Elsevier

The Breast

Volume 24, Issue 2, April 2015, Pages 93-99
The Breast

Review
Review of radiation dose estimates in digital breast tomosynthesis relative to those in two-view full-field digital mammography

https://doi.org/10.1016/j.breast.2014.12.002Get rights and content

Abstract

We examined how radiation dose levels in digital breast tomosynthesis (DBT) differ from those used in 2-view full-field digital mammography (FFDM).

Acquisition parameter settings and information on the average absorbed dose to the glandular tissues within the breasts were reviewed based on clinical studies that evaluated DBT and FFDM. Dose ratios (DDBT/DFFDM) were derived from imaging protocols, which included tomosynthesis in 1- or 2-views alone, and as an adjunct technique to FFDM.

Stand-alone DBT was associated with a much lower to a slightly higher radiation dose compared to that of comparable FFDM units, as summarized in dose ratio ranges of 0.34–1.0 for 1-view DBT, and 0.68–1.17 for 2-view DBT. One of the lowest reported dose estimates was obtained using a photon-counting DBT unit (avg. 0.70 mGy/scan; range: 0.28–1.26 mGy). Breast doses for DBT combined with FFDM are summarized in dose ratio ranges of 1.03–1.5 for 1-view DBT plus FFDM, and 2.0–2.23 for 2-view DBT plus FFDM. In the latter of these settings, the dose was reduced by ∼45% when 2D-views, reconstructed from the DBT images (“synthetic 2D images”), were used as a substitute for FFDM.

Stand-alone DBT operated at lower to slightly higher radiation doses in comparison to FFDM. For DBT combined with FFDM, radiation doses were elevated, at maximum by a factor ∼2 1/4 of that of FFDM alone. In this setting, a replacement of FFDM with synthetic 2D-views reduced the breast dose approximately by half, which has substantial implications for population screening programs.

Introduction

Digital breast tomosynthesis (DBT) has been shown to improve mammographic accuracy [1], [2], [3], [4], [5] and has emerged as a feasible replacement or adjunct technology to full-field digital mammography (FFDM). DBT reconstruction results in pseudo-tomographic images with partial blurring of features outside the selected plane, resulting in a significant reduction of the overlapping tissue effect present in conventional mammography. DBT is increasingly being used as a diagnostic imaging device, is used for screening in some settings in North America and is also being evaluated for population-based screening programs in many countries. Initial results from screening trials have been promising. Increase in breast cancer detection rates of 10%–53% has been achieved often at recall rates reduced by 20%–59% relative to FFDM [1], [6], [7], [8], [9], [10]. The additional breast cancers have been found in patients of different ages and breast density types, implying a potentially broad role for DBT. A high proportion of the DBT-detected cancers have been reported to be invasive carcinomas, which also indicates a potential impact for DBT in mammography screening.

In DBT, the X-ray tube rotates over a limited angular range and a low dose exposure of the compressed breast is acquired every few degrees. The average absorbed dose to the glandular tissues (AGD) is the summation of absorbed doses in the fibro-glandular tissue of the breast from all the multiple low-dose projection images. The concept of low-dose imaging in tomosynthesis has been made feasible due to the development of digital detectors with rapid read-out capabilities, high dose efficiency (high detector quantum efficiency; DQE) and low noise. The projection images become clinically useful as the reconstructed image information is additive. Tomosynthesis imaging includes multiple parameters that may influence the resulting breast dose. The angular range and number of exposures acquired during a scan are specific to the design of a system and thus these parameters are the same across acquisitions for a particular unit. Different manufacturers of DBT units have adopted quite different settings for these parameters, which are also associated with the detector type used and its design, and whether it is stationary or movable. Typically, the number of images acquired ranges from approximately 10 to 25, whereas the angle ranges from about 10 to 50° [11]. The tube loading, voltage and, in some cases, the anode/filter combination are, as in mammography, parameters, which are specific for the individual breast. In clinical units, these parameters are determined by the automatic exposure control (AEC) according to the characteristics of the imaged breast (e.g. breast thickness, glandular composition) so they will vary between acquisitions. In early clinical tomosynthesis studies, before AEC was implemented, the radiographer set these parameters manually using a technique chart. In DBT, the dosimetric effects of using different combinations of acquisition parameters are relatively well known [12], [13], [14], [15]. As the female breast is a radiosensitive organ and because tomosynthesis has been introduced into the screening setting, the radiation absorbed dose to the breast is of special concern. Diagnostic Reference levels (DRLs) were introduced by the International Commission on Radiological Protection (ICRP) as a practical guidance in the management of patient doses in radiology [16], [17]. In North America, FDA standards are outlined in the Mammography Quality Standard Act (MQSA), which set a breast dose restriction of 3 mGy per acquisition of the American College of Radiology (ACR) phantom [18]. To ensure that patient doses in tomosynthesis are within established recommendations or limits, similar absorbed dose levels should be pursued as is currently used in FFDM, although this should not compromise any benefit in clinical performance.

The purpose of this paper is to review and summarize absorbed doses reported in clinical studies using DBT and FFDM and describe the dose contribution from DBT relative that from FFDM.

Section snippets

Review of dose settings and dose estimates

A literature search was performed in reports of clinical studies on breast cancer detection comparing tomosynthesis and full-field digital mammography (FFDM), and which included absorbed dose estimates at FFDM and DBT using equipment developed by different manufacturers and thus of various designs (PubMed search: April 2008 to August 2014; literature search was performed by TS). Information was extracted on how patient-specific acquisition parameters were set and how dose was estimated, if

DBT systems

There were 17 papers found that matched the literature search criteria. These included the use of five different types of DBT units (from GE HealthCare, Siemens, Xcounter, Sectra and Hologic; see appendix for a description of their design). The studies were almost exclusively performed in an experimental or early clinical application setting. All DBT systems were of investigational design (i.e. prototype units) except one that was a clinical unit, the Hologic Selenia Dimensions. The DBT systems

Discussion and conclusion

Evidence on the clinical performance of DBT is rapidly growing, as is the clinical application of this new technology for imaging the breast. This necessitates careful consideration of potential radiation safety issues. Absorbed dose levels for DBT and FFDM in clinical studies (2008–2014) were therefore reviewed and summarized in terms of the relative dose contribution from DBT to that of FFDM. The dose estimates indicate that when tomosynthesis was used as a stand-alone technique, in one or in

Conflict of interest statement

None declared.

Acknowledgement

One of the authors (N.H.) was supported by a National Breast Cancer Foundation (NBCF Australia) Practitioner Fellowship (PRAC-13-01), while another author (I.S.) was supported by the National Cancer Institute (R01CA163746) and the Susan G. Komen Foundation for the Cure (IIR13262248).

References (51)

  • P. Skaane et al.

    Comparison of digital mammography alone and digital mammography plus tomosynthesis in a population-based screening program

    Radiology

    (2013)
  • L. Philpotts et al.

    Breast imaging: screening/emerging technologies (Initial experience with digital breast tomosynthesis in screening mammography)

    Am J Roentgenol

    (2012)
  • B.M. Haas et al.

    Comparison of tomosynthesis plus digital mammography and digital mammography alone for breast cancer screening

    Radiology

    (2013)
  • S.L. Rose et al.

    Implementation of breast tomosynthesis in a routine screening practice: an observational study

    AJR – Am J Roentgenol

    (2013)
  • I. Sechopoulos

    A review of breast tomosynthesis. Part I. The image acquisition process

    Med Phys

    (2013)
  • D.R. Dance et al.

    Estimation of mean glandular dose for breast tomosynthesis: factors for use with the UK, European and IAEA breast dosimetry protocols

    Phys Med Biol

    (2011)
  • A.K. Ma et al.

    Mean glandular dose estimation using MCNPX for a digital breast tomosynthesis system with tungsten/aluminum and tungsten/aluminum+silver X-ray anode-filter combinations

    Med Phys

    (2008)
  • I. Sechopoulos et al.

    Computation of the glandular radiation dose in digital tomosynthesis of the breast

    Med Phys

    (2007)
  • I. Sechopoulos et al.

    Glandular radiation dose in tomosynthesis of the breast using tungsten targets

    J Appl Clin Med Phys

    (2008)
  • ICRP (International Commission on Radiological Protection) Publication 60

    1990 recommendations of the international commission on radiological Protection

    (1991)
  • ICRP (International Commission on Radiological Protection) Publication 73
    (1996)
  • M.G. Wallis et al.

    Two-view and single-view tomosynthesis versus full-field digital mammography: high-resolution X-ray imaging observer study

    Radiology

    (2012)
  • Z. Zanca et al.

    Diagnostic accuracy of digital mammography versus tomosynthesis: effect of radiologists' experience

  • G. Gennaro et al.

    Digital breast tomosynthesis versus digital mammography: a clinical performance study

    Eur Radiol

    (2010)
  • G. Gennaro et al.

    Performance comparison of single-view digital breast tomosynthesis plus single-view digital mammography with two-view digital mammography

    Eur Radiol

    (2013)
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