bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐203: Reconstruction of the Treatment Area by Use of Sinogram in Helical Tomotherapy
Authors: Haga A , Nakagawa K , Maurer C , Ruchala K , Chao E , Casey D , Ida S , Sakata D , Magome T , Nakano M , Masutani Y 
Published: July 2014

Purpose:TomoTherapy (Accuray Co.) has an image‐guided radiotherapy system with megavoltage (MV) X‐ray source and the on‐board imaging device. With the MV computed tomography (MVCT), it became feasible to perform the efficient daily‐3D registration of the patient position before each treatment delivery. This system also allows one to acquire the delivery sinogram during the actual treatment, which partly includes the information of the irradiated object. In this study, we try to develop the image reconstruction during treatment in helical Tomotherapy.Methods:Sinogram data were acquired during helical Tomotherapy delivery using an arc‐shaped detector array that consists of 738 xenon‐gas filled detector cells. In preprocessing, these were normalized by full air‐scan data. A software program was developed that reconstructs 3D images during treatment with corrections as; (1) the regions outside the field were masked not to be added in the backprojection (a masking correction), and (2) each voxel of the reconstructed image was divided by the number of the X‐ray passing through its voxel (a ray‐passing correction).Results:Without masking and ray‐passing corrections, the image reconstruction was failed. The masking correction made the image clear, however, the streak artifact was accompanied. The ray‐passing correction reduced this artifact. Although the SNR (the ratio of mean to standard deviation in homogeneous region) and the contrast of the reconstructed image were slightly improved with the ray‐passing correction, the masking correction only is enough for the visualization purpose.Conclusion:The visualization of the treatment area was feasible by use of the sinogram in helical Tomotherapy. This proposed method can be utilized in the treatment verification.This work was partly supported by JSPS KAKENHI 24234567. No COI, but the data in this paper were prepared by collaborators in Accuray.
SU‐E‐J‐207: Assessing the Validity of 4D‐CT Based Target Volumes and Free Breathing CBCT Localization in Lung Stereotactic Ablative Radiation Therapy (SABR)
Authors: Badkul R , Pokhrel D , Jiang H , Park J , Wang F , Kumar P 
Published: July 2014

Purpose:Four‐dimensional‐computed‐tomography(4D‐CT) imaging for target‐volume delineation and cone‐beam‐tomography(CBCT) for treatment localization are widely utilized in lung‐SABR.Aim of this study was to perform a quantitative‐assessment and inter‐comparison of Internal‐targetvolumes(ITV) drawn on various phases of breathing‐cycle 4D‐CT‐scans, Maximum‐intensity‐projection(MIP), average‐intensity‐projection(AIP)and static CT‐scans of lung‐motion‐phantom to simulate lung‐SABR patient geometry. We also analyzed and compared the ITVs drawn on freebreathing‐ CBCT.Materials & Methods:4D‐CT‐scans were acquired on Philips big‐bore 16slice CT and Bellows‐respiratory monitoring‐system using retrospective phase‐binning method. Each respiratory cycle divided into 10‐phases. Quasar‐Phantom with lung‐inserts and 3cm‐diameter nylonball to simulate tumor and was placed on respiratory‐motion‐platform for 4D‐CT and CBCT‐acquisition. Amplitudes of motions: 0.5,1.0,2.0,3.0cm in superior‐inferior direction with breathing‐cycle time of 6,5,4,6sec, respectively used.4D‐CTs with 10‐phases(0%to90%)for each excursion‐set and 3D‐CT for static‐phantom exported to iPlan treatment‐planningsystem(TPS). Tumor‐volumes delineated in all phases of 4D‐CT, MIP,AIP,CBCT scans using fixed‐HU‐threshold(−500to1000)values automatically.For each 4D‐dataset ITV obtained by unifying the tumorcontours on all phases.CBCT‐ITV‐volumes were drawn in Eclipse‐TPS.Results:Mean volume of tumor contours for all phases compared with static 3D‐CT were 0.62±0.08%, 1.67±0.26%, 4.77±0.54% and 9.27±1.23% for 0.5cm,1cm,2cm,3cm excursions respectively. Differences of mean Union‐ITV with MIP‐ITV were close(≤2.4%).Mean Union‐ITV from expected‐theoretical values differed from −4.9% to 3.8%.Union‐ITV and MIP‐ITV were closer within 2.3%. AIP‐ITVs were underestimated from 14 to 32% compared to union‐ITV for all motion datasets. Differences of −5.9% to −44% and −5% to 6.7% for CBCT‐ITV from MIP‐ITV and AIP‐ITV respectively.Motion excursions and centroid positions were within 2mm for 4D‐CT and CBCT‐ITVs to that of expected values.Conclusion:4D‐CT MIP‐ITV and Union‐ITV showed very good agreement that validates that ITV can be fast contoured on MIP.Contouring ITV in AIP must be avoided as it significantly underestimates the volume with all excursions. Free breathing CBCT‐ITV showed good agreement with AIP‐ITV but underestimated the MIP‐ITV. Estimation of excursions and centroid values for 4D‐CT and CBCT were in good agreement with expected values.
SU‐E‐T‐01: 2‐D Characterization of DLG Among All MLC Leaf Pairs
Authors: Kumaraswamy L , Schmitt J , Bailey D , Xu Z , Podgorsak M 
Published: July 2014

Purpose:The aim of this study is to evaluate the variation of dosimetric leaf‐gap (DLG) along the travel path of each MLC leaf pair. This study evaluates whether the spatial variations in DLG could cause dose differences between TPS‐calculated and measured dose.Methods:The 6MV DLG values were measured for all leaf pairs in the direction of leaf motion using a 2‐D diode array and 0.6cc ion chamber. These measurements were performed on two Varian Linacs, employing the Millennium 120‐leaf MLC and a 2‐D‐DLG variation map was created via in‐house software. Several test plans were created with sweeping MLC fields using constant gaps from 2mm to 10mm and corrected for 2‐D variation utilizing in‐house software. Measurements were performed utilizing the MapCHECK at 5.0cm depth for plans with and without the 2‐D DLG correction and compared to the TPS calculated dose via gamma analysis (3%/3mm).Results:The measured DLGs for the middle 40 MLC leaf pairs (0.5cm width) were very similar along the central superior‐inferior axis, with maximum variation of 0.2mm. The outer 20 MLC leaf pairs (1.0cm width) have DLG values from 0.32mm (mean) to 0.65mm (maximum) lower than the central leaf‐pair, depending on off‐axis distance. Gamma pass rates for the 2mm, 4mm, and 6mm sweep plans increased by 23.2%, 28.7%, and 26.0% respectively using the 2‐D‐DLG correction. The most improved dose points occur in areas modulated by the 1.0cm leaf‐pairs. The gamma pass rate for the 10mm sweep plan increased by only 7.7%, indicating that the 2D variation becomes less significant for dynamic plans with larger MLC gaps.Conclusion:Fluences residing significantly off‐axis with narrow sweeping gaps may exhibit significant variations from planned dose due to large differences between the true DLG exhibited by the 1.0cm leaf‐pairs versus the constant DLG value utilized by the TPS for dose calculation.
SU‐E‐T‐02: 3D Dose Reconstruction of Volumetric Modulated Arc Therapy From Delivered EPID Dose Image
Authors: Yoon J , Jung J , Kim J , Yeo I 
Published: July 2014

Purpose:To evaluate dose reconstruction of volumetric modulated arc therapy (VMAT) from EPID image prediction.Methods:A test VMAT plan with dynamic MLCs was developed on a water equivalent cubic phantom with dimension of 31.4×34×34 cm3. From the initial MLC opening of 5×5 cm2 at gantry 0°, they moved with a constant speed as the gantry rotates, until they reached X1 at −2.5 cm and X2 at = −2.237 cm at gantry 90°. The plan was delivered while cine EPID images were acquired. For the 84 gantry angle segments, doses to the phantom were calculated by XVMC and reconstructed from EPID based on fast density‐scaled model and non‐iterative dose reconstruction method we have previously developed. The reconstructed dose was compared with the forwardly calculated dose individually over 84 gantry angle segments and cumulatively in terms of gamma evaluation and dose volume histogram for PTV (3×3×3 cm3) positioned at the center of the phantom.Results:3D‐gamma pass rate was 97.0 % cumulatively with 3 %/3 mm criteria and maximum 100% individually. The DVHs of PTV were indistinguishable except in the region of high dose (>95% of prescribed dose) where the difference of a few percent in volume was found.Conclusion:Showing good agreement with the forwardly calculated dose, we have extended our model of dose reconstruction successfully to the verification of VMAT. Although more clinical demonstration is to be followed, our study presents a promising tool for time‐resolved and cumulative VMAT validation.
SU‐E‐T‐04: 3D Printed Patient‐Specific Surface Mould Applicators for Brachytherapy Treatment of Superficial Lesions
Authors: Cumming I , Joshi C P , Lasso A , Rankin A , Falkson C , Schreiner L John , Fichtinger G 
Published: July 2014

Purpose:Evaluate the feasibility of constructing 3D‐printed patient‐specific surface mould applicators for HDR brachytherapy treatment of superficial lesions.Methods:We propose using computer‐aided design software to create 3D printed surface mould applicators for brachytherapy. A mould generation module was developed in the open‐source 3D Slicer (www.slicer.org) medical image analysis platform. The system extracts the skin surface from CT images, and generates smooth catheter paths over the region of interest based on user‐defined start and end points at a specified stand‐off distance from the skin surface. The catheter paths are radially extended to create catheter channels that are sufficiently wide to ensure smooth insertion of catheters for a safe source travel. An outer mould surface is generated to encompass the channels. The mould is also equipped with fiducial markers to ensure its reproducible placement. A surface mould applicator with eight parallel catheter channels of 4mm diameters was fabricated for the nose region of a head phantom; flexible plastic catheters of 2mm diameter were threaded through these channels maintaining 10mm catheter separations and a 5mm stand‐off distance from the skin surface. The apparatus yielded 3mm thickness of mould material between channels and the skin. The mould design was exported as a stereolithography file to a Dimension SST1200es 3D printer and printed using ABS Plus plastic material.Results:The applicator closely matched its design and was found to be sufficiently rigid without deformation during repeated application on the head phantom. Catheters were easily threaded into channels carved along catheter paths. Further tests are required to evaluate feasibility of channel diameters smaller than 4mm.Conclusion:Construction of 3D‐printed mould applicators show promise for use in patient specific brachytherapy of superficial lesions. Further evaluation of 3D printing techniques and materials is required for constructing sufficiently thin, rigid and durable surface moulds suitable for clinical deployment.
SU‐E‐T‐07: A Comparison of SSD and Field Size Dependence of Output for Megavoltage Electron Beams for Different Manufacturers
Authors: Dimofte A , Zhu T 
Published: July 2014

Purpose:The purpose of this study was to compare the electron beam in‐air output factor (H) for Varian and Siemens accelerators.Methods:Measurements were performed among four accelerators: Varian CL2300ix, Varian TrueBeam, Siemens Oncor, and Siemens Primus. The nominal electron energy measured ranges from 6 to 21 MeV. Measurements were made in air using a diode detector for different square cone sizes (6 – 25cm) with circular field inserts with radius r between 1 cm and 8 cm and for different SSD (100 – 120 cm). H is defined asH(r,SSD)= X(r,SSD)/X(open,SSD), where X is the charge measured by the diode detector without buildup cap in air.Results:For the same nominal energy, cone size, radius of circular cutout, and SSD, H agreed within a maximum deviation of 2.3% and standard deviation of 1% among Varian accelerators but can be as much as 8.7% different between the Varian and the Siemens accelerators. H is a function of electron energy and cutout radius only when the field radius for H measured at different SSD is renormalized as r = r0*5/(SSD‐95), where r0 is the physical field radius at the end of the cone. The radius dependence of H for five cone sizes (6×6, 10×10, 15×15, 20×20 and 25×25cm2) and three SSD(100, 110 and 120cm) for three energies was measured.Conclusion:The in air output factor (H) measured for the same manufacturer can be treated as identical to within 1.1% for Varian machines and to within 1.6% for Siemens machines, but the difference in H measured for the different manufacturers is large enough (>2%) to require machine specific data set.
SU‐E‐T‐15: A Home Grown Process Improvement Tracking Tool
Authors: Sansourekidou P , Pavord D 
Published: July 2014

Purpose:To evaluate the use of a web based error tracking system.Methods:A web based error tracking system called the PIT (Process Improvement Tracking Tool) was used by all staff members to enter errors found at all parts of the treatment process in four satellite facilities. An error is defined as an action that did not fully comply with policy and procedure. Entries were made in real time by all staff members and require that the user enters the date of the incident, the patient medical record number, the physical location of the site, the process during which the error was found and categorize the incident type.Results:Number of errors is approximately proportional to the number of patient treatments. Errors: VBMC 45%, UROC 25%, FROC 13%, PHC 17%. Treatments: VBMC 38%, UROC 32%, FROC 16%, PHC 14%. Staff members making the most mistakes are therapists (36%), dosimetrists (23%) and physicists (15%). Processes where errors were found: physics weekly 25%, therapist weekly 18%, physics second check 15%, physics peer review 6%, therapists check 5%, treatment 5% and various other steps 26%.Conclusion:Proportionality of the number of patients treated to the number of errors implies homogeneity across four satellites. Differences between staff member error percentages need to be investigated more thoroughly, but possible explanations are workload and staffing levels. Step in the process where errors are found implies the need for improved processes upstream. Specifically, 5% errors discovered during treatment is considered very high and a specific attempt to reduce it will be undertaken. The vast majority of the errors discovered during treatment were found before the treatment was delivered. Only four were discovered after delivery and none involved significant dose errors. Further work is required to identify the exact procedures within the department that will achieve this goal.
SU‐E‐T‐16: A Hybrid VMAT/IMRT Technique for the Treatment of Nasopharyngeal Carcinoma
Authors: Zhao N , Yang R , Wang J 
Published: July 2014

Purpose:To investigate a Hybrid VMAT/IMRT technique which combines volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC).Methods:2 full arcs VMAT, 9‐field IMRT and Hybrid VMAT/IMRT plans were created for 10 patients with NPC. The Hybrid VMAT/IMRT technique consisted of 1 full VMAT arc and 7 IMRT fields. The dose distribution of planning target volume (PTV) and organs at risk (OARs) for Hybrid VMAT/IMRT was compared with IMRT and VMAT. The monitor units (MUs) were also evaluated.Results:The Hybrid VMAT/IMRT technique significantly improved target dose homogeneity compared with IMRT and VMAT for PTV70 and PTV54. For PTV70 and PTV60, the Hybrid VMAT/IMRT technique significantly improved target dose conformity compared with IMRT (0.62 vs 0.47; p<0.05 and 0.64 vs 0.58; p<0.05, respectively) and VMAT (0.62 vs 0.43; p<0.05 and 0.64 vs 0.6; p<0.05, respectively). The near maximum dose (D2%) of temporomandibular joint (TMJ), temporal lobe and mandible for Hybrid plans were 5.5%, 7.9% and 5.2% lower than IMRT plans (p<0.05). The mean dose of TMJ, temporal lobe, mandible and unspecified tissue for Hybrid plans were 12.8%, 11.4%, 4.2% and 4.1% lower than IMRT plans (p<0.05). The mean dose of right parotid, mandible and unspecified tissue for Hybrid plans were 3.3%, 2.4% and 3.1% lower than VMAT plans (p<0.05). The mean MUs needed for IMRT, VMAT and Hybrid plans were 2256, 507 and 1394, respectively.Conclusion:Hybrid VMAT/IMRT technique significantly improved the target dose homogeneity and conformity compared with IMRT and VMAT and reduced the dose of OARs and unspecified tissue compared with IMRT with fewer MUs. Compared with VMAT, Hybrid VMAT/IMRT technique can better protect parotid gland, mandible and unspecified tissue. Ruijie Yang was funded by the grant project: National Natural Science Foundation of China (No. 81071237). Other authors have no competing interest for this work.
SU‐E‐T‐17: A Mathematical Model for PinPoint Chamber Correction in Measuring Small Fields
Authors: Li T , Zhang Y , Li X , Heron D.E. , Huq M.Saiful 
Published: July 2014

Purpose:For small field dosimetry, such as measuring the cone output factor for stereotactic radiosurgery, ion chambers often result in underestimation of the dose, due to both the volume averaging effect and the lack of electron equilibrium. The purpose of this work is to develop a mathematical model, specifically for the pinpoint chamber, to calculate the correction factors corresponding to different type of small fields, including single cone‐based circular field and non‐standard composite fields.Methods:A PTW 0.015cc PinPoint chamber was used in the study. Its response in a certain field was modeled as the total contribution of many small beamlets, each with different response factor depending on the relative strength, radial distance to the chamber axis, and the beam angle. To get these factors, 12 cone‐shaped circular fields (5mm,7.5mm, 10mm, 12.5mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 50mm, 60mm) were irradiated and measured with the PinPoint chamber. For each field size, hundreds of readings were recorded for every 2mm chamber shift in the horizontal plane. These readings were then compared with the theoretical doses as obtained with Monte Carlo calculation. A penalized‐least‐square optimization algorithm was developed to find out the beamlet response factors. After the parameter fitting, the established mathematical model was validated with the same MC code for other non‐circular fields.Results:The optimization algorithm used for parameter fitting was stable and the resulted response factors were smooth in spatial domain. After correction with the mathematical model, the chamber reading matched with the Monte Carlo calculation for all the tested fields to within 2%.Conclusion:A novel mathematical model has been developed for the PinPoint chamber for dosimetric measurement of small fields. The current model is applicable only when the beam axis is perpendicular to the chamber axis. It can be applied to non‐standard composite fields. Further validation with other type of detectors is being conducted.
SU‐E‐T‐18: A New Approach To Cancer Treatment
Authors: Akber S 
Published: July 2014

Purpose:To assess the correlation between mean lethal radiation doses (Do) with NMR water proton spin lattice relaxation time (T1) in different phases of Hela cells.Methods:Analysis of T1 with Do was assessed in M, G1, G2 and S‐phase at energies of 220 kVp, 280 kVp and 1.25 MeV (Co‐60).Results:T1 against Do in M, G1, G2, and S phase at 220 kVp yield a correlation of 0.80. At 280 kVp and 1.25 MeV the correlation is 0.77 and 0.82 respectively.Conclusion:It appears that T1 value decreases from M phase (1020 ± 84 ms) to S phase (534 ± 43 ms). The Do values increases from M phase to S phase. The variation in T1 and Do in different phases of the cell cycles provide a clue to time the mitotic phase at the radiation treatment time. It appears that T1 value decreases from M phase (1020 ± 84 ms) to S phase (534 ± 43 ms). The Do values increases from M phase to S phase. The variation in T1 and Do in different phases of the cell cycles provide a clue to time the mitotic phase at the radiation treatment time.
SU‐E‐T‐19: A New End‐To‐End Test Method for ExacTrac for Radiation and Plan Isocenter Congruence
Authors: Lee S , Nguyen N , Liu F , Huang Y , Sio T , Jung J , Pyakuryal A , Jang S 
Published: July 2014

Purpose:To combine and integrate quality assurance (QA) of target localization and radiation isocenter End to End (E2E) test of BrainLAB ExacTrac system, a new QA approach was devised using anthropomorphic head and neck phantom. This test insures the target localization as well as radiation isocenter congruence which is one step ahead the current ExacTrac QA procedures.Methods:The head and neck phantom typically used for CyberKnife E2E test was irradiated to the sphere target that was visible in CT‐sim images. The CT‐sim was performed using 1 mm thickness slice with helical scanning technique. The size of the sphere was 3‐cm diameter and contoured as a target volume using iPlan V.4.5.2. A conformal arc plan was generated using MLC‐based with 7 fields, and five of them were include couch rotations. The prescription dose was 5 Gy and 95% coverage to the target volume. For the irradiation, two Gafchromic films were perpendicularly inserted into the cube that hold sphere inside. The linac used for the irradiation was TrueBeam STx equipped with HD120 MLC. In order to use ExacTrac, infra‐red head–array was used to correlate orthogonal X‐ray images.Results:Using orthogonal X‐rays of ExacTrac the phantom was positioned. For each field, phantom was check again with X‐rays and re‐positioned if necessary. After each setup using ExacTrac, the target was irradiated. The films were analyzed to determine the deviation of the radiation isocenter in all three dimensions: superior‐inferior, left‐right and anterior‐posterior. The total combining error was found to be 0.76 mm ± 0.05 mm which was within sub‐millimeter accuracy.Conclusion:Until now, E2E test for ExacTrac was separately implemented to test image localization and radiation isocenter. This new method can be used for periodic QA procedures.