텅스텐 엣지 블록을 이용하여 Megavoltage (MV) 영상의 질 평가

민정환,손진현,김기원,이정우,손순룡,백금문,김정민,김연래,정재용,김상영,이도완,최보영,Min, Jung-Whan,Son, Jin-Hyun,Kim, Ki-Won,Lee, Jung-Woo,Son, Soon-Yong,Back, Geum-Mun,Kim, Jung-Min,Kim, Yeon-Rae,Jung, Jae-Yong,Kim, Sang-Young,Lee, Do- 한국의학물리학회 2012 의학물리 Vol.23 No.3

최근 백만 볼트 영상(megavoltage imaging, MVI)에서 급격히 발전해 온 디지털 방사선영상(digital radiography, DR)은 치료용 방사선영상 기술이 발전함에 따라 매우 정확하면서 간단하게 측정할 수 있는 일반적인 정도관리(quality assurance, QA) 방법을 요구하게 되었다. 본 연구의 목적은 일반적인 QA 방법과 computed radiography (CR) 장비를 사용하여 MVI의 변조전달함수(modulation transfer function, MTF), 잡음전력스펙트럼(noise power spectrum, NPS), 양자검출효율(detective quantum efficiency, DQE)를 평가하고자 하였다. 텅스텐으로 구성된 $19{\times}10{\times}1cm^3$ 두께의 엣지(edge) 블록을 사용하였으며, 6 MV energy를 사용하였다. 또한 검출기는 CR-IP (image plate), CR-IP-lead, the CR-IP-back (lanex TM fast back screen), CR-IP-front (lanex TM fast front screen)를 사용하였으며, pre-sampling MTF를 계산하였다. CR-IP의 MTF는 0.70 lp/mm를 나타내었고, CR-IP front의 MTF는 1.10 lp/mm로서 가장 높은 값의 고해상도 공간분해능을 보였다. 가장 우수한 검출기의 NPS는 CR-IP front screen에서 확인되었다. 공간주파수가 증가함에 따라 1.0 cycles/mm의 가까운 DQE를 획득하였다. 본 연구결과로서 자체 제작한 엣지 블록 방법은 MVI의 MTF, NPS, DQE를 평가하는 일반적인 QA 방법으로 사용될 수 있음을 확인하여 주었다. Digital Radiography (DR) has rapidly developed in megavoltage X-ray imaging (MVI). Thus, a very simple and general quality assurance (QA) method is required. The purpose of this study was to evaluate the modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) for MVI using general QA method and computed radiography (CR) device. We used tungsten edge block with $19{\times}10{\times}1cm^3$ thickness and 6MV energy. For detector, CR-IP (image plate), CR-IP-lead, the CR-IP-back (lanex TM fast back screen), CR-IP-front (lanex TM fast front screen) were used and pre-sampling MTF was calculated. The MTF of CR-IP-front showed the highest value with 1.10 lp/mm although the CR-IP showed the only 0.70 lp/mm. The best NPS was observed in CR-IP front screen. According to the increase in spatial frequency, our results showed that DQE was approximately 1.0 cycles/mm. The present study demonstrates that the QA method with our home-made edge block can be used to evaluate MTF, NPS and DQE for MVI.

변조전달함수 방법에서 엣지 장치 설정에 대한 각도 최적화 평가

민정환,정회원,Min, Jung-Whan,Jeong, Hoi-Woun 대한방사선과학회 2020 방사선기술과학 Vol. No.

This study was purpose to evaluation of Modulation Transfer Function in Measurements by using the International electrotechnical commission standard(IEC 62220-1) which were edge device each angle by using edge method. In this study was Aero(Konica, Japan) image receptor which is a indirect Flat panel detector(FPD) was used. The size of matrix 1994 × 2430 (14"× 17" inch) which performed 12 bit processing and pixel pitch is 175 ㎛. The results of shown as MTF measurements at IEC standard. The amount of data seemed reasonable and at an MTF value of 0.1 the spatial frequencies were 2.56 cycles/mm at an angle of 2.4°. MTF value of 0.5 the spatial frequencies were 1.32 cycles/mm at an angle of 2.4°. This study were to evaluate MTF by setting each angle 2.0°~2.8° degrees the most effective optimal edge angle and to suggest the quantitative methods of measuring by using IEC.

디지털 방사선 시스템에서 발생하는 Artifact

민정환(Jung Whan Min),김정민(Jung Min Kim),정회원(Hoi Woun Jeong) 대한방사선과학회(구 대한방사선기술학회) 2015 방사선기술과학 Vol.38 No.4

디지털 방사선 시스템은 영상의학에서 큰 비중을 차지하고 있다. 잘못된 영상이 제공 된다면 이는 환자의 건강에 나쁜 영향을 줄 수 있기에, 올바른 디지털 방사선 영상이 제공되어야만 한다. 또한, artifact는 오진으로 이어질 수 있다. 디지털 방사선 시스템에서 발생하는 artifact를 종류별로 분석하여 그 결과 분석하였다. 본 연구에서 사용된 artifact는 서울의 종합병원 급 의료기관에서 2007년부터 2014년까지 수집된 자료들이다. 수집된 자료는 발생 원인별로 구별하여 그 원인을 분석하였다. artifact는 하드웨어적 artifact, 소프트웨어적 artifact, 사용자 오류, 시스템 artifact 및 기타로 구분하였다. 하드웨어적 artifact는 Ghost가 가장 빈번하게 관찰되었으며, 이는 신호의 잔류에 의한 것이다. 다음은 RF 잡음에 의한 오류, 장비 내 이물질에 의한 오류 순이다. 소프트웨어 artifact는 많은 원인이 있다. 부정확한 영상 교정에 의한 artifact가 가장 많았으며, EDR 인식오류, 접합면 처리 오류 등이 있으며, 소프트웨어 artifact는 매우 다양한 경향을 나타낸다. 사용자 오류는 디지털 의료 영상 시스템을 바르게 이해하지 못해 발생시킨 것들이 많았다. 아울러, 시스템 artifact는 DICOM 헤더 정보 오류, 압축 오류가 있다. 분명하게 나타나는 artifact는 재촬영의 원인이 되어 환자의 피폭을 증가시키고, 불분명하게 나타나는 artifact는 오진을 유발 시킬 수 있다. 따라서 방사선사에게서 이러한 artifact를 바로 구별 할 수 있는 능력이 요구 된다. 그러므로 artifact가 발생되는 원인과 그 특성을 분명하게 이해함으로 지속적인 교육과 안정적인 시스템 운영에 힘써야 할 것으로 사료된다. Digital Radiography is a big part of diagnostic radiology. Because uncorrected digital radiography image supported false effect of Patient's health care. We must be manage the correct digital radiography image. Thus, the artifact images can have effect to make a wrong diagnosis. We report types of occurrence by analyzing the artifacts that occurs in digital radiography system. We had collected the artifacts occurred in digital radiography system of general hospital from 2007 to 2014. The collected data had analyzed and then had categorize as the occurred causes. The artifacts could be categorized by hardware artifacts, software artifacts, operating errors, system artifacts, and others. Hardware artifact from a Ghost artifact that is caused by lag effect occurred most frequently. The others cases are the artifacts caused by RF noise and foreign body in equipments. Software artifacts are many different types of reasons. The uncorrected processing artifacts and the image processing error artifacts oc-curred most frequently. Exposure data recognize (EDR) error artifacts, the processing error of commissural line, and etc., the software artifacts were caused by various reasons. Operating artifacts were caused when the user didn't have the full understanding of the digital medical image system. System artifacts had ap-peared the error due to DICOM header information and the compression algorithm. The obvious artifacts should be re-examined, and it could result in increasing the exposure dose of the patient. The unclear artifact leads to a wrong diagnosis and added examination. The ability to correctly determine artifact are required. We have to reduce the artifact occurrences by understanding its character-istic and providing sustainable education as well as the maintenance of the equipments.

자기공명영상에서 ACR 팬텀을 이용한 잡음전력스펙트럼 평가

민정환(Jung-Whan Min),정회원(Hoi-Woun Jeong) 대한방사선과학회(구 대한방사선기술학회) 2024 방사선기술과학 Vol.47 No.1

This study was purpose to quantitative evaluation of comparison of the image intensity uniformity and noise power spectrum (NPS) by using American college of radiology (ACR) phantom for magnetic resonance imaging (MRI). The MRI was used achiva 3.0T MRI and discovery MR 750, 3.0T, the head and neck matrix shim SENSE head coil were 32 channels receive MR coil. The MRI was used parameters of image sequence for ACR standard and general hospital. NPS value of the ACR standard T2 vertical image in GE equipment was 7.65E-06 when the frequency was 1.0 mm-1. And the NPS value of the ACR hospital T1 region of interest (ROI) 9 over all vertical image in Philips equipment was 9E-08 when the frequency was 1.0 mm-1 and the NPS value of the hospital T2 ROI 9 over all vertical image in Philips equipment was 1.06E-07 when the frequency was 1.0 mm-1. NPS was used efficiently by using a general hospital vertical sequence more than the standard vertical sequence method by using the ACR phantom. Furthermore NPS was the quantitative quality assurance (QA) assessment method for noise and image intensity uniformity characteristics was applied mutatis mutandis, and the results values of the physical imaging NPS of the 3.0T MRI and ACR phantom were presented.

1.5T와 3.0T MRI에서 Saline Phantom을 이용한 자장 균일도 비교 분석

민정환 ( Jung Whan Min ),박훈희 ( Hoon Hee Park ),여화연 ( Hwa Yeon Yeo ),동경래 ( Kyung Rae Dong ) 조선대학교 공학기술연구원 2013 공학기술논문지 Vol.6 No.1

MRI generates a radio frequency (RF) pulse after setting the body in position in a large Gantry that generates a magnetic field. The signal is released by resonance of inner body``s hydrogen nucleus. This technology reorganizes and records the difference of the signal through the Computer. Recently, the use of 1.5T and 3.0T has been increased in the hospitals because 3.0T has higher Signal to noise ratio (SNR) compared to the 1.5T. To confirm the difference of magnetic field according to changes in magnetic field intensity, we used Saline Phantom. We compared SNR to magnetic field uniformity of 1.5T and 3.0T to improve the diagnostic value of image. According to size Field of view (FOV) of MRI equipment, we made a Saline Phantom ourselves. Using the Saline phantom to compare the magnetic field uniformity of 1.5T and 3.0T, we then obtained Axial and Sagittal images. According to the result of experiment, we confirmed that the numerical value of SNR using saline phantom decreased relatively as it went far away from the center of the magnetic field. In other words, a magnetic field become uneven bit by bit as it comes apart from the center. When comparing 1.5T with 3.0T, we figured out that as the intensity of a magnetic field rises, it becomes uneven. The experiment above tells us that magnetic field uniformity of MRI showed some difference depending on the location, isocenter or periphery of the magnetic field; and if the magnetic field uniformity goes off the range, distortion of the image happens. This means that even through without the complicated and highpriced equipments, it is possible to check the efficiency of MRI using simple Saline Phantom which we made by ourselves.

차트 각도를 이용한 해상력 특성 평가

민정환(Jung-Whan Min),정회원(Hoi-Woun Jeong) 대한방사선과학회(구 대한방사선기술학회) 2021 방사선기술과학 Vol.44 No.4

This study aim was quantitative assessment of MTFs of spectrum of the square wave chart images and Coltman chart images for 0o, 1.7o, 2.2o, 2.9o, 4.1o by using chart method. In general device was AccuRay-650 (DK Medical System, Korea) used, indirect flat panel detector(FPD) Aero (Konica, Japan) used and MATLAB R2019a (MathWorks, USA) used. The result of comparison for each angle of MTF the edge image was highest quantitatively value for MTF finding of showed the best value of 0.1 based on the frequency of 3.5 mm-1, value of 0.1 based on the square wave was frequency of 3.0 mm-1 and value of 0.1 based on the Coltman transform was frequency of 2.4 mm-1. In this study it was significant that the methodology of the international Electro-technical Commission was applied mutandis by using the Fujita method within 2∼3o.

CR X선 영상의 복합잡음 감소에 관한 연구

민정환(Jung-Whan Min),김정민(Jung-Min Kim),정회원(Hea-Won Jeong) 대한방사선과학회(구 대한방사선기술학회) 2007 방사선기술과학 Vol.30 No.1

  인위적으로 noise factor를 주고 그 위에 촬영을 하여 노이즈와 영상의 복합물을 만들었다. 그 후 Low Pass Filter(LPF)와 Median Filter(MF)의 두 종류의 필터를 통하여 노이즈를 제거하고 노이즈를 나타내는 지표로 Signal To Noise Ratio(SNR), Peak Signal to Noise Ratio(PSNR), Mean Square Error(MSE)를 비교하였다. 또한 Median Filter의 kernel size에 따라서도 노이즈제거효과를 평가하였다. 각각의 처리된 영상과 원 영상을 비교하여 원 영상에 가까운 영상을 찾아봄으로서 어떤 필터가 유용하며 어떤 주파수대를 제거해야 하는가를 알고자 실험하였다. Cutoff frequency가 다른 필터를 비교 했을 때 noise power 값에는 상관없이 cutoff frequency 2/3π~3/4π까지가 원 영상에 가까우면서 SNR, PSNR이 좋다. 따라서 높은 filter 효과를 나타낸다고 할 수 있다. Median filter의 kernel size가 커짐에 따라서 SNR 값이 커지며 반대로 MSE의 값이 작아져 filter 효과는 좋아 짐을 알 수 있다.<BR>  의료 영상에 filter를 적용하는 것에 대해서 대부분의 영상들이 filter 적용 후에 왜곡된 상이 되곤 하였다. 의료 영상은 다른 영상과는 달리 공간 분해능을 유지하면서 평활화(노이즈 제거)하는 것이 중요한 문제이다. SNR 등 정량적 지표에 의한 비교와 함께 시각적 평가가 병행되어야 할 필요가 있다.   This study is to decrease compound noise in x-ray films. This study compared Signal to noise ratio (SNR), Peak signal to noise ratio(PSNR), Mean square error(MSE) to surface of the earth. In addition, we evaluated noise elimination effect according to the kernel size of Median filter.<BR>  This experiments show that some filters are useful by finding image that is near in circle image comparing circle picture with each processed picture. In noise power value, when cutoff frequency was compared with other filters of cutoff frequency. Cutoff frequency of 2/3π~3/4π is good and it shows good SNR and PSNR. Therefore, it can display high filter effect. As Median Filter"s Kernel size grows SNR value gets bigger, which shows better filter effect.<BR>  Most pictures are distorted after filter application in medical treatment image. It is important to keep spatial resolution in most medical images. Visual estimation as well as quantitative indicators should be necessary for a better image.

디지털 의료영상에서 Noise감소를 위한 필터조합과 임상적 효과에 관한 연구

민정환(Jung-Whan Min),김정민(Jung-Min Kim),정회원(Hea-Won Jeong),옥치일(Chi-Il Ok) 대한방사선과학회(구 대한방사선기술학회) 2007 방사선기술과학 Vol.30 No.4

  의료영상에서 화질저하를 최소화 하면서 Noise를 감소시키기 위하여 Noise가 첨가되어 있는 영상을 대상으로 Low Pass Filter(LPF) 5종, High Pass Filter(HPF) 4종, Median Filter(MF) 11종의 모두 20개의 필터를 복합적으로 사용하여 Noise 제거효과를 검토하였다. Noise를 나타내는 지표로 Peak Signal to Noise Ratio(PSNR), Mean Square Error(MSE)를 비교하였다.<BR>  그 결과 Noise 감소효과가 가장 높은 필터의 조합은 LPF3*3#1+HPF3*3#1+Vertical3*1로 나타났다. 이 필터의 조합을 흉부, 골반, 머리 등의 의료영상에 적용하여 임상적인 Noise 제거효과를 확인하였다.   This paper is for investigation of the noise reduction effect all 20 filters by combining Low Pass Filter (LPF) 5 kinds, High Pass Filter(HPF) 4 kinds, Median Filter(MF) 11 kinds. Noise is added to reduce noise and minimize the quality degradation in medical imaging system. We also compared Peak Signal to Noise Ratio(PSNR), Mean Square Error(MSE) for all the combinations of different filters. As a result, noise decrease appeared in the LPF3*3#1+HPF3*3#1+Vertical3*1 of highest filter.<BR>  We confirmed noise reduction effect by applying the proposed filter combination in many fields of medical imaging applications.

자기공명영상에서 ACR 팬텀을 이용한 해상력 특성 평가

민정환(Jung-Whan Min),정회원(Hoi-Woun Jeong),한지현(Ji-Hyun Han),이시내(Si-Nae Lee),김민지(Min-Ji Kim),김승철(Seung-Chul Kim) 대한방사선과학회(구 대한방사선기술학회) 2022 방사선기술과학 Vol.45 No.1

This study was purpose to quantitative assessment of the resolution characteristics by using American college of radiology(ACR) phantom for magnetic resonance imaging (MRI). The MRI equipment was used (Achiva 3.0T MRI, Philips system, Netherlands) and the head/neck matrix shim SENSE head coil were 32 channels(elements) receive MR coil. And the MRI equipment was used (Discovery MR 750, 3.0T MRI, GE medical system, America) and the head/neck matrix shim MC 3003G-32R 32-CH head coil were receive MR coil. As for the modulation transfer function(MTF) comparison result by using ACR magnetic resonance imaging phantom, the MTF value of the ACR standard T2 image in GE equipment is 0.199 when the frequency is 1.0 mm-1 and the MTF value of the hospital T2 image in Philips equipment is 0.528. It was used efficiently by using a general sequence more than the standard sequence method using the ACR phantom. In addition it is significant that the quantitative quality assurance evaluation method for resolution characteristics was applied mutatis mutandis, and the result values of the physical image characteristics of the 3.0T MRI device were presented.

간접평판형 검출기에서 국제전자기술위원회 기준을 통한 잡음전력스펙트럼 비교 연구

민정환(Jung-Whan Min),정회원(Hoi-Woun Jeong),김기원(Ki-Won Kim),권경태(Kyung-Tae Kwon),정재용(Jae-Yong Jung),손진현(Jin-Hyun Son),김현수(Hyun-Soo Kim) 대한방사선과학회(구 대한방사선기술학회) 2018 방사선기술과학 Vol.41 No.5

The purpose of this study was to compare image quality of indirect digital radiography (IDR) system using the International Electro-technical Commission standard (IEC 62220-1), and to suggest the analysis of noise power spectrum (NPS) which were applied to IEC 62220-1 in medical imaging. In this study, Pixium 4600 (Trixell, France) which is in-direct flat panel detector (FPD) was used. The size of image receptor (IR) is 7 × 17 inch (matrix 3001 × 3001) which performed 14bit processing and pixel pitch is 143 μm. In IEC standard, NPS evaluation were applied to RQA3, RQA5, RQA7 and RQA9. Because of different radiation quality, each region of interesting (ROI) were compared. The results of NPS indicated up to 3.5 mm -¹ including low Nyquist frequency. RQA5 indicated the lowest NPS and the others indicated higher NPS results relatively. NPS result of ROI a38 was higher than ROI a92 and this result indicated that there are more noise in left (cathode) than right (anode). This study were to evaluate NPS by using different radiation quality and setting the each ROI, and to suggest the quantitative methods of measuring NPS