bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐I‐84: FMRI Task and Gray Matter Difference in Schizophrenia Patients Using Voxel Based Morphometry
Authors: Juh R , Suh T
Published: July 2007

Purpose: The prefrontal cortex (PFC) and parietal cortex are important in performing working memory (WM) tasks. In this study we performed fMRI studies to compare the activation regions between the schizophrenic patients and controls using the 2‐back WM task paradigm. In addition, the gray matter (GM) loss between these two groups was compared using the voxel based morphometry (VBM) analysis. The brain regions showing differences in fMRI and VBM studies were compared to investigate the consequence of structural atrophy on functional activation. Method and Materials: This study included 14 schizophrenic patients (M/F: 8/6) and 10 normal controls (M/F: 8/2). The fMRI employed a gradient‐echo echo planar imaging (EPI) sequence) to detect blood oxygenation level dependent (BOLD) signal changes associated with neural activities. After the functional session, high‐resolution 3D anatomical images were acquired for VBM analysis, using a 3D‐FLASH sequence (TE/TR=4/9.7 msec, FA=12, slice thickness = 1.25 mm, 256 × 192 in‐plane matrixThe voxels with the highest z‐values represented the region where GM volume was significantly different between these two groups. Results: The regions showing increased activity in controls included the right superior frontal gyrus (BA8), middle frontal gyrus (left BA6 and right BA8), left precuneus (BA7), left fusiform (BA37), anterior bilateral insula, and left putamen. On the other hand, the patient group showed increased activities in the right inferior frontal gyrus in the lateral PFC (BA10/46) and right parietal lobule (BA40). Conclusions: A more liberal threshold condition of p< 0.001 was applied to examine any threshold‐dependence of laterality in activities in PFC, but the activity was still observed solely on the right PFC. The VBM result show reductions in GM in Schizophrenia versus controls in the anterior cingulate (BA 24.31), medial frontal (BA 10), superior temporal, middle temporal and fusiform gyrus (BA20).
SU‐FF‐I‐88: Using Fast MR Imaging Techniques to Evaluate T1 Changes After Hyperoxygenation of Brain Tumor preliminary Result
Authors: Chen CC , Wai YY , Chen YL
Published: July 2007

Purpose: Use fast MR imaging techniques to evaluate T1 changes after hyperoxygenation of brain tumor. Method and Materials: This study is proceeded on an 1.5 Tesla MRI scanner (Intera, Philips, Netherlands). A fast spin echo (echo‐train‐length = 13) inversion recovery MR imaging technique (TR/TE = 5000/90 ms) is used to record the signal changes according to various inversion time (TI = 100, 500, 1000, 1500, 2000 ms). Each individual scan takes 145 seconds with multiple signal averaged (NSA = 2), and all five scans require 725 seconds. Obtained images are transferred to a PC‐based workstation in DICOM format, and quantitative analysis is performed by self‐coded program. Determination of the T1 value of individual pixel is based on the result of iterative nonlinear curve fitting algorithm. For better estimation, the maximum number of iterations is set to 3000, and the computation time is about 30 minutes to complete a T1 map of a single slice of body part. In this preliminary study, one patient with recurrent glioblastoma multiform(GMB)in right temporal lobe underwent open surgery for tumor removal, radiosurgery and chemotherapy is tested using this proposed T1 measurement method twice prior and after 15 minutes oxygen inhalation. Results: Subtraction of calculated T1 maps shows that T1 values are shortened observed in the area adjacent to post radiosurgery area and prolonged in external side of brain parenchyma. Conclusion: In this preliminary study, an effectively quantitative technique is established and applied to a patient with recurrent brain tumor. Considerable changes of longitudinal magnetization in multiple areas are observed in subtracted map reflecting the hyperoxygenation procedure. More evidences and related studies are investigated and might provide more information about tissue oxygenation level in the future.
SU‐FF‐I‐94: The Assessment of Structural Variations of Multiple Sclerosis Plaques in Clinically Isolated Syndrome (CIS) Using Magnetization (MTI) Parameters
Authors: Riyahi‐Alam N , Fooladi M , Harirchian M , Firuznia K , Oghabian M , Rafee B , Shakiba M
Published: July 2007

Purpose: A segmentation method for detection of masses in digitized mammograms has been developed using two parallel approaches: adaptive thresholding method and fuzzy entropy feature as a CAD scheme. Method and Materials: The algorithm consists of the following steps: a) Preprocessing of the digitized mammograms including identification of region of interest (ROI) as candidate for massive lesion through breast region extraction, b) Image enhancement using linear transformation and subtracting enhanced from the original image, c) Characterization of the ROI by extracting the fuzzy entropy feature, d) Local adaptive thresholding for segmentation of mass areas, e)Combine expert of the last two parallel approaches for mass detection. Results: The proposed method was tested on 78 mammograms (30 normal & 48 cancerous) from the BI‐RADS and local databases. The detected regions validated by comparing them with the radiologists' hand‐sketched boundaries of real masses. The current algorithm can achieve a sensitivity of 87% with 1.57 FP/image. Conclusions: This approach showed that the behavior of local adaptive thresholding and fuzzy entropy technique could be a useful method for mass detection on digitized mammograms. Our results suggest that the proposed method could help radiologists as a second reader in mammographic screening of masses.

Keywords: Breast Masses, Segmentation, Image Enhancement, local adaptive Thresholding, Fuzzy Entropy.
SU‐FF‐I‐95: Separate Water and Fat Imaging with a Novel Phase‐Correction Algorithm
Authors: Zhou Y , Ma J
Published: July 2007

Purpose: The purpose of this study is to describe the implementation of an efficient and robust 2‐point Dixon technique with a novel phase‐correction algorithm and a triple‐echo fast spin‐echo (fTED) data acquisition. Methods and Materials: An fTED pulse sequence was developed and used to collect an in vivo raw dataset on 1.5T GE whole body MRI scanner. The pulse sequence was modified from the FSE pulse sequnece by replacing each readout gradient between each 180° refocusing RF pair with three readout gradients of alternating polarity. The separation between the three readout gradients is timed so that the three corresponding raw images have a relative water and fat phase of 180°, 0, 180°, respectively. A novel phase‐correction algorithm was developed to remove phase errors and produce the water‐only and fat‐only images. The algorithm determines the phase vector direction rather than the phase value. Both the pixel intensity and precalculated phase gradients are used to guide the region growth sequence. The advantages of the algorithm include its easy implementation, computational efficiency, and robustness in the presence of pixels with large phase uncertainty. Results: Clean water and fat separation was achieved using the novel phase‐correction algorithm for all the images. Using only phase gradients for determining the growth sequence, small local regions were noted to have reversed water and fat assignment. Such processing errors were corrected when pixel intensity was included in the determination of the growth sequence. Discussion and Conclusion: We showed that both the pixel intensity and phase gradients can be incorporated in the new phase‐correction algorithm. The pulse sequence and the phase‐correction algorithm were demonstrated to be capable of producing water‐only and fat‐only images with excellent scan time efficiency and processing robustness.

Acknowledgment: This work was supported by a research grant from the Susan Komen Breast Cancer Research Foundation.
SU‐FF‐I‐97: Feasibility of Low Dose X‐Ray Contrast Enhanced Digital Mammography with Gold Nanoparticles
Authors: Suryanarayanan S , Sechopoulos I , Vedantham S , Karellas A
Published: July 2007

Purpose: To study the feasibility of low dose x‐ray contrast enhanced digital mammography (CEDM) with gold nanoparticles as a contrast agent. Method and Materials: Contrast enhanced digital mammography (CEDM) with iodine based agents is currently being explored. However, novel materials such as gold nanoparticles seem very promising for CEDM because of their high x‐ray absorption in the mammographic energy range. Computer generated volumetric breast compositions of 50% and 75% mean glandular fractions and thickness of 5 and 7.5 cm were analytically ray‐traced at various mono‐energetic conditions and spectrally combined with simulated power‐law noise to create 2D projection images with mammogram‐like texture at 100 micron pixel resolution. The projection images were modified in accordance with the system resolution and noise power spectrum of a clinical full‐field digital mammography system (Senographe 2000D, GE Healthcare, WI) and used to generate image data sets. A 6 mm diameter spherical lesion with an inherent glandular fraction of 65% and 100% was used for the 50% and 75% glandular breast conditions respectively. Lesions with contrast agent concentrations of 0.5, 1, 2 and 4 mg/cc were generated. A 26 kVp, Mo/Mo and 31 kVp, Rh/Rh x‐ray spectra were used to generate full‐dose images (∼2 mGy mean glandular dose) for the 5 and 7.5 cm‐thick breasts respectively. A Laguerre‐Gauss Channelized Hotelling observer (LG‐CHO) was implemented to compute the signal‐to‐noise ratio (SNR). Results: Good contrast visualization was observed at ∼0.13 mGy per image frame with CEDM. Contrast agent concentrations between 0.5–2 mg/cc in the lesion resulted in much higher SNRs compared to full dose mammography. Conclusion: This work suggests favorable properties for gold nanoparticles as an x‐ray contrast agent for CEDM. This could potentially benefit high‐risk patient groups such as women with dense breasts. Other potential applications include progress monitoring in neo‐adjuvant treatment regimens.
SU‐FF‐I‐98: Estimating the Volume of Dense Breast Tissue Using a Dual Energy Technique in Digital Mammography
Authors: Liu B
Published: July 2007

Purpose: To investigate a method of estimating the volume of dense breast tissue using a dual energy technique in digital mammography. Method and Materials: Breast was modeled as adipose tissue + dense tissue. For a fixed thickness, Monte Carlo method was used to calculate ratios of the total logarithm attenuation at 17.5 keV to that at 20.2 keV for a breast of 100% adipose tissue (Ra), a breast of 100% dense tissue (Rd), and a breast with a few 100% dense tissue blocks embedded in a 100% adipose background (R). The thickness of embedded dense tissue blocks was then computed from the values of Ra, Rd, R and the total breast thickness. The effects of scatter and polychromatic beam were analyzed and the possibility of applying the method to the imaging systems with Mo/Mo and Rh/Rh target/filter was explored. Results: For thin breast phantoms and mono energetic beams, the estimated dense tissue thicknesses were within 10% of the true values. Conclusion: The volume of the dense breast tissue may be estimated based on 2‐D digital mammograms using the dual target/filter FFDM systems after the effects of scatter and polychromatic beams are properly corrected.
SU‐FF‐I‐100: Experimental Evaluation of Motion Effects by Integration of the 4DCT/4DPET Hybrid GE Discovery VCT Scanner with the CIRS Dynamic Lung Phantom
Authors: Ionascu D , Park S , Killoran J , Mamede M , Thomas S , Gerbaudo V , Chin L , Berbeco R
Published: July 2007

Purpose: The integrated 4DPET/CT scanner has the advantage of accurate body position correspondence between the PET and CT scans as well as 4D acquisition capabilities for both modalities. The former reduces possible errors from misalignment when fusing PET and CT scans taken on different machines, while the latter improves our capability to account for anatomical changes due to respiratory motion. However, owing to the fundamental differences between the scanning techniques, artifacts may differ between the modalities. Materials and Methods: In our investigation we have expanded the advantage of the integrated scanner single reference frame by the improvement of a lung dynamic phantom that can be monitored by both the PET and CT 4D scanning procedures. This was achieved by the development of custom made inserts for the dynamic phantom that can accommodate different sized FDG‐filled spheres. The motion of the dynamic phantom was preprogrammed for trajectories of sine, sine6 and prerecorded traces of lung implanted fiducials from a previous study. In the case of the analytical curves, periods between 3.5 and 8.5 seconds were used along with amplitudes varying from 0.5 to 3cm. Spheres of various sizes filled with FDG of various activities were used. Results: Gated PET and CT images of the same moving target were obtained within the same frame of reference for various amplitudes and periods of motion and for various sizes and activities of FDG‐filled spheres. Comparison of the images from the two modalities shows differences in the motion artifacts, which should be taken into account in radiotherapy planning. Conclusion: We have successfully developed a phantom system for obtaining highly correlated data sets for PET and CT with and without gated (4D) acquisition. Our preliminary results suggest that motions do have significant impact on the images. Further studies will investigate the clinical implications of this work.
SU‐FF‐I‐104: Performance of a PET‐CT Scanner for Hot Lesion at High Activity Concentration
Authors: Luo J
Published: July 2007

Objective: To evaluate PET‐CT scanner for hot lesion at high activity concentration with and without radioactive background. Method: Four hollow spheres (2.96, 2.00, 1.45 and 0.91 cm) were installed to a PET‐SPECT phantom with three inserts: hot lesions, uniformity linearity, cold lesions and cold spheres. 666 MBq of F‐18 was in cylindrical tank with all inserts and the spheres. Two large spheres contained 26 MBq leading to a lesion to background ratio of 13.2, and two small ones were empty as cold lesions. Three bed sets of 15 cm axial field of view (slice thickness is 3.75 mm) each were scanned for a total of 9 minutes, and CT (120 kV/80 mA) scan as well. Images were at 30 min interval for two hours and then 60 min for last three, and reconstructed with OS‐EM. RoIs and VoIs were defined manually. Same RoI for the largest sphere was used to obtain count as background to both RoI and VoI respectively. Result: Artifacts appeared on PET‐AC and PET‐CT images of the hot spheres and the inserts for first four data sets (0, 30, 60 and 90 min respectively) when the total activity was from 666 to 370 MBq. When it dropped from 370 to 147 MBq, images started to appear normal. However, VoI counts of the hot spheres decreased linearly with decay of the activity over the seven scans. This suggested that the PET‐AC images can still yield accurate VoI counts under the high random and scattering counts from high activity in the cylinder‐background and the CT scan will identify the regions even the images appear distorted. Conclusion: PET‐AC images degraded due to increased random events and scatters at high activity. Regional counts can be measured with AC and RoI from CT data (independent of activity from F‐18) in fused images.
SU‐FF‐I‐108: Estimation of Ejection Fractions by Three Quantitative Gated SPECT Software Packages
Authors: Tiapetch O , Tocharoenchai C
Published: July 2007

Purpose: To investigate the accuracy of left ventricular ejection fraction (LVEF) estimated from three quantitative gated SPECT software packages, using echocardiography as a gold standard and the reliability of LVEF from ordered subset expectation maximization (OS‐EM). Method and Materials: Seventy patients with suspected coronary artery disease (CAD) were examined with gated 99mTc‐MIBI SPECT (8 frames/cardiac cycle) at stress. The projection datasets were reconstructed using OS‐EM with 8 angles/subset. The data were smoothed with Gaussian filter with FWHM of 8 pixel width. The iteration numbers were varied for each software: 3 iterations for quantitative gated SPECT (QGS), 5 iterations for the Emory cardiac toolbox (ECTb), and 4 iterations for 4D‐MSPECT. The LVEFs were calculated using these 3 quantitative software packages. To test reliability of LVEF from OS‐EM, the same patient data were again reconstructed using filtered backprojection (FBP) with post‐filtering of Butterworth 5th order, 0.3 cycles/pixel cutoff frequency. A two tailed pair t‐test was used to test the statistically significant difference with p‐value < 0.05. Results: There were no statistically significant differences in LVEFs for all three software packages from echocardiography with p > 0.05. The correlation between LVEF in each pair of package was high (r > 0.9). The LVEFs from OS‐EM were not statistically significantly different from that from FBP (p > 0.05) for QGS and 4D‐MSPECT, but for ECTb, there was a statistically significant difference. The LVEF from OS‐EM correlated well with that from FBP (r >0.9). Conclusion: The LVEF estimated from each software package had different characteristics and the LVEF from OS‐EM was reliable.
SU‐FF‐I‐113: Variation in Exposure‐Dependent SNR Among Systems With Identical Digital Flat Panel Detectors
Authors: Willis C , Vinogradskiy Y , Lofton B , White R
Published: July 2007

Purpose: To establish expected performance of digital flat panel radiography systems with respect to SNR versus detector exposure under clinical conditions for thoracic imaging. Method and Materials: Exposures were made of a LucAl Chest phantom at 125 kVp and 180 cm SID using 16 systems (models XQ/i, XR/d, XR/dII and Definium; GE Medical Systems; Milwaukee, WI). The mAs was modified for exposures above and below the mAs delivered by AEC. Exposures measured free‐in‐air were corrected to the imaging plane by the inverse square law, for attenuation by the phantom, and by the Bucky factor of the grid for this phantom, geometry, and kVp. SNR was the ratio of the mean and standard deviation (SD) of an ROI automatically selected in the center of each unprocessed image. Paired data was collected for 11 systems before and after a major gain and offset calibration. SNR versus detector exposure data were interpolated using a power function to stratify the data into 0.2, 0.5, 1.0, 2.0, and 5.0 mR to the detector. Results: Although mean SNR changed only slightly after calibration, SD of SNR decreased markedly (41%), approaching statistical significance (p=0.061). Systems were segregated into two classes: higher (N=5) and lower (N=6) than the mean SNR. After calibration, differences were noted for both high and low groups, but were significant only for some exposure levels using a one‐tailed t‐test. High and low groups were significantly different (p<0.01) from each other before, but not after calibration. SNRs from 4 of 5 remaining unpaired systems conformed to the 95% confidence intervals of paired data after calibration. Conclusions: Exposure‐dependent SNR measurements under clinical conditions provide criteria for evaluating digital flat panel radiographic systems. Calibration reduces variation among systems.
SU‐FF‐I‐115: Cardiac‐Gated Dual‐Energy Imaging of the Chest: Design and Performance Evaluation of a Cardiac Trigger Based On a Fingertip Pulse Oximeter
Authors: Shkumat N , Siewerdsen J , Dhanantwari A , Williams D , Paul N , Yorkston J , Van Metter R
Published: July 2007

Purpose: A research prototype for high‐performance dual‐energy (DE) imaging of the chest is under development. This paper discusses the development and characterization of a cardiac gating system designed to precisely trigger the imaging system according to cardiac phase and minimize anatomical misregistration due to heart motion. Method and Materials: A fingertip pulse oximeter was employed to measure the peripheral pulse waveform and trigger x‐ray exposures during the quiescent phase of the heart (diastole). Temporal delays accounted in the timing scheme include physiological pulse propagation, waveform processing, and imaging system delays (filter‐wheel, bucky‐grid, and flat‐panel detector). An empirical model of the diastolic period allows calculation of the implemented delay, timp, required to trigger correctly at any patient heart‐rate. Performance was evaluated in terms of accuracy and precision of diastole‐trigger coincidence and expert assessment of cardiac motion artifact in gated and ungated DE images. Results: The model suggests a triggering scheme characterized by two heart‐rate (HR) regimes: below a HR‐threshold, sufficient time exists to expose on the same heartbeat ; above the HR‐threshold, a characteristic timp(HR) delays exposure to the subsequent heartbeat, accounting for all fixed and variable system delays. Initial implementation indicated 83% accuracy in diastole‐trigger coincidence. By modifying the HR estimation method (reduced temporal smoothing of the pulse waveform), trigger accuracy of 100% was achieved. Cardiac‐gated DE patient images demonstrate significantly reduced cardiac motion as assessed by expert radiologists.

Conclusion: A pulse oximeter combined with a cardiac model provides accurate x‐ray triggering and significantly reduces heart motion artifacts. A simple fingertip clip presents logistic, cost, and workflow advantages compared to ECG. The system has been implemented in a clinical research trial, with gated and ungated arms allowing characterization of the impact of cardiac motion artifact on diagnostic performance. Conflict of Interest: Research sponsored in part by Eastman Kodak.
SU‐FF‐I‐120: Integration of a Pressure Sensing Array Into Ultrasonic Strain Imaging
Authors: Kiessel L , Hall T , Jiang J
Published: July 2007

Purpose: Mechanical in vitro tests have shown differences between fibroadenomas and invasive ductal carcinomas (IDCs) in their non‐linear stress/strain behavior, which could be utilized to differentiate between the two lesion types (and potentially eliminate an unneeded biopsy). Stress and strain measurements are required to quantify this non‐linear behavior in vivo. We are investigating the feasibility of integrating a pressure sensor to obtain a surface stress measurement during ultrasound strain image acquisition. The prototype pressure sensor plate design, methods for calibration and initial results will be presented. Methods/Materials: A custom pressure sensing array was obtained from Pressure Profile Systems, Inc. A variety of tests were performed with the array to gauge its stability, sensitivity and calibration in reference to its application in ultrasound elastography. Measurements on elastographic phantoms were also performed with comparisons to finite element analysis (FEA) simulations. In addition, data was collected from a small clinical trial at the University of Wisconsin Breast Center. Results: Initial tests show that the pressure sensor array is stable in an ultrasound imaging environment. A reliable calibration technique was also developed. Measurements on phantoms have shown modest agreement with FEA simulations. However, geometric inhomogeneities on the surface of the sensor as well as the variability of the absolute calibration have made an accurate map of the pressure distribution difficult to obtain. From the clinical work the device has been shown to be sensitive enough to detect initial contact with the breast, a crucial objective in quantifying non‐linear stress/strain behavior. Conclusions: The pressure sensor has demonstrated the ability to measure a relative surface pressure from initial contact to full compression during an ultrasound strain image acquisition, providing a method to quantify the non‐linear stress/strain behavior in breast lesions. However, system limitations may hamper efforts to obtain accurate surface pressure maps for modulus reconstruction.
SU‐FF‐I‐121: Automated Ultrasound QC Tests: A Method That Does Not Require Perfect Transducer Alignment
Authors: Boote E
Published: July 2007

Purpose: The purpose of this project is to develop an approach to automatic quality control testing of ultrasound equipment without the requirement to have perfect alignment of the image plane with the test objects in the phantom. Method and Materials: A standard commercial ultrasound phantom is used to acquire images using a typical clinical ultrasound scanner. The phantom used here is one that employs a set of cylindrical voids to evaluate spatial resolution. The ultrasound scanner is configured to acquire a series of images in a clip file and the data is sent via a DICOM connection. A clip is stored as the transducer is swept across the plane of the test objects (An alternative method would be to use a frame‐grabbing system that can acquire a video signal and store data as a multi‐image file.)

A program has been written in MATLAB to open the DICOM multi‐image file and store the images. Statistical properties of this set of images are used to create a “composite” image that represents a perfect alignment of the transducer. This image may be used for a series of quantitative evaluations of image quality that have previously been described in the literature. These would include lesion detectability (lesion signal to noise ratio) measures as well as sensitivity measurements (maximum depth of penetration). Results: This approach to image acquisition has the potential to save time and effort (and frustration) for either a technologist or a physicist in the ongoing effort to simplify the manual aspects of computerized quality control for ultrasound. Conclusion: This approach is under evaluation against other computerized ultrasound quality control procedures.
SU‐FF‐I‐126: Effect of Threshold Setting On 3D Visualization and Diameter Measurement Accuracy of Blood Vessels for CT Derived Images
Authors: Szczykutowicz T , Rudin S , Yadava G , Patel V , Ionita C , Hoffmann K , Bednarek D
Published: July 2007

Purpose: To investigate the effect on vessel sizing of varying the threshold in 3D volume‐rendered CT images and to verify the results with a 2D computer simulation. Method and Materials: 3D‐rendered images of a phantom with a vessel of varying diameter and of a patient with a basilar tip aneurysm were displayed on a Vitrea 2 workstation. Vessel diameters measured from the images were plotted as a function of gray‐scale threshold and actual vessel diameters measured directly from the phantom. A MatLab program was used to simulate different‐size vessel image models by convolving a rect function with a Gaussian point spread function (PSF) and to investigate the effect of threshold on sizing these vessels. Results: Plots of measured vessel diameter vs. threshold setting for varying real‐vessel diameter exhibit a monotonic decrease; with the slope decreasing both for low thresholds because of the extended tail of the PSF and for high thresholds where the vessel rapidly shrinks and then disappears as the threshold exceeds the vessel gray level. For intermediate thresholds there is a greater rate of fall‐off for smaller vessels below the width of the system PSF. Plots of measured diameter vs. real diameter intersect the 45 degree identity line at increasing diameters for increasing intermediate threshold. The crossing‐point indicates the point where the measured diameter equals the real diameter for the given threshold. Below the crossing point, these curves demonstrate reduced measured diameter for smaller vessels and, above the crossing‐point, larger values for larger vessels. The simplified 2D vessel‐model simulation and workstation data follow similar trends. Conclusion: A threshold set to accurately measure one rendered‐vessel diameter will inaccurately render vessels of other diameters. Using this threshold, smaller vessels will be inaccurately small or not be visualized and larger vessels will be too large.

(Support: NIH R01‐NS43924, R01‐EB002873, Toshiba Corp.).
SU‐FF‐I‐129: Monte Carlo Simulation to Assess Organ Dose From Coronary CT Angiography (CTA) Exams Using Patient‐Based Voxelized Models
Authors: Angel E , Yaghmai N , DeMarco J , Cagnon C , Cody D , Stevens D , McCollough C , Primak A , Goldin J , McNitt‐Gray M
Published: July 2007

Purpose: Technical advances in CT have led to an increase in the number of coronary CT angiography (CTA) exams being performed. These exams often use low pitch values to accomplish retrospective cardiac gating, which results in increased radiation dose. This study aims to estimate the dose to breast and lung tissue from a multidetector coronary CTA exam using voxelized models derived from actual patient anatomy spanning a range of sizes. Method and Materials: Nineteen voxelized models of female patient anatomy were created based on image data from clinical CT exams. Breast tissue was contoured by a radiologist, then glandular and lung tissue were automatically segmented. Previously validated Monte Carlo models of 16 and 64 slice scanners were used taking into account source spectra and path, filtration, collimation, and geometry. Simulated CTA exams used manufacturer‐recommended acquisition parameters and accounted for overscan. Organ dose was calculated for the glandular breast and lung tissues. Results: Glandular breast dose estimates for the nineteen patient models ranged from 7 to 73 mGy, with an average of 47 mGy. Lung dose estimates ranged from 22 to 63 mGy, with an average of 46 mGy. Dose to both organs was significantly greater for smaller patients. Dose on the 16 slice scanner was higher than the 64 by approximately 14% for breast and 10% for lung, a difference not attributable to pitch or mA. Conclusion: Radiation dose to the breast and lung in CTA imaging was estimated using models of actual patient anatomy, scanner specifics, and acquisition protocols. Organ dose was significantly larger for smaller patients, suggesting the need for patient size‐dependent tube current settings for CTA exams.
SU‐FF‐J‐01: Characterization of the Stability of Respiration for Patients Undergoing Motion‐Adaptive Lung Tumor Radiotherapy
Authors: Pokhrel D , Murphy M
Published: July 2007

Purpose: Lung tumor motion is due mainly to respiration. Tumor tracking during radiotherapy requires prediction of the tumor motion to compensate system lag time. Complexity and instability of a patient's breathing will influence its predictability. We have characterized the stability and predictability of the breathing patterns of lung radiotherapy patients by analyzing the time‐dependent behavior of the autocorrelation of the patient's breathing motion. Method and Materials: Breathing motion data were obtained from the CyberKnife Synchrony @ respiratory tracking system at Georgetown University Medical Center. Nine freely breathing lung cancer patients were arbitrarily selected for this study. The patients showed a wide range of breathing behavior. Respiratory motion of the chest surface was recorded for up to sixty minutes during treatment. For each breathing history the autocorrelation coefficient versus delay time was computed in a window of 55 seconds. The decay of the average autocorrelation coefficient over time was computed at various times in the breathing signal history by moving the window. This measured the instability of the breathing pattern over time. Results: The breathing patterns of all nine patients had average autocorrelation coefficients that decayed over time, indicating the breathing was non‐stationary. The rate of decay of the autocorrelation ranged widely for the patients. The predictability of each patient's breathing, as measured in a prior analysis using signal prediction algorithms, was highly correlated with the stability of the breathing pattern, as measured by its autocorrelation. Conclusion: The autocorrelation of a patient's breathing and its decay over time can characterize breathing instability. This makes it possible to compare the results of motion prediction, control and adaptation algorithms that have been tested on a variety of breathing data.
SU‐FF‐J‐03: Real Time Motion Adaptive Delivery—Experimental Validation
Authors: Mauer C , Lu W , Lucas D , Zhang J , Olivera G , Ruchala K
Published: July 2007

Purpose: A real time motion adaptive delivery (MAD) technique to compensate for the effects of intra‐fraction respiratory motion in TopoTherapy/TomoTherapy delivery was developed. This technique was evaluated using dosimetric measurements on a TomoTherapy machine with a motion phantom. Methods: Motion adaptive delivery is a technique that re‐uses the planned sinogram by shuffling its projection and leaf indices, based on instantaneous target position. MAD can be implemented using commercial TomoTherapy systems without hardware modifications. A standard helical plan on a stationary phantom is compared to the same plan on a moving phantom, and a motion adaptive delivery on a moving phantom. The dosimetric differences are measured by delivering plans to film placed on a synchronized motion phantom. The experiment is repeated for different target volume shapes and motion directions. Results: We measured the MAD to be within 2% of dose of a regular treatment delivered to a stationary phantom. These results are consistent for different IMRT target shapes (spherical, ellipsoid, saddle‐shaped), target motions (lateral, inferior‐superior), and field sizes (1.0 and 2.5 cm). Discussions and Conclusions: We present an experimental validation measuring the effects of intra‐fraction motion on helical TomoTherapy plans compared to Motion Adaptive Delivery (MAD). The dose measured in motion adaptive deliveries is within 2% of a regular helical treatment dose to a stationary target.
SU‐FF‐J‐07: Real Time Motion Adaptive Delivery—II. Tomotherapy
Authors: Lu W , Chen Q , Chen M , Ruchala K , Olivera G
Published: July 2007

Purpose: Intra‐fraction target motion hits the fundamental basis of IMRT including tomotherapy. Without modification of simplicity of tomotherapy machine, we develop a technique for delivering helical tomotherapy plan with real time target motion compensation. Methods: Tomotherapy delivery is controlled by a planned projection‐wised leaf sequence (sinogram), which is optimized assuming stationary target. Tomotherapy's gantry rotation synchronizes with its couch proceeding. Both are in constant speed. To compensate longitudinal target motion in real time, instead of sequential execution of the planned sinogram, the projections are out of order executed. That is, a previous or future projection of the planned sinogram is chosen instead. That chosen projection has the same gantry angle and closest planned target position as the current status. The transversal target motion is further compensated by shifting and scaling the open time of each leaf from the chosen projection. Results: We tested different tomotherapy planned sinograms with various tomotherapy machine parameters and target shapes. Arbitrary respiratory motions were simulated. As we delivered a well‐conformed tomotherapy plan without motion compensation to a patient with respiration motion, significant differences between the delivery doses and the planned doses appeared. While we applied the real time motion adaptive delivery (MAD) technique, the delivery doses matched with the planning dose very well in both DVH and dose profiles. The dose errors are well below 3mm and 3% criteria. No hot and cold spots are noticeable. Conclusions and Discussions: We present a novel technique for real time MAD in tomotherapy. Unlike the dynamic MLC based method, this technique only requires instantaneous target position, which greatly simplifies its implementation. This technique re‐uses the planned sinogram by shuffling its projection and leaf indices. It does not involve time consuming operations, such as re‐optimization. The simulations and experiments validated the presented technique.
SU‐FF‐J‐08: Accuracy of Cranial Co‐Planar Beam Therapy with BrainLab ExacTrac Image Guidance
Authors: Vinci J , Hogstrom K , Rosen I , Chu C , Neck D
Published: July 2007

Purpose: To evaluate the positional accuracy (displacement between planned and delivered dose distributions) of cranial co‐planar beam treatments for image guided stereotactic radiation therapy with Novalis. Methods and Materials: Positional accuracy was investigated using a CIRS anthropomorphic head phantom loaded with 6.35cm × 6.35cm sections of EDR2 film oriented to measure dose in the three principal planes. BrainScan was used to develop a treatment plan consisting of seven equally spaced coplanar mMLC beams that conformed to irradiate a 2‐cm diameter by 2‐cm long PTV. Prior to delivery phantom misalignments were imposed in combinations of ±8‐mm offsets in one or more of the principal directions. ExacTrac X‐ray corrections were applied 1–3 times until the reported alignment was within 0.4mm/0.4° in all 6 degrees of freedom based on X‐ray to DRR image fusion prior to treatment delivery. Phantom positions were tracked by the Novalis IR system. The delivered dose distribution was measured with a precision of ±0.3mm. Measured and calculated dose distributions were registered using 4 fiducial rods in the phantom. Results: Based on the 70% dose contour, the displacements of the delivered from the planned dose distributions ranged from 0.7 to 1.3mm, −0.4 to 0mm, and −0.6mm to 0.5mm in Posterior‐Anterior, Right‐Left and Inferior‐Superior directions respectively. For the 80% dose contour, the displacements of the delivered from the planned dose distributions ranged from 0.8 to 1.8mm, 0.1 to 0.8mm, and 0.1 to 1.1mm, respectively. Final displacements were independent of initial misalignments. Conclusions: Using recommended Novalis calibration procedures, the ExacTrac X‐ray image‐guidance system used in our clinic can deliver cranial dose distributions within 1.3mm of the planned dose distributions when initial misalignments are within ±8mm in the three principal directions. 80% isodose contours can have up to 1.8‐mm errors.

This work is part of a research agreement with BrainLab, Inc.
SU‐FF‐J‐11: Defining Picture Archiving and Communication System — Radiation Therapy Extension (PACS‐RT) for Progressive Needs for IGRT, 4D CT/PET, TPS and the RT Workflow Management
Authors: Chen H , Simpson L , Feng W , Liu C , Sarkar A , Grimm J , Lauterbach M
Published: July 2007

Purpose: IGRT has become an essential modality to accurately setup patients for radiation treatment. 4D/CT/PET systems generating multiple phases of respiration image‐sets have greatly helped clinicians contour integrated target volumes. However, IGRT creates 30–40‐times more image data. PACS become important in modern Radiotherapy for massive storage needs. In this study, we defined a new system by expanding PACS into RT extension to cover additional non‐DICOM, RT‐specified data and intra‐departmental communications. Method and Materials: PACS‐RT was designed with two essential core architectures: data storage (archiving) and quality tracking (communications). The RT data stored includes DICOM/RT and non‐DICOM‐objects: TPS, R&V/HIS data/files. Data are stored in a Terabyte RAID5 server, also hosting a relational database system to manage data/query and archive logs. Siemens RT Archive was implemented as PACS‐RT central server. Our dosimetry workflow covering patient procedures from simulation, treatment planning to daily IGRT has been configured. Workflow Manager Software was selected for quality tracking and staff communication. User applications interfacing with PACS‐RT include Siemens Syngo workstations and IKOEtech contouring systems. We also developed some software such as IGRT reporting and unattended backup/restore for Pinnacle to fulfill design requirements. Results: PACS‐RT achieves an environment for patient image/data integrity without any “single point of failure”: no more losing patient data. PACS‐RT also provides convenient access for staff to check their to‐do‐lists and patient progress for scheduling. Although there are still functions and interfacing under refinement, our results demonstrate improved efficiency and quality, as proof of concept for this new hybrid PACS‐RT system. Conclusion: Radiotherapy has known complicated workflow with multidisciplinary staff involved. PACS‐RT was defined to improve management of data/images and communications; it safeguards patient information and tracks quality in each step we perform. In a high‐volume cancer center with advanced treatments, this type of PACS‐RT system is proving essential. Conflict of Interest: N/A.
SU‐FF‐J‐13: Simulated Real Time Image Guided Intra‐Fraction Tracking‐Delivery Method for Prostate IMRT
Authors: Hossain S , Xia P , Chuang C , Mu G , Verhey L , Ma L
Published: July 2007

Purpose: The magnitude and frequency of intrafraction target motion (due to anatomical, physiological and physical changes) has an important role in delivery accuracy for image‐guided radiotherapy. This motion could show significant variations even in few‐second timeframe. However, there are no standard characteristics of target motion that can be assumed for a particular patient. This work aims to study the feasibility of tracking real time prostate motion with subsequent irradiation using Step‐and‐Shoot IMRT. Method and Materials: The prostate motion for actual patient was recorded using image‐tracked Cyberknife system during a 150‐minute single fraction treatment, and subsequently analyzed. Single fraction IMRT plan was planned for the same patient. The plan was normalized such that 95.1% of the CTV received 100% of the prescribed dose. To study the effect of intrafraction prostate motion and how the dose delivered was affected, two groups of IMRT plans were generated, one for 30 (group1) and one for 15 (group2) minutes total delivery time. Group 1 and 2 has 5 and 10 plans, respectively, to reflect the 150 minutes intrafraction prostate movement recorded. In these plans, for each segment, time averaged displacements of the target (AP, LR, and SI movements) were introduced and the MLC positions were shifted accordingly. Results: The dose coverage of the CTV was reduced from the original 95.1% to 92.5 ± 2.6 % in group1, and to 90.4 ± 7.2 % in group2. Plan 5 of group2 shows the lowest dose coverage of 71.2 % due to significant prostate movement (0.5 – 2 cm) within 3601–4500 second period. Dose coverage without plan 5 increased to 92.6 ± 2.7% for group2. Transformed plans receive lower dose to the selected organs‐at‐risk (OAR) compared to original plans. Conclusion: This result indicates the necessity of real time image‐guided compensated IMRT delivery for moving target.
SU‐FF‐J‐16: A Method to Determine the Necessity of Rotational Correction in Image Guided Radiotherapy
Authors: Yue N , Kim S , Jabbour S , Narra V , Haffty B
Published: July 2007

Introduction: IGRT technologies have enhanced the abilities to detect temporal and spatial deviations of target relative to beams. Correcting these deviations may improve the accuracy of dose delivery to target. Frequently, a clinical decision has to be made on the necessity to correct some of the deviations since the relevant dosimetric impact may or may not be significant. The decision should be based on an objective criterion. This study developed a method to determine the necessity of rotational correction during treatment verification process. Method and Materials: At treatment stage, treated volume should be almost geometrically identical to that of the PTV while the goal is to treat the CTV. Various uncertainties may move the CTV outside of the treated volume leading to suboptimum coverage. In many cases, the CTV can be approximated as an elastic semi‐rigid body and its geometry in the treatment space can be derived by using translational and rotational matrices. These matrices can be determined with an image registration tool between plan and treatment verification images. A software package was developed to perform the transformation, and to evaluate whether the transformed CTV remains inside the treatment volume. With the method, the spatial deviation caused by target rotation is computed and the margin size between the PTV and CTV is used as criterion for the necessity of rotational correction. Results: The related equations and algorithm have been developed and was evaluated by applying to a clinical prostate cancer case. For this particular patient, there existed a 26 degree rotation around one axis. Without rotational correction 30% of the CTV would be located outside the treatment volume. Conclusions: A method has been developed to evaluate the necessity of rotational correction. It is potentially useful in IGRT where elastic semi‐rigid body model is a good approximation for target volumes.
SU‐FF‐J‐22: Rapid Fabrication of Custom Router Guides for Craniotomy
Authors: Rajon D , Bova F , Friedman W
Published: July 2007

Purpose: Image guidance allows surgeons to perform accurate and minimally invasive surgical procedures. Advancements in the field of rapid prototyping have provided the opportunity to design patient specific guidance systems. At the University of Florida, this technology has been applied to the fabrication of patient specific routers that allows guiding a surgical drill during craniotomy. Methods and Materials: First, the CT scan of a patient's head is used to model the patient's face. A custom fitted facemask is built from this model and physically fabricated using our subtractive rapid prototyping (SRP) machine. Second, the same CT scan is used to model the patient's skull and to draw a craniotomy contour on the surface of the skull. The model and the contour are then processed to build a router guide that can provide guidance not only for following the craniotomy contour, but also for monitoring the depth of the drill bit as it is moved around the route. The router guide is fabricated with our SRP and attached to the facemask. During surgery, the facemask provides a unique positioning for the router on the skull. A head CT scan was used to fabricate 3 different router guides. A plaster phantom representing a hybrid head (face on the front and skull on the back) was fabricated from the CT scan and used to experiment the router guides. Results: The 3 facemasks provided a unique fit on the phantom and the cut along the route was regular, leaving only a thin layer of bone (from 0.1 to 0.3 mm) that could be easily broken and detached from the skull. Each device was designed and fabricated in less than 4 hours. Conclusion: This experiment demonstrates that a SRP machine can be used for fast and accurate fabrication of custom guides for surgical tools.