Ultrasound-guided optical tomographic imaging of malignant and benign breast lesions: initial clinical results of 19 cases

Abstract

The diagnosis of solid benign and malignant tumors presents a unique challenge to all noninvasive imaging modalities. Ultrasound is used in conjunction with mammography to differentiate simple cysts from solid lesions. However, the overlapping appearances of benign and malignant lesions make ultrasound less useful in differentiating solid lesions, resulting in a large number of benign biopsies. Optical tomography using near-infrared diffused light has great potential for imaging functional parameters of 1) tumor hemoglobin concentration, 2) oxygen saturation, and 3) metabolism, as well as other tumor distinguishing characteristics. These parameters can differentiate benign from malignant lesions. However, optical tomography, when used alone, suffers from low spatial resolution and target localization uncertainty due to intensive light scattering. Our aim is to combine diffused light imaging with ultrasound in a novel way for the detection and diagnosis of solid lesions. Initial findings of two early-stage invasive carcinomas, one combined fibroadenoma and fibrocystic change with scattered foci of lobular neoplasia/lobular carcinoma in situ, and 16 benign lesions are reported in this paper. The invasive cancer cases reveal about two-fold greater total hemoglobin concentration (mean 119 micromol) than benign cases (mean 67 micromol), and suggest that the discrimination of benign and malignant breast lesions might be enhanced by this type of achievable optical quantification with ultrasound localization. Furthermore, the small invasive cancers are well localized and have wavelength-dependent appearance in optical absorption maps, whereas the benign lesions appear diffused and relatively wavelength-independent.

Figure 1

(a) Picture of the combined probe and frequency domain imager. (b) Sensor distribution of the combined probe. Smaller circles in (b) are optical source fibers and big circles are detector fibers. A commercial ultrasound probe is located at the center of the combined probe, and the optical source and detector fibers are distributed at the periphery of the ultrasound probe.

Figure 2

(a) shows a gray scale ultrasound image of a nonpalpable lesion of a 55-year-old woman. The lesion pointed by the arrow was located at the 4 o'clock position of the right breast measuring 8 mm in diameter. Ultrasound showed nodular mass with internal echoes and the lesion was considered suspicious. (b) and (c) are optical absorption maps at 780 and 830 nm, respectively. x and y axes are spatial dimensions of 9 x 9 cm. The slices starting from left to right correspond to absorption maps from 0.7 cm underneath the skin surface to the chest wall in 0.5-cm spacing. (d) is the total hemoglobin concentration and the vertical scale is in micromoles.

Figure 3

This example was obtained from a 56-year-old woman who had nonpalpable lesion located at the 10 o'clock position of the left breast. Ultrasound showed a solid mass (a) with internal echoes measuring 9 mm in size and the lesion was considered suspicious. (b) and (c) are optical absorption maps at 780 and 830 nm, respectively. The slices start from 0.4 cm underneath the skin surface to the chest wall in 0.5-cm spacing. (d) is the total hemoglobin concentration.

Figure 4

(a) shows a solid lesion at the 2 o'clock position measuring 1.1 cm in diameter in ultrasound image. The lesion was diagnosed as having benign appearance because of well-defined boundaries. Ultrasound-guided core biopsy revealed scattered foci of lobular neoplasia, carcinoma in situ but not invasive, and fibroadenoma and fibrocystic changes with associated microcalcifications. (b) and (c) are optical absorption maps at 780 and 830 nm, respectively. The slices start from 0.5 cm underneath the skin surface to the chest wall in 0.5-cm spacing. (d) is the total hemoglobin concentration.

Figure 5

(a) shows an ultrasound image of a solid hypoechogenic lesion located at 9 to 10 o'clock position of a 37-year-old woman's breast. The diagnosis was that the lesion could represent fibroadenoma; however, there was a chance that the lesion could be a carcinoma because of the irregular shape and posterior shadow seen by ultrasound. (b) and (c) are optical absorption maps at 780 and 830 nm, respectively. The slices start from 0.5 cm underneath the skin surface to the chest wall in 0.5-cm spacing. (d) is the total hemoglobin concentration.

Figure 6

The average maximum total hemoglobin concentration obtained from benign fibroadenomas and hyperplasia, and combined fibroadenoma and fibrocystic change with neoplasia/carcinoma in situ (noninvasive) and invasive cancer groups are shown in bars. The standard deviations of three groups are also provided. The average sizes of lesions of the three groups are 1.05 (0.3), 1.1, and 0.9 (0.07) cm, respectively.