RESEARCH SHOWS NEW CT TECHNIQUE PROVIDES HIGHER QUALITY IMAGES OF JOINT REPLACEMENTS
May Reduce Radiation Exposure
Embargoed for Release until Wednesday, Aug. 1, 2012
Bonnie Culbertson, PCI
CHARLOTTE, N.C. – A new method of computed tomography (CT) could produce significantly improved images of knee, spine and hip implants, and may lower radiation exposure, suggests preliminary research being presented today at the 54th Annual Meeting of the American Association of Physicists in Medicine (AAPM).
Many of the millions of Americans who receive joint replacements as treatment of arthritis or trauma need CT scans to assess wear, loosening of the prosthesis, fractures or infection, but due to device interference, the images often are tainted by streaks or blurring, which makes diagnosis and assessment of the area around the implant difficult or impossible.
While conventional CT ignores information about the implant, the method developed at Johns Hopkins University called known component reconstruction (KCR) incorporates a computerized model of the implant’s shape and material content into the three-dimensional image reconstruction process. Therefore, KCR yields higher image quality and could reduce radiation exposure. Researchers are currently studying the method in clinical CT systems and assessing its potential for routine use in hospitals.
“Every year more than 600,000 people get total knee replacements, which are among the most difficult implants to image around. We truly need a better way to image knee replacements and other implants, and this method is promising,” said J. Webster Stayman, Ph.D., faculty research associate in biomedical engineering at Johns Hopkins University, Baltimore. “This technique is particularly well-suited for implant assessment because surgeons typically know the specific model of the implant. Getting that information into the imaging system could allow them to clearly see tissues around the implant and measure its exact orientation.”
Researchers tested the method in computer simulations and the laboratory using knee implants – one of the most difficult implants to image – as well as surgical screws and rods used in spinal fixation. The results they are presenting at today’s meeting verify the method using real data and demonstrate that it potentially could be applied generally to CT machines.
“The KCR technique is an exciting advance that combines iterative reconstruction for reduction in radiation dose with strong prior information about implants that are known to be in the image,” said coauthor W. Zbijewski, Ph.D., senior research scientist at Johns Hopkins. “We’re working on extending the technique to situations in which the implant changes shape and applying it for the first time to new CT systems for diagnostic radiology and surgery.”
In addition to Drs. Stayman and Zbijewski, co-authors of the study being presented at AAPM are Y. Otake, J. Carrino, A. Khanna and J. Siewerdsen.
About Medical Physicists
If you ever had a mammogram, ultrasound, X-ray, MRI, PET scan, or known someone treated for cancer, chances are reasonable that a medical physicist was working behind the scenes to make sure the imaging procedure was as effective as possible. Medical physicists help to develop new imaging techniques, improve existing ones, and assure the safety of radiation used in medical procedures in radiology, radiation oncology and nuclear medicine. They collaborate with radiation oncologists to design cancer treatment plans. They provide routine quality assurance and quality control on radiation equipment and procedures to ensure that cancer patients receive the prescribed dose of radiation to the correct location. They also contribute to the development of physics intensive therapeutic techniques, such as stereotactic radiosurgery and prostate seed implants for cancer to name a few. The annual meeting is a great resource, providing guidance to physicists to implement the latest and greatest technology in a community hospital close to you.
The American Association of Physicists in Medicine (www.aapm.org) is a scientific, educational, and professional organization with nearly 8,000 medical physicists. Headquarters are located at the American Center for Physics in College Park, Md.