Misc Flashcards
Unlike beta particles which scatter in random directions, alpha particles tend to move through matter in _________
Straight lines
NRC and agreement states view exempt quantities of radioisotopes as generally __________ for public use. Exempt activity levels can be found in 10 CFR _____
Safe
30.71
For typical alpha particle energies of 4-8 MeV, the range in air is
2-8 cm
In tissue it drops to 30-90 um
A 1MeV electron has an approximate range in air of
3.5 m
In water it is only about 4 mm
Radium 223 is often generator produced from Actinium 227, created via
Neutron activation
Although radium-223 is formed naturally in trace amounts by the decay of uranium-235, it is generally made artificially,[1] by exposing natural radium-226 to neutrons to produce radium-227, which decays with a 42 minute half-life to actinium-227. Actinium-227 (half-life 21.8 years) in turn decays via thorium-227 (half-life 18.7 days) to radium-223. This decay path makes it convenient to prepare radium-223 by “milking” it from an actinium-227 containing generator or “cow”, similar to the Moly cows widely used to prepare the medically important isotope technetium-99m.[1]
Isotope of Sr used to treat bone cancer
Sr 89
Regulations concerning transportation of radioactive materials are contained mainly in
49 CFR
U.S. Nuclear Regulatory Commission (10 CFR)
U.S. Postal Service (39 CFR)
For the purposes of transportation, exempt quantities contain uniformly distributed activity at a concentration of .002 uCi/g
.002 uCi/g
For transportation, an A1 quantity is
generally the quantity of that radionuclide that will result in a dose rate of 0.1 Sv/h (10 rem/h) at a distance of 1 meter.
Radiopharmaceuticals transported for NM fall into this category according to 49 CFR
Normal form, A2
The transportation index is
mRem/ hr rounded to the nearest tenth at 1 m
e.g, a package reading 10.25 mRem/hr at 1 m has a TI of 10.3
Remember the label dose measurement is done at package surface
If a 100 cm2 area of a package was wipe tested, the maximum activity must be below
2200 dpm for most radioisotopes or 1 nCi
Excepted package dose limit
.5 mR/hr at package surface
Type A packaging must meet these requirements
Water Spray Test, which simulates the package having been left in the rain for a period of 30 minutes, followed by;
Drop Test of 4 feet onto a hard surface, in a most damaging orientation - simulating falling off a vehicle or loading platform.
Puncture Test with a 13 pound steel rod being dropped onto the damp package - simulating a loose object hitting the package.
Crush Test equal to a force of at least 5 times the weight of the package - simulating the damp package being at the bottom of a stack of packages.
A nuclear pharmacy unit dose shipment would be in this type of packaging
Type A
Usually in what’s referred to as an “ammo box”
Radioactive materials being shipped have hazard class
7
Shipping papers for radioactive materials must include
a. The proper shipping name from §172.101;
b. The UN hazard class or division - radioactive material is hazard class 7;
c. The UN Identification number;
d. The net quantity of material by weight or volume.
NOTE: For most radioactive material, it is not required to list the weight or volume, since the additional requirements of §172.203(d) provide better information, i.e., the radioactivity content in Becquerels (Curies). A listing of weight or volume is usually needed only with respect to establishing freight charges;
e. The letters “RQ”, if the shipment is a “hazardous substance” [see §172.101, Appendix A, Table 2 for RQ values of radionuclides].
f. Emergency response telephone number as prescribed in Subpart G, Part 172.
A shipping paper may contain additional information concerning the material, provided it is not inconsistent with, and does not cause confusion with, the basic description. Unless otherwise specified, the additional information must be placed after the required basic description.
One White I, Yellow II and Yellow III shipping labels you must show
Isotope
Activity in SI units (can also have mCi, etc. in parenthesis)
Transportation Index
Requirements for White I label
TI 0
< = 5 mRem / hr at surface
Requirement for Yellow II label
TI greater than 0 but less than 1
More than 0.005 mSv/h (0.5 mrem/h) but not more than 0.5 mSv/h (50 mrem/h) at surface
Requirements for a Yellow III label
TI greater than 1 but less than 10 (for non-exclusive use provision)
More than 0.5 mSv/h
(50 mrem/h) but not more than 2 mSv/h (200 mrem/h) at surface
A key difference between DOT and NRC transportation regs
NRC AND AGREEMENT STATES REGULATE LICENSED SHIPPERS AND RECEIVERS OF RADIOACTIVE MATERIAL PACKAGES. DOT’S AUTHORITY APPLIES TO SHIPPERS AND CARRIERS, NOT TO RECEIVERS.
According to 10 CFR 20, receivers of packages containing radioisotopes must
Except for packages containing gaseous or special form radioactive material, any package bearing either of the three categories of RADIOACTIVE labels must be monitored for external surface contamination;
Required training and testing in the following subjects should be provided when?
- General awareness/familiarization with 49 CFR hazmat transportation requirements;
- Function-specific training; and
- Safety training.
Initial training is required within 90 days of employment on a specific job. The hazmat employee must have recurrent training every three years or within 90 days after assignment to a new job for which training has not already been provided.
For whole body FDG PET-CT scans using 120 kV, the mAs for diagnostic, anatomical localization and attenuation scans are approximately
110-200 mAs (CTDIvol 8-14 mGy, 11-20 mSv)
30-60 mAs (CTDIvol 2-4 mGy, 3-6 mSv) — roughly 1/4
5-10 mAs (CTDIvol .3-1 mGy, .5-1.0 mSv) — roughly 1/20th
Effective dose for a 15 mCi FDG scan is approximately
10 mSv
SUV is calculated as
SUV(t) = C (activity concentration / unit mass)
——————————————-
Injected activity (t) / body weight
If FDG is distributed uniformly throughout the body then the SUV everywhere would have a value of
1
A typical but often invalid threshold for determining malignancy is an SUV threshold of
> 2.5
In PET the best case reconstruction resolution is
4 to 7 mm FWHM
In PET, approximately ____% of photons are absorbed in 3 cm of BGO vs about ____% in NaI(Tl)
95
36
In 3D PET, scatter coincidence can account for approximately _____% of total detected coincidence events
40
Difference in arrival time in coincidence events in PET is less than
1 nano second
Interplane septa in 2D PET are usually
Made of lead or tungsten and about 1 mm thick
The source often used for blank scans or in PET only systems is
Ge-68
The range of positrons from FDG in tissue is about
2-3 mm
8 mm for O-15
Range is total distance traveled which is larger than displacement from the decay site
According to the ACR technical standard annual PET QC should include
- Spatial resolution
- Count rate performance (count rate versus activity), including count loss correction.
- Sensitivity (cps/MBq/mL).
- Image uniformity.
- Image quality.
- Accuracy of attenuation and scatter correction, and SUV measurement
According to the ACR AAPM technical standard annual gamma camera testing should include
The following characteristics should be evaluated at least annually:
1. Intrinsic uniformity
2. System uniformity with all commonly used collimators
3. Intrinsic or system spatial resolution/linearity
4. System sensitivity
a. Count rate per unit activity
b. Interdetector variability
5. Energy resolution
6. Count rate performance7. Formatter/video display a. Uniformity
b. Spatial resolution
8. Overall system performance for single photon emission computed tomography (SPECT)
a. Uniformity
b. Contrast
c. Spatial resolution
9. System interlocks
An alternative but less accurate method of thyroid uptake involves
Intravenous administration of Tc99m pertechnetate
In a thyroid uptake study, the amount of I-123 and associated dose to the thyroid is
100-300 uCi (100-200 for children)
1.2-3.6 rad, 40-120 mRem (.4-1.2 mSv)
Normal values for radio iodine uptake
In the literature, the normal range of values is usually given as between 10 and 35% for 24-hr uptake, and between 6 and 18% for 4-hr up- take. These values must be interpreted loosely, since they were determined with a variety of equipment, standards, uptake phantoms, and in in- dividuals from populations with various levels of iodine intake, which may not be directly compara- ble to the patients under study.
An I-131 patient can be released when
Dose to members of the general public is < 100 mRem (500 mRem for family) or dose rate at 1 m is < 7 mR/ hr or < 33 mCi. See NUREG 1556 V 9 Rev 2, Appendix U
The Benua threshold for dose to the blood from I-131 is
200 cGy (200 Rad or 2 Gy)
LD 5/5 for lung fibrosis with uniform exposure is
30 Gy
LD 5/5 of severe hematopoietic damage with uniform exposure (external beam) is
30 Gy
In I-131 therapy the 48 hour retention limits are
Whole body : 80 mCi with diffuse lung mets or 120 mCi without
In planar imaging the geometric mean is
(AP counts x PA counts)^.5
Patient absorption factor for PET is
About .36
Dose rate constant has these units
(Dose)(length^2)/(activity x time)
Shielding concerns in PET
Workload
Time in uptake room
Rooms and corridors near uptake room and PET
Patient bathroom
Types of persons near uptake room and PET
Tolerance of other imaging systems to radiation from uptake room and PET
Location of hot lab
Composition and thickness of existing structures
As the energy window is decreased for Tc 99m from 20 to 15 to 10%, non uniformity in the flood
Increases
May start to see PMTs
If an intrinsic flood is uniformly “tubey”, you may want to redo
Linearity maps
If a flood point source is too close to the detector (< 5 UFOV), the image may look
More bright in the center due to increased counts
Asymmetric energy windows are used to check the NaI(Tl) detector for effects of possible
hydration, sometimes called measles (because the crystal is hygroscopic), to evaluate the balance or tuning of PM tubes and to reveal electronic problems.
A MUGA scan uses an injection of ________ to calculate LVEF
Tc 99m labeled red blood cells
The CfOV is about ______ % of the UFOV
75%
How does PET resolution vary by radial position?
For multidetector PET scanners, the intrinsic resolution (Ri) is related to the detector size d. Ri is normally given by d/2 on the scanner axis at midposition between the two detectors and by d at the face of either detector. Thus it is best at the center of the FOV and deteriorates toward the edge of the FOV.
In shielding the weekly dose to design to in controlled versus uncontrolled areas
In the US, P=20uSv for uncontrolled areas, corresponding to the 1 mSv/year limit to the general public and P = 100 uSv for ALARA levels in controlled
