Needs for radioactivity standards and measurements in the life sciences

For almost 100 years, radioactivity has been one of the major tools in medi cine. Therapeutic applications that began with Ra-226 and Rn-222 implants h ave rapidly grown to include about 20 radionuclides with radiations specifi cally chosen to treat at different depths in tissue - ranging from a few mi llimeters for intravascular therapy to a few centimeters in the case of lar ge solid tumors. Systemic treatments with radiopharmaceuticals have grown f rom the traditional I-131 to more than ten candidate nuclides which are to be labeled to tumor-specific radiopharmaceuticals. Diagnostic radiopharmace uticals are used in over 13 million procedures in the United States annuall y. About 40 nuclides are under investigation for these applications includi ng single photon emitters for SPECT (single photon emission computed tomogr aphy) and positron emitters for PET (positron emission tomography). In addi tion to the mainstays of therapeutic and diagnostic radiology, radionuclide s are widely used for in vitro tracers in the life sciences and represent o ne of the main tools in the field of molecular biology. (C) 2000 Elsevier S cience Ltd. All rights reserved.