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The effect of angular dose distribution on the detection of microcalcifications in digital breast tomosynthesis
Author(s) -
Hu YueHoung,
Zhao Wei
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3570580
Subject(s) - tomosynthesis , detector , contrast to noise ratio , digital breast tomosynthesis , detective quantum efficiency , iterative reconstruction , observer (physics) , clutter , computer science , optical transfer function , optics , computer vision , physics , artificial intelligence , mammography , image quality , medicine , radar , image (mathematics) , telecommunications , cancer , quantum mechanics , breast cancer
Purpose: Substantial effort has been devoted to the clinical development of digital breast tomosynthesis (DBT). DBT is a three‐dimensional (3D) x‐ray imaging modality that reconstructs a number of thin image slices parallel to a stationary detector plane. Preliminary clinical studies have shown that the removal of overlapping breast tissue reduces image clutter and increases detectability of large, low contrast lesions. However, some studies, as well as anecdotal evidence, suggested decreased conspicuity of small, high contrast objects such as microcalcifications. Several investigators have proposed alternative imaging methods for improving microcalcification detection by delivering half of the total dose to the central view in addition to a separate DBT scan. Preliminary observer studies found possible improvement by either viewing the central projection alone or combining all views with a reconstruction algorithm. Methods: In this paper, we developed a generalized imaging theory based on a cascaded linear‐system model for DBT to calculate the effect of variable angular dose distribution on the 3D modulation transfer function (MTF) and noise power spectrum (NPS). Using the ideal observer signal‐to‐noise ratio (SNR), d ′, as a figure‐of‐merit (FOM) for a signal embedded in a uniform background, we compared the detectability of objects with different sizes under different imaging conditions (e.g., angular dose distribution and reconstruction filters). Experimental investigation was conducted for three different angular dose schemes (ADS) using a Siemens Novation TOMO prototype unit. Results: Our results show excellent agreement between modeled and experimental measurements of 3D NPS with different angular dose distribution. The ideal observer detectability index for the detection of Gaussian objects with different angular dose distributions depends strongly on the applied reconstruction filter as well as the imaging task. For detection tasks of small calcifications with reconstruction filters used typically in a clinical setting, variable angular dose distribution with more dose delivered to the central views may lead to higher d ′ than a uniform angular dose distribution. Conclusions: The conspicuity of the detection of small calcifications may be improved, under certain imaging conditions, by delivering higher dose toward the central views of a tomosynthesis scan, while also reducing the dose at peripheral angles to keep total administered radiation dose equivalent. The degree of improvement depends on the choice of reconstruction filters as well as the imaging task. The improvement is more substantial for high‐frequency imaging tasks and when an aggressive slice‐thickness (ST) filter is applied to reduced the high‐frequency noise at peripheral angles.