Loading
Tumours in the lung, liver and upper abdomen move as you breathe. At the planning scan the team usually records the whole breathing cycle (4D CT) to see how far the tumour moves. They then plan to cover that movement, or reduce it by asking you to hold your breath, pressing gently on your tummy, or switching the beam on only at one point in each breath. They practise the breathing with you first.
AAPM Task Group 76 (Report 91, 2006) recommends measuring three-dimensional tumour motion for each patient where breathing motion may matter, over several breathing cycles; if motion cannot be measured, the prudent course is to assume it is significant and use motion management. Motion management is recommended for consideration when the range of motion exceeds 5 mm in any direction, or when it gives significant normal tissue sparing; the 5 mm threshold may be lower for SBRT. A measured motion should be built into the margin: the whole range if no device is used (an internal target volume), only the residual motion if one is. The patient is coached at simulation and on the first treatment day; a back-up CT without breathing requirements is taken in case the patient cannot comply. TG-76 recommends a qualified physicist at simulation sessions using motion devices and at least the first treatment, the most accurate dose calculation available in lung, written QA for every step, and frequent verification images of the diaphragm or tumour (daily for the first few treatments, then at least weekly). MPPG 9.b (2025) requires 4D CT for thoracic and abdominal SBRT and end-to-end testing with a moving phantom. In the TG-324 survey of AAPM members (2020), 95% used motion management for thoracic and abdominal sites, 60% the internal target volume method, 25% breath-hold or compression and 13% gating or tracking. TG-76 is 20 years old and predates routine cone-beam CT and surface guidance; no newer AAPM report replaces it.
Why: How much a tumour moves differs from person to person, so it must be measured rather than guessed.
“When measuring tumor motion, the motion should be observed over several breathing cycles if possible.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: Assuming no movement could mean part of the tumour is missed.
“If no method exists for measuring motion, for example, with a standard respiratory-gated CT procedure, the prudent approach is to assume that motion is significant and treat with respiratory management (box 6).”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: Small movements are lost among other set-up errors; larger ones are worth controlling to spare healthy lung and organs.
“The Task Group recommends that respiratory management techniques be considered if either of the following conditions occur:”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: The margin is what makes sure the tumour stays inside the beam wherever it is in the breath.
“If a respiratory management device is not used, the entire range of motion should be considered when establishing the internal margin.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: Practice makes breathing more regular and breath-holds more repeatable.
“Coaching the patient at simulation and on the first day of treatment is fairly common and recommended.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: It avoids a second planning visit if breath-hold or gating turns out not to be possible.
“If the potential exists that the patient will be unable to comply with breathing or breath-hold techniques for treatment, a backup CT scan without such a requirement is recommended during simulation.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: The equipment is complex, and problems are easiest to fix at the start.
“The Task Group recommends that, due to the complexity of the management of the respiratory motion problem and the technology used, a qualified medical physicist be present at all treatment-simulation (virtual or otherwise) imaging sessions in which respiratory management devices are used and also for at least the first treatment for each patient.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: Radiation behaves differently in air-filled lung, and simpler calculations get the dose wrong there.
“Due to the complex nature of radiation transport in low-density regions such as the lung, the Task Group recommends that the most accurate dose calculation available be used.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: The link between an outside breathing signal and the tumour inside can change from day to day.
“Daily verification is recommended for the first few treatments, followed by (at least) weekly verification to ensure that the anatomy at the respiratory position used for treatment remains constant.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
Why: It checks that the system actually hits a moving target before any patient is treated with it.
“If the planned scope of clinical services includes treatments affected by respiratory motion, the entire treatment chain (CT simulation, treatment planning, treatment delivery) should be assessed with E2E testing using a dynamic phantom setup with clinically relevant motion parameters (amplitude, cycle time).”
American Association of Physicists in Medicine and Radiosurgery Society (Journal of Applied Clinical Medical Physics) 2025 · Minimum practice guideline (ungraded)
Why: Each device adds steps that can go wrong; checking them regularly keeps treatment accurate.
“Strict QA procedures for the imaging, planning, and delivery of radiotherapy using respiratory management devices are required to ensure the safe and effective use of these devices.”
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Task group recommendation (ungraded)
How care is usually carried out, read from the guidelines and standards cited. Your own team's protocol and their judgement come first; this page is for understanding it, not for doing it yourself.
Measure each patient's tumour motion (4D CT over several breathing cycles); consider active motion management when motion exceeds 5 mm or when it spares significant normal tissue, with a lower threshold for SBRT; otherwise cover the full measured range with an internal margin (AAPM TG-76). Coach the patient at simulation and the first treatment, keep a back-up CT, use the most accurate lung dose calculation, verify the breathing position by imaging, and run written QA (TG-76); for SBRT, test the chain end to end with a moving phantom (MPPG 9.b 2025). Which technique (internal target volume, breath-hold, compression, gating or tracking) is chosen depends on the patient's tolerance and the equipment; no guideline read ranks them and no randomised trial read compares them for outcomes.
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · American Association of Physicists in Medicine and Radiosurgery Society (Journal of Applied Clinical Medical Physics) 2025 · Journal of Applied Clinical Medical Physics 2022
Where it differs: The patient breathes freely and the target volume is drawn over all phases of the 4D CT. The commonest approach in the TG-324 survey (60% of respondents).
Evidence: TG-76 accepts it when the full range of motion is in the margin; it irradiates more normal tissue than techniques that reduce motion.
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Journal of Applied Clinical Medical Physics 2022
Where it differs: Motion is reduced by a voluntary or device-assisted breath-hold, or by a plate or belt pressing on the upper abdomen. Used by 25% of TG-324 respondents.
Evidence: TG-76 describes both and recommends verifying stability within and between breath-holds; tolerance varies and few factors predict who can manage it.
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Journal of Applied Clinical Medical Physics 2022
Where it differs: The beam is switched on only in a chosen phase of breathing, or follows the moving target (for example robotic or MLC tracking, often with implanted markers). Used by 13% of TG-324 respondents.
Evidence: TG-76: internal markers give the most accurate position but need an invasive procedure and can migrate; external surrogates need their relation to the tumour established.
American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 · Journal of Applied Clinical Medical Physics 2022
| Recommendation | Grade, as printed | Source |
|---|---|---|
| Motion management is very widely used in thoracic and abdominal radiotherapy “Overall, 95% of respondents used respiratory motion management for thoracic and abdominal sites, with 36% of respondents using respiratory motion management for at least 90% of thoracic and abdominal patients.” | Practice survey (AAPM members, 2020) | Journal of Applied Clinical Medical Physics 2022 |
| The internal target volume method is the commonest approach “The majority (60%) of respondents used the internal target volume method to treat thoracic and abdominal cancer patients, with 25% using breath hold or abdominal compression and 13% using gating or tracking.” | Practice survey (AAPM members, 2020) | Journal of Applied Clinical Medical Physics 2022 |
| The 5 mm threshold may be lowered for SBRT “The recommended 5-mm motion-limit criterion value may be reduced for special procedures, such as stereotactic body radiotherapy.” | Task group recommendation (ungraded) | American Association of Physicists in Medicine (Keall et al.; also Medical Physics 2006) 2006 |
Shares Deep inspiration breath-hold for left-sided breast radiotherapy, Surface-guided radiotherapy (SGRT), Respiratory gating and tumour tracking systems (RPM, ABC, Calypso, Synchrony), Respiratory motion management (4D-CT, gating, breath-hold, tracking).
Shares Deep inspiration breath-hold for left-sided breast radiotherapy, Surface-guided radiotherapy (SGRT), In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight), Radiotherapy.
Shares Respiratory gating and tumour tracking systems (RPM, ABC, Calypso, Synchrony), In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight), CyberKnife robotic radiosurgery, Radiotherapy.
Shares Surface-guided radiotherapy (SGRT), Respiratory gating and tumour tracking systems (RPM, ABC, Calypso, Synchrony), Respiratory motion management (4D-CT, gating, breath-hold, tracking).
Shares Surface-guided radiotherapy (SGRT), Respiratory gating and tumour tracking systems (RPM, ABC, Calypso, Synchrony), Respiratory motion management (4D-CT, gating, breath-hold, tracking).
Shares Deep inspiration breath-hold for left-sided breast radiotherapy, Surface-guided radiotherapy (SGRT), Respiratory gating and tumour tracking systems (RPM, ABC, Calypso, Synchrony), Respiratory motion management (4D-CT, gating, breath-hold, tracking).