Medical Physics Qualifying Exams

We have a Medical Physics PhD program here at Oakland University, and this was the week we administered the oral qualifying exam to our current crop of graduate students. Happily, they all passed. In August they also took a battery of written exams about theoretical physics, mathematical methods, and biophysical sciences (Physics, Math, and Biology for short). I have mentioned these exams before in this blog. We consider them to be a common core that our graduate students are expected to master.

These exams do not require knowing extremely advance material, but they do cover a broad range of topics. I take them to be a minimum that our students must know, rather than a target they should aim for. A student who has a strong undergraduate background in physics, math and biology should be able to survive. Some of the more advanced homework problems and examples from the 4th edition of Intermediate Physics for Medicine and Biology sometimes make their way onto these exams.

Let me add a few words about our PhD program. It is aimed at producing research students who can apply physics to medical and biological problems, rather than preparing students for traditional medical physics positions in a hospital. We are not CAMPEP accredited, because that accreditation is mainly for programs aimed narrowly at producing clinical medical physicists. Our students get broad training in both mathematics and medicine, and in both physics and physiology. Their depth comes from doing their research dissertation. After graduating, they go on to a variety of positions in academia, industry, and research laboratories.

Readers of IPMB who want to see how well they would do on our qualifying exam can find over ten years of the written exams at https://files.oakland.edu/users/roth/web/qualifierexams.htm. I have four reasons for posting these exams on the web. First, I assume the exams, or at least some of the questions from them, would make the rounds among our graduate students, or at least among some subset of the graduate students, and I would rather they all have equal access. Second, I am often asked to provide guidance and suggestions as to what specific topics might be on these exams (I admit, all of physics, math, and biology is a lot to master), and my answer is have them look at the previous exams. Third, it can be a useful recruiting tool; if a potential applicant wants to know what they are expected to master to succeed in our program, I can send them to the old exams and be confident that they realize what they are getting into. Fourth, failing our qualifying exam is a serious issue. The students only get two tries, and then they must leave the program. I prefer to give a student some direction and help rather wondering if the exam was unfair as I tell them that they failed. The downside to posting these exams is that I need to keep coming up with new problems each year. While some identical problems from old exams appear on later exams, I try to minimize this. So, writing the exams (which I do largely myself, although with input from the other faculty in the program) is a little harder than it otherwise would be. One useful side effect of posting the exams is that they are all “out there” available to anyone, including our dear readers of IPMB. So, feel free to use them as you wish. Sorry, but I don’t have solutions I can send you.

In addition to these written exams, each student must stand in front of a group of (intimidating?) faculty and answer questions about “everything”: all the topics from the written exams, plus questions related to their research, and to any other part of physics, mathematics, or biology that might strike the questioner’s fancy. This grilling is what our students went through on Wednesday, successfully. I think the students fear this part of the exam most of all, but I believe they grow from the experience.

Congratulations to this year’s students. I hope readers of IPMB find these exams useful.

Reinventing Physics For Life-Science Majors

The July issue of Physics Today contained an article by Dawn Meredith and Joe Redish titled “Reinventing Physics for Life-Science Majors.” Much in the article is relevant to the 4th edition of Intermediate Physics for Medicine and Biology. The main difference between the goals of their article and IPMB is that they discuss the introductory physics course, whereas Russ Hobbie and I wrote an intermediate-level text. Nevertheless, many of the aims remain the same. Meredith and Redish begin

Physics departments have long been providing service courses for premedical students and biology majors. But in the past few decades, the life sciences have grown explosively as new techniques, new instruments, and a growing understanding of biological mechanisms have enabled biologists to better understand the physiochemical processes of life at all scales, from the molecular to the ecological. Quantitative measurements and modeling are emerging as key biological tools. As a result, biologists are demanding more effective and relevant undergraduate service classes in math, chemistry, and physics to help prepare students for the new, more quantitative life sciences.

Their section on what skills should students learn reads like a list of goals for IPMB:

• Drawing inferences from equations…. 
• Building simple quantitative models…. 
• Connecting equations to physical meaning…. 
• Integrating multiple representations…. 
• Understanding the implications of scaling and functional dependence…. 
• Estimating….”

Meredith and Redish realize the importance of developing appropriate homework problems for life-science students, which is something Russ and I have spent an enormous amount of time on when revising IPMB. “We have spent a good deal of time in conversation with our biology colleagues and have created problems of relevance to them that are also doable by students in an introductory biology course.” They then offer a delightful problem about calculating how big a worm can grow (see their Box 4). They also include a photo of a “spherical cow”; you need to see it to understand. And they propose the Gauss gun (see a video here) as a model for exothermic reactions. They conclude

Teaching physics to biology students requires far more than watering down a course for engineers and adding in a few superficial biological applications. What is needed is for physicists to work closely with biologists to learn not only what physics topics and habits of mind are useful to biologists but also how the biologist’s work is fundamentally different from ours and how to bridge that gap. The problem is one of pedagogy, not just biology or physics, and solving it is essential to designing an IPLS [Introductory Physics for the Life Sciences] course that satisfies instructors and students in both disciplines.

Rounding Off the Cow

In the October 2012 issue of the American Journal of Physics, Dawn Meredith and Jessica Bolker published an article about “Rounding Off the Cow: Challenges and Successes in an Interdisciplinary Physics Course for Life Science Students” (Volume 80, Pages 913–922). The article is interesting, and much of the motivation for their work is nearly identical to that of Russ Hobbie and I in writing the 4th edition of Intermediate Physics for Medicine and Biology. They focus on an introductory physics class, whereas Russ and I wrote an intermediate level textbook. Nevertheless, many of the ideas and challenges are the same. Here, I want to focus on their Table 1, in which they list topics that are emphasized and deemphasized compared to standard introductory classes.

Table I. Changes in topic emphasis compared to standard course

	Semester 1	Semester 2
Included/stressed	Kinematics	Heat transfer
	Dynamics	Kinetic theory of gases
	Static torque	Entropy
	Energy	Diffusion, convection, conduction
	Stress/strain and fracture	Simple harmonic motion
	Fluids (far more)	Waves (sound, optics)
Omitted/de-emphasized	Projectile motion	Heat engines
	Relative motion	Magnetism (less)
	Rotational motion	Induction (qualitatively)
	Statics	Atomic physics (instrumentation)
	Collisions	Relativity
	Newton’s law of gravitation
	Kepler’s laws

How does this list compare with the content of IPMB? We don’t stress kinematics and dynamics much. In fact, most of our mechanics discussion centers on static equilibrium. Interestingly, Meredith and Bolker emphasize static torque, which is absolutely central to our analysis of biomechanics in Chapter 1. Rotational equilibrium and torque is what explains why bones, muscles and tendons often experience forces far larger than the weight of the body. It also underlies our rather extensive discussion of the role of a cane. We discuss mechanical energy in Chapter 1, but energy doesn’t become an essential topic until our Chapter 3 on thermodynamics. We agree completely with Meredith and Bolker’s listing of “stress/strain and fracture” and “Fluids (far more)”, and I second the “far more”. Our Chapter 1 contains a lot of fluid dynamics, including the biologically-important concept of buoyancy, the idea of high and low Reynolds number, and applications of fluid dynamics to the circulatory system.

The time allotted to an introductory physics class is limited, so something must get deemphasized to free up time for topics like fluids. Meredith and Bolker mention projectile motion (we agree, it is nowhere in IPMB), relative motion (not crucial if not covering relativity), and rotational motion (we don’t emphasize this either, except when analyzing the centrifuge). I don’t really understand the omission of statics, because as I said earlier static mechanical equilibrium is crucial for biomechanics. They deemphasize collisions, and so do we, although we do discuss the collision of an electron with a photon when analyzing Compton Scattering in Chapter 15. Newton’s law of gravity and Kepler’s laws of planetary motion are absent from both our book and their class.

In the second semester, Meredith and Bolker stress heat transfer (convection and conduction), the kinetic theory of gases, and entropy. Russ and I discuss all these topics in our Chapter 3. Diffusion is a topic they emphasize, and rightly so. It is a topic that is typically absent from an introductory physics class, but is crucial for biology. We discuss it in detail in Chapter 4 of IPMB. Meredith and Bolker list simple harmonic motion among the topics they stress. We talk about harmonic motion in Chapter 10, but mainly as a springboard for the study of nonlinear dynamics. Much of the analysis of linear harmonic motion is found in IPMB in an appendix. Finally, they stress waves (sound and optics). We do too, mainly in our Chapter 13 about sound and ultrasound; a new chapter in the 4th edition.

Topics they omit or deemphasize in the second semester include heat engines. We barely mention heat engines at the end of Chapter 3, and the well-known Carnot heat engine is never analyzed in our book. Meredith and Bolker deemphasize magnetism and magnetic induction. As a researcher in biomagnetism, I would hate to see these topics go. Russ and I analyze biomagnetism in Chapter 8. However, I could see how one might be tempted to deemphasize these topics; biomagnetic fields are very weak and do not play a large role in either biology or medicine. I personally would keep them in, and they remain an important part of IPMB. They do not stress “Atomic Physics (Instrumentation)” and I am not sure exactly what they mean, especially with their parenthetical comment about instruments. We talk a lot about atomic physics in Chapter 14 on Atoms and Light. Finally, Meredith and Bolker omit relativity, and so do Russ and I, except as needed to understand photons. We never discuss the more traditional phenomena of relativity, such as the Lorentz contraction, time dilation, or simultaneity.

Some topics should get about the same amount of attention as in a traditional class, but with slight changes in emphasis. For instance, I would cover geometrical optics, including lenses (when discussing the eye and eyeglasses) but I would skip mirrors. I would cover nuclear physics, but I would skip fission and fusion, and focus on radioactive decay, including positron decay (positron emission tomography).

I think that Meredith and Bolker provide some useful guidance on how to construct an introductory physics class for students interested in the life sciences. Russ and I aim at an intermediate class for students who have taken a traditional introductory class and want to explore applications to biology and medicine in more detail. Our book is clearly at a higher mathematical level: we use calculus while most introductory physics classes for life science majors are algebra based. But for the most part, we agree with Meredith and Bolker about what physics topics are central for biology majors and pre-med students.

AAPT Summer Meeting in Portland Oregon

On Tuesday, Russ Hobbie gave a talk about “Medical Physics in the Introductory Physics Course” at the American Association of Physics Teachers Summer Meeting in Portland Oregon. His session, with over 100 people attending, focused on Reforming the Introductory Physics Courses for Life Science Majors, a topic currently of great interest and one that I have discussed before in this blog. You can find the slides that accompanied his talk at the 4th edition of Intermediate Physics for Medicine and Biology website. His talk focused on five topics that he feels are crucial for the introductory course: 1) Exponential growth and decay, 2) Diffusion and solute transport, 3) Intracellular potentials and currents, 4) Action potentials and the electrocardiogram, and 5) Fitting exponentials and power laws to data. All these topics are covered in our book. Russ and I also compiled a list of topics for the premed physics course, and cross listed them to our book, this blog, and other sources. You can find the list on the book website, or download it here.

Our book website is a source of other important information. For instance, you can download the errata, containing a list of known errors in the 4th edition of Intermediate Physics for Medicine and Biology. You will find Russ’s American Journal of Physics paper “Physics Useful to a Medical Student” (Volume 43, Pages 121–132, 1975), and Russ and my American Journal of Physics “Resource Letter MP-2: Medical Physics” (Volume 77, Pages 967–978, 2009). Other valuable items include MacDose, a computer program Russ developed to illustrate the interaction of radiation with matter, a link to a movie Russ filmed to demonstrate concepts related to the attenuation and absorption of x rays, sections from earlier editions of Intermediate Physics for Medicine and Biology that were not included in the 4th edition, and a link to the American Physical Society, Division of Biological Physics December 2006 Newsletter containing an interview with Russ upon the publication of the 4th edition of our book. You can even find a link to the Intermediate Physics for Medicine and Biology facebook group.

Russ and I hope that all this information on the book website, plus this blog, helps the reader of Intermediate Physics for Medicine and Biology keep up-to-date, and increases the usefulness of our book. If you have other suggestions about how we can make our website even more useful, please let us know. Of course, we thank all our dear readers for using our book.

PHY 530, Bioelectric Phenomena

This week I finished up my PHY 530 class (Bioelectric Phenomena), which I discussed once before in this blog. Rather than adopting a textbook, I based this graduate class on a collection of scientific papers. Below I list the three dozen papers we studied. It should not be regarded as a “greatest hits” list. Some are Nobel Prize winning papers, but oftentimes I selected a lesser-known article that happened to cover a specific topic I wanted to teach. Many are cited in the 4th edition of Intermediate Physics for Medicine and Biology (indicated by a *). Students were assigned the 16 papers marked in bold: they had to take a quiz on each of these before we discussed them in class, and the exams often contained questions drawn directly from these papers. The other 20 articles are supplementary: consider them recommended reading, rather than required.

I had two goals in the class: to teach the basic elements of bioelectricity, and to lead a workshop on how to write a scientific paper. The students were given two projects (one was to simulate a squid nerve axon using the Hodgkin-Huxley model, and the other was to determine a dipole source from simulated EEG data) and had to write up their results in a brief (4 page maximum) paper having the classic structure: Abstract, Introduction, Methods, Results, Discussion, References. We read essays related to writing scientific papers, such as "What's Wrong With These Equations?" and "Writing Physics," both by N. David Mermin, and learned to use the Science Citation Index. I am pleased with how the class went, and I hope the students were too.

1. A. L. Hodgkin and A. F. Huxley (1939) “Action Potentials Recorded from Inside a Nerve Fiber,” Nature, Volume 144, Pages 710–711. *

2. A. L. Hodgkin and B. Katz (1949) “The Effect of Sodium Ions on the Electrical Activity of the Giant Axon of the Squid,” Journal of Physiology, Volume 108, Pages 37–77.

3. A. L. Hodgkin and A. F. Huxley (1952) “A Quantitative Description of Membrane Current and its Application to Conduction and Excitation in Nerve,” Journal of Physiology, Volume 117, Pages 500–544. *

4. D. A. Doyle, J. M. Cabral, R. A. Pfuetzner, A. Kuo, J. M. Gulbis, S. L. Cohen, B. T. Chait, and R. MacKinnon (1998) “The Structure of the Potassium Channel: Molecular Basis of K+ Conduction and Selectivity,” Science, Volume 280, Pages 69–77. *

5. O. P. Hamill, A. Marty, E. Neher, B. Sakmann, and F. J. Sigworth (1981) “Improved Patch-Clamp Techniques for High-Resolution Current Recording From Cells and Cell-Free Membrane Patches,” Pflugers Archive, Volume 391, Pages 85–100. *

6. A. L. Hodgkin and W. A. H. Rushton (1946) “The Electrical Constants of a Crustacean Nerve Fibre,” Proceedings of the Royal Society of London, B, Volume 133, Pages 444–479. *

7. W. A. H. Rushton (1951) “A Theory of the Effects of Fibre Size in Medullated Nerve,” Journal of Physiology, Volume 115, Pages 101–122. *

8. R. FitzHugh (1961) “Impulses and Physiological States in Theoretical Models of Nerve Membrane,” Biophysical Journal, Volume 1, Pages 445–466.

9. W. Rall (1962) “Theory of Physiological Properties of Dendrites,” Annals of the New York Academy of Sciences, Volume 96, Pages 1071–1092.

10. F. Rattay (1989) “Analysis of Models for Extracellular Fiber Stimulation,” IEEE Transactions on Biomedical Engineering, Volume 36, Pages 676–682.

11. A. T. Barker, R. Jalimous, and I. L. Freeston (1985) “Non-Invasive Magnetic Stimulation of Human Motor Cortex,” Lancet, Volume 8437, Pages 1106–1107. *

12. M. Hallett and L. G. Cohen (1989) “Magnetism: A New Method for Stimulation of Nerve and Brain,” Journal of the American Medical Association, Volume 262, Pages 538–541. *

13. B. J. Roth, L. G. Cohen and M. Hallett (1991) “The Electric Field Induced During Magnetic Stimulation,” Electroencephalography and Clinical Neurophysiology, Supplement 43, Pages 268–278.

14. R. Plonsey (1974) “The Active Fiber in a Volume Conductor,” IEEE Transactions on Biomedical Engineering, Volume 21, Pages 371–381.

15. B. J. Roth, D. Ko, I. R. von Albertini-Carletti, D. Scaffidi and S. Sato (1997) “Dipole Localization in Patients with Epilepsy Using the Realistically Shaped Head Model,” Electroencephalography and Clinical Neurophysiology, Volume 102, Pages 159–166.

16. M. Schneider (1974) “Effect of Inhomogeneities on Surface Signals Coming From a Cerebral Current-Dipole Source,” IEEE Transactions on Biomedical Engineering, Volume 21, Pages 52–54.

17. B. J. Roth and J. P. Wikswo (1985) “The Magnetic Field of a Single Axon: A Comparison of Theory and Experiment,” Biophysical Journal, Volume 48, Pages 93–109. *

18. M. Hamalainen, R. Hari, R. J. Ilmoniemi, J. Knuutila, and O. V. Lounasmaa (1993) “Magnetoencephalography: Theory, Instrumentation, and Application to Noninvasive Studies of the Working Human Brain,” Reviews of Modern Physics, Volume 65, Pages 413–497. *

19. T.-K. Truong and A. W. Song (2006) “Finding Neuroelectric Activity Under Magnetic-Field Oscillations (NAMO) with Magnetic Resonance Imaging In Vivo,” Proceedings of the National Academy of Sciences, Volume 103, Pages 12598–12601.

20. B. J. Roth and P. J. Basser (2009) “Mechanical Model of Neural Tissue Displacement During Lorentz Effect Imaging,” Magnetic Resonance in Medicine, Volume 61, Pages 59–64.

21. A. T. Winfree (1987) When Time Breaks Down. Princeton Univ Press, Princeton, NJ, Pages 106–107. *

22. B. J. Roth (2002) “Virtual Electrodes Made Simple: A Cellular Excitable Medium Modified for Strong Electrical Stimuli,” The Online Journal of Cardiology, http://sprojects.mmi.mcgill.ca/heart/pages/rot/rothom.html

23. D. W. Frazier, P. D. Wolf, J. M. Wharton, A. S. L. Tang, W. M. Smith and R. E. Ideker (1989) “Stimulus-Induced Critical Point: Mechanism for Electrical Initiation of Reentry in Normal Canine Myocardium,” Journal of Clinical Investigation, Volume 83, Pages 1039–1052.

24. N. Shibata, P.-S. Chen, E. G. Dixon, P. D. Wolf, N. D. Danieley, W. M. Smith, and R. E. Ideker (1988) “Influence of Shock Strength and Timing on Induction of Ventricular Arrhythmias in Dogs,” American Journal of Physiology, Volume 255, Pages H891–H901.

25. J. N. Weiss, A. Garfinkel, H. S. Karagueuzian, Z. Qu and P.-S. Chen (1999) “Chaos and the Transition to Ventricular Fibrillation: A New Approach to Antiarrhythmic Drug Evaluation,” Circulation, Volume 99, Pages 2819–2826.

26. A. Garfinkel, Y.-H. Kim, O. Voroshilovsky, Z. Qu, J. R. Kil, M.-H. Lee, H. S. Karagueuzian, J. N. Weiss, and P.-S. Chen (2000) “Preventing Ventricular Fibrillation by Flattening Cardiac Restitution,” Proceedings of the National Academy of Sciences, Volume 97, Pages 6061–6066. *

27. N. G. Sepulveda, B. J. Roth and J. P. Wikswo, Jr. (1989) “Current Injection into a Two-Dimensional Anisotropic Bidomain,” Biophysical Journal, Volume 55, Pages 987–999. *

28. B. J. Roth (1992) “How the Anisotropy of the Intracellular and Extracellular Conductivities Influences Stimulation of Cardiac Muscle,” Journal of Mathematical Biology, Volume 30, Pages 633–646. *

29. Efimov I. R., Y. Cheng, D. R. Van Wagoner, T. Mazgalev, and P. J. Tchou (1998) “Virtual Electrode-Induced Phase Singularity: A Basic Mechanism of Defibrillation Failure,” Circulation Research, Volume 82, Pages 918–925.

30. Efimov, I. R., Y. N. Cheng, M. Biermann, D. R. Van Wagoner, T. N. Mazgalev, and P. J. Tchou (1997) “Transmembrane Voltage Changes Produced by Real and Virtual Electrodes During Monophasic Defibrillation Shock Delivered by an Implantable Electrode,” Journal of Cardiovascular Electrophysiology, Volume 8, Pages 1031–1045.

31. Roth, B. J. (1995) “A Mathematical Model of Make and Break Electrical Stimulation of Cardiac Tissue Using a Unipolar Anode or Cathode,” IEEE Transactions on Biomedical Engineering, Volume 42, Pages 1174–1184.

32. Cheng, Y., V. Nikolski, and I. R. Efimov (2000) “Reversal of Repolarization Gradient Does Not Reverse the Chirality of the Shock-Induced Reentry in the Rabbit Heart,” Journal of Cardiovascular Electrophysiology, Volume 11, Pages 998–1007.

33. Trayanova, N. A., B. J. Roth, and L. J. Malden (1993) “The Response of a Spherical Heart to a Uniform Electric Field: A Bidomain Analysis of Cardiac Stimulation,” IEEE Transactions on Biomedical Engineering, Volume 40, Pages 899–908.

34. Nielsen, P. M. F., I. J. Le Grice, B. H. Smaill, and P. J. Hunter (1991) “Mathematical Model of Geometry and Fibrous Structure of the Heart,” American Journal of Physiology, Volume 260, Pages H1365–H1378.

35. Krassowska, W., T. C. Pilkington, and R. E. Ideker (1987) “The Closed Form Solution to the Periodic Core-Conductor Model Using Asymptotic Analysis,” IEEE Transactions on Biomedical Engineering, Volume 34, Pages 519–531.

36. Rodriquez, B., J. C. Eason, and N. Trayanova (2006) “Differences Between Left and Right Ventricular Anatomy Determine the Types of Reentrant Circuits Induced by an External Electric Shock: A Rabbit Heart Simulation Study,” Progress in Biophysics and Molecular Biology, Volume 90, Pages 399–413.

How Should We Teach Physics to Future Life Scientists and Physicians?

The American Physical Society publishes a monthly newspaper, the APS News, and the back page of each issue contains an editorial that goes under the name—you guessed it—“The Back Page.” Readers of the 4th edition of Intermediate Physics for Medicine and Biology will want to read The Back Page in the March 2010 issue, subtitled “Physics for Future Physicians and Life Scientists: A Moment of Opportunity.” This excellent editorial—written by Catherine Crouch, Robert Hilborn, Suzanne Amador Kane, Timothy McKay, and Mark Reeves—champions many of the ideas that underlie our textbook. The editorial begins

How should we teach physics to future life scientists and physicians? The physics community has an exciting and timely opportunity to reshape introductory physics courses for this audience. A June 2009 report from the American Association of Medical Colleges (AAMC) and the Howard Hughes Medical Institute (HHMI), as well as the National Research Council’s Bio2010 report, clearly acknowledge the critical role physics plays in the contemporary life sciences. They also issue a persuasive call to enhance our courses to serve these students more effectively by demonstrating the foundational role of physics for understanding biological phenomena and by making it an explicit goal to develop in students the sophisticated scientific skills characteristic of our discipline. This call for change provides an opportunity for the physics community to play a major role in educating future physicians and future life science researchers.

A number of physics educators have already reshaped their courses to better address the needs of life science and premedical students, and more are actively doing so. Here we describe what these reports call for, their import for the physics community, and some key features of these reshaped courses. Our commentary is based on the discussions at an October 2009 conference (www.gwu.edu/~ipls), at which physics faculty engaged in teaching introductory physics for the life sciences (IPLS), met with life scientists and representatives of NSF, APS, AAPT, and AAMC, to take stock of these calls for change and possible responses from the physics community. Similar discussion on IPLS also took place at the 2009 APS April Meeting, the 2009 AAPT Summer Meeting, and the February 2010 APS/AAPT Joint Meeting.

One key distinction between our textbook and the work described in The Back Page editorial is that our book is aimed toward an intermediate level, while the IPLS movement is aimed at the introductory level. Like it or not, premedical students have a difficult time fitting additional physics courses into their undergraduate curriculum. I know that here at Oakland University, I’ve been able to entice only a handful of premed students to take my PHY 325 (Biological Physics) and PHY 326 (Medical Physics) classes, despite my best efforts to attract them and despite OU’s large number of students hoping to attend medical school (these classes have our two-semester introductory physics sequence as a prerequisite). So, I think there’s merit in revising the introductory physics class, which premedical students are required to take, if your goal is to influence premedical education. As The Back Page editorial states, “the challenge is to offer courses that cultivate general quantitative and scientific reasoning skills, together with a firm grounding in basic physical principles and the ability to apply those principles to living systems, all without increasing the number of courses needed to prepare for medical school.” The Back Page editorial also cites the “joint AAMC-HHMI committee … report, Scientific Foundations for Future Physicians (SFFP). This report calls for removing specific course requirements for medical school admission and focusing instead on a set of scientific and mathematical ‘competencies.’ Physics plays a significant role…”

How do you fit all the biomedical applications of physics into an already full introductory class? The Back Page editorial gives some suggestions. For instance, “an extended discussion of kinematics and projectile motion could be replaced by more study of fluids and continuum mechanics... [and] topics such as diffusion and open systems could replace the current focus on heat engines and equilibrium thermal situations.” I agree, especially with adding fluid dynamics (Chapter 1 in our book) and diffusion (Chapter 4), which I believe are absolutely essential for understanding biology. I have my own suggestions. Although Newton’s universal law of gravity, Kepler’s laws of planetary motion, and the behavior of orbiting satellites are fascinating and beautiful topics, a premed student may benefit more from the study of osmosis (Chapter 5) and sound (Chapter 13, including ultrasound). Electricity and magnetism remains a cornerstone of introductory physics (usually in a second semester of a two-semester sequence), but the emphasis could be different. For instance, Faraday’s law of induction can be illustrated using magnetic stimulation of the brain, Ampere’s law by the magnetic field around a nerve axon, and the dipole approximation by the electrocardiogram. In a previous post to this blog, I discussed how Intermediate Physics for Medicine and Biology addresses many of these issues. Russ Hobbie will be giving an invited paper about medical physics and premed students at the July 2010 meeting of the American Association of Physics Teachers. When he gives the talk it will be posted on the book website.

One way to shift the focus of an introductory physics class toward the life sciences is to create new homework problems that use elementary physics to illustrate biological applications. In the 4th edition of Introductory Physics for Medicine and Biology, Russ Hobbie and I constructed many interesting homework problems about biomedical topics. While some of these may be too advanced for an introductory class, others may (with some modification) be very useful. Indeed, teaching a traditional introductory physics class but using a well-crafted set of homework problems may go a long ways toward achieving the goals set out by The Back Page editorial.

Let me finish this blog entry by quoting the eloquent final paragraph of The Back Page editorial. Notice that the editorial ends with the same central question that began it. It is the question that motivated Russ Hobbie to write the first edition of Intermediate Physics for Medicine and Biology (published in 1978) and it is the key question that Russ and I struggled with when working on the 4th edition.

The physics community faces a challenging opportunity as it addresses the issues surrounding IPLS courses. A sizable community we serve has articulated a clear set of skills and competencies that students should master as a result of their physics education. We have for a number of decades incorporated engineering examples into our physics classes. The SFFP report asks us to respond to another important constituency. Are we ready to develop courses that will teach our students how to apply basic physical principles to the life sciences? The challenges of making significant changes in IPLS courses are daunting if we each individually try to take on the task. But with a community-wide effort, we should be able to meet this challenge. The physics community is already moving to develop and implement changes in IPLS courses, and the motivations for change are strong. The life science and medical school communities stress that a working knowledge of physical principles is essential to success in all areas of life science including the practice of medicine. Thus we see significant teaching and learning opportunities as we work to answer the question that opened our discussion: how should we teach physics to future physicians and life scientists?

BIO2010

2010 is finally here. Happy New Year! Let’s celebrate by discussing the National Research Council report BIO2010.

In 2003 the NRC released the report BIO2010: Transforming Undergraduate Education for Future Research Biologists. If I had to sum up the report in one phrase, it would be “they are signing our song.” In the 4th edition of Intermediate Physics for Medicine and Biology, Russ Hobbie and I incorporate many of the ideas championed in BIO2010. The preface of the report recommends

a comprehensive reevaluation of undergraduate science education for future biomedical researchers. In particular it calls for a renewed discussion on the ways that engineering and computer science, as well as chemistry, physics, and mathematics are presented to life science students. The conclusions of the report are based on input from chemists, physicists, and mathematicians, not just practicing research biologists. The committee recognizes that all undergraduate science education is interconnected. Changes cannot be made solely to benefit future biomedical researchers. The impact on undergraduates studying other types of biology, as well as other sciences, cannot be ignored as reforms are considered. The Bio2010 report therefore provides ideas and options suitable for various academic situations and diverse types of institutions. It is hoped that the reader will use these possibilities to initiate discussions on the goals and methods of teaching used within their own department, institution, or professional society.

The executive summary begins

The interplay of the recombinant DNA, instrumentation, and digital revolutions has profoundly transformed biological research. The confluence of these three innovations has led to important discoveries, such as the mapping of the human genome. How biologists design, perform, and analyze experiments is changing swiftly. Biological concepts and models are becoming more quantitative, and biological research has become critically dependent on concepts and methods drawn from other scientific disciplines. The connections between the biological sciences and the physical sciences, mathematics, and computer science are rapidly becoming deeper and more extensive. The ways that scientists communicate, interact, and collaborate are undergoing equally rapid and dramatic transformations, which are driven by the accessibility of vast computing power and facile information exchange over the Internet.

Readers of this blog will be particularly interested in Recommendation #1.3 of the report, dealing with the physics education required by biologists, reproduced below. In the list of concepts the report considers essential, I have indicated in brackets the sections of the 4th edition of Intermediate Physics for Medicine and Biology that address each topic. (I admit that the comparison of the report’s recommended physics topics to those topics covered in our book may be a bit unfair, because the report was referring to an introductory physics class, not an intermediate one.) Some of the connections between the report’s topics and sections in our book need additional elaboration, which I have included as footnotes.

Physics

RECOMMENDATION #1.3

The principles of physics are central to the understanding of biological processes, and are increasingly important in sophisticated measurements in biology. The committee recommends that life science majors master the key physics concepts listed below. Experience with these principles provides a simple context in which to learn the relationship between observations and mathematical description and modeling.

The typical calculus-based introductory physics course taught today was designed to serve the needs of physics, mathematics, and engineering students. It allocates a major block of time to electromagnetic theory and to many details of classical mechanics. In so doing, it does not provide the time needed for in-depth descriptions of the equally basic physics on which students can build an understanding of biology. By emphasizing exactly solvable problems, the course rarely illustrates the ways that physics can be applied to more recalcitrant problems. Illustrations involving modern biology are rarely given, and computer simulations are usually absent. Collective behaviors and systems far from equilibrium are not a traditional part of introductory physics. However, the whole notion of emergent behavior, pattern formation, and dynamical networks is so central to understanding biology, where it occurs in an extremely complex context, that it should be introduced first in physical systems, where all interactions and parameters can be clearly specified, and quantitative study is possible.

Concepts of Physics

Motion, Dynamics, and Force Laws

• Measurement¹: physical quantities [throughout], units [1.1, symbol list at the end of each chapter], time/length/mass [1.1], precision [none]
• Equations of motion²: position [Appendix B], velocity [Appendix B], acceleration [Appendix B], motion under gravity [2.7, Problem 1.28]
• Newton’s laws [1.8]: force [1.2], mass [1.12], acceleration [Appendix B], springs [Appendix F] and related material: stiffness³ [1.9], damping⁴ [1.14, 2.7, 10.6], exponential decay [2.2], harmonic motion [10.6]
• Gravitational [3.9] and spring [none] potential energy, kinetic energy [1.8], power [1.8], heat from dissipation [Problem 8.24], work [1.8]
• Electrostatic forces [6.2], charge [6.2], conductors/insulators [6.5], Coulomb’s law [6.2]
• Electric potential [6.4], current [6.8], units [6.2, 6.4, 6.6, 6.8], Ohm’s law [6.8]
• Capacitors [6.6], R [6.9] and RC [6.11] circuits
• Magnetic forces [8.1] and magnetic fields [8.2]
• Magnetic induction and induced currents [8.6]

Conservation Laws and Gobal [sic] Constraints

• Conservation of energy [3.3] and momentum⁵ [15.4]
• Conservation of charge [6.9, 7.9]
• First [3.3] and Second [3.19] Laws of thermodynamics

Thermal Processes at the Molecular Level

• Thermal motions: Brownian motion [3.10], thermal force (collisions) [none], temperature [3.5], equilibrium [3.5]
• Boltzmann’s law [3.7], kT [3.5], examples [3.8, 3.9, 3.10]
• Ideal gas statistical concepts using Boltzmann’s law, pressure [1.11]
• Diffusion limited dynamics⁶ [4.6], population dynamics [2.9, Problem 2.34]

Waves, Light, Optics, and Imaging

• Oscillators and waves [13.1]
• Geometrical optics: rays, lenses [14.12], mirrors⁷ [none]
• Optical instruments: microscopes and microscopy [Problem 14.45]
• Physical optics: interference [14.6.2] and diffraction [13.7]
• X-ray scattering [15.4] and structure determination [none]
• Particle in a box [none]; energy levels [3.2, 14.2]; spectroscopy from a quantum viewpoint [14.2, 14.3]
• Other microscopies⁸: electron [none], scanning tunneling [none], atomic force [none]

Collective Behaviors and Systems far from Equilibrium

• Liquids [1.11, 1.12, 1.14, 1.15], laminar flow [1.14], viscosity [1.14], turbulence [1.18]
• Phase transitions⁹ [Problem 3.57], pattern formation¹⁰ [10.11.5], and symmetry breaking [none]
• Dynamical networks¹¹: electrical, neural, chemical, genetic [none]

1. Russ Hobbie and I have not developed a laboratory to go along with our book, so we don’t discuss measurement, the important differences between precision and accuracy, the ideas of random versus systematic error, or error propagation.

2. Some elementary topics—such as position, velocity, and acceleration vectors—are not presented in the book, but are summarized in an Appendix (we assume they would be mastered in an introductory physics class). We analyze Newton’s second law specifically, but do not develop his three laws of motion in general.

3. We describe Young’s modulus, but we never introduce the term “stiffness.” We talk about potential energy, and especially electrical potential energy, but we don’t spend much time on mass-spring systems and never introduce the concept of elastic (or spring) potential energy.

4. The term “damping” is used only occasionally in our book, but we discuss several types of dissipative phenomena, such as viscosity, exponential decay plus a constant input, and a harmonic oscillator with friction.

5. We use conservation of momentum when we analyze Compton scattering of electrons in Chapter 15, but we never actually present conservation of momentum as a concept.

6. We don’t discuss “diffusion limited dynamics,” but we do analyze diffusion extensively in Chapter 4.

7. We analyze lenses, but not mirrors, and never analyze the reflection of light (although we spend considerable time discussing the reflection of ultrasonic waves in Chapter 13).

8. I have to admit our book is weak on microscopy: the light microscope is relegated to a homework problem, and we don’t talk at all about electron, scanning tunneling, or atomic force microscopies.

9. We discuss thermodynamic phase transitions in a homework problem, but I believe that the report refers more generally to phase transitions that occur in condensed matter physics (e.g., the Ising model), which we do not discuss.

10. We touch on pattern formation in Chapter 10, and in particular in Problems 10.39 and 10.40 that describe wave propagation in the heart using a cellular automaton. But we do not analyze pattern formation (such as Turing patterns) in detail. Symmetry breaking is not mentioned.

11. We don’t discuss neural networks, or other related topics such as emergent behavior. We can only cover so much in one book.

I may be biased, but I believe that the 4th edition of Intermediate Physics for Medicine and Biology does a pretty good job of implementing the BIO2010 report suggestions into a textbook on physics for biologists. With 2010 now here, it’s important to remind aspiring biology students about the importance of physics in their undergraduate education.

PHY 325

This fall, I am teaching PHY 325, Biological Physics, at Oakland University. Of course, the textbook is the 4th edition of Intermediate Physics for Medicine and Biology. You can follow along on the class website, which includes the syllabus, homework assignments, exams, interesting links, and a section called “hot news” that keeps track of up-to-date news for the class, including homework due dates, exam information, etc. We’ll cover the first ten chapters of the book.

Class starts on Wednesday, September 3, at 8 A.M. sharp (I’I'mm a morning person, and I guess the students will have to put up with waking early this semester, too). Welcome to all my PHY 325 students, including premed students, physics majors, and students in the new Engineering Biology program at Oakland.

http://medicalphysicsweb.org

Readers of the 4th edition of Intermediate Physics for Medicine and Biology who are particularly interested in Medical Physics will find the website http://medicalphysicsweb.org interesting. This “community website” is maintained by the Institute of Physics, the United Kingdom’s professional organization for physicists. The IOP created several community websites to “promote innovation, growth and networking,... [and to] provide both a valuable information source and an international forum within which community members can share and exchange their views.”

Medicalphysicsweb provides “a mix of in-depth news, analysis, opinion and primary research papers across the key disciplines of medical physics.” The site contains editorials, job postings, a buyer’s guide, featured journal articles, and research and industry news. Students who are studying from Intermediate Physics for Medicine and Biology will find this website an easy and free way to become familiar with medical physics as a profession. You can become a member (no cost, but there is a registration procedure) and receive a weekly “What's New” newsletter. I highly recommend it. 


Note added in 2019: The website has changed to https://physicsworld.com/c/medical-physics. 

See Russ Hobbie on YouTube!

In Chapter 15 of the 4th edition of Intermediate Physics for Medicine and Biology, Russ Hobbie and I discuss the interaction of radiation with matter, a topic that is crucial for understanding the medical use of X-rays. Twenty years ago, Russ wrote a computer program called MacDose that provides a two-dimensional simulation of the photoelectric effect, Compton scattering, and pair production; the primary mechanisms of X-ray interaction. MacDose runs on any Macintosh with OS-9 or earlier, including Classic in OS-X. You can download a copy of MacDose, including a student manual and instructors guide, at our book’s website. To learn more about MacDose, see Hobbie’s article in Computers in Physics (Volume 6, Pages 355–359, 1992).

You can also download a 26 minute Quicktime movie in which Russ demonstrates MacDose and explains various concepts related to the attenuation and absorption of X-rays (you can view the movie on either a PC or a Mac). With help from my daughter Stephanie, I have uploaded this movie onto Youtube. Because of a limit on the duration of Youtube videos, Stephanie had to split the movie into three parts. Search on YouTube for “MacDose” and you should find all three. Then pop some popcorn, pour yourself a drink, find a seat, and watch Hollywood’s leading man Russ Hobbie explain how radiation interacts with matter.

 Russ Hobbie Demonstrates MacDose, Part 1

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

 Russ Hobbie Demonstrates MacDose, Part2

https://www.youtube.com/watch?v=Rwp8eeKFycQ&t=2s

 Russ Hobbie Demonstrates MacDose, Part3
https://www.youtube.com/watch?v=hB4U7T0gH6M&t=2s

 

Even More on "Medical Physics: the Perfect Intermediate Level Physics Class"

In 2001, Nelson Christensen of Carleton College published an article in the European Journal of Physics (Volume 22, Pages 421–427) titled “Medical Physics: The Perfect Intermediate Level Physics Class.” (See the Jan 25, 2008 and the Oct 5, 2007 blog entries for my earlier discussions about this paper.) The primary textbook for the class was the 3rd edition of Intermediate Physics for Medicine and Biology. Below is the introduction to his paper.

Physics is changing the way medicine is practised. While a doctor will still use a stethoscope, a diagnosis now often requires devices that make use of sophisticated physics and engineering. The importance of physics in medicine may be best displayed when a physicist needs to visit their doctor: we seem to be the only people who can intimidate doctors as we are the ones who actually know how their devices work. As a consequence of the technological evolution of the discipline, medical schools are admitting more and more students who major in physics or engineering.

Almost all major engineering schools will now have a department of biomedical engineering. There are numerous opportunities in academia in medical physics and biomedical engineering. Students interested in becoming an academic physicist now have a fast-growing field to aim for, a field that is providing more and more opportunities. The industrial sector in biomedical engineering is also advancing and evolving quickly. Physicists and engineers can find numerous and lucrative opportunities with companies.

With all of these opportunities it is no wonder that undergraduates are very interested in knowing more about medical physics. Partly due to student interest, and partly due to the faculty’s desire to provide interesting physics classes, Carleton College offered an intermediate level course in medical physics. This was a course open to students who have completed the first year physics courses. We deliberately designed the medical physics course so that the curriculum would be advanced, thereby negating the possibility that this course alone would satisfy a pre-medical school requirement. At this level we then attracted physics majors and pre-medical students who had a genuine interest in studying more physics.

Teaching Biological Physics

The March 2005 issue of the magazine Physics Today contains an article by Goldstein, Nelson and Powers about “Teaching Biological Physics.” Many of the ideas they champion apply to classes taught from the 4th edition of Intermediate Physics for Medicine and Biology. Goldstein et al. write

Over the past few years, people trained in physics and working in physics departments have taken an unprecedented interest in biological problems. A host of new experimental and theoretical techniques has opened up the quantitative study of systems ranging from single molecules to networks of simple agents performing complex collective tasks. Many departments have begun aggressive programs to hire faculty into the emerging field of biological physics. Engineering departments, too, are investing in the interface of the life and physical sciences, both in bioengineering and in related areas such as chemical engineering, solid mechanics, and materials.

Not surprisingly, the new faculty members, like their colleagues, are interested in teaching subjects that excite them. Meanwhile, physical-science students are beginning to demand courses relevant to the life sciences. And high-level reports such as the National Research Council's Bio2010 have emerged to stress the importance of quantitative, physics-based thinking for future life scientists...

Teaching Medical Physics

In the journal Physics Education (Volume 41, Pages 301–306, 2006) is an article by Gibson, Cook, and Newing about “Teaching Medical Physics.” They write

Medical Physics provides immediate and accessible examples that can assist in the teaching of a range of science subjects. To help teachers, we have produced a teaching pack that will be sent to all UK secondary schools in June 2006 and will be available from www.teachingmedicalphysics.org.uk. Here we discuss the advantages of teaching using applications drawn from Medical Physics, careers in Medical Physics, and some sources of other Medical Physics-related teaching resources.

Their website contains many excellent color pictures and videos that could be used to augment our static, black and white 4th edition of Intermediate Physics for Medicine and Biology. They aim for a lower level and younger audience and than we do in our book, but their power-point presentations might be useful supplementary aids when introducing some of the topics covered in our text.

More on "Medical Physics: the Perfect Intermediate Level Physics Class"

Nelson Christensen's article “Medical Physics: the Perfect Intermediate Level Physics Class” (European Journal of Physics, Volume 22, Pages 421–427, 2001) contains a section devoted to textbooks (see my October 5 blog entry for more on Christensen’s paper). He writes

There are numerable good sources and books that one may draw upon for a course like this, however we found no text that covered all of the topics we wanted. Our class primarily used Intermediate Physics for Medicine and Biology (3rd edn) by Hobbie [1]. This book covers a wide array of topics, and has a large number of problems to draw from. The level of the text was, at times, too advanced for undergraduates, and more suitable to graduate students in biomedical engineering. The book also lacks detailed examinations of imaging techniques, especially ultrasound.

Well, the 4th edition contains a new chapter on Sound and Ultrasound. If Christensen liked the “large number of problems,” he’s going to love having 44% more problems in the latest edition. Is the book at times too advanced for undergraduates? The level didn’t change much between the 3rd and 4th editions. We tried to aim the text toward upper level undergraduates. You’ll have to decide for yourself if we hit the mark.

Term Papers

My friend and the senior author of Intermediate Physics for Medicine and Biology, Russ Hobbie, sent me this blog entry to share with you all:

One of the motivations for developing the course that led to this book is the huge gap between a general physics course and the research literature. Often when I was teaching this course, I had students write a term paper instead of a final exam. The term paper was to take a paper from the research literature and fill in the missing steps. Students selected a candidate research paper early in the term and gave it too me for approval. They could come to me as often as necessary for help understanding the research. The last week of the term they turned in both the research paper and term paper and scheduled a half-hour “oral exam” with me a couple of days later. They knew that I would ask them questions about anything I suspected they did not really understand. I had a grading algorithm that assigned points for the difficulty of the research paper, the clarity of the term paper, and my assessment of how well they understood the research based on the oral exam. I had a lot of informal visits by students the week before the term paper was due. Students seemed to learn a lot, and some of these papers became paragraphs or problems in later editions of our book.

Point/Counterpont

When teaching Medical Physics at Oakland University, I have found an excellent way to expose students to current issues in the field: discuss “Point/Counterpoint” articles from the journal Medical Physics, published by the American Association of Physicists in Medicine. Each issue of Medical Physics contains one 3- or 4-page article discussing a fascinating but controversial claim. The format of each Point/Counterpoint article is a debate between two leading medical physicists (something like the old 60 Minutes TV show segment with the same title, parodied so hilariously on Saturday Night Live.) For instance, the January 2008 issue of Medical Physics debates if “Exposure Limits for Emergency Responders Should be the Same as the Prevailing Limits for Occupational Radiation Workers.” My students seem to enjoy the lively style of these articles, and they have to learn enough medical physics to understand the science and vocabulary underlying the debate. I typically spend 15 minutes discussing one article every Friday afternoon. The Point/Counterpoint articles are a great way to augment our textbook, Intermediate Physics for Medicine and Biology, in a Medical Physics class.

Note added March 2, 2008: You can now download a publication titled Controversies in Medical Physics from http://www.aapm.org/ that contains ten years of Point/Counterpoint articles.

Medical Physics: The Perfect Intermediate Level Physics Class

In 2001, Nelson Christensen of Carleton College published an article in the European Journal of Physics (Volume 22, Pages 421–427) titled “Medical Physics: the Perfect Intermediate Level Physics Class.” The primary textbook for his class was the 3rd edition of Intermediate Physics for Medicine and Biology. Below is the conclusion to his paper.

A medical physics course should be looked upon as a beneficial addition to the undergraduate physics curriculum. The course should be considered as an ideal addition to the intermediate level physics curriculum, as it covers almost all of the major subjects that physics undergraduates should see. Students are often bored by lack of direct applications or good examples when covering physics subjects. In our class we talked about physics within the context of medical applications. For every physical topic there was a medical application; students loved it.

The interdisciplinary nature of a course like medical physics offers other advantages. A course like this provides an opportunity for keen pre-medical students to return to physics. A number of the pre-meds are genuinely interested in physics, but lack a good opportunity or reason to take an upper-level physics course. The differing backgrounds of the physics and pre- medical students presented an additional benefit in that a fantastic environment for stimulating discussions was created. The students would share with one-another their expertise.

Finally, there can be no denying that medical physics and biomedical engineering are evolving at a breakneck pace. There are opportunities available in abundance in these fields. Students are interested in medical physics for a number of reasons. There are equally good reasons for the faculty to provide a course in medical physics. This is exciting physics and exciting science!