Experiences of Nuclear Medicine Technologists Working in PET/CT Facilities in Gauteng Province, South Africa.

The introduction of PET/CT requires staff training, redesign of patient workflow, new skills, problem-solving abilities, and adjustments to radiation protection protocols. When PET/CT was introduced in the U.K., nuclear medicine technologists (NMTs) encountered challenges in defining their roles and unfamiliarity with the new technology and the new working procedures. Since the introduction of PET/CT in South Africa, the experiences of NMTs with this hybrid imaging device have not yet been described. Therefore, the aim of this research study was to explore and describe the experiences of NMTs working in PET/CT facilities in Gauteng Province, South Africa. Methods: This study had a qualitative, exploratory, descriptive design and used a phenomenologic research approach. Semistructured interviews were conducted to collect data until data saturation was reached. A software program was used to manage the codes, categories, and themes. Nine NMTs participated in the study: 5 from public hospitals and 4 from private hospitals. Their age range of 27-58 y provided the ideal heterogeneity for sharing experiences in working in PET/CT facilities. Results: Two overarching themes emerged from the categories: the perspectives of NMTs working in PET/CT facilities and the PET/CT challenges encountered by NMTs. The results suggest that NMTs experience joy and fulfilment from working in PET/CT facilities and regard PET/CT as the future of nuclear medicine. However, NMTs also experience a gap in PET/CT training and are concerned about the high radiation exposure associated with PET/CT imaging and about the lack of psychologic support. Conclusion: Although the NMTs enjoy working in PET/CT, they desire additional clinical training and psychologic support. Since radiation exposure in PET/CT is higher than in general nuclear medicine, radiation monitoring is imperative to minimize exposure to NMTs and patients.

Sparing Swallowing-Related Structures Reduces Post-Radiotherapy Dysphagia in Oropharyngeal Cancer.

OBJECTIVE: To identify swallowing-related structures (SRSs) predicting post-radiotherapy dysphagia in oropharyngeal carcinoma patients. MATERIAL AND METHODS: Between September 2020 and October 2022, oropharyngeal cancer patients who had completed radiotherapy at least one year before without recurrence or residuals were selected. They underwent flexible endoscopic evaluation of swallowing (FEES) assessments and dysphagia grading. The mean radiation doses delivered to their SRSs were recalculated. The correlation between radiation doses to each SRS and FEES scores was analysed. RESULTS: Twenty-nine participants, aged 51-73 years, were enrolled. Six patients had received two-dimensional radiotherapy, eight had undergone three-dimensional conformal radiotherapy, and fifteen had received intensity-modulated radiation therapy. Radiation doses to the inferior pharyngeal constrictor, cricopharyngeus and glottic larynx significantly predicted dysphagia for both semisolids (p = 0.023, 0.030 and 0.001) and liquid diets (p = 0.021, 0.013 and 0.002). The esophageal inlet significantly predicted swallowing outcomes for only the liquid diet (p = 0.007). CONCLUSIONS: This study supports that SRS-sparing during radiotherapy for oropharyngeal cancers improves swallowing outcomes.

Effect of changing the radiation dose range on the in vitro cytogenetic dose response to gamma-rays.

PURPOSE: To examine the distortion of the linear quadratic (LQ) model of in vitro cytogenetic dose response over an extended range of γ-ray doses by analyzing the available literature data, and to establish the dose ranges, in which the LQ dose response curve (DRC) can be most accurately fitted for biological dosimetry. MATERIALS AND METHODS: Data on yields of dicentrics (Dic) or dicentrics plus centric rings (Dic + CR) induced in vitro in human lymphocytes by acute γ-rays were extracted from 108 open sources. The overall dose response dataset in the dose range up to 50 Gy was fitted to a fractional-rational (FR) model, which included a 'basic' LQ function in the numerator, and a reduction factor dependent on the square of the dose in the denominator. Cytogenetic dose response data obtained at Grigoriev Institute for Medical Radiology, Kharkiv, Ukraine (GIMRO) in the range 0.1 - 20.3 Gy acute γ-rays were fitted to the LQ model with the progressive changing minimum or maximum radiation dose. RESULTS: The overall dose response, as expected, followed the LQ function in the dose range ≤5 Gy, but in the extended dose range appeared to be S-shaped, with intensive saturation and a plateau at doses ≥22 Gy. Coefficients of the 'basic' LQ equation in FR model were very close to many published DRCs; calculated asymptote was 17. Fitting of the GIMRO dataset to the LQ model with the shift of the dose range showed the increase in linear coefficient with the increment of either minimum or maximum radiation dose, while the decline of the quadratic coefficient was regulated mostly by the increase of the highest dose. The best goodness of fit, assessed by lower χ2 values, occurred for dose ranges 0.1 - 1.0 Gy; 0.5 - 5.9 Gy; 1.0 - 7.8 Gy; 2.0 - 9.6 Gy, 3.9 - 16.4 Gy and 5.9 - 20.3 Gy. The 'see-saw' effect in changes of LQ coefficients was confirmed by re-fitting datasets published by other laboratories. CONCLUSIONS: The classical LQ model with fixed coefficients appears to have limited applicability for cytogenetic dosimetry at radiation doses >5 Gy due to the saturation of the dose response. Different response of the LQ coefficients to the changes of the dose range must be considered during the DRC construction. Proper selection of minimum and maximum dose in calibration experiments makes it possible to improve the goodness of fit of the LQ DRC.

EFFECT OF IRON ON BONE TISSUE METABOLISM AND THYROID FUNCTION IN CHILDREN LIVING ON RADIOLOGICALLY CONTAMINATED TERRITORIES SINCE THE ChNPP ACCIDENT. / ВПЛИВ ЗАЛІЗА НА ПРОЦЕСИ МЕТАБОЛІЗМУ В КІСТКОВІЙ ТКАНИНІ ТА ФУНКЦІЮ ЩИТОПОДІБНОЇ ЗАЛОЗИ УДІТЕЙ, ЯКІ ЖИВУТЬ НА РАДІОАКТИВНО ЗАБРУДНЕНИХ ТЕРИТОРІЯХ ПІСЛЯ АВАРІЇ НА ЧАЕС.

OBJECTIVE: identification of clinical and metabolic characteristics of osteogenesis and factors affecting bone mineral density (BMD) in children living in radioactively contaminated territories (RCT) after the ChNPP accident for the use of therapeutic and preventive measures aiming to reduce the incidence of disorders. MATERIALS AND METHODS: Children aged 4 to 18 years old (n = 539) were involved in the study within 4 age groups, namely under 7 years old, 7-10 years old, 10-14 years old, older than 14 years old. Studied parameters in children with a reduced BMD (85-65 relative units and under 65 relative units) were estimated vs. the normative BMD (100-85 relative units) cases. Diagnosis of osteopenia and osteoporosis in children was established according to the BMD T-index. Family history of the relatives of children was studied. Body weight at birth, fractures of the long bones, complaints of osalgia, jaw anomalies, dental caries, presence of obesity, and hypermobility syndrome (HMS) were assessed. Peripheral blood biochemical tests were performed featuring the serum total protein, alkaline phosphatase (APh), calcium, vitamin D, creatinine, serum iron (SI), ferritin, cortisol, pituitary thyroid-stimulating hormone (TSH), and free thyroxine (FT4) assay. BMD was measured and radiation doses in children were reconstructed. RESULTS: BMD depended on the age of children. A direct correlation was established between the cholelithiasis and urolithiasis incidence (р < 0.01), cancer and endocrine diseases (р < 0.05) in the relatives of children that had BMD under 65 relative units. Dental caries developed more often (р < 0.05), while obesity was less frequent (р < 0.05) in the subjects with BMD < 65 relative units. A direct correlation was established between the level of serum creatinine and BMD (р < 0.01), and there was an inverse correlation between the serum APh level and BMD (р < 0.001).Every third child had a vitamin D deficiency. Fractures of long bones and increased content of SI and TSH were characteristic for the children having got osteopenia (BMD within 85-65 relative units), while besides a predisposition to bone fractures the higher levels of SI, APh, cortisol both with calcium deficiency were found in children with osteoporosis (BMD < 65 relative units) compared to the general group with a similar BMD. An increased incidence of HMS was characteristic too. Radiation doses in children with osteopenia were higher than in those with osteoporosis: (1.17 ± 0.09) mSv and (0.92 ± 0.06) mSv respectively (р < 0.05). No correlation was found between the radiation doses and clinical signs, blood biochemistry or BMD. CONCLUSIONS: Study of the functional mechanisms of bone structures in children, depending on their metabolism, had made it possible to reveal the factors that affect bone formation in children living in RCT after the ChNPP accident, and to form the population groups for the timely application of therapeutic and preventive measures aiming to reduce the incidence of disorders of musculoskeletal system.

Impact of Modern Low Dose Involved Site Radiation Therapy on Normal Tissue Toxicity in Cervicothoracic Non-Hodgkin Lymphomas: A Biophysical Study.

This biophysical study aimed to determine fitting parameters for the Lyman-Kutcher-Burman (LKB) dose-response model for normal tissue complication probability (NTCP) calculations of acute side effects and to investigate the impact of reduced radiation doses on the probability of their occurrence in supradiaphragmatic non-Hodgkin lymphoma (NHL) irradiation. A cohort of 114 patients with NHL in the cervicothoracic region, treated between 2015 and 2021 at the University Hospitals of Münster, Hamburg, and Essen, with involved site radiation therapy (ISRT), were included. Among them, 68 patients with aggressive NHL (a-NHL) received consolidative radiation therapy with 24-54 Gy following (R-)CHOP chemotherapy. Additionally, 46 patients with indolent NHL (i-NHL) underwent radiotherapy with 22.5-45.0 Gy. Two treatment plans were prospectively created for each patient (a-NHL: 30.0/40.0 Gy; i-NHL: 24.0/30.0 Gy). NTCP were then calculated using the optimized LKB model. The adapted dose-response models properly predicted the patient's probability of developing acute side effects when receiving doses ≤ 50 Gy. In addition, it was shown that reduced radiation doses can influence the NTCP of acute side effects depending on the aggressiveness of NHL significantly. This study provided a foundation to prospectively assess the probability of adverse side effects among today's reduced radiation doses in the treatment of NHL.

Patient Radiation Doses Assessment at Diagnostic X-rays Department of King Khalid hospital (KKH)-Majmaah.

BACKGROUND: The study was conducted on patients who received diagnostic X-rays in King Khalid Hospital (KKH), Majmaah. INTRODUCTION: The study included the seven most frequently performed investigations, which were carried out on over 1504 patients using digital radiography equipment. METHODS: The X-ray tube's output and exposure parameters were used to calculate the effective dose (ED) and patient entry surface air kerma (ESAK). Additionally, based on these results, conversion coefficients were determined. This study also examined the 75th percentile distributions of ESAK and KAP. The findings of this research were compared with the findings of other researchers throughout the country and the world. The study presents the uncertainty U values, as well as the mean ESAK, KAP, and ED values. RESULTS: The results of the ESAK, KAP, and ED values were 0.12-5.74 mGy, 0.9-1.84 Gy cm2, and 0.01-0.23 mSv, respectively. As a result, the dosages were much lower than those previously published for the European DRL, national standards, and other studies. CONCLUSION: The study concludes that during dose surveys, the importance of detecting and comprehending radiation doses, as well as the proper technique for taking the finest photos possible, can be emphasized to patients in order to assist them in avoiding radioactive particles and radiation exposure.

Dose and organ displacement comparisons with breast conservative radiotherapy using abdominal and thoracic deep-inspiration breath-holds: A comparative dosimetric study.

Deep-inspiration breath-hold (DIBH) reduces the radiation dose to the heart and lungs during breast radiotherapy in cancer. However, there is not enough discussion about suitable breathing methods for DIBH. Therefore, we investigated the radiation doses and organ and body surface displacement in abdominal DIBH (A-DIBH) and thoracic DIBH (T-DIBH). Free-breathing, A-DIBH, and T-DIBH computed tomography images of 100 patients were used. After contouring the targets, heart, and lungs, radiotherapy plans were created. We investigated the heart and lung doses, the associations between the heart and left lung displacements, and the thorax and abdominal surface displacements. No significant differences were observed in the target dose indices. However, the heart and lung doses were significantly lower in A-DIBH than in T-DIBH for all the indices; the mean heart and lung doses were 1.69 and 3.48 Gy, and 1.91 and 3.55 Gy in A-DIBH and T-DIBH, respectively. The inferior displacement of the heart and the left lung was more significant in A-DIBH. Therefore, inferior expansion of the heart and lungs may be responsible for the respective dose reductions. The abdominal surface displaced more than the thoracic surface in both A-DIBH and T-DIBH, and thoracic surface displacement was greater in T-DIBH than in A-DIBH. Moreover, A-DIBH can be identified because abdominal surface displacement was greater in A-DIBH than in T-DIBH. In conclusion, A-DIBH and T-DIBH could be distinguished by comparing the abdominal and thoracic surfaces of A-DIBH and T-DIBH, thereby ensuring the implementation of A-DIBH and reducing the heart and lung doses.

Exposure of the heart and cardiac valves in women irradiated for breast cancer 1970-2009.

Purpose: To describe cardiac exposure from breast cancer radiotherapy regimens used during 1970-2009 for the development of dose-response relationships and to consider the associated radiation-risks using existing dose-response relationships. Material and methods: Radiotherapy charts for 771 women in the Netherlands selected for case control studies of heart disease after breast cancer radiotherapy were used to reconstruct 44 regimens on a typical CT-dataset. Doses were estimated for the whole heart (WH), left ventricle (LV) and cardiac valves. Results: For breast/chest wall radiotherapy average WH doses decreased during 1970-2009. For internal mammary chain (IMC) radiotherapy WH doses were highest during the 1980s and 1990s when direct anterior fields were used and reduced in the 2000s when oblique fields were introduced. Average doses varied substantially for IMC regimens (WH 2-33 Gy, LV < 1-23 Gy). For cardiac valves, at least one valve received >30 Gy from most regimens. Conclusions: Radiation-risks of IHD from breast/chest wall regimens likely reduced during 1970-2009. Direct anterior IMC regimens likely increased the risks of IHD and VHD over this time period but the use of oblique IMC fields from 2003 may have lowered these risks. These data provide a unique opportunity to develop dose-response relationships.

Embryo/Fetus Doses from 18F-Fludeoxyglucose Radiopharmaceutical in Positron Emission Tomography/ Computed Tomography.

Aim: The embryo/fetus may be accidentally exposed to ionizing radiation. The aim of this study is to calculate embryo/fetus doses in pregnant women who underwent F-18 fludeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scan. Materials and Methods: Between June 2015 and June 2021, 15 pregnant women underwent F-18 FDG PET/CT applied to the Genetic Research Center (GETAM). The OLINDA/EXM package program was used for internal radiation dosimetry according to the Medical Internal Radiation Dose scheme. FetDose V4 computer software was used to compute the embryo/fetus absorbed dose from CT scan. Results: The amount of the injected F-18 FDG activity to patients varied between 333 and 555 MBq. The mean embryo/fetal dose from F-18 FDG was 7.2 ± 2.8 mGy. In addition, the CT component dose to the embryo/fetus dose ranged from 8.5 to 16 mGy with a mean of 12.14 ± 2.05. Conclusions: The embryo/fetus dose from F-18 FDG PET/CT was <15 mGy, however, questioning the women's childbearing prior to scintigraphy is the first-line strategy to avoid accidental radiation exposure and stochastic risks.

Head and abdomen CT exposures in Portugal.

In Portugal, computed tomography (CT) exposures for adult routine head, adult routine abdomen and paediatric abdomen (5 years old) were evaluated between 2019 and 2020 in 92 CT units. The third quartile value for CTDIvolwas 63.2 mGy for adult head exams, 15.9 mGy for adult abdomen and 5.2 mGy for paediatric abdomen. However, the CTDIvolfor head examination in 7.6% of units exceeded the suspension level proposed in EU report 162 while the number of units exceeding suspension levels for adult and paediatric abdomen were 3.2% and 0.0%, respectively. The used acquisition parameters and the referred CT unit's specifications were studied to understand how radiation dose relates with tube voltage, tube current, rotation time, detector width, slice width, pitch value and the use of automatic exposure control (AEC). The axial acquisition mode was predominant (67%) in the head exams. However, the helical scanning was commonly used in abdomen exams. Dose reduction from adult to paediatric exams was achieved using a lower tube current (a 60% average reduction). AEC is preferably used in abdomen protocols (84% in adult exams and 96% in paediatric exams). Nonetheless, in adult routine head protocols only 27% used this system. Data was gathered from clinics and hospitals covered by this study which allowed an estimate of an annual frequency of 206 CT examinations per 1000 population in Portugal. The estimated dose index (CTDIvol) and frequency of CT examinations for the Portuguese population agreed with data from other countries.

Cancer risk following low doses of ionising radiation - Current epidemiological evidence and implications for radiological protection.

Recent studies suggest that every year worldwide about a million patients might be exposed to doses of the order of 100 mGy of low-LET radiation, due to recurrent application of radioimaging procedures. This paper presents a synthesis of recent epidemiological evidence on radiation-related cancer risks from low-LET radiation doses of this magnitude. Evidence from pooled analyses and meta-analyses also involving epidemiological studies that, individually, do not find statistically significant radiation-related cancer risks is reviewed, and evidence from additional and more recent epidemiological studies of radiation exposures indicating excess cancer risks is also summarized. Cohorts discussed in the present paper include Japanese atomic bomb survivors, nuclear workers, patients exposed for medical purposes, and populations exposed environmentally to natural background radiation or radioactive contamination. Taken together, the overall evidence summarized here is based on studies including several million individuals, many of them followed-up for more than half a century. In summary, substantial evidence was found from epidemiological studies of exposed groups of humans that ionizing radiation causes cancer at acute and protracted doses above 100 mGy, and growing evidence for doses below 100 mGy. The significant radiation-related solid cancer risks observed at doses of several 100 mGy of protracted exposures (observed, for example, among nuclear workers) demonstrate that doses accumulated over many years at low dose rates do cause stochastic health effects. On this basis, it can be concluded that doses of the order of 100 mGy from recurrent application of medical imaging procedures involving ionizing radiation are of concern, from the viewpoint of radiological protection.

Investigation of the Effect of Radiotherapy Dose on Chewing and Swallowing Structures in Head and Neck Cancer Patients Treated with Concomitant Chemoradiotherapy.

Intensity-modulated radiotherapy (IMRT) is a treatment method that is used in the treatment of head and neck cancers. Impairment of chewing and swallowing functions in the early and late periods of radiotherapy is frequent. Therefore, revealing the dose-effect relationship is important. The main purpose of this study is to investigate the dose-effect relationship between chewing and swallowing structures objectively via a standardized videofluoroscopy protocol. The study included 35 participants treated with chemo-IMRT. A videofluoroscopic swallowing study (VFSS) was performed before IMRT, and 3 and 6 months after IMRT. VFSS results were scored according to the Modified Barium Swallow Impairment Profile (MBSImP) and the Penetration-Aspiration Scale (PAS). Maximum interincisor mouth opening, body mass index (BMI), and Functional Oral Intake Scale levels were determined in these cases. The quality of life of participants was evaluated. There was a significant increase in PAS and MBSImP scores and a significant decrease in BMI scores of the patients after treatment. Xerotomy and sticky saliva complaints increased after treatment. The dose to the mastication muscles (> 40 Gy) and the temporomandibular joint (> 46 Gy) were found to be associated with a decrease in BMI; the dose to the superior pharyngeal constructor muscle (> 58 Gy) was found to be associated with pharyngeal stripping wave. The presence of aspiration was associated with the inferior pharyngeal constructor muscle, glottic larynx, supraglottic larynx, and upper esophageal sphincter. Important findings to emerge from this study include detected toxic dose limits. These findings may guide physicians to minimize the side effects of IMRT.

SOME ISSUES OF LIFE ACTIVITIES OF POPULATION IN THE CHORNOBYL EXCLUSION ZONE IN UKRAINE. / DEIaKI ASPEKTY ZhYTTIeDIIaL'NOSTI NASELENNIa V ChORNOBYL'S'KII ZONI VIDChUZhENNIa UKRAÏNY.

BACKGROUND: Radiation accidents at the Chornobyl Nuclear Power Plant (USSR, 1986) and Fukushima-1 (Japan,2011) have shown that global environmental contamination is an intervention in normal human life making nega-tive effect on population health. These accidents highlighted a number of statutory and regulatory both with me-dical and social problems for individuals, who returned voluntarily for permanent residence in the ChornobylExclusion Zone i.e. a radiation-hazardous area (they are named the «self-settlers¼). OBJECTIVE: generalization of experience in the settlement of normative-legal, ecological-dosimetric and medico-social life issues of population living in the Chornobyl NPP (ChNPP) Exclusion Zone («self-settlers¼). OBJECT AND METHODS: The chosen problem is complex, necessitating the generalization of radiation-hygienic, med-ical-biological, socio-economic, demographic and sociological research results obtained by the national and foreignauthors. A set of theoretical research and analysis of empirical data methods on the principles of interdisciplinaryinteraction was used; the systematic, legal, economic, medical-biological, demographic and retrospective-dosimet-ric approaches of research were applied. RESULTS: It was shown that a part of population refused to evacuate or had returned for permanent residence to theradiation-hazardous lands after the ChNPP accident. In 1986-2009 the number of «self-settlers¼ ranged from 150to 2,000 in different years. In 2021 - the 101 people. Those were mainly people of working age, mostly females, single people or widows/widowers. Рrevious medical and dosimetric studies have shown that long-term residence inthe Exclusion Zone affects physical and mental health of «self-settlers¼ and causes atypical aging, includinginvolvement of the central nervous system. According to calculations, the average effective total radiation doseaccumulated by «self-settlers¼ for the first 3 years was 30 % of dose for the entire post-accident period, and thedose accumulated over 20 years was 54 % of the dose accumulated over 35 years. But the effective radiation dosesaccumulated in different periods after the accident differ significantly in residents of different Exclusion Zone settlements. This information needs further study in terms of the «radiation dose - health status¼ dependence. CONCLUSIONS: The effective radiation doses accumulated in different periods after the accident differ significantlyin the residents of different Exclusion Zone settlements. Тhe average effective total radiation dose accumulated by«self-settlers¼ for the first 3 years was 30 % of the dose for the entire post-accident period, and the dose accumulated over 20 years was 54 % of the dose accumulated over 35 years.

Dose-Effects Models for Space Radiobiology: An Overview on Dose-Effect Relationships.

Space radiobiology is an interdisciplinary science that examines the biological effects of ionizing radiation on humans involved in aerospace missions. The dose-effect models are one of the relevant topics of space radiobiology. Their knowledge is crucial for optimizing radioprotection strategies (e.g., spaceship and lunar space station-shielding and lunar/Mars village design), the risk assessment of the health hazard related to human space exploration, and reducing damages induced to astronauts from galactic cosmic radiation. Dose-effect relationships describe the observed damages to normal tissues or cancer induction during and after space flights. They are developed for the various dose ranges and radiation qualities characterizing the actual and the forecast space missions [International Space Station (ISS) and solar system exploration]. Based on a Pubmed search including 53 papers reporting the collected dose-effect relationships after space missions or in ground simulations, 7 significant dose-effect relationships (e.g., eye flashes, cataract, central nervous systems, cardiovascular disease, cancer, chromosomal aberrations, and biomarkers) have been identified. For each considered effect, the absorbed dose thresholds and the uncertainties/limitations of the developed relationships are summarized and discussed. The current knowledge on this topic can benefit from further in vitro and in vivo radiobiological studies, an accurate characterization of the quality of space radiation, and the numerous experimental dose-effects data derived from the experience in the clinical use of ionizing radiation for diagnostic or treatments with doses similar to those foreseen for the future space missions. The growing number of pooled studies could improve the prediction ability of dose-effect relationships for space exposure and reduce their uncertainty level. Novel research in the field is of paramount importance to reduce damages to astronauts from cosmic radiation before Beyond Low Earth Orbit exploration in the next future. The study aims at providing an overview of the published dose-effect relationships and illustrates novel perspectives to inspire future research.

Improved adaptive radiotherapy to adjust for anatomical alterations during curative treatment for locally advanced lung cancer.

Anatomical changes during chemoradiation for lung cancer may decrease dose to the target or increase dose to organs at risk. To assess our ability to identify clinically significant anatomical alterations, we followed 67 lung cancer patients by daily cone-beam CT scans to ensure correct patient positioning and observe anatomical alterations. We also re-calculated the original dose distribution on a planned control CT scan obtained halfway during the treatment course to identify anatomical changes that potentially affected doses to the target or organs at risk. Of 66 patients who completed the treatment, 12 patients needed adaptation, two patients were adapted twice. We conclude that daily cone-beam CT and routines at the treatment machine discover relevant anatomical changes during curative radiotherapy for patients with lung cancer without additional imaging.

Real-World Analysis of the Impact of Radiotherapy on Immunotherapy Efficacy in Non-Small Cell Lung Cancer.

BACKGROUND: Immunotherapy (IO) provides a significant benefit for a subgroup of non-small cell lung cancer (NSCLC) patients. Radiotherapy (XRT) might enhance the efficacy of IO. We evaluated the impact of the specifics of XRT treatments on the OS of IO-treated NSCLC patients. METHODS: Metastatic NSCLC patients treated with IO were retrospectively identified. Parameters included demographics, tumor characteristics, IO and XRT details. Correlation between the parameters and OS was tested with Cox regression. RESULTS: 453 patients were included. No XRT was given to 167 (36.9%) patients, whereas XRT prior and after IO had 182 (40.2%) and 104 (22.9%) patients, respectively. XRT total doses between 30 and 40 Gy had better overall survival (OS) compared to non-irradiated patients (hazard ratio (HR) 0.5, 95% CI 0.25-1.0, p = 0.049). Worse outcome was seen with total doses ≤ 10 Gy (HR 1.67, 95% 1.13-2.5, p = 0.01), XRT fractions of 4.1-8 Gy (HR 1.48, 95% CI 1.05-2.1, p = 0.027) and XRT to the bone (HR 1.36, 95% CI 1.01-1.8, p = 0.04). Several clinical parameters correlated with OS in the univariate analysis of the IO-treated patients. While, in the multivariate analysis, only ECOG-PS, treatment line, type of IO, albumin and NLR remained statistically significant. CONCLUSION: Specific doses, fractions and sites of XRT correlated with the OS of IO-treated NSCLC patients in the univariate analysis, although not in the multivariate analysis.

Doses of intensity-modulated radiotherapy and its association with cardiac disease in esophageal cancer patients.

BACKGROUND: No clear guidelines or available studies exist regarding the effects of intensity-modulated radiotherapy (IMRT) of esophageal cancer (EC) on the cardiovascular system. We therefore analyzed a wide range of cardiac vascular dosimetric parameters and clinical characteristics to assess the prognostic factors for EC patients treated with IMRT. METHODS: A total of 112 patients receiving IMRT at the Qianfoshan Hospital between July 2012 and May 2017 were retrospectively reviewed. The dose per fraction was 1.8-2.0 Gy, and the total dose range was 54-66 Gy. Kaplan-Meier analysis was used to estimate death due to heart disease. Univariate and multivariate logistic regression models were calculated to test for associations between patient characteristics and dose-volume histogram (DVH) parameters. A t-test and chi-squared or Fisher's exact test was used to analyze the comparisons. RESULTS: The maximum and mean doses received by the heart were 57.34±13.51 and 24.83±11.40 Gy, respectively. Among the parameters examined, which included the maximum dose received by the heart, the mean dose received by the right and left ventricle (RV and LV), and the maximum dose received by the right atrium (RA), the mean dose received by the RV predicted survival and was included in our multivariate analysis. The results indicated that patients with basic heart disease who were undergoing concurrent radiochemotherapy were more likely to have cardiac disease. CONCLUSIONS: This is first study to examine the prognosis of cardiovascular vessels exposed to various radiation doses during the treatment of EC, the findings of which suggest that limiting radiation exposure may be an important measure in IMRT application. These findings of this study may provide theoretical support for prediction of radiation-induced heart disease (RIHD). Furthermore, to curb the risk of RIHD, the modality of chemotherapy also needs to be attentively monitored and managed.

Conversion factor for size specific dose estimation of head CT scans based on age, for individuals from 0 up to 18 years old.

Assessing the radiation doses received by patients in computed tomography is still challenging. To overcome this, the American Association of Physicists in Medicine has introduced the concept of the size specific dose estimate (SSDE). However, the calculation of SSDE for head CT scans requires the knowledge of attenuation characteristics of the volume scanned, making its implementation in the daily clinical workflow cumbersome. In this study, we defined conversion coefficients from CTDIvol,16cmto SSDE for head CT scans based solely on the age of the patient. Using the head circumference-for-age from the child growth standards of the World Health Organization (WHO), the effective diameter-for-age was calculated for male and female individuals from 0 to 60 months-old. The effective diameter was converted into a water equivalent diameter-for-age, using a correlation established from the measurements of both quantities in 295 exams of male and female patients, from 0 to 18 years-old. WHO-estimated water equivalent diameter-for-age was validated against the measured water equivalent diameter-for-age. The head circumference-for-age from WHO was extrapolated for male and females individuals up to 18 years-old and their respective water equivalent diameter were estimated. Finally, the SSDE was calculated for all the CT head scans performed in a 9-years period in patients aged from 0 to 18 years old. Typical values of CTDIvol,16cmand DLP were also defined. SSDE varied from 0.80 up to 1.16 of the CTDIvol,16cm, depending on sex and age of the patient. WHO-estimated water equivalent diameter-for-age differed less than 20% from the measured water equivalent diameter-for-age. Typical values of SSDE varied from 28.5 up to 38.9 mGy, while typical values ranged from 30.9 up to 47.6 mGy for the CTDIvol,16cmand from 417.6 up to 861.1 mGy*cm for the DLP. SSDE can be directly calculated for head CT scans once the age of the patient is known.

Higher patient doses through X-ray imaging procedures.

Medical imaging using X-rays has been one of the most popular imaging modalities ever since the discovery of X-rays 125 years ago. With unquestionable benefits, concerns about radiation risks have frequently been raised. Computed tomography (CT) and fluoroscopic guided interventional procedures have the potential to impart higher radiation exposure to patients than radiographic examinations. Despite technological advances, there have been instances of increased doses per procedure mainly because of better diagnostic information in images. However, cumulative dose from multiple procedures is creating new concerns as effective doses >100 mSv are not uncommon. There is a need for action at all levels. Manufacturers must produce equipment that can provide a quality diagnostic image at substantially lesser dose and better implementation of optimization strategies by users. There is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering. It appears that a new monochromatic X-ray source will lead to replacement of X-ray tubes all over the world in coming years and will lead to a drastic reduction in radiation doses. This innovation will impact all X-ray imaging and will help dose reduction. For interventional procedures, the likely employment of robotic systems in practice may drastically reduce radiation exposures to operators- but patient exposure will still remain an issue. Training needs always need to be emphasized and practiced.

Genome-Wide DNA Alterations in X-Irradiated Human Gingiva Fibroblasts.

While ionizing radiation (IR) is a powerful tool in medical diagnostics, nuclear medicine, and radiology, it also is a serious threat to the integrity of genetic material. Mutagenic effects of IR to the human genome have long been the subject of research, yet still comparatively little is known about the genome-wide effects of IR exposure on the DNA-sequence level. In this study, we employed high throughput sequencing technologies to investigate IR-induced DNA alterations in human gingiva fibroblasts (HGF) that were acutely exposed to 0.5, 2, and 10 Gy of 240 kV X-radiation followed by repair times of 16 h or 7 days before whole-genome sequencing (WGS). Our analysis of the obtained WGS datasets revealed patterns of IR-induced variant (SNV and InDel) accumulation across the genome, within chromosomes as well as around the borders of topologically associating domains (TADs). Chromosome 19 consistently accumulated the highest SNVs and InDels events. Translocations showed variable patterns but with recurrent chromosomes of origin (e.g., Chr7 and Chr16). IR-induced InDels showed a relative increase in number relative to SNVs and a characteristic signature with respect to the frequency of triplet deletions in areas without repetitive or microhomology features. Overall experimental conditions and datasets the majority of SNVs per genome had no or little predicted functional impact with a maximum of 62, showing damaging potential. A dose-dependent effect of IR was surprisingly not apparent. We also observed a significant reduction in transition/transversion (Ti/Tv) ratios for IR-dependent SNVs, which could point to a contribution of the mismatch repair (MMR) system that strongly favors the repair of transitions over transversions, to the IR-induced DNA-damage response in human cells. Taken together, our results show the presence of distinguishable characteristic patterns of IR-induced DNA-alterations on a genome-wide level and implicate DNA-repair mechanisms in the formation of these signatures.