Biomedical imaging concentrates on the capture of images for both diagnostic and therapeutic purposes. Snapshots of in vivo physiology and physiological processes can be garnered through advanced sensors and computer technology. Biomedical imaging technologies utilize either x-rays (CT scans), sound (ultrasound), magnetism (MRI), radioactive pharmaceuticals (nuclear medicine: SPECT, PET) or light (endoscopy, OCT) to assess the current condition of an organ or tissue and can monitor a patient over time over time for diagnostic and treatment evaluation.
The science and engineering behind the sensors, instrumentation and software used to obtain biomedical imaging has been evolving continuously since the x-ray was first invented in 1895. Modern x-rays using solid-state electronics require just milliseconds of exposure time, drastically reducing the x-ray dose originally needed for recording to film cassettes. The image quality has also improved, with enhanced resolution and contrast detail providing more reliable and accurate diagnoses.
The limitations of what x-rays could reveal were partially addressed through the introduction of contrast medium to help visualize organs and blood vessels. First introduced as early as 1906, contrast agents, too, have evolved over the years. Today, digital x-rays enable images to more easily be shared and compared.
Digital imaging gave rise to the CT scanner and allows physicians to watch real-time x-rays on a monitor—a technique known as x-ray fluoroscopy—to help guide invasive procedures such as angiograms and biopsies. No longer limited to simple anatomical imaging, current research is focusing on what can be gleaned through functional imaging. Biomedical engineers are using CT and MRI to measure the blood profusion of tissue; especially important after a heart attack or suspected heart attack. Researchers are also using functional MRI (fMRI) to measure different types of brain activity following strokes and traumatic head injuries.
PET scans—which use a radioactive tracer to measure metabolic changes, blood flow and oxygen use—have also improved with technological advancements. PET scans enable researchers to compare, for example, brain activity during periods of depression based on the chemical activity in the brain.
Optical molecular imaging technologies represent a new area of research that can be used to image human cells and molecules without the need for a biopsy or cell culture. Using contrast or imaging agents that attach to specific molecules, disease processes, such as cancer, can be spotted before they render their effects at the level of gross pathology.
Optical coherence tomography (OCT) is a newer form of CT being used in research that constructs images from light that is transmitted and scattered through the body.
The power of ultrasound is being used in conjunction with microbubbles. The microbubbles can be injected directly into a specific location and then burst via ultrasound to emit localized contrast agents for imaging, chemotherapy for cancer treatment, air to help dissolve clots, and genes or drugs which can more easily penetrate cell membranes that are weakened by ultrasound.
New imaging techniques bring new means for peering into the human body, helping to reduce the need for more invasive diagnostic and treatment procedures.
Biomedical Image Processing
Biomedical image processing is similar in concept to biomedical signal processing in multiple dimensions. It includes the analysis, enhancement and display of images captured via x-ray, ultrasound, MRI, nuclear medicine and optical imaging technologies.
Image reconstruction and modeling techniques allow instant processing of 2D signals to create 3D images. When the original CT scanner was invented in 1972, it literally took hours to acquire one slice of image data and more than 24 hours to reconstruct that data into a single image. Today, this acquisition and reconstruction occurs in less than a second.
Rather than simply eyeball an x-ray on a lightbox, image processing software helps to automatically identify and analyze what might not be apparent to the human eye. Computerized algorithms can provide temporal and spatial analysis to detect patterns and characteristics indicative of tumors and other ailments.
Depending on the imaging technique and what diagnosis is being considered, image processing and analysis can be used to determine the diameter, volume and vasculature of a tumor or organ; flow parameters of blood or other fluids and microscopic changes that have yet to raise any otherwise discernible flags.
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