Diffusion-Weighted MRI for Monitoring Tumor Response to Photodynamic Therapy

• Type of Material: Article
• Authors: Hesheng Wang, Emory University; Baowei Fei, Emory University
• Language: English
• Date: 2010-08
• Publisher: Wiley-Blackwell
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2010 Wiley-Liss, Inc.
• Final Published Version (URL): http://onlinelibrary.wiley.com/doi/10.1002/jmri.22247/abstract
• Title of Journal or Parent Work: Journal of Magnetic Resonance Imaging
• ISSN: 1053-1807
• Volume: 32
• Issue: 2
• Start Page: 409
• End Page: 417
• Grant/Funding Information: Contract grant sponsor: National Cancer Institute; Contract grant number: R21CA120536, R24CA110943; Contract grant sponsors: Atlanta Clinical and Translational Science Institute and Georgia Cancer Coalition (Distinguished Clinicians and Scientists Award; PI, Fei).
• Keywords: photodynamic therapy; efficacy assessment; apparent diffusion coefficients (ADC); diffusion-weighted MRI; treatment monitoring; prostate cancer
• Research Categories: Engineering, Biomedical; Health Sciences, Radiology

Abstract

Purpose To examine diffusion-weighted MRI (DW-MRI) for assessing the early tumor response to photodynamic therapy (PDT). Materials and Methods Subcutaneous tumor xenografts of human prostate cancer cells (CWR22) were initiated in athymic nude mice. A second-generation photosensitizer, Pc 4, was delivered to each animal by a tail vein injection 48 h before laser illumination. A dedicated high-field (9.4 Tesla) small animal MR scanner was used to acquire diffusion-weighted MR images pre-PDT and 24 h after the treatment. DW-MRI and apparent diffusion coefficients (ADC) were analyzed for 24 treated and 5 control mice with photosensitizer only or laser light only. Tumor size, prostate specific antigen (PSA) level, and tumor histology were obtained at different time points to examine the treatment effect. Results Treated mice showed significant tumor size shrinkage and decrease of PSA level within 7 days after the treatment. The average ADC of the 24 treated tumors increased 24 h after PDT (P < 0.001) comparing with pre-PDT. The average ADC was 0.511 ± 0.119 × 10−3 mm2/s pre-PDT and 0.754 ± 0.181 × 10−3 mm2/s 24 h after the PDT. There is no significant difference in ADC values pre-PDT and 24 h after PDT in the control tumors (P = 0.20). Conclusion The change of tumor ADC values measured by DW-MRI may provide a noninvasive imaging marker for monitoring tumor response to Pc 4-PDT as early as 24 h.