Analysis of dosimetric differences between active control and passive tracking of jaws / 中国辐射卫生

Objective To analyze the effect of the fixed-jaw technique on dosimetric parameters during dynamic intensity-modulated radiotherapy (DIMRT) planning. Methods Ten patients each with nasopharyngeal carcinoma, postoperative cervical cancer, and right breast cancer after radical surgery were selected for this study; all patients underwent DIMRT in our hospital in 2020. After administration at the prescribed dose, two methods were used to design the radiotherapy plan for each patient: split-field technique (SFT) and fixed-jaw technique (FJT). The two plans were compared for the differences in the dosimetric parameters and plan verification pass rate. Results Compared with SFT, FJT showed significant decreases (P <0.05) in the following parameters for patients with nasopharyngeal carcinoma, postoperative cervical cancer, and right breast cancer after radical surgery: number of radiation fields (down by 41.5%, 47.3%, and 34.9%, respectively, t = 7.954, 24.2, and 4.949, respectively), total number of monitor units (MUs) (down by 5.6%, 5.3%, and 13.5%, respectively, t = 3.211, 2.423, and 5.481, respectively), and actual beam-on time (down by 25.3%, 23.8%, and 13.6%, respectively, t = 5.814, 9.208, and 5.655, respectively). There were significant differences in some of the dosimetric parameters for all three types of cancer patients between the two plans (P <0.05). There were no significant differences in the plan verification pass rate (P >0.05). Conclusion FJT can reduce the total number of MUs and actual beam-on time while meeting the requirements for clinically prescribed doses in DIMRT planning.

Analysis of dosimetric verification results of three verification systems for stereotactic body radiation therapy / 中华放射医学与防护杂志

Objective:To compare the effects of parameters, such as planning target volume (PTV), calculation grid size, and dose threshold, on the dosimetric verification result of three dosimetric verification systems ArcCHECK, SRS MapCHECK, and 3DMap for stereotactic body radiation therapy (SBRT).Methods:Based on the dosimetric verification result of the SBRT plans of 50 patients, this study compared the effects of PTV (<25 cm 3 and ≥25 cm 3), calculation grid size (1.0, 1.5, and 2.0 mm), and dose threshold (5%, 10%, and 15%) on the γ passing rates of the three dosimetric verification systems at five criteria, i. e., 3 mm/3%, 3 mm/2%, 3 mm/1%, 2 mm/3%, and 2 mm/2%. Results:The changes in PTV affected 3DMap more significantly. With an increase in PTV, the γ passing rates of 3DMap at the criteria of 3 mm/3%, 3 mm/2%, 2 mm/3%, and 2 mm/2% increased by 2.2%, 2.2%, 4.4%, and 4.7% ( t=-2.76, -2.17, -4.72, -3.86, P<0.05), respectively. The increase in the calculation grid from 1.0 mm to 1.5 mm had greater effect on MapCHECK, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 3 mm/1%, 2 mm/3% and 2 mm/2% decreased by 0.7%, 1.1%, 1.7%, 0.9%, 1.5% ( t=-6.15, -6.23, -5.98, -5.11, -8.34, P<0.05), respectively. The increases in the calculation grid from 1.0 mm to 2.0 mm had greater impact on ArcCHECK, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 3 mm/1%, 2 mm/3%, 2 mm/2% decreased by 1.0%, 1.7%, 2.4%, 1.7%, 2.7% ( t=-4.75, -7.3, -8.63, -7.11, -8.26, P<0.05), respectively. The increase in the dose threshold from 5% to 10% had greater impact on ArcCHECK, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 2 mm/3% and 2 mm/2% decreased by 1.1%, 1.4%, 2.5%, and 3.0% ( t=5.20, 5.68, 8.17, 9.99, P<0.05), respectively. Moreover, the increase in the dose threshold from 5% to 15% had more impact on 3DMap, with the γ passing rates at the criteria of 3 mm/3%, 3 mm/2%, 2 mm/3%, and 2 mm/2% decreased by 1.6%, 1.7%, 2.8%, and 3.2% ( t=3.25, 2.98, 4.40, 4.21, P<0.05), respectively. Conclusions:Target volume, calculation grid, and dose threshold are influencing factors in the dosimetric verification of three dosimetric verification systems for SBRT. Therefore, the effects of these parameters should be considered for different verification systems in clinical applications.

Application of the ArcherQA three-dimensional dose verification system in intensity-modulated radiotherapy plans for nasopharyngeal carcinoma / 中华放射医学与防护杂志

Objective:To investigate the feasibility of applying the ArcherQA three-dimensional (3D) dosimetric verification system in intensity-modulated radiotherapy (IMRT) plans for nasopharyngeal carcinoma (NPC).Methods:A retrospective analysis was conducted for 105 NPC patients′ IMRT plans developed using the Eclipse treatment planning system (TPS). Dose verification was conducted using the ArcherQA system and through portal dosimetry (PD). Moreover, this study compared γ passing rates (criteria: 3 mm/3%, TH = 10%) between ArcherQA and PD and the doses delivered to the target volume ( Dmean, D90%) and organs at risk (OARs) ( Dmean) between ArcherQA and TPS, and analyzed the 3D γ passing rates of each organ at risk calculated by ArcherQA. Results:The average 3D γ passing rate calculated by ArcherQA was (99.04±1.01)%, and the average 2D γ passing rate measured by PD was (99.49±0.78)%, with statistically significant differences ( t=-3.35, P< 0.05). The dosimetric differences to the target volume between ArcherQA and TPS were as follows: the average difference in Dmean to the gross tumor volume (GTV) was (0.57±0.48)%, and the average difference in D90% was (0.65±0.56)%. For the target volume, the average γ passing rate was (97.67±3.43)% for GTV, (97.80±4.35)% for GTVnd-L, (97.82±4.07)% for GTVnd-R, (97.88±2.44)% for CTV1, and (96.64±4.32)% for CTV2. The mean dose difference of each target volume was CTV1 (0.57±0.46)%, GTVnd-L (0.85±0.55)%, GTVnd-R (0.73±0.55)%, and CTV2 (0.88±0.52)%. For OARs, the mean γ passing rate was (99.93±0.22)% for the brainstem, (99.17±2.82)% for the optic chiasm, (100±0)% for the lens, (99.56±1.05)% for the spinal cord, (99.00±2.06)% for the thyroid, and (87.86±10.42)% for the trachea. Statistically significant differences in the average doses to OARs were observed ( t=-14.62 to 4.82, P<0.05), except for those to the left optic nerve, the right hippocampus, and the right parotid gland. Conclusions:Based on the high-performance GPU platform and the Monte Carlo dose algorithm, ArcherQA can provide accurate 3D dose distribution and 3D γ passing rates inside patients according to CT images and provide the dose volume histogram (DVH) of various regions of interest (ROIs). Therefore, the ArcherQA three-dimensional dose verification system can be applied to IMRT plans for NPC. Moreover, it is inducive to improve the treatment efficiency since it does not occupy the accelerator operation time.

First clinical application and dosimetric verification of total body irradiation with volumetric modulated arc therapy / 中华放射肿瘤学杂志

Objective:To investigate the implementation procedures and dosimetric verification of the first patient treated with total body irradiation (TBI) based on volumetric modulated arc therapy (VMAT).Methods:Two sets of CT images were acquired under the head-in first and foot-in first to contour the planning target volume (PTV) of the cranial and caudal segments to accomplish the treatment of the whole body length, on which two interrelated plans of 5 subsequent isocenters with a total of 15 VMAT fields were performed to cover all PTVs. The plans were prescribed to ensure 90% PTV dose coverage with a total dose of 12 Gy in 6 fractions. Firstly, a dose optimization was performed on the caudal CT images, then the cranial CT images were optimized based on the dose distribution of the caudal CT images. The evaluation of the final treatment plan was carried out based on a plan sum of both two sets of images. The parameters of PTV and organs at risk (OARs) were measured by dose volume histograms from the accumulated plan. The quality assurance comprised the verification of the VMAT plans for each individual isocenter via Delta4 phantom. The dose distribution in the overlapped region between two adjacent central fields was verified with EBT3 film. The absolute dose at the overlapped region between two images was measured via Pinpoint chamber. In vivo dosimetry on the patient′s skin was monitored by MOSFET dosimeters. The results of planning parameters and treatment duration were analyzed. Results:The mean doses of two segments of PTVs were 12.45 Gy and 12.37 Gy. The mean dose for the lung was 10.8 Gy. The machine unit (MU) and mean treatment delivery time were 2 883 MU and 24.3 min, and the mean total time per fraction was 121 min. The mean 3%/3 mmγ-analysis pass rate for each isocenter VMAT plan was (99.74±0.42)%, and the mean 5%/5 mmγ-analysis pass rate for the overlapped region was (90.11±2.72)%. The average deviation of absolute dose in the overlap region of the caudal and cranial images was (3.6±0.4)%. In vivo measurement of 8 points on the patient showed that the dose of each region was ranged from 1.57 Gy to 2.04 Gy. Conclusion:According to the results of dosimetric verification, TBI based on multi-isocenter VMAT can be applied in clinical practice, which remains to be improved in terms of dose distribution, measurement results and clinical efficiency.

Analysis of dosimetric verification results of stereotactic body radiotherapy / 中华放射医学与防护杂志

Objective To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy ( SBRT ) plans, and to investigate the sensitivity of the result to three factors:interpolation of measured data, size of dose calculation grid and assessment threshold. Methods The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation ( 1. 00 mm) and non-interpolation ( 7. 62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i.e., 1. 0 mm, 2. 5 mm and 4. 0 mm were compared respectively. The threshold of dose assessment was selected as 10％, 20％ and 30％, respectively. Three criteria of γ analysis were selected: 2％/2 mm, 3％/2 mm and 3％/3 mm. Results Under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, the average γ passing rates were (86. 3±7. 3)％ and (93. 7±5. 6)％, (94. 1±4. 4)％ and(97. 7±3. 9)％, (97. 7 ±2. 2)％ and (99. 1±1. 7)％, respectively, with and without linear interpolation. Relative to the 1. 0 mm reference grid, the grids of 2. 5 mm and 4. 0 mm significantly decreased γ passing rates by 3. 8％, 1. 9％, 0. 8％ ( t=8. 41, 9. 06, 5. 30, P<0. 05) and by 6. 5％, 6. 0％, 3. 5％ ( t=-13. 76, -13. 15, -9. 80, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Relative to the 10％ reference threshold, the shresholds of 20％ and 30％ significantly decreasedγpassing rates by 2. 4％, 1. 0％, 0. 6％(t=-8. 60, -5. 86, -4. 68, P<0. 05) and by 4. 0％, 1. 7％, 0. 9％ (t=-9. 45, -6. 66, -5. 06, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Conclusions Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients.

Analysis of dosimetric verification results of stereotactic body radiotherapy / 中华放射医学与防护杂志

Objective@#To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy (SBRT) plans, and to investigate the sensitivity of the result to three factors: interpolation of measured data, size of dose calculation grid and assessment threshold.@*Methods@#The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation (1.00 mm) and non-interpolation (7.62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i. e., 1.0 mm, 2.5 mm and 4.0 mm were compared respectively. The threshold of dose assessment was selected as 10%, 20% and 30%, respectively. Three criteria of γ analysis were selected: 2%/2 mm, 3%/2 mm and 3%/3 mm.@*Results@#Under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, the average γ passing rates were (86.3±7.3)% and (93.7±5.6)%, (94.1±4.4)% and(97.7±3.9)%, (97.7 ±2.2)% and (99.1±1.7)%, respectively, with and without linear interpolation. Relative to the 1.0 mm reference grid, the grids of 2.5 mm and 4.0 mm significantly decreased γ passing rates by 3.8%, 1.9%, 0.8% (t=8.41, 9.06, 5.30, P<0.05) and by 6.5%, 6.0%, 3.5% (t=-13.76, -13.15, -9.80, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively. Relative to the 10% reference threshold, the shresholds of 20% and 30% significantly decreased γ passing rates by 2.4%, 1.0%, 0.6%(t=-8.60, -5.86, -4.68, P<0.05) and by 4.0%, 1.7%, 0.9% (t=-9.45, -6.66, -5.06, P<0.05) under criteria of 2%/2 mm, 3%/2 mm and 3%/3 mm, respectively.@*Conclusions@#Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients.

Analysis of VMAT dosimetric verifications with different techniques / 中华放射肿瘤学杂志

Objective To investigate the gamma (γ) passing rates for volumetric-modulated arc therapy (VMAT) dosimetric verification with different techniques.Methods A total of 12 VMAT plans for the treatment of different anatomical sites in cancer patients were chosen.The Octavius 4D system was used to measure the dose distributions in two different settings:the gantry was rotating (three-dimensional (3D) and 2D γ-analysis) and the gantry was fixed at 0°(2D γ-analysis).The γ passing rates were analyzed with 3%/3 mm and 2%/2 mm criteria, using the paired t test or Wilcoxon signed-rank test.The 2D γ passing rates for different irradiation methods were calculated.Results For the 3D and 2D dose distributions obtained at a rotating gantry angle as well as the 2D dose distribution obtained at zero gantry angle, the average γ passing rates were 96.03%, 96.98%, and 98.90% for 3%/3 mm (P=0.227, P=0.000, P=0.003);82.08%, 84.04%, and 90.90% for 2%/2 mm (P=0.379, P=0.000, P=0.000).For the 2D dose distributions obtained with different irradiation methods, the average γ passing rate was 98.99% for 3%/3 mm and 93.68% for 2%/2 mm.Conclusions The VMAT dosimetric verification based on a 3D volumetric dosimeter at a rotating gantry position can be clinically useful for delivery quality assurance (QA), and can achieve the most reliable dose calculation for VMAT, which has more referential values.

A comparative analysis of Matrixx and EPID for dosimetric verification of intensity-modulated radiotherapy / 中华放射肿瘤学杂志

Objective To compare the dosimetric verification results of Varian Portal Dosimetry and Matrixx,and to assess the reliability of the clinical application of electronic portal imaging device (EPID) verification.Methods Varian TrueBeam linear accelerator,which was equipped with a 120-leaf multileaf collimator and an amorphous silicon EPID,as well as portal dose prediction software.IBA I′mRT Matrixx ion chamber array was used.EPID algorithm configuration,dose calibration,and testing before use were performed.The sliding-window protocol was used.There were 77 patients with tumors involving the head and neck (mainly nasopharyngeal carcinoma),mediastinum,abdomen,and pelvic cavity were selected.The verification plan of the portal dose was created with a source-detector distance of 100 cm,and the gantry angle was kept the same as the treatment plan.The verification plan was carried out in the TrueBeam machine,and the data were collected at the same time by EPID.Comparison between the measured and calculated dose images was performed,and the evaluation standard was gamma index (3%/3 mm).The paired t-test was used for difference analysis.Results For the 77 patients,the Gamma passing rates of both methods were above 97%.Except for head and neck carcinoma were a significant difference between the results of dosimetric results using EPID and Matrixx in intensity-modulated radiotherapy (P=0.018) other remaining all P> 0.05.Conclusions The dosimetric verification results of EPID are consistent with those of Matrixx.EPID can be used for dosimetric verification,and Matrixx ion chamber array can be used only in case of a low Gamma passing rate.

Analysis of 2 010 patient-specific intensity-modulated radiation therapy dosimetric verification results / 中华放射医学与防护杂志

Objective To analyze the patient-specific dosimetric verification results of 2010 intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans from different treatment sites,and provide a reference for improving the patient-specific dosimetric verification program.Methods A total of 2 010 (965 IMRT and 1 045 VMAT) patient-specific dosimetric verification results were reviewed for isocenter dose difference and percentage of pixels passing planar dose γ analysis.All plans were designed with Eclipse planning system and delivered with Trilogy linear accelerator from February 2012 to February 2016.The dosimetric verification was performed with MatriXX array together with Muhicube phantom.Point dose difference larger than ± 3％ and/or γ pass rate (3％/ 3 mm) less than 90％ was defined as plan failure.Additional analysis was conducted for trends in difference of pass rates with treatment site and delivery technique (IMRT vs.VMAT).Results The mean isocenter difference between measured and calculated doses was-0.3％ ± 2.4％ for 2 010 plans.The mean percentage of pixels passing the γ criteria was 97.9％ ± 3.4％.88.2％ and 96.7％ of plans passed the point and planar dose verification,respectively.The γ pass rate was different among the treatment sites (F =3.09,P ＜ 0.05).The pass rate of point and planar dose difference was different among the treatment sites(x2 =40.93,39.15,P ＜0.05).There was no difference between IMRT and VMAT plans for both point dose and planar dose evaluation (P ＞ 0.05).Conclusions Most of IMRT and VMAT plans passed the tolerance criteria of ±3％ and 90％ for point and planar dose verification with MatriXX together with Multicube phantom,respectively.Both point and planar dose verification results varied among treatment sites,whereas no significant difference was found between IMRT and VMAT.

Effect of the setup error on the dosimetric verification for the volumetric modulated arc therapy / 中华放射肿瘤学杂志

Objective To evaluate the effect of the setup error on the dosimetric verification for the nasopharyngeal carcinoma patients and cervical carcinoma patients treated with volumetric modulated are therapy (VMAT).Methods VMAT plans for 10 cervical cancer patients and 10 nasopharyngeal carcinoma patients were transplanted into the Delta4 phantom and calculate the dose,next,implement the treatment on the Varian iX linear accelerator.on the Varian iX linear accelerator.To simulate the setup error by moving the treatment couch in,out,up,down,left,right by 3 mm,5 mm,7 mm.Thereby study the effect of the setup error on the pass rate of the dose verification.Results The results for the dose distribution using the gamma evaluation method showed that the pass rate (3％/3 mm) was less than 90％ when the setup error were greater than 3 mm and 5 mm for the nasopharyngeal carcinoma patients and the cervical carcinoma patients.The pass rate of head direction were (64.7 ± 8.2) ％ and (63.3 ± 3.6) ％ on setup error of 5 mm and 7 mm for nasopharyngeal carcinoma patients and cervical carcinoma patients,respectively.Conclusions Setup error has great effect on the dose verification of the VMAT plans,the greater of the setup error,the lower of the pass rate.The setup error of head direction is more sensitive than other directions especially.

Case study of functional performance characteristics and test methods for intensity modulated radiation treatment planning system / 中华放射肿瘤学杂志

Objective To study a series of tests to the IMRT planning system RayStation,and verify the feasibility of this Standard.Referring to the standard Performance and test methods for intensity modulated radiation therapy (IMRT) treatment planning system (Standard).Methods Referring to the Standard,the tests include:dose goals used for planning,point dose calculation accuracy and dose distribution calculation accuracy.And test phantoms include:AAPM TG119 report's test cases and solid water phantom for verification,and IMRT test cases include:multitarget,mock prostate,head/neck and CTshape (easier version and harder version) and so on.Referring to the Standard,we optimize and calculate doses of interest in RayStation,and use the common measurement equipments and tools,such as an ionization chamber,films,a detector array,and etc,to measure the doses on the accelerator,then calculate and analyze the errors between them.Results The results of dose goals for five different mock plans meet the requirements of the Standard.And the point dose ionization chamber measurements are in line with the requirements of the Standard,and the total error of the mock plans was (0.83 ± 1.65) ％.The γpass rates of per-field measurements using detector array are all greater than 99.0％,and the γpass rates of composite film measurements are all greater than 92.5％.Conclusions The results of three trials to IMRT performance of RayStation are in full compliance with the requirements of the Standard.And also it is an evidence for the feasibility of this Standard.

The electronic portal imaging device for dosimetric verification of intensity-modulated radiation therapy / 中华放射医学与防护杂志

Objective To investigate the feasibility and efficiency of electronic portal imaging device for dosimetric verification of intensity-modulated radiation therapy.Methods 10 patients treated with intensity-modulated radiation therapy were verified using the electronic portal imaging device of aS1000 from Varian and MatriXX from IBA.The gamma pass rate and time needed was recorded and compared.Results The gamma pass rate at 3％/3 mm was 95.82％ (94.77％-96.86％) and 99.08％ (98.72％-99.45％) with aS1000 and MatriXX,respectively.The average time needed for dosimetric verification with aS1000 and MatriXX was 12.7 and 47.8 min,respectively.Conclusions The electronic portal imaging device of aS1000 has the potential as a tool for IMRT dosimetric verification.It is more convenient and efficient than MatriXX.

Dosimetric verification of volumetric modulated arc therapy in nasopharyngeal carcinoma using COMPASS 3D patient anatomy based system / 中华放射医学与防护杂志

Objective To investigate the dosimetric performance of COMPASS system,a novel 3D quality assurance system for the verification of nasopharyngeal carcinoma volumetric modulated therapy (VMAT) treatment plan.Methods Eight VMAT treatment plans of nasopharyngeal carcinoma patients were performed with MasterPlan,a treatment planning system (TPS),and then these treatment plans were sent to the COMPASS and MOSAIQ system,a coherent control system,respectively.Comparison of the COMPASS reconstructed dose versus TPS dose was conducted by using the dose volume-based indices:dose received by 95％ volume of target ( D95％ ),mean dose ( Dmean ) and γ pass rate,dose to the 1％ of the spinal cord and brain stem volume ( D1％ ),mean dose of leaf and right parotid ( Dmean ),and the volume received 30 Gy for left and right parotid (V30).COMPASS can reconstruct dose with the real measured delivery fluence after detector commissioning.Results The average dose difference for the target volumes was within 1％,the difference for D95 was within 3％ for most treatment plans,and the γ pass rate was higher than 95％ for all target volumes.The average differences for the D1％ values of spinal cord and brain stem were ( 4.3 ± 3.0) ％ and ( 5.9± 2.9 ) ％ respectively,and the average differences for the Dmean values of spinal cord and brain stem were ( 5.3 ± 3.0 ) ％ and ( 8.0 ± 3.5 ) ％ respectively.In general the COMPASS measured doses were all smaller than the TPS calculated doses for these two organs.The average differences of the Dmean values of the left and right parotids were( 6.1± 3.1 ) ％ and ( 4.7 ± 4.4 ) ％ respectively,and the average differences of the V30 values of the left and right parotids were (9.4 ± 7.5 ) ％ and (9.4 ± 9.9)％ respectively.Conclusions An ideal tool for the VMAT verification,the patient anatomy based COMPASS 3D dose verification system can check the dose difference between the real delivery and TPS calculation directly for each individual organ,either target volumes or critical organs.

Technology and quality assurance of Intensity-Modulated Radiation Therapy / 医疗卫生装备

Intensity-Modulated Radiation therapy(IMRT) is more advanced than normal radiation therapy.It utilizes computer controlled radiation beam delivery to improve the conformity of dose distribution to the shape of the tumor.The quality assurance of IMRT is the key for a successful treatment.