Diagnostic Imaging (1-8) Flashcards by Natalie Bubenheim

how is the energy of an x-ray related to its wavelength

inversely proportional

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this is a discrete bundle of electromagnetic radiation

photon

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these are able to penetrate materials that absorb or reflect visible light, can cause fluorescence in certain materials, and produce an image on photosensitive film

x-rays

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what does damage to tissue by x-rays result from?

direct interaction with DNA
indirect ionization of water molecules leading to formation of radicals

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name 4 most radiation sensitive tissues; they are actively and quickly dividing tissues

bone marrow
epithelial cells of GIT
gonadal cells
embryonic cells

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name the x-ray biological effect

probability of damage increases with dose (cancer, genetic effects); no known lower threshold

stochastic effects

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name the x-ray biological effect

high radiation exposure; damage only over a threshold; severity increases with dose;
erythema, hematopoietic damage, cataract; concern in radiation therapy and nuclear accidents

deterministic effects

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this is the amount of ionization per mass of air

exposure

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name the unit used to measure

exposure

C/kg Roentgen R

(amount of ionization per mass of air)

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this is the amount of energy transferred by radiation per mass

absorbed dose

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name the unit used to measure

absorbed dose

Gray (Gy) = J/kg

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this is a measure of radiation and organ system damage in humans: quality factor for different radiation

effective dose

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name the unit used to measure

effective dose

Sievert (Sv)

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what is the limited effective dose for employees 18+

20 mSv / year

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what is the limited effective dose for for trainees 16-18 years old

6 mSv / year

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what is the limited effective dose for the general public

1 mSv / year

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what is the limited effective dose for pregnant women

< 1 mSv for remainder of pregnancy

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what are the 3 exceptions to vet radiation protection regulation that small animals should be sedatd and restrained with sandbags

critical illness where sedation would deteriorate condition
specific technique requiring presence
patient type (LA)

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name 6 methods of radiation protection

indication
filtration of x-ray tube
time
distance
shielding
collimation
personnel monitoring

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name the law

if the distance from the primary source is doubled, the intensity will decrease by a factor of 4

inverse square law

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what 3 items must be worn for shielding (radiation protection)

lead apron
lead gloves
lead thyroid collar

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how thick must the lead be for aprons to protect againt radiation

0.25 mm

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how thick must the lead be for gloves to protect againt radiation

0.35 mm

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name the method of radiation protection

this is the reduction of the exposed area to the area of interest;
reduces the amount of scatter radiation

collimation

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name 2 types of dosimeter

1. film badge 2. thermoluminescent (TLD)

how often should dosimeters be analyzed

at least quarterly

how are x-rays produced

conversion of kinetic energy of accelerated electrons into electromagnetic radiation

where does production, acceleration and deceleration of electrons take place for x-rays?

w/in the x-ray tube

what is the source of electrons for x-rays

cathode

what causes acceleration of electrons for x-rays

potential difference

what causes deceleration of electrons for x-rays

anode

how much of the energy in the x-ray tube is converted to x-rays? and what is the rest converted to?

<1% x-rays 99% heat

what unit is the x-ray tube current measured in? | (number of electrons flowing per second from filament to target)

mA (milliamperes x seconds)

what unit is the potential difference in the x-ray tube measured in

kVp (kilovolt peak)

what is the best angle for the anode in an x-ray tube

6-20 degrees

if KVp for an x-ray beam is increased, what other 3 things will increase?

1. electrons velocity 2. number of x-ray photons produced 3. energy (penetrating power of each x-ray photon)

if mA is increased for an x-ray beam, what other 2 things will increase?

1. filament heating and tube current 2. number of x-rays being produced

# name the interaction of x-rays with matter this is the decrease in intensity of an x-ray beam as it passed through matter

attenuation

# name the interaction of x-rays with matter when a photon is removed from the beam

absorption

# name the interaction of x-rays with matter when a photon changes direction

scatter

# name the interaction of x-rays with matter x-ray passes through matter without interaction

transmission

# name the effect complete absorption of x-ray photon; photoelectron removed from shell; electron from higher shell falls into space

photoelectric effect

# name the x-ray effect incoming photon ejects free outer shell electron from the tissue atom, photon is scattered; scattered photon has lower energy but may produce ionizations, fog the film and is a radiation safety hazard; results in almost all scatter radiation

compton effect

the photoelectric effect of x-rays is the prdominant interaction in what range of kVp radiation?

low range (up to 30 kVp)

the Compton effect of x-rays is the predominant interaction in what kVp range?

high kVp range

this reduces x-ray scatter to produce a diagnostic quality radiograph; requires increased exposure

grids

# name the type of radiographic image acquisition uses x-ray film, casssetes with intensifying screens, automatic/manual film processor, view box for film review, and an archive for film filing

conventional radiography

name the layers of a double emulsion x-ray film

1. protective coating 2. silver halide emulsion 3. polyester base 4. silver halide emulsion 5. protective coating

name the components and ratios of silver halide crystal in a double emulsion x-ray film

1. 2% Silver ion (Ag+) 2. 98% bromide ion (Br-)

name the 2 parts of exposure effect on silver halide crystals with conventional radiography

1. electron in silver bromide released by light energy 2. silver atom formation at the sensitivity speck

what does 'sensitivity speck' refer to in conventional radiography

trapped electron (in silver halide crystal)

this image reflects the pattern of the part being radiographed and is views through processing | (conventional radiography)

latent image

# name the part of image processing with conventional radiography latent image center catalyzes the reaction which reduced the remaining silver ion into grain of metallic silver

developer

# name the part of image processing with conventional radiography prevents further development and removes undeveloped silver bromide from film

fixer

# name the part of image processing with conventional radiography removes fixer chemicals that would otherwise discolor film over time

wash (rinse & dry)

# name the effect the use of an intensifying screen in x-ray film for conventional radiography; 95% of film exposure is from light given off by the intensifying screen

fluorescent effect

name 3 reasons to use an intensifying screen with conventional radiography

1. reduce personnel exposure 2. reduce patient exposure 3. increased contrast

this is used to absorb scatter radiation to imrove radiographic contrast; recommended when bosy part thickness > 10cm

grid

what must be done to mAs when using a grid with radiography

increased by factore of 2-3

# name the type of radiographic image acquisition image is captures in cassettes containing phosphor storage layer; cassete put into laser film reader; computer generates digital image in DICOM which is sent and stored with PACS (filmless, no chemistry, no darkroom)

computed radiography (CR)

# name the type of radiographic image acquisition imaging receptor plate containing many small detector elements transforming x-rays into electrical signal; images viewed on local workstation then sent to PACS; detector panel often built into table

Direct Digital Radiography (DR)

# name the type of radiographic image acquisition provides moving radiographic images (40 frames/sec); high quality images

Dynamic Digital Radiography

name 4 advantages of computed radiography

1. time efficient 2. good image quality 2. lower radiation dose possible 3. cost effective

name 3 disadvantages of computed radiography

1. laser reader sensitive to dust 2. maintenance of moving part 3. manual labor still required

name 3 advantages of direct digital radiography

1. image obtained w/in several seconds 2. good image quality 3. lower radiation dose possible

name 2 disadvantages of direct digital radiography

1. more expensive 2. more fragile

this is where the x-ray tube takes multiple radiographs and fuses images for up to 1.2 m length; tube rotational and longitudinal rotation to achieve perfect seam of images

image stitching

name 5 advantages of computed and digital radiography (compared to conventional radiography)

1. no acquisition and display flexibility 2. images are viewable from computers 3. all image files in DICOM 4. PACS central digital archive with remote back up data 5. no fil filing, lost film, dark room, or archive room

name 3 features of DICOM

1. unified standard that is vendor independent 2. both file format and communication protocols 3. prevents manipulation of image data

name 3 features of PACS

1. central storage of images 2. replaces hard copies film and storage 3. allows remote access

what does DICOM stand for

Digital Imaging and Communication in Medicine

what does PACS stand for

Picture Archiving and Communication System

List the five radiopacities in order of their opacity

Radiolucent (dark) 1. gas 2. fat 3. soft tissue 4. mineral 5. metallic Radiopaque (light)

what are orthogonal projections

two projections, 90 degrees to each other

this is the enlargement of the radiographic image of an object relative to its actual size; increased film-subject distance

magnification

this is the partially shaded outer region of the shadow cast by an opaque object; increases with magnification

penumbra

this is the misrepresentation of the true shape of an object

distortion

this is the superimposition of structures in different planes

summation

this is two structures of the same radiopacity in contact; their margins cannot be identified

border effacement

the patient right is on this side of the radiograph image

left

the patient rostral/cranial is on this side of the radiograph image

left

name 3 meanings of side markers

1. anatomic left/right side 2. recumbency (which side down) 3. lateral margin on CrCd/DP or oblique vies

name 6 important viewing conditions for digital radiography

1. quite 2. ambient room lighting 3. block out extra light 4. high luminescence and high def monitor 5. uninterrupted 6. not tired/stressed/busy

name 5 things to check for evaluation of radiographic quality

1. exposure 2. collimation 3. patient positioning 4. phase of respiration 5. patient factors

name the 5 Roentgen Signs

1. size 2. shape 3. opacity 4. location 5. number

how to most efficiently use logical and intuitive thinking to interpret a radiograph

in combination with each other (first intuitive, then logical)

systematic search is what type of thinking for radiograph interpretation

logical thinking

pattern recognition is what type of thinking for radiograph interpretation

intuitive thinking

this is what the eye sees

vision

this is what the brain sees

perception

this is the mental completion of incomplete contours based on expected shapes; creates false organ visibility on radiographs

subjective contours (perceptual distortion)

this is where alternative perceptions can both be seen, but not at the same time; bias towards the expected perception

multistability of perception

this is the degree of perceptible difference between two color tones

image contrast

name the colors seen in high image contrast

black and white

name the colors seen in low image contrast

gray and gray

this is the difference in radiographic gray tones between two radiographed structures due to their physical differences

object contrast

this is the ability of an x-ray film to produce a degree of image contrast

film contrast

does fat decrease or enhace radiographic contrast

enhances (except in excessive quantities, then decreases)

does gas decrease or enhace radiographic contrast

enhances

this is a substance applied to patient to enhance the "natural" contrast of the organ of interest

contrast medium

name 2 types of negative contrast media in radiography

air, CO2

what is the purpose of negative contrast media in radiography

outlining of hollow organ walls

name 2 possible adverse effects of negative contrast media in radiography

1. overdistention & rupture 2. gas embolism (with air)

name 2 types of positive contrast media in radiography

Barium Sulphate & Iodinated Compounds

this type of contrast media in radiography has a high absorption of x-rays and is therefore very radiopaque

positive contrast media

this type of contrast media in radiography does not absorb x-rays and is therefore radiolucent

negative contrast media

name 3 purposes of positive contrast media in radiography

1. outlining of internal surface of hollow organs, vessels and ducts 2. organ displacement 3. filling defects

# name the type of positive contrast media in radiography outlines wall and lumen of GI tract (coats mucosa), outlining of mass effect; biologically inert, not hypertonic, metabolized or absorbed

barium sulphate

name 2 adverse effects of barium sulphate as a contrast medium in radiography

1. causes granuloma/adhesion in peritoneal cavity 2. aspiration

# name the type of iodinated contrast media dissociates into cations and anions; hyperosmalar

ionic contrast media

# name the type of ionidated contrast media do NOT dissociate; iso- or low osmolar, slightly more expensive

non-ionic contrast media

# what defect occurs in positive contrast? structures surrounded by positive contrast will appear lucent if less opaque than contrast media (structures change their relative opacity!)

filling defect

what is the advantage of using both positive and negative contrast media? (double contrast studies)

highlight mucosal detail with positive contrast while providing dark background with negative contrast

this is when contrast medium is injected into the subarachnoid space to outline the spinal cord

myelography

what contrast media is used intravenously in computed tomography (CT)

iodinated contrast media

what contrast media is used in magnetic resonance imaging (MRI)

paramagnetic substances (rare earth metals, Gadolinium)

what contrast media is used in ultrasound

agitated saline (cheap) OR encapsulated microbubbles (expensive)

name 6 uses of musculoskeletal imaging

1. lameness 2. pain 3. swelling 4. localized mass 5. known trauma 6. screening tool

name 5 prinicples of interpretation for musculoskeletal radiology

1. adequate projections 2. appropriate centering and collimation 3. appropriate exposure 4. examine 'full image' 5. consider distribution of changes

# name the part of the long bone this is the outer layer of the bone (you don't see it on radiology)

periosteum

# name the part of the long bone this is the actual bone that is seen on the radiograph

cortex

# name the part of the long bone this is the inner layer lining the bone (don't see it on the radiograph)

endosteum

name 5 soft tissue changes that can be seen with musculoskeletal radiography

1. generalized or localized swelling 2. masses 3. calcification 4. wounds 5. joint effusions

name 6 responses of bone to insult

1. new bone formation 2. osteosclerosis 3. osteolysis 4. bone atrophy 5. osteopenia 6. fractures

# name the type of new bone formation new bone at joint surfaces; increased stability to an unstable joint

osteophytosis

# name the type of new bone formation related to ligament/tendon attachments; increased strength of an attachment; can be an indication of soft tissue disease; includes spondylosis deformans

enthesophytosis

# name the type of new bone formation resulting from stimulation of the periosteum (trauma, chronic irritation, bone healing, infection, neoplasia); typically takes 7-10 days to form; can indicate the aggression of teh disease process

periosteal reaction

name the 5 forms of a periosteal reaction

1. smooth 2. lamellated 3. palisading 4. irregular 5. spicular/'sunburst'

# name the type of new bone formation an excessive growth of bone

hyperostosis

# name the resoponse of bone to injury increase in bone density without a change in shape; leads to increased opacity on a radiograph; as a result of Wolff's law; adaptive respose to increased loading

osteosclerosis

state Wolff's Law

bone of healthy person/animal will adapt to loads under which it is placed

# name the resoponse of bone to injury seen in infection, neoplasia or chronic inflammation

osteolysis

# name the resoponse of bone to injury chronic slow growing lesions (cysts and benign neoplasia) can exert chronic pressure on adjacent bone; results in thinning and deviation of adjacent bone structures

bone atrophy

# aggressive or non-aggressive bone lesion? long zone of transition loss of cortex marked periosteal reaction

aggressive

# aggressive or non-aggressive bone lesion? well circumscribed lesion cortical expansion/thinning no periosteal reaction

non-aggressive

# name the resoponse of bone to injury a reduction in bone mineral density; leads to reduced opacity on a radiograph

osteopenia

name the 2 types of osteopenia

1. metabolic 2. disuse

name 3 types (causes) of bone fractures

1. traumatic 2. pathological 3. fatigue (stress)

list the 5 steps of bone fracture healing

1. hematoma formation 2. woven bone + cartilage 3. ossification of cartilage 4. lamellar bone 5. recontoures lamellar bone

whta 5 things should be assessed with fracture healing

1. reduction 2. alignment 3. implants 4. soft tissues 5. bone healing

# name the term inflammation of bone with medulla

osteomyelitis

# name the term inflammation of bone without medulla (skull, phalanx 3)

osteitis

name 4 sequestrum of infectious osteomyelitis

1. small avascular bone fragment from fracture 2. serves as nidus for infection 3. surrounding new bone: involucrum 4. drainage hole: cloaca

name 5 examples of radiological evidence of joint disease

1. osteophytosis 2. alterations in the subchondral bone 3. altered joint space 4. subluxation/luxation 5. periarticular structures

name the 5 steps of image formation in ultrasound

1. pizoelectric crystals in probe emit pulse of sound 2. sound travels through patient 3. reflected sound returns to probe 4. a dot is produced on gray-scale image 5. multiple dots make complete image

give the equation for velocity in ultrasound

velocity = frequency x wavelength

give the equation for frequency in ultrasound

frequency = velocity / wavelength

what is the assumed velocity of sound through tissue | (ultrasound)

1540 m/s

what does attenuation mean? ex: when sound is propagated through a medium it undergoes attenuation

loses strength

the higher the frequency, the (more or less?) sound beam absorption?

absorption of ultrasound beams results in what type of energy?

thermal energy

the amount of sound beam returned depends on what of adjacent tissues

acoustic impedence

what is the equation for acoustic impedance?

acoustic impedance = tissue density x tissue sound velocity | (Z = PV)

what material has the lowest acoustic impedance and therefore slowest velocity of sound?

air

what material has the highest acoustic impedance and therefore the fastest velocity of sound?

bone (skull)

what two materials in the body act as barriers to ultrasound due to their large differences in acoustic impedance?

bone and air

this is the ability of a transducer to differentiate two adjacent individual structures

resolving power (resolution)

name the 2 types of resolution | (ultrasound)

1. lateral 2. axial

# name the type of resolution (ultrasound) the ability to distinguish 2 objects parallel to the sound beam OR 2 objects behind each other

axial resolution

# name the type of resolution (ultrasound) the ability to distinguish 2 objects perpendicular to the sound beam OR 2 objects next to each other

lateral resolution

the (longer or shorter?) the wavelength, the better the resolution | (ultrasound)

shorter

(increasing or decreasing?) frequency improves resolution? | (ultrasound)

increasing

this is when the beam converges at a specified distance to improve lateral resolution | (ultrasound)

focal zone

in this mode of ultrasound, returning signals are displayed as grey dots on a screen with echo intensity displayed as dots of brightness on the screen

B mode (brightness mode)

in B mode of ultrasound, black dots mean this

no echoes

in B mode of ultrasound, grey to white dots mean this

many echoes

in this mode of ultrasound, moving structures with a strip recording made at right angles to the B mode display; used especially in echocardiography

M mode (motion mode)

in this mode of ultrasound, sound is reflected at different frequencies from moving objects; RBCs act as small reflectors

Doppler mode

what does the color blue mean on color doppler mode of ultrasound

away

what does the color red mean on color doppler mode on ultrasound

towards

name the U/S echoginecity pattern for no returning echoes - black

anechoic echo pattern

name the U/S echoginecity pattern forlow intensity returining echoes (dark grey)

hypoechoic echo pattern

name the U/S echoginecity pattern for high intensity returning echoes (appears very light - grey/white)

hyperechoic echo pattern

name the U/S echoginecity pattern for same number of returning echoes as adjacent tissues; used to compare two structures to each other

isoechoic echo pattern

name the U/S echoginecity pattern for when echoes are of the expected intensity

normoechoic echo pattern

name the U/S echoginecity pattern for multiple mixed hyperechoic, hypoechoic, and anechoic echo patterns

complex echo pattern

list the 3 machine assumptions that lead to US artifacts

1. sound only travels in stright lines 2. sound travels at a constant speed 3. returning echoes only result from objects located along the transducer axis

# name the U/S artifact fluid structures attenuate less sound, resulting in a greater beam strength beyond the fluid structure making that area more echogenic ; allows us to tell teh difference between fluids and solids

acoustic enhancement

# name the U/S artifact certain substances absorb all of the sound beam at an acoustic interface leaving an anechoic area beyond the substance (ex. bone); allows us to ID dense structures

acoustic shadow

# name the U/S artifact occurs when sound beam travels at a different velocity at the edge of a rounded structure; sound beam becomes bent and does not return to the trasnducer; normal finding

refractive and reflective shadows

# name the U/S artifact where an acoustic interface reflects so much sound that the transducer/skin interface reflects the sound back into the body again so the structure is assumed to be twice as deep; may be repeated several times resulting in multiple echogenic equidistant lines

reverberation arifacts

reverberation artifacts in U/S are most likely to occur with what material

air

# name the U/S artifact Sound reflected from a curved interface is reflected by another interface before returning to the transducer via the original highly reflective interface

mirror image artifacts

what two rules must be met for a mirror image artifact to occur in U/S

1. presence of a highly reflective interface 2. presence of a highly curved convex/concave structure

# name the U/S artifact false debris in the urinary or gallbladder (pseudosludge)

slice thickness artifact

# name the U/S artifact only show up against fluid-containing structures such as the urinary bladder; scanning in different planes confirms their artifactual nature

side lobe artifact

this knob allows amplitudes of all the echoes on an U/S to be intensified or suppressed

overall gain

this allows all of the image to have the same intensity on the screen; acoustic interfaces deep within the body will be amplified & those close to transducer may be supressed resulting in a homogenous screen image | (ultrasound)

selective gain / time gain compensation

name 5 main vet application of U/S

1. abdominal U/S 2. thoracic U/S 3. tendon U/S (equines) 4. reproductive U/S 5. echocardiography

name 3 major advantages of U/S

1. safe 2. non-invasive 3. low running costs after initial outlay

name 3 disadvantages of U/S

1. operator dependent 2. only sonographer at time of scan can tell how the probe is held relative to the patient 3. cannot penetrate bone or gas so not all tissues accessible

name the 5 main components of a CT unit

1. x-ray tube 2. gantry 3. fan-shaped detector row 4. movable patient couch 5. computer & workstation

# name the CT mode x-ray tube and detectors perform one rotation around patient who does not move; results in many differently angled attenuation values from which a matrix image is reconstructed

sequential/axial mode

how many Hounsfield units (HU) is air for CT

-1000 HU

how many Hounsfield units (HU) is water for CT

0 HU

define voxel (in terms of CT slice)

volume element

define pixel (in terms of CT slice)

picture element

# name the CT mode continuous rotation of the x-ray tube detector set, patient moves through gantry during tube rotation; results in volume data set; allows faster scanning and reduction of motion artifacts

helical/spiral mode

the 'stretch' of the helix in helical/spiral CT mode is called this; it is a unitless ratio = table movement/slice thickness during one rotaion of the x-ray tube

pitch

the slower the pitch in helical/spiral mode CT, the (better or worse?) quality of image

better

# name the type of CT multiple rows of detectors (up to 1000), allows larger coverage of a larger body area per tube rotation with thin slice width; data from each thin detector row can be processed separately as thin slice images or binned/fused as thick slice images

multi-slice/multi-detector-row CT

# thick or thin slice CT images? high spatial resolution & sharpness (important for bone) relatively noisy

thin-slice CT images | (0.3-1mm)

# thick or thin slice CT images? high contrast resolution (important for soft tissue) reduced noise

thick-slice CT images | (2-5mm)

# name the type of CT uses large plate of flat panel detectors; images are reconstructed as a volume of 3D data (not slice-by-slice); results in isometric resolution in any image plane, has higher spatial resolution but slower rotation time of the tube; normal electric plug; very good for bone and teeth

cone beam CT (CBCT) / flat panel detector CT (FPCT)

name 5 advantages of cone beam/flat panel detector CT over multislice CT

1. less expensive 2. mobile 3. units custom-made for animals 4. good image quality for bone and teeth 5. technically higher spatial resolution

name 3 limitations of cone beam/flat panel detector CT compared to multislice CT

1. poor image quality for soft tissue 2. risk of motion artifact (slow tube rotation) 3. involves ionizing radiation

define window center in CT imaging

brightness

define window width in CT imaging

contrast

what size window width do nose, lung, and bone require in CT viewing

wide window

what size window width do soft tissue, brain and post contrast studies require for CT viewing

narrow window

# name the type of CT CT performs repeated, fast, back-and-forward scans over length determined by scanner; computer merges all individual scan data into one space and time-resolved data set

4D-CT

name 3 applications of 4D-CT

1. canine ureter anatomy (ectopic ureters) 2. ECG-gated CT 3. perfusion CT

# name the type of CT image acquisition triggered by ECG; continuous scanning through multiple cardiac cycles; restrospective segmentation into different phases of the cycle (ideally 10% segments)

ECG-gated CT

# name the type of CT allows perfusion assessment of parenchymal organs during contrast bolus injection; based on 4D-CT technology main uses: brain, liver, kidneys, neoplasia

perfusion CT

name 2 causes of decreased cerebral perfusion

1. infarction 2. compression

name 2 causes of increased cerebral perfusion

1. neoplasia 2. inflammatory lesions

# name the diagnostic imaging technique patient is placed in a magnet, a radiowave is sent in, the radiowave is turned off, the patient emits a signal which is recieved by coils; the signal emitted by the patient is used to create the picture

MRI (magnetic resonance imaging)

what type of magnet is used in an MRI scanner? (electromagnets where an electrical current is passed through a superconducting material)

superconductive magnets

what must the wire in an MRI be bathed in?

a cryogen (liquid helium or liquid nitrogen)

# name the type of MRI coil emit radiowaves

transmitter coils

# name the type of MRI coil recieve signal emitted from patient

reciever coils

these have a positive charge, spin around their central axis, and generate an electrical current (have their own magnetic field); used in MRI

protons

# spin-up or spin-down? a proton that is aligned parallel with the direction of the external magnetic field (B0)

spin-up

# spin-up or spin-down? a proton that is aligned anti-parallel to the direction of the external magnetic field (B0)

spin-down

which proton orientation in a magnetic field requires less energy and is therefore preferred

spin-up

why are hydrogen protons used in MRI?

naturally abundant in tissues & have strong magnetic dipole moment

if the total number of protons and neutrons is even, what is teh magnetic moment?

within a stong external magnetic field, protons not only line up, but als orotate eliptically like a spinning top - what is this called

precession

this is the number of times a proton precesses per second

Larmor frequency

what is the Larmor equation

Larmor frequency (MHz) = gyromagnetic ratio x magnetic field strength (T)

the srtonger the magnetic field, the (lower or higher?) the precession frequency

higher

what is the gyromagnetic ratio for hydrogen protons?

42.5 MHz/T

what vector(s) is the longitudinal component of protons

Z (direction of B0)

what vector(s) is the transverse component of protons

x and y

what frequency is the radiofrequency pulse sent in MRI

at the Larmor frequency

what 2 things do protons start doing simultaneously as soon as the RF pulse is switched off?

1. longitudinal relaxation (losing energy and returning to spin-up) 2. transverse relaxation (dephasing)

this is the time taken for all of the protons that became spindown to become spin-up again

longitudinal relaxation time (T1)

longitudinal relaxation time (T1) is the time taken for the longitudinal magnetization to recover to what percent of its maximum value?

63%

the shorter the T1, the (quicker or slower?) the protons exchange therman energy with the lattice

quicker

do liquids have a long or short longitudinal relaxation time (T1)

long

does fat have a long or short longitudinal relaxation time (T1)

short

this is the time taken for the protons to completely dephase | (MRI)

transverse relaxation time (T2)

transverse relaxation time (T2) is the time taken for the transverse magnetization to decay to what percent of its maximum value

37%

the shorter the transverse relaxation time (T2), the (less or more?) inhomogenous the local magnetic field

do pure liquids have a long or short transverse relaxation time (T2)

long

do impure liquids have short or long transverse relaxation time (T2)

short

what is contrast based on in T1W MRI images?

1. T1 characteristics of tissue 2. short TR (amount of time between successive pulse sequences applied to the same slice)

what body material has the shortest T1 and therefore highest signat on TW1 images (brightest)

fat

what body material has the longest T1 and thus the lowest signal on TW1 MRI images (dark)

CSF/pure fluid

what is contrast based on in T2W MRI images?

1. T2 characteristics of tissue 2. long TE (time between the delivery of the RF pulse and the receipt of the echo signal)

what body material has high signal intensity on TW2 MRI images (bright)

fluid

what body material has intermediate signal intensity on TW2 MRI images (medium brightness)

fat

what is the maine indication for MRI

neuroimaging | (intracranial and spinal cord diseases)

does MRI involve ionizing radiation

what is the main safety concern of MRI?

metal

name 3 reasons metal is a safety concern with MRI

1. can become a missile 2. distorts magnetic field (image artifacts) 3. induces electric current and heat (potential burns)

what protection must be offered to patients for MRI?

hearing protection

what is the recommended settling period for microchips before MRI

3 months