Impact of signal-to-noise ratio and contrast definition on the sensitivity assessment and benchmarking of fluorescence molecular imaging systems.

Significance: Standardization of fluorescence molecular imaging (FMI) is critical for ensuring quality control in guiding surgical procedures. To accurately evaluate system performance, two metrics, the signal-to-noise ratio (SNR) and contrast, are widely employed. However, there is currently no consensus on how these metrics can be computed. Aim: We aim to examine the impact of SNR and contrast definitions on the performance assessment of FMI systems. Approach: We quantified the SNR and contrast of six near-infrared FMI systems by imaging a multi-parametric phantom. Based on approaches commonly used in the literature, we quantified seven SNRs and four contrast values considering different background regions and/or formulas. Then, we calculated benchmarking (BM) scores and respective rank values for each system. Results: We show that the performance assessment of an FMI system changes depending on the background locations and the applied quantification method. For a single system, the different metrics can vary up to ∼ 35 dB (SNR), ∼ 8.65 a . u . (contrast), and ∼ 0.67 a . u . (BM score). Conclusions: The definition of precise guidelines for FMI performance assessment is imperative to ensure successful clinical translation of the technology. Such guidelines can also enable quality control for the already clinically approved indocyanine green-based fluorescence image-guided surgery.

Effect of albumin on the fluorescence quantum yield of porphyrin -based agents for fluorescent diagnostics.

BACKGROUND: Among modern methods of tumor diagnosis, fluorescent methods are considered one of the most prospective. Diagnostic agents (DAs) spread throughout the body by the bloodstream, so, the DA molecules are often transported by albumins and can be affected by these proteins. In our study we evaluate the effect of complex formation between bovine serum albumin (BSA) and three fluorescence DA's (Photolon, Photoditazin and Dimegin) on their fluorescent quantum yields. METHODS: Electron absorption spectroscopy and fluorescence spectroscopy were carried out to calculate fluorescence quantum yields of the DAs using Rhodamine 6G as a standard fluorescent dye. RESULTS: For all three DA's dissolved in phosphate buffer with pH 7.5 (close to that of blood) the addition of albumin resulted in bathochromic shift of the Soret band as well as change of amplitudes of absorption bands. Similar changes were observed for fluorescence spectra of all DAs that are connected with complex formation between DA and albumin. The presence of isobestic point suggests that DA can present in the solution only in two states, free and BSA-bound. Chlorine-based DA's demonstrate about 1.5-times higher fluorescence quantum yield in PBS than Dimegin. Nevertheless, the addition of BSA to the solutions of all DA's decreases sharply their fluorescence quantum yield to approximately equal values. CONCLUSION: The complex formation between DA and albumin equalize fluorescence efficacies of all studied DAs, so the results of photodymanic diagnostics using the specific DA will depend on other factors.