US 5,563,566 AGranted

Cryogen-cooled open MRI superconductive magnet

AssigneeGeneral Electric Company

InventorsEvangelos T. Laskaris, Bizhan Dorri, Robert A. Ackermann

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Abstract

An open magnetic resonance imaging (MRI) magnet having longitudinally spaced-apart superconductive main coils surrounded by a dewar containing a cryogenic liquid (e.g., liquid helium) and boiled-off cryogenic gas (e.g., helium vapor). A condenser is in physical contact with the boiled-off vapor and is in thermal contact with a cold stage of a cryocooler coldhead so as to re-liquefy the vapor. This allows the coils to be surrounded by a single (not double) thermal shield which allows the coils structurally to be located closer to the magnet's open space which reduces magnet cost by reducing the amount of coil needed for the same-strength magnetic field.

Claims10

Dependent claims

An open magnetic resonance imaging magnet comprising:

a) a vacuum enclosure including:
(1) a generally toroidal shaped first portion surrounding a first bore and having a generally longitudinal first axis;
(2) a generally toroidal-shaped second portion longitudinally spaced apart from said first portion, surrounding a second bore, and having a generally longitudinal second axis generally coaxially aligned with said first axis;
and
(3) a plurality of tubes each having a first end hermetically connected to said first portion of said vacuum enclosure and having a second end hermetically connected to said second portion of said vacuum enclosure;
b) a thermal shield disposed within and generally spaced-apart from said vacuum enclosure, said thermal shield including:
(1) a generally toroidal-shaped first portion disposed within and generally spaced apart from said first portion of said vacuum enclosure;
(2) a generally toroidal-shaped second portion disposed within and generally spaced apart from said second portion of said vacuum enclosure;
and
(3) a tubular section disposed within and generally spaced apart from at least some of said tubes of said vacuum enclosure, said tubular section having a first end thermally connected to said first portion of said thermal shield and having a second end thermally connected to said second portion of said thermal shield;
c) a dewar disposed within and generally spaced apart from said thermal shield, said dewar containing a cryogenic fluid including a cryogenic liquid and a cryogenic gas boiled-off from said cryogenic liquid, said dewar including:
(1) a generally toroidal-shaped first portion containing some of said cryogenic liquid and some of said cryogenic gas and disposed within and generally spaced apart from said first portion of said thermal shield;
(2) a generally toroidal-shaped second portion containing some of said cryogenic liquid and some of said cryogenic gas and disposed within and generally spaced apart from said second portion of said thermal shield;
and
(3) a tubular segment disposed within and generally spaced apart from at least some of said tubular sections of said thermal shield, said tubular segment having a first end hermetically connected to said first portion of said dewar and having a second end hermetically connected to said second portion of said dewar;
and
d) a generally annular-shaped first superconductive main coil generally coaxially aligned with said first axis, disposed within said first portion of said vacuum enclosure, and disposed in thermal contact with said cryogenic fluid;
e) a generally annular-shaped second superconductive main coil generally coaxially aligned with said second axis, disposed within said second portion of said vacuum enclosure, and disposed in thermal contact with said cryogenic fluid;
f) a cryocooler coldhead including:
(1) a housing connected to said vacuum enclosure;
and
(2) a cold stage operatively connected to said housing and having a temperature cold enough to re-liquefy said cryogenic gas;
and
g) a condenser disposed in thermal contact with said cold stage and disposed in physical contact with said cryogenic gas.

21 more elements

Dependencies are inferred from the claim text.

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Abstract

An open magnetic resonance imaging magnet comprising:

a) a vacuum enclosure including:
(1) a generally toroidal shaped first portion surrounding a first bore and having a generally longitudinal first axis;
(2) a generally toroidal-shaped second portion longitudinally spaced apart from said first portion, surrounding a second bore, and having a generally longitudinal second axis generally coaxially aligned with said first axis;
and
(3) a plurality of tubes each having a first end hermetically connected to said first portion of said vacuum enclosure and having a second end hermetically connected to said second portion of said vacuum enclosure;
b) a thermal shield disposed within and generally spaced-apart from said vacuum enclosure, said thermal shield including:
(1) a generally toroidal-shaped first portion disposed within and generally spaced apart from said first portion of said vacuum enclosure;
(2) a generally toroidal-shaped second portion disposed within and generally spaced apart from said second portion of said vacuum enclosure;
and
(3) a tubular section disposed within and generally spaced apart from at least some of said tubes of said vacuum enclosure, said tubular section having a first end thermally connected to said first portion of said thermal shield and having a second end thermally connected to said second portion of said thermal shield;
c) a dewar disposed within and generally spaced apart from said thermal shield, said dewar containing a cryogenic fluid including a cryogenic liquid and a cryogenic gas boiled-off from said cryogenic liquid, said dewar including:
(1) a generally toroidal-shaped first portion containing some of said cryogenic liquid and some of said cryogenic gas and disposed within and generally spaced apart from said first portion of said thermal shield;
(2) a generally toroidal-shaped second portion containing some of said cryogenic liquid and some of said cryogenic gas and disposed within and generally spaced apart from said second portion of said thermal shield;
and
(3) a tubular segment disposed within and generally spaced apart from at least some of said tubular sections of said thermal shield, said tubular segment having a first end hermetically connected to said first portion of said dewar and having a second end hermetically connected to said second portion of said dewar;
and
d) a generally annular-shaped first superconductive main coil generally coaxially aligned with said first axis, disposed within said first portion of said vacuum enclosure, and disposed in thermal contact with said cryogenic fluid;
e) a generally annular-shaped second superconductive main coil generally coaxially aligned with said second axis, disposed within said second portion of said vacuum enclosure, and disposed in thermal contact with said cryogenic fluid;
f) a cryocooler coldhead including:
(1) a housing connected to said vacuum enclosure;
and
(2) a cold stage operatively connected to said housing and having a temperature cold enough to re-liquefy said cryogenic gas;
and
g) a condenser disposed in thermal contact with said cold stage and disposed in physical contact with said cryogenic gas.

21 more elements