A theoretical study on phase-contrast mammography with Thomson-scattering x-ray sources

• Published in: Medical physics (Lancaster) 2009-10, Vol.36 (10), p.4644-4653
• Main Authors: De Caro, Liberato, Giannini, Cinzia, Bellotti, Roberto, Tangaro, Sabina
• Format: Article
• Language: English
• Subjects: Algorithms; BIOMEDICAL RADIOGRAPHY; Breast Neoplasms - diagnostic imaging; Cancer; Coherence; CROSS SECTIONS; diagnostic radiography; Female; Humans; KEV RANGE 10-100; MAMMARY GLANDS; Mammography; Medical image contrast; Medical image noise; Medical imaging; Models, Biological; NEOPLASMS; PHASE SHIFT; phase‐contrast imaging; Photons; Radiographic Image Enhancement - methods; Radiographic Image Interpretation, Computer-Assisted - methods; RADIOLOGY AND NUCLEAR MEDICINE; Reproducibility of Results; Scattering, Radiation; Sensitivity and Specificity; SIGNAL-TO-NOISE RATIO; SYNCHROTRON RADIATION; SYNCHROTRON RADIATION SOURCES; Thomson effect; THOMSON SCATTERING; tumours; visibility; WAVE PROPAGATION; X RADIATION; X-RAY DIFFRACTION; X-RAY SOURCES; X-Rays; X‐ray optics; X‐ray scattering
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.3213086

Purpose: The x-ray transmitted beam from any material/tissue depends on the complex refractive index ( n = 1 − δ + i β ) , where δ is responsible for the phase shift and β is for the beam attenuation. Although for human tissues, the δ cross section is about 1000 times greater than the β ones in the x-ray energy range from 10 to 150 keV, the gain in breast tumor visualization of phase-contrast mammography (PCM) with respect to absorption contact imaging (AI) is limited by the maximum dose that can be delivered to the patient. Moreover, in-line PC imaging (PCI) is the simplest experimental mode among all available x-ray PCI techniques since no optics are needed. The latter is a fundamental requirement in order to transfer the results of laboratory research into hospitals. Alternative to synchrotron radiation sources, the implementation of relativistic Thomson-scattering (TS) x-ray sources is particularly suitable for hospital use because of their high peak brightness within a relatively compact and affordable system. In this work, the possibility to realize PCM using a TS source in a hospital environment is studied, accounting for the effect of a finite deliverable dose on the PC visibility enhancement with respect to AI. Methods: The contrast-to-noise ratio of tumor-tissue lesions in PCM has been studied on the bases of a recent theoretical model, describing image contrast formation by means of both wave-optical theory and the mutual coherence formalism. The latter is used to describe the evolution, during wave propagation, of the coherence of the wave field emitted by a TS source. The contrast-to-noise ratio for both PCI and AI has been analyzed in terms of tumor size, beam energy, detector, and source distances, studying optimal conditions for performing PCM. Regarding other relevant factors which could influence “tumor” visibility, the authors have assumed simplified conditions such as a spherical shape description of the tumor inclusion, a constant surrounding background, ideal conditions for the calculus of the contrast-to-noise ratio. Results: The results show the possibility to enhance with PCI the signal-to-noise ratio for features in the submillimeter scale. This finding could give PCM a great advantage with respect to AI, opening the possibility to decrease the number of wrong diagnoses before histological exams. The results agree with experimental evidences obtained by Dreossiet al. [D. Dreossi et al. , “The mammography project at the SYRMEP beam