bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐I‐67: Effects of Normalization, Filtration, and Distortion Correction Options On MRI ACR Phantom Images
Authors: Busse N , Page L , Hou P , Reeve D
Published: July 2013

Purpose: Toptimization of clinical MR image quality through protocol design on modern scanners requires understanding a wide variety of image acquisition options. Using ACR phantom analysis results for comparison, we sought to understand the effect of these options on the resulting image quality measurements. Methods: Twenty‐six series were acquired with different combinations of normalization, filtration, distortion correction, radiofrequency mode, and gradient mode using a Siemens Aera (Erlangen, Germany) 1.5T scanner with 20‐channel head/neck phased‐array coil. The ACR T1‐weighted phantom protocol (transverse, TR=500 ms, TE=20 ms, 256×256 matrix, 5mm thickness and gap, 25 cm FOV) was used to scan a large ACR MRI phantom (J.M. Specialty Parts, San Diego, California). All images were acquired in the same session without repositioning the phantom. Automated ACR analysis was implemented in MATLAB (Mathworks, Natlick, Massachusetts) for most tests. The software results were compared to manual analysis for five series. High‐contrast resolution, slice thickness, and low‐contrast detectability (LCD) were evaluated manually for all scans following the recommendations in the ACR's Phantom Test Guidance manual (http://www.acr.org/~/media/∼/media/ACR /Documents/Accreditation/MRI/LargePhantomGuidance.pdf). Results: Scans without normalization failed ACR uniformity (1.5T) and slice thickness requirements and had lower LCD scores. Filtering with the Raw Filter degraded resolution to 1.1 mm and increased the ghosting ratio but resulted in decreased noise. On this scanner 2D (in‐plane) distortion correction can be applied prospectively or retrospectively. Results showed that prospective correction provided better geometric accuracy performance. Images acquired using whisper and fast gradient modes, as well as fast and low SAR options, resulted in poorer LCD scores compared to normal gradient and radiofrequency modes. Conclusion: MR protocol optimization requires compromise to achieve relative balance between signal, noise, uniformity, resolution, geometric accuracy and other image metrics. Phantom studies with quantitative metrics provide a robust method of determining how imaging options affect these image parameters.
SU‐E‐I‐69: Improving Image Quality in Brain MRI Using Blade Sequences
Authors: Mavroidis P , Lavdas E , Kostopoulos S , Glotsos D , Roka V , Topalzikis T , Bakas A , Oikonomou G , Stathakis S , Papanikolaou N , Batsikas G , Kaffes I , Kechagias D
Published: July 2013

Purpose: The purpose of this study is to compare two types of sequences for brain MR examination of uncooperative and cooperative patients. For each group of patients, the pairs of sequences that were compared were two T2‐weighted (T2‐W) fluid attenuated inversion recovery (FLAIR) sequences with different k‐space trajectories (conventional Cartesian and BLADE) and two T2‐TSE weighted (T2‐W) with different k‐space trajectories (conventional Cartesian and BLADE). Methods: Twenty three consecutive unccoperative patients and forty four cooperative patients, who routinely underwent brain MRI examination, participated in the study. Both qualitative and quantitative analyses were performed based on the signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), and relative contrast (ReCon) measures of normal anatomic structures. The qualitative analysis was performed by experienced radiologists. Also, the presence of motion artifacts, other artifacts (e.g. Gibbs, susceptibility artifacts, phase encoding from vessels) and pulsatile flow artifacts was evaluated. Results: In the uncooperative group of patients, BLADE sequences were superior to the corresponding conventional sequences in all the cases. Furthermore, the differences were found to be statistically significant in almost all the cases. In the cooperative group of patients, BLADE sequences were superior to the conventional sequences with the differences of the CNR and ReCon values in nine cases being statistically significant. Furthermore, the BLADE sequences eliminated motion and other artifacts and T2 Flair BLADE sequences eliminated pulsatile flow artifacts. Conclusion: BLADE sequences (T2 TSE and T2 Flair) should be used in brain MR examinations of uncooperative patients. In cooperative patients, T2 TSE BLADE sequences may be used as part of the routine protocol and orbital examinations. T2 Flair BLADE sequences may be used optionally in examinations of AVM, orbits, hemorrhages, ventricular lesions, lesions in the frontal lobe, periventricular lesions, lesions in regions close to artifacts and lesions in posterior fossa.
SU‐E‐I‐76: Review of Reported SAR Values in MRI: Current Status and Historical Trends
Authors: Wang J , Garg N , Guha‐Thakurta N
Published: July 2013

Purpose: Although MRI is generally considered a very safe imaging modality, potential risks do exist for RF heating during the patient imaging studies and there have been reported skin burn incidents and cases of patient discomforts due to RF heating. RF heating‐related safety issues have become more relevant as increasing numbers of high‐field (3.0 Tesla or higher) MRI systems are being installed and used in clinical settings. In this study, we reviewed the SAR values on the spine MRI exams over the past few years at our institution and we studied the over‐all trend of SAR values and their correlations with patient size (weight). Methods: With IRB approval, we selected total of 36,051 MRI scans of the spine, dating from September 2005 to June 2012, from the EMR archive at our institution. For each scan sequence, DICOM header information such as SAR value, body weight, scan date, scanner ID, software version are extracted using a MATLAB program developed in‐house. The header information was exported to Microsoft Excel for further analysis. Results: Most of the scans performed on 1.5T scanners have SAR values less than 2.5W/kg while all the 3T scans have reported SAR values less than 3W/kg. However, there are some scans with SAR values above 4W/kg. Additionally, we noticed a gradual upward trend in the SAR values as well as some inconsistencies in the correlations of the reported SAR values to patient weight. Conclusion: The survey results suggest the need for clinical user involvement in the validation and monitoring of the SAR values. Without proper validation, the reported SAR values may not be accurate and even contain errors, making it difficult to accurately assess the SAR values at the hotspots in patient scans.
SU‐E‐I‐78: Frontal and Limbic Abnormalities in Mild Cognitive Impairment with Depression Using White Matter Track Based Analysis
Authors: Juh R , Suh T
Published: July 2013

Purpose: Mild cognitive impairment with depression (MCID) is common and associated with disability and cognitive impairment, with high probability of relapse. Hypothesize that a sign of WM disintegration would be observed in MCID than MCI nondepression (MCIND), especially in frontal and limbic regions and patients with depression would show reduced GM density in the hippocampus, amygdala, anterior gyrus cingulate, and dorsolateral prefrontal cortex (DLPFC) and dorsomedial prefrontal cortex (DMPFC) the abnormalities of long association fiber tracts integrity are correlated with geriatric depression. Methods: Forty‐two subjects (20 nondepressed, 22 depressed) underwent DTI and cognitive assessment. Depression was initially assessed by means of the Korean version of the 30‐item Geriatric Depression Scale (KGDS). All patients scoring 19 or higher on the K‐GDS were screened as depressed. An automated tract‐based statistical analysis method was used to derive estimates of fractional anisotropy (FA) for each subject. Group effects and correlations with clinical features on DTI parameters were examined. Results: We found cross‐sectional differences in WM tract disintegration on posterior cingulum, splenium of corpus callosum, uncinate fasciculus, genu, thalamus, internal and external capsule of limbic in MCID. These results support changes in the structural integrity of neuronal cells in these specific important brain regions constituting a fronto‐limbic‐cerebellar network during depressive and in particular during the course of depression. The different parts of the frontal lobes have afferent and efferent connections with other neocortical, limbic, and subcortical regions and participate in the limbic cortico striatal pallidal thalamic circuits. Conclusion: Findings are suggestive of loss of integrity in WM fiber within frontal, temporal and limbic regions, increasing the evidence that implicates disruptions to the limbic orbitofrontal networks in the pathogenesis of MCID. These neuroanatomical circuits play an important role in the regulation and modulation of affect and emotion, and contribute to the pathogenesis of late life depression.
SU‐E‐I‐87: Experimental Study of Anisotropic Light Scattering and Polarization Effects of EBT3‐Films
Authors: Schoenfeld A , Poppinga D , Harder D , Poppe B
Published: July 2013

Purpose: Further experiments are needed to understand the underlying optical properties of flat‐bed scanned EBT3‐films. Methods: EBT3‐films, arranged in landscape orientation and irradiated with different doses, were illuminated with a homogeneous spot of unpolarized white light. Polarizer foils could be added in front of and behind the EBT3‐film. The light scattered by the film was collected by a plano‐convex lens and focused onto a diffusing glass plate placed at focal length distance. Thereby, the scattering angle was transformed into an offset from the optical axis, forming a characteristic corona. This image was digitized with a DSLR‐camera and the red color channel used for analysis. The effect of incident light polarization was investigated by stepwise rotating the electrical vector of a polarizer in front of the film, with 0° parallel to the preferred direction of the polymer fibres. The polarization of the scattered light was investigated by a second polarizer behind the lens. Results: With an unpolarized light source, anisotropic scattering is preferently propagated orthogonal to the direction of the active polymers, for both landscape and portrait orientation, and the amount of scattered light increases with dose. Scattering by the EBT3‐film varies from almost zero to a maximum when the electrical vector of the light source varies from parallel to orthogonal with the direction of the active polymers. The electrical vector of the scattered light is rotated by 90° compared with the incident light. Conclusion: By experimental separation between scattered and unscattered transmitted light it was proved that incident light polarization only affects the scattered component. This effect hints upon a role of the magnetic component in the excitation of anisotropic scattering. The effect may be utilized to enhance or suppress scattering influences in EBT‐3 film dosimetry.
SU‐E‐I‐88: Diffuse Optical Tomography for Characterization of Optical Properties in Interstitial PDT
Authors: Sharikova A , Liang X , Zhu T
Published: July 2013

Purpose: To characterize spatial distribution of optical properties (OP) for the interstitial photodynamic therapy (PDT) dosimetry using diffuse optical tomography (DOT). Methods: A spatial distribution of interstitial optical properties (absorption and reduced scattering coefficients) in a solid prostate phantom with OP heterogeneities was measured by scanning optical detector and source fibers with a multi‐channel motorized system. Several algorithms optimizing the scanning process were developed for the data acquisition system. The calculated light fluence rates were compared with measured ones to recover the heterogeneous optical properties. A mathematical phantom was used to test the reconstruction. Results: The ability to correctly separate absorption and scattering coefficients depended on the accuracy of the light fluence source measurement. The difference between measured and reconstructed fluence rates was within 10%. The DOT allowed reliable recovery of the absorption coefficients. Conclusion: The efficacy of PDT depends on the light distribution within the treated tissue. Since the spatial distribution of tissue optical properties affects the light distribution, the accurate determination of the OP spatial distribution is critical for the interstitial PDT treatment. This work is supported by the national Institute of Health (NIH) grants P01 CA87971 and R01 CA154562
SU‐E‐I‐99: Demonstration the Capability of X‐Ray Frequency Modulation Imaging Technique Under Noisy Environment
Authors: Zhang J
Published: July 2013

Purpose: Frequency modulation technique has been proposed for x‐ray imaging applications due to the recent development of carbon nanotube (CNT) field emission based x‐ray source technology, which is capable of modulating x‐ray radiation waveforms with different frequencies. The purpose of this work is to evaluate the performance of x‐ray frequency modulation imaging technique especially under noisy radioactive environment. Methods: A dedicated Matlab based software package written in house was used to simulate and evaluate the imaging performance of x‐ray frequency modulation imaging technique. A full scale imaging system was modeled for our simulation purpose. An x‐ray tube with the capability of generating pulsed x‐ray waveforms with different modulation frequencies was used as the x‐ray source. A simple cylindrical object was used as the imaging object. Random noise signal was added in to simulate the background radiation noise. And a high‐speed flat panel x‐ray camera was used to record the x‐ray radiation signal transmitted through the object. The final image was synthesized by decoding the recorded x‐ray signal based on a Fourier transform based algorithm. Results: Based on the simulation results, the new x‐ray frequency modulation imaging technique has dramatically enhanced the imaging quality by filtering out the background noise as indicated by the improved SNR values. Similar Result was also achieved by applying the same technique on a more realistic human chest x‐ray imaging application. Conclusion: In this paper we have reported some simulation results on the assessment of imaging performance of the novel x‐ray frequency modulation imaging technique under different noise environments. Our results showed that under appropriate imaging conditions, x‐ray frequency modulation imaging technique has the potential to greatly improve the imaging quality under noisy radioactive environment. Once fully developed this imaging technique has its promising potential for a variety of imaging applications.
SU‐E‐I‐100: Clinical Ultrasound Units Modes of Failure Survey
Authors: Davros W , Hoeprich D , Hulme K
Published: July 2013

Purpose: This work was done to establish the frequency and modes of failure for clinical ultrasound units from three vendors and various models. Methods: Ultrasound quality assurance reports from 2012 year were scrutinized for unit‐or transducer‐failures or for less catastrophic mechanical issues. All reports were performed via the American College of Radiology accreditation program guidelines for quality assurance surveys. Aspects of each ultrasound unit that was evaluated included, image quality (edge‐to‐edge uniformity, Vertical or horizontal shading, zone‐to‐zone uniformity), dead zone size, penetration depth, electronic caliper accuracy, axial and lateral resolution and low contrast object detection ability. Also evaluated are mechanical integrity of all cords and cables, transducer housings and scanning surfaces. Monitor cleanliness and general working condition were also evaluated. Tests were performed semi‐annually for 70 ultrasound units. Units included 2 Siemens Ateres, 2 Siemens Elegra, 9 General Electric E9, 3 ATL HDI 5000, 18 Philips iU22, 20 Siemens S2000, 2 Siemens Sonoline, 13 Siemens X3000 and one Zonara. Results: 70 ultrasound base units and 532 transducers were tested twice each over one year yielding 140 reports. Of these 70 base units, two were found to have quality issues needing immediate repair. One had a malfunctioning Time‐Gain‐Compensator control slider and the other had a faulty graphics board creating an artifact on all images independent of the transducer used. Of the 532 transducers evaluated one showed evidence of a non‐functioning crystal array element and was taken from service and another had a torn scan‐surface cover and was also taken from service. Conclusion: Regular quality assurance evaluation of clinical ultrasound units does reveal transducers and base units that have repair or replacement issues. The overall prevalence of such events is less than 1 in 100 for transducers and 1 in 35 for base units. I own GE stock.
SU‐E‐J‐03: Impact of Gated and Conventional 4DCT Acquisition On Imaging Artifacts in a Digital Phantom
Authors: Bernatowicz K , Keall P , Kipritidis J
Published: July 2013

Purpose: A new 4D computed tomography (4DCT) acquisition method based on displacement gating was simulated using a deformable digital cardiac‐torso phantom. Imaging artifacts, delivered dose and acquisition time were compared with conventional image acquisition for lung radiation oncology. Methods: Gated image acquisition was simulated with a computerized time resolved cardiac‐torso (modified XCAT) phantom synchronized to patient tumor motion data. The gating threshold is based on the mean peak‐to‐peak displacement in the superior‐inferior (SI) direction during free breathing. The conventional 4DCT was simulated to mimic typical clinical acquisition parameters, where the imager frequency and couch idle time are determined from the patient breathing trace and Result in slight data oversampling. The quality of gated and conventional images was compared based on anatomical similarity with the known phantom geometry. Scan time and imaging dose were also compared, the latter of which is corresponds to the number of acquired images. Results: The gated approach reduced the amount of imaging artifacts by up to 20% (including duplication, overlapping and incomplete structure) and allowed for better anatomical shape preservation. However, the total acquisition session time using gating increased by 17% compared to the conventional scan. With gating, shorter beam‐on time reduced the dose delivered to the patient by 25% (200 fewer images were acquired with gating). Conclusion: Gated 4DCT acquisition can improve image quality, which is beneficial for the highly conformal image guided radiation therapy planning. Furthermore, gated method lowers imaging dose on a cost of a longer imaging session. Further work will investigate different modes to compute gating tolerances to be tested on more challenging patient cases (e.g. including baseline shift).
SU‐E‐J‐19: Prostate Movement Evaluation During Treatment Delivery Period for Prostate Cancer
Authors: Zhang J , Azawi S , Williams R , Frank E
Published: July 2013

Purpose: To evaluate the intra‐fractional prostate movement during the beam delivery period using orthogonal KV image pairs. Methods: To understand the prostate internal motion range during the beam delivery period of conventional treatment, 11 conventional treatments were utilized. We followed RTOG 0815. The total dose is about 75.6 to 79.2 Gy with 1.8 Gy per fraction. The PTV margin is 5 to 10 mm. 2‐arc RapidArc plans are used for the treatment. Once the first arc was delivered, another orthogonal KV image pair was performed to setup the patient based on the prostate seeds. The shift data and the interval time between the first and second orthogonal KV image pair were recorded. Results: The relative error results of OBI QA were within 1mm. The average shift between two arc beam deliveries was 0.38cm (0.20cm ∼ 0.85cm). The interval time between two orthogonal KV image pairs was 6.71 min (4.64min ∼ 9.22 min). For conventional treatment delivery, the 2 arc beam delivery time is within 3 minutes. Hypofractionated treatment will double the beam delivery time. Accordingly, prostate movement might be larger and impair the targeting of cancer tissue. Studies about the prostate movement during longer treatment period will be carried out in the future. Real time tracking method can be employed to verify patient setup during long treatment. However, the orthogonal KV image pair can be an alternative if real time tracking method is not available. Conclusion: Hypofractionated prostate treatment or prostate SBRT need longer beam delivery time. Also the PTV margin is much less than conventional treatment. Therefore verification of patient setup during the beam delivery is critical. Real time tracking system or orthogonal KV image pairs should be used during the beam delivery period to improve treatment delivery quality.
SU‐E‐J‐23: Automatic Detection of Spherical Gold Fiducials in KV X‐Ray Images Having Scattered KV and MV X‐Ray
Authors: Yamada M , Sawada A , Takahashi K , Mukumoto N , Ueki N , Miyabe Y , Mizowaki T , Kokubo M , Hiraoka M
Published: July 2013

Purpose: In tumor tracking irradiation using Vero4DRT having two sets of a kV x‐ray tube and a flat panel detector (FPD), positions of a tumor are estimated from positions of spherical gold fiducials implanted closely to the tumor. The purpose of this study was to propose a new fiducial detection algorithm in kV x‐ray images having scattered kV and MV x‐ray. Methods: According to the preliminary experiment using a fiducial of 1.5‐mm diameter placed on a water‐equivalent phantom and a single set of a kV x‐ray tube and an FPD, we have observed that the logarithm of a ratio of the background to the fiducial intensity decreased in proportion to the x‐ray path length and that the background intensity was proportion to the inverse of x‐ray path length. By combining the above two regression equations and adding a scattered radiation term by the MV and/or the other kV x‐ray sources, the fiducial intensity could be described as a function of the background intensity and the scattered radiation amount without the x‐ray path length. Here, the scattered radiation amount was given as the minimum value allowing all fiducials to be detected. Finally, the fiducials were specified using the fiducial intensity estimated from the above function and some other features such as the lower limit intensity for non‐fiducials. The detection accuracy was measured using 3,824 fiducials in 900 pairs (for both sets of x‐ray tubes and FPDs) of kV x‐ray image with a resolution of 0.21 mm/pixel at the isocenter. Results: The algorithm detected 99.50% of the fiducials. The positional errors were 0.16, 0.16, and 0.21 mm in left‐right, cranio‐caudal, and anterior‐posterior direction, respectively. Conclusion: We have demonstrated that our proposed fiducial detection algorithm has a high and robust accuracy for the kV x‐ray images with scattered radiation. This research is granted by the Japan Society for the Promotion of Science through the Funding Program for World‐Learning Innovative R&D on Science and Technology, initiated by the Council for Science and Technology Policy. This research was in part sponsored by Mitsubishi Heavy Industries, Ltd., Japan. Akira Sawada, Takashi Mizowaki, Masaki Kokubo, and Masahiro Hiraoka have consultancy agreement with Mitsubishi Heavy Industries, Ltd., Japan. Kunio Takahashi is an employee of Mitsubishi Heavy Industries, Ltd., Japan.
SU‐E‐J‐28: Migration Test of Various Fiducial Markers in Tissue
Authors: Jo K , Ki D , Shin D , Lee S , Lim Y
Published: July 2013

Purpose: For guaranteeing the fidelity of patients registration, we measure the migration of various markers and present a criterion to determine the validity of position information of each fiducial marker. Methods: The migration was tested for various fiducial markers; cylindrical gold marker (35 mg, φ.9×3 mm), spherical gold marker (φp1.5 mm) and gold particle‐based‐polymer (GPP) marker (5 mg, φp0.9×3 mm). In order to see the migration effects in tissue, they were inserted into the pork meat by a metallic needle and the meat was fixed in an acrylic box (6×6×8 cm) which is covered with a cup of paraffin. The migration distance of each marker was measured using X‐ray radiographs taken before and after rotating the acrylic box. Results: GPP marker was the lightest among three markers under test, and cylindrical gold marker had the same weight but the larger surface area than spherical gold marker. In the measurement, GPP marker showed the lowest migration (< 0.5 mm). Cylindrical gold marker was migrated more than 2 mm, and spherical gold marker was migrated more than 5mm. The migration distance seems to be related to the ratio of marker mass (centrifugal force) to its surface area (frictional force). In addition, we proposed an index of migration, Dmci to evaluate the amount of marker migration. Dmci is the ratio of i‐th marker registration error to total margin. Therefore, marker registration with Dmci<1 is valid for patient setup and guarantees the proper beam delivery. Conclusion: We compared the migration of various fiducial markers. GPP marker has the smallest amount of migration. The mass and shape of each fiducial marker affects the amount of migration. Also, we proposed an index of migration, Dmci representing which marker was valid for patient setup or not. This research was supported by Nuclear Energy Research Infrastructure Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant No. 2012‐0005840).
SU‐E‐J‐39: Effect of Jaw Size in MVCT On Image Quality and Dose in Helical Tomotherapy
Authors: Jung J , Suh T , Cho K , Kim Y
Published: July 2013

Purpose: The jaw size for the TomoTherapy Hi‐Art II (TomoTherapy Inc., Madison, WI) was reduced from 4 mm (J4) to 1 mm (J1) to improve the longitudinal resolution in megavoltage computed tomography (MVCT) images. This study evaluated the effect of jaw size on the image quality and dose, as well as the dose delivered to the lens of the eye. Methods: MVCT image quality (image noise, uniformity, contrast linearity, high‐contrast resolution, and full width at half‐maximum) and multiple scan average dose (MSAD) were measured at different jaw sizes. A head phantom and photoluminescence glass dosimeters (PLDs) were used to measure the exposed lens dose (cGy). Different MVCT scan modes (pitch = 1, 2, and 3) and scan lengths (108 mm, 156 mm, and 204 mm) were applied in the MSAD and PLDs measurements. Results: The change in jaw size from J4 to J1 produced no change or only a slight improvement in image noise, uniformity, contrast linearity, and high‐contrast resolution. However, the full‐width at half‐maximum reduced from approximately 6.7 at J4 to 4.1 mm at J1, which represents an enhancement in the longitudinal resolution. The MSAD at the center point changed from approximately 0.69∼2.32 cGy (peripheral: 0.83∼2.49 cGy) at J4 to 0.85∼2.81 cGy (peripheral: 1.05∼2.86 cGy) at J1. The measured lens dose increased from 0.92∼3.36 cGy at J4 to 1.06∼3.91 cGy at J1. Conclusion: The change in jaw size can be expected to accelerate treatment planning and improve image registration accuracy. An additional dose of approximately 3.86 cGy, 1.92 cGy, and 1.22 cGy was delivered at a pitch of 1, 2, and 3, respectively, per fraction in the head and neck treatment plans. Therefore, allowance for an approximately 15% increase in imaging dose over that with J4 should be provided with J1. This research was supported by Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST) (Grant No. 2009‐00420) and program of Basic Atomic Energy Research Institute (BAERI) which is a part of the Nuclear R and D programs (No. 2012000486) funded by the MEST.
SU‐E‐J‐46: Real‐Time Beam‐Eye‐View Monitoring of Prostate Motion During IMRT: A Moving Phantom Study with Cine‐EPID Imaging
Authors: Chen X , Fan J , Xue J , Chen L , Wang L , Ma C
Published: July 2013

Purpose: Intrafractional tumor motion introduces significant dose uncertainty for radiotherapy. Using the portal imaging during IMRT delivery will provide a real‐time beam‐eye‐view (BEV) tumor motion observation. We have developed a gradient‐based gold seed fiducial detection algorithm for MV portal imaging. The purpose of this study is to investigate the use of the algorithm for prostate motion monitoring during external beam IMRT treatment by using a moving phantom with cine‐EPID imaging. Methods: A pelvic phantom mounted on a moving stage was used to mimic prostate patient during IMRT treatment. IMRT fields were delivered to the pelvic phantom with a gold fiducial (1x5 mm) on the Varian Trilogy. Cine‐EPID images were acquired using Varian aSi1000 EPID system with the following settings: continuous mode, 3 averages per image, image size 1024×768 with resolution 0.392mm per pixel, EPID at 140cm SID (source‐imager‐distance). Results: Twenty IMRT fields were delivered and about 250 EPID images were acquired while the pelvic phantom was moving in a sinusoidal pattern. Gold seed fiducial was visible in about 40% of EPID images but was blocked by MLC in the remaining images. A gradient‐based algorithm was able to detect the fiducial successfully and recorded the fiducial location at different time. Conclusion: Intrafractional tumor motion is a clinical concern which cause dosimetric uncertainty delivered to patients. By using cine‐EPID imaging during IMRT delivery combined with an automatic fiducial detection algorithm, beam‐eye‐view tumor motion can be observed and recorded which may be used for on‐treatment tumor motion management. This moving phantom study showed the real‐time BEV monitoring of prostate motion during beam delivery is feasible and may be clinical practical.
SU‐E‐J‐57: A Feasibility Study On Molecular‐Imaging‐Based Real‐Time Tumor Tracking for Gated Radiotherapy
Authors: Ishikawa M , Tanabe S , Yamaguchi S , Ukon N , Yamanaka T , Sutherland K , Miyamoto N , Suzuki R , Katoh N , Yasuda K , Shirato H
Published: July 2013

Purpose: Molecular imaging is one of the important modalities in delineating tumors particularly in radiotherapy treatment planning. If the real‐time tumor position can be detected using molecular imaging during radiotherapy, it may be helpful for gated irradiation. A feasibility study on a beam gating system for radiotherapy using real‐time molecular imaging was conducted by the prototype and simulating a parallel plane PET system. Methods: Assuming that the motion of the positron source is constrained to the central plane, the source position can be calculated from a cross point of the Line of Response (LOR) and the central plane between detector surfaces. If a positron source is located at the ISO center, distribution of the cross points might be blurred due to random/scattered coincidence. Center Located Ratio (CLR) was defined as a ratio of LORs passing through the ISO center divided by the entire LORs. When dislocation for perpendicular direction is occurred, a distribution of cross points will be spread out and associated decrease of CLR value will be expected. Results: The behavior between real measurement and simulation was similar on proto‐type experiments, however, the Result from simulation for demonstrator might be different from actual measurement. RTRT system recognizes the position of a gold marker in the rate of 30 fps using two X‐ray television systems. It is shown that 15,000 events per second will be needed for an appropriate gating irradiation to recognize discrepancy over 2mm of time resolution in the parallel plane PET system demonstrator. Conclusion: A feasibility study was carried out to verify the potential for gating irradiation of tumors with real‐time molecular imaging using a parallel plane PET system. For an parallel plane PET system demonstrator, the possibility of detecting the tumor position with an accuracy of 2 mm from the ISO center with 500 events. This research was a part of the “Innovation COE Program for Future Drug Discovery and Medical Care” project and partially supported by the Grant‐in‐Aid for Project for Developing Innovation Systems of the Japanese Ministry of Education, Culture, Sports, Science and Technology.
SU‐E‐J‐63: Correlation Between Radiation Dose and Molecular Bioluminescence Responses of 4T1 Breast Cancer Cells for Adaptive Radiation Therapy
Authors: Park J , Bazalova M , Graves E , Lee J , Park H , Contag C , Suh T
Published: July 2013

Purpose: To determine the required radiation dose and to compensate the dose distribution during the fractionated adaptive radiation therapy, correlation of dose and individual bioluminescence responses of 4T1 breast cancers cells was evaluated using the in‐vivo bioluminescence tomography (BLT) images. Methods: After a dose of 20 Gy in a single fraction was delivered by 200‐kV X‐ray beams to six female BALB/c mice, radiation responses of the cancer cells were monitored with BLT images in every 2–3 days. The dose distributions on mice were predicted in Monte Carlo simulation using EGSnrc codes (BEAMNRC and DOSXYZNRC). As the bioluminescence distributions were deformed onto the dose maps by applying the vector fields acquired in contour‐based rigid and deformable registration, mathematical correlation of dose and bioluminescence was analyzed. The spatial and quantitative bioluminescence variations were also mapped on the computed tomography images to track the proliferation and metastasis characteristics particularly in tumor marginal progression. Results: Radiation treatment showed the negative correlation between radiation dose and bioluminescence intensity with covariance of up to ‐ 0.4. By comparing and categorizing the bioluminescence responses depending on doses in treated and untreated mice group, amount of delivered dose and the field size could be adjusted for more effective control of cancer cells. Spatial tracking of the bioluminescence variations on anatomical coordinates provided useful tool to differentiate the infiltrative cancer cells. Conclusion: Quantitative BLT images were a useful tool to evaluate dose‐related molecular bioluminescence responses of cancer cells of radiation treatment. Required effective doses would be adaptively delivered based on the BLT images according to the radiation treatment scheme and characteristics of the cancer cells. This research was supported by Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST). (Grant No.2009‐00420)
SU‐E‐J‐72: Shift Invariant Feature Transform (SIFT) Based Image Stitching for Panoramic Cone Beam CT (CBCT)
Authors: Wang X , Chao K , Zhou L , Wang S , Bassalow R , Chang J
Published: July 2013

Purpose: Panoramic CBCT is a novel imaging technique that stitches together projection images from multiple views to increase the imaging volume to as large as practically needed using half (200 degree gantry rotation) scans only. In this study, we investigated a SIFT‐based method to improve the accuracy of image stitching for panoramic CBCT. Methods: Panoramic CBCT data were acquired for a torso phantom using two half scans: (A) the detector at the center position and (B) the detector shifted 148mm toward the right side of the phantom. For each projection image of scan A, a corresponding projection image of the same gantry angle was interpolated for scan B using images of two neighboring gantry angles. The SIFT method was applied to extract ‘matching’ feature points in the overlapping region of the projection images of the same gantry angle from each scan. The rigid (translation and rotation) transform matrix derived from this analysis was then used to stitch together the two projection images for CBCT reconstruction using the simultaneous algebraic reconstruction technique (SART) method. Three overlapping (5‐cm, 3‐cm and 2‐cm) sizes were used for the SIFT analysis to determine the optimal imaging parameters. Results: The CBCT reconstructions using the SIFT stitching method showed significant artifact reduction compared with the direct stitching method. The success rate of matching (less than 0.5 degrees rotation and 2 pixels horizontal/vertical shifts) was close to 100% for 5‐cm overlapping and gradually reduced as the overlapping size decreased. The minimum overlapping size we could reliably apply our method was 2 cm (93.8% success rate) below which significant operator involvement was required to determine the applicable rigid transform parameters. Conclusion: We have demonstrated the effectiveness of the SIFT stitching method for panoramic CBCT reconstruction. We are currently improving the registration technique to further reduce the required overlapping size. This work was partially supported by a DOD grant DOD W81XWH1010862
SU‐E‐J‐76: 3D Soft Tissue Boundary Detection for Automatic Verification of Deformable Image Registration
Authors: Yang D , Wang X , Duan Y , Tan J , Mutic S
Published: July 2013

Purpose: The intermediate goal of this work is to develop a novel 3D image boundary detection algorithm in order to reliably detect the soft tissue boundaries in patient CT images. This is the very critical first step towards a potential solution for the currently unsolved problem ‐ automatic verification of deformable image registration (DIR) on patient images. Our hypothetic procedure of DIR verification is 1) tissue boundary detection, 2) boundary matching, and 3) verification of DIR results using the matched tissue boundaries. Methods: A novel 3D image boundary detection algorithm was developed. Multiple steps were used in the tissue boundary procedure, including 3D gradient computation supporting anisotropic voxels, hysteresis thresholding, non‐maxima suppression directly based on the boundary normal directions, boundary thinning, tissue boundary type selection based on the image intensity values on both sides of the boundaries, boundary separation and voxel reconnection based on boundary probability tests. These steps are innovative and critical to enable reliable detection of separated tissue boundaries that would be used in the following boundary matching step. Preprocessing includes automatic couch table removal and non‐local‐mean noise reduction. Post‐processing includes small piece removal and boundary voxels to point coordinate conversion. Results: The algorithm was implemented in MATLAB and tested using patients' head‐neck and pelvis CT images. Results were visually assessed. Compared to the results of the 3D extension of the standard Canny edge detection algorithm, results of the proposed algorithm are significantly more accurate and reliable. Conclusion: The proposed algorithm is a new approach of medical image processing. Combined with image feature matching methods from computer vision fields, it could lead to a potential solution for DIR verification, which is the current roadblock for many clinical applications including treatment adaptation, automatic segmentation and treatment response evaluation.
SU‐E‐J‐85: Landmark‐Driven Interactive Deformable Image Registration
Authors: Shusharina N , Pieper S , Sharp G
Published: July 2013

Purpose: To build a framework for deformable B‐spline image registration with user controlled accuracy by using the positions of point landmarks as guidance. Methods: Manually identified point landmarks are placed on the reference image and their corresponding locations on the test image. An intensity‐based similarity measure is optimized under the constraint of minimizing the distance between the corresponding landmarks. After the Result of registration is visually inspected, the positions of the landmarks may be manually adjusted to improve matching accuracy. Each landmark adjustment operation triggers a re‐optimization routine, which can be repeated until the desired accuracy is reached. Results: We have tested the method on medical use cases to register CT images of the upper body, common in radiotherapy of head and neck cancer. The registration of these images compensates for position error, including pitch and yaw of the head, and flexion of the spine. Deformable registration of these images is very challenging when there is a large spatial shift of the head position. Placing landmarks on a single cross‐section and running optimization one or two times leads to a satisfactory Result. Conclusion: We have developed a practical method of interactive, intuitive correction of deformable registration of medical images. The method integrates both intensity and landmark matching. Our results prove the feasibility of the method and demonstrate potential of the tool for clinical applications.
SU‐E‐J‐88: Dose Summation Between Multimodality Treatments for Cervical Cancer
Authors: Ding L , Chino J , Cai J , Steffey B , Meltsner S , Yang Y , Craciunescu O
Published: July 2013

Purpose: 1) To explore the feasibility of volumetric dose summation between external beam radiation (EBRT) and high dose rate (HDR) brachytherapy treatments for cervical cancer, and 2) to investigate the differences between two deformable registration platforms: MIM Software (M) and VelocityAI (V). Methods: Five patients treated with combined EBRT (45 Gy) and HDR (5 x 5.5 Gy/FX, T&R) were selected in this study. The doses were converted to EQD2 (α/β of 10 for early and 3 for late effects). The HDR CT sets were registered using rigid (r), based on applicator, and deformable (d) registration. To quantify geometrical similarities between the deformed secondary and the original primary structures, the Dice Similarity Coefficient (DSC) was calculated for HRCTV (for HDR sums only), bladder, and rectum. Each HDR fractional dose was resampled to a primary set. The registration between EBRT and HDR was performed using the HDR primary CT. The metrics HRCTV D90, and bladder/rectum D2cc were extracted from total dose DVHs and compared to the current clinical point dose summation protocol. Results: The average DSC for HRCTV, bladder and rectum was 0.72, 0.71, and 0.56 for MIM and 0.71, 0.70, and 0.51 for Velocity. Volumetric dose summation between the two modalities lead to differences from the point summation of 2.1±1.6% (r, M), 3.2±2.0% (r, V), 2.6±1.9% (d, M), and 3.9±1.5% (d, V) for HRCTV D90, 8.9±6.7% (r, M), 9.9±6.5% (r, V), 10.2± 6.2 (d, M), and 9.4± 4.5% (d, V) for bladder, and 5.2±3.4% (r, M), 5.0± 1.1%(r, V), 5.2± 3.3% (d, M), and 5.3± 3.8% (d, V) for rectum. Conclusion: The two algorithms produced similar results, with expected better DSC for HRCTV and bladder than for rectum. With understanding of the limitations of current deformable registration algorithms, 3D dose summation can be accomplished and composite dose estimates can be improved.
SU‐E‐J‐93: Assessment of Contour Fusion Method for Auto‐Contouring of Head and Neck CT Images
Authors: Larrue A , Kadir T , Gooding M
Published: July 2013

Purpose: The goal of this study is to assess and compare Majority Voting (MV) and STAPLE contour fusion methods for atlas‐based auto‐contouring of Head and Neck CT images. Methods: A dataset of ten expertly contoured and independently validated H&N images was used for the evaluation. 31 Structures including the brainstem, parotids, mandible and lymph nodes level had been contoured. Using a leave‐one‐out methodology, each test patient was auto‐contoured in turn, using all nine remaining atlases with commercial auto‐contouring software (RTx, Mirada Medical, Oxford, UK). Contour fusion of the resulting nine contour sets was performed using MV and STAPLE. Dice Similarity Coefficient was computed for each structure and patient against the ground truth. The Result of contour fusion was compared to the performance of a single fixed atlas and to the single atlas giving the best Result, which represents the Result possible if perfect per‐organ atlas selection was achievable. It is included to act as an upper bound on potential single‐atlas performance. Results: STAPLE was slightly more accurate than MV for 23 structures and than the single atlas for all the structures. Compared to best possible atlas, it was more accurate for 12 structures. The mean DSC for each structure was 0.71 for STAPLE, 0.67 for MV, 0.59 for single atlas and 0.72 for best possible atlas. For the brainstem, left and right parotids, lymph nodes levels and mandible, DSC was 0.85, 0.76, 0.75, 0.75, and 0.86 for STAPLE and 0.81,0.72,0.65, and 0.84 for single atlas. Conclusion: Both contour fusion methods improve over the single fixed atlas for all structures. The performance of STAPLE was slightly better than MV for most structures. STAPLE also produced slightly lower variability across patients. We conclude that contour fusion can improve auto‐contouring Result, and STAPLE is marginally better than MV in H&N contouring. All authors are employees of Mirada Medical. There is no conflict of interest with the research submitted.
SU‐E‐J‐95: Increasing Soft Tissue Contrast by Combining New CT Technologies and Imaging Dose for Radiation Treatment Planning and Delivery Guidance
Authors: Chen G , Tai A , Liu F , Shukla H , Erickson B , Li X
Published: July 2013

Purpose: CT dose is normally minimized based on ALARA principle. For radiation therapy (RT), a slightly increased CT dose in exchange for improved soft‐tissue contrast may be justified. In this work, we investigate the impact of CT imaging dose and other acquisition and reconstruction parameters on CT quality for RT planning and delivery guidance. Methods: CT data of various phantoms were acquired using a CT‐on‐rails (Somaton Definition AS Open, Siemens) with a series of acquisition parameters, such as tube voltage and current, rotation time, pitch, imaging dose control methods, and reconstruction algorithms, and were analyzed based on contrast‐to‐noise ratio (CNR) and dose‐weighted CNR (CNRD) to identify image quality enhancement protocols (IQEP). The IQEPs were then used to acquire CT during daily IGRT for selected patients with head and neck, prostate, and pancreas cancers. The impact of the improved CT images on RT was assessed with (1) accuracy and reproducibility of auto‐segmentation using ABAS (Elekta) and (2) intra‐and inter‐variability of manual contouring of the relevant organs by 10 observers. Results: As expected, the CNR generally increases with mAs from phantom CT data, while CNRD experiences a slow increase with mAs or reaches a plateau and then drops above certain mAs depending phantom size and relative electron density or contrast level. There is complicated interplay between kVp and mAs, particularly with regards to perception. Visual inspection of the patient CTs obtained with IQEPs showed clearer organ boundaries as compared to those from the standard CT protocols. This improvement was supported by the reduced intra‐and inter‐variability of manual contouring. The CT doses with IQEPs were 2–3 times higher than those from the standard protocols. Conclusion: CT quality can be improved by optimizing parameters in CT protocols for modern scanners, leading to improved accuracy of organ delineation for RT planning and delivery.