Evaluation of Dose Reduction and Accuracy of Images According to Scan Mode Change in Pediatric Chest CT

목적: 소아 흉부 CT검사시 방사선 피폭을 최소화 하면서 진단적으로 가치가 높은 영상을 얻기 위해서 Helical mode, High-pitch mode, Volume Axial mode를 적용하여서 선량, 검사시간, 화질을 비교하여 유용성을 평가하고자 한다. 대상 및 방법: Revolution(GE Healthcare, Wisconsin USA)을 이용하여 PBU-70팬텀을 Helical mode, High-pitch mode, Volume Axial mode로 각각의 그룹으로 나누어서 70kVp, 80kVp, 100kVp의 조건으로 30회 검사를 실시하였다. 영상을 획득 한 후에 각각의 영상에 심장(Heart), 뼈(Bone), 폐(Lung), Back-ground air에 ROI를 설정하고 CT number(HU)와 noise(SD)값을 측정하여 평균값을 구하고 SNR과 CNR을 측정 하였고, 장비에서 직접 제공하는 DLP값 비교하였다. 통계적인 유의성을 확인해보기 통계 분석은 PASW을 사용하여 독립 t-검정을 시행하였다. 결과: 영상평가에서는 70 kVp heart의 SNR은 Volume Axial과 Helical에서 유의미한 차이가 있었고 (p<0.05) Volume Axial과 High-pitch는 유의미한 차이가 없었다(p>0.05). Volume Axial(-4.39±0.27), Helical(-4.73±0.22), High-pitch(-4.48±0.15). 80kVp heart의 SNR은 Volume Axial과 Helical에서 유의미한 차이가 있었고(p<0.05) Volume Axial과 High-pitch는 유의미한 차이가 없었다(p>0.05). Volume Axial(-3.27±0.18), Helical(-3.44±0.16), High-pitch(-3.31±0.16). 100kVp heart의 SNR은 Volume Axial과 High-pitch에서 유의미한 차이가 있었고, (p<0.05) Volume Axial과 Helical은 유의미한 차이가 없었다(p>0.05). Volume Axial(-1.81±0.08), Helical(-1.82±0.18) High-pitch(-1.97±0.10). 70kVp lung의 SNR은 Volume Axial과 High-pitch에서 유의미한 차이가 있었고,(p<0.05) Volume Axial과 Helical은 유의미한 차이가 없었다(p>0.05). High-pitch(-75.59±2.44), Helical-70kVp(-80.00±3.71), Volume Axial (-79.01±4.72). 80kVp lung의 SNR은 Volume Axial과 High-pitch에서 유의미한 차이가 있었고(p<0.05) Volume Axial과 Helical은 유의미한 차이가 없었다(p>0.05). High-pitch(-76.70±3.70), Helical(-79.40±4.68) Volume Axial(-81.19±3.59). 100kVp lung의 SNR은 Volume Axial과 High-pitch, Volume Axial과 Helical에서 유의미한 차이가 있었다(p<0.05). Helical(-74.72±6.19), Volume Axial (-79.65±3.02), High-pitch(-77.93±2.83). 70 kVp의 CNR은 Volume Axial과 High-pitch에서 유의미한 차이가 있었고,(p<0.05) Volume Axial과 Helical은 유의미한 차이가 없었다(p>0.05). Helical(58.14±2.65), Volume Axial(56.84±3.36), High-pitch(54.92±1.79). 80 kVp의 CNR은 Volume Axial과 High-pitch에서 유의미한 차이가 있었고(p<0.05) Volume Axial과 Helical은 유의미한 차이가 없었다(p>0.05). Volume Axial(47.72±2.02), Helical(46.91±2.56), High-pitch(45.16±2.13). 100 kVp의 CNR은 Volume Axial과 Helical에서 유의미한 차이가 있었고(p<0.05) Volume Axial과 High-pitch는 유의미한 차이가 없었다(p>0.05). Volume Axial (37.95±1.47), Helical(35.83±2.96), High-pitch(37.31±1.40). 선량 평가에서는 각 mode의 70 kVp의 DLP는 Volume Axial과 Helical, Volume Axial과 High-pitch에서 유의미한 차이가 있었다(p<0.05). Volume Axial(8.20±0.07), Helical(10.41±0.14), High-pitch(11.16±0.13). 80 kVp의 DLP는 Volume Axial과 Helical, Volume Axial과 High-pitch에서 유의미한 차이가 있었다(p<0.05). Volume Axial(9.81±0.18), Helical(12.51±0.18), High-pitch(13.13±0.18).100 kVp의 DLP는 Volume Axial과 Helical, Volume Axial과 High-pitch에서 유의미한 차이가 있었다(p<0.05). Volume Axial(10.42±0.03), Helical(13.37±,0.25), High-pitch(13.79±0.11). 결론: 본 실험을 통해 검사 시 volume axial mode 사용 시 가장 적은 선량으로 영상의 화질 저하 없이 빠른 시간에 검사가 가능하다. 16 cm의 detector coverage 가 모든 소아 흉부 CT검사에 적용하기에 제한점이 있으나 가능한 소아환자에 있어 적극적인 활용을 추천하며 volume axial mode의 다른 검사부위 적용에 대한 지속적인 연구가 필요하리라 사료된다.

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 ped