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Proceedings Paper

Monitoring cancer treatment response using photoacoustic and ultrasound spectral analysis in combination with oxygenation measurements (Conference Presentation)
Author(s): Eno Hysi; Jonathan P. May; Lauren Wirtzfeld; Elijus Undzys; Shyh-Dar Li; Michael C. Kolios
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Paper Abstract

At clinically-relevant depths, the frequency content of photoacoustic signals encodes information about the size, concentration and spatial distribution of non-resolvable blood vessels. This study evaluates whether photoacoustics can detect cancer therapy-induced vascular perturbations. Photoacoustic/ultrasound (PA/US) spectral analysis was combined with functional, PA-based oxygenation and power Doppler (PD) perfusion estimates to assess treatment response. Co-registered, in-vivo US/PA/PD imaging of mice bearing breast cancer tumors was performed pre-treatment and 30m/2h/5h/24h/7d post-treatment (VevoLAZR, Fujifilm VisualSonics). Hyperthermia treatment (1h, 43C) was performed after systemic injections of doxorubicin-loaded thermosensitive liposomes (TSL, n=13) or free doxorubicin (DOX, n=11). Response was classified according to 2h, PA-based oxygenation drop and endpoint (>9d), caliper-based volume reduction. At all time-points/wavelengths (750/850nm), the spectral-slope (SS) was computed from the normalized US/PA power spectra using depth-matched reference phantoms. The percent-vascularity (PV) was estimated for the animal with the largest oxygenation-drop at 2h. TLS-treated responders decreased their PA-SS by 1.9x @750nm and 5.8x @850nm 30m post-treatment and remained constant for 24h; tumor oxygenation followed the same trend. Non-responding SS remained unchanged for 24h. The 750nm SS was 18.7x lower than 850nm suggesting the TSL is sensitive vessel oxygenation. Responder PV decreased 100% when the 30m oxygenation dropped 15% and increased 7x when the 7d oxygenation increased 20%. DOX-responders exhibited similar trends to TSL-responders although the 750nm PA-SS was 1.6x smaller and post-treatment PV was 50% higher. The US-SS remained unchanged until 7d post-treatment suggesting its sensitivity to tumor cell-death. These findings suggest that PA spectral analysis has potential in monitoring cancer treatment response.

Paper Details

Date Published: 27 April 2016
PDF: 1 pages
Proc. SPIE 9708, Photons Plus Ultrasound: Imaging and Sensing 2016, 970824 (27 April 2016); doi: 10.1117/12.2213596
Show Author Affiliations
Eno Hysi, Ryerson Univ. (Canada)
Jonathan P. May, The Univ. of British Columbia (Canada)
Lauren Wirtzfeld, Ryerson Univ. (Canada)
Elijus Undzys, Ontario Institute for Cancer Research (Canada)
Shyh-Dar Li, The Univ. of British Columbia (Canada)
Michael C. Kolios, Ryerson Univ. (Canada)

Published in SPIE Proceedings Vol. 9708:
Photons Plus Ultrasound: Imaging and Sensing 2016
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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