Non-contrast Assessment Research Articles

Inteligencia artificial en la imagen cardiovascular mediante resonancia magnética

Artificial intelligence is rapidly evolving and its possibilities are endless. Its primary applications in cardiac magnetic resonance imaging have focused on: image acquisition (in terms of acceleration and quality improvement); segmentation (in terms of saving time and reproducibility); tissue characterisation (including radiomic techniques and the non-contrast assessment of myocardial fibrosis); automatic diagnosis; and prognostic stratification. The aim of this article is to attempt to provide an overview of the current situation as preparation for the significant changes currently underway or imminent in the very near future.

Kiosk 7R-TB-04 - Non-contrast Assessment of Pulmonary Perfusion Using Pulsed Arterial Spin Labeling on a Mid-field 0.55T Scanner

Kiosk 7R-TB-04 - Non-contrast Assessment of Pulmonary Perfusion Using Pulsed Arterial Spin Labeling on a Mid-field 0.55T Scanner

Non-contrast assessment of blood-brain barrier permeability to water in mice: An arterial spin labeling study at cerebral veins

Blood-brain barrier (BBB) plays a critical role in protecting the brain from toxins and pathogens. However, in vivo tools to assess BBB permeability are scarce and often require the use of exogenous contrast agents. In this study, we aimed to develop a non-contrast arterial-spin-labeling (ASL) based MRI technique to estimate BBB permeability to water in mice. By determining the relative fraction of labeled water spins that were exchanged into the brain tissue as opposed to those that remained in the cerebral veins, we estimated indices of global BBB permeability to water including water extraction fraction (E) and permeability surface-area product (PS). First, using multiple post-labeling delay ASL experiments, we estimated the bolus arrival time (BAT) of the labeled spins to reach the great vein of Galen (VG) to be 691.2 ± 14.5 ms (N = 5). Next, we investigated the dependence of the VG ASL signal on labeling duration and identified an optimal imaging protocol with a labeling duration of 1200 ms and a PLD of 100 ms. Quantitative E and PS values in wild-type mice were found to be 59.9 ± 3.2% and 260.9 ± 18.9 ml/100 g/min, respectively. In contrast, mice with Huntington's disease (HD) revealed a significantly higher E (69.7 ± 2.4%, P = 0.026) and PS (318.1 ± 17.1 ml/100 g/min, P = 0.040), suggesting BBB breakdown in this mouse model. Reproducibility studies revealed a coefficient-of-variation (CoV) of 4.9 ± 1.7% and 6.1 ± 1.2% for E and PS, respectively. The proposed method may open new avenues for preclinical research on pathophysiological mechanisms of brain diseases and therapeutic trials in animal models.

Myocardial Approximate Spin-lock Dispersion Mapping using a Simultaneous T2 and TRAFF2 Mapping at 3T MRI.

Ischemic heart disease (IHD) is one of the leading causes of death worldwide. Myocardial infarction (MI) represents a third of all IHD cases, and cardiac magnetic resonance imaging (MRI) is often used to assess its damage to myocardial viability. Late gadolinium enhancement (LGE) is the current gold standard, but the use of gadolinium-based agents limits the clinical applicability in some patients. Spin-lock (SL) dispersion has recently been proposed as a promising non-contrast biomarker for the assessment of MI. However, at 3T, the required range of SL preparations acquired at different amplitudes suffers from specific absorption rate (SAR) limitations and off-resonance artifacts. Relaxation Along a Fictitious Field (RAFF) is an alternative to SL preparations with lower SAR requirements, while still sampling relaxation in the rotating frame. In this study, a single breath-hold simultaneous TRAFF2 and T2 mapping sequence is proposed for SL dispersion mapping at 3T. Excellent reproducibility (coefficient of variations lower than 10%) was achieved in phantom experiments, indicating good intrascan repeatability. The average myocardial TRAFF2, T2, and SL dispersion obtained with the proposed sequence (68.0±10.7 ms, 44.0±4.0 ms, and 0.4±0.2 ×10-4 s2, respectively) were comparable to the reference methods (62.7±11.7 ms, 41.2±2.4 ms, and 0.3±0.2x 10-4s2, respectively). High visual map quality, free of B0 and B1+ related artifacts, for T2, TRAFF2, and SL dispersion maps were obtained in phantoms and in vivo, suggesting promise in clinical use at 3T. Clinical relevance - and imaging promises non-contrast assessment of scar and focal fibrosis in a single breath-hold using approximate spin-lock dispersion mapping.

Blood pressure variability and neuroplasticity in patients with type 2 diabetes mellitus

Analysis of the role of blood pressure (BP) variability in the formation of neuroplasticity in patients with type 2 diabetes mellitus (DM). 100 patients with type 2 DM were examined, which were divided into groups depending on the presence of cognitive impairment (CI), the control group consisted of 25 people. All examined patients underwent a clinical examination, a standard set of biochemical blood tests, plasma osteopontin levels, 24-hour blood pressure monitoring (ABPM) for 24-26 h MRI of the brain (dynamic contrast and arterial spin marks, proton spectroscopy, tractography). Patients with type 2 diabetes and CI had higher body mass index, blood levels of glycated hemoglobin, glucose, alanine aminotransferase, low-density lipoprotein, triglycerides, total cholesterol, osteopontin, and lower levels of high-density lipoprotein (p≤0.05). The level of osteopontin was higher in patients with overweight, hyperglycemia, dyslipidemia, and in patients with CI in patients with BP variability. When assessing 24-hour blood pressure monitoring (ABPM), a significant difference was found in all standard indicators, while patients with type 2 diabetes were referred to as «non-dipper», in the presence of CI they noted significantly higher values of the index of time and area of stay in the suprathreshold state. BP and variability in SBP and DBP at night, as well as the risk of occult hypertension. A decrease in cerebral blood flow was revealed according to the data of contrast and non-contrast assessment of perfusion in cortical (especially in the frontal lobe) and subcortical (mainly in the putamen) structures, associated with changes in ABPM parameters. Mean SBP and DBP day and night, as well as the index of BP variability, also affect the integrity of the corticospinal, uncinate, lower longitudinal tracts, and arcuate fasciculus. The same parameters change the metabolism of the hippocampus in terms of choline (Cho), creatine (Cr), creatine phosphate (Cr2), as well as the ratio of N-acetylaspartate (NAA)/Cho, NAA/Cr, Cho/Cr. In patients with type 2 diabetes, BP variability contributes to the formation of CI through a pro-inflammatory mechanism (osteopontin), leading to impaired brain vascularization in general, white matter structure, and hippocampal metabolism.

Noncontrast assessment of blood–brain barrier permeability to water: Shorter acquisition, test–retest reproducibility, and comparison with contrast‐based method

Assessment of the blood-brain barrier (BBB) permeability without the need for contrast agent is desirable, and the ability to measure the permeability to small molecules such as water may further increase the sensitivity in detecting diseases. This study proposed a time-efficient, noncontrast method to measure BBB permeability to water, evaluated its test-retest reproducibility, and compared it with a contrast agent-based method. A single-delay water extraction with phase-contrast arterial spin tagging (WEPCAST) method was devised in which spatial profile of the signal along the superior sagittal sinus was used to estimate bolus arrival time, and the WEPCAST signal at the corresponding location was used to compute water extraction fraction, which was combined with global cerebral blood flow to estimate BBB permeability surface area product to water. The reliability of WEPCAST sequence was examined in terms of intrasession, intersession, and inter-vendor (Philips [Ingenia, Best, the Netherlands] and Siemens [Prisma, Erlangen, Germany]) reproducibility. Finally, we compared this new technique to a contrast agent-based method. Single-delay WEPCAST reduced the scan duration from approximately 20 min to 5 min. Extract fraction values estimated from single-delay WEPCAST showed good consistency with the multi-delay method (R = 0.82, P = .004). Group-averaged permeability surface area product values were found to be 137.5 ± 9.3 mL/100 g/min. Intrasession, intersession, and inter-vendor coefficient of variation of the permeability surface area product values were 6.6 ± 4.5%, 6.9 ± 3.7%, and 8.9 ± 3.0%, respectively. Finally, permeability surface area product obtained from WEPCAST MRI showed a significant correlation with that from the contrast-based method (R = .73, P = .02). Single-delay WEPCAST MRI can measure BBB permeability to water within 5 min with an intrasession, intersession, and inter-vendor test-retest reproducibility of 6% to 9%. This method may provide a useful marker of BBB breakdown in clinical studies.

Ultra-high-field arterial spin labelling MRI for non-contrast assessment of cortical lesion perfusion in multiple sclerosis

ObjectivesTo assess the feasibility of using an optimised ultra-high-field high-spatial-resolution low-distortion arterial spin labelling (ASL) MRI acquisition to measure focal haemodynamic pathology in cortical lesions (CLs) in multiple sclerosis (MS).MethodsTwelve MS patients (eight female, mean age 50 years; range 35–64 years) gave informed consent and were scanned on a 7 Tesla Philips Achieva scanner. Perfusion data were collected at multiple post-labelling delay times using a single-slice flow-sensitive alternating inversion recovery ASL protocol with a balanced steady-state free precession readout scheme. CLs were identified using a high-resolution Phase-Sensitive Inversion Recovery (PSIR) scan. Significant differences in perfusion within CLs compared to immediately surrounding normal appearing grey matter (NAGMlocal) and total cortical normal appearing grey matter (NAGMcortical) were assessed using paired t-tests.ResultsForty CLs were identified in PSIR scans that overlapped with the ASL acquisition coverage. After excluding lesions due to small size or intravascular contamination, 27 lesions were eligible for analysis. Mean perfusion was 40 ± 25 ml/100 g/min in CLs, 53 ± 12 ml/100 g/min in NAGMlocal, and 53 ± 8 ml/100 g/min in NAGMcortical. CL perfusion was significantly reduced by 23 ± 9% (mean ± SE, p = 0.013) and 26 ± 9% (p = 0.006) relative to NAGMlocal and NAGMcortical perfusion, respectively.ConclusionThis is the first ASL MRI study quantifying CL perfusion in MS at 7 Tesla, demonstrating that an optimised ASL acquisition is sensitive to focal haemodynamic pathology previously observed using dynamic susceptibility contrast MRI. ASL requires no exogenous contrast agent, making it a more appropriate tool to monitor longitudinal perfusion changes in MS, providing a new window to study lesion development.Key Points• Perfusion can be quantified within cortical lesions in multiple sclerosis using an optimised high spatial resolution arterial spin Labelling MRI acquisition at ultra-high-field.• The majority of cortical lesions assessed using arterial spin labelling are hypo-perfused compared to normal appearing grey matter, in agreement with dynamic susceptibility contrast MRI literature.• Arterial spin labelling MRI, which does not involve the injection of a contrast agent, is a safe and appropriate technique for repeat scanning of an individual patient.

Texture analysis and machine learning of non-contrast T1-weighted MR images in patients with hypertrophic cardiomyopathy—Preliminary results

PurposeTo test in a first proof-of-concept study whether texture analysis (TA) allows for the detection of myocardial tissue alterations in hypertrophic cardiomyopathy (HCM) on non-contrast T1-weighted cardiac magnetic resonance (CMR) images using machine learning based approaches. MethodsThis retrospective, IRB-approved study included 32 patients with known HCM. Thirty patients with normal CMR served as controls. Regions-of-interest for TA encompassing the left ventricle were drawn on short-axis non-contrast T1-weighted images using a freely available software package. Step-wise dimension reduction and texture feature selection was performed for selecting features enabling the detection of myocardial tissue alterations in HCM patients on non-contrast T1-weighted CMR images. ResultsComparing HCM patients and controls, four texture features were identified showing significant differences between groups (Grey-level Non-uniformity [GLevNonU]: 74 ± 17 vs. 38 ± 9, p < .001; Energy of wavelet coefficients in low-frequency sub-bands [WavEnLL]: 58 ± 5 vs. 48 ± 10, p < .001; Fraction: 0.70 ± 0.07 vs. 0.78 ± 0.05, p < .001; Sum Average: 16.6 ± 0.4 vs. 17.0 ± 0.5, p = .007). A model containing the single parameter GLevNonU proved to be the best for differentiating between HCM patients and controls with a sensitivity/specificity of 91%/93%. A cut-off of GLevNonU ≥46 allowed for distinguishing HCM patients from controls with a sensitivity/specificity of 94%/90%. Even in patients without late gadolinium enhancement (LGE), the defined cut-off led to a differentiation of LGE- patients from healthy controls with 100% sensitivity and 90% specificity. ConclusionsTA on non-contrast T1-weighted images allows for the detection of myocardial tissue alterations in the setting of HCM with excellent accuracy, delivering potential novel parameters for a non-contrast assessment of myocardial texture alterations.

Non-contrast assessment of microvascular integrity using arterial spin labeled cardiovascular magnetic resonance in a porcine model of acute myocardial infarction

BackgroundFollowing acute myocardial infarction (AMI), microvascular integrity and function may be compromised as a result of microvascular obstruction (MVO) and vasodilator dysfunction. It has been observed that both infarcted and remote myocardial territories may exhibit impaired myocardial blood flow (MBF) patterns associated with an abnormal vasodilator response. Arterial spin labeled (ASL) CMR is a novel non-contrast technique that can quantitatively measure MBF. This study investigates the feasibility of ASL-CMR to assess MVO and vasodilator response in swine.MethodsThirty-one swine were included in this study. Resting ASL-CMR was performed on 24 healthy swine (baseline group). A subset of 13 swine from the baseline group underwent stress ASL-CMR to assess vasodilator response. Fifteen swine were subjected to a 90-min left anterior descending (LAD) coronary artery occlusion followed by reperfusion. Resting ASL-CMR was performed post-AMI at 1–2 days (N = 9, of which 6 were from the baseline group), 1–2 weeks (N = 8, of which 4 were from the day 1–2 group), and 4 weeks (N = 4, of which 2 were from the week 1–2 group). Resting first-pass CMR and late gadolinium enhancement (LGE) were performed post-AMI for reference.ResultsAt rest, regional MBF and physiological noise measured from ASL-CMR were 1.08 ± 0.62 and 0.15 ± 0.10 ml/g/min, respectively. Regional MBF increased to 1.47 ± 0.62 ml/g/min with dipyridamole vasodilation (P < 0.001). Significant reduction in MBF was found in the infarcted region 1–2 days, 1–2 weeks, and 4 weeks post-AMI compared to baseline (P < 0.03). This was consistent with perfusion deficit seen on first-pass CMR and with MVO seen on LGE. There were no significant differences between measured MBF in the remote regions pre and post-AMI (P > 0.60).ConclusionsASL-CMR can assess vasodilator response in healthy swine and detect significant reduction in regional MBF at rest following AMI. ASL-CMR is an alternative to gadolinium-based techniques for assessment of MVO and microvascular integrity within infarcted, as well as salvageable and remote myocardium. This has the potential to provide early indications of adverse remodeling processes post-ischemia.

4 Non-contrast assessment of myocardial viability in chronic myocardial infarction by native T1 and T2 mapping at 1.5T CMR: comparison with late gadolinium enhancement technique

Background Viability assessment is a key aspect in the management of ischaemic heart disease (IHD). Hypothesis: native T1 and T2 mapping can assess myocardial viability without the use of gadolinium. Methods 30 patients with known MI (>5yrs from MI) and 20 normal healthy controls underwent conventional 1.5T CMR to assess LV function and the presence and extent of myocardial infarction (scar transmurality) using a scale of 0–4 for the 16 AHA segment (0=no scar, 1=1–24%, 2=25–49%, 3=50–74% and 4 ≥75% scar thickness). Segments with Results 800 myocardial segments were analysed (320-healthy controls, 480-MI patients). The mean segmental T1 and T2 values for scar transmurality grade 0–4 were 1031±31 ms, 1070±33 ms, 1103±32 ms, 1164±58 ms, 1206±118 ms (p Conclusions Native T1 mapping can differentiate between normal, viable, and non-viable myocardium with distinctive T1 profiles in chronic MI without the need for gadolinium.

Native T1-mapping for non-contrast assessment of myocardial fibrosis in patients with hypertrophic cardiomyopathy — comparison with late enhancement quantification

BackgroundMyocardial fibrosis was shown to influence prognosis in hypertrophic cardiomyopathy (HCM). It is typically assessed by late gadolinium enhancement (LGE) on cardiac magnetic resonance. Native T1-mapping has been proposed, as a contrast-free method of fibrosis assessment. The aim of the study was to define a cut-off value for native T1 relaxation time that best reflects LGE quantification of myocardial fibrosis. MethodsIn 25 patients with HCM and 20 controls we performed T1-mapping pre-contrast using ShMOLLI technique. This was followed by LGE assessment in the studied group 10 minutes after gadolinium contrast injection. Relative myocardial fibrosis size was calculated for varying T1 time thresholds (940–1100 ms) and compared with 6 standard deviations (6SD) method for LGE. ResultsMedian fibrosis size calculated with T1-mapping was insignificantly different from LGE only for native T1 time threshold of 1060 ms (p = 0.62). Using this threshold, Bland–Altman plots demonstrated very good agreement between fibrosis sizes from the two methods (slightly better only for 1080 ms threshold). For threshold of 1060 ms we also observed good correlation (rho = 0.73) with LGE 6SD method (insignificantly better for lower thresholds, best for threshold of 980 ms-rho = 0.88). In control group with no diagnosis of HCM, fibrosis size <1% was reached for thresholds of 1040 ms and higher. ConclusionNative T1-mapping can be used for non-contrast assessment of myocardial fibrosis in HCM. The 1060 ms threshold of the native T1 relaxation time is characterized by the best balance between agreement and correlation with fibrosis assessed by LGE 6SD method.

Abstract WP35: An ASL Collateral Score Can Identify Improved Quantitative Cerebral Blood Flow in Acute Stroke Patients

Objective: To measure quantitative hemodynamic parameters in acute stroke patients using a tomographic collateral assessment based on arterial spin labeling (ASL) [1]. Methods: Patients were retrospectively identified who met these criteria: symptom onset &lt;27 hrs, DWI volume &gt;=10 ml, and ASL and bolus contrast PWI, 1.5T. Pseudocontinuous 3D fast spin echo ASL was performed with the parameters: TR/TE/label time/post-label delay 5500/9.5/1500/2000 ms. PWI was performed using 0.1 mmol Gd and single-shot EPI with the parameters: TR/TE 1800/40 ms. Automated software (RAPID) was used to measure relative CBF, CBV, and time to peak of the residue function (Tmax) [2]. The combined ASL and DSC method was used to determine quantitative CBF and CBV [3]. A four point collateral score (CS) (0=poor, 1=intermediate, 2=good, 3=antegrade perfusion) [4] was determined based on ASL arterial transit artifact (ATA) in 20 ASPECTS ROI’s in each patient [1]. Tests for significant relationships between CS and each parameter was performed. Findings: 13 patients were identified (4 M, 63±13 yrs, 17±7 hrs from symptom onset, DWI size 61±52 ml, PWI Tmax&gt;6 sec size 84±65 ml). CBF increased with increasing CS, with the highest CBF in the antegrade perfused regions. CBV also increased with CS, but there was no difference between good collateral and antegrade regions. Tmax decreased significantly as CS increased. Acute stroke patients with good and poor collaterals are shown in the Figure (yellow arrows = collaterals). Conclusions: Collaterals are important because they supply CBF. ASL is able to predict the quality of collaterals in acute stroke, as was shown previously in Moyamoya disease [1]. This non-contrast assessment of collaterals on MRI may improve patient selection for stroke therapy.