ABSTRACT
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.
ABSTRACT
Objective To evaluate the clinical feasibility of quality assurance of helical tomotherapy intensity modulated radiation therapy (IMRT) through a series of clinical case studies. Methods Tomotherapy planning system was used to provide optimized IMRT treatment plans. To verify the dose of IMRT plans,the cylindrical Virtual Water phantom,0.056cm3 AISL, ion chamber and EDR2 film were used for getting the absolute and relative doses from tomotherapy IMRT planning. The film and ion chamber were placed into the phantom. The doses of the interesting points and isodose distribution of the axial plane were measured,then the results were compared with those from the calculation in planning system for verification. Before the irradiation,kVCT images of the phantom were registered by tomotherapy MVCT images. So the setup of phantom was guided for verifying the position. Results The isedose distribution (on the axial plane) measured by the film was well consistent with that calculated by tomotherapy planning system. The error between the measured dose and predicted dose in the measured points was less than 3%. The setup error of the phantom was able to be kept within 1 mm. There was 2 mm offset along the vertical direction of couch from the virtual isocenter to beam isocenter,which should be considered during the phantom/patient setup. Conclusions The procedures for quality assurance of tomotherapy IMRT are feasible in our experience. And helical tomotherapy IMRT QA system has been constituted.
ABSTRACT
Objective To research the structure and principle of Helical Tomotherapy, and study the clinical application value of the equipment system. Methods As the first helical radiotherapy system in the mainland of China, its constructions, structure and principle were analyzed and discussed. Results Helical Tomotherapy is a new kind of radiotherapy equipment. The Hi-Art treatment system is a combination of a LINAC and a CT scanner capable of having the function of both systems. It was approved to achieve the best intensity modulated radiation therapy (IMRT), used for adjusting the setup position of the patient with MVCT and as the basis for dose reconstruction and other adaptive radiotherapy processes. It is the first integrated planning, delivery and verification system for IMRT. Conclusion Image-guided radiation therapy (IGRT) and IMRT have introduced a new era in radiation oncology which will better fight cancer and simultaneously improve the patients' quality of life. Having been designed from the ground up for IGRT and IMRT, the tomotherapy system is in the forefront of technical advancements for efficacy and processes to make it efficiently.
ABSTRACT
Radiotherapy physics is a cross subject that studies and solves the scientific problem referring to medicine treatment based on physics.Ceaseless progresses of Radiotherapy equipments such as Cobait-60 treatment machine,Linear Accelerator,Gama Knife,Tomotherapy have provided comprehensive treatment measures for malignant tumor.Therapies including conformal Radiotherapy,Intensity Modulation Radiotherapy and Gama Knife are progressing and being perfected.Further research should be done on dose fraction.Boron Neutron Capture Therapy and Proton Therapy are being studied.Treatment Plan System and Target Delimitation need perfecting.
ABSTRACT
Objective To analyse the long-term effect of non-small cell lung cancer treated with either postoperative irradiation(group A) or intraoperative radiotherapy(IORT) followed by postoperative irradiation(group B).Methods 154 patients with non-small cell lung carcinoma were randomized into two groups(groups A and B) with 77 patients in each.There were 134 squamous,17 adenocarcinoma and 3 adeno-squamous carcinoma.Seventeen patients had stage Ⅰ,76 stage Ⅱ and 61 stage Ⅲ lesions.The dose of postoperative irradiation in both groups was D_T4060?Gy.In group B,the IORT dose was 15-25?Gy,delivered by 9-16 ?MeV electrons.Results The local control rate was 49% and 62% in groups A and B,respectively(P0.05).Sixteen patients died of radiotherapy-induced complication: 2 in group A and 14 in group B.Conclusions Intraoperative radiotherapy followed by postoperative irradiation can enhance the local control rate of non-small cell lung cancer but can not improve the long term survival. The high complication mortality rate of IORT(18%) in contrast to that(3%) of postoperative radiotherapy is worth noticing.