title: Absorbed dose distribution in glioma tumors in rat brain after therapeutic intratumoral injection of 201Tl-chloride.
abstract: Studies on animals with gliomas inoculated in the brain and treated with intratumoral injections of 201Tl-chloride have previously shown very promising results, with a survival several weeks longer than controls. Total regression was found in some animals, and necrosis was found in all the 201Tl-treated brain tumors. This study was undertaken to estimate the absorbed dose and dose distribution to the tumor based on the localization and clearance properties obtained from images with two high-resolution imaging techniques; pinhole single photon emission computed tomography (SPECT) and beta-camera. The images from the beta-camera were used to calculate the absorbed dose rate, using an in-house-developed, voxel-based Monte Carlo program, based on the EGS4 package. To evaluate the effects of different beta-particle energies on the absorbed dose rate distribution, simulations of medium- and high-energy electrons were conducted. Dose-volume histograms from these simulations show that the energy absorption is very locally distributed for 201Tl and medium energy, whereas high-energy beta emitters show a broader dose-volume distribution. The calculated total absorbed dose of 2-8 Gy in the tumor seems to be relativity low when considering the therapeutic effect that was seen. Further investigations, to determine the cause of the high therapeutic efficacy, are needed.
authors.affiliation: Department of Medical Radiation Physics, Lund University, Sweden. kaj.ljunggren@radfys.lu.se
authors.forename: Kaj
authors.initials: K
authors.lastname: Ljunggren
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Liu
authors.forename: Kjell
authors.initials: K
authors.lastname: Erlandsson
authors.forename: Michael
authors.initials: M
authors.lastname: Ljungberg
authors.forename: Leif
authors.initials: L
authors.lastname: Salford
authors.forename: Sven-Erik
authors.initials: SE
authors.lastname: Strand
mesh_terms: D000818:Animals; D001610:Beta Particles; D001921:Brain / Q000187:drug effects; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000188:drug therapy*; D002421:Caudate Nucleus / Q000187:drug effects; D004583:Electrons; D005910:Glioma / Q000175:diagnosis*; D007700:Kinetics; D009010:Monte Carlo Method; D009336:Necrosis; D011874:Radiometry; D011877:Radionuclide Imaging; D051381:Rats; D011916:Rats, Inbred F344; D012044:Regression Analysis; D013794:Thallium Radioisotopes / Q000627:therapeutic use*; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D013794:Thallium Radioisotopes