Glaucoma is a leading cause of blindness. Previously, we quantified the deformations in scleral tissue components through a PAM-FEA methodology. This study furthers our examination of perilimbal sclera (PLS) and aqueous veins in intraocular pressure (IOP) regulation using ex vivo porcine eyes. Our results reveal that the cross-sectional area change of the aqueous veins and strain of PLS are strongly and positively correlated with the steady-state IOP (n=8, R2=0.90, R2=0.57, respectively) and the IOP elevation rate at a constantly increasing flow rate (n=8, R2=0.89, R2=0.58, respectively). These findings support our hypothesis that the PLS and aqueous veins with less deformation are correlated with elevated steady state IOP and less adaptive behavior of eyes to increased aqueous outflow.
Glaucoma is a leading cause of blindness. Previously, we quantified the deformations in scleral tissue components through a PAM-FEA methodology. This study furthers our examination of perilimbal sclera (PLS) and aqueous veins in intraocular pressure (IOP) regulation using ex vivo porcine eyes. Our results reveal that the cross-sectional area change of the aqueous veins and strain of PLS are strongly and positively correlated with the steady-state IOP (n=8, R2=0.90, R2=0.57, respectively) and the IOP elevation rate at a constantly increasing flow rate (n=8, R2=0.89, R2=0.58, respectively). These insights bolster our supposition that a stiffer PLS can lead to heightened IOP and reduced ocular adaptability to aqueous outflow, primarily due to restrictions on aqueous vein dilation.
This study aimed to clinically translate our previously proposed translational needle photoacoustic (PA) probe by integrating it with standard prostate biopsy procedures. The all-optical components, enclosed within an 18G clinical standard steel needle, included an optical fiber diffusor and a fiber hydrophone. During the biopsy, the needle PA probe was inserted into the prostate through a guide needle, monitored by real-time transrectal ultrasound imaging fused with pre-procedure magnetic resonance imaging (MRI). Tunable wavelengths were employed to target specific tissue components. For each patient, we focused on one normal area and one cancerous area, as identified by MRI. We then quantified the PA signals via PA spectral analysis and compared them with histology results. This ongoing study aims to demonstrate the effectiveness of our proposed method in differentiating between normal and cancerous tissues in the human prostate.
Our previous investigations effectively employed an interstitial all-optical needle photoacoustic sensing probe on ex vivo tissue studies. In this study, our goal is to locate aggressive PCa within an intact prostate ex vivo using our latest version translational needle PA probe. Targeting specific tissue components, we utilized wavelengths of 1220nm, 1370nm, 800nm, and 266nm. Evans blue dye was injected at the measured positions for histopathology analysis. The acquired photoacoustic signals were analyzed using PASA, including spectrum slopes and midbandfits derived at all wavelengths. With the limited number of insertions, we were able to identify cancers in 3 out of 4 prostates. This non-invasive methodology holds considerable promise for future clinical applications.
Quantification of fibrosis is critical for the management of inflammatory bowel disease. In this study, photoacoustic (PA) strain imaging were used to estimate intestinal stiffness during the progression of intestinal fibrosis in 23 rabbits in vivo. The tissue was then harvested to measure the young’s modulus ex vivo. Collagen-to-Hb ratio measured using spectroscopic PA imaging was also recorded. Results show that PA-strain is positively correlated to Young’s Modulus with a correlation coefficient of 0.81. PA-strain distinguishes the low histological fibrosis (0-2) and high histological fibrosis (3-5) significantly (p-value<0.001). Collagen-to-Hb ratio and PA-strain are highly correlated with the histological fibrosis (0-5) with correlation of 0.67 and 0.64, respectively.
Purposed at validating the hypothesis that overly stiff sclera undermines the passive and adaptive mechanisms of the aqueous outflow pathway in regulating IOP, we combined photoacoustic microscopy (PAM) and finite element analysis (FEA) technologies to resolve and quantify the strains in the aqueous veins and surrounding perilimbal sclera in human and porcine eyes at high resolution in 3D in our previous study. In this study, we introduced large dynamic range of scleral stiffness in intact porcine eyes by crosslinking and observed the correlations between the principal strains in sclera and aqueous veins during IOP elevations, and between the principal strains and the steady state IOP. The results showed strong correlations in both cases.
Quantification of fibrosis is critical for the management of inflammatory bowel disease. In this study, two measurements, collagen-to-Hb ratio quantified by spectroscopic analysis and tissue stiffness quantified by PA-strain, measured by our PA-US balloon catheter were employed to quantify intestinal fibrosis in 23 rabbits in vivo. Results show that both measurements can distinguish the low histological fibrosis (0-2) and high histological fibrosis (3-5) with statistical significance (p-value<0.001). Collagen-to-Hb ratio and PA-strain are highly correlated with the fibrosis stages with correlation of 0.67 and 0.64, respectively. PA-strain is positively correlated to Young’s Modulus measured ex vivo using microelastometer with correlation 0.81.
Purposed at validating the hypothesis that overly stiff sclera undermines the passive and adaptive mechanisms of the aqueous outflow pathway in regulating IOP, we combined photoacoustic microscopy (PAM) and finite element analysis (FEA) technologies to resolve and quantify the strains in the aqueous veins and surrounding perilimbal sclera in human and porcine eyes at high resolution in 3D in our previous study. In this study, we introduced large dynamic range of scleral stiffness in intact porcine eyes by crosslinking and observed the correlations between the principal strains in sclera and aqueous veins during IOP elevations, and between the principal strains and the steady state IOP. The results showed strong correlations in both cases.
In this study, we developed a prototype interstitial all-optical needle photoacoustic sensing probe for clinical translation of prostate cancer. The performance of the PA needle probe was examined on intact human prostates ex vivo to simulate the transrectal ultrasound (US) guided transperineal prostate biopsy procedures. Analysis based on PA spectrum analysis in 8-28 MHz range of acquired RF signals at multi-wavelengths shows statistical difference between benign and cancerous regions (n=49, p<0.05). Multivariate SVM analysis using linear and midbandfit parameters can obtain an accuracy close to 90%.
In this study, we developed a prototype interstitial all-optical needle photoacoustic (PA) sensing probe for clinical translation. The performance of the PA needle probe was examined with intact human prostates ex vivo in a simulated transrectal ultrasound (US) guided transperineal prostate biopsy procedure. PA spectrum analysis shows statistical difference between the measurements acquired in benign and cancerous regions (n=49, p<0.05). Multivariate analysis using all quantitative measurements can obtain an accuracy close to 90%.
This study examined the performance of a clinical translatable needle photoacoustic sensing probe in intact prostates removed through prostatectomy procedures. Compared to the prototype probe in our previous studies, the latest version probe possesses fiber optic hydrophone with a dome-shaped tip that provides better sensitivity and sampling volume. The optical components were integrated into a customized clinical standard steel needle with a side opening and protected by medical grade polyurethane. The needle probe was examined in a setup mimicking a transrectal ultrasound guided transperineal prostate biopsy procedure. Preliminary tests showed promising results in differentiating between benign and aggressive cancer tissues in prostate.
Stiffness is a biomarker to distinguish intestinal inflammation and fibrosis in Crohn’s disease. This study investigated the performance of an endoscopic photoacoustic (PA)-ultrasound (US) catheter probe in quantifying intestinal stiffness in rabbits in vivo. The probe integrated a miniaturized US array and a side-firing fiber optic inside a medical balloon catheter. During the balloon dilation, the ratios between the intestinal wall deformation and PA signal change were quantified. The strain-PA ratios measured in vivo demonstrated a correlation of 0.8 (n=55, p=0.01) with the Young’s moduli of the assessed intestinal segments determined by microelastometry ex vivo.
This study examines the performance of an all-optical and disposable photoacoustic needle probe for characterizing the aggressiveness of prostate cancer in human samples ex vivo. The needle probe consists of a 800um diameter fiber diffuser and a 200um diameter fiber optics hydrophone. The signals acquired by the needle probes were quantified by photoacoustic spectral analysis and envelop statistic methods. Both methods have differentiated between normal tissues and cancerous tissues (n=30 p<0.005), as well as between indolent and aggressiveness cancer tissues (n=16, p<0.01) with statistical significance.
We developed a photoacoustic imaging (PAI) and finite element analysis (FEA) approach for characterizing the biomechanical behaviors of the aqueous veins and perilimbal sclera, and their roles in the regulation of intraocular pressure (IOP). 3D architectures of the sclera and the aqueous veins perfused with indocyanine green have been resolved by an optical resolution PAI system. The tissue ans strain fields were quantified using FEA. The performance of the proposed method has been validated by tensile test in scleral tissue. The methods have shown the capability of resolving the strain gradients at the vein-sclera interface during the manipulation of IOP.
We developed a photoacoustic imaging (PAI) and finite element analysis (FEA) approach for characterizing the biomechanical behaviors of the aqueous veins and perilimbal sclera, and their roles in the regulation of intraocular pressure (IOP). In this study, an optical resolution PAI system captures the 3D architectures of the sclera and the aqueous veins perfused with indocyanine green. FEA computes tissue and vein strain fields. The performance of the PAI-FEA has been validated by tensile test in scleral tissue. The methods have also shown the capability of resolving the strain gradients at the vein-sclera interface during the manipulation of IOP.
Distinguishing between acute and chronic intestinal obstruction is essential for the treatment of Crohn's disease (CD). We have demonstrated the capability of spectroscopy photoacoustic (PA) imaging in quantifying hemoglobin and collagen changes. We also developed strain-PA imaging as a novel method for quantifying the intestinal stiffness, which is a mechanical marker of CD. In this study, we combined the spectroscopy and stiffness measurements using a catheter probe and examined the proposed approach in a rabbit model of CD in vivo. The quantitative accuracy of the imaging was validated by histology and micro-elastometry.
Photoacoustic (PA) imaging has shown its capability of characterizing intestinal inflammation and fibrosis endoscopically. With the purpose of clinical translation, we developed an endoscopic probe integrating an intracardiac ultrasound array and an 800 µm side-firing fiber optic inside a medical balloon catheter. The catheter probe, when collapsed, fits to the instrument channel of a colonoscope and can inflate for acoustic coupling when positioned at the disease location inside intestine. The performance of the probe in assessing the disease conditions including inflammation, fibrosis and muscle hypertrophy is under investigation in rabbits in vivo. The imaging results are validated by histopathology.
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