Evaluation of patient dose during a digital breast tomosynthesis.

INTRODUCTION: When the patient dose in mammography is assessed, it is important to evaluate both average glandular dose (AGD) and entrance surface dose (ESD). A dose survey on both AGD and ESD in mammography has never been studied in Sri Lanka. Therefore, the present study aimed to evaluate the patient dose received during a full-field digital breast tomosynthesis (DBT) examination by determining both AGD and ESD. METHODS: The study was performed on 140 patients who underwent DBT examination. The AGD, ESD, compression breast thickness (CBT), half-value layer (HVL), target/filter combination, kVp, and mAs values were obtained from the machine, and AGD for each projection was calculated using the equation proposed by the Dance 2011. RESULTS: The measured mean AGDs and ESDs of both the breasts were statistically significantly lower than the reference values given by European protocol (p < 0.05). There were no statistically significant differences in both AGDs and ESDs between the right and left breast, between right craniocauidal (RCC) and left craniocaudal (LCC), and between right mediolateral oblique (RMLO) and left mediolateral oblique (LMLO) examinations (p > 0.05). The measured median AGDs and ESDs received for MLO projections of both breasts were statistically significantly higher than that of CC projections (p < 0.05). CONCLUSION: The patients receive a low radiation dose during their DBT examination with both lowered AGD and ESD than the recommended values. IMPLICATIONS FOR PRACTICE: The results can be used as a baseline to optimize the radiation dose in mammography in Sri Lanka.

Two Atypical Cases of Hantavirus Infection: Experience from a Tertiary Care Unit in Sri Lanka.

Hantaviruses are a large family of enveloped viruses with two medically important families Cricetidae and Muridae which are known to cause rodent-borne diseases worldwide. Some strains cause clinical syndromes with multiorgan involvement in humans such as hantavirus haemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS), which is also known as hantavirus pulmonary syndrome. Clinical differentiation of this infection from other endemic infections in Sri Lanka such as leptospirosis and rickettsial infections is extremely difficult due to overlapping clinical and epidemiologic features such as exposure to rodents and farming. Here, we report two serologically confirmed cases of hantavirus infection from Sri Lanka with different presentation. The first patient had a combination of HCPS and HFRS. The second patient was treated for HPS complicated with acute respiratory distress syndrome (ARDS). Both had a significant clinical, biochemical, and radiological response with early initiation of corticosteroids. However, further studies are required to assess whether steroids hasten the recovery of severe hantavirus infections. We believe that hantavirus infection is an important emerging disease in the country and should be considered as a differential diagnosis in patients presenting with an acute febrile illness as well as in patients presenting with ARDS. Early diagnosis and prompt treatment improve prognosis.

Socio-demographic risk indicators for tooth mortality in rural Sri Lankans.

To explore the socio-demographic factors associated with tooth loss in rural inhabitants of Sri Lanka, a random sample of 2178 males aged 20-60 years was selected using multi-stage cluster sampling procedure. The number of missing and present teeth was recorded excluding third molars and the subjects were interviewed to elicit socio-demographic information as well as oral hygiene and tobacco consumption habits. The mean number of teeth lost in the sample was 5.17 +/- 5.43. Tooth loss increased significantly with age. Sinhalese had significantly fewer lost teeth (5.05 +/- 5.38) compared to Tamils (6.54 +/- 6.18) and Muslims (6.02 +/- 5.21) whereas education, income, oral hygiene practices and tobacco use were significantly associated with tooth loss in the bivariate analysis. A forward stepwise multiple regression analysis revealed that age, Muslim ethnicity and quantified tobacco use were positively associated with tooth loss while better socio-economic conditions and good oral hygiene habits were negatively linked with tooth mortality independent of other factors. Age, Muslim ethnicity, quantified tobacco use, income, education, brushing frequency and substance used for cleaning had significantly affected tooth loss. Quantified tobacco use and oral hygiene may be regarded as modifiable socio-demographic risk indicators associated with tooth mortality in Sri Lankans.

Infrared emission high spectral resolution atlas of the stratospheric limb.

An atlas of high resolution infrared emission spectra identifies a number of gaseous atmospheric features significant to stratospheric chemistry in the 770-900- and 1100-1360-cm(-1) regions at six zenith angles from 86.7 to 95.1 degrees . A balloon-borne Michelson interferometer was flown to obtain ~0.03-cm(-1) resolution spectra. Two 10-cm-1 extracts are presented here.

Cryogenic Fourier spectrometer for measuring trace species in the lower stratosphere.

A cryogenic Fourier transform spectrometer has been built to measure thermal emission of the earth's limb from a balloon-borne platform. Liquid nitrogen cooling of the spectrometer and liquid helium cooling of the detectors has provided sufficient sensitivity to detect, at 5-15 microm, fifteen molecular species relevant to stratospheric ozone chemistry. The spectral resolution achieved, 0.022 cm(-1), is the best yet attained for emission mode data at these wavelengths. The philosophy behind the design of the optical and electronic systems is presented, followed by an analysis of the performance achieved during balloon flight.

Infrared spectroscopy of the lower stratosphere with a balloon-borne cryogenic Fourier spectrometer.

The IR limb emission of the lower stratosphere has been measured using a balloon-borne liquid nitrogencooled Michelson interferometer with liquid helium-cooled Si:Ga detectors. Portions of the thermal emission spectrum have been recorded between 650 and 2000 cm(-1) with an unapodized spectral resolution of 0.03 cm(-1). This is the highest spectral resolution limb emission thus far obtained. A preliminary description is given of these data along with a discussion of the significant features. Species identified to date include CO(2), O(3), CFCl(3), CF(2)Cl(2), H(2)O, CH(4), HNO(3), N(2)O, NO(2), and ClONO(2). A tentative identification is made for NO, representing the first direct spectroscopic detection of NO in emission.

Infrared observations of the saturnian system from voyager 1.

During the passage of Voyager 1 through the Saturn system, the infrared instrument acquired spectral and radiometric data on Saturn, the rings, and Titan and other satellites. Infrared spectra of Saturn indicate the presence of H(2), CH(4), NH(3), PH(3), C(2)H(2), C(2)H(6), and possibly C(3)H(4) and C(3)H(8). A hydrogen mole fraction of 0.94 is inferred with an uncertainty of a few percent, implying a depletion of helium in the atmosphere of Saturn relative to that of Jupiter. The atmospheric thermal structure of Saturn shows hemisphere asymmetries that are consistent with a response to the seasonally varying insolation. Extensive small-scale latitudinal structure is also observed. On Titan, positive identifications of infrared spectral features are made for CH(4), C(2)H(2), C(2)H(4), C(2)H(6), and HCN; tentative identifications are made for C(3)H(4) and C(3)H(8). The infrared continuum opacity on Titan appears to be quite small between 500 and 600 cm(-1), implying that the solid surface is a major contributor to the observed emission over this spectral range; between 500 and 200 cm(-1) theopacity increases with decreasing wave number, attaining an optical thickness in excess of 2 at 200 cm(-1). Temperatures near the 1-millibar level are independent of longitude and local time but show a decrease of approximately 20 K between the equator and north pole, which suggests a seasonally dependent cyclostrophic zonal flow in the stratosphere of approximately 100 meters per second. Measurements of the C ring of Saturn yield a temperature of 85 +/- 1 K and an infrared optical depth of 0.09 +/- 0.01. Radiometer observations of sunlight transmitted through the ring system indicate an optical depth of 10(-1.3 +/-0.3) for the Cassini division. A phase integral of 1.02 +/- 0.06 is inferred for Rhea, which agrees with values for other icy bodies in the solar system. Rhea eclipse observations indicate the presence of surface materials with both high and low thermal inertias, the former most likely a blocky component and the latter a frost.

Infrared spectrometer for Voyager.

The Voyager IR investigation uses a Michelson interferometer with a 4.3-cm(-1) spectral resolution in the 80-2500-cm(-1) range and a single-channel radiometer for the visible and near-IR, 5000-30,000-cm(-1). Both devices share a Cassegrain telescope with a 50-cm diam primary mirror and a 0.25 degrees field of view. Design, calibration, and performance are discussed along with a sample spectrum of Jupiter.

Infrared observations of the jovian system from voyager 2.

Infrared spectra obtainedfrom Voyager 2 have provided additional data on the Jovian system, complementing those obtained from Voyager 1. The abundance ratio of ethane to acetylene in Jupiter's atmosphere appears to be about three times larger in the polar regions than at lower latitudes. A decidedly hemispherical asymmetry exists, with somewhat higher ratios prevailing in northern latitudes. An overall increase in the abundance ratio by a factor of about 1.7 appears to have occurred between the Voyager 1 and 2 encounters. Global brightness temperature maps of Jupiter at 226 and 602 cm(-1) exhibit a large amount of local- and planetary-scale structure, as well as temporal variability. Although heterogeneous cloud structure and ammonia concentration in the lower troposphere may contribute to the appearance of the 226-cm(-1) map, the detail in the 602-cm(-1) maps probably represents the actual horizontal thermal structure near the tropopause and suggests that dynamical heating and cooling processes are important. Low-latitude surface temperatures on the Galilean satellites rangefrom approximately 80 K on the dark sides to 155 K at the subsolar point on Callisto. Below a thin insulating layer, the thermal inertia of Callisto is somewhat greater than that of Earth's moon. Upper limits on the infrared optical depth of the Jovian ring rangingfrom approximately 3 x 10(-4) at 250 cm(-1) to 3 x 10(-3) at 600 cm(-1) have been found.