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KMID : 1149020180200020089
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Journal of Korean Society of Computed Tomographic Technology
2018 Volume.20 No. 2 p.89 ~ p.97
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Analysis of image quality and radiation dose level for lower extremity vein blood flow image by FBP(Filtered Back Projection), MBIR(Model Based Iterative Reconstruction) and ASIR-V(Adaptive Statistical Iterative Reconstruction V)
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Lim Dong-Wook
Yang Chang-Ho
Choi Dae-Yeon
Lee Sang-Hun
Kang Dong-Won
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Abstract
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Purpose: With the fact that the law related with continuous radiation exposure has been strengthened and especially public awareness about radiation exposure caused by medical treatment has been increased, recently, utilizing the new reconstruction technique get activated instead of FBP which is existing iterative reconstruction Technique. It created momentum that improves the quality of image and decrease an amount of radiation innovatively with lower noise on image even on the low tube voltage. This study aims to find out how tube voltage and iterative reconstruction technique affect and change the quality of image and radiation dose.
Material and methods: Subjects are 90 patients admitted to PNUYH for diagnosis of DVT(Deep vein thrombosis). As a retrospective study, subjects are divided into 3 groups of 30 persons with 120 kVp, 80 kVp, 70 kVp. The first group with 120 kVp is examined by fixed tube voltage 120 mA and image is reconstructed by FBP. The Second group with 80 kVp is examined by automatic tube voltage control system and image is reconstructed by MBIR. The third group with 70 kVp is examined by automatic tube voltage control system and image is reconstructed by ASIR-V. Image reconstruction is by using raw data obtained under the condition of both tube voltage and setting including the range from kidney to foot. Contrast medium 2.0 mL/kg is injected at a speed of 3 mL/sec to evaluate DVT(Deep vein thrombosis). As a quantitative evaluation method, the quality of image is evaluated by marking ROI(Region of interest) on regions of IVC(Inferior vena cava, FV(Femoral vein), PopV(Popliteal vein). As qualitative evaluation, the method 2 radiologists give a score 1~3 with each component of quality, noise, image reading is adopted. Dose assessment is analysed by dose report.
Result: As a result of measurement, the level of Vascular enhancement, CNR(Contrast to noise ratio), SNR(Signal to noise ratio) showed the highest in the order of 70 kVp ASIR-V, 80 kVp MBIR, 120 kVp FBP in quantitative evaluation method. And, Noise deceased in the order of 70 kVp ASIR-V, 80 kVp MBIR, 120 kVp FBP. In qualitative evaluation method, specialists evaluated superiority followed by 70 kVp ASIR-V, 80 kVp MBIR, 120 kVp FBP as well. Lastly, in the evaluation of the level of DLP(Dose Length Product) in dose assessment, 120 kVp FBP was 53% higher than 70 kVp ASIR-V, 80 kVp MBIR. And there was no difference in the level of DLP between 70 kVp ASIR-V and 80 kVp MBIR.
Conclusion: MBIR of 80 kVp and ASIR-V of 70 kVp reduced the noise innovatively compare to 120 kVp FBP and decreased
more than 50% of radiation dose. so that low tube voltage is able to be used. Moreover, with increasing contrast enhancement, CNR, SNR, better image information than previous one was obtained. Even though there is no difference in the level of DLP compared between 80 kVp MBIR and 70 kVp ASIR-V, considering reconstructing time and the quality of image exclusively, it is possible to say that 70 kVp ASIR-V is vastly superior to 80 kVp MBIR.
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KEYWORD
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Radiation exposure, kVp, Reconstruction, FBP, MBIR, ASIR-V
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