Uncertainty of active breathing coordinator technology for liver and lung cancer therapy using proton and heavy ion / 中华放射肿瘤学杂志

Objective:To study and analyze the uncertainty of active breathing coordinator (ABC) technology for liver and lung cancer therapy using proton and heavy ion.Methods:Before each treatment, each patient received a verification radiograph through the supporting imaging frame in treatment room. 200 verification radiographs were taken for 20 lung cancer patients and 200 for 20 liver cancer patients. Ipiodol markers, which were fixed relative to the location of the tumor, were injected into the liver cancer patients. The position changes of ipiodol markers could reflect the position changes of liver tumors. Verification radiographs were registered with the vertebral body as the main target, and the change value of tumor location was recorded.Results:For liver cancer cases, the values of position change in the left and right, head and foot, and dorsal abdomendirection were (-0.05± 0.28) cm, (0.15±0.33) cm, (-0.12±0.27) cm, and (-0.03±0.13) cm, (-0.05±0.14) cm and (0.02±0.16) cmfor lung cancer cases, respectively ( P=0.280, <0.001, <0.001). For liver cancer cases, the dispersionin the left and right, head and foot, and dorsal abdomendirectionwas (0.20±0.09) cm, (0.25±0.06) cm, (0.19±0.09) cm, and (0.09±0.03) cm, (0.10±0.03) cm and (0.13±0.03) cm for lung cancer cases, respectively ( P<0.001, <0.001, 0.008). The proportion of tumor location changes of≤5 mm in three directions in liver and lung cancer patientswas (92%, 83%, 93%) vs. (99%, 99%, 100%)( P=0.030, 0.002, 0.007). Conclusion:The application of ABC technology in the proton heavy ion therapy of lung and liver cancer has good reproducibility, and the stability of ABC technology in the treatment of lung cancer is better than that of liver cancer.

Prediction model of local effect model-based rectal dose volume histogram in prostate cancer patients treated with carbon ion radiotherapy / 中华放射肿瘤学杂志

Objective:To establish a local effect model (LEM)-based rectal dose volume histogram (DVH) prediction model in prostate cancer patients treated with carbon ion therapy based on Japanese experience, aiming to provide reference for clinically reducing the incidence of rectal adverse reactions.Methods:The planning CT data of 76 patients with prostate cancer were collected. The microdosimetric kinetic model (MKM) was used for initial planning, and the LEM was selected to recalculate the biological dose based on the same fields to MKM. Then, the geometric features and DVH of the rectum were extracted from the LEM plans. The planning data of 61 cases were used to establish the prediction model with linear regression and the other 15 cases were used for validation.Results:The ratio of the overlapped volume between the rectum and the region of interest (ROI) expended from planning target volume by 1 cm along the left and right directions of the rectum could be proved to be the characteristic parameters for linear regression. The mean goodness-of-fit R2 of predicted and LEM plan-based DVH of 15 cases was 0.964. The results of predicted rectal adverse reactions based on predicted DVH were consistent with those of LEM plan-based DVH. Conclusions:The linear regression method used in this study can establish an accurate prediction model of rectal DVH, which may provide certain reference for reducing the incidence of rectal adverse reactions. Nevertheless, the findings remain to be further verified by clinical trials with larger sample size.

Different optimizing strategies based on spot scanning carbon ion therapy for non-small cell lung cancer / 中华放射肿瘤学杂志

Objective To evaluate the dose variation of target coverage and organs at risk ( OARs) among four planning strategies using spot-scanning carbon-ion radiotherapy for non-small cell lung cancer ( NSCLC) . Methods Ten NSCLC patients utilizing gating motion control were selected to receive dose calculation over multiple acquired 4DCT images. Four optimizing strategies consisted of intensity-modulated carbon-ion therapy ( IMCT-NoAS ) , IMCT combined with internal gross tumor volume ( IGTV ) assigned muscle ( IMCT-ASM ) , single beam optimization ( SBO ) ( SBO-NoAS ) and SBO combined with IGTV assigned muscle (SBO-ASM).The initial plan was re-calculated after the 4DCT data were reviewed and then compared with the initial plan in the dosimetry. Results For re-calculation plans with two reviewing CTs,all four strategies yielded similar planning target volume ( PTV ) coverage. Merely IMCT-NoAS strategy presented with relatively significant variations in dose distribution. Dose variation for OARs between initial and re-calculated plans:for all four strategies,V20 of ipsilateral lung was increased by approximately 2. 0 Gy (relative biological effective dose,RBE),V30 of heart was increased by approximately 1. 0 Gy (RBE) for both IGTV assigned muscle strategies,whereas decreased by approximately 0. 2 Gy ( RBE) for both IGTV non-assigned muscle strategies. The maximum dose of spinal cord was changed by 2. 5 Gy ( RBE ) . Conclusions Carbon-ion radiotherapy is sensitive to the anatomic motion within the tumors along the beam path. When the tumor motion along the head-foot (H-F) direction exceeds 8 mm,SBO-ASM strategy provides better dose coverage of target. Strategies with IGTV assignment may result in dose overshoot to a position deeper than the initial planning dose distribution.

Comparative analysis ofapplication value and setup error between two setup methods in proton and carbon ion therapy for prostate cancer / 中华放射肿瘤学杂志

Objective To compare the application values and setup errors between vacuum bag plus body mask and customized alpha cradle duringproton and carbon therapy using Siemens 6D robotic couch in prostate cancer patients.Methods Nineteen patients received vacuum bag plus body mask setup were allocated into the vacuum bag group andl9 patients with alpha cradle were assigned into the alpha cradle group.Orthogonal X-ray portals were performed to verify the treatment position before beam delivery in every fraction.The couch correction between the portal and reference DRR through manual image registration was recorded as setup errors in 6 directions including the lateral,supine-inferior,anterior-posterior,yaws,roll and pitch,respectively.Two-tail t-test was used to analyze the setup error data from each direction between two groups.Results In total,452 and 436 sets of data errors were collected from the vacuum bag and alpha cradle groups.The average setup errors and standard deviation in the vacuum bag and alpha cradle groups in the lateral,supine-inferior,anterior-posterior,yaws,roll and pitch directions were (0.63±0.48) cm vs.(0.33±0.24) cm (P=0.000),(0.40±0.3) cm vs.(0.31±0.25) cm (P=0.000),(0.69±0.61) cm vs.(0.82±0.69) cm (P=0.006),0.65°±0.47°vs 0.32°±0.25°(P=0.000),1.05°±0.95°vs 1.16°±0.94° (P=0.100) and 0.67°±0.56°vs 0.40°±0.36° (P=0.000),respectively.The maximum setup errors were detected in the pitch direction for both groups.Conclusions During the proton and carbon therapy using Siemens 6D robotic couch,two setup methods using vacuum bag plus body mask and customized alpha cradle should be selected according to the individual conditions of patients.A customized foot fixer should be utilized to reduce the uncertainty in the femoral head region.

Assessment of occupational exposure doses to physicians in clinical practice at Shanghai Proton and Heavy Ion Center / 中华放射医学与防护杂志

Objective To assess the occupational exposure doses received by the physicians in clinical practice at Shanghai Proton and Heavy Ion Center ( SPHIC ) . Methods A total of 40 patients treated from September to November in 2016, including 20 proton cases and 20 carbon cases at SPHIC, were selected using simple random sampling method. Particle type, total particle number and prescribed doses were recorded for all the cases. The dose rates in the control room were measured by using a photon and neutron personal radiation detector during patient treatment. The dose rates around the surface of the patient's tumor 1 min after completion of beam delivery and the dose rates about 30 cm to the tumor surface (where a physician stands) were also measured during unfixing and assisting the patients. Finally, the dose rates surrounding the fixtures, couch, robotic arm and window of BAMS were measured. The factors affecting the occupational exposure of physician were analyzed and the annual dose equivalent was assessed for physicians in SPHIC. Results Proton and heavy ion released nearly all energy in the tumor for Bragg peak advantage, so there was no induced radioactivity in the treatment room. However, the tumor became the main induced radioactivity source to the occupational exposure dose to physicians in clinical practices. The dose rate around the surface of the patient's tumor 1 min after completion of beam delivery was (20. 68 ± 21. 91) μSv/h, which was the highest in the working places of physicians, thus regarded as the main source. A significant positive correlation (r=0. 828, P<0. 05) was shown between dose rates and total number of particles delivered for the treatment. The dose rate measured in the control room was (0. 08 ± 0. 01 )μSv/h, and the dose rate measured surrounding the fixtures, couch, robotic arm and BAMS window was ( 0. 09 ± 0. 01 )μSv/h. No neutron was detected. The dose rate about 30 cm to the tumor surface ( where physicians stand) was ( 2. 03 ± 2. 84 ) μSv/h during unfixing and assisting the patients. The average annual dose to physicians was about 0. 508 mSv. Conclusions The average annual dose to physicians was at a low level in SPHIC

EBT3 and EDR2 film dosimetry for scanning carbon ion beams / 中华放射医学与防护杂志

Objective To investigate EBT3 and EDR2 film responses to different linear energy transfers ( LETs) and doses from carbon ion beams. Methods EBT3 and EDR2 films were calibrated by two methods. In the first method, films were placed at the same depth within a phantom and irradiated by beams with different parameters such as beam energy. In the second method, films were separately placed at different depths in a phantom and irradiated by the same beams. These methods were used to irradiate films with ions of different LETs. Results For EBT3 film, the dose calibration curves correlated with different LETs appeared to be typical hyperbolic curves with a maximum difference between the curves of ± 17％ (1σ). Meanwhile, the shape of the dose calibration curves for EDR2 film appeared to be linear. The values along all these curves were within ± 27.4％ (1σ) of the value for the average curve. The dose responses of both films were inversely proportional to LETs. The sensitivity of EBT3 film was inversely proportional to the dose, while the sensitivity of EDR2 film showed no relationship with the dose. Conclusions Influenced by the dual factor of LET and dose, the application of EBT3 film was limited in carbon ion. However, without no dose dependence, EDR2 film could be used to measure dose distributions created by single LET carbon ion beam.

Progress in charged particle therapy / 中华放射肿瘤学杂志

Charged particle therapy offers a better effect and obvious dosimetric and biological advantages over conventional radiotherapy in tumor control.Charged particles form Bragg peak in the dose distribution in tissue, enable most of energy to be deposited in the target region, and thus enhance tumor control and reduce the damage to normal tissues surrounding the tumor.With the increasing demand for charged particle therapy and the advances in particle accelerator, particle therapy technology is developing rapidly.The core apparatus of particle therapy facility is particle accelerator, and the accelerator type, particle type, and implementation technique determine the performance and therapeutic effect of the facility.This article provides a detailed comparative analysis of various particle therapies.Statistical data show that proton therapy is dominant in particle therapy, and high construction difficulty, large facility size, and extremely high cost have limited the development of heavy ion therapy.Nowadays, there are still some technical problems regarding charged particle therapy, and more clinical trials are required.

Measurement of CT Hounsfield Units and relative stopping powers conversion curve in proton and carbon ion therapy / 中华放射医学与防护杂志

Objective To measure the CT Hounsfield Unit ( HU) and relative stopping power ( RSP) conversion curve. Methods In this study, the RSPs of 12 different tissue equivalent rods were measured with proton and carbon beam in the Shanghai Proton and Heavy Ion Center ( SPHIC) . The same tissue equivalent materials were scanned with CT scanner to acquire the HU. Results Conversion curve for the transformation of HU into RSP was generated for both proton and carbon ion beam. Differences between RSPs measured using proton and carbon beam were ≤0. 64%except lung material. Conclusions A RSP versus HU conversion curve was generated for both protons and carbon ions.

Measurement of CT Hounsfield Units and relative stopping powers conversion curve in proton and carbon ion therapy / 中华放射医学与防护杂志

Objective To measure the CT Hounsfield Unit ( HU) and relative stopping power ( RSP) conversion curve. Methods In this study, the RSPs of 12 different tissue equivalent rods were measured with proton and carbon beam in the Shanghai Proton and Heavy Ion Center ( SPHIC) . The same tissue equivalent materials were scanned with CT scanner to acquire the HU. Results Conversion curve for the transformation of HU into RSP was generated for both proton and carbon ion beam. Differences between RSPs measured using proton and carbon beam were ≤0. 64%except lung material. Conclusions A RSP versus HU conversion curve was generated for both protons and carbon ions.

A study of PET-CT SUV range for dose verification in carbon ion radiation therapy / 中华放射肿瘤学杂志

Objective The positron generated at the dose deposition site by using high-energy carbon ions to hit the material annihilate with the negative electron in the material to release the gamma photon.The positron-emitting isotope (PEI) distributions in the target volume are activated significantly by carbon ions.Therefore, the mean values of positron emission tomography (PET) activity could be related to the delivered doses to the clinical target volume from carbon ion.This specialty can be used for the image registration fusion of the carbon ion treatment planning computed tomography (CT) and treatment verification PET-CT.After radiation in the almost same decay period, the relationship between the different target volume and the PET-CT SUV of different every single fraction dose can be found, then the range of SUV for the radiation target could be decided.So this PET-CT standardized uptake value (SUV) range can also provide a reference for the correlation and consistency in planning target dose verification and evaluation for the clinical trial.Methods The head phantom was used as a simulation of the real human body, the 1 cc, 4 cc, and 10 cc cube volume target contouring were done in the TPS, the 90 degree fixed carbon ion beams were delivered in different single fraction effective dose of 2.5 GyE, 5 GyE, and 8 GyE.After the beam delivery, later the PET-CT scanning was performed and parameters of scanning followed the trial regulation.The MIM Maestro software was used for the image processing and fusion to determine the maximum, minimum, average, and total values of SUV in the virtual clinical target volumes for the different single fraction dose.Results The results showed that for the same target volume, the SUV range of target had an approximate linear correlation with effective dose of target (P=0.000).The same effective dose for the different target volumes got the same SUV range (P>0.05).Conclusions For the carbon ion treatment plan, the SUV range from image registration and fusion of planning CT and PET-CT after treatment can be used to make an evaluation for accuracy of the dose distribution.And this method also could be used in the hyper-fraction treatment plan.In the SUV range research of different decay periods, the similar method can be performed for the exploration.

Simulação e análise dosimétrica de protonterapia e íons de carbono no tratamento do melanoma uveal / Simulation and dosimetric analysis of proton and carbon ion therapy in the treatment of uveal melanoma

OBJETIVO: Este artigo apresenta a avaliação dosimétrica da radioterapia por íons de carbono em comparação à protonterapia. MATERIAIS E MÉTODOS: As simulações computacionais foram elaboradas no código Geant4 (GEometry ANd Tracking). Um modelo de olho discretizado em voxels implementado no sistema Siscodes (sistema computacional para dosimetria em radioterapia) foi empregado, em que perfis de dose em profundidade e curvas de isodose foram gerados e superpostos. Nas simulações com feixe de íons de carbono, distintos valores de energia do feixe foram adotados, enquanto nas simulações com feixe de prótons os dispositivos da linha de irradiação foram incluídos e diferentes espessuras do material absorvedor foram aplicadas. RESULTADOS: As saídas das simulações foram processadas e integradas ao Siscodes para gerar as distribuições espaciais de dose no modelo ocular, considerando alterações do posicionamento de entrada do feixe. Os percentuais de dose foram normalizados em função da dose máxima para um feixe em posição de entrada específica, energia da partícula incidente e número de íons de carbono e de prótons incidentes. CONCLUSÃO: Os benefícios descritos e os resultados apresentados contribuem para o desenvolvimento das aplicações clínicas e das pesquisas em radioterapia ocular por íons de carbono e prótons.

OBJECTIVE: The present paper addresses the dosimetric evaluation of carbon ion radiotherapy as compared with proton therapy. MATERIALS AND METHODS: Computer simulations were undertaken with the Geant4 (GEometry ANd Tracking) code. An eye model discretized into voxels and implemented in the Siscodes system (computer system for dosimetry in radiation therapy) was utilized to generate and superimpose depth dose profiles and isodose curves. Different values for beam energy were adopted in the simulations of carbon ion beams, while in the simulation with proton beams irradiation line devices were included with different absorbing material thicknesses. RESULTS: The simulations outputs were processed and integrated into the Siscodes to generate the spatial dose distribution in the eye model, considering changes in the beam entrance position. The dose rates were normalized as a function of the maximum dose for a beam at a specific entrance position, incident particle energy and number of incident carbon ions and protons. CONCLUSION: The described benefits together with the presented results contribute to the development of clinical applications and researches on carbon ion and proton therapy.