Designing microarray phantoms for hyperspectral imaging validation

Abstract

The design and fabrication of custom-tailored microarrays for use as phantoms in the characterization of hyperspectral imaging systems is described. Corresponding analysis methods for biologically relevant samples are also discussed. An image-based phantom design was used to program a microarrayer robot to print prescribed mixtures of dyes onto microscope slides. The resulting arrays were imaged by a hyperspectral imaging microscope. The shape of the spots results in significant scattering signals, which can be used to test image analysis algorithms. Separation of the scattering signals allowed elucidation of individual dye spectra. In addition, spectral fitting of the absorbance spectra of complex dye mixtures was performed in order to determine local dye concentrations. Such microarray phantoms provide a robust testing platform for comparisons of hyperspectral imaging acquisition and analysis methods.

Multi-layered tissue head phantoms for noninvasive optical diagnostics

“…Such optical measurement systems for biomedical applications rely on tissue-equivalent phantoms for testing system design and comparing di®erent measurement methods. [2][3][4][5][6][7][8][9] Use of real human tissues is impractical since the optical properties of such samples change in various atmospheric conditions (i.e., humidity, temperature) and rapidly degrade over time, thus they are unusable as standards with known and stable properties. Therefore, optical properties of phantoms (scattering coe±cient s , absorption coe±cient a , scattering anisotropy factor g, refractive index n, and thickness L) should be properly tuned to correspond to that of tissues they mimic.…”

Measurements of fundamental properties of homogeneous tissue phantoms

“…The optical signal response of a phantom is then identical to that of a tissue making it valid for instrument calibration. [7][8][9][36][37][38][39] Therefore, the exact reconstruction of the scattering and absorption may be performed based only on accurate measurements. We estimated the coefficients μ a , μ 0 s , and g for each phantom using spectrometric measurements and the IAD calculations.…”

“…[1][2][3][4][5][6][7][8][9][10] The development and evaluation of such methods require frequent calibration of the devices. However, real biological tissues differ greatly from each other and their optical properties are susceptible to rapid changes over time and with varying environmental conditions.…”

Algorithm validation using multicolor phantoms

“…Recently a novel, custom-tailored microarray printing platform was developed[ 5 , 6 ] to create a testbed for characterizing hyperspectral imaging systems and validating algorithm performance. This microarray printing system allows for precise sample composition through variation of dye concentrations and mixture proportions, and high spatial control.…”

“…This overlap presents a considerable challenge when trying to determine the concentration and proportion of a particular dye at a given spatial location where two dyes have been mixed. While not presented here, multicolor phantoms have been developed where the spectral signatures are more distinct, making estimation of the abundance fraction (somewhat) easier[ 11 , 5 , 6 ]. The two remaining signatures correspond to the PEG and background spectra.…”