Lanterna Rally

Author: Bernhard B. Zimmermann

Publisher:

Published: 2017

Total Pages: 102

ISBN-13:

Diffuse optical tomography (DOT) is an emerging noninvasive functional imaging method for breast cancer diagnosis and neoadjuvant chemotherapy monitoring. In particular, the multimodal approach of combining DOT with x-ray digital breast tomosynthesis (DBT) is especially synergistic as DBT prior information can be used to enhance the DOT reconstruction. DOT, in turn, provides a functional information overlay onto the mammographic images, increasing sensitivity and specificity to cancer pathology. We describe a dynamic DOT apparatus designed for tight integration with commercial DBT scanners and providing a fast (1 Hz+) image acquisition rate to enable tracking of hemodynamic changes induced by the mammographic breast compression. The most significant advance enabling fast acquisition was the design and construction of a direct analog-to-digital conversion frequency-domain near-infrared spectroscopy (FD-NIRS) component. It achieves simultaneous dual wavelength operation at 685 nm and 830 nm by concurrent 67.5 MHz and 75 MHz frequency modulation of each laser source, respectively, followed by digitization using a high-speed analog to digital converter and real-time hybrid FPGA-assisted demodulation by discrete Fourier transform (DFT). The overall DOT system integrates 96 CW-NIRS and 24 FD-NIRS source locations, as well as 32 CW-NIRS and 20 FD-NIRS detection locations into low-profile plates that mate to the DBT compression paddle and x-ray detector cover, respectively. The plates and the embedded optical fibers are made of plastic to minimize x-ray absorption and thus allow true simultaneous acquisition of the DBT image. We first characterize each major system component individually, and then demonstrate overall performance using static and dynamic tissue-like phantoms, as well as in vivo images acquired from the pool of patients recalled for breast biopsies at the Massachusetts General Hospital Breast Imaging Division.