Study Design

After initial clinical validation, a Health Insurance Portability and Accountability Act (HIPAA)-compliant institutional review board (IRB)-approved Feasibility Study of OA imaging was undertaken. 155 patients with solid breast masses assessed as BI-RADS 3, BI-RADS 4, or BI-RADS 5 on conventional diagnostic ultrasound imaging were enrolled with informed consent.  All of these patients were subsequently scanned with OA imaging at one of two IRB-approved sites. 79 lesions were biopsied yielding 39 benign and 34 malignant results, with 6 lesions excluded, for a final study population of 30 malignancies. All tumors were evaluated with OA prior to biopsy and underwent standardized histopathology after biopsy.

Imaging Assessment

A scanning protocol was established, which consisted of both conventional B-mode and OA images. Prior to initializing the laser, gray-scale images in the radial and anti-radial planes were obtained with and without measurements in three planes. Subsequently, the laser was activated and the images were repeated. The OA images were viewed as a 6:1 display of the conventional gray-scale image together with five different OA maps consisting of gray long and short wave images and 3 color maps (Figure 3). OA features based on pre-biopsy imaging were analyzed by a radiologist with >30 years of expertise in breast ultrasound (ATS) who was blinded to the histopathology.  OA imaging revealed three distinct zones within breast malignancies – tumor interior, boundary zone, and periphery. Using predefined measures, an OA score was calculated for each zone based on the relative amount of detected hemoglobin (hemoglobin score), the number of individually resolved vessels (vessel score) and the degree of tumor blush representing vessels too small to resolve (blush score). The total OA score was calculated as a sum of the above. The internal OA score was based on features within the tumor interior, while the external OA score combined the features of the tumor boundary zone and periphery.

Histopathologic Evaluation

The tissue cores were evaluated by an independent pathologist with >30 years of experience in breast pathology (FLT) who was blinded to the OA imaging features.  Histologic assessment was based on standard hematoxylin and eosin (H&E) stains.  Measures of histologic grade based on Scarff-Bloom-Richardson (SBR) score, including tubule formation (SBR-T), nuclear atypia (SBR-N), and mitotic count (SBR-M), as well as total score (SBR-TOTAL) were recorded.

Statistical Analysis

Total internal and external OA scores were compared with histopathology measures using ANOVA and Spearman’s rank correlation coefficients. The significance level was 0.05.