Friday, August 28, 2009

Resource Letter MPRT-1: Medical Physics in Radiation Therapy

When Russ Hobbie and I were preparing the 4th Edition of Intermediate Physics for Medicine and Biology, we tried to update our book with the most recent references. But, inevitably, as time passes the book becomes increasingly out-of-date. How does one keep up with the literature? This blog is meant to help our readers stay current, but sometimes more drastic measures are required. Fortunately, the American Journal of Physics publishes Resource Letters, in which the author reviews important sources (mainly textbooks and research articles) on a particular topic. In the September 2009 issue of AJP, Steven Ratliff of Saint Cloud State University published Resource Letter MPRT-1: Medical Physics in Radiation Therapy (volume 77, pages 774-782, 2009). The abstract is reproduced below.
“This resource letter provides a guide to the literature on medical physics in the field of radiation therapy. Journal articles, books, and websites are cited for the following topics: radiological physics, particle accelerators, radiation dose measurements, protocols for radiation dose measurements, radiation shielding and radiation protection, neutron, proton, and heavy-ion therapies, imaging for radiation therapy, brachytherapy, quality assurance, treatment planning, dose calculations, and intensity-modulated and image-guided therapy."
I highly recommend this Resource Letter for anyone interested in radiation therapy. Particularly useful is Ratliff’s concluding section "Recommended Path Through the Literature".
“The best single reference for a newcomer to the field is Goitein (Ref. 14). It is clear, up to date, readable, complete, and gives a good explanation of what medical physicists do. For a person who does not want to enter the field but is just curious or needs to get some information and does not want to spend any money, a good place to start is the free on-line book by Podgorsak (Ref. 153). Van Dyk (Ref. 17) is a good place to start for those who want a clinical emphasis. The book by Turner (Ref. 91) has good problems (some with answers) and covers many aspects of the subject.

For those wanting to make a career of Medical Physics, a small but good starting library would consist of Goitein (Ref. 14), Hendee et al. (Ref. 30), Johns and Cunningham (Ref. 15), Khan (Ref. 16), Podgorsak (Ref. 153), Turner (Ref. 91), and van Dyk (Ref. 17). Khan is more useful once you have learned the material. If you have more money, you could add Attix (Ref. 19) and Podgorsak's book on radiation physics (Ref. 26). Cember and Johnson (Ref. 92) is a good addition if you are interested in the health-physics aspects of radiotherapy.

If you were restricted to one book and wanted to learn as much as possible, then the handbook of Mayles et al. (Ref. 18) is worthy of serious consideration.”
The references Ratliff cites in his conclusion (less than 10% of the 183 publications included in the entire Resource Letter) are listed below.

14. Radiation Oncology—A Physicist's Eye View, Michael Goitein (Springer Science+Business Media, LLC, New York, 2008).

15. The Physics of Radiology, Harold Elford Johns and John Robert Cunningham, 4th ed. (Charles C. Thomas, Springfield, Illinois, 1983).

16. The Physics of Radiation Therapy, Faiz M. Khan, 3rd ed. (Lippincott Williams and Wilkins, Philadelphia, PA, 2003).

17. The Modern Technology of Radiation Oncology—A Compendium for Medical Physicists and Radiation Oncologists, Vols. 1 and 2, edited by Jacob Van Dyk (Medical Physics, Madison, WI, 1999 and 2005).

18. Handbook of Radiotherapy Physics—Theory and Practice, edited by P. Mayles, A. Nahum, and J. C. Rosenwald (Taylor & Francis, New York, 2007).

19. Introduction to Radiological Physics and Radiation Dosimetry, Frank Herbert Attix (Wiley-VCH, Weinheim, Germany, 1986).

26. Radiation Physics for Medical Physicists, E. B. Podgorsak (Springer-Verlag, New York, 2006).

30. Radiation Therapy Physics, William R. Hendee, Geoffrey S. Ibbott, and Eric G. Hendee, 3rd ed. (Wiley, Hoboken, NJ, 2005).

91. Atoms, Radiation, and Radiation Protection, James E. Turner, 2nd ed. (Wiley, New York, 1995).

92. Introduction to Health Physics, Herman Cember and Thomas E. Johnson, 4th ed. (McGraw-Hill Medical, New York, 2009).

153. Radiation Oncology Physics: A Handbook for Teachers and Students, edited by E. B. Podgorsak (International Atomic Energy Agency, Vienna, 2005). (www-naweb.iaea.org/nahu/dmrp/pdf_files/ToC.pdf)

By the way, if you look in the acknowledgments of Ratliff’s publication you will find the ubiquitous Russ Hobbie among those thanked for their helpful suggestions.

Friday, August 21, 2009

The ECG Dance

In Chapter 7 of the 4th edition of Intermediate Physics for Medicine and Biology, Russ Hobbie and I describe the electrocardiogram. I always thought that the best way to teach the ECG was an online cardiac rhythm simulator. But now, thanks to a tip from my former student Debbie Janks, I have found an even better way to teach the ECG. Check out this video on youtube. I will have to try this myself next time I teach Biological Physics.

Friday, August 14, 2009

The Bell Curve

I was browsing through the 4th Edition of Intermediate Physics for Medicine and Biology the other day (I do this sometimes; don’t ask why), and I noticed the footnote at the bottom of page 566 in Appendix H: The Binomial Probability Distribution, which states
“See also A. Gawande, The bell curve. The New Yorker, December 6, 2004, pp. 82-91.”
I thought to myself, “that must be one of the changes Russ Hobbie made when we were preparing the 4th edition, because I don’t remember ever reading the article.” Well, if Russ recommends it, then I want to read it, so I found the article on the web. It turns out to be a lovely, well-written piece about cystic fibrosis (CF), modern medicine, self-evaluation, and striving for excellence. The excerpt below is the one Russ probably had in mind when he added the citation of the article to our book. It describes a discussion between a teenage CF patient, Janelle, her physician Dr. Warwick, and the article’s author Atul Gawande, who is a surgeon and was observing Janelle’s interview as part of an effort to improve cystic fibrosis care. In the quote below, Janelle’s doctor is speaking.

"Let’s look at the numbers,” he said to me, ignoring Janelle. He went to a little blackboard he had on the wall. It appeared to be well used. “A person’s daily risk of getting a bad lung illness with CF is 0.5 per cent.” He wrote the number down. Janelle rolled her eyes. She began tapping her foot. “The daily risk of getting a bad lung illness with CF plus treatment is 0.05 per cent,” he went on, and he wrote that number down. “So when you experiment you’re looking at the difference between a 99.95-per-cent chance of staying well and a 99.5-per-cent chance of staying well. Seems hardly any difference, right? On any given day, you have basically a one-hundred-per-cent chance of being well. But”—he paused and took a step toward me—“it is a big difference.” He chalked out the calculations. “Sum it up over a year, and it is the difference between an eighty-three-per-cent chance of making it through 2004 without getting sick and only a sixteen-per-cent chance.

He turned to Janelle. “How do you stay well all your life? How do you become a geriatric patient?” he asked her. Her foot finally stopped tapping. “I can’t promise you anything. I can only tell you the odds.”

In this short speech was the core of Warwick’s world view. He believed that excellence came from seeing, on a daily basis, the difference between being 99.5-per-cent successful and being 99.95-per-cent successful. Many activities are like that, of course: catching fly balls, manufacturing microchips, delivering overnight packages. Medicine’s only distinction is that lives are lost in those slim margins.

The article describes how one CF center began measuring its own success against the top programs in the country, and their efforts to improve. Gawande concludes

”The hardest question for anyone who takes responsibility for what he or she does is, What if I turn out to be average? If we took all the surgeons at my level of experience, compared our results, and found that I am one of the worst, the answer would be easy: I’d turn in my scalpel. But what if I were a C? Working as I do in a city that’s mobbed with surgeons, how could I justify putting patients under the knife? I could tell myself, Someone’s got to be average. If the bell curve is a fact, then so is the reality that most doctors are going to be average. There is no shame in being one of them, right?

Except, of course, there is. Somehow, what troubles people isn’t so much being average as settling for it. Everyone knows that averageness is, for most of us, our fate. And in certain matters—looks, money, tennis—we would do well to accept this. But in your surgeon, your child’s pediatrician, your police department, your local high school? When the stakes are our lives and the lives of our children, we expect averageness to be resisted. And so I push to make myself the best. If I’m not the best already, I believe wholeheartedly that I will be. And you expect that of me, too. Whatever the next round of numbers may say.”

Friday, August 7, 2009

Technetium Shortage....Again

Readers of this blog (are there any?) may recall two earlier entries on December 14, 2007 and the May 23, 2008, when I discussed a shortage of technetium for medical imaging. It seems that this problem just won’t go away. According to a recent article in the New York Times, we are once again experiencing a global shortage of technetium, caused by the shutdown of nuclear reactors in Canada and the Netherlands. I fear that although the current shortage may be temporary, disruptions of the supply of technetium will reoccur with increasing frequency as nuclear power plants age. A reactor dedicated to technetium production in the United States would go a long way toward solving the problem, but would be expensive.

Russ Hobbie and I discussed technetium in the 4th Edition of Intermediate Physics for Medicine and Biology. Technetium-99m--the key isotope of technetium for medical imaging--is a decay product of Molybdenum-99, which in turn is a nuclear fragment that is produced during the fission of uranium. It is widely used in part because its 140 keV gamma emission and its 6 hour half life are particularly suited to nuclear medicine diagnostic procedures. 99mTc is often combined with other molecules to make radiopharmaceuticals, such as 99mTc-sestamibi and 99mTc-tetrofosmin, that can have very specific effects as tracers. For more about the discovery of technetium, see the March 13, 2009 entry of this blog.