Radiology in Our Changing Climate: A Call to Action

Schoen et al. (2021)
“Radiology in Our Changing Climate:
A Call to Action,”
JACR, 18:1041–1043.

Lately I’ve been thinking more and more about the importance of combating climate change, which may be the most urgent technological challenge of our time. But you haven’t seen much about it in this blog, because climate change doesn’t have much to do with Intermediate Physics for Medicine and Biology. Or does it? Last year, Julia Schoen, Geraldine McGinty, and Cody Quirk published an opinion piece in the Journal of the American College of Radiology titled “Radiology in Our Changing Climate: A Call to Action” (Volume 18, Pages 1041–1043). It’s short, clear, and well worth reading. The introduction begins:

Just as early radiologists did not understand the dangers of high radiation doses, today we are naive to imaging’s carbon footprint and its implications for public health. The world’s temperature has already risen more than 1 °C from preindustrial levels. We see the effects of climate change across the world, from extreme wildfires and stronger storms to rising sea levels and ocean acidification. If we continue with “business as usual,” children born today will experience a planet that is 4 °C warmer than in preindustrial times and the associated health consequences. These consequences are disproportionately felt by children, the elderly, those with preexisting conditions, and outdoor workers. As our climate crisis worsens, radiologists must urgently consider our role in climate change.

According to Schoen et al., the health care system may be responsible for nearly ten percent of American’s greenhouse gas emissions. TEN PERCENT! Yikes. They suggest that radiology departments are “likely a major contributor to energy use within hospital systems.” They identify four ways to address the energy use in radiology.

Imaging Exams

Schoen et al. claim that “over a year, the energy use of one CT [computed tomography] scanner was comparable with that of 5 four-person households, and the energy use of one MR [magnetic resonance] scanner was close to that of 26 four-person households.” I always thought MRI was the ideal imaging method, but it turns out it’s an energy hog, contributing significantly to radiology’s carbon footprint. There are few easy ways to reduce energy use; perhaps use ultrasound more when appropriate and adopt new technologies that shorten imaging time.

Scanners in the Off State

Imaging systems use a lot of energy even in standby mode. You must keep the superconducting coil of a MRI scanner cold all the time, not just when it’s imaging. Solutions are not simple. Schoen et al. suggest using scanners 24 hours a day (patients won’t like that) and working with manufacturers to find ways of reducing energy use when a scanner is not operating.

Wasteful Habits

We have to cut the waste in radiology departments. Simple improvements would be to turn off computers and picture archiving and communication systems (PACSs) at night or when not in use, and reducing excess packaging. I support these easy changes, but wonder if they’ll have a major impact on our carbon footprint.

Energy Sources

Alternative energy sources—including ones like wind, solar, and nuclear—will reduce greenhouse gas emissions. This is something individual radiologists, or even radiology departments, have little control over, but if major health care systems demand cleaner energy sources they might be able to influence regional utilities and politicians.

Conclusion

Schoen, McGinty, and Quirk discuss an important issue, and I thank them for raising it. Their call to action must be addressed by radiologists in collaboration with hospital administrators, academic researchers, and medical device companies. All of us—including the past, present, and future patients needing radiological services—must advocate for reducing our impact on the climate.

I’ll give Schoen et al. the last word by quoting the eloquent final paragraph of their publication.

Radiology faces many challenges, from improving diversity to changes in reimbursement in a budget-neutral system. Addressing climate change is an opportunity to protect vulnerable populations and increase our value in the health care system. Initiatives to address climate change align with the ACR’s [American College of Radiology’s] core purpose of serving both patients and society. Our field has made great strides in patient safety by decreasing radiation doses. Similarly, through our technological expertise and awareness, we can decrease our carbon footprint, with the ultimate goal of mitigating climate change and preventing a looming public health crisis.

 

Listen to a podcast of Julia Schoen discussing sustainability and radiology.

https://www.youtube.com/watch?v=_66M2PgnTxA

The group “Radiologists for a Sustainable Future” is on Twitter. Follow them at @Rads4SF.

Using the Mechanical Bidomain Model to Analyze the Biomechanical Behavior of Cardiomyocytes

During the decade of 2010–2020, my research shifted from bioelectricity and biomagnetism to biomechanics and mechanotransduction. I took the bidomain model of cardiac electrophysiology—described in Chapter 7 of Intermediate Physics for Medicine and Biology— and adapted it to describe growth and remodeling in response to mechanical forces. In other words, I traded resistors for springs. This effort was not entirely successful, but I think it provided some useful insights.

In 2015 I described the mechanical bidomain model in a chapter of Cardiomyocytes: Methods and Protocols. This book was part of the series Methods in Molecular Biology, and each chapter had a unusual format. The research was outlined, with the details relegated to an extensive collection of endnotes. A second edition of the book was proposed, and I dutifully submitted an updated chapter. However, the new edition never come to pass. Rather than see my chapter go to waste, I offer it to you, dear reader. You can download a draft of my chapter for the second edition here. For those of you who have time only for a summary, below is the abstract.

The mechanical bidomain model provides a macroscopic description of cardiac tissue biomechanics, and also predicts the microscopic coupling between the extracellular matrix and the intracellular cytoskeleton of cardiomyocytes. The goal of this chapter is to introduce the mechanical bidomain model, to describe the mathematical methods required for solving the model equations, to predict where the membrane forces acting on integrin proteins coupling the intracellular and extracellular spaces are large, and to suggest experiments to test the model predictions.

The main difference between the chapter in the first edition and the one submitted for the second was a new section called “Experiments to Test the Mechanical Bidomain Model.” There I describe how the model can reproduce data obtained when studying colonies of embryonic stem cells, sheets of engineered heart tissue, and border zones between normal and ischemic regions in the heart. The chapter ends with this observation:

The most important contribution of mathematical modeling in biology is to make predictions that can be tested experimentally. The mechanical bidomain model makes many predictions, in diverse areas such as development, tissue engineering, and hypertrophy.

I particularly like a new figure in the second edition. It’s a revision of a figure created by Xavier Trepat and Jeffrey Fredberg that compares mechanobiology to a game of tug-of-war. I added the elastic properties of the extracellular space (the green arrows), saying “It is as if the game of tug-of-war is played on a flexible surface, such as a flat elastic sheet.” In other words, tug-of-war on a trampoline. 

Enjoy!

The “tug-of-war” model of tissue biomechanics, adapted from an illustrationby Trepat and Fredberg. Top: the intracellular (yellow), extracellular (green) and integrin (blue) forces acting on a monolayer of cells. Middle: The analogous forces among the players of a game of tug-of-war. This figure is extended beyond that of Trepat and Fredberg by allowing both the intracellular and extracellular spaces to move. Bottom: Representation of the mechanical bidomain model by a ladder of springs.

Aquaporins and Peter Agre

In Chapter 5 of Intermediate Physics for Medicine and Biology, Russ Hobbie and I mention aquaporins, a type of membrane channel. In a footnote, we write

Some aquaporins are permeable only to water, and not to any other small molecules or ions, even hydrogen ions (Preston et al. 1992). Aquaporins are formed by proteins that span the cell membrane. Their structure has been determined by x-ray crystallography (Murara et al. 2000). Their selectivity arises from a narrowing of the channel to about 0.3 nm, about the size of a single water molecule. Aquaporins allow water to cross cell membranes at a much higher rate than it could diffuse through. Genetically defective aquaporins may be responsible for some clinical diseases, such as nephrogenic diabetes insipidus and congenital cataracts (Agre et al. 2002).

In 2003, Peter Agre was awarded the Nobel Prize in Chemistry for the discovery of aquaporins. My goal in this post is to provide a bit more detail about aquaporins and Agre. 

To learn more about these water channels, let’s begin with this simple, fun Claymation video.

Claymation video about aquaporins by Sophia Dudte.
https://www.youtube.com/watch?v=7EGPtMqZ7pY

Next is a more rigorous simulation of an aquaporin

A simulation of a water channel in a cell membrane, performed by The Theoretical and Biophysics Group at the NIH Center for Macromolecular Modeling and Bioinformatics.
https://www.youtube.com/watch?v=GSi5-y6NHjY

Russ and I cite the paper by Murara et al. (2000). The full citation is

Murata K, Mitsuoka K, Hirai T, Walz T, Agre P, Heymann JB, Engel A, Fujiyoshi Y (2000) Structural determinants of water permeation through aquaporin-1. Nature, Volume 407, Pages 599–605.

The abstract is listed below.

Human red cell AQP1 is the first functionally defined member of the aquaporin family of membrane water channels. Here we describe an atomic model of AQP1 at 3.8 Å resolution from electron crystallographic data. Multiple highly conserved amino-acid residues stabilize the novel fold of AQP1. The aqueous pathway is lined with conserved hydrophobic residues that permit rapid water transport, whereas the water selectivity is due to a constriction of the pore diameter to about 3 Å over a span of one residue. The atomic model provides a possible molecular explanation to a longstanding puzzle in physiology—how membranes can be freely permeable to water but impermeable to protons.

Below is a illustration of the aquaporin molecule. The view is perpendicular to the membrane, and the little hole in the middle is the pore. 

Illustration of an aquaporin molecule. Drawn by David Goodsell.

Next is the introduction to the Wikipedia article about Agre (references removed).

Peter Agre /ˈɑːɡriː/ (born January 30, 1949) is an American physician, Nobel Laureate, and molecular biologist, Bloomberg Distinguished Professor at the Johns Hopkins Bloomberg School of Public Health and Johns Hopkins School of Medicine, and director of the Johns Hopkins Malaria Research Institute. In 2003, Agre and Roderick MacKinnon shared the 2003 Nobel Prize in Chemistry for "discoveries concerning channels in cell membranes." Agre was recognized for his discovery of aquaporin water channels. Aquaporins are water-channel proteins that move water molecules through the cell membrane. In 2009, Agre was elected president of the American Association for the Advancement of Science (AAAS) and became active in science diplomacy.

You can learn more about Agre in the videos below.

Peter Agre talking about aquaporin channels at the National Institutes of Health. https://www.youtube.com/watch?v=L1TyWo86w4Q 

 

 

Peter Agre answering questions about his life and research 

 https://www.youtube.com/watch?v=F6vETKZtgxU 

 

 

Peter Agre giving a TED Talk (2011)
https://www.youtube.com/watch?v=-eq5tfU1kZY

Are Electromagnetic Fields Making Me Ill? How Electricity and Magnetism Affect Our Health

Are Electromagnetic Fields Making Me Ill?
How Electricity and Magnetism Affect Our Health,
by Brad Roth

Big News! This week Springer published my new book: Are Electromagnetic Fields Making Me Ill? How Electricity and Magnetism Affect Our Health. This book is different from Intermediate Physics for Medicine and Biology: it’s short (122 pages), uses no math, and is aimed at a general audience. Readers of this blog may find parts of the book familiar; over the last couple years I’ve written posts that served as first drafts of some sections. Below is an excerpt from the Introduction.

This book is about electric and magnetic fields, and their effect on your body. We will examine the use of magnets for pain relief, the risk of power line magnetic fields, the safety of cell phones, and the possibility that microwave weapons are responsible for the Havana syndrome. Many medical treatments are based on electromagnetism, including well established ones like heart pacemakers and neural prostheses, and more questionable ones such as bone healing, transcutaneous electrical nerve stimulation, and transcranial direct current stimulation. Innumerable books and articles have been written about each of these topics; my goal in this book is to examine them together, to get the big picture.

This book is not a research monograph. It presents no original discoveries and makes no attempt to be comprehensive. Moreover, it omits numerous details and technicalities that experts often argue about. It does, however, try to offer an overall view of the field that is accurate.

My target readers are nonscientists: journalists, politicians, teachers, students, and anyone who has heard about electric and magnetic fields interacting with biological tissue and wants to learn more. I use no mathematics, avoid jargon, and employ abbreviations only when repeating the same mouthful of words over and over again becomes tedious. I tried my best to make the book understandable to a wide audience….

Sometimes the effect of electric and magnetic fields is controversial. For any debate, I have tried to present both sides. Nevertheless, readers will soon catch on that I’m a skeptic. Each chapter title is a question, of which my answer is usually “probably not” or “no.”

Here is the Table of Contents.

1. Introduction 
2. Can Magnets Cure All Your Ills? 
3. Can a 9-Volt Battery Make You Smarter? 
4. Do Power Lines Cause Cancer? 
5. Will Electrical Stimulation Help Your Aching Back? 
6. Is Your Cell Phone Killing You? 
7. Did 5G Cell Phone Radiation Cause Covid-19? 
8. Did Cuba Attack America with Microwaves? 
9. Is That Airport Security Scanner Dangerous? 
10. Conclusion

Although Russ Hobbie is not a coauthor on my new book, readers familiar with IPMB will see his influence on each page. In one of our last email exchanges before he passed away, I sent Russ an early draft of the book and he claimed to love it (that may have been Russ being kind, as he always was).

Enjoy!

Listen to me read the final chapter of Are Electromagnetic Fields Making Me Ill?

https://www.youtube.com/watch?v=5jJLkBsU4V0