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AIM: This study assessed the myocardial infarction (MI) using a novel fusion approach (multi-flavored or tensor-based) of multi-parametric cardiac magnetic resonance imaging (CMRI) at four sequences; T1-weighted (T1W) in the axial plane, sense-balanced turbo field echo (sBTFE) in the axial plane, late gadolinium enhancement of heart short axis (LGE-SA) in the sagittal plane, and four-chamber views of LGE (LGE-4CH) in the axial plane. METHODS: After considering the inclusion and exclusion criteria, 115 patients (83 with MI diagnosis and 32 as healthy control patients), were included in the present study. Radiomic features were extracted from the whole left ventricular myocardium (LVM). Feature selection methods were Least Absolute Shrinkage and Selection Operator (Lasso), Minimum Redundancy Maximum Relevance (MRMR), Chi-Square (Chi2), Analysis of Variance (Anova), Recursive Feature Elimination (RFE), and SelectPersentile. The classification methods were Support Vector Machine (SVM), Logistic Regression (LR), and Random Forest (RF). Different metrics, including receiver operating characteristic curve (AUC), accuracy, F1- score, precision, sensitivity, and specificity were calculated for radiomic features extracted from CMR images using stratified five-fold cross-validation. RESULTS: For the MI detection, Lasso (as the feature selection) and RF/LR (as the classifiers) in sBTFE sequences had the best performance (AUC: 0.97). All features and classifiers of T1 + sBTFE sequences with the weighted method (as the fused image), had a good performance (AUC: 0.97). In addition, the results of the evaluated metrics, especially mean AUC and accuracy for all models, determined that the T1 + sBTFE-weighted fused method had strong predictive performance (AUC: 0.93±0.05; accuracy: 0.93±0.04), followed by T1 + sBTFE-PCA fused method (AUC: 0.85±0.06; accuracy: 0.84±0.06). CONCLUSION: Our selected CMRI sequences demonstrated that radiomics analysis enables to detection of MI accurately. Among the investigated sequences, the T1 + sBTFE-weighted fused method with the highest AUC and accuracy values was chosen as the best technique for MI detection. [ABSTRACT FROM AUTHOR]

Introduction: Laser markers installed on the walls and ceiling of the bunker are usually used for patient positioning in radiotherapy. Therefore, they directly influence radiotherapy treatment accuracy. The present study aimed to develop a new method without using an external portable laser source or any dedicated laser alignment phantom to align the radiotherapy setup lasers installed in treatment bunkers. Methods: A patient-specific IMRT quality assurance phantom (OCTAVIUS 4D in our study) was used as a phantom having a similar size of patients and surface markers precisely showing the central point of the phantom. After ensuring the precise coincidence between light and radiation isocenters at various gantry angles (0, 90, and 270 degrees), true laser positions were found optically by matching the shadows of all the cross hair lines (CHLs) on the external window of the gantry head and also on the phantom surface at various gantry angles. The distances between the laser lines and light field crosslines on the treatment room walls for our proposed approach were compared with the conventional laser calibration technique (laser calibration with an external laser source positioned in the machine isocenter) and reported as laser alignment accuracy. Results: The mean displacements performed for laser alignment on the phantom surface were 1.2 ± 0.2, 1.1 ± 0.1, and 1.0 ± 0.1 mm for sagittal, coronal, and axial lasers, respectively. These displacements on the gantry head exit plane were 1.4 ± 0.3, 1.2 ± 0.2, and 1.1 ± 0.1 mm, respectively. Mean value of laser alignment accuracy on the wall of the treatment room was 19.5 ± 0.5 mm for our new method, whilst it was 32.7 ± 0.7 mm for adjusting lasers with the conventional method. Conclusion: Our new approach for laser alignment was performed and evaluated successfully. This method can provided a more accurate procedure than the conventional method without needing an external laser source or dedicated laser alignment phantom. [ABSTRACT FROM AUTHOR]

Introduction: EGSnrc software package is one of the computational packages for Monte Carlo simulation in radiation therapy and has several subset codes. Directional bremsstrahlung splitting (DBS) is a technique that applies braking radiations in interactions in this software. This study aimed to evaluate the effect of this technique on the simulation time, uncertainty, particle number of phase-space data, and photon beam spectrum resulting from a medical linear accelerator (LINAC). Materials and methods: The gantry of the accelerator, including the materials and geometries of different parts, was simulated using the BEAMnrc code (a subset code in the EGSnrc package). The phase-space data were recorded in different parts of the LINAC. The DBS values (1, 10, 100, and 1000) were changed, and their effects were evaluated on the simulation parameters and output spectra. Results: Increasing the DBS value from 1 to 1000 resulted in an increase in the simulation time from 1.778 to 11.310 hours, and increasing the number of particles in the phase-space plane (5 590 732-180 328 382). When the DBS had been picked up from 1 to 100, the simulation uncertainty decreased by about 1.29%. In addition, the DBS increment value from 100 to 1000 leads to an increase in uncertainty and simulation time of about 0.71% and 315%, respectively. Conclusion: Although using the DBS technique reduces the simulation time or uncertainty, increasing the DBS from a specific value, equal to 100 in our study, increases simulation uncertainties and times. Therefore, we propose considering a specific DBS value as we obtained for the Monte Carlo simulation of photon beams produced by linear accelerators. [ABSTRACT FROM AUTHOR]

Background: Approximately 50% of dental amalgam is elemental mercury by weight. Accumulating body of evidence now shows that not only static magnetic fields (SMF) but both ionizing and non-ionizing electromagnetic radiations can increase the rate of mercury release from dental amalgam fillings. Iranian scientists firstly addressed this issue in 2008 but more than 10 years later, it became viral worldwide. Objective: This review was aimed at evaluating available data on the magnitude of the effects of different physical stressors (excluding chewing and brushing) on the release of toxic mercury from dental amalgam fillings and microleakage. Material and Methods: The papers reviewed in this study were searched from PubMed, Google Scholar, and Scopus (up to 1 December 2019). The keywords were identified from our initial research matching them with those existing on the database of Medical Subject Headings (MeSH). The non-English papers and other types of articles were not included in this review. Results: Our review shows that exposure to static magnetic fields (SMF) such as those generated by MRI, electromagnetic fields (EMF) such as those produced by mobile phones; ionizing electromagnetic radiations such as X-rays and non- Ionizing electromagnetic radiation such as lasers and light cure devices can significantly increase the release of mercury from dental amalgam restorations and/or cause microleakage. Conclusion: The results of this review show that a wide variety of physical stressors ranging from non-ionizing electromagnetic fields to ionizing radiations can significantly accelerate the release of mercury from amalgam and cause microleakage. [ABSTRACT FROM AUTHOR]

Poly 2-acrylamido-2-methy-1-propanesulfonic acid sodium salt and gelatin (PASSAG) gel dosimeter has a negligible toxicity and also excellent dosimetric characteristics. Nonetheless, the main drawback of this gel dosimeter is its relatively low response–dose sensitivity. In this study, we investigated whether adding glucose into the conventional PASSAG gel dosimeter could increase the response–dose sensitivity. For this purpose, new gel dosimeters of G-PASSAG (glucose and PASSAG) were first fabricated, and then irradiated using 6 MV X-rays. The responses (R2) of gel dosimeters after irradiation were read out by a 1.5 T MRI scanner. In this regard, the R2–dose responses and the R2–dose sensitivities of conventional PASSAG and G-PASSAG gel dosimeters with 3 and 5 wt% glucose were investigated at a 0–10 Gy dose range, 15–24 °C scanning temperatures, and 1–30 days post-irradiation. The findings showed that the R2–dose sensitivities of G-PASSAG gel dosimeters with 3 and 5 wt% glucose (compared to conventional PASSAG gel dosimeter) improved by 6.70 and 27.13%, respectively. Furthermore, there were excellent linear R2–dose responses for these new gel dosimeters in a 0–10 Gy dose range. A relative stability in the R2–dose sensitivity of the gel dosimeters during 20–24 °C scanning room temperatures was also observed. Moreover, G-PASSAG gel dosimeters represented temporal stability at the R2 values during 15–30 days post-irradiation. Additionally, the improved R2–dose sensitivity over post-irradiation time varied 6.06–10.05% and 16.65–27.13% for G-PASSAG gel dosimeters with 3 and 5 wt% glucose, respectively. [ABSTRACT FROM AUTHOR]

Introduction: Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) are primary techniques for rectal cancer treatment. In radiotherapy planning, collimator rotation is a crucial parameter, and its adjustments can lead to dosimetric variations. This study examined the influence of collimator rotation on dosimetric outcomes for different IMRT and VMAT plans for rectal cancer. Methods: CT images from 20 male rectal cancer patients were used for IMRT and VMAT treatment planning with varying collimator angles. Nine IMRT techniques (5, 7, and 9 coplanar fields with collimator angles of 0°, 45°, and 90°) and six VMAT techniques (1 and 2 full coplanar arcs with collimator angles of 0°, 45°, and 90°) were planned for each patient. Dosimetric results for target tissue (conformity index [CI] and homogeneity index [HI]) and sparing of organs at risk (OARs) (parameters from OARs dose - volume histograms [DVH]) were analyzed and compared, along with radiobiological findings. Results: The 7-fields IMRT technique showed lower bladder doses (V40Gy, V45Gy) unaffected by collimator rotation. The 9 - fields IMRT and 2 - arcs VMAT (excluding the 90 - degree collimator) exhibited the lowest V35Gy and V45Gy. A 90 - degree collimator rotation in 2 - arcs VMAT significantly increased small bowel and bladder V45Gy, femoral head doses, and HI values. Radiobiologically, the 90 - degree rotation adversely affected small bowel NTCP (normal tissue complication probability). No superiority was observed for a 45 - degree collimator rotation over 0 or 30 degrees in VMAT techniques. Conclusions: Collimator rotation minimally impacted dosimetric parameters in IMRT planning but significantly affected VMAT techniques. A 90 - degree rotation in VMAT, especially in a 2 - full arc technique, negatively impacted PTV homogeneity index, bladder dose, and small bowel NTCP. Other evaluated collimator angles did not significantly affect VMAT dosimetrical or radiobiological outcomes. [ABSTRACT FROM AUTHOR]

INTRODUCTION: EGSnrc software package is one of the computational packages for Monte Carlo simulation in radiation therapy and has several subset codes. Directional bremsstrahlung splitting (DBS) is a technique that applies braking radiations in interactions in this software. This study aimed to evaluate the effect of this technique on the simulation time, uncertainty, particle number of phase-space data, and photon beam spectrum resulting from a medical linear accelerator (LINAC). MATERIALS AND METHODS: The gantry of the accelerator, including the materials and geometries of different parts, was simulated using the BEAMnrc code (a subset code in the EGSnrc package). The phase-space data were recorded in different parts of the LINAC. The DBS values (1, 10, 100, and 1000) were changed, and their effects were evaluated on the simulation parameters and output spectra. RESULTS: Increasing the DBS value from 1 to 1000 resulted in an increase in the simulation time from 1.778 to 11.310 hours, and increasing the number of particles in the phase-space plane (5 590 732-180 328 382). When the DBS had been picked up from 1 to 100, the simulation uncertainty decreased by about 1.29%. In addition, the DBS increment value from 100 to 1000 leads to an increase in uncertainty and simulation time of about 0.71% and 315%, respectively. CONCLUSION: Although using the DBS technique reduces the simulation time or uncertainty, increasing the DBS from a specific value, equal to 100 in our study, increases simulation uncertainties and times. Therefore, we propose considering a specific DBS value as we obtained for the Monte Carlo simulation of photon beams produced by linear accelerators. [ABSTRACT FROM AUTHOR]

OBJECTIVES: To evaluate skin dose differences between TPS (treatment planning system) calculations and TLD (thermo-luminescent dosimeters) measurements along with the dosimetric effect of applicator misplacement for patients diagnosed with gynecological (GYN) cancers undergoing brachytherapy. METHODS: The skin doses were measured using TLDs attached in different locations on patients' skin in pelvic regions (anterior, left, and right) for 20 patients, as well as on a phantom. In addition, the applicator surface dose was calculated with TLDs attached to the applicator. The measured doses were compared with TPS calculations to find TPS accuracy. For the phantom, different applicator shifts were applied to find the effect of applicator misplacement on the surface dose. RESULTS: The mean absolute dose differences between the TPS and TLDs results for anterior, left, and right points were 3.14±1.03, 6.25±1.88, and 6.20±1.97 %, respectively. The mean difference on the applicator surface was obtained 1.92±0.46 %. Applicator misplacements of 0.5, 2, and 4 cm (average of three locations) resulted in 9, 36, and 61%, dose errors respectively. CONCLUSIONS: The surface/skin differences between the calculations and measurements are higher in the left and right regions, which relate to the higher uncertainty of TPS dose calculation in these regions. Furthermore, applicator misplacements can result in high skin dose variations, therefore it can be an appropriate quality assurance method for future research. [ABSTRACT FROM AUTHOR]

Background: Computed tomography (CT) is a routine procedure for diagnosing using ionization radiation which has hazardous effects especially on sensitive organs. Objective: The aim of this study was to quantify the dose reduction effect of lead apron shielding on the testicular region during routine chest CT scans. Material and Methods: In this measurement study, the routine chest CT examinations were performed for 30 male patients with common lead aprons folded and positioned in testis regions. The patient's mean body mass index (BMI) was 26.2 ± 4.6 kg/m². To calculate the doses at testis region, three thermoluminescent dosimeters (TLD-100) were attached at the top surface of the apron as an indicator of the doses without shielding, and three TLDs under the apron for doses with shielding. The TLD readouts were compared using SPSS software (Wilcoxon test) version 16. Results: The radiation dose in the testicular regions was reduced from 0.46 ± 0.04 to 0.20 ± 0.04 mGy in the presence of lead apron shielding (p < 0.001), the reduction was equal to 56%. Furthermore, the heritable risk probability was obtained at 2.0 ×10-5 % and 4.6 ×10-5 % for the patients using the lead apron shield versus without shield, respectively. Conclusion: Applying common lead aprons as shielding in the testis regions of male patients undergoing chest CT scans can reduce the radiation doses significantly. Therefore, this shield can be recommended for routine chest CT examinations. [ABSTRACT FROM AUTHOR]

This study was conducted to determine first local diagnostic reference levels (DRLs) and achievable doses (ADs) for pediatric patients during the most common computed tomography (CT) procedures in Yazd province. The DRL was obtained based on volume CT dose index (CTDIvol) and dose length product (DLP) for four various age groups of children. Data were collected from the most commonly performed pediatric CT scans, including abdomen–pelvis, chest, brain and sinus examinations, at six high-loaded institutes. The patients' data (766 no.) in terms of CTDIvol and DLP were obtained from four age groups: ≤1-, 1–5-, 5–10- and 10–15-y-old. The 75th percentiles of CTDIvol and DLP were considered as DRL values and the 50th percentiles were described as ADs for those parameters. Consequently, the acquired DRLs were compared with other national and international published values. The DRLs in terms of CTDIvol for abdomen–pelvis, chest, brain and sinus examinations were 3, 8, 9 and 10 mGy; 4, 5, 5 and 5 mGy; 25, 28, 29 and 38 mGy; and 23, 24, 26 and 27 mGy for four different age groups of ≤1-, 1–5-, 5–10- and 10–15-y-old, respectively. The DRL values in terms of DLP were 75, 302, 321 and 342 mGy.cm; 109, 112, 135 and 170 mGy.cm, 352, 355, 360 and 481 mGy.cm; and 206, 211, 228 and 245 mGy.cm, respectively, for the mentioned age groups. In this study, the DRL and AD values in the brain examination were greater among the other studied regions. The DRL plays a critical role in the optimization of radiation doses delivered to patients and in improving their protection. This study provides the local DRLs and ADs for the most common pediatric CT scanning in Yazd province to create optimum situation for the clinical practice. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVE: Radiomics has been widely used in quantitative analysis of medical images for disease diagnosis and prognosis assessment. The objective of this study is to test a machine-learning (ML) method based on radiomics features extracted from chest CT images for screening COVID-19 cases. METHODS: The study is carried out on two groups of patients, including 138 patients with confirmed and 140 patients with suspected COVID-19. We focus on distinguishing pneumonia caused by COVID-19 from the suspected cases by segmentation of whole lung volume and extraction of 86 radiomics features. Followed by feature extraction, nine feature-selection procedures are used to identify valuable features. Then, ten ML classifiers are applied to classify and predict COVID-19 cases. Each ML models is trained and tested using a ten-fold cross-validation method. The predictive performance of each ML model is evaluated using the area under the curve (AUC) and accuracy. RESULTS: The range of accuracy and AUC is from 0.32 (recursive feature elimination [RFE]+Multinomial Naive Bayes [MNB] classifier) to 0.984 (RFE+bagging [BAG], RFE+decision tree [DT] classifiers) and 0.27 (mutual information [MI]+MNB classifier) to 0.997 (RFE+k-nearest neighborhood [KNN] classifier), respectively. There is no direct correlation among the number of the selected features, accuracy, and AUC, however, with changes in the number of the selected features, the accuracy and AUC values will change. Feature selection procedure RFE+BAG classifier and RFE+DT classifier achieve the highest prediction accuracy (accuracy: 0.984), followed by MI+Gaussian Naive Bayes (GNB) and logistic regression (LGR)+DT classifiers (accuracy: 0.976). RFE+KNN classifier as a feature selection procedure achieve the highest AUC (AUC: 0.997), followed by RFE+BAG classifier (AUC: 0.991) and RFE+gradient boosting decision tree (GBDT) classifier (AUC: 0.99). CONCLUSION: This study demonstrates that the ML model based on RFE+KNN classifier achieves the highest performance to differentiate patients with a confirmed infection caused by COVID-19 from the suspected cases. [ABSTRACT FROM AUTHOR]

The aim of this study was to synthesize and characterize the dimercaptosuccinic acid (DMSA) cobalt–zinc (Co–Zn) ferrite magnetic nanoparticles (NPs) and their efficiency as a contrast agent in in vivo MR imaging of rat liver. Co–Zn ferrite NPs were synthesized by the thermal decomposition method and stabilized by DMSA. The NPs were characterized by different analyses to study their physical and magnetic properties and were injected into 6 adult male rats. Liver MRI was performed to measure the signal intensity at different times. The average nanoparticle size was estimated at about 8 ± 1 nm using transmission electron microscopy (TEM). The r2 and r2* relaxivity of these particles were obtained at 32.85 and 168.96 mmol L−1 s−1, respectively, using an agarose phantom imaged by MRI. In the in vivo condition, injection of SNPs (2.5 mg Fe/kg) showed negative contrast in a way that for T2 and T2* weighted the maximum contrast enhancement was 58.46 and 77.13%, respectively. Regarding our results, the synthesized Co–Zn ferrite NPs stabilized by DMSA are appropriate agents for increasing the contrast in both T2 and T2* weighted based on MR imaging in rat liver. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the dosimetric parameters of level II lymph nodes in chest wall three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) of mastectomy patients using dual-isocentric (DIT) and mono-isocentric techniques (MIT). Materials and methods: Computed tomography (CT) images of 20 mastectomy patients undergoing chest wall external radiotherapy were used as the input data for the abovementioned techniques. Selected dosimetric parameters were calculated for the axillary level I–III lymph nodes, chest wall, heart and lung. Paired t-test statistical analysis was used for comparing the results of MIT and DIT in both 3D-CRT and IMRT methods. Results: There were significant differences in Dmin (minimum dose), Dmax (maximum dose) and maximum–minimum dose between MIT and DIT techniques (13, −8·6, −52·2% differences for Dmin, Dmax and maximum–minimum, respectively) in IMRT. There were also significant differences for Dmean (mean dose), Dmax and maximum–minimum dose (7·8, −11·4, −44·6% differences in Dmean, Dmax and maximum–minimum, respectively) in 3D-CRT (p < 0·05). In addition, there were not any differences in the dosimetric parameters for heart, lung and level I and III lymph nodes. Conclusion: In both 3D-CRT and IMRT methods, level II lymph node dose distribution in MIT was closer to the prescribed dose compared with DIT due to the position of these nodes in the field junction area. To achieve a better dose homogeneity, it could be recommended to use MIT instead of DIT in 3D-CRT and IMRT for mastectomy patients. [ABSTRACT FROM AUTHOR]

Introduction and purpose: During the radiation therapy of tumoral breast, the contralateral breast (CB) will receive scattered doses. In the present study, the photon and thermal neutron dose values received by CB surface during breast cancer radiation therapy were measured. Materials and methods: The right breast region of RANDO phantom was considered as CB, and the measurements of photon and thermal neutron dose values were carried out on this region surface. The phantom was irradiated with 18 MV photon beams, and the dose values were measured with thermoluminescent dosimeter (TLD-600 and TLD-700) chips for 11 × 13, 11 × 17 and 11 × 21 cm2 field sizes in the presence of physical and dynamic wedges. Results: The total dose values (photon + thermal neutron) received by the CB surface in the presence of physical wedge were 12·06%, 15·75% and 33·40% of the prescribed dose, respectively, for 11 × 13, 11 × 17 and 11 × 21 cm2 field sizes. The corresponding dose values for dynamic wedge were 9·18%, 12·92% and 29·26% of the prescribed dose, respectively. Moreover, the results showed that treatment field size and wedge type affect the received photon and thermal neutron doses at CB surface. Conclusion: According to our results, the total dose values received at CB surface during breast cancer radiotherapy with high-energy photon beams are remarkable. In addition, the dose values received at CB surface when using a physical wedge were greater than when using a dynamic wedge, especially for medial tangential fields. [ABSTRACT FROM AUTHOR]

Introduction The main purpose of this study was to determine the diagnostic reference level (DRL) for routine digital radiography examinations in Mazandaran province. Materials and methods Thirteen digital radiographic examinations at 18 high-patient-load radiography centres were investigated. The indirect dosimetry method was performed based on the IAEA report. Average entrance skin dose (ESD) and the third quartile of ESD as the DRL were evaluated from the measurement made by a semiconductor dosemeter. Results DRL for the examinations of digital radiography was obtained as: Skull (postero-anterior [PA]): 2.2, skull (lateral [LAT]): 2.4, cervical spine (antero-posterior [AP]): 1.6, cervical spine (LAT): 1.7, thoracic spine (AP): 3.6, thoracic spine (LAT): 9.9, lumbar spine (AP): 5.3, lumbar spine (LAT): 11.8, chest (PA): 1.4, chest (LAT): 2.1, abdomen (AP): 4.3, pelvis (AP): 3.2 and hip (AP): 2.1 mGy. Conclusion Although DRL was not higher compared with the international organisations' levels, it can be reduced by adequate training of radiographers. [ABSTRACT FROM AUTHOR]

Editorial for "The Early-Enhancing Hepatic Vein: Differentiating Focal Nodular Hyperplasia and Hepatic Adenoma With Pathologic Validation in MRI" MRI contest modality is a reliable, safe, and well-oriented modality for patients who have contraindications to using CT contrast enhancement.[6] Differentiation of FNH from other hepatic masses, such as hepatic adenoma through a proper modality, always has been a dilemma.[[7]] Recently, some studies tried to find out some radiological findings for a better evaluation. Focal nodular hyperplasia (FNH) is the second most common benign liver lesion with common features of hepatocyte abnormalities to hepatic adenoma.[1] Middle-aged women (80%-95%) are significantly associated with hepatic adenoma, which is one of the side effects of using oral contraception.[2] Noninvasive differential diagnosis of these hepatic abnormalities is very challenging due to similar texture in both the clinical and the literature assessments. [Extracted from the article]

Background: Radiotherapy is a main method for the treatment of breast cancer. This study aimed to measure the absorbed dose of thyroid gland using Gafchromic EBT2 film during breast cancer radiotherapy. In addition, the relationship between the absorbed dose and thyroid hormone levels was evaluated. Methods: Forty-six breast cancer patients, with the age ranged between 25 and 35 years, undergoing external radiotherapy were studied. The patients were treated with 6 and 18 MV X-ray beams, and the absorbed thyroid dose was measured by EBT2 film. Thyroid hormone levels, thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxin (T4), were measured before and after the radiotherapy. Pearson's, Spearman's, and Chi-square tests were performed to evaluate the correlation between the thyroid dose and hormone levels. Results: The mean thyroid dose was 26 ± 9.45 cGy with the range of 7.85–48.35 cGy. There were not any significant differences at thyroid hormone levels between preradiotherapy and postradiotherapy (P > 0.05). There was a significant relationship between increased thyroid absorbed dose and changes in TSH and T4 levels (P < 0.05), but it was not significant in T3 level (P = 0.1). Conclusion: Regarding the results, the thyroid absorbed dose can have an effect on its function. Therefore, the thyroid gland should be considered as an organ at risk in breast cancer radiotherapy. [ABSTRACT FROM AUTHOR]

BACKGROUND: Rectum and bladder are hallow structures and considered as critical organs in prostate cancer intensity modulated radiotherapy (IMRT). Therefore, dose received by these organ walls must be considered for prediction of radiobiological effects. Contouring the real organ walls is quite difficult and time consuming in CT/MRI images, so the easy contouring artificial walls with uniform thickness could be appropriated alternatives. OBJECTIVE: To compare reconstructed artificial walls with real walls of bladder and rectum in common prostate IMRT techniques based on dose volume-histograms (DVHs) derived from artificial and real walls. METHODS: Artificial walls were reconstructed with 2–10 mm and 2–8 mm thicknesses for bladder and rectum, respectively. Four common IMRT techniques were applied to each patient. Spearman correlation was used to find the relation between the DVHs of true walls with artificial walls and whole organs. Monte Carlo (MC) simulations of the IMRT techniques and dosimetric comparison were also performed on a standard patient data. RESULTS: The 2 mm thickness artificial walls showed the minimum differences with the true bladder and rectum walls based on absolute evaluations (the maximum difference < 10cc and standard deviation < 15cc). However, relative evaluations showed that all the artificial walls had high correlations with real walls for selecting dose volume parameters. There was also good agreement between the treatment planning system and MC simulations results. CONCLUSION: The DVH of whole organs was not a good surrogate of the true wall. The 2 mm artificial walls can be regarded as good alternatives for both of rectum and bladder. However, in relative dose evaluations all studied artificial walls were appropriate. [ABSTRACT FROM AUTHOR]

Introduction With regards to the use of ionisation radiation in the computed tomography (CT), optimal parameters should be used to reduce the risk of incidence of secondary cancers in patients who are constantly exposed to X-rays. The aim of this study was to optimise the parameters used in CT scan of cervical vertebrae and neck soft tissue with minimal loss of image quality in emergency patients. Materials and methods In this study, the patients were divided into two groups. The first group consisted of patients scanned with default parameters and the second group scanned with optimised parameters. All the study has been implemented in emergency settings. The cases included cervical vertebrae and soft tissue protocols. Common CT dose descriptors including weighted computed tomography dose index (CTDIw), volumetric CTDI (CTDIvol), dose length product (DLP), effective dose (ED) and image noise were measured for each group. The ImpactDose program was used to estimate the organs doses. Statistical analysis was performed using Kruskal-Wallis test using SPSS software. Results There was no significant quality reduction in the optimised images. Decreasing in radiation dose parameters for the soft tissue was: kVp=16.7%, mAs=64.3% and pitch=24.1%, and for the cervical vertebrae was: kVp=16.7%, mAs=54.2% and pitch=48.3%. Consequently, decreasing these parameters reduced CTDIw=81.0%, CTDIvol=90.0% and DLP = 90.2% in the cervical vertebral protocol, as well as CTDIw=75.5%, CTDIvol=81.3% and DLP = 81.4% in the soft tissue protocol. Conclusion Regarding the results, the optimised parameters in the mentioned organ scan reduce the radiation dose in the target area and the organs surrounding. Therefore, these protocols can be used for reducing the risk of cancer. [ABSTRACT FROM AUTHOR]

In the current study, radiation dose-reduction factor (DRF) of nanoceria or cerium oxide nanoparticles (CONPs) in MRC-5 Human Lung Fibroblastic Cells and MCF-7 Breast-Cancer Cells was estimated. Characterization of CONPs was determined using scanner electron microscope (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and spectrophotometer. Then, six plans were designed with different radiation dose values on planning target value. The obtained MRC-5 and MCF-7 cells were treated with non-toxic concentrations of CONPs and then exposed. Finally, cell viability (%) of the cell lines was determined using MTT assay. The findings showed that CONPs have no significant radioprotective effect against 10 cGy radiation dose value. Nevertheless, 70 μM CONPs resulted in a significant radioprotection against 100, 200, 300, 400 and 500 cGy radiation dose values compared with the control group in MRC-5 cells. For all radiation dose values, mean cell viability (%) of MCF-7 had not increased significantly at the presence of nanoceria compared with control group. According to the findings, it was revealed that the use of CONPs have a significant radioprotective effect on normal lung cells, while they do not provide any protection for MCF-7 cancer cells. These properties can help to increase therapeutic ratio of radiotherapy. [ABSTRACT FROM AUTHOR]