bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of trigeminal neuralgia radiosurgery plans using two film detectors for the commissioning of small photon beams
Authors: Esparza‐Moreno Karina P. , Garcáa‐Garduño Olivia A. , Ballesteros‐Zebadúa Paola , Lárraga‐Gutiérrez José M. , Moreno‐Jiménez Sergio , Celis‐López Miguel A. 
Published: February 2017

Trigeminal neuralgia (TN) is a chronic, episodic facial pain syndrome that can be extremely intense, and it occurs within the regions of the face that are innervated by the three branches of the trigeminal nerve. Stereotactic radiosurgery (SRS) is the least invasive procedure to treat TN. SRS uses narrow photon beams that require high spatial resolution techniques for their measurement. The use of radiographic or radiochromic films for small‐field dosimetry is advantageous because high spatial resolution and two‐dimensional dose measurements can be performed. Because these films have different properties, it is expected that the calculated dose distributions for TN patients will behave differently, depending on the detector used for the commissioning of the small photon beams. This work is based on two sets of commissioned data: one commissioned with X‐OMAT V2 film and one commissioned with EBT2 film. The calculated dose distributions for 23 TN patients were compared between the commissioning datasets. The variables observed were the differences in the half widths of the 35 and 40 Gy isodose lines (related to the entrance distance to the brainstem) and the volume of the brainstem that received a dose of 12 Gy or more (V12). The results of this comparison showed that there were statistically significant differences between the two calculated dose distributions. The magnitudes of these differences were up to 0.33 mm and 0.38 mm for the 35 and 40 Gy isodose lines. The corresponding difference for the V12 was up to 2.1 cc. It is clear that these differences may impact the treatment of TN patients, and then it must be important to perform this type of analysis when observing complication rates. Clinical reports on irradiation techniques for trigeminal neuralgia should consider that different detectors used for commissioning treatment planning systems might result in small but significant differences in dose distributions.PACS number: 87.55.km
Analytical approach for determining beam profiles in water phantom of symmetric and asymmetric fields of wedged, blocked, and open photon beams
Authors: Birgani Mohamad Javad Tahmasebi , Chegeni Nahid , Arvandi Shole , Ghalaee Sasan Razmjoo , Zabihzadeh Mansoor , Khezerloo Davood 
Published: February 2017

Nowadays, in most radiotherapy departments, the commercial treatment planning systems (TPS) used to calculate dose distributions needs to be verified; therefore, quick, easy‐to‐use, and low‐cost dose distribution algorithms are desirable to test and verify the performance of the TPS. In this paper, we put forth an analytical method to calculate the phantom scatter contribution and depth dose on the central axis based on the equivalent square concept. Then, this method was generalized to calculate the profiles at any depth and for several field shapes — regular or irregular fields—under symmetry and asymmetry photon beam conditions. Varian 2100 C/D and Siemens Primus Plus linacs with 6 and 18 MV photon beam were used for irradiations. Percentage depth doses (PDDs) were measured for a large number of square fields for both energies and for 45° wedge, which were employed to obtain the profiles in any depth. To assess the accuracy of the calculated profiles, several profile measurements were carried out for some treatment fields. The calculated and measured profiles were compared by gamma‐index calculation. All γ–index calculations were based on a 3% dose criterion and a 3 mm dose‐to‐agreement (DTA) acceptance criterion. The γ values were less than 1 at most points. However, the maximum γ observed was about 1.10 in the penumbra region in most fields and in the central area for the asymmetric fields. This analytical approach provides a generally quick and fairly accurate algorithm to calculate dose distribution for some treatment fields in conventional radiotherapy.PACS number: 87.10.Ca
Modulation factors calculated with an EPID‐derived MLC fluence model to streamline IMRT/VMAT second checks
Authors: Steciw Stephen , Rathee Satyapal , Warkentin Brad 
Published: February 2017

This work outlines the development of a robust method of calculating modulation factors used for the independent verification of MUs for IMRT and VMAT treatments, to replace onerous ion chamber measurements. Two‐dimensional fluence maps were calculated for dynamic MLC fields that include MLC interleaf leakage, transmission, and tongue‐and‐groove effects, as characterized from EPID‐acquired images. Monte Carlo‐generated dose kernels were then used to calculate doses for a modulated field and that field with the modulation removed at a depth specific to the calculation point in the patient using in‐house written software, Mod_Calc. The ratio of these two doses was taken to calculate modulation factors. Comparison between Mod_Calc calculation and ion chamber measurement of modulation factors for 121 IMRT fields yielded excellent agreement, where the mean difference between the two was . This validated use of Mod_Calc clinically. Analysis of 5,271 dynamic fields from clinical use of Mod_Calc gave a mean difference of between Mod_Calc and Eclipse‐generated factors. In addition, 99.3% and 96.5% fields pass 5% and 2% criteria, respectively, for agreement between these two predictions. The development and use of Mod_Calc at our clinic has considerably streamlined our QA process for IMRT and RapidArc fields, compared to our previous method based on ion chamber measurements. As a result, it has made it feasible to maintain our established and trusted current in‐house method of MU verification, without resorting to commercial software alternatives.PACS numbers: 87.55.km, 87.55.Qr, 87.55.kd, 87.57.uq
A novel compound 6D‐offset simulating phantom and quality assurance program for stereotactic image‐guided radiation therapy system
Authors: Ngar Dennis Yuen‐Kan , Cheung Michael Lok‐Man , Kam Michael Koon‐Ming , Poon Wai‐Sang , Chan Anthony Tak‐Cheung 
Published: February 2017

A comprehensive quality assurance (QA) device cum program was developed for the commissioning and routine testing of the 6D IGRT systems. In this article, both the new QA system and the BrainLAB IGRT system which was added onto a Varian Clinac were evaluated. A novel compound 6D‐offset simulating phantom was designed and fabricated in the Prince of Wales Hospital (PWH), Hong Kong. The QA program generated random compound 6D‐offset values. The 6D phantom was simply set up and shifted accordingly. The BrainLAB ExacTrac X‐ray IGRT system detected the offsets and then corrected the phantom position automatically through the robotic couch. Routine QA works facilitated data analyses of the detection errors, the correction errors, and the correlations. Fifty sets of data acquired in 2011 in PWH were thoroughly analyzed. The 6D component detection errors and correction errors of the IGRT system were all within and individually. Translational and rotational scalar resultant errors were found to be , respectively. Most individual component errors were shown to be independent of their original offset values. The system characteristics were locally established. The BrainLAB 6D IGRT system added onto a regular linac is sufficiently precise for stereotactic RT This new QA methodology is competent to assure the IGRT system overall integrity. Annual grand analyses are recommended to check local system consistency and for external cross‐comparison. The target expansion policy of 1.5 mm 3D margin from CTV to PTV is confirmed for this IGRT system currently in PWH.PACS numbers: 87.53.Ly, 87.55.Gh, 87.55.Qr, 87.56.Fc
Using patient‐specific phantoms to evaluate deformable image registration algorithms for adaptive radiation therapy
Authors: Stanley Nick , Glide‐Hurst Carri , Kim Jinkoo , Adams Jeffrey , Li Shunshan , Wen Ning , Chetty Indrin J , Zhong Hualiang 
Published: February 2017

The quality of adaptive treatment planning depends on the accuracy of its underlying deformable image registration (DIR). The purpose of this study is to evaluate the performance of two DIR algorithms, B‐spline‐based deformable multipass (DMP) and deformable demons (Demons), implemented in a commercial software package. Evaluations were conducted using both computational and physical deformable phantoms. Based on a finite element method (FEM), a total of 11 computational models were developed from a set of CT images acquired from four lung and one prostate cancer patients. FEM generated displacement vector fields (DVF) were used to construct the lung and prostate image phantoms. Based on a fast‐Fourier transform technique, image noise power spectrum was incorporated into the prostate image phantoms to create simulated CBCT images. The FEM‐DVF served as a gold standard for verification of the two registration algorithms performed on these phantoms. The registration algorithms were also evaluated at the homologous points quantified in the CT images of a physical lung phantom. The results indicated that the mean errors of the DMP algorithm were in the range of for the computational phantoms and 1.9 mm for the physical lung phantom. For the computational prostate phantoms, the corresponding mean error was 1.0–1.9 mm in the prostate, 1.9–2.4 mm in the rectum, and 1.8–2.1 mm over the entire patient body. Sinusoidal errors induced by B‐spline interpolations were observed in all the displacement profiles of the DMP registrations. Regions of large displacements were observed to have more registration errors. Patient‐specific FEM models have been developed to evaluate the DIR algorithms implemented in the commercial software package. It has been found that the accuracy of these algorithms is patient‐dependent and related to various factors including tissue deformation magnitudes and image intensity gradients across the regions of interest. This may suggest that DIR algorithms need to be verified for each registration instance when implementing adaptive radiation therapy.PACS numbers: 87.10.Kn, 87.55.km, 87.55.Qr, 87.57.nj
Comparison of planning techniques when air/fluid is present using the strut‐adjusted volume implant (SAVI) for HDR‐based accelerated partial breast irradiation
Authors: Harmon Joseph F. , Rice Brandon K. 
Published: February 2017

The presence of air/fluid surrounding implantable devices used for partial breast irradiation may significantly impact dose coverage to at‐risk tissue. Of the 67 total patients retrospectively evaluated for this study, 32 (48%) had greater than 1 cc volume of air/fluid extending outside of the strut‐adjusted volume implant (SAVI) device surface and were selected for comparison of planning approaches. The planning approaches utilized two different definitions of PTV_EVAL. One definition of a PTV_EVAL was based on expanding 1 cm beyond the SAVI device only while accounting for the air/fluid using the NSABP Protocol B‐39/RTOG Protocol 0413. The second PTV_EVAL definition was based on expanding 1 cm beyond the cavity (SAVI device plus air/fluid volume). The results indicate use of the B‐39 formalism to account for air/fluid displacing the PTV_EVAL may overestimate the dose coverage to the at‐risk tissue, especially for large contiguous volumes of air/fluid. Using the SAVI device to optimize dose covering the volume surrounding the cavity improves dosimetric coverage to at‐risk tissue by 11.3% and 8.7% for V100 and V90, respectively, while the average V150 and V200 indices for increased by 9.1 cc and 5.0 cc, respectively, and the average maximum rib and skin doses increased by 11. 1% and 6.1%, respectively. The maximum skin dose, rib dose, V150, and V200 all met the planning objectives despite any increase in these parameters.PACS number: 87.55.kh
Prevention of gross setup errors in radiotherapy with an efficient automatic patient safety system
Authors: Yan Guanghua , Mittauer Kathryn , Huang Yin , Lu Bo , Liu Chihray , Li Jonathan G. 
Published: February 2017

Treatment of the wrong body part due to incorrect setup is among the leading types of errors in radiotherapy. The purpose of this paper is to report an efficient automatic patient safety system (PSS) to prevent gross setup errors. The system consists of a pair of charge‐coupled device (CCD) cameras mounted in treatment room, a single infrared reflective marker (IRRM) affixed on patient or immobilization device, and a set of in‐house developed software. Patients are CT scanned with a CT BB placed over their surface close to intended treatment site. Coordinates of the CT BB relative to treatment isocenter are used as reference for tracking. The CT BB is replaced with an IRRM before treatment starts. PSS evaluates setup accuracy by comparing real‐time IRRM position with reference position. To automate system workflow, PSS synchronizes with the record‐and‐verify (R&V) system in real time and automatically loads in reference data for patient under treatment. Special IRRMs, which can permanently stick to patient face mask or body mold throughout the course of treatment, were designed to minimize therapist's workload. Accuracy of the system was examined on an anthropomorphic phantom with a designed end‐to‐end test. Its performance was also evaluated on head and neck as well as abdominalpelvic patients using cone‐beam CT (CBCT) as standard. The PSS system achieved a seamless clinic workflow by synchronizing with the R&V system. By permanently mounting specially designed IRRMs on patient immobilization devices, therapist intervention is eliminated or minimized. Overall results showed that the PSS system has sufficient accuracy to catch gross setup errors greater than 1 cm in real time. An efficient automatic PSS with sufficient accuracy has been developed to prevent gross setup errors in radiotherapy. The system can be applied to all treatment sites for independent positioning verification. It can be an ideal complement to complex image‐guidance systems due to its advantages of continuous tracking ability, no radiation dose, and fully automated clinic workflow.PACS number: 87.55.Qr
Medical Physics Practice Guidelines ‐ The AAPM's minimum practice recommendations for medical physicists
Authors: Chan Maria F. , Prisciandaro Joann I. , Shepard S. Jeff , Halvorsen Per H. 
Published: February 2017

This issue's editorial is an invited commentary authored by Maria F. Chan, Joann I. Prisciandaro, S. Jeff Shepard, and Per H. Halvorsen. It discusses an essential question for practicing medical physicists: What are minimum practice standards and recommendations for clinically active medical physicists? The topic is both timely and essential, as the AAPM and JACMP are beginning to publish community practice standards. This editorial sets the framework and focus of these important articles.Michael D. Mills PhD Editor‐in‐Chief
Dosimetry of gamma chamber blood irradiator using PAGAT gel dosimeter and Monte Carlo simulations
Authors: Mohammadyari Parvin , Zehtabian Mehdi , Sina Sedigheh , Tavasoli Ali Reza , Faghihi Reza 
Published: February 2017

Currently, the use of blood irradiation for inactivating pathogenic microbes in infected blood products and preventing graft‐versus‐host disease (GVHD) in immune suppressed patients is greater than ever before. In these systems, dose distribution and uniformity are two important concepts that should be checked. In this study, dosimetry of the gamma chamber blood irradiator model Gammacell 3000 Elan was performed by several dosimeter methods including thermoluminescence dosimeters (TLD), PAGAT gel dosimetry, and Monte Carlo simulations using MCNP4C code. The gel dosimeter was put inside a glass phantom and the TL dosimeters were placed on its surface, and the phantom was then irradiated for 5 min and 27 sec. The dose values at each point inside the vials were obtained from the magnetic resonance imaging of the phantom. For Monte Carlo simulations, all components of the irradiator were simulated and the dose values in a fine cubical lattice were calculated using tally F6. This study shows that PAGAT gel dosimetry results are in close agreement with the results of TL dosimetry, Monte Carlo simulations, and the results given by the vendor, and the percentage difference between the different methods is less than 4% at different points inside the phantom. According to the results obtained in this study, PAGAT gel dosimetry is a reliable method for dosimetry of the blood irradiator. The major advantage of this kind of dosimetry is that it is capable of 3D dose calculation.PACS number: 87.53.Bn
Comparison of stereotactic plans for brain tumors with two different multileaf collimating systems
Authors: Marrazzo Livia , Zani Margherita , Pallotta Stefania , Greto Daniela , Scoccianti Silvia , Talamonti Cinzia , Biti Giampaolo , Bucciolini Marta 
Published: February 2017

Linac‐based stereotactic radiosurgery (SRS) has been widely used for treating small intracranial lesions. This technique allows conforming the dose distribution to the planning target volume (PTV), providing a steep dose gradient with the surrounding normal tissues. This is realized through dedicated collimation systems. The present study aims to compare SRS plans with two collimating systems: the beam modulator (BM) of the Elekta Synergy linac and the DirexGroup micromultileaf collimator . Seventeen patients (25 PTVs) were planned both with BM and (mounted on an Elekta Precise linac) using the Odyssey (PerMedics) treatment planning system (TPS). Plans were compared in terms of dose‐volume histograms (DVH), minimum dose to the PTV, conformity index (CI), and homogeneity index (HI), as defined by the TPS, and doses to relevant organs at risk (OAR). The mean difference between the and the BM plans in minimum PTV dose was in favor of the plans. No statistically significant difference was found between the distributions of the CI values for the two planning modalities , while the difference between the distributions of the HI values was statistically significant . For both BM and plans, no differences were observed in CI and HI, depending on lesion size and shape. The PTV homogeneity achieved by BM plans was compared to with . Higher maximum and mean doses to OAR were observed in the BM plans; however, for both plans, dose constraints were respected. The comparison between the two collimating systems showed no substantial differences in terms of PTV coverage or OAR sparing. The improvements obtained by using are relatively small, and both systems turned out to be adequate for SRS treatments.PACS numbers: 87.53.Ly, 87.55.dk, 87.56.nk
Feasibility of using nonflat photon beams for whole‐breast irradiation with breath hold
Authors: Wang Yuenan , Vassil Andrew , Tendulkar Rahul , Bayouth John , Xia Ping 
Published: February 2017

Removing a flattening filter or replacing it with a thinner filter alters the characteristics of a photon beam, creating a forward peaked intensity profile to make the photon beam nonflat. This study is to investigate the feasibility of applying nonflat photon beams to the whole‐breast irradiation with breath holds for a potential of delivery time reduction during the gated treatment. Photon beams of 6 MV with flat and nonflat intensity profiles were commissioned. Fifteen patients with early‐stage breast cancer, who received whole‐breast radiation without breathing control, were retrospectively selected for this study. For each patient, three plans were created using a commercial treatment planning system: (a) the clinically approved plan using forward planning method (FP); (b) a hybrid intensity‐modulated radiation therapy (IMRT) plan where the flat beam open fields were combined with the nonflat beam IMRT fields using direct aperture optimization method (mixed DAO); (c) a hybrid IMRT plan where both open and IMRT fields were from nonflat beams using direct aperture optimization (nonflat DAO). All plans were prescribed for of the breast volume receiving the prescription dose of 50 Gy (2.0 Gy per fraction). In comparison, all plans achieved a similar dosimetric coverage to the targeted volume. The average homogeneity index of the FP, mixed DAO, and nonflat DAO plans were , , and , respectively. The average percentage volume of was , , for the FP, mixed, and nonflat DAO plans, respectively. There was no significant difference observed for the defined endpoint doses in organs at risk (OARs). In conclusion, both mixed DAO and nonflat DAO plans can achieve similar plan quality as the clinically approved FP plan, measured by plan homogeneity and endpoint doses to the ORAs. Nonflat beam plans may reduce treatment time in breath‐hold treatment, especially for hypofractionated treatment.PACS number: 87.55
Preventive sparing of spinal cord and brain stem in the initial irradiation of locally advanced head and neck cancers
Authors: Farace Paolo , Piras Sara , Porru Sergio , Massazza Federica , Fadda Giuseppina , Solla Ignazio , Piras Denise , Deidda Maria Assunta , Amichetti Maurizio , Possanzini Marco 
Published: February 2017

Since reirradiation in recurrent head and neck patients is limited by previous treatment, a marked reduction of maximum doses to spinal cord and brain stem was investigated in the initial irradiation of stage III/IV head and neck cancers. Eighteen patients were planned by simultaneous integrated boost, prescribing 69.3 Gy to PTV1 and 56.1 Gy to PTV2. Nine 6 MV coplanar photon beams at equispaced gantry angles were chosen for each patient. Step‐and‐shoot IMRT was calculated by direct machine parameter optimization, with the maximum number of segments limited to 80. In the standard plan, optimization considered organs at risk (OAR), dose conformity, maximum dose to spinal cord and to brain stem. In the sparing plans, a marked reduction to spinal cord and brain stem were investigated, with/without changes in dose conformity. In the sparing plans, the maximum doses to spinal cord and brain stem were reduced from the initial values ( and ), without significant changes on the other OARs. A marked difference ( and ) was obtained at the expense of a small difference from initial coverage . Similar difference ( and ) was obtained compromising dose conformity, but unaffecting and with negligible decrease in ( from the initial ). A marked spinal cord and brain stem preventive sparing was feasible at the expense of a decrease in dose conformity or slightly compromising target coverage. A sparing should be recommended in highly recurrent tumors, to make potential reirradiation safer.PACS number: 87.55.D