Transcript Coronary CT Angiography

Coronary CT Angiography
Seyed Ali Hosseini
Introduction
• 64-slice coronary CT angiography is highly
accurate for the exclusion of significant
coronary artery stenosis (>50% luminal
narrowing)
• with negative predictive values of 97%–100%,
in comparison with invasive selective coronary
angiography.
INTRODUCTION
• patient preparation
• image acquisition
• evaluation techniques
Patient Preparation, Contraindications, Contrast Dosing
PATIENT PREPARATION
Patient Preparation
• Image quality improved at low heart rates (<65 beats
per minute).
• Following steps can affect the heart rate:
1. The inspirational breath hold (-6beats/min)
2. oral ß-blocker (50—100mg oral or 5–20 mg I.V. Metoprolol)
3. Short-acting nitroglycerin (selective coronary angiography )
• The Lab GFR,BUN & Creatinin reports should be brought
• The Diabetic Patients should stop Metformin
administration 48hours prior and post the examination
(if GFR and Creatinin is normal)
Patient Preparation
• If GFR<30, the examination should be stopped.
• Lidocaine / Xylocaine can be used for the correction of AF
arrhythmia (PVC)
• For rapid AF rhythm, Digocsine can be useful (under the
supervision of a cardiologist)
• The patient should be NPO for at least 6-8 hours.
• Supine position
• Sedation for children
Patient Preparation
For the administration
of CM, two Types of
Angiocaths are used:
1) Green
2) Pink
Patient Preparation
• For CABG patients, in order to evaluate the LIMA origin,
the IV line should be taken from the right hand.
• How much the IV line diameters be narrower, the
probability of extravasation increases.
• The Examination procedure and the effects of breath
holding should be explained to the patients.
• The breath holding should be exercised with the
patients for at least 2 times.
Patient Preparation
• The patient lays supine on the table and the IV line
adheres to the injector correctly.
• Just before the examination starts, the NG spray/perl
should be administrated sublingually.
Contraindications
Contrast Dosing
• Contrast volume is determined empirically based on patient
weight
• Nonionic isosmolar contrast medium is often used: 350-370
mg IC.
• Dose: 1.5-2 mL/kg
• Injection Rate: minimum 5-7 ml/s.
• The injection must be done by dual supply injectors. For
wash out of the right heart, the post-CM normal saline
injection is recommended, in order to reduce the right
heart artifacts on RCA.
Instrumentation, Imaging protocol
IMAGE ACQUISITION
Instrumentation
Instrumentation
Instrumentation
• 64 up to 384 MDCT Instrumentation can be
used.
• The imaging time is reduced in higher detector
array lengths.
• The minimal equipment requirement for stateof-the-heart coronary CTA is a 64-slice scanner.
Instrumentation
10 mm detector
Pitch ~0.25
20 mm detector
Pitch ~0.25
40 mm detector
Pitch ~0.25
3 cm in 5 sec
6.2 cm in 5 sec
12.5 cm in 5 sec
Imaging Protocol
1. Topogram
2. Calcium Scoring (Prospective)
3. Timing for the scan starting
1. Test Bolus
2. Bolus Tracking
4. CTA (Sequential/Spiral/FLASH)
5. MIP, VRT, MPR Reconstruction
1. Topogram
2. Calcium Scoring (Prospective)
• The calcium scale (mg/cm^3) is a linear scale
with 4 calcium score categories:
0
1–99
100–400
>400
none
mild
moderate
severe
• Calcium score correlates directly with risk of
events and likelihood of obstructive CAD
2. Calcium Scoring (Prospective)
3. Test Bolus
• Primary injection :12-20 ml dye, 5-7 ml/s.
• Loading the data into the DynEv. Software.
• Drawing a ROI at the ascending Aorta level.
• Addiction of Time-To-Peak (TTP) with 13 ms.
3. Bolus Tracking
• Adjusting the Pre-monitoring at the level of
Ascending Aorta.
• Selecting the HU threshold to the 160 HU with
the scanning interval of 1 ms, for the duration of
50 scans.
3. Bolus Tracking
4. CTA
Retrospective, Prospective
EKG GATING
Basis
Basis
R-R Interval
0%
R-R Interval
100%
1000ms
The percentage of reconstructions is based on the EKG signal temporal
situation
ECG Gating
•
•
•
-Prospective ECG triggering
-Retrospective ECG gating
-Prospective ECG triggered spiral mode or f lash spiral cardiac mode
•
To obtain cardiac images with minimal motion Artifacts , data
acquisition and image reconstruction ically performed during the
diastolic phase Of the cardiac cycle
Flash mode
estimation
phase
60
60
60
Scan
acceleration time
table speed
delay
ti
time
trigger of table
acceleration by CPI
Retrospective ECG triggering:
• X-ray data are acquired
throughout the entire
Cardiac cycle.
• Only data acquired
during the cardiac
phase with the least
motion are used for
image reconstruction.
Sequential ECG triggering:
• X-ray data are acquired only throughout multiple
Diastolic Cardiac cycles.
• In this type of gating, the patient dose becomes
lower than Retrospective type.
Sequential ECG triggering:
FLASH ECG triggering:
• X-ray data are acquired only
throughout one Diastolic
Cardiac cycle.
• In this type of gating, the
patient dose becomes lower
than sequential type.
Techniques to Reduce Radiation
Higher KV
Lower KV
mAs
noise
Image contrast
SNR (Contrast)
SNR (Contrast)
dose
dose
dose
noise
mAs
MAX
20% mM
20% mM
• Low Dose Radiation of Coronary CTA
mAs
MAX
4% mM
4% mM
• Min Dose Radiation of Coronary CTA
• Care Dose Radiation of Coronary CTA:
– It detects the radiation Dose on the topogram
scans.
– Based on topograms and the body thickness, the
scanner changes the mAs.
• Care KV of pediatric CTA:
– It can be switched on or off.
– When it is on, it reduces the kv to the lowest
possible KV, in order to decrease the patient
receiving dose.
– It is usually used in children and pediatric patients.
Data Reconstruction
• After the data acquisition, the image
reconstructions are made based on EKG
gating, with different percentages.
• Form the reconstructed images, 3D and 2D
(MPR, MIP, Curve, VRT) are acquired.
Data Reconstruction
• In image reconstructions, BEST DIASTOLE and
BEST SYSTOLIC phases should be made.
• If any lesion in any percentages is noticed, for
the confirmation, it should be evaluated at
least in 2 other percentages.
Data Reconstruction
• If any section from any artery will not be sharp
in any percentage, for acquiring the best
quality and the best percentage for that
artery, the Preview technique is utilized.
5. MIP & VRT Reconstruction
• In order to evaluate the lesions, both MIP and MPR
techniques are used. Specially the sections with a high
calcium content, MPR can help more.
• If the presentation of any artery’s distance is required in a
single line shape – with no curvature – the CURVE technique
is used. For the presentation of every coronary arteries, the
curve technique should be used by the Coronal, Sagittal, and
Axial planes.
5. MIP & VRT Reconstruction
• VRT technique is mostly utilized for the cardiac Anatomy,
arterial malformations, arterial course, and a nice
presentation of the heart.
• For the stenosis determinacy evaluations, the VRT images
are not in use.
5. MIP & VRT Reconstruction
5. MIP & VRT Reconstruction
5. MIP & VRT Reconstruction
Artifact
• Motion Artifacts: Occur at high rates and most often in
the midsegment of the right coronary artery
• Misalignment and Slab Artifacts: High heart rates,
Heart rate variability, and the presence of irregular or ectopic
heart beats (e.g. PVC, AF, Arrhythmia)
• Blooming Artifacts：High-attenuation structures, such
as calcified plaques or stents, appear enlarged (or bloomed)
because of partial volume averaging effects and obscure the
adjacent coronary lumen, the main cause of false-positive
results in coronary CTA because of overestimation of the
degree of stenosis
A) Motion Artifact at High HR
(76 Rate/min).
B) Curved MPR image of the
Artery with Heart Rate
Motion Artifact.
C) Stair-Step Artifact related to
Arrhythmia.
D&E) Blooming Artifact
Thanks for your attention!