High-Frequency Ultrasound for In Vivo Measurement of Colon Wall Thickness in Mice
Mostafa AbdelrahmanGemma MarstonMark A. HullAlexander F. MarkhamPamela F. JonesJ A EvansP. Louise Coletta
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Ex vivo
Distal colon
Histology
Ex-vivo cardiovascular magnetic resonance (CMR) imaging has played an important role in the validation of in-vivo CMR characterization of pathological processes. However, comparison between in-vivo and ex-vivo imaging remains challenging due to shape changes occurring between the two states, which may be non-uniform across the diseased heart. A novel two-step process to facilitate registration between ex-vivo and in-vivo CMR was developed and evaluated in a porcine model of chronic myocardial infarction (MI).
Angiology
Ex vivo
3d printed
Cardiac magnetic resonance
Image registration
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A study was conducted comparing the pacing and sensing performance of an endocardial pacing lead (5076, Medtronic, Inc., Minneapolis, MN) in vivo to an ex vivo isolated heart model designed to work all four chambers under simulated in vivo physiologic conditions. The lead was implanted in vivo using fluoroscopic guidance. Standard stimulation and sensing parameters were recorded. Using standard cardiac surgical techniques, 8 porcine hearts were excised and reperfused in a working heart model retaining their original lead placement. Following stabilization, the electrical measurements were repeated. Ex vivo electrical values were significantly decreased relative to the in vivo measurements: R-wave amplitude by 39%, P-wave amplitude by 39%, slew rate by 62%, and pacing impedance by 34%. Pacing threshold values were similar in vivo and ex vivo. Variations in performance were in part attributed to local tissue deformation in the isolated heart preparation leading to differences in lead slack and orientation. This comparative study substantiated the value of utilizing the isolated heart model to visualize and simultaneously evaluate lead pacing and sensing performance in comparison with in vivo experimental procedures.
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Lead (geology)
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Background The pathomechanisms of atherosclerosis and vascular remodelling are under intense research. Only a few in vivo tools to study these processes longitudinally in animal experiments are available. Here, we evaluated the potential of micro-CT technology. Methods Lumen areas of the common carotid arteries (CCA) in the ApoE-/- partial carotid artery ligation mouse model were compared between in vivo and ex vivo micro-CT technique and serial histology in a total of 28 animals. AuroVist-15 nm nanoparticles were used as in vivo blood pool contrast agent in a Skyscan 1176 micro-CT at resolution of 18 μmeter voxel size and a mean x-ray dose of 0.5 Gy. For ex vivo imaging, animals were perfused with MicroFil and imaged at 9 μmeter voxel size. Lumen area was evaluated at postoperative days 7, 14, and 28 first by micro-CT followed by histology. Results In vivo micro-CT and histology revealed lumen loss starting at day 14. The lumen profile highly correlated (r = 0.79, P<0.0001) between this two methods but absolute lumen values obtained by histology were lower than those obtained by micro-CT. Comparison of in vivo and ex vivo micro-CT imaging revealed excellent correlation (r = 0.83, P<0.01). Post mortem micro-CT yielded a higher resolution than in vivo micro-CT but there was no statistical difference of lumen measurements in the partial carotid artery ligation model. Conclusion These data demonstrate that in vivo micro-CT is a feasible and accurate technique with low animal stress to image remodeling processes in the murine carotid artery.
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Lumen (anatomy)
Histology
X-ray microtomography
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In the present work the effects of a new low frequency, high intensity ultrasound technology on human adipose tissue ex vivo were studied. In particular, we investigated the effects of both external and surgical ultrasound-irradiation (10 min) by evaluating, other than sample weight loss and fat release, also histological architecture alteration as well apoptosis induction. The influence of saline buffer tissue-infiltration on the effects of ultrasound irradiation was also examined. The results suggest that, in our experimental conditions, both transcutaneous and surgical ultrasound exposure caused a significant weight loss and fat release. This effect was more relevant when the ultrasound intensity was set at 100 % (~2.5 W/cm², for external device; ~19-21 W/cm2, for surgical device) compared to 70 % (~1.8 W/cm² for external device; ~13-14 W/cm2 for surgical device). Of note, the effectiveness of ultrasound was much higher when the tissue samples were previously infiltrated with saline buffer, in accordance with the knowledge that ultrasonic waves in aqueous solution better propagate with a consequently more efficient cavitation process. Moreover, the overall effects of ultrasound irradiation did not appear immediately after treatment but persisted over time, being significantly more relevant at 18 h from the end of ultrasound irradiation. Evaluation of histological characteristics of ultrasound-irradiated samples showed a clear alteration of adipose tissue architecture as well a prominent destruction of collagen fibers which were dependent on ultrasound intensity and most relevant in saline buffer-infiltrated samples. The structural changes of collagen bundles present between the lobules of fat cells were confirmed through scanning electron microscopy (SEM) which clearly demonstrated how ultrasound exposure induced a drastic reduction in the compactness of the adipose connective tissue and an irregular arrangement of the fibers with a consequent alteration in the spatial architecture. The analysis of the composition of lipids in the fat released from adipose tissue after ultrasound treatment with surgical device showed, in agreement with the level of adipocyte damage, a significant increase mainly of triglycerides and cholesterol. Finally, ultrasound exposure had been shown to induce apoptosis as shown by the appearance DNA fragmentation. Accordingly, ultrasound treatment led to down-modulation of procaspase-9 expression and an increased level of caspase-3 active form.
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High-intensity focused ultrasound
Intensity
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The electrical properties of biological tissues differ depending on their structural characteristics. In literature, a lot of study have been carried out with the intent of taking advantage of bioimpedance analysis. Unfortunately, many apparatuses used during these evaluations were not always designed for measurements on living tissues. As a consequence, data could be affected by electrode polarization. In 2016, we presented a new impedance meter, developed for measurements on living tissues. Initially, it was tested only on ex-vivo rabbit's tissues with promising results. As a continuation, this device has been tested on in-vivo samples by placing a needle-probe into 3 tissues (liver, spleen, ovary) of 2 female dogs. Furthermore, was evaluated also the bioimpedance signal of the ovary explanted, comparing it with the in-vivo data. Bioimpedance was analyzed in terms of modulus and phase along a broad spectrum of frequencies (10Hz - 10kHz). Data obtained confirm the possibility of discriminating among the 3 tested tissues, at high frequencies for modulus and at low for phase. Confirmation that values on in-vivo and exvivo tissues are comparable if detected within few minutes after the explant, is also reported. We conclude that this clinical evaluation confirmed, also in-vivo, the good performance of the device previously tested on ex-vivo tissues, and provide more information about the tissue properties and characteristics.
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Abstract A major problem with implantable sensors is their short in vivo lifetime, due to strong tissue reactions (i.e., inflammation and fibrosis) caused by the implant and the failure of sensor components. The tissue reactions to the sensor, the biocompatibility of components, and the function of the sensor must be evaluated by using in vivo models. Current methods of in vivo biosensor testing are time‐ and labor‐ intensive and expensive. In addition, the results often vary on the basis of the surgical skills of the investigator. The in ova chorioallantoic membrane (CAM) of the developing chicken embryo was previously developed in our laboratory as a novel in vivo system to test biomaterials. In this new article, we describe a novel approach for testing biosensors in vivo using the ex ova CAM model as an alternative to the traditional mammalian models. Fertilized chicken eggs were incubated for 3 days in ova and then transferred into a petri dish ( ex ova ) for further incubation at 37°C and 80% humidity. After 1 week of incubation, acetaminophen biosensors, used as model sensors, were placed on top of the CAM and allowed to incorporate for 1 week. Biosensors were then tested for their sensitivity to acetaminophen. CAM venules were injected with 0.2 mL of a 3.6 m M acetaminophen solution. The current produced by the sensor reflected the change in blood acetaminophen levels. Sensors were also assessed by using gross and histological evaluations. We previously reported on the similarity of the tissue response of the CAM with the mammalian models. The low cost, simplicity, and possibility to continuously visualize the sensor test site through a cell culture dish make this animal model particularly attractive for the rapid in vivo screening of biosensors. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 215–223, 2003
Chorioallantoic membrane
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The reproducibility of the pulsed ultrasound technique for the determination of skin thickness was investigated, using two independent observers. No systematic difference was found and a high correlation was obtained. Studies were also undertaken to validate the pulsed ultrasound technique as a measure of true skin thickness. Skin thickness determined in vitro was found to be greater than when in vivo determinations were made by either the pulsed ultrasound or a xeroradiographic technique, probably due to the release of in vivo tension within the dermis after excision. Skin thickness was found to increase linearly with age up to the age of 20 years and to decrease linearly with age subsequently. Differences in skin thickness between the sexes and in different sites of the body were demonstrated.
Skin thickness
Skin Aging
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ABSTKACX The measurement technique developed for in vivo assessment of ultrasound velocity in mammalian tissue is described and discussed from the point of view of the limitations of the technique. Selected experimental results in vivo on farm livestock (beef and pigs) are presented and show that the average values of in vivo ultrasound velocity for muscle, fatty tissue and skin in cattle are: 1604 m/s, 1471 m/s and 1591 m/s, respectively. Corresponding values in pigs are: 1579 m/s, 1426 m/s and 1503 m/s. These in vivo values are compared with ultrasound velocities measured under carefully controlled conditions, 1 hour and 24 hours post mortem. Implications of the results are discussed with particular reference to clinical applications of ultrasound and tissue characterization. The measurement technique developed specifically for in vivo measurements of ultrasonic pressure amplitude and attenuation in human body was de
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Few reports quantitatively compare the performance of photoacoustic tomography (PAT) versus fluorescence molecular tomography (FMT) in vivo. We compared both modalities for the detection of signals from injected ICG liposomes in the tibial medullary space of 10 BALB/c mice in vivo and ex vivo. Signals significantly correlated between modalities (R² = 0.69) and within each modality in vivo versus ex vivo (PAT: R² = 0.70, FMT: R² = 0.76). Phantom studies showed that signals at 4 mm depth are detected down to 3.3 ng ICG by PAT and 33 ng by FMT, with a nominal spatial resolution below 0.5 mm in PAT and limited to 1 mm in FMT. Our study demonstrates comparable in vivo sensitivity, but superior ex vivo sensitivity and in vivo resolution for our ICG liposomes of the VevoLAZR versus the FMT2500. PAT provides a useful new tool for the high-resolution imaging of bone marrow signals, for example for monitoring drug delivery.
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Ex vivo
Magnetic Resonance Elastography
Brain tissue
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