bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐J‐80: Clinical Procedures for Daily Patient Setup Verification Using On‐Board Imager (OBI)
Authors: Hammoud R , Yin F , Yoo S , Guan H , Pradhan D , Ajlouni M , Movsas B
Published: June 2005

Purpose: The newly installed OBI system consists of a kilo‐voltage (KV) X‐ray source and a flat‐ panel detector mounted orthogonally to the megavoltage portal imager (MV) in Varian 21EX machine. These devices are linked to the OBI workstation which provides a platform for acquisition/analysis of images and auto couch motion for repositioning the patient. This paper presents our clinical procedures for patient setup verification using OBI. Method and Materials: In phase I, two sets of orthogonal MV/MV and KV/KV images were acquired to confirm the accuracy of the KV system by comparing daily KV images to traditional MV images and corresponding Digital Reconstructed Radiographs (DRRs). The phase II study acquired only one set of orthogonal MV/KV portal images for daily patient setup verification. An anterior MV and lateral KV images were obtained without gantry rotation. The OBI workstation provided the tools to match the images with DRRs and to analyze the shifts to be made for patient setup correction based on either implanted and/or anatomical markers. The treatment couch was moved automatically based on this analysis. Post‐shift MV/KV images were acquired to reconfirm patient positioning. All images and positioning data were electronically saved and reviewed. Results: Four prostate IMRT patients were included in phase I study. The isocenter alignment of the two sets of images (MV/MV and KV/KV) was found within 2mm relative to DRRs during the entire treatment courses. The phase II study included 30 prostate IMRT patients. The review of post‐shift MV/KV images showed an average of 2 mm deviation relative to DRRs. All procedures could be completed within 3–5 minutes. Conclusion: Phase I study proves that KV images are as reliable as MV portal images with better image quality. Phase II study verifies that matching/analysis tools and auto‐couch motion provide fast and accurate patient positioning.
SU‐FF‐J‐81: Clinical Integration of a MV Conebeam CT System for Image‐Guided Treatment
Authors: Pouliot J , Bani‐Hashemi A , Aubin M , Ghelmansarai F , Chen J , Morin O , Bucci K , Roach M , Verhey L
Published: June 2005

Purpose: To perform the integration of a newly developed image‐guidance system and to describe the main advantages and performance of the first Megavoltage Conebeam CT (MV CBCT) system. Method and Materials: The MV CBCT system, consisting of a new a‐Si flat panel adapted for MV imaging and an integrated workflow application allowing the automatic acquisition of projection images, conebeam CT image reconstruction, CT to CBCT image registration and couch position adjustment was recently introduced in clinic. Template protocols can be used for the acquisition of CBCT images at different dose ranging from 1 to 60 M.U. Geometrical calibration, gain image adjustment and defect pixels correction procedures are performed off‐line. Results: For a typical case, 200 projection portal images and a total exposure of 5 to 8 M.U. are acquired with the 6 MV beam in 45 seconds and the 256×256×256 MV CBCT image is reconstructed less than two minutes after the start of the acquisition. Examples of the image‐guided treatment process including the acquisition of projections images, the reconstruction of the MV CBCT image and its registration with the planning CT, followed by the couch position correction and dose delivery will be presented. Conclusion: MV CBCT provides a 3D patient anatomy volume in the actual treatment position, relative to the treatment isocenter, moments before the dose delivery, that can be tightly aligned to the planning CT, allowing verification and correction of the patient position. Research supported by Siemens Oncology Care Systems.
SU‐FF‐J‐90: An Accurate Method for Determining Prostate Shift and Rotation Using Portal Images with Implanted Fiducial Seeds
Authors: Chen Y , Valicenti R , Suh D , Houser C , Galvin J
Published: June 2005

Purpose: Portal imaging of implanted fiducial seeds is widely used for setup verification of conformal radiotherapy for prostate cancer. Isocenter shift is usually determined by the shifts of two imaging fields required to align the fiducials to their planned positions. Due to prostate rotation, deformation and seed migration, it might not be possible to satisfactorily align the fiducials. We describe here an accurate image‐processing method to determine the isocenter shift and prostate rotation using three fiducial seeds. Method and Materials: Two portal images were obtained using anterior‐oblique beam angles for clear seed imaging. The center of a portal image was determined by field edges. The images were enhanced for seed identification by filtering operations. The 3‐D coordinates of the seeds were determined considering their physical dimensions and the signal strength of processed images. The three seed‐to‐seed distances were checked to avoid using a migrated seed for setup verification. The Triad algorithm was used to find the rotation of the plane of the three seeds to make it exactly parallel to the reference seed plane. The seeds were then shifted and rotated about the common normal vector to the seed plane by iterations for a least‐square fit of imaged and planned seeds. Results: The method was tested on 10 cases with daily portal images. The largest isocenter shift and seed plane rotation were 2 cm and 13 degrees, respectively. The isocenter shifts determined by aligning the seeds on individual images with split differences led to larger than 2 mm errors. The seed‐to‐seed distance was reduced on average by 3–4 mm, indicating the prostate was shrinking during the treatment. Conclusion: An accurate method was developed for determining the shift and rotation of the prostate using portal images, in order to minimize the errors due to lacking the 3‐D correlation of fiducial seeds.
SU‐FF‐J‐93: Treatment Dose Verification for Image‐Guided Stereotactic Radiotherapy of Lung Cancer
Authors: Wang L , Feigenberg S , Paskalev K , Konski A , Xiong W , Ma C
Published: June 2005

Purposes: The purpose of this work is to retrospectively verify treatment dose delivered in patients treated with stereotactic radiotherapy (SRT) to the lung. Method and Materials: In this study, a stereotactic body localizer (SBL) system was used for lung cancer patient immobilization in the CT simulation and stereotactic treatment planning on a prospective dose escalation protocol for malignant lung tumors. Prior to each treatment, a localization CT san was obtained in the treatment room after the patient was immobilized in the SBL. The stereotactic coordinates of three pre‐selected bony landmarks were recorded from the pre‐treatment scan and compared with those of the planning scan. Couch shifts were made based on the bony‐landmark displacements. Image fusion was performed between the simulation CT scan to each pre‐treatment CT scan in order to obtain the same planning target volumes (PTVs) and critical structures. The same treatment plans were re‐loaded onto each pre‐treatment CT scan with their respective stereotactic coordinate system. The changes in dose distributions were assessed by dose‐volume histograms of the PTV and normal structures for the old and new isocenter coordinates using the bony‐landmark shifts. We compared D95, D99, and V95 for the PTV and GTV, and V20 and V30 for the ipsilateral lung. Results: Our preliminary study for 6 patients with 20 dose reconstructions showed that the average D95, D99, and V95 of the PTVs are 95.9%, 93.6%, and 98.4% of the planned values before bony‐landmark shifts. With the bony‐landmark shifts, these values are all improved to 100% of the planned values. The average V20 and V30 are 7–8% higher than the planned values without bony‐landmark shifts and recovered the planned values after the corrections. Conclusion: With near real‐time 3D image guidance for setup error correction, the delivered dose distribution can be ensured for SRT hypofractionated lung treatment.
SU‐FF‐J‐96: The Application of Varian's Markermatch Software in a Retrospective Study of Inter‐Fractional Prostate Motion
Authors: Wang Z , Komanduri K , Wu A , Selvaraj R , Brandner E , Chen A , Bahri S
Published: June 2005

Purpose: MarkerMatch is an automated marker match software feature developed by Varian in on‐board imaging. It may calculate inter‐fractional prostate motion with internal fiducial markers identified on CT scans. Before each treatment, a pair of portal images was taken and fiducial markers are identified. Based on the portal image pair, MarkerMatch calculates the optimized couch displacement in 3D to maximally restore the marker positions to their reference positions. To evaluate MarkerMatch's clinical performance, we did a phantom test and a retrospective study on patients implanted with radio‐opaque fiducial markers. Method and Materials: We used a phantom implanted with 4 cylindrical‐shaped markers of 1mm in diameter and 3mm in length. MarkerMatch localizes the markers based on CT images. In order to test MarkerMatch's ability to handle CT images of different quality, we scanned the phantom with four CT spacing. The portal image pair taken before treatment is normally at AP/Lateral gantry angles, but sometimes it is difficult to identify markers from the lateral image. To test MarkerMatch's ability to handle non‐orthogonal portal image pair, we took portal images at 7 different gantry angles. As a preliminary test for the use of Markermatch in clinic, we retrospectively analyzed five patients implanted with 2–3 gold markers based on 43 pairs of weekly setup portal images. Results: In our phantom test, MarkerMatch is able to measure overall marker displacements within 1mm in each direction, regardless of the spacing used in the CT scans. Using different gantry separation angles, the measured overall marker displacements agree with each other within 1mm. Retrospective analysis of five patients is also presented. Conclusion: Initial studies indicate that MarkerMatch is robust in detecting and analyzing patient motion in 3D and can provide valuable information of inter‐fractional prostate motion in clinic. Conflict of Interest: Funded in part by Varian Research Grant.
SU‐FF‐J‐98: Feasibility of Deformable Structure Registration Towards Calculation of Cumulative Dose Distributions
Authors: Xiong L , Viswanathan A , Stewart A , Haker S , Tempany C , Cormack R
Published: June 2005

Purpose: Cumulative dose distribution in fractionated radiation therapy is one means to evaluate the risk of complications. Yet the calculation of the distribution is highly challenging due to inter‐fraction change in anatomic geometry. This work presents an algorithm for deformable image registration of bladder and cumulative dose calculation in the setting of HDR brachy‐therapy for vaginal cylinder treatment. Method and Materials: CT scans were obtained on 20 patients with gynecological cancer who received fractionated high dose rate brachy‐therapy to the vaginal cuff, with the vaginal cylinder in situ. As part of an IRB approved study, the patients' bladder filling status was intentionally different for each fraction. The bladder was manually contoured for each treatment fraction and its surface was extracted for input to a biomechanical deformable registration algorithm, which models the structure surface as a thin elastic sheet. Three anatomic correspondence points were identified for each fraction. In three patients we observed additional identifiable landmarks against the bladder wall. These extra markers as shown in each fraction were compared with their predicted location based on both the affine and deformable registration. Results: Compared to the bladder volume at the time of the first fraction, the ratio of the bladder volumes for later fractions ranged from 30 to 300%. Rigid and affine registration of the bladder showed poor correlation of the landmark locations. The deformable registration algorithm significantly improved the accuracy of the correlation. While validation was possible for only three patients, eight independent tests were done for different fractions. Conclusion: The deformable registration algorithm provides a means of tracking points on structures despite significant change in size and shape. While further validation is needed, this approach provides a means to calculate cumulative dose distributions that were not previously feasible.
SU‐FF‐J‐103: A Robust Marker Registration Algorithm
Authors: Parra A , Narasimhan G , Samant S
Published: June 2005

Purpose: We present a novel marker registration algorithm for rigid‐body transformations that minimizes sum of least squares between two point sets, and requires no user intervention to handle missing markers. Method and Materials: The novel registration algorithm computes the sum of squared distances by finding the minimum weighted matching of a dense bipartite graph (DPG). The space of rigid‐body transforms (3 translations and 3 rotations) is explored using a branch‐and‐bound method. The minimum weighted bipartite match is calculated using a modified Dijkstra's algorithm[1]. The branch‐and‐bound method is an extension to 3D of the method in [2]. Unlike conventional singular value decomposition (SVD), i) DPG works with point sets with different cardinalities; and ii) no homology or correspondence has to be defined between reference and target point sets. These advantages provide our algorithm with greater robustness for automatic marker detection, and handling missing markers. Though DPG is not limited by number of markers (N), here N=3 to 7 was used to simulate clinical conditions. Results: DPG yielded an accuracy of <0.1mm translational and <0.1° rotational errors, which are within the precision of back projection errors. It was validated using simulated portal images and a high precision table. It was tested on clinical portal imaging data to validate robustness for missing markers. Conclusion: DPG provides an accurate and robust point based registration that works with missing markers and different cardinalities, which can be used in conjunction with automatic marker detection.
SU‐FF‐J‐104: In Vitro Model to Study the Biological Effect of Dose Gradients On a Cell Culture System
Authors: Bromley R , Oliver L , Harvie R , Davey R
Published: June 2005

Purpose: Coupled with improved accuracy of radiation therapy delivery, margins around tumour volumes tend to be much tighter. Radiobiological assessment of the changes in cell death at boundaries between the high and low dose regions would improve our knowledge on what is an adequate treatment margin. We have developed a new method of cellular analysis to assess the spatial response of cells across a gradient radiation dose. Method and Materials: A549 non‐small cell lung cancer cell line was used in a 6 well plate format. The cells were bedded down and maintained at a constant position in the well over the time frame of analysis. Wells 1 and 4 were the unirradiated control wells, wells 2 and 5 were half irradiated and wells 3 and 6 were fully irradiated. Different radiation doses were delivered to the cells in various phases of growth and cell density. The cells were left for various times after irradiation before analysis. The cells were washed with the protein specific Crystal Violet stain and then scanned at 570nM to obtain the protein levels in the well. Results: Crystal Violet cell viability correlated with the MTT cell viability assay. An exponential decrease in cell viability was observed when increasing the dose up to 15Gy. The intensity of Crystal Violet stain across the half‐irradiated wells showed a sigmoid shape at the interface with close correlation between the slope of the stain and the radiation dose. Conclusion: This method provides valuable biological information on the effects of the radiation dose at the beam edge. The results indicate that there may be inter‐cellular communication across the gradient dose interface. This may need to be considered when defining the tumour region.
SU‐FF‐J‐105: Tools for Voxel‐By‐Voxel Correlation of Radiotherapy Dose and MR Signals From Multiple Physiological/functional MRI Modalities
Authors: Ahunbay E , Schmainda K , Lund R , Prost R , Ulmer J , Alaly J , Deasy J , Schultz C , Li X
Published: June 2005

Purpose: The use of multiple physiological/functional MR modalities for radiation therapy is limited by the lack of tools to correlate voxel‐by‐voxel MR signal with voxel‐by‐voxel dosimetric data. Developing such tools is the purpose of this work. Method and Materials: We have developed a process and tools that enable the analysis of the data from multiple forms of MR based biological/functional imaging modalities along with the 3D dose distributions from a commercial radiation treatment planning system. Different types of images (CT and multiple MRs) are registered through commercial software (XIO CMS). A 4×4 registration matrix for the rotation and translation of coordinates is extracted from this software and used by our code written in MATLAB for interpolation of data from one coordinate system to another. The computational environment for radiotherapy research (CERR) served as the main platform for handling and visualization of data. We made additions and modifications to CERR to accomplish multiple secondary image ‐dose display and extraction of voxel‐by‐voxel registered information. This overall system of tools also has the capability of volumetric dose analysis, such as DVHs, and a voxel‐based biological quantify, VED (Voxel uniform dose, similar to EUD except it is calculated in a voxel) can be obtained. Results: The tools are being used in our institution in retrospective voxel‐by‐voxel analyses of radiation responses using various MR modalities, including relative cerebral blood volume (rCBV), Chemical shift imaging (CSI) and Diffusion Tensor Imaging (DTI). Conclusion: In order to integrate multiple functional MR modalities into radiation therapy process (planning and outcome assessment), a necessary step is to understand the relationship between MR data and treatment responses. This requires voxel‐by‐voxel registration between multiple image datasets and voxel‐by‐voxel correlation between image data with radiation dose. The tools developed in this work serve this purpose.
SU‐FF‐J‐106: FMISO‐PET Hypoxia Imaging: A Novel Method to Plan IMRT‐Based Boost Radiation to Hypoxic Subvolumes
Authors: Hendrickson K , Rajendran J , Ford E , Kinahan P , Lewellen B , Phillips M , Krohn K
Published: June 2005

Purpose: To investigate the use of [F‐18] fluoromisonidazole (FMISO) PET and intensity modulated radiation treatment (IMRT) planning to escalate the dose to hypoxic subvolumes in patients with advanced head and neck tumors. Method and Materials: Seventy‐three patients with head and neck cancer underwent FMISO‐PET scans, with fifty‐three of them also undergoing FDG‐PET scans as part of ongoing research studies. An initial treatment plan used a PTV defined with a 0.5‐cm margin around physician‐defined primary GTVs and affected nodal systems. The prescription dose is 70 Gy to the PTV and 50 Gy to the affected nodes, while sparing the spinal cord, mandible, and parotid glands. Physician‐defined regions of enhanced FMISO signal were used to define boost volumes on coregistered FMISO‐PET/CT images. The boost plan prescription dose to the hypoxic subvolumes is an additional 10 Gy. Results: Initial results from example treatment plans for two head and neck cancer patients are as follows (average over patients): to the PTV V100 = 87.2%, Dmin = 6081 cGy, D10 = 7303 cGy and to the nodal system V100 = 95.9%, Dmin = 4764 cGy, D10 = 5280 cGy. The IMRT boost plan yields V100 = 95.1%, Dmin = 979 cGy, D10 = 1012 cGy to the hypoxic PTV. The critical structures of interest received the following dose distributions from the composite IMRT plans: cord D1 = 3890 cGy, left (contralateral) parotid gland D1 = 1965 cGy, right parotid gland D1 = 4907 cGy (same side as primary tumor), and mandible D5 = 6220 cGy. Conclusion: We demonstrate the feasibility of directing dose‐escalated IMRT to hypoxic subvolumes in head and neck cancer using coregistered FMISO‐PET and CT images. Ongoing research and patient studies are expected to provide conclusive information on the clinical role of this procedure.
SU‐FF‐J‐109: Analysis of the Organ Motion Effects On the Fluences for Liver IMRT
Authors: Kuo H , Chuang K , Wu A , Liu W , Lalonde R
Published: June 2005

Purpose: To study the effects of organ motions due to respiration on the fluences of IMRT plans and to develop an acceptable limit of organ motion for gated IMRT with DMLC delivery. Method and Materials: The fluence changes due to organ motion were calculated using Chui's algorithm. We limited our studies on the fluence changes from superior‐inferior organ motion perpendicular to the motion of MLC. 108 fluence maps of 16 IMRT plans for 8 liver patients were calculated, analyzed, and compared without and with gating. The motion effects on the fluence maps were evaluated by both the fluence differences and the χ function which is a revision of the γ function. The max. displacements of the organ motions of all of these cases were analyzed and correlated with the change of fluences for liver IMRT plans. Results: The effective fluence due to organ motion of one of the patients was incorporated in dose plan for illustration. The DVH showed that 5 mm of motion displacement with gating seemed to have a little effect on the PTV and normal liver coverage while 9 mm without gating caused 8% drop in D90 and 3% increase in V30 of normal liver. Furthermore, four test cases with various fluence maps were subject to simulated motion with max. displacement ranging from 5 to 25 mm. To keep the |χ| value >1 percentage for fluence safely below 25% or the percentage of DD>3% below 40% with or without gating, 8 mm max. displacement seems to be a good cutoff. Conclusion: After 108 fluence maps of 8 patients and four test cases of different fluence patterns were analyzed, it is concluded that an 8 mm maximum motion displacement seems to be a practical and acceptable standard with gating technique.
SU‐FF‐J‐112: Design and Applications of a 4D Simulator for Respiratory Motion
Authors: Ayyangar K , Djajaputra D , Zhen W , Enke C
Published: June 2005

Purpose: To design, construct, and evaluate a pneumatic respiratory‐motion simulator for 4D radiotherapy. The device should be able to operate in dynamic mode for real‐time simulation of patient breathing motion as well as snapshot mode for static dose measurement. Method and Materials: A simulator incorporating a cylindrical air reservoir with a piston was constructed as a tool in 4D radiotherapy studies. The piston movement is controlled by a programmable logic controller (PLC) which is interfaced to custom software written in Visual Basic (VB). The air reservoir is connected to a lung phantom made of two pulmonary simulation balloons. The pressure inside the lung phantom is monitored by a detector whose input is feedback to the PLC. The lung phantom is immersed in a water‐filled box to simulate the normal tissue surrounding actual human lungs. The box is connected to a water reservoir to allow breathing of the lung phantom. A rubber ball is attached to the inner side of the phantom to simulate a lung tumor and gold seeds are implanted into it for seed‐tracking studies. Spirometer‐based patient respiratory waveform data in ASCII format were obtained from our department's breath‐hold clinical study. The waveform data are input to the VB program and sent to the simulator for controlling the simulation. Results: Preliminary evaluation of the simulator using several patient waveforms has been conducted. The respiratory motion of the lung phantom is found to be reproducible. Conclusion: A prototype respiratory‐motion simulator has been built which should prove valuable for 4D radiotherapy and related studies (gating, respiratory‐induced organ deformation). Its unique design of using pneumatic means to simulate breathing motion allows more realistic simulation studies including those involving animal lung models.
SU‐FF‐J‐113: Determination of Appropriate Lung Volume for Dosimetric Planning and Analysis From 4D CT
Authors: Stepaniak C , Li X , Gore E
Published: June 2005

Purpose: Lung volumes at different breathing phases are substantially different from each other based on 4D CT. They are also different from the lung volume based on conventional 3D ungated CT. However, the dosimetric criteria and lung toxicity data used in the current planning process are based on the conventional 3D CT lung volume. Determining appropriate lung volume from 4D CT for treatment planning of lung cancer is the purpose of this work. Method and Materials: We obtained 4D CT scans of 10 patients using a GE LightSpeed RT scanner in combination with the Varian RPM respiratory gating system. For two of these patients, we have also obtained conventional 3D CT scans. The 4D CT scans were reconstructed into 10 breathing phases, as well as maximum, minimum, and average intensity projections. The lungs were then contoured for each phase and intensity projection, as well as for the 3D scans, and volumes for these contours were obtained. Results: We find that the average intensity projection (AveIP) is the most consistently close to the 3D CT volume, differing at most by about 3% of the total lung volume. The phase volume most closely approximated by the AveIP is the 20% phase (mid‐exhalation) or the 80% phase (mid‐inhalation), differing from the AveIP on average by 1.8±2.2% and −1.2±1.7%, respectively. The lung volume from the maximum intensity projection (MIP) is on average less than the AveIP volume by 11.4±2.3%. Conclusion: The lung volume from the 20% or 80% phases or the AveIP based on 4D CT should be used in the treatment planning for lung cancer. While the MIP is useful for ITV determination, it underestimates the lung volume compared to the conventional 3D CT.
SU‐FF‐J‐115: Effects of Anatomical Changes Due to Response to IMRT On Radiation Doses to Organs at Risk; A Case Study for Image Guided Adaptive IMRT
Authors: Rahimian J , Iganej S
Published: June 2005

Purpose: The purpose of this study is to evaluate dose volume histograms of the PTV, and the organs at risk (OAR) during a course of IMRT treatment of a patient with olfactory neuroblastoma. The study will help simulate adaptive IMRT for patients with similar disease. Method and Materials: A 46 years old male patient with unresectable right‐sided olfactory neuroblastoma with right eye proptosis of about 1.5cm was treated with IMRT using a Brainlab Novalis SRS system. The daily dose was 180cGy to the isocenter for 35 fractions. The initial PTV volume measured to be 108cc. A Brainlab mask system with a daily positional accuracy of 1mm was used to immobilize the patient. The eyes, optic nerves, and chiasm were defined as organs at risk. 8 step and shoot IMRT beams were defined. The CT images of the patient acquired initially, and at fraction 34 were fused, and compared. Results: The gross tumor volume (GTV) decreased during the course of IMRT from 108cc to 38 cc, a 65% reduction in volume. The right eye moved back to its position by 9mm during the IMRT course of treatment, a linear transition of 0.3mm/FX. The maximum dose to the right orbit increased from initial dose of 90cGy/FX to 180cGy/FX at the last fraction. The original planned OAR dose was significantly increased to both the right orbit, as well as the right optic nerve due to tumor shrinkage compared with the start of the treatment. Conclusion: In the absence of image guided adaptive therapy for tumors, which respond rapidly to radiotherapy, more conservative dose limitations may be necessary for the organs at risk. In addition, imaging studies during the course of the treatment would help evaluate, and possibly modify the IMRT plan.
SU‐FF‐J‐118: Lung Target Volume Inaccuracies Due to Motion in Non‐Gated and Gated CT Images
Authors: Wells D , Lim J
Published: June 2005

Purpose: To quantify lung planning target volume (PTV) inaccuracies due to motion in non‐gated and gated CT images. Method and Materials: A motorized test object: sphere diameter (2.5, 5.0 cm), orbit diameter (1, 2 cm) and period (3–5 sec.) was constructed. For non‐gated helical CT, pitch, slice width, interval and acquisition time was varied. For gated CT, phase and slice acquisition time was varied. Structures were automatically contoured and a 1 cm margin added using a 3D growing tool. A performance metric, normalized volume (NV), was defined as measured PTV divided by theoretical volume (NV=1, static conditions). A uniform margin, based on a spherical model, was calculated over a range of orbital speeds. External marker motion for ten lung cancer patients was measured and minimum residual motion was calculated for a duty cycle spanning CT slice acquisition time. Results: Optimal non‐gated helical protocols (time: 1.0 sec./rotation, pitch: 0.4–0.7, width: 2–3 mm, interval: 1 mm) achieved NV>0.85 over a range of clinically relevant orbital speeds; a standard protocol for lung (time: 1.5 sec./rotation, pitch: 1.5, width/interval: 3 mm) achieved NV>0.70. Gated protocols (time: 1.0 sec./rotation, width/interval 2–3 mm) achieved NV>0.65 over the same range of orbital speeds. For the lung patients, average orbital speed of the external marker ranged from 0.5 to 1.5 cm/sec. and residual motion ranged from 1.5 to 4.6 mm. Assuming a 1:1 ratio of marker to tumor motion, margins for non‐gated CT of 0.7 to 1.5 mm (optimal) and 1.5 to 3 mm (standard) were required to achieve NV=1. For gated CT, margins of 0.3 to 1 mm were required. Conclusion: Inaccuracies in PTV delineation due to tumor motion occur in both non‐gated and gated CT images. Average orbital speed of an external marker for lung patients may be used to estimate tumor motion margin.
SU‐FF‐J‐119: Margin Calculations for Prostate Radiotherapy Using Electronic Portal Imaging, Implanted Fiducials and Three Localization Methods
Authors: Beltran C , Herman M
Published: June 2005

Purpose: To quantify the PTV margin for prostate radiotherapy based on daily electronic portal images (EPIs) of intraprostatic fiducial markers and three localization methods: Skin marks, visual matching and computer aided matching. To correlate with high statistical accuracy the prostate and bony anatomy location based on the EPIs. Method and Materials: A cohort of 20 patients, receiving standard course fractionation, had gold fiducial markers placed in their prostates and marker position relative to isocenter was determined based on CT simulation. Skin marks established initial localization. Daily orthogonal pre‐treatment EPIs were used to visually identify the markers and determine any 3D offsets. Finally, off‐line computer aided localization was performed. 3D localization offsets and margins were determined for each method. Prostate to bony anatomy position correlation was based on an 80 patient cohort and evaluated with Pearson r2 correlation value (r2 > 0.75 suggests strongly correlated). Results: Margins based on localization using skin marks (visual matching) and [computer aided matching] are 5.1 (2.7) [1.5] mm Sup‐Inf, 7.3 (2.9) [2.0] mm Ant‐Post and 5.0 (2.8) [1.0] mm Right‐left. The Pearson r2 correlation value for the bony anatomy vs. prostate is 0.12 Sup‐Inf (not correlated), 0.30 Ant‐Post (not correlated), and 0.79 Right‐Left (strong correlation). Conclusion: There is a substantial reduction in the margin from the skin mark setup to the visually matched localization and further to computer aided localization. A nearly 4 fold decrease from skin mark setup to computer matched localization in the Ant‐Post direction indicates a potential for dose reduction of critical structures and increased dose to the PTV. Correlation results suggest that bony anatomy cannot be used as a predictor of prostate motion (except in the Right‐Left direction), and if so used, may be harmful. Conflict of Interest: Varian Medical Systems partially funded this research.
SU‐FF‐J‐121: Patterns of Intraabdominal Organ Motion as Measured by Quantitative 4D CT
Authors: Ma D , Parikh P , Lu W , Nystrom M , Hubenschmidt J , Wahab S , Singh A , Botero A , Myerson R , Low D
Published: June 2005

Purpose: Many clinics are investigating the use of IMRT for intraabdominal malignancies. Respiratory motion must be measured to determine optimal target and normal tissue margins. The purpose of this study was to quantify the movement of abdominal organs with non‐coached respiration. Method and Materials: Ten patients with hepatobiliary malignancies underwent quantitative spirometry during a multislice‐CT following standard helical‐CT simulation (Philips Brilliance 16‐slice). Abdominal CT images were reconstructed by tidal volume, capturing end‐expiration, mid‐inspiration, end inspiration, and mid‐expiration. Each CT reconstruction was fused with the standard helical‐CT simulation. The liver, spleen, stomach, pancreas, kidneys and surgical clips were contoured for each patient when applicable. The organ motion was determined by measuring the distance between the geometric center of end‐expiration and end‐inspiration contours. Hysteresis was determined by measuring the distance between the geometric centers of the mid‐inspiration and mid‐expiration contours. Results: A total of 72 structures have been contoured in eight patients. Five patients were status‐post pancreatic resection. Hysteresis in organ movement was demonstrated when comparing mid‐inspiratory and mid‐expiratory contours, with differences in mid‐inspiration and mid‐expiration contours of up to 1.59cm. Total max‐inspiratory to max‐expiratory movement for the liver, stomach, kidneys, spleen, and pancreas were 1.00, 1.46, 1.29, 1.52, and 1.16cm. Total mid‐inspiratory to mid‐expiratory movement for the liver, stomach, kidneys, spleen, and pancreas were 0.51, 0.76, 0.71, 0.78, and 1.12cm. The maximal movement for the liver, stomach, kidneys, spleen and pancreas were 1.47, 2.47, 1.90, 2.29 and 1.73cm. Results for the surgical clips were similar. Conclusion: Despite the anatomic variation expected in a diverse population, all the upper abdominal organs moved inferiorly and anteriorly with inspiration. Each organ moved at least 1cm on average, and more than 2cm in certain patients. Hysteresis was significant in some patients. Further work to investigate changes in dose distribution from this movement is ongoing.
SU‐FF‐J‐123: Residual Tumor Motion in Respiratory Gated CT Treatment Planing
Authors: Shen S , Duan J , Spencer S , Fiveash J , Russo S , Bonner J , Ye S , Popple R , Pareek P , Brezovich I
Published: June 2005

Purpose: Respiratory gated CT planning and treatment has been used to reduce widened margins that accounts for motion‐induced uncertainties. This study evaluates the residual tumor motion within the gating window of gated CT scans and associated margin. Method and Materials: Gated CT data were acquired in 24 patients (23 lung cancer, 1 liver cancer) at the end‐of‐expiration and at the end‐of‐inspiration on a PQ5000 CT simulator with a commercial gating system. Three moving spherical phantoms were also used to simulate tumor motions at 2–4 sec/cycle. Gated CT data at the end‐of‐expiration was used for treatment planning for gated intensity modulated radiotherapy (IMRT) or three‐dimensional conformal radiotherapy (3DCRT). Residual target motion within the gating window was determined using target motion determined from the CT pairs, recorded surrogate marker motion at the end‐of‐expiration and end‐of‐inspiration. Results: Phantom study suggests that breathing cycle should be > 2 sec/cycle to avoid image artifacts induced by residual motion. A minimum 3 sec/cycle breathing period is required for patients undergoing gated CT in our institution. In the patient study, most tumors moved in the superior‐inferior direction ranging from 3mm to 17mm. The residual target motion within the gating window ranged 0.6mm to 3.4mm. Based on a mean positioning error of 3.0 mm for gated treatment reported in the literature, a margin of 6.0mm to 9.0mm (within 2σ of independent Gaussian distributions) was required to account for both daily positioning error and residual tumor motion in gated IMRT and 3DCRT, corresponding to an additional margin of 0.1 mm to 3.1 mm comparing to that without accounting for residual tumor motion. Conclusion: Residual tumor motion within the gating window should not be ignored. Additional margin accounting for residual can be estimated from gated CT data and applied to gated treatment.
SU‐FF‐J‐124: The Unappreciated Benefits of Randomness and Slow Delivery with Organ Motion
Authors: Kissick M , Boswell S , Jeraj R , Mackie T
Published: June 2005

Purpose: Expand a groundbreaking study (C. Yu, et al., PMB 43, 91) to explore the implications for helical tomotherapy and to expand it with more exploration of random components of the organ motion function. Method and Materials: Three MatLab codes were independently constructed to simulate sinusoidal motion (amplidute, scan speed, and frequency varied) superimposed upon a constant scan speed as in C. Yu, et al., PMB 43, 91. The fluence at a point in the moving target (tumor) is calculated by the amount of time that point spend in the beam (1 cm wide) assuming a constant fluence rate. These codes with varying resolutions and frames of reference are cross‐checked. A resolution of 0.01 cm and 0.005 sec were found to be sufficient. Results: Motion plots of points in the target are compared to the fluence profiles for a variety of parameters. Hot and cold spots in the target (dose modulations) are small for typical helical tomotherapy couch speeds with longitudinal target organ motion. The edge is blurred because the points move in and out of the beam at both sides. When cycle‐to‐cycle randomness is added to amplitude and frequency, these modulations are high sensitivity to these parameters. However, with multiple fractions at random phases, the modulations decrease quickly and single fraction variability is quickly averaged out. Conclusion: Typically used helical tomotherapy couch speeds imply less concern for dose modulations from longitudinal tumor motion. There is still a need for a large enough PTV for edge blurring. Multiple fractions smooth out modulations that occur in a single fraction from randomly phased motion. Methods that remove this randomness may not benefit from this averaging process.
SU‐FF‐J‐125: Thoracic Organ Motion as Assessed by 4D CT: Prone Versus Supine
Authors: Stepaniak C , Li X , White J , Gore E , Wilson J
Published: June 2005

Purpose: Radiotherapy is sometimes carried out with the patient in prone position. The purpose of this work is to study the changes of respiratory organ motion for patients in prone versus in supine position. Method and Materials: We obtained 4D CT datasets for 15 patients, 5 in prone and 10 in supine position, using a GE LightSpeed 4D CT scanner. Patients in both positions were immobilized by Alpha cradle. Lung movement (the change in lung spatial dimensions between maximum and minimum inspiration) in the superior‐inferior (S/I) direction was measured on the 4D CT, as well as in the anterior‐posterior (A/P) and left‐right (L/R) directions in two transverse CT images near the diaphragm and near T4. We also measured the movement of the anterior chest wall with respect to the table top on the T4 transverse CT image as well as on the transverse image defined by the nipple. Results: Average lung movement changes from supine to prone position were: in 17.8 to 11.5 mm in S/I direction changes, and 1.6 to 0.5 mm in the A/P direction on the T4 image. In the transverse image defined by the nipple, we observed chest wall average movement of 0.1±0.4 mm in prone position versus 1.9±0.4 mm in supine position. Similarly, at the level of T4, the chest wall moved 0.3±0.3 mm in prone setup and 2.0±0.7 mm in supine position. Conclusion: Respiratory organ motions in thorax are generally reduced when patient position is changed from supine to prone. We have found a significant reduction in anterior chest wall movement for the prone position, an advantage of treating breast cancer in the prone position.
SU‐FF‐T‐01: A Newly Designed LDR Brachytherapy Applicator for Treatment of Cervical Cancer with Extension Into the Lower Vagina
Authors: Baker C , Dini S , Meigooni A
Published: June 2005

Purpose: The new applicator was designed at the University of Kentucky for treatment of cervical cancer with the extension into the vaginal. The design incorporates properties of both the Fletcher‐Suit applicator and vaginal cylinder. A dosimetric evaluation of this applicator was performed using TLD measurements and the results were compared to the presently available Fletcher‐suit applicator and a commercially available treatment planning system. Method and Materials: Presently, patients with cervical cancer extending to the lower vaginal are being treated with the standard Fletcher suit applicator followed by treatment with a vaginal cylinder. To eliminate the possibility of overdose to critical organs such as of bladder and rectum, arising from two separate treatments, and also reduce the patient inconvenience a new applicator was designed to combine these treatments. To evaluate the dosimetric characteristics of this applicator, a solid water phantom was constructed to accommodate both the applicator and LiF TLD chips. The positions of the TLD chips were selected to represent the most commonly calculated points including vaginal mucosa and point A, as defined in ICRU report 38. The applicator was then loaded with Cs‐137 sources, using the standard loading scheme. The 1 cm3 TLD chips were placed in the phantom along with the applicator. The experimental results were compared with the calculated values using a treatment planning system. Results: The data compared dose rates at different points in the phantom which represent points along vaginal mucosa with analogous points from the same digitized set‐up in the treatment planning system. The agreement was within or close to 10% for most points. Also, dose rates from the new applicator compared well with the Fletcher‐Suit applicator. Conclusion: This dosimetric evaluation provides solid evidence that this applicator is a safe and effective LDR device to treat cervical cancer with extension into the lower vagina.
SU‐FF‐T‐02: Comparison of a 3D Multi‐Group Sn Particle Transport Code with Monte Carlo for Intracavitary Brachytherapy of the Cervix Uteri
Authors: Gifford K , Horton J , Failla G , Barnett D , McGhee J , Wareing T , Eifel P , Mourtada F
Published: June 2005

Purpose: To calculate and compare 3‐D CT‐based patient dose distributions between Monte Carlo and a 3D multi‐group Sn particle transport code for intracavitary brachytherapy of the cervix uteri. Method and Materials: MCNPX version 2.5.c, a general purpose Monte Carlo code, was used to simulate the tandem and ovoids. An input file was created that simulated the tandem and ovoids together. A reference geometry was created in the input file whereby each applicator could be positioned in each patient CT derived geometry by applying a transformation obtained from the patient CT scan. A 3D multi‐group Sn particle transport code, Attila™ (Transpire, Inc., Gig Harbor, WA) was used to simulate the same applicator set. Each applicator was built in Solidworks™(Solidworks Corp., Concord, MA), a mechanical design package and then assembled with a coordinate transformation and rotation for each patient case. Solidworks™ exported applicator geometries as a parasolid geometry, which were imported into Attila™ for calculation. Water photon kerma rates were converted to dose delivered over the length of one insertion. Dose matrices were overlaid on each patient geometry. Dose volume histograms and point doses were compared for two patient cases. Applicator to applicator comparisons were performed between the two codes. Results: The Attila™ code calculated doses to within ±4% of MCNPX for 95% of the points in a comparison of the ovoid and to within ±4% of MCNPX for 94% of the points in a comparison of the tandem. On average, Attila™ calculated dose fourteen times as fast as MCNPX. Conclusion: The Attila™ code can calculate doses for the tandem and ovoids accurately and with less computational time than MCNPX. Further refinements may decrease calculation times for the Attila™ code. Conflict of Interest: This research was supported in part by a sponsored research agreement with Transpire, Inc., Gig Harbor, WA.
SU‐FF‐T‐07: The Application of Sr‐90/Y‐90 for the Prevention of Abdominal Adhesions
Authors: Rhoades S , Blough M , Hevezi J
Published: June 2005

Recently, a resurgence in the use of beta particles from 90Sr/90Y has occurred, primarily due to its use in intracoronary brachytherapy. 90Sr/90Y has also been employed in the ophthalmologic community for postoperative irradiation of pterygia. Due to these successes and other advantageous results of irradiating benign tumors and diseases, a new use for the 90Sr/90Y ophthalmologic applicator has been hypothesized: the use of beta radiation for the prevention of abdominal adhesions. To characterize the source for this use, preliminary measurements were made in a polystyrene phantom using GafChromic film and TLDs. Our results compared favorably with measured values for clinically relevant depths. Upon completion of the phantom measurements, experiments commenced to test the hypothesis in an animal model. Two potential adhesion sites were created in the abdomen of rats via denudation of the serosa of the small intestine. Irradiation of one site with the 90Sr/90Y beta applicator occurred; the other site was used as a positive control (no radiation). A 10‐day recovery followed, allowing adhesion formation if it occurred; the animals were then euthanized and the injured areas analyzed for efficacy of treatment. Nine Sprague‐Dawley rats were irradiated with varying doses (to determine a dose‐response relationship) to a prescribed depth of 1mm. This choice was based on the Novoste clinical trials, clinical treatment depths for the 90Sr/90Y applicator, and experimental research on 90Sr/90Y beta particles (Buckley et al., 2001). The animals were sacrificed and gross and microscopic pathology was performed. Results show that radiation is effective in preventing adhesion formation. Eight of nine irradiated sections showed no formation of adhesions, while the ninth developed a single adhesion, whereas twelve of thirteen unirradiated sections formed adhesions. The Mann‐Whitney U test yielded a p‐value of 0.022 confirming the effectiveness of adhesion prevention by the addition of small amounts of beta radiation.
SU‐FF‐T‐09: Verification of Dose Point Kernels for Ir‐192 Brachytherapy
Authors: BenComo J , Macey D , Lawyer A
Published: June 2005

Purpose: A simple method for verifying the dose point kernel of Ir‐192 source used in HDR brachytherapy using Kodak EDR2 film in a spiral phantom. Method and Materials: A spiral solid water phantom available from Gammex International for IMRT QA was modified for this study. A CT scan image of the phantom was acquired with a 10 × 12 inch film loaded in the spiral groove. A 3.5 mm long 8.5 Ci pellet of Ir‐192 in a Nucletron HDR system was driven to a snugly fitting catheter located at the center of the phantom. The film loaded in the groove was exposed for a dwell time calculated to deliver doses within the linear range of the film. A calibration film was processed with each film exposed in the groove. The film was scanned with a Vidar 16‐bit scanner and analyzed using the RIT film analysis software. The isodose map and dose profile along the length of the spiral were calculated to a number of selected distances from the center of the source. The conversion of film optical density to dose was procured by measuring the dose at selected points in solid water sheets with a 0.6 cc Farmer ion chamber. The nC recorded at selected distances from the source was converted to cGy using the TG‐21 formalism. Results: The measured dose point kernel measured with the film was compared with published data. Corrections for obliquity and sensitivity of the chamber with energy were ignored since these are less than 2 %. The dose profile for Ir‐192 was found to be in close agreement with published data. Conclusion: A simple film exposed in a spiral phantom can be employed to verify the dose point kernels required for Ir‐192 and other radionuclides being considered for HDR and LDR brachytherapy.