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. 2021 Nov 18;11(11):2138.
doi: 10.3390/diagnostics11112138.

Low-Dose PET Imaging of Tumors in Lung and Liver Regions Using Internal Motion Estimation

Sang-Keun Woo  1 , Byung-Chul Kim  1 , Eun Kyoung Ryu  2 , In Ok Ko  1 , Yong Jin Lee  1
Affiliations

Low-Dose PET Imaging of Tumors in Lung and Liver Regions Using Internal Motion Estimation

Sang-Keun Woo et al. Diagnostics (Basel). .

Abstract

Motion estimation and compensation are necessary for improvement of tumor quantification analysis in positron emission tomography (PET) images. The aim of this study was to propose adaptive PET imaging with internal motion estimation and correction using regional artificial evaluation of tumors injected with low-dose and high-dose radiopharmaceuticals. In order to assess internal motion, molecular sieves imitating tumors were loaded with 18F and inserted into the lung and liver regions in rats. All models were classified into two groups, based on the injected radiopharmaceutical activity, to compare the effect of tumor intensity. The PET study was performed with injection of F-18 fluorodeoxyglucose (18F-FDG). Respiratory gating was carried out by external trigger device. Count, signal to noise ratio (SNR), contrast and full width at half maximum (FWHM) were measured in artificial tumors in gated images. Motion correction was executed by affine transformation with estimated internal motion data. Monitoring data were different from estimated motion. Contrast in the low-activity group was 3.57, 4.08 and 6.19, while in the high-activity group it was 10.01, 8.36 and 6.97 for static, 4 bin and 8 bin images, respectively. The results of the lung target in 4 bin and the liver target in 8 bin showed improvement in FWHM and contrast with sufficient SNR. After motion correction, FWHM was improved in both regions (lung: 24.56%, liver: 10.77%). Moreover, with the low dose of radiopharmaceuticals the PET image visualized specific accumulated radiopharmaceutical areas in the liver. Therefore, low activity in PET images should undergo motion correction before quantification analysis using PET data. We could improve quantitative tumor evaluation by considering organ region and tumor intensity.

Keywords: animal model; imaging; radioisotope; rat; respiratory organ.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The results of motion correction PET image. (a) The left side image represents no motion correction, and the right side is a motion correction image of the lung. (b) The left side of the PET image represents no motion correction in liver, and right side represents a motion correction image.
Figure 2
Figure 2
Results of detected motion variation in lung and liver during the PET image acquisition.
Figure 3
Figure 3
PET images of the molecular sieve in the lung region; (a) a static PET image, (b) a PET image corrected using a fiducial marker, (c) an image corrected using 3D VIBE MRI, (d) an image corrected using 2D FLASH MRI, (e) an image corrected using a 2D tagged MRI.
Figure 4
Figure 4
Motion correction PET image and result of FWHM in vertical and horizontal directions in the lung. (a) No motion correction PET image, (b) motion corrected PET image.
Figure 5
Figure 5
Motion correction PET image and result of FWHM in vertical and horizontal direction of liver. (a) No motion correction PET image, (b) motion corrected PET image.
Figure 6
Figure 6
Gate number effects on the (a) count, (b) SNR, (c) contrast in high- and low-activity PET data.
Figure 7
Figure 7
Detection of specific areas in liver. (A) Acquired CT data before PET scan, (B) Slice section of small animal, (C) high-activity PET image, (D) low-activity PET image.
See this image and copyright information in PMC

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