Prostate - do you have to wait 30 days for MRI after needle biopsy out of 12 biopsies, 3 came back positive, 6, 6, and 7. So they said it's a 7 but want to wait 30 days for mri

It. It is best to wait about a month after the biopsy before having an mri. This is because there can be bleeding or other changes in the prostate after the biopsy that can make it difficult to get accurate images of the prostate. These changes may obscure or mimic cancer and the MRI might not be interpretable. The biopsy changes and bleeding are usually gone after 4 weeks or so.
Yes, wait. Sometimes small amounts of bleeding in the prostate gland after the biopsy. It is beneficial to wait 30 days in order for the blood to resolve and allow a more diagnostic study. The main thing the MRI is looking for is whether there is "extra-capsular" spread of tumor (tumor outside of the gland) which can change treatment from surgery to radiation. Please refer to your urologist.