bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐I‐99: Effect of Average CT On Quantifying PET Imaging in Esophageal Cancer
Authors: Tonkopi E , Mawlawi O , Chi P , Yeung H , Macapinlac H , Pan T
Published: July 2007

Purpose: To quantify the effect of average CT (ACT) on improving the registration of the PET and CT data (Pan et al, JNM 05) in a prospective study of esophageal cancer patients. Method and Materials: We investigated 52 studies of esophageal cancer patients who underwent a routine PET/CT scan followed by a cine CT scan for ACT. The patients were injected with 555–740 MBq of 18F‐FDG and scanned 1 hour after injection. A helical CT (HCT) scan was acquired in 16 s over 90 cm coverage followed by a PET scan of 3 min per bed and a cine CT scan of the thorax for ACT. Patients were free breathing during the HCT and ACT scans, the cine duration was 5.9 s to capture at least one breath cycle. Both HCT and ACT were used for attenuation correction (AC) of PET data. Misalignment between the PET and CT at the level of the diaphragm and the maximum standardized uptake values (SUVmax) of the esophageal tumor were used to assess the difference between the two attenuation correction techniques. Results: 9 patients (17%) showed over 20% increase or decrease in SUVmax due to misregistration between the HCT and PET data with one patient showing a 50% increase in SUVmax. The misalignment at the diaphragm level with the magnitude of over 1 cm was detected in 32 patients (62%) with an average value of 15.1±6.5 mm. ACT was effective in removing the misalignment in 23 cases (44%). Additional radiation dose was 5–10 mGy with an increase in processing time of 5 min. Conclusion: ACT is effective in improving the registration between the CT and the PET data in PET/CT, and is able to improve AC of PET data in 44% of the esophageal cancer studies.
SU‐FF‐I‐101: Combining Magnetic‐Resonance Spectroscopy and Ultrasound Spectral Parameters to Improve Tissue‐Type Imaging of Prostate Cancer
Authors: Feleppa E , Dasgupta S , Porter C , Ramachandran S , Ketterling J , Kalisz A , Lacrampe M , Isaacson C
Published: July 2007

Purpose: To improve prostate‐cancer imaging by making use of independent prostate tissue properties sensed by multiple imaging modalities such as the choline‐to‐citrate ratio detected by magnetic‐resonance (MR) spectroscopy in conjunction with parameters of ultrasound (US) echo‐signal spectra and clinical variables. Method and Materials: Ultrasonic (US) radio‐frequency (RF) echo‐signal data, and clinical variables including prostate‐specific antigen (PSA), were acquired during biopsy examinations. A neural‐network classifier was trained using spectral parameters computed from the RF data. Biopsy‐core histology was used as the gold standard. Classifier performance was assessed using ROC analysis. A look‐up table that returned cancer‐likelihood scores for spectral parameter and PSA combinations was used to generate tissue‐type images (TTIs). 3‐D renderings of the prostate were generated from transverse MR and US scans to determine feasibility of combining the two imaging modalities. The MR 3‐D volume was warped in 3‐D using the US volume as a reference to compensate for the distortions introduced by the larger endorectal probe used in MR imaging. Results: The ROC‐curve area for US neural‐network‐based classification was 0.84 compared to the ROC‐curve area of 0.64 for B‐mode based classification. Cancerous regions that were not visible in conventional US images were revealed in the TTIs. Co‐registration of 3‐D prostate phantom US and MR images after warping was successful. Conclusions: TTIs based on neural‐network classification of US and clinical parameters show promise for improving the detection of prostate cancer. Warping 3‐D renderings of the prostate to compensate for the deformations introduced by different probes appears to be feasible. Consequently, we will be able to produce accurately co‐registered 3‐D data derived from US and MR to improve methods for visualizing prostate‐cancer foci. Success in combining the two imaging modalities will be valuable for depicting cancerous regions in the prostate for biopsy and treatment planning and treatment monitoring.
SU‐FF‐I‐103: Scatter Correction in Camera Specific Attenuation Measurements for Image Quantification in I‐131 Radionuclide Therapy
Authors: Luo J , Jang S
Published: July 2007

Objective: This project was aimed to generate quantitative data to be used to estimate radiation dose for radionuclide therapy with I‐131 labeled compound, for example, TM‐601 (TransMolecular, Inc.) for patients with recurrent or refractory somatic and/or cerebral metastatic solid tumors. Method: A 200 uCi I‐131 in 50 ml vial, a 0.1 uCi I‐131 standard in 10 ml vial, and ten 1″ thick Lucite blocks were used for sensitivity and attenuation measurements on Siemens dual head camera with HEGP collimators. Three windows were set; photopeak at 365 keV (14%), 326 keV (8%) and 403 keV (6%) for lower and upper Compton scatter. Whole body sensitivity scan was performed at 7.5 cm/min over 180 cm. Two series static images of 5 sets each for I‐131 attenuation were acquired using a stack of 10, 8, 4, 3 and 2 Lucite blocks in 5, 4, 3, 2 and 2 minutes, respectively. TEW (Triple Energy Window) and DEW (Dual Energy Window) were employed to compensate for Compton scattering. Measured attenuation coefficient was obtained from scatter corrected images. Initial dose estimate was also conducted using the DEW method. Results: The I‐131 attenuation scan yielded count rate as: 39 cps up to 220 cps when Lucite blocks reduced from 10 to 2 for un‐corrected photopeak image; 10 cps up to 110 cps; and 21 cps up to 153 cps for the TEW and for the DEW scatter corrected images, respectively. The I‐131 photopeak camera sensitivity was 244 cps/Bq/ml. Attenuation coefficients were 0.0849, 0.1173 and 0.0987, respectively. Conclusion: The DEW correction underestimated and the TEW method over estimated scatters. More attenuation effect was observed on scatter corrected images due to higher scattering when increasing the thickness of the Lucite blocks.
SU‐FF‐I‐106: Simulation of Respiratory Motion Gating Using GATE and NCAT
Authors: He J , O'Keefe G , Jones G , Saunder T , Gong S , Scott A , Geso M
Published: July 2007

Purpose: Respiratory motion is a source of artifacts and reduced image quality in PET scanning. Gating techniques are usually able to compensate for the respiratory motion and hence improve image quality. We aimed at developing a data‐driven gating method that utilizes the geometric sensitivity properties of 3D PET. The geometric sensitivity gating (GSG) method is to be simulated using GATE (GEANT4 Application Tomographic Emission) and NCAT (NURBs(Non Uniform Rational B‐Splines) CArdiac Torso) software packages. Method and Materials: With geometric sensitivity gating method, the respiratory motion phases could be gated from list‐mode data in terms of the distribution of counts of coincidences. The simulation processing has five steps: first, setting up GATE in terms of Allegro PET detection characteristics and the NCAT phantom parameters; second, running GATE to obtain the phantom projection data as list‐mode data; third, gating list‐mode data into one frame by proposed method; next, converting the gated frame data into UGM sinogram format; last, obtaining reconstruction from sinogram data. All simulations were made for a source of a 37MBq total activity in the phantom. In addition, GSG method has also been tested on list‐mode data acquired from the clinical acquisition. Results: Simulated results are presented as reconstructed images. Geometric and NCAT plotting curves of frame counts with the static and the motion are clearly different due to geometrical sensitivity distribution. When phantom with no respiratory motion is simulated the frame counts are constant whilst when simulated with the respiratory motion, the frame counts exhibit an oscillatory trend consistent with the respiratory motion parameters consistent with the clinical data. Conclusion: Computer simulations show that GSG data‐driven method can compensate simulated respiratory motion and that the reconstructed images are improved. The results of simulation show good agreement with GSG testing on the clinical acquisition.
SU‐FF‐I‐107: Improving the Accuracy of CT Topograms for Node Localization in Breast Lymphoscintigraphy
Authors: Dickinson R , Erwin W , Bidaut L , Vija A , Williams C , Wendt R
Published: July 2007

Purpose: To characterize and compensate for fan‐beam distortion of a CT topogram, thereby improving a technique for localization using planar lymphoscintigram/topogram fusion by minimizing misregistration between modalities. Method and Materials: We are currently investigating the feasibility of fusing planar scintigrams and CT topograms as a means of localization for breast lymphoscintigraphy and determined a maximum expected lateral offset between modalities of ±2.8 cm for an average size patient. The spatial distortion due to the fan‐beam of the topogram is linearly related to offset from isocenter, suggesting the possibility of rescaling the topograms used for localization. In this work, we have adjusted the anterior topogram by determining the location of the node in the lateral scintigram and using the distance above or below isocenter to apply the appropriate magnification to the topogram so that it is correctly scaled for the plane of the node (vice versa for the lateral topogram). An IDL program [ITT Visual Information Solutions, Boulder CO] was written to facilitate the modification of the topograms; the program was tested with a data set of an anthropomorphic thorax phantom acquired using a hybrid SPECT/CT camera [Symbia®, Siemens Medical Solutions USA, Hoffman Estates IL]. Registration was visually assessed by fusing the scintigram with the original topogram, with the modified topogram, and with the fullthickness coronal‐projection CT to verify the localization. Results: The IDL program has been executed and is successfully modifying topograms to minimize distortion. The visual comparison of the scintigram/modified topogram and scintigram/full‐thickness coronal‐projection CT demonstrates less than ±0.34 cm offset. Conclusion: Appropriately magnified CT topograms have been generated and fused with planar scintigrams that have potential for producing images with improved anatomic localization for breast lymphoscintigraphy compared to the standard‐of‐care Co‐57 sheet source backlighting method. Conflict of Interest: Research sponsored by Siemens Medical Solutions USA.
SU‐FF‐I‐111: Feasibility of Using Higher Energy Beam Pairs to Improve DXA Accuracy
Authors: Wilson C , Carrera G
Published: July 2007

In standard DXA the fat content of the soft tissue containing the bone is assumed to be the same as the soft tissue in the baseline region of the scan adjacent to the bone. Unfortunately, this assumption is rarely correct and inaccuracies in BMD can exceed 20 % in clinically realistic cases. Moreover, changes in fat content resulting from weight loss or gain makes interpretation of changes seen in BMD problematic. The cause of the inaccuracy is the large difference in the attenuation characteristics of fat and lean tissues at the effective energy of the low energy beam used in standard DXA. A mathematical simulation of DXA using monoenergetic photon beams was performed using beam energy pairs higher than used for standard DXA. In the simulation the low energy beam was varied from 80 to 110 keV with the high energy beam held constant at 140 keV. The entrance doses of the simulations were varied to maintain a measurement precision equivalent to that of standard DXA. For simulated DXA using higher beam energy pairs the BMD error due to inhomogeneities in the fat content of soft tissue was eliminated. The entrance skin dose for the higher energy beam pairs needed to be increased to achieve the same measurement precision as standard DXA.

Thus, the accuracy of BMD measurements can be improved by using higher energy beam pairs with a modest increase in entrance dose. This improvement in accuracy allows the accurate assessment of BMD changes in patients experiencing weight change.
SU‐FF‐I‐112: Evaluation of Dose Saving Utilizing AGFA's DirectiX Neddle Based Detector
Authors: Howley J , Seddon M , Donohoe A
Published: July 2007

Purpose: To evaluate the impact of dose reduction on image quality utilizing AGFA's new DirectriX needle‐based detector and scanhead technology versus AGFA's MD 4.0 PSP detector and Compact plus ADC. Method and Materials: The ACR R/F phantom was utilized for image quality evaluations. The phantom was imaged using manual techniques on both the DirectriX needle‐based detector system and the MD 4.0 PSP system. The same GE Proteus XR/a x‐ray system was utilized for all exposures. The image quality was quantified based on human observation of the copper mesh resolution patterns, contrast detail pattern and aluminum contrast holes. A total of 5 observers accessed and scored the phantom images. Phantom images were obtained on multiple plates and the results were averaged for the observers Results: Evaluation of the phantom scores indicates that comparable image quality can be achieved at a 60% decrease in dose. Evaluation of the phantom scores also indicates image quality gains if dose levels are held constant. Conclusion: This work indicates the potential for significant dose reduction for general radiography utilizing the DirectriX needle‐based detector. The works also indicates a potential for significant image quality gains if dose rates are kept constant.
SU‐FF‐I‐114: Comparison of Digital Tomosynthesis Technology with Conventional Technology for Intravenous Pyeolgram (IVP) Studies
Authors: Jones A , Kappadath S
Published: July 2007

Purpose: Digital tomosynthesis is a new spin on an old idea. It has been extensively studied and developed, but is just beginning to find its way into the clinic. We seek to compare digital tomosynthesis to conventional tomography utilizing a computed radiography (CR) system. To this end, we have developed quantitative measures to compare image quality and dose between images acquired using digital tomosynthesis and those acquired using conventional tomography with CR. Materials and methods: “Standard” IVP studies were performed on uniform acrylic phantoms. Dose in terms of entrance air kerma (EAK) was measured for each of the studies. The uniform phantom images were also used to quantify non‐uniformities in the images both globally and locally. Also, images were evaluated for the presence of artifacts. Results: EAK values for a standard IVP study (3 scout images, 3 tomographic cuts during 3 phases) of a “medium” patient consisting of 6 inches of acrylic ranged from 3.54 mGy to 80.1 mGy, depending upon technique, for digital tomosynthesis studies to 51.2 mGy for the same CR study. Also, keep in mind that additional planes or slice thicknesses can be derived from the digital data at no extra dose cost to the patient. Uniformity measures varied significantly in processed images for digital tomosynthesis studies acquired at varying techniques. Uniformity was consistent throughout conventional tomographic studies. Processed digital tomosynthesis images also displayed artifacts, some which mimic pathologic anatomy. Conclusions: Digital tomosynthesis has the potential to significantly reduce patient doses in IVP studies. However, techniques must be chosen appropriately to maximize image quality and minimize the presence of artifacts.
SU‐FF‐I‐117: System Quantification for Micro CT
Authors: Tu S , Chao T , Lee C
Published: July 2007

Purpose: To report our efforts of the development for the software tool with the latest parallel computing techniques to characterize the various physical properties for the micro CT. Method and Materials: Various physical aspects in the micro CT imager were investigated with the strategies of mathematical modeling and computer simulation. The simulated elements included were the x‐ray focal spot blurring, scattering kernel, point spread function, quantum noise, detector blurring, and system noise. The projections of the mathematical phantoms were analytically calculated using the Radon transform formalism. Simulated noises were then added to those projection images and the final images were obtained from the image reconstruction algorithms including the exact, approximate, and iterative methods. A dedicated random number generator for the noise simulation was developed to produce un‐correlated random number sequences. A randomness test of the intra‐ and inter‐correlation for the random number sequences was also developed to validate the quality of noise simulation. The Monte Carlo code, BEAMnrc06, was used to evaluate the x‐ray photon scattering kernel, point spread function, and the simulated exposed dose level. Results: Our preliminary results indicated that the various noise properties can be quantified by using the noise simulation and noise power spectrum calculations. The scattering kernel was determined by using the Monte Carlo method according to the actual x‐ray tube geometry and was in agreement with the experimental measurement. Lower bound of the delivered dose level was determined based on the simulated low‐dose images reconstructed form the higher‐dose images. The motion artifact was also quantified based on the Fourier analysis in the spatial frequency domain. Conclusion: We have developed a computer simulation package where the key substances such as the quantum noise were included. The simulated results were used to quantify the micro CT imager and the optimized system performance can be achieved.
SU‐FF‐I‐118: MicroRT Multi‐Modality Treatment Planning
Authors: Kiehl E , Garbow J , Hubenschmidt J , Khullar D , Apte A , Deasy J , Parikh P , Low D , Hope A
Published: July 2007

Purpose: To evaluate image registration and fusion techniques for multi‐modality microRT treatment planning. Methods and Materials: Subject mice were first anesthetized and positioned within the custom microRT couch/head immobilization assembly. The immobilized subjects were then imaged using both a Phillips 64‐slice Brilliance CT scanner and a small‐animal MR imaging scanner built around a 4.7 T Oxford Instruments magnet and a Varian imaging console. The CT data was imported into CERR using the ‘DICOM‐import’ CERR tool, while the MRI data was imported into CERR using a custom Matlab *.FDF‐importer function. Using the CERR contouring tool, CT contours were generated for the brain, lung, and skin, and MRI contours were generated for the liver, lung and skin. The CT images were then registered to the microRTP treatment planning space using a custom Matlab registration algorithm for the microRT couch. Lastly, the resultant MR images were merged and fused to the registered CT plan, both translationally and rotationally, using the CERR ‘image fusion’ tool. Results: Previously‐published microRT studies have demonstrated the translational and rotational capabilities of CERR image fusion for merged CT plans. As expected, in this study, MRI was qualitatively superior for identifying and contouring target structures that had relatively low contrast variation on CT. Conclusions: CT/MRI co‐registration improves microRT treatment planning by providing verification of target positioning for organs contoured on both imaging modalities, as well as by providing increased target definition for soft‐tissue organs visualized effectively using MRI but not CT. CT/MRI phantom validation studies are currently in progress. Future planned studies include rotational MRI evaluation, as well as additional co‐registration studies evaluating the integration of PET, SPECT, and optical imaging modalities.
SU‐FF‐I‐119: Novel MicroCT Imaging Techniques for In Vivo Quantification of Vascular Volume in Murine Tumor Models
Authors: Nyflot M , Grudzinski J , Jeraj R
Published: July 2007

Purpose: Growing interest in angiogenesis and anti‐angiogenic tumor therapy has created a demand for vascular imaging techniques. This work describes a method for in vivo quantification of vasculature in murine tumor models using contrast enhanced μCT. Method and Materials: Mice from a prostate tumor line were imaged over a span of three weeks to measure growth, and SCC xenograft mice undergoing anti‐angiogenic therapy with Avastin™ were imaged over eleven days to monitor tumor response. Mice were injected with 0.4 mL of a μCT blood pool contrast agent and scanned using a Siemens Inveon μCT/PET scanner. CT images were manually segmented into tumor and vascular volume in a commercial software package (Amira 4.0, Mercury Computer Systems) and tumor volume was compared to vascular volume. Results: Over the span of three weeks, the prostate model increased in tumor volume by a factor of four and the vascular volume increased by a factor of 15. The ratio of vascular volume to tumor volume increased from 1.5% to 6%. In the xenograft models, a measurable decrease in tumor and vascular volume was seen in both mice, but the ratio of vascular volume to tumor volume stayed relatively constant (approximately 4% in the 400 mm3 tumor and 17% in the 100 mm3 tumor). Conclusion: This work demonstrates the capability for in vivo quantification of tumor vasculature with a minimally invasive procedure. In particular, the technique was sufficiently sensitive to monitor vascular growth and to determine a therapeutic effect from molecular therapy over the span of eleven days. This technique may be useful as a tool to better understand the process of tumor‐induced angiogenesis and evaluate the efficacy of targeted molecular therapies.
SU‐FF‐I‐124: Anthropomorphic Uterus Phantoms for Testing Elastography Systems
Authors: Hobson M , Shi H , Jiang J , Frank G , Varghese T , Madsen E
Published: July 2007

Purpose: To develop uterine phantoms for mimicking in vivo ultrasound strain imaging in saline infused sonohysterography (SIS) and employ them to compare strain imaging (elastography) systems. Method and Materials: Dimensions and shapes of the two phantoms simulate the uterus of a pre‐menopausal woman with no previous pregnancy. Phantoms were constructed using tissue‐mimicking (TM) materials consisting of dispersions of safflower oil in gelatin. 10%, 70% and 80%, oil dispersions represent fibroids, endometrial polyps, and fat, respectively. Myometrium and cervical tissues were represented by 40% in one phantom and 50% in the other. In the first uterine phantom, 3‐mm diameter TM fibroids were randomly distributed in TM myometrium. The second uterine phantom has a 10‐mm fibroid on the serosal surface and 5‐mm and 8‐mm spherical fibroids and 5‐mm spherical and 8‐mm × 5‐mm peg shaped endometrial polyps protruding into the endometrial cavity. Samples for determining physical properties were made at the time of phantom production. RF data was acquired during a volume expansion of the endometrial cavity using the Siemens Antares VFX 13‐5 and 9‐4 transducers at 11 and 9 MHz, respectively, on the Aloka SSD 2000 at 7.5 MHz, and on a third system at 4 MHz. Strain images were generated using a 2‐D block matching or a 2‐D multilevel strain estimation technique. Results: Strain images from the first phantom show stiffer 3‐mm inclusions in the myometrium. In the second phantom, strain images show the part of the endometrial polyps projecting into the endometrial cavity appeared stiffer and the part in the myometrium softer compared to the myometrium. Strain images from the Aloka and the third system were of lower quality than the Siemens Antares. Conclusion: Durable uterine SIS phantoms with well‐defined properties can be produced to allow realistic quantitative testing of SIS strain imaging using ultrasound.
SU‐FF‐I‐125: Accuracy and Reliability of Manual Vessel Sizing Measurements Among Different Users and Systems
Authors: Erdemir E , Hoffmann K , Walczak A , Dashkoff N , Iyer V , Gopal A
Published: July 2007

Purpose: Vessel sizing is an essential component of each vascular intervention. While the focus in the literature has been on sizing the stenosis, we have found that the critical interventional data are the proximal and distal vessel sizes and length of the interventional device, e.g., balloon or stent. We investigated the accuracy and reliability of these data for three clinical systems. Method and Materials: X‐ray images were obtained of cylindrical aluminum rod phantoms with different diameters and of patient angiograms of cardiac arteries with stenoses. The systems were manually calibrated using a wire mesh phantom (phantoms) or marker wire (patient) each having 1 cm spacing. Vessel sizes were measured using the same manual interactions on all three systems, indicating points at the edge of the vessel, proximal and distal to the lesion. The length for the device was measured as the distance from the proximal to distal measurement points. Three users performed calibrations and measurements with and without digital zoom. Measurements were repeated three times. Results: Accuracy of manual measurements is high . Using zoomed images improves accuracy and reliability . The variations across users and systems are comparable for clinical images (∼ 0.1 mm (sizes), ∼ 0.35 mm (lengths)). Conclusion: These results indicate that manual measurements of vessel sizes and lengths are accurate and reliable in the clinical arena, although there are variations between users and systems. Conflict of Interest: This study was supported by NIH Grant ♯ HL052567 and Toshiba Medical Systems Corporation.
SU‐FF‐J‐05: A Four‐Dimensional Planning and Monte‐Carlo Dose Calculation Framework for Real‐Time Tumor Motion Compensation
Authors: Van Liew S , Naqvi S , D'Souza W
Published: July 2007

Purpose: To perform 4D dose calculations using a feedback‐controlled treatment couch in 15 lung and abdominal patients Methods: Fifteen patients undergoing 4D CT were considered in this work. The GTV was delineated on ten 3D CT data sets by independent experts, with a planning margin added corresponding to the 2σ deviation from the mean center‐of‐mass. Tumor trajectories were derived from 4D CT data and fitted to a Fourier series expansion. Intra‐ and inter‐fraction statistical variations in amplitude and period were applied by considering literature estimates of the standard deviations. The couch feedback control system was simulated using second‐order couch dynamics and a first‐order controller. The residual tumor trajectory was calculated by inputting the tumor trajectory to the control system. A 7‐beam IMRT plan was generated on the end‐exhale CT with a prescription dose of 66 Gy. The resulting 4D dose distribution was calculated by sampling the isocenter position along the continuous tumor trajectory before and after motion compensation using a previously published Monte Carlo algorithm. Results: The mean tumor motion amplitude was 11.4±3.4 (SD) mm. After compensation the amplitude was 0.42±0.23 mm. Degradation of the tumor dose up to 35% was observed. After compensation, an average of 18.8 ± 4.7% improvement in the 100% dose coverage was seen for end inhale, and 13.4 ± 4.7% for the 90% coverage. For the combined 4D dose, GTV dose coverage was 94.7±4.7% (for 100% coverage) after compensation, but degraded to 87.3±4.5% without compensation. Conclusion: We have developed a framework for performing 4D dose calculations using real‐time tumor trajectories. For IMRT plans, the average improvement in the dose coverage to the PTV for mobile tumors with a feedback‐controlled couch was X% Conflict of Interest: Supported by 3DLine Medical Systems.
SU‐FF‐J‐06: Use of Daily KV Cone‐Beam CT Data to Analyze the Effectiveness of a Weekly Correction Strategy for Lung Cancer Radiotherapy
Authors: Ye J , Wong T , Cao D , Shepard D , Mehta V
Published: July 2007

Purpose: A common practice in lung radiotherapy is the correction of setup errors based on the initial and weekly 2D portal images. We have evaluated the effectiveness of this correction strategy using data collected from daily kV cone‐beam CT (CBCT) imaging. Material and Method: Eighteen lung cancer patients immobilized with a wing board were treated on an Elekta Synergy LINAC using our daily on‐line IGRT protocol. Daily CBCT imaging was performed and setup variations were corrected before treatment. A total of 282 CBCT images were collected and the daily setup errors along the anterior‐posterior, superior‐inferior and right‐left axes were calculated using volumetric image registration. With this data we simulated the weekly correction strategy where patient setup error is adjusted once every five fractions based on weekly 2D portal imaging after the initial setup. 3D shift vectors for the whole treatment course were calculated. The frequencies with which the 3D shifts exceeded 5 mm, 10 mm, 15 mm and 20 mm were used to evaluate the effectiveness of this correction strategy. Results: For these eighteen patients, the setup errors along right‐left, superior‐inferior and anterior‐posterior axes range from −1.17 to 1.34 cm, −1.29 to 1.30 cm and −1.71 to 1.21 cm respectively. The maximum value of the 3D shift vectors was 1.78 cm. Out of a total of 282 treatments, the 3D shift vectors were within 5 mm for 144 fractions (51.1%), within 10 mm for 250 fractions (88.7%), and within 15 mm for 278 fractions (98.6%). Four fractions had errors greater than 15 mm. Conclusion: Daily CBCT data can be used to evaluate different correction strategies. For the lung patients, the setup errors can be large along R‐L, S‐I and A‐P directions. A large margin is warranted to ensure adequate tumor coverage if weekly correction scheme is used.
SU‐FF‐J‐09: An Analysis of Cone‐Beam CT for Determining Setup Errors and Designing Treatment Margins for Non‐Small Cell Lung Cancer Patients
Authors: Wong T , Ye J , Cao D , Shepard D , Mehta V
Published: July 2007

Purpose: KV cone‐beam CT imaging (CBCT) was used to analyze setup errors when treating patients with non‐small cell lung cancer (NSCLC). For patients where an off‐line correction strategy was adopted, CBCT was also used to determine the patient specific planning target volume (PTV). Method and Materials: Eighteen patients with NSCLC were treated with CBCT image‐guided radiotherapy using an Elekta Synergy linac. 4D‐CT imaging was used for treatment planning. Patients were scanned in the supine position during normal relaxed free‐breathing and were immobilized with a wing‐board. The internal target volume (ITV) was determined using the maximum‐intensity‐projection (MiP) CT data to account for organ motion. A 5‐mm PTV margin was used to account for setup error. On‐line setup correction was based on the daily CBCT imaging prior to treatment. The systematic and random errors were analyzed retrospectively. The results were then fit to our CBCT off‐line correction strategy where a setup correction was made at the fifth treatment fraction to correct for the systematic error. The patient specific PTV margin was also analyzed. Results: The systematic and random errors were 5.7 ± 3.2 mm, 4.2 ± 2.6 mm and 4.8 ± 3.1 mm for anterior‐posterior (AP), medial‐lateral (ML) and superior‐inferior (SI) directions respectively. The 3D displacement vectors were 4.1 mm ± 3.1 mm (systematic ± random). If the patients were treated with the off‐line correction strategy, a patient specific PTV margin ranging from 7.0 to 17.4 mm would be needed. Conclusions: The use of a 5 mm PTV margin on the ITV determined by MiP dataset combined with daily CBCT on‐line correction is adequate to avoid geometric miss of the tumor for NSCLC patients. A larger patient specific PTV margin, ranging from 7.0 to 17.4 mm, would be needed if an off‐line correction is used.
SU‐FF‐J‐14: X‐Ray Scatter in a Clinical CBCT System
Authors: Li H , Mohan R , Zhu X
Published: July 2007

Purpose: To investigate the magnitude of x‐ray scatter, and to evaluate the effects of scatter related artifacts on a clinical cone‐beam CT (CBCT) system. Method and Materials: The scattered to primary energy fluence ratio (SPR) was measured as a function of cone angle using lead disks of 3 mm thickness placed on a stack of solid water phantom with thickness of 0, 5, 10, 18, 29 cm, representing air (couch only), extremity, chest, abdomen, and pelvis, respectively. The measurement was repeated with and without bowtie filter in the x‐ray beam. The variation of scatter was evaluated by comparing the measurements with the lead disk placed at different positions in the x‐ray field. The effectiveness of increase air‐gap to reduce SPR was also tested using thickness of 18 and 29 cm of solid water phantom. The air‐gap was increased from the minimum allowance of a clinical scan of about 30 cm to the maximum achievable approximately 42 cm for 18 cm phantom and 38 cm for 29 cm phantom. Results: SPR of the CBCT system increases with thickness of the phantom, from 8% for couch only, to 64% for 29 cm depth of solid water phantom at the maximum cone angle with bowtie. For the depth of 29 cm, SPR varies from 26% at 2° cone angle to 64% at 12° with bowtie. The scatter fluence at different locations of the x‐ray field remains constant without a bowtie filter, indicating the scatter kernel is space invariant. However, when using the half‐fan geometry, the scatter increases with fan angles. As the air‐gap increases, the SPR decreases almost linearly. Conclusion: In CBCT imaging, scatter degrades image quality, especially for large body size, even with an anti‐scatter grid. Scatter removal or correction is necessary for quantitative CBCT measurements. Conflict of Interest: Supported by Varian.
SU‐FF‐J‐15: Onboard CT Imaging Quality and Its Effect On Online Patient Positioning Correction On TomoTherapy and Elekta Synergy Platforms
Authors: Wu C , Liu T , Guo F , Purdy J
Published: July 2007

Purpose: To evaluate online imaging quality of implanted prostate gold markers on two clinical image‐guided radiation therapy (IGRT) platforms — TomoTherapy HI‐ART and Elekta Synergy, and its effect on online patient registration accuracy in a typical IGRT workflow. Methods and Materials: Currently, our institution has two IGRT platforms in clinical use — TomoTherapy HI‐ART (Madison, WI) and Elekta Synergy (Elekta AB, Sweden). In external beam prostate treatment, 3 gold markers (Best Medical International, Springfield, VA) are implanted to help locate prostate on daily pre‐treatment CT scans, in order to register patient with corresponding planning CT images and then perform online positional correction. However, because of very small physical dimensions of the implanted markers and their high Z material, there could be significant image reconstruction artifacts and geometrical distortions on either TomoTherapy's helical Megavoltage CT (MVCT) or Elekta's XVI kilovoltage cone‐beam CT (CBCT) images. As a result, accuracy of patients' inter‐fractional online position adjustment based on registering prostate markers could suffer. In this work, we systematically investigate this issue. First, we use a home‐made prostate marker‐solid water phantom to evaluate reconstructed image artifacts and geometrical distortion on both IGRT platforms. Then, we carefully exam the process and results of patient online position correction by registering pre‐treatment MVCT/CBCT images to corresponding planning CT images, using both phantom images and patient images. Results: On both IGRT systems, significant image reconstruction artifacts and geometrical distortions of the gold markers were found on both the phantom images, and the patient pre‐treatment CT images. However, the effect of this imaging quality problem on the accuracy of patients' inter‐fractional online position adjustment was found to be relatively small — both on phantom setup and patient daily online registrations. Findings are discussed in details and its meanings to general IGRT procedures are discussed in depth.
SU‐FF‐J‐17: Evaluation of Quality Assurance Phantom for Electronic Portal Imaging Device (EPID)
Authors: Das I , Cheng C , Chopra K , Misic V , Schule E
Published: July 2007

Electronic portal imaging device (EPID) has become an essential and integral tool in setup and treatment field verification for precision radiation therapy. Along with geometric verification, EPID is also being used for dosimetric verification. Consistent image quality and stable radiation response is necessary for proper utilization that requires routine quality assurance (QA). A commercial ‘EPID QC’ phantom from PTW is evaluated for EPID QA. The device is a solid 25×25×4.8cm3 phantom and weighs 3.8kg. It consists of 5 essential tools to measure the geometric accuracy, signal to noise ratio (SNR), dose linearity, the low and the high contrast resolutions and are aligned with divergence to measure the imaging and geometric parameters in both x, and y directions. The low contrast tool consists of a series of holes with various diameters and depths in aluminum slab, very similar to the Las Vegas phantom. The high resolution contrast tool provides the modulation transfer function (MTF) in both the x‐ and y‐dimensions to measure the focal spot of linear accelerator. The EPID QC device is tested on the latest and modern amorphous silicon imagers on Elekta, Siemens and Varian linear accelerators. Images were acquired in the anterior and lateral orientations for a 26×26 cm2 field for 1–15 MU at 95.2 cm. The analysis of the images was performed with the EPIDsoft software for automated analysis. The results indicates that all imagers have very good low contrast resolution and MTF(0.5) in the range of 0.3–0.4 lp/mm. All imagers also exhibit satisfactory geometric accuracy, dose linearity and SNR. Our analysis indicated that the imaging parameters are independent of MU and spatial orientations. The software maintains a record for the QA and verifies the parameters for temporal variation. The EPID QA device is easy to use, and allows readily assessment of the performance of any imager.
SU‐FF‐J‐18: Image Guided Neutron Therapy: A Six Degree Correction Method Using Implanted Fiducial Markers
Authors: Wang Y , Burmeister J , Van den Heuvel F , Yudelev M
Published: July 2007

Purpose: To develop and assess the accuracy of a novel repositioning scheme based on implanted gold markers and orthogonal films to reduce the treatment margins in fast neutron radiotherapy. This repositioning scheme corrects for both translational and rotational deviations due to set up error and/or patient organ movement. Method and Materials: The proposed repositioning scheme involves five gold markers that are implanted into the structure to be localized. Geometric errors are estimated based on relative differences in the positions of the gold markers between the CT locations and 3D coordinates reconstructed from two orthogonal films. An in‐house developed computer software automatically calculates the six correction parameters (three translation and three rotation) using a PointSet‐to‐PointSet co‐registration algorithm that iteratively finds the optimal solution. All gold marker coordinates and shifts are referenced to the isocenter. The accuracy of the repositioning scheme was evaluated using phantom experiments. A phantom containing five gold markers was moved and rotated to 23 different positions and the repositioning scheme was applied to each case. These positions include translational and rotational movements in different directions with magnitude ranging from 1–15 mm and 2–10 degrees for translation and rotation, respectively. The calculated correction parameters were compared to the known movements to assess the accuracy of the repositioning method. Results: In all 23 cases, the repositioning scheme was able to very accurately correct the induced geometric errors. The mean correction error, defined as the difference between the calculated correction values and known movements, was 0.37 mm for translation and 0.74 degrees for rotation. Conclusion: The proposed repositioning scheme and software corrects for both translational and rotational geometric errors and achieved very high accuracy in the phantom experiment. Its application in clinical fast neutron radiotherapy will serve to reduce the irradiated volume and associated normal tissue complications.
SU‐FF‐J‐26: A Phantom Study to Assess the Feasibility of Using ExacTrac for Patient Setup for Fractionated Stereotactic Radiotherapy (SRT) Technique
Authors: Gete E , Moiseenko V
Published: July 2007

Purpose: To investigate the feasibility of using ExacTrac for setup error correction for patients treated with fractionated stereotactic (SRT) technique with the BrainLab relocatable mask system. Method and Materials: A phantom study designed to evaluate setup accuracy of the ExacTrac system was performed. An actual treatment process, from making immobilization mask to treatment setup, was simulated. A 3.8 mm diameter lead bb was inserted in a Rando head phantom to represent a mid‐brain target. The phantom was CT scanned with 1 mm slice thickness and 1 mm slice index. A treatment plan was created using BrainScan, with an isocenter placed at the center of the bb. The phantom was setup for treatment with the following two methods:

1. Phantom setup with the BrainLab localizer box.

2. Phantom setup with ExacTrac.

Electronic portal images of a treatment field defined by M3 MLC (12×12 mm2) were taken at various gantry and couch angles. Setup accuracies for the above two methods were calculated from the positions of the bb relative to field center. A Lutz test was performed prior to portal image acquisitions to correct for gantry flex. Results: Setup with ExacTrac showed consistently better accuracy compared with the Localizer box setup. Specifically, in Sup‐Inf direction mean deviations of the center relative to the center of the field were 0.3mm (standard deviation 0.1mm) with ExacTrac setup and 0.4mm (0.5mm) for localizer box. For Left‐Right direction deviations were −0.2 (0.3) and 0.4 (0.5); Ant‐Post 0.2 (0.2) and 0.5 (0.2) mm, for ExacTrac and localizer box, respectively. Conclusions: The BrainLab ExacTrac system has a great potential for setup verification and setup‐ error correction for the fractionated SRT technique with the BrainLab relocatable mask system.
SU‐FF‐J‐35: Clinical Implementation and Initial Experience with Calypso 4D Tracking System for Prostate Cancer Treatment
Authors: Cao D , Ye J , Afghan M , Wong T , Shepard D
Published: July 2007

Purpose: The Calypso 4D tracking system can detect real‐time intra‐fractional tumor motion based on RF signals from the implanted beacons. The initial clinical experience on tracking prostate motion during the treatment is reported. We performed a series of tests to evaluate the calibration accuracy and stability of the system. Material and Methods: The first FDA approved clinical Calypso 4D tracking system was installed and used for this work. With three beacons implemented in the prostate, the system reports the target location in a real time fashion. Seven patients with prostate cancer were localized/tracked using this system. The vender provided a monthly calibration phantom and an in‐house developed stereotactic cone based alignment tool that were used to test the calibration accuracy of the Calypso 4D tracking system. The system stability was also studied using the monthly calibration phantom. Results: For the seven patients treated so far, the average initial setup shifts from the external tattoos were 1.1, 2.2 and 4.0 mm along lateral, longitudinal and vertical directions, respectively. For one patient, the observed maximum shifts along the above three axes were 4.6, 10.9 and 29.2 mm. The range of target motion during treatment was found to be 3.4 (Right‐Left), 9.9 (Superior‐Inferior) and 12.3 (Anterior‐Posterior) mm. The average patient setup time was less then 5 minutes. The daily QA of the system takes around 5 minutes on average.

The vender provided system calibration procedure is based on room lasers with 2 mm error tolerance, which may potentially decrease the overall system accuracy. Our stereotactic cone based alignment tool can achieve sub‐millimeter accuracy. Repeated monthly calibration procedures showed that the system stability is within 1 mm. Conclusion: Calypso system provides efficient and accurate patient setup for prostate treatment. The current calibration procedure can be improved to achieve better accuracy.
SU‐FF‐J‐38: Can a Wireless, Implantable MOSFET Dosimeter Be Used as Fiducial in Image Guided SRS?
Authors: Dieterich S
Published: July 2007

Purpose: Implantable MOSFET dosimeters with wireless readout (DVS, Sicel Technologies, Morrisville, NC) are FDA approved for the prostate and could be used to provide in‐vivo dosimetry in Cyberknife treatments. Method and Materials: A DVS marker was placed on a programmable respiratory motion phantom and a treatment planning CT was acquired. The DVS marker was identified as two fiducials, the readout being one fiducial and radio‐opaque area around the MOSFET itself as second fiducial. All five gold seeds embedded in the phantom were identified as fiducials as well. Two motion paths were run with the simulator, a sinusoidal motion with 15 mm amplitude in sup/inf and a patient motion. Both motion paths were treated with the DVS fiducial switched on, and then with the fiducial switched off as baseline. An image was taken at every non‐blocked beam. Results: The software could track both radio‐opaque areas within the MOSFET as fiducials. Only one in 35 images of both motion paths had a misidentified DVS fiducial, where the software identified a location between the radio‐opaque areas as fiducial. In both incidences, the treatment delivery software created an ESTOP. The Synchrony correlation error for both motion paths and both fiducial tracking configurations was below 0.3 mm at all time, which is within the uncertainty of Synchrony tracking. Conclusion: The Cyberknife software can utilize the DVS marker as an additional fiducial marker. No differences between the Synchrony treatments with and without the DVS marker tracking switched on could be identified. Further studies to test the tracking capabilities of the marker if oriented at different angles in the axial patient plane have to be done. Use of the DVS marker alone, without additional gold markers should be tested first in a solid phantom, and then in an anthropomorphic phantom to simulate soft tissue rotation and deformation.
SU‐FF‐J‐39: A Comparison of Two Methods Extracting Respiratory Information From Ultrasound Video
Authors: Hu G , Yao J , Quan H , Chen W
Published: July 2007

Purpose: To acquire respiratory information used for interventional radiotherapy in thorax and upper abdomen tumours and to compare two methods extracting respiratory information from ultrasound video. Method and Materials: Two test phantoms immersing in water tank were used to mimic moving tumours in intracavity. Phantoms were filled with a variety of wires and plastics to acquire whole images. One is sphere with 4.3 cm and the other is irregular object with maximum distance of 3.1cm and with minimum distance of 2.7cm. Motion range of two phantoms was on order of 3cm in 2D (radial section of ultrasound beam) and motion fashion was also examined in irregular motion as well as period varying from about 2s to 6s, for periodic. A comparison of two methods, correlation coefficient (CC) and quasi geometric centroid (QC) was implemented by metrics, namely, period, phase difference and relative standard deviation of period for period motion. For irregular, only phase difference is examined. Results: Results of comparison show that two methods are almost equal in these metrics, though small differences are exist due to some limited factors, such as imaging quality, selection of reference frame. QC is also appropriate for acquiring respiratory information. Conclusion: Acquisition of respiratory information from extraction video information is a superior method to the other methods which is noninvasive and reliable. Two methods used in the experiment demonstrate similar results, which indicate that QC is also competent to acquire respiratory information in various clinical circumstances. Due to the inherent performance of QC, more information can be obtained than that of correlation coefficient and thereby QC is possibly appropriate for accurate radiotherapy.