The age estimation of biological traces is one of the holy grails in forensic investigations. We developed a method for the age estimation of semen stains using fluorescence spectroscopy in conjunction with a stoichiometric ageing model. The model describes the degradation and generation rate of proteins and fluorescent oxidation products (FOX) over time. The previously used fluorimeter is a large benchtop device and requires system optimization for forensic applications. In situ applications have the advantage that measurements can be performed directly at the crime scene, without additional sampling or storage steps. Therefore, a portable fiber-based fluorimeter was developed, consisting of two optimized light-emitting diodes (LEDs) and two spectrometers to allow the fluorescence protein and FOX measurements. The handheld fiber can be used without touching the traces, avoiding the destruction or contamination of the trace. In this study, we have measured the ageing kinetics of semen stains over time using both our portable fluorimeter and a laboratory benchtop fluorimeter and compared their accuracies for the age estimation of semen stains. Successful age estimation was possible up to 11 days, with a mean absolute error of 1.0 days and 0.9 days for the portable and the benchtop fluorimeters, respectively. These results demonstrate the potential of using the portable fluorimeter for in situ applications.

In this study, four optical techniques—Optical Coherence Tomography, Sidestream Darkfield Microscopy, Laser Speckle Contrast Imaging, and Fluorescence Angiography (FA)—were compared on performing an intraoperative quantitative perfusion assessment of the gastric conduit during oesophagectomy. We hypothesised that the quantitative parameters show decreased perfusion towards the fundus in the gastric conduit and in patients with anastomotic leakage. In a prospective study in patients undergoing oesophagectomy with gastric conduit reconstruction, measurements were taken with all four optical techniques at four locations from the base towards the fundus in the gastric conduit (Loc1, Loc2, Loc3, Loc4). The primary outcome included 14 quantitative parameters and the anastomotic leakage rate. Imaging was performed in 22 patients during oesophagectomy. Ten out of 14 quantitative parameters significantly indicated a reduced perfusion towards the fundus of the gastric conduit. Anastomotic leakage occurred in 4/22 patients (18.4%). At Loc4, the FA quantitative values for “T_1/2” and “mean slope” differed between patients with and without anastomotic leakage (p = 0.025 and p = 0.041, respectively). A quantitative perfusion assessment during oesophagectomy is feasible using optical imaging techniques, of which FA is the most promising for future research.

Near infrared imaging (NIR) camera systems have been clinically deployed to visualize intravenous injected indocyanine green (ICG) spreading through the vascular bed, thereby creating the ability to assess tissue perfusion. While standardization is key to make fluorescence angiography (FA) comparable and reproducible, optical characteristics like field illumination homogeneity are often not considered. Therefore the aim of this study is to investigate light distribution and the center-periphery effect among five different NIR imaging devices in an indocyanine green phantom. A 13 × 13 cm fluorescence phantom was created by diluting ICG in Intralipid (representing 0.1 mg/kg dose in an 80 kg reference male), to evaluate the overall spatial collection efficiency with fluorescent modalities of five different NIR camera systems using a 0-degree laparoscope. The fluorescence signal from the phantom was quantified at a fixed distance of 16 cm using tailor-made software in Python. The results showed considerable variability in regard to light distribution among the five camera systems, especially toward the periphery of the field of view. In conclusion, NIR signal distribution varies between different systems and within the same displayed image. The fluorescence intensity diminishes peripherally away from the center of the field of view. These optical phenomena need to be considered when clinically interpreting the signal and in the development of computational fluorescence quantification.

Background/Objectives: Indocyanine green fluorescence angiography (ICG-FA) enables the real-time visualization of tissue perfusion. However, objective research on microscope-integrated fluorescence angiography (FA) has not been conducted before. This study aims to evaluate the fluorescence light distribution in images formed by ICG-FA in two surgical microscopes using a phantom, and to provide recommendations for their application. Methods: An 11.8 by 6.8 cm ICG and Intralipid phantom was made to evaluate overall spatial fluorescence sensitivity in two surgical microscopes in multiple working distances (WDs) and magnification factors (MFs). The signal was quantified using a tailor-made software in Python 3.8.10. Results: A clear center–periphery effect was present in most settings in both microscopes, with the highest peripheral fluorescence signal loss in the lowest MF: 100% in the Tivato and 83% in the Pentero. Increasing the MF improved homogeneity, where the biggest difference was seen between the first and second MF. A 30 cm WD and 3.5× MF produced the most homogeneous images suitable for free-flap surgery. Manually opening the light beam diameter also reduced the center–periphery effect. Conclusions: Peripheral signal loss in microscope-integrated ICG-FA must be considered during clinical interpretation and for the quantification of tissue perfusion. In clinical practice during reconstructive free-flap surgery, a 30 cm WD, 3.5 MF, and manually opened light beam diameter should be applied to achieve the most homogeneous image.

A technique that enables real-time diagnosis of bladder cancer is needed. Optical coherence tomography (OCT) is a promising technique, but a forward-looking OCT catheter is necessary for OCT to enable bladder cancer diagnosis. This study aims to describe the design of a novel forward-looking microelectromechanical systems (MEMS)-based OCT catheter, assess the performance characteristics, and evaluate its ability to identify histopathological characteristics of bladder specimens. A description of the OCT catheter and systems used is provided. Performance characteristics were measured with a beam profiler and microscopy slide (mirror for dispersion and thickness for lateral calibration). Ex vivo measurements were performed on resected bladder tissue from patients undergoing a radical cystectomy. A forward-looking OCT probe with an outer diameter of 2.52 mm and a rigid length of 17 mm was designed and evaluated. The focus position was measured as 10.9 mm from the MEMS mirror, with a Rayleigh length of 2.55 mm. Several histopathological features could be correlated to OCT features of the ex vivo measurements. In conclusion, a forward-looking OCT probe that can be inserted in the working channel of a rigid cystoscope was designed and evaluated. Performance characteristics were overall in line with simulated expectations.