Optimizing configuration parameters of a stationary digital breast tomosynthesis system based on carbon nanotube x-ray sources

Abstract

The stationary Digital Breast Tomosynthesis System (s-DBT) has the advantage over the conventional DBT systems as there is no motion blurring in the projection images associated with the x-ray source motion. We have developed a prototype s-DBT system by retrofitting a Hologic Selenia Dimensions rotating gantry tomosynthesis system with a distributed carbon nanotube (CNT) x-ray source array. The linear array consists of 31 x-ray generating focal spots distributed over a 30 degree angle. Each x-ray beam can be electronically activated allowing the flexibility and easy implementation of novel tomosynthesis scanning with different scanning parameters and configurations. Here we report the initial results of investigation on the imaging quality of the s-DBT system and its dependence on the acquisition parameters including the number of projections views, the total angular span of the projection views, the dose distribution between different projections, and the total dose. A mammography phantom is used to visually assess image quality. The modulation transfer function (MTF) of a line wire phantom is used to evaluate the system spatial resolution. For s-DBT the in-plan system resolution, as measured by the MTF, does not change for different configurations. This is in contrast to rotating gantry DBT systems, where the MTF degrades for increased angular span due to increased focal spot blurring associated with the x-ray source motion. The overall image quality factor, a composite measure of the signal difference to noise ratio (SdNR) for mass detection and the z-axis artifact spread function for microcalcification detection, is best for the configuration with a large angular span, an intermediate number of projection views, and an even dose distribution. These results suggest possible directions for further improvement of s-DBT systems for high quality breast cancer imaging.

Digital breast tomosynthesis: studies of the effects of acquisition geometry on contrast-to-noise ratio and observer preference of low-contrast objects in breast phantom images

“…In an experimental study using a Hologic a-Se flat panel detector and 31 stationary carbon nano-tube x-ray sources, Tucker et al (Tucker et al , 2012) used a quality factor similar to that of Sechopoulos and Ghetti (Sechopoulos and Ghetti, 2009)(Signal-difference-to-noise ratio / width of ASF at half max). They compared DBT images of an ACR mammography accreditation phantom generated with three different combinations of angular span and number of projection views (14d15p, 28d15p and 28d29p) and 3 dose distributions.…”

“…Many researchers have performed studies to determine the optimum geometry (angular range and number of projection views) for DBT. (Eberhard et al , 2006; Chawla et al , 2009; Chawla et al , 2008; Das et al , 2009; Gang et al , 2010; Gifford et al , 2008; Hu et al , 2008; Lu et al , 2011; Maidment et al , 2005; Maidment et al , 2006; Mertelmeier et al , 2008; Nishikawa et al , 2007; Reiser and Nishikawa, 2010; Ren et al , 2006; Sechopoulos, 2013; Sechopoulos and Ghetti, 2009; Tucker et al , 2012; Tucker et al , 2013; Van de Sompel et al , 2011; Wu et al , 2004; Ren et al , 2009, Young et al, 2013) Most of these studies have involved modeling of the tomosynthesis systems and some included modeling of the observers. Very few of the investigations have been experimental, in most part due to the unavailability of DBT systems that permit investigation of a wide variety of geometries, and because of the unavailability of realistic breast-simulating physical phantoms.…”

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

“…For example, to avoid focal spot blurring due to the x-ray tube motion during acquisition 18 and potentially shorten total acquisition time, a carbon nanotube array of x-ray sources is being investigated as a replacement for the x-ray tube and rotating gantry. [19][20][21][22][23][24][25] In recent work, the investigators replaced the x-ray tube and gantry of a commercial DBT system (Selenia Dimensions, Hologic, Inc., Bedford, MA) with a carbon nanotube array with 31 x-ray sources, spanning 370 mm, resulting in an angular coverage of 30 • . The stationary x-ray source was shown to yield an improved modulation transfer function (MTF) compared to that with a standard rotating x-ray tube, in addition to an increase in the sharpness of phantom microcalcification images.…”

“…Using the same QF metric, Tucker et al arrived at similar conclusions on the impact of angular range and number of projections for DBT performed with stationary carbon nanotube x-ray sources. 24 Using a more advanced image quality metric, specifically the detectability of a simulated lesion as evaluated by an observer model, Chawla et al also studied the impact of total angular range and number of projections on tomosynthe-sis image quality, analyzing both the projections and the reconstructed images. 61,61 Under the constant total dose condition, the results agree with the findings of Sechopoulos and Ghetti; detectability increases with increasing angular range and number of projections, but the latter achieves a maximum beyond which observer performance decreases.…”

Development of realistic physical breast phantoms matched to virtual breast phantoms based on human subject data

“…1,2 These uniform phantoms are used for system characterization and for devising optimized imaging paradigms. [3][4][5][6][7][8][9] However, while these phantoms are effective for characterizing the inherent physical properties of an imaging system, they are far from representing realistic breast background, hence significantly under-representing the sophistication of diagnostic tasks that should be the basis of medical imaging performance. As such, there is a need to design and implement system evaluation phantoms that more closely represent the clinical reality.…”