SCIENCE EDUCATION > Engineering

Biomedical Engineering

This collection describes the central concepts in biomedical engineering with a focus on imaging techniques to visualize and detect medical conditions, methods to quantify biomechanical strain, and computational modeling to simulate blood flow.

  • Biomedical Engineering

    10:47
    Imaging Biological Samples with Optical and Confocal Microscopy

    Source: Peiman Shahbeigi and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut

    Optical microscopes have been around for centuries, and while they reached their theoretical limitation of resolution decades ago, new equipment and techniques, such as confocal and digital image processing, have created new niches within the field of optical imaging. The best optical microscopes will typically have a resolution down to 200 nm in ideal conditions. However, optical microscopes are limited by the diffraction of waves, a function of the wavelength, which is around 500 nm for visible light. While the resolution of optical microscopes does not reach that of electron microscopes, they are the most valuable tools in the imaging of biological macrostructures and are a staple in any biological lab. In conventional light microscopes, the signal produced from the imaged object is from the full thickness of the specimen, which does not allow most of it to be in focus to the observer. This causes the image to have "out of focus blur". The confocal microscope, on the other hand, illuminates the sample through a pin-hole, and is thereofre able to filter out the out-of-focus light from above and below the point of focus in the object. This demonstration provides an introduction to image acquisition using optical and confocal microscopy methods. Here, a sectio

  • Biomedical Engineering

    09:01
    SEM Imaging of Biological Samples

    Source: Peiman Shahbeigi and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut

    A scanning electron microscope (SEM) is an instrument that uses an electron beam to nondestructively image and characterize conductive materials in a vacuum. As an analogy, an electron beam is to the SEM as light is to the optical microscope. The difference is that the electron microscope yields images of much higher resolution and magnification. The best optical microscopes typically have a resolution down to 200 nm, whereas SEMs usually claim a resolution of 0.5 nm. This is due to the fact that optical microscopes are limited by the diffraction of waves, a function of the wavelength, which is around 500 nm for visible light. Conversely, the SEM uses an energized electron beam, which as a wavelength of 1 nm. This characteristic makes them very dependable tools for the study of nano and microstructures. Electron microscopes also enable the study of biological samples with feature sizes too small for optical microscopy. This demonstration provides an introduction to sample preparation and initial image acquisition of biological samples using a scanning electron microscope. In this case, a collagen-hydroxyapatite (HA) cellular scaffold will be studied. The vacuum environment of the SEM and the induced charging by the electron beam on non-conductive samples (such as organic matter)

  • Biomedical Engineering

    13:28
    Biodistribution of Nano-drug Carriers: Applications of SEM

    Source: Peiman Shahbeigi and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut

    Nanoparticles have been increasingly used research towards targeted drug delivery and controlled drug release. While most of these particles have been developed as polymeric or liposomal particles because of their biocompatibility, there is a trend in current research toward the use of metallic and magnetic nanoparticles. These metallic nanoparticles were originally used as a contrast agent in imaging, but recent advances have shown how important they could be in drug and gene delivery and in therapeutics. Gold, silver, and paramagnetic nanoparticles have the greatest share in research being done. They have been shown to have good biocompatibility and certain varieties of magnetic nanoparticles have already been developed and distributed as therapeutic targeted drugs.   These heavy elements are typically imaged for research using fluorescence to evaluate delivery and distribution, but their atomic weights are good qualifications for increased contrast in backscatter electron analysis using a scanning electron microscope (SEM). Energy dispersive X-ray spectroscopy, which uses characteristic X-rays emitted upon electron beam interaction with the sample to identify chemical composition, can also be used with the SEM. These methods have the benefits of increased res

  • Biomedical Engineering

    14:19
    High-frequency Ultrasound Imaging of the Abdominal Aorta

    Authors: Amelia R. Adelsperger, Evan H. Phillips, and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

    High-frequency ultrasound systems are used to acquire high resolution images. Here, the use of a state-of-the-art system will be demonstrated to image the morphology and hemodynamics of small pulsatile arteries and veins found in mice and rats. Ultrasound is a relatively inexpensive, portable, and versatile method for the noninvasive assessment of vessels in humans as well as large and small animals. These are several key advantages that ultraound offers compared to other techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and near-infrared fluorescence tomography (NIRF). CT requires ionizing radiation and MRI can be prohibitively expensive and even impractical in some scenarios. NIRF, on the other hand, is limited by the penetration depth of light required to excite the fluorescent contrast agents. Ultrasound has limitations in terms of imaging depth; however, this may be overcome by sacrificing resolution and using a lower frequency transducer. Abdominal gas and excess body weight can severely diminish image quality. In the first case, the propagation of sound waves is limited, while in the latter case, they are attenuated by overlying tissues, such as fat and connective tissue. As a result, no contrast or faint co

  • Biomedical Engineering

    10:23
    Quantitative Strain Mapping of an Abdominal Aortic Aneurysm

    Authors: Hannah L. Cebull1, Arvin H. Soepriatna1, John J. Boyle2 and Craig J. Goergen1 1Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 2Mechanical Engineering & Materials Science, Washington University in St. Louis, St Louis, Missouri

    The mechanical behavior of soft tissues, such as blood vessels, skin, tendons, and other organs, are strongly influenced by their composition of elastin and collagen, which provide elasticity and strength. The fiber orientation of these proteins depends on the type of soft tissue and can range from a single preferred direction to intricate meshed networks, which can become altered in diseased tissue. Therefore, soft tissues often behave anisotropically on the cellular and organ level, creating a need for three-dimensional characterization. Developing a method for reliably estimating strain fields within complex biological tissues or structures is important to mechanically characterize and understande disease. Strain represents how soft tissue relatively deforms over time, and it can be described mathematically through various estimations. Acquiring image data over time allows deformation and strain to be estimated. However, all medical imaging modalities contain some amount of noise, which increases the difficulty of accurately estimating in vivo strain. The technique

  • Biomedical Engineering

    08:38
    Photoacoustic Tomography to Image Blood and Lipids in the Infrarenal Aorta

    Source: Gurneet S. Sangha and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

    Photoacoustic tomography (PAT) is an emerging biomedical imaging modality that utilizes light generated acoustic waves to obtain compositional information from tissue. PAT can be used to image blood and lipid components, which is useful for a wide variety of applications, including cardiovascular and tumor imaging. Currently used imaging techniques have inherent limitations that restrict their use with researchers and physicians. For example, long acquisition times, high costs, use of harmful contrast, and minimal to high invasiveness are all factors that limit the use of various modalities in the laboratory and clinic. Currently, the only comparable imaging techniques to PAT are emerging optical techniques. But these also have disadvantages, such as limited depth of penetration and the need for exogenous contrast agents. PAT provides meaningful information in a rapid, noninvasive, label-free manner. When coupled with ultrasound, PAT can be used to obtain structural, hemodynamic, and compositional information from tissue, thereby complementing currently used imaging techniques. The advantages of PAT illustrate its capabilities to make an impact in both the preclinical and clinical environment.

  • Biomedical Engineering

    11:37
    Cardiac Magnetic Resonance Imaging

    Source: Frederick W. Damen and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

    In this video, high field, small-bore magnetic resonance imaging (MRI) with physiological monitoring is demonstrated to acquire gated cine loops of the murine cardiovascular system. This procedure provides a basis for assessing left-ventricular function, visualizing vascular networks, and quantifying motion of organs due to respiration. Comparable small animal cardiovascular imaging modalities include high-frequency ultrasound and micro-computed tomography (CT); however, each modality is associated with trade-offs that should be considered. While ultrasound does provide high spatial and temporal resolution, imaging artifacts are common. For example, dense tissue (i.e., the sternum and ribs) can limit imaging penetration depth, and hyperechoic signal at the interface between gas and liquid (i.e., pleura surrounding the lungs) can blur contrast in nearby tissue. Micro-CT in contrast does not suffer from as many in-plane artifacts, but does have lower temporal resolution and limited soft-tissue contrast. Furthermore, micro-CT uses X-ray radiation and often requires the use of contrast agents to visualize vasculature, both of which are known to cause side effects at high doses including radiation damage  and renal injury. Cardiovascular MRI provides a nice compromise between thes

  • Biomedical Engineering

    12:38
    Computational Fluid Dynamics Simulations of Blood Flow in a Cerebral Aneurysm

    The objective of this video is to describe recent advancements of computational fluid dynamic (CFD) simulations based on patient- or animal-specific vasculature. Here, subject-based vessel segmentations were created, and, using a combination of open-source and commercial tools, a high-resolution numerical solution was determined within a flow model. Numerous studies have demonstrated that the hemodynamic conditions within the vasculature affect the development and progression of atherosclerosis, aneurysms, and other peripheral artery diseases; concomitantly, direct measurements of intraluminal pressure, wall shear stress (WSS), and particle residence time (PRT) are difficult to acquire in vivo. CFD allow such variables to be assessed non-invasively. In addition, CFD is used to simulate surgical techniques, which provides physicians better foresight regarding post-operative flow conditions. Two methods in magnetic resonance imaging (MRI), magnetic resonance angiography (MRA) with either time of flight (TOF-MRA) or contrast-enhanced MRA (CE-MRA) and phase-contrast (PC-MRI), allow us to obtain vessel geometries and time-resolved 3D velocity fields, respectively. TOF-MRA is based on the suppression of the signal from static tissue by repeated RF pulses that are applied to the imaged volume. A signal is obtained from unsaturated spins moving into the volume with the flowing blood. CE-MRA is a better techniq

  • Biomedical Engineering

    10:11
    Near-infrared Fluorescence Imaging of Abdominal Aortic Aneurysms

    Source: Arvin H. Soepriatna1, Kelsey A. Bullens2, and Craig J. Goergen1

    1 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

    2 Department of Biochemistry, Purdue University, West Lafayette, Indiana

    Near-infrared fluorescence (NIRF) imaging is an exciting optical technique that utilizes fluorescent probes to visualize complex biomolecular assemblies in tissues. NIRF imaging has many advantages over conventional imaging methods for noninvasive imaging of diseases. Unlike single photon emission computed tomography (SPECT) and positron emission tomography (PET), NIRF imaging is rapid, high-throughput, and does not involve ionizing radiation. Furthermore, recent developments in engineering target-specific and activatable fluorescent probes provide NIRF with high specificity and sensitivity, making it an attractive modality in studying cancer and cardiovascular disease. The presented procedure is designed to demonstrate the principles behind NIRF imaging and how to conduct in vivo and ex vivo experiments in small animals to study a variety of diseases. The specific example shown here employs an activatable fluorescent probe for matrix metalloproteinase-2 (MMP2) to study its uptake in two different rodent models of abdominal aortic aneurysms

  • Biomedical Engineering

    09:30
    Noninvasive Blood Pressure Measurement Techniques

    Authors: Hamna J. Qureshi and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

    Here we will highlight the key similarities and differences of noninvasive blood pressure measurement techniques between humans and rodents and examine the engineering principles that govern blood pressure. The principles that govern current cuff technology to acquire systolic and diastolic pressures will also be discussed. Commercially available cuffs that connect with mobile devices are typically compact and portable, thereby allowing measurements to be taken virtually anywhere. Noninvasive, portable blood pressure cuffs are especially useful for patients with hypertension and other cardiovascular problems that require careful monitoring and early detection of any changes in blood pressure. Similarly, noninvasive blood pressure measurement systems are also available for rodents. This technology is used in laboratory settings and is useful for monitoring animal health throughout a study. While radiotelemetry is the gold standard of blood pressure measurement for rodents, this technique is invasive and can lead to animal mortality if done incorrectly. Noninvasive methods, therefore, are convenient for taking measurements in animals as they can provide valuable data without the need for device implantation. A commercially available system will be used to dem

  • Biomedical Engineering

    11:16
    Acquisition and Analysis of an ECG (electrocardiography) Signal

    Source: Peiman Shahbeigi and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut

    An electrocardiograph is a graph recorded by electric potential changes occurring between electrodes placed on a patient's torso to demonstrate cardiac activity. An ECG signal tracks heart rhythm and many cardiac diseases, such as poor blood flow to the heart and structural abnormalities. The action potential created by contractions of the heart wall spreads electrical currents from the heart throughout the body. The spreading electrical currents create different potentials at points in the body, which can be sensed by electrodes placed on the skin. The electrodes are biological transducers made of metals and salts. In practice, 10 electrodes are attached to different points on the body. There is a standard procedure for acquiring and analyzing ECG signals. A typical ECG wave of a healthy individual is as follows: Figure 1. ECG wave. The "P" wave corresponds to atrial contraction, and the "QRS" complex to the contraction of the ventricles. The "QRS' complex is much larger than the "P" wave due to the relative dfference in muscle mass of the atria and ventricles, which masks the relaxation of the atria. The relaxation of the ventricles can be seen in the form of the "T" wave. There are three main leads responsible for m

  • Biomedical Engineering

    10:08
    Tensile Strength of Resorbable Biomaterials

    Peiman Shahbeigi and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut

    For over 4000 years, sutures have been used as a medical intervention. The earliest records indicate linen was the biomaterial of choice. Catgut, which is still in use today, was reportedly used to treat gladiators around 150 AD. Today, there are numerous materials being used for sutures. Sutures are classified by their composition (natural or synthetic) and their absorption (non-resorbable or resorbable). Resorbable (or absorbable) sutures degrade in the body through either enzymatic degradation or programmed degradation caused by the interaction of water with specific groups in the polymer chain. These sutures are often created from synthetic materials, such as polyglycolic acid, polydioxanone, and polycaprolactone, or natural biomaterials, such as silk. They are usually used for certain internal procedures, like general surgery. Resorbable sutures will hold the wound together for a time frame long enough for healing, but then they eventually disintegrate by the body. On the other hand, non-resorbable sutures do not degrade and must be extracted. They are usually derived from polypropylene, nylon, and stainless-steel. These sutures are usually implemented for orthopedic and cardiac surgery and require a medical professional to remove them at a later date. He

  • Biomedical Engineering

    11:18
    Micro-CT Imaging of a Mouse Spinal Cord

    PI Name: Peiman Shahbeigi and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut

    It's a little-known fact that the discovery and (inadvertent) use of X-rays garnered the first ever Nobel Prize in Physics. The famous X-ray image of Dr. Röntgen's wife's hand from 1895 that sent shock waves through the scientific community looks like most modern day 2D medical X-ray images. Though it is not the newest technology, X-ray absorption imaging is an indispensable tool and can be found in the world's top R&D and university labs, hospitals, airports, among other places. Arguably the most advanced uses of X-ray absorption imaging involve attaining information like the kind found in a 2D medical X-ray but realized in 3D through a computed tomography (CT or micro-CT). By taking a series of 2D X-ray projections, advanced software is capable of reconstructing data to form a 3D volume. The 3D information can, and most likely will include information from the inside of the probed object without having to be cut open. Here, a micro-CT scan will be obtained, and the major factors impacting image quality will be discussed.

  • Biomedical Engineering

    11:08
    Visualization of Knee Joint Degeneration after Non-invasive ACL Injury in Rats

    Source: Lindsey K. Lepley1,2, Steven M. Davi1, Timothy A. Butterfield3,4 and Sina Shahbazmohamadi5, Department of Kinesiology, University of Connecticut, Storrs, CT; 2Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, CT; 3Department of Rehabilitation Sciences, University of Kentucky, Lexington, KY; 4Center for Muscle Biology, Department of Physiology, University of Kentucky, Lexington, KY; 5Biomedical Engineering Department, University of Connecticut, Storrs, CT Anterior cruciate ligament (ACL) injury to the knee dramatically increases the risk of post-traumatic osteoarthritis (PTOA), as approximately one-third of individuals will demonstrate radiographic PTOA within the first decade following ACL injury. Though ACL reconstruction (ACLR) successfully restores knee joint stability, ACLR and current rehabilitation techniques do not prevent the onset of PTOA. Therefore, ACL injury represents the ideal model to study the development of PTOA after traumatic joint injury. Rat models have been used extensively to study the onset and effect of ACL injury on PTOA. The most widely used model of ACL injury is ACL transectio

  • Biomedical Engineering

    09:07
    Combined SPECT and CT Imaging to Visualize Cardiac Functionality

    Source: Alycia G. Berman, James A. Schaber, and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

    Here we will demonstrate the fundamentals of single-photon emission computed tomography/computed tomography (SPECT/CT) imaging using mice. The technique involves injecting a radionuclide into a mouse, imaging the animal after it is distributed throughout the body, and then reconstructing the produced images to create a volumetric dataset. This can provide information about anatomy, physiology, and metabolism to improve disease diagnosis and monitor its progression. In terms of collected data, SPECT/CT provides similar information as positron emission tomography (PET)/CT. However, the underlying principles of these two techniques are fundamentally different since PET requires the detection of two gamma photons, which are emitted in opposite directions. In contrast, SPECT imaging directly measures radiation via a gamma camera. As a result, SPECT imaging has lower spatial resolution than PET. However, it is also less expensive because the SPECT radioactive isotopes are more readily available. SPECT/CT imaging provides both noninvasive metabolic and anatomical information that can be useful for a wide variety of applications.

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