly higher than that prior to this procedure. Only a mild increase in CD4 and CD8 was noted after implantation of the gold alloy. The observed effects are most likely attributable to the surgical trauma, and do not indicate that nickel-containing dental alloys influence T cell subsets in this murine model.

Domestic violence: diurnal mismatch between need and availability of services.

OBJECTIVE: To determine whether a diurnal discordance exists between need and availability of services for victims of domestic violence. METHODS: A consecutive sample of women presenting to a municipal hospital ED with physical injuries suspected to be related to domestic violence were entered into a registry. Date and time of presentation and perceived need for services information were collected from all patients who answered affirmatively a screening question for domestic violence and whose conditions did not preclude administration of the data collection instrument. The Social Service Departments of all of the 53 911-receiving hospitals in New York City were contacted to ascertain availability of social services for victims of domestic violence by time of day. RESULTS: Twenty-eight of 32 (88%; 95% CI: 71%, 97%) victims of domestic violence presented to the ED during hours other than weekday 9 AM to 5 PM. Of these, 63% desired counseling, 32% lacked a safe place to go, and 82% had children. Of those who had children, 48% were concerned for the children's safety. In-hospital social services were universally available weekday daytime (9 AM to 5 PM) but were available in only 11% of hospital (95% CI: 4%, 23%) at other times. CONCLUSION: Approximately nine of ten victims of domestic violence presented to the ED during hours when only about one hospital in ten can provide the special services these patients require. A marked diurnal mismatch appears to exist between availability of domestic violence services in New York City and the need for these services as measured by a representative sample drawn from an ED population.