bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dosimetric comparison of various optimization techniques for high dose rate brachytherapy of interstitial cervix implants
Authors: Shwetha Bondel , Ravikumar Manickam , Katke Aradhana , Supe Sanjay S. , VenkataGiri Golhalli , Ramanand Nanda , Pasha Tanvir 
Published: February 2017

HDR brachytherapy treatment planning often involves optimization methods to calculate the dwell times and dwell positions of the radioactive source along specified afterloading catheters. The purpose of this study is to compare the dose distribution obtained with geometric optimization (GO) and volume optimization (VO) combined with isodose reshaping. This is a retrospective study of 10 cervix HDR interstitial brachytherapy implants planned using geometric optimization and treated with a dose of 6 Gy per fraction. Four treatment optimization plans were compared: geometric optimization (GO), volume optimization (VO), geometric optimization followed by isodose reshape (GO_IsoR), and volume optimization followed by isodose reshape (VO_IsoR). Dose volume histogram (DVH) was analyzed and the four plans were evaluated based on the dosimetric parameters: target coverage (), conformal index (COIN), homogeneity index (HI), dose nonuniformity ratio (DNR) and natural dose ratio (NDR). Good target coverage by the prescription dose was achieved with GO_IsoR (mean of 88.11%), with 150% and 200% of the target volume receiving 32.0% and 10.4% of prescription dose, respectively. Slightly lower target coverage was achieved with VO_IsoR plans (mean of 86.11%) with a significant reduction in the tumor volume receiving high dose (mean of 28.29% and mean of 7.3%). Conformity and homogeneity were good with VO_IsoR (mean and mean ) as compared to the other optimization techniques. VO_IsoR plans are superior in sparing the normal structures while also providing better conformity and homogeneity to the target. Clinically acceptable plans can be obtained by isodose reshaping provided the isodose lines are dragged carefully.PACS number: 87.53 Bn
Validation of Pinnacle treatment planning system for use with Novalis delivery unit
Authors: Feygelman Vladimir , Hunt Dylan , Walker Luke , Mueller Richard , Demarco Mary Lou , Dilling Thomas , Stevens Craig , Zhang Geoffrey 
Published: February 2017

For an institution that already owns the licenses, it is economically advantageous and technically feasible to use Pinnacle TPS (Philips Radiation Oncology Systems, Fitchburg, WI) with the BrainLab Novalis delivery system (BrainLAB A.G., Heimstetten, Germany). This takes advantage of the improved accuracy of the convolution algorithm in the presence of heterogeneities compared with the pencil beam calculation, which is particularly significant for lung SBRT treatments. The reference patient positioning DRRs still have to be generated by the BrainLab software from the CT images and isocenter coordinates transferred from Pinnacle. We validated this process with the end‐to‐end hidden target test, which showed an isocenter positioning error within one standard deviation from the previously established mean value. The Novalis treatment table attenuation is substantial (up to 6.2% for a beam directed straight up and up to 8.4% for oblique incidence) and has to be accounted for in calculations. A simple single‐contour treatment table model was developed, resulting in mean differences between the measured and calculated attenuation factors of 0.0%–0.2%, depending on the field size. The maximum difference for a single incidence angle is 1.1%. The BrainLab micro‐MLC (mMLC) leaf tip, although not geometrically round, can be represented in Pinnacle by an arch with satisfactory dosimetric accuracy. Subsequently, step‐and‐shoot (direct machine parameter optimization) IMRT dosimetric agreement is excellent. VMAT (called “SmartArc” in Pinnacle) treatments with constant gantry speed and dose rate are feasible without any modifications to the accelerator. Due to the 3 mm‐wide mMLC leaves, the use of a 2 mm calculation grid is recommended. When dual arcs are used for the more complex cases, the overall dosimetric agreement for the SmartArc plans compares favorably with the previously reported results for other implementations of VMAT: γ(3%,3mm) for absolute dose obtained with the biplanar diode array passing rates above 97% with the mean of 98.6%. However, a larger than expected dose error with the single‐arc plans, confined predominantly to the isocenter region, requires further investigationPACS numbers: 87.55Qr, 87.56Nk
Pretreatment setup verification by cone beam CT in stereotactic radiosurgery: phantom study
Authors: Fukuda Atsushi 
Published: February 2017

Kilovoltage cone beam computed tomography (CBCT) imaging may be useful in verifying patient position in stereotactic radiosurgery (SRS). To evaluate its efficacy, we investigated isocenter differences in the radiation beam and CBCT with respect to the achievable setup of a conventional frame‐based SRS system. A verification phantom constructed from two plastic boards and Gafchromic‐EBT film pricked with a pin, was scanned by simulation CT. An isocenter at the tip of pin was planned in the treatment planning system and positioned using stereotactic coordinates. Star‐shot irradiation was performed to evaluate the difference between the radiation isocenter and the target (pinhole). CBCT rotation of 200° with a micro multileaf collimator (m3) was performed and measured the isocenter difference between CBCT and the target (tip of pin) by comparing relative coordinates. Data acquisition was performed 13 times on different days and differences were analyzed by calculating mean and standard deviation. The mean difference between the radiation beam and the target (pinhole) and between radiation beam and CBCT isocenter, were and , respectively. The setup accuracy of conventional stereotactic coordinates and the isocenter accuracy of CBCT complied with AAPM Report No. 54.PACS number: 87.53.Ly
Accuracy of iView and PIPSpro registration software
Authors: Pallotta Stefania , Ceroti Marco , Bucciolini Marta 
Published: February 2017

In radiotherapy, treatment portal images and digitally reconstructed radiographs (DRRs) are used to monitor patient setup during clinical routine. The output of the registration between the portal image and the reference DRR indicates the patient displacement. If the registration is not reliable, the patient positioning will not be accurate. The aim of this work is to assess the intrinsic and the global accuracy of iView and PIPSpro, two widely used registration software programs that implement a manual and a semiautomatic approach, respectively. The intrinsic accuracy was tested using a computer generated phantom, while the overall accuracy was evaluated registering the portal images and the DRRs of an Alderson RANDO phantom. For DRRs, four treatment planning systems (TPS) and three CT studies with different slice thicknesses were considered.This study demonstrates that the intrinsic accuracy of iView and PIPSpro were within 1 pixel and 1°. Using a DRR extracted from a 2 mm CT study, the overall accuracy of both methods was about 2 mm and 1°. When thicker CT slices are considered, the global accuracy of both methods worsens, and differences larger than 1.5° between the rotation parameters estimated with iView and PIPSpro are evident. The results obtained with iView and PIPSpro were nearly equivalent.PACS numbers: 87.57.nj, 87.57.cp
Helical TomoTherapy versus sterotactic Gamma Knife radiosurgery in the treatment of single and multiple brain tumors: a dosimetric comparison
Authors: Kumar Tushar , Rakowski Joseph , Zhao Bo , Alkhafaji Mazin , Burmeister Jacob , Austin Tammy , Vlachaki Maria 
Published: February 2017

The objective was to compare the dosimetry of Helical TomoTherapy (TOMO) and Gamma Knife (GK) treatment plans for tumor and normal brain in the treatment of single and multiple brain tumors. An anthropomorphic Rando Head phantom was used to compare the dosimetry of TOMO and GK. Eight brain tumors of various shapes, sizes and locations were used to generate 10 plans. The radiation dose was 20 Gy prescribed to the 100% isodose line for TOMO plans and to the 50% for the GK plans. Dose Volume Histograms for tumor and brain were compared. Equivalent Uniform Dose (gEUD), Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) were performed and used for plan comparisons. Average minimum, mean, median and maximum tumor doses were 19.93, 27.83, 27.38, 39.60 Gy for GK and 20.17, 20.60, 20.59, 20.90 Gy for TOMO. Average gEUD values for tumor and normal brain were 25.0 and 7.2 Gy for GK and 20.7 and 8.1 Gy for TOMO. Conformity indices (CI) were similar for both modalities. Gradient indices (GI) were greater for TOMO. A combination plan was also generated using all eight tumors. TOMO was able to target all eight tumors simultaneously resulting in mean tumor and brain doses of 20.5 and 9.35 Gy, respectively. Due to the maximum limit of 50 beams per plan, GK was unable to provide a treatment plan for all eight tumors. GK provides an advantage for all tumor sizes with respect to tumor and normal brain dose. Clinical studies are needed to correlate these dosimetric findings with patient outcomes.PACS number: 87.55‐x
Monte Carlo investigation of energy response of various detector materials in and brachytherapy dosimetry
Authors: Selvam T. Palani , Keshavkumar Biju 
Published: February 2017

Relative absorbed‐dose energy response correction R for different detector materials in water, PMMA and polystyrene phantoms are calculated using Monte Carlo‐based EGSnrc code system for and brachytherapy sources. The values of R obtained for source are 1.41, 0.92, 3.97, 0.47, 8.32 and 1.10, respectively, for detector materials LiF, , diamond, silicon diode and air. These values are insensitive to source‐to‐detector distance and phantom material. For source, R is sensitive to source‐to‐detector distance for detector materials other than air and . For silicon, R increases from 3 to 4.23 when depth in water is increased from 0.5 cm to 15 cm. For source, the values of R obtained for air and in PMMA and polystyrene phantoms are comparable to that obtained in water. However, LiF, Si and show enhanced response and diamond shows decreased response in PMMA and polystyrene phantoms than in water.PACS number: 87.53.Jw
Practical quantitative measurement of graticule misalignment relative to collimator axis of rotation
Authors: Halabi Tarek , Faddegon Bruce 
Published: February 2017

We design a practical procedure for measuring translational and rotational misalignment of graticule with collimator axis of rotation and collimator jaws, respectively. The procedure's quantitative results are accurate to less than 0.2 mm (at isocenter) and do not assume alignment of radiation focal spot with collimator axis of rotation. When provided with these quantitative results, the manufacturer can custom‐adjust graticules to the purchaser's collimator head.PACS number: 87.56.Fc
Verification of IMRT dose calculations using AAA and PBC algorithms in dose buildup regions
Authors: Oinam Arun S. , Singh Lakhwant 
Published: February 2017

The purpose of this comparative study was to test the accuracy of anisotropic analytical algorithm (AAA) and pencil beam convolution (PBC) algorithms of Eclipse treatment planning system (TPS) for dose calculations in the low‐ and high‐dose buildup regions. AAA and PBC algorithms were used to create two intensity‐modulated radiotherapy (IMRT) plans of the same optimal fluence generated from a clinically simulated oropharynx case in an in‐house fabricated head and neck phantom. The TPS computed buildup doses were compared with the corresponding measured doses in the phantom using thermoluminescence dosimeters (TLD 100). Analysis of dose distribution calculated using PBC and AAA shows an increase in gamma value in the dose buildup region indicating large dose deviation. For the surface areas of 1, 50 and , PBC overestimates doses as compared to AAA calculated value in the range of 1.34%–3.62% at 0.6 cm depth, 1.74%–2.96% at 0.4 cm depth, and 1.96%–4.06% at 0.2 cm depth, respectively. In high‐dose buildup region, AAA calculated doses were lower by an average of , while PBC was overestimated by as compared to TLD measured doses at 0.2 cm depth. However, at 0.4 and 0.6 cm depth, PBC overestimated TLD measured doses by and , respectively, while AAA underestimated the TLD measured doses by and at the same respective depth. In low‐dose buildup region, both AAA and PBC overestimated the TLD measured doses at all depths except by AAA at 0.2 cm depth. The differences between AAA and PBC at all depths were statistically significant in high‐dose buildup region, whereas it is not statistically significant in low‐dose buildup region. In conclusion, AAA calculated the dose more accurately than PBC in clinically important high‐dose buildup region at 0.4 cm and 0.6 cm depths. The use of an orfit cast increases the dose buildup effect, and this buildup effect decreases with depth.PACS number: 87.53.Bn
Study of DQE dependence with beam quality on GE Essential mammography flat panel
Authors: García‐Mollá Rafael , Linares Rafael Ayala Rafael 
Published: February 2017

This paper deals with the analysis of the behavior of objective image quality parameters for the new GE Senographe Essential FFDM system, in particular its dependence with beam quality. The detector consists of an indirect conversion a‐Si flat panel coupled to a CsI:Tl scintillator. The system under study has gone through a series of relevant modifications in flat panel with respect to the previous model (GE Senographe DS 2000). These changes in the detector modify its performance and are intended to favor advanced applications like tomosynthesis, which uses harder beam spectra and lower doses per exposure than conventional FFDM. Although our system does not have tomosynthesis implemented, we noticed that most clinical explorations were performed by automatically selecting a harder spectrum than that of typical use in FFDM (Rh/Rh 28–30 kV instead of Mo/Mo 28 kV). Since flat‐panel optimization for tomosynthesis influences the usual FFDM clinical performance, the new detector behavior needed to be investigated. Therefore, the aim of our study is evaluating the dependence of the detector performance for different beam spectra and exposure levels. In this way, we covered the clinical beam quality range (Rh/Rh 28–30 kV) and we extended the study to even harder spectra (Rh/Rh 34 kV). Detector performance is quantified by means of modulation transfer function (MTF), normalized noise power spectrum (NNPS) and detective quantum efficiency (DQE). We found that flat‐panel optimization results in slightly – but statistically significant – higher DQE values as beam quality increases, which is contrary to the expected behavior. This positive correlation between beam quality and DQE is also diametrically opposite to that of the previous model by the same manufacturer. As a direct consequence, usual FFDM takes advantage of the changes in the detector, as less exposure is needed to achieve the same DQE if harder beams are used.PACS number: 87.59.ej
Small field electron beam dosimetry using MOSFET detector
Authors: Amin Md Nurul , Heaton Robert , Norrlinger Bern , Islam Mohammad K. 
Published: February 2017

The dosimetry of very small electron fields can be challenging due to relative shifts in percent depth‐dose curves, including the location of , and lack of lateral electronic equilibrium in an ion chamber when placed in the beam. Conventionally a small parallel plate chamber or film is utilized to perform small field electron beam dosimetry. Since modern radiotherapy departments are becoming filmless in favor of electronic imaging, an alternate and readily available clinical dosimeter needs to be explored. We have studied the performance of MOSFET as a relative dosimeter in small field electron beams. The reproducibility, linearity and sensitivity of a high‐sensitivity microMOSFET were investigated for clinical electron beams. In addition, the percent depth doses, output factors and profiles have been measured in a water tank with MOSFET and compared with those measured by an ion chamber for a range of field sizes from 1 cm diameter to for 6, 12, 16 and 20 MeV beams. Similar comparative measurements were also performed with MOSFET and films in solid water phantom. The MOSFET sensitivity was found to be practically constant over the range of field sizes investigated. The dose response was found to be linear and reproducible (within for 100 cGy). An excellent agreement was observed among the central axis depth dose curves measured using MOSFET, film and ion chamber. The output factors measured with MOSFET for small fields agreed to within 3% with those measured by film dosimetry. Overall results indicate that MOSFET can be utilized to perform dosimetry for small field electron beam.PACS number: 87.55.Qr
A new approach to measure dwell position inaccuracy in HDR ring applicators – quantification and corrective QA
Authors: Jangda Abdul Qadir , Hussein Sherali , Rehman Zaka 
Published: February 2017

As part of quality assurance (QA) in high dose rate brachytherapy, it is necessary to verify that the source dwell positions correspond to the radiographic markers used in simulation and treatment planning. The procedure is well established for linear tandem applicators. However, with the advent of ring applicators, this has become more critical and challenging. This work describes a new approach to determine positional inaccuracies for ring applicators in which the dummy markers are imaged just once and their dwell positions characterized with respect to an applicator‐defined axis. The radiograph serves as a reference for dummy markers for comparison with all subsequent measurements in which the active sources are autoradiographed at different offsets – thus obviating the back‐and‐forth transferring of setup between afterloader and simulator. The method has been used specifically to characterize the Varian GammaMed 60° ring applicator, but it may be adapted to any other applicator. The results show that an offset of 1–2 mm minimizes the overall inaccuracy to within .PACS numbers: 87.53.Jw, 87.56.Fc, 87.56.B, 87.56.bg, 87.56.‐v
Cone beam CT pre‐ and post‐daily treatment for assessing geometrical and dosimetric intrafraction variability during radiotherapy of prostate cancer
Authors: Reggiori Giacomo , Mancosu Pietro , Tozzi Angelo , Cantone Marie C , Castiglioni Simona , Lattuada Paola , Lobefalo Francesca , Cozzi Luca , Fogliata Antonella , Navarria Piera , Scorsetti Marta 
Published: February 2017

The purpose of this study was to quantify the relationship between treatment time and dose uncertainty due to intrafraction organ motion in prostate cancer radiotherapy (RT). Ten consecutive patients with prostate cancer treated by radical RT by volumetric modulated arc therapy (RapidArc) were considered. For each patient, pre‐ and post‐treatment cone beam computed tomography (CBCT) was performed in 10 fractions. The prostate, rectum and bladder were contoured on each CBCT. The change in organ position, volume and dosimetric uncertainty induced by organ motion were evaluated. Interval time between the two CBCTs ranged between 4 and 16 min (mean min). Treatment with intrafraction prostate motion and were 24% and 5%, respectively. Regarding change in centroid position and volume, a poor time correlation was found for target and rectum, while a constant increase was obtained for bladder. The agreement index was highly correlated to time ( for bladder, for rectum, and for prostate). In terms of difference in dose volume histogram between pre‐ and post‐CBCT, the dose uncertainties for the targets and rectum amplified with the increasing time. The increasing intrafraction dose uncertainty with time requires the use of an RT technique with minimization of treatment time to improve confidence in planning dose distribution.PACS number: 87.55.tm
Interface dosimetry for electronic brachytherapy intracavitary breast balloon applicators
Authors: Segala James J. , Cardarelli Gene A. , Hiatt Jessica R. , Curran Bruce H. , Sternick Edward S. 
Published: February 2017

In this study, we evaluate the attenuation of the dose due to barium‐impregnation in the region between the surface of an electronic brachytherapy (EBT) balloon applicator for accelerated partial breast irradiation (APBI) and the prescription point at 1 cm depth in tissue. To perform the study, depth dose curves were calculated using a general purpose multi‐particle transport code (FLUKA) for a range of balloon wall thicknesses with and without barium impregnation. Numerical data were verified with experimental readings using a parallel plate extrapolation ionization chamber for different wall thicknesses. Depth dose curves computed using both numerical and experimental methods show a 6.0% attenuation of the dose at the 1.0 cm prescription line due to the impregnation of barium in the balloon material, which agrees well with the manufacturer's specification. By applying this single attenuation factor, dose calculations throughout the entire planned volume are uniformly affected. However, at the balloon surface, attenuation on the order of 18.0% is observed. The AAPM TG‐43 source data currently incorporated in commercially‐available treatment planning systems do not account for the variable dose distributions attributable to balloon wall attenuation. Our results show that variable attenuation factors that may have clinical significance should be applied in order to determine near‐surface dose distributions when using barium impregnated balloons for intracavitary breast brachytherapy. Dose distributions at distances greater than 1 cm from the surface of the balloon appear to be accurately represented without further modification.PACS numbers: 87.53.Jw, 87.55.D‐, 87.55.d, 87.55.Qr, 87.55.K‐
RapidArc quality assurance through MapCHECK
Authors: Gloi Aime M. , Buchanan Robert E. , Zuge Corrie L. , Goettler AnnDrea M. 
Published: February 2017

The purpose is to devise a patient‐specific quality assurance procedure for RapidArc radiotherapy using the MapCHECK detector array. We use our existing MapCHECK system and a Solid Water phantom with an embedded ion chamber to develop a quality assurance procedure for RapidArc treatment after commissioning. The ion chamber used to measure the absolute dose is surrounded by 6 cm layers of solid water on the anterior and posterior sides. Partial arcs derived from the treatment planning system were used with MapCHECK to determine the actual shape of the dose and correct for the angular dependence. The ion chamber measurements were within 1% of the absolute doses predicted by the Eclipse treatment system. When using a partial arc from 60° to 300° on the MapCHECK array (gamma index : 3%, 3 mm, 10% threshold), we obtain a 97.52% average passing rate. A combination of ion chamber phantoms, partial arcs and the MapCHECK system can be used for quality assurance of RapidArc therapies.PACS number: 3.6.96.0