Noninvasive diffuse optical monitoring of head and neck tumor blood flow and oxygenation during radiation delivery
Spotlight summary: Functional imaging for cancer therapy monitoring is a dream for oncologists, theoretically enabling additional treatment decisions to be made prior to any tumor size change that may follow. Functional imaging requires monitoring of a biomarker linked to the outcome of the therapeutic intervention. One such example is the effect of tissue oxygenation on the efficacy of radiation therapy, where a well-documented decrease in efficacy is found in hypoxic tissues treated with radiotherapy. Recent studies have utilized magnetic resonance imaging (MRI) and dynamic contrast computed tomography (CT) to detect tumor oxygenation changes during the course of radiation therapy and found that tumors with less perfusion show a poor response. However, use of MRI and CT imaging modalities accounts for significant cost and neither instrument would enable bedside monitoring. Near infrared (NIR) optical methods provide a means for portable, inexpensive, bedside monitoring of oxygenation status of tissue through differentiation of spectral changes in oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb). A number of NIR diffuse optical methods could provide information ranging from noninvasive point measurements on the surface of a tissue to diffuse images of tissue oxygenation status.
In the current study by Dong, et al, NIR diffuse correlation spectroscopy (DCS) flow oximetry was investigated for its utility in monitoring oxygenation in enlarged lymph nodes of patients with head and neck cancer. Due to the portability of the monitoring device, oxygenation status was monitored during radiation therapy administration, as well as throughout the 7-week cycle of fractionated radiotherapy. This marks the first report of oxygenation status changes at the time of radiation therapy administration, thus enabling oxygenation detection during a single radiation administration as well as throughout the course of treatment. Phantom studies were completed to quantify artifacts seen from interaction of the radiation beam with the photodiode detectors to optimize probe placement. In the current study, 11 patients were monitored during therapy, producing large inter-patient variation in tumor hemodynamic response. A significant increase in tumor blood flow was found during the first week of radiotherapy, however only small insignificant changes were seen in blood oxygenation levels. Interestingly, all patients monitored in the current study showed complete response to the radiation therapy illustrating the need for study in an increased patient population to determine the prognostic significance of NIR DCS hemodynamic monitoring during radiotherapy.
ToC Category: Optics in Cancer Research
|OCIS Codes:||(170.0170) Medical optics and biotechnology : Medical optics and biotechnology|
|(170.3660) Medical optics and biotechnology : Light propagation in tissues|
|(170.3880) Medical optics and biotechnology : Medical and biological imaging|
|(170.6480) Medical optics and biotechnology : Spectroscopy, speckle|
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