ADVANCED CORONORY CT / CARDIAC CT

1. LOKESH.D BSC RIT

2. OVERVIEW
 Recent Advances in Coronary CT
 Anatomy and Physiology
 Equipment and Physics
 Indications
 Coronary procedure
 In detail Calcium Score
 Techniques and post processing
 Artefacts
 Case studies
 Contraindications
 Radiation Dose
 Limitations
 Summary and References.

3. RECENT ADVANCES IN CORONARY CT
 New technology supports CT as prime cardiac imaging
modality.
 Perfusion imaging
 Spectral imaging and
 Non invasive Fractional flow reserve dose levels FFR-CT
PERFUSION IMAGING
CT perfusion imaging can accurately assess functional
blood flow in the heart by Software like TERARECON
and VITAL IMAGES etc… without the need for a
nuclear exam/MRI.

4. SPECTRAL IMAGING
 Spectral imaging allow to differentiate anatomical features
which are enhanced and easier to see at different levels
 It can highlight /eliminate specific chemical compounds
based on their atomic numbers including iodine and
calcium
 Enables differentiation between calcified coronary lesion
and iodine contrast in the blood vessel.

5. FFR-CT FRACTIONAL FLOW RESERVE CT
 FFR CT have greatly decreases heart flows lowered cardiac CT radiation dose
levels
 FFR-CT is a web based , computation fluid dynamic software that analyzes
existing CCTA images to provide physicians with detailed data about blood
flow with in the coronary arteries.
 The primary advantage of 256- and 320-slice CT is the increased craniocaudal
coverage.
 In a comparison of prospectively gated 64- and 256-slice CT scanning, the
256-slice scan provided better and more stable image quality, at equivalent
effective radiation dose.

6. CORONARY ANATOMY
The major vessels of the coronary
circulation are
1.the left main coronary that divides
into left anterior descending and
circumflex branches and
2.the right main coronary artery.

7. RIGHT CORONARY ARTERY
ORIGIN
 The right coronary artery originates from the anterior aortic sinus of the ascending
aorta, immediately above the aortic valve.
COURSE
 After arising from the ascending aorta, the RCA first runs forwards between
the pulmonary trunk and the right auricle, and after that it descends just about
vertically in the right AV groove (right anterior coronary sulcus) up to the junction of
the right and the inferior borders of the heart. At the inferior border of the heart, it
turns posteriorly and runs in the groove where it ends by anastomosing with the left
coronary artery.
BRANCHES AND DISTRIBUTION
Right Conus Artery
 It supply the anterior surface of the pulmonary conus (infundibulum of the right
ventricle).
Atrial Branches
 They supply the atria. One of the atrial branches – the artery of sinuatrial node (also
referred to as sinuatrial nodal artery) provides the SA node in 60% cases. In 40% of
individuals it originates from the left coronary artery.

8. Anterior Ventricular Branches
 They’re 2 or 3 and supply the anterior surface of the right ventricle.
 The marginal branch is the largest and runs along the lower margin of the sternocostal
surface to make it to the apex.
Posterior Ventricular Branches
 They may be generally 2 and supply the diaphragmatic surface of the right ventricle.
Posterior Interventricular Artery
 It runs in the posterior interventricular groove up to the apex. It supplies the posterior
part of the interventricular septum, atrioventricular node (AV node) in 60% of the cases,
and right and left ventricles.
 In 10% individuals, the posterior interventricular artery originates from the left coronary
artery.

9. LEFT CORONARY ARTERY
ORIGIN
 The left coronary artery originates from the left posterior aortic sinus of the
ascending aorta, immediately above the aortic valve.
COURSE
 After arising from ascending aorta, the LCA runs forwards and to the left between
the pulmonary trunk and the left auricle. It then divides into an anterior
interventricular and circumflex artery. The anterior interventricular artery (left
anterior descending/LAD) runs downwards in the anterior interventricular groove to
the apex of the heart. It then enters posteriorly around the apex of the heart to go
into the posterior interventricular groove to terminate by anastomosing with the
posterior interventricular artery- a branch of the right coronary artery.
 The circumflex artery winds around the left margin of the heart and continues in
the left posterior coronary sulcus up to the posterior interventricular groove where
it ends by anastomosing with the right coronary artery.

10. BRANCHES AND DISTRIBUTION
1. Anterior interventricular artery/left anterior descending (LAD) artery: It provides (a)
anterior part of interventricular septum, (b) greater part of the left ventricle and part of
right ventricle, and (c) a part of left bundle branch (of His) posterior atrioventricular groove
(right posterior coronary sulcus) up to the posterior interventricular.
2. Circumflex artery: It supplies a left marginal artery that provides the left margin of the
left ventricle up to the apex of the heart.
3. Diagonal artery: It may originate directly from the trunk of the left coronary artery.
4. Conus artery: It supplies the pulmonary conus.
5. Atrial branches: They supply the left atrium.
Anatomic Region of Heart Coronary Artery (most likely associated)
Inferior Right coronary
Anteroseptal Left anterior descending
Anteroapical Left anterior descending (distal)
Anterolateral Circumflex
Posterior Right coronary artery

11. PHYSIOLOGY
 Extravascular compression (shown
to the right) during systole
markedly affects coronary flow;
 therefore, most of the coronary
flow occurs during diastole.
 Because of extravascular
compression, the endocardium is
more susceptible to ischemia
especially at lower perfusion
pressures.

12. EQUIPMENT
64 TO 320 SLICES/DUAL SOUCE CT
PRESSURE INJECTOR
Ecg measuring machine ETC…
18 gauge cannula-Rt cubital vein is recommended

13. INDICATIONS
 1. Ruling out significant luminal stenosis in stable patients with suspected coronary
stenosis, but intermediate pretest likelihood of disease
 2. Ruling out coronary artery disease in acute chest pain
 3. Coronary anomalies
 4. Ruling out stenosis before non coronary cardiac surgery
 5. Determine patency of coronary artery bypass grafts
 6. Using CT as an alternative when cardiac catheterization is impossible or carries a
high risk
 7. Clarifying unclear findings after invasive angiography
 8. Providing pre-interventional information for percutaneous coronary
intervention
 9. Assessing coronary artery stents
 10. Determining the presence and extent of coronary atherosclerotic plaque

14. CORONARY PROCEDURE
.
 Give an appointment with prescribed beta-blockers in higher heart rate
patients
 Serum creatine <1.50
 instruct to avoid eating solid food 4 hours before the study and to increase
fluid intake prior to the exam.
 Standard precautions with regard to contrast allergy are taken.
 Instruct to avoid smoking ,drug chewing and other medication intake.
Administration of beta blockers in adults
Heart rate beta blockers
1. <55 none
2. 70<HR<80 propranolol 40 mg orally 15-45 min berfore the scan
3. >80HR>90 100 mg metaprolol orally 1 hour before the scan

15. Usage of beta-blockers &nitroglycerin
Beta blockers
 Beta-blocker administration is often helpful in cardiac CT scanning to lower the heart rate
and decrease motion artifact. The level to which the heart rate should be lowered depends
on the temporal resolution of the scan.
 However, heart rate variability may be a more important determinant of image quality than
absolute heart rate.
 Beta blockers are also helpful in patients with irregular heart rates, supraventricular
tachycardias, and arrhythmias.
Nitroglycerin
The administration of sublingual nitroglycerin dilates the coronary arteries and increases side
branch visualization.
Nitroglycerin is contraindicated in patients who are allergic to it and in patients who are taking
phosphodiesterase inhibitors for erectile dysfunction. Patients should not have taken a
phosphodiesterase inhibitor for at least 48 hours before the exam.
 Nitroglycerin can cause orthostatic hypotension; it should be used with caution in patients who
have low systolic blood pressure (eg, < 90 mm Hg) and who are volume depleted from diuretic
therapy. Angina caused by hypertrophic cardiomyopathy can also be aggravated

16. CALCIUM SCORE
CALCIUM SCORES
 The amount of calcium in the coronary arteries can be quantitated. Various
methods have been proposed for this purpose.
 The most attractive and the most commonly used is the Agatston score.
Other methods described include calcium volume and mass (mineral) score.
AGATSTON SCORES
 To measure total calcium scores based on the number, areas and peak HU CT
numbers of the calcific lesions detected.
 Subsequent studies have confirmed the high correlation between calcium
scores and histopathologic coronary disease and also that absence of
calcification was highly indicative of absence of CAD .
 Inter reader variability of the Agatston score is about 3%, intra reader
variability is less than 1% and inter scan variability is thought to be about
15%

17. Method of calculation
 The calculation is based on the weighted density score given to the highest
attenuation value (HU) multiplied by area of the calcification speck.
Density factor
 130-199 HU: 1
 200-299 HU: 2
 300-399 HU: 3
 400+ HU: 4
 For example, if a calcified speck has maximum attenuation value of 400 HU and
occupies 8 sq mm area, then its calcium score will be 32.
 The score of every calcified speck is summed up to give the total calcium score.

18. VOLUME SCORE
 The calcium volume can be calculated by multiplying the number of voxels (Vn) with the voxel
volume (Vv ) using a technique of isotropic interpolation as mentioned by Callister.
 The main limitations of this technique, are that a third spatial dimension of the plaque is not
taken into account, and that, there is introduction of an arbitrary attenuation scaling factor .
MASS SCORE
 The mass score is calculated as the product of the calcium concentration and calcified plaque
volume .

19. TECHNIQUES
Patient Preparation
Instruct the patient about procedure and Consent/health history forms
1. Feet first scanning is recommended
2. Position patient on couch, feet first supine (with cushion under knees)
3. Ensure proper skin prep,
4.Place ECG electrodes on patient and connect ECG leads)
5.Verify the ECG wave display on gantry
6.Offset patient on the couch so the patient’s heart is in the middle of
the field of view.
7.Have the patient assume the posture for the scan; raise the arms above the
head.
8. Ask the patient to simulate a breath hold with arms above their head.
observe the ECG signal during the breath hold.

20. .
Select one Coronary CTA protocols.
 Verify the Surview scan parameters.
 It is recommended to do a Dual Surview
 Scan the Surview from the manubrial notch to the mid abdomen Perform
the Surview with a short inspiration
 Plan on Surview
 Verify the Locator scan parameters.
 Position the Locator line one disc level below the carina.
Coronary Note:
CTA start point is placed 1 to 2 cm above the first slice where a coronary artery can be
seen (slightly below the level of the carina).
The end point is 1 to 2 cm below the apex of the left ventricle

21. CONTRAST ADMINISTRATION & CORONARY AQUISION
 Verify the Tracker scan parameters.
 Verify the Coronary CTA scan parameters.
 Use the contrast injection parameters per your site’s requirements
 Bolus Tracking is 150 with a 5 – 8 second post threshold delay
 If desired, define the coronaries and functional phases using the Edit
phase option under the Cardiac tab
 Verify the patient’s heart rate on the ECG viewer
 If needed, adjust
1 rotation time 0.33 and
2 pitch 0.1 based on the patient’s heart rate

22.  Perform the Locator scan
Place the ROI in the descending Aorta, using the Auto ROI feature.
 Perform the Tracker scan
 Follow the on-screen instructions and perform and complete Coronary CTA
scan with a short inspiration
 Adjust the images and edit the ECG as needed.
Acquisition Mode:
For imaging the rapidly moving heart, projection data must be acquired as fast as
possible in order to freeze the heart motion. This is achieved in multiple-row
detector CT either by prospective ECG triggering or by retrospective ECG gating

23. CA ECG GATED ACQISITION

24. POST PROCESSING
3D MIP
 3d VR
 MIP
 CURVED IMAGES
3D VR

25. POST PROCEDURE
Patient observation and instruction after the scan
1. Have patients stand up slowly.
2. Help them walk to a chair and sit with continued IV hydration and observation for
15 min.
3. If oral beta-blockers were given, let them remain at the center for 1 h.
4. Utilize a teaching sheet to remind patients about post-hydration, when they may
eat and when to restart their routine medications (including metformin).
5. Remove the iv cannula.

26. Coronary artery stenosis detection
High-grade stenosis of the mid-right
coronary artery in a 55-year-old man
with atypical chest pain.
(A) A maximum intensity projection,
with a high-grade luminal reduction
distal to a calcified segment.
(B) A curved multiplanar reconstruction.
(C) A three-dimensional rendering of
the heart and right coronary artery.
(D) shows the corresponding coronary
angiogram.
CASE STUDIES

27. ARTEFACTS & REMEDIES
Problem Cause Manifestation Remedy
Artifact
Cardiac motion Heart rate exceeded Blur Prior administration of
speed of acquisition -blockers
Heart rate varied Stepladder artifact Prior administration of
-blockers
Inappropriate recon- Stepladder artifact Selection of appropriate recon-
struction window was struction window
selected
Pulmonary motion Respiration during im- Blur Oxygen supplementation; in-
age acquisition struction in breath holding
Body motion Voluntary motion Stepladder artifact Minimization of anatomic cov-
erage; instruction
Beam hardening
Metallic object Surgical clip, marker, or Blooming artifact Use of nonmetallic materials
and image reconstruction
algorithms; optimization of
the reconstruction window;
observation of distal flow

28. Calcification Atherosclerosis Blooming artifact Use of various reconstructions;
observation of distal flow
Air bubble Contrast material ad- Low-attenuating Use of different reconstruc-
ministration; surgery artifact tions
Structure-related
Contrast mate- Left atrial appendage Obscured coronary Tracing of anatomy
rial —filled artery
structure
Overlying vessel Cardiac veins Obscured coronary Observation of distal flow
artery
Technical errors
Incomplete ana- Incorrect selection of Omission of the Review of surgical records;
tomic coverage volume region of interest scout imaging
Poor contrast en- Inaccurate estimation of Nondepiction of 5-second scanning delay
hancement circulation time coronary artery
or graft vessel
Misregistration Inappropriate pitch for Skipped section Manual selection of pitch
heart rate
Anatomic deletion Erroneous segmentation Nondepiction of Different image reconstruc-
with automated re- part of a coronary tions
construction software vessel or graft
Poor depiction of Competitive, sluggish, or Nondepiction of Comparison with conventional
flow dynamics retrograde blood flow patent vessel angiograms

29. Stairstep artifacts:
Associated with heart rate
variability
Coronary artery motion artifacts:
Result in image blurring

30. RADIATION DOSE
 Radiation doses for CCTA studies, if performed with retrospective gating in helical
mode, are typically relatively high.
 Pitch is inversely related to radiation dose, a low pitch results in a high radiation dose.
 DOSE IN ADULT approx…
SL NO SCAN LABEL SCAN MODE MAS KV CTIvol DLP
mGy mGy*cm
1 Surview surview 120 0.085 2.6
Surview surview 120 0.085 2.6
2 Heart CS axial 70 120 4.8 72
3 locator station 30 120 2.4 2.4
4 tracker station 30 120 24.11 26.4
5 coronary helical 1000 120 65.4 1065

31. CONTRAINDICATIONS
Adverse effects include contrast-induced nephropathy
Extravasation of contrast
 Initial treatment: Elevate extremity. Ice pack recommended three times per day and
may be alternated with warm soaks
Contrast reactions are as follows:
1. Moderate-to-severe itching/flushing/rash.
2. Nausea.
3. Mild respiratory distress such as wheezing.
4. Signs of anaphylaxis.
5.Morbid obesity
6.Asthmatic patients
7.Low blood pressure
8.Anaphylactic shock
9.Cardiac Arrest
10.Other relative contraindications include: the presence of arrhythmias, high coronary
calcification scores

32. LIMITATIONS
 Extensive calcium score > 800
 Stents; spatial reslolution
 Irregular heart rate;poor image quality
 Radiation dose
 Small vessels septal branches/collaterals
 Obese and un cooperative patients

33. SUMMARY
 The most recent MDCT scanner generations allow for robust morphological and functional
imaging of the heart. Clinically, the main focus of cardiac CT is coronary artery imaging. The
assessment of coronary anomalies by coronary CT angiography is straightforward and CT is
indicated for that purpose. Under certain prerequisites, which include a low and regular heart
rate, a carefully performed coronary CT angiography investigation allows for the accurate
detection of coronary artery stenoses. On the basis of clinical considerations and initial
clinical trials, this may be of particular utility in situations that require to reliably rule out CAD
even though the pre-test likelihood for disease is not high, such as in patients with atypical
chest pain, patients with equivocal stress test results, patients with acute chest pain in the
absence of ECG changes or enzyme elevations, or patients before non-coronary cardiac
surgery. In these situations, the rationale for using CT is to achieve more rapid and definitive
stratification and to avoid invasive coronary angiography if CT demonstrates the absence of
stenoses. In patients with a high pre-test likelihood of disease, however, the use of CT
angiography will most likely not result in a ‘negative’ scan that would help to avoid invasive
angiography and is therefore not recommendable.

34.  Besides the detection of coronary stenoses, cardiac CT has the potential to visualize earlier stages
of coronary atherosclerosis. Coronary calcium, a surrogate marker for the presence and amount of
coronary atherosclerotic plaque, can be detected and quantified by non-contrast CT. Coronary
calcium allows to stratify asymptomatic individuals concerning their future cardiovascular risk with
a predictive power that is stronger than and independent of traditional cardiovascular risk factors.
Coronary calcium measurements by CT may be useful in patients who, based on prior assessment
of standard risk factors, seem to be at intermediate risk for future CAD events and may be
appropriate in order to facilitate a decision concerning lipid-lowering therapy or other risk factor
modification.
 Although clinical application of cardiac CT is possible today in the situations outlined earlier, it
can be expected that technology will continue to evolve rapidly. Spatial and temporal resolution
will increase further, current indications as well as cost-effectiveness will be more firmly
established by large clinical trials, and new applications will be developed. In addition, it will be
necessary to establish adequate training programmes for cardiac CT, and to develop
reimbursement structures which, tied to stringent guidelines on specific clinical situations for
which cardiac CT is considered appropriate, will be necessary to allow more widespread use of CT
in the diagnostic workup of patients with cardiac disease.