Relative Biological Effectiveness of Alpha-Particle Emitters In Vivo at Low Doses

• Published in: Radiation research Vol. 137; no. 3; pp. 352 - 360
• Main Authors: Howell, Roger W., Azure, Michael T., Narra, Venkat R., Rao, Dandamudi V.
• Format: Journal Article
• Language: English
• Published: Oak Brook, Il Radiation Research Society 01-03-1994
• Subjects: 560120 - Radiation Effects on Biochemicals, Cells, & Tissue Culture; 990200 - Mathematics & Computers; ALPHA PARTICLES; ANIMALS; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; Biological and medical sciences; BIOLOGICAL EFFECTS; BIOLOGICAL RADIATION EFFECTS; BODY; CALCULATION METHODS; Cell Survival - radiation effects; CHARGED PARTICLES; Dose response relationship; Dose-Response Relationship, Radiation; DOSE-RESPONSE RELATIONSHIPS; Dosimetry; ENERGY TRANSFER; EVEN-EVEN NUCLEI; GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; GONADS; HEAVY NUCLEI; HOURS LIVING RADIOISOTOPES; IMMUNOTHERAPY; IRRADIATION; ISOTOPES; LEAD 212; LEAD ISOTOPES; LET; LOW DOSE IRRADIATION; Male; MALE GENITALS; MAMMALS; Medical sciences; MEDICINE; MICE; NUCLEAR MEDICINE; NUCLEI; ORGANS; Photons; Radiation dosage; RADIATION EFFECTS; Radiation therapy and radiosensitizing agent; RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT; Radioactive decay; RADIOIMMUNOTHERAPY; RADIOISOTOPES; Radioisotopes - metabolism; RADIOLOGY; Radionuclides; RADIOTHERAPY; RBE; Relative biological effectiveness; RODENTS; Solar X rays; Sperm Head - metabolism; Sperm Head - radiation effects; Subcellular Fractions - metabolism; TESTES; Testis - metabolism; Testis - radiation effects; THERAPEUTIC USES; THERAPY; Treatment with physical agents; Treatment. General aspects; Tumors; USES; VERTEBRATES; Alpha irradiation; Spermatogenesis; Low dose; Rodentia; Relative biological effectiveness; Intratesticle administration; Cytotoxicity; Radiotherapy; Testicle; Male genital system; In vivo; Ionizing irradiation; Vertebrata; Mammalia; Radiobiology; Mouse; Animal; Lead; Pharmacokinetics; Radiopharmaceuticals; Daughter product
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3578710

The therapeutic potential of radionuclides that emit α particles, as well as their associated health hazards, have attracted considerable attention. The ^{224}{\rm Ra}$ daughters ^{212}{\rm Pb}$ and 212 Bi, by virtue of their radiation properties which involve emission of α and β particles in their decay to stable ^{208}{\rm Pb}$, have been proposed as candidates for radioimmunotherapy. Using mouse testes as the experimental model and testicular spermhead survival as the biological end point, the present work examines the radiotoxicity of ^{212}{\rm Pb}$ and its daughters. When ^{212}{\rm Pb}$, in equilibrium with its daughters 212 Bi, 212 Po and ^{208}{\rm Tl}$, was administered directly into the testis, the dose required to achieve 37% survival ($D_{37}$) was 0.143 ± 0.014 Gy and the corresponding RBE of the mixed radiation field was 4.7 when compared to the $D_{37}$ for acute external 120 kVp X rays. This datum, in conjunction with our earlier results for 210 Po, was used to obtain an RBE-LET relationship for α particles emitted by tissue-incorporated radionuclides: ${\rm RBE}_{\alpha}=4.8-6.1\times 10^{-2}\ {\rm LET}+1.0\times 10^{-3}\ {\rm LET}^{2}$. Similarly, the dependence of RBE on α-particle energy $E_{\alpha}$ was given by ${\rm RBE}_{\alpha}=22\ E_{\alpha}^{-0.73}$. These relationships, based on in vivo experimental data, may be valuable in predicting biological effects of α-particle emitters.