bluuebunny/crossref_metadata_2025_split huggingface dataset:
A phantom study of the immobilization and the indications for using virtual isocenter in stereoscopic X‐ray image guidance system referring to position localizer in frameless radiosurgery
Authors: Chang Hsiao‐Han , Lee Hsiao‐Fei , Sung Chien‐Cheng , Liao Tsung‐I , Huang Yu‐Jie 
Published: February 2017

A frameless radiosurgery system is using a set of thermoplastic mask for fixation and stereoscopic X‐ray imaging for alignment. The accuracy depends on mask fixation and imaging. Under certain circumstances, the guidance images may contain insufficient bony structures, resulting in lesser accuracy. A virtual isocenter function is designed for such scenarios. In this study, we investigated the immobilization and the indications for using virtual isocenter. Twenty‐four arbitrary imaginary treatment targets (ITTs) in phantom were evaluated. The external Localizer with positioner films was used as reference. The alignments by using actual and virtual isocenter in image guidance were compared. The deviation of the alignment after mask removing and then resetting was also checked. The results illustrated that the mean deviation between the alignment by image guidance using actual isocenter () and the localizer() was (standard deviation, SD), for using virtual isocenter. The deviation of the alignment by the image guidance using actual isocenter to the localizer before and after mask resetting was . The deviations before and after mask resetting were insignificant for the target center from skull edge larger than 80 mm on craniocaudal direction. The deviations between the alignment using actual and virtual isocenter in image guidance were not significant if the minimum distance from target center to skull edge was larger or equal to 30 mm. Due to an unacceptable deviation after mask resetting, the image guidance is necessary to improve the accuracy of frameless immobilization. A treatment isocenter less than 30 mm from the skull bone should be an indication for using virtual isocenter to align in image guidance. The virtual isocenter should be set as caudally as possible, and the sella of skull should be the ideal point.PACS numbers: 87.55.kh, 87.55.ne, 87.55.tm
The use of radiochromic EBT2 film for the quality assurance and dosimetric verification of 3D conformal radiotherapy using Microtek ScanMaker 9800XL flatbed scanner
Authors: Sim GS , Wong JHD , Ng KH 
Published: February 2017

Radiochromic and radiographic films are widely used for radiation dosimetry due to the advantage of high spatial resolution and two‐dimensional dose measurement. Different types of scanners, including various models of flatbed scanners, have been used as part of the dosimetry readout procedure. This paper focuses on the characterization of the EBT2 film response in combination with a Microtek ScanMaker 9800XL scanner and the subsequent use in the dosimetric verification of a 3D conformal radiotherapy treatment. The film reproducibility and scanner uniformity of the Microtek ScanMaker 9800XL was studied. A three‐field 3D conformal radiotherapy treatment was planned on an anthropomorphic phantom and EBT2 film measurements were carried out to verify the treatment. The interfilm reproducibility was found to be 0.25%. Over a period of three months, the films darkened by 1%. The scanner reproducibility was ± 2% and a nonuniformity was along the direction perpendicular to the scan direction. EBT2 measurements showed an underdose of 6.2% at high‐dose region compared to TPS predicted dose. This may be due to the inability of the treatment planning system to predict the correct dose distribution in the presence of tissue inhomogeneities and the uncertainty of the scanner reproducibility and uniformity. The use of EBT2 film in conjunction with the axial CT image of the anthropomorphic phantom allows the evaluation of the anatomical location of dose discrepancies between the EBT2 measured dose distribution and TPS predicted dose distribution.PACS number: 87.55.Qr
Impact of MLC leaf width on volumetric‐modulated arc therapy planning for head and neck cancers
Authors: Lafond Caroline , Chajon Enrique , Devillers Anne , Louvel Guillaume , Toublanc Sandra , Olivier Mickael , Simon Antoine , de Crevoisier Renaud , Manens Jean‐Pierre 
Published: February 2017

This dosimetric study investigated the impact of multileaf collimators (MLC) leaf width in volumetric‐modulated arc therapy (VMAT) for head and neck cancers (HNC), either with a “standard” simultaneously integrated boost technique (S‐SIB) or with a “dose painting” SIB technique (DP‐SIB). HNC patients were planned either with an S‐SIB comprising three dose levels, from 56 to 70 Gy (16 patients), or with a DP‐SIB comprising five dose levels, from 56 to 84 Gy (8 patients), in 35 fractions. Two VMAT plans were calculated for each SIB technique using two Elekta MLCs: MLCi2 with 10 mm leaf width and Beam Modulator (BM) with 4 mm leaf width. Dose distributions were evaluated by comparing doses on PTVs, main OARs, and healthy tissue, and by comparing conformation indexes. Treatment efficiencies were evaluated by comparing the number of monitor units and the number of needed arcs. Comparisons of the two MLCs depending on the two SIB techniques showed: i) Regarding PTVs: Dmean and D2% on lower doses PTV decreased respectively by 0.5 Gy and 0.9 Gy with BM than with MLCi2 for S‐SIB; no significant difference was found for DP‐SIB; ii) Regarding OARs: for spinal cord and brainstem, D2% decreased respectively by 1.2 Gy and 4.2 Gy with BM than with MLCi2 for S‐SIB; for controlateral parotid, D50% decreased by 1.5 Gy with BM than with MLCi2 for S‐SIB; iii) Regarding treatment efficiency : the number of monitor units was 44% and 51% higher with BM for S‐SIB and DP‐SIB, respectively. Two arcs were more frequently needed with BM to reach an acceptable dose distribution. This study demonstrated that Beam Modulator (4 mm leaf width) and MLCi2 (10 mm leaf width) MLCs from Elekta provided satisfactory dose distributions for treatment delivery with VMAT technique for complex HNC cases with standard and dose painting prescriptions. OAR sparing was better with BM, mainly for brainstem and spinal cord. However, delivery efficiency of VMAT plans was better with MLCi2.PACS numbers: 87.56.N‐, 87.56.nk, 87.55.D‐
Optimized Varian aSi portal dosimetry: development of datasets for collective use
Authors: Esch Ann Van , Huyskens Dominique P. , Hirschi Lukas , Scheib Stefan , Baltes Christof 
Published: February 2017

Although much literature has been devoted to portal dosimetry with the Varian amorphous silicon (aSi) portal imager, the majority of the described methods are not routinely adopted because implementation procedures are cumbersome and not within easy reach of most radiotherapy centers. To make improved portal dosimetry solutions more generally available, we have investigated the possibility of converting optimized configurations into ready‐to‐use standardized datasets. Firstly, for all commonly used photon energies (6, 10, 15, 18, and 20 MV), basic beam data acquired on 20 aSi panels were used to assess the interpanel reproducibility. Secondly, a standardized portal dose image prediction (PDIP) algorithm configuration was created for every energy, using a three‐step process to optimize the aSi dose response function and profile correction files for the dosimetric calibration of the imager panel. An approximate correction of the backscatter of the Exact arm was also incorporated. Thirdly, a set of validation fields was assembled to assess the accuracy of the standardized configuration. Variations in the basic beam data measured on different aSi panels very rarely exceeded 2% (2 mm) and are of the same order of magnitude as variations between different Clinacs when measuring in reference conditions in water. All studied aSi panels can hence be regarded as nearly identical. Standardized datasets were successfully created and implemented. The test package proved useful in highlighting possible problems and illustrating remaining limitations, but also in demonstrating the good overall results (95% pass rate for 3%,3 mm) that can be obtained. The dosimetric behavior of all tested aSi panels was found to be nearly identical for all tested energies. The approach of using standardized datasets was then successfully tested through the creation and evaluation of PDIP preconfigured datasets that can be used within the Varian portal dosimetry solution.PACS number: 87.55.km, 87.55.Qr, 87.56.N_
Dosimetric effect of respiratory motion on volumetric‐modulated arc therapy‐based lung SBRT treatment delivered by TrueBeam machine with flattening filter‐free beam
Authors: Li Xiang , Yang Yong , Li Tianfang , Fallon Kevin , E Heron and Dwight. , Huq M. Saiful 
Published: February 2017

The purpose of this study is to investigate the interplay effect between dynamic MLC movement and tumor respiratory motion in volumetric‐modulated arc therapy (VMAT)‐based lung SBRT treatment delivered by the flattening filter‐free (FFF) beam of a Varian TrueBeam machine. Six lung cancer patients with tumor motions ranging between 0.5–1.6 cm were recruited in this study. All patients underwent 4D‐CT scan with audiocoaching. A two‐arc VMAT plan was retrospectively generated using Varian's Eclipse planning system for each patient. To explicitly describe the interplay effect, the contributions of each control point in the original static VMAT plans to each respiratory phase were calculated, and then ten new VMAT plans corresponding to different respiratory phases were generated and imported back into Eclipse planning system to calculate the radiation dose based on the CT images of related respiratory phase. An in‐house 4D dose calculation program with deformable registration capacity was used to calculate the accumulative 4D dose distribution of the targets. For all patients, the PTV coverage dropped significantly with increased respiratory motion amplitude. However, V100 and D90 of the GTV and , which mimic the target with setup error of less than 5 mm, were either unchanged or slightly increased up to 1.2%, and the variations of their minimum doses were less than 3.2%. Our results indicated that for VMAT‐based lung SBRT treatment delivered by FFF beam of TrueBeam machine, the impact of interplay effects on target coverage is insignificant, as long as a sufficient margin was given.PACS number: 87.53.Ly
The performance of the progressive resolution optimizer (PRO) for RapidArc planning in targets with low‐density media
Authors: Kan Monica W.K. , Leung Lucullus H.T. , Yu Peter K.N. 
Published: February 2017

A new version of progressive resolution optimizer (PRO) with an option of air cavity correction has been implemented for RapidArc volumetric‐modulated arc therapy (RA). The purpose of this study was to compare the performance of this new PRO with the use of air cavity correction option (PRO10_air) against the one without the use of the air cavity correction option (PRO10_no‐air) for RapidArc planning in targets with low‐density media of different sizes and complexities. The performance of PRO10_no‐air and PRO10_air was initially compared using single‐arc plans created for four different simple heterogeneous phantoms with virtual targets and organs at risk. Multiple‐arc planning of 12 real patients having nasopharyngeal carcinomas (NPC) and ten patients having non‐small cell lung cancer (NSCLC) were then performed using the above two options for further comparison. Dose calculations were performed using both the Acuros XB (AXB) algorithm with the dose to medium option and the analytical anisotropic algorithm (AAA). The effect of using intermediate dose option after the first optimization cycle in PRO10_air and PRO10_no‐air was also investigated and compared. Plans were evaluated and compared using target dose coverage, critical organ sparing, conformity index, and dose homogeneity index. For NSCLC cases or cases for which large volumes of low‐density media were present in or adjacent to the target volume, the use of the air cavity correction option in PROIO was shown to be beneficial. For NPC cases or cases for which small volumes of both low‐ and high‐density media existed in the target volume, the use of air cavity correction in PRO10 did not improve the plan quality. Based on the AXB dose calculation results, the use of PRO10_air could produce up to 18% less coverage to the bony structures of the planning target volumes for NPC cases. When the intermediate dose option in PRO10 was used, there was negligible difference observed in plan quality between optimizations with and without using the air cavity correction option.PACS number: 87.55.D‐, 87.55.de, 87.56.N‐
Scanner and kVp dependence of measured CT numbers in the ACR CT phantom
Authors: Cropp Robert J. , Seslija Petar , Tso David , Thakur Yogesh 
Published: February 2017

Quality control testing of CT scanners in our region includes a measurement of CT numbers in the American College of Radiology (ACR) CT phantom using a standardized protocol. CT number values are clinically relevant in determining the composition of various tissues in the body. Accuracy is important in the characterization of tumors, assessment of coronary calcium, and identification of urinary stone composition. Effective quality control requires that tolerance ranges of CT number values be defined: a measured value outside the range indicates the need for further investigation and possible recalibration of the scanner. This paper presents the results of CT number measurements on 36 scanners (25 GE, 10 Siemens and 1 Toshiba) at each available kVp. Among the five materials (solid water, air, polyethylene, acrylic, bone‐equivalent) the measured CT numbers exhibit manufacturer and kVp dependence, which should be taken into account when defining tolerances. With this scan protocol, air and solid water values are significantly higher on GE scanners than on Siemens scanners ( at each kVp). The CT numbers of polyethylene and acrylic increase with kVp, while the bone‐equivalent CT number decreases. These results are used to define manufacturer‐ and kVp‐specific tolerance ranges for the CT numbers of each material in this phantom, which will be used in our quality control program.PACS numbers: 87.57.qp, 87.57.C‐
Comparing Gamma Knife and CyberKnife in patients with brain metastases
Authors: Sio Terence T. , Jang Sunyoung , Lee Sung‐Woo , Curran Bruce , Pyakuryal Anil P. , Sternick Edward S. 
Published: February 2017

The authors compared the relative dosimetric merits of Gamma Knife (GK) and CyberKnife (CK) in 15 patients with 26 brain metastases. All patients were initially treated with the Leksell GK 4C. The same patients were used to generate comparative CK treatment plans. The tissue volume receiving more than 12 Gy (V12), the difference between V12 and tumor volume (V12net), homogeneity index (HI), and gradient indices (GI25, GI50) were calculated. Peripheral dose falloff and three conformity indices were compared. The median tumor volume was 2.50 cm3 (range, 0. 044‐19.9). A median dose of 18 Gy (range, 15‐22) was prescribed. In GK and CK plans, doses were prescribed to the 40‐50% and 77‐92% isodose lines, respectively. Comparing GK to CK, the respective parametric values were: minimum dose ( vs. , ); mean dose ( vs., ); maximum dose ( vs., ); and HI ( vs. , ). The median dosimetric indices (GK vs. CK, with range) were: RTOG_CI, 1.76 (1.12‐4.14) vs. 1.53 (1.16‐2.12), ; CI, 1.76 (1.15‐4.14) vs. 1.55 (1.18‐2.21), ; nCI, 1.76 (1.59‐4.14) vs. 1.57 (1.20‐2.30), ; GI50, 2.91 (2.48‐3.67) vs. 4.90 (3.42‐11.68), ; GI25, 6.58 (4.18‐10.20) vs. 14.85 (8.80‐48.37), . Average volume ratio (AVR) differences favored GK at multiple normalized isodose levels . We concluded that in patients with brain metastases, CK and GK resulted in dosimetrically comparable plans that were nearly equivalent in several metrics, including target coverage and minimum dose within the target. Compared to GK, CK produced more homogenous plans with significantly lower mean and maximum doses, and achieved more conformal plans by RTOG_CI criteria. By GI and AVR analyses, GK plans had sharper peripheral dose falloff in most cases.PACS number: 89.20.‐a
An investigation of gantry angle data accuracy for cine‐mode EPID images acquired during arc IMRT
Authors: McCowan Peter M. , Rickey Daniel W. , Rowshanfarzad Pejman , Greer Peter B. , Ansbacher William , McCurdy Boyd M. 
Published: February 2017

EPID images acquired in cine mode during arc therapy have inaccurate gantry angles recorded in their image headers. In this work, methods were developed to assess the accuracy of the gantry potentiometer for linear accelerators. As well, assessments of the accuracy of other, more accessible, sources of gantry angle information (i.e., treatment log files, analysis of EPID image headers) were investigated. The methods used in this study are generally applicable to any linear accelerator unit, and have been demonstrated here with Clinac/Trilogy systems. Gantry angle data were simultaneously acquired using three methods: i) a direct gantry potentiometer measurement, ii) an incremental rotary encoder, and iii) a custom‐made radiographic gantry‐angle phantom which produced unique wire intersections as a function of gantry angle. All methods were compared to gantry angle data from the EPID image header and the linac MLC DynaLog file. The encoder and gantry‐angle phantom were used to validate the accuracy of the linac's potentiometer. The EPID image header gantry angles and the DynaLog file gantry angles were compared to the potentiometer. The encoder and gantry‐angle phantom mean angle differences with the potentiometer were and , respectively. The EPID image header angles analyzed in this study were within of the potentiometer angles only 35% of the time. In some cases, EPID image header gantry angles disagreed by as much as 3° with the potentiometer. A time delay in frame acquisition was determined using the continuous acquisition mode of the EPID. After correcting for this time delay, 75% of the header angles, on average, were within of the true gantry angle, compared to an average of only 35% without the correction. Applying a boxcar smoothing filter to the corrected gantry angles further improved the accuracy of the header‐derived gantry angles to within for almost all images (99.4%). An angle accuracy of was determined using a point‐by‐point comparison of the gantry angle data in the MLC DynaLog file and the potentiometer data. These simple correction methods can be easily applied to individual treatment EPID images in order to more accurately define the gantry angle.PACS numbers: 87.53.Kn, 87.55.T‐, 87.56.bd, 87.59.‐e
Evaluation of techniques for slice sensitivity profile measurement and analysis
Authors: Greene Travis C. , Rong X. John 
Published: February 2017

The purpose of this study was to compare the resulting full width at half maximum of slice sensitivity profiles (SSP) generated by several commercially available point response phantoms, and determine an appropriate imaging technique and analysis method. Four CT phantoms containing point response objects designed to produce a delta impulse signal used in this study: a Fluke CT‐SSP phantom, a Gammex 464, a CatPhan 600, and a Kagaku Micro Disc phantom. Each phantom was imaged using 120 kVp, 325 mAs, head scan field of view, helical scan with a 20 mm beam width and a pitch of 0.969. The acquired images were then reconstructed into all available slice thicknesses . A computer program was developed to analyze the images of each dataset for generating a SSP from which the full width at half maximum (FWHM) was determined. Two methods for generating SSPs were evaluated and compared by choosing the mean vs. maximum value in the ROI, along with two methods for evaluating the FWHM of the SSP, linear interpolation and Gaussian curve fitting. FWHMs were compared with the manufacturer's specifications using percent error and z‐test with a significance value of . The FWHMs from each phantom were not significantly different with an average error of 3.5%. The FWHMs from SSPs generated from the mean value were statistically different . The FWHMs from the different FWHM methods were not statistically different . Evaluation of the SSP is dependent on the ROI value used. The maximum value from the ROI should be used to generate the SSP whenever possible. SSP measurement is independent of the phantoms used in this study.PACS number: 87.
Assessment of setup uncertainties for various tumor sites when using daily CBCT for more than 2200 VMAT treatments
Authors: Oh Young‐Kee , Baek Jong‐Geun , Kim Ok‐Bae , Kim Jin‐Hee 
Published: February 2017

The aim of this study was assess the patient setup errors for various tumor sites based on clinical data from a sufficient number of treatments with volumetric‐modulated arc therapy (VMAT) using daily pretreatment CBCT imaging guidance. In addition, we calculated and compared the planning target volume (PTV) margins for all disease sites based on an analysis of specific systematic and random errors in our institution. All patients underwent pretreatment kV‐CBCT imaging. The various tumor sites were divided into four categories; 21 brain (438 fractions), 35 head‐and‐neck tumors (H&N, 933 fractions), 19 thorax and abdomen tumors (T&A, 313 fractions), and 17 prostate cancer tumors (546 fractions). Overall distributions of setup corrections in all directions, frequencies of 3D vector lengths, institution‐specific setup error, and PTV margins were analyzed. The longitudinal distribution for the T&A site represented an asymmetric offset in the negative direction. Rotational distributions were comparable for all treatment sites, and the prostate site had the narrowest distribution of . The cumulative frequencies of 3D vector length of ≥ 7 mm were rare for brain lesions and H&N, but more common for T&A and prostate lesions at 25.6% and 12.1%, respectively. The overall mean error for all treatment sites were within and , with the exception of the T&A site, which had overall mean error of 2 mm in the negative longitudinal direction. The largest magnitude of systematic error and random error for the brain lesions and H&N was 1.4 mm in the translational directions, and 3.3 mm for T&A and prostate lesions. The PTV margins required in this analysis are ≤ 4 mm for the brain lesions and H&N in all translational directions, but ranged from 4 to 10 mm for T&A and prostate lesions. Analysis of each institution's specific setup errors using daily CBCT is essential for determining PTV margins and reducing setup uncertainties, because setup errors vary according to each immobilization system and patient.PACS number: 87.55.km