QA Sim 1

TG tables

quality control

operational techniques to fulfill requirements: routine maintenance, operating parameters, machines specs

QA

actions to verify procedures/equipment with criteria

quality audit

independent evaluation

QA purpose

identify and reduce the sources of uncertainty and error while taking into account economic, medical, and legal factors

QA measurements

verify that operating parameters have not changes with time

high frequency measurements

high risk for failure, significant impact on patient

low frequency measurements

low risk for failure and less impact on patient

daily checks

seriously affect patient treatment

daily check examples

patient positioning (lasers, ODI)

patient dose (output consistency)

safety (interlocks, audio visual)

monthly frequency

smaller impact on patient treatment (couch indicators)

less likely to change over a month (light and radiation field coincidence, flatness)

many mechanical checks

annual

quantify (verify) all parameters

what does the QA committee consist of

members from medicine, physics, and tx areas

what does the QA committee do

oversee, monitor, and audit the QA program

write policies

meet frequently

QA team

quality control tasks are given to other members-this is the QA team and they should be supported by the QAC

Quality Audit

annual reappraisal of the rad onc QA program

audit is performed by people not responsible for service

resources

the chairman should make sure that resources are available: personnel, QA test tools, time for QA program, and educational programs

ICRU criteria for external beam (photon and electrons)

± 5%

acceptance testing

vendor has to satisfy all criteria in the purchase price (does it meet the agreed safety standards?_

commissioning

determine operating parameters of the equipment before treating: output, field size dependence, depth dose, wedge factor….

done by the physicist

t/f an approved rt equipment need not to be acceptance tested before being put to clinical use

false

machine commissioning is carried out to ensure that the machinery conforms to performance standards set for that equipment t/f

false=this is QA testing

t/f the beam data of any RT equipment can be obtained from another clinic having the same model

false

t/f it is not crucial to carry out QA of a simulator because the risk of radiation exposure is low with this machine

false

t/f the functional performance of rt equipment can change from environmental conditions

false=changes from wear and tear and electronic components-not weather

t/f the montly tolerance for localuzing lasers is ±1mm for non imrt plans

false, ± 2mm

t/f output is a good indicator of field uniformity

false-use flatness and symmetry

t/f the recommended tolerance for identifying the isocenter is the gantry rotation is—-

sphere of 2 mm diameter

t/f the tolerance for rad and light field coincidence on LINAC is 3mm

false, 2 mm or 1% of the field length (whatever is greater)

Roles of Med Physicist

calibrate rad onc equipment

therapy equipment specs:

acceptance testing, comisioning, qa

measurement and analysis of beam data

tabulation of beam data for clinical use

MP-specs of therapy equipment

facility design, safety requirements are met

MP measurement and analysis of beam data

generate beam data for all energies and sources, ane evaluate data quality

tabulation of beam data for clinical use

assure that beam and source data are correctly entered into tps

Role of MP II

establish dose calc procedures

establish treatment planning and treatment procedures

education

tx planning

supervise equipment maintenance

MP-establish tx planning and tx procedures

technical aspects of process (how block is to be cut) and flow of procedures

CMD roles

tx planning

may be involved in sim

dose calcs

education

supervision

radiation measurement

CMD-radiation measurement

helps physicist with special clinical measurements-using ion chamber, tld, or film

assist with machine calibration and qa under MP supervision

may perform source loading, isodose computation, and radiation survey in brachy

CMD supervision

records services for reimbursement

order equipment

schedules preventive maintenance

who does acceptance tests

physicist

manufacturer

who does machine commissioning

physicist

who does annual calibration/check

physicits

who does montly check

dosi, engineer, physisict

who does daily check

therapist

dosi

engineer

physicsist

brachy QA values

dose delivery: ±15%

source calibration: ±5%

what should the description of sealed sources incude

physical and chemical form

source encapsulation

radionuclide distribution and source uniformity

source identification

what should the description of sealed sources include-physical and chemical form

provided by manufacturer

chemical composition of radionuclide and inert filler material

source encapsulation-what should the description of sealed sources incude

available from manufacturer

can influence source calibration, dose distribution, and physical integrity of source

what should the description of sealed sources incude-radionuclide distribution and source uniformity

check uniformity via autoradiography and transmission x rays

what should the description of sealed sources incude-source ID

engraved codes are difficult to read, color coding tends to fade or flake off

color coding recommended and color should be replenished as needed

ICRU reccomendation for source calibration

quantity of radiation emanating from source: “air kerma strength”

calibration must be traced to national or international standards

direct traceability

source has been calibrated at NIST or an AAPM

secondary traceability

the source calibrated in comparison with a source of the same design and comparable strength which has direct traceability or when is calibrated using an instrument with direct traceability

secondary traceability by statistical inference

established for a group of sources for which a suitable random sample has been calibrated with secondary traceability

remote traceability

relies on manufactuer calibration only

do not rely on manufacturer statement of source strength

long half life source calibration

all long half life sources should be calibrated

short half life source calibration

secondary traceability by statistical inference is appropriate-sample 10% of seeds or 2 ribbons

well ionization or reentrant chambers

preferred for conventional strength brachy sources

thimble chamber

measure radiation intensity at a distance and preferred for HDR sources

thimble chambers have been used for ________ and well chambers have been designed for ____

conventional sources, HDR sources