Entrapped foreign body: A diagnostic muddle for the radiologist.

Exact localization of foreign body is important for planning the treatment required for its retrieval without much tissue damage. Plain film radiography is the initial screening modality used for the detection of suspected foreign body. However, about one-third of all the foreign bodies are missed in the initial radiographic examination. In case of a wooden foreign body, only 15% are well-visualized on plain radiographs and are, therefore, often missed or misdiagnosed. Hence, the different radiographic technique should be used to localize the object instead of relying on a single radiographic image. Here, we present a unique case of foreign body entrapped in the soft tissue appeared initially as osteomyelitis and fracture of the mandible in the digital panoramic radiograph, and finally detected as a foreign body in mandibular occlusal radiography.

Location of mental foramen using digital panoramic Radiography.

OBJECTIVE: Comparative evaluation of the location of mental foramen in different age groups. Determine the variation in position of mental foramen with gender using digital panoramic radiography. MATERIALS AND METHODS: Digital panoramic radiographs of 250 patients were reviewed. The study population was divided into five age groups with 50 patients each. Radiographic position of mental foramen was evaluated in each radiograph based on three parameters. Measurements were taken in each radiograph using Planmeca Dimaxis pro version 4.4.0 (Helsinki, Finland). The collected data were subjected to statistical analysis using paired Student's t-test. RESULTS: The mean distance of position of mental foramen showed a significant variation within the five age groups. In the first group, female patients showed an increase in mean distance of mental foramen position in relation to three parameters. From the second to fifth groups, male patient showed an increase in the mean distance of mental foramen position. The first and fifth group showed a reduced mean distance of mental foramen position when compared to other age groups. CONCLUSION: This study concluded that the position of mental foramen varies with age. There was a gender-related variation in position of mental foramen within the population too.

Compact electron gun based on secondary emission through ionic bombardment.

We present a new compact electron gun based on the secondary emission through ionic bombardment principle. The driving parameters to develop such a gun are to obtain a quite small electron gun for an in-flight instrument performing Electron Beam Fluorescence measurements (EBF) on board of a reentry vehicle in the upper atmosphere. These measurements are useful to characterize the gas flow around the vehicle in terms of gas chemical composition, temperatures and velocity of the flow which usually presents thermo-chemical non-equilibrium. Such an instrument can also be employed to characterize the upper atmosphere if placed on another carrier like a balloon. In ground facilities, it appears as a more practical tool to characterize flows in wind tunnel studies or as an alternative to complex electron guns in industrial processes requiring an electron beam. We describe in this paper the gun which has been developed as well as its different features which have been characterized in the laboratory.

High-speed off-axis Cavity Ring-Down Spectroscopy with a re-entrant configuration for spectral resolution enhancement.

Monitoring of changing samples by Cavity Ring-Down Spectroscopy (CRDS) is possible using fast frequency scans of the laser and/or the cavity resonance. Mode-matched cavity excitation improves performance of fast CRDS but data-points result separated by the cavity Free Spectral Range (FSR): low pressure samples demand long cavities. We demonstrate fast CRDS with off-axis injection of a "re-entrant" resonator yielding FSR/N data-points separation. Our N = 4 short-cavity setup is found to perform well compared with other fast-CRDS implementations. Interestingly, the intrinsic chirped ringing affecting ring-down signals in mode-matched fast-CRDS disappear with off-axis injection. This is due to a fine splitting of the re-entrant-cavity degenerate groups of modes by astigmatism.

A compact tunable diode laser absorption spectrometer to monitor CO2 at 2.7 µm wavelength in hypersonic flows.

Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship's Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow.

High-energy single-longitudinal mode nearly diffraction-limited optical parametric source with 3 MHz frequency stability for CO2 DIAL.

We report on a 2.05 microm nanosecond master oscillator power amplifier optical parametric source for CO2 differential-absorption lidar. The master oscillator consists of an entangled-cavity nanosecond optical parametric oscillator based on a type II periodically poled lithium niobate crystal that provides highly stable single-longitudinal-mode radiation. The signal emission is amplified by a multistage parametric amplifier to generate up to 11 mJ in a nearly diffraction-limited beam with an M2 quality factor of approximately 1.5 while maintaining single-longitudinal-mode emission with a frequency stability better than 3 MHz rms. This approach can be readily applied to the detection of various greenhouse gases.