Side readout of long scintillation crystal elements with digital SiPM for TOF-DOI PET.

PURPOSE: Side readout of scintillation light from crystal elements in positron emission tomography (PET) is an alternative to conventional end-readout configurations, with the benefit of being able to provide accurate depth-of-interaction (DOI) information and good energy resolution while achieving excellent timing resolution required for time-of-flight PET. This paper explores different readout geometries of scintillation crystal elements with the goal of achieving a detector that simultaneously achieves excellent timing resolution, energy resolution, spatial resolution, and photon sensitivity. METHODS: The performance of discrete LYSO scintillation elements of different lengths read out from the end/side with digital silicon photomultipliers (dSiPMs) has been assessed. RESULTS: Compared to 3 × 3 × 20 mm(3) LYSO crystals read out from their ends with a coincidence resolving time (CRT) of 162 ± 6 ps FWHM and saturated energy spectra, a side-readout configuration achieved an excellent CRT of 144 ± 2 ps FWHM after correcting for timing skews within the dSiPM and an energy resolution of 11.8% ± 0.2% without requiring energy saturation correction. Using a maximum likelihood estimation method on individual dSiPM pixel response that corresponds to different 511 keV photon interaction positions, the DOI resolution of this 3 × 3 × 20 mm(3) crystal side-readout configuration was computed to be 0.8 mm FWHM with negligible artifacts at the crystal ends. On the other hand, with smaller 3 × 3 × 5 mm(3) LYSO crystals that can also be tiled/stacked to provide DOI information, a timing resolution of 134 ± 6 ps was attained but produced highly saturated energy spectra. CONCLUSIONS: The energy, timing, and DOI resolution information extracted from the side of long scintillation crystal elements coupled to dSiPM have been acquired for the first time. The authors conclude in this proof of concept study that such detector configuration has the potential to enable outstanding detector performance in terms of timing, energy, and DOI resolution.

Lack of correlation between minimal erythema dose and skin phototype in a Colombian scholar population.

BACKGROUND: Sun exposure and skin phototype are the most relevant risk factors for skin cancer. Colombia has high levels of ultraviolet radiation during the whole year, therefore, both, high UVI's and outdoor worker's daily activities, in our country are very important risk factors for the development of cutaneous cancer. To date no study has evaluated the usefulness of Fitzpatrick's skin phototype classification in Colombians and its correlation with the minimal erythema dose (MED) and constitutional skin color. Such information is gaining importance in other nations due to the fact that several country's population is becoming more ethnically diverse. OBJECTIVES: To determine the skin phototype, accumulated sun exposure, sun protection behavior, MED and phenotype in a Colombian school population. METHODS: Last year high school students from the western Antioquia were invited to participate by phone and letter through their respective school directors. A self-questionnaire was handled to each student. A representative sample of the universe was selected for a medical examination by a dermatologist in order to validate the results of the self-questionnaire. The constitutional skin color was determined with the chromameter CR 300 Minolta. The MED was defined as the minimal dose of UVB being able to induce erythema 24 h later. RESULTS: Eight schools of the area agreed to participate in the study, and a total of 911 students (58% girls and 42% boys) filled-out the self-questionnaire. Sun exposure in the majority of individuals was in a level between moderate and very high. Ninety percent of students do not use any sun protection device or cream. Only a 50% of concordance between self-assessed skin phototype vs. medical skin phototype was found, and the highest concordance corresponded to skin phototype II (82%). There was a marked difference in skin photosensitivity of Colombians compared with reports in Caucasians. We observed a marked overlapping in MED's and L* values in phototypes II and III. CONCLUSIONS: The Fitzpatrick's classification was not useful in Hispanic populations such as ours. Therefore, a new skin-phototype classification system is required. In our population the constitutional color was a good predictor of the MED but it did not correlate with skin phototype. The self-assessed questionnaire method was not useful to determine skin cancer risk in our population. The majority of this population has light skin phototypes and is highly exposed to solar UV radiation without proper protection.

Análise facial numérica do perfil de brasileiros padrão I / Numeric facial analysis of the profile in pattern I Brazilians

OBJETIVO: o objetivo do presente estudo foi determinar as medidas do perfil facial de brasileiros portadores de equilíbrio facial, denominados Padrão I. METODOLOGIA: a amostra foi constituída por 50 indivíduos (32 femininos e 18 masculinos), brasileiros, adultos, leucodermas, com idade média de 23 anos. Fotografias padronizadas do perfil foram obtidas. Sobre essas foram executados os traçados por dois avaliadores, que verificaram: 1) ângulo nasolabial; 2) ângulo mentolabial; 3) ângulo interlabial; 4) ângulo de convexidade facial; 5) ângulo de convexidade facial total; 6) ângulo do terço inferior da face; 7) proporção entre a altura facial anterior média e a altura facial anterior inferior e 8) proporção do terço inferior da face. RESULTADOS E CONCLUSÕES: não houve diferença estatística relevante entre as duas medidas realizadas. Os valores de média, desvio-padrão, valores máximos e mínimos obtidos para cada variável estudada foram: 1) ângulo nasolabial: 108,13º ± 9,75º (81º a 127º); 2) ângulo do sulco mentolabial: 132,37º ± 9,82º (110,5º a 152º); 3) ângulo interlabial: 135,35º ± 11,14º (116,5º a 159,5º); 4) ângulo de convexidade facial: 12,32º± 3,93º (4º a 19,5º); 5) ângulo de convexidade facial total: 137,85º ± 4,08º (129,5º a 147,5º); 6) ângulo do terço inferior da face: 103,41º ± 8,12º (88º a 124º); 7) proporção entre os terços médio e inferior da face: 0,93 ± 0,10 (0,80 a 1,21) e 8) proporção do terço inferior da face: 0,45 ± 0,06 (0,30 a 0,67). Propõe-se esse conjunto de medidas como um padrão de referência para avaliação facial numérica de adultos, brasileiros, brancos.

AIM: the aim of this study was to determine measurements of the facial profile in balanced faces of Pattern I Brazilian patients. METHODS: the sample was comprised by 50 Brazilian adults (32 women and 18 men) selected by morphologic facial analysis in frontal and lateral views. Standardized lateral facial photographs were taken. They were measured for two different researches to obtain the following: 1) nasolabial angle; 2) angle of mentolabial fold; 3) interlabial angle; 4) angle of facial convexity; 5) angle of total facial convexity; 6) angle of the lower third of the face; 7) proportion between medium facial height and lower facial height; 8) proportion of the lower third of the face. RESULTS AND CONCLUSIONS: there was no statistical difference between the two measurements. The averages, standard deviation, minimal and maximal values obtained were: 1) nasolabial angle: 108.13º ± 9.75º (81º to 127º); 2) angle of mentolabial fold: 132.37º ± 9.82º (110.5º to 152º); 3) interlabial angle: 135.35º ± 11.14º (116.5º to 159.5º); 4) angle of facial convexity: 12.32º± 3.93º (4º to 19.5º); 5) angle of total facial convexity: 137.85º ± 4.08º (129.5º to 147.5º); 6) angle of lower third of the face: 103.41º ± 8.12º (88º to 124º); 7) proportion between medium facial height and lower facial height: 0.93 ± 0.10 (0.80 to 1.21); 8) proportion of lower third of the face: 0.45 ± 0.06 (0.30 to 0.66). With those results, we intend to determine values of reference for the measurements of facial profile, establishing averages and standard deviation to be used comparatively in the study and treatment of compromised faces of white Brazilians adults.

Lactate measurements in critically ill patients with a hand-held analyser.

OBJECTIVE: To compare a recently introduced hand-held lactate analyser to a reference point of care analyser (POCI) and the hospital laboratory in a critical care setting. SETTING: 10-bed surgical/medical intensive care unit in a teaching hospital. PATIENTS AND METHODS: In 39 critically ill patients, 50 convenience measurement cycles consisting of three paired measurements at 30-min intervals were carried out with a hand-held analyser, reference POCI and hospital laboratory using arterial blood samples. Duplicate measurements with the hand-held analyser were done in 129 blood samples. RESULTS: Lactate levels ranged from 1.1 to 21.0 mmol/l. Regression analysis of the hand-held analyser and laboratory showed a slope of 1.01, bias of -0.38 mmol/l, R(2) = 0.97 and mean error of 14.9 %. Reference POCI versus laboratory: slope = 1.07, bias = -0.29 mmol/l, R(2) = 0.98 and mean error of 6.4 %. Hand-held analyser versus reference POCI: slope = 0.90, bias = 0.09 mmol/l and R(2) = 0. 92. The hand-held analyser showed acceptable precision. CONCLUSION: The hand-held lactate analyser can reliably measure arterial blood lactate levels in critically ill patients.

Estudo da inflamaçäo ocular após a extraçäo extracapsular do cristalino por meio da flare-fotometria a laser / Intraocular inflammation, after extracapsular extraction of cataract by laser-flare photometry

A flare - fotometria a laser é uma técnica näo in-vasiva que pode, objetivamente, quantificar o flare no interior da câmara anterior por meio de um laser de He-Ne acoplado a uma lâmpada de fenda. Este estudo comparou a intensidade da reaçäo inflamatória no humor aquoso em pacientes de diferentes raças humanas e que foram submetidos à facectomia extracapsular com implante de lente intra-ocular em câmara posterior. Foram estudados 30 pacientes (10 brancos, 10 amarelos e 10 negros). A laser fotometria foi realizada nos dia 0, 3, 6, 30, 60 e 90 pós-operatórios. As medidas pré-operatórias de flare em pacientes com catarata senil foram de 8,5; 7,0 e 5,7 fótons/mseg, respectivamente, nas raças branca, amarela e negra. Os pacientes brancos apresentaram menos inflamaçäo

[The photometric determination of the antilysozyme activity of microorganisms]. / Fotometricheskoe opredelenie antilizotsimnoi aktivnosti mikroorganizmov.

The method for the determination of the antilysozyme activity (ALA) of microorganisms, based on the photometric determination of the residual activity of enzyme with the use of Micrococcus lysodeikticus test culture after the incubation of the strain under test and lysozyme, is proposed. The new method enhances the reliability of the determination of the ALA of microorganisms due to an increase in the accuracy of the quantitative determination of ALA. The elimination of the stage of interaction between the growing bacterial culture and lysozyme and the presence of the antilysozyme factor in the supernatant fluid confirm the constructive and secretory character of antilysozyme activity.

Low density of neutral hydrogen and helium in the local interstellar medium: Extreme Ultraviolet Explorer photometry of the Lyman continuum of the hot white dwarfs MCT 0501-2858, MCT 0455-2812, HZ 43, and GD 153.

The first comprehensive sky survey of the extreme ultraviolet (EUV) spectral range performed by the Extreme Ultraviolet Explorer (EUVE) has uncovered a handful of very bright sources at wavelengths longer than the He I 504 angstroms photoionization edge. Among these objects are four white dwarfs with exceptionally low interstellar medium (ISM) column densities along the line of sight. Analysis of EUV photometry of the He-rich DO white dwarf MCT 0501-2858 and the H-rich DA white dwarf MCT 0455-2812 along one line of sight and of the DA white dwarfs HZ 43 and GD 153 near the north Galactic pole indicates that the overall minimum column density of the neutral material centered on the Sun is N(H I)= 0.5-1.0 x 10(18) cm-2. In the case of MCT 0501-2858, EUV photometric measurements provide a clear constraint to the effective temperature (60,000-70,000 K). Given these neutral hydrogen columns, the actual contribution to the density of neutral species from the immediate solar environment (the "local fluff") would only cover a distance of approximately 2-3 pc (assuming an average density n(H I) = 0.1 cm-3) leaving these lines of sight almost entirely within the hot phase of the ISM. A preliminary examination of the complete EUVE long-wavelength survey indicates that these lines of sight are exceptional and set a minimum column density in the solar environment.

HemoCue: evaluation of a portable photometric system for determining glucose in whole blood.

We assessed the HemoCue system for measuring glucose in 5 microL of whole blood. A glucose dehydrogenase-based reaction is used with dried reagents contained in disposable microcuvettes, which are filled with blood by capillary action. Automated hexokinase and YSI 23AM glucose analyzer methods were used for comparison. Overall imprecision (CV) was better than 4.5%, with no significant differences in results between three different HemoCue photometers and four batches of microcuvettes. Regression slopes (+/- SE) were 0.947 (0.011) with the YSI and 0.966 (0.015) with the hexokinase method. Analytical recovery of added glucose was 101-106%, and the system functioned with hematocrits up to 0.65. Bilirubin up to 453 mumol/L did not interfere, but high concentrations of endogenous (greater than 3 mmol/L) and exogenous triglycerides gave positive interference. The system proved stable and robust under a wide range of storage and handling conditions; performance was impaired only at high ambient temperature (37 degrees C). We conclude that the HemoCue system should prove useful for glucose measurement; further testing outside the laboratory is warranted.

Colorimetric determination of potassium in plasma and serum by reflectance photometry with a dry-chemistry reagent.

We evaluated a colorimetric assay of potassium in plasma and serum with the Boehringer Mannheim Reflotron reflectance photometric analyzer, which is designed for near-patient testing in hospitals and physicians' offices. This potassium method does not require calibration or instrument maintenance by the operator. Analysis of 30 microL of plasma or serum takes approximately 140 s. Within-day imprecision (CV) was 1.0-1.2%. Total CVs over a 1-month period were 1.0-1.4%. Patients' results from the Reflotron correlated well with those from the IL 643 flame photometer and the Beckman Synchron CX3 ion-selective electrode methods. The accuracy of Reflotron values was also verified with Standard Reference Material 956 from the National Institute of Standards and Technology.

Single stable reagent (Arsenazo III) for optically robust measurement of calcium in serum and plasma.

We describe a method based on a single stable reagent for the determination of calcium in serum and plasma with use of Arsenazo III, 200 mumol/L in 50 mmol/L 1,4-piperazinediethanesulfonic acid (PIPES) buffer. The method showed significant positive interference in plasma at pH less than 6.6 because of the precipitation of fibrinogen, which was eliminated by increasing the pH to 6.8. The assay showed no interference from as much as 600 mumol of bilirubin and 12 g of hemoglobin per liter when applied in a simple monochromatic procedure at 660 nm. The standard curve for calcium was linear from 0 to 5.0 mmol/L. Addition of Intralipid at concentrations greater than 3 g/L demonstrated positive interference, which could be eliminated by using a 700-nm blanking wavelength. The procedure showed good agreement with all-method mean values from two external quality-control schemes.

Improved sample and reagent pipetting with the MINILAB.

MINILAB is a small photometer designed for use in small labs and physicians' offices. The instrument is preprogrammed for the determination of several analytes either in whole blood, plasma or serum. Each method is provided as a kit containing disposable cuvettes and capillaries for sample or reagent addition. We examined the precision of the MINILAB using the cholesterol and bilirubin methods for serum, following the recommendations provided for each method, and found that the precisions were not acceptable (CV up to 16% for cholesterol and 43% for bilirubin). Suspecting that these variations were due to sample and reagent pipetting, we tried a simple modification using a Microcap for pipetting and were able to improve the precisions, resulting in CVs of 1.4% for cholesterol and 3.5% for bilirubin.

[An evaluation of the Reflotron portable analyzer for cholesterol determination in primary care]. / Evaluación de un analizador portátil, reflotron, para la determinación del colesterol en atención primaria.

We have evaluated serum cholesterol in a primary care center with a recently introduced portable analyzer: Reflotron (Boehringer Mannheim). The linearity and exactitude were investigated with Hitachi 704 (Boehringer Mannheim) used in the reference laboratory. Accuracy was also tested. We found a good accuracy after repeated analysis (n = 30) of two control sera with a variation coefficient of 2.77% in the first (mean = 125.14 mg/dl, SD 3.47) and 2.94% (mean = 254.53 mg/dl, SD 7.49) in the second. We found an overall lack of accuracy of Reflotron with a more pronounced negative bias in capillary blood (mean d = 30.93 mg/dl, dSE 3.25) than in serum (mean d = dSE 1.12). We found a positive linear correlation both using serum (r = 0.9845; n = 45) and capillary blood (r = 0.9094; n = 30). We feel that Reflotron is useful for primary care due to its good accuracy and linearity regarding the reference method, but its inexactitud should be taken into account. We emphasize the need for quality control to investigate its limitations when the results are analyzed.