bluuebunny/crossref_metadata_2025_split huggingface dataset:
Practical dose delivery verification of craniospinal IMRT
Authors: Lee Young K , Kim Anthony T , Zhao Peiying , Karotki Aliaksandr 
Published: February 2017

Craniospinal irradiation (CSI) using IMRT allows dose sparing to organs‐at‐risk (OAR) whilst conforming the dose to the target volume. Due to the complexity of treatment involving several isocenters, the dose distribution created by the inverse‐planned segmented fields must be verified prior to treatment. We propose and test methods to verify dose delivery using commonly available dosimetry equipment for commissioning and routine patient‐specific dose verification of craniospinal IMRT. Ten patients treated with conventional CSI were retrospectively planned with a 3‐isocenter (cranial, upper spine, and lower spine) IMRT technique. The isocenters were placed 25–27 cm away from each other in the longitudinal direction but in the same lateral and anterioposterior positions. The planning target volume (PTV) was defined as the brain with a 0.5 cm margin and spinal canal with a 1.0 cm margin. The plans were prescribed to 36 Gy in 20 fractions to the PTV mean dose. Eleven beams (five cranial, three upper spine, and three lower spine) were optimized simultaneously. The dose delivered by the IMRT plans was then recalculated on several different phantoms and measured using the following methods: 1) ionization chamber inserted in a cylindrical phantom, positioned in the junction regions between cranial/upper‐spine isocenters and upper‐/lower‐spine isocenters; 2) MapCHECK centered in the overlap regions; and 3) ArcCHECK measurement with beams from each isocenter. For 1) dose difference and for 2) and 3) of measured points with a γ‐index for 3% dose difference and 3 mm distance‐to‐agreement were deemed clinically acceptable. The median (range) planned to measured dose differences for the ionization chamber is 0.4% ( to 3.0%) for the cranial/upper‐spine field and 1.8% ( to 2.6%) for the upper‐/lower‐spine field overlap region. The median (range) percentage of MapCHECK diodes with a γ index for 3%/3 mm criterion is 98.0% (95.3% to 99.7%) for the cranial/upper‐spine and 97.3% (95.0% to 99.6%) for the upper‐/lower‐spine field overlap regions. The median (range) percentage of ArcCHECK diodes with a γ index for 3%/3 mm criterion is 99.7% (97.1% to 100%). Three different methods of verifying craniospinal IMRT were compared and tested. All techniques offer different benefits and together can be used for 1) commissioning the treatment technique and, separately, for 2) patient‐specific pretreatment verification measurements.PACS number: 87.55.km
CT radiation profile width measurement using CR imaging plate raw data
Authors: Bjarnason Thorarin A , Yang Chang‐Ying Joseph 
Published: February 2017

This technical note demonstrates computed tomography (CT) radiation profile measurement using computed radiography (CR) imaging plate raw data showing it is possible to perform the CT collimation width measurement using a single scan without saturating the imaging plate. Previously described methods require careful adjustments to the CR reader settings in order to avoid signal clipping in the CR processed image. CT radiation profile measurements were taken as part of routine quality control on 14 CT scanners from four vendors. CR cassettes were placed on the CT scanner bed, raised to isocenter, and leveled. Axial scans were taken at all available collimations, advancing the cassette for each scan. The CR plates were processed and raw CR data were analyzed using MATLAB scripts to measure collimation widths. The raw data approach was compared with previously established methodology. The quality control analysis scripts are released as open source using creative commons licensing. A log‐linear relationship was found between raw pixel value and air kerma, and raw data collimation width measurements were in agreement with CR‐processed, bit‐reduced data, using previously described methodology. The raw data approach, with intrinsically wider dynamic range, allows improved measurement flexibility and precision. As a result, we demonstrate a methodology for CT collimation width measurements using a single CT scan and without the need for CR scanning parameter adjustments which is more convenient for routine quality control work.PACS numbers: 87.57.Q‐, 87.59.bd, 87.57.uq
Jaw position uncertainty and adjacent fields in breast cancer radiotherapy
Authors: Hedin Emma , Bäck Anna , Chakarova Roumiana 
Published: February 2017

Locoregional treatment of breast cancer involves adjacent, half blocked fields matched at isocenter. The objective of this work is to study the dosimetric effects of the uncertainties in jaw positioning for such a case, and how a treatment planning protocol including adjacent field overlap of 1 mm affects the dose distribution. A representative treatment plan, involving 6 and 15 photon beams, for a patient treated at our hospital is chosen. Monte Carlo method (EGSnrc/BEAMnrc) is used to simulate the treatment. Uncertainties in jaw positioning of are addressed, which implies extremes in reality of 2 mm field gap/overlap when planning adjacent fields without overlap and 1 mm gap or 3 mm overlap for a planning protocol with 1 mm overlap. Dosimetric parameters for PTV, lung and body are analyzed. Treatment planning protocol with 1 mm overlap of the adjacent fields does not considerably counteract possible underdosage of the target in the case studied. is for example reduced from 95% for perfectly aligned fields to 90% and 91% for 2 mm and 1 mm gap, respectively. However, the risk of overdosage in PTV and in healthy soft tissue is increased when following the protocol with 1 mm overlap. A 3 mm overlap compared to 2 mm overlap results in an increase in maximum dose to PTV, , from 113% to 121%. for ‘Body‐PTV’ is also increased from to . A treatment planning protocol with 1 mm overlap does not considerably improve the coverage of PTV in the case of erroneous jaw positions causing gap between fields, but increases the overdosage in PTV and doses to healthy tissue, in the case of overlapping fields, for the case investigated.PACS numbers: 87.55.D‐, 87.55.dk, 87.55.Gh, 87.55.K‐, 87.56.J‐
Seed coordinates of a new COMS‐like 24 mm plaque verified using the FARO Edge
Authors: Cutsinger Sarah E. McCauley , Furutani Keith M. , Forsman Renae M. , Corner Stephen M. 
Published: February 2017

A 24 mm COMS‐like eye plaque was developed to meet the treatment needs of our eye plaque brachytherapy practice. As part of commissioning, it was necessary to determine the new plaque's seed coordinates. The FARO Edge, a commercially available measurement arm, was chosen for this purpose. In order to validate the FARO Edge method, it was first used to measure the seed marker coordinates in the silastic molds for the standard 10, 18, and 20 mm COMS plaques, and the results were compared with the standard published Task Group 129 coordinates by a nonlinear least squares match in MATLAB version R2013a. All measured coordinates were within 0.60 mm, and root mean square deviation was 0.12, 0.23, and 0.35 mm for the 10, 18, and 20 mm molds, respectively. The FARO Edge was then used to measure the seed marker locations in the new 24 mm silastic mold. Those values were compared to the manufacturing specification coordinates and were found to demonstrate good agreement, with a maximum deviation of 0.56 mm and a root mean square deviation of 0.37 mm. The FARO Edge is deemed to be a reliable method for determining seed coordinates for COMS silastics, and the seed coordinates for the new 24 mm plaque are presented.PACS number: 87.53.Jw
Characterization of the effect of MRI on Gafchromic film dosimetry
Authors: Reyhan Meral L. , Chen Ting , Zhang Miao 
Published: February 2017

Magnetic resonance (MR) imaging of Gafchromic film causes perturbation to absolute dosimetry measurements; the purpose of this work was to characterize the perturbation and develop a correction method for it. Three sets of Gafchromic EBT2 film were compared: radiation (control), radiation followed by MR imaging , and MR imaging followed by radiation . The T1‐weighted and T2‐weighted MR imaging was performed using a 1.5T scanner with the films wedged between two chicken legs. Doses from 0 to 800 cGy were delivered with a 6MV linac. The time interval between radiation and MR imaging was less than 10 min. Film calibration was generated from the red channel. Microscopic imaging was performed on two pieces of film. The effect of specific absorption rate (SAR) was determined by exposing another three sets of films to low, medium, and high levels of SAR through a series of pulse sequences. No discernible preferential alignment was detected on the microscopic images of the irradiated film exposed to MRI. No imaging artifacts were introduced by Gafchromic film on any MR images. On average, 4% dose difference was observed between or and the control, using the same calibration curve. The pixel values between the or and the control films were found to follow a linear relationship . By applying this correction, the average dose error was reduced to approximately 2%. The SAR experiment revealed a dose overestimation with increasing SAR even when the correction was applied. It was concluded that MR imaging introduces perturbation on Gafchromic film dose measurements by 4% on average, compared to calibrating the film without the presence of MRI. This perturbation can be corrected by applying a linear correction to the pixel values. Additionally, Gafchromic film did not introduce any imaging artifacts in any of the MR images acquired.PACS number: 87.50.cm
On the sensitivity of TG‐119 and IROC credentialing to TPS commissioning errors
Authors: McVicker Drew , Yin Fang‐Fang , Adamson Justus D. 
Published: February 2017

We investigate the sensitivity of IMRT commissioning using the TG‐119 C‐shape phantom and credentialing with the IROC head and neck phantom to treatment planning system commissioning errors. We introduced errors into the various aspects of the commissioning process for a 6X photon energy modeled using the analytical anisotropic algorithm within a commercial treatment planning system. Errors were implemented into the various components of the dose calculation algorithm including primary photons, secondary photons, electron contamination, and MLC parameters. For each error we evaluated the probability that it could be committed unknowingly during the dose algorithm commissioning stage, and the probability of it being identified during the verification stage. The clinical impact of each commissioning error was evaluated using representative IMRT plans including low and intermediate risk prostate, head and neck, mesothelioma, and scalp; the sensitivity of the TG‐119 and IROC phantoms was evaluated by comparing dosimetric changes to the dose planes where film measurements occur and change in point doses where dosimeter measurements occur. No commissioning errors were found to have both a low probability of detection and high clinical severity. When errors do occur, the IROC credentialing and TG 119 commissioning criteria are generally effective at detecting them; however, for the IROC phantom, OAR point‐dose measurements are the most sensitive despite being currently excluded from IROC analysis. Point‐dose measurements with an absolute dose constraint were the most effective at detecting errors, while film analysis using a gamma comparison and the IROC film distance to agreement criteria were less effective at detecting the specific commissioning errors implemented here.PACS number: 87.55.Qr
The impact of spectral filtration on image quality in micro‐CT system
Authors: Ren Liqiang , Ghani Muhammad U , Wu Di , Zheng Bin , Chen Yong , Yang Kai , Wu Xizeng , Liu Hong 
Published: February 2017

This paper aims to evaluate the impact of spectral filtration on image quality in a microcomputed tomography (micro‐CT) system. A mouse phantom comprising 11 rods for modeling lung, muscle, adipose, and bones was scanned with 17 s and 2 min, respectively. The current (μA) for each scan was adjusted to achieve identical entrance exposure to the phantom, providing a baseline for image quality evaluation. For each region of interest (ROI) within specific composition, CT number variations, noise levels, and contrast‐to‐noise ratios (CNRs) were evaluated from the reconstructed images. CT number variations and CNRs for bone with high density, muscle, and adipose were compared with theoretical predictions. The results show that the impact of spectral filtration on image quality indicators, such as CNR in a micro‐CT system, is significantly associated with tissue characteristics. The findings may provide useful references for optimizing the scanning parameters of general micro‐CT systems in future imaging applications.PACS numbers: 87.57.C‐, 87.57.Q‐, 87.64.kd
Gafchromic XR‐QA2 film as a complementary dosimeter for hand‐monitoring in CTF‐guided biopsies
Authors: Sarmento Sandra , Pereira Joana , Sousa Maria José , Cunha Luís , Dias Anabela G. , Pereira Miguel F. , Oliveira Augusto D. , Cardoso João V. , Santos Luís M. , Gouvêa Margarida , Lencart Joana , Alves João G. , Santos João A.M. 
Published: February 2017

Computed tomography fluoroscopy (CTF) is a useful imaging technique to guide biopsies, particularly lung biopsies, but it also has the potential for very high hand exposures, despite use of quick‐check method and needle holders whenever feasible. Therefore, reliable monitoring is crucial to ensure the safe use of CTF. This is a challenge, because ring dosimeters monitor exposure only at the base of one finger, while the fingertips may be exposed to the highly collimated CT beam. In this work we have explored the possibility of using Gafchromic XR‐QA2 self‐developing film as a complementary dosimeter to quantify hand exposure during CTF‐guided biopsies. A glove used in a previous study and designed to contain 11 TLDs was adapted to include Gafchromic strips 7 mm wide, covering the fingers. A total of 22 biopsies were successfully performed wearing this GafTLD glove under sterile gloves, and the IR reported no difficulty or reduction of dexterity while wearing it. Comparison of dose distributions obtained from digitization of the Gafchromic film strips and absolute (0.07) readings from TLDs showed good agreement, despite some positional uncertainty due to relative movement. Per procedure, doses at the base of the ring finger can be as low as 3%–8% of hand dose maximum. Accumulated dose at the base of the ring finger was four times lower than the dose maximum.PACS numbers: 07.57.Kp, 29.40.‐n, 85.25.Pb, 87.57.qp
Automatic planning of head and neck treatment plans
Authors: Hazell Irene , Bzdusek Karl , Kumar Prashant , Hansen Christian R , Bertelsen Anders , Eriksen Jesper G. , Johansen Jørgen , Brink Carsten 
Published: February 2017

Treatment planning is time‐consuming and the outcome depends on the person performing the optimization. A system that automates treatment planning could potentially reduce the manual time required for optimization and could also provide a method to reduce the variation between persons performing radiation dose planning (dosimetrist) and potentially improve the overall plan quality. This study evaluates the performance of the Auto‐Planning module that has recently become clinically available in the Pinnacle3 radiation therapy treatment planning system. Twenty‐six clinically delivered head and neck treatment plans were reoptimized with the Auto‐Planning module. Comparison of the two types of treatment plans were performed using DVH metrics and a blinded clinical evaluation by two senior radiation oncologists using a scale from one to six. Both evaluations investigated dose coverage of target and dose to healthy tissues. Auto‐Planning was able to produce clinically acceptable treatment plans in all 26 cases. Target coverages in the two types of plans were similar, but automatically generated plans had less irradiation of healthy tissue. In 94% of the evaluations, the autoplans scored at least as high as the previously delivered clinical plans. For all patients, the Auto‐Planning tool produced clinically acceptable head and neck treatment plans without any manual intervention, except for the initial target and OAR delineations. The main benefit of the method is the likely improvement in the overall treatment quality since consistent, high‐quality plans are generated which even can be further optimized, if necessary. This makes it possible for the dosimetrist to focus more time on difficult dose planning goals and to spend less time on the more tedious parts of the planning process.PACS number: 87.55.de
Diamond detector in absorbed dose measurements in high‐energy linear accelerator photon and electron beams
Authors: Ravichandran Ramamoorthy , Binukumar John Pichy , Amri Iqbal Al , Davis Cheriyathmanjiyil Antony 
Published: February 2017

Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue‐equivalent properties. We investigated a commercially available ‘microdiamond’ detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1 mm, thickness , the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be (1 SD) . The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stopping power ratios compared well with , water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long‐term stability and reproducibility. Based on micro‐dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance.PACS number(s): 87.56.Da
Development and evaluation of an end‐to‐end test for head and neck IMRT with a novel multiple‐dosimetric modality phantom
Authors: Zakjevskii Viatcheslav V. , Knill Cory S. , Rakowski Joseph. T. , Snyder Michael G. 
Published: February 2017

A comprehensive end‐to‐end test for head and neck IMRT treatments was developed using a custom phantom designed to utilize multiple dosimetry devices. Initial end‐to‐end test and custom H&N phantom were designed to yield maximum information in anatomical regions significant to H&N plans with respect to: (i) geometric accuracy, (ii) dosimetric accuracy, and (iii) treatment reproducibility. The phantom was designed in collaboration with Integrated Medical Technologies. The phantom was imaged on a CT simulator and the CT was reconstructed with 1 mm slice thickness and imported into Varian's Eclipse treatment planning system. OARs and the PTV were contoured with the aid of Smart Segmentation. A clinical template was used to create an eight‐field IMRT plan and dose was calculated with heterogeneity correction on. Plans were delivered with a TrueBeam equipped with a high definition MLC. Preliminary end‐to‐end results were measured using film, ion chambers, and optically stimulated luminescent dosimeters (OSLDs). Ion chamber dose measurements were compared to the treatment planning system. Films were analyzed with FilmQA Pro using composite gamma index. OSLDs were read with a MicroStar reader using a custom calibration curve. Final phantom design incorporated two axial and one coronal film planes with 18 OSLD locations adjacent to those planes as well as four locations for IMRT ionization chambers below inferior film plane. The end‐to‐end test was consistently reproducible, resulting in average gamma pass rate greater than 99% using analysis criteria, and average OSLD and ion chamber measurements within 1% of planned dose. After initial calibration of OSLD and film systems, the end‐to‐end test provides next‐day results, allowing for integration in routine clinical QA. Preliminary trials have demonstrated that our end‐to‐end is a reproducible QA tool that enables the ongoing evaluation of dosimetric and geometric accuracy of clinical head and neck treatments.PACS number(s): 87.55.Qr
Perturbation of water‐equivalent thickness as a surrogate for respiratory motion in proton therapy
Authors: Matney Jason E. , Park Peter C. , Li Heng , Court Laurence E. , Zhu X. Ron , Dong Lei , Liu Wei , Mohan Radhe 
Published: February 2017

Respiratory motion is traditionally assessed using tumor motion magnitude. In proton therapy, respiratory motion causes density variations along the beam path that result in uncertainties of proton range. This work has investigated the use of water‐equivalent thickness (WET) to quantitatively assess the effects of respiratory motion on calculated dose in passively scattered proton therapy (PSPT). A cohort of 29 locally advanced non‐small cell lung cancer patients treated with 87 PSPT treatment fields were selected for analysis. The variation in WET (ΔWET) along each field was calculated between exhale and inhale phases of the simulation four‐dimensional computed tomography. The change in calculated dose (ΔDose) between full‐inhale and full‐exhale phase was quantified for each field using dose differences, 3D gamma analysis, and differential area under the curve (ΔAUC) analysis. Pearson correlation coefficients were calculated between ΔDose and ΔWET. Three PSPT plans were redesigned using field angles to minimize variations in ΔWET and compared to the original plans. The median ΔWET over 87 treatment fields ranged from 1‐9 mm, while the ΔWET 95th percentile value ranged up to 42 mm. The ΔWET was significantly correlated to the ΔDose for all metrics analyzed. The patient plans that were redesigned using ΔWET analysis to select field angles were more robust to the effects of respiratory motion, as ΔAUC values were reduced by more than 60% in all three cases. The tumor motion magnitude alone does not capture the potential dosimetric error due to respiratory motion because the proton range is sensitive to the motion of all patient anatomy. The use of ΔWET has been demonstrated to identify situations where respiratory motion can impact the calculated dose. Angular analysis of ΔWET may be capable of designing radiotherapy plans that are more robust to the effects of respiratory motion.PACS number(s): 87.55.‐x