bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐EF‐303‐01: FEATURED PRESENTATION: Hydrogel Fiducial Markers for In‐Vivo Proton Therapy and Range Verifications Using PET
Authors: Cho J , Campbell P , Wang M , Alqathami M , Mawlawi O , Li H , Sahoo N , Kerr M , Zubarev E , Cho S 
Published: June 2015

Purpose:Currently there are no clinically used techniques for in‐vivo proton treatment/range verification. Our aim was to develop patient implantable markers that can be visualized in CT/x‐ray for treatment‐planning/beam‐positioning, and also in PET for proton treatment/range verification.Methods:Biocompatible/biodegradable hydrogel polymers were immersed in O18‐enriched water and O16 water, respectively to create O18‐water hydrogels (0.5 cm3) and O16‐water hydrogels (1 cm3) (both >99% water and <1% polymer). Also, 5–8 µm Zn powder was suspended in O16 water and O18‐enriched water and cross‐linked with hydrogel polymers to create Zn/16O‐water hydrogels (30%/70% mass ratio, <1% polymer) and Zn/18O‐water hydrogels (10%/90%). A block of extra‐firm “wet” tofu (12.3×8.8×4.9 cm, ρ⁼1) immersed in water was injected with Zn/O16‐water hydrogels (0.9 cm3 each) at four different depths using an 18 gauge needle. Similarly, Zn/18O‐water hydrogels (0.9 cm3) were injected in a different tofu phantom. As a reference, both 16O‐water and O18‐water hydrogels in petri‐dishes were irradiated in a “dry” environment. The hydrogels in the “wet” tofu phantoms and “dry” petri‐dishes were CT‐scanned and treatment‐planned. Then, they were positioned at the proton distal dose fall‐off region and irradiated (2 Gy) followed by PET/CT imaging.Results:Significantly high PET signals were observed only at O18‐water hydrogels in the “dry” environment. Zn/O16‐water hydrogels injected in the tofu phantom showed outstanding CT visibility but provided no noticeable PET signals. Zn/O18‐water hydrogels in the “wet” tofu showed excellent CT visibility and moderate PET visibility, however, weaker PET signals than the “dry” environment possibly due to O18‐water leaching out.Conclusion:The developed hydrogel markers can be used as universal fiducial markers due to their CT/PET/MRI/US visibility. Their PET visibility (possibly contributed more by activated O18‐water than Zn) after proton irradiation can be utilized for proton therapy/range verification. More investigation is needed to slow down the leaching of O18‐water.
WE‐EF‐303‐02: BEST IN PHYSICS (JOINT IMAGING‐ THERAPY): A Comprehensive Simulation of Image Guided Beam Gating for Liver Tumor Treatments Using Scanned Proton Therapy
Authors: Zhang Y , Knopf A , Weber D , Lomax A 
Published: June 2015

Purpose:To evaluate the effectiveness of image guided beam gating for PBS liver treatments under realistic breathing conditions.Methods:We have previously proposed a Beams’ Eye View (BEV) X‐ray image system as an online motion monitoring device for deriving a gating signal for PBS proton therapy. Using dedicated 4D dose calculations (4DDC), in this work we have simulated gated liver treatments using three amplitude‐based gating windows (10/5/3mm) based on motion extracted from BEV imaging of fiducial markers or the diaphragm. In order to improve motion mitigation, BEV guided gating has also been combined with either volumetric (VS) or layered (LS) rescanning. Nine 4DCT(MRI) liver data‐sets have been used for the investigation, which not only consider realistic patient geometries but also motion variations between different breathing cycles. All 4D plans have been quantified in terms of plan homogeneity in the PTV (D5‐D95), the total estimated treatment time and the beam‐on duty cycle.Results:Neither gating nor rescanning can fully retrieve a comparable plan homogeneity to the static case, and considerable reductions of the duty cycle (<10%) were observed as a Result motion variations when small gating windows are used. However, once combined with rescanning, dose homogeneity within 1% of the static plan could be achieved with reasonable prolongation of the treatment time for all 9 subjects. No differences were observed between the efficacy of layered or volumetric re‐scanning, or of gating signals extracted from fiducial or diaphragm motions. However, layered rescanning may be preferred over volumetric rescanning when performed in combination with gating as it is generally more time‐efficient and dosimetrically robust to patient and motion variationsConclusionCombining BEV beam gating with rescanning is an efficient and effective approach to treating mobile liver tumours, and is equally effective if either the diaphragm or fiducial markers are used as motion surrogates.
WE‐EF‐303‐06: Feasibility of PET Image‐Based On‐Line Proton Beam‐Range Verification with Simulated Uniform Phantom and Human Brain Studies
Authors: Lou K , Sun X , Zhu X , Grosshans D , Clark J , Shao Y 
Published: June 2015

Purpose:To study the feasibility of clinical on‐line proton beam range verification with PET imagingMethods:We simulated a 179.2‐MeV proton beam with 5‐mm diameter irradiating a PMMA phantom of human brain size, which was then imaged by a brain PET with 300*300*100‐mm^3 FOV and different system sensitivities and spatial resolutions. We calculated the mean and standard deviation of positron activity range (AR) from reconstructed PET images, with respect to different data acquisition times (from 5 sec to 300 sec with 5‐sec step). We also developed a technique, “Smoothed Maximum Value (SMV)”, to improve AR measurement under a given dose. Furthermore, we simulated a human brain irradiated by a 110‐MeV proton beam of 50‐mm diameter with 0.3‐Gy dose at Bragg peak and imaged by the above PET system with 40% system sensitivity at the center of FOV and 1.7‐mm spatial resolution.Results:MC Simulations on the PMMA phantom showed that, regardless of PET system sensitivities and spatial resolutions, the accuracy and precision of AR were proportional to the reciprocal of the square root of image count if image smoothing was not applied. With image smoothing or SMV method, the accuracy and precision could be substantially improved. For a cylindrical PMMA phantom (200 mm diameter and 290 mm long), the accuracy and precision of AR measurement could reach 1.0 and 1.7 mm, with 100‐sec data acquired by the brain PET. The study with a human brain showed it was feasible to achieve sub‐millimeter accuracy and precision of AR measurement with acquisition time within 60 sec.Conclusion:This study established the relationship between count statistics and the accuracy and precision of activity‐range verification. It showed the feasibility of clinical on‐line BR verification with high‐performance PET systems and improved AR measurement techniques.Cancer Prevention and Research Institute of Texas grant RP120326, NIH grant R21CA187717, The Cancer Center Support (Core) Grant CA016672 to MD Anderson Cancer Center
WE‐EF‐303‐08: Proton Radiography Using Pencil Beam Scanning and Novel Micromegas Detectors
Authors: Dolney D , Mayers G , Newcomer M , Bollinger D , Desai N , Lustig R , Teo B , Maughan R , Solberg T , Hollebeek R 
Published: June 2015

Purpose:While the energy of therapeutic proton beams can be adjusted to penetrate to any given depth in water, range uncertainties arise in patients due in part to imprecise knowledge of the stopping power of protons in human tissues. Proton radiography is one approach to reduce the beam range uncertainty, thereby allowing for a reduction in treatment margins and dose escalation.Methods:The authors have adapted a novel detector technology based on Micromesh Gaseous Structure (“Micromegas”) for proton therapy beams and have demonstrated fine spatial and time resolution of magnetically scanned proton pencil beams, as well as wide dynamic range for dosimetry. In this work, proton radiographs were obtained using Micromegas 2D planes positioned downstream of solid water assemblies. The position‐sensitive monitor chambers in the IBA proton delivery nozzle provide the beam entrance position.Results:Radiography with Micromegas detectors and actively scanned beams provide spatial resolution of up to 300 µm and water‐equivalent thickness (WET) resolution as good as 0.02% (60 µm out of 31 cm total thickness), with the dose delivered to the patient kept below 2 cGy. The spatial resolution as a function of sample rate and number of delivered protons is found to be near the theoretical Cramer‐Rao lower bound. Using the CR bound, we argue that the imaging dose could be further lowered to 1 mGy, while still achieving sub‐mm spatial resolution, by relatively simple instrumentation upgrades and beam delivery modifications.Conclusion:For proton radiography, high spatial and WET resolution can be achieved, with minimal additional dose to patient, by using magnetically scanned proton pencil beams and Micromegas detectors.
WE‐EF‐303‐09: Proton‐Acoustic Range Verification in Proton Therapy
Authors: Ahmad M , Xiang L , Xing L 
Published: June 2015

Purpose:We investigated proton‐acoustic signals detection for range verification with current ultrasound instruments in typical clinical scenarios. Using simulations that included a realistic noise model, we determined the theoretical minimum dose required to generate detectable proton‐acoustic signals.Methods:An analytical model was used to calculate the dose distributions and local pressure rise (per proton) for beams of different energy (100 and 160 MeV) and spot widths (1, 5, and 10 mm) in a water phantom. The acoustic waves propagating from the Bragg peak were modeled by the general 3D pressure wave equation and convolved with Gaussian kernels to simulate various proton pulse widths (0.1 – 10 ms). A realistic PZT ultrasound transducer (5 cm diameter) was simulated with a Butterworth band‐pass filter, and ii) randomly generated noise based on a model of thermal noise in the transducer. The signal‐to‐noise ratio was calculated, determining the minimum number of protons and dose required per pulse. The maximum spatial resolution was also estimated from the signal spectrum.Results:The calculated noise in the transducer was 12–28 mPa, depending on the transducer center frequency (70–380 kHz). The minimum number of protons were on the order of 0.6–6 million per pulse, leading to 3–110 mGy dose per pulse at the Bragg peak, depending on the spot size. The acoustic signal consisted of lower frequencies for wider pulses, leading to lower noise levels, but also worse spatial resolution. The resolution was 1‐mm for a 0.1‐µs pulse width, but increased to 5‐mm for a 10‐µs pulse width.Conclusion:We have established minimum dose detection limits for proton‐acoustic range validation. These limits correspond to a best case scenario with a large detector with no losses and only detector thermal noise. Feasible proton‐acoustic range detection will require at least 10⁷ protons per pulse and pulse widths ≤ 1‐µs.
WE‐EF‐204‐00: The Joint AAPM‐WMIS Symposium: Linking Pre‐Clinical and Clinical Trials: Co‐Clinical Trials
Authors: Cao Yue 
Published: June 2015

As molecular biology breakthroughs in understanding cancers and other diseases, hundreds of new drugs wait testing. In the last decade, mouse models have been evolved to better mimic human diseases genetically and biologically. These reliable mouse models allow us to determine which genetic elements, pathways and mutations impact on therapy. The co‐clinical trial strategy is to conduct a human clinical trial for a therapeutic drug and test it in mouse models at the same time. This strategy has the potential to accelerate the drug testing process and identify the patient population that will respond to the drug. Imaging plays an important role in co‐clinical trials. In this symposium, four speakers will discuss advancements and issues in pre‐clinical imaging, murine models, imaging hardware and software, and funding opportunities in co‐clinical trials.Learning Objectives:

Multi‐modality pre‐clinical imaging hardware and software, and new technologies (e.g., hyperpolarized MRI)
Selection of animal models from physiological and genetic perspectives with examples in colon, pancreatic and lung cancers
NCI funding opportunities
WE‐EF‐207‐04: An Inter‐Projection Sensor Fusion (IPSF) Approach to Estimate Missing Projection Signal in Synchronized Moving Grid (SMOG) System
Authors: Zhang H , Ren L , Kong V , Zhang Y , Giles W , Jin J 
Published: June 2015

Purpose:A synchronized moving grid (SMOG) has been proposed to reduce scatter and lag artifacts in cone beam computed tomography (CBCT). However, information is missing in each projection because certain areas are blocked by the grid. A previous solution to this issue is acquiring 2 complimentary projections at each position, which increases scanning time. This study reports our first Result using an inter‐projection sensor fusion (IPSF) method to estimate missing projection in our prototype SMOG‐based CBCT system.Methods:An in‐house SMOG assembling with a 1:1 grid of 3 mm gap has been installed in a CBCT benchtop. The grid moves back and forth in a 3‐mm amplitude and up‐to 20‐Hz frequency. A control program in LabView synchronizes the grid motion with the platform rotation and x‐ray firing so that the grid patterns for any two neighboring projections are complimentary. A Catphan was scanned with 360 projections. After scatter correction, the IPSF algorithm was applied to estimate missing signal for each projection using the information from the 2 neighboring projections. Feldkamp‐Davis‐Kress (FDK) algorithm was applied to reconstruct CBCT images. The CBCTs were compared to those reconstructed using normal projections without applying the SMOG system.Results:The SMOG‐IPSF method may reduce image dose by half due to the blocked radiation by the grid. The method almost completely removed scatter related artifacts, such as the cupping artifacts. The evaluation of line pair patterns in the CatPhan suggested that the spatial resolution degradation was minimal.Conclusion:The SMOG‐IPSF is promising in reducing scatter artifacts and improving image quality while reducing radiation dose.
WE‐EF‐207‐06: Dedicated Cone‐Beam Breast CT with Laterally‐Shifted Detector: Monte Carlo Evaluation of X‐Ray Scatter Distribution and Scatter‐To‐Primary Ratio
Authors: Shi L , Vedantham S , Karellas A 
Published: June 2015

Purpose:To determine the spatial distribution of x‐ray scatter and scatter‐to‐primary ratio (SPR) in projections during cone‐beam breast CT (CBBCT) with laterally‐shifted detector that results in coronal (fan‐angle) truncation.Methods:We hypothesized that CBBCT with coronal truncation would lower SPR due to reduction in irradiated breast volume, and that the location of maximum x‐ray scatter fluence (scatter‐peak) in the detector plane can be determined from the ratio of irradiated‐to‐total breast volume, breast dimensions and system geometry. Monte Carlo simulations (GEANT4) reflecting a prototype CBBCT system were used to record the position‐dependent primary and scatter x‐ray photon fluence incident on the detector without coronal truncation (full fan‐angle, 2f=24‐degrees) and with coronal truncation (fan‐angle, f+ f=12+2.7‐degrees). Semi‐ellipsoidal breasts (10/14/18‐cm diameter, chest‐wall to nipple length: 0.75xdiameter, 2%/14%/100% fibroglandular content) aligned with the axis‐of‐rotation (AOR) were modeled. Mono‐energy photons were simulated and weighted for 2 spectra (49kVp, 1.4‐mm Al HVL; 60kVp, 3.76‐mm Al HVL). In addition to SPR, the scatter maps were analyzed to identify the location of the scatter‐peak.Results:For CBBCT without fan‐angle truncation, the scatter‐peaks were aligned with the projection of the AOR onto the detector for all breasts. With truncated fan‐beam, the scatter‐peaks were laterally‐shifted from the projection of the AOR along the fan‐angle direction by 14/38/70‐pixels for 10/14/18‐cm diameter breasts. The corresponding theoretical shifts were 14.8/39.7/68‐pixels (p=0.47, 2‐tailed paired‐ratio t‐test). Along the cone‐angle, the shift in scatter‐peaks between truncated and full‐fan angle CBBCT were 2/2/4 ‐pixels for 10/14/18‐cm diameter breasts. CBBCT with fan‐angle truncation reduced SPR by 14/22/28% for 10/14/18‐cm diameter breasts. 60kVp reduced SPR by 21–25% compared to 49kVp. Peak SPR for CBBCT with fan‐angle truncation (60kVp) were 0.09/0.25/0.73 for 10/14/18‐cm diameter breasts.Conclusion:CBBCT with laterally‐shifted detector geometry and with appropriate kVp/beam quality reduces SPR. If residual scatter needs correction, the location corresponding to scatter‐peak can be analytically computed.This work was supported in part by NIH R01 CA128906. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.
WE‐EF‐207‐07: Dual Energy CT with One Full Scan and a Second Sparse‐View Scan Using Structure Preserving Iterative Reconstruction (SPIR)
Authors: Wang T , Zhu L 
Published: June 2015

Purpose:Conventional dual energy CT (DECT) reconstructs CT and basis material images from two full‐size projection datasets with different energy spectra. To relax the data requirement, we propose an iterative DECT reconstruction algorithm using one full scan and a second sparse‐view scan by utilizing redundant structural information of the same object acquired at two different energies.Methods:We first reconstruct a full‐scan CT image using filtered‐backprojection (FBP) algorithm. The material similarities of each pixel with other pixels are calculated by an exponential function about pixel value differences. We assume that the material similarities of pixels remains in the second CT scan, although pixel values may vary. An iterative method is designed to reconstruct the second CT image from reduced projections. Under the data fidelity constraint, the algorithm minimizes the L2 norm of the difference between pixel value and its estimation, which is the average of other pixel values weighted by their similarities. The proposed algorithm, referred to as structure preserving iterative reconstruction (SPIR), is evaluated on physical phantoms.Results:On the Catphan600 phantom, SPIR‐based DECT method with a second 10‐view scan reduces the noise standard deviation of a full‐scan FBP CT reconstruction by a factor of 4 with well‐maintained spatial resolution, while iterative reconstruction using total‐variation regularization (TVR) degrades the spatial resolution at the same noise level. The proposed method achieves less than 1% measurement difference on electron density map compared with the conventional two‐full‐scan DECT. On an anthropomorphic pediatric phantom, our method successfully reconstructs the complicated vertebra structures and decomposes bone and soft tissue.Conclusion:We develop an effective method to reduce the number of views and therefore data acquisition in DECT. We show that SPIR‐based DECT using one full scan and a second 10‐view scan can provide high‐quality DECT images and accurate electron density maps as conventional two‐full‐scan DECT.
WE‐EF‐207‐08: Improve Cone Beam CT Using a Synchronized Moving Grid, An Inter‐Projection Sensor Fusion and a Probability Total Variation Reconstruction
Authors: Zhang H , Ren L , Kong V , Zhang Y , Giles W , Jin J 
Published: June 2015

Purpose:To present a cone beam computed tomography (CBCT) system, which uses a synchronized moving grid (SMOG) to reduce and correct scatter, an inter‐projection sensor fusion (IPSF) algorithm to estimate the missing information blocked by the grid, and a probability total variation (pTV) algorithm to reconstruct the CBCT image.Methods:A prototype SMOG‐equipped CBCT system was developed, and was used to acquire gridded projections with complimentary grid patterns in two neighboring projections. Scatter was reduced by the grid, and the remaining scatter was corrected by measuring it under the grid. An IPSF algorithm was used to estimate the missing information in a projection from data in its 2 neighboring projections. Feldkamp‐Davis‐Kress (FDK) algorithm was used to reconstruct the initial CBCT image using projections after IPSF processing for pTV. A probability map was generated depending on the confidence of estimation in IPSF for the regions of missing data and penumbra. pTV was finally used to reconstruct the CBCT image for a Catphan, and was compared to conventional CBCT image without using SMOG, images without using IPSF (SMOG + FDK and SMOG + mask‐TV), and image without using pTV (SMOG + IPSF + FDK).Results:The conventional CBCT without using SMOG shows apparent scatter‐induced cup artifacts. The approaches with SMOG but without IPSF show severe (SMOG + FDK) or additional (SMOG + TV) artifacts, possibly due to using projections of missing data. The 2 approaches with SMOG + IPSF removes the cup artifacts, and the pTV approach is superior than the FDK by substantially reducing the noise. Using the SMOG also reduces half of the imaging dose.Conclusion:The proposed technique is promising in improving CBCT image quality while reducing imaging dose.
WE‐EF‐207‐09: Single‐Scan Dual‐Energy CT Using Primary Modulation
Authors: Petrongolo M , Zhu L 
Published: June 2015

Purpose:Compared with conventional CT, dual energy CT (DECT) provides better material differentiation but requires projection data with two different effective x‐ray spectra. Current DECT scanners use either a two‐scan setting or costly imaging components, which are not feasible or available on open‐gantry cone‐beam CT systems. We propose a hardware‐based method which utilizes primary modulation to enable single‐scan DECT on a conventional CT scanner. The CT imaging geometry of primary modulation is identical to that used in our previous method for scatter removal, making it possible for future combination with effective scatter correction on the same CT scanner.Methods:We insert an attenuation sheet with a spatially‐varying pattern ‐ primary modulator‐between the x‐ray source and the imaged object. During the CT scan, the modulator selectively hardens the x‐ray beam at specific detector locations. Thus, the proposed method simultaneously acquires high and low energy data. High and low energy CT images are then reconstructed from projections with missing data via an iterative CT reconstruction algorithm with gradient weighting. Proof‐of‐concept studies are performed using a copper modulator on a cone‐beam CT system.Results:Our preliminary results on the Catphan(c) 600 phantom indicate that the proposed method for single‐scan DECT is able to successfully generate high‐quality high and low energy CT images and distinguish different materials through basis material decomposition. By applying correction algorithms and using all of the acquired projection data, we can reconstruct a single CT image of comparable image quality to conventional CT images, i.e., without primary modulation.Conclusion:This work shows great promise in using a primary modulator to perform high‐quality single‐scan DECT imaging. Future studies will test method performance on anthropomorphic phantoms and perform quantitative analyses on image qualities and DECT decomposition accuracy. We will use simulations to optimize the modulator material and geometry parameters.