Level Of Image Quality Research Articles

An investigation into dose optimisation for imaging root canal anatomy using cone beam CT.

To identify a dose as low as diagnostically acceptable and a threshold level of image quality for cone beam CT (CBCT) imaging root canals, using maxillary first molar (M1M) second mesiobuccal (MB2) canals of varying complexity for two CBCT scanners. Dose-area product (DAP) and contrast-to-noise ratio (CNR) were measured for two scanners at a range of exposure parameters. Subjective-image-quality assessment at the same exposures was performed for three M1Ms of varying MB2 complexity, positioned in an anthropomorphic phantom. Nine raters (three endodontists, three dental radiologists and three junior staff) assessed canal visibility, using a 5-point confidence scale rating. Identification of simple-moderate MB2 canal complexity was achieved at a range of protocols, with DAP values of ≥209.3 and ≥203.2 mGy cm² and CNRs of 3 and 7.6 for Promax®3D and Accuitomo-F170® respectively. For complex canal anatomy, target subjective image quality was not achieved, even at the highest DAP values for both scanners. Junior staff classified significantly more images as undiagnostic compared with senior staff (p = 0.043). In this first study to address optimisation of CBCT imaging of root canal anatomy, a similar threshold dose for both scanners was identified for M1Ms with simple-moderate MB2 canal complexity. Increasing dose to enhance visualisation of more complex canal anatomy was ineffective. Selection of standard protocols (while avoiding lower kV/mA protocols) instead of high-resolution scans was a practical means of reducing patient dose. CNR is not a transferable measure of image quality.

Single function crystalline lens capable of mimicking ciliary body accommodation.

The lens is a complex optical component of the human eye because of its physiological structure: the surface is aspherical and the structural entities create a gradient refractive index (GRIN). Most existent models of the lens deal with its external shape independently of the refractive index and, subsequently, through optimization processes, adjust the imaging properties. In this paper, we propose a physiologically realistic GRIN model of the lens based on a single function for the whole lens that accurately describes different accommodative states simultaneously providing the corresponding refractive index distribution and the external shape of the lens by changing a single parameter that we associate with the function of the ciliary body. This simple, but highly accurate model, is incorporated into a schematic eye constructed with reported experimental biometric data and accommodation is simulated over a range of 0 to 6 diopters to select the optimum levels of image quality. Changes with accommodation in equatorial and total axial lens thicknesses, as well as aberrations, are found to lie within reported biometric data ranges.

Application of CareDose 4D combined with Karl 3D technology in the low dose computed tomography for the follow-up of COVID-19

BackgroundCoronavirus disease 2019 (COVID-19) is a highly infectious disease caused by the new coronavirus. Previous studies have shown that the chest CT examination plays an important role in the diagnosis and monitoring of COVID-19. However, some patients with COVID-19 had low white blood cell counts and reduced lymphocyte ratios. Multiple CT examinations may cause radiation damages as well as increase the apoptosis of peripheral blood lymphocytes. A new low-dose CT method should be developed because the regular CT may aggravate the disease.MethodSixty cases were randomly divided into the study group (n = 30) and control group (n = 30). The lung window was reconstructed by Karl 3D iterative technique in the study group. The image quality was subjectively evaluated by two senior chest group diagnostic physicians using a 5-point double-blind method. The value of CT measurement and its standard deviation (SD) was used as an objective evaluation criteria. The volume of CT dose index (CTDIvol), dose length product (DLP) and effective dose (ED) from the two groups were compared and analyzed statistically.ResultThere was no significant difference in the occurrence rates of ground glass opacities, consolidation, crazy-paving pattern, fiber cable shadow and axial interstitial thickening between the study group and control group (p > 0.05). In addition, no significant difference was found for the subjective score of overall image quality and image noise level (SD) between the two groups (p > 0.05). However, significant differences was found in CTDIvol, DLP, and ED between the study group and the control group (p < 0.05). The effective dose of the study group was reduced by 76% compared to the control group.ConclusionCareDose 4D low-dose scanning combined with Karl 3D iterative reconstruction technology can not only greatly reduce the radiation dose, but also provide images that meet the diagnostic criteria of COVID-19, which can be used as a routine method for the follow-up of COVID-19 patients.

Image-based construction of building energy models using computer vision

Improving existing buildings' energy performance requires energy models that accurately represent the building. Computer vision methods, particularly image-based 3D reconstruction, can effectively support the creation of 3D building models. In this paper, we present an image-based 3D reconstruction pipeline that supports the semi-automated modeling of existing buildings. We developed two methods for the robust estimation of the building planes from a 3D point cloud that (i) independently estimate each plane and (ii) impose a perpendicularity constraint to plane estimation. We also estimate external walls' thermal transmittance values using an infrared thermography-based method, with the surface temperatures measured by a thermal camera. We validate our approach (i) by testing the pipeline's ability in constructing accurate surface models subject to different image sets with varying sizes and levels of image quality, and (ii) through a comparative analysis between the calculated energy performance metrics of a ground truth and calculated energy simulation model.

Improving dynamic contrast-enhanced MRI of the lung using motion-weighted sparse reconstruction: Initial experiences in patients

PurposeThe purpose of this study was to evaluate the performance of motion-weighted Golden-angle RAdial Sparse Parallel MRI (motion-weighted GRASP) for free-breathing dynamic contrast-enhanced MRI (DCE-MRI) of the lung. MethodsMotion-weighted GRASP incorporates a soft-gating motion compensation algorithm into standard GRASP reconstruction, so that motion-corrupted motion k-space (e.g., k-space acquired in inspiratory phases) contributes less to the final reconstructed images. Lung MR data from 20 patients (mean age = 57.9 ± 13.5) with known pulmonary lesions were retrospectively collected for this study. Each subject underwent a free-breathing DCE-MR scan using a fat-statured T1-weighted stack-of-stars golden-angle radial sequence and a post-contrast breath-hold MR scan using a Cartesian volumetric-interpolated imaging sequence (BH-VIBE). Each radial dataset was reconstructed using GRASP without motion compensation and motion-weighted GRASP. All MR images were visually evaluated by two experienced radiologists blinded to reconstruction and acquisition schemes independently. In addition, the influence of motion-weighted reconstruction on dynamic contrast-enhancement patterns was also investigated. ResultsFor image quality assessment, motion-weighted GRASP received significantly higher visual scores than GRASP (P < 0.05) for overall image quality (3.68 vs. 3.39), lesion conspicuity (3.54 vs. 3.18) and overall artifact level (3.53 vs. 3.15). There was no significant difference (P > 0.05) between the breath-hold BH-VIBE and motion-weighted GRASP images. For assessment of temporal fidelity, motion-weighted GRASP maintained a good agreement with respect to GRASP. ConclusionMotion-weighted GRASP achieved better reconstruction performance in free-breathing DCE-MRI of the lung compared to standard GRASP, and it may enable improved assessment of pulmonary lesions.

CTPA with a conventional CT at 100 kVp vs. a spectral-detector CT at 120 kVp: Comparison of radiation exposure, diagnostic performance and image quality

PurposeTo compare CT pulmonary angiographies (CTPAs) as well as phantom scans obtained at 100 kVp with a conventional CT (C-CT) to virtual monochromatic images (VMI) obtained with a spectral detector CT (SD-CT) at equivalent dose levels as well as to compare the radiation exposure of both systems. Material and MethodsIn total, 2110 patients with suspected pulmonary embolism (PE) were examined with both systems. For each system (C-CT and SD-CT), imaging data of 30 patients with the same mean CT dose index (4.85 mGy) was used for the reader study. C-CT was performed with 100 kVp and SD-CT was performed with 120 kVp; for SD-CT, virtual monochromatic images (VMI) with 40, 60 and 70 keV were calculated. All datasets were evaluated by three blinded radiologists regarding image quality, diagnostic confidence and diagnostic performance (sensitivity, specificity). Contrast-to-noise ratio (CNR) for different iodine concentrations was evaluated in a phantom study. ResultsCNR was significantly higher with VMI at 40 keV compared to all other datasets. Subjective image quality as well as sensitivity and specificity showed the highest values with VMI at 60 keV and 70 keV. Hereby, a significant difference to 100 kVp (C-CT) was found for image quality. The highest sensitivity was found using VMI at 60 keV with a sensitivity of more than 97 % for all localizations of PE. For diagnostic confidence and subjective contrast, highest values were found with VMI at 40 keV. ConclusionHigher levels of diagnostic performance and image quality were achieved for CPTAs with SD-CT compared to C-CT given similar dose levels. In the clinical setting SD-CT may be the modality of choice as additional spectral information can be obtained.

Video compression to support the expansion of whole-slide imaging into cytology.

.Digital screening and diagnosis from cytology slides can be aided by capturing multiple focal planes. However, using conventional methods, the large file sizes of high-resolution whole-slide images increase linearly with the number of focal planes acquired, leading to significant data storage and bandwidth requirements for the efficient storage and transfer of cytology virtual slides. We investigated whether a sequence of focal planes contained sufficient redundancy to efficiently compress virtual slides across focal planes by applying a commonly available video compression standard, high-efficiency video coding (HEVC). By developing an adaptive algorithm that applied compression to achieve a target image quality, we found that the compression ratio of HEVC exceeded that obtained using JPEG and JPEG2000 compression while maintaining a comparable level of image quality. These results suggest an alternative method for the efficient storage and transfer of whole-slide images that contain multiple focal planes, expanding the utility of this rapidly evolving imaging technology into cytology.

Image Encryption and Decryption Systems Using the Jigsaw Transform and the Iterative Finite Field Cosine Transform

We propose the use of the Jigsaw transform (JT) and the iterative cosine transform over a finite field in order to encrypt and decrypt images. The JT is a nonlinear operation that allows one to increase the security over the encrypted images by adding new keys to the encryption and decryption systems. The finite field is a finite set of integer numbers where the basic mathematical operations are performed using modular arithmetic. The finite field used in the encryption and decryption systems has an order given by the Fermat prime number 257. The iterative finite field cosine transform (FFCT) was used in our work with the purpose of obtaining images that had an uniform random distribution. We used a security key given by an image randomly generated and uniformly distributed. The JT and iterative FFCT was utilized twice in the encryption and decryption systems. The encrypted images presented a uniformly distributed histogram and the decrypted images were the same original images used as inputs in the encryption system. The resulting decrypted images had a high level of image quality in comparison to the image quality of the decrypted images obtained by the actual optical decryption systems. The proposed encryption and decryption systems have three security keys represented by two random permutations used in the JTs and one random image. The key space of the proposed encryption and decryption systems is larger. The previous features of the security system allow a better protection of the encrypted image against brute force and statistical analysis attacks.

Feasibility Evaluation of Commercially Available Video Conferencing Devices to Technically Direct Untrained Nonmedical Personnel to Perform a Rapid Trauma Ultrasound Examination.

Introduction: Point-of-care ultrasound (POCUS) is a rapidly expanding discipline that has proven to be a valuable modality in the hospital setting. Recent evidence has demonstrated the utility of commercially available video conferencing technologies, namely, FaceTime (Apple Inc, Cupertino, CA, USA) and Google Glass (Google Inc, Mountain View, CA, USA), to allow an expert POCUS examiner to remotely guide a novice medical professional. However, few studies have evaluated the ability to use these teleultrasound technologies to guide a nonmedical novice to perform an acute care POCUS examination for cardiac, pulmonary, and abdominal assessments. Additionally, few studies have shown the ability of a POCUS-trained cardiac anesthesiologist to perform the role of an expert instructor. This study sought to evaluate the ability of a POCUS-trained anesthesiologist to remotely guide a nonmedically trained participant to perform an acute care POCUS examination. Methods: A total of 21 nonmedically trained undergraduate students who had no prior ultrasound experience were recruited to perform a three-part ultrasound examination on a standardized patient with the guidance of a remote expert who was a POCUS-trained cardiac anesthesiologist. The examination included the following acute care POCUS topics: (1) cardiac function via parasternal long/short axis views, (2) pneumothorax assessment via pleural sliding exam via anterior lung views, and (3) abdominal free fluid exam via right upper quadrant abdominal view. Each examiner was given a handout with static images of probe placement and actual ultrasound images for the three views. After a brief 8 min tutorial on the teleultrasound technologies, a connection was established with the expert, and they were guided through the acute care POCUS exam. Each view was deemed to be complete when the expert sonographer was satisfied with the obtained image or if the expert sonographer determined that the image could not be obtained after 5 min. Image quality was scored on a previously validated 0 to 4 grading scale. The entire session was recorded, and the image quality was scored during the exam by the remote expert instructor as well as by a separate POCUS-trained, blinded expert anesthesiologist. Results: A total of 21 subjects completed the study. The average total time for the exam was 8.5 min (standard deviation = 4.6). A comparison between the live expert examiner and the blinded postexam reviewer showed a 100% agreement between image interpretations. A review of the exams rated as three or higher demonstrated that 87% of abdominal, 90% of cardiac, and 95% of pulmonary exams achieved this level of image quality. A satisfaction survey of the novice users demonstrated higher ease of following commands for the cardiac and pulmonary exams compared to the abdominal exam. Conclusions: The results from this pilot study demonstrate that nonmedically trained individuals can be guided to complete a relevant ultrasound examination within a short period. Further evaluation of using telemedicine technologies to promote POCUS should be evaluated.

Efficacy of USB microscopes for imaging forensic materials

USB microscopy, a relatively new and developing technology, offers a highly portable and relatively inexpensive means for performing microscopy. However, it has not been established that USB microscopes are capable of imaging at a level deemed sufficient for forensic requirements. The purpose of this study was to determine the value, applicability, and limitations of current USB microscope technology by comparing USB microscopes with traditional microscopes by collecting images of common forensic trace materials. For our tests, we considered image clarity, resolution, magnification, field of view, working distance, ease of use, and reflected versus transmission mode imaging. The USB microscopes were highly portable, easy to work with, and able to take an image in any orientation. They also demonstrated a strong sensitivity to different hues of color and were easily tailored to different forms of microscopy by utilizing additional optical components. USB microscopes do not share the same level of resolution, image quality, or image contrast as the most sophisticated microscopes. However, USB microscopes could add value to forensic investigations when used for preliminary exams, low magnification imaging of samples, and imaging scenarios that require magnification but don’t conform to traditional microscopy.

57.3: Improvement of Image Sticking for High Standard Automotive Application

As the rapid growth of LCD market, higher level of image quality is required. Image sticking is a phenomenon that a faint outline of previously displayed image remains visible on the screen as the frame is refreshed and it is an unvarying problem as the birth of LCD display. Furthermore, it has been a critical issue for high standard automotive application. In essence, the image sticking arises from the residual electric field (DC) in liquid crystal which caused by the ordered arrangement of ionic charges or dielectric polarization under the external DC offset voltage. In this paper, we will summarize the mechanism of the the residual DC voltage generation and image sticking. And an optimum Vcom setting method minimizing external DC offset voltage is introduced to improve image sticking.

Diagnostic assessment of deep learning algorithms for diabetic retinopathy screening

Diabetic retinopathy (DR), the leading cause of blindness for working-age adults, is generally intervened by early screening to reduce vision loss. A series of automated deep-learning-based algorithms for DR screening have been proposed and achieved high sensitivity and specificity ( > 90%). However, these deep learning models do not perform well in clinical applications due to the limitations of the existing publicly available fundus image datasets. In order to evaluate these methods in clinical situations, we collected 13,673 fundus images from 9598 patients. These images were divided into six classes by seven graders according to image quality and DR level. Moreover, 757 images with DR were selected to annotate four types of DR-related lesions. Finally, we evaluated state-of-the-art deep learning algorithms on collected images, including image classification, semantic segmentation and object detection. Although we obtain an accuracy of 0.8284 for DR classification, these algorithms perform poorly on lesion segmentation and detection, indicating that lesion segmentation and detection are quite challenging. In summary, we are providing a new dataset named DDR for assessing deep learning models and further exploring the clinical applications, particularly for lesion recognition.

Preliminary Study of Digital Laminography Parameters on Carbon Steel Plate

Laminography is a technique used to determine the depth of a defect in Radiographic Testing (RT). It enables RT operators to accurately locate the defect from the object’s surface especially for welded components. The technique will ensure the quality of weld components meets the standard requirement for reliability and safety purposes. This paper intends to study the exposure parameters of laminography technique on carbon steel plate by using Radiographic Testing – Digital. (RT-D). The important exposure parameters that are considered in this preliminary study are voltage, current, and frame time. The radiography images with achievable level of contrast sensitivity and image quality are analyzed according to the ISO 17636-2. Discussion on correlation between the normalized Signal to Noise ratio (SNRN) and the exposure parameters are done based on the plotting graphs. The results show the exposure parameters has significantly influenced the value of SNRN. Further experimental works are performed using triangulation technique on welded sample. The deviation between the calculated depth of defects and actual results is less than 1.0mm.

A comparative study of information retrieval in grating-based x-ray phase-contrast imaging

The cosine-model analysis (CMA) method and the small angle x-ray scattering (SAXS) method are two major types of information retrieval algorithms, commonly utilized in x-ray phase-contrast imaging with a grating interferometer. However, there are significant differences between the two methods in algorithm implementation, and the existing literature has not completely revealed their intrinsic relationship. In this paper, we theoretically derive and experimentally verify the intrinsic connections between CMA and SAXS, and it is seen that SAXS can be interpreted well by the cosine-model assumption of CMA. To validate our analysis of the scattering distribution when applying the cosine model to the convolution used in SAXS, we applied a deconvolution process into CMA before using the Fourier transform to get the three contrasts. Furthermore, the principal component analysis (PCA) is introduced in this work, and two PCA-based retrieval algorithms are presented in order to simplify the iteration process of deconvolution in SAXS or to obtain absorption and dark-field signals instead of the Fourier transform in CMA. Applying a quantitative structural similarity (SSIM) index and a profile analysis to the results of an ex vivo mammography, it is proved that retrieved images via CMA and SAXS are consistent with each other (SSIM values are 1.0000, 0.9845 and 0.9767 respectively), and that the extra deconvolution process applied into CMA shows a good performance and our analytical analysis of the scattering distribution is valid when applying the cosine model to the convolution used in SAXS. Besides, it is concluded that PCA shows almost the same performance with the Fourier transform (SSIM values are 1.0000 for both absorption and dark-field images), and the simplified SAXS-analogous method works well with higher efficiency in computation and better stability relative to the original SAXS, while maintaining the similar level of image quality (SSIM values are 1.0000, 0.9839 and 0.9781 respectively).

P‐47: Improvement of Image Sticking for High Standard Automotive Application

As the rapid growth of LCD market, higher level of image quality is required. Image sticking is a phenomenon that a faint outline of previously displayed image remains visible on the screen as the frame is refreshed and it is an unvarying problem as the birth of LCD display. Furthermore, it has been a critical issue for high standard automotive application. In essence, the image sticking arises from the residual electric field (DC) in liquid crystal which caused by the ordered arrangement of ionic charges or dielectric polarization under the external DC offset voltage. In this paper, we will summarize the mechanism of the the residual DC voltage generation and image sticking. And an optimum Vcom setting method minimizing external DC offset voltage is introduced to improve image sticking.

Feasibility study of highly accelerated phase-sensitive inversion recovery myocardial viability imaging using simultaneous multislice and parallel imaging techniques.

Phase-sensitive inversion recovery (PSIR) is a powerful cardiac MRI method to assess myocardial viability, which can eliminate the background phase and preserve the sign of the desired magnetization during inversion recovery. To shorten the acquisition time of myocardial viability imaging by introducing both simultaneous multislice (SMS) and parallel imaging (PI) into PSIR without additional acquisitions for calibration data. Prospective study. A high-resolution phantom and three vials with doped solutions matching typical postcontrast T1 and T2 values of scar, healthy myocardium, and blood; 18 patients (six with known myocardial infarction) were included in this study. 3T/segmented fast spoiled gradient echo pulse sequence. Phantom and in vivo experiments were performed to compare the performance of conventional PSIR, SMS accelerated PSIR (SMS-PSIR, 2× acceleration), and SMS as well as PI accelerated PSIR (SMS + PI-PSIR, 4× acceleration). In phantom experiments, the error maps, local signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated. In in vivo experiments, the image quality and artifact level of each study were qualitatively graded (by three radiologists). G-factor maps were calculated. The infarct size presented as a percentage of the left ventricle was measured (full-width half-maximum). Acquisition time of each study was recorded. One-way analysis of variance, Kruskal-Wallis test. In phantom experiments, SNR and CNR were well preserved for SMS-PSIR, while they dropped for SMS + PI-PSIR, as expected. In 15 subjects, the overall image quality scores were not significantly different among conventional PSIR (3.70 ± 1.06), SMS-PSIR (3.78 ± 0.99), and SMS + PI-PSIR (3.47 ± 0.94; P = 0.20). The artifact level scores were also comparable among conventional PSIR (3.67 ± 1.04), SMS-PSIR (3.77 ± 1.03), and SMS + PI-PSIR (3.45 ± 1.00; P = 0.22). SMS-PSIR achieved negligible g-factor noise amplification (1.04 ± 0.03) and SMS + PI-PSIR showed higher g-factors (2.83 ± 0.48). The infarct size was consistent among conventional PSIR (22.51 ± 25.05%) and SMS-PSIR (22.98 ± 26.19%), as well as SMS + PI-PSIR (22.93 ± 25.68%; P = 0.98). The acquisition time of two short-axis slices for SMS-PSIR (17.6 ± 1.7 sec, 16 heartbeats) and SMS + PI-PSIR (9.8 ± 1.9 sec, 8 heartbeats) was 30% and 17% of that for conventional PSIR (56.2 ± 8.5 sec, 32 heartbeats), respectively. SMS can be implemented in PSIR without additional reference scan. The image quality is comparable with conventional PSIR, while the acquisition time is much shorter. The proposed method is also compatible with PI to further reduce the scan time. 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1964-1972.

Effect of a novel denoising technique on image quality and diagnostic accuracy in low-dose CT in patients with suspected appendicitis

ObjectivesTo determine the effect of a vendor unspecific, DICOM-based denoising technique on image quality and diagnostic performance in low-dose simulated abdominal computed tomography (CT) examinations in patients with suspected appendicitis. Methods and MaterialsWe included 51 patients who underwent contrast-enhanced abdominal CT with Filtered Back Projection due to suspected appendicitis. Realistic Low-Dose simulation generated low-dose datasets at 25% of the original exposition. QuantaStream Denoising, a novel DICOM-based technique denoised the simulated low-Dose datasets. Original (O100), low-dose (LD25) and denoised (DN25) datasets (n = 153) were evaluated regarding subjective image quality (5-point Likert scale; overall quality/image noise/diagnostic confidence), presence/absence of acute appendicitis, free abdominal air and abscess formation and objective image quality (Signal-to-Noise Ratio (SNR) and noise level) by two independent readers. ResultsSubjective image quality was rated highest for O100, followed by DN25 and LD25 with significant differences (p = 0.001). Appendicitis was correctly identified in all datasets (n = 30). Appendicitis specific diagnostic confidence was highest for O100 (p = 0.001), followed by DN25 and LD25 without significant difference. All complications were correctly identified on O100 and DN25. On LD25, diagnostic accuracy decreased for abscess formations (sensitivity:0.714; specificity:1.0) and for free abdominal air (sensitivity:0.750; specificity:0.936). Regarding noise levels DN25 showed non-inferiority to O100. SNRs of O100 and DN25 showed no significant difference (p = 0.06). ConclusionOur findings indicate that QuantaStream Denoising allows for maintained diagnostic image quality and diagnostic accuracy of low-dose abdominal CT examinations (25% of original exposition) in patients with suspected appendicitis without the need for raw sinogram data.

CT automated exposure control using a generalized detectability index

Identifying an appropriate tube current setting can be challenging when using iterative reconstruction due to the varying relationship between spatial resolution, contrast, noise, and dose across different algorithms. This study developed and investigated the application of a generalized detectability index ( ) to determine the noise parameter to input to existing automated exposure control (AEC) systems to provide consistent image quality (IQ) across different reconstruction approaches. This study proposes a task-based automated exposure control (AEC) method using a generalized detectability index ( ). The proposed method leverages existing AEC methods that are based on a prescribed noise level. The generalized metric is calculated using lookup tables of task-based modulation transfer function (MTF) and noise power spectrum (NPS). To generate the lookup tables, the American College of Radiology CT accreditation phantom was scanned on a multidetector CT scanner (Revolution CT, GE Healthcare) at 120kV and tube current varied manually from 20 to 240mAs. Images were reconstructed using a reference reconstruction algorithm and four levels of an in-house iterative reconstruction algorithm with different regularization strengths (IR1-IR4). The task-based MTF and NPS were estimated from the measured images to create lookup tables of scaling factors that convert between and noise standard deviation. The performance of the proposed -AEC method in providing a desired IQ level over a range of iterative reconstruction algorithms was evaluated using the American College of Radiology (ACR) phantom with elliptical shell and using a human reader evaluation on anthropomorphic phantom images. The study of the ACR phantom with elliptical shell demonstrated reasonable agreement between the predicted by the lookup table and measured in the images, with a mean absolute error of 15% across all dose levels and maximum error of 45% at the lowest dose level with the elliptical shell. For the anthropomorphic phantom study, the mean reader scores for images resulting from the -AEC method were 3.3 (reference image), 3.5 (IR1), 3.6 (IR2), 3.5 (IR3), and 2.2 (IR4). When using the -AEC method, the observers' IQ scores for the reference reconstruction were statistical equivalent to the scores for IR1, IR2, and IR3 iterative reconstructions (P>0.35). The -AEC method achieved this equivalent IQ at lower dose for the IR scans compared to the reference scans. A novel AEC method, based on a generalized detectability index, was investigated. The proposed method can be used with some existing AEC systems to derive the tube current profile for iterative reconstruction algorithms. The results provide preliminary evidence that the proposed -AEC can produce similar IQ across different iterative reconstruction approaches at different dose levels.

Analysis of image quality and radiation dose level for lower extremity vein blood flow image by FBP(Filtered Back Projection), MBIR(Model Based Iterative Reconstruction) and ASIR-V(Adaptive Statistical Iterative Reconstruction V)

Analysis of image quality and radiation dose level for lower extremity vein blood flow image by FBP(Filtered Back Projection), MBIR(Model Based Iterative Reconstruction) and ASIR-V(Adaptive Statistical Iterative Reconstruction V)

Assessment of quiet T2 weighted PROPELLER sequence in pediatric abdominal imaging

IntroductionElevated acoustic noise during Magnetic Resonance Imaging (MRI) has been associated with patient anxiety and altered cochlear function. Acoustic Reduction Technique (ART) T2 weighted (T2w) periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) has been studied in brain MR but not abdominopelvic imaging. The purpose of our study was to evaluate the image quality and acoustic noise level of ART T2w PROPELLER sequence in comparison with the conventional T2w PROPELLER sequence in pediatric abdomino-pelvic imaging. MethodsEleven consecutive pediatric patients undergoing abdomino-pelvic MRI were scanned on a 3 Tesla magnet using standard and ART T2w PROPELLER sequences. After scanning completion, objective sound level measurements were performed with a sound level meter and microphone. Mann-Whitney U test was used for a non-parametric two-tailed statistical analysis of acoustics, image rating and scan time with significance level set to 0.05. Overall inter-rater agreement was calculated using Cohen's kappa coefficient. ResultsEleven pediatric patients (4 females and 7 males) between 26 days and 18 years of age (mean = 10.0, SD = 5.8) were included. ART T2w produced lower levels of acoustic noise than standard technique in a comparison of mean decibel readings from eleven trials of standard and ART T2w (p value = 0.00008). Streak artifacts were rated greater in ART T2w by both raters (p-value = 0.00278 and 0.00252). There was no significant difference in bile duct blurring, respiratory ghosting, pulsation, fat suppression or hepatic parenchymal depiction. ConclusionPresence of additional streaking artifacts should be considered along with the benefit of reduced acoustic noise from ART T2w.