Using near-infrared spectroscopy to study static and dynamic hemoglobin contrast associated with breast cancer.
Near-infrared spectroscopy (NIRS) of the breast exploits the inherent contrast of tumors
due to increased hemoglobin absorption of light relative to healthy tissue. Optical
imaging has been used to identify, characterize and monitor breast cancer
non-invasively. This work first describes a new instrument for diffuse optical
mammography in parallel plate geometry that operates over a... read morebroad spectral range of 600
- 1000 nm, features a scan time of 1 - 2 min, and allows for dynamic measurements at a
selected region of interest. Furthermore, this new instrument is capable of depth
discrimination of optical inhomogeneities embedded in the examined tissue by using
multiple off-axis detection fibers. Second, we report on an optical mammography study on
eight patients with breast cancer who underwent neoadjuvant chemotherapy to identify
biomarkers that indicate the patient's degree of response. We found that both the total
hemoglobin concentration and hemoglobin oxygen saturation (SO2) decreased by a greater
amount in responders than in non-responders during therapy. This result applied to both
cancerous and healthy breasts, but the discrimination of responders and non-responders
was more significant with SO2 measurements in the cancerous breast. We developed a
cumulative response index that achieved 100% sensitivity and 100% specificity in
characterizing response half way through chemotherapy. Lastly, induced arterial blood
pressure oscillations result in peripheral hemodynamic oscillations that provide
information about local changes in blood flow and blood volume. We first report on a
comparison of two protocols to induce cerebral hemodynamic oscillations, paced breathing
and cyclic inflation of pneumatic thigh-cuffs. These two protocols induce systemic mean
arterial pressure oscillations of similar magnitude but show varied response in the
dynamics of cerebral oxy- and deoxy-hemoglobin concentrations. This variability may be
due to altered physiological states under the paced breathing protocol, or anatomical
differences between subjects. We then report on an initial attempt at inducing
hemodynamic oscillations using pneumatic thigh-cuffs in patients undergoing neoadjuvant
chemotherapy. We found that in one patient with complete data, we were unable to
distinguish changes in the hemodynamics between healthy and cancerous breasts.
Ultimately, a more robust measurement protocol is needed to ensure that oscillations
driven by mean arterial pressure are reliably induced in the breast. To advance NIRS
into clinical practice, larger studies, with standardized equipment need to be performed
to establish its value for individual
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Biomedical Engineering.
Advisor: Sergio Fantini.
Committee: Irene Georgakoudi, Shuchin Aeron, and Xavier Intes.
Keywords: Biomedical engineering, and Medical imaging.read less