6.1 FFDM-DR/2D, DBT/3D, and Synthesized Imaging

6.1 FFDM-DR/2D, DBT/3D, and Synthesized Imaging

The ARRT Mammography content specifications that took effect September 1, 2025 list three acquisition types under Image Production: full-field digital mammography-direct radiography (FFDM-DR/2D), digital breast tomosynthesis (DBT/3D), and synthesized imaging. Those labels are not interchangeable marketing names. Each one describes a different way the unit collects data, a different exposure pattern, and a different set of images the interpreting physician will hang. Synthesized imaging was added in 2025 because reconstructing a 2D overview from tomosynthesis is now routine mammographer work, not a rare vendor extra.

Why the detector is DR, not CR

Direct radiography (DR) in mammography means a flat-panel detector built into the Bucky. After exposure, the image is available at the acquisition workstation (AWS) within seconds. There is no cassette to pull, no photostimulable plate to scan, and no reader in another room.

Computed radiography (CR) used removable phosphor plates. ARRT removed full-field digital mammography-computed radiography (FFDM-CR) from the Mammography content specifications in 2017. For this exam, do not treat CR as a current mammography acquisition pathway. If a stem mentions plates, cassettes, or a plate reader as the mammography detector, it is describing obsolete workflow, not FFDM-DR.

Two conversion designs still sit inside DR panels:

Both are FFDM-DR. Direct versus indirect is a receptor-design distinction, not a reason to call one system CR.

FFDM-DR/2D produces a conventional projection mammogram: one exposure per view, the entire breast on one detector, overlapping tissues superimposed along the beam. That native 2D image is still the comparison standard many radiologists want hanging next to older FFDM priors, which is exactly why synthesized 2D was invented.

Digital breast tomosynthesis (DBT/3D)

In DBT, the compressed breast stays still while the x-ray tube travels through a limited arc. The unit records a series of low-dose projection images from slightly different angles. Reconstruction software then builds a stack of planes through the breast—thin slices, often about 1 mm thick depending on the vendor.

The clinical point is reduced overlapping tissue. In 2D, a dense island of fibroglandular tissue can hide a mass or mimic one. In DBT, the radiologist pages through planes and watches superimposed structures separate. That is why tomosynthesis can improve lesion conspicuity in dense breasts and can lower unnecessary screening recalls—without changing the fact that positioning, compression, and posterior-tissue inclusion still decide whether the dataset is usable.

DBT is not CT of the breast. The sweep angle is limited (vendor-dependent, commonly on the order of 15 to 50 degrees), in-plane spatial resolution is high, and depth resolution is coarser. Exam items that treat DBT as a fully sampled 3D CT volume are wrong. It is tomosynthesis: angular sampling plus reconstruction of planes.

Synthesized imaging — why ARRT added it in 2025

Synthesized 2D (vendor names such as C-View and similar reconstructions from other manufacturers) is a 2D image built from the DBT dataset. The algorithm collapses tomosynthesis information into a single projection-like image that can be hung like a conventional craniocaudal (CC) or mediolateral oblique (MLO) view.

The operational reason it matters: a separate native 2D FFDM exposure may be avoided. Older combo-mode protocols acquired both a conventional 2D FFDM image and a DBT sweep under the same compression. The patient received the 2D dose plus the DBT dose. With synthesized 2D, the facility can acquire DBT only and still give the radiologist a 2D-style overview for comparison with prior FFDM exams.

ARRT added synthesized imaging to the September 1, 2025 specifications because the practice analysis found that generating and sending synthesized 2D is now a standard task. You are expected to know what it is, what it is made from, and why it changes acquisition choices—not to recite a vendor's reconstruction algorithm.

Combo-mode versus DBT plus synthesized 2D

Same compression still matters. If the patient is released and recompressed between 2D and DBT, the datasets no longer match geometrically, and synthesized 2D cannot stand in for a 2D image that was never acquired in that compression.

Spot compression, magnification, and some implant-displaced or diagnostic views may still be acquired as 2D FFDM-DR even in a tomosynthesis department. Synthesized 2D is a product of a DBT acquisition. It is not a substitute for every 2D technique, and it is not computer-aided detection (CAD).

What you tell the patient versus what you select on the console

Patients hear screening mammogram, 3D mammogram, or tomosynthesis. They do not need product names. A clear explanation is: the tube moves in a small arc and the computer builds thin layers so overlapping tissue is less likely to hide or mimic a finding. If the facility uses synthesized 2D, add that those 3D pictures are also used to create a familiar 2D picture, so a second 2D exposure is often unnecessary.

If last year's exam was 2D only and today's protocol is DBT with synthesized 2D, the extra time is the tube arc, not a second native 2D shot. If the facility still uses combo-mode, say that both a conventional picture and the 3D sweep are taken while she stays compressed—so she should expect a slightly longer compression hold and a higher combined dose than DBT-plus-synthesized.

At the console you are choosing an acquisition protocol: 2D DR, combo, or DBT with synthesized 2D, plus laterality, view, implant, magnification, or tomosynthesis-compatible paddle settings. That choice must match the order, the facility's screening versus diagnostic algorithm, and whether priors are 2D or DBT. Sending only DBT slices when the hanging protocol expects a synthesized 2D—or the reverse—is an informatics failure, not a positioning success.

Exam trap: synthesized 2D is not a second physical exposure. Combo-mode still uses a real second 2D exposure. DBT planes reduce overlap; they do not excuse a missed inframammary fold or a detector that was not flush to the chest wall.