Echo MR Research Articles

Evaluation of 3D T1-weighted spoiled gradient echo MR image quality using artificial intelligence image reconstruction techniques in the pediatric brain

PurposeTo assess image quality and diagnostic confidence of 3D T1-weighted spoiled gradient echo (SPGR) MRI using artificial intelligence (AI) reconstruction.Materials and methodsThis prospective, IRB-approved study enrolled 50 pediatric patients (mean age = 11.8 ± 3.1 years) undergoing clinical brain MRI. In addition to standard of care (SOC) compressed SENSE (CS = 2.5), 3D T1-weighted SPGR images were obtained with higher CS acceleration factors (5 and 8) to evaluate the ability of AI reconstruction to improve image quality and reduce scan time. Images were reviewed independently on dedicated research PACS workstations by two neuroradiologists. Quantitative analysis of signal intensities to calculate apparent grey and white matter signal to noise (aSNR) and grey-white matter apparent contrast to noise ratios (aCNR) was performed.ResultsAI improved overall image quality compared to standard CS reconstruction in 35% (35/100) of evaluations in CS = 2.5 (average scan time = 221 ± 6.9 s), 100% (46/46) of CS = 5 (average scan time = 113.3 ± 4.6 s) and 94% (47/50) of CS = 8 (average scan time = 74.1 ± 0.01 s). Quantitative analysis revealed significantly higher grey matter aSNR, white matter aSNR and grey-white matter aCNR with AI reconstruction compared to standard reconstruction for CS 5 and 8 (all p-values < 0.001), however not for CS 2.5.ConclusionsAI reconstruction improved overall image quality and gray-white matter qualitative and quantitative aSNR and aCNR in highly accelerated (CS = 5 and 8) 3D T1W SPGR images in the majority of pediatric patients.

Quantification of Visceral Fat at the L5 Vertebral Body Level in Patients with Crohn's Disease Using T2-Weighted MRI.

The umbilical or L3 vertebral body level is often used for body fat quantification using computed tomography. To explore the feasibility of using clinically acquired pelvic magnetic resonance imaging (MRI) for visceral fat measurement, we examined the correlation of visceral fat parameters at the umbilical and L5 vertebral body levels. We retrospectively analyzed T2-weighted half-Fourier acquisition single-shot turbo spin echo (HASTE) MR axial images from Crohn's disease patients who underwent MRI enterography of the abdomen and pelvis over a three-year period. We determined the area/volume of subcutaneous and visceral fat from the umbilical and L5 levels and calculated the visceral fat ratio (VFR = visceral fat/subcutaneous fat) and visceral fat index (VFI = visceral fat/total fat). Statistical analyses involved correlation analysis between both levels, inter-rater analysis between two investigators, and inter-platform analysis between two image-analysis platforms. Correlational analysis of 32 patients yielded significant associations for VFI (r = 0.85; p < 0.0001) and VFR (r = 0.74; p < 0.0001). Intraclass coefficients for VFI and VFR were 0.846 and 0.875 (good agreement) between investigators and 0.831 and 0.728 (good and moderate agreement) between platforms. Our study suggests that the L5 level on clinically acquired pelvic MRIs may serve as a reference point for visceral fat quantification.

Comparison of cerebral oxygen extraction fraction using ASE and TRUST methods in patients with sickle cell disease and healthy controls

Abnormal oxygen extraction fraction (OEF), a putative biomarker of cerebral metabolic stress, may indicate compromised oxygen delivery and ischemic vulnerability in patients with sickle cell disease (SCD). Elevated OEF was observed at the tissue level across the brain using an asymmetric spin echo (ASE) MR method, while variable global OEFs were found from the superior sagittal sinus (SSS) using a T2-relaxation-under-spin-tagging (TRUST) MRI method with different calibration models. In this study, we aimed to compare the average ASE-OEF in the SSS drainage territory and TRUST-OEF in the SSS from the same SCD patients and healthy controls. 74 participants (SCD: N = 49; controls: N = 25) underwent brain MRI. TRUST-OEF was quantified using the Lu-bovine, Bush-HbA and Li-Bush-HbS models. ASE-OEF and TRUST-OEF were significantly associated in healthy controls after controlling for hematocrit using the Lu-bovine or the Bush-HbA model. However, no association was found between ASE-OEF and TRUST-OEF in patients with SCD using either the Bush-HbA or the Li-Bush-HbS model. Plausible explanations include a discordance between spatially volume-averaged oxygenation brain tissue and flow-weighted volume-averaged oxygenation in SSS or sub-optimal calibration in SCD. Further work is needed to refine and validate non-invasive MR OEF measurements in SCD.

MRI reveals cerebral iron, calcification and spinal cord atrophy in M83 mouse model of Parkinson’s disease

AbstractBackgroundRodent models of Parkinson’s disease have been crucial tools for understanding the pathogenic mechanisms of alpha‐synuclein‐associated alterations. Here, we employed multiparametric high‐field magnetic resonance imaging (MRI) to examine the molecular alterations and neurodegeneration in the brain and spinal cord of transgenic M83 (A53T) murine model of Parkinson’s disease.MethodTen nontransgenic littermates and twelve M83 mice at 10‐11 months of age were assessed. Gradient echo MR for susceptibility‐weighted imaging (SWI) and T1 MR scans were acquired ex vivo at 9.4 T in the brain and spinal cord of mice. Histology and immunofluorescence staining for alpha‐synuclein inclusions (phospho‐S129), NeuN, GFAP and Iba‐1 for gliosis were used to investigate the nature of the imaging observations.ResultFrom T1 MR, a reduced area of white matter in the thoracic spinal cord (T1) and a reduced area of gray matter in the cervical (C6‐C8) and thoracic (T1) spinal cord were observed in the M83 mice compared to nontransgenic mice. In addition, lower left‐right length measurements in the cervical (C8) spinal cord were observed in M83 mice than in nontransgenic mice. SW images revealed regional hypointensities in the hippocampus, cortex, striatum, midbrain and thalamus of M83 mice, which in corresponding phase images indicated both diamagnetic (calcification) and paramagnetic (iron) lesions in the brains of M83 mice. Immunofluorescence staining demonstrated an increased Iba‐1 level in the brains of M83 mice, indicating microgliosis.ConclusionWe found cerebral iron, calcification, microgliosis and spinal cord atrophy in M83 mice.

Subnodal Correspondence of PSMA Expression and USPIO-MRI in Metastatic Pelvic Lymph Nodes in Prostate Cancer.

Two advanced imaging modalities used to detect lymph node (LN) metastases in prostate cancer patients are prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography and ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI). As these modalities use different targets, a subnodal comparison is needed to interpret both their correspondence and their differences. The aim of this explorative study was to compare ex vivo 111 In-PSMA μSPECT images with high-resolution 7 T USPIO μMR images and histopathology of resected LN specimens from prostate cancer patients to assess the degree of correspondence at subnodal level. Twenty primary prostate cancer patients who underwent pelvic LN dissection were included and received USPIO contrast and 111 In-PSMA. A total of 41 LNs of interest (LNOIs) were selected for ex vivo imaging based on γ-probe detection or palpation. μSPECT and μMRI acquisition were performed immediately after resection. Overlay of μSPECT images on MR images was performed, and the level of correspondence (LoC) between μSPECT and μMR findings was assessed according to a 4-point Likert classification scheme. Forty-one LNOIs could be matched to an LN on ex vivo μMRI. Coregistration of μSPECT and USPIO-enhanced water-selective multigradient echo MR images was successful for all 41 LNOIs. Ninety percent of the lesions showed excellent correspondence regarding the presence of metastatic tissue and affected subnodal site (LoC 4; 37/41). In only 1 of 41 LNOIs, a small metastasis was misclassified by both techniques. Three LNOIs were classified as LoC 3 (7%) and 1 LNOI as LoC 2. All LoC 2 and LoC 3 lesions had PSMA-expressing metastases on final histopathology. Coregistration of μSPECT and USPIO-μMRI showed excellent subnodal correspondence in the majority (90%) of LNs. Ex vivo imaging may thus help localize small cancer deposits within resected LNs and could contribute to improved interpretation of in vivo imaging of LNs.

NIMG-64. IN VIVO METABOLIC PROFILING FOR RECURRENT GLIOMA

Abstract INTRODUCTION The 2021 WHO classification has identified the importance of molecular features in diagnosing adult glioma. The goal of this study was to use short echo MR spectroscopic imaging (MRSI) to evaluate the metabolite profiles at recurrence and characterize in vivo metabolism in relation to pathology by combining it with image-guided tissue samples. METHODS Fifty-one patients with an initial diagnosis of glioma (18 astrocytoma, 14 oligodendroglioma, and 19 glioblastoma) received MR examinations before surgical resection of progressive disease confirmed histologically. The 3D MRSI data were combined, processed, and quantified by LCModel with a simulated basis set. Metabolite levels were compared between contrast-enhancing lesions (CEL), non-enhancing lesions (NEL), and patient groups. Spectra data centered at the tissue target location were correlated to pathological parameters from the samples (0-4 samples/subject). RESULTS 74.5% (38/51) patients had enhancing tumors, with median CEL volume of 4.2 cm3 (min-max: 0.2-28.5 cm3) and median NEL volumes of 50.6 cm3 (4.8-167.2 cm3). The patients with GBM had significantly larger CEL volumes than the others (p=0.009).18/29 (62%) patients with lower-grade glioma had malignant progression to higher grades. Those who progressed from grade 2 to 3 or 4 had higher myo-inositol/choline (mean±SD, 2.62±0.64, N=18) compared to those who recurred as grade 2 (1.88±0.52, N=5, p = 0.015). Of the 51 patients, 40/65 in vivo spectra voxels centered where the tissues were sampled displayed good quality, with 27 having active tumors, 7 having treatment effects, and 6 having mixed tumors/treatment effects. The levels of choline/creatine and myo-inositol+glycline/creatine were significantly correlated with MIB-1 (p&amp;lt; 0.0001, =0.034; r=0.563, 0.349), but no difference was found between the locations with active tumors and treatment effects. DISCUSSION: This study demonstrated metabolite variations at the recurrence. Ongoing studies will further characterize the metabolite profiles for malignant progression and differences between active tumors and treatment effects.

Ablation lesion formation after PVI with cryoballoon versus CLOSE-guided RF ablation assessed by late gadolinium enhancement CMR

Abstract Background Durable pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation. Technological advances like ablation index-guided RF ablation and second generation cryoballoon have substantially improved lesion durability, but PV reconnection remains a key determinant of AF recurrences. Purpose We aimed to compare RF ablation following the CLOSE protocol and latest cryoballoon ablation regarding lesion continuity and durability using late gadolinium enhancement (LGE) CMR. Methods This study was based on a prospective registry in which all patients receive an LGE-CMR at 3 months after AF ablation. LGE-CMRs from consecutive patients that had undergone first-time PVI-only AF ablation, either by CLOSE-guided RF ablation (CLOSE) or cryo-ablation with the arctic front advance balloon (CRYO) were analysed. Gradient echo MR sequences were acquired in sinus rhythm and 3D-reconstruction of left atrium and PVs performed using ADAS-3D software. LGE was quantified based on the signal intensity ratio of each voxel relative to the blood pool, applying a previously validated threshold of &amp;gt;1.2 to define LGE indicative of ablation-induced scarring. LGE discontinuations of &amp;gt;3 mm were considered as gaps, and complete lesions were defined as LGE covering &amp;gt;90% of the peri-antral circumference of ipsilateral PV pairs. The analysis included an assessment of the average number of gaps around PV ostia, the normalized gap length, which was calculated as a percentage of the total gap length and the total PV perimeter. The ablation lesion width was also measured in millimetres. Results Post-ablation LGE-CMR from 87 patients were analysed - 40 patients in the CRYO group (70% paroxysmal AF), 47 in the CLOSE group (47% paroxysmal AF). The post-ablation LGE-lesions encircling ipsilateral PVs covered 74% (CRYO) and 75% (CLOSE) of the peri-antral circumference, obtaining no significant difference in the normalized gap length (26.23% vs 24.74%, p=0.7 ), as presented in figure 1c. Although LGE lesions were significantly wider in the CRYO group (9.33 vs 7.11 mm, p&amp;lt;0.001) as presented in figure 1a and figure 1b; the proportion of PVs with complete circumferential LGE lesions was higher with CLOSE-guided RF ablation (39% vs. 24%, p=0.034). However, the total number of gaps per patient was similar in both groups (2.7 vs 3.2, p=0.16). Of note, in both groups, detectable gaps were more frequent in right vs. left PVs (1.98 vs 1.08, p&amp;lt;0.001). Finally, 12-months arrhythmia-free survival rates did not differ significantly (CRYO 60.0% vs. CLOSE 72.4%; p=0.26), albeit it has to be considered that the study was not powered to detect subtle or moderate between-group differences in clinical endpoints. Conclusion While ablation lesions are significantly wider with cryoballoon ablation, lesions continuity may be better with CLOSE-guided RF ablation.Segmentation and Box plot of RF and CRYO

Intra-examination agreement between multi-echo gradient echo and confounder-corrected chemical shift-encoded MR sequences for R2* estimation as a biomarker of liver iron content in patients with a wide range of T2*/R2* and proton density fat fraction values.

To investigate the intra-examination agreement between multi-echo gradient echo (MEGE) and confounder-corrected chemical shift-encoded (CSE) sequences for liver T2*/R2* estimations in a wide range of T2*/R2* and proton density fat fraction (PDFF) values. Exploratorily, to search for the T2*/R2* value where the agreement line breaks and examine differences between regions of low and high agreement. Consecutive patients at risk for liver iron overload who underwent MEGE and CSE sequences within the same exam at 1.5T were retrospectively selected. Regions of interest were drawn in the right and one in the left liver lobes on post-processed images for R2*(sec-1) and PDFF (%) estimation. Agreement between MEGE-R2* and CSE-R2* was evaluated using intra-class correlation coefficient (ICC) and Bland-Altman analysis. 95% confidence intervals (CI) were computed. Segment-and-regression analysis was performed to find the point where the agreement between sequences is interrupted. Regions of low and high agreement were examined using tree-based partitioning analyses. 49 patients were included. Mean MEGE-R2* was 94.2s-1 (range: 31.0-737.1) and mean CSE-R2* 87.7 (29.7-748.1). Mean CSE-PDFF was 9.12% (0.1-43.3). Agreement was strong for R2* estimations (ICC: 0.992,95%CI 0.987,0.996), but the relation was nonlinear and possibly heteroskedastic. Lower agreement occurred when MEGE-R2* > 235s-1, with MEGE-R2* values consistently lower than CSE-R2*. Higher agreement was observed when PDFF < 14%. MEGE-R2* and CSE-R2* strongly agree, though at higher iron content, MEGE-R2* is consistently lower than CSE-R2*. In this preliminary dataset, a breaking point for agreement was found at R2* > 235. Lower agreement was observed in patients with moderate to severe liver steatosis.

Longitudinal changes in quantitative magnetic resonance imaging metrics in children and young adults with autoimmune liver disease.

To assess longitudinal changes in quantitative MRI metrics in pediatric and young adult patients with autoimmune liver disease (AILD). This prospective, IRB-approved study included 20 children and young adults (median age = 15years) with primary sclerosing cholangitis (PSC)/autoimmune sclerosing cholangitis (ASC) and 19 (median age = 17years) with autoimmune hepatitis (AIH). At a field strength of 1.5-T, T2*-corrected T1 mapping (cT1), 3D fast spin-echo MRCP, and 2D gradient recalled echo MR elastography (MRE) were performed at baseline, one year, and two years. cT1 and quantitative MRCP were processed using LiverMultiScan and MRCP + , respectively (Perspectum Ltd, Oxford, UK). Linear mixed models were used to assess longitudinal changes in quantitative MRI metrics. Spearman rank-order correlation was used to assess relationships between changes in quantitative MRI metrics. Changes in quantitative MRI metrics greater than established repeatability coefficients were measured in six (cT1) and five (MRE) patients with PSC/ASC as well as in six patients (cT1 and MRE) with AIH, although linear mixed models identified no significant changes for the subgroups as a whole. For PSC/ASC, there were positive correlations between change in liver stiffness and changes in bile duct strictures (ρ = 0.68; p = 0.005) and bile duct dilations (ρ = 0.70; p = 0.004) between baseline and Year 2. On average, there were no significant changes in quantitative MRI metrics over a two-year period in children and young adults with AILD. However, worsening cholangiopathy was associated with increasing liver stiffness by MRE in patients with PSC/ASC.

UR-CarA-Net: A Cascaded Framework With Uncertainty Regularization for Automated Segmentation of Carotid Arteries on Black Blood MR Images

We present a fully automated method for carotid artery (CA) outer wall segmentation in black blood MRI using partially annotated data and compare it to the state-of-the-art reference model. Our model was trained and tested on multicentric data of patients (106 and 23 patients, respectively) with a carotid plaque and was validated on different MR sequences (24 patients) as well as data that were acquired with MRI systems of a different vendor (34 patients). A 3D nnU-Net was trained on pre-contrast T1w turbo spin echo (TSE) MR images. A CA centerline sliding window approach was chosen to refine the nnU-Net segmentation using an additionally trained 2D U-Net to increase agreement with manual annotations. To improve segmentation performance in areas with semantically and visually challenging voxels, Monte-Carlo dropout was used. To increase generalizability, data were augmented with intensity transformations. Our method achieves state-of-the-art results yielding a Dice similarity coefficient (DSC) of 91.7% (interquartile range (IQR) 3.3%) and volumetric intraclass correlation (ICC) with ground truth of 0.90 on the development domain data and a DSC of 91.1% (IQR 7.2%) and volumetric ICC with ground truth of 0.83 on the external domain data outperforming top-ranked methods for open-source CA segmentation. The uncertainty-based approach increases the interpretability of the proposed method by providing an uncertainty map together with the segmentation.

Orthotopic Gastric Cancer Targetable Magnetic Nano Complex for T2 Turbo spin echo(TSE) MR Imaging

Novel diagnostic techniques have been developed in many research areas using targetable contrast agents with magnetic resonance imaging (MRI) for cancer diagnosis. It is efficient for cancer diagnosis to use MRI with biocompatible targeting moiety and magnetic nanoparticles (MNPs). Thus, we synthesized MNPs using the thermal decomposition method which enables sensitive T2- or T2 Turbo spin echo (TSE) weighted magnetic resonance imaging. And it was coated with Hyaluronic acid (HA). Also, we carried out that gastric cancer cell line (MKN45) which has cancer stem cell properties was injected in a heterotopic mouse model. Then magnetic resonance sequence (T2) for imaging effects and targeting ability were analyzed into MNPs conjugated HA. We noted that the MDA-MB-231 cell which a high-expressed CD44 ligand was showed contrast-enhanced efficiency through magnetic nanoparticles because of combining a lot of HA. As a result of these studies, we conclude that HA-coated magnetic nanoparticles can be effectively used as a novel probe for visualizing Gastric cancer stem cells.

Visualizing the deep cerebellar nuclei using quantitative susceptibility mapping: An application in healthy controls, Parkinson's disease patients and essential tremor patients.

The visualization and identification of the deep cerebellar nuclei (DCN) (dentate [DN], interposed [IN] and fastigial nuclei [FN]) are particularly challenging. We aimed to visualize the DCN using quantitative susceptibility mapping (QSM), predict the contrast differences between QSM and T2* weighted imaging, and compare the DCN volume and susceptibility in movement disorder populations and healthy controls (HCs). Seventy-one Parkinson's disease (PD) patients, 39 essential tremor patients, and 80 HCs were enrolled. The PD patients were subdivided into tremor dominant (TD) and postural instability/gait difficulty (PIGD) groups. A 3D strategically acquired gradient echo MR imaging protocol was used for each subject to obtain the QSM data. Regions of interest were drawn manually on the QSM data to calculate the volume and susceptibility. Correlation analysis between the susceptibility and either age or volume was performed and the intergroup differences of the volume and magnetic susceptibility in all the DCN structures were evaluated. For the most part, all the DCN structures were clearly visualized on the QSM data. The susceptibility increased as a function of volume for both the HC group and disease groups in the DN and IN (p < .001) but not the FN (p=.74). Only the volume of the FN in the TD-PD group was higher than that in the HCs (p=.012), otherwise, the volume and susceptibility among these four groups did not differ significantly. In conclusion, QSM provides clear visualization of the DCN structures. The results for the volume and susceptibility of the DCN can be used as baseline references in future studies of movement disorders.

Visualization of the importance of the applied timing of the gradient magnetic field in acquiring gradient echo MR images using MRI simulation

Visualization of the importance of the applied timing of the gradient magnetic field in acquiring gradient echo MR images using MRI simulation

Predictive value of late gadolinium enhancement MRI in patients with persistent atrial fibrillation. Multicentric validation of a standardised method

Abstract Background With recurrence rates after PVI in persistent atrial fibrillation (AF) as high as 50%, predictive tools to improve patient selection are clearly needed. Compared to paroxysmal AF, persistent AF is more substrate-dependent. While endocardial low voltage substrate detected by invasive mapping has been shown to predict AF recurrence, to date the only non-invasive method to assess arrhythmogenic substrate is late gadolinium enhancement (LGE)-MRI. In fact, patient selection for PVI based on left atrial (LA) LGE extent according to the UTAH stages has been proposed, However, this approach has not been widely established, in part owed to the lack of standardisation and thus limited reproducibility of the MRI postprocessing method. Moreover, in the recent DECAAF-2 multicenter trial, the UTAH stages failed to predict outcome in patients with persistent AF. Purpose We have recently established a standardised MRI method that aims at reproducible quantification of LGE. Here, the ability of this method to detect arrhythmogenic substrate and to predict outcome after PVI in patients with persistent AF was evaluated by two centers independently. Methods This dual center study consisted of a prospective derivation cohort at centre1 and a validation cohort at centre 2. All patients received an LGE-MRI prior to ablation (PVI only) and were followed systematically with holter ECG at 3, 6 and 12 months. Gradient echo MR sequences were acquired in sinus rhythm and LA 3D-reconstruction performed using ADAS-3D software. LGE was quantified based on the signal intensity ratio of each voxel relative to the blood pool, applying a uniform threshold of &amp;gt;1.2 to define LGE indicative of fibrotic tissue. Invasive mapping served as a reference defining arrhythmogenic substrate (&amp;gt;2 cm2 LA area with bipolar voltage &amp;lt;0.5 mV). Results A ROC analysis of 37 consecutive patients with persistent AF in the prospective derivation cohort yielded a cutoff-value of 12% LGE to predict relevant low-voltage substrate with the highest accuracy. This cutoff-value was also predictive of AF recurrence after PVI (Fig. 1). When applied to the external validation cohort of 182 consecutive patients, the cutoff-value of 12% was also predictive of AF recurrence after PVI – both in the full cohort (odds ratio 3.3, p=0.003) and in the subgroup of 65 patients with persistent AF (odds ratio 3.7, p=0.038). Of note, among patients with persistent AF, recurrence rate was 54% in those with &amp;gt;12% LGE but only 24% in those with &amp;lt;12% (Fig. 2). Conclusion This dual center study established and validated the predicitive value of LGE as determined by a standardised MRI method in patients with persistent AF that can be reproducibly applied across different centers. A cutoff-value of 12% LGE was able to discriminate between responders and non-responders to PVI and may thus guide selection of suitable candidates that are likely to benefit from ablation. Funding Acknowledgement Type of funding sources: None.

Non-invasive assessment of pulmonary vein isolation durability using late gadolinium enhancement MRI

Abstract Background Electrical reconnection of pulmonary veins (PV) is considered an important determinant of recurrent atrial fibrillation (AF) after PV isolation (PVI). However, it requires an invasive repeat procedure to assess durability of PVI. Against this background, in most centers clinically relevant AF recurrences almost automatically trigger repeat ablation procedures aiming at PV re-isolation. However, technological and procedural advances have substantially improved efficacy of catheter ablation. As a result it is increasingly common that all four PVs are found isolated in those repeat procedures. Thus, as ablation of extra-PV targets has failed to show benefit in large randomized trials, more and more often these highly invasive procedures are being performed only to confirm durable PVI. To date, late gadolinium enhancement (LGE)-MRI is the only non-invasive method to assess ablation lesions. However, its predictive value regarding PVI durability has not been systematically determined. Purpose Here we aim to define the ability of LGE-MRI to rule out PV reconnection and its potential to guide patient selection for repeat ablation procedures. Methods This study was based on our prospective registry where all patients receive an LGE-MRI before and after AF ablation. All patients that had undergone a repeat invasive procedure after an initial PVI-only ablation were included, and the ability of LGE-MRI to determine PVI durability was analysed using invasive mapping as a reference. Gradient echo MR sequences were acquired in sinus rhythm and 3D-reconstruction of left atrium and PVs performed using ADAS-3D software. LGE was quantified based on the signal intensity ratio of each voxel relative to the blood pool, applying a previously validated threshold of &amp;gt;1.2 to define LGE indicative of ablation-induced scarring. LGE discontinuations of &amp;gt;3 mm were considered indicative of PV reconnection. For validation, PVI durability was determined invasively based on local bipolar electrograms. Results A total of 142 patients and 284 PV pairs were analysed. LGE-MRI displayed LGE-discontinuations suggestive of PV reconnection in 210 PV pairs (74%). According to invasive mapping, LGE-MRI predicted PV reconnection with high sensitivity (89%), whereas specificity was somewhat lower (48%). Of note, a complete circumferential LGE-lesion reliably ruled out electrical reconnection of the respective PV pair with a negative predictive value of 94.5%. In the patient-based analyses 11% of the patients displayed complete LGE-lesion sets encircling all 4 PVs. None of these patients showed electrical PV reconnection in the invasive repeat procedure. Conclusion Although not frequently encountered, continuous LGE lesions encircling all 4 PVs reliably rule out PV reconnection. Thus, LGE-MRI has the potential to guide treatment decisions in patients with AF recurrences and may help to avoid unnecessary repeat procedures with all their associated risks and costs. Funding Acknowledgement Type of funding sources: None.

Quantifying calcium changes in the fetal spine using quantitative susceptibility mapping as extracted from STAGE imaging.

To evaluate calcium deposition in the fetal spine in vivo during the second and third trimesters using quantitative susceptibility mapping (QSM). Fifty-four pregnant women in their second and third trimesters underwent a 2D multi-echo STrategically Acquired Gradient Echo (STAGE) MR imaging protocol at 3T covering the fetal spine. The first echo data was used for QSM processing. A linear regression model was used to assess the correlation between magnetic susceptibility and gestational age (GA). A paired sample t-test was used to compare the consistency of QSM measurements from each sequence. The magnetic susceptibility of the fetal spine decreased linearly with advancing GA, with a slope of -52.3 parts per billion (ppb)/week and a Pearson correlation coefficient (r) of 0.83 (p < 0.001). In 37 subjects for whom the STAGE local QSM data were available from both flip angles, the average magnetic susceptibility values were -1111 ± 278 ppb and -1081 ± 262 ppb for FA = 8° and FA = 40°, respectively. These means were not statistically different according to a paired sample t-test (p = 0.156). QSM is a reliable technique for evaluating calcium deposition and bone mineral density of fetal vertebrae. Our results demonstrate an increase in fetal calcium levels as a function of GA. These measures might be able to provide reference values for calcium content in the fetal spine during the second and third trimesters. • Calcium deposition and mineralization in the fetal spine, evaluated by vertebral magnetic susceptibility, increased with advancing gestational age. • Our results provide reference values for calcium content in the fetal spine during the second and third trimesters.

Imaging of Transmetallation and Chelation Phenomena Involving Radiological Contrast Agents in Mineral-Rich Fruits.

Exogenous heavy metals or non-metallic waste products, for example lanthanide or iodinated contrast media for radiological procedures, may interfere with the biochemical pools in patients and in common food sources, creating an excess buildup of exogenous compounds which may reach toxic levels. Although the mechanisms are unknown, our experiments were designed to test if this toxicity can be attributed to “transmetallation” or “chelation” reactions freeing up lanthanides or chelated transition metals in acidic fruits used as phantoms representing the biologically active and mineral-rich carbohydrate matrix. The rapid breakdown of stable contrast agents have been reported at a lower pH. The interaction of such agents with native metals was examined by direct imaging of contrast infused fresh apples and sweet potatoes using low energy X-rays (40–44 kVp) and by magnetic resonance imaging at 1.5 and 3T. The stability of the exogenous agents seemed to depend on endogenous counterions and biometals in these fruits. Proton spin echo MR intensity is sensitive to paramagnetic minerals and low energy X-ray photons are sensitively absorbed by photoelectric effects in all abundant minerals and were compared before and after the infusion of radiologic contrasts. Endogenous iron and manganese are believed to accumulate due to interactions with exogenous iodine and gadolinium in and around the infusion spots. X-ray imaging had lower sensitivity (detection limit approximately 1 part in 104), while MRI sensitivity was two orders of magnitude higher (approximately 1 part in 106), but only for paramagnetic minerals like Mn and Fe in our samples. MRI evidence of such a release of metal ions from the native pool implicates transmetallation and chelation reactions that were triggered by infused contrast agents. Since Fe and Mn play significant roles in the function of metalloenzymes, our results suggest that transmetallation and chelation could be a plausible mechanism for contrast induced toxicity in vivo.

The increased iron deposition of the gray matter over the whole brain in chronic migraine: An exploratory quantitative susceptibility mapping study.

BackgroundPrior studies identified iron deposition in deep brain nuclei and the periaqueductal gray matter region in chronic migraine, and less is known about the cerebral iron deposition over the whole cerebral gray matter in CM. The aim of this case–control study is to investigate the cerebral iron deposition of gray matter in CM using an advanced quantitative susceptibility mapping.MethodsA multi-echo gradient echo MR sequence was used to obtain raw quantitative susceptibility mapping data from 12 CM patients and 18 normal controls and the quantitative susceptibility mapping were reconstructed. Three dimensional T1 images were segmented and the gray matter mask was generated to extract the susceptibility value of gray matter over the whole brain. The independent t test and receiver operating characteristic curve Receiver operating characteristics was used to investigate the iron deposition changes in CM patients.ResultsCM presented a higher susceptibility value (1.44 × 10−3 ppm) compared with NC group (0.47 × 10−3 ppm) (p < 0.0001) over the whole cerebral gray matter. There was no correlation between susceptibility value and the clinical variables including disease duration, Visual Analog Scale (VAS), Migraine Disability Assessment Scale (MIDAS), Hamilton Anxiety Scale (HAMA), Hamilton Depression Scale (HAMD), and Montreal Cognitive Assessment (MoCA) scores (p > 0.05). ROC analysis demonstrated the susceptibility had a high diagnostic efficacy (AUC 0.949, sensitivity 77.78% and specificity 100%) in distinguishing CM from NC.ConclusionCM patients had increased iron deposition in total cerebral gray matter which could be considered as a potential diagnostic and evaluated imaging biomarker in CM.

Multiple-echo recombined gradient echo MR imaging of the temporomandibular joint.

The purpose of this study was to compare images generated by a multiple-echo recombined gradient echo (MERGE) with the proton density-weighted fast spin-echo (PD-weighted FSE) sequence, T1-weighted fast spin-echo sequence (T1-weighted FSE), and T2-weighted fast spin-echo sequence (T2-weighted FSE) for the diagnostic imaging of the temporomandibular joint (TMJ). Twenty-three patients with signs and symptoms of TMJ dysfunction were enrolled in this study. The four imaging modalities were used to examine the TMJ. Three images (lateral, middle, and medial parts of the condylar head) were reviewed by two radiologists, who rated the visibility of the disk and cortex of the condylar head. For the medial part of the TMJ, in cases with a normally positioned disk, the results of the MERGE and PD-weighted FSE techniques were significantly better than those of the T1-weighted FSE and T2-weighted FSE. For visibility of the cortex in the normally positioned disk, MERGE was significantly better than PD-weighted FSE [P < 0.0125 (0.05/4)] at the middle and medial parts of the TMJ. MERGE was also significantly better than T1-weighted FSE [P < 0.0125 (0.05/4)] and T2-weighted FSE [P < 0.0125 (0.05/4)]. MERGE is better for visualizing the condylar only at the middle and the medial aspects of the TMJ in a normally positioned disk.

AUTOMATIC EFFUSION MEASUREMENT WITH LIMITED LABELED DATA

Accurate quantification of effusion volume is becoming more important as OA is increasingly recognized to have inflammatory components including joint effusion. Effective clinical management requires accurate quantification of features related to inflammation; particularly synovitis and joint effusion which represents a target for therapy. Rather than relying on highly variable subjective assessment of joint effusions, with the development of deep learning techniques we have witnessed increased automation of radiological assessments. However, most of these techniques use supervised learning and are trained on large annotated datasets. Acquiring “ground truth” labels for large datasets is expensive and time-consuming. This becomes even more complicated and challenging when it comes to detecting medical image features like effusion. Detecting effusions accurately requires a high level of expertise. Because pockets of joint fluid can be in unexpected locations, human experts frequently need to step back to look at the entire image stack multiple times to prevent inattentional error. Therefore, proposing a method for learning from limited labeled data is crucial for medical image analysis. To perform automated measurement of knee effusion volume using minimal labeled data. In this method, we aim to develop an alternative deep learning training strategy based on self-supervised pretraining on unlabeled knee MRI scans. This study requires two sets of data: 1) a large unlabeled dataset, and 2) a small labeled dataset. For the large unlabeled dataset, we have used 4 different OAI MRI sequence data (64k slices have been selected randomly). For the labeled dataset we have used low-resolution sagittal Turbo Spin Echo (TSE) MR sequences from the OAI dataset. Effusion regions were extracted by a trained musculoskeletal radiologist (DC) for 23 participants (a total of 31 scans) using an interactive software developed in-house. We have used 5 scans for the test and 26 scans (a total of 700 slices) for training. In this method, IMaskRCNN deep learning architecture with the ResNet-101 backbone have been used. The training process has been performed in two-phase, self-supervised pretraining, and fine-tuning. The self-supervised pretraining using the fill-blank method was performed on unlabeled images to learn visual representations in musculoskeletal MRIs. After pretraining, we fined-tuned last layers of the network (backbone weights have been frozen) using the training division of the small TSE dataset. The dice similarity coefficient, Intersection over union (IoU) was used to compare the result of the segmentation between the predicted output and the ground truth. Qualitative results of the proposed method is presented in the figure. As shown the network was able to provide a good prediction of effusion location and extracting it. The segmentation model using the proposed pretraining method was successful in finding the location of effusion for 90% of the slices with IoU = 60%. The dice score for the detected effusion is 0.70 indicates a high agreement between the automatic segmentation and the labels provided by the expert. Self-supervised pretraining on the OAI dataset, can be a solution to the scarcity of pixel-wise ground truth (GT) for effusion quantification. Alberta Innovates, AHS Chair in Diagnostic Imaging, Medical Imaging Consultants, CIHR. CORRESPONDENCE ADDRESS: banafshe.felfeliyan@ucalgary.ca