A Monte Carlo (MC) code is a robust method to generate a mammographic x-ray spectrum because the geometry of a mammography system can be flexible and directly modeled in MC simulation. However, simulations from MC code need to be validated before it can be reliably used for specific applications. This study aimed to generate and validate the x-ray spectra of relevant anodes used in mammography and breast tomosynthesis using Particle and Heavy Ion Transport code System (PHITS). PHITS version 3.08 was used to generate the x-ray spectra of molybdenum (Mo), rhodium (Rh), and tungsten (W) anodes. The Mo anode spectrum derived using PHITS was compared with those obtained using other MC codes. The generated spectra of all anodes were compared with the literature. Parameters including spectral shape, K characteristic x-ray yield, heel effect, and half-value layer (HVL) were used for a comparative assessment. The differences in these assessment parameters conducted by PHITS and PHITSEGS5 simulations were studied. Regarding the comparative parameters, PHITSEGS5 simulation improved the accuracy of mammographic x-ray generation compared to PHITS simulation; K x-ray and bremsstrahlung yields of the Mo anode spectrum generated by PHITSEGS5 simulation were a better agreement with those generated by other MC code simulations. The PHITSEGS5 spectra overestimated K x-ray and low-energy bremsstrahlung photons in comparison with measured spectra. Subsequently, HVLs calculated from PHITSEGS5 spectra were 1.0% (Mo/Mo) and 7.0% (W/Al) lower than those derived from measured spectra. For Mo and Rh anodes, relative difference of HVLs calculated from PHITSEGS5 spectra and those obtained from literature and measurement were within the TRS 457 acceptance criteria (±0.02 mm Al). The observed difference exceeded the acceptance criteria for W anode. Regarding existed consistency in HVL between simulation and measurement, PHITSEGS5 simulation can be reliably used to generate x-ray spectra of Mo and Rh anodes. However, its accuracy should be improved for generating W anode spectrum.
Digital breast tomosynthesis (DBT) is an alternative tool for breast cancer screening; however, the magnitude of peripheral organs dose is not well known. This study aimed to measure scattered dose and estimate organ dose during mammography under conventional (CM) and Tomo (TM) modes in a specific DBT system. Optically stimulated luminescence dosimeters (OSLDs), whose responses were corrected using a parallel-plate ionization chamber, were pasted on the surface of custom-made polymethyl methacrylate (PMMA) and RANDO phantoms to measure entrance surface air kerma (ESAK). ESAK measurements were also acquired with a 4.5-cm thick breast phantom for a standard mammogram. Organ dose conversion factors (CFD ) were determined as ratio of air kerma at a specific depth to that at the surface for the PMMA phantom and multiplied by the ratio of mass energy absorption coefficients of tissue to air. Normalized eye lens and thyroid gland doses were calculated using the RANDO phantom by multiplying CFD and ESAK values. Maximum variability in OSLD response to scatter radiation from the DBT system was 33% in the W/Rh spectrum and variations in scattered dose distribution were observed between CM and TM. The CFD values for eye lens and thyroid gland ranged between 0.58 to 0.66 and 0.29 to 0.33, respectively. Mean organ doses for two-view unilateral imaging were 0.24 (CM) and 0.18 (TM) μGy/mAs for the eye lens and 0.24 (CM) and 0.25 (TM) μGy/mAs for the thyroid gland. Higher organ doses were observed during TM compared to CM as the automatic exposure control (AEC) system resulted in greater total mAs values in TM.
Evaluation of radiation dose from medical exposure is important because the use of ionizing radiation in medical field contributes significantly to the exposure of the population. In plain radiography, the entrance skin dose, which is absorbed by the skin as it reaches the patient, is generally estimated. It is calculated from the air kerma at the same focus skin distance on the beam central axis measured with a dosimeter. In fluoroscopy, the indirect monitoring using dose-area product meter is generally performed for estimating the entrance skin dose in real-time to avoid skin injuries. In mammography, the average glandular dose is estimated because mammary glands have more sensitive to radiation than skin. The European Organization for Quality-Assured Breast Screening and Diagnostic Services protocol has been used to estimate average glandular dose from full-field digital mammography in Japan. Although volume CT dose index or dose-length product, as seen on CT consoles, do not represent the actual dose for the patient, they are measured to assist in quality control and optimization as well as the air kerma rate at the patient entrance reference point in fluoroscopy and the average glandular dose in mammography. For the purpose of patient dose evaluation, physical dose measurements using an anthropomorphic phantom and Monte Carlo simulations can estimate patient organ doses from medical exposure.
This study aimed to evaluate the property of small dosimeters used for measuring eye lens doses for medical staff during fluoroscopic examination. Dose linearity, energy dependence, and directional dependence of scattered X-rays were evaluated for small radiophotoluminescence glass dosimeters (RPLDs), those with a tin filter (Sn-RPLDs), and small optically stimulated luminescence dosimeters (OSLDs). These dosimeters were pasted on radioprotective glasses, and accumulated air kerma was obtained after irradiating the X-rays to a patient phantom. Strong correlations existed between fluoroscopic time and accumulated air kerma in all types of dosimeters. The energy dependence of Sn-RPLD and OSLD was smaller than that of RPLD. The relative dose value of the OSLD gradually decreased as the angle of the OSLD against the scattered X-rays was larger or lower than the right angle in the horizontal direction. The ranges of relative dose values of RPLD and Sn-RPLD were larger than that of OSLD in the vertical direction. The OSLDs showed lower doses than the RPLDs and Sn-RPLDs, especially on the right side of the radioprotective glasses. These results showed that RPLDs, Sn-RPLDs, and OSLDs had different dosimeter properties, and influence measured eye lens doses for the physician, especially on the opposite side of the patient.
The accurate diagnosis of pneumonia, tuberculosis, and COVID-19 using computed tomography (CT) images is critical for radiologists. Artificial intelligence (AI) has been introduced as a tool to aid in rapid diagnosis. In this study, we evaluated 4 deep learning models, including AlexNet, GoogleNet, ResNet, and deep convolutional neural network (DCNN), to classify CT images of tuberculosis, pneumonia, and COVID-19. We collected 2,134 normal images, 943 images of tuberculosis, 2,041 images of pneumonia, and 3,917 images of COVID-19 from online datasets. To assess the efficiency of the models, we measured their image classification performance such as accuracy, F1 score, and area under the curve. Our performance evaluation indicated that ResNet was the highest-performing model, with the best accuracy, F1 score, and area under the curve (0.966, 0.931, 0.954, respectively). The second-best performing model was DCNN, while AlexNet and GoogleNet had the next-best performance, respectively. The deep learning models exhibit a capability that could be viewed as a substitute for predicting lung diseases and could be employed to support radiologists in CT image screening. HIGHLIGHTS The four deep learning models including AlexNet, GoogleNet, ResNet, and DCNN can classified for 4 classes (tuberculosis, pneumonia, COVID-19, and normal) The AUC indicates the model's ability to distinguish between positive and negative images, ResNet had the highest AUC for normal, pneumonia, and COVID-19, while AlexNet was highest for tuberculosis The ResNet model performed the best in terms of accuracy of model prediction, correctly predicting the labels for all 4 classes of input data (tuberculosis, pneumonia, COVID-19, and normal) GRAPHICAL ABSTRACT
Background: Optimizing image quality and radiation dose is crucial in general radiography, adhering to the As Low As Reasonably Achievable (ALARA) principle. Objective: This study aimed to evaluate the impact of applying the 10 kVp and 15% rules on image quality and patient dose in extremity X-ray imaging using both computed radiography (CR) and digital radiography (DR) systems. Materials and methods: X-ray imaging of hand, elbow, knee, and foot phantoms was performed using three different exposure techniques on both CR and DR systems. These techniques included the standard technique (ST) based on the established guidelines of the imaging systems, increased 10 kVp with a 50% mAs reduction from ST (10 kVp rule), and increased 15% kVp with a 50% mAs reduction from ST (15% rule). The entrance skin dose (ESD) was measured using nanoDot™placed on the phantom’s surface. The physical image qualities in contrast-to-noise ratio (CNR) and figure of merit (FOM) were utilized to assess the balance between image quality and radiation doses. Results: The ESD was reduced by an average of -16% and -25% when applying the 10 kVp and 15% rules for all extremity imaging. This reduction decreased image CNR by -18% and -12%, respectively. There was no significant difference in CNR between the 15% and 10 kVp rule techniques for all extremity examinations in both CR and DR systems (p>0.05). Meanwhile, the exposure and deviation indexes remained within the established guidelines for CR and DR systems. However, the FOM values tended to be greater with the 15% rule technique than other techniques. Conclusion: The ESD reduction was observed when applying the 10 kVp and 15% rules for all extremity imaging, both in CR and DR systems, with a slight degradation in image quality. The 15% rule represents the best option for optimization of image quality and patient dose based on the FOM results.
Background: Volumetric-modulated arc therapy (VMAT) is an efficient method of administering intensity-modulated radiotherapy beams. The Delta 4 device was employed to examine patient data. Aims and Objectives: The utility of the Delta 4 device in identifying errors for patient-specific quality assurance of VMAT plans was studied in this research. Materials and Methods: Intentional errors were purposely created in the collimator rotation, gantry rotation, multileaf collimator (MLC) position displacement, and increase in the number of monitor units (MU). Results: The results show that when the characteristics of the treatment plans were changed, the gamma passing rate (GPR) decreased. The largest percentage of erroneous detection was seen in the increasing number of MU, with a GPR ranging from 41 to 92. Gamma analysis was used to compare the dose distributions of the original and intentional error designs using the 2%/2 mm criteria. The percentage of dose errors (DEs) in the dose-volume histogram (DVH) was also analyzed, and the statistical association was assessed using logistic regression. A modest association (Pearson’s R -values: 0.12–0.67) was seen between the DE and GPR in all intentional plans. The findings indicated a moderate association between DVH and GPR. The data reveal that Delta 4 is effective in detecting mistakes in treatment regimens for head-and-neck cancer as well as lung cancer. Conclusion: The study results also imply that Delta 4 can detect errors in VMAT plans, depending on the details of the defects and the treatment plans employed.
Background: The nanoDotTM dosimeter, an optically stimulated luminescent dosimeter (OSLD), is compact and precise, ideal for various applications like radiation dosimetry. The nanoDotTM requires calibration before use with the detector alignment perpendicular to the central beam axis. It exhibits angular dependence that may impact the calibration factor, requiring the fabrication of a specific cylindrical phantom for the calibration procedure. Objective: This study aimed to develop a cylindrical phantom for nanoDotTM calibration to facilitate dose measurements in composite fields with various beam angles and to evaluate the nanoDotTM calibration factors for different plans. Materials and methods: The cylindrical phantom was constructed using cast nylon material to accommodate the nanoDotTM or a cylindrical ionization chamber (IC). The novel phantom underwent validation for physical characteristics, including dimensions, density, and uniformity. Validation for the calibration factor, using cylindrical phantom (CF cylin) under standard conditions with a 10x10 cm² field size at 10 cm depth was conducted with 6 MV X-rays, comparing it with calibration factor using slab solid water phantoms (CFsolid). The CFcylin for different numbers of beams were determined and validated against a reference IC in various planning conditions. Furthermore, angular correction factors were determined for their application in the single-beam calibration factor. Results: The cylindrical phantom had dimensions of 20 cm in diameter and 30 cm in length, a density of 1.145 g/cm³ and good uniformity. As a result of single beam, the CF cylin, agreed well with CFsolid, showing a difference of -0.069%. The CFcylin increased with the number of beams, ranging between 1.179 and 1.242. Additionally, the angular correction factor increased as the number of beams increased, peaking at 1.058 with 9 beams. When comparing the results to the IC, it was observed that with an increase in the number of beams to 4 beams, the single-beam calibration factor exhibited a variation of more than 2%. However, when applying the CF cylin specific to the number of beams or correcting for the angular correction factor, the dose differences between nanoDotTM and IC measurements were within 2%. Conclusion: The developed cylindrical phantom is suitable for nanoDotTM calibration under single beam angle and in composite fields with various beam angles. The new calibration factors for specific numbers of beams allow for accurate dose measurements using nanoDotTM, thus reducing the dose difference from the IC to acceptable levels. Further studies should investigate its application in clinical situations.
