Quantitative Measurement Of Mineral Content Of In Vitro Porcine Bones:a Primary Study Of Gemstone Spectral Imaging

Purpose:To evaluation the credibility and accuracy of the gemstone spectral imaging(GSI) for the use of quantitative analysis, and to explore the feasibility of quantitative measuring bone mineral density.Materials and methodsExperiment1:22tubes of iodine-water mixed phantoms,6tubes of HAP-water mixed phantoms and6tubes of HAP-Mixed blood AGAR gel phantoms with different concentration were scanned separately by Discovery750HD CT on GSI mode, and then measured the concentration of each tube on the corresponding base-material density map were measured and compared with the real concentration.Experiment2:5fresh porcine spines which were commercially available with4vertebrae bodies as a group were collected. All the20vertebrae bodies took DXA scans for BMD measurement, CT scans in GSI mode with the QCT phantom for calculating the BMD of QCT of each vertebrae with CT value of the polychrome energy. Then different ways of material decomposition (4types) were used to measure the content of HAP and Ca in each vertebrae bone. Finally, the vertebrae bodies with volume measured were incinerated with high temperature. The density of the bone ashes was calculated and set as golden standard. Statistical comparion was carried on between the GSI measurement and golden standard. The degree of deviation for the results of HAP and QCT measurement were calculated and compared.ResultsExperiment1:the measurement result of iodine-water mixtured phantoms and the truth value totally showed a significant linear correlation(r=0.998). It showed a significant linear correlation (r=0.998,0.995) between the measurement results and the real value in the mid-low and mid-high concentration groups, and there is no difference between them(P>0.05). The correlation coefficient (r=0.966) of the low concentration group is lower than the overall value. There’s some difference between the measurement result and the real value of high concentration group(P<0.05). For the HAP-water mixture phantom, there is a significant linear correlation(r=0.999) without significant difference (P>0.05) between the real value and the measurement results of the content of HAP and Ca. For the HAP-Mixed blood AGAR gel phantoms, there is signification linear correlation (r=0.999) between the measurements results and the real value, but with significant difference (P<0.05) between them.Experiment2:All the data acquired from GSI scan showed significant linear correlations (r>0.8) comparing with the ashes density, which were better than the data acquired from QCT and DXA. The degree of deviation for bone material content measured by GSI scan was lower than QCT (P<0.05).ConclusionGemstone spectral Imaging can accurately measured the Iodine and HAP quantitatively probably with a certain threshold of concentration, which means it might be misregistration if the concentration exceed the threshold. The quantitative analysis for bone mineral content with gemstone spectral CT was more accurate than those of other methods for BMD measurement. So it is prosperous for GSIe applied for quantitative measurement of mineral density of human bones.