Final Flashcards
uses x-rays to present image slices
CT
calculates x-rays ability to pass through or be weakened by tissues
attenuation coefficients
advantage of CT
3-D imaging
each image square
pixel
elongated block of tissue
voxel
CT thickness determined by..
computer programming
pioneer of CT imaging
Godfrey Hounsfield, 1979
what determines Hounsfield units (HU)?
x-ray attenuation coefficient
imaging of choice for head trauma and cerebrovascular events
Head CT axial slices
lymphoma and head/neck neoplasms
Neck CT + C
most helpful for coronal and sagittal planes
MRI
fat looks bright
T1 MRI
water looks bright
T2 MRI
for visualizing normal anatomy
T1
used to detect disease process
T2
allows spatial encoding of the MRI signal and is critical for a wide range of “physiologic” techniques
gradients
receive and transmit signal
patient coils
“atenna” of MRI system
radiofrequency (RF) coils
MRI study is susceptible to
motion artefacts
Dx infections, tumors, vascular pathology
intravenous contrast administration
Dx of internal joint derangement
MR arthrography
detect thromboembolic disease
MRA and CTA
uses gadolinium enhanced contrast medium
MRI (T1)
uses iodinated contrast medium and greater x-ray absorption
CT
may cause nephrogenic systemic fibrosis (NSF)
gadolinium
gradual fibrosis of skin/internal organ
NSF
uses FDG to find malignancies
positron emission tomograhy (PET)
electrical energy converted to burst of high frequency sounds waves (1-10) which are reflected by tissues
ultrasonogrophy (US)
uses Tc99-methylene diphosphate as active agent
radionuclide bone scan
3 phases of bone scans?
- inflow (2-5 s)
- tissue pool (5-15 min)
- delayed (2-4 hours)
evaluates mineral bone density
DEXA
how to maximize patient protection
- minimize time
- maximize distance
- shielding
- tuble filtration
- collimate
- patient cooporation
ALARA
As Low As Reasonably Achievable
what view for thoracic/pelvis for pediatrics to minimize radiation?
P to A
rate of maturation/differ and metabolism –> cell radiosensitivity
1906 Law of Bergonie and Tribondeau
amount of erergy absorbed per unit mass
Rad
rate for energy transfer from ionizing to soft tissues
linear energy transfer (LET)
different amount of potential bio effect for radiation sources
radiation weighting factor
most sensitive age
3-7 FETAL weeks old
halogenated pyrimidines, Vit K, methotrexate
radiosensitizers
sulfhydrils (cysteine)
radioprotectors
principle effects of ionizing radiation on living cells
radiolysis: irradiation of H2O –> free radicals
most cell have overabundance of molecules
target theory
DNA as direct target for x-rays
direct effect
x-rays hit H2O –> ion radical –> DNA
indirect effect
radiation induced cancer, leukemia, and genetic mutations are examples of?
non-threshold linear response
“no photon is safe”
for making safety guidelines in radiography what is used?
linear non-threshold response
leads to cell killing
deterministic effect
expressed by cangerogenesis, mutations, hereditary chcanges and latent cancer
stoachastic effect (non-threshold effect)
period of organogenesis
3-7 fetal weeks
measures radiation exposure/intensity in air
roentgen
measures how much energy is absorbed per unit mass
Rad
human lethal Rad dose
350
1 grey =
100 Rads
unit of radiation exposure measuring potential bio effects
Rem
most radiography stuff
.5 mSv/yr or less
1 sievert (Sv) =
100 Rem
theory based on experimental animals who received low radiation dose express better survival ability
hormesis
