Digital Mammography

Is a low dose Xray of the breast.  This is primary method used for breast screening.  Both Breast Screening facilities in Wellington and Pacific Radiology offer 3D mammography (tomosynthesis).  This is helpful in women with dense breast tissue or when mammogram has detected an abnormality.  There is a slightly higher dose of radiation associated with tomosynthesis.  

A screening mammogram is performed as part of routine screening when there are no abnormalities felt.   A diagnostic mammogram is performed when an abnormality is detected on examination.

Ultrasound

It uses sound waves to image the breast tissue and it is not substitute for mammography.  It is not helpful in diagnosing calcifications.  

MRI

It is only recommended in patients with high risk of breast cancer (usually due to family history or genetic predisposition).  In a patient with new diagnosis of breast cancer it  may be helpful in assessing the extent of the disease (especially in case of lobular cancer or when there is discrepancy in extent on mammogram and ultrasound).  
MRI of the breast is associated with 10-20% of false positive (false alarm) rate  - when MRI shows something suspicious and on other imaging and especially biopsy it proves to be benign.  The safety of Gadolinium, a contrast agent used in breast MRI, has been called into question, but there is a limited information about this.