Cardiovascular imaging Flashcards
What is used for anatomical Studies/imaging?
- General X-Ray
- Computer Tomography
- Interventional Coronary Angiogram
What is the most common radiological examination?
The chest x-ray
How do the general chest x-rays work?
- The image is produced when radiation passes through the body to expose sensitive film on the other side.
- The ability of radiation to penetrate structures depends on their energy and density of the tissues and bones.
- The different absorption of the rays by different tissues creates the image. The image is generally displayed as a negative
What does the chest x-ray show about the heart?
- Size of heart
- Cardiac Thoracic Ratio
- Size and outline of aorta
- Evidence of stents, clips, wires and valves
What technique is used for general chest x-rays?
Projection - P-A (posterior to anterior projection, heart has to be as close as possible to the film)
What do Cardiac CTs show about the heart?
- General – look at the heart and structures
- Calcium Scoring
- CT Coronary angiography
How do Cardiac CTs work?
- The scans are produced by having the source of the x-ray beam encircle or rotate around the patient.
- The X-rays passing through the body are detected by an array of sensors.
- Information from the sensors is computer processed and then displayed as an image on a video screen showing organs of interest at selected levels of the body with each scan being a single slice.
What is calcium scoring?
It assesses calcification within coronary vessels
What is calcification a sign of?
Calcification of coronary arteries is a sign of atherosclerotic disease
How can we found about the amount and site of calcification?
Amount and site of calcification can be quantified with CT using visual interpretation and a computer algorithm
What are the benefits of using CT for detecting calcification/issues in the heart?
- Quick (10-20 seconds acquisition)
- Non-invasive
- Low dose <2mSv (10 CXR’s)
- No preparation required
- No contrast
- Useful prognostic indicator in low risk group – 70% would have no calcium therefore reassured
What is Cardiac CT ECG gating?
- Retrospective / Prospective Gating – we need to take pictures at a specific time/phase
- Image is acquired in seconds with ECG gating (1 breath hold)
What is a coronary artery CT?
- 1990’s - Development of 64 slice with multi-row detector CT scanners allowed high resolution and faster imaging for accurate coronary artery visualisation
- Dose 7-10mSv
- Non-invasive – only i.v. iodinated contrast (need to check renal function) - patient is monitored only for a short period before discharge
What is vessel walking?
Reconstruction of 3D vessel path in one plane with Maximal Intensity Projection (MIP) – makes the images of the vessel clearer/detailed
What is CT Cardiac Angiography (CTCA)?
- More accurate than any other non-invasive imaging modality
- Studies show excellent diagnostic accuracy in detection of significant stenoses: Sensitivity 94% Specificity 97%
- Negative predicative value 95% - if it is reported as “normal” the patient will not have any significant CAD!
CTCA Limitations?
- Slow Heart Rate required (<80/min)
- Medication can be given to slow heart rate
- Difficulty assessing narrowing with severe calcification
- No functional information
- Cannot Intervene
What does the coronary angiogram involve?
Direct Arterial Access with advance of Catheter from Brachial, or Femoral or Approach all the way into Coronary Arteries
It's • Invasive • Direct intervention • Angioplatsy • Stenting
How is Digital Subtraction Angiography (DSA) carried out:
- Iodinated contrast used
* Contrast images electronically overlaid and subtracted from a negative template image
What are the treatments of acute coronary syndromes?
Balloon with a catheter inserted, balloon inflated when the site of plaque reached, balloon squishes the plaque against the wall and even after balloon is removed artery stays open
Coronary Stenting used if balloon doesn’t work:
• Bare metal Stent
• Drug Eluting Stent
o Anti-thrombotic
o Anti-inflammatory
Examples of functional imaging?
- Ultrasound
- MRI
- Nuclear Imaging
How does Cardiac Ultrasound Scan Echocardiography work?
- Uses soundwaves similar to echolocation to create an image
* Happens in real time
How does Duplex (Doppler Ultrasound) work?
- If the red blood cells are moving towards you the frequency is high
- If they are moving away the frequency will be lower
What is M (Motion)/Mode Trace Curves?
The “M” mode using a stationary transducer but a moving recording scanning the ultrasound pattern across the screen so it is possible to study the dynamics of moving structures such as the ventricular wall or the valve leaflets.
What is Pulsatility Index Flowrate?
The combination of Doppler and “M” mode demonstrates the haemodynamics of Blood flowing within the Heart