Hello everyone. I would like to start by thanking ASNIC for this opportunity to discuss incidental findings to know in nuclear cardiology. My name is Prashant Nagpal and I'm a radiologist and I'm also the section chief of cardiovascular imaging at University of Wisconsin-Madison. To start, here are my disclosures. I have served as a consultant for GE healthcare for cardiac MRA imaging. I have no other disclosures. The first question that always comes to my mind is what is an incidental finding? An incidental finding is an incidentally discovered mass or a lesion detected by an examination performed for an unrelated reason. So basically a finding of myocardial ischemia is not an incidental finding on a myocardial perfusion imaging, whereas a lung nodule or a lung mass is an incidental finding. For cardiac spectral PET scans, incidental findings are primarily seen in lungs, mediastinum, bones, and upper abdomen. And we will be discussing these findings in this talk. Before we go further, one of the questions is why are these incidental findings important? There has been some research done on this topic and these are a few of the important papers on the same topic. To summarize a few things from this paper, incidental findings can be seen in as high as 60% of the cases that we report in nuclear cardiology. However, only 0.5 to 1% of these have a potentially altering diagnosis or we find a new cancer or a treatable malignancy. Now the review of these incidental findings is dictated by good patient care as well as medical legal liability. The way this imaging should be reviewed is that we should always review them in soft tissue window, lung window, as well as in bone window. And we'll come to that a little bit later as well. Also, as the availability of hybrid imaging systems and new PET 3D pharmaceuticals is growing, there is an increased scrutiny of reporting of incidental extracardiac findings and now they are the integral part of the overall comprehensive reporting. In many cases, incidental findings can also be the cause of chest pain. So for example, some non-cardiac causes that can explain patient's chest pain are hiatal hernia from recurrent reflux-related disease or rib fractures after trivial injury. Most new PET systems are now hybrid systems and they have 40-slice scanners or more. So even though the true incidence of incidental findings may not be increasing, the resolution of attenuation correction images and hence the detection of these incidental findings is certainly on the rise. I'll be referring to this guideline document a few times in this talk. This is the 2022 ASNIC AAPM SCCT and SNNMI combined guideline for use of CT in hybrid nuclear or CT cardiac imaging. And a few things to highlight from this document is whether to report extracardiac findings depend on the overall certainty of the diagnosis which is based on the image quality. Image quality of these attenuation correction images is certainly different than our routine diagnostic imaging. The reason these are different is because of difference in scanner features, some scan parameters, some patient factors, and CT reconstruction algorithms. You can always modulate and modify these CT settings and this guideline document has this table which summarizes what each factor or CT setting can have effect on the image quality and how it would change the image quality. I would suggest going through this table and understanding how tube potential, tube current, gantry rotation time, pitch, and scanning FOV can affect the image quality. So since this is a very diverse area to learn, the question is what can we focus on learning. This guideline document also summarizes a few things that we should aim not to miss on attenuation correction images and my goal would be to show you some imaging and also highlight when you see such findings what to do as a next step. One basic rule of looking at these attenuation correction or CT images is to always look for findings in appropriate windows. So for example, here is one case which shows the soft tissue window which is frequently the default window for all our imaging systems and on this window I'm looking for mediastinum, some chest wall findings, and upper abdominal findings. Now if you look at the same image, you have no details on the lung parenchyma. If you just move it to lung window, you will see that on the same image there is a large pneumothorax which you would have missed if you would have seen only on the soft tissue window. Also another window to be aware of is the bone window and as you can see in this image that if you would have seen just on the lung window which is here, you get no details of the bone whereas if you would have seen on bone window, you would see that this patient had multiple lytic and sclerotic lesions which is in keeping with patient's known metastases. Here we will move on to some incidental findings that we want you to be aware of and be able to recognize. This is a 69 year old male who presented with history of prior MI and was having reckoning chest pain. So here is the attenuation correction images on this patient and as you can see in the heart, you see some fatty metaplasia as well as some calcifications along the heart in the left anterior descending territory distribution. This is just an image highlighting these findings. The arrows point to the presence of fat in the myocardium also called as fatty metaplasia. So this is an incidental finding of seeing old left anterior descending territory infarct with myocardial calcification and fatty metaplasia, fairly frequently seen in our nuclear imaging. Usually these things are known and typically there is an echocardiogram performed. The way I handle these findings is that I would acknowledge them in the report but sometimes when there is calcification, I am a little careful about these because calcification also happen in layered thrombi. So if there is no echocardiogram, I tend to suggest an echocardiogram for better evaluation especially when there is associated calcification. Here is another example of a 58 year old female with dyspnea on exertion and if you see these attenuation correction images, that in this one, as you look at the apical segments, they are a little asymmetrically ballooned out and then there is calcification in the apex. So interestingly in this case, there was no echocardiogram in our system but when we found a CT which was performed around three weeks earlier, there was this calcification as well as associated hypodensity that proved that this is thrombus with calcification sitting in the LV apex. So this was a case of LV apical aneurysm with calcification. Now coming to other cardiac incidental findings which are typically pericardial, in this patient, 55 year old male with shortness of breath, we did attenuation correction CT which showed extensive pericardial calcifications. These can have different flavors and in this patient, it was pretty remarkable and we could see it even on patients prior chest x-ray as you can see on a frontal and lateral radiograph showing extensive pericardial calcification. So this was exuberant pericardial calcification. In these cases, the next step is typically dependent on the patient's symptoms and degree of calcification. Usually if I see this incidentally without any prior cardiac imaging, I suggest echocardiogram as the first step and if there are any concerns of constrictive physiology, cardiac MRI or cardiac catheterization is a good first step. Now this is the patient that I just showed you which showed biatrial enlargement and some septal bounds in the cine images and we did some real-time imaging to look for ventricular interdependence and we saw that in inspiration there was septal flattening which was consistent with constrictive physiology. Continuing with pericardial incidental findings to know, here is an example of a 59 year old male with atypical chest pain. This is a raw image from the myocardial perfusion exam that showed an area of decreased radiotracer uptake or photopenia around the heart and when we looked at the attenuation correction CT images, we can see that there is small amount of fluid adjacent to the heart and this is pericardial effusion that could explain the photopenia around the heart. So this is basically a medium-sized pericardial effusion. Usually these are known and there is an echocardiogram in the record. If available, I like to compare it with any prior exams. If enlarging or if there is no recent echocardiogram, usually the first step to do in these patients is maybe suggest an echocardiogram to evaluate this pericardial effusion. Here is an example from this guideline document in which this image is showing medium-sized pericardial effusion as well as small bilateral pericardial effusions. So moving on to the next type of incidental findings that's in the aorta. This is an example of a 71 year old female with acute chest pain. These are the attenuation correction CT images and as you can see in this patient, the ascending aorta is pretty prominent and when we measured this ascending aorta, this ascending aorta was approximately 5.1 centimeter consistent with ascending aortic aneurysm. Now the next step in these cases is initially to primarily define whether you call this aneurysm or a dilated aorta. I would suggest for this following the local guidelines. Our local guidelines are that we define ascending aorta more than 4 centimeter as dilated aorta and more than 4.5 centimeter as aortic aneurysms. However, if you go to ACR white paper on managing incidental findings on chest CT which kind of not directly but indirectly applies to the SPECT CT images as well, they defined ascending aorta aneurysm as more than 5 centimeter and more than 4 centimeter as aneurysm for descending thoracic aorta. Moving on to the next incidental finding, this is an 80 year old female with dyspnea on exertion. Here is the rotating images of the SPECT scan and as you can see that there is a linear area of radiolucency or photopenia in the abdomen and when we looked at the raw images we could see that there is a right lower lobe lung nodule but there were no upper abdominal images in this attenuation correction to explain these findings and based on that incidental 1.2 centimeter right lower lobe lung nodule on attenuation correction images we used Fleischner guidelines to get to the next step and in this case it was more than 8 millimeters so we suggested a CT at 3 months or PET CT or tissue sampling. The patient got a CT of chest abdomen and pelvis to define these findings and the finding that explained this patient's photopenia in the abdomen was actually a bilobed infradenal aortic aneurysm and the finding in the right lower lobe was actually an irregular lung nodule in the right lung base which was biopsied as a lung cancer. So again these are the two incidental findings that we could see in this one patient. In this example we'll focus on the breast incidental findings. This is a 52 year old female with history of hypertension and atypical chest pain and a myocardial perfusion exam was done and on the attenuation correction images what we saw was that there was a pretty big lymph node in the right axilla and along with that there was pretty irregular mass in the right breast and these are just the still images to show these findings. This is the breast finding and this was the axillary finding. So basically based on these images patient had a right breast mass and right axillary lymphadenopathy which actually was not previously known. So what we suggested was correlation with any known history or comparison with prior imaging but in this case none of those were available and we suggested mammography just for you to know we suggest mammography for incidental breast masses in patients that are more than 40 year old and ultrasound in patients that are less than 40 years old and this is just the mammography image which showed an irregular speculated breast mass consistent with a breast cancer. Moving on to the next incidental findings that are seen in mediastinum. This is an example of a 73 year old male with progressive shortness of breath and on the spec images formed we saw multi-segment lymph node enlargement in this patient. These are mediastinal lymph node, hilar lymph nodes and as we can see there are so many stations of the lymph nodes that were involved in this patient. So these are just an example. This is the right paratracheal station of the mediastinal lymphadenopathy and this is the right hilar station of the mediastinal lymphadenopathy. So this was extensive multistation mediastinal lymphadenopathy. And next step in these cases is typically clinical consultation, diagnostic CT and especially if there is enlargement of lymph node by more than 1.5 cm in short axis. In the case that I showed, he was diagnosed with lymphoma. Again in these cases you can go to incidental findings paper by ACR guidance statement and in this if you see any time the lymph node size in short axis is more than 15 mm, they suggest clinical consultation and or PET CT and or 3 to 6 month follow up chest CT. Moving on to next type of incidental findings, this time in pleura. This is an example of 36 year old female with chest pain and shortness of breath. And when we looked at the attenuation correction images, there was small pericardial effusion but also there was small layering bilateral pleural effusion. Now as you can see pleural effusions are typically seen in the dependent posterior portion as seen by the posterior yellow arrows. The anterior yellow arrow which is here, this corresponds to the pericardial effusion and here is the pleural effusion. So what we did is we measured the pleural effusion, typically when the attenuation of the fluid is less than 20 attenuation or 20 HU, this is called as a simple pleural effusion and in this patient we suggested serocitis workup and the patient underwent autoimmune workup and was diagnosed with SLE. And this could very well explain patient symptoms of chest pain because early pleurisy or new onset pleural effusion can lead to chest pain. So if small, usually we do not have any specific follow up or recommendations. If large, any comparison with prior imaging is suggested or you can suggest chest x-ray or chest CT. Here is an example from the guideline document showing moderate size or large bilateral pleural effusion. Here is another example of a 73-year-old male with right-sided chest pain. The patient presented to ED and the first step was getting a chest x-ray done. This chest x-ray was read as normal and the patient underwent a nuclear spectra scan but on the attenuation correction images we saw a pretty large right pneumothorax. So we went back to that chest x-ray to see if we could find this pneumothorax on there and retrospectively, as you can see, there is a faint asymmetric lucency on this side versus the other side, although it's very hard to see a pleural edge on this. So we suggested a follow-up chest x-ray in this case and the follow-up chest x-ray clearly showed a well-defined pneumothorax with a pleural edge as you can see going down there. So this patient was diagnosed by pneumothorax and typically in these cases, the next step is calling the ordering team for immediate further management. Coming to further lung pathologies that you can see, this is an example of an 82-year-old man who was an outpatient with left-sided chest pain and on the attenuation correction images we saw pretty dense consolidation in the lingula as well as multiple nodules which were scattered in the left lower lobe. So again, we suggested in this case a follow-up chest CT and on the chest CT you can see that there were nodules even in the right lung as well as in the left lower lobe as well as in the left upper lobe. Now this finding highlighted by the arrows is actually what is called as an air bronchogram sign that means you see air within the bronchi and these bronchi are surrounded by opacity. This is a sign of a consolidation. This is just an illustration of the same sign here and this is basically, this patient was having a multifocal lung obesity and nodules. This was diagnosed as multifocal pneumonia. Next step in these cases is that if this is not known, calling the ordering team, suggesting the diagnosis and any further workup. Now moving forward with the lung findings, this is an example of a 53-year-old female with history of breast cancer and atypical chest pain with shortness of breath. These are the attenuation correction CT images and in these we saw like almost like a non-nodular ill-defined areas of opacification in bilateral lungs and they were along the bronchovascular bundles and some of them were in subplural location. So the way I would describe these is that these are just patchy bilateral lung obesities predominantly along the bronchovascular bundles. One of the primary goal from you is not to really characterize them well but actually to identify them. So knowing normal versus abnormal is the big first step and based on that you can always suggest further diagnostic workup as long as you can recognize that this is not a normal finding. So this patient had multi-lobar lung opacities along the bronchovascular bundles and this patient was diagnosed with COVID-19 pneumonia on the same day based on these findings. So if not known, it's best to call the ordering team and suggest further testing and typically the testing includes chest x-rays and chest CTs for lung opacities. Now COVID-19 pneumonia was particularly prevalent at one point although now the prevalence is decreasing. The knowledge of these findings is still very important because we still see these findings and you can see them as ground glass obesity or a frank consolidation or a varying pattern of ground glass obesity with interstitial thickening or organizing pneumonia lung pattern. But as I mentioned the primary goal is to differentiate normal from abnormal. Moving on to the next incidental finding on the bone incidental findings. This is a 72-year-old female. The stress test was ordered for shortness of breath and on this attenuation correction images we saw extensive multifocal lytic and sclerotic lesions in the bones. In this case we suggested further workup for these lesions and the differential diagnosis was either metastasis or multiple myeloma. So finding sclerotic lesions make multiple myeloma highly unlikely and this was basically a patient in which there was lytic and sclerotic metastasis from occult breast cancer. So if not known the best step is to call the ordering team and suggest further definite diagnostic testing. Other similar findings that you can see and is kind of in the same tune of metastasis. This is an example from the guideline document. This is a patient that had a rib and vertebral metastasis and then this is a patient that had multiple lung nodules and this was multiple pulmonary metastasis and this is the patient actually that had a compression fracture and compression fracture is just loss of the vertical height of a vertebra. This does not have to be from metastasis. The most common reason is from osteoporosis but it's one finding that you should know amongst the bone findings. Now moving on to abdomen, we typically only see the upper abdomen in these attenuation correction images but here are a few things that we expect you to know and learn about and this is a 66 year old woman with recurring episodes of chest pain and on this image, this is a raw image, we saw some radiotracer activity behind the cardiac silhouette and when we looked at that attenuation correction images, we saw that there is a pretty reasonable size hiatal hernia which was sitting behind the heart and that could explain the radiotracer uptake in the lower thorax. So this is a large hiatal hernia and sometimes this large hiatal hernia can also explain recurring episodes of chest pain because of reflux disease. So the next step in this case is actually to report this finding in the impression as this could be etiology of patient symptoms. Moving on to other abdominal findings, this is a 64 year old female and this study was done as a part of a pre-transplant workup. We did not have much details because this was done as an outside patient and we did not have much details but we saw some fluid in the abdomen and we saw it around the liver as well as around the spleen. Whenever I see fluid, I tend to measure the attenuation value. A simple fluid has attenuation values of less than 20 HU and this patient had simple fluid but other things that this patient had is a relatively shrunken liver as well as nodular liver surface and relative hypertrophy of the left lobe. So these findings were consistent with liver cirrhosis with ascites. Actually this is known by the time you have liver cirrhosis with findings of portal hypertension like ascites and all these things, this is known but if by any chance you see this incidentally on your exam, I would suggest starting with ultrasound, with Doppler as well as liver function tests for the first step evaluation. Other common abdominal findings that you can see and these are the findings that are also highlighted in the guideline document. This is presence of gallstone typically seen adjacent to the liver in the right upper abdomen. This is an image from the guideline paper also showing multiple gallstones and this is presence of a renal stone in the right kidney. Another finding that you should be aware of is presence of fatty liver. Now with fatty liver, since these are non-contrast examination, what you are typically looking at is low attenuation of liver and you can even see normal vessels through the liver when it is so low in attenuation like in this case, you can see these hepatic veins and IVC very clearly but objectively we define fatty liver as liver attenuation 10HU lower than spleen or absolute liver attenuation of less than 40HU. In this case the attenuation was 2HU signifying pretty severe hepatic sclerosis or fatty liver. Other common benign findings that you can frequently see on spec. One is presence of ill-defined very faint obesity in the dependent portion of lungs which is also known as dependent atyloid basis. This is very common because the patients are lying down horizontally. You may see this in almost every case that you read. The other findings you know are presence of calcified nodules or calcified granulomas. These are benign and just mean some old infection or inflammation or granulomatous disease and same you can see with calcified hilar or mediastinal lymph nodes. These are benign findings and sometimes in males you can have a little bit of breast tissue, especially in elderly males or in patients with liver disease. So these are very common benign findings and on the same tune you can see some splenic granulomas as a benign marker of prior granulomatous inflammation. There's nothing to be done in these findings and the best thing is you can report them in the findings section of your report but you don't have to put it in your impression. To conclude this talk, incidental findings are common and they can be very diverse. Although in small percentage of patients some findings are clinically relevant either showing an unsuspected pathology or a pathology that can explain patient symptoms. Hybrid imaging with CT has increased the focus on learning as well as increased the focus on finding these incidental extracardiac findings. More than precise diagnosis, the goal should be to identify normal versus abnormal and one of the important piece of this equation is that there has to be good collaboration between cardiology, nuclear medicine and radiology. And whenever you are in doubt, it's always good to err on side of asking the colleagues that may have a little bit more expertise in this area. One thing I would further highlight is knowing some important papers. One of them is the Fleischner Society Statement for Lung Nodules and the other one is Managing Incidental Findings seen on Chest CT and as in most cases you will see chest portion being covered by your attenuation correction images. So this is summary of the incidental findings, what are they, why should we know them and what are the important incidental findings to know. I hope you all learned something, thank you for your attention. If you have any questions, comments or feedback, please feel free to reach out to me, here is my email and cell, thank you.

incidental findings

nuclear cardiology

diagnostic evaluation

collaboration

managing incidental findings

guidelines