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RAD512 > Cardiac MRI > Flashcards

Cardiac MRI Flashcards

1
Q

What resolutions does CMR need?

A

High temporal And high spatial resolutions

But need short acquisition times

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2
Q

What Motion artefact do we see on CMR?
How do we reduce this?

A

The heart is continually beating so : ECG gating
The heart is continually moving up and down so : respiratory gating

We need to scan 30 phases of the hearts cycle in 1 achievable breath hold

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3
Q

What is involved in the CMR process?

A

Patient in the scanner for 45min - 1.5 hours
Respiratory gating - 70+ breath holds
ECG or pulse gating
Injections of contrast for 95% of studies

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4
Q

What are the Contraindications for CMR?

A
  • high BMI
  • Claustrophobia
  • Dementia
  • Learning disability
  • young children
  • Haemodynamically unstable
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5
Q

How do we prep a patient for CMR?

A
  • MRI safety questionnaire
  • MRI, contrast questionnaire
  • Patience, weight and height
  • Insert cannula
  • ECG stickers applied
  • Breathing instructions practised
  • Empty bladder.
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6
Q

What is Prospective gating?

A

Most common for single phase single slice imaging.

Segmented imaging - Acquires images in one breath hold until all the data required by K-space has been acquired

Acquires in Mid-end Diastole

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7
Q

What is Retrospective gating?

A

Acquires data continuously the whole cardiac cycle

Records, the temporal position of the acquired data relative to the R-Wave

Continuous until sufficient K-space lines are filled

Data is sorted into points retrospectively .

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8
Q

What does ECG gating require for the heart?

A

Both methods need
- the R-R interval to remain the same distance apart
- The Heart rate to remain stable

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9
Q

How can we resolve the challenges of ECG gating?

A

= Arrhythmia rejection
= select the correct HR into the machine - check through the scan

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10
Q

Why do we need Respiratory gating?

A

The heart needs to be in the same position for each acquisition

The heart moves up and down with the diaphragm for each breath hold

Consequently, there is a need for respiratory gating alongside ECG gating

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11
Q

Which phase of respiration do they scan on?

A

Arrested expiration

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12
Q

What are some of the Challenges about CMR?

A

~ Many patients become SOB easily. They have poor LV function and struggle to hold their breath
~ Lung disorders: COPD, pulmonary overload, post resuscitation
~ Pt who are HoH
~PT who fall asleep
~ boredom
~ paediatrics
~ Learning disability pts
~ Language barrier
~ trauma

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13
Q

Types of respiratory gating - breath hold

what phase of respiration?
How long is the breath hold?
How many holds per scan?

A

Expiration

1-22 seconds

80+ times per scan

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14
Q

What does continuous breathing use?

A

uses a navigator echo

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15
Q

What is a Respiratory navigator?

A

Position a navigator box over the dome of the liver

The scanner then tracks the rise and fall of the diaphragm and the movement of the liver.

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16
Q

Why do we do Axial localisers?

A

True axial, slices are taken from the aortic arch to the base of the heart.

Essential in patients with complex congenital malformations

Check for any gross Pathologies

Check the systemic and pulmonary systems are anatomically correct

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17
Q

Who may need a cardiac MRI?

A

+ after an ischaemic event such as an MI or cardiac arrest
+ Enlarged heart
+ infection of the heart muscle - myocarditis
+ Angina or SOBOE
+ CHD - congenital heart disease
+ Infiltrative heart disease - sarcoidosis, amyloid and hemochromstosis

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18
Q

Who may need a CMR viability scan?

A
  • those who have had an ischaemia event
  • those who had emergency stenting but their LV function is still poor
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19
Q

What is a Short Axis CINE stack and how does it check LV function?

A

The endocardial and epicardial contours of the ventricles are drawn in an automated analysis software.

The patient weight and height is entered to the calculation to determine the patient’s body surface.

20
Q

What is End diastolic volume (EDV) ?

A

Largest size of the ventricular cavity during diastole (relaxation)

21
Q

What is End systolic volume (ESV)?

A

Smallest size of the ventricular cavity during systole (contraction)

22
Q

What is the Stroke Volume (SV)?

A

EDV - ESV = volume of blood displaced in 1 heart beat

23
Q

What is Ejection Fraction (EF) ?

A

SV/EDV = % blood displaced in 1 heartbeat

24
Q

What is Cardiac output (CO)?

A

SV x Heart rate = total volume of blood displaced in 1 min

25
Q

What is Cardiac index (CI) ?

A

CO/BSA = cardiac output normalised to body surface area

26
Q

How is Delayed hyper-enhancement imaging ( SCAR imaging) performed ?
How does the tissues appear?

A
  • an injection of Gad is given
  • wait 10 min
  • the infarcted tissue or tissues with increased extracellular space accumulates Gad
  • This tissue appears hyper-intense (bright) signal on delayed enhancement sequences
27
Q

What is the outcome of Cardiac viability - without infarction ?

A

Viability preserved

28
Q

What is the outcome of Cardiac viability - 1-25%?

A

Viability preserved

29
Q

What is the outcome Cardiac viability - 26 - 50% infarction?

A

Viability preserved

30
Q

What is the outcome Cardiac viability - 51 - 75% infarction ?

A

Viability absent

31
Q

What is the outcome with Cardiac viability - >75% infarction?

A

Viability absent

32
Q

Why do we perform MR stress tests?

A

To assess the significance of known stenosis in coronary artery/ arteries

To screen patients who have chest pain and risk factors for CAD to assess for ischema, which may be caused by narrowing in one of the coronary arteries .

33
Q

What is the Prep for Stress test?

A

+ pre scan phone call
+ normal safety, checks and question whether the patient has followed the prep
+ 2 x cannulas
+ 12 lead ECG
+ council about the stress part of the test

34
Q

What is Hypertrophic cardiomyopathy?

A

> genetic condition
involves abnormal thickening (hypertrophy) of the heart muscle
involves the left bench and right ventricle becomes thickened in 15% of cases
one and 500 people in the UK - few or no symptoms

35
Q

What are the Symptoms of hypertrophic cardiomyopathy?

A
  • chest pain - caused by reduced O2 supply to the myocardium
  • SOB / SOBOE
  • Lightheaded / dizzy syncope/ fainting
  • Fatigue
  • Arrthymias
36
Q

What are the Treatments for Hypertrophic cardiomyopathy (HCM)?

A

Medication, ICD (implanted cardiac defibrillator) Surgery, lifestyle management, withdrawal form competitive sport

37
Q

What is Myocarditis ?

A

= inflammation of the heart muscle (myocardium)
= reduces the ability of the heart to pump effectively
= can cause rapid and abnormal heart arrhythmias
= commonly caused by a viral infection

38
Q

What are the Symptoms of myocarditis?

A
  • SOB
  • arrhythmias
  • light headedness
  • chest pain/pressure
  • fever
  • fatigue
  • other signs of infection eg: sore throat, muscle or head aches
39
Q

How is SCAR imaging used for Myocarditis?
How does the tissue appeared?

A

Delayed enhancement
Generally patchy and seen in the mid-wall / epicardial

40
Q

What are the Common Congenital heart diseases (CHD)?

A

~ Aortic arch abnormalities: coarctation / graft repair
~ tetralogy of fallot
~ Aortic stenosis
~ ventricular size and function

41
Q

What are the Advantages of CMR?

A
  • Any imaging plane
  • able to measure flow volume and velocity
  • visualisation of the extra cardiac vessels
  • excellent 4D information
  • Reproduceable
42
Q

When is CMR useful?

A
  • poorly visualised areas by echo
  • pulmonary arteries and veins
  • SVC and IVC
  • blood flow
  • myocardial function and perfusion
  • Myocardial and pericardial diseases
43
Q

What is Aortic valves stenosis?

A

Caused when the aortic valve narrows
The heart has to work harder to pump blood to the rest of the body

Can cause your left ventricle to become weakened.

44
Q

What is the Shunt assessment formula?

A

Shunt =. Flow (Aorta) / Flow (pulmonary Artery)

45
Q

Why is CMR the gold standard?

A
  • cardiac MR is generally considered the gold standard for clinical measurement of both LV and Rv function
  • it can be used to assess patients RV function
  • patience with ischaemic heart disease (IHD) - quantification of LV function helps plan the patient’s treatment and is used as the clinical prognostic tool with a poor function indication on a poor prognosis
  • it is useful when following up patients over time to see if there has been any changes in their LV function after a course of treatment or surgery.
  • high reproducibility accuracy and low, intra -observer and inter-observer variability.
46
Q

What is a cardiac viability scan used for?

A

To assess how much damage has been done, and are there any underlying cardiac pathologies.

And whether any of the myocardium can be revascularised

RAD512 (26 decks)

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