CT Dose Simulation Study for Appendicitis

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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Optimizing the Radiation Dose for CT Imaging With Iterative Reconstruction in Diagnosing Acute Appendicitis: Dose Simulation Study

Conditions
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Appendicitis

Intervention / Treatment
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* Radiation: CT


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 18-44 years of age. Emergency department visit with suspected symptoms and signs of acute appendicitis Intravenous contrast-enhanced computed tomography examination requested due to suspicion of appendicitis Exclusion Criteria: having contraindications of intravenous contrast agent

Ages Eligible for Study
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Minimum Age: 15 Years
Maximum Age: 44 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Suspected appendicitis<br>Patients who are suspected as having acute appendicitis | Radiation: CT<br>* 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.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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 | 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 | 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 | 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 | 14 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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. | 2 months | 
| Specificity 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. | 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. | 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. | 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. | 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. | 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. | 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. | 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 | 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 | 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 | 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 | 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 | 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 | 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 | 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 | 14 months | 
| Diagnostic confidence in diagnosing and ruling out appendicitis at original CT: indeterminate CT interpretation | The frequency of indeterminate CT interpretation (grade 3) | 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) | 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) | 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) | 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 | 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 | 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 | 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 | 14 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Appendicitis, Tomography, X-Ray Computed, Receiver operating characteristic (ROC) Curve, Computer Simulation