Characteristics of Users and New Initiators of Single- and Multiple-Inhaler Triple Therapy for Chronic Obstructive Pulmonary Disease in Germany.

Purpose: To assess patient characteristics of users and new initiators of triple therapy for chronic obstructive pulmonary disease (COPD) in Germany. Patients and Methods: Retrospective cohort study of patients with COPD and ≥1 prescription for single-inhaler triple therapy (SITT; fluticasone furoate/umeclidinium/vilanterol [FF/UMEC/VI] or beclomethasone dipropionate/glycopyrronium bromide/formoterol [BDP/GLY/FOR]) or multiple-inhaler triple therapy (MITT), using data from the AOK PLUS German sickness fund (1 January 2015-31 December 2019). The index date was the first date of prescription for FF/UMEC/VI or BDP/GLY/FOR (SITT users), or the first date of overlap of inhaled corticosteroid, long-acting ß2-agonist, and long-acting muscarinic antagonist (MITT users). Two cohorts were defined: the prevalent cohort included all identified triple therapy users; the incident cohort included patients newly initiating triple therapy for the first time (no prior use of MITT or SITT in the last 2 years). Patient characteristics and treatment patterns were assessed on the index date and during the 24-month pre-index period. Results: In total, 18,630 patients were identified as prevalent triple therapy users (MITT: 17,945; FF/UMEC/VI: 700; BDP/GLY/FOR: 908; non-mutually exclusive) and 2932 patients were identified as incident triple therapy initiators (MITT: 2246; FF/UMEC/VI: 311; BDP/GLY/FOR: 395; non-mutually exclusive). For both the prevalent and incident cohorts, more than two-thirds of patients experienced ≥1 moderate/severe exacerbation in the preceding 24 months; in both cohorts more BDP/GLY/FOR users experienced ≥1 moderate/severe exacerbation, compared with FF/UMEC/VI and MITT users. Overall, 97.9% of prevalent triple therapy users and 86.4% of incident triple therapy initiators received maintenance treatment in the 24-month pre-index period. Conclusion: In a real-world setting in Germany, triple therapy was most frequently used after maintenance therapy in patients with recent exacerbations, in line with current treatment recommendations.

Triple therapy (a combination of three different respiratory inhaled medications) is recommended for patients with chronic obstructive pulmonary disease (COPD) who experience repeated short-term symptom flare-ups when taking dual therapy (a combination of two different respiratory medications). Previously, patients had to take triple therapy using two or three separate inhalers. More recently, single-inhaler triple therapies have been developed, meaning patients can take all three different medications at the same time via one single inhaler. This study assessed the characteristics of patients who were already receiving triple therapy, or who started triple therapy (either via multiple inhalers or a single inhaler), in Germany between January 2015 and December 2019. In total, 18,630 patients who were already receiving triple therapy during the study period, and 2932 patients who newly started using triple therapy were included. The study reported that more than two-thirds of included patients had experienced at least one flare-up of COPD symptoms in the 2 years before starting triple therapy. Most patients had also received another therapy for COPD before starting triple therapy. A small proportion of patients started taking triple therapy after receiving no other therapy for COPD in the previous 2 years. The results of the study suggest that triple therapy for COPD in Germany is most often used in accordance with recommendations (patients already receiving therapy and experiencing repeated symptom flare-ups).

Shedding light on pediatric diseases: multispectral optoacoustic tomography at the doorway to clinical applications.

Optoacoustic imaging (OAI), or photoacoustic imaging (PAI), has fundamentally influenced basic science by providing high-resolution visualization of biological mechanisms. With the introduction of multispectral optoacoustic tomography (MSOT), these technologies have now moved closer to clinical applications. MSOT utilizes short-pulsed near-infrared laser light to induce thermoelastic expansion in targeted tissues. This results in acoustic pressure waves, which are used to resolve specific endo- and exogenous chromophores. Especially in the pediatric population, this non-invasive imaging approach might hold fundamental advantages compared to conventional cross-sectional imaging modalities. As this technology allows the visualization of quantitative molecular tissue composition at high spatial resolution non-invasively in sufficient penetration depth, it paves the way to personalized medicine in pediatric diseases.

Real-Time Optoacoustic Tracking of Single Moving Micro-objects in Deep Phantom and Ex Vivo Tissues.

Medical imaging plays an important role in diagnosis and treatment of multiple diseases. It is a field which seeks for improved sensitivity and spatiotemporal resolution to allow the dynamic monitoring of diverse biological processes that occur at the micro- and nanoscale. Emerging technologies for targeted diagnosis and therapy such as nanotherapeutics, microimplants, catheters, and small medical tools also need to be precisely located and monitored while performing their function inside the human body. In this work, we show for the first time the real-time tracking of moving single micro-objects below centimeter thick phantom tissue and ex vivo chicken breast, using multispectral optoacoustic tomography (MSOT). This technique combines the advantages of ultrasound imaging regarding depth and resolution with the molecular specificity of optical methods, thereby facilitating the discrimination between the spectral signatures of the micro-objects from those of intrinsic tissue molecules. The resulting MSOT signal is further improved in terms of contrast and specificity by coating the micro-objects' surface with gold nanorods, possessing a unique absorption spectrum, which facilitate their discrimination from surrounding biological tissues when translated to future in vivo settings.

Multispectral Optoacoustic Tomography of Benign and Malignant Thyroid Disorders: A Pilot Study.

This study aimed at evaluating hybrid multispectral optoacoustic tomography/ultrasound for imaging of thyroid disorders, including Graves' disease and thyroid nodules. Methods: The functional biomarkers and tissue parameters deoxygenated hemoglobin, oxygenated hemoglobin, total hemoglobin, saturation of hemoglobin, fat content, and water content were analyzed in thyroid lobes affected by Graves' disease (n = 6), thyroid lobes with healthy tissue (n = 8), benign thyroid nodules (n = 13), and malignant thyroid nodules (n = 3). Results: In Graves' disease, significantly higher deoxygenated hemoglobin (3.18 ± 0.52 vs. 2.13 ± 0.62; P = 0.0055) and total hemoglobin (8.34 ± 0.88 vs. 6.59 ± 1.16; P = 0.0084) and significantly lower fat content (0.64 ± 0.37 vs. 1.69 ± 1.25; P = 0.0293) were found than in healthy controls. Malignant thyroid nodules showed significantly lower saturation of hemoglobin (55.4% ± 2.6% vs. 60.8% ± 7.2%; P = 0.0393) and lower fat content (0.62 ± 0.19 vs. 1.46 ± 0.87; P = 0.1295) than benign nodules. Conclusion: This pilot study showed the applicability and the potential of hybrid multispectral optoacoustic tomography/ultrasound to semiquantitatively provide tissue characterization and functional parameters in thyroid disorders for improved noninvasive diagnostics of thyroid diseases.

Multispectral Optoacoustic Tomography: Intra- and Interobserver Variability Using a Clinical Hybrid Approach.

Multispectral optoacoustic tomography (MSOT) represents a new imaging approach revealing functional tissue information without extrinsic contrast agents. Using a clinical combined ultrasound (US)/MSOT device, we investigated the interindividual robustness and impact of intra- and interobserver variability of MSOT values in soft tissue (muscle and subcutaneous fat) of healthy volunteers. Semiquantitative MSOT values for deoxygenated (Hb), oxygenated (HbO2) and total hemoglobin (HbT), as well as oxygen saturation (sO2), were calculated for both forearms in transversal and longitudinal probe orientation (n = 3, 8 measurements per subject). For intraobserver reproducibility, the same examiner investigated three subjects twice. Mean values of left vs. right forearm and transversal vs. longitudinal probe orientation were compared using an unpaired Student's t test. Bland Altmann plots with 95% limits of agreement for absolute averages and differences were calculated. Intraclass correlation coefficients (ICC 2,k) were computed for three different examiners. We obtained reproducible and consistent MSOT values with small-to-moderate deviation for muscle and subcutaneous fat tissue. Probe orientation and body side had no impact on calculated MSOT values (p > 0.05 each). Intraobserver reproducibility revealed equable mean values with small-to-moderate deviation. For muscular tissue, good ICC was obtained for sO2. Measurements of subcutaneous tissue revealed good-to-excellent ICCs for all calculated values. Thus, in this preliminary study on healthy individuals, clinical MSOT provided consistent and reproducible functional soft tissue characterization, independent on the investigating personnel.

Inhibiting Interleukin 36 Receptor Signaling Reduces Fibrosis in Mice With Chronic Intestinal Inflammation.

BACKGROUND & AIMS: Intestinal fibrosis is a long-term complication in inflammatory bowel diseases (IBD) that frequently results in functional damage, bowel obstruction, and surgery. Interleukin (IL) 36 is a group of cytokines in the IL1 family with inflammatory effects. We studied the expression of IL36 and its receptor, interleukin 1 receptor like 2 (IL1RL2 or IL36R) in the development of intestinal fibrosis in human tissues and mice. METHODS: We obtained intestinal tissues from 92 patients with Crohn's disease (CD), 48 patients with ulcerative colitis, and 26 patients without inflammatory bowel diseases (control individuals). Tissues were analyzed by histology to detect fibrosis and by immunohistochemistry to determine the distribution of fibroblasts and levels of IL36R ligands. Human and mouse fibroblasts were incubated with IL36 or control medium, and transcriptome-wide RNA sequences were analyzed. Mice were given neutralizing antibodies against IL36R, and we studied intestinal tissues from Il1rl2-/- mice; colitis and fibrosis were induced in mice by repetitive administration of DSS or TNBS. Bone marrow cells were transplanted from Il1rl2-/- to irradiated wild-type mice and intestinal tissues were analyzed. Antibodies against IL36R were applied to mice with established chronic colitis and fibrosis and intestinal tissues were studied. RESULTS: Mucosal and submucosal tissue from patients with CD or ulcerative colitis had higher levels of collagens, including type VI collagen, compared with tissue from control individuals. In tissues from patients with fibrostenotic CD, significantly higher levels of IL36A were noted, which correlated with high numbers of activated fibroblasts that expressed α-smooth muscle actin. IL36R activation of mouse and human fibroblasts resulted in expression of genes that regulate fibrosis and tissue remodeling, as well as expression of collagen type VI. Il1rl2-/- mice and mice given injections of an antibody against IL36R developed less severe colitis and fibrosis after administration of DSS or TNBS, but bone marrow cells from Il1rl2-/- mice did not prevent induction of colitis and fibrosis. Injection of antibodies against IL36R significantly reduced established fibrosis in mice with chronic intestinal inflammation. CONCLUSION: We found higher levels of IL36A in fibrotic intestinal tissues from patients with IBD compared with control individuals. IL36 induced expression of genes that regulate fibrogenesis in fibroblasts. Inhibition or knockout of the IL36R gene in mice reduces chronic colitis and intestinal fibrosis. Agents designed to block IL36R signaling could be developed for prevention and treatment of intestinal fibrosis in patients with IBD.

Use of Multispectral Optoacoustic Tomography to Diagnose Vascular Malformations.

Importance: Differential diagnosis of congenital vascular anomalies is challenging, and misdiagnosis is frequent. Vascular malformations are considered one of the most difficult vascular diseases to treat. A new imaging approach that visualizes anatomical features and quantitatively assesses molecular biomarkers noninvasively would aid diagnosis and monitoring of treatment response of vascular malformations. Objective: To evaluate multispectral optoacoustic tomography (MSOT) for noninvasive assessment of molecular biomarkers for diagnosis and therapeutic monitoring of vascular malformations. Design, Setting, and Participants: This pilot study examined 6 patients with arteriovenous malformation (AVM) and 6 patients with venous malformation (VM) diagnosed according to the classification system of the International Society for the Study of Vascular Anomalies. All patients underwent clinical hybrid MSOT/ultrasonographic (US) imaging before and after treatment at an interdisciplinary vascular malformations clinic by trained MSOT and US examiners. Examiners were blinded to the patient history and stage of disease. Data were collected from April 11 to 25, 2017, and analyzed from May 1 to October 31, 2017. Interventions: Clinical hybrid MSOT/US imaging was performed before or within 1 week after endovascular embolization (for AVM) or percutaneous sclerotherapy (for VM). Main Outcomes and Measures: Region-of-interest analysis of the lesion and contralateral healthy tissue revealed quantitative values for oxygenated (HbO2) and deoxygenated (HbR) hemoglobin by spectral unmixing of optoacoustic data acquired at multiple wavelengths. The HbO2:HbR ratio was calculated for healthy tissue and for AVM and VM before and after treatment. Results: Twelve patients (9 female and 3 male; mean [SD] age, 23 [18] years; age range, 6-59 years) with vascular malformations (6 with AVMs and 6 with VMs) were included. Significantly higher HbO2:HbR ratios for AVMs (mean [SEM], 1.82 [0.08] vs 0.89 [0.03]; P < .001) and for VMs (mean [SEM], 1.12 [0.04] vs 0.89 [0.03]; P = .001) were found on MSOT tissue compared with healthy tissue. Significantly higher HbO2:HbR ratios for AVMs compared with VMs (mean [SEM], 1.82 [0.08] vs 1.12 [0.04]; P < .001) were also found. Therefore, MSOT provided intrinsic biomarker patterns to distinguish both vascular malformations. After therapy, the HbO2:HbR ratio dropped in correlation to treatment success validated by magnetic resonance imaging or angiography. Conclusions and Relevance: This study suggests that different types of vascular malformations are clearly distinguished by MSOT-based, noninvasive assessment of hemoglobin levels in vascular malformations. The therapy effects found in this study could be instantly visualized, and this may offer a new tool for noninvasive diagnosis and monitoring of vascular malformations.

Multispectral optoacoustic tomography of systemic sclerosis.

The study aimed to evaluate the clinical feasibility of hybrid ultrasound/multispectral optoacoustic tomography (MSOT) for assessing microvascular dysfunction in systemic sclerosis (SSc). A handheld US/MSOT imaging system was applied for imaging patients diagnosed with SSc (n = 7) and healthy volunteers (n = 8). Semiquantitative MSOT values for deoxygenated (HbR), oxygenated (HbO2 ) and total haemoglobin (HbT) were analysed for subcutaneous finger tissue of both hands (8 fingers per subject, 120 fingers in total) and used to assess disease activity (progressive vs stable). Grouped data were compared by one-way nested analysis of variance, Tukey post-hoc test as well as student's t test were used for statistical analysis.Subcutaneous finger tissue of patients with SSc provided significantly lower MSOT values for HbO2 (26.16 ± 0.71 vs 38.2 ± 1.54, P = .023) and HbT (55.92 ± 1.62 vs 72.46 ± 1.90, P = .018) compared to healthy volunteers. Patients with progressive SSc had significantly lower MSOT values compared to patients with stable disease and healthy volunteers.This pilot study shows the feasibility of MSOT imaging to resolve microvascular dysfunction in SSc as a marker of disease activity. By providing biological tissue properties not revealed by other imaging modalities, MSOT might help to grade SSc non-invasively and monitor early therapy response.

Fluorescence- and multispectral optoacoustic imaging for an optimized detection of deeply located tumors in an orthotopic mouse model of pancreatic carcinoma.

A crucial point for the management of pancreatic ductal adenocarcinoma (PDAC) is the decrease of R1 resections. Our aim was to evaluate the combination of multispectral optoacoustic tomography (MSOT) with fluorescence guided surgery (FGS) for diagnosis and perioperative detection of tumor nodules and resection margins in a xenotransplant mouse model of human pancreatic cancer. The peptide cRGD, conjugated with the near infrared fluorescent (NIRF) dye IRDye800CW and with a trans-cyclooctene (TCO) tag for future click chemistry (cRGD-800CW-TCO), was applied to PDAC bearing immunodeficient nude mice; 27 days after orthotopic transplantation of human AsPC-1 cells into the head of the pancreas, mice were injected with cRGD-800CW-TCO and imaged with fluorescence- and optoacoustic devices before and 2, 6 and 24 hr after injection, before they were sacrificed and dissected with a guidance of FGS imaging system. Fluorescence imaging of cRGD-800CW-TCO allowed detection of the tumor area but without information about the depth, whereas MSOT allowed high resolution 3 D identification of the tumor area, in particular of small tumor nodules. Highly sensitive delineation of tumor burden was achieved during FGS in all mice. Imaging of whole-mouse cryosections, histopathological analysis and NIRF microscopy confirmed the localization of cRGD-800CW-TCO within the tumor tissue. In principle, all imaging modalities applied here were able to detect PDAC in vivo. However, the combination of MSOT and FGS provided detailed spatial information of the signal and achieved a complete overview of the distribution and localization of cRGD-800CW-TCO within the tumor before and during surgical intervention.

Multispectral optoacoustic tomography of the human breast: characterisation of healthy tissue and malignant lesions using a hybrid ultrasound-optoacoustic approach.

BACKGROUND AND AIM: Multispectral optoacoustic tomography (MSOT) represents a new in vivo imaging technique with high resolution (~250 µm) and tissue penetration (>1 cm) using the photoacoustic effect. While ultrasound contains anatomical information for lesion detection, MSOT provides functional information based on intrinsic tissue chromophores. We aimed to evaluate the feasibility of combined ultrasound/MSOT imaging of breast cancer in patients compared to healthy volunteers. METHODS: Imaging was performed using a handheld MSOT system for clinical use in healthy volunteers (n = 6) and representative patients with histologically confirmed invasive breast carcinoma (n = 5) and ductal carcinoma in situ (DCIS, n = 2). MSOT values for haemoglobin and oxygen saturation were assessed at 0.5, 1.0 and 1.5 cm depth and selected wavelengths between 700 and 850 nm. RESULTS: Reproducible signals were obtained in all wavelengths with consistent MSOT signals in superficial tissue in breasts of healthy individuals. In contrast, we found increased signals for haemoglobin in invasive carcinoma, suggesting a higher perfusion of the tumour and tumour environment. For DCIS, MSOT values showed only little variation compared to healthy tissue. CONCLUSIONS: This preliminary MSOT breast imaging study provided stable, reproducible data on tissue composition and physiological properties, potentially enabling differentiation of solid malignant and healthy tissue. KEY POINTS: • A handheld MSOT probe enables real-time molecular imaging of the breast. • MSOT of healthy controls provides a reproducible reference for pathology identification. • MSOT parameters allows for differentiation of invasive carcinoma and healthy tissue.

Metastatic status of sentinel lymph nodes in melanoma determined noninvasively with multispectral optoacoustic imaging.

Sentinel lymph node (SLN) excision is included in various cancer guidelines to identify microscopic metastatic disease. Although effective, SLN excision is an invasive procedure requiring radioactive tracing. Novel imaging approaches assessing SLN metastatic status could improve or replace conventional lymph node excision protocols. In our first-in-human study, we used noninvasive multispectral optoacoustic tomography (MSOT) to image SLNs ex vivo and in vivo in patients with melanoma, to determine metastatic status. MSOT significantly improved the tumor metastasis detection rate in excised SLN (506 SLNs from 214 melanoma patients) compared with the conventional EORTC (European Organisation for Research and Treatment of Cancer) Melanoma Group protocol (22.9% versus 14.2%). MSOT combined with the near-infrared fluorophore indocyanine green reliably visualized SLNs in vivo in 20 patients, up to 5-cm penetration and with 100% concordance with (99m)Tc-marked SLN lymphoscintigraphy. MSOT identified cancer-free SLNs in vivo and ex vivo without a single false negative (189 total lymph nodes), with 100% sensitivity and 48 to 62% specificity. Our findings indicate that a noninvasive, nonradioactive MSOT-based approach can identify and determine SLN status and confidently rule out the presence of metastasis. The study further demonstrates that optoacoustic imaging strategies can improve the identification of SLN metastasis as an alternative to current invasive SLN excision protocols.

Whole-body live mouse imaging by hybrid reflection-mode ultrasound and optoacoustic tomography.

We present a hybrid preclinical imaging scanner that optimally supports image acquisition in both reflection-mode ultrasonography and optoacoustic (OA) tomography modes. The system comprises a quasi-full-ring tomographic geometry capable of the simultaneous dual-mode imaging through entire cross sections of mice with in-plane spatial resolution in the range of 150 and 350 µm in the respective OA and ultrasound (US) imaging modes with an imaging speed of up to 10 two-dimensional frames per second. Three-dimensional whole-body data is subsequently rendered by rapid scanning of the imaged plane. The system further incorporates rapid laser wavelength tuning for real-time acquisition of multispectral OA data, which enables studies of longitudinal dynamics as well as fast kinetics and biodistribution of contrast agents. In vivo imaging performance is demonstrated by label-free hybrid anatomical scans through living mice, as well as real-time visualization of optical contrast agent perfusion. By setting new standards for whole-body tomographic imaging performance in both the OA and pulse-echo US modes, the developed hybrid imaging approach is expected to benefit numerous applications where the availability of high-quality structural information provided by the tomographic reflection-mode US can ease interpretation of the functional and molecular imaging results attained by the OA modality.

Semi-quantitative Multispectral Optoacoustic Tomography (MSOT) for volumetric PK imaging of gastric emptying.

A common side effect of medication is gastrointestinal intolerance. Symptoms can include reduced appetite, diarrhea, constipation, GI inflammation, nausea and vomiting. Such effects often have a dramatic impact on compliance with a treatment regimen. Therefore, characterization of GI tolerance is an important step when establishing a novel therapeutic approach. In this study, Multispectral Optoacoustic Tomography (MSOT) is used to monitor gastrointestinal motility by in vivo whole body imaging in mice. MSOT combines high spatial and temporal resolution based on ultrasound detection with strong optical contrast in the near infrared. Animals were given Indocyanine Green (ICG) by oral gavage and imaged by MSOT to observe the fate of ICG in the gastrointestinal tract. Exponential decay of ICG signal was observed in the stomach in good correlation with ex vivo validation. We discuss how kinetic imaging in MSOT allows visualization of parameters unavailable to other imaging methods, both in 2D and 3D.

Optoacoustic imaging of blood perfusion: techniques for intraoperative tissue viability assessment.

Reliably assessing tissue viability during surgery is of major importance in surgical procedures. The most basic requirement for viability is sufficient oxygen supply to the tissue. Therefore it is highly desirable to visualize in real-time the dynamic process of blood perfusion up to and within the microvasculature. A modality sensitive to structures in the range of few hundred micrometers and offering high contrast to the embedding tissue is then needed. To this end, a number of methods have been developed, but have had no significant impact on the clinical routine due to various deficiencies. In this paper we demonstrate the applicability of optoacoustic imaging, which combines ultrasonic resolution with strong optical contrast. A method for optoacoustic perfusion assessment, based on a local and repeatable injection of saline, was proposed and assessed ex-vivo on large pig bowels and in-vivo in mouse tails. The obtained dynamic perfusion images highlight the method's potential to enable immediate and quantitative assessment of tissue viability during surgery.

Neurons with GABAergic phenotype in the visual system of Drosophila.

The visual system of Drosophila contains ~60,000 neurons per hemisphere that are organized in parallel, retinotopically arranged columns. The neuroanatomy of these neurons has been mapped in considerable detail at both the light and ultrastructural level. However, studies providing direct evidence for synaptic signaling and the neurotransmitter used by individual neurons are relatively sparse. Here we characterize those neurons in the Drosophila optic lobes that possibly release gamma aminobutyric acid (GABA), the major inhibitory neurotransmitter of the insect central nervous system. We identified 26 different types of neurons of the lamina, medulla, lobula, and lobula plate. Based on the previous Golgi-staining analysis (Fischbach and Dittrich [1989] Cell Tissue Res 258:441-475), the identified neurons are further classified into 11 major subgroups representing lamina monopolar (L), medulla intrinsic (Mi, Mt), bushy T (T), transmedullary (Tm), transmedullary Y (TmY), Y, lobula-complex intrinsic (Lccn), lobula columnar (Lcn), lobula plate intrinsic (Lpi), and lobula tangential (Lt) cell types. This detailed map of neurons with GABAergic phenotype will contribute to the future neurogenetic dissection of information processing circuits in the fly visual system.

Multispectral opto-acoustic tomography (MSOT) of the brain and glioblastoma characterization.

Brain research depends strongly on imaging for assessing function and disease in vivo. We examine herein multispectral opto-acoustic tomography (MSOT), a novel technology for high-resolution molecular imaging deep inside tissues. MSOT illuminates tissue with light pulses at multiple wavelengths and detects the acoustic waves generated by the thermoelastic expansion of the environment surrounding absorbing molecules. Using spectral unmixing analysis of the data collected, MSOT can then differentiate the spectral signatures of oxygenated and deoxygenated hemoglobin and of photo-absorbing agents and quantify their concentration. By being able to detect absorbing molecules up to centimeters deep in the tissue it represents an ideal modality for small animal brain imaging, simultaneously providing anatomical, hemodynamic, functional, and molecular information. In this work we examine the capacity of MSOT in cross-sectional brain imaging of mice. We find unprecedented optical imaging performance in cross-sectional visualization of anatomical and physiological parameters of the mouse brain. For example, the potential of MSOT to characterize ischemic brain areas was demonstrated through the use of a carbon dioxide challenge. In addition, indocyanine green (ICG) was injected intravenously, and the kinetics of uptake and clearance in the vasculature of the brain was visualized in real-time. We further found that multiparameter, multispectral imaging of the growth of U87 tumor cells injected into the brain could be visualized through the intact mouse head, for example through visualization of deoxygenated hemoglobin in the growing tumor. We also demonstrate how MSOT offers several compelling features for brain research and allows time-dependent detection and quantification of brain parameters that are not available using other imaging methods without invasive procedures.

Motion clustering for deblurring multispectral optoacoustic tomography images of the mouse heart.

Cardiac imaging in small animals is a valuable tool in basic biological research and drug discovery for cardiovascular disease. Multispectral optoacoustic tomography (MSOT) represents an emerging imaging modality capable of visualizing specific tissue chromophores at high resolution and deep in tissues in vivo by separating their spectral signatures. Whereas single-wavelength images can be acquired by multielement ultrasound detection in real-time imaging, using multiple wavelengths at separate times can lead to image blurring due to motion during acquisition. Therefore, MSOT imaging of the heart results in degraded resolution because of the heartbeat. In this work, we applied a clustering algorithm, k-means, to automatically separate a sequence of single-pulse images at multiple excitation wavelengths into clusters corresponding to different stages of the cardiac cycle. We then performed spectral unmixing on each cluster to obtain images of tissue intrinsic chromophores at different cardiac stages, showing reduced sensitivity to motion compared to signal averaging without clustering. We found that myocardium images of improved resolution and contrast can be achieved using MSOT motion clustering correction. The correction method presented could be generally applied to other MSOT imaging applications prone to motion artifacts, for example, by respiration and heartbeat.