ABSTRACT
This article presents a method for measuring three-dimensional mechanical displacement and strain fields using stimulated echo MRI. Additional gradient pulses encode internal displacements in response to an externally applied deformation. By limiting the mechanical transition to the stimulated echo mixing time, a more accurate static displacement measurement is obtained. A three-dimensional elasticity reconstruction within a region of interest having a uniform shear modulus along its boundary is performed by numerically solving discretized elasticity equilibrium equations. Data acquisition, strain measurements and reconstruction were performed using a silicone gel phantom containing an inclusion of known elastic properties. A comparison between two-dimensional and three-dimensional reconstructions from simulated and experimental displacement data shows higher accuracy from the three-dimensional reconstruction. The long-term objective of this work is to provide a method for remotely palpating and elastically quantitating manually inaccessible tissues.
Subject(s)
Magnetic Resonance Spectroscopy/methods , Echocardiography/methods , Elasticity , Humans , Image Processing, Computer-Assisted , Magnetic Resonance Imaging , Models, Statistical , Neoplasms/diagnosis , Phantoms, ImagingABSTRACT
Photorefractive polymers with high diffraction efficiency in the visible and near-infrared regions of the electromagnetic spectrum have been developed. These polymers, which have a large dynamic range because of their high orientational birefringence, incorporate a dye designed to have a large dipole moment and a high linear polarizability anisotropy. Such polymers have enabled demonstrations of imaging through scattering media, using a holographic time-gating technique at a wavelength that is compatible with the transparency of biological tissues and with the emission of low-cost semiconductor laser diodes.
Subject(s)
Diagnostic Imaging/methods , Infrared Rays , Polymers , Birefringence , Coloring Agents , Image Processing, Computer-Assisted , Lasers , Refractometry , Scattering, Radiation , TemperatureABSTRACT
We demonstrate the use of a near-infrared-sensitive photorefractive polymer with high efficiency for imaging through scattering media, using an all-optical holographic time gate. Imaging through nine scattering mean free paths is performed at 800nm with a mode-locked continuous-wave Ti:sapphire laser.
