3-dimensional Magnetic Resonance Imaging Research Articles

Aortic dissection assessment by 4D phase-contrast MRI with hemodynamic parameters: the impact of stent type.

To explore the diagnostic performance of 4-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) in evaluating aortic dissection in different clinical scenarios. The study group comprised 32 patients with a known aortic dissection who each underwent computed tomography angiography (CTA), and then 4D PC-MRI with a 1.5-T MR scanner. The 4D PC-MRI images were compared with the CTA images to evaluate the aortic size, branch identification, and iliac and femoral arterial access. The patients were divided into three groups: (I) patients diagnosed with Type B aortic dissection but did not undergo intervention (n=8); (II) patients with residual aortic dissection after open repair of Type A dissection (n=7); (III) patients who underwent endovascular aortic repair with or without open surgery (n=17). Without radiation or contrast media injection, 4D PC-MRI provided similar aortic images for patients in Group 1 and most of those in Group 2. In Group 3, stainless steel stents affected image quality in three patients. High-quality 4D PC-MRI images were obtained for the remaining 14 patients in Group 3, who had non-stainless steel stents, and provided major aortic information comparable to that provided by CTA with contrast media. The hemodynamic parameters of true and false lumens were evaluated between three patients with Type B aortic dissections and three patients who underwent thoracic endovascular aortic repair for their aortic dissection. The stroke volume was higher in the true lumen of the patients with stent-grafts than in the patients with Type B aortic dissection without intervention. The regurgitant fraction, an indicator of nonlaminar flow, was higher in the false lumens than in the true lumens. All 32 patients in this study tolerated 4D PC-MRI without adverse events. 4D PC-MRI is radiation- and contrast media-free option for imaging aortic dissection. It not only provided images comparable in quality to those obtained with CTA but also provided information on hemodynamic parameters, including endoleak detection after thoracic endovascular aortic repair. 4D PC-MRI was safe and accurate in evaluating chronic Type B aortic dissection and residual aortic dissection after surgery for acute Type A aortic dissection. Therefore, it could be a potential tool in treating pathology in aortic dissection, especially for patients with malperfusion syndrome of visceral vessels and in young patients with renal function impairment. However, certain endograft materials, especially stainless steel, may prevent the further application of 4D PC-MRI and should be avoided.

Correction to: Low and Oscillatory Wall Shear Stress Is Not Related to Aortic Dilation in Patients With Bicuspid Aortic Valve: A Time-Resolved 3-Dimensional Phase-Contrast Magnetic Resonance Imaging Study.

Correction to: Low and Oscillatory Wall Shear Stress Is Not Related to Aortic Dilation in Patients With Bicuspid Aortic Valve: A Time-Resolved 3-Dimensional Phase-Contrast Magnetic Resonance Imaging Study.

Effects of different morphologic abnormalities on hemodynamics in patients with venous pulsatile tinnitus: A four-dimensional flow magnetic resonance imaging study.

The effects of morphologic abnormalities, including sigmoid sinus wall dehiscence (SSWD), transverse sinus stenosis (TSS), and sigmoid sinus diverticulum (SSD), on hemodynamics in venous pulsatile tinnitus (PT) patients have not been established. The aim of this study was to evaluate the effects of SSWD, TSS, and SSD on the hemodynamics of transverse‐sigmoid sinus in venous PT patients. This was a prospective study with 44 venous PT patients and 12 healthy controls. A 3 T/four‐dimensional (4D) flow magnetic resonance imaging with fast field echo was used. Computed tomography arteriography/venography was used to assess ipsilateral SSWD, TSS, and SSD. Maximum velocity (V max), average velocity (V avg), and average flow (Flowavg) were measured. Blood flow patterns were independently assessed by three neuroradiologists. One‐way analysis of variance or Kruskal–Wallis test was also used. On the symptomatic side, all patients had SSWD, 33 patients had TSS, and 22 patients had SSD. Compared with healthy controls, patients with TSS, without TSS, with SSD, and without SSD all showed higher V max (all p < 0.050), V avg (all p < 0.050), and Flowavg (all p < 0.050). Patients with TSS showed higher V max (p < 0.050) and V avg (p < 0.050) than those without TSS, and no significant difference in Flowavg was found between the two groups (p = 0.408). No significant differences in V max, V avg, and Flowavg were found between patients with and without SSD (all p = 1.000). Jet‐like flow in the stenosis and downstream of the stenosis was observed in all patients with TSS. Vortex in SSD was observed in 15 patients with SSD (68%). High blood velocity and flow may be characteristic markers of venous PT. SSWD may be a necessary condition for venous PT. TSS may further increase the blood velocity and form a jet‐like flow. SSD may be related to vortex formation but had no significant effect on blood velocity and flow.Level of Evidence2Technical Efficacy Stage3

Ultra-high resolution, 3-dimensional magnetic resonance imaging of the atherosclerotic vessel wall at clinical 7T.

Accurate quantification and characterization of atherosclerotic plaques with MRI requires high spatial resolution acquisitions with excellent image quality. The intrinsically better signal-to-noise ratio (SNR) at high-field clinical 7T compared to the widely employed lower field strengths of 1.5 and 3T may yield significant improvements to vascular MRI. However, 7T atherosclerosis imaging also presents specific challenges, related to local transmit coils and B1 field inhomogeneities, which may overshadow these theoretical gains. We present the development and evaluation of 3D, black-blood, ultra-high resolution vascular MRI on clinical high-field 7T in comparison lower-field 3T. These protocols were applied for in vivo imaging of atherosclerotic rabbits, which are often used for development, testing, and validation of translatable cardiovascular MR protocols. Eight atherosclerotic New Zealand White rabbits were imaged on clinical 7T and 3T MRI scanners using 3D, isotropic, high (0.63 mm3) and ultra-high (0.43 mm3) spatial resolution, black-blood MR sequences with extensive spatial coverage. Following imaging, rabbits were sacrificed for validation using fluorescence imaging and histology. Image quality parameters such as SNR and contrast-to-noise ratio (CNR), as well as morphological and functional plaque measurements (plaque area and permeability) were evaluated at both field strengths. Using the same or comparable imaging parameters, SNR and CNR were in general higher at 7T compared to 3T, with a median (interquartiles) SNR gain of +40.3 (35.3–80.1)%, and a median CNR gain of +68.1 (38.5–95.2)%. Morphological and functional parameters, such as vessel wall area and permeability, were reliably acquired at 7T and correlated significantly with corresponding, widely validated 3T vessel wall MRI measurements. In conclusion, we successfully developed 3D, black-blood, ultra-high spatial resolution vessel wall MRI protocols on a 7T clinical scanner. 7T imaging was in general superior to 3T with respect to image quality, and comparable in terms of plaque area and permeability measurements.

A New Technique for Shaping the Aortic Sinuses and Conserving Dynamism in the Remodeling Operation

Preserving dynamism and recreating the sinuses in the Dacron graft are thought to be important for optimizing results of aortic valve-conserving operations. We describe a novel technique that preserves dynamism and recreates the sinotubular junction. In addition, it tailors 3 sinuses of defined longitudinal and transverse curvatures in a straight Dacron tube during the operation. The technique has been used in 6 patients with varied aortic root pathology. We performed preoperative and postoperative multimodality imaging using computerized image analysis as well as 3-dimensional models. There was no early or midterm death. Upon discharge, patients were clinically well, with echocardiographic evidence of minimal (3 patients) or mild (3 patients) aortic regurgitation. Computed tomography and cardiac magnetic resonance imaging with extensive image analysis of the aortic root size, shape, and function showed partial or complete normalization of these parameters. This included the shape and dynamism of the aortic annulus and the size and shape of the geometric (effective) orifice. The 4-dimensional magnetic resonance imaging pattern of flow in the sinuses and ascending aorta showed favorable vortices in the sinuses, right-handed helical flow, and marked diminution of energy loss in the ascending aorta. The novel technique described here is simple, practical, and cost-effective because it uses a widely available straight Dacron tube. The technique does not use rigid internal or external support. The early results are encouraging. Larger series with longer follow-up are required.

Association of age-related white matter hyperintensity with brain atrophy and cognitive impairment in patients with Parkinson's disease

Objective: To investigate the association of age-related white matter hyperintensity (WMH) with brain atrophy and cognitive impairment in patients with Parkinson's disease (PD). Methods: Consecutive samples of a prospective PD cohort with complete 3-dimensional magnetic resonance imaging in the Department of Movement Disorders in Beijing Tiantan Hospital, Capital Medical University, from October 2018 to August 2019 was retrospectively analyzed. Cognition was evaluated by Mini-Mental State Scale (MMSE) and Montreal Cognitive Assessment (MoCA). The severity of WMH was semi-quantitatively measured by Fazekas scale (0-6 points), and the mean cortical thickness and thalamus volume were calculated by FreeSurfer software. The demographic and disease characteristics, the severity of WMH, the mean cortical thickness and thalamus volume were respectively compared between PD patients with and without dementia. Moreover, univariate and multivariate generalized linear models were used to analyze the correlation of the severity of WMH with brain atrophy and MoCA. Results: A total of 225 patients with PD were included in the study, with a median age of 66 years old. Comparisons between groups suggested that patients with dementia were with severer WMH, older, and had lower levels of serum cholesterol and low-density lipoprotein and more reduced mean cortical thickness than those without dementia (all P<0.05), but no significant difference in the thalamus volume was found between the two groups. The generalized linear model showed that the cognitive impairment of PD patients was significantly correlated with WMH (β=-0.021, 95%CI:-0.040--0.002, P=0.032), but independent of age, cortical thickness, and levels of serum cholesterol and low-density lipoprotein. Conclusion: WMH may worsen PD cognitive impairment independent of brain atrophy. Clinical prevention and treatment of cerebral small vessel disease may have protective effects on cognitive function in patients with PD.

Abstract 14205: Aortic Vorticity, Helicity and Aortopathy in Adult Patients With Tetralogy of Fallot: Preliminary Study Using Four-dimensional Flow Magnetic Resonance Images

Introduction and hypothesis: Flow hemodynamic parameters may relate to aortopathy in adults with tetralogy of Fallot. We aimed to employ quantitative analysis in the vorticity and helicity of the aortic root and the ascending aorta (AAo) in adults with tetralogy of Fallot (TOF), and to evaluate aortopathy and the relevant factors. Methods: Prospectively, 51 consecutive adults with TOF underwent 4 dimensional flow magnetic resonance imaging study for the assessment of vorticity and helicity of in the aortic root and AAo, wall shear stress (WSS), viscous energy loss (EL), and the left ventricular outflow tract - aortic root (LVOT-Ao) angle. Patients were divided into the two groups: dilated aortic root and/or AAo (indexed dimeter&gt;25mm/cm2), Group A (15 patients); non-dilated aortic patients, Group B (36 patients). Ten age matched controls were also enrolled. Results: Group A showed acute LVOT-Ao angle, higher incidence of aortic regurgitation, and initial anatomy of pulmonary atresia, compared to Group B (P&lt;0.0001, 0.02, 0.043). Group A showed greater vorticity at the level of Valsalva, AAo, and proximal arch, helicity, WSS, and EL than in Group B (P&lt;0.001, &lt;0.001, 0.049, 0.02, 0.026). Acute LVOT-Ao angle correlated with the diameter of the aortic root and AAo, vorticity, helicity, WSS, and EL (P=0.004, 0.023, 0.045, 0.004, 0.0004, 0.017). On a univariate logistic analysis, age, acute LVOT-Ao angle, AAo vorticity, AAo helicity, and maximum WSS were relevant factors of AAo dilatation (P=0.03, 0.02, 0.004, 0.03, 0.046). On a multivariate analysis, LVOT-Ao angle was the most important factor of AAo dilatation (odds ratio 0.66, 95%CI 0.46-0.95, P&lt;0.024). Conclusions: TOF Adults with TOF presenting dilated AAo have greater vorticity, helicity, and acute LVOT-Ao angle. Flow eccentricity correlates with vorticity and helicity, which may affect the aortopathy in adults with TOF. AAo vorticity and helicity are also relevant factors of aortic dilatation, and these flow hemodynamic parameters may be adjunctive predictions of aortopathy in this population.

High-Resolution Three Dimensional MRI Findings After Plugging Surgery for Superior Semicircular Canal Dehiscence: A Case Report

: Superior semicircular canal dehiscence (SSCD) is known as abnormal communication of the superior semicircular canal (SCC) to the intracranial space secondary to a bony defect in the canal. Patients who are subjected to surgical repair usually have intractable symptoms, and recently, plugging of SCC using a transmastoid approach has been widely recommended. In this report, we describe a case of incomplete plugging for SSCD in a 37-year-old woman, along with the high-resolution three dimensional magnetic resonance imaging (3D MRI) findings using Pöschl view reconstruction. Postoperative MRI of 3D T2-wieghted sampling perfection with application optimized contrasts using different flip angle evolution (SPACE) Pöschl plane demonstrated an incomplete plugging of the SCC with partially visible perilymphatic fluid in the posterior limb above the common crus. A 3D fluid-attenuated inversion recovery (FLAIR) sequence showed an enhancement involving the vestibule and SCC, suggesting labyrinthitis. Although there are few reports about incomplete plugging for SSCD, this case could demonstrate postoperative status and complication after plugging of SSCD using a high-resolution 3D MRI sequences with Pöschl view reconstruction.

Craniosynostosis: Clinical Presentation, Genetics, and Prenatal Diagnosis.

Craniosynostosis is a fetal condition caused by premature closure of the cranial sutures. Through provider awareness, we can raise suspicion in high-risk individuals, increase prenatal detection, optimize genetic testing, perform appropriate antenatal surveillance and delivery planning, and allow for a comprehensive, multidisciplinary approach to treatment. The aim of this study was to review what is currently known regarding the genetics, pathophysiology, diagnosis, and treatment of craniosynostosis for the obstetric care provider. A comprehensive literature review was performed using the PubMed database with the search term "craniosynostosis." The search was limited to the English language. A total of 220 articles were identified, and a total of 53 were used in completion of this article. The results highlight the multiple factors involved with abnormal suture formation, including various genetic factors. Although rare at this time, prenatal detection can allow families to prepare and practitioners to provide appropriate clinical treatment. Both 3-dimensional sonography and magnetic resonance imaging have been identified as modalities to aid in detection for high-risk individuals. Early referral allows for less-invasive surgical outcomes with lower complication rates. Familiarity with craniosynostosis among obstetric providers can improve patient counseling, prenatal detection rates, and appropriate antepartum, intrapartum, and postpartum counseling.

Aortic Vorticity, Helicity, and Aortopathy in Adult Patients with Tetralogy of Fallot: Pilot Study Using Four-Dimensional Flow Magnetic Resonance Images.

To employ quantitative analysis in the vorticity and helicity of the aortic root and the ascending aorta (AAo) in adults with tetralogy of Fallot (TOF), and to evaluate aortopathy and the relevant factors. Prospectively, 51 consecutive adults with TOF underwent 4 dimensional flow magnetic resonance imaging study for the assessment of vorticity and helicity of the aortic root and AAo, wall shear stress (WSS), viscous energy loss (EL), and the left ventricular outflow tract - aortic root (LVOT-Ao) angle. Patients were divided into the two groups: dilated aortic root and/or AAo (indexed diameter > 25mm/cm2), Group A (15 patients); non-dilated aortic patients, Group B (36 patients). Ten age-matched controls were also enrolled. Group A showed more acute LVOT-Ao angle, higher incidence of aortic regurgitation, and initial anatomy of pulmonary atresia, compared to Group B (P < 0.0001, 0.02, 0.043). Group A showed greater clockwise vorticity at the level of Valsalva, AAo, and proximal arch, sagittal vorticity, AAo helicity, WSS, and EL than in Group B (P < 0.001, < 0.001, < 0.001, 0.045, 0.049, 0.02, 0.026). More acute LVOT-Ao angle correlated with the diameter of the aortic root and AAo, AAo vorticity, helicity, WSS, and EL (P = 0.004, 0.023, 0.045, 0.004, 0.0004, 0.017). On a univariate logistic analysis, more acute LVOT-Ao angle, AAo vorticity, AAo helicity, and maximum WSS were relevant factors of AAo dilatation (P = 0.02, 0.02, 0.045, 0.03, 0.046). On a multivariate logistic analysis, more acute LVOT-Ao angle was the most important factor of AAo dilatation (odds ratio 0.66, 95% CI 0.46-0.95, P < 0.024). TOF adults presenting dilated AAo have greater vorticity, helicity, and acute LVOT-Ao angle. Flow eccentricity and these flow hemodynamic parameters may be adjunctive predictions of aortopathy in this population.

Four-Dimensional Magnetic Resonance Imaging Assessment of Intracranial Aneurysms: A State-of-the-Art Review.

Treatment of unruptured intracranial aneurysms can reduce the risk of subarachnoid hemorrhage and its associated morbidity and mortality. However, current methods to predict the risk of rupture and optimize treatment strategies for intracranial aneurysms are limited. Assessment of intra-aneurysmal flow using 4-dimensional magnetic resonance imaging (4D MRI) is a novel tool that could be used to guide therapy. A systematic search of the literature was performed to provide a state-of-the-art review on 4D MRI assessment of unruptured intracranial aneurysms. A total of 18 studies were available for review. Eccentric flow on 4D MRI is associated with a greater aspect ratio and peak wall shear stress (WSS). WSS, vorticity, and peak velocity are greater in saccular than fusiform aneurysms. Unstable aneurysms are associated with greater WSS, peak wall stress, and flow jet angle and may exhibit wall enhancement. In comparison to computational fluid dynamics (CFD), 4D MRI has a lower spatial resolution and reports lower WSS and velocity magnitudes, but these parameters equalize when spatial resolution is matched. 4D MRI demonstrates the intra-aneurysmal hemodynamic changes associated with flow diversion, including significantly decreased flow velocity. Thus, 4D MRI is a novel, noninvasive imaging tool used for the evaluation of hemodynamics within intracranial aneurysms. Hemodynamic indices derived from 4D MRI appear to correlate well with the simulated (CFD) values and may be used to measure the success of endovascular therapies and risk factors for aneurysm growth and rupture.

All-Epiphyseal Physeal-Sparing Anterior Cruciate Ligament Reconstructive Surgery: A Study of 3-Dimensional Modeling to Characterize a Safe and Reproducible Surgical Approach

PurposeThe purpose of this study was to use 3-dimensional magnetic resonance imaging modeling of the skeletally immature knee to help characterize safe and reproducible tunnel positions, diameters, lengths, trajectories, and distances from anatomic landmarks and the physeal and articular cartilage for physeal-sparing anterior cruciate ligament (ACL) reconstructive surgery.MethodsMagnetic resonance imaging from 19 skeletally immature knees with normal anatomy were gathered. The 3-dimensional models were created, and the relevant anatomic structures were identified. Cylinders simulating tunnel length, diameter and trajectory were superimposed onto the models, and descriptive measurements were performed.ResultsA safe position for the creation of an 8 mm diameter femoral tunnel was described in the lateral femoral condyle. The femoral tunnel length averaged 25.5 ± 2.6 mm. The bony entry point was located 3.8 ± 2.4 mm proximally and 12.7 ± 2.2 mm posteriorly to the lateral epicondyle. The shortest distance from the tunnel edge to the physis and femoral articular cartilage was 2.8 ± 0.7 mm and 3.7 ± 0.9 mm, respectively. The safe position for an 8 mm diameter tibial tunnel was also identified and described in the proximal tibia. The epiphyseal tibial tunnel length from the ACL footprint to the physis averaged 15.5 ± 1.6 mm. The proximal tibial epiphysis was found to accommodate a tibial crosspin measuring 63.5 ± 5.9 mm in length and 8.2 ± 1.5 mm in diameter without disrupting the physis or articular cartilage.ConclusionsThree-dimensional modeling created from magnetic resonance imaging can help define important anatomic relationships for physeal-sparing ACL reconstructive surgery in skeletally immature knees and may assist in reducing the risk of injury to local anatomic structures.Clinical RelevanceKnowledge of the anatomic relationships in skeletally immature knees serves as a valuable reference for surgeons performing physeal-sparing ACL reconstruction surgery.

Measurements of the parapapillary atrophy area and other fundus morphological features in high myopia with or without posterior staphyloma and myopic traction maculopathy.

To investigate the affecting factors of parapapillary gamma and delta zones and other fundus morphological features in high myopia. Seventy high myopia patients were included in this retrospective observational study and 47 patients were female. Patients were divided into three groups: no posterior staphyloma (no PS), PS with myopic traction maculopathy (PS with MTM), and PS without MTM using 3-dimensional magnetic resonance imaging and optical coherence tomography. MTM patients were further classified into three types [epiretinal membrane, macular hole, and macular retinoschisis (MRS)]. Diameters of the gamma and delta zones were measured among other morphometric variables using fundus photographs. Of the 70 individuals (127 eyes), the mean age was 57.46±13.56y. In univariate analysis, morphological features changed most dramatically in PS with MTM patients, who had the largest gamma zone diameters, the largest disk-fovea distance (DFD) and disk-fovea angle, and the smallest angle kappa and vertical distance of temporal arterial arcade. However, their horizontal delta zone diameter was smaller than in the patients with PS yet without MTM. In multivariate analysis, with axial length (AL) and age adjusted, the horizontal diameter in the delta zone of the PS without MTM group was still significantly larger than in the PS with MTM group (P=0.024). Comparing the three subtypes of MTM patients, the diameters of the gamma zone and DFD in MRS group were the largest. The characteristics of the gamma and delta zones change inconsistently in different stages of high myopia. These changes may be associated with anatomical changes caused by local traction. Factors such as PS, AL and age play an important role. These findings may provide a hint about the pathogenesis of traction in high myopia.

Loss of Presynaptic Terminal Integrity in the Substantia Nigra in Early Parkinson's Disease.

It has been hypothesized that the pathology of Parkinson's disease (PD) primarily affects presynaptic terminals and spreads trans-synaptically. The main objective of this study was to assess the magnitude and anatomical extent of presynaptic terminal loss across the brain in early PD. A second objective was to compare loss of presynaptic terminals and cell bodies within the nigrostriatal tract. A total of 30 patients with early PD and 20 age- and gender-matched healthy controls underwent positron emission tomography with 11 C-UCB-J, a ligand for the universal presynaptic terminal marker synaptic vesicle protein 2A (SV2A), and with the dopamine transporter ligand 18 F-FE-PE2I, as well as a detailed clinical assessment. Volumes of interest were delineated based on individual 3-dimensional T1 magnetic resonance imaging. BPND images were calculated. Patients with PD showed significant loss of SV2A binding in the substantia nigra only. Loss of dopamine transporter binding in the PD group was much greater in the putamen than in the substantia nigra. We found no correlations between SV2A or dopamine transporter binding and any of the clinical motor or nonmotor scores. Homologous voxel-based analysis in the PD group showed significant correlations between SV2A and dopamine transporter binding in the caudate and substantia nigra. Presynaptic terminals appear to be the most heavily affected subcellular compartment of nigrostriatal neurons in early PD. Moreover, early PD causes loss of presynaptic terminals that innervate the nigrostriatal neurons. This loss of presynaptic boutons in the substantia nigra may reflect an axonal response to target deprivation or could possibly point to a trans-synaptic mode of propagation of the disease process. © 2020 International Parkinson and Movement Disorder Society.

Distinct Effects of Motor Training on Resting-State Functional Networks of the Brain in Parkinson’s Disease

Background. Nigrostriatal dopaminergic loss is a hallmark of Parkinson’s disease (PD) pathophysiology, leading to motor Parkinsonism. Different intervention protocols have shown that motor and cognitive functions improvement in PD occur via the modulation of distinct motor and cognitive pathways. Objective. To investigate the effects of two motor training programs on the brains’ functional networks in PD patients. Methods. Thirty-seven PD patients were prospectively studied. All enrolled patients underwent either treadmill training (TT) (n = 19) or treadmill with virtual reality (TT + VR) (n = 18) for 6 weeks. Magnetic resonance imaging (MRI) scans (3 T) acquiring 3-dimensional T1-weighted and resting-state functional MRI (rs-fMRI) data sets were performed at baseline and after 6 weeks. Independent component analysis (ICA) was conducted, and functional connectivity (FC) changes within large-scale functional brain networks were examined. Results. In both groups, significant post-training FC decrease in striatal, limbic, and parietal regions within the basal ganglia network, executive control network, and frontal-striatal network, and significant FC increase in the caudate, and cingulate within the sensorimotor network (SMN) were observed. Moreover, a significant time × group interaction was detected where TT + VR training had greater effects on FC levels in the supplementary motor area (SMA) and right precentral gyrus within the SMN, and in the right middle frontal gyrus (MFG) within the cerebellar network. These FC alterations were associated with improved usual and dual-task walking performance. Conclusions. These results suggest that TT with-and-without the addition of a VR component affects distinct neural pathways, highlighting the potential for beneficial neural plasticity in PD. Such distinctive task-specific pathways may foster the facilitation of interventions tailored to the individual needs of PD patients. Registered at Clinicaltrials.gov number: NCT01732653.

3-Dimensional magnetic resonance imaging of the freely moving human eye.

Eye motion is a major confound for magnetic resonance imaging (MRI) in neuroscience or ophthalmology. Currently, solutions toward eye stabilisation include participants fixating or administration of paralytics/anaesthetics. We developed a novel MRI protocol for acquiring 3-dimensional images while the eye freely moves. Eye motion serves as the basis for image reconstruction, rather than an impediment. We fully reconstruct videos of the moving eye and head. We quantitatively validate data quality with millimetre resolution in two ways for individual participants. First, eye position based on reconstructed images correlated with simultaneous eye-tracking. Second, the reconstructed images preserve anatomical properties; the eye's axial length measured from MRI images matched that obtained with ocular biometry. The technique operates on a standard clinical setup, without necessitating specialized hardware, facilitating wide deployment. In clinical practice, we anticipate that this may help reduce burdens on both patients and infrastructure, by integrating multiple varieties of assessments into a single comprehensive session. More generally, our protocol is a harbinger for removing the necessity of fixation, thereby opening new opportunities for ethologically-valid, naturalistic paradigms, the inclusion of populations typically unable to stably fixate, and increased translational research such as in awake animals whose eye movements constitute an accessible behavioural readout.

Machine Segmentation of Pelvic Anatomy in MRI-Assisted Radiosurgery (MARS) for Prostate Cancer Brachytherapy

To investigate machine segmentation of pelvic anatomy in magnetic resonance imaging (MRI)-assisted radiosurgery (MARS) for prostate cancer using prostate brachytherapy MRIs acquired with different pulse sequences and image contrasts. Two hundred 3-dimensional (3D) preimplant and postimplant prostate brachytherapy MRI scans were acquired with a T2-weighted sequence, a T2/T1-weighted sequence, or a T1-weighted sequence. One hundred twenty deep machine learning models were trained to segment the prostate, seminal vesicles, external urinary sphincter, rectum, and bladder using the MRI scans acquired with T2-weighted and T2/T1-weighted image contrast. The deep machine learning models consisted of 18 fully convolutional networks (FCNs) with different convolutional encoders. Both 2-dimensional and 3D U-Net FCNs were constructed for comparison. Six objective functions were investigated: cross-entropy, Jaccard distance, focal loss, and 3 variations of Tversky distance. The performance of the models was compared using similarity metrics, including pixel accuracy, Jaccard index, Dice similarity coefficient (DSC), 95% Hausdorff distance, relative volume difference, Matthews correlation coefficient, precision, recall, and average symmetrical surface distance. We selected the highest-performing architecture and investigated how the amount of training data, use of skip connections, and data augmentation affected segmentation performance. In addition, we investigated whether segmentation on T1-weighted MRI was possible with FCNs trained on only T2-weighted and T2/T1-weighted image contrast. Overall, an FCN with a DenseNet201 encoder trained via cross-entropy minimization yielded the highest combined segmentation performance. For the 53 3D test MRI scans acquired with T2-weighted or T2/T1-weighted image contrast, the DSCs of the prostate, external urinary sphincter, seminal vesicles, rectum, and bladder were 0.90 ± 0.04, 0.70 ± 0.15, 0.80 ± 0.12, 0.91 ± 0.06, and 0.96 ± 0.04, respectively, after model fine-tuning. For the 5 T1-weighted images, the DSCs of these organs were 0.82 ± 0.07, 0.17 ± 0.15, 0.46 ± 0.21, 0.87 ± 0.06, and 0.88 ± 0.05, respectively. Machine segmentation of the prostate and surrounding anatomy on 3D MRIs acquired with different pulse sequences for MARS low-dose-rate prostate brachytherapy is possible with a single FCN.

Correlations and Reproducibility Between Radiographic and Radial Alpha Angles in the Evaluation of Cam Morphology.

Background:The alpha angle used to evaluate cam morphology can be determined on different imaging views; however, 2-dimensional (2D) imaging can present limitations in terms of the reproducibility of the radial alpha angle. Recent developments in 3-dimensional (3D) high-resolution magnetic resonance imaging (MRI) have allowed detailed evaluations of the radial alpha angle.Purpose:To determine whether there are any correlations or discrepancies between the 2D alpha angle on plain radiography and the maximum radial alpha angle on 3D MRI.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:A total of 42 hips from 39 patients (19 males, 20 females) were analyzed, including 22 hips with femoroacetabular impingement (FAI; mean age, 41 years) and 20 hips with borderline developmental dysplasia of the hip (BDDH; mean age, 43 years). Radial images were reconstructed from 3D multiple echo recombined gradient echo (MERGE) MRI. Differences in the maximum radial alpha angle on MRI between hips with FAI and BDDH were evaluated. Correlations and discrepancies between the maximum radial alpha angle on MRI and alpha angles on the anteroposterior, cross-table lateral, and 45° Dunn views of radiography were also evaluated.Results:The maximum radial alpha angle was significantly higher for hips with FAI than for hips with BDDH. On average, the greatest alpha angle on radial MRI was higher than the alpha angle on each of the 3 radiographic views for both FAI and BDDH. The 45° Dunn view revealed the smallest discrepancy for both FAI (P = .005) and BDDH (P = .002). The cross-table lateral view had the highest correlation with the maximum radial alpha angle for BDDH (P < .001).Conclusion:We reconfirmed the utility of the 45° Dunn view, with it presenting the best reproducibility for the maximum radial alpha angle in the evaluation of cam morphology, while the cross-table lateral view revealed the best correlation with the maximum radial alpha angle, particularly for hips with BDDH.

Contracted Extravelar Segments of the Levator Veli Palatini Muscle: A Magnetic Resonance Imaging Morphometric Study

To provide detailed descriptions of contraction-induced morphometric changes in the extravelar segments of the levator veli palatini (LVP) muscle using 3-dimensional (3-D) magnetic resonance imaging (MRI). Three-dimensional MRI data were acquired at rest and during "silent /i/" from 4 singers. During silent /i/, participants voluntarily sustained velar elevation while breathing orally for the entire scan time. Focusing on the extravelar segments, LVP length, angle of the muscle origin, and cross-sectional area (CSA), measurements were obtained and compared between tasks. Three of the 4 participants exhibited the expected patterns of change following concentric contraction of the LVP muscle. Consistent changes from the resting to the contracted state included reductions in LVP length by 13.5% and angle of the muscle origin by 9.8%, as well as increases in CSAs by 22.1%, on average. This study presented high-resolution data of the LVP muscle behavior with the first in vivo 3-D measurements of the contracted LVP muscle, which can be useful for the validation of computational models that aim at describing biomechanical properties of the LVP muscle in future research. The active behavior of the extravelar LVP muscle also provides some insight on optimal LVP muscle geometry to consider during cleft palate repair.

Influences of mitral annuloplasty on left ventricular flow dynamics assessed with 3-dimensional cine phase-contrast flow magnetic resonance imaging

ObjectivesWe assessed the influence of annuloplasty procedures in mitral repair on left ventricular (LV) vortex flow patterns and aortic outflow patterns, and flow energy loss (EL). MethodsTwenty healthy volunteers and 14 patients who had undergone mitral valve repair were examined using 3-dimensional cine phase-contrast magnetic resonance imaging. A band group included 7 patients with semi-rigid and 2 with flexible partial bands. The ring group included 5 patients with semi-rigid complete rings. LV vortex flow patterns, aortic outflow patterns, EL, and aortic annulus changes during one cardiac cycle were evaluated. ResultsMitral repair induced different vortex flow patterns compared with that of healthy volunteers. The vortex beneath the anterior mitral leaflet with semi-rigid devices was double-stranded in early diastole, and it was single-stranded with flexible bands with a large shift toward the apex during diastole. LVEL in patients who underwent mitral repair (0.84 ± 0.42 mW) was greater than that in healthy volunteers (0.47 ± 0.10 mW). Complete rings disturbed aortic outflow patterns, with EL distribution changes. Smaller devices relative to patient body size disturbed LV flow patterns and caused high EL. No significant relationship was found between indexed ring orifice area and transmitral mean pressure gradient (r = −0.25, P = .414), but a negative relationship exists between indexed ring orifice area and LVEL (r = −0.84, P < .001). ConclusionsMitral repair, especially with relatively small annuloplasty rings, induced abnormal LV flow patterns and EL elevation, which have the potential to be a novel hemodynamic evaluation method after mitral repair.