Near-infrared optical mammography for breast cancer detection with intrinsic contrast

Abstract

Optical methods to detect breast cancer on the basis of its increased opacity have been explored for some time. These methods have matured to a point in which they are capable of quantifying the optical properties of breast tissue and translating them into measures of concentrations of relevant tissue components. In particular, near-infrared spectroscopy has been employed to determine the concentrations of hemoglobin, water, and lipids, as well as oxygen saturation of hemoglobin and optical scattering properties in normal and cancerous breast tissue. Dynamic optical measurements can also identify abnormal hemodynamic patterns associated with breast cancer. We review, in this article, a number of results in the field, which show that cancerous tissue is associated with higher hemoglobin and water concentrations, and a lower lipid concentration with respect to normal breast tissue. Indications that breast cancers are characterized by lower hemoglobin saturation and stronger scattering decay as a function of wavelength are less robust, with variable results reported in the literature. Intrinsic sources of optical contrast associated with breast cancer can also be used to monitor individual response to neoadjuvant therapy.

FIG. 1

The continuous line is the absorption spectrum resulting from typical concentrations of HbO, Hb, lipids, and water in breast tissue, namely [HbO] = 36 µM, [Hb] = 17 µM, [Water] = 16%, and [Lipid] = 66% (see references in Table 1). The dashed line is the reduced scattering spectrum given by Eq. (1) with λ₀ = 670 nm, a = 10.5 cm⁻¹, and b = 0.8, which are typical values for breast tissue (see references in Table 1). The chromophores associated with specific absorption peaks are indicated as O (oxy-hemoglobin), D (deoxy-hemoglobin), L (lipids), and W (water). Absorption peaks of individual tissue chromophores giving minor contributions to the overall absorption spectrum are indicated in parenthesis [(D), (L)].

FIG. 2

Representative optical mammograms from the published literature. (a) [HbT] image of a 0.6-cm invasive ductal carcinoma. (b) Dynamic optical image of an intraductal carcinoma during external pressure application to the breast. (c) Hemoglobin saturation image of a 1.3-cm intracystic carcinoma. (d) [HbT] image of 3.4-cm infiltrating ductal carcinoma. (e) Dynamic [Hb] image of a ductal carcinoma during a Valsalva maneuver. (f) Optical tomography image of a 1-cm adenocarcinoma. (g) Absorption image of a 2-cm infiltrating carcinoma. (h) Absorption image of an invasive ductal carcinoma. (i) Absorption image of an invasive ductal carcinoma. (j) Late-gated intensity image of a 1.5-cm lobular invasive carcinoma. (k) [HbT] image of 2.2-cm invasive carcinoma. (l) Spatial second-derivative image and (m) hemoglobin saturation image of a ductal carcinoma in situ (DCIS).