Radiology Flashcards
Who is the father of radiology?
Wilhelm Röntgen – Discovered it in 1895
What is imaging?
Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues.
What are the four imaging tests?
-X-rays
-Ultrasound
-Magnetic resonance imaging (MRI)
-Nuclear medicine
What are the three subdivisions of X-ray?
Plain radiography
Contrast studies (Barium enema, arthrography)
Computed tomography (CT)
What are X-rays? (Scientific answer)
Electromagnetic radiation is produced by an electrical source that pass through body tissue to a degree dependent on its density
What are the five steps of mechanics of producing an X-ray?
- Electric current heats filament cathode
- Electrons are emitted and strike the anode
- Generated x-rays exit window in casing and beam is collimated
- x-rays penetrate the patient and scatter
- Only 1% of x-rays reach the film and contribute to the image
What is PACS and what does it allow?
Picture archiving and communications system allow easier storage, access, and retrieval of digital images.
How do X-rays interact with each tissue?
The denser a tissue, the fewer x-rays pass through it
air lets all x-rays pass through
soft tissue lets some x-rays pass through
cortical bone lets no x-rays pass through
What are the three strengths of X-rays?
- Good at showing things that are surrounded by black air.
- Good at showing things that are surrounded by white bone.
- Good at showing things that destroy white bone- Sclerotic lesion.
What are the two weaknesses of X-rays?
- An abnormality must be of very different density to the tissue that surrounds it.
- A lot of pathologies, especially that affecting soft tissues, is of similar density to its surroundings and isn’t shown by simple x-rays
What are contrast studies?
Contrast radiography is a method of studying organs using X-rays and the administration of a special dye, called a contrast medium.
What are two examples of contrast mediums?
Barium and iodine
Why can X-rays be dangerous and what is it relative to?
X-rays are radiation so can damage cell DNA leading to mutations that may kill the cell or make it turn cancerous
the risk is related to the x-ray dose
What is computed tomography?
A procedure that uses a computer linked to an x-ray machine to make a series of detailed pictures of areas inside the body.
Why is CT better than radiographs at times and what is it often used for?
It is more able than radiographs to distinguish between tissues of similar density and is often used to show soft tissue pathology
What superior characteristic does CT have over X-rays?
Contrast resolution.
With CT, x-rays are ‘fired’ from all around the body and processed by a computer which produces a set of cross-sectional pictures with no superimposition
Why are radiographs not sufficient to diagnose illness?
When obtaining a radiograph, the x-rays are ‘fired’ from only one direction producing an image where all structures between their source and the film are superimposed
What does cross-sectional mean?
A discipline of radiology that encompasses the use of a number of advanced imaging techniques that feature in common the ability to image the body in cross-section
So why don’t we just CT everybody?
-CT gives large doses of ionizing radiation
-Soft tissues of very similar density cannot be distinguished by CT
-CT cannot resolve bone marrow disease
What soft tissues cannot be distinguished by CT?
Pelvic organs (uterus, ovaries, prostate)
Muscles and tendons
Joint cartilage and ligaments
Some areas of the brain
What are the seven steps of the mechanics of ultrasound?
Piezoelectric crystals can convert electrical energy to acoustic energy
These crystals are housed in a transducer which has an electrical supply
The transducer produces pulses of sound waves
The skin is coated with jelly to assist sound transmission into the body
the ultrasound transducer alternately transmits sound pulses and then listens for reflected sound returning
The returning acoustic energy is converted back into an electrical impulse and fed into a computer
The computer ‘knows’ where the sound has come from by the time taken for it to return to the transducer
It uses this to create a cross-sectional picture of the soft tissues that are invisible to x-rays
What is the interaction between ultrasound and body tissues?
Body tissues have different acoustic properties - some tend to transmit sound while others, such masses, tend to reflect it
Is the diagnosis in an ultrasound done after the procedure?
Nope, during the procedure.
What makes a good ultrasound exam? (5)
-Tissues that allow sound transmission
-Good skin – transducer contact, superficial structures, slim patients, and correct transducer selection
-Tissues that have different acoustic properties
-A well-trained and experienced sonographer
-Modern equipment
What makes a poor ultrasound exam?
tissues that prevent sound transmission (gas, bone)
sound can’t reach the target or return to the transducer
poor skin – transducer contact (not enough jelly, hairy pt)
very deep structures
fat patients
incorrect transducer selection
tissues that have identical acoustic properties (reflect the same amount of sound)
an incompetent operator
antique equipment
What are the four strengths of ultrasound?
- ultrasound has a high spatial resolution, useful in imaging MSK soft tissue structures
- body fluids readily transmit ultrasound whereas solid structures within the fluid reflect it
- abnormal fluid collections are well shown by ultrasound as the surrounding tissues reflect more sound and contrast with the black fluid
- soft tissues with different acoustic properties are well differentiated by ultrasound
What are the three ultrasound weaknesses?
bone blocks the US, so it can’t see the brain, the spinal canal, inside joints, or assess bone marrow
gas blocks the US, so ‘windy’ patients are difficult to assess and gas-containing structures like the lungs or bowel can’t be assessed
very fat patients make poor US subjects
What are the mechanics of the MRI?
-the scanner produces a burst of radio signal (RF pulse), which energizes the body’s protons
-the scanner waits
-the scanner listens for a return signal, produced by the protons
-the amount of signal produced depends on the molecular environment of —these protons
-using the returned signal, the scanner’s computer performs some amazingly complex calculations and creates an image
What has MRI caused which makes it hostile?
Frostbite and thermal burns
Deafness
Disturbance of surgical and non-surgical ferrous material
Pacemakers
Heart valves
Mobile ferrous material eg shrapnel, intra-ocular foreign bodies
Missile injuries
What two things should you do to prevent patient injury regarding the MRI?
request card safety questionnaire
patients must remove all ferrous metal
MRI is time-consuming, how long does it take for the spine, knee and ankle?
spine 25-40 minutes
knee 25mins
ankle 30mins
What are the four strengths of MRI?
-MRI provides the most complete assessment of the brain of any modality
-MRI is a sensitive way to assess acute muscle and tendon tears, especially in deep tissues where ultrasound is less accurate
-MRI provides excellent detail of spinal canal disease
-MRI allows the interior of joints to be imaged so that injuries to cartilage and ligaments can be seen
What are the five weaknesses of MRI?
-MRI is expensive
-MRI could harm some patients and is therefore contraindicated
-Some patients find MRI too claustrophobic
-MRI scans take a long time so patients who are in pain or are restless, or those who are unstable or need monitoring can’t be scanned
-MRI is poor at showing detail of the lungs
Tell me the five roles of imaging
To make or confirm a diagnosis
To help narrow a differential diagnosis
To ‘STAGE’ a known disease, eg cancer to inform treatment
To monitor the effects of treatment and follow up on a known disease
To aid intervention/deliver treatment eg image-guided procedures or interventional radiology
What two fields are required in imaging?
Clinical medicine and anatomy
How do you start X-ray interpretation?
Begin chest X-ray interpretation by checking the following details:
Patient details: name, date of birth, and unique identification number.
Date and time the film was taken
Previous imaging: useful for comparison.
How do you assess image quality?
RIPE
-Rotation
-Inspiration
-Projection
-Exposure
What is the golden standard regarding the position in CXR?
Posterior Anterior (PA)
