Spoiled Gradient Research Articles

Determination of optimal parameters for 3D single-point macromolecular proton fraction mapping at 7T in healthy and demyelinated mouse brain.

To determine optimal constrained tissue parameters and off-resonance sequence parameters for single-point macromolecular proton fraction (SP-MPF) mapping based on a comprehensive quantitative magnetization transfer (qMT) protocol in healthy and demyelinated living mice at 7T. Using 3D spoiled gradient echo-based sequences, a comprehensive qMT protocol is performed by sampling the Z-spectrum of mice brains, in vivo. Provided additional T1 , and B0 maps allow for the estimation of qMT tissue parameters, among which three will be constrained, namely the longitudinal and transverse relaxation characteristics of the free pool (R1,f T2,f ), the cross-relaxation rate (R) and the bound pool transverse relaxation time (T2,r ). Different sets of constrained parameters are investigated to reduce the bias between the SP-MPF and its reference based on the comprehensive protocol. Based on a whole-brain histogram analysis about the constrained parameters, the optimal experimental parameters that minimize the global bias between reference and SP-MPF maps consist of a 600° and 6 kHz off-resonance irradiation pulse. Following a Bland-Altman analysis over regions of interest, optimal constrained parameters were R1,f T2,f =0.0129, R=26.5 s-1 , and T2,r =9.1 µs, yielding an overall MPF bias of 10-4 (limits of agreement [-0.0068;0.0070]) and a relative variation of 0.64%±5.95% between the reference and the optimal single-point method across all mice. The necessity of estimating animal model- and field-dependent constrained parameters was demonstrated. The single-point MPF method can be reliably applied at 7T, as part of routine preclinical in vivo imaging protocol in mice.

DTI Tract-Based Quantitative Susceptibility Mapping: An Initial Feasibility Study to Investigate the Potential Role of Myelination in Brain Connectivity Change in Cerebral Palsy Patients During Autologous Cord Blood Cell Therapy Using a Rotationally-Invariant Quantitative Measure.

Previous studies using diffusion tensor imaging (DTI)-based connectome analysis revealed improved connectivity in cerebral palsy (CP) patients who underwent autologous umbilical cord blood (UCB) stem-cell therapy. However, the potential mechanism for the connectivity increase remains unclear and needs to be further elucidated. To develop a technique with improved accuracy for quantitative susceptibility mapping (QSM) with unique sensitivity to myelin, and demonstrate its use in elucidating the underlying mechanism of the observed motor function improvement and brain connectivity increase in CP patients who received autologous UCB stem-cell therapy. Prospective. A cohort of eight pediatric CP patients (2.6 ± 0.6 years of age) with intact corticospinal tracts (CST) from a randomized, placebo-controlled trial of autologous UCB stem-cell therapy in CP children was included in this study. DTI and 3D spoiled gradient recalled (SPGR) QSM at 3.0T. Pre- and posttreatment magnetic susceptibility (χ) and the rotationally-invariant magnetic susceptibility anisotropy (MSA) along the CST were derived. Behavioral changes were assessed using the 66-item Gross Motor Function Measurement. Changes in χ and MSA were compared between patients with and without substantial behavioral improvements. Two-sample t-tests were performed to assess the differences in the changes of measurements of interest (Δχ, ΔMSA, and ΔFA) between patients who significantly improved and those who did not. Patients who demonstrated posttreatment motor improvements exceeding expectations showed significantly more diamagnetic Δχ in the periventricular region along the CST (P = 0.003). Further analysis on the ΔMSA of this region was significantly increased (P = 0.006) for high responders, along with concurrent FA increase. These initial findings suggest that the DTI tract-based QSM method has the potential to characterize white matter changes associated with behavioral improvements in CP children who underwent cord blood stem-cell therapy. 2 TECHNICAL EFFICACY: Stage 2.

Effectively Measuring Exercise-Related Variations in T1ρ and T2 Relaxation Times of Healthy Articular Cartilage.

Determining the compositional response of articular cartilage to dynamic joint-loading using MRI may be a more sensitive assessment of cartilage status than conventional static imaging. However, distinguishing the effects of joint-loading vs. inherent measurement variability remains difficult, as the repeatability of these quantitative methods is often not assessed or reported. To assess exercise-induced changes in femoral, tibial, and patellar articular cartilage composition and compare these against measurement repeatability. Prospective observational study. Phantom and 19 healthy participants. 3T; 3D fat-saturated spoiled gradient recalled-echo; T1ρ - and T2 -prepared pseudosteady-state 3D fast spin echo. The intrasessional repeatability of T1ρ and T2 relaxation mapping, with and without knee repositioning between two successive measurements, was determined in 10 knees. T1ρ and T2 relaxation mapping of nine knees was performed before and at multiple timepoints after a 5-minute repeated, joint-loading stepping activity. 3D surface models were created from patellar, femoral, and tibial articular cartilage. Repeatability was assessed using root-mean-squared-CV (RMS-CV). Using Bland-Altman analysis, thresholds defined as the smallest detectable difference (SDD) were determined from the repeatability data with knee repositioning. Without knee repositioning, both surface-averaged T1ρ and T2 were very repeatable on all cartilage surfaces, with RMS-CV <1.1%. Repositioning of the knee had the greatest effect on T1ρ of patellar cartilage with the surface-averaged RMS-CV = 4.8%. While T1ρ showed the greatest response to exercise at the patellofemoral cartilage region, the largest changes in T2 were determined in the lateral femorotibial region. Following thresholding, significant (>SDD) average exercise-induced in T1ρ and T2 of femoral (-8.0% and -5.3%), lateral tibial (-6.9% and -5.9%), medial tibial (+5.8% and +2.9%), and patellar (-7.9% and +2.8%) cartilage were observed. Joint-loading with a stepping activity resulted in T1ρ and T2 changes above background measurement error. 2 TECHNICAL EFFICACY STAGE: 1 J. MAGN. RESON. IMAGING 2020;52:1753-1764.

Aberrant Fiber Coherence of Amygdala-Accumbens-Pallidum Pathway Is Associated With Disorganized Nigrostriatal-Nigropallidal Pathway in Parkinson's Disease.

Motor disturbances in Parkinson's disease (PD) mainly result from the degeneration of classic motor pathways. Given that the specific limbic pathway participates in movements, it is reasonable to consider that limbic pathway have the pathologic potential of motor disturbance in PD. To explore the white matter changes of limbic and motor pathways and their relations in PD patients. Prospective. 39 PD patients and 55 normal controls. Sagittal 3D T1 -weighted fast spoiled gradient recalled sequence, diffusion-weighted spin echo-echo planar imaging sequence on a 3T scanner. Probabilistic tractography was used to reconstruct the motor pathways (nigrostriatal-nigropallidal and basal ganglia-motor cortex pathways) and limbic pathway (amygdala-accumbens-pallidum pathway). White matter alterations of these pathways were evaluated by fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), neurite density (NDI), and orientation dispersion (ODI). Clinical assessment was conducted by a neurologist. Group comparisons were performed using unpaired t-tests. Pearson or Spearman correlation was used to explore the relationships between variables. Compared with normal controls, PD patients showed decreased ODI as well as increased MD and AD in the bilateral nigrostriatal-nigropallidal pathway (P < 0.05), decreased FA in left basal ganglia-motor cortex pathway (P < 0.05), and decreased ODI in left limbic pathway (P < 0.05). MD and AD in the left nigrostriatal-nigropallidal pathway was negatively correlated with FA in left basal ganglia-motor cortex pathway (r = -0.597, P < 0.05 and r = -0.433, P < 0.05, respectively). MD in the left nigrostriatal-nigropallidal pathway was significantly correlated with ODI in the left limbic pathway (r = -0.404, P < 0.05). ODI was associated with AD within each hemisphere of the nigrostriatal-nigropallidal pathway (r = -0.591, P < 0.05 for left; r = -0.589, P < 0.05 for right). The relationship between the degenerated motor pathways and aberrant limbic pathway suggest the existence of neuronal modulation between motor and limbic pathways, providing novel evidence of the neuromechanism for motor disruption in PD patients. 2 TECHNICAL EFFICACY STAGE: 1 J. MAGN. RESON. IMAGING 2020;52:1799-1808.

Should abbreviated breast MRI be compliant with American College of Radiology requirements for MRI accreditation?

ObjectiveTo evaluate non-inferiority and diagnostic performance of an American College of Radiology compliant abbreviated MRI protocol (AB-MRI) compared with standard-of-care breast MRI (SOC-BMRI) in patients with increased breast cancer risk. Material and methodsWomen with increased lifetime breast cancer risk by American Cancer Society guidelines underwent breast MRI at a single institution between October 2015 and February 2018. AB-MRI was acquired at 3.0 T with T2-weighted extended fast spin echo triple-echo Dixon and pre- and post-contrast 3D dual-echo fast spoiled gradient echo two-point Dixon sequences with an 8-channel breast coil 1–7 days after SOC-BMRI. Three readers independently reviewed AB-MRI and assigned BI-RADS categories for maximum intensity projection images (AB1), dynamic contrast-enhanced (DCE) images (AB2), and DCE and non-contrast T2 and fat-only images (AB3). These scores were compared to those from SOC-BMRI. ResultsCancer yield was 14 per 1000 (women-years) in 73 women aged 26–75 years (mean 53.5 years). AB-MRI acquisition times (mean 9.63 min) and table times (mean 15.07 min) were significantly shorter than those of SOC-BMRI (means 19.46 and 36.3 min, respectively) (p < .001). Accuracy, sensitivity, specificity, and positive and negative predictive values were identical for AB3 and SOC-BMRI (93%, 100%, 93%, 16.7%, and 100%, respectively). AB-MRI with AB1 and AB2 had significantly lower specificity (AB1 = 73.6%, AB2 = 77.8%), positive predictive values (AB1 = 5%, AB2 = 5.9%), and accuracy (AB1 = 74%, AB2 = 78%) than those of SOC-BMRI (p = .002 for AB1, p = .01 for AB2). ConclusionAB-MRI was acquired significantly faster than SOC-BMRI and its diagnostic performance was non-inferior. Inclusion of T2 and fat-only images was necessary to achieve non-inferiority by multireader evaluation.

Three-dimensional Gradient-echo is Effective in Suppressing Radiofrequency Shielding by a Titanium Mesh.

Purpose:To determine which sequence for frequently used general contrast-enhanced brain MRI shows the least radiofrequency shielding effect of a titanium mesh in cranioplasty using a phantom.Methods:A 1.5T MRI scanner was used. Frequently used general 2D and 3D spin-echo sequences (SE) and T1 spoiled gradient echo sequences (GRE) used for MRI in clinical settings were adopted in this study. A titanium mesh was placed above a cubic phantom containing manganese chloride tetrahydrate and sodium chloride. The signal attenuation ratio and normalized absolute average deviation (NAAD) were calculated. Moreover, the flip angle (FA) dependency in SE and area of excitation dependency in 3D sequences were analyzed using NAAD.Results:The signal attenuation ratio at the position nearest to the titanium mesh for 2D SE was 71.8% larger than that at the position nearest to the titanium mesh for 3D GRE. With regard to NAAD, 3D GRE showed the highest values among the sequences. When FA was increased, radiofrequency shielding effect was improved. There were no significant differences between the narrow and wide area of excitation. 3D GRE showed the least radiofrequency shielding effect, and it was considered as the optimal sequence for MRI in the presence of a titanium mesh.Conclusion:3D GRE shows the least radiofrequency shielding effect of a titanium mesh after cranioplasty among frequently used general sequences for contrast-enhanced brain MRI.

Structural and Functional Thalamic Changes in Parkinson's Disease With Mild Cognitive Impairment.

The thalamus is a key node of deep gray matter and previous studies have demonstrated that it is involved in the modulation of cognition. To investigate the volume changes of the thalamus and its subregions and altered thalamus functional connectivity patterns in Parkinson's disease (PD) patients with and without mild cognitive impairment (MCI). Prospective. Thirty-three patients with MCI (PD-MCI), 36 PD patients having no cognitive impairment (PD-NCI), 21 healthy controls (HCs). 3.0T MRI scanner; 3D T1 -weighted fast spoiled gradient recalled echo (3D T1 -FSPGR); resting-state fMRI ASSESSMENT: Voxel-based morphometry (VBM) was performed to calculate the volume of the thalamus and its subregions. The left and right total thalamus were considered seeds and seed-based functional connectivity (FC) was analyzed. Additionally, correlations between volumes and cognitive performance and between FC values and cognitive performance were examined separately. Analysis of covariance (ANCOVA); two-sample t-tests; partial correlation analysis. The volumes of the total thalamus (PD-MCI vs. PD-NCI vs. HCs: 18.39 ± 1.67 vs. 19.63 ± 1.79 vs. 19.47 ± 1.35) and its subregions were significantly reduced in PD-MCI as compared to PD-NCI (total thalamus: P = 0.002) and HCs (total thalamus: P = 0.012). Compared with PD-NCI, PD-MCI showed increased FC between the thalamus and bilateral middle cingulate cortex and left posterior cingulate cortex, and decreased FC between thalamus and the left superior occipital gyrus, left cuneus, left precuneus, and left middle occipital gyrus. Volumes of thalamus and the subregions, as well as the FC of thalamus with the identified regions, were significantly correlated (P < 0.05, FDR-corrected) with neuropsychological scores in PD patients. We noted volume loss and altered FC of thalamus in PD-MCI patients, and these changes were correlated with global cognitive performance. 2 TECHNICAL EFFICIENCY: Stage 2 J. Magn. Reson. Imaging 2020;52:1207-1215.

Hemosiderin deposition in papillary renal cell carcinoma and its potential to mask enhancement on MRI: analysis of 110 cases.

To evaluate the relationship between imperceptible T1 enhancement of papillary renal cell carcinoma (pRCC) on MR and intratumoral hemosiderin deposition. One hundred ten pRCCs (≤ 7 cm) were evaluated by MR with in- and opposed-phase spoiled gradient echo (GRE) and T1-weighted spoiled GRE with fat suppression before and after contrast. Hemosiderin deposition was assessed by SIindex and Dindex on in-andopposed-phase images. SIindex and Dindex are calculated as (SIin - SIopp)/(SIin) × 100, where SIin and SIopp are tumor signal intensities on in- and opposed-phase images and (Din)/(Dopp), where Din and Dopp are tumor diameters on in- and opposed-phase images, respectively. The degree of tumor enhancement was classified as grade 1 (no), grade 2 (subtle), or grade 3 (definite). Tumor enhancement on CT was assessed when available. Five (5%), 10 (9%), and 95 (86%) tumors were categorized as grades 1, 2, and 3 enhancement, respectively. The mean SIindex was - 33.9, - 25.3, and 1.00, whereas the mean Dindex was 1.26, 1.05, and 1.00 in tumors with grades 1, 2, and 3 enhancement, respectively. Tumors with grade 1 enhancement had significantly lower SIindex (p = 0.001) and higher Dindex (p = 0.005) than those with grade 3 enhancement. Among six tumors with grade 1 or 2 enhancement and available CT, four tumors showed > 20 HU enhancement. pRCC with no subjective enhancement on contrast-enhanced MR showed hemosiderin deposition evident by lower SIindex and higher Dindex. Hemosiderin deposition might mask the tumor enhancement on MR. • 5% of papillary renal cell carcinoma showed imperceptible enhancement on contrast-enhanced MR. • Hemosiderin deposition in papillary renal cell carcinoma might mask the tumor enhancement on contrast-enhanced MR due to T2/T2*-shortening effects. • A renal lesion with extensive hemosiderin deposition but no perceptible enhancement on MR should be considered suspicious for papillary renal cell carcinoma.

Harmonization of Quantitative Parenchymal Enhancement in T1 -Weighted Breast MRI.

BackgroundDifferences in imaging parameters influence computer‐extracted parenchymal enhancement measures from breast MRI.PurposeTo investigate the effect of differences in dynamic contrast‐enhanced MRI acquisition parameter settings on quantitative parenchymal enhancement of the breast, and to evaluate harmonization of contrast‐enhancement values with respect to flip angle and repetition time.Study TypeRetrospective.Phantom/PopulationsWe modeled parenchymal enhancement using simulations, a phantom, and two cohorts (N = 398 and N = 302) from independent cancer centers.Sequence Field/Strength1.5T dynamic contrast‐enhanced T1‐weighted spoiled gradient echo MRI. Vendors: Philips, Siemens, General Electric Medical Systems.AssessmentWe assessed harmonization of parenchymal enhancement in simulations and phantom by varying the MR parameters that influence the amount of T1‐weighting: flip angle (8°–25°) and repetition time (4–12 msec). We calculated the median and interquartile range (IQR) of the enhancement values before and after harmonization. In vivo, we assessed overlap of quantitative parenchymal enhancement in the cohorts before and after harmonization using kernel density estimations. Cohort 1 was scanned with flip angle 20° and repetition time 8 msec; cohort 2 with flip angle 10° and repetition time 6 msec.Statistical TestsPaired Wilcoxon signed‐rank‐test of bootstrapped kernel density estimations.ResultsBefore harmonization, simulated enhancement values had a median (IQR) of 0.46 (0.34–0.49). After harmonization, the IQR was reduced: median (IQR): 0.44 (0.44–0.45). In the phantom, the IQR also decreased, median (IQR): 0.96 (0.59–1.22) before harmonization, 0.96 (0.91–1.02) after harmonization. Harmonization yielded significantly (P < 0.001) better overlap in parenchymal enhancement between the cohorts: median (IQR) was 0.46 (0.37–0.58) for cohort 1 vs. 0.37 (0.30–0.44) for cohort 2 before harmonization (57% overlap); and 0.35 (0.28–0.43) vs. .0.37 (0.30–0.44) after harmonization (85% overlap).Data ConclusionThe proposed practical harmonization method enables an accurate comparison between patients scanned with differences in imaging parameters.Level of Evidence3Technical Efficacy Stage4

Numerical approximation to the general kinetic model for ASL quantification.

To develop a numerical approximation to the general kinetic model for arterial spin labeling (ASL) quantification that will enable greater flexibility in ASL acquisition methods. The Bloch-McConnell equations are extended to include the effects of single-compartment inflow and outflow on both the transverse and longitudinal magnetization. These can be solved using an extension of Jaynes' matrix formalism with piecewise constant approximation of incoming labeled arterial flow and a clearance operator for outgoing venous flow. The proposed numerical approximation is compared with the general kinetic model using simulations of pulsed labeling and pseudo-continuous labeling and a broad range of transit time and bolus duration for tissue blood flow of 0.6 mL/g/min. Accuracy of the approximation is studied as a function of the timestep using Monte-Carlo simulations. Three additional scenarios are demonstrated: (1) steady-pulsed ASL, (2) MR fingerprinting ASL, and (3) balanced SSFP and spoiled gradient-echo sequences. The proposed approximation was found to be arbitrarily accurate for pulsed labeling and pseudo-continuous labeling. The pulsed labeling/pseudo-continuous labeling approximation error compared with the general kinetic model was less than 0.002% (<0.002%) and less than 0.05% (<0.05%) for timesteps of 3 ms and 35 ms, respectively. The proposed approximation matched well with customized signal expressions of steady-pulsed ASL and MR fingerprinting ASL. The simulations of simultaneous modeling of flow, T2 , and magnetization transfer showed an increase in steady-state balanced SSFP and spoiled gradient signals. We demonstrate a numerical approximation of the "Bloch-McConnell flow" equations that enables arbitrarily accurate modeling of pulsed ASL and pseudo-continuous labeling signals comparable to the general kinetic model. This enables increased flexibility in the experiment design for quantitative ASL.

Association Functional MRI Studies of Resting-State Amplitude of Low Frequency Fluctuation and Voxel-Based Morphometry in Patients With Occupational Noise-Induced Hearing Loss.

To investigate changes in brain functional activity among occupational noise-induced hearing loss (NIHL) with tinnitus patients, using resting-state brain magnetic resonance imaging (Rs-fMRI) and voxel-based morphometry (VBM). Mild (27) and Relative severe (15) patient groups, 30 matched healthy group, scanned by Rs-fMRI and T1WI 3D fast spoiled gradient echo, FSPGR, using voxel-based morphometry and amplitude of low frequency fluctuation to analyze the differences. Brain gray matter volume was significantly different among the three groups in the left occipitotemporal lateral gyrus, the anterior cingulate gyrus, the bilateral angular gyrus, the precuneus, and near the midline area of the cerebellum. The Rs-fMRI changes showed that amplitude of low frequency fluctuation differed significantly among the three groups in the right superior temporal gyrus, the right inferior frontal gyrus, and the right angular gyrus. All this provides a new perspective for understanding the pathophysiological mechanism of occupational noise-induced hearing loss and provides some theoretical bases for subsequent treatment.

SPARC: Simultaneous Assessment of Gastric Emptying and Motility with Contrast Enhanced Magnetic Resonance Imaging in Humans

PurposeMagnetic resonance imaging (MRI) of the gastrointestinal (GI) tract is an emerging technique for non‐invasive assessment of gastric emptying and motility in animals and humans. However, addition of MRI contrast agents to the test meal is often required to produce high luminal contrast to facilitate image analysis. Here, we reported a recipe of a test meal that is all natural (e.g. gadolinium‐free) and safe for humans. The ingredients of the test meal all contain relatively high concentration of manganese, which allow the lumen of the GI tract to be visible inside MRI. To capture gastric emptying and motility simultaneously, we have developed a dynamic 3D imaging protocol with high spatial and temporal resolution and an image segmentation and analysis algorithm.MethodSix healthy volunteers (3 woman; age 24–31) participated in this study. All subjects were asked to fast for 12 hours. Subjects were scanned using a 3T Siemens Prisma MRI scanner using an 18‐channel body coil and a 32‐channel spine coil. Prior to meal consumption, pre‐prandial gastric volume was quantified using a 3D true fast imaging (TRUFI) with steady‐state free precession sequence under free breathing. Then the subjects were instructed to ingest 350 ml of a semi‐solid test meal (263kcal) that contains blended natural foods (i.e. pineapple, banana, blueberry, firm tofu) with a relatively high concentration of manganese. Post‐meal MRI scans were performed using a 3D Spoiled Gradient Echo Variant (VIBE) sequence under gentle breaths over a 90‐minute time course. Post‐prandial gastric volumes, as well as antral contraction frequency and amplitude of the peristaltic wave, were quantified from the dynamic 3D MRI images using a custom‐built image processing pipeline.ResultsPre‐prandial gastric volume was measured prior to test meal consumption (30.98±12.29 mL). After the subjects consumed the test meal, the presence of manganese in the meal enhanced the contrast of the gastric lumen (Fig. 1). The imaging protocol collected fast real‐time MRI scans of the stomach processing and emptying of a meal and the algorithms quantified gastric motility and emptying rate. The stomach volume decreased at a rate of 1.58±0.50 mL/min, mainly attributed to volume decrease in the fundus and the corpus (1.31±0.53 mL/min) than in the antrum (0.28±0.15 mL/min). The frequency of gastric contractions was 2.79±0.17 cycles/min, which was in line with the frequency of gastric slow wave in humans. The displacement of the luminal wall (i.e. contraction amplitude) was greater at the antrum (7.42±1.39 mm) than at the fundus and the corpus (4.52±0.25 mm), as illustrated in Fig. 2.ConclusionHere, we developed a contrast‐enhanced gastric MRI protocol to non‐invasively monitor gastric emptying and motility in humans. Such experimental protocol was further empowered by advanced image analysis to enable comprehensive assessment of gastric functions and physiology. In summary, the proposed method may become a reliable standard to guide diagnosis and treatment of gastric disorders in humans.Support or Funding InformationNIH SPARC OT2OD023847Example gastric MRI images of the stomach distended with the test meal. The contrast of the gastric lumen was significantly enhanced due to the presence of manganese in the meal.Figure 1Mapping amplitude of gastric contractions on the luminal wall. The displacement of the luminal wall was greatest at the antrum, followed by the corpus, and smallest at the fundus.Figure 2

Identification of Muscle Wasting in Lung Cancer using MRI Proton Density Fat Fraction and Ultrasound

BackgroundMuscle wasting, indicative of poor muscle health, is a hallmark of sarcopenia and cachexia and is one of the most consequential changes associated with aging and disease. Its presence is a strong predictor of frailty, impaired quality of life, and mortality. However, muscle wasting is inaccurately simplified to mean the quantitative loss of mass and reduced clinically to crude visual inspection. This disregards adipose tissue infiltration signifying declining ‘muscle quality’. Chemical‐shift encoded MRI to quantify proton density fat fraction (PDFF) is an established biomarker for quantifying tissue fat content, and provides an opportunity to objectively evaluate muscle quality. We aimed to determine how muscle quality changes with aging and disease using PDFF, in order to develop clinically implementable bedside ultrasound methods.MethodsA single‐center, cross‐sectional, observational pilot study enrolled 21 participants – 10 healthy, young adults; 5 adults with lung cancer undergoing outpatient systemic therapy; and 6 healthy, aged‐matched adults. Participants were scanned on a 3T MRI system (Signa Premier, GE Healthcare, Waukesha, WI) using a 30‐channel flexible coil (GE Healthcare, Waukesha, WI). The protocol included a commercial 3D multi‐echo spoiled gradient echo acquisition (IDEAL IQ, GE Healthcare, Waukesha, WI). Quantitative PDFF maps were reconstructed using a confounder‐corrected magnitude‐fitting least squares algorithm and a 2 cm2 region of interest was measured in the rectus femoris. Similarly, quantitative ultrasound (Acuson, Seimens, Malvern, PA) was used to measure sheer wave elastography (SWE) and echointensity (EI) in a similar area of the rectus femoris. All measurements of the rectus femoris were taken at the midpoint of the thigh between the patella and anterior superior iliac spine.ResultsThere was a strong association between ultrasound EI and PDFF (r=0.74, p&lt;0.001). No associations were found with SWE. Mean PDFF and EI increased between young, older, and age‐matched lung cancer (0.63±0.44, 1.44±1.29, 3.36±2.52 and 53.36±19.84, 71.90±29.6, 92.38±30.5, respectively). The mean differences between the young and lung cancer group reached significance for both PDFF and EI (p&lt;0.05), however not between the lung cancer group and age‐matched adults. Conversely, SWE decreased between young, older, and age‐matched lung cancer (10.34±1.68, 8.90 ±1.17, 8.49±0.85, respectively), but did not reach significance for between group differences.ConclusionMuscle quality decreases in aging and disease as evidenced by PDFF and EI. EI was highly correlated with PDFF as a measure of muscle fat content in the setting of muscle wasting. These results indicate a need for a larger, longitudinal study to examine ultrasound EI as a suitable bedside technique to evaluate muscle wasting in sarcopenia and cachexia.Support or Funding InformationNIH supported University of Wisconsin‐Madison ICTR Pilot Grant

Tear transit time evaluation using real-time technique for dynamic MR dacryocystography

ABSTRACT Purpose: To explore the utility of a novel real-time dynamic magnetic resonance dacryocystography (MRDCG) technique to assess the transit times through the lacrimal drainage system (LDS). Methods: Twenty-six patent LDS of 13 normal and asymptomatic individuals underwent MRDCG using a dynamic recalled three-dimensional spoiled gradient sequence (3DSPGR) on 1.5-Tesla magnetic resonance (1.5T MR) scanner while pre-determined diluted gadolinium drops were instilled into the eyes simultaneously. MR images of 0.8 mm thickness were captured every 9.4 s for 10 min. Evaluated parameters include the time taken for contrast to first appear in lacrimal sac, nasolacrimal duct (NLD), and inferior meatus (IM). Results: Dynamic MRDCG demonstrated contrast outflow in all cases with good structural delineation. The mean transit time for contrast to appear in lacrimal sac was 15.2 s (9.4–66 s; SD, 11.9), 50.4 s for nasolacrimal duct (18.9–151; SD, 32), and 150.5 s for inferior meatus (37.8–490; SD, 135). Contrast appeared in the IM in less than 2 min in 62% (16/26) systems, and only 19% (5/26) required more than 5 min. The maximum time taken for the contrast to reach IM was 6.2 min and all the LDS eventually showed the contrast into the nasal cavity. No statistically significant differences were noted in the transit times between the right and left sides. Conclusion: Dynamic MR-DCG using real-time 3DSPGR sequence reliably demonstrates the structural and physiological assessment of LDS and could be further explored to study the physiology and pathologies of the LDS.

Understanding the undulating pattern of the distal femoral growth plate: Implications for surgical procedures involving the pediatric knee: A descriptive MRI study

IntroductionOperative procedures near the distal femoral physis can result in iatrogenic damage if one is not familiar with the complex anatomy of the growth plate. The purpose of this study was to use physeal-specific MRI sequences to delineate the anatomic dimensions of the distal femoral physis. Materials and methodsSixty patients underwent physeal-specific spoiled gradient 3-D fat saturated (SPGR) MRI analysis of a single knee. Three age groups (eight to 10, 11–13, and 14–16 years) comprised of equal numbers (n = 20) of boys and girls were evaluated. Using the SPGR coronal sequence, the distance of the physis to the femoral articular cartilage was recorded at the medial, mid-medial, notch, mid-lateral and lateral margins of the knee. Coronal measurements were recorded at four locations along the sagittal sequence, as the anteroposterior dimension of the knee was divided into equal quartiles. ResultsWhile little variation in shape was observed in the anterior quartile, the remaining quartiles demonstrated significant variability that increased moving posteriorly (p < .001), therefore reflecting a more concave shape in the posterior aspect of the femur. These observations were statistically significant for age at the posterior two quartiles. ConclusionThese MRI data suggest that while the physis is linear in the anterior part of the femur, it possesses a more concave shape in the posterior aspect of the medial and lateral condyles. Findings were preserved across gender and age. Ultimately, these data can aid in preoperative planning and should be considered when performing operative procedures in the skeletally immature knee.

Chronic Thromboembolic Pulmonary Hypertension Perioperative Monitoring Using Phase-Resolved Functional Lung (PREFUL)-MRI.

The translation of phase-resolved functional lung (PREFUL)-MRI to routine practice in monitoring chronic thromboembolic pulmonary hypertension (CTEPH) still requires clinical corresponding imaging biomarkers of pulmonary vascular disease. To evaluate successful pulmonary endarterectomy (PEA) via PREFUL-MRI with pulmonary pulse wave transit time (pPTT). Retrospective. Thirty CTEPH patients and 12 healthy controls were included. For PREFUL-MRI a 2D spoiled gradient echo sequence and for DCE-MRI a 3D time-resolved angiography with stochastic trajectories (TWIST) sequence were performed on 1.5T. Eight coronal slices of PREFUL-MRI were obtained on consecutive 13 days before and 14 days after PEA. PREFUL quantitative lung perfusion (PREFULQ ) phases over the whole cardiac cycle were calculated to quantify pPTT, the time the pulmonary pulse wave travels from the central pulmonary arteries to the pulmonary capillaries. Also, perfusion defect percentage based on pPTT (QDPpPTT ), PREFULQ (QDPPREFUL ), and V/Q match were calculated. For DCE-MRI, pulmonary blood flow (PBF) and QDPPBF were computed as reference. For clinical correlation, mean pulmonary arterial pressure (mPAP) and 6-minute walking distance were evaluated preoperatively and after PEA. The Shapiro-Wilk test, paired two-sided Wilcoxon rank sum test, Dice coefficient, and Spearman's correlation coefficient (ρ) were applied. Median pPTT was significantly lower post PEA (139 msec) compared to pre PEA (193 msec), P = 0.0002. Median pPTT correlated significantly with the mPAP post PEA (r = 0.52, P < 0.008). Median pPTT was distributed more homogeneously after PEA: IQR pPTT decreased from 336 to 281 msec (P < 0.004). Median PREFULQ (P < 0.0002), QDPpPTT (P < 0.0478), QDPPREFUL (P < 0.0001) and V/Q match (P < 0.0001) improved significantly after PEA. Percentage change of PREFULQ correlated significantly with percentage change of 6-minute walking distance (ρ = 0.61; P = 0.0031) 5 months post PEA. Perioperative perfusion changes in CTEPH can be detected and quantified by PREFUL-MRI. Normalization of pPTT reflects surgical success and improvement of PREFULQ predicts 6-minute walking distance changes. 3 TECHNICAL EFFICACY STAGE: 2 J. Magn. Reson. Imaging 2020;52:610-619.

Altered Functional Connectivity of Hypothalamus in Lifelong Premature Ejaculation Patients.

As one of the most prevalent sexual dysfunctions in men, lifelong premature ejaculation (PE) often leads to patient distress. The hypothalamus is implicated in the ejaculatory control of healthy males. However, we do not know whether the hypothalamus-related intrinsic connectivity is altered in lifelong PE patients. To investigate abnormal intrinsic connectivity of the hypothalamus in lifelong PE patients compared with healthy controls (HCs). Prospective pilot study using cross-sectional data of patients and HCs. Forty-seven lifelong PE patients and 30 HCs were included in this study. 3.0T MRI scanner for T1 -weighted imaging using spoiled gradient recalled echo sequence and functional imaging using a single-shot gradient recalled echo sequence. Preprocessing of MRI data and hypothalamus-seeded functional connectivity (FC) computation were performed using DPABI4.1. The two-sample t-test within SPM12 was adopted to examine possible alterations of intrinsic connectivity of hypothalamus in lifelong PE patients compared with HCs including anxiety and depression scores as covariates (false discovery rate-corrected, P < 0.05). The correlation analysis was then used to assess possible associations between the imaging findings and clinical features in the patient group (Bonferroni-corrected, P < 0.05). Compared with HCs, lifelong PE patients had decreased hypothalamus-seeded FC in the left orbitofrontal cortex, bilateral insula, superior temporal cortex, superior temporal pole, middle temporal cortex, left fusiform, right parahippocampal gyrus, and right cerebellum. The intravaginal ejaculatory latency time positively correlated with the mean z-score from the hypothalamus-insula (r = 0.45) and hypothalamus-cerebellum (r = 0.48) intrinsic connectivity, separately. We have shown that hypothalamus-seeded FC alterations and the correlations between the aforementioned abnormal FC alterations and intravaginal ejaculatory latency time. The current findings may promote the understanding of the hypothalamus-related neural mechanisms involved in the abnormal ejaculatory information processing in lifelong PE patients. 1 TECHNICAL EFFICACY STAGE: 3 J. Magn. Reson. Imaging 2020;52:778-784.

Multi-parametric magnetic resonance imaging characterization of orbital lesions: a triple blind study

ABSTRACTBackground: Multi-parametric MRI used for preoperative assessment of orbital lesions does not routinely include DCE-MRI, since its accuracy in differential diagnosis of orbital mass is still under debate. Aim of this study is to characterize orbital lesions by multi-parametric MRI, analysing the incremental predictive value of DCE-MRI in differential diagnosis of orbital lesions.Methods: In this prospective triple-blind study, 43 consecutive patients with unilateral orbital lesion underwent conventional multimodal MRI and DCE-MRI before biopsy in a tertiary referral centre. Pre-operative MRI examination including conventional unenhanced MRI protocol, DWI with ADC maps, static CE 3D-T1 w and dynamic CE T1 w sequences, was performed within 1 week from surgery (anterior/lateral orbitotomy depending on location of the lesion, to carry out incisional/excisional biopsy).Results: Comparison between conventional T1 w/T2 w, DWI, CE 3D-T1 w and DCE-MRI groups showed a statistically significant difference in scores distribution (p < .001). Statistically significant difference was found between conventional T1 w/T2 w and DWI (p < .005), as well as between DWI and CE 3D-T1 w (p < .001). Conversely, no significant difference was found between CE 3D-T1 w and DCE (p < .005).Conclusions and Relevance: This study confirmed the positive effect of DWI and CE 3D-T1 w on orbital lesions diagnosis when added to conventional T1 w/T2 w sequences, whereas no substantial impact on diagnostic performance was observed with the further addition of DCE-MRI. DCE does not strongly influence diagnostic performance and inter-rater agreement in characterizing orbital lesions; therefore, it should be recommended in selected patients whose assessment of flow dynamics is particularly useful for management.Abbreviations: US = ultrasonography; MRI = magnetic resonance imaging; CT = computed tomography; STIR = Short-TI Inversion Recovery; DWI = diffusion weighted imaging; DCE-MRI = dynamic contrast-enhanced MRI; SE = Spin-Echo; TSE = Turbo Spin-Echo; THRIVE = T1-weighted high resolution Isotropic Volume Examination (dynamic contrast-enhanced ultrafast spoiled gradient echo); ROI = regions of interest; IRR = inter-rater reliability; TIC = time–intensity curve.

Utilization of Novel High-Resolution, MRI-Based Vascular Imaging Modality for Preoperative Stereoelectroencephalography Planning in Children: A Technical Note

Introduction: Stereoelectroencephalography (SEEG) is a powerful intracranial diagnostic tool that requires accurate imaging for proper electrode trajectory planning to ensure efficacy and maximize patient safety. Computed tomography (CT) angiography and digital subtraction angiography are commonly used, but recent developments in magnetic resonance angiography allow for high-resolution vascular visualization without added risks of radiation. We report on the accuracy of electrode placement under robotic assistance planning utilizing a novel high-resolution magnetic resonance imaging (MRI)-based imaging modality. Methods: Sixteen pediatric patients between February 2014 and October 2017 underwent SEEG exploration for epileptogenic zone localization. A gadolinium-enhanced 3D T1-weighted spoiled gradient recalled echo sequence with minimum echo time and repetition time was applied for background parenchymal suppression and vascular enhancement. Electrode placement accuracy was determined by analyzing postoperative CT scans laid over preoperative virtual electrode trajectory paths. Entry point, target point, and closest vessel intersection were measured. Results: For any intersection along the trajectory path, 57 intersected vessels were measured. The mean diameter of an intersected vessel was 1.0343 ± 0.1721 mm, and 21.05% of intersections involved superficial vessels. There were 157 overall intersection + near-miss events. The mean diameter for an involved vessel was 1.0236 ± 0.0928 mm, and superficial vessels were involved in 20.13%. Looking only at final electrode target, 3 intersection events were observed. The mean diameter of an intersected vessel was 1.0125 ± 0.2227 mm. For intersection + near-miss events, 24 were measured. An involved vessel’s mean diameter was 1.1028 ± 0.2634 mm. For non-entry point intersections, 45 intersected vessels were measured. The mean diameter for intersected vessels was 0.9526 ± 0.0689 mm. For non-entry point intersections + near misses, 126 events were observed. The mean diameter for involved vessels was 0.9826 ± 0.1008 mm. Conclusion: We believe this novel sequence allows better identification of superficial and deeper subcortical vessels compared to conventional T1-weighted gadolinium-enhanced MRI.

Simultaneous voxel-based magnetic susceptibility and morphometry analysis using magnetization-prepared spoiled turbo multiple gradient echo.

This study aimed to develop and test a simultaneous acquisition and analysis pipeline for voxel-based magnetic susceptibility and morphometry (VBMSM) on a single dataset using young volunteers, elderly healthy volunteers, and an Alzheimer's disease (AD) group. 3D T1 -weighted and multi-echo phase images for VBM and quantitative susceptibility mapping (QSM) were simultaneously acquired using a magnetization-prepared spoiled turbo multiple gradient echo sequence with inversion pulse for QSM (MP-QSM). The magnitude image was split into gray matter (GM) and white matter (WM) and was spatially normalized. The susceptibility map was reconstructed from the phase images. The segmented image and susceptibility map were compared with those obtained from conventional multiple spoiled gradient echo (mGRE) and MP-spoiled gradient echo (MP-GRE) in healthy volunteers to validate the availability of MP-QSM by numerical measurements. To assess the feasibility of the VBMSM analysis pipeline, voxel-based comparisons of susceptibility and morphometry in MP-QSM were conducted in volunteers with a bimodal age distribution, and in elderly volunteers and the AD group, using spatially normalized GM and WM volume images and a susceptibility map. GM/WM contrasts in MP-QSM, MP-GRE, and mGRE were 0.14 ± 0.011, 0.17 ± 0.015, and 0.045 ± 0.010, respectively. Segmented GM and WM volumes in the MP-QSM closely coincided with those in the MP-GRE. Region of interest analyses indicated that the mean susceptibility values in MP-QSM were completely in agreement with those in mGRE. In an evaluation of the aging effect, a significant increase and decrease in susceptibility and volume were found by VBMSM in deep GM and WM, respectively. Between the elderly volunteers and the AD group, the characteristic susceptibility and volume changes in GM and WM were observed. The proposed MP-QSM sequence makes it possible to acquire acceptable-quality images for simultaneous analysis and determine brain atrophy and susceptibility distribution without image registration by using voxel-based analyses.