Relative Electron Density Research Articles

Characterisation of 3D-printable thermoplastics to be used as tissue-equivalent materials in photon and proton beam radiotherapy end-to-end quality assurance devices

Objective. To investigate the potential of 3D-printable thermoplastics as tissue-equivalent materials to be used in multimodal radiotherapy end-to-end quality assurance (QA) devices. Approach. Six thermoplastics were investigated: Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS), Polyethylene Terephthalate Glycol (PETG), Polymethyl Methacrylate (PMMA), High Impact Polystyrene (HIPS) and StoneFil. Measurements of mass density ( ρ ), Relative Electron Density (RED), in a nominal 6 MV photon beam, and Relative Stopping Power (RSP), in a 210 MeV proton pencil-beam, were performed. Average Hounsfield Units (HU) were derived from CTs acquired with two independent scanners. The calibration curves of both scanners were used to predict average ρ, RED and RSP values and compared against the experimental data. Finally, measured data of ρ, RED and RSP was compared against theoretical values estimated for the thermoplastic materials and biological tissues. Main results. Overall, good ρ and RSP CT predictions were made; only PMMA and PETG showed differences >5%. The differences between experimental and CT predicted RED values were also <5% for PLA, ABS, PETG and PMMA; for HIPS and StoneFil higher differences were found (6.94% and 9.42/15.34%, respectively). Small HU variations were obtained in the CTs for all materials indicating good uniform density distribution in the samples production. ABS, PLA, PETG and PMMA showed potential equivalency for a variety of soft tissues (adipose tissue, skeletal muscle, brain and lung tissues, differences within 0.19%–8.35% for all properties). StoneFil was the closest substitute to bone, but differences were >10%. Theoretical calculations of all properties agreed with experimental values within 5% difference for most thermoplastics. Significance. Several 3D-printed thermoplastics were promising tissue-equivalent materials to be used in devices for end-to-end multimodal radiotherapy QA and may not require corrections in treatment planning systems’ dose calculations. Theoretical calculations showed promise in identifying thermoplastics matching target biological tissues before experiments are performed.

Application of low-dose CT in image-guided radiotherapy based on CT-linac

BackgroundImage-guided radiation therapy (IGRT) involves online medical imaging systems. CT-guided imaging systems not only have high image quality but also allow for direct dose calculation for radiation treatment planning, making it an ideal image guidance method. However, the imaging dose from CT images may pose additional risks to patients. Therefore, the aim of this study was to evaluate the substitutability of using low-dose CT images for IGRT. Materials and methodsThe CIRS-062 phantom, Catphan 604 phantom, CT dose index phantom were used to obtain the conversion curves of the CT values to the relative electron density (RED), image quality, and imaging dose of the low-dose CT, respectively. Catphan 604 phantom and clinical cases were used to analyze the feasibility of low-dose CT for dose calculation. ResultsNo significant differences were observed in the conversion curves of CT values to RED between low-dose and standard-dose CT scans. In terms of image quality, the geometric distortion of low-dose CT was 0.1 mm, which was the same as that of standard-dose CT. The spatial resolution of the images was 0.42–0.45 lp/mm, which was slightly better than that of standard-dose CT (0.40–0.44 lp/mm). The image uniformity was 98.4%–99.0%, slightly worse than that of standard-dose CT (99.4%–99.5%), but still met the clinical requirements. The imaging dose was 2.96–4.62 mGy, significantly lower than that of standard-dose CT (9.71–26.68 mGy), especially for head CT protocol. In terms of dose calculation, the γ passing rates were not lower than 98% for either the Catphan 604 phantom or the clinical cases. ConclusionLow-dose CT can significantly reduce the imaging dose without a significant loss of image quality and can be directly used for dose calculation in radiation treatment planning, providing a safer and more effective image guidance method for IGRT.

Linac- and CyberKnife-based MRI-only treatment planning of prostate SBRT using an optimized synthetic CT calibration curve.

CT Hounsfield Units (HUs) are converted to electron density using a calibration curve obtained from physical measurements of an electron density phantom. HU values assigned to an MRI-derived synthetic computed tomography (sCT) may present a different relationship with electron density compared to CT HU. Correct assignment of sCT HU values is critical for accurate dose calculation and delivery. The goals of this work were to develop a sCT calibration curve using patient data acquired on a clinically commissioned CT scanner and assess for CyberKnife- and volumetric modulated arc therapy (VMAT)-based MR-only treatment planning of prostate SBRT. Same-day CT and MRI simulation in the treatment position were performed on 10 patients treated with SBRT to the prostate. Dixon in-phase and out-of-phase MRIs were acquired on a 3T scanner using a 3D T1-weighted gradient-echo sequence to generate sCTs using a commercial sCT algorithm. CT and sCT datasets were co-registered and HU values compared using mean absolute error (MAE). An optimized HU-to-density calibration curve was created based on average HU values across an institutional patient database for each of the four sCT tissue types. Clinical CyberKnife and VMAT treatment plans were generated on each patient CT and recomputed onto corresponding sCTs. Dose distributions computed using CT and sCT were compared using gamma criteria and dose-volume-histograms. For the optimized calibration curve, HU values were -96, 37, 204, and 1170 and relative electron densities were 0.95, 1.04, 1.1, and 1.7 for adipose, soft tissue, inner bone, and outer bone, respectively. The proposed sCT protocol produced total MAE of 94±20HU. Gamma values mean±std (min-max) were 98.9%±0.9% (97.1%-100%) and 97.7%±1.3% (95.3%-99.3%) for VMAT and CyberKnife plans, respectively. MRI-derived sCT using the proposed approach shows excellent dosimetric agreement with conventional CT simulation, demonstrating the feasibility of MRI-derived sCT for prostate SBRT treatment planning.

Osteolytic Bone Metastasis: Different Radiotherapy Fractionation Schedules Compared Clinically and Radiographically.

The purpose of this study is to compare three commonly used radiotherapy fractionation schedules for bone metastasis in terms of clinical and radiological effectiveness. A total of 93 patients with osteolytic bone metastasis were randomized to receive 8 Gyin a single fraction (group A), 20 Gy in 5 fractions (group B) and 30 Gy in 10 fractions (group C). Changes in bone density were measured using the Relative Electron Density (RED) type corrected by Thomas (pe = HU/1.950 + 1.0), where HU is Hounsfield Units. Pain response was assessed according to the Brief Pain Inventory tool. Quality of life was estimated using the EORTC QLQ-C30 and the MD Anderson Symptom (MDAS) tools.After RT, RED, together with the parameters of EORTC QLQ-C30, MDAS and SAT, significantly increased in all groups (p < 0.001).Specifically, the increase of RED was higher in group C compared to group Athree months post-RT (p = 0.014). Group C was also superior to group A in terms of QoL and BPI three months post-treatment. Multifractionated radiotherapy for osteolytic bone metastasis is superior to single fraction radiotherapy in terms of improvement in quality of life and bone remineralization three months post-RT.

Magnetic Component of Quasi-Coherent Mode of Plasma Fluctuations in Ohmic Plasma of the T-10 Tokamak

In this work the phenomenon of the quasi-coherent mode of plasma fluctuations in purely ohmic plasmas of the T-10 tokamak is investigated. The plasma magnetic fluctuation spectra along with spectra of relative electron density oscillations and plasma potential fluctuation spectra were studied. The presence of both electrostatic and magnetic components of the quasi-coherent mode has been established in the core and as well at the edge regions of the plasma column. This fact allows one to consider the quasi-coherent mode as one of the types of electromagnetic turbulence of fusion plasma.

Quality assurance of an established online adaptive radiotherapy program: patch and software upgrade.

The ability to dynamically adjust target contours, derived Boolean structures, and ultimately, the optimized fluence is the end goal of online adaptive radiotherapy (ART). The purpose of this work is to describe the necessary tests to perform after a software patch installation and/or upgrade for an established online ART program. A patch upgrade on a low-field MR Linac system was evaluated for post-software upgrade quality assurance (QA) with current infrastructure of ART workflow on (1) the treatment planning system (TPS) during the initial planning stage and (2) the treatment delivery system (TDS), which is a TPS integrated into the delivery console for online ART planning. Online ART QA procedures recommended for post-software upgrade include: (1) user interface (UI) configuration; (2) TPS beam model consistency; (3) segmentation consistency; (4) dose calculation consistency; (5) optimizer robustness consistency; (6) CT density table consistency; and (7) end-to-end absolute ART dose and predicted dose measured including interruption testing. Differences of calculated doses were evaluated through DVH and/or 3D gamma comparisons. The measured dose was assessed using an MR-compatible A26 ionization chamber in a motion phantom. Segmentation differences were assessed through absolute volume and visual inspection. (1) No UI configuration discrepancies were observed. (2) Dose differences on TPS pre-/post-software upgrade were within 1% for DVH metrics. (3) Differences in segmentation when observed were small in general, with the largest change noted for small-volume regions of interest (ROIs) due to partial volume impact. (4) Agreement between TPS and TDS calculated doses was 99.9% using a 2%/2-mm gamma criteria. (5) Comparison between TPS and online ART plans for a given patient plan showed agreement within 2% for targets and 0.6 cc for organs at risk. (6) Relative electron densities demonstrated comparable agreement between TPS and TDS. (7) ART absolute and predicted measured end-to-end doses were within 1% of calculated TDS. An online ART QA program for post-software upgrade has been developed and implemented on an MR Linac system. Testing mechanics and their respective baselines may vary across institutions, but all necessary components for a post-software upgrade QA have been outlined and detailed. These outlined tests were demonstrated feasible for a low-field MR Linac system; however, the scope of this work may be applied and adapted more broadly to other online ART platforms.

CT-Filters and Radiation Therapy Planning Accuracy: Curve CT-to-ED Recalibration Necessary?

Relevance: This article examines the effect of the presence or absence of an ImAR filter on the calibration curve for converting X-ray tomography (CT) data to relative electron density (CT-to-ED) values for the abdominal region and head. On CT images this results in distortion of Hounsfield Units (HU) values. The latter, in turn, can lead to inaccuracies in the CT-to-ED calibration curve. Conclusions: If the filters are set up correctly and applied according to the planning system manufacturer's recommendations, changes in the CT-to-Ed curve should be negligible. CT-to-ED curves are an important tool for improving the accuracy and quality of radiation therapy for cancer

Conversion of single-energy CT to parametric maps of dual-energy CT using convolutional neural network.

We propose a deep learning (DL) multitask learning framework using convolutional neural network for a direct conversion of single-energy CT (SECT) to 3 different parametric maps of dual-energy CT (DECT): virtual-monochromatic image (VMI), effective atomic number (EAN), and relative electron density (RED). We propose VMI-Net for conversion of SECT to 70, 120, and 200 keV VMIs. In addition, EAN-Net and RED-Net were also developed to convert SECT to EAN and RED. We trained and validated our model using 67 patients collected between 2019 and 2020. Single-layer CT images with 120 kVp acquired by the DECT (IQon spectral CT; Philips Healthcare, Amsterdam, Netherlands) were used as input, while the VMIs, EAN, and RED acquired by the same device were used as target. The performance of the DL framework was evaluated by absolute difference (AD) and relative difference (RD). The VMI-Net converted 120 kVp SECT to the VMIs with AD of 9.02 Hounsfield Unit, and RD of 0.41% compared to the ground truth VMIs. The ADs of the converted EAN and RED were 0.29 and 0.96, respectively, while the RDs were 1.99% and 0.50% for the converted EAN and RED, respectively. SECT images were directly converted to the 3 parametric maps of DECT (ie, VMIs, EAN, and RED). By using this model, one can generate the parametric information from SECT images without DECT device. Our model can help investigate the parametric information from SECT retrospectively. DL framework enables converting SECT to various high-quality parametric maps of DECT.

Effect of Bolus Thickness-Based Base Eichhornia crassipes Powder (Water Hyacinth) on Radiotherapy Bolus Homogeneity

Bolus radiotherapy aims to make the radiation dose more homogeneous, and increase the surface dose to the skin. Exploration of alternative materials for substitute mixtures that are relatively safer is needed to reduce the weaknesses in the use of plasticine mixtures. To develop the basic ingredients for making bolus using biopolymers in water hyacinth (Eichhornia crassipes). This research was conducted using the method of Research and Development. The suitability of the physical characteristics of the bolus (homogeneity judged by CT number; Relative Electron Density is calculated by a formula ?b;% surface dose is obtained from TPS (Treatment Planning System) in the test and the 3 variations of the thickness (0.5 cm, 1.0 cm and 1.5 cm). The feasibility of the bolus product was determined based on the flexibility of the texture and resistance to cold temperatures. Result: Water hyacinth (Eichhornia crassipes) can be used as a reference for alternative bolus materials in radiotherapy due to the response of water hyacinth (Eichhornia crassipes) to radiation Water hyacinth (Eichhornia crassipes-based bolus has same RED (Relative Electron Density) value as soft and solid tissue in all thickness variations and has a surface dose value of ±100% for all thickness variations. Water hyacinth (Eichhornia crassipes) based bolus is homogeneous against radiation and can increase the dose surface so that water hyacinth (Eichhornia crassipes) has benefits and can be used as an alternative bolus material in radiotherapy

Estimation of Proton Stopping Power Ratio and Mean Excitation Energy Using Electron Density and Its Applications via Machine Learning Approach.

The purpose of this study was to develop a simple flexible method for accurate estimation of stopping power ratio (SPR) and mean excitation energy (I) using relative electron density (ρ e). The model was formulated using empirical relationships between SPR, mean excitation energy I, and relative electron density. Some examples were implemented, and a comparison was carried out using other existing methods. The needed coefficients in the model were estimated using optimization tools. Basis vector method (BVM) and Hunemohr and Saito (H-S) method were applied to estimate the ρ e used in the application section. 80 kVp and 150 kVpSn were used as low and high energy, respectively, for the implementation of dual-energy methods. All the examples of the proposed method considered have modeling error that is ≤0.32% and testing root mean square error (RMSE) ≤0.92% for SPR with a mean error close to 0.00%. The method was able to achieve modeling RMSE of 2.12% for mean excitation energy with room for improvement. Similar or better results were achieved in application to BVM. The method showed robustness in application by achieving lower testing error than other presented methods in most cases. It achieved accurate estimation which can be improved using the machine learning algorithm since it is flexible to implement in terms of the function (model) degree and tissue classification.

Automated size-specific dose estimates framework in thoracic CT using convolutional neural network based on U-Net model.

This study aimed to develop an automated method that uses a convolutional neural network (CNN) for calculating size-specific dose estimates (SSDEs) based on the corrected effective diameter (Deff corr ) in thoracic computed tomography (CT). Transaxial images obtained from 108 adult patients who underwent non-contrast thoracic CT scans were analyzed. To calculate the Deff corr according to Mihailidis etal., the average relative electron densities for lung, bone, and other tissues were used to correct the lateral and anterior-posterior dimensions. The CNN architecture based on the U-Net algorithm was used for automated segmentation of three classes of tissues and the background region to calculate dimensions and Deff corr values. Then, 108 thoracic CT images and generated segmentation masks were used for network training. The water-equivalent diameter (Dw ) was determined according to the American Association of Physicists in Medicine Task Group 220. Linear regression and Bland-Altman analysis were performed to determine the correlations between SSDEDeff corr(automated) , SSDEDeff corr(manual) , and SSDEDw . High agreement was obtained between the manual and automated methods for calculating the Deff corr SSDE. The mean values for the SSDEDeff corr(manual) , SSDEDw , and SSDEDeff corr(automated) were 14.3±2.1 mGy, 14.6±2.2 mGy, and 14.5±2.4 mGy, respectively. The U-Net model was successfully trained and used to accurately predict SSDEs, with results comparable to manual-labeling results. The proposed automated framework using a CNN offers a reliable and efficient solution for determining the Deff corr SSDE in thoracic CT.

Karakterisasi Bolus Berbahan Campuran Beeswax dan Petroleum Jelly Menggunakan Berkas Elektron Pada Energi 6 MeV dan 9 MeV

In radiotherapy cases of cancer on the surface of the skin generally use electron beams. The electron beam has not been able to provide the optimum surface radiation dose. Therefore, a material that is able to increase the dose of surface radiation is needed, which is called a bolus. This study tested a bolus made from a mixture of beeswax and petroleum jelly. The bolus test includes the determination of density, the value of Relative Electron Density (RED) and the determination of the absorbed dose. The absorbed dose value was obtained by irradiating using a Linear Accelerator (LINAC) at 6 MeV and 9 MeV energies. The RED value was obtained from the bolus tomography image using a CT-simulator by determining the Region of Interest (ROI). The bolus density values obtained from physical measurements using the TPS program have almost the same average density values. The RED bolus value obtained at a thickness of 0.2 cm to 0.8 cm has a lower RED value than the RED value of the breast, which is 0.976. However, at 1.0 cm thickness, the RED value is equivalent to breast tissue. The value of the absorbed dose in a bolus made from a mixture of beeswax and petroleum jelly, the thicker the bolus used, the smaller the increase in the absorbed dose. The results of this study indicate that a bolus made from a mixture of beeswax and petroleum jelly can be the choice of bolus material during radiotherapy.

Deep inspirational breast hold (DIBH) for right breast irradiation: Improved sparing of liver and lung tissue

ObjectiveTo reduce liver and lung dose during right breast irradiation while maintaining optimal dose to the target volume. This dose reduction has the potential to decrease acute side effects and long-term toxicity. Materials and Methods16 patients treated with radiation therapy for localized carcinoma of the right breast were included retrospectively. For the planning CT, each patient was immobilised on an indexed board with the arms placed above the head. CT scans were acquired in free-breathing (FB) as well as with deep inspiration breath hold (DIBH). Both scans were acquired with the same length. Planning target volumes (PTV's) were created with a 5 mm margin from the respective clinical target volumes (CTV's) on both CT datasets. The liver was outlined as scanned. Dose metrics evaluated were as follows: differences in PTV coverage, dose to the liver (max, mean, V90%, V50%, V30%), dose to lung (mean, V20Gy, relative electron density) and dose to heart (Dmax). The p-values were calculated using Wilcoxon signed-rank tests. A p-value was significant when <0.05. ResultsDifferences in PTV coverage between plans using FB and DIBH were less than 2 %. Maximum liver dose was significantly less using DIBH: 17.5 Gy versus FB: 40.3 Gy (p < 0.001). The volume of the liver receiving 10 % of the dose was significantly less using DIBH with 1.88 cm3 versus 72.2 cm3 under FB (p < 0.001). The absolute volume receiving 20 Gy in the right lung was larger using DIBH: 291 cm3 versus 230 cm3 under FB (p < 0.001) and the relative volume of lung receiving dose greater than 20 Gy was smaller with DIBH: 11.5 % versus 14 % in FB (p = 0.007). The relative electron density of lung was significantly less with DIBH: 0.59 versus 0.62 with FB, (p < 0.001). This suggests that the lung receives less dose due to its lower density when using DIBH. ConclusionRadiation of the right breast using DIBH spares liver and lung tissue significantly and thus carries the potential of best practice for right sided breast cancer.

A virtual phantom for patient-specific QA On A 1.5T MR-linac.

Create a virtual ArcCHECK-MR phantom, customized for a 1.5TMR-linac, with consideration of the different density regions within the quality assurance (QA) phantom, aiming to streamline the utilization of this specialized QA device. A virtual phantom was constructed in the treatment planning system (TPS) to replicate the ArcCHECK-MR's composition, consisting of five distinct layers: "Outer" (representing the outer PMMA ring), "Complex" (simulating the printed circuit boards), "Detectors" (encompassing the detector area), "Inner" (signifying the inner PMMA ring) and "Insert" (representing the PMMA insert). These layers were defined based on geometric data and represented as contour points on a set of dummy CT images. Additionally, a setup platform was integrated as contoured structures. To determine the relative electron density (RED) values of the external and internal PMMA components, measurements were taken at 25 points in the insert using an ion chamber. A novel method for establishing the exit/entrance dose ratio (EEDR) for ArcCHECK-MR was introduced. The RED of higher density region was derived by evaluating the local gamma index passing rate results with criteria of 2% dose difference and 2mm distance-to-agreement. The performance of the virtual phantom was assessed for Unity 7 FFF beams with a 1.5T magnetic field. The radii of the five ring structures within the virtual phantom measured 133.0mm, 110.0mm, 103.4mm, 100.0mm, and 75.0mm for the "Outer," "Complex," "Detectors," "Inner" and "Insert" regions, respectively. The RED values were as follows: ArcCHECK-MR PMMA had a RED of 1.130, "Detectors" were assumed to have a RED of 1.000, "Complex" had a RED of 1.200, and the setup QA phantom justified a RED of 1.350. Early validation results demonstrate that the 5-layer virtual phantom, when compared to the commonly used bulk overridden phantom, offers improved capability in MR-linac environments. This enhancement led to an increase in passing rates for the local gamma index by approximately 5 ∼ 6%, when applying the criteria of 2%, 2mm. We have successfully generated a virtual representation of the distinct regions within the ArcCHECK-MR using a TPS, addressing the challenges associated with its use in conjunction with a 1.5T MR-linac. We consistently observed favorable local gamma index passing rates across two 1.5T MR-linac and ArcCHECK-MR unit combinations. This approach has the potential to minimize uncertainties in the creation of the QA phantom for ArcCHECK-MR across various institutions.

ULTRASTRUCTURAL CHANGES IN RATS SKIN SEBOCYTES DURING EXPERIMENTAL CHRONODESTRUCTION

Purpose of the study ultrastructural changes in rat skin sebocytes during experimental chronodestruction. In the experiments, 22 white outbred male rats with a body weight of 170-220 g were used. The experimental animals, in accordance with the experimental design, were randomly divided into 3 groups: group 1 - intact (n = 8) - animals under standard fixed conditions lighting (12 hours light/12 hours dark); group 2 (n=8) – animals with simulated light deprivation in conditions of round-the-clock darkness (24-hour darkness) for 21 days; group 3 (n=6) – animals with simulated dark deprivation under conditions of round-the-clock lighting (24 hours light) for 21 days. For morphometric assessment, 30 non-overlapping fields of view were analyzed in each preparation at a magnification of 100,000. The number of mitochondria and lysosomes was calculated per 100 μm2 area of the cytoplasm of cells of a certain morphological type. Using the ImageScopeM application program, the average cross-sectional area of mitochondria (μm2) and the average relative electron density of their matrix were determined. During chronodestruction, significant ultrastructural changes are observed in sebocytes, which indicate a change in the functional activity of the cells. During dark deprivation, the functional activity of sebocytes increases, and this, in turn, leads to a significant change in their secretory activity. At the same time, light deprivation leads to an increase in proliferative activity in the sebaceous gland with a simultaneous change in the chemical composition of sebum (polymorphism of granules).

Implication of Filters on the Accuracy of Radiotherapy Planning and the Need for Recalibration of the CT-to-ED Curve

This article examines the effect of the presence or absence of an ImAR filter on the calibration curve for converting X-ray tomography (CT) data to relative electron density (CT-to-ED) values for the abdominal region and head. On CT images this results in distortion of Hounsfield Units (HU) values. The latter, in turn, can lead to inaccuracies in the CT-to-ED calibration curve.&#x0D; Conclusions: If the filters are set up correctly and applied according to the planning system manufacturer's recommendations, changes in the CT-to-Ed curve should be negligible. CT-to-ED curves are an important tool for improving the accuracy and quality of radiation therapy for cancer.

CT number calibration audit in photon radiation therapy.

Inadequate computed tomography (CT) number calibration curves affect dose calculation accuracy. Although CT number calibration curves registered in treatment planning systems (TPSs) should be consistent with human tissues, it is unclear whether adequate CT number calibration is performed because CT number calibration curves have not been assessed for various types of CT number calibration phantoms and TPSs. The purpose of this study was to investigate CT number calibration curves for mass density (ρ) and relative electron density (ρe ). A CT number calibration audit phantom was sent to 24 Japanese photon therapy institutes from the evaluating institute and scanned using their individual clinical CT scan protocols. The CT images of the audit phantom and institute-specific CT number calibration curves were submitted to the evaluating institute for analyzing the calibration curves registered in the TPSs at the participating institutes. The institute-specific CT number calibration curves were created using commercial phantom (Gammex, Gammex Inc., Middleton, WI, USA) or CIRS phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA)). At the evaluating institute, theoretical CT number calibration curves were created using a stoichiometric CT number calibration method based on the CT image, and the institute-specific CT number calibration curves were compared with the theoretical calibration curve. Differences in ρ and ρe over the multiple points on the curve (Δρm and Δρe,m , respectively) were calculated for each CT number, categorized for each phantom vendor and TPS, and evaluated for three tissue types: lung, soft tissues, and bones. In particular, the CT-ρ calibration curves for Tomotherapy TPSs (ACCURAY, Sunnyvale, CA, USA) were categorized separately from the Gammex CT-ρ calibration curves because the available tissue-equivalent materials (TEMs) were limited by the manufacturer recommendations. In addition, the differences in ρ and ρe for the specific TEMs (ΔρTEM and Δρe,TEM , respectively) were calculated by subtracting the ρ or ρe of the TEMs from the theoretical CT-ρ or CT-ρe calibration curve. The mean±standard deviation (SD) of Δρm and Δρe,m for the Gammex phantom were -1.1±1.2g/cm3 and -0.2±1.1, -0.3±0.9g/cm3 and 0.8±1.3, and -0.9±1.3g/cm3 and 1.0±1.5 for lung, soft tissues, and bones, respectively. The mean±SD of Δρm and Δρe,m for the CIRS phantom were 0.3±0.8g/cm3 and 0.9±0.9, 0.6±0.6g/cm3 and 1.4±0.8, and 0.2±0.5g/cm3 and 1.6±0.5 for lung, soft tissues, and bones, respectively. The mean±SD of Δρm for Tomotherapy TPSs was 2.1±1.4g/cm3 for soft tissues, which is larger than those for other TPSs. The mean±SD of Δρe,TEM for the Gammex brain phantom (BRN-SR2) was -1.8±0.4, implying that the tissue equivalency of the BRN-SR2 plug was slightly inferior to that of other plugs. Latent deviations between human tissues and TEMs were found by comparing the CT number calibration curves of the various institutes.

Perbandingan Dosis Serap Bolus Berbahan Playdough, Plastisin, dan Silicone Rubber pada Radioterapi Berkas Elektron 6 MeV dan 9 MeV

Comparison of absorbed dose bolus made from playdough, plasticine, and silicone rubber in electron beam radiotherapy has been assessed. This study aims to compare the absorbed dose, calculate the Relative Electron Density (RED) value, and physical density of playdough, plasticine, and silicone rubber bolus. The boluses were made with dimension of 15 cm×15 cm and thickness of (0,5; 1,0; 1,5; and 2,0) cm. RED value was obtained from tomographic image using CT-Simulator by determining 5 Region of Interest (ROI) regions. The physical density was calculated based on the mass and volume ratio. The absorbed dose was measured using a plan parallel chamber detector with a Linear Accelerator (LINAC) energy variation of 6 MeV and 9 MeV. The results are playdough, plasticine, and silicone rubber bolus have a homogeneous material composition with RED values is above the RED of water. The physical density of playdough and plasticine bolus is above the density of skin tissue but lower than bone tissue, while the physical density of silicone rubber bolus is close to the density of water, muscle, liver, kidney, and lung tissue. The absorbed dose value of silicone rubber bolus with a thickness of 0.5 cm is closer to the absorbed dose without bolus, so bolus of silicone rubber that are better used at energy of 6 MeV and 9 MeV are silicone rubber bolus.

Experimental Investigation of X-Ray Radiation Shielding and Radiological Properties for Various Natural Composites.

Shielding from radiation and plan dose verification is vital during the potential applications in industrial and medical applications. A number of natural composites have been investigated for protecting against high-energy X-ray shielding. The aim is to learn about how natural composites behave under various X-ray energies at STP. The radiological parameters of wood samples were determined using computed tomography imaging, specifically relative electron density (RED), Hounsfield units (HUs), and mass density (MD). Percentage attenuation was measured using a semiflux ionization chamber incorporated with a brass build-up cap and an ionization chamber placed at the beam Isocenter for a different type of natural composite. Measurements are being carried out on a Linear accelerator at an SSD of 110 cm with different collimator sizes. Measured values of HUs, RED, and MD were -232 ± 40, 0.738 ± 0.039, 0.768 ± 0.024 g/cc,-368 ± 41, 0.662 ± 0.047, 0.632 ± 0.024 g/cc, -334 ± 44, 0.639 ± 0.042, 0.666 ± 0.026 g/cc, -370±61, 0.604±0.059, 0.63± 0.036 g/cc, -433±39, 0.543±0.038, 0.608 ± 0.035 g/cc, -382±54, 0.5±0.052, 0.618 ± 0.0316 g/cc, -292±68, 0.680±0.066, 0.708 ± 0.039 g/cc, -298±27, 0.680±0.0229, 0.702± 0.131 g/cc, for Acacia Nilotica, Mangifera Indica, Azadirachta Indica, Tectona Grandis L, Ficus Religiosa, Tecomella Undulata, Sesamum Indicum, Pinus respectively. Measurements show that attenuation is affected by the energy of incident photons, collimator opening, and the type of density of the wood. Various radiological parameters were determined for wood samples that can be utilized to create inhomogeneous phantoms in dosimetry. The largest attenuation is found in Acacia Nilotica and Sesamum Indicum, while the lowest attenuation is found in Ficus religiosa.

Usefulness of Quantitative Analysis Using Relative Electron Density-Based Image of Subsolid Nodule in Chest HRCT

To study the usefulness of quantitative analysis using the relative electron density-based image in the diagnosis of subsolid nodule by chest high-resolution CT. The phantom study measured the CT number(HU), relative electron density(%EDW) and maximum diameter of the nodules by placing artificial nodules in the chest phantom. The patient study was conducted on 172 patients with subsolid nodules from April 2022 to January 2023. The volume and diameter of subsolid nodules in the CT number-based image and relative electron density-based image were measured separately after dividing the two groups: mixed ground-glass nodule and pure ground-glass nodule. The correlation studied between measuring the CT number(HU) and relative electron density(%EDW) by setting the region of interest. The CT number(HU) and diameter values in the phantom study were not significantly different from the actual values of the artificial nodules.(P&gt;0.05) As a result of the patient study, the volume and diameter of subsolid nodules were increased in the relative electron density-based image compared to the CT number-based image for both the mixed ground-glass nodule and pure ground-glass nodule groups.(P&lt;0.05) The CT number(HU) and relative electron density(%EDW) showed a strong positive correlation in both the phantom and patient study.(P&lt;0.05) Providing visual imaging information using CT number-based and relative electron density-based images simultaneously can offer many advantages in establishing future treatment plans through accurate quantitative analysis of subsolid nodules.