Coronary CT Angiography: Protocols Contrast Media Optimization
James A. Brink, M.D.
Yale University
School of Medicine
Cardiac CT Angiography
• Intravenous Contrast Material• Flow Rate• Concentration• Type• Duration (Volume)• Scan Delay
Iodine Concentration in Blood/Tissue
Concentration (I mg/cc)
0
100
200
300
400
500
600
700
800
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
120 Kvp
137 Kvp
Tissue Concentration (I mg/ml)
25 HU per mg I / ml
Peak Enhancement vs. Flow Rate
ComputerSimulation
0
50
100
150
200
250
300
350
0 5 10 15 20 25 30 35
Time after the start of injection (sec)
Recirculation
Increase in bloodflow caused bythe injection
Courtesy of Ty Bae
InjectionDuration
Injection Duration
0
50
100
150
200
250
300
350
Aor
ta E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35
Time after the start of injection (sec)
Porcine Model
0
50
100
150
200
250
300
350
Aor
tic E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35 40
Time after the start of injection (sec)
30-sec injection20-sec injection12-sec injection8-sec injection5-sec injection3-sec injection1-sec injection
Computer Simulation
Bae KT. Radiology 2003;227:809-816
Duration(Volume)Duration(Volume)
IV Contrast for CTA
Injection Duration = Scan Duration
0
50
100
150
200
250
300
350
Aor
tic E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35 40
Time after the start of injection (sec)
30-sec20-sec12-sec8-sec5-sec3-sec1-sec
30 sec4DCT
8 sec16DCT
InjectionDuration
30 sec4DCT8 sec
16DCT
0
50
100
150
200
250
300
350
Aor
tic E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35 40
Time after the start of injection (sec)
30-sec20-sec12-sec8-sec5-sec3-sec1-sec
8 sec16DCT
8 sec16DCT
InjectionDuration
8 sec16DCT
IV Contrast for CTA
Injection Duration = Scan DurationSDCT and 4DCT:
Injection Duration = Scan Duration + 1016DCT and 64DCT:
Saline Flush
• Facilitated with double-barrel injector
• Eliminates messy loading of saline on top of contrast in single-barrel systems
Saline Flush
• Eliminates excess contrast in tubing
• Flushes contrast from peripheral veins into central veins
• Permits reduction in contrast volume by about 20 to 40%
• Reduces beam hardening artifact in RCA
64DCT – Uni Flow• 2 Injection Phases:
• Contrast
• Saline
• Less contrast material, but no visualization of right heart w/ dilute contrast
• Better definition / segmentation of left heart and coronary arteries
64DCT – Uni Flow
64DCT – Uni Flow (Yale)
• 2 Injection Phases: (Iodixanol 320, 5ml/s)
• Contrast 70 ml (14s)
• Saline 30 ml (6s)
• Scan duration = 3-5 sec • Injection duration = 14 sec • Injection duration = Scan duration + 10 sec
0
50
100
150
200
250
300
350
Aor
tic E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35 40
Time after the start of injection (sec)
30-sec20-sec12-sec8-sec5-sec3-sec1-sec
InjectionDuration
14-sec
3-5 sec64DCT
3-5 sec64DCT
64DCT -- Dual Flow
• 3 Injection Phases:
• Contrast
• Contrast + Saline
• Saline
• Permits visualization of right heart and interventricular septum w/ dilute contrast
64DCTDual Flow
64DCT -- Dual Flow
RCA LAD LCX
64DCT -- Dual Flow (Yale)
• 3 Injection Phases: (Iodixanol 320, 5ml/s)
• Contrast 60 ml (12s)
• Contrast(60%) + Saline(40%) 50 ml (10s)
• Saline 40 ml (8s)
• Scan duration = 3-5 sec • ‘Effective’ Injection duration = 18-22 sec
‘Effective’ ID = SD + 15 sec
0
50
100
150
200
250
300
350
Aor
tic E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35 40
Time after the start of injection (sec)
30-sec20-sec12-sec8-sec5-sec3-sec1-sec
‘Effective’InjectionDuration
3-5 sec64DCT
3-5 sec64DCT
64DCT – Dual Flow
• Right heart visualization
• Right heart mass
• Valve disease
• Prolonged injection duration:• Triple Rule-Out• Complete thorax (CABG)
64DCT – Dual Flow – Triple R/O
Prospective Gating
(100 kV; 5-7 mSv)
Scan DelayScan Delay
Scan Delay for Cardiac CTA
• Scan Delay
• May be fixed for patients presumed to have normal cardiac output - risky
• Pitfall
• Abnormal cardiac output --> marked delay in vascular enhancement
• test bolus or bolus tracking
Cardiac Output --> Aortic Enhancement
Time (min)
0
50
100
150
200
250
300
350
400
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
c.o. = 25%
c.o. = 50%
c.o. = 100%
c.o. = 200%
Computer Simulation, 5ml/sec. Bae, Heiken, Brink. Radiology Radiology 1998; 207:657-662
Test Bolus
• Measure circulation time• 20 ml @ 5 ml/sec (4 sec inj.)• Scan at carina (Asc. Aorta & PAs):
• 10 - 30 sec q 1-2 sec
• Plot enhancement curve and find peak• If no peak, change arm position, repeat
Test Bolus
0
20
40
60
80
14 16 18 20 22 24 26 28 30 32 34
Time (sec)
4 sec
4DCT 64DCT
0
50
100
150
200
250
300
350
Aor
tic E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35 40
Time after the start of injection (sec)
30-sec20-sec12-sec8-sec5-sec3-sec1-sec
‘Effective’InjectionDuration
3-5 sec64DCT
3-5 sec64DCT
Peak + 4-8 sec
Timing for Dual Flow 64DCT CCTA
Bolus Tracking
• ROI in aorta (usually descending aorta)
• Low-dose monitoring scans q 1-2 sec
• Trigger when enhancement > 100 HU• Absolute value of 150 HU
• Add delay to initiate scanner, breath-hold patient, and allow adequate enhancement
0
50
100
150
200
250
300
350
Aor
tic E
nhan
cem
ent (
HU
)
0 5 10 15 20 25 30 35 40
Time after the start of injection (sec)
30-sec20-sec12-sec8-sec5-sec3-sec1-sec
‘Effective’InjectionDuration
3-5 sec64DCT
3-5 sec64DCT
ContrastArrival
‘Eff’ Inj Duration+ -Scan
Duration
3-5 sec64DCT
Timing for Dual Flow 64DCT CCTA
Triple Rule-Out: Test Bolus
Scan delay is mid-point between time to peak in PA and Aorta
10 sec64DCT
10 sec64DCT16 36
Pulmonary Artery
25 45
Aorta
Triple Rule-Out: Dual Flow 64DCT ‘Effective’InjectionDuration: 20 sec
Cardiac CTA: Protocol Development
• Technique
• Flow Rate
• Concentration
• Volume
• Scan Delay
• 64DCT Uni Flow
• 5 ml/sec
• 320-370 mgI/ml
• 70(100%), 30(NS)
• Test Bolus + 4-8 sec*
• 64DCT Uni Flow
• 5 ml/sec
• 320-370 mgI/ml
• 70(100%), 30(NS)
• Test Bolus + 4-8 sec*
* Bolus Tracking: Contrast Arrival + Injection Duration - Scan Duration
Cardiac CTA: Protocol Development
• Technique
• Flow Rate
• Concentration
• Volume
• Scan Delay
• 64DCT Dual Flow
• 5 ml/sec
• 320-370 mgI/ml
• 60(100), 50(60/40), 40(NS)
• Test Bolus + 4-8 sec*
• 64DCT Dual Flow
• 5 ml/sec
• 320-370 mgI/ml
• 60(100), 50(60/40), 40(NS)
• Test Bolus + 4-8 sec*
* Bolus Tracking: Contrast Arrival + Injection Duration - Scan Duration