Improving a student Radiographer's handling of X-ray equipment

Back in 1992 I was a first year student radiographer at the Johannesburg General Hospital. We had excellent tutors on site at the School of Radiography and these tutors took care of the majority of our initial practical training. The academic side was handled by lecturers at the Technikon Witwatersrand.

In the early stages of our training the hospital tutors spent a lot of time getting us familiarised with the equipment, focusing on tube handling and the placement of cassettes. I believe now (just as my tutors must have done back then) that a student's confidence in the X-ray room can be greatly boosted by getting them to become dexterous with the tube and image receptor placement. Back in 1992 this was achieved by the tutors placing various "targets" in the X-ray room and having us aim the X-ray tube at them. Once we could achieve that, the objective was to do the same exercise with the tube carefully positioned so that the central ray would be perpendicular to the target, or cassette.

Thank you Lesley Crockart and Danuta Blanckaert - like many things from those times I did not realise the importance of those exercises until many years later!

Over the years a lot has changed with the image receptor technology (we didn't have CR or DR when I trained, it was all film). However the basic tube mechanics and most of the table limits have not changed much. If you were trained to position a film cassette back in 1992 you can position a CR or wireless DR cassette just the same today.

These days when I get a new student working in my X-ray room, the first thing I do is get them to understand how the X-ray tube moves. The student must be shown the locks and they must understand to what degree each released lock allows the tube to move.

Below you can see the tube controls of a Philips Digital Diagnost system, with the locks labelled. This is where it starts - the student must become familiar with the position of each lock and know what it does:

I have found that students have the most difficulty with the Z-axis lock. The tube cannot go 360 degrees around the Z-axis, it has a stop which will limit Z-axis movement to different extents, depending whether you go clockwise or anti-clockwise in the Z-axis. It doesn't mean you cannot X-ray 360 degrees around the Z-axis, it just means you may have to use the roll lock also in order to get the tube aimed correctly. To start off with, the student needs to "play" with the tube to see what the movement limits are. I will also show the student the centering of the X-ray tube to the DR detectors (table and wall) and discuss the various pitfalls associated with those manouevres.

I then reveal my secret weapon, which is a simple ball bearing. You can buy these fairly cheaply online:

The great thing about a ball bearing is that has a symmetrical pattern when X-rayed. Here is one positioned on the DR wall detector, and the resultant radiograph:

That is an easy one to do because the DR detector can be locked level and it is a trivial matter to get the tube aimed perpendicular to the ball bearing and centered in the middle of the ball bearing. When the setup is correct, all the spaces around the bearings are equal in appearance and the inner circle of the ball bearing housing is perfectly circular on the radiograph.

When the central ray of the X-ray tube is not perpendicular to the ball bearing and the image receptor, you get elongation or foreshortening distortion and the ball bearing appears out of round on the radiograph. As soon as I see that, I announce grandly that the student has cooked me an egg:

X-raying perpendicular to a fixed DR unit is not difficult. Where it gets interesting is if the ball bearing is angled. The student then has to use a cassette or wireless DR plate otherwise they cannot aim the central ray perpendicular to the ball bearing and the receptor. Essentially, they need to be able to angle the receptor so that it is parallel to the ball bearing. I use CR cassettes for this exercise and I tape the ball bearing to the flexible arm of a calibration device.

Here is one such challenge, where the ball bearing is angled in one direction only. You can think of this as Level 1:

In the case above the student will be encouraged to use pads, sand bags or whatever other immobilising devices are needed to get the cassette parallel to the ball bearing. They are not allowed to move the bearing or the stand supporting the bearing. Once good cassette positioning has been achieved, they can get the tube positioned so that the central ray passes through the middle of the ball bearing perpendicular to the bearing and the cassette. Here is one possible solution:

Note that I am not concerned about magnification of the ball bearing. All the student has to do is get the whole bearing in the exposure and make sure it appears round on the radiograph. The exposure has to be at least 77 kV to penetrate the side plate of this bearing. I use 77 kV and 4 mAs and window the image on the modality console. This is how the radiograph turned out:

That Level 1 challenge is not too difficult because the student has to contend with the roll lock only. The positioning of the tube and cassette becomes much more difficult if a second angle is introduced. Have a look at Level 2:

That positioning now requires the use of the Z-axis lock in addition to the roll lock. On this system the Z-axis lock does not engage at any angle you like. The correct angle required may be at a point where the Z-axis lock does not fully engage a detent or notch on the X-ray column. If that happens, the student has to use two hands to center the tube, so as not to lose the tube angle whilst moving the tube in one of the three remaining axes (transverse, longitudinal or elevation). Depending how the bearing was positioned, the student may find they cannot achieve the correct tube positioning by going clockwise on the Z-axis and they may have to spin it anti-clockwise for example.

Level 3 is where I introduce the cassette holder. I encourage students to familiarise themselves with the locks on the cassette holder so that they are able to position a cassette in any plane required. This is what we sometimes do in adaptive techniques when we have a wheelchair or trolley patient in the fracture clinic.

Once the student can X-ray that ball bearing properly at any angle using the cassette holder, they will have learned the tube handling skills needed to improve confidence in the X-ray room. The key thing to note is it takes time to achieve this. Both the trainer and the student need access to a working room and in my experience they either need a whole day to to do it properly, or at least several hours in one week to do it. I have had good feedback from the students and it is quite satisfying seeing them produce good radiographs of these ball bearings. I have set up timed competitions between two students to add an extra incentive. It has been well-received.

After the students have cracked those first three basic levels, they can try more advanced challenges. You are limited only by your imagination! And remember, both the trainer and the student get to use these sessions to contribute to CPD (Continuing Professional Development).