bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐T‐29: Application of Optically‐Stimulated‐Luminescence Dosimeters in Partial‐Breast‐Irradiation Brachytherapy
Authors: Paliza M Morales , Ding G , Coffey C
Published: April 2010

Purpose: To study the application of in‐vivo optically‐stimulated‐luminescence (OSL) dosimeters in high‐dose‐rate (HDR) partial‐breast‐irradiation (PBI) brachytherapy. Methods and Materials: In PBI brachytherapy treatment planning using HDR Ir‐192, one of the organs at risk is the skin. With the recent clinical introduction of multi‐dwell position and multi‐lumen PBI treatment devices, optimization dose algorithms allow improved treatment volume (PTV‐EVAL) dose distributions. However this gain in improved tumor volume coverage may oftentimes be at the risk of increasing the overlying skin tissues to radiation tolerance doses. Hence, there is increasing concern to validate the calculated skin dose with experimental in‐vivo determinations. Using Landauer OSL chip dosimeters, we clinically measured the dose to a reference point in the skin surface and correlated this measured dose with our treatment planning computer predictions. Location of calculation points was validated using surface markers via computed tomography. Care was taken to provide 1‐cm thickness of 4 × 4‐cm2‐area backscatter‐factor material. Results: The chip dosimeters were calibrated using a 6‐MV‐linear‐accelerator‐photon beam. Mean dose measured values on two patients to date were within 3% of error with respect to the planned values. Conclusions: OSL dosimetry provided a direct way to measure in‐vivo doses for HDR brachytherapy procedures, verifying accuracy for 380‐keV average photon energy. Our treatment protocol now includes these dosimeters for estimation of skin dose. We will discuss specific energy response differences and dose calibration procedures for the OSL dosimeter for application using HDR Ir‐192 brachytherapy. Accuracy, versatility of placement and straightforward way of reading these dosimeters make them a valuable alternative to thermo‐luminescence, diode and MOSFET‐based dosimeters.

Conflict of interest: This study is sponsored by Landauer, Inc., Glenwood, Illinois
SU‐FF‐T‐39: Investigating Thermal Properties of a Thermobrachytherapy Radioactive Seed for Concurrent Brachytherapy and Hyperthermia Treatments: Design Considerations
Authors: Shvydka D , Gautam B , Parsai E , Feldmeier J
Published: April 2010

Purpose: Hyperthermia has been demonstrated to be one of the most effective radiation sensitizers. It offers significant improvement in both tumor control and survival rate after radiation therapy without considerable increase in side effects. Previous studies show that the time interval between administrations of both modalities has to be rather short, preferably, within an hour. We propose a new Thermobrachytherapy radioactive seed model, serving as a heat source for concurrent administration of brachytherapy and hyperthermia.

Method and Materials: A new combination seed is based on the BEST Model , where tungsten marker core is replaced with a ferromagnetic material, capable of producing heat when subjected to external alternating electro‐magnetic field. Such a replacement does not noticeably change the dose rate distribution, and has only minor effect on the radiographic properties of the seed. A finite‐element partial differential equation solver package “COMSOL Multiphysics” was used to evaluate thermal distribution of the heat induced in the ferromagnetic core. Results: The induction heat source has relatively low efficiency due to losses associated with a considerable distance between the ferromagnetic core and induction coil. However, the temperature distribution is tunable based on the number of seeds used during the treatment, their locations, coil diameter, and the frequency of the electro‐magnetic field. A model with a solid radiographic marker is preferable for the proposed application since it offers the highest heat output. We found that the implementation of the proposed seed will require only small changes in the internal structure of a standard commercial model, and will not affect significantly the dose rate and other TG43 factors characterizing radiation distribution. Conclusion: We will present the radiation and thermal properties of the new seed model which has high potential for implementation of concurrent brachytherapy and hyperthermia.
SU‐FF‐T‐42: A Novel Approach to Scar Boost in Mesothelioma Treatment
Authors: Doyle L , Showalter T , Liu H , Xiao Y , Yu Y , Harrison A
Published: April 2010

Purpose: To evaluate the potential advantages of high dose rate(HDR) brachytherapy for boosting mesothelioma incisions extending beyond the hemithoracic target volume. HDR treatment was compared with abutted, enface electron fields. Methods and Materials: One case describes catheter placement, dosimetric advantages, setup uncertainties, and treatment delivery. The right lateral decubitus position, in alpha cradle, was selected to permit consideration of HDR versus electrons. Comparative analyses of treatment plans were performed, and HDR setup and dosimetry were preferred. The HDR treatment utilized 3 catheters atop 5mm of bolus. The HDR setup required physician to confirm catheter placement. Tape, 5mm bolus, and wet towels secured the catheters and provided shielding. The prescription was 3.0Gy to 1.2cm from catheter including bolus (7mm depth in tissue). Dwell positions every 5mm were used to cover the entire length of the scars (22cm and 34cm). The corresponding electron plan required 5 thin strip cutouts and a physician present to approve field setup and feathering of the junctions. A phantom was used to simulate treatment of lesion with electrons and entire process was timed. Results: The total setup and treatment time for 6 HDR treatments was approximately 270minutes (time varies with activity, prescription dose, and volume) compared with 450minutes for 15 electron fractions (2Gy/fraction). Planning time for either modality is comparable. Electron treatments involve additional time for cutting blocks, measuring cutout factors, and physician approved junction changes. One additional concern is dose homogeneity caused by feathering electrons versus brachytherapy which provides a reliable dose distribution. Conclusions: HDR brachytherapy provided an optimal solution over the complicated and time‐consuming electron treatment and should be considered as a viable option for mesothelioma patients with a considerable scar length beyond hemithoracic target volume. Clinical data to support the use of brachytherapy over electrons for coverage of incisional scars is still needed.
SU‐FF‐T‐49: Investigating Radiation Properties of a New Radioactive Seed for Concurrent Brachytherapy and Hyperthermia Treatments: A Monte Carlo Study
Authors: Khan N , Parsai E , Feldmeier J , Shvydka D
Published: April 2010

Purpose: Concurrent delivery of Radiation and hyperthermia has not been documented and is believed to be complementary. The purpose of this research project was two folds: a) to design a new thermobrachytherapy radioactive seed that can be used for concurrent delivery of radiation and heat by insertion of ferromagnetic materials for heat source, and b) to use MNCP5 Monte Carlo simulation code to model this new thermobrachytherapy seed and compare the TG‐43 factors, to both the Book values and the calculated Best Model. Method and Materials: A newly designed seed was modeled based on the BEST seed Model 2301, where tungsten marker core is replaced with a ferromagnetic material, capable of producing heat when subjected to external alternating electro‐magnetic field. Monte Carlo Simulations using MCNP5 was used to compute the AAPM TG43 factors and compare the results to Book values as published by Sowards et al and the TG43 report. Results: In Liquid Water, the dose rate constant calculated for the Best Seed model ♯2301 is 1.056±0.0055 Gy*h−1*U−1 (Book value of 1.01: with a percentage difference of 4.6%). The value measured for thermobrachytherapy seed is 1.057 ±0.031 cGy*h−1U−1. Radial dose function was computed from 0.1cm to 10cm at 0.1cm intervals, and Anisotropy Function was calculated from 1cm to 7cm in 1cm increments at 0°–90° at 10° increments. Conclusions: The newly designed thermobrachytherapy seed appears comparable in all TG43 factors to the existing Best seed model 2301. Maximum deviations for radial dose function and anisotropy function in the range of distance and angles studied were 4.5% and 4.8% respectively. Geometry function remained essentially unchanged.
SU‐FF‐T‐50: Clinical Implementation of New Endometrial Cylinder Applicator for Electronic Brachytherapy
Authors: Cardarelli G , Hiatt J , Curran B , Segala J , Sternick E , Markelewicz R , Hepel J , Puthawala Y , Shioshiansi S , Wazer D
Published: April 2010

Introduction: Cylindrical applicators for vaginal cuff irradiation are now commercially available for use with a 50 kV electronic brachytherapy (EB) source and are similar in size and shape to cylinders that have been long employed with iridium‐192 brachytherapy (IB). Although the insertion of the new applicator is relatively the same, the implementation from simulation to treatment can be quite different than conventional IB. This study describes the clinical implementation process of the first ever treatment of a patient using this applicator. Methods: The EB endometrial cylinder applicator (Axxent Vaginal Applicator) was supplied and manufactured by Xoft Inc., Sunnyvale, CA. Prior to treatment, a detailed analysis was performed to verify the position of dwell positions, dose distribution verification using gafchromic film and applicator geometry measurements to verify length and diameter. Finally, treatment plans were generated using PLATO software (Nucletron Corp., Columbia, MD) on CT scan data and verified using TLD data. Results: The results of the dwell position verification show that the dummy seed insert agree with the gafchromic film measurements. The distance from dwell position 1 and the surface of the apex of the applicator vary with cylinder size. The dose distribution can be verified at the point of prescription. Discussion: The results of this study show that the EB endometrial cylinder applicator can and has been implemented safely. It should be noted that this applicator has some differences from the traditional IB applicators and need to be accounted for.
SU‐FF‐T‐54: Quantification of CT Artifact Reduction of Second Generation Intracavitary Brachytherapy Applicator
Authors: Yu Z , Balter P , Zhang Y , Klopp A , Price M , Eifel P , Mourtada F
Published: April 2010

Purpose: A second generation CT‐friendly applicator with movable shields has been developed for cervical carcinoma intracavitary brachytherapy (ICBT). We report on a method to quantify the reduction in CT artifact in a phantom study using this applicator. Methods and Material: A gynecological phantom was fabricated to mimic a realistic patient anatomy and to fit a standard intrauterine tandem (45 degrees) and 20‐mm diameter colpostats. Once the applicator is inserted, packing using gauze was inserted around the colpostats to reduce air cavity. The phantom with the applicator set was scanned using a CT simulator (AcQSimCT, Philips) using axial mode (2.5 mm slice, 120 kVp, 110mAs). To eliminate image artifacts, two non‐overlapping, 30° gantry tilt axial CT scanning series which met at the middle of the ovoid were used. Shields were moved before each series scan to the opposite side of the ovoid. A second CT scan without moving the shields was performed to compare artifacts. The image sets were then rigidly aligned globally using mutual information. A region of interest inside the phantom from the slice with greatest CT artifacts visually was picked for quantitative analysis. The CT number from each voxel was tallied and summary statistics were calculated. Because the images are aligned, we could determine the difference in CT numbers between corresponding voxels from both images. Results: Visually, the CT scan set with shields moved out of the way were almost completely free of artifacts. The average %diff between all the voxels was 0.6%±42% (2σ), with maximum %diff of 1,039% for voxels with the largest artifact. Conclusions: The new applicator provides artifact‐free CT imaging without compromising the shields. We found the CT protocol with tilted gantry is easy to perform using CT simulators available in the radiation oncology department.
SU‐FF‐T‐57: Evaluation of CT‐Based High Dose Rate Brachytherapy Treatment Planning in Nasopharynx Using Dose Volume Indices
Authors: Senthil G , Muthulingam S , Shankar V , Prajapathi J
Published: April 2010

Purpose: Treatment of the nasopharyngeal tumour can be particularly challenging. Because it is surrounded by multiple critical organ. Conventional Radiograph based treatment planning is lack of quantitative information about target volume (TV) and other critical organs. But on CT based dosimetry provides the dose distribution on the patient images and enable to quantify the dosimetric outcome using Dose Volume Histogram(DVH). The aim of this study is to evaluate the different dose points(DP) normalization with optimization techniques and compare the dose volume indices(DVI). Method and Materials: Four patients were underwent image guided Rotterdam nasopharyngeal catheter with dummies followed by 3mm slice thickness of CT images were transferred to virtual simulation Dosimetrist for contouring target and other structures. PLATO BPS V14.3.5 used to catheter reconstruction and DP generation and dose distribution. Here three techniques were used. Plan1 (P1) is DP were generated at 5mm around the target. Plan 2(P2) is DP were generated at 5mm around the target combined with dose point optimization. Plan 3(P3) is DP is generated on catheters (+U) 7mm distance from two catheters. In all plans prescription dose is normalize to DP. Dosimetry outcome from these 3 different plans were compared quantitatively using DVI. Which includes Dose homogeneity index(DHI),External Volume Index(EI) and Conformal Index(COIN).COIN is taken in to consideration of coverage of target volume (TV) and also unwanted irradiation of normal tissue (soft palate) outside the TV Results: In all four patients the volume of target is ranging from 9.11 to 31.23 cc. DHI for P3 is better optimal 0.5506±0.0334(0.5938–0.5407) and EI also optimal 0.1060±0.1172(0.0240–0.06). But COIN is Suboptimal for P3.But in P2 COIN is optimal 0.4784±0.070(0.3947–0.5455), DHI and EI also optimal 0.394±0.0907,0.2763±0.0468 respectively. Conclusion: If TV is less than 10cc, P3 show all indices are optimal. But TV is more than 15cc. P2 shows all indices are optimal
SU‐FF‐T‐61: Determination of Neutron and Gamma Dose Rates in Water Surrounding a New Interstitial Cf‐252 Brachytherapy Source
Authors: Wang C , Kelm R
Published: April 2010

Purpose: A new generation of high‐activity miniature 252Cf sources for interstitial brachytherapy has recently been encapsulated at the Oak Ridge National Laboratory (ORNL). The purpose of this study is to determine the neutron and gamma dose rates in water surrounding the new 252Cf source. Method & Materials: The neutron and gamma dose components of the new 252Cf source in water were determined by the measurements of two miniature ion chambers (T1 and M1 of Standard Imaging, Inc.) that have similar gamma responses but very different neutron responses. A Lucite‐walled water phantom was built to conduct the experiment. The experimental setup was also modeled by the Monte Carlo transport code MCNP. Results: The results show that the measured neutron absorbed dose rates were approximately 25% lower than that predicted by MCNP for all dose positions in water. The measured gamma absorbed dose rates in water, on the contrary, are higher than that predicted by MCNP. The differences between the measured and MCNP‐predicted gamma dose rates are most pronounced (∼a factor of two) at the distance of 1 cm, and fall to approximately 30% at distances 2 cm and beyond. Conclusions: The measured neutron and gamma dose rates do not agree with the dose rates predicted by MCNP. The discrepancies between the two results suggest that the true 252Cf content of the new source is approximately 25% less than the ORNL estimate and that the new source emits significantly more low‐energy gamma rays than the large 252Cf sources (e.g. the AT source) used in the previous studies. Acknowledgement: This research is supported by Isotron Inc.
SU‐FF‐T‐62: Dosimetric Evaluation of An Internal Shielding Used with a HDR Skin Applicator
Authors: Granero D , Ballester F , Perez‐Calatayud J , Lliso‐Valverde F , Meseguer V Carmona , Richart J
Published: April 2010

Purpose: The Valencia HDR skin applicators are accessories of the microSelectron HDR afterloading system (Nucletron) cup shaped to limit the dose to the irradiation area. Applicators sizes are: diameter 2 and 3 cm. The typical prescription depth is 3 mm. This work aims to evaluate the backscatter and electron contamination of an internal shielding used to reduce the dose to the ocular globe when the lesion is located at the eyelid. Monte Carlo (MC) and experimental methods have been used. Method and Materials: The geometry has been: the Valencia applicator (2 cm diameter) on the surface of a solid polystyrene slab phantom; inside, a 2 mm lead slab located at 3 mm depth. MC simulation characteristics: GEANT4 code (Version 9.0); Scored absorbed dose; Cell size: 0.1 mm in the depth axis; Photon histories: 3×108. Radichromic EBT film dosimetry setup and processing: Films depths: 1,5, 3, 5 and 7 mm, inside the phantom; Irradiations, with and without the lead shielding slab; Flatbed scanner; Matlab software to obtain the red channel and to filter noise; Verisoft (PTW) software utilities to calibrate the optical density against dose and to analyse the results. Results: MC simulation gives an overdose close the lead (backscatter component) of about 190% (range: 0.5 mm). The electron contamination under the lead is about 130% (range: 1 mm). These results agree with measurements with radichromic film within experimental uncertainties. The dose reduction behind the shield is about 60%. Conclusion: The use of an internal 2 mm lead shielding, in eyelid skin treatments with the Valencia applicators has been evaluated. The reduction in dose to the ocular globe with a 2 mm lead shielding is about 60%. A minimum bolus of 0.5 mm and 1 mm thickness must be added above and below the shielding, respectively to remove the dose contamination.
SU‐FF‐T‐69: An Inter‐Fraction Adaptive Strategy for High‐Dose Rate Prostate Brachytherapy
Authors: Pouliot J , Foster W , Cunha AJ , Hsu I‐C
Published: April 2010

Purpose: To determine the dosimetric impact of interfraction organ‐catheter displacements and settle on an adaptive strategy to maintain the quality of the implant. Methods & Material: 10 patients received HDR prostate implants on Day‐1 with CT‐based dose plan optimized with the inverse planning tool IPSA to deliver the first of two fractions of 9.5 Gy. On Day‐2 before the second fraction, a CBCT was acquired and fused with the Day‐1 CT. Initial prostate and urethra contours were transferred to CBCT images. Bladder and rectum contours were drawn and catheters digitized on the CBCT. Day‐1 dwell times were applied to the CBCT dataset. The plan was also re‐optimized with IPSA using the volumes from CT, catheters from CBCT, and the same constraints as Day‐1. The same physician re‐contoured the prostate and urethra on CBCT, and two new plans were obtained as above. Four adaptive scenarios per patient were thus created with the CBCT images, using initial/new contours with initial/new plannings. For each strategy, the prostate V100 and V150, urethra V120, bladder and rectum V75 from Day‐2 were compared to Day‐1. Results: Relative organ‐to‐catheter displacements on Day‐2 cause prostate V100 to decrease and dose to other organs to increase as compared to Day‐1. Relative organ‐catheter displacements of more than 6 mm can be used to trigger a replanning. Among adaptive strategies, re‐optimizing the plan with the catheters defined on the CBCT was found sufficient to maintain the quality of the implant, while minimizing workload increase. Conclusion: Visual inspection of catheters on fused CBCT‐CT allows for an accurate and rapid evaluation of the integrity of the implant. When replanning is required, dwell times can be reoptimized using the catheters defined on CBCT, insuring that all dosimetric indices are within required values at each delivered fraction. This work is supported in part by Nucletron.
SU‐FF‐T‐72: Dosimetric Comparison of SAVI, MammoSite, Contura and Clearpath for Accelerated Partial Breast Irradiation
Authors: Scanderbeg D , Barna P , Jiang S , Pawlicki T , Yashar C
Published: April 2010

Purpose: The number of intracavitary hdr brachytherapy devices available to treat women with early stage breast cancer has increased significantly in the past several years. Blending the dosimetry of interstitial and the ease of use of MammoSite; SAVI, Contura, and Clearpath have made their way into the arena. One would postulate that the evolution of the devices in the sense of dose modulation, from least to greatest, would be MammoSite, Contura, Clearpath, and finally SAVI. This stems from the location of peripheral struts in relation to the cavity boundary. In this study, we compare the dosimetry between the 4 devices and assess their efficacy through dose volume histograms (DVH) and maximum point doses of critical structures. Comparing these modalities will help determine either the best overall treatment device or the best device for a particular type of patient. Materials and Methods: Nine patients treated with SAVI at UC San Diego were selected for this comparison. CT scans were retrospectively evaluated for delivery of APBI via MammoSite, Contura and Clearpath by simulating them in place of the SAVI in the lumpectomy cavity. The anterior tissue surrounding the balloon devices was linearly expanded to simulate tissue displacement by the balloon. All plans were generated using Brachyvision TPS (Varian Medical Systems, Palo Alto, CA). Results: DVHs of the target volume were evaluated against planning criteria taken from the NSABP B‐39 protocol. All devices met the criteria and had similar target coverage (V90 ∼ 98%). However, there were differences in the dose received by normal tissue with skin dose lowest in SAVI patients (∼71% of prescribed dose). This was followed by Contura, MammoSite and Clearpath, respectively. Conclusions: All devices had similar coverage of the target volume, but SAVI had the most dose flexibility for patients with close skin spacing and chestwall proximity.
SU‐FF‐T‐73: Evaluation of Inverse Planning Dose Optimization for HDR Brachytherapy in Treatment of Cervical Cancer
Authors: Tao L , Taylor B
Published: April 2010

Purpose: We investigated the differences between geometrical optimization and inverse planning simulated annealing (IPSA) for the treatment of cervical cancer. Methods and Materials: Patients were selected and two optimization plans for each patient were generated with geometrical optimization and IPSA. The clinic target volume and critical organs were contoured using Oncentra MasterPlan Version 3.1(Nucletron Corp., Veenendaal, The Netherlands). For each patient, the dose constrains and optimization parameters were set to meet clinic goal for all plans. The dose volume histograms (DVH) of target and critical organs were generated for comparison. Results: We found that IPSA significantly improved the target dose homogeneity compared with geometrical optimization. For the tumors adjacent to critical structures, IPSA dramatically spared the volume of the critical structures to be irradiated. Conclusions: IPSA is superior over geometrical optimization in terms of target coverage and minimizing normal structures irradiated.
SU‐FF‐T‐74: Preplanning of Suture Coordinates for Episcleral Plaque Therapy
Authors: Astrahan M
Published: April 2010

Purpose: Episcleral plaques are attached to the eye by sutures which affix eyelets to the sclera. Historically, plaque position was determined by transilluminating the eye to cast a shadow of the tumor onto the sclera, outlining this shadow, and subsequently deciding where to suture the eyelets. 3D modeling enables scleral coordinates for each eyelet to be determined prior to surgery. Methods: The retinal diagram is a polar map of the retinal surface in which the posterior pole is located at the center of the map surrounded by radial spokes representing meridians and concentric rings of lattitude which terminate at the limbus which is the border of the cornea and sclera. Eyelet coordinates on an equivalent scleral diagram can be expressed using a meridian, a chord distance from the limbus along that meridian, and the chord distance between the eyelets. It is common to express diagram meridians as clock hours so coordinates for a plaque with two eyelets might be something like: eyelet ♯1 along the 12:40 o'clock meridian, 9.1 mm from the limbus, eyelet ♯2 along the 2:10 meridian 9.4 mm from the limbus, and 9.2 mm between the eyelets. Results: Over 300 patients have been treated at USC using calculated suture coordinates. Only in a handful of cases involving anterior tumors for which fundus photography was impossible was it necessary to empirically adjust coordinates. Admittedly subjective observation suggests that plaque placement to within about 8 degrees circumferentially and 0.5 mm radially of the planned position is routinely achievable. Examples will be presented. Conclusion: When the tumor location can be accurately determined from fundus photography, the placement of a plaque and its suture eyelets can be accurately preplanned. Conflict of Interest: Software which implements this technology is licensed by BEBIG GmbH for distribution under the name Plaque Simulator.
SU‐FF‐T‐76: Non‐Template Dosimetry for Prostate Seed Implant
Authors: Fu  , Liu H , Xiao Y , Yu Y
Published: April 2010

Purpose: Template guidance has been used in modern prostate brachytherapy with 3D image‐based planning. In robotically assisted prostate seed implants, template is only a virtual concept for the planning procedure, because the robot can insert needles at any desired location. A non‐template dosimetry concept was presented and compared with traditional template dosimetry plan. Materials and Methods: Variseed (V7.1) planning software was used to create the non‐template plans. Based on 12 pretreated patients' contours, both template and non‐template plans were created for comparison. Two different template plans were used: one used modified periphery needle pattern and the other used the same number of needles as non‐template. Novel planning rules were designed to create more periphery‐conformable non‐template needle patterns. For all methods, inverse planning was used to optimize the seed spacing along the needles after needle pattern was determined. Dosimetry parameters (prostate V100, V150, urethra D1 and rectum V100) and number of needles and seeds were compared. The correlation of dosimetry outcome between two methods was analyzed. Isodose distributions were compared. Results & Discussion: Compared to the template plan using modified periphery needle pattern, the non‐template plans decreases number of needles by 20% and increases average V100 by 1%. Compared to the limited number of needle template plans, the non‐template plans resulted in 2% increase in V100 and 4% decrease in maximum urethra dose, but the rectum V100 increased by 0.02 cc (mean). The correlation between urethra dose decrease and rectum dose increase has p‐value 0.00032. That was because the needles inserted below the urethra and above the rectum play an important role to affect both doses. Non‐template plan generally has greater conformal dose coverage than the template plan. Conclusions: Non‐template plan dosimetry has observable advantage over template one with similar number of needles.
SU‐FF‐T‐78: High Dose Rate Interstitial Brachytherapy (HDRIB) for Localized Breast Cancer: New Plan Evaluation Criteria
Authors: Nair M , Mark R , Anderson P , White M , Ho Y , Banwo B , Nair S
Published: April 2010

Purpose: To present our technique for HDRIB for treatment of localized breast cancer using a custom made template. The plan evaluation criteria, in correlation with clinical outcome are also discussed. Materials and Method: We have developed a breast implant template and successfully used in over 200 patients. The template has been modified successively in order to yield better clinical results. The holes were drilled at locations such that the neighboring holes formed a triangle with base and row separated at 1 cm apart. The catheters were implanted under ABBY mammography image guidance in order to cover the surgical clips, with margin. Planning CT images were taken at 3 mm slice thickness. Using Plato brachytherapy software the catheters were reconstructed and plan was developed using graphical optimization tool. The criteria that we have been using for plan evaluation, based upon our clinical tolerance for least toxicity, was to use 1.5× Dref (510 cGy) to receive ⩽30% of PTV and 2× Dref (680 cGy) to receive ⩽ 10% of PTV. The PTV was designed to cover 95 to 100% reference dose. Result: Using the new template we have treated 105 patients. The PTV for these patients varied from 24 to 245 cc with median value of 99. The criteria ♯1 followed a % PTV volume in the range of 18 to 31 with a median value of 24, well within the limit. The criteria ♯2 followed a % PTV volume in the range of 16 to 31 at a median value of 24%, also within limit. Conclusion: Using the above criteria, there were no adverse complications such as fat necrosis or skin scarring. The patients have tolerated the treatment very well
SU‐FF‐T‐81: Automated Planning for Fast On‐Line CT‐Guided Adaptive Re‐Planning in IMRT for Prostate Cancer Patients
Authors: Pan X , Zhang X , Li Y , Li X , Wang X , Mohan R
Published: April 2010

Purpose: The purpose of this study was to evaluate the potential of our recently developed automated planning method for automated on‐line re‐planning to account for inter‐fractional changes encountered in prostate IMRT. Method and Materials: Three prostate cancer patients treated in our institution were randomly selected for this study. For each patient, an initial plan was generated on the planning CT using automated optimization algorithm (AOA) without trial and error. Three on‐line image guided strategies were evaluated: 1) the original plan applied to the repeated CT scan using the prostate‐center‐of‐mass alignment; 2) re‐optimized plan using the same objectives as those in the original plan; and 3) automated re‐optimized plan by AOA. Results: On average for 3 plans on 8 repeat CTs, V40, V60, and V70 for the rectum, V60 and V70 for the bladder of strategy 3 were reduced by at least 30.03%, 18.32%, and 12.12%, 6.98% and 5.43%, respectively, compared to those of strategies 1 and 2 for patient 1, by 22.23%, 14.89%, and 10.08%, 5.15% and 3.89%, respectively, for patient 2, and by 14.81%, 9.21%, and 6.90%, 4.56% and 3.77%, respectively, for patient 3. Strategy 3 also reduced the doses to the normal tissues (body excluding rectum, bladder and PTV) than strategy 1 and 2. CTV coverage for patient 2 in strategy 1 was compromised, but adequate for all other strategies for all three patients. Conclusion: Fully automated, without trial and error IMRT re‐planning is an effective approach for on‐line compensation of the target dose deficit and critical organ overdose caused by inter‐fractional anatomical change for CT‐guided adaptive IMRT for prostate cancer.
SU‐FF‐T‐82: Rapid Dose Calculation for IMRT Fields in Heterogeneous Medium
Authors: Zhu T , Hu Y , Finlay J
Published: April 2010

Purpose: To develop a fast algorithm to calculate patient specific 3D dose distribution for megavoltage photon beams. Method and Materials: In our PC‐based convolution algorithm, the ratio of scatter‐to‐primary dose, Ds/Dp, for a 2‐D non‐uniform field is calculated as a 3D convolution:
urn:x-wiley:00942405:media:mp1555:mp1555-math-0001 with and is the 2D intensity profile within the IMRT field, pi is 1 inside field and 0 outside field collimation for segment field i of the IMRT field. A(z) is the attenuation function. This convolution is calculated using a Fast Fourier Transform. The parameters a, w, and d0 characterize the phantom scatter properties and can be determined from measured PDD and Sp. In a CT phantom, fast ray‐tracing is used to calculate radiological depth for the attenuation function. Results: SPR calculated using MC simulation for 6 and 15 MV Mohan Spectrum is compared with the FFT convolution algorithm. They agree very well for depths beyond electron contamination. Agreement is also compared between FFT convolution and MC simulation in a heterogeneous phantom. They agree to within 1%, relative to the primary dose. Conclusion: This algorithm is ideally suitable for calculating patient‐specific MU for quality assurance of patient specific IMRT fields for photon beams. The major attraction is the fast speed, which allows potential real‐time applications.
SU‐FF‐T‐85: Adaptive Planning Due to Daily Dose Variations in Bladder and Rectum with Image‐Guided Radiotherapy
Authors: Wu X , Jacob R , Carlisle J , Gui M , Popple R , Fiveash J
Published: April 2010

PURPOSE: To study the daily variations in bladder and rectum during a course of definitive prostate radiotherapy and evaluate the necessity of adaptive planning for patients. METHODS and MATERIALS: Two patients who finished the hypofactionated radiotherapy with the prescribed dose 60 Gy in 20 fractions were selected to have the retrospective analysis. Daily MV‐CT images were obtained and registered. Contours of bladder, rectum and prostate were redrawn. The delivered doses of bladder and rectum were recalculated. In order to sum the cumulative doses of these two organs, the demons algorithm was used to register the daily image sets to reconstruct the total delivered doses. RESULTS: The rectum volumes in simulation were 85.85 cc and 84.67 cc for patient 1 and 2 respectively. During treatment, their average volumes were 136.8 cc (±38.6) and 127.9 cc (±30.1). The mean rectum volume encompassed by the prescription dose was 14.3% less in patient 1 and 46.6% more in patient 2. The mean bladder volumes in treatment were 6.8% less (166.2 ± 18.7 cc) and 4.5% more (124.3 ±39.6 cc) for patient 1 and 2 compared to their simulation volumes. The bladder volumes encompassed by the prescription dose were 14.3% and 12.5% higher in patient 1 and 2 respectively. The demons algorithm was used to register the daily MV‐CT image set to the first fraction MV‐CT image set. CONCLUSIONS: Significant variations of bladder and rectum doses were found during the course of prostate treatment. These variations can be ‘blurred’ out during a protracted, fractionated radiotherapy because of the randomness of these variations. They can be significant in hypofractionation radiotherapy. Cumulative doses can be obtained through demons algorithm and adaptive plans can be generated by using the adaptive tool.
SU‐FF‐T‐91: Initial Dosimetric Experience with Mega Voltage Computed Tomography (MVCT) Detectors and Estimation of Pre and Post‐Repair Dosimetric Parameters of a First Helical Hi‐Art II Tomotherapy Machine in India
Authors: Kinhikar R , Tambe C , Dhote D , Deshpande D
Published: April 2010

Purpose: On‐board mega voltage computed tomography (MVCT) detectors of a Helical Tomotherapy™ (HT) machine are routinely used for imaging and dosimetric purpose. First objective of this study was to estimate dosimetric and general capability (TomoImage registration, reconstruction, spatial resolution, artifacts free image and dose during TomoImage) of MVCT detectors. Second objective was to investigate system dosimetric stability (output and energy) of HT after major repairs. Methods and Materials: The lateral beam profiles were first measured in water at a depth of 1.5 cm with an A1SL (0.05 CC) ion chamber and later with the MVCT detectors for 5 cm jaw width with source to axis distance (SAD) of 85 cm. After a period of eight months, due to degraded image quality and gas leakage with the detector mechanism, the MVCT detectors were replaced. Due to frequent fluctuations in output and energy, the target was also replaced within the same period. Fixedgantry/ fixed‐couch measurements were made daily to investigate system stability. Static gantry output and energy measurements were measured with the manufacturer supplied and the independent (third party) dosimeters. Central axis depth dose (CADD) was measured and compared. The surface dose was also estimated. Thermoluminescense dosimeters (TLDs) were used subsequently. Results: The spatial resolution of MVCT detectors was optimal and the dose during TomoImage was 2 cGy. The results of lateral beam profiles showed an excellent agreement between the two normalized plots. The HT system has maintained its calibration to within ± 2% and energy to within ± 1.5% over the initial twelve months period. CADD measured with three dosimeters showed good agreement with each other. Conclusion: Based on the consistency in the lateral beam profile shape, the on‐board detectors proved to be a viable dosimetric quality assurance tool for HT. Tomotherapy output and energy was found stable after major repairs.
SU‐FF‐T‐92: A Dosimetric Analysis of IMRT Used to Replace and Mimic HDR Brachytherapy in the Treatment of Gynecologic Malignancy
Authors: Lamba M , Weatherford J , Elson H , Kassing W
Published: April 2010

Purpose: To evaluate the ability of intensity modulated radiation therapy (IMRT) to mimic the dose distribution of high‐dose rate (HDR) intracavitary brachytherapy in the treatment of gynecologic malignancy, including regions of high dose in the target volume while limiting doses to organs at risk (OAR). Methods: The HDR treatment planning CT scans of 4 patients with gynecologic malignancy were used in creating 3 different types of IMRT treatment plans. HDR dose levels were contoured and exported as volumes to the IMRT treatment planning system. The IMRT300% and IMRT100% plans were designed to mimic V300%(HDR) and V100%(HDR), respectively. No attempt was made to spare the OAR. Results of IMRT300% and IMRT100% were used to determine the limitations of IMRT in order to create IMRTTx: a compromised plan, designed to replicate the V100%(HDR) and the highest isodose volume possible, while sufficiently sparing the OARs. Results: The IMRT300% and IMRT100% plans showed an increase in V50% by a factor of 10 and 2, respectively. The IMRTTx plan mimicked V200%(HDR) to within a mean of 16.4% while concurrently replicating V100%(HDR) to within a mean of 79.7%. An associated mean of 510% and a mean D2cc increase of 61.7% and 102.7% for the bladder and rectum were realized. Moreover, for the patients who received supplementary conventional external‐beam radiation therapy (CXRT), nodal treatment was integrated with IMRTTx in order to replace CXRT. The nodal mean D90(IMRT) was within 3.9% of D90(CXRT). For all patients, IMRTTx OAR doses were below the regions of interest (ROI) constraints used clinically. Conclusion: The present study suggests that IMRT may be capable of mimicking HDR brachytherapy in the treatment of gynecologic malignancy. As V200%(HDR) and V100%(HDR) are mimicked, increased V50% and OAR doses must be accepted. Compliance to clinical ROI constraints can be achieved.
SU‐FF‐T‐94: Dosimetric Evaluation of the Setup and Breathing Motion Effect for Modulated Electron Radiation Therapy of Breast Cancer
Authors: Jin L , Li J , Fan J , Wang L , Chen L , Xu Q , Price R , Shan G , Ma CM
Published: April 2010

Purpose: In conventional photon breast therapy, the effect of setup and breathing motion is accounted for by adding a margin to the clinical target volume (CTV). In modulated electron radiation therapy (MERT), since the electron beams can be arranged nearly along the direction of the organ motion, the effect of breathing motion is greatly reduced. This work is aimed to estimate the dosimetric changes caused by setup and breathing motion for MERT of breast cancer. Method and Materials: Monte Carlo (MC) based inverse treatment planning was used based on the CT data of a breast phantom. The dosimetric accuracy of the MERT delivery using the Siemens photon MLC (pMLC) was verified previously. In this work, five Monte Carlo calculated plans were compared with different static displacements (along the beam direction) of the phantom from its normal position, i.e. ±1cm, ±0.5cm and 0cm. Comparisons were performed in terms of 2D isodose distributions, dose‐volume histograms (DVHs), minimum dose (Dmin), mean dose (Dmean) and maximum dose (Dmax). Results: For ±1cm target displacements, dose differences from the nominal plan (without target motion) are relatively large in both 2D dose distributions and DVHs. For example, the difference in Dmean for this case is about 3.4%, indicating a visible target dose reduction. For ±0.5cm target displacements, a minor difference is seen for the 90% isodose lines, and the difference in Dmean is less than 2%. The integrated dose distributions remain unchanged, indicating the effect of breathing motion on the dose coverage of the target is ignorable. Conclusions: Due to the relatively small SSDs used for pMLC‐based MERT the effect of patient setup may become significant (displacement >0.5cm). Breathing motion has little effect for en‐face electron irradiation. The magnitude of the setup effect can be estimated with the inverse‐square relationship with an accurately determined “effective” SSD.
SU‐FF‐T‐96: Clinical Study of the Necessity of Replanning IMRT Treatment for Patients with Nasopharyngeal Carcinoma
Authors: Yang H , Hu W , Wang W , Ding W , Shan G , Yu C , Wang B , Yan Y , Zhu H , Xu Q
Published: April 2010

Purpose: To investigate the necessity of replan for patients diagnosed with nasopharyngeal carcinoma (NPC) during IMRT treatment. Method and Materials: Twenty‐eight NPC patients treated with IMRT were selected in this study. The patients were prescribed of 70 to 76 Gy for Gross Tumor Volume (GTV) in 33 fraction treatment. Before the 25th fraction of the treatment, a new simulation CT were acquired for all the patients. GTV, Clinical Target Volume (CTV) and the surrounding critical normal structures in the new CT were manually delineated by the same oncologist for the original plan contouring. The original prescription dose for GTVnx, GTVnd, CTV1, CTV2 was 70∼76Gy, 66∼70Gy, 60∼66Gy, and 56∼60Gy respectively. The target dose distributions in the new CT were obtained after recalculating based on the original plan in CORVUS 6.3 treatment planning system. The doses of the spinal cord and parotid glands in two plans were quantified and compared, as well as for normal critical structures. Results: Significant decrease of the transverse diameter of the nasopharyngeal and the left and right parotid glands volume were observed before the 25th fraction, comparing to the original planning CT (p<0.0001). The mean decreases were 6.60±4.28mm, 4.49±4.77cm3 and 3.44±3.62cm3 respectively. The maximum dose of the spinal cord, mean dose of the left and right parotid were increased significantly at the 25th fraction (p<0.01). The mean of the increased dose were 5.18±8.41Gy, 4.15±9.21Gy and 5.29±9.278Gy respectively. Based on dose constraint criterion in the RTOG0225 protocol, the dose of the normal critical structures for 50%(14/28) of the regenerated plans were out of limit comparing to 3%(1/28) of the original plans (p<0.0001). Conclusion: Based on our observation, it is necessary to replan for patients with NPC to cover the targets and spare normal critical structures.
SU‐FF‐T‐97: Dosimetric Comparison of Whole‐Breast Irradiation Techniques: Supine Versus Prone Positions Using Helical Tomotherapy
Authors: Wang Y , Chang S , Chen W
Published: April 2010

Purpose: Whole breast irradiation is typically delivered in supine position. However, prone position delivery has also been proposed as an alternative technique for women with large breasts. The aim of this study was to compare the dosimetric results of whole breast irradiation delivered in prone and supine positions using helical Tomotherapy. Methods and Materials: Twenty patients with clinical stage 0‐II breast cancer underwent CT imaging in both supine and prone positions and were selected for treatment planning using the Tomotherapy Hi‐Art planning system. Dose‐volume histogram analysis was performed and the mean dose value as well as other dosimetric parameters of PTV and organs‐at‐risk (OAR) were compared in all patient cases. Results: In all twenty patient cases, the completed treatment plans were able to deliver at least 97% of the prescribed dose to PTV and the maximal dose was no larger than 108% in both supine and prone positions. The PTV coverage for prone position (97.98%) was slightly better (p=0.0009) than that of supine position (97.47%). There were no significant differences between the prone and supine positions in terms of hot spots and field homogeneity. The mean dose and V5 in OARs such as lung, heart and ipsilateral breast were significantly lower (29%–86% reduction depending on specific OAR) in prone position than in supine position plans. Conclusion: The prone‐position radiotherapy technique performed better than the supine‐position technique for breast cancer treatment in Tomotherapy with improved target coverage and lower incidental radiation doses to heart, lung and contralateral breast. However, comparing to the supine position technique, the prone‐position technique has limitations for big body size patients due to the requirement of positioning the prone board inside the bore of the Tomotherapy device.
SU‐FF‐T‐98: Evaluation of RapidArc for Locoregional Radiotherapy of Left‐Sided Breast Cancer: Comparison with Conventional Intensity Modulated Radiotherapy(cIMRT)
Authors: Popescu C , Wai E , Olivotto I , Beckham W
Published: April 2010

Purpose: RapidArc is a novel volumetric modulated arc technique with dynamically variable MLC positions, dose rate and gantry speed. RapidArc is highly efficient and has the potential to reduce monitor units and treatment times compared to cIMRT. This report presents our first experience in performing treatment planning for breast cancer using Eclipse RapidArc optimization software 8.4.10 that supports multiple arcs. RapidArc plans were compared with cIMRT for locoregional radiotherapy of left‐sided breast cancer, including the internal mammary nodes (IMN). Method and Materials: 4 patients previously treated with cIMRT to the left breast/chest wall and regional nodes, including internal mammary chain, were planned (50Gy/25fractions) using the same contours and CT dataset with the RapidArc technique. Different RapidArc planning strategies were investigated. The endpoints of the comparison between RapidArc and cIMRT plans were breast PTV homogeneity, conformity of the plans, heart V30, left lung V20, mean doses to surrounding structures, number of monitor units (MUs) and treatment time. Results: 2 arcs were used due to the large treatment volumes to be optimized and the finite travel range of the multileaf collimator (MLC). Treatment plans generated using RapidArc optimization resulted in similar PTV homogeneity as compared with cIMRT. The best RapidArc plans (2 short arcs of 190 degrees each) reduced the mean dose to heart from 11.2±1.0Gy to 9.7±0.7Gy and ipsilateral lung from 14.5±0.8 to 13.6±0.6Gy. The number of MUs was reduced by 50% and the mean beam on time was reduced from 5.85±1.04 minutes to 1.4±0.05 minutes for RapidArc as compared with cIMRT. Conclusions: RapidArc optimization employing 2 arcs is feasible and yielded similar dosimetric plan quality as compared to cIMRT. RapidArc reduced the MUs and significantly reduced the beam on time as compared to cIMRT.