An orthotopic xenograft (AsPC-1) murine model () for PaC PDT was used in accordance with the policies and approved protocol of the Institutional Animal Care and Use Committee (IACUC) at Dartmouth College.5 The animals were fed a chlorophyll-free diet (MP Biomedicals, Solon, OH) to minimize autofluorescence. The tumors were imaged after they had reached a volume of by measurement with externally applied calipers. MR images were obtained using a Phillips Achieva 3.0T X-series MRI with a modified rodent coil (Philips Research Europe, Hamburg, Germany), as previously described.5,6 Gd-based contrast enhancement (, Magnevist®) was delivered via a catheter (MTV-01, Braintree Scientific Inc., Braintree, MA) placed in the intraperitoneal (i.p.) cavity. After a preliminary survey, a T2-weighted turbo spin echo (T2W-TSE) sequence was performed in sagittal, axial, and coronal imaging planes. The tumor was identified in each imaging plane, and the best orientation for tumor resection, slicing, and image correlation was chosen. Typically, the axial T2W-TSE image sequence was selected for the tissue-slicing plane and the coronal T2W-TSE was used to align the image scans with the outermost edge of the tumor, termed the tumor origin [Fig. 1(a)]. After the scanning slices were aligned to the tumor, the images used for analysis were collected as follows: a T1-weighted turbo spin echo [T1W-TSE, Fig. 1(b)] image sequence was performed; Magnevist® was administered; a T2W-TSE image sequence [Fig. 1(c)] was collected during contrast localization and then a postcontrast T1W-TSE [Fig. 1(d)] image sequence was performed 10 min after injection. The T1W-TSE contrast difference [T1W-CD=(post-Gd T1W-TSE)−(pre-Gd T1W-TSE), Fig. 1(e)] image sequence was calculated using the Phillips MRI software.