SU-E-T-620: Effect of Different Motion Management Strategies in Liver Cancer Using Four-Dimesional Computed Tomography Image and Active Breathing Control Technology
0
Citation
0
Reference
10
Related Paper
Abstract:
Purpose: To evaluate patients Dose Volume Histogram (DVH) parameters in cummulative healthy liver dose using four-dimesional computed tomography (4DCT) image and active breathing control (ABC) manner. Methods: Ten liver cancer patients were analysed retrospectively. The static plan was designed on reference CT image from the free breathing status scanning and the organ at risk(OAR) dose were evaluated.The tracking accumulative dose were calculated on 10 different breathing phases of 4DCT based on relative time weight. The mean healthy liver dose were calculated in different exhale and inhale breath hold using ABC technology. Three motion management strategies plans were compared and analysed. Results: The maxinum difference of mean healthy liver dose in 4DCT image was 9.5% between phase 10 and phase 60. The largest absolute dose in mean healthy liver was 5.05Gy between the tracking dose and the deep inhale breath hold(P﹤0.05). The difference using ABC between the deep inhale and exhale breah hold was maximum 1.45Gy and no significance was obsered between the calm inhale and exhale breah hold. Also there was no signifcance between the target tracking and any breath phase in 4DCT image. Conclusions: The target tracking dose was the actual dilevered dose to the patient. The difference in breath hold and the target tracking dose was significantly. Therefore, We suggest the deep inhale breath hold was used in the liver radiotherapy treatment using ABC technology. However, we needed more patients to further study to get the more accurate result.Keywords:
Image-guided radiation therapy
Dose-volume histogram
Liver Cancer
Computed radiography
Dose-volume histogram
Cite
Citations (125)
The first quality assurance process for validating dose-volume histogram data involving brachytherapy procedures in radiation therapy is presented. The process is demonstrated using both low dose-rate and high dose-rate radionuclide sources. A rectangular cuboid was contoured in five commercially available brachytherapy treatment planning systems. A single radioactive source commissioned for QA testing was positioned coplanar and concentric with one end. Using the brachytherapy dosimetry formalism defined in the AAPM Task Group 43 report series, calculations were performed to estimate dose deposition in partial volumes of the cuboid structure. The point-source approximation was used for a 125I source and the line-source approximation was used for a 192Ir source in simulated permanent and temporary implants, respectively. Hand-calculated, dose-volume results were compared to TPS-generated, dose-volume histogram (DVH) data to ascertain acceptance. The average disagreement observed between hand calculations and the treatment planning system DVH was less than 1% for the five treatment planning systems and less than 5% for 1 cm ≤ r ≤ 5 cm. A reproducible method for verifying the accuracy of volumetric statistics from a radiation therapy TPS can be employed. The process satisfies QA requirements for TPS commissioning, upgrading, and annual testing. We suggest that investigations be performed if the DVH %Vol(TPS) "actual variance" calculations differ by more than 5% at any specific radial distance with respect to %Vol(TG-43), or if the "average variance" DVH %Vol(TPS) calculations differ by more than 2% over all radial distances with respect to %Vol(TG-43).
Dose-volume histogram
Cuboid
Cite
Citations (10)
Dose-volume histogram
Left breast
Cite
Citations (0)
Dose-volume histograms provide key information to radiation oncologists when they assess the adequacy of a patient treatment plan in radiation therapy. It is important therefore that all clinically relevant data be accurate. In this article we present the first quality assurance routine involving a direct comparison of planning system results with the results obtained from independent hand calculations. Given a known three-dimensional (3-D) structure such as a parallelepiped, a simple beam arrangement, and known physics beam data, a time-efficient and reproducible method for verifying the accuracy of volumetric statistics (DVH) from a radiation therapy treatment planning system (TPS) can be employed rapidly, satisfying the QA requirements for (TPS) commissioning, upgrades, and annual checks. Using this method, the maximum disagreement was only 1.7% for 6 MV and 1.3% for 18 MV photon energies. The average accuracy was within 0.6% for 6 MV and 0.4% for 18 MV for all depth-dose results. A 2% disagreement was observed with the treatment planning system DVH from defined volume comparison to the known structure dimensions.
Dose-volume histogram
Parallelepiped
Cite
Citations (6)
Objective To compare the dosimetric difference in planning target volume(PTV)and organ at risk(OAR)with conventional and the three-dimensional treatment planning for limlted-stage small cell lung cancer.Methods Ten patients with limited-stage small cell lung cancer were chosen in the present study.Two treatment planning were designed twice respectively with the Cadplan R 3.1.2 treatment planning system for each patient in two-course.The total radiation dose was 50 Gy.The dosimetric parameters were assessed with dose volume histograms in PIT and OAR.Results For the first course,the dose homogeneity indices(HI)of PTV1,conformal indices(CI)of PTV2,contralateral lung V3o and eontralateral mean lung dose in the three-dimensional treatment planning were better than that in the conventional treatment planning.For the second course,the HI,CI and mean dose of PTV1,CI and mean dose of PTV2 in the three-dimensional treatment planning were better than that in the conventional treatment planning.Conclusions By comparison with conventional treatment planning,the three-dimensional conformal treatment planning could meet the demands of dosimetrie requirements well for limited-stage small cell lung cancer with three-dimensional conformal radiotherapy,but with no significant dnsimetric differences in the OAR.
Key words:
Limited-stage small cell lung cancer; Three dimensional eonformal radiotherapy; Conventional radiotherapy; Dose volume histograms
Dose-volume histogram
Cite
Citations (0)
This study evaluated the gating-based 4-D conformal radiation therapy (4D-CT) treatment planning by a comparison with the common 3-D conformal radiation therapy (3D-CT) treatment planning and examined the change in treatment field size and dose to the tumors and adjacent normal tissues because an unnecessary dose is also included in the 3-D treatment planning for the radiation treatment of tumors in the chest and abdomen. The 3D-CT and gating-based 4D-CT images were obtained from patients who had undergone radiation treatment for chest and abdomen tumors in the oncology department. After establishing a treatment plan, the CT treatment and planning system were used to measure the change in field size for analysis. A dose volume histogram (DVH) was used to calculate the appropriate dose to planning target volume (PTV) tumors and adjacent normal tissue. The difference in the treatment volume of the chest was 0.6 and 0.83 cm on the X- and Y-axis, respectively, for the gross tumor volume (GTV). Accordingly, the values in the 4D-CT treatment planning were smaller and the dose was more concentrated by 2.7% and 0.9% on the GTV and clinical target volume (CTV), respectively. The normal tissues in the surrounding normal tissues were reduced by 3.0%, 7.2%, 0.4%, 1.7%, 2.6% and 0.2% in the bronchus, chest wall, esophagus, heart, lung and spinal cord, respectively. The difference in the treatment volume of the abdomen was 0.72 cm on the X-axis and 0.51 cm on the Y-axis for the GTV; and 1.06 cm on the X-axis and 1.85 cm on the Y-axis for the PTV. Therefore, the values in the 4D-CT treatment planning were smaller. The dose was concentrated by 6.8% and 4.3% on the GTV and PTV, respectively, whereas the adjacent normal tissues in the cord, Lt. kidney, Rt. kidney, small bowels and whole liver were reduced by 3.2%, 4.2%, 1.5%, 6.2% and 12.7%, respectively. The treatment field size was smaller in volume in the case of the 4D-CT treatment planning. In the DVH, the 4D-CT treatment planning showed a higher dose concentration on the part to be treated than the 3D-CT treatment planning with a lower dose to the adjacent normal tissues. Overall, the gating-based 4D-CT treatment planning is believed to be more helpful than the 3D-CT treatment planning.
Dose-volume histogram
Cite
Citations (0)
Thorax (insect anatomy)
Dose-volume histogram
Cite
Citations (17)
To analyse the frequency of re-planning and its variability dependent on the IGRT correction strategy and on the modification of the dosimetric criteria for re-planning for the spinal cord in head and neck IG-IMRT. Daily kV-control-CTs of six head and neck patients (=175 CTs) were analysed. All volumes of interest were re-contoured using deformable image registration. Three IGRT correction strategies were simulated and the resulting dose distributions were computed for all fractions. Different sets of criteria with varying dose thresholds for re-planning were investigated. All sets of criteria ensure equivalent target coverage of both CTVs, but vary in the tolerance threshold of the spinal cord. The variations of the D95 and D2 in respect to the planned values ranged from -7% to +3% for both CTVs, and -2% to +6% for the spinal cord. Despite different correction vectors of the three IGRT strategies, the dosimetric differences were small. The number of fractions not requiring re-planning varied between 0% and 11% dependent on the applied IGRT correction strategy. In contrast, this number ranged between 32% and 70% dependent on the dosimetric thresholds, even though these thresholds were only gently modified. The more precise the planned dose needs to be maintained over the treatment course, the more frequently re-planning is required. The influence of different IGRT correction strategies, even though geometrically notable, was found to be of only limited relevance for the re-planning frequency. In contrast, the definition and modification of thresholds for re-planning have a major impact on the re-planning frequency.
Image-guided radiation therapy
Cite
Citations (16)
Objective
To develop an automatic algorithm to predict the dose-volume histogram (DVH) and implement it in clinical practice.
Methods
Based on the prior information in the existing plan, such as dosimetric results of organs at risk (OARs) and OAR-target spatial relationship, a two-dimensional kernel density estimation was implemented to predict the DVH of OARs. The predicted DVH curves were converted into objective functions that would be implemented in the Pinnacle treatment planning system. Comparisons between predicted and actual values and between Auto-plan and manual planning were made by paired t test.
Results
We applied this algorithm to 10 rectal cancer patients, 10 breast cancer patients, and 10 nasopharyngeal carcinoma patients. The predicted DVH of OARs showed that the deviation between the actual and predicted values at important clinical dose points were within 5%(P>0.05). The re-planning for the 10 breast cancer patients using Auto-plan showed that the heart dose was significantly reduced and the target coverage was increased, which was consistent with the predicted results.
Conclusions
The method proposed in this study allows for accurat DVH prediction, and, combined with Auto-plan, can be used to generate clinically accepted treatment plans.
Key words:
Intensity modulated radiation therapy; Dose volume histogram; Kernel density estimation; Automatic treatment planning
Pinnacle
Dose-volume histogram
Kernel (algebra)
Cite
Citations (0)
The normal tissue complication probability (NTCP) is a predictor of radiobiological effect for organs at risk (OAR). The calculation of the NTCP is based on the dose‐volume‐histogram (DVH) which is generated by the treatment planning system after calculation of the 3D dose distribution. Including the NTCP in the objective function for intensity modulated radiation therapy (IMRT) plan optimization would make the planning more effective in reducing the postradiation effects. However, doing so would lengthen the total planning time. The purpose of this work is to establish a method for NTCP determination, independent of a DVH calculation, as a quality assurance check and also as a mean of improving the treatment planning efficiency. In the study, the CTs of ten randomly selected prostate patients were used. IMRT optimization was performed with a PINNACLE 3 V 6.2b planning system, using planning target volume (PTV) with margins in the range of . The DVH control points of the PTV and OAR were adapted from the prescriptions of Radiation Therapy Oncology Group protocol P‐0126 for an escalated prescribed dose of . This paper presents a new model for the determination of the rectal NTCP . The method uses a special function, named GVN (from G y, V olume, N TCP), which describes the if of the volume of intersection of the PTV and rectum is irradiated uniformly by a dose of . The function was “geometrically” normalized using a prostate‐prostate ratio (PPR) of the patients’ prostates. A correction of the for different prescribed doses, ranging from , was employed in our model. The argument of the normalized function is the , and parameters are the prescribed dose, prostate volume, PTV margin, and PPR. The of another group of patients were calculated by the new method and the resulting difference was in comparison to the NTCP calculated by the PINNACLE 3 software where Kutcher's dose‐response model for NTCP calculation is adopted.
Dose-volume histogram
Pinnacle
Tomotherapy
Cite
Citations (11)