bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐I‐152: CCD Vs CdTe X‐Ray Methods to Estimate Fat Content in Breast Biopsies
Authors: Maraghechi B , Tang R , Spooner S , Cerilli E , LeClair R
Published: November 2011

Purpose: This work focuses on analyzing CCD vs CdTe x‐ray methods to estimate fat in breast biopsies. Methods: A digital specimen radiography system consisting of a 2″× 2″ phosphor coupled to a 1″ × 1″ CCD was used. We obtained ADU signals as a function of the energy incident signals for different plastic biopsies each 5 mm in diameter and of varying thicknesses. Simulations were performed for 231 combinations of polycarbonate (lexan), lucite and polyethylene (polyet). These plastics mimic respectively fibrous tissue, cancer, and fat. The thickness for heterogeneous biopsies was restricted to 5mm. The average ADU and sigma calculated for 21 subgroups of % polyet reveal significant overlaps between groups. The ADUmean values provide a way to estimate the % polyet experimentally. 26 kV (0.3 mA) beams and exposure times of 3.8 seconds gave X=7.5E‐4 C/kg. Region of interests (ROIs) consisting of 15960 pixels were generated and corresponded to a 1.36 mm diameter lesion in the object plane. Using a single pixel CdTe detector, the thickness of polyet can be estimated by assuming the biopsies are composed of two materials, namely polyet and a 50:50 mixture of lexan and lucite. 15 kV (0.15 mA) beams and 1 minute exposures yielded X=1.9E‐4 C/kg per measurement. The diameter of the beam at the sample is 1.36 mm. The weighted means of the estimated thicknesses were evaluated using data from 8 keV to 10.6 keV in steps of 0.2 keV. Results: The root mean square between estimated and actual % polyet for the CCD was 13.8 and 9.2 for the CdTe detector. Conclusions: The preliminary analysis shows a minor advantage using the CdTe based system. Extending the study to a pixilated CdTe (or CZT) detector could allow larger ROIs to be analyzed. We anticipate better results with breast tissue since contrast is higher.
SU‐E‐I‐154: Cardiac SPECT/CT: Comparing Slow‐Rotation and Fast‐Rotation CT for Attenuation Correction in Cardiac Imaging
Authors: Sabondjian E , Patrick J , Stodilka R , King M , Wisenberg G , Prato F
Published: November 2011

Purpose: The hybridisation of SPECT with X‐ray CT is expanding the utility of SPECT. In addition to image fusion, CT enables improved attenuation maps (AM) for SPECT. Two CT designs are used in SPECT/CT: slow‐ rotation and fast‐rotation. The “slow‐rotation” CT completes a full‐rotation in 15 seconds to provide an AM that is acquired over several frames of the respiratory cycle; hence includes motion related physiologic artifacts. The “fast‐rotation” CT completes a full‐rotation in 0.6 seconds to provide an AM that is comparatively free of breathing artifacts. Neither is similar to SPECT, which is acquired in a step‐and‐shoot manner, where each projection is acquired over all frames of the respiratory cycle. Methods: We compared cardiac SPECT/CT acquisitions with the General Electric Infinia/Hawkeye‐4 which incorporates a slow‐rotating CT and the Siemens Symbia/T6 which incorporates a fast‐rotating CT. Three canine experiments were performed comparing SPECT reconstructions that were corrected for attenuation with no respiratory motion between SPECT and CT (gold standard). These were compared with SPECT reconstructions that incorporated respiratory motion and corrected for attenuation using either the slow or fast‐CT AMs. The SPECT reconstructions were compared using a Root‐Mean‐Squared (RMS) metric and scatter plots, calculated pixel‐by‐ pixel in a region‐of‐interest through a central slice of the heart. Results: The canine experiments showed improvements in both the RMS error and correlation coefficients for all canines when using the fast‐CT AM. The average RMS error improved from 28% to 17%, while the average correlation coefficient improved from 0.85 to 0.96. Canine studies confirmed respiratory motion has the potential to corrupt CT data and can effect attenuation correction in SPECT. Conclusions: Artifacts in the attenuation map due to physiologic motion propagate into the SPECT image reconstructions causing erroneous results. Therefore, for SPECT to become more quantitative an attenuation map with fewer artifacts is desirable.
SU‐E‐I‐156: CT Dose in Pediatric PET/CT Examinations
Authors: Tonkopi E , Ross A , MacDonald A
Published: November 2011

Purpose: To optimize CT protocols for pediatric whole‐body PET/CT examination and to evaluate radiation dose. Methods: We developed pediatric whole‐body CT acquisition protocols used for attenuation correction and localization of the PET data. Patients were categorized in 6 groups according to their weight and age, similar to the Broselow—Luten color‐coded scale. X‐ray tube current modulation was employed in all protocols with maximum mAs ranging from 25 to 55. The acquisition parameters were as follows: 100 kVp; 16×1.25 mm X‐ray beam collimation; 27.1 Noise Index; 1.35:1 pitch; 0.5 s rotation time; and 3.75 mm reconstructed slice thickness. For the senior group of 12 – 17 years of age (50 – 70 kg) we used 120 kVp and 50 max mAs. All data were acquired on a GE Discovery STE 16 PET/CT scanner, and patients were injected with 5.55 MBq (0.15 mCi) of 18F‐FDG per kg of weight. We surveyed pediatric studies performed in our institution during the period of 2009 – 2010. There were 27 patients from 18 months to 17 years of age, and 12 of them had had multiple exams (up to 6). Overall, 54 pediatric studies were performed over the two‐year period. Effective CT dose was calculated using the dose length product (DLP) values from the patientsˈ dose reports and conversion factors (normalized effective dose per DLP), dependant on the patient age. Results: Effective CT doses were in the range from 0.91 mSv to 3.6 mSv for all patient categories. Comparison with published data based on 11 patient weight categories demonstrated lower dose in each patient group achieved with the acquisition protocols developed in our institution. Conclusions: Pediatric CT protocols for 6 patient weight/age‐based categories were developed for the whole‐body PET/CT. Patientsˈ dose survey demonstrated lower effective CT dose than reported in the literature for each weight category.
SU‐E‐I‐168: An Image Quality Assurance Phantom for Positron Emission Mammography (PEM)
Authors: Luo W , Disher N , Lu X
Published: November 2011

Purpose: Due to the compact geometry of Positron Emission Mammography (PEM), WB‐PET phantoms are not suitable for PEM scanners. This study aims to develop an image quality phantom that can be used for PEM image quality assessment. Methods: A phantom with dimensions of 240 × 160 × 60 mm was designed to assess image quality (uniformity, contrast, linearity, resolution). It has three main components: 1), a cylinder quality phantom with 110 mm ID that consists of 5 suspended hot sphere lesion inserts of varying ID (4,6,8,12,16 mm) filled with 8:1 lesion‐to‐background activity ratio and a 16 mm cold lesion. The center background region (ID = 30 mm, thickness = 28 mm) is selected for uniformity calculation. The lesion‐to‐ background ratio (LTB) is defined by the maximum of the region of interest (ROI) for the inserts divided by the mean of the background ROI. Image contrast is defined by (LTB‐1)/(Actual Activity Ratio‐1). 2), a 120 mm line source with 3.0 mm ID perpendicular to the detector motion for linearity evaluation. 3), fillable bar phantoms (ID =1.1 mm) in X and Y direction with the bar center to center separation increased from 3.0 to 7.5 mm. An optional point source can be added for spatial resolution. A 10 minute, full field of view scan was performed. Results: Quantitative analysis shows in‐ plane spatial resolution of 2.4 mm and uniformity of 7.0%. The image contrasts for the 5 spheres are 74%, 63%, 41%, 25% and 7%. The visual inspection shows the PEM scan detects all sphere inserts. The bar phantom and line source do not show linear distortion. The 3 mm bar phantom can be distinguished in high resolution mode (pixels size 0.4 mm). Conclusions This phantom demonstrates it can be useful for visual and quantitative evaluation of PEM imaging.

Research sponsored by Naviscan, Inc.
SU‐E‐I‐169: Optimizing Image Quality and Accurate SUVs in Four Different PET Scanners within the Same Institution
Authors: Campbell J , Roumayah Y , Johnson M , Wong C , Beaumont William
Published: November 2011

Purpose: PET performance measurements were done on 4 PET scanners from 3 manufacturers; GE, Siemens, Philips. This presentation compares the test results and evaluates their impact on clinical studies. Accuracy of SUV determination is compared between the different manufacturers. Methods: Testing of PET performance included quantitative analysis of spatial resolution, count rate, sensitivity, uniformity, and accuracy of corrections. Test results were tabulated for comparison. Additional testing included imaging using the Jaszczak Deluxe PET phantom (Data Spectrum, NC). Testing of SUV accuracy was performed using F‐18 activity (range of SUVs, 2 –20) within cylinders and background to simulate typical tumor/normal tissue ratios. Images were acquired using parameters optimized for clinically interpretable image quality. The maximum SUV for each cylinder was recorded using a consistent region of interest. Curves were developed of SUV versus volume to evaluate partial volume effect. The SUV of the largest diameter cylinder (2.5 mm) was used to develop a curve of expected versus measured SUV values. Results: Significant variability is demonstrated between each PET scanner. The image quality and SUV accuracy varied depending on acquisition and reconstruction protocols. The GE 2D, 3D and Philips Non‐ToF were the most accurate in predicting expected SUV for all activity concentrations. The Siemens HD was 9–17% higher than expected, increasing as SUV value increased. The Philips ToF was 5–19% lower than expected, decreasing as SUV value increased (attached curve of measured versus expected values). Conclusions: While image quality is often improved with PET scanner options, the quantitative component of interpretation, SUV, varies with reconstruction algorithm. This can be of concern when patients are scanned on different PET scanners during the course of their disease. Optimizing image quality and developing an SUV calibration curve has allowed us to maintain confidence in the use of the SUV from different PET systems.
SU‐E‐I‐171: On the Potential for the Production of 99Mo and 99mTc from Light‐ Ion Reactions Based Zirconium + Lithium
Authors: Guo F. Q. , Zhai Y , Chen Z , Nath R
Published: November 2011

Purpose: To explore alternative methods based upon light‐ion beams to generate 99Mo and/or 99mTc, used in nuclear medicine imaging, due to a worldwide supply shortage of these materials from nuclear reactors. Method and Materials:Fusion‐evaporation statistical Monte Carlo code PACE4 was used to evaluate the excitation functions, i.e. cross‐sections vs. energies, of nuclear reactions that may have a potential for the production of 99Mo or 99mTc. The calculated results were compared with the experimental data to validate the code and to estimate the scale‐up or ‐down factors. Results: For reactions involving evaporating neutrons, the calculation has the right trend but overestimates cross sections by about 7 times. The maximum calculated cross sections for 96Zr(7Li, 4n)99mTc, 96Zr(6Li, 3n)99mTc, and 94Zr(7Li, 2n)99mTc are 1130 mb, 801 mb, and 146 mb, respectively. The actual cross sections may be lower, but even the scaled down values of 161 mb (1130/7) and 114 mb (801/7) are still quite high and could be used to generate significant amount of 99mTc . For those reactions with exiting charged particles besides neutrons, the code underestimates the cross sections by about 10 times. The maximum calculated cross sections for 96Zr(7Li, d2n)99Mo, 96Zr(6Li, dn)99Mo, and 94Zr(7Li, d)99Mo are 42.6 mb, 21.6 mb, and 8.51 mb. The actual cross sections could be higher. If scaled cross sections of 426 mb and 216 mb are realistic, it will be much easier to get 99Mo from 96Zr(7Li, d2n)99Mo and 96Zr(6Li, dn)99Mo, not to mention that the specific activity of 99Mo could be much higher under the optimized reaction conditions. Conclusions: Specific activity and cross sections of nuclear reactions based on zirconium target using a light‐ion beam of helium or lithium may be much higher than those based on molybdenum target. These reactions should be investigated experimentally.
SU‐E‐I‐179: Evaluation of a SPECT Camera with CZT Detectors and Multipinhole Collimator for Nuclear Cardiology Imaging
Authors: Luo J , Deitz N , Pantelic D , Cowling D , Jang S
Published: November 2011

Purpose: This study was to evaluate performance characteristics and to validate cardiac imaging of patients on a newly installed SPECT camera using CZT (Cadmium Zinc Telluride) solid state detector technology, and to compare the CZT camera with a NaI crystal based camera using both phantom data and patient studies. Methods: An Anthropomorphic Torso Phantom (Data Spectrum, Inc.) with a Cardiac Insert with Solid Defect in myocardium region was prepared for SPECT imaging using a CZT camera with multipinhole collimator (GE Discovery 530C). Tl‐201 and Tc‐99m were used individually to test energy response and together to check crosstalk in SPECT imaging. Phantom preparation included: 650 uCi Tc‐ 99m and 65 uCi Tl‐201 were injected to the heart insert to simulate myocardium ratio of 1.82 for each isotope respectively; 4 mCi Tc‐99m and 0.4 Tl‐201 were added to the phantom as background activity; two 500 cc saline bags were installed on the phantom to simulate breast attenuation. Same phantom was scanned on a regular SPECT using NaI crystal for comparison. Then twenty two patients were imaged on the CZT and on the NaI cameras respectively for clinical validation. Standard image acquisition and processing protocols were used for both phantom and patient studies. Results: Visual inspection on phantom images demonstrated that the CZT camera could provide same or better quality of images with lower dose and less time (half dose half time). Myocardium defect was clearly identified from Tc‐99m imaging and from Tl‐201 scan as well. There was no significant crosstalk when imaging Tc‐99m with presence of Tl‐201. Patient scans were consistent on both cameras. There were not different diagnoses using images from the two scanners. Conclusions: SPECT camera with CZT detectors and multipinhole collimator demonstrated excellent performance characteristic especially on energy resolution and counting statistics. Those features allow lower dose and shorter acquisition time in clinical studies.
SU‐E‐I‐180: Simulation of Arterial First Pass and Recirculation Input Functions Using a Series of Related Gamma Variate Function
Authors: Yee S , Ogden K
Published: November 2011

Purpose: Any tracer kinetic analysis requires an arterial input function (AIF) when the analysis is performed for quantitative measurements of concerned variables such as blood flow (BF) or blood volume (BV) as in the case of dynamic CT, PET or MR perfusion studies. The AIF is often measured at the middle cerebral artery (MCA) or only the first pass AIF is modeled using a single gamma variate function. However, the recirculating input, which is sometimes disregarded for the computational convenience or sometime modeled using too simplistic function (e.g. straight line), has not well been formulated. Here, a full AIF including recirculating input is modeled using a series of gamma variate functions that have related parameters, and the feasibility was tested by a computer simulation. Methods: The simulation was performed using an in‐house program developed in MATLAB. The shape of a gamma variate function was defined using two parameters (α,, reference). In addition, recirculation time (T) and fraction (f), i.e. the first arrival time and fraction after leaving the brain, were included in the simulation. A single recirculation was described as a related gamma variate function (reference), and the total recirculation was described as the sum of all related gamma variate functions. Results: The arterial input function, including the first pass and recirculating inputs, can be modeled using the sum of a series of related gamma variate functions. Conclusions: The arterial input function in its complete form can be modeled using a series of related gamma variate functions. From this modeling, the AIF can be described as its complete form, which might benefit the quantitative measurements of BF, BV or mean transit time (MTT) in those dynamic contrast based perfusion imaging technique such as in CT, PET or MRI.
SU‐E‐J‐50: Fully Automatic Segmentation of Brain Tumor in CT Images
Authors: Gao M , Wei D , Chen S
Published: November 2011

Purpose: A new approach is presented to automatically extract brain tumor in CT images. Methods: The method uses a sequence of brain CT images. Firstly, use morphology operations and wavelets based filter for denoising. Secondly, find out whether CT images contain brain tumor according to the symmetry of the brain CT images, extract the unsymmetric part and its neighbor as the region of interest (ROI). Then, extract the feature (e.g. texture, contrast, homogeneity, etc.) of the ROI. Finally, use k‐means clustering and support vector machines (SVM) for classification with the extracted feature of the ROI and get the contour of the brain tumor. Results: Compared with manually contoured by the physicians, this method enables accurate and automatic extraction of brain tumor in CT images. Conclusions: The method is shown with better performance than current methods. And itˈs a fully automatic, fast and accurate method in precise diagnosis and treatment of brain tumor patients.
SU‐E‐J‐53: Multi Observation PET Image Fusion for Patient Follow‐Up Quantitation in Oncology
Authors: David S , Hatt M , Visvikis D
Published: November 2011

Purpose: In Positron Emission Tomography (PET) imaging, an early therapeutic response can be assessed based on variations of semi‐quantitative parameters such as maximum standardized uptake values (SUV max) measured in PET scans carried out before and during the treatment. However, these measurements do not reflect tumor volume or radiotracer uptake distribution variations.Methods: The proposed approach is based on multi‐observation image statistical analysis for merging several PET acquisitions to assess tumour metabolic volume and uptake variations. The parameters defining the mixture distribution are estimated using the stochastic expectation maximization (SEM) method combined with adaptive spatial correlation estimation (ASEM). The proposed fusion process (ASEM) has been applied to simulated and clinical follow‐up PET images of patients classified as partial responders (PR). We have compared the multi‐observation fusion with threshold‐based (TB) used in clinical practice for the assessment of the therapeutic response, applied independently to each follow‐up scans. Volume errors (VE) and quantitative variations of SUV measurements and tumour volume (dV) were considered on simulated and clinical datasets respectively.Results: : On simulated datasets, the adaptive threshold applied independently on both images led to significantly (p<0.05) higher errors than the ASEM fusion in the first follow‐up scan (VE ASEM = −1±7%, VE TB = 21±8%), and higher for the second follow‐up scan (VE ASEM = −22±19%, VE TB = 28±9%). This trend was enhanced with the clinical datasets, for which the adaptive threshold exhibited incoherent volume variations of +14±167% due to large overevaluation of tumor volumes in the second scan due to challenging conditions of contrast and noise. On the other hand, dV ASEM was −65±11% which is more appropriate since patients are PR Conclusions: The ASEM method demonstrated more accurate tumor volume evolution estimation than threshold‐based independent segmentations. Future work will consist in applying the method to clinical multi‐tracers datasets.
SU‐E‐J‐55: Gradient‐Based Delineation of the Primary GTV on FLT‐PET in Esophageal Cancer and Influence to Radiotherapy Planning
Authors: Zhang G , Lu J , Liu T , Yin Y
Published: November 2011

Purpose: The aim of this study was to validate a gradient‐based segmentation method for GTV delineation on FLT‐PET in EC through surgical specimen, in comparison with threshold‐based approaches and CT. Discuss the influences of gradient‐based methods delineate the primary GTV to radiotherapy planning. Methods: Ten patients with esophageal carcinoma treated with radical surgery were enrolled and detected by 18F‐FLT PET/CT before operation transferred the images to MIM software. For each patient, four GTVs were defined. GTV‐ct was based on CT data alone. GTV‐GRAD, GTV‐1.4, GTV‐30%max were automatically segmented on PET images using the gradient‐based method, fixed threshold values at 1.4 and 30% of SUVmax, respectively. The GTV‐GRAD, GTV‐1.4, GTV‐30%max were compared with GTV‐CT by overlap index. Lengths of GTVs were recorded as LCT, LGRAD, L1.4, L30%max, respectively. The length of surgical specimen was recorded as LPath, and compared with LCT, LGRAD, L1.4, L30%max. Next, two radiotherapy plans were designed for each patient based on GTV‐GRAD (plan‐GRAD) and GTV‐CT (plan‐CT). The radiation dose was prescribed as 60 Gy in 30 fractions. The dose‐volume parameters of target volume and normal tissues, CI and HI of plan‐GRAD and plan‐CT were compared. Results: The mean LPath was 6.47±2.7. The mean Lct, LGRAD, L1.4 and L30%max were 7.17±2.28, 6.22±2.61, 6.23±2.80, 5.95±2.5.The correlation coefficients were 0.862, 0.989, 0.920 and 0.920 when compared with LPath, respectively. The overlap index of GTV‐GRAD,GTV‐1.4,GTV‐30%max when compared with GTV‐CT were 0.75±0.12, 0.71±0.12, 0.57±0.10.The values for mean lung dose, total‐lung volume receiving more than 5, 10, 20, and 30Gy, mean heart dose and heart volume receiving more than 30Gy of plan‐GRAD were significant lower than plan‐CT. Conclusions: The gradient‐based method provided the closest estimation of GTV length. The gradient‐based method radiotherapy planning reduced the irradiated volume in the lung, heart and other normal tissues.
SU‐E‐J‐58: Investigation of Joint Registration/segmentation for Multimodality Target Definition in Image‐Guided Radiotherapy
Authors: El Naqa I
Published: November 2011

Purpose: In the era of image‐guided radiotherapy, there has been increased use of multimodality imaging to accurately define target volumes. However, current methods to define the overall target volume based on multimodality imaging are restricted to manual contouring using visual judgment and limited by lack of semi‐ or automated segmentation algorithms that can handle multiple images at the same time. Moreover, the problem is compounded by the fact that images from different modalities are typically misaligned. Therefore, in this work we investigate and contrast the performance of sequential registration/segmentation with joint registration/segmentation for optimal target definition from multimodality images. Methods: For demonstration of the proposed multimodality framework for target definition, we will consider the challenging case of prostate cancer target definition by combining MRI with CT images. The multimodality framework is based on active deformable models with mutual information using a geometric level set objective function with segmentation and registration terms. Results: Our preliminary results indicate that multimodality image definition of the prostate target volume is improved by using MRI/CT compared to individual definition by either modality. Moreover, joint registration/segmentation produced improved correspondence and agreement with manual contouring compared to sequential registration followed by segmentation. It is also noticed that in this framework the registration correspondence improves weak boundary definition during segmentation while segmentation improves region matching during registration. Conclusions: This work demonstrates the potential of joint registration/segmentation using deformable active contours for target definition in radiotherapy treatment planning from multimodality imaging.
SU‐E‐J‐62: Absorbed Dose Rate Measurements Around a Single 192Ir Intravascular Brachytherapy Seed Using a High‐Spatial Resolution Gel Dosimetry System
Authors: Massillon‐JL G
Published: November 2011

Purpose: Investigate the absorbed dose rate distribution at sub‐millimeter distances close to a192Ir intravascular brachytherapy seed using a high‐spatial‐resolution gel dosimetry system. Method: One BANG3‐Pro‐1 gel phantom was used for the seed irradiation and one for calibration. A small format laser computer tomography scanner has been used to acquire the data. The measurements were performed with a spatial‐resolution of 100 μm in all dimensions. Since this gel is energy independent for photons between 20 keV and 1250 keV, it was calibrated using a small (1cm2) 60Co gamma beam. The air kerma strength was measured using the NIST well‐ion chamber. The dose‐rate constant was measured and the absorbed‐dose‐rate was obtained at distances between 0.6 and 12 mm from the seed. Results: A dose rate constant of (1.140 0.052) cGyh‐1U‐1 was obtained which agrees with published data. At distances between 2.5 and 6 mm, an enhancement on the absorbed dose‐rate is observed. This observation agrees quantitatively with data for the same seed reported previously using Gafchromic film MD‐55‐2. On the other hand, published Monte Carlo data that take into account the emitted beta particles from the seed describe qualitatively this feature, but quantitatively, difference up to 20 % is observed in the enhancement region. Conclusion: This study and the reported data using MD‐55‐2 suggest that the argument from the AAPM TG‐149 protocol where the absorbed dose to the tissues from beta particles is considered to be insignificant is not quite correct and the AAPM TG‐149 protocol should be revised. Finally, experimental method that provide high spatial resolution and water‐equivalent tissue may be the best option to determinate absorbed dose at close distances to brachytherapy seeds since for Monte Carlo calculation, precise knowledge of the seed core is of great importance, which is generally very difficult to accomplish.
SU‐E‐J‐68: Plan Rejections during Treatment Planning: A Part of Normal Process Or An Opportunity for Improvement
Authors: Santanam L , Moore K , Brame S , LaBrash J , Danieley J , Mutic S
Published: November 2011

Purpose: To describe a process for learning from radiation treatment plan(RTP) rejections by physicians and physicists for improvement of quality, safety, and efficiency of treatment planning. In our clinic IMRT treatment plans are pre‐checked by physicists for technical and quality validation before review by the physician. Any problems identified during physics or physician reviews of RTPs offer an opportunity to identify systematic and random deviations and to develop tools, processes, and training to eliminate or reduce such problems in the future. We describe a process wherein the collection of plan rejections and related reasons is considered a part of normal process and not as additional work. Methods: In our clinic we use the DMAIC formalism for management of our operations, whereby processes are understood as comprising of define, measure, analyze, improve and control activities. Systematically quantifying plan rejections and the corresponding reasons offers an opportunity for improvement of treatment planning process and monitoring the effectiveness of corrective measures. This was accomplished through a set of features in our electronic whiteboards that seamlessly and effectively collect rejection information that were further analyzed for identification of improvement opportunities. Efficacy of any implemented improvement measures can then also be evaluated by quantifying future rejections. In this study we concentrate on plan rejections by physicists. Results: There were 110 plan rejections by physicists from September 2010 to Mar 2011. The rejections were due to plan‐quality, plan technical integrity and in some cases data‐entry errors. These rejections were used to identify systematic opportunities for training and better education and for design of in‐house developed auto‐planning and quality‐control scripts. Conclusions: Systematic and sustainable collection of treatment plan rejections for purposes of process improvement is possible. We have demonstrated that this data collection can be seamlessly integrated in normal treatment planning process through the use of electronic white boards.
SU‐E‐J‐79: Proton Density Weighted MRI for MR‐Guided Radiotherapy for Cervical Cancer
Authors: Hu Y , Mutic S , Esthappan J , Richardson S , Gay H , Schwarz J , Grigsby P
Published: November 2011

Purpose: For cervical cancer patients treated by MR‐guided HDR brachytherapy, the accuracy of radiation delivery depends on accurate localization of both tumors and the “tandem and ovoid” applicator. Although T2‐weighted (T2W) MRI has a good tumor contrast, it is not a good choice for defining the applicator because of signal dropout and geometric distortion around the titanium applicator. In this study, we evaluated the possibility of using proton density weighted (PDW) MRI to improve the definition of the applicator. Methods: Both T2W and PDW images in the para‐sagittal plane were obtained from a 1.5T MRI scanner. For both images sets, in‐plane resolution was 1mm*1mm, spacing between slices was 0mm, TR was set to be between 3000ms and 6000ms, and FOV and the number of slices was adjusted based on the anatomy of individual patients. TE was 90ms and 5.5ms; slice thickness was 5mm and 2.5mm for T2W and PDW MRI respectively. PDW MRI had a smaller coverage in R/L direction. Images were sent to a workstation for treatment planning and another workstation after de‐identification for further image analysis. Results: Images from 10 patients were retrospectively reviewed. PDW MRI had a better definition of the applicator for all cases. A smaller ROI was placed around the tip of the tandem, which only included two structures: the tandem and the uterus. Histograms of signal intensity within the ROI showed that two peaks corresponding to the two structures were clearly separated in PDW MRI but not in T2W MRI. Conclusions: We showed that PDW MRI could provide a good visualization of the applicator. Therefore, we recommend adding PDW MRI to the imaging protocol for MR‐guided radiotherapy for cervical cancer. This will enable us to precisely localize both tumors and the applicator, which is essential for ensuring dose delivery accuracy.
SU‐E‐J‐80: Small Beam Dosimetry Using MAGIC Gel with a 7T Micro‐MRI Scanner
Authors: Ding X , Bourland J , Best R , Bennett M , McGowin I , Olsen J , Dorand J
Published: November 2011

Purpose: Dose distribution characteristics for small radiation fields can be very difficult to determine. In this work a MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) 3D polymer gel is combined with 7T micro‐MR imaging for high resolution measurements of the small field (<1cm) 3D dose distributions. Methods: MAGIC(Gelatin 9%; Methacrylic acid 4%; CuSO4 0.1 mM; Ascorbic ascid 2mM; Glucose 22%) 3D gel phantoms were irradiated with very small 6MV x‐ray beams (5x5 mm2 and 10 × 10 mm2 square fields; 2mm diameter round field). Gel dose measurements were performed in Bruker 7T mirco‐MRI and GE Signa 3T scanners and with simultaneously‐obtained radiochromic films. T2 maps were acquired using a 10‐echo‐Multi‐Spin Multi‐Echo (MSME) pulse sequence on both MR scanners. Normalized 3D dose maps were calculated in Matlab. Results: Dose distributions determined from 30 minute scans for the 5×5 mm2 and 10×10 mm2 square fields on the 7T MR unit were superior to 3T MR unit in spatial resolution (7T: 0.156mm × 0.156mm × 1mm voxel; 3T: 0.254mm × 0.254mm × 2mm voxel). For the very small field size (2mm diameter), the MAGIC gel with 7T MRI provided even better quality dose distribution images (1.5hour scan; spatial resolution 79um ×79um × 1mm and; 12 hour scan: spatial resolution 38um × 38um × 1mm), 3T MRI was not able to read accurate dose profile due to a low SNR in the same 1.5hour scan time. Conclusions: This study indicates that the MAGIC polymer gel with 7T micro‐MRI for 3D dose readout can potentially be used for dosimetric characterization of very small radiation beams, including measurements for micro‐beams (field size ∼ 100um). Techniques and limitations for MAGIC gel dosimetry via high field MR imaging for dosimetric assessment are detailed in this work.
SU‐E‐J‐85: A New Approach to Evaluating the Impact of Organ Sub‐Volume Sensitivity to Irradiation by Deforming Cohort Dose Data Onto a Single ‘reference Human’
Authors: Saleh Z , Apte A , Sharp G , Deasy J
Published: November 2011

Purpose: We propose a new approach to normal tissue complication probability (NTCP) investigations by deforming doses from a patient cohort onto a single anatomic frame of reference in order to identify crucial anatomic features. Methods: To perform this study, IMRT treatment plans of seven different prostate cancer patients were used. Organs of interest (rectum, prostate) were delineated manually by an expert physician. CT scans, structures, and prescription dose distributions were exported into DICOM and then imported into the Computational Environment for Radiotherapy Research (CERR). The contrast of the organ of interest was enhanced at the surface boundary using the contour lines and overwriting the Hounsfield Unit (HU) of the CT scan. CTscans [2,7] were deformed onto reference scan CT1 using B‐spline method for deformable image registration available in Plastimatch. The warping of doses [2,7] was then performed utilizing the corresponding B‐spline transformation files. Results: Examination of the Dose Volume Histograms (DVHs) of the prostate reveals a substantial agreement in the mean dose within 1% between the initial prescribed dose and warped dose. However, for organs with large irregularity and heterogeneous dose distribution such as rectum, the DVHs of the warped dose showed larger deviation from the initial prescribed dose. Dose variance shows a significant variation along the rectum anterior wall. Conclusions: This study shows the feasibility of deforming a patient cohort onto a standard anatomy while retaining the dosimetric and volumetric information. This technique works better with organs which have simple geometry that can be indentified on the CT scan. Discrepancies between the initial and warped dose can be attributed to the low resolution CT scans and the choice of the DIR algorithm. This might be improved by mapping onto a reference anatomy with a high resolution CT scan such as the one provided by the Visible Human Project.

NIH R01 CA85181
SU‐E‐J‐89: An Imaging Technique for Surveillance MR Imaging Using 0.23T MR Scanner for Peditaric Craniopharyngioma Patients Who Receive Proton Therapy
Authors: Huh S , Indelicato D , Marcus R , Zhao T , Carpenter M , Li Z
Published: November 2011

Purpose: Surveillance MR image procedure has been developed to monitor possible cyst growth of the pediatric craniopharyngioma patients (6 to 14 years old) without anesthesia using the 0.23T PanoramaTM MR Scanner (Philips, Netherlands) Methods: We developed the MR‐safe base‐of‐skull (BOS) immobilization device made of graphite and generic wood without thermoplastic masks, and optimized the scanning pulse sequences like T1FFE3D (220mm*220, 192*912 matrix, and 2.5mm slice thickess), B‐FFE3D (100mm*100mm, 92*92 matrix with 1.5mm slice thickness), and Dual Turbo Spin Echo (DTSE with 3.5mm slice thickness to generate proton‐density images and heavily T2‐weighted images). Each sequence has 2 sets: axial and sagittal images to improve better contrast due to the limitation of the slice thickness (1.5 to 3.5mm) for small size (2 to 4cc GTV) of the craniopharyngioma. The plan MR (used to do image fusion with Plan CT, T1 or T2 3D volume images with 1 or 1.5T MR scanners with <1mm3 resolution are commonly used) is used as a reference to monitor the cyst growth during entire treatment session. Within 2–3 days of the proton treatment, the surveillance MR images are taken, and thereafter weekly MR images are taken, and correlated with the Plan MR and previous Surveillance MR images.Results: The accuracy of the surveillance MR images (T1FFE3D) are found to be ∼2mm, the BFFE images are sensitive to inhomogeneous region where the target is located in the brain. Their geometrical distortions are approximately 2mm from another surveillance MR images as well the plan MR. Conclusions: This technique has been used to monitor 4 patients and the image quality is good enough for clinicians to estimate the possible cyst changes. In the preliminary trails with 4 patients, all the cysts are stable diseases. It will be used to scan the pediatric patients with anesthesia.
SU‐E‐J‐90: Quantitative PET Imaging to Evaluate Clinical Complications Associated with Stereotactic Body Radiotherapy in Non‐Small Cell Lung Tumors
Authors: Ali I , Confer M , Ahmad S
Published: November 2011

Purpose: To investigate correlation of standard‐uptake values (SUV) from post‐treatment PET imaging representing clinical complications such as muscular inflammation with dose delivered in non‐small cell lung cancer patients treated with large hypo‐fractions using stereotactic body radiation therapy (SBRT). Method and Materials: Clinical complications represented as chronic inflammation and rib fractures in ten non‐small cell lung cancer patients treated with large hypo‐fractionated stereotactic body radiation therapy were investigated. SBRT was delivered in three fractions with each fraction 20 Gy or five fractions with each 12 Gy. These patients were scanned with PET imaging at three and seven months after treatment for follow up to evaluate tumor control and clinical complications post‐ radiotherapy. The dose distributions calculated by treatment planning and delivered were extracted and compared with SUV distributions obtained from PET imaging. The correlation between dose deposited in the chest wall and clinical complications represented by higher SUV from PET imaging were quantified. Results: The dose distribution calculated by treatment planning from the different beams overlaid on a CT axial image for a lung patient correlates strongly with SUV obtained from PET imaging. The enhanced SUV represents chronic inflammation of the chest wall tissue that has received high doses by the individual entering beams. The profiles from the regions in the chest wall that have received high dose deposition correspond to enhanced SUV in anatomically matching regions from PET images. Significant proportion of pixels from dose distribution correlates linearly with corresponding pixels that have high SUV‐dose in the chest wall. Conclusions: Large doses deposited in normal tissue from SBRT in treatment of non‐small cell lung tumor correlate well with the SUV values measured by PET images. This correlation may be useful in predicting clinical complications by measurement of the delivered dose and SUV values associated with SBRT.
SU‐E‐J‐91: Patient‐Specific Virtual Radiation Oncology: Predicting and Quantifying Treatment Response in Individual Glioblastoma Patients
Authors: Rockne R , Rockhill J , Mrugala M , Swanson K
Published: November 2011

Purpose: To quantify and predict response to radiation therapy in vivo prior to treatment on a patient‐specific basis using mathematical modeling.Methods: Glioblastoma multiforme (GBM) are highly invasive primary brain tumors that diffusely invade the surrounding normal appearing tissue and yields short life expectancies despite aggressive treatment. The differential motility of glioma cells throughout the brain characterize tumor invasion. We present and apply a patient‐specific, mathematical model for glioma growth that quantifies response to radiation therapy (RT) in vivo in the 3D anatomy of the human brain. The mathematical model uses net rates of proliferation and migration of tumor cells to characterize the tumorˈs growth and invasion along with the linear‐quadratic model for response to radiation therapy. Results: Patient individualized simulations of tumor growth and radiation response are performed in 9 GBM patients validating a predictive relationship between the net rate of proliferation rate and radiosensitivity. The simulations accurately predict the imageable tumor post‐treatment within 2.4 mm. Because the patient‐specific net proliferation rate of the tumor is calculated prior to treatment, this result provides quantitative predictions of radiosensitivity on a patient‐by‐patient basis. Conclusions: This work presents the first mathematical model to quantify patient‐specific radiosensitivity based on in vivo data. Our results indicate that, using our model, clinicians will be able to identify the degree to which any given glioma patient will respond to radiation therapy prior to treatment. That is, a virtual in silico tumor with the same growth kinetics as a particular patient combined with the complex anatomy of the brain can predict treatment response in individual patients in vivo. This work marks a paradigm shift in the quantification of treatment response and provides a basis for individualizing radiation treatment according to both the dynamics of each tumor but also their diffuse extent.
SU‐E‐J‐94: FLT PET Imaging for Evaluating Bone Marrow Recovery after Chemoradiation Therapy in Cervical Cancer Patients
Authors: McGuire S , Jacobson G , Menda Y , Ponto L Boles , Gross B , Bayouth J
Published: November 2011

Purpose: To evaluate the ability of FLT PET imaging to measure bone marrow recovery from chemoradiation therapy in cervical cancer patients. Methods: Two cervical cancer patients were enrolled in an IRB approved protocol to obtain FLT PET images at simulation, during chemoradiation, and ∼30 days post chemoradiation therapy. WBC counts and bone marrow FLT uptake change inside and outside the radiation therapy (RT) field were measured to correlate with recovery measured with FLT uptake 30 days post‐therapy. Bone marrow response and recovery was measured within the RT field in 1 Gy/week dose volumes and outside the field within the lumbar vertebral bodies. Results: Each subject was unique in her bone marrow recovery due to chemoradiation therapy when compared to pre‐therapy values. Inside the RT field, subject 1 bone marrow that received < 3 Gy/week recovered ∼85% while bone marrow that received > 6 Gy/week recovered at least 50% of pre‐therapy FLT uptake 30 days post‐therapy. However, subject 2 bone marrow that received < 3 Gy/week recovered ∼45% and bone marrow that received > 6 Gy/week recovered ∼35% of pre‐therapy FLT uptake. Outside the RT field, subject 1 L1 FLT mean SUV increased over initial values 60.6% after 3 weeks of RT and 59.1% 30 days post‐therapy. Subject 2 L1 FLT mean SUV increased over initial values only 18.5% after 3 weeks of RT and 10.6% 30 days post‐therapy. Pre‐therapy bone marrow activity may also influence bone marrow recovery. Subject 1 had lower initial WBCs and FLT uptake than subject 2 (5.3 vs. 12.2 K/mm3 and 10.4 vs. 13.6 max SUV). Conclusion: This preliminary data shows that bone marrow recovery, pre‐therapy FLT uptake, and compensatory response can be quantified with FLT PET. These metrics may be valuable in correlating pre‐, during, and post‐therapy response to radiation dose and long‐term systemic toxicity.
SU‐E‐J‐103: Feasibility of a Quantitative, Patient‐Specific Image Planning System for Radiation Therapy
Authors: Molloy J , Thapa B
Published: November 2011

Purpose: We studied the feasibility of developing an Image Planning System (IPS) for radiotherapy guidance that will allow clinicians to prospectively choose an imaging goal, for example, soft tissue contrast versus boney anatomy and predict the optimal imaging parameters. The IPS will allow ensure that imaging dose is appropriate for the imaging goal (neither over, nor under dose) and that imaging frequency (for example, real‐time fluoroscopy) is applied with well‐defined and predetermined patient doses. Methods: We characterized a commercial, linear‐accelerator‐mounted diagnostic x‐ray imaging system with flat panel detector, in terms of low‐contrast object detectability as a function of patient thickness and x‐ray technique factors. A commercial contrast test object and homogeneous tissue equivalent phantom was used for this. The feasibility of predicting low contrast resolution analytically was tested using a clinical CT scan and a respiratory motion phantom. Optimal image‐acquisition and display parameters where experimentally determined for an anthropomorphic phantom and using clinical images, thus assessing whether soft tissue contrast is a viable imaging goal. Contrast‐noise ratio and low contrast detectability where used as metrics. Results: Characteristic curves of the response of the detector demonstrate a broad plateau over which image quality is relatively constant. All combinations of phantom thickness and technique parameters possessed both low‐dose and high‐dose reductions in low contrast quality. Analytical calculations of local soft tissue contrast predict superior low‐contrast resolution using lower kVp settings (as expected) and are capable of resolving discrete objects. Conclusions: Optimal imaging techniques can be derived from these data in which the feasibility of the imaging goal is assessed, coupled with prospective calculation of technique factors that apply minimal patient dose and allow for maximum imaging repetition. Analytical, energy‐dependent calculation models can be used to predict image contrast and plan optimal imaging dose.
SU‐E‐J‐119: Development of Voxel‐by‐Voxel Respiratory Lung Motion Simulation Model
Authors: Tesfamicael B , Lee T
Published: November 2011

Purpose: 1. To justify the respiratory induced lung tumor motion is correlated to volume change in lung 2.To show that such motion is a hysteresis type of motion, i.e. the inspiration and expiration paths the tumor follows are different. Methods: The model equation was generated based on the data obtained from the axial displacement versus volume plot of the lung by Verschakelen et al (1989). The time variation of the lung volume change was introduced using linear and non‐linear functions. After comparison with literature (Lu et al, 2006), we verified the non‐linear time variation is more reliable. The lung motion amplitude as a function of time was then plotted and fitted with sinusoidal function. The dynamic 3D lung motion was simulated as a function of time based on the model equation. Two independent simulations were performed and compared: 1. Independent tumor motion amplitude and lung volume change. 2. Lung tumor motion dependent on the lung volume change. Results: 1.The model function generated from the fitting curve is periodic function with even power. This agrees with the periodic nature of respiration induced lung motion and also with the fact that longer time is spent at the end of exhalation than at the end of inhalation, which is proven by other researchers too. 2.Based on the simulated dynamic lung motion, we observe that the lung tumor motion is well correlated to the lung volume change. Conclusions: Clinically, chest wall as well as diaphragm amplitude measurements are used to provide lung motion gating window. In this study, we observe that respiration induced motion of the lung tumor is correlated to the lung volume change, and this can give a good prediction of: 1. The 3D location of the lung tumor. 2. Density change of the lung.