MSK Imaging Flashcards
How much radiation from an X-ray gets scattered and could pose a harm to other individuals in the room (who are not the patient)?
10-20%
X-ray projection (aka the color that shows up on film) depends on what?
thickness of the material that is to be penetrate
When there is no tissue to penetrate (aka air), the corresponding picture on x-ray will be what color?
black
As tissue becomes more dense/thicker, how does the corresponding picture on x-ray correlate?
the greater the depth/density, the lighter the grey (bone shows up light grey, metal shows up white)
What is fluoroscopy?
it is a type of imaging format that uses continuous x-ray imaging to create a real time look into internal structures
When is fluoroscopy imging used?
useful for dynamic procedures such as injections (joint injections to see where the needle is, etc), biopsies, angiograms (intavascular such as procedures in the cath lab), and gastrointestinal evaluations.
How much radiation does fluroscopy imaging use?
uses continuous radiation, so be mindful of the duration of time you are using it for
What is a CT?
essentially a rotating x-ray
what is the advantage of using a CT?
Able to measure and display varying x-rays attenuations of the tissues in a section of the body by passing x-rays through the section from many different angles then using computers to reconstruct the image you see
what are the strengths of CT?
- fast
- good resolution of bony lesions
- less epensive than MRI
what are the weaknesses of CT?
- ionizing radiation
- expensive
- poor soft tissue contrast
- tissue densities behind vdry dense tissue distorted
What does “MRI” stand for and how does it work?
MRI= Magnetic Resonance Imaging.
Magnetized polarized photons release energy that gives the computer information on tissue densities and can translate that information into an image.
What is MRI best used for?
soft tissue imaging
What are “T1” weighted images?
- General rule: good for visulaizing normal anatomy.
- T1 refers to how quickly it can become magnetized
- results in
- fat relatively bright
- water relatively dark
What are T2 weighted images?
- General rule: good for detecting pathology (can better visualize edema in the tissue)
- How quickly it loses its magentization
- results in
- fat relatively dark
- water relatively bright
Mneumonic for T2 weighted images
World War 2
WW= “Water is White on T2”
What are the strengths of MRI imaging?
- Strengths
- no ionizing radiation
- entire cross-sections without interference
- superior soft tissue contrast
What are the weaknesses of MRI imaging?
- Weaknesses
- subject to motion artifact
- inferior to CT in detecting acute hemorrhage
- Inferior to CT in detection of bony injury
- requires prolonged aquisition time for many images (takes a long time)
What are MRI/CT arthrograms used for?
a contrats medium is injected into a joint to detect tears in labrum or cartilage
What is an ultrasound?
- type of imaging that works by sending sound waves out of a transducer, and creates an image based on the waves coming back
What does the term “echogenicity” mean when refering to ultrasound?
a measure in the qulaity/strength of reverberation/vibration that is coming back from those vibrations
hyper-echogenicity=”whiter”
hypo-echogenicity= “darker”
What is a DEXA scan?
- readiograph tube generates photon beams of two different energy levels, thus the term “dual-energy”
- the difference in attenuation (reduction in intensity) of the two photon beams as they pass through body tissue of variable composition distinguishes bone from soft tissue and allows quantification of bone mineral density (BMD)
- T-score, the value used for osteoporosis
- z-score, used to compare a patients BMD to a population of peers
When ordering an x-ray, how many views should you get?
multiple. you need more than one 2D picture to figure out what is going on.
what the difference between an “open” fracture vs a “closed” fracture?
- open fracture (compound)
- has penetrated skin
- think “open to air”
- closed fracture
- bone has been fractured yet has not penetrated the skin
What is the risk associated with an open fracture?
risk of infection to bone is increased (osteomyelitis)
Greenstick fractures are common in what patient population?
pediatrics
Describe the SALTER Harris classification system
- Describes the fracture in relation to the growth plate. This is important because the patient is still growing and this can cause limb length discrepancies if not treated correctly.
- See attached picture.
Which part of the bone is a Giant Cell Tumor found?
Epiphysis
What is the pathology behind Giant Cell tumors?
- multinucleate osteoclast-type giant cells (“osteoclastoma”)
- Localized but highly destructive resorption of bone matrix by reactive osteoclasts
- Benign, but locally agressive
What is the demographic for Giant Cell Tumors?
- seen in younger adults, 20-40 years old
- question stem may have a healthy young adult who fell and now has a leg fracture near the knee
Describe a Giant Cell tumor
- Most commonly:
- solitary
- at the end of long bones (epiphysis)
- often causes arthritis-like symptoms but patients mahy present with pathologic fractures
X-Ray finding for Giant Cell tumor
“Soap bubble” appearance in distal aspect of long bones
Describe an Osteochondroma
- most common benign bone tumor
- lateral bony projection of growth plate (continuous with marrow space) covered by cartilaginous cap
- most commonly arise from the metaphysis of long tubular bones, particularly around the knee
Name the pathology
Osteochondroma
What is the demographic for osteochondroma?
- most commonly:
- seen in men (diagnosed in late adolescence through early adulthood)
- solitary
- pedunculated and between 1-20 cm
- frequently diagnosed incidentally, but may present as a slow-growing mass which can be painful if it impinges a nerve or if the stalk is fractured
How are Osteoid Osteoma and Osteoblastoma alike?
they are both benign and have the same histology
How is Osteoid Osteoma different from Osteolastoma?
-
Osteoid Osteoma
- size= <2cm
- site of origin= appendiclar skeleton
- demographic= men in teens-20’s
- presentation= severe nocturnal pain
- ASA responsiveness= relieved by ASA and other NSAIDs
How is Osteoblastoma different than Osteoid Osteoma?
-
Osteoblastoma
- size= >2cm
- site of origin= posterior spine
- demographic= men in teens
- presentation= chronic pain
- ASA responsiveness= unresponsive to ASA and other NSAIDs
What is Chondrosarcoma?
- malignant
- produces cartilage
- most commponly in the axial skeleton (pelvis, ribs, shoulder)
- presents as painful, progressively enlarging mass
Name the Pathology
chondrosarcoma
What is the demographic of Chondromsarcoma?
- most commonly seen in men who are in their 40’s or older
What is Osteosarcoma?
- most common primary malignant tumor of bone
- produces osteoid matrix (mineralized bone)
- most commonly arise from metaphysis of long bones of extremities (frequently around knee)
- present as painful, progressively enlarging masses
What are the genetic mutations associated with Osteosarcoma?
mutations in RB (retinoblastoma) and TP53
That is the demographic for Osteosarcoma?
-
Bimodal age distribution
- <20 years old
- older adults
- most commonly seen in Men
- exposure to radiation
Name the pathology
Osteosarcoma;“sunburst pattern”, “Codman triangle” on plain film
Red arrow= Codman’s triangle
Yello arrow= “sunburst pattern”
What is Ewing Sarcoma?
- Malignant, primitive neuroectodermal tumor (PNET)
- Primitive round blue cells
- commonly arise from diaphysis of long tubular bones (femur) and the flat bones of the pelvis
- present as painful enlarging masses with the affected site oftem being warm, swollen, and tender
- frequently presents with systemic symptoms (ex: fever, malaise)
What is the demographic for Ewing Sarcoma?
- pediatric, caucasian
- most commonly seen in white boys <20 years of age
What is the genetic translocation associated with Ewing Sarcoma?
(11;22) translocation –> EWS-FL1 fusion protein
Name the Pathology
Ewing sarcoma
“onion skin” on plain film
may be described as: multi-laminal layering or multi-layer periosteal reaction
What is osteomyelitis?
- inflammation of the bone and marrow
- almost always secondary to infection (pyogenic bacteria and mycobacteria)
Name three pathways for organisms to reach bone:
- hematogenous spread
- extension from a contiguous site (surrounding tissue/joint)
- direct implantation (trauma or surgery)
Name the most common cause of pyogenic osteomyelitis. Name some special scenerios.
- staphylococcus aureus
- special clinical scenerios:
- IV drug user: staph aureus
- UTI-associated osteomyelitis: E.coli, pseudomonas, klebsiella
- neonates: H. influenzae, group B Streptococci
- Sickle cell disease: salmonella
- Sexually acitve young adults: N. gonorrhea
Presentation of patient with acute osteomyelitis
- presents with gradula onset of sx over several day
- may include dull pain at the involved site (not necissarily exacerbated by movement)
- involved site may be tender, warm, swollen
- systemic sx may be present (fever, chills)
- if the infection is at a joint and the joint capsule breaks–> septic arthritis secondary to osteomyelitis
What imaging modality would you order if you suspect osteomyelitis?
- less than 2 weeks with signs and sx of osteomyelitis
- X-ray
- if it looks like osteomyelitis on x-ray OR the pt has had sx more than 2 weeks
- MRI
Name the pathology
Osteomyelitis
black=air produced by bacteria
What is an indication of chronic osteomyelitis that shows up on x-ray?
remodeling
symptoms of osteoarthritis
- function-limiting knee pain
- effect on walking distances
- pain at night or rest
- activity induced swelling
- knee stiffness
- mechanical
- instability, locking, catching sensation
What is the pathology?
osteoarthritis
- joint space narrowing
- osteophytes
- eburnation of bone
- subchondral sclerosis
- subchondral cysts
Diagnostic criteria/symptoms with Rheumatoid Arthritis
- morning stiffness > or = to 1 hr
- swelling in > or = 3 joints
- Rheumatoid nodules
- radiographic changes of the hand including bony erosions and decalcification
- symmetric arthritis
- serum rheumatoid facotr
- arthritis of the hand (MCP, PIP) and wrist
- have > or = 4 of 7 criteria for a 6 week period
how does RA present on Xray? MRI?
- X-ray= periarticular erosions
- MRI= soft tissue inflammation and pannus
RA vs parvovirus
parvovirus will go away, RA is chronic
T Score in Osteopenia
L2-4 lumbar density 1 to 2.5 standard deviations (T score -1 to -2.5) below the peak bone mass of a 25 year old individual
T score in osteoporosis
L2-4 lumbar density >2.5 standard deviations (T score <-2.5) below the peak bone mass of a 25 year old individual
How do you clinically diagnose Osteoporosis ?
Decreased bone mass, all other labs normal
Name the pathology
osteoporosis
decreased bone mass, presence of vertebral wedge fractures
- pt presents with:
- arthritis in hands
- rash with silvery plaques on extensor surfaces
- dactylitis in hands (sausage fingers), nail pitting
- pencil in cup deformity on imaging
diagnosis?
Psoriatic arthritis
- An imbalance between osteoblastic and osteoclastic activity, causing an increase in disordered and structurally unsound bone mass
- elevated alkaline phosphatase with (usually) normal calcium and phosphorus
- mosaic pattern of lamellar bone on histology
- older patients
- radionuclide bone scan for staging
- increased risk of high output heart failure secondary to increased AV shunts
- increased risk of osteosarcoma
- increased head circumference
Paget Disease of the Bone
Radiology shows “subperiosteal bone resorption on the radial aspect of the middle phalanges”. What is the diagnosis?
Osteitis fibrosa cystica (due to hyperparathyroidism)
What is Osteopetrosis?
- A group of diseases characterized by:
- a reduction of bone resorption
- diffuse, symmetric skeletal sclerosis secondary to impaired osteoclasts
- mutation in carbonic anhydrase II
- pts may be asymptomatic or present with fracture, pancytopenia, extramedullary hematopoiesis
what is this?
osteopetrosis
“bone in bone”
