Exploration of X-ray imaging modalities for mammographic applications

Karla Denaly Palma Alejandro

IEAP CTU in Prague

Abstract: Despite the rise of alternative imaging modalities, such as MRI, surpassing the performance of X-ray imaging in several applications, there is still a number of diagnostic problems which leave no viable alternative to this method in terms of image quality and resolution. Promising approaches towards enhanced mammographic imaging by radiography involve state-of-the-art technology equipment and advanced methodology. Besides the application of high-resolution detectors and modern X-ray sources, such as microfocus tubes and the expensive synchrotrons, challenging procedures for X-ray phase-contrast imaging have been explored as possible candidates for this particular application. Phase-contrast imaging turns out to deliver most promising results in mammography due to its capability to distinguish soft tissue by very small variations of refractive index. However, the complexity of the setup and the need to time-consuming alignment makes the application of this methodology impractical for clinical conditions. For this reason, a different method which also exploits differences in refractive indices, but with a significantly simpler implementation is explored in the current work. The method is known as Propagation-Based Phase-Contrast or In-line Holography and exploits small angle scattering typically present at the edge of the sought-after features. Given a sufficient deviation of the scattered photons path, sufficient contrast, and high enough spatial resolution of the detector, the contrast of phase transitions within the sampled volume is amplified in radiographic projection. The latter allows distinguishing structures which cannot be resolved due to differences in absorption itself. The question arising is whether the resulting enhanced contrast provides sufficient information to detect features relevant in mammography. Hence, the results should be compared to standard radiography in terms of discriminability of features and applied dose. In the presented work, a standard microfocus table-top radiographic setup equipped with high-resolution hybrid pixel detectors was used to assess the resulting image. A systematic optimization of the acquisition parameters and the data processing has been performed to improve the mammographic resolution while maintaining the applied dose. The systematic work was focused on the acquisition of high-resolution images and phase-contrast enhancement, including the data processing. Within this work, several parameters were taken into account, such as the X-ray tubes spectrum, its current and focal-spot size as well as detector features (noise, efficiency, energy threshold, etc.), propagation path, dose, acquisition time, etc. A number of objects and phantoms were evaluated, including a mammography accreditation phantom, in order to demonstrate the impact of the proposed method. The in-line phase-contrast technique has been successfully employed in X-ray imaging to image mammographic complex samples demonstrating a high reliability of the method. Thus the potential of the technique for mammographic applications has been demonstrated together with the proposed instrumentation and optimized parameters, resulting in higher discrimination of features and low applied dose. The thesis, therefore, presents a successful implementation of an easy to use and robust phase-contrast methodology on the level of mammographic design requirements. The comparison to a standard X-ray detector clearly reveals the superiority of hybrid pixel detectors in this field of application.

Seminar takes place on Tuesday, February 6th 2018 at 2:00 PM
in the IEAP meeting room, Praha 2 ‐ Albertov, Horská 3a/22.

doc. Dr. André Sopczak
seminar organizer
doc. Ing. Ivan Štekl, CSc.
headmaster
doc. Dr. André Sopczak
IEEE CS - NPSS chair

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IEEE Czechoslovakia section
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