Four layers, four jobs
Most SBRT departments already run three layers of motion management. The vacuum cushion conforms to the patient and reproduces their shape. Cone-beam CT verifies the position before the beam comes on. Surface guidance watches the skin during delivery and holds the beam when it moves.
Conforming, verifying and watching were covered. Holding the patient still was not. A camera observes motion; a frame restrains it.
What a cushion does, and does not do
It reproduces the patient's shape well and is comfortable. It is also soft: it has no rigid reference to hold the patient against, and nothing to mount a compression plate on.
Rigid walls around the cushion limit lateral shift and roll. Rails carry a compression arch to a recorded position. Scales on the frame carry the isocenter coordinates, so the setup reproduces from numbers rather than from skin marks alone.
The two are complementary. The patient lies in their own solidified vacuum bag inside the frame; nothing about the cushion workflow changes.
What only a frame adds
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 needs something rigid to push against. The published motion reductions above come from rigid body frames with compression; a cushion alone cannot apply a prescribed, reproducible compression depth.
Frame coordinates instead of more tattoos
The patient carries two alignment dots. The isocenter is recorded as three readings on the frame's scales and reproduced by moving the frame until the room lasers meet those numbers again — then image guidance confirms it, as the IFU requires.
The old objections to frames
| Objection | AerFrame |
|---|---|
| Frames are heavy | 9.1 lb base frame. One lift onto the couch. |
| Frames attenuate the beam | Under 2% measured at 6, 10 and 15 MV away from the side rails; −928 HU on CT. |
| Frames need adapters | Indexes to any couchtop by friction. LINAC-agnostic. |
| Frames slow the setup | Four steps at every fraction, from a worksheet. Two tattoos. |
| Frames can't go near MR | MR Conditional per labeling, with an MR Safe compression arch for the MR suite. |
Extracranial SBRT was born in a body frame at Karolinska in 1994. AerFrame is that lineage, rebuilt for adaptive platforms. The system →
Questions
Do I have to stop using vacuum cushions?
No. AerFrame is designed to be used with the patient's own vacuum bag. The bag goes inside the frame; the cushion workflow does not change.
Does a frame still make sense if we have surface guidance?
Yes, and the two do different jobs. Surface guidance observes the skin and holds the beam when it moves; it cannot stop the motion. A frame physically restrains the body and gives compression a fixed reference. Departments run both.
Is image guidance still needed with a frame?
Yes. The IFU requires image guidance to confirm the alignment before every fraction. The frame makes the setup reproducible; imaging verifies it.
What about thermoplastic or other body shells?
AerFrame is a frame, not a shell. It holds whatever cradle the patient is positioned in — in practice, a solidified vacuum bag — and adds rigid restraint and frame-mounted compression around it.
How long does a frame setup take?
At each fraction: place the frame and bag, verify the two marks with the arch and laser box, align the frame to the room lasers, remove the arch and image. Therapists run it themselves during a demonstration.