Synchrotron radiation micro-CT and automatic marker watershed image segmentation for quantifying local bone tissue and blood vessels of tibia in mouse models of breast cancer tibia metastasis
Objective To explore the value of synchrotron radiation micro-CT(SR-pCT)and automatic marker watershed image segmentation for quantifying three-dimensional local bone tissue and blood vessels in mouse models of breast cancer tibia metastasis.Methods Mouse models with breast cancer bone metastasis in tibia were established and underwent oral Vatalanib,injection of Bevacizumab,combination of Vatalanib or Bevacizumab,or injection of placebo,respectively.On the 8th day(time point T1)and the 22nd day(time point T2)after injection of tumor cells,the tibia bone was scanned using combined vascular contrast injection and SR-pCT,and high-resolution simultaneous imaging of local bone tissue and vascular network were achieved.Then bone tissue and vessels on images were segmented using automatic marker watershed image-segmentation method,global threshold method and region growing method,respectively,and the quality of segmentations were assessed with Dice similarity coefficient(DSC).The anatomical quantitative parameters of tibia with breast cancer metastasis were obtained,including the fraction of bone volume in total volume(BV/TV),fraction of vessel volume in total volume(VV/TV),the mean thickness of bone(B.Th)and the mean thickness of vessel(V.Th).The anatomical quantitative parameters were compared among different treatments at the same time point,also between different time points under the same treatment.Results DSC for segmentation of local tibia bone tissue and vascular structures based on automatic marker watershed image segmentation method were all greater than 0.95,higher than that of other methods(all P＜0.05).No significant difference of anatomical quantitative parameters was found under different treatments at T1(all P＞0.05),and V.Th under the combined treatment were lower than that under other treatments at T2(all P＜0.05).Compared with T1,BV/TV and B.Th at T2 increased while VV/TV at T2 decreased in tibia metastasis under combination treatment(all P＜0.05),BV/TV,B.Th and V.Th at T2 increased under Vatalanib or Bevacizumab treatment(all P＜0.05),and BV/TV and B.Th at T2 increased under placebo(both P＜0.05).Conclusion The combination of SR-pCT and automatic marker watershed method could be used to initially quantify three-dimensional structures of local bone tissue and blood vessels in mouse models of breast cancer tibia metastasis.
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