1.Background:
The current clinical standard of breast screening is an X-ray mammogram, and recent evidence confirms that mammograms provide substantial benefits for early cancer detection. However, mammography is hampered by a significant false-positive rate, which is especially high for women with dense breast tissue. The dense breast population is a particularly important subset of women because they experience higher morbidity and mortality due to the disease. Other imaging modalities such as CT and MRI are very expensive and usually provide only low-specificity of tumor morphology. More recently, a novel NIR diffuse correlation spectroscopy (DCS) technique has been developed for the direct measurement of blood flow index (BFI) in deep tissues. However, earlier probe-tissue contact-based DCT methods were at a disadvantage due to compression-induced hemodynamic alterations when applied in tissue models in vivo. For the first time, a newly developed non-contact DCT system was used to achieve three-dimensional (3-D) imaging of blood flow distribution in deep tissues without touching tissue.
2.Research Methods:
2.1 Experimental participant.
Two women with low-grade breast cancer, one 59-year-old and one 49-year-old, were recruited.
2.2 Experimental Materials.
Lamellar and breast-like tissues, see Figure 1.
2.3 Experimental Procedure.
In this experiment, a commercial 3-D camera was used to acquire breast surface geometry and then convert it to a solid volume mesh for NCDCT image reconstruction. In silico simulations were performed to characterize the performance of the NCDCT system for imaging anomalies (tumors) with different flow contrast and depth within tissue volumes under different surface boundaries. The malignancy within the human breast (as determined by ultrasound imaging) was then scanned using the NCDCT probe and a high contrast of the tumor to normal blood flow was observed in the reconstructed images. The patient is in the supine position, and the radiologist uses ultrasound imaging to determine the major tumor lesion within the breast prior to optical measurements. Mark the edge of the tumor mass along the radiological direction on the ultrasound image. The NCDCT probe is driven by a stepper motor to rotate around the breast nipple to scan the breast tumor area. 15 and 21 scan steps were used to cover the tumour areas in both breasts, respectively. Following the NCDCT measurement, the S (median reduced scattering coefficient) and A (median absorption coefficient) of breast tissue at three different locations were measured. The average s and a on multiple sites are used as the initial inputs for the stream image reconstruction.
2.4 Data Acquisition and Processing.
S and A were measured using a commercial frequency-domain tissue oximeter (IMAGENT, ISS).
3.Findings:
3.1 Computer simulation NCDCT
NCDCT recovers anomalies within the volume of tabular and mammary tissue with similar accuracy in the simulation, and achieves higher reconstruction accuracy in the simulation when the anomaly is located within the sensitive region of diffuse light.
3.2 NCDCT and blood oxygen detection in humans.
In vivo imaging results are consistent with in silico simulations, allowing accurate restoration of the tumor center when the tumor is located in a diffuse light-sensitive area. The contrast of blood flow in the tumor area is higher compared to the surrounding tissue. The contrast between peak and mean tumor blood flow was 8 in both subjects3x and 59 times, and 140x and 106 times.
4.Conclusions of the experiment.
The non-contact design of the NCDCT system has the potential to be used to image blood flow distribution in soft and fragile tissues without distorting the hemodynamics of the tissue.
5.References and DOI numbers.
he, l., lin, y., huang, c., irwin, d., szabunio, m.m. and yu, g., 2015. noncontact diffuse correlation tomography of human breast tumor. journal of biomedical optics, 20(8), p.086003.
doi: 10.1117/1.jbo.20.8.086003
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