Engineering topics

Gore, E

Publications and source records attributed to Gore, E.

4 records

DOE OSTI2016

SU-F-R-54: CT-Texture Based Early Tumor Treatment Response Assessment During Radiation Therapy Delivery: Small Cell Versus Non-Small Cell Lung Cancers

Purpose: Tumor treatment response may potentially be assessed during radiation therapy (RT) by analyzing changes in CT-textures. We investigated the different early RT-responses between small cell (SCLC) and non-small cell lung cancer (NSCLC) as assessed by CT-texture. Methods: Daily diagnostic-quality CT acquired during routine CT-guided RT using a CT-on-Rails for 13-NSCLC and 5-SCLC patients were analyzed. These patient had ages ranging from 45–78 and 38–63 years, respectively, for NSCLC and SCLC groups, and tumor-stages ranging from T2-T4, and were treated with either RT or chemotherapy and RT with 45–66Gy/ 20–34 fractions. Gross-tumor volume (GTV) contour was generated on each daily CT by populating GTV contour from simulation to daily CTs with manual editing if necessary. CT-texture parameters, such as Hounsfield Unit (HU) histogram, mean HU, skewness, kurtosis, entropy, and short-run high-gray level emphasis (SRHGLE), were calculated in GTV from each daily CT-set using an in house software tool. Difference in changes of these texture parameters during RT between NSCLC and SCLC was analyzed and compared with GTV volume changes. Results: Radiation-induced changes in CT-texture were different between SCLC and NSCLC. Average changes from first to the last fractions for NSCLC and SCLC in GTV were 28±10(12–44) and 30±15(11–47) HU (mean HU reduction), 12.7% and 18.3% (entropy), 50% and 55% (SRHGLE), 19% and 22% (kurtosis), and 5.2% and 22% (skewness), respectively. Good correlation in kurtosis changes and GTV was seen (R{sup 2}=0.8923) for SCLC, but not for NSCLC (R{sup 2}=0.4748). SCLC had better correlations between GTV volume reduction and entropy (SCLC R{sup 2}=0.847; NSCLC R{sup 2}=0.6485), skewness (SCLC R{sup 2}=0.935; NSCLC R{sup 2}=0.7666), or SRHGLE (SCLC R{sup 2}=0.9619; NSCLC R{sup 2}=0.787). Conclusion: NSCLC and SCLC exhibited different early RT-responses as assessed by CT-texture changes during RT-delivery. The observed larger changes in various CT-texture parameters for SCLC indicate that SCLC may respond to RT more rapid than NSCLC.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-F-J-162: Is Bulky Electron Density Assignment Appropriatefor MRI-Only Based Treatment Planning for Lung Cancer?

Purpose: To assess the appropriateness of bulky electron density assisment for MRI-only treatment planning for lung cancer via comparing dosimetric difference between MRI- and CT-based plans. Methods: Planning 4DCTs acquired for six representative lung cancer patients were used to generate CT-based IMRT plans. To avoid the effect of anatomic difference between CT and MRI, MRI-based plans were generated using CTs by forcing the relative electron density (rED) of organ specific values from ICRU report 46 and using the mean rED value of the internal target volume (ITV) of the patient for the ITV. Both CT and “MRI” plans were generated using a research planning system (Monaco, Elekta) employing Monte Carlo dose calculation the following dose-volume-parameters (DVPs): D99 – dose delivered to 99% of the ITV/PTV volume; D95; D5; D1; Vpd –volume receiving the prescription dose; V5 – volume of normal lung irradiated > 5 Gy; and V20. The percent point difference and dose difference was used for comparison for Vpd-V5-V20 and D99-D1, respectively. Four additional plans per patient were calculated with rEDITV = 0.6 and 1.0 and rEDlung = 0.1 and 0.5. Results: Noticeable differences in the ITV and PTV point doses and DVPs were observed. Variations in Vpd ranged from 0.0–6.4% and 0.32–18.3% for the ITV and PTV, respectively. The ITV and PTV variations in D99, D95, D5 and D1 were 0.15–3.2 Gy. The normal lung V5 & V20 variations were no larger than 1.9%. In some instances, varying the rEDITV between rEDmean, 0.6 and 1.0 resulted in D95 increases ranging from 3.9–6.3%. Uniform rED assignment on normal lung affected DVPs of ITV and PTV by 4.0–9.8% and 0.3–19.6%, respectively. Conclusion: The commonly-used uniform rED assignment in MRI-only based planning may not be appropriate for lung-cancer. A voxel based method, e.g. synthetic CT generated from MRI data, is required. This work was partially funded by Elekta, Inc.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

SU-E-J-31: Monitor Interfractional Variation of Tumor Respiratory Motion Using 4D KV Conebeam Computed Tomography for Stereotactic Body Radiation Therapy of Lung Cancer

Purpose: 4DCT has been widely used to generate internal tumor volume (ITV) for a lung tumor for treatment planning. However, lung tumors may show different respiratory motion on the treatment day. The purpose of this study is to evaluate 4D KV conebeam computed tomography (CBCT) for monitoring tumor interfractional motion variation between simulation and each fraction of stereotactic body radiation therapy (SBRT) for lung cancer. Methods: 4D KV CBCT was acquired with the Elekta XVI system. The accuracy of 4D KV CBCT for image-guided radiation therapy (IGRT) was tested with a dynamic thorax motion phantom (CIRS, Virginia) with a linear amplitude of 2 cm. In addition, an adult anthropomorphic phantom (Alderson, Rando) with optically stimulated luminescence (OSL) dosimeters embedded at the center and periphery of a slab of solid water was used to measure the dose of 4D KV CBCT and to compare it with the dose with 3D KV CBCT. The image registration was performed by aligning\ each phase images of 4D KV CBCT to the planning images and the final couch shifts were calculated as a mean of all these individual shifts along each direction.A workflow was established based on these quality assurance tests for lung cancer patients. Results: 4D KV CBCT does not increase imaging dose in comparison to 3D KV CBCT. Acquisition of 4D KV CBCT is 4 minutes as compared to 2 minutes for 3D KV CBCT. Most of patients showed a small daily variation of tumor respiratory motion about 2 mm. However, some patients may have more than 5 mm variations of tumor respiratory motion. Conclusion: The radiation dose does not increase with 4D KV CBCT. 4D KV CBCT is a useful tool for monitoring interfractional variations of tumor respiratory motion before SBRT of lung cancer patients.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

SU-E-J-134: Optimizing Technical Parameters for Using Atlas Based Automatic Segmentation for Evaluation of Contour Accuracy Experience with Cardiac Structures From NRG Oncology/RTOG 0617

Purpose: Accurate contour delineation is crucial for radiotherapy. Atlas based automatic segmentation tools can be used to increase the efficiency of contour accuracy evaluation. This study aims to optimize technical parameters utilized in the tool by exploring the impact of library size and atlas number on the accuracy of cardiac contour evaluation. Methods: Patient CT DICOMs from RTOG 0617 were used for this study. Five experienced physicians delineated the cardiac structures including pericardium, atria and ventricles following an atlas guideline. The consistency of cardiac structured delineation using the atlas guideline was verified by a study with four observers and seventeen patients. The CT and cardiac structure DICOM files were then used for the ABAS technique.To study the impact of library size (LS) and atlas number (AN) on automatic contour accuracy, automatic contours were generated with varied technique parameters for five randomly selected patients. Three LS (20, 60, and 100) were studied using commercially available software. The AN was four, recommended by the manufacturer. Using the manual contour as the gold standard, Dice Similarity Coefficient (DSC) was calculated between the manual and automatic contours. Five-patient averaged DSCs were calculated for comparison for each cardiac structure.In order to study the impact of AN, the LS was set 100, and AN was tested from one to five. The five-patient averaged DSCs were also calculated for each cardiac structure. Results: DSC values are highest when LS is 100 and AN is four. The DSC is 0.90±0.02 for pericardium, 0.75±0.06 for atria, and 0.86±0.02 for ventricles. Conclusion: By comparing DSC values, the combination AN=4 and LS=100 gives the best performance. This project was supported by NCI grants U24CA12014, U24CA180803, U10CA180868, U10CA180822, PA CURE grant and Bristol-Myers Squibb and Eli Lilly.

60 APPLIED LIFE SCIENCES↗