Design and application of a structured phantom for detection performance comparison between breast tomosynthesis and digital mammography

Abstract

This paper introduces and applies a structured phantom with target objects for the comparison of detection performance of digital breast tomosynthesis (DBT) against full field digital mammography (FFDM). The phantom consists of a 48 mm thick breast-shaped polymethyl methacrylate (PMMA) container filled with water and PMMA spheres of different diameters. Three-dimensionally (3D) printed spiculated masses (diameter range: 3.8-9.7 mm) and non-spiculated masses (1.6-6.2 mm) along with microcalcifications (90-250 µm) were inserted as targets. Reproducibility of the phantom application was studied on a single system using 30 acquisitions. Next, the phantom was evaluated on five different combined FFDM & DBT systems and target detection was compared for FFDM and DBT modes. Ten phantom images in both FFDM and DBT modes were acquired on these 5 systems using automatic exposure control (AEC). Five readers evaluated target detectability. Images were read with the four-alternative forced-choice (4-AFC) paradigm, with always one segment including a target and 3 normal background segments. The percentage of correct responses (PC) was assessed based on 10 trials of each reader for each object type, size and modality. Additionally, detection threshold diameters at 62.5 PC were assessed via non-linear regression fitting of the psychometric curve. The reproducibility study showed no significant differences in PC values. Evaluation of target detection in FFDM showed that microcalcification detection thresholds ranged between 110 and 118 µm and were similar compared to the detection in DBT (range of 106-158 µm). In DBT, detection of both mass types increased significantly (p=0.0001 and p=0.0002 for non-spiculated and spiculated masses respectively) compared to FFDM, achieving almost 100% detection for all spiculated mass diameters. In conclusion, a structured phantom with inserted targets was able to show evidence for detectability differences between FFDM and DBT modes for five commercial systems. This phantom has potential for application in task-based assessment at acceptance and commissioning testing of DBT systems.

The threshold detectable mass diameter for 2D-mammography and digital breast tomosynthesis

“…Alternatively, simulation methods are sensitive and useful for investigating the imaging technology. Observer studies with lesions inserted into physical phantoms (anthropomorphic or structured) [15,16] or fully simulated breast images [17][18][19][20] have yielded useful results, while image metrics such as contrast-to-noise ratio (CNR), CNR/ASF (artefact spread function) [21][22][23] have also been used successfully.…”

A four‐alternative forced choice (4AFC) methodology for evaluating microcalcification detection in clinical full‐field digital mammography (FFDM) and digital breast tomosynthesis (DBT) systems using an inkjet‐printed anthropomorphic phantom

“…Furthermore, the use of thin gold disks is questionable for use in assessing DBT image quality because they are anisotropic, being much larger in the x-y direction than the z-direction. Cockmartin et al 14 have described a clever "shakable" anthropomorphic phantom with background consisting of PMMA spheres of various shapes placed into water. In that phantom, MC signals were modeled by gluing specks of calcium carbonate (CaCO3) to a PMMA plate of thickness 2 mm.…”

“…Scores were computed as the proportion correct (PC), the number of images a reader correctly located out of all cases. The PC provides a measure of reader performance directly the 4AFC data …”

Systematic approach to a channelized Hotelling model observer implementation for a physical phantom containing mass-like lesions: Application to digital breast tomosynthesis

“…It is likely that the practice of physical phantom evaluation, initially scored by human observers, will be carried over to the assessment and optimization of DBT devices. One such candidate is the 3D structured phantom developed by Cockmartin et al [13], which contains clinically relevant targets and was developed for comparative studies of FFDM and DBT. Future applications may include the use in routine QC and in technical optimization of DBT systems.…”

“…There is currently little consensus on the selection or development of CHOs for physical test objects. The goal of this study was therefore to describe the systematic development and validation of a CHO algorithm for use with the physical phantom described by Cockmartin [13], with the focus on channel design, the generation of signal templates and the number of images required for a robust estimate of the covariance matrix.…”