Nevin Manimala

Phys Med Biol. 2021 May 21. doi: 10.1088/1361-6560/ac03ca. Online ahead of print.

ABSTRACT

We propose a novel Prompt-Gamma (PG) imaging modality for real-time monitoring in proton therapy: PG Time Imaging (PGTI). By measuring the Time-Of-Flight (TOF) between a beam monitor and a PG detector, our goal is to reconstruct the PG vertex distribution in 3D. In this paper, a dedicated, non-iterative reconstruction strategy is proposed (PGTI reconstruction). Here, it was resolved under a 1D approximation to measure a proton range shift along the beam direction. In order to show the potential of PGTI in the transverse plane, a second method, based on the calculation of the Centre-Of-Gravity (COG) of the TIARA pixel detectors’ counts was also explored. The feasibility of PGTI was evaluated in two different scenarios. Under the assumption of a 100 ps (rms) time resolution (achievable in single proton regime), MC simulations showed that a millimetric proton range shift is detectable at 2σ with 10⁸incident protons in simplified simulation settings. With the same proton statistics, a potential 2 mm sensitivity (at 2σ with 10⁸incident protons) to beam displacements in the transverse plane was found using the COG method. This level of precision would allow to act in real-time if the treatment does not conform to the treatment plan. A worst case scenario of a 1 ns (rms) TOF resolution was also considered to demonstrate that a degraded timing information can be compensated by increasing the acquisition statistics: in this case, a 2 mm range shift would be detectable at 2σ with 10⁹incident protons. By showing the feasibility of a time-based algorithm for the reconstruction of the PG vertex distribution for a simplified anatomy, this work poses a theoretical basis for the future development of a PG imaging detector based on the measurement of particle TOF.

PMID:34020438 | DOI:10.1088/1361-6560/ac03ca

J Breath Res. 2021 May 21. doi: 10.1088/1752-7163/ac0414. Online ahead of print.

ABSTRACT

BACKGROUND: Current diagnostic testing for coronavirus disease 2019 (COVID-19) is based on detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in nasopharyngeal swab samples by reverse transcription polymerase chain reaction (RT-PCR). However, this test is associated with increased risks of viral dissemination and environmental contamination and shows relatively low sensitivity, attributable to technical deficiencies in the sampling method. Given that COVID-19 is transmitted via exhaled aerosols and droplets, and that exhaled breath condensate (EBC) is an established modality for sampling exhaled aerosols, detection of SARS-CoV-2 in EBC offers a promising diagnostic approach. However, current knowledge on the detection and load of the virus in EBC collected from COVID-19 patients remains limited and inconsistent. The objective of the study was to quantify the viral load in EBC collected from COVID-19 patients and to validate the feasibility of SARS-CoV-2 detection from EBC as a diagnostic test for the infection.

METHOD: EBC samples were collected from 48 COVID-19 patients using a collection device, and viral loads were quantified by RT-PCR targeting the E gene. Changes in detection rates and viral loads relative to patient characteristics and days since disease onset were statistically evaluated.

RESULTS: Need for mechanical ventilation was significantly associated with higher viral load (p<0.05). Need for oxygen administration or mechanical ventilation, less than 3 days since onset, and presence of cough or fever were significantly associated with higher detection rates (p<0.05). Among spontaneously breathing patients, viral load in EBC attenuated exponentially over time. The detection rate was 86% at 2 days since onset and deteriorated thereafter. In mechanically ventilated patients, detection rate and viral load were high regardless of days since onset.

CONCLUSION: These results support the feasibility of using RT-PCR to detect SARS-CoV-2 from EBC for COVID-19 patients within 2 days of symptom onset.

PMID:34020435 | DOI:10.1088/1752-7163/ac0414

Phys Med Biol. 2021 May 21. doi: 10.1088/1361-6560/ac03cb. Online ahead of print.

ABSTRACT

Online ion range monitoring in hadron therapy can be performed via detection of secondary radiation, such as prompt γ-rays, emitted during treatment. The prompt γ emission profile is correlated with the ion depth-dose profile and can be reconstructed via Compton imaging. The line-cone reconstruction, using the intersection between the primary beam trajectory and the cone reconstructed via a Compton camera, requires negligible computation time compared to iterative algorithms. A recent report hypothesised that time of flight (TOF) based discrimination could improve the precision of the γ fall-off position measured via line-cone reconstruction, where TOF comprises both the proton transit time from the phantom entrance until γ emission, and the flight time of the γ-ray to the detector. The aim of this study was to implement such a method and investigate the influence of temporal resolution on the precision of the fall-off position. Monte Carlo simulations of a 160 MeV proton beam incident on a homogeneous PMMA phantom were performed using GATE. The Compton camera consisted of a silicon-based scatterer and CeBr3 scintillator absorber. The temporal resolution of the detection system (absorber + beam trigger) was varied between 0.1 and 1.3 ns RMS and a TOF-based discrimination method applied to eliminate unlikely solution(s) from the line-cone reconstruction. The fall-off position was obtained for varying temporal resolutions and its precision obtained from its shift across 100 independent γ emission profiles compared to a high statistics reference profile. The optimal temporal resolution for the given camera geometry and 108 primary protons was 0.2 ns where a precision of 2.30 ± 0.15 mm (1σ) on the fall-off position was found. This precision is comparable to current state of-the-art Compton imaging using iterative reconstruction methods or 1D imaging with mechanically collimated devices, and satisfies the requirement of being smaller than the clinical safety margins.

PMID:34020434 | DOI:10.1088/1361-6560/ac03cb

J Neurosurg. 2021 May 21:1-9. doi: 10.3171/2020.11.JNS202580. Online ahead of print.

ABSTRACT

OBJECTIVE: Magnetic resonance imaging-guided focused ultrasound (MRgFUS) provides real-time monitoring of patients to assess tremor control and document any adverse effects. MRgFUS of the ventral intermediate nucleus (VIM) of the thalamus has become an effective treatment option for medically intractable essential tremor (ET). The aim of this study was to analyze the correlations of clinical and technical parameters with 12-month outcomes after unilateral MRgFUS thalamotomy for ET to help guide future clinical treatments.

METHODS: From October 2013 to January 2019, data on unilateral MRgFUS thalamotomy from the original pivotal study and continued-access studies from three different geographic regions were collected. Authors of the present study retrospectively reviewed those data and evaluated the efficacy of the procedure on the basis of improvement in the Clinical Rating Scale for Tremor (CRST) subscore at 1 year posttreatment. Safety was based on the rates of moderate and severe thalamotomy-related adverse events. Treatment outcomes in relation to various patient- and sonication-related parameters were analyzed in a large cohort of patients with ET.

RESULTS: In total, 250 patients were included in the present analysis. Improvement was sustained throughout the 12-month follow-up period, and 184 (73.6%) of 250 patients had minimal or no disability due to tremor (CRST subscore < 10) at the 12-month follow-up. Younger age and higher focal temperature (Tmax) correlated with tremor improvement in the multivariate analysis (OR 0.948, p = 0.013; OR 1.188, p = 0.025; respectively). However, no single statistically significant factor correlated with Tmax in the multivariate analysis. The cutoff value of Tmax in predicting a CRST subscore < 10 was 55.8°C. Skull density ratio (SDR) was positively correlated with heating efficiency (β = 0.005, p < 0.001), but no significant relationship with tremor improvement was observed. In the low-temperature group, 1-3 repetitions to the right target with 52°C ≤ Tmax ≤ 54°C was sufficient to generate sustained tremor suppression within the investigated follow-up period. The high-temperature group had a higher rate of balance disturbances than the low-temperature group (p = 0.04).

CONCLUSIONS: The authors analyzed the data of 250 patients with the aim of improving practices for patient screening and determining treatment endpoints. These results may improve the safety, efficacy, and efficiency of MRgFUS thalamotomy for ET.

PMID:34020416 | DOI:10.3171/2020.11.JNS202580

Food Chem. 2021 May 11;360:130056. doi: 10.1016/j.foodchem.2021.130056. Online ahead of print.

ABSTRACT

Metabolomics of complex biological matrices conducted by means of ¹H NMR leads to spectra suffering from severe signal overlapping. Previously, we have developed a high-resolution spectral treatment method to help solving this issue in ¹H NMR of triacylglycerols. In this work, we tested the potential of the developed method in the characterization and authentication of food products from animal origin using egg yolk as a model matrix. The approach consisted in a spectral deconvolution guided by the precision obtained on the deconvoluted peaks after reference lineshape adjustment of spectra. Thus, 135 peaks were quantitated and successfully used as biomarkers of origin, of hens breed, and of farming system. This required multivariate statistical analyses for classification. The same pool of variables allowed construction of multivariate quantitation models for individual fatty acids. Furthermore, minute amounts of conjugated fatty acids were quantitated and used as fingerprints of samples from backyard and free-range farming.

PMID:34020363 | DOI:10.1016/j.foodchem.2021.130056

Seizure. 2021 May 9;89:65-72. doi: 10.1016/j.seizure.2021.04.025. Online ahead of print.

ABSTRACT

OBJECTIVE: The differential diagnosis between epileptic and psychogenic nonepileptic seizures (PNES) is challenging, yet suspicion of PNES is crucial to rethink treatment strategies and select patients for diagnostic confirmation through video EEG (VEEG). We developed a novel scale to prospectively suspect PNES.

METHODS: First, we developed a 51-item scale in two steps, based upon literature review and panel expert opinion. A pilot study verified the applicability of the instrument, followed by a prospective evaluation of 158 patients (66.5% women, mean age 33 years) who were diagnosed for prolonged VEEG. Only epileptic seizures were recorded in 103 patients, and the other 55 had either isolated PNES or both types of seizures. Statistical procedures identified 15 items scored between 0 and 3 that best discriminated patients with and without PNES, with a high degree of consistency.

RESULTS: Internal consistency reliability of the scale for suspicion of PNES was 0.77 with Cronbach’s Alpha Coefficient and 0.95 with Rasch Item Reliability Index, and performance did not differ according to the patient’s gender. For a cut-off score of 20 (of 45) points, area under the curve was 0.92 (95% IC: 0.87-0.96), with an accuracy of 87%, sensitivity of 89%, specificity of 85%, positive predictive value of 77%, and negative predictive value of 94% (95% IC) for a diagnosis of PNES.

CONCLUSIONS: The scale for suspicion of PNES (SS-PNES) has high accuracy to a reliable suspicion of PNES, helping with the interpretation of apparent seizure refractoriness, reframing treatment strategies, and streamlining referral for prolonged VEEG.

PMID:34020344 | DOI:10.1016/j.seizure.2021.04.025

Soc Sci Med. 2021 May 6;280:113946. doi: 10.1016/j.socscimed.2021.113946. Online ahead of print.

ABSTRACT

INTRODUCTION: Many adolescents living with HIV in sub-Saharan Africa (SSA) experience poverty and have access to limited resources, which can impact HIV and mental health outcomes. Few studies have analyzed the impact of economic empowerment interventions on the psychosocial wellbeing of adolescents living with HIV in low resource communities, and this study aims to examine the mediating mechanism(s) that may explain the relationship between a family economic empowerment intervention (Suubi + Adherence) and mental health outcomes for adolescents (ages 10-16 at enrollment) living with HIV in Uganda.

METHOD: We utilized data from Suubi + Adherence, a large-scale six-year (2012-2018) longitudinal randomized controlled trial (N = 702). Generalized structural equation models (GSEMs) were conducted to examine 6 potential mediators (HIV viral suppression, food security, family assets, and employment, HIV stigma, HIV status disclosure comfort level, and family cohesion) to determine those that may have driven the effects of the Suubi + Adherence intervention on adolescents’ mental health.

RESULTS: Family assets and employment were the only statistically significant mediators during follow-up (β from -0.03 to -0.06), indicating that the intervention improved family assets and employment which, in turn, was associated with improved mental health. The proportion of the total effect mediated by family assets and employment was from 42.26% to 71.94%.

CONCLUSIONS: Given that mental health services provision is inadequate in SSA, effective interventions incorporating components related to family assets, employment, and financial stability are crucial to supporting the mental health needs of adolescents living with HIV in under-resourced countries like Uganda. Future research should work to develop the sustainability of such interventions to improve long-term mental health outcomes among this at-risk group.

PMID:34020312 | DOI:10.1016/j.socscimed.2021.113946

J Environ Manage. 2021 May 18;292:112739. doi: 10.1016/j.jenvman.2021.112739. Online ahead of print.

ABSTRACT

Climate change is affecting the growth and distribution of trees in the Chinese boreal forest. Such changes in China, the southern terminus of the extensive Eurasian boreal forests, reflect on the changes that could occur further north under a warming climate. Most studies have found that tree growth increases with increasing temperature and precipitation in boreal forests, but there is little observational evidence of the climate thresholds that might slow these growth rates at the more extreme temperatures which are predicted to occur under future global warming. Here, we examine growth responses of this dominant boreal tree species (Larix gmelinii) to climate based on the data from plantation sample plots across a broad region (40° 51′-52° 58’N, 118° 12’E-133° 42’E) in northeast China. From statistically significant fits to quadratic equations, temperature and precipitation are the important climatic factors determining tree growth in L. gmelinii plantations at two age classes (<10 year and 10-30 year-old stands). The maximum rates of tree height and diameter at breast height (DBH) were about 0.53 m/year and 0.46 cm/year at <10 year stands, and about 0.63 m/year and 0.60 cm/year at 10-30 year stands, respectively. For stands with the highest values of mean annual increment (MAI), the corresponding optimal mean annual temperature (MAT_opt) focused between 0.66 °C and 1.57 °C. The optimal mean annual precipitation (MAP_opt) between 663 mm and 708 mm produced the maximal growth increments. With mean annual temperature of -2.4 °C and precipitation of 470 mm averaged over 1954-2005 in Chinese boreal forest region as baseline, we conservatively estimated that trees in Chinese boreal forest appear to have higher growth potentials with the maximum temperature increase of 3.6 °C and precipitation increase of 40%.

PMID:34020307 | DOI:10.1016/j.jenvman.2021.112739

J Environ Manage. 2021 May 18;292:112733. doi: 10.1016/j.jenvman.2021.112733. Online ahead of print.

ABSTRACT

Timely and accurate monitoring of the spatiotemporal changes in drought is very important for the reduction in the social losses caused by drought. The Optimized Meteorological Drought Index (OMDI), originally established in southwestern China, showed great potential for drought monitoring over large regions on a large scale. However, the applicability of the index requires further evaluation, especially when used throughout China, which has a different agricultural divisions, variable climatic conditions, complex terrain and diverse land cover. In addition, the OMDI model relies on training data to construct local parameters for the model. On a large scale, it is of great significance to use multisource remote sensing data sets to construct OMDI model parameters. In this paper, the constrained optimization method was used to establish weights for the MODIS-derived Vegetation Conditional Index (VCI), TRMM-derived Precipitation Condition Index (PCI), and GLDAS-derived Soil Moisture Condition Index (SMCI) and calculate the OMDI based on the Standard Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI) and weather stations. The accuracy of the OMDI model was evaluated by using the correlation coefficient. Moreover, the spatiotemporal changes in drought were also analyzed through trend analysis, Mann-Kendall (MK) statistics and the Hurst index on the monthly and annual scales. The results showed that (1) the highest positive correlation between the OMDI and the SPI was SPI-1, which was higher than that for any other month interval, such as 3 months, 6 months, 9 months and 12 months of the SPI. The results indicated that the OMDI was suitable to monitor meteorological drought. (2) In the nine agricultural subareas in China, the degree of drought in the Yangtze River (DYR) area had the most severe evolution and change frequency. This region was very sensitive to drought in the past two decades. (3) The area with OMDI variation coefficient less than 0.1 accounted for 94%, indicating that the degree of drought fluctuates little; The linear tendency rate is 0.0004, and the area greater than 0 reaches 66.44%, indicating that the drought is developing in a lightning trend. (4) The Hurst index value is mostly higher than 0.5 (the area ratio is 56.31%), and the area of “Positive-Consistent” and “Negative- Opposite” accounted for 54.02%, indicating that more than half of China’s area drought changes will show a trend of mitigation in the future.

PMID:34020305 | DOI:10.1016/j.jenvman.2021.112733

Environ Int. 2021 May 18;156:106643. doi: 10.1016/j.envint.2021.106643. Online ahead of print.

ABSTRACT

Particulate radioactivity, a characteristic of particulate matter, is primarily determined by the abundance of radionuclides that are bound to airborne particulates. Exposure to high levels of particulate radioactivity has been associated with negative health outcomes. However, there are currently no spatially and temporally resolved particulate radioactivity data for exposure assessment purposes. We estimated the monthly distributions of gross beta particulate radioactivity across the contiguous United States from 2001 to 2017 with a spatial resolution of 32 km, via a multi-stage ensemble-based model. Particulate radioactivity was measured at 129 RadNet monitors across the contiguous U.S. In stage one, we built 264 base learning models using six methods, then selected nine base models that provide different predictions. In stage two, we used a non-negative geographically and temporally weighted regression method to aggregate the selected base learner predictions based on their local performance. The results of block cross-validation analysis suggested that the non-negative geographically and temporally weighted regression ensemble learning model outperformed all base learning model with the smallest rooted mean square error (0.094 mBq/m³). Our model provided an accurate estimation of particulate radioactivity, thus can be used in future health studies.

PMID:34020300 | DOI:10.1016/j.envint.2021.106643