Tips For Mobile Chest X-Rays

Mobile (or portable) chest x-rays can be particularly difficult to perform as there are often a lot of external factors to consider (e.g. difficult patient position, patient condition, patient size, artefacts etc). Plus, there is the added annoyance of (assuming you use a CR system) having to return to the department to process the image and return to the ward if it requires repeating.
Here are a few tips I have learned, which make mobile chest x-rays just a little easier!

  Patient Position

• Have the patient as erect as possible
• Always check with nursing staff before moving a patient as their condition may not allow them to move safely
• A supine x-ray is considered less diagnostics as the lung fields appear shortened, the heart is magnified and air fluid levels are not seen
• Watch for lines and tubing connected to the patient when you move them
• If the patient can’t pull themselves forward, have someone help you pull them forward using the sheet behind them and slide the cassette behind the sheet – this is less painful on the patient’s back

Cassette Position

• Place the top of the cassette at C7 (the notch on the back of the neck)
• Place your hand on top of the patient’s shoulder and ensure that your finger tips are not above the top of the cassette
• Consider also that the top of the cassette doesn’t need to be much above your fingers as the patient’s lungs can’t exceed their shoulders
• Put your hands on either side of the patient’s chest to feel that the cassette extends past your hands sideways – this will make sure you don’t cut off the side of the lungs

Landscape vs Portrait

• Generally, landscape will fit most patients and allows you more room to be off centre
• If the patient is particularly tall and skinny consider placing the cassette portrait
• Put your hand on the edge of the patient’s chest to ensure the cassette extents further sideways than your hand to ensure you don’t cut off the side of the lungs

Tube Angle

• The straighter the patient, the less you have to angle
• The best way to check for correct tube angle is to come to the side of the bed so the patient is on one side and the tub on the other
• If necessary, put your hand on the LBD to get the angle and follow it to the patient’s chest to see if they match up
• As a general rule, you will probably need to angle down slightly more than you think!

Centering and Collimation

• Don’t worry about which specific vertebrae to centre at – it’s too difficult to figure out – centre at what appears to be the centre of the chest!
• Open your collimators so you see them just above the shoulders but make sure you aren’t including too much abdomen, this will just throw off your exposure
• Include the shoulders. Additional pathology may be present or they may be used identify a patient if there is a confusion with patient identification (i.e. if you do 2 mobile x-rays and get the cassettes confused, one may have an identifying shoulder pathology which you can confirm with a previous film – not an ideal method but can come in handy!!)

Patient Directions

• Tell the patient that the cassette is cold and hard but that it won’t be there for long
• Ask them to try and hold still and not adjust their position even though the cassette is uncomfortable as the cassette will move and may need to be repositioned
• Tell the patient that you will call out for them to breathe in an hold their breath and to try not to raise their shoulders when they breathe in – when they raise their shoulders it often causes them to lean back, making the image more lordotic and may cause you to miss the apices
• If the patient is not conscious or is unresponsive, watch for their breathing and expose on inspiration – watch for a few breathes to gauge timing
• Ask the patient how they would like to be positioned after the x-ray is complete (sitting up, lying down etc)
• Return everything you have moved (side table, remotes, safety pins etc)
•  

Exposure

• Varies greatly depending on the machine, cassette and whether or not a grid is being used
• With a digital machine (no grid), I have used 80kVp, 4mAs for “regular” sized patients and 90kVp, 5mAs for large patients
• With an older CR machine, it was necessary to use 90kVp, 4mAs for even small patients
• Check the kind of machine you are using to determine exposure
• Increase exposure if you are looking for CVC placement, especially in larger patients as it is often difficult to visualize the tip

Markers

• Using a L/R marker (and Erect/Supine and Mobile where possible) will save you considerable time in post processing, especially if you have a whole ICU round to do!
• Try to use the same marker every time, where possible. This way, if you use a pillow case or slider you know you are putting the cassette in the right way every time

Organisation

• If you are doing multiple patients (assuming you are using a CR system) put the patient request or patient sticker on the cassette so as to not get them confused when it comes to post process
• This will also stop you from re using an already exposed cassette

When should it be repeated?

• If the apices are cut off --> may still be acceptable if you are only checking for NG tube placement
• If the bases are cut off  --> may still be acceptable if you are only checking for line placement (e.g. CVC, Swan Ganz catheter)
• Rotation (the clavicles are not equidistant from the spine) à may not be possible to correct due to patient condition, however try to adjust with aid of nurse
• Under exposure (too much noise)
• Insufficient inspiration à should see at least 7 ribs, however if the patient is not responsive a deeper breath may not be possible
• If any of these points occur, you should show the x-ray to the referring doctor to see if they require it to be repeated. They may, for example, only be looking for line placement and hence if a small amount of anatomy isn’t seen it may not matter
• In this case, an accurate request form is necessary so the reporting radiologist knows what is expected in the report