Finite Element Analysis-Based Vertebral Bone Strength Prediction Using MDCT Data: How Low Can We Go?

Abstract

Objective: To study the impact of dose reduction in MDCT images through tube current reduction or sparse sampling on the vertebral bone strength prediction using finite element (FE) analysis for fracture risk assessment. Methods: Routine MDCT data covering lumbar vertebrae of 12 subjects (six male; six female; 74.70 ± 9.13 years old) were included in this study. Sparsely sampled and virtually reduced tube current-based MDCT images were computed using statistical iterative reconstruction (SIR) with reduced dose levels at 50, 25, and 10% of the tube current and original projections, respectively. Subject-specific static non-linear FE analyses were performed on vertebra models (L1, L2, and L3) 3-D-reconstructed from those dose-reduced MDCT images to predict bone strength. Coefficient of correlation (R 2), Bland-Altman plots, and root mean square coefficient of variation (RMSCV) were calculated to find the variation in the FE-predicted strength at different dose levels, using high-intensity dose-based strength as the reference. Results: FE-predicted failure loads were not significantly affected by up to 90% dose reduction through sparse sampling (R 2 = 0.93, RMSCV = 8.6% for 50%; R 2 = 0.89, RMSCV = 11.90% for 75%; R 2 = 0.86, RMSCV = 11.30% for 90%) and up to 50% dose reduction through tube current reduction method (R 2 = 0.96, RMSCV = 12.06%). However, further reduction in dose with the tube current reduction method affected the ability to predict the failure load accurately (R 2 = 0.88, RMSCV = 22.04% for 75%; R 2 = 0.43, RMSCV = 54.18% for 90%). Conclusion: Results from this study suggest that a 50% radiation dose reduction through reduced tube current and a 90% radiation dose reduction through sparse sampling can be used to predict vertebral bone strength. Our findings suggest that the sparse sampling-based method performs better than the tube current-reduction method in generating images required for FE-based bone strength prediction models.

Predicting Vertebral Bone Strength Using Finite Element Analysis for Opportunistic Osteoporosis Screening in Routine Multidetector Computed Tomography Scans—A Feasibility Study

“…Fifth, in this study, we have considered only static compression loading configuration for comparison purposes; however, in other loading configurations, the FEpredicted failure load values and the differences among the models may vary. Sixth, the observed bias in this study could be influenced when we expand to a larger dataset acquired in different scanners and site locations by variations in scanning parameters (gantry tilt, tube voltage, reconstruction kernel, and slice orientation) and intravenous contrast application (time interval) (20,52,53). Seventh, the variations in the material strength data from Hounsfield value due to partial volume effect is not considered in the current study.…”

Prediction of Incidental Osteoporotic Fractures at Vertebral-Specific Level Using 3D Non-Linear Finite Element Parameters Derived from Routine Abdominal MDCT

“…In step 3, compression loading condition was applied on the vertebrae and nonlinear FE analysis was performed using a commercial software Abaqus (version 6.10, Hibbitt, Karlsson, and Sorensen, Pawtucket, RI, USA) to calculate the FE failure load, and displacement [ 22 , 32 ]. In step 3, in addition to FE based results, we have also calculated the BMD values from MDCT images [ 33 ]. Lastly, in step 4 the obtained parameters were analyzed to identify those parameters and their combinations that predict incidental vertebral fracture best.…”

“…In step 2, patient-specific 3D model has been generated and this model was then meshed using tetrahedral elements, image intensity based non-linear material properties were applied to the FE mesh. In step 3, compression loading condition was applied on the vertebrae and nonlinear FE analysis was performed using a commercial software Abaqus (version 6.10, Hibbitt, Karlsson, and Sorensen, Pawtucket, RI, USA) to calculate the FE failure load, and displacement [22,32]. In step 3, in addition to FE based results, we have also calculated the BMD values from MDCT images [33].…”

“…Mesh sensitivity study was performed to maintain the accuracy of the FE model. In this study, we varied the maximum element edge length from 1.5 to 3 mm [22,32] with an increment of 0.25 mm and identified that 2 mm was giving the mesh independent results and the same size was used for all vertebral models.…”

“…In FE analysis, patientspecific three-dimensional (3D) tissue models are generated from the MDCT image data. Then, the image intensity (Hounsfield units (HU))-based material properties are assigned to the FE mesh and realistic loading and boundary conditions are applied to calculate the biomechanical response [17,[22][23][24][25].…”