These cases are usually done with the surgeon seated by the side table. Because this places the limb at a low height they are done with the intensifier flipped underneath and the X-ray tube above. Don't forget to flip the image with the left flip button. As you push the C-arm forwards, sight it in line with the area to be screened. Look to see if its' central to the table or off to one side and stop accordingly. Once in position the machine should be raised until it is almost touching the underside of the table. This increases the chance of the area of interest being on screen and is therefore worth your time. If you haven't selected the left flip the limb will not appear as the surgeon is viewing it. Now go and stand perpendicular to the C-arm, off to the side. Sight down from the tube centre to see if an adjustment needs to be made forwards or back. Use the cross arm to correct; then you are ready to take your first image.

 

Orientation

If using a surgeon viewpoint machine (e.g. Siemens) looking from the other side of the limb will show you the image orientation. If using an operator viewpoint machine (e.g. Philips Endura) the image will appear as you are looking at it from the back of the C-arm. For instance if the hand is pointing to your left side then it will appear pointing left on screen. Once you have rotated clockwise 90 degrees the hand will be pointing to the top of the screen as required. Now you know which way to move, if the hand appears towards the left of the screen move the cross arm to the left side of the limb which in this case is back towards you. If the hand appears at the edge of the screen then you need to move six centimeters in that direction. Half way between centre and edge of screen is three centimeters etc. These are correct for a standard 30cm diameter intensifier at a distance of 30cms or less from the faceplate.

 

Press the save image button every time the surgeon changes the wrist rotation. A good surgeon will rotate the wrist in place but some will rotate to one side and then back again causing the Radiographer to have to adjust centering continuously.

If the wrist appears off centre to the left move the intensifier in the direction you have identified as left. Use the panoramic arc motion of the C-arm to make small adjustments to each side as needed. If you can, arrange a panoramic scale in degrees on your intensifier. Each one degree of pan equals two centimeters of sideways movement; so three degrees moves from the centre of the image to the edge. Use this to centre in one go from your initial 'scoping' shot.

 

A note on dose risk

Extremity pulsed screening is an inherently low dose procedure. It is important to avoid screening the surgeon's hands where possible; use of perfect centering and the round collimator are key to this. Occasional images showing the surgeon's fingertips may be unavoidable, however the surgeon should be made aware and care taken to minimise dose. Scattered radiation at the low kilo-voltages utilised is negligible. Lead protection is mainly precautionary as automatic screening kVp may increase without warning, on accidentally screening over a metal table edge for example. Side collimation may be counterproductive as it does not protect the surgeon's hands proximally or distally. Applied closely it also does not allow for sideward motion or changing of the limb’s ‘skew’. Magnification always increases dose slightly but the relative effect is not great where strict collimation was not used on the un-magnified views. Its use should therefore be encouraged during small fragment surgery of the hand and wrist.

 

Key points

Ask surgeon where to situate C-arm

Position monitor on opposite side of main table

Flip intensifier underneath

Activate left flip button

Centre cross arm and zero the pan or ‘wag’

Set low dose pulse

Ask surgeon to lift sterile cloth

Drive ‘in line’ and check from side

Fine correct cross and pan

Raise height

Rotate image with fingers to top of screen

Look from elbow end to see which side is left screen

Save with each turn of wrist

Use round cone with perfect centering

When limb off-center to left of screen, move C-arm to side identified as left.