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Objective:To explore the clinical application of the electronic portal imaging device (EPID) based on the linear accelerator produced by Shanghai United Imaging Healthcare Co., Ltd. (UIH) to in vivo dose verification. Methods:A total of 68 patients (32 cases with head and neck tumors, 16 cases with chest tumors, and 20 cases with abdomen and pelvis tumors) who were treated with volumetric modulated arc therapy (VMAT) in the Henan Provincial People′s Hospital were selected in this study. Each patient underwent the pre-treatment dose verification using an Arccheck device (Pre Arccheck), the pre-treatment dose verification using an EPID (Pre EPID), and the in vivo dose verification using an EPID (In vivo EPID). Moreover, the position verification based on fan beam computed tomography (FBCT) was also performed for each patient in the first three treatments and then once a week. The patients were treated when the setup error in any direction ( x: left-right, y: head-foot, z: vertical) was less than 3 mm; otherwise, position correction would be conducted. The three-dimensional setup deviation d was calculated according to setup errors x, y, and z. Results:The γ passing rates of dose verifications Pre EPID and In vivo EPID of 68 patients were (99.97±0.1)% and (94.15±3.84)%, respectively, significantly different from that (98.86±1.48)% of the Pre Arccheck dose verification ( t = -6.12, 9.43; P < 0.05). The γ passing rates of the chest, abdomen and pelvis, and head and neck in the In vivo EPID dose verification showed no significant differences ( P > 0.05). The difference in the γ passing rates (5.56±3.72)% between dose verifications Pre EPID and first In vivo EPID was unrelated to the three-dimensional setup deviation d (1.46±1.51 mm) ( P > 0.05). As the treatment proceeded, the γ passing rate of In vivo EPID gradually decreased from (94.15±3.84)% in the first week to (92.15±3.24)% in the fifth week. From the third week to the fifth week, the γ passing rates of In vivo EPID were significantly different from those in the first week ( t = 2.48, 2.75, 3.09, P < 0.05). Conclusions:The setup errors within 3 mm do not affect the γ passing rate of in vivo dose verification. The clinically acceptable threshold for the γ passing rate of in vivo EPID needs to be further determined. In addition, in vivo dose verification can support the clinical application of adaptive radiotherapy to a certain extent.
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Objective:To study the effects of gantry acceleration limitations of a linear accelerator (linac) on the dosimetry of volumetric modulated arc therapy (VMAT) plans, machine efficiency, and dose verification result of VMAT plans and to explore the optimal selection of gantry motion models in the Pinnacle treatment planning system.Methods:Ten cases of nasopharyngeal carcinoma, non-small cell lung cancer, sigmoid adenocarcinoma with retroperitoneal lymph node metastasis, and invasive ductal carcinoma of the breast were each selected for this study. Then two models were set up in the Pinnacle v9.10 treatment planning system, namely the one allowing gantry acceleration and the one limiting gantry acceleration. The same field arrangement, optimized target parameters, and optimized weights of VMAT plans were adopted in the two models, in order to analyze the dosimetric variations in targets and organs at risk (OARs) and compare the differences in treatment time and gamma passing rates.Results:The treatment time of the enrolled patients under the model allowing gantry acceleration was significantly lower than that of the patients under the model limiting gantry acceleration was adopted ( t=-6.751, -0.209, -19.523, -28.999; P< 0.05) and decreased by 15.27%, 18.07%, 19.71%, and 28.75%, respectively. Meanwhile, the conformity and uniformity of target areas were affected, while there was no statistical significance in the gamma passing rates in the validation of VMAT plans ( P>0.05). For the cases of nasopharyngeal carcinoma (NPC), the maximum dose to brainstem PRV increased by 1.25%. For the cases of lung cancer, the maximum dose to the spinal cord and lung V20 increased by 1.19% and 1.21%, respectively, while lung V5 decreased by 1.21%. For the cases of sigmoid adenocarcinoma with retroperitoneal lymph node metastasis, the mean doses to bilateral kidneys, livers, small intestine, and colon all increased. For the cases of breast cancer, lung V10 on the opposite side of cancer increased by 1.66% and the mean dose to the lungs on the same side of cancer decreased by 7.45%. Conclusions:The model allowing gantry acceleration allows the treatment time to be significantly shortened and the treatment efficiency improved. Although this model had the shortcomings such as affecting the conformity and uniformity of target areas to a certain extent and increasing the doses to some OARs, clinical requirements for dosimetry were still met. Therefore, it is recommended to use the model allowing gantry acceleration in the Pinnacle planning system.
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Objective:Based on the AAPM-TG218 report, the dose verification of intensity-modulated radiotherapy (IMRT) plans were classified to understand the current status, establish the process and determine the limits of dose verification in our hospital.Methods:Different combinations of tumor locations, accelerators, treatment planning systems and verification devices in our hospital were verified and compared to determine the tolerance limits and action limits of each combination. The measurement requirement was adopted according to the AAPM-TG218 report, and 80 cases were selected for each measurement. The measurement procedures were implemented based upon the AAPM-TG218 report and clinical experience of our hospital.Results:The clinical action limits of IMRT plans in our hospital could meet the recommended range of the AAPM-TG218 report, and the tolerance limits were slightly lower than the AAPM-TG218 report′s recommendation (93.94% for 3%/2 mm). The measurement of verification devices was related to the sensitivity. The tolerance limits measured by EPID were higher than ArcCHECK, especially when the dose/distance requirements were more stringent (94.12% and 92.03% for 3%/2 mm, P=0.074; 86.82% and 74.61% for 2%/2 mm, P=0.017). Conclusion:Through the AAPM-TG218 report, the work flow of IMRT dose verification and the limit range are established in our hospital, providing guidance for subsequent clinical dosimetric measurement.
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Objective To investigate the effect of respiratory movement of different amplitude,period and direction on the dose distribution of target area in dynamic intensity modulated radiation therapy.Methods A total of 30 cases of lung cancer were selected and divided into three groups according to the volume size of the target area,including groups A (72.0-200.2 cm3),B (271.7-380.0 cm3) and C (498.9-684.9 cm3).The average volume was 151.5,327.1 and 583.3 cm3,respectively.Breathing motion simulation platform was used to drive the mode body with two-dimensional ionization chamber matrix along the Gun-Target direction,then turn the collimator to 0° and 90°,respectively.The doses were collected at the central level in different amplitudes of 0,4,8,12 and 15 mm,periodic respiratory movement at the intervals of 3,4 and 5 s and respiratory motion measurement with a cycle of 4 s 5 times.The difference of dose distribution between the collected dose and TPS output was analyzed by taking the absolute dose and γ-passing rate (3 mm/3％) as indicators.Results In the two-sided upward,respiratory movement reduced the dose at the medial edge of the target area and increased the dose at the lateral edge of the target area.The difference of γ-passing rate between respiration cycle was up to 3.54％ (t=2.301,P＜0.05),and when the respiration movement was more than 8 mm,the γ-passing rate was less than 90％ and decreased with the increase of amplitude.The difference of γ-passing rate between static and respiratory motion was negatively correlated with the volume of target area,and the average γ-passing rate of A,B and C three groups increased gradually.The γ-passing rate of 5 composited dose was higher than that of single dose,and the difference was statistically sigificant(t=-9.36--5.95,P＜0.05).Conclusions The dose distribution of dynamic IMRT target area is mainly influenced by respiration range and its own volume,and the respiration cycle has an effect on dose distribution under partial amplitude.After implementing the multiple doses,some single dose implementation errors can be eliminated.Physicians need to expand the target area reasonably according to the range of respiratory movement,and optimize the amount of marginal tissue in the target area in the direction of respiratory movement.For patients with small target volume and large respiratory movement,respiratory management technology should be adopted to improve the accuracy of target dose implementation.
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Objective:To analyze the attenuation of immobilization baseplate of carbon fiber for ray and the change of dose verification results for enhanced radiation field of MatriXX. And to primarily research the influence of this immobilization baseplate for the dose distribution of radiation field of radiotherapy.Methods: 20 patients with cervical cancer were enrolled in the research. The angle of gantry was 180°in the enhanced plan of immobilization field, and the corresponding verification plans were designed. When the verification plan was implemented on the Varian Clinac iX of accelerator, the two-dimensional ionization chamber array (MatriXX) was used to measure dose distributions of the plan. The immobilization baseplate of carbon fiber (ORFIT AIO) was used in the research. The situations of no baseplate (A group), one baseplate (B group), two baseplates (C group)and three baseplates (D group)between the handpiece of accelerator and Matri XX were researched, respectively. The data of the 4 groups were obtained by using software (OminiPro I'mRT), and the largest dose point and passing rate of Gamma in plane of radiation field were counted and analyzed.Results: Compared with A group, the average attenuation factors for ray on the largest dose point of B, C and D group in the plane of radiation field were (1.73±0.11)％, (3.44±0.36)％, and (5.48±0.44)％, respectively. The passing rates of Gamma in the 4 groups were (94.87±2.31)％, (99.18±0.61)％, (99.79±0.27)％ and (96.24±1.99)％, respectively. And the differences of passing rate between each group and A group were statistical significance (t=9.788,t=9.261,t=2.256,P<0.05).Conclusion:The immobilization baseplate of carbon fiber has influence for the attenuation of high-energy X-rays and it can affect the dose distribution of radiation field which has passed baseplate in some degrees. And when physicists calculates the dose, they should consider the effect of immobilization baseplate of carbon fiber for dose distribution of radiation field.
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Objective To develop the methodology for using TLDs and films to measure absorbed dose and 2D dose distribution produced by the multi-leaf collimator (MLC) in intensity modulated radiotherapy (IMRT),in order to provide the guidance on dose quality audit in IMRT.Methods A total of 30 different-typed accelerators were selected from 27 hospitals in Jiangsu,Sichuan,Hubei and Henan provinces,including 17 Varian accelerators,10 Elektas and 3 Simens.The same batch of films and TLDs were put in a 2 cm-thick solid plate for fixation and then loaded in a 15 cm × 15 cm × 15 cm polysyrene solid phantom supplied by International Atomic Energy Agency(IAEA) in terms of 90 cm SSD,19 cm depth,10 cm × 10 cm field at different doses.The standard dose curves wcrc established for film and TLD,respectively.The irradiated film was measured and then sent to the External Audit Group (EAG) in China.The TLD-and film-absorbed doses were compared with TPS-calculated doses.The 2D dose distribution on the IRMT MLC field was measured using films.The homogeneous phanton of 30 cn × 30 cm was scanned by CT and the image was transferred to the TPS.The IMRT was implemented with 6 Gy fractionated irradiation by placing a 25 cm × 25 cm film on the phantom surface at 95 cm SSD and at 5 cm depth.The irradiated film was sent to the IAEA dosimetry laboratory for measurement and calculation.2D dose distribution verification was conducted in thc same way consistent with the procedure of international multi-radiotherapy center.The 3 mm/3％ passing rate was calculated for 2D dose distribution and compared with the film-measured and TPS calculated result.Results IAEA requires the relative deviation of TLD and film measured absorbed dose are with in ± 5％.The relative deviation of TLD-and filmmeasured to TPS-calculated absorbed dose was within the range of ±0.7％-± 8.5％ and within ±0.3％ ±7.8％ in Jiangsu,Sichuan,Hubei and Henan provinces,respectively.IAEA requires the 3 mm/3％ passing rate of film-measured 2D distribution to be 90％.The result of the present study were up to 94.0％.The verification result of 2D dose distribution were within 70.0％-99.9％ in Sichuan,Jiangsu,Hubei and Henan provinces.Conclusions The adsorbed dose and 2D distribution can be audited using TLDs and films for MLC in IRMT.The method is scientific and applicable,economical and convenient for development of dose quality audit for a wide range of IRMT.
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Objective To perform 3D dose reconstruction based on electronic portal imaging device ( EPID) of linear accelerator for the static intensity-modulated using Edose, a dose verification system, Aiming to assist the radiotherapy professionals to better understand the radiotherapy organs at risk and target dose changes. Methods CBCT image was acquired for patients with head and neck cancer and thoracic cancer once a week for a total of six times. Subsequently,CBCT images and planning CT images were subject to rigid registration and exported to the Edose software. According to the setup error, EPID-based three-dimensional dose reconstruction was performed by using Edose software. The gamma passing rate and dose of different organs at risk ( OARs ) were analyzed and statistically compared. Results For patients with nasopharyngeal carcinoma,the intra-fractional Dmax of the spinal cord was more significantly fluctuated and higher compared with the planning dose, whereas the intra-fractional Dmax of the brainstem did not significantly fluctuate. The V30 of the parotid gland significantly changed with a maximum increase of 28. 69％ per fraction. For patients with thoracic tumors,the Dmax of the spinal cord was slightly changed,and the actual doses in the lung and heart were higher than the planning doses. The average deviation of the pulmonary V5 was up to 16. 99％ between the actual and planning doses with statistical significance ( P<0. 05).According to the analysis of gamma passing rate,significant dose changes occurring in the OARs were detected in the 16th fraction for the head and neck cancer and the 24th fraction for the thoracic neoplasms. Conclusions The dose changes in the OARs can be obtained by reconstructing the EPID-based 3D dose distribution using the Edose software for each fraction, which can better protect the OAR, enhance the coverage of target dose and provide certain reference for dose-guided and self-adaptive radiotherapy.
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Objective To evaluate dose variations induced by gravity of multi-leaf collimator to provide references for clinical intensity-modulated radiotherapy.Methods Two-dimensional dose distributions in the central plane of IMRT fields were measured by use of a 2D ion chamber array.All measurements were repeated at two collimator angles (C=0 and 90°),for each of the following gantry angles:G=0 and 270°.Comparisons were made to dose distributions generated at G=0°and their differences were analyzed using gamma index analysis (3％/3 mm and 1％/1 mm).Results Under the radiation field of 10 cm×10 cm,the gamma passing rate was higher than 99％ for 3％ 3 mm anch close to 95％ for 1％/1mm Under a 3％/3mm error standard,the average matching rate for step & shoot fields was (96.46±0.33)％ and for DMLC fields was (94.67±0.54)％ at C=0°;The average matching rate for step & shoot fields was (94.59±0.47)％ and for DMLC fields was (92.60±0.52)％ at C=90°.Under a 1％/1mm error standard,the average matching rate for step & shoot fields was (89.83 ±1.06)％ and for DMLC fields was (85.84±0.57)％ at C=0°;The average matching rate for step & shoot fields was (86.91 ±1.71)％ and for DMLC fields was (83.89±0.69)％ at C=90°.Concusion MLC weight effect affects IMRT delivery dose,and DMLC fields are more sensitive to gravity than step & shoot fields.
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Objective To find out the weak points of students through analyzing the scores of medical licensing examination, to explore the causes and to put forwards some advices. Methods Excel 2007 was used to statistically analyze the average scores, average passing rate and the mastering rate of 3 060 candidates who took the exam from 2006 to 2011. Literatures were reviewed to find out reforming measures taken by other schools. Results The average scores changed lightly. The master-ing rate changed differently. The average passing rate declined from 83.6% in 2006 to 71.65% in 2011. Conclusions Score of medical licensing examination is an important index of the teaching quality of medical universities, which should be emphasized on. Some practicable methods are put forward taken into all related factors:adjusting course setting, strengthening teaching of practical skills, reforming teaching methods and examination systems, placing more emphasis on examination work.
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Objective To verify IMRT plans in point,planar and 3D dose,and to concretely analyze the dose differences of 3D anatomic structure based on Gamma passing rate.Methods Thimble ion-chamber,Matrixx and ArcCheck were separately used to measure six nasopharyngeal carcinoma treatment plans and six lung cancer treatment plans.The dose measurement deviation of the center point was compared as well as the Gamma passing rate of dose verification under the criteria of both 3％/3 mm and 2％/2 mm,the group t-test and one-way ANOVA were also proceeded.3DVH system was used to analyze the dose measurement deviation of target volume (TV) and organ at risk (OAR) through DVH.Results For IMRT and VMAT treatment plans,the mean deviation of point dose was (0.59 ± 1.31) ％ and (-1.00 ± 1.03)％ respectively,and the maximum deviation was less than 3％.Under the criterion of 3％/3 mm,the Gamma passing rate measured by Matrixx,ArcCheck and 3DVH for IMRT plans was 96.28％,97.55％ and 99.02％ respectively,and for VMAT plans,the corresponding results of three different detectors were 97.24％,99.67％ and 98.48％.The results analyzed and compared by 3DVH showed that even under the condition of high Gamma pass rate (more than 95％ for a Gamma criterion of 3％/3 mm),the DVH metrics of both TV and OAR in two cases (account for 16.7％ of the total plan) were significantly different on the clinical parameters,including GTV,spinal cord and brain stem etc.Conclusions The analysis of dose difference of the measurement results based on Gamma pass rate and on anatomic structure of 3D images can more effectively evaluate the influence of dose error to the implementing of clinical plan and the impact to the clinical treatment.
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Objective To study the effect of the uncertain deflection of the Delta4 phantom (ScandiDos AB,Sweden) in setting up on the Gamma index passing rate during the VMAT plan verification.Methods Two patients with head and neck cancer,two with lung cancers and one with pelvic cancer receiving VMAT radiotherapy were randomly chosen.By means of Eclipse8.6 TPS the treatment plans elaborated for the five patients were picked up to make the verification plans and Delta4 was used to perform dose verification On VARIAN Clinac Ⅸ.The Delta4 phantom was precisely set up first,and then it was deflected in a given angle towards the horizontal direction in relation to the center of the linear accelerator isocenter to perform the dose verification for 11 times successively.To figure out the relationship between the deflection angle of the Delta4 phantom and the Gamma index passing rate.Results As the Delta4 phantom was deflected by 0.0°,0.2°,0.4°,0.6°,0.8°,1.0°,1.2°,1.4°,1.6°,1.8° and 2.0° in sequence,the measured Gamma index passing rates presented a slight decline,but all greater than 90％ (DD 3％,DTA 3 mm).Conclusions In the VMAT plan verification,the Gamma index passing rate of Delta4 has no dependence on the uncertain deflection of the Delta4 phantom provided that the uncertain deflection of the Delta4 phantom is no greater than 2°,but the passing rates of DD and DTA vary significantly with the uncertain deflection of the Delta4 phantom.
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Objective To evaluate the effect of carbon fiber couch on dose distribution of radiotherapy planning and verification pass rate.Methods Establishing the carbon fiber treatment couch model in Pinnacle8.0m Treatment Planning system (TPS),and then this model was used to correct dose calculations of oblique fields in the treatment plans of 10 cases of nasopharyngeal carcinoma,10 cases of breast cancer and 10 cases of lung cancer and evaluate the effect of carbon fiber couch on the whole dose distribution of the plans.Then these plans were measured by three-dimensional dose verification equipment Delta4 to confirm the improvement extent of Gamma pass rate after considering the carbon fiber treatment couch.Results For the majority of plans,when the carbon fiber couch was taken into consideration,the target doses was significantly reduced (4772 cGy-7266 cGy vs.4859 cGy-7347 cGy,P=0.000-0.002) and the relative deviation of D95 was 1％ to 3％.Measurement results of Delta4 showed that Gamma pass rate (3 mm/3％ criteria) increased in all plans (96.4％-98.8％ vs.93.4％-97.3％,P =0.000),some of that were up to 5 percentage when the couch model was applied.Conclusions Target doses will be overestimated if the treatment couch is ignored in TPS measurement.,However it should arouse enough attention when the disease with smaller doses corresponding gradient.
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Objective To investigate the factors of effecting with yindex analysis of delivery for helical tomotherapy (HT).Methods Measuring γindex with the ArcCheck device for introduced errors in HT.The errors include setup errors in three-dimensional,the gantry angle error,calculating the dose in the phantom,low dose rate.All the results were compared with the 3％/3 mm and 2％/2 mm criteria.The effect of the accuracy in the application of kilovoltage computed tomography (KVCT) and mega-voltage computed tomography (MVCT) images in HT was also analyzed.Paired-t test method was used for difference compared.Results When the errors were introduced to the HT,theγpassing rate of left-right,superior-inferior,anterior-posterior direction dropped 2.7％,7.2％,3.6％ under the 3％/3 mm criteria (P =0.002,0.022,0.007),with 4.6％,15.7 ％,7.6％ under the 2％/2 mm criteria (P =0.001,0.003,0.002) respectively.There was no statistical significance for theγpassing between scanning the ArcCheek phantom with the KVCT and MVCT under the 3％/3 mm and 2％/2 mm criteria (98.6％ vs 98.7％,P =0.859 and 92.7％ vs 92.8％,P =0.984).Conclusions The errors of the setup position and machine paraments can lead to the dose delivery errors in HT,the quality accurance of machine and plan should be enhanced to minimize the dose errors.The results also showed that there is no difference of KVCT and MVCT image on the delivery of HT.
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Objective To evaluate the sensitivity of patient-specific volumetric-modulated arc therapy (VMAT) quality assurance (QA) to minor multileaf collimator (M LC) positioning errors.Methods Systematic multileaf collimator (MLC) positioning errors (+0.5 mm,+ 1 mm and +2 mm) were introduced into the clinical VMAT patient plans with 2 types of MLC positioning errors:systematic MLC gap width errors and systematic MLC shift errors for 6 cases,including 3 cases with prostatic cancer and 3 cases with nasopharyngeal cancer.The planar dose distributions of the original and modified plans were measured using ArcCheck array.The coincidence between the measured results and the calculated results was evaluated using both absolute distance-to-agreement (AD-DTA) analysis with 3％/3 mm and 2％/2 mm criteria.Results The average passing rate of the 6 original VMAT plans was 96.0％ with the ADDTA criteria of 3％/3 mm which was commonly adopted in clinical practice.For the MLC gap width errors of + 1 mm,+2 mm,and-2 mm and the MLC shift errors of 2 mm,the drop levels in average passing rate with the AD-DTA criteria of 3％/3 mm were 8.8％,15.5％,6.1％ and 7.9％,respectively.The + 2 mm MLC positioning errors and + 1 mm MLC gap width errors could be detected by the patient-specific VMAT QA procedure.The AD-DTA criteria of 2％/2 mm was more sensitive compared with the criteria of 3％/3 mm.Conclusions Patient-specific VMAT QA is not sensitive enough to detect the systematic MLC positioning errors within 1 mm.Additional MLC QA is needed to guarantee the accuracy of VMAT delivery.
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@#Objective To describe the results of the Universal Newborn Hearing Screening (UNHS) in Beijing in 2010; and investigatethe factors related with the results. Methods The result of the UNHS investigated by 106 maternity hospitals were reported. These hospitalswere investigated with the self-made questionnaire. Results In 2010, 159888 infants (91.99%) were screened in 106 maternity hospitals inBeijing as the 1st stage UNHS. 10.32% of them failed OAE tests. 72.30% received the 2nd stage UNHS and 13.27% of them failed testsagain. The referral rate was 0.99% in the end. The screening rate of both the 1st and 2nd stage was more in the newborn with Beijing householdregistration than in those with other household registration, as well as the hospitals in urban than in rural areas. For the rate fail in the1st stage UNHS, it was more in hospitals in urban than in rural areas, with distortion product otoacoustic emission (DPOAE) than with transientevoked otoacoustic emissions (TEOAE), by the bed than in the special room, and screening only once than screening again. ConclusionThe quality of UNHS is as high as in the developed countries in the newborn with Beijing household registration. To further improvethe screening rate, it is important to focus on the newborn with other household registers and the hospitals in rural areas. The instrument, personnelqualifications, environment and operation need to be further standardized.
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We analyzed the final test paper of Endodontics among the 2001th grade students of the seven-year-educational mode in our university.The results indicate that the test paper has standard form,reasonable distribution of content,moderate quantity of questions and comprehensive test items.showing that most students mastered the basic principles and knowledge of this course,reflecting satisfactory teaching effect.
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OBJECTIVE To probe the possibility for CQI to raise the passing rate of hand-washing liquid. METHODS From Jul 2007 to Sep 2007,we applicated continuous quality improvement(CQI) in the management of the use of hand-washing liquid. RESULTS The failure rate of hand-washing liquid was decreased markedly (64% in July,36% in August,and in 12%September),and the difference among three months was significant (P