Development and validation of a simulation procedure to study the visibility of micro calcifications in digital mammograms

Abstract

The visibility of micro calcifications is a determining factor for digital mammography. To address the problem of quantification, we developed a procedure to simulate micro calcifications into real mammograms. First, the shapes, sizes and x-ray transmission coefficients of real micro calcifications were derived from the appearance of biopsy specimens in the raw data of magnified, digital images acquired at 27 kVp and Mo/Mo anode-filter combination. This allowed us to create "ideal templates" of micro calcifications. The x-ray transmissions of the real micro calcifications values were expressed in Al-equivalent thickness. This made it possible to recalculate the x-ray transmission characteristics of a particular ideal template for other x-ray beam qualities. Extra corrections for differences in spatial resolution were based on the presampled two-dimensional modulation transfer functions and on the difference in pixel size. Three radiologists compared the appearance of real and simulated micro calcifications in a two-alternative forced choice (2AFC) evaluation. They perceived no differences between real and simulated lesions. Preliminary results show that it is possible to simulate micro calcifications with well defined characteristics that are indistinguishable from real ones. It should be noted, however, that the full potential of the approach has not been proven. In future work, these templates may be useful to evaluate particular aspects of digital mammograms, such as the effects of processing and of viewing conditions on the visibility of micro calcifications.

Investigation of the effect of tube motion in breast tomosynthesis: continuous or step and shoot?

“…Figure 7 shows that the drop in peak contrast from an ideal MTF (MTF(u,v) = 1) towards the theoretical MTF condition of the step and shoot is larger than between the MTF conditions of the step and shoot and the continuous mode. These results provide further evidence that the inclusion of system MTF, incorporating scatter or motion blurring effects for example, can give valuable insight when modeling the influence of system resolution characteristics in a detection study 24 .…”

Development and implementation of a user friendly and automated environment for the creation of databases of digital mammograms with simulated microcalcifications

“…The results presented in this work provide an extension of those already published by AK Carton (1,2). Already existing microcalcification templates and new ones have been used to calculate new templates for different detectors, different energies and different breast thickness.…”

“…The earlier method developed in our group for the simulation of microcalcification templates (1,2), and that we use also in present work for the creation of the database, was based on a similar work by Lefebvre (3) and Lado (4). Only essential details are recalled here:…”

“…As an example, preliminary radiological experience with full field digital mammography (FFDM) had shown that the visibility of microcalcifications was a crucial and determining parameter for system validation in clinical practice (1). Earlier work in our group has focused on the detectability of small microcalcifications (1,2).…”

Computer aided system for segmentation and visualization of microcalcifications in digital mammograms.

“…Namely, as noted earlier, calcifications are represented by small bright spots not belonging to background tissue, usually in the form of clusters, and characterized by sharp change of local contrast just at their edges [46,47]. In multifractal terminology, normal human tissue is characterized by high degree of self-similarity [26][27][28] while the tissue anomalies are considered as structural "defects", i.e., as deviations from global regularity of the background.…”