How strongly an agent speeds up relaxation
A contrast agent works by making the signal of nearby water relax faster. Relaxivity is the measure of how effective an agent is: the increase in the relaxation rate for each unit of concentration. It is read from the slope of the relaxation rate plotted against concentration, and it is the number that links a development candidate or a production batch to its performance in imaging.
Where it is used
- Gadolinium and manganese complexes
- Iron oxide and other magnetic nanoparticles
- Formulations of agents, coated and functionalised particles, and production batches
Typical tasks are ranking candidates in development, checking that batches meet the same relaxivity, following relaxivity during stability studies, and studying how a coating, a particle size, the temperature or the surrounding medium changes it.
A dilution series and a straight line
A series of dilutions is prepared, T1 and T2 are measured for each, and the rates are plotted against concentration. The slope is the relaxivity, and agents or batches can be compared directly.
What it adds
- Small sample volumes and a temperature-controlled holder, for example at body temperature
- Results in the same quantities that imaging uses: relaxation times
- No cryogens, and no time booked on an imaging scanner
- Practical for screening many candidates or checking many batches
Points that matter in practice
- Relaxivity depends on the magnetic field strength, so the instrument should be chosen with the target application in mind. Time-domain instruments exist for several field strengths
- The medium matters. Values in water can differ from values in serum or plasma
- Stay within the range where the plot is a straight line. Particles can aggregate at high concentration
- The method ranks and checks agents. It does not replace imaging studies, and any use for batch release has to be validated
From your candidates to a routine method
Send or bring your candidates or batches. MSY Consulting runs feasibility measurements, helps you choose conditions that match your application, and trains your team until the method is part of your routine.
Let's talk about your application
Send an email describing your instrument and your application, and you will get a reply.
contact@msyconsulting.euMSY CONSULTING SAS · Wissembourg, France · LinkedIn