Imaging heterogeneous absorption distribution of advanced breast cancer by optical tomography

Abstract

Tumor vascular patterns of advanced breast cancers are complex and heterogeneous. Two typical light absorption patterns of periphery enhancement and posterior shadowing have been observed when imaging these advanced cancers using optical tomography guided by ultrasound. We perform a series simulation and phantom experiments to systemically evaluate the effects of target parameters, target locations, and target optical properties on imaging periphery enhancement absorption distribution using reflection geometry. Large tumors are modeled as concentric semiellipsoidal targets of different outer shell and inner core optical properties. We show that larger targets of more than 3 to 4 cm diameter with outer shell thicknesses less than 1 cm can be resolved at a depth less than 3 cm. A clinical example is given to show the complex vasculature distributions seen from an advanced cancer.

Figures

Figure 1

Probe geometry used for simulation and phantom experiments (a) without and (b) with closer-to-center center sources.

Figure 2

(a) Geometry of the photon propagation to the boundary of a concentric semi-ellipsoidal target and (b) ΔW inside the 3-D volume summed in the x direction (left), the y direction (middle), and the z direction (right), respectively, and projected into the y-z plane, the x-z plane, and the x-y plane, respectively.

Figure 3

Illustration of measuring reconstructed inner radius.

Figure 4

Example of a concentric semiellipsoidal target phantom: (a) front view and (b) bottom view of the phantom.

Figure 5

Reconstruction results of a concentric semiellipsoidal target with a diameter of 5 cm and a height of 2 cm: (a) simulation and (b) phantom experiment.

Figure 6

Simulation results of a concentric semiellipsoidal target of outer shell diameter 5 cm, inner core diameter 2.5 cm, and height 2 cm of different layer thicknesses (a) 0.5, (b) 0.8, and (c) 1.0 cm.

Figure 7

Phantom experimental results of a concentric semiellipsoidal target of outer shell diameter 5 cm, inner core diameter 2.5 cm, and height 2 cm of different layer thickness (a) and (b) 0.5 cm and (c) and (d) 1.0 cm. (a) and (c) are US images and (b) and (d) are the corresponding absorption maps.

Figure 8

Simulation results of concentric semiellipsoidal targets with fixed layer thickness t = 0.5 cm and different target sizes: (a) outer shell diameter of 2.5 cm and inner core diameter of 1.5 cm; (b) outer shell diameter of 3 cm and inner core diameter of 2 cm; (c) outer shell diameter of 3.5 cm and inner core diameter of 2.5 cm; and (d) outer shell diameter of 5 cm and inner core diameter of 4.0 cm.

Figure 9

Phantom result of a small concentric semiellipsoidal target with an outer shell diameter of 2.5 cm, an inner core diameter of 1.5 cm, a height of 1.5 cm, and a layer thickness of 0.5 cm. (a) US image and (b) reconstructed absorption map.

Figure 10

Simulation results of a concentric semiellipsoidal target of outer shell diameter 5 cm, inner core diameter 2.5 cm, height 2 cm, and layer thickness 0.5 cm located at different depths. The distances between the bottom of the target and the probe surface were (a) 2.3, (b) 2.5, (c) 2.8, and (d) 3.0 cm. The probe of Fig. 1b was used for image reconstruction.

Figure 11

Simulation results of a concentric semiellipsoidal target of outer shell diameter 5 cm, inner core diameter 2.5 cm, height 2 cm, and layer thickness 0.5 cm located at different depths. The distances between the bottom of the target and the probe surface were (a) 2.3, (b) 2.5, (c) 2.8, and (d) 3.0 cm. The probe of Fig. 1a was used for image reconstruction.

Figure 12

Phantom results of a concentric semiellipsoidal target with an outer shell diameter of 5 cm, an inner core diameter of 2.5 cm, a height of 2 cm, and a layer thickness of 0.5 cm located at different depths. The distances between the bottom of the target and the probe surface were (a) 2.3, (b) 2.5, (c) 2.8, and (d) 3.0 cm. The probe of Fig. 1b was used for image reconstruction.

Figure 13

Phantom results of a semiellipsoidal target with an outer shell diameter of 5 cm, an inner diameter of 2.5 cm, a height of 2 cm, and a layer thickness of 0.5 cm located at different depths. The distances between the bottom of the target and the probe surface were (a) 2.3, (b) 2.5, (c) 2.8, and (d) 3.0 cm. The probe of Fig. 1a was used for image reconstruction.

Figure 14

Plot of contrast ratio (left y axis) and reconstructed inner diameter (right y axis) versus target depths.

Figure 15

Simulation results of a concentric semiellipsoidal target of outer shell diameter 5 cm, inner core diameter 2.5 cm, height 2 cm, and layer thickness 0.5 cm with different inner core absorption coefficients. The probe shown in Fig. 1b was used for image reconstruction. The inner core absorption coefficients were (a) 0.03, (b) 0.06, (c) 0.08, and (d) 0.15 cm−1, respectively.

Figure 16

Phantom results of a concentric semiellipsoidal target of outer shell diameter 5 cm, inner diameter 2.5 cm, height 2 cm, and layer thickness 0.5 cm with different inner core absorptions imaged. The probe shown in Fig. 1b was used for image reconstruction. The inner core absorption coefficients were (a) 0.03, (b) 0.06, (c) 0.08, and (d) 0.15 cm−1, respectively.

Figure 17

Plot of contrast ratio (left y axis) and reconstructed inner diameter (right y axis) versus different inner core absorption.

Figure 18

Simulation results of a concentric semiellipsoidal target of outer shell diameter 5 cm, inner core diameter 2.5 cm, height 2 cm, and layer thickness 0.5 cm of different inner core diameters. The probe shown in Fig. 1b was used for image reconstruction. Inner core diameters were (a) 1.0, (b) 1.5, (c) 2.0, and (d) 2.5 cm.

Figure 19

Phantom results of a concentric semiellipsoidal target of outer shell diameter of 5 cm, inner core diameter of 2.5 cm, height of 2 cm, and layer thickness 0.5 cm of different inner core diameters. The probe shown in Fig. 1b was used for image reconstruction. Inner diameters were (a) 1.0, (b) 1.5, (c) 2.0, and (d) 2.5 cm.

Figure 20

Plot of contrast ratio (left y axis) and reconstructed inner diameter (right y axis) versus the inner core diameter.

Figure 21

Clinical example of an advanced cancer: (a) coregistered US showing a suspicious mass of a semispherical shape with top and bottom located at 0.5 and 2.5 cm from the skin surface. A core biopsy revealed a high-grade ductal carcinoma. (b) Optical absorption map reconstructed at 780 nm, (c) absorption map reconstructed at 830 nm, and (d) computed total hemoglobin concentration map.