What distance and beam angle does an abdomen AP supine need?

100 cm from the tube to the receptor. The beam passes front to back (AP), straight on to the receptor.

What size receptor, and do you need a grid?

Use a 35 × 43 cm receptor, portrait, in the table bucky. A grid is needed.

What should the patient do with their breathing?

Ask them to breathe out and hold it while you expose.

What goes wrong most often on an abdomen AP supine?

Diaphragm not shown. Usual cause: centring too low for a tall patient. The fix: recentre higher or add an upper film.

AP supine abdomen X-ray positioning (AXR)

One of the routine abdomen views. The patient lies on their back, the beam passes front to back (AP), straight on to the receptor, and the centring point is the midline at the level of the iliac crests.

By the ScanFlo Editorial Team · Updated 12 October 2026

In this section · X-ray positioning

X-ray positioning/Abdomen

Still being checked: a radiographer is reviewing this guide. If your department does it differently, follow your department.

Patient position

Supine. Lay the patient supine, head on a small pillow, arms by the sides, mid-sagittal plane on the table midline.

Centring & collimation

Central ray

Centre: the midline at the level of the iliac crests.

Beam: AP, perpendicular to the receptor.

Collimate: diaphragm to pubic symphysis, flank to flank

Distance, receptor & grid

Setting	Value	Notes
SID	100 cm
Receptor	35 × 43 cm	portrait
Placement	Table bucky	Grid in
Angulation	None	Perpendicular to the receptor

Marker & breathing

Marker: R marker
Breathing: Breathe out and hold.

Exposure by patient size

Treat these as a starting point. Your detector, your generator and the patient in front of you will all move the numbers.

Patient size	kV	mAs (chart)	mAs (DR default)
XS	70	10	5
S	70	16	8
M	70	20	10
L	70	32	16
Child	70	10	5

These start from a classic film-screen chart (70 kV, 40 mAs at 140 cm) and are adjusted for a digital detector at 100 cm. The DR column is what ScanFlo's console suggests; each step up or down changes the mAs by about a quarter.

Image quality checklist

The diaphragm and the pubic symphysis are both included (take two films if needed).
Psoas outlines and renal outlines are visible.
No rotation: spinous processes central.
The anatomical side marker is visible, correct and clear of the anatomy.
Collimation borders are visible on all sides, no wider than the area requested.

Faults & how to fix them

Fault	Cause	Fix
Diaphragm not shown	Centring too low for a tall patient	Recentre higher or add an upper film.
Symphysis cut off	Long abdomen	Add a bladder view.

Common questions

Where do you centre for an abdomen AP supine X-ray?: The centring point is the midline at the level of the iliac crests.
What distance and beam angle does an abdomen AP supine need?: 100 cm from the tube to the receptor. The beam passes front to back (AP), straight on to the receptor.
What size receptor, and do you need a grid?: Use a 35 × 43 cm receptor, portrait, in the table bucky. A grid is needed.
What should the patient do with their breathing?: Ask them to breathe out and hold it while you expose.
What goes wrong most often on an abdomen AP supine?: Diaphragm not shown. Usual cause: centring too low for a tall patient. The fix: recentre higher or add an upper film.

Try it in ScanFlo: the ScanFlo XR X-ray Room, coming soon, lets you set up a abdomen ap supine in a 3D room and score your positioning. See ScanFlo XR →

Written by the ScanFlo team from everyday radiographic practice.

← All abdomen projections

← Abdomen AP erect (infant)Intravenous urography (IVU) series →