Limits...
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

Regression analysis between the standardized uptake value ratio (SUVR) values measured with individual volume of interest (FSVOI) and those derived from five different spatial normalization methods (A and B), and correlation between the regional SUVR values and the clinical severity scores (C and D).In A and B, regression lines for each diagnostic group are presented with green (healthy controls; HC) and red (Parkinson’s disease; PD) dotted lines. Closed (HC) and open (PD) circles represent regional SUVR values of individual subjects. The R2 values for regression analysis in all subjects are presented in the right lower corner of each graph. The PET-guided spatial normalization method excessively overestimates striatal SUVR values in PD patients, and results in higher discrepancy in the regression line between the controls and PD patients. In C and D, closed circles represent individual striatal SUVR values and the red lines represent regression lines. The SUVR values derived from all five spatial normalization methods are correlated with clinical severity of PD, but the statistical power is lowest for the PET-guided method. 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
getmorefigures.php?uid=PMC4492980&req=5

pone.0132585.g005: Regression analysis between the standardized uptake value ratio (SUVR) values measured with individual volume of interest (FSVOI) and those derived from five different spatial normalization methods (A and B), and correlation between the regional SUVR values and the clinical severity scores (C and D).In A and B, regression lines for each diagnostic group are presented with green (healthy controls; HC) and red (Parkinson’s disease; PD) dotted lines. Closed (HC) and open (PD) circles represent regional SUVR values of individual subjects. The R2 values for regression analysis in all subjects are presented in the right lower corner of each graph. The PET-guided spatial normalization method excessively overestimates striatal SUVR values in PD patients, and results in higher discrepancy in the regression line between the controls and PD patients. In C and D, closed circles represent individual striatal SUVR values and the red lines represent regression lines. The SUVR values derived from all five spatial normalization methods are correlated with clinical severity of PD, but the statistical power is lowest for the PET-guided method. 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: Similarly, in PD and control subjects combined, SUVR values derived from all four structure-guided methods well correlated with those measured with FSVOI (P < 0.0001; R2 for caudate > 0.84, R2 for putamen > 0.94). However, the PET-guided method excessively overestimated striatal SUVR values in the PD patients, and thereby spoiled the linearity between the striatal SUVR values in all subjects (Fig 5A and 5B). The striatal regional SUVR values derived from all four structure-guided spatial normalization methods correlated well with those measured by subregional FSVOI. However, except ventral striatum in which binding is relatively preserved, the correlation between the subregional SUVR values derived from the PET-guided method and those measured by subregional FSVOI was the lowest (S3 Fig).


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)

Regression analysis between the standardized uptake value ratio (SUVR) values measured with individual volume of interest (FSVOI) and those derived from five different spatial normalization methods (A and B), and correlation between the regional SUVR values and the clinical severity scores (C and D).In A and B, regression lines for each diagnostic group are presented with green (healthy controls; HC) and red (Parkinson’s disease; PD) dotted lines. Closed (HC) and open (PD) circles represent regional SUVR values of individual subjects. The R2 values for regression analysis in all subjects are presented in the right lower corner of each graph. The PET-guided spatial normalization method excessively overestimates striatal SUVR values in PD patients, and results in higher discrepancy in the regression line between the controls and PD patients. In C and D, closed circles represent individual striatal SUVR values and the red lines represent regression lines. The SUVR values derived from all five spatial normalization methods are correlated with clinical severity of PD, but the statistical power is lowest for the PET-guided method. 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.g005: Regression analysis between the standardized uptake value ratio (SUVR) values measured with individual volume of interest (FSVOI) and those derived from five different spatial normalization methods (A and B), and correlation between the regional SUVR values and the clinical severity scores (C and D).In A and B, regression lines for each diagnostic group are presented with green (healthy controls; HC) and red (Parkinson’s disease; PD) dotted lines. Closed (HC) and open (PD) circles represent regional SUVR values of individual subjects. The R2 values for regression analysis in all subjects are presented in the right lower corner of each graph. The PET-guided spatial normalization method excessively overestimates striatal SUVR values in PD patients, and results in higher discrepancy in the regression line between the controls and PD patients. In C and D, closed circles represent individual striatal SUVR values and the red lines represent regression lines. The SUVR values derived from all five spatial normalization methods are correlated with clinical severity of PD, but the statistical power is lowest for the PET-guided method. 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: Similarly, in PD and control subjects combined, SUVR values derived from all four structure-guided methods well correlated with those measured with FSVOI (P < 0.0001; R2 for caudate > 0.84, R2 for putamen > 0.94). However, the PET-guided method excessively overestimated striatal SUVR values in the PD patients, and thereby spoiled the linearity between the striatal SUVR values in all subjects (Fig 5A and 5B). The striatal regional SUVR values derived from all four structure-guided spatial normalization methods correlated well with those measured by subregional FSVOI. However, except ventral striatum in which binding is relatively preserved, the correlation between the subregional SUVR values derived from the PET-guided method and those measured by subregional FSVOI was the lowest (S3 Fig).

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