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Background and purpose: Radiation therapy has entered the era of precise radiotherapy. Set-up error becomes important factor affecting the effects of radiotherapy. The aim of this study was to analyze the set-up accuracy of the in-house developed technique of body plate with vacuum cushion and thermoplastic mask (Group A) and the conventional technique of arm support (Group B) in thoracic tumor radiotherapy. Methods: A total of 19 patients with thoracic tumor were enrolled in this study and randomly separated into Group A and Group B. The patients of Group A underwent the secondary set-up: align the marker on vacuum cushion and patient's body to the room laser, cover the patient's body with thermoplastic mask and align the marker on the mask to the room laser. The patients of Group B were directly setup by aligning the marker on the patient's body to the room laser. The kilo-voltage cone beam computed tomography (KV-CBCT) was performed on each patient to collect the pre- and post-treatment CBCT images. The CBCT images were registered to the planning CT to analyze the translational error of Group A and Group B. Results: The pre-treatment set-up errors of Group A vs Group B were (1.06±0.58) vs (1.82±0.82) mm in left and right (LR) direction, (1.31±0.40) vs (2.18±1.20) mm in superior and inferior (SI) direction, and (1.28±0.66) vs (2.94±1.81) mm in anterior and posterior (AP) direction. The post-treatment set-up errors of Group A vs Group B were (0.86±0.54) vs (1.29±0.58) mm in LR direction, (1.07±0.58) vs (1.08±0.45) mm in SI direction, and (0.98±0.53) vs (1.56±0.63) mm in AP direction.Conclusion: The in-house developed immobilization technique of body plate with vacuum cushion and thermoplastic mask was more accurate and reproducible than the conventional immobilization technique of arm support in thoracic tumor radiotherapy.
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Objective To investigate the dose calculation accuracy and feasibility of using kilovoltage cone-beam CT (KVCBCT) for esophageal cancer radiotherapy.Methods Hounsfield unit (HU) values and profile along the horizontal line of Catphan (R) 600 phantom in KVCBCT images acquired on Trilogy linear accelerator were compared to those in the planning CT.The KVCBCT value-density calibration curve was established.The intensity modulated radiotherapy plans were created on the planning CT images and copied to KVCBCT images.The dose distribution was recalculated by means of the KVCBCT value-density calibration curve in the treatment planning system.The dosimetric comparisons were performed between the KVCBCT and planning CT plans on the phantom and 10 patients with esophageal cancer.ResultsThe KVCBCT value was stable with a maximum variation of 1.6％,and there was no significant time trend.CT value profiles showed good agreement within 1％ variation except the peripheral regions.The dosimetric differences were less than 1.33％and 3.65％for the phantom case and the patient ones,respectively.The dose distribution comparison was also in good agreements.Conclusions The accurate dose caleulation based on KVCBCT for esophageal cancer is feasible.The KVCBCT images can be used for monitoring the dosimetric changes during the treatment.
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Objective To investigate the advantage of the intensity-modulated radiotherapy treatment (IMRT) by allowing dose heterogeneity in the target volume in esophageal cancer treatment planning.Methods Two sets of 5-field IMRT planning were designed for 10 esophageal cancer patients upon the condition of appropriate clinical tolerance level with the prescription dose of 60 Gy to 95% of the planned target volume (PTV) and the maximum dose of 45 Gy to the spinal cord:the IMRT with rigid restriction of the maximum homogeneous dose to the PTV within 63 Gy prescribing a homogeneous dose ( IMRThom ) and the IMRT allowing dose heterogeneity by loosening the constraints on maximum dose in the PTV to 69 Gy ( IMRTinhom ).Dosimetric comparison was conducted by using dose-volume histograms.Results Compared to IMRThom, the minimum dose (t = -3.37,P =0.012), maximum dose (t = - 23.58,P = 0.000), mean dose ( t = - 4.95, P = 0.002 ), and heterogeneity index ( t = - 11.06, P =0.000) in PTV of the IMRTinhom were all significantly increased, and the values of V5 (t = 6.96, P =0.000), V10(t=5.24,P=0.001) , V15(t=4.73,P=0.002) , V20(t=8.08,P=0.000) , V25(t=8.58,P = 0.000), and mean dose (t = 7.28,P = 0.000) of the normal lungs were all significantly lower.There were no significant differences in all the indexes for the mean dose to the heart and maximum dose to the spinal cord between these 2 set of planning.Conclusions The IMRT plan allowing dose heterogeneity in the PTV escalates the prescription dose and decreases the doses to the lungs.
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Objective To assess the rotational set-up errors in patients with thoracic neoplasms. Methods 224 kilovohage cone-beam computed tomography (KVCBCT) scans from 20 thoracic tumor pa-tients were evaluated retrospectively. All these patients were involved in the research of " Evaluation of the residual set-up error for online kilovohage cone-beam CT guided thoracic tumor radiation". Rotational set-up errors, including pitch, roll and yaw, were calculated by 'aligning the KVCBCT with the planning CT, using the semi-automatic alignment method. Results The average rotational set-up errors were -0.28°±1.52°, 0.21°± 0.91° and 0.27°± 0. 78° in the left-fight, superior-inferior and anterior-posterior axis, respective-ly. The maximal rotational errors of pitch, roll and yaw were 3.5°, 2.7° and 2.2°, respectively. After cor-rection for translational set-up errors, no statistically significant changes in rotational error were observed. Conclusions The rotational set-up errors in patients with thoracic neoplasms were all small in magnitude. Rotational errors may not change after the correction for translational set-up errors alone, which should be e-valuated in a larger sample future.
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Objective To select the optimal registration method for on-line kilovoltage cone-beam CT (KVCBCT) guided lung cancer radiation and evaluate the reproducibility of the selected method. MethodsSixteen patients with non-small cell lung cancer were enrolled into this study.A total of 96 pre treatment KVCBCT images from the 16 patients were available for the analysis.Image registration methods were bone-based automatic registration,gray-based automatic registration,manual registration and semi-auto matic registration.All registrations were accomplished by one physician.Another physician blindly evaluated the results of each registration,then selected the optimal registration method and evaluated its reproducibili ty.Results The average score of the bone-based automatic registration,gray-based automatic registration, manual registration and semi-automatic registration methods was 2.4,2.7,3.0 and 3.7,respectively.The score of the four different groups had statistics significant difference (F = 42.20,P < 0.001).Using the semi-automatic registration method,the probability of the difference between two registration results more than 3 ram in the left-right,superior-inferior,and anterior-posterior directions was 0,3% and 6% by the same physician,0,14% and 0 by different physicians,and 8%,14% and 8% by physician and radiation therapist.Conclusions Semi-automatic registration method,possessing the highest score and accepted re producibility,is appropriate for KVCBCT guided lung cancer radiation.
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Objective To observe the results and side effects of radiotherapy(RT) combined with hyperthermia(HT) for non-small cell lung cancer(NSCLC)with lesion(T) ≥5?cm in diameter.Methods Patients conforming to T≥5?cm or T volume ≥125?cm~3 in the lung and other required eligibilities were given RT and HT.The temperature of HT in the center of Ts was automatically programmed between 43.0℃ and 43.5℃ by a computer.RT dose of D_T60-66?Gy was delivered in 30-33 fractions with in 1 hour after HT.Results From October 2001 to April 2004,30 patients were registered for this study.Among all patients,23 males and 7 female with median age of 61 years(32-81);22 squamous cancer and 8 adenocarcinoma type;6 stage Ⅰb,1 Ⅱb,10 Ⅲa,8 Ⅲb and 5 Ⅳ lesions.The mean volumes of T was 275.45?cm~3(125-900?cm~3).The mean number of HT given was 7.2 times(2-14).The mean irradiation dose was 59.10?Gy(23.96-9.67?Gy).Five out of 30 patients were dropped from this trial due to reasons un-related to acute side effects of RT or HT.None complained of breathlessness or aggravation of respiratory symptom during heating.No change had been observed in blood pressure,pulse or frequency of breath before or after HT,nor was there any hardening of subcutaneous fatty tissue as well as lipid nodules or severer than grade Ⅲ acute irradiation side effects.Complete response was observed in 23%,partial response in 50%,no change or progression in 27%.Loco-regional control rate was 83% with a median of median locoregional duration of 19.2 months.Eleven patients had died,including 2 of hemoptysis.The median survival duration was 19.7 months and 1-year survival rate was 75%.Conclusions Radiotherapy combined with hyperthermia modal can be used for NSCLC with primary lesion≥5?cm as it carries better efficiency and loco-regional control without server side effects.