bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐FF‐I‐167: Non‐Contact Ultrasound Imaging Applied to Cortical Bone Phantoms for Determination of Bone Mineral Density, Speed of Sound, and Ultrasound Attenuation
Authors: Bulman J , Ganezer K
Published: April 2010

A non‐contact ultrasound imaging (NCU) system including transmitting and receiving transducers coupled to the air was applied to custom designed cortical bone phantoms to determine bone mineral density, speed of sound, integrated acoustical response and attenuation for possible medical applications in quantitative ultrasound imaging. Air gaps of greater than a centimeter for two non‐contact transducers specially designed for thin cortical bones such as those in the distal radius, two transmission as well as two reflection paths, and a digital signal processor were used to collect data on cortical bone phantoms of nominal density that varied from 1.17 g/cm3 to 2.25 g/ cm3, with nominal bone mineral density (BMD) from 0 g/ cm3 to 1.7 g/cm3. Good correlation between nominal density and measured speed of sound, integrated acoustical response, and attenuation was obtained for all of our phantoms and techniques for limiting various sources of systematic errors were studied. In particular, reproducibility, agreement with contact ultrasound, and stability for speed of sound and other parameters versus phantom BMD was found to be at a level of a few (about 1–3) percent over a period of several months when the NCU system was carefully and routinely optimized and calibrated. The results of these investigations suggest that non‐contact ultrasound might find applications in quantitative bone assessment and in medical imaging in the near future.
SU‐FF‐I‐171: New High‐Resolution Detector Changer for a Clinical Fluoroscopic C‐Arm Unit
Authors: Wang Weiyuan , Keleshis C , Kuhls‐Gilcrist A , Ionita C , Jain A , Bednarek D , Rudin S
Published: April 2010

Purpose: To investigate a means to alternate image acquisition between a high‐resolution region‐of‐interest (ROI) detector and a standard flat‐panel detector (FPD) when used for neurovascular image‐guided interventions with a clinical fluoroscopic C‐arm so that the larger area detector could be used during initial parts of a procedure and the high‐resolution detector used during critical parts of the intervention when better images are needed. Method and Materials: A new detector changer was designed, fabricated, and mounted on a clinical fluoroscopic unit to allow a ROI detector such as the Micro‐Angiographic Fluoroscope (MAF) or Solid‐State X‐ray Image Intensifier (SSXII) to be introduced in front of the standard FPD to enable high‐resolution fluoroscopy, DSA, and conebeam computed tomography. The x‐ray collimation automatically adjusts the field‐of‐view (FOV) when the changer inserts or retracts the ROI detector so that the correct FOV, smaller for the ROI detector or larger for the FPD, respectively, is implemented. A touch sensor at the front of the ROI detector holder causes the entire imaging unit (FPD and ROI detector) to retract upon physical contact in order to avoid collision with a patient or other objects on or near the table. Results: The new detector changer has been installed onto a Toshiba Infinix clinical fluoroscopic C‐arm unit. The changer provides stable support for the ROI detector, allowing operator selection of high‐resolution ROI or standard FPD. The collision avoidance and automatic collimation features have worked reliably during laboratory evaluation and should provide a patient‐safe imaging capability. Conclusion: The new detector changer mounted on a commercial clinical fluoroscopic C‐arm unit provides a safe and rapid means to exchange imaging detectors to accommodate the resolution requirements of angiographic and interventional vascular imaging during the course of a procedure.

(Partial support: NIH Grants R01‐EB008425, R01‐EB002873)
SU‐FF‐J‐03: Quantitative Assessment of Three Dead Detector Interpolative Correction Methods for Cone Beam CT Images
Authors: Nelms D , Shukla H , Nixon E , Bayouth J , Flynn R
Published: April 2010

Purpose: Dead detectors can occur in the electronic portal imaging devices (EPIDs) used for cone beam computed tomography (CBCT), and their presence can lead to image degradation and artifacts. Methods exist to correct for dead detectors, and the determination of the limitations of these methods could aid in the design of more efficient and longer‐lasting imaging systems in the future. We quantitatively assessed the effectiveness of three dead detector correction methods using megavoltage CBCT (MVCBCT) as a test system. Method and Materials: The dead detector correction methods considered were: bidirectional linear interpolation (BLI), quad‐directional linear interpolation (QLI), and a Laplacian solution (LS) method. A total of 288 MVCBCT test images of an image quality phantom were reconstructed from projections that were acquired from four linear accelerators (linacs). Both 8 and 60 monitor unit (MU) head‐and‐neck scanning protocols were used for the acquisitions. Dead detector maps were simulated for the cases of randomly distributed singular dead detectors and 13‐dead‐detector clusters, each with six dead detector percentages: 2%, 25%, 75%, 80%, 90%, and 95%. Results: Quantitative image quality assessment was done by calculation of the standard deviation of the test and baseline image differences. Test image quality did not deviate substantially from the baseline case (<0.5% dead detectors) for any of the algorithms until the dead detector fraction reached 80% for the clusters of 13 dead detectors, and 90% for the singular dead detectors. Conclusion: It was determined that MVCBCT images are relatively insensitive to randomly distributed dead detectors until 80–90% of the EPID detectors are dead. Image degradation for the same percentage of dead detectors was more pronounced when the EPID was covered with clusters of 13 dead detectors than with singular dead detectors, and was weakly dependent on the MU used during the image acquisition. No conflict of interest
SU‐FF‐J‐05: Motion Estimation Using Cone‐Beam CT Projection Images
Authors: Becker N , Kay I
Published: April 2010

Purpose: To investigate the motion information that can be extracted from the raw cone‐beam CT(CBCT) projection data of a fiducial marker in a respiratory motion phantom. Methods and Materials: A CBCT was acquired of a programmable respiratory phantom embedded with a gold seed fiducial marker. During acquisition, 650 raw projection images were sequentially captured as the imager rotated in a 360 degree arc. With a 60 second CBCT, and a 4 second respiratory period, the raw dataset contained motion information from 15 complete motion cycles. The images were binned based on respiratory phase, and the location of the gold seed in each image was determined. The back‐projections of the fiducial at the same phase but from different cycles (and therefore different gantry angles) produced a set of points representing fiducial positions at that phase. By using the average position, and by reconstructing positions for all phases, a trajectory was built. Results: When the fiducial's motion was identical from cycle to cycle, the difference between the actual and reconstructed average motion was less than 1mm. When the motion changes between cycles, an ‘average trajectory’ can be constructed, whose fidelity to the true average depends on the degree of variability of the true motion cycle to cycle. Conclusions: There is motion information present in the raw CBCT dataset that can be exploited with the use of an implanted fiducial marker. This particular example might provide a useful characterization of the internal motion at the treatment unit from the same dataset as is used for patient and target setup.
SU‐FF‐J‐08: Evaluation of 4DCT and Soft‐Tissue Registration in the Clinical Process for SBRT Patient Treatment
Authors: Smith C , Gulam M , Hammoud R , Nurushev T , Ajlouni M , Chetty IJ
Published: April 2010

Purpose: Soft‐tissue‐based registrations are routinely performed for 3D alignment in SBRT. One approach often reported is to perform registration of the ITV (reconstructed over multiple phases of a 4D‐CT) with the daily, free‐breathing CBCT, using first bony‐landmark alignment followed by soft‐tissue matching. As the ITV and free‐breathing CBCT target volumes are both spatially and temporally different, alignment of them to determine daily shifts is questionable. We performed a study to compare the 4D‐ITV with the free‐breathing CBCT target volume to assess the extent of differences in these volumes, ultimately to determine whether soft‐tissue matching is beneficial or desirable. Method and Materials: Free‐breathing helical and 4D‐CT scans (4 phases sorted retrospectively) were acquired on a Philips, 16‐slice 4D‐CT scanner. KV‐CBCT scans were then acquired on the treatment unit using the on‐board‐imager. 3D/3D auto matches (between the CBCT and ITV) were performed analogously to daily setup for SBRT patients. Multiple 4D‐CT scans were then acquired to sample the interplay between breathing phase and starting point of the helical scan and to determine the influence of this interplay on the reconstructed ITV. Results: The calculated shift from registration of 5 CBCT scans using a structure VOI showed a variation of up to 3mm. CBCT volumes were significantly smaller than the ITV but were always enveloped within the ITV; the center‐of‐mass location of the CBCT volume within the ITV varied between CBCT scans up to 3mm. Target volume differences were also noted between the free‐breathing CT and CBCT scans, due to increased volume averaging with CBCT. Conclusions: Daily shifts determined using soft‐tissue alignment of 4D‐ITV and CBCT and may introduce a source of systematic error in the delivery process, which may not be properly accounted for in the ITV‐to‐PTV margin design. Based on these, albeit preliminary findings, we are considering modifying our clinical procedures.
SU‐FF‐J‐09: Limited‐Angle Imaging for Target Positioning Using Orthogonal Conebeam X‐Ray Systems
Authors: Bowsher J , Giles W , Roper J , Ren L , Yin F
Published: April 2010

Purpose: To investigate limited‐angle imaging using orthogonal x‐ray systems, with regard to use for target positioning onboard external beam radiation therapy (EBRT) machines. Method and Materials: Image reconstruction was performed using projection data acquired with a single conebeam CT (CBCT) system for an anonymized head‐and‐neck patient onboard an EBRT machine. The original data set included 678 angles over 360°. Four subsets of this data were generated corresponding to the following angular ranges of the x‐ray tube: (i) Dual−40°: −110° to −70° plus −20° to 20°; (ii) Single−80°: −130° to −50°; (iii) Dual−80°: −130° to −50° plus −40° to 40°; (iv) all 360°. Images were reconstructed from each data set by an ordered‐subsets iterative statistical method (OSTR). Sagittal, coronal, and transverse slices were obtained from the reconstructed images and evaluated. This study design does not include the cross‐scatter that would occur between two orthogonally mounted CBCT systems. Results: Equal‐dose comparisons of Dual−40° and Single−80° images showed that the Dual−40° provided sufficient sharpness to position the target along all 3 dimensions. The Single−80° images did not provide adequate sharpness along the lateral direction. Equal‐time comparisons of Dual−80° and Single−80° images showed marked improvement in image quality in all 3 slices and all 3 dimensions. Conclusion: Dual−40° scans have approximately equal dose to Single−80° scans, allow positioning along all 3 dimensions, and require only half the imaging time. Reduced imaging time can reduce motion artifacts in the image and reduce probability of motion between imaging and treatment. Dual−80° scans have approximately twice the dose of Single−80° scans, but they provide much better image quality with no increase in scan time. Onboard limited‐angle imaging with dual orthogonal CBCT systems thus has advantages over limited‐angle imaging with a single CBCT system.
SU‐FF‐J‐16: Reference Dosimetry During CBCT Acquisition Using Radiochromic Film
Authors: Tomic N , Seuntjens J , DeBlois F , Devic S
Published: April 2010

Purpose: We describe a 2D reference dosimetry technique for measuring dose from cone‐beam computed tomography (CBCT) scans using on‐board imager (OBI) on Varian Clinac‐iX linear accelerator that employs XR‐QA radiochromic film model, specifically designed for dose measurements at low energy photons. We report on surface dose and percent depth dose (PDD) measurements during clinical CBCT procedures carried out on a humanoid Rando phantom. Method and Materials: Response of XR‐QA model GAFCHROMIC™ film reference dosimetry system was calibrated in terms of air kerma in air. To measure surface dose during CBCT acquisitions, pieces of XR‐QA films were taped on surface of the Rando phantom. Also, film strips were placed between Rando slices in vertical and lateral direction in order to measure PDDs during CBCT scans for different sites and different CBCT protocols available on our imaging system. Spatial dosimetry was performed using Epson Expression 10000XL document scanner. Change in optical reflectance of the unexposed film piece was subtracted from the exposed one to obtain final netR, which was converted to dose using previously determined calibration curve. Results: Our measurements show that skin dose can range from 0.07 cGy in Low Dose Head, to 4.64 cGy in Pelvis Spot Light CBCT protocol with uncertainty of 2% at higher doses, rising to 4% at 0.5 cGy and 12% at the lowest measured dose. Profiles obtained from film strip measurements show different dose distributions depending on the CBCT technique used and the anatomical site imaged. Conclusions: In this work, we describe an air kerma in air based technique of measuring dose during CBCT scans using XR‐QA model GAFCHROMIC™ film in combination with flat‐bed document scanner. Main advantage of this system is that it does not require a priori knowledge of the backscatter factors and it provides 2D reference dosimetry at low kVp photon beams.
SU‐FF‐J‐23: Treatment Margins for Pancreatic Cancer Based On Daily IGRT with Cone Beam CT (CBCT)
Authors: Khan MK , Gajdos S , Juliano J , Stephens K
Published: April 2010

PURPOSE: To evaluate interfraction pancreatic motion as evidence by daily image guided radiotherapy (IGRT) using daily CBCT. MATERIALS AND METHODS: Daily kilovoltage CBCT was used during the definitive treatment of seven patients. Daily CBCT images were registered to planning CT with automatic software tools that put higher importance on boney anatomy as proxy for pancreatic motion. Validation scans were employed when preset constraints were not met. A single treating physician reviewed and approved each fusion. Data regarding interfraction deviation from these daily shifts are analyzed for translation and rotation in the anterior‐posterior (AP), right‐left (RL), and superior‐inferior (SI) directions. RESULTS: One hundred and eighty registration scans were utilized and revealed average shifts of 0.24, 0.15, and .01 cm in the SI, AP, and RL directions, respectively with standard deviations of 0.42, 0.27, and 0.45 cm. Using this data in the Van‐Herk model suggests treatment (PTV) margins of 0.39 cm in RL, 0.91 cm in SI, and 0.58 cm in AP direction to ensure that 90% of all of the clinical target volumes (CTV) receive 95% of the prescribed dose. The average vector displacement was 0.61 cm with a standard deviation of 0.41 cm. The maximum observed vector shift was 1.95 cm in the SI direction. The registration yielded an average rotation of 0.97°, −.06°, and −.20° in the coronal, sagittal, and axial planes respectively with standard deviations of 0.8°, 1.25°, and 1.1°. The maximum rotation noted in any direction was 4.6°. CONCLUSIONS: CBCT is an important tool to monitor interfraction pancreatic motion. Bony fusion as proxy provides some confidence and may translate into smaller margins. However, further assessment with soft tissue fusion and the use of internal fiducials are needed to help provide further confidence.
SU‐FF‐J‐24: Functional Planning for Tomotherapy‐Based Stereotactic Body Radiotherapy (SBRT) for Peripheral Lung Tumors
Authors: Cai J , McLawhorn R , Read P , Larner J , Sheng K , Altes T , de Lange E , Benedict S
Published: April 2010

Purpose: To investigate the impact of incorporating hyperpolarized heliume‐3 (HP He‐3) MRI ventilation images to Tomotherapy‐based stereotactic body radiation therapy (SBRT) planning for peripheral lung tumors. Method and Materials: CT and HP He‐3 MRI ventilation images of 6 subjects were co‐registered for segmentation. Highly functional lungs (HFL) were defined as the 70‐percentile hyperventilation lungs and less functional lungs (LFL) were subsequently calculated. A cylinder‐shaped artificial object was created in peripheral lungs to mimic planning‐target‐volume (PTV). Two Tomotherapy‐based IMRT plans, a anatomical plan (Plan 1) and a functional plan (Plan 2), were designed with SBRT‐type prescription (60Gy in 5 fractions) and normal tissue constrains. The following dosimetric parameters were compared between two plans: total lung V20 (TLV20), highly functional lungs V20 (HFLV20), less functional lungs V20 (LFLV20), mean total lung dose (MTLD), mean highly functional lung dose (MHFLD), mean less functional lung dose (MLFLD), max dose to organs at risk (OARs) and conformality index (CI). Results: Compared to Plane 1, Plan 2 significantly reduced HFLV20 (median reduction 2.1%, range 0.7–2.9%, p‐value=0.031), TLV20 (median reduction 1.6%, range 0.5–2.1%, p‐value=0.031), MHFLD (median reduction 0.8Gy, range 0.4–1.0Gy, p‐value=0.031), and MTLD (median reduction 0.7Gy, range 0.1–1.0Gy, p‐value=0.031). There was no significant difference in LFLV20 and MLFLD (p‐value is 0.438 and 0.156 respectively). Dose constrains for OARs were satisfied in all plans and max doses to OARs were not significantly changed in Plan 2 (p‐values range: 0.063–0.563). CI was generally reduced in Plan 2 (median reduction 0.02) but the difference is insignificant (p‐value=0.125). Conclusions: The incorporation of HP He‐3 MRI ventilation information to the Tomotherapy‐based SBRT planning for peripheral lung cancer improved the sparring of radiation dose to highly functional lungs and can potentially preserve more highly functional lungs.

Conflict of Interest: Dr. Paul W. Read serves as a consultant for Tomotherapy Inc.
SU‐FF‐J‐25: Visibility Study of Fiducial Marker for Real‐Time MLC Beam Tracking Delivery Using MV Fluence Video
Authors: Liu Yaxi , Roland Teboh , Shi C , Swanson G , Mavroidis P , Papanikolaou N
Published: April 2010

Purpose: The objective of this study was to assess the visibility of fiducial marker for beam tracking delivery using MV fluence video. Method and Material: Target visibility in MV images is crucial in real time tracking. The assessment of visibility become complicated as marker visibility may be affected by many factors. Our work focused on the dependence on fiducial marker size, dose rate and video frame rate. A dynamic phantom was used to mimic patient respiratory motion. Three sizes (3 mm in length, 0.8, 1.2 and 1.6 mm in diameter) of fiducial markers were implanted in the phantom insert. Dose rates of 160, 240 320 and 400 MU/min were used with various video frame rates at 6.5, 8.33, 12.5 and 25 frames per second. Contrast‐to‐noise ratio was calculated to assess the quality of MV fluence video. Two prostate patients participated in the fiducial marker visibility study for beam tracking delivery. An optimized combination of the three factors is to be selected for patients study. Results: The fiducial marker visibility was observed to be closely related to marker size, dose rate and video frame rate. The bigger diameter markers, 1.2 and 1.6 mm, provided better video quality as a result of a higher contrast‐to‐noise ratio. A high contrast‐to‐noise ratio exists when dose rate and frame rate belong to a certain zone. After selecting frame rate of 8.33 FPS and dose rate of 240 MU/Min, we operated the tracking functionality for the prostate patient with acceptable quality of fiducial marker. Conclusion: Fiducial marker visibility in tracking systems turns out to be complicated as it depends on many factors. Among the three factors investigated, the marker size was observed to have a predominant impact on the image visibility. Appropriate combinations of video frame rate and dose rate are necessary for high quality visibility.
SU‐FF‐J‐27: Calibration of the Dual‐Transducer Focused Acoustic Radiation Field for a Multimodal Sono‐Contrast NIR Spectroscopy System
Authors: Yan K , Huang K , Podder T , Yu Y
Published: April 2010

Purpose: To calibrate the dual‐transducer focused acoustic radiation field, register the focus center in the imaging ultrasound system, and establish a monthly calibration protocol for a noninvasive multi‐modal breast cancer scanning system. Method and Materials: The scanhead incorporated two 1MHz focused transducers aligned orthogonally to deliver acoustic radiation force (ARF) in a 2.4cm region. A commercial ultrasound probe, located in the same vertical plane as the focused transducers, was used in the system for image co‐registration. Dielectric fluid was filled into the scanhead as the ultrasound transmission media. The scanhead was merged into a water tank filled with degassed distilled water. A function generator connected with an amplifier was used to drive the focused transducers. The imaging ultrasound probe was connected to a commercial ultrasound system. The focused transducers were excited by 1MHz continuous sine wave with amplitude of 200mv from a function generator, amplified by the amplifier. A hydrophone was aligned vertically below the bottom plate and moved by a 3D motion platform (resolution 0.05mm) in the 3D Cartesian space at a step of 0.1mm. An oscilloscope was connected with the hydrophone for data display and acquisition of the voltage signals for calculating the acoustic intensity. Results: The focal spot that has the maximum peak‐positive voltage signal on the oscilloscope was found at 2.34 cm below the bottom plate, which is the designed intersection of the axes of the two focused transducers. The Spatial Peak Temporal Average Intensity was determined to be 0.4 W⋅cm−2, below the FDA therapeutic ultrasound limits (0.72 W⋅cm−2). The focal spot was then registered in the imaging ultrasound images. Conclusions: This study established the baseline of the dual‐transducer focus acoustic radiation field. A monthly calibration protocol has been developed following the same procedure for the focused acoustic radiation field.

Acknowledgement: supported by NCI Grant CA107860.
SU‐FF‐J‐35: Severe Inter‐Fractional Anatomic Changes and Their Dosimetric Impact in Abdominal Irradiation, An Indication for Adaptive Re‐Planning
Authors: Qi X , Wang K , Siker M , Firat S , Erickson B , Li X
Published: April 2010

Purpose: To study the dosimetric impact of inter‐fractional anatomic changes in the abdominal region during the course of radiation therapy and to determine the frequency of adaptive re‐planning. Methods and material: Daily CT images acquired for selected abdominal cancer patients treated on a helical Tomotherapy unit were analyzed. The targets and organs at risk (OAR), such as kidneys, liver, cord and stomach, were delineated based on daily CT registered with the planning CT. The 3D dose distribution and dose volume histograms (DVHs) delivered to the patient on the day were reconstructed based on the CT of the day and the shifts performed (verification dose) using the Planned Adaptive software in the Tomotherapy planning system. The daily patient anatomy including body weight and locations, volumes and shapes of targets and OARs, as well as dose volume parameters including DVHs, maximum, minimum and mean doses and equivalent uniform dose (EUD) were compared to those from the planning CT. Results: Significant interfractional anatomic changes were observed for a patient with severe weight loss. In this patient with a suprarenal tumor, significant weight loss was observed during the second week (day 8) of radiotherapy, which led to 6.2%, 10.3% and 7% increases in maximum doses for PTV, the cord and unspecified tissue, respectively, from their values in the original plan. Compared to the original plan, the EUD changed by 24.6%, 11.3% and 14.6% respectively, for the right kidney, liver and stomach. In a cholangiocarcinoma case, dramatically organ volumetric and/or geometric changes for the liver and stomach were observed, resulting in changes in EUD of 16%, 22% and 46% for the liver, stomach and left‐kidney, respectively.

Conclusion: Dramatic inter‐fractional anatomic changes in abdominal region, which can result in significant dosimetric impact and therefore, should be accounted for by an adaptive strategy, such as re‐planning.
SU‐FF‐J‐42: Imaging Study to Determine Appropriate Implanted Fiducial Markers for Proton Or Photon Image Guided Radiation Therapy
Authors: Kudchadker R , Li H , Johnson J , Lee A
Published: April 2010

Purpose: Fiducial markers are used to verify and correct prostate position during x‐ray intensity modulated radiation therapy or proton therapy. However, each commercially available marker has some advantages and disadvantages associated with their use. We have conducted an imaging study to determine the appropriate type of marker to be used for prostate patients undergoing x‐ray or proton imaged guided radiation therapy (IGRT). Method and Materials: Four types of markers were evaluated: a) gold (0.8 mm × 3.0 mm); b) gold (1.2 mm × 3.0 mm); c) carbon (1.0 mm × 3.0 mm); d) plastic (1.0 mm × 5.0 mm). The markers were inserted into the pelvis of a Rando phantom and a computed tomography (CT) was obtained. The radiographic visibility of the markers, were assessed by visual inspection of radiographs using a linac kilovoltage (kV) and megavoltage (MV) x‐ray imaging system. Results: Under CT imaging, the large gold marker produced the greatest artifact followed by the small gold marker. The carbon and plastic markers produced minimal CT artifact. Under kV imaging, all four fiducials were clearly visible. Under MV imaging, both the gold fiducials were visible, however, both carbon or plastic fiducials were not‐visible. Conclusion: Due to CT artifacts, gold markers are inaccurate to contour on the CT dataset resulting in approximate marker locations on the digitally reconstructed radiographs (DRR's). This limitation adds to patient setup uncertainty during daily IGRT. Gold markers, especially the smaller marker, would be a suitable choice when imaging with MV beams. Carbon or plastic markers provide high resolution kV localization with minimal CT artifacts. Fewer artifacts leads to more accurate DRR's. Gold markers cause dose perturbation in patients receiving proton radiotherapy. Low density carbon markers could be used instead. Carbon markers would also be a great choice for patients receiving x‐ray kV IGRT.
SU‐FF‐J‐45: Performance of a PET‐Guided Breast Biopsy System
Authors: Matthews CG , Kalinyak JE , Payne S , Kassab R , Luo W
Published: April 2010

Purpose: Positron emission mammography (PEM) imaging has identified lesions with no anatomic correlate, thereby creating a need to sample using only PET guidance. Bench tests were designed to validate the first PET‐guided breast biopsy system for clinical use. Method and Materials: A commercially available Naviscan PET scanner with its Stereo Navigator breast biopsy accessory is used with third party, vacuum‐assisted, core needle biopsy (CNB) devices. A series of bench tests with phantoms determined the performance of the system for breast biopsy. The targeting accuracy test series compared the physical versus image coordinates in 3D of radioactive targets. The guidance accuracy test series checked the placement in guiding biopsy needles to the correct position such that it would intersect with a Na‐22 point source, i.e., replicating the guidance of a biopsy needle to a suspected lesion in a human breast. The glyph placement accuracy series verified the software glyph overlays correlated to the physical location of the guidance hardware and biopsy needle. The biopsy sampling test series evaluated the ability of the system to accurately target an FDG lesion, to confirm localization of the lesion using a Ge‐68 line source, and to verify accurate sampling with CNB tools Results: Targeting accuracy was found to be 0.5 ± 0.3 mm in‐plane and 1.0 ± 0.9 cross‐plane. The needle guidance accuracy was 0.9 ± 0.6 mm parallel to the needle and 2.3 ± 1.3 perpendicular to the needle. The computer‐generated glyphs were correctly placed with respect to the physical target location 100% of the time. The biopsy sampling was 96% successful. Conclusion: Bench testing of the first PET‐guided breast biopsy system demonstrated a high degree of guidance accuracy for use in PEM‐identified breast lesion sampling. The system was cleared for clinical use.

Conflict of Interest: Research sponsored by Naviscan, Inc.
SU‐FF‐J‐46: Treatment of Bone Metastases Using MR Guided Focused Ultrasound
Authors: Chen L , Ma C , Richardson T , Freedman G , Konski A
Published: April 2010

Purpose: To evaluate the safety and efficacy of MR guided focused ultrasound (MRgFUS) treatment for bone metastases. Method and Materials: A 50‐year‐old patient with painful scapula bone metastases refractory to pain medication was recruited in this study. The treatment was performed under local IRB approval using an MRgFUS system consisting of an Insightec ExAblate 2000 with a GE 1.5T MR scanner. The focal region is approximately 2mm in diameter and 10mm in length. Beside the regular monthly and annual quality assurance (QA) measurements, pre‐treatment machine calibration included the functionality of the treatment software and the mechanical motion control. The focal spot was verified using MR thermometry. The safety system and panic buttons were checked. The patient is positioned on a gel pad on the treatment table in line with the transducer. The gel pad was immersed in degassed water that acts as an interface between the treatment table and the gel pad for acoustic coupling. Caution was taken with all gas bubbles removed between the interfaces. Treatment was performed under conscious sedation. Six sonications were delivered with frequency 1 MHz, acoustic power 32 ±4 W, energy 628±78 J and 20s durations. Phase MR Images were used to monitor the temperature change in real‐time. Based on the treatment feed back, acoustic power was adjusted to reach designed temperatures (⩾60 °C) for individual sonications. Results: The patient tolerated the MRgFUS treatment well. There were no treatment‐related adverse events including skin toxicity. The patient reported rapid pain decrease from 8 out of 10 (0 – 10 scale) pretreatment to 2 within 24 hrs, and has continued to report between 2 – 2.5 up to 2 months following treatment.

Conclusions: MRgFUS is a safe, effective and noninvasive treatment modality for bone palliation and pain relief. A comprehensive QA program has been developed for the MRgFUS system.
SU‐FF‐J‐49: Geometric Validation Of MV‐Topograms And Digitally Reconstructed KV‐Topograms
Authors: Goddu S , Palaniswaamy G , Moore K , White B , Yang D , Rangaraj D , Mutic S , Low D
Published: April 2010

Purpose: While Tomotherapy offers volumetric Imaging for image‐guided radiation‐therapy, it suffers from the drawbacks of slow image‐reconstruction, and lack of planar imaging capability. Megavoltage (MV) topograms and kilo‐voltage digitally reconstructed topograms (kV‐DRTs), have the potential for reducing daily‐localization times and patient‐dose. Both kV‐DRTs and MV‐topograms were generated using our in‐house Topographic Registration (TopoReg) Software. Primary goals of these tests were to validate the geometric integrity of the topograms in all 3‐ dimensions. Methods: TopoReg software uses high‐resolution CT‐datasets for reconstructing the kV‐DRTs while the MV‐topograms are created from the Tomotherapy exit detector data. TopoReg software includes several tools for image enhancement and registration. Geometric verification of the reconstructed topograms was done in three steps; planar, volumetric, and anthropomorphic. The first phantom includes four 17×17×0.5 cm3 water‐equivalent plastic (WEP) plates fixed on top of a 40×40×1 cm3 WEP for planar verification. There were two sets of holes on each WEP plate, separated by 12.5 cm. The second phantom was a Styrofoam cube (30×30×30 cm3) with embedded WEP plates; two plates on the diagonal axis and one plate on each side. Head and neck, thorax, and pelvis phantoms were also imaged and compared. The phantoms were imaged using Brilliance Large bore CT scanner and kV‐DRTs were generated. MV‐topograms were generated from the exit detector data. Results: Geometric verification was conducted by comparing fiducial positions on the topograms. MV‐topograms are overlaid on kV‐DRTs for registration. Both translations and rotations were allowed during image registration. Geometric accuracy was within ±1 mm in all 3‐dimensions and the image quality of the topograms was adequate for bony anatomy‐based registrations. Conclusion: TopoReg software is valid and the geometric accuracy of the MV‐topograms and kV‐DRTs was acceptable for clinical implementation.

This work supported in part by a grant from Tomotherapy.
SU‐FF‐J‐53: Experience and Comparison of Two Image Guidance Methods for SBRT Treatment: 4D CT and ExacTrac Respiratory‐Triggered Imaging
Authors: Wang B , Rassiah‐Szegedi P , Zhao H , Salter B
Published: April 2010

Purpose: For Stereotactic Body Radiation Therapy (SBRT) treatment of lung and liver, we quantified the differences between two image guidance methods: 4D CT and ExacTrac respiratory triggered images. Method and Materials: 5 liver lesions and 1 lung lesion for a total of 21 fractions were studied. For the 4D CT method, a manual registration method was used between the 4D CT image sets from initial simulation and treatment day. 4D CT derived image guidance shifts were ascertained from comparison to the same breathing phase at simulation. We also used ExacTrac respiratory triggered imaging to verify the target positioning and calculated the differences in image guidance shifts for the two methods. Results: The mean of the observed differences in image guided shifts between 4D CT image guidance and ExacTrac respiratory triggered image guidance was x = 1.6 mm, y = 1.9 mm, z = 2.8 mm, with no difference larger than 5.0 mm noted in any given direction for any individual case. As expected, the largest error occurred in S/I direction, with a mean of 2.8 mm for the six patients. This is expected because respiratory motion and the resulting uncertainties are most pronounced in this S/I direction. The ExacTrac images triggered at two extreme breathing phase, e.g., full exhale vs. inhale, agreed well (< 2.0mm) with each other. Conclusion: The two very promising image guidance methods of 4D CT and ExacTrac respiratory triggered imaging have been presented and compared for SBRT of lung and liver. The mean differences in image guided shifts between the two methods were less than 3 mm, with no individual direction difference greater than 5 mm for the six SBRT patients, 21 delivered fractions evaluated in this study. Potential contributing factors to the disagreement were presented and will be studied further in future work.
SU‐FF‐J‐55: Acceptance Testing and Quality‐Assurance Protocols for the Calypso® 4D Localization System™ and Q‐Fix®/Calypso® Couchtop
Authors: O'Daniel J , Wu QJ , McMahon R , Maurer J , Lee WR , Yin F
Published: April 2010

Purpose: To develop quality‐assurance (QA) protocols for the Calypso® 4D Localization System including acceptance testing, commissioning, daily QA, monthly QA, and annual QA. Method and Materials: The following acceptance testing/commissioning/QA protocols were developed following the implementation of the Calypso System at our institution. Both the Calypso System itself and a new Q‐fix/Calypso couch‐top were tested. The Calypso System tests consisted of (1) transponder imaging and treatment planning, (2) localization and tracking accuracy, (3) accuracy of motion measurements, (4) operational range of the array and system integration, (5) on‐board x‐ray imaging when using the array, (6) safety and collision checks, (7) automatic couch repositioning accuracy and functionality, (8) clinical application protocols and workflow. The Q‐fix/Calypso® couch‐top tests included mechanical tests (accuracy of motion along the three axes, angle indicator accuracy, isocentricity, and sag) as well as measurements of the attenuation through the new couch top and rails. Results: Localization/Tracking Accuracy: The Calypso‐measured displacements agreed with the known displacements within 1mm. Motion: The Calypso System measured the period and amplitude of the longitudinal sinusoidal motion within 0.1s and 0.1cm. Operational Range: We measured the operational range of the Calypso® array to be 14cm lateral, 15.8cm longitudinal, and 28.7cm vertical. Imaging: kV imaging clearly delineates the transponders. The presence of the array introduces significant noise into the CBCT scan, but still allows for localization of the transponders. Safety Checks: The appropriate warning messages were generated when the test patient plans were used. Automatic Couch Repositioning: The ACR correctly repositioned the phantom within 0.05cm of a known 3D shift. Q‐Fix/Calypso® Couch‐top: Recalibrating the vertical couch position was required (3mm change). The maximum couch attenuation was 3.6%, and rail attenuation was 9.9%. Conclusion: The Calypso® 4D Localization System was successfully implemented. Collection of baseline accuracy is important to ensure the continuing functionality of the system.
SU‐FF‐J‐57: IBreathe: Monitoring Respiration with the Accelerometer in An IPod Touch
Authors: Lam K , Hadley S , Balter J
Published: April 2010

Purpose: The breathing pattern for respiration management is obtained by various methods, including infra‐red reflector monitored by a camera (RPM by Varian), spirometer (ABC by Elekta), belt connected to a bellows (4D‐CT by Phillips), or inductive belt (commonly used in sleep studies). We are exploring the use of the accelerometer in the widely available iPod‐Touch as a wireless device to monitor the breathing pattern for respiration management in radiation therapy. This device has wireless communication built into a compact form factor and powered by a battery. It can potentially be a convenient portable device for acquiring breathing patterns. Method and Materials: The iPod‐Touch has a three‐axis accelerometer so that it can detect the magnitude and direction of the local gravitational field relative to its housing. The angular resolution achievable is 0.1 degrees. The iPod‐Touch is placed on a Styrofoam platform with three adjustable legs for leveling. The platform is placed on the abdomen or chest of the patient, depending on the application. The change in inclination of the platform during respiration is detected by the accelerometer and recorded by the iPod‐Touch. For the current study, the recorded inclinations are sent as an attachment in an email for analysis. Results: Breathing traces of healthy subjects were acquired. The amplitude of the change in inclination corresponding to tidal volume was greater than 5 degrees peak‐to‐peak. The breathing trace was recorded at >10 Hz. For a 10 breath‐per‐minute breathing cycle, there are >60 recorded samples per breath. Conclusion: The accelerometer in an iPod‐Touch is sensitive enough to detect the breathing pattern and the recorded trace can be sent wirelessly for analysis. Further work will establish a wireless link between this device and a computer to continuously acquire real‐time breathing data. Supported in part by NIH P01‐CA59827.
SU‐FF‐J‐58: Inter‐Transponder Distance Change and Its Effect On Prostate Localization
Authors: Li JS , Xu Q , Ma CM
Published: April 2010

Purpose: To report the inter‐transponder distance variation and its effect on prostate IMRT for transponder‐based target localization. Materials and Method: Real‐time electromagnetic tracking systems, such as the Calypso 4D localization system, monitor the prostate motion by tracking the positions of implanted transponders. Three transponders were usually implanted in the prostate gland one week before the CT simulation. The inter‐transponder distances detected by the system at the first and last treatment were compared with those obtained from the simulation CT scans for 105 patients. Cone beam computerized tomography (CBCT) has been taken for some patients to verify the inter‐transponder distance change and the prostate deformation. Results: Comparing with the simulation CT, the average changes of the distance from the transponder at apex to the one at right base and to the one at left base, and from the right to the left base are −0.84, −0.88, −0.23mm at the fist treatment and −1.72, −2.0, −1.27mm at the last treatment, respectively. The inter‐transponder distances can increase by 7mm or decrease by 16mm while most changes are from −5mm to 3mm. The percentages of patients have inter‐transponder distance variation more than 2, 4 and 6mm at the last treatment are 58%, 24% and 5%. The distance changes continuously during the treatment for most patients and the change varies between −4mm and 2mm from the first to the last treatments for most patients and the maximum changes are −6.6mm and 7.3mm. The inter‐transponder distance has been confirmed by CBCT and the potential causes are transponder migration, prostate shrinkage and deformation due to rectal/bladder fillings. The effect on the centroid position and thus the isocenter accuracy is within 2.5mm for most patients. Conclusions: The inter‐transponder distance changes significantly for some patients and its effect need to be considered clinically for transponder‐based target localization.
SU‐FF‐J‐60: A Video Guided Breath Hold Treatment Technique for Cardiac Sparing Breast Radiotherapy
Authors: Gierga DP , Sharp GC , Spadea MF , Turcotte JC
Published: April 2010

Purpose: The purpose of this work was to examine the reproducibility of the treatment position for a breath hold treatment technique for left sided breast cardiac sparing treatments. The feasibility of three dimensional video feedback for breath hold was also examined. Method and Materials: Patients with left sided breast cancer and unfavorable cardiac anatomy were treated with a breath hold cardiac sparing technique. One cohort of patients was treated without any feedback and with only simple verbal instructions. Three dimensional surface images during breath hold were obtained using the AlignRT system (VisionRT, London, UK). The reproducibility of the position of the breast surface was tested by registering the surfaces to a reference image taken on the first day. The daily surfaces were also registered with the skin surface generated from the CT simulation to check for systematic setup errors. The feasibility of a video‐based patient feedback system was tested using simple video goggles that interfaced with the AlignRT system. Patients were able to visualize the relationship of their current breast surface during breath hold relative to the CT‐based reference surface used for treatment planning in near real time. Results: The variation of the breath hold surface without feedback was significant. The overall standard deviation of the breath hold surface was approximately 3–4 mm, but the range of positions of the surface was in some cases as large as 10–15 mm. Surface registration with the CT‐based reference surface showed setup errors that were in some cases as large as 10 mm. Surface matching was shown to reduce the discrepancies between the daily and reference surface. Furthermore, video feedback appears promising as a method to reduce day‐to‐day breath hold variations. Conclusion: Surface imaging is a useful tool in image guided breath hold breast treatments.
SU‐FF‐J‐62: Calculation of Delivered Dose From Calypso Tracking Data: And Subsequent Evaluation of Reasonable Treatment Interruption Tolerance Limits
Authors: Zhao H , Wang B , Rassiah‐Szegedi P , Szegedi M , Salter B
Published: April 2010

Purpose: Calypso is a recently introduced prostate positioning technique which can be used to localize and track prostate position during radiation therapy. In this study the composite delivered dose based on daily Calypso tracking‐data‐stream and different tolerance limits were calculated. Method and Materials: All IMRT treatment plans were calculated using Corvus treatment planning system. Two IMRT plans which have PTV margins of 5mm and 3 mm were computed for a prostate cancer patient. Composite doses for 22 fractions were computed based on daily Calypso tracking‐data for both plans. Composite doses based on Calypso tolerance shifts were computed for two tolerance levels: 5mm and 3mm. For each level, composite doses for eight combinations of tolerance shifts were computed. The maximum, mean, minimum doses for CTV, PTV, bladder and rectum were recorded. The volumetric coverage of CTV, PTV, bladder, and rectum for 100% and 95% prescription dose were calculated, along with that of bladder and rectum for 65Gy and 40Gy. Results: Composite doses based on Calypso tracking‐data‐stream for both 5mm and 3mm PTV margins were similar to the original plan. The difference of maximum, mean, and minimum doses for CTV, PTV, bladder, and rectum was less than 1.3%. The volumetric coverage difference of CTV, PTV, bladder, and rectum for 100% and 95% prescription dose was less than 1.1%, as was of bladder and rectum for 65Gy and 40Gy. For 5mm PTV margin, the prescription dose coverage of CTV volume for composite dose of eight combinations of tolerance shifts for both 3mm and 5mm was over 99.5%. For 3mm PTV margin, that coverage was 98.6% and 88.6% for 3mm and 5mm composite shifts respectively. Conclusion: A realistic prediction of delivered composite dose can be calculated using tracking‐data‐stream provided by Calypso. Calculated composite doses were agreed with the planed doses.
SU‐FF‐J‐63: A Method for Alignment Test of An X‐Ray Positioning System for Proton Therapy
Authors: Yang J , Bues M , Zhu M , Smith A
Published: April 2010

Purpose: To develop a method to test the alignment of an on‐board x‐ray positioning system for proton therapy. Methods and materials: Each treatment portal at the proton therapy center in Houston (PTC‐H) is equipped with three orthogonal x‐ray imaging devices. We developed a method to test the alignment of imaging devices using a custom built phantom. The phantom is 30 × 30 × 30 cm in size and is positioned on a base plate, which attaches to the robotic patient couch. The phantom position was calibrated against a 2‐mm diameter tungsten ball placed at radiation isocenter. On each side of the phantom, there are radiopaque markers of known sizes and locations. With the measurement of the marker locations in the x‐ray images, we calculated the alignment of the x‐ray source to that of the major axis of the proton machine reference frame. By using points 15 cm away from isocenter, we test the alignment not only with iso center, but also with the reference frame axes to avoid angulations between imaging axis and machine axis. We also derived source‐to‐axis‐distance (SAD), source‐to‐imager distance (SID) for the x‐ray source, and pixel size for the image receptor. The phantom design allowed for alignment of all three imaging systems without couch movement once the phantom was positioned at isocenter. Results: We used this method to test the alignment of imaging positioning system at a proton portal at PTC‐H. We found the measured results to be within 0.4 mm at iso for x‐ray sources alignment at all 3 x‐ray/receptor systems at gantry of 270 degree. The pixel size was within 1%. SAD, SID were within 2% of manufacturer's specifications. Conclusion: We developed a method to align the x‐ray positioning system for a proton gantry to the precision necessary for proton therapy.