MRI gradient coil having non-uniform coolant passageway within gradient coil conductor

1. A gradient coil unit configured for a magnetic resonance imaging apparatus comprising:

gradient coils configured for forming gradient fields in mutually orthogonal three axis directions,

wherein at least one of said gradient coils includes:

a gradient current conductor part extending along a coil pattern; and

a holding part holding the gradient current conductor part that extends along the coil pattern, securely in place along said coil pattern, wherein at least a portion of an outer surface of said gradient current conductor part, along said coil pattern is not in contact with said holding part, and

wherein a coolant passage for transmission of a coolant is formed at least partially inside of or within the at least one gradient coil conductor part, the formed coolant passage having a non-constant cross-sectional area extending along said coil pattern.

2. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 comprising:

an X-axis gradient coil, a Y-axis gradient coil, and a Z-axis gradient coil for forming gradient magnetic fields respectively in mutually orthogonal an X-axis direction, a Y-axis direction, and a Z-axis direction as the three axis directions,

said X-axis gradient coil, said Y-axis gradient coil, and said Z-axis gradient coil having:

a first gradient current conductor part along a coil pattern of said X-axis gradient coil;

a first holding part holding the coil pattern of said X-axis gradient coil;

a second gradient current conductor part along a coil pattern of said Y-axis gradient coil;

a second holding part holding the coil pattern of said Y-axis gradient coil;

a third gradient current conductor part along a coil pattern of said Z-axis gradient coil; and

a third holding part holding the coil pattern of said Z-axis gradient coil,

wherein at least a portion of an outer surface of at least one of said first, second or third gradient current conductor part is not in contact with corresponding said first, second or third holding part, and

wherein the coolant passage for transmission of the coolant is formed inside at least one of said X-axis gradient coil, Y-axis gradient coil and Z-axis gradient coil and is surrounded by at least one of said first gradient current conductor part, said first holding part, said second gradient current conductor part, said second holding part, said third gradient current conductor part and said third holding part, the passage having a non-constant cross section area along a coil pattern.

3. A magnetic resonance imaging apparatus comprising:

said gradient coil unit of claim 1 ; and

an imaging system configured to perform magnetic resonance imaging of an object using said gradient coil unit.

4. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 , wherein the coolant passage is formed inside said gradient current conductor part, said gradient current conductor part forming a wall surface of the coolant passage.

5. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 , wherein said gradient current conductor part and said holding part jointly form a wall surface of the passage for coolant to flow along while simultaneously in contact with both said gradient current conductor part and said holding part along the coil pattern.

6. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 , wherein said gradient current conductor part consists of laminated and bonded platy members forming a void corresponding to the coolant passage, each of the platy members consisting of a conductive material.

7. A gradient coil unit for a magnetic resonance imaging apparatus of claim 6 , wherein said gradient current conductor part consists of the platy members bonded by diffusion bonding.

8. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 , wherein at least one of a branching passage of the coolant passage and a confluent passage of the coolant passage is formed inside said gradient current conductor part.

9. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 , wherein the non-constant cross section area of the coolant passage increases in correspondence with increases in density of the coil pattern.

10. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 , wherein said holding part consists of an insulating material.

11. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 , wherein an insulating sheet is arranged between said holding part and said gradient current conductor part.

12. A gradient coil unit for a magnetic resonance imaging apparatus of claim 1 comprising:

an X-axis gradient coil, a Y-axis gradient coil, and a Z-axis gradient coil for forming gradient magnetic fields respectively in mutually orthogonal an X-axis direction, a Y-axis direction, and a Z-axis direction as the three axis directions,

wherein at least one of said X-axis gradient coil and said Y-axis gradient coil includes:

said gradient current conductor part; and

said holding part, and

wherein the coolant passage is formed inside at least one of said gradient current conductor part and said holding part.

13. A method for manufacturing a gradient coil unit for a magnetic resonance imaging apparatus comprising:

positioning and laminating plural platy members together along a coil pattern of the gradient coil unit so as to form a void corresponding to a coolant passage located inside the laminated platy members, each of the platy members consisting of a conductive material that together form a gradient current conductor part; and

bonding said gradient current conductor part made of laminated platy members to an electrical insulating holding part which holds the gradient current conductor part of laminated platy members securely in place along said coil pattern,

wherein at least a portion of an outer surface of said laminated platy members along the coil pattern is not in contact with said bonded electrical insulating holding part, and

wherein the platy members are formed so as to create said coolant passage having a non-constant cross-sectional area extending along the coil pattern.