Circumferential resection margin positivity due to direct or indirect tumour involvement in rectal cancer - a call for better stratification

BACKGROUND

A positive circumferential resection margin (CRM) after rectal cancer surgery, which can be the result of direct or indirect tumour involvement, has consistently been associated with increased local recurrence and poorer survival. However, little is known of the differential impact of the mode of tumour involvement on outcomes.

METHODS

1460 consecutive patients undergoing rectal cancer resection between 2003 and 2018 were retrospectively assessed. Histopathology reports for patients with a positive CRM were reviewed to determine cases of direct (R1-tumour) or indirect tumour involvement (R1-other). Disease-free survival (DFS) and overall survival (OS) were assessed by Kaplan-Meier analysis. The role of the mode of CRM positivity was examined by univariate and multivariate Cox proportional hazards models.

RESULTS

Eighty-five patients had an R1 resection due to CRM involvement (5.8%). Of those, 69 were due to direct tumour involvement, while 16 were from indirect causes. Kaplan-Meier analysis revealed that R1-other was associated with increased OS (hazard ratio 0.40, log-rank P = 0.006) and DFS (P = 0.043). Multivariate regression confirmed that the mode of CRM positivity was an independent predictor of OS. More interestingly, the patterns of recurrence were different between the two groups, with R1-tumour leading to significantly more local recurrence (P = 0.04).

CONCLUSIONS

Our data strongly suggests that direct tumour involvement of the CRM confers worse prognosis after rectal cancer surgery. Importantly, differences in the site and frequency of recurrences make a case for better stratification of patients with a positive CRM to guide treatment decisions.

Tumor attachment to Major intrahepatic vascular for Colorectal liver metastases

BACKGROUND

Colorectal liver metastases attached major intrahepatic vessels has been considered to be a risk factor for survival outcome after liver resection. The present study aimed to clarify the outcomes of R1 surgery (margin < 1 mm) in CRLM patients, distinguishing parenchymal margin R1 and attached to major intrahepatic vessels R1.

METHODS

In present study, 283 CRLM patients who were evaluated to be attached to major intrahepatic vessels initially and underwent liver resection following preoperative chemotherapy. They were assigned to two following groups: R0 (n = 167), R1 parenchymal (n = 58) and R1 vascular (n = 58). The survival outcomes and local recurrence rates were analyzed in each group.

RESULTS

Overall, 3- and 5-year overall survival rates after liver resection were 53.0% and 38.2% (median overall survival 37 months). Five-year overall survival was higher in patients with R0 than parenchymal R1 (44.9%% vs. 26.3%, p = 0.009), whereas there was no significant difference from patients with vascular R1 (34.3%, p = 0.752). In the multivariable analysis, preoperative chemotherapy > 4 cycles, clinical risk score 3-5, RAS mutation, parenchymal R1 and CA199 > 100 IU/ml were identified as independent predictive factors of overall survival (p < 0.05). There was no significant difference for local recurrence among three groups.

CONCLUSION

Parenchymal R1 resection was independent risk factor for CRLM. Vascular R1 surgery achieved survival outcomes equivalent to R0 resection. Non-anatomic liver resection for CRLM attached to intrahepatic vessels might be pursued to increase patient resectability by preoperative chemotherapy.

Target Site of Prepulse Inhibition of the Trigeminal Blink Reflex in Humans

Despite the clinical significance of prepulse inhibition (PPI), the mechanisms are not well understood. Herein, we present our investigation of PPI in the R1 component of electrically induced blink reflexes. The effect of a prepulse was explored with varying prepulse test intervals (PTIs) of 20-600 ms in 4 females and 12 males. Prepulse-test combinations included the following: stimulation of the supraorbital nerve (SON)-SON [Experiment (Exp) 1], sound-sound (Exp 2), the axon of the facial nerve-SON (Exp 3), sound-SON (Exp 4), and SON-SON with a long trial-trial interval (Exp 5). Results showed that (1) leading weak SON stimulation reduced SON-induced ipsilateral R1 with a maximum effect at a PTI of 140 ms, (2) the sound-sound paradigm resulted in a U-shaped inhibition time course of the auditory startle reflex (ASR) peaking at 140 ms PTI, (3) facial nerve stimulation showed only a weak effect on R1, (4) a weak sound prepulse facilitated R1 but strongly inhibited SON-induced late blink reflexes (LateRs) with a similar U-shaped curve, and (5) LateR in Exp 5 was almost completely absent at PTIs >80 ms. These results indicate that the principal sensory nucleus is responsible for R1 PPI. Inhibition of ASR or LateR occurs at a point in the startle reflex circuit where auditory and somatosensory signals converge. Although the two inhibitions are different in location, their similar time courses suggest similar neural mechanisms. As R1 has a simple circuit and is stable, R1 PPI helps to clarify PPI mechanisms.SIGNIFICANCE STATEMENT Prepulse inhibition (PPI) is a phenomenon in which the startle response induced by a startle stimulus is suppressed by a preceding nonstartle stimulus. This study demonstrated that the R1 component of the trigeminal blink reflex shows clear PPI despite R1 generation within a circuit consisting of the trigeminal and facial nuclei, without startle reflex circuit involvement. Thus, PPI is not specific to the startle reflex. In addition, PPI of R1, the auditory startle reflex, and the trigeminal late blink reflex showed similar time courses in response to the prepulse test interval, suggesting similar mechanisms regardless of inhibition site. R1 PPI, in conjunction with other paradigms with different prepulse-test combinations, would increase understanding of the underlying mechanisms.

Prevention and treatment of a positive proximal margin after gastrectomy for cardia cancer

A tumour-positive proximal margin (PPM) after extended gastrectomy for oesophagogastric junction (OGJ) adenocarcinoma is observed in approximately 2-20% of patients. Although a PPM is an unfavourable prognostic factor, the clinical relevance remains unclear as it may reflect poor tumour biology. This narrative review analyses the most relevant literature on PPM after gastrectomy for OGJ cancers. Awareness of the risk factors and possible measures that can be taken to reduce the risk of PPM are important. In patients with a PPM, surgical and non-surgical treatments are available but the effectiveness remains unclear.

Modeling the Effect of Hyperoxia on the Spin-Lattice Relaxation Rate R1 of Tissues

PURPOSE

Inducing hyperoxia in tissues is common practice in several areas of research, including oxygen-enhanced MRI (OE-MRI), which attempts to use the resulting signal changes to detect regions of tumor hypoxia or pulmonary disease. The linear relationship between PO₂ and R1 has been reproduced in phantom solutions and body fluids such as vitreous fluid; however, in tissue and blood experiments, factors such as changes in deoxyhemoglobin levels can also affect the ΔR1.

THEORY AND METHODS

This manuscript proposes a three-compartment model for estimating the hyperoxia-induced changes in R1 of tissues depending on B0, SO₂ , blood volume, hematocrit, oxygen extraction fraction, and changes in blood and tissue PO₂ . The model contains two blood compartments (arterial and venous) and a tissue compartment. This model has been designed to be easy for researchers to tailor to their tissue of interest by substituting their preferred model for tissue oxygen diffusion and consumption. A specific application of the model is demonstrated by calculating the resulting ΔR1 expected in healthy, hypoxic and necrotic tumor tissues. In addition, the effect of sex-based hematocrit differences on ΔR1 is assessed.

RESULTS

The ΔR1 values predicted by the model are consistent with reported literature OE-MRI results: with larger positive changes in the vascular periphery than hypoxic and necrotic regions. The observed sex-based differences in ΔR1 agree with findings by Kindvall et al. suggesting that differences in hematocrit levels may sometimes be a confounding factor in ΔR1.

CONCLUSION

This model can be used to estimate the expected tissue ΔR1 in oxygen-enhanced MRI experiments.

A General Model to Calculate the Spin-Lattice Relaxation Rate (R1) of Blood, Accounting for Hematocrit, Oxygen Saturation, Oxygen Partial Pressure, and Magnetic Field Strength Under Hyperoxic Conditions

BACKGROUND

Under normal physiological conditions, the spin-lattice relaxation rate (R1) in blood is influenced by many factors, including hematocrit, field strength, and the paramagnetic effects of deoxyhemoglobin and dissolved oxygen. In addition, techniques such as oxygen-enhanced magnetic resonance imaging (MRI) require high fractions of inspired oxygen to induce hyperoxia, which complicates the R1 signal further. A quantitative model relating total blood oxygen content to R1 could help explain these effects.

PURPOSE

To propose and assess a general model to estimate the R1 of blood, accounting for hematocrit, SO2 , PO2 , and B0 under both normal physiological and hyperoxic conditions.

STUDY TYPE

Mathematical modeling.

POPULATION

One hundred and twenty-six published values of R1 from phantoms and animal models.

FIELD STRENGTH/SEQUENCE

5-8.45 T.

ASSESSMENT

We propose a two-compartment nonlinear model to calculate R1 as a function of hematocrit, PO2 , and B0. The Akaike Information Criterion (AIC) was used to select the best-performing model with the fewest parameters. A previous model of R1 as a function of hematocrit, SO2 , and B0 has been proposed by Hales et al, and our work builds upon this work to make the model applicable under hyperoxic conditions (SO2  > 0.99). Models were assessed using the AIC, mean squared error (MSE), coefficient of determination (R2 ), and Bland-Altman analysis. The effect of volume fraction constants W RBC and W plasma was assessed by the SD of resulting R1. The range of the model was determined by the maximum and minimum B0, hematocrit, SO2 , and PO2 of the literature data points.

STATISTICAL TESTS

Bland-Altman, AIC, MSE, coefficient of determination (R2 ), SD.

RESULTS

The model estimates agreed well with the literature values of R1 of blood (R2  = 0.93, MSE = 0.0013 s-2 ), and its performance was consistent across the range of parameters: B0 = 1.5-8.45 T, SO2  = 0.40-1, PO2  = 30-700 mmHg.

DATA CONCLUSION

Using the results from this model, we have quantified and explained the contradictory decrease in R1 reported in oxygen-enhanced MRI and oxygen-delivery experiments.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 1.

Magnetic resonance imaging T1 indices of the brain as biomarkers of inhaled manganese exposure

Excessive exposure to manganese (Mn) is linked to its accumulation in the brain and adverse neurological effects. Paramagnetic properties of Mn allow the use of magnetic resonance imaging (MRI) techniques to identify it in biological tissues. A critical review was conducted to evaluate whether MRI techniques could be used as a diagnostic tool to detect brain Mn accumulation as a quantitative biomarker of inhaled exposure. A comprehensive search was conducted in MEDLINE, EMBASE, and PubMed to identify potentially relevant studies published prior to 9 May 2022. Two reviewers independently screened identified references using a two-stage process. Of the 6452 unique references identified, 36 articles were retained for data abstraction. Eligible studies used T1-weighted MRI techniques and reported direct or indirect T1 measures to characterize Mn accumulation in the brain. Findings demonstrate that, in subjects exposed to high levels of Mn, deposition in the brain is widespread, accumulating both within and outside the basal ganglia. Available evidence indicates that T1 MRI techniques can be used to distinguish Mn-exposed individuals from unexposed. Additionally, T1 MRI may be useful for semi-quantitative evaluation of inhaled Mn exposure, particularly when interpreted along with other exposure indices. T1 MRI measures appear to have a nonlinear relationship to Mn exposure duration, with R1 signal only increasing after critical thresholds. The strength of the association varied depending on the regions of interest imaged and the method of exposure measurement. Overall, available evidence suggests potential for future clinical and risk assessment applications of MRI as a diagnostic tool.

Nexus Between Economic Efficiency, Healthcare, and Environmental Expenditures: A Perspective of BRI Countries

Public health and the environment are the most essential pillars, and play a vital role in the economy. In order to better public health, the economic and environmental atmosphere must be stable and clean, respectively. Thus, this paper emphasizes on nexus between economic, public health, and the environment. Therefore, the objective of this paper is whether healthcare and environmental expenditures affect economic efficiency and vice versa. So, this study evaluates the performance of the country's economic efficiency and investigates the effect of healthcare and environmental expenditures for 62 Belt and Road Initiative countries for the period from 1996 to 2020. Suitable input-output variables are employed under the framework of DEA-window and Malmquist Index Productivity, and Stochastic Frontier Analysis (SFA). In addition, this study estimates the relationship between economic efficiency, healthcare, and environmental expenditures by fixed and random effects models. Therefore, the analytical outcomes reveal that countries are economically efficient. On the contrary, SFA estimation concludes that countries are found to be inefficient, because higher variation is exists in efficiency change compared to technological efficiency change and total factor productivity change on average. In addition, it is worth notable that healthcare and environmental expenditures improve the country's economic efficiency. Furthermore, public health is also influenced by economic efficiency. Thus, this study suggests that countries should better utilize given resources and invest a specific portion of national income in order to improve economic efficiency.

A simplified empirical model to estimate oxygen relaxivity at different magnetic fields

The change in longitudinal relaxation rate (R1 ) produced by oxygen has been used as a means of inferring oxygenation levels in magnetic resonance imaging in numerous applications. The relationship between oxygen partial pressure (pO2 ) and R1 is linear and reproducible, and the slope represents the relaxivity of oxygen (r1Ox ) in that material. However, there is considerable variability in the values of r1Ox reported, and they have been shown to vary by field strength and temperature. Therefore, we have compiled 28 reported empirical values of the relaxivity of oxygen as a resource for researchers. Furthermore, we provide an empirical model for estimating the relaxivity of oxygen in water, saline, plasma, and vitreous fluids, accounting for magnetic field strength and temperature. The model agrees well (R2  = 0.93) with the data gathered from the literature for fields ranging from 0.011 to 8.45 T and temperatures of 21-40 °C. This provides a useful resource for researchers seeking to quantify pO2 in simple fluids in their studies, such as water and saline phantoms, or bodily fluids such as vitreous fluids, cerebrospinal fluids, and amniotic fluids.

Asian innovation in pharmaceutical and medical device industry - beyond tomorrow

The Asian region has passed a long and rocky road during the past several decades to establish itself as the second leading regional biotech market globally. China has become the second largest pharmaceutical market while Japan holds a strong second position as the global hub for medical devices development and innovation. Pharmaceutical expenditure continues to outpace real GDP growth in most of these countries. The trend is likely to be continued for a decade ahead, driven by a myriad of factors ranging from aging populations, rapidly growing welfare and increased citizen expectations raising demand for novel medicines and technologies. Satisfaction of these unmet needs in terms of supply is coming from the large multinational companies in wealthier among these societies. Domestic born and largely state-owned manufacturing industries continue to play a crucial role in an array of middle-income countries. Global biotech hub of Singapore is hosting over 1.5 times more headquarters of large pharmaceutical companies than Beijing, Tokyo, Shanghai and Hong Kong combined together. Japanese Takeda, Astellas, Daiichi Sankyo and Otsuka and Chinese Sinopharm, Guangzhou Pharmaceuticals Corporation, SPH and Yunnan Baiyao are now enlisted in leading Top 25 pharmaceutical companies rankings as per their annual net revenues in 2020-2021. Global industry landscape is evolving with ever more Asian companies obtaining the sharp innovative competitiveness leading development of cutting-edge medical technologies. Asian societies demand for pharmaceuticals and medical services continue to be characterized with unmet needs and striving to increase supply capacities. Financial obstacles of affordability of life saving medicines to the ordinary citizens shall be gradually overcome with an array of reimbursement strategies and extended insurance coverage policies. Observing the broad landscape throughout Asian region, we may witness that optimism in terms of domestic real GDP growth and consecutive biotech industry forecasts remains firmly rooted in years to come. Biosimilars are not a focus of the paper.

Dual-phase 18F-florbetaben PET provides cerebral perfusion proxy along with beta-amyloid burden in Alzheimer's disease

BACKGROUND

This study investigated changes in brain perfusion and Aβ burden according to the progression of Alzheimer's disease (AD) by using a dual-phase ¹⁸F-florbetaben (FBB) PET protocol.

METHODS

Sixty subjects, including 12 with Aβ-negative normal cognition (Aβ^-NC), 32 with Aβ-positive mild cognitive impairment (Aβ⁺MCI), and 16 with Aβ-positive AD (Aβ⁺AD), were enrolled. A dynamic PET scan was obtained in the early phase (0-10 min, eFBB) and delayed phase (90-110 min, dFBB), which were then averaged into a single frame, respectively. In addition to the averaged eFBB, an R1 parametric map was calculated from the eFBB scan based on a simplified reference tissue model (SRTM). Between-group regional and voxel-wise analyses of the images were performed. The associations between cognitive profiles and PET-derived parameters were investigated.

RESULTS

Both the R1 and eFBB perfusion reductions in the cortical regions were not significantly different between the Aβ^-NC and Aβ⁺MCI groups, while they were significantly reduced from the Aβ⁺MCI to Aβ⁺AD groups in regional and voxel-wise analyses. However, cortical Aβ depositions on dFBB were not significantly different between the Aβ⁺MCI and Aβ⁺AD groups. There were strong positive correlations between the R1 and eFBB images in regional and voxel-wise analyses. Both perfusion components showed significant correlations with general and specific cognitive profiles.

CONCLUSION

The results of this study demonstrated the feasibility of dual-phase ¹⁸F-FBB PET to evaluate different trajectories of dual biomarkers for neurodegeneration and Aβ burden over the course of AD. In addition, both eFBB and SRTM-based R1 can provide robust indices of brain perfusion.

Notoginsenoside R1 activates the NAMPT-NAD+-SIRT1 cascade to promote postischemic angiogenesis by modulating Notch signaling

Nicotinamide phosphoribosyltransferase (NAMPT) maintains mitochondrial function and protects against cerebral ischemic injury by improving energy metabolism. Notoginsenoside R1 (R1), a unique constituent of Panax notoginseng, has been shown to promote the proliferation and tube formation of human umbilical vein endothelial cells. Whether R1 has proangiogenesis on the activation of NAMPT in ischemic stroke remains unclear. The purpose of this study was to investigate the pharmacodynamic effect and mechanism of R1 on angiogenesis after ischemic stroke. We used male Sprague-Dawley (SD) rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). R1 was administered via intraperitoneal (i.p.) injection immediately after ischemia induction. The promotion of R1 on angiogenesis were detected by immunofluorescence staining, 3D stereoscopic imaging and transmission electron microscopy detection. HBMEC cells were pretreated with different concentrations of R1 for 12 h before oxygen-glucose deprivation/reoxygenation (OGD/R) exposure. Afterward, scratch assay, EdU staining and tube formation were determined. Western blot analyses of proteins, including those involved in angiogenesis, NAMPT-SIRT1 cascade, VEGFR-2, and Notch signaling, were conducted. We showed that R1 significantly restored cerebral blood flow, improved mitochondrial energy metabolism and promoted angiogenesis. More importantly, incubation with 12.5-50 μM R1 significantly increased the migration, proliferation and tube formation of HBMECs in vitro. The promotion of R1 on angiogenesis were associated with the NAMPT-NAD⁺-SIRT1 cascade and Notch/VEGFR-2 signaling pathway, which was partially eliminated by inhibitors of NAMPT and SIRT1. We demonstrated that R1 promotes post-stroke angiogenesis via activating NAMPT-NAD⁺-SIRT1 cascade. The modulation of Notch signaling and VEGFR-2 contribute to the post-stroke angiogenesis. These findings offer insight for exploring new therapeutic strategies for neurorestoration via R1 treatment after ischemic stroke.

Influence of positive margins on tumour recurrence and overall survival after gastrectomy for gastric cancer

BACKGROUND

Incidence of positive surgical margins after curative gastrectomy ranges from 1% to 20%. It has been suggested that positive surgical margin is an adverse prognosis factor, with a higher local recurrence and worse overall survival (OS). However, the management of these patients remains unclear.

METHODS

A total of 267 patients who underwent gastrectomy with curative intent between January 2010 and December 2018 in our centre were enrolled in this study. Post-operative histological analysis revealed positive resection margins in 18 patients (8%). Clinicopathological features and outcome of patients undergoing gastrectomy with negative and positive margins were compared.

RESULTS

Patients with positive margins were associated with higher American Joint Committee on Cancer (AJCC) stage, T stage, N stage, median number of positive nodes, diffuse Lauren type, whole stomach involved and poorly differentiated tumours. Local recurrence was described in 50% of cases with positive margins. The multivariate analysis demonstrated that the TNM stage was the only independent prognostic factor associated with recurrence. OS for positive margins at 1, 3 and 5 years was 75%, 57% and 26%, respectively. The median survival in patients with positive margins was 38.33 versus 81.17 months for R0 patients (p = 0.027). Multivariate analysis showed that age (hazard ratio [HR] 1.041, 95% confidence interval [CI] 1.02-1.07, sex (HR 2.00, 95% CI 1.22-3.30) and TNM stage (p < 0.001) were independent factors of OS.

CONCLUSION

Positive resection margin was an indication of advanced and more aggressive disease rather than an independent prognosis factor for OS or recurrence in gastric cancer.

Quantitative measurement of macromolecular tissue properties in white and gray matter in healthy aging and amnestic MCI

Healthy and pathological aging influence brain microstructure via complex processes. Discerning these processes requires measurements that are sensitive to specific biological properties of brain tissue. We integrated a novel quantitative R1 measure with multi-shell diffusion weighted imaging to map age-associated changes in macromolecular tissue volume (MTV) along major white matter tracts in healthy older adults and patients with amnestic Mild Cognitive Impairment (aMCI). Reduced MTV in association tracts was associated with older age in healthy aging, was correlated with memory performance, and distinguished aMCI from controls. We also mapped changes in gray matter tissue properties using quantitative R1 measurements. We documented a widespread decrease in R1 with advancing age across the cortex and decreased R1 in aMCI compared with controls in regions implicated in episodic memory. Our data are the first to characterize MTV loss along major white matter tracts in aMCI and suggest that qMRI is a sensitive measure for detecting subtle degeneration of white and gray matter tissue that cannot be detected by conventional MRI and diffusion measures.

Microscopic resection margins adversely influence survival rates after surgery for colorectal liver metastases: An open ambidirectional Cohort Study

BACKGROUND

Liver resection is the most effective treatment for patients with colorectal liver metastases (CRLMs). Patients with tumour at the resection margin (R1) are reported to have worse survival compared to those with an uninvolved resection margin (R0). Recent data has questioned this finding. This study investigates whether R1 resections adversely influence survival when compared to R0 resections.

MATERIAL AND METHODS

Patients undergoing surgery for CRLM, identified from a prospectively maintained database, from January 2007 to January 2017, were included. Univariate and multivariate survival analyses were performed. p < 0.05 was significant.

RESULTS

282 patients were included. Median age 72 (32-90) years. 236 patients (83.7%) had chemotherapy and surgery, whilst 46 (16.3%) had surgery alone. 149 patients (52.8%) were alive at the end of the study period. R1 resection on univariate survival analysis was associated with better survival (HR 2.12, 95%CI 1.60-4.61, p = 0.0002). Multivariate analysis controlling for age and gender, identified presence of extrahepatic disease (HR 2.03, 95%CI 1.17-3.52, p < 0.001), R0 resection (HR 0.33, 95%CI 0.19-0.59, p = 0.003), primary tumour stage (HR 1.57, 95%CI 1.04-2.40, p = 0.034) and primary tumour differentiation (HR 2.56, 95%CI 1.01-6.46, p = 0.047), as prognostic factors for poorer survival. Five-year and 10-year survival were 54.3% and 41.7% respectively in patients with an R0 resection and, 25.8% and 17.2% in those with an R1 resection.

CONCLUSION

The presence of extrahepatic disease, an R1 resection margin, advanced T-stage and poorer tumour differentiation were associated with worse survival in CRLM surgery and R0 resection is recommended.

Whole-brain R1 predicts manganese exposure and biological effects in welders

Manganese (Mn) is a neurotoxicant that, due to its paramagnetic property, also functions as a magnetic resonance imaging (MRI) T1 contrast agent. Previous studies in Mn toxicity have shown that Mn accumulates in the brain, which may lead to parkinsonian symptoms. In this article, we trained support vector machines (SVM) using whole-brain R1 (R1 = 1/T1) maps from 57 welders and 32 controls to classify subjects based on their air Mn concentration ([Mn]_Air), Mn brain accumulation (ExMn_Brain), gross motor dysfunction (UPDRS), thalamic GABA concentration (GABA_Thal), and total years welding. R1 was highly predictive of [Mn]_Air above a threshold of 0.20 mg/m³ with an accuracy of 88.8% and recall of 88.9%. R1 was also predictive of subjects with GABA_Thal having less than or equal to 2.6 mM with an accuracy of 82% and recall of 78.9%. Finally, we used an SVM to predict age as a method of verifying that the results could be attributed to Mn exposure. We found that R1 was predictive of age below 48 years of age with accuracies ranging between 75 and 82% with recall between 94.7% and 76.9% but was not predictive above 48 years of age. Together, this suggests that lower levels of exposure (< 0.20 mg/m³ and < 18 years of welding on the job) do not produce discernable signatures, whereas higher air exposures and subjects with more total years welding produce signatures in the brain that are readily identifiable using SVM.

The Role of Adjuvant Therapy in Patients With Margin-Positive (R1) Esophagectomy: A National Analysis

BACKGROUND

We performed a nationwide analysis to assess the impact of adjuvant therapy on survival after a microscopically margin-positive (R1) resection for esophageal cancer.

METHODS

The National Cancer Database was used to identify patients with R1 resection for esophageal cancer (2004-2015). Patients were grouped by type of adjuvant therapy. Patients who had other margin status, M1 disease, neoadjuvant chemotherapy and radiation, missing survival, and no or unknown treatment were excluded. The primary outcome was overall survival. A 1:1 propensity score-matched sensitivity analysis was also performed comparing patients who received no adjuvant therapy with those who received adjuvant chemoradiation.

RESULTS

Of 546 patients, 279 (51%) received adjuvant therapy and 267 (49%) did not. Patients receiving adjuvant therapy were more likely to be younger, have more advanced pathologic stage, have nonsquamous histology, and have shorter hospitalization. In multivariable analysis, adjuvant chemotherapy, radiation, and chemoradiation were all associated with improved survival compared with no adjuvant therapy. In a propensity score-matched analysis of 123 patient pairs, adjuvant chemoradiation was associated with improved survival compared with no adjuvant therapy (adjusted HR: 0.30; 95% CI: [0.22, 0.40]).

CONCLUSIONS

Adjuvant therapy is associated with improved survival compared with no adjuvant therapy in patients with R1 resection for esophageal cancer even after adjustment for pathologic stage. Adjuvant therapy should be considered in patients with incompletely resected esophageal cancer in concordance with national guidelines.

B-Cell Receptor-Associated Protein 31 Negatively Regulates the Expression of Monoamine Oxidase A Via R1

B-cell receptor-associated protein 31 (Bap31) is a three trans-membrane protein of the endoplasmic reticulum (ER). Patients who have loss of function of Bap31 suffered from X-linked syndrome, such as motor and intellectual disabilities, dystonia, and sensorineural deafness. However, the underlying mechanism of Bap31 on X-linked syndrome remains unclear. Here, we found that a total of 21 proteins (9 up-regulated and 12 down-regulated proteins) related with X-linked syndrome were screened from shRNA-Bap31 transfected cells with the isobaric tags for relative and absolute quantification (iTRAQ) technique. One gene with the greatest change trend, monoamine oxidase A (MAOA), was identified. MAOA expression was up-regulated by Bap31 knockdown. However, Bap31 did not affect the ubiquitination degradation of MAOA protein. Of note, Bap31 selectively regulated the expression of cell division cycle associated 7-like (R1/RAM2/CDCA7L/JPO2, a transcriptional repressor of MAOA) and the binding activity of R1 with MAOA promoter, thereby affecting MAOA expression. This study demonstrates the molecular mechanisms of Bap31 in MAOA via R1 and supports the potential function of Bap31 on X-linked syndrome.

Three-dimensional motion-corrected T1 relaxometry with MPnRAGE

PURPOSE

To test the performance of the MPnRAGE motion-correction algorithm on quantitative relaxometry estimates.

METHODS

Twelve children (9.4 ± 2.6 years, min = 6.5 years, max = 13.8 years) were imaged 3 times in a session without sedation. Stabilization padding was not used for the second and third scans. Quantitative T₁ values were estimated in each voxel on images reconstructed with and without motion correction. Mean T₁ values were assessed in various regions determined from automated segmentation algorithms. Statistical tests were performed on mean values and the coefficient of variation across the measurements. Accuracy of T₁ estimates were determined by scanning the High Precision Devices (Boulder, CO) MRI system phantom with the same protocol.

RESULTS

The T₁ values obtained with MPnRAGE agreed within 4% of the reference values of the High Precision Devices phantom. The best fit line was T₁ (MPnRAGE) = 1.02 T₁ (reference)-0.9 ms, R²  = 0.9999. For in vivo studies, motion correction reduced the coefficients of variation of mean T₁ values in whole-brain tissue regions determined by FSL FAST by 74% ± 7%, and subcortical regions determined by FIRST and FreeSurfer by 32% ± 21% and 33% ± 26%, respectively. Across all participants, the mean coefficients of variation ranged from 0.8% to 2.0% for subcortical regions and 0.6% ± 0.5% for cortical regions when motion correction was applied.

CONCLUSION

The MPnRAGE technique demonstrated highly accurate values in phantom measurements. When combined with retrospective motion correction, MPnRAGE demonstrated highly reproducible T₁ values, even in participants who moved during the acquisition.

Analysis of the reiteration regions (R1 to R5) of varicella-zoster virus

The varicella-zoster virus (VZV) genome, comprises both unique and repeated regions. The genome also includes reiteration regions, designated R1 to R5, which are tandemly repeating sequences termed elements. These regions represent an understudied feature of the VZV genome. The R4 region is duplicated, with one copy in the internal repeat short (IRs) which we designated R4A and a second copy in the terminal repeat short (TRs) termed R4B. We developed primers to amplify and Sanger sequence these regions, including independent amplification of both R4 regions. Reiteration regions from >80 cases of PCR-confirmed shingles were sequenced and analyzed. Complete genome sequences for the remaining portions of these viruses were determined using Illumina MiSeq. We identified 28 elements not previously reported, including at least one element for each R region. Length heterogeneity was substantial in R3, R4A and R4B. Length heterogeneity between the two copies of R4 was common.

From bench to board-side: Academic teaching careers

Teaching positions provide a rewarding career pathway for Ph.D.s wishing to stay in academia outside of the research-focused position. The balance of teaching and research expectations on faculty can vary greatly depending on the type of institution. Faculty at primarily undergraduate institutions may be required to be researchactive and mentor undergraduates in the laboratory, while teaching faculty at a research-centered university may not have a research lab. In addition, faculty are expected to actively contribute to the shared governance of the institution, in the name of service. The career in teaching has become highly competitive and offers unexpected rewards and benefits. Considered here are the differences found among teaching positions to serve as a guide when considering teaching as a career option. We include our personal career narratives to illustrate the driving forces that led each of us to this challenging yet fulfilling academic path.

Exploring Lipid and Membrane Protein Dynamics Using Lipid-Bilayer Nanodiscs and Solution-State NMR Spectroscopy

The relationship of membrane protein function and the surrounding lipid bilayer goes far beyond simple hydrophobic interactions. At least from the 1980s, it is speculated that a certain fluid lipid state may be important not only for the lateral diffusion of membrane proteins (MPs) but also for modulating the catalytic activity of MPs (Lenaz. Bioscience Rep 7 (11):823-837, 1987). Indeed, acyl chain length, hydrophobic mismatch, and lipid headgroups are determinants for enzymatic and transport activities of MPs (Dumas et al. Biochemistry 39(16):4846-4854, 2000; Johannsson et al. Biochim Biophys Acta 641(2):416-421, 1981; Montecucco et al. FEBS Lett 144(1):145-148, 1982; Martens et al. Nat Struct Mol Biol 23(8):744-751, 2016). Moreover, it is speculated that changes in membrane lipid dynamics are important in the field of thermosensation (Vriens J, Nilius B, Voets T, Nat Rev Neurosci 15:573-589, 2014). Atomic insights into lipid-mediated modulation of membrane protein dynamics would therefore provide new insights with the potential to fundamentally extend our understanding on dynamic lipid-protein interdependencies.This chapter describes the expression and purification of nanodiscs assembled from membrane scaffold protein (MSP) as well as the expression and purification of the outer membrane protein X (OmpX). Subsequently, the incorporation of OmpX into MSP-derived nanodiscs is explained in detail. The chapter concludes with the setup of nuclear magnetic resonance (NMR) relaxation experiments and the extraction of relaxation rates for OmpX and the surrounding lipids.

18F-FDG PET, the early phases and the delivery rate of 18F-AV45 PET as proxies of cerebral blood flow in Alzheimer's disease: Validation against 15O-H2O PET

INTRODUCTION

Dual-biomarker positron emission tomography (PET), providing complementary information on cerebral blood flow and amyloid-β deposition, is of clinical interest for Alzheimer's disease (AD). The purpose of this study was to validate the perfusion components of early-phase ¹⁸F-florbetapir (eAV45), the ¹⁸F-AV45 delivery rate (R1), and ¹⁸F-FDG against ¹⁵O-H₂O PET and assess how they change with disease severity.

METHODS

This study included ten controls, 19 amnestic mild cognitive impairment, and 10 AD dementia subjects. Within-subject regional correlations between modalities, between-group regional and voxel-wise analyses of covariance per modality, and receiver operating characteristic analyses for discrimination between groups were performed.

RESULTS

FDG standardized uptake value ratio, eAV45 (0-2 min) standardized uptake value ratio, and AV45-R1 were significantly associated with H₂O PET (regional Pearson r = 0.54-0.82, 0.70-0.94, and 0.65-0.92, respectively; P < .001). All modalities confirmed reduced cerebral blood flow in the posterior cingulate of patients with amnestic mild cognitive impairment and AD dementia, which was associated with lower cognition (r = 0.36-0.65, P < .025) and could discriminate between patient and control groups (area under the curve > 0.80). However, eAV45 was less sensitive to reflect the disease severity than AV45-R1 or FDG.

DISCUSSION

R1 is preferable over eAV45 for accurate representation of brain perfusion in dual-biomarker PET for AD.

Tools for Open Source, Subnational CGE Modeling with an Illustrative Analysis of Carbon Leakage

This paper introduces the Wisconsin National Data Consortium (WiNDC) framework for producing self-consistent accounts based on publicly available datasets that can be used in sub-national economic equilibrium analysis in the United States. We describe the process used to generate regional social accounting matrices and a calibrated static multi-regional, multi-sectoral computable general equilibrium model conformal with the constructed dataset. As illustration, we show how the core model can be applied for the analysis of energy-environment issues. We use an energy-economy extension of the core model to assess the effectiveness of several state level greenhouse gas mitigation proposals. Sub-national abatement measures result in carbon leakage - mandated reductions in controlled areas may be vitiated by increased emissions in uncontrolled jurisdictions. Using a WiNDC-based model, we calculate leakage rates and show how these depend on the underlying trade model. Our calculations demonstrate the importance of both data and modeling assumptions for the simulation of policy experiments.

Evaluation of the environmental sustainability of different waste-to-energy plant configurations

Residual municipal solid waste (MSW) has an average lower heating value higher than 10GJ/Mg in the EU, and can be recovered in modern Waste-to-Energy (WtE) plants, producing combined heat and power (CHP) and reaching high levels of energy recovery. CHP is pinpointed as the best technique for energy recovery from waste. However, in some cases, heat recovery is not technically feasible - due to the absence of a thermal user (industrial plant or district heating) in the vicinity of the WtE plant - and power production remains the sole possibility. In these cases, there are some challenges involved in increasing the energy performance as much as possible. High energy recovery efficiency values are very important for the environmental sustainability of WtE plants. The more electricity and heat is produced, the better the saving of natural resources that can be achieved. Within this frame, the aim of this work is to carry out an environmental assessment, through Life Cycle Assessment, of an MSW WtE plant, considering different sizes and operated in different ways, from power production only to full cogeneration. The main assumption is that the electric conversion efficiency increases as the plant size increases, introducing technical improvements thanks to the economies of scale. Impact assessment results were calculated using ReCiPe 2008 methods. The climate change indicator is positive when the WtE plant is operated in power production only mode, with values decreasing for the increasing size. Values for the climate change are negative when cogeneration is applied, requiring increasing cogeneration ratios for decreasing size. Similarly, the fossil fuel depletion indicator benefits from increase of both the plant size and the cogeneration rate, but it is always negative, meaning that the residual MSW burning with energy recovery always provides a saving of fossil primary energy. Other indicator values are in general negative and are also beneficially affected by increasing the plant size, but they worsen when increasing the cogeneration rate. The remaining indicators - i.e. human toxicity and terrestrial ecotoxicity - always have positive values, which decrease for increasing plant size and increase as the cogeneration rate increases. However, the local context should be evaluated carefully with reference to the type of electricity which is substituted and in view of a future massive production of renewable electricity, because conclusions change accordingly. Finally, it was evaluated that the inclusion of bottom ash recovery - instead of landfilling - can significantly improve the values of several impact assessment indicators.

A practical method to calculate the R1 index of waste-to-energy facilities

According to Directive 98/2008/EC, the operation carried out by an incinerator of Municipal Solid Waste (MSW) is classified either as energy recovery (R1) or as disposal (D10) depending on the result achieved by the application of the R1 formula. In 2011 the DG Environment of the European Commission (EC) issued some non-binding guidelines on the interpretation of such a formula that clarified many aspects related to its application. A point not fully clarified by the EC guidelines is the determination of the energy contained in the treated waste (E_W). For this term of the formula, reference is made to the indirect method for the calculation of boiler thermal efficiency, as defined by the norm EN 12952-15. However, the application of such a norm to an entire year of operation of a Waste-to-Energy (WtE) boiler is not immediate. Therefore, a practical method for the calculation of the E_W term has been developed in the framework of a collaboration between the MatER Study Centre and the Lombardy Region (Italy). The method is based on: (i) the identification of the most reliable data available from the Distributed Control System (DCS) of the plant; (ii) the definition of a control volume around the boiler(s) also based on the availability of data; (iii) the closure of the mass balance for such a control volume; (iv) the energy balance of the same control volume that gives, thus, the E_W term of the R1 formula. The method has been applied in 2015-2016 to nine plants, generating a number of interesting data reported and discussed in this work, such as R1 index values, Lower Heating Values (LHV) of the treated wastes, main sources of energy losses in WtE boilers, etc. For one case study, discussed in detail in this work, the law of propagation of uncertainties has been applied according to the ISO/IEC Guide 98-3, leading to the assessment of the accuracy of the method, which resulted in ±2.4% with a confidence level of circa 95%.

YARP-ROS Inter-Operation in a 2D Navigation Task

This paper presents some recent developments in YARP middleware, aimed to improve its integration with ROS. They include a new mechanism to read/write ROS transform frames and a new set of standard interfaces to intercommunicate with the ROS navigation stack. A novel set of YARP companion modules, which provide basic navigation functionalities for robots unable to run ROS, is also presented. These modules are optional, independent from each other, and they provide compatible functionalities to well-known packages available inside ROS framework. This paper also discusses how developers can customize their own hybrid YARP-ROS environment in the way it best suits their needs (e.g., the system can be configured to have a YARP application sending navigation commands to a ROS path planner, or vice versa). A number of available possibilities is presented through a set of chosen test cases applied to both real and simulated robots. Finally, example applications discussed in this paper are also made available to the community by providing snippets of code and links to source files hosted on github repository https://github.com/robotology.¹

Comparison of ferumoxytol-based cerebral blood volume estimates using quantitative R1 and R2* relaxometry

PURPOSE

Cerebral perfusion is commonly assessed clinically with dynamic susceptibility contrast MRI using a bolus injection of gadolinium-based contrast agents, resulting in semi-quantitative values of cerebral blood volume (CBV). Steady-state imaging with ferumoxytol allows estimation of CBV with the potential for higher precision and accuracy. Prior CBV studies have focused on the signal disrupting T2* effects, but ferumoxytol also has high signal-enhancing T₁ relaxivity. The purpose of this study was to investigate and compare CBV estimation using T₁ and T2*, with the goal of understanding the contrast mechanisms and quantitative differences.

METHODS

Changes in R₁ (1/T₁ ) and R2* (1/ T2*) were measured after the administration of ferumoxytol using high-resolution quantitative approaches. Images were acquired at 3.0T and R₁ was estimated from an ultrashort echo time variable flip angle approach, while R2* was estimated from a multiple gradient echo sequence. Twenty healthy volunteers were imaged at two doses. CBV was derived and compared from relaxometry in gray and white matter using different approaches.

RESULTS

R₁ measurements showed a linear dependence of blood R₁ with respect to dose in large vessels, in contrast to the nonlinear dose-dependence of blood R2* estimates. In the brain parenchyma, R2* showed linear dose-dependency whereas R₁ showed nonlinearity. CBV calculations based on R2* changes in tissue and ferumoxytol blood concentration estimates based on R₁ relaxivity showed the lowest variability in our cohort.

CONCLUSIONS

CBV measurements were successfully derived using a combined approach of R₁ and R2* relaxometry. Magn Reson Med 79:3072-3081, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Association of exposure to manganese and iron with relaxation rates R1 and R2*- magnetic resonance imaging results from the WELDOX II study

OBJECTIVE

Magnetic resonance imaging is a non-invasive method that allows the indirect quantification of manganese (Mn) and iron (Fe) accumulation in the brain due to their paramagnetic features. The WELDOX II study aimed to explore the influence of airborne and systemic exposure to Mn and Fe on the brain deposition using the relaxation rates R1 and R2* as biomarkers of metal accumulation in regions of interest in 161 men, including active and former welders.

MATERIAL AND METHODS

We obtained data on the relaxation rates R1 and R2* in regions that included structures within the globus pallidus (GP), substantia nigra (SN), and white matter of the frontal lobe (FL) of both hemispheres, as well as Mn in whole blood (MnB), and serum ferritin (SF). The study subjects, all male, included 48 active and 20 former welders, 41 patients with Parkinson's disease (PD), 13 patients with hemochromatosis (HC), and 39 controls. Respirable Mn and Fe were measured during a working shift for welders. Mixed regression models were applied to estimate the effects of MnB and SF on R1 and R2*. Furthermore, we estimated the influence of airborne Mn and Fe on the relaxation rates in active welders.

RESULTS

MnB and SF were significant predictors of R1 but not of R2* in the GP, and were marginally associated with R1 in the SN (SF) and FL (MnB). Being a welder or suffering from PD or HC elicited no additional group effect on R1 or R2* beyond the effects of MnB and SF. In active welders, shift concentrations of respirable Mn>100μg/m³ were associated with stronger R1 signals in the GP. In addition to the effects of MnB and SF, the welding technique had no further influence on R1.

CONCLUSIONS

MnB and SF were significant predictors of R1 but not of R2*, indicative of metal accumulation, especially in the GP. Also, high airborne Mn concentration was associated with higher R1 signals in this brain region. The negative results obtained for being a welder or for the techniques with higher exposure to ultrafine particles when the blood-borne concentration was included into the models indicate that airborne exposure to Mn may act mainly through MnB.

Co-resident plasmids travel together

Conjugative plasmids encode genes that enable them to transfer, by conjugation, from a given host cell to another cell. Conjugative transfer, despite being an important feature of conjugative plasmids, is not constitutive for most plasmids, the reason being that genes involved in horizontal transfer are mostly repressed. Only upon their transient de-repression are plasmids able to transfer horizontally. If host cells harbour multiple plasmids, their simultaneous transfer depends on simultaneous transient de-repression of all plasmids. If de-repression of different plasmids was random and independent events, simultaneous de-repression should be a rare event because the probability of simultaneous de-repression would be the product of the probabilities of de-repression of each plasmid. Some previous observations support this hypothesis, while others show that co-transfer of plasmids is more frequent than this reasoning indicates. Here, we show that co-transfer of multiple plasmids mainly results from non-independent events: the probability that all plasmids within a cell become de-repressed is much higher than if de-repression of plasmids genes were independent. We found a simple model for the probability of co-transfer: the plasmid having the lowest conjugation rates is the one who limits co-transfer. In this sense, cells receiving the plasmid with the lower transfer rate also receive the other plasmid. If de-repression happens simultaneously on co-resident plasmids, common cues may stimulate de-repression of distinct plasmids.

Multiple plasmid interference - Pledging allegiance to my enemy's enemy

As shown in the previous article, two distinct conjugative plasmids sometimes interact within bacterial cells, implicating changes of transfer rates. In most cases of interactions within bacteria, the transfer of one of the plasmids decreases. Less frequently, the transfer rate of one of the plasmids increases. Here we analyse what happens if three distinct conjugative plasmids colonize the same bacterial cell. Our aim is to understand how interactions between two plasmids affect the transfer rate of the third plasmid. After showing that plasmids interact in 59 out of 84 possible interactions we show that, with some exceptions, if the transfer rate of a plasmid decreases in the presence of a second plasmid, a decrease is also observed in the presence of a third plasmid. Moreover, if the conjugation rate of a plasmid increases in the presence of another, an increase is also observed if there is a third plasmid in the cell. Both types of interactions are mostly independent of the third plasmid's identity, even if sometimes the third plasmid quantitatively distorts the interaction of the other two plasmids. There is a bias towards negative intensifying interactions, which provide good news concerning the spread conjugative plasmids encoding antibiotic-resistance genes and virulence factors.

Conjugation efficiency depends on intra and intercellular interactions between distinct plasmids: Plasmids promote the immigration of other plasmids but repress co-colonizing plasmids

Conjugative plasmids encode the genes responsible for the synthesis of conjugative pili and plasmid transfer. Expression of the conjugative machinery (including conjugative pili) may be costly to bacteria, not only due to the energetic/metabolic cost associated with their expression but also because they serve as receptors for certain viruses. Consequently, the presence of two plasmids in the same cell may be disadvantageous to each plasmid, because they may impose a higher fitness cost on the host. Therefore, plasmids may encode mechanisms to cope with co-resident plasmids. Moreover, it is possible that the transfer rate of a plasmid is affected by the presence of a distinct plasmid in the recipient cell. In this work, we measured transfer rates of twelve natural plasmids belonging to seven incompatibility groups in three situations, namely when: (i) donor cells contain a plasmid and recipient cells are plasmid-free; (ii) donor cells contain two unrelated plasmids and recipient cells are plasmid-free; and (iii) half of the cells contain a given plasmid and the other half contain another, unrelated, plasmid. In the third situation, recipient cells of a plasmid are the donor cells of the other plasmid. We show that there are more negative interactions (reduction of a plasmid's conjugative efficiency) between plasmids if they reside in the same cell than if they reside in different cells. However, if plasmids interacted intercellularly, the transfer rate of one of the plasmids was often higher (when the unrelated conjugative plasmid was present in the recipient cell) than if the recipient cell was plasmid-free - a positive effect. Experimental data retrieved from the study of mutant plasmids not expressing conjugative pili on the cell surface suggest that positive effects result from a higher efficiency of mating pair formation. Overall, our results suggest that negative interactions are significantly more frequent when plasmids occupy the same cell. Such interactions may determine how antibiotic resistance disseminates in bacterial populations.

Welding-related brain and functional changes in welders with chronic and low-level exposure

Although an essential nutrient, manganese (Mn) can be toxic at high doses. There is, however, uncertainty regarding the effects of chronic low-level Mn-exposure. This review provides an overview of Mn-related brain and functional changes based on studies of a cohort of asymptomatic welders who had lower Mn-exposure than in most previous work. In welders with low-level Mn-exposure, we found: 1) Mn may accumulate in the brain in a non-linear fashion: MRI R1 (1/T1) signals significantly increased only after a critical level of exposure was reached (e.g., ≥300 welding hours in the past 90days prior to MRI). Moreover, R1 may be a more sensitive marker to capture short-term dynamic changes in Mn accumulation than the pallidal index [T1-weighted intensity ratio of the globus pallidus vs. frontal white matter], a traditional marker for Mn accumulation; 2) Chronic Mn-exposure may lead to microstructural changes as indicated by lower diffusion tensor fractional anisotropy values in the basal ganglia (BG), especially when welding years exceeded more than 30 years; 3) Mn-related subtle motor dysfunctions can be captured sensitively by synergy metrics (indices for movement stability), whereas traditional fine motor tasks failed to detect any significant differences; and 4) Iron (Fe) also may play a role in welding-related neurotoxicity, especially at low-level Mn-exposure, evidenced by higher R2* values (an estimate for brain Fe accumulation) in the BG. Moreover, higher R2* values were associated with lower phonemic fluency performance. These findings may guide future studies and the development of occupation- and public health-related polices involving Mn-exposure.

Reporting the margin in pancreaticoduodenectomies: R0 versus R1

AIM

This study was conducted to analyze the changes in margin positivity in pancreaticoduodenectomies, on using a standardized protocol, which bread loafs the pancreas and duodenum in the axial plane for adenocarcinomas arising in the pancreatic head, ampulla, terminal common bile duct (CBD), and duodenum, and then to assess whether these tumor subsets involve the margins in different ways.

METHODS

The analysis was performed on 70 consecutive specimens, the pre-protocol specimens serving as the control group.

RESULTS AND CONCLUSIONS

Tumors originating from the pancreatic head, ampulla, terminal CBD, and duodenum showed a consistent increase in their R1 incidence, post-protocol. Ampullary tumors showed the greatest upward change in R1 positivity. The highest incidence of margin positivity was seen in pancreatic head adenocarcinomas (80%), then distal CBD tumors (60%), and finally the ampullary tumors (39%). In pancreatic head adenocarcinomas, R1 increased from 55% to 80%, distal CBD from 50% to 60%, and ampullary from 17% to 39%. Duodenal adenocarcinomas had no R1 in both pre- and post-protocol groups. The tumors also had different patterns of margin involvement. Ampullary tumors involved only the posterior margin, pancreatic adenocarcinomas involved the superior mesenteric vein (SMV) groove more often than the posterior margin, and distal CBD tumors involved the posterior margin and SMV groove equally. The size of the tumor made a significant difference in pancreatic head carcinomas with tumor size less than or equal to 2 cm, showing an R1 incidence of 38%, while those above 2 cm had an R1 incidence of 68%.

Longitudinal T1 relaxation rate (R1) captures changes in short-term Mn exposure in welders

OBJECTIVES

We demonstrated recently that the T1 relaxation rate (R1) captured short-term Mn exposure in welders with chronic, relatively low exposure levels in a cross-sectional study. In the current study, we used a longitudinal design to examine whether R1 values reflect the short-term dynamics of Mn exposure.

METHODS

Twenty-nine welders were evaluated at baseline and 12 months. Occupational questionnaires estimated short-term welding exposure using welding hours in the 90days prior to each study visit (HrsW₉₀). In addition, blood Mn levels, the pallidal index (PI; globus pallidus T1-weighted intensity (T1WI)/frontal white matter T1WI), and R1 values in brain regions of interest (ROIs) were determined as Mn biomarkers at each visit. Associations between changes in estimated welding exposure and changes in purported Mn biomarkers were assessed by Spearman's correlations with adjustment for age and baseline R1, HrsW₉₀, and blood Mn values.

RESULTS

Changes in welding hours (HrsW₉₀: the short-term welding exposure estimate), was associated significantly with changes in R1 values in the putamen (r=0.541, p=0.005), caudate (R=0.453, p=0.023), globus pallidus (R=0.430, p=0.032), amygdala (R=0.461, p=0.020), and hippocampus (R=0.447, p=0.025), but not with changes in blood Mn levels or the PI.

DISCUSSION

Changes in R1 values correlated with changes in the short-term welding exposure estimate, but not with more traditional measures of Mn exposure (blood Mn levels or PI). These results suggest that R1 may serve as a useful marker to capture the short-term dynamics in Mn brain accumulation related to welding exposure.

R1 correction in amide proton transfer imaging: indication of the influence of transcytolemmal water exchange on CEST measurements

Amide proton transfer (APT) imaging may potentially detect mobile proteins/peptides non-invasively in vivo, but its specificity may be reduced by contamination from other confounding effects such as asymmetry of non-specific magnetization transfer (MT) effects and spin-lattice relaxation with rate R1 (=1/T1). Previously reported spillover, MT and R1 correction methods were based on a two-pool model, in which the existence of multiple water compartments with heterogeneous relaxation properties in real tissues was ignored. Such simple models may not adequately represent real tissues, and thus such corrections may be unreliable. The current study investigated the effectiveness and accuracy of correcting for R1 in APT imaging via simulations and in vivo experiments using tumor-bearing rats subjected to serial injections of Gd-DTPA that produced different tissue R1 values in regions of blood-brain-barrier breakdown. The results suggest that conventional measurements of APT contrast (such as APT* and MTRasym ) may be significantly contaminated by R1 variations, while the R1 -corrected metric AREX* was found to be relatively unaffected by R1 changes over a broad range (0.4-1 Hz). Our results confirm the importance of correcting for spin-lattice relaxation effects in quantitative APT imaging, and demonstrate the reliability of using the observed tissue R1 for corrections to obtain more specific and accurate measurements of APT contrast in vivo. The results also indicate that, due to relatively fast transcytolemmal water exchange, the influence of intra- and extracellular water compartments on CEST measurements with seconds long saturation time may be ignored in tumors.

Feasibility and reproducibility of BOLD and TOLD measurements in the liver with oxygen and carbogen gas challenge in healthy volunteers and patients with hepatocellular carcinoma

PURPOSE

To quantify baseline relaxation rates R2* and R1 in the abdomen, their changes after respiratory challenges, and their reproducibility in healthy volunteers and patients with hepatocellular carcinoma (HCC) at 1.5T and 3.0T.

MATERIALS AND METHODS

R2* measurements were acquired in the liver in 8 volunteers and 27 patients with 34 HCCs using multiecho T2* at baseline and after respiratory challenges with 100% oxygen (O2 ) and carbogen (CB = 95%O2 /5%CO2 ). R1 was measured at 1.5T in one volunteer and 21 patients with 23 HCCs. Test-retest coefficient of variation (CV) was assessed in 10 subjects. Intra- and interobserver variability of R2* and R1 measurements was assessed in 12 and 10 patients, respectively. Parameters for HCC, liver, and muscle were compared between baseline and after gas challenges.

RESULTS

We observed that R2* and R1 imaging of HCCs with O2 and CB is feasible and reproducible (test-retest CV R2*<15%/R1 <5%; intra- and interobserver intraclass correlation coefficient R2*>0.88/R1 >0.7 and CV R2*<7%/R1 <3% at 1.5T). R2* measurements were observed to be less reproducible at 3.0T (CV<35%). There was a statistically significant decrease in R2* values in HCC before and after O2 (P = 0.02) and increase in R1 after O2 (P = 0.004). CB had no significant effect (P R2* = 0.47/R1  = 0.278).

CONCLUSION

R2* measurements in HCC and liver parenchyma are more reproducible at 1.5T than at 3.0T, and with O2 than with CB challenge. We observed a decrease in R2* and an increase in R1 of HCCs from baseline in response to O2 challenge, as expected with increased tissue and blood oxygenation.

T1 Relaxation Rate (R1) Indicates Nonlinear Mn Accumulation in Brain Tissue of Welders With Low-Level Exposure

Although the essential element manganese (Mn) is neurotoxic at high doses, the effects of lower exposure are unclear. MRI T1-weighted (TIW) imaging has been used to estimate brain Mn exposure via the pallidal index (PI), defined as the T1W intensity ratio in the globus pallidus (GP) versus frontal white matter (FWM). PI may not, however, be sensitive to Mn in GP because Mn also may accumulate in FWM. This study explored: (1) whether T1 relaxation rate (R1) could quantify brain Mn accumulation more sensitively; and (2) the dose-response relationship between estimated Mn exposure and T1 relaxation rate (R1). Thirty-five active welders and 30 controls were studied. Occupational questionnaires were used to estimate hours welding in the past 90 days (HrsW) and lifetime measures of Mn exposure. T1W imaging and T1-measurement were utilized to generate PI and R1 values in brain regions of interest (ROIs). PI did not show a significant association with any measure of Mn and/or welding-related exposure. Conversely, in several ROIs, R1 showed a nonlinear relationship to HrsW, with R1 signal increasing only after a critical exposure was reached. The GP had the greatest rate of Mn accumulation. Welders with higher exposure showed significantly higher R1 compared either with controls or with welders with lower exposure. Our data are additional evidence that Mn accumulation can be assessed more sensitively by R1 than by PI. Moreover, the nonlinear relationship between welding exposure and Mn brain accumulation should be considered in future studies and policies.

Surgical management of microscopic positive resection margin after gastrectomy for gastric cancer: a systematic review of gastric R1 management

BACKGROUND

The prognosis after a curative resection for gastric cancer is modified by the lymph node involvement, while the prognostic significance of a microscopically-positive resection margin is debated. We systematically reviewed the literature from 1998 to 2013 to describe the role of surgery in the management of gastric cancer with a R1 after gastrectomy.

MATERIALS AND METHODS

The research was systematically performed on Pubmed, EMbase, Cochrane Library, CILEA Archive, BMJ Clinical Evidence and Up ToDate databases. Twelve studies were included in this review, for a total of 15,008 patients.

RESULTS

The results reported in literature are inconsistent and the impact of surgical and oncological therapies is unknown. Intraoperative frozen sections should be performed to achieve a negative margin with intraoperative re-excision.

CONCLUSION

A surgical re-excision of an R1 resection should be considered for patients with fewer than three disease-positive nodes because survival is more likely to be governed by positive margins than by nodal status.

Pathology of pancreatic ductal adenocarcinoma: Facts, challenges and future developments

Despite major improvements concerning its diagnosis and treatment, pancreatic ductal adenocarcinoma (PDAC) remains an aggressive disease with an extremely poor prognosis. Pathology, as interface discipline between basic and clinical medicine, has substantially contributed to the recent developments and has laid the basis for further progress. The definition and classification of precursor lesions of PDAC and their molecular characterization is a fundamental step for the potential identification of biomarkers and the development of imaging methods for early detection. In addition, by integrating findings in humans with the knowledge acquired through the investigation of transgenic mouse models for PDAC, a new model for pancreatic carcinogenesis has been proposed and partially validated in individuals with genetic predisposition for PDAC. The introduction and validation of a standardized system for pathology reporting based on the axial slicing technique has shown that most pancreatic cancer resections are R1 resections and that this is due to inherent anatomical and biological properties of PDAC. This standardized assessment of prognostic relevant parameters represents the basis for the successful conduction of multicentric studies and for the interpretation of their results. Finally, recent studies have shown that distinct molecular subtypes of PDAC exist and are associated with different prognosis and therapy response. The prospective validation of these results and the integration of molecular analyses in a comprehensive pathology report in the context of individualised cancer therapy represent a major challenge for the future.

Disentangling in vivo the effects of iron content and atrophy on the ageing human brain

Evidence from magnetic resonance imaging (MRI) studies shows that healthy aging is associated with profound changes in cortical and subcortical brain structures. The reliable delineation of cortex and basal ganglia using automated computational anatomy methods based on T1-weighted images remains challenging, which results in controversies in the literature. In this study we use quantitative MRI (qMRI) to gain an insight into the microstructural mechanisms underlying tissue ageing and look for potential interactions between ageing and brain tissue properties to assess their impact on automated tissue classification. To this end we acquired maps of longitudinal relaxation rate R1, effective transverse relaxation rate R2* and magnetization transfer - MT, from healthy subjects (n=96, aged 21-88 years) using a well-established multi-parameter mapping qMRI protocol. Within the framework of voxel-based quantification we find higher grey matter volume in basal ganglia, cerebellar dentate and prefrontal cortex when tissue classification is based on MT maps compared with T1 maps. These discrepancies between grey matter volume estimates can be attributed to R2* - a surrogate marker of iron concentration, and further modulation by an interaction between R2* and age, both in cortical and subcortical areas. We interpret our findings as direct evidence for the impact of ageing-related brain tissue property changes on automated tissue classification of brain structures using SPM12. Computational anatomy studies of ageing and neurodegeneration should acknowledge these effects, particularly when inferring about underlying pathophysiology from regional cortex and basal ganglia volume changes.

A general linear relaxometry model of R1 using imaging data

PURPOSE

The longitudinal relaxation rate (R1 ) measured in vivo depends on the local microstructural properties of the tissue, such as macromolecular, iron, and water content. Here, we use whole brain multiparametric in vivo data and a general linear relaxometry model to describe the dependence of R1 on these components. We explore a) the validity of having a single fixed set of model coefficients for the whole brain and b) the stability of the model coefficients in a large cohort.

METHODS

Maps of magnetization transfer (MT) and effective transverse relaxation rate (R2 *) were used as surrogates for macromolecular and iron content, respectively. Spatial variations in these parameters reflected variations in underlying tissue microstructure. A linear model was applied to the whole brain, including gray/white matter and deep brain structures, to determine the global model coefficients. Synthetic R1 values were then calculated using these coefficients and compared with the measured R1 maps.

RESULTS

The model's validity was demonstrated by correspondence between the synthetic and measured R1 values and by high stability of the model coefficients across a large cohort.

CONCLUSION

A single set of global coefficients can be used to relate R1 , MT, and R2 * across the whole brain. Our population study demonstrates the robustness and stability of the model.

Use of adjuvant chemotherapy (CT) and radiotherapy (RT) in incompletely resected (R1) early stage Non-Small Cell Lung Cancer (NSCLC): a European survey conducted by the European Society for Medical Oncology (ESMO) young oncologists committee

BACKGROUND

Early stage Non-Small Cell Lung Cancer (NSCLC) is potentially curable with surgery. ESMO guidelines recommend cisplatin-based adjuvant chemotherapy (CT) for completely resected stage II-III NSCLC. There is limited evidence for the use of adjuvant CT and/or radiotherapy (RT) in incompletely resected (R1) early stage NSCLC.

MATERIALS AND METHODS

A European survey of thoracic oncologists was conducted to evaluate use of adjuvant CT and RT for R1-resected NSCLC and to identify factors influencing treatment decisions. Demographics and information on clinical stage, regimens, cycles planned, radiotherapy sites, multidisciplinary management and discussion about inconclusive evidence with the patient were collected. Univariate and multivariate analyses were performed.

RESULTS

768 surveys were collected from 41 European countries. 82.9% of participants were medical oncologists; 49.3% ESMO members; 37.1% based in University Hospitals; 32.6% practicing oncology for over 15 years and 81.4% active in research. 91.4% of participants prescribed adjuvant CT and mostly cisplatin/vinorelbine (81.2%) or cisplatin/gemcitabine (42.9%). 85% discussed limited clinical evidence with the patient. In the univariate analysis, a statistically significant association with CT prescription was found for medical oncology specialty (p<0.001), ESMO membership (p<0.001), activity in clinical research (p=0.002) and increased frequency of ESMO guidelines consultation (p for trend <0.001). 48.3% of participants prescribed adjuvant RT and its prescription were associated with radiation oncology specialty (p<0.001), not being an ESMO member (p<0.001), years practicing specialty (p for trend=0.001), workload of lung cancer patients (p for trend=0.027) and decreased frequency in consulting ESMO guidelines (p<0.001). In the multivariate analysis, medical oncology and radiation oncology were the best discriminator for prescription of adjuvant CT and RT, respectively.

CONCLUSION

This survey demonstrates that adjuvant CT and RT are commonly used in clinical practice for R1-resected NSCLC despite limited evidence. Prospective trials are necessary to clarify optimal management in this setting.

Widespread age-related differences in the human brain microstructure revealed by quantitative magnetic resonance imaging

A pressing need exists to disentangle age-related changes from pathologic neurodegeneration. This study aims to characterize the spatial pattern and age-related differences of biologically relevant measures in vivo over the course of normal aging. Quantitative multiparameter maps that provide neuroimaging biomarkers for myelination and iron levels, parameters sensitive to aging, were acquired from 138 healthy volunteers (age range: 19–75 years). Whole-brain voxel-wise analysis revealed a global pattern of age-related degeneration. Significant demyelination occurred principally in the white matter. The observed age-related differences in myelination were anatomically specific. In line with invasive histologic reports, higher age-related differences were seen in the genu of the corpus callosum than the splenium. Iron levels were significantly increased in the basal ganglia, red nucleus, and extensive cortical regions but decreased along the superior occipitofrontal fascicle and optic radiation. This whole-brain pattern of age-associated microstructural differences in the asymptomatic population provides insight into the neurobiology of aging. The results help build a quantitative baseline from which to examine and draw a dividing line between healthy aging and pathologic neurodegeneration.

Absolute oxygen R1e imaging in vivo with pulse electron paramagnetic resonance

PURPOSE

Tissue oxygen (O2) levels are among the most important and most quantifiable stimuli to which cells and tissues respond through inducible signaling pathways. Tumor O2 levels are major determinants of the response to cancer therapy. Developing more accurate measurements and images of tissue O2 partial pressure (pO2), assumes enormous practical, biological, and medical importance.

METHODS

We present a fundamentally new technique to image pO2 in tumors and tissues with pulse electron paramagnetic resonance (EPR) imaging enabled by an injected, nontoxic, triaryl methyl (trityl) spin probe whose unpaired electron's slow relaxation rates report the tissue pO2. Heretofore, virtually all in vivo EPR O2 imaging measures pO2 with the transverse electron spin relaxation rate, R2e, which is susceptible to the self-relaxation confounding O2 sensitivity.

RESULTS

We found that the trityl electron longitudinal relaxation rate, R1e, is an order of magnitude less sensitive to confounding self-relaxation. R1e imaging has greater accuracy and brings EPR O2 images to an absolute pO2 image, within uncertainties.

CONCLUSION

R1e imaging more accurately determines oxygenation of cancer and normal tissue in animal models than has been available. It will enable enhanced, rapid, noninvasive O2 images for understanding oxygen biology and the relationship of oxygenation patterns to therapy outcome in living animal systems.