Photoacoustic Lymph Node Imaging

The study is centered on determining whether photoacoustic imaging of blood oxygen saturation can detect lymph node metastases. Patients who are returning for an ultrasound exam after detection of a suspicious node via magnetic resonance imaging will be enrolled in the study. Enrolled patients will receive a clinical ultrasound exam, as is the current standard of care. Suspicious nodes will be identified and imaged with combined ultrasound and spectroscopic photoacoustic imaging. Measurements will be acquired with three to five replicates with slightly modified transducer positioning to measure system and intranodal variance of the measurements. One to five contralateral axillary lymph nodes will be imaged to serve as a control and to determine patient-to-patient variability in lymph node saturated oxygen. The distance from the skin to the lymph node will also be measured with ultrasound imaging for each node. If the ultrasound imaging identifies a suspicious node, patients will undergo ultrasound guided biopsy to confirm the true metastatic state of the nodes. Suspicious nodes will be clipped to facilitate identification at the time of axillary node dissection. During the sentinel node procedure, investigators will use intraoperative photoacoustic imaging to measure the blood oxygenation in the sentinel lymph node immediately prior to its removal. Histology will be performed on all biopsy samples and excised nodes to determine the true metastatic state of the node(s).