We sincerely thank F. Bierry for assistance in video production and editing.

All procedures involving animal subjects have been approved by the University Hospital Institutional Animal Care committee.
1. Intraarticular Bacterial Inoculation
<ol>
	<li>Before injection, anesthetize rabbits by means of intramuscular injection of ketamine (30 mg/kg of body weight) mixed with xylazine (4 mg/kg) within Erector Spinae muscle. Ensure animals are fully anesthetized by checking that they fail to respond to paw pinch. This protocol provides sufficient anesthesia for the intraarticular injection of the knee joint. Place the animals under oxygen mask during anesthesia.</li>
	<li>Shave animals&#39; knee. Prepare the knee for aseptic injection by 3 alternating wipes of povidone-iodine scrub and alcohol followed by application of povidone-iodine solution.</li>
	<li>Manually identify the patellar tendon as an elastic structure at the anterior aspect of the knee using a sterile needle cap as shown or a sterile probe.</li>
	<li>With visual control and by using an anterior approach, place a 25 G&#160;needle percutaneously in the right knee of each of the 12 rabbits through the patellar tendon.</li>
	<li>Inject each knee with 1 ml of a bacterial suspension of Staphylococcus aureus (Neumann strain) at a concentration of 106&#160;UFC/ml. An injection without resistance confirms the intraarticular location of the tip of the needle.</li>
	<li>After injection procedures, keep the animal under convective source to avoid heat loss and monitor respiratory rate by observing movement of the chest. Once awake, keep animals in cages with free access to food and water.</li>
	<li>Manage pain by administering an intramuscular injection of 0.1&#160;mg/kg buprenorphine every 8 hr.</li>
	<li>Clinically observe rabbits each day, monitoring consumed quantities of food and water, weight loss, temperature, and general behavior.</li>
	<li>To image the acute phase of infection perform the first MR imaging session as soon as an animal presents substantial weight loss (10%); generally this occurs after about 2 days.</li>
	<li>If intravenous drug administration is required before MRI examination, an auricular venous access could be installed (cf. below).</li>
</ol>
2. MRI Examination
When imaging live animals, a careful animal installation is a key feature to ensure animal comfort and optimal anesthesia. This will allow for best imaging results and ensure a reproductive image acquisition for longitudinal studies. Due to the size of the animal, the use of a clinical-sized MR unit (1.5 T or 3 T) is most suitable. 8-channel clinical knee coil is used as it provides suitable resolution and contrast-to-noise ratio for rabbit knee exploration.
<ol>
	<li>Before installation on the imaging system, install a peripheral venous access through an auricular vein. This access will serve to inject the contrast agent.
	<ol>
		<li>Shave and disinfect the ear.</li>
		<li>Perform local anesthesia by subcutaneous injection of lidocaine.</li>
		<li>Insert a 25 G catheter inside the lateral auricular vein.</li>
		<li>Assess the permeability by injection of 1 ml sterile physiological serum.</li>
		<li>Maintain the catheter with adhesive tapping.</li>
	</ol>
	</li>
	<li>Anesthetize animals by means of intramuscular injection of ketamine (30 mg/kg of body weight) mixed with xylazine (4 mg/kg). Animals are fully anesthetized once they fail to respond to paw pinch. Place a facial mask on the rabbit, giving it oxygen with a flow rate of 200 ml/min.</li>
	<li>Once fully anesthetized, take animals to the MR imaging unit. Place animals so that the knees are located in the center of the MR coil. Place the animals&#39; legs in complete extension, so that the long axis of the tibia is parallel to the MR imaging unit table. Use Velcro fasteners or sand bags to maintain optimal leg position.</li>
	<li>Cardio-respiratory monitoring of the animals is not required as the anesthesia protocol allows deep anesthesia on spontaneous breathing, but animals have to be covered to avoid anesthesia-induced heat loss.</li>
	<li>MR protocol is detailed in Table 1. The average time for total acquisition including optimal installation is about 20 min.</li>
	<li>Perform MR imaging in different planes. Nevertheless, the transverse plane of the knees (orthogonal to the tibia) is the reference plan as it ensures anatomic reproducibility of image position for sequential longitudinal examinations and allows optimal correlation with histologic slices.</li>
	<li>At the completion of unenhanced sequences, inject the UPSIO contrast agent through the auricular venous access. Slowly administer the iron oxide particles in a single dose of 150 &#956;mol Fe/kg. Rinse the catheter by injection of 1 ml of sterile physiological serum.</li>
	<li>Repeat the enhanced GRE weighted sequence 24 hr after the injection. This delay allows the particles to be phagocytized by the macrophages.</li>
	<li>For longitudinal studies evaluating drugs effect (antibiotics, steroids, anti-macrophage antibodies, etc.), repeat sequential MR examinations using the above-described protocol.</li>
</ol>
3. Image Analysis
<ol>
	<li>For longitudinal evaluation perform measurements at the same anatomic level, and define an easily identifiable landmark. For instance, acquisition through the axial plane where the greatest diameter of the patella is observed is a reliable way to obtain reproducible measurement (Figure 1).</li>
	<li>Perform image analysis using a DICOM-based software (such as Osirix) or an image processing software (ImageJ).</li>
	<li>Using ImageJ software, perform the segmentation of the synovial area that demonstrates signal loss on USPIO-enhanced GRE T2-weighted image using the &#34;irregular area&#34; drawing tool. Once the synovium with dark signal is outlined, click on &#34;Analyze&#34; to obtain the area/ number of pixels (Figure 2).</li>
</ol>

<ol>
	<li>Madri, J., Kissane, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+and+healing.">Inflammation and healing.</a> Anderson's Pathology. , 67-110 (1990).</li><li>Sephel, G., Woodward, S., Rubin, R., Strayer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repair,+regeneration,+and+fibrosis.">Repair, regeneration, and fibrosis.</a> Rubin's Pathology. , 71-98 (2008).</li><li>Verdrengh, M., Tarkowski, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+macrophages+in+Staphylococcus+aureus-induced+arthritis+and+sepsis.">Role of macrophages in Staphylococcus aureus-induced arthritis and sepsis.</a> Arthritis Rheum. 43 (10), 2276-2282 (2000).</li><li>Heale, J., Speert, D., Burke, B., Lewis, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophages+in+bacterial+infection.">Macrophages in bacterial infection.</a> The Macrophage. , 210-252 (2008).</li><li>Bierry, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+activity+in+infected+areas+of+an+experimental+vertebral+osteomyelitis+model:+USPIO-enhanced+MR+imaging--feasibility+study.">Macrophage activity in infected areas of an experimental vertebral osteomyelitis model: USPIO-enhanced MR imaging--feasibility study.</a> Radiology. 248 (1), 114-123 (2008).</li><li>Bierry, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MRI+of+macrophages+in+infectious+knee+synovitis.">MRI of macrophages in infectious knee synovitis.</a> AJR Am. J. Roentgenol. 194 (6), W521-W526 (2010).</li><li>Lutz, A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+synovial+macrophages+in+an+experimental+rabbit+model+of+antigen-induced+arthritis:+ultrasmall+superparamagnetic+iron+oxide-enhanced+MR+imaging.">Detection of synovial macrophages in an experimental rabbit model of antigen-induced arthritis: ultrasmall superparamagnetic iron oxide-enhanced MR imaging.</a> Radiology. 233 (1), 149-1457 (2004).</li><li>Weissleder, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasmall+superparamagnetic+iron+oxide:+an+intravenous+contrast+agent+for+assessing+lymph+nodes+with+MR+imaging.">Ultrasmall superparamagnetic iron oxide: an intravenous contrast agent for assessing lymph nodes with MR imaging.</a> Radiology. 175 (2), 494-498 (1990).</li><li>Lefevre, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Septic+arthritis:+monitoring+with+USPIO-enhanced+macrophage+MR+imaging.">Septic arthritis: monitoring with USPIO-enhanced macrophage MR imaging.</a> Radiology. 258 (3), 722-728 (2011).</li><li>Sigovan, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid-clearance+iron+nanoparticles+for+inflammation+imaging+of+atherosclerotic+plaque:+initial+experience+in+animal+model.">Rapid-clearance iron nanoparticles for inflammation imaging of atherosclerotic plaque: initial experience in animal model.</a> Radiology. 252 (2), 401-409 (2009).</li></ol>

The authors have nothing to disclose.

While nonspecific gadolinium-based contrast agents provide information about the volume and perfusion of the extracellular space, macrophage imaging by USPIO-enhanced MR allows a precise anatomical localization and a qualitative evaluation of macrophage infiltration within infected synovium without the need of tissue sampling9. Due to their high sensitivity, USPIO can demonstrate even subtle cellular infiltrate present in the early phases of infection. Under successful antibiotic therapy, as the pathogens are ...

Magnetic resonance imaging (MRI) is considered to be the imaging modality of choice for the demonstration of infectious synovitis due to its high spatial resolution and soft tissue contrast. Signal changes observed on MRI in arthritis low T1 and high T2 signal reflecting the increased presence of extracellular water content, and a marked enhancement after gadolinium based-contrast agent administration, consistent with the histologically findings of increased vascularity owing to vasodilation and angiogenesis1. Nevertheless, MRI is often unable to demonstrate resolution of infection during antibiotic therapy as persistent enhancement can be observed in the joints of patients with clinically and biologically healed septic arthritis due to persistence of enlarged extracellular space (granulation tissue, fibrotic scar)2. Besides extracellular changes, inflammatory cells including an intense recruitment of macrophages massively infiltrate the infected synovia. Macrophages play a major role in both the acute and chronic phase of bacterial infection 3. They induce the inflammatory reaction required to eradicate pathogenic microorganisms, and coordinate inflammation resolution, as macrophage-induced inflammation persists as long as necrotic tissues are not removed, preventing repair to begin4. Thus, the reduction of macrophage infiltration within infected synovia after efficient therapy can be a reliable indicator of the resolution of the infection. Cellular imaging is able to demonstrate specific cellular infiltration inside pathologic tissue. Specific macrophage MR imaging using targeted contrast agent has been widely investigated and has demonstrated its ability to demonstrate joint inflammation or infection5-7. After intravenous injection, such targeted contrast agents such as USPIO (ultrasmall superparamagnetic iron oxides) particles are taken up by phagocytic cells such as macrophages and, due to their magnetic properties, induce signal changes in tissues presenting macrophage infiltration8. The longitudinal follow up of those MR signal changes therapy allows for an in vivo noninvasive evaluation of macrophage infiltration, and a reduction of USPIO loaded-macrophages related signal changes would demonstrate therapy success. The purpose of this report is to present how to perform macrophage MR imaging to noninvasively monitor septic arthritis by demonstrating the reduction of macrophage infiltration within the synovia.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>P904</td>
			<td>Guerbet</td>
			<td></td>
			<td>Dose: 150 &#956;mol Fe/kg</td>
		</tr>
		<tr>
			<td>Ketamine (500 mg/ml ketamine)</td>
			<td>Virbac</td>
			<td></td>
			<td>Dose: 30 mg/kg</td>
		</tr>
		<tr>
			<td>Rompun (20 mg/ml Xylazine)</td>
			<td>Axience</td>
			<td></td>
			<td>Dose: 4 mg/kg</td>
		</tr>
		<tr>
			<td>Buprenorphine</td>
			<td>Vetoquinol</td>
			<td></td>
			<td>Dose: 0.1 mg/kg/8 hr</td>
		</tr>
		<tr>
			<td>BD 22 G, 1 inch</td>
			<td>BD Biosciences</td>
			<td>381423</td>
			<td></td>
		</tr>
		<tr>
			<td>BD 25 G, 5/8 inch</td>
			<td>BD Biosciences</td>
			<td>305122</td>
			<td></td>
		</tr>
	</tbody>
</table>

in vivo macrophage imaging using mr targeted contrast agent for longitudinal evaluation of septic arthritis

Macrophages are key-cells in the initiation, the development and the regulation of the inflammatory response to bacterial infection. Macrophages are intensively and increasingly recruited in septic joints from the early phases of infection and the infiltration is supposed to regress once efficient removal of the pathogens is obtained. The ability to identify in vivo macrophage activity in an infected joint can therefore provide two main applications: early detection of acute synovitis and monitoring of therapy.
In vivo noninvasive detection of macrophages can be performed with magnetic resonance imaging using iron nanoparticles such as ultrasmall superparamagnetic iron oxide (USPIO). After intravascular or intraarticular administration, USPIO are specifically phagocytized by activated macrophages, and, due to their magnetic properties, induce signal changes in tissues presenting macrophage infiltration. A quantitative evaluation of the infiltrate is feasible, as the area with signal loss (number of dark pixels) observed on gradient echo MR images after particles injection is correlated with the amount of iron within the tissue and therefore reflects the number of USPIO-loaded cells.
We present here a protocol to perform macrophage imaging using USPIO-enhanced MR imaging in an animal model of septic arthritis, allowing an initial and longitudinal in vivo noninvasive evaluation of macrophages infiltration and an assessment of therapy action.

On unenhanced images, the synovium of infected knees presents a diffuse swelling of intermediate signal that is non distinguishable from surrounding soft tissue, while femur and patella appear as low signal structures (Figure 1).
On the USPIO-enhanced images, 24 hr after the contrast agent administration, synovial area containing USPIO-loaded macrophages will demonstrate signal loss (Figures 1 and 2).
Macrophage inf...

Watch this Scientific Journal Video about In vivo Macrophage Imaging Using MR Targeted Contrast Agent for Longitudinal Evaluation of Septic Arthritis at JoVE.com

In vivo Macrophage Imaging Using MR Targeted Contrast Agent for Longitudinal Evaluation of Septic Arthritis

We demonstrate how to perform macrophage MR imaging using ultrasmall superparamagnetic contrast agent (USPIO) in septic arthritis, allowing an initial and longitudinal in vivo non-invasive evaluation of macrophages infiltration and an assessment of therapy efficacy.

In vivo Macrophage Imaging Using MR Targeted Contrast Agent for Longitudinal Evaluation of Septic Arthritis

Macrophages are key-cells in the initiation, the development and the regulation of the inflammatory response to bacterial infection. Macrophages are ...

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9.2K Views.  University Hospital of Strasbourg. We demonstrate how to perform macrophage MR imaging using ultrasmall superparamagnetic contrast agent (USPIO) in septic arthritis, allowing an initial and longitudinal in vivo non-invasive evaluation of macrophages infiltration and an assessment of therapy efficacy.

Video: In vivo Macrophage Imaging Using MR Targeted Contrast Agent for Longitudinal Evaluation of Septic Arthritis

Contrast Enhanced Vessel Imaging using MicroCT

Microscopic computed tomography (microCT) offers high-resolution volumetric imaging of the anatomy of living small animals. However, the contrast between different soft tissues and body fluids is inherently poor in micro-CT images 1. Under these circumstances, visualization of blood vessels becomes a nearly impossible task. To overcome this and to improve the visualization of blood vessels exogenous contrast agents can be used. Herein, we present a methodology for visualizing the vascular network in a rodent model. By using a long-acting aqueous colloidal polydisperse iodinated blood-pool contrast agent, eXIA 160XL, we optimized image acquisition parameters and volume-rendering techniques for finding blood vessels in live animals. Our findings suggest that, to achieve a superior contrast between bone and soft tissue from vessel, multiple-frames (at least 5-8/ frames per view), and 360-720 views (for a full 360&deg; rotation) acquisitions were mandatory. We have also demonstrated the use of a two-dimensional transfer function (where voxel color and opacity was assigned in proportion to CT value and gradient magnitude), in visualizing the anatomy and highlighting the structure of interest, the blood vessel network. This promising work lays a foundation for the qualitative and quantitative assessment of anti-angiogenesis preclinical studies using transgenic or xenograft tumor-bearing mice.

Contrast enhanced small animal vessel imaging by microCT is a rapid, cost-effective and high-throughput technique for serial in situ examination for tumor development, for analyzing the network of blood vessels that nourish them, and for following the response of tumors to preclinical therapeutic intervention(s).

Microscopic computed tomography (microCT) offers high-resolution volumetric imaging of the anatomy of living small animals. However, the contrast between ...

Longitudinal Evaluation of Mouse Hind Limb Bone Loss After Spinal Cord Injury using Novel, in vivo, Methodology

Spinal cord injury (SCI) is often accompanied by osteoporosis in the sublesional regions of the pelvis and lower extremities, leading to a higher frequency of fractures 1. As these fractures often occur in regions that have lost normal sensory function, the patient is at a greater risk of fracture-dependent pathologies, including death. SCI-dependent loss in both bone mineral density (BMD, grams/cm2) and bone mineral content (BMC, grams) has been attributed to mechanical disuse 2, aberrant neuronal signaling 3 and hormonal changes 4. The use of rodent models of SCI-induced osteoporosis can provide invaluable information regarding the mechanisms underlying the development of osteoporosis following SCI as well as a test environment for the generation of new therapies 5-7 (and reviewed in 8). Mouse models of SCI are of great interest as they permit a reductionist approach to mechanism-based assessment through the use of null and transgenic mice. While such models have provided important data, there is still a need for minimally-invasive, reliable, reproducible, and quantifiable methods in determining the extent of bone loss following SCI, particularly over time and within the same cohort of experimental animals, to improve diagnosis, treatment methods, and/or prevention of SCI-induced osteoporosis.
An ideal method for measuring bone density in rodents would allow multiple, sequential (over time) exposures to low-levels of X-ray radiation. This study describes the use of a new whole-animal scanner, the IVIS Lumina XR (Caliper Instruments) that can be used to provide low-energy (1-3 milligray (mGy)) high-resolution, high-magnification X-ray images of mouse hind limb bones over time following SCI. Significant bone density loss was seen in the tibiae of mice by 10 days post-spinal transection when compared to uninjured, age-matched control (na&iuml;ve) mice (13% decrease, p&lt;0.0005). Loss of bone density in the distal femur was also detectable by day 10 post-SCI, while a loss of density in the proximal femur was not detectable until 40 days post injury (7% decrease, p&lt;0.05). SCI-dependent loss of mouse femur density was confirmed post-mortem through the use of Dual-energy X-ray Absorptiometry (DXA), the current "gold standard" for bone density measurements. We detect a 12% loss of BMC in the femurs of mice at 40 days post-SCI using the IVIS Lumina XR. This compares favorably with a previously reported BMC loss of 13.5% by Picard and colleagues who used DXA analysis on mouse femurs post-mortem 30 days post-SCI 9. Our results suggest that the IVIS Lumina XR provides a novel, high-resolution/high-magnification method for performing long-term, longitudinal measurements of hind limb bone density in the mouse following SCI.

Longitudinal Evaluation of Mouse Hind Limb Bone Loss After Spinal Cord Injury using Novel, in vivo, Methodology

A longitudinal examination of bone loss in the femurs and tibiae of adult mice was performed following spinal cord injury using sequential low-dose X-ray scans. Tibia bone loss was detected throughout the study, while bone loss in the femur was not detected until 40 days post injury.

Spinal cord injury (SCI) is often accompanied by osteoporosis in the sublesional regions of the pelvis and lower extremities, leading to a higher ...

Transplantation into the Anterior Chamber of the Eye for Longitudinal, Non-invasive In vivo Imaging with Single-cell Resolution in Real-time

Intravital imaging has emerged as an indispensable tool in biological research. In the process, many imaging techniques have been developed to study different biological processes in animals non-invasively. However, a major technical limitation in existing intravital imaging modalities is the inability to combine non-invasive, longitudinal imaging with single-cell resolution capabilities. We show here how transplantation into the anterior chamber of the eye circumvents such significant limitation offering a versatile experimental platform that enables non-invasive, longitudinal imaging with cellular resolution in vivo. We demonstrate the transplantation procedure in the mouse and provide representative results using a model with clinical relevance, namely pancreatic islet transplantation. In addition to enabling direct visualization in a variety of tissues transplanted into the anterior chamber of the eye, this approach provides a platform to screen drugs by performing long-term follow up and monitoring in target tissues. Because of its versatility, tissue/cell transplantation into the anterior chamber of the eye not only benefits transplantation therapies, it extends to other in vivo applications to study physiological and pathophysiological processes such as signal transduction and cancer or autoimmune disease development.

Transplantation into the Anterior Chamber of the Eye for Longitudinal, Non-invasive In vivo Imaging with Single-cell Resolution in Real-time

A new approach combining intraocular transplantation and confocal microscopy enables longitudinal, non-invasive real-time imaging with single-cell resolution within grafted tissues in vivo. We demonstrate how to transplant pancreatic islets into the anterior chamber of the mouse eye.

Intravital imaging has emerged as an indispensable tool in biological research.  In the process, many imaging techniques have been developed to study ...

MR Molecular Imaging of Prostate Cancer with a Small Molecular CLT1 Peptide Targeted Contrast Agent

Tumor extracellular matrix has abundance of cancer related proteins that can be used as biomarkers for cancer molecular imaging. In this work, we demonstrated effective MR cancer molecular imaging with a small molecular peptide targeted Gd-DOTA monoamide complex as a targeted MRI contrast agent specific to clotted plasma proteins in tumor stroma. We performed the experiment of evaluating the effectiveness of the agent for non-invasive detection of prostate tumor with MRI in a mouse orthotopic PC-3 prostate cancer model. The targeted contrast agent was effective to produce significant tumor contrast enhancement at a low dose of 0.03 mmol Gd/kg. The peptide targeted MRI contrast agent is promising for MR molecular imaging of prostate tumor.

To demonstrate MR cancer molecular imaging with a small peptide targeted MRI contrast agent specific to clotted plasma proteins in tumor stroma in a mouse prostate cancer model.

Tumor extracellular  matrix has abundance of cancer related proteins that can be used as biomarkers  for cancer molecular imaging. In this work,  we ...

In Vivo Optical Imaging of Brain Tumors and Arthritis Using Fluorescent SapC-DOPS Nanovesicles

We describe a multi-angle rotational optical imaging (MAROI) system for in vivo monitoring of physiopathological processes labeled with a fluorescent marker. Mouse models (brain tumor and arthritis) were used to evaluate the usefulness of this method. Saposin C (SapC)-dioleoylphosphatidylserine (DOPS) nanovesicles tagged with CellVue Maroon (CVM) fluorophore were administered intravenously. Animals were then placed in the rotational holder (MARS) of the in vivo imaging system. Images were acquired in 10&#176; steps over 380&#176;. A rectangular&#160;region of interest (ROI) was placed across the full image width at the model disease site. Within the ROI, and for every image, mean fluorescence intensity was computed after background subtraction. In the mouse models studied, the labeled nanovesicles were taken up in both the orthotopic and transgenic brain tumors, and in the arthritic sites (toes and ankles). Curve analysis of the multi angle image ROIs determined the angle with the highest signal. Thus, the optimal angle for imaging each disease site was characterized. The MAROI method applied to imaging of fluorescent compounds is a noninvasive, economical, and precise tool for in vivo quantitative analysis of the disease states in the described mouse models.

In Vivo Optical Imaging of Brain Tumors and Arthritis Using Fluorescent SapC-DOPS Nanovesicles

We describe a multi-angle rotational optical imaging (MAROI) system for in vivo quantitation of a fluorescent marker delivered by saposin C (SapC)-dioleoylphosphatidylserine (DOPS) nanovesicles. Employing mouse models of cancer and arthritis, we demonstrate how the MAROI signal curve analysis can be used for the precise mapping and biological characterization of disease processes.

We describe a multi-angle rotational optical imaging (MAROI) system for in vivo monitoring of physiopathological processes labeled with a fluorescent ...

Longitudinal In Vivo Imaging of the Cerebrovasculature: Relevance to CNS Diseases

Remodeling of the brain vasculature is a common trait of brain pathologies. In vivo imaging techniques are fundamental to detect cerebrovascular plasticity or damage occurring overtime and in relation to neuronal activity or blood flow. In vivo two-photon microscopy allows the study of the structural and functional plasticity of large cellular units in the living brain. In particular, the thinned-skull window preparation allows the visualization of cortical regions of interest (ROI) without inducing significant brain inflammation. Repetitive imaging sessions of cortical ROI are feasible, providing the characterization of disease hallmarks over time during the progression of numerous CNS diseases. This technique accessing the pial structures within 250 &#956;m of the brain relies on the detection of fluorescent probes encoded by genetic cellular markers and/or vital dyes. The latter (e.g., fluorescent dextrans) are used to map the luminal compartment of cerebrovascular structures. Germane to the protocol described herein is the use of an in vivo marker of amyloid deposits, Methoxy-O4, to assess Alzheimer&#39;s disease (AD) progression. We also describe the post-acquisition image processing used to track vascular changes and amyloid depositions. While focusing presently on a model of AD, the described protocol is relevant to other CNS disorders where pathological cerebrovascular changes occur.

Longitudinal In Vivo Imaging of the Cerebrovasculature: Relevance to CNS Diseases

This manuscript describes a procedure to track the remodeling of the cerebrovasculature during amyloid plaque accumulation in vivo using longitudinal two-photon microscopy. A thinned-skull preparation enables the visualization of fluorescent dyes to assess the progression of cerebrovascular damage in a mouse model of Alzheimer&#39;s disease.

Remodeling of the brain vasculature is a common trait of brain pathologies. In vivo imaging techniques are fundamental to detect cerebrovascular ...

Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery

Phase contrast magnetic resonance imaging (PC-MRI) is a noninvasive approach that can quantify flow-related parameters such as blood flow. Previous studies have shown that abnormal blood flow may be associated with systemic vascular risk. Thus, PC-MRI can facilitate the translation of data obtained from animal models of cardiovascular diseases to pertinent clinical investigations. In this report, we describe the procedure for measuring blood flow in the common carotid artery (CCA) of rats using cine-gated PC-MRI and discuss relevant analysis methods. This procedure can be performed in a live, anesthetized animal and does not require euthanasia after the procedure. The proposed scanning parameters yield repeatable measurements for blood flow, indicating excellent reproducibility of the results. The PC-MRI procedure described in this article can be used for pharmacological testing, pathophysiological assessment, and cerebral hemodynamics evaluation.

The overall goal of this procedure is to measure the blood flow in the rat common carotid artery by using noninvasive phase contrast magnetic resonance imaging.

Phase contrast magnetic resonance imaging (PC-MRI) is a noninvasive approach that can quantify flow-related parameters such as blood flow. Previous ...

Quantitative [18F]-Naf-PET-MRI Analysis for the Evaluation of Dynamic Bone Turnover in a Patient with Facetogenic Low Back Pain

Imaging techniques that reflect dynamic bone turnover may aid in characterizing a wide range of bone pathologies. Bone is a dynamic tissue undergoing continuous remodeling with the competing activity of osteoblasts, which produce the new bone matrix, and osteoclasts, whose function is to eliminate mineralized bone. [18F]-NaF is a positron emission tomography (PET) radiotracer that enables visualization of bone metabolism. [18F]-NaF is chemically absorbed into hydroxyapatite in the bone matrix by osteoblasts and can thus noninvasively detect osteoblastic activity, which is occult to conventional imaging techniques. Kinetic modeling of dynamic [18F]-NaF-PET data provides detailed quantitative measures of bone metabolism. Conventional semi-quantitative PET data, which utilizes standardized uptake values (SUVs) as a measure of radiotracer activity, is referred to as a static technique due to its snapshot of tracer uptake in time.&#160; Kinetic modeling, however, utilizes dynamic image data where tracer levels are continuously acquired providing tracer uptake temporal resolution. From the kinetic modeling of dynamic data, quantitative values like blood flow and metabolic rate (i.e., potentially informative metrics of tracer dynamics) can be extracted, all with respect to the measured activity in the image data. When combined with dual modality PET-MRI, region-specific kinetic data can be correlated with anatomically registered high-resolution structural and pathologic information afforded by MRI. The goal of this methodological manuscript is to outline detailed techniques for performing and analyzing dynamic [18F]-NaF-PET-MRI data. The lumbar facet joint is a common site of degenerative arthritis disease and a common cause for axial low back pain.&#160; Recent studies suggest [18F]-NaF-PET may serve as a useful biomarker of painful facetogenic disease.&#160; The human lumbar facet joint will, therefore, be used as a prototypical region of interest for dynamic [18F]-NaF-PET-MRI analysis in this manuscript.

Quantitative [18F]-Naf-PET-MRI Analysis for the Evaluation of Dynamic Bone Turnover in a Patient with Facetogenic Low Back Pain

Imaging techniques that reflect dynamic bone turnover may aid in characterizing a wide range of bone pathologies. We present detailed methodologies for performing and analyzing dynamic [18F]-NaF-PET-MRI data in a patient with facetogenic low back pain using the lumbar facet joints as a prototypical region of interest.

Imaging techniques that reflect dynamic bone turnover may aid in characterizing a wide range of bone pathologies. Bone is a dynamic tissue undergoing ...

Quantitative Mapping of Specific Ventilation in the Human Lung using Proton Magnetic Resonance Imaging and Oxygen as a Contrast Agent

Specific ventilation imaging (SVI) is a functional magnetic resonance imaging technique capable of quantifying specific ventilation &#8213; the ratio of the fresh gas entering a lung region divided by the region&#8217;s end-expiratory volume &#8213; in the human lung, using only inhaled oxygen as a contrast agent. Regional quantification of specific ventilation has the potential to help identify areas of pathologic lung function. Oxygen in solution in tissue shortens the tissue&#8217;s longitudinal relaxation time (T1), and thus a change in tissue oxygenation can be detected as a change in T1-weighted signal with an inversion recovery acquired image. Following an abrupt change between two concentrations of inspired oxygen, the rate at which lung tissue within a voxel equilibrates to a new steady-state reflects the rate at which resident gas is being replaced by inhaled gas. This rate is determined by specific ventilation. To elicit this sudden change in oxygenation, subjects alternately breathe 20-breath blocks of air (21% oxygen) and 100% oxygen while in the MRI scanner. A stepwise change in inspired oxygen fraction is achieved through use of a custom three-dimensional (3D)-printed flow bypass system with a manual switch during a short end-expiratory breath hold. To detect the corresponding change in T1, a global inversion pulse followed by a single shot fast spin echo sequence was used to acquire two-dimensional T1-weighted images in a 1.5&#160;T MRI scanner, using an eight-element torso coil. Both single slice and multi-slice imaging are possible, with slightly different imaging parameters. Quantification of specific ventilation is achieved by correlating the time-course of signal intensity for each lung voxel with a library of simulated responses to the air/oxygen stimulus. SVI estimations of specific ventilation heterogeneity have been validated against multiple breath washout and proved to accurately determine the heterogeneity of the specific ventilation distribution.

Specific ventilation imaging is a functional magnetic resonance imaging technique that allows for quantification of regional specific ventilation in the human lung, using inhaled oxygen as a contrast agent. Here, we present a protocol to collect and analyze specific ventilation imaging data.

Specific ventilation imaging (SVI) is a functional magnetic resonance imaging technique capable of quantifying specific ventilation &#8213; the ratio of ...

Stabilized Longitudinal In Vivo Cellular-Level Visualization of the Pancreas in a Murine Model with a Pancreatic Intravital Imaging Window

Direct in vivo cellular-resolution imaging of the pancreas in a live small animal model has been technically challenging. A recent intravital imaging study, with an abdominal imaging window, enabled visualization of the cellular dynamics in abdominal organs in vivo. However, due to the soft sheet-like architecture of the mouse pancreas that can be easily influenced by physiologic movement (e.g., peristalsis and respiration), it was difficult to perform stabilized longitudinal in vivo imaging over several weeks at the cellular level to identify, track, and quantify islets or cancer cells in the mouse pancreas. Herein, we describe a method for implanting a novel supporting base, an integrated pancreatic intravital imaging window, that can spatially separate the pancreas from the bowel for longitudinal time-lapse intravital imaging of the pancreas microstructure. Longitudinal in vivo imaging with the imaging window enables stable visualization, allowing for the tracking of islets over a period of 3 weeks and high-resolution three-dimensional imaging of the microstructure, as evidenced here in an orthotopic pancreatic cancer model. With our method, further intravital imaging studies can elucidate the pathophysiology of various diseases involving the pancreas at the cellular level.

Stabilized Longitudinal In Vivo Cellular-Level Visualization of the Pancreas in a Murine Model with a Pancreatic Intravital Imaging Window

In vivo high-resolution imaging of the pancreas was facilitated with the pancreatic intravital imaging window.

Direct in vivo cellular-resolution imaging of the pancreas in a live small animal model has been technically challenging. A recent intravital imaging ...