The Picture of Health
Written by Peter A. Buxbaum
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Medical imaging has improved diagnoses, treatments and outcomes, but it is not without controversy.
Medical imaging has brought measurable advances to the practice of medicine, say its advocates, because it allows for the examination and treatment of internal organs without surgery. This has had a profound impact on the diagnosis and treatment of heart disease, cancer and other maladies by enabling physicians to provide treatment non-invasively and without blood loss and other related risks. More patients qualify for care, they note, than if surgery were the only option.
The latest innovations in medical imaging rely less on advances in scanning equipment and gadgetry and more on enhancements in the computing power attached to them. Advances in computer renderings of X-ray, CT scan, and magnetic resonance imaging allow clinicians to see clearer and sharper images, to view organ function in real time, to highlight aspects of images of most interest to them, and to inspect the anatomy and physiology of organs at the same time.
But the phenomenon of medical imaging is not without controversy. A 2005 U.S. Congressional report concluded that imaging was being used too frequently, and that its increases in costs were not justified, within the Medicare system. (See sidebar.) As a result, Congress, in an effort to reduce the fiscal year 2007 federal budget deficit, decided to cut back on Medicare reimbursements for imaging procedures, a move now being resisted by imaging advocates.
“Imaging is a central piece of data to be considered amidst all other data to make sure that proper treatment is being delivered,” said Colonel Dr. Allen Taylor, the chief of cardiology at the Water Reed Army Medical Center in Washington. “Imaging makes for good medical practice. It is cost effective and is central to what we do.”
Taylor, speaking at a recent Washington gathering to discuss imaging innovations and Medicare policy, noted that many of his recent patients have benefited from medical imaging. A 31-year old patient diagnosed with a hole in his heart, for example, had the condition repaired non-invasively with guidance from X-ray images. “Ten years ago, this would have required open heart surgery,” Taylor recounted. “The patient would have stayed in the hospital for a week and would have been out of work for six weeks.”
In some cases, medical imaging allows for a quick negative diagnosis. Taylor told of a 61-year old woman complaining of chest pain. Her stress and nuclear imaging tests were normal, allowing her to leave the hospital immediately. “In the past she would have been in for three days of tests,” Taylor related. “This way she left the hospital two days earlier and avoided an invasive catheterization.”
Further, a 70-year old heart attack patient diagnosed with a partially occluded coronary artery was able to have the artery opened with a stent using X-ray diagnostic techniques. “In the past, this would have required open heart surgery,” Taylor noted.
The use of medical imaging in cardiac ablation is emblematic of how technology has aided in the treatment of coronary disease. Ablation is an increasingly prevalent non-surgical procedure being used to treat arrhythmias. Arrhythmias are most often caused by aberrations in cardiac electrical activity.
The procedure involves inserting catheters into a blood vessel and winding the wire up into the heart in order to disable the portion of the muscle that is malfunctioning. The journey to the heart muscle is navigated by images created by a fluoroscope, an X-ray-like machine that provides continuous images of the catheter and tissue.
Taylor diagnosed a 59-year old patient with atrial fibrillation with the use of a CT scan and performed the ablation by importing the CT scan into the ablation console.
Cardiac ablation is successful nearly 100 percent of the time for many kinds of arrhythmias when it is aided by imaging, according to Richard Robb, Ph.D., professor of medical research, biophysics, and computer science at the Mayo Clinic College of Medicine in Rochester, Minn. The record without imaging is around 70 percent. “If I can see it, I can fix it,” is the attitude of many heart surgeons, he said.
“It is a daring procedure,” Robb added, “because you have to pinpoint the site of the arrhythmia.” Advanced CT scans can now create a dynamic, real-time model of a patient’s cardiac electrophysiology and guide the physician to the location of the arrhythmia.
“Not only is this an effective treatment,” said Robb, “but you see treatment results within a few minutes.”
Medical imaging has moved from its beginnings in the late nineteenth century from the twodimensional X-ray, to three-, four-, and even five-dimensional imaging, according to Robb. Four-dimensional imaging refers to the ability to view the functioning of an organ over time. Five-dimensional imaging refers to the ability to fuse the results of different imaging modalities, allowing a clinician to inspect the anatomy and functionality of an organ at the same time.
Advances in medical imaging are largely associated with the ability of computers to better manipulate the images derived from X-ray, CT scan, and MRI machines, and are proceeding along a number of related fronts. The processing challenge involves the enhancement of images to give a three-dimensional rendering of bodily structures. “Computers can now map colors on CT scan images to make very realistic three-dimensional images of bones and soft tissues,” Robb said.
Segmentation allows highlighting of features most of interest to the user in order to put them into sharper relief and under closer inspection. “Even though they look better on the computer, these are still bad images without sharp edges and no boundaries,” Robb explained. “Advances in computing algorithms allow users to isolate and analyze those features of most interest to them.”
Fusion is at the frontier of imaging, Robb said. It involves bringing multiple multimodal images together temporally in order to inspect the anatomy as well as the physiology of a given organ. “With fusion, you tag organs and slice through them” to look for irregularities, Robb said. For example, a fivedimensional cardiac image might segment heart chambers by color and fuse several images together to measure their physiological function. The images might depict heart chamber contractions through changes in color.
Medical imaging now provides clinicians with many other diagnostic and treatment tools, according to Robb. Virtual colonoscopies now noninvasively look through the colon for polyps and malignancies. Imageguided renal angioplasty opens blocked kidney arteries without surgery. Physicians use image-guided embolization to correct uterine fibroid tumors without hysterectomy.
CT and MRI imaging allow doctors to identify the location and nature of a stroke in order guide the treatment choice between surgery and anti-clotting drugs. They use CT and MRI scans, rather than exploratory surgery, to visualize and pinpoint brain tumors and aneurysms, and view them in three dimensions, allowing them to develop better treatment approaches.
In cancer care, physicians use imaging to perform minimally invasive bone biopsies, allowing patients to avoid the complications, long recuperations and extensive scarring associated with surgery. Physicians can also use stereotactic radiosurgery to target narrow and powerful beams of radiation on small brain tumors and early metastases. This substitute for brain surgery requires no hospitalization.
Physicians use ultrasound to identify ovarian cancer earlier and faster. This information allows them to begin treatment before the progression of the disease makes it uncontrollable. During liver cancer surgery, surgeons use ultrasound to help them differentiate between diseased and healthy tissue, thus improving surgical precision, reducing blood loss and speeding healing.
At Walter Reed, Taylor also uses ultrasound to measure the effectiveness of different therapies. “We use imaging as a surrogate for testing the effectiveness of therapies by viewing changes in artery structure,” he explained. “This approach shortens time horizons for patient treatment and recovery.”
Advances in medical imaging, according to Robb, have yielded outcomes that include improved rates of treatment success, reductions in risk and morbidity, less time in procedure and recovery, and higher throughput and fewer costs for hospitals.
“Advanced cardiovascular imaging is already widely available at most Army medical centers,” said Taylor, including the latest in echocardiography, nuclear imaging and cardiac CT scans. “The bottom line is, if it can help deliver the best care, we feel such equipment is a necessity.” Taylor also believes that medical imaging has helped in the military’s ongoing efforts in Iraq. “They have some imaging technology in Iraq,” he said. “They perform stress echocardiograms for every patient not sent out of theater. This saves the costs of evacuating patients to Landstuhl [Regional Medical Center in Germany] and potentially keeps them with their unit to preserve the fighting force in Iraq.” ♦