I am looking to characterize a contrast agent I'm developing for relaxivity. At my university, I have access to a Esaote Vet-MR Grande. Is it possible to get relaxation time measurements from this machine or do you need a machine that is specialized for quantified MRI? If it is possible, how? I've found various protocols giving parameters for machine settings but we are new to this and need help starting at the very beginning if it is possible. Thanks!
I don't know the specific system at your site, so I can make only some general suggestions:
- You could search for any existing protocols on your system that include descriptions like "T1 mapping", "relaxometry", "R1 mapping", etc. (Or, if you are interested in r2 instead of r1, then of course check for T2 instead of T1 etc.).
- If there are no such protocols, you could work with more basic pulse sequences, e.g. an inversion-recovery spin-echo sequence (IR-SE) for T1-weighted MRI. You could acquire image data with different inversion times (TI) and calculate T1 maps from these images. Alternatively, you could use a spoiled gradient-echo pulse sequence and acquire data with different flip angles (the so-called variable flip-angle (VFA) method). For T2, you would use a spin-echo sequence with different echo times (TE).
- If you are interested in the relaxivity, you'll need T1 data for several different concentrations of your contrast agent.
- There are at least 2 related questions here: https://www.researchgate.net/post/How-can-I-measure-relaxivities-of-mri-constrast-agents and https://www.researchgate.net/post/How-can-I-measure-the-relaxation-time-T1-and-T2-of-sample-in-the-form-of-nanoparticles-for-contrast-agents-application
I would start by reaching out to the vendor of the system, specifically their applications group. Generally, any NMR/MRI system should allow the measurement of T1 and T2, it is a question of finding the easiest way with the given hardware/software available.
In the mid-80's we made measurements on early clinical 1.5T systems by using spectroscopy hardware and software. Somethings to be aware of on a clinical system that is set up to use automatic system adjustments:
1) make sure that the only acquisition parameter that are changing is the delay time you are changing for the time points.
2) make sure that any post-acquisition automatic scaling is turned off.
Even without any programming you can get T1 measurements using saturation recovery. This is the LEAST effective method but it can be done even if your system doesnt have a inversion recover sequence.
Using a Gradient echo sequence - you increment TR in a simple series of scans. You will need to turn off Auto leveling in your out put and manually set your receiver gain but this can be done. Then you acquire a number of scans with TR incremented in like something like a power of 2 series
(10ms, 20ms, 40ms, 80ms, 160ms, 320ms, etc). You can either perform the log-lin fits to get the T1 or use the plugin that is available for ImageJ.
You probably have a spin-echo sequence in your system. Use a long TR (after you determine it above). And increment a series of scans in TE similarly described. It won't be as accurate as a multi-echo technique but better then none. Again you can do the fits yourself or ImageJ.
No autoscaling. Must be absolute value. And this will work for the complex modulus images your scanner will produce..
Hope that helps.
- Badges
- Science method