Fluorescence Imaging-Guided Identification of Thymic Masses Using Low-Dose Indocyanine Green.

BACKGROUND: Indocyanine green (ICG) fluorescence imaging has been used to detect many types of tumors during surgery; however, there are few studies on thymic masses and the dose and time of ICG injection have not been optimized. OBJECTIVE: We aimed to evaluate the optimal ICG injection dose and timing for detecting thymic masses during surgery. METHOD: Forty-nine consecutive patients diagnosed with thymic masses on preoperative computed tomography (CT) and scheduled to undergo thymic cystectomy or thymectomy were included. Patients were administered 1, 2, or 5 mg/kg of ICG at different times. Thymic masses were observed during and after surgery using a near-infrared fluorescence imaging system, and the fluorescence signal tumor-to-normal ratio (TNR) was analyzed. RESULTS: Among the 49 patients, 14 patients with thymic cysts showed negative fluorescence signals, 33 patients with thymoma or thymic carcinoma showed positive fluorescence signals, and 2 patients showed insufficient fluorescence signals. The diagnosis of thymic masses based on CT was correct in 32 (65%) of 49 cases; however, the differential diagnosis of thymic masses based on NIR signals was correct in 47 of 49 cases (96%), including 14 cases of thymic cysts (100%) and 33 cases of thymomas or thymic carcinomas (94%). In addition, TNR was not affected by the time or dose of ICG injection, histological type, stage, or tumor size. CONCLUSIONS: Low-dose intravenous injection of ICG at flexible time can detect thymic tumors. In addition, thymic cysts can be distinguished from thymomas or thymic carcinomas during surgery by the absence of ICG fluorescence signals.

Fluorescent and Iodized Emulsion for Preoperative Localization of Pulmonary Nodules.

OBJECTIVE: This study was conducted to develop a fluorescent iodized emulsion comprising indocyanine green (ICG) solution and lipiodol (ethiodized oil) and evaluate its feasibility for use in a clinical setting. BACKGROUND: ICG use for the preoperative localization of pulmonary nodules is limited in terms of penetration depth and diffusion. METHODS: First, fluorescent microscopy was used to investigate the distribution of ICG-lipiodol emulsions prepared using different methods. The emulsions were injected in 15 lung lobes of 3 rabbits under computed tomography fluoroscopy guidance; evaluation with imaging and radiography was conducted after thoracotomy. Subsequently, the emulsions were used to preoperatively localize 29 pulmonary nodules in 24 human subjects, and wedge resections were performed using fluorescent imaging and C-arm fluoroscopy. RESULTS: The optimal emulsion of 10% ICG and 90% lipiodol mixed through 90 passages had even distribution and the highest signal intensity under fluorescent microscopy; it also had the best consistency in the rabbit lungs, which persisted for 24 hours at the injection site. In human subjects, the mean diameter of pulmonary nodules was 0.9 ±â€Š0.4 cm, and depth from the pleura was 1.2 ± 0.8 cm. All emulsion types injected were well localized around the target nodules without any side effects or procedure-related complications. Wedge resection with minimally invasive approach was successful in all pulmonary nodules with a free resection margin. CONCLUSIONS: A fluorescent iodized emulsion prepared by mixing ICG with lipiodol enabled accurate localization and resection of pulmonary nodules.

A Novel Singular Value Decomposition-Based Denoising Method in 4-Dimensional Computed Tomography of the Brain in Stroke Patients with Statistical Evaluation.

Computed tomography (CT) is a widely used medical imaging modality for diagnosing various diseases. Among CT techniques, 4-dimensional CT perfusion (4D-CTP) of the brain is established in most centers for diagnosing strokes and is considered the gold standard for hyperacute stroke diagnosis. However, because the detrimental effects of high radiation doses from 4D-CTP may cause serious health risks in stroke survivors, our research team aimed to introduce a novel image-processing technique. Our singular value decomposition (SVD)-based image-processing technique can improve image quality, first, by separating several image components using SVD and, second, by reconstructing signal component images to remove noise, thereby improving image quality. For the demonstration in this study, 20 4D-CTP dynamic images of suspected acute stroke patients were collected. Both the images that were and were not processed via the proposed method were compared. Each acquired image was objectively evaluated using contrast-to-noise and signal-to-noise ratios. The scores of the parameters assessed for the qualitative evaluation of image quality improved to an excellent rating (p < 0.05). Therefore, our SVD-based image-denoising technique improved the diagnostic value of images by improving their quality. The denoising technique and statistical evaluation can be utilized in various clinical applications to provide advanced medical services.

Single-shot and phase-shifting digital holographic microscopy using a 2-D grating.

We demonstrate digital holographic microscopy that, while being based on phase-shifting interferometry, is capable of single-shot measurements. A two-dimensional (2-D) diffraction grating placed in a Fourier plane of a standard in-line holographic phase microscope generates multiple copies of a sample image on a camera sensor. The identical image copies are spatially separated with different overall phase shifts according to the diffraction orders. The overall phase shifts are adjusted by controlling the lateral position of the grating. These phase shifts are then set to be multiples of π/2. Interferograms composed of four image copies combined with a parallel reference beam are acquired in a single shot. The interferograms are processed through a phase-shifting algorithm to produce a single complex image. By taking advantage of the higher sampling capacity of the in-line holography, we can increase the imaging information density by a factor of 3 without compromising the imaging acquisition speed.

Single-shot digital holographic microscopy for quantifying a spatially-resolved Jones matrix of biological specimens.

Field-based polarization measurements are essential for the completeness of information when exploiting the complex nature of optical responses of target objects. Here, we demonstrate digital holographic microscopy for quantifying a polarization-sensitive map of an object with a single-shot measurement. Using the image-splitting device generating four different copies of an object image and a separate reference beam of an off-axis configuration enables single-shot and multi-imaging capability. With the use of two polarization filters, four complex field images containing an object's polarization response are obtained simultaneously. With this method, we can construct a complete set of 2-by-2 Jones matrix at every single point of the object's images, and thus clearly visualize the anisotropic structures of biological tissues with low level of birefringence. This method will facilitate the high-precision measurements for fast dynamics of the polarization properties of biological specimens.

High-resolution, dual-depth spectral-domain optical coherence tomography with interlaced detection for whole-eye imaging.

Dual-depth spectral-domain optical coherence tomography (SD-OCT) enables high-resolution in vivo whole-eye imaging. Two orthogonally polarized beams from a source are focused simultaneously on two axial positions of the anterior segment and the retina. For the detector arm, a 1×2 ultrafast optical switch sequentially delivers two spectral interference signals to a single spectrometer, which extends the in-air axial depth range up to 9.44 mm. An off-pivot complex conjugate removal technique doubles the depth range for all anterior segment imaging. The graphics-processing-unit-based parallel signal processing algorithm supports fast two- and three-dimensional image displays. The obtained high-resolution anterior and retinal images are measured biometrically. The dual-depth SD-OCT system has an axial resolution of ∼6.4 µm in air, and the sensitivity is 91.79 dB at 150 µm from the zero-delay line.

Spectral domain optical coherence tomography with balanced detection using single line-scan camera and optical delay line.

We propose a spectral domain optical coherence tomography (SD-OCT) system that uses a single line-scan detection scheme for balanced detection. Two phase-opposed spectra, generated by two optical fiber couplers, were detected by using a spectrometer with fast optical switching. A 2.69 km optical fiber was introduced to provide a proper time delay to prevent phase errors caused by the difference in measurement time between the two opposing spectra and unstable output voltages for controlling the galvano-scanner. Hence, a phase difference of π was obtained between the spectra over the sample depth without a phase error, which improved sensitivity by approximately 6 dB compared to that of conventional SD-OCT. We directly showed and compared the OCT images before and after applying the proposed balanced detection method in a phantom and in vivo sample.

Intraoperative fluorescence image-guided pulmonary segmentectomy.

BACKGROUND: The intraoperative color and fluorescence-merged imaging system (ICFIS) is a new technology that may aid the demarcation of intersegmental borders during pulmonary segmentectomy. This study was performed to validate, for the first time, image-guided segmentectomy using ICFIS and to find the optimal dosage of fluorescent dye to ensure safe and sustained imaging during surgery. METHODS: Nine rabbits were subjected to pulmonary segmentectomy. These constituted three groups of three rabbits each. After ligation of the segmental pulmonary artery supplying the targeted segment, the rabbits were injected intravenously with indocyanine green (ICG) at a concentration of 0.3, 0.6, or 3.0 mg/kg, depending on their group assignment. The optimal dose was determined from the rabbit study and then used to guide ICFIS during pulmonary segmentectomy in five pigs. RESULTS: The fluorescent signal contrast ratios of the targeted area to the normal lung using ICG concentrations of 0.3, 0.6, or 3.0 mg/kg were 1.9 ± 0.25, 2.0 ± 0.17, and 2.1 ± 0.06, respectively. The mean ICG washout times were 1, 3, and 6 min, respectively. Proceeding with an ICG concentration of 0.6 mg/kg, the mean washout time was found to be longer in pigs (15 min). This provided adequate time for successful ICFIS-guided segmentectomy in all five pigs, without the requirement for additional procedures for intersegmental plane demarcation. CONCLUSIONS: ICG image-guided segmentectomy using ICFIS enabled immediate visualization of the intersegmental planes. The washout time using the ICG dose determined in this study was long enough to ensure that visualization was sustained throughout the surgery.

Thoracoscopic color and fluorescence imaging system for sentinel lymph node mapping in porcine lung using indocyanine green-neomannosyl human serum albumin: intraoperative image-guided sentinel nodes navigation.

PURPOSE: This study was performed to validate a newly developed sentinel lymph node (SLN) targeting tracer, indocyanine green-neomannosyl human serum albumin (ICG:MSA), and a thoracoscopic version of the intraoperative color and fluorescence imaging system (ICFIS) for lung cancer SLN mapping. METHODS: ICG alone or ICG:MSA (5 µg/kg) was injected into the rat thigh, and the results were compared. The fluorescence signal-to-background ratios of SLNs were recorded and evaluated over a 2-h period by using ICFIS. Additionally, a SLN biopsy was performed via video-assisted thoracoscopic surgery with the use of ICG:MSA in porcine lung by using thoracoscopic ICFIS. RESULTS: The newly developed ICG:MSA showed a significantly improved signal-to-background ratio compared with ICG alone throughout the trials. All SLNs were identified in both rats (ten SLNs in ten rat thighs) and pigs (ten SLNs in ten porcine lungs) under in vivo conditions. All SLNs were dissected successfully by using video-assisted thoracoscopic surgery with the help of thoracoscopic ICFIS. DISCUSSION: ICG:MSA accumulates in the SLN by uptake and retention through the mannose-specific receptors on macrophages. Thoracoscopic ICFIS successfully assisted SLN mapping despite low near-infrared light transmission in the commercial thoracoscope. On the basis of the results of the thoracoscopic SLN mapping, we anticipate that ICG:MSA and thoracoscopic ICFIS can be translated to clinical trials in the near future.

Convolutional neural networks can detect orthostatic hypotension in Parkinson's disease using resting-state functional near-infrared spectroscopy data.

Neurological disorders such as Parkinson's disease (PD) often adversely affect the vascular system, leading to alterations in blood flow patterns. Functional near-infrared spectroscopy (fNIRS) is used to monitor hemodynamic changes via signal measurement. This study investigated the potential of using resting-state fNIRS data through a convolutional neural network (CNN) to evaluate PD with orthostatic hypotension. The CNN demonstrated significant efficacy in analyzing fNIRS data, and it outperformed the other machine learning methods. The results indicate that judicious input data selection can enhance accuracy by over 85%, while including the correlation matrix as an input further improves the accuracy to more than 90%. This study underscores the promising role of CNN-based fNIRS data analysis in the diagnosis and management of the PD. This approach enhances diagnostic accuracy, particularly in resting-state conditions, and can reduce the discomfort and risks associated with current diagnostic methods, such as the head-up tilt test.

Detection of metastatic lymph node and sentinel lymph node mapping ​using mannose receptor targeting in in vivo mouse footpad tumor models and rabbit uterine cancer models.

BACKGROUND: This study aimed to evaluate the effectiveness of neo-mannosyl human serum albumin-indocyanine green (MSA-ICG) for detecting metastatic lymph node (LN) and mapping sentinel lymph node (SLN) using mouse footpad uterine tumor models. Additionally, the authors assessed the feasibility of MSA-ICG in SLN mapping in rabbit uterine cancer models. MATERIALS AND METHODS: The authors compared the LN targeting ability of MSA-ICG with ICG. Six mouse footpad tumor models and two normal mice were each assigned to MSA-ICG and ICG, respectively. After the assigned tracers were injected, fluorescence images were taken, and the authors compared the signal-to-background ratio (SBR) of the tracers. A SLN biopsy was performed to confirm LN metastasis status and CD206 expression level. Finally, an intraoperative SLN biopsy was performed in rabbit uterine cancer models using MSA-ICG. RESULTS: The authors detected 14 groin LNs out of 16 in the MSA-ICG and ICG groups. The SBR of the MSA-ICG group was significantly higher than that of the ICG group. The metastatic LN subgroup of MSA-ICG showed a significantly higher SBR than that of ICG. CD206 was expressed at a high level in metastatic LN, and the signal intensity difference increased as the CD206 expression level increased. SLN mapping was successfully performed in two of the three rabbit uterine cancer models. CONCLUSIONS: MSA-ICG was able to distinguish metastatic LN for an extended period due to its specific tumor-associated macrophage-targeting property. Therefore, it may be a more distinguishable tracer for identifying metastatic LNs and SLNs during uterine cancer surgery. Further research is needed to confirm these results.

Novel locally nebulized indocyanine green for simultaneous identification of tumor margin and intersegmental plane.

BACKGROUND: Segmentectomy, recommended for early-stage lung cancer or compromised lung function, demands precise tumor detection and intersegmental plane identification. While indocyanine green (ICG) commonly aids in these aspects using near-infrared imaging, its separate administrations through different routes and times can lead to complications and patient anxiety. This study aims to develop a lung-specific delivery method by nebulizing low-dose ICG to targeted lung segments, allowing simultaneous detection of lung tumors and intersegmental planes across diverse animal models. METHODS: To optimizing the dose of ICG for lung tumor and interlobar fissure detection, different doses of ICG (0.25, 0.1, and 0.05 mg/kg) were nebulized to rabbit lung tumor models. The distribution of locally nebulized ICG in targeted segments was studied to evaluate the feasibility of detecting lung tumor and intersegmental planes in canine lung pseudotumor models. RESULTS: Near-infrared fluorescence imaging demonstrated clear visualization of lung tumor margin and interlobar fissure using local nebulization of 0.1 mg/kg ICG for only 4 min during surgery in the rabbit models. In the canine model, the local nebulization of 0.05 mg/kg of ICG into the target segment enabled clear visualization of pseudotumor and intersegmental planes for 30 min. CONCLUSIONS: This innovative approach achieves a reduction in ICG dose and prolonged the visualization time of the intersegmental plane and effectively eliminates the need for the hurried marking of tumors and intersegmental planes. The authors anticipate that lung-specific delivery of ICG will prove valuable for image-guided limited resection of lung tumors in clinical practice.

Simultaneous Visualization of Lung Tumor and Intersegmental Plane during Pulmonary Segmentectomy by Intravenous Injection of Indocyanine Green.

Segmentectomy is a targeted surgical approach tailored for patients with compromised health and early-stage lung cancer. The key to successful segmentectomy lies in precisely identifying the tumor and intersegmental planes to ensure adequate resection margins. In this study, we aimed to enhance this process by simultaneously visualizing the tumor and intersegmental planes through the intravenous injection of indocyanine green (ICG) at different time points and doses. Lung tumors were detected by intravenous injection of ICG at a dose of 2 mg/kg 12 h before surgery in a rabbit model. Following the dissection of the pulmonary artery, vein, and bronchi of the target segment, 0.6 mg/kg of ICG was injected intravenously to detect the intersegmental plan. Fluorescent images of the lung tumors and segments were acquired, and the fluorescent signal was quantified using the signal-to-background ratio (SBR). Finally, a pilot study of this method was conducted in three patients with lung cancer. In a preclinical study, the SBR of the tumor (4.4 ± 0.1) and nontargeted segments (10.5 ± 0.8) were significantly higher than that of the targeted segment (1.6 ± 0.2) (targeted segment vs. nontarget segment, p < 0.0001; target segment vs. tumor, p < 0.01). Consistent with preclinical results, lung tumors and the intersegmental plane were successfully detected in patients with lung cancer. Consequently, adequate resection margins were identified during the surgery, and segmentectomy was successfully performed in patients with lung cancer. This study is the first to use intravenous ICG injections at different time points and doses to simultaneously detect lung cancer and intersegmental planes, thereby achieving segmentectomy for lung cancer.

Erratum: Functional Near-Infrared Spectroscopy as a Personalized Digital Healthcare Tool for Brain Monitoring.

This corrects the article on p. 115 in vol. 19, PMID: 36854332.

Functional Near-Infrared Spectroscopy as a Personalized Digital Healthcare Tool for Brain Monitoring.

The sustained growth of digital healthcare in the field of neurology relies on portable and cost-effective brain monitoring tools that can accurately monitor brain function in real time. Functional near-infrared spectroscopy (fNIRS) is one such tool that has become popular among researchers and clinicians as a practical alternative to functional magnetic resonance imaging, and as a complementary tool to modalities such as electroencephalography. This review covers the contribution of fNIRS to the personalized goals of digital healthcare in neurology by identifying two major trends that drive current fNIRS research. The first major trend is multimodal monitoring using fNIRS, which allows clinicians to access more data that will help them to understand the interconnection between the cerebral hemodynamics and other physiological phenomena in patients. This allows clinicians to make an overall assessment of physical health to obtain a more-detailed and individualized diagnosis. The second major trend is that fNIRS research is being conducted with naturalistic experimental paradigms that involve multisensory stimulation in familiar settings. Cerebral monitoring of multisensory stimulation during dynamic activities or within virtual reality helps to understand the complex brain activities that occur in everyday life. Finally, the scope of future fNIRS studies is discussed to facilitate more-accurate assessments of brain activation and the wider clinical acceptance of fNIRS as a medical device for digital healthcare.

Optical coherence microscopy with a split-spectrum image reconstruction method for temporal-dynamics contrast-based imaging of intracellular motility.

Biomedical researchers use optical coherence microscopy (OCM) for its high resolution in real-time label-free tomographic imaging. However, OCM lacks bioactivity-related functional contrast. We developed an OCM system that can measure changes in intracellular motility (indicating cellular process states) via pixel-wise calculations of intensity fluctuations from metabolic activity of intracellular components. To reduce image noise, the source spectrum is split into five using Gaussian windows with 50% of the full bandwidth. The technique verified that F-actin fiber inhibition by Y-27632 reduces intracellular motility. This finding could be used to search for other intracellular-motility-associated therapeutic strategies for cardiovascular diseases.

Optimization of Indocyanine Green for Intraoperative Fluorescent Image-Guided Localization of Lung Cancer; Analysis Based on Solid Component of Lung Nodule.

ICG fluorescence imaging has been used to detect lung cancer; however, there is no consensus regarding the optimization of the indocyanine green (ICG) injection method. The aim of this study was to determine the optimal dose and timing of ICG for lung cancer detection using animal models and to evaluate the feasibility of ICG fluorescence in lung cancer patients. In a preclinical study, twenty C57BL/6 mice with footpad cancer and thirty-three rabbits with VX2 lung cancer were used. These animals received an intravenous injection of ICG at 0.5, 1, 2, or 5 mg/kg, and the cancers were detected using a fluorescent imaging system after 3, 6, 12, and 24 h. In a clinical study, fifty-one patients diagnosed with lung cancer and scheduled to undergo surgery were included. Fluorescent images of lung cancer were obtained, and the fluorescent signal was quantified. Based on a preclinical study, the optimal injection method for lung cancer detection was 2 mg/kg ICG 12 h before surgery. Among the 51 patients, ICG successfully detected 37 of 39 cases with a consolidation-to-tumor (C/T) ratio of >50% (TNR: 3.3 ± 1.2), while it failed in 12 cases with a C/T ratio ≤ 50% and 2 cases with anthracosis. ICG injection at 2 mg/kg, 12 h before surgery was optimal for lung cancer detection. Lung cancers with the C/T ratio > 50% were successfully detected using ICG with a detection rate of 95%, but not with the C/T ratio ≤ 50%. Therefore, further research is needed to develop fluorescent agents targeting lung cancer.

Clinical application of functional near-infrared spectroscopy for burn assessment.

Significance: Early assessment of local tissue oxygen saturation is essential for clinicians to determine the burn wound severity. Background: We assessed the burn extent and depth in the skin of the extremities using a custom-built 36-channel functional near-infrared spectroscopy system in patients with burns. Methods: A total of nine patients with burns were analyzed in this study. All second-degree burns were categorized as superficial, intermediate, and deep burns; non-burned skin on the burned side; and healthy skin on the contralateral non-burned side. Hemodynamic tissue signals from functional near-infrared spectroscopy attached to the burn site were measured during fNIRS using a blood pressure cuff. A nerve conduction study was conducted to check for nerve damage. Results: All second-degree burns were categorized into superficial, intermediate, and deep burns; non-burned skin on the burned side and healthy skin on the contralateral non-burned side showed a significant difference distinguishable using functional near-infrared spectroscopy. Hemodynamic measurements using functional near-infrared spectroscopy were more consistent with the diagnosis of burns 1 week later than that of the degree of burns diagnosed visually at the time of admission. Conclusion: Functional near-infrared spectroscopy may help with the early judgment of burn extent and depth by reflecting differences in the oxygen saturation levels in the skin.

Identification of Metastatic Lymph Nodes Using Indocyanine Green Fluorescence Imaging.

Indocyanine green (ICG) has been used to detect several types of tumors; however, its ability to detect metastatic lymph nodes (LNs) remains unclear. Our goal was to determine the feasibility of ICG in detecting metastatic LNs. We established a mouse model and evaluated the potential of ICG. The feasibility of detecting metastatic LNs was also evaluated in patients with lung or esophageal cancer, detected with computed tomography (CT) or positron-emission tomography (PET)/CT, and scheduled to undergo surgical resection. Tumors and metastatic LNs were successfully detected in the mice. In the clinical study, the efficacy of ICG was evaluated in 15 tumors and fifty-four LNs with suspected metastasis or anatomically key regional LNs. All 15 tumors were successfully detected. Among the fifty-four LNs, eleven were pathologically confirmed to have metastasis; all eleven were detected in ICG fluorescence imaging, with five in CT and seven in PET/CT. Furthermore, thirty-four LNs with no signals were pathologically confirmed as nonmetastatic. Intravenous injection of ICG may be a useful tool to detect metastatic LNs and tumors. However, ICG is not a targeting agent, and its relatively low fluorescence makes it difficult to use to detect tumors in vivo. Therefore, further studies are needed to develop contrast agents and devices that produce increased fluorescence signals.