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By Dr. Stefano Pacifici, Centro di Diagnostica per Immagini ‘Ecotomografia Medica S.r.l.’ – Unità di Diagnostica Senologica, Rome, Italy

improved the sensitivity of the method, especially in dense breasts, the number of false negatives (FN) is still high. This is largely due to the presence of dense tissue that may affect lesions conspicuity. The mammogram is in fact a ‘summation image’ that displays on a single plane a more or less visible representation of any structure crossed by the x-ray beam between input and output surfaces (figure 1). The theoretical solutions to the problem


exist with the main one being MRI. This is not the radical solution, however, because it is expensive, time-consuming and, in most cases, not available in the same department. What is needed instead is a solution

that is: A. Affordable (an add-on on the price of a mammogram) B. Fast (the radiologist must be able to perform the complementary examination immediately after evaluating the mammographic images)


espite the fact that direct digital mammography (FFDM - Full Field Digital Mammography) has

C. Practice (the examination should be performed in the same physical area by the same operators) D. Simple (a new method would require technicians and radiologists to learn new procedures for examination and assessment). The phenomena of summation and subtraction, potentially responsible for the production of false positive findings (FP) and for masking of true positive findings (TP), led Alessandro Vallebona to create and implement the ‘stratigraphy’ in 1930 (later referred to as ‘tomography’). It is a complementary radiodiagnostic technique aimed at reading analytical images, namely representative just of the structures including in the pre-selected layers of the concerned region. Such a technique was not without its critics, which include:  limited contrast resolution allowed by the intrinsic shading of the image  presence of parasitic shadows (i.e. background noise)  high total dose delivered in multiple sequential acquisitions of considered useful layers.

DIGITAL BREAST TOMOSYNTHESIS Thanks to the flat-panel technology, a re-interpretation in the digital key of Vallebona’s tomography has been proposed as a new tool for early detection: the DBT - Digital Breast Tomosynthesis. DBT is an imaging technique that allows a volumetric reconstruction of the whole breast from a finite number of low-dose two-dimensional projections obtained by different x-ray tube angles, with a geometric principle very similar to that applied in the stratigraphic technique (figure 2). In DBT the x-ray tube makes an arc, during which a series of images is aquired, each of which is delivered a dose equal to a fraction of that provided in a standard mammogram.During the acquisition, the detector element receives related information on each object volume element.The set of digital projections thus contains a complete structural information on all the object layers in the form of raw data.These are sent to a computer, where appropriate reconstruction algorithms will reconstruct the order and the correct

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