Cardiac CT and MRI can be used to evaluate the heart and coronary arteries. Cardiac CT uses calcium scoring to detect calcifications and assess risk of heart events. Coronary CT angiography uses contrast injection and ECG-gating to obtain images of the coronary arteries and detect stenoses. Retrospective and prospective ECG-gating techniques are used to optimize image quality while reducing radiation dose. Cardiac MRI provides better soft tissue definition than CT but poorer coronary artery imaging. It uses dark blood spin echo sequences and white blood gradient echo sequences to obtain anatomical and functional images of the heart without radiation.

1. Cardiac CT

2. Indications
 cardiac or coronary anatomy
 Diagnose coronary artery disease
 Patency of coronary artery bypass grafts or
implanted coronary stents
 cardiac function

5. Technique
Calcium scoring
 When evaluating the heart for potential coronary artery
disease, usually a nonenhanced calcium scoring sequence
is first performed.
 This low-dose technique allows for a detection of
calcifications of the coronary arteries.
 Though this technique does not give any information
about potential hemodynamically relevant stenoses,
an Agatston score can be calculated based on that data.
 The calculated Agatston score allows for an early risk
stratification of patients with a high Agatston score
(>160) have an increased risk for a major adverse cardiac
event

6. Coronary CT angiography
 Contrast media injection, usually between 4-5
mL/sec through an antecubital vein.
 To allow for an improved image quality and dose
reduction, cCTA is usually ECG-triggered to adapt
the scan sequence to the patient's heartbeat.

7. Retrospectively ECG-gated cCTA protocols
 After detection of the heart rhythm, the scan covers
the whole heart during multiple cardiac cycles.
 Heart is scanned in all phases
 Retrospective selection of best phases for
reconstruction of images.
 Optimal phase of reconstruction is in diastole.

8. Prospective triggering
 ECG signals are used to trigger scanning(During the
R wave)
 Dose reduction upto 87% compare to retrospective
technique.

10. Post-processing
 Due to the usually tortuous anatomy of the
coronary arteries, curved multiplanar
reconstructions (MPR) or maximum intensity
projections (MIP) are usually generated to allow for
assessment of coronary lumina on a dedicated
workstation.
 In these images, coronary stenoses can be evaluated
and lumen reduction can be measured.

11. Contraindications
 It is not indicated in some situations:
 if the patient is having an acute myocardial
infarction (heart attack)
 screening of asymptomatic patients with low-to-
intermediate risk of CAD
 evaluation of coronary artery stents <3 mm
 evaluation of asymptomatic patients post CABG (<5
years old) and post stent (<2 years old)

12. C A R D I A C M R I

13. Advantages
 The main advantages of cardiac MRI in comparison
with other techniques are:
 better definition of soft tissues
 use of different types of sequences improves
diagnostic accuracy
 no ionising radiation

14. Limitation
 The main limitation of MRI, compared to cardiac
CT, is the poorer evaluation of the coronary arteries.
 MRI incompatable implants.

15. Dark blood Imaging
 Dark blood imaging involves spin echo sequences. Its
main advantage is a fast acquisition that minimises
respiratory and cardiac movement artefacts.
 Its main issue is a low signal/noise ratio and, therefore, a
deficient spatial resolution.
 These can be T1, T2, or proton density weighted
sequences:
 T1 weighted sequences achieve better anatomic
definition
 T2 and PD weighted sequences reach better tissue
characterization

16. White blood Imaging
 White blood imaging involves gradient echo
sequences and steady-state free precession MRI
(SSFP).
 The main advantage of white blood imaging is its fast
acquisition. It can obtain movement sequences and
allows studying cardiac function and movement.