Compact gamma detector module for radiation monitoring

Modern unmanned technologies make it possible to implement them in almost all industries, including radiation monitoring. Already in 2011, at the Fukushima nuclear power plant accident, the first drones were demonstrated to measure the radiation background of the territories. Improvement of such devices is one of the topical directions. Our research team has proposed the concept of a gamma radiation detector module for unmanned aerial vehicles. The concept is represented by a matrix of modernized silicon photomultipliers based on silicon structures. The new structures have a design of deep pixel photodiodes of the MLPD type. Today experimental samples have superiority in such parameters as high efficiency of registration of ionizing radiation. Also, such parameters as low sensitivity to vibrations and low power consumption of photodiodes make it possible to integrate them into unmanned and small-sized radiation monitoring systems

Performance of a plastic scintillator developed using styrene monomer polymerization

This paper presents a newly developed plastic scintillator produced in collaboration with Turkiye Energy, Nuclear and Mineral Research Agency (TENMAK). The scintillator is manufactured using thermal polymerization of commercially available styrene monomer. The absorption spectrum of the scintillator exhibited two absorption bands at 225 nm and 340 nm, with an absorption edge observed at 410 nm. The wavelength of the emitted light was measured in the range of 400-800 nm, with a maximum intensity at 427 nm. Monoenergetic electrons from the 137Cs source were used to evaluate the characteristics of the new scintillator, particularly its light yield. As the light readout the MAPD-3NM type silicon photomultiplier array (4 x 4) with an active area of 15 x 15 mm2, assembled using single MAPDs with an active area of 3.7 x 3.7 mm2, was used. The light yield of the scintillator was determined to be 6134 photons/MeV. In addition, the efficiency of the scintillator for gamma rays with an energy of 662 keV was found to be approximately 1.8 %. A CmBe neutron source was employed to evaluate its fast neutron detection performance. However, neutron/gamma discrimination using pulse shape discrimination (charge integration) method was not observed. The results demonstrate the potential of a newly produced plastic scintillator for various applications, particularly in radiation monitoring and detection systems.Comment: 7 pages, 7 figure

Влияние предоперационного лечения на частоту послеоперационных осложнений при раке верхнеампулярного отдела прямой кишки

Background. The need of neoadjuvant treatment for upper rectal cancer remains the object of discussion, which makes further study of this topic important.Аim. To estimate the postoperative complications rate depending on the type of neoajuvant treatment.Materials and methods. A retrospective cohort multicenter study, that analyzed data of medical records of patients with upper rectal cancer from the archive of N.N. Blokhin Cancer Research Center of the ministry of Health of Russia, Ryzhikh national medical Research Center of Coloproctology of the ministry of Health of Russia and Stavropol Regional Clinical Oncology Center for 2007–2020. Patients were devided into 3 groups: the group of radiotherapy (5*5 gy), the group of neoadjuvant chemotherapy (4 courses of XELOX before surgery) and the group of surgery. The main endpoint was the study of anastomotic leak rate. Also we estimated the postoperative complications rate III–Iv degree (Clavien– Dindo), the sphincter-preserving surgery rate, the stoma creation rate, the postoperative mortality.Results. we included 110 patients in radiotherapy group, 188 patients in neoadjuvant chemotherapy group, 103 patients in surgery group. Study groups were comparable by sex, ASA status and histological grade. Postoperative grade III– Iv complications (in all cases were associated with anastomotic leak) developed in 8 (6.8 %) patients in neoadjuvant chemotherapy group versus 11 (10.0 %) patients in radiotherapy group (p = 0.379) and 12 (11.7 %) patients in surgery group (p = 0.208). There weren»t any significant differences in this parameter between the radiotherapy and the surgery group (p = 0.698). R0-resection was performed in 117 (99.2 %) patients in neoadjuvant chemotherapy group versus 107 (97.3 %) patients in radiotherapy group (p = 0.280) and 103 patients (100 %) in surgery group (p = 0.349). Radiotherapy and surgery groups didn’t differ significantly in R0-resection rate (p = 0.091). 1 patient (0.84 %) in neoadjuvant chemotherapy died before surgery, in other groups there weren’t any lethal outcomes (p = 0.283). Only the male sex, had a statistically significant effect on the anastomotic leak rate (risk ratio (HR) 2.875; 95 % confidence interval (CI) 1.24–6.63; p = 0.003).Conclusions. A study of these case histories of patients with cancer of the upper ampullary rectum, conducted by us, showed that neoadjuvant treatment didn»t affect the postoperative complications rate.Введение. Необходимость предоперационного лечения при раке верхнеампулярного отдела прямой кишки остается предметом обсуждений, что делает актуальным дальнейшее изучение этой темы.Цель исследования – оценка частоты послеоперационных осложнений в зависимости от вида предоперационного лечения.Материалы и методы. Ретроспективное когортное многоцентровое исследование, в ходе которого проанализированы данные историй болезни больных раком верхнеампулярного отдела прямой кишки из архива ФГБУ «НМИЦ онкологии имени Н. Н. Блохина» Минздрава России, ФГБУ «НМИЦ колопроктологии имени А. Н. Рыжих» минздрава России и ГБУЗ Ставропольского края «Ставропольский краевой клинический онкологический диспансер» за период с 2007 г. по 2020 г. Пациенты были разделены на 3 группы: лучевой терапии (ЛТ) (5 × 5 Гр), неоадъювантной химиотерапии (НАХТ) (4 курса XELOX (capecitabine plus oxaliplatin) до операции) и хирургии. Основным изучаемым параметром была частота развития несостоятельности анастомоза (НА). Также оценивали общую частоту послеоперационных осложнений III–Iv степени тяжести по классификации хирургических осложнений Clavien–Dindo, проведения сфинктеросохраняющих операций, формирования стомы, послеоперационную летальность.Результаты. В группы ЛТ, НАХТ и хирургии вошли 110, 188 и 103 пациента соответственно. Исследуемые в группах были сопоставимы по полу и статусу согласно классификации Американского общества анестезиологов (American Society of Anesthesiologists, ASA) и степени дифференцировки опухоли. Послеоперационные осложнения III– Iva степени тяжести по Clavien–Dindo (во всех случаях были связаны с развитием НА) развились у 8 (6,8 %) пациентов из группы НАХТ в сравнении с 11 (10,0 %) пациентами из группы ЛТ (р = 0,379) и 12 (11,7 %) из группы хирургического лечения (р = 0,208). между группами ЛТ и хирургии не зафиксировано достоверных различий по этому показателю (р = 0,698). R0-резекцию удалось провести у 117 (99,2 %) пациентов в группе НАХТ в сравнении с 107 (97,3 %) пациентами в группе ЛТ (р = 0,280) и 103 (100 %) в группе хирургического лечения (р = 0,349). Группы ЛТ и хирургии также достоверно не различались по показателю частоты проведения R0-резекций (р = 0,091). Летальный исход зарегистрирован у 1 (0,84 %) пациента на фоне проведения НАХТ, в других группах летальных исходов на фоне лечения не отмечено (р = 0,283). Статистически значимо на частоту НА влиял только один параметр – мужской пол: отношение рисков (ОР) 2,875; 95 % доверительный интервал (ДИ) 1,24–6,63; р = 0,003.Заключение. Исследование данных историй болезни больных раком верхнеампулярного отдела прямой кишки, проведенное нами, показало, что предоперационное лечение не влияло на частоту возникновения послеоперационных осложнений

Прогностическое значение наличия в крови циркулирующей опухолевой ДНК как маркера минимального резидуального заболевания при колоректальном раке I–III стадии

Introduction. Studies on non-metastatic colorectal cancer have demonstrated the prognostic role of circulating tumor (ctDNA) after surgery, and the ability to identify patients with the greatest risk of progression. This makes it possible in the future to personalize neoadjuvant and adjuvant treatment.The study objective – to evaluate the correlation of the ctDNA status before and after surgery with a clinical outcome in patients with stage I–III colorectal cancer.Materials and methods. The study included data from patients with morphologically verified colorectal cancer with stage I–III who were treated at the N. N. Blokhin National Oncology Research Center in the period from 2016 to 2021. Blood samples were collected before and after surgical treatment (on the 7–10th day after surgery). The minimum permissible concentration at which ctDNA in a plasma sample was considered positive was 0.4 copies of mutant DNA in 1 mcL of plasma. The main criterion of effectiveness was disease-free survival (DFS). The presence of cDNA before and after surgery was a negative prognostic factor for progression in stage I–III of CRC. Patients with positive cDNA after surgery had worse DFS results despite adjuvant chemotherapy. Patients with stage II CRC with negative ctDNA, regardless of adjuvant CT after surgery, did not have disease progression in 100 % of cases.Results. The study included 146 patients with stage I–III colorectal cancer. Progression was detected in 34 patients. The median follow-up time was 22 months (0–66 months). Data on progression were known in 119 patients. Positive cDNA data were detected before surgery in 55 of 120 patients (45 %), after surgery in 46 of 119 (38.6 %). In the group with positive cDNA before surgery, the median DFS was 35 months (95 % confidence interval (CI) 24,0–45.9), in the group with negative cDNA before surgery, the median DFS was not achieved (hazard ratio (HR) 4.6; 95 % CI 2.0–10.4), 1‑year DFS in the cDNA positive group was 62 % versus 100 % in the cDNA negative group (p <0.001). In the group with positive cDNA after surgery, the median DFS was 20 months (95 % CI 8,1–31,9), in the group with negative cDNA was not achieved (HR 27,7; 95 % CI 6,6–116,6; p <0,001). Patients with positive cDNA after surgery had worse DFS scores despite adjuvant chemotherapy. Patients with stage II CRC without ctDNA after surgery in 100 % did not have disease progression regardless of adjuvant CT.Conclusion. The presence of cDNA before and after surgery was a negative prognostic factor of progression after surgical treatment at stage I–III. The high negative prognostic value of cDNA makes it possible to select patients with stage II who do not need adjuvant chemotherapy.Введение. Исследования, посвященные неметастатическому колоректальному раку, продемонстрировали прогностическое значение анализа циркулирующей опухолевой ДНК (цоДНК) после операции, что в перспективе позволит персонализировать как неоадъювантное, так и адъювантное лечение.Цель исследования – изучить прогностическое значение статуса цоДНК до и после операции у пациентов с колоректальным раком I–III стадии.Материалы и методы. В исследование были включены данные пациентов с морфологически верифицированным колоректальным раком I–III стадии, проходивших лечение в Национальном медицинском исследовательском центре онкологии им. Н. Н. Блохина в период с 2016 по 2021 г. Забор образцов крови осуществлялся до и после хирургического лечения (на 7–10‑е сутки после операции). Минимально допустимая концентрация, при которой цоДНК в образце плазмы считали позитивной, – 0,4 копий мутантного ДНК в 1 мкл плазмы. Основным критерием эффективности являлась выживаемость без признаков болезни (ВБПБ).Результаты. В исследование были включены 146 пациентов с колоректальным раком I–III стадии. Прогрессирование выявлено у 34 больных. Медиана времени наблюдения составила 22 мес (1–66 мес). Данные о прогрессировании заболевания получены для 119 пациентов. Положительный цоДНК-статус до операции выявлен у 55 (45 %) из 120 больных, после хирургического вмешательства – у 46 (38,6 %) из 119. В группе цоДНК+ медиана ВБПБ до операции составила 35 мес (95 % доверительный интервал (ДИ) 24,0–45,9), в группе цоДНК она не была достигнута (отношение рисков (ОР) 4,6; 95 % ДИ 2,0–10,4). Однолетняя ВБПБ в группах положительного и отрицательного статуса цоДНК оказалась равна 62 и 100 % соответственно (p <0,001). При цоДНК+ медиана ВБПБ после операции составила 20 мес (95 % ДИ 8,1–31,9), при цоДНК– она не была достигнута (ОР 27,7; 95 % ДИ 6,6–116,6; p <0,001). Пациенты с положительным статусом цоДНК после операции имели худшие показатели ВБПБ, несмотря на проведение адъювантной химиотерапии. При колоректальном раке II стадии и отрицательном цоДНК-статусе после операции в 100 % случаев прогрессирования заболевания не наблюдалось (независимо от проведения адъювантной химиотерапии).Заключение. Наличие цоДНК до и после операции является негативным прогностическим фактором прогрессирования заболевания при колоректальном раке I–III стадии. Высокое негативное прогностическое значение цоДНК позволяет выбирать пациентов с заболеванием II стадии, не нуждающихся в проведении адъювантной химиотерапии

Gamma ray detection performance of newly developed MAPD‑3NM‑II photosensor with LaBr3 (Ce) crystal

This paper presents the gamma-ray detection performance of the newly developed MAPD-3NM-II type SiPM sensor array (4 [Formula: see text] 4) with [Formula: see text](Ce) scintillator. The gamma-ray spectra of various sources have been measured in the energy range from 26 keV up to 1332 keV. The newly developed array based on MAPD-3NM-II sensors proved [Formula: see text] 22% enhancement in energy resolution in comparison to the former MAPD-3NM-I based array. The energy resolution of 662 keV gamma-rays measured by MAPD-3NM-II was 3.3% while clearly surpassing 4.25% resolution of MAPD-3NM-I predecessor. The enhancement is related to the high PDE of the new MAPD-3NM-II. Obtained results show that the new MAPD-3NM-II demonstrated good energy resolution and linearity in the studied energy region. The energy resolution of the new detector developed based on MAPD-3NM-II was better than all previous products of MAPD

Gamma-ray spectroscopy with MAPD array in the readout of LaBr3:Ce scintillator

This paper presented a new detector module consisting of a micropixel avalanche photodiode (MAPD-3NM), LaBr3:Ce scintillator, and a compact read-out interface system for detecting gamma-rays in a wide energy range. The MAPD array (4 × 4 channels) was assembled using a singleMAPD-3NMcharacterized by its high photon detection efficiency (∼25%),pixel density (10 000 pixels/mm2), lowoperation voltage (74.5 V), and lowdark current. An active area of a singleMAPD-3NMwas 3.7 × 3.7 mm2, while this value was 17 × 17 mm2 for the assembled array with pixel density of 2190 000. The size of the tested LaBr3:Ce scintillator was 15 × 15 × 15 mm3. According to the characteristics of the detector module, a compact read-out interface device (SPECTRIG MAPD) was developed. SPECTRIG MAPD was designed as a miniature device with low power consumption, which continues to provide a wide spectrum of functions needed for measurement and test silicon photomultipliers (SiPM) and scintillation detectors on their basis. The various experiments were implemented to test the detection performance of a detector module to gamma radiation in the range from 30 keV to 4400 keV

Improvement of parameters of micro-pixel avalanche photodiodes

The paper is concerned with the parameter study of a new generation of micro-pixel avalanche photodiodes (MAPD) with deeply buried pixel structure, also named silicon photomultipliers (SiPM) or multi-pixel photon counter (MPPC). The new MAPD of type MAPD-3NM was manufactured in the frame of collaboration with Zecotek Company. Measurements were carried out and discussed in terms of the important parameters such as the current-voltage and capacitance-voltage characteristic, gain, the temperature coefficient of breakdown voltage, breakdown voltage, and gamma-ray detection performance using an LFS scintillator. The obtained results showed that the newly developed MAPD-3NM photodiode outperformed the previous generation in most parameters and can be successfully applied in space application, medicine, high-energy physics, and security. New proposals are also discussed, for further improvement of the parameters of the MAPD photodiodes that will be produced in the coming years. © 2022 IOP Publishing Ltd and Sissa Medialab.The paper is concerned with the parameter study of a new generation of micro-pixel avalanche photodiodes (MAPD) with deeply buried pixel structure, also named silicon photomultipliers (SiPM) or multi-pixel photon counter (MPPC). The new MAPD of type MAPD-3NM was manufactured in the frame of collaboration with Zecotek Company. Measurements were carried out and discussed in terms of the important parameters such as the current-voltage and capacitance-voltage characteristic, gain, the temperature coefficient of breakdown voltage, breakdown voltage, and gamma-ray detection performance using an LFS scintillator. The obtained results showed that the newly developed MAPD-3NM photodiode outperformed the previous generation in most parameters and can be successfully applied in space application, medicine, high-energy physics, and security. New proposals are also discussed, for further improvement of the parameters of the MAPD photodiodes that will be produced in the coming years. © 2022 IOP Publishing Ltd and Sissa Medialab