Default Protocol Research Articles

#1128 Accuracy of shorter iohexol glomerular filtration rate measurement protocols in individuals with preserved kidney function

Abstract Background and Aims Measuring glomerular filtration rate (mGFR) using exogenous tracers is recommended in a number of settings with plasma one-compartment multi-sample protocols (MSP) being the most commonly used and iohexol being the dominant tracer. The accuracy of MSP protocols has mostly been evaluated in the setting of reduced GFR where delayed initial and final samples are recommended. Much less is known about MSPs when GFR is not decreased and the default protocol tends to include initial sampling at 120 minutes and final sampling at 240 minutes post iohexol injection. The objective of this study was to assess the performance of shorter MSPs with earlier initial (60 and 90 minutes) and final (150, 180, and 210 minutes) sampling times in individuals with preserved GFR. Method Participants were recruited from a 4-year prospective, observational study evaluating the cardiovascular, renal, and bone health profile of young adults with Type 1 Diabetes. The reference mGFR was calculated using a plasma iohexol clearance one compartment slope intercept method with 5 samples collected between 120-240 minutes post iohexol injection. Four different combinations of shorter sampling strategies were investigated: 60-150 min, 60-180 min, 90-180 min and 90-210 min. Performance was evaluated using measurements of bias, precision, and accuracy (P2, P5, and mean absolute error). Results Mean age of the 43 participants was 23.9 ± 1.9 yrs with a mean eGFRCKiD-1 of 95.5 ± 15.9 ml/min/1.73 m2 and mean reference mGFR (120-240 min) of 102.3 ± 13.7 ml/min/1.73 m2. All exploratory shorter mGFRs performed well, with median biases less than 1 ml/min/1.73 m2 and mean absolute error less than 1.6 ml/min/1.73 m2. All shorter mGFRs were within 5% of the reference mGFR and the majority were within 2%. Conclusion These results demonstrate that shortening the mGFR procedure in individuals with preserved GFR provided very similar results to the current standard while significantly decreasing procedure time. The cost savings and improved feasibility of these shortened protocols should reduce some of the barriers to more widespread adoption of GFR measurement.

Direct measurement of the ciliary sulcus diameter using optical coherence tomography: Inter‐rater variability

Aims/Purpose: To develop a method for measuring the exact dimensions of the ciliary sulcus in order to improve the predictability of accommodative intraocular lens sizing.Methods: Patients scheduled for cataract surgery have been pre‐operatively examined with the anterior segment optical coherence tomographer (AS‐OCT) CASIA2 (Tomey, Nagoya, Japan). Optimized scan protocols were defined to improve the image quality of the ciliary structures. The horizontal scan from 0° to 180° was taken to represent the space where a sulcus‐fixated accommodative intraocular lens (IOL), whose diameter must agree with that of the ciliary sulcus, may be placed. The images were corrected for the optical distortion induced by the cornea's refraction. The sulcus‐to‐sulcus (STS) size as well as the depth of the sulcus plane (SPD) was measured using the integrated software calliper by two independent raters. Inter‐rater variability and correlation were evaluated. In addition, STS measurements were compared to other ocular diameter measures, such as angle‐to‐angle (ATA) and anterior chamber width (ACW). Data were analysed by means of correlation coefficient R2 and Bland–Altmann analysis.Results: 55 eyes of 28 patients were included in the study. The optimized scan protocols improved overall image quality and subjective visibility of ciliary anatomy compared to the default protocol. STS ranged from 10.66 mm to 12.89 mm, ACW from 10.76 mm to 12.74 mm and ATA from 10.69 to 12.46 mm. SPD ranged from 3.73 mm to 5.0 mm, while ATA depth was between 2.74 mm and 3.95 mm. Readings of both raters were highly correlated (R2 > 0.98). Manual readings of STS correlated poorly with automated ACW and ATA measurements (R2 < 0.66). The mean difference was 0.018 mm for STS and −0.011 mm for SPD. The levels of agreement were within [−0.109; +0.145] mm for STS and [−0.112; +0.091] mm for SPD.Conclusions: Despite the absorption of light by the iris pigment, the infrared light from the AS‐OCT is able to penetrate the posterior chamber to some degree. Therefore, the new AS‐OCT method for sulcus‐to‐sulcus and ciliary dimensions measurements seems to be feasible, reliable and is less bothersome for the patients compared to ultrasound bio‐microscopy. This approach could be useful for sulcus fixated accommodative IOLs and for sizing determination of posterior chamber phakic IOLs.

Comparison of selected photon shield and organ-based tube current modulation for radiation dose reduction in head computed tomography: A phantom study.

The aim of this study is to investigate the radiation dose and image quality of head CT using SPS and OBTCM techniques. Three anthropomorphic head phantoms (1-yr-old, 5-yr-old, and adult) were used. Images were acquired using four modes (Default protocol, OBTCM, SPS, and SPS+OBTCM). Absorbed dose to the lens, anterior brain (brain_A), and posterior brain (brain_P) was measured and compared. Image noise and CNR were assessed in the selected regions of interest (ROIs). Compared with that in the Default protocol, the absorbed dose to the lens reduced by up to 28.33%,71.38%, and 71.12% in OBTCM, SPS, and SPS+OBTCM, respectively. The noise level in OBTCM slightly (≤1.45HU) increased than that in Default protocol, and the SPS or SPS+OBTCM mode resulted in a quantitatively small increase (≤2.58HU) in three phantoms. There was no significant difference in CNR of different phantoms under varies scanning modes (p > 0.05). During head CT examinations, the SPS mode can reduce the radiation dose while maintaining image quality. SPS+OBTCM couldn't further effectively reduce the absorbed dose to the lens for 1-yr and 5-yr-old phantoms. Thus, SPS mode in pediatric and SPS+OBTCM mode in adult are better than other modes, and should be used in clinical practice.

Feasibility of energy‐guided short duration protocol of laser balloon based pulmonary vein isolation for atrial fibrillation (EG‐Laser Study)

AbstractBackgroundLaser balloon‐based pulmonary vein isolation (LB‐PVI) is available for atrial fibrillation (AF) ablation. The lesion size depends on laser energy; however, the default protocol is not an energy‐based setting. We hypothesized that an energy‐guided (EG) short‐duration protocol may be an alternative to shorten the procedure time without affecting efficacy and safety.MethodsWe evaluated the efficacy and safety of the EG short‐duration protocol (EG group) (target energy 120 J/site [12W/10s; 10W/12s; 8.5W/14s; 5.5W/22s]) compared with the default protocol (control group) (12W/20s; 10W/20s; 8.5W/20s; 5.5W/30s).ResultsA total of 52 consecutive patients (EG: n = 27 [103veins] and control: n = 25 [91veins]) undergoing LB‐PVI (64 ± 10 years, 81% male, 77% paroxysmal) were enrolled. The EG group had a shorter total time in the pulmonary vein (PV) (43.0 ± 13.9 min vs. 61.1 ± 16.0 min, p < .0001), a shorter total laser application time (1348 ± 254 sec vs. 2032 ± 424 sec, p < .0001), and lower total laser energy (12455 ± 2284J vs. 18084 ± 3746J, p < .0001). There was no difference in the total number of laser applications (p = 0269) or first‐pass isolation (p = .725). Acute reconduction was identified only in one vein in the EG. No significant differences were observed in the incidence of pinhole rupture (7.4% vs. 4%, p = 1.000) or phrenic nerve palsy (3.7% vs. 12%, p = .341). During a mean follow‐up of 13.5 ± 6.1 months, Kaplan‐Meier analysis revealed no significant difference in atrial tachyarrhythmia recurrence (p = .227).ConclusionLB‐PVI with the EG short‐duration protocol may be achieved in a shorter procedure time to avoid deterioration of efficacy and safety. The EG protocol is feasible as a novel point‐by‐point manual laser‐application approach.

Characterizing the Bitcoin network topology with Node‐Probe

AbstractIn blockchain networks, topology discovery is a prerequisite when investigating the network characteristics (e.g., performance and robustness), which can provide a deeper comprehension of the behavior of the nodes and topology dynamicity. In this paper, we conduct a longitudinal study on the Bitcoin topology by collecting network snapshots from 2018 to 2022 with Node‐Probe, our topology discovery technique that uses recursive scanning to find all reachable nodes in the Bitcoin network. Using Node‐Probe, we have collected 5‐week‐long snapshots (36‐day‐long snapshots) of the Bitcoin main network and analyzed the network properties, community structure, and topology dynamicity. We confirm that our approach achieves a precision of 99% with a recall of 98% in inferring the topology. Analytical results on community structure show that the Bitcoin network has more communities than what should be expected from a random network. Meanwhile, analytical results on dynamicity indicate that the topology stands firmly on heavy and long‐running nodes. Improving the propagation mechanism using master nodes could improve the propagation delay by proximity compared with the Bitcoin default protocol. Considering a K‐anonymity attack, any transaction from one of the autonomous systems containing only a single Bitcoin node can easily be linked to real users' IP information.

A Review on the Usage of Bone Single-Photon Emission Computed Tomography/Computed Tomography in Detecting Skeletal Metastases in the Post-COVID-19 Era: Is it Time to Ditch Planar and Single-Photon Emission Computed Tomography only Gamma Camera Systems?

Planar whole-body bone scanning (WBS) is widely used to evaluate skeletal lesions seen in cancer and noncancer cases. Frequently, degenerative, or other benign bony changes may give rise to indeterminate lesions that mimic bone metastases. In the post-COVID-19 era, there is an evolutionary phase that puts importance on global development and adaptability, which encompasses to include nuclear medicine practices worldwide. Single-photon emission computed tomography/computed tomography (SPECT/CT) can be used to improve the characterization of these lesions and help to resolve the diagnostic conundrum while reducing the need for patients to undergo multiple different examinations at various imaging departments. The fusion of SPECT and CT allows morphological characterization of functional abnormality detected by focal tracer uptake on planar scintigraphy, which provides a one-stop center imaging in nuclear medicine departments. The objective of this study was to review the diagnostic accuracy of SPECT/CT in diagnosing bone metastases in a variety of oncology and nononcology cases and to determine the feasibility of performing bone SPECT/CT in all suspected cancer cases, including cases of bone infection instead of planar imaging alone. The utilization of hybrid SPECT/CT in indeterminate bone lesions detected on planar WBS can significantly increase the diagnostic confidence and accuracy of image interpretation. Recognition of patterns of disease identified using hybrid imaging can improve the management of patients with potentially lower costs in the long term. Currently, hybrid SPECT/CT machines are becoming a norm in nuclear medicine departments, thus potentially making single planar application machines obsolete in the near future. We hypothesize that in the interest of providing a meaningful interpretation of isotope bone scans, the default protocol should involve the option of acquiring SPECT/CT images rather than relying on whole-body scans only. Departments choosing to upgrade existing equipment or those choosing to invest in only one gamma camera should proactively opt for hybrid SPECT/CT systems.

Visibility of anatomical landmarks in the region of the mandibular third molar, a comparison between a low-dose and default protocol of CBCT

Objective Optimization of radiographic examinations is essential for radiation protection. The objective of the study was to investigate the clinical applicability of a low-dose CBCT protocol as compared to the default for pre-surgical evaluation of mandibular third molars. Material & Methods Forty-eight patients (62 teeth) referred for pre-surgical mandibular third molar investigation were recruited after justification for CBCT. Two CBCT scans of each site were made using a default protocol and a low-dose protocol (Veraviewepocs 3D F40, J Morita Corp, Kyoto, Japan). The low-dose protocol had the same tube potential (90 kV) and exposure time (9.4 s) as the default, but with reduced tube current, from 5 mA to 2 mA. Four observers evaluated the visibility of five relevant anatomical variables. Image quality was ranked on a 3-point scale as diagnostically acceptable, doubtful, or unacceptable. The Wilcoxon signed-rank test compared differences between the two protocols. The significance level was set at p ≤ .05. Results No significant differences were found between the two protocols for any observer regarding the visibility of the relationship and proximity between the roots and the mandibular canal; root morphology; and possible root resorption of the second molar. The periodontal ligament differed significantly in visibility between the two protocols (p ≤ .05). Conclusions This study indicates that a low-dose CBCT protocol with a 60% reduction of the tube current provides, in most cases, acceptable image quality for pre-surgical assessment of mandibular third molars. Optimization of CBCT protocols should be a priority according to recommended guidelines.

A within-person approach to the relation between quality of task motivation, performance and job satisfaction in everyday working life

Research generally shows that autonomous forms of motivation are associated with higher performance and job satisfaction, whereas controlled forms of motivation are linked to worse outcomes. These relationships are largely based on between-persons data from cross-sectional studies or longitudinal studies with few measurement points. However, motivation quality, performance, and job satisfaction can vary considerably from day to day and from task to task. It is unclear whether and how these experiences and behaviors covary over time within individuals at work in daily life. The present study assessed this using a diary approach. With a default protocol of 30 working days, an ecological momentary assessment application prompted 19 white-collar workers five times a day to report their autonomous and controlled motivation for work tasks and their productivity and job satisfaction at the end of each day. Fourteen participants gathered sufficient data to compute within-person relations and individual networks. At the between-person level, results were somewhat in line with prior survey-based research, whereas results at the within-person level present more nuanced findings and demonstrate that these will not inherently align with previous between-person findings. Individual network analyses indicated considerable interindividual heterogeneity, especially in the relationships between motivation and job satisfaction. In conclusion, these findings point to significant variability in the observed relations between task-related motivation, performance and job satisfaction in everyday life, and highlight the added value of a within person approach and individual networks in addition to between-persons approaches. The implications of these findings for occupational wellbeing research are discussed.

A multi-view framework for BGP anomaly detection via graph attention network

As the default protocol for exchanging routing reachability information on the Internet, the abnormal behavior in traffic of Border Gateway Protocols (BGP) is closely related to Internet anomaly events. The BGP anomalous detection model ensures stable routing services on the Internet through its real-time monitoring and alerting capabilities. Previous studies either focused on the feature selection problem or the memory characteristic in data, while ignoring the relationship between features and the precise time correlation in feature (whether it is long or short term dependence). In this paper, we propose a multi-view model for capturing anomalous behaviors from BGP update traffic, in which Seasonal and Trend decomposition using Loess (STL) method is used to reduce the noise in the original time-series data, and Graph Attention Network (GAT) is used to discover feature relationships and time correlations in feature, respectively. Our results outperform the state-of-the-art methods at the anomaly detection task, with the average F1 score up to 96.3% and 93.2% on the balanced and imbalanced datasets respectively. Meanwhile, our model can be extended to classify multiple anomalous and to detect unknown events.

Evaluation of optimal kilovoltage-cone beam technique on image quality, registration accuracy, time of imaging and relative dose for head radiotherapy: A phantom study

Background: Image-guided radiation therapy (IGRT) has improved geometry accuracy of patient positioning in radiotherapy. Nowadays, a kilo-voltage cone-beam computed tomography (kV-CBCT) is widely applied in IGRT to confirm daily patient positioning. However, one problem with IGRT is the increased dose to normal tissue outside the target area. Reduction in the dose of kV-CBCT verification imaging leads to deterioration in image quality and registration results. Objectives: The objective of this study was to evaluate an optimal kV cone-beam technique on image quality, registration accuracy, relative dose, and imaging time using different combinations of angular range, angular separation, and mA (in total eight protocols) in the head phantom. Materials and methods: Catphan® 503 phantom was used to evaluate image quality and a PIXY Anthropomorphic Training/Teaching Phantom was used to verify image registration accuracy. The kV-CBCT imaging was performed using an X-ray volumetric imaging (XVI) system mounted on an Elekta Versa HD linear accelerator. The absorbed dose of kV-CBCT imaging was determined using the head phantom with an ionization chamber. The eight protocols were analyzed for image quality, image registration, relative dose change, and imaging delivery time. Results: Image quality parameter results showed that maximum contrast to noise ratio (CNR) increased by approximately 65% at 100 kV, 20 mA, θ=360°, and Δθ=0.54°, while uniformity compared with 100 kV, 10 mA, θ=200°, Δθ=0.54° (default protocol) varied within 7%. The spatial resolution showed no change (0.167 cm), with geometric distortions of less than 0.2 mm. Image registration errors were within 0.2 cm, with the highest magnitude of error seen in the vertical direction. Imaging dose can be reduced using 100 kV, 10 mA, θ=200°, Δθ=1.09° about 50% and 100 kV, 10 mA, θ=360°, Δθ=1.09° about 15% with similar CNR of default protocol. Imaging time decreased by approximately 2-folds, while Δθ increased by 2-folds. Conclusion: The suggested protocols suitable for optimal kV-CBCT image quality, accuracy of image registration, decreased imaging time, and reduced image dose in the head region were 1) 10 mA, θ=200°, Δθ=1.09° 2) 10 mA, θ=360°, Δθ=1.09°, and 3) 20 mA, θ=360°, Δθ=1.09°. These protocols decreased imaging dose about 50%, 15%, and 2%, respectively. The developing kV-CBCT technique should be counterbalanced by careful consideration of imaging dose, image quality, imaging time, and accuracy of image registration.

Clinical outcomes of transepithelial photorefractive keratectomy with epithelial ablation targeting actual epithelial thickness vs default laser platform values.

To investigate the clinical outcomes of transepithelial photorefractive keratectomy (tPRK) with actual epithelial thickness vs default software values. Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Prospective controlled study. Patients with refractive spherical error of -1.50 to -7.00 diopters (D) and refractive astigmatism up to 4.00 D were consecutively enrolled and divided into 2 groups: group 1 undergone tPRK with actual central and peripheral epithelial thickness input in right eyes, group 2 undergone tPRK with actual central and 10 mm higher peripheral epithelial thickness in right eyes. Left eyes in both groups underwent tPRK with default protocol. Outcome measures were induced refractive error, achieved optical zone (OZ), and wasted stromal tissue. 83 patients were included in this study. Mean ± SD of induced spherical equivalent was +0.15 ± 0.39 D and +0.01 ± 0.35 D in right and left eyes of group 1 (P = .01) and +0.04 ± 0.22 D and +0.03 ± 0.23 D in right and left eyes of group 2 (P = .75), respectively. There was no statistically significant difference between wasted tissue between right and left eyes in group 1 and group 2 (P = .77 and P = .49, respectively). OZ contraction was significantly higher in right compared with left eyes in group 1 (P = .05), but not in group 2 (P = .95). In tPRK, refractive outcomes, wasted tissue, and OZ contraction depend little on preexisting corneal epithelial thickness in corneas with normal range epithelial thickness. However, OZ contraction may be a concern in lower amount of ablations.

A Multi-View Framework for Bgp Anomaly Detection Via Graph Attention Network

As the default protocol for exchanging routing reachability information on the Internet, the abnormal behavior in traffic of Border Gateway Protocols (BGP) is closely related to Internet anomaly events. The BGP anomalous detection model ensures stable routing services on the Internet through its real-time monitoring and alerting capabilities. Previous studies either focused on the feature selection problem or the memory characteristic in data, while ignoring the relationship between features and the precise time correlation in feature (whether it's long or short term dependence). In this paper, we propose a multi-view model for capturing anomalous behaviors from BGP update traffic, in which Seasonal and Trend decomposition using Loess (STL) method is used to reduce the noise in the original time-series data, and Graph Attention Network (GAT) is used to discover feature relationships and time correlations in feature, respectively. Our results outperform the state-of-the-art methods at the anomaly detection task, with the average F1 score up to 96.3% and 93.2% on the balanced and imbalanced datasets respectively. Meanwhile, our model can be extended to classify multiple anomalous and to detect unknown events.

EVALUATION OF RADIATION DOSES USING CONE BEAM COMPUTED TOMOGRAPHY IN ENDOVASCULAR AORTIC REPAIR AND SCOLIOSIS PROCEDURES

The aim of this project was to evaluate the radiation dose to patients for cone beam computed tomography (CBCT) in endovascular aortic repair (EVAR) and scoliosis procedures and to compare radiation doses between CBCT and computed tomography (CT). An anthropomorphic phantom and Siemens and General Electric X-ray equipment were used. Default protocol settings were used for comparison of protocols and modalities. The ratio between the highest and lowest CBCT effective dose, for each equipment, had a maximum of 13 (Artis Pheno) for EVAR and 1.8 (Artis Zeego) for scoliosis. It is difficult to predict which modality gives the highest effective dose, e.g. for the CT protocol 'Aorta before EVAR' the ratio between effective doses varied from 0.12 to 1.8, between CBCT and CT. For CBCT EVAR, the effective dose and dose area product decreased using collimation or zoom.

Functional Brain Networks of Trait and State Anxiety in Late-Life Depression

<h3>Introduction</h3> Late-life depression (LLD) is associated with psychiatric comorbidities that may worsen mood outcomes in older adults, yet the neural mechanisms that underlie these comorbid conditions remain understudied. Anxiety and neuroticism have been independently associated with LLD, and its mood and cognitive outcomes. In a preliminary behavioral data analysis we found that anxiety measures correlated with depression measures in older adults. We also found that several baseline neuroticism and anxiety traits predicted depression scores over time. In this study, we analyzed neuroimaging data in the setting of anxiety and neuroticism measures in LLD and hypothesized that there would be differences in resting state activity patterns in the Salience network (SN), Default-Mode network (DMN) and Executive Control network (ECN) related to severity of: (1) generalized anxiety, (2) state and trait anxiety, and (3) neuroticism. <h3>Methods</h3> This was a cross-sectional secondary data analysis on clinical and MRI data collected from our NBOLD project. LLD patients without dementia were included. Generalized anxiety disorder (GAD) symptoms, state and trait anxiety, neuroticism and depression were assessed using a GAD questionnaire, State-Trait Anxiety Inventory (STAI), NEO Personality Inventory (NEO PI), and Montgomery-Asberg Depression Rating Scale (MADRS), respectively. A study psychiatrist confirmed or ruled out diagnosis of depression. There were 102 older adults with LLD, and among them, 87 subjects who had measures of STAI-trait, STAI-state anxiety, GAD symptoms and neuroticism as well as usable neuroimaging data were included into our final analyses. The neuroimaging data was collected from 3T Siemens Skyra scanner. The imaging parameters for T1-weighted images were: TR/TE=2200/2.8ms, flip angle=13^o, matrix = 256 × 256 × 169, Voxelsize=1×1×1mm³. The 7-min resting-state fMRI data was collected using EPI sequence with FOV=240mm, flip angle=90^o, TR/TE=2000/31ms, matrix=64×64×34, voxelsize = 3.8×3.8×3.75mm³. The fMRI data was preprocessed using the default protocol setting recommend by DPABI software. The Amplitude of Low-Frequency Fluctuations (ALFF) was calculated using DPABI. Multiple regression model was used to examine the association between ALFF and GAD, state and trait anxiety as well as neuroticism controlled for age, gender and depression severity (MADRS) using SPM12. Significance was set at p<0.05 with FDR correction for multiple comparisons. <h3>Results</h3> Data analyses revealed that trait anxiety was positively correlated with greater ALFF in the ECN (left dorsolateral prefrontal cortex - dlPFC, bilateral inferior parietal cortex - IPS, and precuneus) and lateral orbitofrontal cortex (OFC). Higher state anxiety was correlated with lower ALFF in bilateral OFC and frontal pole. GAD symptom severity was positively correlated with ALFF in the right superior temporal cortex (STG), Heschl's gyrus, and dorsomedial frontal cortex (dMFC). The GAD symptom severity was also negatively correlated with ALFF in the right hippocampus, parahippocampus and temporal pole (TP), whereas there was no significant clusters found between ALFF and neuroticism after regressing out the covariates. <h3>Conclusions</h3> This is one the few studies that examined resting state neural oscillation pattern (ALFF) specific to state and trait anxiety and GAD symptoms in LLD. Higher trait anxiety was associated with greater ALFF in the ECN and OFC, all of which are related to emotion regulation, whereas higher state anxiety was correlated with lower ALFF in regions related to emotion regulation. Higher GAD was specifically correlated with higher ALFF in brain regions related to sound and social information processing, but with lower ALFF in regions related to memory. No significant clusters were found related to neuroticism suggesting that neuroticism might be able explained by trait and state anxiety as well as GAD. These results suggests a distinct neural construct that may distinguish state and trait anxiety in LLD. Uncovering the brain connectivity changes related to state and trait anxiety would deepen our understanding in the neural mechanisms and mood outcomes of LLD. Future studies are needed to determine differences in these networks between depressed and non-depressed individuals. <h3>Funding</h3> The Leo and Anne Albert Charitable Trust, National Institute of Mental Health Grant R01 MH108578, The University of Connecticut Department of Psychiatry

Resting-State Functional Connectivity and Anxiety Predict Relapse in Remitted Late-Life Depression

<h3>Introduction</h3> Late-life depression (LLD) refers to depression occurring in older age and is associated with a multitude of psychosocial and biological factors, including conditions related to pathological aging, including cardiovascular and cerebrovascular diseases, and dementia. Relevant psychosocial factors comprise personality disorders, neuroticism, trauma and stress. Depending on the relative contribution of conditions related to pathological aging versus psychosocial factors, some patients may not respond to antidepressants and others may be prone to relapse even when they achieved initial remission on an antidepressant. The neural mechanisms related to recurrence of LLD are not clear. About 50% of individuals who have recovered from a first episode of depression will suffer from at least one additional episode. Therefore, identifying patients prone to relapse is important for developing tailored treatment regimens, preventing suicide, and reducing economic burdens and other morbidities. To understand the neural mechanisms related to relapse of depression, and identify neuroimaging markers to predict individuals who tend to relapse, we conducted a secondary data analysis on clinical and fMRI data collected from our NBOLD project. We hypothesized that, compared with individuals who did not relapse during a two-year clinical follow-up period, those who relapsed would show significantly altered resting-state activity patterns in core neural networks related to LLD including the default mode, executive control and salience networks. <h3>Methods</h3> The sample included 102 adults with LLD who were free of medication for at least two weeks before study enrollment. Depression severity was measured by MADRS and was assessed by a study psychiatrist at each study visit, which occurred frequently while the subject remained depressed and quarterly when remission was achieved. Among the enrolled participants, 52 (age range of 60 – 89) achieved depression remission after antidepressant treatment (MADRS< 8 for at least 2 months). We defined relapse as having a MADRS > 15 for at least two weeks. Individuals were classified as non-relapsed if they maintained a MADRS <13 after remission during the two follow-up years. Among the 52 LLD patients, 27 of them relapsed and 25 did not. We also measured trait and state anxiety and neuroticism using State-Trait Anxiety Inventory (STAI), NEO Personality Inventory (NEO PI). The neuroimaging data was collected from 3T Siemens Skyra scanner. The imaging parameters for T1-weighted images were: TR/TE=2200/2.8ms, flip angle=13^o, matrix = 256 × 256 × 169, voxelsize=1 × 1 × 1mm³. The 7-min resting-state fMRI data was collected using EPI sequence with FOV=240mm, flip angle=90^o, TR/TE=2000/31ms, matrix=64 × 64 × 34, voxelsize=3.8 × 3.8 × 3.75mm³. The resting-state fMRI data was preprocessed using the default protocol settings in Conn Toolbox version17f. The preprocessed data was entered to DPABI software for calculating the Amplitude of Low-Frequency Fluctuations (ALFF). Functional connectivity (FC) was done using Conn Toolbox version17f. Two sample t-tests were conducted to compare resting-state activity, ALFF, and FC to examine differences in ALFF and FC between relapsed and non-relapsed LLD groups (age and gender were controlled). Significance was set at p<0.05 with FDR correction for multiple comparisons. <h3>Results</h3> There were no significant differences between relapsed and non-relapsed groups in age, gender, state anxiety or neuroticism. Those who relapsed during the two-year follow-up had less severe depressive symptoms at baseline (mean (SD) MADRS=18.40(4.06) than those non-depressed group (mean (SD) MADRS=20.81(6.23) with p=0.001), whereas the relapsed group had higher STAI-trait anxiety than the non-relapsed group (p=0.04). Two-sample t-tests on FC showed that the relapsed group had a lower FC between the right parahippocampus and the superior and inferior parietal cortex. The relapsed group also had a reduced FC between the right globus pallidum and the right superior frontal gyrus. In addition, the relapsed group had significantly greater ALFF in the left amygdala and globus pallidum compared with the non-relapsed group; however, the significance was lost after controlling for depression severity and STAI-trait anxiety. <h3>Conclusions</h3> This is one of few studies that have examined clinical and neural characters in relapsed LLD. Lower FC between the right parahippocampus and the superior and inferior parietal cortex suggests a potential reduction in attention for memory. Low FC between the right globus pallidum and the right superior frontal gyrus may indicate reduced executive function in relapsed individuals. Importantly, the relapsed group also showed lower depressive symptoms yet higher trait anxiety. These results suggest that depression comorbid with anxiety might be an essential factor of relapse tendency. Future studies will examine whether the relapsed group also has lower executive function.

The Nottingham radiation protocol for O-arm navigation in paediatric deformity patients: a feasibility study

O-arm assisted pedicle screw placement has been proven to be more accurate than free-hand technique. Radiation exposure remains the primary drawback. We determined thefeasibility and safety of a reduced radiation protocol in paediatric patients undergoing scoliosis correction. A reduced radiation protocol for a medtronic O-arm navigational system was devised. 3D CT reconstructions of an anthropomorphic pelvic phantom indicated adequate image quality after reduction to 14% of current manufacturer default factors. A feasibility study to test the image quality was undertaken on four patients, one with syndromic and three with idiopathic scoliosis each receiving progressively reducing radiation exposure of 60%, 50%, 40% and 14% of what would have been delivered using the manufacturer default protocol. This represented 32% of the mayo clinic protocol. It was achieved by reducing the x-ray tube current to 10mA while keeping the tube potential at 90kVp. A low dose O-arm protocol was able to generate adequate image quality while delivering as little as 14% (for lumbar region reconstructions) of the recommended protocol radiation dose. The total radiation dose delivered with this protocol was approximately 0.8 milliSieverts for a single spin. This effective dose represents < 1/3 of average UK and < 1/6 average US annual radiation exposure. There were no neurological or implant-related complications. Our low dose O-arm radiation protocol significantly reduces the radiation exposure compared to the manufacturer recommended Mayo clinic protocol providing operational image quality to allow accurate screw placement in spinal deformity.

Comparative evaluation of Octopus semi-automated kinetic perimeter with Humphrey and Goldmann perimeters in neuro-ophthalmic disorders.

Purpose:The aim of this study was to compare the performance of Octopus 900(OVF) kinetic module with Goldmann perimeter (GVF) and Humphrey 750i (HVF) perimeters in neuro-ophthalmic disorders.Methods:During this prospective observational cross-sectional study, 17 patients (26 eyes) with neuro-ophthalmic disorders underwent visual field examination on the three perimeters. Field defects on OVF were matched with HVF and GVF for the number of quadrants involved. An unmasked observer, and a masked observer (unaware of the clinical diagnosis) were made to separately diagnose the type of field defects on all three fields for the same patient. The pattern of field defect on OVF was compared with GVF and HVF field defects for both observers.Results:When OVF was compared with HVF and GVF, 88% eyes correctly matched for normal or abnormal visual fields, while quadrant-matching was 80% and 89% respectively. For the unmasked observer, the pattern of field defects on OVF was similar to HVF and GVF in 58% and 65% eyes respectively while for a masked observer, it was 54% and 62%. Central and paracentral scotomas showed unmatched fields when OVF was compared with HVF and GVF. When these patients were excluded, sensitivity of OVF increased to 95%.Conclusion:Clinical correlation aids in better characterisation of a field defect. All 3 perimeters are concurrent in the pattern of field defects for non-central defects. However, the default protocol on OVF may not be enough to demarcate the central and para-central scotomas. Development of a customised protocol for the assessment of central and centrocecal field defects increases the accuracy of OVF.

Quantification of 3D microstructural parameters of trabecular bone is affected by the analysis software.

Over the last decades, the use of high-resolution imaging systems to assess bone microstructural parameters has grown immensely. Yet, no standard defining the quantification of these parameters exists. It has been reported that different voxel size and/or segmentation techniques lead to different results. However, the effect of the evaluation software has not been investigated so far. Therefore, the aim of this study was to compare the bone microstructural parameters obtained with two commonly used commercial software packages, namely IPL (Scanco, Switzerland) and CTan (Bruker, Belgium). We hypothesized that even when starting from the same segmented scans, different software packages will report different results. Nineteen trapezia and nineteen distal radii were scanned at two resolutions (20 μm voxel size with microCT and HR-pQCT 60 μm). The scans were segmented using the scanners' default protocol. The segmented images were analyzed twice, once with IPL and once with CTan, to quantify bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number (Tb.N) and specific bone surface (BS/BV). Only small differences between IPL and CTan were found for BV/TV. For Tb.Th, Tb.Sp and BS/BV high correlations (R2≥0.99) were observed between the two software packages, but important relative offsets were observed. For microCT scans, the offsets were relative constant, e.g., around 15% for Tb.Th. However, for the HR-pQCT scans the mean relative offsets ranged over the different bone samples (e.g., for Tb.Th from 14.5% to 19.8%). For Tb.N, poor correlations (0.43≤R2≤0.81) for all tested cases were observed. We conclude that trabecular bone microstructural parameters obtained with IPL and CTan cannot be directly compared except for BV/TV. For Tb.Th, Tb.Sp and BS/BV, correction factors can be determined, but these depend on both the image voxel size and specific anatomic location. The two software packages did not produce consistent data on Tb.N. The development of a universal standard seems desirable.

Evaluation of a low-dose protocol for cone beam computed tomography of the temporomandibular joint.

Objective:Evaluation of cone beam CT (CBCT) examination with a low-dose scanning protocol for assessment of the temporomandibular joint (TMJ).Methods:34 adult patients referred for CBCT imaging of the TMJ underwent two examinations with two scanning protocols, a manufacturer-recommended protocol (default) and a low-dose protocol where the tube current was reduced to 20% of the default protocol. Three image stacks were reconstructed: default protocol, low-dose protocol, and processed (using a noise reduction algorithm) low-dose protocol. Four radiologists evaluated the images. The Sign test was used to evaluate visibility of TMJ anatomic structures and image quality. Receiver operating characteristic analyzes were performed to assess the diagnostic accuracy. κ values were used to evaluate intraobserver agreement.Results:With the low-dose and processed protocols, visibility of the TMJ anatomical structures and overall image quality were comparable to the default protocol. No significant differences in radiographic findings were found for the two low-dose protocols compared to the default protocol. The area under the curves (Az) averaged for the low-dose and processed protocols, according to all observers, were 0.931 and 0.941, respectively. Intraobserver agreement was good to very good.Conclusion:For the CBCT unit used in this study, the low-dose CBCT protocol for TMJ examination was diagnostically comparable to the manufacturer-recommended protocol, but delivered a five times lower radiation dose. There is an urgent need to evaluate protocols for CBCT examinations of TMJ in order to optimize them for a radiation dose as low as diagnostically acceptable (the as low as diagnostically acceptable principle recommended by NCRP).

Determination of radiation dose and low-dose protocol for digital chest tomosynthesis using radiophotoluminescent (RPL) glass dosimeters

PurposeThis study aimed to determine a low-dose protocol for digital chest tomosynthesis (DTS). MethodsFive simulated nodules with a CT number of approximately 100 HU with size diameter of 3, 5, 8, 10, and 12 mm were inserted into an anthropomorphic chest phantom (N1 Lungman model), and then scanned by DTS system (Definium 8000) with varying tube voltage, copper filter thickness, and dose ratio. Three radiophotoluminescent (RPL) glass dosimeters, type GD-352 M with a dimension of 1.5 × 12 mm, were used to measure the entrance surface air kerma (ESAK) in each protocol. The effective dose (ED) was calculated using the recorded total dose-area-product (DAP). The signal-to-noise ratio (SNR) was determined for qualitative image quality evaluation. The image criteria and nodule detection capability were scored by two experienced radiologists. The selected low-dose protocol was further applied in a clinical study with 30 pulmonary nodule follow-up patients. ResultsThe average ESAK obtained from the standard default protocol was 1.68 ± 0.15 mGy, while an ESAK of 0.47 ± 0.02 mGy was found for a low-dose protocol. The EDs for the default and low-dose protocols were 313.98 ± 0.72 µSv and 100.55 ± 0.28 µSv, respectively. There were small non-significant differences in the image criteria and nodule detection scoring between the low-dose and default protocols interpreted by two radiologists. The effective dose of 98.87 ± 0.08 µSv was obtained in clinical study after applying the low-dose protocol. ConclusionsThe low-dose protocol obtained in this study can substantially reduce radiation dose while preserving an acceptable image quality compared to the standard protocol.