Gradient coil unit with separately drivable conductor pattern pairs
The disclosure relates to a gradient coil unit comprising a hollow cylindrical primary coil longitudinally surrounding a cylinder axis and designed to generate a magnetic field gradient in a first spatial direction, which primary coil comprises two primary conductor pattern pairs. Each primary conductor pattern pair of the two primary conductor pattern pairs is separately drivable, spans one half of the primary coil in each case, and comprises two spiral conductor patterns, which are formed by an electrical conductor implemented as a hollow conductor.
1 . Gradient coil circuitry, comprising:
a hollow cylindrical primary coil longitudinally surrounding a cylinder axis and configured to generate a magnetic field gradient in a first spatial direction,
wherein the hollow cylindrical primary coil comprises:
two primary conductor pattern pairs, each one of the two primary conductor pattern pairs being driven separately and spanning one half of the hollow cylindrical primary coil; and
two spiral conductor patterns that are formed by an electrical conductor configured as a hollow conductor, and
wherein a portion of the electrical conductor of one of the two primary conductor pattern pairs corresponds to a spiral conductor pattern of the two spiral conductor patterns that is (i) subdivided into two serially interconnected sections, and (ii) arranged spirally in turns such that two adjacent turns of the electrical conductor correspond to two mutually different sections.
2 . The gradient coil circuitry as claimed in claim 1 , wherein the portion of the electrical conductor is arranged such that the two adjacent turns run in pairs.
3 . The gradient coil circuitry as claimed in claim 1 , wherein the two adjacent turns of the electrical conductor comprise an outer turn and an inner turn, and
wherein the portion of the electrical conductor is arranged such that the outer turn of the two adjacent turns is at a smaller distance from an adjacent inner turn than an adjacent outer turn.
4 . The gradient coil circuitry as claimed in claim 1 , further comprising:
a first cooling circuit comprising a first coolant;
a second cooling circuit comprising a second coolant,
wherein the electrical conductor in a first section of the two serially interconnected sections encloses the first coolant as a hollow conductor, and
wherein the electrical conductor in a second section of the two serially interconnected sections encloses the second coolant as a hollow conductor.
5 . The gradient coil circuitry of claim 4 , wherein the portion of the electrical conductor is arranged such that the two adjacent turns run in pairs.
6 . The gradient coil circuitry as claimed in claim 1 , wherein the electrical conductor is arranged spirally in turns such that each of the two spiral conductor patterns comprises at least 35 turns.
7 . The gradient coil circuitry as claimed in claim 1 , wherein the electrical conductor has a cross-sectional area of less than 35 mm 2 .
8 . The gradient coil circuitry of claim 7 , wherein the electrical conductor is configured to conduct an electric current with a strength between 800 amps and 1500 amps, and
wherein the hollow conductor comprises a hollow region configured to hold a coolant, the hollow region having a cross-sectional area between 9 mm 2 and 16 mm 2 .
9 . The gradient coil circuitry as claimed in claim 1 , wherein each of the two spiral conductor patterns is configured to at least partially surround two predetermined points in a spiral manner.
10 . The gradient coil circuitry as claimed in claim 1 , wherein the two primary conductor pattern pairs are separated from one other by a plane that is perpendicular to the cylinder axis.
11 . The gradient coil circuitry as claimed in claim 1 , further comprising:
a further hollow cylindrical primary coil configured to generate a magnetic field gradient in a second spatial direction corresponding to a longitudinal direction that aligns with the cylinder axis,
wherein the further hollow cylindrical primary coil comprises two helical conductor patterns surrounding the cylinder axis,
wherein the two helical conductor patterns are spatially separated from each other by a plane perpendicular to the cylinder axis and are separately drivable, and
wherein each of the two helical conductor patterns comprises a further electrical conductor in the form of a hollow conductor.
12 . The gradient coil circuitry as claimed in claim 11 , wherein the further electrical conductor of one of the two helical conductor patterns is subdivided into two serially interconnected sections, and
wherein the further electrical conductor is arranged helically in further turns such that two adjacent further turns of the further electrical conductor correspond to two mutually different sections.
13 . The gradient coil circuitry as claimed in claim 12 , further comprising:
a first cooling circuit having a first coolant; and
a second cooling circuit having a second coolant,
wherein the electrical conductor in a first further section of the two serially interconnected sections encloses the first coolant as a hollow conductor, and
wherein the electrical conductor in a second additional section of the two serially interconnected sections encloses the second coolant as a hollow conductor.
14 . The gradient coil circuitry as claimed in claim 1 , further comprising:
a secondary coil configured to shield the magnetic field gradient generated by the hollow cylindrical primary coil in a periphery of the gradient coil circuitry, the secondary coil comprising two secondary conductor pattern pairs,
wherein one of the two secondary conductor pattern pairs (i) is disposed in the same half as one of the two primary conductor pattern pairs and is coupled in series with the one of the two primary conductor pattern pairs, and (ii) comprises an electrical conductor that is arranged at least partially in a spiral manner.
15 . The gradient coil circuitry as claimed in claim 14 , further comprising:
a cooling circuit comprising a coolant,
wherein the electrical conductor comprised by one of the two secondary conductor pattern pairs comprises a hollow conductor and encloses the coolant.
16 . The gradient coil circuitry of claim 1 , further comprising:
a secondary coil configured to shield the magnetic field gradient, the secondary coil comprising at least one secondary conductor pattern pair,
wherein the at least one secondary conductor pattern pair has less than 60% of the turns of one of the two primary conductor pattern pairs.
17 . The gradient coil circuitry of claim 1 , wherein the hollow cylindrical primary coil is configured to generate a magnetic field gradient with (i) a gradient amplitude of at least 180 mT/m, and (ii) a slew rate of at least 180 mT/m/ms.
18 . The gradient coil circuitry of claim 1 , further comprising:
a cooling circuit configured to pass coolant sequentially through the first section and the second section of the two serially interconnected sections,
wherein the arrangement of the two adjacent turns corresponding to two mutually different sections provides a more uniform cooling distribution across the spiral conductor pattern compared to a sequential arrangement of turns along a single coolant flow path.
19 . A gradient system, comprising:
a hollow cylindrical primary coil longitudinally surrounding a cylinder axis and configured to generate a magnetic field gradient in a spatial direction, the hollow cylindrical primary coil comprising:
two primary conductor pattern pairs, each one of the two primary conductor pattern pairs being driven separately and spanning one half of the hollow cylindrical primary coil; and
two spiral conductor patterns that are formed by an electrical conductor configured as a hollow conductor;
a first gradient amplifier; and
a second gradient amplifier,
wherein the first gradient amplifier is coupled to a first one of the two primary conductor pattern pairs,
wherein the second gradient amplifier is coupled to a second one of the two primary conductor pattern pairs, and
wherein a portion of the electrical conductor of one of the two primary conductor pattern pairs corresponds to a spiral conductor pattern of the two spiral conductor patterns that is (i) subdivided into two serially interconnected sections, and (ii) arranged spirally in turns such that two adjacent turns of the electrical conductor correspond to two mutually different sections.
20 . A magnetic resonance apparatus, comprising:
a main magnet;
radio frequency (RF) antenna circuitry;
gradient coil circuitry, comprising a hollow cylindrical primary coil longitudinally surrounding a cylinder axis and configured to generate a magnetic field gradient in a spatial direction, the hollow cylindrical primary coil comprising (i) two primary conductor pattern pairs, each one of the two primary conductor pattern pairs being driven separately and spanning one half of the hollow cylindrical primary coil, and (ii) two spiral conductor patterns that are formed by an electrical conductor configured as a hollow conductor; and
a gradient controller coupled to the gradient coil circuitry and configured to control the gradient coil circuitry to generate a magnetic field gradient in the spatial direction,
wherein a portion of the electrical conductor of one of the two primary conductor pattern pairs corresponds to a spiral conductor pattern of the two spiral conductor patterns that is (i) subdivided into two serially interconnected sections, and (ii) arranged spirally in turns such that two adjacent turns of the electrical conductor correspond to two mutually different sections.