Thermal noise calculation method for precise estimation of the signal-to-noise ratio of ultra-low-field MRI with an atomic magnetometer

► We proposed new method to calculate thermal noise of MR model. ► Noise is calculated as the variance of noise magnetic flux generated by sample. ► Proposed method is applicable to the MR model using atomic magnetometer as a sensor. ► By increasing NEX, enough SNR could be obtained with MRI using atomic magnetometer.