E 4 1 5What ' s known on the subject? and What does the study add? Optical Coherence Tomography (OCT) was developed in the early 1990s for ophthalmological application and is currently widely accepted in ophthalmology for retinal imaging purposes. In kidneys, the fi rst experiments were performed on transplant kidneys to investigate the ability of OCT to assess ischaemic damage of kidneys. An ex vivo pilot study on the ability of OCT to differentiate normal renal tissue from malignant renal tissue, showed positive results and here we present the results of the fi rst in vivo experiment.

Single fiber reflectance (SFR) spectroscopy is a technique that is sensitive to small-scale changes in tissue. An additional benefit is that SFR measurements can be performed through endoscopes or biopsy needles. In SFR spectroscopy, a single fiber emits and collects light. Tissue optical properties can be extracted from SFR spectra and related to the disease state of tissue. However, the model currently used to extract optical properties was derived for tissues with modified Henyey-Greenstein phase functions only and is inadequate for other tissue phase functions. Here, we will present a model for SFR spectroscopy that provides accurate results for a large range of tissue phase functions, reduced scattering coefficients, and absorption coefficients. Our model predicts the reflectance with a median error of 5.6% compared to 19.3% for the currently used model. For two simulated tissue spectra, our model fit provides accurate results.

. Significance : Optical coherence tomography (OCT) is an interferometric imaging modality, which provides tomographic information on the microscopic scale. Furthermore, OCT signal analysis facilitates quantification of tissue optical properties (e.g., the attenuation coefficient), which provides information regarding the structure and organization of tissue. However, a rigorous and standardized measure of the precision of the OCT-derived optical properties, to date, is missing. Aim : We present a robust theoretical framework, which provides the Cramér –Rao lower bound for the precision of OCT-derived optical attenuation coefficients. Approach : Using a maximum likelihood approach and Fisher information, we derive an analytical solution for when the position and depth of focus are known. We validate this solution, using simulated OCT signals, for which attenuation coefficients are extracted using a least-squares fitting procedure. Results : Our analytical solution is in perfect agreement with simulated data without shot noise. When shot noise is present, we show that the analytical solution still holds for signal-to-noise ratios (SNRs) in the fitting window being above 20 dB. For other cases ( , focus position not precisely known), we show that the numerical calculation of the precision agrees with the derived from simulated signals. Conclusions : Our analytical solution provides a fast, rigorous, and easy-to-use measure for OCT-derived attenuation coefficients for signals above 20 dB. The effect of uncertainties in the focal point position on the precision in the attenuation coefficient, the second assumption underlying our analytical solution, is also investigated by numerical calculation of the lower bounds. This method can be straightforwardly extended to uncertainty in other system parameters.