Development and testing of a single frequency terahertz imaging system for breast cancer detection

Abstract

The ability to discern malignant from benign tissue in excised human breast specimens in Breast Conservation Surgery (BCS) was evaluated using single frequency terahertz radiation. Terahertz (THz) images of the specimens in reflection mode were obtained by employing a gas laser source and mechanical scanning. The images were correlated with optical histological micrographs of the same specimens, and a mean discrimination of 73% was found for five out of six samples using Receiver Operating Characteristic (ROC) analysis. The system design and characterization is discussed in detail. The initial results are encouraging but further development of the technology and clinical evaluation is needed to evaluate its feasibility in the clinical environment.

Fig. 1

Focusing element layout.

Fig. 2

Photograph of focusing element layout.

Fig. 3

Beam width by position. Mirror numbers are as given in Fig. 1.

Fig. 4

Bolometer Detector Frequency Response.

Fig. 5

Conceptual illustration of air and water calibration measurements.

Fig. 6

Simulation of the reflected power from quartz covered samples as a function of the quartz thickness. The air and water samples have refractive indices of n = 1 and n = 2, respectively. The thickness of 1.9128 mm that corresponds with the measured calibration data is marked.

Fig. 7

Periodic points of minimum reflectivity..

Fig. 8

Mapping between |n_sample| and |Γ_{coveredSample}|².

Fig. 9

Agilent ADS Simulation Model.

Fig. 10

Acrylic sample holder.

Fig. 11

Horizontal resolution measurement.

Fig. 12

Superimposed optical and THz images of sample 7A (a) Optical. (b) Optical and THz. (c) THz.

Fig. 13

Off-sample mask, sample 7A.

Fig. 14

Spline interpolation, sample 7A.

Fig. 15

Histological micrograph.

Fig. 16

Map and mask. (a) Histology map. (b) Cancer mask.

Fig. 17

Varying Refractive Index Threshold (a) n_thres = 0.98 (b) n_thres = 1.38 (c) n_thres = 1.46 (d) n_thres = 1.60 (e) n_thres = 1.71.

Fig. 18

ROC with Color Mapping for n_threshold.

Fig. 19

Compound normalized refractive index, off-sample mask, and cancer mask for samples 7A, 8A, 9A, 10A, 11A, and 12A.

Fig. 20

Compound ROC (72% discrimination).

Fig. 21

Refractive index of non-cancerous areas, 7A.

Fig. 22

Refractive index of cancerous areas, 7A.

Fig. 23

Distribution of cancerous and non-cancerous pixels.