OK, thank you very much indeed, Phil, for that introduction and welcome everyone to this webinar on radiation safety and best practise. I hope I can make this as practical as as possible. We do have to cover some of the legal aspects, which can be a little bit turgid, but I'll try and interculcate some practical tips along the way.
The first thing we should discuss is why do we do, why do we need to enhance the safety for radiation? And the fact is that ionising radiations are harmful to living tissue. And that includes X-rays, but also some other electromagnetic radiation, such as gamma rays as well.
And the thing about X-rays and gamma rays is that they have a very short wavelength, which means that they have very high frequency. And because the energy of these these beams are associated with their frequency, they have high energy, and that means that they can pass through. Ah, objects and get absorbed by those objects to produce the radiographs that we use clinically.
Now the fact is that as they pass through tissue and the energy is absorbed by the tissue, then that causes ionisation of atoms within the tissues, and those atoms, it knocks out the electrons from the outer shells of the atoms, and that means that there is energy imparted to those molecules that live in the tissue and that can damage them. Now, the measures of radiation dose, which you don't need to worry too much, but just so you're aware of the terms that we'll be using, the absorbed dose, that is the energy absorbed by the tissue, is measured in greys by the SI units, or in old terms, it was the RAD, and there are 100 RADs in one grey. Now, what is used really for radiation safety is a dose equivalent, and this is the product of the absorbed dose times the quality factor.
And we're just lucky in diagnostic radiology that X-rays have a quality factor of one. So effectively a grey equals the dose equivalent, which would be a Sievert. 1st equals 100EMs.
Now, these are large doses, in fact. And so what we'll be talking about when it comes down to radiation safety is millisieverts, which of course is a 1000 of a st. Now, the degree of damage depends on the amount and the type of radiation, and obviously for this presentation, we're dealing just with X-rays, as well as the tissue that's irradiated.
And in general terms, fast growing or fast multiplying, fast dividing cells are going to be most sensitive to radiation. And the thing about radiation is the effects are cumulative and irreversible. And so it's not just a single high exposure that can cause the damage, but repeated low-level exposure.
And this has been shown up by the early radiologists, who many of them died from cancers that were induced by ionising radiation over a long period of time. Now, the radiation, ionising radiation causes both deminiistic and stochastic effects. And the derma sorry, the deterministic effects, are those effects.
Sorry. Are those effects that are dose related. So the severity depends on the dose that is received, but will only produce effects when it is above a certain threshold.
And this is, for example, with skin erythema, hair loss, particularly on the backs of the hands, and cataract formation. Whereas the stochastic effects are associated with probability of occurrence, and that probability of occurrence increases as the dose received increases, and that includes tumour genesis and mutiny genesis as well. So the deterministic effects occur usually relatively quickly after radiation, usually within about a month of a dose of radiation.
Although that's not true in every effect, in every case. And, and this results in inflammation. Retardation of growth.
So here we have a blister association with excess radiation, then it leads to ulceration, and this ulceration won't heal because of the retardation of cell growth. And also tissue necrosis, as you can see here. And the information about the deterministic effects comes from, you know, human tragedies where people have been exposed to high levels of radiation.
Particularly the atom bombs that were released in Japan in Hiroshima and Nagasaki in the Second World War, but also from more recent things like Chernobyl, the wind scale incidents of the late 1960s, and that information as well as experimental animal exposure has given rise to this, deterministic effects. Now, of course, sometimes we use the deterministic effects to kill tissue that we don't want. So, radiation therapy works on the principle that we have a tumour that is actively dividing.
It has very active mitosis, and therefore, it's going to be sensitive to radio. And if we can confine the dose of radiation just to that tumour by positioning the animal and and using different entry points for the radiation, then we can concentrate the radiation on that tumour and kill off the tumour cells. However, as I've mentioned, the deterministic effects depend on the type of tissue radiated.
And with fast dividing tissues such as the bone marrow, radiation of the bone marrow can lead to loss of the erythropoietic and white cell precursors, leading to bleeding, anaemia, and overwhelming infections, which are commonplace in patients that have received excessive radiation. In terms of the skin, there can be hair loss, particularly on the back of the hands, erythema associated with damage to the germinative cells of the skin, dryness and then atrophy of the skin, leading to ulceration, which will not usually heal quickly. Also, the cells within the gastrointestinal tract are fast growing cells, and they are subject to damage by radiation, leading to intestinal disruption and endotoxemia.
Many of the people that were exposed to radiation from the atom bombs didn't die from the explosion, but died from overwhelming infections from the damage to their intestinal mucosa. And then, of course, the gonads which have fast growing cells, then, exposure to radiation can cause temporary or even permanent sterility. So these deterministic effects have a dose response curve that has a lag period.
So in this area here, we can be exposed to radiation, but we wouldn't show any of these deterministic effects until we reach a certain point and then the effects that we see are directly relation to the dose. So there is a threshold for the development of these deterministic effects that relates to the type of tissue that's being irradiated. And in the early days of radiation safety, this led to a term called the maximum permissible dose, and this was thought to be, if we kept within the maximum permissible dose, then we would be safe from radiation.
But because of the stochastic effects, this has been shown to be totally wrong and inadequate in terms of radiation safety. So there's just stochastic effects are governed by the laws of chance, and these include both the developments of tumours and the developments of of mutants. Now, the carcinogenic effects of radiation, increase the incidence of malignancy, and This occurs after a latent period, usually of several years.
So, for example, a radiation of a patient could give rise to leukaemia after a period of 3 to 5 years. Or alternatively, solid tumours may take longer, 20 to 30 years. So these are quite late onset changes that occur from radiation, usually a cumulative dose of radiation that increases the chance of developing a tumour.
Now, People will develop tumours anyway, so there is no threshold for the dose of radiation that we've received. And it's been worked out that if you have a single chest X-ray, then that will increase your possi probability of getting a tumour by about 1 to 2 per million, so quite low. In terms of risk, and that's because you're only receiving 0.1 millisievert in terms of radiation.
That is equivalent to the background radiation in some areas of the country of about 10 days. Whereas if you have an abdominal CT that can increase your risk of tumour development to about 100 to 350 per million. So quite an increase.
And that's because the dose of radiation is about 10 millisieverts or 100 times a single. Chest X-ray. Now, if you then have a contrast abdominal CT, so a CT and then contrast, and then another CT, that of course doubles that risk.
So you have to think in terms of humans as to what is the risk benefit of doing. A particular procedure and in human radiography and radiology, that is a major part to play. Now if you look at an abdominal CT that's equivalent to about 3 years background radiation.
So, quite a significant increase in the dose of radiation. Now, the mutagenic effect, is that irradiation of germinative cells in the gonads will, apart from the deterministic effect that we've already mentioned, increase the mutation rate, and the mutation rate in, sperm and in ovum, can lead, of course, to inherited abnormalities in the offspring, and that would be a, you know, a major problem for people. And the thing about the stochastic effect is that there is no threshold.
We're all have a possibility of developing either inherited defects or the tumours that I've already mentioned, and they only increase when we're exposed to a dose of radiation. So it's really the stochastic effects that radiation safety is trying to reduce to an absolute minimum. And of course, it won't be removing it altogether because just standing in Cornwall or in some other areas of the country, you will get quite a high background radiation dose from the rocks in that area.
Now the responsibility for looking after radiation safety, started off by being a moral responsibility by the employee, and that was associated with a number of codes of practise that people were supposed to follow. But it became clear that that wasn't going to be sufficient. And in 1974, the Health and Safety at Work Act was introduced, and that is the basis, for the control, of, health and safety at work, which includes, of course, radiation.
That led to the ionising radiation regulations of 1999, which most of you should be aware about, the approved code of practise and the veterinary guidance notes for ionising radiations all produced around about that time. But in 2017, very late in 2017, in fact, the ionising radiation regulations of 2017 were released. And from those, there is an approved code of practise and guidance called the Work with ionising radiation, which includes the ionising radiation regulations of 2017.
And that is available from the HSE either as a booklet. Which I, I think is about 60 pounds to buy, but you can download it for nothing, from the health and safety executive website. And so I would advise all practises to have, the PDF downloaded from that for reference by all members of staff, but particularly those that are involved in radiation.
And just recently, the BVA have updated their veterinary guidance notes to the guidance notes for safe use of ionising radiation in veterinary practise, which incorporates the latest changes in the ionising radiation regulations of 2017. And this is available to BVA members for about 30 pounds, for non-members for 60 pounds, and all practises. Should have a copy of that.
Certainly, if you're going to be inspected by the RCVS for practise standards, then they will expect you really to have a copy of, of that. So I will recommend that to everybody. Now the main legislation between IRR 1999 and IRR 17 is the introduction of a graded approach requiring employers to notify and gain registration, and or consent from the Health and Safety Executive for the use of ionising radiations.
And this must be done before starting work with ionising radiations. So if you're in a practise, this should have been done by Monday, the 5th of February 2018. There is a fee of £25 for registering your practise for using ionising radiations and failure to register will lead to some enforcement activity by the HSE and can lead up to prosecution levels.
For larger veterinary groups, it's only necessary often to have one registration per company. So you get, all the practises, registered for just 25 pounds. Another change in IRR 17 was the reduction of the dose limit for the eyes from 150 millisieverts down to 2 millisieverts per annum.
It's well recognised that small amounts of radiation over a period of time increases the risk of cataract formation. And for those people that are exposed to higher levels of radiation, then, radiation, glasses, should be used to protect the eyes from, radiation. Also in IRR 17, the term radiation employer, which was used previously, has been replaced by employers, so it eliminates the ambiguity, and the legally responsive responsible person, is the employer now that is made absolutely clear in the new regulations.
Also, there was a removal of the specific reference to dose limits to the abdomen of women of reproductive capacity. And that is because it was quite confusing. You need to, to know that they were likely to be pregnant and, and because of, you know, personal information transfer, that's not always possible.
So that has been taken out and the dose rates have, have, have been reduced. There is also now a requirement to estimate the dose levels to members of the public, and this should be defined in the risk assessment, and we'll talk about the risk assessment a little bit later. .
There should, however, be few incidents, instances in veterinary practise, where the figure will not be zero. The public should not be exposed to radiation in the normal process of radiation examinations. If this is not possible, it must be given, consideration, in the risk assessment.
And the other change is that you need to have contingency planning. And this contingency planning should include what happens if there is an, a, an error in the radiation exposure, and what happens in those radiation accidents and how it's documented and how it's stored. So those are the basic changes from IRR 17 from IRR 99.
Now, terms that are important to understand and terms that we will go through in some detail, are the radiation protection advisor. The radiation protection supervisor. The local rules and the written arrangements, which used to be called the system of work.
So the local rules and system of work is, is how they were defined previously, they now prefer it if it's the local rules and the written arrangements. They like changing the names sometimes just to keep you on your toes about radiation safety. Now, the RPA, the Radiation Protection Advisor, is, is somebody who will provide advice to you as to how you should safely carry out the radiation, within your practise.
And although there are certain circumstances where you don't need an RPA, the fact is that you actually need an RPA to tell you that you don't need an RPA. So for all intents and purposes, you should have a radiation protection advisor attached to your practise. And the employer must consult a suitably qualified RPA, as necessary to provide the advice and the observance of the IRR 17.
And this, appointment of the RPA must be in writing and must include the scope of the activities on which the person is required, in a letter of appointment. And that letter of appointment should be retained by the practise for demonstration that the person is employed to do that work. To be a suitable RPA, you need to possess the knowledge, experience, and competent, competence needed to give advice on particular working conditions for which he or she is being appointed.
And in some instances, for example, within the university, we may have more than one, RPA. Ideally, these RPAs should visit the practise. I would say that that's an essential part of the process.
I don't think that you can do this job without visiting the practise and seeing the premises. And the RPA should provide advice on the radiation risk assessments, and we'll talk about that a little bit later. Everything now has to be risk assessed, including radiation.
So this is. Is one area where the RPA can really help. They will also help and provide advice on the designation of the controlled area, drawing up local rules and written arrangements, handling of various investigations that need to be had had if there's evidence of radiation leakage or exposure, drawing up contingency plans.
And dose assessment and recording that's required by the practise to maintain the the the, the rules of the IRR 17. Now the RPS or the Radiation Protection Supervisor will be a member of the practise with responsibility for the radiography and radiology. The employer must appoint one or more RPSs.
So if you have, for example, a CT and a radiotherapy, unit, you may then have more than one RPS within the practise who is is designated to deal with the, the IRR regulations for that particular area. Now the employer must provide the means necessary for the RPS to perform their role. So in some ways, they are more important than the employer.
If they say that this is not safe and they have good reason for that, then, of course, they should document that and the changes will occur. The RPS must be named in the local rules. The local rules must be displayed, outside the controlled area.
So everyone should know who the RPS is, and on the local rules, the contact details will be there, so it will be possible to contact, the RPS quickly in the case of emergency. The RPS must command, therefore, sufficient authority, and, to be able to carry out this work. They need to know and understand the requirements of IRR 17.
And they must be, sufficient resources and training to carry out their functions. They need to attend a RPS, teaching session at least every 5 years. The RPAS must know what to do in an emergency.
That is one of their key roles, if there is a problem, they must know how to deal with it immediately. Ionising radiation should only be used, of course, where there is a clear justification for carrying out the procedure. In human medicine, if there isn't a clear justification, then it would be very difficult to get that, examination done.
And, and we need to enforce the same sort of regulations that there should be a clinical justification for carrying out the procedure that we want to undertake, and then we should carry it out safely. Now, of course, the, Health and Safety Executive are really only interested in a radiation of people, but we ought to be mindful of the fact that we are radiating our patients as well, and, apart from reducing the exposure to our staff, we need to control the radiation to our patients for the reasons that I mentioned early on in this presentation. Any exposure of personnel to ionising radiation should be as low as reasonably practical.
That means the AARP principle needs to be maintained, and no dose limit should ever be exceeded. Even if we get a reading on our badges, we have an investigation as to why that reading might have occurred, even though the reading, if it was repeated monthly, would never get anywhere near the dose limit. Now the terms LARP, which is the the IRR 17 uses now as low as reasonably practical, was previously known as low as low as reasonably achievable, or the AAA principle.
Again, changing the name just to keep people on their toes to make sure that they're covering the areas. And what does that mean? Where does the radiation come from?
Well, the radiation can come from the tube head. The tube head is lined with lead, which normally protect the beam from coming out sideways, but we need to make sure that that lead's intact. Then it comes out through the collimation, that's the useful beam down to the animal from which there will be scattered radiation when it hits the animal, scattered radiation when it hits the table, scattered radiation when it hits the floor, and it's the scattered radiation that we have to be really mindful of, because we can't see the radiation.
It's not detected by the light beam diaphragm in any way at all. It's just Around that those objects that I've discussed already. We also need to think about where the beam goes.
So if we're using a standard table, the X-rays will go through a wooden table, and therefore will expose the floor, and the exposure of the floor if somebody's feet is under it, will get exposed at a much higher dose to the primary radiation. And of course, if we have a floor with people working below, then those people below can also get radiation. So we have to think as to where the primary beam is going to end up, if it's not contra contained and restricted just to the patient.
And that's why tight collimation is so important, when we're doing, radiographs of our patients. We'll talk about protective, personal protective equipment, the lead aprons, leg gloves, etc. Later on, but do remember that the protective, personal protective equipment that is provided only protects against the scattered radiation, which is low energy radiation.
It will not protect. Against the primary beam, which will go straight through a lead apron. So we have to think about where the radiation is going to end up and how the scattered radiation is going to be effective around us.
So the sources of the radiation are the X-ray tube. We have to think about the primary filtration of the beam to take out the low energy radiation that should be fixed in the machine. It should be checked every time the machine is serviced, and of course the machine should be serviced on an annual basis, and documentation of that service should be kept in the practise in the health and safety file.
Colluation of the primary beam is important, as I've already alluded to, to try to confine the beam within the patient so that the minimum amount of scattered radiation will come from hitting other objects such as the X-ray table and the and the floor. Because scattered radiation is, is what we have to worry about, and back scattered radiation from when it goes through, the, detected device or the detective device or the cassette and bounce back from materials such as the table beyond that, is, is, is also important. So if we look at a X-ray tube.
It has a lead lining. That lead lining can get damaged, so we need to, think about, whether that could be providing some, some radiation, which would be, of course, for a vertical beam about head height to a person, and we have the filtration here of the primary beam to take out the low energy radiation, and then we have our primary beam which we collimate below that. Now, in the old days, we used to often check radiation leakage from the X-ray tube.
This should now be done by your engineer that comes to service the machine, but you can do it by putting some film. Around the X-ray tube head or using a dosimeter under the guidance of your RPA to see whether there is likely to be any leakage from the head from damage to that lead lining. Now these cones, which don't have a light beam, mean that you can't identify exactly where the primary beam is.
These were used in older X-ray equipment, and if you have one of these cones without a light beam diaphragm, you cannot now use that legally to manually restrain an animal. And of course, you should only Manually restrained animals in exceptional circumstances. So it is an absolute no.
And the reason for that is that you can't see where the primary beam will end up. You can look at this and think it's going to go out to this sort of area, that sort of distance, but it would be very easy if you were X-raying something small to get your hands within the primary beam. And worse than that, if you're using a cassette that is smaller than the area provided by the primary beam by these sort of wide cones, and you only get a corner of that, of course, all of this area has been irradiated by the primary beam.
And, and you may have people or parts of of people within that area that could be exposed if in exceptional circumstances you would have been, manually holding these animals. So here's a particular, it's a bad x-ray, of course, it's of the neck and full leg, but this is the edge of the beam. You can imagine that it includes the animal's head.
Had the animal been Strained, then a hand on the head would have been exposed to the primary beam. If a hand was holding the leg, that would have also been exposed to the primary beam. So this is why, unless you've got a light beam diaphragm, you cannot manually restrain animals and you should, as I've stressed before, only be manually restraining them in exceptional circumstances.
Now, if you do have a light beam diaphragm, it's the light is shined down the pathway of the primary beam by a mirror reflecting light from a light bulb. And so this is what you see, something similar to that. But it's quite easy, particularly if the tube is taken around or moved around the practise for that mirror to get slightly knocked and tilted.
And so you need to check that the light beam diaphragm. Is accurate. And by doing that, you just place some coins across the edge of the light beam and take an exposure.
And when you take the exposure, then what you see is that if you've got accurate alignment, the area that is exposed should pass between those two coins placed at the edge. Whereas if here we find that actually the area of the primary beam is bigger than we thought from the light beam, then we should get that fixed, and the engineer should be called that. Image intensified fluoroscopy requires some separate regulations, and I'm not going to talk too much about that.
But again, you've got to keep well away from the primary beam. Animals should be where possible, so they. Or anaesthetized.
This animal's having a barium swallow, so we need to keep everybody as far away from the primary beam, which is collimated down to the intensified the intensifier here, and the intensifier. Intensifies the light produced from the fluorescent skin screen by many thousands of times. So that's why the dose rates are quite limited, but there'll be controls over the time you're allowed to do this for because, people can get carried away.
Now the control of radiation means that you need to have a suitable room of adequate size. You need to have radiation warning signs, you need to have the X-ray machine regularly serviced on an annual basis, and I said you should keep a record of all those reports because they will be looked at if you ever get a visitation from the health and safety executive and probably will be checked if you have a practise standards . Visit as well.
If you have your exposure button on a cable rather than on the console, then you need to have a cable that is at least 2 metres long so that you can get well away from the primary beam and preferably outside the controlled area. When you release the exposure button, that must terminate the exposure, and that is something, of course, the engineers will, will check. But if you suspect that the button is faulty, then you need to replace that as quickly as possible and not use the machine in the meantime.
So people often ask, what is a controlled area? And the X-ray room is usually a defined room that becomes the controlled area, and it's easy to define a controlled area if you have a room with borders around it. It's much more difficult to define a controlled area if, for example, you're out on a stable yard taking X-rays of horses.
You can do it in the stable, that can become your controlled area. But if you can't easily define it, then for the purposes of doing it outside, then it should be a 2 metre, area from the tube head that it would be considered to be, safe, providing the primary beam isn't pointed at any one of those areas. It's desirable but not essential that the room is used solely for radiography.
So some practises, of course, you know, are small. They have to have other things going on in the X-ray room. And so you need to define the controlled area as existing when the X-ray machine is connected to the power supply and capable, therefore, of emitting X-rays.
Then it's a controlled area and the local rules come into force if you want to enter the controlled area. If the machine is not plugged in, then it is possible to use that room for other purposes and it's no longer deemed as a controlled area. And that should be laid out quite clearly in the local rules.
I told Hello. Hi, can you hear me? I can, Mike.
OK, yeah. I think what we do is everyone's hung on, really appreciate everyone doing that, and I think just resume from the point you were at and OK, OK. Thank you.
I don't know what happened, but anyway fault. OK, so, the inverse square law is, is a really important principle to have in mind, because the, if you double the distance from the source of the radiation. You reduce the intensity of the beam by a factor of 4.
So distance is really a protective measure for radiation protection. A lot of what we do in radiation protection is associated with Apologies. So the radiographer should be able to stand outside the controlled area or be shielded by a screen or other suitable lead equivalent structure within the controlled area.
So if you have a room that has adequate shielding, then if you can take your extended lead with the exposure button outside the room, then that is fine. If you want to stay inside the room, then even if you're wearing protective personal protective equipment and lead coating, you should be behind a lead screen or a lead equivalent structure, such as you see, for example, in the larger X-ray rooms in, in, in hospitals. The controlled area should be defined by physical boundaries as far as is possible, which means that the whole room will become the controlled area rather than just part of the room, which you could actually define as a controlled area, but for simplicity, it should be the whole of the controlled area and the RPA will advise you on the extent of the controlled area.
Now the makeup of the construction of the controlled area is really important, particularly with modern building techniques and the way that buildings are put together. So if you have a single layer of brick or high density blocks as the wall structure, then that will be adequate shielding against scattered radiation. If it's a partition wall with plasterboard and stud work, then it will not be sufficient for constraining scattered radiation, and you have to think then as to what the next room would be exposed to and what happens if that is a public area, for example, that would not make it possible to have that controlled area defined in that way.
Walls that are double layer brick, ie outside walls, or have double high density block work, would be adequate to protect and irradiate from primary. Beam radiation, and that is if you're using a horizontal beam for equine work or if you are in the rare situations using a horizontal beam for small animal work, then it must be pointed at a double brick area where it won't go through the brickwork and expose people the other side of that brickwork. Doors obviously being wooden, will often require additional shielding, or be shielded by a lead a lead screen in front of them.
Shielding of ceilings and floors should also be considered if they're occupied areas either above or below the X-ray room. And that's really important to think about where the X-ray beams, even scattered radiation, will end up if there's not a constraining wall to control it, and warning signs and lights should be provided at each entrance and the The warning signs should be the ones that are approved by the Health and Safety Executive, and they are also listed in IRR 17. The warning light should be wired, so it illuminates automatically when the X-ray equipment is connected to the power supply.
The warning light should also contain a fail-safe mechanism by which if the light fails, exposures of the X-ray machine will not be possible, so you couldn't walk in inadvertently to a controlled area when the X-ray is actually being taken. Now some of you may have fixed or portable battery powered X-ray machines that don't require mains input apart from when they're being charged. And it may not be possible to establish an automatic warning light as you would for a standard X-ray room, and then you'll need your RPA to provide you with information as to what would be appropriate and what would be legally possible.
The exposure button should be a two-stage exposure button, and that means that you prepare the machine and then the second press actually takes the exposure. And if possible, as you can see here, you should be able to leave the room to avoid exposure. The last principle we've mentioned, you need to justify the radiographic examination, use the lowest exposure factors, and fastest film combination.
Now most people use either CR or DR, although the exposure factors are slightly higher than The fast film screen combinations that we use, the number of X-rays is likely to be reduced because of the reduction because of the latitude that the detectors now have compared with old film screen combinations. So avoid repeating films through inadequate technique and quality, so pay particular attention to your technique and quality, anaesthetize or sedate patients wherever possible. We have a policy of not manually restraining any of our small animal patients, and we haven't.
Held an animal for some 30 odd years. So it's really important to understand that actually sedation may be a safer option, or even anaesthesia may be a safer option when they're on oxygen than struggling with an animal that is already slightly distressed. So if you have a practise, manual restraint should only ever be used in exceptional circumstances.
An exceptional circumstance would not be, for example, for a hip dysplasia screening X-ray, it would be because the patient. Is too sick or compromised to allow sedation or anaesthesia. Otherwise, what happens is you get an X-ray like this.
This would be difficult to interpret. You've clearly got a fracture in the pelvis here. It looks as though something is going on in the hip joint here.
If you straighten that out, position it better, you can see that there's a fracture to the pelvis. Both through the pubis and there's a dislocated hip. So positioning is really important and getting the best possible positioning will allow you to really assess the images and make a much better diagnosis than if you've got a poorly positioned film.
Obviously for positioning, if you're not manually restraining, you need positioning aids such as foam wedges, sandbags, tapes, cradles. You should use cassette holders and long handles if you're doing X-rays of horses to avoid exposure to the primary beam, and you need a 1 millimetre lead equivalent on the top of the table to prevent backscatter. Either on the top of the table or below the bucky tray with the grid on it.
Lead screens for protective staff or staff should leave the room. That's really important in the LA principle. So here's some pictures of our sort of positioning aids, and foam wedges, and loosely filled thin sandbags.
Bags that are very good for helping position some ties and some heavier sandbags, as well as some cradles that you can see here, and a foam wedge underneath the sternum here. These dogs are just sedated for this positioning. If you do use a horizontal beam, you have to think very carefully as to the dangers of the primary beam and where it will end up.
You can see this person here will get a full exposure to the primary beam that hasn't been absorbed by the large animal there. If you're doing it with small animals, then again, manual restraint shouldn't be there. These people shouldn't be close to the equipment.
They should be behind lead screens, and you just have to think about the ability to carry out these these examinations safely for your practise. This was a picture that was in the vet record only in June of this year. Now I take it it was a mock up for a particular article in the vet record, but what you can see here, this is a DR system, is that somebody's holding the DR with ungloved hands.
It's out in the bright light, so the chances of you being able to see the The light beam diaphragm on the detector will be quite remote. The person is very close to the X-ray tube again with unprotected hands. Really, that's very, very poor radiation safety and the exposure levels that people would get over a period of time would be quite significant.
So if you use cassettes and the cassette holder, then you should be able to get good radiographs of the limbs of horses with a horizontal beam thinking, of course, all the time as to what might be going on in line with the primary beam, where that primary beam is going to end up, preferably at a double brick wall. This cone is attached to a light beam diaphragm, so that it concentrates the primary beam to a much smaller area, much more effectively than just a light beam diaphragm on its own. This is an improvised cassette holder.
The cassette's been put in a plastic carrier on a drip stand and could be used for taking, for example, the backs of horses, where you require higher exposures, and more scattered radiation without anyone having to be in the vicinity of the holder. So what about protective clothing? Well, protective clothing should be against scattered radiation.
It doesn't provide protection against the primary beam. It will have a lead equivalent, usually of 0.25 to 0.35 millimetres of lead.
The correct design is important if you You have a two-sided apron, then that's much easier to manage than just having a heavy apron at the front, always sort of holding your neck and clinging to your neck. People like the kilts with a top as well provide slightly more comfort. But however you have these protective lead clothing, they should be stored appropriate.
They're expensive. The lead aprons are about 500 pounds, and if you leave them screwed up on the floor, they will get damaged very quickly and the lead rubber will break and crack, and then it will allow radiation through. So protective clothing should be regularly checked for cracks, cuts, and other damage.
We also screen our lead aprons using the image intensifier to make sure that they are not. Damaged in any way, and we replace them if there's any sign of cracking or damage. And we keep a record of these regular checks dated in the file associated with radiation safety.
These are the sort of ways in which they should be hung, these sort of wide tube hangers. They are quite expensive. They need to be put into a wall because these are quite heavy.
They come in various lengths and you need to think about the length you need for the size of the person you have, particularly if you're doing horses with a horizontal beam using with the feet or fat locks, then you need them as long as possible for those people. Lead sleeves and lead gloves may be necessary if you're going to do any manual restraint. This will be away from the primary beam.
Lead sleeves are easier in my experience, because you can put your hand. The poor and hold the paw easily and slide the lead shield up the leg so that it's well protected from the scattered radiation. Trying to hold the pool with these thick non-compliant gloves is much more difficult.
The gloves also tend to crack. The lead rubber cracks usually at the joint surface. And remember again that these are not for primary control of primary radiation.
The person that was holding this animal for a barium study will have got quite an exposure of their hand because it's in the primary beam. If you do use manual restraint, then try and get as far away as possible from the X-ray tube. So here we have a really poor technique.
This person's leaning forwards, so any scattered radiation will hit their head, particularly their thyroid area, although they're wearing gloves and lead apron, also into the eyes. So try and stand back as far as possible. This person is standing back, but their hands have slipped out of the lead shield, so they will get radiated from scattered radiation, even if the primary beam is well collimated within the patient at that area.
So leaning back, standing as way as far as possible from the source of the radiation is the best way to protect you if in exceptional circumstances you are doing any manual restraint. These are all X-rays that have been sent in to me for interpretation, and this really just upsets me so much. This is an animal that is anaesthetized, that nobody has any positioning aids, so they've used their own hands, and their hands are in the primary being.
You know, they may have said in the older days, well, I've had my children, it doesn't matter any longer, but this does matter because those will get the skin will get damaged from repeated exposure to primary radiation. And in this case, there is a glove being used, but the glove isn't very effective at reducing the primary radiation, so you can still see the person's bones through those those gloves there. And again, totally unnecessary because the animal is actually anaesthetized for that position.
So improving your radiographic technique is a really good way of trying to improve radiation safety. And when you get a visit or if you get a visit from the Health and safety executive, they will want to see some of your images to make sure that what you're doing. Complies with radiation safety standards.
So they'll want to see that the light beam diaphragm is used to collate the beam, that you're using the correct sort of exposures that you have in your practise a standardised processing technique. Still using processing, you'd have an exposure chart for the use of the exposures. You'd make sure that the animals were well positioned where a grid is used, it's used correctly and ensure adequate radiation protection and monitoring of staff.
From personal safety points of view, it's important to exclude all unnecessary people from the controlled area, and usually that means everybody from the controlled area. So try and get everybody out. Remember the inverse square law, keep your distance.
No manual restraint except in exceptional circumstances, and the practise should provide really adequate protective clothing if somebody is going to be in the controlled area at any time during the exposure. They should of course be behind a lead screen when they're doing that. And then personal dosymmetry.
And what do we mean by personal dosymmetry? Well, most of us probably have personal dose metres to measure the radiation to which we are exposed. And the fact is that these monitors are very useful.
They're quite expensive, of course. They can not only be used for measuring the exposure of Personnel, but they can also measure environmental exposure. So if you have a wall that you're perhaps not totally convinced is adequate for controlling radiation, you could put a monitor on the other side of the wall and see whether it gets a reading after say 3 or 6 months to make sure that people don't get exposed to radiation if they're in an adjacent room.
It also monitors the practise within the facility, so we don't expect anyone ever to get any reading on their dosimeters. And if they do, then there's usually an investigation as to why that might have happened. And what that shows us is that our working practises are safe.
Now we could say, well, you don't need to do the personal to symmetry, but actually we wouldn't know then whether somebody walked in front of a primary beam and got a big exposure. And so it's important to check that the way in which you carry out your radiation work is, is, is. There are film badges which have standard film that's processed.
They have different philtres that allow the monitoring company to detect exactly how much radiation you've been exposed to and what type of radiation you've been exposed to. And they're the thermaloluminescent dose metres which contain lithium fluoride. Most of you will probably have those.
These are heated up and give off light, which is proportional to the dose that has been absorbed. Now, whatever dose metre you have, you need to have one on your body underneath lead. Protective clothing if you're wearing lead protective clothing.
So it is a measure of the amount of radiation that your body is actually receiving. So on your chest or around your waist. We also occasionally use extremity dosimeters.
This is a lithium fluoride in a finger car or a wristband or a ring that can be used if we're doing, for example, interventional radiology where we get or can get quite close to the image intensified fluoroscopy beam. And to make sure that we don't get radiation that way. The local rules and written arrangements are really important.
They should, as I've said, contain the names and contact details of the employer, the RPA and the RPS. They should identify the controlled area. They should identify the X-ray equipment that is used in the controlled area, and how it's used in the controlled area.
They should talk about the use of the personal protective equipment, when it should be used, how it should be used. The symmetry arrangements, when a formal investigation level is exceeded, the type of formal investigation that will be carried out, contingency plans if there is an accident, and the sort of workload that goes on. So here, and without going through it in any detail is the local rules and written arrangements that we have.
The points that I would point out is that they are dated. So they were revised in February this year, and there's a renewal date for reviewing them for February next year. They should be looked at annually.
It's very easy to produce these local rules and think, oh yes, I did that fairly recently and find that actually it was probably 2 or 3 years ago that you did it. They must be kept up to date. So names and addresses and contact details down here.
The RPS is again named over here as well as being named over here. The investigation levels, so if anything, any people receive an effective dose greater than 1 millisiever, that's 0.1 per month, then there will be a formal investigation.
And the control area is defined, how the system is used for working practises in the X-ray room, and then the contingency plan at the end. In addition to that, you also need to have the risk assessments, and these need to be written and agreed with the between the RPA and the RPS that include and consider the source of ionising radiation, the estimated dose rates to which anyone should be exposed, the results of previous personal as symmetry, and what that may mean and how it could be better controlled. Advice about the safe use and maintenance of equipment, the effectiveness and suitability of personal protective equipment as to whether you need thyroid shields, whether you need X-ray, protective glasses, what happens in accident situations and the sort of accidents that might happen, including, of course, a horse reacting when it's in the X-ray room.
All of that should be included. Consequences of possible failures of control measures and steps to prevent unidentified accident situations should all be considered in the risk assessment, and that should be completed. So I hope that in this presentation, I haven't been able to cover all aspects of radiation protection.
I do suggest that you try to get hold of the BVA book that I mentioned earlier because it contains a lot of useful information, some sort of draught ideas as to the local rules and the written arrangements and how they should be formed. Very helpful indeed. So with that, I apologise for the break in transmission due to the internet going down, but I'm happy to answer any questions that you might have.
Thank you very much indeed for listening. Oh, Mike, yeah, thank you as well. Yeah, it's such an important and fascinating subject, and your presentation was actually very informative and superbly presented.
Under the conditions, you did extremely well. So hopefully there'll be a few questions to come through. We'll just hold on for a minute or two.
Yeah, Mike, while people are deciding if they want to put some questions through, is when you talked about exposures, I'm not a vet, I'll be honest with you, but I I come out of photography. And when you're talking about exposures, are you talking about, is it all automatic now with the aperture, you know, sort of the F stops and you know, so you don't get an underexposed or an overexposed X-ray plate? Well, it's all digital now, so how does that actually work?
It works on the fact that you need. A certain quality of being that's controlled by the killer voltage that you put across the tube to generate the higher energy radiation that will go through a bigger animal. So the KB it allows you to get through the animal, and then we use a combination of milliamps, which is the flow of X-rays and the time in seconds, usually milliseconds to for the actual exposure and.
Obviously, to try and get the exposure time so you don't get movement blur, as you would in photography, we use the maximum amount of MA that we can to keep the MAS constant and the time in the MAS product as short as possible. Oh, very interesting. Well, so far it looks like your presentation was, so good, there's no questions needed.
So, really appreciate your time and as I said earlier, fantastic presentation. And due to the technical problems, you know, apologies again from all of us, you know, these things cannot be avoided sometimes. So thanks very much.
We have one. We've got one person saying it was really good. All my questions were answered.
Thank you so much for a great lecture. There you go. Thank you very much.
But it was, but it was, yeah, no, very, very, very good subject. So, I think based on that, Mike, thanks very much for the presentation and thanks to everyone listening in. And, you know, we look forward to seeing everyone next week and, good evening.
Thank you, Mike. OK, thank you. Goodbye.
Bye.