bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the sensitivity of two 3D diode array dosimetry systems to setup error for quality assurance (QA) of volumetric‐modulated arc therapy (VMAT)
Authors: Li Guangjun , Bai Sen , Chen Nianyong , Henderson Lansdale , Wu Kui , Xiao Jianghong , Zhang Yingjie , Jiang Qingfeng , Jiang Xiaoqin
Published: February 2017

The purpose of this study is to evaluate the sensitivities of 3D diode arrays to setup error for patient‐specific quality assurance (QA) of volumetric‐modulated arc therapy (VMAT). Translational setup errors of , and mm in the RL, SI, and AP directions and rotational setup errors of and in the pitch, roll, and yaw directions were set up in two phantom systems, ArcCHECK and , with VMAT plans for 11 patients. Cone‐beam computed tomography (CBCT) followed by automatic correction using a HexaPOD 6D treatment couch ensured the position accuracy. Dose distributions of the two phantoms were compared in order to evaluate the agreement between calculated and measured values by using γ analysis with 3%/3 mm, 3%/2 mm, and 2%/2 mm criteria. To determine the impact on setup error for VMAT QA, we evaluated the sensitivity of results acquired by both 3D diode array systems to setup errors in translation and rotation. For the VMAT QA of all patients, the pass rate with the 3%/3 mm criteria exceeded 95% using either phantom. For setup errors of 3 mm and 2°, respectively, the pass rates with the 3%/3 mm criteria decreased by a maximum of 14.0% and 23.5% using ArcCHECK, and 14.4% and 5.0% using . Both systems are sensitive to setup error, and do not have mechanisms to account for setup errors in the software. The sensitivity of both VMAT QA systems was strongly dependent on the patient‐specific plan. The sensitivity of ArcCHECK to the rotational error was higher than that of . In order to achieve less than 3% mean pass rate reduction of VMAT plan QA with the 3%/3 mm criteria, a setup accuracy of 2 mm/1° and 2 mm/2° is required for ArcCheck and devices, respectively. The cumulative effect of the combined 2 mm translational and 1° rotational errors caused 3.8% and 2.4% mean pass rates reduction with 3%/3 mm criteria, respectively, for ArcCHECK and systems. For QA of VMAT plans for nasopharyngeal cancer (NPC) using the ArcCHECK system, the setup should be more accurate.

PACS numbers: 87.55.ne, 87.55.Qr, 87.55.km
Effects of interportal error on dose distribution in patients undergoing breath‐holding intensity‐modulated radiotherapy for pancreatic cancer: evaluation of a new treatment planning method
Authors: Takakura Toru , Nakamura Mitsuhiro , Shibuya Keiko , Nakata Manabu , Nakamura Akira , Yukinori Matsuo , Shiinoki Takeshi , Higashimura Kyoji , Teshima Teruki , Hiraoka Masahiro
Published: February 2017

In patients with pancreatic cancer, intensity‐modulated radiotherapy (IMRT) under breath holding facilitates concentration of the radiation dose in the tumor, while sparing the neighboring organs at risk and minimizing interplay effects between movement of the multileaf collimator and motion of the internal structures. Although the breath‐holding technique provides high interportal reproducibility of target position, dosimetric errors caused by interportal breath‐holding positional error have not been reported. Here, we investigated the effects of interportal breath‐holding positional errors on IMRT dose distribution by incorporating interportal positional error into the original treatment plan, using random numbers in ten patients treated for pancreatic cancer. We also developed a treatment planning technique that shortens breath‐holding time without increasing dosimetric quality assurance workload. The key feature of our proposed method is performance of dose calculation using the same optimized fluence map as the original plan, after dose per fraction in the original plan was cut in half and the number of fractions was doubled. Results confirmed that interportal error had a negligible effect on dose distribution over multiple fractions. Variations in the homogeneity index and the dose delivered to 98%, 2%, and 50% of the volume for the planning target volume, and the dose delivered to 1 cc of the volume for the duodenum and stomach were , on average, in comparison with the original plan. The new treatment planning method decreased breath‐holding time by 33%, and differences in dose‐volume metrics between the original and the new treatment plans were within . An additional advantage of our proposed method is that interportal errors can be better averaged out; thus, dose distribution in the proposed method may be closer to the planned dose distribution than with the original plans.

PACS number: 87.53.Bn, 87.55.D‐, 87.55.‐x
Monte Carlo characterization of biocompatible beta‐emitting glass seed incorporated with the radionuclide as a SPECT marker for brachytherapy applications
Authors: Hadadi Asghar , Sadeghi Mahdi , Sardari Dariush , Khanchi Alireza , Shirazi Alireza
Published: February 2017

A glass seed consisting of the ‐emitting radionuclide incorporated with radionuclide as SPECT marker is proposed for potential application in brachytherapy in order to reduce the undesirable dose to healthy adjacent organs. The aim of this work is to determine the dosimetric characteristics, as suggested in the AAPM TG‐60/TG‐149 reports, for this seed using Monte Carlo simulation. Monte Carlo codes MCNP5, EGSnrc, and FLUKA were used to calculate the absorbed dose distribution around the seed. Dosimetric parameters, such as reference absorbed dose rate, radial dose function, and one‐dimensional (1D) and two‐dimensional (2D) anisotropy functions, were obtained. The computational results from these three codes are in agreement within 5.4% difference on average. The absorbed dose rate at the reference point was estimated to be 5.01 cGy and self absorption of YAS glass seed amounted to 30.51%. The results showed that, with thermal neutron bombardment of 5 hours in a typical flux, sufficient activity for applications in brachytherapy may be achieved. With a 5 mCi initial activity, the total dose of a YAS glass seed was estimated to be 1.38 Gy at 1.0 cm from the seed center. Comparing with gamma emitting seeds, the seed could reduce undesirable doses to adjacent organs, because of the rapid dose falloff of beta ray. Because of the high value of 5.5 mm, fewer number of seeds will be required for an interstitial brachytherapy treatment using permanent implant, in comparison with other beta‐emitting seeds. The results would be helpful in the development of the radioactive implants using glass seeds for the brachytherapy treatment.

PACS numbers: 87.53.Jw, 87.56.bg
A feasibility study using TomoDirect for craniospinal irradiation
Authors: Langner Ulrich W. , Molloy Janelle A. , Gleason John F. , Feddock Jonathan M.
Published: February 2017

The feasibility of delivering craniospinal irradiation (CSI) with TomoDirect is investigated. A method is proposed to generate TomoDirect plans using standard three‐dimensional (3D) beam arrangements on Tomotherapy with junctioning of these fields to minimize hot or cold spots at the cranial/spinal junction. These plans are evaluated and compared to a helical Tomotherapy and a three‐dimensional conformal therapy (3D CRT) plan delivered on a conventional linear accelerator (linac) for CSI. The comparison shows that a TomoDirect plan with an overlap between the cranial and spinal fields might be preferable over Tomotherapy plans because of decreased low dose to large volumes of normal tissues outside of the planning target volume (PTV). Although the TomoDirect plans were not dosimetrically superior to a 3D CRT linac plan, the patient can be easily treated in the supine position, which is often more comfortable and efficient from an anesthesia standpoint. TomoDirect plans also have only one setup position which obviates the need for matching of fields and feathering of junctions, two issues encountered with conventional 3D CRT plans. TomoDirect plans can be delivered with comparable treatment times to conventional 3D plans and in shorter times than a Tomotherapy plan. In this paper, a method is proposed for creating TomoDirect craniospinal plans, and the dosimetric consequences for choosing different planning parameters are discussed.

PACS number: 87.55.D‐
Quantifying variability of intrafractional target motion in stereotactic body radiotherapy for lung cancers
Authors: Chan Mark K.H. , Kwong Dora L.W. , Tam Eric , Tong Anthony , Ng Sherry C.Y.
Published: February 2017

In lung stereotactic body radiotherapy (SBRT), variability of intrafractional target motion can negate the potential benefits of four‐dimensional (4D) treatment planning that aims to account for the dosimetric impacts of organ motion. This study used tumor motion data obtained from CyberKnife SBRT treatments to quantify the reproducibility of probability motion function (pmf) of 37 lung tumors. The reproducibility of pmf was analyzed with and without subtracting the intrafractional baseline drift from the original motion data. Statistics of intrafractional tumor motion including baseline drift, target motion amplitude and period, were also calculated. The target motion amplitude significantly correlates with variations (1 SD) of motion amplitude and baseline drift. Significant correlation between treatment time and variations (1 SD) of motion amplitude was observed in anterior‐posterior (AP) motion, but not in craniocaudal (CC) and left‐right (LR) motion. The magnitude of AP and LR baseline drifts significantly depend on the treatment time, while the CC baseline drift does not. The reproducibility of pmf as a function of time can be well described by a two‐exponential function with a fast and slow component. The reproducibility of pmf is over 60% for the CC motion and over 50% for the AP and LR motions when baseline variations were subtracted from the original motion data. It decreases to just over 30% for the CC motion and about 20% for the AP and LR motion, otherwise. 4D planning has obvious limitations due to variability of intrafractional target motion. To account for potential risks of overdosing critical organs, it is important to simulate the dosimetric impacts of intra‐ and interfractional baseline drift using population statistics obtained from SBRT treatments.

PACS number: 87.55.‐x
Stability of percutaneously implanted markers for lung stereotactic radiotherapy
Authors: Persson Gitte F. , Josipovic Mirjana , von der Recke Peter , Aznar Marianne C. , Juhler‐Nøttrup Trine , Munck af Rosenschöld Per , Korreman Stine , Specht and Lena
Published: February 2017

The purpose of this study was to evaluate the stability of complex markers implanted into lung tumors throughout a course of stereotactic body radiotherapy (SBRT). Fifteen patients referred for lung SBRT were prospectively included. Radio‐opaque markers were implanted percutaneously, guided by computed tomography (CT). Deep inspiration breath‐hold CT scans (BHCT) were acquired at planning and on three treatment days. The treatment days' BHCTs were registered to the planning BHCT. Intraobserver uncertainty in both tumor and marker registration was determined. Deviations in the difference between tumor and marker‐based image registrations of the BHCT scans during treatment quantified the marker stability. Marker position deviation relative to tumor position of less than 2 mm in all three dimensions was considered acceptable for treatment delivery precision. Intra‐observer uncertainties for image registration in the left‐right (LR), anterior‐posterior (AP), craniocaudal (CC) directions and three‐dimensional vector (3D) were 0.9 mm, 0.9 mm, 1.0 mm, and 1.1 mm (SD) for tumor registration and 0.3 mm, 0. 5 mm, 0.7 mm, and 0.7 mm (SD) for marker registration. Mean 3D differences for tumor registrations on all days were significantly larger than for 3D marker registrations . Overall median differences between tumor and marker position were 0.0 mm (range ‐2.9 to 2.6 mm) in LR, 0.0 mm (‐1.8 to 1.5 mm) in AP, and ‐0.2 mm (‐2.6 to 2.8 mm) in CC directions. Four patients had deviations exceeding 2 mm in one or more registrations throughout the SBRT course. This is the first study to evaluate stability of complex markers implanted percutaneously into lung tumors for image guidance in SBRT. We conclude that the observed stability of marker position within the tumor indicates that complex markers can be used as surrogates for tumor position during a short course of SBRT as long as the uncertainties related to their position within the tumor are incorporated into the planning target volume.

PACS number: 87.57.nj, 87.55.ne
Collision indicator charts for gantry‐couch position combinations for Siemens ONCOR and Elekta Infinity linacs
Authors: Becker Stewart J. , Culberson Wes , Flynn Ryan T.
Published: February 2017

Noncoplanar radiation fields from a linear accelerator can be used to deliver radiation dose distributions that are superior to those delivered using coplanar radiation fields. Noncoplanar radiation field arrangements are especially valuable when delivering stereotactic body radiation therapy (SBRT). Noncoplanar radiation fields, however, are geometrically more challenging to deliver than coplanar radiation fields, and are associated with a greater risk of collisions between the gantry, treatment couch, and patient. Knowledge of which treatment couch offset, treatment couch angle, and gantry angle combinations provide a collision‐free radiotherapy delivery is useful in the treatment planning process, as the risk of requiring replanning due to improperly selected treatment parameters can be minimized. Such tables are by default specific to the linear accelerator make and model used for treatment. In this work a set of plots is presented indicating which combination of treatment couch lateral offsets (‐10 cm to 10 cm), couch angles (270° to 90°), and gantry angles (0° to 360°), will result in collision‐free radiation delivery using Siemens ONCOR linear accelerators equipped with a 160‐leaf multileaf collimator and a 550 TxT treatment table, and a Elekta Infinity linear accelerator with an MLCi2 and Elekta iBEAM evo Couchtop EP. The patient was assumed to have a width of 50 cm and a height of 25 cm.

PACS numbers: 87.55.‐x, 87.56.‐v
Reducing excess radiation from portal imaging of pediatric brain tumors
Authors: Tam Moses , Mathew Maya , Hitchen Christine J. , Narayana Ashwatha
Published: February 2017

Previously we have shown that our routine portal imaging (PI) of the craniofacial region in pediatric brain tumor patients contributed an additional 2%‐3% of the prescribed dose and up to 200 cGy to the planning target volume (PTV) and nearby organs at risk (OARs). The purpose of this study is to quantify the reduction in dose to PTV and OARs from portal imaging (PI) of the craniofacial region of pediatric patients treated after the implementation of changes in our portal imaging practices. Twenty consecutive pediatric patients were retrospectively studied since the implementation of changes to our portal imaging procedure. Each received portal imaging of treatment fields and orthogonal setup fields to the craniofacial region. PI modifications included a reduction in the field size of setup orthogonal fields without loss of radiographic information needed for treatment verification. In addition, treatment fields were imaged using a single exposure, rather than double exposure. Dose‐volume histograms were generated to quantify the dose to the target and critical structures through PI acquisition. These results were compared with our previous cohort of 20 patients who were treated using the former portal imaging practices. The mean additional target dose from portal imaging following the new guidelines was 1.5% of the prescribed dose compared to 2.5% prior to the new portal image practices . With the new portal imaging practices, the percentage decrease in portal imaging dose to the brainstem, optic structures, cochlea, hypothalamus, temporal lobes, thyroid, and eyes were 25%, 35%, 35%, 51%, 45%, 80%, and 55%, respectively. Reductions in portal imaging doses were significant in all OARs with exception of the brainstem, which showed a trend towards significance. Changes to portal imaging practices can reduce the radiation dose contribution from portal imaging to surrounding OARs by up to 80%. This may have implications on both late toxicity and second cancer development in pediatric brain tumors.

PACS number: 87
Effect of audio instruction on tracking errors using a four‐dimensional image‐guided radiotherapy system
Authors: Nakamura Mitsuhiro , Sawada Akira , Mukumoto Nobutaka , Takahashi Kunio , Mizowaki Takashi , Kokubo Masaki , Hiraoka Masahiro
Published: February 2017

The Vero4DRT (MHI‐TM2000) is capable of performing X‐ray image‐based tracking (X‐ray Tracking) that directly tracks the target or fiducial markers under continuous kV X‐ray imaging. Previously, we have shown that irregular respiratory patterns increased X‐ray Tracking errors. Thus, we assumed that audio instruction, which generally improves the periodicity of respiration, should reduce tracking errors. The purpose of this study was to assess the effect of audio instruction on X‐ray Tracking errors. Anterior‐posterior abdominal skin‐surface displacements obtained from ten lung cancer patients under free breathing and simple audio instruction were used as an alternative to tumor motion in the superior‐inferior direction. First, a sequential predictive model based on the Levinson‐Durbin algorithm was created to estimate the future three‐dimensional (3D) target position under continuous kV X‐ray imaging while moving a steel ball target of 9.5 mm in diameter. After creating the predictive model, the future 3D target position was sequentially calculated from the current and past 3D target positions based on the predictive model every 70 ms under continuous kV X‐ray imaging. Simultaneously, the system controller of the Vero4DRT calculated the corresponding pan and tilt rotational angles of the gimbaled X‐ray head, which then adjusted its orientation to the target. The calculated and current rotational angles of the gimbaled X‐ray head were recorded every 5 ms. The target position measured by the laser displacement gauge was synchronously recorded every 10 msec. Total tracking system errors were compared between free breathing and audio instruction. Audio instruction significantly improved breathing regularity . The mean ± standard deviation of the 95th percentile of was (range: 1.1–2.6 mm) under free breathing () and (range: 1.2–2.7 mm) under audio instruction . was larger than for five patients; no significant difference was found between and . Correlation analysis revealed that the rapid respiratory velocity significantly increased . Although audio instruction improved breathing regularity, it also increased the respiratory velocity, which did not necessarily reduce tracking errors.

PACS number: 87.55.ne, 87.57.N‐, 87.59.C‐,
Using mean dose rate to compare relative dosimetric efficiency with respect to source type and source change schedules for HDR brachytherapy°
Authors: Davis Stephen D. , Parker William , Evans Michael D.C.
Published: February 2017

Remote afterloading devices used for high‐dose‐rate (HDR) brachytherapy may be supplied with different sources, and these sources typically have differing initial source strengths. In addition, the proposed frequency for source changes may also vary, depending upon the source type. Dosimetric parameters unique to each source are often used to compare source types. However, when considering the relative dosimetric efficiency between two HDR sources, the combined effect of source type, initial source strength, and source change scheme must be considered. A method of quantifying this combined effect by calculating mean dose rate from specific dosimetric source data is discussed. This method suggests an objective manner of comparing source scheme equivalency to facilitate performing a cost ratio analysis between different HDR sources and source change schemes.

PACS numbers: 87.53.Jw, 87.56.bg
Validation of the photon convolution‐superposition algorithm applied to fast neutron beams
Authors: Kalet Alan M. , Sandison George A. , Phillips Mark H. , Parvathaneni Upendra
Published: February 2017

We evaluate a photon convolution‐superposition algorithm used to model a fast neutron therapy beam in a commercial treatment planning system (TPS). The neutron beam modeled was the Clinical Neutron Therapy System (CNTS) fast neutron beam produced by 50 MeV protons on a Be target at our facility, and we implemented the dose calculation model for computing neutron doses. Measured neutron data were acquired by an IC30 ion chamber flowing 5 cc/min of tissue equivalent gas. Output factors and profile scans for open and wedged fields were measured according to the Pinnacle physics reference guide recommendations for photon beams in a Wellhofer water tank scanning system. Following the construction of a neutron beam model, computed doses were then generated using 100 monitor units (MUs) beams incident on a water‐equivalent phantom for open and wedged square fields, as well as multileaf collimator (MLC)‐shaped irregular fields. We compared Pinnacle dose profiles, central axis doses, and off‐axis doses (in irregular fields) with 1) doses computed using the Prism treatment planning system, and 2) doses measured in a water phantom and having matching geometry to the computation setup. We found that the Pinnacle photon model may be used to model most of the important dosimetric features of the CNTS fast neutron beam. Pinnacle‐calculated dose points among open and wedged square fields exhibit dose differences within 3.9 cGy of both Prism and measured doses along the central axis, and within 5 cGy difference of measurement in the penumbra region. Pinnacle dose point calculations using irregular treatment type fields showed a dose difference up to 9 cGy from measured dose points, although most points of comparison were below 5 cGy. Comparisons of dose points that were chosen from cases planned in both Pinnacle and Prism show an average dose difference less than 0.6%, except in certain fields which incorporate both wedges and heavy blocking of the central axis. All clinical cases planned in both Prism and Pinnacle were found to be comparable in terms of dose‐volume histograms and spatial dose distribution following review by the treating clinicians. Variations were considered minor and within clinically acceptable limits by the treating clinicians. The Pinnacle TPS has sufficient computational modeling ability to adequately produce a viable neutron model for clinical use in treatment planning.

PACS numbers: 87.53 Bn, 28.20.Pr, 87.53.Bn
Effects of flattening filter‐free and volumetric‐modulated arc therapy delivery on treatment efficiency
Authors: Thomas Evan M. , Popple Richard A. , Prendergast Brendan M. , Clark Grant M. , Dobelbower Michael C. , Fiveash John B.
Published: February 2017

Flattening filter‐free (FFF) beams are available on an increasing number of commercial linear accelerators. FFF beams have higher dose rates than flattened beams of equivalent energy which can lead to increased efficiency of treatment delivery, especially in conjunction with increased FFF beam energy and arc‐based delivery configurations. The purpose of this study is to quantify and assess the implications of improved treatment efficiency for several FFF delivery options on common types of linac applicable radiotherapy. Eleven characteristic cases representative of a variety of clinical treatment sites and prescription doses were selected from our patient population. Treatment plans were generated for a Varian TrueBeam linear accelerator. For each case, a reference plan was created using DMLC IMRT with 6 MV flat beams. From the same initial objectives, plans were generated using DMLC IMRT and volumetric‐modulated arc therapy (VMAT) with 6 MV FFF and 10 MV FFF beams (max. dose rates of 1400 and 2400 MU/min, respectively). The plans were delivered to a phantom; beam‐on time, total treatment delivery time, monitor units (MUs), and integral dose were recorded. For plans with low dose fractionations (1.8–2.0 & 3.85 Gy/fraction), mean beam‐on time difference between reference plan and most efficient FFF plan was 0.56 min (41.09% decrease); mean treatment delivery time difference between the reference plan and most efficient FFF plan was 1.54 min (range: 0.31–3.56 min), a relative improvement of 46.1% (range: 29.2%‐59.2%). For plans with high dose fractionations (16–20 Gy/fraction), mean beam‐on time difference was 6.79 min (74.9% decrease); mean treatment delivery time difference was 8.99 min (range: 5.40–13.05 min), a relative improvement of 71.1% (range: 53.4%‐82.4%). 10 MV FFF VMAT beams generated the most efficient plan, except in the spine SBRT case. The distribution of monitor unit counts did not vary by plan type. In cases where respiratory motion management would be applicable, 10 MV FFF DMLC IMRT reduced beam‐on time/field to less than 12 sec. FFF beams significantly reduced treatment delivery time. For radiosurgical doses, the efficiency improvement for FFF beams was clinically significant. For conventional fractionation, a large improvement in relative treatment delivery time was observed, but the absolute time savings were not likely to be of clinical value. In cases that benefit from respiratory motion management, beamon/field was reduced to a time for which most patients can comfortably maintain deep inspiratory breath hold.

PACS numbers: 87.55.D‐, 87.55.de, 87.56.bd, 87.56.N‐
Feasibility of improving cone‐beam CT number consistency using a scatter correction algorithm
Authors: Li Jun , Yao Weiguang , Xiao Ying , Yu Yan
Published: February 2017

The study was to explore the feasibility of improving cone‐beam CT (CBCT) number (corresponding to the Hounsfield units in computed tomography) consistency using a scatter‐correction algorithm, with the aim of using CBCT images for treatment planning with density correction. A scatter‐correction algorithm was applied to a Varian OBI CBCT and an Elekta XVI CBCT, and was evaluated for improving CBCT number consistency. CBCT numbers of phantom materials were compared between images with and without bolus, which introduced additional scatter, and with and without scatter‐correction processing. It was observed that CBCT numbers were different in the images with and without bolus in both CBCT studies, and the differences were reduced remarkably after scatter‐correction processing. Results showed that CBCT number consistency was significantly improved by use of the scatter‐correction algorithm.

PACS number: 87.55‐x
Review of backscatter measurement in kilovoltage radiotherapy using novel detectors and reduction from lack of underlying scattering material
Authors: Eaton David J. , Doolan Paul J.
Published: February 2017

Lack of underlying material can lead to dose reduction in kilovoltage radiotherapy treatments because of backscatter reduction. Conversely, the use of lead shielding can lead to large dose enhancement close to the lead interface. GAFCHROMIC film has been shown to be of use in verification of local backscatter factors compared to reference data in codes of practice, but careful handling and multiple readings are required to reduce systematic uncertainties to between 3% and 4%. Monte Carlo modeling of the specific treatment unit should be performed in cases which are found to differ from reference values before alternative values are adopted clinically, but these cases are expected to be few. GAFCHROMIC film may also be used to estimate backscatter reduction more readily than customized ionization chambers, for a range of beam qualities, applicator sizes and depth, with and without lead shielding. Differences were found between different studies, and it is not clear to what extent these are due to variation in equipment and/or technique. However, a layer of wax around lead shielding of 1 mm thickness should be sufficient to eliminate lead enhancement effects for all kilovoltage energies from 40 kV to 300 kV

PACS numbers: 87.55.Qr, 87.56.jk
Migration check tool: automatic plan verification following treatment management systems upgrade and database migration
Authors: Hadley Scott W , White Dale , Chen Xiaoping , Moran Jean M. , Keranen Wayne M.
Published: February 2017

Software upgrades of the treatment management system (TMS) sometimes require that all data be migrated from one version of the database to another. It is necessary to verify that the data are correctly migrated to assure patient safety. It is impossible to verify by hand the thousands of parameters that go into each patient's radiation therapy treatment plan. Repeating pretreatment QA is costly, time‐consuming, and may be inadequate in detecting errors that are introduced during the migration. In this work we investigate the use of an automatic Plan Comparison Tool to verify that plan data have been correctly migrated to a new version of a TMS database from an older version. We developed software to query and compare treatment plans between different versions of the TMS. The same plan in the two TMS systems are translated into an XML schema. A plan comparison module takes the two XML schemas as input and reports any differences in parameters between the two versions of the same plan by applying a schema mapping. A console application is used to query the database to obtain a list of active or in‐preparation plans to be tested. It then runs in batch mode to compare all the plans, and a report of success or failure of the comparison is saved for review. This software tool was used as part of software upgrade and database migration from Varian's Aria 8.9 to Aria 11 TMS. Parameters were compared for 358 treatment plans in 89 minutes. This direct comparison of all plan parameters in the migrated TMS against the previous TMS surpasses current QA methods that relied on repeating pretreatment QA measurements or labor‐intensive and fallible hand comparisons.

PACS numbers: 87.55.T, 87.55.Qr
Experience with an online helpdesk for equipment fault reporting in a radiation oncology department
Authors: McNamara Joanne , Williams Matthew , Carolan Martin
Published: February 2017

The safe and accurate delivery of radiotherapy requires that the various items of equipment used in the treatment process are in proper working order. Unusual equipment behavior, interlocks, and faults need to be communicated promptly to the appropriate personnel, the issue investigated, and information regarding the nature of faults and any subsequent reparative measures recorded in a readily accessible location. At the Illawarra Cancer Care Centre, an online help desk was introduced for the purposes of reporting and tracking equipment faults. In the three years since its introduction, there have been in excess of 1,300 entries made, and it has proven to be a suitable alternative to the use of a physical logbook. Key benefits identified were improved accessibility, automated fault notification, and the ability to search, review and update entries for particular equipment faults. It has been a useful tool for assessing the long‐term performance of each piece of equipment, identifying specific servicing needs, and for substantiating the effectiveness of the service performed. The online help desk has not replaced the need for direct methods of verbal communication between the various professional groups involved with monitoring equipment performance. However, it is a very useful tool for supporting that communication.

PACS number: 87.55.‐x, 87.56.bd
A comprehensive comparison study of three different planar IMRT QA techniques using MapCHECK 2
Authors: Keeling Vance P. , Ahmad Salahuddin , Jin Hosang
Published: February 2017

The purpose of this study is to determine comparability of three different planar IMRT QA techniques: patient gantry angle composite (PGAC), single gantry angle composite (SGAC), and field by field (FBF), using MapCHECK 2 device and the γ test as performance metrics; and to assess the dependency of these techniques on intensity modulation, couch attenuation, and detector position (angular dependency). Ten highly modulated head and neck (H&N) and ten moderately modulated prostate IMRT validation plans were delivered using different techniques and were intercompared using the Student's t‐test. The IMRT QA measurements were evaluated by percentage of points passing the γ test for three different criteria: 1% (dose difference)/1 mm (distance to agreement (DTA)) (C1), 2%/2 mm (C2), and 3%/3 mm (C3). To investigate dependency of the IMRT validation on treatment couch, ionization chamber measurements, as well as the conventional MapCHECK 2 QAs, were performed with PGAC and PGAC‐WOC (without couch; using an extended tennis racket‐type insert with negligible attenuation assumed). To determine angular dependency of the MapCHECK 2, patient gantry field‐by‐field (PG‐FBF) technique was delivered and evaluated separately for each field. The differences of γ passing rates between SGAC and FBF were statistically insignificant, while these were statistically significant when compared to PGAC. SGAC and FBF techniques showed statistically insignificant differences between different levels of intensity modulation (H&N vs. Prostate) at C2 and C3 criteria, while PGAC could not for any criteria. The treatment couch has a significant impact on γ passing rates (PGAC vs. PGAC‐WOC), but an ionization chamber‐based IMRT validations showed clinically insignificant dose errors (< 2%) in all cases. This study showed that the MapCHECK 2 device has large angular dependency, especially at gantry angles of 90° and 270°, which dramatically affected the γ passing rates of PGAC. With proper consideration of couch attenuation and beam arrangement, the MapCHECK 2 will produce clinically comparable QA results using the three different planar IMRT QA techniques.

PACS numbers: 87.55.km, 87.55.Qr, 87.56.Fc
A comparison of anatomical and dosimetric variations in the first 15 fractions, and between fractions 16 and 25, of intensity‐modulated radiotherapy for nasopharyngeal carcinoma*
Authors: Yang Haihua , Tu Yu , Wang Wei , Hu Wei , Ding Weijun , Yu Changhui , Zhou Chao
Published: February 2017

The purpose of this study was to compare anatomical and dosimetric variations in first 15 fractions, and between fractions 16 and 25, during intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC). Twenty‐three NPC patients who received IMRT in 33 fractions were enrolled. Each patient had two repeat computed tomography (CT) scans before the 16th and 25th fraction. Hybrid IMRT plans were generated to evaluate the dosimetric changes. There was a significant decrease of the transverse diameter of nasopharyngeal and neck as well as gross tumor volume (GTV) in the primary nasopharyngeal carcinoma (GTVnx) and involved lymph nodes (GTVnd) during the first 15 fractions, and between fraction 16 and 25 . Consequently, there was a significant reduction of the percentage of the volume receiving the prescribed dose of CTV1 and GTVnd, which was more prominent after the first 15 fractions treatment compared to that between fraction 16 and 25 . Additionally, there was a significant increase in the mean dose (Dmean) and percentage of volume receiving to the bilateral parotid in the first 15 fractions , but not between fraction 16 and 25. While the maximum dose to the spinal cord was significantly increased both in the first 15 fractions, and between fraction 16 and 25 , the increase of the percent of spinal cord volume receiving was significantly higher in the first 15 fractions compared to that between fraction . Based on the dose constraint criterion in the RTOG0225 protocol, a total of phantom plan 1 (generated by applying the beam configurations of the original IMRT treatment plan to the anatomy of the second CT scan) and of phantom 2 (generated by applying the beam configurations of the replan 1 to the anatomy of the third CT scan) were out of limit for the dose to the normal critical structures. In conclusion, our data indicated that anatomic changes resulted in more predominant dosimetric effects in the first 15 fractions, and between fractions 16 and 25, of IMRT.

PACS number: 87.53.Bn, 87.55.de, 87.55.Qr
Review of online educational resources for medical physicists
Authors: Prisciandaro Joann I.
Published: February 2017

Medical physicists are often involved in the didactic training of graduate students, residents (both physics and physicians), and technologists. As part of continuing medical education, we are also involved in maintenance of certification projects to assist in the education of our peers. As such, it is imperative that we remain current concerning available educational resources. Medical physics journals offer book reviews, allowing us an opportunity to learn about newly published books in the field. A similar means of communication is not currently available for online educational resources. This information is conveyed through informal means. This review presents a summary of online resources available to the medical physics community that may be useful for educational purposes.

PACS number: 87.10.‐e
Commissioning and validation of BrainLAB cones for 6X FFF and 10X FFF beams on a Varian TrueBeam STx
Authors: Wiant David B. , Terrell Jonathon A. , Maurer Jacqueline M. , Yount Caroline L. , Sintay Benjamin J.
Published: February 2017

Small field dosimetry is a challenging task. The difficulties of small field measurements, particularly stereotactic field size measurements, are highlighted by the large interinstitution variability that can be observed for circular cone collimator commissioning measurements. We believe the best way to improve the consistency of small field measurements is to clearly document and share the results of small field measurements. In this work we report on the commissioning and validation of a BrainLAB cone system for 6 MV and 10 MV flattening filter‐free (FFF) beams on a Varian TrueBeam STx. Commissioning measurements consisted of output factors, percent depth dose, and off‐axis factor measurements with a diode. Validation measurements were made in a polystyrene slab phantom at depths of 5 cm, 10 cm, and 15 cm using radiochromic film. Output factors for the 6xFFF cones are 0.689, 0. 790, 0.830, 0.871, 0.890, and 0.901 for 4 mm, 6 mm, 7.5 mm, 10 mm, 12.5 mm, and the 15 mm cones, respectively. Output factors for the 10xFFF cones are 0.566, 0. 699, 0.756, 0.826, 0.864, and 0.888 for 4 mm, 6 mm, 7.5 mm, 10 mm, 12.5 mm, and the 15 mm cones, respectively. The full width half maximum values of the off‐axis factors agreed with the nominal cone size to within 0.5 mm. Validation measurements showed an agreement of absolute dose between calculation and plan of ≤ 3.6%, and an agreement of field sizes of ≤ 0.3 mm in all cases. Radiochromic film validation measurements show reasonable agreement with beam models for circular collimators based on diode commissioning measurements.

PACS numbers: 87.53.Ly, 87.53.Bn, 87.56.nk, 87.55.D‐, 87.55.km
A two‐point scheme for optimal breast IMRT treatment planning
Authors: Yao Weiguang
Published: February 2017

We propose an approach to determining optimal beam weights in breast/chest wall IMRT treatment plans. The goal is to decrease breathing effect and to maximize skin dose if the skin is included in the target or, otherwise, to minimize the skin dose. Two points in the target are utilized to calculate the optimal weights. The optimal plan (i.e., the plan with optimal beam weights) consists of high energy unblocked beams, low energy unblocked beams, and IMRT beams. Six breast and five chest wall cases were retrospectively planned with this scheme in Eclipse, including one breast case where CTV was contoured by the physician. Compared with 3D CRT plans composed of unblocked and field‐in‐field beams, the optimal plans demonstrated comparable or better dose uniformity, homogeneity, and conformity to the target, especially at beam junction when supraclavicular nodes are involved. Compared with nonoptimal plans (i.e., plans with nonoptimized weights), the optimal plans had better dose distributions at shallow depths close to the skin, especially in cases where breathing effect was taken into account. This was verified with experiments using a MapCHECK device attached to a motion simulation table (to mimic motion caused by breathing).

PACS number: 87.55 de
Feasibility of using the Vero SBRT system for intracranial SRS
Authors: Burghelea Manuela , Verellen Dirk , Gevaert Thierry , Depuydt Tom , Poels Kenneth , Simon Viorica , Ridder Mark De
Published: February 2017

The Vero SBRT system was benchmarked in a planning study against the Novalis SRS system for quality of delivered dose distributions to intracranial lesions and assessing the Vero system's capacity for SRS. A total of 27 patients with one brain lesion treated on the Novalis system, with 3 mm leaf width MLC and C‐arm gantry, were replanned for Vero, with a 5 mm leaf width MLC mounted on an O‐ring gantry allowing rotations around both the horizontal and vertical axis. The Novalis dynamic conformal arc (DCA) planning included vertex arcs, using 90° couch rotation. These vertex arcs cannot be reproduced with Vero due to the mechanical limitations of the O‐ring gantry. Alternative class solutions were investigated for the Vero. Additionally, to distinguish between the effect of MLC leaf width and different beam arrangements on dose distributions, the Vero class solutions were also applied for Novalis. In addition, the added value of noncoplanar IMRT was investigated in this study. Quality of the achieved dose distributions was expressed in the conformity index (CI) and gradient index (GI), and compared using a paired Student's t‐test with statistical significance for p‐values . For lesions larger than 5 cm3, no statistical significant difference in conformity was observed between Vero and Novalis, but for smaller lesions, the dose distributions showed a significantly better conformity for the Novalis mainly due to the smaller MLC leaf width. Using IMRT on Vero reduces this conformity difference to nonsignificant levels. The cutoff for achieving a GI around 3, characterizing a sharp dose falloff outside the target volume was 4 cm3 for Novalis and 7 cm3 for Vero using DCA technique. Using noncoplanar IMRT, this threshold was reduced to 3 cm3 for the Vero system. The smaller MLC and the presence of the vertex fields allow the Novalis system to better conform the dose around the lesion and to obtain steeper dose falloff outside the lesion. Comparable dosimetric characteristics can be achieved with Vero for lesions larger than 3 cm3 and using IMRT.

PACS number: 87.55.D
Reproducibility of the external surface position in left‐breast DIBH radiotherapy with spirometer‐based monitoring
Authors: Fassi Aurora , Ivaldi Giovanni B. , Meaglia Ilaria , Porcu Patrizia , de Fatis Paola Tabarelli , Liotta Marco , Riboldi Marco , Baroni Guido
Published: February 2017

Deep inspiration breath hold (DIBH) in left‐sided breast cancer radiotherapy treatments allows for a reduction in cardiac and pulmonary doses without compromising target coverage. The selection of the most appropriate technology for DIBH monitoring is a crucial issue. We evaluated the stability and reproducibility of DIBHs controlled by a spirometric device, by assessing the variability of the external surface position within a single DIBH (intra‐DIBH) and between DIBHs performed in the same treatment session (intrafraction) or in different sessions (interfraction). The study included seven left‐breast cancer patients treated with spirometer‐based DIBH radiotherapy. Infrared optical tracking was used to record the 3D coordinates of seven to eleven passive markers placed on the patient's thoraco‐abdominal surface during 29‐43 DIBHs performed in six to eight treatment sessions. The obtained results showed displacements of the external surface between different sessions up to 6.3 mm along a single direction, even at constant inspired volumes. The median value of the interfraction variability in the position of breast passive markers was 2.9 mm (range 1.9‐4.8 mm) in the latero‐lateral direction, 3.6 mm (range 2.2‐4.6 mm) in the antero‐posterior direction, and 4.3 mm (range 2.8‐6.2 mm) in the cranio‐caudal direction. There were no significant dose distribution variations for target and organs at risk with respect to the treatment plan, confirming the adequacy of the applied clinical margins (15 mm) to compensate for the measured setup uncertainties. This study demonstrates that spirometer‐based control does not guarantee a stable and reproducible position of the external surface in left‐breast DIBH radiotherapy, suggesting the need for more robust DIBH monitoring techniques when reduced margins and setup uncertainties are required for improving normal tissue sparing and decreasing cardiac and pulmonary toxicity.

PACS number: 87.55.Km
Comparison of an anthropomorphic PRESAGE® dosimeter and radiochromic film with a commercial radiation treatment planning system for breast IMRT: a feasibility study
Authors: Iqbal Khalid , Gifford Kent A , Ibbott Geoffrey , Grant Ryan L , Buzdar Saeed Ahmad
Published: February 2017

This work presents a comparison of an anthropomorphic PRESAGE® dosimeter and radiochromic film measurements with a commercial treatment planning system to determine the feasibility of PRESAGE® for 3D dosimetry in breast IMRT. An anthropomorphic PRESAGE® phantom was created in the shape of a breast phantom. A five‐field IMRT plan was generated with a commercially available treatment planning system and delivered to the PRESAGE® phantom. The anthropomorphic PRESAGE® was scanned with the Duke midsized optical CT scanner (DMOS‐RPC) and the OD distribution was converted to dose. Comparisons were performed between the dose distribution calculated with the Pinnacle3 treatment planning system, PRESAGE®, and EBT2 film measurements. DVHs, gamma maps, and line profiles were used to evaluate the agreement. Gamma map comparisons showed that Pinnacle3 agreed with PRESAGE® as greater than 95% of comparison points for the PTV passed a criterion when the outer 8 mm of phantom data were discluded. Edge artifacts were observed in the optical CT reconstruction, from the surface to approximately 8 mm depth. These artifacts resulted in dose differences between Pinnacle3 and PRESAGE® of up to 5% between the surface and a depth of 8 mm and decreased with increasing depth in the phantom. Line profile comparisons between all three independent measurements yielded a maximum difference of 2% within the central 80% of the field width. For the breast IMRT plan studied, the Pinnacle3 calculations agreed with PRESAGE® measurements to within the gamma criterion. This work demonstrates the feasibility of the PRESAGE® to be fashioned into anthropomorphic shape, and establishes the accuracy of Pinnacle3 for breast IMRT. Furthermore, these data have established the groundwork for future investigations into 3D dosimetry with more complex anthropomorphic phantoms.

PACS number: 87.53.Jw, 87.55.D‐, 87.55.dk