Downgrading BI-RADS 4a and 4b Benign Masses Using Functional Images of Hemoglobin and Blood Oxygen Saturation Coregistered with Ultrasound Provide Differentiation of Breast Tumors

Abstract

CONCLUSION
The fused functional OA and gray scale anatomic information significantly improved downgrading of benign breast masses, especially within the critical BI-RADS 4a and 4b categories.

BACKGROUND
Patients with breast masses were assessed with Opto-acoustics(OA). All masses were biopsied and histology was the gold standard. OA employs near-infrared laser pulses at two different wavelengths (to provide contrast between oxygenated hemoglobin in benign lesions and de-oxygenated hemoglobin in malignant lesions) to illuminate tissues through a fiberoptic bundle incorporated into a hand-held opto-acoustic probe. It detects the laser pulse induced acoustic pressure waves that are then used for reconstruction of two-dimensional functional and anatomical images. OA maps of total hemoglobin and blood oxygen saturation provide functional information that is co-registered with the morphological information from B-mode gray scale ultrasound images.

EVALUATION
Five blinded readers independently assessed POM for OA without clinical data for 74 breast masses. All 34 cancer masses remained at original BI-RADS per site PI while, for 40 benign masses, downgrades were achieved for 12/22 BI-RADS 4a to 3 and for 3/13 BI-RADS 4b to 3. OA could potentially spare 50% of BI-RADS 4a cases and 20% of BI-RADS 4b cases.

DISCUSSION
OA allows visualization of blood pooling and vascular structures superimposed onto co-registered gray scale.