Multitapered x-ray capillary optics for mammography.

Abstract

X-ray mammography is currently the primary tool used for breast cancer detection. However, studies have shown that 5%-15% of breast cancers are not visualized mammographically. The long term goal of this project is to improve the x-ray mammographic imaging system using capillary optics. A post-patient capillary optic lens has the potential to increase spatial resolution and eliminate the detection of scattered x rays, thereby improving image contrast and the signal-to-noise ratio (SNR). Several individual and two prototype multitapered optics were studied to determine the feasibility of a full-field multitapered optic. Scatter fraction, contrast, transmission, uniformity, and the modulation transfer function (MTF) were measured for a Mo target tube/computed radiography (CR) imaging system when this prototype was applied. The results were compared with standard grid and airgap techniques. The multitapered optic lens removed 85% of the scattered photons as compared to 66% and 39% for the air gap and grid methods, respectively. This resulted in an improvement of contrast by approximately 80% for the optics, 51% for the air gap, and 30% for grid methods. The single optic lens improved the limiting resolution (5% MTF level) of the CR detector by 78% due to magnification with very little focal spot blurring, while the multitapered prototype improved resolution significantly, but not as much as the single optic. These measurements have shown that it is feasible to create a multitapered optic lens that significantly improves system MTF and virtually eliminates scatter. With continued improvements in fabrication techniques, a full-field multitapered lens will be feasible.