Radiation Dose Levels Research Articles

Sunflower seed oil effect on some physiological cases of adult chickens. Running Title: Gamma ray effects as oxidant stress on several physiological cases

This study aims to evaluate the effects of gamma-ray oxidation stress (ionization of biological cell as sperm) on the adult chicken reproductive system. In this research, we used cocks chicken at 36-54 weeks of age and find the importance of semen volume in (ml / brid / ejac). Concentration in (Million cells / ml.) and total sperm (Million cells / ejaculation). The value of semen volume, semen concentration and total sperm significantly increased with increased age of cock chicken but not at all ages, only at limited ages considered as control group. These values were found at irradiation with low dose rate (low intensity) of gamma ray (33, 42, and 75 mGy/h) which is a chronic dose rate (long time of irradiation) at 8 h/day for 40 days, which was significant decrease with increase low dose rate gradually. The semen volume decrease ratio with irradiation doses of approximately 5-14% and with semen concentration of approximately 5-12% for three chronic low doses relative to the control group for each cock generation. The average value of both groups showed a substantial decrease in all parameters with increased gamma radiation dose levels. The current study also aimed to identify the problems that may arise from exposure to a slow and equal dose of radiation on certain sperm parameters for a relatively long period of time and to compare them with the findings of previous work on the same mechanism and Use of sunflower seed oil as a protective and protective material against oxidative stresses resulting from radiation exposure and work Reducing its percentage, especially on certain sperm parameters in male chickens.

Assessing the safety and feasibility of neoadjuvant hormone and radiation therapy followed by robot-assisted radical prostatectomy for treating locally advanced prostate cancer: protocol for an open-label, dose-escalation, single-centre, phase I clinical trial

IntroductionPatients with locally advanced prostate cancer are at high risk of recurrence after definitive treatment. There are emerging data that radical prostatectomy can delay the progression of castration resistance and...

Deep-learning-based direct inversion for material decomposition.

To develop a convolutional neural network (CNN) that can directly estimate material density distribution from multi-energy computed tomography (CT) images without performing conventional material decomposition. The proposed CNN (denoted as Incept-net) followed the general framework of encoder-decoder network, with an assumption that local image information was sufficient for modeling the nonlinear physical process of multi-energy CT. Incept-net was implemented with a customized loss function, including an in-house-designed image-gradient-correlation (IGC) regularizer to improve edge preservation. The network consisted of two types of customized multibranch modules exploiting multiscale feature representation to improve the robustness over local image noise and artifacts. Inserts with various densities of different materials [hydroxyapatite (HA), iodine, a blood-iodine mixture, and fat] were scanned using a research photon-counting detector (PCD) CT with two energy thresholds and multiple radiation dose levels. The network was trained using phantom image patches only, and tested with different-configurations of full field-of-view phantom and in vivo porcine images. Furthermore, the nominal mass densities of insert materials were used as the labels in CNN training, which potentially provided an implicit mass conservation constraint. The Incept-net performance was evaluated in terms of image noise, detail preservation, and quantitative accuracy. Its performance was also compared to common material decomposition algorithms including least-square-based material decomposition (LS-MD), total-variation regularized material decomposition (TV-MD), and U-net-based method. Incept-net improved accuracy of the predicted mass density of basis materials compared with the U-net, TV-MD, and LS-MD: the mean absolute error (MAE) of iodine was 0.66, 1.0, 1.33, and 1.57mgI/cc for Incept-net, U-net, TV-MD, and LS-MD, respectively, across all iodine-present inserts (2.0-24.0mgI/cc). With the LS-MD as the baseline, Incept-net and U-net achieved comparable noise reduction (both around 95%), both higher than TV-MD (85%). The proposed IGC regularizer effectively helped both Incept-net and U-net to reduce image artifact. Incept-net closely conserved the total mass densities (i.e., mass conservation constraint) in porcine images, which heuristically validated the quantitative accuracy of its outputs in anatomical background. In general, Incept-net performance was less dependent on radiation dose levels than the two conventional methods; with approximately 40% less parameters, the Incept-net achieved relatively improved performance than the comparator U-net, indicating that performance gain by Incept-net was not achieved by simply increasing network learning capacity. Incept-net demonstrated superior qualitative image appearance, quantitative accuracy, and lower noise than the conventional methods and less sensitive to dose change. Incept-net generalized and performed well with unseen image structures and different material mass densities. This study provided preliminary evidence that the proposed CNN may be used to improve the material decomposition quality in multi-energy CT.

Overview of the main radiation transport codes

Abstract. Accurate predictions of expected radiation dose levels on Mars are often provided by specific radiation transport codes that have been adapted to space conditions. Unsurprisingly, several of the main space agencies and institutions involved in space research and technology tend to work with their own in-house radiation codes. We present the codes that are related to the simulation of the radiation on Mars' surface under different scenarios. All of these codes have similar fields of application, but they differ with respect to several aspects, including the energy range and types of projectiles considered as well as the models of nuclear reactions considered.

The Association Between Radiotherapy Dose and Overall Survival In Patients with Grade 2 Intracranial Infiltrative Glioma Treated with Concurrent and/or Adjuvant Chemotherapy

Previous trials have shown no benefit for radiotherapy (RT) dose escalation (59.4 – 64.8 Gy) compared with standard dose (45 – 50.4 Gy) when RT is given as adjuvant monotherapy for infiltrative low-grade glioma (LGG). However, the standard of care is now adjuvant RT with concurrent and/or adjuvant (conc/adj) chemotherapy (CTX) based on an overall survival (OS) benefit demonstrated in RTOG 98-02. The effect of RT dose escalation in the setting of conc/adj CTX is not well delineated. We used the National Cancer Database (NCDB) to select records for adult (age ≥ 18 years) patients with intracranial grade 2 LGG diagnosed between 2004 – 2015. Patients must have received adjuvant external beam RT between 45 and 65 Gy with conc/adj CTX (defined as starting within 7 days of RT initiation or up to 45 days after RT completion). Patients with brainstem glioma were excluded. RT dose level was categorized as standard (45 – 54 Gy) or high (>54 Gy - 65 Gy). The association between adjuvant RT dose level and OS was assessed using Cox multivariable and propensity score matched analyses. The study cohort consisted of 1043 patients, of which 644 (62%) received standard dose (median 54 Gy) and 399 (38%) received high dose RT (median 60 Gy). Histology was 45% astrocytoma, 31% oligodendroglioma, 21% mixed, and 3% glioma not otherwise specified. 1p/19q codeletion status was known in 251 pts (24%), of which 115 (46%) were codeleted. There were significant imbalances between RT dose cohorts at baseline for age, year of diagnosis, extent of resection, histology, and 1p/19q codeletion status. Univariable analysis demonstrated significantly worse OS with high dose vs. standard dose RT with 5-year OS of 63% and 72%, respectively (p = 0.004). Multivariable analysis demonstrated older age, male sex, higher Charlson-Deyo score, unknown tumor size, and astrocytoma histology as significantly associated with worse OS. RT dose level was not associated with OS (hazard ratio [HR] 1.2, p = 0.1). Propensity score matching yielded 380 matched pairs (n = 760). All baseline characteristics were well balanced between RT dose groups in the matched cohort. There was no difference in OS for high dose vs. standard dose RT in the matched cohort (5-year OS 64% vs. 69%, p = 0.14). Cox analysis for OS stratified by propensity score quintile demonstrated similar results (HR 1.2, p = 0.15). No difference in OS based on RT dose level was also noted in prespecified subgroups of astrocytoma histology and 1p/19q non-codeleted within the matched cohort. Adjuvant RT dose escalation above 54 Gy in the setting of conc/adj CTX was not associated with a benefit in OS for patients with infiltrative LGG in this NCDB retrospective study. This was also true for the subgroups of patients with less CTX sensitive disease, including astrocytoma histology and 1p/19q non-codeleted. Methods to improve OS other than RT dose escalation in the setting of conc/adj CTX should be investigated for patients with unfavorable LGG.

Prior-image-based Reconstruction for On-board CBCT Imaging: Application in Image-guided Radiotherapy for Head and Neck Cancer

On-board cone-beam CT (CBCT) imaging has been widely used to reduce set-up errors in head and neck cancer treated with IMRT/VMAT. However, its frequent use has raised concerns for excessive imaging dose and increased risk of developing secondary malignancies. This work investigates the feasibility of significantly reducing CBCT radiation dose by taking advantage of high-quality planning CT and a prior-image-based reconstruction approach. In image-guided radiotherapy for head and neck cancer, one standard protocol (Full-fan, 200 deg rotation, 100 kVp, 0.3 mAs/projection, 500 projections, 150 mAs in total) is employed for kV-CBCT scans. Since the high-quality planning CT scan is a rich source of patient-specific anatomical knowledge, it offers an opportunity to integrate the planning CT into on-board CBCT reconstruction for radiation dose reduction. Therefore, we studied a prior-image-based reconstruction approach for on-board CBCT imaging, which only requires partial projections and thus substantially reduces radiation dose. The prior-image-based reconstruction takes into consideration differences in attenuation coefficients (via histogram matching) and patient positioning (via affine registration) between the planning CT and on-board CBCT scans. Additionally, proper prior information control is applied to ensure the prior-image-based reconstruction does not introduce false features when there are anatomical changes between scans. An anthropomorphic head phantom and two head and neck patient datasets were used to validate the efficacy of the proposed approach. We extracted certain number of projections from the 500 projections to emulate different radiation dose levels. As we decrease the number of projections to as low as 100 (30 mAs equivalent, CTDIvol = 0.63 mGy), the standard FDK reconstructed images are degraded with severe noise and streak artifacts, and the conventional model-based iterative reconstruction generates images with inferior image quality, which could jeopardize the accuracy of patient set-up. In contrast, our proposed prior-image-based reconstruction can yield comparable image quality as the ground truth images reconstructed with the full projections, in terms of noise, resolution, and contrast-to-noise ratio. This indicates an 80% radiation dose reduction for on-board CBCT imaging by the proposed reconstruction scheme. The proposed prior-image-based reconstruction framework provides an opportunity to substantially reduce the radiation dose for on-board CBCT, without compromising image quality. This work offers a solution to reduce cumulative imaging dose as the use of CBCT for image-guided radiotherapy increases.

Intensity Modulated Radiation Therapy for Pleural Recurrence of Thymoma: A Prospective Phase 2 Study

This study aimed to evaluate the efficacy and safety of intensity modulated radiation therapy (IMRT) for pleural recurrence of thymoma that was not suitable for surgery and had progressed after chemotherapy. From February 2012, consecutive patients with pleural recurrence of thymoma were prospectively enrolled. Due to dose restrictions to normal tissue (lung, liver, and kidney), 3 different levels of radiation doses (30 Gy, 40 Gy, and 50 Gy) were prescribed for pleural lesions of different sizes and locations, with a daily fraction dose of 2 Gy. The objective response rate, local control time (LCT), overall survival time, and toxicity were recorded, respectively. By August 2016, 31 patients had completed the IMRT treatment. There were 21 male and 10 female patients, with a median age of 49 (range, 22-70) years. B3 thymoma was the major (62%) tumor subtype observed. During the median follow-up of 48 (24-70) months, the objective response rate was 97%, and the median LCT was 49 (95% confidence interval, 40.4-58.1) months. However, 29 (93.5%) patients developed out-of-field recurrence, among whom 10 (32%; 30 Gy, n = 7; 40 Gy, n = 3) developed both out-of-field and in-field recurrence. The median progression-free survival was 19 months, and no in-field recurrence occurred in the 50 Gy group. Moreover, a higher dose was related to a longer LCT. No toxicities higher than a grade 4 occurred after IMRT within the normal-tissue dose limitation. The 5-year overall survival of the patients was 81%. IMRT for pleural recurrence may act as an alternative treatment when surgery is not feasible, with a higher dose resulting in a longer LCT. In this study, out-of-field recurrence was considerably common, but repeated IMRT for new recurrence should be cautiously carried out due to the high risk of radiation-induced pneumonitis.

Dosimetry of tumor targeting imaging by convergent X-ray beam as compared with nuclear medicine

During decades nuclear medicine procedures, based on radiolabeled agents, have proved to be efficient for diseases diagnosis and treatment. Radiation emerging from patient is detected aimed at localizing radiotracer distribution that is further correlated with biochemical/metabolic physiological processes. However, a significant drawback associated with current nuclear medicine procedures implementing radionuclide infusion regards to the inherent absorbed dose as well as radiopharmaceuticals' production, storage and elimination from patient body, thus representing a risk at patient and public health level.In the recent years, alternative methods have been proposed to reduce/eliminate radionuclides in some nuclear medicine procedures. The combination of high atomic number nanoparticles infused within patient body with incident X-ray beam, like tumor targeting and treatment, appears as a potential alternative method capable of theranostics. The process is based on inducing X-ray fluorescence and secondary electrons emission in high atomic number nanoparticles by means of excitation with an external X-ray beam, avoiding employing radioactive substances.The present work reports on the dosimetry performance of both methods, comparing whenever the external convergent X-ray beam alternative may involve less or larger radiation dose levels, according to comparable signal/image quality during the procedure. To this aim, a simplified theoretical model is proposed and associated Monte Carlo simulations are performed in order to compare typical case of nuclear medicine imaging with potential performance of an innovative method, called OXIRIS (Orthovoltage X-ray Induced Radiation and Integrated System), based on convergent X-ray beam exciting high atomic number nanoparticles infused in patient.The obtained results support the proposed alternative method's feasibility, once demonstrated that patient absorbed dose levels are relative similar to those currently used by nuclear medicine procedures, whereas dose to targeted region (tumor) are significantly higher, which may be useful for treatment purposes.

Taller staff occupationally exposed to less radiation to the temple in cardiac procedures, but risk higher doses during vascular cases

This study aimed to evaluate the effect of nurse and doctor height on occupational dose to the temple during fluoroscopically guided cardiovascular procedures. Additionally, an evaluation of the relationship between doctor height and table height was performed. Staff exposed during fluoroscopic procedures may be at elevated risk of cardiovascular damage or oncogenesis and have demonstrated a higher incidence of subscapular cataracts. The heads of taller staff may be exposed to reduced levels of radiation due to the increased distance from the area of highest intensity X-ray scatter. Limited research has been performed investigating height as a predictor of head dose to nursing staff. The level of radiation dose at the level of the temple to the doctor (n = 25), scrub (n = 28), and scout nurse (n = 29) was measured in a prospective single-center, observational study using Philips DoseAware badges. Procedural characteristics were recorded for vascular and cardiac cases performed in three dedicated angiography suites. Data were also collected to investigate relationships between doctor height and table height. Data were collected for 1585 cardiac and 294 vascular procedures. Staff height was a statistically significant predictor of temple dose for doctors, scrub, and scout nurses when considering the full data sample. The log temple dose demonstrated an inverse relationship to staff height during cardiac procedures, but a positive relationship for scrub and scout nurses during vascular studies. This observational study has demonstrated that taller staff are exposed to less cranial exposure dose during fluoroscopically guided cardiac examinations but has revealed a positive correlation between height and temple dose during vascular procedures. It was also determined that doctor height was correlated with average procedural table height and that vascular access point influences the choice of table elevation.

Observer Performance for Detection of Pulmonary Nodules at Chest CT over a Large Range of Radiation Dose Levels.

Background There is a wide variation in radiation dose levels that can be used with chest CT in order to detect indeterminate pulmonary nodules. Purpose To compare the performance of lower-radiation-dose chest CT with that of routine dose in the detection of indeterminate pulmonary nodules 5 mm or greater. Materials and Methods In this retrospective study, CT projection data from 83 routine-dose chest CT examinations performed in 83 patients (120 kV, 70 quality reference mAs [QRM]) were collected between November 2013 and April 2014. Reference indeterminate pulmonary nodules were identified by two nonreader thoracic radiologists. By using validated noise insertion, five lower-dose data sets were reconstructed with filtered back projection (FBP) or iterative reconstruction (IR; 30 QRM with FBP, 10 QRM with IR, 5 QRM with FBP, 5 QRM with IR, and 2.5 QRM with IR). Three thoracic radiologists circled pulmonary nodules, rating confidence that the nodule was a 5-mm-or-greater indeterminate pulmonary nodule, and graded image quality. Analysis was performed on a per-nodule basis by using jackknife alternative free-response receiver operating characteristic figure of merit (FOM) and noninferiority limit of -0.10. Results There were 66 indeterminate pulmonary nodules (mean size, 8.6 mm ± 3.4 [standard deviation]; 21 part-solid nodules) in 42 patients (mean age, 51 years ± 17; 21 men and 21 women). Compared with the FOM for routine-dose CT (size-specific dose estimate, 6.5 mGy ± 1.8; FOM, 0.86 [95% confidence interval: 0.80, 0.91]), FOM was noninferior for all lower-dose configurations except for 2.5 QRM with IR. The sensitivity for subsolid nodules at 70 QRM was 60% (range, 48%-72%) and was significantly worse at a dose of 5 QRM and lower, whether or not IR was used (P < .05). Diagnostic image quality decreased with decreasing dose (P < .001) and was better with IR at 5 QRM (P < .05). Conclusion CT images reconstructed at dose levels down to 10 quality reference mAs (size-specific dose estimate, 0.9 mGy) had noninferior performance compared with routine dose in depicting pulmonary nodules. Iterative reconstruction improved subjective image quality but not performance at low dose levels. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by White and Kazerooni in this issue.

Determination of dose rate during the inspection of spent fuel element in the testing cell

Testing cell a hot cell is responsible for inspecting the spent fuel elements in open pool type reactor. Because the spent fuel elements examination in the testing cell would result in rising in radiation dose level, a previous precaution should be estimated to ensuring the radiation protection safety and the prevention of radiation hazard for the workers during the process. The most efficient precaution against these kinds of work is the estimation of the predicted radiation dose level around the hot cell during the inspection process. In this regard, a MCNP model was performed to simulate the spent fuel element inspection inside the hot cell to estimate the radiation dose level around the testing cell during the process. The dose rate, during the inspection of the spent fuel element, would be estimated at different decay times for different burn-up. The calculations show that the minimal decay times required to manipulating the spent fuel element would range between 120 to 270 days for burn-up ranging between 18745 and 101224.4 MWD/TU.

Cone Beam CT Imaging of the Paranasal Region with a Multipurpose X-ray System—Image Quality and Radiation Exposure

Besides X-ray and fluoroscopy, a previously introduced X-ray scanner offers a 3D cone beam option (Multitom Rax, Siemens Healthcare). The aim of this study was to evaluate various scan parameters and post-processing steps to optimize image quality and radiation exposure for imaging of the parasinus region. Four human cadaver heads were examined with different tube voltages (90–121 kV), dose levels (DLs) (278–2180 nGy) and pre-filtration methods (none, Cu 0.2 mm, Cu 0.3 mm and Sn 0.4 mm). All images were reconstructed in 2 mm slice thickness with and without a metal artifact reduction algorithm in three different kernels. In total, 80 different scan protocols and 480 datasets were evaluated. Image quality was rated on a 5-point Likert scale. Radiation exposure (mean computed tomography volume index (CTDIvol) and effective dose) was calculated for each scan. The most dose-effective combination for the diagnosis of sinusitis was 121 kV/DL of 278/0.3 mm copper (CTDIvol 1.70 mGy, effective dose 77 µSv). Scan protocols with 121 kV/DL1090/0.3 mm copper were rated sufficient for preoperative sinus surgery planning (CTDIvol 4.66 mGy, effective dose 212 µSv). Therefore, sinusitis and preoperative sinus surgery planning can be performed in diagnostic image quality at low radiation dose levels with a multipurpose X-ray system.

Diagnostic Reference Level of Radiation Dose and Image Quality among Paediatric CT Examinations in A Tertiary Hospital in Malaysia.

Pediatrics are more vulnerable to radiation and are prone to dose compared to adults, requiring more attention to computed tomography (CT) optimization. Hence, diagnostic reference levels (DRLs) have been implemented as part of optimization process in order to monitor CT dose and diagnostic quality. The noise index has recently been endorsed to be included as a part of CT optimization in the DRLs report. In this study, we have therefore set local DRLs for pediatric CT examination with a noise index as an indicator of image quality. One thousand one hundred and ninety-two (1192) paediatric patients undergoing CT brain, CT thorax and CT chest-abdomen-pelvis (CAP) examinations were analyzed retrospectively and categorized into four age groups; group 1 (0–1 year), group 2 (1–5 years), group 3 (5–10 years) and group 4 (10–15 years). For each group, data such as the volume-weighted CT dose index (CTDIvol), dose-length product (DLP) and the effective dose (E) were calculated and DRLs for each age group set at 50th percentile were determined. Both CT dose and image noise values between age groups have differed significantly with p-value < 0.05. The highest CTDIvol and DLP values in all age groups with the lowest noise index value reported in the 10–15 age group were found in CT brain examination. In conclusion, there was a significant variation in doses and noise intensity among children of different ages, and the need to change specific parameters to fit the clinical requirement.

ESTIMASI NILAI DOSIS RADIASI EFEKTIF PASIEN DARI CITRA MEDIS CT SCAN ASTEION MULTI 32 SLICE BAGIAN ABDOMEN

Receipt of radiation doses in patients by CT scan media really contributed to the radio diagnostic field. So far, volume Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) are the dose parameters used as a prescription of the dose to the patients from the examination process on the CT scan. However, these parameters have the disadvantage that they only describe the dose output from the device without regard to patient size. Size Specific Dose Estimate (SSDE) is a dose correction based on patient size and an effective dose is the dose value that arises due to differences in biological sensitivity values. Calculation of SSDE values and total effective doses were carried out in this study from data of patients who had undergone an abdominal CT scan examination. Patient radiation dose data were obtained from documents collected from the Radiology Department at the Prima Pekanbaru hospital. The data was obtained from examination results of Toshiba Asterion Multi (CTB 400 tube) CT scan of the abdomen of 20 patients. The data analysis shows that the average value of SSDE for male and female patients are 19.64 mGy and 17.4 mGy and the average total effective dose for male and female patients are 12.63 mSv and 9.16 mSv. These data indicate that the level of radiation dose received by patients is below the threshold that has been evaluated based on BAPETEN provisions.

Noise and spatial resolution properties of a commercially available deep learning-based CT reconstruction algorithm.

To characterize the noise and spatial resolution properties of a commercially available deep learning-based computed tomography (CT) reconstruction algorithm. Two phantom experiments were performed. The first used a multisized image quality phantom (Mercury v3.0, Duke University) imaged at five radiation dose levels (CTDIvol : 0.9, 1.2, 3.6, 7.0, and 22.3mGy) with a fixed tube current technique on a commercial CT scanner (GE Revolution CT). Images were reconstructed with conventional (FBP), iterative (GE ASiR-V), and deep learning-based (GE True Fidelity) reconstruction algorithms. Noise power spectrum (NPS), high-contrast (air-polyethylene interface), and intermediate-contrast (water-polyethylene interface) task transfer functions (TTF) were measured for each dose level and phantom size and summarized in terms of average noise frequency (fav ) and frequency at which the TTF was reduced to 50% (f50% ), respectively. The second experiment used a custom phantom with low-contrast rods and lung texture sections for the assessment of low-contrast TTF and noise spatial distribution. The phantom was imaged at five dose levels (CTDIvol : 1.0, 2.1, 3.0, 6.0, and 10.0mGy) with 20 repeated scans at each dose, and images reconstructed with the same reconstruction algorithms. The local noise stationarity was assessed by generating spatial noise maps from the ensemble of repeated images and computing a noise inhomogeneity index, , following AAPM TG233 methods. All measurements were compared among the algorithms. Compared to FBP, noise magnitude was reduced on average (± one standard deviation) by 74±6% and 68±4% for ASiR-V (at "100%" setting) and True Fidelity (at "High" setting), respectively. The noise texture from ASiR-V had substantially lower noise frequency content with 55±4% lower NPS fav compared to FBP while True Fidelity had only marginally different noise frequency content with 9±5% lower NPS fav compared to FBP. Both ASiR-V and True Fidelity demonstrated locally nonstationary noise in a lung texture background at all radiation dose levels, with higher noise near high-contrast edges of vessels and lower noise in uniform regions. At the 1.0mGy dose level values were 314% and 271% higher in ASiR-V and True Fidelity compared to FBP, respectively. High-contrast spatial resolution was similar between all algorithms for all dose levels and phantom sizes (<3% difference in TTF f50% ). Compared to FBP, low-contrast spatial resolution was lower for ASiR-V and True Fidelity with a reduction of TTF f50% of up to 42% and 36%, respectively. The deep learning-based CT reconstruction demonstrated a strong noise magnitude reduction compared to FBP while maintaining similar noise texture and high-contrast spatial resolution. However, the algorithm resulted in images with a locally nonstationary noise in lung textured backgrounds and had somewhat degraded low-contrast spatial resolution similar to what has been observed in currently available iterative reconstruction techniques.

Nested matched case control study for the Japan Fukushima Health Management Survey's first full-scale (second-round) thyroid examination.

Since Fukushima nuclear accident in 2011, thyroid ultrasound examinations have been conducted. The first full-scale examination detected 71 thyroid-cancer cases. This study examined whether radiation exposure was associated with thyroid-cancer incidence.Subjects were participants in the baseline screening and newborns during the 2011 fiscal year. Under nested matched case-control study design, 10 controls per each case were selected by matching the age, sex, baseline screening results, and interval between examinations. With 3 dose levels of external radiation: 1.3 + mSv (upper), 0.8 to 1.3 (middle), and 0.0 to 0.8 (reference), we applied 2 logistic models adjusting for 3 participation-proportions (primary, secondary, and fine-needle aspiratory cytology), overweight, and the B-result of baseline screening (Model 1), and past medical history, family history of thyroid cancer, and frequencies of eating seafood and seaweed in addition to the parameters in Model 1 (Model 2). We examined each model in 3 ways: (a) excluding subjects with a missing radiation exposure dose; and substituting (b1) median or (b2) mean dose of the municipality with missing dose.Odds ratios (ORs) of middle-dose exposure were (a) 1.35 (0.46-3.94), (b1) 1.55 (0.61-3.96), and (b2) 1.23 (0.50-3.03) for Model 1, and (a) 1.18 (0.39-3.57), (b1) 1.31 (0.49-3.49), and (b2) 1.02 (0.40-2.59) for Model 2. For upper-dose exposure, similar results were obtained. Past medical history was significantly associated (odds ratio = 2.04-2.08) with both (b1) and (b2) in Model 2.No significant associations were obtained between the external radiation exposure and thyroid-cancer incidence.

Radiation doses during cardiac catheterisation procedures in India: a multicentre study: Radiation dose study.

Established, evidence-based measures of radiation are required to minimise its hazards, while maintaining adequate image quality. The aim of this study is to evaluate radiation data and generate reference radiation levels for commonly performed coronary catheterisation procedures in India. In this prospective, observational study, all procedures were performed in accordance with the established standards using Innova IGS 520/2100-IQ catheterisation laboratories. Demographic, procedural and radiation data were collected. Dose reference limits (DRL) were established as the 75th percentile of the total distribution. There were 2,906 coronary angiograms (CAG), 750 percutaneous coronary interventions (PCI) and 715 CAG+PCI. DRLs for dose area product were: 19.6 Gy·cm2 for CAG, 49.8 Gy·cm2 for PCI and 72.0 Gy·cm2 for CAG+PCI, respectively. Median cumulative air kerma levels were: 185 mGy for CAG, 533mGy for PCI, and 891 mGy for CAG+PCI. Male gender, higher BMI, combining CAG+PCI, fluoroscopy time, number of cine frames, and image acquisition settings were significant contributors to increased radiation dose. This study established reference radiation dose levels for diagnostic and interventional coronary procedures in India, which were comparable to and in the lower range of international standards.

Introduction rates of radiation defects in electron irradiated semiconductor crystals of n-Si and n-GaP

A study was made of the introduction rate of radiation defects ΔNdef/ΔD versus the fast electron irradiation dose (D) in semiconductor crystals of n-Si and n-GaP. We take the concentration of radiation defects concentration Ndef to be the difference between the carrier concentration of semiconductors before n0 and after irradiation n(D) at the dose D, delivered at room temperature. By application of an appropriate fitting function to the dose dependent curves of the Ndef(D), it was demonstrated that the empiric exponential law of the form Ndef=n0(1−exp(−D/D0)) gives the best agreement with the experimental data, irrespective of the electron energy and irradiation dose. D0 is the irradiation dose, at which the carrier concentration n(D) at a temperature T=300K decreases by a factor of e. The results showed that the formation of radiation defects in the samples studied is not a linear process and ΔNdef/ΔD are found to decrease exponentially with increasing irradiation dose, according to their particular character. Using the same fitting method, it was found that for certain samples, beyond a particular radiation dose level, the rate of carrier mobility versus radiation dose also decreased exponentially.

Variability of quantitative measurements of metastatic liver lesions: a multi-radiation-dose-level and multi-reader comparison.

To evaluate the variability of quantitative measurements of metastatic liver lesions by using a multi-radiation-dose-level and multi-reader comparison. Twenty-three study subjects (mean age, 60years) with 39 liver lesions who underwent a single-energy dual-source contrast-enhanced staging CT between June 2015 and December 2015 were included. CT data were reconstructed with seven different radiation dose levels (ranging from 25 to 100%) on the basis of a single CT acquisition. Four radiologists independently performed manual tumor measurements and two radiologists performed semi-automated tumor measurements. Interobserver, intraobserver, and interdose sources of variability for longest diameter and volumetric measurements were estimated and compared using Wilcoxon rank-sum tests and intraclass correlation coefficients. Inter- and intraobserver variabilities for manual measurements of the longest diameter were higher compared to semi-automated measurements (p < 0.001 for overall). Inter- and intraobserver variabilities of volume measurements were higher compared to the longest diameter measurement (p < 0.001 for overall). Quantitative measurements were statistically different at < 50% radiation dose levels for semi-automated measurements of the longest diameter, and at 25% radiation dose level for volumetric measurements. The variability related to radiation dose was not significantly different from the inter- and intraobserver variability for the measurements of the longest diameter. The variability related to radiation dose is comparable to the inter- and intraobserver variability for measurements of the longest diameter. Caution should be warranted in reducing radiation dose level below 50% of a conventional CT protocol due to the potentially detrimental impact on the assessment of lesion response in the liver.

Detection and Characterization of Monosodium Urate and Calcium Hydroxyapatite Crystals Using Spectral Photon-Counting Radiography: A Proof-of-Concept Study

ObjectiveTo assess the potential of spectral photon-counting (PC) radiography (SPCR) for the detection and characterization of monosodium urate (MSU) and calcium hydroxyapatite (HA) crystals, based on effective atomic number (Zeff) values derived from specific X-ray attenuation characteristics at different energy levels. MethodsSuspensions of either pure agar, synthetic MSU (200 mg/ml) or HA (100 and 150 mg/ml) crystals in agar were sealed in industry-standard polystyrene vials and supported on a 2.5-mm-thick plastic table. Samples were scanned using a vendor microfocus X-ray tube and a spectral PC detector prototype with four energy thresholds per acquisition (15, 25, 30, and 35 keV). Material decomposition calibration was performed using polymethyl methacrylate (PMMA) and polyvinylchloride (PVC) slabs. Using a custom post-processing software based on polynomial material decomposition, Zeff of the respective samples were computed. All samples were additionally scanned using dual-energy CT (DECT, 80 kV and tin-filtered 150 kV) and analyzed with a proprietary post-processing algorithm for gout. ResultsMSU crystal suspension attenuated significantly less than both HA samples. MSU and HA suspensions differed significantly in Zeff (mean ± SD: 7.74 ± 0.28 vs. 9.43 ± 0.41, p < .001). Zeff values from SPCR were comparable to DECT-based reference values (p = 0.16) and were independent of the radiation dose level (0.18 – 18 mAs, p = 1). DiscussionThis in vitro feasibility study demonstrates the potential of SPCR for discriminating MSU from HA crystal suspensions based on Zeff differences. Further studies have to corroborate these initial findings ex vivo and in vivo, and to compare the diagnostic performance of SPCR with DECT in imaging of crystal-associated arthropathies.