Imaging Exam 1: 1.1-1.6?

what does the wisconsin state practice act say about PTs and imaging?

PT cannot administer roentgen rays or radium —> must create an order. cannot make medical diagnosis

what is the biggest barrier to PTs utilizing imaging?

lack of education/awareness

what is the value of medical imaging (structurally, statistically, professionally)?

structural: fx vs. dislocation, complexity of injury

statistically: appropriate imaging pathology

professionally: discuss orders, reordering imaging

what are the benefits of PT education on imaging?

reducing amount of radiographs ordered lowers costs, time, and radiation exposure. rapid results = fewer office visits

relevance of clinical decision making for imaging

important to evaluate MSK system well to determine need/value of imaging. do not rely on imaging

types of ionizing radiation imaging

radiography, CT, DXA

which imaging modality has the most exposure to radiation?

CT

types of reflective imaging

MRI, DUS

types of emission (nuclear) imaging

bone scan (scintigraphy)

tissues with the most density (radiodense) appear ____ on radiographs

lighter/white

five principle densities from least to most dense

1. Air/gas = black

2. Fat = dark grey

3. Soft tissue/water = light grey

4. Bone/calcification = white

5. Metal = bright white

what is the term for metal in radiology and what does it mean?

radiopaque = non-biological

what are contrast agents and what are examples?

used to enhance anatomy and demonstrate pathology. radiolucent contrast, radiopaque (positive) contrast

what does an OVERexposed radiograph look like?

too radiolucent → black. think burnt toast*

what does an UNDERexposed radiograph look like?

too radiopaque → white. think underwear*

what to watch for to limit image distortion?

static position (is the patient moving), central ray (central ray centered to the detector)

advantages of radiography**

rapid results, non-invasive, cost, excellent bone definition

disadvantages of radiography

ionizing radiation, contrast in bone density is limited, soft tissues poorly defined, superimposition, 2D image of 3D structure

what is ALARA?

As low as reasonably achievable → avoiding unnecessary radiation exposure

the patient’s ____ side is always facing you in a radiograph (L/R)

Left (except fingers & toes always pointed up)

why are some fractures commonly missed?

did not order radiography, did not see fx on radiograph, subtle fxs, distracting injuries

commonly missed fractures of the spine

C1, C2, C6, C7 & OP fx of the thoraco-lumbar spine

commonly missed fractures in the LE

Hip, patella, calcaneus (low density & fat pad), posterior acetabulum

commonly missed fractures in the UE

radial head, triquetrum, distal radius, scaphoid

what to do if radiograph is negative but you still suspect a fracture?

repeat imaging with new angles or advanced imaging

why don’t we order or make interpretations off of one radiograph view?

one view is no view

search pattern for radiographs (ABCS)

A: anatomic appearance & alignment

B: bone density

C: cartilage spaces

S: soft tissues

A: Anatomic appearance

general skeletal architecture, contour of bone, relationship to other bones

A: Alignment

look for continuity of cortical outline

B: bone density

assess general density for changes in cortical & cancellous bone, local density for sclerosis & coarsening

how to assess cortical bone density?

sum of cortical bone should be 50% of total bone width

C: cartilage spaces

assess for joint space narrowing, spurs, erosions, growth plates, intervertebral discs

S: soft tissues

muscle - wasting or swelling

fat pads - parallel to bone

periosteum - swelling/“lifting”, onion skin

how to identify sclerosis and coarsening of bone

sclerosis: bone build up

coarsening: dense trabecular bone appearance

what is the metaphysis?

widening near the end of long bones before epiphysis

fracture documentation includes:

name of bone, location, orientation, condition of overlying tissues, description

transverse fractures are ____ to long axis of the bone & results from ____ force

perpendicular, tension or bending

oblique fractures are ____ to long axis of bone and result from ____ force

oblique, twisting

spiral fractures result from what kind of force?

torsion

longitudinal fractures result from

axial compression

what is a communited fracture?

bone breaks into several pieces. high energy, more soft tissue involved & worse prognosis

open vs closed fx

open: skin is broken, high risk of infection or complications

closed: skin and soft tissues intact

what are pathological fractures?

occur secondary to underlying pathology or disease processes (infection, metabolic, medication)

what is an avulsion fracture?

ligament or tendon remains intact with bone but failure occurs at bone rather than soft tissue. has good healing potential

what is a stress fracture?

occur after repetitive trauma, ongoing attempted healing response from repeated loading can be visualized on imaging

what is an intra-articular fracture?

fx involves the joint surface

what is an impaction fracture?

long bone fracture that occurs when bones or fragments driven into each other

depression & compression fractures?

depression: type of impaction fx

compression: impaction fx in vertebrae

displacement vs angulation

displacement: loss of position & contact

angulation: loss of alignment, requires minimum 2 views to determine direction

dislocation vs subluxation

dislocation: loss of position when no contact between articulating surfaces

subluxation: partial articulating contact maintained

*types of pediatric fractures

green stick, torus (buckle), physeal (Salter-Harris)

greenstick fracture

breaks cortex on one side, causes plastic deformation (bending). “incomplete fracture”

torus (buckle) fracture

bony cortex in metaphysis is compressed and bulges resulting in bucking deformity. “incomplete fracture”

epiphyseal/physeal fractures

disruption or separation of epiphysis or epiphyseal plate. can cause premature closing of plate and growth abnormalities.

Salter-Harris Type I

complete separation of epiphyseal plate without a fracture

Salter-Harris Type II

separation of epiphysis with fracture of metaphysis

Salter-Harris Type III

fracture of epiphysis extending from plate through articulation surface

Salter-Harris Type IV

fracture extending through joint surface, epiphysis, plate and metaphysis

Salter-Harris Type V

crushing of epiphyseal plate, bone cannot grow longer

What does “Salter-Harris” stand for?

S: shear load/ straight across

A: angulation/ above plate

L: loss of cartilage/ lower than plate

TE: through everything

R: really poor prognosis/ crush

secondary healing - inflammatory phase

hematoma, removal of dead tissue, sharp fx line, soft tissue swelling

secondary healing - reparative phase 1

around weeks 2-8, larger fx line, soft callus: disorganized & weak remodeling

secondary healing - reparative phase 2

seen on radiograph around week 6, bony callus

secondary healing remodeling phase

callus of woven bone replaced by hard lamellar bone

what is the importance of clinical union in bone repair?

point where bone can be loaded and will result in better healing response. happens around week 8

indications for CT

high risk trauma, complex fx, subtle fx when radiographs (-), surgical planning, spine eval

advantages of CT

available, highly detailed anatomy, bone, no superimposition, less time, lower cost

disadvantages of CT

high radiation, less detail for soft tissue, costs more than rads

MRI is the ideal imaging modality for detecting ____ or ____ pathology

subtle, early. ex: stress fx, AVN, tumors

indications for MRI

Best for MSK soft tissues (tendon tear), can eval bone marrow, AVN, IVD pathology

advantages of MRI

no radiation, excellent resolution of soft tissues, stress fxs

disadvantages of MRI

cost, imaging time, patient comfort, bone resolution, ferrous metal, pregnancy safety

bone scintigraphy has ___ sensitivity and ___ specificity

high, low

indications for bone scan

tumors, bone metastasis, metabolic bone disease

advantages of bone scan

high sensitivity for bone metabolism changes, lower cost than MRI & CT, availability

disadvantages of bone scan

high radiation, residual radioactivity, low specificity, poor detail, time intensive

Dual-Energy Absorptiometry is important for determining…

healthy bone, osteopenia, osteoporosis

advantages of DEXA

minimal radiation, non-invasive, quick

disadvantages of DEXA

some ionizing radiation

indications for DUS

all soft tissues, nerves, feedback

advantages of DUS

no radiation, real time imaging, dynamic, low cost, portable/accessible, rapid

disadvantages of DUS

operator dependent, cannot use for fx unless displaced, may be hard with obesity

what is the scout image in a CT?

preliminary image taken at the beginning of CT mainly for positioning and gross anatomy

what is a “voxel” in CT

pixel x slice thickness

what is “windowing” in CT?

image processing technique that adjusts the contrast and brightness of a scan to highlight specific tissues

clinical uses of CT

bone: subtle or complex fxs, surgical planning, degenerative changes.

health of IVD, rehab planning

what is the workhorse of an MRI machine?

RF coils - produce and receive energy

how does MRI work?

magnet aligns protons → RF pulse → relaxation

high vs low signal intensity

high: bright/white

low: dark/black

TR & TE

time of repetition: tike when RF pulse is repeated to displace protons again

time echo: time when signal is captured

MRI T1 sequence

*anatomy*, short TR & TE, fat has high signal intensity

MRI T2 sequence

*pathology*, long TR & TE, water has high signal intensity

alternative MRI sequences

STIR: ideal for stress fx, everything black except water

Gradient Echo: CV imaging

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