bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐J‐206: Systematic Evaluation of the Minimum Detectable Shift Using a Range‐ Finding Camera
Authors: Platt M , Platt M , Lamba M , Mascia A , Huang K 
Published: July 2016

Purpose:The robotic table used for patient alignment in proton therapy is calibrated only at commissioning under well‐defined conditions and table shifts may vary over time and with differing conditions. The purpose of this study is to systematically investigate minimum detectable shifts using a time‐of‐flight (TOF) range‐finding camera for table position feedback.Methods:A TOF camera was used to acquire one hundred 424 × 512 range images from a flat surface before and after known shifts. Range was assigned by averaging central regions of the image across multiple images. Depth resolution was determined by evaluating the difference between the actual shift of the surface and the measured shift. Depth resolution was evaluated for number of images averaged, area of sensor over which depth was averaged, distance from camera to surface, central versus peripheral image regions, and angle of surface relative to camera.Results:For one to one thousand images with a shift of one millimeter the range in error was 0.852 ± 0.27 mm to 0.004 ± 0.01 mm (95% C.I.). For varying regions of the camera sensor the range in error was 0.02 ± 0.05 mm to 0.47 ± 0.04 mm. The following results are for 10 image averages. For areas ranging from one pixel to 9 × 9 pixels the range in error was 0.15 ± 0.09 to 0.29 ± 0.15 mm (1σ). For distances ranging from two to four meters the range in error was 0.15 ± 0.09 to 0.28 ± 0.15 mm. For an angle of incidence between thirty degrees and ninety degrees the average range in error was 0.11 ± 0.08 to 0.17 ± 0.09 mm.Conclusion:It is feasible to use a TOF camera for measuring shifts in flat surfaces under clinically relevant conditions with submillimeter precision.
SU‐F‐J‐208: Prompt Gamma Imaging‐Based Prediction of Bragg Peak Position for Realistic Treatment Error Scenarios
Authors: Xing Y , Macq B , Janssens G , Bondar L 
Published: July 2016

Purpose:To quantify the accuracy in predicting the Bragg peak position using simulated in‐room measurements of prompt gamma (PG) emissions for realistic treatment error scenarios that combine several sources of errors.Methods:Prompt gamma measurements by a knife‐edge slit camera were simulated using an experimentally validated analytical simulation tool. Simulations were performed, for 143 treatment error scenarios, on an anthropomorphic phantom and a pencil beam scanning plan for nasal cavity. Three types of errors were considered: translation along each axis, rotation around each axis, and CT‐calibration errors with magnitude ranging respectively, between −3 and 3 mm, −5 and 5 degrees, and between −5 and +5%. We investigated the correlation between the Bragg peak (BP) shift and the horizontal shift of PG profiles. The shifts were calculated between the planned (reference) position and the position by the error scenario. The prediction error for one spot was calculated as the absolute difference between the PG profile shift and the BP shift.Results:The PG shift was significantly and strongly correlated with the BP shift for 92% of the cases (p<0.0001, Pearson correlation coefficient R>0.8). Moderate but significant correlations were obtained for all cases that considered only CT‐calibration errors and for 1 case that combined translation and CT‐errors (p<0.0001, R ranged between 0.61 and 0.8). The average prediction errors for the simulated scenarios ranged between 0.08±0.07 and 1.67±1.3 mm (grand mean 0.66±0.76 mm). The prediction error was moderately correlated with the value of the BP shift (p=0, R=0.64). For the simulated scenarios the average BP shift ranged between −8±6.5 mm and 3±1.1 mm. Scenarios that considered combinations of the largest treatment errors were associated with large BP shifts.Conclusion:Simulations of in‐room measurements demonstrate that prompt gamma profiles provide reliable estimation of the Bragg peak position for complex error scenarios.Yafei Xing and Luiza Bondar are funded by BEWARE grants from the Walloon Region.The work presents simulations results for a prompt gamma camera prototype developed by IBA.
SU‐F‐J‐210: A Preliminary Study On the Dosimetric Impact of Detector Based Spectral Ct On Proton Therapy Treatment Planning
Authors: Cheng C , Lee S , Muzic R , Wessels B , Jesseph F , Ellis R , Mansur D , Dhanantwari A 
Published: July 2016

Purpose:To compare the difference in Hounsfield unit‐relative stopping power and evaluate the dosimetric impact of spectral vs. conventional CT on proton therapy treatment plans.Method:The Philips prototype (IQon), a detector‐based, spectral CT system (spectral) was used to scan calibration and Rando phantoms. Data were reconstructed with and without energy decomposition to produce monoenergetic 70 keV, 140 keV, and the Zeff images. Relative stopping power (RSP) in the head and lung regions were evaluated as a function of HU in order to compare spectral and conventional CT. Treatment plans for the Rando phantom were also generated and used to produce DVHs of fictitious target volume and organ‐at‐risk contoured on the head and lung.Results:Agreement of the Zeff of the tissue‐substitute materials determined using spectral CT agrees to within 1 to 5% of the Zeff of the known phantom composition. The discrepancy is primarily attributed to non‐uniformity in the phantom. Differences between the HU‐RSP curves obtained using spectral and conventional CT were small except for in the lung curve at HU>1000. The large difference in planned doses using Spectral vs. conventional CT occurred in a low‐dose brain region (1.7mm between the locations of the 100 cGy lines and 3 mm for 50 cGy lines).Conclusion:Conventionally, a single HU‐RSP from CT scanner is used in proton treatment planning. Spectral CT allows site‐specific HU‐RSP for each patient. Spectral and conventional HU‐RSP may result in different distributions as shown here. Additional study is required to evaluate the impact of Spectral CT in proton treatment planning.This study is part of a research agreement between Philips and University Hospitals/Case Medical Center.
SU‐F‐J‐212: Enabling Conventional Cone Beam CT with the Capability of Dual Energy Imaging Using a Simple Add‐On Beam Modifier
Authors: Vinke R , Takao S , Umegaki K , Shirato H , Peng H , Xing L 
Published: July 2016

Purpose:In searching for a robust, efficient and cost‐effective dual energy cone beam CT (DECBCT) solution for various radiation oncology applications, in particularly for improved proton dose planning/replanning accuracy and DE‐CBCT guided radiation therapy, we investigate a novel energy modulation scheme using a beam modifier placed between the source and patient and optimize its geometric configuration for routine clinical use.Methods:The study was performed using a Hitachi CBCT scanner and the tube voltage was set at 125 kVp. The higher energy beam was obtained by filtering the incident utilizing a beam modulation layer (material: copper, thickness: 1.8 mm). To avoid the need for double scans (one with and one without the energy modulator), the modulation layer was configured to cover only the half of the X‐ray beam so that two sets of sinograms corresponding low and high energies were collected after a single gantry rotation of 360 deg. The average high energy and low energy HU numbers (HUhigh and HUlow) were derived for pixels in a defined region‐of‐interest, respectively.Results:The beam modifier increased the threshold of the energy spectrum from ∼20 keV up to ∼50 keV. Two complete sets of images were obtained with good alignment between the high energy and low‐energy cases without any artifact observed (Fig. 2). The HUlow/HUhigh is ∼0/0 (water), ∼394/238 (brain), ∼1283/1085 (cortical bone) and ∼3000/1800 (titanium).Conclusion:The feasibility of the proposed DECT implementation using a beam modifier has been demonstrated. Compared to the existing DECT solutions, the proposed scheme is much more cost‐effective and requires minimum hardware modification. The work lays foundation for us to study the quantification of HU values to derive material density images and atomic number (and electron density) of substances.
SU‐F‐J‐214: Dose Reduction by Spatially Optimized Image Quality Via Fluence Modulated Proton CT (FMpCT)
Authors: De Angelis L , Landry G , Hansen D , Rit S , Belka C , Dedes G , Parodi K 
Published: July 2016

Purpose:Proton CT (pCT) is a promising imaging modality for reducing range uncertainty in image‐guided proton therapy. Range uncertainties partially originate from X‐ray CT number conversion to stopping power ratio (SPR) and are limiting the exploitation of the full potential of proton therapy. In this study we explore the concept of spatially dependent fluence modulated proton CT (FMpCT), for achieving optimal image quality in a clinical region of interest (ROI), while reducing significantly the imaging dose to the patient.Methods:The study was based on simulated ideal pCT using pencil beam (PB) scanning. A set of 250 MeV protons PBs was used to create 360 projections of a cylindrical water phantom and a head and neck cancer patient. The tomographic images were reconstructed using a filtered backprojection (FBP) as well as an iterative algorithm (ITR). Different fluence modulation levels were investigated and their impact on the image was quantified in terms of SPR accuracy as well as noise within and outside selected ROIs, as a function of imaging dose. The unmodulated image served as reference.Results:Both FBP reconstruction and ITR without total variation (TV) yielded image quality in the ROIs similar to the reference images, for modulation down to 0.1 of the full proton fluence. The average dose was reduced by 75% for the water phantom and by 40% for the patient. FMpCT does not improve the noise for ITR with TV and modulation 0.1.Conclusion:This is the first work proposing and investigating FMpCT for producing optimal image quality for treatment planning and image guidance, while simultaneously reducing imaging dose. Future work will address spatial resolution effects and the impact of FMpCT on the quality of proton treatment plans for a prototype pCT scanner capable of list mode data acquisition. Acknowledgement: DFG‐MAPDFG ‐ Munich‐Centre for Advanced Photonics (MAP)
SU‐F‐J‐215: Non‐Thermal Pulsed High Intensity Focused Ultrasound Therapy Combined with 5‐Aminolevulinic Acid: An in Vivo Pilot Study
Authors: Wang B , He W , Cvetkovic D , Chen L , Ma C 
Published: July 2016

Purpose:It has recently been shown that non‐thermal pulsed high intensity focused ultrasound (pHIFU) has a cell‐killing effect. The purpose of the study is to investigate the sonosensitizing effect of 5‐Aminolevulinic Acid (5‐ALA) in non‐thermal pHIFU cancer therapy.Methods:FaDu human head and neck squamous cell carcinoma cells were injected subcutaneously in the flanks of nude mice. After one to two weeks, the tumors reached the volume of 112 ± 8 mm3 and were assigned randomly into a non‐thermal pHIFU group (n=9) and a non‐thermal sonodynamic therapy (pHIFU after 5‐ALA administration) group (n=7). The pHIFU treatments (parameters: 1 MHz frequency; 25 W acoustic power; 0.1 duty cycle; 60 seconds duration) were delivered using an InSightec ExAblate 2000 system with a GE Signa 1.5T MR scanner. The mice in the non‐thermal sonodynamic group received 5‐ALA tail‐vein injection 4 hours prior to the pHIFU treatment. The tumor growth was monitored using the CT scanner on a Sofie‐Biosciences G8 PET/CT system.Results:The tumors in this study grew very aggressively and about 60% of the tumors in this study developed ulcerations at various stages. Tumor growth delay after treatments was observed by comparing the treated (n=9 in pHIFU group; n=7 in sonodynamic group) and untreated tumors (n=17). However, no statistically significant differences were found between the non‐thermal pHIFU and non‐thermal sonodynamic group. The mean normalized tumor volume of the untreated tumors on Day 7 after their first CT scans was 7.05 ± 0.54, while the normalized volume of the treated tumors on Day 7 after treatment was 5.89 ± 0.79 and 6.27 ± 0.47 for the sonodynamic group and pHIFU group, respectively.Conclusion:In this study, no significant sonosensitizing effects of 5‐ALA were obtained on aggressive FaDu tumors despite apparent tumor growth delay in some mice treated with non‐thermal sonodynamic therapy.
SU‐F‐J‐217: Accurate Dose Volume Parameters Calculation for Revealing Rectum Dose‐Toxicity Effect Using Deformable Registration in Cervical Cancer Brachytherapy: A Pilot Study
Authors: Zhen X , Chen H , Liao Y , Zhou L , Hrycushko B , Albuquerque K , Gu X 
Published: July 2016

Purpose:To study the feasibility of employing deformable registration methods for accurate rectum dose volume parameters calculation and their potentials in revealing rectum dose‐toxicity between complication and non‐complication cervical cancer patients with brachytherapy treatment.Method and Materials:Data from 60 patients treated with BT including planning images, treatment plans, and follow‐up clinical exam were retrospectively collected. Among them, 12 patients complained about hematochezia were further examined with colonoscopy and scored as Grade 1–3 complication (CP). Meanwhile, another 12 non‐complication (NCP) patients were selected as a reference group. To seek for potential gains in rectum toxicity prediction when fractional anatomical deformations are account for, the rectum dose volume parameters D0.1/1/2cc of the selected patients were retrospectively computed by three different approaches: the simple “worstcase scenario” (WS) addition method, an intensity‐based deformable image registration (DIR) algorithm‐Demons, and a more accurate, recent developed local topology preserved non‐rigid point matching algorithm (TOP). Statistical significance of the differences between rectum doses of the CP group and the NCP group were tested by a two‐tailed t‐test and results were considered to be statistically significant if p < 0.05.Results:For the D0.1cc, no statistical differences are found between the CP and NCP group in all three methods. For the D1cc, dose difference is not detected by the WS method, however, statistical differences between the two groups are observed by both Demons and TOP, and more evident in TOP. For the D2cc, the CP and NCP cases are statistically significance of the difference for all three methods but more pronounced with TOP.Conclusion:In this study, we calculated the rectum D0.1/1/2cc by simple WS addition and two DIR methods and seek for gains in rectum toxicity prediction. The results favor the claim that accurate dose deformation and summation tend to be more sensitive in unveiling the dose‐toxicity relationship.This work is supported in part by grant from VARIAN MEDICAL SYSTEMS INC, the National Natural Science Foundation of China (no 81428019 and no 81301940), the Guangdong Natural Science Foundation (2015A030313302)and the 2015 Pearl River S&T Nova Program of Guangzhou (201506010096).
SU‐F‐J‐223: Patterns of Failure for Laryngeal Cancer Patients Treated with Definitive IMRT: Comparing Two Different Methods for Determining the Origin of Recurrence From Follow‐Up PET/CT Scans
Authors: Brodin P , Kabarriti R , Vogelius I , Guha C , Kalnicki S , Garg M , Tome W 
Published: July 2016

Purpose:To determine patterns of failure in laryngeal cancer treated with definitive IMRT by comparing two different methods for identifying the recurrence epicenter on follow‐up PET/CT.Methods:We identified 20 patients treated for laryngeal squamous cell carcinoma with definitive IMRT who had loco‐regional recurrence diagnosed on PET/CT. Recurrence PET/CT scans were co‐registered with the original treatment planning CT using deformable image registration with the VoxAlign deformation engine in MIM Software. Recurrence volumes were delineated on co‐registered follow‐up scans using a semi‐automatic PETedge tool and two separate methods were used to identify the recurrence point of origin: a) Finding the point within the recurrence volume for which the maximum distance to the surface of the surrounding recurrence volume is smaller than for any other point. b) Finding the point within the recurrence volume with the maximum standardized uptake value (SUVmax), without geometric restrictions.For each method the failure pattern was determined as whether the recurrence origin fell within the original high‐dose target volumes GTV70, CTV70, PTV70 (receiving 70Gy), intermediate‐risk PTV59 (receiving 59.4Gy) or low‐risk PTV54 (receiving 54.1Gy), in the original treatment planning CT.Results:23 primary/nodal recurrences from the 20 patients were analyzed. The three‐dimensional distance between the two different origins was on average 10.5mm (std.dev. 10mm). Most recurrences originated in the high‐dose target volumes for both methods with 13 (57%) and 11 (48%) in the GTV70 and 20 (87%) and 20 (87%) in the PTV70 for method a) and b), respectively. There was good agreement between the two methods in classifying the origin target volumes with 69% concordance for GTV70, 89% for CTV70 and 100% for PTV70.Conclusion:With strong agreement in patterns of failure between two separate methods for determining recurrence origin, we conclude that most recurrences occurred within the high‐dose treatment region, which influences potential risk‐adaptive treatment strategies.
SU‐F‐J‐224: Impact of 4D PET/CT On PERCIST Classification of Lung and Liver Metastases in NSLC and Colorectal Cancer
Authors: Meier J , Lopez B , Mawlawi O 
Published: July 2016

Purpose:To quantify the impact of 4D PET/CT on PERCIST metrics in lung and liver tumors in NSCLC and colorectal cancer patients.Methods:32 patients presenting lung or liver tumors of 1–3 cm size affected by respiratory motion were scanned on a GE Discovery 690 PET/CT. The bed position with lesion(s) affected by motion was acquired in a 12 minute PET LIST mode and unlisted into 8 bins with respiratory gating. Three different CT maps were used for attenuation correction: a clinical helical CT (CT_clin), an average CT (CT_ave), and an 8‐phase 4D CINE CT (CT_cine). All reconstructions were 3D OSEM, 2 iterations, 24 subsets, 6.4 Gaussian filtration, 192×192 matrix, non‐TOF, and non‐PSF. Reconstructions using CT_clin and CT_ave used only 3 out of the 12 minutes of the data (clinical protocol); all 12 minutes were used for the CT_cine reconstruction. The percent change of SUVbw_peak and SUVbw_max was calculated between PET_CTclin and PET_CTave. The same percent change was also calculated between PET_CTclin and PET_CTcine in each of the 8 bins and in the average of all bins. A 30% difference from PET_CTclin classified lesions as progressive metabolic disease (PMD) using maximum bin value and the average of eight bin values.Results:30 lesions in 25 patients were evaluated. Using the bin with maximum SUVbw_peak and SUVbw_max difference, 4 and 13 lesions were classified as PMD, respectively. Using the average bin values for SUVbw_peak and SUVbw_max, 3 and 6 lesions were classified as PMD, respectively. Using PET_CTave values for SUVbw_peak and SUVbw_max, 4 and 3 lesions were classified as PMD, respectively.Conclusion:These results suggest that response evaluation in 4D PET/CT is dependent on SUV measurement (SUVpeak vs. SUVmax), number of bins (single or average), and the CT map used for attenuation correction.
SU‐F‐J‐225: Histology Study of MR Guided Pulsed Focused Ultrasound On Treatment of Prostate Cancer in Vivo
Authors: Chen L , Cvetkovic D , Chen X , Wang B , Gupta R , Ma C 
Published: July 2016

Purpose:Our previous study demonstrated significant tumor growth delay in the mice treated with pulsed high intensity focused ultrasound (pHIFU). The purpose of this study is to understand the cell killing mechanisms of pHIFU.Methods:Prostate cancer cells (LNCaP), were grown orthotopically in 17 nude mice. Tumor‐bearing mice were treated using pHIFU with an acoustic power of 25W, pulse width 100msec and 300 pulses in one sonication under MR guidance. Mutiple sonications were used to cover the whole tumor volume. The temperature (less than 40 degree centigrade in the focal spot) was monitored using MR thermometry. Animals were euthanized at pre‐determined time points (n=2) after treatment: 0 hours; 6 hrs; 24 hrs; 48 hrs; 4 days and 7 days. Two tumorbearing mice were used as control. Three tumor‐bearing mice were treated with radiation (RT, 2 Gy) using 6 MV photon beams. RT treated mice were euthanized at 0 hr, 6 hrs and 24 hrs. The tumors were processed for immunohistochemical (IHC) staining for PARP (a surrogate of apoptosis). A multispectral imaging analysis system was used to quantify the expression of PARP staining. Cell apoptosis was calculated based on the PARP expression level using the DAB analysis software.Results:Our data showed that PARP related apoptosis peaked at 48 hrs and 7 days in pHIFU treated mice, which is comparable to that for the RT group at 24 hrs. The preliminary results from this study were consistent with our previous study on tumor growth delay using pHIFU.Conclusion:Our results demonstrated that non‐thermal pHIFU increased apoptotic tumor cell death through the PARP related pathway. MR guided pHIFU may have a great potential as a safe, noninvasive treatment modality for cancer therapy. This treatment modality may synergize with PARP inhibitors to achieve better therapeutic result.
SU‐F‐T‐02: Estimation of Radiobiological Doses (BED and EQD2) of Single Fraction Electronic Brachytherapy That Equivalent to I‐125 Eye Plaque: By Using Linear‐Quadratic and Universal Survival Curve Models
Authors: Kim Y , Waldron T , Pennington E 
Published: July 2016

Purpose:To test the radiobiological impact of hypofractionated choroidal melanoma brachytherapy, we calculated single fraction equivalent doses (SFED) of the tumor that equivalent to 85 Gy of I125‐BT for 20 patients. Corresponding organs‐at‐risks (OARs) doses were estimated.Methods:Twenty patients treated with I125‐BT were retrospectively examined. The tumor SFED values were calculated from tumor BED using a conventional linear‐quadratic (L‐Q) model and an universal survival curve (USC). The opposite retina (α/β = 2.58), macula (2.58), optic disc (1.75), and lens (1.2) were examined. The % doses of OARs over tumor doses were assumed to be the same as for a single fraction delivery. The OAR SFED values were converted into BED and equivalent dose in 2 Gy fraction (EQD2) by using both L‐Q and USC models, then compared to I125‐BT.Results:The USC‐based BED and EQD2 doses of the macula, optic disc, and the lens were on average 118 ± 46% (p < 0.0527), 126 ± 43% (p < 0.0354), and 112 ± 32% (p < 0.0265) higher than those of I125‐BT, respectively. The BED and EQD2 doses of the opposite retina were 52 ± 9% lower than I125‐BT. The tumor SFED values were 25.2 ± 3.3 Gy and 29.1 ± 2.5 Gy when using USC and LQ models which can be delivered within 1 hour. All BED and EQD2 values using L‐Q model were significantly larger when compared to the USC model (p < 0.0274) due to its large single fraction size (> 14 Gy).Conclusion:The estimated single fraction doses were feasible to be delivered within 1 hour using a high dose rate source such as electronic brachytherapy (eBT). However, the estimated OAR doses using eBT were 112 ∼ 118% higher than when using the I125‐BT technique. Continued exploration of alternative dose rate or fractionation schedules should be followed.