visualization-low-level-gamma-radiation-sources-using-low-cost-high

Visualization of Low-Level Gamma Radiation Sources Using a Low-Cost, High-Sensitivity, Omnidirectional Compton Camera

We present experimental protocols for visualizing various low-level gamma radiation sources in the ambient environment. Experiments were conducted by ...

National Cancer Center Hospital East

Whereas Monte Carlo (MC) simulation is widely utilized in estimation of the scatter component, a simulation model which can calculate the scatter fraction (SF) of each patient is needed for making an accurate image quality assessment for clinical PET images based on the noise equivalent count. In this study, an MC simulation model was constructed which can calculate the SF for various phantoms. We utilized the Geant4 toolkit based on MC simulation to make a model of a PET scanner with a scatter phantom, and SFs calculated with this model were compared with the SF (SF: 44%) measured with use of an actual PET scanner. Additionally, the SF values for an anthropomorphic phantom were calculated from its voxel phantom. Furthermore, we evaluated the impact on the SF due to the difference in the source distribution inside the phantom. The SF calculated from the scatter phantom in the MC simulation was 44%, the same as the SF value. The average SF for the anthropomorphic phantom was 41%, but there was a maximum of 14 percentage points difference between each scan range, and the maximum difference in the SF was 8 percentage points for the difference in the source distribution. We constructed an MC simulation model which can calculate SFs for various phantoms. The SF was confirmed to be affected significantly by the source distribution. We judged that the actually measured SF obtained from the PET scanner with the scatter phantom was not suitable for the assessment of the quality of all patient images.

A simulation study for estimating scatter fraction in whole-body F-FDG PET/CT.

The bone scan index (BSI) is calculated from a whole-body bone scan image; it shows the tumor burden in bone as a percentage of total skeletal mass. It has been used to determine the prognosis and to assess treatment effects; however, little has been reported on whether the BSI calculated using a two-dimensional image can accurately evaluate the three-dimensional spread in tumor volume. We investigated the relationship between tumor volume and BSI using Monte Carlo simulation (MCS). We simulated a gamma camera and constructed a voxel phantom based on an anthropomorphic phantom computed tomography (CT) image and gamma rays emitted from each part according to technetium-99m-labeled methylene diphosphonate (Tc-MDP) uptake (bone 1, soft tissue 0.2, tumor 2-32). We constructed bone scan images from the obtained counts and analyzed them using the BSI calculation software. The BSI increased with increased tumor uptake (two- to 32-fold). However, there was not always a significant difference between change in BSI and tumor uptake of eight times or greater than that of bone. When BSI was calculated with a tumor having an uptake of four-to-eight times higher than that of bone, the BSI was consistent with tumor volume, but decreased to about half the tumor volume when tumors were in the thoracic spine (Th-spine) segment. The BSI can be a good indicator of tumor volume in most segments, even though it is affected by the tumor's Tc-MDP uptake. Nevertheless, values calculated from the Th-spine should be interpreted carefully.

Article	Year
A simulation study for estimating scatter fraction in whole-body F-FDG PET/CT. Radiological physics and technology\| PubMed ID: 28032297	2017
Relationship between tumor volume and quantitative values calculated using two-dimensional bone scan images. Radiological physics and technology\| PubMed ID: 28983807	2017

Daisuke Kano

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