Two motions, two mechanisms
A lung target moves with every breath, and the patient drifts over a long SBRT fraction. Image guidance corrects the position at the start; what happens during delivery depends on the immobilization.
The frame stabilizes the body. A U-shaped composite base gives rigid support around the patient, limiting lateral shift and roll through treatment. Compression stabilizes the diaphragm. The compression arch slides onto the rails to a recorded position, and the compression screw turns down to the prescribed depth. Both numbers go on the worksheet and are reproduced at every fraction.
Published motion reduction
Negoro IJROBP 2001 (n=10) · Heinzerling IJROBP 2008 (n=10) · comparable rigid frame systems; benefit varies by patient and tumor location.
Frame-mounted abdominal compression has been studied in rigid body frames since the first Karolinska series. The benefit is largest for lower-lobe tumors, which move with the diaphragm; upper-lobe tumors gain less. Compression is optional: the frame also works as restraint alone, and the compression plate can be used or omitted patient by patient.
Lung windows in CT
Lung SBRT plans are sensitive to anything in the beam path, and the frame surrounds the patient. AerFrame measures under 2% single-beam attenuation at 6, 10 and 15 MV away from the side rails, with a mean target D95 loss of 1.1% across eleven patients. Beams through a side rail are the one exception, exceeding 3% at 6 and 10 MV: avoid rail angles in IMRT planning where geometry allows; VMAT generally does not require this.
Data on file, Stabilix. Available on request.
Every fraction, learned once
- Place. Frame and the patient's own vacuum-bag cradle onto the couch. Patient into the bag.
- Verify the marks. Coordinate arch and laser box to the registration position. The two dots land on the patient's marks; shift the patient in the frame if they don't.
- Frame to the room. Arch to the isocenter position on the rail. Move the frame until the room lasers meet X, Y and Z on the arch.
- Remove and verify. Arch off. Image guidance confirms the alignment before every fraction, as the IFU requires.
Compression is set at simulation: plate on the abdomen, arch to its rail position, screw to the prescribed depth. The same two numbers reproduce it at every fraction. The full system, component by component →
Questions
How much does abdominal compression reduce lung tumor motion?
In published series with rigid body frames, mean lung tumor motion fell from 12.3 mm to 7.0 mm with compression (Negoro, IJROBP 2001, n=10) and mean lung and liver tumor motion from 13.6 mm to 7.2 mm (Heinzerling, IJROBP 2008, n=10). These figures come from comparable rigid frame systems; the benefit varies by patient and tumor location and is largest for lower-lobe tumors.
Can I use AerFrame without compression?
Yes. The compression arch and plate are used when abdominal compression is needed. Without them the frame still provides rigid restraint of the body, and the setup is the same.
Does compression work with breath-hold or gating?
AerFrame is a positioning and immobilization device; it does not replace a respiratory management technique. Many departments use compression to reduce motion amplitude and image guidance to confirm the position. How compression combines with your motion-management protocol is a clinical decision for your team.
Is the frame visible on the planning CT?
Yes, faintly. It renders at about −928 HU, close to air, and it is included in the planning CT like any other device. The attenuation data package has the measurements your physicist will want.
Does it fit on the CT and the treatment couch?
AerFrame indexes to any couchtop by friction, so the same frame is used at simulation and at treatment without adapters.