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Radiation Therapy · Records, Consent & Process Literacy
Machine Quality Assurance — How They Know the Dose Is Correct
Medically reviewed by Dr. Kirti Ranjan Mohanty, Radiation Oncologist, MBBS · MD (Radiation Oncology), Senior Consultant · Last reviewed August 2026
Machine quality assurance is the scheduled testing that proves a radiotherapy machine is delivering the dose it was asked to deliver. The beam is measured every treatment morning, before the first patient. Wider checks run monthly and annually. None of it depends on you noticing that something is wrong.
- Checked before the first patient — the beam output is measured against a reference value each treatment morning, and the safety interlocks are tested, before anyone is set up.
- A named physicist owns it — a qualified medical physicist calibrates the machine, runs the checks and signs the records. You are allowed to ask who that person is.
- Your own plan is checked too — complex plans are usually delivered to a measurement device, or recalculated independently, before your first session.
- Where your treatment happens — your radiotherapy is delivered at an NABH-accredited partner centre; CION Cancer Clinics coordinates your treatment plan, your oncology team and your care throughout.
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The short answer
What is radiotherapy machine quality assurance?
Machine quality assurance is a scheduled programme of measurements that confirms a treatment machine is delivering the dose it has been asked to deliver, in the right place. It runs daily, monthly and annually. It is documented and signed. It happens whether or not anyone suspects a problem, which is exactly the point.
The fear underneath this question is usually simpler than the answer: what if the machine gives me the wrong dose. The honest response is that a radiotherapy machine is not trusted on its own. Its output is measured before the first patient every treatment day. Your position is checked with imaging at the couch. For most modern techniques, your specific plan is proven on the machine before it is ever used on you.
Nothing here rests on a single check. The design is layered, so that a fault has to survive several independent tests to reach a patient. Machine QA is the routine, unglamorous part of that design, and it is the part patients almost never see.
This page describes general practice at radiotherapy centres in India and internationally, so that you can ask better questions. It is patient information, not a promise about any particular centre or machine, and not a substitute for what your own oncology team tells you.
Did you know?
Independent dose auditing for radiotherapy is older than most of the machines it checks. Under a long-running IAEA and WHO postal dose audit programme, a small dosimeter is mailed to a radiotherapy centre, irradiated on that centre’s own machine to a stated dose, and mailed back to be read by an outside laboratory. The centre does not grade itself — an independent body reports whether the beam delivered what it claimed.
Question one
What is checked on the machine, and how often?
Six layers, on six different clocks. The beam output and the safety systems are checked every treatment morning. Beam shape and mechanical accuracy are checked monthly. A full recalibration is done annually. Your plan is verified before session one. Your position is imaged at the couch. An outside laboratory audits the dose independently.
Every treatment day
Beam output, interlocks and lasers
Before the first patient, a physicist or trained technologist measures the beam output against a reference value and tests the door interlocks, emergency stops and positioning lasers. If a reading falls outside the tolerance band, the machine is not used until it is investigated.
Every session
Your position, verified by imaging
A perfectly calibrated beam still has to land on the right anatomy. Imaging taken on the treatment couch is compared with the planning scan, and the couch is adjusted before the beam is switched on.
Monthly
Beam quality, symmetry and mechanics
A fuller set of measurements looks at how flat and symmetrical the beam is, how accurately the gantry, collimator and couch move, and whether the imaging system and the treatment beam still agree on where the centre of the target is.
Annually
Full recalibration against a reference
Once a year the machine is recalibrated using a reference-standard measuring instrument, and the mechanical and dosimetric tests are repeated in depth. This is the check that anchors every daily reading taken during the year.
Before session one
Patient-specific plan verification
For shaped-beam techniques, the plan drawn for you is commonly delivered to a measurement device on the couch instead of to you, and the measured dose pattern compared with the calculated one. Some centres verify by independent recalculation instead, or do both.
Independently
External dose audit
An outside laboratory irradiates and reads a dosimeter exposed on the centre’s machine, and reports whether the delivered dose matched the stated dose. It is the one check the centre cannot mark for itself.
Professional protocols such as the AAPM Task Group 142 report set out what belongs on each of these schedules. In India, periodic output checks, radiation surveys and record-keeping are also conditions of the machine licence issued by the Atomic Energy Regulatory Board.
Question two
Who verifies it — and who checks the checkers?
A qualified medical physicist owns the programme, and four other layers sit around them. Technologists run the daily routine. A radiological safety officer covers radiation safety. Your radiation oncologist approves the plan and reviews verification images. The national regulator licenses the machine. An external laboratory audits the dose from outside.
- The medical physicist — calibrates the machine against a reference standard, designs and signs the QA schedule, checks treatment plans, and decides whether a machine is fit to treat on any given morning. This is the person whose name is worth knowing.
- The radiation therapy technologists — run the daily checks, position you, take the verification imaging and record every session. They are the ones who notice when something behaves differently from yesterday.
- The radiological safety officer — a named, qualified appointee required at every licensed radiotherapy facility in India, responsible for radiation safety, staff dose badges and regulatory records.
- Your radiation oncologist — approves the treatment intent, the dose and the target, and reviews the verification images through the course. Machine accuracy is meaningless if the plan itself is not right, and that judgement is clinical.
- The regulator — in India, the Atomic Energy Regulatory Board licenses the machine and the room, and makes periodic output checks, surveys and record-keeping licence conditions rather than optional good practice.
- An independent laboratory — through external dose-audit programmes, an outside body reports on the centre’s delivered dose. It is the layer that stops a centre from being the only judge of its own accuracy.
CION Cancer Clinics does not own or operate a linear accelerator or any radiotherapy equipment, and is not itself NABH-accredited. The machine, its licence and its quality-assurance programme belong to the NABH-accredited partner centre that operates it; CION coordinates your treatment plan, your oncology team and your care throughout.
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Comparing centres on technology? Ask about the checks too
A newer machine with a thin QA programme is not an upgrade. A radiation oncologist can tell you what a solid answer sounds like — free and confidential.
Do this yourself
How can I check a centre’s machine quality assurance myself?
Six questions. About twenty minutes, on a visit you were making anyway. You are not auditing the physics — you are finding out whether the centre can answer plainly.
Ask who the medical physicist is, what is checked each morning, when the annual calibration was done, whether an external dose audit is carried out, whether your own plan is verified before session one, and how your position is imaged at each session. Write the answers down.
Ask who the medical physicist is
Every radiotherapy centre must have a qualified medical physicist responsible for calibrating the machine and running the QA programme. Ask for the name. The answer should come back immediately, without a search.
Ask what is checked before the first patient each morning
You are listening for beam output measured against a reference value, plus interlocks and lasers. Then ask the follow-up that matters: what happens if a reading falls outside the tolerance band. The right answer is that the machine is not used until it is corrected.
Ask about the monthly and annual checks
Ask when the machine was last given its full annual calibration, and whether the monthly QA records are maintained. Dates are more informative than reassurances. A centre that knows its own dates keeps its own records.
Ask whether an independent external dose audit is done
This is the question few patients ask and the one that separates centres. An external audit means an outside laboratory, not the centre, reports on the delivered dose. Ask whether the centre takes part in such a programme and when it last did.
Ask whether your own plan is verified before session one
For shaped-beam techniques, ask whether patient-specific QA is performed — the plan delivered to a measurement device, or independently recalculated, and compared with the plan. Ask when it is scheduled for you, so you know it has happened.
Ask how your position is verified at each session
Ask how often imaging is taken on the treatment couch, and who reviews it. Then take anything unclear back to your radiation oncologist rather than leaving with a half-answer. That single habit is what turns being processed into being informed.
Not comfortable asking in English? Ask your care coordinator to make the call with you — Telugu-speaking coordinators do this with district families every week, and they know the wording that gets a straight answer.
Side by side
Daily, monthly, annual: what happens when
A general picture of how radiotherapy QA schedules are structured. Exact test lists vary by machine, technique and centre protocol.
| When | What is checked | Who does it | What it protects you from |
|---|---|---|---|
| Every treatment morning | Beam output against a reference value; door interlocks, emergency stops, positioning lasers | Medical physicist or trained technologist | Overnight drift in machine output reaching the first patient of the day |
| Every session | Your position on the couch, compared against the planning scan using imaging | Radiation therapy technologists, reviewed by the radiation oncologist | An accurate beam landing on slightly the wrong anatomy |
| Weekly, in many centres | A review of your treatment record, imaging and, where relevant, your weight and fit in the immobilisation device | The treating team, at a chart round | Gradual change in your own body during a multi-week course |
| Monthly | Beam flatness and symmetry, gantry, collimator and couch movement accuracy, imaging-to-beam alignment | Medical physicist | Slow mechanical wander too small to see on a daily check |
| Annually | Full recalibration against a reference-standard instrument; in-depth repeat of mechanical and dose tests | Medical physicist, with the reference standard traceable to a standards laboratory | The whole year of daily readings being anchored to a wrong baseline |
| Before your first session | Patient-specific plan QA: the plan delivered to a measurement device, or independently recalculated | Medical physicist, approved by the radiation oncologist | A plan the machine cannot actually reproduce being used on a person |
| Periodically, from outside | Independent dose audit: a dosimeter irradiated on the centre’s machine, read by an outside laboratory | An external audit body, not the centre | A centre being the only judge of its own accuracy |
The regulator sets the floor, professional protocols set the detail, and the centre’s own protocol sets the rest. Where a centre goes beyond the minimum, that is a fair thing to ask it to describe.
Question three
What can go wrong — and what is designed to stop it?
The realistic risks are drift and mismatch, not sudden dramatic failure. Output drifts slowly, which the daily measurement catches. A moving part loses accuracy, which the monthly tests catch. A plan is transferred wrongly, which independent checks and record-and-verify software catch. Your body changes, which weekly review catches.
That layering is deliberate, and it is the honest answer to the fear behind this page. For a wrong dose to reach a patient, it would have to pass the morning output measurement, the plan verification, the independent calculation check, the record-and-verify system that refuses settings that do not match the approved plan, and the imaging taken at the couch. Each layer is imperfect on its own. They are not designed to be used on their own.
Human factors matter as much as machine factors, which is why so much of QA is about paperwork discipline: naming conventions, a second person verifying a transferred plan, a documented handover when a plan is changed mid-course. Centres that treat records seriously tend to be the ones that catch mismatches early, and that is a reasonable thing to judge a centre on.
If a check does fail, the expected response is that treatment on that machine stops until a physicist has investigated and corrected it. A short delay for a QA issue is not a bad sign; it is the system doing what it is meant to do. Ask for the reason, ask when treatment resumes, and ask for it to be written into your record.
What machine QA cannot tell you is whether the right treatment was prescribed in the first place. A perfectly calibrated machine will faithfully deliver a plan you had doubts about. If it is the plan you want examined rather than the equipment, ask for a clinical second opinion — a different request, and one you can make without leaving your current centre.
A note on consent: the radiation consent form you sign is a clinical document about your treatment, not a technical certificate about the machine. If any clause is unclear, ask the treating team to explain it before you sign, and take the time you need. This page is general patient information and is not legal advice.
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Whether you are the patient or the relative doing the homework, a radiation oncologist can help you ask clearly and read the answer properly.
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Common questions
Radiotherapy machine quality assurance — your questions answered
What is checked on a radiotherapy machine, and how often?
Checks run on a schedule rather than on suspicion. Each treatment morning, before the first patient, the beam output is measured against a reference value and the safety interlocks, door switches and positioning lasers are tested. Each month, a fuller set of measurements covers beam quality, flatness and symmetry, the accuracy of the moving parts, and the alignment between the imaging system and the beam. Once a year the machine is fully recalibrated against a reference standard, and the mechanical and dosimetric tests are repeated in depth. Separately, most complex plans are verified patient by patient before the first session. Professional protocols such as the AAPM Task Group 142 report set out what belongs in each of those lists, and the schedule is a condition of the machine licence in India.
Who verifies that a radiotherapy machine is delivering the correct dose?
A qualified medical physicist owns the programme. They calibrate the machine against a reference standard, run and sign the daily, monthly and annual checks, and verify treatment plans before delivery. A radiological safety officer covers radiation safety and staff dose monitoring. The radiation therapy technologists who treat you run the daily checks and the imaging at the couch. Your radiation oncologist approves the plan and reviews the verification images. Above all of them sits the regulator: in India the Atomic Energy Regulatory Board licenses the machine and makes periodic output checks and record-keeping a licence condition. Many centres also take part in an independent external dose audit, where an outside laboratory reads a dosimeter irradiated on the centre's own machine.
What can go wrong with a radiotherapy machine, and what stops it?
The realistic risks are drift and mismatch rather than a sudden dramatic failure. A machine's output can drift slowly, which is exactly what the daily measurement is designed to catch before a patient is treated. A moving component can lose accuracy, which the monthly mechanical tests look for. A plan can be transferred incorrectly, which independent plan checks and the record-and-verify software are designed to catch. Your own anatomy can change over weeks, which is why weight and position are monitored during the course. The protection is layered: no single check is trusted alone, and if a result falls outside the tolerance band, treatment on that machine stops until a physicist investigates and corrects it. That is general practice internationally, not a promise about any one centre.
Can I ask a radiation centre to see its quality assurance records?
You can ask, and asking is reasonable. In practice you are more likely to be given a clear verbal account than a folder of raw measurement logs, because those logs are technical documents that need a physicist to interpret. What you can usually establish quickly is the name of the medical physicist, that daily checks are done before the first patient, when the annual calibration was last performed, and whether the centre takes part in an external dose audit. A centre that answers those four questions plainly is telling you a good deal. Evasiveness is itself information. If you want a written record of your own treatment instead, ask the records desk for your treatment summary and daily record sheet.
Does machine quality assurance mean my treatment plan is correct?
No, and this is the distinction worth carrying into a consultation. Machine QA confirms that the equipment can deliver what it is asked to deliver. It says nothing about whether the right thing was asked for. Your treatment intent, the total dose, how that dose is divided into sessions, the area treated and the dose limits set for nearby healthy organs are clinical judgements made by your radiation oncologist and medical physicist and discussed by a tumour board. If it is the plan you want checked rather than the machine, what you are asking for is a clinical second opinion, and you can request one without leaving your current centre.
Is the machine checked again for my specific treatment plan?
For modern shaped-beam techniques, usually yes. Before your first session the plan is commonly delivered to a measurement device placed on the treatment couch instead of to you, and the measured dose pattern is compared with the calculated one. Some centres verify instead by recalculating the plan with independent software, or use both methods. For simpler plans, an independent calculation check may be considered sufficient. Whichever route is used, the point is the same: the plan is proven on the machine before it is used on a person. Ask your team which method applies to your technique, and when it is scheduled, so you know it has happened.
This page explains, in general terms, how quality assurance works on radiotherapy treatment machines in India and internationally. It is patient information, not legal advice, and it is not a substitute for guidance from your own oncology team about your diagnosis, your treatment plan and the consent you are asked to give.