There are different types of radiation detectors (gas-filled, semiconductor, scintillator etc.) and various working principles (ionization, electron-hole pair production, excitation) used in ...radiation detection. It is important that any detector is selected according to its intended use and that the detector is operated under appropriate conditions. NaI(Tl) scintillation detectors are widely used in nuclear spectroscopic studies due to their known advantages. Prior to carrying out such studies, it is first necessary to know the response function of the detector against radiation under the expected operating conditions and to perform the appropriate calibrations. It is important that certain factors are optimized, such as the experimental setup (source-to-detector position, shielding, source activity etc.), gain, bias voltage, and shaping time, which can each significantly affect the response function. In addition, in computational studies based on experimentation, optimization is gain more significant since it is assumed that such experimental studies are carried out under optimum conditions. In this study, in order to determine the most suitable operating conditions for a 3 × 3 inch NaI(Tl) detector; a coaxial sample holder was manufactured to enable different source-to-detector distances (5–15 cm) to be tested, and spectra were then obtained using different bias voltages (750–850 V) and sources with different energies in the range of 81–1332 keV. Through the use of efficiency values obtained for each condition, line and 3D surface plots were drawn and the relations between efficiency and distance, energy and bias voltage examined. The results showed that the efficiency value had an exponentially decreasing characteristic that was dependent on the energy and source-detector distance, and had the highest value at a bias voltage of around 800 V.
To investigate the exposure parameters for thoracic spine/(TS) radiography that allows the image acquisition at the lowest dose possible, while maintaining an adequate image quality/(IQ) to identify ...all relevant anatomical criteria.
An experimental phantom study was conducted, and 48 different radiographs of TS (24 AP/24 lateral) were acquired. The Automatic Exposure Control/(AEC) with the central sensor was used to select the beam intensity, while Source-to-Detector-Distance/(SDD) (AP:115/125 cm; Lateral:115/150 cm), tube potential (AP:70/81/90 kVp; Lateral: 81/90/102 kVp), use of grid/no grid and focal spot (fine/broad) were manipulated. IQ was assessed by observers with ViewDEX. Effective Dose (ED) was estimated using PCXMC2.0 software. Descriptive statistics paired with intraclass correlation coefficient (ICC) were applied to analyse data.
The ED increased with a greater SDD for lateral-view, presenting a significant difference (p = 0.038), however IQ was not affected. For both AP and lateral, the use of grid had a significant effect on ED (p < 0.001). Despite the images acquired without grid had lower IQ scores, the observers considered the IQ adequate for clinical use. A 20% reduction in ED (0.042mSv–0.033 mSv) was observed when increasing the beam energy from 70 to 90 kVp for AP grid in. The observers ICC ranged from moderate to good (0.5–0.75) in lateral and good to excellent (0.75–0.9) for AP views.
The optimised parameters in this context were 115 cm SDD, 90 kVp with grid for the best IQ and lowest ED. Further studies in clinical setting are necessary to enlarge the context and cover different body habitus and equipment.
The SDD impacts on dose for TS; Higher kVp and grid are necessary to better image quality.
Transducers, such as photodiodes, phototransistors, and photovoltaic cells are promising radiation detectors. However, for accurate radiation detection and dosimetry, signals that emanate from these ...devices have to be sufficient to facilitate accurate calibrations, i.e., assigning a quantity of radiation dose to a specific magnitude of the signal. More so, purposely fabricated for luminescence, LEDs produce significantly low signals during radiation detection applications. Therefore, this paper investigates the enhancement and augmentation of photovoltaic signals that were generated when LED strips were being exposed to diagnostic X-rays. Initially, signal amplification was achieved through increasing the effective LED active area (from 60 to 120 chips); by successively connecting LED strips. Further, signal amplification was undertaken by injecting the raw LED strip signal into an amplifier board with adjustable gains. In both the signal amplification techniques, the tube voltage (kVp), tube current-time product (mAs), and source-to-detector distance (SDD) were varied. The principal findings show that effective active area-based signal amplifications produced an overall average of 91.16% signal enhancement throughout all of the X-ray parameter variations. On the other hand, the amplifier board produced an average of 36.48% signal enhancement for the signals that were injected into it. Chip number increment-based signal amplifications had a 0.687% less coefficient of variation than amplifier board signal amplifications. The amplifier board signal amplifications were impaired by factors, such as dark currents, amplifier board maximum operational output voltage, and saturation. Therefore, future electronic signal amplification could use amplifier boards having low dark currents and high operational voltage headroom. The low-cost and simplicity that are associated with active-area amplification could be further exploited in a hybrid amplification technique with electronic amplification and scintillators.
밀도가 알려진 4개의 모형시험공에서 이격실험을 하고 얻어진 비이격 및 이격 측정 자료를 분석함으로서 기준선과 이격선의 특성을 파악할 수 있었다. 특히 선원을 출발하여 검출기에 도달하기까지의 감마선 경로의 형태, 기준선과 이격선의 궤적 특성, 궤적에 미치는 밀도 및 검출기 조합의 영향을 추적할 수 있었으며 이격보정을 위한 최적의 검출기 조합까지 확인할 수 ...있었다. 기준선과 이격선의 기울기 모두 검출기 조합별 긴거리와 짧은거리 간의 선원-검출기 거리비에 비례하는 함수의 형태로 표시될 수 있음을 확인하였다. 이 연구는 기준선 및 이격선의 기울기에 대한 기본 개념 이해에도 효과적으로 적용되었다.
A series of density log data were obtained from the standoff experiments made in the four physical model boreholes of different densities, and the properties of spine and rib curves have been derived by the analysis of the gamma-gamma data. Particularly, the shape of gamma ray propagation path between source and detector, the geometrical property of spine and rib curves, the influence of borehole density and the detector combination on the properties of the curves, and the adequate detector combination for standoff compensation could be discussed. It was also confirmed that spine and rib slopes can be expressed as proportional to source-to-detector distance ratio between far and near detectors. The result of this experiment was also effectively applied for understanding the basic concept of spine and rib slopes.
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