Densitometric analysis of brain computed tomography as a new prognostic factor in patients with acute subdural hematoma.

OBJECTIVE: Acute subdural hematoma (ASDH) is a major cause of mortality and morbidity after traumatic brain injury (TBI). Surgical evacuation is the mainstay of treatment in patients with altered neurological status or significant mass effect. Nevertheless, concerns regarding surgical indication still persist. Given that clinicians often make therapeutic decisions on the basis of their prognosis assessment, to accurately evaluate the prognosis is of great significance. Unfortunately, there is a lack of specific and reliable prognostic models. In addition, the interdependence of certain well-known predictive variables usually employed to guide surgical decision-making in ASDH has been proven. Because gray matter and white matter are highly susceptible to secondary insults during the early phase after TBI, the authors aimed to assess the extent of these secondary insults with a brain parenchyma densitometric quantitative CT analysis and to evaluate its prognostic capacity. METHODS: The authors performed a retrospective analysis among their prospectively collected cohort of patients with moderate to severe TBI. Patients with surgically evacuated, isolated, unilateral ASDH admitted between 2010 and 2017 were selected. Thirty-nine patients were included. For each patient, brain parenchyma density in Hounsfield units (HUs) was measured in 10 selected slices from the supratentorial region. In each slice, different regions of interest (ROIs), including and excluding the cortical parenchyma, were defined. The injured hemisphere, the contralateral hemisphere, and the absolute differences between them were analyzed. The outcome was evaluated using the Glasgow Outcome Scale-Extended at 1 year after TBI. RESULTS: Fifteen patients (38.5%) had a favorable outcome. Collected demographic, clinical, and radiographic data did not show significant differences between favorable and unfavorable outcomes. In contrast, the densitometric analysis demonstrated that greater absolute differences between both hemispheres were associated with poor outcome. These differences were detected along the supratentorial region, but were greater at the high convexity level. Moreover, these HU differences were far more marked at the cortical parenchyma. It was also detected that these differences were more prone to ischemic and/or edematous insults than to hyperemic changes. Age was significantly correlated with the side-to-side HU differences in patients with unfavorable outcome. CONCLUSIONS: The densitometric analysis is a promising prognostic tool in patients diagnosed with ASDH. The supplementary prognostic information provided by the densitometric analysis should be evaluated in future studies.

Densitometric Validation and Optimisation of Polyphenols in Ocimum sanctum Linn by High Performance Thin-layer Chromatography.

INTRODUCTION: Ocimum sanctum Linn (Sanskrit: Tulasi; family: Libiaceae), popularly known as holy basil or Ocimum teinufolium, is found throughout the semitropical and tropical parts of India. In Ayurveda, Tulasi has been well known for its therapeutic potentials. OBJECTIVE: To optimise and develop a standard method to quantify seven polyphenols simultaneously by HPTLC. METHODS: A three-level factor Box-Behnken statistical design was used for optimisation, where extraction time (min), temperature (°C) and methanol:water ratio (% v/v) are the independent variables with polyphenols as the dependent variable. The separation was archived on a silica-gel 60 F254 HPTLC plate using toluene:ethyl acetate:formic acid:methanol (3:3:0.8:0.2 v/v) as the mobile phase. Densitometric analysis of polyphenols was carried out in the absorbance mode at 366 nm. RESULTS: The quantification of polyphenols was carried out based on peak area with a linear calibration curve at concentration ranges of 60-240, 20-200, 100-1600, 40-200, 200-1400, 10-160, 200-1400, 100-5000 ng/band for caffeic acid, ellagic acid, rutin, kaempferol, catechin, quercetin, eupalitin and epicatechin respectively. The method was validated for peak purity, precision, accuracy, limit of detection (LOD) and quantification (LOQ). Method specificity was confirmed using the retention factor value and visible spectra correlation of marker compounds. CONCLUSIONS: A validated HPTLC method was newly developed for simultaneous quantification of seven polyphenols in an Ayurvedic preparation of O. sanctum. The proposed method is simple, precise, specific, accurate, cost-effective, less time consuming and has the ability to separate the polyphenols from other constituents.

Impact on the population of different bone mineral density testing criteria and appropriateness of densitometries in the ESOSVAL cohort, Spain.

CONTEXT: There is little consensus regarding which individuals should be recommended for bone mineral density (BMD) testing, a situation that could eventually affect the appropriateness of routine clinical practice. OBJECTIVES: The aim of this study was to estimate the impact on the population of the application of the BMD testing criteria provided by the National Osteoporosis Guideline Group (NOGG), National Osteoporosis Foundation (NOF), and Osteoporosis Canada and to assess the appropriateness of the BMD tests currently performed. DESIGN: A cross-sectional study was conducted using the baseline data of the ESOSVAL cohort. PARTICIPANTS: Participants included 11 035 men and women aged 50 years old and over attending primary health care centers in the Valencia region, Spain (2009-2010). MAIN OUTCOME AND MEASURES: BMD testing by dual-energy X-ray absorptiometry was recorded. RESULTS: Of the 10 710 people included in the study, 1617 (15.1%; 95% confidence interval [CI]: 14.4-15.8) received a BMD test. When applying the NOGG criteria, BMD testing would be recommended in 17.4% (95% CI: 16.7-18.1) of individuals, whereas this percentage would rise to 74.6% (95% CI: 73.7-75.4) and 80.1% (95% CI: 79.4-80.9) when using the Osteoporosis Canada and the NOF criteria, respectively. Regarding the appropriateness of the BMD tests performed in the ESOSVAL cohort, 40.7% (95% CI: 38.3-43.1), 86.0% (95% CI: 84.3-87.7), and 82.2% (95% CI: 80.3-84.1) of individuals having a BMD test met the NOGG, NOF, and the Canadian guidelines criteria, respectively. Of the tests performed, 40.7% would be deemed as appropriate, whereas 10.7% would be considered inappropriate. CONCLUSIONS: The impact on the population of the different recommendations is enormous, varying from 17% to 80% of the population over 50 who would be tested. Although in men it seems that a clinical rationale exists between the presence of risk factors and the rates of BMD testing, this pattern does not seem to exist in women. One in 10 of the densitometric tests performed were inappropriate according to all the guidelines.

Application of TLC method with video scanning in estimation of daily dietary intake of specific flavonoids--preliminary studies.

Flavonoids, substances present in foods of plant origin, play an important role in many metabolic processes. Numerous properties of these substances were described, including their anti-allergic, antitumor and antioxidant properties. Therefore, an increased intake of these nutrients may play a beneficial role in human health. The aim of the presented study was to estimate the daily intake of specific flavonoid compounds using thin layer chromatography (TLC) combined with densitometric qualitative and quantitative analysis. Performed investigations revealed the presence of two flavonoids in the extracts from daily food rations--naringenin and hesperidin. Naringenin content in the daily food ration of women was calculated to be 179-537 mg, whereas in the group of men it ranged around 181-550 mg, depending on the conducted method of extraction and solvent system used. Daily dietary intake of hesperidin was calculated to be 193-534 mg in the group of women and 194-562 mg in the group of men. The highest degree of extraction of these flavonoids was obtained for the mixture of acetone and water (7 : 3, v/v) by means of accelerated solvent extraction (ASE).

Investigation on dynamic calibration for an optical-fiber solids concentration probe in gas-solid two-phase flows.

This paper presents a review and analysis of the research that has been carried out on dynamic calibration for optical-fiber solids concentration probes. An introduction to the optical-fiber solids concentration probe was given. Different calibration methods of optical-fiber solids concentration probes reported in the literature were reviewed. In addition, a reflection-type optical-fiber solids concentration probe was uniquely calibrated at nearly full range of the solids concentration from 0 to packed bed concentration. The effects of particle properties (particle size, sphericity and color) on the calibration results were comprehensively investigated. The results show that the output voltage has a tendency to increase with the decreasing particle size, and the effect of particle color on calibration result is more predominant than that of sphericity.

Reference values for areal bone mineral density among a healthy Mexican population / Valores de referencia para la densidad mineral ósea expresada en área para una población mexicana sana

OBJECTIVE: Compare the influence of ethnicity in the prevalence of osteopenia and osteoporosis in various Mexican populations using two normal dual X-ray absorptiometry (DXA) reference databases: manufacturer's incorporating US Hispanic population and a normal mestizo Mexican population. MATERIAL AND METHODS: MMP included 9 946 subjects participating in an ongoing long-term cohort study focusing on lifestyle and chronic diseases, of which 6 487 MMP males and females aged 7 to 80 years were the normal subjects used to determine bone density T- and Z-scores, following WHO criteria, and peak bone mass values. Abnormal bone mass density values estimated by the manufacturer's and peak bone mass reference values were compared. RESULTS AND CONCLUSIONS: Our results show that by using the manufacturer's T-score values in the mestizo Mexican population we are underestimating the number of abnormal bone mass BMD populations.

OBJETIVO: Comparar la influencia de la etnicidad en la prevalencia de osteopenia y osteoporosis en varias poblaciones mexicanas utilizando dos bases de referencia normal de densitometría de rayos X (DXA): referencia del fabricante que incorpora hispanos en Estados Unidos y datos de una población mestiza mexicana. MATERIAL Y MÉTODOS: Un total de 9 946 sujetos de población mestiza mexicana participantes en una cohorte de largo plazo dirigida al estudio de estilos de vida y ocurrencia de enfermedades crónicas; de los cuales 6 487 sujetos sanos de ambos sexos, con edad entre los 7 y los 80 años, fueron utilizados para determinar los valores T, Z, de acuerdo a los criterios de la OMS, así como a los valores de masa ósea pico. Se compararon los casos de densidad mineral ósea anormal de acuerdo a los valores de referencia del fabricante y los valores de masa ósea pico de la población mestiza. RESULTADOS Y CONCLUSIÓN: Las bases de referencia del fabricante subestima significativamente el número de casos con densidad mineral ósea anormal en la población mestiza mexicana.

Quantitative bone matrix density measurement by water- and fat-suppressed proton projection MRI (WASPI) with polymer calibration phantoms.

The density of the organic matrix of bone substance is a critical parameter necessary to clinically evaluate and distinguish structural and metabolic pathological conditions such as osteomalacia in adults and rickets in growing children. Water- and fat-suppressed proton projection MRI (WASPI) was developed as a noninvasive means to obtain this information. In this study, a density calibration phantom was developed to convert WASPI intensity to true bone matrix density. The phantom contained a specifically designed poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend, whose MRI properties (T(1), T(2), and resonance linewidth) were similar to those of solid bone matrix (collagen, tightly bound water, and other immobile molecules), minimizing the need to correct for differences in T(1) and/or T(2) relaxation between the phantom and the subject. Cortical and trabecular porcine bone specimens were imaged using WASPI with the calibration phantom in the field of view (FOV) as a stable intensity reference. Gravimetric and amino acid analyses were carried out on the same specimens after WASPI, and the chemical results were found to be highly correlated (r(2) = 0.98 and 0.95, respectively) to the WASPI intensity. By this procedure the WASPI intensity can be used to obtain the true bone matrix mass density in g cm(-3).

Accuracy study on "Osteorisk": a new osteoporosis screening clinical tool for women over 50 years old.

CONTEXT AND OBJECTIVE: Osteoporosis is the greatest cause of quality-of-life reductions, morbidity and mortality among postmenopausal women, with growing incidence as populations age. Clinical tools like Osteorisk provide an easy-access and low-cost alternative method that helps physicians to reduce the need for dual-energy X-ray absorptiometry (DXA), the expensive gold standard examination for diagnosing osteoporosis. The aim here was to study the accuracy of Osteorisk using heel ultrasonography for bone mineral density (BMD). DESIGN AND SETTING: Cross-sectional study, at Faculdade de Medicina do ABC. METHODS: A structured questionnaire was applied to 615 postmenopausal women, with anthropometric measurements, Osteorisk calculations and quantitative ultrasound on the heel using Sonost 2000 equipment. RESULTS: 461 women were included, with mean age 60 +/- 9 years, weight 67.6 +/- 12.9 kg and body mass index (BMI) 28.8 +/- 5.0 kg/m(2). Their Osteorisk classifications were: 61.0% low-risk, 28.4% medium-risk and 10.6% high-risk. Quantitative ultrasound showed 81.3% low-risk, 10.0% medium-risk and 8.7% high-risk regarding osteoporosis. Statistically significant results were observed (p < 0.001) when Osteorisk was correlated with age, years since menopause and BMI. Correlating these same variables with quantitative ultrasound, statistically significant results were observed for age (p < 0.001), years since menopause (p < 0.001) and BMI (p < 0.006). The sensitivity, specificity, negative predictive value and positive predictive value for Osteorisk were 64%, 6.7%, 89% and 30.6%, respectively. CONCLUSION: Osteorisk is a valid tool for screening for women at low risk of osteoporosis, making it possible for these women not to have to undergo densitometry.

Accuracy study on "Osteorisk": a new osteoporosis screening clinical tool for women over 50 years old

CONTEXT AND OBJECTIVE: Osteoporosis is the greatest cause of quality-of-life reductions, morbidity and mortality among postmenopausal women, with growing incidence as populations age. Clinical tools like Osteorisk provide an easy-access and low-cost alternative method that helps physicians to reduce the need for dual-energy X-ray absorptiometry (DXA), the expensive gold standard examination for diagnosing osteoporosis. The aim here was to study the accuracy of Osteorisk using heel ultrasonography for bone mineral density (BMD). DESIGN AND SETTING: Cross-sectional study, at Faculdade de Medicina do ABC. METHODS: A structured questionnaire was applied to 615 postmenopausal women, with anthropometric measurements, Osteorisk calculations and quantitative ultrasound on the heel using Sonost 2000 equipment. RESULTS: 461 women were included, with mean age 60 ± 9 years, weight 67.6 ± 12.9 kg and body mass index (BMI) 28.8 ± 5.0 kg/m². Their Osteorisk classifications were: 61.0 percent low-risk, 28.4 percent medium-risk and 10.6 percent high-risk. Quantitative ultrasound showed 81.3 percent low-risk, 10.0 percent medium-risk and 8.7 percent high-risk regarding osteoporosis. Statistically significant results were observed (p < 0.001) when Osteorisk was correlated with age, years since menopause and BMI. Correlating these same variables with quantitative ultrasound, statistically significant results were observed for age (p < 0.001), years since menopause (p < 0.001) and BMI (p < 0.006). The sensitivity, specificity, negative predictive value and positive predictive value for Osteorisk were 64 percent, 6.7 percent, 89 percent and 30.6 percent, respectively. CONCLUSION: Osteorisk is a valid tool for screening for women at low risk of osteoporosis, making it possible for these women not to have to undergo densitometry.

CONTEXTO E OBJETIVO: Osteoporose é a principal causa de redução de qualidade de vida, morbidade e mortalidade entre as mulheres no climatério, com aumento na incidência conforme o envelhecimento da população. Ferramentas clínicas como Ostorisk fornecem uma alternativa de acesso fácil e de baixo custo que ajudam o clínico a melhorar a eficácia da solicitação da densitometria óssea, exame padrão ouro, porém caro para o diagnóstico de osteoporose. O objetivo deste artigo foi estudar a acurácia do Ostorisk tendo a ultrassonometria de calcâneo como método de avaliação da densidade mineral óssea. TIPO DE ESTUDO E LOCAL: Estudo transversal, na Faculdade de Medicina do ABC. MÉTODO: Um questionário estruturado foi aplicado em 615 mulheres menopausadas, com medidas antropométricas, cálculo do Osteorisk e realização de ultrassonometria quantitativa do calcâneo com o aparelho Sonost 2000. RESULTADOS: 461 mulheres foram incluídas, com uma idade média de 60 ± 9 anos, peso de 67,6 ± 12,9 kg e índice de massa corpórea (IMC) 28,8 ± 5.0 kg/ m². A classificação do Osteorisk para o grupo estudado foi: 61,0 por cento baixo risco, 28,4 por cento médio risco, e 10,6 por cento alto risco. A ultrassonometria de calcâneo mostrou 81,3 por cento baixo risco, 10,0 por cento médio risco e 8,7 por cento alto risco para osteoporose. Os resultados estatisticamente significantes foram observados (p < 0,001) quando o Osteorisk foi correlacionado com idade, anos de menopausa e índice de massa corpórea (IMC). Correlacionando essas mesmas variedades com a ultra-sonometria, resultados estatisticamente significantes foram observados para idade (p < 0,001), anos de menopausa (p < 0,001) e IMC (p < 0,006). A sensibilidade, especificidade, o valor preditivo negativo e o valor preditivo positivo para o Osteorisk foram 64 por cento, 6,7 por cento, 89 por cento e 30,6 por cento, respectivamente. CONCLUSÃO: Osteorisk é uma ferramenta válida para o rastreamento...

Standardized bending and breaking test for the normal and osteoporotic metaphyseal tibias of the rat: effect of estradiol, testosterone, and raloxifene.

UNLABELLED: The fracture of bone plays a key role in osteoporosis. BMD measurement, however, is only an indirect parameter of this phenomenon. We therefore developed a highly sensitive three-point bending test for the metaphyseal tibias in rats to evaluate stiffness and strength. This was validated in a right-left comparison and a bioassay with soy-free food, estradiol, raloxifene, and testosterone in orchidectomized rats. INTRODUCTION: Osteoporosis becomes manifest predominantly in the metaphyseal rat tibia. The anti-osteoporotic character of substances should, therefore, be tested (mechanically) in this bone area. MATERIALS AND METHODS: We evaluated a new three-point bending test for the metaphyseal tibia in rats in a right-left trial. In an animal experiment, we studied the change of bone quality under estradiol (E)-, raloxifene (R)-, and testosterone (T)-supplemented food and compared it with trabecular BMD (qCT). RESULTS: In the right-left comparison, the mean difference between the metaphyseal loads of both tibias in 37 rats was 8.43% for the maximum load (Fmax) and 6.46% for the failure load (fL). These results show the high reproducibility of the test, because they are close to the usual intraindividual difference of the two extremities. In a second experiment, four groups of 11 3-month-old male orchidectomized rats were fed with soy-free food only (C) or with the additives E, T, or R for 12 weeks. E and R were similar for Fmax and fL. There were significant differences in the stiffness (E = 406.92 N/mm versus R = 332.08 N/mm), the yield load (yL; E = 99.17 N versus R = 83.33 N), and the ratio between yL and Fmax (E = 86.33% versus R = 76.37%). T was similar to the controls concerning F(max), fL, and stiffness. There were significant differences in yL (T = 49.00N versus C = 39.5N) and the ratio between yL and Fmax (T = 64.28% versus C = 51.28%). CONCLUSIONS: Estradiol is superior to raloxifene concerning stiffness and yield load, and both are superior to testosterone. We conclude that the described three-point bending test for the metaphyseal tibia is a highly sensitive method to study hormones and substances with regard to their osteoprotective character. The precision and the low SD of the presented results are superior to the data from qCT and the calculated index of stiffness (SSI).

Determination of the standard value of circulating blood volume during anesthesia using pulse dye-densitometry: a multicenter study in Japan.

PURPOSE: The standard value for circulating blood volume (BV) during anesthesia was determined by a multicenter study in Japan. The significance of BV on the reduction of blood pressure after the induction of anesthesia was also examined. METHODS: The study included 184 patients from eight university hospitals. After the induction of anesthesia, pulse dye-densitometry was performed according to a uniform protocol. Factors contributing to reduced blood pressure after induction of anesthesia were examined by multiple logistic regression analysis. RESULTS: The mean and standard deviation of BV was 80.0 +/- 13.9 ml x kg(-1); for females and 84.2 +/- 15.3 ml x kg(-1) for males (P > 0.05). There was no age difference in terms of BV. After adjusting for the effects of height, weight, and age, the factors predisposing to a reduction in blood pressure of >20 mmHg after induction of anesthesia were found to be age (P < 0.01) and BV (ml x kg(-1)) (P < 0.001). CONCLUSION: We determined the BV of anesthetized patients before surgery in Japan using pulse dye-densitometry. It is suggested that age is not a factor regarding BV, and that blood pressure tends to be reduced in hypovolemic patients after induction of anesthesia.

Screening for childhood anaemia using copper sulphate densitometry.

OBJECTIVE: To evaluate copper sulphate densitometry to screen for childhood anaemia in a primary care setting, with a view to identifying children requiring definitive diagnostic testing and treatment. DESIGN: A cross-sectional screening study. Results of densitometry with a copper sulphate solution of specific gravity (SG) 1.048, corresponding to a haemoglobin (Hb) concentration of 10 g/dl, were compared with laboratory Hb determination. SETTING: Outpatient department of Pretoria Academic Hospital (73 children) and a local crèche (27 children). SUBJECTS: One hundred consecutive children, aged between 6 months and 6 years, with informed written consent by parents. OUTCOME MEASURE(S): Accuracy of copper sulphate densitometry in screening for Hb concentration below 10 g/dl in terms of sensitivity, specificity, positive and negative predictive values, as well as likelihood ratio. RESULTS: The prevalence of anaemia (Hb < 10 g/dl) was 17% (95% confidence interval (CI) 10.2; 25.8). Copper sulphate densitometry had a sensitivity of 88.2% (95% CI 62.3; 97.9), a specificity of 89.2% (95% CI 79.9; 94.6), a positive predictive value of 62.5% (95% CI 40.8; 80.5) and a negative predictive value of 97.4% (95% CI 90.0; 99.5) in screening for anaemia. The likelihood ratio of a positive screening test was 8.17. CONCLUSIONS: Copper sulphate densitometry was accurate in screening for childhood anaemia.

Urine protein analysis by gel electrophoresis and laser densitometry after chemotherapy in pediatric cancer patients.

A common side effect of chemotherapy is reversible or nonreversible nephrotoxicity. SDS polyacrylamide gel electrophoresis combined with laser densitometry was evaluated as a suitable method to analyze pathologic urine proteins. A total of 52 pediatric patients were followed during and 63 patients were followed after therapy. During therapy renal damage was recorded in 43% of the leukemia patients, in 56% of nephroblastoma patients, and 75% of patients with other tumors. Three or more months after therapy pathologic patterns were seen in 25% of acute lymphoblastic leukemia patients, in 35% of patients with nephroblastoma, and in 62% of other patients. Patients with persistent complete tubular proteinuria and mixed glomerular/tubular proteinuria were found to have a high risk for irreversible renal damage and should be controlled periodically. This method permits a rapid and reliable analysis of urine proteins and is suitable for follow-up tests of renal function during and after chemotherapy.

Determination of Ole e 1 by enzyme immunoassay and scanning densitometry. Validation by skin-prick testing.

Ole e 1 is an important allergen in Olea europaea pollen extracts. This study describes the development of two new methods that can be used to estimate the Ole e 1 content in olive tree pollen extracts. They are based on (1) an enzyme immunoassay that uses rabbit polyclonal, monospecific antibodies and purified Ole e 1, and (2) scanning densitometry of SDS-PAGE gels. Twelve extracts were evaluated by in vivo and in vitro methods. The in vivo biological potency was estimated by prick skin testing 17 allergic individuals; the in vitro allergenic potency by direct IgE and IgE inhibition assays. The enzyme immunoassay showed an operative range of 0.03-100 microg/ml and demonstrated to be specific for Ole e 1. The Ole e 1 content ranged from 1% to 5% of the total protein in the 12 extracts. The amount of Ole e 1, assessed by gel scanning densitometry significantly correlated with the Ole e 1 content obtained by the immunoassay (r = 0.92; p < 0.001). The Ole e 1 content showed a significant correlation with the total allergenic potency of the extracts, evaluated by direct IgE, specific IgE inhibition and skin-prick testing. These two methods can be used to determine the Ole e 1 content in olive pollen extracts. The content of Ole e 1 can vary from 1% to 5% of the total protein in the extracts.

Measurement of blood concentration of indocyanine green by pulse dye densitometry--comparison with the conventional spectrophotometric method.

OBJECTIVE: Pulse dye densitometry (PDD) uses two wavelengths (805 and 890 nm) in association with pulse oximetry to compute the arterial blood concentration ratio of indocyanine green (ICG) to hemoglobin (Hb). When Hb is measured in the usual way, this permits the PDD to compute cardiac output, plasma or blood volume, and liver blood flow following an intravenous injection of ICG. In this study, we evaluate the accuracy of the PDD calculation of dye concentration by comparing it with measurement of the dye concentration in blood (Cb) measured by the spectrophotometric cuvette method during dye clearance in patients. METHODS: In 25 patients receiving major abdominal surgery, ICG (10, 20, or 40 mg) was injected into a central vein and arterial ICG concentration was continuously and simultaneously monitored at nose and finger by PDD; concurrently, ICG concentrations were measured by a spectrophotometer at 805 nm in 4 radial arterial blood samples. Repeated measures or one-way ANOVA were used for comparison of ICG concentrations and percent errors by PDD at the nose, finger, and Cb. RESULTS: The percent error (bias) of calculated dye concentration and its standard deviation (precision) was -3.9 +/- 16.8% (p < 0.01) with the probe on a nostril and 3.4 +/- 12.6% using the finger probe. These errors were found to be greatest when the mean transit time of the dye was rapid (-20.7 +/- 6.8% at nose p < 0.01 and -8.5 +/- 2.5% at finger p < 0.05) due to factors other than the time delay of blood sampling. CONCLUSION: These errors are of similar size to those associated with thermal cardiac output measurement, suggesting that PDD should be valuable clinically as a noninvasive tool especially since it provides values for blood volume and liver blood flow.

Energy fluctuations in an excimer laser during photorefractive keratectomy.

We performed an experiment with the MEL 60 excimer laser (Aesculap Meditec Technology) to demonstrate the variations of energy of the laser beam that could happen during a refractive surgical procedure. In order to quantify such variations, we measured the whitening of a photographic paper after a series of exposures to the laser beam with the X rite 400 B/W reflection densitometer. The energy fluctuations noted between two series of pulses averaged 11.02% (minimum 0; maximum 46). These fluctuations tended to decrease progressively during the procedure. The energy of the laser beam decreased with time. At the end of the experiment, the total loss of energy was 45.16%. These results suggest that clinically meaningful energy variations could happen during the photorefractive keratectomy and reduce refractive predictability.

A determination of the minimum radiopacification necessary for radiographic detection of an aspirated or swallowed object.

It was hoped that it might be possible to establish some standard or starting point which could be used by future investigators to judge adequate levels of radiopacity of radiopaque denture-base materials. Aluminum and copper were used to define a suitable radiopacity scale. The scale was represented by two sets of specimens--one of regular outline and uniform thickness, the other of irregular shape and tapering thickness. Radiographs of the chest and abdominal regions of a cadaver were exposed, with the specimens placed on the film side and then on the opposite side of the cadaver. The results showed that it was more difficult to locate the beveled irregular specimens, that there was little difference between the chest and the abdomen with respect to ease of locating the same objects, and that the closer an object is to the film the easier it is to locate. For 95 per cent observability, an object should have a level of radiopacity at least equal to that produced by 0.20 mm. of copper.