Vocabulary Flashcards
accuracy
closeness of a measurement
Ipsilateral
Same side
precision
how reproducible or consistent a measurement is
electrostatic force or Coulomb F
force b/n charged particles like e- & nucleus
strong nuclear force
force b/n p+ & n in nucleus
intensity
of photons per unit area
divergence
widening of the beam, but travel in straight line
attenuation
- intensity of the beam decr as beam is attenuated
- combo of absorption & scatter
absorption means
all E given up
transmission is
passing thru matter w/o being affected
mass E absorption coef
probability of E absorption thru photon interaction
scatter is
change in direction
saturation
add of more voltage does not result in more ionization
recombination
rejoining of + & - ions which then fails to be counted
commissioning
calib & gathering of beam data for linac prior to pt tx
acceptance testing
testing of linac to verify it meets performance stds & safety req prior to pt use
threshold dose
dose of rad @ which biological response is noted
therapeutic ratio
- ratio of dose response b/n norm cells & tumor cells
- norm tissue tol dose/tumor lethal dose
tort law
law governs rights b/n indiv in noncriminal actions
integral dose meaning
total dose imparted to tissue/med during irrad
systemic errors are within
measuring device
random errors results to
chance that are unavoidable
blunders
- human error
- in calc or improper use of measuring device
linac temp
- 40 dec C
- 104 deg F
cerrobend melting point
74 deg C
sentinel node is
primary drainage lymph node
chemo drug associated with cardiotoxicity w/radiation
doxorubicin (adriamycin)
positive contrast shows as
white; high Z
tonsils produce
lymphocytes
thymus location
along trachea sup to heart & post to sternum
thoracic duct location
L side of body
MRI uses ? in body
p+
NM Tc 99m emits
gamma rays
binding E of nucleus represents
mass defect in the nucleus
outer shell e- based on
chemical properties
ionization is
addition or removal of an e- from orbit
excitation is
incr in E raises an e- to higher orbital shell
betas result from
radioactive decay
alphas result from
radioactive decay
gamma originates from
nucleus
isotope has same
Z
isotone has same
n
isobar has same
A
isomer has same
same A & Z
LET definition
deposition of E measured per unit path length
n LET #
23kev/micrometer
monoenergetic (homogeneous) HVL thickness
every HVL is same thickness b/c E of beam always same
x-ray & gamma LET #
< 3.5 kev/micrometer
what does the 1st HVL do
“hardens” the beam by absorbing low E photons
2nd HVL
“hardened” from 1st
does the 2nd HVL harden the beam?
yes- “hardened” from 1st
does the 3rd HVL harden the beam?
yes-“hardened” from 2nd BUT ***HVL beyond this point does NOT increase
E measured in:
J or e- volt
HVL definition
absorbed thickness that attenuates orig intensity to 50%
mean free path definition
absorbed thickness that attenuates beam intensity to 1/e= 36.8%
EPID metal plate converts incident x-rays into
e-
homogeneity index is
degree of dose uniformity in target volume
brachy task group
TG43
QA task group
TG40
clinical ref dosimetry output task group
TG51 (new) or TG21 (old)
file transfer protocol (FTP) transfers
large files over internet
dicom rt contains
images, structure, dose, iso..
dicom transfers
digital images
PACS stands for
picture archiving communication system
photon dmax is depth where what 2 things are =?
dose & kerma
pinning is the use of
reference points on skin for s/u
triangulation means using
3 points of reference
physical penumbra is defined as the
- lat distance b/n 2 specific isodose curves at dmax
- often 90% & 20%
backscatter is the radiation
scattered back toward surface of pt
collimator setting is the field size
- set @ collimator when fs at 100 cm
- so 10x10 coll=10x10 fs on skin at 100 SSD
backscatter depends on (3)
-beam E, beam geometry, scatter
verification ensures
- volume is correct
- aka port films
bolus
- replaces missing tissue
- reduction of e- beam penetration
- incr skin dose
- compensates for lack of scatter
- unnecessary for superficial beams
integral dose is the product of
mass x dose
peta
- P
- 10^15
tera
- T
- 10^12
giga
- G
- 10^9
mega
- M
- 10^6
kilo
- k
- 10^3
hecto
- h
- 10^2
deka
- da
- 10^1
deci
- d
- 10^-1
centi
- c
- 10^-2
milli
- m
- 10^-3
micro
- u
- 10^-6
nano
- n
- 10^-9
pico
- p
- 10^-12
femto
- f
- 10^-15
buildup region is where
b/n surface & dmax
isodose curve definition
one passing thru points of equal dose & representing % of dose @ ref point
geometric field size is defined by
intersection of 50% isodose line & surface
beam flatness is produced by a ?
flattening filter that reduces dose along cax @ specific depth, usu 10 cm
integral dose unit
J/kg or Gy-kg
random errors examples
- accidental movement of pt during setup
- electronic noise
sarcoma is what tissue
connective
carcinoma is what tissue
epithelium
thoracic duct size relating to R duct
larger
betas are emitted from
nucleus
betas are
e- that are positively or negatively charged
EMR speed
speed of light = 3 x 10^8 m/s or 3 x 10^10 cm/s
isotope has different #
n
isotone has different #
p+
isobar has different #
p+
e- resting E
0.511 MeV
n resting E
939.5 MeV
n mass
1.68 x 10^-26 kg
p+ resting E
938.2 MeV
p+ mass
1.67 x 10^-27 kg
LET unit
kev/micrometer
p+ LET #
23 kev/micrometer
alpha LET #
53 kev/micrometer
polyenergetic (heterogeneous) HVL thickness
thickness increases from 1st HVL to 3rd HVL
dicom stands for
digital imaging & communication in medicine
PACS stores info for different
modalities
photon dmax is max range of what
secondary e-
photon dmax is depth where what occurs
e- equilibrium
geometric field is same shape as
collimator but not same size
cerrobend consists of
- 50% Bi
- 26.7% Pb
- 13.3% Sn
- 10% Cd
cerrobend has ? Z
high
cerrobend has ? density
high
cerrobend cools at what temperature
room
cerrobend weight compared to Pb
lighter
cerrobend melts at what temp
70deg C or 158 deg F
how much dose cerrobend block weigh
5-25lbs
what is thickness of cerrobend block
6-8 cm
thickness of cerrobend compared to Pb
20% greater
cerrobend attenuation
attenuates less than 5% of unblocked beam intensity
PTV req’d for
conformal tx plan
integral dose unit
gram-rad, kg-Gy, J
integral dose compares
dose distrib for different quality beams
increase E, ? integral dose
decrease
HVT is equivalent to
- penetration
- quality
- hardness
HVT is the thickness of material that
decreases intensity of beam to half original value
does penumbra depends on distance?
yes
1 joule = ? erg
10^7
1 Ci = ? Bq
3.7 x 10^10 37 MBq (1 mCi)
1 eV = ? J
1.6 x 10^-19
1 R = ? C/kg
2.58 x 10^-4
1 rad = ? Gy & ? cGy
10^-2 Gy
1 cGy
1 rem = ? Sv & ? cSv
10^-2 Sv
1 cSv
Velocity of light
3 x 10^8 m/s
Base of natural logarithms
e = 2.7183
Electronic charge q =
1.602 x 10^-19 C
Electron mass
9.11 x 10^-31 kg
Fluence
Number of photons passing through a unit cross sectional area
Fluence rate (flux)
Number of photons passing through a unit cross sectional area per unit time
