Accuracy and Quality in Radiotherapy Flashcards
(27 cards)
What is meant by quality assurance in radiotherapy?
All those procedures that ensure consistency of the medical prescription as regards to dose to the target volume, together with minimal dose to normal tissue, minimal exposure to personnel, and adequate patient monitoring aimed at determining the end result of treatment.
For radiotherapy with curative intent, good quality is defined as delivering the prescribed dose within ___ and within a geometric accuracy of ___.
±3%
3mm
For radiotherapy with palliative intent, good quality is defined as delivering the prescribed dose with an uncertainty of __ and a geometric accuracy of ___.
7%
10mm
What is a PDCA cycle?
A plan, do, check, act cycle
Describe each stage of a PDCA cycle
Plan: establish objectives and processes necessary to deliver the required results.
Do: implement the process.
Check: monitor and measure the processes against policies/objectives/requirements and report the results.
Act: take actions to continually improve.
What is the ICEPPS accreditation scheme?
The improving clinical engineering and physical science service accreditation scheme. It is an accreditation scheme managed by UKAS to standardise medical physics processes, including quality assurance.
State 5 features of a successul quality system
1) Clinical basis (designed to meet clinical requirements)
2) Inclusion of the whole radiotherapy process
3) Full documentation
4) Detailed records
5) Regular audit
Define accuracy
The closeness of the agreement between the result of measurement and the true value of the measurement. It is a qualitative concept.
Define precision
The repeatability and reproducibility of a measurement, based on the consistency of repeated measurements. Precision can be limited by the resolution of an instrument.
Random errors are _________ and combined in __________.
Measurable
Quadrature
Systematic errors have to be _________ and can either be ________ or combined in _________.
Estimated
Additive
Quadrature
Are random errors type A or type B?
Type A
Are systematic errors type A or type B?
Type B
What 4 factors is dose prescription based on?
- Patient tolerance (including response based on height/weight)
- Standard protocols
- Data from other centres
- Radiobiological data
What does FMEA stand for?
Failure mode effect analysis
Define failure mode effect analysis (FMEA)
A structured approach used to identify potential failures in a system or process. It allows teams to prioritise the most critical failure modes.
What are the 3 categories used to outline potential failures if FMEA?
O: the probability that a specific cause will result in a failure.
S: the severity of the consequences of failure.
D: probability that the failure will be undetected.
How does failure mode analysys work?
For every potential failure, each of the 3 categories (O, S, and D) are ranked from 1-10, and the risk is assessed as O x S x D. Any issues scoring <125 represent little cause for concern.
Describe the process tree (patient pathway) for radiotherapy
State 6 sources of error in radiotherapy
- Incorrect calibration of the machine, resulting in % errors in dose
- Incorrect calibration of the machine, resulting in mm errors in position
- Incorrect patient setup, resulting in % errors in dose
- Incorrect patient setup, resulting in mm errors in position
- Machine interlock failure, resulting in % errors in dose
- Human error, reulting in % errors in dose
Give 5 examples of sources of error in radiotherapy
- Error in SSD
- Error in depth
- Error in temperature
- Accelerator output variation
- Lateral movement at beam centre
- Lateral movement at beam edge
- Differences in prescription point
- Incer-centre prescription differences
- Wrong wedge
- Wrong part if patient
State the 11 critical stages to identify error in radiotherapy
1) Commissioning
2) Periodic calibration
3) Identification of the patient
4) Localisation
5) Preparation of the treatment plan
6) Prescription
7) Simulation
8) First treatment session
9) Daily positioning and parameter selection
10) Accululation of doses on treatment sheet
11) Maintenance of equipment
Why is communication vital in preventing errors?
Because it allows information to be transmitted correctly to the right person, both orally and in writing. It can be used to correct the mistakes of an unqualified person.
Define process integration
The coordination and unification of different processes, systems, and workflows to continuously improve a service.
