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In diffuse optical tomography (DOT) and spectroscopy (DOS) using handheld probes, tissue curvature can cause bad fiber-to-tissue contact. Understanding and minimizing image artifacts caused by these coupling errors would significantly improve DOT and DOS image quality. In this work, we utilized Monte Carlo simulations and experiments with gelatin-Intralipid phantoms to systematically study the influence of source or detector (optode) coupling errors. Optode coupling errors can increase the amplitude and decrease the phase of the measured diffuse reflectance, creating artifacts in the reconstructed absorption maps, such as hot spots on the edges. We propose an outlier removal algorithm that can correct these image artifacts, and we demonstrate its performance using simulations, phantom experiments, and breast patient data acquired with bad probe contact due to a dense or small breast. Further, we designed and implemented a new resistance-type thin-film force sensor array that provides real-time optode coupling feedback and guides the outlier removal to minimize optode coupling errors. Our approaches and study results have significant implications for reducing image artifacts arising from handheld probes, which are commonly used with mobile and wearable DOT and DOS devices.

Background: Neoadjuvant Therapy (NAT) permits less aggressive breast and axillary surgery and better assessment of systemic response. Establishing accurate and early predictors of NAT response would help limit morbidity of ineffective regimens through modification of treatment regimens and thereby optimize clinical outcomes. The purpose of the study was to assess the utility of tumor biomarkers, ultrasound (US) and US-guided diffuse optical tomography (DOT) in early prediction of breast cancer response to NAT.MethodsThis prospective HIPAA compliant study was approved by the institutional review board. Forty one patients were imaged with US and US-guided DOT prior to NAT, at completion of the first three treatment cycles, and prior to definitive surgery from February 2017 to January 2020. Miller-Payne grading was used to assess pathologic response. Receiver operating characteristic curves (ROCs) were derived from logistic regression using independent variables, including: tumor biomarkers, US maximum diameter, percentage reduction of the diameter (%US), pretreatment maximum total hemoglobin concentration (HbT) and percentage reduction in HbT (%HbT) at different treatment time points. Resulting ROCs were compared using area under the curve (AUC). Statistical significance was tested using two-sided two-sample student t-test with P ResultsThirty-eight patients (mean age =47, range 24-71 years) successfully completed the study, including 15 HER2+ of which 11 were ER+; 12 ER+ or PR+/HER2-, and 11 triple negative. The combination of HER2 and ER biomarkers, %HbT at the end of cycle 1 (EOC1) and %US (EOC1) provided the best early prediction, AUC = 0.941 (95% CI: 0.869­–1.0). Similarly an AUC of 0.910 (95% CI: 0.810–1.0) with %US (EOC1) and %HbT (EOC1) can be achieved independent of HER2 and ER status. The most accurate prediction, AUC = 0.974 (95% CI: 0.933–1.0), was achieved with %US at EOC1 and %HbT (EOC3) independent of biomarker status. ConclusionThe combined use of tumor HER2 and ER status, US, and US-guided DOT may provide accurate prediction of NAT response as early as the completion of the first treatment cycle. Clinical Trial Registration number: NCT02891681Registration time: September 7, 2016https://clinicaltrials.gov/ct2/show/NCT02891681

This review of optical breast imaging describes basic physical and system principles and summarizes technological evolution with a focus on multi-modality platforms and recent clinical trial results. Ultrasound-guided diffuse optical tomography and co-registered ultrasound and photoacoustic imaging systems are emphasized as models of state of the art optical technology that are most conducive to clinical translation.

Rectal adenocarcinoma is a common cancer in the United States. Current standard of care techniques (colonoscopy and MRI) have notable drawbacks and surgeons have aggressively put most patients into surgical intervention. Developing an efficient and sensitive method to evaluate rectal cancer is urgently needed. Here we have developed a new handheld co-registered ultrasound and acoustic-resolution photoacoustic endoscope (AR-PAE) to evaluate human rectal cancer in vivo. Normal rectal ultrasound images revealed typical layered structure, while photoacoustic images resolved rich vascular supply of submucosa. Our pilot patient data suggest that AR-PAE is effective to distinguish rectal cancer from normal rectum.

The current gold standard diagnostic test for colorectal cancer remains histological inspections of endoluminal neoplasia in biopsy specimens. However, biopsy site selection requires visual inspection of the bowel, typically with a white-light endoscope. Therefore, this technique is poorly suited to detect small or innocuous-appearing lesions. We hypothesize that an alternative modality—multiwavelength spatial frequency domain imaging (SFDI)—would be able to differentiate various colorectal neoplasia from normal tissue. In this ex vivo study of human colorectal tissues, we report the optical absorption and scattering signatures of normal, adenomatous polyp and cancer specimens. An abnormal vs. normal adaptive boosting (AdaBoost) classifier is trained to dichotomize tissue based on SFDI imaging characteristics, and an area under the receiver operating characteristic (ROC) curve (AUC) of 0.95 is achieved. We conclude that AdaBoost-based multiwavelength SFDI can differentiate abnormal from normal colorectal tissues, potentially improving endoluminal screening of the distal gastrointestinal tract in the future.

One of the challenges of quantitative Photoacoustic (PA) imaging is unmixing the optical absorption (μa) of the tissue from system response (C) and Gruneisen parameter (Γ). In this study, we have calculated the absorption coefficient and functional parameters, i.e. total hemoglobin (tHb) and oxygen saturation (sO2) of 5 blood tubes with sO2 values ranging from 24.9% to 97.6% at different depths in intralipid solution. Beer’s law is used to calculate the optical fluence in the target area. Initial values for μa and C×Γ are found by fitting a line to the log of PA beam data. These initial values are iteratively updated using a conjugate gradient method. This process is repeated for all 11 wavelengths. The absorption coefficient spectrum follows the molar extinction coefficient spectrum of deoxy hemoglobin for lower sO2 percentages, and it becomes closer to the spectrum of oxy hemoglobin when the sO2 percentage increases. The calculated absorption coefficients at 11 wavelengths are used to estimate the absolute value of the tHb and sO2 of each blood sample at different depths. The mean error of the estimated tHb values for blood tubes at all depths with respect to the real values are less than 13%. Moreover, the largest sO2 estimation error is 7.5% for the blood sample with sO2 of 24.9%. Our quantitative PA method performed well for the data collected from blood samples. We are investigating this method on our clinical data.

Colorectal cancer is the second most common malignancy diagnosed globally and the 4th leading cause of cancer mortality. Critical gaps exist in diagnostic and surveillance imaging modalities for colorectal neoplasia. We have conducted a pilot study using a real-time co-registered photoacoustic (PAT) and ultrasound (US) tomography system. A total of 23 ex vivo human colorectal tissue samples (19 colon and 4 rectum) were imaged immediately after surgical resection. These results indicate potential of using PAT/US for future cancer screening and post-treatment surveillance of colon and rectum. The image resolution of the current system is low (~ 250 μm axial resolution) due to the commercial endo-cavity ultrasound transducer array (6 MHz central frequency, 80% bandwidth). To solve the problem of image resolution, we decoded the pin configuration of a high-frequency transducer array (15 MHz central frequency, 9-18 MHz bandwidth) and adapted it to our home-made 128 channels ultrasound pulsing and receiving system to perform high-frequency PAT/US imaging. We achieved a lateral resolution of ~ 150 μm and axial resolution of ~ 120 μm. We also imaged a post-treated human rectum sample to evaluate the system performance.

The laser illumination delivery method is important in designing probes that achieve high imaging quality and deep tissue penetration. Here we present a novel, to the best of our knowledge, fiber diffuser tip using microspheres dispersed within an ultraviolet adhesive to scatter light. This diffuser keeps the skin surface fluence under the maximum permissible exposure, while enabling higher laser energy injection to enhance the photoacoustic (PA) signal generated from the tissue. We compare the light diffusion effects of different microsphere materials, sizes, and concentrations, and find that 10 µm silica microspheres provide the best light scattering with minimal 5% output energy loss. With the Zemax simulation and experimental validation, we show that this fiber diffuser tip is a valuable tool for endo-cavity PA imaging.

Ultrasound (US)-guided diffuse optical tomography (DOT) is a promising non-invasive functional imaging technique for diagnosing breast cancer and monitoring breast cancer treatment response. However, because larger lesions are highly absorbing, reconstructions of these lesions using reflection geometry may exhibit light shadowing, which leads to inaccurate quantification of their deeper portions. Here we propose a depth-regularized reconstruction algorithm combined with a semi-automated interactive neural network (CNN) for depth-dependent reconstruction of absorption distribution. CNN segments co-registered US to extract both spatial and depth priors, and the depth-regularized algorithm incorporates these parameters into the reconstruction. Through simulation and phantom data, the proposed algorithm is shown to significantly improve the depth distribution of reconstructed absorption maps of large targets. Evaluated with 26 patients with larger breast lesions, the algorithm shows 2.4 to 3 times improvement in the top-to-bottom reconstructed homogeneity of the absorption maps for these lesions.

A multi-wavelength spatial frequency domain imaging (SFDI) system combined with AdaBoost classifier was used to automatically classify ex vivo human colorectal tissues. A sensitivity of 89.7% and a specificity of 91.8% were achieved.

We present a handheld co-registered acoustic-resolution photoacoustic endoscope and ultrasound system and initial clinical results using the system and a neural network to predict rectal cancer chemoradiation treatment response.

This clinical study validates an early treatment window for predicting complete or near-complete pathological response of breast cancer patients based on pretreatment total-hemoglobin level (THb), early changes of THb and ultrasound measurements following neoadjuvant chemotherapy.

Multi-step classification combining both functional and data features improve breast cancer diagnosis with sensitivity 91.1% and specificity 85.4%. Proposed method increased specificity by more than 10% compared to diagnosis with Ultrasound and functional feature only.

We proposed a shape-based diffuse optical tomography (DOT) algorithm which incorporates a target shape obtained from co-registered ultrasound image into a regularization matrix for DOT reconstruction. Simulations, phantom experiments and clinical data have shown significantly improvement of reconstructed large lesion optical absorption maps.

A finite element method (FEM) and experiment on phantoms were used to study the influence of breast contour mismatch and probe-tissue coupling mismatch in ultrasound-guided diffuse optical tomography for breast cancer imaging.

Ovarian cancer is the leading cause of death among gynecological cancers, but is poorly amenable to preoperative diagnosis. In this study, we investigate the feasibility of “optical biopsy,” using high-optical-resolution photoacoustic microscopy (OR-PAM) to quantify the microvasculature of ovarian and fallopian tube tissue. The technique is demonstrated using excised human ovary and fallopian tube specimens imaged immediately after surgery. Quantitative parameters are derived using Amira software. The parameters include three-dimensional vascular segment count, total volume and length, which are associated with tumor angiogenesis. Qualitative results of OR-PAM demonstrate that malignant ovarian tissue has larger and more tortuous blood vessels as well as smaller vessels of different sizes, while benign and normal ovarian tissue has smaller vessels of uniform size. Quantitative analysis shows that malignant ovaries have greater tumor vessel volume, length and number of segments, as compared with benign and normal ovaries. The vascular pattern of benign fallopian tube is different than that of benign ovarian tissue. Our initial results demonstrate the potential of OR-PAM as an imaging tool for fast assessment of ovarian tissue and fallopian tube and could avoid unnecessary surgery if the risk of the examined ovary is extremely low.

The development of low-cost and fast photoacoustic microscopy systems enhances the clinical applicability of photoacoustic imaging systems. To this end, we present a laser scanning laser diode-based photoacoustic microscopy system. In this system, a 905 nm, 325 W maximum output peak power pulsed laser diode with 50 ns pulsewidth is utilized as the light source. A combination of aspheric and cylindrical lenses is used for collimation of the laser diode beam. Two galvanometer scanning mirrors steer the beam across a focusing aspheric lens. The lateral resolution of the system was measured to be ∼21 μm using edge spread function estimation. No averaging was performed during data acquisition. The imaging speed is ∼370 A-lines per second. Photoacoustic microscopy images of human hairs, ex vivo mouse ear, and ex vivo porcine ovary are presented to demonstrate the feasibility and potentials of the proposed system. Keywords: Photoacoustic imaging, Diode lasers, Medical imaging, Biological imaging, Low-cost sources

A machine learning model with physical constraints (ML-PC) is introduced to perform diffuse optical tomography (DOT) reconstruction. DOT reconstruction is an ill-posed and under-determined problem, and its quality suffers by model mismatches, complex boundary conditions, tissue-probe contact, noise etc. Here, for the first time, we combine ultrasound-guided DOT with ML to facilitate DOT reconstruction. Our method has two key components: (i) a neural network based on auto-encoder is adopted for DOT reconstruction, and (ii) physical constraints are implemented to achieve accurate reconstruction. Both qualitative and quantitative results demonstrate that the accuracy of the proposed method surpasses that of existing models. In a phantom study, compared with the Born conjugate gradient descent (Born-CGD) reconstruction method, the ML-PC method decreases the mean percentage error of the reconstructed maximum absorption coefficient from 16.41% to 13.4% for high contrast phantoms and from 23.42% to 9.06% for low contrast phantoms, with improved depth distribution of the target absorption maps. In a clinical study, better contrast was obtained between malignant and benign breast lesions, with the ratio of the medians of the maximum absorption coefficient improved from 1.63 to 2.22.

The synthesis and photophysical properties of a tetra-PEG-modified and freely water-soluble quinoline-annulated porphyrin are described. We previously demonstrated the ability of quinoline-annulated porphyrins to act as an in vitro NIR photoacoustic imaging (PAI) contrast agent. The solubility of the quinoline-annulated porphyrin derivative in serum now allowed the assessment of the efficacy of the PEGylated derivative as an in vivo NIR contrast agent for the PAI of an implanted tumor in a mouse model. A multi-fold contrast enhancement when compared to the benchmark dye ICG could be shown, a finding that could be traced to its photophysical properties (short triplet lifetimes, low fluorescence and singlet oxygen sensitization quantum yields). A NIR excitation wavelength of 790 nm could be used, fully taking advantage of the optical window of tissue. Rapid renal clearance of the dye was observed. Its straight-forward synthesis, optical properties with the possibility for further optical fine-tuning, nontoxicity, favorable elimination rates, and contrast enhancement make this a promising PAI contrast agent. The ability to conjugate the PAI chromophore with a fluorescent tag using a facile and general conjugation strategy was also demonstrated.

Ultrasound (US) guided diffuse optical tomography has demonstrated great potential for breast cancer diagnosis, treatment monitoring, and chemotherapy response prediction. Optical measurements of four different wavelengths are used to reconstruct unknown optical absorption maps, which are then used to calculate the hemoglobin concentration distribution of the US visible lesion. Reconstructed absorption maps are prone to image artifacts from outliers in measurement data from tissue heterogeneity, bad coupling between tissue and light guides, and motion by patient or operator. We propose an automated iterative perturbation correction algorithm to reduce image artifacts based on the structural similarity index (SSIM) of absorption maps of four optical wavelengths. The initial image is estimated from the truncated pseudoinverse solution. The SSIM was calculated for each wavelength to assess its similarity with other wavelengths. An absorption map is repeatedly reconstructed and projected back into measurement space to quantify projection error. Outlier measurements with highest projection errors are iteratively removed until all wavelength images are structurally similar with SSIM values greater than a threshold. Clinical data demonstrate statistically significant improvement in image artifact reduction.

Ovarian cancer is a heterogeneous disease at the molecular and histologic level. Optical coherence tomography (OCT) is able to map ovarian tissue optical properties and heterogeneity, which has been proposed as a feature to aid in diagnosis of ovarian cancer. In this manuscript, depth-resolved en face scattering maps of malignant ovaries, benign ovaries, and benign fallopian tubes obtained from 20 patients are provided to visualize the heterogeneity of ovarian tissues. Six features are extracted from histograms of scattering maps. All features are able to statistically distinguish benign from malignant ovaries. Two prediction models were constructed based on these features: a logistic regression model (LR) and a support vector machine (SVM). The optimal set of features is mean scattering coefficient and scattering map entropy. The LR achieved a sensitivity and specificity of 97.0% and 97.8%, and SVM demonstrated a sensitivity and specificity of 99.6% and 96.4%. Our initial results demonstrate the feasibility of using OCT as an "optical biopsy tool" for detecting the microscopic scattering changes associated with neoplasia in human ovarian tissue.

In this study, a low-cost procedure using evaporated milk is followed to make a gelatin-based phantom with ultrasound and optical properties close to soft tissues. To find out the effect of concentrations of gelatin and evaporated milk on the ultrasound properties, we first made two sets of phantoms. The first set was made by mixing different amounts of gelatin with deionized water (no evaporated milk in this set), while in the second set, evaporated milk concentration was changed (constant gelatin concentration). We measured the ultrasound attenuation of these phantoms at low and high frequency ranges and show that when the gelatin concentration is kept at 5 %, the ultrasound attenuation can vary from 0.4 to 0.6 dB/MHz/cm as the evaporated milk concentration increases from 20 % to 50 %. After getting some idea about the proper concentrations of evaporated milk and gelatin on ultrasound properties, n-propanol alcohol, glass microspheres, and Germall plus preservative were added to our recipe. We then measured the optical properties of the resulted phantom. A diffuse optical tomography system (DOT) was employed for this purpose to measure the optical absorption and reduced scattering coefficients of our phantom at four different wavelengths.

Endoscopic evaluation of the colorectum is limited to the mucosal surface and provides no functional or structural information regarding subsurface changes. Targeted diagnostics and individualized treatment, however, requires this information. In this ex vivo study of human colorectal tissue, we use swept-source optical coherence tomography to create quantified subsurface scattering coefficient maps of normal and cancerous tissue. Specifically, we use a novel wavelet-based-curve-fitting method to generate subsurface scattering coefficient maps. The angular spectra of scattering coefficient maps of normal tissues exhibit a spatial feature distinct from those of abnormal tissues. The en face scattering coefficient maps of the normal colon contain a large area of homogenous scattering coefficients with periodic dot patterns, while the scattering coefficient map of cancer region shows a large area of heterogeneous scattering coefficients. An angular spectrum index to quantify the differences between the normal, abnormal, and treated tissues is derived, and its strength in revealing subsurface cancer in ex vivo samples is statistically analyzed. Using this index, we differentiate malignant from normal colonic tissue. Additionally, we also found that rectal cancers completely destroyed by preoperative treatment appear much more similarly to normal tissue than the original malignancy. The study demonstrates that the angular spectrum of the scattering coefficient map can effectively reveal subsurface colorectal cancer and help clinicians identify patients who don’t require surgical intervention.

Diffuse Optical Tomography (DOT) provides quantitative information about optical absorption and total hemoglobin concentration of breast tumors which is directly related to tumor angiogenesis. However, measurements errors caused by tissue heterogeneity may introduce artifacts in reconstructed absorption and total hemoglobin maps and therefore cause errors in quantitative characterization of lesions. With ultrasound-guided DOT, these artifacts can be recognized if they are isolated and located at edges of the absorption maps. However, effectively recognize image artifacts and automatically remove them is a challenge because artifacts can be merged partially with lesions maps. A new two-step algorithm is proposed to iteratively identify and remove measurement outliers based on assignment of local outlier factors and hence to reduce image artifacts and produce more consistent absorption maps among different wavelengths. In first step, perturbation measurements were ranked based on data density and the local outlier factor which is the probability of each measurement being an outlier. In second step, outliers are iteratively removed until normalized pattern correlation of different wavelength absorption maps is beyond a specified threshold. The proposed algorithm is evaluated on 20 clinical cases and it has demonstrated its capability to automatically reconstruct more consistent images for different wavelengths. The improvement on characterizing benign breast lesions is more dramatic because outliers can cause the reconstructed benign lesions with higher optical absorption and therefore high hemoglobin contrast.

A multi-spectral, portable, hand-held LED based spatial frequency domain imaging system was used for ex vivo imaging pretreatment and post treatment human colon and rectal tissues. Freshly excised human colon and rectal tissue samples were imaged with the hand-held SFDI probe with 9 wavelengths extending from visible to NIR (660-950 nm). Important tumor biomarkers such as hemoglobin, scatter amplitude, scatter spectral slope, water and lipid content were quantitatively extracted from the SFDI absorption and scattering images. Significant differences were observed between the absorption as well as scattering distribution of normal, tumor and polyp tissue as well as between pretreated and post-treated tumors.

Colorectal cancer diagnosis currently relies on histological detection of endoluminal neoplasia in biopsy specimens. However, clinical visual endoscopy provides no quantitative subsurface cancer information. In this ex vivo study of nine fresh human colon specimens, we report the first use of quantified subsurface scattering coefficient maps acquired by swept-source optical coherence tomography to reveal subsurface abnormities. We generate subsurface scattering coefficient maps with a novel wavelet-based-curve-fitting method that provides significantly improved accuracy. The angular spectra of scattering coefficient maps of normal tissues exhibit a spatial feature distinct from those of abnormal tissues. An angular spectrum index to quantify the differences between the normal and abnormal tissues is derived, and its strength in revealing subsurface cancer in ex vivo samples is statistically analyzed. The study demonstrates that the angular spectrum of the scattering coefficient map can effectively reveal subsurface colorectal cancer and potentially provide a fast and more accurate diagnosis.

Colorectal cancer is the second most common malignancy diagnosed globally. Critical need exists for imaging and diagnosis of rectal tumors for both staging and therapeutic response evaluations. We have conducted a pilot study to image and characterize colorectal masses using a real-time co-registered photoacoustic (PAT) and ultrasound (US) system. A total of 8 tissue samples including pre- and post-treatment colorectal cancer, polyps have studied. Four different wavelengths (730, 780, 800, 830 nm) were used to illuminate the sample and a scanning stage was used to scan a large area and obtain a sequence of B-scans. For the pre-treatment colorectal cancer, photoacoustic images have shown significantly higher vascular level than neighbor benign regions of the same sample. The pre-treatment colorectal cancer PAT signal level is also higher than polyps and post-treatment colorectal cancer. Additionally, the quantitative features extracted from PAT and US power spectrum such as spectral slope, mid-band fit and zero MHz intercept have shown statistical significance between pre-treatment colorectal cancer and other 3 categories using t-test. Our initial results have demonstrated that PAT/US has a great potential to reveal tumor angiogenesis development or residual tumors after treatment.

Surgery for rectal cancer is associated with significant side effects including wound infections, incontinence, sexual and bladder dysfunction, and long-term ostomies. Though studies have shown that patients who completely respond to preoperative treatment can safely avoid surgery, nonoperative options remain limited by the poor performance of MRI and endorectal ultrasound after initial therapy. Therefore, new imaging modalities are needed to improve posttreatment tumor assessment and enable the widespread adoption of nonoperative management in rectal cancer. An acoustic resolution photoacoustic microscope (AR-PAM) was constructed with high frequency ultrasonic transducer and near infrared laser. We performed initial phantom, and then imaged ex vivo human colorectal specimens to evaluate different AR-PAM characteristics in each tissue type (normal, untreated tumor, and treated tumor). Our data suggest that photoacoustic imaging can differentiate the distorted vasculature of rectal tumors from normal vascular patterns. However, the vascular distribution of rectal tissue in pathological complete responders showed similar distribution as the normal colorectal tissue; mucosa, submucosa and muscle layer are clearly presented in ultrasound images, while photoacoustic images have revealed that most vasculatures distribute in submucosa. Encouraged by these initial results, we are developed a high-speed scanning (1 second for 20mm B-scan) AR-PAM with laser pulse repetition rate of 1kHz for large field 3D imaging. Lateral resolution of 65μm, axial resolution of 45μm, and 8mm tissue imaging depth can be achieved.

Adenocarcinoma is a type of cancers that forms in mucus-secreting glands throughout the body. For example, adenocarcinomas make up around 96% of colorectal cancers and some cervical cancers (10%). Depth of invasion for early adenocarcinoma is generally around 1-7 mm. In this report, we propose an optimal design, implementation, and evaluation of an optical fiber-based transvaginal photoacoustic/ultrasound prototype imaging probe for endo-cavity imaging of adenocarcinoma with ball-shaped fiber tips (refractive index = 1.517, radius 0.75 mm), to improve the light illumination homogeneity and increase the light delivery fluence on the central imaging area of the tissue surface. The light delivery system consists of light coupling optics, a custom-made transducer sheath, four 1-mm-core multimode optical fibers with the ball-shaped fiber tip arranged around the transducer. The probe design was optimized by simulating the light fluence distribution of the fibers with and without ball-shaped tips using a 3D model in Zemax for different design parameters such as fiber effective numerical aperture, fiber displacement from the probe base, sheath taper angle, ball-shaped fiber tips’ diameter and refractive index, etc. The laser fluence profiles were experimentally recorded through calibrated intralipid solution by camera at various imaging depths. The output power on the central imaged areas were experimentally measured by calculating the PAT signal strengths from the black threads buried inside chicken breast tissue at various depths and in-vivo photoacoustic imaging of one palmar vein proximal to the human wrist.

2-Nitroimidazole is a well-known chemical probe targeting hypoxic environments of solid tumors, and its derivatives are widely used as imaging agents to investigate tissue and tumor hypoxia. However, the underlying chemistry for the hypoxia-detection capability of 2-nitroimidazole is still unclear. In this study, we deployed a biotin conjugate of 2-nitroimidazole-indocyanine green (2-nitro-ICG) for the investigation of in vivo hypoxia-probing mechanism of 2-nitro-ICG compounds. By implementing mass spectrometry-based proteomics and exhaustive data mining, we report that 2-nitro-ICG and its fragments modify mouse serum albumin as the primary protein target but at two structurally distinct sites and possibly via two different mechanisms. The identification of probe-modified peptides not only contributes to the understanding of the in vivo metabolism of 2-nitroimidazole compounds but also demonstrates a competent analytical workflow that enables the search for peptides with undefined modifications in complex proteome digests.

Near-infrared diffuse optical tomography (DOT) has demonstrated a great potential as an adjunct modality for differentiation of malignant and benign breast lesions and for monitoring treatment response in patients with locally advanced breast cancers. The path toward commercialization of DOT techniques depends upon the improvement of robustness and user-friendliness of this technique in hardware and software. In this study, we introduce our recently developed ultrasound-guided DOT system, which has been improved in system compactness, robustness, and user-friendliness by custom-designed electronics, automated data preprocessing, and implementation of a new two-step reconstruction algorithm. The system performance has been tested with several sets of solid and blood phantoms and the results show accuracy in reconstructed absorption coefficients as well as blood oxygen saturation. A clinical example of a breast cancer patient, who was undergoing neoadjuvant chemotherapy, is given to demonstrate the system performance.

Ovarian cancer is the fifth most common cause of death due to cancer, and it is the deadliest of all gynecological cancers. Diagnosing ovarian cancer via conventional photoacoustic delay-and-sum beamforming (DAS) presents several challenges, such as poor image resolution and low lesion to background tissue contrast. To address these concerns, we propose an improved beamformer named lag-based delay multiply and sum combined with coherence factor (DMAS-LAG-CF). Simulations and phantom experiments demonstrate that compared with the conventional DAS, the proposed algorithm can provide 1.39 times better resolution and 10.77 dB higher contrast. For patient data, similar performance on contrast ratios has been observed. However, since the diagnostic accuracy between cancer and benign/normal groups is a significant measure, we have extracted photoacoustic histogram features of mean, kurtosis and skewness. DMAS-LAG-CF can improve cancer diagnosis with an AUC of 0.91 for distinguishing malignant vs. benign ovarian lesions when mean and skewness are used as features.

Purpose To investigate ultrasonography (US)-guided diffuse optical tomography to distinguish the functional differences of hemoglobin concentrations in a wide range of malignant and benign breast lesions and to improve breast cancer diagnosis in conjunction with conventional US. Materials and Methods The study protocol was approved by the institutional review boards and was HIPAA compliant. Written informed consent was obtained from all patients. Patients (288 women; mean age, 50 years; range, 17-94 years) who underwent US-guided biopsy were imaged with a handheld US and optical probe. The US-imaged lesion was used to guide reconstruction of light absorption maps at four wavelengths, and total hemoglobin (tHb), oxygenated hemoglobin (oxyHb), and deoxygenated hemoglobin (deoxyHb) were computed from the absorption maps. A threshold (80 μmol/L) was chosen on the basis of this study population. Two radiologists retrospectively evaluated US images on the basis of the US Breast Imaging Reporting and Data System lexicon, and a lesion was considered malignant when a score of 4C or 5 was given or a lesion had tHb greater than 80 μmol/L. A two-sample t test was used to calculate significance between groups, and Spearman ρ was computed between hemoglobin parameters and tumor pathologic grades. Results Three tumors were Tis, 37 were T1, 19 were T2-T4 carcinomas, and 233 were benign lesions. The mean maximum tHb, oxyHb, and deoxyHb of Tis-T1 and T2-T4 groups were 89.3 μmol/L ± 20.2 (standard deviation), 65.0 μmol/L ± 20.8, and 33.5 μmol/L ± 11.3, respectively, and 84.7 μmol/L ± 32.8, 57.1 μmol/L ± 19.8, and 34.7 μmol/L ± 18.9, respectively. The corresponding values of benign lesions were 54.1 μmol/L ± 23.5, 38.0 μmol/L ± 17.4, and 25.2 μmol/L ± 13.8, respectively. The mean maximum tHb, oxyHb, and deoxyHb were significantly higher in the malignant groups than the benign group (P

Extending our previous work with 2-nitroimidazole-indocyanine dye-conjugate 4 , we prepared the 4-nitroimidazole-piperazine-indocyanine derivative ( 6 ). We also prepared imidazole derivative 5 as a control. We compared the in vivo hypoxia targeting performance of both 5 and 6 with the previously tested 4 , and 6 showed a higher fluorescent intensity after 15 min post-injection, about 1.5-fold higher than 4 and 2.5-fold higher than 5 . Cells treated with 6 under hypoxic conditions showed a higher fluorescence yield when compared to the cells kept under normoxic conditions. All findings were supported with fluorescence images of histological sections of tumor samples using a Li-COR scanner and an immunohistochemistry technique for tumor hypoxia.

Ultrasound (US)-guided near-infrared diffuse optical tomography (DOT) has demonstrated great potential as an adjunct breast cancer diagnosis tool to US imaging alone, especially in reducing unnecessary benign biopsies. However, DOT data processing and image reconstruction speeds remain slow compared to the real-time speed of US. Real-time or near real-time diagnosis with DOT is an important step toward the clinical translation of US-guided DOT. Here, to address this important need, we present a two-stage diagnostic strategy that is both computationally efficient and accurate. In the first stage, benign lesions are identified in near real-time by use of a random forest classifier acting on the DOT measurements and the radiologists’ US diagnostic scores. Any lesions that cannot be reliably classified by the random forest classifier will be passed on to the second stage which begins with image reconstruction. Functional information from the reconstructed hemoglobin concentrations is employed by a Support Vector Machine (SVM) classifier for diagnosis at the end of the second stage. This two-step classification approach which combines both perturbation data and functional features, results in improved classification, as denoted by the receiver operating characteristic (ROC) curve. Using this two-step approach, the area under the ROC curve (AUC) is 0.937 ± 0.009, with a sensitivity of 91.4% and specificity of 85.7%. In comparison, using functional features and US score yields an AUC of 0.892 ± 0.027, with a sensitivity of 90.2% and specificity of 74.5%. Most notably, the specificity is increased by more than 10% due to the implementation of the random forest classifier.

Colorectal cancer is the second leading cause of cancer death in the United States. Significant limitations in screening and surveillance modalities continue to hamper early detection of primary cancers or recurrences after therapy. In this study, we describe a new registered ultrasound (US) and acoustic-resolution photoacoustic microscopy (AR-PAM) system and report its initial testing in ex vivo human colorectal tissue. A total of 8 colorectal specimens were imaged, which included 2 polyps, 4 malignant colon cancers, and 2 treated colorectal cancers. In each specimen, normal tissue was also imaged for internal control. Initial data have demonstrated the feasibility of identifying colorectal cancer imaging features and the invasion depth using co-registered US and an AR-PAM system. In normal tissue, we found that our system consistently demonstrates the multi-layer structure of normal colonic tissue while differentiating layers with elevated vascularity; these findings highly correlated with histologic findings of each specimen. For malignant colorectal samples, the tissue structure is highly disorganized as seen in US, and photoacoustic imaging revealed distorted vascular distribution inside the tumor. Notably, AR-PAM of tumor beds after complete tumor destruction by radiation and chemotherapy yielded a pattern identical to benign tissue. Quantitative analysis of photoacoustic spectral slope has demonstrated more high-frequency components in malignant tissue as compared to the normal colon tissue, which may be caused by significantly increased microvessel networks. In summary, we demonstrate the successful differentiation of benign and malignant colorectal tissue with our co-registered ultrasound and photoacoustic system.

pColorectal cancer is the second most common malignancy diagnosed globally. Critical gaps exist in diagnostic and surveillance imaging modalities for colorectal neoplasia. Although prior studies have demonstrated the capability of photoacoustic imaging techniques to differentiate normal from neoplastic tissue in the gastrointestinal tract, evaluation of deep tissue with a fast speed and a large field of view remains limited. To investigate the ability of photoacoustic technology to image deeper tissue, we conducted a pilot study using a real-time co-registered photoacoustic tomography (PAT) and ultrasound (US) system. A total of 23italicex vivo/italichuman colorectal tissue samples were imaged immediately after surgical resection. Co-registered photoacoustic images of malignancies showed significantly increased PAT signal compared to normal regions of the same sample. The quantitative relative total hemoglobin (rHbT) concentration computed from four optical wavelengths, the spectral features, such as the mean spectral slope, and 0.5-MHz intercept extracted from PAT and US spectral data, and image features, such as the first- and second-order statistics along with the standard deviation of the mean radon transform of PAT images, have shown statistical significance between untreated colorectal tumors and the normal tissue. Using either a logistic regression model or a support vector machine, the best set of parameters of rHbT and PAT intercept has achieved area-under-the-curve (AUC) values of 0.97 and 0.95 for both training and testing data sets, respectively, for prediction of histologically confirmed invasive carcinoma./p.

We present a low-cost, compact, and multispectral spatial frequency domain imaging prototype. Illumination components, including 9 LEDs (660 nm - 950 nm) placed on a custom-designed printed circuit board, linear and rotational motors, a printed sinusoidal pattern, and collimation and projection optics as well as the detection components are incorporated in a compact custom-designed 3D-printed probe. Reconstruction of absorption and reduced scattering coefficients is evaluated via imaging tissue mimicking phantoms and potentials of the probe for biological tissue imaging are evaluated via imaging human ovarian tissue ex vivo.

Background Breast cancer pathologic complete response (pCR) to neoadjuvant chemotherapy (NAC) varies with tumor subtype. The purpose of this study was to identify an early treatment window for predicting pCR based on tumor subtype, pretreatment total hemoglobin (tHb) level, and early changes in tHb following NAC. Methods Twenty-two patients (mean age 56 years, range 34–74 years) were assessed using a near-infrared imager coupled with an Ultrasound system prior to treatment, 7 days after the first treatment, at the end of each of the first three cycles, and before their definitive surgery. Pathologic responses were dichotomized by the Miller-Payne system. Tumor vascularity was assessed from tHb; vascularity changes during NAC were assessed from a percentage tHb normalized to the pretreatment level (%tHb). After training the logistic prediction models using the previous study data, we assessed the early treatment window for predicting pathological response according to their tumor subtype (human epidermal growth factor receptor 2 (HER2), estrogen receptor (ER), triple-negative (TN)) based on tHb, and %tHb measured at different cycles and evaluated by the area under the receiver operating characteristic (ROC) curve (AUC). Results In the new study cohort, maximum pretreatment tHb and %tHb changes after cycles 1, 2, and 3 were significantly higher in responder Miller-Payne 4–5 tumors (n = 13) than non-or partial responder Miller-Payne 1–3 tumors (n = 9). However, no significance was found at day 7. The AUC of the predictive power of pretreatment tHb in the cohort was 0.75, which was similar to the performance of the HER2 subtype as a single predictor (AUC of 0.78). A greater predictive power of pretreatment tHb was found within each subtype, with AUCs of 0.88, 0.69, and 0.72, in the HER2, ER, and TN subtypes, respectively. Using pretreatment tHb and cycle 1 %tHb, AUC reached 0.96, 0.91, and 0.90 in HER2, ER, and TN subtypes, respectively, and 0.95 regardless of subtype. Additional cycle 2 %tHb measurements moderately improved prediction for the HER2 subtype but did not improve prediction for the ER and TN subtypes. Conclusions By combining tumor subtypes with tHb, we predicted the pCR of breast cancer to NAC before treatment. Prediction accuracy can be significantly improved by incorporating cycle 1 and 2 %tHb for the HER2 subtype and cycle 1 %tHb for the ER and TN subtypes. Trial registration ClinicalTrials.gov, NCT02092636 . Registered in March 2014.

Ultrasound-guided diffuse optical tomography (DOT) is very favorable and promising imaging technique for the early detection of breast cancer. The technique uses a hand-held probe capable of providing multiple wavelengths measurements in few seconds. These measurements are used to estimate optical proprieties of lesions inside tissue, and calculate the total hemoglobin concentration (tHb). The accurate recovery of breast lesion optical properties requires an effective image reconstruction method. Errors in the measurements caused by low signal-to-noise ratio data and/or movements during data acquisition would reduce the accuracy of reconstructed optical properties. Here is an attempt to preprocess the data based on multiple wavelength measurements for image reconstruction. This approach combines data collected from multiple sets of lesion measurements of different wavelengths to detect and correct outliers in the perturbation. The initial results obtained from the phantom experiments are promising. The approach has enhanced the consistency of the reconstructed images among multiple wavelengths.

We have conducted a pilot study to image and characterize ovarian masses using a co-registered ultrasound (US) and photoacoustic imaging (PAI) system. A total of seven patients who have ovarian masses and scheduled for surgical removal of both ovaries and Fallopian tubes, has enrolled to the study. A standard transvaginal US probe is used first to locate ovarian masses, measure ovary sizes in long and short axises . Then a second probe with four light-delivery fibers surrounded the US probe is inserted transvaginally to perform co-registered US and photoacoustic imaging in real-time with four optical wavelengths (730, 780, 800 and 830 nm). For the total of 7 patients, one patient had high-grade serous carcinoma involving both ovaries, one patient had a 2.2 cm endometrioid adenocarcinoma in right ovary, one patient had metastatic appendiceal adenocarcinoma involving both ovaries, one patient has serous borderline carcinoma involving both ovaries and the rest three patients had either abnormal or benign ovaries. For the malignant ovaries, photoacoustic images have showed significantly higher signal levels as quantitatively evaluated from maximum signal strengths from region-of-interest identified by co-registered US. Additionally, the quantitative features extracted from co-registered US and photoacoustic images, such as spectral slope, mid-band fit and zero MHz intercept, spatial heterogeneity of PAI distribution, the blood oxygen saturation, have showed significant differences between malignant and benign ovaries. Our initial results have demonstrated that photoacoustic imaging has a great potential to aid transvaginal US to quantitatively and effectively image and diagnose ovarian cancer.

Colorectal cancer is the second leading cause of cancer death in the United States. According to American Cancer society, the overall lifetime risk of developing colorectal cancer is about 4.7% for men and 4.4% for women. We have developed a rigid, endoscopic photoacoustic microscopy (PAM) probe for imaging of in vivo human colorectal cancers. In order to accommodate colon sections with different size (typically from 50 to 70mm), our 10mm diameter rigid probe uses an off-optical-axis, external mechanical scanning mechanism with a speed of 35deg/s instead of an on-optical-axis, internal mechanical scan mechanism. 532-nm pulsed laser light enters the ridged probe through a photonic crystal single mode fiber before it is collimated and refocused by a water-immersed objective lens onto the colon surface. A focused ultrasound ring transducer (40.5 MHz, 6.5mm focal length) receives photoacoustic signal from chromophores excited by laser beam. Imaging system performance specifications including resolution (6μm) and signal-to-noise ratio are quantified and verified from phantom imaging tests. Ex vivo human colon samples are studied to reveal microscopic features of normal colon, benign polyps, adenocarcinoma and cancer.

About 85-90% of all ovarian cancers are carcinomas; these manifest clinically as mass-forming epithelial proliferations involving the ovary. In this study, a visible light spatial frequency domain imaging (SFDI) system was used for multispectral ex vivo imaging and quantitative evaluation of freshly excised benign and malignant human ovarian tissues. A total of 14 ovaries from 11 patients undergoing oophorectomy were investigated. Using a logistic regression model with seven significant spectral and spatial features extracted from SFDI images, a sensitivity of 94.06% and specificity of 93.53% were achieved for prediction of histologically confirmed invasive carcinoma.

It is important to provide timely information to surgeons on diagnosis of a suspicious ovarian tissue before excision to avoid unnecessary surgery, especially for young women. In this report, we introduce a new 3-D surface mapping technique to map ovarian tissue scattering properties by fitting the swept-source optical coherence tomography (SS-OCT) signals to a scattering model. We observed that lower scattering coefficients and heterogeneous spatial distribution were associated with malignant ovarian tissues, and higher scattering coefficients and homogeneous spatial distribution indicated benign ovarian tissues. The initial results suggest that the 3-D scattering map has potential to be an effective tool to characterize normal and malignant ovarian tissues.

More than 80% of the ovarian cancers are diagnosed at late stages and the survival rate is less than 50%. Currently, there is no effective screening technique available and transvaginal US can only tell if the ovaries are enlarged or not. We have developed a new real-time co-registered US and photoacoustic system for in vivo imaging and characterization of ovaries. US is used to localize ovaries and photoacoustic imaging provides functional information about ovarian tissue angiogenesis and oxygenation saturation. The system consists of a tunable laser and a commercial US system from Alpinion Inc. The Alpinion system is cable of providing channel data for both US pulse-echo and photoacoustic imaging and can be programmed as a computer terminal for display US and photoacoustic images side by side or in coregistered mode. A transvaginal ultrasound probe of 6-MHz center frequency and bandwidth of 3-10 MHz is coupled with four optical fibers surrounded the US probe to deliver the light to tissue. The light from optical fibers is homogenized to ensure the power delivered to the tissue surface is below the FDA required limit. Physicians can easily navigate the probe and use US to look for ovaries and then turn on photoacoustic mode to provide real-time tumor vasculature and So2 saturation maps. With the optimized system, we have successfully imaged first group of 7 patients of malignant, abnormal and benign ovaries. The results have shown that both photoacoustic signal strength and spatial distribution are different between malignant and abnormal and benign ovaries.

We present a handheld and low-cost spatial frequency domain imaging system that utilizes up to 9 LEDs. Its feasibility is evaluated by imaging human wrist in vivo and it is used for characterization of ex vivo ovarian and colon cancer samples.

In this abstract a calibration method based on depth and size information provided from ultrasound images is introduced. The method utilizes the forward data simulated by finite element method to calibrate the reconstructed absorption map.