Abstract
Fluoroscopic procedures involving radionuclides would benefit from interventional nuclear imaging by obtaining real-time feedback on the activity distribution. We have previously proposed a dual-layer detector that offers such procedural guidance by simultaneous fluoroscopic and nuclear planar imaging. Acquisition of single photon computed tomography (SPECT) and cone beam computed tomography (CBCT) could provide additional information on the activity distribution. This study investigates the feasibility and the image quality of simultaneous SPECT/CBCT, by means of phantom experiments and simulations.Simulations were performed to study the obtained reconstruction quality for (i) clinical SPECT/CT, (ii) a dual-layer scanner configured with optimized hardware, and (iii) our (non-optimized) dual-layer prototype. Experiments on an image quality phantom and an anthropomorphic phantom (including extrahepatic depositions with volumes and activities close to the median values encountered in hepatic radioembolization) were performed with a clinical SPECT/CT scanner and with our dual-layer prototype. Nuclear images were visually and quantitatively evaluated by measuring the tumor/non-tumor (T/N) ratio and contrast-to-noise ratio (CNR).The simulations showed that the maximum obtained CNR was 38.8 ± 0.8 for the clinical scanner, 30.2 ± 0.9 for the optimized dual-layer scanner, and 20.8 ± 0.4 for the prototype scanner. T/N ratio showed a similar decline. The phantom experiments showed that performing simultaneous SPECT/CBCT is feasible. The CNR obtained from the SPECT reconstruction of largest sphere in the image quality phantom was 43.1 for the clinical scanner and 28.6 for the developed prototype scanner. The anthropomorphic phantom showed that the extrahepatic depositions were detected with both scanners.A dual-layer detector is able to simultaneously acquire SPECT and CBCT. Both CNR and T/N ratio are worse than that of a clinical system, but the phantom experiments showed that extrahepatic depositions with volumes and activities close to the median values encountered in hepatic radioembolization could be distinguished.
Highlights
In recent years, significant progress has been made in the development of hybrid medical scanners
This study investigates the feasibility and the image quality of simultaneous single photon emission computed tomography (SPECT)/cone beam computed tomography (CBCT), by means of phantom experiments and simulations
The lung shunt fraction and potential extrahepatic depositions are determined on SPECT/computed tomography (CT) to decide whether the treatment can safely continue
Summary
Significant progress has been made in the development of hybrid medical scanners. Together with software improvements in e.g. scatter correction and resolution modeling, SPECT/CT is increasingly considered a quantitative modality (Bailey and Willowson 2014). In hepatic radioembolization, where yttrium-90 (90Y) labeled microspheres are injected into the liver (Kennedy et al 2012, Braat et al 2015), a separate pre-treatment fluoroscopy-guided interventional procedure with technetium-99m-labeled macroaggregated albumin (99mTc-MAA) is performed. After this procedure, the lung shunt fraction and potential extrahepatic depositions are determined on SPECT/CT to decide whether the treatment can safely continue. The results from this SPECT/CT scan would be directly available during the interventional procedure, so that both 99mTc pre-treatment and 90Y treatment administrations could be merged into a single fluoroscopic interventional session (Gabr et al 2016)
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