Stone protocol CT: Why, How and Pitfalls
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Brief discussion on what contributes "stone protocol" CT, radiation dose optimization and interpretive pitfalls.
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Stone protocol CT: Why, How and Pitfalls
- 1. Hello…. CT Stone Protocol Why, How and Pitfalls Rathachai Kaewlai, MD Division of Emergency Radiology, Department of Radiology Ramathibodi Hospital, Bangkok, Thailand For RCRT-RST Annual Scientific Meeting, 24 Mar 2016
- 2. Why – How – Pitfalls
- 3. Why NCCT for KUB Stone?
- 4. Virtually All KUB Stones Are Radiopaque on CT Composition Frequency (%) Radiopacity Radiograph Shade of White on CT Calcium phosphate 10 4 Calcium phosphate/ oxalate 40 3-4 Calcium oxalate 30 3 Struvite 10 2-3 Cystine 1 1 Uric acid 10 0 Genitourinary Imaging: the Requisite
- 5. Stone Types Based On CT Characteristics
- 6. Detection of Stones X-ray IVU Ultrasound NCCT Sensitivity (%) 44-77 52-87 19-93 94-100 Specificity (%) 80-87 94-100 84-100 92-100
- 7. ACR Appropriateness Criteria (2015)
- 8. ACR Appropriateness Criteria (2015)
- 9. ACR Appropriateness Criteria (2015)
- 11. Factor Definition Level Points Sex Female Male 0 2 Timing Duration of pain from onset to presentation, h >24 6-24 <6 0 1 3 Origin Race Black Nonblack 0 3 Nausea Presence of nausea and vomiting None Nausea only Vomiting 0 1 2 Erythrocyte Hematuria on urine dip Absent Present 0 3 Total 0-13 STONE score for uncomplicated ureteral stone in ED Moore CL, et al. BMJ 2014;348:g2191
- 12. Points Probability of symptomatic stone on CT % Recent validation (n=264) 0 to 5 Low 10% 10% 6 to 9 Moderate 10-90% (~50%) 60% 10 to 13 High >90% 89% STONE score for uncomplicated ureteral stone in ED Moore CL, et al. BMJ 2014;348:g2191 Moore CL, et al. Radiology 2016 March
- 13. STONE score Sensitivity Specificity Low probability (n=144) without ultrasound with ultrasound 3 64 67 87 Moderate probability (n=411) without ultrasound with ultrasound 41 60 42 71 High probability (n=280) without ultrasound with ultrasound 55 69 91 60 Daniels B, et al. Ann Emerg Med 2016 March STONE PLUS for uncomplicated ureteral stone in ED
- 14. Daniels B, et al. Ann Emerg Med 2016 March
- 15. Ramathibodi Protocol (WIP) < 80 kg >/= 80 kg kVp 100 120 mA 70-250 70-350 Rotation time (s) 0.6 0.6 SureExposure 3D 20 20 PF/HP 0.828/53 0.828/53 Slice thickness/interval (mm) 2.0/1.5 2.0/1.5
- 16. Stone CT Radiation Dose
- 17. Stone CT Radiation Dose: How Low Can We Go?
- 18. Moore CL, et al. Ann Emerg Med 2015;65:189 N=201 Prospective, head-to-head comparison standard v reduced-dose CT Two groups: BMI <30 v. BMI >30
- 20. Initial CT F/U CT (known stone) Can accept more noise to reduce dose 8.3 mSv 3.7 mSv
- 21. How About Giving IV Contrast?
- 22. Forniceal rupture with urinoma due to obstructing Lt UVJ stone UVJ stone Delayed nephrogram Perinephric fluid Urine extravasation confirmed at delayed scan although this phase is not necessary
- 23. McLaughlin PD, et al. Insights Imaging 2014;5:217 5.1 mSv (ASiR) 5.1 mSv (FBP) 0.56 mSv (FBP) 0.56 mSv (40% ASiR) 0.56 mSv (70% ASiR) 0.56 mSv (90% ASiR) CT Doses Even Lower than Abdominal Radiograph N=33 Comparing routine and sub-mSv CT (with iterative recon) Calculi >3 mm: Sensitivity 87%, specificity 100% 1 missed appendicitis 1 missed dermoid Advanced scanner can reduce dose further with iterative reconstruction
- 24. High-density calcium stone in renal pelvis with obstruction Advanced scanner can predict which stone is uric acid (medical) or non-uric acid
- 25. How We Interpret CT Stone Protocol
- 26. Soft tissue rim sign = ureteral stone
- 27. Stone Size and Appearance
- 29. Risks for Stone Formation Identifiable on Imaging
- 31. Distal ureteric stone with obstruction Typical Cases Hydronephrosis & minimal perinephric fat stranding stone
- 32. Unilateral Perinephric Fat Stranding w/o Stone - DDx
- 33. Mimickers on CT of:
- 34. Moore CL, et al. Acad Emerg Med 2013;20:470 N=5383 Descriptive study No comparison Two EDs Alternative Diagnosis
- 35. Incidental Findings Samim MM, et al. JACR 2015;12:63
- 36. Samim MM, et al. JACR 2015;12:63 N=5383 Descriptive study, no comparison Two emergency departments