Machine learning framework for automatic image quality evaluation involving a mammographic American College of Radiology phantom.

PURPOSE

The image quality (IQ) of mammographic images is essential when making a diagnosis, but the quality assurance process for radiological equipment is subjective. We therefore aimed to design an automatic IQ evaluation architecture based on a support vector machine (SVM) dedicated to evaluating images taken of mammography American College of Radiology (ACR) phantom.

METHODS

A total of 461 phantom images were acquired using mammographic equipment from 10 vendors. Two experienced medical physicists scored the images by consensus. The phantom datasets were randomly divided into training (80%) and testing (20%) sets. Each phantom image (with 6 fibers, 5 specks, and 5 masses) was detected by using bounding boxes, then cropped and divided into 16 pattern images. We identified 159 features for each pattern image. Manual scores were used to assign 3 labels (visible, invisible, and semivisible) to each pattern image. Multiclass-SVM models were trained with 3 types of patterns. Sub-datasets were randomly selected at 10% increments of the total dataset to determine a minimal effective training subset size for the automatic framework. A feature combination test and an analysis of variance were performed to identify the most influential features.

RESULTS

The accuracy of the model in evaluating fiber, speck, and mass patterns was 90.2%, 98.2%, and 88.9%, respectively. The performance was equivalent when the sample size was at least 138 (30% of 461) phantom images. The most influential feature was the position feature.

CONCLUSIONS

The proposed SVM-based automatic IQ evaluation framework applied to a mammographic ACR phantom accurately matched manual evaluations.