IR Source Research Articles

Interstitial Brachytherapy for Locally Advanced Tongue Cancer: Analysis of the Long-Term Treatment Results for Survival and Complications

<h3>Purpose/Objective(s)</h3> The purpose of this study was to evaluate the long-term treatment results of interstitial brachytherapy (IBT) in patients with locally advanced tongue cancer. <h3>Materials/Methods</h3> between 1994 and 2015, 60 patients (18 females and 42 males) with locally advanced tongue cancer treated by IBT using Ir-192 sources and Au-198 seeds were analyzed. The median age was 63 years (range, 22–86 years). All histological type was squamous cell carcinoma. T3/T4a/T4b was noted in 51/9/0 patients, respectively. The median depth of invasion was 11 mm (3–27 mm). The growth type was infiltrative/exophytic/superficiality in 54/0/6 patients, respectively. In all cases, no lymph node metastasis was not found at diagnosis. IBT was performed using Ir-192 in 56 patients and Au-198 in 4 patients. Median irradiation doses of Ir-192 and Au-198 were 60 Gy (29–77 Gy) and 68 Gy (64–73 Gy), respectively. External beam radiation therapy (EBRT) was performed before IBT in 41 patients (68%). Median dose of EBRT was 30 Gy (30–50 Gy). Chemotherapy was combined with IBT in 42 patients. <h3>Results</h3> Median follow-up time for survivors was 103 months (36–230 months). CR rate was 98%. The 10-year overall/cause specific survival (OS, CSS) rate was 67/84%, respectively. According to T factors, the 10-year OS/CSS rates for T3 and T4a were 64/85% and 77/77%, respectively. There was no significant difference in OS and CSS between T3 and T4a. The10-year local/regional control rates were 78/72%, respectively. The 75% of the regional metastasis was occurred within 1 year, and more than 90% was within 2 years. The 10-year local control rates for T3 and T4a were 75% and 88%, respectively. The 10-year regional control rates for T3 and T4a were 71% and 77%, respectively. There was no significant difference in local/regional control between T3 and T4a. In the multivariate analysis, significant differences in OS were seen with elderly age, patients having double cancer and having late regional lymph node recurrence. According to CTCAE ver. 5.0, grade 2 soft tissue complications were observed in 33 (55%) patients and grade 2 mandibular complications in 2 (3%) patients. There were no grade 3 or more late complications. <h3>Conclusion</h3> Our 10-year treatment results of IBT for locally advanced tongue cancer showed favorable survival and low occurrence rate in patients with severe late complications.

Proposed Model of Dose Escalation in Localized Pancreatic Cancer Patients Eligible for Surgical Exploration: Neoadjuvant Intensity Modulated Radiation Therapy (IMRT) vs. Stereotactic Body Radiation Therapy (SBRT) and Intra-Operative Radiotherapy (IORT)

Multi-agent chemotherapy and radiation therapy (RT) has increased the proportion of locally advanced pancreatic cancer (LAPC) patients (pts) able to undergo resection and improve overall survival compared to those who are not resected. However, prior data from our institution (2016-2019) indicate that despite an R0 rate of 88%, LF developed in > 30% of LAPC pts resected after neoadjuvant therapy (NAT). This high LF rate is a rationale to explore dose escalation (DE) in the NAT setting, as data highlighting the value of DE have been limited to unresectable disease. Importantly, the optimal method for DE remains unclear. While conformal external beam RT can ablate part of the target, under-coverage in close proximity to the stomach and bowel remains problematic. For pancreatic head tumors, Whipple resection presents an opportunity for subsequent DE with IORT, as the duodenum is resected and direct access to microscopic peri-vascular residual disease is allowed. It also allows for precise DE based on the surgeons' recommendations. Herein, we model DE approaches, comparing pre-operative DE-IMRT with an approach in which a high-dose rate (HDR)-IORT boost is given after SBRT, with a goal biological effective dose (BED10) of 100 Gy.Ten consecutive LAPC pts were modeled with both DE-IMRT to 75 Gy in 25 fractions and SBRT to 40 Gy in 5 fractions followed by HDR-IORT to 15 Gy, using an 192Ir source. Notably, to minimize LF after surgery, our clinical tumor volume (CTV) has been the "Heidelberg Triangle" of tissue between the celiac, superior mesenteric, and common hepatic arteries and portal vein, which contains perineural and lymphatic tissue at risk of harboring subclinical disease. A 5mm planning tumor volume (PTV) expansion was used. A 3mm expansion on stomach and bowel was constrained to 60 Gy and 40 Gy for DE-IMRT and SBRT, respectively. For IORT modeling, the Freiburg Flap was superimposed on the planning CT, and dose was prescribed to the target volume surface. Given rapid dose fall-off with HDR-IORT, SBRT was optimized to compensate for IORT under-coverage, with higher dose allowed posteriorly but with an overall hotspot less than 50 Gy. Descriptive statistics were generated for coverage to target structures.With DE-IMRT, mean V75Gy for the CTV and PTV was only 79% +/- 14.4% and 52% +/- 13%, respectively. In comparison, posteriorly optimizing the SBRT plan in anticipation of anterior IORT supplementation improved coverage with ablative BED. For the anterior half of the target volume, HDR-IORT created a dose gradient of 10-15 Gy, whereas for the posterior half of the target volume, HDR-IORT created a dose gradient of 5-10 Gy. Optimizing the SBRT plan to complement this with 40 Gy to the anterior half of the volume and 45 Gy to the posterior half of the volume was feasible with > 90% coverage with BED10 of 100Gy in composite.Dose escalation with SBRT/IORT may allow for better target coverage with ablative RT dose as compared to DE-IMRT and should be explored clinically.

Fabrication of clay soil/CuFe2O4 nanocomposite toward improving energy and shielding efficiency of buildings

In this research, the energy and shielding efficiency of brick, fabricated by clay soil, as a practical building material was reinforced using CuFe2O4 nanoparticles. Initially, the nanoparticles were fabricated using the sol–gel method and then loaded in the brick matrix as a guest. The architected samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), diffuse reflection spectroscopy (DRS), field emission scanning electron microscopy (FE-SEM), High-resolution transmission electron microscopy (HRTEM), vibrating-sample magnetometer (VSM), differential scanning calorimetry (DSC) thermograms, and vector network analyzer (VNA) analyses. IR absorption of the tailored samples was monitored under an IR source using an IR thermometer. IR absorption and energy band gap attested that inserting the nanoparticles in brick medium led to the acceleration of a warming brick, desirable for energy efficiency in cold climates. It is worth noting that the brick/CuFe2O4 nanocomposite achieved a strong reflection loss (RL) of 58.54 dB and gained an efficient bandwidth as wide as 4.22 GHz (RL > 10 dB) with a thickness of 2.50 mm, meanwhile it shielded more than 58% of the electromagnetic waves at X-band by only a filler loading of 10 wt%. The microwave absorbing and shielding characteristics of the composite are mainly originated from conductive loss, electron hopping, natural and exchange resonance, relaxation loss, secondary fields, as well as eddy current loss. Interestingly, the shielding property of the nanocomposite was significantly generated from its absorbing features, reducing the secondary electromagnetic pollutions produced by the shielding materials applying the impedance mismatching mechanism.

Time-resolved QA and brachytherapy applicator commissioning: Towards the clinical implementation

PurposeBrachytherapy has a busy workflow relying on manual steps to ensure accurate delivery of the treatment. Systematic treatment errors have been reported due to faulty equipment, inadequate quality assurance (QA) and applicator commissioning methods. This study describes the use of a novel method, the Iridium Imaging System for QA (IrIS – QA), to automate and improve the applicator commissioning for HDR 192Ir brachytherapy. Methods and MaterialsA 3D printed holder attached to an Imaging Panel (IP) has been developed to: (1) acquire a high-definition projection of the applicator using the gamma rays of the 192Ir source for imaging; (2) Track the source within the applicator verifying in a time-resolved manner the dwell positions and dwell times with a high resolution. Results obtained for two applicator models are described in this manuscript. ResultsIrIS-QA is capable of measuring the dwell times with an accuracy better than 0.1 s and interdwell distances with submillimetre precision. The applicators tested in the study showed good agreement between planned and delivered dwell times and positions, with mean and maximum dwell position deviations below 0.5 mm and 1.3 mm, respectively. Dwell time measurements showed agreement superior to 0.05 s except for the first dwell position for which up to 0.15 s differences were observed. ConclusionsIrIS-QA is a compact system that includes many features necessary to improve the accuracy and efficiency of applicator commissioning and daily QA. No commercial system exists with similar capabilities. IrIS-QA is intended to replace current clinical procedures using film dosimetry.

Two-Color IRMPD Applied to Conformationally Complex Ions: Probing Cold Ion Structure and Hot Ion Unfolding.

Two-color infrared multiphoton dissociation (2C-IRMPD) spectroscopy is a technique that mitigates spectral distortions due to nonlinear absorption that is inherent to one-color IRMPD. We use a 2C-IRMPD scheme that incorporates two independently tunable IR sources, providing considerable control over the internal energy content and type of spectrum obtained by varying the trap temperature, the time delays and fluences of the two infrared lasers, and whether the first or second laser wavelength is scanned. In this work, we describe the application of this variant of 2C-IRMPD to conformationally complex peptide ions. The 2C-IRMPD technique is used to record near-linear action spectra of both cations and anions with temperatures ranging from 10 to 300 K. We also determine the conditions under which it is possible to record IR spectra of single conformers in a conformational mixture. Furthermore, we demonstrate the capability of the technique to explore conformational unfolding by recording IR spectra with widely varying internal energy in the ion. The protonated peptide ions YGGFL (NH3+-Tyr-Gly-Gly-Phe-Leu, Leu-enkephalin) and YGPAA (NH3+-Tyr-Gly-Pro-Ala-Ala) are used as model systems for exploring the advantages and disadvantages of the method when applied to conformationally complex ions.

Characterization of new primary air kerma standards for dosimetry in Co-60, Cs-137 and Ir-192 gamma ray sources

Introduction. To be better suited for measurements at air kerma rates which are common for the calibration of detectors for dosimetry in brachytherapy and radiation protection, two graphite-wall, air-filled cavity ionization chambers (PS-10 and PS-50 built by PTW of Freiburg, Germany) were characterized for use as primary standards at the Physikalisch-Technische Bundesanstalt (PTB) for 60Co, 137Cs and 192Ir gamma ray sources. Methods. Applying experimental or Monte Carlo methods, corrections were determined for wall effects, stem scattering effects, point-source non-uniformity, saturation effects, and deviations from Spencer-Attix cavity theory. The geometrical cavity volume of the ionization chambers was determined by a special experimental method. Non-charge-collecting parts of the volume were calculated by finite-element simulations. In addition, mass electronic stopping powers and mass-energy absorption coefficients were reevaluated in close agreement with ICRU 90. To compare the results to an already established air kerma standard, measurements of air kerma rates were taken for gamma rays from all three sources. Results. In contrast to the standards currently in use, the newly characterized ionization chambers show significant wall effects up to 4.17% (192Ir). For the PS-10 ionization chamber, the geometric volume differs by 0.42% from the charge collecting volume. For the ^192Ir source, Spencer-Attix corrections were applied exceeding 0.30% for both ionization chambers. Applying the derived corrections factors, air kerma rates measured with the two ionization chambers at the three sources did not differ by more than 0.13%. Comparing the results to an already established air kerma standard, deviations ranged up to 0.61%. The uncertainty budget for the determination of air kerma rates resulted in a relative combined standard uncertainty of 0.35%. Conclusion. Both ionization chambers can be used as primary air kerma standards for 60Co, 137Cs and 192Ir gamma ray sources using the values of corresponding physical quantities and correction factors derived in this work.

Validation of 3D printing materials for high dose-rate brachytherapy using ionisation chamber and custom phantom

Methods. Measurements were taken with the Exradin A20 (Standard Imaging) ionisation chamber, and the ‘homemade’ MARM phantom was made with the 3D Ultimaker 2+ printer using PLA material. The material used for validation was ABS Medical from Smart Materials 3D. The irradiation was undertaken with a 192Ir source by means of Varian’s GammaMed Plus iX HDR equipment. EBT3 films were used to run additional tests. We compared different measurements for PLA, ABS Medical, and water. Additional validation methods, described in the bibliography, were also compared. Results. The measurements with the ionisation chamber that we obtained using the MARM phantom with PLA and ABS within the clinically relevant range (0.5–1.5 cm) differ with respect to the measures in the water reference, by 2.3% and 0.94%, respectively. Discussion. The literature describes highly heterogeneous validation methods, complicating the performance of systematic reviews and comparisons between materials. Thus, creating a phantom represents a single effort that will quickly pay off. This system enables comparisons, ensuring that geometric conditions remain stable—something that is not always possible with radiochromic films. The use of a calibrated ionisation chamber in the corresponding energy range, combined with the ‘homemade’ MARM phantom applied according to the proposed methodology, allows a differentiation between the attenuation of the material itself and the drop in the dose due to distance. Conclusion. The validation method for 3D printing materials, using an ionisation chamber and the MARM PLA phantom, represents an accessible, standardisable solution for manufacturing brachytherapy applicators.

Radiobiological comparison between Cobalt-60 and Iridium-192 high-dose-rate brachytherapy sources: Part I-cervical cancer.

This study aimed to compare the biological effective doses (BEDs) to clinical target volume (CTV) and organs at risk (OARs) for cervical cancer patients treated with high-dose-rate (HDR) Iridium-192 (192 Ir) or Cobalt-60 (60 Co) brachytherapy (BT) boost and to determine if the radiobiological differences between the two isotopes are clinically relevant. Considering all radiosensitivity parameters and their reported variations, the BEDs to CTV and OARs during HDR 60 Co/192 Ir BT boost were evaluated at the voxel level. The anatomical differences between individuals were also taken into account by retrospectively considering 25 cervical cancer patients. The intrafraction repair, proliferation, hypoxia-induced radiosensitivity heterogeneity, relative biological effectiveness (RBE), and source aging dose-rate variation were also taken into account. The comparisons in CTV were performed based on equivalent uniform BED (EUBED). Considering nominal parameters with no RBE correction, the CTV EUBEDs were almost similar with a median ratio of ∼1.00 (p<0.00001), whereas RBE correction resulted in 3.9%-5.5% (p=0.005, median=4.8%) decrease for 60 Co with respect to 192 Ir. For OARs, the median values of D2cc (in EQD23 ) for 60 Co were lower than that of 192 Ir up to 9.2% and 11.3% (p<0.00001) for nominal parameters and fast repair conditions, respectively. In addition, for a nominal value (reported range) of radiosensitive parameters, the CTV EUBED differences of up to 6% (5%-10%) were assessed for HDR-BT component. The RBE values are the most important cause of discrepancies between the two sources. By comparing BED/EUBEDs to CTV and OARs between 60 Co and 192 Ir sources, this numerical study suggests that a dose escalation to ∼4% is feasible and safe while sparing well the surrounding normal tissues. This 4% dose escalation should be benchmarked with clinical evidences (such as the results of clinical trials) before it can be used in clinical practice.

First Responder Safety in the Event of a Dirty Bomb Detonation in Urban Environment

The malevolent dispersion of radioactive material, with the aim of contaminating people and the environment, is considered a credible terroristic threat. This article analyzes a hypothetical Dirty Bomb detonation in an urban area, estimating the radiological consequences to the involved population and to first responders. The dispersion of radioactive material is simulated using the HOTSPOT code, considering the explosion of devices containing (alternatively) 60Co, 137Cs, 192Ir, 238Pu or 241Am sources, frequently used in medical or industrial settings. Each source is evaluated separately. The resulting ground deposition is used to calculate the effective dose received by first responders in two different scenarios. Based on the dispersed radionuclide, the influence of the use of personal protective respirators is analyzed. Confirming previous published results, this article illustrates that the radioactive material is diluted by the detonation, resulting in relatively low doses to the general public. However, the emergency workers’ stay time in the most contaminated area must be carefully planned, in order to limit the received dose. Due to the general fear of radiation, extensive psychological effects are expected in the public, irrespective of the evaluated radiation dose.

High dose rate 192Ir versus high dose rate 60Co brachytherapy: an overview of systematic reviews of clinical responses of gynecological cancers from 1984 to 2020

The Purpose. Radioisotope of 192Iradium (192Ir) has a half-life (74 days) and is not easily accessible in developing countries. As a result, by the time source shipment clearance and the customs paperwork are completed, a large proportion of useful activity had already been decayed away. In fact, 60Cobalt (60Co) remote afterloading systems are commercially available by many venders. As a result, it may well become an alternative source to 192Ir and conform many of these challenges. The aim of this study is that to report clinical responses of different types of gynaecological cancers treated with high dose rate (HDR) 192Ir and HDR60Co brachytherapy in order to check whether HDR 60Co could be used as an alternative brachytherapy, source to HDR 192Ir. Materials and Methods. A retrospective study of clinical responses of different types of gynaecological cancers, staged from I to IV according to recommendations of International Federation of Gynaecology and Obstetrics (FIGO), treated by brachytherapy alone, radiotherapy alone (combined brachytherapy and radiotherapy) and combined radiotherapy and chemotherapy (brachytherapy, radiotherapy and chemotherapy) between 1984 and December 2020 was conducted. The patients were treated with external beam radiotherapy 45–51 Gy boosted with HDR 192Ir and HDR 60Co afterloading brachytherapy of 18–30 Gy to point A. The results. The study scrutinized the data of 11086 patients with different types of gynaecological cancers. Most of the patients, 70 percent of them, were diagnosed with gynaecological cancers in stages II and III. For patients treated with 192Ir brachytherapy source 5-years overall survival rate (OS), local control, 2-years, 5-years and 10-years disease free survival (DFS), complications of gastro-intestine (GI) and complications of genito-urinary (GU) were 63.5%, 92%, 72.6%, 64.07%, 43.75%, 3.9% and 5.92%, but for those treated with 60Co they were 57.7%, 86.63%, 82.5%, 53.35%, 43.75%, 4.8% and 3.7%, respectively. Conclusions. The use of HDR 60Co brachytherapy has the capacity to produce overall survival rate and disease control in patients with carcinoma of the gynaecology comparable to that reported for HDR 192Ir brachytherapy. Currently, the toxicity and damage of the normal tissues and radiation-related second cancers are of a similar incidence to that of standard HDR 192Ir brachytherapy. Source exchange frequency is not a serious concern because it requires less frequency of replacement, and commissioning can be accomplished within years; hence, replacing HDR 192Ir with HDR 60Co brachytherapy achieves significant cost saving. Therefore, we recommend that 60Co source ought to be the first choice for low resource radiotherapy setting as it offers economic advantages over 192Ir and have comparable clinical outcomes to that of 192Ir source.

Hot air‐assisted continuous infrared dryer for anchovy fish drying

AbstractThis study was performed to assess the application of a hot air‐assisted continuous infrared dryer for anchovy drying and to examine the drying characteristics of small‐ and large‐sized anchovy fish. Experiments were carried out at the infrared radiation intensities of 1,000, 2,000, 3,000 W/m2 and IR source‐sample distances of 5, 10, 15 cm. The impact of IR intensity and distance between the IR source and sample on moisture content, drying efficiency, drying time, specific energy consumption, water activity, rehydration ratio, shrinkage, and surface color change were evaluated using statistical analysis. The most efficient drying parameters were observed at 2,000 W/m2, 10 cm, and 2,000 W/m2, 5 cm for small and large anchovy fish, respectively, based on the drying and quality characteristics of dried anchovy fish. This study ensured the potential application of a hot air‐assisted infrared drying system to acquire dried anchovy fish with increased shelf life.Practical ApplicationsAnchovies are highly nutritious and possess a lot of health benefits. They are rich in minerals, vitamins, and omega‐3 fatty acids, which help to promote brain and heart health. However, they are highly perishable because of the high moisture content. Hence, the shelf life can be extended by preservation using drying techniques. Dried anchovy fish is one of the popular traditional fish products, which can be added in curries and pickles because of their strong flavor. A better drying process will be resulted in good quality dried product and fetch high demand in the market. One such better drying method is infrared radiation drying, which provides rapid heating and faster moisture removal than other drying methods. Thus, hot air‐assisted infrared drying was employed in this study to produce dried anchovy fish with increased shelf life and better quality characteristics.

Antitumor efficiency of contact radiotherapy in combination with a chlorin-based photosensitizer in experiment

Authors have studied the antitumor efficacy of contact radiation therapy (CRT) in combination with a chlorin-based photosensitizer (PS) in an experiment on laboratory animals with transplanted tumors. The experimental study was performed in 50 white outbred rats weighing 250±50 g. Subcutaneously transplanted Pliss lymphosarcoma (PLS) and alveolar liver cancer RS1 (RS1) were used as tumor models. Chlorinbased PS photolon (RUE «Belmedpreparaty», Republic Belarus) was injected intravenously at a dose of 2.5 mg/kg. The radiation sessions were carried out 2.5–4 hours (depending on the tumor model) after the administration of the PS using the device «microSelectron HDR V3 Digital» («Nucletron», Netherlands) with a 192-Ir radiation source in single focal doses 5 and 10 Gy. All laboratory animals (for PLS and RS1) were subdivided into 5 groups of 5 animals each: intact control, CRT 5 Gy, CRT 10 Gy, PS + CRT 5 Gy, PS + CRT 10 Gy. For the PLS tumor model – on the 14th day from the beginning of the experiment Vav. in groups were 26.31±5.81; 22.45±6.97; 18.99±4.86; 10.75±5.18 and 28.06±2.85 cm3, respectively (p˂0.05). The coefficients of tumor growth inhibition in the experimental groups were 14.67%, 27.82%, 59.14% and 6.65%, respectively. The frequency of complete tumor regressions 60 days after the start of the experiment was 0%, 20%, 20%, 60%, and 20%, respectively. On RS1 tumor model – on the 14th day from the beginning of the experiment Vav. in groups were 4.48±1.03; 0.80±0.21; 0.29±0.09; 0.19±0.07 and 0.32±0.08 cm3, respectively (p=0.009). The coefficients of tumor growth inhibition in the experimental groups were 82.14%, 93.53%, 95.76% and 92.86%, respectively. The frequency of complete tumor regressions 60 days after the start of the experiment was 0%, 0%, 20%, 0%, and 0%, respectively. Systemic administration of chlorin-based PS before the CRT session increases the antitumor efficacy of radiation therapy in animals with transplantable tumors of different histological structure and growth patterns. The data obtained indicate that further studies of the radiosensitizing properties of PS are promising.

PO-1594 Implementation of a QC procedure based on absolute dosimetry of 192-Ir HDR sources by microionization chamber

PO-1594 Implementation of a QC procedure based on absolute dosimetry of 192-Ir HDR sources by microionization chamber

Low and high-dose-rate brachytherapy in combination with external beam radiotherapy for high risk prostate cancer

Background. Prostate cancer (PCa) in the Russian Federation takes the leading place in the prevalence of cancer among the male population.Objective: to investigate the effect of increasing a single focal dose in high-dose-rate brachytherapy (HDR-BT) in combination with external beam radiotherapy on biochemical failure-free survival and local control in patients with high-risk PCa. Materials and methods. The study included 350 men with PCa in the group of high and extremely high risk of progression. All patients included in the study were divided into 4 groups. Groups 1, 2 and 3 included 276 patients who received HDR-BT with a 192Ir source with a single dose per fraction: 10 Gy (n = 83), 12 Gy (n = 46) and 15 Gy (n = 147). Group 4 included 74 patients who received low-dose-rate brachytherapy with 125I sources up to a total focal dose of 110 Gy. At the 2 stage, external beam radiotherapy was a conventional fractionation (single dose of 2 Gy, total - 44-46 Gy).Results. Of 350 patients over a 5-year follow-up period, PCa recurrence was noted in 65 (18.6 %). The 3- and 5-year biochemical failure-free survival rates in the general cohort of patients were 87.4 and 81.4 %. 5-year biochemical failure-free survival was significantly higher in group 3 relative to group 4 and amounted to 89.8 and 74.2 % (p = 0.03). Increasing the dose for HDR-BT from 10 to 12 Gy per fraction significantly reduced the frequency of local relapses from 15.7 % (in group 1) to 2.2 % (in group 2) (p = 0.0001) while maintaining the level of genitourinary and gastrointestinal toxicity. Conclusion. The use of a combination of brachytherapy and external beam radiotherapy in patients with high risk PCa is highly effective in achieving local control of the tumor. The optimal fractionation regime for HDR-BT remains a matter of debate. The use of 15 Gy per fraction for HDR-BT in combination with external beam radiotherapy is the most optimal fractionation regimen in patients with high-risk PCa.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Development of a Negligible Zero-Drift NDIR Analyzer for Measuring NH3 Emitted from an Urban Household Solid Waste Incinerator

An analyzer for measuring NH3 emitted from a combustion process has been developed based on a simple non-dispersive infrared (NDIR) technique because of its cost-effective benefit. The weakness of the NDIR analyzer due to interference and zero-drift has been overcome. A least-interfering bandpass filter (BPF) was found and manufactured to compensate for the interfering effects of gases emitted from a combustion process (e.g., CO, NOx, SO2, CO2, H2O, HCl, formaldehyde, acetaldehyde and toluene). It was found that there was no significant interference in the least-interfering BPF with respect to gases of concern. Measurement errors by the analyzer were less than 2.5% in a range of 1 to 10 ppmv of NH3 compared to a standard method when the compound was measured in complicated mixing gases. For the zero-drift, using BPFs with identical center wavelength with respect to different incident infrared intensity was found to help minimize the zero-drift of the NDIR analyzer. As a result, the analyzer could cut approximately 19% of zero-drift caused by the aging effect of both IR source and detector. It suggests that the analyzer could be applied for measuring NH3 emitted from combustion processes with good accuracy and reproducibility.

Assessment of the Quality of the Combined Radiotherapy Plans for Patients with Advanced Cervical Cancer

Purpose: To assess the quality of planning for the combined radiotherapy of patients with advanced cervical cancer (cervical cancer). To assess the impact of taking into account not only the external, but also the internal wall of the organ of risk during contouring on the magnitude of the radiation load on the organ of risk (OR). Estimate the total dose to the OR from the remote and intracavitary components.Material and methods: The planning quality assessment was carried out for three technologies of remote exposure, namely: 3DCRT, IMRT and IMRT in the rotational RapidArc mode. Radiotherapy was performed on linac Clinac iX models (Varian, USA) with photon energy of 6 MeV, intracavitary RT (IRT) — on a MicroSelectron apparatus with a 192Ir source. The calculation was carried out on the treatment planning system Eclipse (Varian, USA) and Oncentra Brachy.Results: The evaluation of the quality of conformal radiotherapy planning was carried out in 69 patients with locally advanced cervical cancer 2b–3b stages according to homogeneity and dose conformance indexes in target volumes and OR in combined radiation therapy programs. The best values of the indices of homogeneity and conformity were obtained with the IMRT technology and 3DCRT. The values of the conformity index CI for PTV for the IMRT technology has advantages in terms of doses to OR. For a group of 94 patients, an analysis of dose loads on the rectum, bladder was carried out with only the external contour of the OR and taking into account the inner wall. For 37 patients, the total values of doses to OR for combined RT were evaluated.Conclusion: The quantitative advantages of homogeneity and conformance indices for the tumor and dose loads in OR of 3D CRT and IMRT technologies for patients with cervical cancer 2b–3b are revealed. We removed from the use of technology RapidArc for this group of patients. The advantages of contouring with or without thickness are not revealed. The contouring for all the mentioned cases of technology can be carried out along the outer contours of the OR.

Therapeutic irradiation in the management of gynecological cancer and predictability of radiation-induced complications

Background. Today, applying radiotherapy (RT) in management of both primary and secondary vaginal cancer (SVC) take pride of place in the spectrum of specialized treatments for cancer patients. Secondary vaginal tumors are more common (6% to 33%) in cervical cancer (CC) patients, while in uterine cancer (UC) occur in 8–10% of cases treated either surgically, or by means of radiotherapy, otherwise via a combination approach. Therefore, RT is administered in about 80% of primary vaginal cancer and particularly SVC patients. When using even the most advanced radiotherapy equipment implying the cutting-edge technologies, there is a risk of radiation-induced complications in healthy organs and tissues that fall under the irradiation area. Keeping in mind the key radiobiological paradigms makes it possible not only to predict the probability of tumor resorption upon radiation exposure, but also to assess the biological effectiveness of absorbed dose, as well as the risk of late radiation complications.&#x0D; Purpose – to enhance the effectiveness and assess the toxicity of SVC RT via ascertaining BT (brachytherapy) most suitable techniques depending on the type of ionizing radiation and exploring predictability of radiation-induced complications in terms of biomolecular cell properties.&#x0D; Materials and methods. Clinical study was performed at the National Cancer Institute Clinic (Radiation Oncology Department), using a high-energy BT unit with a HDR 192Ir source. The SVC patients (n = 106) were treated according to the developed BT methods. They had been pretreated for the CC (n = 65) with squamous cell carcinoma histologically diagnosed in the most cases or UC (n = 41) with histologically prevalent adenocarcinoma of a variable grade. Patients had a locally advanced pelvic tumor process with tumor staging II–III, T2-3N0-1M0. Along with clinical study the radiobiological research was conducted to count the apoptotic cells in both intact and irradiated peripheral blood lymphocytes (PBL), as well as the level of SH-groups of plasma proteins and peptides in gynecological cancer patients and healthy donors to predict the risk of radiation-induced complications.&#x0D; Results and discussion. Given the delayed effect of RT, the treatment effective- ness was analyzed immediately after RT session and also 3 months upon completion of the conservative therapy. Thus, positive tumor response upon three months of observation over time was registered in 67.9 ± 5.2% of patients in study group I, in 72.5 ± 6.9% in study group II, and in 51.3 ± 6.8% in comparison group. Hence the values in study groups were higher than in comparison group by 16.6% and 21.2% respectively. All patients tolerated BT satisfactorily. Neither general nor local rectum or bladder severe (above grade II) toxicities were noted both during treatment and over the next 3 months upon its completion in all the patients regardless of study group. Results obtained in radiobiological studies correlated with clinical and literature data.&#x0D; Conclusions. Decrease in manifestations of RT toxicity, namely of the ear- ly radiation reactions from interfacing critical organs was established in groups I and II vs comparison group I, especially in group I where a high- energy 192Ir source was used in the SBD irradiation mode of 3 Gy twice a week. The obtained results of the experimental study suggest that the content of SH-groups in blood plasma and the level of PBL apoptosis can be considered as additional predictive measures of radiosensitivity of non-malignant cells from the irradiated tumor environment.

Experimental determination of Gd dose enhancement and Gd dose sparing by 192Ir brachytherapy source with Gafchromic EBT3 dosimeter

This work evaluates experimentally the dose enhancement factor (DEF) and dose sparing factor (DSF) due to radiation self-shielding, produced by Gd infused in tumor phantom irradiated with brachytherapy HDR 192Ir source by Gafchromic EBT3 dosimeter. The phantom was made of a set of solid water slabs (30 × 30 × 1.0) cm3 and three acrylic slabs of (30 × 30 × 0.5) cm3 machined to contain in the central axis acrylics vials of (1 × 1 × 5) cm3. The first and second acrylic vials were filled with an identical Gd solution of 0, 10 and 20 mg/ml, simulating Gd-doped and undoped tumor, and the third vial was filled in all the measurement only with water, representing an organ at risk. Additional solid water slabs were used to complete a phantom of (30 × 30 × 16) cm3. In the phantom center an acrylic slab was machined to introduce the 2.5 mm flexible guide tube of GammaMed plus iX equipment and positioning the 192Ir source in the phantom central part. EBT3 fragments of (0.9 × 4) cm2 were placed on the inner edge of the second and third vials to measure dose enhancement and dose sparing simultaneously. Phantom CT images were acquired for planning and to prescribe a dose of 6.0 Gy at 2.0 cm of the source, achieving an isodose curve of 44.5% at 3.0 cm (positions of the EBT3 films). Additionally, Monte Carlo simulation of the identical experimental setup was implemented to compare measurement values. The results showed the feasibility of measuring a DEF of 1.15 ± 0.05 in 20 mg/ml of Gd concentration consistent with the Monte Carlo DEF of 1.112 ± 0.005 for the same concentration. DEF value for concentration of 10 mg/ml would not be detected (1.00 ± 0.04) by an expected under measurement of the EBT3 films associated with the non-detection of photoelectrons and Auger electrons of very low energy that cannot reach the radiosensitive substrate.

A multiline study of the filamentary infrared dark cloud G351.78–0.54

ABSTRACT We present results of a multiline study of the filamentary infrared dark cloud G351.78–0.54 in the 1.3 and 0.8 mm wavelength bands. The lines of the three isotopologues of carbon monoxide CO, N2H+, CH3CCH, and HNCO were observed. The aim was to study the general structure of the filamentary cloud, its fragmentation, and physical parameters with the emphasis on properties of dense clumps in this cloud. Several dense clumps are identified from the N2H+ (3–2) data, their masses and virial parameters are determined using the C18O (2–1) line. Temperatures of some clumps are estimated from the CH3CCH and HNCO data. Almost all clumps appear to be gravitationally unstable. The density estimates obtained from the C18O (3–2)/(2–1) and N2H+ (3–2)/(1–0) intensity ratios are in the range n ∼ (0.3–3) × 105 cm−3. The HNCO emission is detected exclusively towards the first clump which contains the luminous IR source IRAS 17233–3606, and indicates an even higher density. It is observed in the outflow, too. The velocity shift of the higher excitation HNCO lines may indicate a movement of the hot core relative to the surrounding medium. In some clumps there is a velocity shift ∼1 km s−1 between N2H+ (3–2) and CO isotopologues. The large widths of the N2H+ (3–2) line in the clumps indicate an increase of the velocity dispersion in their dense interiors, which may be related to the star formation process. The N2H+ abundance drops towards the luminous IR source.