bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐I‐28: Evaluating the Organ Dose From Computed Tomography Using Monte Carlo Calculations
Authors: Ono T , Araki F 
Published: July 2014

Purpose:To evaluate organ doses from computed tomography (CT) using Monte Carlo (MC) calculations.Methods:A Philips Brilliance CT scanner (64 slice) was simulated using the GMctdospp (IMPS, Germany) based on the EGSnrc user code. The X‐ray spectra and a bowtie filter for MC simulations were determined to coincide with measurements of half‐value layer (HVL) and off‐center ratio (OCR) profile in air. The MC dose was calibrated from absorbed dose measurements using a Farmer chamber and a cylindrical water phantom. The dose distribution from CT was calculated using patient CT images and organ doses were evaluated from dose volume histograms.Results:The HVLs of Al at 80, 100, and 120 kV were 6.3, 7.7, and 8.7 mm, respectively. The calculated HVLs agreed with measurements within 0.3%. The calculated and measured OCR profiles agreed within 3%. For adult head scans (CTDIvol) =51.4 mGy), mean doses for brain stem, eye, and eye lens were 23.2, 34.2, and 37.6 mGy, respectively. For pediatric head scans (CTDIvol =35.6 mGy), mean doses for brain stem, eye, and eye lens were 19.3, 24.5, and 26.8 mGy, respectively. For adult chest scans (CTDIvol=19.0 mGy), mean doses for lung, heart, and spinal cord were 21.1, 22.0, and 15.5 mGy, respectively. For adult abdominal scans (CTDIvol=14.4 mGy), the mean doses for kidney, liver, pancreas, spleen, and spinal cord were 17.4, 16.5, 16.8, 16.8, and 13.1 mGy, respectively. For pediatric abdominal scans (CTDIvol=6.76 mGy), mean doses for kidney, liver, pancreas, spleen, and spinal cord were 8.24, 8.90, 8.17, 8.31, and 6.73 mGy, respectively. In head scan, organ doses were considerably different from CTDIvol values.Conclusion:MC dose distributions calculated by using patient CT images are useful to evaluate organ doses absorbed to individual patients.
SU‐E‐I‐32: Improving Vessel Delineation in Brain Using Susceptibility Weighted MRI and Group Sparse Reconstruction
Authors: Stefan W , Hwang K , Hazle J , Stafford R 
Published: July 2014

Purpose:To optimize small vessel delineation on non‐contrast enhanced susceptibility weighted MRI protocol for MRI guided intervention in the brain.Methods:Multiple 5mm slices of the brain in a healthy volunteer were acquired with a 16‐echo gradient echo sequence and a 32 channel head coil on a 3T scanner. K‐space was under‐sampled by a factor of 2. Images were reconstructed using 1) the vendor ASSET algorithm, 2) sparsity enforcing TV regularization applied to each slice and echo individually, and 3) group sparse reconstruction on each slice individually but all echoes simultaneously. The group sparse reconstruction increases the signal‐tonoise ratio SNR of later echoes by utilizing the shared edges of brain structure between the echoes, which include the blood vessels. Quantitative PPM maps are computed from the complex images and are post processed by a method that removes background off‐resonance effects. Magnitude images and corrected PPM maps are compared.Results:PPM maps show blood vessels with high contrast. The magnitude images and ppm maps using method 1 appear blurry compared to methods 2 and 3 because of anti‐ringing filters. While small vasculatures appear very sharp in the ppm maps of methods 2 and 3, method 3 appears to have less smoothed magnitude images.Conclusion:To obtain useful blood vessel delineation, low noise susceptibility weighted images are needed. Standard methods like SWI or SWAN require the combination of several slices using a minimum intensity projection to delineate vessels. The method considered here delineates vasculature with high spatial resolution and high SNR in a single slice. Iterative reconstruction methods have superior image quality but also require much more computation time. By reconstructing all echoes simultaneously, group sparse reconstruction produces the sharpest and clearest images.
SU‐E‐I‐36: Investigation of Geometric Image Distortion Correction Using the Bricks Phantom for Multi‐Modality Imaging
Authors: Hong C , Cho H , Lee D , Ahn B 
Published: July 2014

Purpose:To investigate the feasibility of geometric image distortion correction using the LEGO bricks phantom without plastic container, the geometric MR image distortion was evaluated through the procedure of CT to MR image registrationMethod and Materials:Architecturally stable stacked LEGO bricks phantom, 20 cm in diameter, was scanned on a 1.5 T MRI by using T2 FSE sequence and on a 16 slice CT scanner in the sliceslice mode using 120 kVp and 100 mA. The size of each LEGO brick was 31.60 mm2 including four stud 6.47 mm in inner diameter. The space between stud‐and‐tube couplings of the LEGO bricks were filled with distilled water. The geometric distortion was evaluated based on fiducial arrays and control circles which defined by stud pieces. Control circles were determined by the difference between the diameters of the stud pieces in the MR image and the corresponding diameters of stud pieces in the CT image.Results:The fiducial arrays of the LEGO bricks without plastic container were easily visualized in the MR and CT images and there was no water leakage detection within one hour. The control circles were identified and registered. The magnitude of geometric distortion in MR image was gradually increased from near the isocenter to off‐center regions of the magnet, maximum 3%. These results are in good agreement with the standard phantom result.Conclusions:The LEGO are inexpensive, good physical accuracy and easy to construct. The bricks are injection molded in Acrylonitrile butadiene styrene (ABS) and are the geometric tolerance with quite tight. However, plastic container for filling with a solution limits clinical applications in terms of flexibility of phantom design. We measured the geometric MR image distortion using the LEGO bricks phantom precisely without plastic container and it can be easily customized for multimodality imaging.
SU‐E‐I‐45: Reconstruction of CT Images From Sparsely‐Sampled Data Using the Logarithmic Barrier Method
Authors: Xu H 
Published: July 2014

Purpose:To develop and investigate whether the logarithmic barrier (LB) method can result in high‐quality reconstructed CT images using sparsely‐sampled noisy projection dataMethods:The objective function is typically formulated as the sum of the total variation (TV) and a data fidelity (DF) term with a parameter λ that governs the relative weight between them. Finding the optimized value of λ is a critical step for this approach to give satisfactory results. The proposed LB method avoid using λ by constructing the objective function as the sum of the TV and a log function whose augment is the DF term. Newton's method was used to solve the optimization problem. The algorithm was coded in MatLab2013b. Both Shepp‐Logan phantom and a patient lung CT image were used for demonstration of the algorithm. Measured data were simulated by calculating the projection data using radon transform. A Poisson noise model was used to account for the simulated detector noise. The iteration stopped when the difference of the current TV and the previous one was less than 1%.Results:Shepp‐Logan phantom reconstruction study shows that filtered back‐projection (FBP) gives high streak artifacts for 30 and 40 projections. Although visually the streak artifacts are less pronounced for 64 and 90 projections in FBP, the 1D pixel profiles indicate that FBP gives noisier reconstructed pixel values than LB does. A lung image reconstruction is presented. It shows that use of 64 projections gives satisfactory reconstructed image quality with regard to noise suppression and sharp edge preservation.Conclusion:This study demonstrates that the logarithmic barrier method can be used to reconstruct CT images from sparsely‐amped data. The number of projections around 64 gives a balance between the over‐smoothing of the sharp demarcation and noise suppression. Future study may extend to CBCT reconstruction and improvement on computation speed.
SU‐E‐I‐54: Volumetric Breast Density: Comparison of Estimates From Tomosynthesis Reconstructions with Mammography
Authors: Shi L , Vedantham S , Michaelsen K , Krishnaswamy V , Shenoy A , Pogue B , Karellas A , Paulsen K 
Published: July 2014

Purpose:To measure the volumetric breast density (VBD) from digital breast tomosynthesis (DBT) reconstructions and compare with estimates from mammography.Methods:A kernel‐based fuzzy c‐means algorithm developed to segment DBT reconstructed slices to provide anatomic priors for near‐infrared spectroscopy (NIRS) in a multimodality NIRS/DBT clinical‐prototype imaging system was used to quantitate VBD. The VBD was determined from 17 DBT reconstructions of 11 breasts from 9 subjects (6 subjects—unilateral 2‐view, 1 subject—unilateral craniocaudal (CC) view, 2 subjects—bilateral CC view) who underwent multimodality NIRS/DBT imaging. VBD from mammography (Quantra, Hologic Inc.) matched for subject, breast laterality and view was used for comparison. To account for differences in compressed breast thickness (T) between the modalities, the metric normalized VBD (nVBD = VBD/T) was considered.Results:All data satisfied normality assumption (Shapiro‐Wilks, p>0.06). Pearson's correlation (r) and paired t‐tests were used for analysis. The normalized VBD (nVBD) was statistically correlated (r=0.66, p<0.01) between the two modalities, but the VBD was not (r=0.47, p=0.06), as the compressed breast thickness (p=0.01, difference=6.6+/−9.8 mm) and the total breast volume (p<0.01, difference=183+/−169 cc) were higher with mammography than with clinical‐prototype NIRS‐coupled DBT system, while the fibroglandular volume was not different (p=0.21). The intra‐modality nVBD assessed between 2‐views of the same breast (n=6) were better correlated (r=0.86, p=0.03) in DBT than in mammography (r=0.57, p=0.24).Conclusion:Normalized VBD (nVBD) could be a better metric when compressed breast thickness differs between the modalities. nVBD estimated from DBT is better correlated between 2‐views of the same breast than mammography and could improve the consistency in the estimate. The algorithm, in addition to providing anatomic priors for NIRS reconstruction, may also be suitable for breast density estimation. Ability to use DBT reconstructions could facilitate widespread adaptation. Future studies will investigate VBD from images acquired on a combined mammography/DBT system.This work was supported in parts by National Institutes of Health (NIH) grants R01CA139449 and R21CA176470. The contents are solely the responsibility of the authors and do not represent the official views of the NIH or the National Cancer Institute.
SU‐E‐I‐71: KVp Dependence of Transmitted Exposure for a Radiography Unit
Authors: Liang Y , Lynch D , So J , Dutta A 
Published: July 2014

Purpose:To investigate the kVp dependence of the transmitted exposure for a radiography x‐ray unit.Methods:The study used a GE DiscoveryTM XR656 DR unit, a 30 (L) × 30 (W) × 25 cm thick Lucite phantom, two anthropomorphic phantoms (an Alderson RS‐310 chest phantom and a 3M skull phantom), an Unfors detector, and a Radcal 10×9‐6 ion chamber. We measured the entrance exposure and transmitted exposure of each phantom at 60, 70, 80, 90, 100, 110, 120 kVp for mAs range from 2.5 to 200 mAs, without any additional filter. The FOV is 30×30 cm for the Lucite and chest phantom (AP view), and 20×20 cm for skull phantom (Lateral view). The transmitted exposure was measured at the phantom center of the x‐ray exit side. For chest phantom, the transmitted exposures at 3 inch upper right and upper left from the center were also measured. We also checked the reproducibility and accuracy of the DR unit.Results:For each phantom, at every kVp and mAs setting, the transmitted exposure per mAs was calculated and normalized by the relative entrance exposure; the averaged transmitted exposure per mAs at each specific kVp was then determined. For chest phantom, the mean transmitted exposure per mAs was the average of three exit locations. The averaged transmitted exposure per mAs was fit as a power function of kVp. The result showed the transmitted exposure per mAs was approximately proportional to third power of the kVp for two anthropomorphic phantoms and forth power of the kVp for the Lucite phantom.Conclusion:The traditional assumption of fifth power kVp dependence to the transmitted exposure is inaccurate. At the normal radiography kVp range, the transmitted exposure is approximately proportional to third power of the kVp for a typical patient and up to forth power of the kVp for a large patient.
SU‐E‐I‐78: Improving Prostatic Delineation Using Dual‐Energy CT
Authors: Gersh J , Fried D 
Published: July 2014

Purpose:Visual prostatic definition is difficult using conventional CT. This is because the prostate is surrounded closely with tissue of similar electron density. Definition is further hindered when the region contains high‐Z material (such as fiducial markers). Dual‐energy CT (DECT) is a technique where images are rendered using two tube voltages during a single scan session. This study evaluates DECT as a means of improving prostatic volume delineation for radiation oncology.Methods:The patients were scanned using a Definition AS20 (Siemens Healthcare, Malvern, PA). This device uses a single‐tube configuration, where two scans of differing energies are performed in serial. The scans are acquired with tube voltage of 80kVp and 140kVp. Following acquisition, these scan data were used to generate effective monoenergetic scans ranging from 40keV to 190keV. In the current study, the data were presented to observers using a novel program, which allows real‐time adjustment of window, level, and effective keV; all while scrolling through volumetric slices. Three patients were scanned, each with a different high‐contrast material in or around the prostate: I‐125 seeds, gold fiducial markers, and prostatic calcifications. These images are compared to a weighted average of the 80kVp and 140kVP scans, which yield a scan similar to that of a 120 kVp scan, which is a common tube voltage in radiation oncology.Results:Prostatic definition improved in each case. Differentiation of soft tissue from surrounding adipose improved with lower keV, while higher keV provided a reduction of high‐z artifacts. Furthermore, the dynamic adjustment of the keV allowed observers to better recognize regions of differing tissue composition within this relatively homogeneous area.Conclusion:By simultaneously providing the observer with the benefits of high‐energy images and low‐energy images, and allowing adjustment in real‐time, improved imaging in highly homogeneous regions such as the male pelvis is achievable.
SU‐E‐I‐80: Beta‐Minus Emitting Radiotracers Improves Molecular Endoscopy
Authors: Carpenter C , Ma X , Sun C , Pratx G , Cheng Z , Xing L 
Published: July 2014

Purpose:Molecular Endoscopy using Cerenkov Luminescence can be used to monitor the distribution of many clinically‐available PET and SPECT probes for endoscopic applications. A main limitation of Cerenkov is its limited sensitivity to small concentrations of radiotracer when using light guides s. Herein we demonstrate that the use of a high energy beta emitting radioisotope, exemplified here with 90Y provides superior sensitivity to 18F because of its higher light output and its lack of corresponding gamma emission.Methods:A series of phantom experiments were performed to compare the sensitivity and noise of the CLE system for imaging 90Y and 18F. Three vials of known concentrations of 90Y (0.008 μCi, 0.08 μCi, 1 μCi) were placed in centrifuge tubes and isolated from each other. One vial of 18F (100 μCi) was placed in the imaging chamber and imaged over the course of decay (19 hours, 43 minutes, or ∼10 half‐lives). Image time‐points were formed from 5‐minute integrations.Results:Using an SNR of 10 to define the noise‐floor, the 90Y minimum detectable activity was 0.056 μCi. To the contrast, the minimum detectable activity for 18F was 11.63 μCi. These data demonstrate a 207‐fold improvement in SNR of 90Y compared to 18F, when controlled for activity.Conclusion:This study demonstrated that a pure β‐ radionuclide such as 90Y be used is superior to 18F for Cerenkov Endoscopy. Further study is needed to demonstrate its utility in preclinical studies, endoscopic applications, intraoperative, and radiotherapy applications.
SU‐E‐I‐88: Mammography Imaging: Does Positioning Matter?
Authors: Zhang J , Szabunio M 
Published: July 2014

Purpose:In mammography, compression is imperative for quality images and glandular radiation exposure dose. The thickness of the compressed breast directly determines mammography acquisition parameters. The compressed thickness varies due to variation in technologist practice, even for the same patient imaged at different time. This study is to investigate potential effect of the variation in breast positioning on radiation dose and image quality.Methods:Radiation dose at different thicknesses was measured with a BR‐12 breast phantom for both conventional craniocaudal view and tomosynthesis in a Hologic Tomosynthesis mammography system. The CIRS stereotactic needle biopsy training phantom embedded dense masses and microcalcification in various sizes were imaged for image quality evaluation. Radiologists evaluated images. Clinical mammograms from the same patient but acquired at different time were retrospectively retrieved to evaluate potential effects of variation in positioning.Results:Acquisition parameters (kVp and mAs) increase with the increased phantom thickness. Radiation exposure increases following an exponential trend. The stereotactic phantom images showed loss of spatial and contrast resolution with inappropriate positioning. The compressed pressure may not be a good indicator for appropriate positioning. The inclusion of different amount of pectoralis muscle may lead to the same compressed pressure but different compressed thickness. The initial retrospective study of 3 patients showed that there were potential large variations in positioning the same patient at different examination time, resulting in large variations in patient radiation dose and image quality.Conclusion:Variations in patient positioning potentially influence patient radiation dose and image quality. The technologist has the critical responsibility to position patient to provide quality images in spite of different breast and body types. To reduce intra and inter practice variations in positioning patient, a training program among each breast imaging center may be a need.
SU‐E‐I‐89: Assessment of CT Radiation Dose and Image Quality for An Automated Tube Potential Selection Algorithm Using Pediatric Anthropomorphic and ACR Phantoms
Authors: Mahmood U , Erdi Y , Wang W 
Published: July 2014

Purpose:To assess the impact of General Electrics automated tube potential algorithm, kV assist (kVa) on radiation dose and image quality, with an emphasis on optimizing protocols based on noise texture.Methods:Radiation dose was assessed by inserting optically stimulated luminescence dosimeters (OSLs) throughout the body of a pediatric anthropomorphic phantom (CIRS). The baseline protocol was: 120 kVp, 80 mA, 0.7s rotation time. Image quality was assessed by calculating the contrast to noise ratio (CNR) and noise power spectrum (NPS) from the ACR CT accreditation phantom. CNRs were calculated according to the steps described in ACR CT phantom testing document. NPS was determined by taking the 3D FFT of the uniformity section of the ACR phantom. NPS and CNR were evaluated with and without kVa and for all available adaptive iterative statistical reconstruction (ASiR) settings, ranging from 0 to 100%. Each NPS was also evaluated for its peak frequency difference (PFD) with respect to the baseline protocol.Results:For the baseline protocol, CNR was found to decrease from 0.460 ± 0.182 to 0.420 ± 0.057 when kVa was activated. When compared against the baseline protocol, the PFD at ASiR of 40% yielded a decrease in noise magnitude as realized by the increase in CNR = 0.620 ± 0.040. The liver dose decreased by 30% with kVa activation.Conclusion:Application of kVa reduces the liver dose up to 30%. However, reduction in image quality for abdominal scans occurs when using the automated tube voltage selection feature at the baseline protocol. As demonstrated by the CNR and NPS analysis, the texture and magnitude of the noise in reconstructed images at ASiR 40% was found to be the same as our baseline images. We have demonstrated that 30% dose reduction is possible when using 40% ASiR with kVa in pediatric patients.
SU‐E‐I‐90: Medical Physicists' Implication in Diagnostic CT in Switzerland: Results of After One Year of Experience
Authors: Ryckx N. , Elandoy C. , Bize J. , Verdun F.R. 
Published: July 2014

Purpose:Since January 1st 2008, the Swiss ordinance on radiation protection requires the involvement of a medical physicist to support the optimization process of medical imaging techniques using ionizing radiation. After a long process of implementation, this requirement is satisfied all over the country since the beginning of 2013. The goal of this contribution is to summarize the main results obtained in this first year of experience in CT.Methods:We assessed the output and clinical use of 45 CT units using a three‐pronged approach. First, we assessed the output of the device (CTDIvol, primary beam collimation and HU in water at different tube tensions). Secondly, we characterized the local chest and abdomen acquisition and reconstruction protocols using the Catphan 600 phantom. Lastly, we assessed the clinical use of the machine by analyzing an extract of a dozen clinical examinations per unit.Results:9 out of 45 units had incorrect collimator settings, e.g. 4mm instead of 1mm. We witnessed also a large spread in reconstruction parameters, especially for reconstructed slice thickness, thus showing notable variations in low contrast detectability performances. Clinical practice is also clearly spread out. For example, estimated patient effective dose per abdomen examination lies at 18.7+/−12.7mSv (min: 2.0mSv — max: 112.0mSv). Chest and brain scans have a narrower dispersion, but patient effective dose is also spread by about a factor of 10 to 20.Conclusion:The spread in clinical practice being fairly large, it appears of crucial importance to collaborate more closely with radiologists and technologists to assess it. The lack of statistical precision will imply that we analyze clinical practice according to a specific medical demand rather than an anatomical region. Furthermore, low contrast sensitivity (LCD) being a crucial parameter, an objective method using a model observer will be used to assess LCD.