i.This is Dr. David Bluemke in Madison, Wisconsin.I’m the function; metabolic syndrome and MRI of the whole body, why Editor of the journal Radiology.This is part two of our March, do some abdominal aneurysms grow and others do not, and finally, H2020 podcast.The goal of these podcasts is to present a brief iodine contrast and renal function in pediatric patients. Next, on to summary of key research in our field to keep you up-to-date.To- our research topics for March. day four topics: The beneficial effect of bariatric surgery on lung Lung Parenchymal and Tracheal CT Morphology: Evaluation before and after Bariatric Surgery Radiology 2020;294:669-675 Susan J. Copley, MB BS, FRCR, FRCP, MD (Res) • Lalani Carlton Jones, MA, MBBS, MRCS, FRCR, PGDipMedEd •Neil D. Soneji, MB BS, MRCS, FRCR • Jonathan Cousins, FRCA, FFICM • Anthony Edey, MB BS, MRCP, FRCR •Ahmed R. Ahmed, PhD, FRCS (Gen) • Athol U. Wells, MBChB, MD, FRACP, FRCP, FRCR

ur first topic CT after bariatric surgery. The title “Lung Paren- classified as overweight. The reason, muscle is heavier than fat. The chymal and Tracheal CT Morphology: Evaluation before and BMI is incorrectly high for athletes. So if you considered yourself Oafter Bariatric Surgery.” The first author Dr. Susan Copley, the to be like Michael Jordan feel free to ignore the BMI calculators. senior author Dr. Athol Wells. The study is from the UK. Our first Instead look at waist circumference. Patients with massive obesity author is from Hammersmith Hospital in London. Background: have compromised breathing including greater airway resistance, You’ve probably heard of Hammersmith Hospital. First, it’s not in obstructive sleep apnea, plus fat is inflammatory. The inflammatory Hammersmith which is a district of West London. It’s about four fat makes these patients more likely to have asthma as well. Purpose: miles north in White City. Hammersmith is a well-known research Use CT to determine change in lung function after bariatric sur- hospital especially for heart, renal, and endocrine disease. This study gery. Methods: Fifty-one patients, average age of 52, all had inspi- is about bariatric surgery. When diet and exercise are not enough ratory and expiratory chest CT before surgery and then six months and the patient’s health is compromised there are several surgical after surgery. Results: There were 31 women and 20 men. Nice to procedures, but the bottom line, bariatric surgery can reduce mor- finally see a study with more women with men. Before surgery the tality in these patients by about half. Surgery is considered when BMI was 45. After surgery a huge decrease at six months, BMI was body mass index is 40 or more. Remember that BMI up to 25 is 34. Twenty-five percent decrease. For my height that would mean I considered normal, 25-30 overweight, obesity is 30 or more. In would lose almost 100 pounds, more than 40 kg after surgery. The the US, two-thirds of the population is considered overweight or biggest effect on the lungs something called expiratory air trapping. obese. Extreme obesity at 40 kg/m²or more. Body mass index is sort When we exhale air is supposed to move out of the lungs without of controversial. The index was invented about 200 years ago by a difficulty. But before surgery more than 90 percent of these patients Belgian mathematician. The formula, weight divided by the square had lungs that had lung collapse on CT during expiration. It’s called of your height. But why do you square the height? Sort of a good air trapping. The lung density was abnormally increased when the question and the formula does not account for waist size, but that’s patient exhaled. After surgery only 30 percent had lung collapse the first thing you notice for people who are overweight. Optimal and air trapping. Even the trachea collapsed before surgery, but waist size for a size foot tall man said to be 36 inches or less. For the size of the trachea got 15 percent larger after bariatric surgery. a 5’4” woman, waist of 32 inches or less. And of course BMI does Conclusion: A nice straight-forward study. CT to look at changes not work at all for athletes. One report looked at every starting in the lung before and after surgery. After surgery the patients felt quarterback in the National Football League. Every one of them they were less short of breath. The main CT feature that correlated was classified as overweight. Tom Brady, New England Patriots, had with improvement was less air trapping or less lung collapse at end a BMI of more than 27 and he’s certainly doing okay. In basket- expiration. This is one of the first CT studies that objectively shows ball, Michael Jordan had a BMI of about 29. Lebron James also improvement in the function of the lungs after bariatric surgery. Voxel-wise Study of Cohort Associations in Whole-Body MRI: Application in Metabolic Syn- drome and Its Components Radiology 2020;294:559-567 Lars Lind, MD, PhD • Robin Strand, PhD • Karl Michaëlsson, MD, PhD • Håkan Ahlström, MD, PhD • Joel Kullberg, PhD

opic two, also on body composition. The title “Voxel-wise all in the hips not good. Or belly fat. That fat is associated with Study of Cohort Associations in Whole-Body MRI: Applica- inflammation. So we can go ahead and guess one organ at a time. Is Ttion in Metabolic Syndrome and Its Components.” The first fat in the liver associated with high cholesterol or hypertension or author Dr. Lars Lind, senior author Dr. Joel Kullberg. The study is all the metabolic components. Let’s look at another approach using from Uppsala University Hospital in Uppsala, Sweden. Uppsala is MRI. Instead of looking at each organ one at a time, look at all well known for its universities. There are more than 40,000 students organs in the body at the same time. Even better, with MRI look at in the city. The overall population of Uppsala is about 225,000. each individual pixel of an organ individually. Where exactly is your Again, sort of like Madison, Wisconsin. There seems to be some body fat located? How much is there and is that fat associated with combination of top-notch, large universities in cities this size. Up- high blood pressure? What about triglycerides? Purpose: Determine psala is only about a one hour drive north of Stockholm. At this the relationship of every voxel location in the entire body in men time of the year in March the average high temperature in Uppsala and women with metabolic syndrome. Methods: Whole body MRI is about 4 degrees Celsius or 40 degrees Fahrenheit. Background: was done. Each and every location in the entire body each of two The topic is metabolic syndrome. We all have an idea of metabolic million voxels in the body was mapped as either fat or water. The syndrome, right? We know it’s related to excess fat, diabetes, that relationship of every location in the body to metabolic syndrome sort of thing. But what do we mean by a syndrome? Syndromes are was determined in more than 300 men and women. Results: The not diseases. They’re groups or signs or symptoms that tend to occur results are maps of the entire body color coded by how strongly each together. An example is irritable bowel syndrome. Irritable bowel point in the body is associated with metabolic syndrome. For exam- syndrome is associated with diarrhea or constipation, abdominal ple, let’s say you’re a male patient. The amount of fat in your thigh discomfort. But also different diseases, infection, Crohn’s, ulcerative muscles has a strong association with metabolic syndrome and your colitis could all cause IBS. In a similar way, metabolic syndrome is a waist size. Maybe get on the treadmill. Work the legs and abdomen set of conditions that tend to occur together. Metabolic syndrome is shrinks too. But in women the legs don’t matter nearly as much. defined when a patient has at least three of the five following condi- Women get fat deposits in the lower anterior abdominal wall. That tions: hypertension, hyperlipidemia, hyperglycemia, high triglycer- area, along with the liver, has the worst association with metabolic ide levels, and abdominal obesity. Metabolic syndrome is useful for syndrome. Conclusion: This is just a quick intro to new research on clinicians. Maybe one syndrome is easier to remember than each of fat metabolism. MRI especially has a huge role. In this work each the individual conditions. But we don’t treat metabolic syndrome. of two million voxels in the body was mapped to see if they had a We treat the high cholesterol, the hypertension, the high glucose. role in five different cardiovascular risk factors. This type of work Let’s switch gears to fat. We know some types of fat are worse than perhaps combined with artificial intelligence could likely identify other types. For example, let’s say the patient eats too much and a lot more about how our bodies work without having to examine the body starts storing fat not only in the liver, but maybe even in each organ one at a time. Maybe you feel fat in one area or another. the heart. Yikes! When our normal organs are used to store just fat You could take a look at the pictures in this article to see if those then the body really gets into trouble. But we already know a fair areas of fat are associated with metabolic syndrome or any of its five amount about fat in the wrong place. Measure waist circumference components.

Intraluminal Thrombus Predicts Rapid Growth ofAbdominal Aortic Aneurysms Radiology 2020;294:707-713 Chengcheng Zhu, PhD • Joseph R. Leach, MD, PhD • Yuting Wang, MD • Warren Gasper, MD • David Saloner, PhD • Michael D. Hope, MD

ext article, the title, “Intraluminal Thrombus Predicts Rapid monitor aneurysms, which ones grow, which ones stay the same. It’s Growth of Abdominal Aortic Aneurysms.” First author Dr. sort of boring to measure these. In a year or two I’m sure all of it NChengcheng Zhu, senior author Dr. Michael Hope at the will be done automatically by AI. I hope. So there’s no real intellect University of California, San Francisco. I have to admit I chose this in measuring aortic aneurysms and not that much to talk about on topic for our residents at the University of Wisconsin and maybe these cases. There are so many aneurysms that don’t change at all or also for me. We see a remarkable number of abdominal aortic an- they change very slowly, but every once in a while a large growth in eurysms at our hospital. I think I mentioned my own theory is the certain aneurysms. Why? It seems like by now we should be able to combination of beer and cheese in our area. So part of our job is to have some idea of why which aneurysms will grow and which do not. Abdominal aneurysms occur more often in men, more com- age age was 72. Nearly all had hypertension. About one-third were mon in smokers. But my first patient in the intensive care unit in smokers. Results: The average aneurysm size was 4 cm. The average Chicago was an elderly woman. The history was pretty common in growth rate was only 1.1 mm per year. That’s the average in 225 Chicago for our patients. She was found down, found unconscious patients, but we can’t even accurately measure 1.5 mm change in an in her home, rushed to the hospital and admitted to the intensive individual patient. But if you follow guidelines and follow-up after care unit and unresponsive. So imagine a third year medical student, three years that’s a respectable 5 mm change, probably detectible. So and I’m supposed to admit this patient who cannot speak or answer which aneurysms grew faster? What do you think is the major factor any questions related to why she’s there in the first place. On the on CT associated with faster growth? The answer, size. If the aneu- other hand, nearly all acute events are cardiac or stroke related. So rysm was 5.5 cm or more the average growth rate was twice as great, I could take a blood pressure and pulse, do a little neurological ex- about 3 mm per year. That’s the easy question. What other factors amination, listen to heart and lungs, palpate the abdomen. She was were associated with greater rate of aneurysm growth? A few things, quite old. We estimated about 80, very frail, perhaps 80 pounds. older age and obesity and one more interesting factor. That factor, We were taught to palpate the abdomen in each quadrant. So I tried if there was intraluminal thrombus in the aneurysm. I’m sure you’ve this out. Each quadrant was pretty soft towards the edges of the seen this all of the time some quite large aneurysms have a perfectly abdomen, but in the middle her abdomen was rock hard. It didn’t smooth thin wall, no thrombus. Others can truly have remarkable make sense to me. Rock hard like bone. Maybe by pushing on her amounts of thrombus in the aortic wall. If the thrombus was pres- abdomen I was feeling the lumbar spine? But it seemed bigger than ent, the aneurysms grew faster over time. Even more interesting, for that. What rock hard non-movable mass should be in the middle smaller aneurysms the effect was larger. Three to four centimeters of the abdomen? Nothing. Time to get my attending. In the next in size the aneurysm grew twice as fast if thrombus was present hour the patient was rushed to a CT scan, the rock hard mass was versus no thrombus. Conclusion: When I see a lot of thrombus a 10 cm calcified aortic aneurysm. Pretty large. We get worried a 5 in an aneurysm I suppose the first thing that comes to my mind cm and then the problem started. She was dehydrated and anemic. maybe the thrombus will break off and travel to the legs and toes. Fluids were given for hydration and to raise blood pressure. She The new knowledge, thrombus is associated with faster growing un- regained consciousness. But by raising blood pressure we triggered stable aneurysms. Why? Here’s what the authors think and I believe her giant aortic aneurysm to leak with subsequent massive rupture. it makes a lot of sense. The clot in the aneurysm forms because of The patient unfortunately died just a few hours later. So the ques- an injury to the aortic wall. With injury there is inflammation and tion remains who has an aneurysm and which ones grow? In the the inflammation itself can cause breakdown of the aortic wall. The United States the recommendation is for men to have screening collegian in the aortic wall is weaker, it can enlarge more easily. for an aneurysm between age 65 and 75 with ultrasound especially Larger aneurysms also grow faster because there is more tension on for smokers. Why? Abdominal aneurysms are silent. You have no the aortic wall. Laplace’s law from physics, the tension on the wall is idea if an aneurysm is there or not. One option maybe have a vir- proportional to the radius. But it seems like the clot is a marker of tual CT colon. Get your abdominal aorta checked at the same time inflammation and injury to the aorta. Those grow faster as well. Last at an early age. For women, not enough evidence that aneurysm question; let’s say you have a patient with a lot of clot in the aortic screening is necessary. Perhaps useful for women who smoke. In the wall. The middle of the aorta, the lumen size might be only 2.5 cm, United States 200,000 AAA’s per year. An aneurysm is present when but when you measure the outer diameter of the aorta the size is 4 the diameter of the aorta is 3 cm or more. Treatment recommended cm. Which number do you report, the inner diameter or the outer at 5.5 cm or more. If less than 5.5 cm follow at three year inter- diameter? Answer, the outer diameter. Remember that the greater vals. Purpose: Determine which factors on CT are associated with tension on the wall leads to aneurysm growth. That greatest tension growth of abdominal aortic aneurysms. Methods: 225 patients with is related to the outer 4 cm diameter. You can report the amount of abdominal aortic aneurysm evaluated over a three year period. Most thrombus as well, but surgery and follow-up are based on the outer follow-up was with CT. Some patients also had MRI. The aver- contour diameter.

Risk of Acute Kidney Injury Following Contrast-enhanced CT in Hospitalized Pediatric Patients: A Propensity Score Analysis Radiology 2020;294:548-556 Leah A. Gilligan, MD • Matthew S. Davenport, MD • Andrew T. Trout, MD • Weizhe Su, MS • Bin Zhang, PhD •Stuart L. Goldstein, MD • Jonathan R. Dillman, MD, MSc

inal topic for today. Let’s start with a short quiz for the residents. An MRI was done to get the stiffness of the aorta before vaping, I’ll use the example of an article that we published last year on then the young people were removed from the MRI scan and asked FE cigarettes. I’ll give you the study design; you decide where the to vape nicotine-free E cigarettes. The young people did 16 puffs on logic is wrong, possible false conclusion. Here we go. The research- the E cigarette. Then the MRI was repeated. The researchers found ers wanted to test if E cigarettes could cause abnormal function of the aorta was stiffer after vaping than before. The researchers con- blood vessels by using MRI. The MRI test measured stiffness of cluded that vaping E cigarettes caused worse vascular function. So the blood vessels. That portion was highly validated in prior stud- what do you think? Any problems with the study? MRI at baseline, ies. More vascular disease, stiffer blood vessels. So far, so good. The puff on an E cigarette, then have another MRI. The MRI changes study design, recruit 30 young people who had never vaped before. for the worse. We conclude that vaping the E cigarette liquid caused the problem. But is that conclusion correct? Why are why not. I’d ney function decreased. Must be the iodine contrast right? No, not like to give you a moment to think about it but we need to move right. Again, no control group. Nine-nine percent of all research is on. Here’s the problem. We really don’t have a control group. To retrospective. Search the medical record for patients who had renal be certain about our conclusion we need to have another group function GFR before and after CT with contrast. But what if you of 30-year-olds. Have a baseline MRI and then have them vape, search for patients with GFR before and after ultrasound or before but don’t but any of the vaping liquid in the E cigarette devise. and after non-contrast CT? Those are control groups and we find Maybe just water. Have them puff a little steam. Now repeat the even patients with ultrasound or non-contrast CT have worse re- MRI. Is it possible that my control group might also have a stiffer nal function after the tests. Why? We really don’t know. Perhaps aorta on the second MRI? Yes it is. For many people MRI is quite if you’re a patient who needs renal function testing every few days stressful. In one of my research studies we did 8 hours of different something’s going wrong. Maybe you’re getting chemotherapy, per- types of medical tests on 7,000 people across the United States. CT haps post-surgery, perhaps infection. So after 30 years we now rec- scan, questionnaires, blood tests, blood pressure measurement, ul- ognize that when the GFR is 30 mils per minute or more we can’t trasound and MRI, 8 hours. We wanted people to stay in the study seem to detect any injury by iodine contrast on renal function. But for the next five or ten years so we asked about the best and worst all the major studies have been done so far in adults. Purpose: De- parts of their day. The part they disliked the most, the MRI. Many termine the effect of iodine contrast on renal function in children people find it to be uncomfortable. Maybe the 30-year-olds also get age 0 to 18 years of age. Methods: Retrospective date over ten years stressed out by MRI, adrenaline released or anxiety about going into at the University of Cincinnati Children’s Hospital. One group had the MRI scanner for the second time. It could be anything. Maybe GFR then a CT scan with contrast, then another GFR within 48 they were rushed in the scanner without a bathroom break. It really hours. The control group had a GFR, then ultrasound, then GFR helps to have a control group. That long example is directly related within 48 hours. Results: More than 18,000 peds patients, 900 had to our next article. The title: “Risk of Acute Kidney Injury Fol- CT, 900 had ultrasound. They were matched for age and 23 other lowing Contrast-enhanced CT in Hospitalized Pediatric Patients: A perimeters that just might cause renal failure. So here’s the result, Propensity Score Analysis.” The first author Dr. Leah Gilligan, the 22 patients in the CT group had evidence of acute renal injury after senior author Dr. Jonathan Dillman. Both authors are from the De- the CT, but 24 patients in the ultrasound group had evidence of partment of Radiology Cincinnati Children’s Hospital. I gave the acute renal injury. No difference. Conclusion: Just like in adults, MRI example because of the lack of a control group. The parallel we should conclude that iodine does not cause acute kidney injury to this study, for about 30 years all radiologists and nephrologists in children. That’s terrific except, always an exception, the authors were convinced that iodine contrast causes renal failure. If you’ve had almost no patients with poor or baseline kidney function. More been practicing radiology for a while like me you might still think than 95 percent of these patients had a baseline GFR of 60 mils that iodine causes acute kidney injury and you offer proof. Take per minute or greater. For GFR less than 60, the best guidelines 10,000 patients in your hospital who had kidney function at base- are probably those that we have for adults. Recently published this line, then these 10,000 people had a CT scan with iodine contrast. month in Radiology, I discussed these guidelines from the ACR and Look in the medical record, find the next GRF measurement. Kid- the National Kidney Foundation in our part one March podcast.

hat concludes this week’s articles. I hope these podcasts were helpful to you. Until next time, this is Dr. David Bluemke for the journal TRadiology. I hope you have a good rest of your week.