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Recommended exposure for imaging a phantom hand?
I posted this in another forum, and it was suggested that I post it here, where it is probably more appropriate.
Can you please take a look at these images? These are supposed to be images of a phantom used to support a 510K FDA submission for a new medical system, one taken with the new system and the other one with a “legacy system,” both with some unspecified post-processing involved. The phantom’s soft tissue is likely urethane based resin (specific gravity: 1.06) with synthetic bone from epoxy resin (specific gravity: 1.31).
My questions are:
1. What kV/mAs combination would you generally recommend for taking this particular image of a phantom? Please specify whether film or CR or DR (for equipment that you are familiar with)
2. Can you tell whether any of the two images were severely underexposed or severely overexposed?
3. Are any of these two images useful? If not, what is the problem – wrong exposure, post-processing, too-much image compression?
4. Anything else remarkable about these images?
Image A:
[image]https://i.imgur.com/3NDAbX3.png[/image]
Image B:
[image]https://i.imgur.com/ytarXoO.png[/image]
I am not a tech/radiologist and am simply conducting due diligence for a potential investment. -
5 Replies
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I sent RXR here. Are there any techs that can throw him a bone?
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In case anyone is wondering, the manufacturer of this particular phantom recommends 48kV, 5mAs.
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I will at least reply……..
The image density looks adequate from a broad perspective.
Not over or underexposed.
The images as they appear are not very diagnostic as far as seeing fine details or trabecular pattern.
So without more information as to what you are hoping to achieve with them as well as the exposure index number and type of equipment, I don’t know what more to add.
Hope that was at least some help.
Please feel free to PM me. Maybe we can discuss further.
AC
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Thank you – that was very helpful – I will check with the phantom manufacturer about the fine details/pattern.
Quote from A C
Hope that was at least some help.
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I can throw my 2 cents in here.
What would be the equivalent film/speed combination on this detector? I know it’s old school but helps me to figure out the technique. 48 kvp sounds super low for the kvp side of things. Generally diagnostic techniques would be 55-60 kvp. 55 kvp @1 mas or 60 kvp @ .8 mas should get you in the ball park of technique on most detectors out there today. Doing the math in my head a bit if you use the higher kvp and adjust the mas from the current point you’ll want to go in the 2.5 range for mas. Many customers will find that much of a dose unacceptable these days. Also make sure that you are exactly at 40″ SID to the receptor. Even being off by a few inches can affect the dose to the detector fairly significantly at that low of technique.
My eyes say that it’s a bit under penetrated. The forearm area of the phantom looks a bit grainy. Some of the detail could also be lost with the improper dose. I would also look at the dose indication number of the system (please tell me there is one. I’ve had some in the past that didn’t have one). That should also tell you more about the dose.
I can see some post processing on the bottom image but it is not enough on either. There’s way too much fuzziness on the edges of the bone on both images. Customers will demand a lot better detail than what is being presented. I would talk to your engineering and see if that could be adjusted.
Hopefully this helps!
