bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐EE‐A3‐02: Exact Fan‐Beam Image Reconstruction Algorithm for a Specific Truncation Problem: Asymmetrically Positioned Half‐Size Detector
Authors: Zhuang T , Leng S , Nett B , Chen G
Published: June 2005

Purpose: In nuclear medicine imaging, diagnostic x‐ray CT imaging, and image guided radiation therapy truncation of the projection data may be present due to patient motion, inaccurate positioning or simply an insufficient detector. For fan‐beam geometry, images reconstructed with truncated data suffer sever artifacts when reconstructed with the conventional filtered backprojection (FBP) algorithm. A new exact fan‐beam image reconstruction algorithm is developed to solve a special case of the data truncation problem. In this configuration, fan‐beam projection data are acquired using an asymmetric detector that covers only half of the field of view. Method and Materials: In order to solve this data truncation problem, the newly developed fan‐beam image reconstruction algorithm via filtering the backprojection image of the differentiated projection data (FBPD) was employed. This algorithm enables line by line reconstruction in image space. The following observations about this FBPD algorithm are crucial to solve the data truncation problem: (1) for a given point in the backprojection image space, only one projection from each view angle is required to properly construct the backprojection image; (2) for each ray passing through a given image point from one source position, there is a conjugate ray passing through the same point. With truncated data, a 2π full scan is required to reconstruct the whole object, and a ROI reconstruction can be obtained using projection data from less than a 2π full scan. Results: Numerical simulations have been conducted using a Shepp‐Logan phantom. Images reconstructed from the truncated data for scans of the entire object validate this reconstruction algorithm for the full 2π scan. In addition ROI reconstruction has been validated using projection data from less than a 2π full scan. Conclusion: This algorithm enables exact fan‐beam image reconstruction from projection data acquired using an asymmetric detector which covers only half of the field of view.
TU‐EE‐A2‐01: Determination of Output Factors for Small Photon Beams
Authors: Sauer O , Wilbert J , Laqua D
Published: June 2005

Purpose: Due to the strong field size dependence and differences in response of different detectors, the determination of output factors for small fields is still ambiguous. By means of careful measurements and a sophisticated analysis of the values, the uncertainty was minimized. Method and Materials: For beams of 6 and 10 MV collimated with the Elekta Beam Modulator the output versus field size was measured with different detectors. Field sizes were from 4*4mm2 to 160*210mm2. An analytical curve comprising a sigmoidal part for the primary dose and an asymptotic exponential for the scatter part was fitted to the measured values: The ratios with respect to the ionization chamber measurement for large fields (>50*50mm2) were linearly extrapolated. The measured values for small fields were corrected with these ratios. Results: The measured data could be fitted very well with the proposed function. The statistical uncertainty was small enough to clearly demonstrate the differences of the different detector signals. For large fields the slope of an unshielded mini diode was highest, followed by the MOSFET and the Pinpoint chamber curves. The diamante detector, the shielded diode and the 0.125ccm chamber showed approximately the same slope of the output function. Due to their size, the chambers measured a too low output at field sizes below 20*20mm2. The other detectors agreed within 5%. Correcting with the sensitivity ratio this spread could be reduced to 1.6%. Conclusion: A physically meaningful function was proposed and successfully tested, to describe the photon output for all field sizes. The Pinpoint chamber is not suitable for small field measurements. For the MOSFET we used the signal was too noisy. All other detectors give the same output down to field sizes of 4*4mm2, if the proposed correction is performed. The shielded Si‐diode may be used without further correction.
TU‐EE‐A2‐02: Effect of Respiratory Motion On the Delivery of Breast Radiotherapy Using Physical Compensators and SMLC Intensity Modulation
Authors: Liu Q , McDermott P , Burmeister J
Published: June 2005

Purpose: This study evaluates the effects of respiratory motion on breast radiotherapy delivered using physical compensators and sMLC intensity.2109 2005 AAPM Meeting Program 2109 Medical Physics, Vol. 32, No. 6, June 2005 modulation. Method and Materials: An anthropomorphic breast phantom was constructed of polyethylene plates between which radiographic films are inserted. The phantom is mounted on a moving platform which simulates one‐dimensional sinusoidal oscillation with variable amplitude and frequency. The respiratory motion effect of three breast radiotherapy techniques was evaluated, including sMLC IMRT (Corvus TPS), custom‐designed physical compensators, and aperture based IMRT. The treatment plans for the latter two techniques were generated using an in‐house TPS. Film comparisons were performed to check experimental reproducibility and evaluate the effects of respiratory motion. Results: Subtraction residues between two films measured under identical experimental conditions are well within 5%, which is within the uncertainties in experimental setup and dosimetric technique. The largest motion‐induced differences occur at the posterior field edge where high dose gradients exist. This is due to dose blurring effects and does not depend on the delivery technique. The subtraction residue in the remainder of the treatment region is within 7%, with the exception of the apex of the breast in the Corvus IMRT plan. A virtual bolus region is created during Corvus planning to allow expansion of the intensity map outside of the skin contour. This region of “flash” is given an electron density of zero. The anterior hot spots observed in the Corvus plan are thought to result from the high intensity delivered to this virtual bolus region. Conclusion: This work indicates that respiratory motion induced dose variations are generally less than about 2%, which is not considered clinically significant. However, further investigation is warranted to assure that the dose to the apex of the breast is not excessive when using the virtual bolus method to provide flash for Corvus IMRT plans.
TU‐FF‐A3‐01: Automating Data Processing for Image‐Guided Adaptive Radiotherapy
Authors: Kessler M , Roberson M , Keranen W , McShan D
Published: June 2005

Purpose: To facilitate the adaptive radiotherapy process by automating the flow and processing of data required to accurately transfer, integrate and accumulate information such as tissue boundaries and computed doses between serial 3D and 4D patient imaging studies. Method and Materials: Specific tasks in the data flow for adaptive radiotherapy have been implemented as independent software components that can be instantiated on a single computer or across a network. These components include data access, rigid and deformable image registration, data mapping, and dose accumulation. The data access component retrieves and pushes information to and from a variety of data stores and the other components. The image registration component supports various transformation models (affine, thin‐plate spline and B‐splines) and intensity‐based similarity metrics (sum of squared differences and mutual information) and can handle both global and limited field of view registrations. Required initialization steps are handled using site specific protocols and data‐driven image processing. A generalized transformation representation was developed to ensure interoperability with other processing components. The data mapping component operates on geometry and voxel‐based information such as tissue boundaries, computed doses and image volumes. The dose accumulation component accommodates different re‐sampling and summing schemes. The flow of data from one step is sequenced using simple top‐down data flow or a script‐based sequencer. Results: A flexible system that automates many of the steps involved in adaptive radiotherapy has been implemented. This system has been used to map and integrate dose and geometric information from a variety of image studies (serial and 4D CT, multimodality data) and clinical sites (brain, lung, liver, prostate). Conclusion: Automation of data processing to support the adaptive radiotherapy process is possible for a wide variety of clinical sites and imaging situations. This automation should make more widespread adoption of adaptive radiotherapy possible. Supported by NIH P01‐CA59827
TU‐FF‐A3‐05: A Novel Algorithm for Spatial Noise Compensation in IBM”s 9.2‐MP LCD: A Fuzzy Classification Approach
Authors: Poolla A , Suri J
Published: June 2005

Purpose: This paper presents a new fuzzy‐pixel classification algorithm to compensate spatial noise in LCD displays. Method and Materials: Our noise compensation technique was tested on 30 images acquired using the CCD camera. We measured the MTF and NPS parameters before and after the compensation. The compensation protocol is as follows: displaying a uniform test pattern with known digital value on the LCD display; acquiring the image (640 × 480 pixel size) of the displayed pattern using CCD camera; bi‐cubic down‐sampling the image to 64 × 48 pixel size; use the optimized fuzzy‐pixel classification algorithm to detect the noisy pixels and obtain a mask of the noisy pixels; applying noise compensation on the raw image using the noisy mask; applying Gaussian smoothing on compensated image; display the compensated image on the LCD display for MTF and NPS measurements. Results: The results demonstrate that overall mean of the vertical MTF is higher than that obtained using the conventional method. Also the overall mean of the vertical NPS is lower using the fuzzy compensation technique. The peaks in the horizontal NPS are lower and less wide compared to the non‐compensated NPS. The vertical MTF and NPS have improved using the noise compensation technique, and horizontal NPS is almost comparable in compensated and non‐compensated images. Conclusion: We developed and demonstrated a new fuzzy‐pixel classification algorithm for noise compensation in LCD displays. The compensated algorithm shows an MTF improvement of 5.6% when compared with non‐compensated case. A very similar trend was observed in the horizontal and vertical NPS plots. We can conclude from the above‐presented results that the fuzzy‐pixel classification algorithm is effective in detecting the pixels contributing towards the noise of the image. In future, if images are processed before display to compensate for spatial noise of the LCDs, diagnosis efficiency can be increased.
TU‐FF‐A4‐04: Target Volume Definition by 4D CT Imaging and Temporal Projections
Authors: Hristov D , Gangadharan B
Published: June 2005

Purpose: To develop a fast method for the definition of intra thoracic target volumes by 4D CT imaging, temporal projections as well as interactive visualization and drawing. Furthermore, to evaluate the utility of the method in the context of respiratory correlated and gated treatments. Method and Materials: After retrospectively gated 4D CT scanning, a 4D dataset comprising three‐dimensional datasets corresponding to different phases of the breathing cycle is reconstructed. For the purpose of respiratory correlated or gated radiation treatments, after visual assessment of the magnitude of the lesion motion with respect to the respiratory signal, a subset of the 4D dataset is collapsed/projected in the time dimension with user selectable transfer function. Some sensible choices are maximum intensity or average value projections. Then, for a particular 2D slice, the user defines a target contour on the composite temporal projection image. Upon completion of the drawing, cine loop is played through time for the particular slice. If corrections are necessary, the cine is stopped: the user browses through the various time points of the particular 2D slice and adjusts the contours. Once the adjustments are completed, the target definition process continues with the next slice. Results: The proposed method was implemented in a software prototype and evaluated for several datasets. In comparison to the scenario of drawing target volumes on temporally sequential 3D datasets, the proposed method reduces target definition times by a factor of 5 to 10. Conclusion: A fast and efficient method has been developed for the definition of intra thoracic target volumes to be used in the planning of respiratory correlated or gated radiation treatments. Conflict of Interest : Research supported by Siemens.
TU‐FF‐A1‐03: Comparison of Tumor Control Probability and Lung Complication Probability for Lung Cancer Treatment with and Without Heterogeneity Correction
Authors: Xiong W , Wang L , Li J , Price R , Ma C
Published: June 2005

Purpose: To compare the tumor control probability (TCP) and lung complication probability (LCP) for lung patients planned with and without heterogeneity correction. Method and Materials: Twenty‐one previously treated lung cancer patients were selected for the TCP and LCP comparison. The treatment plans were initially generated with a commercial treatment planning system. The dose calculations were recalculated using Monte Carlo simulations in homogenous and heterogeneous geometry rebuilt from patient CT data and using identical beam parameters. A linear quadratic model was used for the TCP analysis. A modified parallel quantal model was used for the LCP calculation. Dose volume data from the Monte Carlo results were used as input for the TCP and LCP calculations. Results: Although the dose calculated for 50% of the target (D50) in heterogeneous geometry is slightly higher than the dose in homogeneous geometry, TCP with heterogeneity correction is significantly lower than that without heterogeneity correction due to the existence of cold spots. For 8 patients with similar prescription doses, the average TCP falls from 97% in homogeneous geometry to 72% in heterogeneous geometry. The LCP is similar for heterogeneous geometry and homogeneous geometry: the difference is less than 2% although the LCP is slightly higher for heterogeneous geometry because of the slightly higher dose. Conclusion: The outcome for lung treatment may be compromised by inaccurate dose calculation (without the use of heterogeneity correction). Cold spots in the target volume are the major cause for the lower TCP for lung plans recalculated with heterogeneity correction. In some cases, the beam shape and/or field size can be modified to remove such cold spots. Our results suggest that heterogeneity correction is necessary for lung cancer treatment planning to ensure adequate target coverage and dose uniformity.
TU‐FF‐A1‐06: Monte Carlo Based Retrospective Dose Calculations for Outcomes Modeling
Authors: Lindsay P , El Naqa I , Hope A , Bradley J , Vicic M , Deasy J
Published: June 2005

Purpose: To improve the dosimetric accuracy of archived lung treatment plans, we use a novel Monte Carlo recalculation method based on pencil beam optimization methods. The impact of the dose corrections on outcome modeling of pneumonitis was assessed. Method and Materials: For 189 archived non‐small cell lung cancer plans, dose distributions were re‐calculated using the VMC++ Monte Carlo code (I. Kawrakow). Nominal input spectra for 6 or 18 MV photons were used; only radiation transport through the patient was modeled, using each patient's pre‐treatment CT scan. We derived approximate beam weights and wedge effects with a novel method based on optimization of MC‐derived pencil beams: MC and treatment planning results were matched for the water‐based (non‐heterogeneity corrected) results. Heterogeneity‐corrected plans were then produced using Monte Carlo with the derived beam profiles and weights. Results: The method showed good agreement when compared against a small series of treatment plans using a convolution‐superposition dose calculation. For the lung plans, the average absolute differences in metrics of interest (V20, maximum lung dose, and mean GTV dose) between water‐based TPS and water‐based MC data were 0.5%, 0.9 Gy, and 0.8 Gy; for water‐based TPS versus heterogeneity‐corrected MC data the absolute differences were greater: 2.0%, 1.8 Gy, and 2.5 Gy (typically heterogeneity corrected dose distributions produced higher dose values). The correlations between V20 and occurrence of pneumonitis for water‐based TPS, water‐based MC, and heterogeneity corrected MC data were (using Spearman's rank correlation coefficient) 0.13, 0.13, and 0.14 (respectively). For maximum lung dose, the correlations were 0.15, 0.14, and 0.09. Conclusion: The differences in some metrics (e.g., maximum lung dose) between water‐based and heterogeneity corrected data may have a significant impact on modeling treatment outcome. This method could be applied to any multi‐institutional data sets for which RTOG format plan archives are available.
WE‐A‐T‐6B‐01: NCI Talk On Funding
Authors: Deye J
Published: June 2005

The National Institutes of Health is composed of 27 Institutes and Centers, with the National Cancer Institute (NCI) being the oldest and the National Institute of Biomedical Imaging and Bioengineering (NIBIB) the youngest. Medical physicists have a major stake in the pursuits of these institutes since they have a large influence on everything from the research that is funded to the clinical protocols and methods that are employed in both therapy and diagnosis. Yet these institutes are themselves experiencing very significant extrinsic and intrinsic factors that affect the ways that they interact with the medical community. A partial list would include: the NIH budget in the post‐doubling period; the creation of NIH‐wide Roadmap Initiatives and NCI‐wide Enterprise Initiatives; the adaptation of the NIBIB to the other Institutes; budget set‐asides for the war on terrorism; the dawning of translational research methods; the blurring of boundaries between disciplines; and an increasing role for industry, to name a few. The ramifications of these changes will be explored with regard to the institute budgets, priorities and relationships; and the presentation will outline some of the current research agendas and the mechanisms which are used to implement them.
WE‐C‐I‐609‐05: Temporal Radiographic Texture Analysis for the Detection of Periprosthetic Osteolysis
Authors: Wilkie J , Giger M , Chinander M , Engh C , Hopper R , Martell J
Published: June 2005

Purpose: We have been investigating temporal radiographic texture analysis (RTA) as a method to help detect the disease periprosthetic osteolysis associated with total hip arthroplasties. This disease is a common but difficult to detect long‐term complication for total hip replacement patients. It typically goes unnoticed on radiographs until at least seven years after the operation. The goal of our research is to assess the ability of temporal RTA to detect osteolysis before it is visible radiographically. Method and Materials: We obtained digitized pelvis radiographs from 84 total hip replacement cases from the Anderson Orthopaedic Research Institute. Each case included a baseline image taken shortly after surgery and follow‐up images taken at various time intervals. The cases were assessed for osteolysis by an orthopaedic surgeon and regions of interest (ROIs) were selected within the osteolytic region (or a comparable region for normal cases) on the final image of each case. These ROIs were then visually matched on all previous images. Fourier‐based, fractal‐based and correlation‐based features were calculated for each ROI. To measure temporal trends in feature values, we calculated the slope of the least squares fitted line for each case using data through five year and nine year time ranges, respectively. Temporal feature performance was examined using Receiver Operating Characteristic (ROC) analysis. Results: Forty‐four cases were determined to have osteolysis while forty were normal. Az values from ROC curves ranged from 0.6 to 0.75 for the task of distinguishing between osteolysis and normal cases for both time ranges. Conclusion: Temporal RTA appears to have the potential to help detect periprosthetic osteolysis before visual radiographic appearance of the disease. More development of temporal RTA and analysis with a larger patient database is therefore warranted. Conflict of Interest: M.L.G. is a shareholder in R2 Technology, Inc. (Sunnyvale, CA).
WE‐C‐J‐6C‐01: Residual Motion of Lung Tumors in Gated Radiotherapy with External Respiratory Surrogates
Authors: Berbeco R , Nishioka S , Shirato H , Chen G , Jiang S
Published: June 2005

Purpose: To mitigate the motion‐induced irradiation of healthy lung tissue, clinics have begun using external markers to gate the therapy beam. This technique assumes that the correlation between the external signal and the internal tumor position remains constant inter‐fractionally and intra‐fractionally. A study has been performed to assess the validity of this correlation assumption within a gating window. Method and Materials: Eight lung patients with implanted fiducials were studied. Synchronized internal and external data was taken during the entire course of treatment. Stereoscopic imaging was used to find the internal markers in four dimensions. The data was used retrospectively to assess conventional external surrogate respiratory‐gated treatment. Both amplitude and phase‐based gating methods were investigated. For each method, three gating windows were investigated, each giving 40%, 30% and 20% duty cycle, respectively. The residual motion of the internal marker within these six gating windows was calculated. The beam‐to‐beam variation and day‐to‐day variation in the residual motion were calculated for both gating modalities. Results: We found that the residual motion (95th percentile) was between 0.9–6.2 mm for a 40% duty cycle window. There is no clear preference for either gating modality. Large fluctuations (>300%) were seen in the residual motion between some beams. Overall, the mean beam‐to‐ beam variation was 37% and 42% for amplitude and phase‐based gating, respectively, compared to the previous beam. The day‐to‐day variation was 29% and 34% for amplitude and phase‐based gating, respectively, compared to the previous day. Conclusion: Although gating significantly reduced tumor motion, the residual motion behaved unpredictably. Treatment margins that account for motion should be individualized and daily imaging should be performed to ensure that the residual motion is not exceeding the planned motion on a given day. Conflict of Interest: This work was sponsored, in part, by a grant from Varian Medical Systems, Inc.
WE‐C‐J‐6C‐02: Investigation of Variables Affecting Residual Motion for Respiratory Gated Radiotherapy
Authors: George R , Ramakrishnan V , Siebers JV , Chung TD , Keall PJ
Published: June 2005

Purpose: Breathing training may help improve respiration motion regularity. This study was conducted to statistically and clinically determine if residual motion was affected by some characteristics of patients. The aims of this study were: 1) To identify significant characteristics affecting respiratory motion for respiratory‐gated radiotherapy, 2) To investigate time trends of respiration motion over a period of days (inter‐session) and 3) To investigate time trends of respiration motion within the same day (intra‐session). Method and Materials: 24‐lung cancer patients were enrolled in an IRB approved protocol; acquiring 331, 4‐minute, respiration motion traces with free breathing, audio‐instructions and audio‐visual biofeedback for approximately 5‐sessions each. The residual motion was quantified by the standard deviation of the displacement within the gating window. The generalized linear model was used to obtain coefficients for each variable within the model and evaluate the clinical and statistical significance. The statistical significance was determined by a p‐value <0.05 while effect sizes of ⩾0.05cm were considered clinically significant. Effect size is calculated as the product of estimated coefficients with the range of that variable. This data analysis was applied to: time independent analysis, inter‐session analysis and intra‐session analysis. Results: Disease type and dose‐per‐fraction were significant for both inhale and exhale‐based gating. In addition, for inhale‐based gating visual training displacement, breathing type and Karnosky‐performance status values were significant for inhale‐based gating. The inter‐session and intra‐session analysis did not show significant time trends for any of the variables considered. Conclusion: Certain variables were found to be significant for time independent analysis. The results of the inter‐session analysis indicated that the margin component to account for residual motion during gated radiotherapy remained constant throughout the treatment. Also, the patients breathing did not alter over a period of time within a session and they could maintain the reproducibility during a treatment fraction.
WE‐C‐T‐617‐02: Direct Calibration of Ionization Chambers in Linac Photon Beams
Authors: McEwen M , Ross C
Published: June 2005

Purpose: Currently, the starting point for dosimetry in the radiotherapy clinic is an ion chamber calibrated at the standards laboratory in a beam. Conversion factors obtained from a protocol such as TG‐51 are then required to derive the dose in a linac beam. This paper details the measurement of these kQ factors in photon beams from a clinical linac. Method and Materials: The NRC primary standard water calorimeter was used to calibrate a set of NE2571 Farmer‐type ion chambers in 6, 10 & 25 MV photon beams from an Elekta Precise linac installed at NRC. A number of influence quantities — water purity, temperature sensors, temperature measurement system — were investigated in detail. In addition, significant effort was put into monitoring the stability of the linac to ensure that output variations did not significantly affect the measurements. Results: The kQ factors obtained were in good agreement with previous measurements using the NRC Vickers research linac reported by Seuntjens et al in 2000. This indicates no dependence on accelerator type and validates the use of %dd10x as a beam quality specifier for megavoltage photon beams. The calculated factors given in TG‐51 also agree well with these measured kQ factors. The standard uncertainty in the calibration of an ion chamber is estimated to be 0.45%, a significant improvement over using the calculated values. Conclusion: A clinical linac can be successfully used for primary standards dosimetry. Absorbed dose calibration factors for a set of NE2571 chambers have been obtained for 6, 10 & 25 MV photon beams. Factors for other chambers can be determined by direct comparison with these reference chambers in a water phantom.
WE‐D‐I‐609‐01: Design and Calibration of a Robotic Needle Positioning System for Small Animal Imaging Applications
Authors: Waspe A , Cakiroglu HJ , Lacefield J , Fenster A
Published: June 2005

Purpose: A needle‐positioning robot is being developed for three‐dimensional micro‐ultrasound guided interventions. This device will be used to perform minimally invasive injections and biopsies into small animals with high accuracy and precision. Method and Materials: The robot has three degrees of freedom for positioning the needle in three dimensions. Two rotational joints are used to control needle orientation (roll and pitch). Another joint linearly translates the needle to perform insertion. The design features a four‐bar linkage mechanism that translates the roll axis of rotation from an actuator to a remote axis that intersects the pitch and needle axes. The three intersecting axes create a remote center of motion (RCM) that acts as a fulcrum for the three‐dimensional orientation of the needle. The RCM corresponds to the insertion point of the needle into the animal. In order for the robot to achieve high accuracy, it must be calibrated to ensure that the three axes intersect at a single point, and the needle tip must be positioned at the RCM. The calibration was performed using a macro lens CCD camera to find the center of rotation about the pitch and roll axes separately. The position of the needle was adjusted until it was aligned with the RCM. Results: The range of motion is ±30°, ±45°, and 20 mm for the pitch, roll, and needle axes, respectively. Initial calibration results indicate that the distance from the needle to the pitch and roll axes are 24 ± 30 μm (mean ± standard deviation of five trials) and 18 ± 15 μm, respectively. The pitch and roll axes are separated by 11 ± 3 μm. Conclusion: The expected maximum needle positioning error computed from the calibration results is 32 μm when the needle tip is moved to the boundary of the workspace.
WE‐D‐I‐609‐04: Comparison Between PET And Bioluminescence Imaging For Quantitative Assessment Of Tumor Burden
Authors: Maxim P , Thorndyke B , Boyer A , Contag C , Gambhir S , Xing L
Published: June 2005

Purpose: A number of imaging modalities have been described for the study of rodent models of human biology and disease. Several of these modalities are based on traditional clinical imaging approaches, such as MRI, CT, PET/SPECT, and can often serve as methods for validating some of the newer modalities such as bioluminescence imaging (BLI), which has shown to be a highly sensitive tool for visualizing tumors, neoplastic development, metastatic spread and response to therapy. In this report, the ability of BLI to noninvasively quantitate the growth of orthotopic rat neuroblastomas was investigated. Method and Materials: Male nude (nu/nu) mice 7 – 8 weeks of age were used in this study (N=6). Orthotopic rat neuroblastomas derived from N2A neuroblastoma cells genetically engineered to stably express firefly luciferase (N2ALuc) were implanted subcutaneously by injecting 100 μl NaCl (0.9%) containing 3×106 viable cells in the left hind flank of the mice. Tumor burden was monitored over time by quantitation of photon emission and viable tumor volume using a cryogenically cooled CCD camera and positron emission tomography (PET), respectively. Animals were injected 200uCi of one hour before PET imaging. The viable tumor boundary was delineated on PET images using an in‐house software at each time point and the tumor volume was then calculated. Results: A comparison between the BLI findings and the PET‐defined tumor volume revealed a good correlation (R2=0.8) between detected photons and viable tumor volume. Conclusion: Before small animal imaging as a means to assess tumor growth and response to therapy in orthotopic tumor models, animal survival was used as the primary therapeutic end point. The ability of imaging to follow temporal changes in tumor volume and response to treatment in an individual animal provides an accurate and rapid method for assessment of experimental therapeutics.
WE‐D‐I‐609‐05: Optical Imaging of Tumor Microvasculature in 3D
Authors: Oldham M , Oliver T , Dewhirst M
Published: June 2005

Purpose: Great interest exists at present in determining methods to image and understand tumor micro‐vasculature structure and how it can be perturbed by a variety of agents, including radiation and anti‐angiogenic drug therapies. Present methods including micro MRI and micro CT can yield high spatial resolution, but limited contrast in micro‐vasculature makes determining subtle 3D structure problematic. We have developed a non‐destructive optical method for imaging tumor micro‐vasculature which can yield significantly greater image resolution and micro‐vasculature contrast than achievable with existing technique. Method and Materials: Murine tumor micro‐vasculature staining was achieved by in‐vivo tail vein injection of dark‐dye solution. After several minutes the HTC116 (human colon cancer) tumor was removed, washed in saline solution and set in 1% agarose gel. Tumor tissue was then taken through a clearing process prior to optical imaging. Light from a diffuse white light source was caused to traverse through the tumor tissue and a projection image was acquired using focussing optics and a CCD camera. Quantitative images of microvasculature density were reconstructed from projections acquired at multiple angles. Results: Good optical transmission was achieved through significant tumor samples (e.g. 1×1×1cm). Excellent contrast was observed between microvasculature and surrounding tumor tissue. Very high resolution (5 micron) isotropic 3D reconstructions were achieved through large whole mount murine tumor sample. The method can provide quantitative maps of micro‐vasculature density throughout the tumor sample. Conclusion: We present a novel technique for imaging 3D micro‐vasculature in tumor and normal tissue with unprecedented image resolution and contrast. Quantitative analysis of microvascular density in whole mount (i.e. unsliced or undisturbed) large tumor specimens is possible. The technique has potential as a valuable new tool for the analysis of tumor microvasculature and the effects of vascular perturbing agents (e.g. anti‐angiogenic drugs and radiation).
WE‐D‐T‐6C‐04: MRI and MR Spectroscopic Imaging of Cancer Therapy Assessment
Authors: Vigneron D , Kurhanewicz J , Nelson S
Published: June 2005

Purpose: To describe the use of Magnetic Resonance Spectroscopic Imaging in the assessment of treatment response for prostate cancer and brain tumor patients. Method and Materials: Specialized 3D MR spectroscopic imaging acquisition techniques were developed for both 1.5T and 3 T MR scanners. Novel analysis and display software was developed for the processing and interpreting the MR metabolic imaging data. These techniques were applied in brain tumor and prostate cancer cohorts prior to and following radiation and/or hormonal therapy. Changes in metabolite levels were calculated and correlated with treatment response measures. Results: The MR spectroscopic imaging techniques demonstrated the ability to reliably detect metabolite levels at both 1.5T and 3 T. Significant metabolite ratios differences were observed between normal and cancerous tissues with greater spatial resolution at 3T. Following both successful hormonal therapy and radiation treatment, significant reductions in choline levels were observed in prostate cancer patients. Similarly decreases in choline correlated with therapeutic response in brain tumor patients and increased choline significantly correlated with recurrent/residual tumor. Conclusion: These studies demonstrate the ability of MR spectroscopic imaging to detect metabolic differences between cancer and normal tissues in brain tumor and prostate cancer patients and the ability to detect metabolic changes following therapy.
WE‐D‐T‐617‐02: The Dose Response of Radiochromic Gel Dosimeters: Dose Fractionation Effects
Authors: Babic S , Jordan K , Battista J
Published: June 2005

Purpose: To investigate the magnitude of dose fractionation effects on the dose response of radiochromic Ferrous — Xylenol orange — Gelatin (FXG) and gelatin‐free FX dosimeters. Method and Materials: The FXG gels contained distilled water, 50mM sulfuric acid, 0.3mM ferrous‐ammonium‐sulfate, 0.05mM xylenol orange (XO) from suppliers Sigma(X0127) and Aldrich(22785‐4), and 4% by mass of gelatin. On preparation, the liquid gel was poured into 1cm polymethymethacrylate cuvettes, sealed with Parafilm and refrigerated to 4°C. Samples were irradiated using a unit to 0–5Gy. Thirty minutes after irradiation, optical transmissions through the samples were measured (referenced to 1cm water‐filled cuvettes) at 589nm using a spectrophotometer (Hitachi‐Perkin‐Elmer‐139). Samples were re‐irradiated to the same doses, followed by optical transmission measurements. The procedure was repeated with gelatin‐free FX aqueous solutions containing XO supplied by Sigma, Sigma‐Aldrich(398187‐5G) and Aldrich, respectively. Optical transmission measurements were made through 10cm pathlength cuvettes to detect smaller differences. Results: For the FXG gel made with Aldrich XO, a linear dose response was observed in the first fraction irradiation but only above a threshold dose of 0.5Gy. Use of reagent grade Sigma XO lowered the dose sensitivity and threshold dose value to 0.2Gy. For both FXG gels, the threshold dose was removed by pre‐irradiation with the first radiation fraction or by storing the gels for two weeks in the dark at 4°C. FX solutions exhibited a similar behaviour as FXG gels thus suggesting that gelatin per se is not responsible for the threshold dose effect. Conclusion: FXG gels exhibit dose fractionation effects which can potentially lead to inaccurate dosimetry for segmented radiotherapy. Manufacturing FXG dosimeters with reagent grade XO lowers the magnitude of the threshold dose. It appears that accelerated oxidation by a uniform pre‐irradiation or by auto‐oxidation (through storage of gels for a pre‐determined time) is needed to eliminate the threshold dose effect.
WE‐D‐T‐617‐05: Evaluation of the New Exradin A16 Micro‐Chamber for the Purpose of Water Measurements of Small SRS Collimator by Comparison to Film Dosimetry and Monte‐Carlo Calculations
Authors: Schifter D , McColl W , Khadija M , Lee C , Feldmeier J , Parsai E
Published: June 2005

Purpose: Direct water measurements of small fields in general and small SRS collimators in specific have been a long known problem. The typical ion chambers, which are used with 3D water phantoms have a volume of about 0.125cc, which is not suitable for measuring small fields. The recently introduce Exradin A16 chamber, with a volume of 0.007cc was designed to overcome the problem by allowing accurate measurements of small fields in water. The purpose of this work is to validate the suitability of this chamber for small fields water measurements. Method and Materials: In order to evaluate the suitability of the A16, depth dose curves and a set of profiles were taken with this ionization chamber using SRS collimators ranging from 1cm to 4cm in diameter, in steps of 0.25cm increment. The scans were then compared with film dosimetry of the same collimators and Monte‐Carlo simulations. The films used were the Kodak XDR extended range films in Perspex phantom, which were scanned and analyzed using the Vidar 16 scanner and the RIT software. The Monte‐Carlo simulation was done using the BEAMnrc code. For the larger collimators (2.5cm and up) a set of water measurement were performed also using the standard Wellhoffer chambers (0.125cc) Results: The result showed excellent matching between all evaluations media (water measurements with the A16 and the standard chamber, film dosimetry and Monte‐Carlo simulation). The only discrepancy was with deeper depths in the films, which was due to the phantom used. Conclusion: The A16 is suitable and should be used for small field water measurements.
MO‐A‐I‐609‐01: The Role of the Physicist in the Planning and Design of Digital Image Management Systems (PACS)
Authors: Peck D , Flynn M
Published: June 2005

A Digital Image Management System encompasses all information related to Diagnostic or Therapeutic images used in a clinical setting. This includes the order entry process, movement of the order information to a Modality, image acquisition and processing, movement of the image data to an archive, movement of the images and order data to Radiologist and Clinician viewing stations, and reporting the interpretation of the images. Note that a Digital Image Management System includes more than just image storage and viewing inferred by the title Picture Archive and Communication System (PACS). Therefore when a Physicist is asked to consult in planning a PACS they should be thinking about the workflow and data required to produce the final product, i.e. the Radiologist Report with associated images, and so they are actually consulting on the implementation of a Digital Image Management System. The areas that a Physicist should provide information to a site when planning such systems include:

1. Digital image acquisition/modality options for each study,

2. Modality integration and testing,

3. Bandwidth and storage requirements,

4. Radiologist and clinician softcopy viewing requirements,

5. Digital imaging Quality Assessment (QA) protocols

The needs in each of these areas relative to planning a Digital Image Management System will be reviewed with suggestions on further educational resources.

Educational Objectives:

1. Understand the workflow and Modality requirements in a Digital Image Management System.

2. Understand softcopy reading requirements compared to film based and considering the increasing image size and volume.

3. Consider the QA needs and methodologies with digital imaging systems.
MO‐A‐T‐6C‐01: Managing Respiratory Motion in Radiation Oncology
Authors: Keall P , Mageras G
Published: June 2005

Intrafraction motion is an issue that is becoming increasingly important in the era of image‐guided radiotherapy. Intrafraction motion can be caused by the respiratory, skeletal muscular, cardiac and gastrointestinal systems. Of these three systems, much research and development to date has been directed towards accounting for respiratory motion. Respiratory motion causes deleterious effects during the imaging, planning and delivery of radiation therapy. The management of respiratory motion in radiation oncology is the subject of this continuing education class which aims to advise medical physicists involved in the external beam radiation therapy of patients with thoracic and abdominal tumors that move due to respiratory motion. This session will describe the magnitude of respiratory motion, discuss radiotherapy‐specific problems caused by respiratory motion, explain techniques that explicitly manage respiratory motion during radiotherapy and give recommendations in the application of these techniques for patient care, including quality assurance guidelines for these devices. The techniques to be described include respiratory gating, breath‐hold techniques, forced shallow breathing and respiration‐synchronized radiotherapy. This session intends to reflect the current state of the scientific understanding and technical methodology in imaging, treatment planning and radiation delivery for radiation oncology patients with tumors affected by respiratory motion. Issues requiring further study will also be raised. The educational objectives of this course include:

1. Appreciate the effects of respiratory motion during the imaging, planning and delivery of radiotherapy.

2. Learn the various techniques that have been clinically applied to manage respiratory motion.

3. Understand the general and specific quality assurance requirements for different respiratory management techniques.

4. Describe the clinical process for managing patients with tumors affected by respiratory motion.
MO‐B‐I‐611‐01: The Role of the Medical Physicist in Preparing for Radiation Disasters
Authors: Hartman M
Published: June 2005

Since 9/11, hospitals have seen the need to examine their emergency management plans to ensure that radiation disasters are adequately addressed. Hospitals need to be ready to deal with radiation casualties in addition to the possibility of many self‐presenters who want to know whether they are contaminated. Hospitals need to be prepared to handle this situation in the first day or two after a disaster until state and federal agencies can mobilize. Medical physicists will play a vital role as responders and sources of accurate information for hospital staff, patients and the public. Medical physicists will be asked to assist in the decision‐making process if an event does occur. This course provides information on the handling of patients who are injured and may be irradiated and/or contaminated with radioactive material. The Center for Disease Control website has guidance on ways to handle self‐presenters who may exceed the number of radiation casualties. The psychosocial considerations after a disaster will be discussed and its effects on staff, patients and the public. The course will also address issues to be anticipated for facility recovery after a disaster.

Educational Objectives:

1. To provide resources that are available for developing emergency plans that address radiation disasters and their unique policy considerations.

2. To show how to utilize radiation protection procedures and practices and know how to prepare the facility for radiological emergency medical response.

3. To provide a framework for handling self‐presenters who will seek help from their local hospital to determine whether they are contaminated.

4. To understand the psychosocial considerations in responding to a radiological emergency.

5. To know what activities can occur during facility's recovery from a radiation disaster.
WE‐C‐I‐611‐01: Basic System Design and Application
Authors: Rudin S
Published: June 2005

The use of real‐time or rapid sequence x‐ray imaging has been increasing. Not only are the GI and cardiology applications to diagnostic procedures of continuing interest, but new image guided interventional procedures are being developed which rely on the combination of high spatial and temporal resolution x‐ray imaging. In particular, rotational angiographic sequences combined with cone‐beam computed tomography have enabled advances in minimally invasive endovascular interventional procedures to often replace invasive surgical procedures. In this symposium, after a review of some of the clinical applications of dynamic x‐ray imaging including fluoroscopy and angiography, we will discuss some of the unique problems associated with image quality evaluation for such total x‐ray imaging systems, as well as review some of the new developments in detector design with a comparison of flat panel and image intensifier‐based systems. Also we will discuss developments in cone‐beam computed tomography with specific application to angiography and ultimately to the potential for changing the treatment paradigm for vascular disease through the combination of computerized blood flow analysis and angiographic image guided interventions.

Educational Objectives:

1. To appreciate the widening clinical application of dynamic x‐ray imaging to diagnostic and interventions.

2. To indicate the quality evaluation issues in total x‐ray imaging systems as well as the new developments of digital detectors and cone‐beam computed tomography.

(Partial support: NIH Grants R01EB002873 and R01NS43924, Toshiba Medical Systems Corp., UB Foundation, UB‐STOR, Guidant Corp.).
A robust spatial filtering technique for multisource localization and geoacoustic inversion
Authors: Stotts S. A.
Published: June 2005

Geoacoustic inversion and source localization using beamformed data from a ship of opportunity has been demonstrated with a bottom-mounted array. An alternative approach, which lies within a class referred to as spatial filtering, transforms element level data into beam data, applies a bearing filter, and transforms back to element level data prior to performing inversions. Automation of this filtering approach is facilitated for broadband applications by restricting the inverse transform to the degrees of freedom of the array, i.e., the effective number of elements, for frequencies near or below the design frequency. A procedure is described for nonuniformly spaced elements that guarantees filter stability well above the design frequency. Monitoring energy conservation with respect to filter output confirms filter stability. Filter performance with both uniformly spaced and nonuniformly spaced array elements is discussed. Vertical (range and depth) and horizontal (range and bearing) ambiguity surfaces are constructed to examine filter performance. Examples that demonstrate this filtering technique with both synthetic data and real data are presented along with comparisons to inversion results using beamformed data. Examinations of cost functions calculated within a simulated annealing algorithm reveal the efficacy of the approach.