Magnetic Resonance Imagining - Essay Example

1. What are the names of the main rooms used in magnetic resonance imaging? 

The operator room, the technical room, and the magnet room 

1. List the major components inside the magnet and briefly describe their functions 

1. Transmitter coils work to excite the nuclear spin system when the receiver coils receive signals as MRI pulsation occurs. 

1. The receiver coils facilitate the optimization of SNR (signal-to-noise ratio). 

1. Radiofrequency coils have mainly two functions. One function of the coils is to broadcast radiofrequency waves, and the other one is to facilitate the reception of radio frequency signals. 

1. The gradient coil set encodes processional frequency with spatial data. It makes the information be in line with the excited radiofrequency. Also, it enables the display of images as opposed to NMR spectra.  

3. Describe the path of radiofrequency pulses through the units of the MRI instrument

The process of generating and receiving radiofrequency fields in the MRI instrument is comparable to the process involved in radio broadcasting, although in the former case an antenna responsive to low magnitude signals together with one that transmits high power is used. The MR signals pass through radiofrequency coils working in the near field and create fields that are transverse in orientation to the static field applied. 

4. What basic units do the MR signals pass through before arriving at the central computer?

The signals pass through the gradient coils, a receiver unit, and the transmitter coils. 

5. Why does a magnet need to be shimmed?  

To eliminate small impurities in the static magnetic field 

6. In a 3T MRI system that has just been passively shimmed, the variation of the resonance frequency of a small spherical sample filled with water varies from 150 Hz to 300Hz over the surface of a sphere of diameter 45cm. what is this variation in parts per million (ppm)? Is such a variation reasonable?

Shimming is done to remove field distortions and improve homogeneity. In this case, it is 4 parts per million Vrms before shimming will apply, which is reasonable. 

7. Above what field strength is it necessary to construct MR magnets from superconductors?     

Beyond 0.3T, a superconducting system is more ideal compared to electromagnets and permanent magnets.  

8. For Niobium Titanium (NbTi) superconducting wire, what are the values of the critical field strength and critical temperature above which the wire ceases to act as a superconductor?

Critical temperature – 4.2 Kelvins. Above this temperature, which is helium’s boiling point, the critical field strength would go below 10T and superconductivity would not apply due to the increase in resistance. 

9. As the magnetic field in which a superconducting wire resides, does its consequent current carrying capability increase or decrease? What would happen if the temperature is reduced simultaneously? 

The current-carrying capacity increases. If the temperature is lowered together with the immersed field, the ability to carry the current rises. 

10. What is the optimal separation for 2 current carrying circular loops of radius 20cm and each carrying 20amps, to ensure that the total magnetic field produced in a region enclosed by the two coils is as uniform as possible?

The magnetic field strength due to electric current flowing in a cable is a factor of the current carried, temperature, and the number of coils. In this case, critical strength would be about 0.5T and 20 Kelvins for temperature.  

Part 2 

1-MR gradient coils: action and performance  

 I am interested in researching how to optimally design MR gradient coils. This way, I will learn how to maximize coil performance and minimize costs associated with its design and functioning.  

2- RF resonators for MR applications  

 I wish to learn about the various applications of radiofrequency resonators in magnetic resonance imaging. More specifically, I am interested in learning how MRI can be used to visualize the distribution of resonators in the magnetic field. 

3-Peripheral Nerve Stimulation by MR gradient coils 

I wish to learn how MR gradient coils are applicable to the stimulation of body organs.