bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐J‐117: Assessing Response to Radiochemotherapy Treatment On 18F‐FDG PET in Non‐Small Cell Lung Cancer Using Approaches of Histogram and Gray Level Co‐Occurrence Matrix
Authors: Ma C
Published: July 2013

Purpose: The aim of this study was to propose and investigate gray level histogram and texture features information provided by 18F‐FDG PET to assess patients imaging response to radiochemotherapy in non‐small cell lung cancer (NSCLC). Methods: Twelve patients with newly diagnosed NSCLC treated with combined radiochemotherapy were involved in this study. Patients were categorized under three headings (non‐responders, partial responders and complete responders) by experienced radiologists on the basis of RECIST according PET scans changes between pretreatment and 1 month after treatment. We analyzed the percentage variation of PET density using histogram analysis approach which characterizes global change of tumor region on PET. Texture parameters variation between pretreatment and 1 month after treatment completion which describe local voxel spatial distribution were extracted from Gray Level Co‐occurrence Matrix (GLCM). Correlation between characteristics variation and three type response status were analyzed. Results: The uniformity of gray level histogram on the whole and the maximum percentage decrease in histogram was well associated with tumor shrinkage and response status. The above indices derived from histogram were capable to differentiate three groups tumor response to radiochemotherapy. Texture parameters variation (ASM, ENT and IDM) were able to differentiate the 3 response groups considering a high correlation with response status. Conclusion: We demonstrated that histogram and texture analysis methods on baseline 18F‐FDG PET scans provided robust, discriminative stratification in assessing response to combined radiochemotherapy and may have a good application prospect in clinical practice.
SU‐E‐J‐119: Geometric Accuracy Verification for Gated RapidArc Using Gated CBCT Reconstructed From Continuously Triggered KV Images
Authors: Cheung Michael LM , Lee Louis KY , Kam Michael KM , Yu Brian KH , Chan Anthony TC
Published: July 2013

Purpose: To develop a method using continuously triggered kV images acquired during gated RapidArc to reconstruct a gated CBCT for geometric accuracy verification of a moving target. Methods: A gated RapidArc treatment was planned to be delivered to a commercial breathing simulation phantom embedded with metallic markers using a Varian TrueBeam™ linear accelerator. The phantom was setup to the treatment position using 2D/2D match followed by marker match IGRT procedure. Continuously triggered on‐board‐imager kV images were taken immediately before each MV beam on cycle at various gantry angles during the gated RapidArc delivery. The kV images obtained were imported into an in‐house developed software to reconstruct a gated CBCT corresponding to the beam on triggering phase. The gated CBCT was then imported into a commercial treatment planning system. The geometric displacement of the target in the gated CBCT from its counterpart in the planning CT was determined through image registration based on marker alignment. The entire process was repeated 10 times using a variety of target movement magnitudes in the range of 1cm to 3cm and periods in the range of 4s to 8s. Results: The magnitude of the translational shifts of the target at the beam on triggering phase was 0.18+/−0.11mm in left/right direction, 0.38+/−0.15mm in anterior/posterior direction and 0.56+/−0.19mm in the superior/inferior direction. The composite 3D translational shift was 0.74+/−0.12mm. Conclusion: Gated CBCT reconstruction could be a practical and efficient way of utilizing continuously triggered kV images acquired during gated RapidArc treatments to verify geometric accuracy of a moving target.
SU‐E‐J‐124: Prediction of the Characteristics of Moving Lung Tumor in CBCT Imaging Using Virtual CBCT Image Simulated From 4‐D CT Dataset
Authors: Li X , Li T , Yang Y , Zhang Y , Heron D , Huq M
Published: July 2013

Purpose: Due to the slow scanning speed of on‐board CBCT imaging, the characteristics of moving lung tumor acquired by such system could be complicated. Recent phantom studies have shown that the maximum intensity projection (MIP) image, which was used for target delineation in treatment planning, might overestimate the target volume determined by CBCT imaging. The purpose of this study is to propose a new strategy to predict the characteristics of moving lung tumor in CBCT imaging. Methods: Six non‐small‐cell‐lung cancer (NSCLC) patients were retrospectively selected in this study. All patients underwent 4D CT scan using GE LightSpeed scanner under audio coaching. The respiratory motion of all patients ranged from 7.5mm to 12.5mm. For each patient, ten sets of phase‐sorted CT images and a MIP image including all respiratory phases were acquired. To simulate the respiratory motion effect in CBCT imaging, 4‐D projection images were generated using ray‐tracing algorithm based on the 3‐D CT images of the corresponding phase at each gantry angle. Filtered‐back‐projection algorithm was used to reconstruct this simulated virtual CBCT (SVCBCT) image. The targets were then contoured at the MIP image, SVCBCT image and the clinic CBCT image acquired at first treatment, respectively. Results: For the three cases volume differences between SVCBCT and MIP image were less than 5%. For the other three cases the target volume determined by SVCBCT image were 30%∼62% less than that of MIP image, and the distance of target center between those two images could be up to 6mm. In comparison, for all patients, the volume differences between SVCBCT and CBCT were all less than 4%. Conclusion: The characteristics of a moving lung tumor determined by CBCT imaging are highly dependent on the specific respiratory motion pattern of each patient, and could be well predicted by SVCBCT image.
SU‐E‐J‐125: Influence of Contouring Style On Accuracy of Atlas‐Based Auto‐Contouring
Authors: Stevenson G , Durrant L , Eccles C , Chu K , Kadir T , Gooding M
Published: July 2013

Purpose: This study aims to investigate the impact of atlas‐based auto‐contouring upon the accuracy of contouring for operators with varying training and familiarity with a particular contouring convention. Methods: A set of ten head and neck CT datasets were contoured by Contourer 1 and validated by another expert clinician. A single dataset was selected to serve as an atlas to auto‐contour the remaining nine cases using commercial deformable image registration software (Mirada RTx, Mirada Medical, UK). For each of these nine cases, the brainstem, spinal cord, all parotid and submandibular glands were independently contoured by Contourers 1, 2 and 3 (a) manually from scratch and (b) by editing the auto‐contours. Contourer 2 was familiar with the contouring convention of the atlas whilst Contourer 3 was not. Dice similarity coefficient (DSC) was used to compare manual contours and the edited contours against the original contours of Contourer 1 . Results: Mean DSC for all structures for Contourers 1, 2 and 3 were 0.89, 0.85 and 0.66 for the scratch contours and 0.87, 0.84 and 0.74 for the edited auto‐contours. The greatest effect of using the auto‐contours for Contourer 3 DSC occurred for the parotids (0.52 to 0.67) and submandibular glands (0.77 to 0.85) and the least for the brainstem (0.84 to 0.85) and cord (0.55 to 0.55). Conclusion: Atlas‐based auto‐contouring using deformable image registration was found to improve the accuracy of Contourer 3 only and only for the parotids and submandibular glands. DSC for Contourers 1 and 2 are largely unaffected by auto‐contours. This suggests that familiarity with contouring convention, or lack thereof, is an important factor in assessing auto‐contouring efficacy but that auto‐contouring may improve accuracy to a standard. Within a clinical setting, or for clinical trials, atlas‐based contouring may have benefit in training and quality assurance in developing consensus. G.S,M.G and T.K are employees of Mirada Medical and there was no conflict of interest with the research submitted.
SU‐E‐J‐128: Setup Variation in Deep Inspiration Breath‐Hold for Radiotherapy of Breast Cancer Tumor Bed Assessed with RPM‐Guided CBCT
Authors: Shen S , Duan J , Keene K , Yuan Y , Klepczyk L , Meredith R
Published: July 2013

Purpose: Deep inspiration breath hold (DIBH) can reduce irradiated cardiac volume during tangential left breast radiotherapy. Commonly the setup position for DIBH is verified using gated on‐board orthogonal kV imaging (OBI) of the rib cage. This study assessed positional variation of the tumor bed in the boost treatment with gated orthogonal kV image‐guided setup and CBCT. Methods: 8 patients with median age of 66 (57–85), received a boost dose to the tumor bed in the left breast. After setup positions were aligned using gated orthogonal kV imaging, RPM system‐guided, voluntary DIBH, CBCTs were acquired in 2 DIBH of 30 sec or 3 DIBH of 20 sec. Positional difference of the tumor bed between the planning CT and CBCT were assessed. Results: Left breast volume range was 611–2184 cm3 among 8 patients. Positional change in tumor bed was 0–1.5 cm lateral, 0–2.5 cm vertical, and 0–0.7 cm longitudinal, resulting in 0.4−3.0 cm 3D positional change. The magnitude of 3D positional change was associated with breast volume (r=0.83). The magnitude increased as breast volume increased, with a change of ∼ 1.5 cm for a breast volume of ∼ 1500 cm3. Conclusion: Feedback‐guided, DIBH CBCT can be used to verify tumor bed position for boost treatment. DIBH setup using gated orthogonal kV imaging may be adequate for patients with small breasts. More data are needed for this ongoing study to establish the minimum breast volume for which by DIBH CBCT guided setup becomes necessary.
SU‐E‐J‐129: Dosimetric Impact of Interfractional Anatomy Changes On Breast Radiotherapy Based On Accumulative Dose: IMRT Versus 3DCRT
Authors: Morrow N , Ahunbay E , Currey A , Li X
Published: July 2013

Purpose: Interfractional anatomy changes (e.g., changes in breast shape and volume) in breast radiotherapy (RT) can be significant and cannot be fully accounted for by the current IGRT repositioning practice. This work aims to quantify dosimetric impact of these changes based on accumulative dose for IMRT and 3DCRT. Methods: Daily CT data acquired using a CT‐on‐Rails (CTVision, Siemens) during IGRT for 5 representative breast cancer patients treated in prone position were analyzed. Each daily CT was registered with corresponding planning CT by aligning the lumpectomy cavity, mimicking the IGRT repositioning. Contours of breast, lumpectomy PTV and critical structures on daily CTs were generated using an auto‐segmentation tool (ABAS, Elekta) based on deformable image registration. For each patient, plans for IMRT and 3DCRT with wedge were developed, and were applied to each registered daily CT set to reconstruct the daily doses with the deformation fields from ABAS which were used to compute the accumulative dose. Results: Daily variations in D95 (dose received by 95% of treated breast volume) and D50 were not significantly different between 3DCRT and IMRT plans (within 0.5–2%). Variation of daily dose maximum for IMRT was statistically significantly higher than that for the 3DCRT plans, with some fractions increased by up to 15–20%. However, the variations of the accumulated doses from the original plans for both 3DCRT and IMRT plans are comparable. Conclusion: Although daily doses from IMRT are more sensitive to the interfractional anatomy changes than those from 3DCRT, the variations of the accumulated doses from the original plans are comparable, as the higher variation in the hot spots for IMRT were “washed out” due to the random interfractional changes.
SU‐E‐J‐133: The Comparison of Modified Demons Algorithm and FFD Algorithm Based On B‐Spline and Analysis of Morphology of Normal Liver and Tumor by Breathing Motion
Authors: Gong G , wang H , Yin Y
Published: July 2013

Purpose: Through comparing the modified demons algorithm and FFD algorithm based on B‐spline, and combing four‐dimensional computed tomography (4D‐CT), we discussed the morphology of normal liver and tumor by breathing motion of hepatocellular carcinoma patients. Methods: 8 hepatocellular carcinoma (HCC) patients accepted radiotherapy and TACE was selected, the simulate positioning was in four‐dimensional computed tomography (4D‐CT) pattern and 4D‐CT images were segmented into 10‐series CT images which were named CT0, CT10 to CT80, CT90 according to the respiratory phases. We used the modified demons algorithm and FFD algorithm based on B‐spline respectively to deform the images, and the end‐exhale image CT50 was the reference image. The normalized mutual information (NMI), hausdorff distance (NMI) and time consuming were used to verify the performance of the registration methods. Results: The average NMI for the end‐inhale and end‐exhale images of 8 HCC patients after demons registration method in mode 1 improved 1.76% comparing with that in mode 2 and 4.75% improving than FFD algorithm. And the difference of after demons method reduced 15.2% comparing with FFD model algorithm. In addition, demons algorithm has the absolute advantage in time consuming. Conclusion: The breathing movement for deformation of normal liver and tumor targets is significant, and the modified demons registration method can deform 4D‐CT images effectively.
SU‐E‐J‐134: Development of the 4D Cone‐Beam CT Modelling Software to Investigate Effects of Imaging Parameters
Authors: Kim D , Kim T , Kang S , Suh T
Published: July 2013

Purpose: Four‐dimensional (4D) cone‐beam computed tomography (CBCT) is an adaptive imaging technique which can be improved x‐ray beam delivery accuracy during radiation therapy accompanied organ motions by respiration. However, a major drawback to the technique is that 4D CBCT image quality is affected by several parameters. Therefore, in this study, we implemented a preliminary study that developed a predictive modeling software for investigating effects of applied parameters to 4D CBCT imaging. Methods: The 4D CBCT imaging parameters in this software such as related with geometry, projection data acquisition, and image reconstruction can be selected arbitrarily by user. The software provides digital phantom projection images applied input a practical or virtual respiratory signal if real projections do not exist. The projection images and the signal amplitudes were sorted into ten phase bins ranging from 0% to 90% in this simulation. We employed Feldkamp‐Davis‐Kress (FDK) algorithm based on filtered backprojection (FBP) as a reconstruction method. Results: The program could provide projection images, 4D CBCT reconstruction images, internal target volume and quantitative values for residual motion in each phase. Conclusion: The developed program would be useful to verify quantitatively for effects of 4D CBCT imaging parameters and target motions. In addition, it is possible to simulate without heavy workload for experimental set‐up. This program was supported by the program of Basic Atomic Energy Research Institute (BAERI) which is a part of the Nuclear R and D programs (No. 20120004886) funded by the Ministry of Education, Science and Technology (MEST) and a grant (No. 2012K001141) from the Korea Heavy‐ion Medical Accelerator project grant funded by the Ministry of Education, Science and Technology (MEST) and Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea(NRF)(No.2009‐00420) funded by the Ministry of Education, Science and Technology (MEST) of Korea.
SU‐E‐J‐137: Hybrid EOE and EOI Dynamic Gating for Effective Image Guided Radiation Treatment
Authors: Yan R , Wu H
Published: July 2013

Purpose: Respiratory gating can potentially reduce normal tissue complications and increase tumor local control, however, with prolonged treatment delivery time. To enhance the efficiency of beam delivery, dynamic hybrid gating approaches have been proposed. Methods: Three approaches have been proposed and they are differ when to update the gating window. (1) to update the gating window whenever a peak EOI (end‐of‐inhale) is not in the current gating window; (2)to update the gating window whenever a new peak EOI is identified, where weighting factors will be used to determine gating window position. The variations of the sliding windows of previously acquired data used in gating window determination have also been investigated. Evaluation metrics, including duty cycle, beam delivery time, beam toggling rate, and their changes have been quantified and compared along with static EOE (end‐of‐exhale) gating and static hybrid EOE‐and‐EOI gating. Results: Simulated over motion data of 400 treatment fractions from 15 patients have been performed. For static gating, gating window sizes of 2, 3, 4, and 5 mm have been performed. Duty cycles of both EOE and EOI gating increase with the gating window sizes, with EOE gating triples EOI gating. The beam toggling rate of EOI gating is lower than that of EOE gating. With hybrid dynamic gating, the mean beam delivery time was decreased by more than 25% from static EOE gating to static hybrid gating and over 5% from static hybrid gating to dynamic hybrid gating. The average beam toggling rate increased within 20% from static EOE gating to static hybrid gating and decreased over 5% from static hybrid to dynamic hybrid gating. Comparison of the three dynamic hybrid gating approaches showed that there was no significant difference among them. Conclusion: The dynamic hybrid gating will improve the accuracy of gated radiation treatment and reduce gated treatment time.
SU‐E‐J‐138: Breathing Motion Model Comparison Inside and Outside the Lung
Authors: Gaudio S , Thomas D , White B , Jani S , Lee P , Lamb J , Low D
Published: July 2013

Purpose: To compare the results of our deformable image registration algorithm inside and outside the lungs for our novel fast 4DCT technique in order to quantify the sliding motion between the lung and other organs in the thorax. Methods: : Data was acquired with a fast helical protocol. We used a 64‐slice CT scanner. 25 low dose whole‐lung scans were obtained in alternating directions for five patients. Images were obtained continuously under free breathing conditions. A pneumatic bellows was placed around the abdomen as a respiratory surrogate. Each image slice was assigned a unique bellows voltage signal. The lungs were segmented in each scan and, all scans were deformably registered, and were then deformed to the first scan geometry. The motion model was fit to the breathing surrogate to obtain the model parameters at each voxel inside the lung. Separately, all tissue outside the lungs was segmented, registered and fit to the motion model. Separate segmentation and registration of tissues inside and outside the lung boundary is necessary to properly treat the sliding motion that occurs at the interface of lung and chest wall. The object of this study was to determine if the separately treated inside and outside regions could be matched at the lung boundary. Results: Discontinuity in the superior‐inferior motion vectors was observed at the edges of the lungs, as expected, due to shear motion. Motion vectors in the left‐right and anterior‐posterior directions were continuous across the lung border, due to the lack of shear motion in those directions. Two masks representing the lung surface were deformed separately using the interior and the exterior motion models and found to be consistent. Conclusion: : We obtain a validation of the lung motion model and demonstrated that it can be used to reproduce accurate images for tissues outside the lung NIH grant number: ROI CA096679
SU‐E‐J‐140: Dual‐Gated Radiotherapy with PTV Partition Technique: A Feasibility Study
Authors: Kim H , Choi K , Ye S
Published: July 2013

Purpose: Dual‐gated radiotherapy is a promising method to reduce overall treatment time in which a dose is delivered at inhale and exhale phases. However, problems still remain associated with the phase shift and the target motion artifact. Dual‐gated method deals with both phases — inhale and exhale, hence the delivered dose uncertainties due to the residual motion may be doubled. In order to account for these uncertainties, we applied PTV partition technique to dual‐gated radiotherapy method. Methods: An IMRT plan for a lung cancer patient was optimized in Eclipse TPS at exhale phase. The PTV on the exhale CT was partitioned into three regions along the superior‐inferior axis; head, mid, and tail region. The dose distribution on PTV was reformed as follows: a) no dose is given to the head region, b) a gradient dose (zero to the prescription dose) is given to the mid region, and c) a hundred percent of prescription dose is given to the tail region. The reformed exhale phase dose distribution and structures were deformed to the inhale phase CT using MIM software. Thereafter the dose distribution on PTV at inhale phase was reformed in order that complement of the prescription dose is given to each region. Results: The dose‐volume histogram for PTV in the dual‐gated plan with partitioned PTV was comparable to that in the conventional gating plan while the presented technique gives robustness to the residual motion. Conclusion: The proposed method using the PTV partition technique is promising to assess dose uncertainties due to the phase shift and the target motion artifact. Further assessment of the robustness to the residual motion by experiments using thorax phantom is warranted in this regard.
SU‐E‐J‐142: Respiratory Guidance for Lung Cancer Patients: An Investigation of Audiovisual Biofeedback Training and Effectiveness
Authors: Pollock S , Lee D , Kim T , Yamamoto T , Loo B , Yang J , Keall P
Published: July 2013

Purpose: Irregular breathing can exacerbate errors in medical imaging and radiotherapy. The audiovisual biofeedback (AV) system has been proposed to facilitate regular patient respiration. The purpose of this work was to identify predictive factors from two lung cancer studies to extract information regarding each study's results and conduct to determine how to produce maximal respiratory guidance effectiveness for future studies. Methods: An analysis of respiratory regularity was performed on respiratory traces from two AV biofeedback lung cancer studies: one from a recent study performed at Stanford (Stanford study) and another, retrospectively, using data from George, et al (2006) (VCU study). Stanford study: 10 lung cancer patients, each had their external respiratory motion monitored whilst they breathed both with and without the guidance of AV biofeedback. VCU study: 24 lung cancer patients. Each patient participated in up to 5 study sessions, received training with the AV biofeedback system and shorter study sessions. Breathing regularity was quantified as the root mean square error (RMSE) of displacement and period. Results: The VCU study demonstrated AV biofeedback to be effective in producing regular respiration over free breathing (reduction in RMSE of 20% (p < 0.001) and 14% (p = 0.06) for displacement and period, respectively). However, the Stanford study did not (no reduction in RMSE displacement and reduction of RMSE in period by 31% (p = 0.17)). Distinguishing features in the conduct between these two studies was the AV biofeedback training, and the repeated and shorter sessions provided in the VCU study. Conclusion: This is the first study to retrospectively analyze the conduct and results from AV biofeedback studies and demonstrate the importance of patient familiarity and training with the AV biofeedback system. This will be used to develop ideal training and information for patients to maximize the efficiency of future AV biofeedback sessions. This work was supported by Sydney Medical School New Staff/Early; Career Researcher Scheme grant, NIH/NCI R01CA93626 and an NHMRC Australia Fellowship.
SU‐E‐J‐143: Improvement in Accuracy of Respiratory Gated Radiation Therapy Using Respiratory Training System
Authors: Kang S , Kim T , Kim D , Suh T
Published: July 2013

Purpose: The accuracy of respiratory gated radiation therapy (RGRT) depends on the respiratory regularity because external respiratory signals are used for gating the radiation beam at particular phases. Many studies have applied a respiratory guiding system to improve the respiratory regularity. This study aims to evaluate the effect of an in‐house developed respiratory guiding system to improve the respiratory regularity for RGRT. Methods: To verify the effectiveness of this system, respiratory signals were acquired from 5 volunteers. The improvement in respiratory regularity was analyzed by comparing the standard deviations of amplitudes and periods between free and guided breathing. The reduction in residual motion at each phase was analyzed by comparing the standard deviations of sorted data within each corresponding phase bin as obtained from free and guided breathing. Results: The results indicate that the respiratory guiding system improves the respiratory regularity, and most volunteers show significantly lesser average residual motion at each phase. The average residual motion measured at phases of 40, 50, and 60%, which showed lower variation than other phases, were respectively reduced by 41, 45, and 44% during guided breathing. Conclusion: The results show that the accuracy of RGRT could be improved using the in‐house developed respiratory guiding system. Furthermore, this system should reduce artifacts caused by respiratory motion in 4D CT imaging. This program was supported by the program of Basic Atomic Energy Research Institute (BAERI) which is a part of the Nuclear R and D programs (No. 20120004886) funded by the Ministry of Education, Science and Technology (MEST) and a grant (2012‐007883) from the Mid‐career Researcher Programfunded by the Ministry of Education, Science and Technology (MEST) and Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea(NRF)(Grant No.2009‐00420) funded by the Ministry of Education, Science & Technology (MEST) of Korea.
SU‐E‐J‐144: Control of Respiratory Motion by Hypnosis Intervention During Radiotherapy of Lung Cancer
Authors: Li R , Xie Y , Yu S , Yang Y , Wu S , An M
Published: July 2013

Purpose: To effectively control respiratory motion during radiotherapy of lung cancer without any side effects. Methods: A novel motion control scheme, hypnosis, has been introduced in lung cancer treatment. As we know, the uncertain position of lung tumor compromises the treatment effect. However, during hypnosis the respiration becomes uniform and stability compared to normal respiration. Therefore, hypnosis can be a helpful technique for respiratory control. Six volunteers are selected with a wide range of distribution of height, weight, and vital capacity. A set of experiments have been conducted for each volunteer, which is guided by a professional hypnotist. The amplitude of respiration has been recorded in the normal state and hypnosis state, respectively. Statistics approaches are used to analysis the data after experiments. All the experiments are repeated twice in the same condition. Results: The mean and root‐mean‐square (RMS) of the breathing amplitude are calculated for each experiment. The stability of the peaks and the similarity of the adjacent wave are also analyzed. The mean and the RMS of the amplitude are 16.2mm and 8.6mm during hypnosis state, while they are 37.4mm and 23.9mm during normal state. It can be seen that the mean and the RMS during hypnosis state are 56.6% and 64.2% smaller than during normal state, respectively. Moreover, the passing ratio of γ index between one of the 13 adjacent cycles and the others during hypnosis state is 16.4% higher than during normal state. Conclusion: The hypnosis intervention can be an alternative way for respiratory control, which can effectively reduce the respiratory amplitude and increase the stability of respiratory cycle. It will find useful application in image guided radiotherapy. This work is supported in part by grants from National Natural Science Foundation of China (NSFC: 81171402), NSFC Joint Research Fund for Overseas Research Chinese, Hong Kong and Macao Young Scholars (30928030), National Basic Research Program 973 (2010CB732606) from Ministry of Science and Technology of China, and Guangdong Innovative Research Team Program (No. 2011S013) of China.
SU‐E‐J‐147: Internal Brain Motion Between CT and MR Scanning
Authors: Xu Q , Chen Y , Zhai Y , Fan J , Wang E , Croce R , Asbell S , LaCouture T , Kubicek G
Published: July 2013

Purpose: To evaluate the internal brain motion between two imaging studies of CT and MRI. A study with 30 healthy volunteers with MRI scans in 4 different positions showed significant brain to skull motion up to 1 cm. Such motion among patients for radiotherapy to the brain is evaluated in this study. Methods: Twenty‐five patients underwent MRI and CT scans in the same day for radiotherapy planning were recruited. A whole brain fusion was first performed. Three to five pairs of control points were selected on both CT and MRI for starting an automated intensity based registration. The fusion was reviewed and fine‐tuned for the best skull‐to‐skull matching. To study potential internal brain motion, a subsequent fine‐tuning of the fusion was performed by matching the visible features, such as gyri, sulci and fissures, near the tumor site. The second fusion was reviewed and fine‐tuned by two physicists until the best visible feature matching could be agreed upon. The resulting rotation and translation between the whole brain and feature‐based fusions indicated potential internal brain motion between the two scans. Results: Between two fusions the mean internal shifts in x (LR), y (AP) and z (SI) were 0.34±0.95 mm, 0.21±1.18 mm and −0.34±0.8 mm, respectively. The mean overall shift was 1.4±1.1 mm, and the largest shift was 3.5 mm. The mean rotation angles were 0.22±1.32° (pitch), 0.14±0.4° (yaw) and 0.08±0.53° (roll), respectively. The pitch motion was predominant (head up and down) due to difference of couch tops of CT and MRI scanners. Conclusion: Our study showed small but measurable internal brain motion among radiotherapy patients with typical clinical setting for CT and MRI imaging. Therefore the CT‐MRI fusion should be carefully checked for internal structure matching. An additional treatment margin may be needed if an internal motion is observed.
SU‐E‐J‐153: Correlation and Variation of a Multi‐Modal Sensor Setup for Respiratory Motion Prediction and Correlation
Authors: Bruder R , Duerichen R , Davenport L , Wissel T , Ernst F , Schweikard A
Published: July 2013

Purpose: In robotic radiosurgery, tumor movements are compensated by tracking external optical surrogates. These surrogates are used to compensate for time delays (prediction) and to calculate the internal fiducial position (correlation). We aim to increase the accuracy and robustness by using a multi‐modal sensor approach including different physiological sensors. We evaluate the correlation coefficient of a strain belt, acceleration and air flow sensor with respect to external standard optical sensors and an internal landmark in the liver tracked using 3D ultrasound and evaluate the variance for a measurement over 20 minutes. Methods: We recorded sensor data from 6 subjects (5 male/1 female). All sensors have been synchronized and downsampled to the optical sampling rate (fs = 47 Hz) or in case of internal correlation to the ultrasound sampling rate (fs = 17 Hz). Pearson's correlation coefficient r was calculated for each minute, discarding the first and last minute. Results: The mean (standard deviation) external correlation coefficients over all subjects and time periods were obtained as: 0.88 (0.036) for strain, 0.75 (0.024) for flow and 0.73 (0.052) for acceleration with respect to an optical marker on the chest. The mean (standard deviation) internal correlation coefficients are: 0.81 (0.045) for strain, 0.76 (0.041) for flow, 0.58 (0.088) for acceleration and 0.80 (0.057) for the optical marker on the chest with respect to the internal landmark. Conclusion: This study indicates that apart from the optical markers, strain and flow data show the best correlation to external and internal motion and seem to be promising for increasing the prediction and correlation accuracy as well as robustness. Among the investigated sensors, the strain data have the lowest standard deviation for internal and external correlation, being even lower than the standard deviation of the optical chest marker.
SU‐E‐J‐160: A Simple Technique for Quick In‐Vivo Dose Measurements for KV CBCT and Diagnostic X‐Ray Planar Imaging Using MicroMOSFET Dosimeters
Authors: Charpentier P , Chan P , Neicu T , Kaplan S , Li S
Published: July 2013

Purpose: To present a practical method for dose measurement of kV CBCT scans and diagnostic X‐ray planar imaging according to typical IGRT in radiotherapy and chest and pelvis diagnostic imaging protocols by using microMOSFET dosimeters. Once calibrated, in‐vivo measurements can be easily performed on patients on surface and/or in internal cavities. Methods: The calibration procedure uses two ADCL calibrated ion chambers for diagnostic kV X‐ray beams, one 6 cc farm chamber and one large parallel plane chamber for absolute dose references, and the microMOSFET with high sensitivity settings for calibration in air and in phantom. The calibration covered the possible dose range from 1 to 25 mGy. The calibrated dosimeters were then placed at anterior, posterior, right lateral and center of an anthromorphic phantom to measure the dose for CBCT scans using the appropriate calibration file according to kVp and dose range. Also, the dosimeters were placed inside two cadavers for internal dose measurement for typical x‐ray imaging. Results: Our measured results showed that the dose from CBCT scans were typically 16% ‐ 39% higher than the nominal dose presented by the vendor per protocol. The dose from 4D CBCT scan, 2.16 cGy, was approximately 39.4% higher than the nominal dose of 1.55 cGy. The Prostate M10 scan of 3.458 cGy was approximately 16.8% higher than the nominal dose of 2.96 cGy. The Pelvis/Chest M20 scan 2.972 cGy, was approximately 35.1% higher than the nominal dose of 2.2 cGy. Large variation was observed for planar X‐ray imaging due to use of shielding and tissue attenuations. Conclusion: The ease of implementation and using microMOSFETs for CBCT scans and X‐ray imaging allows quick and accurate in‐vivo dose measurements. Vendor specified doses are verified by this technique and should be added to increase patient quality assurance and safety.
SU‐E‐J‐161: In Vivo Dose Measurement During IGRT with KV Cone Beam CT
Authors: Ravindran P , Kumar S , Sharma S , John S
Published: July 2013

Purpose: The purpose of this study is to perform in vivo dose measurements during image guidance kV CBCT using MOSFET dosimeter. Methods: Dose measurements were performed on a Clinac 2100 C/D unit with the integrated kV CBCT.for patient positioning. CBCT imaging of head and neck is usually performed with full cone beam and half gantry rotation and that of breast and pelvis with half cone beam and full gantry rotation. In this study we used mobile MOSFET dosimeters along with dose verification system supplied by the BEST Medicals Canada. The MOSFETs used in this study are of high sensitivity, i.e 9 mV/cGy for standard and 30 mV/cGy for high bias setting. The mobile MOSFETs were calibrated against parallel plate ion chamber, with air kerma calibration factor (Nk) traceable to the primary standard. Radiation dose measurements during kV CBCT were performed for patients undergoing IGRT treatments for head & Neck, breast and pelvis. The kV CBCT doses to ipsi‐lateral and contralateral eyes were measured by placing the MOSFET on the eye lid for 15 patients. Similarly doses to ipsi‐lateral and contra‐lateral breasts for kV CBCT of breast patients and on the surface of the pelvis for prostate patients were measured. Results: The maximum doses to the contra‐lateral and ipsi‐lateral eyes were 4.0 mGy and 5.7 mGy respectively with an average of 2.0 and 3.0 mGy. Breast dose measurements performed on five patients showed maximum dose of 11 mGy and 9.1 mGy to the ipsi‐lateral and contra‐lateral breasts with an average of 10.7 mGy and 6.6 mGy respectively. The average dose to the surface of the pelvis was 31 mGy. Conclusion: The dose measurements performed in this study closely agrees with those of published values. Dose reduction strategies should be employed to reduce dose during IGRT. Funded by the Board of Research in Nuclear Sciences, Department of Atomic Energy, Govt. of India
SU‐E‐J‐162: Evaluation of the Geometric Accuracy and Image Quality of KV CBCT Based IGRT System
Authors: Ravindran P , Kumar S , Peace T
Published: July 2013

Purpose: To evaluate the geometric accuracy and image quality of kV CBCT based image guided Radiotherapy system. Methods: A cube phantom with a radio opaque marker was used to determine the geometric accuracy of the isocenter of the CBCT unit. The cube phantom is positioned such that the radio‐opaque ball is at the isocenter. Radiographic images were acquired at various gantry angles and the ball center is matched with the imager center on the OBI software. The image quality assessment was performed with a CatPhan phantom that has objects to asses the low contrast resolution, uniformity of HU, geometric accuracy and special resolution. CBCT images of the phantom were acquired for Full Fan beam (FF) and Half Fan beam (HF) for large field of view. The radiation dose was estimated with a CTDI pelvic phantomResults: The maximum isocentre shift estimated with the Winston‐Lutz test tool was <1mm for most gantry angles. The maximum variation in the HU uniformity was 15 in one region and the rest were within 10 units for FF beam. The special resolution was 8lp /mm for FF beam and 4lp/mm for HF beam. The low contrast resolution, about 5 of the 1% supra slice discs were seen and about two .5% supra slice discs were seen with FF beam. CBCT images of the CatPhan with FF beam during a regular QA showed a ring artifact that was not reflected in patient images. This was identified to be due to a shift in the position of the bow‐tie filter that was subsequently corrected. Conclusion: This work shows that the CBCT image guidance system is suitable for position verification in Radiotherapy application. However, it is essential to have a periodic quality assurance program for CBCT in place to identify issues due to mechanical misalignment
SU‐E‐J‐164: Photodynamic Activity of Alternative Photosensitizers with Mamma Carcinoma Cell Lines (MCF‐7)
Authors: Kumari G Dheva Shantha
Published: July 2013

Purpose To promote the degree of cytotoxicity and photodynamic activity in photodynamic therapy, the mamma carcinoma cell lines with various photosensitizers like naturally occuring quinones extracted from folklore plants were studied. Methods Photosensitizers viz Cat E, Cat Q, MPTQ and Etoposide VP16, 1 were obtained both photochemically or synthetically. The quinones were dissolved in NaCl solution and stored in the dark. Working solutions of various quinones were prepared SOS from stock solutions. Mamma carcinoma cell lines were grown in the laboratory conditions. Results The percentage of cells damage as the function of optical dose for different photosensitizers was studied, found that cell damage increased as the optical dose increased. Studies of oxygen, glucouse, consumption, intra cellular ATP content and the viability of cell lines after photodynamic treatemnt in presence and absence of different quinones in human breast cancer cell lines were done. Conclusion The degree of cytotoxicity promoted by the alternative sensitizers like naturally occuring quinones extracted from folklore plants to improve the photodynamic therapy efficacy have been studied. The vital bio parameters that are essential for the survival of living cells such as the exclusion capacity of TB, dye uptake ability, cell viability test by vital dye and MTT assay are studied by microscopic quantitative HTS assays. HTS assays are expected to an overall damaging to membrane of the cells. HTS assay is useful modality on studying the morphological information on the status of individual cell because such information study on subcellular fraction cannot be available from the biochemical read outs. The cytotoxic effect and increased photodynamic activity based on different methods studied proved that, naturally occuring quinones takes the following order MPT quinoline tan analoges of natural alkaloids), has greater effect than etoposide an analog of natural podophyllotoxin has greater effect than emodin‐quinone and anthraquinone.
SU‐E‐J‐172: Dose Estimation in Lung Brachytherapy Using Voxelized Phantom 4DCT and MCNP
Authors: Hadad K , Zaker N
Published: July 2013

Purpose: The purpose of this study is to accurately estimate the difference between 4DCT and 3DCT dose estimation due to respiratory motion and free breathing. Methods: A 10‐phase 4DCT DICOM images of a patient, provided by the department of ?radiation oncology, University of Arizona, with a tumor in left lung is used to produce voxelized phantoms as input to MCNP. The voxelized phantoms are prepared with an in‐house developed MATLAB program. The image resolution is 512×512 with voxel dimension of 0.9765625 × 0.9765625 × 3 mm3. The resolution of the voxel phantoms are reduced to half so that MCNP could handle the dosimetry calculation. 1 billion histories are used to achieve a relative error of less than 1 percent. Treatment planning for brachytherapy dose delivery is done based on the free‐breathing data with 36 iodine‐125 seeds implanted in the tumor, 2×2×1.8 cm3, to deliver 140 Gy to PTV. MCNP execution are performed on a 10 node cascade computer which compromises 10 processors of Intel Core i7, 3.4 GHz. MCNP execution for 10 phases takes a month to complete on the aforementioned platform. Results: Comparing the dose estimation of 4DCT and 3DCT shows that 3DCT underestimates dose in lung and low density tissue regions. Meanwhile, 4DCT underestimates dose in the organ at risks, which is due to taking into consideration their movements by 4DCT dosimetry. The dose to segments of heart and spinal cord in the level of tumor are underestimated by 15% ?and 20% respectively. The dose to lung tissue is overestimated by 32% with 4DCT. Conclusion: For an accurate treatment planning in lung brachytherapy, a 4DCT dose estimation is essential for optimum dose delivery.
SU‐E‐J‐177: Comparison Between VMAT CT Planning and Segmented MRI Images with Assigned Bulk Density: A Dosimetric Study for Intact Prostate Patients
Authors: Sharif A , Paloor S , Sheim S , McGarry M , Pienaar S , Perkins G , Hammoud R , Al Hammadi N
Published: July 2013

Purpose: Variability in CT delineation and visualization of target volume has long been a problem in radiotherapy. USe of MR based radiotherapy(MR‐RT) is currently being extensively investigated due to the superior soft tissue contrast which can be enhanced by using appropriate pulse sequences. Current MR Systems ensure that there is no loss of geometric accuracy and distortion however lack of electron density information remains a problem for MR‐RT. This is a retrospective study using VMAT planning on segmented MR images with bulk density assigned for intact prostate patients. Methods: MR images for 10 patients were acquired on GE Optima MRI scanner and segmented, the bulk density was assigned as per ICRU 46 to the contours. VMAT plans were created and optimized on Varian Eclipse TPS using the AAA algorithm on the Pseudo CT/ MR study data. The resulting dose distributions were assessed for PTV coverage and OAR constraints to obtain clinically valid plans.The resulting VMAT plan dose distributions were assessed by re calculating the MR optimized plans on the original CT data sets keeping the plan parameters the same. Using plan analysis features available in Eclipse the resulting differences in the dose distributions were analyzed using DVH data as well as slice by slice dose distribution. The TCP and NTCP were calculated for both sets of plans. The optimized results for TCP and NTCP data will be presented for PTVs and OARs together with DVH comparisons. Quantitative analysis of the differences in dose distribution using Gamma Index Analysis will be performed using SunNuclear ArccheckTM and all results will be presented. Results: Detailed data analysis of the 10 Patients results will be presented. Conclusion: Initial assessment of the data indicates VMAT planning on MR only images with appropriately assigned bulk density information is clinically acceptable for intact prostate cases.
SU‐E‐J‐179: The Accurate Electron Density Image Containing Metal Prosthesises Through the Hybrid Sinogram for Tomotherapy: A Phantom Study
Authors: Jeon H , Youn H , Park D , Kim Y , Kim H , Park H , Nam J , Kim W , Ki Y , Lee J
Published: July 2013

Purpose: To obtain the hybrid CT images, which have both the high contrast of kV‐CT and very low metal artifact of MV‐CT, for tomotherapy patients with metal prosthesisesMethods: We used a standard cheese phantom containing four metal inserts (copper, silver, tin, tungsten) to acquire a kV‐sinogram by a CT simulator and a MV‐CT image by Tomotherapy. The MV‐sinogram was acquired by the forward projection of the MV‐CT image using the geometry of kV‐CT system. Both sinograms were normalized with their total length of x‐ray attenuation and then were converted to the mean electron densities using corresponding calibration curves. The metal data in the MV‐sinogram were segmented using a given density threshold and transplanted to the kV‐sinogram row by row to acquire the normalized hybrid sinogram. The misalignment between metal data of two sinograms was corrected by mutual information technique. The hybrid CT image was finally obtained through de‐normalization and back‐projection procedures. For the experimental verification, film measurements were performed and analyzed using three head and neck treatment plans. Results: We found that the hybrid CT image of the cheese phantom containing four metal inserts has similar contrast and very low metal artifact compared to the kV‐CT image. Moreover, the metal densities on the hybrid CT‐image were accurate with the mean deviation of 3.3%. As the Result of film measurements, the average gamma pass rate of kV‐CT plan and hybrid‐CT plan were 93.7% and 96.5% with the criteria of 2%/2mm, and 67.1% and 81.4% with the criteria of 1%/1mm. Conclusions: This work indicated that the hybrid CT image can improve the accuracy of tomotherapy treatment plan with metal prosthesises without additional imaging dose. Our further study is to acquire and evaluate hybrid CT images from clinical kV‐sinograms and MV‐CT images.