Journal of Biomedical Optics最新文献

Significance: Shortwave-infrared (SWIR) imaging is reported to yield better contrast in fluorescence-guided surgery than near-infrared (NIR) imaging, due to a reduction in scattering. This benefit of SWIR was shown in animal studies, however not yet in clinical studies with patient samples.

Aim: We investigate the potential benefit of SWIR to NIR imaging in clinical samples containing cetuximab-IRDye800CW in fluorescence-guided surgery.

Approach: The potential of the epidermal growth factor-targeted NIR dye cetuximab-IRDye800CW in the shortwave range was examined by recording the absorption and emission spectrum. An ex vivo comparison of NIR and SWIR images using clinical tumor samples of patients with penile squamous cell carcinoma (PSCC) and head and neck squamous cell carcinoma (HNSCC) containing cetuximab-IRDye800CW was performed. The comparison was based on the tumor-to-background ratio and an adapted contrast-to-noise ratio (aCNR) using the standard of care pathology tissue assessment as the golden standard.

Results: Based on the emission spectrum, cetuximab-IRDye800CW can be detected in the SWIR range. In clinical PSCC samples, overall SWIR imaging was found to perform similarly to NIR imaging (NIR imaging is better than SWIR in the 2/7 criteria examined, and SWIR is better than NIR in the 3/7 criteria). However, when inspecting HNSCC data, NIR is better than SWIR in nearly all (5/7) examined criteria. This difference seems to originate from background autofluorescence overwhelming the off-peak SWIR fluorescence signal in HNSCC tissue.

Conclusion: SWIR imaging using the targeted tracer cetuximab-IRDye800CW currently does not provide additional benefit over NIR imaging in ex vivo clinical samples. Background fluorescence in the SWIR region, resulting in a higher background signal, limits SWIR imaging in HNSCC samples. However, SWIR shows potential in increasing the contrast of tumor borders in PSCC samples, as shown by a higher aCNR over a line.

Significance: Head and neck squamous cell carcinoma (HNSCC) has the sixth highest incidence worldwide, with $>\mathrm{650,000}$ cases annually. Surgery is the primary treatment option for HNSCC, during which surgeons balance two main goals: (1) complete cancer resection and (2) preservation of normal tissues to ensure post-surgical quality of life. Unfortunately, these goals are not synergistic, where complete cancer resection is often limited by efforts to preserve normal tissues, particularly nerves, and reduce life-altering comorbidities.

Aim: Currently, no clinically validated technology exists to enhance intraoperative cancer and nerve recognition. Fluorescence-guided surgery (FGS) has successfully integrated into clinical medicine, providing surgeons with real-time visualization of important tissues and complex anatomy, where FGS imaging systems operate almost exclusively in the near-infrared (NIR, 650 to 900 nm). Notably, this spectral range permits the detection of two NIR imaging channels for spectrally distinct detection.

Approach: Herein, we evaluated the utility of spectrally distinct NIR nerve- and tumor-specific fluorophores for two-color FGS to guide HNSCC surgery. Using a human HNSCC xenograft murine model, we demonstrated that facial nerves and tumors could be readily differentiated using these nerve- and tumor-specific NIR fluorophores.

Results: The selected nerve-specific fluorophore showed no significant difference in nerve specificity and off-target tissue fluorescence in the presence of xenograft head and neck tumors. Co-administration of two NIR fluorophores demonstrated successful tissue-specific labeling of nerves and tumors in spectrally distinct NIR imaging channels.

Conclusions: We demonstrate a comprehensive FGS tool for cancer resection and nerve sparing during HNSCC procedures for future clinical translation.

[This corrects the article DOI: 10.1117/1.JBO.29.12.120501.].

Significance: Tracking changes in the vasculature of patients with peripheral arterial disease (PAD) may identify the need for follow-up treatment within only weeks after an initial intervention, enabling timely support and improving patient outcomes.

Aim: We aim to evaluate dynamic vascular optical spectroscopy's (DVOS's) ability to accurately monitor the hemodynamics of affected arteries in patients with PAD after a surgical intervention and predict long-term clinical outcomes.

Approach: A DVOS system non-invasively monitored the blood flow through 256 lower extremity arteries in 80 PAD patients immediately before, immediately after, and 3 to 4 weeks after they underwent a surgical intervention.

Results: Hemodynamic changes measured by DVOS after a revascularization procedure (RP) classified patient long-term ( $6.2\pm 4.4$ months) outcomes with high accuracy [81.6% for patients with ulcers ( $n=31$ ); 81.1% for patients without ulcers ( $n=54$ )] by 3 to 4 weeks after the RP, outperforming available ankle-brachial index and ultrasound measurements. In addition, DVOS parameters distinguished between patients who underwent only a catheter angiography (CA) and patients who underwent both a CA and RP ( $P<0.05$ ).

Conclusions: The DVOS system was able to classify patient long-term clinical outcomes with high accuracy within one month after an RP and distinguish among different interventions. DVOS may be a promising alternative or adjunct to existing monitoring approaches.

Significance: Cellular metabolic dynamics can occur within milliseconds, yet there are no optimal tools to spatially and temporally capture these events. Autofluorescence imaging can provide metabolic information on the cellular level due to the intrinsic fluorescence of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] and flavin adenine dinucleotide (FAD).

Aim: Our goal is to build and evaluate a widefield microscope optimized for rapid autofluorescence imaging of metabolic changes in cells.

Approach: A widefield, fluorescence microscope was assembled from an inverted microscope base, an light-emitting diode (LED) for excitation, and an image splitter for simultaneous but separate imaging of two bandwidths of emission (451/106 and 560/94 nm) on a single scientific complementary metal-oxide-semiconductor (sCMOS) camera. MCF-7 cells and primary murine hippocampal neurons were metabolically perturbed using cyanide and imaged to optimize illumination and camera exposure. To capture a rapid change in metabolism, MCF-7 cells were starved for 1 h and imaged while reintroduced to glucose.

Results: Significant differences in the optical redox ratio (ORR) and intensity of NAD(P)H divided by the summed intensities of NAD(P)H and FAD were quantified for cyanide-treated neurons and MCF-7 cells at illumination powers above 0.30 mW and camera exposures as low as 5 ms; however, low illumination and camera exposures hindered the ability to identify subcellular features. Minimal photobleaching was quantified for 30 s of continuous imaging for illuminations at 4.14 mW and below. Using the optimized illumination power of 4.14 mW and an exposure of 10 ms, continuous autofluorescence imaging of starved MCF-7 cells demonstrated a rapid, yet heterogeneous, increase in the ORR of cells upon exposure to glucose.

Conclusions: Ultimately, this widefield autofluorescence imaging system allowed for dynamic imaging and quantification of cellular metabolism at 99.6 Hz.

Significance: Alzheimer's disease (AD) is a predominant form of dementia that can lead to a decline in the quality of life and mortality. The understanding of the pathological changes requires monitoring of multiple cerebral biomarkers simultaneously with high resolution. Photoacoustic microscopy resolves single capillaries, allowing investigations into the most affected types of vessels. Combined with confocal fluorescence microscopy, the relationship between plaque deposition and small vessel pathology could be better understood.

Aim: We aim to introduce a dual-modality imaging system combining photoacoustic microscopy (PAM) and confocal fluorescence microscopy (CFM) to provide a comprehensive view of both cerebral cortical vessels and amyloid- $\beta$ ( $A\beta$ ) plaque in AD mouse model in vivo and to identify the pathological changes of these two biomarkers.

Approach: We developed a dual-modality imaging system to image both cerebral vessel structure and $A\beta$ plaque on groups of mice with different ages and phenotypes. Vessel imaging is enabled by PAM, whereas $A\beta$ plaque is imaged by CFM with the aid of fluorescent dye.

Results: The small vessel density in the AD group was significantly lower than in the control group, whereas the $A\beta$ plaque density in the AD group was not only higher but also increased with age.

Conclusions: This dual-modality system provides a powerful platform for biomarker monitoring of AD expressing multi-dimensional pathological changes.

Significance: Imaging deep structures with optical coherence tomography (OCT) is difficult in highly scattering biological tissue, such as the sclera. There is a need to visualize the suprachoroidal space and choroid through the sclera to study suprachoroidal drug delivery.

Aim: We aim to develop optical methods to image through the highly scattering sclera with a custom-built OCT system to visualize the suprachoroidal space and drug delivery within.

Approach: We developed a custom handheld OCT scanner to image the anterior segment and suprachoroidal space in ex vivo eye models. Tartrazine (Yellow 5) solution, which has been shown to optically clear biological tissue in the visible regime, was tested as a clearing agent to optimize near infrared OCT imaging through the sclera.

Results: Tartrazine dramatically increased OCT signal return from the deeper sclera and choroid and thus enabled visualization of the suprachoroidal drug delivery after transscleral injection.

Conclusions: We demonstrated successful optical clearing of the thick, porcine sclera with a compact handheld OCT system to image the suprachoroidal space. We believe there is broader potential to use optical clearing with handheld OCT for a variety of previously inaccessible, highly scattering tissue samples.

Significance: Cellular metabolism is highly dynamic and strongly influenced by its local vascular microenvironment, gaining a systems-level view of cell metabolism in vivo is essential in understanding many critical biomedical problems in a broad range of disciplines. However, very few existing metabolic tools can quantify the major metabolic and vascular parameters together in biological tissues in vivo with easy access.

Aim: We aim to fill the technical gap by demonstrating a point-of-care, easy-to-use, easy-to-access, rapid, systematic optical spectroscopy platform for metabolic and vascular characterizations on biological models in vivo to enable scientific discoveries to translate more efficiently to clinical interventions.

Approach: We developed a highly portable optical spectroscopy platform with a tumor-sensitive fiber probe and easy-to-use spectroscopic algorithms for multi-parametric metabolic and vascular characterizations of biological tissues in vivo. We then demonstrated our optical spectroscopy on tissue-mimicking phantoms, human subjects, and small in vivo tumor models. We also validated the proposed easy-to-use algorithms with the Monte Carlo inversion models for accurate and rapid spectroscopic data processing.

Results: Our tissue-mimicking phantom, human subjects, and in vivo animal studies showed that our portable optical spectroscopy along with the new spectroscopic algorithms could quantify the major metabolic and vascular parameters on biological tissues with a high accuracy. We also captured the highly diverse metabolic and vascular phenotypes of head and neck tumors with different radiation sensitivities.

Conclusions: Our highly portable optical spectroscopy platform along with easy-to-use spectroscopic algorithms will provide an easy-to-access way for rapid and systematic characterizations of biological tissue metabolism and vascular microenvironment in vivo, which may significantly advance translational cancer research in the future.

Significance: A data-based calibration method with enhanced depolarization contrast in polarization-sensitive optical coherence tomography (PS-OCT) was developed and demonstrated effective for detecting melanin content in the eye.

Aim: We aim to mitigate the dependence between the measured depolarization metric and the intensity signal-to-noise ratio (SNR) for improved visualization of depolarizing tissues, especially in low SNR regions, and to demonstrate the enhanced depolarization contrast to evaluate melanin presence.

Approach: A function for calibrating the depolarization metric was experimentally derived from the young albino guinea pig, assuming depolarization free in the retina. A longitudinal study of guinea pigs (9 weeks) was conducted to assess the accumulation of melanin during early eye growth. Furthermore, the melanin content of the sub-macular choroid was compared in eyes with light and dark irides involving 14 human subjects in early middle adulthood.

Results: We observed an increase in the improved depolarization contrast, which indicates potential melanin accumulation in the early eye development with age in the pigmented guinea pig eyes. We found a significant difference in melanin content between human eyes with light and dark colors.

Conclusions: Our proposed calibration method enhanced the visualization of depolarizing structures in PS-OCT, which can be generalized to all kinds of polarization-sensitive imaging and can potentially monitor melanin in healthy and pathological eyes.

Significance: The eye can be used as a potential monitoring window for screening, diagnosis, and monitoring of neurological diseases. Alzheimer's disease (AD) and vascular cognitive impairment (VCI) are common causes of cognitive impairment and may share many similarities in ocular signs. Multimodal ophthalmic imaging is a technology to quantify pupillary light reaction, retinal reflectance spectrum, and hemodynamics. This provides multidimensional ocular metrics from a non-invasive approach to ocular biomarkers and differential diagnosis of AD and VCI.

Aim: We aim to investigate the changing pattern of ocular metrics in patients with AD and VCI using multimodal ophthalmic imaging.

Approach: Patients with subjective cognitive complaints in the memory clinic were subdivided into AD, VCI, and cognitively healthy individuals using neuropsychological and neuroimaging examinations, including positron emission tomography. All subjects underwent a medical history review, blood pressure measurement, medical optometry, intraocular pressure measurement, and custom-built multimodal ophthalmic imaging. Multidimensional parameters were analyzed by one-way analysis of variance and post hoc comparisons.

Results: This study included 19 patients with AD, 24 patients with VCI, and 37 cognitively healthy age- and sex-matched subjects. Both AD and VCI patients showed abnormal pupillary light reactions, including decreased resting pupil diameter, pupil constriction amplitude, and maximum constriction velocity. Compared with the control group, the AD group presented increased retinal reflectance at 548 nm, whereas the VCI group presented an increased resistivity index and decreased blowout score in retinal hemodynamics.

Conclusions: We demonstrate that pupillary light reaction-related neurodegeneration is the common pathological change in both AD and VCI. In addition, AD is characterized by alterations in retinal spectral signatures, whereas VCI is characterized by alterations in retinal hemodynamics. These findings suggest that multimodal ophthalmic imaging may have the potential to be used as a screening tool for detecting AD and VCI.