Medical Imagining Flashcards
When is imaging not needed?
- when the image will not change the treatment
- when there is no treatment available
- when the patient will not consent to the treatment
When is imaging needed?
there are different scales and rules used to determine a patient’s need for imaging
- Canadian C-spine rule
- Ottawa ankle index
- Ottawa knee index
- nation emergency X-ray utilization study low risk rule
What are some factors for decision making according to the American college of radiology appropriateness criteria?
- age
- individual risk facttors
- trauma presence/absence: physical appearance
- mechanism of injury
- neurological status/deficits
- prior surgery
- pain provocation/reduction of physical functional tests
- other imaging results
- weight bearing ability
- tenderness to palpation
Radiography
X-rays
- produce analog or digital image
- ionizing radiation (what can cause cancer)
- what to keep it to ALARA (As Low As Reasonably Available)
What are some factors to consider when keeping the radiation of an X-ray ALARA
- intensity of radiation
- number and types of images (most cases need 2)
- distance from beam
- patient shielding
X-Rays: How can they are affect the body and how are the images produced?
- can ionize matter/change cellular function
- can disrupt cellular processes
- can be used to produce an image through attenuation
Attenuation
- Occurs as X-rays passes through the body
- reduction in number of x-ray photons in beam
- occurs as photons interact with matter
- the photons will scatter which is dependent on density of tissue
- photoelectric absorption
Attenuation radio density of tissues: rank from least dense to most dense
- air
- fat
- water
- bone
- metal
Other shades of imaging: contrast images
- positive vs negative contrast
- Contrast images: something is ingrested or injected to show certain tissue
- Eg: barium
- makes soft tissue more visible on radiograph
- positive contrast media,show up/lights up
- negative contrast such as air shows up black
Other shades: metal
- surgical metal
- accidents, trauma (GSW)
- the thickness affects the radio-density such as edges of bones are not as dense as the middle
What are the different views that can be used for radiography
- anterior-posterior (enters anterior exits posterior)
- posterior-anterior (enters posterior/exits anterior)
- lateral (left or right)
- 2 oblique views
describe the lateral views
- left lateral: enters right and exits left
- right lateral: enters left and exits right
what are some considerations when looking at a radiography
- distortion
- exposure
- contrast
- motion
Osteoporosis in an image
- edges have high density
- grey on the inside
- decrease in bone density means they are more likely to sustain a fracture
Ankylosing Spondylitis
- fusing of the spine with inflammation
- an inflammatory process that caused the spine to fuse
CT/CAT scan
- computed axial tomography
- cross-sections slices
CT uses
- subtle and or complex fractures
- degenerative changes in bone and joints
- serious trauma (can image bone and soft tissue)
- spinal stenosis (impingement of spinal nerves)
- intervertebral disk
- loose body in joints
- bony alignments in any place
CT imaging
- acquired?
- density
- slices thickness
- images can be acquired in coronal, sagittal or axial plane
- image density can be selected to emphasize soft tissue or bone
- thickness of slices can allow for more detailed views of structures
CT vs MRI
- CT is faster
- less incidence of claustrophobia
- less expensive than MRI
- MRI is better at looking at differences in soft tissue
- MRI does not use radiation
MRI: How it works?
- uses protons in hydrogen atoms in the patients body and an electromagnet to produce an image
- hydrogen found in body in
~free water in body fluids (CSF)
~ water bound to large molecules like proteins
~hydrogen atoms in fat
What are the types of MRI imaging
- T1
- T2
- others: FLAIR, SPIN, STIR
T1 MRI
- shortest acquisition time
- can see fat, acute hemorrhage will appear brightest (highest signal intensity)
T2 MRI
- longer acquisition time
- can see free water with inflammation, tumors, synovial fluid, CSF will appear brightest
Other types of MRI: FLAIR, SPIN, STIR
- used for specific diagonostic purpose eg CNS and brain injury
Clinical uses for MRI
- excellent for soft tissue assessment
- musculoskeletal and sports injury
- can assess integrity of tendons, ligaments, menisci
- bone marrow changes, eg. neoplasm, stress fracture, avascular necrosis
- disc herniation, nerve root impingement
Limitations to MRI
- time: takes a long time 40 min. to an hour
- expensive
- availability is limited
- contraindications: any ferrous metal in body risks injury or death
- precautions: pacemaker, claustrophobia
Iodine-containing contrast medium
- used for X-ray and CT to better view soft tissues
- Oral, IV, injection or other
- cautions: for Iodine-containing contrast medium
- patients with reduced kidney function (contrast-induced nephropathy/kidney disease)
- patients with iodine allergy (mild to severe)
- elimination is through the kidney and can damage it
Gadolinium-based contrast
- 1 in 3 MRI use contrast
- given through IV
cautions for Gadolinium-based contrast
- patients with reduced kidney function (nephrogenic systems fibrosis)
- less risk of allergic reaction than iodine
- elimination in about 24 hours
Other medications that can be used with
1. CT or MRI
2. CT with contrast
- medication to reduce anxiety or claustrophobia
- steroid if previous allergic reaction
Ultrasound (MSKUS)
- can be used instead of MRI to assess soft tissue
- uses sound waves
- other healthcare workers can do it
- can vary in time
Ultrasound advantages
- portability, ease of use, lower cost
- no known contraindications
- movement is not a concern
- quick comparison to opposite side
- high resolution
- can follow a structure from beginning to end
- shows internal architecture of muscle tendon, and ligaments better than an MRI
Doppler US
- evaluates blood flow
- vascular for blockage
- DVT diagnosis
- cardiovascular
- joint capsule
Abdominal US
- used to assesinternal organs
- complete abdominal US also includes
1. kidney
2. spleen
3. bladder
4. abdominal blood vessels
- Right upper quadrant
- right lower quadrant
- left upper quadrant
- left lower quadrant
- liver, pancreas, gallbladder, duodenum, right kidney, hepatic flexure
- cecum, appendix, right ureter
- stomach, spleen, left lobe of liver, left kidney, spleenic flexture
- descending colon, sigmoid colon
Abdominal ultrasound common conditions
- bladder stones
- gallstones
- cholecystitis: gallbladder inflammation
- enlarge spleen (splenomegaly)
- pancreatitis
- cancer (stomach or pancreatic)
- fatty liver disease
- abdominal aortic aneurysm
Arthrography
can identify abnormalities of synovium, ligaments, articular cartilage and joint capsule
Myelography
- generally used to look at things with the spine
- type of X-ray
Tomogram
- used before CT
- X-ray tool that can be moved
Nuclear Medicine
- uses a radioactive substance called a tracer
- the tracer is administered to the patient with injection, inhalation, or ingestion
- the tracer allows for evaluation of the function of a specific organ
- image produced using a gamma camera
- can create static or moving images
(look at things like how blood is flowing through an organ or the GI tract
Nuclear medicine types
- bone scan/bone scintigraphy: looks for areas of hyper function, increased mineral turnover (new bone being laid down)
- positron emission scan (PET scan) : mostly in neuro
- single positron emission CT (SPECT): used for detecting small abnormalities in bone, heart, brain, or liver (organs)
What is interventional radiology
- epidural steriod injections
- spinal nerve blocks
- radiofrequency ablation (heart surgery to get rid of excess tissue)
- percutaneous needle biopsy (through the skin)
- vertebroplasty, kypoplasty (plasty means repair - these are postural repairs)
