Abstract
Photoacoustic tomography is a recently developed imaging modality that can provide high spatial-resolution images of hemoglobin distribution in tissues such as the breast. Because breast cancer is an angiogenesis-dependent type of malignancy, we evaluated the clinical acceptability of breast tissue images produced using our first prototype photoacoustic mammography (PAM) system in patients with known cancer. Post-excisionally, histological sections of the tumors were stained immunohistochemically (IHC) for CD31 (an endothelial marker) and carbonic anhydrase IX (CAIX) (a marker of hypoxia). Whole-slide scanning and image analyses were used to evaluate the tumor microvessel distribution pattern and to calculate the total vascular perimeter (TVP)/area for each lesion. In this clinical study, 42 lesions were primarily scanned using PAM preoperatively, three of which were reported to be benign and were excluded from statistical analysis. Images were produced for 29 out of 39 cancers (visibility rate = 74.4%) at the median depth of 26.5 (3.25–51.2) mm. Age, menopausal status, body mass index, history of neoadjuvant treatment, clinical stage and histological tumor angiogenesis markers did not seem to affect the visibility. The oxygen saturation level in all of the measured lesions was lower than in the subcutaneous counterpart vessels (Wilcoxon test, p value<0.001), as well as in the counterpart contralateral normal breast region of interest (ROI) (Wilcoxon test, p value = 0.001). Although the oxygen saturation level was not statistically significant between CAIX-positive vs. -negative cases, lesional TVP/area showed a positive correlation with the oxygen saturation level only in the group that had received therapy before PAM. In conclusion, the vascular and oxygenation data obtained by PAM have great potential for identifying functional features of breast tumors.
Highlights
In 2012, breast cancer represented one out of every four cancer diagnoses worldwide [1]
Seventeen cases were excluded from photoacoustic mammography (PAM) measurement due to small breast size, anatomical location of the lesion, physical difficulty of the patient laying in the prone position or patient withdrawal
For 10 cases, no lesion-associated signal was detected after adjusting with the magnetic resonance imaging (MRI) image
Summary
In 2012, breast cancer represented one out of every four cancer diagnoses worldwide [1]. Breast cancer is the second most common cancer in the world and the most frequent cancer among women but has a favorable survival rate when diagnosed in the early stages. Lesions in dense breasts are difficult to detect by MMG or even CBE [4], ultrasonography (US) is a useful approach for evaluating dense breasts, as well as for confirming cysts. Other imaging modalities, such as magnetic resonance imaging (MRI), can be applied as an additional diagnostic step when an abnormality is detected by MMG or CBE. MRI can be a screening option for certain high-risk women, such as those with a positive family history of breast cancer or a history of therapeutic chest irradiation at earlier ages, it has not yet been proven to be beneficial for the general population [5]
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