Scanning Irradiation Research Articles

Three-dimensional radiation dosimetry of carbon ion beams using surfactant hydrogels: Fundamental investigation.

In carbon ion radiotherapy, accurate measurement of the three-dimensional (3D) absorbed dose distribution is critical for effectively targeting tumors. Although micellar gel dosimeters exhibit considerable potential for measuring 3D absorbed dose distributions, few studies have focused on radiotherapy using carbon ion beams. This study investigated the applicability of the surfactant hydrogel dosimeter (SHD), a micellar gel dosimeter, to measuring a 3D dose absorbed through carbon ion beam irradiation. A cubic target region of 34mm per side was established at a depth of 46mm below the upper surface of an SHD specimen. Scanning irradiation was performed using a pencil beam of carbon ions at the Ion-beam Radiation Oncology Center in Kanagawa ("i-ROCK"), Japan, under irradiation conditions set by the treatment planning system ("Monaco for Carbon", Ver. 5.20, Elekta AB, Sweden) to create a spread-out Bragg peak within the target. The physical dose was set to 10Gy at the isocenter, situated at the center of the target. The SHD responsiveness was measured twice using optical computed tomography (CT) ("Vista 15", Modus Medical Devices, Canada) for three irradiated specimens, and six types of measured optical attenuation coefficient (OAC) were obtained. To assess whether the OAC represented the absorbed dose expected in the treatment plan, we compared the relative distribution of the OAC and that of the absorbed dose. Relative fraction (RF) was used to measure the difference between the relative value of the OAC and that of the absorbed dose. Moreover, the distribution of OH radical (•OH) concentration obtained by Monte Carlo simulation ("PHITS" ver. 3.24 JAEA, Japan) and that of the OAC were compared. In the direction of beam travel, the relative distribution of the OAC was lower than that of the absorbed dose. This discrepancy could be attributed to a decrease in the concentration of •OH produced by irradiation owing to the recombination reaction, which does not accurately reflect the absorbed dose. By contrast, the distributions in the plane perpendicular to the beam travel were consistent. The RF increased from±3% to±13% along the beam travel direction. The small RF in the plane perpendicular to the beam travel could be attributed to the constant distribution of linear energy transfer, regardless of the irradiation position, and the generation of radicals proportionally to the absorbed dose. The increase in RF along the beam travel direction was ascribed to ring artifacts in the irradiated region. The measurement of the absorbed dose distribution in the beam travel direction should be improved. The observed discrepancy is attributed to the reduced reactivity of the SHD due to a high liner energy transfer near the Bragg peak. However, the absorbed dose distribution can be effectively evaluated in the plane perpendicular to the direction of beam travel.

Correlation between local instantaneous dose rate and oxygen pressure reduction during proton pencil beam scanning irradiation

Background and purposeOxygen dynamics may be important for the tissue-sparing effect observed at ultra-high dose rates (FLASH sparing effect). This study investigated the correlation between local instantaneous dose rate and radiation-induced oxygen pressure reduction during proton pencil beam scanning (PBS) irradiations of a sample and quantified the oxygen consumption g-value. Materials and methodsA 0.2 ml phosphorescent sample (1 μM PtG4 Oxyphor probe in saline) was irradiated with a 244 MeV proton PBS beam. Four irradiations were performed with variations of a PBS spot pattern with 5 × 7 spots. During irradiation, the partial oxygen pressure (pO2) was measured with 4.5 Hz temporal resolution with a phosphorometer (Oxyled) that optically excited the probe and recorded the subsequently emitted light. A calibration was performed to calculate the pO2 level from the measured phosphorescence lifetime. A fiber-coupled scintillator simultaneously measured the instantaneous dose rate in the sample with 50 kHz sampling rate. The oxygen consumption g-value was determined on a spot-by-spot level and using the total pO2 change for full spot pattern irradiation. ResultsA high correlation was found between the local instantaneous dose rate and pO2 reduction rate, with a correlation coefficient of 0.96–0.99. The g-vales were 0.18 ± 0.01 mmHg/Gy on a spot-by-spot level and 0.17 ± 0.01 mmHg/Gy for full spot pattern irradiation. ConclusionsThe pO2 reduction rate was directly related to the local instantaneous dose rate per delivered spot in PBS deliveries. The methodology presented here can be applied to irradiation at ultra-high dose rates with modifications in the experimental setup.

Preparation of hierarchical microgroove textures on the surface of Al-based wicks by roller pressing and laser scanning irradiation

Fabrication of high-performance heat pipe wicks has become a major challenge due to the increase of heat dissipation requirements for electronic devices. In this paper, we propose a two-step method for the preparation of aluminum liquid-absorbing wicks with hierarchical groove structures by roller pressing and laser irradiation techniques. The effects of laser fluence and velocity on the groove morphology, wettability and capillary effect of the aluminum wicks with hierarchical grooves processed by laser scanning are investigated. The study demonstrates that sub-scale grooves with a period of 20 μm can be created on the surface of the aluminum wick using a laser fluence of 7.166 J/cm2, scanning velocities of 560 mm/s and 630 mm/s, and a pulse distance of 1 μm. The surface roughness of the irradiated aluminum wick was increased and energy dispersive spectroscopy tests showed an increase in the oxygen content of the machined surface, resulting in a surface amplification effect and the formation of a large number of hydrogen bonds in contact with the liquid. Capillary rise experiments demonstrate that hierarchical microgrooves enhance capillary action on the surface of the aluminum wick more effectively than single-scale grooves. This is due to the pumping effect in microgrooves and the diffusion effect in Ω-grooves. The hierarchical microgroove prepared under the above parameters had a capillary rise height of 88.5 mm and a capillary rise speed of 5.5 mm/s. This work proposes a method for producing high-performance wicks that are both efficient and cost-effective.

Clinical Viability of an Active Spot Scanning Beam Delivery System With a Newly Developed Carbon-Ion Treatment Planning System

PurposeAlthough active spot scanning irradiation technique is theoretically superior to passive-scattered broad beam irradiation with respect to normal tissue sparing, corroborations of the clinical benefit of carbon-ion spot scanning have remained scarce. This study aims to investigate the feasibility and clinical implementation of an active spot scanning beam calculation algorithm in a homemade carbon-ion treatment planning system (TPS) by comparing it with a conventional passive uniform scanning technique. Materials and methodsCarbon-ion plans were initially formulated using spot/uniform scanning methods in 22 participants enrolled in a prospective observational clinical trial. Subsequently, two additional plans were designed, resulting in three carbon-ion plans for each participant: uniform and spot scanning with mini-ridge filters (MRFs) of 2mm and 4mm, respectively. ResultsThe findings revealed no significant differences in dose homogeneity; however, significant differences in dose conformity were found between the active and passive scanning plans. For dose drop-off outside the target volume, the average gradient index (GI) values were 1.94 (95% confidence interval (CI): 1.79%-2.09%), 1.87 (95% CI: 1.73%-2.01%), and 3.20 (95% CI: 2.80%-3.61%) for the MRF4, MRF2, and uniform scanning plans, respectively. The pre-treatment tumor volume was 124.7 cm3 (range, 54.2-234 cm3), and the average shrinkage observed was 38.4% (95% CI: 17.6%-59.4%). Seven participants experienced grade 1 acute toxicity, and four experienced grade 2 acute toxicity. However, none of the patients developed grade 3 acute toxicity. ConclusionsIncreasing evidence suggests that potential clinical advantages of spot scanning delivery underlie its technical characteristics. As one among the few institutions currently utilizing carbon-ion radiotherapy, the investigation also provides promising safety and efficacy outcomes from the initial groups of treated participants, thereby contributing to the established clinical evidence supporting the effectiveness and superiority of carbon-ion therapy.

Influence of Femtosecond Laser Surface Modification on Tensile Properties of Titanium Alloy.

Titanium alloy components often experience damage from impact loads during usage, which makes improving the mechanical properties of TC4 titanium alloys crucial. This paper investigates the influence of laser scanning irradiation on the tensile properties of thin titanium alloy sheets. Results indicate that the tensile strength of thin titanium alloy sheets exhibits a trend of initial increase followed by a decrease. Different levels of enhancement are observed in the elongation at break of a cross-section. Optimal improvement in the elongation at break is achieved when the laser fluence is around 8 J/cm2, while the maximum increase in tensile strength occurs at approximately 10 J/cm2. Using femtosecond laser surface irradiation, this study compares the maximum enhancement in the tensile strength of titanium alloy base materials, which is approximately 8.54%, and the maximum increase in elongation at break, which reaches 25.61%. In addition, the results verify that cracks in tensile fractures of TC4 start from the middle, while laser-induced fracture cracks occur from both ends.

EFFECT OF LOW-POWER LASER IRRADIATION ON THE SHEAR BOND STRENGTH AND THERMAL CHANGES ACROSS DIFFERENT ZIRCONIA THICKNESSES USING DIFFERENT IRRADIATION TIMES.

To investigate the effect of irradiation time and zirconia thickness using low power Er,Cr:YSGG laser irradia)on (for debonding purposes) on the thermal changes and shear bond strength (SBS) of resin-bonded 3% mol yIrium oxide stabilized tetragonal zirconia polycrystal (3YTZP) specimens. 3Y-TZP slices of 0.5-, 2-, and 3- mm thick were used. The temperatures during laser irradiation using single spot irradiation at different times (30 seconds, 60 seconds, 90 seconds, and 120 seconds) and line scanning irradiation from one spot to another at three different distances (2, 4, and 6 mm) were recorded. Single spot and line scanning irradiation data were analyzed using three-way ANOVA (α = .05) and generalized linear mixed model, respectively. Nonirradiated (control) and irradiated resin-bonded 3Y-TZP specimens were shear tested, and the data were analyzed using two-way ANOVA (α = .05). Under single spot irradiation, the laser-induced temperature was higher through thin 3Y-TZP at any time compared to thick 3Y-TZP. For the line scanning method, short distances (2 and 4 mm) resulted in a significant increase in temperature for 0.5-mm thick specimens. Laser irradiation significantly decreased the SBS of the 0.5-mm group compared to the nonirradiated group. After irradiation, the bond strength of the 2- and 3-mm thick 3Y-TZP was similar to the nonirradiated group. The temperature and bond strength of low-power laser irradiated 3Y-TZP specimens was affected by the specimen thickness but not by the irradiation time tested. Low-power laser irradiation is an effective debonding method for thin Y-TZP restorations.

Beam delivery characteristics of the Hitachi carbon ion scanning system at Osaka Heavy Ion Medical Accelerator in Kansai (HIMAK).

Using the pencil beam raster scanning method employed at most carbon beam treatment facilities, spots can be moved without interrupting the beam, allowing for the delivery of a dose between spots (move dose). This technique is also known as Dose-Driven-Continuous-Scanning (DDCS). To minimize its impact on HIMAK patient dosimetry, there's an upper limit to the move dose. Spots within a layer are grouped into sets, or "break points," allowing continuous irradiation. The beam is turned off when transitioning between sets or at the end of a treatment layer or spill. The control system beam-off is accomplished by turning off the RF Knockout (RFKO) extraction and after a brief delay the High Speed Steering Magnet (HSST) redirects the beam transport away from isocenter to a beam dump. The influence of the move dose and beam on/off control on the dose distribution and irradiation time was evaluated by measurements never before reported and modelled for Hitachi Carbon DDCS. We conducted fixed-point and scanning irradiation experiments at three different energies, both with and without breakpoints. For fixed-point irradiation, we utilized a 2D array detector and an oscilloscope to measure beam intensity over time. The oscilloscope data enabled us to confirm beam-off and beam-on timing due to breakpoints, as well as the relative timing of the RFKO signal, HSST signal, and dose monitor (DM) signals. From these measurements, we analyzed and modelled the temporal characteristics of the beam intensity. We also developed a model for the spot shape and amplitude at isocenter occurring after the beam-off signal which we called flap dose and its dependence on beam intensity. In the case of scanning irradiation, we measured move doses using the 2D array detector and compared these measurements with our model. We observed that the most dominant time variation of the beam intensity was at 1 kHz and its harmonic frequencies. Our findings revealed that the derived beam intensity cannot reach the preset beam intensity when each spot belongs to different breakpoints. The beam-off time due to breakpoints was approximately 100 ms, while the beam rise time and fall time (tdecay ) were remarkably fast, about 10 ms and 0.2 ms, respectively. Moreover, we measured the time lag (tdelay ) of approximately 0.2 ms between the RFKO and HSST signals. Since tdelay ≈ tdecay at HIMAK then the HSST is activated after the residual beam intensity, resulting in essentially zero flap dose at isocenter from the HSST. Our measurements of the move dose demonstrated excellent agreement with the modelled move dose. We conducted the first move dose measurement for a Hitachi Carbon synchrotron, and our findings, considering beam on/off control details, indicate that Hitachi's carbon synchrotron provides a stable beam at HIMAK. Our work suggests that measuring both move dose and flap dose should be part of the commissioning process and possibly using our model in the Treatment Planning System (TPS) for new facilities with treatment delivery control systems with higher beam intensities and faster beam-off control.

Pengaruh Slice Thickness terhadap Signal to Noise Ratio (SNR) dari Hasil Penyinaran CT Scan di RSUP Prof. Dr. I.G.N.G Ngoerah

A research has been carried out on the effect of slice thickness on SNR values from the results of CT Scan irradiation at Prof. Dr. I.G.N.G Ngoerah Hospital. Variations in the thickness of the slices used are 1 mm, 3 mm, 5 mm, and 7 mm. The tube voltage, tube current, and FOV used are constant, namely 120 kV, 200 mA, and 380 mm. SNR value analysis was calculated using the average object value and SD background for each material. Based on the results of a simple linear regression test, the thickness of the slices obtained has an effect of 99.9% on the SNR value. These results indicate that the greater the thickness of the slice used, so the SNR value will increasesas the SNR value increases, it will improve image quality.

Penentuan Dosis Efektif Pada Abdo Pelvis dan Organ Kritis dari Hasil Penyinaran Computed Tomography Scanner (CT Scan)

Determination of the effective dose on the abdo pelvis and organs at risk has been carried out from the results of the CT Scan irradiation at Sanglah General Hospital.The study began by collecting secondary data from the results of an abdominal CT scan, namely the CTDIvol and DLP values. Then the data was grouped based on gender of 40 patients with an age range of 20-70 years. The value of the effective dose in the abdo pelvis is obtained by multiplying the DLP value and the conversion coefficient k. While the effective dose to organs at risk is obtained from the product of the CTDIvol and wt. The results of the effective dose in the abdo pelvis were obtained in the range of 4.596-6.738 mSv for male patients while for female patients it was 4.209-5.232 mSv. The results of the effective dose in the abdo pelvis are still at the threshold set by BAPETEN, which is 13.275 mSv, so the CT scan is still suitable for use. Average effective dose values for critical organs were 0.2882 mSv for the liver, 0.8646 mSv for the kidney, and 0.5764 mSv for the gonad. The highest dose was received by the gonads. This shows that the gonads are the organs that have the highest sensitivity in receiving radiation doses in the abdo pelvis

Visible Pulsed Laser-Assisted Selective Killing of Cancer Cells with PVP-Capped Plasmonic Gold Nanostars.

A new generation of nanoscale photosensitizer agents has improved photothermal capabilities, which has increased the impact of photothermal treatments (PTTs) in cancer therapy. Gold nanostars (GNS) are promising for more efficient and less invasive PTTs than gold nanoparticles. However, the combination of GNS and visible pulsed lasers remains unexplored. This article reports the use of a 532 nm nanosecond pulse laser and polyvinylpyrrolidone (PVP)-capped GNS to kill cancer cells with location-specific exposure. Biocompatible GNS were synthesized via a simple method and were characterized under FESEM, UV-visible spectroscopy, XRD analysis, and particle size analysis. GNS were incubated over a layer of cancer cells that were grown in a glass Petri dish. A nanosecond pulsed laser was irradiated on the cell layer, and cell death was verified via propidium iodide (PI) staining. We assessed the effectiveness of single-pulse spot irradiation and multiple-pulse laser scanning irradiation in inducing cell death. Since the site of cell killing can be accurately chosen with a nanosecond pulse laser, this technique will help minimize damage to the cells around the target cells.

Creation, evolution, and future challenges of ion beam therapy from a medical physicist’s viewpoint (Part 2). Chapter 2. Biophysical model, treatment planning system and image guided radiotherapy

When an ion beam penetrates deeply into the body, its kinetic energy decreases, and its biological effect increases due to the change of the beam quality. To give a uniform biological effect to the target, it is necessary to reduce the absorbed dose with the depth. A bio-physical model estimating the relationship between ion beam quality and biological effect is necessary to determine the relative biological effectiveness (RBE) of the ion beam that changes with depth. For this reason, Lawrence Berkeley Laboratory, National Institute of Radiological Sciences (NIRS) and GSI have each developed their own model at the starting of the ion beam therapy. Also, NIRS developed a new model at the starting of the scanning irradiation. Although the Local Effect Model (LEM) at the GSI and the modified Microdosimetric Kinetic Model (MKM) at the NIRS, the both are currently used, can similarly predict radiation quality-induced changes in surviving fraction of cultured cell, the clinical RBE-weighted doses for the same absorbed dose are different. This is because the LEM uses X-rays as a reference for clinical RBE, whereas the modified MKM uses carbon ion beam as a reference and multiplies it by a clinical factor of 2.41. Therefore, both are converted through the absorbed dose. In PART 2, I will describe the development of such a bio-physical model, as well as the birth and evolution of a treatment planning system and image guided radiotherapy.

Ion recombination correction factors and detector comparison in a very-high dose rate proton scanning beam

PurposeAccurate dosimetry is paramount to study the FLASH biological effect since dose and dose rate are critical dosimetric parameters governing its underlying mechanisms. With the goal of assessing the suitability of standard clinical dosimeters in a very-high dose rate (VHDR) experimental setup, we evaluated the ion collection efficiency of several commercially available air-vented ionization chambers (IC) in conventional and VHDR proton irradiation conditions. MethodsA cyclotron at the Orsay Proton Therapy Center was used to deliver VHDR pencil beam scanning irradiation. Ion recombination correction factors (ks) were determined for several detectors (Advanced Markus, PPC05, Nano Razor, CC01) at the entrance of the plateau and at the Bragg peak, using the Niatel model, the Two-voltage method and Boag’s analytical formula for continuous beams. ResultsMean dose rates ranged from 4 Gy/s to 385 Gy/s, and instantaneous dose rates up to 1000 Gy/s were obtained with the experimental set-up. Recombination correction factors below 2 % were obtained for all chambers, except for the Nano Razor, at VHDRs with variations among detectors, while ks values were significantly smaller (0.8 %) for conventional dose rates. ConclusionsWhile the collection efficiency of the probed ICs in scanned VHDR proton therapy is comparable to those in the conventional regime with recombination coefficiens smaller than 1 % for mean dose rates up to 177 Gy/s, the reduction in collection efficiency for higher dose rates cannot be ignored when measuring the absorbed dose in pre-clinical proton scanned FLASH experiments and clinical trials.

Effect of laser surface modification on the tensile properties of ultra-thin titanium sheet

Laser scanning irradiation (LSI) was a promising method to improve the surface hemo-compatibility of vascular stent (VS). This paper firstly studied the effect of LSI on the tensile properties of ultra-thin Ti sheet, the thickness of which was close to that of VS’s wall. Meanwhile, the influence of plastic deformation on the hydrophilicity of LSI sheets and the hydrophobicity of the ones modified with fluorosilane was evaluated. The results indicated that the tensile properties of Ti sheets gradually declined with increasing laser fluence (Fp) and decreasing scanning speed (v). As using laser gentle ablation (LGA) with Fp = 1.1 ∼ 2.9 J/cm2, the declination degree of tensile properties was relative slight, but it was obviously sharper as using laser strong ablation (LSA) with Fp = 4.0 ∼ 6.6 J/cm2. In addition, the tensile and yield strengths of LSA samples using v = 42 mm/s were much smaller than those using higher v of 126 ∼ 630 mm/s, owning to the much larger laser-ablated depth in the surfaces. All of the LSA surfaces exhibited superhydrophilicity, and after fluorination they rapidly turned to be superhydrophobic with low adhesion to water. Interestingly, plastic deformation within the tensile fracture point slightly improved the super-hydrophilicity or superhydrophobicity of these LSA surfaces rather than destroyed it. Therefore, LSA with v = 126 ∼ 630 mm/s was more suitable to be applied in the stent, which could not only obtain super-hydrophilicity/hydrophobic surfaces with hierarchical microtextures but just slightly affect the stent’s tensile properties.

Local Crystallization of Amorphous Aluminum Oxide Thin Film Using Electron Beam Irradiation by SEM

Amorphous thin film thinned for transmission electron microscopy observation is reported to crystallize by electron beam (EB) irradiation of TEM. If thin film deposited on substrates can be crystallized by EB irradiation of scanning electron microscopy (SEM), new nanoscale devices can be fabricated such as electronic nanoscale circuits in amorphous thin films. Therefore, an amorphous AlOx (am-AlOx) thin film is deposited onto a Si substrate by atomic layer deposition (ALD) and point and area scan irradiation of EBs were performed by SEM. Then, structure and elemental analyses are carried out by TEM. Only the point EB irradiated area crystallized from the surface to the interface between am-AlOx and the Si substrate, and γ-Al2O3 appeared. Moreover, the oxygen content of the not irradiated area close to the irradiated area was lower than that of the not irradiated area far from the irradiated area. These results show that the EB irradiated area was positively charged by the emission of secondary and Auger electrons under point irradiation conditions, and that oxygen was supplied by attracting its negative charge to the EB irradiated area. Also, the electrostatic repulsion between positively charged atoms and the structure relaxation due to electron excitation were additional driving forces for the crystallization.

Influence of Pulsed, Scanning and Constant (16- and 24-h) Modes of LED Irradiation on the Physiological, Biochemical and Morphometric Parameters of Lettuce Plants (Lactuca sativa L.) while Cultivated in Vertical Farms

In city farming, when growing green crops, a significant part of the production cost is the cost of electricity for lighting. The physiology, biochemistry, morphology and productivity of plants can be affected by changing irradiation modes and these changes reduce electricity costs. However, the results of studies in the literature are contradictory. In this work, we investigated the effect of impulse (frequency 1000 Hz and duty cycle 67%), scanning (the principle of running lights) and constant 16 h and 24 h modes of operation of white light LED irradiators on the physiological, biochemical and morphometric parameters of lettuce with red and green leaves. The daytime integral of light in all variants remained unchanged ~15.6 mol m−2 day−1. Daily electricity consumption also did not differ significantly. Plants were grown on racks in a climatic chamber up to 35 days of age. For lettuce with red leaves, the most optimal for biomass accumulation and synthesis of anthocyanins was the impulse illumination mode, while for lettuce with green leaves, no statistically significant differences in biomass were observed under different irradiation modes. For red-leaved lettuce, it was found that the highest concentration of carotenoids in the leaf was observed under constant (24 h) and scanning irradiation, which is associated with a more active reaction of the photosynthetic system to prolonged irradiation and increased intensity during scanning irradiation. Also, increased photosynthetic activity was found in both varieties of lettuce at 16 h of operation of LED irradiators, which, however, did not affect their final productivity. The results may be useful for the development of LED illuminators for use in rack growing.

Effect of exposure to ionizing radiation on competitive proliferation and differentiation of hESC

Purpose We studied the effects of computed tomography (CT) scan irradiation on proliferation and differentiation of human embryonic stem cells (hESCs). It was reported that hESC is extremely radiosensitive; exposure of hESC in cultures to 1 Gy of ionizing radiation (IR) results in massive apoptosis of the damaged cells and, thus, they are eliminated from the cultures. However, after recovery the surviving cells proliferate and differentiate normally. We hypothesized that IR-exposed hESC may still have growth rate disadvantage when they proliferate or differentiate in the presence of non-irradiated hESC, as has been shown for mouse hematopoietic stem cells in vivo. Materials and methods To study such competitive proliferation and differentiation, we obtained cells of H9 hESC line that stably express green fluorescent protein (H9GFP). Irradiated with 50 mGy or 500 mGy H9GFP and non-irradiated H9 cells (or vice versa) were mixed and allowed to grow under pluripotency maintaining conditions or under conditions of directed differentiation into neuronal lineage for several passages. The ratio of H9GFP to H9 cells was measured after every passage or approximately every week. Results We observed competition of H9 and H9GFP cells; we found that the ratio of H9GFP to H9 cells increased with time in both proliferation and differentiation conditions regardless of irradiation, i.e. the H9GFP cells in general grew faster than H9 cells in the mixtures. However, we did not observe any consistent changes in the relative growth rate of irradiated versus non-irradiated hESC. Conclusions We conclude that population of pluripotent hESC is very resilient; while damaged cells are eliminated from colonies, the surviving cells retain their pluripotency, ability to differentiate, and compete with non-irradiated isogenic cells. These findings are consistent with the results of our previous studies, and with the concept that early in pregnancy omnipotent cells injured by IR can be replaced by non-damaged cells with no impact on embryo development.

Creation, evolution, and future challenges of ion beam therapy from a medical physicist's viewpoint (part 1). Introduction and Chapter 1. accelerator and beam delivery system.

Radiation therapy for cancer using the Bragg peak of an ion beam has been making steady progress after being proposed by Robert Wilson in 1946. At the end of 2020, 12 dedicated treatment devices existed in operation worldwide, and approximately 40,000 patients have been treated with ion beams (mostly carbon ions). To date, ion beam therapy is superior to other treatments for rare cancers in the head and neck as well as bone and soft tissues; however, most recently, evidence submitted in Japan for the 2022 revision of public health insurance shows that ion beam therapy outperforms photon therapy for intractable common cancers such as pancreatic cancer and liver cancer. This may greatly expand its indications. Lawrence Berkeley Laboratory in the United States started research of ion beam therapy, National Institute of Radiological Sciences in Japan built the first dedicated device Heavy Ion Accelerator in Chiba and started systematic clinical research, and GSI in Germany developed the scanning irradiation method and rotating gantry for the first time. This paper presents the history and future challenges of ion beam therapy in three fields: accelerator and beam delivery system, physical/biological model and treatment planning system, and clinical research. This study is divided into three parts describing the achievements and roles of the three laboratories. In Part 1, accelerator and beam delivery system are described.

Ultra-High Dose-Rate Carbon-Ion Scanning Irradiation with a Compact Type Medical Synchrotron toward FLASH Research

<h3>Purpose/Objective(s)</h3> To establish an irradiation system to enable the ultra-high dose-rate (uHDR; FLASH) scanned carbon-ion irradiation with a compact type medical synchrotron. <h3>Materials/Methods</h3> After technical adjustments of the accelerator operation parameters, the medical synchrotron extracted ≥1.0 × 10⁹ carbon-ions (2.0 nC/spill) at 208.3 MeV/u (86 mm in range) within a maximum 100 ms. The uHDR carbon-ion beam delivery system was designed to prevent damage to monitors in the nozzle due to the uHDR beam by avoiding passage through the nozzle. The dose amount was adjusted by the extraction time of the total spill with a function generator. The carbon-ion beam was scanned once to create a field within the extraction time. Advanced Markus chamber and radiographic film were used to measure the absolute dose and the field size respectively, at a plateau depth. Operation voltage of the chamber was set to 400 V at the uHDR. <h3>Results</h3> The FLASH irradiation utilizing beam scanning was confirmed with a dose of 5.4 Gy (homogeneity of ±2%) for the beam in a volume of at least 16 mm × 16 mm in a square field and a corresponding dose-rate of 95 Gy/s (± 1%). The dose was changed to about 0.7, 1.5, 2.9 Gy for the dose-rate and the field size. Details of the results are shown in Table1. <h3>Conclusion</h3> The FLASH dose-rates >40 Gy/s at different dose levels were achieved in a useful field size for research created by the scanned carbon-ion beams with the compact type medical synchrotron. This study reported promising beam characteristics of uHDR scanned carbon-ion beams, at different dose levels, and can be used for further investigation of carbon-ion FLASH research. The dose and dose-rate established with the uHDR irradiation system can be applied in biological experiments.

Low-level laser therapy with different irradiation methods modulated the response of bone marrow mesenchymal stem cells in vitro.

Low-level laser therapy (LLLT) also known as photobiomodulation is a treatment to change cellular biological activity. The exact effects of LLLT remain unclear due to the different irradiation protocols. The purpose of this study was to investigate the effects of LLLT by three different irradiation methods on the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro. BMSCs were inoculated in 24-well plates and then irradiated or not (control) with a laser using three different irradiation methods. The irradiation methods were spot irradiation, covering irradiation, and scanning irradiation according to different spot areas (0.07 cm2 or 1.96 cm2) and irradiation areas (0.35 cm2 or 1.96 cm2), respectively. The laser was applied three times at energy densities of 4J/cm2. The cell proliferation by CCK-8. ALP activity assay, alizarin red, and quantitative real-time polymerase chain reaction (RT-PCR) were performed to assess osteogenic differentiation and mineralization. Increases in cell proliferation was obvious following irradiation, especially for covering irradiation. The ALP activity was significantly increased in irradiated groups compared with non-irradiated control. The level of mineralization was obviously improved following irradiation, particularly for covering irradiation. RT-PCR detected significantly higher expression of ALP, OPN, OCN, and RUNX-2 in the group covering than in the others, and control is the lowest. The presented results indicate that the biostimulative effects of LLLT on BMSCs was influenced by t he irradiation method, and the covering irradiation is more favorable method to promote the proliferation and osteogenic differentiation of BMSCs.

Design and Magnetic Field Measurement of the Superconducting Magnets for the Next-Generation Rotating Gantry

This paper describes the design and reports the test results of the world's most compact rotating gantry for a heavy-ion therapy system mounted with superconducting bending and focusing magnets. A rotating gantry is cylindrical irradiation equipment with magnets for beam transport and beam scanning that delivers energetic carbon ions at up to 430 MeV/u precisely to a tumor from any direction without changing the posture of the patient. However, because of the high magnetic rigidity of therapeutic carbon ions, the rotating gantry was too big to be installed at general hospitals. Therefore, the superconducting rotating gantry had been developed in collaboration with Yamagata University. In the project, to achieve further downsizing of the rotating gantry, the length of the scanning irradiation system is reduced and the magnetic field of the superconducting magnet is increased to 3.5 T from the 2.88 T of the first superconducting gantry installed in the National Institutes for Quantum and Radiological Science and Technology (QST). As a result, the gantry is downsized to 2/3 of the first superconducting rotating gantry. This next-generation small superconducting rotating gantry has already been installed and is undergoing preclinical commissioning at Yamagata University.