Objective To study the real?time dose verification with 2D array ion chamber array in volumetric modulated arc therapy ( VMAT) with a 2D array ion chamber array. Methods The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source?detector distance (SDD) was 140 cm. 8 mm RW3 solid water was added to the 2D array to improve the signal noise ratio. Patient plans for esophageal, prostate and liver cancers were selected to be delivered on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real?time patient transit dose measurements were performed at each fraction. Dose distributions were evaluated using gamma index criteria of 3 mm DTA and 3% dose difference referred to the first time result. Results The gamma index pass rate in the Cheese phantom were about 98%;the gamma index pass rate for esophageal, prostate and liver cancer patient were about 92%, 92% and 94%, respectively. Gamma pass rate for all single fraction were more than 90%. Conclusions The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.

Objective To evaluate the feasibility of active breathing control (ABC) in conformal radiotherapy (CRT) for patients with non-small cell lung cancer (NSCLC). Methods From Feb 2005 to Mar 2008, 29 patients with inoperable NSCLC (stage Ⅱ-Ⅳ) were evaluated. For each patient, two series of CT scans were obtained with free breathing (FB) and ABC system during simulation, respectively. Then two confonnal radiotherapy (CRT) plans were finished based on the two sets of reconstructed images. The pattern of post-inspiratory breath-hold was triggered at 80% of the peak of inspiration curve. The margin of clinical target volume (CTV) to planning target volume (PTV) was 0. 6 cm for lesions of the superior lobe, and 1.0 cm for the lesions of middle and inferior lobes. Three to five coplanar fields were performed in conformal radiotherapy. The gross tumor volume (GTV), CTV, PTV, volume of the bilateral lungs (Volume_(lung)), V_(20) and mean lung dose (MLD) of two plans were evaluated by dose-volume histogram (DVH). The World Health Organization criteria and National Cancer Institute Common Toxicity Criteria 3.0 (NCI-CTC3.0) scale were used to assess the immediate response and acute side-effect, respectively. Results Significant differences of GTV, CTV, FIN, Volum_(lung), V_(20) and MDL were observed between the two plans (36. 35 cm~3 vs. 31.40 cm~3, t = 9. 70, P <0. 001 ;82. 33 cm~3 vs. 70. 83 cm~3, t = 8. 19, P < 0. 001 ; 230. 73 cm~3 vs. 197.59 cm~3 ,t=5.72,P <0. 001 ;21.66% vs. 18. 76% ,t = 11.16,P <0. 001 ;1329. 07 Gy vs. 1143. 14 Gy, t = 13. 24, P < 0. 001). With ABC, all patients completed their treatment successfully except one patient for financial problems. The median radiation dose to the GTV was 64 Gy (60 -64 Gy). The overall immediate response rate was 64% (18/28). According to the NCI-CTC 3.0, grade 1 and 2 acute radiation-related toxicities occurred in 68% (19/28) and 18% (5/28) of patients for esophagitis, 82% (23/28) and 7% (2/28) for pneumonitis, respectively. Grade 1, 2 and 3 bone marrow suppression occurred in 57% (16/28), 25% (7/28) and 14% (4/28) of patients, respectively. Grade 1 and 2 acute cardiac injuries occurred in 86% (24/28) and 14% (4/28) of patients. Conclusions During CRT for patients with NSCLC, the use of ABC can decrease the radiation dose and acute complications of normal tissues.

Objective The aim of this work is to compare the performances of EDR2 film dosimetry with two-dimensional ion chamber array (2DICA) in quality assurance (QA) procedures and to investigate the origin of possible discrepancies between the two methods.Methods A 2DICA, I′mRT MatriXX and MULTICube equivalent solid water phantom from IBA Company were used to verify the dose distribution of 15 tomotherapy plan cases.The combined phantom which includes EDR2 film on the array was set up to measure the dose distribution from coronal and sagittal orientations.After the irradiation, the dose distributions of 2DICA and film were compared with those calculated in the planning system for verification.The results and efficiency were evaluated independently in the two methods.Results The mean number of points satifying γ parameter ≤1 in the coronal and sagittal planes was 97.00%±1.56%& 95.98%±2.52%(t=-2.22,P=0.043) and 98.28%±1.55%& 95.42%±1.99%(t=0.75,P=0.464) of the 15 cases respectively for 2DICA and EDR2 film.The ratio of more than 90% and 95% were 93.3% and 66.7%.The results we presented show a very good agreement between the two methods when used to assess the dose distribution between calculated and measured doses,and a certain degree of correlation (r=0.14,P=0.001).Conclusions The 2DICA may effectively replace both film and ion chamber dosimetry in routine IMRT QA.The good agreement between 2DICA and EDR2 film may give a possible check regularly just as a gold standard.

Objective To investigate the feasibility of dose verification of intensity modulated (IM) planning of helical tomotherapy (HT) using two-dimensional ion chamber array (2DICA),and develop an efficient way to validate the dose delivered under the parameters mirroring those during the treatment. Meth-ods A 2DICA,I'mRT MatriXX and MULTICube equivalent solid water phantom from IBA company were used to verify the dose distribution of 10 IM planning. The combined phantom was set up to measure the dose distributions on coronal and sagittal surface. The precise setup of phantom was guided by HTMVCT images. After the irradiation, the measured dose distributions on the coronal and sngittal plane were compared with those calculated by the IM planning system for verification. The results were evaluated and the feasibility of the different measuring methods was studied. Results The dose distribution measured by the MatriXX 2DICA was well consistent with that calculated by the treatment planning system. The errors between the measured dose and predicted dose in the selected points were within ±3%. In the comparison of the pixel-segmented ionization chamber versus treatment planning system using the 3 mm/3% γ criteria, the passing ratio of pixels with γ parameter ≤1 was 97.76% and 96.83%, respectively. Conclusions MatriXX is a-ble to measure the absolute and relative dose distributions simultaneously,which can be used for dose verifi-cation of IM planning.

Objective To compare the dosimetric characteristics of helical tomotherapy(HT)and step-and-shoot intensity modulated radiotherapy(IMRT)for post-operative cervix cancer patients. Methods Ten patients with post-operative cervix cancer were enrolled in this study.HT and IMRT plans were developed for each patient.The dose distributions of the targets,organs at risk(OARs),CI and HI were analyzed and compared.The prescribed dose was 60 Gy/25 f for CTV1,50 Gy/25 f for CTV2.The iso-dose line of 50 Gy was used.Results The homogeneity indexes(HI)(0.94±0.03),conformity index(C1)(1.28±0.02)in HT group were better than in IMRT group(0.85±0.01 and 1.36±0.03),respectively(t=5.12,-6.34,P<0.001).The Dmean of PTV in HT group(51.77 Gy)was lower than that in IMRT group(54.53 Gy)(t=-8.01,P<0.05).The Dmax ,Dmean,V30,V40 and V50 of bladder、rectum and small bowel were lower in HT group than those in IM RT group.The Dmax,Dmean,V30 and V40 of right and left femoral head were lower in HT group than those in IMRT group.Conclusion Helical tomotherapy treatment plan has a better homogeneity,steeper dose gradient,and a better protection for organs at risk.

Objective To investigate the dosimetric characteristics of helical tomotherapy(HT),intensity-modulated radiation therapy(IMRT)and three.dimensional conformal radiation therapy(3D-CRT)for the post-operative breast cancer as well as their comparison in protecting the normal tissues.Methods The CT images of 10 postoperative patients with early stage breast cancer were transferRed into HT and IMRT and 3D- CRT planning system respectively after the target region and normal tissues were drawn out with the same doctor.Each prescribed dose for three kinds of plans was 50 Gy/25 fractions.Inrradiation doses and volume at heart and double lungs as well as conformity index(CI)and homogeneity index(HI)were evaluated.Results The PTV volume of prescribed target dose of 95% and 100%in HT, IMRT and 3D-CRT groups were 99.13%and 95.87%,97.80%and 94.05%,96.37%and 87.29%.respectively.The CI and HI in HT.IMRT and 3D-CRT groups were 0.80±0.10 and 1.09 ±0.03,0.65±0.07 and 1.14±0.02,0.40±0.08 and 1.17±0.04,respectively V5,V10 and V20 of the heart were the lowest at 3D-CRT than HT and lM RT.V5 of the diseased lung was the lowest at 3D-CRT compared to HT and IMRT.V5 and V10 of the healthy lung were the lowest at 3 D-CRT compared to other groups.Conclusions Compared with IMRT and 3D-CRT.HT technique in treating breast cancer had the best conformity index and homogeneity index as well as steeper dose gradient.Irradiated doses and volume at the heart was the lowest at 3D- CRT and the highest at IMRT.Irradiated doses and volume of the heart and healthy lung as well as the diseased lung were the lowest at 3D-CRT compared to HT and IMRT groups.

Objective: To evaluate the feasibility of hypofractionated intensity-modulated radiation therapy (IMRT) combined with concurrent chemotherapy in patients with locally advanced squamous cell carcinoma of the hypopharynx. Methods:Patients with stageⅢ-ⅣA carcinoma of the hypopharynx were treated with IMRT and cisplatin-based concurrent chemotherapy. Two groups were di-vided according to the prescription dose to the primary gross tumor volume, as follows:Cohort-1 comprised patients who were recruit-ed before February 2013 (70 Gy/33 F and 2.12 Gy/F);and Cohort-2 comprised patients who were recruited since February 2013 (69 Gy/30 F and 2.30 Gy/F). Acute toxicities were evaluated. This study was registered with the number ChiCTR-ONRC-14004240. Results:Between August 2008 and December 2014, a total of 76 patients (35 in Cohort-1 and 41 in Cohort-2) were recruited. No xerostomia of grade 3 and higher was observed in all patients, who showed low incidences of grade 3 skin reaction, oral mucositis, and dysphagia. All patients did not show acute toxicities of higher than grade 4. No statistical differences in acute toxicities were observed between the two cohorts. No statistical difference was observed in acute toxicities between the IMRT techniques. Induction chemotherapy was the inde-pendent prognostic factor for grade 2 xerostomia (P=0.002). Conclusion:The 69 Gy/30 F hypofractionated IMRT was safe and effec-tive in the treatment of locally advanced squamous cell carcinoma of the hypopharynx. Late toxicities and long-term outcome need to be investigated further.

To investigate the patient-specific dose verification method using ArcCHECK for total marrow irradiation (TMI) with Volumetric Modulated Arc Therapy (VMAT) and Helical Tomotherapy (HT). The kVCT images collected from 8 patients were respectively designed for RapidArc and Tomotherapy plans in total marrow irradiation. ArcCHECK was used for dose verification for the head-neck, chest-abdomen and pelvic. The merging function of ArcCHECK was used in VMAT and the method of double plans (reference and delivery plans) were used in HT. The γ-analysis passing rates for the head-neck, chest-abdomen, pelvic were 98.9% ± 1.9%, 98.4% ± 1.8%, 97.4% ± 2.1% for VMAT plans and 94.3% ± 1.5%, 96.5 ± 1.2%, 94.1% ± 1.9% for HT plans. The results show that using the merging function of ArcCHECK can achieve the dose verification well for VMAT plans with TMI. The method of double plans was done for the dose verification of HT plans with TMI as well as the plans with the targets keeping away from the set-up center.
Bone Marrow ; radiation effects ; Humans ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; Radiotherapy, Intensity-Modulated

Objective: Quality assurance (QA) of intensity modulated radiotherapy (IMRT) dosimetry is a laborious task. The goal of this work is to evaluate the dosimetric characteristics of a new 2D diode array and assess the role it can play in routine MRT QA. Methods: A diode array, MapCHECK~(TM) and MapPHAN phantom from Sun Nuclear corporation (USC) were used for verifying the dose distribution of 10 tomotherapy IMRT plan cases. The combined phantom was set up to measure the dose distribution from coronal and sagittal orientations. After MVCT registration, the measured dose distributions of the coronal and sagittal planes were compared with those from calculation in the planning system. The results were evaluated by the absolute doses. The feasibility of the different measuring methods were studied. Results: The dose distribution measured by the MapCHECK~(TM) 2D array was well consistent with that calculated by tomotherapy planning system. In the comparison of the MapCHECK~(TM) measured versus planning system calculated using the 3mm/3% and 4mm/4% γ criteria, the number of detectors with γ parameter ≤ 1 was 96.8%/99.38% and 96.99%/99.49% average of the 10 cases respectively, for coronal and sagittal orientations. The acceptance criteria which is the combined 3mm/3% analysis would be introduced. And the number of points required to pass was generally 90%. Conclusions: MapCHECK~(TM) with MapPHAN phantom has been successfully tested for HT dose verification, and offers users an accurate and convenient rotational dosimetry solution.

To investigate the dose effect of isocenter difference during IMRT dose verification with the 2D chamber array. The samples collected from 10 patients were respectively designed for IMRT plans, the isocenter of which was independently defined as P(o), P(x) and P(y). P(o) was fixed on the target center and the other points shifted 8cm from the target center in the orientation of x/y. The PTW729 was used for 2D dose verification in the 3 groups which beams of plans were set to 0 degrees. The γ-analysis passing rates for the whole plan and each beam were gotten using the different standards in the 3 groups, The results showed the mean passing rate of γ-analysis was highest in the P(o) group, and the mean passing rate of the whole plan was better than that of each beam. In addition, it became worse with the increase of dose leakage between the leaves in P(y) group. Therefore, the determination of isocenter has a visible effect for IMRT dose verification of the 2D chamber array, The isocenter of the planning design should be close to the geometric center of target.
Gamma Rays ; Humans ; Radiotherapy Dosage ; Radiotherapy, Intensity-Modulated ; instrumentation ; methods