Tomosynthesis: Beyond Breast Imaging

December 18, 2013

Use of tomosynthesis for orthopedic and chest imaging offers greater study clarity and reduced dose.

When you hear about tomosynthesis in the news, your mind likely jumps automatically to 3D breast imaging. It is, by far, one of the most common ways the modality has been used to date. However, according to providers throughout the industry, tomosynthesis can also play a role in imaging throughout the body.

As a modality, tomosynthesis is basically an X-ray/CT mix - an X-ray that produces CT-esque, thin slices that allow you to gather 360-degree images. Currently, mammography is the only modality that has a tomosynthesis unit approved by the U.S. FDA.

A growing number of providers, however, are beginning to recognize the benefits of tomosynthesis to orthopedics and chest imaging as it exposes patients to lower radiation doses without limiting the number of images you can gather. The growing use of flat-screen panels in healthcare facilities has also bolstered the technique’s popularity.

Tomosynthesis in orthopedics

Just as with breast imaging, using tomosynthesis in orthopedics can help confirm diagnoses and support providers in identifying the best treatment protocol. The technique, according to industry experts, can be particularly helpful with spinal imaging.

“In orthopedics, supplementing fluoroscopy of the spine with functional radiography using tomosynthesis, especially for spinal disease, can help identify dynamic factors contributing to pathology,” Hogaku Gen, director of orthopedics and spine center director at Japan’s Chiba Central Medical Center, said in a written statement. “It is also very useful when artifacts from an implant make it difficult to determine the presence of bone fractures or synostosis.”

For example, in one case, an 84-year-old woman fell after having hip surgery at his facility. Despite her complaints of pain in the same hip, X-rays were unable to find any evidence of a fracture. However, with tomosynthesis, providers quickly identified and treated the re-fracture.

In addition to Chiba Central, several U.S. healthcare facilities are exploring orthopedic tomosynthesis. At Henry Ford Hospital, providers have used this imaging method with knees, hips, and shoulders. Harvard providers use it to measure changes in bone structure, such as joint narrowing.

Researchers at Boston University School of Medicine (BUSOM) have also tested the efficacy of tomosynthesis in diagnosing the bony spurs and fluid-filled cysts that are characteristic of knee osteoarthritis. The investigation, funded by GE and published in Radiology, revealed that tomosynthesis can identify more bony spurs and cysts than CT, 178 to 150 and 31 to 15, respectively. Additional existing research shows tomosynthesis effectively pinpoints 20 percent more lesions associated with rheumatoid arthritis in the hands and wrists than does radiography.

Alongside controlling radiation dose, tomosynthesis gathers images faster and is more physically comfortable for your patients.

“CT is a more sophisticated technology than tomosynthesis, but patients must be lying down in order for it to work. That prevents us from getting images of the knee being exposed to tension that usually arises from standing or walking under normal conditions,” said Daichi Hayashi, PhD, the BUSOM musculoskeletal radiology research fellow who led the knee osteoarthritis study. “Tomosynthesis lets us image the patient when the knee is exposed to gravity and weight.”

Using tomosynthesis in orthopedics also has other benefits, Gen said. The technique is more resistant to artifacts that frequently blur images, and it makes it easier for you to find the bone fractures, callus formations, fusings, and bone and joint structures that are difficult to locate with general radiography.

There are, however, drawbacks to using tomosynthesis. For example, you must tailor X-ray and reconstruction parameters to each patient to make sure the studies produce stable images. Tomosynthesis-generated images are also data-heavy. Downloading them to your electronic health record could be a slow process, creating a wait time for outpatients who are waiting for imaging analysis.

Chest tomosynthesis

In addition to orthopedics, tomosynthesis is also gaining ground in chest imaging. To date, the technique has proven effective in identifying pulmonary nodules.

In fact, several studies have demonstrated using chest tomosynthesis is an effective method for pinpointing pulmonary nodules associated with lung cancer. A 2009 study from Duke University Medical Center published in the European Journal of Radiology showed chest tomosynthesis identified nearly three times as many pulmonary nodules as conventional chest radiography - 70 percent compared to 22 percent. And, according to study author and Duke associate professor of radiology James T. Dobbins III, PhD, these results indicate using this technique can potentially improve both the sensitivity and specificity of pulmonary nodule detection.

More recent research published in the June issue of the Journal of Thoracic Oncology also determined chest tomosynthesis performed at baseline and after one year found a comparable number of non-calcified lung nodules as those detected with low-dose CT for lung cancer screening. Out of approximately 1,850 study participants, all of whom were current or previous smokers, tomosynthesis zeroed-in on lung abnormalities in 268 individuals, 14.5 percent of the study population. Based on these findings, subsequent PET/CT identified early lung cancer in 18 participants.

These results, said study authors and Italian researchers Alberto Terzi, MD, and Luca Bertolaccini, MD, reveal the potential for chest tomosynthesis to play a pivotal role in early lung cancer diagnosis. The lower dose and lower cost are particularly attractive.

“If present data on the ability of chest digital tomosynthesis to detect lung nodules and lung cancer in the same percentage of [low-dose CT] can be confirmed by other studies and clinical trials, chest digital tomosynthesis could become the first-line lung cancer screening tool among patients at high-risk of lung cancer (who should undergo a CT scan),” Terzi and Bertolaccini wrote in an editorial in the October issue of Lung Cancer Management.

Unlike orthopedic tomosynthesis, however, using this technique with chest imaging doesn’t offer the same resistance to artifact interference. If patients breathe during a scan, according to a poster presentation by Hong Sik Byun, MD, of the radiology department of Sungkyunkwan University School of Medicine in Seoul, ghost artifacts can appear.

Despite the potential drawbacks of using tomosynthesis for orthopedic and chest imaging, both you and your patients stand to benefit from continued research into how this technique can be used. Enough evidence doesn’t exist yet to warrant everyone using tomosynthesis in their everyday clinical activities, Hayashi said, but the current body of knowledge supports the need for future investigations.

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(A) Conventional posteroanterior knee radiograph shows osteophytes at the joint margins of medial and lateral femur (white arrows) but they are overlapped by the contours of femoral condyles and the exact size is difficult to assess. (B) On a tomosynthesis image, these osteophytes are more clearly depicted and exact shape can be appreciated. Thanks to the tomographic nature, contours of the femoral condyles do not overlap with these osteophytes. Also note moderate to large osteophytes at the medial and lateral tibial margins.

Photo credit: Daichi Hayashi, MD, PhD, Boston University School of Medicine