Tissue phantoms in multicenter clinical trials for diffuse optical technologies

Abstract

Tissue simulating phantoms are an important part of instrumentation validation, standardization/training and clinical translation. Properly used, phantoms form the backbone of sound quality control procedures. We describe the development and testing of a series of optically turbid phantoms used in a multi-center American College of Radiology Imaging Network (ACRIN) clinical trial of Diffuse Optical Spectroscopic Imaging (DOSI). The ACRIN trial is designed to measure the response of breast tumors to neoadjuvant chemotherapy. Phantom measurements are used to determine absolute instrument response functions during each measurement session and assess both long and short-term operator and instrument reliability.

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.…”

Preparation of a skin equivalent phantom with interior micron-scale vessel structures for optical imaging experiments

“…The refractive index of phantom is lower than the real value at 500 nm [22]. Nevertheless, this is not disturbing, when μ a and μ s approach the values of the ex-vivo tissue [23]. Summarizing from the previous results, we have successfully fabricated the object phantom with 4 seperate rows of vessels and a transparent phantom to ensure the feasibility of including liquid into the hollow vessels.…”

Diffuse optical tomography to monitor the photocoagulation front during interstitial photothermal therapy: Numerical simulations and measurements in tissue-simulating phantoms

“…To determine the change in optical properties required to match the measured and simulated data, simulations were repeated using a range of optical properties. Full agreement was achieved when the background absorption was 2 × greater than the absorption of the anomaly, significantly higher than the measured contrast (∼1:1) and beyond any measurement error in the optical properties of the silicone phantom [36,39]. The limited mesh resolution (2 mm node-to-node distance) may also contribute to the discrepancy; the large volume required to model the experimental set-up limited the resolution.…”

“…The absorption spectrum, μ a (λ), of India ink was measured in a spectrophotometer and added to the intrinsic absorption of the silicone and Intralipid ® [35]. The reduced scattering spectrum, ( ) s µ λ ′ , of the solid phantom was measured using an established frequencydomain diffuse reflectance technique [36,37], while the reduced scattering coefficients of various dilutions of the 20% Intralipid ® stock solution at 690 nm were measured using an in-house CW-DOT system that will be the basis for the first clinical prototype and will be described in a future publication. The values at each of the three wavelengths were then calculated using the following equation, which is based on Mie scattering theory [38]:…”