Award Date


Degree Type


Degree Name

Master of Science (MS)


Health Physics and Diagnostic Sciences

First Committee Member

Steen Madsen

Number of Pages



The response of human glioma spheroids to ALA-mediated photodynamic therapy subjected to various optical dose delivery schemes is investigated. In particular, the effects of fluence, fluence rate, light dose fractionation and long-term repeat PDT is considered. Improved PDT response was found for low fluence rate photodynamic treatments i.e. those at or below 25 mW cm-2 . Results are consistent with the self-sensitized singlet oxygen mediated photobleaching model of Georgakoudi et al (Georgakoudi, 1998., in which the response is attributed to the deposition of singlet oxygen to a larger volume, i.e., deeper into the spheroid. The efficacy of high-fluence rate PDT (150 mW cm-2) can be improved by the introduction of dark intervals---an approximately 35% enhanced spheroid response was observed with cyclic intervals of between 15 and 45 s. Shorter on/off cycles appear more effective than longer cycles; Repetitive PDT consisting of multiple weekly treatments at sub-optimal fluences (12.5 or 25 J cm-2) revealed marked improvements in efficacy. (Abstract shortened by UMI.).


Delivery; Glioma; Human; Investigation; Light; Photodynamic; Schemes; Spheroids; Therapy

Controlled Subject

Medicine; Radiation; Nuclear physics; Oncology; Diagnostic imaging

File Format


File Size

2201.6 KB

Degree Grantor

University of Nevada, Las Vegas




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