Dynamic near infrared imaging with ultrasound guidance (dNIRUS): analytical model and benchtop validation on multilayer tissue simulating phantoms

Abstract

We proposed a dynamic near infrared/ultrasound dual modal imaging system (dNIRUS) for characterizing suspicious breast lesions non-invasively. dNIRUS measures the change of tissue mechanical and physiologic parameters in response to dynamic stimuli such as cyclic mechanical compression. It integrates near infrared imaging of tumor physiologic properties, ultrasound imaging of tumor deformation/displacement, and real time pressure monitoring under a designated cyclic compression load. The concept of dNIRUS was quantitatively verified on multi-layer tissue simulating phantoms under cyclic compression. A lumped visco-elastic model was used to characterize the phantom mechanical properties and to simulate the tissue deformation. The diffusion equations were solved analytically in Fourier domain with the moving boundary. The theoretical models were verified by a series of bench top tests where a sensor head integrating an ultrasound probe and a near infrared probe was installed on a load frame. A cyclic compression force was applied to a two-layer tissue simulating phantom. Phantom displacement, compressive pressure and diffuse optical reflectance were recorded simultaneously. Deformation of each layer of the phantom was reconstructed from ultrasound images and was consistent with the load frame measurements as well as the theoretical predictions. Diffuse reflectance amplitude showed corresponding fluctuation during compression, while the phase did not change significantly at the oscillation frequency of 0.5Hz. Further work is necessary to develop forward and inverse algorithms for dynamic characterization of suspicious breast lesions.