bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐I‐136: Lesion Detectability of a PEM System with a Proposed Breast Image Quality Phantom
Authors: Luo W , Matthews CG , Lu X , Landor HP , Anashkin E
Published: April 2010

Purpose: The aim of this study is to evaluate the lesion detectability of a PEM scanner using a proposed PEM specific breast image phantom with lesions of various sizes and activities. Method and Materials: A customized image quality phantom was designed with hot rod inserts and a warm background that simulated a breast with lesions. The phantom was about the size of a breast (130 mm × 130 mm × 66 mm). The inserted hot rods had diameters approximately 10 mm, 5 mm, 4 mm, 3 mm and 2 mm. Activities were 3.5, 6.8 and 12.7 times the background activity. The background activity was 0.05 μCi/cc. The scan protocol was 20 minutes full field of view. The 3D image array (200 × 136 2466 × 24 voxels) was generated for analysis. We analyzed the recovery coefficients of the rods as a function of the activity and rod size. From a fit to the data, we extrapolated the minimum detectable lesion size for each activity level. Results: The results showed that the PEM scanner can detect 1.2 mm hot rod that had 12.7 times background activity and 1.5 mm hot rod that had 6.8 times the background activity. It could also detect the hot rod with 3.5 times background activity down to the 3.3 mm rod. Conclusion: This study investigated the performance of a PEM scanner in detecting small lesions with various activities. The result quantified the potential limit of the lesion size that can be distinguished from the background in clinical practice. The proposed phantom showed its design was well suited for this kind of study. Conflict of Interest: Research sponsored by Naviscan, Inc.
SU‐FF‐I‐150: Impact of VOI Size On PET Image Quantification Following Partial Volume Correction
Authors: Chang T , Chang G , Pan T , Clark J , Mawlawi O
Published: April 2010

Objectives: Partial volume correction (PVC) techniques based on a‐priori knowledge of object size and scanner's point spread function (PSF) have been previously proposed and evaluated. This approach however results in sharp peaks at the object edges in the corrected images which overestimates the corresponding mean activity concentration (AC). The aim of this abstract is to investigate the effect of varying the size of a VOI on determining the accuracy of mean AC in a lesion following PVC. Methods: An IEC phantom containing six spheres (1–3.7cm) was scanned on a GE DRX PET/CT scanner. The sphere to background ratio (SBR) was (4:1, 6.5:1, 11.1:1). In each case, the background AC was set to 0.1uCi/cc to emulate the background AC of clinical PET studies. PET data was acquired in 3D mode for 3 minutes. For PVC, the measured AC was divided by the convolution of the scanner's PSF with a binary map of the true sphere size obtained from CT. The PSF used included the effects of the reconstruction filter. Concentric VOIs of decreasing diameters (100–10% the sphere diameter) were then drawn in the center of each sphere to calculate the mean AC following PVC. Plots of the mean AC versus sphere size for the different VOIs were generated and compared to the true value. Results: For an SBR of 4:1 and sphere size of 10mm, the improvement in mean AC between the 100 and 50% diameter VOI was 24%. This value dropped to 3% between a 50 and 20% VOI diameter. For an SBR of 6.5:1 these values were 15 and 0% respectively. Conclusion: Decreasing VOI size improves the accuracy of mean AC following PVC in PET imaging, especially for small SBRs and tumor sizes. This improvement diminishes for VOI sizes smaller than 50% the true object size.
SU‐FF‐I‐155: A Novel Technique to Generate 3D Lung Volumes From 2D Hodgkin Lymphoma Planning Datasets Using Combined Deformable Image Registration and Navigator Channels
Authors: Ng A , Moseley J , Nguyen TN , Hodgson D , Sharpe M , Brock K
Published: April 2010

Purpose: To validate the use of deformable image registration and navigator channels (NC) to generate 3D lung volumes from 2D images, for retrospective dose calculation of Hodgkin Lymphoma (HL) patients treated with 2D planning. Methods and Materials: Forty‐seven HL patients with 3D images were acquired. Six patients were used to construct a population lung model, which was then registered, using a biomechanical model‐based deformable registration algorithm, MORFEUS, into 24 additional HL ‘reference’ patients to develop a lung motion model. This model was refined to describe the 3D lung volume and position of 17 HL ‘test’ patients, using only information in the 2D DRR constructed from 3D images. The refinement was performed by: 1) matching a reference patient to each test patient (using lung width and length measurements), 2) placing four NCs, or small regions of interest, on the lung boundary of the reference patient and automatically placing the corresponding NC on the test image in the same geometric position, 3) converting the image intensity in the NC into a 1D shift to match that location, 4) refining the lung motion model using the four 1D shifts to describe the 3D volume and position of the test patient's lung. The refined lung model was then compared to the actual 3D lung contour of the 17 test patients by computing the volume overlap. Results: The average percentage overlapping and non‐overlapping volumes between the NC‐refined lung model and test lungs were 89.2±3.9% (Right Lung=88.8%; Left Lung=89.6%) and 10.8±3.9% (Right=11.2%; Left=10.4%), respectively. NCs made a statistically significant improvement to the population lung model shape (T‐test: p < 0.05). Conclusion: This technique will be used to generate 3D lung volumes for retrospective patients treated with 2D planning for longitudinal studies to improve understanding of the dose‐risk relationship and various late effects.
SU‐FF‐I‐156: Unerasable Latent Images Observed in Computed Radiography and Their Complete Erasing
Authors: Ohuchi H
Published: April 2010

Purpose: Some unexpected effects in Computed Radiography (CR) have become known, i.e., the phenomena of unerasable and reappearing latent images, particularly for a film irradiated at high dose and/or a subsequently irradiated film. The aim was to evaluate the usefulness of our new erasing method to erase unerasable and reappearing latent images in CR. Method and Materials: Several types of photo‐stimulated luminescent (PSL) material, BaFBrI:Eu2+ were examined for properties of causing unerasable latent images. PSL sheets were exposed to X‐ray beams of 150 kV in the range 8.07 mGy ‐ 24.2 Gy. After fully erasing with visible light, the latent images were read out by the stimulation of Eu2+ luminescence with 633 nm He‐Ne laser light of a conventional Fuji reader. Our new method of simultaneously exposing PSL sheets with an ultraviolet light and a fluorescent light has been applied to unerasable latent images. UV lights (shorter than 270 nm) excite Eu2+ ions, inducing strong luminescence. To avoid excitation of the Eu ion, we used ultraviolet light filtered by the UV‐29 ultraviolet transmitting optical filter, which cuts out 50% of light at 290 nm, to do the erasing. Results: Unerasable latent images were observed in all types of PSL sheets after X‐ray irradiation. After repeated treatment by the new erasing method, unerasable latent images were completely erased without reappearing PSL signals. Deep electron centers created by high X‐ray irradiation or pre‐existing centers may act as competitive trap centers to the F centers. Electrons from deep electron centers can be supplied to the F centers, causing unerasable latent images. UV lights around 290 nm can excite the deep centers relevant to the unerasable and reappearing PSL. Conclusion: The new erasing method can be used to erase unerasable and reappearing latent images effectively, reducing artifacts and improving image quality in CR.
SU‐FF‐I‐157: Activity Quantification of Micro PET Imaging Using Hollow Spheres in a Small ECT Phantom
Authors: Luo J , Jang S
Published: April 2010

Purpose: To evaluate quantification of F‐18 activity distribution in Micro PET images of a set of hollow spheres inserted in a small ECT phantom. Method: Six hollow spheres (Data Spectrum Micro Spheres: diameter: 12.43, 9.89, 7.86, 6.23, 4.95 and 3.95 mm) in a cylindrical phantom (net volume: 110 mL with cold rods insert) were injected with F‐18 and imaged using a Micro PET scanner (Rodent R4. Concorde Microsystems). Hollow sphere activities were prepared in one syringe for the same activity concentration and measured with a dose calibrator as 153, 102, 52, 22, 19 and 7 uCi respectively. Two sets of images were acquired using the same protocol. Second imaging started 65 minutes after completion of the first scan to compare dead time effect. Each 20‐minute scan was set to reduce statistical fluctuation. Image reconstruction used a 3‐D reprojection method with Fourier rebinning. Region of interests of the hollow spheres were defined manually on the 1st scan and then copied to the 2nd image for consistency. Result: True count rate dropped from 445 kcps, 44% dead time (1st scan) to 280 kcps, 27% dead time (2nd scan). About 5.5% decrease was due to dead time. Significant partial volume effect appeared for spheres with diameter less than 6 mm. Recovery coefficient curve was generated for quantification of brain image of rats. Total activities in the spheres were consistent with both images, and agreed with readings from the dose calibrator. Conclusion: Phantom imaging could be used to generate recovery curve and calibration factors that are necessary for quantification of small animal scans. Partial volume effect starts when the object size is much greater than the camera spatial resolution that is measured with point or line source in air.
SU‐FF‐I‐160: SpekCalc: A Free and User‐Friendly Software Program for Calculating X‐Ray Tube Spectra
Authors: Poludniowski G , Deblois F , Landry G , Evans P , Verhaegen F
Published: April 2010

Purpose: To develop a free and easy‐to‐use software program to model the x‐ray spectra emitted from x‐ray tubes. Such a program is useful for the education of physicists, technicians and technologists working in radiation physics but also as a research tool. Method and Materials: A Graphical User Interface (GUI) was created using REALbasic (REAL software, Inc.). This GUI, designated the name SpekCalc, allows the user to calculate and display the x‐ray spectra emitted from tungsten‐anode x‐ray tubes. The underlying theoretical description for the bremsstrahlung and characteristic x‐ray production is taken from a recent published model. Results: The user selects the tube potential in kVp, the take‐off angle and the amount of filtration. At a click of a button the resulting spectrum is calculated, displayed and can be saved for later use. Beam quality parameters such as the half‐value‐layer, in mm of aluminum and copper, and the mean beam energy, in keV, are also presented to the user. The range of potentials that can be modeled is wide (40–300 kVp) making Spekcalc useful to both the diagnostic imaging and keV photon radiotherapy fields. Filtration can be selected in mm, for 7 materials: aluminium, copper, tungsten, tin, beryllium, water and air. This allows an in‐depth exploration of the filtration effects of materials of differing atomic number. Over 300 individuals have downloaded this program thus‐far, for reasons as diverse as teaching in universities, to learn interactively about x‐ray tubes, for research in radiology and radiotherapy. Conclusion: A useful educational tool for physicists, technicians and technologists has been created, in the form of freely‐available software utility to calculate x‐ray tube spectra.
SU‐FF‐I‐162: Depth of Field in Radiography
Authors: Siddique S , Bartolac SJ , Bootsma G , Mail N , Fiume E , Jaffray D
Published: April 2010

Purpose: Depth of field (DoF) is a well developed concept in photography. Several recent advances in photography have capitalized on DoF to optimize the information that can be extracted from images. This study explores an analogous concept to DoF in radiography and its implications. Method and Materials: Hypothesis 1: Given an X‐ray source with a finite focal spot size and a detector with a known pixel size, objects appear sharpest when placed at the point of intersection of the lines joining the opposite ends of the width of the source and that of the central pixel. A fixed source to detector distance of 1560mm was selected. A tilted lead sheet was then imaged at a number of locations between the source and the detector, and the spatial frequency (mm−1) at 50% MTF was reported for each of these locations. Hypothesis 2: It is possible to disambiguate between layers within a patient by moving the source and/or the detector along the source‐detector axis. A foam block with two perforated aluminum sheets attached on opposite sides was imaged. These sheets are representative of different imaging planes within a patient. A second image of this block was acquired using a source position further away from the detector. The acquired images were then merged using knowledge of the geometrical transform and the imaging plane of interest to sharpen one of the two sheets and blur out the other. Results: Structures with size of the order of the pixel pitch of the detector can best be resolved at the DoF. Using the proposed technique, it is possible to selectively sharpen layers of interest within a patient. Conclusion: An understanding of the DoF can facilitate expansion of the DoF allowing more planes within a patient to be imaged sharply (“focused”). Moreover, it can allow focusing at desired depths within a patient.
SU‐FF‐I‐168: Morphological Characterization of Arterial Trees in An Experimental Hindlimb Ischemia Model
Authors: Kagadis G , Skoura A , Megalooikonomou V , Diamantopoulos A , Katsanos K , Karnabatidis D , Mihailidis D , Nikiforidis G
Published: April 2010

Purpose: The objective of this study was the morphological analysis of the arterial trees depicted in digital subtraction angiographic (DSA) images from a well known mammalian experimental hindlimb ischemia model. Our purpose was to provide insight into the discriminative characteristics of arterial trees in normal, acute and chronic ischemic limbs. Method and Materials: We present three characterization methods for extracting information from arterial trees in order to capture tree features; topological patterns, asymmetry and branch density. The first method proposes the Prüfer encoding of the trees followed by the tf‐idf technique and the cosine similarity metric to compare the topological patterns of trees. The second uses the tree asymmetry index to quantify the asymmetry of tree topologies and the final one is based on Sholls' analysis to compute the tree branch density. These methods were applied on a series of DSA images of segmented collateral vessels in the aforementioned model (three subjects). Results: Ischemia was induced in day number 0 on one limb of each animal while the contralateral was left intact. Revascularization, through normal angiogenesis, is known to have been accomplished after 40 days. The topological patterns were evaluated in three groups; the chronic ischemic (group A), the normal (group B) and the acute ischemic (group C) arterial trees. Our results demonstrate that the arterial structures from group A have similar topological patterns to group B, compared to group C (mean similarity percentage=78% and 66% respectively). Moreover, the arterial trees from group A appear more asymmetric and with increased density of branches compared to the acute ischemic arterial trees (group C). Conclusion: In this study we presented three techniques for characterizing and analyzing the arterial tree‐like structures in a series of DSA images, thus illustrating the potential of the proposed tree characterization framework.
SU‐FF‐I‐170: Control, Acquisition, Processing, and Image Display System (CAPIDS) for the Solid‐State X‐Ray Image Intensifier (SSXII)
Authors: Wang Weiyuan , Keleshis C , Kuhls‐Gilcrist A , Ionita C , Bednarek D , Hoffmann K , Rudin S
Published: April 2010

Purpose: A new control, acquisition, processing, and image display system (CAPIDS) for the Solid‐State X‐Ray Image Intensifier (SSXII) was developed and implemented using Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW). Method and Materials: The SSXII is an EMCCD‐based x‐ray detector that was designed to satisfy the high‐resolution and real‐time needs of neurovascular imaging. The SSXII includes a CsI(Tl) scintillator and a fiber‐optic taper (FOT) coupled to an EMCCD camera with fiber‐optic input window. The SSXII can be mounted on and used with a clinical fluoroscopic c‐arm unit (Toshiba Infinix). The new CAPIDS provides controls for several radiographic imaging modes including: fluoroscopy, roadmapping, radiography, and digital‐subtraction‐angiography (DSA). Complete functionality of the SSXII is also provided in research mode, including the ability to modify the detector‐element binning, exposure time, video gain, and electron‐multiplying gain of the camera. A camera control‐panel window can be accessed using a keyboard shortcut; this window shows the status parameters of the camera and allows control for all functions. Status words are saved to a text file for reference by the system control program. Results: The CAPIDS provides a user‐friendly interface that allows control of several clinical radiographic imaging modes using the SSXII including: fluoroscopy, roadmapping, radiographic mode, and DSA. Examples of each mode will be demonstrated. Additional features, including recursive filtering, contrast enhancement, patient registry and image archival have been implemented and should facilitate the clinical use of the new EMCCD‐based detector system. Conclusion: The control, acquisition, and display capabilities along with the electron multiplication gain (1–2000×), high‐resolution, high‐sensitivity and real‐time imaging capabilities of the SSXII should provide angiographers and interventionalists with an improved ability to visualize details of small vessels and endovascular devices (such as stents), making diagnoses and image‐guided interventions more accurate.

(Research partially supported by: NIH Grants R01‐EB008425, R01‐EB002873)
SU‐FF‐J‐11: Implementation and Characterization of a 320‐Slice Volumetric CT Scanner for Simulation in Radiation Oncology
Authors: Coolens C , Breen S , Purdie T , Jaffray D
Published: April 2010

Purpose: A novel volumetric CT scanner (Aquilion One, Toshiba) has been installed at the Princess Margaret Hospital for implementation into routine CT simulation. This technology offers great advantages for anatomical and functional imaging in both scan speed and coverage. This work aims to evaluate the logistics and integration of the system in our radiotherapy department, the imaging performance and quality. Method and Materials: The Aquilion One uses a wide‐area design and can acquire a volume of 160 mm in 350msec. It can also be used as a 64‐slice scanner and perform spiral acquisitions. Room shielding was adjusted from the conventional CT simulators due to the extra scatter generated from the wider X‐ray cone angle in the 320‐slice scanner. CT dose measurements were done with the CTDI “body” and “neck” phantom using additional build‐up material for more realistic scatter conditions. Electron density measurements were done at 120 and 135kVp and HU consistency checked across the scan volume. Image quality and noise and spatial integrity were assessed with the CATPhan phantom and large‐are water‐equivalent phantoms. Results: At 1m from the isocentre the scatter could be as much as 6 times the dose from a 16‐slice CT (μGy/mAs). CTDI measurements were consistent with those published in the literature. Electron density curves are comparable to existing HU calibration data from our other CT‐simulators. In volumetric mode the HU variation across the volume is less than 10% for materials with a density less than or equal to water. Image quality and noise were deemed acceptable. Conclusion: A novel 320‐slice CT scanner has been successfully commissioned for routine radiotherapy simulation. Initial evaluation shows good performance and stability of volumetric scanning at isocentre. In‐field variations in HU calibration are present for higher density materials but within the range that could arise from using different tube potentials.
SU‐FF‐J‐14: An Optimized Protocol for Using Small Field MV Cone‐Beam CT Imaging in Image‐Guided Radiotherapy (IGRT)
Authors: Yembi‐Goma G , Lu L , Li K , Wang J , Zhang H , Martin D , Gupta N
Published: April 2010

Purpose: The aim of this study was to develop an optimal protocol for imaging different body sites in patients during MV Cone Beam CT (MVCBCT) based IGRT for small field of view (FOV) imaging for Stereotactic Radiosurgery and other applications. Methods and Materials: Clinically delivered MVCBCT imaging systems have built‐in protocols that are optimized for large FOV imaging. For our protocol optimization study, we chose a field size of 12cm × 10cm to acquire CBCT images. Our study was conducted using our Siemens Oncor Impression Linac, an image quality phantom, an offline reconstruction tool prototype software, a prototype visualization tool, a dicom image extractor tool, and the ImageJ open source software from NIH. Five regions of the image quality phantom were imaged and the raw data was processed using the offline reconstruction tool by changing various reconstruction parameters. Our study was focused on two specific regions of the phantom, corresponding to electron densities of 9% and 17%. A useful projection image size of 448 × 373 pixels on the flat panel detector was used for the filtered backprojection. The dicom images were extracted with the dicom extractor from the reconstructed images for post processing and quantitative image analysis using the ImageJ software. Results: Our efforts in optimizing the image reconstruction and processing chain resulted in the development of protocols that result in superior images. We have developed quantitative methods to analyze the results and determine the optimal protocol. We are currently repeating the imaging process with the Image Quality phantom to check for reproducibility of our methods and protocols. Conclusions: Our preliminary result provides a valuable reference to setup an optimal protocol for using small field MVCBCT for IGRT. Once we confirm the reproducibility of our protocol, we plan on imaging a series of patients to clinically test the protocol.
SU‐FF‐J‐15: A Retrospective Study of the Variation in Organ Dose as a Function of Table Shifts Using Megavoltage Cone‐Beam CT
Authors: Zhang D , Singhvi M , Lin C , Lin K , Lee S , Lee P , Zachary Z , Hussain A , Steinberg M , DeMarco J
Published: April 2010

Purpose: This study analyzes the variation in patient setup based upon daily megavoltage cone‐beam CT (MVCBCT) prior to treatment. The variation in organ dose as a function of table shifts is quantified in order to understand the effect of systematic versus random setup error for head and neck (H&N) IMRT patients. Methods and Materials: Sixty patients with H&N cancer were imaged on a daily basis prior to treatment using MVCB CT imaging with the initial clinical setup based upon in‐room lasers and mask marks. After imaging the patients were repositioned based upon registration of the MVCB CT to the original planning CT. The average shift, standard deviation and root mean square values were calculated based upon the daily shift values in the lateral (LAT), superior‐inferior (LONG), and anterior‐posterior (VERT) dimensions. The mean shift values were incorporated into the treatment planning system to recalculate the dosimetry for each patient, assuming the shifts were not performed on a daily basis. Results: Comprehensive tables were generated to evaluate the dose difference for each patient as a function of the CTV, spinal cord, and optic chiasm assuming the mean table shift values were not performed on a daily basis. The maximum and mean dose difference for the CTV, averaged across nine patients in the study group, was −4.0% (range of −9.5% to 0.5%) and −5.7% (range of −11.7% to 0.2%). The maximum and mean dose difference for the spinal cord was −3% (range of −12.4% to 13.6%) and −6.1% (range of −12.9% to 1.2%). Conclusion: The dosimetry difference is not trivial before and after table shifts based upon MVCB CT imaging. Further study is needed to quantify the effect on the delivered dose distribution as a function of systematic versus random setup error.
SU‐FF‐J‐17: Image‐Guided Radiotherapy Using Nanotube Stantionary Tomosynthesis Technology
Authors: Chang S , Frederick B , Liu X , Tracton G , Lawrence M , Lalush D , Pizer S
Published: April 2010

Purpose: To develop image guidance approaches for clinical application of Nanotube Stationary Tomosynthesis (NST), a nanotechnology‐based online image‐guided radiotherapy (IGRT) technology that is capable of unprecedented temporal‐resolution and imaging speed. Method and Materials: NST is an accelerator gantry‐mounted multi‐source array kV imaging technology under development by Siemens. Using a single image panel, the patient can be imaged by 50 x‐ray sources on the array in the treatment volume within ∼ 2 sec before and even during treatment. However, translating the NST's imaging acquisition strengths into real clinical benefits requires significant software development including new image registration tools that take full advantage of the real‐time aspects of tomosynthesis imaging while minimizing its intrinsic resolution limitation. We propose a fast, versatile image registration approach that: integrates information from the large field‐of‐view projection images, the high‐temporal resolution tomosynthesis images, and the high spatial‐resolution planning 3D CT image; has tradeoffs to balance the user's needs of quality vs. speed; and potentially extracts a daily image deformation from NST tomosynthesis image for soft tissue based IGRT and treatment course dose accumulation. Results: We have developed the initial image registration approaches for clinical testing of the first protocol type NST IGRT system. In this presentation we will describe the proposed NST IGRT image registration approaches in lung and prostate treatments and discuss imaging dose and imaging dose reduction approaches. Other aspects of the NST technology including system design, NST reconstruction, image registration, and imaging geometry may be presented separately in the meeting. Conclusion: We have demonstrated that Nanotube Stationary Tomosynthesis technology has the potential to offer temporal resolution and imaging speed ‐ important features that have not been adequately addressed by the existing IGRT technology today.

Conflict of Interest: This work is partially funded by a grant from Siemens Oncology Care System.
SU‐FF‐J‐143: A Feasibility Study of Using O‐18 Enriched Water to Develop a Method of In‐Vivo Range Verification in Proton Therapy
Authors: Cho J , Schulte R , Patyal B
Published: April 2010

Purpose: To report a feasibility study of using oxygen‐18 (O‐18) enriched water in combination with PET to develop a method of in vivo range verification in proton therapy. O‐18 enriched water is non‐toxic and non‐radioactive and can be safely administered to patients before proton treatment. When protons interact with O‐18, it is converted to F‐18 which decays back to O‐18 by positron emission with a half‐life of 110min. For the O18(p,n)F18 reaction, the interaction cross‐section is larger, the energy threshold lower, and the half‐life longer compared to most other inelastic proton interactions in patients leading to positron decay. Method and Materials: O‐16 water, 98% O‐18 enriched water, and 10% O‐18 enriched water samples were placed inside a polystyrene phantom and irradiated with a modulated 149 MeV proton beam with a 6 cm wide Spread Out Bragg Peak (SOBP) at three depths (mid‐entrance region, proximal, and distal third of the SOBP). The activity decay of each water sample was measured using a NaI detector for 1–2 hours. Additional information was obtained by scanning the irradiated water samples with a high‐resolution animal PET scanner. Results: As expected O‐16 irradiated water had a higher initial activity than 10% O‐ 18 and 98% O‐18 enriched water at each depth. However, at later times, the activity in the O‐18 samples was larger due to the short half‐times of positron‐emitting products resulting from O‐16 irradiation. Furthermore, there was a larger reduction of activity of irradiated O‐16 across the SOBP as compared to O‐18 irradiated water. Conclusion: Application of O‐18 enriched water has features that make it an attractive method for in‐vivo range verification of proton beams. It is likely that this method could also be useful for in vivo dose verification.
SU‐FF‐J‐146: Sequential Volume Change Estimation of Breast Tumor From Whole Breast Automated Ultrasound by Reader Study
Authors: Narayanasamy G , Roubidoux M , LeCarpentier G , Li J , Moskalik A , Joe A , Carson P
Published: April 2010

Purpose: To evaluate use of image based registration in volume change estimation of breast tumor by expert reader study of three‐dimensional (3D) ultrasound (US) whole breast image volumes. Methods: 3D US volumes of tumors in nearly whole breast sweeps using mammography‐style compression were acquired using the Logiq‐9 10L transducer (GE Healthcare, Waukesha, WI). Nearly whole breast scanning was performed before, during and after 115±14 days of chemotherapy on 7 patients. Three breast radiologists marked a 3D ellipsoid around the tumor on pairs of pre‐ chemotherapy with mid‐ or post‐chemotherapy US image volumes, spatially unregistered or registered in a pseudo‐random order. Additional information including pre‐chemotherapy US hand scan(s), mammograms and a clinical findings report without tumor dimensions was provided. Results: Preliminary results on the first 3 of 7 cases showed that registration provided a nearly significant reduction in the statistical uncertainty in reader estimates of normalized fractional tumor volume change due to chemotherapy (p‐value<0.08). The time taken to mark the tumor boundary decreased significantly from 10 min (9.8–10.3) without registration to 5.5 min (3.6–6.6) with registration (p‐value<0.02). Mean intersection‐to‐union volume ratio also improved with registration, by 33% from 0.15±0.1 (p‐value<0.05). A negligible improvement in confidence in identifying tumor margin in the automated US image volumes was seen with registration. The normalized, between‐reader, mean separation of the centers of identified tumors decreased insignificantly with registration by 47% (p‐value<0.3). Conclusion: Successful spatial registration appears to aid ultrasound measurement of tumor changes in response to neoadjuvant chemotherapy. Visual segmentation speed and volume overlap between readers were increased with the help of registration. Larger studies would be appropriate with focus on treatment response, breast cancer screening and diagnostic applications.
SU‐FF‐J‐151: Fabrication and Testing of An Agar‐Based Heat‐Sensitive Gel for Thermal Dosimetry
Authors: Siddiqi A , Cho S
Published: April 2010

Purpose: To develop a novel heat‐sensitive gel made of non‐toxic materials that can be used to measure heat resulting from illumination of gold nanoshells/nanorods with near‐infrared (NIR) 808 nm laser. Method and Materials: The heat‐sensitive gel is made by mixing 1.5 weight percent agar in distilled water and the solution is allowed to mix completely while heating it to 90 °C. Once the agar has completely melted and the solution becomes clear, it is allowed to cool to 50 °C, when 20–30 weight percent bovine serum albumin (BSA) is added to the agar mixture. The gel can be poured into any container or mold and allowed to solidify to become various shapes of phantoms. BSA is a heat sensitive protein that will undergo denaturing and result in an optical density change at the areas where temperature exceeds 70 °C. The phantom made of this gel can contain a small cavity where gold nanoshells and nanorods will be concentrated to simulate the tumor. The phantom can be read with T2 weighted magnetic resonance imaging (MRI) for quantification and visualization of heat damage around the cavity due to NIR laser illumination. Results: The agar based gel has shown to be heat‐sensitive and T2 weighted MRI imaging can be used to visualize the permanent heat damage. The average T2 value corresponding to the damaged areas was 90.2 ms compared to 78.9 ms to non‐damaged sites. Conclusion: The agar based heat‐sensitive gel has the thermal stability to withstand relatively high temperatures. It also can be made easily for the experimental verification of various clinical applications without using any toxic chemicals which are required for many existing heat‐sensitive gel recipes.

This work has been supported by the US Department of Defense, Breast Cancer Research Program, Concept Award, W81XWH‐08‐1‐0686.
SU‐FF‐J‐173: Tumor Volume Delineation: A Comparison of Imaging Protocols for Lung Tumors
Authors: Wu J , Betzing C , Srisuthep A , Fuss M , D'Souza W
Published: April 2010

Purpose: To investigate differences in tumor contours delineated on free breathing (FB), four dimensional (4D), maximum intensity projection (MIP), average intensity projection (AIP), and slow‐CT (SCT) images. Methods and Materials: Data from ten patients who underwent stereotactic body radiation therapy of lung cancers were retrospectively investigated. For each patient, a FB CT and a 4D CT scan was acquired during simulation. Following the scan, MIP and AIP images were reconstructed. Since the 4D CT scan was acquired at a low pitch, a slow‐CT scan was also reconstructed. These scans were repeated prior to each treatment, resulting in 48 CT data sets. The GTV was delineated on FB, MIP, AIP, and SCT images and was compared with the internal target volume (ITV), which comprised the union of GTVs delineated on each phase of the 4DCT. Three evaluation metrics were used for contour comparison: GTV volume, overlap index (OI), and root‐mean‐squared (RMS) distance. Results: On average GTVFB, GTVMIP, GTVAIP, and GTVSCT volumes were 0.66±0.13 (p<0.01), 0.88±0.08 (p<0.01), 0.64±0.13 (p<0.01), and 0.64±0.12 (p<0.01) times smaller than the ITV, respectively. The OI of the ITV with GTVFB, GTVMIP, GTVAIP, and GTVSCT was 60%, 81%, 61% and 64%, respectively. The average RMS distances of the GTVFB, GTVMIP, GTVAIP, and GTVSCT relative to the ITV were 0.44cm, 0.30cm, 0.45cm and 0.40cm, respectively. The OI of GTVFB with GTVMIP, GTVAIP, and GTVSCT was 62% 68% and 71%, respectively and the corresponding RMS distances were 0.34cm, 0.36cm and 0.35cm, respectively. Conclusions: ITV is statistically larger than GTVMIP, and they are both larger than GTVFB, GTVAIP and GTVSCT. Even though GTVFB, GTVAIP and GTVSCT have similar size, the surface mismatch among them is still distinguishable.
SU‐FF‐T‐08: Morphological Seed Identification and Removal of the Post‐Implant Prostate Brachytherapy Patients in Cone‐Beam CT Sinogram Projections
Authors: Pokhrel D , Lazos D , Murphy M , Lu J , Zheng D , Williamson J
Published: April 2010

Purpose: To digitally extract and remove elongated seed features from measured 2D cone‐beam CT (CBCT) sinogram projections of the post‐implant prostate brachytherapy patients. Methods and materials: The method identifies the seeds at the projections and removes them by 2D spatial‐interpolation. Theragenics Model‐200 seed images were identified and removed from 2D patient projections by (a) normalizing the image intensity by finding its maximum and minimum values in the image, (b) top‐hat‐filtering, (c) thresholding using the 3σ‐value of the pixel intensity histogram, and (d) labeling to create a binary mask of each seed in each projection. The binary masks were subtracted from the corresponding raw projection. The subtracted images were then interpolated in the seed regions using natural‐neighbor interpolation method to recover the missing soft‐tissues information's obscured by the implanted seed images. Four post‐implant patients were scanned using an Acuity‐digital‐simulator with full‐660 projections CBCT (in half/full‐fan‐mode) for post‐implant dosimetry. In‐house filtered‐back projection algorithm was used to reconstruct CBCT images before and after seed removal applications. To quantify this method, we compared the reconstructed CBCT images before and after corrections, image‐profiles and a difference image on a single central slice to demonstrate the effects of seeds removal. Results: For the example cases, the streaking artifact is reduced by a factor of 3.5 and artifact spatial extend. The corrected images exhibit significantly improved image quality in and around the prostate. Discussion: Our preliminary results indicate that this method can be used to mitigate metal‐streaking artifacts specific to the brachytherapy seed implant geometry. By reducing streak and associated noise propagation artifacts, significant clinical value can be added to brachytherapy CBCT imaging. Improving the auto‐segmentation method and applying scatter‐subtraction corrections will be further study to improve the CBCT image quality for the intra/postoperative brachytherapy patient's images.
SU‐FF‐T‐12: Comparison of Biological Effective Dose Between Protons and Seed Implant Plus IMRT for Prostate Treatment
Authors: Sheu R , Hua C , Svoboda A , Cesaretti J , Stock R , Lo Y
Published: April 2010

Purpose: To use biological effective dose (BED) as a metric to compare the dosimetric difference between mixed modality photon treatment (LDR seed implant followed by IMRT treatment) and intensity‐modulated proton therapy (IMPT) for prostate cancer. Methods and Material: An in‐house program was developed to calculate the total BED for three patients who received mixed modality photon treatment (MMPT). These patients first received brachytherapy using Pd‐103 prescribed to a dose of 100 Gy to 90% of the prostate volume (112 Gy BED) followed by IMRT prescribed to a dose of 45‐Gy IMRT (85.5 Gy BED) to 95% of the PTV (6‐mm margin posteriorly and 1 cm elsewhere). To simulate IMPT, the inverse treatment planning system KonRad from German Cancer Research Center was used to design a two‐field opposed lateral IMPT plan delivered using the spot scanning technique and was prescribed to a total dose of 81 Gy to 95% of the PTV volume (153.9 Gy BED). Results: In all three cases, MMPT shows minimal difference in target coverage (98% of the prostate) compared to IMPT. MMPT had higher dose heterogeneity due to the high dose gradient close to the implanted seeds, but the areas of high dose are completely confined within the target borders The rectal and bladder biological effective DVH (BEDVH) both show that the histogram curve is higher for BEDs less than 100 Gy for MMPT compared to IMPT. The curves cross at 100 Gy and the MMPT histogram curve is lower than IMPT for all doses greater than 100 Gy. Conclusion: MMPT provides superior high BED (>100 Gy) normal tissue sparing compared to proton therapy for similar target coverage. In addition, considering the high‐cost of a proton facility, MMPT provides a more financially viable alternative to prostate cancer treatment.
SU‐FF‐T‐16: Evaluation of the Dose Perturbation Caused by Tungsten Shields Within a Fletcher‐Suit Delclos Applicator in Ir‐192 HDR Brachytherapy
Authors: Stanley T , Tran T , Bakhtiari M , Jaggernauth W , Malhotra H
Published: April 2010

Purpose: To evaluate the dose perturbation in bladder and rectal regions caused by tungsten shielding within the ovoids of a Fletch‐Suit Delclos gynecological applicator in Ir‐192 HDR brachytherapy procedures. Method and Materials: A Fletcher‐Suit Delclos (FSD) gynecological applicator, assembled with Tungsten shielded ovoids, was rigidly suspended within a water tank. 28 sheets of gafchromic film were then secured in 6.20 mm increments in regions representative of a patient's bladder and rectum. A treatment plan was created (PLATO) to deliver 650 cGy to a user defined pseudo point A. Each film was scanned and analyzed to ascertain it's dosimetric distribution. The data was arranged into two three‐dimensional matrices based on the physical dimensions of the films and their locations with respect to a pseudo origin (intersection of the central tandem with the ovoids). Dosimetric data was also extracted from the planning system at points corresponding to specific locations on the gafchromic films. The entire process was then repeated for an FSD applicator without shielding in the ovoids. Results: The measured shielded data was compared to the planning system data (computed) that accounted for the tungsten shielding within the ovoids. It was evident that the measured doses in both the bladder and rectal regions were significantly lower than the computed data predicted. The largest reduction was roughly 24% in the bladder region, and 23% in the rectal region. Similar values were noticed in the unshielded comparison, where the unshielded FSD measurements were compared to computed data not accounting for ovoid shielding. This verifies a consistent discrepancy between the computed predictions and the measured doses. Conclusion: With the current dose tolerances for critical organs being estimated using shielded applicators, an accurate assessment of dose is imperative. This study provides a quantitative estimate for adjusting these accepted standards of bladder and rectal dose.
SU‐FF‐T‐32: Optimized Dose Distribution of Gammamed Plus Vaginal Cylinders
Authors: Chandraraj V , Supe S , Manickam R
Published: April 2010

Purpose: The aim of this study was to optimize dose distribution for Gammamed plus vaginal cylinders and the placement of dose optimization points was evaluated for its effect on optimized dose distributions. Materials and methods: The HDR source travels through the central tandem, distal to proximal, stopping at dwell positions defined by step sizes. Two different dose optimization point models were used in this study namely, non apex (dose optimization points only on periphery) and apex (dose optimization points on periphery and along the curvature including the apex points). Thirteen dwell positions were used for the HDR dosimetry to obtain a 6 cm active length. Diameters of vaginal cylinders varied from 2.0 to 4.0 cm. Iterative optimization routine was utilized for all optimizations. The effects of various optimization routines (iterative, geometric, equal times) was studied for the 3.0 cm diameter vaginal cylinder. The effect of source travel step size on the optimized dose distributions for vaginal cylinders was also evaluated. Results: For both non‐apex and apex models of vaginal cylinders, doses for apex point and three dome points were higher for apex model compared to non‐apex model. Mean doses to the optimization points for both the cylinder models and all the cylinder diameters were 6 Gy matching with the prescription dose of 6.00 Gy. Iterative optimization routine resulted in the highest dose to apex point and dome points. The mean dose for optimization point was 6.01 Gy for iterative optimization and was much higher than 5.74 Gy for geometric and equal times routines. Conclusion: In our study best doses were obtained for the optimization points for 1 cm step size and iterative optimization routine for the apex model vaginal cylinder. Selection of dose optimization points for the derivation of optimized dose distributions for vaginal cylinders affects the dose distributions.
SU‐FF‐T‐38: Dosimetric Characteristics of a P‐32 Conformal Source for Irradiation of Paraspinal Tumors
Authors: Turcotte J , Mauceri T , Seco J
Published: April 2010

Purpose: A foil encased in a titanium plaque has been used to irradiate the dura for patients with paraspinal tumors. The plaque is applied to the dura intraoperatively after radiotherapy and surgery. Rapid falloff of the %DD allows the dura's surface to be treated, while sparing the spinal cord a few millimeters below. A new plaque, the RIC Conformal Source, utilizing embedded in a polymeric film and bonded to a polycarbonate backing has been developed for surface irradiations. This new plaque has advantages over previous designs. The lower energy of (1.709 MeV) allows for increased dose sparing of the cord over (2.28 MeV). Additionally, a longer half life of 14.28 days for versus 2.67 days for , as well as a simpler manufacturing process make this new source worthy of investigation. Method and Materials: To study the dosimetric characteristics of this new plaque, a flat plaque was constructed for measurements with radiochromic film. Surface profiles and %DD were measured and compared to Monte Carlo (Penelope) data. The data was also compared to the data to show viability of the new source for treatment. Surface profiles were evaluated using a Therapeutic Width Index (TWI), defined as the width of the surface profile at 90% divided by the width of the source. Results: The plaque's surface profiles and %DD measurements agreed well with Penelope. Comparison of %DD showed a more rapid falloff for (2.3% at 3mm) than for (14.1% at 3mm). The TWI for was 0.82 and was 0.88 for the . Conclusion: Better %DD characteristics and similar surface profiles show the new plaque utilizing to be clinically acceptable. Inhomogeneities in the polymeric film need to be further evaluated before clinical use of this source.
SU‐FF‐T‐55: A Novel Applicator System for HDR Treatment of Endometrial and Cervical Cancer
Authors: Zhang Z , Parsai E , Feldmeier J
Published: April 2010

Purpose: A new HDR applicator system has been designed to treat gynecological cancers with following specific goals in mind: 1) ability to do volumetric image based patient specific dosimetry, 2) ability to significantly spare the surrounding critical structures, 3) Performing volumetric dosimetry based on delineated target volume and moving away from Manchester point calculation, and 4) provide patient comfort during the implant. It is expected that this system will provide all the functionality of a Fletcher‐Suit‐Delclos (FSD) device and has more versatility in treatment of these cancers. Method and Materials: A disposable applicator manufactured* from plastic material with inflatable partitioned sections to displace rectum and bladder away from the radiation source has been designed. Monte Carlo simulations were performed to compare dosimetry with conventional Manchester system and show superiority of this device in delivering dose to the target volume while sparing rectum and bladder. Comparable optimized plans with conventional FSD system were made using BrachyVision system. Results: Preliminary trials of this applicator used on cadavers revealed superiority in inserting the system in cervical canal through stent, filling the vaginal cavity with liquid contrast for proper CT/MRI imaging. The unaccounted attenuation from the Stainless Steel tubing in FSD applicator is no longer an issue when this applicator is implemented. This new applicator manufactured from all disposable plastic materials, is CT & MR friendly, allows 3‐D treatment planning executable to accurately deliver dose to the target volume as prescribed, allows sparing the normal tissue structure at any desirable level. Our dosimetric studies indicate superior volumetric dose coverage to PTV and easy detachment from the conventional Manchester system. Conclusions: The new applicator once applied will overcome most of the disadvantages from the conventional FSD device and offers numerous superior clinical advantages for patients with gynecological cancer.

*Project supported by Varian Medical‐system