Physicist1992
Newbie level 1
Hello!
I’m trying to simulate birdcage quadrature RF coil for MRI in the CST MWS 2016. Please help me to understand several issues:
1) What is the difference between H field and B1+ field? I’ve searched for the answer everywhere but I couldn’t find the explanation. When authors use the phrase “the magnetic field generated by RF coil” in some articles, what do they mean – H field or B1+ field? Before using the CST, I always thought that any transmit RF coil produces B1+ field which is transmit magnetic field, any receive RF coil receives the B1- magnetic field, and any transceiver RF coil produces transmit B1+ field and receives B1- field.
2) When simulating the birdcage RF coil in the CST, has it sense to claim that I am simulating the transceiver birdcage coil? Or the word “transceiver” is meaningless when we tell about simulation in CST? For example, I’d like to simulate the quadrature high-pass 8-rung birdcage coil. I placed 16 discrete ports in the gaps on two end-rings between the rungs. I used them for capacitors. Then I placed 2 additional discrete ports on one end-ring between the coil and RF shield. These 2 ports are used for matching, tuning and for excitation. In the “schematic” tab in CST, I connected two external ports (yellow squares) to the 2 discrete ports mentioned above. So these external ports are stimulating ports, i.e. for the excitation. Returning to the beginning of the question, I’d like to understand – can I say that these 2 external ports are also the receivers for the electric signal? Will it be correct?
3) The arrows of B1+ and B1- fields simulated in CST using the “Template Based Post Processing -> MRI Toolbox” are directed along the rungs of birdcage coil, i.e. the B1+ and B1- vectors have the same direction as surface current! How can it be? It is known that vectors of B1+ and B1- fields are directed perpendicularly with respect to the vector of B0 field (constant magnetic field directed along Z axis). At the same time, the arrows of H field in CST are directed perpendicularly with respect to rungs, i.e. perpendicularly with respect to the vector of B0 field.
I've attached the printscreens of H field, surface current, B1+ field and B1- field. I assume that B0 field is directed onto the positive direction of Z axis.
Kind regards,
Elnur
I’m trying to simulate birdcage quadrature RF coil for MRI in the CST MWS 2016. Please help me to understand several issues:
1) What is the difference between H field and B1+ field? I’ve searched for the answer everywhere but I couldn’t find the explanation. When authors use the phrase “the magnetic field generated by RF coil” in some articles, what do they mean – H field or B1+ field? Before using the CST, I always thought that any transmit RF coil produces B1+ field which is transmit magnetic field, any receive RF coil receives the B1- magnetic field, and any transceiver RF coil produces transmit B1+ field and receives B1- field.
2) When simulating the birdcage RF coil in the CST, has it sense to claim that I am simulating the transceiver birdcage coil? Or the word “transceiver” is meaningless when we tell about simulation in CST? For example, I’d like to simulate the quadrature high-pass 8-rung birdcage coil. I placed 16 discrete ports in the gaps on two end-rings between the rungs. I used them for capacitors. Then I placed 2 additional discrete ports on one end-ring between the coil and RF shield. These 2 ports are used for matching, tuning and for excitation. In the “schematic” tab in CST, I connected two external ports (yellow squares) to the 2 discrete ports mentioned above. So these external ports are stimulating ports, i.e. for the excitation. Returning to the beginning of the question, I’d like to understand – can I say that these 2 external ports are also the receivers for the electric signal? Will it be correct?
3) The arrows of B1+ and B1- fields simulated in CST using the “Template Based Post Processing -> MRI Toolbox” are directed along the rungs of birdcage coil, i.e. the B1+ and B1- vectors have the same direction as surface current! How can it be? It is known that vectors of B1+ and B1- fields are directed perpendicularly with respect to the vector of B0 field (constant magnetic field directed along Z axis). At the same time, the arrows of H field in CST are directed perpendicularly with respect to rungs, i.e. perpendicularly with respect to the vector of B0 field.
I've attached the printscreens of H field, surface current, B1+ field and B1- field. I assume that B0 field is directed onto the positive direction of Z axis.
Kind regards,
Elnur
