coil types in MRI

COIL TYPES IN MRI

RESISTIVE COILS:
-air core
-either 1 coil pair (2 coils) (Helmholtz coil) or
2 pairs (4 coils)
-diameter of coils describe surface of a sphere
-magnetic field (either longitudinal or transverse
-iron core
-windings directly around poles of electromagnet
(either C or H configuration)
-transverse field

SUPERCONDUCTIVE COIL:
-winding solenoid (around gantry)
-made of NbTi filaments in a copper matrix
-longitudianl field

RF COILS:
-for transverse fields
(solenoidal configuration
(2 times more SNR than saddle shaped coils
-for longitudinal fields
(saddle shaped coils
-surface coil
(circular coils placed directly over ROI
(RF receiver

GRADIENT COILS:
-Maxwell pair
(current flow in opposite direction
(used in slice selection gradient- in direction of Bo
-Golay coil
(opposing parallel side coils
(curved over the cylindrical surface of the gantry bore
(2 sets – 90 degree to each other- used in x , y plane
gradients

SHIM COILS:
-small coils
-within gantry
-make Bo more uniform


Ravi
BS (RT)