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!