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KMID : 1001220140160020009
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Journal of the Korean Society of Digital Medical Imaging Technology
2014 Volume.16 No. 2 p.9 ~ p.14
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A study of image evaluation and exposure dose with the application of Tube Voltage and ASIR of Low dose CT Using Chest Phantom
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Hwang Hye-Seong
Kim Nu-Ri
Jeong Yoon-Ji
Goo Eun-Hoe
Kim Ki-Jeong
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Abstract
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Purpose: The purpose of this study has attempted to evaluate and compare the image evaluation and exposure dose by respectively applying Filtered Back Projection(FBP), the existing test method, and Adaptive Statistical Iterative Reconstruction(ASIR) with different values of tube voltage during the Low Dose Computed Tomography(LDCT).
Materials and Methods: With the image reconstruction method as basis, Chest Phantom was utilized with the FBP and ASIR set at 10%, 20% respectively, and the change of Tube Voltage (100kVp, 120kVp). For image evaluation, Back ground noise, Signal to Noise ratio(SNR) and Contrast to Noise ratio(CNR) were measured, and, for dose evaluation, CTDIvol and DLP were measured respectively. The statistical analysis was tested with SPSS(ver. 22.0), followed by ANOVA Test conducted after normality test and homogeneity test. (p<0.05).
Results: In terms of image evaluation, there was no outstanding difference in Ascending Aorta(AA) SNR and Infraspinatus Muscle(IM) SNR with the different values of ASIR application(p<0.05), but a significant difference with the different amount of tube voltage(p>0.05). Also, there wasn't noticeable change in CNR with ASIR and different amount of Tube Voltage (p<0.05). However, in terms of dose evaluation, CTDIvol and DLP showed contrasting results(p<0.05). In terms of CTDIvol, the measured values with the same tube voltage of 120kVp were 2.6mGy with No-ASIR and 2.17mGy with 20%-ASIR respectively, decreased by 0.43mGy, and the values with 100kVp were 1.61mGy with No-ASIR and 1.34mGy with 20%-ASIR, decreased by 0.27mGy. In terms of DLP, the measured values with 120kVp were 103.21mGy·cm with No-ASIR and 85.94mGy·cm with 20%-ASIR, decreased by 17.27mGy·cm(about 16.7%), and the values with 100kVp were 63.84mGy·cm with No-ASIR and 53.25mGy·cm with
20%-ASIR, a decrease by 10.62mGy·cm(about 16.7%).
Conclusion: At lower tube voltage, the rate of dose significantly decreased, but the negative effects on image evaluation was shown due to the increase of noise. For the future, through the result of the experiment, it is considered that the method above would be recommended for follow-up patients or those who get health checkup as long as there is no
interference on the process of diagnosis due to the characteristics of Low Dose examination.
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KEYWORD
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Chest Phantom, Low dose CT, ASIR
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