Optimizing CT Image Quality: Clinical Practice

November 2011 PART 6: CLINICAL PRACTICE EXPECTATIONS: ADULTS Expectations: Adults Expectations: Children Troubleshooting Dose Savings Adult Head Angiography 100 kV Non-contrast Small CTDIvol 15 mGy [S] DLP 300 mGy-cm Contrast Moderate enhanced Quality Reference mAs 175 CT Angiography Big Effective Dose 0.6 mSv Adult Abdomen (+ Contrast) MUSC CT Dose Bj University MEDICAL UNIVERSITY of Glasgow 120 kV of SOUTH CAROLINA Comparison CTDIvol 12 mGy [L] DLP 250 mGy-cm Quality Reference mAs 190 Effective Dose 4 mSv Part 6 (Clinical Practice) Huda 1 November 2011 Head CT Abdomen/Pelvis 1.9 mSv 15 mSv 1.8 mSv 8.4 mSv 1.8 mSv 9.5 mSv Attenuation Based kV selection CARE kV “On” Anna Winklehner et al. CARE Dose4D M CARE KV On Investigative Radiology Off 46 (2011) 767-773 Eff. mAs 172 kV Semi On On Organ characteristic: Abdomen CTDIvol (32cm): 6,80 mGy DLP: 169.5 mGy"cm kV used selected Thoracoabdominal “by CARE kV” CTA Topogram  Attenuation Info Tube Currents at Constant CNR Identical “Image Quality” mA 140 kV 120 kV topogram diameter profile AM1 08 Part 6 (Clinical Practice) Huda 2 November 2011 Some kV Values “Not Possible” Body Mass Index (BMI) CTDI BMI= weight (kg) height2 (m2) (metric) 120 kVp ..... 8 - - -- ----- TANDU ....... 75 kg & 1.73 m Select kV with BMI = 25 kg/m2 “Lowest Dose” Study Findings 100 kV  58% 80KV 120 kV  36% ...... 140kV 40 Patients Body CTA of the Aorta Body CTA of the Aorta + kV selection 75 kg Reference kV 75 kg 120 kV 100 kV Quality Reference mAs Eff. mAs 143 110 mAs CTDIvol CTDIvol 6.4 mGy 10.6 mGy  40% Part 6 (Clinical Practice) Huda 3 November 2011 EXPECTATIONS: CHILDREN Yu et al., Mayo Clinic, Rochester MN RadioGraphics --- - Children should never be considered small adults! 31 (2011) 835-848 Pediatric Abdominopelvic Dose Savings from kV Modification 5 year old [20 kg] Abdomen/Pelvic 15 100 kV 120 kV CTDIvol[L] Optimized ACR CT Ref Dose 80 kVp CTDIvol (mGy) = 100 kVp 120 kVp CTDIvol[S] 8 mGy CTDIvol[S] 20 mGy 0 0.0 10.0 200 300 40.0 50.0 Patient Weight (kg) CTDIvol[L] 4 mGy  kV Optimized CTDIvol[S] 8 mGy  60% TROUBLESHOOTING Improper Centering (Too High) Ox-ray tube Patient lector Distorted topogram does nfluence the mAs calculation! Higher dose Iso-center AEC Assumes Patient “Large” Part 6 (Clinical Practice) Huda 4 November 2011 Improper Centering Dose optimization slider is (Too Low) in correct position y tube Dose saving optimized for: Patie X Distorted topogram does 2 5 8 10 11 0 - influence the mas calculation! 12 Soft Tissues  3 AEC Assumes Patient “Small” (Non-contrast) CTA  11 Check Reference Techniques Adult Head kV and mAs Reference Doses (mGy) Quality ref. mAs 210 |Ref. V 120 United States 75 (American College of ACR Radiology) Body Part Britain 65 (Health Protection Agency) [AKA NRPB] Adult Abdomen Check CARE Dose4D Curves Reference Doses (mGy) Size/Pediatric United States 25 ACR Child Adult slim Adult obese (American College of Aber De Gerade -verade Radiology) Strength Britain 14 Body region Child (Health Protection Agency) Average Neck Very weak Shoulder Weak Thorax Average Strong Abdomen Very strong Part 6 (Clinical Practice) Huda 5 November 2011 CLINICAL PRACTICE SUMMARY X-ray tube voltage (kV) selection Lower kV Higher kV Task “Lesion” Dose Trouble- Contrast Reductions shooting guide Small Patient Positioning IQ Settings Large Ref. kV & Quality Ref. mAs CARE Dose4D Settings (Protocol) 40 QUESTIONS THE END [email protected] 30 + Correct  CE certificate asrt. NT Radiologic Technologists Part 6 (Clinical Practice) Huda 6