Theranostic SPECT reconstruction for improved resolution: application to radionuclide therapy dosimetry

Abstract

Background SPECT-derived dose estimates in tissues of diameter less than 3× system resolution are subject to significant losses due to the limited spatial resolution of the gamma camera. Incorporating resolution modelling (RM) into the SPECT reconstruction has been proposed as a possible solution; however, the images produced are prone to noise amplification and Gibbs artefacts. We propose a novel approach to SPECT reconstruction in a theranostic setting, which we term SPECTRE (single photon emission computed theranostic reconstruction); using a diagnostic PET image, with its superior resolution, to guide the SPECT reconstruction of the therapeutic equivalent. This report demonstrates a proof in principle of this approach. Methods We have employed the hybrid kernelised expectation maximisation (HKEM) algorithm implemented in STIR, with the aim of producing SPECT images with PET-equivalent resolution. We demonstrate its application in both a dual 68Ga/177Lu IEC phantom study and a clinical example using 64Cu/67Cu. Results SPECTRE is shown to produce images comparable in accuracy and recovery to PET with minimal introduction of artefacts and amplification of noise. Conclusion The SPECTRE approach to image reconstruction shows improved quantitative accuracy with a reduction in noise amplification. SPECTRE shows great promise as a method of improving SPECT radioactivity concentrations, directly leading to more accurate dosimetry estimates in small structures and target lesions. Further investigation and optimisation of the algorithm parameters is needed before this reconstruction method can be utilised in a clinical setting.

(An overview of) Synergistic reconstruction for multimodality/multichannel imaging methods

“…The reconstruction then becomes an optimisation problem in terms of ζ. This approach has been used in MMI : see [76,77,78] (PET with MRI), [79] (SPECT with PET), [80] (fluorescence molecular tomography with CT or MRI), [81] (DOT with CT), but also for MCMI : PET dynamic imaging using static images as guide [76] or temporal features derived from the raw data [82].…”

Cerebrovascular Segmentation Model Based on Spatial Attention-Guided 3D Inception U-Net with Multi-Directional MIPs

“…MIP obtains a two-dimensional image by the projection method [24], which is generated by calculating the maximum-density pixels encountered along each ray of the scanned object as illustrated in Figure 2. Despite its simplicity, MIP has been widely adopted in medical image analysis, such as reconstruction [32,33], detection [34,35], and segmentation [36][37][38]. The paper proposing the JointVesselNet [23] applied the idea of MIP to cerebrovascular segmentation.…”

Multimodality imaging of nanoparticle‐based vaccines: Shedding light on immunology

“…For instance, the emergence of radionuclide therapy, in which a radiolabeled molecule is used to target and damage a tumor rather than simply provide an image, has increased interest in the use of many molecules radiolabeled by a β À (electron) emitter, such as the clinically approved 177 Lu-DOTATATE (lutathera) (Strosberg et al, 2017). In radionuclide therapy, it is sometimes desirable to be able to image the distribution of radioisotope for a variety of purposes, ranging from tumor tracking to internal dosimetry (Marquis et al, 2021). This approach is termed "theranostics."…”

“…For instance, the emergence of radionuclide therapy, in which a radiolabeled molecule is used to target and damage a tumor rather than simply provide an image, has increased interest in the use of many molecules radiolabeled by a β − (electron) emitter, such as the clinically approved 177 Lu‐DOTATATE (lutathera) (Strosberg et al, 2017). In radionuclide therapy, it is sometimes desirable to be able to image the distribution of radioisotope for a variety of purposes, ranging from tumor tracking to internal dosimetry (Marquis et al, 2021). This approach is termed “theranostics.” While it sometimes involves dual‐radiolabeling with both a positron emitter for PET imaging and a β − emitter for therapy, some β − emitters may also emit gamma rays at a rate desirable for SPECT imaging, allowing one to use a single radioisotope for both therapy and imaging.…”