Optimization of SPECT-CT Hybrid Imaging Using Iterative Image Reconstruction for Low-Dose CT: A Phantom Study

• Published in: PloS one Vol. 10; no. 9; p. e0138658
• Main Authors: Grosser, Oliver S., Kupitz, Dennis, Ruf, Juri, Czuczwara, Damian, Steffen, Ingo G., Furth, Christian, Thormann, Markus, Loewenthal, David, Ricke, Jens, Amthauer, Holger
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 21.09.2015; Public Library of Science (PLoS)
• Subjects: Abdomen; Adult; Algorithms; Attenuation; CAT scans; Computation; Computed tomography; Diagnostic software; Diagnostic systems; Drug dosages; Emissions; Exposure; Humans; Image Enhancement - methods; Image processing; Image Processing, Computer-Assisted - methods; Image quality; Image reconstruction; Iterative methods; Laboratories; Medical diagnosis; Medical imaging; Methods; Multimodal Imaging - instrumentation; Multimodal Imaging - methods; Noise; Nuclear medicine; Optimization; Pediatrics; Phantoms, Imaging; Photon emission; Positron emission; Positron emission tomography; Quality; Radiation; Radiation Dosage; Radiation effects; Radiology; Reproducibility of Results; Single photon emission computed tomography; Tomography; Tomography, Emission-Computed, Single-Photon - instrumentation; Tomography, Emission-Computed, Single-Photon - methods; Tomography, X-Ray Computed - instrumentation; Tomography, X-Ray Computed - methods; X ray tubes; X-Rays; Germany; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0138658

Hybrid imaging combines nuclear medicine imaging such as single photon emission computed tomography (SPECT) or positron emission tomography (PET) with computed tomography (CT). Through this hybrid design, scanned patients accumulate radiation exposure from both applications. Imaging modalities have been the subject of long-term optimization efforts, focusing on diagnostic applications. It was the aim of this study to investigate the influence of an iterative CT image reconstruction algorithm (ASIR) on the image quality of the low-dose CT images. Examinations were performed with a SPECT-CT scanner with standardized CT and SPECT-phantom geometries and CT protocols with systematically reduced X-ray tube currents. Analyses included image quality with respect to photon flux. Results were compared to the standard FBP reconstructed images. The general impact of the CT-based attenuation maps used during SPECT reconstruction was examined for two SPECT phantoms. Using ASIR for image reconstructions, image noise was reduced compared to FBP reconstructions for the same X-ray tube current. The Hounsfield unit (HU) values reconstructed by ASIR were correlated to the FBP HU values(R2 ≥ 0.88) and the contrast-to-noise ratio (CNR) was improved by ASIR. However, for a phantom with increased attenuation, the HU values shifted for low X-ray tube currents I ≤ 60 mA (p ≤ 0.04). In addition, the shift of the HU values was observed within the attenuation corrected SPECT images for very low X-ray tube currents (I ≤ 20 mA, p ≤ 0.001). In general, the decrease in X-ray tube current up to 30 mA in combination with ASIR led to a reduction of CT-related radiation exposure without a significant decrease in image quality.