Suitable Image Quality Research Articles

Attention-Based MultiOffset Deep Learning Reconstruction of Chemical Exchange Saturation Transfer (AMO-CEST) MRI.

One challenge of chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is the long scan time due to multiple acquisitions of images at different saturation frequency offsets. k-space under-sampling strategy is commonly used to accelerate MRI acquisition, while this could introduce artifacts and reduce signal-to-noise ratio (SNR). To accelerate CEST-MRI acquisition while maintaining suitable image quality, we proposed an attention-based multioffset deep learning reconstruction network (AMO-CEST) with a multiple radial k-space sampling strategy for CEST-MRI. The AMO-CEST also contains dilated convolution to enlarge the receptive field and data consistency module to preserve the sampled k-space data. We evaluated the proposed method on a mouse brain dataset containing 5760 CEST images acquired at a pre-clinical 3 T MRI scanner. Quantitative results demonstrated that AMO-CEST showed obvious improvement over zero-filling method with a PSNR enhancement of 11 dB, a SSIM enhancement of 0.15, and a NMSE decrease of [Formula: see text] in three acquisition orientations. Compared with other deep learning-based models, AMO-CEST showed visual and quantitative improvements in images from three different orientations. We also extracted molecular contrast maps, including the amide proton transfer (APT) and the relayed nuclear Overhauser enhancement (rNOE). The results demonstrated that the CEST contrast maps derived from the CEST images of AMO-CEST were comparable to those derived from the original high-resolution CEST images. The proposed AMO-CEST can efficiently reconstruct high-quality CEST images from under-sampled k-space data and thus has the potential to accelerate CEST-MRI acquisition.

Left atrial stiffness index – an early marker of left ventricular diastolic dysfunction in patients with coronary heart disease

AimsTo evaluate the correlation between left atrial stiffness index (LASI) and left ventricular diastolic function in patients with coronary heart disease (CHD) by Autostrain LA technique.MethodsThis was a retrospective analysis that included a total of 82 CHD patients who had suitable image quality for left atrial strain measurement. According to the 2016 ASE/EACVI guidelines for the echocardiographic assessment of diastolic dysfunction, the patients were divided into three groups: normal left ventricular diastolic function group (n = 26), indeterminate left ventricular diastolic function (n = 36), and left ventricular diastolic dysfunction (LVDD) (n = 20). The left atrial conduit strain (LAScd), Left atrial contractile strain (LASct), left atrial reservoir strain (LASr) and its derived parameters, including LASI and left atrial filling index (LAFI), were compared among the three groups. Furthermore, we conduct a correlation analysis between LASI and left ventricular diastolic function in patients with CHD.ResultsLASr and LAScd in normal group were higher than those in indeterminate group, LASr and LAScd in indeterminate group were higher than those in LVDD group, LASI in normal group was lower than that in indeterminate group, and LASI in indeterminate group was lower than that in LVDD group (P < 0.001). LASct in both normal and indeterminate groups was higher than that in LVDD group (P < 0.05). The LAFI of normal group was lower than that of indeterminate group and LVDD group (P < 0.001). LASI was positively correlated with E/e’(r = 0.822) (P < 0.001). LASr and E/e’ were negatively correlated (r = -0.637) (P < 0.001).ConclusionLASI is closely related to the changes of left ventricular diastolic function in CHD patients.

Abstract 15881: Progression of Significant Functional Mitral Regurgitation in Medically Managed High Surgical Risk Patients

Background: Functional mitral valve regurgitation (FMR) remains a clinical challenge in patients with high operative risk. Medical therapy alone in FMR is associated with poor outcomes but data regarding MR and left ventricular (LV) systolic function changes over time are limited. Objective: Study the progression of MR severity and LV function in medically managed MR patients with high surgical risk who survived at least 6 months. Methods: Between Jan 1st, 2000 and Aug 31st, 2010, we identified patients with medically managed moderate to severe MR that fulfilled the EVEREST II High Risk Registry (HRR) criteria. All patients were selected based on optimal propensity matching and were required to have a follow up echocardiogram &gt;6 months from the index study. Demographic, clinical and echocardiographic data was compared between baseline and follow up. Paired measurements of global longitudinal strain (GLS) were obtained in a subset of patients with suitable image quality. Results: 159 patients (mean age 73.5, female 45%) fulfilled the study criteria. 130 patients(81%) had moderate and severe MR. Median STS score was 8.9 (IQR: 5.2-14.8) and betablockers as well as ACEI/ARB was used by 71% and 73% respectively. During a median follow-up of 441 days (IQR: 272-780), MR decreased in severity in 82 patients (51.6%) and remained unchanged or worsened in 77 patients (49.4%) Among patients with moderate MR at baseline, improvement was seen in 62 (47.5%), worsening in 6 (5%), and unchanged severity in 62 (47.5%).Among patients with severe MR at baseline, improvement was seen in 17 (58.5%) and 12 (41.5%) remained unchanged. Median LVEF did not change from baseline to follow-up (45%; IQR: 30-55 vs. 45%, IQR: 30-55, p=0.51). Among 43 patients with evaluable paired GLS measurements, GLS did not significantly change over time (-11.8 to -12.6; p=0.36) Conclusions: Despite the high mortality in medically managed MR patients, a substantial number of survivors improve their MR grade at follow-up.

Prognostic Implications of Left Atrial Stiffness Index in Heart Failure Patients With Preserved Ejection Fraction

BackgroundThe left atrium (LA) plays an important role in the pathophysiology and disease progression of heart failure with preserved ejection fraction (HFpEF). ObjectivesThis study sought to assess the prognostic potential of LA stiffness index in patients who have HFpEF. MethodsThis study retrospectively screened patients with elevated left ventricular end-diastolic pressure (≥16 mm Hg) and preserved ejection fraction (≥50%) between January 1, 2004, and December 31, 2019. All patients underwent left heart catheterization to measure left ventricular end-diastolic pressure. Among these, 307 patients who had suitable image quality for left peak atrial longitudinal strain (PALS) measurement were analyzed. The study population was classified into low LA stiffness (n = 178, early diastolic transmitral inflow velocity/mitral annulus early diastolic velocity [E/e′]/PALS ≤0.26) and high LA stiffness (n = 129, E/e′/PALS >0.26) according to the best LA stiffness index (E/e′/PALS) cutoff value. The primary outcome was a composite of mortality or hospitalization caused by heart failure during follow-up. ResultsLA stiffness index showed good correlations with E/e′ (r = 0.737; P < 0.001), LA volume index (r = 0.529; P < 0.001), right ventricular systolic pressure (r = 0.404; P < 0.001), and log N-terminal pro–B-type natriuretic peptide (r = 0.540; P < 0.001). LA stiffness index demonstrated better predictive performance than echocardiographic diastolic parameters did (P < 0.001). Patients with low LA stiffness had better clinical outcomes than those with high LA stiffness during a median follow-up of 6 years did (P < 0.001). In multivariable analysis, LA stiffness index was independently associated with increased risk of the composite endpoint of death or heart failure hospitalization (HR: 1.59 [95% CI: 1.01-2.51]; P = 0.044). ConclusionsIncreased LA stiffness was associated with increased risk for all-cause mortality and hospitalization caused by heart failure in patients who have HFpEF, and its prognostic role was more pronounced than that of indexes of left ventricular filling pressure.

Performance evaluation of a preclinical SPECT/CT system for multi-animal and multi-isotope quantitative experiments

The aim was to study the performance of the U-SPECT6/CT E-class system for preclinical imaging, to later demonstrate the viability of simultaneous multi-animal and multi-isotope imaging with reliable quantitative accuracy. The performance of the SPECT was evaluated for two collimators dedicated for mouse (UHS-M) and rat imaging (UHR-RM) in terms of sensitivity, energy resolution, uniformity and spatial resolution. Point sources, hot‑rod and uniform phantoms were scanned, and additional tests were carried out to evaluate singular settings such as simultaneous multi-isotope acquisition and imaging with a multi-bed system. For in-vivo evaluation, simultaneous triple-isotope and multi-animal studies were performed on mice. Sensitivity for 99mTc was 2370 cps/MBq for the UHS-M collimator and 493 cps/MBq for the UHR-RM. Rods of 0.6 mm and 0.9 mm were discernible with the UHS-M and UHR-RM collimators respectively, with optimized reconstruction. Uniformity in low counting conditions has proven to be poor (> 75%). Multi-isotope and multi-bed phantom acquisitions demonstrated accurate quantification. In mice, simultaneous multi-isotope imaging provided the separate distribution of 3 tracers and image quality of the multi-mouse bone scan was adequate. The U-SPECT6/CT E-class has shown good sensitivity and spatial resolution. This system provides quantitative images with suitable image quality for multi-mouse and multi-isotope acquisitions.

Application of deep learning reconstruction of ultra-low-dose abdominal CT in the diagnosis of renal calculi

BackgroundRenal calculi are a common and recurrent urological disease and are usually detected by CT. In this study, we evaluated the diagnostic capability, image quality, and radiation dose of abdominal ultra-low-dose CT (ULDCT) with deep learning reconstruction (DLR) for detecting renal calculi.MethodsSixty patients with suspected renal calculi were prospectively enrolled. Low-dose CT (LDCT) images were reconstructed with hybrid iterative reconstruction (LD-HIR) and was regarded as the standard for stone and lesion detection. ULDCT images were reconstructed with HIR (ULD-HIR) and DLR (ULD-DLR). We then compared stone detection rate, abdominal lesion detection rate, image quality and radiation dose between LDCT and ULDCT.ResultsA total of 130 calculi were observed on LD-HIR images. Stone detection rates of ULD-HIR and ULD-DLR images were 93.1% (121/130) and 95.4% (124/130). A total of 129 lesions were detected on the LD-HIR images. The lesion detection rate on ULD-DLR images was 92.2%, with 10 cysts < 5 mm in diameter missed. The CT values of organs on ULD-DLR were similar to those on LD-HIR and lower than those on ULD-HIR. Signal-to-noise ratio was highest and noise lowest on ULD-DLR. The subjective image quality of ULD-DLR was similar to that of LD-HIR and better than that of ULD-HIR. The effective radiation dose of ULDCT (0.64 ± 0.17 mSv) was 77% lower than that of LDCT (2.75 ± 0.50 mSv).ConclusionULDCT combined with DLR could significantly reduce radiation dose while maintaining suitable image quality and stone detection rate in the diagnosis of renal calculi.

Image distortion inference based on correlation between line pattern and character

Samsung introduced pixel-merging technologies such as Tetrapixel, and these enabled the mobile image sensors to reproduce colors properly depend on light conditions. High resolution image can be acquired when in well-lit area, by reorganize colors on the color filter array to RGB Bayer pattern. The aforementioned process is called remosaic algorithm, based on estimating direction information. It causes some artifacts on edges with various or unclear direction, for example in text-image, especially at high spatial frequencies. We focused on such artifacts caused by remosaicing, and proposed suitable image quality metric that can measure a degree of the artifacts.

Low dose contrast media in step-and-shoot coronary angiography with third-generation dual-source computed tomography: feasibility of using 30 mL of contrast media in patients with body surface area

Reducing contrast media volume in coronary computed tomography angiography minimizes the risk of adverse events but may compromise diagnostic image quality. We aimed to evaluate coronary computed tomography angiography's diagnostic image quality while using 30 mL of contrast media in patients with a body surface area <1.7 m2. This prospective study included patients who underwent coronary computed tomography angiography from May 2018 to June 2019. The patients were divided into a low-dose group, who received 30 mL of contrast media, and a routine-dose group, who received contrast media based on body weight. Patient characteristics, coronary computed tomography angiography results, and quantitative and qualitative image results were assessed and compared. In total, 103 patients with a body surface area <1.7 m2 were 53 in the low-dose group and 50 in the routine-dose group. Sex, age, body surface area, body weight, and heart rate were similar between the groups (P>0.05). A contrast media volume of 30±0 mL was used for the low-dose group, and 41.62±4.59 mL was used for the routine-dose group. The low-dose group's computed tomography values were significantly different from those of the routine-dose group (P<0.05). The radiologists demonstrated agreement regarding diagnostic image quality and accuracy (kappa =0.91 and 0.85, respectively). Using 30 mL of contrast media for coronary computed tomography angiography in patients with a body surface area <1.7 m2 provided a suitable diagnostic image quality for coronary artery disease diagnosis. Although radiation doses were similar between the groups, the decreased contrast media volume was likely beneficial for the patients.

Optimization for customized trajectories in cone beam computed tomography

PurposeWe developed a target‐based cone beam computed tomography (CBCT) imaging framework for optimizing an unconstrained three dimensional (3D) source‐detector trajectory by incorporating prior image information. Our main aim is to enable a CBCT system to provide topical information about the target using a limited angle noncircular scan orbit with a minimal number of projections. Such a customized trajectory should include enough information to sufficiently reconstruct a particular volume of interest (VOI) under kinematic constraints, which may result from the patient size or additional surgical or radiation therapy‐related equipment.MethodsA patient‐specific model from a prior diagnostic computed tomography (CT) volume is used as a digital phantom for CBCT trajectory simulations. Selection of the best projection views is accomplished through maximizing an objective function fed by the imaging quality provided by different x‐ray positions on the digital phantom data. The final optimized trajectory includes a limited angular range and a minimal number of projections which can be applied to a C‐arm device capable of general source‐detector positioning. The performance of the proposed framework is investigated in experiments involving an in‐house‐built box phantom including spherical targets as well as an Alderson‐Rando head phantom. In order to quantify the image quality of the reconstructed image, we use the average full‐width‐half‐maximum (FWHMavg) for the spherical target and feature similarity index (FSIM), universal quality index (UQI), and contrast‐to‐noise ratio (CNR) for an anatomical target.ResultsOur experiments based on both the box and head phantom showed that optimized trajectories could achieve a comparable image quality in the VOI with respect to the standard C‐arm circular CBCT while using approximately one quarter of projections. We achieved a relative deviation <7% for FWHMavg between the reconstructed images from the optimized trajectories and the standard C‐arm CBCT for all spherical targets. Furthermore, for the anatomical target, the relative deviation of FSIM, UQI, and CNR between the reconstructed image related to the proposed trajectory and the standard C‐arm circular CBCT was found to be 5.06%, 6.89%, and 8.64%, respectively. We also compared our proposed trajectories to circular trajectories with equivalent angular sampling as the optimized trajectories. Our results show that optimized trajectories can outperform simple partial circular trajectories in the VOI in term of image quality. Typically, an angular range between 116° and 152° was used for the optimized trajectories.ConclusionWe demonstrated that applying limited angle noncircular trajectories with optimized orientations in 3D space can provide a suitable image quality for particular image targets and has a potential for limited angle and low‐dose CBCT‐based interventions under strong spatial constraints.

Study of breast implants mammography examinations for identification of suitable image quality criteria

PurposeTo characterise the mammography technique used in breast cancer screening programmes for breast implants (BI) and to identify if the image quality (IQ) criteria available in literature are applicable to BI imaging.MethodsThe study was conducted in two phases: literature review to find IQ criteria used in mammography combining keywords in several sources; and assessment of 1207 BI mammograms using the criteria that was identified previously to see if they were achieved or not. An observation grid was used to collect information about positioning, beam energy, compression force, and exposure mode. Descriptive statistics and Student’s t test and χ2 test were performed according to the nature of the variables.ResultsForty-seven out of 2188 documents were included in the analysis, with 13 items identified to assess the quality of positioning, 4 for sharpness, 3 for artefacts, and 2 for exposure parameters. After applying the criteria to BI mammograms, retroglandular fat was not included in 37.3% of the images. The “Pectoral-Nipple-Line” criterion was achieved in 35% of MLO/ML images. The placement of the implant (subpectoral/subglandular) or performing the Eklund had significant influence on the visible anatomy (p = < 0.005), alongside whether the breast was aligned to the detector’s centre.ConclusionsSome of the criteria used to assess standard mammograms were not applicable to BI due to implant overlap. The alignment of the image with the detector’s centre seems to have an impact on the amount of visible tissue. Further studies are necessary to define the appropriate protocol, technique, and suitable quality criteria to assess BI mammograms.

Can the anode heel effect be used to optimise radiation dose and image quality for AP pelvis radiography?

IntroductionA study was conducted to determine whether the anode heel effect can be used to influence optimisation of radiation dose and image quality (IQ) for AP pelvis radiography. MethodsATOM dosimetry phantom and an anthropomorphic phantom were positioned for AP pelvis. Using a CR system, images were acquired and doses were measured with phantom feet toward anode and then feet toward cathode. Exposure factors (kVp, mAs and SID) were systematically generated using a factorial design. Images were scored visually for quality using relative visual grading together with a 3 point Likert scale. Signal to noise ratio was also calculated as a physical measure of image quality. Dosimetry data were collected for the ovaries and testes. ResultsThe optimum technique for male, which resulted in lower dose and suitable image quality, was with feet positioned toward the anode (0.80 ± 0.03 mGy; SNR of 38 ± 2.9; visual IQ score 3.13 ± 0.35). The optimum technique for female was with feet toward anode (0.23 ± 0.02 mGy; SNR of 34.7 ± 2.6; visual IQ score 3.15 ± 0.26). kVp had the biggest effect on both visual and physical image quality metrics (p < 0.001) for both tube orientations, whereas SID had the lowest effect on both visual and physical image quality metrics compared with mAs and kVp (p < 0.001). The effect of SID on the SNR was not significant (p > 0.05) with feet toward anode. ConclusionPositioning the patient with feet toward the anode, as opposed to the cathode, has no adverse effect on visual image quality assessment but it does have an effect on physical image quality. Implications for practiceThis study would add a new clinical concept in positioning of AP pelvis radiography especially for male positioning.

Twin Robotic X-Ray System for 3D Cone-Beam CT of the Wrist: An Evaluation of Image Quality and Radiation Dose.

OBJECTIVE. The purpose of this study was to assess image quality and radiation dose of a novel twin robotic x-ray system's 3D cone-beam CT (CBCT) function for the depiction of cadaveric wrists. MATERIALS AND METHODS. Sixteen cadaveric wrists were scanned using dedicated low-dose and standard-dose CBCT protocols as well as clinical MDCT for comparison. Three readers assessed overall image quality, noise, and artifacts in bone and soft tissue on 5-point Likert scales. For radiation dose analysis, volume CT dose indexes (CTDIvol) were compared. RESULTS. Overall image quality of most studies was very good or excellent in MDCT (for readers 1, 2, and 3: 100%, 100%, and 88%, respectively), standard-dose CBCT (100%, 100%, and 94%), and low dose CBCT (100%, 94%, and 88%) with two readers favoring standard-dose CBCT over MDCT image quality (readers 1 and 2; p ≤ 0.046). In soft tissue, standard-dose (readers 1, 2, and 3; p ≤ 0.021) and low-dose (all p ≤ 0.001) CBCT images had more noise than MDCT in all cases. Standard-dose (all p ≤ 0.003) and low-dose (all p < 0.001) CBCT images also displayed more artifacts. In osseous tissue, one reader observed more noise (p < 0.001) and artifacts (p = 0.020) for low-dose CBCT than for MDCT, whereas no difference was found between standard-dose CBCT and MDCT. Mean CTDIvol was significantly lower for standard-dose (5.2 ± 0.6 mGy; p < 0.001) and low-dose CBCT (1.8 ± 0.2 mGy; p < 0.001) than for clinical MDCT without automatic dose modulation (15.0 ± 0.0 mGy). CONCLUSION. The tested CBCT function delivers suitable image quality for clinical wrist imaging at significantly lower radiation levels than conventional MDCT. In combination with comfortable positioning options and the ability to perform additional radiographic and fluoroscopic examinations, the twin robotic x-ray system may hold the potential to be a one-stop shop device for trauma-associated wrist imaging.

Optimization of radiation dose for CT detection of lytic and sclerotic bone lesions: a phantom study

To determine the best compromise between low radiation dose and suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis. A phantom was scanned using the routine protocol (STD, 13mGy) and six decreasing dose levels. Raw data were reconstructed using level 3 of iterative reconstruction (IR3) with 1-mm slice thickness for the STD protocol and highest IR levels with 3-mm slice thickness for the others. CTDIvol was used for radiation dose assessment. Quantitative criteria (noise power spectrum [NPS], task-based transfer function [TTF], and the detectability index [d']), as well as qualitative analysis, were used to compare protocols. NPS and TTF were computed using specific software (imQuest). d' was computed for two imaging tasks: lytic and sclerotic bone lesions. A subjective analysis was performed to validate the image quality obtained on the anthropomorphic phantom with the different dose values. Similar d' values were found for CTDIvol from 3 to 4mGy with IR4 and from 1 to 2mGy for IR5 compared with d' values using the STD protocol. Image quality was validated subjectively for IR4 but rejected for IR5 (image smoothing). Finally, for the same d', the dose was reduced by 74% compared with the STD protocol, with the CTDIvol being 3.4mGy for the lumbar spine and for the pelvis. A dose level as low as 3.4mGy, in association with high levels of IR, provides suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis. • A CTDI volof 3.4mGy, in association with high iterative reconstruction level, provides suitable image quality for the detection of lytic and sclerotic bone lesions, both at objective and subjective analysis. • Compared with the standard protocol, radiation dose can be reduced up to 74% for the lumbar spine and pelvis. • A task-based image quality assessment using the detectability index represents an objective method for the assessment of image quality and bridgesthe gap between complex physical metrics and subjective image analysis.

Optimization of Bremsstrahlung imaging in Yttrium internal radiation therapy

Introduction: Treatment efficacy of radiation therapy using Yttrium-90 radionuclide is evaluated by the bremsstrahlung SPECT imaging following radiation therapy. The radioisotopic images have the ability to provide reliable activity map of 90Y distribution. But these images have a low quantitative accuracy in the 90Y bremsstrahlung SPECT imaging, therefore the optimization of some imaging important indicators i.e. the energy window width and collimator geometry, which heavily affect acquisition images quality, is necessary. The aim of this paper is to estimate the effects of the energy window width and the hole diameter of a ME collimator on the image contrast of the 90Y bremsstrahlung SPECT images obtained using SIMIND Monte Carlo simulation program and improve image quality which could be used to estimate activity distribution after radiation therapy. Materials and Methods: In this paper we simulated the SPECT system and a Jaszczak phantom consist of six hot spheres in different diameters by use of the SIMIND Monte Carlo simulation program to study 90Y SPECT images by assessment of the holes diameter of a ME collimator including 2.35, 2.59, 2.82, 2.94, 3.06 and 3.3 mm with fixed values of the collimator and septa thicknesses (3.2 cm and 1.14mm, respectively) in the two energy windows including 60- 160 keV and 60-400 keV. SPECT imaging protocol is selected according to the clinical study. An activity of 1.5GBq 90Y was considered for the hot spheres without background activity. We used OS-EM algorithm to reconstruct projections and evaluated the contrast of the reconstructed images of six hot spheres of Jaszczak phantom with selection of proper ROIs. Results: The comparison of the images contrast of Jaszczak phantom spheres indicated that generally with increasing the hole diameter of collimator, the images contrast of the spheres were decreased. In order to, in comparison to the 1st energy window (60–160 keV), the 2nd energy window (60-400 keV) was increased the image contrast. The results showed that for a fixed collimator and septa thickness values (3.2 cm and 1.14mm, respectively), the optimal value of the hole diameter was found 2.35 mm. Also from the stand point of the image contrast, the optimal energy window was found ranging from 60 to 400 keV. Conclusion: By use of the evaluation of the images contrast of Jaszczak phantom by SIMIND Monte Carlo simulation study, the best contrast is obtained when by use of the wide energy window ranging from 60 to 400 keV, which increased the imaging system sensitivity and decreased variance of the activity estimation. Moreover, a ME collimator with fixed values of 3.2 cm and 1.14 mm for the collimator and septa thicknesses, respectively and a hole diameter of 2.35 mm can improve the 90Y activity estimation and provide a suitable image quality for the 90Y bremsstrahlung SPECT imaging.

2516 Ultra-low Na18F tracer dosing for preclinical skeletal imaging enables new concepts in digital PET/CT

OBJECTIVES/SPECIFIC AIMS: The aim of this study was to assess the ultra-dose Na18F dPET protocol feasibility for skeleton imaging in a canine model with reduced radiation dose and preserved quantitative characteristics. We hypothesized that administering an ultra-low Na18F dose would provide suitable image quality while reducing subject’s exposure to radiation. METHODS/STUDY POPULATION: In total, 13 adult male beagles [weight (kg) mean±SD; 14.3±2.2] were scanned. The dogs were administered 3 different Na18F doses: 3 (standard dose/SD), 1 (low dose/LD), and 0.05 (ultra-low dose/ULD) mCi. Imaging started ≃45 minutes post injection for ≃ 33 minute total acquisition time. Covering the whole body, 11 bed positions, acquiring 120 (3 mCi) and 180 (1, 0.05 mCi) seconds per bed position. All imaging was performed on a digital photon counting system (Philips Vereos, pre-commercial release). PET list mode data were reconstructed using Time-of-flight with 4, 2, and 1 mm3 voxel volumes. Point spread function, and Gaussian filtering were applied. Two experienced blinded readers evaluated image sets overall quality, tissue characterization, and quality of background in the whole body skeleton. Three-dimensional (3D) regions of interest (ROI) were traced over the distal femur, first lumbar vertebra, and a portion of the liver, recording standard uptake values (SUVmax and SUVmean). RESULTS/ANTICIPATED RESULTS: All the scans and reconstructions were successfully completed in all subjects. Decreasing Na18F dose from the standard dose (3 mCi) to the ultra-low dose/ULDO (0.05 mCi), demonstrated acceptable image quality and quantification. Ultra-low dose Na18F SUVmean values for the 3D ROIs reported (mean±SD) 2.6±0.7, 2.5±1.1, 9±1.6, and 0.6±0.3 from the right and left distal femur, first lumbar vertebra, and a portion of the liver, respectively. When compared the SD with the LD and ULD, dPET demonstrated acceptable image quality and definition for qualitative overall assessment. This was also found for the overall quantitative ROI assessment of the healthy canine skeletons. DISCUSSION/SIGNIFICANCE OF IMPACT: Ultra-low dose Na18F at a level of 50 μCi for a 14 kg canine appears to be diagnostically feasible and a robust option to reduce (60-fold) radiotracer doses in a translational animal model using a dPET system. Furthermore, it allows us to move preclinical nuclear medicine imaging forward with substantial reduced exposure levels while preserving image quality. Both visual and quantitative results indicate that the standard-dose bone Na18F dPET can be decreased with a satisfactory diagnostic image quality. Ultra-low Na18F dose is indeed important for younger populations, control patients, and nononcological diseases/conditions. Favorable pharmacokinetics of Na18F (such as high bone uptake, minimal binding to serum proteins, rapid single-pass extraction, and fast clearance from the soft tissues) in addition to the technological capabilities of dPET/CT demonstrated feasibility enabling dose reduction strategies. Ultra-low dose has diagnostic reproducibility and lower radiation burden compared with higher fixed dose techniques in current available guidelines [Society of Nuclear Medicine and Molecular Imaging; SNMMI (5–10 mCi)]. Na18F dPET/CT provides higher sensitivity and diagnostic accuracy, which enables high-quality images with lower tracer activity in this translational animal model. Future research will apply the same methodology to other anatomical targets as well as to the use of different tracers. Preclinical nuclear medicine imaging using ultra-low tracer doses, demonstrated the potential to obtain reasonable quality images and diminishing radiation surveillance in accordance with as low as reasonably achievable tracer levels.

Assessment of Speckle Noise Reduction in Digital Images using Nonlinear Anisotropic Diffusion: An Experimental Investigation

Objectives: To investigate on choice of suitable image quality assessment techniques and effect of parameters such as gradient threshold, time step, number of iterations etc. on anisotropic diffusion filtering. Methods/Statistical Analysis: Various diffusivity functions and the individual contribution of associated parameters are compiled and evaluated. Edge preservation in smoothing is an important issue while filtering digital images. A recently proposed image quality metrics is used for evaluating the edge preserving ability of filters. A comparative study is carried out on the basis of experiments and their performance is tested on standard test images using 16 different image quality metrics. Findings: The experimental findings show that most of the true edges got lost for higher number of iterations along with more smoothening of images in techniques namely, Perona and Malik diffusion, Speckle Reducing Anisotropic Diffusion (SRAD) and Weickert anisotropic diffusion. Further, in robust anisotropic diffusion it is found that conduction coefficient plays significant role in filtering process. Higher value of conduction coefficient results in more smoothening with blurring of sharp details and edges. It is concluded that image quality measures such as universal Quality index (Q), Edge Retrieval Index (ERI) and Structural Content (SC) can give significant information about image quality even in cases where conventional image quality metrics such as Picture Signal To Noise Ratio (PSNR), Mean Square Error (MSE), Root Mean Square Error (RMSE), geometric average error (GAE), normalized absolute error (NAE) etc. fail to do so. Proposed approach can give significant information when conventional metrics fail to assess the filtered image quality. Application/Improvements: The behavioural characteristics of techniques studied will be suggestive when applied on real time noisy images such as ultrasound images which inherently contain speckle.

An Empirical Study on the Influence of Image Filters in Effective Closed Contour Extraction of Lakes in Satellite Images

Objectives: The water contour extraction models using satellite images could be highly useful in monitoring the long term changes in river tributaries, lakes and other coastal areas. The lakes are termed for a localized basin of varied size where the water from river tributaries got reserved. These lakes are one among the prime source of water consumption for human needs. Hence, change monitoring in water levels of lakes is a highly needed measure for sustainability. Methods/Statistical Analysis: Though use of bathymetry and elevation data can aid the coastal monitoring models, a simple automated closed contour extraction model can support shape based change monitoring or satellite image based water volume assessment models. In general, the contour extraction of lakes or any water bodies is relatively difficult when compared with urban structures from spatial data. It is due to the indefinite shape of water bodies on varying levels of water. The use of image filters to improve the power of boundary discrimination is inevitable. However, it may also deteriorate the image quality leading to loss of information. Hence, the proposed model has examined the influence of widely used image filters both for smoothening and sharpening with respect to satellite image on applying suitable image quality assessment metrics. Findings: On the empirical analysis of the chosen image filters, the Adaptive wiener and Gaussian filters are found to be the more effective sharpening and smoothening filters respectively for satellite images. Further, the outstanding image filters found on evaluation is combined with local thresholding; shape based filtering and morphological operations in a sequence to extract an effective closed contour of water bodies. Applications: The proposed model can be applied for satellite image preprocessing for effective noise suppression and edge preservation. The closed contour extraction can be applied with change detection based applications for satellite images.

Investigations on edge preservation and smoothening of frequency domain filters for speckle removal in breast ultrasound images

Spatial domain methods for reducing speckle noise are more efficient but their performance is highly sensitive to size, shape of window and threshold used during filtering process. Hence frequency domain filtering is more appropriate if suitable and straightforward kernel or threshold cannot be found in the spatial domain. Unfortunately, they result in over smoothening, loss of edges and sharp details. In this paper various frequency domain techniques for the suppression of speckle noise are compiled and investigated. Further, they were evaluated using suitable image quality metrics and visual perception evaluation by two experts. Experiments were conducted on 37 breast ultrasound images. The results of comparative study using various image quality metrics show that wavelet filter with first level decomposition and eliminated HH band [Wav(HH/1)] outperformed others. On the other hand, homomorphic filter with wavelet filter function Wav(HH/1) outperformed others in visual assessment carried out by two experts.

High capacity data hiding scheme based on multi-bit encoding function

Secret message capacity and stego image quality are the two important measures for stenography. In this paper, a high hiding capacity and acceptable stego image quality steganographic scheme is proposed based on multi-bit encoding function. Using our method, the embedding capacity is as high as 4.5bpp (with acceptable stego image quality, i.e., PSNR better than 30dB). There are two major contributions of this scheme. It does not need additional complex steps to embed the secret data and no additional external information is needed to recover the secret data. From our experimental results and discussion, we show that our proposed scheme achieves higher capacity than other data hiding schemes based on encoding function while maintaining suitable image quality.

Optimization-based wavefront sensorless adaptive optics for multiphoton microscopy.

Optical aberrations have detrimental effects in multiphoton microscopy. These effects can be curtailed by implementing model-based wavefront sensorless adaptive optics, which only requires the addition of a wavefront shaping device, such as a deformable mirror (DM) to an existing microscope. The aberration correction is achieved by maximizing a suitable image quality metric. We implement a model-based aberration correction algorithm in a second-harmonic microscope. The tip, tilt, and defocus aberrations are removed from the basis functions used for the control of the DM, as these aberrations induce distortions in the acquired images. We compute the parameters of a quadratic polynomial that is used to model the image quality metric directly from experimental input-output measurements. Finally, we apply the aberration correction by maximizing the image quality metric using the least-squares estimate of the unknown aberration.