X-ray energy separation method using a CdTe semiconductor X-rayimaging sensor and photon counting method

A multichannel X-ray imaging sensor using a CdTe compound semiconductor radiation detector in photon counting mode was developed and tested for digital X-ray imaging and an X-ray energy separation capability. The X-ray imaging sensor was constructed of CdTe detector elements at a pitch of 0.25 mm. High band amplifiers, discriminators, and counters attached to each element formed the pulse counting circuit. Charge pulses generated by absorbed X-ray photons were directly counted and separated into two energy regions. Digitized X-ray images containing energy information were thus obtained. Using this sensor two separate X-ray images of different energy can be obtained simultaneously. A 256-channel X-ray imaging sensor was prepared and used to provide spatial resolution measurement for an X-ray charge. Low and high energy images of a hand phantom were thus obtained and both a soft tissue image and a bone image were produced using an energy subtraction method     

Seaweed intake and blood pressure levels in healthy pre-school Japanese children

Background

Low diet quality and depression symptoms are independently associated with poor glycemic control in subjects with type 2 diabetes (T2D); however, the relationship between them is unclear. The aim of this study was to determine the association between diet quality and symptoms of depression among Cuban-Americans with and without T2D living in South Florida.

Methods

Subjects (n = 356) were recruited from randomly selected mailing list. Diet quality was determined using the Healthy Eating Index-2005 (HEI-05) score. Symptoms of depression were assessed using the Beck Depression Inventory (BDI). Both linear and logistic regression analyses were run to determine whether or not these two variables were related. Symptoms of depression was the dependent variable and independent variables included HEI-05, gender, age, marital status, BMI, education level, A1C, employment status, depression medication, duration of diabetes, and diabetes status. Analysis of covariance was used to test for interactions among variables.

Results

An interaction between diabetes status, gender and HEI-05 was found (P = 0.011). Among males with a HEI-05 score ≤ 55.6, those with T2D had a higher mean BDI score than those without T2D (11.6 vs. 6.6 respectively, P = 0.028). Among males and females with a HEI-05 score ≤ 55.6, females without T2D had a higher mean BDI score compared to males without T2D (11.0 vs. 6.6 respectively, P = 0.012)

Conclusions

Differences in symptoms of depression according to diabetes status and gender are found in Cuban-Americans with low diet quality.     

Evaluation of K X-ray escape and crosstalk in CdTe detectors andmulti-channel detectors

The simple structure of CdTe semiconductor detectors facilitates their downsizing, and their possible application to radiographic sensors has been studied. The escape of K X-rays from these detectors increases with reduction of their dimensions and affects the measurements of X- and gamma-ray spectra. K X-rays also produce crosstalk in multi-channel detectors with adjacent channels. Therefore, K X-rays which escape from the detector elements degrade both the precision of energy spectra and spatial resolution. The ratios of escape peak integrated counts to total photon counts for various sizes of CdTe single detectors were calculated for gamma rays using the Monte Carlo method. Also, escape and crosstalk ratios were simulated for the CdTe multi-channel detectors. The theoretical results were tested experimentally for 59.54-keV gamma rays from a ²⁴¹Am radioactive source. Results showed that escape ratios for single detectors were strongly dependent on element size and thickness. The escape and crosstalk ratios increased with closer channel pitch. Our calculated results showed a good agreement with the experimental data. The calculations made it clear that K X-rays which escaped to neighboring channels induced crosstalk more frequently at smaller channel pitch in multi-channel detectors. A radiation shielding grid which blocked incident photons between the boundary channels was also tested by experiment and by calculation. It was effective in reducing the probability of escape and crosstalk     

A high-speed cadmium telluride radiation detector

A small CdTe detector capable of high repetition pulse rate with possibilities for applications in radiation monitoring and similar uses was developed. The hole transit time through the crystal was shortened by decreasing the crystal thickness of 0.3 mm (1×1 mm) and by applying fields as high as 10 kV/cm. The electron transit time, although short, was electrically elongated by applying appropriate capacitance to the amplifier, and the output pulse waveform was designed to be similar to that for the holes. High, uniform output pulses with widths of 30 ns were thus obtained. The energy resolution was 9 keV for 59.4-keV photons from ²⁴¹Am using a 100-ns-response amplifier     

X-ray imaging sensor using CdTe crystals for dual energy X-rayabsorptiometry

The authors have designed and built a multi-channel cadmium telluride detector array to test its suitability as an X-ray imaging sensor for dual energy X-ray absorptiometry. The X-ray imaging sensor was constructed of 64 CdTe detector elements with high frequency current amplifiers, discriminators, and counters. The detector elements were operated in the photon counting mode and output pulses induced by the X-ray photons were separated into two energy levels according to their height. The energy resolution of the detector elements was 18.7% to 59.54 keV gamma-rays. In combination with a K-edge filter to produce dual energy X-rays, the X-ray imaging sensor was able to generate two energy X-ray images simultaneously over a short time. By applying a simple energy subtraction method to these images, bone phantoms were distinguished from the overlying tissue phantoms and their densities could be successfully measured. It was clearly demonstrated that this X-ray imaging sensor using CdTe crystals has good potential for high speed bone densitometry     

CdTe semiconductor X-ray imaging sensor and energy subtractionmethod using X-ray energy information

A multichannel X-ray imaging sensor using a CdTe compound semiconductor radiation detector was developed. Both the digital X-ray imaging and energy-information-generating analyzing method were studied. The X-ray imaging sensor consisted of 512-channel CdTe detector elements at a pitch of 0.2 mm. X-ray photons were directly detected using a photon-counting method and high- and low-energy images were obtained simultaneously. The specific resolution was obtained over 2.5 line pairs/mm in the channel direction and 1.6 line pairs/mm in the scanning direction with a scanning pitch of 0.2 mm. The energy subtraction method was found to be effective in distinguishing an object's component materials