Miscellaneous Flashcards
1 Gy in rad
100 rad
1 Sv in rem
100 rem
Roentgen
2.58*10^-4 C/kg
what is in NCRP 116?
• Similar to ICRP 103, which is more recent anyway (2007 vs. 1993)
• Guidance for emergency occupational exposure: only actions involving life saving justify acute exposures significantly in excess of annual effective dose limit.
o Older workers with low lifetime accumulated effective doses should be chosen when possible
o For equivalent doses > 0.5 Sv to a large portion of the body in a short time, workers need to understand not only the potential for acute effect but also the substantial increase in lifetime cancer risk.
what is NCRP
National council on radiation protection and measurements
NCRP 107 is on what?
ALARA for medical and dental personnel
is it enough for licensee to just respect dose limits?
not per ALARA- licensee must do all they can to reduce dose within reason
what happens if licensee demonstrated that occupational doses are unlikely to exceed 1 mSv/yr and public doses 50 uSv/yr?
CNSC may decided ALARA assessment is not required
-motivation for 1 mSv is because background variation is ~ 1 mSv
limitations of personal dosimeters
- may be orientation or energy dependen
- accuracy of readout
- relationship between reading and effective dose
MDL
minimum detectable limit
mean annual whole body dose of all medical workers in 1980 in Ontario
0.6 mSv/yr
what 2 things does detriment take into account?
probability and severity
collective dose equivalent
product of dose equivalent in whole body or any specified organ and number of members in exposed group
NIRL
negligible individual risk level = annual individual dose equivlanet below which the average excess risk of health detriment is so low as to make unwarranted any further effort to reduce exposure = 0.01 mSv/y
IRR
individual reference range = range of dose equivalent values that, if exceeded, automatically triggers optimization activity.
CRR
collective reference range = bounds of CRR are 1 and 2 SD above mean collective dose equivalent. Is collective analog of IRR
How do you choose IRR and CRR?
Average annual dose equivalent = 0.55 mSv, average of monitored employees that receive at least one measurable reading during the year = 0.9 mSv. Maximum yearly dose equivalent received by any individual = 3.75 mSv. Average yearly collective dose equivalent= 5.5 person-mSv.
Choose IRR from 0.55 to 1 mSv per quarter and CRR from 1.5 to 1.9 mSv per quarter (doses are typically reviewed quarterly)
most significant significant souce of exposure for RO pesonnel
brachy without remote afterloader
what happens if xray beam if not collimated to size of image receptor?
must shielf therapy simulation rooms with primary radiation barriers
exposure due to Co-60
head leakage is always present, not just when the machine is on. Exposure to Co-60 head leakage may result in 1 to 2 mSv/year average dose equivalent to technologists working solely with Co-60. The same study noted that technologists working solely with 4 MV and 6 MV linacs never received measurable monthly film badge exposures, but that those working on a 25 MV linac did (due to radioisotopes produced by photoactivation of air and accelerator components)
is the 5 year dosimetry period rolling specific to each worker?
No
first one began Jan 1 2001
limit for total occupational dose
5 * (N-18) where N is age
• Total effective dose received by NEW during full working life should not exceed 1 Sv (assuming 50 working years, this corresponds to 20 mSv/year
nominal risk coefficients and detriment-adjusted risk coefficients for workers and all persons
Detriment adjusted values are smaller because a non-fatal cancer is “less detrimental” than a fatal cancer although it still causes harm in terms of loss of QOL and years of life lost.
- nominal = 17.2 % /Sv for all persons, detriment adjusted is 5.7%/Sv
- nominal = 11.8%/Sv for all working population, detriment adjusted is 4.2%/Sv
-these numbers include cancer and heritable
cancer only= 5.5 and 4.1%/Sv
heritable: 0.2 and 0.1%/Sv
relative risk vs ERR vs EAR
• Relative risk: rate of disease in exposed population divided by rate of disease in unexposed population
• Excess relative risk (ERR): relative risk minus 1 (typically expressed per Sv or per Gy)
• Excess absolute risk (EAR): rate of disease in exposed population minus rate of disease in unexposed population.
o Use when risk of disease does NOT depend on normal rate of occurrence of that disease.
detriment adjusted nominal risk coeff for exposure to low doses and dose rates
0.1%/Sv for adults, 0.2 %/Sv for whole
using DDREF of 2
heritable effects considered in nominal risk coeff are to which generation?
second
why do we use DDREF?
because estimates are based on atomic bomb survivors, which received a relatively high amount of dose in a short amount of time
-have to account for lower dose and dose rate
lethality fraction for genetic diseases
80%
most radiation-induced mutations are multigene or single gene (Mendelian) deletions?
multi-gene
baseline frequencies of genetic diseases imn humans
total 73.8%
65 %= chronic multifactorial 6 % = congenital abnormalities multifactorial 0.4% = chromosomal 0.95% = mendelian autosomal dominant 0.05%= mendelian x-linked 0.25% = mendelian autosomal recessive
does reduction in gonadal tissue weighting factor in ICRP 103 compare to ICRP 60 provide justification for allowable controllable gonadal exposures to increase in magnitude
NO
lethal effects of dose to embryi/fetus
infrequent < 100 mGy
increase with dose
when does max sensitivity to malformations occur?
organogenesis
treshold of 100 mGy
when does growth disturbance occur for fetus?
-growth disturbance without malformation can be induced at all stages of development but more common in latter part of pregnancy
Embryos exposed during early organogenesis show the greatest growth retardation (due to cell depletion). A significant effect on the frequency of microencephaly is observed when radiation exposure occurs prior to 16 weeks post-ovulation. Probability of microencephaly increases with dose and there is little evidence for a threshold
when does severe mental retardation occur for fetus?
- most sensitive 8-15 weeks post conception
- Can also occur due to irradiation during weeks 16 to 25, but the risk is four times smaller.
- Approximately 25 IQ points are lost per Gy.
- treshold is 300 mGy
why is embryo/fetus more sensitive to radiation?
o Embryo and fetus has more rapidly proliferating cells (less well differentiated cells) and is therefore more radiosensitive than an adult
risk of cancer due to in-utero irradiation
be similar to that following irradiation in early childhood (at most about 3 times that of the population as a whole)
should woman terminate pregancy because she needs DI exam?
• For pregnant patients, risk to the mother of not doing the diagnostic radiology exam is almost always greater than the risk of potential harm to the embryo/fetus. Doses below 100 mGy are not a concern. Higher doses to embryo/fetus during RT may motivate termination of pregnancy
what % of population is very radiosensitive due to inhereted mutations in DNA damage-sensing or repair genes?
<1 %
ataxia-telangiectasia
RBE for high LET radiation (neutrons, alphas) at low and high doses
the RBE for deterministic effects (at high doses) is lower than the RBE for stochastic effects at low doses
RBE tends to increase with decreasing radiation dose, and with decreasing dose per fraction.
LD50/60 for humans
- half die in 60 days
- 4 Gy without medical care, 6 Gy with medical care
acute radiation syndrome (ARS)
effects of ionizing radiation on whole organism
stages of ARS
prodromal syndrome
latent period
manifest illness
recovery/death
prodormal is early (few days), then latent period, then potential life-threatening symptom
what is radiosensitvity proportional to?
inversely proportional to cells degree of differentiation
for what dose do detectable blood changes occur?
- low cell counts for doses > 0.25 Sv
- nausea and vomiting >1-2 Sv
lowest dose that may cause symptoms of radiation sickness (nausea, vomiting)
1 Sv if received within 24 h
lowest dose at which damage to organs/tissues have been observed following acute exposure?
100 mSv
haemopoietic failure
- cause of death for doses = 5 Gy
- death in 1-2 months
- damage to bone marrow
- depletion of stem cells for circulating blood cells
gastrointestinal failure
- cause of death for doses 5-15 Gy
- occurs in addition to haemopoietic’
- extensive bloody diarrhea and destruction of GI mucosa
- death in 1-2 weeks (i.e 7-20 days)
- LD50 ~ 10 Gy without medical care
- Depletion of stem cells means inability to renew endothelial cells on the villi (finger like structures lining the intestines to increase surface area). This results in denudation of the villi, which can be followed by further damage to GI tract by e.g., ulceration leading to sepsis.
If some marrow and most of the gut are spared due to inhomogeneous irradiation, then 10 Gy to lungs will result in severe pneumonitis possibly resulting in death. Death within 60-150 days
cerebrovascular syndrome
Doses toward 50 Gy, > 15 Gy
acute damage to nervous and cardio system
-death in a few days (<5)
what happens to LD50 if length of time that dose is delivered is extended?
LD50 may increase
direct reading personal dosimeter
used for tracking doses received by pregnant NEWs in addition to dosimetry badge. Also used for tracking dose received in special operations (e.g., emergency, source loading). Allow for instantaneous display of accumulated dose at any time. There are two categories:
- self-reading pocket dosimeters
- electronic personal dosimeters
self-reading pocket dosimeter
consists of an ion chamber that acts as a capacitor, which starts out fully charged. Exposure to radiation discharges the capacitor, which moves a quartz filament on the readout scale. Not as popular as EPDs in recent years.
electronic pocket dosimeter
miniature GM counters or silicon detectors. Flashing or chirping frequency proportional to dose equivalent rate so that changes in radiation field can be recognized immediately.
how values of wt are decided upon?
- Determine lifetime cancer incidence risk estimates for radiation-induced cancers (find ERRs and EARs) [e.g., determined from atomic bomb survivors]
- Apply DDREF = 2 (i.e., divide by 2). Exception: leukemia, where LQ model for risk already accounts for DDREF
- Transfer risk estimates across populations: ERR:EAR weights are established to provide reasonable basis for generalizing across populations with different baseline risks
- Apply these weighted risk estimates across western and Asian populations (having different baseline risks) to determine nominal risk coefficients
- Adjust for lethality: convert to fatal cancer risks by multiplying by lethality fractions derived from representative national cancer survival data.
- Adjust for QOL: account for morbidity and suffering associated with non-fatal cancers.
- Adjust for years of life lost (age distributions of types of cancers differ)
- Radiation detriment for a particular tissue is calculated as (nominal risk of fatal disease) plus (nominal risk of non-fatal disease multiplied by a weight reflecting reduced QOL) – then this sum is multiplied by the average life lost due to disease as a fraction of the average over all cancers.
Nuc Med shielding considerations
-shielding provided by scanner is ignored in calc, but patient attenuation is not ignored like it is for linacs
amu
approx equal to molar mass (g/mol)
class IA in CNSC
nuclear fission/fusion power plants and other reactor facilities
class IB in CNSC
nuclear fuel processing facilities and waste facilities
what can you do without a license for class II facility?
- construct/operate/modify/decommission/abandon a class II nuclear facility that includes a geophysical logging particle accelerator
- decommission a class II nuclear facility that includes a brachytherapy remote afterloader
- possess/transfer/produce class II prescribed equipment that does not contain a nuclear substance.
general safety requirements for class II facilities
- These requirements apply to licensees who operate of class II nuclear facilities OTHER THAN facilities that include brachy remote afterloaders that incorporate pure beta emitters as their only nuclear substances OR facilities that include particle accelerators used for geophysical logging
- Door interlocks:
a. Equipment stops when door is opened. Equipment cannot be used when door is open.
b. Last person out (LPO) switch (activated from within the room; person must leave and close the door within a preset time).
c. Door should only lock from the outside (i.e., no one should ever be locked inside the room). - If there is no door [i.e., there is a maze]
a. Equipment stop when person passes through entrance [due to motion detection system at threshold]
b. Equipment cannot be used until LPO activated - Visual monitoring system [we have audio, intercom system as well].
- Beam status indicator display at entrance to room that indicates irradiation state of equipment.
- Every room in which a class II prescribed equipment (other than a particle accelerator) is located shall be equipped with an independent radiation monitor which produces an audible alarm when someone enters the room while the beam is on, and which has an independent back up power supply.
- In a room with a class II prescribed equipment that does not treat people, there should be a continuous audible alarm before irradiation begins that is of sufficient duration such that it enables a person inside the room to operate one of the emergency stop buttons.
- Emergency stop buttons throughout treatment room that cause the equipment to revert to a safe state until the safety circuit is reset from inside that room and a switch on the control console is operated.
- The emergency stop button should be unobstructed, accessible and located at the following places (as a minimum):
a. at control console
b. near entrance of room,
c. (not for brachy remote afterloader) on both sides of equipment or on the wall on both sides of equipment - For a teletherapy machine, these buttons should not be in the machine’s direct primary beam.
- A sign indicating 24-hour emergency contact name or job title and telephone number.
- Device should be password/key protected so that only authorized personnel may operate the device.
- Following service, the licensee must perform test or inspection that establishes that the device is functioning as prescribed.
- Items 2, 3, 7, 9b, 9c do NOT apply to particle accelerators that meet at least one of the following criteria [no door interlocks, no LPO, no audible alarm, emergency stop only a console]:
a. Max dose rate at 30 cm ≤ 0.2 mSv/h, located in a locked room that can only be accessed by persons authorized by the licensee
b. Max dose rate at 30 cm ≤ 0.025 mSv/h - Items 2b, 3b, 9b (no LPO, no emergency off on either side of equipment) do not apply to brachy remote afterloaders that contain a source that (if exposed) would produce a radiation dose rate in air of less than 10 mGy/h at 1 m
a. For comparison: air kerma rate constant for 192Ir = 108 uGy m2 / (GBq h). For 370 GBq at 1 m: 40 mGy / h
when does RSO have to pass exam>
for class II -not for facilities that are not class II and are not exempt- in this case CNSC assesses their qualifications but there is no exam
CNSC requireents specific to remote afterloaders
Following treatment, patients must be surveyed to ensure they are free of nuclear substances.
A remote alarm system which detects and warns of any interruption in treatment.
A shielded storage container for emergencies (e.g., when the source doesn’t retract).
Remote handling tools necessary to recover the radioactive sources in an emergency.
o A separate, locked storage room for storing old sources before they get shipped, and for new sources before they are installed is also required for brachytherapy remote afterloaders
CNSC requirements after sealed source installation
- Following sealed source installation, take measurements of dose rates when equipment is not in irradiation mode (i.e., when source is in shielded position). Notify CNSC if dose rate exceeds manufacturer’s specifications.
- For radioactive source teletherapy machine, measure radiation doses at all accessible locations outside the room when operating under conditions that yield max dose rate for each location.
what happens if you receive a package and leakage of > 200 Bq is detected?
[notify RSO], discontinue use, attempt to limit spread of radioactivity as much as possible, notify CNSC. Package up the sealed source or radiation device and send it back to the licensed service provider for repair/disposal
records to be kept
- Record of measurements of dose rates should be retained for the period ending 3 years after the earlier of the expiry date or date of revocation
- Record of daily output, training (record to be kept as long as worker is employed), inspection/verification/servicing/measurement/test
- Record of transfer of equipment (name of person to whom equipment was transferred, model/serial number)
- Leak tests, radiation surveys
- Licensees who hold licence to service must have record of services performed
license to operate has what 2 types?
- commission
- routine operation
license to service- what 2 types?
license to service by operator
license to service (3rd party)
class II prescribed equipment licenses
licence to construct, operate, decommission, service
class II prescribed facilities licenses
licence to construct, operate (for the purpose of commissioning), operate (for routine operation), decommission
license from radiation protection regulations
• Licence to operate dosimetry service – the company that provides our TLD badges
shielding construction inspection should include what?
i. Location and width of primary barrier wrt isocentre (include picture of ruler held up against edge of wall)
ii. Thickness and density of concrete
iii. Thickness of any other materials used for barriers
iv. Metal and BPE neutron shielding adequacy
v. Adequacy of door [esp. check around door frame]
vi. Thickness of metal used to compensate for recesses in the concrete (e.g., for lasers)
vii. Thickness/composition of HVAC baffle
viii. Location/size of pipes/conduits
what does management system include in CNSC?
o RSO job description o Organizational management o Radiation safety committee o Reporting requirements (policies and procedures) o QA program o Control of records
concepts included in radiation protection
o ALARA policy
o Procedures for personal dose monitoring; action levels
o Radiation detection instruments: calibration and instructions for use
o Room signage
o Brachytherapy sealed source change procedure, post-treatment patient survey
o Fire response
how long are CNSC licenses valid for?
operating = 10 years
all other types- 5 years is typical
7 parts of application for class II nuc facility
• General information
• Facility construction
• Commissioning
• Management system and radiation protection program
o Think of this section as describing the essential components of a radiation safety program
• Routine operation and confirmation of facility design
• Decommissioning plan
• Licence renewal
license requirements if I want to replace true beam with another true beam?
may bypass the construction licensing phase and apply for a licence to operate for the purpose of commissioning, provided the new equipment has the same isocentre, same or smaller maximum field size and same or lower energy of the equipment it is replacing
2 relevant agencies for transport of nucs
CNSC
Transport Canada
exclusive use
package can’t be in cargo of airplane or other conveyance with passengers
TDG
transport of dangerous goods
necessary markings for shipping
o Identification of either consignor or consignee, or both – need durable and legible marking
o Radiation trefoil symbol should be on outermost receptacle; should be water and fire resistant.
o Different types of shipping labels:
Category I white label with trefoil symbol giving list of radioactive components (name of radionuclide and form it is in) and the activity.
Category II or III yellow labels also include transport index (TI)
excpeted packages- necessary markings
require no outside label, but does need warning inside with the word “radioactive” visible when the package is opened
when is a package excepted?
if the dose rate at the surface is < 0.005 mSv/h and it also depends on the A1 and A2 values, whether it is an instrument/article or material, whether it is solid/liquid/gas
excepted means not category I, II or III? - i.e. doesn’t need license?
Type A vs Type B vs Type C packages
o Type A: activity < A1 for special form radioactive material, activity < A2 otherwise
o Type B: less robust than type A. Can contain any quantity of any type of radioactive material up to that allowed by its approval certificate. However, if transported by air, then limits are 3000 A1 or 100,000 A2 (whichever is lower) for special forms and 3000 A2 for all other forms.
Type B(U) is unilaterally approved (approved by one jurisdiction and accepted elsewhere without further approvals)
Type B(M) is multilaterally approved (must be approved by each country crossed by the shipment)
o Type C: Intended for the shipment of very large quantities of radioactive material by air where impact velocities from aircraft crashes can be significantly greater than those from other modes of transport. This is a very robust type of package.
o Additionally, if the material is fissile, then packaging must also be designed to ensure criticality safety under a variety of conditions (want to prevent uncontrolled nuclear fission chain reaction).
who issues the transport of dangerous goods certificate of training?
employer
- ground transport is good for 3 years, air for 2 years
- o Untrained individual can prepare a package for transport under direct supervision of trained individual.