디지털 방사선 시스템의 노출 유형에 따른 임상 적용 시 입사표면선량 및 Entropy 비교분석을 통한 자동노출제어장치의 유용성 평가

최지안,황준호,이경배 한국콘텐츠학회 2019 한국콘텐츠학회논문지 Vol.19 No.8

The purpose of this study is to evaluate the usefulness of automatic exposure control (AEC) by analyzing entrance surface dose (ESD) and entropy on using automatic exposure and manual exposure. The experimental method was to measure the dose by placing a semiconductor dosimeter on the Rando Phantom for the Pelvis, Abdomen, Skull, and Chest regions. The DICOM file was simultaneously acquired and then entropy was analyzed by using Matlab. As a result, when using the automatic exposure control, dose of all sites was lower than manual exposure’s dose and entropy was high. In addition, paired t-test was performed for each item and p<0.05 was found in each item. In conclusion, the use of automatic exposure control can be a useful method to contribute to the optimization of the exposure dose and the image quality by reducing the amount of unnecessary radiation amount and information loss that can occur in X-ray examination. 본 연구는 자동노출제어장치(Automatic Exposure Control, AEC)와 수동노출 이용 시 입사표면선량(Entrance Surface Dose, ESD)과 Entropy를 분석하여 자동노출제어장치의 유용성에 대해 알아보고자 하였다. 실험방법은 Skull, Chest, Abdomen, Pelvis 부위에 대하여 란도팬텀(Rando Phantom)에 반도체 선량계를 위치시켜 선량을 측정하였고, 동시에 획득한 DICOM(Digital Imaging and Communications in Medicine) 파일을 Matlab으로 Entropy 분석을 하였다. 그 결과 자동노출제어장치 이용 시 모든 부위의 입사표면선량이 수동노출보다 낮았고 Entropy 수치는 높았으며, paired -test는 p<0.05로 유의한 차이가 있음을 알 수 있었다. 결론적으로 자동노출제어장치의 사용은 X선 검사 시 발생할 수 있는 불필요한 방사선량과 정보의 손실량을 줄여서 피폭선량과 영상 화질의 최적화에 기여할 수 있는 유용한 방법이 될 수 있다.

인터벤션에서 자동노출제어장치와 수동노출 사용 시 두께 변화에 따른 선량감소 방안 연구

황준호(Jun-Ho Hwang),정구민(Ku-Min Jung),최지안(Ji-An Choi),김현수(Hyun-Soo Kim),이경배(Kyung-Bae Lee) 대한방사선과학회(구 대한방사선기술학회) 2018 방사선기술과학 Vol.41 No.2

We aims to perform comparative analysis on the dose area and image qualities varying on the slice thickness when using Automatic Exposure Controller (AEC) and manual exposure; thus, it wants to suggest a measure to reduce exposure dose by setting the optimal examination condition for each slice thickness. The method was to set the thickness as Thin, Normal, and Heavy adult and evaluate the dose area, spatial resolution, low contrast resolution, Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR) according to each slice thickness by using the AEC and the manual ex-posure controller. The dose area according to each slice thickness all increased both when using the AEC and the man-ual exposure. However, the manual exposure showed lower dose area product than the AEC. Spatial resolutions and low contrast resolutions were all observed to be higher than the evaluation standard. Also, the SNR and CNR of each thick-ness all increased when using the AEC. When using the manual exposure, SNR and CNR increased in all cases other than the Heavy Adult. Consequently, the Thin and Normal Adult showed dose reduction about 2 times when using the manual exposure controller, while ensuring the image quality. Heavy adult was able to maintain good image quality by using AEC.

Evaluation of the usefulness of deep neural networks in classifying X-ray images according to radiation exposure level for automatic exposure control of digital radiography

Hwang Jun-Ho,Park Chang-Kyu,Lee Kyung-Bae,Lee Tae-Soo 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.2

In medicine, X-ray imaging has to have stable image quality while minimizing radiation exposure. In recent digital radiography (DR), the radiation exposure and image quality are controlled by employing automatic exposure control (AEC) technology. In such an environment, the technology needs the capability of accurately classifying the level of radiation exposure despite statistical X-ray fluctuations. Therefore, the purpose of this study was to implement a radiation exposure classifier that could objectively determine the level using the deep neural network (DNN) method. Datasets containing 2000 images were used for training and validation of the DNN. This was done by changing the sensitivity of the AEC of the DR system to S200, S400, S800, and S1000. The changes in sensitivity generated four groups of 500 X-ray images each: overexposure, normal exposure (2), normal exposure (1), and underexposure. The results showed a classification accuracy of 93.83% and a loss 38.9%. In conclusion, through deep learning with X-ray images, an objective radiation exposure classifier was implemented and is expected to be used for the AEC of DR systems and to improve diagnostic accuracy.

Comparison of Radiation Dose of Abdomen Pelvis CT with Automatic Exposure Control according to Different Scout Image Acquisition: Standard and Obese Phantom Study

김용민(Yong-Min Kim),이기백(Ki Baek Lee) 대한CT영상기술학회 2021 대한CT영상기술학회지 Vol.23 No.2

자동노출조절장치를 사용한 복부 CT 검사에서 scout 영상을 획득 시 관전압, 관전류를 변화시켰을 때 실제 검사의 선량 측면에 어떤 영향이 있는지 보고자 하였다. 연구는 G사, S사 두 사의 장비와 standard body phantom, obese body phantom을 사용하여 진행이 되었다. Scout 영상을 획득 시 관전압은 80, 100, 120 kVp, 관전류는 10 ~ 80 mA를 이용하여 적용하였다. 선량 분석은 먼저 복부 CT검사에 AEC 기능이 잘 적용되는지 알아보았고, 팬텀의 단면에 흡수된 선량을 mAs 값으로 그리고 전체 CT 선량 수치도 비교하였다. 그 결과 G사, S사 장비를 이용하여 scout 영상의 획득 시 관전류의 변화는 실제 CT 검사에서 크게 영향을 미치지 않았다. 반면에, 관전압을 변화시킬 때에는 scout 획득 관전압이 낮을수록 실제 CT 검사 시 선량이 증가되는 것을 확인할 수 있었다. 장비를 사용할 때 전체 CT검사의 선량을 줄이기 위해 scout 획득 관전압을 무조건 낮게 설정하여 영상을 획득한다면 실제 CT검사에서 더 많은 선량이 발생하는 것을 초래할 가능성이 있다. 결과적으로 scout 영상 획득 시 관전압의 사용은 실제 CT 검사의 관전압과 가능한 일치시켜야 한다. Automatic Exposure Control(AEC) is usually utilized in Abdomen Pelvis CT(APCT) according to attenuation profiles of patient’s body. Here, it is very imperative to acquire an ideal scout image. There were a lot of research which dealt with the relationship between scout scan and AEC function. However, most studies had done fewer parameters in scout image based on a standard body size. So, we acquired the various scout images with lots of parameters such as tube voltages(80, 100, 120 kVp) and tube currents(from 10 to 80 mA) using two different size of phantoms and two manufacturers. APCT scans underwent from liver to anus portion. The dose distributions of all axial APCT images and mAs at specific portions were measured and compared. As a result, there were no significant differences of radiation dose according to all different tube currents. However, dose change had occurred at different tube voltages. In conclusion, it is very important to use same tube voltage at the scout and the APCT. Lastly, we recommend that small amount of mA should be utilized at scout scan.

Low Dose CT Colonography(LDCTC)를 이용한 Automatic Exposure Controll(AEC)와 Beam Collimation의 변화에 따른 유용성 평가와 Effective Dose의 평가치에 대한 연구

여상근(Sang Geun Yeo),정한별(Han Byeol Jeong),대창민(Chang Min Dae),민관홍(Kwan Hong Min),김성룡(Seong Ryong Kim) 대한CT영상기술학회 2008 대한CT영상기술학회지 Vol.10 No.1

Purpose To considerate the efficiency of Automatic Exposure Controller(AEC) and Beam Collimation with the value of Effective Dose obtained with the alteration of Automatic Exposure Controller(AEC) and Beam Collimation. Materials and methods 50 out-patients (Male:36, Female:14, mean age:45 years) underwent Low Dose CT Colonography with 16 MDCT from 1st June 2007 to 31th July 2007 were selected. The Effective Dose was produced with the alteration of DoseRight Automatic Current Selector(ACS) & DoseRight D-Dose modulation(D-DOM), Beam Collimation in same patients. Results On the assumption that Effective Dose without AEC is 100%, 8% was decreased with only ACS, 9% was declined with D-DOM, and 16% was decreased with using ACS & D-DOM. On the same condition, 8% was decreased with the Beam Colliniation increased double. Conclusion 8%~16% of Effective Dose was decreased with AEC Program(ACS, D-DOM) and Beam Collimation. Although 30%-40% of decrease effectiveness was not obtained like the previous papers about dose, the use of Automatic Exposure Controller and Beam Collimation decrease effective dose. The use of AEC and Beam Collimation maintain the high quality of images and extend the tube life time of CT modality.

SPECT/CT에서 자동노출제어(AEC)를 이용함으로써 얻어지는 영상의 질 평가와 피폭선량 감소에 관한 고찰

윤석환,이성환,조성욱,김진의,Yoon, Seok-Hwan,Lee, Sung-Hwan,Cho, Seong-Wook,Kim, Jin-Eui 대한핵의학기술학회 2014 핵의학 기술 Vol.18 No.2

SPECT의 기능적인 영상과 CT의 해부학적 영상을 융합하여 영상 진단의 시너지 효과를 창출하는 SPECT/CT는 부가적인 CT의 사용으로 환자의 피폭선량을 증가시킨다. SPECT/CT를 사용함으로서 불가피한 피폭선량에 대한 선량감소 효과를 위해 CT의 방사선 노출 시 선량이 환자의 크기와 모양에 따라 자동조절 되는 CT장비의 자동노출제어(Automatic exposure control, AEC)시스템을 SPECT/CT에 적용함으로써 피폭선량의 감소효과와 영상의 질의 변화를 비교 및 평가하고자 하였다. 실험에 사용된 SPECT/CT는 GE사의 Discovery 670이며, AEC 기법으로는 Smart mA를 선원은 $^{99m}Tc$을 사용하였다. CT선량 변화에 따른 SPECT영상과 CT영상의 질을 비교하기 위해 CT의 조건을 첫 번째 관전압 80, 100, 120, 140 kVp, 관전류 10, 30, 50, 100, 150, 200, 250 mA, 두 번째 AEC기법은 (10-250 mA)로 설정하여 실험하였으며, SPECT영상의 resolution과 contrast를 평가하기 위해 triple line phantom과 Flangeless Esser PET phantom을 사용하였으며, CT영상과 선량을 평가하기 위해서 anthropomorphic chest phantom을 이용하였다. Torso protocol (120 kVp, 150 mA)을 적용하였으며 AEC기법(120 kVp, 10-200 mA)으로 촬영하여 noise와 uniformity를 측정하였으며, CTDI (mGy), DLP (mGycm)값을 구하였다. 관전압, 관전류의 변화와 AEC 적용에 대한 감쇠보정 한 SPECT영상에서의 Resolution은 FWHM [mm] left 3.48 mm, center 3.65 mm, right 3.60 mm로 일정한 값을 보였다. Contrast의 결과 값은 cold spot에 대한 감쇠물질 정도에 따른 공기, 물에 대해서는 큰 차이를 나타내지 않았으며, 뼈에 대해서는 관전압이 증가할수록 감소하는 값을 보였다. Hot spot에 대해서는 관전압과 관전류의 변화 그리고 AEC를 적용 시 큰 차이를 보이지 않았다. CT영상에서의 noise값을 각각 비교한 결과 15.4, 18.5으로 AEC적용 시 noise 값은 증가하였지만 noise값의 coefficient variation (CV)값은 각각 33.8, 24.9으로 AEC 사용 시 노이즈 값의 변동이 작아 uniformity한 영상을 얻을 수 있었다. 선량평가를 위한 비교에서 DLP[mGy-cm]값은 426.78, AEC 적용 시 352.09의 값을 보여 AEC적용 시 피폭선량이 약 18% 감소함을 알 수 있었다. 본 실험을 통하여, SPECT/CT 영상에서 CT선량변화에 따른 SPECT 영상의 감쇠보정은 차이가 없음을 확인 할 수 있었으며, CT선량의 증가는 CT영상의 질은 향상되지만, 피폭선량이 증가하므로 피폭선량을 줄이기 위해 AEC기법을 적용하여 동일한 감쇠 보정된 SPECT영상과 noise가 균일한 CT영상을 획득할 수 있으며 피폭선량이 감소할 수 있을 것으로 기대된다. Purpose Auto exposure control (AEC) in SPECT/CT automatically controls the exposure dose (mA) according to patient's shape and size. The aim of this study was to evaluate the effect of AEC in SPECT/CT on exposure dose reduction and image quality. Materials and Methods The model of SPECT/CT used in this study was Discovery 670 (GE, USA), Smart mA for AEC; and $^{99m}Tc$ as a radioisotope. To compare SPECT and CT images by CT exposure dose variation, we used a standard technique set at 80, 100, 120, 140 kVp, 10, 30, 50, 100, 150, 200, 250 mA, and AEC at 80, 100, 120, 140 kVp, 10-250 mA. To evaluate resolution and contrast of SPECT images, triple line phantom and flangeless Esser PET phantom were used. For CT images, noise and uniformity were checked by anthropomrphic chest phantom. For dose evaluation to find DLP value, anthropomorphic chest phantom was used and the CT protocol of torso was applied by standard technique (120 kVp, 100 mA) and AEC (120 kVp, 10-250 mA). Results When standard and AEC were applied, the resolutions at SPECT images with attenuation correction (AC) were the same as FWHM by center 3.65 mm, left 3.48 mm, right 3.61 mm. Contrasts of standard and AEC showed no significant difference: standard 53.5, 29.8, 22.5, 15.8, 6.0, AEC 53.5, 29.6, 22.4, 15.7, 6.1 In CT images, noise values at standard and AEC were 15.4 and 18.5 respectively. The application of AEC increases noise but the value of coefficient variation were 33.8, 24.9 respectively, obtaining uniform noise image. The values of DLP at standard and AEC were 426.78 and 352.09 each, which shows that the application of AEC decreases exposure dose more than standard by approximately 18%. Conclusion The results of our study show that there was no difference of AC in SPECT images based on the CT exposure dose variation at SPECT/CT images. It was found that the increased CT exposure dose leads to the improvement of CT image quality but also increases the exposure dose. Thus, the use of AEC in SPECT/CT contributes to obtaining equal AC SPECT images, and uniform noise in CT images while reducing exposure dose.

경부 CT 검사 프로토콜 변화에 따른 화질 및 선량에 관한 연구

정욱진,김도훈,이효영 국제차세대융합기술학회 2022 차세대융합기술학회논문지 Vol.6 No.4

본 연구는 환자 피폭선량의 감소를 위한 목적으로 일개 병원에서 시행되는 경부 ct 검사의 촬영조건에서 관 전압과 영상처리 알고리즘의 적절한 적용으로 기존 영상 화질과 유사한 촬영조건과 방사선량을 평가하였다. 2021년 6월부터 11월까지 내원한 여성 환자 150명을 대상으로 경부 CT 검사를 시행하였다. 촬영조건은 80kV, 100kV, 120kV 자동 노출 조절 방법으로 영상을 획득하였다. 쵤영 후 영상 재구성 알고리즘인 SAFIRE를 단계적 0, 1, 3, 5 로 적용하였고, 경부 주변 조직에 관심 영역을 설정하여 신호대잡음비(Signal to noise, SNR)와 대조도비(Contrast to noise ratio, CNR)로 영상을 정량적 분석하였다. 그룹 간 비교에서 SAFIRE의 강도가 증가할수록 노이즈가 감소 하였으며 신호대잡음비, 대조도비가 증가하는 양상을 보였다. 또한 120kV의 자동 노출 조절 방법과 SAFIRE 강도 3과 비교적 유사한 영상의 화질을 가지는 조건은 100kV의 자동 노출 조절 방법과 SAFIRE 강도 3으로 나타났다. 120kV 자동 노출 조절 방법에서 100kV 자동 노출 조절 방법으로 낮추었더니 방사선량이 13.73%로 감소하였다. This study evaluated the imaging conditions and radiation dose similar to the existing image quality by appropriate application of tube voltage and image processing algorithm in the imaging conditions of a cervical ct test performed at a hospital for the purpose of reducing the patient's exposure dose. Cervical CT scans were performed on 150 female patients who visited the hospital from June to November 2021. Images were acquired by automatic exposure control method of 80kV, 100kV, and 120kV under the shooting conditions. SAFIRE, a post-image reconstruction algorithm, was applied in steps of 0, 1, 3, and 5, and the region of interest was set in the surrounding tissues of the neck to obtain images with Signal to Noise (SNR) and Contrast to Noise Ratio (CNR). was quantitatively analyzed. In comparison between groups, as the intensity of SAFIRE increased, the noise decreased, and the signal-to-noise ratio and contrast ratio increased. In addition, the conditions of the automatic exposure control method of 120kV and the image quality relatively similar to SAFIRE intensity 3 were the automatic exposure control method of 100kV and SAFIRE intensity 3. When it was lowered from the 120kV automatic exposure control method to the 100kV automatic exposure control method, the radiation dose was reduced to 13.73%.

DR(Digital Radiography)에서 관전압 및 자동노출제어장치의 감도 변화에 따른 검출기의 동적 범위 성능평가 방법연구 -Dynamic Step Wedge와 히스토그램 평가를 중심으로

황준호,최지안,김현수,이경배 한국콘텐츠학회 2019 한국콘텐츠학회논문지 Vol.19 No.4

This study proposes a method to evaluate the performance of a detector by analyzing the dynamic step wedge and histogram according to the change of the tube voltage and sensitivity when using the Automatic Exposure Control (AEC). The performance of a detector was evaluated by measuring X-ray quality, Entrance Surface Dose (ESD), tube current, dynamic range corresponding to detector sensitivities of S200, S400, S800, S1000 per tube voltage of 60, 70, 81, 90 kVp. As a results, all of the qualities satisfied the acceptance criteria, and the Entrance Surface Dose and tube current were decreased stage by stage as sensitivity was set higher. In the dynamic step wedge, the observable dynamic range has also increased as tube voltage became higher. The histogram showed the quantization separation phenomena as the tube voltage was set higher. The higher the sensitivity, the more the underflow and overflow occurred in which the amount of information on both ends of the histogram was lost. In conclusion, the deterioration in the performance of the detector was found to be insufficient to realize the change of the tube voltage and sensitivity when using the Automatic Exposure Control, and it is useful to use dynamic step wedge and histogram in evaluating detector performance evaluation. 본 연구는 자동노출제어장치 사용 시 관전압과 감도 변화에 따른 dynamic step wedge와 히스토그램의 동적 범위 분석을 통해 검출기의 성능을 평가하는 방법을 제안하고자 하였다. 실험방법은 관전압 60, 70, 81, 90 kVp 별로 검출기 감도 S200, S400, S800, S1000에 해당하는 선질, 입사표면선량, 관전류량, 동적 범위를 측정하여 검출기의 성능을 평가하고자 하였다. 그 결과 선질은 모두 합격 기준에 부합하였고, 입사표면선량과 관전류량은 감도가 높게 설정될수록 단계적으로 감소하였다. Dynamic step wedge는 관전압이 높아질수록 관찰 가능한 동적 범위도 함께 증가하였고, 또한 히스토그램은 관전압과 감도가 높게 설정될수록 양자화 이격 현상과 히스토그램 양단의 정보량이 상실되는 언더플로우와 오버플로우가 나타났다. 결론적으로 검출기가 성능 저하로 인하여 자동노출제어장치 사용 시 관전압과 감도 변화에 따른 동적 범위를 제대로 구현해내지 못한다는 것을 알 수 있었고, 검출기 성능평가 시 dynamic step wedge와 히스토그램을 통한 평가가 유용하다는 점을 알 수 있었다.

동전을 이용한 제조사 별 디지털 방사선 영상 시스템의 자동노출제어 성능 평가

임세훈(Se-Hun Lim),성열훈(Youl-Hun Seoung) 대한방사선과학회(구 대한방사선기술학회) 2022 방사선기술과학 Vol.45 No.1

In this study, we proposed an image quality control for an automatic exposure control (AEC) of digital radiographic imaging system and tried to analyze the performance of the AEC by various manufacturer. The subjects of the experiment were analyzed for the AEC image quality evaluation using digital radiation generators from four manufacturer such as PHILIPS, GE Healthcare, SAMSUNG Healthcare, DK Medical Solution. We used as materials for the implementation of the image quality evaluation by coins (500 won, KOMSCO, Korea). This study evaluated the performance evaluation of the AEC as image quality and exposure dose (Milliampere-seconds; mAs). The image quality evaluation was tried visual assessment by two radiologic technologists and contrast to noise (CNR) by ImageJ. The exposure dose investigated mAs on digital radiation generators. The radiographic coin images acquired 360 images based on change in the control factors of the AEC, which were kVp, the consistency of field configuration and dominant zone, sensitivity and density. As a result, there was a significant difference in the AEC performance between manufacturer. The CNR by the AEC for each manufacturer showed a difference of up to about 1.9 times. The exposed tube current by the AEC for each manufacturer showed a difference of up to about 5.8 times. It is expected that our proposed evaluation method using coins could be applied as the AEC performance evaluation method in the future.

Rando 팬텀을 이용한 Multi-detector Computed Tomography의 Automatic Exposure Control 특성 평가

김정훈(Jung Hoon Kim),김상현(Sang Hyun Kim),김선기(Sean Ki Kim),김기홍(Ki Hong Kim) 대한CT영상기술학회 2010 대한CT영상기술학회지 Vol.12 No.2

Purpose To assess reaction characterization of automatic exposure controller(AEC) system by each manufacturer according to changing of subject thickness and changes of image quality acquired by them and phantom. Materials and methods 64 multi-detector computed tomography by four manufacturers including Siemens(Somatom Definition, Erlangen, Germany), GE Healthcare(Lightspeed VCT, Milwaukee, USA), Philips(Brilliance, Cleaveland, USA), and Toshiba(Aquillion, Tokyo, Japan) were used for this study. The Rando phantom(AR1-200X, Fluke Biomedical, USA) which was to change thickness was used also. General scan condition was used in abdominal pelvic examination and all available function of AEC was used. We displayed in graph changing of each mAs value, and measured standard deviation of each noise value according to change of subject thickness. Results The range of fluctuation of mAs value by each manufacturers’ AEC was 207 mAs(from 265 to 58 mAs), 179,5 mAs(from 197 to 18 mAs), 127.5 mAs(from 184.5 to 57 mAs), and from 174 mAs(from 196 to 22 mAs) in S, G, P, T, respectively. Noise values measured in phantom images were 9.1±2.4, 11.43±2.65, 7.9±2.59, 8.96±2.67, in S, G, P, T, respectively. Standard deviation of each noise value according to change of subject thickness was maintained a regular value as from ±2.4 to ±2.67 in all the four equipments. Conclusion AEC system is valuable technique to reduce radiation exposure based on geometric structure of patient and clinical demand. Therefore, characterization of AEC system should be recognized, and needed for periodical phantom scan to confirm primary function.