Tomosynthesis image : Determining orientation

Question

I am trying to find the orientation (head-feet, lateral-medial) of Digital Breast Tomosynthesis multi-frame DICOM images. Anyone can tell me how to achieve this? Basically which DICOM tags I should check?

Answer 1

If I understand your question correctly, the patient orientation on the image is determined solely by the PatientOrientation Tag (0x0020, 0x0020). For breast imagery, this tag should tell you where the chest wall and pectoral muscle (or what direction the patient head) are on the image.

Tag    Chest wall location on the image
A\*      Left
P\*      Right

Tag       Pectoral muscle location on the image
*\*F       Top
*\*H       Bottom

I would be surprised to see any mammo image have anything other than A (Anterior - toward the front) or P (Posterior - toward the back) in the first value of this tag. The second value is a little more subtle. In a CC view, this value includes either L (patient's left) or R (patient's right). On a left breast, L would mean moving away from the cleavage and R is toward the cleavage. On a right breast, its the other way around. On ML and MLO views, you often have an F (foot) or H (head) that generally points the way to the pectoral muscle.

On a Tomo image, hopefully the vendor has already corrected the slices for you so that they all have the same PatientOrientation tag. I hope they are not just throwing the raw pixel dumps at you with different orientation. If they did that, each frame should have its own PatientOrientation tag.