Non-contrast MR Research Articles

Generative Adversarial Network Based Contrast Enhancement: Synthetic Contrast Brain Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a vital tool for diagnosing neurological disorders, frequently utilising gadolinium-based contrast agents (GBCAs) to enhance resolution and specificity. However, GBCAs present certain risks, including side effects, increased costs, and repeated exposure. This study proposes an innovative approach using generative adversarial networks (GANs) for virtual contrast enhancement in brain MRI, with the aim of reducing or eliminating GBCAs, minimising associated risks, and enhancing imaging efficiency while preserving diagnostic quality. In this study, 10,235 images were acquired in a 3.0 Tesla MRI scanner from 81 participants (54 females, 27 males; mean age 35 years, range 19-68 years). T1-weighted and contrast-enhanced images were obtained following the administration of a standard dose of a GBCA. In order to generate "synthetic" images for contrast-enhanced T1-weighted, a CycleGAN model, a sub-model of the GAN structure, was trained to process pre- and post-contrast images. The dataset was divided into three subsets: 80% for training, 10% for validation, and 10% for testing. TensorBoard was employed to prevent image deterioration throughout the training phase, and the image processing and training procedures were optimised. The radiologists were presented with a non-contrast input image and asked to choose between a real contrast-enhanced image and synthetic MR images generated by CycleGAN corresponding to this non-contrast MR image (Turing test). The performance of the CycleGAN model was evaluated using a combination of quantitative and qualitative analyses. For the entire dataset, in the test set, the mean square error (MSE) was 0.0038, while the structural similarity index (SSIM) was 0.58. Among the submodels, the most successful model achieved an MSE of 0.0053, while the SSIM was 0.8. The qualitative evaluation was validated through a visual Turing test conducted by four radiologists with varying levels of clinical experience. The findings of this study support the efficacy of the CycleGAN model in generating synthetic contrast-enhanced T1-weighted brain MR images. Both quantitative and qualitative evaluations demonstrated excellent performance, confirming the model's ability to produce realistic synthetic images. This method shows promise in potentially eliminating the need for intravenous contrast agents, thereby minimising the associated risks of their use.

Chylous Reflux in Pediatric Primary Lymphedema of the Lower Limbs and Genitalia: A Retrospective Study of 167 Patients.

Background: Chylous reflux (CR) in primary lymphedema (PL) of the lower extremities is rare and requires particular diagnostic procedures. This study aimed to determine clinical and lymphoscintigraphic traits for efficient screening. Methods and Results: Pediatric patients with PL of lower extremities treated in our institution between January 2020 and December 2023 were reviewed. The medical history, lymphoscintigraphy, non-contrast MR lymphography, and direct lymphangiography were analyzed. Lymphoscintigraphic visual patterns were classified to detect CR. Patients with CR showed significantly higher proportions of childhood symptom onset (65.63% vs. 25.19%, p < 0.01), genital lymphedema (62.50% vs. 19.26%, p < 0.01), and proximal-to-distal swelling (31.25% vs. 8.89%, p < 0.01). Eight patients without skin lesions had milk discharge after acupuncture or skin breakdown. Pattern 4 shows diffused dermal backflow of the leg and an absence of superficial lymphatic drainage, or normal initial cephalad flow with subsequent reflux of tracer into the affected limb. CR showed significantly higher percentages of pattern 4 (87.50% vs. 12.59%, p < 0.01), normal/widened iliac lymphatics (78.13% vs. 11.11%, p < 0.01), and thigh/calf outlining (87.50% vs. 29.63%, p < 0.01). Genital swelling preceding limb swelling and genital radioactivity were more common in the CR group. Conclusions: CR tends to occur in childhood initially, begin centrally and progress distally, and involve genitals prior to lower extremities. Milk discharge after acupuncture or skin breakdown is important for screening CR without chylous vesicles. The patterns with typical "profiling of the leg" and normal or widened iliac lymphatic trunks strongly correlate with CR. Genital lymphedema with increased radioactivity indicates CR.

Peripheral Non-Contrast MR Angiography Using FBI: Scan Time and T2 Blurring Reduction with 2D Parallel Imaging.

Non-contrast magnetic resonance angiography (NC-MRA), including fresh blood imaging (FBI), is a suitable choice for evaluating patients with peripheral artery disease (PAD). We evaluated standard FBI (sFBI) and centric ky-kz FBI (cFBI) acquisitions, using 1D and 2D parallel imaging factors (PIFs) to assess the trade-off between scan time and image quality due to blurring. The bilateral legs of four volunteers (mean age 33 years, two females) were imaged in the coronal plane using a body array coil with a posterior spine coil. Two types of sFBI and cFBI sequences with 1D PIF factor 5 in the phase encode (PE) direction (in-plane) and 2D PIF 3 (PE) × 2 (slice encode (SE)) (in-plane, through-slice) were studied. Image quality was evaluated by a radiologist, the vessel's signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured, and major vessel width was measured on the coronal maximum intensity projection (MIP) and 80-degree MIP. Results showed significant time reductions from 184 to 206 s on average when using sFBI down to 98 to 162 s when using cFBI (p = 0.003). Similar SNRs (averaging 200 to 370 across all sequences and PIF) and CNRs (averaging 190 to 360) for all techniques (p > 0.08) were found. There was no significant difference in the image quality (averaging 4.0 to 4.5; p > 0.2) or vessel width (averaging 4.1 to 4.9 mm; p > 0.1) on coronal MIP due to sequence or PIF. However, vessel width measured using 80-degree MIP demonstrated a significantly wider vessel in cFBI (5.6 to 6.8 mm) compared to sFBI (4.5 to 4.7 mm) (p = 0.022), and in 1D (4.7 to 6.8 mm) compared to 2D (4.5 to 5.6 mm) (p < 0.05) PIF. This demonstrated a trade-off in T2 blurring between 1D and 2D PIF: 1D using a PIF of 5 shortened the acquisition window, resulting in sharper arterial blood vessels in coronal images but significant blur in the 80-degree MIP. Two-dimensional PIF for cFBI provided a good balance between shorter scan time (relative to sFBI) and good sharpness in both in- and through-plane, while no benefit of 2D PIF was seen for sFBI. In conclusion, this study demonstrated the usefulness of FBI-based techniques for peripheral artery imaging and underscored the need to strike a balance between scan time and image quality in different planes through the use of 2D parallel imaging.

Noncontrast MR Lymphangiography to Identify Progression of Lymphatic Abnormalities over the Course of Fontan Completion.

Noncontrast MR Lymphangiography to Identify Progression of Lymphatic Abnormalities over the Course of Fontan Completion.

Lymphatic morphology and function in chronic right heart failure due to secondary tricuspid valve regurgitation

BackgroundIn heart failure, the capacity of the lymphatic system dictates symptoms of circulatory congestion. This study aimed at describing structural and functional changes of the lymphatic system in patients with chronic right-sided heart failure. MethodsIndividuals with long-standing severe tricuspid valve regurgitation and symptoms of heart failure were compared with age- gender- and weight-matched controls. Lymphatic structure and function were examined using non-contrast MR lymphangiography and near-infrared fluorescence imaging. Microvascular fluid dynamics and distribution were evaluated using strain gauge plethysmography and bio-impedance. ResultsIn total nine patients and nine controls were included. Lymphatic morphology was unchanged in cases compared to controls with similar thoracic duct diameters 3.1(2.1–3.5) mm vs. 2.0(1.8–2.4) mm (p-value = 0.11), similar lymphatic classifications (p-value 0.34), and an identical number of lymphatic vessels in the legs 6 ± 1 vs. 6 ± 3 vessels/field (p-value = 0.72). Lymphatic function was comparable with contraction frequencies of 0.5 ± 0.2 and 0.5 ± 0.3 /min (p-value = 0.52) and a maximal lymphatic pumping pressure of 60 ± 13 and 57 ± 12 mmHg (p-value = 0.59) for cases and controls respectively. Finally, microvascular capillary filtration, isovolumetric threshold, and fluid distribution were similar between groups (p-value≥0.16 for all comparisons). ConclusionIn this small exploratory study, individuals with severe secondary tricuspid valve regurgitation and right-sided heart failure displayed a largely similar lymphatic anatomy and function. Thoracic duct diameter displayed a trend towards increased size in the patient group. We speculate that cases were indeed stable and optimally treated at the time of examination, and with a lymphatic system largely unaffected by any of the current or prior hemodynamic changes.

Non-contrast MR angiography: physical principles and clinical applications in chest, abdomen and pelvis imaging.

This review article focuses on the advancements in non-contrast magnetic resonance angiography (NC-MRA) and its increasing importance in body imaging, especially for patients with renal complications, pregnant women, and children. It highlights the relevance of NC-MRA in chest, abdominal, and pelvis imaging and details various bright-blood NC-MRA techniques like cardiac-gated 3D Fast Spin Echo (FSE), balanced Steady-State Free Precession (bSSFP), Arterial Spin Labeling (ASL), and 4D flow methods. The article explains the operational principles of these techniques, their clinical applications, and their advantages over traditional contrast-enhanced methods. Special attention is given to the utility of these techniques in diverse imaging scenarios, including liver, renal, and pelvic imaging. The article underscores the growing importance of NC-MRA in medical diagnostics, offering insights into current practices and potential future developments. This comprehensive review is a valuable resource for radiologists and clinicians, emphasizing NC-MRA's role in enhancing patient care and diagnostic accuracy across various medical conditions.

Inter-observer and inter-modality concordance of non-contrast MR angiography and CT angiography for preoperative assessment of potential renal donors

BackgroundMagnetic resonance angiography (MRA) is rapidly being employed as an effective substitute for CTA, particularly in situations of poor kidney function. We aimed to examine the inter-observer and inter-modality reliability of non-contrast MR angiography (NC-MRA) and CTA as a non-invasive tool for assessing the anatomical findings of potential living kidney donors.ResultsAll potential donors were referred from specialized kidney transplantation center and underwent NC-MRA of the renal arteries using a respiratory-triggered magnetization prepared 3D balanced steady-state free precession (b-SSFP) with inversion recovery pulses and fat saturation (Inhance 3D Inflow Inversion Recovery (IFIR)). Two experienced radiologists reviewed NC-MRA images and were asked to evaluate both renal arteries anatomy and their branching pattern, presence of accessory or aberrant renal arteries, and identify any anatomical variant. Lin’s correlation test was performed to test MRA readings by each of the two observers against CTA findings which considered as the gold standard for assessment of renal arteries. Additionally, observers were asked to assess the image quality. The study included 60 potential kidney donors (43 males and 17 females) with mean age ± SD of 31.3 ± 5.6 years. Excellent to very good inter-observer agreement was found between both observers in the assessment of renal arteries by NC-MRA. There was perfect concordance between MRA and CTA findings in detecting early arterial division, caliber, and length of left extra-parenchymal segmental branches. Moderate concordance was found in the assessment of the supplied segments of extra-parenchymal segmental renal arterial branches and substantial concordance between both MRA observers’ findings in the remaining variables of the study. There was excellent agreement between both observers in the assessment of image quality parameters.ConclusionsNC-MRA for the renal arteries is an effective alternative for CTA without the risks of radiation or contrast media.

Successful Recanalization by Mechanical Thrombectomy in a Child with Arterial Thrombotic Stroke Involving Posterior Circulation: A Case Report with Review of the Literature

Background: Mechanical thrombectomy (MT) for arterial ischemic stroke, although established in adults, is not endorsed routinely for children. The procedure is even rare in children with stroke involving posterior circulation. Here we describe, a child with ischemic stroke due to thrombotic occlusion in the posterior circulation, which was successfully treated with MT. Clinical Description: A 12-year-old boy presented with sudden-onset vertigo, imbalance, slurring of speech, inability to stand, associated with headache and vomiting for 8 hours, without any associated fever, trauma, or seizures. On initial examination, his National Institute of Health Stroke Scale (NIHSS) score was 8. Other systems were within normal limits and there was no cutaneous rash. Management and Outcome: Investigations revealed a normal complete hemogram, lipid profile, serum homocysteine, fibrinogen, and D-dimer levels along with a normal hemoglobin electrophoresis profile. The electrocardiography, two-dimensional echocardiography were normal and even antinuclear antibodies, antiphospholipid antibodies were negative. Magnetic resonance imaging (MRI) of the brain demonstrated multiple acute infarcts in bilateral cerebellar hemispheres, pons, and right anterior thalamus. Noncontrast MR angiography (MRA) of the head and digital subtraction angiography showed distal basilar artery cutoff and right vertebral artery dominance. As the NIHSS score worsened to 10, a MT with solitaire was done (after 12 hours of onset of symptoms), and reperfusion was achieved in two passes. The child showed remarkable improvement in NIHSS score to 2 by 5 days. At discharge, the child had residual mild ataxia. Despite investigations, the cause of thrombosis remained unknown. Conclusion: Our case highlights that in case of significant large arterial occlusion with rapid worsening of symptoms, MT may be considered, even if it involves posterior circulation, and the child presents beyond the usual window of 4–6 hours.

Liver non-contrast perfusion in diffuse liver diseases diagnostic algorithm: the new diagnostic criteria

Purpose: to define the new criteria for contrast-free ASL perfusion using for the management of diffuse liver diseases (DLD).Material and methods. Clinical and laboratory data, results of MRI with non-contrast MR perfusion (ASL-perfusion) of the liver were estimated in a group of patients with DLD (three-year research).Results. Potentials of assessment of liver ASL perfusion for patients with DLD (including complicated cases) are described in the article. It was established that ASL liver perfusion is useful for DLD clinical forms differential diagnosis, predicting the risk of liver cirrhosis, as well as complications (hepatic encephalopathy, sialoadenitis) and DLD exacerbation. The strategy of contrast-free MR perfusion using in patients with DLD management algorithm was developed.Conclusion. Liver ASL perfusion is a promising for the study and application method for the management of DLD.

Quantification of water exchange across the blood-brain barrier using noncontrast MR fingerprinting.

A method is proposed to quantify cerebral blood volume ( ) and intravascular water residence time ( ) using MR fingerprinting (MRF), applied using a spoiled gradient echo sequence without the need for contrast agent. An in silico study optimized an acquisition protocol to maximize the sensitivity of the measurement to and changes. Its accuracy in the presence of variations in , , and was evaluated. The optimized protocol (scan time of 19 min) was then tested in a exploratory healthy volunteer study (10 volunteers, mean age 24 3, six males) at 3 T with a repeat scan taken after repositioning to allow estimation of repeatability. Simulations show that assuming literature values for and , no variation in , while fitting only and , leads to large errors in quantification of and , regardless of noise levels. However, simulations also show that matching , , , and , simultaneously is feasible at clinically achievable noise levels. Across the healthy volunteers, all parameter quantifications fell within the expected literature range. In addition, the maps show good agreement between hemispheres suggesting physiologically relevant information is being extracted. Expected differences between white and gray matter (p < 0.0001) and (p < 0.0001) are observed, and show no significant differences, p = 0.4 and p = 0.6, respectively. Moderate to excellent repeatability was seen between repeat scans: mean intra-class correlation coefficient of , , , and . We demonstrate that regional simultaneous quantification of , , , and using MRF is feasible in vivo.

DYNAMIC ASSESSMENT OF CEREBRAL PERFUSION BLOOD FLOW IN THE EARLY POST-STROKE PERIOD ACCORDING TO NON-CONTRAST MRI DATA

HighlightsThe non-contrast perfusion MR sequence pCASL (pseudocontinuous arterial spin labeling) is a technique that allows specialist to quantify and trace the changes in cerebral blood flow in the early post-stroke period. At the same time, there is a change in perfusion indices not only in the ischemic stroke area, but also in visually intact areas of the ipsilateral and contralateral hemispheres of the brain, which indicates the involvement of the blood supply area and the brain as a whole in the pathological process. The obtained data on the dynamics in perfusion, verified by the results of cognitive tests, open up the prospect of a comprehensive study of stroke as a complex brain disease with the possibility of predictive assessment of rehabilitation. Aim. To assess the dynamics of microcirculatory changes in the brain in the early post-stroke period by non-contrast perfusion MRI.Methods. The study included 42 patients with acute ischemic stroke. The patients were examined by 3T MRI using the following sequences: DWI-EPI, 3D FLAIR-SPIR, T2-TSE, T1W 3D-TFE, and pseudocontinuous arterial spin labeling (pCASL) on 1–3 days, 7–10 days and 3 months later after the manifestation of acute ischemic stroke. The cerebral blood flow (CBF) was obtained in 4 supratentorial regions of the brain: in the ischemic stroke and contralateral areas, as well as in a visually intact area of the ipsilateral and contralateral hemispheres (mL/100g/min).Results. In the ischemic stroke area, CBF increased from 19.86±5.69 (mean+Std) to 27.57±4.86 by first to the second examination, which was associated with the infusion therapy, local inflammatory response and compensatory reperfusion. By the 3rd examination CBF decreased to 14.48±3.66 (Student t-test, p&lt;0.05), which reflects cystic and atrophic transformation of the affected area. In visually intact white matter of the ipsilateral and contralateral hemispheres, CBF increased from hypoperfused to normoperfused from the first to the third examination. There was a significant decrease (p&lt;0.001) in tissue blood flow (by 54% for the 1st, 38% for the 2nd, 67% for the 3rd examination) in the ischemia area relative to intact parts of the brain.Conclusion. The pCASL allowed us to assess CBF in the post-stroke period in the ischemic area and in visually intact area, nevertheless, it requires additional pre- and postprocessing of data to obtain quantitative values. At the same time, we observed changes in perfusion in the ischemic stroke area, and in the visually intact areas of the ipsilateral and contralateral hemispheres of the brain, indicating the involvement of the cerebral blood flow and brain as a whole in the pathological process.

Non-contrast MRI of micro-vascularity of the feet and toes.

This study aimed to develop novel non-contrast MR perfusion techniques for assessing micro-vascularity of the foot in human subjects. All experiments were performed on a clinical 3T scanner using arterial spin labeling (ASL). Seven healthy subjects (30-72years old, 5 males and 2 females) were enrolled and bilateral feet were imaged with tag-on and tag-off alternating inversion recovery spin labeling for determining micro-vascularity. We compared an ASL technique with 1-tag against 4-tag pulses. For perfusion, we determined signal increase ratio (SIR) at varying inversion times (TI) from 0.5 to 2s. SIR versus TI data were fit to determine perfusion metrics of peak height (PH), time to peak (TTP), full width at half maximum (FWHM), area under the curve (AUC), and apparent blood flow (aBF) in the distal foot and individual toes. Using analysis of variance (ANOVA), effects of tag pulse and region of interest (ROI) on the mean perfusion metrics were assessed. In addition, a 4-tag pulse perfusion experiment was performed on patients with peripheral artery disease (PAD) and Raynaud's disease. Using ourMR perfusion techniques, SIR versus TI data showed well-defined leading and trailing edges, with a peak near TI of 0.75-1.0s and subsiding quickly to near zero by TI of 2s, particularly when 4-tag pulses were used. When imaged with 4-tag pulse, we found significantly greater values in perfusion metrics, as compared to 1-tag pulse. The patients with PAD and Raynaud's disease showed a reduced or scattered perfusion curves compared to the healthy control. MR perfusion imaging of the distal foot shows greater SIR and perfusion metrics with the 4-tag pulse compared to the 1-tag pulse technique. This will likely benefit those with low perfusion due to aging, PAD, diabetic foot, and other vascular diseases.

Synthesizing Contrast-Enhanced MR Images from Noncontrast MR Images Using Deep Learning.

Recent developments in deep learning methods offer a potential solution to the need for alternative imaging methods due to concerns about the toxicity of gadolinium-based contrast agents. The purpose of the study was to synthesize virtual gadolinium contrast-enhanced T1-weighted MR images from noncontrast multiparametric MR images in patients with primary brain tumors by using deep learning. We trained and validated a deep learning network by using MR images from 335 subjects in the Brain Tumor Segmentation Challenge 2019 training data set. A held out set of 125 subjects from the Brain Tumor Segmentation Challenge 2019 validation data set was used to test the generalization of the model. A residual inception DenseNet network, called T1c-ET, was developed and trained to simultaneously synthesize virtual contrast-enhanced T1-weighted (vT1c) images and segment the enhancing portions of the tumor. Three expert neuroradiologists independently scored the synthesized vT1c images by using a 3-point Likert scale, evaluating image quality and contrast enhancement against ground truth T1c images (1 = poor, 2 = good, 3 = excellent). The synthesized vT1c images achieved structural similarity index, peak signal-to-noise ratio, and normalized mean square error scores of 0.91, 64.35, and 0.03, respectively. There was moderate interobserver agreement between the 3 raters, regarding the algorithm's performance in predicting contrast enhancement, with a Fleiss kappa value of 0.61. Our model was able to accurately predict contrast enhancement in 88.8% of the cases (scores of 2 to 3 on the 3-point scale). We developed a novel deep learning architecture to synthesize virtual postcontrast enhancement by using only conventional noncontrast brain MR images. Our results demonstrate the potential of deep learning methods to reduce the need for gadolinium contrast in the evaluation of primary brain tumors.

Non-contrast free-breathing 2D CINE compressed SENSE T1-TFE cardiovascular MRI at 3T in sedated young children for assessment of congenital heart disease.

Cardiac MRI is a crucial tool for assessing congenital heart disease (CHD). However, its application remains challenging in young children when performed at 3T. The aim of this retrospective single center study was to compare a non-contrast free-breathing 2D CINE T1-weighted TFE-sequence with compressed sensing (FB 2D CINE CS T1-TFE) with 3D imaging for diagnostic accuracy of CHD, image quality, and vessel diameter measurements in sedated young children. FB 2D CINE CS T1-TFE was compared with a 3D non-contrast whole-heart sequence (3D WH) and 3D contrast-enhanced MR angiography (3D CE-MRA) at 3T in 37 CHD patients (20♂, 1.5±1.4 years). Two radiologists independently assessed image quality, type of CHD, and diagnostic confidence. Diameters and measures of contrast and sharpness of the aorta and pulmonary vessels were determined. A non-parametric multi-factorial approach was used to estimate diagnostic accuracy for the diagnosis of CHD. Linear mixed models were calculated to compare contrast and vessel sharpness. Krippendorff's alpha was determined to quantify vessel diameter agreement. FB 2D CINE CS T1-TFE was rated superior regarding image quality, diagnostic confidence, and diagnostic sensitivity for both intra- and extracardiac pathologies compared to 3D WH and 3D CE-MRA (all p<0.05). FB 2D CINE CS T1-TFE showed superior contrast and vessel sharpness (p<0.001) resulting in the highest proportion of measurable vessels (740/740; 100%), compared to 3D WH (530/620; 85.5%) and 3D CE-MRA (540/560; 96.4%). Regarding vessel diameter measurements, FB 2D CINE CS T1-TFE revealed the closest inter-reader agreement (Krippendorff's alpha: 0.94-0.96; 3D WH: 0.78-0.94; 3D CE-MRA: 0.76-0.93). FB 2D CINE CS T1-TFE demonstrates robustness at 3T and delivers high-quality diagnostic results to assess CHD in sedated young children. Its ability to function without contrast injection and respiratory compensation enhances ease of use and could encourage widespread adoption in clinical practice.

Proposal of an Abbreviated Noncontrast MR Enterography Protocol for Patients With Crohn Disease.

MR enterography (MRE) protocols used in patients with Crohn disease are burdened by long acquisition time, high cost, and suboptimal patient experience. For several indications, highly diagnostic MRE can be performed in five or fewer sequences, without IV contrast material or antiperistaltic medication and with an examination room time of less than 12 minutes. As such, MRE could be more patient friendly, more frequently performed, and require fewer health care resources.

Age-related Decline of Intrinsic Cerebrospinal Fluid Outflow in Healthy Humans Detected with Non-contrast Spin-labeling MR Imaging.

Clearance of cerebrospinal fluid (CSF) is important for the removal of toxins from the brain, with implications for neurodegenerative diseases. Imaging evaluation of CSF outflow in humans has been limited, relying on venous or invasive intrathecal injections of contrast agents. The objective of this study was to introduce a novel spin-labeling MRI technique to detect and quantify the movement of endogenously tagged CSF, and then apply it to evaluate CSF outflow in normal humans of varying ages. This study was performed on a clinical 3-Tesla MRI scanner in 16 healthy subjects with an age range of 19-71 years with informed consent. Our spin-labeling MRI technique applies a tag pulse on the brain hemisphere, and images the outflow of the tagged CSF into the superior sagittal sinus (SSS). We obtained 3D images in real time, which was analyzed to determine tagged-signal changes in different regions of the meninges involved in CSF outflow. Additionally, the signal changes over time were fit to a signal curve to determine quantitative flow metrics. These were correlated against subject age to determine aging effects. We observed the signal of the tagged CSF moving from the dura mater and parasagittal dura, and finally draining into the SSS. In addition, we observed a possibility of another pathway which is seen in some young subjects. Furthermore, quantitative CSF outflow metrics were shown to decrease significantly with age. We demonstrate a novel non-invasive MRI technique identifying two intrinsic CSF clearance pathways, and observe an age-related decline of CSF flow metrics in healthy subjects. Our work provides a new opportunity to better understand the relationships of these CSF clearance pathways during the aging process, which may ultimately provide insight into the age-related prevalence of neurodegenerative diseases.

A Non-Contrast Multi-Parametric MRI Biomarker for Assessment of MR-Guided Focused Ultrasound Thermal Therapies.

We present the development of a non-contrast multi-parametric magnetic resonance (MPMR) imaging biomarker to assess treatment outcomes for magnetic resonance-guided focused ultrasound (MRgFUS) ablations of localized tumors. Images obtained immediately following MRgFUS ablation were inputs for voxel-wise supervised learning classifiers, trained using registered histology as a label for thermal necrosis. VX2 tumors in New Zealand white rabbits quadriceps were thermally ablated using an MRgFUS system under 3 T MRI guidance. Animals were re-imaged three days post-ablation and euthanized. Histological necrosis labels were created by 3D registration between MR images and digitized H&E segmentations of thermal necrosis to enable voxel-wise classification of necrosis. Supervised MPMR classifier inputs included maximum temperature rise, cumulative thermal dose (CTD), post-FUS differences in T2-weighted images, and apparent diffusion coefficient, or ADC, maps. A logistic regression, support vector machine, and random forest classifier were trained in red a leave-one-out strategy in test data from four subjects. In the validation dataset, the MPMR classifiers achieved higher recall and Dice than a clinically adopted 240 cumulative equivalent minutes at 43 °C (CEM 43) threshold (0.43) in all subjects. The average Dice scores of overlap with the registered histological label for the logistic regression (0.63) and support vector machine (0.63) MPMR classifiers were within 6% of the acute contrast-enhanced non-perfused volume (0.67). Voxel-wise registration of MPMR data to histological outcomes facilitated supervised learning of an accurate non-contrast MR biomarker for MRgFUS ablations in a rabbit VX2 tumor model.

The impact of mechanical thrombectomy on the blood–brain barrier in patients with acute ischemic stroke: A non-contrast MR imaging study using DP-pCASL and NODDI

Background and purposeWhile mechanical thrombectomy (MT) achieves restoration of cerebral blood flow to the area at risk in patients with acute ischemic stroke (AIS), the influx of blood flow may exacerbate the blood–brain barrier (BBB) disruption and extravasation across the BBB, and it therefore remains unclear how reperfusion impacts the blood–brain barrier integrity. In this study, we use diffusion-prepared pseudocontinuous ASL (DP-pCASL) and Neurite Orientation Dispersion and Density Imaging (NODDI) sequence to measure the water exchange rate (kw) in patients who underwent either MT or medical management and determine its impact on the brain tissue microstructure in order to elucidate the impact of MT on BBB complex integrity. Materials and methodsWe prospectively enrolled 21 patients with AIS treated at our institution from 10/2021 to 6/2023 who underwent MR imaging at a 3.0-Tesla scanner. Patients underwent DP-pCASl and NODDI imaging in addition to the standard stroke protocol which generated cerebral blood flow (CBF), arterial transit time (ATT), water exchange rate (kw), orientation dispersion index (ODI), intracellular volume fraction (ICVF), and free water fraction (FWF) parametric maps. ResultsOf the 21 patients, 11 underwent MT and 10 were treated non-operatively. The average age and NIHSS for the MT cohort and non-MT cohorts were 69.3 ± 16.6 years old and 15.0 (12.0–20.0), and 70.2 ± 10.7 (p = 0.882) and 6.0 (3.8–9.0, p = 0.003) respectively. The average CBF, ATT, and kw in the infarcted territory of the MT cohort were 38.2 (18.4–59.6), 1347.6 (1182.5–1842.3), and 107.8 (79.2–140.1) respectively. The average CBF, ATT, and kw in the stroke ROI were 16.0 (8.8–36.6, p = 0.036), 1090.8 (937.1–1258.9, p = 0.013), 89.7 (68.0–122.7, p = 0.314) respectively. Linear regression analysis showed increasing CBF (p = 0.008) and undergoing mechanical thrombectomy (p = 0.048) were significant predictors of increased kw. ConclusionUsing our multimodal non-contrast MRI protocol, we demonstrate that increased CBF and mechanical thrombectomy increased kw, suggesting a better functioning BBB complex. Higher kw suggests less disruption of the BBB complex in the MT cohort.

Highly accelerated, Dixon-based non-contrast MR angiography versus high-pitch CT angiography

ObjectivesTo compare a novel, non-contrast, flow-independent, 3D isotropic magnetic resonance angiography (MRA) sequence that combines respiration compensation, electrocardiogram (ECG)-triggering, undersampling, and Dixon water-fat separation with an ECG-triggered aortic high-pitch computed tomography angiography (CTA) of the aorta.Materials and methodsTwenty-five patients with recent CTA were scheduled for non-contrast MRA on a 3 T MRI. Aortic diameters and cross-sectional areas were measured on MRA and CTA using semiautomatic measurement tools at 11 aortic levels. Image quality was assessed independently by two radiologists on predefined aortic levels, including myocardium, proximal aortic branches, pulmonary veins and arteries, and the inferior (IVC) and superior vena cava (SVC). Image quality was assessed on a 5-point Likert scale.ResultsAll datasets showed diagnostic image quality. Visual grading was similar for MRA and CTA regarding overall image quality (0.71), systemic arterial image quality (p = 0.07–0.91) and pulmonary artery image quality (p = 0.05). Both readers favored MRA for SVC and IVC, while CTA was preferred for pulmonary veins (all p < 0.05). No significant difference was observed in aortic diameters or cross-sectional areas between native MRA and contrast-enhanced CTA (p = 0.08–0.94).ConclusionThe proposed non-contrast MRA enables robust imaging of the aorta, its proximal branches and the pulmonary arteries and great veins with image quality and aortic diameters and cross-sectional areas comparable to that of CTA. Moreover, this technique represents a suitable free-breathing alternative, without the use of contrast agents or ionizing radiation. Therefore, it is especially suitable for patients requiring repetitive imaging.

Machine Learning Diagnosis of Small-Bowel Crohn Disease Using T2-Weighted MRI Radiomic and Clinical Data.

BACKGROUND. Radiologists have variable diagnostic performance and considerable interreader variability when interpreting MR enterography (MRE) examinations for suspected Crohn disease (CD). OBJECTIVE. The purposes of this study were to develop a machine learning method for predicting ileal CD by use of radiomic features of ileal wall and mesenteric fat from noncontrast T2-weighted MRI and to compare the performance of the method with that of expert radiologists. METHODS. This single-institution study included retrospectively identified patients who underwent MRE for suspected ileal CD from January 1, 2020, to January 31, 2021, and prospectively enrolled participants (patients with newly diagnosed ileal CD or healthy control participants) from December 2018 to October 2021. Using axial T2-weighted SSFSE images, a radiologist selected two slices showing greatest terminal ileal wall thickening. Four ROIs were segmented, and radiomic features were extracted from each ROI. After feature selection, support-vector machine models were trained to classify the presence of ileal CD. Three fellowship-trained pediatric abdominal radiologists independently classified the presence of ileal CD on SSFSE images. The reference standard was clinical diagnosis of ileal CD based on endoscopy and biopsy results. Radiomic-only, clinical-only, and radiomic-clinical ensemble models were trained and evaluated by nested cross-validation. RESULTS. The study included 135 participants (67 female, 68 male; mean age, 15.2 ± 3.2 years); 70 were diagnosed with ileal CD. The three radiologists had accuracies of 83.7% (113/135), 88.1% (119/135), and 86.7% (117/135) for diagnosing CD; consensus accuracy was 88.1%. Interradiologist agreement was substantial (κ = 0.78). The best-performing ROI was bowel core (AUC, 0.95; accuracy, 89.6%); other ROIs had worse performance (whole-bowel AUC, 0.86; fat-core AUC, 0.70; whole-fat AUC, 0.73). For the clinical-only model, AUC was 0.85 and accuracy was 80.0%. The ensemble model combining bowel-core radiomic and clinical models had AUC of 0.98 and accuracy of 93.5%. The bowel-core radiomic-only model had significantly greater accuracy than radiologist 1 (p = .009) and radiologist 2 (p = .02) but not radiologist 3 (p > .99) or the radiologists in consensus (p = .05). The ensemble model had greater accuracy than the radiologists in consensus (p = .02). CONCLUSION. A radiomic machine learning model predicted CD diagnosis with better performance than two of three expert radiologists. Model performance improved when radiomic data were ensembled with clinical data. CLINICAL IMPACT. Deployment of a radiomic-based model including T2-weighted MRI data could decrease interradiologist variability and increase diagnostic accuracy for pediatric CD.