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.
what must consignore include when shipping packages containing nuclear substances?
UN number- determined according to type of source
-tre-foil symbol sticker includes UN class 7, radionuclides, chemical form, and max activity, category I,II, or III plus appropriate color, TI (if II or III), word radioactive
-trefoil sticker thing must be on 2 opposite sides of package and min. 10 cm
-documents with package contents
-certificates of approval from relevant authoraties
-specify exclusive use if relevant
-tamper proof seal
-vehicle placards on 4 sides of vehicle for Yellow-III only
-o Emergency response guide number is used by first responders to reference the response required (given in the guidebook) in the event of an accident.
o A 24-hour number where technical information can be obtained.
o Contamination limits: 4 Bq/cm2 for beta and gamma radiation; 0.4 Bq/cm2 for alpha radiation, averaged over 300 cm2.
when conflict in regs?
follow most restrictive
do you need regs for shipping between buildings on same property?
no, but if you cross public road, then need regs
UN number for non-fissile type A special form
3332
UN number for non-special form, type A, non fissile or fissile-excepted
2915
UN number for non-fissile or fissile-excepted, type B(U),
2916
UN number for non-fissile or fissile-excepted, type B(M),
2917
what do you do if unplanned patient dose is different than total prescribed dose?
must notify CNSC within 30 days when unplanned total patient dose differs from total prescribed dose by > +/-10% or unplanned patient dose > 25% in excess of Rx dose resulting from machine malfunction. It is deemed a “CNSC medical event” if these differences are > 20% and > 50%, respectively (and then have to inform in one day and report within 15 days).
CNSC medical events that must be reported (other than patient getting different dose)
- report within 1 day, written rport within 15 days
- wrong radioactive drug, wrong delivery route, wrong patient, wrong treatment mode, leaking source.
label/sign for container containing radioactive substance
needs label: “RAYONNEMENT – DANGER – RADIATION” as well as the name, quantity, date of measurement and form of the nuclear substance [regardless of whether or not it is exempt].
Exceptions: is essential component for operation of nuclear facility, is for immediate use and is under continuous direct supervision of licensee, quantity is ≤ exemption quantity, or if it is used for transport and is labelled in accordance with Packaging and Transport of Nuclear Substances Regulations.
o Sign with radiation warning symbol and words “RAYONNEMENT – DANGER – RADIATION” are required if there is a radioactive nuclear substance in a quantity > 100 times exemption quantity, or if effective dose rate is > 25 μSv/h.
what is prescribed limit of contamination for place where no licensed activity is being carried out?
that which may increase person’s effective dose by 1 mSv or more per year in excess of background for that place
when must major spill be reported to CNSC?
(> 100 times activity given in column 3 of schedule 1 or a spill of any quantity of nuclear substance not given in column 1 of schedule 1, of general nuclear safety and control regulations
Type I inspection
in-depth and last several days. CNSC staff observe and interview staff. Final report is sent to licensee within 60 days
-preliminary report at end of inspection
Type II inspection
less in-depth. No interviews are performed. Final report is sent to licensee within 30 days.
–preliminary report at end of inspection
what does annual compliance report to CNSC include?
o Transfers, purchases, disposals of nuclear substances and radiation devices
o Dosimetry information
o Inventory [of nuclear substances, radiation devices, prescribed equipment]
o Changes in the radiation protection program
nuclear energy worker
worker likely to receive > 1 mSv per year
- Personal dosimetry is required for NEWs who have a reasonable probability of receiving an effective dose > 5 mSv in a one-year dosimetry period.
what happens if worker leaves badge in treatment room?
RSO does calc to show the reading makese sense- reports to dosimetry service
-record can be removed if calc and measurement make sense
what does NEW do with dosimetry badge if they go work at another institution?
If NEW temporarily goes to another hospital to work, they should NOT bring their dosimetry badge from their home institution since these badges are institution-specific and are used to track exposure trends (e.g., to monitor what happens when a new treatment technique is introduced). The NEW should receive a separate badge for the duration of their work at another institution.
regulations for diagnostics
- don’t fall under CNSC
- health canada has guidelines (safety code 35) but regs are provincial
essential safety components of radiation safety program in RO department
- ensure staff have training
- protect environment, health and safety, maintain security
- inventory of equipment, radioactive sources
what document is not relevant for class II nuc facility?
Nuclear substances and radiation devices regulations
where do the nuclear substances and radiation devices regs apply?
all nuclear substances and sealed sources, as well as all radiation devices not included in class II prescribed equipment (unless it is an exempt quantity)
is ortho regulated by CNSC?
No
not considered radiation device
When is the possession, use, transfer, import, export, abandonment and storage of nuclear substances licensed by the CNSC
-when amount of nuclear substance is greater than exemption quantity, which is radionuclide dependent
when is the possession, use, transfer, import, export, abandonment, storage and servicing of radiation devices licensed by the CNSC?
when the amount of nuclear substances contained within the radiation device reaches 10 times the exemption quantity
how many types of licenses (use types) can be issues for nuclear substances and radiation devices?
60
- examples:
- possessin more than 10GBq of unsealed nuclear substance (radiopharmacy)
- diagnostic nc medicine
- therapeutic nuc medicine (i.e. I-131)
licenses NSHA has for class II facilities
Operate and service an isotope production accelerator facility [e.g., cyclotron]
Operate and service the medical accelerator and other radiotherapy facilities
• This includes all linacs (and their maximum operating energies), the brachytherapy remote afterloader containing a sealed source (including replacement or spent source). 370 MBq Sr-90 check source is also included in this licence.
o Max Ir-192 quantity is 444 GBq = 12 Ci
exemption quantity for Ir-192
10 Bq/g - 10^4 Bq
exemption quantity for I-125
10^3 Bq/g- 10^6Bq/g
not class II- signage required at opening to radiation device
RAYONNEMENT-DANGER-RADIATION
safety posters for unsealed nuclear substances
o Basic level: Quantity handled by any worker does not exceed 5 times the annual limit on intake (ALI)
o Intermediate level: “ “ “ does not exceed 50 times “ “ “
o High level: “ “ “ does not exceed 500 times “ “ “
o Containment level: “ “ “ exceeds 500 times “ “ “
o These posters give 24-hour emergency contact (name and phone number) as well as guidelines which are more stringent for higher levels: e.g., don’t eat or drink or store food in this room, restrict access to authorized workers, check all packages containing nuclear substances for damage upon receipt, wash hands regularly and monitor them for contamination frequently, evacuate in case of ventilation failure, etc.
general precaution if nuclear spill
Inform people in the area and keep them away from the contaminated area
Cover the spill with absorbent material to prevent spread of contamination
minor spill
< 100 times exemption quantity
Wear protective clothing. Wipe up spills with absorbent paper and put in plastic paper for transfer to waste container.
Avoid spreading contamination. Work outside to inside
Do wipe test or survey to check for residual contamination.
Check hands, clothing, shoes
Report spill and cleanup to RSO
Record details of spill and contamination monitoring results. Adjust inventory and waste records
major spill
> 100 exemption activity
Clear the area. Persons not involved in the spill should leave the immediate area. Limit the movement of all personnel who may be contaminated until they are monitored.
If the spill occurs in a laboratory, leave the fume hood running to minimize the release of volatile nuclear substances to adjacent rooms and hallways.
Close off and secure the spill area to prevent entry. Post warning sign(s).
Notify the RSO or person in charge immediately.
The RSO or person in charge will direct personnel decontamination and will decide about decay or cleanup operations.
Decontaminate personnel by removing contaminated clothing and flushing contaminated skin with lukewarm water and mild soap.
Follow the procedures for minor spills or proceed in accordance with authorized procedure.
Record the names of all persons involved in the spill. Note the details of any personal contamination.
If required, the RSO or person in charge will arrange for any necessary bioassay measurements.
If required, submit a written report to the RSO or person in charge.
[Report to CNSC] The RSO or person in charge must notify the CNSC immediately and submit a full report within 21 days.
proper care and use of personal dosimeteres
avoid exposing to high temp, water, fluorescent light
-whole body dosimeter between waist and neck
if lost or stolen, don’t work until you have a replacement
-don’t share dosimeters
steps when receiving a package
-verify delivery address
-o Excepted packages: no external labeling is required, and the safety mark “RADIOACTIVE” must be visible upon opening the package. The radiation level at any point on the external surface of the package must not exceed 0.005 mSv/h.
o Compare the nuclear substance, the quantity, and other details with the information on the packing slip and with the purchase order. Log the shipment details and any anomalies in the inventory record.
o Report any anomalies (radiation levels in excess of the package labeling, incorrect transport index, contamination, leakage, short or wrong shipment) to the RSO.
Verify that all information on shipping labels is correct (e.g., measure TI with survey meter – pancake-type GM detector only measures the presence of contamination but does not measure actual dose rate – need proportional counter for this)
Open the outer package and check for possible damage to the contents, broken seals, or discoloration of packing materials. If the contents appear to be damaged, isolate the package to prevent further contamination and notify the RSO.
If no damage is evident, wipe test all 6 sides of the inner package or primary container which holds the unsealed nuclear substance [for liquid vials, wipe the glass vial or inside of the lead pot]. If contamination is detected, monitor all packaging and, if appropriate, all locations in contact with the package, for contamination. Contain the contamination, decontaminate, and dispose in accordance with the conditions of the Nuclear Substances and Radiation Devices licence.
• A clean control wipe may be used to obtain background count.
• If wipe tests show no evidence of contamination, the remove labels (or cross out with marker) before disposing of packaging.
Keep a receiving record (date, supplier, shipper, shipment document ID number) and also update inventory (isotope name, activity, volume chemical form, lot number, results of receiving inspection [e.g., wipe test, dose rate measurement to verify TI])
Notify RSO if: incorrect address and you signed for it by accident, incorrect TI or dose rate > 2 mSv/hr, wipe test fails, package is damaged or leaking or there is evidence of tampering, shipment is lost in the mail.
How is F-18 produced?
o First F-18 is produced in a cyclotron by bombarding O-18 enriched water with protons to create a (p,n) reaction. The protons come from hydrogen gas.
uptake time of F-18
30-90 min
Patients are kept in quiet resting state to avoid uptake in skeletal muscles
half life of F-18
110 min
decays by positron emision 97% of time, yields stable O-18
hot cell
shielded nuclear radiation containment chamber
used to produce FDG from F-18
How does TC-99 m decay?
- used for spect
- Tc-99m decays by gamma emission ~88% of the time, resulting in 140.5 keV gamma rays 98.6% of the time. ~12% of the time, Tc-99m decays by internal conversion (pure gamma emission is desirable for decay mode – these IC electrons contribute to patient dose but do not improve image quality).
How is Tc-99m produced?
Fission of highly enriched uranium (high U-235 concentration; U-235 is fissionable but makes up only 1 part in 140 of natural uranium) yields Mo-99 (the parent of Tc-99m; half-life = 66 hours), which is the transportable source of Tc-99m. Uranium fission of U-235 targets is achieved by neutron bombardment.
half life of Tc-99m
6 hours
biological half life = 1 day
what does Tc-99 decay to?
decays with half-life of ~200,000 to stable ruthenium (Ru)-99, emitting soft beta radiation (no gamma radiation)
I-131 half life
8 days
I-131 dose for thyroid cancer
100-200 mCi
how do you measure the amount of activity in the thyroid?
- uptake probe
- measure activity in thyroid to what was administered
-uptake probe is a NaI scintillator with a PMT and collimatore directed toward thyroid
how does I-131 decay?
by beta minus, yielding electrons with Emax 606 keV. Then decays by gamma emission- 364 keV gammas
how to create I-131
neutron bombardment of tellurium
Is I-131 volatile?
yes
prepared in fume hood
where is I-123 used?
thyroid diagnostic imaging
- half life of 13 h
- gamma of 159 keV. Used for SPECT with gamma camera
what do you do with nuc waste from nuc med patients?
-store on site until decayed to background levels before disposal
nuc med inpatients- max dose to adjacent rooms
0.5 mSv
nuc med outpatients- max dose to public, caregivers etc
1 mSv
caregiver- 5 mSv in one event
quaterly doses for cyclotron operators
up to 1 mSv
need to open cyclotron and replace target
. Inside the cyclotron, there may be long-lived radioactivity due to photoneutron production and subsequent neutron activation – hence it is not even allowable to open the cyclotron immediately after production.
average F-18 used per patient
10-15 mCi
cyclotron shielding
has Pb and high density concrete, which contains boron
unit dose vs bulk dose in nuc med
unit dose= for one patient
bulk dose = for multiple patients
why are therapists on PET-CT cycled among different units?
• Therapists who work on the PET-CT are cycled amongst different units for the purpose of ALARA since setting up PET patients on the PET-CT couch is the largest contribution to their dose.
bathrooms for PET patients?
own dedicated bathroom
must consider where pipes flow for radiation safety
typical diagnostic nuc med dose of Tc-99m
tens of mCis or hundreds of MBqs
how does moly-cow work
-used to extract Tc-99m from decaying sample of Mo-9 Mo-99 has a half-life of 66 hours, which will be more convenient for transport.
Mo-99 can be obtained through fission of uranium-235 obtained via neutron bombardment.
Typically replace moly cow once a week.
Mo-99 in the form of MoO42- is adsorbed onto Al2O3 (alumina). When Mo-99 decays, it forms TcO4-, which, because of its single charge, is less tightly bound. Pouring normal saline solution through the column elutes the Tc-99m, resulting in a saline solution containing Tc-99m.
“Elute” = remove an adsorbed substance by washing with a solvent.
9
-
shielding for alpha particles
relatively easy to shield due to their relatively large mass and charge – their range in most media is limited to a few tens of microns or a few cm in air. Typically, they cannot penetrate the dead layer of human skin. However, inside the body, they do considerable damage because of these same properties
o Also presents a challenge for detection because they need to penetrate detector window/encapsulation in order to be detected. Because they typically are absorbed within a few cm of air, it is easy to miss highly contaminated areas if the detector is in the wrong place.
beta particle shielding
• Beta particles have limited range in most media because they are charged particles and will dissipate energy as they traverse a medium by ionization and bremsstrahlung production. Typical ranges on the order of mm in dense media (the path is tortuous). Range of a few meters in air.
o Determine max range of highest energy beta particle and choose thickness of shielding that matches (or exceeds slightly, to be safe) this range.
proton and light ion shielding
• Protons and light ions. Like other charged particles, attenuation occurs by ionization (and not by probabilistic exponential processes, like for photons). Therefore, the range is definitive. Shielding thickness can be determined by the max range of the most energetic particle in the beam. For charged particles, some bremsstrahlung may be produced, and this must also be accounted for, especially for high energies and high atomic number shielding materials.
survey limit requirement for patient release who had radiopharmaceutical
NRC: < 500 mrem (i.e 5 mSv) to member of public
D= 1.44 * half life * occupancy factor at 1 m * dose rate at 1 m
For I-131, this is < 7 mrem/h at 1 m
for I-125, it is < 1 mrem/h at 1 m
I-131 gamma is 0.22R/m^2hCi
1/2 life = 8 days for I-131
5 mSv PER INSTANCE to caregive (still 1 mSv to other members of public)
as a radiation worker, if you separarely undergo radiation therapy, does this affect your annual dose limit?
no, the dose limit is occupational only
types of radiation dosmetry badges
-TLD, OSLD, x-ray film
what is the ACR recommendation regarding an independent check (second check) of initial dose calcs?
conduct it before 3rd fraction or before 20 % of dose is delivered for < 10 fractions
3 ways to define medical event in RT, other than exceeding permissible and calculated doses
wrong patient
wrong treatment
wrong site
definition of medical event for radioactive material
- one or more sealed sources are leaking
- administering wrong drug/material
- administer to wrong person
- administer by wrong mode of treatment
- delivered dose deivated > 20 % from prescription
if there is medical event, how long do you have to notify the referring physician?
24 h
how long do you keep record of medical event?
3 years
for what energy should a high dose rate brachy room using Ir-192 be shielded?
1.06 MeV- max energy of spectrum (even though average is 0.38 MeV)
is more shielding required in patient holding area or scanning room?
-patient spends more time in holding area and also injection occurs before the scan - holding area requires more shielding
TI of spent brachy source (HDR) Ir-192
~0.4
~140 GBq
CNSC inspections- level of things they may tell you to do
non-compliance
recommendation
-you have to respond by date given in report
what do centers do with old sources?
-can let them decay for 10 half lives
(below exemption value) in shielded locked room as in CNSC license
-must be labelled, inventory controlled
4 important CNSC safety considerations
- management control over work practises (ie procedure)
- personnel qualifications and training
- control of exposure to radiation (ie shielding, time, distance)
- planning for unusual situations
3 important concepts from ICRP 60
- justification
- application of dose limits
- optimization
how to do wipe test
- alcohol swab all 6 sides- air dry- label bag with isotope, date, time, etc- detect on well counter
- use gloves!
limit for leak per CNSC
200 Bq
what training does someone who accepts a package have to have
transportation of dangerous goods
what do you do with the package for the source once it is emptied?
remove trefoil signage, UN number etc.
what does licensee have to do for 3rd party service people?
- provide training on emergency response, evacuation, how to contact RSO, safety procedures etc
- At NSHA we are present with service person for security reason, not for safety
you are told a package is wet
- if package wasn’t accepted, refuse package
- if package was already accepted, barricade and clear area of people
- use GM and survey meter to determine dose rate in area
- if dose rate, keep area clear and barricaded
- investigate if anyone touched package, etc, may need to survey people, de-contaminate
- report to consigner and CNSC
- work with manufacturer to clean the area
- investigate the cause and how to prevent it from recurring
- report findings to CNSC in 21 days
how do people base their fears?
on emotions, not on stats
causes as determined by ICRP
- deficiencies in education and training
- deficiencies in procedures and protocols
- equipment faults
- deficient communication and transfer of essential information
- lack of independent checks
- inattention and unawareness
- unsecured long term storage and abandonment of radiotherapy sources
-accidents often had several underlying causes
incident learning system
- determines basic causes for incidents
- clinical incident severity, occupational, operationl, and environmental
6 categories of severity within clinical incident severity
- minor
- potential serious
- serious
- potential major
- major
- critical incident
common terminology criteria for adverse effects (CTCAE) scale
0 = no adervse effect 1= mild event 2= moderate event 3= severe and undesirable event 4= life-threatening or disabling event 5= death
RTOG developed tool to grade acute and late effects
examples of measurement errors with radiation measurement systems
- dosimeter calibration report was dose to water but interpreted as dose to air
- PP chamber was incorrectly labelled- new physicist took wrong measurements and miscalibrated beam
- pressure at airport was used for Ptp, but hoospital pressure was 1000 m above sea level
- lack of consistenvcy between dosimetry at affiliated institutions
examples of commissioning and calibration errors
- beam miscalibrated- new physicist applied wrong conversion factor based on old physicist’s notes
- physicist didn’t check Co-60 output just kept decaying source- eventually decay curve was incorrect
- incorrect calibrations- no QA done to notice it
- RO used rad/min output when physicist was using Roentgen/min
- power supply led to interlock systme fail- FFF/target never delpoyed- patient got hot spot of radiation from electron beam
- manually changed energy when console didn’t work- but machine was in a mode that ignored the bad console and kept treating at the high energy…
- wedge shifted when gantry was rotated
- linac lost power- dose monitoring system stopped functioning properly and it wasn’t recognized before patients were affected
- inappropriate measuring device for commissioning
errors in treatment prescription, preparation, and information transfer
- hospitla had 2 sets of data- one wrong
- incorrect TMR entries
- wedge factor already included in TPS was also applied manually
- incorrect basic data in TPS
- some parameters imported into TPS manually and others automatically- confusion led to wrror (calculated per new system, but then MU were scaled up per old system)
- institution changed from hard to soft wedges- treatment planners selected fixed wedge instead of dynamic wedge- MU were manually transfered and were too high
- computer crashed- tretment plan saved fluence but not control points. Patient treated with open fields.
errors in treatment delivery and specification
- misunderstanding verbal instructions
- incorrectly identifying patient
- treatment setup based on another patient’s chart
- fracitonal and total dose was confused
- beam is wrongly positioned
- used wrong tattoo in treatment setup
- language communication issues
- wrong setup- treat or image wrong side
- improper patient positioning
general lessons learned
- inadequate standards
- not following standards
- inadequae communication
- inadequate risk assessment
- equipment used wrong
- inadequate documentation
- personnel availability
- inadequate training
- unclear roles
- lack of communication
- inadequate direction/information
name of CNSC license application form
REGDOC
all the CNSC docs are called this
when immediately reporting an event to CNSC, is email ok?
No, have to directly speak with a person (CNSC duty officer)
3 types of “reports” to CNSC
- immediate
- notification (ex exceeding action level, cannot deliver to consignee)
- report
is the death of a critically ill patient in a class II facility reportable?
yes, because any death in a class II facility is reportable to CNSC
does a patient injury due to human error of linac need to be reported?
no, if it is 100% clear that it is solelyt human error and not to do with the class II equipment \-same thing for example, someone drops I-125 seed on patient and quickly picks it up
if dose reading is high on opersonal dosimeter but we know it is because the dosimeter was left in the vault, do we need to report this to CNSC?
No
Units are using more modulated treatments at 6 MV- is this a concern for workload?
since lower energy, not super concerning since machines were often shielded for higher energy beams
however, the higher use of modulation could mean the leakage workload is a lot higher
when a source is being shipped from outside canada, who becomes the consignor?
the receiver in Canada
most common non compliance for Class II facilities
failure to adhere to procedures (ex daily QA)
do you need license to decommossion bracy after-loader?
No, but require revocation of operating license
licenses that keep getting renwed- when is there every an expiry after which records can be destroyed?
when machine is decommissioned or removed can be considered expiry date
what is applicant authority
person accountable for ensuring complicance with all licensee obligation
-appoints RSO
who keeps the record of service when a third party services equipment?
both the third party service and the licensee (owner) of equipment
2 types of demands CNSC can give
- notice of non-compliance (more serious, licensee not complying)
- action notices- recommendation
how must licensees inform NEWs of their dose
in writing
making info accessible but expecting NEWs to go get it is insufficient
how does CNSC recommend planning for unplanned situations
dry runs of emergencies
everyone knows their role
practise at least annually
example is HDR stuck source
top 3 most common non-compliances Class II facilities
- not following policies/procedure submitted to CNSC
- All reasonable safety precautions not taken (ex. inspector sees staff doing something unsafe, but it doesn’t follow into a specific non-compliance, testing not at frequency specified in license, room cannot be seen from LPO location, procedures don’t accurately represent process)
- using policies/procedures not submitted to CNSC
what is safety barrier
components in a program that are designed to prevent errors
what is defense in depth
layers of “defense”- uses redundant and diverse control systems
manner to investigate safety incidents
root cause analysis
probability risk assessment
- event or process trees model the plant response to each initiating event
- fault tress model plant systems in detail
- human reliability analysis is used to evaluate human errors that are important to the outcome of an event
- MC methods compute the risks or an error
process tree analysis for brachy HDR
- tree is successful completion of a brachy event
- branches are process steps that must be completed
- leaves are activities in each step
fault tree analysis
- identifies all possible ways a treatment could go wrong and trace these back to initiating error
- not based on event, focused on part of procedure that failed in a hypothetical situation
FMEA
- failure mode and effect analysis
- identifies all possible failures
- looks at consequences of failure, frequency of occurrence, ease of detection, to prioritize actions
RPN
- risk probability number
- in FMEA analysis
- product of severity, occurence, and probability failure is undetected
- higher RPN activities are worked on first
scoring system for severity FMEA
- 1 = no effects
- 2 = dose change 5 %
- 4= minimal delay in care
- 6= allergic reactions, moderate delay in care
- 8= dose change 20% reportable
- 10= patient dies
scoring system for occurrence FMEA
- 1= less than every 5 years
- 2= every 2-5 years
- 3= once a year
- 4= several times a year
- 5= once a month
- 6= several times a month
- 7= once a week
- 8= several times a week
- 9= once a day\
- 10= several times a day
scoring system for detectability FMEA
- 2= very easy to detect
- 4= easy to detect
- 6= mildly difficult to detect
- 10= impossible to detect
examples of voluntary incident reporting systems
- radiation oncology safety information system
- SAFRON by IAEA- safety in radiation oncology
-CNSC is mandatory
5 general areas for improving radiotherapy safety
- education, training, and staffing
- equipment design and infrastructure- mainintaing, commissioning properly, external dosimetry audit
- quality management and procedures- periodic procedure review, quality audits
- safety culture, safety barriers, and defense-in-depth- working with awareness, communication, rounds
- regulations
Ottawa hospital ortho incident
> 300 patients underdosed because ratios of backscatter factors were not applied (re-commissioning only covered 10x10 field, did not get factors for cones…)
- output tables not properly made
- 2nd check not done
- error not discovered for 3 years
- overall blamed on staffing shortage
common error with small fields
using wrong dosimeter- machine is calibrated wrong
-always compare to other hospitals
