Magnetic resonance imaging correlated with the histopathological effect of Pd-bacteriopheophorbide (Tookad) photodynamic therapy on the normal canine prostate gland.
OBJECTIVE
To determine the optimal magnetic resonance imaging (MRI) methodology to assess photodynamic therapy (PDT)-induced histopathological responses in the prostate.


METHODS
Laparotomy was performed in five healthy dogs. Cylindrical diffuser was placed in the prostates to deliver light of 50-300 J/cm at 150 mW/cm and 763 nm to activate IV-injected Tookad (1 mg/kg b.w.). Fast spin echo (FSE) T2-weighted, post-contrast-enhanced T1-(CE-T1) and diffusion weighted images (DWI) were obtained pre- and 2 days, 7 days, and 1 month post-PDT. Radiological-histopathological correlation was performed at 7 days (n = 4) and 1 month (n = 1) after PDT. A qualitative assessment of signal changes and apparent diffusion coefficient (ADC) mapping was performed.


RESULTS
At 2 or 7 days post-PDT, there was good spatial correlation between PDT-induced hemorrhagic necrosis and unenhanced regions on CE-T1 images. There was a rapidly and persistently enhancing rim corresponding to edema and inflammation. FSE T2 and DWI showed altered signal but did not clearly define necrosis in all cases. At 1 month, it was hard to correlate MR images to histopathologic changes as they represented a mixture of necrosis and developing fibrosis, which led to a mixed signal intensity and less demarcated contrast enhancement.


CONCLUSIONS
At 7 days after PDT, gadolinium DTPA contrast-enhanced MRI is superior to DWI and T2 imaging in assessing the boundary of Tookad PDT-induced tissue necrosis in the normal canine prostate.
Huang
Zheng
Z
Radiation Oncology Department, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80045, USA. huang@msn.com
Haider
Masoom A
MA
Kraft
Susan
S
Chen
Qun
Q
Blanc
Dominique
D
Wilson
Brian C
BC
Hetzel
Fred W
FW
D000818:Animals; D001429:Bacteriochlorophylls / Q000494:pharmacology*; D003238:Connective Tissue / Q000473:pathology; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging; D004285:Dogs; D004487:Edema / Q000175:diagnosis / Q000473:pathology; D004848:Epithelium / Q000473:pathology; D005355:Fibrosis; D019786:Gadolinium DTPA; D006470:Hemorrhage / Q000175:diagnosis / Q000473:pathology; D007089:Image Enhancement; D007963:Leukocytes, Mononuclear / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D009336:Necrosis; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*; D010865:Pilot Projects; D011467:Prostate / Q000187:drug effects* / Q000473:pathology; D013997:Time Factors
D001429:Bacteriochlorophylls; D003287:Contrast Media; D017319:Photosensitizing Agents; C456120:palladium-bacteriopheophorbide; D019786:Gadolinium DTPA