• Journal of the Korean Society of Radiology
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• v.12 no.1
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• pp.85-91
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• 2018

Computed tomography, which obtains section images from reconstruction process using projection images, has been applied to various fields. The spatial resolution of the reconstructed image depends on the device used in CT system, the object, and the reconstruction process. In this paper, we investigates the effect of the number of projection images and the pixel size of the detector on the spatial resolution of the reconstructed image under the parallel beam geometry. The reconstruction program was written in Visual C++, and the matrix size of the reconstructed image was $512{\times}512$. The numerical bar phantom was constructed and the Min-Max method was introduced to evaluate the spatial resolution on the reconstructed image. When the number of projections used in reconstruction process was small, artifact like streak appeared and Min-Max was also low. The Min-Max showed upper saturation when the number of projections is increased. If the pixel size of the detector is reduced to 50% of the pixel size of the reconstructed image, the reconstructed image was perfectly recovered as the original phantom and the Min-Max decreased as increasing the detector pixel size. This study will be useful in determining the detector and the accuracy of rotation stage needed to achieve the spatial resolution required in the CT system.

• Journal of Biomedical Engineering Research
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• v.21 no.2
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• pp.119-127
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• 2000

금속판/형과스크린 계측기와 CCD 카메라를 이용한 방사선영상장치가 현재 전자포탈영상에 널리 쓰이고 있다. 이 장치의 효율적인 영상획득을 위해 계측효율이 좋고, 공간분해능력이 뛰어난 금속판/ 형과스크린 계측기의 두께를 최적화할 필요가 있었다. 이 논문에서는 금속판과 형광스크린의 두께가 계측효율과 공간분해능에 미치는 영향이 연구되었다. 이 결과는 치료 엑스선 영상장치에 쓰일 수 있는 금속판/형과스크린 계측기의 최적화된 두께를 결정하는데 쓰일 수 있다. 몬테칼로 방법을 이용하여 계산한6 MV 선형가속기에서 발생되는 엑시선의 에너지 스펙트럼을 바탕으로, 여러 가지 두께의 금속판/형광스크린에 대하여 계측효율과 공간분해능을 계산하였고, 이를 실험을 통해 검증하였다. 계측효율은 입사된 엑스선의 에너지가 형광스크린에 흡수된 비율로 계산되며, 공간분해능은 흡수된 에너지의 공간 분포를 통해 계산되었다. 계측효율은 금속판의 두께에 의해, 공간분해능은 형광스크린의 두께에 의해 결정될 수 있음을 본 연구를 통해 확인할 수 있었고, 이로써 특정이용에 관련된 금속판/형광스크린의 두께에 대한 서로 보상 (trade-off) 관계에 있음을 계산과 측정결과를 통해 확인할 수 있었고, 이로써 특정이용에 관련된 금속판/형광스크린 계측기의 최적화된 두께를 산출할 수 있게 되었다. 계산을 바탕으로 CCD를 이용한 전자포탈영상장치의 시작품을 설계 및 제작하였고 팬텀을 이용하여 영상을 얻었다. 단일 프레임 영상은 노이즈가 많으나, 프레임 평균 방법을 이용하여 영상의 질을 향상시킬 수 있었다.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.407-414
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• 2014

The aim of the present study was to carry out quantitative analysis of spatial resolution for the influence of the focus size and digital image post-processing on the Computed Radiography (CR). The modulation transfer functions of an edge measuring method (MTF) was used for the evaluation of the spatial resolution. The focus size of X-ray tube was used the small focus (0.6 mm) and the large focus (1.2 mm). We evaluated the 50% and 10% of MTF for the enhancement of edge and contrast by using multi-scale image contrast amplification (MUSICA) in digital image post-processing. As a results, the edge enhancement than the contrast enhancement were significantly higher the spatial resolution of MTF 50% in all focus. Also the spatial resolution of the obtained images in a large focus were improved by digital image processing. In conclusion, the results of this study should serve as a basic data for obtain the high resolution clinical images, such as skeletal and chest images on the CR.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.631-636
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• 2016

Hitherto, spatial resolution has commonly been evaluated by test patterns or phantoms built on some specific distances (from close to far) between two objects (or double targets). This evaluation method's shortcoming is that resolution is restricted to target distances of phantoms made for test. Therefore, in order to solve the problem, this study proposes and verifies a new method to efficiently test spatial resolution with a single target. For the research I used PSF and JND to propose an idea to measure spatial resolution. After that, I made experiments by commonly used phantoms to verify my new evaluation hypothesis inferred from the above method. To analyse the hypothesis, I used LabVIEW program and got a line pixel from digital image. The result was identical to my spatial-resolution hypothesis inferred from a single target. The findings of the experiment proves only a single target can be enough to relatively evaluate spatial resolution on a digital image. In other words, the limit of the traditional spatial-resolution evaluation method, based on double targets, can be overcome by my new evaluation one using a single target.

• The Journal of the Korea Contents Association
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• v.16 no.7
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• pp.681-688
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• 2016

This study assess their quality of radiation on analysis of the spectrum of resolution suggesting IEC 61267 in radiation quality that RQA3, RQA5, RQA7, RQA9 and combination of clinical condition using several quality of radiation. In experiments edge method first, the spatial resolution assessment used image of the additional filter and SID is obtained the IEC 62220-1, spatial resolution and sharpness of the obtained image was evaluated in the MTF value 10%(0.1), MTF value 50%(0.5) using a Matlab program. Second, MCNPX simulation used spatial resolution analysis was radiation quality particle fluence and spectrum analysis in energy. As a result, make use of additional filter, image quality evaluation of SID that RQA3 radiation quality combination qualification is higher spatial resolution and sharpness make unused of additional filter and SID 100cm. RQA7 radiation quality combination qualification is higher that spatial resolution make unused of additional filter and SID 150cm. RQA9 radiation quality combination qualification is higher that spatial resolution and sharpness make used of additional filter and SID 180cm. spectrum analysis of radiation quality by reducing consequent errors occurring in the experiment that error due to the reproducibility of the X-ray tube, occur in an error of correction the detector suggest ideal conditions from spectrum analysis through MCNPX simulation. In conclusion, by suggesting spatial resolution and sharpness of result for various radiation quality, It provide basic data that radiation quality condition and quantitative assessment method for laboratory in clinical using detector evaluation.

• Journal of the Korean Society of Radiology
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• v.16 no.5
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• pp.499-504
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• 2022

Positron emission tomography (PET) uses a very small scintillator to achieve exellent spatial resolution. Therefore, in this study, a PET system using a scintillator to 0.8 mm size was designed and the performance was evaluated. Anihilation radiation was generated from the center of the field of view (FOV) to the outskirts at intervals of 10 mm, and counted simultaneously. The image was reconstructed using the coincidence data, and the spatial resolution was calculated by acquiring the full width at half maximum through the profile. The spatial resolution at the center of the FOV was 1.02 mm, showing a very good result, and the spatial resolution decreased as it was located at the outer edge. To evaluate the phantom image, the Derenzo phantom was constructed to acquire the image, and the degree of classification between radiation sources was evaluated through profile analysis. The result showed that the distance between the radiation sources was larger than the spatial resolution of the radiation sources at each location, and it was confirmed that the radiation sources were distinguished through this. When the PET system designed in this study is applied to PET for small animals, it is considered that excellent performance can be secured through the characteristic of very good spatial resolution.

• Journal of the Korean Society of Radiology
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• v.4 no.3
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• pp.27-31
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• 2010

Spatial resolution is determined by the performance of x-ray optics used in the x-ray imaging system. A zone plate was designed for obtaining a high spatial resolution image at x-ray energy of 8.5keV. A spatial resolution of 80 nm was estimated by the ray tracing when an x-ray tube of tungsten targe was used instead of synchrotron radiation. The designed zone plate of outermost zone width of 40nm was successfully fabricated by the electron-beam lithography.

• Journal of Digital Convergence
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• v.11 no.8
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• pp.273-279
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• 2013

The purpose of the study was to present basic data to evaluation of the spatial resolution for exposure class(EC) in computed radiography(CR) by using the modulation transfer function(MTF). In this study, MTF was measured the edge method by using image plate(IP) of $100{\mu}mm$ pixels. A standard beam quality RQA5 based on an international electro-technical commission(IEC) standard was used to perform the X-ray imaging studies. Digital imaging began to set the sensitivity to EC 50, 100, 200, 300, 400, 600, 800, 1200 in X-ray irradiated to IP. The MTF 50% and 10% in the final images was analysis by using an authorized image analysis program the Origin 8.0 and the image J. As a results, the EC 200 was the best spatial resolution at MTF 50% ($1.979{\pm}0.114lp/mm$) and MTF 10% ($3.932{\pm}0.041$). Therefore, the EC 200 could be useful for the diagnosis of diseases that require high spatial resolution such as fractures.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.477-486
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• 2020

The purpose of this study was to evaluate the effects of reconstruction filters, X-ray source trajectories and intervals in the quality of digital tomosynthesis (DT) images, and the results was clinically validated. The filtered back-projection was implemented by using Ramp, Shepp-Logan, Cosine, Hamming, Hann and Blackman filters, and the X-ray source trajectories were simulated with 1 × 36, 2 × 18, 3 × 12, 4 × 9 and 6 × 6 arrays. The X-ray source intervals were 5, 10, 20, 30 and 40 mm. The depth resolution, spatial resolution and noise of DT image were evaluated by measuring artifact spread function (ASF), full width at half maximum (FWHM) and signal-to-noise ratio (SNR), respectively. The results showed that the spatial resolution and noise properties of DT images were maximized by the Ramp and Blackman filters, respectively, and the depth resolution and noise properties of the DT images obtained with a 1 × 36 X-ray source trajectory were superior to the other trajectories. The depth resolution and noise properties of DT images improved with an increase of X-ray source intervals, and the high X-ray source intervals degraded the spatial resolution of DT images. Therefore, the characteristics of DT images are highly dependent on reconstruction filters, X-ray source trajectories and intervals, and it is necessary to use optimal imaging parameters in accordance with diagnostic purpose.

• Journal of the Korean Society of Radiology
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• v.18 no.2
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• pp.65-71
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• 2024

To achieve high resolution and sensitivity of positron emission tomography (PET) for small animals, the detector is constructed using very thin and long scintillation pixels. Due to the structure of these scintillation pixels, spatial resolution deterioration occurs outside the system's field of view. To solve this problem, we designed a detector that could improve spatial resolution by measuring the interaction depth and improve sensitivity by using a quasi-block scintillator. A quasi-block scintillator size of 12.6 mm x 12.6 mm x 3 mm was arranged in four layers, and optical sensors were placed on all sides to collect light generated by the interaction between gamma rays and the scintillator. DETECT2000 simulation was performed to evaluate the performance of the designed detector. Flood images were acquired by generating gamma-ray events at 1 mm intervals from 1.3 mm to 11.3 mm within the scintillator of each layer. The spatial resolution and peak-to-peak distance for each location were measured in an 11 x 11 array of flood images. The average measured spatial resolution was 0.25 mm, and the average distance between peaks was 1.0 mm. Through this, it was confirmed that all locations were separated from each other. In addition, because the light signals of all layers were measured separately from each other, the layer of the scintillator that interacted with the gamma rays could be completely separated. When the designed detector is used as a detector in a PET system for small animals, it is considered that excellent spatial resolution and sensitivity can be achieved and image quality can be improved.