Spiral Inductor Q calculation

Hello. I have simulated a spiral inductor in RF mode Momentum and i have a question regarding Q. I use 2 definitions/methods to calculate it, the one concerning the resonant frequency and the 3 dB bandwidth and the other with the imaginary over real part of the impedance. While the 2 methods agree very well for low frequencies, for relatively high freqs the Im/Re method gives a lower Q than the f/BW method. Can you please explain why? Also what is the range of validity of these 2 expressions?
Thank you in advance,
George

Because of skindepth effect and Eddy currents effects are not included in calculations.

In low frequency, PCB parasitics effect will be low.
But in high frequency, PCB parasitics effect will be high.
So calculate your Q based on Reactance/Resistance (Im/Re).