No Abstract No Abstract No Abstract

Purpose: A physical phenomenon, scattering the radiation by the atmosphere above the room to the points at ground level around the linac treatment room is known as skyshine radiation. This study aimed to estimate photon and neutron skyshine from a linac in a high-energy radiation therapy facility.

Materials and Methods: The empirical method of NCRP report 151 and MC simulations were employed to estimate skyshine radiation dose from the 18MV linac photon beam. A linac and its bunker were modeled and skyshine dose equivalent from photons and secondary neutrons were derived and compared in the control room, corridor, sidewalk and, parking.

Results: The photon skyshine dose rates calculations by the MC method varied from 0.43 µSv/h at the sidewalk to 6.2 µSv/h at the control room. The ratios of NCRP to MCNP calculations varied from 3.58 for the corridor to 16.14 for the control room. For the neutron skyshine dose rate at distances shorter than 20m, it was found to be 10.4 nSv/h and the ratios of the NCRP to MCNP were 1.26 at the control room and 3.34 at the sidewalk.

Conclusion: It was concluded that the empirical method overestimates photon and neutron skyshine dose rates in comparison to the MCNPX code. The refinement of the proposed empirical method of NCRP 151 and application of MC methods are strongly suggested for more reliable calculations of skyshine radiations.

ABSTRACT

Background: Excessive use of computed tomography (CT) has become a worrying issue due to the potential risks corresponding to the radiation exposure.

Purpose: This study was to investigate trends in CT usage in Yazd Province, Iran.

Material and Methods: Patients were categorized in regard to sex and their age into two general groups, pediatrics (<18 years old) and adults (≥18 years old) ), each group fall into multiple subcategorizations. The performed CT scans have been classified into six categories, based on the anatomical area of interest, including head/neck, chest, spine, abdomen-pelvis, extremities, and CT angiography (CTA). The data were collected for the period 2015–2018.

Results: The number of CT scans province increased by the compound annual growth rate of 11%. We found points to the growth rate of CT was higher in men than in women. Across the procedures, head/neck by an average contribution of 52% to all the CT scans was the most frequently examined region but spine examinations have decreased by 32%. More than half of the scans are performed on people over the age of 90 and among age<18 years old, most CT scan rates are related to 13-18 years old children.

Conclusion: The number of CT services is clearly increasing in Yazd. Some increase may be warranted because of improvements in the diagnostic power of CT. The estimated number of pediatric CT scans has more than past. Due to the risk of cancer, efforts should be made to reduce unnecessary CT scans.

Purpose: This study aimed at evaluating the image quality characteristics of advanced noise-optimized and traditional virtual monochromatic images compared with conventional 120-kVp images from second-generation Dual-Source CT.

Materials and Methods: For spiral scans six syringes filled with diluted iodine contrast material (1, 2, 5, 10, 15, 20 mg I/ml) were inserted into the test phantom and scanned with a second-generation dual-source CT in both single-energy (120-kVp) and dual-energy modes. Images set contain conventional single-energy 120-kVp, and virtual monochromatic were reconstructed with energies ranging from 40 to 190-keV in 1-keV steps. An energy-domain noise reduction algorithm was applied and the mean CT number, image noise, and iodine CNR were calculated.

Results: The iodine CT number of conventional 120-kVp images compared with monochromatic of 40-, 50-, 60- and 70-keV images showed increase. The improvement ratio of image noise on Advanced Virtual Monochromatic Images (AVMIs) compared with the Traditional Virtual Monochromatic Images (TVMIs) at energies of 40-, 50-, 60, 70-keV was 52.9%, 35.7%, 8.1%, 2.1%, respectively. At AVMIs from 75- to 190-keV, the image noise value was less than conventional 120-kVp images. CNR improvement ratio at 20 mg/ml of iodinated contrast material for TVMIs and AVMIs compared to 120-kVp CT images and AVMIs compared to TVMI was 18.3% and 56.3%, 32.1% respectively.

Conclusion: Both TVMIs (in energies ranging from 54 to 71-keV) and AVMIs (in energies ranging from 40 to 74-keV) represent improvement in the iodine contrast-to-noise ratio than conventional 120-kVp CT images for the same radiation dose. Also, AVMIs compared to TVMIs have been obtained considerable noise reduction and CNR improvement for low-energy virtual monochromatic images. In the present study, we show that virtual monochromatic image and its Advanced version (AVMI) may boost the dual-energy CT advantages by providing higher CNR images in the same exposure value compared to routinely acquired single-energy CT images.

Purpose: This study aimed to investigate the impact of image preprocessing steps, including Gray Level Discretization (GLD) and different Interpolation Algorithms (IA) on ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) radiomics features in Non-Small Cell Lung Cancer (NSCLC).

Materials and Methods: One hundred and seventy-two radiomics features from the first-, second-, and higher-order statistic features were calculated from a set of Positron Emission Tomography/Computed Tomography (PET/CT) images of 20 non-small cell lung cancer delineated tumors with volumes ranging from 10 to 418 cm3 regarding five intensity discretization schemes with the number of gray levels of 16, 32, 64, 128, and 256, and four Interpolation algorithms, including nearest neighbor, tricubic convolution and tricubic spline interpolation, and trilinear were used. Segmentation was based on 3D region growing-based. The Intraclass Correlation Coefficient (ICC), Overall Concordance Correlation Coefficient (OCCC), and Coefficient Of Variations (COV) were calculated to demonstrate the features' variability and select robust features. ICC and OCCC < 0.5 presented weak reliability, ICC and OCCC between 0.5 and 0.75 illustrated appropriate reliability, values within 0.75 and 0.9 showed satisfying reliability, and values higher than 0.90 indicate exceptional reliability. Besides, features with less than 10% COV have been selected as robust features.

Results: All morphology family (except four features), statistic, and Intensity volume histogram families were not affected by GLD and IA. And the rest of them, 10 and 61 features showed COV ≤ 5% against GLD and IA, respectively. Ten and 80 features showed excellent reliability (ICC values greater than 0.90) against GLD and IA. Eight and 60 features showed OCCC≥0.90 against GLD and IA, respectively. Based on our results Inverse difference normalized and Inverse difference moment normalized from Grey Level Co-occurrence Matrix (GLCM) were the most robust features against GLD and Skewness from intensity histogram family and Inverse difference normalized and Inverse difference moment normalized from GLCM were the most robust features against IA.

Conclusion: Preprocessing can substantially impact the 18F-FDG PET image radiomic features in NSCLC. The impact of gray level discretization on radiomics features is significant and more than Interpolation algorithms.

Purpose: Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive imaging technology with widespread use in cognitive sciences and clinical studies. It indirectly measures neural activation by measuring alterations of oxyhemoglobin (HbO₂) and deoxyhemoglobin (Hb) in tissues. This study used mental arithmetic task for analyzing the activation of the frontal cortex.

Materials and methods: The fNIRS instrument was used for measuring the alterations of HbO₂ and Hb in healthy subjects during the task. Then the recorded signals were filtered in the frequency range of 3 to 80 mHz. The Continuous Wavelet Transform (CWT) of each of the HbO₂ and Hb signals in each channel was calculated in the intended frequency range, followed by the calculation of the energy of obtained coefficients. Finally, for the performed tasks, the average energy of each channel in each region was obtained. Then the energies of spatially symmetric channel pairs in the two hemispheres were compared using the t-test.

Results: Results demonstrated that the average energy of HbO₂ signal for corresponding channels in the temporal, Medial Prefrontal Cortex (MPFC), and Dorsolateral Prefrontal Cortex (DLPFC) regions had significant differences (P<0.05). Also, a significant difference was observed in the temporal, medial prefrontal, and Ventrolateral Prefrontal Cortex (VLPFC) regions for Hb signal.

Conclusion: The obtained results indicate activation in both HbO2 and Hb signals in the DLPFC, temporal, and MPFC regions, considering the performance of memory and the frontal cortex under mental arithmetic tasks. Therefore, it can be concluded that this technique is effective and appropriate for analyzing alterations of brain oxygen levels during cognitive activity.

Purpose: Mammography is the most important diagnostic modality for early detection of breast cancer, however, concerns related to the side effects induced by ionizing radiation are still present. In the current study, the Mean Glandular Dose (MGD) values for mammography examinations as well as a local Diagnostic Reference Level (DRL) were obtained for mammography centers in Kashan, Iran.

Materials and Methods: Three mammography devices from three radiology centers were selected to obtain the MGD values of mammography examinations. To assess the MGD values, the technical parameters for patients’ imaging at these three radiology centers were extracted. Then, the incident air kerma (in mGy) value received by each patient was measured by a UNIDOS E electrometer (PTW, Germany) along with a SFD mammography ionization chamber (PTW, Germany). Finally, the incident air kerma values were converted to the MGD values by specific conversion factors. Based on the obtained MGD values, a local DRL was also established for mammography examinations.

Results: Mean MGD values per exposure were obtained 2.39 ± 1.46 mGy for Right Craniocaudal (RCC), 2.64 ± 1.67 mGy for Left Craniocaudal (LCC), 2.82 ± 1.89 mGy for Right Mediolateral Oblique (RMLO), and 3.09 ± 1.90 mGy for left mediolateral oblique views. Moreover, a local DRL obtained from mammography examinations, which was established as the overall median of MGD value, was 1.72 mGy (1.91 mGy for digital and 1.32 mGy for analog mammography).

Conclusion: The MGD values for different views obtained in this study are in the range of previously reported values. Considering the European guidelines for quality assurance in breast cancer screening and diagnosis, it can be mentioned that the obtained DRL was less than the recommended dose level (2.0 mGy).

Purpose: Multimodal Cardiac Image (MCI) registration is one of the evolving fields in the diagnostic methods of Cardiovascular Diseases (CVDs). Since the heart has nonlinear and dynamic behavior, Temporal Registration (TR) is the fundamental step for the spatial registration and fusion of MCIs to integrate the heart's anatomical and functional information into a single and more informative display. Therefore, in this study, a TR framework is proposed to align MCIs in the same cardiac phase.

Materials and Methods: A manifold learning-based method is proposed for the TR of MCIs. The Euclidean distance among consecutive samples lying on the Locally Linear Embedding (LLE) of MCIs is computed. By considering cardiac volume pattern concepts from distance plots of LLEs, six cardiac phases (end-diastole, rapid-ejection, end-systole, rapid-filling, reduced-filling, and atrial-contraction) are temporally registered.

Results: The validation of the proposed method proceeds by collecting the data of Computed Tomography Coronary Angiography (CTCA) and Transthoracic Echocardiography (TTE) from ten patients in four acquisition views. The Correlation Coefficient (CC) between the frame number resulted from the proposed method and manually selected by an expert is analyzed. Results show that the average CC between two resulted frame numbers is about 0.82±0.08 for six cardiac phases. Moreover, the maximum Mean Absolute Error (MAE) value of two slice extraction methods is about 0.17 for four acquisition views.

Conclusion: By extracting the intrinsic parameters of MCIs, and finding the relationship among them in a lower-dimensional space, a fast, fully automatic, and user-independent framework for TR of MCIs is presented. The proposed method is more accurate compared to Electrocardiogram (ECG) signal labeling or time-series processing methods which can be helpful in different MCI fusion methods.

Purpose: Magnetic field is one of the effective and non-invasive modalities on biology and angiogenesis. Studies on the effects of magnetic fields on angiogenesis showed that the shape of the magnetic field could potentially affect angiogenesis. Therefore, this study aimed to control the frequency, intensity, and duration of exposure of magnetic field while investigating the effect of the shape of the magnetic field on the viability of Human Umbilical Vein Endothelial Cells (HUVECs).

Materials and Methods: The HUVECs were exposed to various shapes of 50 and 60 Hz magnetic fields with intensities of 0.5 and 1 mT in acute and chronic exposure regimes. The viability of HUVECs was assessed via MTT assay.

Results: Results showed that the sin type 50 and 60 Hz magnetic fields are more effective in decreasing the viability. The rectified 100 and 120 Hz with 1 and 0.5 mT could increase and decrease the viability compared with 50 and 60 Hz, respectively.

Conclusion: It can be concluded that the shape of the magnetic field can be an effective factor in biology and must be controlled to have a reliable response.

Purpose: Awareness of personnel who are professionally involved with ionizing radiation on the principles of radiation protection is very important; especially for operation room personnel, because they do not receive radiation protection training during their university education in Iran. The aim of this study was to evaluate knowledge and practice of radiographers and operating room personnel about the principles of radiation protection.

Materials and Methods: A validated researcher-made questionnaire was used and the study was conducted on 328 medical staff in 2021. Factors such as age, gender, university degree, working years, occupation, and knowledge and practice about radiation protection were recorded. The collected data were analyzed by independent t-test and Pearson correlation analysis using SPSS software.

Results: The results of the study showed that age, gender and university degree have no significant effect on the knowledge and practice of radiographers and operating room personnel (p > 0.05). The knowledge and practice of radiographers were significantly higher than operating room personnel (p < 0.05). With regard to working years, there were significant relationships with the knowledge of personnel (p= 0.034), and with practice (p= 0.038). There was a significant correlation between passed training courses of radiation protection and knowledge (p=0.012), and practice (p=0.033). There was a significant correlation between knowledge about radiation protection and practice (p=0.002).

Conclusion: It is necessary to encourage staff with lower working years and operating room personnel to participate in radiation protection courses and workshops. It can be suggested to add training programs about radiation protection in university education or in-service education for operating room personnel.