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

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

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

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

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

DSCT advantage  High temporal resolution 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

7

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

9

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

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

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

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

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

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

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 no BB if dose increased (retropective scan). >105, BB 16

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

Noisy 18

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

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

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

22

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

24

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

ECG controlled dose modulation - retrospective 26

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

28

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

Multiphase reconstructions 30

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

32

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

34

35

36

37

Adaptive Cardio Sequence  -ECG-Triggered Sequential CT 38

ADAPTIVE 39

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

FLASH 41

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

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

Kv modification as per weight 44

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

FLASH 46

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

FLASH 48

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

Graft 50

Stenosis 51

HR 85 Prospective 52

HR 83 Retrospective 53

Stent 54

Pediatric 55

56

Adaptive with arrythmia 57

FLASH 58

FLASH 59

FLASH 60

TEAM CTA 61