[en] Portal images have a unique feature among the imaging modalities used in radiotherapy: they provide direct visualization of the irradiated volumes. However, contrast and spatial resolution are strongly limited due to the high energy of the radiation sources. Because of this, imaging modalities using x-ray energy beams have gained importance in the verification of patient positioning, replacing portal imaging.

The purpose of this work was to develop a method for the enhancement of local contrast in portal images. The method operates in the sub-bands of a wavelet decomposition of the image, re-scaling them in such a way that coefficients in the high and medium resolution sub-bands are amplified—an approach totally different from those operating on the image histogram, widely used nowadays.

Portal images of an anthropomorphic phantom were acquired in an electronic portal imaging device. Then, different re-scaling strategies were investigated, studying the effects of the scaling parameters on the enhanced images. Also, the effect of using different types of transform was studied. Finally, the implemented methods were combined with histogram equalization methods like the contrast limited adaptive histogram equalization, and these combinations were compared.

Uniform amplification of the detail sub-bands shows the best results in contrast enhancement. On the other hand, linear re-escalation of the high resolution sub-bands increases the visibility of fine detail in the images, at the expense of an increase in noise levels. Also, since processing is applied only to detail sub-bands, not to the approximation, the mean gray level of the image is minimally modified and no further display adjustments are required.

It is shown that re-escalation of the detail sub-bands of portal images can be used as an efficient method for the enhancement of both the local contrast and the resolution of these images. (paper)

[en] The noise power spectrum (NPS) of a digital x-ray imaging device is usually estimated from the average of periodograms of ROIs in images obtained with uniform radiation fields. The purpose of this work was developing a new estimator for calculating the NPS and comparing its uncertainties with those of the smoothed periodogram.

The new estimator is built by removing those addends in the summation of the periodogram that do not contain information on stochastic noise. This was carried out by applying a short-length lag window to the autocorrelation function of noise. The length of the window was obtained from the support of this function. It has to be large enough not to eliminate information on noise autocorrelation and it has be as short as possible to minimize uncertainty. In this work, this length was set to three times the support of the autocorrelation function of noise.

The new truncated sum (TS) estimator is shown to be unbiased and to have a much higher precision than that of the periodogram. The combined process of applying lag windows to the autocorrelation function of noise and removing addends with null expected values from the periodogram summation has a double effect on NPS curves. On the one hand, the curves are smoothed and, on the other hand, the uncertainties in the calculated values are highly reduced. (paper)

[en] The noise power spectrum (NPS) of a digital x-ray imaging device is usually estimated from the average of periodograms of regions of interest (ROIs) in images obtained with uniform radiation fields. In order to mitigate low frequency trends, present in the images and not arising from stochastic processes, detrending methods are applied to the images before being Fourier transformed. The most common of these methods subtracts a second-order polynomial fit from the image.

In this work, it is shown that the characteristics of low frequency trends can deviate from the quadratic dependence on spatial coordinates. This results in large residual trends that give rise to important correlations in the detrended images and produce an inaccurate rise of the NPS calculations at low frequencies.

A new detrending method of uniform images is presented. The method operates in the subbands of a wavelet transform, removing the low frequency contents of the uniform image. To do this, the approximation subband of the highest level of the wavelet transform is cancelled.

The effect on the NPS calculations for three digital detectors is shown and the importance of the parameters of the wavelet transform is discussed. The main result states that the performance of the new method improves those of two polynomial detrending methods commonly used and is close to the performance of the subtraction of uniform exposure images method.

Finally, guidelines for the implementation of the procedure, like the number of levels in the wavelet decomposition, are provided. As the number of levels in the wavelet transform increases, the removal of trends is restricted to lower frequencies. The selection of the number of levels should be guided by the shape of the autocorrelation function of the detrended image, which has to resemble the shape expected from the propagation of noise through the imaging chain. (paper)

[en] The optical density (OD) range for the scanners used in film dosimetry is limited due to saturation and noise. As the OD increases, saturation causes the rate of change of the output with respect to the input to become smaller, while at the same time noise remains fairly constant or increases. The combined effect leads to a degradation of the signal-to-noise ratio (SNR) at high optical densities. In this study, the uncertainty in the OD measurement, d_m, is expressed as a function of the optical density d. The functional relationship obtained gives the amplitude w of an interval around d in which d_m will be found with a given probability p. The relationship w = w(d, p) is later used to determine which OD ranges fulfil a set of requirements on w and p. As an application of the procedure, the noise and saturation characteristics of a commercial film digitizer system are measured. Their contribution to the uncertainties of the dosimetric procedure is reported, and the data are used to provide an optical density range for a given uncertainty and confidence level associated with the digitizer. These data can be further combined with the data from other sources of noise such as film noise in order to estimate the final uncertainty of the dosimetric process. (note)

[en] Based on experience gathered during the pilot actions in the cities of Lisbon, Lyon, Malmoe, Munich, Paris and Vitoria-Gasteiz, these guidelines were developed to support the adaptation of urban planning procedures with the aim of boosting solar energy in cities or towns. POLIS - identification and mobilisation of solar potentials via local strategies was a European project co-funded by the Intelligent Energy - Europe (IEE) programme aiming at the implementation of strategic urban planning and local policy measures to activate the solar ability of urban structures in European cities. The POLIS partners have identified a total of ten guidelines necessary to implement a coherent planning policy in favour of solar energy. They address how to identify and mobilise the solar potential, optimise solar urban planning processes, and adapt local policies and legislation. Each of the ten guidelines (covering the entire process from data collection to policy development and legislation), solar urban planning tools and practices, and participation of citizens will help replicate these successful experiences in other cities, benefiting from the lessons learned in practice. All the guidelines are presented in a standard format. They: provide a short description of the background and general approach, propose concrete methods and instruments, offer tips on necessary local conditions and which partners to involve, highlight financial aspects, analyse success factors as well as risks and barriers, specify necessary input, results and outcomes, describe - wherever possible - the impact on greenhouse gas emissions, and refer to lessons learned during the POLIS pilot actions. In order to know more about the legal and technical framework of each country of city partner, country conditions sheet are attached in appendix for France, Germany, Portugal and Spain

[en] A new strategy integrating the straight synthesis of carbon dots (CDs) and their direct use for the determination of heavy metals by means of fluorescence quenching is presented. The proposal consists of a modular analyzer, which includes a low temperature co-fired ceramics (LTCC) microreactor for the synthesis of CDs and a cyclic olefin copolymer (COC) microfluidic platform, which automatically performs a reverse flow injection analysis (rFIA) protocol for the determination of heavy metal ions in water by CD fluorescence quenching. As a proof of concept, nitrogen-doped CDs were synthesized from acrylic acid and ethylenediamine (ED) with quantum yields (QYs) of up to 44%, which are selective to cobalt. With the described system, we synthesized homogeneous CDs without the need for further purification and with the minimum consumption of reagents, and optimized fluorescence measurements can be performed with freshly obtained luminescent nanomaterials that have not undergone decomposition processes. They have an average hydrodynamic diameter of 4.2 ± 0.9 nm and maximum excitation and emission wavelengths at 358 nm and 452 nm, respectively. The system allows the automatic dilution and buffering of the synthesized CDs and the sample prior to the determination of cobalt. The concentration of cobalt was determined with good sensitivity and a limit of detection of 7 μg·L⁻¹ with a linear range of 0.02–1 mg·L⁻¹ of Co²⁺. Spiked tap water and river water samples were analyzed, obtaining recovery from 98 to 104%. This demonstrates the potential of the equipment as an efficient on-site control system for heavy metal monitoring in water. Graphical abstract

[en] In this work poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with ethylene glycol (EG) and SnO or SnO${}_2$ nanoparticles are mixed in a controlled way to create hybrid composites in form of thin films via spin coating. The potential applicability of these composites as gas sensors and as thermoelectric materials is tested, while insights are achieved in the comprehension of the underlying physical mechanisms. The addition of SnO in the composite promotes an enhancement in the chemoresistive response upon ethanol gas exposure at room temperature. Based on the Seebeck coefficient and Hall effect measurements, improvement of the power factor (PF) is achieved by the controlled addition of SnO nanoparticles in the composite. These results promise well for progress in the use of hybrid composites in these areas paving the way for future improvement in research on hybrid electronics, involving improved scalability and energy saving. (© 2022 Wiley‐VCH GmbH)

[en] Radiation Protection issues concerning patients, public and staff must be considered carefully in hemodialysis for chronic renal failure patients scheduled for ¹³¹I high dose therapy. In order to assess the risks related to this medical procedure, hemodialysis clearance of ¹³¹I and contamination measurements were carried out. We have studied 12 hemodialysis procedures corresponding to 2 cases of hyperthyroidism disease (555MBq of ¹³¹I administered) and 3 patients with carcinoma of the thyroid (5550 MBq of ¹³¹I administered). The arterio-venous difference of ¹³¹I across the artificial kidney and dose rate reduction at one meter of patient were measured. Contamination levels of the dialyser machine, filters and tubes were measured after dialysis with a contamination monitor. Direct read-out dosimeters were used to assess the radiation doses to nursery staff involved. The result obtained for mean ¹³¹I clearance in blood was 75±11%. The mean dose rate reduction at one meter of the patient was 58±18%. We also checked that contamination levels for the dialyser machine, filters, tubes and accessories were lower than 10Bq/cm². For the nursery staff the radiation dose was found to be lower than 0.1mSv. (author)

[en] Intra-lot, inter-scan and other variabilities in radiochromic film dosimetry may have a severe impact on absolute dosimetry with this dosimeter. In the literature, several dosimetry protocols may be found characterized by different calibration functions and different film response variables. Also, the re-calibration methods found in the literature correct and minimize the impact of the variabilities in the absolute dose estimates. In this work, several recalibration methods and dosimetry protocols are evaluated. In order to find optimal configurations, their accuracy is compared, and the accuracy level that can be reached in each case is discussed. The efficient protocol and the parameter escalation are used to recalibrate EBT3 films from two different film batches. The mean absolute deviations between known doses and estimated doses for eight dose levels are obtained and compared with the self calibration of each reading, named intrinsic film calibration. Eight film sheets from two different lots and two digitizers are used. The parameter escalation method with a four-level recalibration using net optical density (NOD) and a power law as dosimetry protocol obtains the highest accuracy. Regarding the number of control strips, increasing the number from two to three makes the parameter escalation protocol to come close to intrinsic film calibration in all cases, but has a less important effect on the efficient protocol. Regardless the choice of the sensitometric variables, using the appropriate recalibration method results in accuracy levels typical of self calibration of the film. In addition, the parameter escalation method provides better results than the efficient protocol with three calibration strips. (paper)

[en] The small fields in radiotherapy are widely used due to the development of techniques such as intensity-modulated radiotherapy and stereotactic radio surgery. The measurement of the dose distributions for small fields is a challenge. A perfect dosimeter should be independent of the radiation energy and the dose rate and should have a negligible volume effect. The radiochromic (RC) film characteristics fit well to these requirements. However, the response of RC films and their digitizing processes present a significant spatial inhomogeneity problem. The present work uses a method for two-dimensional (2D) measurement with RC films based on the reduction of the spatial inhomogeneity of both the film and the film digitizing process. By means of registering and averaging several measurements of the same field, the inhomogeneities are mostly canceled. Measurements of output factors (OFs), dose profiles (in-plane and cross-plane), and 2D dose distributions are presented. The field sizes investigated are 0.5 × 0.5 cm², 0.7 × 0.7 cm², 1 × 1 cm², 2 × 2 cm², 3 × 3 cm², 6 × 6 cm², and 10 × 10 cm² for 6 and 15 MV photon beams. The OFs measured with the RC film are compared with the measurements carried out with a PinPoint ionization chamber (IC) and a Semiflex IC, while the measured transversal dose profiles were compared with Monte Carlo simulations. The results obtained for the OFs measurements show a good agreement with the values obtained from RC films and the PinPoint and Semiflex chambers when the field size is greater or equal than 2 × 2 cm². These agreements give confidence on the accuracy of the method as well as on the results obtained for smaller fields. Also, good agreement was found between the measured profiles and the Monte Carlo calculated profiles for the field size of 1 × 1 cm². The presented method can be used to perform accurate measurements of small fields. (author)