The study will explore CT radiation dose as low as reasonably achievable in diagnosing acute appendicitis, by using of dose simulation technique and iterative reconstruction.
Three sequential non-inferiority tests are planned. First, three readers will review the original 2-mSv images. Second, the readers will review the 75%-dose images. After the readers review the 75%-dose images and before the readers reviewed the 50%-dose images, the non-inferiority of 75% dose to the original dose will be tested. If the non-inferiority is not accepted, the study will be terminated with the conclusion of 2 mSv as the lowest acceptable dose. If the non-inferiority is accepted, the study will be continue to the next step. In the same manner, the readers will review the next lower-dose images (50% and then 25%), and then the noninferiority will be tested against the original dose.
Study Type
OBSERVATIONAL
Enrollment
30
Contrast-enhanced CT images of the abdomen and pelvis will be obtained during the portal venous phase using a 256-channel CT system (Philips Healthcare, Cleveland, OH). The target median dose-length product (DLP) is 130 mGy·cm, which corresponded to an effective dose of 2 mSv with a conversion factor of 0.015 mSv·mGy-1·cm-1. The radiation output was automatically adjusted according to the individual patient's body size.
Seoul National University Bunadang Hospital
Seongnam-si, Gyeonggi-do, South Korea
Diagnostic performance at original dose (2 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
The pooled area under curve (AUC) from three radiologists
Time frame: 2 months
Diagnostic performance at 75% dose (1.5 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
The pooled AUC from three radiologists
Time frame: 1 months
Diagnostic performance at 50% dose (1.0 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
\*The analysis of 50%-dose CT images will be performed only if non-inferiority of 75%-dose CT to the original CT is proven in terms of the pooled AUC. The pooled AUC from three radiologists
Time frame: 8 months
Diagnostic performance at 25% dose (0.5 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
\*The analysis of 25%-dose CT images will be performed only if non-inferiority of 50%-dose CT is proven to the original CT in terms of the pooled AUC. The pooled AUC from three radiologists
Time frame: 14 months
Sensitivity at original dose (2 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 2 months
Specificity at original dose (2 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
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For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 2 months
Sensitivity at 75% dose (1.5 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 1 month
Specificity at 75% dose (1.5 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 1 month
Sensitivity at 50% dose (1.0 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 8 months
Specificity at 50% dose (1.0 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 8 months
Sensitivity at 25% dose (0.5 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 14 months
Specificity at 25% dose (0.5 mSv) using 5-grade Likert score for the likelihood of appendicitis assigned by each radiologist
For calculation of sensitivity and specificity, the 5-grade scores are collapsed into binary responses with a decision threshold of a score ≥ 3 as positive for the diagnosis.
Time frame: 14 months
Diagnostic confidence in diagnosing and ruling out appendicitis at original CT: the likelihood score for appendicitis
Likelihood score for appendicitis in patients confirmed as having appendicitis Likelihood score for appendicitis in patients confirmed as not having appendicitis
Time frame: 2 months
Diagnostic confidence in diagnosing and ruling out appendicitis at 75%-dose CT: the likelihood score for appendicitis
Likelihood score for appendicitis in patients confirmed as having appendicitis Likelihood score for appendicitis in patients confirmed as not having appendicitis
Time frame: 1 month
Diagnostic confidence in diagnosing and ruling out appendicitis at 50%-dose CT: the likelihood score for appendicitis
Likelihood score for appendicitis in patients confirmed as having appendicitis Likelihood score for appendicitis in patients confirmed as not having appendicitis
Time frame: 8 month
Diagnostic confidence in diagnosing and ruling out appendicitis at 25%-dose CT: the likelihood score for appendicitis
Likelihood score for appendicitis in patients confirmed as having appendicitis Likelihood score for appendicitis in patients confirmed as not having appendicitis
Time frame: 14 month
Diagnostic confidence in diagnosing and ruling out appendicitis at original CT: normal appendix visualization rate
The frequency of normal appendix visualization at CT
Time frame: 2 month
Diagnostic confidence in diagnosing and ruling out appendicitis at 75%-dose CT: normal appendix visualization rate
The frequency of normal appendix visualization at CT
Time frame: 1 month
Diagnostic confidence in diagnosing and ruling out appendicitis at 50%-dose CT: normal appendix visualization rate
The frequency of normal appendix visualization at CT
Time frame: 8 months
Diagnostic confidence in diagnosing and ruling out appendicitis at 25%-dose CT: normal appendix visualization rate
The frequency of normal appendix visualization at CT
Time frame: 14 months
Diagnostic confidence in diagnosing and ruling out appendicitis at original CT: indeterminate CT interpretation
The frequency of indeterminate CT interpretation (grade 3)
Time frame: 2 months
Diagnostic confidence in diagnosing and ruling out appendicitis at 75%-dose CT: indeterminate CT interpretation
The frequency of indeterminate CT interpretation (grade 3)
Time frame: 1 month
Diagnostic confidence in diagnosing and ruling out appendicitis at 50%-dose CT: indeterminate CT interpretation
The frequency of indeterminate CT interpretation (grade 3)
Time frame: 8 months
Diagnostic confidence in diagnosing and ruling out appendicitis at 25%-dose CT: indeterminate CT interpretation
The frequency of indeterminate CT interpretation (grade 3)
Time frame: 14 months
Alternative diagnoses at original CT: the radiologists will record possible alternative diagnosis if the patients are presumed to be not having appendicitis
The numbers of important alternative diagnoses established
Time frame: 2 months
Alternative diagnoses at 75%-dose CT: the radiologists will record possible alternative diagnosis if the patients are presumed to be not having appendicitis
The numbers of important alternative diagnoses established
Time frame: 1 month
Alternative diagnoses at 50%-dose CT: the radiologists will record possible alternative diagnosis if the patients are presumed to be not having appendicitis
The numbers of important alternative diagnoses established
Time frame: 8 months
Alternative diagnoses at 25%-dose CT: the radiologists will record possible alternative diagnosis if the patients are presumed to be not having appendicitis
The numbers of important alternative diagnoses established
Time frame: 14 months