Accurate and reproducible automated segmentation of human hippocampal subfields is of interest to study their roles in cognitive functions and disease processes. Multispectral structural MRI methods ...have been proposed to improve automated hippocampal subfield segmentation accuracy, but the reproducibility in a multicentric setting is, to date, not well characterized. Here, we assessed test–retest reproducibility of FreeSurfer 6.0 hippocampal subfield segmentations using multispectral MRI analysis pipelines (22 healthy subjects scanned twice, a week apart, at four 3T MRI sites). The harmonized MRI protocol included two 3D-T1, a 3D-FLAIR, and a high-resolution 2D-T2. After within-session T1 averaging, subfield volumes were segmented using three pipelines with different multispectral data: two longitudinal (“long_T1s” and “long_T1s_FLAIR”) and one cross-sectional (“long_T1s_FLAIR_crossT2”). Volume reproducibility was quantified in magnitude (reproducibility error—RE) and space (DICE coefficient). RE was lower in all hippocampal subfields, except for hippocampal fissure, using the longitudinal pipelines compared to long_T1s_FLAIR_crossT2 (average RE reduction of 0.4–3.6%). Similarly, the longitudinal pipelines showed a higher spatial reproducibility (1.1–7.8% of DICE improvement) in all hippocampal structures compared to long_T1s_FLAIR_crossT2. Moreover, long_T1s_FLAIR provided a small but significant RE improvement in comparison to long_T1s (
p
= 0.015), whereas no significant DICE differences were found. In addition, structures with volumes larger than 200 mm
3
had better RE (1–2%) and DICE (0.7–0.95) than smaller structures. In summary, our study suggests that the most reproducible hippocampal subfield FreeSurfer segmentations are derived from a longitudinal pipeline using 3D-T1s and 3D-FLAIR. Adapting a longitudinal pipeline to include high-resolution 2D-T2 may lead to further improvements.
ABSTRACT
Purpose
Impaired olfactory function is one of the main features of Parkinson’s disease. However, how peripheral olfactory structures are involved remains unclear. Using diffusion tensor ...imaging fiber tracking, we investigated for MRI microstructural changes in the parkinsonian peripheral olfactory system and particularly the olfactory tract, in order to seek a better understanding of the structural alternations underlying hyposmia in Parkinson’s disease.
Methods
All patients were assessed utilizing by the Italian Olfactory Identification Test for olfactory function and the Unified Parkinson’s Disease Rating Scale-III part as well as Hoehn and Yahr rating scale for motor disability. Imaging was performed on a 3 T Clinical MR scanner. MRI data pre-processing was carried out by DTIPrep, diffusion tensor imaging reconstruction, and fiber tracking using Diffusion Toolkit and tractography analysis by TrackVis. The following parameters were used for groupwise comparison: fractional anisotropy, mean diffusivity, radial diffusivity, axial diffusivity, and tract volume.
Results
Overall 23 patients with Parkinson’s disease (mean age 63.6 ± 9.3 years, UPDRS-III 24.5 ± 12.3, H&Y 1.9 ± 0.5) and 18 controls (mean age 56.3 ± 13.7 years) were recruited. All patients had been diagnosed hyposmic. Diffusion tensor imaging analysis of the olfactory tract showed significant fractional anisotropy, and tract volume decreases for the Parkinson’s disease group compared with controls (
P
< 0.05). Fractional anisotropy and age, in the control group, were significant for multiple correlations (
r
= − 0.36,
P
< 0.05, Spearman’s rank correlation).
Conclusions
Fiber tracking diffusion tensor imaging analysis of olfactory tract was feasible, and it could be helpful for characterizing hyposmia in Parkinson’s disease.
Brain iron load is one of the most important neuropathological hallmarks in movement disorders. Specifically, the iron provides most of the paramagnetic metal signals in the brain and its ...accumulation seems to play a key role, although not completely explained, in the degeneration of the basal ganglia, as well as other brain structures. Moreover, iron distribution patterns have been implicated in depicting different movement disorders. This work reviewed current literature on Magnetic Resonance Imaging for Brain Iron Detection and Quantification (MRI-BIDQ) in neurodegenerative processes underlying movement disorders.
Introduction
Several functional neuroimaging studies on healthy controls and patients with migraine with aura have shown that the activation of functional networks during visual stimulation is not ...restricted to the striate system, but also includes several extrastriate networks.
Methods
Before and after 4 min of visual stimulation with a checkerboard pattern, we collected functional MRI in 21 migraine with aura (MwA) patients and 18 healthy subjects (HS). For each recording session, we identified independent resting-state networks in each group and correlated network connection strength changes with clinical disease features.
Results
Before visual stimulation, we found reduced connectivity between the default mode network and the left dorsal attention system (DAS) in MwA patients compared to HS. In HS, visual stimulation increases functional connectivity between the independent components of the bilateral DAS and the executive control network (ECN). In MwA, visual stimulation significantly improved functional connectivity between the independent component pairs salience network and DAS, and between DAS and ECN. The ECN Z-scores after visual stimulation were negatively related to the monthly frequency of aura.
Conclusions
In individuals with MwA, 4 min of visual stimulation had stronger cognitive impact than in healthy people. A higher frequency of aura may lead to a diminished ability to obtain cognitive resources to cope with transitory but important events like aura-related focal neurological symptoms.
Brain iron load is one of the main neuropathologic hallmarks of Parkinson's disease (PD). Previous studies indicated that iron in the substantia nigra (SN) is related to disease duration and motor ...impairment. We explore, through a cross-sectional study, the association between brain iron distribution, evaluated by T2*-weighted magnetic resonance imaging (T2*), and clinical features in a cohort of patients with PD. Thirty-two patients with PD, compared with 10 control subjects, were evaluated for motor and cognitive features (attention and working memory, executive functions, language, memory, and visuospatial function). They underwent a magnetic resonance imaging protocol including T2* analysis of specific brain regions of interest to measure iron load compared with healthy control subjects. We found that iron content of the SN correlated positively with both disease duration and Unified Parkinson's Disease Rating Scale III off score. Montreal Cognitive Assessment, Spatial Span, and Graded Naming Test scores were inversely associated with iron load of the SN, whereas Wechsler Adult Intelligence Scale-IV Similarities score showed an inverse relationship with iron content in all the regions of interest examined. Our findings suggest a relationship between topographic brain iron distribution and cognitive domain impairment.
•Brain iron load is an important marker of neurodegeneration in Parkinson’s disease.•Iron content of the Substantia Nigra correlates positively with motor impairment.•Brain iron distribution is associated with specific cognitive domains impairment.
•Liquid scintillation did not discover 3H in non-irradiated 18OH2O.•3H, 52,54Mn, 56,57,58Co, 95m,96Tc, 109Cd, 184Re found in the irradiated 18OH2O.•A total impurity activity <6.2 kBq measured in the ...irradiated 18OH2O.•The decay curve of the irradiated 18OH2O revealed a negligible 13N activity.•A 18FFMCH radionuclide purity >99.9999998% was estimated.
18FFluoromethylcholine (18FFMCH) is a radiopharmaceutical used in positron emission tomography (PET) imaging for the study of prostate, breast, and brain tumors. It is usually synthesized in cyclotron facilities where 18F is produced by proton irradiation of 18OH2O through 18O(p,n)18F reaction. Due to the activation of target materials, the bombardment causes unwanted radionuclidic impurities in 18OH2O, that need to be removed during the radiopharmaceutical synthesis. Thus, the aim of this study is to quantify the radionuclide impurities in the 18F production process and in the synthesized 18FFMCH, demonstrating the radionuclidic purity of this radiopharmaceutical.
Long-lived radionuclide impurities were experimentally assessed using high-resolution gamma and liquid scintillation spectrometries, while short-lived impurities were monitored analyzing the decay curve of the irradiated 18OH2O with an activity calibrator. As spectrometric radionuclide library, a Geant4 Monte Carlo simulation of the 18F-target assembly was previously performed.
3H, 52,54Mn, 56,57,58Co, 95m,96Tc, 109Cd, and 184Re were found in the irradiated 18OH2O, but no radionuclide was found in the non-irradiated 18OH2O neither in the final 18FFMCH solution with an activity concentration greater than the minimum detectable activity concentration. A total impurity activity <6.2 kBq was measured in the irradiated 18OH2O, whereas a 18FFMCH radionuclide purity >99.9999998% was estimated. Finally, the decay curve of the irradiated 18OH2O revealed a very low maximum of 13N activity (<0.03% of 18F) even immediately after the end of bombardment.
This study demonstrated the radionuclidic purity of 18FFMCH according to the EU Pharmacopeia.
The purpose of this multicenter phantom study was to exploit an innovative approach, based on an extensive acquisition protocol and unsupervised clustering analysis, in order to assess any potential ...bias in apparent diffusion coefficient (ADC) estimation due to different scanner characteristics. Moreover, we aimed at assessing, for the first time, any effect of acquisition plan/phase encoding direction on ADC estimation.
Water phantom acquisitions were carried out on 39 scanners. DWI acquisitions (b-value = 0–200-400–600-800–1000 s/mm2) with different acquisition plans (axial, coronal, sagittal) and phase encoding directions (anterior/posterior and right/left, for the axial acquisition plan), for 3 orthogonal diffusion weighting gradient directions, were performed. For each acquisition setup, ADC values were measured in-center and off-center (6 different positions), resulting in an entire dataset of 84 × 39 = 3276 ADC values. Spatial uniformity of ADC maps was assessed by means of the percentage difference between off-center and in-center ADC values (Δ).
No significant dependence of in-center ADC values on acquisition plan/phase encoding direction was found. Ward unsupervised clustering analysis showed 3 distinct clusters of scanners and an association between Δ-values and manufacturer/model, whereas no association between Δ-values and maximum gradient strength, slew rate or static magnetic field strength was revealed. Several acquisition setups showed significant differences among groups, indicating the introduction of different biases in ADC estimation.
Unsupervised clustering analysis of DWI data, obtained from several scanners using an extensive acquisition protocol, allows to reveal an association between measured ADC values and manufacturer/model of scanner, as well as to identify suboptimal DWI acquisition setups for accurate ADC estimation.
•ADC inter-center assessments.•ADC spatial variation across different scanners.•ADC bias in LR an HF directions.•ADC quality assurance protocol.
To propose an MRI quality assurance procedure that can ...be used for routine controls and multi-centre comparison of different MR-scanners for quantitative diffusion-weighted imaging (DWI).
44 MR-scanners with different field strengths (1 T, 1.5 T and 3 T) were included in the study. DWI acquisitions (b-value range 0–1000 s/mm2), with three different orthogonal diffusion gradient directions, were performed for each MR-scanner. All DWI acquisitions were performed by using a standard spherical plastic doped water phantom. Phantom solution ADC value and its dependence with temperature was measured using a DOSY sequence on a 600 MHz NMR spectrometer. Apparent diffusion coefficient (ADC) along each diffusion gradient direction and mean ADC were estimated, both at magnet isocentre and in six different position 50 mm away from isocentre, along positive and negative AP, RL and HF directions.
A good agreement was found between the nominal and measured mean ADC at isocentre: more than 90% of mean ADC measurements were within 5% from the nominal value, and the highest deviation was 11.3%. Away from isocentre, the effect of the diffusion gradient direction on ADC estimation was larger than 5% in 47% of included scanners and a spatial non uniformity larger than 5% was reported in 13% of centres.
ADC accuracy and spatial uniformity can vary appreciably depending on MR scanner model, sequence implementation (i.e. gradient diffusion direction) and hardware characteristics. The DWI quality assurance protocol proposed in this study can be employed in order to assess the accuracy and spatial uniformity of estimated ADC values, in single- as well as multi-centre studies.
•Hp(0.07) does not underestimates equivalent dose to eye lens obtained by Hp(3).•Hp(0.07) can be used instead of Hp(3) to evaluate Hlens in exposed workers.•Equivalent dose to eye lens of the ...analyzed workers was always smaller than 3 mSv.
Individual dosimetry allows to quantify doses from ionizing radiation of exposed workers. Scientific and epidemiological evidences highlight the need for adequate measures for a greater protection of the eye and a reduction in annual doses. ICRP Publication 103, illustrating the operational dose quantity Hp(d) for the individual monitoring, proposes a depth d = 3 mm for eye lens monitoring, indicating that even the Hp(0.07) can be used. In this study, it was investigated if there are differences in the evaluation of the equivalent dose to eye lens (Hlens) using Hp(3) or Hp(0.07).
A slab phantom calibration was performed by an Accredited Calibration Laboratory in terms of Hp(3) and Hp(0.07) using ext-rad TLD-100 (LiF:Mg,Ti) dosimeters. Hp(0.07) and Hp(3) were measured for 26 exposed workers to assess Hlens. The measuring took place monthly in 2017 to obtain both semestral and annual doses.
Hlens(0.07) was always smaller than Hlens(3). However, the differences were not statistically significant (Mann-Whitney test, p > 0.05) for both semestral and annual doses. The percentage differences were 7 ± 3%, 6 ± 3% and 7 ± 2% for I semester, II semester and whole year, respectively. The mean underestimation index <10%, intra-class correlation coefficient >0.99, coefficient of variation <3% and the excellent correlation (R2 ≈ 0.999) for both semestral and annual doses highlighted that Hp(0.07) can be used to evaluate Hlens instead of Hp(3).
No statistical evidence was found that the use of Hp(0.07) underestimates the equivalent dose to eye lens obtained through Hp(3).
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