Global Regions Of Interest Research Articles

DSTAN: A Deformable Spatial-temporal Attention Network with Bidirectional Sequence Feature Refinement for Speckle Noise Removal in Thyroid Ultrasound Video.

Thyroid ultrasound video provides significant value for thyroid diseases diagnosis, but the ultrasound imaging process is often affected by the speckle noise, resulting in poor quality of the ultrasound video. Numerous video denoising methods have been proposed to remove noise while preserving texture details. However, existing methods still suffer from the following problems: (1) relevant temporal features in the low-contrast ultrasound video cannot be accurately aligned and effectively aggregated by simple optical flow or motion estimation, resulting in the artifacts and motion blur in the video; (2) fixed receptive field in spatial features integration lacks the flexibility of aggregating features in the global region of interest and is susceptible to interference from irrelevant noisy regions. In this work, we propose a deformable spatial-temporal attention denoising network to remove speckle noise in thyroid ultrasound video. The entire network follows the bidirectional feature propagation mechanism to efficiently exploit the spatial-temporal information of the whole video sequence. In this process, two modules are proposed to address the above problems: (1) a deformable temporal attention module (DTAM) is designed after optical flow pre-alignment to further capture and aggregate relevant temporal features according to the learned offsets between frames, so that inter-frame information can be better exploited even with the imprecise flow estimation under the low contrast of ultrasound video; (2) a deformable spatial attention module (DSAM) is proposed to flexibly integrate spatial features in the global region of interest through the learned intra-frame offsets, so that irrelevant noisy information can be ignored and essential information can be precisely exploited. Finally, all these refined features are rectified and merged through residual convolution blocks to recover the clean video frames. Experimental results on our thyroid ultrasound video (US-V) dataset and the DDTI dataset demonstrate that our proposed method exceeds 1.2 1.3dB on PSNR and has clearer texture detail compared to other state-of-the-art methods. In the meantime, the proposed model can also assist thyroid nodule segmentation methods to achieve more accurate segmentation effect, which provides an important basis for thyroid diagnosis. In the future, the proposed model can be improved and extended to other medical image sequence datasets, including CT and MRI slice denoising. The code and datasets are provided at https://github.com/Meta-MJ/DSTAN .

Race, Purpose and Meaning of Life, and Markers of Brain Health for Alzheimer’s Disease

AbstractBackgroundMeaning and purpose in life (M&P) represents goal direction and meaning for an individual. Literature has shown associations between higher M&P and better global cognition. However, papers included either predominantly White or Black samples. We aim to replicate these results in a sample with roughly equal Black and White participants and assess racial differences in the association between M&P and markers of brain health (global cognition and amyloid). We hypothesize that higher M&P scores will be associated with better markers of brain health and that the association will be stronger among Black compared to White individuals.Methods263 adults aged 50‐89 years (Table 1) from the Pittsburgh Human Connectome Project were included. M&P was measured by the NIH Toolbox questionnaire. Brain health was characterized as general cognitive function by the Montreal Cognitive Assessment (MoCA) and amyloid burden from positron emission tomography with Pittsburgh compound B (PiB) using a global region of interest. Race was self‐reported as either White or Black/African American; individuals of other races (n = 6) were not included in these analyses. The association of M&P with brain outcomes was assessed by linear regression adjusted for years of education, sex, and age. Effect modification by race was assessed with inclusion of an interaction term in the models. Analyses were conducted in the whole sample and then again, in only those considered cognitively normal.ResultsThere was no association between M&P and either marker of brain health (global amyloid: β = 0.0008, p = 0.52; cognition: β = 0.019, p = 0.28). There was no statistically significant effect modification by race for either outcome (all p for interaction>0.1). When restricting to those considered cognitively normal, results remained the same.ConclusionIn contrast to prior findings, we found no association between M&P and markers of brain health in contrast to other studies. This difference is not likely due to racial composition as we found no differences by race but may be due to differences in measurements used. Further research should explore potential differences in associations based on cognitive domain.

Exploring Contextual Relationships for Cervical Abnormal Cell Detection.

Cervical abnormal cell detection is a challenging task as the morphological discrepancies between abnormal and normal cells are usually subtle. To determine whether a cervical cell is normal or abnormal, cytopathologists always take surrounding cells as references to identify its abnormality. To mimic these behaviors, we propose to explore contextual relationships to boost the performance of cervical abnormal cell detection. Specifically, both contextual relationships between cells and cell-to-global images are exploited to enhance features of each region of interest (RoI) proposal. Accordingly, two modules, dubbed as RoI-relationship attention module (RRAM) and global RoI attention module (GRAM), are developed and their combination strategies are also investigated. We establish a strong baseline by using Double-Head Faster R-CNN with a feature pyramid network (FPN) and integrate our RRAM and GRAM into it to validate the effectiveness of the proposed modules. Experiments conducted on a large cervical cell detection dataset reveal that the introduction of RRAM and GRAM both achieves better average precision (AP) than the baseline methods. Moreover, when cascading RRAM and GRAM, our method outperforms the state-of-the-art (SOTA) methods. Furthermore, we show that the proposed feature-enhancing scheme can facilitate image- and smear-level classification. The code and trained models are publicly available at https://github.com/CVIU-CSU/CR4CACD.

An end‐to‐end infant brain parcellation pipeline

ObjectiveAccurate infant brain parcellation is crucial for understanding early brain development; however, it is challenging due to the inherent low tissue contrast, high noise, and severe partial volume effects in infant magnetic resonance images (MRIs). The aim of this study was to develop an end-to-end pipeline that enabled accurate parcellation of infant brain MRIs. MethodsWe proposed an end-to-end pipeline that employs a two-stage global-to-local approach for accurate parcellation of infant brain MRIs. Specifically, in the global regions of interest (ROIs) localization stage, a combination of transformer and convolution operations was employed to capture both global spatial features and fine texture features, enabling an approximate localization of the ROIs across the whole brain. In the local ROIs refinement stage, leveraging the position priors from the first stage along with the raw MRIs, the boundaries of the ROIs are refined for a more accurate parcellation. ResultsWe utilized the Dice ratio to evaluate the accuracy of parcellation results. Results on 263 subjects from National Database for Autism Research (NDAR), Baby Connectome Project (BCP) and Cross-site datasets demonstrated the better accuracy and robustness of our method than other competing methods. ConclusionOur end-to-end pipeline may be capable of accurately parcellating 6-month-old infant brain MRIs.

Pre-Trained Deep Neural Network-Based Computer-Aided Breast Tumor Diagnosis Using ROI Structures

Deep neural network (DNN) based computer-aided breast tumor diagnosis (CABTD) method plays a vital role in the early detection and diagnosis of breast tumors. However, a Brightness mode (B-mode) ultrasound image derives training feature samples that make closer isolation toward the infection part. Hence, it is expensive due to a meta-heuristic search of features occupying the global region of interest (ROI) structures of input images. Thus, it may lead to the high computational complexity of the pre-trained DNN-based CABTD method. This paper proposes a novel ensemble pre-trained DNN-based CABTD method using global- and local-ROI-structures of B-mode ultrasound images. It conveys the additional consideration of a local-ROI-structures for further enhancing the pre-trained DNN-based CABTD method’s breast tumor diagnostic performance without degrading its visual quality. The features are extracted at various depths (18, 50, and 101) from the global and local ROI structures and feed to support vector machine for better classification. From the experimental results, it has been observed that the combined local and global ROI structure of small depth residual network ResNet18 (0.8 in %) has produced significant improvement in pixel ratio as compared to ResNet50 (0.5 in %) and ResNet101 (0.3 in %), respectively. Subsequently, the pre-trained DNN-based CABTD methods have been tested by influencing local and global ROI structures to diagnose two specific breast tumors (Benign and Malignant) and improve the diagnostic accuracy (86%) compared to Dense Net, Alex Net, VGG Net, and Google Net. Moreover, it reduces the computational complexity due to the small depth residual network ResNet18, respectively.

Association of Jump-Landing Biomechanics With Tibiofemoral Articular Cartilage Composition 12 Months After ACL Reconstruction.

Background:Excessively high joint loading during dynamic movements may negatively influence articular cartilage health and contribute to the development of posttraumatic osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Little is known regarding the link between aberrant jump-landing biomechanics and articular cartilage health after ACLR.Purpose/Hypothesis:The purpose of this study was to determine the associations between jump-landing biomechanics and tibiofemoral articular cartilage composition measured using T1ρ magnetic resonance imaging (MRI) relaxation times 12 months postoperatively. We hypothesized that individuals who demonstrate alterations in jump-landing biomechanics, commonly observed after ACLR, would have longer T1ρ MRI relaxation times (longer T1ρ relaxation times associated with less proteoglycan density).Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 27 individuals with unilateral ACLR participated in this cross-sectional study. Jump-landing biomechanics (peak vertical ground-reaction force [vGRF], peak internal knee extension moment [KEM], peak internal knee adduction moment [KAM]) and T1ρ MRI were collected 12 months postoperatively. Mean T1ρ relaxation times for the entire weightbearing medial femoral condyle, lateral femoral condyle (global LFC), medial tibial condyle, and lateral tibial condyle (global LTC) were calculated bilaterally. Global regions of interest were further subsectioned into posterior, central, and anterior regions of interest. All T1ρ relaxation times in the ACLR limb were normalized to the uninjured contralateral limb. Linear regressions were used to determine associations between T1ρ relaxation times and biomechanics after accounting for meniscal/chondral injury.Results:Lower ACLR limb KEM was associated with longer T1ρ relaxation times for the global LTC (ΔR 2 = 0.24; P = .02), posterior LTC (ΔR 2 = 0.21; P = .03), and anterior LTC (ΔR 2 = 0.18; P = .04). Greater ACLR limb peak vGRF was associated with longer T1ρ relaxation times for the global LFC (ΔR 2 = 0.20; P = .02) and central LFC (ΔR 2 = 0.15; P = .05). Peak KAM was not associated with T1ρ outcomes.Conclusion:At 12 months postoperatively, lower peak KEM and greater peak vGRF during jump landing were related to longer T1ρ relaxation times, suggesting worse articular cartilage composition.

Pathological correlates of impaired self‐awareness of memory function in dementia

AbstractBackgroundImpaired self‐awareness of memory function (a.k.a. anosognosia) is a common symptom observed in Alzheimer’s disease (AD), however it’s pathological correlates remain unclear. Here we investigated the impact of amyloid and tau on memory self‐awareness in a cohort of clinically normal or impaired participants.MethodThis study included 216 clinically normal (CDR=0) and 156 clinically impaired (CDR≥0.5) participants part of the Alzheimer's Disease Neuroimaging Initiative (ADNI) project. Using the E‐Cog memory subscale, a participant‐informant discrepancy index was computed such that a negative score indicates a participant’s underestimation of difficulties as compared to the partner. Linear models were performed with discrepancy as the dependent variable, and amyloid (Florbetapir) from global region of interest (ROI) and tau (Flortaucipir) from two ROI (i.e. inferior temporal and entorhinal cortices in two separate models) as independent variables. Demographics (i.e. Age, Gender, Years of Education) were added as covariates.ResultWe found that clinically impaired individuals were significantly older (p = 0.01), more educated (p < 0.001), and included more women (p = 0.01) as compared to the clinically normal group. In general, clinically impaired individuals had lower awareness scores as compared to clinically normal individuals (p < 0.001). A significant three‐way interaction was observed between clinical status and biomarkers (i.e., amyloid and tau burden, p = 0.009 and 0.033 for entorhinal and inferior temporal cortices, respectively). Post hoc analyses revealed no significant difference between groups in individuals at low levels of pathology (p > 0.05; Figures A and B, right panels). However, at higher levels of pathology (i.e., both amyloid and tau), clinically impaired individuals demonstrated significantly lower awareness scores as compared to clinically normal participants (Figures A and B, left panels).ConclusionThese findings better characterize the evolution of anosognosia in AD. Specifically, data suggest that impaired self‐awareness of memory function is associated with higher levels of amyloid and tau, providing further support that discordant subjective and objective measures may be important for clinical consideration.

Assessment of mechanical properties of articular cartilage with quantitative three-dimensional ultrashort echo time (UTE) cones magnetic resonance imaging

Conventional magnetic resonance imaging (MRI) is not capable of detecting signal from the deep cartilage due to its short transverse relaxation time (T2). Moreover, several quantitative MRI techniques are significantly influenced by the magic angle effect. The combinations of ultrashort echo time (UTE) MRI with magnetization transfer (UTE-MT) and Adiabatic T1ρ (UTE-AdiabT1ρ) imaging allow magic angle-insensitive assessments of all regions of articular cartilage. The purpose of this study was to investigate the correlations between quantitative three-dimensional UTE MRI biomarkers and mechanical properties of human tibiofemoral cartilage specimens. In total, 40 human tibiofemoral cartilage specimens were harvested from three male and four female donors (64 ± 18 years old). Cartilage samples were scanned using a series of quantitative 3D UTE Cones T2* (UTE-T2*), T1 (UTE-T1), UTE-AdiabT1ρ, and UTE-MT sequences in a standard knee coil on a clinical 3T scanner. UTE-MT data were acquired with a series of MT powers and frequency offsets to calculate magnetization transfer ratio (MTR), as well as macromolecular fraction (MMF) and macromolecular T2 (T2mm) through modeling. Cartilage stiffness and Hayes elastic modulus were measured using indentation tests. Correlations of 3D UTE Cones MRI measurements in the superficial layer, deep layer, and global regions of interest (ROIs) with mechanical properties were investigated. Cartilage mechanical properties demonstrated highest correlations with UTE measures of the superficial layer of cartilage. AdiabT1ρ, MTR, and MMF in superficial layer ROIs showed significant correlations with Hayes elastic modulus (p < 0.05, R = −0.54, 0.49, and 0.66, respectively). These UTE measures in global ROIs showed significant, though slightly lower, correlations with Hayes elastic modulus (p < 0.05, R = −0.37, 0.52, and 0.60, respectively). Correlations between other UTE MRI measurements (T2*, T1, and T2mm) and mechanical properties were non-significant. The 3D UTE-AdiabT1ρ and UTE-MT sequences were highlighted as promising surrogates for non-invasive assessment of cartilage mechanical properties. MMF from UTE-MT modeling showed the highest correlations with cartilage mechanics.

Design of a new breast vacuum bag to reduce the global and local setup errors and to reduce PTV margin in post-mastectomy radiation therapy.

To design a new breast vacuum bag to reduce global and local setup errors in post-mastectomy radiation therapy (PMRT). A total of 24 PMRT patients were immobilized with an old vacuum bag and 26 PMRT patients were immobilized with a new vacuum bag. The registration results were analysed using four regions of interest (ROI): the global ROI [including the whole region of the planning target volume (PTV), GROI], the supraclavicular area (SROI), the ipsilateral chest wall region (CROI) and the ipsilateral arm region (AROI). The global and local setup errors of the two groups were compared. The global setup errors of the new vacuum group were significantly smaller than those in the old vacuum group with the exception of yaw axes (P < 0.05). The systematic error (Σ) and random error (σ) ranged from 1.21 to 2.13 mm. In the new vacuum group, the local setup errors in the medial-lateral (ML) direction and roll axes for CROI (the Σ and σ ranged from 0.65 to 1.35 mm), and the local setup errors in ML and superior-inferior (SI) directions for SROI were significantly smaller than those in the old vacuum group. The total required PTV margins for the chest wall in ML, SI, and anterior-posterior (AP) were 4.40, 3.12 and 3.77 mm respectively. The new vacuum bag can significantly reduce the global setup errors and local setup errors in PMRT. The respiratory motion of the chest wall was negligible, and the 5 mm PTV margin could cover the local setup errors in PMRT using the new vacuum bag with cone beam CT (CBCT) correction.

Convincing evidence for magic angle less-sensitive quantitative T1ρ imaging of articular cartilage using the 3D ultrashort echo time cones adiabatic T1ρ (3D UTE cones-AdiabT1ρ ) sequence.

To investigate the magic angle effect in three-dimensional ultrashort echo time Cones Adiabatic T1ρ (3D UTE Cones-AdiabT1ρ ) imaging of articular cartilage at 3T. The magic angle effect was investigated by repeated 3D UTE Cones-AdiabT1ρ imaging of eight human patellar samples at five angular orientations ranging from 0° to 90° relative to the B0 field. Cones continuous wave T1ρ (Cones-CW-T1ρ ) and Cones- sequences were also applied for comparison. Cones-AdiabT1ρ , Cones-CW-T1ρ and Cones- values were measured for four regions of interest (ROIs) (10% superficial layer, 60% transitional layer, 30% radial layer, and a global ROI) for each sample at each orientation to evaluate their angular dependence. 3D UTE Cones-AdiabT1ρ values increased from the radial layer to the superficial layer for all angular orientations. The superficial layer showed the least angular dependence (around 4.4%), while the radial layer showed the strongest angular dependence (around 34.4%). Cones-AdiabT1ρ values showed much reduced magic angle effect compared to Cones-CW-T1ρ and Cones- values for all four ROIs. On average over eight patellae, Cones-AdiabT1ρ values increased by 27.2% (4.4% for superficial, 23.8% for transitional, and 34.4% for radial layers), Cones-CW-T1ρ values increased by 76.9% (11.3% for superficial, 59.1% for transitional, and 117.8% for radial layers), and Cones- values increased by 237.5% (87.9% for superficial, 262.9% for transitional, and 327.3% for radial layers) near the magic angle. The 3D UTE Cones-AdiabT1ρ sequence is less sensitive to the magic angle effect in the evaluation of articular cartilage compared to Cones- and Cones-CW-T1ρ .

A Flow feature detection framework for large-scale computational data based on incremental proper orthogonal decomposition and data mining

ABSTRACTA framework based on incremental proper orthogonal decomposition (iPOD) and data mining to perform large-scale computational data analysis is presented. It includes iPOD to incrementally reduce data dimensions and decouple dynamic flow structures in massive CFD data; data mining to classify and identify candidate global regions of interest (ROIs) for focused analysis; feature detection to capture key flow features and ultimate ROIs (UROIs); and targeted data storage and visualisation. Quantitative results show that iPOD is able to process large datasets that overwhelm the batch-POD, leading to 4–16× data reduction in the temporal domain. Data mining and feature detection algorithms, respectively, identify 50–70% of the spatial domain with high probability of flow feature occurrence and only 2–30% containing key flow features. The UROI and associated data can be selectively stored and visualised. In contrast to batch-POD, iPOD reduces memory usage by more than 10× and time by up to 75%.

Introducing a globally consistent orbital‐based localization system

AbstractIn spite of the good performance of space exploratory missions, open issues still await to be solved. In autonomous or composite semi‐autonomous exploration of planetary land surfaces, rover localization is such an issue. The rovers of these missions (e.g., the MER and MSL) navigate relatively to their landing spot, ignoring their exact position on the coordinate system defined for the celestial body they explore. However, future advanced missions, like the Mars Sample Return, will require the localization of rovers on a global frame rather than the arbitrarily defined landing frame. In this paper we attempt to retrieve the absolute rover's location by identifying matching Regions of Interest (ROIs) between orbital and land images. In particular, we propose a system comprising two parts, an offline and an onboard one, which functions as follows: in advance of the mission a Global ROI Network (GN) is built offline by investigating the satellite images near the predicted touchdown ellipse, while during the mission a Local ROI Network (LN) is constructed counting on the images acquired by the vision system of the rover along its traverse. The last procedure relies on the accurate VO‐based relative rover localization. The LN is then paired with the GN through a modified 2D DARCES algorithm. The system has been assessed on real data collected by the ESA at the Atacama desert. The results demonstrate the system's potential to perform absolute localization, on condition that the area includes discriminative ROIs. The main contribution of this work is the enablement of global localization performed on contemporary rovers without requiring any additional hardware, such as long range LIDARs.

Real-Time and Spatial Quantification Using Contrast-Enhanced Ultrasonography of Spinal Cord Perfusion During Experimental Spinal Cord Injury

Experimental study in male Wistar rats. To quantify temporal and spatial changes simultaneously in spinal cord blood flow and hemorrhage during the first hour after spinal cord injury (SCI), using contrast-enhanced ultrasonography (CEU). Post-traumatic ischemia and hemorrhage worsen the primary lesions induced by SCI. Previous studies did not simultaneously assess temporal and spatial changes in spinal cord blood flow. SCI was induced at Th10 in 12 animals, which were compared with 11 sham-operated controls. Spinal cord blood flow was measured in 7 adjacent regions of interest and in the sum of these 7 regions. Blood flow was quantified using CEU with intravenous microbubble injection. Spinal cord hemorrhage was measured on conventional B-mode sonogram slices. CEU allowed us to measure the temporal and spatial changes in spinal cord blood flow in both groups. In the SCI group, spinal cord blood flow was significantly decreased in the global region of interest (P = 0.0016), at the impact site (epicenter), and in the 4 regions surrounding the epicenter, compared with the sham group. The blood flow decrease was maximum at the epicenter. No statistically significant differences between the sham groups were found for the most rostral and caudal regions of interest. Hemorrhage size increased significantly with time (P < 0.0001), from 30.3 mm(2) (±2) after 5 minutes to 39.6 mm(2) (±2.3) after 60 minutes. CEU seems reliable for quantifying temporal and spatial changes in spinal cord blood flow. After SCI, bleeding occurs in the spinal cord parenchyma and increases significantly throughout the first hour.

Cigarette smoking and white matter microstructure in schizophrenia

The majority of patients with schizophrenia smoke cigarettes. Both nicotine use and schizophrenia have been associated with alterations in brain white matter microstructure as measured by diffusion tensor imaging (DTI). The purpose of this study was to examine fractional anisotropy (FA) in smoking and non-smoking patients with schizophrenia and in healthy volunteers. A total of 43 patients (28 smoking and 15 non-smoking) with schizophrenia and 40 healthy, non-smoking participants underwent DTI. Mean FA was calculated in four global regions of interest (ROIs) (whole brain, cerebellum, brainstem, and total cortical) as well as in four regional ROIs (frontal, temporal, parietal and occipital lobes). The non-smoking patient group had a significantly higher intellectual quotient (IQ) compared with the patients who smoked, and our results varied according to whether IQ was included as a covariate. Without IQ correction, significant between-group effects for FA were found in four ROIs: total brain, total cortical, frontal lobe and the occipital lobe. In all cases the FA was lower among the smoking patient group, and highest in the control group. Smoking patients differed significantly from non-smoking patients in the frontal lobe ROI. However, these differences were no longer significant after IQ correction. FA differences between non-smoking patients and controls were not significant. Among smoking and non-smoking patients with schizophrenia but not healthy controls, FA was correlated with IQ. In conclusion, group effects of smoking on FA in schizophrenia might be mediated by IQ. Further, low FA in specific brain areas may be a neural marker for complex pathophysiology and risk for diverse problems such as schizophrenia, low IQ, and nicotine addiction.

T2-mapping in volunteers: influence of sequence, spatial orientation and interindividual variability

Background CMR T2-mapping is a promising tool for characterizing myocardial edema. We applied T2-mapping in volunteers to compare two mapping sequences and to assess feasibility, reproducibility and spatial homogeneity. Methods We scanned 26 volunteers (10 female, 20-70 years, mean 32±13 years, median 28 years, BMI 23±3 kg/m2) with a normal ECG, no cardiac disease and no symptoms of inflammation. Using a 1.5 T scanner and a dedicated 12-element cardiac coil we applied a FLASH-based and SSFP-based mapping sequence in midventricular short axis (SAX) and four-chamber-view (4CV). The map was based on three images with an echo time of 0, 24 and 55 ms. Spatial resolution was 2.1 mm/pixel. Scan time was 12 heart beats. In Osirix 3.3.2. we manually drew 6 segments in SAX and 4CV, each. Additionally, we drew a global region of interest (ROI) covering the whole LV myocardium in SAX and 4CV. The same investigator analyzed 10 data sets twice. 5 volunteers were scanned twice on separate days. Results were compared with a paired student t-test. Results After excluding one subject due to obvious pathologies, 25 datasets with sufficient image quality were evaluated. Table 1 gives mean and range for global ROI. FLASH and SSFP correlated better in 4CV than in SAX (correlation coefficient 0.92 vs. 0.80; p< 0.04). T2-values did not correlate with heart rate (p=0.3). With both sequences anteroseptal segments had higher T2-values than inferior and inferolateral segments in SAX (for FLASH 58±6 vs. 48±4; p< 0.001). In 4CV the basal septum had higher T2-values than the anterolateral segment with FLASH (62±7 vs. 54±8 ms; p<0.001), but not with SSFP (58±6 vs. 60±11 ms; p=0.3). Mean absolute difference between a single segment and a global measurement was 4±1 ms and 3±1 ms for FLASH and SSFP in SAX and 5±2 ms for FLASH and SSFP in 4CV (p=0.3). Mean difference for repeated analysis was 1.6±1.9 ms (correlation coefficient 0.9) and 2.2±2.2 ms (correlation coefficient 0.7) for repeated scans. Conclusion T2-mapping is feasible with low intraobserver variability and does not depend on heart rate. SSFP-based T2mapping resulted in slightly higher values than FLASH. Mapping in 4CV resulted in higher T2-values than in SAX. We could detect small spatial differences across the heart. However, these intraindividual spatial variations were smaller than considerable interindividual variability.

Cartilage T2 Assessment at 3-T MR Imaging: In Vivo Differentiation of Normal Hyaline Cartilage from Reparative Tissue after Two Cartilage Repair Procedures—Initial Experience

To prospectively compare cartilage T2 values after microfracture therapy (MFX) and matrix-associated autologous chondrocyte transplantation (MACT) repair procedures. The study had institutional review board approval by the ethics committee of the Medical University of Vienna; informed consent was obtained. Twenty patients who underwent MFX or MACT (10 in each group) were enrolled. For comparability, patients of each group were matched by mean age (MFX, 40.0 years +/- 15.4 [standard deviation]; MACT, 41.0 years +/- 8.9) and postoperative interval (MFX, 28.6 months +/- 5.2; MACT, 27.4 months +/- 13.1). Magnetic resonance (MR) imaging was performed with a 3-T MR imager, and T2 maps were calculated from a multiecho spin-echo measurement. Global, as well as zonal, quantitative T2 values were calculated within the cartilage repair area and within cartilage sites determined to be morphologically normal articular cartilage. Additionally, with consideration of the zonal organization, global regions of interest were subdivided into deep and superficial areas. Differences between cartilage sites and groups were calculated by using a three-way analysis of variance. Quantitative T2 assessment of normal native hyaline cartilage showed similar results for all patients and a significant trend of increasing T2 values from deep to superficial zones (P < .05). In cartilage repair areas after MFX, global mean T2 was significantly reduced (P < .05), whereas after MACT, mean T2 was not reduced (P > or = .05). For zonal variation, repair tissue after MFX showed no significant trend between different depths (P > or = .05), in contrast to repair tissue after MACT, in which a significant increase from deep to superficial zones (P < .05) could be observed. Quantitative T2 mapping seems to reflect differences in repair tissues formed after two surgical cartilage repair procedures. (c) RSNA, 2008.

Effect of hyperoxia on regional oxygenation and metabolism after severe traumatic brain injury: Preliminary findings*

To determine the effect of normobaric hyperoxia on cerebral metabolism in patients with severe traumatic brain injury. Prospective clinical investigation. Neurosciences critical care unit of a university hospital. Eleven patients with severe traumatic brain injury. Cerebral microdialysis, brain tissue oximetry (PbO2), and oxygen-15 positron emission tomography (15O-PET) were undertaken at normoxia and repeated at hyperoxia (FiO2 increase of between 0.35 and 0.50). Established models were used to image cerebral blood flow, blood volume, oxygen metabolism, and oxygen extraction fraction. Physiology was characterized in a focal region of interest (surrounding the microdialysis catheter) and correlated with microdialysis and oximetry. Physiology was also characterized in a global region of interest (including the whole brain), and a physiologic region of interest (defined using a critical cerebral metabolic rate of oxygen threshold). Hyperoxia increased mean +/- sd PbO2 from 28 +/- 21 mm Hg to 57 +/- 47 mm Hg (p = .015). Microdialysate lactate and pyruvate were unchanged, but the lactate/pyruvate ratio showed a statistically significant reduction across the study population (34.1 +/- 9.5 vs. 32.5 +/- 9.0, p = .018). However, the magnitude of reduction was small, and its clinical significance doubtful. The focal region of interest and global 15O-PET variables were unchanged. "At-risk" tissue defined by the physiologic region of interest, however, showed a universal increase in cerebral metabolic rate of oxygen from a median (interquartile range) of 23 (22-25) micromol x 100 mL(-1) x min(-1) to 30 (28-36) micromol x 100 mL(-1) x min(-1) (p < .01). In severe traumatic brain injury, hyperoxia increases PbO2 with a variable effect on lactate and lactate/pyruvate ratio. Microdialysis does not, however, predict the universal increases in cerebral metabolic rate of oxygen in at-risk tissue, which imply preferential metabolic benefit with hyperoxia.

Regional cerebral blood flow in unipolar depression measured with Tc-99m-HMPAO single photon emission computed tomography: Negative findings

Recent studies have reported that patients with unipolar major depression may show a lower whole brain cerebral blood flow (CBF) and reduced regional CBF in frontal, temporal, and parietal lobes. The present study used single photon emission computed tomography (SPECT) with the CBF marker Tc-99m-hexamethylpropyleneamineoxine (HMPAO) to measure the cortical CBF of six individual regions of interest (ROIs), total ROI, and left or right hemispheric total ROI in 43 unipolar depressed subjects and 12 normal control subjects. There were no significant differences in the distribution of Tc-99m-HMPAO uptake into total ROI, right or left global ROI, prefrontal, motor frontal, parietal, temporal, visual cortex, or associative visual cortex between patients with melancholic depression, simple major depression, or minor depression and healthy control subjects. There were also no significant differences in the right-left distribution of uptake between the patients and the control subjects. Hypoperfusion was observed in motor frontal and parietal cortex of patients who had been taking benzodiazepines during the study period. It is concluded that cortical CBF, as assessed with Tc-99m-HMPAO SPECT, is relatively intact in the present sample of patients with severe depression.