Imaging Flashcards
Strengths of x-rays
- Good at showing things surrounded by air
- Good at showing things surrounded by bone
- Good at showing things that destroy white bone (e.g. cancer)
Weaknesses of x-rays
along side with the danger of radtion
its very diffculte to distingusih tissues with similar density
How do x-rays produce an image?
- Electric current heats cathode
- Electrons are emitted + strike anode
- X-rays exit window, penetrate patient and scatter
- X-ray film is blackened when the X-ray hits the film.
X-ray studies are more dangerous than computerized tomography in terms of ionising radiation. True/False
False CT scans usually require more exposure to radiation than common x-rays because they use a series of x-ray images.
How does a CT scan produce an image?
Combines a series of X-ray images taken from different angles around the patient and uses computer processing to create cross-sectional images
Q5. Which of the following is not true for an MRI.
A. MRI is the most suitable assessment for the brain
B. MRI is a great technique to measure acute tendon and muscle tears.
C. MRI is poor at showing details of the lungs
D. MRI has no contraindications
D
How does an MRI produce an image?
- Scanner creates strong magnetic field
- Scanner produces a burst of radio signal which energizes the body’s protons
- Scanner listens for return signal produced by protons and uses signal to produce image
Computerized Axial Tomography (CAT) scan is essentially:
A. X-ray of soft tissues
B. A finer X-ray of bones
C. A detailed x-ray
D. X-ray of brain
C
The cooling agent for the MRI magnet is
Helium
If an MRI was done for a long bone, the part of the bone that will be imaged is the
A. Bone salts
B. Bony Prominence
C. Inflamed Joints
D. Bone Marrow
D
Strengths of MRI
-
No ionizing radiation
- Can assess acute muscle and tendon tears, especially in deep tissues
- Interior of joints can be imaged e.g BONE MARROW
- Most complete assessment of the brain
Weaknesses of MRI
- Expensive
- Can be harmful
- Some patients may find the process claustrophobic
- Scans take a long time
How is an ultrasound image produced?
- Piezoelectric crystals convert electrical energy into acoustic energy; crystals are housed in a transducer which has an electrical supply
- US machine transmits sound pulses into patient
- Some sound waves get reflected, some travel further until they reach another boundary and get reflected
- Machine calculates the distance from the probe to structure, and forms a 2D image on the screen
Strengths of US
-
No ionizing radiation
- High spatial resolution – can show organs, muscles and tendons
Weaknesses of US
- Bone and gas block US
- Difficult to perform on fat patients
