Vaijayantee Belle, Ali Anka, Nathan Cross, Paul Thompson, Eric Mott, Rahul Sharma, Kayla Gray, Ruozhen Zhang, Yueshuo Xu, Jiayang Sun, Chris Flask, Nancy Oleinick, David Dean
Introduction: Dynamic Contrast-Enhanced-Magnetic Resonance Imaging (DCE-MRI) appears to provide an
unambiguous means of tracking the outcome of photodynamic therapy (PDT) of brain tumors with the photosensitizer
Pc 4. The increase in Gd enhancement observed after Pc 4-PDT may be due to a temporary opening of the blood-brain-barrier
which, as noted by others, may offer a therapeutic window. Methods: We injected 2.5 x 105 U87 cells into the
brains of 9 athymic nude rats. After 8-9 days peri-tumor DCE-MRI images were acquired on a 7.0 T microMRI scanner
before and after the administration of 150 μL Gd. DCE-MRI scans were repeated three times following Pc 4-PDT.
Results: The average, normalized peak enhancement in the tumor region, approximately 30-90 seconds after Gd
administration, was 1.31 times greater than baseline (0.03 Standard Error [SE]) prior to PDT and was 1.44 (0.02 SE)
times baseline in the first Post-PDT scans (Day 11), a statistically significant (p ≈ 0.014, N=8) increase over the Pre-
PDT scans, and was 1.38 (0.02 SE) times baseline in the second scans (Day 12), also a statistically significant (p ≈ 0.008,
N=7) increase. Observations were mixed in the third Post-PDT scans (Day 13), averaging 1.29 (0.03 SE) times baseline
(p ≈ 0.66, N=7). Overall a downward trend in enhancement was observed from the first to the third Post-PDT scans.
Discussion: DCE-MRI may provide an unambiguous indication of brain tumor PDT outcome. The initial increase in
DCE-MRI signal may correlate with a temporary, PDT-induced opening of the blood-brain-barrier, creating a potential
therapeutic window.
Introduction: Dynamic Contrast-Enhanced-Magnetic Resonance Imaging (DCE-MRI) may provide a means of tracking
the outcome of Pc 4-sensitized photodynamic therapy (PDT) in deeply placed lesions (e.g., brain tumors). We previously
determined that 150 μL of gadolinium (Gd-DTPA) produces optimal enhancement of U87-derived intracerebral tumors
in an athymic nude rat glioma model. We wish to determine how consistently DCE-MRI enhancement will detect an
increase in Gd-enhancement of these tumors following Pc 4-PDT. Methods: We injected 2.5 x 105 U87 cells into the
brains of 6 athymic nude rats. After 7-8 days pre-Pc 4 PDT peri-tumor DCE-MRI images were acquired on a 7.0T
microMRI scanner before and after administration of 150 μL Gd. DCE-MRI scans were repeated on Days 11, 12, and 13
following Pc 4-PDT (Day 8 or 9). Results: Useful DCE-MRI data were obtained for these animals before and after Pc 4-
PDT. In the pre-Pc 4-PDT DCE-MRI scans an average normalized peak Gd enhancement was observed in tumor tissue
that was 1.297 times greater than baseline (0.035 Standard Error [SE]). The average normalized peak Gd enhancement in
the tumor tissue in the scan following PDT (Day 11) was 1.537 times greater than baseline (0.036 SE), a statistically
significant increase in enhancement (p = 0.00584) over the pre-PDT level. Discussion: A 150 μL Gd dose appears to
provide an unambiguous increase in signal indicating Pc 4-PDT-induced necrosis of the U87-derived tumor. Our DCEMRI
protocol may allow the development of a clinically robust, unambiguous, non-invasive technique for the
assessment of PDT outcome.
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