NUKS Flashcards
Beta minus
too many?
what’s emitted?
What kind of transition
Too many neutrons
N > P
electron (beta particle) emitted from nucleus
Neutrino also emitted to balance energy
ISOBARIC - neutron and proton have same mass
ATOMIC NUMBER GOES UP
Beta emitter shielding?
PLASTIC
low Z
High Z would produce Brems
\
\
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Beta Minus
Energy down, Z up
I
I
/
/
/
Energy lost and Z goes down
Proton to neutron
Beta positive decay
requires 1.02 MeV
Positron and a neutrino
511 keV x2 when positron hits electron
ISOBARIC
/
/
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No steep initial drop
loss of proton and energy
ELECTRON CAPTURE
ISOBARIC
isobaric transitions
Beta emission
positron emission
electron capture
“Isometric transitions”
when do they occur?
after an isobaric (A the same) transition
leftover energy released
Gamma emission
what type of transition
isomeric transition
nucleus emits extra energy
I
I
V
Between Isobaric transition and subsequent isomeric (GAMMA EMITTING) transitions
These usually happen bam bam, but some hang out for a minute before gamma emission, these are METASTABLE
Tc 99m example of isobaric metastable isomeric
Mo99 —> Tc99m (ISOBARIC Beta MINUS, electron emitted)
Tc99m ——> Tc99 (ISOMERIC, gamma photon (140keV))
Tc99m hangs out as metastable for a couple hours
Enemy of gamma photon emission
Internal conversion
instead of gamma emission
energy given to an electron —–> characteristic Xray or Auger
Alpha decay
use?
helium nuclei
2 protons, 2 neutrons
Slow and fat
rare treatmentn situations
bone pain cancer mets via rAdium 223 (Alpha2protons2 neutrons)
Production
Bombardment
Striking targets with
Neutrons - in a reactor
Charged particles (alpha, protons, deuterons) - in a cyclotron
Bombardment
downside to using a reactor
(bombarding with neutrons)
Leftover parent to clean up
NOT “carrier free”
Cyclotron produces via transmutation, no parents to clean up, “carrier free”
Production
Fission
Neutrons fired into large elements
split into pieces, random crap made
effective half life formula
1/effective = 1/physical + 1/biologic
What does ‘activity’ measure
units
Specific activity
disintegrations per second
Curie = Ci = 3.7x10^10 disintegrations per second
SI unit = becquerel Bq = one disintegration per second
Specific activity = activity per unit mass (Bq/g)
(longer half life = lower specific activity)
Gamma camera general set up
Photons
Collimator
Crystal
PMT’s
computer
gamma photons –> light pulse –>voltage –> picture
MC collimator “work horse”
parallel hole
Parallel hole energies and examples
low
medium
high
LOW 1 - 200 keV (Tc99, I123, Xe133, TI201)
MEDIUM 200-400 keV (Ga67, In111) (medium needs to GaIn)
High > 400 keV (I131)
Sensitivity and Resolution
when are high sensitivity collimators good
Inversely related
High sensitivity collimator allows twice as many counts to be imaged with shitty resolution
High sensitivity good for dynamic imaging (flow phase)
Distance effect on sensitivity and resolution
NO EFFECT on sensitivity (net counts the same, bigger FoV)
Resolution WORSENS with distance
Pinhole collimator
what does?
what for?
?mag
magnifies and inverts
thyroids and small parts
pinhole to detector = f
patient to pinhole = b
F>B = mag
Pinhole cons
distorts large objects
Shitty sensitivity
Converging collimator
what look like?
what does?
fan out towards detector
mags without inverting
Diverging collimator
what is
what does
Opposite of converging
fan towards patient
MINIMIZES
Able to image a large body part on a small crystal
After collimator, photons hit?
Scintillation crystal
scintillation crystal made of?
what does
NaI doped with Thallium
when hit with a gamma photon, produces a pulse of light
Thick vs thin scintillator crystal?
Thick = super sensitive, fewer pass through. PMT’s are further away = WORSE resolution
Thin = less sensitive, better resoltution
After scintillator crystal?
PMT’s
PMT’s
do what?
more means what
what do they record
detect light and convert to an electric signal
More = more light picked up, greater resolution
PMT’s record X,Y location- read by computer and..
Z location/intensity goes to pulse height analyzer
Pulse height analyzer
job?
distinguishing, discarding background crap
Compton scatter from patient is very close in energy to what you want, but can really fuck it up
Downscatter
high energy photons spill into the window of a low energy emitter, mostly via Compton scatter
Ex
V/Q with Tc (140) and Xe (81)
Tc scatter will range down from 135 -90
So if you give Tc first, subsequent Xe image will be covered in Tc scatter
USE LOWER ENERGY FIRST
SPECT and matrix
SPECT overall improves spatial resolution
image longer, looks better
Bigger matrix better but takes longer (motion problem)
and fewer counts per pixel = worse image contrast
Startifact
“septal penetration”
using medium energy collimator instead of high
Gamma camera QC
Uniformity
% allowed
what is test?
extrinsic vs intrinsic
2-5% non-uniformity
1% for SPECT
Test = Flood
Extrinsic = with collimator
Intrinsic = without
test with Co57 or NaPertech
EXTRINSIC DAILY, INTRINSIC WEEKLY
Gamma camera QC
Window setting
when?
how?
DAILY
Use a symmetric window set at peak energy used for desired test
source = syringe or vial
Gamma camera QC
Linearity and Spatial resolution
When?
How?
WEEKLY
lead line phantoms placed between collimator and a Co57 sheet. Want straight not wavy lines
linearity = lines
spatial res = they’re separate
Gamma camera QC
Center of rotation
WEEKLY
SPECT
monitor for alignment offset at COR
Tc99 point sources along axis of rotation, axis should be straight with minimal deviation
Instruments
NaI well counter
what is
con
basically a small gamma camera with a single PMT
EASILY OVERWHELMED
used for in vitro blood or urine samples, “wipe test” samples
Instruments
Thyroid probe
what is
Modified NaI counter
shielding with a small opening pointed at patient, at a precise distance, compared to a calibrated capsule of same radionuclide
Instruments
Geiger-Muller
dead time?
gas ionization chamber
sensitive to large dose, must wait for ionization to dissipate before it can respond again.
max dose = 100mR/h
Instruments
Ion chamber
no dead time problem
0.1 - 100R/h (big unit)
higher doses
less sensitive than GM counter
excellent for accurate estimates (or exposure)
Personal dosimeters
Pocket ionization detector
uses a mini-chamber
real time estimated dose
must be charged and zero’d
NOT used anymore
Solid state dosimeter
accumulated dose or rate can be read real time with LCD display
solid state think LCD
Personal dosimeters
Film badge
thin metallic radiosensitive film
degree of darkening (relative optic density) corresponds to dose
sensitive to damage by temp, humidity
Personal dosimeters
optically stimulated
Replaced film badge
chips/strips placed under a filter
Personal dosimeters
ring badge
dominant index, label in
Thermo-luminescent
Dose calibrator QA
Consistency
DAILY
should be within 5%
Dose calibrator QA
accurate readout over whole range of potentially encountered activities
check either with a large (200mCi) amount of Tc and decaying it down
or easier
use a kit with sheets of varied thickness of lead
QUARTERLY
Camera linearity and spatial res
vs
Dose calibrator linearity
Camera linearity and spatial res - WEEKLY
vs
Dose calibrator linearity - QUARTERLY
Calibrator QA
Accuracy
Standard measurements measured and compared to what they shoud be
INSTALLATION AND ANNUALLY
Dose calibrator QA
Geometry
Correction for different positioning and size (different volumes of samples with same activity)
INSTALLATION AND ANY TIME YOU MOVE DEVICE
calibrator QA mnemonic
GALCulations (decreasing frequency)
Geometry - install/move
Accuracy- annual
Linearity- quarterly
Consistency - DAILY
Major spills
Tc99
> 100 mCi
Major spills
Tl - 201
>100 mCi
Major spills
In-111
> 10 mCi
Major spills
Ga-67
> 10mCi
Major spills
I 131
> 1mCi
Major vs minor spill who ya gonna call
minor - clean it yourself
major call RSO
Minor spill to do list
1) address a sick patient first
2) Confine/limit - secure area
3) Clean up (gloves)
4) survey cleanup items
5) survey cleanup people
General public regs
annual dose limit
100 mrem
“unrestricted area” max dose
2 mrem per hour
Restricted area =
any area getting over 2mrem per hour
“radiation area”
.005 rem (.05 mSv) in 1 hour at 30 cm
“high radiation area”
0.1 rem (1mSv) in 1 hour at 30 cm
“Very High radiation area”
500 rads (5Gy) in 1 hour at 1 meter
Occupational dose limits
Total body dose per year
5 rem (50mSv)
Lens
2 rem per year (20 mSv)
Total equivalent organ dose
50 rem (500 mSV)
Extremity dose per year
50 rem (500mSv)
fetus dose for 9 months
0.5 rem (5mSv)
Unit fuckery
rad rem
rad Gy
mSv mrem rem
1 rad = 1 rem
1 rad = 0.01 Gy
1mSv = 100 mrem = 0.1 rem
NRC
part 19
Notices, instructions, reports to workers
NRC
part 20
Standards for protection
NRC
part 35
Medical use of by-product material
Medical event vs recordable event
medical event = wrong drug, patient, or dose
or dose to unintended body part other than intended treatment site 50% or more over dose expected
AND
Have to harm the patient
-whole body dose > 5 rem or single organ dose > 50 rem
Recordable
Whole body <5rem
Single organ < 50rem
For medical events what u do
call the doctor, patient, NRC
Recordable… record it (document) and keep for 5 years
Receiving and storage
survey package within 3 hours
GM at surface and 1 meter away
surface wipes
Package labels
White 1
NO special handling
<0.5 mrem/hr at surface
0 mrem/hr at 1 meter
Labels
Yellow 2
Special handling required
surface <50 mrem/hr
1 meter <1 mrem/hr
Labels
Yellow 3
Special handling required
surface <200mrem/hr
1 meter <10mrem/hr
Transport index
measured max dose at 1 meter
Radioactive 1, white 1, no TI, too low
Radioactive II, yellow 2, < 1.0 mR per hour
Radioactive III, yellow 3, TI > 1.0mR per hour
how Tc is made
Mo and Tc
Mo - 67 hours
Tc - 6 hours
Mo-99 lined aluminum canister, as it decays can be washed off with saline
Tc comes out stuck to Na (Na99Tc04)
+7 valence state, must be reduced to be used
Reduced with Stannous ions
How Tc is made
moly breakthrough
If Mo comes out in the wash
“break through”
assayed behind a lead shield
Mo (740 keV) will penetrate
Mo breakthrough, what kind of purity?
allowed?
RADIONUCLIDE PURITY
0.15 microCi of Mo per 1 mCi of Tc
15 micro per milli Mo to Tc
ratio must be known at time of ADMINISTRATION
Chemical purity
Al oxide can wash off, clump with Tc and show up in liver or cause sulfur colloid aggregation and show up in the lungs
Test?
pH paper
<10 micrograms Al per 1ml
Testing for chemical purity NOT REQUIRED in NRC states
Radiochemical purity
Tc comes out of generator as Na99TcO4, needs to be reduced with SnCl2
Assessed with thin layer chromotography
limits for free Tc
95% for Na99TcO4
92% for Tc sulfur colloid (MAA)
91% for the rest
Equilibria
Equilibrium
[] of parent and daughter are equal
Transient equilibrium
half life of daughter is shorter than parent (not by a ton)
moly and Tc after 4 half lives
Secular equilibrium
half life of daughter is way way way shorter than parent
Critical Organ
Indium
Liver
Critical Organ
I 131 MIBG
Liver
Critical Organ
Sulfur Colloid (IV)
Liver
Critical Organ
Octreotide
Spleen
Critical Organ
Damaged RBC
Spleen
Critical Organ
pertechnetate
Stomach
Critical Organ
Gallium
Distal colon
Critical Organ
Mag3
bladder
Critical Organ
DTPA
bladder
Critical Organ
I 123 MIBG
bladder
Critical Organ
MDP
bladder
Critical Organ
Sestamibi
Proximal colon
Critical Organ
sulfur colloid (oral)
proximal colon
Critical Organ
DMSA
Renal CORTEX
Critical Organ
Thallium
Renal cortex
Critical Organ
HIDA
GB wall
SPECT vs PET
?depth dependent
SPECT is depth dependent
PET IS NOT
Main advantage to SPECT?
Improved contrast from overlapping structures
SPECT center of rotation artifact
TUNING FORK appearance
misregistration
Crystals in PET
(vs SPECT)
PET tends to use thicker crystals (BGO, LSO, LYSO)
(SPECT uses planar crystals, NaI)
PET
limiting factor for spatial res?
BIG thick crystals (bigger means fewer)
Positron range
actually detecting location of anihilation event
positron can travel 1-2mm prior to event
PET
angulation
sometimes 180 is a generalization
180.5, will be off a little bit in localization
PET coincidence events detected
3 types
True
Scatter coincidence - one of pair is scatterd, hits within time window but not in right location)
Random coincidence - Different anihilation events, land within same coincident window creating false calculation
PET
2d vs 3d
2D has lead septa - also decreasing sensitivity for unscattered photons
3D no septa - MORE sensitive, allows for decreased tracer dose.
3D usually done with small parts - CNS and PEDS
PET
3d disadvantages
Dead time
more random events - no septa
More scatter - no septa
SUV’s
equation
Tissue radioactivity concentration at time point 1 x patient weight
Injected dose activity
SUV’s and fat people
LBM vs weight
SUV’s are overestimated in fat people
More accurate to use LBM
PET and glucose
PET and small stuff
High glucose lowers SUV
Smaller than 1cm, lower SUV
Truncation PET FOV vs CT FOV
CT FOV is SMALLER
Lesion in the outlying blubber gets cut off by CT, seen by PET
Lesion appears ARTIFICIALLY HOT at the margin, ARTIFICIALLY COLD outside the CT FOV
PET prep
?fasting
Causes of muscle uptake?
Brown fat drugs
4 hours minimum fasting
exercise, eating or insulin
Propranolol and valium
PET QA
Blank scan
DAILY
equivalent of uniformity
keeps attenuation correction data accurate
‘start each day with a blank slate’
PET QA
Normalization scan
MONTHLY
disrepancies in the detector elements
scan a calibrated position source
NM Normal month
HORIZONTAL LINEAR STREAKS if normalization is off
PET QA
bucket setup
dark block rotating on a sinogram
power surge or sudden power loss
TRACER TRIVIA- Tc99
Analog
Energy
Physical half life
140 keV - LOW
6 hours
TRACER TRIVIA- I 123
Analog
Energy
Physical half life
Iodine
159 keV - LOW
13 hours
TRACER TRIVIA- Xenon 133
Analog
Energy
Physical half life
81 keV - LOW
PHYSICAL 125 hours
BIOLOGIC 30 seconds
TRACER TRIVIA- Thallium 201
Analog
Energy
Physical half life
Potassium
LOW 135, 167 keV
USE daughter Hg xrays
TRACER TRIVIA- Indium 111
Analog
Energy
Physical half life
MEDIUM 173 keV, 247 keV
67 hours
TRACER TRIVIA- Ga 67
Analog
Energy
Physical half life
IRON
93, 184, 300, 393 (100, 200, 300, 400)
78 hours
TRACER TRIVIA- I 131
Analog
Energy
Physical half life
Iodine
365 keV HIGH
8 days
TRACER TRIVIA- F 18
Analog
Energy
Physical half life
GLUCOSE
511 keV HIGH
110 minutes
Treatment radionuclides 1/2 life
Strontium 89
50.5 days (14 days in bone)
Treatment radionuclides 1/2 life
Samarium 153
46 hours
Treatment radionuclides 1/2 life
Y 90
64 hours
Treatment radionuclides 1/2 life
Radium 223
11.4 days