Treatment system for whole bladder wall photodynamic therapy with in vivo monitoring and control of light dose rate and dose.
A system is described for in vivo monitoring and control of light dose rate and dose during whole bladder photodynamic therapy (PDT). A modified cystoscope admits an isotropic light source (fiber with diffusing tip, connected to a dye laser) and three translucent nylon catheters that are unfolded in three directions along the bladder wall. An isotropic light detector (0.8 mm. diameter probe on 200 microns. fiber) is inserted into each catheter and connected to an amplifier displaying light dose rate (in mW/cm.2) and integrated light dose (in J/cm.2) for each probe. Before treatment a low light level is used to optimize the position of the light source, requiring equal readings by each of the three dosimetry probes. Uniformity of irradiation is checked by moving the probes through their respective catheters along the bladder wall. With red light (wavelength 630 nm.) a dose rate uniformity of +/- 20% could be achieved in vivo in dog bladder. With green light (514.5 nm.) uniform irradiation was difficult, most likely due to a much smaller contribution of scattered light. Measurements during clinical PDT show that optimizing the light source position by suprapubic transvesical ultrasound may not secure uniform irradiation. Half-way into the treatment a difference of 100% between the readings of two probes was noted. Adjusting the position of the light source resulted in integrated light dose variations of less than 20% among the three probes at the end of treatment.
Marynissen
J P
JP
Dr. Daniel den Hoed Cancer Center, Department of Clinical Physics, Rotterdam, The Netherlands.
Jansen
H
H
Star
W M
WM
D000818:Animals; D003558:Cystoscopy; D004285:Dogs; D005260:Female; D006801:Humans; D010778:Photochemotherapy / Q000295:instrumentation / Q000379:methods*; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation / Q000379:methods; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy*