bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐I‐81: Assessment of CT Radiation Dose and Image Quality for An Automated Tube Potential Selection Algorithm Using Adult Anthropomorphic and ACR Phantoms
Authors: Mahmood U , Erdi Y , Wang W
Published: July 2014

Purpose:

To assess the impact of General Electrics (GE) automated tube potential algorithm, kV assist (kVa) on radiation dose and image quality, with an emphasis on optimizing protocols based on noise texture.

Methods:

Radiation dose was assessed by inserting optically stimulated luminescence dosimeters (OSLs) throughout the body of an adult anthropomorphic phantom (CIRS). The baseline protocol was: 120 kVp, Auto mA (180 to 380 mA), noise index (NI) = 14, adaptive iterative statistical reconstruction (ASiR) of 20%, 0.8s rotation time. Image quality was evaluated by calculating the contrast to noise ratio (CNR) and noise power spectrum (NPS) from the ACR CT accreditation phantom. CNRs were calculated according to the steps described in ACR CT phantom testing document. NPS was determined by taking the 3D FFT of the uniformity section of the ACR phantom. NPS and CNR were evaluated with and without kVa and for all available adaptive iterative statistical reconstruction (ASiR) settings, ranging from 0 to 100%. Each NPS was also evaluated for its peak frequency difference (PFD) with respect to the baseline protocol.

Results:

The CNR for the adult male was found to decrease from CNR = 0.912 ± 0.045 for the baseline protocol without kVa to a CNR = 0.756 ± 0.049 with kVa activated. When compared against the baseline protocol, the PFD at ASiR of 40% yielded a decrease in noise magnitude as realized by the increase in CNR = 0.903 ± 0.023. The difference in the central liver dose with and without kVa was found to be 0.07%.

Conclusion:

Dose reduction was insignificant in the adult phantom. As determined by NPS analysis, ASiR of 40% produced images with similar noise texture to the baseline protocol. However, the CNR at ASiR of 40% with kVa fails to meet the current ACR CNR passing requirement of 1.0.
SU‐E‐I‐83: Parallel Programming Upgrades for the Control Acquisition, Processing and Image Display System (CAPIDS) of the Micro Angiographic Fluoroscope (MAF)
Authors: S Setlur Nagesh , Loughran B , Rana R , Ionita C , Bednarek D , Rudin S
Published: July 2014

Purpose:

CAPIDS is a unique software platform designed to control and acquire images from the high‐resolution MAF detector, process them and display them in a clinical environment. The images are then stored for optional playback at a later stage. CAPIDS also acquires and records the exposure parameters from the x‐ray unit. We present new parallel programming modifications using the host computer system's Graphics Processing Unit (GPU) and Central Processing unit (CPU) to improve the system performance for the various MAF imaging tasks.

Methods:

Multicore CPU's allow for concurrent tasks to be executed at the same time in parallel. During runtime, CAPIDS has three concurrent tasks: image acquisition and processing, image saving, and exposure parameter acquisition. Parallel programming constructs from LabVIEW allow each tasks to be executed on a separate core.GPU's allow for the same task to be performed on independent data sets in parallel. During runtime, all the image processing including flat‐field correction, digital image subtraction, image averaging, and temporal recursive filtering are performed on the GPU.

Results:

The new version of CAPIDS with all the parallel programming updates was successfully used for the first time to control the MAF, acquire the images, process the images and display the images during an actual clinical intervention. The images were acquired under fluoroscopy, digital subtraction angiography, and roadmap modes.

Conclusion:

Distributing concurrent tasks to different cores of a multicore CPU results in an efficient utilization of resources, efficient power management and increases operation speed. Use of GPU's for image processing further enhances the speed of operation.

Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation
SU‐E‐I‐84: MRI Relaxation Properties of a Pre‐Clinical Hypoxia‐Sensitive MRI Contrast Agent
Authors: Yee S , Wilson G , Chavez F
Published: July 2014

Purpose:

A possible hypoxia‐sensitive MRI agent, hexamethyldisiloxane (HMDSO), has been tried to image oxygen level in proton‐based MRI (Kodibagkar et al, NMR Biomed, 2008). The induced changes of T1 (or R1) value by the HMDSO as the oxygenation level changes are the principle that the hypoxia agent is based on: the R1 increases as the oxygen level increases. However, as reported previously, the range of R1 values (0.1–0.3 s‐1, corresponding to 3–10 s of T1) is not in the range where a regular MRI technique can easily detect the change. In order for this agent to be widely applied in an MRI environment, more relaxation properties of this agent, including T1 in the rotating frame (T1rho) and T2, need to be explored. Here, the relaxation properties of this agent are explored.

Methods:

A phantom was made with HMDSO, water and mineral oil, each of which was prepared with oxygen and nitrogen, and was imaged in a 3T MRI system. The T1 properties were explored by the inversion recovery (TR=3000ms, TE=65ms) while varying the inversion time (TI), and also by the fast‐field‐echo (TR=2 ms, TE=2.8ms) while varying the flip angle (FA). T1rho was explored with a 5‐pulse spin‐locking technique (TR=5000ms, TE=10ms, spin‐lock field=500Hz) while varying the spin‐lock duration. T2 was explored with multi‐shot TSE (TR=2500ms) while varying TE.

Results:

With the variable FA and TI, the signals of HMDSO with oxygen and nitrogen change in a similar way and do not respond well by the change of oxygen level, which confirms the large T1 value of HMDSO. The T1rho and T2, however, have a better sensitivity.

Conclusion:

For the possible pre‐clinical hypoxia MRI agent (HMDSO), the detection of T1 (or R1) changes may be more challenging than the detection of other relaxation properties, particularly T2, as the oxygen level changes.
SU‐E‐I‐86: Evaluation of the New RaySafe Unfors X2 Dosimetry System
Authors: Heintz P , Chambers G , Sandoval D
Published: July 2014

Purpose:

To evaluate the new RaySafe Unfors X2 (X2) dosimetry system and compare it to the operation of the RaySafe Unfors Xi (Xi) and Radcal Accugold (RCAG) dosimetry systems. The comparison was done for the radiographic/fluoroscopic detectors, mammography detectors and the CT ionization chambers.

Methods:

This study used several R/F rooms, GE AMX4 portable x‐ray unit, Siemens Biograph 16 slice CT scanner and a Hologic Dimensions mammography unit to evaluate the dosimetry systems. The three X2 detectors were compared to similar detectors of the older Xi and RCAG detectors under clinical conditions used for diagnostic medical physics testing. Measurements of kVp, HVL and exposure were made under identical conditions.

Results:

For radiography and fluoroscopy the three systems agreed to within +2 kVp in the 60 to 140 kVp range, HVL measurements agreed to within +2 mm Al and the exposures agreed to within +5%. The RCAG 6 cc ionization chamber measured at least 3% higher than the diode systems. The X2 R/F detector appeared to be transparent to the fluoroscopy AEC system. For exposures made using both the CT ACR dose phantoms, the X2 agreed to within +3% of the other two systems. For mammography measurements, the three systems agreed to within +0.4kVp (25‐49 kVp range), HVL measurements agreed to within +0.05 mm Al and the exposures agreed to within +1% of the ionization chamber.

Conclusion:

The X2 system is a new version of the older Xi system. The system is faster, more robust, very easy to use, has a larger dynamic range, produced less errors and stores 1000 exposures. The measurements showed that the system performs well in the clinical environment and the X2 is within + 5% agreement of the other two calibrated systems.
SU‐E‐I‐87: Automated Liver Segmentation Method for CBCT Dataset by Combining Sparse Shape Composition and Probabilistic Atlas Construction
Authors: Li Dengwang , Liu Li , Chen Jinhu , Li Hongsheng
Published: July 2014

Purpose:

The aiming of this study was to extract liver structures for daily Cone beam CT (CBCT) images automatically.

Methods:

Datasets were collected from 50 intravenous contrast planning CT images, which were regarded as training dataset for probabilistic atlas and shape prior model construction. Firstly, probabilistic atlas and shape prior model based on sparse shape composition (SSC) were constructed by iterative deformable registration. Secondly, the artifacts and noise were removed from the daily CBCT image by an edge‐preserving filtering using total variation with L1 norm (TV‐L1). Furthermore, the initial liver region was obtained by registering the incoming CBCT image with the atlas utilizing edge‐preserving deformable registration with multi‐scale strategy, and then the initial liver region was converted to surface meshing which was registered with the shape model where the major variation of specific patient was modeled by sparse vectors. At the last stage, the shape and intensity information were incorporated into joint probabilistic model, and finally the liver structure was extracted by maximum a posteriori segmentation.Regarding the construction process, firstly the manually segmented contours were converted into meshes, and then arbitrary patient data was chosen as reference image to register with the rest of training datasets by deformable registration algorithm for constructing probabilistic atlas and prior shape model. To improve the efficiency of proposed method, the initial probabilistic atlas was used as reference image to register with other patient data for iterative construction for removing bias caused by arbitrary selection.

Results:

The experiment validated the accuracy of the segmentation results quantitatively by comparing with the manually ones. The volumetric overlap percentage between the automatically generated liver contours and the ground truth were on an average 88%–95% for CBCT images.

Conclusion:

The experiment demonstrated that liver structures of CBCT with artifacts can be extracted accurately for following adaptive radiation therapy.

This work is supported by National Natural Science Foundation of China (No. 61201441), Research Fund for Excellent Young and Middle‐aged Scientists of Shandong Province (No. BS2012DX038), Project of Shandong Province Higher Educational Science and Technology Program (No. J12LN23), Jinan youth science and technology star (No.20120109)
SU‐E‐I‐92: Is Photon Starvation Preventing Metal Artifact Reduction Algorithm From Working in KVCT?
Authors: Paudel M , MacKenzie M , Fallone B , Rathee S
Published: July 2014

Purpose:

High density/high atomic number metallic objects create shading and streaking metal artifacts in the CT image that can cause inaccurate delineation of anatomical structures or inaccurate radiation dose calculation. A modified iterative maximum‐likelihood polychromatic algorithm for CT (mIMPACT) that models the energy response of detectors, photon interaction processes and beam polychromaticity has successfully reduced metal artifacts in MVCT. Our extension of mIMPACT in kVCT did not significantly reduce metal artifacts for high density metal like steel. We hypothesize that photon starvation may result in the measured data in a commercial kVCT imaging beam.

Methods:

We measured attenuation of a range of steel plate thicknesses, sandwiched between two 12cm thick solid water blocks, using a Phillips Big Bore CTTM scanner in scout acquisition mode with 120kVp and 200mAs. The transmitted signal (y) was normalized to the air scan signal (y0) to get attenuation [i.e., ln(y/y0)] data for a detector.

Results:

Below steel plate thickness of 13.4mm, the variations in measured attenuation as a function of view number are characterized by a quantum noise and show increased attenuation with metal thickness. On or above this thickness the attenuation shows discrete levels in addition to the quantum noise. Some views have saturated attenuation value. The histograms of the measured attenuation for up to 36.7mm of steel show this trend. The detector signal is so small that the quantization levels in the analog to digital (A‐to‐D) converter are visible, a clear indication of photon starvation.

Conclusion:

Photons reaching the kVCT detector after passing through a thick metal plate are either so low in number that the signal measured has large quantum noise, or are completely absorbed inside the plate creating photon starvation. This is un‐interpretable by the mIMPACT algorithm and cannot reduce metal artifacts in kVCT for certain realistic thicknesses of steel hip implants.

Moti Raj Paudel is supported by the Vanier Canada Graduate Scholarship, the Endowed Graduate Scholarship in Oncology and the Dissertation Fellowship at the University of Alberta. The authors acknowledge the CIHR operating grant number MOP 53254.
SU‐E‐I‐94: Automated Image Quality Assessment of Radiographic Systems Using An Anthropomorphic Phantom
Authors: Wells J , Wilson J , Zhang Y , Samei E , Ravin Carl E.
Published: July 2014

Purpose:

In a large, academic medical center, consistent radiographic imaging performance is difficult to routinely monitor and maintain, especially for a fleet consisting of multiple vendors, models, software versions, and numerous imaging protocols. Thus, an automated image quality control methodology has been implemented using routine image quality assessment with a physical, stylized anthropomorphic chest phantom.

Methods:

The “Duke” Phantom (Digital Phantom 07‐646, Supertech, Elkhart, IN) was imaged twice on each of 13 radiographic units from a variety of vendors at 13 primary care clinics. The first acquisition used the clinical PA chest protocol to acquire the post‐processed “FOR PRESENTATION” image. The second image was acquired without an antiscatter grid followed by collection of the “FOR PROCESSING” image. Manual CNR measurements were made from the largest and thickest contrast‐detail inserts in the lung, heart, and abdominal regions of the phantom in each image. An automated image registration algorithm was used to estimate the CNR of the same insert using similar ROIs. Automated measurements were then compared to the manual measurements.

Results:

Automatic and manual CNR measurements obtained from “FOR PRESENTATION” images had average percent differences of 0.42%±5.18%, −3.44%±4.85%, and 1.04%±3.15% in the lung, heart, and abdominal regions, respectively; measurements obtained from “FOR PROCESSING” images had average percent differences of ‐0.63%±6.66%, −0.97%±3.92%, and −0.53%±4.18%, respectively. The maximum absolute difference in CNR was 15.78%, 10.89%, and 8.73% in the respective regions. In addition to CNR assessment of the largest and thickest contrast‐detail inserts, the automated method also provided CNR estimates for all 75 contrast‐detail inserts in each phantom image.

Conclusion:

Automated analysis of a radiographic phantom has been shown to be a fast, robust, and objective means for assessing radiographic image quality. The method reduces the burden of manual measurements and provides a means by which to monitor and compare radiographic system performance.
SU‐E‐I‐96: A Study About the Influence of ROI Variation On Tumor Segmentation in PET
Authors: Li L , Lu W , D' Souza W , Tan S
Published: July 2014

Purpose:

To study the influence of different regions of interest (ROI) on tumor segmentation in PET.

Methods:

The experiments were conducted on a cylindrical phantom. Six spheres with different volumes (0.5ml, 1ml, 6ml, 12ml, 16ml and 20 ml) were placed inside a cylindrical container to mimic tumors of different sizes. The spheres were filled with 11C solution as sources and the cylindrical container was filled with 18F‐FDG solution as the background. The phantom was continuously scanned in a Biograph‐40 True Point/True View PET/CT scanner, and 42 images were reconstructed with source‐to‐background ratio (SBR) ranging from 16:1 to 1.8:1. We took a large and a small ROI for each sphere, both of which contain the whole sphere and does not contain any other spheres. Six other ROIs of different sizes were then taken between the large and the small ROI. For each ROI, all images were segmented by eitht thresholding methods and eight advanced methods, respectively. The segmentation results were evaluated by dice similarity index (DSI), classification error (CE) and volume error (VE). The robustness of different methods to ROI variation was quantified using the interrun variation and a generalized Cohen's kappa.

Results:

With the change of ROI, the segmentation results of all tested methods changed more or less. Compared with all advanced methods, thresholding methods were less affected by the ROI change. In addition, most of the thresholding methods got more accurate segmentation results for all sphere sizes.

Conclusion:

The results showed that the segmentation performance of all tested methods was affected by the change of ROI. Thresholding methods were more robust to this change and they can segment the PET image more accurately.

This work was supported in part by National Natural Science Foundation of China (NNSFC), under Grant Nos. 60971112 and 61375018, and Fundamental Research Funds for the Central Universities, under Grant No. 2012QN086. Wei Lu was supported in part by the National Institutes of Health (NIH) Grant No. R01 CA172638.
SU‐E‐I‐97: Smart Auto‐Planning Framework in An EMR Environment (SAFEE)
Authors: Zhang B , Chen S , Mutaf Y , Prado K , D' Souza W
Published: July 2014

Purpose:

Our Radiation Oncology Department uses clinical practice guidelines for patient treatment, including normal tissue sparing and other dosimetric constraints. These practice guidelines were adapted from national guidelines, clinical trials, literature reviews, and practitioner's own experience. Modern treatment planning systems (TPS) have the capability of incorporating these practice guidelines to automatically create radiation therapy treatment plans with little human intervention. We are developing a software infrastructure to integrate clinical practice guidelines and radiation oncology electronic medical record (EMR) system into radiation therapy treatment planning system (TPS) for auto planning.

Methods:

Our Smart Auto‐Planning Framework in an EMR environment (SAFEE) uses a software pipeline framework to integrate practice guidelines,EMR, and TPS together. The SAFEE system starts with retrieving diagnosis information and physician's prescription from the EMR system. After approval of contouring, SAFEE will automatically create plans according to our guidelines. Based on clinical objectives, SAFEE will automatically select treatment delivery techniques (such as, 3DRT/IMRT/VMAT) and optimize plans. When necessary, SAFEE will create multiple treatment plans with different combinations of parameters. SAFEE's pipeline structure makes it very flexible to integrate various techniques, such as, Model‐Base Segmentation (MBS) and plan optimization algorithms, e.g., Multi‐Criteria Optimization (MCO). In addition, SAFEE uses machine learning, data mining techniques, and an integrated database to create clinical knowledgebase and then answer clinical questions, such as, how to score plan quality or how volume overlap affects physicians' decision in beam and treatment technique selection.

Results:

In our institution, we use Varian Aria EMR system and RayStation TPS from RaySearch, whose ScriptService API allows control by external programs. These applications are the building blocks of our SAFEE system.

Conclusion:

SAFEE is a feasible method of integrating clinical information to develop an auto‐planning paradigm to improve clinical workflow in cancer patient care.
SU‐E‐J‐05: A Dose‐Based Metric to Assess the Accuracy of Deformable Image Registration
Authors: Annis S , Heath E
Published: July 2014

Purpose:

To examine the correlation between landmark‐based spatial registration error and a novel metric for evaluating dose mapping error.

Methods:

The dose mapping error was calculated from the difference between the dose distributions obtained using two different dose mapping techniques. One method calculates the dose on a deformed geometry while the other calculates the dose on the target geometry. In both cases the dose distributions are mapped in a consistent manner back to the reference geometry. For a realistic clinical lung plan, dose distributions were mapped to the Exhale phase for repeated deformable registrations with different average spatial registration accuracies as determined by distance to agreement of 300 manually identified landmarks. The dose mapping error and spatial registration error were compared at each landmark and the correlation was assessed.

Results:

No clear correlation was observed between spatial registration accuracy and dose mapping error, however, the average dose mapping error was found to increase as average spatial registration accuracy increased. The relationship between the dose mapping error and spatial error at each landmark point was found to be influenced by the dose gradient, density gradients and voxel size.

Conclusion:

The dose mapping error was found to not have any direct relationship with spatial registration error but depends on a number of factors including: dose gradient, density gradient and voxel size. Our results indicate that landmark analysis on its own is not a sufficient predictor of the accuracy of dose mapping and that metrics that directly assess the dose mapping error should be used.

Natural Sciences and Engineering Research Council
SU‐E‐J‐06: A Feasibility Study On Clinical Implementation of 4D‐CBCT in Lung Cancer Treatment
Authors: Hu Y , Ruan C , Stanford J , Duggar W , Rajaguru P , He R , Yang C
Published: July 2014

Purpose:

Four‐dimensional cone‐beam CT (4D‐CBCT) is a novel imaging technique to setup patients with pulmonary lesions in radiation therapy. This paper is to perform a feasibility study on the implementation of 4D‐CBCT as image guidance for (1) SBRT and (2) Low Modulation (Low‐Mod) IMRT in lung cancer treatment.

Methods:

Image artifacts and observers variability are evaluated by analyzing the 4D‐CT QA phantom and patient 4D image data. There are two 4D‐CBCT image artifacts: (1) Spatial artifact caused by the patient irregular breathing pattern will generate blurring and anatomy gap/overlap; (2) Cone beam scattering and hardening artifact will affect the image spatial and contrast resolution. The couch shift varies between 1mm to 3mm from different observers during the 4D‐CBCT registration. Breath training is highly recommended to improve the respiratory regularity during CT simulation and treatment, especially for SBRT. Elekta XVI 4.5 Symmetry protocol is adopted in the patient 4DCBCT scanning and intensity‐based registration. Physician adjustments on the auto‐registration are involved prior to the treatment. Physician peer review on 4D‐CBCT image acquisition and registration is also recommended to reduce the inter‐observer variability. The average 4D‐CT in reference volume coordinates is exported to MIM Vista 5.6.2 to manually fuse to the planning CT for further evaluation.

Results:

(1) SBRT: 4DCBCT is performed in dry‐run and in each treatment fraction. Image registration and couch shift are reviewed by another physician on the 1st fraction before the treatment starts. (2) Low‐Mod IMRT: 4D‐CBCT is performed and peer reviewed on weekly basis.

Conclusion:

4D‐CBCT in SBRT dry‐run can discover the ITV discrepancies caused by the low quality 4D‐CT simulation. 4D‐CBCT during SBRT and Low‐Mod IMRT treatment provides physicians more confidence to target lung tumor and capability to evaluate inter‐fractional ITV changes. More advanced 4D‐CBCT scan protocol and reconstruction algorithm may be needed in the future.
SU‐E‐J‐10: A Moving‐Blocker‐Based Strategy for Simultaneous Megavoltage and Kilovoltage Scatter Correction in Cone‐Beam Computed Tomography Image Acquired During Volumetric Modulated Arc Therapy
Authors: Ouyang L , Lee H , Wang J
Published: July 2014

Purpose:

To evaluate a moving‐blocker‐based approach in estimating and correcting megavoltage (MV) and kilovoltage (kV) scatter contamination in kV cone‐beam computed tomography (CBCT) acquired during volumetric modulated arc therapy (VMAT).

Methods:

XML code was generated to enable concurrent CBCT acquisition and VMAT delivery in Varian TrueBeam developer mode. A physical attenuator (i.e., “blocker”) consisting of equal spaced lead strips (3.2mm strip width and 3.2mm gap in between) was mounted between the x‐ray source and patient at a source to blocker distance of 232mm. The blocker was simulated to be moving back and forth along the gantry rotation axis during the CBCT acquisition. Both MV and kV scatter signal were estimated simultaneously from the blocked regions of the imaging panel, and interpolated into the un‐blocked regions. Scatter corrected CBCT was then reconstructed from un‐blocked projections after scatter subtraction using an iterative image reconstruction algorithm based on constraint optimization. Experimental studies were performed on a Catphan 600 phantom and an anthropomorphic pelvis phantom to demonstrate the feasibility of using moving blocker for MV‐kV scatter correction.

Results:

MV scatter greatly degrades the CBCT image quality by increasing the CT number inaccuracy and decreasing the image contrast, in addition to the shading artifacts caused by kV scatter. The artifacts were substantially reduced in the moving blocker corrected CBCT images in both Catphan and pelvis phantoms. Quantitatively, CT number error in selected regions of interest reduced from 377 in the kV‐MV contaminated CBCT image to 38 for the Catphan phantom.

Conclusions:

The moving‐blockerbased strategy can successfully correct MV and kV scatter simultaneously in CBCT projection data acquired with concurrent VMAT delivery.

This work was supported in part by a grant from the Cancer Prevention and Research Institute of Texas (RP130109) and a grant from the American Cancer Society (RSG‐13‐326‐01‐CCE).
SU‐E‐J‐12: A New Stereological Method for Tumor Volume Evaluation for Esophageal Cancer
Authors: Feng Y , Pan R , Wang P , Yang C , Lin W , Sa Y
Published: July 2014

Purpose:

Stereological method used to obtain three dimensional quantitative information from two dimensional images is a widely used tool in the study of cells and pathology. But the feasibility of the method for quantitative evaluation of volumes with 3D image data sets for radiotherapy clinical application has not been explored. On the other hand, a quick, easy‐to‐use and reliable method is highly desired in image‐guided‐radiotherapy(IGRT) for tumor volume measurement for the assessment of response to treatment. To meet this need, a stereological method for evaluating tumor volumes for esophageal cancer is presented in this abstract.

Methods:

The stereology method was optimized by selecting the appropriate grid point distances and sample types. 7 patients with esophageal cancer were selected retrospectively for this study, each having pre and post treatment computed tomography (CT) scans. Stereological measurements were performed for evaluating the gross tumor volume (GTV) changes after radiotherapy and the results was compared with the ones by planimetric measurements. Two independent observers evaluated the reproducibility for volume measurement using the new stereological technique.

Results:

The intraobserver variation in the GTV volume estimation was 3.42±1.68cm3 (the Wilcoxon matched‐pairs test Resultwas Z=−1.726,P=0.084>0.05); the interobserver variation in the GTV volume estimation was 22.40±7.23 cm3 (Z=−3.296,P=0.083>0.05), which showed the consistency in GTV volume calculation with the new method for the same and different users. The agreement level between the results from the two techniques was also evaluated. Difference between the measured GTVs was 20.10±5.35 cm3 (Z=−3.101,P=0.089>0.05). Variation of the measurement results using the two techniques was low and clinically acceptable.

Conclusion:

The good agreement between stereological and planimetric techniques proves the reliability of the stereological tumor volume estimations. The optimized stereological technique described in this abstract may provide a quick, unbiased and reproducible tool for tumor volume estimation for treatment response assessment.

Supported by NSFC (#81041107, #81171342 and #31000784)
SU‐E‐J‐14: A Novel Approach to Evaluate the Dosimetric Effect of Rectal Variation During Image Guided Prostate Radiotherapy
Authors: Murray J , McQuaid D , Dunlop A , Buettner F , Nill S , Hall E , Dearnaley D , Gulliford S
Published: July 2014

Purpose:

Deformable registration establishes the spatial correspondence back to the reference image in order to accumulate dose. However, in prostate radiotherapy the changing shape and volume of the rectum present a challenge to accurate deformable registration and consequently calculation of delivered dose. We explored an alternative approach to calculating accumulated dose to the rectum, independent of deformable registration.

Methods:

This study was performed on three patients who received online image‐guided radiotherapy (IGRT) with daily CBCT (XVI‐system,Elekta) and target localization using intraprostatic fiducials. On each CBCT, the rectum was manually contoured and bulk density assignments were made allowing dose to be calculated for each fraction. Dose‐surface maps (DSM) were generated (MATLAB,Mathworks,Natick,MA) by considering the rectum as a cylinder and sampling the dose at 21‐equispaced points on each CT slice. The cylinder was “cut” at the posterior‐most position on each CT and unfolded to generate a DSM. These were normalised in the longitudinal direction by interpolation creating maps of 21×21 pixels. A DSM was produced for each CBCT and the dose was accumulated.

Results:

The mean accumulated delivered rectal surface dose was on average 7.5(+/−3.5)% lower than the planned dose. The dose difference maps consistently show that the greatest variation in dose between planned and delivered dose is away from where the rectal surface is adjacent to the prostate.

Conclusion:

Estimation of dose accumulation using DSM provides an alternative method for determining actual delivered dose to the rectum. The dose difference is greatest in areas away from the region where the rectal surface abuts the prostate, the region where set‐up is verified. The change in size and shape of the rectum was shown to resultin a change in the accumulated dose compared to the planned dose and this will have an impact on determining the relationships between dose delivered and toxicity. We acknowledge funding from CRUK and acknowledge NHS funding to the NIHR Biomedical Research Centre for Cancer.

Patients were treated within the CHHiP IGRT sub‐study (CRUK/06/016, ISRCTN:97182923) funded by CRUK. RayStation was used under an evaluation agreement with RaySearch Laboratories AB.
SU‐E‐J‐20: Adaptive Aperture Morphing for Online Correction for Prostate Cancer Radiotherapy
Authors: Sandhu R , Qin A , Yan D
Published: July 2014

Purpose:

Online adaptive aperture morphing is desirable over translational couch shifts to accommodate not only the target position variation but also anatomic changes (rotation, deformation, and relation of target to organ‐atrisks). We proposed quick and reliable method for adapting segment aperture leaves for IMRT treatment of prostate.

Methods:

The proposed method consists of following steps: (1) delineate the contours of prostate, SV, bladder and rectum on kV‐CBCT; (2) determine prostate displacement from the rigid body registration of the contoured prostate manifested on the reference CT and the CBCT; (3) adapt the MLC segment apertures obtained from the pre‐treatment IMRT planning to accommodate the shifts as well as anatomic changes. The MLC aperture adaptive algorithm involves two steps; first move the whole aperture according to prostate translational/rotational shifts, and secondly fine‐tune the aperture shape to maintain the spatial relationship between the planning target contour and the MLC aperture to the daily target contour. Feasibility of this method was evaluated retrospectively on a seven‐field IMRT treatment of prostate cancer patient by comparing dose volume histograms of the original plan and the aperture‐adjusted plan, with/without additional segments weight optimization (SWO), on two daily treatment CBCTs selected with relative large motion and rotation.

Results:

For first daily treatment, the prostate rotation was significant (12degree around lateral‐axis). With apertureadjusted plan, the D95 to the target was improved 25% and rectum dose (D30, D40) was reduced 20% relative to original plan on daily volumes. For second treatment‐fraction, (lateral shift = 6.7mm), after adjustment target D95 improved by 3% and bladder dose (D30, maximum dose) was reduced by 1%. For both cases, extra SWO did not provide significant improvement.

Conclusion:

The proposed method of adapting segment apertures is promising in treatment position correction, including target translational displacement, rotation and deformation. Additional SWO could improve ROIs dose distribution.
SU‐E‐J‐21: Advantages of Ultra Fast Radiation Dose Delivering
Authors: Feng Y
Published: July 2014

Purpose:

For delivering conformed dose to a moving tumor and sparing normal tissue, we presented an innovation that was combined a linear accelerator and a storage ring to generate ultra high dose rate. This innovation allows delivering prescribed dose to a moving target in such a short time period, for an example 0.1 second, during which the displacement of the target could be ignored.

Methods:

The advantages of this approach were evaluated based on normal tissue sparing, feasibility, accuracy, and time saving in clinical treatment. The target volume reduction with this innovation approach was demonstrated by analyzing the values of GTVs, ITVs, and PTVs obtained from 15 patients who had been diagnosed with malignant neoplasm of lung and treated with SBRT. The processes of SBRT treatment were investigated and advantages of this innovation in improving SBRT lung treatment were evaluated.

Results:

With the ultra‐high dose rate, the target volumes could be reduced by ∼30% to 50%. The innovation combining with IGRT technique could deliver prescribed dose to moving target accurately with simpler procedures than that of adaptive approach. This new approach could reduce the time of guiding treatment by many times. The new technique make a new strategy became feasible that was to deliver the dose to a target when it moved to a desirable location, such as away from critical organs.

Conclusion:

Combining with IGRT technique, this innovation could significantly improve the accuracy to deliver dose to moving targets with a shorter time than conventional techniques. The innovation opens a door for new strategies to deliver dose to moving targets.
SU‐E‐J‐26: Analysis of Image Quality in CBCT QA Using a Treatment Planning System
Authors: Xu M
Published: July 2014

Purpose:

The objective of this study is to propose an alternative QA technique that analyzes imaging quality(IQ) in CBCT‐QA processing.

Methods:

A catphan phantom was used to take CT imaging data set that were imported into a treatment planning system – Eclipse. The image quality was analyzed in terms of in‐slice geometry resolution, Hounsfield numbers(HU) accuracy, mean‐slice thickness, edge‐to‐center uniformity, low contrast resolution, and high contrast spatial resolution in Eclipse workstation. The CBCT‐QA was also analyzed by OBI‐workstation and a commercial software. Comparison was made to evaluation feasibility in a TPS environment.

Results:

The analysis of IQ was conducted in Eclipse v10.0 TPS. In‐slice geometric resolution was measured between 2‐rods in section CTP404 and repeated for all 4 rods with the difference between expected and measured values less than +/−0.1 cm. For HU, the difference between expected and measured values in HU was found much less than +/−40. Mean slice thickness measured by a distance on the wire proportional to scanner increment multiplying by a factor of 0.42. After repeating measurements to 4 wires, the average difference between expected and measured values was less +/−0.124 mm in slice thickness. HU uniformity was measured in section CTP486 with the tolerance less than +/−40 HU. Low contrast resolution in section CTP515 and high contrast resolution in section CTP528 were found to be 7 disks in diameter of 4 mm and 6 lp/cm, respectively. Eclipse TPS results indicated a good agreement to those obtained in OBI workstation and ImagePro software for major parameters.

Conclusion:

An analysis of IQ was proposed as an alternative CBCT QA processing. Based upon measured data assessment, proposed method was accurate and consistent to IQ evaluation and TG142 guideline. The approach was to utilize TPS resource, which can be valuable to re‐planning, verification, and delivery in adaptive therapy.
SU‐E‐J‐28: Assessment of Rotational Misalignment in Cervical Spine Treatments and Potential for 6DOF Couch Corrections
Authors: Williams B , Gladstone D
Published: July 2014

Purpose:

To quantify the magnitude of angular misalignments that may arise during spinal radiosurgery for metastases to cervical vertebrae and assess the ability of six‐degree of freedom (6DOF) alignment systems to apply appropriate corrections.

Methods:

A retrospective analysis of the distributions of rotational misalignments of cervical vertebrae based on planning CT and CBCT acquired for verification of patient positioning was performed. Fifteen patients being treated for cancers of the head and neck were immobilized using Type‐S head‐only thermoplastic masks mounted to an overlay board. Rigid registration was performed using commercially available software for individual vertebrae of each patient. Distributions of rotations were tabulated across all patients and vertebrae, modeled with a normal distribution, and 95% confidence intervals were estimated. Dosimetric consequences of maximal and 6DOF correctable misalignments are simulated.

Results:

Across all patients and vertebrae, 2/105 pitch rotations were >3° (1.9%), including 2/15 (13%) patients. Upper and lower 95% confidence intervals for pitch, yaw, and roll misalignments were [−2.3°, 3.3°], [−1.8°, 1.4°], and [−2.6°, 2.2°], respectively. Rotations for each vertebra were also considered. The greatest need for rotation appears to be for pitch correction of vertebra C4, with misalignment of 0.2° ± 1.9° observed, which predicts that a rotation >3° would be necessary 11.5% of the time that this vertebra is of interest.

Conclusion:

Empirical and model data presented here suggest that approximately 2–4% of vertebrae would require a rotation >3° in the sagittal plane, with some vertebrae more prone to rotational misalignments than others. Uncorrected rotational misalignment has the potential to alter dose distributions with respect to both treatment volumes and organs at risk and rotations >3° may require physical repositioning of the patient. Implementation of six‐degree of freedom couch systems may facilitate clinical flow after rotational misalignment is detected, and allow expeditious, automated setup corrections.

Varian and Dartmouth‐Hitchcock Medical Center are parties to a customer acceptance evaluation agreement regarding the Varian 6 degree of freedom couch.
SU‐E‐J‐29: Audiovisual Biofeedback Improves Tumor Motion Consistency for Lung Cancer Patients
Authors: Lee D , Greer P , Arm J , Hunter P , Pollock S , Makhija K , Kim T , Keall P
Published: July 2014

Purpose:

To investigate whether the breathing‐guidance system: audiovisual (AV) biofeedback improves tumor motion consistency for lung cancer patients. This will minimize respiratory‐induced tumor motion variations across cancer imaging and radiotherapy procedues. This is the first study to investigate the impact of respiratory guidance on tumor motion.

Methods:

Tumor motion consistency was investigated with five lung cancer patients (age: 55 to 64), who underwent a training session to get familiarized with AV biofeedback, followed by two MRI sessions across different dates (pre and mid treatment). During the training session in a CT room, two patient specific breathing patterns were obtained before (Breathing‐Pattern‐1) and after (Breathing‐Pattern‐2) training with AV biofeedback. In each MRI session, four MRI scans were performed to obtain 2D coronal and sagittal image datasets in free breathing (FB), and with AV biofeedback utilizing Breathing‐Pattern‐2. Image pixel values of 2D images after the normalization of 2D images per dataset and Gaussian filter per image were used to extract tumor motion using image pixel values. The tumor motion consistency of the superior‐inferior (SI) direction was evaluated in terms of an average tumor motion range and period.

Results:

Audiovisual biofeedback improved tumor motion consistency by 60% (p value = 0.019) from 1.0±0.6 mm (FB) to 0.4±0.4 mm (AV) in SI motion range, and by 86% (p value < 0.001) from 0.7±0.6 s (FB) to 0.1±0.2 s (AV) in period.

Conclusion:

This study demonstrated that audiovisual biofeedback improves both breathing pattern and tumor motion consistency for lung cancer patients. These results suggest that AV biofeedback has the potential for facilitating reproducible tumor motion towards achieving more accurate medical imaging and radiation therapy procedures.
SU‐E‐J‐31: Biodynamic Imaging of Cancer Tissue and Response to Chemotherapy
Authors: Nolte D , Turek J , Matei D , Childress M , An R , Merrill D
Published: July 2014

Purpose:

To measure intracellular motions inside three‐dimensional living cancer tissue samples to establish a novel set of biodynamic biomarkers that assess tissue proliferative activity and sensitivity or resistance to chemotherapy.

Methods:

Biodynamic imaging (BDI) uses digital holography with low‐coherence low‐intensity light illumination to construct 3D holograms from depths up to a millimeter deep inside cancer tissue models that include multicellular tumor spheroids and ex vivo cancer biopsies from canine non‐Hodgkins lymphoma and epithelial ovarian cancer (EOC) mouse explants. Intracellular motions modulate the holographic intensity with frequencies related to the Doppler effect caused by the motions of a wide variety of intracellular components. These motions are affected by applied therapeutic agents, and BDI produces unique fingerprints of the action of specific drugs on the motions in specific cell types. In this study, chemotherapeutic agents (doxorubicin for canine lymphoma and oxoplatin for ovarian) are applied to the living tissue models and monitored over 10 hours by BDI.

Results:

Multicellular spheroids and patient biopsies are categorized as either sensitive or insensitive to applied therapeutics depending on the intracellular Doppler signatures of chemotherapy response. For both lymphoma and EOC there is strong specificity to the two types of sensitivities, with sensitive cell lines and biopsies exhibiting a global cessation of proliferation and strong suppression of metabolic activity, while insensitive cell lines and biopsies show moderate activation of Doppler frequencies associated with membrane processes and possible membrane trafficking.

Conclusion:

This work supports the hypothesis that biodynamic biomarkers from three‐dimensional living tumor tissue, that includes tissue heterogeneity and measured within 24 hours of surgery, is predictive of near‐term patient response to therapy. Future work will correlate biodynamic biomarkers with progression free survival times.

This work is supported by NIH 1R01EB016582 and NSF 1263753‐CBET. Nolte, Turek and An have a financial interest in Animated Dynamics, Inc. that will be licensing technology from Purdue University.
SU‐E‐J‐32: Calypso(R) and Laser‐Based Localization Systems Comparison for Left‐Sided Breast Cancer Patients Using Deep Inspiration Breath Hold
Authors: Robertson S , Kaurin D , Kim J , Fang L , Sweeney L , Holloway K , Tran A
Published: July 2014

Purpose:

Our institution uses a manual laser‐based system for primary localization and verification during radiation treatment of left‐sided breast cancer patients using deep inspiration breath hold (DIBH). This primary system was compared with sternum‐placed Calypso(R) beacons (Varian Medical Systems, CA). Only intact breast patients are considered for this analysis.

Methods:

During computed tomography (CT) simulation, patients have BB and Calypso(R) surface beacons positioned sternally and marked for free‐breathing and DIBH CTs. During dosimetry planning, BB longitudinal displacement between free breathing and DIBH CT determines laser mark (BH mark) location. Calypso(R) beacon locations from the DIBH CT are entered at the Tracking Station. During Linac simulation and treatment, patients inhale until the cross‐hair and/or lasers coincide with the BH Mark, which can be seen using our high quality cameras (Pelco, CA). Daily Calypso(R) displacement values (difference from the DIBH‐CT‐based plan) are recorded. The displacement mean and standard deviation was calculated for each patient (77 patients, 1845 sessions). An aggregate mean and standard deviation was calculated weighted by the number of patient fractions.Some patients were shifted based on MV ports. A second data set was calculated with Calypso(R) values corrected by these shifts.

Results:

Mean displacement values indicate agreement within 1±3mm, with improvement for shifted data (Table).

Conclusion:

Both unshifted and shifted data sets show the Calypso(R) system coincides with the laser system within 1±3mm, demonstrating either localization/verification system will Resultin similar clinical outcomes. Displacement value uncertainty unilaterally reduces when shifts are taken into account.
SU‐E‐J‐33: Cardiac Movement in Deep Inspiration Breath‐Hold for Left‐Breast Cancer Radiotherapy
Authors: Kim M , Lee S , Suh T
Published: July 2014

Purpose:

The present study was designed to investigate the displacement of heart using Deep Inspiration Breath Hold (DIBH) CT data compared to free‐breathing (FB) CT data and radiation exposure to heart.

Methods:

Treatment planning was performed on the computed tomography (CT) datasets of 20 patients who had received lumpectomy treatments. Heart, lung and both breasts were outlined. The prescribed dose was 50 Gy divided into 28 fractions. The dose distributions in all the plans were required to fulfill the International Commission on Radiation Units and Measurement specifications that include 100% coverage of the CTV with ≥ 95% of the prescribed dose and that the volume inside the CTV receiving > 107% of the prescribed dose should be minimized. Displacement of heart was measured by calculating the distance between center of heart and left breast. For the evaluation of radiation dose to heart, minimum, maximum and mean dose to heart were calculated.

Results:

The maximum and minimum left‐right (LR) displacements of heart were 8.9 mm and 3 mm, respectively. The heart moved > 4 mm in the LR direction in 17 of the 20 patients. The distances between the heart and left breast ranged from 8.02–17.68 mm (mean, 12.23 mm) and 7.85–12.98 mm (mean, 8.97 mm) with DIBH CT and FB CT, respectively. The maximum doses to the heart were 3115 cGy and 4652 cGy for the DIBH and FB CT dataset, respectively.

Conclusion:

The present study has demonstrated that the DIBH technique could help to reduce the risk of radiation dose‐induced cardiac toxicity by using movement of cardiac; away from radiation field. The DIBH technique could be used in an actual treatment room for a few minutes and could effectively reduce the cardiac dose when used with a sub‐device or image acquisition standard to maintain consistent respiratory motion.