bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hot-Wire Measurements Around a Controlled Diffusion Airfoil in an
Open-Jet Anechoic Wind Tunnel
Authors: Moreau Stéphane , Neal Douglas , Foss John 
Published: July 2006

Abstract
The aeroacoustic measurements in the large anechoic wind tunnel of Ecole Centrale de Lyon, which previously focused on the wall pressure distribution and the far-field acoustic pressure, are extended to velocity measurements by hot-wire probes in the nozzle jet and in the vicinity of a Controlled Diffusion airfoil. The present work focuses on the flow conditions corresponding to a Reynolds number based on the airfoil chord length Rec=1.6×105 and a geometric angle of attack αg of 8°. Midspan measurements were achieved at the exit plane of the wind tunnel nozzle upstream of the test airfoil and in a large eddy simulation domain that was embedded in the potential core around the airfoil mockup. The inlet measurements by a single hot-wire probe provided insight into the free-stream turbulence intensity upstream of the profile. The X-probe measurements on the upper and lower computational boundaries show the overall deflection of the jet potential core by the cambered airfoil. These are compared to previous Reynolds averaged Navier-Stokes predictions. The X-probe measurements in the airfoil wake provide information on the development of the airfoil boundary layer and the resulting wake after separation. The measured wake velocity defect has been compared with both numerical predictions.
SU‐DD‐A2‐01: On the Accuracy of a Moving Average Algorithm for Tracking Respiratory Motion During Radiation Therapy Treatment Delivery
Authors: George R , Williamson J , Murphy M , Weiss E , Keall P 
Published: July 2006

Introduction: Real‐time motion tracking (RTT) treatment delivery has several advantages toward the improvement of accuracy for radiotherapy. However, currently there are certain limitations to this technique. The purpose of this study was to investigate an alternative treatment scenario using a moving average algorithm (MA) for treatment which could potentially be approaching the accuracy of RTT. Method: A comparison was performed between three different treatment scenarios.(1)RTT: ;(2)MA: ;(3) Static beam delivery(SB) .Where Xest(t) and Xact(t) are the estimated and actual position at time t, n in seconds is the averaging period (5–25 seconds range). The data used for this analysis was 331 respiration‐motion traces from 24 lung‐cancer patients acquired using three different breathing types (free breathing(FB), audio coaching(A) and audio‐visual biofeedback(AV)). The metrics used for comparison were the group systematic error(M), the standard deviation(SD) of the systematic error(Σ), and the root mean square of the random error(σ). The averaging period was varied to study the effect on the various metrics. Margins were calculated using the formula by Stroom et al.(IJROBP 1999;43(4)) Results: M and Σ are negligible for both MA[M ∈ (−0.01,0), Σ ∈ (0,0.01)] and RTT[M ∈ (0), Σ ∈ (0)] compared to SB[M ∈ (−0.15,−0.02), Σ ∈ (0.05–0.20)]. MA(0.48–0.54) has a slightly reduced σ than SB(0.53–0.57). Negligible improvements were found by varying the average periods for M and Σ . σ was found to be insensitive to the different averaging periods(0.53–0.56 for A). From the margin calculations FB is most affected by the different treatment scenarios. (All values in cm). Conclusions: MA has accuracy advantages over SB and practical advantages over RTT. MA significantly reduces M and Σ compared with SB. MA and SB require less margins for AV than that for FB and A. The margins required for RTT are independent of breathing training type. There is a group systematic error caused by intrafraction motion during FB.
SU‐DD‐A3‐03: A Dose‐Guided Adaptive Therapy Process for Treatment Evaluation and Correction
Authors: Ruchala K , Olivera G , Lu W , Haimerl J , Schnarr E , Chen Q , Meeks S , Langen K , Kupelian P 
Published: July 2006

Purpose: To develop an adaptive therapy process for off‐line radiotherapy evaluation and modification. Method and Materials: An adaptive therapy process was developed to analyze and adjust a patient treatment. This included:Daily Online Processes• Daily CT imaging• Patient repositioningWeekly Offline Processes• Automatic dose recalculation on each daily image• Automatic deformable registration of each image with the planning image• Automatic deformation‐based recontouring of each image• Automatic deformation‐based dose accumulation• Cumulative plan evaluation• Replanning, as neededThe on‐line imaging and repositioning was performed with the TomoTherapy MVCT system and integrated registration software. The off‐line processes were performed on a standalone workstation.Head and neck cases were studied with this process. Cumulated doses were typically analyzed at the end of each week, and modifications were performed mid‐course. Remaining treatments were then performed with the adapted plan. Results: It was found that CT‐guided soft‐tissue positioning alone did not protect against dosimetric changes due to patient weight loss. Without plan adaptation, the right parotid gland would have received a dose of 10 Gy above the plan, due to its medial motion towards the target region. However, since mid‐course adaptive replanning was used, the dose was only 2.5 Gy above the original plan. The use of an additional plan adaptation could have further reduced this discrepancy. Conclusion: An adaptive therapy process was developed for off‐line contouring, dose recalculation, dose accumulation, and replanning. This process was applied to clinical head and neck patients to evaluate on‐going treatments, adjust plans, and retrospectively assess the results. This process reduced unexpected parotid dose for these patients. This process also indicated that ability to recalculate to accumulate doses on daily CT images is important for addressing systematic errors, such as anatomical changes, that may arise during a treatment.Supported by TomoTherapy, Inc.
SU‐DD‐A3‐05: Evaluation of Respiration‐Correlated Digital Tomosynthesis for Soft Tissue Visualization
Authors: Kriminski S , Lovelock D , Mageras G , Yorke E , Rosenzweig K , Mostafavi H , Ling C , Amols H 
Published: July 2006

Purpose: To find optimal parameters for digital tomosynthesis (DTS) image acquisition, assess DTS imaging for soft tissue visualization and patient positioning, and determine if DTS can be acquired fast enough to avoid blur caused by the respiratory motion Methods and Materials: We have used Varian gantry‐mounted kV on‐board imaging system to acquire DTS images as well as reference cone‐beam CT (CBCT) scans. An external respiratory monitor system recorded patient respiration together with the x‐ray on/off signal during imaging for retrospective sorting of projections based on respiration phase. DTS reconstruction used backprojection followed by a deblur. For a lung tumor subject to the respiratory motion we also reconstructed DTS images during a short time interval (∼ 1 s = 6° arc at 1 rpm) around the end‐exhalation.Results: Phantom studies indicate that image quality increases with DTS arc length; however, longer arc lengths cause image blur and degradation. Optimal DTS arc length is 10–20.° Patient studies also indicate that at approximately 15° arc length image quality, as judged visually, is the best. For longer arcs image blur increases, while for shorter arcs out of plane objects become more pronounced. For all arc lengths tumor visualization was possible. Both manual and automatic 2D registrations of DTS and CBCT were possible in most cases. For short (6°) or long (30°) arc lengths manual registration became more challenging and automatic registration less precise, but still possible. Registration of a respiratory correlated DTS image over a 6,° non‐optimal arc, was possible. Conclusions: DTS is capable of soft tissue and bone visualization and can be an efficient imaging modality for image‐guided radiotherapy. DTS can be acquired, with some tradeoff in image quality, during a ∼1s time interval, allowing reduction of respiratory motion artefacts. Conflict of interest: Research sponsored by NCI Grant P01‐CA59017 and Varian Medical Systems.
SU‐EE‐A4‐06: A Novel Approach for Metal Artifacts Reduction Due to Tooth Filling
Authors: Yazdi M , Beaulieu L 
Published: July 2006

Introduction: The aim of this study is to present a conceptually new method for metal artifact reduction (MAR), especially for patients who have multiple metal objects with small sizes. Metallic implants such as dental fillings cause serious artifacts in reconstructed CT images. Although the previous methods based on conventional projection‐interpolation successfully reduced artifacts in the case of large metal objects such as hip prostheses, their performance appears to depend highly on the complexity of the structures examined and they are very sensitive in correctly detection of missing projections resulting still many artifacts in the final reconstruction for the case of multiple‐near metal objects. Methods and Materials: The proposed method is based on modifying the raw CT data acquired during patient's examination. First, the projection data affected by metal objects (missing projections) are detected in sinogram using a simple thresholding algorithm. Then, the missing projections are replaced by corresponding 180 degrees projections, which are not affected by metal objects. The idea beyond the replacing scheme is due to the fact that the two projections along the same path but in the opposite sides would be the same in the absence of table motion. So, in the presence of table motion, like an helical CT exam, the opposite side projections still constitute very good approximations for the corresponding missing projections. In order to make the replacing scheme more reliable, we start the process simultaneously from each side of missing projections area. Finally, the modified sinogram is transferred back to the CT scanner device where CT slices are regenerated using the built‐in reconstruction operator.Experimental Results: The resulting tomography by the proposed approach show significant improvements in image quality, especially for regions near the metallic implants, compared to those by interpolation‐based approaches.
SU‐FF‐I‐06: A Portable Test Platform for Image Acquisition and Calibration for Cone Beam Computed Tomography (CBCT) and Region of Interest CBCT (ROI‐CBCT) On a Commercial X‐Ray C‐Arm System
Authors: Rangwala H , Chityala R , Rudin S , Hoffmann K 
Published: July 2006

Purpose: We have developed a unique portable test platform (PTP) which enables CBCT for specimens and phantoms on standard commercial clinical x‐ray systems. This PTP can be used to acquire ROI‐CBCT projection images, where a lower resolution, lower dose image peripheral to a high resolution ROI is acquired. This is achieved either by acquiring an image using an Image Intensifier (II) with an ROI filter in the x‐ray beam or by combining images acquired separately with low and high resolution x‐ray detectors. Method and Materials: The CBCT images are acquired as the object rotates on the computer‐controlled rotary table of the PTP. For ROI‐CBCT, a micro‐angiography (MA) detector or an ROI filter is mounted on the PTP. The PTP also provides for relative X, Y, Z adjustments. After coarse alignment adjustments of the PTP, fine translational and angular adjustments are made based on fluoroscopic imaging of a cylindrical calibration phantom. Results: The PTP allows quick assembly of the parts required for CBCT or ROI‐CBCT reconstruction, reduces initial setup time to < 45 min, and provides for setup reproducibility. The system can be aligned to within one pixel (43 micron for the MA detector), with angular alignments of pitch and roll of the object better than 0.7° and 0.1° respectively. Conclusion:, The PTP allows fast and reliable set‐up and alignment of CBCT specimens, for standard and for ROI‐CBCT applications. The PTP may enable wider use of CBCT and ROI‐CBCT for specimens and phantoms without a costly dedicated system.(Partial support from NIH Grants R01‐NS43924, R01‐EB02873, R01‐HL52567, R01‐EB02916, and Toshiba Medical Systems Corporation).
SU‐FF‐I‐16: Volume‐Of‐Interest (VOI) Cone Beam CTwith Dual Resolution Image Acquisition
Authors: Chen L , Shaw C , Meng Y , Altunbas M , Wang T , Tu S , Liu X , Lai C 
Published: July 2006

In this study, we investigate the feasibility of using VOI projection data acquired at high resolution in conjunction with full width projection data acquired at low resolution to reconstruct cone beam CT images for the VOI. To simulate cone beam CT with dual resolution image acquisition, flat panel images of a mastectomy specimen, acquired in the non‐binning mode, were converted into low resolution full width projection data. High resolution VOI projection data were directly extracted from the original data. To prepare for reconstruction, the low resolution projection data were first interpolated, re‐sampled to fill in the truncated space outside the VOI. The dual resolution full width projection data, consisting of true high resolution data in the VOI and interpolated data outside the VOI, were then used to reconstruct the 3‐D image for the VOI. Reconstructed images obtained with dual resolution projection data were compared with those obtained with low resolution data and those obtained with high resolution data for the visibility of small calcifications. We have successfully demonstrated the use of dual resolution projection data for VOI cone beam CT imaging. While the low resolution full width projection data did not allow smaller calcifications to be seen in the reconstructed images, addition of high resolution projection data for the VOI only could make them visible. The use of interpolated low resolution projection data to pad the truncated space outside the VOI did not affect the spatial resolution of reconstructed images inside the VOI. With the dual resolution technique, it would be possible to selectively image a VOI at very high resolution without requiring excessively long acquisition and reconstruction or unnecessarily overexposing the patient outside the VOI.(This work was supported in part by a research grant CA104759 from the NCI and a research grant EB‐00117 from the NIBIB).
SU‐FF‐I‐69: The Impact of Sparse Data Sets On the Quality of MR Images
Authors: Sobol W , Bankston J 
Published: July 2006

Purpose: To evaluate the impact of reduction in acquired data size on the final appearance of MR images and to assess the synergetic impact of image interpolation, used in softcopy viewing, on the perception of image quality. Method and Materials: A rapid progress in signal quality of the MRI data acquired with modern MRI hardware, coupled with a desire to speed up the acquisition times as much as possible, promotes a practice where drastic reductions in the size of acquired data are implemented by the MRI system operator. Routinely, the physician viewing the MR images is presented with incomplete and confusing information about the true size of the acquired data. Most physicians are oblivious to the potential impact of complex acquisition algorithms on the quality of images. The situation is further confounded by various image interpolation techniques used by softcopy display systems.A standard spin echo imaging sequence (270/10, FOV 30 cm, slice thickness 5 mm, gap 5 mm, 11 slices, 1 NEX, BW=2*15.63 kHz) was used to generate a baseline image with 256*256 acquisition matrix. This was followed by an acquisition of a 512*512 image that served as a “golden reference standard”, given the fact that the standard MR displays use 512*512 image size as a default. The baseline protocol was then repeated by varying options and parameters that affected the sizes of the acquisition matrix, processing matrix, or display matrix. Results: Images other than the golden reference standard exhibit artifacts whose strength strongly depends on the resampling algorithm applied. The extent and severity of observed artifacts increases with the number of options used to generate the image. Conclusion: The image acquisition parameters and display resampling algorithms need to be carefully accounted for when evaluating image artifacts in MR images.
SU‐FF‐I‐79: Java‐Based Plugin for Tomographic Reconstruction for SPECT Data
Authors: Andrade M , Costa M , Marques da Silva A 
Published: July 2006

Purpose: To implement a plugin for the software ImageJ, a public domain and open source software, written in JAVA, used for image processing and analysis, able to perform the filtered backprojection (FBP) algorithm for tomographic reconstruction of SPECT data. Method and Materials: New classes were added to the software ImageJ in order to implement the plugin. The following classes have been developed: (1) the backprojection process, in which data from projections or filtered projection are smeared back into the image matrix; (2) the tomographic reconstruction ramp filter with other windowing possibilities using loss‐pass filters such as Butterworth, Shepp‐Logan and Hamming; (3) the one‐dimensional Fourier transform to perform the projection filtering; (4) and the user interface of the plugin. The plugin was tested with Monte Carlo simulated projection data of Zubal brain phantom, NCAT phantom and patient data. Results: The plugin is able to reconstruct sinograms of 8, 16 and 32‐bits. Users can choose filter/window combinations. After the user sets the parameters needed for each combination (cutoff frequency and/or order), the filter curve can be visualized. When no filtering is choosen, simple backprojection is performed. The final reconstructed image is displayed and can be visualized or analyzed using segmentation and processing tools available in ImageJ. Conclusion: The outcome of this work consists of a plugin for the software ImageJ to reconstruct images from SPECT data as sinograms using filtered backprojection or simple backprojection. The plugin is plataform independent and runs either in Windows or Linux, freely downloadable and accessible, and based on open source code. Further implementations will allow this plugin to work with DICOM images and offer iterative methods of tomographic reconstruction.Research sponsored by FRIDA Program/LACNIC and CNPq.
SU‐FF‐J‐02: 3D Target Localization Using Cone‐Beam CT for Head and Neck IMRT Patients
Authors: Wu Q 
Published: July 2006

Purpose: To evaluate clinical effectiveness of target localization using cone‐beam CT (CBCT) for H&N IMRT treatment. Method and Materials: All H&N patients treated with an IRB approved protocol were imaged on the first day of treatment and weekly thereafter with Varian On‐Board Imager. After the patient was aligned with skin markers, 2D kilovoltage portal images were acquired and compared to the planning DRRs for set‐up corrections (2D‐based correction). Then, CBCT images were acquired and registered with the planning CT by matching both soft tissue and bony landmarks, which generated the 3D‐based corrections. The difference between two correction measurements yielded the treatment isocenter variation using the 3D/3D matching method. Dose distributions with different isocenter deviations were re‐constructed on the planning CT. The treatment DVHs of PTVs and critical structures were compared with those in the original plan. Results: A total of 12 CBCT were analyzed for 3 patients during their first 4‐weeks of treatment. Compared to set‐up variations, anatomical shrinkage/deformation was negligible. The mean isocenter deviations after 2D‐based corrections were 1.1mm in AP direction (max 3.0mm), 2.6mm in lateral direction (max 5.0mm), and 3.8mm in SI direction (max 6.0mm). For the worst isocenter deviation, the reconstructed mean PTV dose was reduced by 3.6% from the planned mean value. For two patients, the mean brainstem dose increased from 33% to 49.5% and from 36.9% to 66.8%, respectively, in worst cases after 2D‐based correction. Other critical structures that received significantly higher doses were cord (max dose changed from 41.8% to 64%), eye (mean dose changed from 37.5% to 83.9%) and parotid (mean dose changed from 58% to 72.5%). Conclusion: For H&N IMRT treatment, CBCT image‐guidance improves localization accuracy compared to 2D‐based technique and should be the method of choice for target localization when tight margins are applied.Partially supported by Varian research grant.
SU‐FF‐J‐10: A Novel Signal‐Processing Strategy for in Vivo Ultrasonic Imaging of Brachytherapy Seeds
Authors: Mamou J , Feleppa E J , Wuu C‐S 
Published: July 2006

Purpose: Brachytherapy is proving to be a well‐accepted means of treating prostate cancer. Unfortunately, implantation using needles inserted transperineally causes gland movement, and the resulting distortion may cause seed misplacement and dosimetry errors. Our approach employs novel methods of digitally processing ultrasound echo signals to markedly improve ultrasonic imaging of seeds during the implantation procedure. This approach will enable the radiation oncologist to determine where all implanted seeds are located and to make additional implantations to correct for dosimetry errors cause by misplaced seeds.Method and Materials: Our signal‐processing strategy uses singular spectrum analysis (SSA) and shows promise for ultrasonically detecting and imaging radioactive seeds implanted in the prostate. This SSA‐based strategy utilizes pairs of eigenvalues derived from the autocorrelation matrix of envelope‐detected radiofrequency echo signals to identify seed‐specific signal repetitions. The power spectrum associated with a repetition signal is computed to derive a P‐value indicative of the likelihood of the presence of a seed at the location of that repetitive signal. P‐values throughout each scan plane are then color‐coded and superimposed on the corresponding conventional grayscale ultrasound images. These new ultrasound images are thus readily usable by clinicians to locate seeds. Results: Simulations assessing performance as a function of different levels of white and speckle noise and in the presence of signals at repetition periods not associated with seeds; experiments in an ideal scattering environment; and in vitro experiments using seeds implanted in beef were conducted and led to encouraging results. Simulations showed robustness to noise (signal‐to‐noise ratio < 25 dB) and in vitro experiments allowed for seed detection and imaging. Conclusion: Overall, our SSA‐based strategy shows encouraging potential for seed detection and imaging in the operating room. Clinical implementation of this methodology would be straightforward because it uses enveloped‐detected signals directly available from clinical scanners.