Diagnostic Imaging- FInal Exam: Intro to CT and MRI

computed tomography

what does CT stand for?

x-ray based imaging modality

what is a CT?

there is an x-ray tube and set of detectors that rotate around the patient

how does a CT work?

true

T/F: the image a CT shows is cross sectional

-cross sectional

-greater tissue contrast

-can manipulate images to emphasize tissue contrast

-objective measurements of density

-highlight vasculature and pathology via contrast

what are the advantages of CT over radiography?

CT

is the left image a CT or MRI?

blue- gantry

pink- bore

purple- couch/table

ID parts of CT machine

x-ray tube and detectors

what two parts does the gantry of the CT machine include?

FALSE, can be positioned in multiple ways depending on body part scanned

T/F: the patient has to be in one position no matter the body part being scanned

false!! can use both

T/F: you cannot use sedation for CTs

no, CT imaging is fairly fast so it is not necessary

do you have to use general anesthesia for CT scans?

transverse

CT images are typically acquired in transverse/sagittal/dorsal?

left- bone window

right- tissue window

which CT window shows bone window or tissue window?

left- soft tissue window

right- bone window

ID the CT windows

iodine

which contrast medium do you use for CT?

IV

iodine is generally given IV or IM or orally?

pre contrast

make sure to get a __________ scan first for comparison before doing a contrast CT

vasculature

an iodine contrast CT highlights what?

in areas of abnormal or increased vascularity

for a contrast CT with iodine, the contrast accumulates where?

left- pre contrast

right- post contrast

window- soft tissue window

which CT images are pre and post contrast? what type of window is being shown in both?

Hounsfield Unit (HU)

what unit is tissue density measured in CT?

water

Hounsfield Unit (HU) is based off of what material?

positive, negative

anything more dense than water will be _______ and anything less dense than water will be _______ in Hounsfield Units (HU)

tissue density

what is this CT measuring?

-size

-shape

-location

-number

-margination

-density

what are the roentgen signs for CT?

-gas

-fat

-fluid/soft tissue

-bone

-metal

what are the different densities that can be interpreted with CT?

-lumps/bumps

-trauma

-lung disease

-nasal disease

-orbital masses

-bone disease

-IVDD

-abdominal disease

what are some CT indications?

-surgical planning

-radiation therapy planning

-3D printing

CT is primarily used for diagnosing problems, but can also be used for what three other things?

CT volume rendering/3D reconstruction

what is the image on the left showing?

magnetic resonance imaging

what does MRI stand for?

utilizes strong magnetic field and radio frequency waves

how does an MRI operate?

true

T/F: MRI images are cross sectional

no! non ionizing

is MRI ionizing?

no!

is MRI an x-ray based modality like CT is?

MRI

does CT or MRI have better soft tissue contrast?

MRI

can MRI or CT determine tissue/lesion composition by signal intensities in different sequences

MRI

which takes longer, CT or MRI?

MRI, takes a long time and LOUD

does CT or MRI REQUIRE general anesthesia? why?

MRI

is MRI or CT the gold standard for imaging of most neurologic conditions

left- CT

right- MRI

which images are CT and which are MRI?

the hydrogen nucleus

in regards to MRI physics, the MRI manipulates what?

the magnetic fields line up from the spinning proton of the hydrogen nucleus

when the patient is put into an MRI machine, what occurs in regards to the magnetic fields?

they disturb the small magnetic fields that are lined up

the radio frequency waves do what in an MRI?

they release energy which is detected by the MRI machine

as the protons return to their original orientation in an MRI, what then occurs?

return to their original orientation

differences in rate at which protons in different tissues _____________ determines what we see

top- bore

middle- RF coil

bottom- couch/table

what are the parts of the MRI machine from top to bottom?

yes!

does strength matter in MRI?

better

the higher the main magnet field strength usually the _______ the images

tesla (T)

what is the unit of magnetic field strength?

Same as CT but actually acquired in different planes, not post processing like in CT

what are the MRI planes compared to CT?

different tissue types

different sequences of MRI can be produced to highlight or suppress what?

by the timing of the radiofrequency pulses applied from the machine and received from the tissues

how are MRI sequences determined?

TR (time of repetition) and TE (time to echo)

what are the two parameters of MRI sequences?

-T1 weighted

-T2 weighted

what are the two main MRI sequences?

left- T1 weighted

right- T2 weighted

which image is T1 weighted and which is T2 weighted?

Size

Shape

Location

Number

Margination

Intensity

what are the roentgen signs of MRI?

NO! based off of intensity

T/F: MRI is interpreted based off of opacity/echogenicity

-hyperintense

-hypointense

MRI signal intensity is described as bright or ___________ OR dark or _________

amount of protons in a tissue and sequence selection

MRI signal intensity depends on what?

anatomy

T1 weighted images are good for ________

pathology

T2 weighted images are good for identifying __________

hyperintense

Pathologic tissues such as tumors or areas of inflammation are "juicy" so they are what intensity?

left- T1 weighted

right- T2 weighted

which MRI image is T1 or T2 weighted?

Gadolinum

what contrast can be given for MRI?

IV

Gadolinum is given SQ/IM/IV?

T1 weighted

are contrast MRIs done in T1 weighted or T2 weighted?

Differentiates abnormal tissue from surrounding tissue

what is the benefit of doing a contrast MRI?

left- pre contrast

right- post contrast

which MRI is pre and post contrast?

MRI

is this an MRI or CT?

magnet

the MRI is a big _________, so be careful!

CT

should you do a CT or MRI for the thorax/metastasis?

MRI

should you do a CT or MRI for the brain/seizures?

CT

should you do a CT or MRI for the elbows/suspected elbow dysplasia ?

MRI

should you do a CT or MRI for the suspected intervertebral disc disease?

CT

should you do a CT or MRI for a cervical spine problem in a dog with a pacemaker?

-cross sectional

-same area

-TRANSVERSE PLANE

how are these images the same?

right- bright bone

left- less bright bone, more definition in tissue

how are these images different?

left- MRI

right- CT

which one is the CT and which is the MRI?