Detection of Breast Cancer: Dynamic Infrared Imaging

The dynamic infrared imaging (DIRI) technique has been employed for the detection of breast cancer efficiently. Quantum well infrared photodetectors (QWIP) constructed as a focal plane array were developed as part of the Star Wars initiative and are now available for biomedical research. Detectors available for this purpose contain a GaAs QWIP, are configured as a 256 × 256 scanned focal plane array, and allow for rapid imaging. This new generation of infrared sensor has improved thermal and spatial resolution and can image dynamically. High sensitivity and frame rate allow dynamic interrogation of biological systems. Breast cancer detection by infrared could be described using two simple models that include primitive tumor vasculature or tumor-generated nitric oxide (NO). In the first model, angiogenesis leads to the formation of new vessels associated with malignancy that lack smooth muscle fibers rendering them unreceptive to control by vasoconstrictors. As a result of these primitive vessels, greater blood flow and larger modulations such as cardiogenic are in evidence. An alternative model is based on the finding that tumors of the breast are greatly influenced by steroid hormones such as progesterone activates inducible nitric oxide synthase (iNOS). Patients with iNOS positive breast carcinomas have a significantly worse overall survival rate versus those with negative stains. The increased perfusion results, as NO is a vasodilator. While this signal may be associated with the tumor itself, it will also be associated with any tissue into which NO has diffused. This mechanism also predicts larger infrared flux modulations from the cardiac cycle (cardiogenic DIRI signal).