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Hi,

Mike is correct in his explanation but if I may go further with extra detail in that:

In the UK, radiology equipment and other medical devices are treated separately by different professions so documents or guidance reflect accordingly and now goes so far as to be treated separately by imaging, radiotherapy or nuclear medicine professionals. In summary - treat separately to other devices for the many reasons Mike lists.

Geoff raises comparisons with older x-ray technology. I think this needs to be discussed separately as a chat rather than the discussion request. I teach BEng and MEng Biomedical students and those that do not listen to my lectures go on to refer to the internet where there is vast amounts of "old" information instead of using my slides. The bottom line for up and coming radiology engineers is - don't look back and stick to what you are taught about current equipment - then take history lessons from oldies like me and Mike.

Hope the above doesn't sound flippant but I'm trying to distill issues.

WRT - "in my experience, the highest risk of unnecessary patients doses arose from "repeat" exposures due (in the main) to what we might call "operator error" (bad patient positioning, incorrect selection of factors, etc.)."
This is all covered by the IR(ME)R Regs and is about patient exposure and very little is now due to x-ray equipment. What clouded the regulatory aspects of equipment in the past was that HSE got involve with all equipment failures but the latest change in law in 2017 saw this move to the IRMER2017. This is where you need to understand about the latest handover form as well. You also have to be able to distinguish device failures (MHRA) and exposure failures that are QA related.

"Aren't we really talking about the welcome change from film cassettes (and wet-processing) to Computerised Radiography? And won't most (almost all) exposures these days be terminated by AEC techniques such as (Siemens) Iontomat? Has anyone we know had a go at retro-fitting CR to old x-ray systems? Was it a cost-effective solution? And (perhaps most importantly) did patient doses decrease - or even increase?"
This overlap period has now waned and is a massive discussion in itself. Exposures are still terminated by the HT generator but software and detector technology has put it into the black box category and you can't fix it any more like most stuff.

"Meanwhile, I am interested in the matter of x-ray exposure dose. Myself, I doubt that dose for equivalent examinations have decreased that much over the last ten, twenty (or perhaps even thirty) years. I know that early CT blasted out hefty doses of the "magic rays", but I reckon they improved quite quickly (maybe as far back as thirty years ago). But I am more interested in traditional (conventional) radiography (the sort of thing that Dr.Röntgen would instantly recognise). Does anyone have any documentation (charts etc.) about exposure dose-rates over the years?"

UKHSA (was PHE) have responsibility for national dose reference levels. These are updated and require a lot of work to collate what to post on this site by Medical Physics Experts at UKSHA. https://www.gov.uk/government/publi...l-diagnostic-reference-levels-ndrls/ndrl

Hope this helps?

Ian

Yes Ian, thanks for that. All very well for the UK et al ... but I wonder how much "conventional x-ray" gear continues to soldier on out in (the rest of) the World. It would be nice see survey results (or even feedback from members of this forum).

Lastly (and by the way), I remembered later that my list of "operator errors" (especially those leading to unnecessarily high patient doses) should have included "poor collimation". Indeed, in my experience this was the most common example of (what I would call) sloppy practice by radiographers - hopefully not the case in the UK, though.

But we need a new thread (and I wonder why we don't seem to have touched on this stuff before).

quote:

" Has anyone we know had a go at retro-fitting CR to old x-ray systems? Was it a cost-effective solution? And (perhaps most importantly) did patient doses decrease - or even increase?"

We have digitized 30 centers with different rates of use that worked with a wet system and x-ray equipment without an exposure meter.
An increase in the dose used is noted, eventually there are excesses of up to 7 times what is necessary according to the exposure index.
I have seen that underdoses give poor quality images that are discarded by the end user, but overexposures are not recorded and windowed. Without care in the use of that radiation.

Sadly, I'm not surprised that patient doses have increased ... but by seven times seems a tad excessive. So much for ALARA!

How are you measuring those patient doses (and how - if at all - were they measured before)?

Lastly, what "exposure index" are you referring to?

It is definitely not an instrumental measurement but a collection of data from users and the manual techniques chosen for similar projections. They state to use 3 to 5 Kv more or 10% of mAs.

At Dicom fields , AGFA and Fuji systems reports:
(0018,1411) Exposure index
(0018,1412) Target EI
(0018,1413) Deviation Index

That's interesting about the DICOM fields (but we've strayed off topic). I'm a bit (maybe very much) out of date now, but I recall that the various manufacturers of DR equipment seemingly liked to use their own "exposure indexes" (with calibration requirements based upon differing physical factors - as in "physics" - μGy, HVL and what-have-you). Perhaps by now there has been a move towards standardisation.

Which technologies (manufacturers) are you using? I'm guessing Agfa and Fuji.

If I'm reading you correctly, your radiographers have been "cranking up" factors slightly since adopting DR. I'm assuming (hopefully) that patient doses are not unduly affected, as the AEC circuitry should terminate exposures once meaningful images (what we used to have thought of as contrast, or "film blackening") have been obtained. There should be a DICOM field that records actual exposure duration (as well as the current-time product - mAs).

As you probably know, there are many fields (or "Tags") in the DICOM header, including one (0018,115E) that gives patient dose. DICOMlookup is very useful.

For reference, these are the DICOM tags you have indicated.

Pertinent clarification, none of the digitized x-ray generators have automatic exposure control.
Digitization is indirect (CR) and was done with Agfa and Fuji systems
We have a single device Konica Minolta, it do not use 1412/13/14 dicom fields

Ah yes; put simply, with CR the "magic rays" have to penetrate more layers in the detector stack (when compared to DR, which came along later).

That also probably explains the tendency of radiographers to elevate selected factors - the phenomenon known as “exposure creep”. In the early days of CR radiologists often complained of poor quality ("under-exposed") images; so radiographers became used to avoiding grief by cranking up the factors. Unfortunately, the higher patient doses did not seem to count for much.

The technical reason for those "poor quality" images was actually due to the higher quality (broad dynamic range) of digital detectors (when compared to traditional film) - this in turn produced noise (digital, or signal, noise) that could be eliminated (or at least much improved) by increasing exposure factors.

Also, of course with CR the cassettes have to be read as a separate process, thereby introducing yet another opportunity for loss of image definition (that may be overcome, yet again, by cranking up exposure factors). To my mind the unavoidable - and undesirable - increase in patient doses that all this leads to is a good (?) example of the "Law of Unintended Consequences"!

Lastly, it would be nice if someone could produce some data showing that patient doses have now decreased (using the latest DR technology, presumably).

Hi, I hope you don't mind me saying this but this forum is the wrong group of people for your radiation exposure settings. It sounds as if you have a different screen combination than with film and you should be using a medical physics expert to investigate the exposure parameters. In the UK this is a legal requirement. It is also reportable to the enforcement authority when a patient is under or over-exposed.
If you do not have a medical physicist to hand, then you need to study the previous and current screen "speeds".

No doubt you're right about involving a Health Physicist, Ian ... but I think you'll find that notions of speed ("Speed Class", "Sensitivity" and what-have-you) - 100, 300, 400 etc. - do not directly relate to the algorithms pertinent to CD/DR ... hence the use of the "Exposure Index" in modern systems.

On the other hand (and rather confusingly) I have seen data from various manufacturers (Agfa, Fuji) - that may well be out of date by now - that do indeed mention "speed" in some of their published algorithms (for instance, "equivalent screen/film system speed" - referred to as S-value).

The EI is related to the radiation dose received by the imaging plate and should be similar for all exposures made for a specific examination (eg, lumbar spine AP, and what-have-you). This provides a way to monitor and record the radiation dose submitted and to determine if there are changes due to specific radiographers, particular x-ray rooms, or over time etc.. The EI is a useful metric for quality control.

The trouble is that (for instance) the Fuji S-value differs to the Philips EI, which does not relate directly with the Agfa EI ... etc., etc. ... so yes, great care needs to be taken by "clever people" concerned (such as the Physicist)!

Back in Ye Olde days of film cassettes, we needed to be careful about "speed" ... not only in terms of intensifying screens (inside film cassettes) but also regarding he film itself ("fast" film etc.). Needless to say, there are many interesting aspects involved in the production of x-ray images.

Meanwhile (for anyone else interested), there is a lot of this stuff available on line:- this report (.pdf) for example. This .pdf is also good. Looking up "Agfa MUSICA" should prove interesting as well (for those seeking current "state of the art"). I find myself wishing we had info. like this available "back in the day".