I have an MR Dicom file having values of repetition time, echo time, Inversion time, flip angle, etc. I want to calculate T1 and T2 from this Dicom file. Is there any way to calculate this from the Dicom file or there any software to do T1 and T2 map from the Dicom file?
Prashant Kharey , your question could be referred to quantitative MR imaging. Based on the principle of MR imaging, you could calculate T1, T2, T2* and Proton density. Generally, MR signal S follows the equation, S = S0 ( 1 - exp(-TR/T1) ) exp (-TE/T2) where S0 stands proton density. You could control TR (repetion time) and TE (echo time). For example, you could freeze TR, and tune TE several times, based on acquired images, you could find the signal should be S'= C (-TE/T2). Using signal fitting, you could get T2. In a similar way, you freeze TE and tune TR several times, you could get T1. For full details, please refer to some "quantitative MR imaging", such as " Principles of Quantitative MR Imaging with Illustrated Review of Applicable Modular Pulse Diagrams " or Dr. E Mark Haacke's books. I hope it could help.
The short answer is that you can not determine T1 or T2 from a single image.
Correct measurement of T1 require that the delay be at least 5 times the length of the longest T1 that you are measuring, since this is quite a time penalty, most T1 measurements likely slightly under reporting the true T1.
Thank you @ William sir...
Sir, I have different concentrations of some samples, If I want to check the T1 or T2 relaxation times. I should take the range of (TR/TE) values at each concentration for the measurements or can take T1 or T2 images of different conc. at the single TR & TE value ?
like for each conc. TR= x,yz & TE= a
OR TR= x & TE= a would be sufficient ?
Hi Prashant,
In theory you could do it either way (I once had a phantom with 6 small chambers with solutions of varied T1 and T2). Experimentally it is much easier to deal with one solution at a time.
I am not sure of the best on-line resource to recommend. Wikipedia looks pretty solid on the subject https://en.wikipedia.org/wiki/Relaxation_(NMR). You should also look at the references and the Spin-Spin and Spin-Lattice links.
Good Luck.
What maximum concentration of magnetic nanoparticles (in phantom) I can try for contrast measurements ??
Hi Prashant,
If there are multiple ions in the solution, you might find some complex relationships. You will have search the literature for work similar to yours, or start will low concentrations and titrate up.
Cheers,
Bill
Why generally iron oxide reduce T2 signals while Gadolinium T1?
Also, In some literature, it is reported that both, iron oxide and gadolinium work as dual T1 and T2. What is the basic behind this?
Here is a simplistic answer. The detailed math can likely be found in Abragam - "The Principles of Nuclear Magnetism" if you can find a copy. A remarkable book written in 1961.
T1 contrast if by transfer of energy from the agent to water in rapid exchange with the exogenous paramagnetic metal ion complexes.
When the concentration of the ion gets high enough the "large" (this is a relative term) anisotropic (magnetic) susceptibility causes local magnetic field gradients. These gradients (small compared to the magnetic field or the magnetic field gradients used to create the image), dephase the transverse magnetization therefore changing (shortening) the T2 (often noted as T2*).
Liver relaxation times are interesting due to the Iron in that tissue.
I have prepared six phantoms for MRI (one without contrast agent and other with increasing concentrations of agent) and acquired T1 (at different TR and fix TE) and T2 (at fixing TR and different TE) -weighted images and can see the intensity difference between them. Now, I want to calculate T1 and T2 relaxation time from these Images using the equations, S = S0 ( 1 - exp(-TR/T1) ) and
S = S0 (exp (-TE/T2) ). I got stuck at this step. I have some confusion in solving these. It would be great help If someone can help regarding this.
I want to know:
1. Can I do this calculation by opening these images on Image J software?
2. If yes, then to obtain the intensities (S &S0), I have to choose an ROI on phantoms and measure the pixel by pixel or average Intensity of that region?
3. or how to get the value of S & S0 from these images on Image J to further calculate T1 and T2?
4. Also, Is S0 the value of the intensity of sample with no contrast agent?
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