Improving technetium-99m methylene diphosphonate bone scan images using histogram specification technique

In this study, we have proposed and validated that histogram of a good-quality bone scan image can enhance a poor-quality bone scan image. The histograms of two good-quality technetium-99m methyl diphosphonate bone scan images I(A) and I(B) recommended by nuclear medicine physicians (NMPs) were used to enhance 87 poor-quality bone scan images. Processed images and their corresponding input images were compared visually by two NMPs with scoring and also quantitatively using entropy, Structural similarity index measure, edge-based contrast measure, and absolute brightness mean error. Barnard's unconditional test was applied with a null hypothesis that the histogram of both I(A) and I(B) produces similar output image at α =0.05. The mean values of quantitative metrices of the processed images obtained using I(A) and I(B) were compared using Kolmogorov–Smirnov test. Histogram of a good-quality bone scan image can enhance a poor-quality bone scan image. Visually, histogram of I(B) improved statistically significantly higher proportion (P < 0.0001) of images (86/87) as compared to histogram of I(A) (51/87). Quantitatively, I(B) performed better than I(A,) and the Chi-square distance of input and I(B) was smaller than that of I(A). In addition, a statistically significant (P < 0.05) difference in all the quantitative metrics among the outputs obtained using I(A) and I(B) was observed. In our study, reference histogram of good-quality bone scan images transformed the majority of poor-quality bone scan images (98.85%) into visually good-quality images acceptable by NMPs.