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1.
Nan Fang Yi Ke Da Xue Xue Bao ; 40(6): 799-805, 2020 Jun 30.
Artigo em Chinês | MEDLINE | ID: mdl-32895192

RESUMO

ObjectiveTo explore a method for calculating water equivalent diameter (Dw) based on localizer CT images for calculation of the size specific dose estimates (SSDE).MethodGE Revolution CT and LightSpeed VCT were used to scan CT dose index phantoms 16 cm and 32 cm in diameter at the tube voltages of 80, 100 and 120 kV to obtain the axial image and anteroposterior localizer radiograph. According to the definition of CT Hounsfield unit, the axial images were used to calculate the conversion factors that convert the phantom thickness to water equivalent thickness. The gray value of the localizer radiograph and the water equivalent thickness were calibrated with a linear equation, and the parameters of the calibration were used to calculate the water equivalent thickness. The method was verified using 2 CT dose index phantoms and in 22 patients undergoing chest and abdominal CT examination.ResultComparison of the water equivalent diameter (Dw) based on the localizer radiograph and axial image of the 2 phantoms showed that the percentage difference between Dw from the axial images and from the localizer radiograph was below 3%. The trend of Dw variations with location in the two methods was sonsistent. The difference in Dw in intermediate region of interest between the axial image and the localizer radiograph from the 22 patients was below 6.6%. With the mean Dw in the ROI, the maximum percentage difference was 7.5%.ConclusionCalibration of the gray value of the localizer radiograph and the water equivalent thickness using the axial image and localizer radiograph of CT dose index phantoms allows quick calculation of the SSDE based on the parameters of calibration.


Assuntos
Tomografia Computadorizada por Raios X , Calibragem , Humanos , Imagens de Fantasmas , Doses de Radiação , Água
2.
Medicine (Baltimore) ; 99(38): e21964, 2020 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-32957314

RESUMO

BACKGROUND: The aim of this study was to investigate the link between heart dose and overall survival, the link between heart dose and cardiac events and whether radiation-induced heart diseases were associated with overall survival in lung cancer radiotherapy. METHODS: We performed a literature search by using Pubmed, Embase, China National Knowledge Infrastructure (CNKI) databases. Pairs of reviewers independently screened literature according to the inclusion criteria, extracted data, assessed methodological quality, and publication bias. The primary end points included overall survival and cardiac events. I was calculated in a heterogeneity assessment. Publication bias was evaluated by using Begg funnel plot and Egger test. RESULTS: Ten studies including 1 randomized controlled trial, 3 post hoc analysis of prospective trials, and 6 cohort studies were identified. The meta-analysis showed that heart volume receiving ≥5 Gy (HV5) (hazard ratio [HR] = 1.01; 95% confidence interval [CI]: 1.00-1.01), heart volume receiving ≥30 Gy (HV30) (HR = 1.01; 95% CI: 1.00-1.02), heart volume receiving ≥50 Gy (HV50) (HR = 1.05; 95%CI: 1.00-1.10), and mean heart dose (MHD) (HR = 1.01; 95%CI:1.00-1.02) all were associated with worse overall survival. In addition, the MHD (HR = 1.03; 95% CI: 1.02-1.05), HV5 (HR = 1.02; 95% CI: 1.01-1.03), and HV30 (HR = 1.02; 95% CI: 1.01-1.03) were significantly associated with all grade cardiac events. Meanwhile, compared with those who did not receive radiotherapy, the radiotherapy group experienced a significantly increased risk for cardiac-specific mortality (HR = 1.297; 95% CI: 1.213-1.387). However, the results did not show that cardiac events were associated with overall survival in lung cancer radiotherapy (HR = 1.472; 95% CI: 0.988-2.193). CONCLUSION: Exposure of the heart to radiation increased the risk of cardiac events during radiotherapy for lung cancer. Meanwhile, heart dose including HV5 and HV30 were predictors of overall survival in lung cancer radiotherapy. It is necessary to constrain the heart dose when perform thoracic radiation therapy to decrease the incidence of cardiac events and improve the overall survival.


Assuntos
Volume Cardíaco/efeitos da radiação , Cardiopatias/etiologia , Neoplasias Pulmonares/mortalidade , Neoplasias Pulmonares/radioterapia , Lesões por Radiação/epidemiologia , Cardiopatias/mortalidade , Estudos Prospectivos , Doses de Radiação , Lesões por Radiação/mortalidade
3.
J Environ Radioact ; 222: 106325, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32892899

RESUMO

The current spatial distribution of the risk of terrestrial gamma radiation in China were investigated by using spatial interpolation. And the driving factors influence on the terrestrial gamma radiation dose (TGRD) distribution were identified using the geographic detector, a new statistical method based on the nonlinear hypothesis. The results showed that the values of TGRD were range from 60 to 195 nGy h-1 with the average of 86.5 nGy h-1, and the higher values were recorded in Qingahi-Tibet Plateau, which were all within the range of background value in China. In addition, the radiological indices, ELCR (Excess Lifetime Cancer Risk), TGRD and AEDE (Annual Effective Dose Equivalent) were also within the acceptable range of values by risk assessment. The results by use of the geographic detector showed that sunshine duration, atmosphere pressure, altitude, and rainfall condition have closely related to the TGRD distribution. In addition, these meteorological factors and altitude had more impact on TGRD than the air pollution-related factors. Our study can provide useful information on studying the influence mechanism of the TGRD distribution, the variability of the natural terrestrial gamma radiation in China, and exposure data for risk assessment from low dose chronic exposures.


Assuntos
Raios gama , Monitoramento de Radiação , Poluentes Radioativos do Solo , Radiação de Fundo , China , Doses de Radiação , Medição de Risco , Tibet
4.
Hua Xi Kou Qiang Yi Xue Za Zhi ; 38(4): 415-418, 2020 Aug 01.
Artigo em Chinês | MEDLINE | ID: mdl-32865361

RESUMO

OBJECTIVE: The effects of different tube currents and voltages on image quality and radiation dose were studied to provide a theoretical basis for low-dose cone beam computed tomography (CBCT) scanning in children. METHODS: Different tube currents and voltages were used to scan the incisor area of fresh Bama pig heads by CBCT. The radiation dose was recorded, and image quality was evaluated. RESULTS: As the tube current or voltage decreased, the radiation dose and image quality gradually decreased. The computed tomographic dose index (CTDIvol) of 90 kV, 2.5 mA and 60 kV, 7.0 mA were all 1.7 mGy. The image quality score of the former was higher than that of the latter, and the difference between them was statistically significant (P<0.05). CONCLUSIONS: Low-dose CBCT scanning appears to be able to reduce the necessary tube current during imaging by improving image quality.


Assuntos
Tomografia Computadorizada de Feixe Cônico , Cabeça , Animais , Criança , Estudos de Viabilidade , Humanos , Doses de Radiação , Suínos
5.
J Int Med Res ; 48(9): 300060520950990, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32951493

RESUMO

OBJECTIVE: To evaluate temporal lung changes in coronavirus disease 2019 (COVID-19) in high-resolution computed tomography (HRCT) and to determine the appropriate computed tomographic (CT) follow-up time. METHODS: Eighty-six patients with two or more HRCT scans who were diagnosed with COVID-19 were included. The CT score and major CT findings were evaluated. RESULTS: Eighty-two (95.3%) patients had lesions on the initial HRCT scans. Most scans showed bilateral, multifocal lung lesions, with multiple lobes involved and diffuse distribution. For fifty-seven patients with type I (progress compared with the initial CT score), the CT score reached a peak at 12 days and the nadir at 36 days. For twenty-nine patients with type II (no progress compared with the initial CT score), the lowest CT score was reached at 23 days. On the final HRCT scans (>21 days), patients with a reticular pattern were older than those without a reticular pattern. CONCLUSION: The appropriate follow-up time of CT scans is during the second week (approximately 12 days) and the fourth to fifth weeks (approximately 23-36 days) from the onset of illness. These times could help reduce the CT radiation dose and show timely changes in the course of the disease by CT.


Assuntos
Infecções por Coronavirus/diagnóstico por imagem , Infecções por Coronavirus/patologia , Pulmão/patologia , Pneumonia Viral/diagnóstico por imagem , Pneumonia Viral/patologia , Adolescente , Adulto , Idoso , Betacoronavirus , Infecções por Coronavirus/diagnóstico , Progressão da Doença , Feminino , Humanos , Pulmão/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Pandemias , Pneumonia Viral/diagnóstico , Doses de Radiação , Tomografia Computadorizada por Raios X , Adulto Jovem
6.
Medicine (Baltimore) ; 99(33): e21719, 2020 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-32872052

RESUMO

The study was aimed to evaluate the image quality and radiation dose during female chest computed tomography (CT) screening using organ-based tube current modulation technology X-ray combined applications to reduce exposure (XCARE).Five hundred sixty female individuals undergoing chest CT scan were prospectively enrolled and divided into 4 groups based on body mass index (BMI). Then they were randomly and equally divided into control and experimental subgroup and respectively accepted conventional low-dose and XCARE technology spiral CT scan with same parameters. Signal-to-noise ratio and contrast-to-noise ratio were calculated. The quality of the images was evaluated by 2 radiologists using a 5-point scale.Among experimental subgroups of the 4 BMI groups, Signal-to-noise ratios, CT dose index of volume, dose-length product, effective dose, and contrast-to-noise ratio all displayed significant differences, as well as in control subgroups (P < .001). Both the experimental and control subgroups showed an increasing trend in radiation dose with the increasing of BMI. Parameters of image quality and radiation dose displayed no significant differences between control and experimental subgroups in the 4 groups. In multiple linear regression analysis, age and scanning protocol were not associated with radiation dose (P > .05), while BMI was significantly associated with increased CT dose index of volume (P < .05). The display of the lesions for the patients in the control and experimental subgroups of the 4 groups with different BMIs exhibited no statistically significant difference.The same image quality and radiation dose can be obtained using XCARE technology compared to conventional chest CT scans, which can be used regularly in female patients.Advances in knowledge: Using automatic tube current modulation technology to reduce exposure in breast. In this study, we sought a radiation protection method for sensitive tissue in chest CT screening.


Assuntos
Neoplasias Pulmonares/diagnóstico por imagem , Programas de Rastreamento/métodos , Lesões por Radiação/prevenção & controle , Radiografia Torácica/métodos , Tomografia Computadorizada Espiral/métodos , Adulto , Feminino , Humanos , Pessoa de Meia-Idade , Estudos Prospectivos , Melhoria de Qualidade , Doses de Radiação
7.
Artigo em Japonês | MEDLINE | ID: mdl-32963140

RESUMO

It is important to optimize the exposure dose when conducting interventional radiology, but optimization is difficult for medical centers to achieve independently. In 2005, we administered a questionnaire on the measurement of dose rates and awareness of exposure reduction when performing percutaneous coronary intervention. Ten years later, we conducted a follow-up survey of the same 31 centers to determine the current situation and identify trends. The results of the survey showed that the mean fluoroscopy dose rate decreased to 55% of the 2005 value, from 28.2 to 15.6 mGy/min, and the mean radiography dose rate decreased to 71% of the 2005 value, from 4.2 to 3.0 mGy/s. Dose rates for both fluoroscopy and radiography decreased by 84% of facilities. The results also indicated greater cooperation by physicians compared to 10 years ago. In particular, there was a considerable increase in the exchange of ideas with physicians regarding exposure, suggesting a stronger level of interest in exposure. The overall score for questionnaire items was 33% higher than that in the previous survey. These results show that in the past 10 years, awareness of exposure reduction has improved, and dose optimization has been a major factor in the downward trend in dose rates in radiography and fluoroscopy.


Assuntos
Intervenção Coronária Percutânea , Radiografia Intervencionista , Angiografia Coronária , Fluoroscopia , Seguimentos , Doses de Radiação , Inquéritos e Questionários , Raios X
8.
Clin Imaging ; 67: 226-236, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32871427

RESUMO

PURPOSE: Digital radiography has the potential to improve the practice of radiography but it also has the potential to significantly increase patient doses. Considering rapidly growing digital radiography in many centers, concerns rise about increasing the collective dose of the human population and following health effects. This study aimed to estimate organ and effective doses and calculate the lifetime attributable risk (LAR) of cancer incidence and mortality in digital radiography procedures in Iran. METHODS: Organ and effective doses of 12 routine digital radiography examinations including the skull, cervical spine, chest, thoracic spine, lumbar spine, pelvic and abdomen were estimated using PCXMC software based on Monte Carlo simulation method. Then, LARs of cancer incidence and mortality were estimated using the BEIR VII method. RESULTS: Organ doses ranged from 0.01 to a maximum of 2.5 mGy while effective doses ranged from 0.01 to 0.7 mSv. Radiation risk showed dependence on the X-ray examination type and the patient's sex and age. In skull and cervical X-rays, the thyroid; in the chest and thoracic spine X-rays, the lung, and breast; and in the lumbar spine, pelvic and abdominal X-rays, the colon and bladder had the highest LAR of cancer incidence and mortality. Furthermore, younger patients and also females were at higher radiation risk. CONCLUSION: The lifetime attributable risk of cancer incidence and mortality due to radiation exposure is not trivial. Therefore efforts should be made to reduce patient doses while maintaining image quality.


Assuntos
Neoplasias Induzidas por Radiação/epidemiologia , Abdome , Mama , Feminino , Humanos , Incidência , Masculino , Método de Monte Carlo , Pescoço , Neoplasias Induzidas por Radiação/etiologia , Pelve , Doses de Radiação , Intensificação de Imagem Radiográfica , Radiografia , Fatores de Risco , Software , Coluna Vertebral , Tórax
9.
J Water Health ; 18(4): 566-573, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32833682

RESUMO

As one of the drinking water quality parameters, natural radioactivity parameters are recommended to prevent a potential health threat to the public. In this study, the gross-α and gross-ß activity concentrations in 15 different brands of commercial bottled mineral water consumed in China were analyzed to evaluate the quality and corresponding health impact on the population. The activity concentrations of gross-α and gross-ß in different samples varied from 4.4 to 130.6 and 17.3-320.3 mBq L-1, respectively. The values of the annual effective dose equivalent rate (AED) for infants, children and adults ranged from 1.3 to 21.6, 2.9-52.5 and 5.5-97.8 µSv y-1, respectively. The average excess lifetime cancer risk caused by the consumption of bottled mineral water samples was estimated as 6.0 × 10-5. These results show that all the measured gross-α and gross-ß are found to be obviously less than the guidance level by WHO and the domestic standard. The values of AED are below the World Health Organization (WHO) recommended limit of 0.1 mSv y-1. Combined with the lifetime cancer risk assessment, it is concluded that there is no significant risk for consumption of the observed brands of bottled mineral water and it can be consumed safely.


Assuntos
Água Potável , Águas Minerais , Monitoramento de Radiação , Radioatividade , Poluentes Radioativos da Água , Adulto , Criança , China , Humanos , Lactente , Doses de Radiação
10.
Cancer Radiother ; 24(6-7): 676-686, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32861608

RESUMO

Continuous improvements have been made in the way to prescribe, record and report dose distributions since the therapeutic use of ionizing radiations. The international commission for radiation units and measurement (ICRU) has provided a common language for physicians and physicists to plan and evaluate their treatments. The PTV concept has been used for more than two decades but is becoming obsolete as the CTV-to-PTV margin creates a static dose cloud that does not properly recapitulate all planning vs. delivery uncertainties. The robust optimization concept has recently emerged to overcome the limitations of the PTV concept. This concept is integrated in the inverse planning process and minimizes deviations to planned dose distribution through integration of uncertainties in the planning objectives. It appears critical to account for the uncertainties that are specific to protons and should be accounted for to better exploit the clinical potential of proton therapy. It may also improve treatment quality particularly in hypofractionated photon plans of mobile tumors and more widely to photon radiotherapy. However, in contrast to the PTV concept, a posteriori evaluation of plan quality, called robust evaluation, using error-based scenarios is still warranted. Robust optimization metrics are warranted. These metrics are necessary to compare PTV-based photon and robustly optimized proton plans in general and in model-based NTCP approaches. Assessment of computational demand and approximations of robust optimization algorithms along with metrics to evaluate plan quality are needed but a step further to better prescribe radiotherapy may has been achieved.


Assuntos
Neoplasias Encefálicas/radioterapia , Carga Tumoral/efeitos da radiação , Humanos , Doses de Radiação , Radioterapia/métodos , Planejamento da Radioterapia Assistida por Computador
11.
Cancer Radiother ; 24(6-7): 576-585, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32830054

RESUMO

Cancer and cardiovascular disease (CVD) are the leading cause of mortality worldwide, and breast cancer (BC) the most common malignancy affecting women worldwide. Radiotherapy is an important component of BC treatment and participates in CVD occurrence. It seems, therefore, crucial to gather both radiation oncology and cardiology medical fields to improve the follow-up quality of our BC patients. This review aims at updating our knowledge regarding cardiotoxicities risk factors, and consequently, doses constraints in case of 3D-conformal and IMRT treatment planning. Then we will develop how to reduce cardiac exposure and what kind of cardiac follow-up we could recommend to our breast cancer patients.


Assuntos
Neoplasias da Mama/radioterapia , Cardiotoxicidade/etiologia , Cardiotoxicidade/fisiopatologia , Assistência ao Convalescente , Feminino , Humanos , Planejamento de Assistência ao Paciente , Guias de Prática Clínica como Assunto , Doses de Radiação , Radioterapia Conformacional , Fatores de Risco
12.
Cancer Radiother ; 24(6-7): 482-492, 2020 Oct.
Artigo em Francês | MEDLINE | ID: mdl-32839105

RESUMO

Radiation therapy has benefited from many developments over the past 20 years. These developments are mainly linked to the technology, imaging and informatics evolutions which allow better targets definitions, ensure better organs-at-risk sparing and excellent reproducibility of treatments, with a perfect control of patient positioning. In breast cancer radiotherapy, the evolution was marked by the possibility of reducing the duration of treatments from 6-7 to 3-4 weeks by using hypofractionated regimens, or by further reducing the irradiation to one week when treatment is solely focalised to the tumour bed. This concept of accelerated partial breast irradiation has challenged the paradigm of the obligation to irradiate the whole breast after conservative surgery in all patients. In addition, the technical mastery of accelerated partial breast irradiation and the development of stereotactic radiotherapy techniques are currently contributing to the development of research projects in neoadjuvant settings. Thus, numerous ongoing studies are evaluating the impact of high-dose preoperative tumour irradiation, alone or in combination with systemic treatments, on biological tumor changes, on anti-tumour immunity, and on the pathologic complete response, which is considered as predictive of better long-term survival in some molecular breast cancer subtypes. In this review, we discuss all these developments which allow breast radiation therapy to enter the era of personalisation of treatments in oncology.


Assuntos
Neoplasias da Mama/radioterapia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/cirurgia , Feminino , Humanos , Terapia Neoadjuvante , Doses de Radiação , Radioterapia Adjuvante
13.
PLoS One ; 15(8): e0237114, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760099

RESUMO

BACKGROUND: This study aimed to investigate the correlation between primary tumor volume and cancer failure patterns in esophageal squamous cell carcinoma (ESCC) treated with definitive concurrent chemoradiotherapy (CCRT) and examine whether increasing radiation dose can improve the outcome. METHODS: We retrospectively reviewed 124 patients with stage III ESCC treated by definitive CCRT. The primary tumor volume calculated from the radiotherapy planning computed tomography scans was correlated to treatment response, time to disease progression, and overall survival. We further analyzed whether a higher radiation dose correlated with better disease control and patient survival. RESULTS: Patients with poor CCRT response had a larger primary tumor volume than those with good response (97.9 vs 64.3 cm3, P = 0.032). The optimal cutoff value to predict CCRT response was 55.3 cm3. Large primary tumor volume (≥ 55.3 cm3) correlated with shorter time to tumor progression in the esophagus (13.6 vs 48.6 months, P = 0.033) compared with small tumor volume (< 55.3 cm3). For the large esophageal tumors (≥ 55.3 cm3), radiation dose > 60 gray significantly prolonged the time to tumor progression in esophagus (20.3 vs 10.1 months, P = 0.036) and overall survival (12.2 vs 8.0 months, P = 0.030), compared with dose ≤ 60 gray. In contrast, higher radiation dose did not benefit local disease control or overall survival in the small esophageal tumors (< 55.3 cm3). CONCLUSION: Large primary tumor volume correlates with poor local control and overall survival in ESCC treated with definitive CCRT. Radiation dose > 60 gray can improve the outcomes in patients with large primary tumor. Further prospective dose escalation trials are warranted.


Assuntos
Carcinoma de Células Escamosas/terapia , Quimiorradioterapia/métodos , Neoplasias Esofágicas/terapia , Doses de Radiação , Idoso , Carcinoma de Células Escamosas/patologia , Neoplasias Esofágicas/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dosagem Radioterapêutica , Carga Tumoral
14.
Medicine (Baltimore) ; 99(34): e21831, 2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32846829

RESUMO

Adoption of interventional endoscopic procedures is increasing with increasing prevalence of diseases. However, medical radiation exposure is concerning; therefore, radiation protection for medical staff is important. However, there is limited information on the usefulness of an additional lead shielding device during interventional endoscopic procedures. Therefore, we aimed to determine whether an additional lead shielding device protects medical staff from radiation.An X-ray unit (CUREVISTA; Hitachi Medical Systems, Tokyo, Japan) with an over-couch X-ray system was used. Fluoroscopy-associated scattered radiation was measured using a water phantom placed at the locations of the endoscopist, assistant, nurse, and clinical engineer. For each location, measurements were performed at the gonad and thyroid gland/eye levels. Comparisons were performed between with and without the additional lead shielding device and with and without a gap in the shielding device. Additionally, a clinical study was performed with 27 endoscopic retrograde cholangiopancreatography procedures.The scattered radiation dose was lower with than without additional lead shielding at all medical staff locations and decreased by 84.7%, 82.8%, 78.2%, and 83.7%, respectively, at the gonad level and by 89.2%, 86.4%, 91.2%, and 87.0%, respectively, at the thyroid gland/eye level. Additionally, the scattered radiation dose was lower without than with a gap in the shielding device at all locations.An additional lead shielding device could protect medical staff from radiation during interventional endoscopic procedures. However, gaps in protective equipment reduce effectiveness and should be eliminated.


Assuntos
Exposição Ocupacional/prevenção & controle , Exposição à Radiação/prevenção & controle , Proteção Radiológica/instrumentação , Radiografia Intervencionista/efeitos adversos , Colangiopancreatografia Retrógrada Endoscópica/efeitos adversos , Colangiopancreatografia Retrógrada Endoscópica/estatística & dados numéricos , Fluoroscopia/efeitos adversos , Gônadas/efeitos da radiação , Humanos , Traumatismos Ocupacionais/prevenção & controle , Imagens de Fantasmas/estatística & dados numéricos , Equipamentos de Proteção/normas , Doses de Radiação , Lesões por Radiação/prevenção & controle , Proteção Radiológica/métodos , Glândula Tireoide/efeitos da radiação
15.
Medicine (Baltimore) ; 99(34): e21886, 2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32846848

RESUMO

BACKGROUND: As the gold standard for imaging sinus disease, the main disadvantage of computed tomography (CT) of the pediatric paranasal sinus is radiation exposure. Because of this, 1 protocol for CT should reduce radiation dose while maintaining image quality. The aim of this study is to evaluate the image quality of dose-reduced paranasal sinus computed tomography (CT) using an ultralow tube voltage (70 kVp) combined with iterative reconstruction (IR) in children. METHODS: CT scans of the paranasal sinus were performed using different protocols [70 kVp protocols with IR, Group A, n = 80; 80 kVp protocols with a filtered back projection algorithm, Group B, n = 80] in 160 pediatric patients. Then, the volume-weighted CT dose index, dose-length product, and effective dose were estimated. Image noise, the signal-to-noise ratio and the diagnostic image quality were also evaluated. RESULTS: For the radiation dose, the volume-weighted CT dose index, dose-length product and effective dose values were significantly lower for the 70 kVp protocols than for the 80 kVp protocols (P < .001). Compared with the 80 kVp protocols, the 70 kVp protocols had significantly higher levels of image noise (P = .001) and a lower signal-to-noise ratio (P = .002). No significant difference in the overall subjective image quality grades was observed between these 2 groups (P = .098). CONCLUSION: The ultralow tube voltage (70 kVp) technique combined with IR enabled a significant dose reduction in CT examinations performed in the pediatric paranasal sinus while maintaining diagnostic image quality with clinically acceptable image noise.


Assuntos
Aumento da Imagem/instrumentação , Doenças dos Seios Paranasais/diagnóstico por imagem , Exposição à Radiação/efeitos adversos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/instrumentação , Adolescente , Algoritmos , Criança , Pré-Escolar , China/epidemiologia , Estudos de Viabilidade , Feminino , Humanos , Masculino , Estudos Prospectivos , Doses de Radiação , Exposição à Radiação/estatística & dados numéricos , Razão Sinal-Ruído
16.
PLoS One ; 15(8): e0236466, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32764764

RESUMO

AIM: The present work concerns the comparison of the performances of three systems for dosimetry in RPT that use different techniques for absorbed dose calculation (organ-level dosimetry, voxel-level dose kernel convolution and Monte Carlo simulations). The aim was to assess the importance of the choice of the most adequate calculation modality, providing recommendations about the choice of the computation tool. METHODS: The performances were evaluated both on phantoms and patients in a multi-level approach. Different phantoms filled with a 177Lu-radioactive solution were used: a homogeneous cylindrical phantom, a phantom with organ-shaped inserts and two cylindrical phantoms with inserts different for shape and volume. A total of 70 patients with NETs treated by PRRT with 177Lu-DOTATOC were retrospectively analysed. RESULTS: The comparisons were performed mainly between the mean values of the absorbed dose in the regions of interest. A general better agreement was obtained between Dose kernel convolution and Monte Carlo simulations results rather than between either of these two and organ-level dosimetry, both for phantoms and patients. Phantoms measurements also showed the discrepancies mainly depend on the geometry of the inserts (e.g. shape and volume). For patients, differences were more pronounced than phantoms and higher inter/intra patient variability was observed. CONCLUSION: This study suggests that voxel-level techniques for dosimetry calculation are potentially more accurate and personalized than organ-level methods. In particular, a voxel-convolution method provides good results in a short time of calculation, while Monte Carlo based computation should be conducted with very fast calculation systems for a possible use in clinics, despite its intrinsic higher accuracy. Attention to the calculation modality is recommended in case of clinical regions of interest with irregular shape and far from spherical geometry, in which Monte Carlo seems to be more accurate than voxel-convolution methods.


Assuntos
Lutécio/química , Imagens de Fantasmas/estatística & dados numéricos , Radioisótopos/química , Radiometria/estatística & dados numéricos , Receptores de Peptídeos/isolamento & purificação , Algoritmos , Humanos , Método de Monte Carlo , Doses de Radiação , Receptores de Peptídeos/química , Estudos Retrospectivos
17.
J Occup Environ Hyg ; 17(9): 390-397, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32795221

RESUMO

The SARS-CoV-2 pandemic has led to a global decrease in personal protective equipment (PPE), especially filtering facepiece respirators (FFRs). Ultraviolet-C wavelength is a promising way of decontamination, however adequate dosimetry is needed to ensure balance between over and underexposed areas and provide reliable results. Our study demonstrates that UVGI light irradiance varies significantly on different respirator angles and propose a method to decontaminate several masks at once ensuring appropriate dosage in shaded zones. An UVGI irradiator was built with internal dimensions of 69.5 × 55 × 33 cm with three 15 W UV lamps. Inside, a grating of 58 × 41 × 15 cm was placed to hold the masks. Two different flat fold respirator models were used to assess irradiance, four of model Aura 9322 3 M of dimensions 17 × 9 × 4 cm (tri-fold), and two of model SAFE 231FFP3NR (bi-fold) with dimensions 17 × 6 × 5 cm. An STN-SilverNova spectrometer was employed to verify wavelength spectrum and surface irradiance. A simulation was performed to find the irradiance pattern inside the box and the six masks placed inside. These simulations were carried out using the software DIALUX EVO 8.2. The data obtained reveal that the irradiance received inside the manufactured UVGI-irradiator depends not only on the distance between the lamps' plane and the base of the respirators but also on the orientation and shape of the masks. This point becomes relevant to assure that all the respirators inside the chamber receive the correct dosage. Irradiance over FFR surfaces depend on several factors such as distance and angle of incidence of the light source. Careful irradiance measurement and simulation can ensure reliable dosage in the whole mask surface, balancing overexposure. Closed box systems might provide a more reliable, reproducible UVGI dosage than open settings.


Assuntos
Infecções por Coronavirus/epidemiologia , Descontaminação/métodos , Pneumonia Viral/epidemiologia , Dispositivos de Proteção Respiratória/microbiologia , Raios Ultravioleta , Betacoronavirus , Reutilização de Equipamento , Humanos , Pandemias , Doses de Radiação
19.
Phys Med ; 77: 36-42, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32771702

RESUMO

PURPOSE: To assess the impact of iterative reconstructions on image quality and detectability of focal liver lesions in low-energy monochromatic images from a Fast kV-Switching Dual Energy CT (KVSCT) platform. METHODS: Acquisitions on an image-quality phantom were performed using a KVSCT for three dose levels (CTDIvol:12.72/10.76/8.79 mGy). Raw data were reconstructed for five energy levels (40/50/60/70/80 keV) using Filtered Back Projection (FBP) and four levels of ASIR (ASIR30/ASIR50/ASIR70/ASIR100). Noise power spectrum (NPS) and task-based transfer function (TTF) were measured before computing a Detectability index (d') to model the detection task of liver metastasis (LM) and hepatocellular carcinoma (HCC) as function of keV. RESULTS: From 40 to 70 keV, noise-magnitude was reduced on average by -68% ± 1% with FBP; -61% ± 3% with ASIR50 and -52% ± 6% with ASIR100. The mean spatial frequency of the NPS decreased when the energy level decreased and the iterative level increased. TTF values at 50% decreased as the energy level increased and as the percentage of ASIR increased. The detectability of both lesions increased with increasing dose level and percentage of ASIR. For the LM, d' peaked at 70 keV for all reconstruction types, except for ASIR70 at 12.72 mGy and ASIR100, where d' peaked at 50 keV. For HCC, d' peaked at 60 keV for FBP and ASIR30 but peaked at 50 keV for ASIR50, ASIR70 and ASIR100. CONCLUSIONS: Using percentage of ASIR above 50% at low-energy monochromatic images could limit the increase of noise-magnitude, benefit from spatial resolution improvement and hence enhance detectability of subtle low contrast focal liver lesions such as HCC.


Assuntos
Carcinoma Hepatocelular/diagnóstico por imagem , Neoplasias Hepáticas/diagnóstico por imagem , Fígado/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Humanos , Imagens de Fantasmas , Doses de Radiação , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/instrumentação
20.
Artigo em Japonês | MEDLINE | ID: mdl-32814735

RESUMO

PURPOSE: To compare the radiation dose and image quality using the conventional method for performing the front and side scout view and a new method for performing the side scout view, and then correct the table height at the scan isocenter and perform the front scout view. METHODS: We retrospectively analyzed fifty-six children who had underwent computed tomography (CT) examination between June 2014 and August 2018. We divided them into two groups. The conventional method was performed in 3 steps: 1. obtain the front scout view, 2. obtain the side scout view, and 3. main scan. Without table position correction, the new method was performed in 4 steps: 1. obtain the side scout view with table position correction, 2. patient correction at the scan isocenter, 3. obtain the front scout view, and 4. main scan. We used a 64-row CT scanner (LightSpeed VCT; GE Healthcare). Scan parameters were tube voltage 80 kV, automatic tube current modulation, noise index 16, slice thickness 5 mm, rotation time 0.4 s/rot, helical pitch 1.375, and reconstruction kernel standard. We recorded the volume dose index (CTDIvol) and dose length product (DLP) on the CT console and compared the radiation dose in both groups. To evaluate the image quality in both groups, the mean standard deviation of CT number (SD value) was measured within an approximately 5-10 mm2  circular region of interest. We measured the scan length of the pediatric patient and accuracy of pediatric positioning at the CT examination. A grid was displayed on the CT axial image, taken to evaluate the error from the scan isocenter during alignment, and the error between the height of half the body thickness and the scan isocenter was recorded. RESULTS: Scan lengths were median (minimum-maximum) values of 16.2 cm (10.8-21.5 cm) and 16.8 cm (11.5-23.0 cm). There were no significant differences in the scan length between both groups (p=0.47). In the group with table position correction, median (minimum-maximum) values for CTDIvol, DLP and SD value were 0.40 mGy (0.3-0.7 mGy), 7.6 mGyï½¥cm (4.4-11.5 mGyï½¥cm), and 24.0 HU (18.3-37.5 HU), respectively. In the group without the table position correction, median (minimum-maximum) values for CTDIvol, DLP and SD value were 0.40 mGy (0.3-0.6 mGy), 7.1 mGyï½¥cm (4.2-13.8 mGyï½¥cm), and 20.3 HU (11.3-28.8 HU), respectively. There were no significant differences in the CTDIvol and DLP values between both groups (p=0.42 and p=0.44, respectively); however, there were significant differences in the SD value in both groups (p<0.01). The error for the accuracy of pediatric positioning was 0 mm (0 to 0 mm) and 10 mm (-16 to+59 mm) using the conventional and new methods (p<0.01), respectively. CONCLUSIONS: It was suggested that the optimum image could be obtained during CT scan with automatic tube current modulation by using this potential new method (1. obtain the side scout view, 2. patient correction at the scan isocenter, 3. obtain the side scout view, and 4. main scan).


Assuntos
Ruído , Tomografia Computadorizada por Raios X , Criança , Humanos , Doses de Radiação , Estudos Retrospectivos , Tomógrafos Computadorizados
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