bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐G‐IeP4‐06: Feasibility of External Beam Treatment Field Verification Using Cherenkov Imaging
Authors: Black P , Na Y , Wuu C 
Published: July 2016

Purpose:Cherenkov light emission has been shown to correlate with ionizing radiation (IR) dose delivery in solid tissue. In order to properly correlate Cherenkov light images with real time dose delivery in a patient, we must account for geometric and intensity distortions arising from observation angle, as well as the effect of monitor units (MU) and field size on Cherenkov light emission. To test the feasibility of treatment field verification, we first focused on Cherenkov light emission efficiency based on MU and known field size (FS).Methods:Cherenkov light emission was captured using a PI‐MAX4 intensified charge coupled device(ICCD) system (Princeton Instruments), positioned at a fixed angle of 40° relative to the beam central axis. A Varian TrueBeam linear accelerator (linac) was operated at 6MV and 600MU/min to deliver an Anterior‐Posterior beam to a 5cm thick block phantom positioned at 100cm Source‐to‐Surface‐Distance(SSD). FS of 10×10, 5×5, and 2×2cm2 were used. Before beam delivery projected light field images were acquired, ensuring that geometric distortions were consistent when measuring Cherenkov field discrepancies. Cherenkov image acquisition was triggered by linac target current. 500 frames were acquired for each FS. Composite images were created through summation of frames and background subtraction. MU per image was calculated based on linac pulse delay of 2.8ms. Cherenkov and projected light FS were evaluated using ImageJ software.Results:Mean Cherenkov FS discrepancies compared to light field were <0.5cm for 5.6, 2.8, and 8.6 MU for 10×10, 5×5, and 2×2cm2 FS, respectably. Discrepancies were reduced with increasing field size and MU. We predict a minimum of 100 frames is needed for reliable confirmation of delivered FS.Conclusion:Current discrepancies in Cherenkov field sizes are within a usable range to confirm treatment delivery in standard and respiratory gated clinical scenarios at MU levels appropriate to standard MLC position segments
SU‐G‐IeP4‐07: Feasibility of Low Dose 18FDG PET in Pediatric Oncology Patients
Authors: Zhang J , Binzel K , Hall NC , Natwa M , Knopp MI , Knopp MV 
Published: July 2016

Purpose:To evaluate and demonstrate the feasibility of low dose FDG PET in pediatric oncology patients using virtual dose reduction as well as true patients PET/CT scans.Methods:Wholebody 18F‐FDG PET/CT of 39 clinical pediatric patients (0.16±0.06MBq/kg) were scanned on a Gemini TF 64 system at 75±5 min post FDG injection using 3min/bed. Based on the 180s/bed listmode PET data, subsets of total counts in 120s, 90s, 60s, 30s and 15s per bed position were extracted for PET reconstruction to simulate lower dose PET at 2/3th, 1/2th, 1/3th, 1/6th and 1/12th dose levels. PET/CT scans of Jaszczak PET phantom with 6 hot hollow spheres varying with sizes and contrast ratios were performed (real PET versus simulated PET) to validate the methodology of virtual dose PET simulation. Region of interests (ROIs) were placed on lesions and normal anatomical tissues with quantitative and qualitative assessment performed. Significant lower FDG dose PET/CT of 5 research adolescents were scanned to validate the proposal and low dose PET feasibility.Results:Although all lesions are visible on the 1/12th dose PET, overall PET image quality appears to be influenced in a multi‐factorial way. 30%–60% dose reduction from current standard of care FDG PET is recommended to maintain equivalent quality and PET quantification. An optimized BMI‐based FDG administration is recommended (from 1.1±0.5 mCi for BMI < 18.5 to 4.8±1.5 mCi for BMI > 30). A linear lowest “Dose‐BMI” relationship is given. SUVs from 1/12th to full dose PETs were identified as consistent (R2 = 1.08, 0.99, 1.01, 1.00 and 0.98). No significant variances of count density, SUV and SNR were found across certain dose ranges (p<0.01).Conclusion:Pediatric PET/CT can be performed using current time‐of‐flight systems at substantially lower PET doses (30–60%) than the standard of care PET/CT without compromising qualitative and quantitative image quality in clinical.
SU‐G‐IeP4‐08: Initial Investigations of Up‐Converting Nanoparticles (UCNP) for 3D Tissue Imaging in Optical‐ECT
Authors: Yoon S , Langloss B , Boss M , Birer S , Dewhirst M , Oldham M 
Published: July 2016

Purpose:Near‐IR absorptive up‐converting nanoparticles (UCNPs) is a novel contrast for optical‐ECT that allows auto‐fluorescence‐free 3D imaging of labeled cells in a matrix of large (∼1cm3) unsectioned normal tissue. This has the potential to image small metastases or dormant cells that is difficult with down‐converting fluorescing dyes due to auto‐fluorescence. The feasibility of imaging UCNP in agarose phantoms and a mouse lung is demonstrated, aided by a 3D‐printed optical‐ECT stage designed to excite UCNP in a mouse lung.Methods:The UCNP, NaYF4:Yb/Er (20/2%), studied in this work up‐converts 980nm light to visible light peaking sharply at ∼540nm. To characterize the UCNP emission as a function of UCNP concentration, cylindrical 2.5%wt agarose phantoms infused with UCNP at concentrations of 25µg/mL and 50µg/mL were exposed to 1.5W 980nm laser coupled to an optical fiber. The fiber was held stably at 1cm above the stage via a custom 3D‐printed stage. An optically cleared lung harvested from a BALBc mice was then injected with 100µL of 1mg/mL UCNP solution ex vivo. Tomographic imaging of the UCNP emission in lung was performed.Results:The laser beam tract is visualized within the agarose phantom. A line profile of UCNP emission at 25µg/mL versus 50µg/mL shows that increasing the UCNP concentration increases emission count. UCNPs injected into a cleared mouse lung disperse throughout the respiratory tract, allowing for visualization and 3D reconstruction. Excitation before and after UCNP injection shows the tissue exhibits no auto‐fluorescence at 980nm, allowing clear view of the UCNP without any obscuring features such as conventional down‐converting fluorescent tags.Conclusion:We confirm that up‐conversion in tissue circumvents completely tissue auto‐fluorescence, which allowed background‐free 3D reconstruction of the UCNP distribution. We also confirm that raising the UCNP concentration increases emission and that UCNPs are retained in agarose samples during the optical clearing process.
SU‐G‐IeP4‐15: Ultrasound Imaging of Absorbable Inferior Vena Cava Filters for Proper Placement
Authors: Mitcham T , Bouchard R , Melancon A , Eggers M , Melancon M 
Published: July 2016

Purpose:Inferior vena cava filters (IVCFs) are used in patients with a high risk of pulmonary embolism in situations when the use of blood thinning drugs would be inappropriate. These filters are implanted under x‐ray guidance; however, this provides a dose of ionizing radiation to both patient and physician. B‐mode ultrasound (US) imaging allows for localization of certain implanted devices without radiation dose concerns. The goal of this study was to investigate the feasibility of imaging the placement of absorbable IVCFs using US imaging to alleviate the dosage concern inherent to fluoroscopy.Methods:A phantom was constructed to mimic a human IVC using tissue‐mimicking material with 0.5 dB/cm/MHz acoustic attenuation, while agar inclusions were used to model acoustic mismatch at the venous interface. Absorbable IVCF's were imaged at 15 cm depth using B‐mode US at 2, 3, 5, and 7 MHz transmit frequencies. Then, to determine temporal stability, the IVCF was left in the phantom for 10 weeks; during this time, the IVCF was imaged using the same techniques as above, while the integrity of the filter was analyzed by inspecting for fiber discontinuities.Results:Visualization of the inferior vena cava filter was possible at 5, 7.5, and 15 cm depth at US central frequencies of 2, 3, 5, and 7 MHz. Imaging the IVCF at 5 MHz yielded the clearest images while maintaining acceptable spatial resolution for identifying the IVCF's, while lower frequencies provided noticeably worse image quality. No obvious degradation was observed over the course of the 10 weeks in a static phantom environment.Conclusion:Biodegradable IVCF localization was possible up to 15 cm in depth using conventional B‐mode US in a tissue‐mimicking phantom. This leads to the potential for using B‐mode US to guide the placement of the IVCF upon deployment by the interventional radiologist.Mitch Eggers is an owner of Adient Medical Technologies. There are no other conflicts of interest to disclose.
SU‐G‐JeP4‐02: An Investigation of Respiratory Surrogate Motion Data Requirements for Multiple‐Step Ahead Prediction
Authors: Zawisza I , Ren L , Yin F 
Published: July 2016

Purpose:Respiratory‐gated radiotherapy and dynamic tracking employ real‐time imaging and surrogate motion‐monitoring methods with tumor motion prediction in advance of real‐time. This study investigated respiratory motion data length on prediction accuracy of tumor motion.Methods:Predictions generated from the algorithm are validated against a one‐dimensional surrogate signal of amplitude versus time. Prediction consists of three major components: extracting top‐ranked subcomponents from training data matching the last respiratory cycle; calculating weighting factors from best‐matched subcomponents; fusing data proceeding best‐matched subcomponents with respective weighting factors to form predictions. Predictions for one respiratory cycle (∼3‐6seconds) were assessed using 351 patient data from the respiratory management device. Performance was evaluated for correlation coefficient and root mean square error (RMSE) between prediction and final respiratory cycle.Results:Respiratory prediction results fell into two classes, where best predictions for 70 cycles or less performed using relative prediction and greater than 70 cycles are predicted similarly using relative and derivative relative. For 70 respiratory cycles or less, the average correlation between prediction and final respiratory cycle was 0.9999±0.0001, 0.9999±0.0001, 0.9988±0.0003, 0.9985±0.0023, and 0.9981±0.0023 with RMSE values of 0.0091±0.0030, 0.0091±0.0030, 0.0305±0.0051, 0.0299±0.0259, and 0.0299±0.0259 for equal, relative, pattern, derivative equal and derivative relative weighting methods, respectively. Respectively, the total best prediction for each method was 37, 65, 20, 22, and 22. For data with greater than 70 cycles average correlation was 0.9999±0.0001, 0.9999±0.0001, 0.9988±0.0004, 0.9988±0.0020, and 0.9988±0.0020 with RMSE values of 0.0081±0.0031, 0.0082±0.0033, 0.0306±0.0056, 0.0218±0.0222, and 0.0218±0.0222 for equal, relative, pattern, derivative equal and derivative relative weighting methods, respectively. Respectively, the total best prediction for each method was 24, 44, 42, 30, and 45.Conclusion:The prediction algorithms are effective in estimating surrogate motion in advance. These results indicate an advantage in using relative prediction for shorter data and either relative or derivative relative prediction for longer data.
SU‐G‐JeP4‐06: Evaluation of Interfractional and Intrafractional Tumor Motion in Stereotactic Liver Radiotherapy, Based On Four‐Dimensional Cone‐Beam Computed Tomography Using Fiducial Markers
Authors: Shimohigashi Y , Araki F , Toya R , Maruyama M , Nakaguchi Y 
Published: July 2016

Purpose:The purpose of this study was to evaluate the interfractional and intrafractional motion of liver tumors in stereotactic body radiation therapy (SBRT), based on four‐dimensional cone‐beam computed tomography using fiducial markers. (4D‐CBCT).Methods:Seven patients with liver tumors were treated by SBRT with abdominal compression (AC) in five fractions with image guidance based on 4D‐CBCT. The 4D‐CBCT studies were performed to determine the individualized internal margin for the planning simulation. The interfractional and intrafractional changes of liver tumor motion for all patients was measured, based on the planning simulation 4D‐CBCT, pre‐SBRT 4D‐CBCT, and post‐SBRT 4D‐CBCT. The interfractional motion change was calculated from the difference in liver tumor amplitude on pre‐SBRT 4D‐CBCT relative to that of the planning simulation 4D‐CBCT for each fraction. The intrafractional motion change was calculated from the difference between the liver tumor amplitudes of the pre‐ and post‐SBRT 4D‐CBCT for each fraction. Significant interfractional and intrafractional changes in liver tumor motion were defined as a change ≥3 mm. Statistical analysis was performed using the Pearson correlation.Results:The values of the mean amplitude of liver tumor, as indicated by planning simulation 4D‐CBCT, were 1.6 ± 0.8 mm, 1.6 ± 0.9 mm, and 4.9 ± 2.2 mm in the left‐right (LR), anterior‐posterior (AP), and superior‐inferior (SI) directions, respectively. Pearson correlation coefficients between the liver tumor amplitudes, based on planning simulation 4D‐CBCT, and pre‐SBRT 4D‐CBCT during fraction treatment in the LR, AP, and SI directions were 0.6, 0.7, and 0.8, respectively. Interfractional and intrafractional motion changes of ≥3 mm occurred in 23% and 3% of treatment fractions, respectively.Conclusion:The interfractional and intrafractional changes of liver tumor motion were small in most patients who received liver SBRT with AC. In addition, planning simulation 4D‐CBCT was useful for representing liver tumor movement in patients undergoing SBRT.This work was supported by JSPS KAKENHI Grant Number 26861004.
SU‐G‐JeP4‐09: Impact of Interfractional Motion On Hypofractionated Pencil Beam Scanning Proton Therapy for Prostate Cancer
Authors: Moteabbed M , Trofimov A , Sharp G , Wang Y , Zietman A , Efstathiou J , Lu H 
Published: July 2016

Purpose:To investigate the impact of anatomy/setup variations on standard vs. hypofractionated anterolateral pencil beam scanning (PBS) proton therapy for prostate cancer.Methods:Six prostate cancer patients treated with double‐scattering proton therapy, who underwent weekly verification CT scans were selected. Implanted fiducials were used for localization, and endorectal balloons for immobilization. New PBS plans using combination of lateral and anterior‐oblique (AO) (±35 deg) beams were created. AO beams were added to spare the femoral heads during hypofractionation. Lateral beams delivered 50.4 Gy(RBE) to prostate plus 5‐15mm of seminal vesicles and AO beams 28.8 Gy(RBE) to prostate, in 44 fractions. PTV was laterally expanded by 2.5% to account for range uncertainty. No range margins were applied for AO beams, assuming delivery with in‐vivo range verification. Field‐specific apertures with 1.2cm margin were used. Spot size was ∼9.5mm sigma for 172MeV @isocenter in air. Plans were optimized as single‐field‐uniform‐dose with ∼5% maximum non‐uniformity. The planned dose was recomputed on each weekly CT after aligning the fiducials with the simulation CT, scaled and accumulated via deformable image registration. Hypofractionated treatments with 12 and 5 fractions were considered. Equivalent doses were calculated for prostate (α/β= 1.5Gy), bladder and rectum (α/β= 3Gy).Results:The biological equivalent prostate dose was 86.2 and 92.9 Gyeq for the hypofractionation scenarios at 4.32 and 7.35 Gy/fx, respectively. The equivalent prostate D98 was degraded by on average 2.7 Gyeq for standard, and 3.1 and 4.0 Gyeq for the hypofractionated plans after accumulation. Differences between accumulated and planned Dmean/D2/EUD were generally reduced when reducing the number of fractions for bladder and rectum. The average Dmean/D2/EUD differences over all patients and organs‐at‐risk were 0.74/4.0/9.23, 0.49/3.64/5.51, 0.37/3.21/3.49 Gyeq for 44, 12 and 5 fractions.Conclusion:Hypofractionation makes proton therapy of prostate more susceptible to interfractional motion‐induced target dose degradation compared to the standard fractionation.
SU‐G‐JeP4‐10: Measurement of Prostate Motion Trajectories During Prostate SBRT Boost Treatments with a Rectafix
Authors: Legge K , Nguyen D , Ng J , Wilton L , Booth J , Keall P , Martin J , O'Connor D J , Greer P 
Published: July 2016

Purpose:To determine prostate motion during SBRT boost treatments with a Rectafix rectal sparing device in place using kV imaging during treatment.Methods:Patients each had three gold fiducial markers inserted into the prostate and received two VMAT boost fractions of 9.5–10 Gy under the PROMETHEUS clinical trial protocol with a Rectafix rectal retractor in place. Two‐dimensional kilovoltage images of fiducial markers were acquired continuously during delivery. Three patients were treated on a Varian Clinac iX linear accelerator (6X, 600 MU/min), where kV images were acquired at 5 Hz during treatment. Seven patients were treated on a Varian Truebeam linear accelerator (10XFFF, 2400 MU/min) where kV images were acquired every 3 seconds. Images were processed off‐line using the Kilovoltage Intrafraction Monitoring (KIM) software after treatment. KIM determines prostate position in three dimensions from 2D kV projections using a probability density model and a pre‐treatment kV arc. The 3D displacement of the prostate was quantified as a function of time throughout each fraction.Results:From all fractions analyzed, it was found that the prostate had moved less than 1 mm in any direction from its initial position 84.6% of the time. The prostate was between 1 and 2 mm from its initial position 14.2% of the time, between 2 and 3 mm of its initial position 0.8% of the time and was greater than 3 mm from its initial position only 0.4% of the time.Conclusion:The amount of prostate motion observed during prostate SBRT boost treatments with a Rectafix device in place was minimal and lower than that observed in non‐Rectafix studies. The Rectafix device reduces rectal dose as well as immobilizing the prostate. Kimberley Legge is the recipient of an Australian Postgraduate Award.
SU‐G‐JeP4‐12: Real‐Time Organ Motion Monitoring Using Ultrasound and KV Fluoroscopy During Lung SBRT Delivery
Authors: Omari E , Tai A , Cooper D , Lachaine M , Li X 
Published: July 2016

Purpose:Real‐time ultrasound monitoring during SBRT is advantageous in understanding and identifying motion irregularities which may cause geometric misses. In this work, we propose to utilize real‐time ultrasound to track the diaphragm in conjunction with periodical kV fluoroscopy to monitor motion of tumor or landmarks during SBRT delivery.Methods:Transabdominal Ultrasound (TAUS) b‐mode images were collected from 10 healthy volunteers using the Clarity Autoscan System (Elekta). The autoscan transducer, which has a center frequency of 5 MHz, was utilized for the scans. The acquired images were contoured using the Clarity Automatic Fusion and Contouring workstation software. Monitoring sessions of 5 minute length were observed and recorded. The position correlation between tumor and diaphragm could be established with periodic kV fluoroscopy periodically acquired during treatment with Elekta XVI. We acquired data using a tissue mimicking ultrasound phantom with embedded spheres placed on a motion stand using ultrasound and kV Fluoroscopy. MIM software was utilized for image fusion. Correlation of diaphragm and target motion was also validated using 4D‐MRI and 4D‐CBCT.Results:The diaphragm was visualized as a hyperechoic region on the TAUS b‐mode images. Volunteer set‐up can be adjusted such that TAUS probe will not interfere with treatment beams. A segment of the diaphragm was contoured and selected as our tracking structure. Successful monitoring sessions of the diaphragm were recorded. For some volunteers, diaphragm motion over 2 times larger than the initial motion has been observed during tracking. For the phantom study, we were able to register the 2D kV Fluoroscopy with the US images for position comparison.Conclusion:We demonstrated the feasibility of tracking the diaphragm using real‐time ultrasound. Real‐time tracking can help in identifying such irregularities in the respiratory motion which is correlated to tumor motion. We also showed the feasibility of acquiring 2D KV Fluoroscopy and registering the images with Ultrasound.
SU‐G‐JeP4‐14: Assessment of Inter‐ and Intra‐Fractional Motion for Extremity Soft Tissue Sarcoma Patients by Using In‐House Real‐Time Optical Image‐Based Monitoring System
Authors: Kim H , Kim I , Ye S 
Published: July 2016

Purpose:This study aimed to assess inter‐ and intra‐fractional motion for extremity Soft Tissue Sarcoma (STS) patients, by using in‐house real‐time optical image‐based monitoring system (ROIMS) with infra‐red (IR) external markers.Methods:Inter‐ and intra‐fractional motions for five extremity (1 upper, 4 lower) STS patients received postoperative 3D conformal radiotherapy (3D‐CRT) were measured by registering the image acquired by ROIMS with the planning CT image (REG_ROIMS). To compare with the X‐ray image‐based monitoring, pre‐ and post‐treatment cone beam computed tomography (CBCT) scans were performed once per week and registered with planning CT image as well (REG_CBCT). If the CBCT scan is not feasible due to the large couch shift, AP and LR on‐board imager (OBI) images were acquired. The comparison was done by calculating mutual information (MI) of those registered images.Results:The standard deviation (SD) of the inter‐fractional motion was 2.6 mm LR, 2.8 mm SI, and 2.0 mm AP, and the SD of the intra‐fractional motion was 1.4 mm, 2.1 mm, and 1.3 mm in each axis, respectively. The SD of rotational inter‐fractional motion was 0.6° pitch, 0.9° yaw, and 0.8° roll and the SD of rotational intra‐fractional motion was 0.4° pitch, 0.9° yaw, and 0.7° roll. The derived averaged MI values were 0.83, 0.92 for REG_CBCT without rotation and REG_ROIMS with rotation, respectively.Conclusion:The in‐house real‐time optical image‐based monitoring system was implemented clinically and confirmed the feasibility to assess inter‐ and intra‐fractional motion for extremity STS patients while the daily basis and real‐time CBCT scan is not feasible in clinic.
SU‐G‐TeP4‐02: A Method for Evaluating the Direct Impact of Failed IMRT QAs On Patient Dose
Authors: Geneser S , Butkus M 
Published: July 2016

Purpose:We developed a method to calculate patient doses corresponding to IMRT QA measurements in order to determine and assess the actual dose delivered for plans with failed (or borderline) IMRT QA. This work demonstrates the feasibility of automatically computing delivered patient dose from portal dosimetry measurements in the Varian TPS system, which would provide a valuable and clinically viable IMRT QA tool for physicists and physicians.Methods:IMRT QA fluences were measured using portal dosimetry, processed using in‐house matlab software, and imported back into Eclipse to calculate dose on the planning CT. To validate the proposed workflow, the Eclipse calculated portal dose for a 5‐field sliding window prostate boost plan was processed as described above. The resulting dose was compared to the planned dose and found to be within 0.5 Gy. Two IMRT QA results for the prostate boost plan (one that failed and one that passed) were processed and the resulting patient doses were evaluated.Results:The max dose difference between IMRT QA #1 and the original planned and approved dose is 4.5 Gy, while the difference between the planned and IMRT QA #2 dose is 4.0 Gy. The inferior portion of the PTV is slightly underdosed in both plans, and the superior portion is slightly overdosed. The patient dose resulting from IMRT QA #1 and #2 differs by only 0.5 Gy. With this new information, it may be argued that the evaluated plan alteration to obtain passing gamma analysis produced clinically irrelevant differences.Conclusion:Evaluation of the delivered QA dose on the planning CT provides valuable information about the clinical relevance of failed or borderline IMRT QAs. This particular workflow demonstrates the feasibility of pushing the measured IMRT QA portal dosimetry results directly back onto the patient planning CT within the Varian system.