bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐483: Treatment Planning Study of Volumetric Modulated Arc Therapy for Left‐Sided Breast and Chestwall Cancers
Authors: Xu H 
Published: July 2014

Purpose:To perform the comparison of dose distributions and dosevolume‐ histograms generated by VMAT and conventional field‐in‐field technique for left‐sided breast and chestwall cancers; to determine whether VMAT offers more dosimetric benefits than does the field‐in‐field technique.Methods:All VMAT and field‐in‐filed plans were produced in Eclipse(version 10). Five plans were generated for left‐sided breast and leftsided chestwall with supraclavicular nodes, respectively. A clockwise arc (CW) and a counter‐clockwise arc (CCW) were used with start and stop angles being 310o±10o and 140o±10o. Collimator angles were 30o for CW and 330o for CCW. The conformity index (CI) is the ratio of V95% over PTV. The homogeneity index (HI) is the ratio of the difference between D2% and D98% over the prescribed dose. The V5, as an indicator of low dose bath to organs‐at‐risk, was used for ipsilateral lung, heart, contralateral lung, and contralateral breast. The V20, as an indicator of radiation pneumonitis, was used for ipsilateral lung.Results:Breast/chestwall VMAT delivers much higher low dose bath to ipsilateral lung, contralateral lung and contralateral breast/chestwall for both intact breast and chestwall with nodes. V5 for heart is increased in VMAT plans. V20 for ipsilateral lung is lower in VMAT plans. PTV coverage is similar for both techniques. For one particular chestwall patient with supraclavicular and internal mammary nodes, VMAT offers superior dose coverage of PTVs with slightly more low‐dose‐wash to heart, contralateral lung and contralateral breast.Conclusion:This study indicates that there is generally no benefit using VMAT for left‐sided intact breast, due to large low‐dose‐bath (5Gy) to normal tissues with insignificant improvement in PTV coverage. Dosimetric benefits will be seen in VMAT plans for some chestwall patients with large size, and/or internal mammary nodes, etc. Whether a chestwall patient is treated with VMAT should be carefully analyzed on an individual basis.
SU‐E‐T‐516: Measurement of the Absorbed Dose Rate in Water Under Reference Conditions in a CyberKnife Unit
Authors: Aragon‐Martinez N , Gomez‐Munoz A , Hernandez‐Guzman A , Massillon‐JL G 
Published: July 2014

Purpose:This paper aims to measure the absorbed‐dose‐rate in a CyberKnife unit reference‐field (6cm diameter) using three ionization chambers (IC) following the new IAEA/AAPM formalism and Gafchromic film (MD‐V3‐55 and EBT3) protocol according to our work reported previously.Methods:The absorbed‐dose‐rates were measured at 90cm and 70cm SSD in a 10cmx10cm field and at 70cm SSD in a 5.4cmx5.4cm equivalent to 6cm diameter field using a linac Varian iX. All measurements were performed at 10cm depth in water. The correction factors that account for the difference between the IC response on the reference field and the CyberKnife reference field, k_(Q_msr,Q)^(f_msr,f_ref), were evaluated and Gafchromic film were calibrated using the results obtained above. Under the CyberKnife reference conditions, the factors were used to measure the absorbed‐dose‐rate with IC according to the new formalism and the calibrated film was irradiated in water. The film calibration curve was used to evaluate the absorbed‐dose‐rate in the CyberKnife unit.Results:Difference up to 2.56% is observed between dose‐rate measured with IC in the reference 10cmx10cm field, depending where the chamber was calibrated, which was not reflected in the correction factor k_(Q_msr,Q)^(f_msr,f_ref) where variations of ~0.15%‐0.5% were obtained. Within measurements uncertainties, maximum difference of 1.8% on the absorbed‐dose‐rate in the CyberKnife reference field is observed between all IC and the filmsConclusion:Absorbed‐dose‐rate to water was measured in a CyberKnife reference field with acceptable accuracy (combined uncertainties ~1.32%‐1.73%, k=1) using three IC and films. The MD‐V3‐55 film as well as the new IAEA/AAPM formalism can be considered as a suitable dosimetric method to measure absorbed‐dose‐rate to water in small and non‐standard CyberKnife fields used in clinical treatments However, the EBT3 film is not appropriated due to the high uncertainty provided (combined uncertainty ~9%, k=1)This work is partially supported by Conacyt grant 127409 and PAPIITUNAM grant IN10581
SU‐E‐QI‐03: Compartment Modeling of Dynamic Brain PET – The Effect of Scatter and Random Corrections On Parameter Errors
Authors: Häggström I , Schmidtlein C , Karlsson M , Larsson A 
Published: July 2014

Purpose:To investigate the effects of corrections for random and scattered coincidences on kinetic parameters in brain tumors, by using ten Monte Carlo (MC) simulated dynamic FLT‐PET brain scans.Methods:The GATE MC software was used to simulate ten repetitions of a 1 hour dynamic FLT‐PET scan of a voxelized head phantom. The phantom comprised six normal head tissues, plus inserted regions for blood and tumor tissue. Different time‐activity‐curves (TACs) for all eight tissue types were used in the simulation and were generated in Matlab using a 2‐tissue model with preset parameter values (K1,k2,k3,k4,Va,Ki). The PET data was reconstructed into 28 frames by both ordered‐subset expectation maximization (OSEM) and 3D filtered back‐projection (3DFBP). Five image sets were reconstructed, all with normalization and different additional corrections C (A=attenuation, R=random, S=scatter): Trues (AC), trues+randoms (ARC), trues+scatters (ASC), total counts (ARSC) and total counts (AC). Corrections for randoms and scatters were based on real random and scatter sinograms that were back‐projected, blurred and then forward projected and scaled to match the real counts. Weighted non‐linearleast‐ squares fitting of TACs from the blood and tumor regions was used to obtain parameter estimates.Results:The bias was not significantly different for trues (AC), trues+randoms (ARC), trues+scatters (ASC) and total counts (ARSC) for either 3DFBP or OSEM (p<0.05). Total counts with only AC stood out however, with an up to 160% larger bias. In general, there was no difference in bias found between 3DFBP and OSEM, except in parameter Va and Ki.Conclusion:According to our results, the methodology of correcting the PET data for randoms and scatters performed well for the dynamic images where frames have much lower counts compared to static images. Generally, no bias was introduced by the corrections and their importance was emphasized since omitting them increased bias extensively.
SU‐E‐QI‐05: Denoising Intravoxel Incoherent Motion Magnetic Resonance Images Using Non‐Local Mean Technique for Oropharyngeal Cancer Study
Authors: Ding Y , Fuller C , Mohamed A , He R , Wang J , Frank S , Rosenthal D , Colen R , Hazle J 
Published: July 2014

Purpose:Intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) normally shows a low signal to noise ratio (SNR) due to the presence of noise which complicates and biases the estimation of quantitative diffusion parameters. In this study, a Non‐local Means (NLM) approach was applied to remove the noise in oropharyngeal cancer IVIMMRI images.Methods:Eight male patients with squamous cell carcinoma of the oropharynx were included in this study under an approved IRB protocol. IVIM‐MRI was carried out on a 3.0‐T GE MRI. NLM denoising technique was performed using the MIPAV (V7, NIH). IVIM parameters (D, pure diffusion coefficient; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated on a pixel‐by‐pixel basis using a bi‐exponential model implemented within ImageJ (V1.47, NIH) with ten b‐values ranging from 0 – 800 s/mm2. SNR with and without denoising processing was calculated and compared in tumor regions. The agreements of IVIM‐MRI parameters estimated between with and without NLM processing in tumor region were assessed by Bland‐Altman plots.Results:Examples of IVIM images (b=800 s/mm2) and parametric maps (D, D* and f) with and without NLM applied are illustrated in Fig. 1 for an oropharynx cancer patient. Results of SNR and IVIM diffusion parameters between two different processing, as mean and standard deviation on 8 patients, are reported in Table 1. Bland‐Altman plots (Fig. 2) between the two approaches show better concordance for D (0.22% ± 1.42%) and f (0.56% ± 3.49%), whereas larger discrepancies were found for D* (0.86% ± 6.25%).Conclusion:NLM approach gives better SNR and quantitative data quality, also shows a good agreement between the IVIM parameters processed with and without NLM approaches. Therefore, NLM denoising technique can be applied to improve performance in terms of denoising quality and estimation of IVIM parameter as a post‐processing step without increasing the scanning time.
SU‐E‐QI‐06: Design and Initial Validation of a Precise Capillary Phantom to Test Perfusion Systems
Authors: Wood R , Iacobucci G , Khobragade P , Ying L , Snyder K , Wack D , Rudin S , Ionita C 
Published: July 2014

Purpose:To design a precise perfusion phantom mimicking capillaries of the brain vasculature which could be used to test various perfusion protocols and algorithms which generate perfusion maps.Methods:A perfusion phantom was designed in Solidworks and built using additive manufacturing. The phantom was an overall cylindrical shape of diameter and height 20mm and containing capillaries of 200μm or 300μm which were parallel and in contact making up the inside volume where flow was allowed. We created a flow loop using a peristaltic pump and contrast agent was injected manually. Digital Subtraction Angiographic images and low contrast images with cone beam CT were acquired after the contrast was injected. These images were analyzed by our own code in LabVIEW software and Time‐Density Curve, MTT and TTP was calculated.Results:Perfused area was visible in the cone beam CT images; however, individual capillaries were not distinguishable. The Time‐Density Curve acquired was accurate, sensitive and repeatable. The parameters MTT, and TTP offered by the phantom were very sensitive to slight changes in the TDC shape.Conclusion:We have created a robust calibrating model for evaluation of existing perfusion data analysis systems. This approach is extremely sensitive to changes in the flow due to the high temporal resolution and could be used as a golden standard to assist developers in calibrating and testing of imaging perfusion systems and software algorithms.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation
SU‐E‐QI‐07: Early Evaluation of Tumor Response to Therapy Via More Accurate Apparent Diffusion Coefficient Maps
Authors: Ma B , Li X , Kuang Y 
Published: July 2014

Purpose:We investigated the impact of more accurately computed apparent diffusion coefficient (ADC) maps, generated by registration of high‐b‐value and low‐b‐value diffusion weighted MR volumes, on early evaluation of tumor response to therapy.Methods:As in previous work, voxel‐by‐voxel ADC changes in diffusion MR exams during the course of cancer treatment have been shown to be capable of predicting therapeutic response earlier and more accurately than conventional methods. Here we further improved the prediction accuracy using better estimated ADC values. Due to the different susceptibility effects of the different b‐field acquisitions, the low‐ and high‐b‐value diffusion weighted MR volumes can be markedly out of alignment. Nonlinear registration was employed to align these two volumes and more accurate ADC values were produced. Therapeutic efficacy was then evaluated using the voxel‐by‐voxel ADC change analysis on the registered pre‐ and post‐treatment ADC maps.Results:We have applied the described method to 14 sets of pre‐ and post‐treatment diffusion MRI volumes of breast cancer patients. The post‐treatment exams were acquired in average five weeks after the initiation of treatment. Voxel‐by‐voxel ADC change analysis with logistic regression (p=0.009) demonstrated that the probability of a responsive treatment is significantly associated with increased ADC values. There were 2 false positives and 1 false negative (sensitivity=80%, specificity=75%). Using more accurate ADC values estimated with nonlinear registration, ADC change analysis yielded 1 false positive and 1 false negative for a sensitivity of 90% and a specificity of 75%.Conclusion:The study suggests registration of high‐b‐value and low‐b‐value diffusion weighted MR volumes ensures their voxel correspondence and the subsequent estimation of ADC values are more accurate than ADC computation without registration. The improved ADC maps could increase the accuracy of voxelby‐ voxel ADC change analysis of registered interval exams in early assessment of treatment response.NIH/NIGMS U54 GM104944, Lincy Endowed Assistant Professorship
SU‐E‐QI‐08: Fourier Properties of Cone Beam CT Projection
Authors: Bai T , Yan H , Jia X , Jiang Steve B. , Mou X 
Published: July 2014

Purpose:To explore the Fourier properties of cone beam CT (CBCT) projections and apply the property to directly estimate noise level of CBCT projections without any prior information.Methods:By utilizing the property of Bessel function, we derivate the Fourier properties of the CBCT projections for an arbitrary point object. It is found that there exists a double‐wedge shaped region in the Fourier space where the intensity is approximately zero. We further derivate the Fourier properties of independent noise added to CBCT projections. The expectation of the square of the module in any point of the Fourier space is constant and the value approximately equals to noise energy. We further validate the theory in numerical simulations for both a delta function object and a NCAT phantom with different levels of noise added.Results:Our simulation confirmed the existence of the double‐wedge shaped region in Fourier domain for the x‐ray projection image. The boundary locations of this region agree well with theoretical predictions. In the experiments of estimating noise level, the mean relative error between the theory estimation and the ground truth values is 2.697%.Conclusion:A novel theory on the Fourier properties of CBCT projections has been discovered. Accurate noise level estimation can be achieved by applying this theory directly to the measured CBCT projections.This work was supported in part by NIH(1R01CA154747‐01), NSFC((No. 61172163), Research Fund for the Doctoral Program of Higher Education of China (No. 20110201110011) and China Scholarship Council.
SU‐E‐QI‐09: In Vivo Monitoring of Fluorinated Inhalational Anesthetics Using 19F MRI: A Pilot Study
Authors: Bednarz B , Ludwig K , Fain S 
Published: July 2014

Purpose:Despite the widespread use of fluorinated hydrocarbons for inhalational anesthesia very little is known about the role of these anesthetics in postoperative cognitive impairment. There is a compelling need for safe and effective quantitative and qualitative imaging techniques to monitor the spatial distribution of inhalational anesthetics in vivo to appropriately assess this role. Herein we present a pilot study on the use of 1 9F MRI to image fluorinated anesthetics in vivo.Methods:The spatial distribution of isoflurane in a healthy C57BL/6 mouse subject to a constant flow rate of gas was image using a 4.7T small animal MRI system (Aligent Technologies, Santa Clara, CA). Multiple coronal 19F 2 mm slice images were acquired using a volumetric quadrature coil tunable to 1 9F frequency (187.9 MHz) averaging over 4 different time points (30, 35, 60 and 75 minutes). 1 9F images were overlaid onto T2‐weighted fast echo multi‐slice (FSEMS) 1H images of soft tissue anatomy.Results:An average over the 4 collection time points clearly demonstrates the distribution of isoflurane in vivo with peak uptake in muscle and fatty tissue as well as in the frontal lobe of the mouse brain. A time resolved imaging sequence demonstrates the increasing uptake of isoflurane in each of these compartments.Conclusion:A novel technique to image fluorinated gas anesthetics in vivo has been demonstrated. To the best of our knowledge, this is the first time isoflurane has been imaged in vivo using MRI.
SU‐E‐QI‐10: Intravoxel Incoherent Motion Imaging for MR‐Guided Cryoablation
Authors: Yung J , Ahrar K , Hazle J , Stafford R 
Published: July 2014

Purpose:Percutaneous renal cryoablation for renal tumors has been shown to be nephron sparing and have low morbidity. Post‐treatment verification of the ablated tissue often utilizes contrast‐enhanced MR imaging (ce‐MRI) to assess the region of altered perfusion. However, particularly within this population, some patients are contraindicated for contrast injection. Intravoxel incoherent motion (IVIM) MRI is a technique that measures diffusion and perfusion characteristics from the measured diffusion signals of multiple b values. In this study, IVIM MRI is evaluated versus ce‐MRI to assess its feasibility for differentiating normal and ablated tissue.Methods:Under real‐time MR guidance, 3 cryoprobes were introduced to a patient with renal cell carcinoma in the right kidney. Two cycles of cryoablation were performed with each cycle consisting of 12 minutes and a thaw cycle of 10 minutes. Dynamic ce‐MRI was performed following the last thaw cycle and diffusion‐weighted imaging. IVIM MRI was obtained using a respiratory navigator triggered single‐shot echo planar imaging sequence on a 1.5T clinical scanner. The diffusion coefficient D and the perfusion f parameters were estimated by fitting the diffusion for b values higher and lower than 200 sec/mm2 signal, respectively, using the IVIM model. Regions of interest (ROI) were manually placed in non‐enhancing and enhancing regions according to the post‐treatment contrast‐enhanced images and compared to one another.Results:The perfusion fraction and diffusion coefficient values decreased in the ablated tissue (5.51 ± 7.28 and 0.94 ± .30) compared to the normal kidney tissue (13.13 ± 10.37 and 1.68 ± 0.22). The perfusion fraction and diffusion coefficient maps demonstrate good agreement with the contrast‐enhanced images.Conclusion:In these preliminary results, the use of IVIM parameters could help verify treatment without the use of contrast. In the future, more patients undergoing MRguided cryoablation will be analyzed to determine the accuracy of these damage predictions.
SU‐E‐QI‐11: Measurement of Renal Pyruvate‐To‐Lactate Exchange with Hyperpolarized 13C MRI
Authors: Adamson E , Gordon J , Johnson K , Fain S 
Published: July 2014

Purpose:Previous work [1] modeling the metabolic flux between hyperpolarized [1‐13C]pyruvate and [1‐13C]lactate in magnetic resonance spectroscopic imaging (MRSI) experiments failed to account for vascular signal artifacts. Here, we investigate a method to minimize the vascular signal and its impact on the fidelity of metabolic modeling.Methods:MRSI was simulated for renal metabolism in MATLAB both with and without bipolar gradients. The resulting data were fit to a two‐site exchange model [1], and the effects of vascular partial volume artifacts on kinetic modeling were assessed. Bipolar gradients were then incorporated into a gradient echo sequence to validate the simulations experimentally. The degree of diffusion weighting (b = 32 s/mm2) was determined empirically from 1H imaging of murine renal vascular signal. The method was then tested in vivo using MRSI with bipolar gradients following injection of hyperpolarized [1‐13C]pyruvate (∼80 mM at 20% polarization).Results:In simulations, vascular signal contaminated the renal metabolic signal at resolutions as high as 2 × 2 mm2 due to partial volume effects. The apparent exchange rate from pyruvate to lactate (kp) was underestimated in the presence of these artifacts due to contaminating pyruvate signal. Incorporation of bipolar gradients suppressed vascular signal and improved the accuracy of kp estimation. Experimentally, the in vivo results supported the ability of bipolar gradients to suppress vascular signal. The in vivo exchange rate increased, as predicted in simulations, from kp = 0.012 s‐1 to kp = 0.020‐1 after vascular signal suppression.Conclusion:We have demonstrated the limited accuracy of the two‐site exchange model in the presence of vascular partial volume artifacts. The addition of bipolar gradients suppressed vascular signal and improved model accuracy in simulations. Bipolar gradients largely affected kp estimation in vivo. Currently, slow‐flowing spins in small vessels and capillaries are only partially suppressed, so further improvement is possible.Funding support: Seed Grant from the Radiological Society of North America, GE Healthcare, University of Wisconsin Graduate School
SU‐E‐QI‐12: Morphometry Based Measurements of the Structural Response to Whole Brain Radiation
Authors: Fuentes D , Castillo R , Castillo E , Guerrero T 
Published: July 2014

Purpose:Although state of the art radiation therapy techniques for treating intracranial malignancies have eliminated acute brain injury, cognitive impairment occurs in 50–90% of patients who survive >6mo post irradiation. Quantitative characterization of therapy response is needed to facilitate therapeutic strategies to minimize radiation induced cognitive impairment [1]. Deformation based morphometry techniques [2, 3] are presented as a quantitative imaging biomarker of therapy response in patients receiving whole brain radiation for treating medulloblastoma.Methods:Post‐irradiation magnetic resonance imaging (MRI) data sets were retrospectively analyzed in N=15 patients, >60 MR image datasets. As seen in Fig 1(a), volume changes at multiple time points post‐irradiation were quantitatively measured in the cerebrum and ventricles with respect to pre‐irradiation MRI. A high resolution image Template, was registered to the pre‐irradiation MRI of each patient to create a brain atlas for the cerebrum, cerebellum, and ventricles. Skull stripped images for each patient were registered to the initial pre‐treatment scan. Average volume changes in the labeled regions were measured using the determinant of the displacement field Jacobian.Results:Longitudinal measurements, Fig 1(b‐c), show a negative correlation p=.06, of the cerebral volume change with the time interval from irradiation. A corresponding positive correlation, p=.01, between ventricular volume change and time interval from irradiation is seen. One sample t‐test for correlations were computed using a Spearman method. An average decrease in cerebral volume, p=.08, and increase in ventricular volume, p<.001, was observed. The radiation dose was seen directly proportional to the induced volume changes in the cerebrum, r=−.44, p<.001, Fig 1(d).Conclusion:Results indicate that morphometric monitoring of brain tissue volume changes may potentially be used to quantitatively assess toxicity and response to radiation and may provide insight in developing new therapeutic approaches and monitoring efficacy.