Imaging - Advanced Imaging Techniques

Computed tomography (CT)

creates imaged using multiple x-rays (ionizing radiation) in cross sectional (axial) slices, created by up to 1,000 projections from different angles

During rotation around the patient the x-ray source produces a narrow, fan shaped beam of x-ray that passes through a section of patient's body

How does a CT scanner work?

detectors in rows opposite the x-ray source

What registers the image in a CT scan?

Scout image

two-dimensional digital radiograph produced by the CT scanner that is used to localize the structures to be scanned

sagittal

What view of a CT is this?

axial

What view of a CT is this?

coronal

What view of a CT is this?

reflection of tissue radiodensity without superimposition of other tissues

What do you see on a CT image?

to reduce the range of radiodensities displayed and focus on a particular tissue

Why would you window a CT image?

anatomy (larger for larger joints)

What is slice thickness dependent on?

volume is smaller

What does a thinner slice mean in terms of image volume?

Three-Dimensional CT

Multiplanar reconstruction

CT myelogram

injection of contrast material into the spinal fluid

Cone beam CT

single volume of data means shorter scanner time, less radiation (used in dental practice)

subtle or complex fractures

degenerative changes

trauma causing injuries to bone and soft tissue

Spinal stenosis

Disc condition

loose bodies in a joint

What is CT best at imaging?

less time consuming

less expensive

What are benefits to using a CT scan?

radiation exposure

radiodensity

What are limitations of a CT?

Neuroimaging

Cardiac Imaging

Pulmonary imaging

What other medical specialties are CTs common in?

levels imaged

contiguous or interrupted slices

slice thickness

reforming/reconstructions

angulation of gantry

windows provided

use of contrast agent

What is reported in a CT report?

- signal generation based on the properties of magnetic resonance

- relaxation process

- signal detection

- encoding of spatial information

- reconstruction of the image from the signal

- manipulation of tissue-dependent contrast

What is the process to create an MRI image?

early signal decay

What does T1 weighted image capture?

late stage of signal decay

What does T2 weighted image capture?

Longitudinal relaxation (T1)

process for radiofrequency energy to be transferred back to the surroundings

Transverse Relaxation/Spin-Spin Relaxation (T2)

loss of transverse magnetization due to loss of phase coherence or order among the protons in the transverse plane

the time it takes for 63% of the original excited transverse magnetization to remain

What does T2 refer to?

the time it takes for the tissue to recover 63% of its original longitudinal magnetization

What does T1 refer to?

No

Do tissues show up the same on T1 and T2 images?

T1

T2

proton density

What is contrast in an image based on differences in?

time to repetition (TR)

time to echo (TE)

What are the 2 parameters most important for creating contrast in an MRI image?

time to repetition (TR)

time at which the signal is captured

time to echo (TE)

time at which the RF pulse is repeated to again displace protons

short TR and TE times

What is T1 imaging characterized by?

long TR and TE times

What is T2 imaging characterized by?

very low

What is 1?

intermediate

What is 2?

intermediate to low

What is 3?

high

What is 4?

low

What is 5?

intermediate

What is 6?

low

What is 7?

very low

What is 8?

low to intermediate

What is 9?

intermediate

What is 10?

intermediate

What is 11?

low

What is 12?

intermediate

What is 13?

high

What is 14?

high

What signal intensity shows up brighter?

low

What signal intensity shows up darker?

greater ability to scan claustrophobic or obese patients

reduction of noise

possibility to perform tests or procedure during scan

What are advantages of an open MRI scanner?

lower field strength

lower signal to noise ratio

longer time

What are disadvantages of an open MRI scanner?

examine spine under WB conditions

can patients too large to fit in normal

scan pt who must stay in upright position

What are advantages of an upright MRI scanner?

longer time

possible image degradation

pt may be in painful position

What are disadvantages of an upright MRI scanner?

variations in bone marrow

soft tissue detail

disc herniations

neoplasms

What is MRI good at imaging?

Ferromagnetic surgical clips can be displaced

orthopedic hardware can cause distortion

no pacemakers

claustrophibia

What are disadvantaged to an MRI?

MR arthrography

gadolinium in iodine is injected into joint and created bright signal which allows the radiologist to see small defects in the capsule, articular surfaces, ligaments, or labra

MR myelography

study of the spinal canal and subarachnoid space using high resolution MRI with strong T2 weighting

greater contrast resolution

better or organs surrounded by bone

no radiation

less risk of missing disease processes

What are advantages of MRI over CT?

less expensive

greater availability

faster

less operative involved

thinner slice

not as affected by motion

easier with metal implants

What are advantages of CT over MRI?

higher resolution

lower cost

no known hazards

easy comparison

ability to follow structure

can modify area being examined

What are advantages to ultrasound over MRI?

small field of view

operator dependt

does not penetrate bone

does not cross air interfaces

harder on obese pts

What are limitations of an ultrasound?

pulser

transductor

What equpimnet is needed to complete an ultrasound?

reflection of sound wave

What is the ultrasound image based on?

echogenicity

difference in acoustic impedance of tissues at interface

smoothness of the reflecting interfaces

angle of reflection

What is the amount of reflection of sound waves during an ultrasound determined by?

different in acoustic impedance between the two tissues types

angle of incidence

What does refraction of a sound wave during an ultrasound depend on?

angle of incidence

the farther from the perpendicular, the greater the refraction

blood flow in an artery or vein

What does a doppler ultrasound measure?

sagittal slice

What does a longitudinal sonogram result in?

axial image

What does a transverse sonogram result in?

Hyperechoic structures

reflect more energy than other surrounding structures

Hypoechoic structures

reflect less energy than other surrounding structures

white/lighter

How do hyperechoic structures appear?

black/darker

How do hypoechoic structures appear?

Anechoic structures

do not reflect energy

bone

tendon/ligament

nerve

muscle

subcortical bone

What is the order of tissues from hyperechoic to hypoechoic?

hyperechoic relative to muscle

How does a tendon/ligament show up on an ultrasound?

hypoechoic line

How does a bursa show up on an ultrasound?

hypoechoic relative to fascia or tendons

How does a muscle show up on an ultrasound?

hypoechoic layer

How does hyaline cartilage show up on an ultrasound?

hyperechoic

How does fibrocartilage show up on an ultrasound?

hypoechoic to tendon, hyperechoic to muscle

How does a nerve show up on an ultrasound?

bright echo

How does a bone-soft tissue interface show up on an ultrasound?

hypo or anechoic

How does subcortical bone show up on an ultrasound?

hyperechoic, smooth, continuous

What is 1?

hyperechoic, distinct parallel fiber pattern

What is 2?

hyperechoic, with parallel fibrous hyperechoic bands

What is 3?

thin hypoechoic line

What is 4?

hypoechoic layer next to cortex

What is 5?

Hyperechoic, relative to muscle

What is 6?

Anechoic

What is 7?

hyperechoic, smooth, continuous

What is the normal findings of cortical bone in an ultrasound?

hyperechoic;distinct parallel fiber pattern

What is the normal findings of tendons and ligaments in an ultrasound?

hypoechoic with parallel fibrous hyperechoic bands

What is the normal findings of muscle in an ultrasound?

thin hypoechoic line

What is the normal findings of bursa in an ultrasound?

hypoechoic layer next to cortex

What is the normal findings of hyaline cartilage in an ultrasound?

hyperechoic, relative to the muscle

What is the normal findings of nerves in an ultrasound?

anechoic

What is the normal findings of cysts in an ultrasound?

break in continuity, uneven surfaces

What are abnormal findings of cortical bone on an ultrasound?

strains: thickening of mixed echogenicity (hypoechoic if inflammation occurs or a hematoma) and disrupted fiber pattern

ruptures: disruption of structure, initially filled with hypoechoic hematoma and separation of ends

What are abnormal findings of tendons and ligaments on an ultrasound?

increased width. In later stages, hyperechoic thickining of the walls

What are abnormal findings of bursa on an ultrasound?