NMR and MRI Theory: Understanding Relaxivity for Contrast in Imaging

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In summary, the conversation discusses an experiment on nuclear magnetic resonance and the effects of proton concentration on spin-lattice and spin-spin relaxation times. The experiment used two sets of ionic solutions and the results will be analyzed by looking at T1 and T2 vs. concentration levels. The main question revolves around the importance of relaxivity and sources for MRI relaxivity theory are requested. The conversation concludes with a summary of how MRI imaging uses voxels and the relationship between T1 and T2 relaxation times and pixel intensity.
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NMR and MRI -- questions!

I'm currently doing an experiment on nuclear magnetic resonance for an undergrad physics lab. Our experiment was based around determining the effects of proton concentration on spin-lattice and spin-spin relaxation times. We used two separate sets of ionic solutions (cupric sulfate solutions and ferric nitrate solutions.)

To analyze the results I'll be looking at T1 and T2 vs. concentration level as well as the supposed 1/T1 1/T2 relaxivity vs concentration. My problem is I can find little to no theory whatsoever that describes to me in detail the importance of relaxivity. I'm aware that relaxivity affects contrast in MRI images and to what extent it can do so, however I'm not sure about what makes a substance good for T2 imaging versus good for T1 imaging?

I guess in short, other than that main question at the end, I'm looking for sources about MRI relaxivity theory. Any help would be greatly appreciated.

EDIT: Sorry about posting this in the main forum. Since I was just looking for sources on MRI theory, I thought it'd be just as fine to post in the general forum.
 
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Found the answer to my own question.. may as well post it in case someone else is needing the same help one day.

MRI imaging uses voxels that are governed by an intensity equation based off of T1 and T2 relaxation times. For 2d images, the pixel intensity is related as:

[tex] I = \kappa \rho(x,y) (1-exp({\frac{-\tau_R}{T_1}})) exp({\frac{-\tau_e}{T2}}}) [/tex]

Where [tex]\tau_R[/tex] and [tex]\tau_e[/tex] are the repetition time and echo pulse time respectively, [tex]\rho(x,y)[/tex] is the proton density w.r.t 2 dimensions, and [tex]\kappa[/tex] is a proportionality (normalization) constant.

As can be seen shortening T1 will increase pixel intensity, where as shortening T2 will decrease pixel intensity.. this naturally leads to T1 and T2-weighted imaging in MRI application.

Gyah, I hope that helps someone someday. Ah. For sources, try and find any modern book on MRI technology.. NMR books generally don't mention this stuff.
 
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Related to NMR and MRI Theory: Understanding Relaxivity for Contrast in Imaging

1. What is the difference between NMR and MRI?

NMR (Nuclear Magnetic Resonance) and MRI (Magnetic Resonance Imaging) are both techniques that use magnetic fields and radio waves to produce images of the body. The main difference between the two is that NMR is primarily used for analyzing the chemical structure of molecules, while MRI is used for medical imaging. Additionally, NMR uses a stronger magnetic field and different radio frequencies compared to MRI, which allows for more detailed information about the molecules being studied.

2. How does NMR and MRI work?

NMR and MRI both work by utilizing the phenomenon of nuclear magnetic resonance. This is where the nuclei of certain atoms, such as hydrogen, can absorb and emit electromagnetic radiation at specific frequencies when placed in a magnetic field. In NMR, this is used to analyze the chemical structure of molecules by measuring the frequencies at which the nuclei resonate. In MRI, this is used to produce images of the body by measuring the signals emitted by the hydrogen atoms in the body's tissues.

3. What are the main applications of NMR?

NMR has many applications in various fields such as chemistry, biochemistry, and materials science. In chemistry, it is used to determine the structure and composition of molecules, as well as study their dynamics and interactions. In biochemistry, it is used to analyze the structure and function of proteins and other biomolecules. In materials science, it is used to study the properties of materials at the atomic level.

4. Are there any risks associated with MRI?

MRI is considered a safe imaging technique and does not use ionizing radiation like X-rays. However, there are potential risks associated with MRI such as the presence of metal objects in the body, which can be pulled towards the strong magnetic field of the machine. It is important to inform the MRI technician if you have any metal implants, devices, or objects in your body before undergoing an MRI scan.

5. How is MRI used in medical diagnosis?

MRI is a vital tool in medical diagnosis as it can produce highly detailed images of the body's tissues and organs. These images can help doctors detect various health conditions, such as tumors, injuries, and abnormalities, and determine the best course of treatment. MRI is commonly used to diagnose conditions affecting the brain, spine, joints, and soft tissues, and is also used to monitor the progression of diseases and the effectiveness of treatments.

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