Application of multi-slice CT postprocessing techniques in diagnosing lumbar spondylolysis of pilots

Objective To evaluate the clinical application value of multi-slice CT (MSCT)postprocessing techniques in diagnosing lumbar spondylolysis (LS) of pilots. Methods Three hundred and eighty-five transformed pilots, who were grouped by age (23-28 yr, 29-34yr, 35-40 yr and 41-46 yr) and by flying hours (≤800 h, 801-1600 h and 1601-2400 h), underwent volumetric MSCT scanning in physical examination. Then various postprocessing techniques including multiplanar reconstruction (MPR), maximum intensity projection (MIP) and volume rendering (VR) were carried out at workstation for getting the LS information of pilots. The efficacy of MIP, MPR and VR were compared in diagnosing LS. Results There were 16 cases (at 33 places) of LS in 385 pilots,including 13 bilateral and 3 unilateral LS. Nine cases were accompanied with lumbar spondylolisthesis.The diagnosis rate by MPR images was 100% (33/33), and in which collar of Scottish hound,double articular process sign and lumbar spondylolisthesis was respectively and clearly revealed on oblique sagittal plane, oblique axial plane and median sagittal plane. MIP images also screened out all LS cases but the viewing of soft tissue was not as good as MPR's. The diagnosis rate by VR imagines was 75. 76% (25/33) but it showed closely to the real anatomy structure of lumbar spine and stereoscopically displayed LS. Conclusions Postprocessing techniques, such as MPR, MIP and VR show good ability in diagnosing spondylolysis and its secondary abnormity. The oblique sagittal (along vertebral arch) and oblique axis (parallel to arch) MPR images are the first choice of reconstruction technique in diagnosing spondylolysis of pilots. Key words: Lumbar vertebrae;  Spondylolysis;  Tomography, spiral computed;  Image processing, computer-assisted