Medical imaging equipment

Sunday, 07 January 2007

Medical imaging is one of the most useful diagnostic tools available in modern medicine. Medical diagnostic and imaging systems are ubiquitous in modern health care facilities. Medical imaging allows medical personnel to non-intrusively look into a living body in order to detect and assess many types of injuries, diseases, conditions, etc. The advantages of early detection of potential lesions and suspicious masses within bodily tissue have been well-established. Increasingly, screening for common cancers of the breast, lung, colon, and prostate has gained support and acceptance in the medical community. Medical imaging allows doctors and technicians to more easily and correctly make a diagnosis, decide on a treatment, prescribe medication, perform surgery or other treatments, etc. In the medical imaging field, for example, systems are typically considered by imaging modality. A medical imaging system typically includes at least one medical modality that generates input pixel data representative of an image and a medical imager that forms a visible representation of the image based on the input pixel data. Different imaging modalities, may be used for imaging patient body parts. Examples of imaging modalities include magnetic resonance imaging (MRI) systems, computed tomography (CT) systems, ultrasound systems, x-ray systems, positron emission tomography (PET) systems, and nuclear imaging. Such systems provide invaluable tools for identifying, diagnosing and treating physical conditions and greatly reduce the need for surgical diagnostic intervention. Depending upon the physics involved in acquiring and reconstructing useful images, these systems call upon different control and processing circuitry, as well as peripheral devices for data acquisition, processing, storage, and output or viewing. In many instances, these modalities complement one another and offer the physician a range of techniques for imaging particular types of tissue, organs, physiological systems, and so forth. Health care institutions often dispose of several such imaging systems at a single or multiple facilities, permitting its physicians to draw upon such resources as required by particular patient needs.

There are medical imaging processes of many types and for many different purposes, situations, or uses. They commonly share the ability to create an image of a bodily region of a patient, and can do so non-invasively. The image may capture various details of the subject, which may include bones, organs, tissues, ducts, blood vessels, nerves, previous surgical artifacts such as implants or scar tissue, etc. The image or images may be two-dimensional or three-dimensional. In addition, the image capture may produce an image sequence or video that shows live operation, such as a functioning organ. Many modern medical imaging devices produce time domain images, that is, the time at which such images are produced is diagnostically important. Such medical imaging devices typically capture a sequential series of images portraying movement of a structure under study. Advances in computer technology, including increases in the amounts of available processing power, have enabled more sophisticated ways of capturing and displaying medical image data, such as stereoscopic rendering, animation, and virtual surgery. The primary distinction between the different systems is the medical imaging modality that is used, such as, x-ray, magnetic resonance, ultrasound or nuclear. In addition, a broad range of capabilities and features are typically offered in each imaging modality. For example, a magnetic resonance imaging (MRI)system may be offered with a range of polarizing magnetic strengths and configurations and with a range of different optional features such as magnetic resonance angiography (MRA), cardiac imaging and functional magnetic resonance imaging (fMRI). Medical imaging scanning devices, such as computer tomography (CT) systems, x-ray systems, magnetic resonance imaging (MRI) systems, positron emission tomography (PET) systems are defined by a number of subsystems that control the major functionalities of the device. For example, some subsystems of an x-ray scanner include an x-ray generator, a table positioner, a system control, and an operator console. These subsystems may be further subdivided into subsystems of the subsystem, or micro-subsystems. Proper coordination of subsystems and peripheral devices in imaging systems is critical to the capture, processing and display of desired images. In particular, many subsystems and peripheral devices must be appropriately calibrated to account for device-to-device variances and tolerances, as well as for similar tolerances within individual devices.

All medical imaging systems include an operator interface which enables a particular image acquisition to be prescribed, a data acquisition apparatus which uses one of the imaging modalities to acquire data from the subject, an image reconstruction processor for reconstructing an image using acquired data, and storage apparatus for storing images and associated patient information. Typically, hardware is designed to carry out these functions and system software is designed and written for each hardware configuration. With respect to generating, processing, and displaying medical images, the development of medical imaging applications generally requires significant software development effort. A medical imaging system contains application programs which direct the imaging system to perform particular types of scans, image reconstructions and post processing applications. For example, an MRI system may include application software which directs the imaging system to perform a fast spin-echo scan, or a fast gradient-recalled echo scan, or a functional MRI scan, or a cardiac cine scan. The application software also directs the imaging system to reconstruct images from acquired data. Typically, a medical imaging system will include software programs to reconstruct one or more images from a set of acquired data, wherein the algorithms are designed to process the acquired data differently to reconstruct, for example, either stationary skeletal or tissue images, or images of blood flow through a body. Computerized image processing generally requires that the image data conform to some sort of protocol, with the protocol being a set of rules and standards that ensure that the information may be efficiently communicated and manipulated among different apparatus. Many medical imaging systems, have the ability to communicate with other electronic devices, such as computers, located a great distance from the electronic device. These devices may be connected to the Internet or some other communication system that enables them to communicate with other electronic devices. Diagnostic medical imaging requires accurate positioning of imaging equipment around a patient. Depending on the size and complexity of the equipment, the equipment can be positioned manually or through motorization of the equipment. A radiation therapy or diagnostic imaging device generally includes a gantry which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment or diagnostic imaging. A patient is supported in a substantially rigid position on a tabletop while the patient is exposed to a radiation source or imaging is performed. In medical diagnostic imaging apparatus, for example, computed or magnetic resonance tomography device, a region to be imaged in an examination subject is positioned in an imaging volume of the apparatus for producing images of this region. Particularly in a magnetic resonance tomography apparatus, positioning of the subject occurs with the assistance of a support device that is displaceable in at least one direction on which the examination subject is positioned.

Tomographic imaging devices are frequently used to assist in the diagnosis and treatment of a variety of anatomical structures and physiologic functions within the body of a subject patient, while minimizing the need for invasive procedures. Such devices typically utilize scanners that obtain data or information about such structures and functions from the patient at specified, discrete locations along the length of a patient. A tomographic camera utilizes a scanner having an array of radiation detectors forming a ring or bore that surrounds a patient. The scanner gathers information along a plane defined by the detector ring, which intersects the patient substantially perpendicularly to the length of the patient. Magnetic resonance imaging (MRI) systems are well known tomographic imaging systems, and well used by the medical establishment to analyze injuries and diseases. In an MRI system, image data is acquired by imposing magnetic fields on a subject, including a primary magnetic field and a series of gradient fields. After imposition of radio frequency pulses, transverse moments are produced in gyromagnetic material of the subject through the slice, and echo signals from the material can be sensed and processed to identify the intensity of the response at the various locations in the slice. After data processing, an image can be reconstructed based upon the acquired and processed data. Magnetic resonance apparatuses are being increasingly utilized for obtaining images in the examination of patients, since they enable a relatively stress-free examination of the patient as well as the assessment of a large variety of body areas. Computed tomography (CT) systems are well known x-ray based medical imaging systems, and well used by the medical establishment to analyze injuries and diseases. CT systems typically function by irradiating a patient with X-rays and recording the images generated thereby. Nuclear medicine (NM) gamma-ray based medical imaging systems are well known tomographic imaging systems, and used by the medical establishment to analyze injuries and diseases. Nuclear medicine involves injection of a radiopharmaceutical into a patient and measurement of the intensity distribution of gamma radiation emitted from the patient's body. Nuclear medicine systems typically function by recording the images from radiation such as gamma rays which are emitted by the patient. The patient emits this radiation as a result of irradiated material introduced into the patient's body prior to the nuclear medicine scan. In all of these systems, the act of acquiring data may be referred to as a scan. Nuclear medicine imaging techniques include single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Single-photon emission computed tomography (SPECT) is a type of nuclear camera imaging system wherein the radiation detector of the camera system is rotated about an organ or tissue (referred as an object of interest) and images of the object of interest are recorded at discrete angles of rotation. SPECT imaging is based on the detection of individual gamma rays emitted from the body, while PET imaging is based on the detection of gamma ray pairs that are emitted in coincidence in opposite directions due to electron-positron annihilations. PET imaging is therefore often referred to as "coincidence" imaging.

An ultrasound imaging machine is an electronic device including a signal transmission and detection apparatus for producing an ultrasound image. A medical ultrasound imaging machine is used for uninvasive in vivo visualization so that anatomical structures within a body of a patient are displayed and analyzed. Ultrasound is a valuable diagnostic imaging technique for studying various areas of the body including, for example, the vasculature, such as tissue microvasculature. Ultrasonic diagnostic imaging systems produce images of the interior of the body by transmitting ultrasonic waves which are steered and focused along transmit beam paths. Echoes are received from along the transmit beam path which are used to produce an image of the structure or motion encountered along the beam path. The ultrasonic apparatus generates the tomographic image based on a time difference required for the arrival of the reflected wave caused by a difference in acoustic impedance among respective tissues of the examinee. Ultrasound involves the exposure of a patient to sound waves. Generally, the sound waves dissipate due to absorption by body tissue, penetrate through the tissue, or reflect off of the tissue. The reflection of sound waves off of tissue, generally referred to as backscatter or reflectivity, forms the basis for developing an ultrasound image. Ultrasound imaging techniques often involve the use of contrast agents. Contrast agents can serve to improve the quality and usefulness of images which are obtained with ultrasound. The ultrasonic apparatus is widely utilized since it is compact and excellent in portability and can recognize the cross-sectional shape of the tissue while keeping out of contact with the examinee. Ultrasound provides certain advantages over other diagnostic techniques. Diagnostic techniques involving nuclear medicine and X-rays generally results in exposure of the patient to ionizing electron radiation. Such radiation can cause damage to subcellular material, including deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and proteins. Ultrasound does not involve such potentially damaging radiation. In addition, ultrasound is relatively inexpensive as compared to other diagnostic techniques, such as magnetic resonance imaging (MRI), which can require elaborate and expensive equipment. Ultrasound imaging has been widely used in diagnosis of diseases in organs, such as heart, liver, kidney, breast, prostate, thyroid, fetus, blood vessels and others.

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