Radiography remains orthopedics’ mainstay, with more than 75 percent of imaging studies still x-ray based. Digital radiography is the flavor of choice in 2008, making good business sense in a digital environment. The combination of remote access to imaging results, better management of large imaging volumes and more accurate patient diagnoses are key selling points for using DR in orthopedic imaging, whether it is in a small community hospital, critical access center, outpatient facility or orthopedic physician practice.
What distinguishes musculoskeletal radiography is the number of specialized views that require special positioning of the patient and the angulation of the x-ray system and the detector. Because the musculoskeletal system is so complex, over time, people have learned that a radiographic projection recording in a particular position will be most important. One key element has been coming up with different ways to mount the system in such a way that it is flexible enough to get these complex views, according to Michael Flynn, PhD, senior staff medical physicist, at the Henry Ford Health System in Detroit.
DR + tomo = more detail
Henry Ford Health System serves Southeast Michigan with seven hospitals, approximately 18,000 employees including 80 radiologists and performs about 1 million procedures per year. The Henry Ford Hospital in Detroit is using the Sonialvision Safire II system from Shimadzu Medical specifically for orthopedic studies.
The Sonialvision Safire II supports general radiography, fluoroscopy, tomography and, in particular, supports tomosynthesis. The clinic uses the system predominantly for musculoskeletal applications. The high resolution of the Selenium direct DR detector records fine bone details. For tomosynthesis, 75 precisely registered views are acquired over a 40 degree arc and reconstructed using specialized software. For a typical joint, this results in a stack of about 75 tomographic images with 1 mm spacing. “Our focus and utilization has been on musculoskeletal joint imaging where we find that it is superior for revealing occult fractures which tend to be subtle and not revealed on general radiographs,” he says.
Why is it superior? The cross-sectional tomographic depiction of the anatomy is important for removing overlying structures that obscure small fractures and for demonstrating high contrast for fracture lines that are rarely aligned optimally for detection with conventional radiographs. “We have done comparisons of this particular tomosynthesis system to studies done with thin 64-slice CT and we do find that the tomosynthesis has about three times as better spatial resolution in plane than CT does,” he notes.
Flynn says the orthopedic specialists routinely use DR with tomosynthesis in cases where the finding is particularly subtle or uncertain, such as suspected hip fractures that present in the ER.
“What we are finding with tomosynthesis is it reveals more directly the fracture line and the extent to which the fracture line might be traversing the bone which will influence the way one manages that patient in terms of surgery or release,” Flynn says.
Specialty views in HD
Orthopaedic Specialists of North County in Oceanside, Calif., a specialty orthopedic group, chose to make the jump from analog to digital x-ray three and a half months ago with the purchase of the Stryker HD DR 3000 powered by Swissray for general orthopedic radiography procedures, according to Lead Technologist Laurie Corning. Last year, the practice provided almost 10,000 imaging studies.
Certain specialized orthopedic views, such as Merchant or Sunrise views, have historically been more easily obtained using CR cassettes than by using DR. With the Swissray system, this is no longer the case. “Special angles or views like Merchant or axillary can be pre-programmed, which is a time-saver for our techs when they are really busy,” she notes. “This is the main reason we chose the system—because of the special auto-positioning settings.”
Previously, for Merchant views, patients had to get up on the table and put their legs through a wooden stand. Now, patients can sit in a chair leaning slightly to the side, so that the x-ray comes across to show the patellas, as opposed to lying down. With the HD post-processing,