How to

Use AR slice-through on a table

After this page you will be able to put a scan on the table in front of you at its true size, walk your phone through it, and watch the cross-section update as if the device were a slicing plane.

What it is for

MPR shows you three fixed planes. AR slice-through replaces the plane with your hand. The scan is anchored on a flat surface at life size, and wherever the device is, the app renders the cut through the volume at that position and orientation, in real time. Moving the phone forward through the arch is the same motion as scrolling an axial stack, except that your body now knows where anterior and posterior are. It is a spatial reasoning exercise, not a display mode, and it is the fastest way we know to teach the relationship between the three planes described in axial, coronal and sagittal planes. The feature overview is on AR slice-through.

Steps

Open a case and tap the AR button. It is the blue button at the bottom right of the case, with the cube icon and the label "Show on the table". The first time, iOS asks for camera access; the app explains that nothing is recorded or sent anywhere.
Scan the table. Point the camera at a flat surface and follow the message in the reticle: "Move the phone slowly across the table". Sweep gently until the dot in the circle turns green and the message says you are ready.
Tap "Place jaw here". The volume appears on the surface at life size, rendered with the current window preset. A small frame at the top right labelled "Cut position" shows where your current cut lies within the scan.
Move the device through the anatomy. Lower the phone toward the table and the cut deepens; tilt it and the cut tilts. A chip says "Point the phone at the jaw" if you drift away. Use the bar on the right, from "Surface" to "Deeper", to push the cut further in without moving your hand; its readout shows the depth in mm.
Use the controls at the bottom. "Lock slice" freezes the current cut so you can walk around it; it reads "Locked" while active. "Hide jaw" hides the 3D volume to leave only the cross-section, "Show jaw" brings it back. "Move" lets you place the scan again. "Photo" captures the current AR view into the case. The window picker switches between "Bone" and "Soft Tissue".
Finish with "Done". The button at the top left returns to the viewer. If you took a photo in AR, it becomes the last page of the PDF summary.

Lighting and space

ARKit tracks the room by finding visual features, so a plain white table under dim light is the hardest case. Use a surface with some texture (wood grain, a patterned cloth, a sheet of printed paper), daylight or even room lighting, and avoid glossy or glass tops that reflect the ceiling. You need about a metre of free space around the table to walk around the scan, and a full-arch volume occupies roughly 13 cm square on the surface.

Hold the device with two hands and move slowly; an orange banner tells you when tracking is limited. If it appears, stop for a second and let the camera re-acquire the surface. AR works well in pairs: one student holds the phone, the other names structures as the cut passes them, starting with the mandibular canal.

If it does not work

"Augmented reality needs a physical iPhone or iPad". You are in the Simulator or on a device without world tracking. The 3D and Slice views work everywhere.

The reticle never turns green. The surface has too little texture or too little light. Put a printed page on the table and try again, and tilt the phone so it looks down at the surface, not across the room.

"Aim a little lower onto the surface". You are pointing at the wall or at the far edge. Angle the device down toward the table in front of you.

The scan drifts or jumps. Tracking was lost, usually from moving too fast or covering the camera. Tap "Move" and place the jaw again.

Camera permission was denied. Open the iOS Settings app, find JawAtlas, and switch Camera on.

Questions students ask

Why does the AR view say it needs a physical iPhone or iPad?

AR slice-through uses ARKit world tracking, which needs the camera and motion sensors of a real device. It does not run in the iOS Simulator. Every iPhone and iPad that runs iOS 18 supports the world tracking JawAtlas uses.

Is the scan really life-size in AR?

Yes. The volume is placed using the voxel spacing from the DICOM header, so a 127 mm wide demo scan occupies 127 mm on the table. If the scale looks wrong, the spacing in the export was wrong, and the MPR scale ruler will be wrong too.

Does the AR view record or upload anything?

No. The camera is used only to track the table and draw the overlay; nothing is recorded or sent anywhere, and the app has no networking code. If you tap the capture button, the photo stays in the case for the PDF summary.

JawAtlas is an education and training aid. It is not a medical device and must not be used for diagnosis, treatment planning or any clinical decision.

Last reviewed 2026-10-13