bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐I‐70: A Skeletal Model for Marrow Dosimetry in the ICRP Reference Adult Female
Authors: Sinclair L , Pafundi D , Bolch W
Published: April 2010

Purpose: The skeleton is of critical interest in internal radiation dosimetry. Accurate absorbed dose estimates to the hematopoietic tissues in the active (red) bone marrow and osteogenic tissues in the shallow active bone marrow are of primary importance in predicting the short‐term deterministic (myelotoxicity) and long‐term stochastic (leukemia and/or osteosarcomas induction) effects of radiation exposure. Presently, there are no international standards for skeletal reference models that are based upon a female subject. The purpose of this project is to complete the skeletal model for the ICRP reference adult female. Method and Materials: The development of this female skeletal reference model involves harvesting of major skeletal sites, as well as ex‐vivo CT imaging of the skeletal sites. The ex‐vivo CT scans provide image data for quantifying both trabecular spongiosa and cortical bone ratios within the bone site through manual image segmentation and constructing 3D anatomic models of the bone site for subsequent paired‐image radiation transport simulations. After review of each bone site's ex‐vivo CT scan, samples of spongiosa are strategically excised for imaging via microCT. Next, the microCT scans of each bone site's microstructure and ex‐vivo CT scans of each bone site's macrostructure are coupled and imported into the PIRT (Paired‐Image Radiation Transport) code. PIRT is able to track particle energy deposition both at the macroscopic scale and the microscopic scale simultaneously. Results: The end result of running these simulations will be absorbed dose estimates to the active bone marrow from the following sources: cortical bone surface and volume sources, trabecular bone surface and volume sources, and the trabecular active marrow itself. These will be compiled and available for use in estimating dose for the reference adult female. Conclusion: This reference skeletal model will be used to determine skeletal masses and accurate bone marrow dose estimates from radiation exposures.
SU‐FF‐I‐72: Evaluation and Comparison of Image Quality Figures for Digital Mammography
Authors: Tsai HY , Liu HL , Hwang YS , Chen CC
Published: April 2010

Purpose: To survey the image quality of digital mammographic units in Taiwan using a mammographic contrast‐detail phantom and an ACR accreditation phantom, and to compare image quality figures from those two phantoms. Method and Materials: The scope of the survey covered most digital mammographic units in Taiwan. On‐site measurements included phantom image acquisitions and entrance surface doses (ESD). Image acquisitions of an ACR accreditation phantom (Victoreen N‐566 18‐220) and ESD measurements were following the protocols of the ACR Mammography Quality Control Manual. A mammographic contrast‐detail phantom (CDMAM type 3.4, Artinis) with 1‐cm PMMA‐equivalent thickness was placed on the PMMA of 3 cm. The CDMAM assembling was exposed using the same technical factors as the ACR accreditation phantom. Signal‐difference‐to‐noise Ratios (SDNR) of the largest mass inside the ACR phantom were calculated by the equation, . Inverse Image quality figures (IQFinv) were calculated according to the threshold diameter (Di,min) at each contrast‐column (Ci), . Results: Fifty‐seven digital units were surveyed, including 44 DR units and 13 CR units. The tube voltage, tube current‐time product, and ESD range from 23 to 29 kV, 36 to 182 mAs, and 3.22 to 12.4 mGy for imaging the ACR phantom. The mean values and standard deviation of SDNR are 1.97±0.31 for GE 2000D, 1.50±0.91 for GE DS, and 1.76±0.20 for Hologic Lorad Selenia. The mean values and standard deviation of IQFinv are 127±10 for GE 2000D, 120±11 for GE DS, 135±28 for Hologic Lorad Selenia, and 101±0 for Siemens Novation DR. The correlation between SNDR and IQF are mild (R2=0.414 for GE 2000D; 0.520, GE DS; 0.446, Hologic Lorad Selenia). Conclusion: The SNDR obtained from the ACR phantom mildly correlates with the IQFinv evaluated from the CDMAM phantom.
SU‐FF‐I‐77: Diagnostic X‐Ray Beam Hardening as a Function of Patient Size
Authors: Behrman R , Yanch J
Published: April 2010

Purpose: To investigate changes in x‐ray energy spectrum as a function of depth in phantoms representing lean and overweight individuals. Methods: Three phantom torsos comprised of tissue equivalent material were modeled as elliptical cylinders using MCNPX. Two x‐ray beams used in planar radiography (80 kVp HVL = 2.42 mm Al; 140 kVp HVL = 5.15 mm Al) and one beam used in CT (140 kVp HVL =9.09 mm Al) irradiated each phantom and normalized photon spectrum was examined at several depths. Separate comparisons were also made with data presented by Birch et al who examined spectral changes as a function of depth but did not include Compton scattered photons. Results: Good agreement with data from Birch et al is obtained for the lean phantom when Compton scattered photons are not included. These results show substantial beam hardening as evidenced by a shift in the peak beam energy from 32 keV (entrance) to 54 keV (exit) for the 80 kVp beam and 40 keV to 64 keV for the 140 kVp (HVL=5.15 mm Al) beam. However, substantial beam hardening is not observed when Compton scattered photons are included in the measurement. For the 80 kVp beam, the average energy of the photons traversing the phantom changes by only 15 % in traversing the lean, 20 cm diameter thick phantom, and by only 18% in traversing the very overweight 45 cm thick phantom. For the hardest beam (140 kVp HVL=9.09 mm Al), average beam energy changes by only 7.4% in traversing through 45 cm tissue. Conclusion: Under conditions of broad beam geometry such as radiography, spectral hardening of the radiography and CT x‐ray beams examined is not substantial, even after traversal through very thick phantoms. However, when narrow beam geometry is approximated, spectral beam hardening is significant.
SU‐FF‐I‐83: Quantitative Analysis of Low Contrast Image Quality in Fluoroscopic Systems
Authors: Dave J , Gingold E
Published: April 2010

Purpose: Visual assessment methods lack the precision to detect subtle changes in the low contrast performance of portable fluoroscopes used for surgical guidance. The purpose of this study is to develop a simple and reproducible quantitative method for measuring the low contrast imaging capability of portable fluoroscopes for quality assurance purposes. Method and Materials: Images of a low contrast detectability phantom were captured using a portable fluoroscope routinely used for intraoperative imaging. The phantom consisted of a 2.5 cm acrylic sheet containing 6 circular holes of 1.9 cm diameter, each filled with a different concentration of iodine. Two different dose rate modes were employed, and copper filtration was varied between 0 and 3 mm to produce a set of images spanning a range of subject contrast and quantum noise. Fluoroscopic last‐image‐hold frames were saved in DICOM format and transferred to a computer for analysis. The absolute contrast, contrast‐to‐noise ratio (CNR) and signal‐difference‐to‐noise ratio (SdNR) were calculated for each low contrast target. Five blinded human observers evaluated and scored the phantom images by counting the number of visible objects. The human observer scores were pooled and ranked, as were the quantitative metrics. The rankings were compared using the non‐parametric Spearman rank correlation coefficient. Results: The rank correlation coefficients between human scoring and quantitative scoring were statistically significant for absolute contrast (rs=0.869, p<0.01), CNR (rs=0.940, p<0.005) and SdNR (rs=0.940, p<0.005). Conclusion: The agreement with human observer ranking indicates that these quantitative image quality measurements may be suitable for use in the routine assessment of fluoroscopic systems for quality control purposes. This method eliminates the subjectivity, variability and bias inherent in quality control based on visual assessment by an individual observer.
SU‐FF‐I‐84: Pateient Exposure Vs. Scattered Radiation to the Operator of Fluoroscopy
Authors: Lin P
Published: April 2010

Purpose: To evaluate and identify which of the two following conditions is better for the patient and the fluoroscopist. Circumstance: During radiation safety in‐services, various questions are raised by the fluoroscopists pertaining to the radiation received by both the patient and the physician. One such questions; “is it better to employ a large field of view (FOV) with collimated radiation field? Or, is it better to use the magnified mode FOV”. The underlining question here is “what is the patient entrance exposure” as opposed to “how much scattered radiation dose the fluoroscopist receives” under these two different operating conditions while the irradiation geometry is the same. The answer to this question is actually a lot more complex than it appears. There are few factors involved, as will be shown, namely; (1) “better” to whom, (2) dependent on whether it is equipped with an image intensifier or a flat panel image receptor and (3) the automatic dose rate control logic of the equipment. Method and Materials: In this study, three different types of fluoroscopy systems were selected for investigation of patient entrance exposure and scattered radiation to the fluoroscopist. They are; a cardiovascular angiography system, a conventional fluoroscopy system and a mobile C‐arm fluoroscopy system. The patient entrance exposure and the scattered radiation at the location where the fluoroscopist stands are measured as functions of varying phantom thickness under the same irradiation geometry. While the irradiation geometry may be the same, the fluoroscopic automatic dose rate control logic may not respond in the same manner under the conditions of (a) the large FOV with collimated radiation filed, and (b) the magnified mode FOV. Conclusions: The preliminary data showed both expected and unexpected results. The findings should of great interests to the fluoroscopists and medical physicists alike. Detailed analysis will be presented.
SU‐FF‐I‐90: A Clinical Evaluation of the M‐Rep‐Based Automatic Prostate Segmentation
Authors: Tang X , Kimple R , Harris S , Foskey M , Tracton G , Chang S , Chaney E , Pizer S , Deschesne K
Published: April 2010

Purpose: To evaluate the clinical application readiness of a statistically trainable deformable shape model, called an m‐rep, for automatic segmentation of the prostate from CT images by comparison with manual contouring. Method and Materials: ConStruct, an in‐house automatic prostate segmentation tool featuring m‐rep (medial representations) models, was used in this study. This study is to test the robustness of the m‐rep models for prostate treatment planning segmentation in routine use. For each patient case, an m‐rep was initialized and automatically deformed to segment the prostate. Ground truth was taken to be the contour set used for treatment planning. Two radiation oncologists each manually created an additional contour set. The average distance between m‐rep segmentation (or manual segmentation) and the ground truth was calculated. Retrospective clinical validation was also carried out in all cases. Two radiation oncologists blindly scored all the contour sets including the ground truth. Score 1: perfect contour—no corrections needed; 2: minor correction—less than one third of the slices require correction; 3: major correction—more efficient than redrawing all the contours from scratch; 4: not acceptable. Results: Averaged over five patients, the average distances between m‐rep, set 1 and 2 manual contour sets and the ground truth are 0.51, 0.45, and 0.42 cm, respectively. The average scores for m‐rep, set 1, set 2 contour sets, and the ground truth are 2.4, 2.4, 2.0, and 2.1, respectively. Conclusion: The qualitative and clinical validations were performed on m‐rep‐based automatic segmentation by comparing it to manual contouring. M‐reps appeared to produce reasonable and acceptable prostate contour sets when compared to those generated by clinicians. We propose that m‐reps be used to improve clinical efficiency by automatically contouring the prostate as a starting shape and then manually editing when needed. Further validation on a larger patient cohort is indicated.
SU‐FF‐I‐93: The Effect of Surface Rendering On Anatomical Structures Arising From Deformable Image Registration
Authors: Lynch B , Xia J , Palta J , Samant S
Published: April 2010

Purpose: Volume rendering is important in deformable image registration (DIR) and hyperdimensional imaging (>3D). Interpolation and the use of finite volume element grids to describe the image and 3D surface/volume datasets can cause partial occupancy when structures are mapped by deformation vectors. The choice of surface rendering technique directly impacts the agreement between manually and automatically delineated structures. The purpose of this study was to investigate the effect different surface rendering algorithms have for CT imaging sets mapped by DIR. Method and Materials: 4DCT clinical lung imaging was used in this study. A single expert user with secondary confirmation contoured the GTV, right lung, and left lung on the FBCT as well as on all ten phases of the 4DCT. The Juggler DIR algorithm was used to calculate the deformation vectors between the free breathing CT and each phase of the 4DCT. The deformation vectors were then applied to the contours of the FBCT, and different surface rendering techniques were applied (including thresholding and [Christiansen.s mosaic method) to reconstruct the volume. Reconstructed structures were compared with manually delineated structures and agreement was evaluated based on volume, center‐of‐mass position, similarity index, and 3D distance maps. Results: We found the center‐of‐mass for all organs over all phases to be invariant to rendering technique. Percent volume difference varied greatly depending on the technique and organ, ranging from −23% to +56% for the gtv to −3.75% to +13.58% for the left lung volume. Conclusion: TH50% and SR1 gave the best results, but significant differences can arise between DIR‐generated structures and manually delineated structures depending on the rendering technique used. We suggest rigorous QA before implementation of such a system prior clinical use.
SU‐FF‐I‐96: Motion Adaptation for Registering Daily Online CBCT Images to Planning CT Images
Authors: Nguyen T‐N , Moseley J , Dawson L , Jaffray D , Brock K
Published: April 2010

Purpose: Perform online image guidance (IGRT) and motion assessment using deformable registration by adapting patient liver motion models. Materials and Methods: 4DCT and daily 4DCBCT images were obtained for 15 patients treated under a stereotactic‐body radiotherapy protocol. Finite element models of patient liver respiratory motion were generated using a biomechanical‐model based platform, MORFEUS from 4DCT images. Motion was assessed using a Navigator channels (NC) technique. Five NCs, rectangular regions of interest, were placed on two images at corresponding spatial locations to define left (LR), anterior‐posterior (AP), and superior‐inferior (SI) liver edges. To determine interfraction liver/tumour positioning, the 4DCT exhale and daily 4DCBCT exhale images were used, while intrafraction liver/ tumour motion used exhale and inhale 4DCBCT images. The NC determines the 1D displacement between both images. This 1D motion adapts the MORFEUS‐based liver motion model. NC adaptation accuracy was evaluated by comparing the results with MORFEUS registration. Results: NC refinement has been performed on 8 patients to date in less than 2 mins each. Inter‐fraction motion of the liver exceeded 1 cm. Inter‐fraction NC technique accuracy (absolute mean (SD)) was 0.15 (0.11), 0.16 (0.10), and 0.15 (0.09) cm, in the LR, AP, and SI directions, respectively. Intra‐fraction motion exceeded 1.5cm. NC technique accuracy was 0.14 (0.10), 0.15 (0.08), and 0.18 (0.09) cm, in the LR, AP, and SI directions, respectively. The accuracy of the NC technique to identify the center of mass shift of the tumour for intra‐fraction motion was 0.16 (0.15), 0.14 (0.12), and 0.15 (0.10) cm, in the LR, AP, and SI directions, respectively. Conclusion: NC adaptation technique can accurately and efficiently integrate deformable registration into the IGRT process to account for inter and intra‐fraction motion.

Research sponsored by the National Cancer Institute of Canada‐Terry Fox Foundation, Elekta Oncology Systems, and NIH 5RO1CA124714‐02.
SU‐FF‐I‐97: Comparison of End of Exhalation (EE) 4DCT Phase and Breadth‐Hold Scans
Authors: Michalski D , Andrade R , Mutaf Y , Heron D , Huq M
Published: April 2010

Purpose: 1)compare congruency of phase 50 with EE breath‐hold scan 2)demonstrate improvement of the demons image registration algorithm with hierarchical regularization component. Method and Materials: We consider 10 cases with motion exceeding 0.5 cm. The tumor was contoured on phase 50. Image registration provided the transfer of a contour to EE scan. Contour comparison is afforded by the same DICOM‐coordinates. Dice coefficient and centroids' shift between scans gauge tumor congruence. Multiresolution image registration is based on the fluid version of the demons algorithm. Algorithm is improved by the hierarchical regularization component. SSD is used to compare image fusions. Deformation maps are compared and described with maximal and mean magnitude of the deformation vector and its standard deviation. Number of iteration reveals the speed up of performance. Results: The tumor volumes ranged from 2.27cc to 37.21cc on phase 50. Transferred to EE differed on average by 7%. Tumor centroids shifts ranged upto 5 mm along the lateral, upto 7mm along ventro‐dorsal and upto 7 mm along the superior‐inferior axis. The ipsilateral lung volume between the scans differed upto 15%. The Dice coefficient did not exceed 0.7. Adaptive regularization accelerates convergence and improves on all scoring criteria. Conclusion: Data indicate incongruency between phase 50 and EE breath‐hold scan, which precludes the latter in any emulation or substitution for phase 50 scan. Possible reasons are: relatively small tumor sizes, motion above 0.5cm and different air intake in both scans. Hierarchical application of the deformation field regularization provides more robust performance and heuristically can be seen as an adaptation to scale‐size changes during iterations.
SU‐FF‐I‐98: Accelerating B‐Spline Registration Using Graphics Processing Units
Authors: Sagedy C , Kandasamy N , Sharp G
Published: April 2010

Purpose: To develop a highly data‐parallel version of B‐spline registration within the stream‐processing model, suitable for use on cheap stream processors such as graphics processing units (GPUs). Method and Materials: We first develop a grid‐alignment technique and a data structure that greatly improves the computation speed of B‐spline registration on the CPU. The basic idea here is to align the B‐spline grid with the voxel grid, so that the volume is partitioned into tiles of equal size. The use of equal sized tiles is important since it allows the coefficient multipliers used for B‐spline interpolation to be pre‐computed. Then, using this data structure, we develop a data‐parallel version of B‐spline registration suitable for use on a GPU. We have developed a streaming algorithm for B‐spline registration within the Compute Unified Device Architecture (or CUDA), a programming abstraction for general‐purpose computing on GPUs, recently introduced by NVidia. Results: Using both phantom (swine lung) and synthetic images, we have validated and compared the GPU‐based algorithm with the B‐spline registration routines in the Insight Toolkit (ITK version 3.10.1). Our CPU implementation that uses the grid‐alignment technique runs up to 400 times faster than ITK. The GPU‐based algorithm achieves further speedup; it runs about four times faster per iteration than our CPU version, that is, about 1600 times faster than ITK B‐splines. The registration quality achieved by the GPU was found to be excellent, with nearly identical displacement vectors compared to the CPU version. Conclusions: Improvements in the processing speed of deformable registration algorithms are a powerful driving force for clinical applications. Interventional procedures such as image‐guided surgery and image‐guided radiotherapy require very low latencies in imaging and analysis, and improvements in processing speed mean that deformable registration can be used in such settings.
SU‐FF‐I‐100: Study of Automatic Patient Positioning System Based On the Correlation of Two Edge Images in Proton Therapy
Authors: Yoon M , Cheong M , Kim J , Shin D , Kim D , Lim Y , Ahn S , Lee S , Park S
Published: April 2010

Purpose: To clinically evaluate the accuracy of an automatic patient positioning system based on the image correlation of two edge images in radiotherapy. Method and Materials: Ninety‐six head & neck images from eight patients undergoing proton therapy were compared with a digitally reconstructed radiograph (DRR) of planning CT. Two edge images, a reference image and a test image, were extracted by applying a Canny edge detector algorithm to a DRR and a 2D x‐ray image, respectively, of each patient before positioning. The value for patient positioning was determined using an optimization algorithm based on an image correlation factor, which recognizes shifts between two edge images by translating and rotating the test image with respect to the reference image. Results: In a simulation using a humanoid phantom, performed to verify the effectiveness of the proposed method, no registration errors were observed for given ranges of rotation, pitch and translation in the x, y and z directions. For real patients, however, there were discrepancies between the automatic positioning method and manual positioning by physicians or technicians. Using edged head coronal‐ and sagittal‐view images, the average differences in registration between these two methods for the x, y and z directions were 0.10 cm, 0.09 cm and 0.11 cm, respectively, whereas the maximum discrepancies were 0.34 cm, 0.38 cm, and 0.50 cm, respectively. For rotation and pitch, the average registration errors were 0.96° and 1.25°, respectively, and the maximum errors were 3.6° and 2.3°, respectively. Conclusion: The proposed automatic patient positioning system based on edge image comparison was relatively accurate for head & neck patients. However, image deformation during treatment may render the automatic method less accurate, since the test image many differ significantly from the reference image.
SU‐FF‐I‐101: Inverse Consistency Deformable Image Registration On Partially Matched Images
Authors: Yang D , El Naqa I , Lu W , Goddu S , Pechenaya O , Deasy J , Low D
Published: April 2010

Purpose: For many RT applications, deformable image registrations (DIR) are often carried out between two images that only match partially. In addition, it is often desirable to use inverse consistency DIR to improve accuracy and to compute both the forward and backward deformation vector fields (DVF) simultaneously and consistently. Inverse consistency is especially important for adaptive radiotherapy applications because doses and structures need to be remapped between the planning image and the daily image using both forward and backward DVFs. Image mismatching (superior‐inferior coverage difference, field‐of‐view (FOV) cutoff, etc) makes it difficult for inverse consistency DIR algorithms which normally need both images to have matched image content and dimensions. Therefore, we propose a method in this study to perform inverse consistency DIR for these image mismatch situations. Method: Our method is based on the inverse consistency optical flow algorithm (Yang, PMB, 2008). The idea of allowing image mismatching is to extend the image volumes and define the extension voxel (outside the original image volume) values as NaN (not‐a‐number). NaN values are transparent to all floating‐point arithmetic computations in the DIR computation, including re‐sampling, interpolation, etc. With the NaN voxels, registrations are carried out with one additional rule that a NaN voxel can match any voxel. In this way, the matched sections of the images are registered properly, and the mismatched sections of the images are registered to NaN voxels. Results: We demonstrate the proposed method with Tomotherapy MVCT images with FOV cutoff problems and smaller volumetric coverage. Our results suggest that the proposed method could significantly improve image registration accuracy, especially near or in the mismatched image regions. Conclusion: This proposed method makes it possible to obtain inverse consistent DVFs on partially matched images that are usually difficult to register otherwise.
SU‐FF‐I‐110: Dynamic Model for Validation and Quality Assurance of Quantification of DCE Imaging
Authors: Cao Y , Li D , Shen Z
Published: April 2010

Introduction: Dynamic contrast enhanced (DCE) MR imaging is emerging as a biomarker for assessment of cancer therapy and normal tissue toxicity. It is extremely important to standardize DCE MR imaging acquisition and evaluate software of pharmacokinetic (PK) quantification for multi‐center clinical trials. A synthesized dynamic model with known values of physiological parameters could provide a platform to evaluate PK modeling software. This study aims to create and validate a synthesized model for evaluation of quantification of the general Toft's model. Methods: The synthesized DCE model has Ktrans values from 0 to 0.5 min−1, and νp from 0.01 to 0.1, and kep from 0.0 to 3.33 min−1. The temporal sampling is 1 second. The dynamic series is ̃4 minutes. The Gaussian‐distributed random noise was added to the theoretic model to yield contrast‐to‐noise ratios (CNR) of 10, 20, 50, 100, and indefinite. For each parameter combination, the synthesized data were generated 2500 times for each of the CNR levels to evaluate the mean, relative SD, and relative error between the known and estimated values of the vascular parameters derived from quantification software. The relative SD and error assess the stability and accuracy (or bias) of an estimated parameter, respectively. Results and Discussions: Without noise, the estimated values of the three vascular parameters by our in‐house software are equal to the known values, suggesting the excellent quality of the dynamic model. With noise, the relative SDs and errors increase with a decrease in CNRs. For both stability and accuracy, νp is superior compared to Ktrans and kep, suggesting the different tolerances to noise. For Ktrans values of 0 and 0.001 and vp values of 0.1, stability and accuracy were substantial worse than other conditions, suggesting that it is necessary to determine acceptable parameter ranges with given CNRs and acquisition.

Supported by 3P01CA59827
SU‐FF‐I‐112: A Quantitative Evaluation of Four Dimensional Computed Tomography
Authors: Noice L , Robinson D
Published: April 2010

Purpose: Four dimensional computed tomography (4DCT) is a clinically emerging imaging modality capable of creating time resolved images of mobile anatomy. A quantitative assessment of its accuracy is a necessary prerequisite to clinical implementation for radiation treatment planning. Method and Materials: A mechanical motion phantom was used in conjunction with PMMA spheres of 1, 3, and 5 cm diameters. 4DCT images where acquired using a Phillip's Big Bore CT Scanner using both the Philip's Bellows respiratory monitoring device and Varian's Real‐time Position Management system. Images acquired were segmented in Matlab. Imaged motions and sphere sizes were compared to their true physical values. Volume, centroid position, eccentricity, as well as mean and standard deviation of CT numbers within the mobile spheres were determined as a function of segmentation threshold. An assessment of 4DCT image quality was also performed. Results: Maximum discrepancies between physical and imaged tumor volumes, for all sphere sizes and motion ranges, did not exceed 2.2 mm (mean = 1.3 mm, standard deviation = 0.3 mm). Differences between true and segmented volumes for the 1cm sphere did not exceed 9.2%, (mean = 2.5%, standard deviation = 2.3%). Maximum volumetric differences of 0.78% were observed for the 5cm sphere (mean = 0.26%, standard deviation = 0.22%). Noise was increased by 365%, and SNR's were reduced by 80% in 4DCT images in comparison to standard clinical protocol values. MTF's of both standard clinical and 4DCT acquisitions showed no significant difference at frequencies below 0.4 lp/mm. 4DCT acquisition caused shifts in median CT number for stationary objects, and in both mean and median CT number for mobile objects under 4DCT acquisition. Conclusion: 4DCT reproduces target volumes and motion paths with reasonable accuracy but image quality can be significantly degraded.
SU‐FF‐I‐122: Assessment of Lung Tumors Treatment Accuracy Using CyberKnife Synchrony Model
Authors: Wu H , Zhang Y , Zhao Q , Lord B
Published: April 2010

Purpose: The Synchrony Respiratory Tracking System treats moving targets with much tighter margins. Due to the complex and erratic breathing motion of lung tumors, it is a challenging task to build a reliable internal/external correlation model and predictive algorithm. This study is to assess the treatment accuracy of lung tumors using the Synchrony system. Method and Materials: 21 lung patients with 97 fractions treated by a Synchrony system were studied. Available treatment data includes (i) tumor positions from sparsely acquired x‐ray image pairs; (ii) three surface LED markers motion continuously tracked by three Infrared detectors; (iii) the modeled motion calculated using the LED motion and the internal‐external correlation model and (iv) the predicted motion to compensate system latency. The correlation models can be validated by comparing the x‐ray image pairs determined tumor positions and the calculated modeled motion. The prediction precision can be evaluated using the modeled and predicted motion. The comparison of the x‐ray image pairs determined tumor positions and the predicted motion will assess the treatment effectiveness and provide feedback for the optimized margin expansion, computed using either a rolling ball method or un‐even margin expansions in X, Y, and Z directions. Results: Preliminary analysis showed the predictive model worked well with fast motion during inhale and exhale and decreased at the end of inhale and the end of exhale, especially at the reflection points. The fidelities of the correlation model changes over time, with correlation error up to 11.5mm in 3D distance for some fraction. The margin expansions required for different coverage percentages were calculated using both the rolling ball approach and un‐even expansion for each treatment direction. Conclusion: Evaluation of the correlation model, predictive results, and margin expansions were performed and the results are important to improve lung tumor treatments using the Synchrony System.
SU‐FF‐I‐140: Cone Beam Breast CT Versus Mammography for Breast Density Measurement
Authors: Han T , Lai C , Chen L , Shen Y , Zhong Y , Liu X , Ge S , Yi Y , You Z , Wang T , Whitman G , Yang W , Shaw C
Published: April 2010

Purpose: To compare breast density measurements using CBCT with those based on mammograms. Materials and Methods: 19 mastectomy specimens were imaged with a bench top aSi/CsI flat panel based CBCT system. Scans were performed at 80 kVp with a voxel size of 0.29 mm and an estimated dose level of 24 mGy at the isocenter. The reconstructed images were corrected and segmented to separate glandular tissue from adipose tissue. The voxel numbers for glandular tissue and the entire breast were counted from the segmented images and used to calculate the volume based breast density. The breast density was also calculated based on mammograms using a commercial software package. The number of pixels for dense tissue regions was counted and divided by that for the entire breast to compute the area based breast density. These two breast densities were used for comparison. The volume based breast densities were also converted into BI‐RADS categories for comparison with those from mammographic reading as recorded in the diagnostic report. Results: The volume based breast densities were mostly equal or lower than the mammographic ones (fig. 1 and Table 1) with a correlation (coefficient = 0.73) between the two. Comparison based on the BI‐RADS categories, more breasts with volume based measure were classified as categories 1 and 2 while most breasts with mammographic reading were classified as category 3 (Fig. 2) with a correlation coefficient of 0.55. Conclusion: It was found that breast densities calculated from CBCT images were significantly lower than those from mammograms for the 19 patients studied. Implication to the use of CBCT breast density as a risk factor for breast cancer remains to be investigated.

This work was supported in part by grants CA104759 and CA124585 from NIH‐NCI, a grant EB00117 from NIH‐NIBIB, and a subcontract from NIST‐ATP.
SU‐FF‐I‐143: The Study On Protection of Lung Function in Radiotherapy by Referring SPECT Lung Perfusion Images
Authors: Chen J , Yin Y
Published: April 2010

Purpose: This study is aimed to prove the efficacy and feasibility of protecting lung function in lung cancer radiation therapy, by referring to SPECT lung perfusion Images. Methods and Materials: 10 patients with lung cancer were selected. Each patient received CT simulation location, and then in the same body position, single photon emission computed tomography (SPECT) lung perfusion scans was performed to examine their lung function. After that in the planning system, the image registration and fusion of the CT location images and the lung perfusion images were operated. Based on the CT location images solely, a intensity modulated radiation therapy plan (IMRT) was designed (named as T1). The second step: after the fusion, functional lung areas (lung‐Fs) were contoured on the CT images referring to lung perfusion images. Accordingly a conformal radiation therapy (CRT) plan and a IMRT plan (named as T2 and T3) based on lung‐Fs were designed. To optimized both two plans above, the radiation dose was minimized in lung‐Fs. In several other key organs, such as the spine‐cord, the heart and the esophagus, such restrictions were also set. Total radiation dose was set at 66 Gy (2Gy×33 fractions). Results: compared T1 to T3, significant dose decrease (P<0.05) of both lung‐Fs and total‐lung were observed. The average reductions in the percentage of volume irradiated with >5 Gy, >10 Gy, >20Gy, >30Gy and >40Gy in T3 were 6.50%, 10.21%, 14.02%, 22.30% and 23.46%, respectively. Then compared T2 to T3, there were no significant differences (P>0.05) between the two plans in V20 either in lung‐Fs or total‐lung. Conclusion: For lung cancer patients with lung perfusion defects, it's salutary to design a radiation therapy plan referring to lung perfusion images. The CRT and IMRT plans have same effects as to protect lung‐Fs and alleviate the complications.
SU‐FF‐I‐144: Compare with Phase Correlated Image Registration to 4D CT for Liver Stereotactic Radiosurgery with Image Guidance Cone Beam CT
Authors: Juh R , Suh T , Kim S
Published: April 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. Seppenwoolde et al (2002) calculated the hysteresis as a phase difference between the fitted parameterized curves of the average breathing cycles of two directions. From 3D tumor trajectories, they showed that the hysteresis ranged from 0.1 to 0.6 cm for 20 tumors.
SU‐FF‐I‐145: The Effect of Brownian Motion On Nanoparticle Magetization
Authors: Weaver J , Rauwerdink A
Published: April 2010

The magnetization of nanoparticles in a sinusoidal applied field is a balance between Lorentz forces tending to align the nanoparticle magnetizations and Brownian motion tending to randomize the nanoparticle magnetizations. The result is a distorted sinusoid where the distortion is larger for larger applied fields or smaller nanoparticle Brownian motion. The ratio of the harmonics of the magnetization is one way to characterize the distortion and therefore the Brownian motion of the nanoparticles. The harmonics can be measured in vivo because there is no other signal present and the bandwidths can be extremely small if the signal is measured over many cycles. We have explored how the material in which the nanoparticles reside affects the harmonics. We compared the effects of phase changes and viscosity changes on the harmonics and found a coherent pattern. It showed the ratio of the harmonics decreases with temperature but exhibits a very large increase as it passes through a phase change from ice to water. The change is roughly equal to what a 20°K change in temperature would produce. The measurements are accurate to less than one degree. The nanoparticle signal is very sensitive to phase changes and to viscosity changes. Further, the changes in the harmonics induced are significant enough to easily be observed in vivo. Brownian motion measurements should have a wide array of uses including identification of ablated regions in ablation therapy, identification of cellularity in cancer and inflammatory responses such as rheumatoid arthritis. Moreover it is a measure of the microscopic surroundings of the nanoparticles so antibody targeted nanoparticles can reflect the environment adjacent to the targeted cells without averaging over a wider volume such as an MRI voxel.
SU‐FF‐I‐146: Reconstruction of Absorber Concentration Using a Linear Source Model for Interstitial Spectroscopic Diffuse Optical Tomography
Authors: Wang K , Finlay J , Zhu T
Published: April 2010

Purpose: Light, photosensitizer and oxygen are the major components of Photodynamic therapy (PDT). With the implementation of interstitial diffuse optical tomography (iDOT), the optical properties of tumor tissue can be reconstructed spatially using an inverse algorithm. Further, the spatially‐resolved hemoglobin oxygen saturation and sensitizer distribution are expected to be established with the reconstructed optical properties. In this study, we incorporate a spectroscopy system with the existed iDOT to reconstruct the spatial distributions of absorber concentration. We especially focus on linear source system, because the acquisition time for a linear source system is much shorter than that for a point source system, making it more suitable for clinical use. Methods and Materials: A spectroscopic iDOT system has been developed to characterize the hemoglobin oxygen saturation and sensitizer concentration of the prostate gland during PDT. During data acquisition, isotropic detectors and the cylindrical fibers coupled to a white light source are inserted into the prostate gland, and absorption spectra are acquired along the detector insertion axis under the control of a motorized system. For our CW iDOT system, two dimensional optical properties of the prostate gland are reconstructed by solving the inverse problem with the use of an adjoint model based on diffusion theory. Results: To verify the accuracy of our methodology, we have performed measurements in an optically heterogeneous solid tissue‐simlulating phantom of known composition. We compare the spatial distribution images of optical properties and absorber concentration reconstructed for the phantom with the known results based on material composition. Results of clinical data reconstruction are also shown in this study. Conclusion: The results demonstrate that it is feasible to reconstruct the optical properties of the sample and the distributions of absorbers with known absorption spectra, indicating that reconstruction of hemodynamic and drug concentration in vivo is practical in clinical applications.
SU‐FF‐I‐148: Performance Comparison of An In‐House and a Commercially Available Amplitude Gating Device for PET Imaging
Authors: Chang G , Chang T , Jackson J , Clark J , Mawlawi O
Published: April 2010

Objective: To compare the performance characteristics of an in‐house amplitude gating device to the Anzai respiratory gating system in PET imaging. Methods: A MLT‐1132 respiration transducer was coupled to a cDAQ‐9172 data‐acquisition device to digitize the respiratory signal. A Labview® program was designed to inject triggers into PET List streams whenever the respiration amplitude crossed the edges of a user‐set amplitude‐range (gate) and stop the scan when the accumulated gated scan‐duration reached a user‐set interval. To test its performance, a phantom containing one stationary (33mm) and 2 moving spheres (33&17mm) was imaged in 3D mode on a GE‐DRX PET/CT scanner (SBR=5.1). The two moving spheres were attached to a moving platform (2cm‐pp‐sinusoid, 5sec‐cycle) while the MLT‐1132 and Anzai transducers were secured to the platform simultaneously. Respiration signals from the two transducers were synchronized using triggers from the Anzai device. The gated amplitude‐range and scan‐duration were 80–100% of the motion amplitude and 3min respectively which resulted in 10min of total scan‐duration. The List data was first filtered by only keeping data within the gate and then reconstructed (3D‐IR) to generate a MLT‐1132‐gated image. Furthermore, the same list data was retrospectively gated based on the Anzai respiratory signal and an Anzai‐gated image was also reconstructed. In addition, two ungated images (10&3min) were unlisted and reconstructed from the same list data. All images were compared using line profiles, contrast, max and mean activity concentration (AC) for all spheres. Results: The respiratory waveforms recorded by the two devices and their respective Fourier transforms were identical and had a correlation coefficient of 0.97 & 0.99 respectively. The two gated images showed similar contrast (<3% difference) and AC (<2% difference) and exhibited similar improvement in contrast & AC when compared to ungated images. Conclusion: Our in‐house amplitude‐gating device has similar performances compared to the Anzai equipment
SU‐FF‐I‐151: Effects of Varying Slice Overlap On Image Noise and SNR in 3D PET Imaging
Authors: Chang G , Chang T , Khalil M , Clark J , Mawlawi O
Published: April 2010

Objective: To investigate the effects of different number of slice overlaps (SO) on image noise and SNR in 3D PET data acquisition. Materials and Methods: Three phantoms were scanned to simulate different patient sizes: (1) an ACR phantom with three cold inserts, (2) a NEMA/IEC phantom, and (3) a NEMA/IEC phantom coupled to a second NEMA/IEC phantom to act as a scatter source. The background activity concentration in the phantoms ranged between 3.5–5 kBq/cc. All phantoms were scanned in 3D on a GE‐DRX PET/CT scanner using two bed positions (3min/bed) with three different number of SOs (3, 7&11) between the two bed positions. This paradigm resulted in 91, 87 & 83 PET image slices for SO 3, 7 & 11 respectively. 3D‐IR (2 iterations, 21 subsets) was used for all image reconstructions. For each phantom and each SO, a 7×7 square ROI was drawn on all slices of the phantom background, and the average & STD of the ROI were calculated to represent the phantom background AC and noise content. SNR was then determined as the ratio between AC and noise. Noise and SNR were plotted versus different image slices for all the phantoms and SOs. Results: Increasing the slice overlap decreased the noise and improved the SNR in the overlap region. The improvement in SNR between SO3 and SO11 was 46% on average over all phantoms; while the improvement between SO7 and SO11 was 19%. For the ACR and NEMA/IEC, the SO7 and SO11 images showed relatively similar noise and SNR, while for the NEMA/IEC+Scatter, the SO3 and SO7 had similar results. Conclusion: Increasing SO improves SNR in the overlap region. An SO of 7 is optimal for intermediate size objects and should be increased to 11 for larger cross section particularly with scatter from outside the FOV.
SU‐FF‐I‐152: Influence of Oxygen Tensions and Tissue Optical‐Properties On Optical Reporter Genes
Authors: Cui G , Maxim P , Graves E
Published: April 2010

Purpose: To quantify the effects of oxygen concentrations on optical reporter genes imaging methods, by modeling the influence of oxygen tensions on reporter protein signal generation activity as well as the propagation of reporter fluorescent and bioluminescent photons from locations within tissues to measurement apparatus. Method and Materials: A reporter gene construct composed of Renilla luciferase and monomeric red fluorescent protein was modeled using analytic techniques. Previous in vitro work was performed to measure the imaging signal produced by this construct when exposed to reduced oxygen levels. The relationship between the luminescent intensities and different oxygen levels was studied for the reporter gene. The setup depicted in the model consisted of a point source with a fixed amount of reporter protein and oxygen at depth in tissue. The bioluminescent signals as well as fluorescent signals upon illumination by a pencil beam source were modeled for this setup using Michaelis‐Menten enzyme kinetics and photon diffusion theory. Results: The model developed produced results that agree well with the in vitro measures of bioluminescent and fluorescent reporter activity. The relative fluorescent and bioluminescent signals can be combined to infer the oxygenation of the sample, although this relationship varies with depth in tissue. Conclusion: This work indicates that the adverse effect of oxygen tensions on bioluminescent report activity can be modeled by enzyme kinetics, which provides insight into forming methods to differentiate reporter expression from activity based on optical measurements. This technique could then be applied towards quantitating measurements from reporter genes constructs including hypoxia‐driven expression schemes. This study also shows that, to a first order approximation, fluorescent signals can be used as a control for bioluminescent measurements since the fluorescent reporter activity does not vary substantially under different low oxygen levels.