Test 2: lecture 11 and 12 CT, MRI, nuclear Flashcards
___ uses x-rays. Measures attenuation of x-rays by tissue (number of x-rays absorbed or scattered). Gives cross-sectional anatomy
CT → slices through the patient
why does superimposition decrease in CT scans
slices are so thin, there is very little overlap
why does CT have better contrast
can detect 4000 shades of grey
vs an xray that can detect 5 opacities
how does CT work
gantry: xrays taking 360 around patient and then moves slowly down
computer takes this info and turns it into slices
can make a 3D model from the slices
a + CT number =
a - CT number =
attenuation greater then water (bone)
attenuation less then water (fat or gas)
disadvantages of CT
increases radiation dose
artifact- metal will cause artifact (confuses the computer)
soft tissue contrast- MRI is better for tiny lesions in brain
benefit of MRI
no ionizing radiation
what is the term used for opaque in CT and MRI
CT: hyper attenuating
MRI hyper intense
white
how to tell CT vs MRI
CT bone will be hyper attenuating → very white
fat→ hypo attenuating → black
MRI bone is hypo intense→ grey
Fat→ hyper intense → white
which one CT which one MRI
CT bone will be hyper attenuating → very white
fat→ hypo attenuating → black
MRI bone is hypo intense→ grey
Fat→ hyper intense → white
CT or MRI
MRI
fat is bright → white
MRI contrast
Paramagnetic substances such as rare earth metals: Gadolinium
In chelate form (Gd is toxic)
Principle: acts paramagnetic = enhances magnetic properties of neighboring molecules (shortens T1 relaxation)
Increased contrast uptake: increased vascularity, leaky vessels (tumor), BBB interruption, vascularized vs. non-vas
why use MRI
better picture for brain and Spine then CT
no radiation
what is better for nasal picture and why
nasal → CT cause bone is white
in MRI bone is dark so cant really see as much detail
scintigraphy
diagnostic imaging branch of nuclear medicine
___ images provide information about the function of cells and tissues imaged.
Scintigraphic (nuclear medicine)
radionuclide has an ___ nucleus and will undergo ___ by
unstable nucleus (excess protons or neutrons)
radioactive decay
photon and/or particulate emission
MDP is used for ___
bone nuclear imaging
binds to the crystals in bones
highly sensitive for bone disease, but also non specific because increase uptake could be from a bunch of stuff: fracture, disease, infection, normal growth
this is a bone scan using 99mTc MDP
nuclear imaging → scintigraphy
99mTcO4- thyroid scan
technitium is taken up by thyroid gland, salivary gland, gastric mucosa and choroid plexus
nuclear medicine → Scintigraphy
Which of the following is a good choice of imaging modality?
Ultrasound to rule out a brain tumor
MRI to rule out pulmonary metastatic disease
Radiography to rule out nasal tumor
Scintigraphy for surgical planning of a liver mass removal
CT to evaluate a maxillary mass
CT to evaluate a maxillary mass
A gamma camera…
Attracts ferromagnetic objects
Is used after administration of a radionuclide
Is used to image the distribution of gadolinium throughout the body
Delivers high resolution images
Emits x-rays
Is used after administration of a radionuclide (scintigraphy)
Which of the following involves ionizing radiation?
Scintigraphy
Ultrasound
Gadolinium-enhanced MRI
Non-gadolinium MRI
Contrast ultrasound
Scintigraphy
On which of the following will urine appear darker?
Delayed post contrast CT
T1-weighted MRI
Bone scintigraphy
Cystogram
Plain radiography
T1-weighted MRI
On which combination of imaging modality is cortical bone black?
Radiography and MRI
Radiography and ultrasound
CT and Nuclear Medicine
T1-weighted and T2-weighted MRI
CT and radiography
T1-weighted and T2-weighted MRI
