MTF Curves Research Articles

Volumetric limiting spatial resolution analysis of four-dimensional digital subtraction angiography

C-Arm CT three-dimensional (3-D) digital subtraction angiography (DSA) reconstructions cannot provide temporal information to radiologists. Four-dimensional (4-D) DSA provides a time series of 3-D volumes utilizing temporal dynamics in the two-dimensional (2-D) projections using a constraining image reconstruction approach. Volumetric limiting spatial resolution (VLSR) of 4-D DSA is quantified and compared to a 3-D DSA. The effects of varying 4-D DSA parameters of 2-D projection blurring kernel size and threshold of the 3-D DSA (constraining image) of an in silico phantom (ISPH) and physical phantom (PPH) were investigated. The PPH consisted of a 76-micron tungsten wire. An [Formula: see text] scan protocol acquired the projection data. VLSR was determined from MTF curves generated from each 2-D transverse slice of every (248) 4-D temporal frame. 4-D DSA results for PPH and ISPH were compared to the 3-D DSA. 3-D DSA analysis resulted in a VLSR of 2.28 and [Formula: see text] for ISPH and PPH, respectively. Kernel sizes of either [Formula: see text] or [Formula: see text] with a 3-D DSA constraining image threshold of 10% provided 4-D DSA VLSR nearest to the 3-D DSA. 4-D DSA yielded 2.21 and [Formula: see text] with a percent error of 3.1 and 1.2% for ISPH and PPH, respectively, as compared to 3-D DSA. This research indicates 4-D DSA is capable of retaining the resolution of 3-D DSA.

Comparison of the Optical Quality between Small Incision Lenticule Extraction and Femtosecond Laser LASIK.

Purpose. To investigate the visual quality after SMILE and Femto-LASIK. Methods. About 123 eyes from 63 patients were enrolled in this study. The parameters were measured preoperatively and 1 week, 1 month, and 3 months postoperatively using Sirius System. Results. The MTF curve increase slightly from low to high frequency at 3 mm and 6 mm pupil diameter after SMILE surgery (P < 0.05) during the follow-up time comparing with the preoperative values. And the SR has a significant increase at various pupil diameters as well (P < 0.05). However, there was little increase for MTF at intermediate to high frequency at 3 mm pupil diameter after Femto-LASIK procedure (P < 0.05). And the SR had only significant increase at 3 mm pupil diameter. Between SMILE and Femto-LASIK, there was no statistic difference both in MTF and SR (P > 0.05) at 3 mm pupil diameter at vertical and horizontal meridian. However, significant difference was found in MTF at low to mediate frequency at 6 mm pupil diameter at vertical meridian at 1 week postoperatively (P < 0.05). Conclusions. Both SMILE and Femto-LASIK show a great improvement in optical quality at small diameter. It was found that SMILE shows better optical quality than Femto-LASIK at larger pupil diameter, which might be good for the night vision.

Monte-Carlo simulation of a slot-scanning X-ray imaging system

We present a method for simulating slot-scanning X-ray imaging using the general-purpose Monte Carlo simulation package PENELOPE and penEasy Imaging. Different phantoms can be defined with the PENGEOM package, which defines bodies as combinations of volumes limited by quadric surfaces. The source-detector geometry, the position of the object, the collimator, the X-ray tube properties, the detector material and the pixel dimensions are defined. The output of the time-delay integration detector is simulated using sequential slot outputs derived from penEasy Imaging. The simulations are validated using tungsten and aluminium test objects, which are both simulated and imaged. The simulations are compared to the X-ray images using standard image quality metrics. The MTF, NPS and DQE curves show that the real and simulated X-ray images are comparable in terms of spatial resolution, noise and frequency information. The implementation can be modified to suit alterations in the system being simulated.

A Study on Parallel Imaging for the Improvement of Sharpness in MRCP for Liver Transplantation

In order to evaluate hepatobiliary in MRCP of liver donors, accurately, this study attempted to look into the availability of the parallel imaging technique for the enhancement of sharpness along with the reduction of the time of examination of the liver donors. From July 2014 through August 2014, MRCP was conducted with six patients and seven normal volunteers, and the sharpness of the pancreaticobiliary duct was evaluated. Of them, 11 were male and two were female, and their age distribution was between 21 and 67 (average age 39.15±6.53 years old). As the equipment used for the examination, GE Signa Excite HDxt 1.5T (Signa HDxt, GE Healthcare, Milwaukee, WI, USA) and 8ch phased array torso coil (GE Healthcare) were used. With the images obtained using FSE pulse sequences, parts with strong linearity in the liver duct, bile duct and pancreatic duct were selected using Image J(version. 1.49h, Wayne Rasband, National Institutes of Health, USA) with ROI. It was 0.4264±0.1227[lp/mm] on average in the image applying the parallel imaging technique, which was higher than 0.2672±0.1085 [lp/mm] on average in the image not applying it, and the result of a paired t-test of 50% MTF curve of sharpness evaluation was statistically very significant (t=12.929, p=0.000). The application of the parallel image technique in MRCP of donors for liver transplantation shortens the time of patient examination and enhances the sharpness of the image of the pancreaticobiliary, and it is judged that it can maximize the accuracy of diagnosis and the efficiency of the MRCP.

SU-D-204-06: Dose and Image Quality Evaluation of a Low-Dose Slot-Scanning X-Ray System for Pediatric Orthopedic Studies

Purpose: Children in early teens with scoliosis require repeated radiographic exams over a number of years. The EOS (EOS imaging S.A., Paris, France) is a novel low-dose slot-scanning digital radiographic system designed to produce full-spine images of a free-standing patient. The radiation dose and image quality characteristics of the EOS were evaluated relative to those of a Computed Radiography (CR) system for scoliosis imaging. Methods: For dose evaluation, a full-torso anthropomorphic phantom was scanned five times using the default standard clinical protocols for both the EOS and a CR system, which include both posteroanterior and lateral full-spine views. Optically stimulated luminescent dosimeters (OSLDs), also known as nanoDots™ (Landauer, Inc., Glenwood, IL), were placed on the phantom's surface to measure entrance skin dose. To assess image quality, MTF curves were generated from sampling the noise levels within the high-contrast regions of a line-pair phantom. Vertical and horizontal distortions were measured for the square line-pair phantom with the EOS system to evaluate the effects of geometric magnification and misalignment with the indicated imaging plane. Results: The entrance skin dose was measured to be 0.4 to 1.1 mGy for the EOS, and 0.7 to 3.6 mGy for the CR study. MTF comparison shows that CR greatly outperforms the EOS, despite both systems having a limiting resolution at 1.8 line-pairs per mm. Vertical distortion was unaffected by phantom positioning, because of the EOS slot-scanning geometry. Horizontal distortion increased linearly with miscentering distance. Conclusion: The EOS system resulted in approximately 70% lower radiation dose than CR for full-spine images. Image quality was found to be inferior to CR. Further investigation is required to see if EOS system is an acceptable modality for performing clinically diagnostic scoliosis examinations.

SU‐E‐J‐36: Comparison of CBCT Image Quality for Manufacturer Default Imaging Modes

PurposeCBCT is being increasingly used in patient setup for radiotherapy. Often the manufacturer default scan modes are used for performing these CBCT scans with the assumption that they are the best options. To quantitatively assess the image quality of these scan modes, all of the scan modes were tested as well as options with the reconstruction algorithm.MethodsA CatPhan 504 phantom was scanned on a TrueBeam Linear Accelerator using the manufacturer scan modes (FSRT Head, Head, Image Gently, Pelvis, Pelvis Obese, Spotlight, &amp; Thorax). The Head mode scan was then reconstructed multiple times with all filter options (Smooth, Standard, Sharp, &amp; Ultra Sharp) and all Ring Suppression options (Disabled, Weak, Medium, &amp; Strong). An open source ImageJ tool was created for analyzing the CatPhan 504 images.ResultsThe MTF curve was primarily dictated by the voxel size and the filter used in the reconstruction algorithm. The filters also impact the image noise. The CNR was worst for the Image Gently mode, followed by FSRT Head and Head. The sharper the filter, the worse the CNR. HU varied significantly between scan modes. Pelvis Obese had lower than expected HU values than most while the Image Gently mode had higher than expected HU values. If a therapist tried to use preset window and level settings, they would not show the desired tissue for some scan modes.ConclusionKnowing the image quality of the set scan modes, will enable users to better optimize their setup CBCT. Evaluation of the scan mode image quality could improve setup efficiency and lead to better treatment outcomes.

Complex Wavelet Package Image Restoration to Support Operational Application

Operational application image restoration method with high quality, high efficiency and robustness is presented, for high resolution optical remote sensing satellite. Firstly, images are block segmented according to CCD characteristics, and periodic plus smooth decomposition and dequantization are processed. Then, noise and MTF curves are estimated adaptively using spectrum masking for taking into account the on-orbit dynamical imaging properties. Thirdly, deconvolution filters are optimized in different frequency in order to balance among the blurring, aliasing, noise and ringing effects, based on known noise and MTF’s shape and value. Fourthly, adaptive threshold to color noise are treated rapidly utilizing the shift invariance and the direction selectivity of complex wavelet package(CWP) unique features. Fifthly the weak texture regions are reserved. Experiments shows that the method can significantly improve image sharpness, with universality adaption, and has a good operational application prospects.

Application of 3-dimensional printing technology to construct an eye model for fundus viewing study.

ObjectiveTo construct a life-sized eye model using the three-dimensional (3D) printing technology for fundus viewing study of the viewing system.MethodsWe devised our schematic model eye based on Navarro's eye and redesigned some parameters because of the change of the corneal material and the implantation of intraocular lenses (IOLs). Optical performance of our schematic model eye was compared with Navarro's schematic eye and other two reported physical model eyes using the ZEMAX optical design software. With computer aided design (CAD) software, we designed the 3D digital model of the main structure of the physical model eye, which was used for three-dimensional (3D) printing. Together with the main printed structure, polymethyl methacrylate(PMMA) aspherical cornea, variable iris, and IOLs were assembled to a physical eye model. Angle scale bars were glued from posterior to periphery of the retina. Then we fabricated other three physical models with different states of ammetropia. Optical parameters of these physical eye models were measured to verify the 3D printing accuracy.ResultsIn on-axis calculations, our schematic model eye possessed similar size of spot diagram compared with Navarro's and Bakaraju's model eye, much smaller than Arianpour's model eye. Moreover, the spherical aberration of our schematic eye was much less than other three model eyes. While in off- axis simulation, it possessed a bit higher coma and similar astigmatism, field curvature and distortion. The MTF curves showed that all the model eyes diminished in resolution with increasing field of view, and the diminished tendency of resolution of our physical eye model was similar to the Navarro's eye. The measured parameters of our eye models with different status of ametropia were in line with the theoretical value.ConclusionsThe schematic eye model we designed can well simulate the optical performance of the human eye, and the fabricated physical one can be used as a tool in fundus range viewing research.

Rapid Monte Carlo simulation of detector DQE(f)

Performance optimization of indirect x-ray detectors requires proper characterization of both ionizing (gamma) and optical photon transport in a heterogeneous medium. As the tool of choice for modeling detector physics, Monte Carlo methods have failed to gain traction as a design utility, due mostly to excessive simulation times and a lack of convenient simulation packages. The most important figure-of-merit in assessing detector performance is the detective quantum efficiency (DQE), for which most of the computational burden has traditionally been associated with the determination of the noise power spectrum (NPS) from an ensemble of flood images, each conventionally having 10(7) - 10(9) detected gamma photons. In this work, the authors show that the idealized conditions inherent in a numerical simulation allow for a dramatic reduction in the number of gamma and optical photons required to accurately predict the NPS. The authors derived an expression for the mean squared error (MSE) of a simulated NPS when computed using the International Electrotechnical Commission-recommended technique based on taking the 2D Fourier transform of flood images. It is shown that the MSE is inversely proportional to the number of flood images, and is independent of the input fluence provided that the input fluence is above a minimal value that avoids biasing the estimate. The authors then propose to further lower the input fluence so that each event creates a point-spread function rather than a flood field. The authors use this finding as the foundation for a novel algorithm in which the characteristic MTF(f), NPS(f), and DQE(f) curves are simultaneously generated from the results of a single run. The authors also investigate lowering the number of optical photons used in a scintillator simulation to further increase efficiency. Simulation results are compared with measurements performed on a Varian AS1000 portal imager, and with a previously published simulation performed using clinical fluence levels. On the order of only 10-100 gamma photons per flood image were required to be detected to avoid biasing the NPS estimate. This allowed for a factor of 10(7) reduction in fluence compared to clinical levels with no loss of accuracy. An optimal signal-to-noise ratio (SNR) was achieved by increasing the number of flood images from a typical value of 100 up to 500, thereby illustrating the importance of flood image quantity over the number of gammas per flood. For the point-spread ensemble technique, an additional 2× reduction in the number of incident gammas was realized. As a result, when modeling gamma transport in a thick pixelated array, the simulation time was reduced from 2.5 × 10(6) CPU min if using clinical fluence levels to 3.1 CPU min if using optimized fluence levels while also producing a higher SNR. The AS1000 DQE(f) simulation entailing both optical and radiative transport matched experimental results to within 11%, and required 14.5 min to complete on a single CPU. The authors demonstrate the feasibility of accurately modeling x-ray detector DQE(f) with completion times on the order of several minutes using a single CPU. Convenience of simulation can be achieved using GEANT4 which offers both gamma and optical photon transport capabilities.

Optical Projection System Design of the Infrared Dynamic Scene Simulator Based on DMD

Infrared dynamic target simulator can simulate infrared scene practicality in the laboratory, and reduce the research cost of the optical electrical system and offer recycle experiment environments， which are used to evaluate and test the infrared imaging system performance. Infrared scene projection technology based on the digital micro-mirror device (DMD) has been developed and applied to infrared target simulator, whose infrared images were obtained by modulating the launch of infrared radiation. Compared with the traditional simulator, the infrared scene simulator based on digital micro-mirror device (DMD) has a high spatial resolution and high frame rate, no dead pixels and good uniformity of characteristics. Firstly, the basic structure and the principle of the digital-mirror device are briefly introduced, and the kind and the advantage of the DLP(Digital Light Procession) system based on digital micro-mirror device (DMD) are analyzed. The key technology of the DLP(Digital Light Procession) projection system when it used in infrared wave band is analyzed. Secondly, the design process of the projection system is detailed. According to the design index required and the size of the digital micro-mirror device (DMD), a projection system consisting of three lenses and the transmissive type and aspheric technology was designed by ZEMAX optical-design software. The work wave-band is 8～12μm.The MTF curve is close to the diffraction limited curve and the size of the spot diagram is smaller than the airy disk. The result indicates that the system satisfies the design requirement and the structure of system is good.

Monte Carlo Simulation of Electron Scattering in Ion Barrier Film in Generation III Image Intensifier

In Generation III image intensifier tubes, the input of the microchannel plate is typically coated with a thin Al2O3 film to prevent ions penetrating and damaging the delicate Cs-O activation layer of GaAs cathode. While the application of an ion barrier film to the MCP greatly improves the mean time to failure of the image intensifier tube, it unfortunately produces electron scattering to cause a significant degradation in the Modulation Transfer Function and resolution of the image tubes. To obtain an overview of the role of the ion barrier in Generation III image intensifiers, in this paper, we present the results of a Monte Carlo simulation on scattering electron transport through Al2O3 film with various photocathode voltage, density, thickness, and stoichiometry. Using Monte Carlo simulation on scattering electron ways, we get the MTF curve of film at the accelerating voltage of 400v, a thickness of 10nm, and a density of 0.3 g/cm3. The simulation results play an important role on optimizing the quality and facture technique of ion barrier film.

TH-E-217BCD-03: Image Contrast Dependent Spatial Resolution Differences for Varying Levels of ASiR™ Implementation

Purpose: Introduce MTF calculation technique for contrast dependent spatial resolution measurements of ASiR™ using the first module of the ACR CT phantom. Compare three approaches to account for spatially variant MTF for CT.Methods: Each material insert within module one of the ACR phantom was imaged with a pixel pitch of 0.188. An MTF methodology described by Boone was used to validate the use of the ACR phantom. To account for spatially variant MTF of CT, three MTF calculation methodologies were investigated: an ensemble of edge response functions (ERFs) were aligned and averaged to produce one MTF;MTF curves were calculated for each ERF and averaged into one; and a cumulative distribution function was created by integrating a 300 bin histogram for one MTF calculation. Three reconstruction filters were investigated: standard, bone, and lung.Results: ACR phantom and Boone methodology MTF curves agreed to within 12%. Three methodologies investigated to account for spatially variant CT agreed to within 1%; histogram methodology was susceptible to number of bins used to form the histogram, and was not reliable. High‐contrast resolution improved by 10% when 100% ASiR™ was compared to 0% ASiR™; this trend agreed with previous reports and with Boone methodology calculations. Lung and bone reconstruction filters measured increased spatial resolution with increased levels of ASiR™: 10% and 17% for 0 and 100% ASiR™, respectively. Intermediary contrast resolution measured at acrylic‐water and at polyethylene‐water interfaces did not change with increasing ASiR™ reconstruction. Conclusions: ACR phantom MTF calculations agreed with the Boone methodology. Of the three methodologies investigated to account for spatially variant MTF in CT, method three varied depending on sampling interval. MTF values for high‐contrast objects were found to improve between 10–17% with 100% ASiR™ reconstruction. ASiR™ did not affect intermediary contrast object spatial resolution.

SU-E-I-54: Evaluation of High Contrast Resolution for Model Based Iterative Reconstruction of Sinus Examinations.

To evaluate high contrast resolution of Model Based Iterative Reconstruction used with typical sinus examination acquisition parameters. MBIR has recently become available as a recon option on a clinical scanner (Discovery HD750, GE Healthcare). In this work, we evaluate high contrast resolution for scan and reconstruction options that are available for sinus examinations. For this study we used our adult sinus CT protocol reconstructed with filtered back projection, and two alternative scans reconstructed with IR. Our conventional adult sinus CT protocol utilizes a high resolution scan mode which is not compatible with the scanner's IR recon option. The two additional scans are with high resolution option off, one with the head SFOV, and one with the body SFOV. Using IR and the head SFOV, reconstructed images have a 1024 × 1024 pixel matrix. Using IR and the body SFOV, reconstructed images have a 512 × 512 pixel matrix. Three evaluations of high contrast resolution are made for these images. A wire phantom is scanned for assessment of image modulation transfer function. The bar patterns of the ACR phantom are visually assessed for quality in both axial and coronal reformats. MTF curves show 50% values of 6.8, 7.5, and 7.7 lp/cm for Body IR 512 × 512, Head IR 1024 × 1024, and filtered back projection with HD Bone kernel. The 10% MFT curves for these reconstructions are 11.2, 11.9, and 12.1 lp/cm. Visual evaluation of the ACR phantom at 15 cm display field of view demonstrates resolution of the 10 lp/cm bar patterns for all reconstructions with better visualization of the axial versus coronal recons. MBIR reconstruction demonstrates high contrast resolution that is comparable with our conventional sinus examination.

SU-E-I-52: Noise Level and Contrast Dependent Behavior of MTF in Iterative Reconstruction CT Imaging.

Iterative reconstruction (IR) technique is growingly used in clinical CT imaging due to its ability to provide improved image quality at lower patient doses. However, the nonlinear frequency response of IR technique, which may affect quantitative analysis, is rarely explored. This study evaluates noise level and contrast dependent behavior of MTF in IR CT imaging with a multi-contrast slit phantom scanned at different dose levels. A multi-contrast slit phantom was created consisting of acrylic panel and aluminum foils of different thickness. Images were acquired on multi-detector CT (Discovery CT750 HD: GE) at two dose levels (10mAs and 200mAs), and were reconstructed using FBP and two IR technique (ASIR50 and VEO). Line spread functions were extracted across slits of two different thickness (80um and 144um) on images scanned at two dose levels, and were Fourier transformed to evaluate the MTFs of IR and FBP reconstruction techniques, producing a total of 12 MTF curves. MTF of 200mAs scan showed clearly higher responses up to 28% than that of 100mAs scan in VEO, marginally higher values up to 5% in ASIR50, and were in good agreement in FBP. At same dose level, the MTFs with higher contrast slit (144um) showed marginally higher response than that of lower contrast slit (80um) in VEO and ASIR50. Our study revealed that MTF of IR technique degrades depending on noise level at low dose scan. Therefore, we recommend that its characteristic should be considered in quantitative analysis such as lesion size measurement.

基于联合变换相关器的远红外变焦光学系统设计

In order to meet the requirement of tank sight and improve the ability of joint transform correlator in target tracking and recognition,an infrared continuous refractive zoom optical system for 8~12 μm wave-band is designed for 1 inch infrared CCD detector.The zoom system uses mechanical compensation.The relative aperture is invariant during the zoom process.The F number of the system is 2,and the zoom ratio is 4∶1.The focal length from 50 mm to 200 mm could be changed continuously.Variable magnification curve and compensation curve are smooth.The range of tank sight searching targets was expanded.The optical system image quality is evaluated with ZEMAX optical design software.The results have shown when spatial frequency is 17lp/mm,the MTF curve in the whole range of focal length are all above 0.55 which is closed to the diffraction limited curve.The stability of the image plane is well.The result of this system meets the requirement of technical specification.

Design of the Wide-view Collimator Based on ZEMAX

As for the optical measurement, the longer the focal length of collimator is, the less the measurement error is. However, the longer the focal length is, the more difficult the optical design is. It’s higher application value to design long focal length collimator with wide-view. The paper designs a collimator with 2000mm focal length, 4 degree field of view and its wavelength range is from 480nm to 750nm. The collimator is employed in the camera resolution detection system. It adopts the apochromatism three-piece-type structure and the secondary spectrum is corrected. The paper analyses the imaging quality of the optical system and the MTF curve is presented.

Development of the 3D volumetric micro-CT scanner for preclinical animals

A high resolution micro computed tomography (micro-CT) system for live small animal imaging has been developed. The system consists of an x-ray source with micro focus spot and high brightness, rotating gantry with a x-ray tube and flat panel detector pair and a stationary and a horizontally positioned small animal bed to achieve a conebeam mode scan. The system is optimized for in vivo small animal imaging and the capability of administering respiratory anesthesia during scanning. The Feldkamp algorithm was adopted in image reconstruction with graphic processing unit (GPU). We evaluated the spatial resolution, image contrast, and uniformity of system using phantom. As the result, the spatial resolution of the system was the 56lp/mm at 10% of the MTF curve, and the radiation dose to the sample was 98mGy. The minimal resolving contrast was found to be less than 46 CT numbers on low-contrast phantom. We present the image test results of the bone and lung, and heart of the live mice.

Scintillator technology for enhanced resolution and contrast in X-ray imaging

Abstract A structured scintillator has been fabricated by filling a deep pore array in silicon with scintillating material. The pitch of the pores is significantly smaller ( 15.7 μ m , hexagonal pattern) than for scintillators previously produced by Scint-X. The resulting MTF curves are presented, and show an improvement of 50–100% compared to other scintillator types. The camera used for comparisons is a Vosskuhler CCD-11000XR detector.

Space Camera Dynamic Image Quality Measurement and Evaluation

By using analysis of the infinity image of the space camera, we intend to obtain the curve of the dynamic modulation transfer function. We extract the pixel gray values at the image edge which distribute as a knife-edge function, and make differential calculation and Fourier transformation of it, and then we can obtain the dynamic MTF curve of the optical system. The value of the curve at the Nyquist frequency is the most important parameter that reflects the image quality. We add push-scanning imaging and environmental effects to the static MTF of space camera and compare the MTF value with the dynamic MTF at Nyquist frequency. The comparison result can help us verify the accuracy of the calculating results and the feasibility of our method.

SU-GG-I-36: Initial Performance Evaluation of GE CT 750HD Scanner

Purpose: To present an initial performance evaluation of GE Discovery CT 750HD scanner in four imaging modes: Regular, Adaptive Statistical Iterative Reconstruction (ASIR), High Resolution (Hi-Res), and Gemstone Spectral Imaging (GSI) mode, in an effort to better understand the potential advantages of the scanner, including improved spatial resolution, reduced dose, and material separation capability. Method and Materials: The scanner was tested with the clinical protocol frequently used for adult abdomen scans (120 kVp, helical, 5 mm slice thickness, 1.375 pitch, Median Body SFOV, 40 mm beam collimation). Preset 11 was used for GSI mode, as it has settings similar to the above protocol. Regular, Hi-Res, and GSI were used under the same CTDIvol (19.1 mGy), while in ASIR mode 100% ∼ 40% of this dose level were used. Catphan phantom was employed as the imaging target: low contrast detectability and CNR were compared for Regular, ASIR, and GSI mode; high contrast resolution patterns and MTF curves were compared for regular, Hi-Res, and GSI mode using all reconstruction kernels. Patterns that are made of iodine compounds were imaged to compare the measured and nominal iodine concentration levels.Results: Using ASIR, image quality of low contrast patterns was maintained with 40% less dose compared with regular mode. Regular and GSI mode have almost identical MTF curves. Hi-Res mode provides improvements in terms of the highest visible resolution pattern and MTF by 1∼3 lp/cm for different reconstruction kernels, but high frequency artifacts were observed in point spread functions acquired with HD-Ultra and HD-Edge kernels. The measured and nominal iodine concentrations showed discrepancies. Conclusion: 750HD scanner demonstrated potentials to improve spatial resolution and to reduce dose in clinical applications. We will perform further studies for more comprehensive evaluation of the GSI mode.