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General Radiology
Image is produced when radiation passes through the body to expose sensitive film from
the other side
Ability of radiation to penetrate structures depends on their energy and density of tissues/
bones
Bones absorb x-rays, lungs let them pass
When the rays are absorbed film goes black (so lungs would be white) but its easier if
seen in negative - so Absorbed = white (e
...
bones and heart)
Projection technique - the closer the patient to the film - the more correct the size is
Further away = bigger picture

CTR: A+B should be half of C (chest)

Dextrocardia - heart on wrong side

Computed Tomography (CT)
CT can image the internal portion of organs and separate
overlapping structures precisely (shows organs of interest at
selected levels of the body) - each scan is a single slice
Scans are produced by having the source of the x-ray beam rotate
around the patient
...
Info is then processed and displayed as an image
Stacking the individual slices can give a detailed organ study

Cardiac CT
Can use:
General CT - shows heart chambers
Calcium scoring
Can show coronary calcification (sign
of atherosclerosis)
Amount of calcium can be quantified by
CT
Quick & non-invasive
No preparation or contrast needed
CT coronary angiography
Old CT scanners lacked the resolution to image the heart (before the 64 multi slice
scanners with high resolution) and so invasive coronary angiography was the only
way to see the vessels
Coronary artery CT
Non-invasive (only IV iodinated contrast - so need a good renal function to excrete it)
Quick - measured in seconds - hold breath to stop breathing artefacts
If heart rate is more than 60 - use ECG gating (image taken at exact same point)
Can assess valves, aorta and grafts

Reduces radiation (looks as if the heart has stopped moving due to images being taken in
exact same time frame

You can add false colour and create 3D anatomical reconstruction to view a more detailed
structure of the heart

CT Cardiac Angiography
More accurate than any other non-invasive modality
Excellent diagnostic accuracy
Limitations:
Slow HR (<80) needed (but meds can be given to slow the heart)
Difficulty assessing narrowing with severe calcification - contrast is quite dense
No functional information
Cannot intervene
Cardiac MRI
Anatomical and functional
Creates images by decoding radio-frequency signals emitted from the body's hydrogen
atoms

Patients who are dependant upon cardiac pacemakers or those who have metallic foreign
objects in the brain or around the eye cannot be scanned with an MRI

Scanner subjects nuclei of body's atoms to a radio signal - temporarily knocking select
ones out of alignment
When the signal stops, nuclei return to the aligned position releasing their own faint radio
frequencies which the scanner and computer can use to produces detailed anatomical
pictures
MRI can produce an infinite number of projections through the body
Magnetic Resonance Angiography (MRA)
MRI studies can be done with a contrast agent (Gadolinium) with reconstruction of
vascular structures MIP (Maximum Intensity Projections)
MRI cine-Mode projection - functional studies are obtained by stacking images acquired
from separate time points of the cardiac cycle in a cine-loop
Cardiac isotope scan
Nuclear heart scan uses Technetium (as it has a short half life of 6 hrs) - so radioactive
exposure is limited
Technetium accumulates in damaged heart tissue leaving hot spots that can be detected
by the camera
Gamma camera
Detects source of radiation to build a picture

Technetium Heart Scan
Test usually done 12 hrs after suspected heart attack and repeated after several weeks to
see if any further damage has occurred
Scan done 3 hrs after Technetium injection - entire test takes 1 hr
More accurate than ECG when it comes to detecting heart attacks
SPECT scanner
Multiple images taken at different rotation angels to obtain 3-D information
3-D picture can then be reconstructed using matrix which is then inverted to reveal the
source distribution

Myocardial Perfusion Scan
Used to study blood flow to the heart
Can identify conditions that could lead to a heart
attack
Non invasive nuclear imaging technique
Uses radioactive imaging agents to assess
coronary blood flow to the LV myocardium
Radioactive tracer injected into vein travels
through coronary arteries and settles into LV
myocardium
A narrowed/diseased coronary artery will not
allow as much tracer through it as normal one resulting in reduced amount of tracer to settle in
the effected area of the myocardium

MP stress test
Exercise causes coronary dilation
Patients with CAD - exercise exaggerates the narrowing of coronary arteries
Comparison of stress and rest images - differentiates between reversible ischaemia and
established myocardial infarct
Can use treadmill exercise or pharmacological stress agents (e
...
old people with bad
hips)
Adenosine, Dobutamine
Reversible ischaemia - defect on stress only (poor perfusion on stress but better
perfusion on rest)
Fixed defect on both studies - established infarct (poor perfusion on stress and rest indicates MI)
Coronary Angiogram
Invasive
Direct intervention
Angioplasty
Stenting
Direct access to coronary arteries by brachial or
femoral approach
Iodinated contrast used
Coronary Angioplasty

If coronary angioplasty doesn't work - coronary stenting
Coronary Stenting
Stays in the artery
Types:
Bare metal stent
Drug eluting stent (stops the body's platelets
sticking and the attempt of foreign body
removal)
Anti-thrombotic
Anti-inflammatory

Cardiac Ultrasound Scan
Anatomical and Functional
Echocardiography
Non-invasive
Bright spots are echos
Doppler Ultrasound
Blood flow
Red - towards
Blue - away

M (Motion)-Mode Trace Curves
Can study the dynamics of moving structures such as ventricular wall or valve leaflets
(using a stationary transducer but a moving recording scanning the US pattern across the
screen)
M-Mode + Doppler = Pulsatility Index Flowrate
(Haemodynamics of the heart) (How much is
flowing, where it is flowing and how fast it is
flowing)

*MPS = Myocardial Perfusion Scan



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