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1.
PLoS One ; 17(5): e0267741, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35511918

RESUMO

INTRODUCTION: In radiotherapy, the presence of air gaps near a tumour can lead to underdose to the tumour. In this study, the impact of air gaps on dose to the surface was evaluated. 3D-printing was used to construct a Eurosil-4 Pink bolus customised to the patient and its dosimetric properties were compared with that of Paraffin wax bolus. METHODS: Surface dose was measured for flat sheets of Eurosil-4 Pink bolus with different thicknesses. Different air gap thicknesses were inserted between the bolus and the surface, and dose was measured for each air gap using 10 cm × 10 cm fields. This was repeated with the effective field size calculated from the patient plan. Surface dose was measured for varying angles of incidence. A customised chest phantom was used to compare dose for two customised Eurosil-4 Pink boluses, and commonly used Paraffin wax bolus. RESULTS: The surface dose was found to be highest for 1.1 cm thick bolus. The decrease in surface dose for the Eurosil-4 Pink bolus was minimal for the 10 cm × 10 cm field, but higher for the effective field size and larger angles of incidence. For instance, the dose was reduced by 6.2% as a result of 1 cm air gap for the effective field size and 60 degree angle of incidence. The doses measured using Gafchromic film under the customised Eurosil-4 Pink boluses were similar to that of the Paraffin wax bolus, and higher than prescribed dose. CONCLUSIONS: The impact of air gaps can be significant for small field sizes and oblique beams. A customised Eurosil-4 Pink bolus has promising physical and dosimetric properties to ensure sufficient dose to the tumour, even for treatments where larger impact of air gaps is suspected.


Assuntos
Neoplasias , Parede Torácica , Humanos , Neoplasias/radioterapia , Parafina , Imagens de Fantasmas , Radiometria , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
2.
PLoS One ; 17(5): e0268087, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35536852

RESUMO

In this study, we report our experience in commissioning a commercial treatment planning system (TPS) for fast-raster scanning of carbon-ion beams. This TPS uses an analytical dose calculation algorithm, a pencil-beam model with a triple Gaussian form for the lateral-dose distribution, and a beam splitting algorithm to consider lateral heterogeneity in a medium. We adopted the mixed beam model as the relative biological effectiveness (RBE) model for calculating the RBE values of the scanned carbon-ion beam. To validate the modeled physical dose, we compared the calculations with measurements of various relevant quantities as functions of the field size, range and width of the spread-out Bragg peak (SOBP), and depth-dose and lateral-dose profiles for a 6-mm SOBP in water. To model the biological dose, we compared the RBE calculated with the newly developed TPS to the RBE calculated with a previously validated TPS that is in clinical use and uses the same RBE model concept. We also performed patient-specific measurements to validate the dose model in clinical situations. The physical beam model reproduces the measured absolute dose at the center of the SOBP as a function of field size, range, and SOBP width and reproduces the dose profiles for a 6-mm SOBP in water. However, the profiles calculated for a heterogeneous phantom have some limitations in predicting the carbon-ion-beam dose, although the biological doses agreed well with the values calculated by the validated TPS. Using this dose model for fast-raster scanning, we successfully treated more than 900 patients from October 2018 to October 2020, with an acceptable agreement between the TPS-calculated and measured dose distributions. We conclude that the newly developed TPS can be used clinically with the understanding that it has limited accuracies for heterogeneous media.


Assuntos
Terapia com Prótons , Carbono , Humanos , Método de Monte Carlo , Imagens de Fantasmas , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Eficiência Biológica Relativa , Água
3.
Radiat Oncol ; 17(1): 87, 2022 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-35525993

RESUMO

BACKGROUND: A new compact superconducting synchrocyclotron single-room proton solution delivers pulsed proton beams to each spot through several irradiation bursts calculated by an iterative layer delivery algorithm. Such a mechanism results in a new beam parameter, burst switching time (BST) in the total beam delivery time (BDT) which has never been studied before. In this study, we propose an experimental approach to build an accurate BDT and sequence prediction model for this new proton solution. METHODS: Test fields and clinical treatment plans were used to investigate each beam delivery parameter that impacted BDT. The machine delivery log files were retrospectively analyzed to quantitatively model energy layer switching time (ELST), spot switching time (SSWT), spot spill time (SSPT), and BST. A total of 102 clinical IMPT treatment fields' log files were processed to validate the accuracy of the BDT prediction model in comparison with the result from the current commercial system. Interplay effect is also investigated as a clinical application by comparing this new delivery system model with a conventional cyclotron accelerator model. RESULTS: The study finds that BST depends on the amount of data to be transmitted between two sequential radiation bursts, including a machine irradiation log file of the previous burst and a command file to instruct the proton system to deliver the next burst. The 102 clinical treatment fields showed that the accuracy of each component of the BDT matches well between machine log files and BDT prediction model. More specifically, the difference of ELST, SSWT, SSPT, and BST were (- 3.1 ± 5.7)%, (5.9 ± 3.9)%, (2.6 ± 8.7)%, and (- 2.3 ± 5.3)%, respectively. The average total BDT was about (2.1 ± 3.0)% difference compared to the treatment log files, which was significantly improved from the current commercial proton system prediction (58 ± 15)%. Compared to the conventional cyclotron system, the burst technique from synchrocyclotron effectively reduced the interplay effect in mobile tumor treatment. CONCLUSION: An accurate BDT and sequence prediction model was established for this new clinical compact superconducting synchrocyclotron single-room proton solution. Its application could help users of similar facilities better assess the interplay effect and estimate daily patient treatment throughput.


Assuntos
Terapia com Prótons , Ciclotrons , Humanos , Terapia com Prótons/métodos , Prótons , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Estudos Retrospectivos
4.
Radiat Oncol ; 17(1): 86, 2022 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-35526019

RESUMO

PURPOSE: This study implemented a piecewise volumetric modulated arc therapy (P-VMAT) for realizing whole-brain radiation therapy (WBRT) with simultaneous integrated boost (SIB) for multiple brain metastases (> 40 metastases) with a conventional C-arm linear accelerator. MATERIALS AND METHODS: This study retrospectively analyzed 10 patients with multiple brain metastases (40-120 metastases, median 76), who underwent WBRT and SIB using helical tomotherapy (HT). The prescribed doses were 40 Gy/20 f and 60 Gy/20 f for WBRT and SIB, respectively. Corresponding new HT plans were designed with P-VMAT using 7 arcs. For each arc, the collimator was rotated to 45°, and the field width was limited to 2.5 cm with 0.5 cm overlap with adjacent arcs. Thus, each arc covered only one section of the brain target volume. A conventional dual arc VMAT (DA-VMAT) plan was also designed. HT, P-VMAT, and DA-VMAT plans were compared using dose distribution reviews and dosimetric parameters. ArcCHECK phantom measurements were performed for verification of P-VMAT plans. RESULTS: No significant differences in the mean coverage of the whole-brain target and metastases were observed between HT and P-VMAT (p > 0.05). The conformity index for the whole-brain target improved with P-VMAT compared with HT (p < 0.05). Furthermore, the volume of 44 Gy V44 (110% of prescribed dose for WBRT) received for whole-brain significantly reduced with P-VMAT from 38.2 ± 12.9% to 23.3 ± 9.4% (p < 0.05), and the maximum dose for organs at risks such as the hippocampus, optical nerve, optical chiasm, and spinal cord declined with P-VMAT (p < 0.05). Unlike HT and P-VMAT, DA-VMAT was clinically unacceptable because V44 in the whole-brain was too high (54.7 ± 8.2%). The mean absolute dose gamma passing rate for P-VMAT plans was 97.6 ± 1.1% (3%/3 mm criterion, 10%). CONCLUSIONS: P-VMAT is favorable for WBRT and SIB for multiple brain metastases. It provides comparable coverage of whole-brain target and SIB, with better conformity, lower V44, and better dose sparing of organs at risk compared with HT. Furthermore, results show that DA-VMAT fails clinical practice even for a relatively large number of brain metastases with a high degree of plan complexity. The patient specific verification demonstrates the feasibility of P-VMAT for clinical application.


Assuntos
Neoplasias Encefálicas , Radioterapia de Intensidade Modulada , Artrogripose , Neoplasias Encefálicas/radioterapia , Neoplasias Encefálicas/secundário , Colestase , Irradiação Craniana/métodos , Feminino , Hipocampo , Humanos , Masculino , Órgãos em Risco , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos , Insuficiência Renal , Estudos Retrospectivos
5.
Ann Palliat Med ; 11(4): 1326-1335, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35523741

RESUMO

BACKGROUND: This study explored the effects of air cavity on the dose distribution of radiotherapy in patients after extensive hysterectomy. In patients who have an air cavity in the intestines near the planning target volume (PTV), the photon beams may interact with the air cavity to cause electron disequilibrium (ED), resulting in a reduction in the absorbed dose by the surrounding tissues. In this paper, the electron density assignment (EDA) of the air cavity was used to simulate the disappearance of the intestinal gas, and the effects of the intestinal air cavity on the volume modulated arc therapy (VMAT) results were examined. METHODS: A total of 21 patients who underwent VMAT after extensive hysterectomy were enrolled in this retrospective analysis. The dose parameters from the selected treatment plan were used the experimental reference. The treatment plan of the reference group was copied, and the intestinal air cavity structure was identified using the computed tomography (CT) simulation image. The electron density value of the intestine near the cavity was measured and averaged according to the intestinal electron density value recommended by International Commission Radiological Units (ICRU) report No. 46. The averaged value was assigned to the air cavity structure. Subsequently, the treatment plan was re-calculated without changing other parameters, and the resulting treatment plan was defined as the experimental group. The dose parameters of the PTV and organs at risk (OAR) in the 2 groups were assessed, and the influence of the intestinal air cavity on the VMAT dose distribution in cervical cancer patients was analyzed. RESULTS: The minimum dose (D98) and the maximum dose (D2) of the PTV was significantly different between the experimental group and the control group (P<0.05), however, mean dose of the PTV was comparable between the 2 groups. The dose parameters of OARs were not significantly different between the two groups except the bone structural organs. CONCLUSIONS: When the intestinal air cavity is large and related to the target area, the intestinal air cavity should be intervened, and the patient should be treated with radiotherapy after the intestinal gas decreases.


Assuntos
Radioterapia de Intensidade Modulada , Neoplasias do Colo do Útero , Feminino , Humanos , Intestinos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos , Estudos Retrospectivos , Neoplasias do Colo do Útero/radioterapia
6.
Radiat Oncol ; 17(1): 99, 2022 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-35597956

RESUMO

BACKGROUND: Due to respiratory motion, accurate radiotherapy delivery to thoracic and abdominal tumors is challenging. We aimed to quantify the ability of mechanical ventilation to reduce respiratory motion, by measuring diaphragm motion magnitudes in the same volunteers during free breathing (FB), mechanically regularized breathing (RB) at 22 breaths per minute (brpm), variation in mean diaphragm position across multiple deep inspiration breath-holds (DIBH) and diaphragm drift during single prolonged breath-holds (PBH) in two MRI sessions. METHODS: In two sessions, MRIs were acquired from fifteen healthy volunteers who were trained to be mechanically ventilated non-invasively We measured diaphragm motion amplitudes during FB and RB, the inter-quartile range (IQR) of the variation in average diaphragm position from one measurement over five consecutive DIBHs, and diaphragm cranial drift velocities during single PBHs from inhalation (PIBH) and exhalation (PEBH) breath-holds. RESULTS: RB significantly reduced the respiratory motion amplitude by 39%, from median (range) 20.9 (10.6-41.9) mm during FB to 12.8 (6.2-23.8) mm. The median IQR for variation in average diaphragm position over multiple DIBHs was 4.2 (1.0-23.6) mm. During single PIBHs with a median duration of 7.1 (2.0-11.1) minutes, the median diaphragm cranial drift velocity was 3.0 (0.4-6.5) mm/minute. For PEBH, the median duration was 5.8 (1.8-10.2) minutes with 4.4 (1.8-15.1) mm/minute diaphragm drift velocity. CONCLUSIONS: Regularized breathing at a frequency of 22 brpm resulted in significantly smaller diaphragm motion amplitudes compared to free breathing. This would enable smaller treatment volumes in radiotherapy. Furthermore, prolonged breath-holding from inhalation and exhalation with median durations of six to seven minutes are feasible. TRIAL REGISTRATION: Medical Ethics Committee protocol NL.64693.018.18.


Assuntos
Respiração Artificial , Respiração , Suspensão da Respiração , Humanos , Pulmão , Imageamento por Ressonância Magnética/métodos , Planejamento da Radioterapia Assistida por Computador/métodos
8.
Dis Markers ; 2022: 9978282, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35510039

RESUMO

Nasopharyngeal carcinoma (NPC) is a clinically multiple malignant tumor. At present, with the increase in the infection rate of Epstein-Barr virus, the incidence of nasopharyngeal carcinoma is also increasing day by day. To explore the effect of body size change on off-center cervical point and face doses in patients with nasopharyngeal carcinoma (NPC) undergoing radiotherapy, in total, 100 patients with NPC from January 2019 to May 2020 in our hospital were selected for retrospective analysis, and they all received intensity-modulated radiation therapy. Bodyweight, horizontal longitudinal diameter of the odontoid process, longitudinal diameter of the third cervical spine, maximum radiation dose, and average radiation dose of normal organs in the first and last treatments were assessed, and the correlation between normal organ irradiation dose and body size was analyzed. Bodyweight, horizontal longitudinal diameter of the odontoid process, and longitudinal diameter of the third cervical spine in the last treatment were lower than those in the first treatment, with a statistically significant difference. There was no statistically significant difference in the maximum normal organ irradiation dose to the left eyeball, right eyeball, left crystalline lens, right crystalline lens, and maximum irradiation dose to optic nerve between the last treatment and the first treatment. In the last treatment, the maximum dose to the left parotid gland, right parotid gland, spinal cord, and brain stem was higher than that in the first treatment. The average irradiation dose to the left eye bulb, right eye bulb, left lens, right lens, optic nerve in the last treatment, and that in the first treatment showed no significant difference. The average dose to the left parotid gland, right parotid gland, spinal cord, and brain stem in the last treatment was higher than that in the first treatment. The irradiation dose to the left parotid gland, right parotid gland, spinal cord, and brain stem was significantly negatively correlated with body weight, horizontal longitudinal diameter of the odontoid process, and longitudinal diameter of the third cervical spine. After NPC radiotherapy, the body size of patients can change, which can have different effects on irradiation doses. Therefore, the target area and dose should be corrected during treatment to ensure the efficacy and safety of the treatment.


Assuntos
Infecções por Vírus Epstein-Barr , Neoplasias Nasofaríngeas , Tamanho Corporal , Herpesvirus Humano 4 , Humanos , Carcinoma Nasofaríngeo/radioterapia , Neoplasias Nasofaríngeas/patologia , Neoplasias Nasofaríngeas/radioterapia , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Estudos Retrospectivos
9.
J Cancer Res Ther ; 18(1): 190-199, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35381783

RESUMO

Background: Pancreatic adenocarcinoma is a lethal condition with poor outcomes by various treatment modalities and an increasing incidence. Aim: The aim of this study is to evaluate the advantages of field-in-field (FIF) versus three-field and four-field radiation treatment planning techniques in three-dimensional treatment of patients with pancreatic cancer. Materials and Methods: The evaluations of these planning techniques were performed in terms of physical and biological criteria. Radiotherapy treatment data of 20 patients with pancreatic cancer were selected and evaluated for FIF, three-field, and four-field treatment techniques. The patients were treated by 6 MV photon beam of a medical linac, and these three treatment planning techniques were evaluated for all the 20 patients. The plans were compared based on dose distribution in the target volume, monitor unit (MU), and dose to organs at risk (OARs). Results: The results have shown that, with assuming the same prescribed dose to planned target volume, FIF plans have some advantages over three-field and four-field treatment plans, based on MU values, V20 Gy in the right lung, V20 Gy in the left lung, Dmean in the left kidney, Dmean in the liver, and Dmean in the spinal cord. Based on the obtained results, the use of FIF technique reduces MUs compared to the three-field and four-field techniques. Conclusion: Having a less MU for performing treatment reduces scattered radiation and therefore reduces the risk of secondary cancer in normal tissues. In addition, the use of FIF technique has advantage of less radiation dose to some OARs.


Assuntos
Adenocarcinoma , Neoplasias Pancreáticas , Radioterapia de Intensidade Modulada , Adenocarcinoma/radioterapia , Humanos , Órgãos em Risco , Neoplasias Pancreáticas/radioterapia , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos
10.
J Cancer Res Ther ; 18(1): 312-315, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35381810

RESUMO

Extradural primary primitive neuroectodermal tumor (PNET) is a rare aggressive disease mostly occurring in young adults. We present a locally recurrent case of dorsal PNET in the fifth decade of life after a prolonged disease-free interval of 10 years. The patient received radiation therapy in fairly large fields twice in his lifetime and was planned for third-time radiation to a few overlapping paraspinal areas over a period of three decades. Keeping in mind previous irradiations, possible target volume in proximity to organs at risk (OARs) patient was planned for consolidtive radiation using the most conformal technique available, which is proton beam therapy with image guided pencil beam scanning technique. Special dose constraints for the spinal cord and other OARs were set, and proton therapy plan was generated at our institute. When compared with parallelly generated intensity-modulated radiation therapy plan with the same dose prescription and dose constraints using helical tomotherapy, intensity-modulated proton therapy plan showed superior dosimetric benefit in terms of coverage and significant sparing of OARs.


Assuntos
Tumores Neuroectodérmicos Primitivos , Terapia com Prótons , Radioterapia de Intensidade Modulada , Reirradiação , Humanos , Tumores Neuroectodérmicos Primitivos/radioterapia , Órgãos em Risco/efeitos da radiação , Terapia com Prótons/métodos , Prótons , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos , Reirradiação/métodos , Adulto Jovem
11.
Radiat Oncol ; 17(1): 82, 2022 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-35443714

RESUMO

BACKGROUND: Robotic linac is ideally suited to deliver hypo-fractionated radiotherapy due to its compact head and flexible positioning. The non-coplanar treatment space improves the delivery versatility but the complexity also leads to prolonged optimization and treatment time. METHODS: In this study, we attempted to use the deep learning (pytorch) framework for the plan optimization of circular cone based robotic radiotherapy. The optimization problem was topologized into a simple feedforward neural network, thus the treatment plan optimization was transformed into network training. With this transformation, the pytorch toolkit with high-efficiency automatic differentiation (AD) for gradient calculation was used as the optimization solver. To improve the treatment efficiency, plans with fewer nodes and beams were sought. The least absolute shrinkage and selection operator (lasso) and the group lasso were employed to address the "sparsity" issue. RESULTS: The AD-S (AD sparse) approach was validated on 6 brain and 6 liver cancer cases and the results were compared with the commercial MultiPlan (MLP) system. It was found that the AD-S plans achieved rapid dose fall-off and satisfactory sparing of organs at risk (OARs). Treatment efficiency was improved by the reduction in the number of nodes (28%) and beams (18%), and monitor unit (MU, 24%), respectively. The computational time was shortened to 47.3 s on average. CONCLUSIONS: In summary, this first attempt of applying deep learning framework to the robotic radiotherapy plan optimization is promising and has the potential to be used clinically.


Assuntos
Radioterapia de Intensidade Modulada , Procedimentos Cirúrgicos Robóticos , Humanos , Órgãos em Risco , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos
12.
J Radiat Res ; 63(3): 435-442, 2022 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-35467750

RESUMO

The purpose of this study is to evaluate the detection accuracy of a 3-dimensional (3D) body scanner, VOXELAN, in surface-guided radiotherapy (SGRT) of each part of the human body using a whole-body human phantom. We used A Resusci Anne was used as the whole-body phantom. The detection accuracy of VOXELAN in a radiotherapy treatment room with a linear accelerator (LINAC) was evaluated for two reference images: reconstruction of the planning computed tomography (CT) image (CT reference) and scanning by VOXELAN before the treatment (scan reference). The accuracy of the translational and rotational directions was verified for four treatment sites (open face shell, breast, abdomen, and arm), using the magnitude of the 6D robotic couch movement as the true value. Our results showed that the detection accuracy improved as the displacement from the reference position decreased for all the sites. Using the scan reference, the average accuracy of the translational and rotational axes was within 1.44 mm and 0.41°, respectively, for all sites except the arms. Similarly, using the CT reference, the average accuracy was within 2.45 mm and 1.35°, respectively. Additionally, it was difficult for both reference images to recognize misalignment of the arms. In conclusion we discovered that VOXELAN achieved a high detection accuracy for the head with an open face shell, chest, and abdomen, indicating that the system is useful in a clinical setting. However, it is necessary to pay attention to location matching for areas with few features, such as surface irregularities and potential errors, when the reference image is created from CT.


Assuntos
Braquiterapia , Radioterapia Guiada por Imagem , Humanos , Aceleradores de Partículas , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador , Radioterapia Guiada por Imagem/métodos , Tomografia Computadorizada por Raios X
13.
Phys Med Biol ; 67(10)2022 05 02.
Artigo em Inglês | MEDLINE | ID: mdl-35417903

RESUMO

Objective. Kilovoltage computed tomography (kVCT) is the cornerstone of radiotherapy treatment planning for delineating tissues and towards dose calculation. For the former, kVCT provides excellent contrast and signal-to-noise ratio. For the latter, kVCT may have greater uncertainty in determining relative electron density (ρe) and proton stopping power ratio (SPR). Conversely, megavoltage CT (MVCT) may result in superior dose calculation accuracy. The purpose of this work was to convert kVCT HU to MVCT HU using deep learning to obtain higher accuracyρeand SPR.Approach. Tissue-mimicking phantoms were created to compare kVCT- and MVCT-determinedρeand SPR to physical measurements. Using 100 head-and-neck datasets, an unpaired deep learning model was trained to learn the relationship between kVCTs and MVCTs, creating synthetic MVCTs (sMVCTs). Similarity metrics were calculated between kVCTs, sMVCTs, and MVCTs in 20 test datasets. An anthropomorphic head phantom containing bone-mimicking material with known composition was scanned to provide an independent determination ofρeand SPR accuracy by sMVCT.Main results. In tissue-mimicking bone,ρeerrors were 2.20% versus 0.19% and SPR errors were 4.38% versus 0.22%, for kVCT versus MVCT, respectively. Compared to MVCT,in vivomean difference (MD) values were 11 and 327 HU for kVCT and 2 and 3 HU for sMVCT in soft tissue and bone, respectively.ρeMD decreased from 1.3% to 0.35% in soft tissue and 2.9% to 0.13% in bone, for kVCT and sMVCT, respectively. SPR MD decreased from 1.8% to 0.24% in soft tissue and 6.8% to 0.16% in bone, for kVCT and sMVCT, respectively. Relative to physical measurements,ρeand SPR error in anthropomorphic bone decreased from 7.50% and 7.48% for kVCT to <1% for both MVCT and sMVCT.Significance. Deep learning can be used to map kVCT to sMVCT, suggesting higher accuracyρeand SPR is achievable with sMVCT versus kVCT.


Assuntos
Terapia com Prótons , Prótons , Elétrons , Aprendizado de Máquina , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador
14.
J Vis Exp ; (181)2022 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-35404343

RESUMO

A rat glioblastoma model to mimic chemo-radiation treatment of human glioblastoma in the clinic was previously established. Similar to the clinical treatment, computed tomography (CT) and magnetic resonance imaging (MRI) were combined during the treatment-planning process. Positron emission tomography (PET) imaging was subsequently added to implement sub-volume boosting using a micro-irradiation system. However, combining three imaging modalities (CT, MRI, and PET) using a micro-irradiation system proved to be labor-intensive because multimodal imaging, treatment planning, and dose delivery have to be completed sequentially in the preclinical setting. This also results in a workflow that is more prone to human error. Therefore, a user-friendly algorithm to further optimize preclinical multimodal imaging-based radiation treatment planning was implemented. This software tool was used to evaluate the accuracy and efficiency of dose painting radiation therapy with micro-irradiation by using an in silico study design. The new methodology for dose painting radiation therapy is superior to the previously described method in terms of accuracy, time efficiency, and intra- and inter-user variability. It is also an important step towards the implementation of inverse treatment planning on micro-irradiators, where forward planning is still commonly used, in contrast to clinical systems.


Assuntos
Glioblastoma , Animais , Glioblastoma/diagnóstico por imagem , Glioblastoma/patologia , Glioblastoma/radioterapia , Imageamento por Ressonância Magnética/métodos , Imagem Multimodal/métodos , Tomografia por Emissão de Pósitrons/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Ratos , Tomografia Computadorizada por Raios X/métodos
15.
Phys Med ; 97: 44-49, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35367851

RESUMO

PURPOSE: Image guided radiotherapy (IGRT) strategies allow detecting and monitoring anatomical changes during external beam radiotherapy (EBRT). However, assessing the dosimetric impact of anatomical changes is not straightforward. In current IGRT strategies dose volume histograms (DVH) are not available due to lack of contours and dose recalculations on the cone-beam CT (CBCT) scan. This study investigates the feasibility of using automatically calculated DVH parameters in CBCTs using an independent dose calculation engine and propagated contours. METHOD: A prospective study (NCT03385031) of thirty-one breast cancer patients who received additional CBCT imaging (N = 70) was performed. Manual and automatically propagated contours were generated for all CBCTs and an automatic dose recalculation was performed. Differences between planned and CBCT-derived DVH parameters (mean and maximum dose to targets, 95% volume coverage to targets and mean heart dose (MHD)) were calculated using the dose verification system with manual and propagated contours and, in both cases, benchmarked against DVH differences quantified in the TPS using manually contoured CBCTs. RESULTS: Differences in DVH parameters between the TPS and dose verification system with propagated contours were -1.3% to 0.7% (95% CI) for mean dose to the target volume, -0.3 to 0.2 Gy (95% CI) in MHD and -3.9% to 2.9% (95% CI) in target volume coverage. CONCLUSION: The use of an independent fully automatic dose verification system with contour propagation showed to be feasible and sufficiently reliable to recalculate CBCT based DVHs during breast EBRT. Volume coverage parameters, i.e. V95%, proved to be especially sensitive to contouring differences.


Assuntos
Radioterapia Guiada por Imagem , Radioterapia de Intensidade Modulada , Tomografia Computadorizada de Feixe Cônico/métodos , Humanos , Estudos Prospectivos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem/métodos , Radioterapia de Intensidade Modulada/métodos
16.
Asian Pac J Cancer Prev ; 23(4): 1397-1403, 2022 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-35485702

RESUMO

OBJECTIVE: To study the dosimetric importance of Jaw tracking technique in reducing the doses to organs at risk (OAR) while achieving the optimal dose coverage for the target. METHODS: We retrospectively selected ten Glioblastoma cases and for each patient, two plans were created namely Static Jaw Technique Dynamic Intensity Modulated Radiotherapy plan and Jaw Tracking Technique D-IMRT plan with 6 MV for Varian Truebeam™ STx machine using Eclipse Treatment planning system. Both plans were analyzed and compared based on various dosimetric parameters for Planning Target Volume (PTV) and OARs. The dose agreement between the Portal dose image prediction and the portal dosimetry measurement was also analysed  using gamma analysis criteria of 3%/3mm, 2%/2mm and 1%/1mm of dose distance/distance-to-agreement. RESULTS: The dosimetric parameters evaluated for both plans showed that most of the parameters gave significant P values, where D50% of PTV showed a mean difference (Δ) of 0.45 with significant P value, 0.0104. Similarly mean dose, D2%, D98%, D80% to PTV, Conformity Index and Conformation number showed Δ values of 0.45, 0.51, 0.41, 0.40, 0.02 and 0.01 with their significant P values as 0.0138, 0.0172, 0.0313, 0.0466, 0.0279, 0.0561 respectively. The Δ values and significant P values obtained among OARs are 0.54;0.0224 for brainstem, 0.54;0.0017 for RT optic nerve, 0.52;0.0001 for LT optic nerve, 0.59;0.0040 for optic chiasm and for the healthy tissues it showed the values with their mean dose, V5 and V30 parameters as 0.19;0.0115, 0.59;0.0067 and 0.25;0.0125 respectively. The JTT plans showed better passing results of gamma analysis criteria when compared to SJT plans. CONCLUSION: The findings in the studies emphasize the importance of using JTT technique in the radiotherapy treatment plans as it lowers the risk of acute or late toxicity and secondary radiogenic cancers in patients by reducing the OAR doses and achieves better tumor control.


Assuntos
Glioblastoma , Planejamento da Radioterapia Assistida por Computador , Humanos , Radiometria/métodos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Estudos Retrospectivos
17.
Radiat Oncol ; 17(1): 73, 2022 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-35413924

RESUMO

BACKGROUND: Radiotherapy (RT) is part of the curative treatment of approximately 70% of breast cancer (BC) patients. Wide practice variation has been reported in RT dose, fractionation and its treatment planning for BC. To decrease this practice variation, it is essential to first gain insight into the current variation in RT treatment between institutes. This paper describes the development of the NABON Breast Cancer Audit-Radiotherapy (NBCA-R), a structural nationwide registry of BC RT data of all BC patients treated with at least surgery and RT. METHODS: A working group consisting of representatives of the BC Platform of the Dutch Radiotherapy Society selected a set of dose volume parameters deemed to be surrogate outcome parameters, both for tumour control and toxicity. Two pilot studies were carried out in six RT institutes. In the first pilot study, data were manually entered into a secured web-based system. In the second pilot study, an automatic Digital Imaging and Communications in Medicine (DICOM) RT upload module was created and tested. RESULTS: The NBCA-R dataset was created by selecting RT parameters describing given dose, target volumes, coverage and homogeneity, and dose to organs at risk (OAR). Entering the data was made mandatory for all Dutch RT departments. In the first pilot study (N = 1093), quite some variation was already detected. Application of partial breast irradiation varied from 0 to 17% between the 6 institutes and boost to the tumour bed from 26.5 to 70.2%. For patients treated to the left breast or chest wall only, the average mean heart dose (MHD) varied from 0.80 to 1.82 Gy; for patients treated to the breast/chest wall only, the average mean lung dose (MLD) varied from 2.06 to 3.3 Gy. In the second pilot study 6 departments implemented the DICOM-RT upload module in daily practice. Anonymised data will be available for researchers via a FAIR (Findable, Accessible, Interoperable, Reusable) framework. CONCLUSIONS: We have developed a set of RT parameters and implemented registration for all Dutch BC patients. With the use of an automated upload module registration burden will be minimized. Based on the data in the NBCA-R analyses of the practice variation will be done, with the ultimate aim to improve quality of BC RT. Trial registration Retrospectively registered.


Assuntos
Neoplasias da Mama , Neoplasias da Mama/radioterapia , Feminino , Humanos , Países Baixos , Órgãos em Risco/efeitos da radiação , Projetos Piloto , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos
18.
Sci Rep ; 12(1): 5974, 2022 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-35396569

RESUMO

Metal artefacts degrade clinical image quality which decreases the confidence of using computed tomography (CT) for the delineation of key structures for treatment planning and leads to dose errors in affected areas. In this work, we investigated accuracy of doses computed by the Eclipse treatment planning system near and inside metallic elements for two different computation algorithms. An impact of CT metal artefact reduction methods on the resulting calculated doses has also been assessed. A water phantom including Gafchromic film and metal inserts was irradiated (max dose 5 Gy) using a 6 MV photon beam. Three materials were tested: titanium, alloy 600, and tungsten. The phantom CT images were obtained with the pseudo-monoenergetic reconstruction (PMR) and the iterative metal artefact reduction (iMAR). Image sets were used for dose calculation using an Eclipse treatment planning station (TPS). Monte Carlo (MC) simulations were used to predict the true dose distribution in the phantom allowing for comparison with doses measured by film and calculated by TPS. Measured and simulated percentage depth doses (PDDs) were not statistically different (p > 0.618). Regional differences were observed at edges of metallic objects (max 8% difference). However, PDDs simulated with and without film were statistically different (p < 0.002). PDDs calculated by the Acuros XB algorithm based on the dose-to-medium approach best matched the MC reference regardless of the CT reconstruction methods and inserts used (p > 0.078). PDDs obtained using other algorithms significantly differ from the MC values (p < 0.011). The Acuros XB algorithm with a dose-to-medium approach provides reliable dose calculation in all metal regions when using the Varian system. The inability of the AAA algorithm to model backscatter dose significantly limits its clinical application in the presence of metal. No significant impact on the dose calculation was found for a range of metal artefact reduction strategies.


Assuntos
Artefatos , Planejamento da Radioterapia Assistida por Computador , Algoritmos , Metais , Método de Monte Carlo , Imagens de Fantasmas , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos
19.
J Healthc Eng ; 2022: 4998997, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35422981

RESUMO

Background: This retrospective study aimed to evaluate the radiation dose delivered to dental structures in intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) without dental dose constraints, compare the dosimetry differences of dental structures between the two radiation techniques, and determine whether dental structures should be one of the organs at risk for IMRT and VMAT plans according to the dosimetric analysis. Materials and Methods: A total of 138 head and neck cancer patients (nasopharyngeal, oral cavity, pharyngeal, hypopharynx, and larynx), who underwent IMRT (69 patients) or VMAT (69 patients) from March 2016 to March 2021 in our hospital, were included to assess the dosimetry difference between two radiotherapy techniques for dental structures. Results: The radiation dose delivered by IMRT and the mean maximum doses delivered by VMAT to the maxillary teeth of nasopharyngeal cancer patients were significantly higher than the dose received by the mandibular teeth. In contrast, the mandibular teeth of oral cavity cancer, oropharynx cancer, and laryngeal cancer received higher radiation doses than maxillary teeth. Except for mandibular teeth of oral cancer patients, the molars received significantly high-dose radiation than premolars and/or incisors in both radiotherapy techniques. No significant difference was observed between IMRT and VMAT in the dosimetric comparison of dental structures, except that oral cavity cancer patients treated with VMAT received a significantly higher mean average dose than those treated with IMRT. When PTV included level Ib, the radiation doses of the mandibular teeth delivered by both radiotherapy techniques were significantly higher than that in PTV when level Ib was excluded. Conclusion: Without dental dose constraints, no major difference was observed between IMRT and VMAT plans in tooth dose distribution. We suggest that dental structures should be delineated as part of the organ at risk (OAR) when IMRT and VMAT are planned. Meanwhile, attention should be paid to dental structures that might have a high-dose area according to the specific tumor location.


Assuntos
Neoplasias de Cabeça e Pescoço , Neoplasias Nasofaríngeas , Radioterapia de Intensidade Modulada , Neoplasias de Cabeça e Pescoço/radioterapia , Humanos , Neoplasias Nasofaríngeas/etiologia , Órgãos em Risco , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/efeitos adversos , Radioterapia de Intensidade Modulada/métodos , Estudos Retrospectivos
20.
J Radiat Res ; 63(3): 428-434, 2022 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-35420693

RESUMO

The commercial flat bolus cannot form perfect contact with the irregular surface of the patient's skin, resulting in an air gap. The purpose of this study was to evaluate the feasibility of using a 3D customized bolus from silicone rubber. The silicone rubber boluses were studied in basic characteristics. The 3D customized bolus was fabricated at the nose, cheek and neck regions. The point dose and planar dose differences were evaluated by comparing with virtual bolus. The hardness, thickness, density, Hounsfield unit (HU) and dose attenuation of the customized bolus were quite similar to a commercial bolus. When a 3D customized bolus was placed on the RANDO phantom, it can significantly increase buildup region doses and perfectly fit against the irregular surface shape. The average point dose differences of 3D customized bolus were -1.1%, while the commercial bolus plans showed -1.7%. The average gamma results for planar dose differences comparison of 3D customized bolus were 93.9%, while the commercial bolus plans were reduced to 91.9%. Overall, A silicone rubber bolus produced the feasible dosimetric properties and could save cost compared to a commercial bolus. The 3D printed customized bolus is a good buildup material and could potentially replace and improve treatment efficiency.


Assuntos
Impressão Tridimensional , Elastômeros de Silicone , Humanos , Imagens de Fantasmas , Radiometria , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
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