Use of Receiver Operating Curve Analysis and Machine Learning With an Independent Dose Calculation System Reduces the Number of Physical Dose Measurements Required for Patient-Specific Quality Assurance.

PURPOSE: Our purpose was to assess the use of machine learning methods and Mobius 3D (M3D) dose calculation software to reduce the number of physical ion chamber (IC) dose measurements required for patient-specific quality assurance during corona virus disease 2019. METHODS AND MATERIALS: In this study, 1464 inversely planned treatments using Pinnacle or Raystation treatment planning software (TPS) were delivered using Elekta Versa HD and Varian Truebeam and Truebeam STx linear accelerators between June 2018 and November 2019. For each plan, an independent dose calculation was performed using M3D, and an absolute dose measurement was taken using a Pinpoint IC inside the Mobius phantom. The point dose differences between the TPS and M3D calculation and between TPS and IC measurements were calculated. Agreement between the TPS and IC was used to define the ground truth plan failure. To reduce the on-site personnel during the pandemic, 2 methods of receiver operating characteristic analysis (n = 1464) and machine learning (n = 603) were used to identify patient plans that would require physical dose measurements. RESULTS: In the receiver operating characteristic analysis, a predelivery M3D difference threshold of 3% identified plans that failed an IC measurement at a 4% threshold with 100% sensitivity and 76.3% specificity. This indicates that fewer than 25% of plans required a physical dose measurement. A threshold of 1% on a machine learning model was able to identify plans that failed an IC measurement at a 3% threshold with 100% sensitivity and 54.3% specificity, leading to fewer than 50% of plans that required a physical dose measurement. CONCLUSIONS: It is possible to identify plans that are more likely to fail IC patient-specific quality assurance measurements before delivery. This possibly allows for a reduction of physical measurements taken, freeing up significant clinical resources and reducing the required amount of on-site personnel while maintaining patient safety.

Energy response calibration of photon-counting detectors using x-ray fluorescence: a feasibility study.

Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using x-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for x-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm(2) in detection area. The angular dependence of x-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded x-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of x-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of x-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic x-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the x-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory.

[Local health policies and health planning from the viewpoint of the decision-makers of the local authorities]. / Lokale Gesundheitspolitik und Gesundheitsplanung aus der Sicht der EntscheidungsträgerInnen des kommunalen politisch-administrativen Systems.

In 1997 the new law about Public Health Service (OGDG) in Northrhine-Westfalia was put into operation. It included two new sets of compulsory tasks: local health reporting (GBE) and local health conferences (KGK). These new tasks are installed as planning and steering instruments aiming for a better health-care on the local level. The central object is the knowledge-based formation of local health policies. Thereby, local representatives concerned with health and social services should participate as well as administrators and politicians. Since the middle of the 1990 s both new tasks have been established by the public health department of the county of Heinsberg in Northrhine-Westfalia. The experience of this department over almost ten years is the background for the empirical research project that is described in this paper. The study investigates the vocational practices, the decision-making and the health-related attitudes of the relevant local administrative and political representatives. The impulse for the start of the study was given by the constant reluctance of political and administrative top managers to make use of these new planning instruments in agenda setting and decision making. 44 high-ranking staff members and politicians (mayors, party chairmen, heads of departments far beyond the health office) were personally interviewed. Although they are not part of the health administration they claim to be occupied with quite a few health-related tasks. The overlapping of their set of tasks with the local health policies is evident for the interviewed managers. How-ever, this does not cause them to use the two new planning instruments. In particular, they do not participate in the local health conferences. They rather prefer the traditional path of policy making (parties, committees, fractions) even if these paths are less efficient than the new ones. The health conference is much more used by health-service providers as a platform for setting priorities and organising their implementation effectively. So far, the inclusion of the other local representatives (administrative managers, etc.) although they are concerned with health issues has not been achieved. This is also true for local politicians who are responsible for health-care policies. The authors of the paper see it to be the task of the local public health department to convince all these players that the health conference is a productive tool and a useful platform for the discussion of the health problems in the county and the coordination of necessary actions to be taken. The most important focus point is seen in the intersection of health policies with other local policies.

Indoor environment and respiratory symptoms in children living in the Dutch-German borderland.

OBJECTIVE: To investigate the relation between indoor environmental risk factors and respiratory symptoms in 7-8-year-old children living in the Dutch-German borderland. METHODS: A nested case-control study was conducted among children participating in a large longitudinal study on respiratory health. Parents of all 781 children with respiratory complaints and an equal number of randomly selected controls were asked to complete a questionnaire, including questions on indoor environment. RESULTS: The parents of 1191 children (76.2%) participated. Past exposure to environmental (OR = 2.73, 95% CI 1.14-6.67) as well as in utero exposure (OR = 2.28, 95% CI 1.15-4.53) to tobacco smoke, use of an unvented geyser for water heating (OR = 3.01, 95% CI 1.21-7.56), long-term exposure to dampness (OR = 2.98, 95% CI 1.10-8.28) or pets (OR = 2.18, 95% CI 1.39-3.42) increased the risk of asthmatic symptoms in 7-8-year-old children. A middle or low socio-economic status also increased the risk of asthmatic symptoms. An inverse association with asthmatic symptoms was seen for wall-to-wall carpeting (OR = 0.57, 95% CI 0.33-0.95) and insulation measures (OR = 0.46, 95% CI 0.25-0.83). Except for the presence of an unvented geyser, these environmental risk factors also presented a risk for coughing symptoms in children. CONCLUSION: This study showed an increased risk of respiratory symptoms in children exposed to several indoor environmental risk factors.

Tris(tert-butyl)phosphine sulfide, a phosphine sulfide with three bulky substituents.

The title compound, C12H27PS, has crystallographic C3 symmetry. The bond angles at phosphorus are tetrahedral [C--P--S 109.31 (12) degrees and C--P--C 109.63 (12) degrees ] and the P--C bond length is 1.899 (4) A. The shortest intermolecular contacts exist between methyl H atoms and the S atom (3.09, 3.12 and 3.28 A). A survey of various phosphine sulfides containing three equal ligands (Me3PS, Et3PS, Cy3PS, tBu3PS, etc.) shows the influence of substituents with different steric demand on the geometry at phosphorus and on the P--C bond length.

[Interreg II--European regional study of chronic respiratory tract diseases in children in the Germany-Netherlands border zone]. / Interreg II--Euregionale Untersuchungen zu chronischen Atemwegserkrankungen bei Kindern im deutsch-niederländischen Grenzraum.

AIM OF THE STUDY: In Westelijke Mijnstreek (WM), Midden-Limburg (ML), both The Netherlands, and Kreis Heinsberg (HS), Germany, the relationship between quality of the indoor environment and respiratory symptoms in children was studied, finally resulting in proposals for prevention of respiratory symptoms in the three regions. This paper presents the results of the first part of the study, investigating prevalences of respiratory complaints. METHODS AND RESULTS: A brief questionnaire was used to document prevalences of respiratory complaints, physicians diagnoses and treatment in about 7,000 children 5-6 resp. 7-8 years of age from HS, ML and WM, in 1995 and 1997. Prevalences of respiratory symptoms differed slightly between the regions, but there were differences in physician-diagnosed asthma and bronchitis and treatment of the children. PERSPECTIVES: The brief questionnaire is a useful instrument to get an overview on respiratory symptoms. Since 1995, it is used by several German Municipal Health Services for Public Health Reports.

[Community health documentation as an instrument for further developing recommendations in community health]. / Kommunale Gesundheitsberichterstattung als Instrument zur Weiterentwicklung von Handlungsempfehlungen auf kommunaler Ebene.

The local health conference in a North Rhine-Westphalian county of Germany has made proposals to improve immunisation rates against measles, mumps and rubella. Another target was to prevent decubitus by elderly patients in hospitals, nursing homes and in the outpatient nursing. Local public health reports were the basis for the development of (local) health targets in the health conference. The data of 12,830 immunisation papers from 11-19-year old students showed immunisation rates against measles, mumps and rubella from 44% to 14% depending on the type of school. Virus hepatitis B immunisation rates are 32% in the county. There were also great differences between local towns of the county. The decubitus data showed rates from 2.3% in nursing homes to 5.1% in the outpatient sector. It is also shown that health reports and health conferences help to improve local conditions in public and individual health.

Tris(tert-butyl)phosphine selenide, the missing link in tris(tert-butyl)phosphine chalcogenide structures (t)Bu(3)P==X (X = O, S, Se, Te).

In tris(tert-butyl)phosphine selenide, C(12)H(27)PSe, all the methyl ligands are disordered over two sites in the ratio 70/30. The molecule displays crystallographic C(3) symmetry. The bond angles at the P atom are distorted tetrahedral [C--P--C 110.02 (5) degrees and Se==P--C 108.91 (5) degrees ]. The P--C and P==Se bond lengths are 1.908 (1) and 2.1326 (6) A, respectively. A comparison of the structural data of the complete series of tris(tert-butyl)phosphine chalcogenides ((t)Bu(3)PO, (t)Bu(3)PS, (t)Bu(3)PSe and (t)Bu(3)PTe) with the corresponding data of other phosphine chalcogenides substituted by smaller organic groups shows the great influence of the bulky tert-butyl ligands.

Synthesis and biological evaluation of integrin antagonists containing trans- and cis-2,5-disubstituted THF rings.

The synthesis of a series of RGD mimetics is described. All compounds consist of a central 2,5-disubstituted tetrahydrofuran core, a variable linker to a guanidino group, and a beta-amino alanine unit to mimic the carboxylic acid. Three types of linkers were investigated: a simple four-atom methylene chain (type A, compounds 14, 15, 16, and 17), a four-atom methylene chain with an additional chiral center, and a nitrogen substituent (type B, compounds 38, 39, and 40), and an amide linker of different length with an additional chiral center (type C, compounds 59, 60, 61, and 62). A variety of compounds were tested as potential integrin antagonists in a receptor binding assay (alphaIIbbeta3, alphavbeta3, and alphavbeta5). The relative and absolute configuration of the chiral centers at the THF ring had a pronounced effect on the binding activity and selectivity. Compound 14 proved to be a selective inhibitor of alphaIIbbeta3 (IC50=20nM), whereas compound 40 exhibited high activity for binding of alphaIIbbeta3 (IC50=67nM) and alphavbeta3 (IC50=52nM).

Dimethylphenylsulfonium trifluoromethanesulfonate and methyldiphenylsulfonium trifluoromethanesulfonate.

The bonding geometry of sulfur in the cations of the title compounds, C(8)H(11)S(+).CF(3)SO(3)(-) and C(13)H(13)S(+).CF(3)SO(3)(-), respectively, is similar and is independent of the ratio of the Me/Ph substituents. As expected, in both cations, the S-Ph bonds are somewhat shorter than the S-Me bonds. In both crystal structures, the interaction between cations and anions is similar.

(1R*,2R*)-1,2-(2,3-Dimethoxybutane-2,3-dioxy)cyclohexane.

The title compound, 2,3-dimethoxy-2,3-dimethyl-5,6,7,8-tetrahydro-4-oxachroman, C(12)H(22)O(4), was synthesized as a model compound for substituted diequatorial fixed vicinal trans-cyclohexanediols.

Pyridinium dihydrogenmonothiophosphate.

By reaction of pyridine dithiomonometaphosphoryl fluoride with ethyldiphenylphosphine in the presence of traces of water, we isolated crystals of the title compound, (I). In the structure of this salt, two kinds of hydrogen bonds were detected. They link N-H (part of the cation), as well as one O-H group (part of the anion), to the phosphoryl O atom of the anion. The donor-acceptor distances are 2.654 (1) and 2.568 (1) A, respectively. The P-O and P-S bond lengths are 1.514 (2) and 1.967 (1) A, respectively, which fall therefore in the range of a 1.5-fold bond.

A monoclinic polymorph of bis(tert-butylperthiophosphonic) dianhydride.

In comparison with the known orthorhombic polymorph oftrans-2,4-di-tert-butyl-2,4-dithioxo-1,3-dithia-2,4-diphosphetane, C(8)H(18)P(2)S(4), (I) [Shore, Pennington, Noble & Cordes (1988). Phosphorous Sulfur, 39, 153-157], the new crystallographic modification is monoclinic and the corresponding solid density is markedly higher. In both structures, the molecules have 2/m symmetry imposed by space-group symmetry and all corresponding bond lengths and angles are equal within the limits of errors.

[Vaccination status and implementation of recommendations for vaccination with special reference to measles-mumps-rubella vaccination. 1995 program for school entrance]. / Impfstatus und Umsetzung von Impfempfehlungen unter besonderer Berücksichtigung der Masern-Mumps-Röteln-Impfung. Eine Aktion bei der Einschulung 1995.

Children who took part in the medical examination for elementary school starters and who could present a certificate of vaccination were given a written vaccination recommendation. On the first day of school the recommendation sheets filled out by the family doctor or a paediatrician were collected and analysed anonymously. 2194 of 2965 children received a vaccination recommendation. 1047 sheets could be interpreted. Based on the current recommendation of the STIKO (German official vaccination council) a MMR (measles, mumps, rubella) vaccination was suggested in 1001 cases. Only 53.1% of the proposed vaccinations have been given, despite consultation with the family doctor or paediatrician.