[Nescafe]

Hi,

I am posting this topic because I am super confused.

So from my understanding in MRI we are basically doing a NMR of the water molecules. Gadolinium has 7 unpaired electrons so it generates a strong and fluctuating magnetic field which can heavily impact the motion of water molecules. From my readings I am learning that it relaxes the waters by coordinating to them but I really do not understand the difference between T1 and T2 weighted images and the articles I have been reading throw these two around like salads. The other thing I am confused about is how Gadolinium has been used to image Brain. I mean how is it even capable of passing the Blood Brain Barrier? Is it not very hydrophilic? Also how does it help us get contrast picture of tumors is it because it is retained in the tumors more so because they are leaky and more penetrable?

I am generally confused on this topic so any advice is highly appreciated,

Nescafe. 

[Arkcon]

A quick Google led me to this Wikipedia topic:  http://en.wikipedia.org/wiki/MRI_contrast_agent , which says they use a chleated preparation of the gadolinium ion.  There are many things in your question: bio-availability, paramagnetism, NMR, and MRI, but the simple question is, experts find a way.

[curiouscat]

 The other thing I am confused about is how Gadolinium has been used to image Brain. I mean how is it even capable of passing the Blood Brain Barrier? Is it not very hydrophilic? Also how does it help us get contrast picture of tumors is it because it is retained in the tumors more so because they are leaky and more penetrable?

Are you sure they inject  Gadolinium neat? I doubt it.

Typically these atoms are attached to a ligand and it is the ligand that is capable of passing the barrier and the atom just hitches a ride. Also, the ligands are chosen such that they are ones uptaken selectively or more actively by the tumor type in question.

In general tumor cells grow and differentiate more rapidly I think than normal non-tumor cells which makes them liable to uptake a lot of metabolites much faster than the background. That helps too.

Maybe someone who knows more will chime in..

[vex]

There was just a talk on this at my school.

I'm not sure the difference between T1 and T2 relaxation times (must not have been paying that great of attention, ha), but the reason you can use gadolinium to image tumor cells is that the tumor cells don't have a blood-brain barrier. They just want a ton of blood so they can keep growing, so they aren't selective. Therefore, the tumor takes up the gallium and it shows up in the MRI, where the rest of the non-cancerous brain just looks grey because it hasn't taken up any gadolinium.