Purpose: This study evaluated the properties of a scintillation sheet-based dosimetry system for beam monitoring with high spatial resolution, including the effects of this system on the treatment beam. The dosimetric characteristics and feasibility of this system for clinical use were also evaluated. 

Introduction: The purpose of this study was to evaluate a plastic scintillating plate‑based beam monitoring system to perform quality assurance (QA) measurements in pencil beam scanning proton beam. 

This study was designed to investigate the correlation between the impulse by dielectrophoretic force applied inside a dividing cell during alternating electric fields therapy and the inhibition of cell proliferation. Distributions of the electric field and dielectrophoretic force inside a dividing cell were calculated using the finite element method of COMSOL Multiphysics. Based on the results, the average magnitude of the impulse by the dielectrophoretic force applied to the cleavage furrow inside a dividing cell placed in various directions was calculated as a function of electric field intensity at an extracellular reference point. The simulation results showed that the average magnitude of the impulse to the cleavage furrow inside a dividing cell ranged from 1.51 × 10−9 to 1.49 × 10−7 N s when tumor treating fields with an intensity ranging from 0.1 to 1 V/cm is applied at an extracellular reference point for 6 h. To verify the relationships between the impulse by the dielectrophoretic force and the inhibition of cell proliferation, the survival fractions of the four cancer cell lines were determined as a function of intensity and time duration of the electric field. The correlation between the magnitude and application time of the electric field and the survival fractions of the four cell lines showed similar trends in vitro. These results suggest that both the dielectrophoretic force and the time required for the force to act are proportionally related to the inhibitory effect on dividing cells, enabling this impulse to be used as a reference to quantify the inhibition of cell proliferation.

This study aimed to quantitatively analyze the effciency of the fast non-local means (FNLM) filter in increasing the nodule detection sensitivity in pediatric chest computed tomography (CT) using 3D-printed lung nodules. For that purpose, we compared filtered back projection (FBP) with FNLM filter with iterative reconstruction (IR) method. The performance of the proposed FNLM filter was compared through various quantitative evaluations by modeling the previously used noise reduction methods. When the FNLM filter was applied to the acquired FBP reconstruction method-based CT image, the coeffcient of variation and contrast-to-noise ratio values in the lung nodule region showed similar values to those of the IR method. In addition, it was demonstrated that the point spread function value that can evaluate sharpness can be improved by using the FNLM filter. In conclusion, the results of this study are expected to maximize the image quality and reduce the dose by fusing the CT image reconstructed by the FBP method and the FNLM filter with excellent characteristics.

Background: Despite extensive efforts to obtain accurate segmentation of magnetic resonance imaging (MRI) scans of a head, it remains challenging primarily due to variations in intensity distribution, which depend on the equipment and parameters used. Purpose: The goal of this study is to evaluate the effectiveness of an automatic segmentation method for head MRI scans using a multistep Dense U-Net (MDU-Net) architecture. 

The present study investigated the therapeutic potential of combining tumor-treating fields (TTF), a novel cancer treatment modality that employs low-intensity, alternating electric fields, with 5-fluorouracil (5-FU), a standard chemotherapy drug used for treating pancreatic cancer. The HPAF-II and Mia-Paca II pancreatic cancer cell lines were treated with TTF, 5-FU, or their combination. Combination treatment produced a significantly greater inhibitory effect on cancer cell proliferation than each single modality. Furthermore, combination therapy induced a substantially higher rate of pancreatic cancer cell apoptosis and exhibited a synergistic effect in clonogenic assays. Additionally, combination treatment showed a greater inhibition of cancer cell migration and invasion than either TTF or 5-FU alone. In conclusion, these findings suggest that the synergistic properties of TTF and 5-FU result in greater therapeutic efficacy against pancreatic cancer cells than either modality alone and may improve survival rates in patients with pancreatic cancer.

This study describes the development of a simple method to assess inter-fractional deviations of delivered proton beams in treatment rooms. To monitor the treatment beam, we measured the field-by-field beam fluences by attaching the EBT3 film to the snout, followed by a simple constancy check based on comparisons between the reference beam fluences (acquired during the pre-treatment quality assurance process) and the test beam fluences (acquired during treatment). The feasibility of the proposed treatment beam-monitoring system was confirmed by evaluating 12 treatment fields for each of six patients (brain, liver, prostate, lung, cranial and spinal area, and head and neck). The constancy of the treatment beams was verified by using a gamma index analysis to compare three measurements per field with the reference beam fluence. On the basis of the 3%/3 mm criterion, the average gamma-index passing rates for all measurements were over 99.6%. These results suggest that the constancy of fractional proton beams delivered to patients in treatment rooms can be verified with EBT3 film-based proton-beam monitoring system that can be easily attached to the treatment nozzle and is cost effective.

The amount of potentially lethal damage repair (PLDR) is a significant factor in the process of modeling the survival curves of cells irradiated with fractionated carbon beams. Because the amount of PLDR generally depends on the features of the cells and the linear energy transfer (LET), the amount of PLDR of cells irradiated with fractionated carbon beams shows distinct differences from that of cells irradiated with X-rays. This study considered a new parameter dependent on the correlation between the PLDR trait (T) of the cells over a time interval (Δ) at the fractionated carbon beam irradiation. The survival curves of the cells irradiated with fractionated carbon beams n times were predicted using the ζ and the Ψ values from the delay assay. This study aims to overcome the barriers of traditional methods by developing a new survival curve model with new parameters based on an analysis of the PLDR traits of cells over time interval in fractionated carbon beam irradiation and to suggest a model that produces results significantly closer to the experimental data.

Monte Carlo simulations can classify DNA damage into different types and predict the amount of energy deposited. Geant4-DNA was used to predict simple and complex DNA damage induced by irradiation of low-energy electrons at 0.1–50 keV. The number of molecules generated at different energy levels of radiation was analyzed after observing the gradual changes in the level of water radiolysis. ADNA model was used to categorize direct damage according to the location of strand breaks at the atomic level. The parameters of energy threshold (minimum amount of energy needed to break DNA strands) and 10 base pairs (maximum distance that separates two strand breaks) were set. All instances of water radiolysis including the main OH radical occurred most frequently at 1 keV followed by at 1.5 and 0.5 keV. Direct strand breaks most commonly occurred at 0.5 keV followed by at 0.3 keV. Finally, most of strand breaks occurred more frequently at 0.5 keV than at 0.3 keV. The computational measure-ment results for indirect and direct effects of irradiation depend on the type of simulation code and the DNA model used. Values used in Geant4 (physics list, chemical interaction time and energy threshold)may also influence the results.

Background

Tumor-treating fields (TTFields) is an emerging non-invasive cancer-treatment modality using alternating electric fields with low intensities and an intermediate range of frequency. TTFields affects an extensive range of charged and polarizable cellular factors known to be involved in cell division. However, it causes side-effects, such as DNA damage and apoptosis, in healthy cells.

Objective

To investigate whether thymidine can have an effect on the DNA damage and apoptosis, we arrested the cell cycle of human glioblastoma cells (U373) at G1/S phase by using thymidine and then exposed these cells to TTFields.

Methods

Cancer cell lines and normal cell (HaCaT) were arrested by thymidine double block method. Cells were seeded into the gap of between the insulated wires. The exposed in alternative electric fields at 120 kHz, 1.2 V/cm. They were counted the cell numbers and analyzed for cancer malignant such as colony formation, Annexin V/PI staining, γH2AX and RT-PCR.

Results

The colony-forming ability and DNA damage of the control cells without thymidine treatment were significantly decreased, and the expression levels of BRCA1, PCNA, CDC25C, and MAD2 were distinctly increased. Interestingly, however, cells treated with thymidine did not change the colony formation, apoptosis, DNA damage, or gene expression pattern.

Conclusions

These results demonstrated that thymidine can inhibit the TTFields-caused DNA damage and apoptosis, suggesting that combining TTFields and conventional treatments, such as chemotherapy, may enhance prognosis and decrease side effects compared with those of TTFields or conventional treatments alone.

Hyesun Jeong, Sunghoi Hong

School of Biosystems and Biomedical Sciences, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea

Hyesun Jeong, Sunghoi Hong

Department of Public Health Science, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea

Yunhui Jo, Myonggeun Yoon

Department of Bio- Convergence Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea

Genes Genom 43, 995–1001 (2021)

Background 

This study describes a method that uses a genetic algorithm to select optimal beam angles in proton therapy and evaluates the effectiveness of the proposed algorithm in actual patients. In the use of the genetic algorithm to select the optimal angle, a gene represents the angle of each field and a chromosome represents the combination of beam angles. The fitness of the genetic algorithm, which represents the suitability of the chromosome to the solution, was quantified by using the dose distribution. The weighting factors of the organs used for fitness were obtained from clinical data through logistic regression, reflecting the dose characteristics of actual patients. Genetic operations, such as selection, crossover, mutation, and replacement, were used to modify the population and were repeated until an evaluation based on fitness reached the termination criterion. The proposed genetic algorithm was tested by assessing its ability to select optimal beam angles in three patients with liver cancer. The optimal results for fitness, planning target volume (PTV), normal liver, and skin in the population were compared with the clinical treatment plans, a process that took an average of 36.8 minutes. The dose-volume histograms (DVHs) and the fitness of the genetic algorithm plans did not differ significantly from the actual treatment plans. These findings indicate that the proposed genetic algorithm can automatically generate proton treatment plans with the same quality as actual clinical treatment plans.

Personal dosimeters are used to measure the amount of radiation exposure in individual radiation workers. We aimed to replace existing personal dosimeters and evaluate a real-time scintillator-based dosimeter by monitoring its radiation dose and checking the location exposed to radiation in the workspace. The developed dosimeter measured the radiation dose based on a scintillating fiber (SF) bundle, and comprised a silicon photomultiplier (SiPM), ultra-wide-band (UWB)-based location detecting system, and Bluetooth system. The SF bundle was exposed to radiation-emitted light, and the photons were amplified and converted to electrical signals through the SiPM. These signals were transferred to the user through the Bluetooth system and monitored. To evaluate the feasibility of this mechanism as a dosimeter, we performed characteristic tests, such as dose linearity, dependence on dose rate, energy, exposed angle, and location coordinate mapping. Also, the dose distribution formed in circles around the iso-center was measured to confirm the feasibility of monitoring the exposure dose and location and to enable the radiation worker to move freely in a workspace. We confirmed dose linearity, independence from energy and angle, and accuracy of location monitoring in our device. The user’s locations were measured with a difference of − 6 cm and − 4.8 cm on the x- and the y-axes, respectively. The measured doses on our developed dosimeter were 62.7, 32.3, 21.0, and 15.4 mSv at distances of 50, 100, 150, and 200 cm from the iso-center. In other words, all measured doses at several points showed an error within 5% as compared to doses provided by the conventional pocket dosimeter. These results show that the developed SF-based dosimeter is advantageous in monitoring the exposure dose and location in real time, and has significant potential as a new personal dosimeter for radiation workers.

Purpose: The entrance beam fluence of therapeutic proton scanning beams can be monitored using a gantry-attachable plastic scintillating plate (GAPSP). This study evaluated the clinical application of the GAPSP using amethod that measures intensity modulated proton therapy (IMPT) beams for patient treatment.

Methods: IMPT beams for the treatment of nine patients, at sites that included the spine, head and neck, pelvis, and lung, were measured using the GAPSP, composed of an EJ-212 plastic scintillator and a CMOS camera. All energy layers distinguished by the GAPSP were accumulated to determine the dose distribution of the treatment field. The evaluated fields were compared with reference dose maps verified by quality assurance.

Results: Comparison of dose distributions of evaluation treatment fields with reference dose distributions showed that the 3%/1 mm average gamma passing rate was 96.4%, independent of the treatment site, energy range and field size. When dose distributions were evaluated using the same criteria for each energy layer, the average gamma passing rate was 91.7%.

  Conclusions: The GAPSP is a suitable, low-cost method for monitoring pencil beam scanning proton therapy, especially for non-spot scanning or additional collimation. The GAPSP can also estimate the treatment beam by the energy layer, a feature not common to other proton dosimetry tool.