<Li> Positron emission tomography (PET) uses coincidence detection to image functional processes . Short - lived positron emitting isotope, such as F, is incorporated with an organic substance such as glucose, creating F18 - fluorodeoxyglucose, which can be used as a marker of metabolic utilization . Images of activity distribution throughout the body can show rapidly growing tissue, like tumor, metastasis, or infection . PET images can be viewed in comparison to computed tomography scans to determine an anatomic correlate . Modern scanners may integrate PET, allowing PET - CT, or PET - MRI to optimize the image reconstruction involved with positron imaging . This is performed on the same equipment without physically moving the patient off of the gantry . The resultant hybrid of functional and anatomic imaging information is a useful tool in non-invasive diagnosis and patient management . </Li> <P> Fiduciary markers are used in a wide range of medical imaging applications . Images of the same subject produced with two different imaging systems may be correlated (called image registration) by placing a fiduciary marker in the area imaged by both systems . In this case, a marker which is visible in the images produced by both imaging modalities must be used . By this method, functional information from SPECT or positron emission tomography can be related to anatomical information provided by magnetic resonance imaging (MRI). Similarly, fiducial points established during MRI can be correlated with brain images generated by magnetoencephalography to localize the source of brain activity . </P> <P> Medical ultrasonography uses high frequency broadband sound waves in the megahertz range that are reflected by tissue to varying degrees to produce (up to 3D) images . This is commonly associated with imaging the fetus in pregnant women . Uses of ultrasound are much broader, however . Other important uses include imaging the abdominal organs, heart, breast, muscles, tendons, arteries and veins . While it may provide less anatomical detail than techniques such as CT or MRI, it has several advantages which make it ideal in numerous situations, in particular that it studies the function of moving structures in real - time, emits no ionizing radiation, and contains speckle that can be used in elastography . Ultrasound is also used as a popular research tool for capturing raw data, that can be made available through an ultrasound research interface, for the purpose of tissue characterization and implementation of new image processing techniques . The concepts of ultrasound differ from other medical imaging modalities in the fact that it is operated by the transmission and receipt of sound waves . The high frequency sound waves are sent into the tissue and depending on the composition of the different tissues; the signal will be attenuated and returned at separate intervals . A path of reflected sound waves in a multilayered structure can be defined by an input acoustic impedance (ultrasound sound wave) and the Reflection and transmission coefficients of the relative structures . It is very safe to use and does not appear to cause any adverse effects . It is also relatively inexpensive and quick to perform . Ultrasound scanners can be taken to critically ill patients in intensive care units, avoiding the danger caused while moving the patient to the radiology department . The real time moving image obtained can be used to guide drainage and biopsy procedures . Doppler capabilities on modern scanners allow the blood flow in arteries and veins to be assessed . </P> <P> Elastography is a relatively new imaging modality that maps the elastic properties of soft tissue . This modality emerged in the last two decades . Elastography is useful in medical diagnoses, as elasticity can discern healthy from unhealthy tissue for specific organs / growths . For example, cancerous tumours will often be harder than the surrounding tissue, and diseased livers are stiffer than healthy ones . There are a several elastographic techniques based on the use of ultrasound, magnetic resonance imaging and tactile imaging . The wide clinical use of ultrasound elastography is a result of the implementation of technology in clinical ultrasound machines . Main branches of ultrasound elastography include Quasistatic Elastography / Strain Imaging, Shear Wave Elasticity Imaging (SWEI), Acoustic Radiation Force Impulse imaging (ARFI), Supersonic Shear Imaging (SSI), and Transient Elastography . In the last decade a steady increase of activities in the field of elastography is observed demonstrating successful application of the technology in various areas of medical diagnostics and treatment monitoring . </P>

A method of obtaining an image of the interior of the body that does not use radiation