Digital X-Ray Tomosynthesis Current State Of The Art

DBT images require a large amount of storage space, especially in screening programs, due to the high numbers of participating women and considering that storage requirements will increase with time as more patients will have previous DBT studies for comparison.

DBT image files size are 10–20 times that of 2D conventional mammography; the number of slices for each DBT set depends on the breast thickness, but an average combined DBT/FFDM study is about 1GB of data, which could be reduced to approximately 250 MB if the DBT images are stored with a 4:1 reversible (lossless) compression [40, 55].

DBT images are low-dose, with a mean glandular doses (MGD) of an average-sized breasts of about 2.3 m Gy per view, which is about 1 to 1.5-times higher than the dose per view for FFDM [32]; the use in combination of FFDM and DBT doubles approximately the radiation dose [33], therefore, the radiation exposure is one of the main concerns of DBT, especially when using DBT in any program of population screening, also considering that radiation dose is cumulative over time.

In a phantom study on radiation exposure from DBT, Feng and Sechopoulos [34] demonstrated a MGD range of 0.309 - 5.26 m Gy for a single caudocranial view acquisition in FFDM mode and of 0.657 - 3.52 m Gy for the DBT mode acquisition; for a breast with a compressed thickness of 5 cm and 50% glandular fraction, the MGD of DBT was only 8% higher than that of FFDM acquisition (1.30 and 1.20 m Gy, respectively, per view), while, for a breast with a compressed thickness of 6 cm and glandular fraction of 14.3%, the DBT resulted in a 83% higher MGD compared to FFDM (2.12 versus 1.16 m Gy): therefore the range of radiation dose is highly variable, depending on breast size and composition.

Studies have shown that interpretation time for 2D plus DBT is about twice that of conventional mammography [47].

Skaane [49] described an increase in reading time of about 33%.

This review aims at describing current DBT technique, analyzing DBT in clinical practice and providing an overview of published studies on clinical experience with DBT in the screening and diagnostic settings.

Screening asymptomatic women for breast cancer with mammography can reduce cancer-related mortality up to 30%, since breast carcinoma is a progressive disease and early detection enables better prognosis [1-7].

The angle range (from 15 to 50° [20]), the tube motion, the arc length and the time needed to obtain a whole set of projection images vary among different manufacturers [27, 28] (Table 1). Characteristics of Clinical DBT Systems FBP = Filtered Back Projections ST = Standard Mode HR = High Resolution Mode a Se = amorphous selenium a Si/Csl = amorphous silicon/cesium iodine *Continuous scanning mode with short pulses of radiation In the post processing, raw data from DBT projections can be reconstructed to obtain a series of images of the whole breast, typically with 1 mm spacing, parallel to the DBT platform plane [29]: this process allows a pseudo-3D evaluation of breast tissue distribution.

Due to the limited angle of the projections, DBT has a high spatial resolution in the plane parallel to the detector, but a lower spatial resolution in the perpendicular direction [28]; however, spatial resolution in the depth direction is sufficient to reduce the effects of breast tissue overlapping [29, 30].

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