Nuclear medicine imaging has the potential to provide quantitative information about the distribution of an injected radiopharmaceutical in the body. The therapeutic use of radiopharmaceuticals (targeted radionuclide therapy) is one of the nuclear medicine applications that requires images that are quantitatively accurate. In this case, absolute quantification of the uptake of injected activity in various organs over time is needed to predict absorbed doses in different organs and tumour lesions and therefore the toxicity and/or efficacy of the treatment.
To address the need for harmonized protocols and guidelines for acquiring quantitative information from nuclear medicine imaging procedures, the IAEA initiated the Coordinated Research Project (CRP) E21007, involving 13 research institutions from 12 countries. Individual research activities included development and testing of dosimetric protocols for a variety of radionuclides, dosimetric software development, intercomparison of radionuclide calibrators, etc., with the results presented at various international conferences or published in peer-reviewed journals.
Major achievements of this CRP include the development of the guidance document IAEA Human Health Reports 9 on Quantitative Nuclear Medicine Imaging and the results of the multicentre intercomparison with Ba-133 sources. The purposes of the study were to i) investigate the capabilities for quantitative single photon imaging at different sites worldwide, including sites where resources are limited; ii) develop and test quantitative imaging methods in nuclear medicine practice; iii) assess the need for standardization and harmonization of quantitative nuclear medicine on an international scale; and iv) assess the achievable accuracy of absolute activity quantitation for different nuclear medicine methodologies. The study investigated quantitative imaging capabilities at sites with a variety of experience and equipment and assessed levels of errors in activity quantitation in planar, SPECT and SPECT/CT imaging. The Ba-133 sources were calibrated for activity by the National Institute of Standards and Technology (NIST), but the activity was initially unknown to the participants. Two trials were carried out in which the participants first estimated the activities using their local standard protocols, and then repeated the measurements using a standardized acquisition and analysis protocol. Finally, processing of the imaging data from the second trial was repeated by a single centre using a fixed protocol.
The project demonstrated the need for training and standardized protocols to achieve good levels of quantitative accuracy and precision in a multicentre setting. Absolute quantification of simple objects with no background was possible with the strictest protocol to about 6% with planar imaging and SPECT, and within 2% for SPECT/CT. The study underlined the superiority of SPECT/CT over other modalities for quantitative imaging purposes. In fact, SPECT/CT showed the best accuracy and lowest variability due to the built-in inherent and theoretically rigorous correction methods.
Overall, this study showed, for the first time, that international multicentre trials for image quantification in molecular radiotherapy can be carried out and may be the first step towards improved traceability of dosimetry studies in patients.
13 research institutions from 12 countries have participated in this CRP: Bangladesh, Brazil, Croatia, Cuba, France, Germany, South Africa, Sweden, Thailand, Uruguay, the United Kingdom, and the USA.
The IAEA Human Health Reports 9 “Quantitative Nuclear Medicine Imaging: Concepts, Requirements and Methods” was developed in the frame of this CRP. https://www-pub.iaea.org/books/iaeabooks/10380/Quantitative-Nuclear-Medicine-Imaging-Concepts-Requirements-and-Methods
For more information, please see the CRP description: