1.
Sousa, João M., et al.
(author)
Accuracy and precision of zero-echo-time, single- and multi-atlas attenuation correction for dynamic [11C]PE2I PET-MR brain imaging
2020
In: EJNMMI Physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 7:1
Journal article (peer-reviewed) abstract
BACKGROUND: A valid photon attenuation correction (AC) method is instrumental for obtaining quantitatively correct PET images. Integrated PET/MR systems provide no direct information on attenuation, and novel methods for MR-based AC (MRAC) are still under investigation. Evaluations of various AC methods have mainly focused on static brain PET acquisitions. In this study, we determined the validity of three MRAC methods in a dynamic PET/MR study of the brain.METHODS: Nine participants underwent dynamic brain PET/MR scanning using the dopamine transporter radioligand [11C]PE2I. Three MRAC methods were evaluated: single-atlas (Atlas), multi-atlas (MaxProb) and zero-echo-time (ZTE). The 68Ge-transmission data from a previous stand-alone PET scan was used as reference method. Parametric relative delivery (R1) images and binding potential (BPND) maps were generated using cerebellar grey matter as reference region. Evaluation was based on bias in MRAC maps, accuracy and precision of [11C]PE2I BPND and R1 estimates, and [11C]PE2I time-activity curves. BPND was examined for striatal regions and R1 in clusters of regions across the brain.RESULTS: For BPND, ZTE-MRAC showed the highest accuracy (bias < 2%) in striatal regions. Atlas-MRAC exhibited a significant bias in caudate nucleus (- 12%) while MaxProb-MRAC revealed a substantial, non-significant bias in the putamen (9%). R1 estimates had a marginal bias for all MRAC methods (- 1.0-3.2%). MaxProb-MRAC showed the largest intersubject variability for both R1 and BPND. Standardized uptake values (SUV) of striatal regions displayed the strongest average bias for ZTE-MRAC (~ 10%), although constant over time and with the smallest intersubject variability. Atlas-MRAC had highest variation in bias over time (+10 to - 10%), followed by MaxProb-MRAC (+5 to - 5%), but MaxProb showed the lowest mean bias. For the cerebellum, MaxProb-MRAC showed the highest variability while bias was constant over time for Atlas- and ZTE-MRAC.CONCLUSIONS: Both Maxprob- and ZTE-MRAC performed better than Atlas-MRAC when using a 68Ge transmission scan as reference method. Overall, ZTE-MRAC showed the highest precision and accuracy in outcome parameters of dynamic [11C]PE2I PET analysis with use of kinetic modelling.
2.
Appel, Lieuwe, et al.
(author)
Use of C-11-PE2I PET in Differential Diagnosis of Parkinsonian Disorders
2015
In: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 56:2, s. 234-242
Journal article (peer-reviewed) abstract
In idiopathic Parkinson disease and atypical parkinsonian disorders, central dopaminergic and overall brain functional activity are altered to different degrees, causing difficulties in achieving an unambiguous clinical diagnosis. A dual examination using I-123-FP-CIT (I-123-N-omega-fluoropropyl- 2 beta-carbomethoxy-3 beta-(4-iodophenyl) nortropane, or I-123-ioflupane) SPECT and F-18-FDG PET provides complementary information on dopamine transporter (DAT) availability and overall brain functional activity, respectively. Parametric images based on a single, dynamic C-11-PE2I (N-(3-iodoprop-2E-enyl)-2 beta-carbomethoxy-3 beta-(4-methyl-phenyl) nortropane) scan potentially supply both DAT availability (nondisplaceable binding potential [BPND]) and relative cerebral blood flow (relative delivery [R-1]) at voxel level. This study aimed to evaluate the validity of C-11-PE2I PET against the dual-modality approach using I-123-FP-CIT SPECT and F-18-FDG PET.Methods: Sixteen patients with parkinsonian disorders had a dual examination with F-18-FDG PET and I-123-FP-CIT SPECT following clinical routines and additionally an experimental C-11-PE2I PET scan. Parametric BPND and R-1 images were generated using receptor parametric mapping with the cerebellum as a reference. T1-weighted MR imaging was used for automated definition of volumes of interest (VOI). The DAT VOIs included the basal ganglia, whereas the overall brain functional activity was examined using VOIs across the brain. BPND and R-1 values were compared with normalized I-123-FP-CIT and F-18-FDG uptake values, respectively, using Pearson correlations and regression analyses. In addition, 2 masked interpreters evaluated the images visually, in both the routine and the experimental datasets, for comparison of patient diagnoses.Results: Parametric C-11-PE2I BPND and R-1 images showed high consistency with I-123-FP-CIT SPECT and F-18-FDG PET images. Correlations between C-11-PE2I BPND and I-123-FP-CIT uptake ratios were 0.97 and 0.76 in the putamen and caudate nucleus, respectively. Regional C-11-PE2I R-1 values were moderately to highly correlated with normalized F-18-FDG values (range, 0.61-0.94). Visual assessment of DAT availability showed a high consistency between C-11-PE2I BPND and I-123-FP-CIT images, whereas the consistency was somewhat lower for appraisal of overall brain functional activity using I-123-FP-CIT and F-18-FDG images. Substantial differences were found between clinical diagnosis and both neuro-imaging diagnoses.Conclusion: A single, dynamic C-11-PE2I PET investigation is a powerful alternative to a dual examination with I-123-FP-CIT SPECT and F-18-FDG PET for differential diagnosis of parkinsonian disorders. A large-scale patient study is, however, needed to further investigate distinct pathologic patterns in overall brain functional activity for various parkinsonian disorders.
3.
4.
Sousa, Joao M., 1989-, et al.
(author)
Comparison of quantitative [11C]PE2I brain PET studies between an integrated PET/MR and a stand-alone PET system
2024
In: Physica medica (Testo stampato). - : Elsevier. - 1120-1797 .- 1724-191X. ; 117
Journal article (peer-reviewed) abstract
PET/MR systems demanded great efforts for accurate attenuation correction (AC) but differences in technology, geometry and hardware attenuation may also affect quantitative results. Dedicated PET systems using transmission-based AC are regarded as the gold standard for quantitative brain PET. The study aim was to investigate the agreement between quantitative PET outcomes from a PET/MR scanner against a stand-alone PET system.Nine patients with Parkinsonism underwent two 80-min dynamic PET scans with the dopamine transporter ligand [11C]PE2I. Images were reconstructed with resolution-matched settings using 68Ge-transmission (standalone PET), and zero-echo-time MR (PET/MR) scans for AC. Non-displaceable binding potential (BPND) and relative delivery (R1) were evaluated using volumes of interest and voxel-wise analysis.Correlations between systems were high (r >= 0.85) for both quantitative outcome parameters in all brain regions. Striatal BPND was significantly lower on PET/MR than on stand-alone PET (-7%). R1 was significantly overestimated in posterior cortical regions (9%) and underestimated in striatal (-9%) and limbic areas (-6%). The voxel-wise evaluation revealed that the MR-safe headphones caused a negative bias in both parametric BPND and R1 images. Additionally, a significant positive bias of R1 was found in the auditory cortex, most likely due to the acoustic background noise during MR imaging. The relative bias of the quantitative [11C]PE2I PET data acquired from a SIGNA PET/MR system was in the same order as the expected test-retest reproducibility of [11C]PE2I BPND and R1, compared to a stand-alone ECAT PET scanner. MR headphones and background noise are potential sources of error in functional PET/MR studies.
5.
Sousa, Joao M., 1989-, et al.
(author)
Comparison of quantitative [11C]PE2I PET scans acquired on PET/MR and stand-alone PET
In: Journal of Cerebral Blood Flow and Metabolism. - 0271-678X .- 1559-7016.
Journal article (pop. science, debate, etc.) abstract
Dedicated PET systems using transmission-based attenuation correction (AC) are regarded as the gold standard for quantitative brain PET. PET/MR systems demanded great efforts for accurate AC but differences in technology, geometry and hardware attenuation may also affect quantitative results. This study compares PET quantitative outcomes between a stand-alone PET and PET/MR scanner. Ten patients with parkinsonism underwent two 80-min dynamic PET scans with the dopamine transporter ligand [11C]PE2I. Images were reconstructed using resolution-matched settings and transmission scans (stand-alone PET) and zero-echo-time (PET/MR) for AC. SUV, relative delivery (R1), and dopamine transporter availability (BPND) were compared on a VOI- and voxel-basis. Correlations between systems were high (≥ 0.85) for all quantitative parameters. On VOI-basis, striatal BPND was significantly lower on PET/MR than on stand-alone PET (-7%). R1 was significantly overestimated in posterior cortical regions (9%) and underestimated in striatal (-9%) and limbic areas (-6%). SUV showed a similar pattern as R1. Voxel-by-voxel analysis showed significant positive bias of R1 in the auditory cortex. PET/MR significantly underestimated striatal BPND, similar to previously reported [11C]PE2I BPND test-retest variability. The acoustic noise in the PET/MR environment may attribute to an overestimation of R1 in the auditory cortex, which needs consideration when using PET/MR data.
6.
Sousa, Joao M., 1989-, et al.
(author)
Composite 68Ge attenuation correction for quantitative brain PET/MR
Other publication (other academic/artistic) abstract
Accurate attenuation correction (AC) in positron emission tomography (PET) imaging is a prerequisite for obtaining quantitatively correct images and 68Ge-AC is considered the gold standard for PET AC. In this study we developed an alternative AC method for PET/MR, based on the registration of a database of 68Ge-AC maps and T1-weighted MR image pairs. The present work aimed to evaluate this composite 68Ge transmission AC (CTR-AC) method’s reliability compared to 68Ge-AC. The CTR database comprised 125 pairs of previously acquired 68Ge-AC maps and T1-MRI scans. Ten patients underwent 80-min dynamic PET scans with the dopamine transporter ligand [11C]PE2I on a SIGNA PET/MR. Images were reconstructed using a CTR-AC map and a previously acquired patient-specific 68Ge-AC map on a stand-alone PET scanner. SUV as well as outcome parameters of [11C]PE2I kinetic analysis, i.e., relative delivery (R1) and dopamine transporter availability (BPND), were compared on a VOI and voxel-by-voxel basis.CTR-AC showed high accuracy, with a mean bias of 0 ± 3% for whole-brain SUV, -0.1 ± 3.2% for whole-brain R1, and 3.7 ± 8.1% for striatal BPND. The precision of SUV and R1 was modest and lowest in the anterior cortex, with an R1 bias of -1.1 ± 6.4%.CTR-AC is straightforward and provides MRAC maps with continuous linear attenuation coefficient values. The method’s accuracy is comparable to the best MRAC methods published so far, with a near-zero bias in SUV and a bias similar to that previously found for ZTE-AC in outcome parameters of kinetic modelling.
7.
Sousa, João M., et al.
(author)
Evaluation of zero-echo-time attenuation correction for integrated PET/MR brain imaging-comparison to head atlas and 68Ge-transmission-based attenuation correction
2018
In: EJNMMI Physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 5:20
Journal article (peer-reviewed) abstract
Background: MRI does not offer a direct method to obtain attenuation correction maps as its predecessors (stand-alone PET and PET/CT), and bone visualisation is particularly challenging. Recently, zero-echo-time (ZTE) was suggested for MR-based attenuation correction (AC). The aim of this work was to evaluate ZTE- and atlas-AC by comparison to 68Ge-transmission scan-based AC.Nine patients underwent brain PET/MR and stand-alone PET scanning using the dopamine transporter ligand 11C-PE2I. For each of them, two AC maps were obtained from the MR images: an atlas-based, obtained from T1-weighted LAVA-FLEX imaging with cortical bone inserted using a CT-based atlas, and an AC map generated from proton-density-weighted ZTE images. Stand-alone PET 68Ge-transmission AC map was used as gold standard. PET images were reconstructed using the three AC methods and standardised uptake value (SUV) values for the striatal, limbic and cortical regions, as well as the cerebellum (VOIs) were compared. SUV ratio (SUVR) values normalised for the cerebellum were also assessed. Bias, precision and agreement were calculated; statistical significance was evaluated using Wilcoxon matched-pairs signed-rank test.Results: Both ZTE- and atlas-AC showed a similar bias of 6–8% in SUV values across the regions. Correlation coefficients with 68Ge-AC were consistently high for ZTE-AC (r 0.99 for all regions), whereas they were lower for atlas-AC, varying from 0.99 in the striatum to 0.88 in the posterior cortical regions. SUVR showed an overall bias of 2.9 and 0.5% for atlas-AC and ZTE-AC, respectively. Correlations with 68Ge-AC were higher for ZTE-AC, varying from 0.99 in the striatum to 0.96 in the limbic regions, compared to atlas-AC (0.99 striatum to 0.77 posterior cortex).Conclusions: Absolute SUV values showed less variability for ZTE-AC than for atlas-AC when compared to 68Ge-AC, but bias was similar for both methods. This bias is largely caused by higher linear attenuation coefficients in atlas- and ZTE-AC image compared to 68Ge-images. For SUVR, bias was lower when using ZTE-AC than for atlas-AC. ZTE-AC shows to be a more robust technique than atlas-AC in terms of both intra- and inter-patient variability.
8.
