Sunday, February 28. 2010
Through her Little House series of books, author Laura Ingalls Wilder became one of the leading exponents of self-reliance. The original eight volumes depict life growing up on a frontier family homestead during the 1870s and 1880s. I first read these books as an adult, fascinated by Ingalls Wilder’s description of how her father built a log cabin in Little House on the Prairie.
Technology is, at its most basic level, simply the application of knowledge. Ingalls Wilder’s books are filled with great examples of how resourceful pioneers lived off the land, worked out a system of division of labor with their neighbors, and overcame adversity. A log cabin is hardly what anyone would consider advanced technology, but it demonstrates how a little knowledge plus simple materials provided by nature can be used to great effect. Though it seems Ingalls Wilder’s father moved the family whenever he felt their current location was getting too crowded, at one point he worked for a railroad, and the family benefitted from transportation technology both as a source of supplies and for access to distant markets. Ingalls Wilder’s daughter Rose Wilder Lane would later take advantage of another technology, the printing press.
Today’s technology should be a much greater enabler of individualism—and to some extent it is. Think of the Internet as virtual printing press and virtual railroad rolled into one. However, the ability to make a living on your own is endangered by tax increases, copyleft, inflation, open source, net neutrality, and crony capitalism. And the reason is simple: many of our leaders have discovered that it is easier for them to amass unearned power and wealth under collectivism.
Saturday, February 27. 2010
This post is the sixth in a series based on my soon-to-be published book, The History & Future of Medical Technology. Each week I’ll present highlights from one of thirteen chapters.
Demystifying MRI
Experienced patients know some of the differences between “CAT scans” and “MRIs.” CAT scans are generally fast and easy, but you don’t want to have them repeatedly, because they use x-rays. MRIs are often not as pleasant; you are asked a lot of questions, and then they slide you into a very narrow tube, where you’ll stay for about an hour—assuming you don’t scream “Get me out of here!” before the scan is finished. Whether a CAT scan or MRI is prescribed depends on what your doctor is looking for. Both are expensive.
Perhaps the best way to understand the MRI machine is to compare it with the x-ray machine and CAT scan machine.
A traditional x-ray picture is made by aiming parallel x-ray beams at your body. A piece of film records the amount of x-ray energy that makes it through to the other side. In other words, the image on an x-ray film is a shadow.
A CAT scan also uses x-rays, but with a major twist. Pretend that your body is at the center of a big wheel with spokes. Now imagine that half of the spokes are x-ray beams heading towards your body and the other half of the spokes are the x-ray beams that passed through your body and are heading towards detectors distributed around the edge of the wheel. And yes, the wheel rotates.
Unlike a traditional x-ray, a CAT scan image is not a shadow. Because the x-ray beams rotate around your body, it’s possible to calculate the relative density of specific points inside your body. The result is a finely detailed image of a cross-section of tissue. Repeat the process for adjacent tissue slices, and a three-dimensional image can be constructed.
MRI uses magnetic fields and radio signals instead of x-rays. The first thing you must understand is that the nuclei of many (but not all) types of atoms behave like little magnets. When you get an MRI, you are placed in a very strong magnetic field that causes the little magnets (nuclei) to line up with each other. Actually, just over half line up face forward, and just under half line up face backward. Now, if you turn on a relatively weak radio signal at the right frequency, then it will make a bunch of the little magnets flip around; turn the radio signal off again, and the nuclei gradually return to equilibrium.
What good is this? You may recall from high school physics that thrusting a magnet in and out of a coil of wire produces an electric current in the coil. Similarly, if you can make the nuclei of many atoms swing around in unison, they will produce a signal that can be detected by a coil.
Now that we have a signal, is there any way to extract more information? Yes. One thing I didn’t mention is that the frequency of the radio signal can be set to resonate with a specific type of atom. The most popular choice is hydrogen, because the body is largely composed of water. Another thing I didn’t mention is that if we superimpose a gradient magnetic field on the very strong magnetic field, then there will be slight differences in field strength at each point in the body. We can use these differences to localize the data.
OK, now we can detect the strength and location of the hydrogen signal. Luckily, the signal also varies depending upon the composition of the surrounding tissue. Plus, what I just described is the T1 signal; there is also a related T2 signal. (My book explains more fully how MRI works and how it was developed.)
The original Star Trek television series featured a portable “Tricorder” that could quickly scan a patient—human or alien—providing detailed, on-the-spot diagnosis. A portable device employing MRI’s basic operating principles and using a planet’s ambient magnetic field is not only conceivable, it’s already available for applications such as emergency medicine. Nor is the incredible wealth of data and sophisticated analysis depicted on Star Trek inconceivable. We have only just scratched the surface in exploiting MRI.
Next time: The Nuclear Option
Note: If you would like to be notified when The History & Future of Medical Technology is published, please go to Telescope Books and enter your email address in the newsletter sign-up field on the left menu bar. This email list is only used to announce book offers from Telescope Books; your email address will not be shared with third parties.
Tuesday, February 16. 2010
This post is the fifth in a series based on my soon-to-be published book, The History & Future of Medical Technology. Each week I’ll present highlights from one of thirteen chapters.
The First Cyborgs
The human heart is one of nature’s engineering masterpieces. This modest size organ, a little larger than its owner’s fist, is actually two pumps; one for circulating blood through the lungs where it picks up oxygen and the other for supplying the oxygenated blood to the body. The heart pumps a huge volume of blood during a lifetime, roughly 200 million liters in 75 years, beating two to three billion times without downtime. The heart is also amazingly efficient, feeding itself enough oxygenated blood to meet its own energy requirements. But it all depends on a precision pacing system. When its electric clockwork goes bad, the heart can beat too slowly, too rapidly, or too irregularly.
The implantable pacemaker is one of mankind’s engineering masterpieces. This small device, much smaller than its owner’s fist, is a kind of metronome for the heart, helping it keep proper rhythm. As the pioneer implantable device, the cardiac pacemaker has taught researchers invaluable lessons about designing enclosures, power sources, electrodes, and wires for the body’s internal environment. These lessons have been exploited by subsequent devices such as cochlear implants, diaphragm pacemakers and deep brain neurostimulators.
The path that led to today’s pacemakers and implantable cardiac defibrillators presents crucial lessons. For starters, great technology is often the product of incremental advances made in the face of extreme skepticism, indifference, and even opposition. Second, nature offers shortcuts to those who possess the optimism and determination to look for them. Third, there are often simple solutions to seemingly intractable problems.
We take pacemakers for granted today, but not that long ago people died from heart block—the heart’s inability to reliably deliver the electrical signals from its natural pacemaker to its main pumping chambers, the ventricles.
The first solution to this problem was for many patients worse than the disease. External pacemakers paced the heart by delivering nasty shocks to the chest. Patients jumped with each beat; suffered burns where the electrodes touched the skin; and were tethered most of the time to standard power outlets. Some patients turned their external pacemakers off, preferring death.
The second solution was to attach the electrodes directly to the heart. This was major surgery with its long recovery time, discomfort, and risks. Surgeons found that the voltages required to pace the heart with implanted electrodes rose over time. Several advances were necessary to bring that problem under control. Making sure the electrodes were ultra-clean was one of them.
Finally, researcher Seymour Furman discovered how to use catheters to deploy the electrodes, making pacemaker implantation a relatively minor procedure. Here was nature’s shortcut.
But it’s the convergence of biological and artificial solutions that could make cyborgs of most of us in the future. A technology called cell encapsulation promises to augment or replace failing organs. Transplanted cells are placed inside a capsule with a semi-permeable membrane. The cells could, for example, produce insulin while being protected against immune rejection. Such a device could be combined with a continuous glucose monitor.
As such devices proliferate, it may become hard to tell where the machine ends and the human begins.
Next time: Wireless Chemistry
Note: If you would like to be notified when The History & Future of Medical Technology is published, please go to Telescope Books and enter your email address in the newsletter sign-up field on the left menu bar. This email list is only used to announce book offers from Telescope Books; your email address will not be shared with third parties.
Saturday, February 13. 2010
Steve Jobs expressed something that many of us have felt for a long time when he proclaimed that Google’s “Don’t be evil” mantra is BS. Google’s corporate motto makes us uneasy, but it’s hard to say exactly why. Even Jobs only managed to lash out—missing an opportunity to clarify an important issue.
“Don’t be evil” sets the bar way too low. Some deeply religious individuals may consider all unethical behavior evil, but most people reserve the word “evil” for extreme acts—the kind that inflict pain or involve violence. “Don’t be evil” leaves the door open to things you know are wrong but somehow manage to rationalize.
“Don’t be evil” is way too vague. People have debated what types of behavior are and are not ethical since the beginning of recorded history. Most organizations that care about what’s right go to much greater pains to stipulate what’s wrong. Often that means establishing and promulgating a code of ethics. Life, including business life, presents us with many ethical dilemmas and it helps to have guidelines to remind us of what’s expected in different situations.
“Don’t be evil” is way too subjective. People may disagree about whether a specific act is evil or just in bad taste—particularly if one happens to be the offender and the other happens to be the offended. It also leaves it entirely up to individuals to decide whether it’s OK to do something bad as a means of accomplishing something good.
They say the road to Hell is paved with good intentions. Socrates taught that doing the right thing is not a matter of intention but a matter of knowledge. With its “Don’t be evil” motto, Google does more to sidestep ethical issues than to set a worthy standard.
This post is the fourth in a series based on my soon-to-be published book, The History & Future of Medical Technology. Each week I’ll present highlights from one of thirteen chapters.
Reverse Engineering the Human Body
Companies often use reverse engineering to keep pace with competitors. Instead of copying products, which would likely violate patents, engineers figure out how to imitate the competitors’ products. Reverse engineering is likewise a powerful tool for medicine, because while restoring even partial function can be immediately beneficial, it may be a long time before we understand the underlying natural processes well enough to recreate them.
Through the process of reverse engineering, biomedical engineers are learning how to alleviate pain, prevent seizures, repair the senses, restore involuntary muscle function, and re-enable voluntary muscle function.
Many great inventions were the result of reverse engineering: the battery, artificial pacemakers, and implantable cardiac defibrillators are good examples, all of which involved bioelectricity.
Reverse engineering is a two-step process. This first step is to acquire an accurate and reliable understanding of the target’s external behavior. The second step is to design and construct a device that behaves similarly. (An important exception: an implantable cardiac defibrillator does not behave like a heart’s electrical system, but restores a heart’s electrical system to its normal behavior.)
Chapter 4, “Human Electricity,” chronicles the first phase of the process, focusing on the development of electrocardiography and 3D cardiac mapping. It’s a fascinating bit of history. In essence, medical researchers discovered that the behavior of the heart’s electrical system could be monitored and analyzed based on electrical signals appearing on the surface of the skin.
The first electrocardiograph was actually a frog’s innervated gastrocnemius muscle as described here. In 1856, Heinrich Muller and Rudolph von Kolliker used what became known as the rheoscopic frog to show that electric currents are produced during the heartbeat. The sciatic nerve of the rheoscopic frog was laid across the beating ventricle of another frog’s heart. They observed one and sometimes two contractions of the rheoscopic frog’s leg muscle with each beat. That’s right: The first electrocardiogram was displayed as a twitching frog muscle.
No one was going to lay a frog’s sciatic nerve across the beating ventricle of a human heart. Needed was a device sufficiently sensitive and fast-responding to detect the signals generated by the heart’s natural pacemaker at points on the skin. Such a device, the capillary electrometer, was invented by Gabriel Lippmann in 1872. Lippmann placed mercury and then dilute sulfuric acid in a U-shaped glass tube. Inserting wires at either end, the interface between the mercury and sulfuric acid changed shape in response to tiny, fast-changing electrical currents.
William Einthoven showed that a mathematical correction had to be applied to the capillary electrometer tracing in order to get the actual electrocardiogram. Einthoven went on to develop an instrument that directly displayed the actual electrocardiogram: the string galvanometer. Einthoven also identified the segments in a normal electrocardiogram, labeling them PQRST, and defined the standard electrocardiograph leads. Because his laboratory was about one mile from the nearest hospital, he even developed a way to acquire electrocardiograms over a phone line.
The electrocardiogram has become a standard diagnostic tool. It also helped guide development of artificial pacemakers and implantable cardiac defibrillators, as discussed in the next chapter.
In medicine, reverse engineering may be a waypoint rather than the final destination. With 3D cardiac mapping and ablation systems it’s sometimes possible to re-engineer the heart’s electrical system. Today, ablation is a common treatment for tachycardia (very rapid heart beat). Electrophysiologist Jason Jacobson at Northwest Memorial Hospital suggests that in the future we may use tissue engineering to treat heart block (very slow heart beat).
Next time: The Rhythm of Life
Note: If you would like to be notified when The History & Future of Medical Technology is published, please go to Telescope Books and enter your email address in the newsletter sign-up field on the left menu bar. This email list is only used to announce book offers from Telescope Books; your email address will not be shared with third parties.
Saturday, February 6. 2010
This post is the third in a series based on my soon-to-be published book, The History & Future of Medical Technology. Each week I’ll present highlights from one of thirteen chapters.
Fantastic Voyage
In the 1966 movie Fantastic Voyage (starring Stephen Boyd and Raquel Welch), a crew including two doctors boards a submarine which is miniaturized using new technology and injected into a scientist’s body on a mission to remove a life-threatening blood clot.
We are closer to doing this than you might think. Virtual endoscopy lets physicians fly through the body using three-dimensional computed tomography (CT). Conventional endoscopy (minimally invasive surgery) is being enhanced with surgical robotics and high resolution video. Swallow Given Imaging’s PillCam, and doctors can examine your gastro-intestinal tract.
19th century physicians were thwarted even when they tried to peer inside the living eye--an open window. Hermann Helmholtz knew that others were illuminating the eye from one side and trying to catch a reflection from the other side. Instead, Helmholtz positioned himself as close to the line of the incident light as possible, and was able to catch just enough of the light bouncing back to the source to see the retina through a lens. His invention, the ophthalmoscope, was an immediate hit.
Wilhelm Roentgen’s discovery of x-rays was more disruptive. Roentgen placed some coins in an opaque, wooden box and produced an x-ray photograph showing the coins. When news of Roentgen's discovery spread, people feared they would need lead-lined underwear. (They would never get past today’s airport security with that, however.) Suddenly, it was possible to see through solid objects.
The first medical x-rays required long exposures and physicians were ignorant of the dangers. Thomas Edison’s assistant Clarence Dally died from overexposure and Edison terminated his x-ray research. Ironically, Michael Pupin used one of Edison’s inventions, a fluorescent screen, to dramatically reduce exposure times. An x-ray photograph that had required one hour could now be taken in a few seconds.
Conventional x-rays were good for examining bones but not soft tissues. An Austrian mathematician, Johann Radon, developed a way to calculate 3D images from a series of imaginary pencil beams. Radon's scheme offered a way, at least on paper, of visualizing soft tissues.
The British company EMI made a fortune producing the Beatles’ records and, therefore, it's said that the group contributed to the development of CT scanners. That’s a bit of a stretch. EMI engineer Godfrey Hounsfield came up with the idea of producing 3D x-rays of the head while relaxing in the country. EMI turned down Hounsfield’s request for funding, but when he obtained funding from a government agency he was allowed to conduct the research at EMI’s facilities. Unfamiliar with Radon’s technique (now known as “back projection”), Hounsfield used brute force math, and managed to secure orders for three CT scanners.
When Nuclear Magnetic Resonance imaging was introduced a few years later, some feared that “NMR” meant “No More Roentgen.” NMR had its own public relations problem—use of the word “nuclear”—and is now known as Magnetic Resonance Imaging (MRI). While MRI doesn’t use x-rays, scans can take an hour or longer. CT is much faster.
Before Roentgen, the inside of the living body was so tantalizingly close—and yet so inaccessible. Now, by combining computed tomography with stereotactic radiosurgery it’s possible to not only look inside the body from the outside, but to perform totally non-invasive procedures. Which is good thing, because that way there’s less risk of getting trapped inside the body as almost happened to the crew of the fictional submarine in the movie Fantastic Voyage.
Next time: Human Electricity
Note: If you would like to be notified when The History & Future of Medical Technology is published, please go to Telescope Books and enter your email address in the newsletter sign-up field on the left menu bar. This email list is only used to announce book offers from Telescope Books; your email address will not be shared with third parties.
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