# Method for Measuring Absolute Optical Properties of Turbid Samples in a Standard Cuvette
## 4 Discussion
Therefore, we expect that an instrumental design for this method would include a cuvette designed for high \(n_{o}\). Additionally, the current model considers a cuvette closed on all sides so that \(n_{o}\) is the same on all six faces. This is unrealistic for a typical cuvette which would have one side open to the air. When this method is implemented in practice, either a lid with the same material as the cuvette would need to be incorporated or the air boundary on one side considered. If a top air boundary is considered the SR\(\{\widetilde{T}\}\)s would not be the same in theory, but the SC/DS coupling cancellation would still apply. The model would need to be more complex since \(\mathrm{DR}\{\widetilde{T}\}\) would no longer equal the theoretical SR\(\{\widetilde{T}\}\) but instead the average of the two since theoretical SR\(\{\widetilde{T}\}\)s would not be equal, but given the correct model an inversion is still expected to work. Further, we also note that examining the expression for \(\widetilde{\mu}_{eff}\) (Equation (11)) ones sees that \(\mu_{a}\) and \(\mu_{s}^{\prime}\) are coupled to \(n_{i}\). This means that any diffuse measurement using such theory would actually measure \(\mu_{s}^{\prime}n_{i}\) and \(\mu_{a}/n_{i}\). Therefore, cross-talk with \(n_{i}\) is a necessary consequence of the theory and can only really be suppressed, not removed. This is seen by examining the data-sheet for the SphereSpecto which utilizes the integrating sphere measurement method [14; 15]. The SphereSpecto states that with a \(n\) uncertainty of 0.06 one should expect a \(\mu_{a}\) uncertainty of 12 % and a \(\mu_{s}^{\prime}\) of 7 % [39]. Therefore, the method presented here is, at least in theory, comparable to existing instruments. Finally, we revisit the idea of calibration. In Section 3.1.2, we showed that this method takes the advantages of SC [24]/DS [29; 30] meaning that the measurements of \(\ln|\text{DR}\{\widetilde{T}\}|\) and \(\angle\text{DR}\{\widetilde{T}\}\) are insensitive to instrumental coupling. However, due to the fact that this method utilizes a small geometry and is highly affected by boundary conditions, other instrumental calibration may be required. First, since this diffusion theory solution (Equation (10)) is for such a small geometry, calibration of the inverse model maybe necessary if factors exist which are not modeled by \(\widetilde{C}\) (Section 3.1.2). Three options are available for creating an inverse model:  
* Diffusion theory based cost minimization (shown here). * Look-up table with Monte-Carlo generated data. * Look-up table with instrumental measurements of known samples. Option I is the most elegant which is why it was chosen here, but option III (being the most brute-force and likely infeasible in practice due to the extensive calibration phantom preparation and measurement needed for each unique instrument) would almost definitely work, and allows for correction of systematic confounds, provided that the measurements are repeatable. The auto-calibration in Section 3.1.2 is expected to significantly help with this repeatability, but the biggest secondary factor is repeatable boundary conditions. The investigation here showed promise to alleviate the boundary conditions issue by using high \(n_{o}\), but future work will investigate the repeatability of measurements of cuvettes with various boundary conditions experimentally. Of course, this future work would involve experimental implementation of the measurement. For this we plan to utilize the Imagent which utilizes fiber bundles that will be coupled to the sides of a standard cuvette. Regardless of the coupling method, we expect the SC/DS method to compensate for optode and coupling losses. However, these optodes will not act as true pencil beams or point detectors as is modeled here. This is another condition which could cause errors in the measurement and would need to be modeled or calibrated for.