Imaging tumor vascularization for detection and diagnosis of breast cancer

Breast cancer is one of the major causes of morbidity and mortality in western women. Current screening and diagnostic imaging modalities, like x-ray mammography and ultrasonography, focus on morphological changes of breast tissue. However, these techniques still miss some cancers and often falsely detect cancer. The sensitivity and specificity for detecting the disease can probably be improved by focusing on the consequences of tumor angiogenesis: the increased microvessel density with altered vascular characteristics. In this review, various techniques for imaging breast tumor vasculature are discussed. Dynamic contrast enhanced magnetic resonance imaging is the most-used imaging modality in this field. It has a proven high sensitivity, but a low specificity and cannot be applied in all women. Moreover, it has problems with detecting ductal carcinoma in situ (DCIS). On the contrary, contrast enhanced digital mammography can detect DCIS, but requires the use of ionizing radiation. Contrast enhanced ultrasound provides real-time information about true intravascular blood volume and flow. However, this technique still has difficulties with discriminating benign from malignant tissue. Moreover, these three imaging modalities all require the injection of contrast agents. Two relatively new techniques that do not use external contrast agents are diffuse optical imaging and photoacoustic imaging. Both visualize the increased concentration of hemoglobin in malignant tissue and thereby provide a high intrinsic contrast.