Why are some MRI's "open" and some are not?
The highest field-strength scanners
all use what are known as "superconducting" magnets.
The reason such magnets are known as superconductors or "supercons"
is that their magnets are comprised of miles and miles of
special wire which, when immersed in a bath of liquid helium
and initial connection to a power source, is capable of conducting
electricity indefinitely, even when disconnected from the
power source. In order for this phenomenon to occur, the liquid
helium must be maintained at a temperature of about minus
273.15 degrees Celsius, very close, in other words, to absolute
zero, and the liquid helium must be replenished periodically.
The architecture associated with such a magnet requires that
the patient be positioned in the center of the magnet with
the magnet coils surrounding the patient. Thus, superconducting
magnets are always shaped like a cylinder and the patient
being scanned is positioned in a narrow, hollow tube in the
center of the cylinder. This architecture is necessarily much
less conducive to an open environment. It is therefore much
more confining for the patient and, for some, much more claustrophobic.
The architecture of vertical-field scanners are not restricted
in the same way by the magnet design. After Dr. Damadian constructed
Indomitable, his prototype scanner, he determined that for
commercial development of his scanner, he would forsake the
superconducting type of magnet he had used for that machine,
which required periodic, costly refilling with liquid helium,
and that his next scanner would use a permanent magnet. Later,
because of weight considerations that he had to overcome when
he developed the world's first mobile MRI scanner, he also
designed a water-cooled, vertical-field electromagnet. All
of these commercial units have been "open" in their
design and as the scientists at FONAR have developed more
and more efficient magnet designs and coil systems, they have
been able to increase that openness even more. For a long
time, FONAR scanners have been known as the ones in which
patients could spread out their arms and relax, free of claustrophobia.
And in FONAR's latest machine, the QUAD 7000, the vertical
dimension within the patient gap has been increased by nearly
50 percent to its greatest height ever, unmatched by any other
manufacturer. For that reason, radiologists sometimes have
to refer large or claustrophobic patients to FONAR machines,
even if they are located some distance beyond the nearest
competitive machine. If you are a larger patient, you shouldn't
have to be crammed into an MRI scanner with a shoehorn. If
large patients who weigh 300 to 400 pounds fit into FONAR
scanners but not those others, it stands to reason that a
person weighing 130 pounds or 180 pounds will feel much less
confined in a FONAR scanner. Fortunately, there's another
option-the FONAR MRI Scanner. Some patients who are claustrophobic
simply cannot tolerate lying down for extended periods of
time in the confining spaces typical of most MRI scanners.
Because of their claustrophobia, they often refuse to enter
the scanner, even though an MRI may well prove critical for
the accurate diagnosis of their illness. Even though these
patients often admit their fear is irrational, for them it's
a fact of life. If you are a patient with claustrophobic tendencies,
you shouldn't have to endure unnecessary anxiety just to get
an MRI. Remember, however, that not all "open" MRI
scanners are created equal. Most of them are underpowered
and thus of diminished image quality. In some cases, that
diminished image quality could be enough to cause a radiologist
to miss an important detail, critical perhaps to an accurate
diagnosis. A FONAR scanner provides both power and openness.