Effect of glandularity on the detection of simulated cancers in planar, tomosynthesis, and synthetic 2D imaging of the breast using a hybrid virtual clinical trial

Abstract

The purpose of this study was to measure the threshold diameter of calcifications and masses for 2D imaging, digital breast tomosynthesis (DBT), and synthetic 2D images, for a range of breast glandularities. This study shows the limits of detection for each of the technologies and the strengths and weaknesses of each in terms of visualizing the radiological features of small cancers. Methods: Mathematical voxel breast phantoms with glandularities by volume of 9%,18%,and 30% with a thickness of 53 mm were created.Simulated ill-defined masses and calcification clusters with a range of diameters were inserted into some of these breast models. The imaging characteristics of a Siemens Inspiration X-ray system were measured for a 29 kV, tungsten/rhodium anode/filter combination. Ray tracing through the breast models was undertaken to create simulated 2D and DBT projection images. These were then modified to adjust the image sharpness, and to add scatter and noise. The mean glandular doses for the images were 1.43, 1.47, and 1.47 mGy for 2D and 1.92, 1.97, and 1.98 mGy for DBT for the three glandularities. The resultant images were processed to create 2D, DBT planes and synthetic 2D images. Patches of the images with or without a simulated lesion were extracted, and used in a four-alternative forced choice study to measure the threshold diameters for each imaging mode, lesion type, and glandularity. The study was undertaken by six physicists. Results: The threshold diameters of the lesions were 6.2, 4.9, and 6.7 mm (masses) and 225, 370, and 399 µm, (calcifications) for 2D, DBT, and synthetic 2D, respectively, for a breast glandularity of 18%. The threshold diameter of illdefined masses is significantly smaller for DBT than for both 2D (p≤0.006) and synthetic 2D (p≤0.012) for all glandularities. Glandularity has a significant effect on the threshold diameter of masses, even for DBT where there is reduced background structure in the images. The calcification threshold diameters for 2D images were significantly smaller than for DBT and synthetic 2D for all glandularities. There were few significant differences for the threshold diameter of calcifications between glandularities, indicating that the background structure has little effect on the detection of calcifications. We measured larger but nonsignificant differences in the threshold diameters for synthetic 2D imaging than for 2D imaging for masses in the 9% (p = 0.059) and 18% (p = 0.19) glandularities. The threshold diameters for synthetic 2D imaging were larger than for 2D imaging for calcifications (p < 0.001) for all glandularities.

Computer simulations of case difficulty in digital breast tomosynthesis using virtual clinical trials

“…In the current study, the methods previously used for simulating breast pathologies were revised to avoid non‐clinical images. Alternative methods clearly exist, such as hybrid VCTs 42,43 in which lesions are added to clinical images, but this presupposes that the novel system already exists. Similarly, alterative phantoms which simulate breast anatomy exist 44–47 .…”

Hyperia: A novel methodology of developing anthropomorphic breast phantoms for X‐ray imaging modalities – Part I: Concept and initial findings

“…Such phantoms include the American College of Radiology mammography accreditation phantom (ACR, Reston, VA, USA), the CDMAM phantom (Artinis Medical Systems, Elst, Netherlands), and the CIRS DBT QC phantom (CIRS, Norfolk, VA, USA). Aside from the quality control though, several studies have highlighted the limitations of this phantom on performance analysis of an imaging system 1–3 . The quality of such higher‐level studies highly depends on the structural complexity of the phantoms.…”

“…Aside from the quality control though, several studies have highlighted the limitations of this phantom on performance analysis of an imaging system. [1][2][3] The quality of such higher-level studies highly depends on the structural complexity of the phantoms. For these applications, therefore, it is important to use phantoms that are as similar as possible to the intended object, with realistic texture.…”