• Title/Summary/Keyword: image artifact

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Metal artifact SUV estimation by using attenuation correction image and non attenuation correction image in PET-CT (PET-CT에서 감쇠보정 영상과 비감쇠보정 영상을 통한 Metal Artifact 보정에 대한 고찰)

  • Kim, June;Kim, Jae-II;Lee, Hong-Jae;Kim, Jin-Eui
    • The Korean Journal of Nuclear Medicine Technology
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    • v.20 no.2
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    • pp.21-26
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    • 2016
  • Purpose Because of many advantages, PET-CT Scanners generally use CT Data for attenuation correction. By using CT based attenuation correction, we can get anatomical information, reduce scan time and make more accurate correction of attenuation. However in case metal artifact occurred during CT scan, CT-based attenuation correction can induce artifacts and quantitative errors that can affect the PET images. Therefore this study infers true SUV of metal artifact region from attenuation corrected image count -to- non attenuation corrected image count ratio. Materials and Methods Micro phantom inserted $^{18}F-FDG$ 4mCi was used for phantom test and Biograph mCT S(40) is used for medical test equipment. We generated metal artifact in micro phantom by using metal. Then we acquired both metal artifact region of correction factor and non metal artifact region of correction factor by using attenuation correction image count -to- non attenuation correction image count ratio. In case of clinical image, we reconstructed both attenuation corrected images and non attenuation corrected images of 10 normal patient($66{\pm}15age$) who examined PET-CT scan in SNUH. After that, we standardize several organs of correction factor by using attenuation corrected image count -to- non attenuation corrected count ratio. Then we figured out metal artifact region of correction factor by using metal artifact region of attenuation corrected image count -to- non attenuation corrected count ratio And we compared standard organs correction factor with metal artifact region correction factor. Results according to phantom test results, metal artifact induce overestimation of correction factor so metal artifact region of correction factors are 12% bigger than the non metal artifact region of correction factors. in case of clinical test, correction factor of organs with high CT number(>1000) is $8{\pm}0.5%$, correction factor of organs with CT number similar to soft tissue is $6{\pm}2%$ and correction factor of organs with low CT number(-100>) is $3{\pm}1%$. Also metal artifact correction factors are 20% bigger than soft tissue correction factors which didn't happened metal artifact. Conclusion metal artifact lead to overestimation of attenuation coefficient. because of that, SUV of metal artifact region is overestimated. Thus for more accurate quantitative evaluation, using attenuation correction image count -to-non attenuation correction image count ratio is one of the methods to reduce metal artifact affect.

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Artifacts in Digital Radiography (디지털 방사선 시스템에서 발생하는 Artifact)

  • Min, Jung-Whan;Kim, Jung-Min;Jeong, Hoi-Woun
    • Journal of radiological science and technology
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    • v.38 no.4
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    • pp.375-381
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    • 2015
  • 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 occurred 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 appeared 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 characteristic and providing sustainable education as well as the maintenance of the equipments.

Quantitative Evaluation of CT Artifact Elimination with various Cut-off Frequency of Hann Filter (Hann 필터의 Cut-off 주파수 변화에 따른 CT 영상의 Artifact 제거효과에 대한 정량적 평가)

  • Kang, Bo-Sun
    • Journal of the Korean Society of Radiology
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    • v.2 no.3
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    • pp.5-9
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    • 2008
  • In the computerized tomography(CT), various filters are using in the reconstruction algorithm to reduce or eliminate the artifacts which are intrinsically induced by the imperfection of mathematical methods for reconstruction, lack of real informations about anatomic structures in the projection image, errors in data acquisition and so on. Hann filter was used to evaluate the filter effects on the elimination of reconstruction artifact in the CT image. The quantitative study was done by changing cut-off frequency of Hann filter from 0.1 to 0.9 with frequency increasement by 0.2. NPS analysis was fulfilled for the quantitative evaluation of filter effect.

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Image Analysis Using Grid Suppression Software to Remove Moire Artifact from Micro Lesions of Sprague Dawley Rat (Sprague Dawley Rat의 미세병변에서 Moire Artifact를 제거하기 위한 Grid suppression software 사용 후 영상분석)

  • Lee, Sang-Ho
    • Journal of radiological science and technology
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    • v.40 no.4
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    • pp.575-580
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    • 2017
  • Because moire artifacts overlap with fine lesions and frequency bands, image processing software that removes moire artifacts can lead to loss of micro lesions. In this study, microscopic lesions such as microcalcification and microfracture were randomly formed on SD (Sprague Dawley) rats and image and optimized grid images were compared and analyzed using reference image and grid suppression software. The images were read by two consecutive radiologists using a McNemar's test. Among the 73 microcalcifications, in the 13 cases after grid suppression, the image of the optimized grid shows the loss of image in 3 cases, and the image after grid suppression shows statistically significant image loss (p=0.021). In all 53 fracture lines, there were 19 cases of image loss after the grid suppression, and only one case of the optimized grid showed no image loss. Therefore, the use of grid suppression software to remove moire artifacts should be carefully considered in the diagnosis of micro lesions.

The Method for Removing Jagging Artifact (Jagging Artifact 억제 기법)

  • Yang Seoung-Joon;Lee In-Hwan;Kwon Young-Jin
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.54 no.3
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    • pp.194-197
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    • 2005
  • Digital display products are gradually becoming diversified and pursuing high-quality image display. Digital TV supports various video signal formats from conventional SD to digital HD because the format conversion of video image is required. Traditional format conversion of the video image is achieved by a 1-dimensional linear interpolator applying both horizontal and vertical direction. Jagging artifact can be expressed as the linkage of line segments in several directions. In this paper, we present the method that removes jagging artifact effectively using PCA (Principle Component Analysis) and reserve the detail in a given image.

A Bilateral Filtering Based Ringing Elimination Approach for Motion-blurred Restoration Image

  • Wang, Weiqing;Wang, Weihua;Yin, Jiao
    • Current Optics and Photonics
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    • v.4 no.3
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    • pp.200-209
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    • 2020
  • We describe an approach that uses a bilateral filter to reduce the ringing artifact in motion-blurred restoration image. It takes into account the specific physical structure of the ringing artifact combined with the properties of the human visual system. To properly reduce the ringing artifact, each of the adjacent pixels is limited in a straight line which has a given direction. To protect the edges and the texture regions of an image, our algorithm divides the image into texture regions and flat regions, and the artifact reduction algorithm is only applied to the flat region. Finally, we use 8 typical images and 5 objective quality evaluation indices to evaluate our algorithm. Experimental results show that our algorithm can obtain better results in subjective visual effect and in objective image quality evaluation.

Evaluation of the Usefulness of PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) Technique to Reduce the Magnetic susceptibility artifact (Magnetic susceptibility artifact를 줄이기 위한 PROPELLER 확산강조영상기법의 유용성에 대한 평가)

  • Cho, Jae-Hwan
    • Journal of Digital Contents Society
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    • v.11 no.1
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    • pp.73-78
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    • 2010
  • This study attempted to examine whether the propeller diffusion weighted image method may remove magnetic susceptibility artifacts caused by metallic materials. A comparison of occurrence rates of magnetic susceptibility artifacts in the four regions, both temporal lobes, pons, and orbit, between b = 0 and b = 1,000 s/mm2 images was made after obtaining echo-planar diffusion weighted image, propeller diffusion weighted image, and ADC map images, respectively, from a total of 20 patients who had MRI shots taken of their brain and were found to be with retained metallic foreign bodies within their teeth using a 3.0T MR scanner. In the case of echo-planar diffusion weighted image technique, the presence of metallic materials may bring in some limits on accurate diagnosis due to magnetic susceptibility artifacts, while the propeller diffusion weighted image technique where magnetic susceptibility artifacts decrease is expected to be more useful in ensuring accurate diagnosis in the clinical context.

The Study about the Positioning Block Artifact in Digital Radiography Environment (Digital Radiography 환경에서 Positioning Block Artifact에 관한 연구)

  • Kim, Byung-Ki;Choi, Jun-Gu;Lee, Jun;Lee, Min-Woo;Kim, Sun-Bae;Kim, Gyeong-Su
    • Korean Journal of Digital Imaging in Medicine
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    • v.10 no.1
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    • pp.13-19
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    • 2008
  • Purpose : In sponge quality of the material in digital radiography environment coating because do position blocks two that do not become coating done positioning blocks two that do not become coating done positioning block and sponge quality of the material to testing bench image artifact's difference compare. Method of study : In digital radiography environment positioning block of different two products same sunshine or effect that image and positioning block artifact gents in image analyze. the target used positioning block 2 when examine hand, rib and examination condition did each differently according to used positioning block. reflex compared picture that do image and verify that examine first time. Result : 1. In sponge quality of the material coating in done product artifact appear. Did not appear in product that do not become coating. 2. Can know coating's existence, that artifact according to radish happens. 3. Quality of the material coating's existence, there was difference of slippage according to radish Conclusion : Quality of the material coating phenomenon that done positioning block thus, it may have to be considered that use after estimate degree that get in image.

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Reduction of Metal Artifact by Using VAT-SEMAC in MRI (VAT-SEMAC을 이용한 보철물에 의한 허상 감소)

  • Kim, Hyung-Tae;Lim, Jong-Nam;Chon, Kwon Su
    • Journal of the Korean Society of Radiology
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    • v.13 no.2
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    • pp.227-232
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    • 2019
  • MRI examination for patients with metal objects has in poor image quality. Metallic implants can result in poor image because magnetic susceptibility causes signal loss and distortion and makes poor imaging, which is called magnetic susceptibility artifact or metal artifact. There are several approaches to reduce metal artifacts. In this study, we study the reduction of metal artifact by VAT and SEMAC techniques. A metal implant used for orthopedic surgery was attached to the phatom and the distortion caused by the artifact was measured under T1WI and T2WI protocols. Several techniques of VAT only and VAT and SEMAC for the reduction of metal artifact were compared. The metal artifact showed a reduction of at least 8% to a maximum of 26% in the VAT-SEMAC. The VAT-SEMAC technique can be applied to patients with orthopedic implants to improve image quality. If scan time and image quality are simultaneously considered in VAT-SEMAC technique, metal artifact will be reduced in clinical practice.

A Quantizer Reconstruction Level Control Method for Block Artifact Reduction in DCT Image Coding (양자화 재생레벨 조정을 통한 DCT 영상 코오딩에서의 블록화 현상 감소 방법)

  • 김종훈;황찬식;심영석
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.28B no.5
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    • pp.318-326
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    • 1991
  • A Quantizer reconstruction level control method for block artifact reduction in DCT image coding is described. In our scheme, quantizer reconstruction level control is obtained by adding quantization level step size to the optimum quantization level in the direction of reducing the block artifact by minimizing the mean square error(MSE) and error difference(EDF) distribution in boundary without the other additional bits. In simulation results, although the performance in terms of signal to noise ratio is degraded by a little amount, mean square of error difference at block boundary and mean square error having relation block artifact is greatly reduced. Subjective image qualities are improved compared with other block artifact reduction method such as postprocessing by filtering and trasform coding by block overlapping. But the addition calculations of 1-dimensional DCT become to be more necessary to coding process for determining the reconstruction level.

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