Radiographs & Other Medical Imaging Flashcards
What do PTs look at x-rays for
Body alignment
fracture configuration
X-ray wavelength to energy relationship
indirect
shorter wavelength = higher E and greater penetration of dense substances
What is needed to produce a radiograph?
X-ray beam source
patient
x ray film/image receptor
T or F: X ray film cassettes have many layers
True - as the x-ray passes through it forms the image w/cassette at the bottom
How does the x-ray tube work
It is a cathode and anode enclosed in glass envelope to maintain a vacuum w/electrodes driven from cathode to strike the anode to create the x-rays via energy consumption
Define attenuation
gradual loss of intensity as a result of passing through a medium (human body)
How is a radiograph made?
Current beamed through shutteres through the body to undergo attenuation, it is absorbed by the body and then the x-ray is sensitive to light and radiation and chem rxn occurs causing the image to be produced w/final radiodensity represented
What is radiodensity?
The amount of blackening on the radiograph determined by atomic weight and thickness of an object
What is radiolucent?
Black on x-ray due to not absorbing much radiation
What is radiopaque?
white on x-ray due to absorption of radiation
What is the density of tissues from radiolucent to radiopaque?
Black (radiolucent) - air - fat - water - soft tissue - bone - heavy metals White (radiopaque)
relationship of thickness and radiodensity
more thick = more radiopaque
T or F: Enough info is received from a 2D radiograph
FALSE! need to take two projections at 90 deg from eo
What are the main body positions for getting an x-ray?
AP (source from top w/cassette underneath person)
Lateral
Oblique
What structures are seen well w/PA approach (x-ray)?
The lungs
What structures are seen well w/AP approach(x-ray)?
Spinal structures
When do you use a tangential or “sunrise” x-ray?
patella view
What is important to know when looking at an x-ray?
- you are the x-ray beam
- consider anatomy
- closer to film = more accurate picture
what kind of markers are on an x-ray?
- Pt ID
- Anatomical Side
- INT or EXT
- WB/NWB
- erect or decubitus (laying)
- INSP or EXP
- radiographers initials
What is the general rule for contrast?
Use the highest kVp (Energy) and lowest mA (miliamperage) to yield the best diagnostic info necessary for pt intervention
What is the primary controlling factor for detail?
Motion!
What factors can blur an x-ray
- MOTION
- beam source diameter
- distance b/t source and film
- distance b/t beam and pt
What is the distortion of radiographs and causes?
30% larger than actual structure and can be enlargement elongation or shortening from: beam pt film alignment position of the central ray
What is enlargment
Distortion of x-ray bc the beam ray is too wide or the patient is too close
What is elongation/foreshortening
Distortion of x-ray from it being on an incline and not hitting the tissue evenly
What is superimposition?
When anatomic structures are stacked the x-ray must penetrate multiple structures which may create artificial lines, shapes, and foms
What are the ABCD’S of radiographs?
Alignment Bone Density Cartilage Space Disc Space Soft Tissue
What is the A of ABCD’S (x-ray)
Alignment
- look at general structural arcitecture and contour of bone as well as the alignment of bone relative to adjacent bones
What is the B of ABCD’S (x-ray)
Bone Density
- general bone density, local bone density changes, and texture abnormalities
- more grey = possible fracture
What is the C of ABCD’s (x-ray)
Cartilage Space
- joint space width
- subchondral bone
- epiphyseal plates
- uniform distance
What is the D of ABCD’s (x-ray)
Disc Space (for vertebrae)
What is the S of ABCD’S (x-ray)
Soft Tissue
- mm
- fat pads
- joint capsules
- periosteum
- other
What are contrast-enhanced radiographs?
Medium injected or ingested to improve visualization in areas w/low contrast that can be radiolucent or radiopaque
What is the main difference b/t computed radiography and traditional x-ray?
It uses a phosphor imaging plate that stores the radiation level, is scanned in, which is then converted into an electric signal that can be viewed as an image
Advantages of CR
- less expensive
- no silver-based film (more environmentally safe)
- easier to store
- faster acquisition
- can adjust exposure
Disadvantages of CR
- requires handling & can be erased if exposed to fluorescent light
- very expensive
- geometric sharpness less than conventional
- lower resolutoin
What is the main difference of Digital Radiography and x-ray
Does not use a processing agent but a digital receptor
What are the advantages of DR
- manipulate acquired image to produce alternatives (contrast and brightness)
- spatial resolution can be maximized
- can use subtraction technique to isolate what you want
What are disadvantages of DR
- expose to more x-ray than necessary
- not as affordable as a CR system, higher costs because the existing systems
What is tomography?
An x-ray tube and the film move about a fulcrum so that just a specific plane or slice of the body is in focus (where they overlap) w/all else blurred computerized or conventional
What are the advantages of tomography?
- can more clearly see fx of irregular shaped bones
- no superimposition and focused on what you want
What are the disadvantages of tomography?
- poor soft tissue detail
- higher radiation doses
- difficult to get exact plane/image esp w/trauma pts
What is computed tomography?
A thin x-ray beam rotates around an area of the body to generate a full 3-D image of the internal structures
What is CT the first choice for?
Serious trauma as it can view both bone and soft tissue injuries
What are limitations of CT?
- average volume effect (computer displays only one shade of grey even tho its multiple tissues)
- similar exposure to x-ray
- better in thinner pts
CT is good for?
- bone and soft tissue tumors
- fx (and fragments)
- intra-articular abnormalities
- degen. changes of bone
- mineral analysis
- spinal stenosis
- less time consuming and more cost effective than an MRI
What are the components of fluroscopy?
X-ray tube
Image intensifier unit
Fluoroscopic carriage
What are advantages and disadvantages of fluoroscopy?
Adv: patient is moving, low cost
Dis: radiation
What are the components of an MRI?
- radiofrequency signals
- magnetic field
- computer to capture proton energy reaction moving back to realignment
What is the principal element used in an MRI?
Hydrogen (has a single proton) that lines up either parallel or anti-parallel to the magnetic field
What is Te in a MRI?
Time to echo: time at which the signal is captured
What is Tr in a MRI?
Time to repetition: time at which the RF is repeated which displaces the protons again
What contributes to the image creation of an MRI?
Tissue relaxation properties, both T1 and T2 each characterized by the timing of events done during image acquisition
What is a T1 image MRI?
Short TR and TE times
- Fat = bright
- water= dark
- bone = dark
- early signal
- good for anatomy review
What is a T2 image MRI?
Long TR and TE times
- fat = dark
- water = bright
- bone = lighter
- late signal
- good for pathology
Advantages of MRI
- no radiation
- greater ability to image brain and SC
- ST eval of brain and body is superior
Disadvantages of MRI
- not as quick to admin as a CT scan
- claustrophobia
- any ferrous metal can be displaced
- contraindicated w/pacemakers
Diagnostic Ultrasound
Examines the effect of injury or disease on mm, ligaments, tendons
Rehabilitative Ultrasound
Evaluates mm structure and behaviour and uses USI as a biofeedback mechanism that is aimed at improving neuromuscular function
Define ultrasound
Sound w/a frequency greater than 20,000 Hz
What is the piezoelectric effect?
Transducer collects reflected sound waves (echoes) and converts them back into electric signals
How does US work?
It sends out sound waves and converts them into electric signals which are then converted to a digital image based upon the echo strength
What is a MSK Diagnostic US
It looks at ligaments, tendons, nerves, mm, tumors, and foreign bodies
