Abstract
Birefringence imaging, including polarization sensitive optical coherence tomography (PS-OCT), can provide valuable insight into the microscopic structure and organization of many biological tissues. In this paper, we report on a method to fabricate tissue-like birefringence phantoms for such imaging modalities. We utilize the photo-elastic effect, wherein birefringence is induced by stretching a polymer sample after heating it above its glass-transition temperature. The cooled samples stably exhibit homogeneous birefringence, and were assembled into phantoms containing multiple well-defined regions of distinct birefringence. We present planar slab phantoms for microscopy applications and cylindrical phantoms for catheter-based imaging and demonstrate quantitative analysis of the birefringence within individual regions of interest. Birefringence phantoms enable testing, validating, calibrating, and improving PS-OCT acquisition systems and reconstruction strategies.
Highlights
Resolution test targets and tissue-mimicking phantoms are essential to test, optimize, calibrate, and evaluate optical imaging systems [1]
In optical coherence tomography (OCT), the axial resolution often exceeds the resolution in the lateral direction, and the axial point spread function (PSF) can be readily measured from a reflecting surface
The birefringence phantoms that we fabricated generate a tissue-like backscattering signal and contain spatially confined areas with a homogeneous, predictable amount of birefringence, in a range comparable to the birefringence reported in biological tissues such as muscle and collagen [38,39]
Summary
Resolution test targets and tissue-mimicking phantoms are essential to test, optimize, calibrate, and evaluate optical imaging systems [1]. The USAF 1951 resolution test target is frequently used to test an imaging system’s lateral resolution. In optical coherence tomography (OCT), the axial resolution often exceeds the resolution in the lateral direction, and the axial point spread function (PSF) can be readily measured from a reflecting surface. To directly assess the three dimensional PSF, targets containing point-like scatterers, such as laser marks or beads embedded in a transparent matrix can be used [2,3]. Beyond characterization of the PSF, to evaluate the structural and functional imaging performance, phantoms that mimic the optical, structural, and possibly mechanical properties of real biological tissue are highly valuable [1]. To test imaging performance and software segmentation accuracy, Baxi et al developed a phantom precisely replicating retinal morphology [7]
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