Dr Richard Slaughter - ADSS Symposium 17 October 2018

Thank you very much. In 2011, when I stopped work at Prince Charles, I thought life was going to be easy, but this man made sure it wasn't. As he said, I'm a radiologist and my talk is going to be very different from Ralph's, because I'm going to talk about imaging and its role in asbestos-related diseases. You all know that asbestos-related diseases are basically caused by the inhalation of asbestos fibers. This little thing is actually very small, especially the US5 is smaller, and you can see red cells there. So these things are quite small, and they're inhaled into the lungs, travel out into the airways, into the periphery of the lungs, where they're toxic and cause damage and scarring, resulting in disease that damages the lungs. The interesting thing is that the disease also occurs outside the lungs, in the lining of the lungs. How it gets there, we're not quite sure, because there's a gap between the lung and the pleura on the inside of the chest wall, but somehow the asbestos bodies get across the lymphatics or go through the pleural space, irritate the pleura, and give rise to disease there. So what I'd like to do is to talk a little bit about the methods that as a radiologist we use to make these diagnoses, and then the manifestations of these diseases that we can see radiologically. The manifestations are predominantly benign processes. A lot of people feel that if they have a disease due to asbestos exposure, it might be fatal or universally terrible. Not the case at all. Most people live very good and useful lives and can live very long lives after being diagnosed with asbestos-related conditions. Unfortunately, there are some very nasty ones as well, but in most cases, the process is fairly slowly progressive, and people do very well. The benign pleural disease consists of several different things: pleural plaques, which I'll show you later, which can be calcified or non-calcified; pleural effusions, which is fluid in the pleural space; and diffuse pleural thickening, which is an interesting and significant process. Benign lung disease within the lung itself consists of pleura parenchymal bands, which are very common, and a condition called rounded atelectasis, which is part of what's sometimes called trapped lung, representing large areas of fibrosis. And the condition that most people are concerned about is asbestosis. The malignant conditions are mesothelioma, which is primary carcinoma of the pleura, and lung carcinoma, which is primary carcinoma of the lung. These conditions take a while to develop in most patients. You all know that there are quite a lot of lag times, and this is a representation of that: it doesn't manifest straight away, and it might be 20 years later that this disease manifests itself. So we always have to remember that when we're looking at things now. First of all, I'd like to talk about the basic techniques, because I don't know how much people understand about the role of the chest radiograph and CT scans. The chest radiograph is the basic examination that we use to detect asbestos-related disease. It's been around a long time and it's very helpful. In this condition, the patient stands in front of the detector system, the x-ray tube is over here, the x-ray beam goes from the tube through the patient and is picked up on detectors. When I was in radiology most of my life, we used x-ray film to record images. Now times have moved on, and they're digital images detected on digital detectors. But the x-ray beam passes through the patient, and as it goes through, it's blocked by various things. If things are high atomic number or very dense, they block the x-rays, so coming out of the side of the patient, there's a modified x-ray beam that reflects the pathology. We turn that into an x-ray image using film or digital techniques. This is what a normal chest x-ray looks like. On the left-hand side is the posterior-anterior chest x-ray, and on the right side is the lateral view. As you can see, the white thing in the middle is the heart, which absorbs a lot of x-rays. Behind it is the spine, which is calcified and absorbs more. The ribs are white, they absorb x-rays, and in between, the dark areas are the lungs. Inside the lung, you can see little vessels. The problem with this chest radiograph is that the x-ray beam has to go from the back to the front, through a lot of different things, so the density represents all those things. It's a composite density. So we do a lateral view, and the two together help us understand things. But there are areas in the chest x-ray that you can't see very well. If you look down at that film, behind the diaphragm, we don't see it. There are areas against the spine that are very hard to see on the PA film. So although it's a very useful examination, it has limitations. This is basically just the anatomy: the lungs on both sides, the ribs, the mediastinum in the center, and the spine. What's interesting is that the lungs are in the thorax, and on the outside of the lungs, there's a thin line of visceral pleura that coats the surface of the lung. I always think of it like cling wrap stuck on the surface. Then there's a cavity, a very small cavity, and a similar lining of pleura on the inside surface of the chest wall. The chest wall has ribs, muscles, and fascia, and there's another layer. In between them, there's a thin pleural space that normally has about 15 milliliters of fluid, which acts as a lubricant so that when you breathe, the lungs can slide over the chest wall. This is where fluid accumulates. Pleural plaques form on the outside layer of the pleura, the parietal pleura, not on the lung surface. The lung is divided into lobes with fissures, and the visceral pleura goes into those fissures, whereas the parietal pleura just coats the inside of the chest wall. The other technique that has become more important in recent years is CT scanning. This is a totally different technique. In a CT scan, the patient goes into a machine, a tunnel, with an x-ray tube on one side and a large set of detectors on the other. The x-ray beams go through the patient, and the whole gantry, the x-ray tube and detectors, rotates around the patient while the patient moves through the machine. These machines can scan a whole chest very quickly, in a couple of seconds, so we get a big volume of data, and the images are mathematically reconstructed. We get an image that looks like a cross-section, very different from a chest radiograph. It has a thickness of one millimeter to ten millimeters, so it's a very different type of presentation, with the lungs on the outside, the pleura running around the edge, the heart in the middle, and the arteries and veins running out into the lungs. The pleura around the chest are those two colored lines with a thin layer in between; this is where fluid accumulates. This is a normal CT scan of the chest. The first thing you notice is that you can't see everything on a single image because there's such a broad range of densities. We have to look at it under different circumstances to see things. The one on the left is presented to look at the soft tissues; you can see the greyness of the muscle in the chest, the lungs are completely black, and inside the lungs, there are some vessels showing. This patient has had x-ray dye, which makes the aorta stand out, but the lungs are all black and we can't really see anything going on in the lungs apart from a few vessels. But when we window it so that we can see the lungs, we make the rest of it white, and now we can see the detail in the lungs. What we are seeing: the vessels are the pulmonary arteries and veins, which take deoxygenated blood to the lungs and bring oxygenated blood back, and the airways. You can't see many airways; you can see the central ones, but the peripheral ones are small and hard to see because they're filled with air and have thin walls. What I'd like you to notice is that if you look at the periphery of the lung, it's very sharp and clean. The vessels are very small because they start here and go out that way, then back, so the small ones are in the periphery. We don't see much in the peripheral five millimeters of lung; it's normally clear. We like to do special types of CT scans for asbestos-related diseases, one of them is high-resolution scanning. High-resolution scanning doesn't necessarily mean it's better than non-high-resolution scanning; it means it's more appropriate for looking at fine lung details. The one on the right is a thick slice, and you can see how fuzzy the disease down here is. If you look at the fissures in the lungs, this is the visceral pleura, you can see it beautifully there, but here it's quite fuzzy. But we get an effect of linearity here, so vessels look longer, making it easier to detect small nodules as they stand out more from the vessels. For most asbestos work, we like high-resolution work, and we like to do it in deep inspiration, with a good inspiratory effort. The reason is that if you breathe out, the air exits the lungs, the lungs collapse and become denser, so you can artificially see stuff on the expiration scan that looks like disease. You think you've got something nasty, but when you take a nice breath, it goes away. So it's very important we get good inspiratory films. Now, to go on to the various conditions I mentioned, we'll start with pleural plaques. Pleural plaques are fibrous areas of thickening that occur on the pleura on the chest wall, not on the lung, very rarely on the lung itself. You can see them on a chest radiograph as whiter areas, because they absorb more radiation, a little denser than the lungs. Often you see one side clearly and the other side fades into the chest wall. They can be difficult to see, especially against the spine because we can't see that well. If we take a CT scan, it's very easy to see the plaques; they stick out and are easy to see because of the way the image is taken. These are plaques that are calcified; you can see the white stuff here in front of the rib. That white line is a calcified pleural plaque. Plaques calcify with time. Pleural plaques are benign; they usually don't cause problems and are regarded more as a marker of asbestos exposure than a measure of it. You can get pleural plaques with very small exposure. You'd be surprised at the number of people in the community who have a few pleural plaques who don't even remember how they got them, and many live with them without knowing. But they can get very thick; this plaque is over a centimeter thick and heavily calcified. They can be big, chunky things that cover a lot of the chest wall, and when they do, we wonder how much they might impair lung function. The other important thing we see in asbestos exposure is pleural fluid. Sometimes fluid accumulates in that pleural space, and in asbestos-related conditions, we often get an inflammatory effusion. It's blood-stained, a little thicker, full of cells, and people can get pain and fever with it, just like an infection. Pleural fluid from something like heart failure is thin, almost like water or beer, and doesn't cause the same problems. This pleural fluid can cause significant problems. On a chest radiograph, the fluid goes to the bottom because the patient is standing up. On a CT scan, it goes to the back. Here is pleural fluid running around the inside of the chest, with some calcified plaque in the same place. The fluid tracks around in that pleural space, which has negative pressure. Pleural fluid from dust exposure can resolve or can go on to form diffuse pleural thickening because it's an inflammatory process that thickens the pleura, and the two layers get stuck together like glue. Suddenly you have thick pleura, not just plaques; it involves both visceral and parietal pleura stuck together. So when you breathe in, the lung can't slide over the chest wall, and the lung can't expand and contract under the visceral pleural thickening. These changes are not usually regarded as asbestos but can cause significant respiratory impairment. On a chest x-ray, it's difficult; you can see the angles are not sharp as in a normal one, and there's thickening. But with a CT scan, you can see tracking around the lung, a layer of thick pleura, a little denser, which can be very extensive. I've seen patients where it covers the surface of both lungs. This thick pleura stops the lungs expanding and causes changes. What we call pleura parenchymal bands: this big thick thing is a fibrous band extending into the lung from thick pleura. These are smaller ones running parallel, some run inwards. What happens is the visceral pleura on the surface of the lung gets involved with fibrosis, and the fibrosis extends in along the septa between the lobes. The lung gets stiff, can't expand, thickens, and becomes fibrotic. It can be very bad. This is a really bad case: calcified plaque, diffuse pleural thickening about 8 millimeters thick, big bands extending into the lower lobes, the fissure is depressed, and the lower lobes are severely diseased by these bands and rounded atelectasis. Rounded atelectasis is another process; it's a large lump against the pleura with strands running into it. In a soft-tissue window, it looks like a lump that could be a cancer. This patient has pleural thickening, fluid, and a large area of rounded atelectasis with comet tails going into the lung. They contract because they're fibrotic, and I've seen lower lobes virtually nonexistent, completely contracted and not functioning. Rounded atelectasis is benign, can remain very stable for years, can look like cancer, and causes lung contraction in association with diffuse pleural thickening. The other benign lung process is asbestosis. I'll spend a bit more time on this because it's what most people worry about. Asbestosis in general is a relatively benign process; most people I see with it live good, healthy lives and can have a normal life expectancy. But it can progress and kill them, though usually very slowly. The asbestos fibers go to the periphery of the lung, get stuck in the respiratory bronchioles, set up a toxic reaction, the body coats them with iron, but they cause fibrosis that extends into the adjacent lung. The process occurs in the periphery. These films are taken upside down to help us see the lung base better, as the process is most common in the lung bases posteriorly. You can see in the periphery small dots, little lines, and reticular patterns. This is established but relatively mild asbestosis. This is not questionable asbestosis; it's asbestos, and it only involves the periphery of the lung. In another case, we have linear bands parallel to the surface, and ground glass densities, a descriptive term meaning you can see through them. It often represents fibrosis but can represent other things. We see lines, some of which are vessels we wouldn't normally see this far out, because the periphery is starting to collapse and suck them in against the chest wall. This is a plaque, and this process is asbestosis. Sometimes the changes form linear, curved shapes parallel to the surface. This is said to be relatively specific for asbestosis, but like everything in chest radiology, it's not specific. Most things in the lungs are not entirely specific. I'd like to stress that radiology taken in isolation is not the same as radiology taken in conjunction with a good clinical story. Some changes we see are not specific for asbestosis; they can occur in idiopathic pulmonary fibrosis, connective tissue diseases, and drug-induced changes. So we have to correlate with the clinical story, but these lines occur more in asbestosis than any other interstitial lung condition I know. This is a coronal view with thickened lines, thickening lobular septa, very much like the lines with diffuse pleural thickening, but they occur in the absence of that. In diffuse pleural thickening, they occur from fibrosis of the pleura extending inward along septa. These occur from inside the lung out: the fibers in the periphery cause a reaction around the airways and lobules, causing these lines as part of asbestosis. We do the films upside down, prone, because lying on your back can cause changes that look like interstitial lung disease. The posterior lung doesn't move much, blood vessels have a head of pressure, and there's lack of movement, causing some collapse and changes that mimic disease. When we roll the patient onto their stomach, the changes go away. So if there's any question of disease, we always want a prone examination. Sometimes it's difficult if people are short of breath, but it's worth persisting. The radiation dose is very small: a CT scan with prone films might be two to three times your natural radiation from living in Brisbane for a year, so about three years' worth. We can do a scan with about one year's worth, but because we're looking for very fine structures, we need good scans. This is a patient with more advanced disease, with fibrosis and honeycomb cyst formation. When fibrosis gets severe, it destroys the architecture and looks like honeycomb. This is relatively advanced asbestosis, with bands, honeycombing, and traction bronchiectasis, where fibrosis contracts and pulls airways apart. Now, to finish briefly, malignant conditions: mesothelioma is a cancer of the pleura, usually occurring various stages after exposure, presenting with weight loss or pain. The chest radiograph usually shows a pleural effusion. On CT, you see thickened areas of pleura, big thick nodules, and the lower chest filled with tumor encasing the lung. This is typical advanced mesothelioma, starting in the parietal pleura. Lung cancer starts in the lung itself. That's all I have time for. Thank you very much. I'm happy to answer questions.

I think there's no evidence to suggest that's the case. Pleural plaques tend to steadily progress, particularly with calcification, but very slowly. Once we first see them, they don't usually get much bigger over time. They're a remarkably benign process, and I don't know of anything that modifies or changes their progression.

Well, first, just to say about monitoring disease in the chest: with plaques, there's no great need to monitor them because they don't lead to mesothelioma. Mesothelioma develops de novo, often in association with plaques, though 50% of patients with mesothelioma don't have plaques. I assume you're speaking about mesothelioma which affects the linings. It can affect the peritoneal lining in the abdomen in two ways: it can invade from the chest through the diaphragm, or start off separately in the abdomen. It's more difficult to see in the abdomen or assess its extent because the peritoneal cavity is very complex, unlike the chest. The only way would be with CT scanning, but it's not as accurate as in the chest. Radiation doses in CT scanning are pretty low today, and if you're monitoring something life-threatening, there's no real issue. PET scanning is used, but mesothelioma only takes up FDG moderately, and you wouldn't want to do PET scans regularly due to higher radiation dose. CT would be the only real option.

That's a very large issue, but I'll give you my perspective briefly. I think there was a thought that black lung had disappeared. In Queensland, there was a monitoring process using chest radiographs and lung function testing. Unfortunately, because no cases had been seen for a long time, it was neglected and not done well. Cases weren't stored properly or always looked at by appropriate people, and some doctors in the industry had never seen a case. Things got slack. There's no doubt there's been an error. A new process is in place now that should be much better. I think the problem is not as bad as the press sometimes makes out. The last time I saw, there were only about 20 patients in Queensland diagnosed with black lung, and most had mild disease. It takes about 20 years of underground mining. Mining has changed; they never had longwall mining years ago. When the early program was set up, people were exposed to a lot more dust. Today, there's an attempt to keep levels low, but it's difficult wearing that apparatus in a hot underground mine. I think any preventable disease should be prevented. It's a tragedy that anyone has silicosis or coal workers' pneumoconiosis because it's preventable. The trouble with asbestosis is it took a long time to realize. With black lung, we took our foot off the pedal, got lazy, and the mining industry changed with more dust, and people just forgot about it. Today, we use chest radiographs for screening because this disease occurs in remote places like mining towns where CT scanners and qualified radiologists are not available. We believe it's appropriate to use x-ray as a screening test, reporting it using the ILO classification, an epidemiologic classification. We weren't doing that very satisfactorily in Australia. The problem is not with the people in Australia; they're just as qualified as in the United States. In fact, the US has greater problems because they don't have a compulsory screening process; it's voluntary, and many miners with disease don't want it known because it pulls them from underground work and they lose bonuses. Here, there is a compulsory process, and disease can be picked up early. If something is picked up on chest radiograph, more than 1/0 on the ILO classification, that's very early disease. A CT scan is highly accurate, but the chest radiograph at that level has many false positives and some false negatives. As it gets more, it gets more accurate. The new process should be pretty good. With much more awareness, mine dust levels will be legislated lower, and there'll be more interest. Some people have severe disease, but most of the patients I've seen, maybe 25, have had relatively mild disease.

I don't think you have to monitor pleural plaques closely at all. As I said, pleural plaques themselves don't progress to cancer. They're benign and stay benign. But people with pleural plaques have a higher chance of getting mesothelioma because plaques show significant past exposure. Monitoring with regular x-ray or CT scans to detect mesothelioma has not been helpful. Finding mesothelioma in an asymptomatic patient is rare. So I wouldn't want to monitor pleural plaques. Maybe every two years at the closest, or even longer, because it's not really going to help much. You don't really need a CT scan; if you have any symptoms or problems, that's when you have a scan.

Well, if you get mesothelioma, and hopefully you don't, you will get symptoms. If you do a CT scan now, your chances of detecting very early mesothelioma are remote. It's not like breast screening where you see a tiny little thing. Most cases of mesothelioma present with pleural fluid, which causes symptoms, so patients immediately get symptoms. Sometimes we can't even find the tumor; it's so small. So doing regular screenings like breast screening doesn't work that way. I think you can relax a little bit. It depends on your exposure. If it's high exposure, you're at greater risk, but if you have any symptoms, you certainly need to see someone and get imaged.

Yes, it affects the pleura and the lungs, and it affects the membrane in the abdomen, the peritoneal membrane, because that's very similar to the pleura. You can get mesothelioma starting in the abdomen all by itself, though most cases I've seen are chest mesothelioma that went through the diaphragm. It can start in the lining of the abdominal cavity. It doesn't affect other organs like kidneys or liver except as a secondary response. It's a cancer and will metastasize, but you won't start off getting a mesothelioma in your kidney.