Fast magnetic resonance elastography with multiphase radial encoding and harmonic motion sparsity based reconstruction

Objective: To achieve fast magnetic resonance elastography (MRE) at a low frequency for better shear modulus estimation of the brain. Approach: We proposed a multiphase radial DENSE MRE (MRD-MRE) sequence and an improved GRASP algorithm utilizing the sparsity of the harmonic motion (SH-GRASP) for fast MRE at 20 Hz. For the MRD-MRE sequence, the initial position encoded by one spatial modulation of magnetization (SPAMM) was decoded by an arbitrary number of readout blocks without increasing the number of phase offsets. Based on the harmonic motion, a modified total variation and temporal Fourier transform were introduced to utilize the sparsity in the temporal domain. Both phantom and brain experiments were carried out and compared with that from multiphase Cartesian DENSE-MRE (MCD-MRE), and conventional gradient echo sequence (GRE-MRE). Reconstruction performance was also compared with GRASP and compressed sensing. Main results: Results showed the scanning time of a fully sampled image with four phase offsets for MRD-MRE was only 1/5 of that from GRE-MRE. The wave patterns and estimated stiffness maps were similar to those from MCD-MRE and GRE-MRE. With SH-GRASP, the total scan time could be shortened by additional 4 folds, achieving a total acceleration factor of 20. Better metric values were also obtained using SH-GRASP for reconstruction compared with other algorithms. Significance: The MRD-MRE sequence and SH-GRASP algorithm can be used either in combination or independently to accelerate MRE, showing the potentials for imaging the brain as well as other organs.

Visual search training benefits from the integrative effect of enhanced covert attention and optimized overt eye movements

Visual search in a complex environment requires efficient discrimination between target and distractors. Training serves as an effective approach to improve visual search performance when the target does not automatically pop out from the distractors. In the present study, we trained subjects on a conjunction visual search task and examined the training effects in behavior and eye movement from Experiments 1 to 4. The results showed that training improved behavioral performance and reduced the number of saccades and overall scanning time. Training also increased the search initiation time before the first saccade and the proportion of trials in which the subjects correctly identified the target without any saccade, but these effects were modulated by stimulus' parameters. In Experiment 5, we replicated these training effects when eye movements and EEG signals were recorded simultaneously. The results revealed significant N2pc components after the stimulus onset (i.e., stimulus-locked) and before the first saccade (i.e., saccade-locked) when the search target was the trained one. These N2pc components can be considered as the neural signatures for the training-induced boost of covert attention to the trained target. The enhanced covert attention led to a beneficial tradeoff between search initiation time and the number of saccades as a small amount of increase in search initiation time could result in a larger reduction in scanning time. These findings suggest that the enhanced covert attention to target and optimized overt eye movements are coordinated together to facilitate visual search training.

Effective Study: Development and Application of a Question‐Driven, Time‐Effective Cardiac Magnetic Resonance Scanning Protocol

Background Long scanning times impede cardiac magnetic resonance (CMR) clinical uptake. A “one‐size‐fits‐all” shortened, focused protocol (eg, only function and late‐gadolinium enhancement) reduces scanning time and costs, but provides less information. We developed 2 question‐driven CMR and stress‐CMR protocols, including tailored advanced tissue characterization, and tested their effectiveness in reducing scanning time while retaining the diagnostic performances of standard protocols. Methods and Results Eighty three consecutive patients with cardiomyopathy or ischemic heart disease underwent the tailored CMR. Each scan consisted of standard cines, late‐gadolinium enhancement imaging, native T1‐mapping, and extracellular volume. Fat/edema modules, right ventricle cine, and in‐line quantitative perfusion mapping were performed as clinically required. Workflow was optimized to avoid gaps. Time target was <30 minutes for a CMR and <35 minutes for a stress‐CMR. CMR was considered impactful when its results drove changes in diagnosis or management. Advanced tissue characterization was considered impactful when it changed the confidence level in the diagnosis. The quality of the images was assessed. A control group of 137 patients was identified among scans performed before February 2020. Compared with standard protocols, the average scan duration dropped by >30% (CMR: from 42±8 to 28±6 minutes; stress‐CMR: from 50±10 to 34±6 minutes, both P <0.0001). Independent on the protocol, CMR was impactful in ≈60% cases, and advanced tissue characterization was impactful in >45% of cases. Quality grading was similar between the 2 protocols. Tailored protocols did not require additional staff. Conclusions Tailored CMR and stress‐CMR protocols including advanced tissue characterization are accurate and time‐effective for cardiomyopathies and ischemic heart disease.

Potential quality pitfalls of digitalized whole slide image of breast pathology in routine practice

Using digitalized whole slide images (WSI) in routine histopathology practice is a revolutionary technology. This study aims to assess the clinical impacts of WSI quality and representation of the corresponding glass slides. 40,160 breast WSIs were examined and compared with their corresponding glass slides. The presence, frequency, location, tissue type, and the clinical impacts of missing tissue were assessed. Scanning time, type of the specimens, time to WSIs implementation, and quality control (QC) measures were also considered. The frequency of missing tissue ranged from 2% to 19%. The area size of the missed tissue ranged from 1–70%. In most cases (>75%), the missing tissue area size was <10% and peripherally located. In all cases the missed tissue was fat with or without small entrapped normal breast parenchyma. No missing tissue was identified in WSIs of the core biopsy specimens. QC measures improved images quality and reduced WSI failure rates by seven-fold. A negative linear correlation between the frequency of missing tissue and both the scanning time and the image file size was observed (p < 0.05). None of the WSI with missing tissues resulted in a change in the final diagnosis. Missing tissue on breast WSI is observed but with variable frequency and little diagnostic consequence. Balancing between WSI quality and scanning time/image file size should be considered and pathology laboratories should undertake their own assessments of risk and provide the relevant mitigations with the appropriate level of caution.

A COMPARISON OF LASER AND STRUCTURED LIGHT SCANNING TECHNOLOGIES FOR ARCHAEOLOGICAL APPLICATIONS

Reverse engineering and in particular three-dimensional digitization have become an essential part of the documentation of archaeological findings. 3D scanning produces a high-precision digital reference document. The factors that influence the quality of the 3D scanned data are the scanned object’s surface colour, its glossiness and geometry, and the ambient light during the scanning process. However, the actual equipment and scanning technologies are of primary importance. The current paper presents a qualitative and quantitative comparison between two 3D scanning devices of different technologies; structured light 3D scanning and laser 3D scanning. The benchmark for this comparison is an ancient Roman vase from the city of Thessaloniki, Greece. The object was scanned with every possible setting on each scanner, but only one configuration of settings on each device was selected for the final comparison. The main criterion for the final selection of the two 3D models acquired with the use of the two technologies was the proximity in the number of points and polygons produced for digitally restoring the ancient vase in the best possible way. The results indicate important differences regarding the accuracy of the final digital model. The laser technology produced better accuracy but with a significant cost in scanning time and model data size. On the other hand, the structured light technology achieved the optimal combination of scanning quality and accuracy, along with reduced acquisition time of scan data.

Study on Memory Function of Stroke Patients under Exercise Relearning Based on DWI Image Analysis Based on Optimized Registration Algorithm

Objective. This paper uses an optimized registration algorithm to analyze the diffusion-weighted imaging (DWI) scan parameters of acute ischemic stroke (AIS) in the memory function of stroke patients under exercise relearning (MRP). Methods. This study used a random case-control study. 65 patients with stroke and hemiplegia were randomly divided into a control group: conventional rehabilitation intervention (32 cases), and a treatment group: MRP (33 cases). Each patient uses 4 parameters for DWI examination and obtains 4 sets of images, group 1 is the control sequence, group 2 uses parallel acquisition technology, group 3 uses parallel acquisition technology and reduces the number of excitations, group 4 uses parallel acquisition technology to reduce repetition time (TR) and echo time (TE) and enlarge the field of view, and the scan time of each group is 177, 81, 23, and 18 s in sequence. At the time of enrollment and after 12 weeks of treatment, patients in each group were evaluated with Fugl-Meyer motor function score (FMA) and modified Pap index (MBI) for hand and wrist motor function and ADL. Results. After treatment, the FMA and MBI values of the treatment group were significantly higher than those of the control group ( P < 0.05 ). Conclusion. By adopting a parallel acquisition technique and reducing the number of excitations (group 3) scanning scheme, not only the scanning time is significantly shortened, but also the image quality can meet the diagnostic requirements, which has great application value for AIS patients who need emergency treatment. MRP can obviously promote the hand and wrist motor function and daily living ability of stroke hemiplegic patients.

High-Resolution Simultaneous Multi-Slice Accelerated Turbo Spin-Echo Musculoskeletal Imaging: A Head-to-Head Comparison With Routine Turbo Spin-Echo Imaging

Background/Aim: The turbo spin-echo (TSE) sequence is widely used for musculoskeletal (MSK) imaging; however, its acquisition speed is limited and can be easily affected by motion artifacts. We aimed to evaluate whether the use of a simultaneous multi-slice TSE (SMS-TSE) sequence can accelerate MSK imaging while maintaining image quality when compared with the routine TSE sequence.Methods: We prospectively enrolled 71 patients [mean age, 37.43 ± 12.56 (range, 20–67) years], including 37 men and 34 women, to undergo TSE and SMS sequences. The total scanning times for the wrist, ankle and knee joint with routine sequence were 14.92, 13.97, and 13.48 min, respectively. For the SMS-TSE sequence, they were 7.52, 7.20, and 6.87 min. Quantitative parameters, including the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), were measured. Three experienced MSK imaging radiologists qualitatively evaluated the image quality of bone texture, cartilage, tendons, ligament, meniscus, and artifact using a 5-point evaluation system, and the diagnostic performance of the SMS-TSE sequences was evaluated.Results: Compared with the routine TSE sequences, the scanning time was lower by 49.60, 48.46, and 49.04% using SMS-TSE sequences for the wrist, ankle, and knee joints, respectively. For the SNR comparison, the SMS-TSE sequences were significantly higher than the routine TSE sequence for wrist (except for Axial-T2WI-FS), ankle, and knee joint MR imaging (all p &lt; 0.05), but no statistical significance was obtained for the CNR measurement (all p &gt; 0.05, except for Sag-PDWI-FS in ankle joint). For the wrist joint, the diagnostic sensitivity, specificity, and accuracy were 88.24, 100, and 92%. For the ankle joint, they were 100, 75, and 93.33%. For the knee joint, they were 87.50, 85.71, and 87.10%.Conclusion: The use of the SMS-TSE sequence in the wrist, ankle, and knee joints can significantly reduce the scanning time and show similar image quality when compared with the routine TSE sequence.

106 The effective study: development and application of a question-driven, time-effective cardiac magnetic resonance scanning protocol

Aims Long scanning times impede cardiac magnetic resonance (CMR) clinical uptake. A ‘one-size-fits-all’ shortened, focused protocol [e.g. only function and late-gadolinium enhancement (LGE)] reduces scanning time and costs, but provide less information. We developed two question-driven CMR and stress-CMR protocols, including tailored advanced tissue characterization, and tested their effectiveness in reducing scanning time while retaining the diagnostic performances of standard protocols. Methods and results Eighty-three consecutive patients with cardiomyopathy or ischaemic heart disease underwent the tailored CMR. Each scan consisted of standard cines, LGE imaging, native T1-mapping, and extracellular volume. Fat/oedema modules, right ventricle cine, and in-line quantitative perfusion mapping were performed as clinically required. Workflow was optimized to avoid gaps. See Figure 1 for protocol details. Time target was &lt;30 min for a CMR and &lt;35 min for a stress-CMR. CMR was considered impactful when its results drove changes in diagnosis or management. Advanced tissue characterization was considered impactful when it changed the confidence level in the diagnosis. Images’ quality was assessed. A ‘control group’ of 137 patients was identified among scans performed before February 2020. Compared to standard protocols, the average scan duration dropped by &gt; 30% (CMR: from 42 ± 8 to 28 ± 6min; stress-CMR: from 50 ± 10 to 34 ± 6min, both P &lt; 0.0001). Independent on the protocol, CMR was impactful in ∼60% cases, and advanced tissue characterization was impactful in &gt; 45% of cases. Quality grading was similar between the two protocols. Tailored protocols did not require additional staff. Conclusions Tailored CMR and stress-CMR protocols including advanced tissue characterization are accurate and time-effective for cardiomyopathies and ischaemic heart disease.

Application Progress of Gd-EOB-DTPA-Enhanced MRI T1 Mapping in Hepatic Diffuse Diseases

Background: In recent years, T1 mapping imaging based on Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) has resulted in new research and clinical applications in hepatic diseases. Objective: The objective of the study is to analyze, prospect, and summarize the Gd-EOB-DTPA-enhanced MRI T1 mapping technology in hepatic diseases in recent years. Main Findings: Gd-EOB-DTPA-enhanced T1 mapping has been used more frequently in liver diseases regardless of 1.5T or 3.0T MRI equipment. Volume interpolated body examination (VIBE) mapping sequence seems to be the recommended MRI scan sequence. In the evaluation of T1 value on liver function, the hepatobiliary phase 10 minutes after enhancement is the recommended time point. The fat fraction and hepatic steatosis grade based on MRI-derived biomarkers are easier to implement and popularize than a liver biopsy. Gd-EOB-DTPA-enhanced MRI T1 mapping can not only be used to evaluate the degree of liver injury, the stage of liver fibrosis, and the liver reserve function of patients with liver cirrhosis but also to distinguish focal liver lesions and predict the differentiation degree of hepatocellular carcinoma. At the same time, it has some value in predicting tumor immunohistochemical indexes, such as Ki67, CD34. Conclusion : Gd-EOB-DTPA-enhanced MRI T1 mapping has great potential in the application of diffuse and focal liver lesions. It is a quantitative study, trying to select homogeneous research objects and try to use the same standards in scanning sequence and scanning time, especially for the study of liver function, which is a focus of future research. The research on the relationship between T1 value and tumor immunohistochemical indexes is worth consideration.

Whole Three-Dimensional Dosimetry of Carbon Ion Beams with an MRI-Based Nanocomposite Fricke Gel Dosimeter Using Rapid T1 Mapping Method

MRI-based gel dosimeters are attractive systems for the evaluation of complex dose distributions in radiotherapy. In particular, the nanocomposite Fricke gel dosimeter is one among a few dosimeters capable of accurately evaluating the dose distribution of heavy ion beams. In contrast, reduction of the scanning time is a challenging issue for the acquisition of three-dimensional volume data. In this study, we investigated a three-dimensional dose distribution measurement method for heavy ion beams using variable flip angle (VFA), which is expected to significantly reduce the MRI scanning time. Our findings clarified that the whole three-dimensional dose distribution could be evaluated within the conventional imaging time (20 min) and quality of one cross-section.