bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐F‐I‐49: Vendor‐Independent, Model‐Based Iterative Reconstruction On a Rotating Grid with Coordinate‐Descent Optimization for CT Imaging Investigations
Authors: Young S , Hoffman J , Noo F , McNitt‐Gray M
Published: July 2016

Purpose:

Iterative reconstruction methods show promise for improving image quality and lowering the dose in helical CT. We aim to develop a novel model‐based reconstruction method that offers potential for dose reduction with reasonable computation speed and storage requirements for vendor‐independent reconstruction from clinical data on a normal desktop computer.

Methods:

In 2012, Xu proposed reconstructing on rotating slices to exploit helical symmetry and reduce the storage requirements for the CT system matrix. Inspired by this concept, we have developed a novel reconstruction method incorporating the stored‐system‐matrix approach together with iterative coordinate‐descent (ICD) optimization. A penalized‐least‐squares objective function with a quadratic penalty term is solved analytically voxel‐by‐voxel, sequentially iterating along the axial direction first, followed by the transaxial direction. 8 in‐plane (transaxial) neighbors are used for the ICD algorithm. The forward problem is modeled via a unique approach that combines the principle of Joseph's method with trilinear B‐spline interpolation to enable accurate reconstruction with low storage requirements. Iterations are accelerated with multi‐CPU OpenMP libraries. For preliminary evaluations, we reconstructed (1) a simulated 3D ellipse phantom and (2) an ACR accreditation phantom dataset exported from a clinical scanner (Definition AS, Siemens Healthcare). Image quality was evaluated in the resolution module.

Results:

Image quality was excellent for the ellipse phantom. For the ACR phantom, image quality was comparable to clinical reconstructions and reconstructions using open‐source FreeCT_wFBP software. Also, we did not observe any deleterious impact associated with the utilization of rotating slices. The system matrix storage requirement was only 4.5GB, and reconstruction time was 50 seconds per iteration.

Conclusion:

Our reconstruction method shows potential for furthering research in low‐dose helical CT, in particular as part of our ongoing development of an acquisition/reconstruction pipeline for generating images under a wide range of conditions. Our algorithm will be made available open‐source as “FreeCT_ICD”.

NIH U01 CA181156; Disclosures (McNitt‐Gray): Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics
SU‐F‐I‐50: Finite Element‐Based Deformable Image Registration of Lung and Heart
Authors: Penjweini R , Kim M , Zhu T
Published: July 2016

Purpose:

Photodynamic therapy (PDT) is used after surgical resection to treat the microscopic disease for malignant pleural mesothelioma and to increase survival rates. Although accurate light delivery is imperative to PDT efficacy, the deformation of the pleural volume during the surgery impacts the delivered light dose. To facilitate treatment planning, we use a finite‐element‐based (FEM) deformable image registration to quantify the anatomical variation of lung and heart volumes between CT pre‐(or post‐) surgery and surface contours obtained during PDT using an infrared camera‐based navigation system (NDI).

Methods:

NDI is used during PDT to obtain the information of the cumulative light fluence on every cavity surface point that is being treated. A wand, comprised of a modified endotrachial tube filled with Intralipid and an optical fiber inside the tube, is used to deliver the light during PDT. The position of the treatment is tracked using an attachment with nine reflective passive markers that are seen by the NDI system. Then, the position points are plotted as three‐dimensional volume of the pleural cavity using Matlab and Meshlab. A series of computed tomography (CT) scans of the lungs and heart, in the same patient, are also acquired before and after the surgery. The NDI and CT contours are imported into COMSOL Multiphysics, where the FEM‐based deformable image registration is obtained. The NDI and CT contours acquired during and post‐PDT are considered as the reference, and the Pre‐PDT CT contours are used as the target, which will be deformed.

Results:

Anatomical variation of the lung and heart volumes, taken at different times from different imaging devices, was determined by using our model. The resulting three‐dimensional deformation map along x, y and z‐axes was obtained.

Conclusion:

Our model fuses images acquired by different modalities and provides insights into the variation in anatomical structures over time.
SU‐F‐I‐52: An Approach to Estimate Noise in Patient Image by Computing the Minimal Difference in Neighborhoods
Authors: Maitree R , Curcuru A , Gach H , Yang D
Published: July 2016

Purpose:

To quantitatively evaluate and compare the accuracy of two advanced methods that can estimate the level of noise per voxel in patient images. These noise estimation methods show promises in: 1) assuring the performance of imaging systems and algorithms, 2) guiding image processing tasks for clinical and research applications, i.e. by optimization of the parameters, and 3) quantifying patient image quality and assisting image quality improvements.

Methods:

We conducted an experiment of 34 repeated MRI scans (TrueFISP sequence) of a swine head in order to obtain a ground truth noise dataset. Two published noise estimation methods were implemented in this study: 1) Minimal Difference in Neighborhoods (MDiN) and 2) high‐pass MDiN. Noise estimation accuracies of two methods were quantitatively measured using the ground truth data and patient MRI images with added Rician noise.

Results:

The experimental results with both swine head images and patient images showed that the MDiN method is more accurate. The high‐pass MDiN method is slightly less but still sufficiently accurate. The MDiN method could be obtained within a 90% accuracy when tested on the ground‐truth dataset.

Conclusion:

We verified the performance of two efficient methods to automatically estimate per voxel noise levels in patient images. Our results suggest that these methods could be confidently used to assist and guide clinical and research applications that require such noise information.

Senior Author Dr. Deshan Yang received research funding form ViewRay and Varian.
SU‐F‐I‐54: Spatial Resolution Studies in Proton CT Using a Phase‐II Prototype Head Scanner
Authors: Plautz Tia E. , Johnson R. P. , Sadrozinski H. F.‐W. , Zatserklyaniy A. , Bashkirov V. , Hurley R. F. , Schulte R. W. , Piersimoni P. , Giacometti V.
Published: July 2016

Purpose:

To characterize the modulation transfer function (MTF) of the pre‐clinical (phase II) head scanner developed for proton computed tomography (pCT) by the pCT collaboration. To evaluate the spatial resolution achievable by this system.

Methods:

Our phase II proton CT scanner prototype consists of two silicon telescopes that track individual protons upstream and downstream from a phantom, and a 5‐stage scintillation detector that measures a combination of the residual energy and range of the proton. Residual energy is converted to water equivalent path length (WEPL) of the protons in the scanned object. The set of WEPL values and associated paths of protons passing through the object over a 360° angular scan is processed by an iterative parallelizable reconstruction algorithm that runs on GP‐GPU hardware. A custom edge phantom composed of water‐equivalent polymer and tissue‐equivalent material inserts was constructed. The phantom was first simulated in Geant4 and then built to perform experimental beam tests with 200 MeV protons at the Northwestern Medicine Chicago Proton Center. The oversampling method was used to construct radial and azimuthal edge spread functions and modulation transfer functions. The spatial resolution was defined by the 10% point of the modulation transfer function in units of lp/cm.

Results:

The spatial resolution of the image was found to be strongly correlated with the radial position of the insert but independent of the relative stopping power of the insert. The spatial resolution varies between roughly 4 and 6 lp/cm in both the the radial and azimuthal directions depending on the radial displacement of the edge.

Conclusion:

The amount of image degradation due to our detector system is small compared with the effects of multiple Coulomb scattering, pixelation of the image and the reconstruction algorithm. Improvements in reconstruction will be made in order to achieve the theoretical limits of spatial resolution.
SU‐F‐I‐55: Performance Evaluation of Digital PET/CT: Medical Physics Basis for the Clinical Applications
Authors: Zhang J , Miller M , Knopp MV
Published: July 2016

Purpose:

Replacement of conventional PMT‐based detector with next generation digital photon counting (DPC) detector is a technology leap for PET imaging. This study evaluated the performance and characteristics of the DPC system and its stability within a 1 year time window following its installation focusing on the medical physics basis for clinical applications.

Methods:

A digital PET/CT scanner using 1:1 coupling of 23,040 crystal: detector elements was introduced and became operational at OSU. We tested and evaluated system performance and characteristics using NEMA NU2‐2012. System stabilities in timing resolution, energy resolution, detector temperature and humidity (T&H) were monitored over 1‐yr. Timing, energy and spatial resolution were characterized across clinically relevant count rate range. CQIE uniformity PET and NEMA IEC‐Body PET with hot spheres varying with sizes and contrasts were performed. PET reconstructed in standard(4mm), High(2mm) and Ultra‐High(1mm) definitions were evaluated.

Results:

NEMA results showed PET spatial resolution (mm‐FWHM) from 4.01&4.14 at 1cm to 5.82&6.17 at 20cm in transverse & axial. 322±3ps timing and 11.0% energy resolution were measured. 5.7kcps/MBq system sensitivity with 24kcps/MBq effective sensitivity was obtained. The peak‐NECR was ∼171kcps with the effective peak‐NECR >650kcps@50kBq/mL. Scatter fraction was ∼30%, and the maximum trues was >900kcps. NEMA IQ demonstrated hot sphere contrast ranging from ∼62%±2%(10mm) to ∼88%±2%(22mm), cold sphere contrast of ∼86%±2%(28mm) and ∼89%±3%(37mm) and excellent uniformity. Monitoring 1‐yr stability, it revealed ∼1% change in timing, ±0.4% change in energy resolution, and <10% variations in T&H. CQIE PET gave <3% SUV variances in axial. 60%–100% recovery coefficients across sphere sizes and contrast levels were achieved.

Conclusion:

Characteristics and stability of the next generation DPC PET detector system over an 1‐yr time window was excellent and better than prior experiences. It demonstrated improved and robust system characteristics and performance in spatial resolution, sensitivity, timing and energy resolution, count rate and image quality.

Michael Miller is an employee of Philips Healthcare
SU‐F‐I‐57: Evaluate and Optimize PET Acquisition Overlap in 18F‐FDG Oncology Wholebody PET/CT: Can We Scan PET Faster?
Authors: Zhang J , Natwa M , Hall NC , Knopp MU , Zhang B , Tung C , Knopp MV
Published: July 2016

Purpose:

The longer patient has to remain on the table during PET imaging, the higher the likelihood of motion artifacts due to patient discomfort. This study was to investigate and optimize PET acquisition overlap in 18F‐FDG oncology wholebody PET/CT to speed up PET acquisition and improve patient comfort.

Methods:

Wholebody 18F‐FDG PET/CT of phantoms, 8 pre‐clinical patients (beagles) and 5 clinical oncology patients were performed in 90s/bed on a time‐of‐flight Gemini TF 64 system. Imaging of phantoms and beagles was acquired with reduced PET overlaps (40%, 33%, 27%, 20%, 13% and no overlap) in addition to the system default (53%). In human studies, 1 or 2 reduced overlaps from the listed options were used to acquire PET/CT sweeps right after the default standard of care imaging. Image quality was blindly reviewed using visual scoring criteria and quantitative SUV assessment. NEMA PET sensitivity was performed under different overlaps.

Results:

All PET exams demonstrated no significant impact on the visual grades for overlaps >20%. Blinded reviews assigned the best visual scores to PET using overlaps 53%–27%. Reducing overlap to 27% for oncology patients (12‐bed) saved an average of ∼40% acquisition time (11min) compared to using the default overlap (18min). No significant SUV variances were found when reducing overlap to half of default for cerebellum, lung, heart, aorta, liver, fat, muscle, bone marrow, thighs and target lesions (p>0.05), except expected variability in urinary system.

Conclusion:

This study demonstrated by combined phantom, pre‐clinical and clinical PET/CT scans that PET acquisition overlap in axial of today's systems can be reduced and optimized. It showed that a reduction of PET acquisition overlap to 27% (half of system default) can be implemented to reduce table time by ∼40% to improve patient comfort and minimize potential motion artifacts, without prominently degrading image quality or compromising PET quantification.
SU‐F‐I‐58: Image Quality Comparisons of Different Motion Magnitudes and TR Values in MR‐PET
Authors: Patrick J , Tavallaei M , Thompson R , Stodilka R , Drangova M , Gaede S
Published: July 2016

Purpose:

The aim of this work is to evaluate the accuracy and sensitivity of a respiratory‐triggered MR‐PET protocol in detecting four different sized lesions at two different magnitudes of motion, with two different TR values, using a novel PET‐MR‐CT compatible respiratory motion phantom.

Methods:

The eight‐compartment torso phantom was setup adjacent to the motion stage, which moved four spherical compartments (28, 22, 17, 10 mm diameter) in two separate (1 and 2 cm) linear motion profiles, simulating a 3.5 second respiratory cycle. Scans were acquired on a 3T MR‐PET system (Biograph mMR; Siemens Medical Solutions, Germany). MR measurements were taken with: 1) Respiratory‐triggered T2‐weighted turbo spin echo (BLADE) sequence in coronal orientation, and 2) Real‐time balanced steady‐state gradient echo sequence (TrueFISP) in coronal and sagittal planes. PET was acquired simultaneously with MR. Sphere geometries and motion profiles were measured and compared with ground truths for T2 BLADE‐TSE acquisitions and real time TrueFISP images. PET quantification and geometry measurements were taken using standardized uptake values, voxel intensity plots and were compared with known values, and examined alongside MR‐based attenuation maps. Contrast and signal‐to‐noise ratios were also compared for each of the acquisitions as functions of motion range and TR.

Results:

Comparison of lesion diameters indicate the respiratory triggered T2 BLADE‐TSE was able to maintain geometry within −2 mm for 1 cm motion for both TR values, and within −3.1 mm for TR = 2000 ms at 2 cm motion. Sphere measurements in respiratory triggered PET images were accurate within +/− 5 mm for both ranges of motion for 28, 22, and 17 mm diameter spheres.

Conclusion:

Hybrid MR‐PET systems show promise in imaging lung cancer in non‐compliant patients, with their ability to acquire both modalities simultaneously. However, MR‐based attenuation maps are still susceptible to motion derived artifacts and pose the potential to affect PET accuracy.
SU‐F‐I‐59: Quality Assurance Phantom for PET/CT Alignment and Attenuation Correction
Authors: Lin T , Hamacher K
Published: July 2016

Purpose:

This study utilizes a commercial PET/CT phantom to investigate two specific properties of a PET/CT system: the alignment accuracy of PET images with those from CT used for attenuation correction and the accuracy of this correction in PET images.

Methods:

A commercial PET/CT phantom consisting of three aluminum rods, two long central cylinders containing uniform activity, and attenuating materials such as air, water, bone and iodine contrast was scanned using a standard PET/CT protocol. Images reconstructed with 2 mm slice thickness and a 512 by 512 matrix were obtained. The center of each aluminum rod in the PET and CT images was compared to evaluate alignment accuracy. ROIs were drawn on transaxial images of the central rods at each section of attenuating material to determine the corrected activity (in BQML). BQML values were graphed as a function of slice number to provide a visual representation of the attenuation‐correction throughout the whole phantom.

Results:

Alignment accuracy is high between the PET and CT images. The maximum deviation between the two in the axial plane is less than 1.5 mm, which is less than the width of a single pixel. BQML values measured along different sections of the large central rods are similar among the different attenuating materials except iodine contrast. Deviation of BQML values in the air and bone sections from the water section is less than 1%.

Conclusion:

Accurate alignment of PET and CT images is critical to ensure proper calculation and application of CT‐based attenuation correction. This study presents a simple and quick method to evaluate the two with a single acquisition. As the phantom also includes spheres of increasing diameter, this could serve as a straightforward means to annually evaluate the status of a modern PET/CT system.
SU‐F‐I‐60: ICC MIWG Displays: Final Recommendations for Visualization of Medical Content On Color Display Systems
Authors: Kimpe T , Green P , Revie C , Flynn M
Published: July 2016

Purpose:

Use of color images in medical imaging has increased significantly the last few years. There is no agreement yet on what is an appropriate visualization framework for color medical images. This lack of standardization results into large variability of color appearance and makes consistency and quality assurance a challenge. The ICC Medical‐Imaging‐Working‐Group (MIWG) has defined recommendations for visualization of medical content on color display systems, whereby DICOM GSDF images, pseudo color images and color accurate images can all be presented effectively on the same display.

Methods:

The MIWG characterized a wide range of color display systems (consumer, professional and medical), and collected representative greyscale and color medical images. Simulations and bench testing was done to quantitatively compare the performance of various architectures and imaging pipelines in an ICC framework context. This allowed making recommendations on imaging pipeline architectures, and defining minimum requirements to guarantee minimum performance levels.

Results:

The ICC framework specification supports many possible architectures, profile types and pipeline characteristics. Numerous experiments have been performed to understand the effects related to choice of System design choices such as architecture, profile type (matrix, LUT, device, …) and pipeline specifications (eg. bit depth, LUT size). The impact of inaccurate estimation of display luminance/contrast/tone rendering curve has also been studied. Specific recommendations have been made related to system configuration, ICC framework/CMM, and calibration process.

Conclusion:

There is a need to standardize how medical color images need to be visualized. The ICC Medical Imaging Working Group has defined recommendations for visualization of medical content on color display systems. It has been shown that it is possible to achieve accurate greyscale, pseudo color and absolute color visualization of medical images by means of the ICC framework, at least when appropriate choices are made related to profile specification, imaging pipeline and calibration procedure.

Tom Kimpe, employee Barco NV
SU‐F‐I‐61: Assessment and Characterization of the Built‐in Internal Photometer of Primary Diagnostic Monitors
Authors: Ruuge A , Erdi Y , Mahmood U
Published: July 2016

Purpose:

The conformance of Primary Diagnostic Monitors (PDMs) to the DICOM GSDF is increasingly required by several state and city regulators. Our purpose was to quantitatively characterize the luminance performance of the internal, built in photometer of BARCO monitors against an externally calibrated luminance meter.

Methods:

Thirty one PDMs (BARCO) were included in our analysis. An externally calibrated photometer (RaySafe Solo Light) was used to measure the luminance and illuminance values. Measured monitors were located at various hospital sites, radiology physicians’ offices and radiology reading rooms. All measured PDMs were equipped with the manufacturer's built‐in photometers and connected to Barco MediCal QA web service for manual and automatic quality control measurements. PDM combinations included 1, 2 and 4 monitors depending on the location. TG‐18 and SMPTE test patterns were used to evaluate monitor performance.

Results:

All the PDMs exceeded the luminance ratio of 250:1, as required by NYC PDM guidelines. One PDM failed the NYC requirement for the minimal luminance level of 350 cd/m2. As compared to the external photometer, the difference in measurement of the maximum luminance with the built‐in photometer was found to exceed 5% on 6 of the PDM measured, with a maximum deviation of 10%. The age of the monitors that failed was on average 5 years. All monitors passed the luminance uniformity test, which was 30% from the center of the monitor to the 4 corner locations. Four PDMs failed the Gray Scale Display Function (GSDF) calibration.

Conclusion:

For the consistent display of medical images and continued conformance with the DICOM GSDF standard, it is essential to compare the performance of the built‐in photometer with an externally calibrated photometer for monitors that are older than 5 years.
SU‐F‐I‐65: Fatty Acid Quantification in High‐Fat‐Diet Induced Abnormal Intrahepatic Triglyceride Storage Using Internal Standard Method at 3.0 T
Authors: Song K‐H , Yoo C‐H , Lim S‐I , Choe B‐Y
Published: July 2016

Purpose:

The objective of this study was to determine the metabolic changes in a rat model of high‐fat‐diet‐induced non‐alcoholic fatty liver disease (NAFLD) by using single‐voxel 1H‐MRS with a 3.0 T MRI scanner.

Methods:

The examination were performed on a 3.0T scanner using a 4‐channel animal coil for higher resolution. This method used point‐resolved spectroscopy (PRESS) (repetition time (TR)/echo time (TE) = 6000/35 ms; number of signal averages (NSA) = 64). To measure the lipid content, we quantified total lipids ((‐CH2‐)n/noise), total saturated fatty acids (3(‐CH2‐)/2(‐CH3)), total unsaturated fatty acids (3(‐CH2‐C=C‐CH2‐)/4(‐CH3)), total unsaturated bonds index (3(‐CH=CH‐)/2(‐CH3)), and polyunsaturated bonds index (3(=C‐CH2‐C=)/2(‐CH3)) by separating each peak area of (CH2)n, CH2C=CCH, =CCH2C=, and CH=CH by CH3. The ‐CH3 (0.90 ppm) peak was used as an internal chemical shift reference.

Results:

Total lipids and total saturated fatty acids were substantially upregulated in high‐fat‐diet‐fed rats in comparison with baseline values (total lipids, 16.22±6.60×10−4; total saturated fatty acids, 10.26±1.91). The resulting data on lipid accumulation were statistically significant in terms of total lipids at 3 weeks (78.65±36.20, p = 0.002), 6 weeks (88.14±22.36, p < 0.001), 9 weeks (78.55±31.29, P < 0.001), and 15 weeks (107.87±39.95, p < 0.001) after initiation of the high‐fat diet.

Conclusion:

Our results of noninvasive in vivo MRS are based on accurate monitoring of the changes in lipid content, which were verified using the data on saturated fatty acids and unsaturated fatty acids. We can conclude that localized MRS holds promise as an indicator of fatty liver diseases in humans and in animal models for monitoring treatment.
SU‐F‐I‐66: The Effects of Nicotinic Agonists On Rat Hippocampal Glutamatergic Fluctuation by Using Proton Magnetic Resonance Spectroscopy at 9.4T
Authors: Lim S‐I , Song K‐H , Yoo C‐H , Woo D‐C , Choe B‐Y
Published: July 2016

Purpose:

Nicotine exerts its effects through the activation of nicotinic acetylcholine receptors (nAChRs). Varenicline, a smoking cessation aid, is a partial agonist acting at the α4β2 nAChRs. Although nicotine and varenicline contribute to the reward system at the same time, the influence of the substances on hippocampal neurochemical changes has not been investigated yet. We therefore studied the effects of repeated nicotine exposure and varenicline administration on hippocampus of rats by using in vivo proton magnetic resonance spectroscopy (1H MRS) at 9.4T.

Methods:

Male Wistar rats (n = 11; mean body weight, 304.9 ± 9.9 g) were divided into 3 groups: control rats (control, n = 3); nicotine‐induced rats (nicotine, n = 4); and nicotine‐ and varenicline‐induced rats (varenicline, n = 4). Acquisition of in vivo MRS was conducted by using 9.4 T Agilent Scanner. The linear combination of model spectra (LCModel, version 6.3, Stephen W. Provencher) fitting software was used to quantify the metabolites in the frequency domain, using the basis metabolites.

Results:

In this study, the results show the tendency of increased Glu level in nicotine group than in the control and varenicline groups. Moreover, GSH and NAA levels tended to decrease in the nicotine group in comparison with those in the control and varenicline groups.

Conclusion:

These findings indicate that the hippocampus is integrally linked to the brain reward sensitization involved in addiction and glutamate release through mobilization of intracellular calcium stores. Further, oxidative stress and toxicity of nicotine on brain would cause the decline of GSH and NAA. In conclusion, we found that varenicline effectively inhibits the reward cycle.
SU‐F‐I‐67: Neurometabolic Effect Induced by Repeated Exposure to Dizocilpine On Prefrontal Cortex of Schizophrenic Animal Model Using In Vivo Proton Magnetic Resonance Spectroscopy at 9.4 T
Authors: Yoo C‐H , Song K‐H , Lim S‐I , Woo D‐C , Choe B‐Y
Published: July 2016

Purpose:

Repeated exposure of dizocilpine (MK‐801) can provide a pathophysiological model for progressive development of schizophrenia. In vivo proton magnetic resonance spectroscopy (1H MRS) was widely used for non‐invasive measurement of neurometabolites, and assessment of disease‐induced neurometabolic alterations. The purpose of this study was to investigate neurometabolic alteration in prefrontal cortex (PFC) with respect to progression (from first‐episode to chronic stage) of schizophrenia by using in vivo 1H MRS.

Methods:

We used high‐field 1H MRS to investigate the neurometabolic alteration in the PFC region of the rats (N = 13) by comparing before and after 6 day of MK‐801 (0.5 mg/kg) treatment. A point‐resolved spectroscopy (PRESS) sequence was used to obtain spectra in a 22.5 µL of volume of interest carefully located in PFC region with parameters like follow; repetition time, 5000ms; echo time (TE), 13.4 ms; averages = 256. Another experiment group (N = 11) were conducted behavior test by recording the behavior for 20 min.

Results:

All the rats showed hyperlocomotion, stereotyped behaviors before initiation of MRS. Significantly increased level (N = 7, p < 0.05) of N‐acetylasrparate (NAA), glutamate (Glu), taurine and decreased level (N = 6, p < 0.05) of NAA, Glu and phosphocreatine were observed between baseline and day 6. Both metabolic alterations are consistent with results of first‐episode and chronic schizophrenia respectively.

Conclusion:

From our findings, the repeated MK‐801 model could be a pathophysiological model which can provide an insight into the transition from first‐episode to chronic stage. This is first time to investigate effects of repeated MK‐801 using high‐field in vivo 1H MRS. We expect our findings can contribute to combining previous diverging results into one pathophysiological interpretation, which can postulate the origin of diverging results to the progression of schizophrenia.
SU‐F‐I‐70: Investigation of Gafchromic EBT3 Film Energy Dependence Using Proton, Photon, and Electron Beams
Authors: Ferreira C , Schnell E , Ahmad S , De La Fuente Herman T
Published: July 2016

Purpose:

To investigate the energy dependence of Gafchromic EBT3 film over a range of clinically used proton, photon and electron energies.

Methods:

Proton beam energies of 117 and 204 MeV, corresponding respectively to ranges in water of 10 cm and 27 cm from a Mevion S250 double scatter system unit were used. Electron energies of 6 and 20 MeV and photon energies of 6 and 18 MV from a Varian Clinac 21EX Linac were used. Two pieces of film (5×5 cm2) were irradiated sequentially for doses of 100, 500, and 1000 cGy for all energies and modalities. Films were placed on the central beam axis for a 10×10 cm2 field size in the middle of spread out Bragg peak (SOBP) for proton and in respective dmax for photon and electron energies. Films were scanned on a flatbed Epson Expression 10000 XL scanner on the central region of the scanning window using 48‐bit, 300 dpi, and landscape orientation after 48 hours post‐irradiation of film to account for optical density (OD) stabilization. Film analysis of the red channel was performed using ImageJ 1.48v (National Institutes of Health).

Results:

The energy dependency of EBT3 among all energies and modalities for all doses studied was small within measurement uncertainties (1σ = ± 4.1%). The mean net OD in red channel for films receiving the same dose in the same energy modality had standard deviations within 0.9% for photons, 4.9% for electrons and 1.8% for protons. It was observed that film pieces were activated during proton irradiation, e.g., 7 mR/hr at surface after 30 minutes of irradiation, lasting for 2 hours post irradiation.

Conclusion:

EBT3 energy dependency was evaluated for clinically used proton, photon, and electron energies. The film self‐activation may have contributed to fog and negligible dose.
SU‐F‐I‐76: Fluoroscopic X‐Ray Beam Profiles for Spectra Incorporating Copper Filtration
Authors: Wunderle K , Godley A , Shen Z , Rakowski J , Dong F
Published: July 2016

Purpose:

The purpose of this investigation is to characterize and quantify X‐ray beam profiles for fluoroscopic x‐ray beam spectra incorporating spectral (copper) filtration.

Methods:

A PTW (Freiburg, Germany) type 60016 silicon diode detector and PTW MP3 water tank were used to measure X‐ray beam profiles for 60, 80, 100 and 120 kVp x‐ray beams at five different copper filtration thicknesses ranging from 0–0.9 mm at 22 and 42 cm fields of view and depths of 1, 5, and 10 cm in both the anode‐cathode axis (inplane) and cross‐plane directions. All measurements were acquired on a Siemens (Erlangen, Germany) Artis ZeeGo fluoroscope inverted from the typical orientation providing an x‐ray beam originating from above the water surface with the water level set at 60 cm from the focal spot.

Results:

X‐ray beam profiles for beam spectra without copper filtration compared well to previously published data by Fetterly et al. [Med Phys, 28, 205 (2001)]. Our data collection benefited from the geometric orientation of the fluoroscope, providing a beam perpendicular to the tank water surface, rather than through a thin side wall as did the previously mentioned study. Profiles for beams with copper filtration were obtained which have not been previously investigated and published. Beam profiles in the anode‐cathode axis near the surface and at lower x‐ray energy exhibited substantial heel effect, which became less pronounced at greater depth. At higher energy with copper filtration in the beam, the dose falloff out‐of‐field became less pronounced, as would be anticipated given higher scatter photon energy.

Conclusion:

The x‐ray beam profile data for the fluoroscopic x‐ray beams incorporating copper filtration are intended for use as reference data for estimating doses to organs or soft tissue, including fetal dose, involving similar beam qualities or for comparison with mathematical models.
SU‐F‐I‐80: Correction for Bias in a Channelized Hotelling Model Observer Caused by Temporally Variable Non‐Stationary Noise
Authors: Favazza C , Fetterly K
Published: July 2016

Purpose:

Application of a channelized Hotelling model observer (CHO) over a wide range of x‐ray angiography detector target dose (DTD) levels demonstrated substantial bias for conditions yielding low detectability indices (d’), including low DTD and small test objects. The purpose of this work was to develop theory and methods to correct this bias.

Methods:

A hypothesis was developed wherein the measured detectability index (d'b) for a known test object is positively biased by temporally variable non‐stationary noise in the images. Hotelling's T2 test statistic provided the foundation for a mathematical theory which accounts for independent contributions to the measured d'b value from both the test object (d'o) and non‐stationary noise (d'ns). Experimental methods were developed to directly estimate d'o by determining d'ns and subtracting it from d'b, in accordance with the theory. Specifically, d'ns was determined from two sets of images from which the traditional test object was withheld. This method was applied to angiography images with DTD levels in the range 0 to 240 nGy and for disk‐shaped iodine‐based contrast targets with diameters 0.5 to 4.0 mm.

Results:

Bias in d’ was evidenced by d'b values which exceeded values expected from a quantum limited imaging system and decreasing object size and DTD. d'ns increased with decreasing DTD, reaching a maximum of 2.6 for DTD = 0. Bias‐corrected d'o estimates demonstrated sub‐quantum limited performance of the x‐ray angiography for low DTD. Findings demonstrated that the source of non‐stationary noise was detector electronic readout noise.

Conclusion:

Theory and methods to estimate and correct bias in CHO measurements from temporally variable non‐stationary noise were presented. The temporal non‐stationary noise was shown to be due to electronic readout noise. This method facilitates accurate estimates of d’ values over a large range of object size and detector target dose.
SU‐F‐J‐01: Measurement of Blood Flow During PDT Using Diffuse Correlation Spectroscopy
Authors: Ong Y , Penjweini R , Yodh A , Zhu T
Published: July 2016

Purpose:

To investigate the variation in blood flow during PDT and to determine the oxygen supplying rate, g, to refine the empirical macroscopic model.

Methods:

RIF tumors were propagated in female C3H mice by injecting cell suspension at a concentration of 1×106 cells/ml on the shoulder region. Photosensitizer(e.g., HPPH) was injected into the mice through tail vein at a concentration of 0.25 mg/kg when the tumors grew to ∼6 mm in diameter and depth. Temporal changes of tissue oxygen concentration were recorded prior, during and post PDT treatment using OxyLite single‐channel tissue pO2 monitor(OXFORD OPTRONIX). [3O2] was approximated by multiplying the measured pO2 with 3O2 solubility in tissue(1.295 µM/mmHg). The experimental [3O2] profile were compared with those simulated with the macroscopic model with and without considering the blood flow changes. The dynamical change of blood flow during PDT was simulated by making parameter g to be time dependent, in which the g function was obtained from Photofrin‐mediated PDT in RIF tumors. The relative blood flow changes in the tumors prior, during and post PDT treatment were measured using diffuse correlation spectroscopy (DCS) in a non‐contact configuration.

Results:

Both macroscopic models, with and without blood flow changes, show reasonably good agreement with the experimental [3O2] measurements. However, a rapid increase in the measured [3O2] between 700–1200s during PDT treatment could not be simulated with our empirical models. As blood flow is the direct measure of tissue oxygen supply and different photosensitizers might impact the blood flow differently, detailed studies are essential to investigate the variation in blood flow changes and the impact on the [3O2] consumption using different photosensitizers.

Conclusion:

DCS can be used to monitor relative blood flow noninvasively. The continuous input of oxygen supply rate is essential to refine our empirical macroscopic model to better predict PDT treatment outcome.
SU‐F‐J‐05: The Effect of Air Pockets in the Urinary Bladder During Bladder Hyperthermia Treatment
Authors: Schooneveldt G. , Kok H.P. , Bakker A. , Geijsen E.D. , de Reijke T.M. , Crezee J.
Published: July 2016

Purpose:

Hyperthermia combined with Mitomycin C is used for the treatment of non‐muscle invasive bladder cancer (NMIBC), using a phased array system of microwave antennas for bladder heating. Often some air is present in the bladder, which effectively blocks the microwave radiation, potentially preventing proper treatment of that part of the bladder. Air can be a relevant fraction of the bladder content and large air pockets are expected to have a noticeable influence on achieved temperatures.

Methods:

We analysed 14 NMIBC patients treated at our institute with our AMC‐4 hyperthermia device with four 70MHz antennas around the pelvis. A CT scan was made after treatment and a physician delineated the bladder on the CT scan. On the same scan, the amount of air present in the bladder was delineated. Using our in‐house developed hyperthermia treatment planning system, we simulated the treatment using the clinically applied device settings. We did this once with the air pocket delineated on the CT scan, and once with the same volume filled with bladder tissue.

Results:

The patients had on average 4.2ml (range 0.8–10.1ml) air in the bladder. The bladder volume was delineated by the physician, that is including air pocket and bladder wall, was on average 253ml (range 93–452ml). The average volume in which changes exceeded 0.25°C was 22ml (range 0–108 ml), with the bladder being up to 2°C cooler when an air pocket was present. Except for extreme cases, there was no evident relation between the quantity of air and the difference in temperature.

Conclusion:

The effect of an air pocket in the bladder during bladder hyperthermia treatment varies strongly between patients. Generally, this leads to lower temperatures in the bladder, potentially affecting treatment quality, and suggesting that care need be taken to minimise the size of air pockets during hyperthermia treatments.

The KWF Dutch Cancer Society financially supported this work, grant UVA 2012‐5539.
SU‐F‐J‐08: Quantitative SPECT Imaging of Ra‐223 in a Phantom
Authors: Yue J , Hobbs R , Sgouros G , Frey E
Published: July 2016

Purpose:

Ra‐223 therapy of prostate cancer bone metastases is being used to treat patients routinely. However, the absorbed dose distribution at the macroscopic and microscopic scales remains elusive, due to the inability to image the small activities injected. Accurate activity quantification through imaging is essential to calculate the absorbed dose in organs and sub‐units in radiopharmaceutical therapy, enabling personalized absorbed dose‐based treatment planning methodologies and more effective and optimal treatments.

Methods:

A 22 cm diameter by 20 cm long cylindrical phantom, containing a 3.52 cm diameter sphere, was used. A total of 2.01 MBq of Ra‐223 was placed in the phantom with 177.6 kBq in the sphere. Images were acquired on a dual‐head Siemens Symbia T16 gamma camera using three 20% full‐width energy windows and centered at 84, 154, and 269 keV (120 projections, 360° rotation, 45 s per view). We have implemented reconstruction of Ra‐223 SPECT projections using OS‐EM (up to 20 iterations of 10 subsets) with compensation for attenuation using CT‐based attenuation maps, collimator‐detector response (CDR) (including septal penetration, scatter and Pb x‐ray modeling), and scatter in the patient using the effective source scatter estimation (ESSE) method. The CDR functions and scatter kernels required for ESSE were computed using the SIMIND MC simulation code. All Ra‐223 photon emissions as well as gamma rays from the daughters Rn‐219 and Bi‐211 were modeled.

Results:

The sensitivity of the camera in the three combined windows was 107.3 cps/MBq. The visual quality of the SPECT images was reasonably good and the activity in the sphere was 27% smaller than the true activity. This underestimation is likely due to partial volume effect.

Conclusion:

Absolute quantitative Ra‐223 SPECT imaging is achievable with careful attention to compensate for image degrading factors and system calibration.
SU‐F‐J‐16: Planar KV Imaging Dose Reduction Study
Authors: Gershkevitsh E , Zolotuhhin D
Published: July 2016

Purpose:

IGRT has become an indispensable tool in modern radiotherapy with kV imaging used in many departments due to superior image quality and lower dose when compared to MV imaging. Many departments use manufacturer supplied protocols for imaging which are not always optimised between image quality and radiation dose (ALARA).

Methods:

Whole body phantom PBU‐50 (Kyoto Kagaku ltd., Japan) for imaging in radiology has been imaged on Varian iX accelerator (Varian Medical Systems, USA) with OBI 1.5 system. Manufacturer's default protocols were adapted by modifying kV and mAs values when imaging different anatomical regions of the phantom (head, thorax, abdomen, pelvis, extremities). Images with different settings were independently reviewed by two persons and their suitability for IGRT set‐up correction protocols were evaluated. The suitable images with the lowest mAs were then selected. The entrance surface dose (ESD) for manufacturer's default protocols and modified protocols were measured with RTI Black Piranha (RTI Group, Sweden) and compared. Image quality was also measured with kVQC phantom (Standard Imaging, USA) for different protocols. The modified protocols have been applied for clinical work.

Results:

For most cases optimized protocols reduced the ESD on average by a factor of 3(range 0.9–8.5). Further reduction in ESD has been observed by applying bow‐tie filter designed for CBCT. The largest reduction in dose (12.2 times) was observed for Thorax lateral protocol. The dose was slightly increased (by 10%) for large pelvis AP protocol.

Conclusion:

Manufacturer's default IGRT protocols could be optimised to reduce the ESD to the patient without losing the necessary image quality for patient set‐up correction. For patient set‐up with planar kV imaging the bony anatomy is mostly used and optimization should focus on this aspect. Therefore, the current approach with anthropomorphic phantom is more advantageous in optimization over standard kV quality control phantoms and SNR metrics.
SU‐F‐J‐22: Lung VolumeVariability Assessed by Bh‐CBCT in 3D Surface Image Guided Deep InspirationBreath Hold (DIBH) Radiotherapy for Left‐Sided Breast Cancer
Authors: Gutierrez A , Stanley D , Papanikolaou N , Crownover R
Published: July 2016

Purpose:

With the increasing use of DIBH techniques for left‐sided breast cancer, 3D surface‐image guided DIBH techniques have improved patient setup and facilitated DIBH radiation delivery. However, quantification of the daily separation between the heart and left breast still presents a challenge. One method of assuring separation is to ensure consistent left lung filling. With this in mind, the aim of this study is to retrospectively quantify left lung volume from weekly breath hold‐CBCTs (bh‐CBCT) of left‐sided breast patients treated using a 3D surface imaging system.

Methods:

Ten patients (n=10) previously treated to the left breast using the C‐Rad CatalystHD system (C‐RAD AG, Uppsala Sweden) were evaluated. Patients were positioned with CatalystHD and with bh‐CBCT. bh‐CBCTs were acquired at the validation date, first day of treatment and at subsequent weekly intervals. Total treatment courses spanned from 3 to 5 weeks. bh‐CBCT images were exported to VelocityAI and the left lung volume was segmented. Volumes were recorded and analyzed.

Results:

A total of 41 bh‐CBCTs were contoured in VelocityAI for the 10 patients. The mean left lung volume for all patients was 1657±295cc based on validation bh‐CBCT. With the subsequent lung volumes normalized to the validation lung volume, the mean relative ratios for all patients were 1.02±0.11, 0.97±0.14, 0.98±0.11, 1.02±0.01, and 0.96±0.02 for week 1, 2, 3, 4, and 5, respectively. Overall, the mean left lung volume change was ≤4.0% over a 5‐week course; however left lung volume variations of up to 28% were noted in a select patient.

Conclusion:

With the use of the C‐RAD CatalystHD system, the mean lung volume variability over a 5‐week course of DIBH treatments was ≤4.0%. By minimizing left lung volume variability, heart to left breast separation maybe more consistently maintained.

AN Gutierrez has a research grant from C‐RAD AG.
SU‐F‐J‐28: Development of a New Imaging Filter to Remove the Shadows From the Carbon Fiber Grid Table Top
Authors: Maehana W , Nagao T
Published: July 2016

Purpose:

For the image guided radiation therapy (IGRT), the shadows caused by the construction of the treatment couch top adversely affect the visual evaluation. Therefore, we developed the new imaging filter in order to remove the shadows. The performance of the new filter was evaluated using the clinical images.

Methods:

The new filter was composed of the band‐pass filter (BPF) weighted by the k factor and the low‐pass filter (LPF). In the frequency region, the stop bandwidth were 8.3×103 mm−1 on u direction and 11.1×103 mm−1 on v direction for the BPF, and the pass bandwidth were 8.3×103 mm−1 on u direction and 11.1×103 mm−1 on v direction for the LPF. After adding the filter, the shadows from the carbon fiber grid table top (CFGTT, Varian) on the kV‐image was removed. To check the filter effect, we compared the clinical images, which are thorax and thoracoabdominal region, with to without the filter. The subjective evaluation tests was performed by adapting a three‐point scale (agree, neither agree nor disagree, disagree) about the 15 persons in the department of radiation oncology.

Results:

We succeeded in removing all shadows of CFGTT using the new filter. This filter is very useful shown by the results of the subjective evaluation having the 23/30 persons agreed to the filtered clinical images.

Conclusion:

We concluded that the proposed method was useful tool for the IGRT and the new filter leads to improvement of the accuracy of radiation therapy.
SU‐F‐J‐41: Experimental Validation of a Cascaded Linear System Model for MVCBCT with a Multi‐Layer EPID
Authors: Hu Y , Fueglistaller R , Rottmann J , Myronakis M , Wang A , Shedlock D , Morf D , Star‐Lack J , Berbeco R
Published: July 2016

Purpose:

The purpose of this study was to validate the use of a cascaded linear system model for MV cone‐beam CT (CBCT) using a multi‐layer (MLI) electronic portal imaging device (EPID) and provide experimental insight into image formation. A validated 3D model provides insight into salient factors affecting reconstructed image quality, allowing potential for optimizing detector design for CBCT applications.

Methods:

A cascaded linear system model was developed to investigate the potential improvement in reconstructed image quality for MV CBCT using an MLI EPID. Inputs to the three‐dimensional (3D) model include projection space MTF and NPS. Experimental validation was performed on a prototype MLI detector installed on the portal imaging arm of a Varian TrueBeam radiotherapy system. CBCT scans of up to 898 projections over 360 degrees were acquired at exposures of 16 and 64 MU. Image volumes were reconstructed using a Feldkamp‐type (FDK) filtered backprojection (FBP) algorithm. Flat field images and scans of a Catphan model 604 phantom were acquired. The effect of 2×2 and 4×4 detector binning was also examined.

Results:

Using projection flat fields as an input, examination of the modeled and measured NPS in the axial plane exhibits good agreement. Binning projection images was shown to improve axial slice SDNR by a factor of approximately 1.4. This improvement is largely driven by a decrease in image noise of roughly 20%. However, this effect is accompanied by a subsequent loss in image resolution.

Conclusion:

The measured axial NPS shows good agreement with the theoretical calculation using a linear system model. Binning of projection images improves SNR of large objects on the Catphan phantom by decreasing noise. Specific imaging tasks will dictate the implementation image binning to two‐dimensional projection images.

The project was partially supported by a grant from Varian Medical Systems, Inc. and grant No. R01CA188446‐01 from the National Cancer Institute.