When a mamogram is done it can be read by a technician, checked by software & scanned by compturized scanner. If it is misread which one is responsible.
The answer is really none of these, although "technician" comes the closest.
According to "The Mammography Quality Standards Act: Misread Mammograms, Malpractice, and The Politics of Regulation" the true problem lies with the way the radiologists interprets the results.
Radiologists receive 60 hours of training before being allowed to assess mamograms independently but this seems to not be sufficeint:
"the most prevalent issue associated with their treatment of patients was their tendency to misread mammograms. Of the number of claims against radiologists, 75.2 percent fell into the class of misread mammograms."