Upright Tomosynthesis of the Lumbar Spine

Abstract

This experimental study investigates the potential of lumbar spine tomosynthesis to offset the traditional limitations of radiographic and computed tomography imaging, that is, superimposition of anatomy and disregard of physiological load-bearing. A gantry-free twin robotic scanner was used to obtain lateral radiographs and tomosyntheses of the lumbar spine under weight-bearing conditions in eight body donors. Tomosynthesis protocols varied in terms of sweep angle (20 versus 40°), scan time (2.4 versus 4.8seconds), and framerate (16 versus 30 fps). Image quality and vertebral endplate assessability were evaluated by five radiologists with 4-8 years of skeletal imaging experience. Aiming to identify potential diagnostic deterioration near the scan volume margins, readers additionally determined the craniocaudal extent of clinically acceptable image quality. Tomosynthesis scans effectuated a substantial dose reduction compared to standard radiographs (3.8±0.2 to 15.4±0.8 dGy*cm2 versus 77.7±34.8 dGy*cm2; p≤0.021). Diagnostic image quality and endplate assessability were deemed highest for the 30 fps wide-angle tomosynthesis protocol with good to excellent interrater reliability (intraclass correlation coefficients: 0.846 and 0.946). Accordingly, the craniocaudal extent of acceptable image quality was substantially larger compared to radiography (26.9 versus 18.9cm; p<0.001), whereas no significant difference was ascertained for the tomosynthesis protocols with 16 fps (15.3-22.1cm; all p≥0.058). Combining minimal radiation dose with superimposition-free visualization, 30 fps wide-angle tomosynthesis superseded radiography in all evaluated aspects. With superior diagnostic assessability despite significant dose reduction, load-bearing tomosynthesis appears promising as an alternative for first-line lumbar spine imaging in the future.