Dual-energy CT hybridation and kernel processing effects on the estimation of bone mineral mass and density: a calcination study on ex vivo human femur.

INTRODUCTION: Recent technological advances with dual-energy quantitative computed tomography (DEQCT) allow to combine two images of different level of energy to obtain simulated mono-energetic images at 60 keV (SIM60KeV-QCT) with improved image contrast in clinical practice. This study includes three topics: (1) compare bone mineral content (BMC), areal and volumetric bone mineral density (aBMD, vBMD) obtained with SIM60KeV-QCT, single-energy QCT (SEQCT), and dual X-ray absorptiometry (DXA); (2) compare ash density and weight with respective vBMD and BMC assessed on SIM60KeV-QCT, SEQCT, and DXA; and (3) compare the influence of reconstruction kernels on the accuracy of vBMD and BMC using ash density and ash weight as the reference values. METHODS: DXA, SEQCT, and DEQCT acquisitions were performed ex vivo on 42 human femurs. Standard kernel (SK) and bone kernel (BK) were applied to each stack of images. Ten diaphyses and 10 femoral necks were cut, scanned, and reconstructed using the techniques described above. Finally, the bone specimens were calcined to obtain the ash weight. RESULTS: QCT analysis (SEQCT, SIM60KeV-QCT) underestimated BMC value compared to DXA. For femoral necks, all QCT analyses provided an unbiased estimate of ash weight but underestimated ash density regardless of the kernel used. For femoral diaphysis, SEQCT BK, SIM60KeV-QCT BK, and SK underestimated ash weight but not ash density. CONCLUSION: BMC and vBMD quantifications with the SIM60KeV-QCT gave similar results as the SEQCT. Further studies are needed to optimize the use of SIM60KeV-QCT in clinical situations. SK should be used given the effect of kernels on QCT assessment.

Assessment of Dural Ectasia Using Computed Tomodensitometry as a Criterion in Marfan Syndrome.

OBJECTIVE: The aim of this study was to reevaluate dural ectasia criteria in Marfan syndrome patients fulfilling the revised Ghent criteria. METHODS: Lumbar computed tomography scans of 19 Marfan patients and 30 matched control subjects were retrospectively assessed. Dural sac ratio (DSR), nerve root sleeve diameter, pedicle width, and a scalloping or meningocele presence were each assessed by 2 readers blinded from the diagnosis. Mann-Whitney-Wilcoxon tests compared the patient and control groups. Receiver operating characteristic curve analysis and multivariate models determined the optimal cutoff value. RESULTS: A DSR value greater than 0.69 at L5 (DSR-L5) such as L4 scalloping of more than 2.65 mm (scall-L4) and 6 or more vertebrae showing a scalloping of more than 3 mm (6-scall) were found very specific but with limited sensitivity. Multivariate model combining DSR-L5 + scall-L4 showed good positive predictive value, whereas model combining DSR-L5 + 6-scall showed good negative predictive value. CONCLUSIONS: Assessment of DSR and vertebral scalloping allows valuable depiction of dural ectasia in Marfan syndrome patients.