Digital X-Ray Tomosynthesis Current State Of The Art

Digital X-Ray Tomosynthesis Current State Of The Art-9
Such acquisition enables the visualization of a sequential set of thin sections of the breast, allowing overcomes the masking effect of overlapping fibroglandular tissue, improving carcinoma detection and reducing the number of false-positives [21].This technique showed better sensitivity and specificity compared to FFDM, especially for detection of non-calcified breast cancer [22] and it has been proven to be an efficient tool either in screening and diagnostic settings, since its introduction in the clinical setting after the approval by the Food and Drug Administration (FDA) in 2011.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.

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The introduction of full field digital mammography (FFDM) has also allowed the development of new diagnostic breast techniques like digital breast tomosynthesis (DBT).

DBT is an X-ray mammography technique where multiple low-dose projection images of the breast are acquired moving the X-ray tube in an arc over a limited angular range, and subsequently reconstructed in multiple tomographic images creating a pseudo-3D mammogram [20, 21].

Recent studies showed that the screening performances of SM plus DBT are not inferior to those achieved with FFDM plus DBT [46] and it is likely that SM will replace FFDM in the near future, with a remarkable dose reduction.

The interpretation of a DBT examination consists of the evaluation of the 2D mammography plus the analysis of the DBT dataset, with a variable number of slices, depending on patient’s breast thickness: the largest number of images to read in comparison to the only FFDM causes an increase of the interpretation time.

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%.

MGD is also strongly influenced by some characteristics of the DBT system such as detection process (direct/indirect), scan angle, number of projections, tube motion and reconstruction algorithms, with a large variability among the investigated systems [35], but in any case the dose remains below the FFDM threshold limits established by the European Reference Organization for Quality Assured Breast Screening and Diagnostic Service [36].

The DBT examination may be performed using different combinations [21, 37], including 2-view DBT plus 2-view FFDM or single-view DBT plus single-view FFDM [38, 39], and varies among vendors; the use of a single-view DBT reduces the MGD [39-42].

The breast is compressed and held between the compression paddle and the detector, as in performing FFDM.

The x-ray tube moves across a limited arc above the breast, acquiring a sequence of low-dose exposures at preset intervals, each from a different angle, resulting in a series of projection images [24-26].

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