X-RAY TOMOSYNTHESIS: A REVIEW OF ITS USE FOR BREAST AND CHEST IMAGING
Anders Tingberg1,2,* 1 Department of Radiation Physics, Malmo University Hospital, Malmo, Sweden ¨ ¨ 2 Department of Medical Radiation Physics, Lund University, Malmo University Hospital,Malmo Sweden ¨ ¨,
Downloaded from rpd.oxfordjournals.org at Pontificia Universidad Cat?lica de Chile on November 11, 2010
*Corresponding author: email@example.com
Tomosynthesis is a three-dimensional imaging technique based on the reconstruction of several planar radiographs. During the image acquisition in tomosynthesis, the X-ray tube moves around the detector which is oftenstationary, and a number of projection images are taken from different angles. Individual slices from the reconstructed volume can be studied. With the effective reduction of the visibility of the overlapping normal tissue, the detection of pathological lesions is improved when compared with projection radiography. Up to now, tomosynthesis has mainly been used for breast and chest examinations and, tosome extent, also for orthopaedic, angiographic and dental investigations. For chest, tomosynthesis is used as an alternative to computed tomography with signiﬁcantly lower cost and radiation dose to the patient. Breast tomosynthesis has, in several studies, proved to be an effective tool for improving detection of breast lesions. As tomosynthesis has many properties that make it suitable as amodality for screening, including good diagnostic performance, short examination time and low radiation dose, it is a strong competitor to the current gold standard breast screening modality, i.e. mammography. In this paper, the principles of tomosynthesis will be presented as well as a few clinical studies showing the potential role of tomosynthesis in clinical routine examinations.
INTRODUCTIONThe term ‘tomosynthesis’ was deﬁned by Grant in 1972(1) by combining the two Greek words ‘tomos’—a section, a slice or a cutting—and ‘synthesis’—a process which combines together two or more pre-existing elements, resulting in the formation of something new. Early experiments(2), for example with X-ray ﬁlms(1,3), and with image intensiﬁers(4), showed proof of concept. However, it was not until thelast decade that tomosynthesis developed from being a technique used in the laboratory settings, into being implemented in commercial products. The number of scientiﬁc papers indexed in PubMed on tomosynthesis (Figure 1, accessed on 16 December 2009) is an indicator of how the interest has increased over the years. All papers published or to be published in 2009 have not yet been registered. Since2004, breast tomosynthesis (BT) has dominated the scientiﬁc publications in this ﬁeld. Anatomical background Even though mammography is the gold standard for breast cancer screening, mammography has relatively low sensitivity. Laming and Warren(5) reported a sensitivity of 70–85 %, and it has been shown that a majority of the missed cancers are in dense breasts(6,7). For chest radiography, thesituation is similar; for the detection of nodules of different sizes, Vikgren et al. (8) reported a 16 % lesion localisation fraction, LLF(9) (¼ fraction correctly located lesions) for all nodule sizes in the study. For nodules .8 mm in size,
the LLF was around 50 %, but for nodules ,8 mm in size the LLF was only around 5 %. In conventional projection radiography, the image of a three-dimensional(3D) object is projected onto a two-dimensional (2D) plane. Organs and tissue along the trajectories of the X-ray beam are superimposed, and this results in the loss of ‘depth vision’. The normal anatomical background may hide a lesion. In fact, it has been shown that the anatomical background is the main reason for nondetection of tumours in mammography(10) and chest radiography(11), and thus...