General Electric Scanner Research Articles

NEMA NU 2-2018 evaluation and image quality optimization of a new generation digital 32-cm axial field-of-view Omni Legend PET-CT using a genetic evolutionary algorithm

A performance evaluation was conducted on the new General Electric (GE) digital Omni Legend PET-CT system with 32 cm extended field of view. The first commercially available clinical digital bismuth germanate system. The system does not use time of flight (ToF). Testing was performed in accordance with the NEMA NU2–2018 standard. A comparison was made between two other commercial GE scanners with extended fields of view; the Discovery MI − 6 ring (ToF enabled) and the Discovery IQ (non-ToF). A genetic evolutionary algorithm was developed to optimize image reconstruction parameters from image quality assessments. The Omni demonstrated average spatial resolutions at 1 cm radial offset as 3.9 mm FWHM. The total system sensitivity at the center was 44.36 cps/kBq. The peak NECR was measured as 501 kcps at 17.8 kBq ml−1 with a 35.48% scatter fraction. The maximum count-rate error below NECR peak was 5.5%. Using standard iterative reconstructions, sphere contrast recovery coefficients were from 52.7 ± 3.2% (10 mm) to 92.5 ± 2.4% (37 mm). The PET-CT co-registration accuracy was 2.4 mm. In place of ToF, the Omni employs software corrections through a pre-trained neural network (PDL) (trained on non-ToF to ToF) that takes Bayesian penalized likelihood reconstruction (Q.Clear) images as input. The optimum parameters for image reconstruction, determined using the genetic algorithm were a Q.Clear parameter, β, of 350 and a ‘medium’ PDL setting. Using standard iterative reconstructions, the Omni initially showed increased background variability compared to the Discovery MI. With optimized PDL reconstruction parameters selected using the genetic algorithm the performance of the Omni surpassed that of the Discovery MI on all NEMA tests. The genetic algorithm’s demonstrated ability to enhance image quality in PET-CT imaging underscores the importance of algorithm driven optimization and underscores the requirement to validate its use in the clinical setting.

Avulsions in adolescent soccer players: preliminary results of radiographic, ultrasonographic and magnetic resonance findings

Objectives: The main objective of this study was to characterize soccer related avulsions radiologically. The secondary objectives were to describe the athletes' clinical profile and other musculoskeletal changes associated with avulsions. Materials and methods: Cross-sectional study with adolescent athletes from a Brazilian team soccer academy. Inclusion criteria were age between 11 and 16 years and clinical and magnetic resonance imaging (MRI) diagnosis of avulsion. Exclusion criteria were exams with an unacceptable technical standard and absence of clinical data. Four radiologists revised the exams consensually (two for each method). The equipment used was a General Electric (GE) US scanner, model Logic 10, and a 1.5 T MRI GE scanner, Optima MR 360 model, and a Shimadzu RX scanner, Radspeed MC model. Results and discussion: Nine showed signs of avulsion from a sample of 37 athletes. The mean age was 13.1 years, and all were male. Four athletes were injured during the matches (44.4%), and another five were in training (55.6%). Clinically, one injury was considered mild (11.1%), two moderate (22.2%), and six severe (66.7%). The anatomical locations and frequencies of avulsions were: five in the anterior inferior iliac spine (AIIS) (55.6%), two in the ischiatic tuberosity (IT) (22.2%), and two in the iliac crest (22.2%). Ultrasonography (US) was performed in 10 cases and detected seven avulsions (77.8%). All lesions not detected by US occurred at the IT. A pelvic radiograph was performed in seven cases and was positive in five athletes (77.8%). Undetected cases occurred at the AIIS. Avulsions occurred in isolation in eight cases (88.9%), simultaneously with indirect trauma in three (33.3%) and direct trauma in two (22.2%). Conclusion: In adolescent soccer players, a quarter of traumatic injuries are avulsions, which are more common at the AIIS. US proved ineffective in identifying some IT lesions and radiography, some others at the AIIS.

Cytomegalovirus infection associated with smaller cerebellum in severe mental illness

IntroductionPostnatal cytomegalovirus (CMV) infection of immunocompetent hosts is usually inapparent but typically results in lifelong latency. Congenital CMV infections as well as CMV infections in patients with immunodeficiencies have been linked to major cerebellar pathology. Patients with severe mental illness have been repeatedly found to have smaller cerebellum, and they may be particularly susceptible to CMV infections. Finally, both animal and human studies have shown a differential male and female immune response to CMV.ObjectivesWe evaluated whole cerebellar grey matter volumes (CGMV) in CMV immunoglobulin G (IgG) seropositive (CMV+) and seronegative (CMV-) patients with severe mental illness and healthy controls (HC). We hypothesized that CMV seropositivity, reflecting previous infection and current latency, is associated with smaller CGMV in patients but not in HC, and that such a putative association may be sex-dependent.MethodsWe included 529 adult patients with severe mental illness (CMV+ 57%, women 48%), i.e., 324 patients with schizophrenia spectrum disorders and 205 patients with bipolar spectrum disorders, and 494 HC (CMV+ 56%, women 45%). MRI scans were obtained with a 1.5T Siemens scanner (n=596) and two 3.0T General Electric scanners (n=427), and processed with FreeSurfer v6.0. Circulating CMV IgG concentrations were measured with immunoassays. In age-, scanner- and estimated total intracranial volume-adjusted analyses of covariance (ANCOVAs), we investigated main and interaction effects of CMV status and sex on CGMV in patients and HC.ResultsCMV+ patients had smaller CGMV than CMV- patients (p=0.042). There was no CGMV difference between CMV+ and CMV- HC (p=0.858). The adjusted CGMV means in CMV+ patients and CMV- patients were 115078 mm3 and 116725 mm3, respectively (p=0.042); the adjusted CGMV means in CMV+ and CMV- HC were 117980 mm3 and 117840 mm3, respectively (p=0.858) (Image). Among patients, a trend towards CMV-by-sex interaction (p=0.073) was found. Post-hoc analyses showed a significant CMV-CGMV association in the female patient group (p=0.005), with no association among male patients (p=0.840).Image:ConclusionsCMV IgG seropositivity is associated with smaller cerebellum in severe mental illness, an effect driven by the female patients, but not among HC. This may indicate a CMV-related deleterious impact on cerebellum restricted to patients.Disclosure of InterestNone Declared

Reliability of multi-site UK Biobank MRI brain phenotypes for the assessment of neuropsychiatric complications of SARS-CoV-2 infection: The COVID-CNS travelling heads study.

Magnetic resonance imaging (MRI) of the brain could be a key diagnostic and research tool for understanding the neuropsychiatric complications of COVID-19. For maximum impact, multi-modal MRI protocols will be needed to measure the effects of SARS-CoV-2 infection on the brain by diverse potentially pathogenic mechanisms, and with high reliability across multiple sites and scanner manufacturers. Here we describe the development of such a protocol, based upon the UK Biobank, and its validation with a travelling heads study. A multi-modal brain MRI protocol comprising sequences for T1-weighted MRI, T2-FLAIR, diffusion MRI (dMRI), resting-state functional MRI (fMRI), susceptibility-weighted imaging (swMRI), and arterial spin labelling (ASL), was defined in close approximation to prior UK Biobank (UKB) and C-MORE protocols for Siemens 3T systems. We iteratively defined a comparable set of sequences for General Electric (GE) 3T systems. To assess multi-site feasibility and between-site variability of this protocol, N = 8 healthy participants were each scanned at 4 UK sites: 3 using Siemens PRISMA scanners (Cambridge, Liverpool, Oxford) and 1 using a GE scanner (King's College London). Over 2,000 Imaging Derived Phenotypes (IDPs), measuring both data quality and regional image properties of interest, were automatically estimated by customised UKB image processing pipelines (S2 File). Components of variance and intra-class correlations (ICCs) were estimated for each IDP by linear mixed effects models and benchmarked by comparison to repeated measurements of the same IDPs from UKB participants. Intra-class correlations for many IDPs indicated good-to-excellent between-site reliability. Considering only data from the Siemens sites, between-site reliability generally matched the high levels of test-retest reliability of the same IDPs estimated in repeated, within-site, within-subject scans from UK Biobank. Inclusion of the GE site resulted in good-to-excellent reliability for many IDPs, although there were significant between-site differences in mean and scaling, and reduced ICCs, for some classes of IDP, especially T1 contrast and some dMRI-derived measures. We also identified high reliability of quantitative susceptibility mapping (QSM) IDPs derived from swMRI images, multi-network ICA-based IDPs from resting-state fMRI, and olfactory bulb structure IDPs from T1, T2-FLAIR and dMRI data. These results give confidence that large, multi-site MRI datasets can be collected reliably at different sites across the diverse range of MRI modalities and IDPs that could be mechanistically informative in COVID brain research. We discuss limitations of the study and strategies for further harmonisation of data collected from sites using scanners supplied by different manufacturers. These acquisition and analysis protocols are now in use for MRI assessments of post-COVID patients (N = 700) as part of the ongoing COVID-CNS study.

Inter-Rater Reliability and Correlation of L1 Hounsfield Unit Measurements with DXA Scores

Introduction: While prior studies have generally reported rigorous protocols using prespecified CT scanner settings for HU measurements, the present study sought to report on the correlation between DXA and HUs recorded using several CT scanners with varying sequences, simulating measurements performed in “real-world” hospital and Emergency Department (ED) settings. Methodology: Six raters performed HU measurements of trabecular bone at the L1 vertebral body for forty consecutive patients on Phillips and General Electric (GE) abdominal CT scans obtained between 2017 and 2021. Inter-rater reliability of the HU measurements and their correlations with recorded DXA-based bone assessments were determined. Correlation coefficients were calculated for the HU measurements between scanner vendors as well as for the CT HUs with each DXA measurement. Results: The ICC for L1 HUs read on the Phillips and GE scanners were 0.85 and 0.82, respectively, indicating excellent agreement. The correlation coefficient for the mean HUs on the Phillips and GE scanners was 0.92, also indicating excellent correlation. For both scanner vendors, the HU values most closely correlated with the total femur and femoral neck T-scores. Conclusions: HU values recorded on a Phillips and GE scanner both demonstrated excellent inter-rater reliability. Correlations were strongest between L1 HU values and total femur DXA T-scores. Readily available abdominal CT image data across multiple hospital settings can be utilized by providers of varying level of imaging interpretation expertise to determine vertebral body Hounsfield units that may help identify osteoporosis risk without additional radiation exposure or cost.

Investigation of the Inter- and Intrascanner Reproducibility and Repeatability of Radiomics Features in T1-Weighted Brain MRI.

Radiomics is the high throughput analysis of medical images using computer algorithms, which specifically assess textural features. It has increasingly been proposed as a tool for the development of imaging biomarkers. However, an important acknowledged limitation of radiomics is the lack of reproducibility of features produced. To assess reproducibility and repeatability of radiomics variables in brain MRI through a multivisit, multicenter study. Retrospective. Fourteen individuals visiting three institutions twice, 10 males with the mean age of 36.3 years and age range 25-51. 3D T1W inversion recovery on three 1.5-T General Electric scanners. Radiomics analysis by a consultant radiologist performed on the T1W images of the whole brain on all visits. All possible radiomics features were generated. Concordance correlation coefficient (CCC) and dynamic range (DR) for all variables were calculated to assess the test-retest repeatability. Intraclass correlation coefficients (ICCs) were calculated to investigate the reproducibility of features across centers. Of 1596 features generated, 57 from center 1, 15 from center 2, and 22 from center 3 had a CCC > 0.9 and DR > 0.9. Eight variables had CCC > 0.9 and DR > 0.9 in all centers. Forty-one variables had an ICC of >0.9. No variables had CCC > 0.9, DR > 0.9, and ICC > 0.9. Repeatability and reproducibility of variables is a significant limitation of radiomics analysis in 3DT1W brain MRI. Careful selection of radiomic features is required. 4 TECHNICAL EFFICACY STAGE: 2.

Myocardial T1 Values at 1.5 T: Normal Values for General Electric Scanners and Sex-Related Differences.

No data are available about normal ranges for native T1 in human myocardium using General Electric (GE) scanners. To establish normal ranges for myocardial T1 values and evaluate regional variability and the influence of physiological factors. Prospective. One hundred healthy volunteers with normal electrocardiogram, no cardiovascular/systemic diseases, or risk factors (age range: 20-70 years; 50 females). 1.5 T/Steady-state free precession cine and a modified Look-Locker inversion recovery sequence in diastole (also in systole for 61 volunteers). Image analysis was performed by operators with >10 years experience in cardiac MR using commercially available software. T1 values were calculated for 16 myocardial segments, and the global value was the mean. Segments were grouped according to circumferential region (anterior, septal, inferior, and lateral) and to level (basal, medial, apical). Twenty images were analyzed twice by the same operator and by a different operator to assess reproducibility. Independent-samples t-test or Mann-Whitney test; paired sample t-test or Wilcoxon signed-rank test; one-way repeated measures ANOVA or Friedman tests; Pearson's or Spearman's correlation. Reproducibility evaluated using coefficient of variability (CoV). Due to artifacts and/or partial-volume effects, 45/1600 (2.8%) segments were excluded. A good intra- and inter-operator reproducibility was detected (CoV < 5%). There were significant differences in segmental T1 values (P< 0.05). A significant circumferential variability was present (P < 0.05): the mean native T1 value over the lateral region was significantly lower than in the other three regions. An increasing gradient from basal to apical slices was detected (P< 0.05). Segmental and global T1 values were not associated with age (range P=0.052-0.911) but were significantly lower in males than in females (global: 993 ± 32 vs. 1037 ± 27 ms; P < 0.05) and significantly correlated with heart rate (range R for segmental values=0.247-0.920; P< 0.05). Almost all segmental T1 values were inversely correlated with wall thickness (R from -0.233 to -0.514; P< 0.05). Systolic T1 values were significantly lower than diastolic values in basal anteroseptal segment, in all medial segments except the inferior one, and in all apical segments (P < 0.05). Myocardial T1 values differ among myocardial regions, are influenced by sex, heart rate, and wall thickness and vary according to the cardiac cycle in healthy adults. 2 TECHNICAL EFFICACY: Stage 2.

Deep learning for mass detection in Full Field Digital Mammograms

In recent years, the use of Convolutional Neural Networks (CNNs) in medical imaging has shown improved performance in terms of mass detection and classification compared to current state-of-the-art methods. This paper proposes a fully automated framework to detect masses in Full-Field Digital Mammograms (FFDM). This is based on the Faster Region-based Convolutional Neural Network (Faster-RCNN) model and is applied for detecting masses in the large-scale OPTIMAM Mammography Image Database (OMI-DB), which consists of ∼80,000 FFDMs mainly from Hologic and General Electric (GE) scanners. This research is the first to benchmark the performance of deep learning on OMI-DB. The proposed framework obtained a True Positive Rate (TPR) of 0.93 at 0.78 False Positive per Image (FPI) on FFDMs from the Hologic scanner. Transfer learning is then used in the Faster R-CNN model trained on Hologic images to detect masses in smaller databases containing FFDMs from the GE scanner and another public dataset INbreast (Siemens scanner). The detection framework obtained a TPR of 0.91±0.06 at 1.69 FPI for images from the GE scanner and also showed higher performance compared to state-of-the-art methods on the INbreast dataset, obtaining a TPR of 0.99±0.03 at 1.17 FPI for malignant and 0.85±0.08 at 1.0 FPI for benign masses, showing the potential to be used as part of an advanced CAD system for breast cancer screening.

Perinatal DHA Supplementation Alters Brain Functional Organization in a Piglet Model

Docosahexaenoic acid (DHA) is the most abundant n3 poly‐unsaturated fatty acid (PUFA) in the central nervous system that accumulates most rapidly during the third trimester of gestation and early postnatal life. While maternal fish intake and infant DHA status were suggested positively associated with cognitive function during early years from observational studies, intervention trials supplementing DHA during gestation and/or lactation yielded controversial findings in healthy infants. This study aims to investigate whether maternal supplementation of DHA during late gestation and lactation imparts advantages to fiber bundle maturation and functional organization of the developing brain which may contribute to cognitive development in healthy offspring using a piglet model. Pig is a robust translational animal model for brain research that shares similar growth patterns with human infants. Pregnant sows (n=8) were fed a control diet only (CON) or diet containing DHA (DHA, 75 mg/kg BW/day) from late gestation until lactation. DHA supplementation drastically increased colostrum n3‐PUFA levels including DHA. Healthy piglets (n=7 in CON and DHA) underwent magnetic resonance imaging (MRI) in a 3.0 Tesla General Electric scanner to acquire anatomical, diffusion tensor imaging (DTI), and resting‐state functional MRI (rs‐fMRI) data at weaning (21d old). Maternal DHA supplementation during gestation and lactation increased fiber tract length (p=.0061) and tend to increase fractional anisotropy value (p=.0906) in the hippocampus of the offspring compared to the piglets born to CON sows. The mean diffusivity showed no difference between the two groups (p&gt;.05). This indicated that DHA may enhance myelination of fiber bundles and improve fiber tract integrity that potentiates efficient neural communication. The subsequent rs‐fMRI analysis examined the six resting‐state networks including executive control network, cerebellum network, visual network, sensorimotor network, auditory network, and default mode network. Using sparse dictionary learning approach, we found that piglets from DHA‐fed sows had a significant 11.9 % enhanced connectivity within visual network encompassing primary, secondary, and associative visual cortex (p=.0012). In addition, piglets born to DHA‐fed sows showed a 10.1% decrease in functional connectivity in the sensorimotor network encompassing primary motor cortex, somatosensory association cortex, and premotor cortex compared to that of CON piglets (p=.0001). This suggested that DHA may result in higher intrinsic activity in the visual system and prevent activation of sensorimotor network in the absence of external stimuli. In conclusion, maternal DHA supplementation during late gestation and lactation may enhance fiber tract integrity and alter brain functional organization of the offspring which resulted in increased exploratory behaviors and improved learning and memory function we observed previously.Support or Funding InformationThe study was supported by Georgia Experimental Agricultural Station, HATCH #GEO00795, faculty research grant from Office or Research at the UGA, and Division of Research at PCOM‐19131. DHA was kindly provided by DSM, Inc

Objective quantification of contrast enhancement of unruptured intracranial aneurysms: a high-resolution vessel wall imaging validation study.

High-resolution vessel wall imaging (HR-VWI) has emerged as a valuable tool in assessing unruptured intracranial aneurysms (UIAs). There is no standardized method to quantify contrast enhancement of the aneurysm wall. Contrast enhancement can be objectively measured as signal intensity (SI) or subjectively adjudicated. In this study, the authors compared the different methods to quantify wall enhancement of UIAs and determined the sensitivity and specificity of each method as a surrogate of aneurysm instability. They also compared SI quantification between scanners from different manufacturers. The University of Iowa HR-VWI Project database was analyzed. This database compiles patients with UIAs who prospectively underwent HR-VWI using a 3T MRI scanner. The mean and maximal SI values of the aneurysm wall, pituitary stalk, and genu of the corpus callosum were used to compare 3 different measurement methods: 1) aneurysm enhancement ratio AER = (SIwall post - SIwall pre)/SIwall pre; 2) aneurysm-to-pituitary stalk contrast ratio CRstalk = SIwall post/SIstalk post; and 3) aneurysm enhancement index AEI = ([SIwall post/SIbrain post] - [SIwall pre/SIbrain pre])/(SIwall pre/SIbrain pre) (where "pre" indicates precontrast images and "post" indicates postcontrast images). Size ≥ 7 mm was used as a surrogate of aneurysm instability for receiver operating characteristic (ROC) curve analysis. To determine if the objective quantification of SI varies among scanners from different manufacturers, 9 UIAs underwent the same HR-VWI protocol using a 3T General Electric (GE) scanner and a 3T Siemens scanner. Three UIAs also underwent a third scanning procedure on a unit with a different magnet strength (7T GE). Eighty patients with 102 UIAs were included in the study. The mean age was 64.5 ± 12.2 years, and 64 (80%) patients were women. UIAs ≥ 7 mm had significantly higher SIs than smaller UIAs (< 7 mm): AER = 0.82 vs 0.49, p < 0.001; CRstalk = 0.84 vs 0.61, p < 0.001; and AEI = 0.81 vs 0.48, p < 0.001. ROC curves demonstrated optimal sensitivity of 81.5% for CRstalk ≥ 0.60, 75.9% for AEI ≥ 0.50, and 74.1% for AER ≥ 0.49. Intermanufacturer correlation between 3T GE and 3T Siemens MRI scanners for CRstalk using mean and maximal SI values was excellent (Pearson coefficients > 0.80, p < 0.001). A similar correlation was identified among the 3 UIAs that underwent 7T imaging. CRstalk using maximal SI values was the most reliable objective method to quantify enhancement of UIAs on HR-VWI. The same ratios were obtained between different manufacturers and on scans obtained using magnets of different strengths.

Age-related deficits in intracortical myelination in young adults with bipolar disorder type I

Previous studies have implicated white-matter-related changes in the pathophysiology of bipolar disorder. However, most of what is known is derived from in vivo subcortical white-matter imaging or postmortem studies. In this study, we investigated whole-brain intracortical myelin (ICM) content in people with bipolar disorder type I and controls. Between Sept. 1, 2014, and Jan. 31, 2017, we used a 3 T General Electric scanner to collect T1-weighted images in 45 people with bipolar disorder type I and 60 controls aged 17 to 45 years using an optimized sequence that was sensitive to ICM content. We analyzed images using a surfacebased approach. We used general linear models with quadratic age terms to examine the signal trajectory of ICM across the age range. In healthy controls, the T1-weighted signal followed an inverted-U trajectory over age; in people with bipolar disorder type I, the association between ICM and age followed a flat trajectory (p < 0.05, Bonferroni corrected). Exploratory analyses showed that ICM signal intensity was associated with duration of illness, age of onset, and anticonvulsant and antipsychotic use in people with bipolar disorder type I (p < 0.05, uncorrected). Because of the cross-sectional nature of the study, we were unable to comment on whether the effects were due to dysmyelination or demyelination in bipolar disorder. This foundational study is, to our knowledge, the first to show global age-related deficits in ICM maturation throughout the cortex in bipolar disorder. Considering the impact of myelination on the maintenance of neural synchrony and the integrity of neural connections, this work may help us better understand the cognitive and behavioural deficits seen in bipolar disorder.

Comparison of Programmable Ventriculoperitoneal Shunt Artifacts between 3.0 and 1.5 T MR Scanner : A proGAV2.0 Device (Aesculap) Study using General Electric Scanner

Comparison of Programmable Ventriculoperitoneal Shunt Artifacts between 3.0 and 1.5 T MR Scanner : A proGAV2.0 Device (Aesculap) Study using General Electric Scanner

A New MRI Masking Technique Based on Multi-Atlas Brain Segmentation in Controls and Schizophrenia: A Rapid and Viable Alternative to Manual Masking.

Brain masking of MRI images separates brain from surrounding tissue and its accuracy is important for further imaging analyses. We implemented a new brain masking technique based on multi-atlas brain segmentation (MABS) and compared MABS to masks generated using FreeSurfer (FS; version 5.3), Brain Extraction Tool (BET), and Brainwash, using manually defined masks (MM) as the gold standard. We further determined the effect of different masking techniques on cortical and subcortical volumes generated by FreeSurfer. Images were acquired on a 3-Tesla MR Echospeed system General Electric scanner on five control and five schizophrenia subjects matched on age, sex, and IQ. Automated masks were generated from MABS, FS, BET, and Brainwash, and compared to MM using these metrics: a) volume difference from MM; b) Dice coefficients; and c) intraclass correlation coefficients. Mean volume difference between MM and MABS masks was significantly less than the difference between MM and FS or BET masks. Dice coefficient between MM and MABS was significantly higher than Dice coefficients between MM and FS, BET, or Brainwash. For subcortical and left cortical regions, MABS volumes were closer to MM volumes than were BET or FS volumes. For right cortical regions, MABS volumes were closer to MM volumes than were BET volumes. Brain masks generated using FreeSurfer, BET, and Brainwash are rapidly obtained, but are less accurate than manually defined masks. Masks generated using MABS, in contrast, resemble more closely the gold standard of manual masking, thereby offering a rapid and viable alternative.

SAT0168 Validation of Musculoskeletal US of Hands and Wrists in Patients with Systemic Sclerosis

BackgroundThere is no published work validating the techniques for examining joint and tendon pathology with musculoskeletal ultrasound (MSUS) in systemic sclerosis (SSc).ObjectivesTo examine MSUS of the joints and tendons of...

Whole brain quantitative T2 MRI across multiple scanners with dual echo FSE: Applications to AD, MCI, and normal aging

The ability to pool data from multiple MRI scanners is becoming increasingly important with the influx in multi-site research studies. Fast spin echo (FSE) dual spin echo sequences are often chosen for such studies based principally on their short acquisition time and the clinically useful contrasts they provide for assessing gross pathology. The practicality of measuring FSE-T2 relaxation properties has rarely been assessed. Here, FSE-T2 relaxation properties are examined across the three main scanner vendors (General Electric (GE), Philips, and Siemens). The American College of Radiology (ACR) phantom was scanned on four 1.5 T platforms (two GE, one Philips, and one Siemens) to determine if the dual echo pulse sequence is susceptible to vendor-based variance. In addition, data from 85 subjects spanning the spectrum of normal aging, mild cognitive impairment (MCI), and Alzheimer's disease (AD) was obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to affirm the presence of any phantom based between vendor variance and determine the relationship between this variance and disease. FSE-T2 relaxation properties, including peak FSE-T2 and histogram width, were calculated for each phantom and human subject. Direct correspondence was found between the phantom and human subject data. Peak FSE-T2 of Siemens scanners was consistently at least 20 ms prolonged compared to GE and Philips. Siemens scanners showed broader FSE-T2 histograms than the other scanners. Greater variance was observed across GE scanners than either Philips or Siemens. FSE-T2 differences were much greater with scanner vendor than between diagnostic groups, as no significant changes in peak FSE-T2 or histogram width between normal aged, MCI, and AD subject groups were observed. These results indicate that whole brain histogram measures are not sensitive enough to detect FSE-T2 changes between normal aging, MCI, and AD and that FSE-T2 is highly variable across scanner vendors.

Evidence That MR Diffusion Tensor Imaging (Tractography) Predicts the Natural History of Regional Progression in Patients Irradiated Conformally for Primary Brain Tumors

Stereotactic radiotherapy (SRT) is fast becoming the method of choice for treatment of nonsuperficial brain lesions. SRT treatment plans of malignant brain tumors typically incorporate a 20-mm isotropic margin to account for microscopic tumor spread; however, distant or progressive tumors occur outside this margin. Our hypothesis is that paths of elevated water diffusion may provide a preferred route for transport or migration of cancer cells. If our hypothesis is correct, then future SRT treatment volumes could be modified to provide elongated treatment margins along the paths of elevated water diffusion, thereby creating a biologically better treatment plan that may reduce the incidence of progression. Magnetic resonance diffusion tensor imaging (DTI) datasets were acquired on patient subjects before the appearance of >5 mm diameter progressive lesions or secondary tumors. DTI was performed using an echo-planar imaging sequence on a 1.5T clinical General Electric scanner with voxel dimensions of 0.98 x 0.98 x 6 mm. After SRT, patients were given repeated magnetic resonance imaging follow-ups at regular intervals to identify early tumor progression. When progressive disease was detected, DTIstudio and FMRIB Software Library software was used to compute paths of preferred water diffusion through the primary tumor site and the site of progression. Our preliminary results on 14 patient datasets suggest a strong relationship between routes of elevated water diffusion from the primary tumor and the location of tumor progression. Further investigation is therefore warranted. Future work will employ more sophisticated fiber analysis in a prospective study.

Reader and platform reproducibility for quantitative assessment of carotid atherosclerotic plaque using 1.5T Siemens, Philips, and General Electric scanners

To evaluate the platform and reader reproducibility of quantitative carotid plaque measurements. A total of 32 individuals with >or=15% carotid stenosis by duplex ultrasound were each imaged once by a 1.5T General Electric (GE) whole body scanner and twice by either a 1.5T Philips scanner or a 1.5T Siemens scanner. A standardized multisequence protocol and identical phased-array carotid coils were used. Expert readers, blinded to subject information, scanner type, and time point, measured the lumen, wall, and total vessel areas and determined the modified American Heart Association lesion type (AHA-LT) on the cross-sectional images. AHA-LT was consistently identified across the same (kappa = 0.75) and different scan platforms (kappa = 0.75). Furthermore, scan-rescan coefficients of variation (CV) of wall area measurements on Siemens and Philips scanners ranged from 6.3% to 7.5%. However, wall area measurements differed between Philips and GE (P = 0.003) and between Siemens and GE (P = 0.05). In general, intrareader reproducibility was higher than interreader reproducibility for AHA-LT identification as well as for quantitative measurements. All three scanners produced images that allowed AHA-LT to be consistently identified. Reproducibility of quantitative measurements by Siemens and Philips scanners were comparable to previous studies using 1.5T GE scanners. However, bias was introduced with each scanner and the use of different readers substantially increased variability. We therefore recommend using the same platform and the same reader for scans of individual subjects undergoing serial assessment of carotid atherosclerosis.

Hypothalamic Abnormalities in Schizophrenia: Sex Effects and Genetic Vulnerability

This is a unique hypothalamic magnetic resonance imaging (MRI) study in schizophrenia, an important region in the limbic system. We hypothesized abnormal volumetric increases, with greater severity in multiplex families (more than one ill member) compared with simplex families (one ill). We tested the hypothesis that normal hypothalamic sexual dimorphism is disrupted in schizophrenia. Eighty-eight DSM-III-R schizophrenia cases (40 simplex and 48 multiplex), 43 first-degree nonpsychotic relatives, and 48 normal comparisons systematically were compared. A 1.5-Tesla General Electric scanner was used to acquire structural MRI scans, and contiguous 3.1-mm slices were used to segment anterior and posterior hypothalamus. General linear model for correlated data and generalized estimating equations were used to compare cases, relatives, and controls on right and left hypothalamus, controlled for age, sex, and total cerebral volume. Spearman's correlations of hypothalamic volumes with anxiety were calculated to begin to examine arousal correlates with structural abnormalities. Findings demonstrated significantly increased hypothalamic volume in cases and nonpsychotic relatives, particularly in regions of paraventricular and mammillary body nuclei, respectively. This increase was linear from simplex to multiplex cases, was positively correlated with anxiety, and had a greater propensity in women. Findings suggest important implications for understanding genetic vulnerability of schizophrenia and the high rate of endocrine abnormalities.

Gray matter density reduction in the insula in fire survivors with posttraumatic stress disorder: A voxel-based morphometric study

Voxel-based morphometry (VBM) is an objective whole-brain technique for characterizing regional cerebral volume and tissue concentration differences in structural magnetic resonance images. In the current study, we used VBM to examine possible cerebral gray matter abnormalities in patients with posttraumatic stress disorder (PTSD) due to fire. The subjects included 12 victims of a fire disaster with PTSD and 12 matched victims of the same fire without PTSD. Magnetic resonance images were obtained on a 1.5-Tesla General Electric scanner at Central South University, and an entire brain volume of 248 contiguous slices was obtained for each subject. Then, gray matter density in patients with PTSD and control groups was compared by using a VBM approach in SPM2. Group analysis was thresholded at P < 0.001, uncorrected, at the voxel level. The following three regions of reduced gray matter volume were found in patients with PTSD compared with controls: left hippocampus, left anterior cingulate cortex (ACC), and bilateral insular cortex. It was concluded that there are structural abnormalities of the hippocampus, the ACC and the insular cortex in patients with PTSD due to fire.

Masticatory muscle right-left differences in controls and hemifacial microsomia patients.

One aim of this study was to assess right-left differences in the volume of masticatory muscles in controls so as to be able to distinguish between normal variations and pathological differences. The other aim was to compare the masticatory muscle volume of the nonaffected side of hemifacial microsomia patients with the smaller side of controls so as to test the compensation hypothesis. The study group consisted of 39 children with hemifacial microsomia and the control group of 52 children. Computed tomography scans were made using a Philips Tomoscan 350 and a Pro Speed S Fast Spiral General Electric scanner. The normal right-left differences in volume of the masticatory muscle of the controls, calculated as a percentage of the total, demonstrated small mean differences of 2.57% to 2.88% (SD:1.98-2.74). For hemifacial microsomia patients, the relative difference was about 10 times the difference for controls. For controls, the averages of the right-left differences (%) were all below the generally accepted SEM of 4%. Testing the compensation hypothesis of all effects, only the age effect was multivariately significant (P < 0.001). No overcompensation of the masticatory muscles of the nonaffected side of hemifacial microsomia patients could be demonstrated.