Patient-specific internal radionuclide dosimetry

Abstract

The development of patient-specific treatment planning systems is of outmost importance in the development of radionuclide dosimetry, taking into account that quantitative three-dimensional nuclear medical imaging can be used in this regard. At present, the established method for dosimetry is based on the measurement of the biokinetics by serial gamma-camera scans, followed by calculations of the administered activity and the residence times, resulting in the radiation-absorbed doses of critical organs. However, the quantification of the activity in different organs from planar data is hampered by inaccurate attenuation and scatter correction as well as because of background and organ overlay. In contrast, dosimetry based on quantitative three-dimensional data can be more accurate and allows an individualized approach, provided that all effects that degrade the quantitative content of the images have been corrected for. In addition, inhomogeneous organ accumulation of the radionuclide can be detected and possibly taken into account. The aim of this work is to provide adequate information on internal emitter dosimetry and a state-of-the-art review of the current methodology and future trends.

MIRD Pamphlet No. 23: Quantitative SPECT for Patient-Specific 3-Dimensional Dosimetry in Internal Radionuclide Therapy

“…The accuracy of dose calculations has improved with the use of the patient’s own images in Monte Carlo radiation transport calculations instead of generic anatomic models, such as reference man (Fig. 1) (10–12). As a result, accurate estimation of the time-integrated activity has become even more pressing.…”

“…The voxel S value and dose point–kernel approaches are considered to be a reasonable compromise between simplified body or organ model–based calculations and more computer-intensive and time-consuming methods based on Monte Carlo radiation transport. Functional (e.g., from SPECT) and anatomic (e.g., from CT) imaging coupled with direct Monte Carlo radiation transport is generally considered to be the most accurate and most patient-specific of all currently available dose estimation methods (10). …”

Development and validation of RAYDOSE: a Geant4-based application for molecular radiotherapy

“…dose (MIRD) schema (Bolch et al 2009). However, the accuracy of this method is limited because it is mainly based on the evaluation of the mean absorbed dose to an organ/lesion and on mathematical phantom models (Tsougos et al 2010). Lesions whose dimensions are large with respect to the spatial resolution of the imaging system commonly exhibit non-uniform uptake, and dosimetry based on mean absorbed dose may result in the administration of a sub-optimal radionuclide activity.…”

“…Many authors have contributed to the creation of databases of S voxel values (Dieudonné et al 2010, Lanconelli et al 2012 and of dose point kernel for different radionuclides (Botta et al 2011, Papadimitroulas et al 2012. Nevertheless, MC techniques are considered to provide the most accurate approach to personalized radiotherapy dose calculation (Mohan 1997, Tsougos et al 2010, Dewaraja et al 2012. A number of MC codes have been developed for 3D patient-specific dose calculation, implementing different approaches.…”

Relevance of artefacts in 99mTc-MAA SPECT scans on pre-therapy patient-specific 90Y TARE internal dosimetry: a GATE Monte Carlo study

“…Threedimensional (3D) internal dosimetry has an increasingly important role in the planning and monitoring of radionuclide therapy treatments, for the purpose of optimizing the activity administration (Strigari et al 2014, Stokke et al 2017, Cicone et al 2019. Among the 3D dosimetry methods available, the direct MC simulation of radiations emitted in radionuclide decays and their interaction with living matter, based on morphological and functional tomographic imaging, is considered the most accurate and patient-specific approach (Tsougos et al 2010, Dewaraja et al 2012, Amato et al 2018. However, this is true as long as the simulated system modeled from imaging actually reproduces accurately the real system, which is the patient's body and the radionuclide biodistribution within it.…”