MRI

MY husband just turned 70 last week. In 2009, his PSA was 10+ and last year up to 18.8. He has a very big prostate---140 and his PSA density is 1.34 (which is a good number. ) When his PSA jumped to 18.8 last year, his urologist advised him to take MRI and found a small suspicious level 5 spot. He then had a fusion biopsy, the result came out negative, no cancer found. ( only some fat....) The doctor said he was not happy because there was no glands and tissues in the five sample he took. We then go to another urologist. The second urologist suggested my husband to take another MRI and then fusion biopsy again. I asked this doctor since the suspicious spot was smaller than two rice big and the previous doctor did 5 biopsy needles, if there is cancer, how can it not be detected? He said that the urologist might miss the spot. My question is: under 3T MRI and a ultrasound biopsy, how can it be missed? Is it possible? Anyone has the same experience ? Any suggestion or advice are mostly welcome. TIA! Btw, he schedules the second MRI in early March. I am very nervous.