DIBH deep inspiration breath-hold explained

A guide for radiation therapy students · ~8 min read

Deep inspiration breath-hold (DIBH) is one of the most common ways radiation therapy protects the heart during left-breast treatment. The patient takes a deep breath and holds it; the inflated lungs move the heart away from the treatment field; and the beam only turns on while that breath-hold sits inside a tight window. This guide explains why DIBH works, how the breath-hold is monitored and gated, and what good breath-hold coaching looks like.

What is DIBH?

Deep inspiration breath-hold is a delivery technique in which the patient breathes in deeply and holds that breath while each treatment field is delivered. Instead of treating through the patient's normal in-and-out breathing, the team treats only at a single, reproducible point near full inspiration. Each beam is broken into short segments that fit inside one comfortable breath-hold, with the patient breathing freely in between.

The technique trades a little extra time and coordination for a meaningful clinical gain: in the right anatomy, holding a deep breath physically moves healthy tissue out of the path of the beam.

Why DIBH spares the heart

The headline application is left-sided breast cancer. The heart sits just behind the left chest wall, close to the tangent fields used to treat the breast or chest wall. During a normal shallow breath, part of the heart — and in particular the left anterior descending (LAD) coronary artery — can fall inside or right at the edge of the treated volume.

When the patient takes a deep breath in, two things happen:

• The lungs inflate and the diaphragm drops, which pulls the heart inferiorly and posteriorly — down and away from the chest wall.
• The chest wall lifts forward, increasing the distance between the breast tissue being treated and the heart behind it.

The net effect is more air and more distance between the target and the heart, which can substantially reduce the mean heart dose and the dose to the LAD. Because cardiac dose is linked to long-term cardiac risk, that reduction matters for patients who may live for decades after treatment.

How the breath-hold is monitored

For DIBH to be safe, the team has to know the patient is holding the planned breath — not a shallower or deeper one — at the moment the beam is on. The breath-hold level is tracked in real time, usually one of two ways:

• Optical surface guidance. Cameras map the surface of the chest and abdomen and report how far it has moved, with no markers on the patient.
• Marker-block / respiratory-gating tracking. A reflective block sits on the patient's chest or abdomen and an infrared camera follows it. The vertical motion of the block is the breathing signal.

Either way, the system produces a live amplitude trace — a line that rises as the patient breathes in and falls as they breathe out, scrolling across the screen like a respiratory waveform.

The gating window and beam gating

On top of that trace, the plan defines a gating window: a narrow band of amplitude that corresponds to the breath-hold position captured on the planning CT. The rule is simple and strict:

This is called respiratory gating: the beam is automatically gated on and off by where the trace sits. The live line is typically shown green when it is inside the gate and amber when it drifts out, so the therapist can see at a glance whether it is safe to treat. If the patient coughs, relaxes, or the hold drifts out of the band mid-exposure, the beam interrupts immediately.

The DIBH treatment workflow

1. Planning in breath-hold. The planning CT is acquired with the patient holding the same deep breath they will use at treatment, so the plan is built around that anatomy.
2. Set up to marks and lasers with the patient breathing freely.
3. Coach a practice breath-hold and confirm the trace reaches the gating window comfortably and reproducibly.
4. Image and verify in breath-hold — setup imaging (for example 2D/2D or CBCT) is taken at the held-breath position so it matches the plan.
5. Gate the beam on. The patient breathes in and holds; the therapist confirms the trace is in-gate and stable, then delivers a segment that fits inside the hold.
6. Repeat per segment / per field. The patient relaxes and breathes between holds; each breast tangent or field is delivered across one or more clean breath-holds.

Coaching the breath-hold

The part that takes real skill is coaching — talking the patient into and out of a reproducible hold. A natural full breath often lands above or below the planned window, so the therapist guides it in with small, calm instructions:

• "Take a deep breath in and hold" — the patient inhales toward their full-inspiration level and locks it there.
• "A little more in" / "a little less" — fine nudges to move the held level up or down into the gate, rather than asking for a whole new breath.
• "Hold it right there" — catch a rising breath at the right level before it overshoots.
• "Breathe normally" — release between segments.

Good coaching is steady and unhurried: patients can only hold comfortably for so long, so the therapist confirms the trace is in-gate and settled before turning the beam on, and keeps the patient calm through the exposure. Each field is captured at its own breath-hold, so the rhythm of coach → confirm in-gate → beam → relax repeats for every segment.

Where else DIBH is used

Beyond left-breast treatment, breath-hold is used wherever inflating the lungs helps:

• Right breast and chest wall — sometimes used to reduce lung dose even when cardiac sparing is less of a concern.
• Lung and mediastinal tumours — a held breath freezes respiratory tumour motion, so the target sits still during delivery and the margin around it can be smaller.
• Mediastinal lymphoma (e.g. Hodgkin) — often young patients, where reducing heart and lung dose has a large long-term payoff.
• Some upper-abdominal sites — where breath-hold reproducibly repositions mobile anatomy.

Common pitfalls

• An inconsistent breath-hold. If the held level wanders from day to day, the anatomy no longer matches the plan. Coaching to the window, not just "a big breath", keeps it consistent.
• Beaming before the hold is settled. Delivering while the trace is still rising risks the level drifting out mid-exposure. Confirm in-gate and stable first.
• Coaching too fast. Rushing the patient leads to overshoot, fatigue, and aborted holds. Calm, incremental cues work better than one big command.
• Ignoring a cough or drift. Any interruption should stop the beam; the segment is simply repeated on a clean hold.
• Forgetting to image in breath-hold. Verification imaging has to be taken at the held position, or it won't represent the treated anatomy.

How to practice DIBH coaching

Breath-hold coaching is a timing-and-communication skill, and like image matching it rewards repetition with feedback. The RT Image Matching Trainer includes a Breast L · DIBH case that simulates exactly this: a live respiratory amplitude trace with a shaded gating band, a patient whose natural breath usually lands outside the window so you have to coach them in, and a beam that only delivers while the hold is in-gate and settled — interrupting if it drifts, coughs, or relaxes. You coach with the same cues a therapist uses (the case is voice-coached), capture each breast field at its own breath-hold, and get a coaching score at the end. It pairs naturally with the breast tangent image-matching that follows.

Microphone setup for voice coaching

The trainer's Breast L · DIBH case is voice-coached: you speak the breath-hold cues — “take a deep breath in”, “a little more in”, “hold it”, “breathe normally” — and the trainer recognises them, the way a therapist coaches a real patient over the room intercom. That needs a working microphone, so the case checks for one before it starts. What students need:

• A supported browser — Google Chrome or Microsoft Edge on a desktop or laptop. (Speech recognition isn't available in Firefox or in iOS home-screen web apps.)
• A secure connection — the trainer runs over HTTPS at rtimagematch.com, which is what browsers require before granting microphone access; there is nothing extra to configure.
• A one-time “Allow” — the first time the case opens, the browser asks for microphone permission. Choosing Allow (rather than “Allow this time”) is remembered for the site, so it won't ask again on that device.

When the case opens it runs a quick microphone check — pick an input and watch the level bar move while you talk — so you can confirm the mic is heard before coaching begins. If access is ever blocked or unavailable, the trainer falls back to on-screen buttons for the same cues, so a session is never stuck.

A privacy note: speech recognition is performed by the browser itself, and in Chrome and Edge the audio may be processed on the browser vendor’s servers (for example, Google’s for Chrome) to be transcribed. The trainer never records or uploads audio itself, and nothing is stored. Details are in our privacy policy.

For IT and computer labs

On managed lab machines you can remove the per-student permission prompt entirely by pre-authorising the microphone for the trainer's address in the browser's enterprise policy:

This is a browser / device-management setting controlled by your institution, not something the website can grant itself — the per-site prompt is a browser security boundary by design. One caveat: voice recognition always uses the browser's default microphone, so if a station has more than one input, set the intended one as the system default.

Frequently asked questions