bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐I‐24: Design and Fabrication of a Multi‐Functional Neck and Thyroid Phantom for Medical Dosimetry and Calibration
Authors: Mehdizadeh S , Sina S , Karimipourfard M , Lotfalizadeh F , Faghihi R , Babaei A
Published: July 2014

Purpose:

The purpose of this study is the design and fabrication of a multipurpose anthropomorphic neck and thyroid phantom for use in medical applications (i.e. quality control of images in nuclear medicine, and dosimetry).

Methods:

The designed neck phantom is composed of seven elliptic cylindrical slices with semi‐major axis of 14 and semi‐minor axis of 12.5 cm, each having the thickness of 2cm. Thyroid gland, bony part of the neck, and the wind pipe were also built inside the neck phantom.

Results:

The phantom contains some removable plugs,inside and at its surface to accommodate the TLD chips with different shapes and dimensions, (i.e. rod, cylindrical and cubical TLD chips)for the purpose of medical dosimetry (i.e. in radiology, radiotherapy, and nuclear medicine). For the purpose of quality control of images in nuclear medicine, the removable thyroid gland was built to accommodate the radioactive iodine. The female and male thyroid glands were built in two sizes separately.

Conclusion:

The designed phantom is a multi‐functional phantom which is applicable for dosimetry in diagnostic radiology, radiotherapy, and quality control of images in nuclear medicine.
SU‐E‐I‐31: Image‐Based Kernel Conversion Technique Normalizes the Reconstruction Kernel Effects in the Measurement of Emphysema Index in CT
Authors: Jin H , Kim J
Published: July 2014

Purpose:

The emphysema index (EI) in CT is a quantitative measure of emphysema, which is known to be affected by reconstruction kernel. This study presents an image‐based kernel conversion technique which converts CT image of sharp kernel to that of standard kernel and evaluates its impact on EI normalization for images obtained with different kernels.

Methods:

Sixty cases of CT exams obtained with 120kVp, 40mAs, 1mm thickness, of 2 reconstruction kernels (B30f, B50f) were selected from the low dose lung cancer screening database of our institution. An image‐based kernel conversion technique, which converts by applying a conversion function, was performed to the CT data set of B50f to create a converted B30f data set. The conversion function(Fcon) which is the ratio of the spectral components of target and source kernel images, was produced using a training dataset. To test variability due to training dataset, two versions of conversion functions were produced using two different training dataset. The EI (RA950) was measured with a software package (Pulmonalizer, Seoul, South Korea) and compared for data sets of B50f, B30f, and the converted B30f. The accuracy of kernel conversion was evaluated with the mean and standard deviation of pair‐wise differences in EI.

Results:

Population mean of EI was 28.89±6.48% for B50f data set, 10.96±6.37% for the B30f data set, and 11.27±6.83% for the converted B30f data set. The mean of pair‐wise differences in EI between B30f and the converted B30f is 0.82% for Fcon1 and 1.07% for Fcon2. The correlation between the EI of two data sets was 0.99.

Conclusion:

Our study demonstrates the feasibility of image‐based kernel conversion technique for normalization of kernel effect in measurement of EI. This technique has a potential to be used in evaluating the longitudinal changes of EI even when the CT was reconstructed with different kernels.

The research was supported by the Ministry of Trade, Industry & Energy (10043118)
SU‐E‐I‐34: Intermittent Low‐ and High‐Dose Ethanol Exposure Alters Neurochemical Responses in Adult Rat Brain: An Ex Vivo 1H NMR Spectroscopy at 11.7 T
Authors: Lee Do‐Wan , Kim Sang‐Young , Song Kyu‐Ho , Choe Bo‐Young
Published: July 2014

Purpose:

The first goal of this study was to determine the influence of the dose‐dependent effects of intermittent ethanol intoxication on cerebral neurochemical responses among sham controls and low‐ and high‐dose‐ethanol‐exposed rats with ex vivo high‐resolution spectra. The second goal of this study was to determine the correlations between the metabolite‐metabolite levels (pairs‐of‐metabolite levels) from all of the individual data from the frontal cortex of the intermittent ethanol‐intoxicated rats.

Methods:

Eight‐week‐old male Wistar rats were divided into 3 groups. Twenty rats in the LDE (n = 10) and the HDE (n = 10) groups received ethanol doses of 1.5 g/kg and 2.5 g/kg, respectively, through oral gavage every 8‐h for 4 days. At the end of the 4‐day intermittent ethanol exposure, one‐dimensional ex vivo 500‐MHz proton nuclear magnetic resonance spectra were acquired from 30 samples of the frontal cortex region (from the 3 groups).

Results:

Normalized total‐N‐acetylaspartate (tNAA: NAA + NAAG [N‐acetylaspartyl‐glutamate]), gamma‐aminobutyric acid (GABA), and glutathione (GSH) levels were significantly lower in the frontal cortex of the HDE‐exposed rats than that of the LDE‐exposed rats. Moreover, compared to the CNTL group, the LDE rats exhibited significantly higher normalized GABA levels. The 6 pairs of normalized metabolite levels were positively (+) or negatively (−) correlated in the rat frontal cortex as follows: tNAA and GABA (+), tNAA and Aspartate (Asp) (−), myo‐Inositol (mIns) and Asp (−), mIns and Alanine (+), mIns and Taurine (+), and mIns and tNAA (−).

Conclusion:

Our results suggested that repeated intermittent ethanol intoxication might result in neuronal degeneration and dysfunction, changes in the rate of GABA synthesis, and oxidative stress in the rat frontal cortex. Our ex vivo 1H high‐resolution‐magic angle spinning nuclear magnetic resonance spectroscopy results suggested some novel metabolic markers for the dose‐dependent influence of repeated intermittent ethanol intoxication in the frontal cortex.
SU‐E‐I‐37: Low‐Dose Real‐Time Region‐Of‐Interest X‐Ray Fluoroscopic Imaging with a GPU‐Accelerated Spatially Different Bilateral Filtering
Authors: Chung H , Lee J , Pua R , Jung W , Cho S
Published: July 2014

Purpose:

The purpose of our study is to reduce imaging radiation dose while maintaining image quality of region of interest (ROI) in X‐ray fluoroscopy. A low‐dose real‐time ROI fluoroscopic imaging technique which includes graphics‐processing‐unit‐ (GPU‐) accelerated image processing for brightness compensation and noise filtering was developed in this study.

Methods:

In our ROI fluoroscopic imaging, a copper filter is placed in front of the X‐ray tube. The filter contains a round aperture to reduce radiation dose to outside of the aperture. To equalize the brightness difference between inner and outer ROI regions, brightness compensation was performed by use of a simple weighting method that applies selectively to the inner ROI, the outer ROI, and the boundary zone. A bilateral filtering was applied to the images to reduce relatively high noise in the outer ROI images. To speed up the calculation of our technique for real‐time application, the GPU‐acceleration was applied to the image processing algorithm. We performed a dosimetric measurement using an ion‐chamber dosimeter to evaluate the amount of radiation dose reduction. The reduction of calculation time compared to a CPU‐only computation was also measured, and the assessment of image quality in terms of image noise and spatial resolution was conducted.

Results:

More than 80% of dose was reduced by use of the ROI filter. The reduction rate depended on the thickness of the filter and the size of ROI aperture. The image noise outside the ROI was remarkably reduced by the bilateral filtering technique. The computation time for processing each frame image was reduced from 3.43 seconds with single CPU to 9.85 milliseconds with GPU‐acceleration.

Conclusion:

The proposed technique for X‐ray fluoroscopy can substantially reduce imaging radiation dose to the patient while maintaining image quality particularly in the ROI region in real‐time.
SU‐E‐I‐39: Molecular Image Guided Cancer Stem Cells Therapy
Authors: Abdollahi H
Published: July 2014

Purpose:

Cancer stem cells resistance to radiation is a problematic issue that has caused a big fail in cancer treatment.

Methods:

As a primary work, molecular imaging can indicate the main mechanisms of radiation resistance of cancer stem cells. By developing and commissioning new probes and nanomolecules and biomarkers, radiation scientist will able to identify the essential pathways of radiation resistance of cancer stem cells. As the second solution, molecular imaging is a best way to find biological target volume and delineate cancer stem cell tissues. In the other hand, by molecular imaging techniques one can image the treatment response in tumor and also in normal tissue. In this issue, the response of cancer stem cells to radiation during therapy course can be imaged, also the main mechanisms of radiation resistance and finding the best radiation modifiers (sensitizers) can be achieved by molecular imaging modalities. In adaptive radiotherapy the molecular imaging plays a vital role to have higher tumor control probability by delivering high radiation doses to cancer stem cells in any time of treatment. The outcome of a feasible treatment is dependent to high cancer stem cells response to radiation and removing all of which, so a good imaging modality can show this issue and preventing of tumor recurrence and metastasis.

Results:

Our results are dependent to use of molecular imaging as a new modality in the clinic. We propose molecular imaging as a new radiobiological technique to solve radiation therapy problems due to cancer stem cells.

Conclusion:

Molecular imaging guided cancer stem cell diagnosis and therapy is a new approach in the field of cancer treatment. This new radiobiological imaging technique should be developed in all clinics as a feasible tool that is more biological than physical imaging.
SU‐E‐I‐41: Non‐Cartesian MR Image Reconstruction with Integrated Gradient Non‐Linearity Correction
Authors: Tao S , Trzasko JD , Polley TW , Shu Y , Bernstein MA
Published: July 2014

Purpose:

Nonlinearities in the spatial encoding gradients of MRI systems cause geometric distortion in images. Typically, this is retrospectively corrected via image‐domain interpolation (a.k.a., “gradwarp”) albeit with a loss of spatial resolution. For non‐Cartesian MRI, the latter problem is exaggerated by noise and undersampling artifact. In this study, we describe a novel correction strategy that accounts for gradient nonlinearities during — rather than after — non‐Cartesian MRI reconstruction, and demonstrate that this approach mitigates the resolution loss that can occur with standard methods.

Methods:

To test the proposed method, the American College of Radiology (ACR) quality control phantom was scanned on at 1.5 T (General Electric, v16.0, “zoom” gradient) using a 1.6x undersampled 3D non‐ Cartesian Shells trajectory (GRE, FOV=24 cm3, 120 shells, 16552 shots, 512 readout, matrix=2403). Image reconstruction was first performed via standard k‐space density‐compensated gridding and retrospectively corrected via cubic spline interpolation. Image reconstruction was then separately performed using a k‐space and image‐domain densitycompensated type‐3 non‐uniform fast Fourier transform (NUFFT), which provides a direct mapping between non‐Cartesian k‐space samples and warped image space voxel locations. Thus, no separate distortion correction procedure is needed for the proposed approach. The gradient distortion field was determined using vendor provided calibration data.

Results:

Phantom scan results show that both processing approaches successfully correct geometric distortion. However, visual inspection of the ACR phantom spatial resolution inserts shows that the proposed strategy preserves the resolution of the nominal (uncorrected) reconstruction while “gradwarp” imparts marked spatial blurring (especially for the 1.0 and 1.1 mm inserts) and thus resolution loss.

Conclusion:

We' ve presented a novel reconstruction strategy for non‐Cartesian MRI that corrects for gradient nonlinearities during — rather than after — reconstruction, and thus better preserves image resolution than traditional interpolation‐based methods. This approach is expected to be especially advantageous when imaging with non‐standard magnet geometries.

NIH RR018898; NIH EB10065
SU‐E‐I‐43: Pediatric CT Dose and Image Quality Optimization
Authors: Stevens G , Singh R
Published: July 2014

Purpose:

To design an approach to optimize radiation dose and image quality for pediatric CT imaging, and to evaluate expected performance.

Methods:

A methodology was designed to quantify relative image quality as a function of CT image acquisition parameters. Image contrast and image noise were used to indicate expected conspicuity of objects, and a wide‐cone system was used to minimize scan time for motion avoidance. A decision framework was designed to select acquisition parameters as a weighted combination of image quality and dose. Phantom tests were used to acquire images at multiple techniques to demonstrate expected contrast, noise and dose. Anthropomorphic phantoms with contrast inserts were imaged on a 160mm CT system with tube voltage capabilities as low as 70kVp. Previously acquired clinical images were used in conjunction with simulation tools to emulate images at different tube voltages and currents to assess human observer preferences.

Results:

Examination of image contrast, noise, dose and tube/generator capabilities indicates a clinical task and object‐size dependent optimization. Phantom experiments confirm that system modeling can be used to achieve the desired image quality and noise performance. Observer studies indicate that clinical utilization of this optimization requires a modified approach to achieve the desired performance.

Conclusion:

This work indicates the potential to optimize radiation dose and image quality for pediatric CT imaging. In addition, the methodology can be used in an automated parameter selection feature that can suggest techniques given a limited number of user inputs.

G Stevens and R Singh are employees of GE Healthcare.
SU‐E‐I‐47: Simultaneous Acquisition Quality Assurance and Design of Fused MRIMRS Phantom for the Performance Evaluation
Authors: Song Kyu‐Ho , Lee Do‐Wan , Kim Sang‐Young , Choe Bo‐Young
Published: July 2014

Purpose:

The objectives of this study were to develop MRI‐MRS fused phantom with metabolite inserts for QA, to optimize simultaneously QA parameters using fused phantom and to conduct quantitative analysis of sixteen metabolites solution with layered shape vials using localization sequence.

Methods:

The circular cylinder body was filled with waterdiluted CuSO4(0.7g/L) for having a T1 time shorting function and NaCl(75mM) to make similarly with bodily salt. The solutions of the 10 metabolites were prepared at about 100mM and pH of the solution was adjusted using K2HPO4(72mM) and KH2PO4(28mM) in H2O at pH 7.0. All measurements of MRI, MRS were made using a 3.0 T scanner (Achiva Tx 3.0 T) with SENSE – 32 channel head coil. The water signal of each volume of interest (VOI) was suppressed by variable pulse powers and optimized relaxation delays (VAPOR) applied before progress of the scan. The MRS scan parameters were as follows: point‐resolved spectroscopy (PRESS) sequence; TR, 2000 ms; TE, 35 ms; shim, iterative VOI; NSA, 64. In addition, this study was conducted with jMRUI‐5.0 software, with AMARES for spectral fitting.

Results:

Results of measured magnetic resonance imaging (MRI) factors were as follows: geometric accuracy (191.23±0.60), low contrast object detectability (28.13±0.835), image‐shift distortion (0.41±0.0032). Results of measured magnetic resonance spectroscopy (MRS) factors were as follows: signal‐to‐noise ratio (SNR) of the NAA (25.95±0.35), water suppression percent (99.70±0.09 %), line width of water peak (5.75±0.91 Hz).

Conclusion:

This study was to perform QA on SVS technique using the ACR‐MRS phantom which was refered ACR test guideline. The present study is being measured the quantitative accuracy of the metabolite and the accuracy of the position of the VOI which could be performed by layered shape vials. When QA protocol factors is established in this experiment, it is possible as MVS QA guideline.
SU‐E‐I‐50: Ultrahigh Resolution Reduced Field‐Of‐View Diffusion Tensor Imaging in the Spinal Cord
Authors: Gaggl W , Reuss J , Field A
Published: July 2014

Purpose:

Diffusion Tensor Imaging (DTI) is a well‐established MRI imaging modality for applications in the brain. The typically attainable imaging resolution for clinical DTI sequences is insufficient to image small lesions and assess injury with microstructural changes in the spinal cord (SC). Attempts to reduce the field‐of‐view (FOV) for increasing the imaging resolution have been made using rectangular FOV geometries that work well to efficiently image the sagittal plane. The highest structural details in the SC are however in the axial plane, most efficiently covered by a circular FOV. The aim of this study was to increase the axial DTI resolution in the SC to distinguish the dorsal spinal white‐matter bundles within clinically acceptable acquisition times.

Methods:

A multishot reduced FOV DTI technique named eZOOM that utilizes spatially selective radio‐frequency (RF) pulses and spiral readout has recently been developed by the author (Gaggl, MRM 2014) for application in the brain. In this study the method was adapted to the unique geometry of multichannel spinal RF coil arrays, with improved correction of blurring and misregistration and including peripheral gating to minimize cerebrospinal fluid flow‐artifacts. Several diffusion metrics including the novel normalized axial diffusivity DAn=λ1/∑λ (Gaggl, ASFNR 2013) were calculated and compared to current methods.

Results:

Sub‐millimeter square‐voxel imaging resolutions with image voxel volumes of approximately 1mm3 for a circular axial 8‐cm FOV and 15 diffusion weighting gradient directions were achieved in human for multislice image stacks in the SC with total imaging times of less than 30 minutes at 3T, enabling the separation of important spinal fiber tracts.

Conclusion:

The presented technique improves imaging resolution for DTI in the spinal cord compared to current clinical sequences while allowing to prescribe imaging geometries that excite only a small axial circular FOV in and around the spinal cord and reducing blurring and artifacts.
SU‐E‐I‐51: Use of Blade Sequences in Cervical Spine MR Imaging for Eliminating Motion, Truncation and Flow Artifacts
Authors: Mavroidis P , Lavdas E , Kostopoulos S , Ninos C , Strikou A , Glotsos D , Vlachopoulou A , Oikonomou G , Economopoulos N , Roka V , Sakkas G , Tsagkalis A , Statkahis S , Papanikolaou N , Batsikas G
Published: July 2014

Purpose:

To assess the efficacy of the BLADE technique to eliminate motion, truncation, flow and other artifacts in Cervical Spine MRI compared to the conventional technique. To study the ability of the examined sequences to reduce the indetention and wrap artifacts, which have been reported in BLADE sagittal sequences.

Methods:

Forty consecutive subjects, who had been routinely scanned for cervical spine examination using four different image acquisition techniques, were analyzed. More specifically, the following pairs of sequences were compared: a) T2 TSE SAG vs. T2 TSE SAG BLADE and b) T2 TIRM SAG vs. T2 TIRM SAG BLADE. A quantitative analysis was performed using the signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR) and relative contrast (ReCon) measures. A qualitative analysis was also performed by two radiologists, who graded seven image characteristics on a 5‐point scale (0:non‐visualization; 1:poor; 2:average; 3:good; 4:excellent). The observers also evaluated the presence of image artifacts (motion, truncation, flow, indentation).

Results:

Based on the findings of the quantitative analysis, the ReCON values of the CSF (cerebrospinal fluid)/SC (spinal cord) between TIRM SAG and TIRM SAG BLADE were found to present statistical significant differences (p<0.001). Regarding motion and truncation artifacts, the T2 TSE SAG BLADE was superior compared to the T2 TSE SAG and the T2 TIRM SAG BLADE was superior compared to the T2 TIRM SAG. Regarding flow artifacts, T2 TIRM SAG BLADE eliminated more artifacts compared to the T2 TIRM SAG.

Conclusion:

The use of BLADE sequences in cervical spine MR examinations appears to be capable of potentially eliminating motion, pulsatile flow and trancation artifacts. Furthermore, BLADE sequences are proposed to be used in the standard examination protocols based on the fact that a significantly improved image quality could be achieved.
SU‐E‐I‐52: Validation of Multi‐Frequency Electrical Impedance Tomography Using Computed Tomography
Authors: Kohli K , Liu F , Krishnan K
Published: July 2014

Purpose:

Multi‐frequency EIT has been reported to be a potential tool in distinguishing a tissue anomaly from background. In this study, we investigate the feasibility of acquiring functional information by comparing multi‐frequency EIT images in reference to the structural information from the CT image through fusion.

Methods:

EIT data was acquired from a slice of winter melon using sixteen electrodes around the phantom, injecting a current of 0.4mA at 100, 66, 24.8 and 9.9 kHz. Differential EIT images were generated by considering different combinations of pair frequencies, one serving as reference data and the other as test data. The experiment was repeated after creating an anomaly in the form of an off‐centered cavity of diameter 4.5 cm inside the melon. All EIT images were reconstructed using Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS) package in 2‐D differential imaging mode using one‐step Gaussian Newton minimization solver. CT image of the melon was obtained using a Phillips CT Scanner. A segmented binary mask image was generated based on the reference electrode position and the CT image to define the regions of interest. The region selected by the user was fused with the CT image through logical indexing.

Results:

Differential images based on the reference and test signal frequencies were reconstructed from EIT data. Result illustrated distinct structural inhomogeneity in seeded region compared to fruit flesh. The seeded region was seen as a higherimpedance region if the test frequency was lower than the base frequency in the differential EIT reconstruction. When the test frequency was higher than the base frequency, the signal experienced less electrical impedance in the seeded region during the EIT data acquisition.

Conclusion:

Frequency‐based differential EIT imaging can be explored to provide additional functional information along with structural information from CT for identifying different tissues.
SU‐E‐I‐53: Variation in Measurements of Breast Skin Thickness Obtained Using Different Imaging Modalities
Authors: Nguyen U , Kumaraswamy N , Markey M
Published: July 2014

Purpose:

To investigate variation in measurements of breast skin thickness obtained using different imaging modalities, including mammography, computed tomography (CT), ultrasound, and magnetic resonance imaging (MRI).

Methods:

Breast skin thicknesses as measured by mammography, CT, ultrasound, and MRI were compared. Mammographic measurements of skin thickness were obtained from published studies that utilized standard positioning (upright) and compression. CT measurements of skin thickness were obtained from a published study of a prototype breast CT scanner in which the women were in the prone position and the breast was uncompressed. Dermatological ultrasound exams of the breast skin were conducted at our institution, with the subjects in the upright position and the breast uncompressed. Breast skin thickness was calculated from breast MRI exams at our institution, with the patient in the prone position and the breast uncompressed.

Results:

T tests for independent samples demonstrated significant differences in the mean breast skin thickness as measured by different imaging modalities. Repeated measures ANOVA revealed significant differences in breast skin thickness across different quadrants of the breast for some modalities.

Conclusion:

The measurement of breast skin thickness is significantly different across different imaging modalities. Differences in the amount of compression and differences in patient positioning are possible reasons why measurements of breast skin thickness vary by modality.
SU‐E‐I‐57: Evaluation and Optimization of Effective‐Dose Using Different Beam‐Hardening Filters in Clinical Pediatric Shunt CT Protocol
Authors: Gill K , Aldoohan S , Collier J
Published: July 2014

Purpose:

Study image optimization and radiation dose reduction in pediatric shunt CT scanning protocol through the use of different beam‐hardening filters

Methods:

A 64‐slice CT scanner at OU Childrens Hospital has been used to evaluate CT image contrast‐to‐noise ratio (CNR) and measure effective‐doses based on the concept of CT dose index (CTDIvol) using the pediatric head shunt scanning protocol. The routine axial pediatric head shunt scanning protocol that has been optimized for the intrinsic x‐ray tube filter has been used to evaluate CNR by acquiring images using the ACR approved CT‐phantom and radiation dose CTphantom, which was used to measure CTDIvol. These results were set as reference points to study and evaluate the effects of adding different filtering materials (i.e. Tungsten, Tantalum, Titanium, Nickel and Copper filters) to the existing filter on image quality and radiation dose. To ensure optimal image quality, the scanner routine air calibration was run for each added filter. The image CNR was evaluated for different kVps and wide range of mAs values using above mentioned beam‐hardening filters. These scanning protocols were run under axial as well as under helical techniques. The CTDIvol and the effective‐dose were measured and calculated for all scanning protocols and added filtration, including the intrinsic x‐ray tube filter.

Results:

Beam‐hardening filter shapes energy spectrum, which reduces the dose by 27%. No noticeable changes in image low contrast detectability

Conclusion:

Effective‐dose is very much dependent on the CTDIVol, which is further very much dependent on beam‐hardening filters. Substantial reduction in effective‐dose is realized using beam‐hardening filters as compare to the intrinsic filter. This phantom study showed that significant radiation dose reduction could be achieved in CT pediatric shunt scanning protocols without compromising in diagnostic value of image quality.
SU‐E‐I‐63: Quantitative Evaluation of the Effects of Orthopedic Metal Artifact Reduction (OMAR) Software On CT Images for Radiotherapy Simulation
Authors: Jani S
Published: July 2014

Purpose:

CT simulation for patients with metal implants can often be challenging due to artifacts that obscure tumor/target delineation and normal organ definition. Our objective was to evaluate the effectiveness of Orthopedic Metal Artifact Reduction (OMAR), a commercially available software, in reducing metal‐induced artifacts and its effect on computed dose during treatment planning.

Methods:

CT images of water surrounding metallic cylindrical rods made of aluminum, copper and iron were studied in terms of Hounsfield Units (HU) spread. Metal‐induced artifacts were characterized in terms of HU/Volume Histogram (HVH) using the Pinnacle treatment planning system. Effects of OMAR on enhancing our ability to delineate organs on CT and subsequent dose computation were examined in nine (9) patients with hip implants and two (2) patients with breast tissue expanders.

Results:

Our study characterized water at 1000 HU with a standard deviation (SD) of about 20 HU. The HVHs allowed us to evaluate how the presence of metal changed the HU spread. For example, introducing a 2.54 cm diameter copper rod in water increased the SD in HU of the surrounding water from 20 to 209, representing an increase in artifacts. Subsequent use of OMAR brought the SD down to 78. Aluminum produced least artifacts whereas Iron showed largest amount of artifacts. In general, an increase in kVp and mA during CT scanning showed better effectiveness of OMAR in reducing artifacts. Our dose analysis showed that some isodose contours shifted by several mm with OMAR but infrequently and were nonsignificant in planning process. Computed volumes of various dose levels showed <2% change.

Conclusions:

In our experience, OMAR software greatly reduced the metal‐induced CT artifacts for the majority of patients with implants, thereby improving our ability to delineate tumor and surrounding organs. OMAR had a clinically negligible effect on computed dose within tissues.

Partially funded by unrestricted educational grant from Philips
SU‐E‐I‐64: X‐Ray Coherent Scatter Mammography Simulation
Authors: Hassan L R , MacDonald C A
Published: July 2014

Purpose:

Conventional mammography has poor contrast between healthy and cancerous tissues due to the small difference in attenuation properties. Coherent scatter potentially provides more information because interference of coherently scattered radiation depends on the average intermolecular spacing, and can be used to characterize tissue types. However, typical coherent scatter analysis techniques are not compatible with rapid low dose screening modalities. Coherent scatter slot scan imaging is a novel imaging technique which provides new information with higher contrast. In this work a simulation was performed of coherent scatter slot scan imaging to assess its performance and provide system optimization.

Methods:

In coherent scatter imaging, the coherent scatter is exploited using a conventional slot scan mammography system with anti‐scatter grids tilted at the characteristic angle of cancerous tissues. A Monte Carlo simulation was used to simulate the coherent scatter imaging. System optimization was performed across several parameters, including source voltage and filtration, tilt angle, source and grid distances, grid ratio, and shielding geometry.

Results:

The contrast was high and increased as the grid tilt angle was increased beyond the characteristic angle for the modeled carcinoma, and as the source voltage increased. Source filtration did not have a significant effect on contrast. Increasing grid ratio improved contrast at the expense of decreasing the signal to noise ratio (SNR). As the tumor size is decreased, additional shields to block the fat signal are necessary in order to detect the cancer signal.

Conclusion:

Coherent scatter analysis using a wide slot setup is promising as an enhancement for screening mammography.

This work was supported by National Institutes of Health, # 7 R01EB009715
SU‐E‐I‐66: Radiomics and Image Registration Updates for the Computational Environment for Radiotherapy Research (CERR)
Authors: Apte A , Wang Y , Deasy J
Published: July 2014

Purpose:

To present new tools in CERR for Radiomics, image registration and other software updates and additions.

Methods:

Radiomics: CERR supports generating 3‐D texture metrics based on gray scale co‐occurance. Two new ways to calculate texture features were added: (1) Local Texture Averaging: Local texture is calculated around a voxel within the userdefined bounding box. The final texture metrics are the average of local textures for all the voxels. This is useful to detect any local texture patterns within an image. (2) Image Smoothing: A convolution ball of user‐defined radius is rolled over an image to smooth out artifacts. The texture metrics are then computed on the smooth image. Image Registration: (1) Support was added to import deformation vector fields as well as non‐deformable transformation matrices generated by vendor software and stored in standard DICOM format. (2) Support was added to use image within masks while computing image deformations. CT to MR registration is supported. This registration uses morphological edge information within the images to guide the deformation process. In addition to these features, other noteworthy additions to CERR include (1) Irregularly shaped ROI: This is done by taking intersection between infinitely extended irregular polygons drawn on any of the two views. Such an ROI is more conformal and useful in avoiding any unwanted parts of images that cannot be avoided with the conventional cubic box. The ROI is useful to generate Radiomics metrics. (2) Ability to insert RTDOSE in DICOM format to existing CERR plans. (3) Ability to import multi‐frame PET‐CT and SPECT‐CT while maintaining spatial registration between the two modalities. (4) Ability to compile CERR on Unix‐like systems.

Results:

The new features and updates are available via https://www.github.com/adityaapte/cerr.

Conclusion:

Features added to CERR increase its utility in Radiomics, Image‐Registration and Outcomes modeling.
SU‐E‐I‐67: X‐Ray Fluorescence for Energy Response Calibration of a Photon Counting Detector: A Simulation Study
Authors: Cho H , Ding H , Ziemer B , Molloi S
Published: July 2014

Purpose:

To investigate the feasibility of energy calibration and energy response characterization of a photon counting detector using x‐ray fluorescence.

Methods:

A comprehensive Monte Carlo simulation study was done to investigate the influence of various geometric components on the x‐ray fluorescence measurement. Different materials, sizes, and detection angles were simulated using Geant4 Application for Tomographic Emission (GATE) Monte Carlo package. Simulations were conducted using 100 kVp tungsten‐anode spectra with 2 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm2 in detection area. The fluorescence material was placed 300 mm away from both the x‐ray source and the detector. For angular dependence measurement, the distance was decreased to 30 mm to reduce the simulation time. Compound materials, containing silver, barium, gadolinium, hafnium, and gold in cylindrical shape, were simulated. The object size varied from 5 to 100 mm in diameter. The angular dependence of fluorescence and scatter were simulated from 20° to 170° with an incremental step of 10° to optimize the fluorescence to scatter ratio. Furthermore, the angular dependence was also experimentally measured using a spectrometer (X‐123CdTe, Amptek Inc., MA) to validate the simulation results.

Results:

The detection angle between 120° to 160° resulted in more optimal x‐ray fluorescence to scatter ratio. At a detection angle of 120°, the object size did not have a significant effect on the fluorescence to scatter ratio. The experimental results of fluorescence angular dependence are in good agreement with the simulation results. The Kα and Kβ peaks of five materials could be identified.

Conclusion:

The simulation results show that the x‐ray fluorescence procedure has the potential to be used for detector energy calibration and detector response characteristics by using the optimal system geometry.
SU‐E‐I‐70: Quantification of Noise Reduction Dependency On Spatial Granularity With Adaptive Statistical Iterative Reconstruction
Authors: Zhou Y , Scott A
Published: July 2014

Purpose:

Adaptive statistical iterative reconstruction (ASIR) is often used for noise reduction. However, it may not be clear whether the noise reduction is uniform across different spatial scales. As this is important for lesion detection, we attempted to quantify the noise reduction dependency on spatial scales under different ASIR blending fractions.

Methods:

An abdomen phantom (CIRS TE‐07) simulating the medium sized patient was used. The phantom contains a cylindrical void of 4 cm diameter, filled with an insert containing six groups of cylindrical targets (1% and 2% contrast) of 1.2 mm to 7 mm. Helical scans were conducted using a GE 750HD with 120 kVp, 330 mAs and pitch of 1.375 (CTDI_vol = 18 mGy). The images were reconstructed to 5 mm thickness with filtered‐back projection (FBP) and with ASIR at blending fractions of 10% to 100%. The uniform sections of the contiguous slices were subtracted and the resulted regions were divided into matrices of cells matching the target size from 1.2 mm–7.0 mm. Standard deviations (sd) from the means of all cells were computed as a measure of noise at the target size. The noise reduction factor (NRF) was defined as the ratio of the sd from ASIR to the sd of FBP. The NRF was fitted to ASIR blending percentages (ASIRP) at different target sizes (d).

Results:

The NRF versus ASIRP was fitted to a linear relationship with an intercept of approximately 1.0 and a slope dependent on d (R square = 0.99). The slope versus d was fitted to a power relationship with a power index of – 0.80 and a proportion factor of −0.005 (R square = 0.978).

Conclusion:

The noise reduction with ASIR increases nonlinearly as the spatial scale (or target size) decreases. The result can be of help for ASIR use in target‐specific diagnoses.
SU‐E‐I‐72: First Experimental Study of On‐Board CBCT Imaging Using 2.5MV Beam On a Radiotherapy Linac
Authors: Xu Q , Li R , Yang Y , Xing L
Published: July 2014

Purpose:

Varian TrueBeam version 2.0 comes with a new inline 2.5MV beam modality for image guided patient setup. In this work we develop an iterative volumetric image reconstruction technique specific to the beam and investigate the possibility of obtaining metal artifact free CBCT images using the new imaging modality.

Methods:

An iterative reconstruction algorithm with a sparse representation constraint based on dictionary learning is developed, in which both sparse projection and low dose rate (10 MU/min) are considered. Two CBCT experiments were conducted using the newly available 2.5MV beam on a Varian TrueBeam linac. First, a Rando anthropomorphic head phantom with and without a copper bar inserted in the center was scanned using both 2.5MV and kV (100kVp) beams. In a second experiment, an MRI phantom with many coils was scanned using 2.5MV, 6MV, and kV (100kVp) beams. Imaging dose and the resultant image quality is studied.

Results:

Qualitative assessment suggests that there were no visually detectable metal artifacts in MV CBCT images, compared with significant metal artifacts in kV CBCT images, especially in the MRI phantom. For a region near the metal object in the head phantom, the 2.5MV CBCT gave a more accurate quantification of the electron density compared with kV CBCT, with a ∼50% reduction in mean HU error. As expected, the contrast between bone and soft‐tissue in 2.5MV CBCT decreased compared with kV CBCT.

Conclusion:

On‐board CBCT imaging with the new 2.5MV beam can effectively reduce metal artifacts, although with a reduced softtissue contrast. Combination of kV and MV scanning may lead to metal artifact free CBCT images with uncompromised soft‐tissue contrast.
SU‐E‐I‐73: Clinical Evaluation of CT Image Reconstructed Using Interior Tomography
Authors: Zhang J , Ge G , Winkler M , Cong W , Wang G
Published: July 2014

Purpose:

Radiation dose reduction has been a long standing challenge in CT imaging of obese patients. Recent advances in interior tomography (reconstruction of an interior region of interest (ROI) from line integrals associated with only paths through the ROI) promise to achieve significant radiation dose reduction without compromising image quality. This study is to investigate the application of this technique in CT imaging through evaluating imaging quality reconstructed from patient data.

Methods:

Projection data were directly obtained from patients who had CT examinations in a Dual Source CT scanner (DSCT). Two detectors in a DSCT acquired projection data simultaneously. One detector provided projection data for full field of view (FOV, 50 cm) while another detectors provided truncated projection data for a FOV of 26 cm. Full FOV CT images were reconstructed using both filtered back projection and iterative algorithm; while interior tomography algorithm was implemented to reconstruct ROI images. For comparison reason, FBP was also used to reconstruct ROI images. Reconstructed CT images were evaluated by radiologists and compared with images from CT scanner.

Results:

The results show that the reconstructed ROI image was in excellent agreement with the truth inside the ROI, obtained from images from CT scanner, and the detailed features in the ROI were quantitatively accurate. Radiologists evaluation shows that CT images reconstructed with interior tomography met diagnosis requirements. Radiation dose may be reduced up to 50% using interior tomography, depending on patient size.

Conclusion:

This study shows that interior tomography can be readily employed in CT imaging for radiation dose reduction. It may be especially useful in imaging obese patients, whose subcutaneous tissue is less clinically relevant but may significantly increase radiation dose.
SU‐E‐I‐75: Evaluation of An Orthopedic Metal Artifact Reduction (O‐MAR) Algorithm On Patients with Spinal Prostheses Near Spinal Tumors
Authors: Shen Z , Klahr P , Xia P , Djemil T
Published: July 2014

Purpose:

To evaluate the impact of a commercial orthopedic metal artifact reduction (O‐MAR) algorithm on CT image quality and dose calculation for patients with spinal prostheses near spinal tumors.

Methods:

A CT electron density phantom was scanned twice: with tissue‐simulating inserts only, and with a titanium insert replacing solid water. A patient plan was mapped to the phantom images in two ways: with the titanium inside or outside of the spinal tumor. Pinnacle and Eclipse were used to evaluate the dosimetric effects of O‐MAR on 12‐bit and 16‐bit CT data, respectively. CT images from five patients with spinal prostheses were reconstructed with and without O‐MAR. Two observers assessed the image quality improvement from O‐MAR. Both pencil beam and Monte Carlo dose calculation in iPlan were used for the patient study. The percentage differences between non‐OMAR and O‐MAR datasets were calculated for PTV_min, PTV_max, PTV_mean, PTV_V100, PTV_D90, OAR_V10Gy, OAR_max, and OAR_D0.1cc.

Results:

O‐MAR improved image quality but did not significantly affect the dose distributions and DVHs for both 12‐bit and 16‐ bit CT phantom data. All five patient cases demonstrated some degree of image quality improvement from O‐MAR, ranging from small to large metal artifact reduction. For pencil beam, the largest discrepancy was observed for OARV_10Gy at 5.4%, while the other seven parameters were ≤0.6%. For Monte Carlo, the differences between non‐O‐MAR and O‐MAR datasets were ≤3.0%.

Conclusion:

Both phantom and patient studies indicated that O‐MAR can substantially reduce metal artifacts on CT images, allowing better visualization of the anatomical structures and metal objects. The dosimetric impact of O‐MAR was insignificant regardless of the metal location, image bit‐depth, and dose calculation algorithm. O‐MAR corrected images are recommended for radiation treatment planning on patients with spinal prostheses because of the improved image quality and no need to modify current dose constraints.

This work was supported by a research grant from Philips Healthcare. Paul Klahr is an employee of Philips Healthcare.
SU‐E‐I‐76: Matching Primary and Scattered X‐Ray Spectra for Use in Calculating the Diagnostic Radiation Index of Protection
Authors: Pasciak A , Jones A , Wagner L
Published: July 2014

Purpose:

Lightweight lead‐free or lead‐composite protective garments exploit k‐edge interactions to attenuate scattered X‐rays. Manufacturers specify the protective value of garments in terms of lead equivalence at a single kVp. This is inadequate, as the protection provided by such garments varies with radiation quality in different use conditions. We present a method for matching scattered X‐ray spectra to primary X‐ray spectra. The resulting primary spectra can be used to measure penetration through protective garments, and such measurements can be weighted and summed to determine a Diagnostic Radiation Index for Protection (DRIP).

Methods:

Scattered X‐ray spectra from fluoroscopic procedures were modeled using Monte Carlo techniques in MCNP‐X 2.7. Data on imaging geometry, operator position, patient size, and primary beam spectra were gathered from clinical fluoroscopy procedures. These data were used to generate scattered X‐ray spectra resulting from procedural conditions. Technical factors, including kV and added filtration, that yielded primary X‐ray spectra that optimally matched the generated scattered X‐ray spectra were identified through numerical optimization using a sequential quadratic programming (SQP) algorithm.

Results:

The primary spectra generated with shape functions matched the relative flux in each bin of the scattered spectra within 5%, and half and quarter‐value layers matched within 0.1%. The DRIP for protective garments can be determined by measuring the penetration through protective garments using the matched primary spectra, then calculating a weighted average according to the expected clinical use of the garment. The matched primary spectra are specified in terms of first and second half‐value layers in aluminum and acrylic.

Conclusion:

Lead equivalence is inadequate for completely specifying the protective value of garments. Measuring penetration through a garment using full scatter conditions is very difficult. The primary spectra determined in this work allow for practical primary penetration measurements to be made with equipment readily available to clinical medical physicists.
SU‐E‐I‐79: Effect of Number of Pinholes in Onboard Robotic Multi‐Pinhole SPECT System
Authors: Touch M , Bowsher J , Yan S , Yin F
Published: July 2014

Purpose:

To study the effect of number of pinholes for a novel Single Photon Emission Computed Tomography (SPECT) system for onboard molecular and functional imaging.

Methods:

Comparison studies were performed using simulation for the 49‐pinhole SPECT system and a series of reductions in number of pinholes. Trajectories about the breast of a supine patient were considered. Minimum distances, radii of rotation (RORs), were determined by requirements to fully view the region of interest (ROI) and to avoid collision between the detector and the patient. Reductions in RORs translate into improvements in sensitivity. Starting from the 49‐pinhole system, pinholes were removed pod by pod. The furthest two end pods in the Sup‐Inf direction were removed first for their higher likelihood of alleviating the collision avoidance criteria. After iterating through different combinations of pinhole pods, and selecting three combinations, the corresponding RORs were used to analytically calculate sensitivities.

Results:

Based on the Methods procedure, 3 combination of pods removal were identified: 1) Superior peripheral pod 2) Inferior peripheral pod 3) both pods. RORs were reduced at only one multi‐pinhole stop. Analytic calculation showed that sensitivities were reduced from 0.032 for the 49‐pinhole system to 0.028 for 42‐pinhole and to 0.023 for 39‐pinhole system respectively. The sensitivity per pinhole detector was approximately the same for all three cases.

Conclusion:

For the trajectories considered, only minimal improvements in RORs were identified by removing pinhole pods. Consequently, sensitivities decreased in proportion to the number of pinholes. Studies of other anatomical sites are needed to determine if in some cases sensitivity per pinhole can be improved by removing some pinholes.

PHS/NIH/NCI grant R21‐CA156390‐01A1