3D Absorbed Dose Calculations Based on SPECT: Evaluation for 111-In/90-Y Therapy using Monte Carlo Simulations

Abstract

A general method is presented for patient-specific three-dimensional (3D) absorbed dose calculations based on quantitative SPECT activity measurements. The computational scheme includes a method for registration of the CT study to the SPECT image, and compensation for attenuation, scatter, and collimator-detector response including septal penetration, performed as part of an iterative reconstruction method. From SPECT images, the absorbed dose rate is calculated using an EGS4 Monte Carlo code, which converts the activity distribution to an absorbed dose rate distribution. Evaluation of the accuracy in the activity quantification and the absorbed dose calculation is based on realistic Monte Carlo simulated SPECT data of a voxel-computer phantom and (111)In and (90)Y. Septal penetration was not included in this study. The SPECT-based activity concentrations and absorbed dose distributions are compared to the actual values; the results imply that the corrections for attenuation and scatter yield results of high accuracy. The presented method includes compensation for most parameters deteriorating the quantitative image information. Inaccuracies are, however, introduced by the limited spatial resolution of the SPECT system, which are not fully compensated by the collimator-response correction. The proposed evaluation methodology may be used as a basis for future inter-comparison of different dosimetry calculation schemes.

An Evidence-Based Review of Quantitative SPECT Imaging and Potential Clinical Applications

“…This method was subsequently applied to human subjects with suspected recurrent brain malignancies, and a correlation was found between lower SUV and prolonged survival (35). Iida et al have also used quantitative 201 Tl SPECT in dynamic myocardial perfusion imaging to extract the uptake and washout kinetics of the tracer in dogs and compared their results against those for 51 Co-microspheres (36). This was one of the first reports of fully quantitative kinetic analysis in SPECT of the myocardium and underlines the potential of new applications for quantitative SPECT.…”

“…These include 111 In-labeled antibodies and tumor-seeking radiopharmaceuticals (37)(38)(39), 131 I uptake in tumors (40,41), 177 Lu for dosimetry calculations in therapeutic applications (42,43), 186 Re in palliative bone cancer therapy (44), and even quantitative bremsstrahlung imaging of 90 Y (45).…”

Pharmacokinetic digital phantoms for accuracy assessment of image-based dosimetry in177Lu-DOTATATE peptide receptor radionuclide therapy

“…The pixel values were then replaced by random deviates drawn from a Poisson distribution using the re-normalized pixel values as the mean values. The simulated studies were exported to the clinically used implementation of LundADose, a software package for 2D/3D dosimetry developed at our institution (Sjögreen et al 2002, Ljungberg et al 2003.…”

MIRD Pamphlet No. 25: MIRDcell V2.0 Software Tool for Dosimetric Analysis of Biologic Response of Multicellular Populations

“…However, there have been dramatic improvements in dosimetry models that reflect the substructure of organs as well as tissue elements within them (3)(4)(5). These models rely on improved nuclear medicine imaging capabilities that facilitate determination of activity within the voxels that represent tissue elements that are about 0.2-1 cm 3 in volume (6)(7)(8)(9). However, even these improved approaches assume that all cells within the tissue element receive essentially the same absorbed dose.…”