Performance of binary MLC using real-time optical sensor feedback system.

The Radixact system (Accuray Inc., Sunnyvale, CA) is the latest platform release based on the TomoTherapy technology. The most recent system does not apply a leaf latency model correction after plan optimization to ensure the correct MLC leaf-open time (LOT) agreement between the TPS and machine delivery. The MLC uses optical sensors to measure the delivered LOTs in real-time and individual leaf-specific latency corrections are made to ensure agreement. The aim of this study was to assess the performance of the Radixact MLC with leaf-specific latency correction using the optical sensor's real-time feedback. Specifically, the study statistically evaluated the MLC LOT errors observed from 290 plan-specific quality assurance (PSQA) measurements. Repeatability testing was performed to quantify the uncertainty in the MLC feedback system delivery by analyzing > 1300 delivered treatment fractions throughout the course of radiotherapy. The clinical impact was evaluated by estimating the resulting dose difference in the patient targets due to the measured plan latencies. Our study measured an average plan latency equal to 2.0 ± 0.4 ms (0.6% ± 0.2%) for 290 PSQAs. Repeatability tests showed a mean standard deviation in plan latencies measuring 0.05 ms (0.02%). The deviation from the TPS in the mean target dose due to the plan latencies was estimated to be 0.0% ± 0.2% (range: -0.7%-1.1%). The current MLC system with real-time optical sensor feedback is capable of accurately delivering the TPS-generated sinograms. Repeatability test results showed that the system allows for high reliability in daily sinogram delivery. The MLC latency deviations were shown to have minimal clinical impact on the overall target dosimetry.

Early-phase pandemic in Italy: Covid-19 spread determinant factors.

Although the Covid-19 pandemic is still ongoing, the environmental factors beyond virus transmission are only partially known. This statistical study has the aim to identify the key factors that have affected the virus spread during the early phase of pandemic in Italy, among a wide set of potential determinants concerning demographics, environmental pollution and climate. Because of its heterogeneity in pollution levels and climate conditions, Italy provides an ideal scenario for an ecological study. Moreover, the selected period excludes important confounding factors, as different virus variants, restriction policies or vaccines. The short-term relationship between the infection maximum increase and demographic, pollution and meteo-climatic parameters was investigated, including both winter-spring and summer 2020 data, also focusing separately on the two seasonal periods and on North vs Centre-South. Among main results, the importance of population size confirmed social distancing as a key management option. The pollution hazardous role undoubtedly emerged, as NO2 affected infection increase in all the studied scenarios, PM2.5 manifested its impact in North of Italy, while O3 always showed a protective action. Whereas higher temperatures were beneficial, especially in the cold season with also wind and relative humidity, solar irradiance was always relevant, revealing several significant interactions with other co-factors. Presented findings address the importance of the environment in Sars-CoV-2 spread and indicated that special carefulness should be taken in crowded areas, especially if they are highly polluted and weakly exposed to sun. The results suggest that containment of future epidemics similar to Covid-19 could be supported by reducing environmental pollution, achieving safer social habits and promoting preventive health care for better immune system response, as an only comprehensive strategy.

Admission criteria in critically ill COVID-19 patients: A physiology-based approach.

INTRODUCTION: The COVID-19 pandemic required careful management of intensive care unit (ICU) admissions, to reduce ICU overload while facing limitations in resources. We implemented a standardized, physiology-based, ICU admission criteria and analyzed the mortality rate of patients refused from the ICU. MATERIALS AND METHODS: In this retrospective observational study, COVID-19 patients proposed for ICU admission were consecutively analyzed; Do-Not-Resuscitate patients were excluded. Patients presenting an oxygen peripheral saturation (SpO2) lower than 85% and/or dyspnea and/or mental confusion resulted eligible for ICU admission; patients not presenting these criteria remained in the ward with an intensive monitoring protocol. Primary outcome was both groups' survival rate. Secondary outcome was a sub analysis correlating SpO2 cutoff with ICU admission. RESULTS: From March 2020 to January 2021, 1623 patients were admitted to our Center; 208 DNR patients were excluded; 97 patients were evaluated. The ICU-admitted group (n = 63) mortality rate resulted 15.9% at 28 days and 27% at 40 days; the ICU-refused group (n = 34) mortality rate resulted 0% at both intervals (p < 0.001). With a SpO2 cut-off of 85%, a significant correlation was found (p = 0.009), but with a 92% a cut-off there was no correlation with ICU admission (p = 0.26). A similar correlation was also found with dyspnea (p = 0.0002). CONCLUSION: In COVID-19 patients, standardized ICU admission criteria appeared to safely reduce ICU overload. In the absence of dyspnea and/or confusion, a SpO2 cutoff up to 85% for ICU admission was not burdened by negative outcomes. In a pandemic context, the SpO2 cutoff of 92%, as a threshold for ICU admission, needs critical re-evaluation.

Low PEEP Mechanical Ventilation and PaO2/FiO2 Ratio Evolution in COVID-19 Patients.

Invasive mechanical ventilation (IMV) is the standard treatment in critically ill COVID-19 patients with acute severe respiratory distress syndrome (ARDS). When IMV setting is extremely aggressive, especially through the application of high positive-end-expiratory respiration (PEEP) values, lung damage can occur. Until today, in COVID-19 patients, two types of ARDS were identified (L- and H-type); for the L-type, a lower PEEP strategy was supposed to be preferred, but data are still missing. The aim of this study was to evaluate if a clinical management with lower PEEP values in critically ill L-type COVID-19 patients was safe and efficient in comparison to usual standard of care. A retrospective analysis was conducted on consecutive patients with COVID-19 ARDS admitted to the ICU and treated with IMV. Patients were treated with a lower PEEP strategy adapted to BMI: PEEP 10 cmH2O if BMI < 30 kg m-2, PEEP 12 cmH2O if BMI 30-50 kg m-2, PEEP 15 cmH2O if BMI > 50 kg m-2. Primary endpoint was the PaO2/FiO2 ratio evolution during the first 3 IMV days; secondary endpoints were to analyze ICU length of stay (LOS) and IMV length. From March 2 to January 15, 2021, 79 patients underwent IMV. Average applied PEEP was 11 ± 2.9 cmH2O for BMI < 30 kg m-2 and 16 ± 3.18 cmH2O for BMI > 30 kg m-2. During the first 24 h of IMV, patients' PaO2/FiO2 ratio presented an improvement (p<0.001; CI 99%) that continued daily up to 72 h (p<0.001; CI 99%). Median ICU LOS was 15 days (10-28); median duration of IMV was 12 days (8-26). The ICU mortality rate was 31.6%. Lower PEEP strategy treatment in L-type COVID-19 ARDS resulted in a PaO2/FiO2 ratio persistent daily improvement during the first 72 h of IMV. A lower PEEP strategy could be beneficial in the first phase of ARDS in critically ill COVID-19 patients.

Indoor gaseous air pollutants determinants in office buildings-The OFFICAIR project.

The aim of this study was to identify determinants of aldehyde and volatile organic compound (VOC) indoor air concentrations in a sample of more than 140 office rooms, in the framework of the European OFFICAIR research project. A large field campaign was performed, which included (a) the air sampling of aldehydes and VOCs in 37 newly built or recently retrofitted office buildings across 8 European countries in summer and winter and (b) the collection of information on building and offices' characteristics using checklists. Linear mixed models for repeated measurements were applied to identify the main factors affecting the measured concentrations of selected indoor air pollutants (IAPs). Several associations between aldehydes and VOCs concentrations and buildings' structural characteristic or occupants' activity patterns were identified. The aldehyde and VOC determinants in office buildings include building and furnishing materials, indoor climate characteristics (room temperature and relative humidity), the use of consumer products (eg, cleaning and personal care products, office equipment), as well as the presence of outdoor sources in the proximity of the buildings (ie, vehicular traffic). Results also showed that determinants of indoor air concentrations varied considerably among different type of pollutants.

Practical application of Octavius® -4D: Characteristics and criticalities for IMRT and VMAT verification.

Octavius® -4D is a very effective device in radiotherapy treatment quality assurance (QA), due to its simple set-up and analysis package. However, even if it is widely used, its main characteristics and criticalities were only partially investigated. Taking start from its commissioning, the aim of this work was to study the main dependencies of the device response. The outcome dependence was studied comparing results by different delivery techniques [Intensity Modulated Radiation Therapy, IMRT (n = 29) and RapidArc, RA (n = 15)], anatomical regions [15 head/neck, 19 pelvis and 10 pancreas] and linear accelerators [DHX (n = 14) and Trilogy (n = 30)]. Moreover, the agreement dependency on the section of the phantom was assessed. Plan evaluations obtained by 2D, 3D, and volumetric γ-index (both local and global) were also compared. Generally, high dose gradient resulted critically managed by the assembly, with a smoother effect in RA technique. Worse agreements emerged in the 2D γ-index vs those of 3D and volumetric (P < 0.001), that were instead statistically comparable in global metric (P > 0.300). Volumetric plan evaluation was coherent with the average of passing rates on the 3 phantom axes (r ≥ 0.9), but transversal section provided best agreements vs sagittal and coronal ones (P < 0.050). The three studied districts furnished comparable results (P > 0.050) while the two LINACs provided different agreements (P < 0.005). The study pointed out that the phantom transversal section better fits the planned dose distribution, so this should be accounted when a two-dimensional evaluation is needed. Moreover, the major reliability of the 3D metric with respect to the 2D one, as it better agrees with the dosimetric evaluation on the whole volume, suggests that it should be preferred in a two-dimensional evaluation. Better agreements, obtained with RA vs IMRT technique, confirm that Octavius® -4D is specifically conceived for rotational delivery. Lastly, the assembly resulted sensitive to different technology.

Accuracy of TomoEDGE dynamic jaw field widths.

Dynamic jaw delivery on the TomoTherapy H-series platform, entitled TomoEDGE™, is an effective tool to decrease the patient dose along the superior and inferior edges of the treatment target. The aperture of the TomoTherapy jaws, that is, field width (FW), defines the longitudinal dose profile. A consistent FW dose profile is an important quantity for accurate and reproducible dose delivery in TomoTherapy. To date, no evaluation has been made of the accuracy and precision of the dose profiles produced by dynamic jaws. This study aims to provide a long-term evaluation of the dynamic jaw FW dose profiles obtained on TomoTherapy utilizing the TomoTherapy Quality Assurance procedure (TQA). A total of 840 dose profiles were measured during 84 TQA procedures, performed over a 2-yr period. The full width at half maximum (FWHM) and constancy of the FW dose profile measurements were analyzed and compared with the tolerances proposed by AAPM Task Group 148 (TG-148) and those used by the manufacturer. The FWHM evaluation showed that the FWs > 2.0 cm respect the TG-148 tolerance of 1%, while the asymmetric FWs ≤ 2.0 cm were outside the limit in 17.3% of measurements. Constancy results evaluated along the full profiles showed that 95.2% of measurements were within 3% of the baseline for symmetric FWs and 94.8% of measurements were within 4% of the baseline for asymmetric FWs. In conclusion, the analysis confirms the accuracy and precision of TomoEDGE™ technology in jaw positioning. This study has identified the potential to establish an appropriate QA tolerance for the asymmetric FWs used in dynamic jaw movement. Finally, the clinical significance of the observed discrepancies should be studied further to understand the dosimetric effect on patient treatments.

Particulate-bound polycyclic aromatic hydrocarbon sources and determinants in residential homes.

Human exposure to polycyclic aromatic hydrocarbons (PAHs) in indoor environments can be particularly relevant because people spend most of their time inside buildings, especially in homes. This study aimed to investigate the most important particle-bound PAH sources and exposure determinants in PM2.5 samples collected in 19 homes located in northern Italy. Complementary information about ion content in PM10 was also collected in 12 of these homes. Three methods were used for the identification of PAH sources and determinants: diagnostic ratios with principal component and hierarchical cluster analyses (PCA and HCA), chemical mass balance (CMB) and linear mixed models (LMMs). This combined and tiered approach allowed the infiltration of outdoor PAHs into indoor environments to be identified as the most important source in winter, with a relevant role played by biomass burning and traffic exhausts to be identified as a general source of PAHs in both seasons. Tobacco smoke exhibited an important impact on PAH levels in smokers' homes, whereas in the whole sample, cooking food and natural gas sources played a minor or negligible role. Nitrate, sulfate and ammonium were the main inorganic constituents of indoor PM10 owing to the secondary formation of ammonium sulfates and nitrates.

[Evaluation of radon levels in bank buildings: results of a survey on a major Italian banking group]. / Valutazione delle concentrazioni di radon nel settore bancario: risultati di una indagine condotta in un gruppo bancario di rilevanza nazionale.

UNLABELLED: Radon, the second cause of lung cancer after smoking, is a natural, radioactive gas, which originates from the soil and pollutes indoor air, especially in closed or underground spaces. Italian legislation recommends an action level of 500 Bq/m3 per year for occupational exposure in underground premises. OBJECTIVES: Since banks usually use various underground premises (archives, safe-deposit room), a study was made of the radon levels on such premises with the aim of identifying useful monitoring strategies. METHODS: 134 branches of a major Italian banking group were examined using 1817 nuclear track dosimeters at ground level and underground level premises. The branches were located in 7 Italian regions in the north (Piedmont, Lombardy, Veneto), centre (Lazio) and south (Campania, Apulia, Sicily). Information on measurement points was recorded in a technical sheet and statistical analysis was carried out. RESULTS: Annual underground measurements gave an average concentration of 157 Bq/m3, with 5.1% for 400 < C < 500 Bq/m3 and 2.9%for C > 500 Bq/m3. Seasonal variability was reflected in a significant decrease in concentrations between winter and spring (delta(mean)% = -47.3%) and good stability between autumn and winter (delta(mean)% = 3%); moreover quarterly concentrations account for 85% of the variability of the corresponding annual level. A multiple linear regression model (R2 = 0.33) indicated geographic location as the principal factor in radon accumulation, followed by underground level, humidity, use, lack of windows, heating and natural ventilation, and direct contact of at least one wall with ground rock; whereas the safe-deposit room structure seems to protect from radon accumulation. Moreover, the ground level measurement results were significantly associated with the corresponding underground average concentrations (p < 0.001). CONCLUSIONS: The results could be a useful tool in planning a monitoring strategy for assessment of bank worker exposure, especially for banking groups with a large number of branches.