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Feasibility of Computed Tomography-Guided Methods for Spatial Normalization of Dopamine Transporter Positron Emission Tomography Image.

Kim JS, Cho H, Choi JY, Lee SH, Ryu YH, Lyoo CH, Lee MS - PLoS ONE (2015)

Bottom Line: The CT images were modified in two ways, skull-stripping (ssCT) and intensity transformation (itCT).The SUVR values measured with FreeSurfer-generated VOIs (FSVOI) overlaid on original PET images were also used as a gold standard for comparison.Putaminal SUVR values were highly effective for discriminating PD patients from controls.

View Article: PubMed Central - PubMed

Affiliation: Molecular Imaging Research Center, Korea Institute Radiological and Medical Sciences, Seoul, South Korea.

ABSTRACT

Background: Spatial normalization is a prerequisite step for analyzing positron emission tomography (PET) images both by using volume-of-interest (VOI) template and voxel-based analysis. Magnetic resonance (MR) or ligand-specific PET templates are currently used for spatial normalization of PET images. We used computed tomography (CT) images acquired with PET/CT scanner for the spatial normalization for [18F]-N-3-fluoropropyl-2-betacarboxymethoxy-3-beta-(4-iodophenyl) nortropane (FP-CIT) PET images and compared target-to-cerebellar standardized uptake value ratio (SUVR) values with those obtained from MR- or PET-guided spatial normalization method in healthy controls and patients with Parkinson's disease (PD).

Methods: We included 71 healthy controls and 56 patients with PD who underwent [18F]-FP-CIT PET scans with a PET/CT scanner and T1-weighted MR scans. Spatial normalization of MR images was done with a conventional spatial normalization tool (cvMR) and with DARTEL toolbox (dtMR) in statistical parametric mapping software. The CT images were modified in two ways, skull-stripping (ssCT) and intensity transformation (itCT). We normalized PET images with cvMR-, dtMR-, ssCT-, itCT-, and PET-guided methods by using specific templates for each modality and measured striatal SUVR with a VOI template. The SUVR values measured with FreeSurfer-generated VOIs (FSVOI) overlaid on original PET images were also used as a gold standard for comparison.

Results: The SUVR values derived from all four structure-guided spatial normalization methods were highly correlated with those measured with FSVOI (P < 0.0001). Putaminal SUVR values were highly effective for discriminating PD patients from controls. However, the PET-guided method excessively overestimated striatal SUVR values in the PD patients by more than 30% in caudate and putamen, and thereby spoiled the linearity between the striatal SUVR values in all subjects and showed lower disease discrimination ability. Two CT-guided methods showed comparable capability with the MR-guided methods in separating PD patients from controls and showed better correlation between putaminal SUVR values and the parkinsonian motor severity than the PET-guided method.

Conclusion: CT-guided spatial normalization methods provided reliable striatal SUVR values comparable to those obtained with MR-guided methods. CT-guided methods can be useful for analyzing dopamine transporter PET images when MR images are unavailable.

No MeSH data available.


Related in: MedlinePlus

Striatal standardized uptake value ratio (SUVR) values (A: caudate, B: putamen) of healthy controls (HC) and Parkinson’s disease (PD) patients.The horizontal red bars represent mean and standard deviation (SD). T- and P-values for comparing two groups with independent t-test are presented on the top of the graphs. Abbreviations: FSVOI = FreeSurfer-generated volume of interest, cvMR = MR-guided spatial normalization with conventional normalization tool, dtMR = MR-guided spatial normalization with DARTEL toolbox, ssCT = skull-stripped CT-guided spatial normalization, itCT = intensity transformed CT-guided spatial normalization, PET = PET-guided spatial normalization.
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pone.0132585.g003: Striatal standardized uptake value ratio (SUVR) values (A: caudate, B: putamen) of healthy controls (HC) and Parkinson’s disease (PD) patients.The horizontal red bars represent mean and standard deviation (SD). T- and P-values for comparing two groups with independent t-test are presented on the top of the graphs. Abbreviations: FSVOI = FreeSurfer-generated volume of interest, cvMR = MR-guided spatial normalization with conventional normalization tool, dtMR = MR-guided spatial normalization with DARTEL toolbox, ssCT = skull-stripped CT-guided spatial normalization, itCT = intensity transformed CT-guided spatial normalization, PET = PET-guided spatial normalization.

Mentions: Using subject-specific striatal FSVOIs, we measured SUVR values of the caudate (mean SUVR in HC = 7.2 ± 1.4 and that in PD = 5.2 ± 1.5) and putamen (mean SUVR in HC = 8.9 ± 1.3 and that in PD = 4.6 ± 1.1) for the comparison with those measured with striatal template VOIs overlaid on the PET images normalized by five different spatial normalization methods (Table 1). Although there were highly significant differences in caudate and putaminal SUVR values between the controls and PD patients (P < 10-4 for caudate, P < 10-22 for putamen), there was greater range of overlapping SUVR values derived from the PET-guided method between the two diagnostic groups (Fig 3). The cvMR-, dtMR-, ssCT-, and itCT-guided methods resulted in overestimation of caudate SUVR values by 8.5 to 17.6%, compared to those measured by FSVOI. For the putamen, the bias was much smaller for those four structure-guided methods (-1.9 to 9.0%). The biases of SUVR values derived from the PET-guided method were almost similar to those derived from structure-guided methods in the controls (caudate: 10.8%, putamen: 0.8%), but markedly greater in PD patients (caudate: 33.5%, putamen: 33.4%). These overestimation biases of the PET-guided method in PD patients were greater in the regions contralateral to the clinically worse side than in the regions contralateral to the clinically better side, most prominent in the anterior putamen (57.6%) and lowest in the ventral striatum (17.1%) (Table 1).


Feasibility of Computed Tomography-Guided Methods for Spatial Normalization of Dopamine Transporter Positron Emission Tomography Image.

Kim JS, Cho H, Choi JY, Lee SH, Ryu YH, Lyoo CH, Lee MS - PLoS ONE (2015)

Striatal standardized uptake value ratio (SUVR) values (A: caudate, B: putamen) of healthy controls (HC) and Parkinson’s disease (PD) patients.The horizontal red bars represent mean and standard deviation (SD). T- and P-values for comparing two groups with independent t-test are presented on the top of the graphs. Abbreviations: FSVOI = FreeSurfer-generated volume of interest, cvMR = MR-guided spatial normalization with conventional normalization tool, dtMR = MR-guided spatial normalization with DARTEL toolbox, ssCT = skull-stripped CT-guided spatial normalization, itCT = intensity transformed CT-guided spatial normalization, PET = PET-guided spatial normalization.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492980&req=5

pone.0132585.g003: Striatal standardized uptake value ratio (SUVR) values (A: caudate, B: putamen) of healthy controls (HC) and Parkinson’s disease (PD) patients.The horizontal red bars represent mean and standard deviation (SD). T- and P-values for comparing two groups with independent t-test are presented on the top of the graphs. Abbreviations: FSVOI = FreeSurfer-generated volume of interest, cvMR = MR-guided spatial normalization with conventional normalization tool, dtMR = MR-guided spatial normalization with DARTEL toolbox, ssCT = skull-stripped CT-guided spatial normalization, itCT = intensity transformed CT-guided spatial normalization, PET = PET-guided spatial normalization.
Mentions: Using subject-specific striatal FSVOIs, we measured SUVR values of the caudate (mean SUVR in HC = 7.2 ± 1.4 and that in PD = 5.2 ± 1.5) and putamen (mean SUVR in HC = 8.9 ± 1.3 and that in PD = 4.6 ± 1.1) for the comparison with those measured with striatal template VOIs overlaid on the PET images normalized by five different spatial normalization methods (Table 1). Although there were highly significant differences in caudate and putaminal SUVR values between the controls and PD patients (P < 10-4 for caudate, P < 10-22 for putamen), there was greater range of overlapping SUVR values derived from the PET-guided method between the two diagnostic groups (Fig 3). The cvMR-, dtMR-, ssCT-, and itCT-guided methods resulted in overestimation of caudate SUVR values by 8.5 to 17.6%, compared to those measured by FSVOI. For the putamen, the bias was much smaller for those four structure-guided methods (-1.9 to 9.0%). The biases of SUVR values derived from the PET-guided method were almost similar to those derived from structure-guided methods in the controls (caudate: 10.8%, putamen: 0.8%), but markedly greater in PD patients (caudate: 33.5%, putamen: 33.4%). These overestimation biases of the PET-guided method in PD patients were greater in the regions contralateral to the clinically worse side than in the regions contralateral to the clinically better side, most prominent in the anterior putamen (57.6%) and lowest in the ventral striatum (17.1%) (Table 1).

Bottom Line: The CT images were modified in two ways, skull-stripping (ssCT) and intensity transformation (itCT).The SUVR values measured with FreeSurfer-generated VOIs (FSVOI) overlaid on original PET images were also used as a gold standard for comparison.Putaminal SUVR values were highly effective for discriminating PD patients from controls.

View Article: PubMed Central - PubMed

Affiliation: Molecular Imaging Research Center, Korea Institute Radiological and Medical Sciences, Seoul, South Korea.

ABSTRACT

Background: Spatial normalization is a prerequisite step for analyzing positron emission tomography (PET) images both by using volume-of-interest (VOI) template and voxel-based analysis. Magnetic resonance (MR) or ligand-specific PET templates are currently used for spatial normalization of PET images. We used computed tomography (CT) images acquired with PET/CT scanner for the spatial normalization for [18F]-N-3-fluoropropyl-2-betacarboxymethoxy-3-beta-(4-iodophenyl) nortropane (FP-CIT) PET images and compared target-to-cerebellar standardized uptake value ratio (SUVR) values with those obtained from MR- or PET-guided spatial normalization method in healthy controls and patients with Parkinson's disease (PD).

Methods: We included 71 healthy controls and 56 patients with PD who underwent [18F]-FP-CIT PET scans with a PET/CT scanner and T1-weighted MR scans. Spatial normalization of MR images was done with a conventional spatial normalization tool (cvMR) and with DARTEL toolbox (dtMR) in statistical parametric mapping software. The CT images were modified in two ways, skull-stripping (ssCT) and intensity transformation (itCT). We normalized PET images with cvMR-, dtMR-, ssCT-, itCT-, and PET-guided methods by using specific templates for each modality and measured striatal SUVR with a VOI template. The SUVR values measured with FreeSurfer-generated VOIs (FSVOI) overlaid on original PET images were also used as a gold standard for comparison.

Results: The SUVR values derived from all four structure-guided spatial normalization methods were highly correlated with those measured with FSVOI (P < 0.0001). Putaminal SUVR values were highly effective for discriminating PD patients from controls. However, the PET-guided method excessively overestimated striatal SUVR values in the PD patients by more than 30% in caudate and putamen, and thereby spoiled the linearity between the striatal SUVR values in all subjects and showed lower disease discrimination ability. Two CT-guided methods showed comparable capability with the MR-guided methods in separating PD patients from controls and showed better correlation between putaminal SUVR values and the parkinsonian motor severity than the PET-guided method.

Conclusion: CT-guided spatial normalization methods provided reliable striatal SUVR values comparable to those obtained with MR-guided methods. CT-guided methods can be useful for analyzing dopamine transporter PET images when MR images are unavailable.

No MeSH data available.


Related in: MedlinePlus