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3D Printing a Trauma Trolley X-ray detector Laser Alignment tool.
This is a small practical project to accurately align the X-ray imaging plate (Detector) under patients on trauma trolleys.  The X-ray machine has a light which shows where the beam will be centered on the patient. There is no light to show where the imaging plate goes however! This isn't an issue for smaller body parts but is for pelvis and abdomen where the patient is as large or larger than the plate! The plate has to be centered accurately in a narrow slot underneath the trolley surface where it's difficult to see.
To solve this problem I attached a small laser to the X-ray unit, it crosses the line laser which is built into the unit, at a fixed point to the Radiographers side of the trolley. An alignment target is then fixed (somehow) to the side of the Imaging plate and where the lasers cross is a fixed distance to the centre of the plate. This used to be easy as the plate was in a frame which was ferromagnetic so the alignment tool simply had magnets attached.
As time moved on we got new equipment which is incompatible with this solution. The frame is now of a Nylon plastic and the trolleys have small vertical supports at intervals which get in the way of the alignment tool. To design around the supports I made the tool reversible and with a bend so that it's possible to centre on or near the supports.
Now I am trying to simplify the design and 3D print it. I have already printed a laser mount and now I've designed a Mark 1 plastic tool which I'm hoping will be light enough to not require extra support in use.
Neodymium magnets set in place
20 mm by depth of 3mm leaves a 1mm inset to aid location.
Completed tool shown
This is an attempt to have a one piece design, as opposed to the two parts of the Alloy version.
The mounting unit fitted.
This shows the mounting clamp fitted to the image plate. The black and white part is the imaging plate. You can see the line and spot lasers are superimposed and the plate has been moved until they cross at the point marked for abdominal X-rays (Portrait). The landscape position is 4cm further in and marked as Pelvis as this is the common landscape image we take.
Here are the two parts.
This shows the tool unmounted. Two parts were needed to support the weight of the alloy tool on the ferrous discs. The Ferrous discs are glued to the Nylon (HDPE?) imaging plate cover. No magnets are allowed on the cover as it has to be patient compatible e.g. Pacemaker safety.
The mounting unit fitted.
This shows the mounting clamp fitted to the image plate.
The add on laser.
This shows the second laser mounted to the X-ray unit. It has a spot beam which crosses the machines built in line laser at a set point of height and distance.
The add on laser.
This shows the second laser from the front. It is projected both inwards to the centre and forwards towards a point on the alignment tool which projects from under the trolley surface.
Finished Targeting Tool.
Here is the finished 3D printed tool in place on the imaging plate. The laser can be seen incident on the location circle. The tool is reversible and can be flipped over to avoid the location of small upright supports in the trolleys' cassette slot.
3D Printed Laser Mount.
This mount was printed in carbon PLA. The objective is to make several as opposed to laborious engineering by hand. 
3D Printed Filter Holder.
This filter holder was printed to adjust the brightness of the spot laser which was a bit strong for some rooms which have low ambient lighting. The filter body can be rotated to further adjust brightness due to the polarized filter orientation . There is a slot in the holder to allow the laser alignment screws to be accessed.
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