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Portable device for measuring bulk breast composition

10 Apr | By Biophotonics.World
Portable device for measuring bulk breast composition
A portable version of the Cups optical spectroscopy device developed at the University of Toronto/University Health Network.
By: Lothar Lilge

A portable, low-cost optical spectroscopy device for measuring bulk breast composition has been developed by the Biophotonics group at the University Health Network/University of Toronto. A study recently published in the Journal of Biophotonics demonstrates that the device could be used to identify women with very high mammographic density, a known strong breast cancer risk factor.

 

A woman’s risk of developing breast cancer depends on a variety of factors, including genetics, exposures and lifestyle factors. A large number of lifestyle factors affect breast cancer risk, many of which exert their strongest influence on lifetime risk early in life. As a result, the earlier in a woman’s life her breast cancer risk can be established, the more effective interventions such as lifestyle changes can be. To date, strong risk indicators are either only applicable to a small fraction of women (e.g. BrCa genetic mutations) or are only measured late in life (such as mammographic density). However, in the case of mammographic density, the risks associated with mammography result in a high cost-benefit ratio for young women. Prior studies by Dr. Lilge’s group and various collaborators demonstrated strong relationships between bulk breast tissue optical spectra and established breast cancer risk factors such as mammographic density, age and pregnancy/parity. The advantages of optical spectroscopy (OS) as a technique for assessing breast cancer risk are that the technique is safe to use at any age, with any frequency, and the method does not require a highly skilled operator or physician interpretation, as bulk properties rather than an image are acquired. The technique could also theoretically be implemented as a low-cost, portable technology. However, to use OS as a risk assessment tool in younger women or as a pre-screening tool to identify women at elevated risk, it is necessary to establish OS parameters as independent risk factors and to determine how the risk relationships change for different age groups. This requires large, long-term studies at multiple institutions because of the number of confounding factors to be accounted for, including age, menopausal status, ethnicity and family history. The device used for the prior studies described above was unsuitable for multi-institution, large-scale studies due to a range of problems including strong operator dependence and fragile, bulky spectrometers. A modified device was developed, called the Cups OS device,taddress these issues. The devicehas13-wavelength laser module light sources instead of a broadband halogen light source and PIN photodiode detectors at fixed positions in cups rather than a single source-detector fibre bundle pair coupled to a spectrometer for detection.

Wavelengths for the Cups device were selected based on spectra obtained from previous studies, using the principal components analysis originally intended to reduce the dimensionality of the data. Wavelengths which captured the local absolute maxima of the principal component vectors were selected as these wavelengths capture most of the spectral variation seen in the prior study population. Fixed source and detector positions of the Cups were determined using Monte Carlo modelling of light propagation through the breast for both the average geometries for different breast sizes for the prior broadband device and the potential Cups. The final Cups geometries were selected to match the original system based on breast volume sampled, the sampling uniformity and the confounding signal from the adjacent pectoral muscle.

The Cups device was validated in two stages. First, by reducing the full-spectrum data from previous studies to the 13 wavelengths of the Cups device and repeating the analyses relating spectral properties to known breast cancer risk factors. This demonstrated that the reduced spectral content did not affect the ability to distinguish between different breast cancer risk groups. As a second validation, a comparison study was carried out where breast composition was measured using both the original full-spectrum and the modified Cups device, and the resulting spectra were compared to the women’s breast density measured by mammography. Both devices were able to identify women in the high-risk (high-density group) with no significant difference in predictive ability between the two devices.

 

Based on the success of the comparison study, copies of the Cups device have been built for 3 collaborating institutions, and large population surveillance studies are planned to evaluate OS parameters directly in relation to breast cancer risk. Additionally, these studies will simultaneously evaluate the utility of the device as a pre-screening tool to stratify women into risk groups to personalize mammography-based breast screening, which will be of particular utility in resource-limited environments.

 

“It is time that mammography only screening is modified, not only because of the ionization radiation-based risk but also the discomfort associated with the current approach. Additionally, the number of mammograms required to prevent one breast cancer-related death keeps increasing and is approaching 1 per 1000 screening procedures. It is time to rethink the entire breast cancer screening approach,” says Dr. Lilge, principal investigator on the study.

Area of application: Oncology
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