Comparison of micro-CT image enhancement after use of different vascular casting agents.

Background: Microvascular visualization is crucial in understanding the mechanisms of several pathologies. For instance, visualization of the tumor microenvironment is important in understanding angiogenesis and role in cancer progression. Visualization would provide insights to cancer diagnosis, predicting metastatic growth, and evaluating therapeutic protocols. Similarly, understanding the microvascular network could be beneficial for study of degenerative diseases and tissue repair. The use of microscale computed tomography (micro-CT) and vascular casting agents provides high-resolution images of tissue vasculature in volumetric space. The purpose of this research was to compare a selection of commercially available contrast agents to determine the optimal solution for vascular visualization. Methods: A population of 16 female nude athymic mice (Charles Rivers Laboratories) were implanted with MDA-MB-231 breast cancer cells (ATCC) orthotopically in the lower left mammary fat pad to investigate the tumor microenvironment. Once tumors reach sufficient size, animals were equally divided into four groups based on the micro-CT agent to be administered, namely, control (no contrast agent), barium sulfate (BaSO4), Vascupaint, or Microfil. Animals were anesthetized prior to transcarotid micro-cannulation to infuse 2 mL of the specific contrast agent for intravascular distribution throughout the animal. The jugular vein on the other side of the carotid artery was opened to drain blood flow. Following successful perfusion, animals and extracted organs underwent high-resolution micro-CT scanning (OI/CT, MILabs). Images were reconstructed and analyzed using analysis software to extract mean intensity signals. Results: Preliminary post-mortem micro-CT results reveal Vascupaint and BaSO4 are useful for microvascular visualization. Both Vascupaint and BaSO4 produced significant contrast-enhanced micro-CT image enhancement in the brain (3.39±0.93 and 6.27±3.78, respectively) and kidney (12.85±1.98 and 32.87±10.03, respectively) as compared to Microfil (0.22±0.07 and 0.91±0.63, respectively; P<0.05). For the various contrast agents, there were no differences in image enhancement from the liver, spleen, or tumor tissue (P>0.21). Moreover, use of Vascupaint and BaSO4 allowed for visualization of smaller microvascular structures with average diameters of 20.54±4.15 and 25.82±3.75 µm, which were smaller compared to the 91.66±24.91 µm measurements from Microfil-enhanced micro-CT images (P<0.004). Conclusions: Our study suggests that the use of Vascupaint and BaSO4 is more than sufficient for ex vivo visualization of microvascular structures with contrast-enhanced micro-CT imaging as these contrast agents more effectively perfused smaller blood vessels.

A single photodynamic priming protocol augments delivery of ⍺-PD-L1 mAbs and induces immunogenic cell death in head and neck tumors.

Photodynamic priming (PDP) leverages the photobiological effects of subtherapeutic photodynamic therapy (PDT) regimens to modulate the tumor vasculature and stroma. PDP also sensitizes tumors to secondary therapies, such as immunotherapy by inducing a cascade of molecular events, including immunogenic cell death (ICD). We and others have shown that PDP improves the delivery of antibodies, among other theranostic agents. However, it is not known whether a single PDP protocol is capable of both inducing ICD in vivo and augmenting the delivery of immune checkpoint inhibitors. In this rapid communication, we show for the first time that a single PDP protocol using liposomal benzoporphyrin derivative (Lipo-BPD, 0.25 mg/kg) with 690 nm light (75 J/cm2 , 100 mW/cm2 ) simultaneously doubles the delivery of ⍺-PD-L1 antibodies in murine AT-84 head and neck tumors and induces ICD in vivo. ICD was observed as a 3-11 fold increase in tumor cell exposure of damage-associated molecular patterns (Calreticulin, HMGB1, and HSP70). These findings suggest that this single, highly translatable PDP protocol using clinically relevant Lipo-BPD holds potential for improving immunotherapy outcomes in head and neck cancer. It can do so by simultaneously overcoming physical barriers to the delivery of immune checkpoint inhibitors, and biochemical barriers that contribute to immunosuppression.

An osmium(II) methane complex: Elucidation of the methane coordination mode.

The activation of inert C─H bonds by transition metals is of considerable industrial and academic interest, but important gaps remain in our understanding of this reaction. We report the first experimental determination of the structure of the simplest hydrocarbon, methane, when bound as a ligand to a homogenous transition metal species. We find that methane binds to the metal center in this system through a single M···H-C bridge; changes in the 1JCH coupling constants indicate clearly that the structure of the methane ligand is significantly perturbed relative to the free molecule. These results are relevant to the development of better C─H functionalization catalysts.

Taste and pheromonal inputs govern the regulation of time investment for mating by sexual experience in male Drosophila melanogaster.

Males have finite resources to spend on reproduction. Thus, males rely on a 'time investment strategy' to maximize their reproductive success. For example, male Drosophila melanogaster extends their mating duration when surrounded by conditions enriched with rivals. Here we report a different form of behavioral plasticity whereby male fruit flies exhibit a shortened duration of mating when they are sexually experienced; we refer to this plasticity as 'shorter-mating-duration (SMD)'. SMD is a plastic behavior and requires sexually dimorphic taste neurons. We identified several neurons in the male foreleg and midleg that express specific sugar and pheromone receptors. Using a cost-benefit model and behavioral experiments, we further show that SMD behavior exhibits adaptive behavioral plasticity in male flies. Thus, our study delineates the molecular and cellular basis of the sensory inputs required for SMD; this represents a plastic interval timing behavior that could serve as a model system to study how multisensory inputs converge to modify interval timing behavior for improved adaptation.

Assessment of Transarterial Chemoembolization Using Super-resolution Ultrasound Imaging and a Rat Model of Hepatocellular Carcinoma.

OBJECTIVE: Hepatocellular carcinoma (HCC) is a highly prevalent form of liver cancer diagnosed annually in 600,000 people worldwide. A common treatment is transarterial chemoembolization (TACE), which interrupts the blood supply of oxygen and nutrients to the tumor mass. The need for repeat TACE treatments may be assessed in the weeks after therapy with contrast-enhanced ultrasound (CEUS) imaging. Although the spatial resolution of traditional CEUS has been restricted by the diffraction limit of ultrasound (US), this physical barrier has been overcome by a recent innovation known as super-resolution US (SRUS) imaging. In short, SRUS enhances the visible details of smaller microvascular structures on the 10 to 100 µm scale, which unlocks a host of new clinical opportunities for US. METHODS: In this study, a rat model of orthotopic HCC is introduced and TACE treatment response (to a doxorubicin-lipiodol emulsion) is assessed using longitudinal SRUS and magnetic resonance imaging (MRI) performed at 0, 7 and 14 d. Animals were euthanized at 14 d for histological analysis of excised tumor tissue and determination of TACE response, that is, control, partial response or complete response. CEUS imaging was performed using a pre-clinical US system (Vevo 3100, FUJIFILM VisualSonics Inc.) equipped with an MX201 linear array transducer. After administration of a microbubble contrast agent (Definity, Lantheus Medical Imaging), a series of CEUS images were collected at each tissue cross-section as the transducer was mechanically stepped at 100 µm increments. SRUS images were formed at each spatial position, and a microvascular density metric was calculated. Microscale computed tomography (microCT, OI/CT, MILabs) was used to confirm TACE procedure success, and tumor size was monitored using a small animal MRI system (BioSpec 3T, Bruker Corp.). RESULTS: Although there were no differences at baseline (p > 0.15), both microvascular density levels and tumor size measures from the complete responder cases at 14 d were considerably lower and smaller, respectively, than those in the partial responder or control group animals. Histological analysis revealed tumor-to-necrosis levels of 8.4%, 51.1% and 100%, for the control, partial responder and complete responder groups, respectively (p < 0.005). CONCLUSION: SRUS imaging is a promising modality for assessing early changes in microvascular networks in response to tissue perfusion-altering interventions such as TACE treatment of HCC.

Low-Volume and High-Volume Readers of Neurological and Musculoskeletal MRI: Achieving Subspecialization in Radiology.

OBJECTIVE: Differentiate high- versus low-volume radiologists who interpret neurological (Neuro) MRI or musculoskeletal (MSK) MRI and measure the proportion of Neuro and MSK MRIs read by low-volume radiologists. METHODS: We queried the 2015 Medicare Physician and Other Supplier Public Use File for radiologists who submitted claims for Neuro or MSK MRIs. Radiologists were classified as high-volume versus low-volume based on their work relative value units (wRVUs) focus or volume of studies interpreted using three different methodologies: Method 1, percentage of wRVUs in Neuro or MSK MRI; Method 2, absolute number of Neuro or MSK MRIs interpreted; and Method 3, both percentage and absolute number. Multiple thresholds with each methodology were tested, and the percentage of Neuro or MSK MRIs interpreted by low-volume radiologists was calculated for each threshold. RESULTS: With Method 1, 33% of Neuro MRI and 50% of MSK MRI studies were interpreted by a radiologist whose wRVUs in Neuro or MSK MRI were less than 20% (Method 1). With Method 2, 22% of Neuro MRIs and 37% of MSK MRIs were interpreted by radiologists who read fewer than the mean number of Neuro or MSK MRIs interpreted by an "average full-time radiologist" whose wRVUs in Neuro or MSK MRI were approximately 20%. With Method 3, 38% of Neuro MRIs and 57% of MSK MRIs were interpreted by "low-volume" radiologists. If instead a 50% wRVU threshold is used for Methods One, Two, and Three, then 70%, 58%, and 77% of Neuro MRIs and 86%, 80%, and 90% of MSK MRIs are read by low-volume radiologists. DISCUSSION: A large number of radiologists read a low volume of Neuro or MSK MRIs; these low-volume Neuro or MSK MRI radiologists read a substantial portion of Neuro or MSK MRIs. It is unknown which of the methods for distinguishing low-volume radiologists, combined with which threshold, may best correlate with high-performing or low-performing radiologists.

Scrotal Ultrasound for Pain: Low Frequency of Absolute Surgical Indications.

OBJECTIVE: To examine the results of scrotal ultrasounds (US) conducted for scrotal or testicular pain and review the pathologic findings of orchiectomies done for lesions that were suspicious for malignancy on US. MATERIALS AND METHODS: We retrospectively reviewed the indications and findings of all scrotal US completed at our institution from 2002 to 2014. If a patient underwent an orchiectomy for an intratesticular lesion that was concerning for malignancy on US, the pathology report was also reviewed. RESULTS: There were 18,593 scrotal US performed, with 7,668 (41.2%) conducted for scrotal pain. Of the US performed for pain, 80.4% revealed benign or normal findings, and only 2.2% demonstrated a finding that is an absolute indication for surgery (intratesticular lesion suspicious for malignancy 0.8%, abscess 0.7%, torsion 0.6%, infiltrative process such as lymphoma 0.1%). For those patients undergoing an orchiectomy, 75% had malignancy on pathologic analysis. CONCLUSION: The majority of the 7668 US performed to evaluate scrotal or testicular pain reveal normal or benign findings. A low percentage demonstrates a finding that necessitates urgent or emergent surgery.

Aortic Volumetry at Contrast-Enhanced Magnetic Resonance Angiography: Feasibility as a Sensitive Method for Monitoring Bicuspid Aortic Valve Aortopathy.

OBJECTIVES: Bicuspid aortic valve patients can develop thoracic aortic aneurysms and therefore require serial imaging to monitor aortic growth. This study investigates the reliability of contrast-enhanced magnetic resonance angiography (CEMRA) volumetry compared with 2-dimensional diameter measurements to identify thoracic aortic aneurysm growth. MATERIALS AND METHODS: A retrospective, institutional review board-approved, and Health Insurance Portability and Accountability Act-compliant study was conducted on 20 bicuspid aortic valve patients (45 ± 8.9 years, 20% women) who underwent serial CEMRA with a minimum imaging follow-up of 11 months. Magnetic resonance imaging was performed at 1.5 T with electrocardiogram-gated, time-resolved CEMRA. Independent observers measured the diameter at the sinuses of Valsalva (SOVs) and mid ascending aorta (MAA) as well as ascending aorta volume between the aortic valve annulus and innominate branch. Intraobserver/interobserver coefficient of variation (COV) and intraclass correlation coefficient (ICC) were computed to assess reliability. Growth rates were calculated and assessed by Student t test (P < 0.05, significant). The diameter of maximal growth (DMG), defined as the diameter at SOV or MAA with the faster growth rate, was recorded. RESULTS: The mean time of follow-up was 2.6 ± 0.82 years. The intraobserver COV was 0.01 for SOV, 0.02 for MAA, and 0.02 for volume (interobserver COV: 0.02, 0.03, 0.04, respectively). The ICC was 0.83 for SOV, 0.86 for MAA, 0.90 for DMG, and 0.95 for volume. Average aortic measurements at baseline and (follow-up) were 42 ± 3 mm (42 ± 3 mm, P = 0.11) at SOV, 46 ± 4 mm (47 ± 4 mm, P < 0.05) at MAA, and 130 ± 23 mL (144 ± 24 mL, P < 0.05). Average size changes were 0.2 ± 0.6 mm/y (1% ± 2%) at SOV, 0.5 ± 0.8 mm/y (1% ± 2%) at MAA, 0.7 ± 0.7 mm/y (2% ± 2%) at DMG, and 6 ± 3 mL/y (4% ± 3%) with volumetry. CONCLUSIONS: Three-dimensional CEMRA volumetry exhibited a larger effect when examining percentage growth, a better ICC, and a marginally lower COV. Volumetry may be more sensitive to growth and possibly less affected by error than diameter measurements.