Medical Imaging and Radiology Flashcards
2 examples of Plain Film Imaging
2 examples of Cross-Sectional Imaging
Plain: X-Ray, Fluoroscopy
Cross: CT, MRI
What is an X-Ray and how does it work?
Focused beam of high energy electrons, pass through body onto receiver
How do denser materials appear on an X-Ray and why?
Higher attenuation of electrons, so lighter appearance
Rank Air, Bone, Soft Tissue, Metal, Fat from Low to High Density
Which appear darkest and lightest on an X-Ray?
Air (Darkest) Fat Soft Tissue Bone Metal (Lightest)
List advantages and disadvantages of X-Rays
Give some uses of X-Rays
Pros:
- Quick
- Portable
- Cheap
Cons:
- Radiation
- 2D (Can’t visualise all areas)
- Poor soft tissue imaging
Uses: Looking for fractures and trauma
What is Fluoroscopy?
Uses a constant stream of X-rays, often enhanced by contrast (E.g Barium absorbs x-rays)
Give advantages and disadvantages of Fluoroscopy
Give uses as well
Pros:
- Cheap
- Can be used during interventional procedures
Cons:
- Radiation
Uses:
- Angiography (Looking inside blood vessels, organs)
- Screening in theatre
- Contrast GI studies
- Joint studies
How does Computed Tomography (CT) work?
What are it’s uses?
- Rotating gantry
- X-Ray tube on side, Detectors on the other
Uses:
- Diagnosing (E.g. Cancer/ Strokes)
- Monitor treatments (E.g Cancer)
Advantages and Disadvantages of CT Scanning
Pros:
- Quick, cheap
- Good spatial resolution
- Scan Most areas
Cons:
- Radiation
- Requires breath holding
- Overused
- Artefact Production
How does an MRI work?
- Magnetic field aligns H atoms, but some remain unmatched
- Radiofrequency Pulse applied-> Unmatched atoms absorb energy and spin
- Pulse removed-> Atoms spin back and release energy
- Energy converted to image by computer
Give advantages and disadvantages of MRI
Give uses as well
Pros:
- No Radiation
- Good contrast resolution
Cons:
- Expensive, Loud, Time consuming
- Patients May not fit/ be claustrophobic
Uses:
- Bones, Brain, Circulatory System, Organs
Compare T1 and T2 MRI scanning
T1:
Fat appears white, Water appears black
T2:
Water appears white, Fat appears black
- T2= High signal H2O
What is Positron Emission Technology?
What is it often combined with?
Where is it used?
What are “hot spots”
- Radionuclides decay, emitting positrons
- Often combined with CT/ MRI
Hot Spots- Areas of High Glucose Metabolism
Used in Oncology
How does an Ultrasound work?
How do you determine Distance and Impedance?
- High frequency sound waves reflected by tissues where density (Impedance) differs
- Reflected waives detected by probe
Distance: Time taken for waves to return
Impedance: Proportion of waves that return
Explain Hyper, Hypo, Anechoic in an Ultrasound
Hyperechoic: More waves reflected= White
Hypoechoic: Less waves reflected= Grey
Anechoic: No waves reflected= Black
Explain how the Doppler Effect is used in Ultrasounds
Blood coming towards you: Increased frequency
Blood going away from you: Decreased frequency
Give advantages and disadvantages of Ultrasound
Give uses as well
Pros:
- Cheap, portable
- No Radiation
- Real Time image
Cons:
- Depends on operator
- Can obscure deep structures
- Low resolution
Uses:
- Pregnancy
- Body cavities
- Solid Organs
What is Radiology?
Science of medical imaging used to treat/ diagnose using ionising radiation
What are contrast media and when are they used?
Substances used to help distinguish tissue types
Fluoroscopy
CT, MRI
Arteriograms
Compare Positive and Negative contrast media
Give examples
Positive- Show up as white on scan (Barium, Iodine)
Negative- Show up as black on scan (Water, CO2, Air)
What are the ideal factors for contrast media to be effective?
- Low osmolality and viscosity
- High water solubility
- Biologically inert
- Chemically stable
- Cost-effective
How can contrast media be administered?
- Orally
- Rectally
- Intravenously
- Into cavities
How is contrast media excreted?
What is it’s half life?
- Gomerular Filtration (requires good kidney function)
- 30 to 60 mins
Compare the two types of side effects of contrast media
Idiosyncratic:
- Unpredictable, within 20 mins
- Can be Mild, Moderate, Severe
Non-Idiosyncratic:
- Predictable
- Delayed Reactions of 30 mins to 7 days
