1. DUAL SOURCE CARDIAC CT ANGIOGRAPHY Dr Ravi Mathai, MD. Consultant Radiologist, Dar Al Shifa Hospital 1

2. Role of CTA  risk stratification ; high CAC score + intermediate FRS = reclassified as high risk  acute chest pain - presence of stenoses + determine the necessity of further treatment.  ruling out stenosis in patients with intermediate pretest likelihood of disease  Detect stenotic lesions in symptomatic patients  Follow-Up of Percutaneous Coronary Intervention -in-stent restenosis  Follow-Up After Bypass Surgery - patency of the bypass graft - in course, anastomotic site and native vessels 2

3. Role of CTA  exact analysis of anomalous coronary arteries.  assess morphology and function eg valvular motion, wall motion, EF, CO.  CT angiography (CTA) has high negative predictive value. 3

4. Caveats  Use of CT angiography in asymptomatic persons as a screening test for atherosclerosis (noncalcific plaque) is not yet recommended  Not recommended for acute coronary syndrome 4

5. Limitations of CTA  overestimate disease severity  limited spatial resolution = +-accurate grading of the severity of stenosis  Pronounced coronary calcifications  motion artefacts  trigger artefacts - cardiac cycle phase  high image noise can prevent reliable evaluation  radiation dose 5

6. DSCT advantage  High temporal resolution - 0.28 seconds rotation time = temporal resolution of upto 0.75 seconds - at a pitch of 3.2 (FLASH)  Mayo Clinic study 2009 showed no differences in quantitative measures of image quality between single-source scans at pitch = 1 and dual-source scans at pitch = 3.2  Regular and low heart rates prerequisite for CCTA by 64 slice MDCT 6

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8. Flash advantage  high pitch (3.2)  dual tube quarter rotation data acquisition  0.28s scan time  very low dose  limitations - obese, high HR >75 8

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10. Goals of CTA  primary goal diagnostic IQ  second goal - low dose  protocol aims at the above 10

11. Components of a cardiac scan:  Patient selection  Breathold  HR  Medications  Ecg and gating  Contrast timing and dose  Scan mode selection - prospective, retrospective, pulse off, flash.  kV techniques  ROI  Reconstruction kernels  Low dose techniques  Image processing 11

12. Patient selection  CTA rule out in acute chest pain  Ruling out stenosis in patients with intermediate pretest likelihood of disease  For the assessment of obstructive disease in symptomatic patients  For detecting re-stenosis after stent placement  Follow-Up After Bypass Surgery -bypass graft - native vessels-  Exact analysis of anomalous coronary arteries. 12

13. Contraindications to CTA  Contrast hypersensitivity (absolute)  Renal failure (absolute)  Poor breathhold  AF 13

14. Breathold  Breathe in -- breathe out – breathe in – hold your breath (13 seconds)  Patient training 14

15. Heart rate  for S64 - <60  for DSCT <95  look for ectopics, arrythmias 15

16. Medications  for S64 -Oral ß-Blockers 1 h before scan if heart rate > 60/min e.g., 100 mg Atenolol  i.v. metoprolol (up to 6 x 5 mg) if heart rate in CT scanner is still > 60/min  for DSCT - no BB required for HR upto 85. 85-105 no BB if dose increased (retropective scan). >105, BB 16

17. ECG  ECG -must be noise free  Gating - prospective and restrospective  Scan protocols 17

18. Noisy 18

19. Standard Scan Protocol - DSCT  Collimation 0.6 mm  Rotation: 330 ms  kV: 120 kV  mAs: 400 mAs  Pitch: Enter expected heart rate manually  ECG Pulsing: 70-70% for heart rates < 65/min  40-70% for heart rates > 65/min  Delay: Contrast time + 2 seconds 19

20. Contrast Injection  5 ml/s for the duration of the scan  At least 50 ml + Follow by 50 ml saline (or 20% contrast) at 5 ml/s 20

21. Contrast injection and Bolus  Type of CM: Concentration min. 350mg/ ml, better 370mg/ ml  Flow rate: average size patients (~70kg / 150lb) 5cc/ sec; larger patients 7cc/ sec  i.v. line: min 18g, better 16g  Test Bolus: 10cc contrast/ 50cc saline (Care bolus ROI AA, threshold 100HU)  ROI : Measure in ascending aorta 21

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23. Coronary CTA injector options  Normal injector:  Volume of contrast = scan time x flow rate + 10cc + 50cc saline; min 45cc, max 100cc  Dual flow option:  Volume of contrast = scan time x flow rate + 10cc contrast  1st phase: total volume of contrast  2nd phase: 50cc of volume (20% contrast + 80%saline) = (10cc contrast + 40cc of saline) 23

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25. Scan modes  Scan mode selection - prospective, retrospective, pulse off, flash. 25

26. ECG controlled dose modulation - retrospective 26

27. ROI  AA for test and care bolus  extend for bypass grafts 27

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29. Reconstruction  Reconstruction Slice thickness: 0.6 mm  Kernel: B26f (B46 f for Stents, Ca++)  Phase: Initially: Best Diast / Best Syst  DSCT: Usually 75% R-R best ; Preset: BD, BS, 70%, 75%, 40%  S64: Usually 70% R-R best; Preset: 65%, 70%, 35%, 40% 29

30. Multiphase reconstructions 30

31. low dose techniques  1.“CARE Dose4D” – Real-time Anatomic Exposure Control  2. “Adaptive ECG-Pulsing” – ECG-Controlled Dose Modulation for Cardiac Spiral CT  3. “Adaptive Cardio Sequence” – ECG-triggered Sequential CT  4. “Adaptive Dose Shield” – Asymmetric Collimator Control  5. “Flash Spiral” – ECG-Triggered Dual Source Spiral CT Using High Pitch Values  6. “X-CARE” – Organ Based Dose Modulation  7. “IRIS” – Iterative Reconstruction in Image Space 31

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33. Adaptive ECG-Pulsing  -ECG-Controlled Dose Modulation for Cardiac Spiral CT 33

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38. Adaptive Cardio Sequence  -ECG-Triggered Sequential CT 38

39. ADAPTIVE 39

40. High pitch -FLASH  With a single source CT, the spiral pitch is limited to values below 1.5 to ensure gapless volume coverage along the z-axis. If the pitch is increased, sampling gaps occur  With DSCT systems, data acquired with the second measurement system a quarter rotation later can be used to fill these gaps.In this way, the pitch can be increased up to 3.4 40

41. FLASH 41

42. FLASH  ECG-triggered DSCT scan data acquisition and image reconstruction at very high pitch.  images reconstructed in this mode with an acquisition time of 250 ms, a temporal resolution of 75 ms, 100 kV and 0.8 mSv. 42

43. Modification of protocols  Beta Blockers - preferable above HR 85.  Saline vs. 20% contrast flush. - full functional assessment  6 (7) ml flow for heavy patients  XXL for heavy patients  100 kV for slim patients 43

44. Kv modification as per weight 44

45. sub mSv CTA  100kv  320mAs  120mm scan range  flash mode 45

46. FLASH 46

47. pediatric protol  Flash mode  80kv  104mAs  120mm scan range  Dose less than 1mSv 47

48. FLASH 48

49. Image processing  2d images MIP best for diagnosis  3d complementary  stenosis grading - software Syngovia - automatic calculation. 49

50. Graft 50

51. Stenosis 51

52. HR 85 Prospective 52

53. HR 83 Retrospective 53

54. Stent 54

55. Pediatric 55

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57. Adaptive with arrythmia 57

58. FLASH 58

59. FLASH 59

60. FLASH 60

61. TEAM CTA 61