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Imaging for Postgraduate Orthopaedic Exams
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Imaging for Postgraduate Orthopaedic Exams
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Transcript:
Language: EN.
Segment:0 .
Good evening, everyone, and welcome to the Orthopaedic Academy webinar program, which is streaming in conjunction with OrthoTV today. My name is Nikki Evans and I'll be your host for this evening. I'm delighted to welcome Mr Joe Gouda as our speaker this evening and the rest of the orthopedic Academy faculty, Mr.
Fira Arnaout and Mr. Shwan Henari, Mr David Hughes, Mr Justin Leong and Mr Ashcroft from OrthoTV. The agenda for this evening will be a presentation by Mr Gouda on orthopedic imaging for the FRCS exam and will follow that with an MCQ poll of three questions. These are anonymous so we can fill them in as quickly as possible and then we'll go through the answers. We'll also have some time for invited questions.
If you put your questions into the chat box, then we will ask at the end and hopefully get them answered for you. This evening, we will also do a hot seat practice with feedback. Each viba session is 5 minutes long. We need three candidates who could make yourself known to David or Shwan, or for us. The idea of these is not to embarrass you.
We think it gives you the best practice for the exam, so everybody is welcome to volunteer. So just a reminder of our upcoming courses, there they are, the case based discussion course, which at the moment we're running to and the mock exam course, which we've run through the year and has always been very popular and gets booked out really quickly.
And that's how you can book them. You can look on our website there. Orthopaedic Academy co.uk and you can follow us on Twitter, YouTube and Facebook. And you can also message us to join our Orthopaedic Academy telegram group group. So without any further interruptions, I will hand you over to Mr Joe Gouda, who is our presenter for this evening.
Thank you, Joe. Oh, thank you very much for this introduction. Delighted so. I would share my screen. Good so today we are going to discuss about imaging for FRCS trauma and orthopedic exam. This is very much a very common ask the question in the FRCS especially, of course, in the basic science.
And it will give you some of the, Uh, some of the information for the other tables as well, like the adult pathology and of course, the trauma. First of all. We have to know the regulations behind asking for an X-ray. There is something called an IRMER or IRMER which is the ionizing radiation medical exposure regulations.
And this is particularly in the UK. It is commonly asked in the MCQ, and I believe as well it can be asked in the basic science, and this was done to protect the patient from ionizing radiation. Basically, not all the radiation, of course, because without ionizing radiation, we cannot diagnose, but from a non essential, non important ionizing radiation and it defined for duty holders.
The first one is the referrer, who is basically you, the orthopedic surgeon who actually requests the X-ray. And you have to in the X-ray form, you have to write why you want this imaging to be done. This is how you justify it. Then the practitioner, which is the radiographer, all the radiologist who is basically the one who says, yes, this type of X-ray can be justified and is needed for this to answer that question, then the operator, basically, it's the radiographer who will press the button and the employer who actually makes the framework for all these duty holders to work the employer.
If you want to do a quality improvement program, this is where you aim to the framework. Then what is the X-ray here, the x ray? You have to have a clear definition to x-rays. It is a high energy. Electromagnetic waves are usually study in threes, so three bullet points or three buzzwords to answer any question.
So X-rays or high energy, that's one word electromagnetic waves two words and it is wavelengths is shorter than the visible light. That's the third buzzword. If you say these three buzzwords, you have the definition on. There is again, three things we need to know in the X-ray the structure of the X-ray machine. The thermal something called the thermal ionic emission, which is the process by which the X-ray is formed and attenuation.
So first of all, the structure, as you can see, this is the X-ray to. On our right hand side, there is tungsten foam filament, which is heated. That's why it's called thermal ionic, so thermal. So it's heated to about 2,200 degrees Celsius to emit electrons from the trouble, from the negative cathode to the positive anode once it hits it.
OK all this in the vacuum tube, once it's hit the A it can hit it in one of three positions either the outer or the high or the higher level electrons, and that produces heat, the inner electrons and that produces about 20% of the X-rays and the nucleus, which is basically it. It produces about 80% of the X-ray radiation.
Remember, from high school electrons, traveling and radiation are more or less the same. There is an interaction between them. This is a basic physics. Think that you don't need to know for your FRCS exam? So then the attenuation when the x-rays are emitted from the X-ray machine, it hits a body and it depends about the amount of absorption of each element that.
So bones have a high attenuation. That means they attenuate or absorb a lot of X-ray X-ray radiation. This is in contrast to water or air that has low beam attenuation, so most of the X-rays will pass by. And then there is something called scattering, which is so much important. We will later in the presentation.
This is the vision of the X-rays after hitting something, hitting the object or hitting the thing that you are x-rays. Then we have three main types of X-rays conventional screen film radiography, which we stopped using it in the whole UK. Now digital radiography, we use it and fluoroscopy. So the conventional screen radiography again, three things. It's a film between two forceful intensify, intensifying the screen.
These this screen is basically to transform the non visible X-rays to light to visible light. So and then hitting the film to produce the image. Digital radiography is slightly different, although the same principle. It's either that direct radiography or computed radiography. The difference between them is that direct radiography is that the receptors are generates each receptor generate a pixel and the computer computed radiography is that you take everything on a cassette and you have to put it in a machine, which has a laser light that transforms the X-rays to two light rings.
And then you have, of course, the computer which processes the imaging and you have the PACs system. All of us uses Pac system now, which is pictured archiving and communication system. That's where all the images are stored. And you can easily see them, and they are meaning a means of communication between the radiology department and any other computer in the trust.
Advantages of the direct of the digital radiographer over the conventional one is basically it's economic, but on the long run, it's less exposure as you need less X-ray intensity and it's easier to retrieve, you have it forever. Although the first one gives you a hard copy, but this hard copy can be affected by sun and water. Then you have the fluoroscopy, which is the second.
Main question in the FRCS exam. You have the X-ray tube with the same generating the same everything, but you have an image intensifier and here you need an intensifier because the amount or the intensity of the X-ray used in fluoroscopy is way less than the X-ray used in the Department downstairs. So the intensifier has multiple levels from an input window to an input force for sheet, which transforms X-rays into light and then light electrons, which actually is transferred to your screen.
But the aim of this is basically the single X-ray beam will be accentuated by thousands of times. That's why you can use it. OK, you take like 10, 20, 30 images in theaters compared to a single image in the outpatient clinic. And still, you're in the safe in the safe zone. That's because of the brilliance of presence of the intensifier.
Then fluoroscopy, it has to be there is a very important guideline, which is the ALARA. ALARA is basically as low as reasonably achievable, and that is again three buzz words time distance shield. So less time of exposure, no longer distance from the machine and the thicker the shields, then we have the advantages of the X-rays in general.
They're good for diagnosis. They're ready. They're cheap, but they are. They have disadvantages. Are radiation ionizing radiation exposure and it is. It misses. the subtle pathology, especially soft tissue. And it's to the. Then there is a modification to the X-ray to become a computer tomography or the CT scan.
To see this scan depends on the presence of the donut, which is the country again formed of the country is formed of three. At three parts, the coordinated and coordinated means presence of multiple lenses to actually focus the radiation on the source or on the image that is aimed towards X-ray source fan shaped that gives you a fan shaped X-ray beam to hit a limited detector.
To create an image, you have to have the source and the detector combination. That means they have to be perfectly aligned together because they are rotating in the country and that's how they produce the image in the cityscape. So basically, the X-ray and the X-ray tube and the X-ray detector actually are against each other and they have to be precisely aligned after having the image or on with the X-ray beam, they rotate a full rotation and then the whole country, or basically the bed of the patient's bed move moves when it moves another circle or another cut is taken.
That's how its linear movement of the country. This produces something called a Voxel, not a pixel. So rather than a for e of either a black or white color? No, it produces more or less a rectangle or a rectangular cube. So what are the types of computer tomography again? There are three conventional helical, which is basically the movements of the x-ray, of the X-ray or the detector and the country are linear and continuous multitude after which can give you a 3D image.
Advantages of the helical multi detector is basically to reduce the time 3D image and reduce the motion artifacts. Then there is a very common MCQ question, which is the home slow Hounsfield unit Hounsfield unit is basically if you can remember the attenuation from the X-ray. This is the attenuation coefficient and with water being 0.
So the lower the Hounsfield unit, the less likely you will appear on the X-ray or the CT scan, it will be black, the higher the Hounsfield unit, it it will be white. So what are the advantages of a CT scan? 3D imaging. Veterans of tissue better, of course, compared to the X-ray. And you can use contrast.
The disadvantages, it's a high radiation. And lower soft tissue than the MRI scan that will reach us to an MRI scan. What is the MRI scan? So the definition of first is basically that it is. A modality to create a high contrast image that's the main aim of having an MI scan to create high contrast image, which means that you have more details in your image than both the city and the X-ray.
It is superconducting magnets with the radiofrequency coil and aiming to manipulate the hydrogen ions. So if you say these three buzzwords you have, answer the question of the definition then. Now, imagine that each proton is spinning around its longitudinal axis, so it has an axis.
It's like you standing and actually spinning around one foot, but at the same time you are actually spinning, your axis is rotating. That's called precision. Then we have something called parallelism. We will know what is that meaning in the next image. This is so much important. So if you can see that here.
This is the longitudinal axis of the hydrogen ion or the proton, and this is its victim. And it's a spinning look at eudaly around this axis. If you can, if you can see that there is, this axis actually is rotating in that direction, if you can see my arrow here. This is the precision when you put this protons in a very high energy magnet.
All these all the atoms will basically be parallel because it's North and South will be parallel with the longitudinal axis of the magnet. But the precision everyone will actually will dance a different beat. So all of them will dance, will dance together. But on each proton will dance with a different beat because you can't control the precision when you hit it with the radial frequency.
So again, these are the Reds, the Reds axes or the axes of the spinning and the precision. You can see that each atom or each proton is in a different location in the precision circle. Or the precision roundabout, I call it, when you apply a radial frequency pulse, what happens, all of them become precise, but they lose their parallelism with the longitudinal axis of the MRI scan, so all of them now going together.
Precision wise. But all of them is spinning on their own an angle to the longitudinal axis of the MRI scan. Hopefully, this is a bit more clear than usual because this was a very important. This is a very important point in the MRI scan. Then when the radiofrequency is lifted. Two things happen. They lose, they come back into the longitudinal axis.
And they lose their synchronization of the precision, right? The loss of the synchronization of precision. Is the verdict is the vertical is the vertical relaxation point. But the. The loss of the actually the regaining of the parallelism with the long axis of the MRI scan of the magnet is the transverse relaxation type again.
T1 is the longitudinal relaxation time, which is basically the loss of the synchronization of precision. T2 is the transverse relaxation time, which is basically gaining of the parallelism with the long axis of the magnetic field. That's so much important, then a few more definitions. You have the time of repetition, TR and time of echo, which is basically between the time you hit the radial frequency and between the time you are receiving the waves back from the proto T1 weighted, which the thing that you can see until one is basically one.
So it's what one thing is right which and two things are white. That's how I remember them. So one, it's only fat white T2 is fat and water are white. OK, T1 weight it. You have a short repeat repetition time and short equal time. And this gives you anatomy. But the T2 weighted, it gives you pathology and it has long repetition and long time to occur.
The stare is a way to do fat suppression. You don't need to know more than that in the MRI scan for the steer sequence. So the advantages of having an MI scan is basically it's an excellent for soft tissue, no ionizing radiation. You're using a magnet in radiofrequency and you can use a contrast. It's called gadolinium, which is a magnetic a pro magnetic element.
You have the disadvantages of that. It's expensive, not readily available, and there is the claustrophobia. And of course, in the conventional MRI scan, we have the image artifact. Now we have metal subtraction MRI scans. The next is the ultrasound and the ultrasound. Again, you have to know that the sound frequency is above the audible sound and you have to know the transmission and the reflection.
So these sound waves are transmitted to the body and head. The body reflected back to the introducer or the transducer. Then they are. It is transformed to the monitor again. It's called composed of a transducer, which is the thing in your hand, a monitor and the computer and the waves are either hyper or quick. That means this thing is mostly solid.
It is actually. It's like a drum. It transfers back the sound waves or hypothermic. It is less reflecting. It reflects the sound waves less efficiently. The advantages of the ultrasound is basically there is no ionizing radiation. It's good for soft tissue because it gives you the dynamic bit and it's cheap.
The disadvantages, that it's operator dependent. You don't have a hard copy to actually to compare with previous images or to ask another, you know, another radiologist. There's no no archiving with it and it's pouring the bony anatomy. The next one is bones integrity. It's a form of nuclear medicine, which is basically it studies the distribution of a radiolabeled tracer by the means of detecting the gamma radiation that is emitted from this radiolabeled tracer.
The most common used is technechium 99m, which is combined with methylphosphate, and that's why it is a detects the function or the activity of osteoblasts and Indium 111. How it works, so you have a gamma camera. And this gamma camera detects three phases the flow phase, which is basically the arteriogram while the tracer is going to the bone.
The pool phase, which is 5 minutes and it is the how vascular it is and static phase, which is the three hours. This is bone activity. It has disadvantages and advantages. Its advantages are it's very sensitive. And it localizes, but the disadvantage is it's more radiation than any of the other modalities, it's deep and it's close.
Low and specificity gives you there is a lesion here, but you don't know what lesion it is. Can be inflammation, infection, tumor, anything. Fjords or positron emission tomography? It is formed of true, which is positron emission particles, and these particles are attached to a tracer and this bioactive component. So we have the radioactive isotope attached to our bioactive element, which is usually fludioxonil glucose.
And that's why it. See, what is the distribution of the glucose and the tissues that are hyperactive? Use more glucose. That's why how it detects how high is the biologically active by a biologically active tissue is. You have the DEXA scan, which is basically for osteoporosis, and it's a dual energy X-ray absorptiometry, which you're using two types of x-rays with two different energy.
And both of them, this are aimed at the specific region of the body. The difference between the scattering or the scattering of these X-ray beams is actually the amount of the bone mass density. So the bone mass density is calculated and you should know the WHO definition, which is basically less than 2.5. A standard deviation compared to the same to compare to a young adult of the same race and sex, that's the T score.
If it's the same race and sex, but with age in consideration, that's the z-score. And that is just for. OK, this is osteoporotic because it is pathological, not normal osteoporosis. So secondary types. Then you have the quantitative CTE, which is basically has the advantage of normal DEXA scan is that it differentiates between the cortical and the cancer cells osteoporosis and you have the quantitative ultrasound and basically it has no radiation.
This is the report. Usually it comes like that. And it has two elements a graph and figures. These are the most common parts that are detected. Lumbar spine. A hips and distal and are. There are positive false positives and false negatives with the osteoporosis. The DEXA scan like false, it can say that there is osteoporosis, so that's positive, but it's false.
If you have laminectomy example, there is no bone in. Or it can be or it can be false negative. Like there is no osteoporosis and there is osteoporosis. And then if you are between negative 1 negative five, that's a stupid idea. More than 2.5 standard deviation, that's osteoporosis, as you can see from the green, yellow and red.
So, so how many bones do you have in your skeleton? That's the question. Thank you very much. And now I believe with the MCQs. Yeah, thanks, Joe, Thanks for that great presentation. I like the fact that you learn things in threes, that's how I learnt it, because it's quite easy to remember. And so everyone, we're going to go for the MCQ questions next. So we're going to share the poll.
If you answer the questions as soon as you can, then we can move on and Joe will talk us through the answers to the questions. And then if you have any questions, we'll ask them after the MCQ poll. So if you don't mind if you don't mind Joe just taking us through the answers and some explanation, please. Yes so first question is, where does the scattering happen in x rays?
You remember in I will read the answers first. So as electrodes struggle between the cathode and the anode, that is actually 43% as X-ray struggled through the vacuum tube. Well, OK, this is 7% as X-ray travel in from source to body. That's 29% as X-rays struggle from body to receptor. That's 21% OK, so back to the deep scattering attenuation, the attenuation slide.
We have three types of X-rays that after hitting the body, it's either reflected back or absorbed. So that's high beam attenuation. There pass through that slow beam attenuation or scatter, so it can't happen between before hitting the body. That's the main point. It has to hit something, so it deviates from the normal path. A capturing is not the spread of the X-rays.
No, it is actually the deviation from a straight line. That's the main point. OK so I believe it's the fourth answer. The second one is during application of a radiofrequency pulse. Of course, this is an MRI scanner synchronization synchronized precision and gain parallel loss of precision gain less synchronized precision loss of [inaudible] [inaudible] precision loss per lives.
So when you apply the magnetic fields, all of them become part of it. All right. All of them become longitudinal axis, so all the axes become positive, negative or north-south, but the axis itself. There is no precision between them. This is rotating like this. This is rotating like this as well, but they are rotating in different frequencies.
So they can in different precision. OK, but when you apply the radiofrequency, you lose this parallel because they become. All of them become deviated, but they rotate. They have the same precision. So the answer will be synchronized precision and loss of parallelism to the longitudinal, to the longitudinal axis of the MRI. Then the third one in positron emission tomography, the tracer analyzes what is it?
The glucose metabolism, the phosphate metabolism, calcium metabolism, amino acid metabolism. If you remember from the talk, it is combined with fluid glucose, so it is the first answer, which is the glucose metabolism. Correct? thank you. I think 79 answered the last one correctly, so that's a good one.
At least one is good. So difficult, these are difficult topics and very good questions. Thank you very much. Thank you. Explain that really nicely. Great, I think, Nikki, you're here. All right.
Thanks, Joe. So I think David has got any questions. So one question I know it's a very popular particularly of MRI gadolinium type theory. How does that help in terms of contrast? MRI arthrogram? OK Yeah. So gadolinium is a pro magnetic element. OK, it's injected to differentiate.
So as an orthopedic surgeon, you don't really need to know how is it working, but you need to know why, because you are requesting plus or minus MRI scan plus or minus contrast. Yes so that's the main point. So the contrast actually differentiate between fluid and fibrosis, and most of the it is very popular.
In post discectomy, MRI scans to differentiate between is it a new disk prolapse or is it arthrofibrosis if it's fibrosis? You don't do anything because basically going there again and trying to do a surgery, it will not. It will cause more arthrofibrosis. But if it's a recurrent disk prolapse, that's when you go and remove the disk. So it's basically to differentiate between two white things, according to the affinity of it.
OK fine. It thank you. OK anything else? No, I think actually you answer all the questions in your favor in your presentation. I think that's it. Unless anyone else has any burning questions I'd like to ask, please put them forward in the chat.
The box, but I say I do remember the cabinet, him being a very popular question when it's been when they've asked about MRI scans in the viva. Yes, and usually it is with the recurrent recurrent disc or basically to differentiate between arthrofibrosis and disc prolapse imposts discrepancy, of course. OK, Thanks. Thanks, David and Joe.
As far as I can see, there's no more questions. So what we'll do is we will stop the recording. believe we have one candidate at the moment.
Segment:0 .
Good evening, everyone, and welcome to the Orthopaedic Academy webinar program, which is streaming in conjunction with OrthoTV today. My name is Nikki Evans and I'll be your host for this evening. I'm delighted to welcome Mr Joe Gouda as our speaker this evening and the rest of the orthopedic Academy faculty, Mr.
Fira Arnaout and Mr. Shwan Henari, Mr David Hughes, Mr Justin Leong and Mr Ashcroft from OrthoTV. The agenda for this evening will be a presentation by Mr Gouda on orthopedic imaging for the FRCS exam and will follow that with an MCQ poll of three questions. These are anonymous so we can fill them in as quickly as possible and then we'll go through the answers. We'll also have some time for invited questions.
If you put your questions into the chat box, then we will ask at the end and hopefully get them answered for you. This evening, we will also do a hot seat practice with feedback. Each viba session is 5 minutes long. We need three candidates who could make yourself known to David or Shwan, or for us. The idea of these is not to embarrass you.
We think it gives you the best practice for the exam, so everybody is welcome to volunteer. So just a reminder of our upcoming courses, there they are, the case based discussion course, which at the moment we're running to and the mock exam course, which we've run through the year and has always been very popular and gets booked out really quickly.
And that's how you can book them. You can look on our website there. Orthopaedic Academy co.uk and you can follow us on Twitter, YouTube and Facebook. And you can also message us to join our Orthopaedic Academy telegram group group. So without any further interruptions, I will hand you over to Mr Joe Gouda, who is our presenter for this evening.
Thank you, Joe. Oh, thank you very much for this introduction. Delighted so. I would share my screen. Good so today we are going to discuss about imaging for FRCS trauma and orthopedic exam. This is very much a very common ask the question in the FRCS especially, of course, in the basic science.
And it will give you some of the, Uh, some of the information for the other tables as well, like the adult pathology and of course, the trauma. First of all. We have to know the regulations behind asking for an X-ray. There is something called an IRMER or IRMER which is the ionizing radiation medical exposure regulations.
And this is particularly in the UK. It is commonly asked in the MCQ, and I believe as well it can be asked in the basic science, and this was done to protect the patient from ionizing radiation. Basically, not all the radiation, of course, because without ionizing radiation, we cannot diagnose, but from a non essential, non important ionizing radiation and it defined for duty holders.
The first one is the referrer, who is basically you, the orthopedic surgeon who actually requests the X-ray. And you have to in the X-ray form, you have to write why you want this imaging to be done. This is how you justify it. Then the practitioner, which is the radiographer, all the radiologist who is basically the one who says, yes, this type of X-ray can be justified and is needed for this to answer that question, then the operator, basically, it's the radiographer who will press the button and the employer who actually makes the framework for all these duty holders to work the employer.
If you want to do a quality improvement program, this is where you aim to the framework. Then what is the X-ray here, the x ray? You have to have a clear definition to x-rays. It is a high energy. Electromagnetic waves are usually study in threes, so three bullet points or three buzzwords to answer any question.
So X-rays or high energy, that's one word electromagnetic waves two words and it is wavelengths is shorter than the visible light. That's the third buzzword. If you say these three buzzwords, you have the definition on. There is again, three things we need to know in the X-ray the structure of the X-ray machine. The thermal something called the thermal ionic emission, which is the process by which the X-ray is formed and attenuation.
So first of all, the structure, as you can see, this is the X-ray to. On our right hand side, there is tungsten foam filament, which is heated. That's why it's called thermal ionic, so thermal. So it's heated to about 2,200 degrees Celsius to emit electrons from the trouble, from the negative cathode to the positive anode once it hits it.
OK all this in the vacuum tube, once it's hit the A it can hit it in one of three positions either the outer or the high or the higher level electrons, and that produces heat, the inner electrons and that produces about 20% of the X-rays and the nucleus, which is basically it. It produces about 80% of the X-ray radiation.
Remember, from high school electrons, traveling and radiation are more or less the same. There is an interaction between them. This is a basic physics. Think that you don't need to know for your FRCS exam? So then the attenuation when the x-rays are emitted from the X-ray machine, it hits a body and it depends about the amount of absorption of each element that.
So bones have a high attenuation. That means they attenuate or absorb a lot of X-ray X-ray radiation. This is in contrast to water or air that has low beam attenuation, so most of the X-rays will pass by. And then there is something called scattering, which is so much important. We will later in the presentation.
This is the vision of the X-rays after hitting something, hitting the object or hitting the thing that you are x-rays. Then we have three main types of X-rays conventional screen film radiography, which we stopped using it in the whole UK. Now digital radiography, we use it and fluoroscopy. So the conventional screen radiography again, three things. It's a film between two forceful intensify, intensifying the screen.
These this screen is basically to transform the non visible X-rays to light to visible light. So and then hitting the film to produce the image. Digital radiography is slightly different, although the same principle. It's either that direct radiography or computed radiography. The difference between them is that direct radiography is that the receptors are generates each receptor generate a pixel and the computer computed radiography is that you take everything on a cassette and you have to put it in a machine, which has a laser light that transforms the X-rays to two light rings.
And then you have, of course, the computer which processes the imaging and you have the PACs system. All of us uses Pac system now, which is pictured archiving and communication system. That's where all the images are stored. And you can easily see them, and they are meaning a means of communication between the radiology department and any other computer in the trust.
Advantages of the direct of the digital radiographer over the conventional one is basically it's economic, but on the long run, it's less exposure as you need less X-ray intensity and it's easier to retrieve, you have it forever. Although the first one gives you a hard copy, but this hard copy can be affected by sun and water. Then you have the fluoroscopy, which is the second.
Main question in the FRCS exam. You have the X-ray tube with the same generating the same everything, but you have an image intensifier and here you need an intensifier because the amount or the intensity of the X-ray used in fluoroscopy is way less than the X-ray used in the Department downstairs. So the intensifier has multiple levels from an input window to an input force for sheet, which transforms X-rays into light and then light electrons, which actually is transferred to your screen.
But the aim of this is basically the single X-ray beam will be accentuated by thousands of times. That's why you can use it. OK, you take like 10, 20, 30 images in theaters compared to a single image in the outpatient clinic. And still, you're in the safe in the safe zone. That's because of the brilliance of presence of the intensifier.
Then fluoroscopy, it has to be there is a very important guideline, which is the ALARA. ALARA is basically as low as reasonably achievable, and that is again three buzz words time distance shield. So less time of exposure, no longer distance from the machine and the thicker the shields, then we have the advantages of the X-rays in general.
They're good for diagnosis. They're ready. They're cheap, but they are. They have disadvantages. Are radiation ionizing radiation exposure and it is. It misses. the subtle pathology, especially soft tissue. And it's to the. Then there is a modification to the X-ray to become a computer tomography or the CT scan.
To see this scan depends on the presence of the donut, which is the country again formed of the country is formed of three. At three parts, the coordinated and coordinated means presence of multiple lenses to actually focus the radiation on the source or on the image that is aimed towards X-ray source fan shaped that gives you a fan shaped X-ray beam to hit a limited detector.
To create an image, you have to have the source and the detector combination. That means they have to be perfectly aligned together because they are rotating in the country and that's how they produce the image in the cityscape. So basically, the X-ray and the X-ray tube and the X-ray detector actually are against each other and they have to be precisely aligned after having the image or on with the X-ray beam, they rotate a full rotation and then the whole country, or basically the bed of the patient's bed move moves when it moves another circle or another cut is taken.
That's how its linear movement of the country. This produces something called a Voxel, not a pixel. So rather than a for e of either a black or white color? No, it produces more or less a rectangle or a rectangular cube. So what are the types of computer tomography again? There are three conventional helical, which is basically the movements of the x-ray, of the X-ray or the detector and the country are linear and continuous multitude after which can give you a 3D image.
Advantages of the helical multi detector is basically to reduce the time 3D image and reduce the motion artifacts. Then there is a very common MCQ question, which is the home slow Hounsfield unit Hounsfield unit is basically if you can remember the attenuation from the X-ray. This is the attenuation coefficient and with water being 0.
So the lower the Hounsfield unit, the less likely you will appear on the X-ray or the CT scan, it will be black, the higher the Hounsfield unit, it it will be white. So what are the advantages of a CT scan? 3D imaging. Veterans of tissue better, of course, compared to the X-ray. And you can use contrast.
The disadvantages, it's a high radiation. And lower soft tissue than the MRI scan that will reach us to an MRI scan. What is the MRI scan? So the definition of first is basically that it is. A modality to create a high contrast image that's the main aim of having an MI scan to create high contrast image, which means that you have more details in your image than both the city and the X-ray.
It is superconducting magnets with the radiofrequency coil and aiming to manipulate the hydrogen ions. So if you say these three buzzwords you have, answer the question of the definition then. Now, imagine that each proton is spinning around its longitudinal axis, so it has an axis.
It's like you standing and actually spinning around one foot, but at the same time you are actually spinning, your axis is rotating. That's called precision. Then we have something called parallelism. We will know what is that meaning in the next image. This is so much important. So if you can see that here.
This is the longitudinal axis of the hydrogen ion or the proton, and this is its victim. And it's a spinning look at eudaly around this axis. If you can, if you can see that there is, this axis actually is rotating in that direction, if you can see my arrow here. This is the precision when you put this protons in a very high energy magnet.
All these all the atoms will basically be parallel because it's North and South will be parallel with the longitudinal axis of the magnet. But the precision everyone will actually will dance a different beat. So all of them will dance, will dance together. But on each proton will dance with a different beat because you can't control the precision when you hit it with the radial frequency.
So again, these are the Reds, the Reds axes or the axes of the spinning and the precision. You can see that each atom or each proton is in a different location in the precision circle. Or the precision roundabout, I call it, when you apply a radial frequency pulse, what happens, all of them become precise, but they lose their parallelism with the longitudinal axis of the MRI scan, so all of them now going together.
Precision wise. But all of them is spinning on their own an angle to the longitudinal axis of the MRI scan. Hopefully, this is a bit more clear than usual because this was a very important. This is a very important point in the MRI scan. Then when the radiofrequency is lifted. Two things happen. They lose, they come back into the longitudinal axis.
And they lose their synchronization of the precision, right? The loss of the synchronization of precision. Is the verdict is the vertical is the vertical relaxation point. But the. The loss of the actually the regaining of the parallelism with the long axis of the MRI scan of the magnet is the transverse relaxation type again.
T1 is the longitudinal relaxation time, which is basically the loss of the synchronization of precision. T2 is the transverse relaxation time, which is basically gaining of the parallelism with the long axis of the magnetic field. That's so much important, then a few more definitions. You have the time of repetition, TR and time of echo, which is basically between the time you hit the radial frequency and between the time you are receiving the waves back from the proto T1 weighted, which the thing that you can see until one is basically one.
So it's what one thing is right which and two things are white. That's how I remember them. So one, it's only fat white T2 is fat and water are white. OK, T1 weight it. You have a short repeat repetition time and short equal time. And this gives you anatomy. But the T2 weighted, it gives you pathology and it has long repetition and long time to occur.
The stare is a way to do fat suppression. You don't need to know more than that in the MRI scan for the steer sequence. So the advantages of having an MI scan is basically it's an excellent for soft tissue, no ionizing radiation. You're using a magnet in radiofrequency and you can use a contrast. It's called gadolinium, which is a magnetic a pro magnetic element.
You have the disadvantages of that. It's expensive, not readily available, and there is the claustrophobia. And of course, in the conventional MRI scan, we have the image artifact. Now we have metal subtraction MRI scans. The next is the ultrasound and the ultrasound. Again, you have to know that the sound frequency is above the audible sound and you have to know the transmission and the reflection.
So these sound waves are transmitted to the body and head. The body reflected back to the introducer or the transducer. Then they are. It is transformed to the monitor again. It's called composed of a transducer, which is the thing in your hand, a monitor and the computer and the waves are either hyper or quick. That means this thing is mostly solid.
It is actually. It's like a drum. It transfers back the sound waves or hypothermic. It is less reflecting. It reflects the sound waves less efficiently. The advantages of the ultrasound is basically there is no ionizing radiation. It's good for soft tissue because it gives you the dynamic bit and it's cheap.
The disadvantages, that it's operator dependent. You don't have a hard copy to actually to compare with previous images or to ask another, you know, another radiologist. There's no no archiving with it and it's pouring the bony anatomy. The next one is bones integrity. It's a form of nuclear medicine, which is basically it studies the distribution of a radiolabeled tracer by the means of detecting the gamma radiation that is emitted from this radiolabeled tracer.
The most common used is technechium 99m, which is combined with methylphosphate, and that's why it is a detects the function or the activity of osteoblasts and Indium 111. How it works, so you have a gamma camera. And this gamma camera detects three phases the flow phase, which is basically the arteriogram while the tracer is going to the bone.
The pool phase, which is 5 minutes and it is the how vascular it is and static phase, which is the three hours. This is bone activity. It has disadvantages and advantages. Its advantages are it's very sensitive. And it localizes, but the disadvantage is it's more radiation than any of the other modalities, it's deep and it's close.
Low and specificity gives you there is a lesion here, but you don't know what lesion it is. Can be inflammation, infection, tumor, anything. Fjords or positron emission tomography? It is formed of true, which is positron emission particles, and these particles are attached to a tracer and this bioactive component. So we have the radioactive isotope attached to our bioactive element, which is usually fludioxonil glucose.
And that's why it. See, what is the distribution of the glucose and the tissues that are hyperactive? Use more glucose. That's why how it detects how high is the biologically active by a biologically active tissue is. You have the DEXA scan, which is basically for osteoporosis, and it's a dual energy X-ray absorptiometry, which you're using two types of x-rays with two different energy.
And both of them, this are aimed at the specific region of the body. The difference between the scattering or the scattering of these X-ray beams is actually the amount of the bone mass density. So the bone mass density is calculated and you should know the WHO definition, which is basically less than 2.5. A standard deviation compared to the same to compare to a young adult of the same race and sex, that's the T score.
If it's the same race and sex, but with age in consideration, that's the z-score. And that is just for. OK, this is osteoporotic because it is pathological, not normal osteoporosis. So secondary types. Then you have the quantitative CTE, which is basically has the advantage of normal DEXA scan is that it differentiates between the cortical and the cancer cells osteoporosis and you have the quantitative ultrasound and basically it has no radiation.
This is the report. Usually it comes like that. And it has two elements a graph and figures. These are the most common parts that are detected. Lumbar spine. A hips and distal and are. There are positive false positives and false negatives with the osteoporosis. The DEXA scan like false, it can say that there is osteoporosis, so that's positive, but it's false.
If you have laminectomy example, there is no bone in. Or it can be or it can be false negative. Like there is no osteoporosis and there is osteoporosis. And then if you are between negative 1 negative five, that's a stupid idea. More than 2.5 standard deviation, that's osteoporosis, as you can see from the green, yellow and red.
So, so how many bones do you have in your skeleton? That's the question. Thank you very much. And now I believe with the MCQs. Yeah, thanks, Joe, Thanks for that great presentation. I like the fact that you learn things in threes, that's how I learnt it, because it's quite easy to remember. And so everyone, we're going to go for the MCQ questions next. So we're going to share the poll.
If you answer the questions as soon as you can, then we can move on and Joe will talk us through the answers to the questions. And then if you have any questions, we'll ask them after the MCQ poll. So if you don't mind if you don't mind Joe just taking us through the answers and some explanation, please. Yes so first question is, where does the scattering happen in x rays?
You remember in I will read the answers first. So as electrodes struggle between the cathode and the anode, that is actually 43% as X-ray struggled through the vacuum tube. Well, OK, this is 7% as X-ray travel in from source to body. That's 29% as X-rays struggle from body to receptor. That's 21% OK, so back to the deep scattering attenuation, the attenuation slide.
We have three types of X-rays that after hitting the body, it's either reflected back or absorbed. So that's high beam attenuation. There pass through that slow beam attenuation or scatter, so it can't happen between before hitting the body. That's the main point. It has to hit something, so it deviates from the normal path. A capturing is not the spread of the X-rays.
No, it is actually the deviation from a straight line. That's the main point. OK so I believe it's the fourth answer. The second one is during application of a radiofrequency pulse. Of course, this is an MRI scanner synchronization synchronized precision and gain parallel loss of precision gain less synchronized precision loss of [inaudible] [inaudible] precision loss per lives.
So when you apply the magnetic fields, all of them become part of it. All right. All of them become longitudinal axis, so all the axes become positive, negative or north-south, but the axis itself. There is no precision between them. This is rotating like this. This is rotating like this as well, but they are rotating in different frequencies.
So they can in different precision. OK, but when you apply the radiofrequency, you lose this parallel because they become. All of them become deviated, but they rotate. They have the same precision. So the answer will be synchronized precision and loss of parallelism to the longitudinal, to the longitudinal axis of the MRI. Then the third one in positron emission tomography, the tracer analyzes what is it?
The glucose metabolism, the phosphate metabolism, calcium metabolism, amino acid metabolism. If you remember from the talk, it is combined with fluid glucose, so it is the first answer, which is the glucose metabolism. Correct? thank you. I think 79 answered the last one correctly, so that's a good one.
At least one is good. So difficult, these are difficult topics and very good questions. Thank you very much. Thank you. Explain that really nicely. Great, I think, Nikki, you're here. All right.
Thanks, Joe. So I think David has got any questions. So one question I know it's a very popular particularly of MRI gadolinium type theory. How does that help in terms of contrast? MRI arthrogram? OK Yeah. So gadolinium is a pro magnetic element. OK, it's injected to differentiate.
So as an orthopedic surgeon, you don't really need to know how is it working, but you need to know why, because you are requesting plus or minus MRI scan plus or minus contrast. Yes so that's the main point. So the contrast actually differentiate between fluid and fibrosis, and most of the it is very popular.
In post discectomy, MRI scans to differentiate between is it a new disk prolapse or is it arthrofibrosis if it's fibrosis? You don't do anything because basically going there again and trying to do a surgery, it will not. It will cause more arthrofibrosis. But if it's a recurrent disk prolapse, that's when you go and remove the disk. So it's basically to differentiate between two white things, according to the affinity of it.
OK fine. It thank you. OK anything else? No, I think actually you answer all the questions in your favor in your presentation. I think that's it. Unless anyone else has any burning questions I'd like to ask, please put them forward in the chat.
The box, but I say I do remember the cabinet, him being a very popular question when it's been when they've asked about MRI scans in the viva. Yes, and usually it is with the recurrent recurrent disc or basically to differentiate between arthrofibrosis and disc prolapse imposts discrepancy, of course. OK, Thanks. Thanks, David and Joe.
As far as I can see, there's no more questions. So what we'll do is we will stop the recording. believe we have one candidate at the moment.
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