bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐T‐33: 3D Conformal Brachytherapy for Partial Breast Irradiation
Authors: Zhu J , Crossan P , Griffin V
Published: April 2010

Purpose: Partial‐breast brachy irradiation following the lumpectomy is effective in treatment women with early‐stage breast cancer and is being broadly implemented in clinic. However, the current popular radiation treatments are limited to treat regularly shaped, spherical or ellipsoid, targets with strictly defined skin and rib distances. In reality, many treatment targets cannot be defined perfectly spherical or ellipsoid due to the irregularly shaped lumpectomy cavity and/or skin distance or nearby critical organ limits. In such cases, the 3D conformal brachytherapy becomes necessary. Methods and Materials: Multiple channel breast brachytherapy applicator is used to replace the single channel applicator for 3D conformal brachytherapy. Patient is CT scanned with slice thickness at 1 mm. The target and critical organs are delineated by radiation oncologist and planning staff. Brachytherapy source dwell positions and dwell time are the parameters for treatment planning optimization. The inverse planning and graphic optimization of Plato treatment planning system (Nucletron, Columbia, Maryland) are utilized to achieve conformal radiation dose to the target and spare the critical organs. Treatment plans are evaluated based on the isodose curves displayed on top of CT images, the dose conformality to the target and the dose volume histograms of target and critical organs. Results: Clinic cases with irregularly shaped targets and/or short skin distance, or closely located critical organs are planned and treated with 3D conformal brachytherapy. All the plans are achieved with satisfied dose distribution, i.e. good dose conformality to the target and sparing of critical organs. The after treatment following up demonstrates successful radiation treatment and good control of patient skin reaction. Conclusion: The 3D conformal brachytherapy for partial breast irradiation allow us to better treat the irregularly shaped targets and spare the critical organs. It also releases the restrictions of skin distance and air cavity volume in the selection of patients.
SU‐FF‐T‐36: Prostate Brachytherapy Seed Immobilization: Three Novel Techniques as Potential Candidates for Robotic Implementation
Authors: Podder T , Yan K , Yu Y
Published: April 2010

Purpose: Local movement and distant migration of radioactive seeds from prostate implants are known to occur frequently. We have developed three novel techniques amendable to robotic delivery for reducing seed migration/movement. This study compares the efficacy of these techniques and investigates the effect of these techniques on I‐125 radioactive seeds. Method and Materials: Three techniques developed for preventing seed movement/migration were: surgical glue (BioGlue®) to seal needle track, Diathermy Coagulation, and Laser Coagulation. The selection of mode and power for laser and diathermy were based on the effectiveness of tissue welding with least tissue lesion, charring and smoke. Dummy seeds were implanted in fresh bovine liver phantoms with and without applying immobilization techniques; then the phantoms were given 10hr continuous rocking motion. Seed movements were measured from initial and final x‐ray films. Sustainability of radioactive seeds in these techniques was evaluated by exposing live I‐125 radioactive seeds (0.63mCi/seed) in surgical glue, laser and diathermy energy. Activities of the seeds were individually measured and recorded before and after exposing to glue, laser and diathermy. Wipe test was performed to ensure no leakage. Results: Without applying the immobilization techniques, seed movements were (max/mean): 34.4mm/18.7mm. Seed movements after using immobilization techniques were (max/mean): in Surgical glue 1.1mm/0.9mm; in Diathermy coagulation 2.1mm/1mm; in Laser coagulation 2.9mm/1.1mm. Evaluation of dosimetric distribution indicated that non‐immobilized seed movement would alter planned dose distribution considerately, while by using immobilization techniques the deviations in dose distribution were greatly reduced. No significant effects of immobilization techniques were observed on radioactivity of the seeds. Wipe test ensured no leakage. Conclusions: Results from the experiments revealed that these three novel techniques are quite promising for improving dose distribution by reducing seed movement and migration. Moreover, these methods did not alter normal radioactivity of I‐125 seeds and preserved encapsulation. Acknowledgement: supported by DOD‐W81XWH‐06‐1‐0227.
SU‐FF‐T‐43: Feasibility of Using Radioactive Bone Cement to Treat Vertebral Metastases
Authors: Kaneko T , Sehgal V , Skinner H , Al‐Ghazi M , Hoang B , Ramsinghani N , Keyak J
Published: April 2010

Purpose: To evaluate the feasibility of using radioactive bone cement to deliver therapeutic radiation to the vertebral body without undue risk to the spinal cord, i.e. vertebral brachytherapy. Method and Materials: CT‐scan based Monte Carlo N‐Particle radiation transport models, consisting of a three‐dimensional rectangular lattice of 0.625×0.625×1.25‐mm voxels, were created of a T‐12 human cadaveric vertebra. Trabecular and cortical bone were both represented by a spectrum of thirty complementary volume fractions of solid cortical bone and bone marrow, and all soft tissue was represented as a single material. A cylindrical volume of radioactive bone cement was simulated within the model, and two candidate radioisotopes were studied: P‐32 and Sr‐89. Thirty million particle histories were simulated (MCNPX v.2.5.0) to characterize the dose distribution within the vertebral body. Results: The dose distributions for both radioisotopes were axisymmetric about the cement implant and rapidly decreased with increasing distance from the cement. Initial activities of 0.94 mCi and 0.51 mCi for P‐32 and Sr‐89, respectively, would deliver >300 Gy to bone within 1.6 mm of the cement implant and >80 Gy to bone within 2.8 mm, while keeping the dose at 3.4 mm under 45 Gy. Conclusion: The predicted dose distributions show that a therapeutic radiation dose would be delivered to all bone within ∼3 mm of the cement without undue risk to tissue beyond 3.4 mm (such as the spinal cord), indicating preliminary feasibility of this technique. With further development, this technology may yield a clinically‐feasible procedure that would eliminate the need for 10 radiotherapy sessions, making it convenient for the patient, while potentially improving the clinical outcome by delivering a higher dose to the tumor and a lower dose to the spinal cord than conventional radiotherapy.

Conflict of Interest (only if applicable): Research sponsored by Bone‐Rad Therapeutics, Inc.
SU‐FF‐T‐51: Robotically‐Assisted Minimally Invasive Brachytherapy: Dosimetric Aspects
Authors: Hanley J , Napoli J , Barbiere J , Tuna M , Smith D , Godfrey L
Published: April 2010

Purpose: To investigate the dosimetric aspects of robotically‐assisted minimally invasive brachytherapy. Materials and Methods: Using the Intuitive Surgical DaVinci S System, the following were inserted into a porcine abdominopelvic cavity through a 12 mm auxiliary port and sutured directly to the pelvic sidewall: three 6‐French catheters; the Xoft Axxent delivery system; a prototype minimally invasive applicator (MIA). Plans were generated in Nucletron's treatment planning software for an Ir‐192 source and the Xoft 50 kV source. The ability of the prototype MIA to reproducibly position catheters was tested using film dosimetry. Other applicators were designed to allow an en face application of the source, and various catheter arrangements were investigated. For the en face application, the sensitivity of the delivered dose to random deviations from normal incidence of the catheters (⩽ 5 degrees) and regular catheter spacing were tested. Results: All three trials for introducing the catheters were performed with ease by the surgeon. After the apparatus was sutured into place, it maintained a fixed geometry. The dosimetric measurements using GafChromic EBT film showed a uniform distribution of dose. The treatment plan for the en‐face arrangement using the Xoft source with 16 catheters at random angles showed a deviation from the planned dose of ⩽ 0.39%.

Conclusions: The feasibility of performing robotically‐assisted minimally invasive brachytherapy was demonstrated for techniques utilizing both parallel and en face geometries. A customized applicator was designed to deliver a uniform dose to the target. The reproducibility of the device was confirmed with film dosimetry. For the geometries tested, the en face application was found to be insensitive to random deviations of the catheters of up to 5 degrees from normal incidence. These techniques may be used for minimally invasive intra‐operative or post‐operative brachytherapy procedures using real‐time or atlas‐based planning.
SU‐FF‐T‐52: A Method to Measure the Output of IORT Applicators Used with the Axxent Electronic Brachytherapy System
Authors: Sabbas A , Kulidzhanov F , Trichter S , Chen H , Parashar B , Chao C
Published: April 2010

Purpose: To measure the output of IORT applicators used with the miniaturized 50 kVp X‐Ray source of the Axxent electronic brachytherapy system. Method and Materials: Brachytherapy dose calculations are based on a set of measured or calculated dosimetry parameters for the Axxent X‐Ray source. They are used to calculate dose when the X‐Ray source is surrounded by soft tissue. Clinical examples are partial breast irradiation or intracavitary vaginal applications. In situations though, where the X‐Ray source is within an applicator external to the tissue, direct output measurements for the specific treatment geometry are needed. The Axxent shielded test fixture was first used to obtain a calibration factor for a pinpoint chamber. The fixture allows for both the chamber and the source to be inserted in separate channels within a phantom. The source dwell position is set directly opposite to the chamber and at a set distance. The TG43 parameters and the dwell time are used to calculate the dose at the chamber's location. The calibration factor is obtained from the chamber's reading. The applicator with the radiation source inside is then made to touch the phantom. The chamber is positioned within the phantom at the appropriate depth. The output calculation is based on the chamber's reading and the source's dwell time and is referenced to a nominal Air Kerma Strength. We have supplemented our chamber measurements with relative GAFCHROMIC film dosimetry at various depths in a Solid Water phantom. Results: We have used the Axxent radiation source to deliver a single dose radiation treatment intra‐operatively. A table of dwell times vs. dose for various applicators is prepared for use in the O.R. Conclusion: We have found the use of a list of dwell times versus prescription dose and applicator type easy and convenient to implement during IORT cases.
SU‐FF‐T‐65: A Phantom Study to Characterize a Doppler Ultrasound Scanner for Application in Prostate Brachytherapy
Authors: Sandhu G , Khan R , Dunscombe P
Published: April 2010

Purpose: To characterize the Doppler modes of an ultrasound scanner, in a phantom, for potential use in prostate brachytherapy. Method and Materials: A flow phantom has been designed and fabricated. The one‐directional flow was generated with the help of peristaltic pump. Images of the phantom were obtained using the color Doppler (CD) and power Doppler (PD) modes. The effect of the instrument's parameters, viz color gain, pulse repetition frequency and wall filter, on flow detection by these Doppler modes has been studied. Results: The Doppler gain has a significant effect on the flow detection in both CD and PD modes. Flow detection in the color Doppler mode is found to be affected by the pulse repetition frequency (PRF). The wall filter shows no effect on flow detection by CD mode, however reducing the wall filter to low value gives aliasing in PD mode. Conclusion: This study can help to identify the optimal setting for acquisition of prostate images using Doppler modes. Inappropriate setting of these parameters can either display incorrect information or can hide useful clinical information. Recognizing the flow in the prostate can help to identify regions of increased blood flow. As an increased flow in prostate vessels may demonstrate the presence of cancer; it can help to recognize the regions within the prostate gland, which could be histopathologically positive for cancer. By delivering a relatively large number of seeds to the areas of hyperflow, dose can be maximized to the cancerous region and possibly be reduced to the surrounding critical organs. This has the potential to improve the treatment outcome and reduce treatment related complications.
SU‐FF‐T‐66: Dwell Position Inaccuracy in the Varian GammaMed HDR Ring Applicator
Authors: Stern R , Liu T
Published: April 2010

Purpose: Varian has issued two Product Notification Letters warning of known inaccuracies in dwell position for their GammaMed HDR ring applicators. This study measures actual dwell positions for two sets of ring applicators and tests a correction methodology. Method and Materials: Ring applicators were taped onto Kodak Ready‐Pack EDR2 film. Solid water was placed under the film and on top of the applicators, primarily for stability and immobilization. An x‐ray exposure was made using a conventional simulator, then an autoradiograph was made with the HDR source at different dwell positions. A total of 22 double exposures were made for each of the three ring applicators (30°, 45°, and 60°) of set 1 and 4 double exposures for each applicator in set 2. Source position measurement was performed within the BrachyVision treatment planning program, per Varian recommendations. Films were digitized and imported in BrachyVision, and the distance from the inner tip of the ring to the center of each dwell was determined using system measurement tools. Measured distance was compared to the programmed/expected distance. Results: For all but the most distal dwell positions, which are indistinguishable due to drag of the source within the ring, the autoradiograph was distal to the expected position. Differences averaged 0.34 cm (range 0.17 cm – 0.59 cm) across all positions in all rings. To correct for this displacement, during planning the tip of the ring is extrapolated distally beyond its actual position in the patient image set and a proximal offset of the same distance is applied to the dwell positions. A global shift of 0.3 mm corrected all but the most proximal dwell to within ±2mm of the planned position. Conclusion: Measured source positions were shifted distally from expected positions. A single shift value can be used to correct all rings to within ±2mm.
SU‐FF‐T‐84: DIRART ‐ a Software Suite for Deformable Image Registration and Adaptive Radiotherapy Research
Authors: Yang D , El Naqa I , Apte A , Wu Y , Goddu S , Mutic S , Deasy J , Low D
Published: April 2010

Purpose: Recent years have witnessed tremendous progress in IGRT technology and potential possibilities for adapting treatment planning on a daily basis. However, there is a lack in having software tools toward this goal. Therefore, we have implemented a software suite, DIRART, for deformable image registration (DIR) plus adaptive radiotherapy (ART) research. Method: DIRART is a large set of programs developed using MATLAB. It contains DIR algorithms, common ART functions, integrated graphics user interfaces, visualization features, and dose metrics analysis functions. In addition, it complementarily works together with CERR (Computational Environment for Radiotherapy Research) to offer more functions. DIRART is designed around the concepts of the interactive RT objects, including images, structures, doses and deformation vector fields (DVF) etc. Results: By exchanging RT objects with TPS via DICOM‐RT files, DIRART provides a full featured working environment for ART related research tasks. It is capable of transforming dose distributions and structures between the planning CT and the daily images according to the computed DVF so that such RT information could be viewed and evaluated on either image sets. It can also rescale, subtract and sum up the transformed doses, and convert isodose lines to structures. For DIR applications, DIRART is a toolbox which provides 20+ DIR algorithms, including the newer inverse consistency algorithms to provide consistency DVF in both directions with better accuracy. As a DIR research environment, DIRART dose not only provide a good set of image preprocessing algorithms and post‐processing functions to facilitate the development and testing of DIR algorithms, but also offers a good amount of options for results visualization, evaluation and validation. Conclusion: DIRART is designed in a data‐oriented style with focus on usability, user‐friendliness, performance, accuracy, flexibility, features, configurability and stability. It has great potential for the ART and DIR research.
SU‐FF‐T‐86: The Effect of Set‐Up Errors On the Final Target Dose Distribution in Step‐And‐Shoot IMRT Plans Compared to Helical Tomotherapy Plans
Authors: Sarkar V , Shi C , Papanikolaou N
Published: April 2010

Purpose: To compare the effect of small setup errors on the final target dose distribution when using step and shoot IMRT and helical tomotherapy. Method and Materials: For three head and neck patients, two plans were created: one for delivery on a Tomotherapy system and the second one, using the Pinnacle treatment planning system, for delivery as step‐and‐shoot IMRT. After the patient was set up on the Tomotherapy couch, a megavoltage CT was acquired. This CT was imported to the adaptive planning module of Tomotherapy and the dose was recalculated assuming the patient was not repositioned prior to treatment. The shifts that would have been required to correctly position the patient were used to alter the treatment isocenter in the pinnacle plan and the dose was recalculated. This process was repeated for seven fractions in each patient and the doses from all fractions were summed up to create a PTV DVH for each case. Results: For all three cases, the final delivered DVH showed deviations from the planned DVH. It was apparent that the discrepancy between the planned and delivered DVHs was much larger for the tomotherapy plans than the step‐and‐shoot plans. Conclusion: The results show that extra care should be exhibited in properly positioning the patient when treating with tomotherapy.
SU‐FF‐T‐87: Dose Reconstruction of Intracranial Hypofractionated Helical Tomotherapy Treatments for Adaptive Planning
Authors: Sheth N , Yang C , Murphy S , Weiss M , Sim S
Published: April 2010

Purpose: To evaluate the dosimetry of delivered hypofractionated image guided helical tomotherapy treatments for adaptive planning. Method and Materials: Twelve patients with intracranial lesions received hypofractionated radiation treatments using helical tomotherapy. Image guidance MVCTs are merged with the planning kVCT images. The treatment deliveries then are calculated with a fine dose grid over the associated merged images. The summation dosimetry of the delivered treatments to the targets are analyzed using TomoTherapy adaptive planning software (TomoTherapy, Madison, WI) to determine if tuning the current plan to the patient's daily treatment position would have been desirable. Results: On average, the difference between the planned treatments and delivered treatments in the coverage of the GTVs (n=33) by the prescription dose for all patients is 4.6%±13.1%. When selecting 99% of the prescription dose, the difference of mean GTV coverage between planned and delivered treatments reduces to 0.1%±0.4%. For the PTVs (n =33), the mean variation in coverage from the planned to delivered treatments by the prescription dose is 5.2%±10.0%. The average difference between planned versus delivered treatment coverage of the PTVs reduces to 0.5%±1.0% at 99% of the prescription dose. Conclusion: Due to the short course and high dose per delivery of hypofractionated radiation treatments, the importance of evaluating and if necessary adapting the planned treatment is pronounced for intracranial patients. As these IMRT plans create a sharp dose gradient there is notable incongruence between the planned and delivered coverage of the targets encompassed by the prescription dose. While changing the treatment plan to perform adaptive therapy seems to be the best solution, however, revision of the treated plans in this study would not be necessary as there is excellent agreement of target coverage between the planned and the delivered image guided helical tomotherapy treatments by the selected 99% of the prescription dose.
SU‐FF‐T‐88: Image Registration for Real‐Time Dose Calculation of Adaptive Radiation Therapy
Authors: Hu Y , Zhu T
Published: April 2010

Purpose: To enhance the speed and accuracy of certain treatment plan in radiation therapy, a real‐time dose calculation strategy is performed based on Fast Fourier Transformation (FFT) and CT image registration. For this purpose, different registration methods are achieved by using Insight Segmentation and Registration Toolkit (ITK) in MATLAB. Method and materials: Our group developed an efficient method for kernel calculation for pencil beam convolution‐superposition based on FFT. In this paper, different image registration methods are developed in MATLAB by using ITK, such as rigid 3D, similarity 3D, Demons deformation and BSpline based Free Form. As ITK is written and used in a C++ template, smart pointer and generic structure, an open source wrapper MATITK is modified to facilitate the use of its image processing capabilities while working in the high‐level environment of MATLAB. The image registration methods are demonstrated on head and neck (H&N) CT image sets of 6 patients. The results of evaluation and visualization for the registration are presented. Results and discussion: Transformation similarity and computation complexity as evaluation criteria are compared between rigid and deformable registration methods. Judging from the mutual information histogram and mean square metric, the deformable registration will get more improvement on similarity than the rigid registration. Checkerboard composites of the reference and registered images are displayed. The computational time of deformable registration are 10∼20 times longer with the whole set of images because of the pre‐processing, complicated transformation matrix and more parameters. A similarity3D registration method is adopted for the image registration of H&N radiation therapy to trade off between registration effect and the time consumption. Conclusion: The image registration can greatly contribute to the automatic contour adjustment and dose deformation for adaptive radiation therapy. A GUI program will be designed for the customized deformation region to speed up deformable registration.
SU‐FF‐T‐90: Adaptive Radiotherapy Treatment Re‐Planning For Head And Neck Cancer Patients
Authors: Al‐Basheer A , Greskovich J , Boerste M
Published: April 2010

Purpose: To demonstrate the need for adaptive treatment re‐planning in Head and Neck (H&N) cancer patients undergoing Intensity Modulated Radiation Therapy (IMRT). Radiation induced anatomical changes can lead to significant variation of dose delivered compared to the initial planned dose distribution. Methods and Materials: 3 H&N cancer patients with locally advanced stage IVA or IVB disease with large lymph nodes (4cm, 5.5cm, 7cm) underwent a second PET‐CT scan at 36Gy for adaptive re‐planning since they clinically had a partial response to definitive chemoradiation. We overlaid the initial CT scan into the new CT scan to accurately calculate dose delivered by the new IMRT plan to the initial CT scan. We evaluated the changes in the different volumes including critical organs. Further, we evaluated the changes in the dose‐volume histogram (DVH) for the new ROIs (spinal cord, salivary glands, CT‐GTV, PTV). Results: Comparison between the two CT scans showed significant change in target and normal tissue volumes. For one study case, the left parotid volume decreased by 21% while the GTV decreased by 37%. The DVH analysis for the superimposed second CT with the initial IMRT plan showed small but meaningful underdosing to CT‐GTV and PTV. Moreover, 1% of the new CT‐GTV received <54Gy (prescribed dose: 58Gy); 1% of the new PTV received <46Gy (prescribed dose: 58Gy). The maximum spinal cord dose increased 27.1% from 27.7Gy to 35.2Gy. The mean left parotid dose was the same. The mean right parotid dose increased by 15.8%. Conclusions: For H&N cancer, adaptive mid‐treatment re‐planning should be considered for more accurate dose delivery especially when significant clinical response is noted on physical exam or daily/weekly imaging. Significant changes in the DVH can take place for normal structure as well as the CTV and the CT‐GTV due to anatomical changes during the course of treatment.
SU‐FF‐T‐104: Simultaneous Boost and Skin Dose Toxicity Reduction for Breast Cancer Treatments Using IMRT and RapidArc
Authors: Roa D , Chung R , Ramsinghani N , Al‐Ghazi M
Published: April 2010

Purpose: To reduce the overall treatment fractions by about a week and minimize the skin dose toxicity by treating stage I‐II breast cancer patients with IMRT and eventually RapidArc both, incorporating a simultaneous boost to the tumor bed. Background: Radiation therapy is prescribed to breast cancer patients after receiving a lumpectomy or mastectomy to remove cancerous tissue. In the past, treatments using two 6MV tangential fields with wedges followed by an electron boost to the tumor bed have often resulted in unnecessary dose to unaffected tissue. As a consequence, patients experienced edema, pain, desquamation, discoloration, and other negative side‐effects. IMRT and RapidArc are treatment techniques where the dose can be tailored to the shape of the target, reducing the exposure of adjacent tissues to unnecessary radiation and potential damage. Methods and Materials: Skin dose measurements using TLDs from 35 patients receiving conventional radiotherapy were collected over a period of 9 months. Seven 3×3×1 mm3 TLD chips were placed on the 4 quadrants of a patient's breast and 3 on the inframmary fold. Same TLD arrangement was used for patients receiving IMRT or RapidArc which, in addition, incorporated a simultaneous boost of an additional ∼10Gy delivered to the tumor bed, within the regular 28 treatment sessions. Results: Preliminary data indicates percent differences of 4–20% less skin dose on the IMRT/RapidArc cases, primarily in the inframammary fold region. Furthermore, our skin dose data on the IMRT/RapidArc treatments indicates a strong correlation to the size and shape of the breast under treatment suggesting that patients with large breast may experience little skin sparing — confirming observations reported elsewhere. Dose to heart, lungs and contralateral breast were kept to a minimum. Conclusion: This work continues with more breast patients receiving IMRT or RapidArc, and thus far the data continues to support our preliminary observations.
SU‐FF‐T‐115: Dosimetric Comparison of Helical Tomotherapy with Conventional Techniques for Simultaneous Irradiation of Prone Breast and Regional Lymph Nodes
Authors: Kainz K , White J , Chen G , Li X
Published: April 2010

Purpose: to determine whether helical tomotherapy can simultaneously irradiate the prone breast and regional lymph nodes with target coverage and organ‐at‐risk (OAR) sparing comparable to what is achievable using conventional 3DCRT or fixed‐beam IMRT techniques. Method and Materials: plans were generated upon the CT images of a right‐breast patient previously simulated and treated prone. Target structures included the ipsilateral breast, axillary nodes, supraclavicular nodes, and internal mammary chain nodes. At least 95% of each target was to receive 45 Gy in 25 fractions. OAR contours included the contralateral breast, each lung, heart, spinal cord, esophagus, and thyroid. The tomotherapy plan was generated using the TomoTherapy Hi‐Art System (TomoTherapy, Inc., Madison, WI). The XiO treatment planning system (CMS, Inc., St. Louis, MO) was used to produce a conventional 3DCRT plan (field‐in‐field technique) and a 5‐field IMRT plan. Results: target dose homogeneity for the tomotherapy plan was for most dose‐volume parameters comparable to or better than that achieved by 3DCRT or IMRT. In particular, the V45, V40.5, and V42.8 values from tomotherapy were comparable to 3DCRT and IMRT for all targets except the supraclavicular nodes, for which the tomotherapy and IMRT plans were superior. For the ipsilateral lung, tomotherapy did better than 3DCRT or IMRT in sparing the lung from doses above 10 Gy, and V5 from tomotherapy was substantially better than from IMRT. For the contralateral breast, V5 was substantially better from tomotherapy than from 3DCRT or IMRT. Conclusion: helical tomotherapy can simultaneously cover the entire ipsilateral breast and regional lymph nodes with dose uniformity comparable to or better than what is achievable using conventional techniques. The improved target‐dose uniformity achievable using tomotherapy may justify the slightly high doses to the lungs. Since minimizing contralateral breast dose is essential, tomotherapy may be preferable to 3DCRT or IMRT.
SU‐FF‐T‐117: Dosimetric Impact of Bladder Contrast On Prostate Helical Tomotherapy Treatments
Authors: Schubert L , Westerly D , Tome W , Paliwal B
Published: April 2010

Purpose: To quantify the effect of bladder contrast on helical tomotherapy prostate dose distributions Method and Materials: Five anonymous early‐stage prostate patients consecutively treated with hypofractionated helical tomotherapy were retrospectively analyzed. All patients were planned at 4.3 Gy per fraction for 12 fractions. Contrast was used in the bladder at the time of simulation, but was not converted to water at the time of planning and not used during treatment. The mean density within the contoured bladder was 1.1 g/cm3 averaged over all patients, and bladder volumes ranged from 176.7 cm3 to 341.5 cm3. Matlab® software was used to retrospectively override the density of the bladder contents on the planning image to that of water (1 g/cm3). Original treatment plans were recomputed on the density‐overridden planning images using Planned Adaptive® software. Fractional dose distributions of original plans were compared with the treatment plans recomputed on density‐overridden images. Dose difference maps were created by subtracting the original plan distributions from the density‐overridden distributions and normalizing to the prescribed fraction dose. Results: Differences in dose distributions of up to +3% were observed in all patients, with maximum values ranging from +2.6% to +3.4%. These differences were located primarily within the bladder and along the superior edges of the prostate bordering the bladder. Conclusion: Planning with bladder contrast but treating without contrast can cause dose distribution differences of up to 3% for helical tomotherapy prostate treatments. This effect should be considered at the time of planning. It should also be taken into account as a possible factor when assessing dose distributions on daily images for the purposes of adaptive radiotherapy.
SU‐FF‐T‐118: Improvements to the Histogram Analysis in Radiation Therapy (HART) Open‐Source Software System
Authors: Pyakuryal A , Myint K , Gopalakrishnan M , Jang S , Sathiaseelan V , Logemann J , Mittal B
Published: April 2010

Purpose: The histogram analysis in radiation therapy (HART) software has been widely used for the research in intensity modulation radiation therapy (IMRT) treatments in cancer. The common application of HART is the precise and efficient dose volume histogram (DVH) analysis of structures in IMRT plans as presented earlier (Med Phys.35(6), p.2812 (2008)). The tool has been further developed with additional features, such as multi‐dimensional dose histogram (MDH) computational module, dose response modeling (DRM) and plan‐specific outcome analysis (POA) features. Methods and Materials: Matlab based codes were designed to read RTOG data formats exported from the Pinnacle3 treatment planning system (TPS; Philips Healthcare, Best, Netherlands), and to write into a simpler HART format. HART computes the MDH differential data utilizing the information on the raw dose values and the co‐ordinates of the primary dose grids for a given structure in the TPS. The DRM utilizes the polynomial models for cumulative DVH in order to simulate the optimal dose response models for structures. The POA feature can also be used for evaluations of IMRT plans using various biological modeling. DVH analysis results extracted by HART, can also be exported into customizable output formats. Results: HART offers MDH computational capability, DRM simulations, a simpler POA feature, and the DVH analysis module for IMRT plans. MDH computations and DRM simulations for an IMRT plan were accomplished relatively in 15–30 minutes with the clock speed of 1.8 GHz and 2 GB RAM support. The MDH and DVH analysis results were validated with the Pinnacle3 data. Conclusions: Several applications have been incorporated into a simpler, user‐friendly, and automated software package (HART). We have also implemented an open‐source mechanism for various users. We expect to develop HART for various applications in radiotherapy research, and its expansion to other TPSs. This work was partially supported by NIH/NIDCD grant.
SU‐FF‐T‐123: Comparison of Elekta VMAT with Tomotherapy: Plan Quality, Delivery Efficiency and Accuracy
Authors: Rao M , Yang W , Sheng K , Chen F , Ye J , Mehta V , Shepard D , Cao D
Published: April 2010

Purpose: Helical Tomotherapy and Volumetric Modulated Arc Therapy (VMAT) are arc‐based approaches to IMRT delivery. The objective of this study is to compare VMAT and helical tomotherapy in terms of plan quality, delivery efficiency and accuracy. Method and Materials: Twelve cases including 4 prostate, 4 head & neck, and 4 lung were selected for this study. Tomotherapy plans were developed using a Hi‐Art II planning station. VMAT plans were generated using both the Pinnacle3 SmartArc IMRT module and our home‐grown arc‐sequencing algorithm. The same set of CT images and contours were used for both VMAT and tomotherapy plans. The percentage volume of the PTV that received 95% of the prescribed dose (V95) was used to compare the target coverage. VMAT and tomotherapy plans were delivered using Elekta's PreciseBeam VMAT® control system and TomoTherapy HI_ART II system, respectively. VMAT plan QA was performed using the IBA MatriXX system, and an ion‐chamber and films were used for tomotherapy plan QA. Results: For prostate cases, VMAT provided slightly improved V95 (98.1% vs. 97.6%) and lower dose to the rectum and the bladder. Tomotherapy attained slightly higher target coverage and uniformity in HN cases, with improved V95 (98.9% vs. 98.3%) and reduced standard deviation of the PTV dose (1.2 Gy vs. 1.4 Gy). In lung cases, VMAT provided similar target coverage with improved sparing of the cord and total lung. In terms of delivery efficiency, VMAT plans on average took 2.2 minutes for prostate and lung cases, and 5.4 minutes for HN cases. These values increase to 4.8 and 7.6 minutes for tomotherapy plans. Both VMAT and tomotherapy plans can be delivered accurately based on their own QA standard. Conclusion: VMAT is able to provide ∼40% reduction in treatment time while maintaining comparable plan quality to that of helical tomotherapy. Research supported by Elekta.
SU‐FF‐T‐126: Initial Experience with Philips SmartArc On An Elekta Linac
Authors: Shepard D , Ca D , Rao M , Chen F , Mehta V
Published: April 2010

Purpose: The recent introduction of delivery control systems capable of delivering intensity modulated arc therapy (IMAT) has led to renewed interest in arc‐based IMRT delivered on a conventional linac. A key challenge to successful implementation of IMAT is the need for robust inverse planning tools capable of properly accounting for IMAT delivery constraints. In this work, we evaluate a new IMAT planning module, called SmartArc, designed for the Pinnacle3 treatment planning system. Method and Materials: In February 2009, we received an alpha version of the SmartArc planning module for the Pinnacle3 treatment planning system. The SmartArc tools were developed by RaySearch and build on the existing direct machine parameter optimization (DMPO) functionality in Pinnacle3. The SmartArc module was used to create 9 IMAT plans (4 head‐and‐neck, 2 lung, and 3 prostates). Each plan was verified on an Elekta Synergy with the PreciseBeam VMAT delivery control system using the IBA Matrixx 2D ionization chamber array. Each plan was compared with a corresponding fixed‐field IMRT or helical tomotherapy plan in terms of both plan quality and delivery efficiency. Results: A single arc was sufficient to produce highly conformal IMAT treatment plans for the prostate and lung cases. On average, the prostate plans required 536 monitor units and delivered in 1.9 minutes while the lung plans required 750 monitor units and delivered in 2.2 minutes. For the more complex head‐and‐neck cases, the use of two arcs was necessary to meet the treatment goals and an average of 607 monitor units and 5.4 minutes were required. Conclusion: The SmartArc module in Pinnacle3 serves as a robust IMAT planning tool capable of planning both single arc and multiple arc deliveries. 2D gamma analysis showed that all plans verified with greater than 95% of the measured points meeting our 3%/3mm criteria.

Research supported by Elekta
SU‐FF‐T‐131: Assessing the Dosimetric Impact of Intra‐Fraction Prostate Motion On Step‐And‐Shoot IMRT Plans
Authors: Langen K , Moore J , Kupelian P , Siebers J
Published: April 2010

Purpose: To assess the dosimetric impact of intra‐fraction prostate motion for step‐and‐shoot IMRT plans. Method and Materials: For step‐and‐shoot IMRT plans, fluence maps for each segment are exported from the Pinnacle treatment planning system. Each fluence map segment is modified to simulate the effect of prostate motion observed during the simulated delivery. Modified fluence maps are re‐imported into Pinnacle for dose calculations. Calculated dose distributions are compared with unmodified fluence maps dose distributions to assess the impact of intrafraction motion on the dose delivery. Measured Calypso motion tracks for 16 patients (515 tracks) are used. Changes in prostate (4–6 mm margin) and PTV (zero‐margin) D95% are scored for each fraction and for the cumulative simulated delivery. Results: Average D95% changes (± 1SD) in the PTV and prostate are −0.5±1.1% and −0.2±0.5%. Maximum per‐fraction D95% changes are −12.7% and −6.4%. 12% and 4% of all fractions suffered a PTV and prostate D95% change in excess of 1 percent. Only 2% and 0.2% of all fractions suffered respective changes in excess of 3%. The patient specific cumulative D95% changes in the PTV and prostate average −0.15±0.2% and 0.07±0.15%. The maximum cumulative D95% variations for a single patient are −0.6% and 0.5%. After the delivery of 5 fractions the cumulative D95% variations for a single patient are −1% and 0.4% for the PTV and prostate. Conclusion: Inter‐fraction prostate motion has little effect on the dosimetric target coverage for step‐and‐shoot prostate plans. Very few fractions (2 and 0.2% for the PTV and prostate) suffered D95% changes in excess of 3%. After the delivery of all fractions the effect on the both the PTV and prostate was negligible.

(Supported, in part, by by NIH P01CA116602 and T32CA113277)
SU‐FF‐T‐133: RapidArcTM: Commissioning and Dose Escalation Possibilities
Authors: Crijns W , Depuydt T , Defraene G , Verstraete J , Haustermans K , Budiharto T , Junius S , Van den Heuvel F
Published: April 2010

Purpose: This paper reports our experience in commissioning RapidArc™ for use in clinical practice. Additionally, we performed a dose escalation planning study using radiobiological parameters to compare the outcome of IMRT and RapidArc plans. Method and Materials: For commissioning we used a standard set of guidelines as outlined by C. Ling et al. This augmented with dosimetry checks, including absolute point measurements in phantom and relative comparisons in air. In addition, we introduced more automated methodologies for picket fence testing of the MLC during RapidArc delivery. Because of different couch systems than presumed in the implementation by the manufacturers a new parameterization of the couch was introduced. In a preliminary dose escalation study of 8 clinical patients we evaluated the treatment plans on a radiobiological basis. Results: For Commissioning: the measurements differed not more than 2% of the predicted values. For Dose Escalation: NTCP calculations for grade 2 rectal bleeding showed a significant reduction (p=0.03) of the mean NTCP from 2.6% to 1.9%, even in this small group of patients. TCP values did not differ significantly (TCP(IMRT)=75.5%, TCP(RA)=75.4%). Conclusion: Methods described in this report lead to successful implementation of RapidArc in clinical practice. At time of presentation we expect to increase the statistics to 25 patients.

Conflict of Interest: Research sponsored by Varian Medical Systems, Palo Alto, California, USA
SU‐FF‐T‐134: Segmented Field Electron Conformal Therapy with An Electron Multi‐Leaf Collimator
Authors: Eley J , Hogstrom K , Matthews K , Parker B , Price M
Published: April 2010

Purpose: To investigate the potential of a prototype electron multi‐leaf collimator (eMLC) to deliver segmented‐field electron conformal therapy (ECT) and to improve dose homogeneity to the planning target volume (PTV) by feathering the abutting edge of the higher energy electron fields. Method and Materials: Electron beams (6–20 MeV) using a prototype eMLC were commissioned for the pencil beam dose algorithm in the Pinnacle treatment planning system. A discrete Gaussian edge spread function was used to match electron dose penumbras of differing energies at a specified depth in a water phantom. The effect of edge feathering on dose homogeneity was computed for a segmented‐field ECT treatment plan for a cylindrical, 2‐step PTV in a water phantom (depths = 2.5 and 4 cm). Results: For abutting 9 and 16 MeV fields, Gaussian edge feathering reduced the standard deviation of dose in the PTV from 5.6% to 3.5%. The treatment plan with edge feathering delivered 90% of the prescription dose to 94% of the PTV, while the treatment plan with no feathering delivered 90% of the dose to 88% of the PTV. Conclusions: An eMLC was found to improve dose homogeneity in the 2‐step PTV for segmented‐field ECT through 1D edge feathering of the leaf positions for the higher energy electron field.
SU‐FF‐T‐136: Improved Dose Characteristics From Proton Arc Therapy
Authors: Hecht A
Published: April 2010

Purpose: IMRT is common for x‐ray treatment, but proton treatment is still only performed at a few angles. Expanding proton radiation therapy to many angles may reduce dose to surrounding tissue. Beam technologies are moving forward (e.g., dielectric wall accelerator) making this practicable. This study seeks to quantify the reduction in dose to surrounding healthy tissue using proton arc therapy. Materials and Methods: Monte Carlo simulations were performed using Geant4. Proton beams impinged on a 100mm radius cylindrical water phantom with a 10mm radius treatment region. Protons were delivered equally over all angles with −r initial direction, producing kernals of rings of dose for each of several energies. Results: Reduction in dose outside of the treatment region is dramatic for the high dose regions. Single beam therapy PDD is presented, the entrance dose is a large portion of the total dose, with a >50% of peak dose from 60mm from peak. The entrance dose may be spread through the typical clinical use of 2 or 3 angles, but this still leaves significant entrance dose. The lateral drop off can be sharp though. The PDD is presented for proton arc therapy. The difference from the large entrance dose is significant. The distance to 50% dose is similar to the lateral drop‐off with traditional beams, and drops to 10% within 25mm of peak, leading to a much lower average dose to irradiated tissue outside the prescription area. Proton arc therapy has the conformity of the lateral dose — without similar entrance dose — of traditional proton therapy. Calculations are ongoing for avoidance regions and comparison with few angle treatments. Conclusions: Proton arc therapy shows great potential for reduction of high dose to tissues outside the treatment region compared with traditional proton treatment.
SU‐FF‐T‐140: The Inter‐ and Intra‐Fraction Reproducibility of Three Common IMRT Delivery Techniques
Authors: Buckey C , Stathakis S , Gutiérrez A , Esquivel C , Mavroidis P , Mihailidis D , Papanikolaou N
Published: April 2010

Purpose: To investigate and compare the inter‐ and intra‐fraction reproducibility of three popular methods of IMRT delivery: step‐and‐shoot, sliding window, and solid compensator delivery. Method and Materials: A seven‐field IMRT plan for a head and neck case was created using the Pinnacle3 treatment planning system (TPS). The intensity maps were realized using solid compensators and MLC segments. The IMRT QAs were measured using the MatriXX and Kodak EDR2 film. The plans were delivered on 10 consecutive days and the first delivery was used as reference. Each delivery was evaluated using gamma index, profiles and isodose distributions. Dose rate, the number of MUs per segment and two gantry angles (90 or 180 degrees) to study gravity effects on the MLC were investigated. Results: Both the compensator and MLC‐based fields have results that are within the clinically acceptable tolerance of 3% dose difference, 2mm DTA and gamma value less than 1 (95% of the pixels). However, when using stricter criteria: 2%, 2mm, and gamma tolerance of 0.5, it becomes clear that the compensator based delivery has a definite advantage over comparable MLC‐based competitors in terms of inter‐fraction reproducibility. It was observed that the increase in dose rate or the increase of MU/segment degrades the quality of the plan. Gravity did not affect the MLC delivery. Conclusion: The inherent baseline resolution of the compensators is better than that of the MLC modulated fields based solely on the methods used to generate the modulations themselves. The inter‐fraction reproducibility is as good, and often better, than delivery with the MLCs. Fewer monitor units are required to deliver each portal, and thus patient outcomes can be improved and unwanted side effects to both patients and therapists can be reduced. Conflict of Interest (only if applicable): .decimal Inc supported the investigation.