Breast tumor segmentation in high resolution x-ray phase contrast analyzer based computed tomography.

PURPOSE: Phase contrast computed tomography has emerged as an imaging method, which is able to outperform present day clinical mammography in breast tumor visualization while maintaining an equivalent average dose. To this day, no segmentation technique takes into account the specificity of the phase contrast signal. In this study, the authors propose a new mathematical framework for human-guided breast tumor segmentation. This method has been applied to high-resolution images of excised human organs, each of several gigabytes. METHODS: The authors present a segmentation procedure based on the viscous watershed transform and demonstrate the efficacy of this method on analyzer based phase contrast images. The segmentation of tumors inside two full human breasts is then shown as an example of this procedure's possible applications. RESULTS: A correct and precise identification of the tumor boundaries was obtained and confirmed by manual contouring performed independently by four experienced radiologists. CONCLUSIONS: The authors demonstrate that applying the watershed viscous transform allows them to perform the segmentation of tumors in high-resolution x-ray analyzer based phase contrast breast computed tomography images. Combining the additional information provided by the segmentation procedure with the already high definition of morphological details and tissue boundaries offered by phase contrast imaging techniques, will represent a valuable multistep procedure to be used in future medical diagnostic applications.

[Phase contrast imaging of the breast. Basic principles and steps towards clinical implementation]. / Phasenkontrastbildgebung der Brust. Grundlagen und Schritte zur klinischen Implementierbarkeit.

CLINICAL/METHODICAL ISSUE: Breast cancer is the most common cancer and the leading cause of cancer deaths in women worldwide. STANDARD RADIOLOGICAL METHODS: Mammography is the only imaging technique approved for nationwide breast cancer screening. Digital full field mammography has improved mammographic image quality. Nevertheless, mammography has a low positive predictive value and a low sensitivity especially in mammographically dense breasts. One of the major limitations is the inherently low contrast between healthy breast parenchyma and breast cancer. METHODICAL INNOVATIONS: Phase contrast imaging is based on the phase shift that occurs when X-rays encounter a change in refractive index between different materials. PERFORMANCE: The improved soft tissue contrast makes the technology particularly promising for breast diagnostics. ACHIEVEMENTS: The studies presented here suggest that phase contrast imaging provides additional diagnostic information both using phase contrast mammography and phase contrast computed tomography (CT). PRACTICAL RECOMMENDATIONS: This paper provides an overview of the basic principles of the phase contrast imaging and describes recent developments towards in vivo and ex vivo phase contrast imaging of the breast.