bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐GG‐I‐155: Physical Imaging Properties and Detectability of Simulated Microcalcifications of Digital Magnification Mammography with Matched Incident Exposure
Authors: Tanaka N , Higashida Y , Naka K , Toyofuku F , Ohki M , Morishita J
Published: August 2010

Purpose: To improve the image resolution over that obtainable with contact radiography, digital magnification mammographies under the same incident exposure conditions with contact mammography were performed. Method and Materials: Magnification radiographies of 1.2 – 1.8 times in addition to contact radiography were performed with the same incident exposure in combination with focal spot sizes of 0.1 mm and 0.3 mm, with and without grid techniques. A computed radiography system (FCR PROFECT CS, Fuji Film), including the imaging plate (HR‐BD, 50 μm pixel pitch, Fuji Film), was used in this study. Basic imaging properties, namely; scatter fractions, total modulation transfer functions (MTFs) at object plane and the noise power spectra (NPSs) were measured. Visibilities of contrast‐detail mammography (CDMAM) phantom and simulated microcalcification images were evaluated by using a contrast‐detail curve and a free‐response receiver operating characteristic (FROC) analysis, respectively. Results: Scatter fractions decreased considerably as the magnification factor increased for the no‐grid technique. In the grid technique, scatter fractions for all magnification techniques were comparable. The total MTFs at object plane improved significantly for magnification technique with a combination of 0.1 mm focal spot size compared with conventional contact technique. However, the total MTFs with a combination of 0.3 mm focal spot size slightly improved or were comparable. The NPSs degraded with an increase of the magnification factor compared with contact radiography due to the maintained incident dose to object. Observer performance tests indicated that the magnification techniques using the 0.1 mm focal spot size provided higher detectability than the contact technique. Conclusion: It is expected that the use of digital magnification mammography under the same incident exposure conditions with contact mammography improved the detectability of microcalcifications.
SU‐GG‐I‐157: Phase Correlated Image Registration to 4D CT for Liver Stereotactic Radiosurgery with Image Guidance CT
Authors: Juh R , Suh T
Published: August 2010

Purpose: Stereotactic radiosurgery (SRS) is characterized by high doses delivered to small targets in a few fractions. Image guidance systems, cone beam computed tomography (CBCT), that yield volume imaging and sufficient soft‐tissue contrast have permitted daily imaging of bony anatomy and target permitting online correction of tumor position prior to treatment delivery, but CBCT is not perfectly support in phase correlated image guidance for targeting. The main objective was to overcome breathing induced uncertainties in the process of image guided RT using phase correlated image registration both the planning CT scan and CBCT for verification imaging scan. Methods and materials: For 20 patients with liver SRS, respiratory correlated 4D CT scan and CBCT for image guidance was acquired. Internal target volume (ITV) is determined utilizing 50% phase end exhalation reconstructed images by 4DCT, In order to check the accuracy of maximum intensity projection for various target motion, especially for target moving irregularly with three implanted gold seed. The data analyzed were respiratory‐induced peak‐to‐trough distance, 3D motion from LR, AP and SI directions and motion nonlinearity and hysteresis. Motion hysteresis occurs when three seed follows different paths between inhale and exhale phases during a respiratory cycle. Results: The overall mean respiratory‐induced peak‐to‐trough distance is 0.48 cm, with individual treatment fraction means ranging from 0.02 to 1.44 cm. The overall mean respiratory period is 3.8 s, with individual treatment fraction means ranging from 2.2 to 6.4 s. Conclusions: The motion nonlinearity and hysteresis are important characteristics of respiratory tumor motion. From 3D tumor trajectories, they showed that the hysteresis ranged from 0.1 to 0.6 cm for 20 tumors.
SU‐GG‐I‐159: In‐Vivo Iron Measurement through Nuclear Resonance Fluorescence
Authors: Kapadia A , Agasthya G , Cumberbatch L , Howell C
Published: August 2010

In‐vivo quantitative measurement of iron has been the focus of several studies related to iron disorders in the human body. Techniques such as SQUID and MRI have been used to detect liver iron stores in patients afflicted with hemochromatosis and thalassemia. Here we present a gamma‐stimulated spectroscopy method to detect iron in an aqueous sample through nuclear resonance fluorescence. A high‐energy tuned gamma‐ray beam was used to excite characteristic gamma emission from an iron sample suspended in water. The gamma‐beam was generated using the free‐electron‐laser source at Duke University and tuned to 6.93 MeV to resonate with the 6926 keV energy state in natural iron (56‐Fe). The beam was collimated and focused onto a sample of natural iron immersed in water corresponding to an iron concentration of 180 mg/g. An identical phantom of copper immersed in water was used to obtain an estimate of the background noise from the spectroscopic acquisition setup. Emitted gamma spectra were generated for each sample using a high‐purity germanium (HPGe) detector and background corrected using time‐of‐flight techniques. The resulting spectrum showed a strong gamma line at 6926 keV originating from 56‐Fe in the sample. This experiment demonstrates the ability to selectively stimulate and quantify a specific energy level in iron through nuclear resonance gamma‐stimulated spectroscopy. Through tomographic imaging the technique can be expanded to obtain three‐dimensional quantitative maps of iron stores in the liver or other organs in the body in a manner that is both non‐invasive and in‐vivo.
SU‐GG‐I‐160: Magnetocardiographic Assessment of Fetal Long‐QT Syndrome
Authors: Yu S , Cuneo B , Strasburger J , Horigome H , Wakai R
Published: August 2010

Purpose: Cardiac repolarization abnormalities, such as QTc prolongation and T‐wave alternans, comprise a class of potentially lethal fetal anomalies that cannot be detected by echocardiography. Fetal magnetocardiography (fMCG) was used to characterize the heart rate and rhythm of a cohort of fetuses with confirmed long QT syndrome (LQTS) and to identify risk factors for adverse events, such as torsades de pointes (TdP), a virulent ventricular tachycardia, and second‐degree AV block. Method and Materials: We reviewed the medical records and fMCG recordings of pregnancies referred to the Biomagnetism Laboratories at Institute of Clinical Medicine at the University of Tsukuba (Tsukuba, Japan) and the Department of Medical Physics, University of Wisconsin‐Madison. Indications for inclusion in our study were referral for evaluation of family history of LQTS (10 fetuses) and fetal bradycardia (14 fetuses). The fMCG recordings were taken at 25.4–31.7 weeks' gestation, using a 37‐channel SQUID magnetometer in a magnetically‐shielded room. Results: Of 10 fetuses with family history of LQTS, QTc prolongation (512–590 msec) was present in 5. Of 14 fetuses with bradycardia and 1:1 AV conduction QTc prolongation (554–700 msec) was present in 7. Mean heart rate was below the 3% prediction interval in 11 of the 12 subjects with QTc prolongation. Three subjects had perinatal TdP and second‐degree AV block, and all had fetal QTc> 580 ms. Of these, one had a SCN5A mutation, one had a KCNQ1 mutation, and one had no recognized mutation. Conclusion: The QTc determined by fMCG predicts the severity of symptoms in fetal LQTS. Fetal QTc of > 580 ms increases the likelihood of either fetal or neonatal 2° AV block and/or torsade des pointes. We speculate that fMCG findings may risk‐ stratify the care of infants with LQTS. This research was supported by grant R01 HL063174 from the National Institutes of Health.
SU‐GG‐I‐163: A Scatter Correction Algorithm for Quantitative Yttrium‐90 SPECT Imaging
Authors: Kappadath SC
Published: August 2010

Purpose: To develop a scatter correction algorithm for quantitative 90Y bremsstrahlung SPECT (90Y QSPECT). Method and Materials: 90Y SPECT/CT scans were acquired for 1mCi/10cc vial within a large acrylic phantom (STD) and anthropomorphic torso phantom with 13 μCi/cc in liver insert and two 16cc spheres with 1.66 mCi/sphere (sphere‐to‐liver ratio, S/L = 8). SPECT was acquired with two primary (PI: 65–95 & P2: 95–151 keV) and one scatter (S: 252–302 keV) window. Correlation analysis of projection profiles distal to 90Y sources established that scatter in each P image could be modeled as a fraction of the S image to calculate scatter fractions (SFs). S projections scaled by the SF and smoothed with a 9.6 mm FWHM Gaussian filter were subtracted from the P projections, followed by 3D‐OSEM reconstruction of the scatter‐corrected P projections with CT‐based attenuation and system resolution compensations. Iterations (IT) and subsets (SUB) that yielded the correct S/L ratio was determined. SPECT reconstruction of the STD was used for 90Y SPECT sensitivity calibration. Accuracy of 90Y QSPECT was evaluated by comparing the calculated 90Y activities in the RSD phantom to the true values. Results: The SFs for P1 and P2 were 1.06 and 1.23, respectively. The optimal IT and SUB for 90Y SPECT were found to be 8 and 16. Based on 90Y QSPECT images, the calculated activity (%error) in the RSD phantom liver insert was 14.2 (11%) & 13.1 (3%) μCi/cc for P1 & P2, while those for the two spheres (mCi) were 1.60 & 1.52 (6%) for P1, and 2.29 & 1.86 (25%) for P2. Conclusions: The measured accuracies for the liver insert (P1 & P2) and spheres (P1) are encouraging. The overestimation of sphere activity with P2 suggests improvements of the calibration and scatter correction algorithms are needed.
SU‐GG‐I‐172: Phase‐Contrast Enhancements within Digital Tomosynthesis Images
Authors: Hammonds J , Price R , Donnelly E , Pickens D
Published: August 2010

Purpose: Phase‐contrast edge enhancement uses x‐ray phase shifts to enhance the visualization of boundaries between different materials. While observable in phase‐contrast radiographs or in phase‐contrast computed tomography images, the impact of digital tomosynthesis on this edge enhancement effect has not been studied previously. An experiment was performed to determine if phase‐contrast edge enhancement is improved by using digital tomosynthesis. While this work was performed using phantoms, the ultimate goal is to improve soft‐tissue lesion detectability in clinical mammography. Materials and Methods: An unmodified, commercially available cabinet x‐ray system (Faxitron LX‐60) was used in this experiment. This system contains a tungsten anode x‐ray tube that was operated at 24 kVp and 3 mAs for each radiographic image taken, with an effective focal spot size of about 0.010 mm. The digital detector uses CsI/CMOS with a pixel size of 0.054mm × 0.054mm. The phantom used was a 50mm long, 14mm diameter cylinder made from resin with three holes, each with a 2mm diameter, drilled into it. The phantom was attached to a computer‐controlled rotating motor and was rotated ± 25 degrees about a central position in one degree increments. At each increment, three phase‐contrast radiographs were taken and then averaged to reduce the effect of noise. These images were then placed into our custom written tomosynthesis algorithm (as an ImageJ plugin) that produced a series of 56 longitudinal tomographic images reconstructed with an image offset increment of about 0.7mm. Results: Tomographic z‐plane resolution was measured to be <4.7 mm and, when compared to planar PC images, the tomosynthesis images exhibited an improvement in the edge contrast. Conclusion: The results of this work show that one may combine digital tomosynthesis with phase‐contrast edge enhancement that may be used to further improve soft‐tissue conspicuity.
SU‐GG‐I‐175: Evaluation of Osteolytic Metastases and Myeloma Multiple Skeletal Lesions on Digitized Radiographs with Gray Level Parameters
Authors: Sánchez A Baltasar , Sistal A González
Published: August 2010

Purpose: To evaluate the diagnostic usefulness of gray level parameters in order to distinguish osteolytic metastases (OL) from multiple myeloma (MM) on digitized radiographs. Materials and Methods: We digitized 45 OL and 11 MM radiographs corresponding to 56 different patients of both sexes (0.175‐mm pixel and 12 bit gray scale levels). The components of the characterization computerized scheme developed by our department were: (1) image enhancement by filtering, (2) region of interest selection, (3) parameters output and (4) data processing to distinguish between bone groups. The parameters derived from digitized radiographs were based on gray level histogram analysis of regions‐of‐interests. The SDGL parameter corresponds to standard deviation of the gray values used to generate the mean gray value. Results: The results indicate that there are significant differences (p<0.05) between osteolytic metastases and multiple myeloma skeletal lesions. The SDGL values were: OL= 266 ± 18.76 and MM= 252 ± 12. Conclusion: Our results show that the use of gray level parameters quantify OL and MM zones on digitized radiographs. This may be helpful as a complementary method for differential diagnosis.
SU‐GG‐I‐176: Issues Related to a Digital Portable X‐Ray Iin a Clinical Setting
Authors: Natarajan V , Koehler V
Published: August 2010

With the advancement of new Digital Portable x‐ray machines in digital/Pacs environment while the dose reduction is obvious, other clinical and technical issues need to be addressed. To understand it better, this study will evaluate Film‐screen, CR and DR using abdomen pelvic phantom images made with grid and non‐grid techniques. This study will evaluate the necessity of using a grid with a DR portable in Trauma situations. Further, positioning issues using a grid with DR portables will be explored. It will also address whether quality is sacrificed in case of Hip, Pelvis or AP spine portable examinations using a DR portable with and without a grid. Clinically significant detail, contrast and over‐all density will be evaluated by clinicians. Medical physicist will evaluate the technique factors. In conclusion the practical and useful nature of the study will determine the positioning issues, scatter issues and technical factor issues that everyone must be aware of while using the digital portable x‐ray equipments.
SU‐GG‐I‐178: Numerical Simulations of the SonoKnife's Acoustic Edge
Authors: Moros E , Chen D , Xia R , Chen X , Shafirstein G , Corry P
Published: August 2010

Purpose: A numerical parametric study was performed to characterize the acoustic edge of the SonoKnife applicator for the selection of optimal design parameters for non‐invasive thermal ablation of advanced head and neck tumors and neck malignant nodes. Method and Materials: SonoKnife is a novel thermal therapy concept: a cylindrical ultrasound transducer composed (single element array). This geometry generates a line‐focus (acoustic edge) instead of the typical ellipsoidal focus generated by spherical radiators. Potential advantages of line‐focusing, in contrast to spot‐focusing, are lower peak intensities, which minimize nonlinear propagation and cavitation effects, and shorter treatment times. Acoustic simulations were performed varying the following parameters: transducer size and f‐number, line‐focus depth, frequency, and SSD. Simulations were generated using the free access software FOCUS (http://www.egr.msu.edu/focus‐ultrasound). Results: Dimensions (FWHM) and depth of the focal volume as a function of design parameters were calculated. Minimum transducer surface area to ensure sufficient energy for ablation (52–60°C for several seconds) was determined for several tumor sizes and locations. Results showed the acoustic edge size decreases and its average intensity increases with increasing frequency and increasing aperture. Simulations also indicated that increasing the radius of curvature increases the size of the acoustic edge and decrease its average intensity. SonoKnife's spatial peak intensities were compared to spherically focused radiators of equivalent radiating area. Conclusions: Simulations showed that thermal ablation with the SonoKnife is feasible and designed parameters must be selected depending on tumor size and location. Peak intensities for equivalent area transducers were lower for Sonoknifes than for spherical radiators. Further characterization will include nonlinear effects and thermal simulations. Finally, FOCUS software was a useful and efficient tool for this initial characterization of the SonoKnife's acoustic edge.
SU‐GG‐I‐180: Application of Molecular Imaging in the Monitoring of Angiogenesis of a Hindlimb Ischemia Model
Authors: Kagadis G , Tsioupinaki K , Loudos G , Diamantopoulos A , Soultanidis G , Karnabatidis D , Mihailidis D , Nikiforidis G
Published: August 2010

Purpose: Avβ3 integrin expression is a characteristic feature of the angiogenic phenotype of endothelial cells. Targeted molecular imaging of integrins may be a further step forward in the evaluation of specific and early aspects of angiogenesis. The purpose of our study was to investigate the potential of molecular imaging with the aid of a dedicated high resolution γ camera in the rabbit hindlimb ischemia model. Method and Materials: A 99mTc labeled cyclic RGD peptide ([c RGDfk‐His]‐99mTc) was employed for angiogenesis imaging in the New Zealand white rabbits hindlimb ischemia model. Imaging of αvβ3 expression was performed in two animal groups. In group A imaging was employed 3 days and in group B 9 days post femoral artery occlusion (2 rabbits in each group). Each rabbit was injected intravenously with 200 μl of [c RGDfk‐His]‐99mTc (0.5 mCi). Consequently dynamic planar imaging was performed with a high resolution gamma camera with FOV 5×10 cm, equipped with a parallel hole collimator. Static 8 minute images at 80 minutes post injection of the radiotracer were acquired. Results: We have imaged 4 rabbits. An increase of 12.2% was observed in group A in relative radiotracer retention at the ischemic hindlimb compared to control. In group B this relative radiotracer retention was increased to 25.8%. The control limbs showed an increase in the radiotracer retention at day 9 but still much lower compared to ischemic limbs. Moreover, radiotracer accumulation was observed to a region distal to the original area of occlusion, where the newly formed proximal collaterals are located. Conclusion: Our study demonstrates that the phenomenon of angiogenesis proceeds and is maximized within on day 9 following induction of ischemia in a mammalian experimental model. Further studies are deemed necessary in order to establish this conclusion and provide quantitative results.
SU‐GG‐I‐181: Noise Characterization of a Clinical Flat‐Panel Cone‐Beam Computed Tomography (CBCT) System
Authors: Vedantham S , Gounis M , van der Bom M , Karellas A , Wakhloo A
Published: August 2010

Purpose: To quantitatively characterize the noise performance of a neurointerventional c‐arm based flat‐panel cone‐beam computed tomography (FP‐CBCT) system with an aim of exploring the feasibility of performing cerebral blood volume (CBV) calculations. Method and Materials: Five CBCT scans of ∼11 cm diameter water phantom positioned at the isocenter were acquired at 120kVp and reconstructed to 5123 matrix with 0.33mm voxels. Central Regions of Interest (ROIs) of 1933 matrix corresponding to ∼(63mm)3 were extracted from each scan. Spatial uniformity was determined using the standard deviation (SD) in Hounsfield Units (HU) and repeatability was measured using the root‐mean‐squared deviation (RMSD) of mean signal and using the coefficient of variation (COV) of SD metrics. 3‐D noise power spectra (NPS) were computed with and without subtraction of the average ROI volume from each ROI, which allowed determination of structural noise. Results: Mean signal and SD determined from (193)3 matrix and averaged over the 5 scans were 9.3HU (range: 8.4–10.3; RMSD=0.5) and 19.1HU (range: 19.05–19.15; COV<0.3%). Mean signal determined from (193)2 matrix in each axial plane along the cone‐beam direction indicated small variations (< 5HU). NPS analysis indicated high noise power at zero‐frequency, suggestive of aliasing effects. Increased noise power was also observed along the axes, which were not associated with fixed‐pattern structural noise. Conclusion: Variability in mean signal across multiple scans and its difference from theory suggest the need for improved HU calibration. While the observed noise (SD) suggest the potential feasibility of performing CBV calculations with FP‐CBCT, methods for noise reduction may improve the quantitative accuracy of such studies. Supported in part by NIH R01CA128906 and R21EB007767. Contents are solely the responsibility of the authors and do not represent the views of NIH, NCI, or NIBIB. Conflict of Interest: Institutional master research agreement with Philips Healthcare.
SU‐GG‐I‐182: Adjustment of Angiographic Time‐Density‐Curves Temporal Parameters for More Accurate Healing Prediction of Stent‐Treated Aneurysms
Authors: Ionita C , Wang W , Bednarek D , Rudin S
Published: August 2010

Purpose: Immediate treatment assessment of intracranial aneurysms using flow modifying stents, can be done using comparative analysis of pre‐ and post‐stented normalized time density curves (NTDC). Previous study showed poor correlation of the time‐related NTDC parameters with the treatment outcome. A parameter normalization method to improve the NTDC parameters‐treatment outcome correlation, is proposed and investigated. Method and Materials: Elastase animal aneurysms model were treated using Asymmetric Vascular Stent prototypes. Angiograms were acquired pre‐ and post‐treatment and after four‐weeks. NTDC's parameters: time‐to‐peak TTP, mean‐transit‐time MTT and wash‐out‐time WOT, were measured and normalized to the corresponding quantities derived from main artery bolus TDC. Aneurysms displaying small area with contrast filling localized at the aneurysm neck were dropped from the analysis. The results are further presented in terms of pre‐stented/post‐stented ratios to describe the flow changes due to stent treatment. Based on a four week follow‐up angiogram, a five grade scale was used to generate a “healing” grade. The correlation between the parameter ratios and healing grade was calculated using Spearman correlation factor (SCF). Results: The pre‐/post‐stented ratio parameters after normalization were: TTP=0.30±0.28, MTT=0.42±0.42 and WOT=0.29±0.28. The SCF's between the time‐related ratios and the healing grade before the correction were under 0.52. After corrections implementation, all SCF's were above 0.82. Conclusion: After implementation of the proposed adjustments the measured parameters agree better with the treatment outcome, hence a better treatment assessment scale can be built for accurate aneurysm occlusion prediction (Support: R01NS43924 and R01EB002873 and Toshiba Medical Systems Corp)
SU‐GG‐I‐183: Parameterization of Time‐Density Curves (TDC) and Regional‐TDC's to Quantify Flow Modification Inside Aneurysms Treated with Flow‐Modifying Devices (FMD) Following Endovascular Image‐Guided Interventions
Authors: Dohatcu A , Ionita C , Sherman J , Bednarek D , Hoffmann K , Rudin S
Published: August 2010

Purpose: Digital Subtraction Angiography (DSA) is used to evaluate endovascular treatments, either visually or using time‐density curves (TDC), which present change of contrast as a function of time for either the entire aneurysm or sub‐volumes within (R‐TDC). Quantitative parameters such as peak‐density‐value, time‐to‐peak, input rate, influx, residence time, wash‐out‐time, and wash‐out‐rate were used in this study to examine the hemodynamic implications of several treatments using FMDs. Method and Materials: Flow evaluations for aneurysms (saccular and bifurcation geometries) were done using elastomer‐based replicas of clinical human cases. These phantoms were placed in in‐vitro pulsatile flow loops containing a blood‐simulating solution of glycerin‐water. One‐cc boluses of iodinated contrast were delivered at the proximal end of parent vessel of each aneurysm via 5‐Fr catheters using an automatic injector. DSA sequences were acquired at 30 frames/sec (5‐inch II‐mode). The necks of the aneurysms were covered using different‐porosity FMDs. TDCs were obtained pre‐and‐post‐treatment.Results: R‐TDC metrics indicate important modifications of flow occurred in different areas inside the aneurysm that are not evident from the total‐volume TDC. For example, in a sub‐region of saccular aneurysm treated with a zero‐porosity‐patch FMD, occluding the proximal portion of the aneurysmal orifice, peak‐density decreased 49% compared to untreated case and the flow behavior is changed from continuous to oscillatory, while the total aneurysm measurement shows a decrease in peak‐density of 21% and an increase of wash‐out‐time of 171% versus untreated case. In a sub‐region of the bifurcation aneurysm treated with non‐zero‐porosity patch FMD placed to occlude the entire neck, time‐to‐peak increased 67%, and input rate decreased 71% compared to untreated case, while the total aneurysm measurement shows a time‐to‐peak increase of 20% and an input rate of 50% versus untreated case.Conclusion: Proposed parameterization of TDC's is rapid and terms have physical meaning. Support: NIH R01‐NS43924, R01‐EB002873, Toshiba Corp.
SU‐GG‐I‐185: Extraction of Blood Flow Patterns from Coronary Angiographic Data
Authors: Gao M , Chen S , Wei D
Published: August 2010

Purpose: A new approach presented to extract the coronary artery and blood flow patterns from the angiographic data. Materials and methods: The method uses a sequence of coronary angiographic data. Firstly, the morphological erosion and the half‐thresholding are used for removing points except coronary area. Secondly, use morphological closing to join the gaps of the vessel. Thirdly, select the vessel points in the image sequence which is similar to the seed points. Make the seed points, which is also the whole skeleton of the vessel, continuously growing by the vessel points in the image sequence. Finally, compare the initial image sequence (grey value 0 to 1) with the seed image (binary image) which can bring the change of grey value in the vessel without the change of grey value in the background and save the result image sequence to AVI file. Result: The accurate boundary of the coronary artery is obtained and the blood flow is clearly present. Conclusion: The method is shown with better performance than current methods, particularly in modeling the flow pattern. And it's a very simple, fast and accurate method in precise diagnosis and treatment of patients. Key words: coronary artery, extraction, flow pattern, seed.
SU‐GG‐J‐01: 3D‐3D Deformable Registration Based on Bifurcations of Tubular Organs for the 4D Computed Tomography (4DCT) Image Sets
Authors: Zhou J , Jabbour S , Kim S , Goyal S , Haffty B , Chen T , Yue N
Published: August 2010

Purpose: To develop an accurate feature based 3D‐3D deformable registration method for patient‐specific motion model used in external beam radiation treatment of lung cancers based on a 4D computed tomography (4DCT) image set by utilizing unique features of the bifurcations of tubular organs. Method and Materials: Each 4DCT set consisted of 10 phases of 3DCT volumes during one breath cycle. A 3D tubular organ segmentation was first performed on each of the phases to extract the centerlines of bronchial trees, estimate radius of bronchial trees and automatically detect the bifurcation points by applying learning algorithm with specially designed filters. A novel deformable registration method was applied to minimize the distances of the corresponding bifurcation points between a target phase and a reference phase (e.g., between 0% phase and 50% phase) to capture the transformation between different phases. The results were evaluated by using volume and distance based estimators. Results: The learning method was trained and tested with positive and negative examples. The generalization error of the learning method was estimated using bootstrapping with the mean error rate 4.6%. The detailed quantitative and qualitative registration results are shown in the supporting materials. The mean distance estimator yielded results ranging from 1.93 mm to 4.46 mm between the corresponding points between the 0% phase images and the 50% phase images after the deformable registration. The root‐mean‐square error ranged from 1.99 mm to 5.13 mm. Conclusions: A novel and accurate 3D‐3D registration method based on the bifurcations of the tubular organs was developed to capture the transformation between the 3D CT images in the 4D computed tomography (4DCT) image sets. These preliminary results show that the proposed method is robust, fast and accurate for the deformable registration of the tubular organ in the lung.
SU‐GG‐J‐02: Dose Painting by Numbers Based on SUV Data for Advanced Lung Tumors
Authors: Steenhuijsen J , Meijer G , Zwanenburg A , Bal M
Published: August 2010

Purpose: to develop a plugin with user interface for the Pinnacle TPS (Philips Medical Systems) to directly integrate SUV data obtained by PET‐scanning into the optimization process for lung tumor IMRT plans. Method and Materials: A plugin generating a grid with the prescribed dose per voxel was developed. The prescribed dose values are based on the underlying SUV data per voxel, not on contours. Various user‐defined functions can be used to give the relation between SUV data and prescribed dose. New objective functions were generated to calculate a cost based on the voxel‐by‐voxel difference between the actual dose distribution and the prescribed dose distribution. During the IMRT optimization these (biological) objective functions are used in conjunction with conventional dose volume objectives process. Further tools were developed to create a SUV‐Volume Histogram, showing the SUV distribution in any ROI, and to visualize the quality of the resulting plan by showing the distribution of the voxel‐by‐voxel differences between prescribed and actual dose distribution. Results: With the plugin SUV‐based dose prescriptions were made. After optimization with the plugin, which took only several minutes per plan, plans were evaluated with the newly devised tools. Optimization resulted in doses to regions with high SUV of typically 130% – 200% of the current clinical dose. Mean lung dose and other dose objectives, which were unaltered from standard IMRT optimization, were met for all plans. Conclusion: A plugin was developed enabling us to steer the dose within the lung GTV based on the underlying SUV distribution. Using these tools we were able to boost voxels with high SUV up to a dose level of up to 200% of the current clinical dose with only very limited dose increase to the normal structures as lung and spine.

Conflict of Interest: Research sponsored by Philips Medical Systems
SU‐GG‐J‐03: Emission Guided Radiation Therapy System: A Feasibility Study
Authors: Mazin S , Nanduri A , Pelc N
Published: August 2010

Purpose: To evaluate the feasibility of a combined PET‐Linac system for real‐time guidance of radiation therapy for tumors that move due to respiration. Method and Materials: We are developing a treatment system that will simultaneously deliver radiation during PET acquisition. A method to compensate for respiratory motion will be to deliver radiation beam‐lets along individual PET lines‐of‐response (LOR's) as they are detected. The system involves rotating a radiation source and PET detectors on a gantry while dynamically controlling a binary multi‐leaf collimator to deliver the beam‐let responses in a 2D helical mode. Simulations were conducted using GATE to model 300 seconds of PET list‐mode acquisition of a ‘hot’ 3 cm diameter tumor exhibiting 3.7 second periodic 2 cm peak‐to‐peak motion in a ‘warm’ background. A 5 cm planning target volume (PTV) was used as a filter to reject LOR's that did not intersect this volume. LOR's that intersected the PTV and whose timestamps were within a 500 ms cutoff window were responded to. A voxel‐based Monte Carlo simulation package was used to model the resultant dose distributions comparing the emission guided (EGRT) method with uniform coverage of the PTV. Results: Composite dose volume histograms were calculated using 10 phases of the motion cycle. Dose to the non‐tumor volume was normalized to the same mean value for both scenarios. The EGRT approach exhibited a non‐uniform dose distribution to the tumor compared to uniform PTV coverage. However, even with the non‐uniformity, there was a 30% relative increase in minimum dose to the tumor volume for the EGRT approach. Conclusion: Although non‐uniform dose delivery to the tumor volume needs to be addressed, the feasibility of using PET to guide radiation delivery in real‐time has been demonstrated.

Conflict of Interest: SRM and ASN are co‐founders of a company commercializing emission guided radiation therapy.
SU‐GG‐J‐04: Determination of Tumor Volume Using a Joint Motion‐PVE Correction Technique in PET/CT Imaging
Authors: Chang G , Chang T , Clark J , Mawlawi O
Published: August 2010

Objective: 4D‐CT has been used to determine the tumor volume (TV) for lung/thoracic radiation therapy treatment planning primarily due to its ability to detect the tumor motion extent and trajectory. However, 4‐D CT is usually characterized by high patient radiation exposure. The objective of this abstract is to propose and evaluate an approach that relies on a single static PET/CT scan than can determine the TV by simultaneously correcting for respiratory motion artifact and partial volume effect (PVE) thereby eliminating the need for 4D‐CT and reducing patient exposure.Materials and Methods: The proposed joint correction approach incorporates a model of motion blurring, PVE and object size/shape. A motion blurring kernel (MBK) is then estimated from the deconvolution of the joint model while the TV is derived from convolving the MBK by the object size/shape obtained from the CT image. To test this technique, two studies were performed using 2 spheres of different sizes moving in a 2cm 1D‐sinusoidal and 2D‐circular waveforms respectively. In both cases, a 4D‐CT and a PET/CT of the 2 spheres were acquired. For both studies, the TV from the proposed technique was compared to the maximum‐intensity projection (MIP) volume of the 4D‐CT. Also a Dice coefficient of the two volumes was calculated. Results: The TV of the proposed technique was on average 3% different from the MIP volume. The average Dice coefficient was 0.87. The motion trajectory derived from the proposed technique is continuous while that of the 4D‐CT is discrete. Conclusion: Using this approach, a single static PET/CT can replace a 4D‐CT to determine the TV. This approach also has the ability to determine the tumor motion extent and trajectory and has the added advantage of reducing patient radiation exposure and determining the tumor locale probability (or MBK) compared to 4D‐CT.
SU‐GG‐J‐05: Monte Carlo Investigation and Measurements of Distal Edge Degradation in Lung Phantoms with Therapeutic Proton Beams
Authors: Perles L , Sawakuchi G , Mirkovic D , Mohan R , Titt U
Published: August 2010

Purpose: To validate a computational lung model and investigate distal edge degradation of therapeutic proton beams. Methods and Materials: We used the Monte Carlo code MCNPX to simulate therapeutic proton beams traversing a computational lung model. The computational lung model consisted of a slab constituted of randomly distributed voxels of air and plastic resin. Two computational lung slabs with different voxel resolutions were studied including: i) a high resolution slab (0.5 mm cubic voxels), which was assembled by randomly distributing the air and plastic resin voxels. This slab assembly reproduces the density gradient found in real lung‐equivalent plastic slabs (realistic lung‐equivalent slab); and ii) a low resolution slab (2 mm cubic voxels), which was generated by merging neighbor voxels and appropriately scaling the density and atomic fractions. This slab has a similar density distribution to a CT image (CT‐equivalent slab). All simulations were done using a validated MCNPX model of the passive scattering beam line from the Proton Therapy Center at M.D. Anderson Cancer Center. Our simulations were compared to measured depth doses of a therapeutic proton beam traversing a lung‐equivalent plastic slab. Results: The distal edge degradation predicted by the simulations of the realistic lung‐equivalent slab was in agreement with the experimental data. However simulations of proton doses from beams traversing the CT‐equivalent lung slab did not show any distal edge degradation. Conclusion: Our findings show that a computational lung phantom model with high resolution is needed to accurately predict the distal edge of proton dose distributions.
SU‐GG‐J‐09: Effective Tracking of Intrafractional Organ Motion Due to Breathing Using a Siemens 160 MLC
Authors: Krauss A , Nill S , Oelfke U
Published: August 2010

Purpose: In this work we demonstrate effective tracking of highly irregular breathing motion using a dynamic Siemens 160 MLC™ and a neural network predictor to compensate for the relatively large end‐to‐end system latency of 500 ms. Method and Materials: One‐dimensional breathing patterns were recorded from several radiotherapy patients using the ANZAI pressure belt system. The pressure belt signal was reproduced by a programmable phantom, which has embedded electromagnetic transponders for target localization and tracking (Calypso® Medical Technologies, Inc.). The aperture of a Siemens 160 MLC™ was adapted in real‐time to the target position provided by the Calypso system. Due to the highly irregular nature of breathing motion, advanced prediction methods are required to accurately compensate the system latency. We therefore implemented a feedforward neural network predictor. The network was trained on a 120 second sample of breathing data which preceded the data that was used for the subsequent tracking experiments. The geometric tracking accuracy was determined through an analysis of portal images acquired during radiation delivery. A metal ball attached to the phantom allowed the reconstruction of the phantom trajectory from the portal images. Tracking errors were quantified as the difference between the phantom trajectory and the geometric centroid of the radiation field on the portal images. Results: In an offline cross‐validation study, we could identify a common set of model parameters of the neural network, which yielded good prediction performance for all the breathing patterns under consideration. The analysis of the images acquired during the tracking experiments yielded root mean squared tracking errors of 1.21 mm, 1.29 mm and 1.58 mm for the three investigated motion patterns. Conclusion: In spite of the relatively large system latency, we achieved highly accurate MLC tracking for irregular breathing patterns.

Conflict of Interest: Supported by Siemens Healthcare OCS and Calypso Medical Technologies, Inc.
SU‐GG‐J‐10: Investigation of a Novel Algorithm for True 4D VMAT Planning and Delivery
Authors: Chin E , Otto K
Published: August 2010

Purpose: To quantify the ability of our 4D VMAT planning algorithm to generate deliverable plans over a range of target motions. Method and Materials: Our 4D VMAT planning algorithm is an extension of the 3D algorithm by Otto (Med Phys 35 2008, 310–317) and fully incorporates target and organ motion during optimization. Delivery of each MLC aperture is synchronized to a specific phase of the target motion. The magnitude of motion between each phase is 2.5 or 5 mm. Using a phantom consisting of a cylindrical target nested within a half‐ring avoidance structure, treatment plans for a range of uniform target motions (0.5 – 4 cm) and periods (2.5 – 5.5 s) were generated. Dose prescription was 60 Gy. DVHs from the 4D VMAT plans were compared against the 3D VMAT DVH as well as 3D motion degraded DVHs. Results: 4D VMAT plans were similar in quality or superior to the 3D plan. For motion ranges of 1.5 cm and 4 cm, the volume of the avoidance structure receiving more than 20 Gy was decreased by 10.4% and 28.6% respectively while the target volume receiving greater than 58 Gy increased by 6.5% and 16.5%. Total treatment time ranged from 141 – 181 minutes to deliver the full 60 Gy prescription or 4.7 – 6.1 minutes for a 2 Gy fraction assuming maximum dose rate is 600 MU/min. Motion of 1 cm can cause noticeable degradation of the 3D DVH. Conclusion: Our 4D VMAT planning algorithm can create plans equal to or superior to 3D plans. Future work will investigate whether these benefits can be extended to actual 4D clinical patient data.
SU‐GG‐J‐11: Contrast to Noise Ratio Measurements for Real Time MR Lung Tumour Imaging Sequences at Lower Fields — A Phantom Study
Authors: Yip E , Yun J , Wachowicz K , Rathee S , Fallone B
Published: August 2010

Purpose: Magnetic Resonance Imaging (MRI) has been proposed for real‐time image guidance during lung radiotherapy treatment. Dynamic lung MR studies in the literature have demonstrated the feasibility of real‐time tumour tracking at 1.5T scanners. Lower field magnets offer several advantages over high field magnets, but has lower signal to noise ratio and a different contrast environment due to field strength dependences in T1 and T2*. The purpose of this study was to determine the expected contrast to noise ratio (CNR) at 0.2T for several rapid MR sequences by performing experiments in a 3T MRI. Method and Materials: Lung tumour is simulated by loading solution containing CuSO4 and MnCl2 in a sphere. To simulate the lower relative proton densities (PD) of lung parenchyma, 2mm acrylic beads are uniformly suspended in gelatin. T1, T2 and T2* and relative PD are measured for the phantom in 3T and compared against their expected values at 0.2T from literature. For real time imaging, rapid gradient echo sequences (FLASH and balanced SSFP) are used to acquire images from 3–10 frames per second using acceleration techniques of halfscan and parallel acquisition. A dynamic noise scan is used to estimate noise and is adjusted to reflect the lower SNR at 0.2T. Measurements are repeated using a body coil and a 6 channel thoracic SENSE coil for parallel imaging. Results: The measured T1, T2 and T2* and relative PD of the phantom are similar to the values given in literature. For dynamic lung images, CNR ranges from 9.4–31.7 for bSSFP and 4.0–13.8 for FLASH. In house auto‐contouring algorithm shows good quality contours of spherical tumours with CNR > 2.5. Conclusion: In this phantom study, dynamic lung imaging sequences are shown to provide sufficient tumour‐tissue CNR and temporal resolution for real time MR lung tumour tracking at 0.2T.
SU‐GG‐J‐12: On‐Line Fluoroscopic Image of a Slice of Interest Using the X‐Ray Images and a Priori Anatomical Information
Authors: Yi B , Zhang J , Lasio G , Yu C
Published: August 2010

Purpose: On‐line 4‐D imaging is required for managing intra‐treatment organ motion. A new method which enables fluoroscopic imaging of a slice of interest (SOI) is developed and tested. This new technique uses projection images from the on‐board imaging system and does not use breathing surrogates. Method and Materials: Tomographic image via background subtraction (TIBS) uses a priori anatomical information from a previous cone beam or fan beam CT scan to isolate a SOI from a planar kV image by factoring out the attenuations by tissues outside the SOI (background). This study extends TIBS to 1) allow an SOI be imaged at any beam angle rather than only from that perpendicular to the SOI and 2) generate a temporal sequence of the SOI. The background is generated by substracting the SOI which is orthogonal to the desired viewing angle rather than to the gantry anlgle. Therefore, projection images taken during a gantry rotation can be used to generate images of the SOI of the same viewing angle but at different times, forming a fluoroscopic sequence of the SOI. A 14cm diameter cylindrical water phantom containing objects subject to one‐dimensional cyclic motion is used to test the feasibility. Results: The fluoroscopic image of the SOI containing moving objects was acquired by combining the SOI images from different gantry angles acquired at different times. Contrast of the objects is improved. Breathing surrogate or sorting process is not needed. Like tomosynthesis, a slice of interest can be clearly imaged. Unlike tomosysthesis, TIBS maintains the independence of each of the projections thereby reveals temporal variations within the SOI. Conclusion: A new technique which directly generates the fluoroscopic images of a SOI with x‐ray projections from the different angles is developed and proven feasible. This technique can be used for on‐line imaging of moving targets.
SU‐GG‐J‐13: Geometric Accuracy of Real‐Time Tumor Tracking with the Gimbaled Linac System of the Novel VERO SBRT System
Authors: Depuydt T , Verellen D , Erbel S , Haas O , De Ridder M , Storme G
Published: August 2010

Purpose: The VERO system, a novel platform for image guided stereotactic body radiotherapy, is a joint product of BrainLAB and MHI. A new type of 6MV linac with attached MLC is mounted on an O‐ring gantry. Orthogonal gimbals hold the linac‐MLC assembly, which allows pan and tilt motions of the therapeutic beam. This offers the possibility to perform tracking of moving tumors. A prototype is currently installed in our hospital which can actively track an IR marker with the beam using the gimbals system. The purpose is to determine the geometric accuracy of the tumor tracking. Methods and Materials: A video camera based detection unit was developed to simultaneously acquire the position of the tracked object and of the tracking beam using the light field of the linac system, at a 30fps frame rate. An assessment was made of the tracking capabilities in terms of tracking errors, system lag and the equivalence of pan and tilt motion performance. To determine the tracking error, an IR marker was placed on a 1D moving phantom. A sinusoidal motion was produced by the phantom with different frequencies from 0.085Hz to 0.5Hz, and a fixed amplitude of 20mm. The tracking error was characterized in terms of systematic error, root mean square error (RMSE) and 90% percentile of the absolute tracking error (E90%). Results: Systematic tracking errors were below 0.21mm. The system lag was 47.7ms (2.3ms) and 47.6ms (2.0ms) for the pan and tilt respectively. The system can track the IR marker sinusoidal motion accurately, with an E90% < 0.82mm, up to frequencies of 0.5Hz with similar performance for pan and tilt. Additionally, the tracking is demonstrated for representative patient signals. Conclusion: The accuracy is considered adequate for real‐time tracking of tumors. The performance for pan‐tilt is equivalent. Conflict of Interest: Research sponsored by BrainLAB.