A new orthopedic CT system promises to improve the standard of care for knee imaging. On the CurveBeam LineUp, patients are scanned while standing upright and fully weight bearing.
Traditional CT and MR images are acquired in a non-weight bearing position, leading to “missed diagnoses of meniscal damage,” according to Dr. Neil Segal, who has been overseeing research efforts using a LineUp prototype, first at the University of Iowa and currently at the University of Kansas.
Although plain radiographs can be acquired while the patient is in a full weight-bearing position, the optimal degree of knee flexion and X-Ray beam tilt to best visualize the joint surface is person specific.
“Difficulty in reproducing the same view of the joint over time impairs ability to detect joint disease, and the 2D nature of radiographs makes these images of overlapping bony anatomy very insensitive for detecting abnormalities until there is advanced joint damage,” Dr. Segal said.
The LineUp was developed by CurveBeam, a Pennsylvania-based company that specializes in extremity cone beam CT systems for orthopedics. CurveBeam anticipates it will submit an application for and receive FDA 510(k) clearance for the LineUp in 2017. The LineUp will be on display at RSNA at Booth #8008 in the North Hall.
CurveBeam introduced the pedCAT, a bilateral weight bearing CT system dedicated to the foot and ankle, in 2012. Since then, the device has been added to the imaging services of hospital foot & ankle sections, orthopedic clinics and podiatry offices.
Like the pedCAT, the LineUp will provide isotropic, three-dimensional volumes of the anatomy with a high resolution output of between 0.2 mm and 0.3 mm slices. The LineUp will be the only cone beam CT system that can provide bilateral, weight bearing scans.
A study led by Dr. Segal focused on osteophytes, one structure linked to pain in people with knee osteoarthritis. Knees of community-dwelling adults with knee OA were imaged with MRI (reference), fixed-flexion radiographs, and weight bearing CT. The sensitivity and accuracy for detecting osteophytes and subchondral cysts were higher with weight bearing CT imaging in comparison to fixed-flexion radiographs. The study was published in the August 2016 issue of the Journal of Orthopedic Research.
“Clinically, this is a highly meaningful improvement,” Dr. Segal said. “It suggests that weight-bearing CT could replace radiographs as the recommended means of assessing knee OA. This advancement is even more significant given that it was made without significantly increasing the radiation dose (0.01 mSv for SCT vs. 0.005–0.102 mSv for a series of knee radiographs).”
Another research effort led by Dr. Segal indicates weight-bearing CT arthrography studies can provide outstanding delineation of articular cartilage with better differentiation between cartilage and subchondral bone then MRI studies, while also visualizing the cruciate ligaments. In knees with osteoarthritis, meniscal tears not visualized on MRI were detectable on weight-bearing CT.
“Thus, we found that some potential advantages of weight-bearing CT over non-weight-bearing MRI/MRA include 3D measures of meniscal position, detection of pathology not detected in unloaded positions, and ability to bear weight in a functional position, thus better recreating the magnitude of body weight and muscle forces acting around the knee during usual standing,” Dr. Segal said.