Download CT for TAVR with low contrast Dose

CTA for Pre TAVR Evaluation with
Low Contrast Dose
Tariq A Hameed, M.D.
Indiana University School of Medicine
Indianapolis, Indiana
Co-authprs:
Aashish Patel,
M.D.
Jonas Rydberg,
Disclosures:
No relevant financial disclosure
Preprocedure Evaluation for
TAVR
• Aortic Valve Annulus
– ECG gated Imaging
• Aorta and Iliac arteries
Contrast-Induced Nephropathy
• The risk is higher
– in patients with pre existing renal insufficiency
– with higher contrast dose
CTA with Low Contrast Dose
18 – 35 mL
Goal
• Achieve adequate contrast enhancement in
aorta and iliac arteries
Contrast Enhancement in Aorta
X-Ray beam energy (KVp)
80 > 100 > 120 > 140
Need for 40% less iodine
120 kVp
80 kVp
240 HU
240 HU
100 ml
62 ml
80KVp technique (k-edge of Iodine)
Iodine - relative attenuation
relative mass attenuation coefficient
Relative no. of photons and
1,0
K-edge 33.2 keV
0,8
80 kVp x-ray spectra
0,6
120 kVp x-ray spectra
0,4
0,2
0,0
20
40
60
80
100
120
Photon energy (keV)
Courtesy: Ulf Nyman, MD, Trelleborg, Sweden
• High noise
• High noise
High mAs
Contrast Enhancement in Aorta
• Iodinated Contrast
– Volume
– Concentration
Contrast Enhancement in Aorta
Iodinated contrast Injection rate
Kyongtae T. Bae; Radiology 2010, 256, 32-61
Contrast Enhancement in Aorta
Time of Imaging (scan delay) relative to arrival of
contrast
Figure 8a: Simulated contrast enhancement curves of the (a) abdominal aorta and (b) liver based on a hypothetical adult male (30 years old; weight, 70 kg; height,
170 cm) subjected to three volumes (75, 125, and 175 mL) of contrast medium (350 mg of iodine per milliliter) injected at the same rate of 2 mL/sec. A larger
volume requires a longer duration to inject. Both the time to and the magnitude of the peaks of enhancement increase with the contrast medium volume (injection
duration).
Radiology,
http://pubs.rsna.org/doi/abs/10.1148/radiol.10090908
Published in: Kyongtae T. Bae; Radiology 2010, 256, 32-61.
DOI: 10.1148/radiol.10090908
© RSNA, 2010
One PowerPoint slide of each figure may be downloaded and used for educational, non-promotional purposes by an author for slide presentations only. The RSNA citationKyongtae
line must appear
in at least
10-point type
on all256,
figures32-61
in all
T. Bae;
Radiology
2010,
presentations. Pharmaceutical and Medical Education companies must request permission to download and use slides, and authors and/or publishing companies using the slides for new article creations for books or journals must
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Kyongtae T. Bae; Radiology 2010, 256, 32-61
Contrast Enhancement in Aorta
• Patient size
– Decreased enhancement with higher BMI/weight
Bae et al, AJR 2008 190:3, 777-784
Contrast Enhancement in Aorta
• Patient size
– Decreased enhancement with higher BMI/weight
• Cardiac Output
– Higher enhancement with low cardiac output
Cardiac Output
Figure 7a: Simulated contrast enhancement curves of the (a) abdominal aorta and (b) liver based on a hypothetical adult male (30 years old; weight, 70 kg; height,
170 cm) who underwent injection of 125 mL of contrast agent (350 mg of iodine per milliliter) at 4 mL/sec. A set of aortic and hepatic contrast enhancement curves
was generated by reducing the baseline cardiac output (CO) by 20%, 40%, and 60%. With a reduced cardiac output, contrast material bolus arrives slowly and clears
slowly, resulting in delayed contrast material bolus arrival and delayed and elevated peak arterial and hepatic parenchymal enhancement.
Radiology,
http://pubs.rsna.org/doi/abs/10.1148/radiol.10090908
Published in: Kyongtae T. Bae; Radiology 2010, 256, 32-61.
DOI: 10.1148/radiol.10090908
© RSNA, 2010
One PowerPoint slide of each figure may be downloaded and used for educational, non-promotional purposes by an author for slide presentations only. The RSNA citation line must appear in at least 10-point type on all figures in all
presentations. Pharmaceutical and Medical Education companies must request permission to download and use slides, and authors and/or publishing companies using the slides for new article creations for books or journals must
apply for permission. For permission requests, please contact the publisher at [email protected]
Bolus triggering - wasting of CM
Up to 6 seconds of bolus train can be wasted!
TIMING RUN replaces bolus triggering
Determine the exact time it takes for the
contrast media to reach a certain
anatomical location.
Contrast media
Volume:
Injection rate:
Saline Push
Volume:
Injection rate:
1 ml – 2 ml
3.5 ml / sec
30 ml
3.5 ml / sec
CT Imaging Protocol
1. CT scanner with capability for high tube
current and fast imaging
2. Retrospective ECG gated imaging of Thoracic
Aorta. - Run the scan to the groins!
3. Routine helical CTA imaging of abdominal aorta
and iliac arteries
(This scan may not be necessary if first scan is successful)
Case 1 - 35 mL
•
•
•
•
•
•
80 KVp
mAs 1500
Total contrast media volume 35 mL
2 Timing runs
Chest-Abdomen scan (cardiac gated)
Pelvic scan (not cardiac gated)
Timing Run 1
1 ml @ 3.5 mL/sec + saline chase
16 sec
35
Timing Run 2
2 ml @ 3.5 mL/sec + saline chase
16 sec
35
22 sec
Chest-Abdomen
20 mL Contrast Media 370 mg/mL
1. 10 mL @ 3.5 ml/sec
2. 10 mL @ 2.0 ml/sec
- 3 sec bolus train
- 5 sec bolus train
Total bolus train 8 sec
Saline chaser
20 mL @ 2.0 mL/sec
35
Start scan near back end of bolus train
16 sec + 8 sec = 24 sec
Start scan from above arch at 22 sec
35
Ascending Aorta and Iliac arteries
35
Postprocessing for
annulus size + distance to coronary arteries
35
Pelvic imaging
12 ml Contrast Media 370 mg/mL
1. 10 ml @ 3.5 mL/sec
2. 2 ml @ 2.0 mL/sec
Saline chaser
25 ml @ 2.0 mL/sec
35
Case 2 - 31 mL (1+2+15+13)
TIMING RUNS
31
Contrast media
Timing run 1 (Asc aorta):
Timing run 2 (Groin):
Injection rate:
1 mL
2 mL
3.5 mL / sec
Saline chaser
Volume:
Injection rate:
30 mL
3.5 mL / sec
Chest-Abdomen
• KVp 80
• mAs 1500
– 15 mL
5 ml @ 3.5 mL/s
10 ml @ 2.0 mL/s
BOLUS TRAIN 6.4 sec
• Saline
25 ml @ 2 mL/s
31
Adequate enhancement of the aorta
171 HU
31
Chest-Abdomen
•
•
•
KVp 80
mAs 1500
– 15 mL
5 mL @ 3.5 mL/s
10 mL @ 2.0 mL/s
BOLUS TRAIN 8.3 sec
Saline
25 mL @ 2 mL/s
Pelvis CTA
13 mL CM 370 mg/mL
5mL @ 3.5/s
8mL @ 2.0/s
25 mL saline @ 2.0/s
31
Aortic valve measurements
31
Centerline stack images
31
Case 3 - 28 mL (1+2+25)
•
•
•
•
•
80 KVp
mAs 1525
Main scan 25 mL
2 Timing runs (1 + 2 mL)
Chest-Abdomen-pelvis scan (cardiac gated)
Timing Bolus
18 sec
22 sec
25 mL
Scan Length: 42.2 cm
Scan Time: 8 sec
Injection:
10mL @ 3.5 mL/s
15 mL @ 2mL/s
Injection Duration: 10 sec
333 HU
Case 4 - 22 mL
• KVp 80 mAs 1500
• 1mL each for 2 timing runs
• Main scan 20 mL:
– 10 mL injected at 3 mL/s (3.3 s)
– 10 mL @2 mL/s (5.0 s)
• BOLUS TRAIN 8.3 sec
• Saline 20 mL @ 2 mL/s.
22
Case 4 - 22 mL
Arterial
attenuation
> 250 HU
22
Noise reduction with Iterative Reconstructions
15 ml thoracic aorta scan
Ascending aorta = 280 HU
Improved noise reduction with Model Based
Iterative Reconstructions
Regular
IR
Moderate
Heavy
SD = 20
SD = 15
Model Based
IR
SD = 8
Summary
Goal: Achieve adequate arterial enhancement
for the preoperative evaluation.
Scanner
- 80kV technique
- Retrospective cardiac gating
- IR or MBIR
Contrast media technique
- Timing run
- Saline chaser