A new phantom for performance evaluation of bone mineral densitometry using DEXA and QCT

Abstract

Accurate performance assessment of bone mineral density (BMD) methods is crucial due to the fact that a high level of exact estimation of bone situation is needed for correct diagnosis. Variation of parameters like sensitivity and error ratio highly affects the densitometry results that may induce some level of uncertainty in diagnosis. So, designing an algorithm for correction is necessary to assure examiners about measurement results. In this study several phantoms consisting of soft tissue and bone-equivalent material were devised to accurately test bone densitometry systems. It should be noted that to the best of our knowledge there is no unique phantom to be able to use for evaluation of both Dual Energy X-ray Absorptiometry (DEXA) and Quantitative Computed Tomography (QCT). The main motivation of this study was to design a reliable and easy to use phantom. A QCT quality control, quality assurance, and Plexiglas cylindrical phantoms as a spine phantom were designed and constructed to assess different bone densities. Four inserts in spine phantom with precisely wide range of K2HP04 solutions were used for simulation of bone tissues and to determine the BMD systems characteristics. The designed phantoms were also used for performance assessment of BMD systems. In this research it is demonstrated that by decreasing of bone mineral densities an increasing trend in error ratio of measured densities and declining trend in methods sensitivities were observed, that may cause some level of uncertainty in low densities.

Patient-Specific Phantomless Estimation of Bone Mineral Density and Its Effects on Finite Element Analysis Results: A Feasibility Study

“…Five regions of interest (ROIs) for the five different mineral contents of the reference phantom (Mindways Inc., Austin, TX, USA) were recorded in the same CT images. For the CT image of each patient, the phantom-based calibration algorithm [28, 29] determined the linear correlation between the known mineral densities and their corresponding HU values as follows:BMDphantom=α×HU+β,where α and β are the patient-specific values that are to be determined. Thus, using equation (1) with the determined α and β , the voxelwise BMD values of the lumbar spine and hip of each patient were calculated as the ground truth.…”

A novel dual energy method for enhanced quantitative computed tomography

“…This means that DEQCT can improve the accuracies in bone assessment. In particular research efforts and treatment follow-ups wherein highly accurate measurements are required, DEQCT can be the only candidate for bone assessment [16], because, as we also show in this work, the accuracy of SEQCT is limited when dealing with low bone masses in the presence of thick surrounding soft tissues such as fat [17]. It is worth noting that a number of promising dose reduction strategies have been proposed by using advanced image processing on DECT which lead to higher contrast-to-noise ratios and eliminate unnecessary non-contrast CT scans [18][19][20].…”

“…In conducting the present effort, we designed a series of dedicated in-house phantoms with abilities to support a wide range of densities and uses in different QCT techniques [31]. The QCT calibration phantom is used to obtain a calibration curve in order to convert the Hounsfield Units (HU) to the corresponding BMD values.…”

“…In order to estimate the mineral density, a calibration curve-based algorithm was implemented that converted the HU values to mineral contents in mg/cm3. To validate the output of designed software, values from ImageJ software (National Institute of Health, US) and a series of analyzing and analytical calculations such as Amide software (Medical Image Data Examiner) were used [17,31]. Via the in-house QCT software, an ROI is selected by user; mean, SD, and CT# are calculated (figure 4), and therefore, the average bone mineral density can be calculated and compared to age and sex matched controls (figure 5).…”

Design and Validation of Synchronous QCT Calibration Phantom: Practical Methodology

“…To date, quantitative extraction of structural features using 3D bone scans could open the door to introducing a practical method for accurate diagnosis of bone-related diseases. There are several different BMD quantification strategies using a CT scanner, with different calibration phantoms (solid and liquid) or only CT number base [2,[11][12][13]. Hence, owing to the role of the calibration phantom, which translates the computed tomography Hounsfield units to the bone units (mg/cm 3 ) in this study, one should pay attention to practical methodology for making an in-house QCT calibration phantom.…”