Title Page

Contents

Abstract 9

Ⅰ. Introduction 11

Ⅱ. Materials and methods 13

1. Sample size estimation and patient enrollment 13

2. CT protocol 15

3. Radiation dose evaluation 18

4. Image analysis 18

A. Objective assessment of image quality 18

B. Subjective image quality analysis 19

5. Statistics 21

Ⅲ. Results 22

1. Patient demographics and radiation dose 22

2. Objective image analysis 24

3. Subjective image analysis 28

Ⅳ. Discussion 35

Ⅴ. References 40

Abstract 45

Appendices 47

〈A1〉 STROBE statement-checklist of items that should be included in reports of case-control studies. 47

〈A2〉 The contrast agent administration adjustment table of t he 90-kVp pancreas dynamic CT protocol. 52

〈A3〉 Summary of a 5-point score of subjective image quality analysis. 53

Table 1. Comparison of CT scan protocol, radiation dose and contrast agent volume reduction. 17

Table 2. Paired t-test results of objective image quality. 26

Table 3. Intra-rater and inter-rater agreement of subjective image quality score. 33

Table 4. Paired comparison of subjective image quality by the Wilcoxon signed-rank test. 34

Fig 1. Patient selection flowchart. From July 2020 to June 2021, 271 patients were eligible for the study, and according to the inclusion and exclusion criteria, final 51 subjects were selected as the study population. 14

Fig 2. Violin plot comparison of size-specific dose estimation. The blue graph represents the reduction protocol group, while the red graph represents the standard protocol group in the violin plot chart.... 23

Fig 3. The box plot comparison of the contrast-to-noise ratio of each abdominal organs (AortaArterial phase and AortaPortal phase are value measured on arterial and portal phase, respectively). 25

Fig 4. The box plot comparison of each organ's figure of merit between the reduction and standard protocol groups. The figures of merit of the reduction protocol group were significantly higher than... 27

Fig 5A. A 53-year-old woman with a branch duct type intraductal papillary mucinous tumor in the pancreas tail. A & B, Arterial and pancreatic parenchymal phase of computed tomography images of... 29

Fig 5B. A 53-year-old woman with a branch duct type intraductal papillary mucinous tumor in the pancreas tail. A & B, Arterial and pancreatic parenchymal phase of computed tomography images of... 30

Fig 5C. A 53-year-old woman with a branch duct type intraductal papillary mucinous tumor in the pancreas tail. A & B, Arterial and pancreatic parenchymal phase of computed tomography images of... 31

Fig 5D. A 53-year-old woman with a branch duct type intraductal papillary mucinous tumor in the pancreas tail. A & B, Arterial and pancreatic parenchymal phase of computed tomography images of... 32