Short Scan Time Research Articles

Deep Learning Enables 60% Accelerated Volumetric Brain MRI While Preserving Quantitative Performance: A Prospective, Multicenter, Multireader Trial.

In this prospective, multicenter, multireader study, we evaluated the impact on both image quality and quantitative image-analysis consistency of 60% accelerated volumetric MR imaging sequences processed with a commercially available, vendor-agnostic, DICOM-based, deep learning tool (SubtleMR) compared with that of standard of care. Forty subjects underwent brain MR imaging examinations on 6 scanners from 5 institutions. Standard of care and accelerated datasets were acquired for each subject, and the accelerated scans were enhanced with deep learning processing. Standard of care, accelerated scans, and accelerated-deep learning were subjected to NeuroQuant quantitative analysis and classified by a neuroradiologist into clinical disease categories. Concordance of standard of care and accelerated-deep learning biomarker measurements were assessed. Randomized, side-by-side, multiplanar datasets (360 series) were presented blinded to 2 neuroradiologists and rated for apparent SNR, image sharpness, artifacts, anatomic/lesion conspicuity, image contrast, and gray-white differentiation to evaluate image quality. Accelerated-deep learning was statistically superior to standard of care for perceived quality across imaging features despite a 60% sequence scan-time reduction. Both accelerated-deep learning and standard of care were superior to accelerated scans for all features. There was no difference in quantitative volumetric biomarkers or clinical classification for standard of care and accelerated-deep learning datasets. Deep learning reconstruction allows 60% sequence scan-time reduction while maintaining high volumetric quantification accuracy, consistent clinical classification, and what radiologists perceive as superior image quality compared with standard of care. This trial supports the reliability, efficiency, and utility of deep learning-based enhancement for quantitative imaging. Shorter scan times may heighten the use of volumetric quantitative MR imaging in routine clinical settings.

Spiral gradient echo versus cartesian turbo spin echo imaging for sagittal contrast-enhanced fat-suppressed T1 weighted spine MRI: an inter-individual comparison study.

To compare a novel 3D spiral gradient echo (GRE) sequence with a conventional 2D cartesian turbo spin echo (TSE) sequence for sagittal contrast-enhanced (CE) fat-suppressed (FS) T1 weighted (T1W) spine MRI. In this inter-individual comparison study, 128 patients prospectively underwent sagittal CE FS T1W spine MRI with either a 2D cartesian TSE ("TSE", 285 s, 64 patients) or a 3D spiral GRE sequence ("Spiral", 93 s, 64 patients). Between both groups, patients were matched in terms of anatomical region (cervical/thoracic/lumbar spine and sacrum). Three readers used 4-point Likert scales to assess images qualitatively in terms of overall image quality, presence of artifacts, spinal cord visualization, lesion conspicuity and quality of fat suppression. Spiral achieved a 67.4% scan time reduction compared to TSE. Interreader agreement was high (alpha=0.868-1). Overall image quality (4;[3,4] vs 3;[3,4], p<0.001 - p=0.002 for all readers), presence of artifacts (4;[3,4] vs 3;[3,4] p=0.027 - p=0.046 for all readers), spinal cord visualization (4;[4,4] vs 4;[3,4], p<0.001 for all readers), lesion conspicuity (4;[4,4] vs 4;[4,4], p=0.016 for all readers) and quality of fat suppression (4;[4,4] vs 4;[4,4], p=0.027 - p=0.033 for all readers), were all deemed significantly improved by all three readers on Spiral images as compared to TSE images. We demonstrate the feasibility of a novel 3D spiral GRE sequence for improved and rapid sagittal CE FS T1W spine MRI. A 3D spiral GRE sequence allows for improved sagittal CE FS T1W spine MRI at very short scan times.

Simultaneous T1 -weighted and T2 -weighted 3D MRI using RF phase-modulated gradient echo imaging.

T1 -weighted and T2 -weighted (T1w and T2w) imaging are essential sequences in routine clinical practice to detect and characterize a wide variety of pathologies. Many approaches have been proposed to obtain T1w and T2w contrast, although many challenges still remain, including long acquisition time and limitations that favor 2D imaging. In this study, we propose a novel method for simultaneous T1w and T2w imaging using RF phase-modulated 3D gradient-echo imaging. Configuration theory is used to derive closed-form equations for the steady state of RF phase-modulated gradient-echo signal. These equations suggest the use of small RF phase increments to provide orthogonal signal contrast with T2w and T1w in the real and imaginary components, respectively. Background phase can be removed using a two-pass acquisition with opposite RF phase increments. Simulation and phantom experiments were performed to validate our proposed method. Volunteer images of the brain and knee were acquired to demonstrate the clinical feasibility. The proposed method was compared with T1w and T2w fast spin-echo imaging. The relative signal intensity of images acquired using the proposed method agreed closely with simulations and fast spin-echo imaging in phantoms. Images from volunteer imaging showed very similar contrast compared to conventional fast spin-echo imaging. Radiofrequency phase-modulated gradient-echo with small RF phase increments is an alternative method that provides simultaneous T1w and T2w contrast in short scan times with 3D volumetric coverage.

Effect of digital intraoral full-arch scan strategies on scan time and accuracy on conditions of intraoral head-simulator

Objective: To comparatively evaluate the accuracy and the scan time of three full-arch scan strategies on the head-simulator, to explore a full-arch scan strategy with better clinical operability and high accuracy. Methods: A cross-controlled study design was used. A model with melamine-formaldehyde resin teeth and silica gel gingiva of an upper dental arch which can be fixed on a head simulator was scanned with an optical scanner (ATOS Core) in order to obtain the standard tessellation language (STL) dataset as reference. Intraoral scans were performed on the model fixed on the head simulator with four intraoral scanners (IOS) [A (TRIOS 3), B (CS 3600), C (CEREC Omnicam), D (iTero)]. The STL datasets were obtained from each of the four different IOS systems by using three scan strategies (scan strategies 1, 2 and 3 were composed of 10, 5 and 7 paths respectively) all by one attending doctor with 3 years of intraoral scanning experience. For each scanner and each scan strategy, nine scans were acquired. And the scan time was recorded for each scan. Following the scan strategy, the scan path was completed to obtain a full-arch digital model, and the scan time was recorded as full-arch scan time. Complementary scans were performed to fill the missing image, and this scan time was recorded as complementary scan time. The total scan time was obtained by adding full-arch scan time and complementary scan time. Through the Geomagic Wrap software, the three-dimensional (3D) models were overlaid by best fit alignment function and compared to obtain the root mean square values of the discrepancies by 3D compare function. The intraoral scanning datasets were compared with the reference for trueness. The nine intraoral scanning datasets were cross compared with same scan strategy and same intraoral scanner for precision. Results: There were no significant differences among the three scan strategies for trueness (P>0.05), while the differences among the three scan strategies for precision were affected by difference IOSs (P<0.05), and only scan strategy 3 showed the highest precision with all the four IOS. The full-arch scan time of scan strategies 1, 2 and 3 were (130±24), (72±17) and (90±19) s respectively (P<0.05). For complementary scan time, scan strategy 2 [(50±24) s] took longer time than scan strategy 1 [(26±18) s] and scan strategy [(25±21) s] (P<0.05), while no significant differences between the latter two (P>0.05). For total scan time, scan strategy 1 [(156±31) s] took longer time than scan strategy 2 [(122±30) s ] and scan strategy 3 [(115±29) s ] (P<0.05), while no significant differences between the latter two (P>0.05). Conclusions: Full-arch scanning on the head-simulator with scan strategy 3 which can obtain scanning datasets with high accuracy, was more convenient to operate and took shorter scan time, and is generally suitable for intraoral scanners commonly used in clinic.

Abstract 1122‐000033: Automated Detection of Intracerebral Hemorrhage Using Artificial Intelligence: Pilot Deployment of Viz ICH

Introduction : Stroke is a major cause of morbidity and mortality. Hemorrhagic strokes are often more severe and associated with higher mortality when compared to ischemic stroke and account for approximately 13% of all strokes. Initial care for patients with intracerebral hemorrhage (ICH) is in part guided by neuroimaging findings. Non‐contrast computed tomography (NCCT) is often the first imaging obtained in the work up of the acute stroke patient given its diagnostic accuracy for hemorrhage, ubiquity, low cost, and short scan time. Immediate evaluation of imaging by stroke experts, such as neurologists, neurosurgeons, and radiologists, is essential. Artificial intelligence tools can help to expedite image assessment and careteam coordination thereby accelerating time to treatment. In this study, we report on the use of Viz ICH, an AI‐enhanced ICH detection platform, to identify ICH on initial CT and coordinate emergent care in an urban health system with an ICH Center. Methods : All consecutive stroke codes presenting with ICH from May 2019 to August 2019 were eligible for analysis. Non‐contrast CT (NCCT) was conducted for each patient and submitted to the Viz ICH in a prospective fashion. An automated volumetric analysis of these NCCTs was conducted by Viz ICH and assessment was conducted for potential ICH. If suspected ICH was detected, Viz ICH sent an automated prompt to the stroke care team for review. CT impressions provided by radiologists served as the clinical reference standard test and Viz ICH output served as the index test. Diagnostic accuracy tests were then performed. Results : A total of 682 patients were analyzed for ICH, out of which 28 patients were positive for intracerebral hemorrhage (ICH) (4%) and 654 were negative for hemorrhage (96%) based on radiology impressions. Viz ICH was able to correctly identify hemorrhages in 25/28 patients and non‐hemorrhages in 650/654 patients. Overall, the software had high diagnostic accuracy with 89.3% sensitivity, 99.4% specificity, and an overall accuracy of 99.0%. The software also had a positive predictive value of 86.2%, a negative predictive value of 99.5%, a positive likelihood ratio of 145.98, and a negative likelihood ratio of 0.108. Conclusions : Viz ICH is an AI‐enhanced platform that may help in the diagnosis and detection of ICH, with a sensitivity of 89.3 and a specificity of 99.4% in this preliminary study. Though future validation studies with a larger cohort of patients positive for each type of hemorrhage must be conducted for true diagnostic accuracy data, Viz ICH has the potential to be an adjunct tool to streamline ICH triage, reduce treatment delays, and improve outcomes of patients presenting with ICH.

SNR and total acquisition time analysis of multi-echo FLASH pulse sequence for current density imaging

Magnetic Resonance Current Density Imaging (MRCDI) is an imaging modality providing cross-sectional current density (J¯) information inside the body. The clinical applicability of MRCDI is highly dependent on the sensitivity of the acquired noisy current-induced magnetic flux density (B∼z) distributions.Here, a novel analysis is developed to investigate the combined effect of relevant parameters of the RF spoiled gradient echo (FLASH) pulse sequence on the SNR level and the total acquisition time (TAT) of the acquired B∼z images. The proposed analysis then is expanded for a multi-echo FLASH (ME-FLASH) pulse sequence to take advantage of combining the multiple echoes to achieve B∼zcomb distribution with a higher SNR than the one achievable with a single echo acquisition.The optimized sequence parameters to acquire a B∼z distribution with the highest possible SNR for a given acquisition time or the desired SNR in the shortest scan time are estimated using the proposed analysis. The analysis also provides different sets of sequence parameters to acquire B∼z distributions with the same SNR at almost the same TAT. Furthermore, the effects of intensive utilization of the gradients and the magnetohydrodynamic (MHD) flow velocity on the acquired B∼z distribution in MRCDI experiments is investigated.The analytical results of the proposed analysis are validated experimentally using an imaging phantom having the conductivity and the relaxation parameters of the brain white matter tissue.

Deep learning-accelerated T2-weighted imaging of the prostate: Impact of further acceleration with lower spatial resolution on image quality

PurposeTo compare image quality in prostate MRI among standard T2-weighted imaging (T2-std), accelerated T2-weighted imaging (T2WI) with high resolution (T2-HR) and more accelerated T2WI with lower resolution (T2-LR) using both conventional reconstruction (C) and deep learning reconstruction (DL). Materials and methodsIn 46 consecutive patients, T2-std, T2-HR and T2-LR were acquired in 3:32 min, 1:06 min and 0.52 min, respectively. Both reconstruction techniques (C and DL) were applied to T2-HR and T2-LR. Five sets of images (T2-std, T2-HRC, T2-LRC, T2-HRDL, and T2-LRDL) for each patient were independently evaluated by two radiologists. Quantitative analysis including the signal-to-noise ratio (SNR) and contrast ratio (CR) and qualitative analysis with a 5-point scale for the sharpness of structures, ghosting or other artifacts, noise and overall image quality were performed. ResultsThe SNR was not different in either the peripheral zone (PZ) or transition zone (TZ) between T2-LRDL and T2-std with the median value of 21.7 versus 22.6 in PZ and 16.5 versus 17.3 in TZ, respectively. The CR between the prostate gland and muscle was significantly lower on T2-HRC and T2-LRC than on T2-std. Most of the evaluated factors showed significantly lower scores on T2-HRC and T2-LRC than on T2-std. Although noise and overall image quality on T2-HRDL and other artifacts on T2-LRDL were rated significantly lower than on T2-std (median value 4.0 versus 4.5, P < 0.001; 4.5 versus 5.0, P = 0.001; 4.5 versus 5.0, P = 0.006, respectively), other factors did not differ between T2-std and T2-HRDL or T2-LRDL. ConclusionDL is useful to improve image quality in accelerated T2WI of the prostate gland. Using DL, accelerated T2WI with lower spatial resolution than T2-std can be achieved with similar image quality in much shorter scan time (75.5% reduction in the acquisition time).

Особливості топографії правого каналу нижньої щелепи людини при атрофії кісткової тканини, зумовленої втратою зубів

The aim is to determine the peculiarities of the topography of the right channel of the lower jaw in the bone atrophy, due to the terminal dentition defect. Objective. In general, for this research the method of "clinical sampling" involved sixty-eight computer-tomographic scans of the human mandible, which provide the best opportunities for diagnosis and carry proper information content for the task of this work, divided into four age groups, namely: the first group – up to 45 years old, the second group – 46-60 years old, the third group – 61-75 years old and the monitoring group – 25-75 years old, persons with natural dentition. Materials and methods. A set of research materials was conducted after paraclinical examination of digital records of 243 computed tomography cone-digital scans, which were taken by the Vatech PaX-I 3D Green extra-oral radiography system with a scan size range of 16 x 9 cm, which minimize the possibility of artifacts caused by patient movement, a focal spot of 0.5 mm (EC60336) on a 14-bit greyscale with a size of 0.2/0.3 voxels and due to the short scanning time, high-quality images were obtained. Results. Absolute values of the location of the mandibular canal of the patient of the first study group (control) with a natural dentition (48 years) in the projection: 1) 4.6 teeth in relation to: the upper edge of the alveolar part of the lower jaw (UE) is – 13.1 mm; the edge of the base of the lower jaw (EB) – 7.3 mm; the buccal surface of the body (BS) – 6.4 mm; the lingual surface of the mandibular body (LS) is – 1.6 mm; 2) 4.7 teeth in relation to: UE – 10 mm, EB – 5.0 mm, BS – 4.2 mm, LS – 1.4 mm. In the second study group, a 35-year-old patient with a terminal dentition defect, the topography of the right mandibular canal is characterized by morphometric values in the projection of the missing: 1) 4.6 tooth in relation to: UE – 13.1 mm EB – 5.4 mm, BS – 3.3 mm, LS – 1.6 mm; 2) 4.7 tooth in relation to: UE – 11.8 mm, EB – 6.8 mm, BS – 3.3 mm, LS – 1.9 mm. A 52-year-old patient of the third study group with a terminal dentition defect, the topography of the right mandibular canal is characterized by morphometric values in the projection of the missing: 1) 4.6 tooth in relation to: UE – 13.9 mm, EB – 7.4 mm, BS – 3.9 mm, LS – 5.7 mm, 2) 4.7 tooth in relation to: UE – 11.7 mm, EB – 7.6 mm, BS – 5.2 mm, LS – 4.6 mm. Topographic differences in the right mandibular canal are represented by a 64-year-old patient of the fourth study group with a terminal dentition defect, characterized by morphometric values in the projection of the missing: 1) 4.6 tooth in relation to: UE – 11.6 mm, EB – 5.7 mm, BS – 3.8 mm, LS – 4.9 mm; 2) 4.7 tooth (fig. 9) in relation to: UE – 10.0 mm, EB – 5.0 mm, BS – 4.2 mm, LS – 4.2 mm. Conclusion. The topography of the mandibular canal, and accordingly the laying of the neurovascular bundle in it, remain a guide when drawing up a treatment plan and for choosing rehabilitation procedures for patients with tooth loss, following existing and approved protocols. The analysis of the obtained absolute values does not reveal the corresponding patterns of topographic changes in the mandibular canal, depending on bone atrophy caused by the loss of the molars, in different age categories

Spiral 2D T2-Weighted TSE Brain MR Imaging: Initial Clinical Experience.

Spiral MR imaging may enable improved image quality and higher scan speeds than Cartesian trajectories. We sought to compare a novel spiral 2D T2-weighted TSE sequence with a conventional Cartesian and an artifact-robust, non-Cartesian sequence named MultiVane for routine clinical brain MR imaging. Thirty-one patients were scanned with all 3 sequences (Cartesian, 4 minutes 14 seconds; MultiVane, 2 minutes 49 seconds; spiral, 2 minutes 12 seconds) on a standard clinical 1.5T MR scanner. Three readers described the presence and location of abnormalities and lesions and graded images qualitatively in terms of overall image quality, the presence of motion and pulsation artifacts, gray-white matter differentiation, lesion conspicuity, and subjective preference. Image quality was objectivized by measuring the SNR and the coefficients of variation for CSF, GM, and WM. Spiral achieved a scan time reduction of 51.9% and 21.9% compared with Cartesian and MultiVane, respectively. The number and location of lesions were identical among all sequences. As for the qualitative analysis, interreader agreement was high (Krippendorff α > .75). Spiral and MultiVane both outperformed the Cartesian sequence in terms of overall image quality, the presence of motion artifacts, and subjective preference (P < .001). In terms of the presence of pulsation artifacts, gray-white matter differentiation, and lesion conspicuity, all 3 sequences performed similarly well (P > .15). Spiral and MultiVane outperformed the Cartesian sequence in coefficient of variation WM and SNR (P < .01). Spiral 2D T2WI TSE is feasible for routine structural brain MR imaging and offers high-quality, artifact-robust brain imaging in short scan times.

Reproducibility of Longitudinal Changes in Cortical Thickness Determined by Surface-Based Morphometry Between Non-Accelerated and Accelerated MR Imaging.

Scan acceleration such as parallel imaging reduces scan time, but shorter scan time may reduce the signal-to-noise ratio and affect image quality. The reproducibility of longitudinal changes in the brain structure between non-accelerated and accelerated imaging by surface-based analysis is unclear. To determine the reproducibility of longitudinal changes in cortical thickness, measured by surface-based morphometry, between non-accelerated and accelerated structural T1 -weighted imaging in the healthy elderly and those with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Retrospective. Fifty healthy elderly subjects (age=73 ± 5 years, 29 females, 21 males), 54 MCI patients (age=71 ± 7 years, 23 females, 31 males), and 8 AD patients (age=78 ± 6 years, 6 females, 2 males). 3 T, magnetization-prepared rapid gradient-echo. Longitudinal changes in cortical thickness estimated by the longitudinal stream in FreeSurfer from 2-year interval data, and visual assessment of image quality by three radiologists. Intraclass correlation coefficient (ICC) and Kruskal-Wallis test. A P value <0.05 was considered significant. Healthy elderly subjects, MCI patients, and AD patients showed different patterns in the ICC maps. For the smoothing of 20 mm full width at half maximum, the mean ICC was 0.45 overall (healthy elderly, 0.33; MCI patients, 0.49; AD patients, 0.31). The within-subject SDs of the symmetrized percent changes were similar between healthy elderly subjects (mean, 1.3%/year) and MCI patients (mean, 1.3%/year) but larger in AD patients (mean, 1.7%/year). Image quality did not significantly differ per group (P=0.18). The results of this study indicate the reproducibility of longitudinal changes in cortical thickness measured by surface-based morphometry between non-accelerated and accelerated imaging, and that the reproducibility varies by disease and region. 3 TECHNICAL EFFICACY: Stage 1.

A silent gradient axis for soundless spatial encoding to enable fast and quiet brain imaging.

PurposeA novel silent imaging method is proposed that combines a gradient insert oscillating at the inaudible frequency 20 kHz with slew rate‐limited gradient waveforms to form a silent gradient axis that enable quiet and fast imaging.MethodsThe gradient insert consisted of a plug‐and‐play (45 kg) single axis z‐gradient, which operated as an additional fourth gradient axis. This insert was made resonant using capacitors and combined with an audio amplifier to allow for operation at 20 kHz. The gradient field was characterized using field measurements and the physiological effects of operating a gradient field at 20 kHz were explored using peripheral nerve stimulation experiments, tissue heating simulations and sound measurements. The imaging sequence consisted of a modified gradient‐echo sequence which fills k‐space in readout lanes with a width proportional to the oscillating gradient amplitude. The feasibility of the method was demonstrated in‐vivo using 2D and 3D gradient echo (GRE) sequences which were reconstructed using a conjugate‐gradient SENSE reconstruction.ResultsField measurements yielded a maximum gradient amplitude and slew rate of 40.8 mT/m and 5178T/m/s at 20 kHz. Physiological effects such as peripheral nerve stimulation and tissue heating were found not to be limiting at this amplitude and slew rate. For a 3D GRE sequence, a maximum sound level of 85 db(A) was measured during scanning. Imaging experiments using the silent gradient axis produced artifact free images while also featuring a 5.3‐fold shorter scan time than a fully sampled acquisition.ConclusionA silent gradient axis provides a novel pathway to fast and quiet brain imaging.

Whole-Heart 4D Flow MRI for Evaluation of Normal and Regurgitant Valvular Flow: A Quantitative Comparison Between Pseudo-Spiral Sampling and EPI Readout.

BackgroundPseudo‐spiral Cartesian sampling with compressed sensing reconstruction has facilitated highly accelerated 4D flow magnetic resonance imaging (MRI) in various cardiovascular structures. However, unlike echo planar imaging (EPI)‐accelerated 4D flow MRI, it has not been validated in whole‐heart applications.HypothesisPseudo‐spiral 4D flow MRI (PROUD [PROspective Undersampling in multiple Dimensions]) is comparable to EPI in robustness of valvular flow measurements and remains comparable as the undersampling factor is increased and scan time reduced.Study TypeProspective.PopulationTwelve healthy subjects and eight patients with valvular regurgitation.Field Strength/Sequence3.0 T; PROUD and EPI 4D flow sequences, 2D flow and balanced steady‐state free precession sequences.AssessmentValvular blood flow was quantified using valve tracking. PROUD‐ and EPI‐based measurements of aortic (AV) and pulmonary (PV) flow volumes and left and right ventricular stroke volumes were tested for agreement with 2D MRI‐based measurements. PROUD reconstructions with undersampling factors (R) of 9, 14, 28, and 56 were tested for intervalve consistency (per valve, compared to the other valves) and preservation of peak velocities and E/A ratios.Statistical TestsWe used repeated measures ANOVA, Bland‐Altman, Wilcoxon signed rank, and intraclass correlation coefficients. P < 0.05 was considered statistically significant.ResultsPROUD and EPI intervalve consistencies were not significantly different both in healthy subjects (valve‐averaged mean difference [limits of agreement width]: 3.2 ± 0.8 [8.7 ± 1.1] mL/beat for PROUD, 5.5 ± 2.9 [13.7 ± 2.3] mL/beat for EPI, P = 0.07) and in patients with valvular regurgitation (2.3 ± 1.2 [15.3 ± 5.9] mL/beat for PROUD, 0.6 ± 0.6 [19.3 ± 2.9] mL/beat for EPI, P = 0.47). Agreement between EPI and PROUD was higher than between 4D flow (EPI or PROUD) and 2D MRI for forward flow, stroke volumes, and regurgitant volumes. Up to R = 28 in healthy subjects and R = 14 in patients with valvular regurgitation, PROUD intervalve consistency remained comparable to that of EPI. Peak velocities and E/A ratios were preserved up to R = 9.ConclusionPROUD is comparable to EPI in terms of intervalve consistency and may be used with higher undersampling factors to shorten scan times further.Level of Evidence1Technical Efficacy Stage2

Fractionated deep-inspiration breath-hold ZTE Compared with Free-breathing four-dimensional ZTE for detecting pulmonary nodules in oncological patients underwent PET/MRI

The zero echo time (ZTE) technique has improved the detection of lung nodules in PET/MRI but respiratory motion remains a challenge in lung scan. We investigated the feasibility and performance of fractionated deep-inspiration breath-hold (FDIBH) three-dimensional (3D) ZTE FDG PET/MRI for assessing lung nodules in patients with proved malignancy. Sixty patients who had undergone ZTE FDG PET/MRI and chest CT within a three-day interval were retrospectively included. Lung nodules less than 2 mm were excluded for analysis. Two physicians checked the adequacy of FDIBH ZTE and compared the lung nodule detection rates of FDIBH 3D ZTE and free-breathing (FB) four-dimensional (4D) ZTE, with chest CT as the reference standard. FDIBH resolved the effect of respiratory motion in 49 patients. The mean number and size of the pulmonary nodules identified in CT were 15 ± 31.3 per patient and 5.9 ± 4.6 mm in diameter. The overall nodule detection rate was 71% for FDIBH 3D ZTE and 70% for FB 4D ZTE (p = 0.73). FDIBH 3D ZTE significantly outperformed FB 4DZTE in detecting lung base nodules (72% and 68%; p = 0.03), especially for detecting those less than 6 mm (61% and 55%; p = 0.03). High inter-rater reliability for FDIBH 3D ZTE and FB 4D ZTE (k = 0.9 and 0.92) was noted. In conclusion, the capability of FDIBH 3D ZTE in respiratory motion resolution was limited with a technical failure rate of 18%. However, it could provide full expansion of the lung in a shorter scan time which enabled better detection of nodules (< 6 mm) in basal lungs, compared to FB 4D ZTE.

Value of cone-beam computer tomography in the middle and inner ear observation

Objective:To identified the feasibility and normal range of cone beam computer tomography（CBCT） in the measurement of temporal bone. Methods:15 formalin fixed human cadaver head specimens were scanned by CBCT, high resolution CT, and Micro CT, respectively. Morphological parameter measurements of the middle and inner ear structures including ossicular chain, cochlea, semicircular canal and facial nerve were performed, and the results measured by the three scanning methods were compared. Results:None of the parameters measured by the three scanning methods were statistically significant except the thickness of stapes footplate（P<0.01） and the diameter of cochlear basal turn（P<0.01）. CBCT was superior in detecting facial nerve bony canal dehiscence. Conclusion:CBCT has the advantages of short scanning time, low radiation dose and high resolution. It can accurately display the morphological characteristics of the temporal bone structures, and is a reliable evaluation method for otological surgery.

Evaluation of peripheral nerve acute crush injury in rabbits: comparison among diffusion kurtosis imaging, diffusion tensor imaging and electromyography.

Diffusion kurtosis imaging (DKI) has been proven to provide additional value for assessing many central nervous system diseases compared with conventional diffusion tensor imaging (DTI); however, whether it has the same value in peripheral nerve injury is unclear. This study aimed to investigate the performance of DKI, DTI, and electromyography (EMG) in evaluating peripheral nerve crush injury (PNCI) in rabbits. A total of 27 New Zealand white rabbits were selected to establish a PNCI model. Longitudinal DTI, DKI, and EMG were evaluated before surgery and 1day, 3days, 1week, 2weeks, 4weeks, 6weeks, and 8weeks after surgery. At each time point, two rabbits were randomly selected for pathological examination. The results showed that fractional anisotropy (FA) derived from both DKI and DTI demonstrated a significant difference between injured and control nerves at all time points (all P < 0.005) mean kurtosis of the injured nerve was lower than that on the control side after 2-8weeks (all P < 0.05). No statistically significant difference was found in radial kurtosis, axial kurtosis, and apparent diffusion coefficient at almost every time point. The difference in compound muscle action potential (CMAP) of the bilateral gastrocnemius at each time point was statistically significant (all P < 0.001). CMAP was a sensitive and reliable method to assess acute PNCI without being affected by perineural edema. DKI may not be superior to DTI in evaluating peripheral nerves, DTI with a shorter scanning time was preferred as an effective choice for evaluating acute peripheral nerve traumatic injury.

Acquisition count dependence of the specific binding ratio in 123I-FP-CIT SPECT.

In the [123I]FP-CIT single-photon emission computed tomography (SPECT) examination, the specific binding ratio (SBR), calculated from the ratio of the striatal specific to extra-striatal background non-specific binding in the brain, is now commonly used as a quantitative index of parkinsonian syndrome. The purpose of this study was to examine the influence of count reduction on the SBR and to clarify the reliability of SBR values in patients with shorter scan times. A striatum phantom was used in a phantom study, with the radioactivity concentration adjusted so that the right striatum:left striatum:brain parenchyma ratio was 8:4:1. Changes in SBR values and image quality, expressed as the % coefficient of variation (%CV) and normalized mean squared error (NMSE), with decreasing acquisition counts were evaluated. In the clinical study, 106 patients (73.1 ± 9.6years) with suspected parkinsonian syndrome underwent [123I]FP-CIT SPECT, and SBR values from normal 30min acquisitions (fullSBR) and half-count acquisitions (halfSBR) were compared. SBR values were calculated using the Tossici-Bolt (SBRTB) and a fully automatic count-based (SBRcb) methods. In the phantom study, image quality decreased with a reduction of acquisition counts. The %CV and NMSE decreased by up to 52.5% and 81.5%, respectively. SBR values decreased slightly as acquisition counts decreased. In the clinical study, the mean values of halfSBR were lower than those of fullSBR, and they were significantly different except for SBRTB without attenuation correction. halfSBR and fullSBR values correlated well, with halfSBR values 1-8% lower than fullSBR. The accuracy of diagnosis did not decrease even after acquisition counts were reduced by half. This study demonstrated that SBR values decrease as a function of reduced acquisition counts. Since halfSBR and fullSBR showed excellent correlation, it is suggested that fullSBR can be estimated from halfSBR using a calibration formula when scan times are reduced.

Use of advanced cardiac imaging in congenital heart disease: growth, indications and innovations.

Significant improvements in the diagnosis and management of patients with congenital heart disease (CHD) have led to improved survival. These patients require life-long noninvasive evaluation. The use of advanced imaging such as cardiac magnetic resonance imaging (CMR) and cardiac computed tomography (CCT) has increased to support this need. The purpose of this review is to discuss the basics of advanced cardiac imaging, indications and review the recent innovations. Recent literature has demonstrated the increasing reliance of advanced imaging for CHD patients. In addition, research is focusing on CMR techniques to shorten scan time and address previous limitations that made imaging younger and sicker patients more challenging. CCT research has involved demonstrating high-quality images with low radiation exposure. Advances in digital technology have impacted the interactivity of 3D imaging through the use of virtual and augmented reality platforms. With the increased reliance of advanced imaging, appropriate use criteria have been developed to address possible under or over utilization. The utilization of advanced cardiac imaging continues to increase. As CMR and CCT continue to grow, increased knowledge of these modalities and their usage will be necessary for clinicians caring for CHD patients.

Multi-Perspective Analysis of Building Orientation Effects on Microstructure, Mechanical and Surface Properties of SLM Ti6Al4V with Specific Geometry.

Building orientation is important in selective laser melting (SLM) processes. Current studies only focus on the horizontal and vertical building orientations without considering different modes of horizontal orientations. In fact, for horizontal orientation, different surfaces of the sample that contact the substrate will affect the heat transfer mode and efficiency, and in turn affect the microstructure and material properties. In this paper, the effect of two modes of horizontal building orientations on microstructure, mechanical and surface properties of SLM Ti6Al4V was studied. Current research about building orientation is deficient because the geometry of samples or test surfaces are not strictly defined, which seriously influences the results due to their different heat transfer efficiency and mode. Therefore, the geometry of the samples and test surfaces were clearly defined, and its necessity was proved in this study. To achieve the research goal, three test samples were prepared: sample SLM-PB-S with the building orientation parallel to the substrate and the shorter side L1 contacts it, sample SLM-PB-L with the building orientation parallel to the substrate and the longer side L2 contacts it and sample SLM-VB with the building orientation vertical to the substrate. Subsequently, the microstructure, grain information, densification, residual stress, micro-hardness, tensile properties and surface topography of different samples were analyzed and compared. In the results, SLM-PB-S exhibited denser microstructure and better mechanical properties than SLM-PB-L, including smaller grain size, stronger texture, higher density, micro-hardness, tensile strength, plasticity and better surface quality. It originates from a higher cooling rate and shorter scanning time between layers during SLM-PB-S fabrication, leading to finer grains, lower porosity and better interlayer metallurgical bonding, thus resulting in better material properties. This study can provide a reference to select the proper building orientation in SLM.

Optimized Reconstruction Algorithm Based Analysis of Effects of Exercise Therapy Combined with Celecoxib Capsules on the Rehabilitation of Knee Osteoarthritis Using Computed Tomography Images

The aim was to explore the application value of computed tomography (CT) images based on optimized reconstruction algorithm (ORA) in knee osteoarthritis (KOA) and to analyze the rehabilitation effect of exercise therapy combined with celecoxib capsules on KOA. On the basis of iterative reconstruction algorithm, sparse data and compressed sensing (CS) algorithm were introduced in this study for the image reconstruction and were compared with the reconstruction effects of other algorithms. 105 patients with KOA were selected as the subjects investigated, who were treated in the hospital from December 2018 to January 2020. They were divided randomly into group A (exercise therapy), group B (celecoxib capsule therapy), and group C (exercise therapy combined with celecoxib capsules), with 35 patients in each group. All the patients were scanned by CT. Visual analogue score (VAS) method was adopted to compare the pain symptoms of patients in the three groups before and after treatment. The Lysholm knee function score was employed to evaluate the knee function of the patient before and after treatment, and finally the difference in the total effective rate of treatment was compared. The results showed that the reconstruction algorithm in this study had a higher degree of coincidence with the original image, and its root mean square error (RMSE), peak signal-to-noise ratio (PSNR), and structural similarity (SSIM) were greatly higher than those of filtered back-projection (FBP) algorithm. There was no huge difference between Lysholm score and VAS in patients of the three groups before treatment ( P &gt; 0.05 ). Besides, Lysholm score in all dimensions and its total score after treatment were higher than those of patients in the three groups before treatment ( P &lt; 0.05 ), and those of patients in group C increased extremely in contrast to group A ( P &lt; 0.05 ). VAS after treatment were all lower in patients of the three groups than those before treatment ( P &lt; 0.05 ), and VAS of patients in group C were sharply lower than those of group A ( P &lt; 0.05 ), but the total effective rate of patients in group C was dramatically higher than the rate of group A ( P &lt; 0.05 ). It indicated that an algorithm with short scanning time and good image quality was established based on iterative reconstruction algorithm. Exercise therapy combined with celecoxib capsules could alleviate the pain symptoms and improve the function of knee joint, which was more advantageous than the simple rehabilitation comprehensive therapy. Therefore, it had higher clinical value for the patients with KOA.

Imaging modalities for endoleak surveillance.

As the global population ages, the issue of abdominal aortic aneurysm continues to grow. With the evolution of new devices and refined operative technique, aneurysm treatment via endovascular aortic repair is becoming increasingly favourable. This, however, is not without drawbacks, where regular surveillance is paramount to long‐term success and detection of post‐procedure complications. Of these complications, endoleak is the most notable and poses the greatest risk of potential future aortic rupture. The purpose of this review paper is to discuss the armada of imaging modalities used in the detection and evaluation of endoleak and their varying usefulness. Plain abdominal X‐ray is a cost‐effective tool in detecting gross graft abnormalities such as stent migration or deformity (kinking or fracture). Though it may raise suspicion for endoleak, X‐ray does not allow accurate classification of endoleak type when used alone. Duplex ultrasonography quantifies both aortic anatomy and real time flow dynamics. Most screening programmes are conducted using two‐dimensional ultrasound. Unfortunately, observer and equipment variability may lead to surveillance discrepancies—but reduced when utilising a dedicated vascular sonography laboratory. Contrast enhanced ultrasonography is a promising alternative to computed tomography, though still is emerging. Computed tomography angiography certainly has disadvantages (ionising radiation, contrast‐nephropathy, limited differentiation of endoleak type)—however, it provides near‐real surgical dimensions and highlights graft complications and concomitant disease (such as neighbouring infection). With widespread availability and short scan time, it certainly remains valuable in surveillance. Magnetic resonance angiography has a similar sensitivity to computed tomography (minus the radiation), however is plagued by movement and metal artefact. Other novel modalities in endoleak surveillance include four‐dimensional ultrasound, multiplanar intra‐operative probes, nuclear medicine and wall stress analysis.