· New Imaging Technique Rivals Liver Biopsy
· Panel Finds More CT Education Needed

New Imaging Technique Rivals Liver Biopsy

Researchers have shown that a new magnetic resonance-based imaging technique developed at the Mayo Clinic can help identify liver fibrosis noninvasively without the need for biopsy. Using this technique, termed magnetic resonance elastography (MRE), an image called an elastogram is produced. The elastogram is color-coded to represent the organ’s elasticity or stiffness, with red indicating that a region is stiffest and violet indicating that a region is most flexible.

Jayant Talwalkar, MD, MPH, a coinvestigator on the study and Mayo Clinic hepatologist, explains, “A healthy liver is very soft, while a liver with early disease begins to stiffen. A liver with cirrhosis, advanced liver disease, can be rock hard.” This is due to the formation of fibrous scar tissue in the damaged liver. Thus, a stiff liver is an indicator of disease. But what makes a measure of elasticity so valuable is its strong correlation with pathologic processes and the wide range of values it takes, thus allowing diagnosis in the early phases of disease.

Talwalkar stresses the importance of early diagnosis: “Our goal in hepatology is to be able to diagnose liver disease early so that novel as well as established therapies can be provided to our patients.” Often, these treatments, accompanied by lifestyle changes, can halt the progression of hepatic fibrosis to eventual liver failure, which would require major transplant surgery.

The study, performed by Mayo Clinic researchers on 113 patients ranging in age from 19 to 78 and with weight from normal to obese, showed the detection of liver disease by MRE compared favorably with the industry’s current gold standard: liver biopsy. MRE detection of cirrhosis was 88% accurate compared to biopsy, while patients with nonalcoholic fatty liver disease but no significant inflammation or fibrosis were identified correctly 97% of the time.

“Results showed that elastography was highly accurate in detecting moderate to severe hepatic fibrosis even with variety in age, types of liver disease, and body size,” Talwalkar said. “Using MRE, we can confidently avoid liver biopsies for patients with no evidence of advanced fibrosis, as well as for patients with cirrhosis.”

Richard Ehman, MD, lead researcher on the MRE project, highlighted some of the potential issues with liver biopsy, saying, “In a needle biopsy, we obtain a tiny specimen of liver tissue, and we then need to assume that it reflects the condition of the entire organ. The procedure is invasive and not without potential complications such as bleeding and infection—and the accuracy of liver biopsy is affected by the sampling tissue.” This can lead to an underestimation of the degree of hepatic fibrosis.

On the other hand, Talwalkar notes, “For patients with cirrhosis, MRE does not appear to misclassify [them] as having lesser degrees of fibrosis.”

The MRE technology itself uses “shear waves” delivered to the liver by a drum-like device placed against the body. This device is powered by a remotely located low-frequency audio speaker. The shear waves impart mechanical energy to the liver, slightly displacing the region it is passing through. Using a modified phase contrast gradient echo MRE sequence that includes motion-sensitizing gradients synchronized to the drum frequency, the different displacements and, hence, elasticities within the liver can be quantified.

The technique is so sensitive that it can reveal cyclic motions smaller than the wavelength of light while acquiring these elastograms in less than a minute.

Similar MRE techniques are currently being investigated for application in the breast, thyroid, skeletal muscle, and brain.

—Ed Wilson

Panel Finds More CT Education Needed

Medical imaging and radiation therapy professionals need more education about CT operation, application, and dose, according to an industry panel cosponsored by the American Society of Radiologic Technologists (ASRT) and the American Registry of Radiologic Technologists (ARRT).

A 32-member panel of experts discussed how the rapidly evolving role of CT in health care will affect future education and practice needs.

The 32-member panel of experts in health policy, CT manufacturing, clinical practice, and education met in August 2007 and April 2008 to discuss how the rapidly evolving role of CT in health care will affect future education and practice needs.

“Five years ago, we would have considered CT to be a specialty area,” said Myke Kudlas, director of instructional technology in the ASRT education department. “But now it’s really becoming a core area of radiology because it touches every other modality.”

The panel discussed how the emergence of CT will affect the roles of radiographers, nuclear medicine technologists, and radiation therapists; the impact of these changing roles on education and certification; and related safety, health policy, and regulation concerns.

“Because the technology continues to expand so quickly and exponentially, the technologist’s challenge is keeping up with the rapid pace of growth in the field,” Kudlas said.

Currently, many techs receive on-the-job training in CT operation from their peers. The panel recommends more formalized education that will give imaging professionals a more thorough understanding of the science behind the technology.

“On-the-job training is good, but the thing that’s always been missing is the theory behind the technology—learning about the radiation protection, learning about the radiation physics and biology,” says Michael Delvecchio, RT(R), a member of the ARRT Board of Trustees and technical director of the Department of Radiology for Brigham & Women’s Hospital in Boston.

Developing this education means paying attention to the different roles of different imaging professionals. “Sometimes the physics of what the nuclear medicine tech is learning is not the same physics as the CT tech is learning,” Delvecchio said.

The key is to focus on the national curriculum. “There has to be a shift in the national curriculum for the education of the operators, and I think that’s beginning to happen,” Delvecchio said. “We’re seeing a lot of crossover into basic principles being incorporated into curricula for nuclear medicine technologists, radiation therapists, and radiographers.”

By giving professionals such as radiographers more formal CT training in national programs, many will graduate with a basic knowledge of CT operation. “A lot of CT content is being put into the general radiography curriculum,” Kudlas said. “Now, radiographers are going to be able to come right out of a radiography program and have a foundational understanding of CT.”

In addition to these programs, vendors and professional societies will continue to play a role in furthering CT education. For example, the ASRT has recently begun podcasting educational programs to disseminate information more quickly.

Plans for formal CT education efforts will take time to develop and finalize. In the meantime, Delvecchio recommends that imaging professionals seek out local resources, such as online courses offered through community colleges, to further their understanding of CT technology and the science behind it.

“It’s really important not to become overreliant on just the equipment,” he said. “They need to know the background; they need to know the theory, the physics.”

A consensus paper titled “Computed Tomography in the 21st Century: Changing Practice for Medical Imaging and Radiation Therapy Professionals” contains the panel’s full recommendations. It is available (as a downloadable pdf) on the ASRT Web site at www.asrt.org/CTconsensus and on the ARRT Web site at www.arrt.org/CTconsensus.

—Ann H. Carlson