Test 1 Flashcards
• Examples of ionizing radiation for imaging:
X-rays
• Computed Tomography (CT)
• Bone Mineral Density scans (DEXA
“Reflective” imaging:Examples
Ultrasonography (sound waves)
• MRI (radio frequency waves)
Emitted energy imaging examples?
radionuclide scans (bone scans, tagged RBC scan)
Thallium scans (functional cardiac imaging)
Positron emission tomography (PET) scan
The longer the wavelength the?
lower the energy
X-rays are generally in the wavelength range of
10-9
to 10-11 meters (.1-10 angstroms)
The shorter the wavelength, the
higher the
energy
Air, appears ? on the final x-ray image.
black
Bone therefore appears ? on the final x-ray image.
white
Fat is more dense than air, but far less dense than bone, so fat tissue appears
? on the final x-ray
dark gray
Water, which is the major component of soft tissue is much more dense than air or
fat, but less dense than bone, so water will appear ?
whitish gray
Substances that absorb x-rays are called
radiopaque
Radiopaque substances will appear ? on the x-ray images.
white
Substances that allow more x-rays to pass through are called ?
radiolucent
• Radiolucent substances will appear ? on the final x-ray images.
darker
something further away on xray appears
larger (magnified)
the body part of interest needs to be
closest to the film or detector
objects closer to the film or detector will be
sharper and better defined
objects farther away from film or detector will be s
blurred, or have less precise edge
One structure may obscure another by eliminating contrast at the edges, a
phenomenon called
“silhouette sign”
• Exposure depends on two things:
energy of the x-ray and exposure time
higher kVp means higher energy of the x-rays,
• Milliamps,(mA): corresponds to the quantity of x-rays produced
how to control scatter?
KVP, grids, air gap
X-rays are excellent tools for
Fractures and dislocations
infections
neoplasmsw
• Some organs are known to be more sensitive to radiation effects than others:
Thyroid • Breast tissue • Gonads and reproductive organs eyes, skin, bone marrow, and vascular structures
Lesions involving new bone formation
• Increased density (radiopaque)
Blastic lesions
Reactive bone from any process
• Reparative phase after a bony injury
fracture naming conventions
site (distal, proximal, midshaft
Extent
• Complete, incomplete, comminuted
Type
• spiral, transverse, buckle or torus
•
Alignment and displacement of fracture fragments
- Direction of fracture lines
- Special features
- Associated abnormalities
how does cortical bone heal?
• Large hematoma, external callous, fluid matrix, periosteal sleeve
how does cancellous bone heal?
• Internal callous, better vascularity usually, faster healing
promotes healing?
good immobilization
- growth hormone
- thyroid hormone
- calcitonin
- insulin
- vitamins A&D
- hyaluronidase
- electric currents
- oxygen
- physical exercise
- young age
retard healing
- motion
- corticosteroids
- anticoagulants
- anemia
- radiation
- poor blood supply
- infection
- osteoporosis
- osteonecrosis
- comminution
- old age
Expected Fracture Healing Times
metacarpal
4-6 wk
Expected Fracture Healing Times
metatarsal
4-8 wk
Expected Fracture Healing Times
distal radius (extraarticular)
6-8 wk
Expected Fracture Healing Times
distal radius (intrarticular)
6-10 wk
Expected Fracture Healing Times
humeral shaft
12 wk
Expected Fracture Healing Times
femoral shaft
12 wk
Expected Fracture Healing Times
radius and ulnar shaft
16 wk
Expected Fracture Healing Times
tibial shaft
16-24 wk
Expected Fracture Healing Times
femoral neck
24 wk
Expected Fracture Healing Times
femoral neck
24 wk
Epiphysis remains intact
• Prognosis is good with treatment
• Salter-Harris Types I and II
Epiphysis is injured
• Prognosis is poorer, therefore repair must be more precise to prevent growth
abnormality
• Salter-Harris Types III and IV
Crush injury
• Usually occurs along with one of the types I-IV.
• Prognosis poor even with repair.
type V
for salter harris injuries the test of choice for diagnosis is?
plain x-ray
The biggest advantage of CT over plain radiography is
markedly enhanced detail of
the final image, especially for soft tissue structures (compared to plain films)
• Although ? (see next section) is still the best modality for soft tissues
MRI
“Slice thickness” (thickness of the plane that is in focus) can be variable. For most
CT images it is usually between
1-20 mm
can detect occult pneumothorax or effusion?
CT
CT has to use contrast to see ?
vascular
Slit length determines the width of the section to be imaged in relation to the long axis of the whole part being imaged. In other words, this determines how wide a slice through the body is obtained on a given CT scan. • Think of it as if the body is being sliced into pies. • Slit length determines how thick each entire pie is.
Shorter slit length results in narrower
pies, meaning there is higher
discrimination (you can see the pie
filling better)
Slit width determines the size of the slice of
tissue plane imaged with each beam of x-rays.
• In other words, how wide or narrow are the
slices in each pie.
•
Again, smaller width usually means more
detail, because the pie slices are narrower, but
also means more slices per pie (images per
slice) and therefore more radiation exposure
(x-ray absorption or transmission) of each pixel is averaged
by the computer from the multiple images that contain the spot that
corresponds to that pixel.
attenuation
average attenuation is called the ???, and is
applied to each of the pixels that make up the final image
“attenuation coefficient”
• This is a “grayness” scale that extends from -1000 to +1000
• Hounsfield scale:
• ? density is assigned a value of -0-, and defines the midpoint of the scale
Water
• ? is the least radiodense substance, and is assigned a value of -1000
Air
• Very dense ? is the most dense, and is assigned a value of +1000
bone
A bone window, for example, may set water (0 Hounsfield units) as completely
black, and shades of gray for everything above it.
Likewise a lung window may set water (0 Hounsfield units) as completely
white, allowing better grayness discrimination for less dense structures as seen
in the lungs
• With contrast, CT is excellent for visualizing details of vascular structures • CT angiography is the test of choice for ?
pulmonary embolus detection
Excellent modality for detecting fresh blood in tissue spaces (fresh blood has
an extremely high Hounsfield coefficient, but this decreases as clot formation
progresses )
• Non contrast CT is the test of choice for detecting
intracranial bleeding
non contrast CT Also excellent for
soft tissue hematomas
non contrast CT Also excellent for
soft tissue hematomas
• CT is excellent for observing fine detail in areas with high contrast:
Soft tissue masses in lungs
• Pneumothorax in lungs
• Calcification in muscle or brain, etc..
(“wobbles”) about the axis of its magnetic vector, the way that a
spinning top precesses as it spins
precesses
• It must be the EXACT frequency (energy level).
Larmor frequency
• This released energy is referred to as their ??, and this can be measured.
echo
This return to original state is referred to as
T1
which represents the return to
longitudinal equilibrium with the external magnetic field (parallel/antiparallel)
T1
When these transverse (xy plane) vectors reach a certain percentage of their original state (67% to be exact), this is designated as.
T2
• T2 is far more dependent on the local environment than T1
• T2 is always shorter than T1
represents decay from high energy state to low energy state, and is a function
of loss of energy
T1
is often referred to as the thermal relaxation time or spin
lattice relaxation time.
T1
though is not a return to a resting energy state, but a loss of phase coherence
between adjacent protons
T2
is sometimes called the spin-spin relaxation
time.
T2
time to repetition
• The time between subsequent RF pulses which are given in sequence
TR=
time to echo
• Time from application of a radiofrequency pulse to peak echo signal
TE
• ?? will be longer in tissue that contains more water.
T1
?? weighting uses shorter TR and TE, causing tissue with more water to
appear darker, and tissue with less water to appear brighter
T1
bone marrow is much whiter on
T2
CSF T1?
BLACK
CSF T2
WHITE
• Fat T1
white
Fat T2
black/dark gray
CNS gray matter T1
dark gray
CNS gray matter T2
light gray
Cns white matter T1
light gray
Cns white matter t2
dark gray
Cns white matter t2
dark gray
soft tissue edema t1
dark
soft tissue edema t2
light
acute stroke t1
dark
actue stroke t2
light
T1 shows usefulness for?
acute hematoma
fat yellow marrow
lipoma
T2 shows useful for
chronic hematoma
fluid/edema
soft tissue tumors
bone marrow is seen well on
MRI
• This is an imaging technique that can assess function as well as anatomy
PET scan
• Usually, Fluorine-18 labeled Fluorodeoxyglucose
PET SCAN
is used, usually in conjunction with a CT scan, to detect
metabolically active disorders, such as:
• Cancer or metastases,
• Or to assess metabolic activity of tissue
• CNS in Alzheimer’s
• Cardiac blood flow in certain types of ischemic heart disease
pet scan
-Sound waves are transmitted through the structure, and not
reflected back to the sound transducer.
• Area will appear black on the image
• Most air or fluid filled structures such as cartilage or joint effusions
anechoic
structures with low level echos.
• These appear gray on the final image, and include muscle, synovium,
nerve structures
hypoechoic
denser structures that are more reflective of sound waves
• Appear bright or white on the USG image
• Bone, tendon, foreign bodies, areas of calcification
hyperechoic
acoustic “void” that appears behind a very reflective object
shadowing
Occurs where highly curved surfaces distort or block sound transmission
• Gallbladder, long bone diaphyses, intermuscular interfaces
refractile/critical angle
Useful for cyst identification
ultrasound
useful for real time vascular imaging
• Carotid, cardiac, peripheral arteries as well as veins
ultrasound
• Real time localization of fluid and abscesses
in ED- cardiac tamponade, pleural effusions, ascites
• in clinic- joint effusions, abscesses
ultrasound
Distends joint capsule
• Helps mobilize capsolabral sleeve
• Highlights cartilage defects
Arthrography-
• Screening recommended for those with risk factors for osteoporosis
Bone Mineral density imaging
Less than 2.5 standard deviations below
mean= high fractures risk, with treatment
recommended
• DEXA: Dual Energy X-ray Absorptiometry
• Useful for detecting metastatic cancer and for staging primary tumors
and for fracture age
bone scan
Complex regional pain syndrome (RSD)
• Metabolic bone abnormalities such as Paget disease
bone scan
• C1 does not have a vertebral body.
Stabilization of C1 depends on:
• Transverse ligament
• Facet articulations with C2.
• There is no intervertebral disk between C1 and C2
• The transverse ligament of C1 is anchored to the odontoid
American College of Radiology (ACR) Guideline to the Performance of Spine
Radiography: Indications for imaging:
- Pain or neurologic symptoms
- Spinal trauma
- Surgical planning
- Previous surgery, follow-up or suspected complications
- Neoplastic (benign and malignant) lesions
- Congenital anomalies
- Previously detected abnormality
- Alignment abnormalities
- Infection
- Arthropathy
- Degenerative disorders
- Spine instability or limitation of motion
- Osteoporosis
Complete cervical series should include:
• Routine:
- AP
- Lateral
- Open mouth odontoid views
- Complete cervical series should include:
* Trauma patients:
- AP
- Open mouth odontoid
- Cross-table lateral before moving the patient
- If the spine cannot be adequately examined, obtain CT or MRI
c-spine • When assessment of the neural foramina is necessary.
• Bilateral oblique views
c-spine• Assessment of the facets, particularly following trauma
• Pillar views
c-spine• When assessment of cervical instability is necessary
• Neutral, flexion, and extension lateral views
Oblique views are done whenever there is any suspicion for
neuroforaminal
stenosis
With lateral views, it is absolutely necessary to see
• If not the view is inadequate:
all 7 cervical vertebrae, and the
superior end plate of T1
•??? is usually the image of choice to visualize C7-T1.
A swimmers lateral view
??? should be obtained in trauma patients if a swimmers view is not
available or attainable
CT
SCIWORA-
Spinal Cord Injury Without Radiographic Abnormality
• Special case occurring in trauma patients, especially children
AP cervical spine films are obtained with patient sitting
or standing The X-ray beam directed toward
C-4 (about Adam’s
apple level)
AP C-SPINE is used to assess the anteroposterior portion
of
C3-C7.
AP Difficult to assess cartilage on this view,
??? is better
lateral
hyperextend the neck
• May occasionally be done when an unobstructed view of the odontoid is absolutely required
Fuchs View
usually the most informative cspine
view
lateral
Straightening of the normal lordotic
curve may indicate ???, associated with occult injury
cervical muscle
spasm
Reversal of the lordotic curve, or
kyphosis may indicate???
an unstable injury
The atlanto-dens interval, ADI, (distance
between the anterior ring of C1 and the
odontoid process) must be no more than ???
3
mm
• A wider ADI indicates ???
C1-C2 instability
Look for soft tissue swelling in the retropharyngeal
tissue anterior to C2.
• Normally, the soft tissue in this area is ????
in width.
< 7 mm
Similarly, look at the soft tissue in the retrotracheal
space at C6-7
• Normal soft tissue thickness at this level is ???
<22
mm
They are taken with the patient rotated 45
degrees to the plane of the film/detector
Oblique views
• T- spine is a common location for
metastatic cancer
standard exams for thoracic spine?
AP
lateral
t-spine lateral view Technique similar to lateral CXR:
• Patient erect, arms elevated• X-ray focused at ?
T-6 level
•lumbar standard examination includes :
• AP and lateral (or PA and lateral)
In general clinical practice for most adults, five standard views are usually obtained: l-spine
AP • Lateral • Right and left obliques • Cone down sacral view • Oblique views
• lumbar AP X-ray beam directed at the ?
mid-abdomen
lumbar later view • X-ray beam directed toward
L3
Particularly useful for evaluation of the zygoapophyseal joints
• Best views to assess spondylolysis and spondylolisthesis.
oblique
oblique view l-spine Side-lying with knees & hips flexed and rotated 45 degrees
• Beam directed toward L3
*only thing that moves is the patient
oblique view l-spine Side-lying with knees & hips flexed and rotated 45 degrees
• Beam directed toward L3
*only thing that moves is the patient
Scotty dog eyes:
• Pedicles:
Scotty dog ears:
superior
• Scotty dog legs:
inferior
• Scotty dog tail:
superior process,
opposite side
• Scotty dog nose
Transverse process
scotty dog neck
par interarticularis
scotty dog wearing collar =?
spondylolysis
scotty dog decapitated?
spondylolisthesis
Sensitivity about 70%/specificity about 90% for fracture, OA and osteonecrosis
of the HIP
CT is much more sensitive for fracture and osteonecrosis (approaching 100%)
test of choice to confirm osteonecrosis (specificity ~100%, but sensitivity
only about 38%) of the HIP
MRI
American College of Radiography (ACR) recommends the following views for hip?
AP LATERAL (frog leg or true lateral)
American College of Radiography (ACR) recommends the following views for the pelvis?
AP
American College of Radiography (ACR) recommends the following views for the femur?
ap
lateral
• Shows femoral head and neck and greater and lesser trochanters
FROG LEG
Inferior lip of the anterior surface of
acetabulum
radiographic u
ilioischial line,
acetabular articular surface, and
radiographic U sign
teardrop
Imaginary line formed along the inferior border of the superior pubic rami
(superior border of the obturator foramen) and along the inferomedial
border of the femoral neck
shenton’s line
Same patient position as AP
• X-ray tube angled about 30
degrees cranially
for the hip?
ferguson view (pelvic inlet)
Technique is similar to Ferguson view, but x-ray tube is angled about 60
degrees
pelvic outlet
• AP view taken with patient in a 45 degree oblique position of the hip?
Affected hip anterior gives better view of anterior column and posterior
acetabular rim
Affected hip posterior shows better visualization of posterior column and
anterior acetabular rim
judet vidw
