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KMID : 1149020190210020049
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Journal of Korean Society of Computed Tomographic Technology
2019 Volume.21 No. 2 p.49 ~ p.59
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Evaluation of Dose Reduction and Accuracy of Images According to Scan Mode Change in Pediatric Chest CT
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Kim Gu
Kim Do-Hoon
Kim Min-Jae
Lee Byung-Hyun
Kang Dong-Won
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Abstract
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Purpose: The purpose of this study is to obtain diagnostic high-value images while minimizing radiation exposure during a child's chest CT examination. Radiation dose, test time and quality are compared by applying the Medical mode, High-pitched mode, and Volume axial mode.
Materials and method: The PBU-70 phantom was utilized with the Medical mode, High-pitch mode, and Volume axial mode using Revolution (GE Healthcare, Wisconsin USA). 70kVp, 80kVp, 100kVp were tested via 30 times for each. After acquiring the images,we set up the ROI to Back-ground air in the each image of Heart, Bone, and Lung. The CT number (HU) and noise (SD) was measured and the averaged values was used to estimate SNR and CNR. The SNR and CNR was compared to DLP directly obtained from the equipment. Statistical analysis was conducted by using independent t-test with the Predictive Analytics SoftWare (PASW).
Results: In image evaluation, the SNR of 70kVp heart was significantly different between Volume Axial and Helical(p<0.05), but there was no significant difference between Volume Axial and High-pitch(p>0.05). Volume Axial(-4.39±0.27), Helical(-4.73±0.22), High-pitch(-4.48±0.15). The SNR of 80kVp heart was significantly different between Volume Axial and Helical (p<0.05), but there was no significant difference between Volume Axial and High-pitch(p>0.05). Volume Axial(-3.27±0.18), Helical(-3.44 ±0.16), High-pitch(-3.31±0.16). The SNR of 100kVp heart was significantly different between Volume Axial and High-Pitch(p<0.05), but there was no significant difference between Volume Axial and Helical(p>0.05). Volume Axial(-1.81±0.08), Helical(-1.82±0.5) High-pitch(-1.97±0.10). The SNR of 70kVp lung was significantly different between Volume Axial and High-Pitch(p<0.05), but there was no significant difference between Volume Axial and Helical(p>0.05). High-pitch(-75.59±2.44), Helical(-80.00±3.71), Volume Axial(-79.01±4.72). The SNR of 80kVp lung was significantly different between Volume Axial and High-Pitch (p<0.05), but there was no significant difference between Volume Axial and Helical(p>0.05). High-pitch(-76.70±3.70), Helical(-79.40±4.68), Volume Axial(-81.19±3.59). The SNR of 100kVp lung was significantly different between Volume Axial and High-pitch, Volume Axial and Helical(p<0.05), Helical(-74.72±6.19), Volume Axial(-79.65±3.02), High-pitch(-77.93±2.83). The CNR of 70kVp lung was significantly different between Volume Axial and High-Pitch(p<0.05), but there was no significant difference between Volume Axial and Helical(p>0.05). Helical(58.14±2.65), Volume Axial(56.84±3.36), High-pitch(54.92±1.79). The CNR of 80kVp lung was significantly different between Volume Axial and High-Pitch(p<0.05), but there was no significant difference between Volume Axial and Helical(p>0.05). Volume Axial(47.72±2.02), Helical(46.91±2.56), High-pitch(45.16±2.13). The CNR of 100kVp heart was significantly different between Volume Axial and Helical(p<0.05), but there was no significant difference between Volume Axial and High-pitch(p>0.05). Volume Axial(37.95±1.47), Helical(35.83±2.96), High-pitch(37.31±1.40). In the dose assessment, DLP of 70kVp in each mode was significantly different from Volume Axial and Helical, Volume Axial and High-Pitch(p<0.05). Volume Axial(8.20±0.07), Helical(10.41±0.14), High-pitch(11.16±0.13). The 80kVp DLP showed a significant difference between Volume
Axial and Helical, Volume Axial and High-Pitch(p<0.05) Volume Axial(9.81±0.18), Helical(12.51±0.18), High-pitch 13.13±0.18). The 100kVp DLP showed a significant difference in volume axis and helical, volume axis and high-pitch(p <0.05). Volume Axial(10.42±0.03), Helical(13.37±0.25), High-pitch(13.79±0.11).
Conclusions: In this study, the volume axial mode showed the best inspection result with the least radiation dose and without compromising image quality in a short period of time. The detector coverage of 16 cm has some limits to applying to all pediatric chest CT examinations. However, it is strongly recommended to use for pediatric patients as far as possible. It is necessary to study continuously on the application of volume axial mode to other examination parts.
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KEYWORD
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volume axial, SNR, CNR
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