If i had breast cancer, mastectomy, and implant on left side, will mammograms be able to pick up new tumor in leftover tissue?

Not needed: Mastectomies, by definition, involve removal of (almost) all of the breat tissue present. While it is true that microscopic amounts of breast tissue can be left behind, this is not amenable to mammographic evaluation, regardless of whether a reconstruction was done. Careful physical examination remains the best way to screen for local cancer recurrence following a mastectomy.

Yes: Mammography would be useful. If questions arise MRI would be best but ultrasound would be useful.

Breast: I agree with both of the answers posted. I would say that it is difficult because each breast is different and the fat plan decreases as you get closer to the nipple are polar complex. If any event a mammogram is not needed after mastectomy and implant recon but can be used to evaluate the remaining tissue. Physical exam by the doctor is very important help guide any studies needed.