Cardiac MRI basics and interpretation.pptx

Cardiac MRI (Magnetic Resonance Imaging) is a non-invasive imaging modality that provides detailed images of the heart and its blood vessels. Here are the basics:

Indications:

1. Coronary artery disease evaluation
2. Cardiomyopathy (e.g., hypertrophic, dilated)
3. Heart failure
4. Cardiac tumor evaluation
5. Valve disease
6. Congenital heart disease
7. Cardiac sarcoidosis

Basic MRI Sequences:

1. T1-weighted: Visualizes cardiac anatomy, myocardial thickness
2. T2-weighted: Detects myocardial edema (inflammation)
3. Steady-state free precession (SSFP): Evaluates cardiac function, valve disease
4. Gradient echo: Visualizes cardiac chambers, valves
5. Delayed enhancement: Identifies myocardial scar/fibrosis

Cardiac MRI Techniques:

1. Cine imaging: Dynamic imaging of cardiac motion
2. Phase contrast imaging: Measures blood flow/velocity
3. Tagging: Evaluates myocardial strain
4. Late gadolinium enhancement (LGE): Detects myocardial scar/fibrosis

Key Parameters:

1. Left ventricular (LV) function: Ejection fraction, volume
2. Right ventricular (RV) function: Ejection fraction, volume
3. Myocardial thickness
4. Valve function (regurgitation, stenosis)
5. Cardiac output

Protocols:

1. Standard: T1, T2, SSFP, gradient echo
2. Stress (adenosine or dobutamine): Evaluates coronary artery disease
3. Viability (LGE): Identifies myocardial scar/fibrosis

Advantages:

1. High spatial resolution
2. No radiation exposure
3. Non-invasive
4. Excellent tissue characterization

Limitations:

1. Claustrophobia
2. Pacemaker/Metallic device compatibility
3. Respiratory motion artifacts
4. Long examination time

Clinical Applications:

1. Diagnosis and monitoring of cardiac diseases
2. Pre-procedural planning (e.g., valve replacement)
3. Post-procedural follow-up (e.g., cardiac transplant)
4. Research and clinical trials

This summary provides a foundation for understanding cardiac MRI basics. For more detailed information, consult with a radiologist or cardiologist.
Cardiac MRI (Magnetic Resonance Imaging) is a non-invasive imaging modality that provides detailed images of the heart and its blood vessels. Here are the basics:

Indications:

1. Coronary artery disease evaluation
2. Cardiomyopathy (e.g., hypertrophic, dilated)
3. Heart failure
4. Cardiac tumor evaluation
5. Valve disease
6. Congenital heart disease
7. Cardiac sarcoidosis

Basic MRI Sequences:

1. T1-weighted: Visualizes cardiac anatomy, myocardial thickness
2. T2-weighted: Detects myocardial edema (inflammation)
3. Steady-state free precession (SSFP): Evaluates cardiac function, valve disease
4. Gradient echo: Visualizes cardiac chambers, valves
5. Delayed enhancement: Identifies myocardial scar/fibrosis

Cardiac MRI Techniques:

1. Cine imaging: Dynamic imaging of cardiac motion
2. Phase contrast imaging: Measures blood flow/velocity
3. Tagging: Evaluates myocardial strain
4. Late gadolinium enhancement (LGE): Detects myocardial scar/fibrosis

1. CARDIAC MRI

2. In this session…. Why CMR/ Advantages Indications Contraindications Technical Aspects Minimum hardware requirements, 1.5 vs 3T Technical Challenges – Gating for ECG/ Respiration Planning Sequences Imaging Modules Cardiac Diseases where in CMR is done

3. LARGE FIELD OF VIEW. DIFFERENT PLANES OF EVALUATION. BEST TECHNIQUE FOR EVALUATION OF RV AND BRANCH PULMONARY ARTERIES. THREE-DIMENSIONAL IMAGING WITH HIGH SPATIAL RESOLUTION. TISSUE CHARACTERIZATION. FREEDOM FROM ARTIFACTS LIKE SURGICAL PATCH PROSTHESES AND CALCIFICATION. SERIAL ACCURATE MEASUREMENTS OF VENTRICULAR FUNCTION REPRODUCIBILITY. MOST ACCURATE METHOD FOR FLOW VELOCITY/VOLUME QUANTIFICATION, INCLUDING QP/QS, STROKE VOLUMES, REGURGITANT FRACTIONS. 10. EXCELLENT IMAGE CONTRAST. 11. ADEQUATE TEMPORAL RESOLUTION LIMITATION – EVALUATION OF CORONARY CALCIFICATIONS ON COMPARISON TO CT. WHY CMR- Advantages over ECHO/ Cath

4. Defining cardiac anatomy Congenital heart disease PERICARDIAL-Constrictive pericarditis Cardiac neoplasm or thrombus Quantifying left and right ventricular function    • Cardiomyopathy     • Heart failure    • Arrythmogenic right ventricular dysplasia (ARVD)    • Pulmonary hypertension Perfusion :  Suspected ischemic heart disease Quantifying blood flow   •  Valvular disease (e.g. AR, MR ,AS, etc.)   • Shunts: ASD, VSD, and PDA  ASSESSING MYOCARDIAL SCAR / VIABILITY     • IDENTIFYING HIBERNATING MYOCARDIUM BEFORE REVASCULARIZATION    • DIFFERENTIATING CARDIOMYOPATHY FROM OLD MYOCARDITIS CORONARY ARTERY MRA :  FOR ANOMALOUS CORONARY ARTERIES ADULT CHD Ischemic heart disease Cardiomyopathy Myocarditis PEDIATRICS CHD Morphology Function INDICATIONS FOR CMR

5. ABSOLUTE CONTRAINDICATION FOR PATIENTS WITH ACTIVE PACEMAKERS, OTHER IMPLANTED ELECTRICAL STIMULATORS, FREE PARTICULATE IRON IN THE OPTIC GLOBE, INTRACEREBRAL ANEURYSM CLIPS. ALL FERROMAGNETIC IMPLANTS, VALVES AND STENTS ARE TO BE CHECKED FOR MR COMPATIBILITY- MAY PRODUCE ARTIFACTS. GFR < 30 CONTRAINDICATIONS

6. TECHNICAL ASPECTS MINIMUM HARDWARE REQUIREMENTS, 1.5 VS 3T TECHNICAL CHALLENGES – GATING FOR ECG/ RESPIRATION PLANNING SEQUENCES

7. 1.5T Vs 3T Currently used for the majority of examinations. Less artefacts Better cine images INCREASED SNR INCREASED SPATIAL AND/OR TEMPORAL RESOLUTION SHORTER SCAN TIME ADVANTAGEOUS FOR FIRST PASS CONTRAST-ENHANCED PERFUSION IMAGING MORE ARTEFACTS

8. Coils Body coil- easy availability, good SNR, High SAR Cardiac coil- expensive, better SNR, Low SAR ECG leads Metallic leads- cheap, artefacts+, risk of magnetisation and projectile formation. Graphite leads- expensive, no risk of magnetisation MR compatible- infusion pumps and monitors

9. Patient preparation Atleast 2hrs fasting All ECG,Echo and angio reports to be verified If stress imaging- smoking and caffeine avoided for 24- 48hrs. Properly explain about scan duration and noisy environment of MR gantry. Positioning No free metal on body, change to hospital gown Graphite ECG leads placed in L pattern Supine position with body coil on anterior chest wall No air gap between body coil and chest wall

10. Technical challenges- Gating rapid and complex motion of the heart and pulsatility of the great vessels due to normal contractility –cause technical challenges . In addition, the effects of respiratory motion and systolic ventricular blood velocities up to 200 cm/s further complicate cardiac imaging These issues are generally mitigated by implementation of ECG (cardiac) gating; navigator echo respiratory gating; breath-hold techniques; rapid, high-performance gradients; improved field homogeneity; and advanced pulse sequences.

11. ECG GATING CAN BE EITHER PROSPECTIVE OR RETROSPECTIVE. PROSPECTIVE -WHERE MR DATA ACQUISITION ONLY BEGINS AFTER DETECTION AN R-WAVE ADV- ONLY THE NECESSARY DATA ARE COLLECTED. HOWEVER, EXCESSIVE HEART RATE VARIABILITY LIMITS THE APPLICATION OF THIS TECHNIQUE. RETROSPECTIVE GATING - CONTINUOUS IMAGE ACQUISITION THROUGHOUT THE CARDIAC CYCLE - RETROSPECTIVELY SELECTING THE DESIRED DATA SUBSEQUENTLY DURING POST-PROCESSING. ECG- Gating

12. 2 Methods of ECG gating Prospective Triggering Retrospective Triggering

13. NAVIGATOR ECHO RESPIRATORY GATING ENABLES IMAGE ACQUISITION DURING FREE BREATHING. AN EXCITATION PULSE AT THE LEVEL OF THE DIAPHRAGM OR HEART IS USED TO TRACK PATIENT BREATHING: IMAGES ARE ACQUIRED ONLY DURING END-EXPIRATION Respiratory Gating

14. Pulse sequences The components of a pulse sequence are termed “imaging engines” and “modifiers”. Imaging engines are integral features of a pulse sequence, whereas modifiers are optional additions. Imaging engines include fast spin-echo (FSE), gradient-echo (GRE), steady-state free precession (SSFP), echo-planar imaging (EPI), and single-shot versus segmented modes. Modifiers include fat suppression, inversion prepulse , saturation prepulse , velocity-encoded, and parallel imaging

15. PULSE SEQUENCES BLACK BLOOD IMAGING- SPIN ECHO SEQUENCE REFERS TO THE LOW-SIGNAL-INTENSITY APPEARANCE OF FAST-FLOWING BLOOD AND IS MAINLY USED TO DELINEATE ANATOMYAND MORPHOLOGICAL DETAILS, PERICARDIAL IMAGING AND MEDIASTINAL ABNORMALITIES. CAN BE T1WI OR T2WI AND DOUBLE OR (STIR )TRIPPLE IR SEQUENCES. BRIGHT BLOOD IMAGING- GRADIENT ECHO DESCRIBES THE HIGH SIGNAL INTENSITY OF FAST-FLOWING BLOOD AND IS TYPICALLY USED TO EVALUATE CARDIAC FUNCTION THESE ARE CINE SEQUENCES- BSSFP/SPOILED GE Used in functional imaging, flow images and CE-MR Angio

16. Phase Contrast – Quantify flow & Velocity, Stenosis Non contrast technique that is frequently used to estimate pulmonary blood flow ( Qp ) and systemic blood flow (Qs) to calculate the pulmonary-to-systemic flow ratio ( Qp:Qs ) to determine shunt fraction. A Qp:Qs > 1.5 usually indicates a significant left to-right shunt. Saturation-recover preparatory pulses - improve T1-weighted imaging. -perfusion-weighted imaging

17. Contrast Dynamic perfusion imaging - useful for characterizing myocardial viability Evaluation of myocardial viability with MRI is based on the phenomenon of delayed enhancement-approximately 10 minutes after injection of a gadolinium-based contrast medium. Areas of myocardial infarct characteristically display enhancement when imaging is performed at an inversion time at which signal in the myocardium is maximally nulled. For tumor imaging, T1- WI are typically performed immediately after gadolinium injection Tumors- Hemangioma, paraganglioma enhance during this phase Contrast MR angiogram

18. Imaging Planes The two main coordinate systems used -the body planes and the cardiac planes. Body planes oriented orthogonal to the long axis of the body(axial, sagittal & coronal). used to derive the scout images and provide a qualitative overview of cardiac morphology. However, the obliquity (≈ 45°) of these planes to the walls of the heart precludes accurate anatomic and functional characterization.

19. AXIAL MORPHOLOGY AND RELATIONSHIP OF THE FOUR CARDIAC CHAMBERS AND THE PERICARDIUM, PULM A SAGITTAL CONNECTION BETWEEN THE VENTRICLES AND THE GREATER VESSELS CORONAL LV, LA, PULMONARY VEINS

20. Different from other body parts because of anatomical orientation Eg . True sag is not true in cardiac CARDIAC PLANES

21. Cardiac Planes short axis, horizontal long axis (four-chamber view), and vertical long axis (two-chamber view). These planes are prescribed along a line extending from the cardiac apex to the center of the mitral valve (long axis of the heart) using the axial body plane images. The short-axis plane extends perpendicular to this true long axis of the heart at the level of the mid left ventricle. The horizontal long axis is generated by selecting the horizontal plane that is perpendicular to the short axis, whereas the vertical long axis is prescribed along a vertical plane orthogonal to the short-axis plane. Ventricular volumetric measurements are routinely derived from the short-axis views.

22. 4 CHAMBER SHORT AXIS 2 CHAMBER True coronal of the heart = 4 chamber True sagittal = 2 chamber True axial = Short axis Long axis of the heart - line extending from cardiac apex to the center of MV Short axis – perpendicular to the long axis at the level of mid LV 2 CH- along a vertical plane orthogonal to the short-axis plane 4 CH- horizontal plane that is perpendicular to the short axis

23. COMMON IMAGING PLANES PLANES FOR ANATOMY AND FUNCTIONAL ASSESSMENT ANATOMICAL PLANES SHORT AXIS VIEW 2 CHAMBER VIEW 4 CHAMBER VIEW PLANES FOR FUNCTIONAL ASSESSMENTS RVOT LVOT TV MV

24. SEQUENCES USED IN CARDIAC MRI True FISP/FIESTA (b SSFP) --- Bright Blood sequences HASTE /SPIN ECHO/DIR --- Black blood sequences TRUEFISP with IR or --- Delayed enhancement and Myocardial Perfusion Turbo FLASH or Saturation recovery 3DTRUEFISP --- Coronary/anatomy 3D SPGR --- CEMRA

25. Tissue characterisation Flow Assessment Functional Assessment- For volumes and EF Early and Late gadolinium enhancement Perfusion Parametric Mapping T1/ T2/ T2* IMAGING MODULES

26. Tissue Characterization Module T1 T2 T2 STIR or T2 FS

27. Tissue characterisation Flow Assessment Functional Assessment- For volumes and EF Early and Late gadolinium enhancement Perfusion Parametric Mapping T1/ T2/ T2*

28. Left ventricular and RV structure and function module

29. CMR Tissue characterisation Flow Assessment Functional Assessment- For volumes and EF Early and Late gadolinium enhancement Perfusion Parametric Mapping T1/ T2/ T2*

30. Flow Module For optimal results, the imaging plane should be Centered in the vessel of interest Aligned perpendicular to the expected main blood flow direction in two spatial directions Centered in the iso-center of the magnet NB : Deviations of more than 15° cause significant errors in the peak velocity and flow rate.

31. CMR Tissue characterisation Flow Assessment Functional Assessment- For volumes and EF Early and Late gadolinium enhancement Perfusion Parametric Mapping T1/ T2/ T2*

32. <10s Perfusion 10-20 min Infarct [ Gd ] time “ F IRST PASS” MPI : TIME-INTENSITY CURVES Normal Ischemia/Infarct LV Blood pool Perfusion defects

33. Hypointense on first pass perfusion ISCHEMIC Hypointense on first pass perfusion ISCHEMIC + Non enhancement in delayed scan ( reversible with intervention) Myocardial Perfusion Hypointense on first pass perfusion INFARCT + Enhanced 10mts or later (nonreversible)

34. Segmental anatomy of LV 6 Antero lateral 5 Infero lateral 4 Inferior 3 Infero septal 2 Antero septal 1 Anterio r Basal………………...6 mid cavity…………..6 Apical…………….....4 Apex ……………….1

35. Vascular territories : LAD RCA LCX BASAL 1 2 3 4 5 6 MIDCAVITY 7 8 9 10 11 12 APICAL 13 14 15 16 6 Antero lateral 5 Infero lateral 4 Inferior 3 Infero septal 2 Antero septal 1 Anterior Course of Coronaries apex

36. CMR Tissue characterisation Flow Assessment Functional Assessment- For volumes and EF Early and Late gadolinium enhancement Perfusion Parametric Mapping T1/ T2/ T2*

37. Late gadolinium enhancement module Need at least 10 minute wait after gadolinium injection LGE DENOTES AREAS OF SCARRED MYOCARDIUM

38. PRE CONTRAST POST CONTRAST ENHANCEMENT In myocardial infarction for assessment of viability, if LGE involves <= 50% myocardial thickness  indicates viable myocardium

39. CMR Tissue characterisation Flow Assessment Functional Assessment- For volumes and EF Early and Late gadolinium enhancement Perfusion Parametric Mapping T1/ T2/ T2*