본 연구에서는 폐기종에 대해 고해상도 CT와 비교한 저선량 CT 의 유용성에 대해 평가하였다. 고해상도 CT와 저선량 CT 노출조건에서 선량과 영상 잡음을 3회 반복 측정하였다. 비슷한 노출조건에서 획득한 146명의 고해상도 CT와 저선량 CT 영상에 대해 2명의 흉부영상의학과전문의 합의 판독결과에서 폐기종 소견 만을 본 연구에 사용하였다. SPSS ver. 19.0 프로그램 사용하여 고해상도 CT와 저선량 CT 간에 폐기종에 대한 진단 차이는 McNemar's tests, 일치도는 unweighted kappa tests, 선량과 잡음 차이는 Mann-Whitney U-test 로 분석하였다. 선량은 고해상도 CT가 저선량 CT 보다 높았지만(1.95 mGy vs. 0.35 mGy, p=0.008), 잡음은 낮았다(40.1 HU vs. 99.6 HU, p=0.021). 폐기종 진단에 대해서는 두 영상 간에 높은 일치도를 보였다(k-value=0.88). 폐기종 점수는 두 영상 간에 통계적인 유의한 차이를 보이지 않았고, 높은 상관성을 보였다(r=0.599, p < 0.001). 선량과 잡음을 고려했을 때, 저선량 CT는 폐기종 진단에 표준 진단 방법 인 고해상도 CT를 대신하여 사용할 수 있을 것으로 사료된다.
본 연구에서는 폐기종에 대해 고해상도 CT와 비교한 저선량 CT 의 유용성에 대해 평가하였다. 고해상도 CT와 저선량 CT 노출조건에서 선량과 영상 잡음을 3회 반복 측정하였다. 비슷한 노출조건에서 획득한 146명의 고해상도 CT와 저선량 CT 영상에 대해 2명의 흉부영상의학과전문의 합의 판독결과에서 폐기종 소견 만을 본 연구에 사용하였다. SPSS ver. 19.0 프로그램 사용하여 고해상도 CT와 저선량 CT 간에 폐기종에 대한 진단 차이는 McNemar's tests, 일치도는 unweighted kappa tests, 선량과 잡음 차이는 Mann-Whitney U-test 로 분석하였다. 선량은 고해상도 CT가 저선량 CT 보다 높았지만(1.95 mGy vs. 0.35 mGy, p=0.008), 잡음은 낮았다(40.1 HU vs. 99.6 HU, p=0.021). 폐기종 진단에 대해서는 두 영상 간에 높은 일치도를 보였다(k-value=0.88). 폐기종 점수는 두 영상 간에 통계적인 유의한 차이를 보이지 않았고, 높은 상관성을 보였다(r=0.599, p < 0.001). 선량과 잡음을 고려했을 때, 저선량 CT는 폐기종 진단에 표준 진단 방법 인 고해상도 CT를 대신하여 사용할 수 있을 것으로 사료된다.
The purpose of this study was to evaluate the usefulness of low-dose CT (LDCT) for emphysema compared with high-resolution CT (HRCT). Measurements of radiation dose and noise were repeated 3 times in same exposure condition which was similar with obtaining HRCT and LDCT images. We analysed reading r...
The purpose of this study was to evaluate the usefulness of low-dose CT (LDCT) for emphysema compared with high-resolution CT (HRCT). Measurements of radiation dose and noise were repeated 3 times in same exposure condition which was similar with obtaining HRCT and LDCT images. We analysed reading results of 146 subjects. Six images per participants selected for emphysema grading. Emphysema was graded for all 6 zones on the left and right sides of the lungs by the consensus reading of two chest radiologists using a 4-point scale. Between the HRCT and LDCT images, diagnostic differences and agreements for emphysema were analyzed by McNemar's and unweighted kappa tests, and radiation doses and noise by a Mann-Whitney U-test, using the SPSS 19.0 program. Radiation dose from HRCT was significantly higher than that of LDCT, but the noise was significantly lower in HRCT than in LDCT. Diagnostic agreement for emphysema between HRCT and LDCT images was excellent (k-value=0.88). Emphysema grading scores were not significantly different between HRCT and LDCT images for all six lung zones. Emphysema grading scores from LDCT images were significantly correlated with increased scores on HRCT images (r=0.599, p < 0.001). Considering the tradeoff between radiation dose and image noise, LDCT could be used as the gold standard method instead of HRCT for emphysema detection and grading.
The purpose of this study was to evaluate the usefulness of low-dose CT (LDCT) for emphysema compared with high-resolution CT (HRCT). Measurements of radiation dose and noise were repeated 3 times in same exposure condition which was similar with obtaining HRCT and LDCT images. We analysed reading results of 146 subjects. Six images per participants selected for emphysema grading. Emphysema was graded for all 6 zones on the left and right sides of the lungs by the consensus reading of two chest radiologists using a 4-point scale. Between the HRCT and LDCT images, diagnostic differences and agreements for emphysema were analyzed by McNemar's and unweighted kappa tests, and radiation doses and noise by a Mann-Whitney U-test, using the SPSS 19.0 program. Radiation dose from HRCT was significantly higher than that of LDCT, but the noise was significantly lower in HRCT than in LDCT. Diagnostic agreement for emphysema between HRCT and LDCT images was excellent (k-value=0.88). Emphysema grading scores were not significantly different between HRCT and LDCT images for all six lung zones. Emphysema grading scores from LDCT images were significantly correlated with increased scores on HRCT images (r=0.599, p < 0.001). Considering the tradeoff between radiation dose and image noise, LDCT could be used as the gold standard method instead of HRCT for emphysema detection and grading.
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문제 정의
To the best of our knowledge, there have been rarely studies investigating radiation dose and noise in the use of LDCT for emphysema detection. Therefore, The purpose of this study was to evaluate the usefulness of LDCT for emphysema compared with HRCT.
제안 방법
Emphysema was documented as a presence or absence and graded for all 6 zones on the left and right sides of the lungs by the consensus reading of 2 chest radiologists using a 4-point scale: normal (score 0), absence; mild (score 1), up to 15% of the area from one zone; moderate (score 2), between 15 and 30%; and severe (score 3) ≥ 30% of the area from one zone.
Emphysema was re-graded into 4 categories (normal, total score = 0; mild, total score = 1-6; moderate, total score = 7–12; severe, total score = 13–18) from a total score (ranging from 0 to 18) summed the grades of the six zones of the lungs using a 4-point scale.
The diagnostic differences and agreements for emphysema between the HRCT and LDCT images were analyzed using McNemar’s and unweighted kappa tests.
Two images from each zone of the lungs (upper, the arch of the aorta and above; middle, from the arch of the aorta to the inferior pulmonary vein; and lower, the inferior pulmonary vein and below, including the diaphragm) were acquired. The readers were blinded to the technical parameters used in the CT images acquisition (e.g., kVp, mAs, slice thickness, and resolution). Emphysema was documented as a presence or absence and graded for all 6 zones on the left and right sides of the lungs by the consensus reading of 2 chest radiologists using a 4-point scale: normal (score 0), absence; mild (score 1), up to 15% of the area from one zone; moderate (score 2), between 15 and 30%; and severe (score 3) ≥ 30% of the area from one zone.
대상 데이터
We analyzed retrospectively reading results for emphysema of 146 participants and parameters on HRCT (1.2 mm, 120 kVp, 180 mAs) and LDCT (2.0 mm, 120 kVp, 30 mAs) images without any informations of participants.
데이터처리
The linear relationships for emphysema grading scores between HRCT and LDCT images were calculated using Pearson’s correlation coefficient.
The p-value was calculated using a Mann–Whitney U-test.
Data are expressed as the mean and standard deviation. The p-value was calculated using a paired t-test.
The radiation doses and image noise between the HRCT and LDCT images were compared using a Mann– Whitney U-test.
The radiation doses and image noise between the HRCT and LDCT images were compared using a Mann– Whitney U-test. The total emphysema grading scores between the HRCT and LDCT images were compared using a paired t-test. A value of p < 0.
성능/효과
Emphysema grading scores from LDCT images were significantly correlated with increased scores on HRCT images; the correlation coefficient was 0.599 (p < 0.001) .
In screening for emphysema, we have to consider reducing the radiation dose by using a lower current-time product. In this study, a reduction from 180 mAs to 30 mAs with a fixed tube voltage of 120 kVp resulted in decreasing the radiation dose of LDCT by up to one-sixth; however, the increase in image noise was 2.5-time larger than that of HRCT.
Emphysema grading scores were not significantly different between HRCT and LDCT images for all six lung zones (Table 4, Figure 1). The total emphysema grading score from LDCT images was higher than that from HRCT images; however, the difference was not statistically significant (p=0.734). The relationships between the emphysema grading scores from HRCT and LDCT images are shown in Figure 2.
To summarize, LDCT is effective in terms of reducing radiation dose, although image noise is greater than in HRCT. There was excellent agreement between the HRCT and LDCT images, and the imaging modalities did not show a difference in ability to diagnose emphysema. Therefore, considering the tradeoff between radiation dose and image noise, LDCT could be used as the gold standard method instead of HRCT for emphysema detection and grading.
Three (7.7%) out of 39 participants with emphysema on HRCT images were detected as negative for emphysema on LDCT images, and 4 (3.7%) out of 107 participants without emphysema on HRCT images were detected as positive on LDCT images.
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