For Medscape's 20th anniversary, radiologist Dr Saurabh Jha reviews the evolution in medical imaging, from the humble chest x-ray to CT, and how imaging became the poster child for healthcare waste.
"The past is a foreign country: they do things differently here" begins L.P. Hartley's novel The Go-Between. The past in radiology is a foreign planet. Patients drank barium milkshakes, not known for their delectable taste, to opacify the bowel. Radiologists then took targeted spot radiographs to display anatomy and reveal pathology. This is not to belittle projectional imaging or its interpreters; the roentgenographic analysis of chest radiographs and barium enemas demands visual intelligence, perception, deep knowledge of pathology and, most important, clinical context.
As a medical student, I realized that context makes a radiologist. I sought a second opinion on a chest radiograph of a dyspneic male. The first opinion was mine: "That's a chest x-ray." After hearing the history, the radiologist asked, "Did you say he has a sick budgie?" I ran to the ward and changed my diagnosis to psittacosis, which the patient had. I became known as the medical student "who knows something about parrot fever." The chest x-ray and the radiologist were symbiotic. Each allowed the other to shine. The radiologist saw shadows which no one else could see, leaving some wondering whether "fluffy opacities" were not fluffy figments of a radiologist's imagination. The radiologist was the ventriloquist to the chest x-ray, allowing it to speak.
Perhaps this is an apocryphal story. The raucous genius Ben Felson, chest radiology's titan, while lecturing once about interstitial lung disease, found that his slides were mixed up, meaning that all of the images were out of sync with the diseases. He casually shrugged his shoulders and said, "Interstitial lung diseases—they all look the same."
CT: The Second Helix to Transform Medicine
CT was adopted not because radiographs weren't good enough but because CT was too damn good. CT advanced, gingerly at first, with "step and shoot" or axial scanning. Acquisitions took so long that patients had to hold their breath almost as long as a free diver.
The slip ring, an engineering feat of genius and modest simplicity, shifted the paradigm. CT scans rotated and translated simultaneously, creating a spiral acquisition pattern. "Spiral" is incorrect, technically; it's actually helical, which is befitting: CT is the second helix to have transformed medicine. Detectors increased in multiples of two, creating multidetector CT. Gantries rotated faster. Table speed increased. It was like taking broader panoramic shots from faster-moving trains using cameras with faster shutter speeds.
Vendors outdid each other with detectors—an arms race of sorts. After the Radiological Society of North America's trade show, I could no longer recall one machine from another. Technology had reached its asymptote. Once, after I lectured on the strengths of various CT scans, a radiologist asked which vendor he should choose. "Flip a coin," I replied. He wasn't pleased with my answer. With so many detectors, CT need not move. CT can cover the whole heart, or kidneys, or brain with a hop, step, and a jump. From helical CT we're back to axial scanning. We have come full spiral.
With more body in the same time zone because of faster acquisitions, and with fast delivery of contrast by power injectors, we saw arteries with mind-boggling clarity. CT, the choice for pulmonary embolism (PE) and vascular disease, restricted catheter angiograms to the needy and then relegated them to needless.
Once bothered by the diaphragm's motion, CT now freezes cardiac motion at high heart rates. Thanks to 3D platforms, we can follow tortuous coronary arteries along their curvature so that narrowing is accurately measured. Such advances would have been pointless without digitization, the picture archive and computing system (PACS). If radiologists were hanging thousands of sub-millimeter images on a view box, it is unlikely that we would have demanded finer resolution and more films to hang.
MRI Playing Catch-up
In 1995, you would have been forgiven for believing that radiology was doomed by Hillarycare, and for betting on MRI over CT. MRI's value proposition is soft tissue contrast. MRI tells tissues apart. MRI sees water, or edema—acute pathology's mark of Zorro. MRI sees fingerprints of disease which CT simply can't see. In the brain, bones, liver, and heart, MRI reveals and imposes. Mr Jones no longer "might have had a stroke." MRI makes it clear whether Mr Jones had a stroke or not.
Hardware gives MRI its strength. But MRI became stronger because it played with—cheated, actually—a phantom zone known as k-space. Cleverness is MRI's curse. Just like overachievers, MRI developed an identity crisis. It tried beating CT in imaging of pulmonary and coronary arteries, but it failed. It's trying to beat echocardiography in measuring the heart's physiology, and it isn't succeeding. Recently, MRI merged with PET, which leaves one doubly stunned—stunned by the costs, stunned by the futility.
Also stunning is our envying pathology. Anatomical pathology, I can understand. The pathologist is the last word. Envy over chemical pathology puzzles. A movement in radiology is emerging which, troubled by the vicissitudes of judgment and variations inherent in judging, wants numbers to arbitrate health and disease. Radiology reports increasingly resemble the uniform rendition of a basic metabolic panel.
Mammograms and Cost Containment
The art of medicine has relented to precision—pseudoprecision, to be precise. What art, you ask? Length, intensity, and attenuation: Was not imaging always about numbers? It was said that a radiologist with a ruler is a radiologist in trouble; a radiologist with several rulers is a radiologist commoditized.
With digitization came teleradiology. When radiologists in Philadelphia slept, Bangalore woke up. What the sleeping radiologists didn't realize was that if you can send the acute diverticulitis case to a radiologist in India at 3 AM, then why not also send the lung nodule at 3 PM?
Radiologists are like TSA agents, hunting fastidiously for that needle in a haystack, permanently on orange alert for lung nodules and other slowly ticking bombs. Better safe than sorry, says society. Affluence and anxiety are reliable bedfellows. We prefer not to fall sick if we can avoid it. But, preemptive strikes cause collateral damage. Screening's collateral damages, false positives and overdiagnosis, have made mammography controversial.
As the Affordable Care Act covered more people, the mammography debate reached its apotheosis. The debate was confined to medicine's rational skeptics. It dare not be political. The one thing Democrats and Republicans agree about is mammograms: We need more, not less, screening. Meanwhile, screening has become radiology's raison d'être, the treatment effect, the proof that imaging saves lives, the link between the radiologist in a dark room and the people.
With Greater Imaging Comes...
Radiology changed clinical medicine, but not like Semmelweis, Pasteur, or Salk. It did so by shining light, a light which brightens our view but darkens our path.
Were it not for advances in imaging, it is unlikely that thrombolytics would be used for acute stroke. Better imaging allowed electrophysiologists to ablate tiger territories for ventricular tachycardia; oncologists to fret about nonresponders to chemotherapy; transplant surgeons to carry on transplanting; and emergency medicine to grow into an efficient, Emergency Medical Treatment and Active Labor Act (EMTALA)-abiding healthcare machine. Cars are getting better even if they're still not flying.
Imaging dared physicians and it scared physicians. Woe betide the surgeon who takes out a normal appendix. Appendicitis is a tricky diagnosis. It was tricky 20 years ago. CT made it trickier by teasing the physician: "I know the answer. I know you want me to tell you. Just ask. Just click the box to order. You know you want to." Imaging reduced uncertainty as it generated uncertainty—supplier-induced uncertainty. Strictly speaking, this is more regret than uncertainty. How would you feel if you missed a PE when the patient could so easily have had a CT? Imaging clarified but confused. Imaging revealed too much, too soon. It unleashed a river of "incidentalomas." Imaging increased our knowledge but widened our ignorance. Imaging defined new disease but invented pseudodisease. Imaging enriched radiologists financially but impoverished them clinically.
I was once asked to rule out a PE and an occlusion of the femoral artery in a patient. With a bit of luck this is possible by CT. Imaging, the globalizer, brought distant body parts so close together that there seemed little value to clinical granularity. Twenty years ago, "triple rule-out" was unheard of, but today it is a feat of technology. Physicians can exclude aortic dissection, PE, and acute coronary syndrome in one sitting. But to what avail? If we know that the road ahead is straight, what value is a GPS? Mr Jones had a mini stroke in his left parietal lobe. Thank you, diffusion-weighted MRI. Now what?
Policymakers, fearing that imaging's upward trajectory would bankrupt Medicare, told us to "clip its wings" without specifying which patients' wings. Imaging became a poster child of waste, of imprudence, of greed in an overmaligned payment structure. Why is imaging demonized? Because it is everywhere. Imaging is the mirror, mirror on the wall. We despise it because it tells us that clinical medicine sucks for not delivering the utopian precision to which we believe we're entitled.
Imaging is a rite of medical passage. Imaging makes right the passage of feeding tubes, central lines, and endotracheal tubes. We needed imaging to declare disease. We still do. We now need imaging to declare health. If imaging has no bounds, it is because our insecurities have no bounds.
What happened to the chest x-ray? It's still standing but has lost gravitas. It no longer diagnoses psittacosis; rather, the chest x-ray parrots "diffuse airspace process, blood, pus or edema; correlate clinically." If pushed, it sputters "pneumonia not excluded." If pushed further, it finally relents "recommend chest CT." It is in the chest x-ray that the soul of its ventriloquist lies.
Medscape Radiology © 2015 WebMD, LLC
Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Clarity and Uncertainty: 20 Years of Radiology - Medscape - Jun 11, 2015.