MRI Magnets and How They Operate

The MRI lets medical professionals see an image of internal structures. Before 1977, when the first human MRI was performed, surgery was the only way to visualize internal body structures. The first MRI back then took 5 hours to produce just one very unclear picture. Since that time, vast improvements in technology have resulted in MRI scans that take 60 to 90 minutes and result in very high-quality images.

Though very safe, MRI’s are not totally safe for all individuals. The “magnetic” part of the name is what allows the representation to be created. The MRI magnet relies on a strong magnetic field to produce the image. This magnetic field is also the source of the danger. Any metal that contains iron can be attracted to the MRI magnet. Therefore, items that can be problematic or dangerous include: jewelry, pacemakers, dental implants, paperclips, pens, keys, or other small objects. These objects can be forcibly pulled out of pockets and travel at high rates of speed into the MRI magnet core of the MRI unit. This poses a great risk for the patient being scanned. Due to this, the MRI technicians are very meticulous about determining if a patient has any metal in or on their bodies. Some people with any sort of internal metal implant may be denied an MRI, due to a possible threat from the high magnetic field.

The magnetic field used in an MRI is expressed in two comparative values: Tesla and gauss. One Tesla is equivalent to 20,000 gauss. The magnetic field produced by the earth is 0.5 gauss. The most common MRI magnets used today are 0.5 Tesla to 2.0 Tesla (magnets greater than 2 Tesla have not been approved for human use, but are used in research). This means that the magnetic field used by a typical MRI is approximately 40,000 times stronger than the gravitational field of the earth.

This large and powerful magnetic field is why MRI technicians carefully control who and what enter the MRI scanner suite.

The most common MRI magnets used in contemporary scanners are called superconducting magnets. This is a typical resistive MRI magnet, composed of coils or windings of wire, through which a current of electricity is passed. The MRI magnet has a significant distinctiveness: the coiled wire is bathed in a solution of liquid helium. Helium becomes a liquid at 452.4° below zero. This extremely low temperature lowers the electrical resistance of the wire to near zero, allowing relatively small amounts of power to create the large magnetic field.

In general, two types of MRI magnets make up the scanner. The superconducting magnet produces a very large magnetic field of uniform strength and stability. Smaller gradient MRI magnets are used to create small variations in the magnetic field. It is the interaction of these two magnetic fields that allows an image to be produced. A complex and powerful computer system interprets the interaction of these magnetic fields, to produce the viewable image that is the inside of your body.

MRI magnets of all kinds can be found in the MedWOW marketplace, as well as all types of imaging equipment systems and parts. MedWOW is committed to providing medical professionals around the world with secure alternatives to finding replacement parts that match their systems and at competitive prices.

Some of the MRI magnets and MRI magnet replacement parts that can be found on MedWOW include: GE Healthcare Signa Horizon 1.0T Magnet Enclosure #450009, Siemens Mobile MAGNETOM Impact SYPHON MAGNET END #1644728, GE Healthcare Signa Horizon LX 1.5T Magnet Encloser Power Supply and many more examples.

What You Need to Know About Your CT Scanner Gantry

In this continuing informational CT scanner blog series, this time we are discussing the CT scanner gantry. The CT scanner gantry is the doughnut-shaped part of the CT scanner that houses the apparatus necessary to produce and detect x-rays in order to create a CT image. The x-ray tube and detectors are positioned exactly opposite each other and rotate around the CT scanner gantry aperture. Continuous rotation in one direction without cable wrap around is possible due to the use of low-voltage slip rings.

By definition, a CT scanner gantry is a moveable frame that contains the x-ray tube, including: collimators and filters, detectors, data acquisition system, rotational components including slip ring systems, and all associated electronic accessories such as the CT scanner gantry angulation motors and positioning laser lights. The CT scanner gantry is the largest of all of the CT parts. The rotating frame, rotates at a speed of 100 – 200 RPM. A heavy x-ray tube is mounted on it, as well as a banana-shaped detector arch and other associated CT scanner gantry parts. Electric power, preconditioning lines and signal lines are provided by slipping rings. In the newer models, the signals are transmitted by a wireless system. The inclusion of slip ring technology into a CT system scanners allows for continuous scanning without cables getting in the way. A CT scanner gantry can be angled up to 30 degrees in both directions (forwards and backwards). CT scanner gantry angulation allows the operator to line up the part of the patient’s body which needs to be evaluated with the scanning plane, for precise imaging.

In the newer systems, the CT scanner gantry is continuously rotated to acquire important and comprehensive data, as the patient table is smoothly moved through the CT scanner gantry. The resulting route of the tube and detectors, in relation to the patient, forms a helical or spiral path. This powerful concept, called either helical CT or spiral CT, facilitates quick scans of entire regions of interest, in some cases within a few seconds. So significant were improvements in body CT quality and throughput that helical scanning became the standard of care for body CT scanners. This is very important for patients who suffer from claustrophobia.

Hospitals or imaging departments of healthcare facilities understand the importance of maintaining an up-to-date CT scanner gantry, as the technological advances allow great patient comfort, as well as much better imaging for diagnosis and treatment.

MedWOW has an enormous parts department, with a major focus on CT scanner gantries and other imaging equipment. If you need a replacement CT scanner gantry for your CT equipment, if it isn’t found on the MedWOW portal, the MedWOW parts finder team will conduct a thorough international search and find it for you.

There are currently nearly 2,000 CT scanner gantries parts available through the MedWOW marketplace, representing Esaote, GE Healthcare, Ige, Philips, Picker, Shimadzu, Siemens, Toshiba and other manufacturers. MedWOW’s search engines allow you to filter for make, model, price, condition, location and other variables.

Advances in CT Scanner X-Ray Tubes

Wilhelm Roentgen, is best known is best known for the discovery of "Roentgen Rays", now univerally known as x-rays. Around this time, in 1985, various scientists were investigating the movement of electrons through a glass apparatus known as a Crookes tube. Roentgen wanted to visually capture the action of the electrons, so he wrapped his Crookes tube in black photographic paper. When he ran his experiment, he noticed that a plate coated with a fluorescent material, which just happened to be lying nearby the tube, glowed. This was unexpected, because no visible light was being emitted from the wrapped tube. Upon further investigation, he found that indeed there was some kind of invisible light produced by this tube, and it could penetrate materials such as wood, aluminum, and even human skin.

As the field of radiography expanded, x-ray technology steadily improved. One of the major limitations of conventional x-rays was that they lacked depth; therefore many internal structures were superimposed on each other, making it difficult to read results. With the help of computers, scientists developed methods to solve this problem. One such method was computed tomography (CT), or computerized axial tomography (CAT). The first CT scanner was demonstrated in 1970 by Godfrey Hounsfield and Allen Cormack. Over the next 20 years, significant advances were made in CT scanner design, which have resulted in the high-quality imaging scanners used today, and still constantly improving.

A CT scanner x-ray tube is a special type of vacuum-sealed, electrical diode that was designed and developed to produce x-rays. The CT scanner x-ray tube is comprised of two electrodes: the cathode and anode. To generate x-rays, a filament in the cathode is charged with electricity from a high -voltage generator. This causes the filament to heat up and emit electrons. Using their natural attraction and a special focusing cup, the electrons travel directly toward the positively charged anode. X-rays are indiscriminately released when the electrons strike the anode. The anode, which can be rotating or not, then conducts the electricity back to the high-voltage generator to complete the circuit. To focus the x-rays into a beam, the CT scanner x-ray tube is contained inside a protective housing. This housing is lined with lead, except for a small window at the bottom. Functional x-rays are able to escape out this window, while the lead prevents the escape of stray radiation in other directions.

CT scanner x-ray tubes have gone through several generations of technological evolution. In the third generation, developers realized that if a pure rotational scanning motion could be used, rather than the slam-bang translational motion, then it would be possible to use higher power, rotating CT scanner x-ray tubes and therefore improve scan speeds in thicker, harder to penetrate body parts. A standard machine which most x-ray technicians are familiar with, uses a large fan beam, so that the patient is completely covered by the fan and the detector elements are aligned along the arc of a circle centered on the focus of the CT scanner x-ray tube. The CT scanner x-ray tube and detector array rotate as one through 360 degrees, different projections are attained during rotation by pulsing the x-ray source, and bow-tie shaped filters are chosen to suit the body or head shape by some manufacturers to avoid extreme variations in signal strength.

The fourth generation of CT scanners uses rotate-fixed ring geometry, where a ring of fixed detectors completely surrounds the patient. The x-ray tube rotates inside the detector ring through a full 360 degrees with a wide fan beam producing a single image.

A limiting factor in image acquisition used to be the CT scanner x-ray tube. The need for long, high intensity exposures and very stable output placed enormous demands on both the CT scanner x-ray tube and generator (power supply). Very high performance rotating anode CT scanner x-ray tubes were developed to keep up with demand for faster imaging, as were the regulated 150 kV switched mode power supplies to drive them. Current CT scanning systems have power ratings up to 100 kW.

The most popular, international marketplace for all types of medical equipment, featuring a large selection of CT scanner x-ray tubes, MedWOW, is an excellent place to find reliable and good-quality imaging equipment and parts. When purchasing or selling CT scanner x-ray tubes, MedWOW’s comprehensive portal attracts nearly 12,000 medical equipment professionals daily, making it easy to find what you seek. MedWOW has recently upgraded its imaging and CT scanner x-ray tubes section with additional manufacturers, including refurbished equipment and new and used CT scanner x-ray tubes. CT scanner x-ray tubes manufacturers represented on MedWOW include: Elscint, Esaote, GE Healthcare, Philips, Picker, Shimadzu, Siemens, Toshiba and more.

The Technology of CT Scanner Detectors: from 1 to 256 Slices and Beyond

The CT scanner is made up of a complex combination of an x-ray source, detectors and computers, which produce high-resolution, cross-sectional images of the body. The patient lies on a table that passes through a gantry which resembles a donut hole, containing the x-ray tube and multiple detectors. The walls of the opening into the gantry are wedge-shaped, designed so that claustrophobia is not a considerable problem in most cases. A series of cross-sectional images are taken of the area to be examined in a matter of seconds. The raw data from the multiple detectors are then reconstructed by specially programmed computers, to present images of the internal structures of the area scanned.

The Multiple Values of Diagnostic Ultrasound Scanning

Diagnostic ultrasound is a scan used to demonstrate internal body structures. It works by emitting high-frequency sound waves, directed at the tissue being examined, and recording the reflected sound or in professional terms, echoes to produce an analytic 2-, 3- or 4-dimensional image.

The diagnostic ultrasound scan is non-invasive and some of the standard reasons for ultrasound scanning include investigations of the abdominal and pelvic organs, musculoskeletal and vascular systems and to check fetal development during pregnancy.

The diagnostic ultrasound scan emits high-frequency sound waves, directed at the internal body part being examined. The reflected sounds (echoes) are recorded to generate an image that can be viewed on a monitor. The sound waves are emitted and received from a small, hand-held diagnostic ultrasound part probe. As the high frequency sound cannot be detected by the human ear, it is called ultrasound.

In general, a diagnostic ultrasound scan is a non-invasive procedure. However, some diagnostic ultrasound scans are done with a special probe that is inserted into the vagina (for special obstetric or pelvic examinations), the rectum (for special prostate examinations) or the esophagus (for to examine the heart). In addition, diagnostic ultrasound scanning may be used to monitor and guide invasive procedures, including breast or thyroid biopsy procedures.

There are many uses for diagnostic ultrasound including:

• Abdominal diagnostic ultrasound scan – may be used to investigate abdominal pain, nausea, vomiting, abnormal sounds and lumps. Structures that may be examined include the gallbladder, bile ducts, liver, pancreas, spleen, kidneys and large blood vessels. Structures that contain air (such as the stomach and bowels) can’t be examined easily by diagnostic ultrasound, because air prevents the transfer of sound waves produced by the scanner.
• Pelvic scan – may be performed if a woman is suffering pelvic pain or has abnormal periods, fibroids, cysts or other conditions associated with the female reproductive system.
• Pregnancy scan – used to check for fetal abnormalities (including growth abnormalities, Downs Syndrom or diseases such as spina bifida), check the age and position of the fetus, and monitor fetal growth and development. A diagnostic ultrasound scan during pregnancy is now considered routine in most parts of the world.
• Other uses of diagnostic ultrasound scan – musculoskeletal scans (to check regions like shoulder, hip and elbow), breast scans (for example, to further investigate an abnormality picked up by physical examination or mammogram) and a scan of the eye (to check its internal structures). A special type of diagnostic ultrasound scan, called a ‘Doppler ultrasound’, is sometimes used to detect the speed and direction of blood flow in certain regions of the body, including neck arteries and leg veins.

MedWOW, the multilingual global medical equipment platform, offers a a huge selection of thousands of both new and used diagnostic ultrasound scanners for sale from inventories all over the world. MedWOW currently offers diagnostic ultrasound scanners manufactured by Acoustic Imaging, Acuson, Agilent, Aloka, Alpinion, Ardent Sound, ARI, ATL, Biosound Esaote, BK Medical, Bruel & Kjaer, Carewell, Corometrics, Diasonics Vingmed, Dornier MedTech, Edan, EMP, Esaote, Fukuda Denshi, GE Healthcare, Hewlett Packard, Hitachi, Honda, Kontron Medical, Kranzbuehler, Kretz, Lead Medi Tech, Medison, Mindray, Mochida, and Zonare Medical Systems.

Not only that, if you are looking for diagnostic ultrasound parts, MedWOW can find almost any diagnostic ultrasound part in existence as they represent an inventory of almost 10,000 from manufacturers all over the world from 1990-present, so what you need is likely among their comprehensive listings.

If there is a particular diagnostic ultrasound part that you can’t find in MedWOW’s representative inventories, you can post a request or take advantage of any of MedWOW’s location services.