What is the definition of Ct value?

Question

What is the definition of Ct value?

Answer 1

Ct stands for Cycle threshold and it's a measure of the number of PCR cycles (in Real-time PCRs) needed to get a fluorescent signal.  In other words, it's how many times you need to run the PCR to get enough product.  It depends on how much DNA you began with.  If you started with a lot, then it takes fewer cycles to get the signal.