Spin-echo Magnetic Resonance Research Articles

A hybrid (iron-fat-water) phantom for liver iron overload quantification in the presence of contaminating fat using magnetic resonance imaging.

Assessment of iron content in the liver is crucial for diagnosis/treatment of iron-overload diseases. Nonetheless, T2*-based methods become challenging when fat and iron are simultaneously present. This study proposes a phantom design concomitantly containing various concentrations of iron and fat suitable for devising accurate simultaneous T2* and fat quantification technique. A 46-vial iron-fat-water phantom with various iron concentrations covering clinically relevant T2* relaxation time values, from healthy to severely overloaded liver and wide fat percentages ranges from 0 to 100% was prepared. The phantom was constructed using insoluble iron (II, III) oxide powder containing microscale particles. T2*-weighted imaging using multi-gradient-echo (mGRE) sequence, and chemical shift imaging spin-echo (CSI-SE) Magnetic Resonance Spectroscopy (MRS) data were considered for the analysis. T2* relaxation times and fat fractions were extracted from the MR signals to explore the effects of fat and iron overload. Size distribution of iron oxide particles for Magnetite fits with a lognormal function with a mean size of about 1.17µm. Comparison of FF color maps, estimated from bi- and mono-exponential model indicated that single-T2* fitting model resulted in lower NRMSD. Therefore, T2* values from the mono-exponential signal equation were used and expressed the relationship between relaxation time value across all iron (Fe) and fat concentration as [Formula: see text], with R-squared = 0.89. The proposed phantom design with microsphere iron particles closely simulated the single-T2* behavior of fatty iron-overloaded liver in vivo.

Measurement of spinal root angle at spinal canal and foraminal levels in cases of facet arthropathy: T2-weighted turbo spin echo magnetic resonance myelography with SPACE technique.

Magnetic resonance myelography (MRM) with three-dimensional (3D) T2-weighted (T2W) turbo spin echo (TSE) sampling perfection with application-optimized contrasts using different flip angle evolution (SPACE) may be a guide to the etiology of low back pain. To research the efficiency of a 3D T2W TSE SPACE MRM sequence for visualization of anatomic details of spinal nerve root at the spinal canal and lateral recess levels in the patients with low back pain. Lumbar spinal MRM 3D T2W TSE SPACE was performed in a total of 70 patients (median age 46 years). Patients were imaged while lying in a supine position with straightened legs. According to the degree of facet arthropathy findings, patients were divided into four separate subgroups in our retrospective cross-sectional study. Spinal nerve root angle was measured within the spinal canal and at lateral recess level, and facet joint angle and lumbar lordosis measurements were measured by two radiologists, independently. Lumbar level was strongly negatively correlated with facet joint angle (r = -0.95) as well as nerve root angle within the spinal canal (NRASC) (r = -0.857) and at the lateral recess level (NRALR) (r = -0.947). Intracanal decline of the spinal root angle caused by spinal stenosis findings was also observed (P < 0.05). For the measurements of NRASC and NRALR, inter-observer correlation was 0.85 and 0.82 for the spinal canal and at lateral recess level, respectively. 3D T2W SPACE in NRASC and NRALR provided high resolution images for evaluation. Therefore, this method may be a qualitative guide for the clinician and the surgeon in terms of root anatomy before any intervention.

Validation of contrast enhanced cine steady-state free precession and T2-weighted CMR for assessment of ischemic myocardial area-at-risk in the presence of reperfusion injury.

The purpose of the study was to validate by histopathology, contrast enhanced cine steady-state free precession and T2-weighted CMR for the assessment of ischemic myocardial area-at-risk (AAR) in the presence of microvascular obstruction (MVO). Eleven anesthetized pigs underwent CMR 7 to 10 days post infarction. The area-at-risk was measured from T2-weighted fast spin echo (T2-STIR) and contrast-enhanced steady-state free precession magnetic resonance imaging (CE-SSFP) images using semi-automated algorithms based on a priori knowledge of perfusion territory. Also, late gadolinium enhancement (LGE) was performed to measure final infarct size (FIS). Histopathological comparison with Evans blue dye to define AAR and triphenyltetrazolium chloride to define FIS served as the reference. All infarcts demonstrated MVO on LGE images. Bland-Altman analysis showed no significant bias in AAR or myocardial salvage between T2-STIR and CE-SSFP or between CMR and histopathology. The mean differences ± 2SD from Bland-Altman analysis were: AAR: Evans Blue vs. T2-STIR [0.7%; +13.5%; -12.1%]; AAR: Evans Blue vs. CE-SSFP [0.1%; +13.8%; -13.7%]; AAR: T2-STIR vs. CE-SSFP [0.7%; +6.2%; -4.9%]; Salvage: Evans Blue-TTC vs. T2-STIR-LGE [0.8%; +11.1%; -9.6%]; Salvage: Evans Blue-TTC vs. CE-SSFP-LGE [0.1%; +9.9%; -9.6%]; Salvage: CE-SSFP-LGE vs. T2-STIR-LGE [0.7%; +6.2%; -4.9%]. Both T2-STIR and CE-SSFP sequences allow for unbiased quantification of AAR in the presence of ischemia/reperfusion injury when analysed by semi-automated algorithms. These experimental data, which was validated by histopathology, supports the use of CMR for the assessment of myocardial salvage during the subacute phase.

Diagnostic Accuracy of Noncontrast MR Angiography Protocols at 3T for the Detection and Characterization of Lower Extremity Peripheral Arterial Disease

PurposeTo compare the diagnostic accuracy of established non–gadolinium (Gd)-enhanced magnetic resonance (MR) angiography protocols with Gd-enhanced MR angiography at 3T for evaluating lower extremity peripheral arterial disease (PAD). Materials and MethodsFrom February 2014 to 2015, 20 patients with PAD and intermittent claudication (16 men; age range, 51–76 y; Fontaine stage II) underwent 3-station (abdominopelvic, thigh, and calf) non-Gd MR angiography and bolus-chase Gd MR angiography protocols performed at 3T (Siemens Tim Trio), including quiescent-interval single-shot (QISS) MR angiography for all 3 stations and a combination of quadruple inversion recovery (QIR) MR angiography for the abdominopelvic station and electrocardiogram-gated fast spin echo (ECG-FSE) MR angiography for the extremities. Two radiologists independently evaluated vessel segments for vascular stenosis, diagnosis confidence, graft presence, and Trans-Atlantic Inter-Society Consensus (TASC) II classification for each station. Diagnostic accuracies and κ agreement were assessed. ResultsOf 573 vascular segments imaged, 16.9% (97/573, 19/20 patients) demonstrated hemodynamically significant abnormalities. Reader confidence was sufficient for diagnosis in 98% of segments with Gd MR angiography, 93% with QIR/ECG-FSE, and 95% with QISS. Overall reader confidence was higher with QISS than QIR/ECG-FSE within all 3 stations combined (P < .05). With low-confidence segments treated as misdiagnosis, sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and κ agreement for all 3 stations combined were 81.4/87.2/57.0/95.8/86.2%/0.578 for QIR/ECG-FSE and 75.0/90.6/61.6/94.7/88.0%/0.597 for QISS. Using TASC II criteria to assess severity, QISS and QIR/ECG-FSE had no statistical difference in agreement with Gd MR angiography. ConclusionsQISS and QIR/ECG-FSE MR angiography protocols demonstrate comparable diagnostic accuracies with high specificity. Either protocol provides an alternative to Gd MR angiography at 3T for patients with PAD.

Patellar tendon enthesis abnormalities and their association with knee pain and structural abnormalities in older adults

Purpose: The patellar tendon works together with the quadriceps tendon to enable knee flexion. Its attachment site (enthesis) is at risk of micro damage and degeneration. Recent studies suggest that enthesis abnormalities are associated with development of osteoarthritis through the synovio-entheseal complex. However, no studies have assessed the presence of patellar enthesis abnormalities in older adults and its association with osteoarthritis outcomes. Therefore, we aimed to describe associations between presence of patellar tendon enthesis (PTE) abnormalities visible on magnetic resonance (MR) images at baseline and knee pain, physical function limitations, and osteoarthritic structural abnormalities both cross-sectionally and longitudinally over 10.7 years. Methods: Patellar tendon enthesis abnormalities, defined as presence of abnormal bone signal and/or bone erosion were measured on T2-weighted fat suppressed fast spin echo MR images at baseline in 961 community-dwelling older adults. Knee pain and physical function limitation score were assessed using WOMAC at baseline and 10.7 years. Tibial, femoral, and patella bone marrow lesions (BMLs), cartilage volume and cartilage defects were assessed at baseline and 10.7 years, tibial bone area at baseline and 2.7 years, and infrapatellar fat pad area at baseline using validated methods. Associations were assessed using hurdle, log binomial, linear, and mixed models, after adjusting for confounders. Results: 20% of participants had bone signal and/or erosion at PTE. Cross-sectionally, presence of PTE abnormalities were associated with greater intensity of pain while going up and down stairs (β = 0.22 (95% CI; 0.03, 0.41)), greater risk of having a femoral (RR = 1.46 (1.22, 1.90)) BML, greater lateral tibial bone area (β = 25.95 (1.00, 50.91)), smaller infrapatellar fat pad area (β = −0.26 (−0.46, −0.05)), and a worse tibial cartilage defect score (RR = 1.70 (1.16, 2.47), after adjustment for age, sex, BMI, and structural confounders. Longitudinally, presence of PTE abnormalities at baseline predicted an increased risk of deleterious changes in tibial BML size (RR = 1.52 (1.12, 2.05)) only over 10.7 years but not pain or other structural changes. Conclusions: Patellar tendon enthesis abnormalities are common in the elderly. The presence of cross-sectional but not longitudinal associations suggests they commonly co-exist with other knee structural abnormalities. This suggests they may not be a major player in symptom development or structural changes with the exception of tibial BMLs.

Assessment of advanced hepatic MR elastography methods for susceptibility artifact suppression in clinical patients.

To assess the success rate, image quality, and the ability to stage liver fibrosis of a standard 2D gradient-recalled echo (GRE) and four different spin-echo (SE) magnetic resonance elastography (MRE) sequences in patients with different liver iron concentrations. A total of 332 patients who underwent 3T MRE examinations that included liver fat and iron quantification were enrolled, including 136 patients with all five MRE techniques. Thirty-four patients had biopsy results for fibrosis staging. The liver stiffness, region of interest area, image quality, and success rate of the five sequences were compared in 115/136 patients. The area under the receiver operating characteristic curves (AUCs) and the accuracies for diagnosing early-stage fibrosis and advanced fibrosis were compared. The effect of BMI (body mass index), the R2* relaxation time, and fat fraction on the image quality and liver stiffness measurements were analyzed. The success rates were significantly higher in the four SE sequences (99.1-100%) compared with GRE MRE (85.3%) (all P < 0.001). There were significant differences of the mean ROI area between every pair of sequences (all P < 0.0001). There were no significant differences in the AUC of the five MRE sequences for discriminating advanced fibrosis (10 P-values ranging from 0.2410-0.9171). R2* had a significant effect on the success rate and image quality for the noniron 2D echo-planar imaging (EPI), 3D EPI and 2D GRE (all P < 0.001) sequences. BMI had a significant effect on the iron 2D EPI (P = 0.0230) and iron 2D SE (P = 0.0040) sequences. All five techniques showed good diagnostic performance in staging liver fibrosis. The SE MRE sequences had higher success rates and better image quality than GRE MRE in 3T clinical hepatic imaging. 3 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018;47:976-987.

Associations between systemic bone mineral density, knee cartilage defects and bone marrow lesions in patients with knee osteoarthritis.

The relationship between bone mineral density (BMD) and osteoarthritis (OA) remains controversial. This study aimed to explore the cross-sectional associations between BMD at the total body, hip and spine and joint structural abnormalities including cartilage defects and bone marrow lesions (BMLs) in patients with knee OA. One hundred and eight-five subjects with symptomatic knee OA were included in this study. T2-weighted fast spin echo magnetic resonance imaging was used to assess knee cartilage defects and BMLs. Total body, hip and spine BMD were measured using dual-energy X-ray absorptiometry. After adjustment for potential confounders, total hip BMD was negatively associated with medial tibial cartilage defects, lateral femoral cartilage defects, medial tibial BMLs and lateral tibial BMLs. Spine and total body BMD were negatively associated with lateral femoral cartilage defects, but not with BMLs. We concluded that BMD particularly at the hip was negatively associated with knee cartilage defects and BMLs.

Abstract 2873: Imaging tumor heterogeneity after multikinase inhibitor therapy in rat hepatocellular carcinoma

Abstract Purpose To assess tumor tissue perfusion and vascular permeability through multiparametric functional imaging, and to evaluate their correspondence with histopathologic parameters of necrosis and hypoxia in a rat model of hepatocellular carcinoma treated with a multikinase inhibitor. Materials and Methods Rat hepatoma McA-RH7777 cells were implanted in the left liver lobe of nineteen male Buffalo rats. Exactly 2 weeks after tumor inoculation, the animals were randomly assigned to remain untreated (n=10) or to receive a daily dose of 7.5 mg/kg sorafenib by oral gavage (n=9) for 2 additional weeks. T2-weighted spin-echo magnetic resonance imaging (MRI), dynamic contrast-enhanced (DCE) and contrast-enhanced ultrasound (CEUS) were performed weekly. All tumors were harvested 4 weeks post-implantation &amp;gt;90 minutes after injecting 60mg/kg pimonidazole. Tissue sections were stained for hematoxylin-eosin and pimonidazole for quantitative assessment of necrosis and hypoxia, respectively. Differences between treatment groups were assessed using the Mann-Whitney test, and the correlation of imaging and histopathology parameters was determined by Spearman correlation analysis. Results In spite of the relatively low dose and short treatment duration, the response to sorafenib therapy was characterized by a significantly higher median tumor necrosis (60 vs 15%, P &amp;lt; 0.0001) and increased tumor tissue hypoxia (35 vs 18.5% pimonidazole binding, P &amp;lt; 0.0001). Similarly, the sorafenib regimen caused a substantial decrease in vascular permeability, measured by DCE-MRI Ktrans (P = 0.002) as well as reduction in tumor perfusion evaluated by CEUS peak enhancement (PE) (P =0.043). Our findings show a strong correlation between the two histopathologic parameters we assessed, tumor tissue necrosis and hypoxia (r = 0.645, P=0.002). Furthermore, our results demonstrate significant correlation of functional imaging parameters of vascular permeability, namely DCE-MRI Ktrans and DCE-MRI normalized initial area under the curve (NIAUC), with histopathologic tissue hypoxia (r=-0.663, P= 0.002, and r= -0.512, P=0.029, respectively). In contrast, histopathologic tumor necrosis appears more strongly correlated with a functional imaging parameter of tumor perfusion, specifically, CEUS PE (r = -0.547, P = 0.028). Conclusion Tumors exhibited wide heterogeneity in vascular perfusion and hypoxia after treatment. Interestingly, functional MRI parameters appear to correlate more strongly with tissue oxygenation, whereas functional CEUS parameters correlate with tumor viability. Novel predictive imaging biomarkers of treatment response may be developed through further analyses of spatial tumor heterogeneity in our animal model. Citation Format: Nina M. Muñoz, Adeeb A. Minhaj, Kiersten L. Maldonado, Charles Kingsley, Hideyuki Nishiofuku, Keith A. Michel, Andrea C. Cortes, James A. Bankson, Asif Rashid, Rony Avritscher. Imaging tumor heterogeneity after multikinase inhibitor therapy in rat hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2873. doi:10.1158/1538-7445.AM2017-2873

Functional neuro-imaging with magnetic resonance elastography

Evaluate changes in the shear modulus of brain tissue as a new measure of localized brain function. A spin-echo magnetic resonance elastography (MRE) sequence was modified to allow two interleaved paradigms: stimulus ON/OFF. To avoid neuronal habituation, a paradigm was active for 9s before switching to the other paradigm. After each paradigm switch, a period of 1.8 s was allowed for hemodynamic equilibrium. Seven healthy black mice were studied. An electrical current to the hind limb, ~1 mA, 3 Hz, pulse width ~250 ms, was used as the functional stimulus. A separate control scan was also performed where no stimulus was applied for either paradigm. Vibration frequency = 1kHz. In six of the seven animals, a localized increase in G’ was observed in the somatosensory and motor cortex areas, whereas no difference was observed in the control scan. The average increase of G’ = 14%. Two potential mechanisms were considered: (i) a vascular effect similar to BOLD in fMRI and (ii) calcium influx into the neurons. The first mechanism was ruled out based on results from an additional experiment where hypercapnia was induced to cause vasodilation. This implies the mechanism responsible is a primary measure of neuronal activation.

Luminal Water Imaging: A New MR Imaging T2 Mapping Technique for Prostate Cancer Diagnosis.

Purpose To assess the feasibility of luminal water imaging, a quantitative T2-based magnetic resonance (MR) imaging technique, for the detection and grading of prostate cancer (PCa). Materials and Methods Eighteen patients with biopsy-proven PCa provided informed consent to be included in this institutional human ethics board-approved prospective study between January 2015 and January 2016. Patients underwent 3.0-T MR imaging shortly before radical prostatectomy. T2 distributions were generated with a regularized non-negative least squares algorithm from multiecho spin-echo MR imaging data. From T2 distributions, maps of seven MR parameters, Ncomp, T2short, T2long, geometric mean T2 (gmT2), luminal water fraction (LWF), Ashort, and Along, were generated and compared with digitized images of hematoxylin-eosin-stained whole-mount histologic slices. A paired t test was used to determine significant differences between MR parameters in malignant and nonmalignant tissue. Correlation with Gleason score (GS) was evaluated with the Spearman rank correlation test. Diagnostic accuracy was evaluated by using logistic generalized linear mixed-effect models and receiver operating characteristic (ROC) analysis. Results The average values of four MR parameters (gmT2, Ashort, Along, and LWF) were significantly different between malignant and nonmalignant tissue. All MR parameters except for T2long showed significant correlation (P < .05) with GS in the peripheral zone. The highest correlation with GS was obtained for LWF (-0.78 ± 0.11, P < .001). ROC analysis demonstrated high accuracy for tumor detection, with the highest area under the ROC curve obtained for LWF (0.97 in the peripheral zone and 0.98 in the transition zone). Conclusion Results of this pilot study demonstrated the feasibility of luminal water imaging in the detection and grading of PCa. A study with a larger cohort of patients and a broader range of GS is required to further evaluate this new technique in clinical settings. © RSNA, 2017.

Congenital Unilateral Fallopian Tube and Renal Agenesis in a Patient with Primary Infertility

A 35-year-old nulligravid normo-ovulatory woman presented for the evaluation of primary infertility. Hysterosalpingography revealed normal filling (Fig. 1A) and intraperitoneal spillage of radiographic contrast through the right fallopian tube (Fig. 1B). No fill or spillage of contrast was noted through the left fallopian tube. A diagnostic hysteroscopy confirmed the presence of the right ostium (Fig. 2A); the left ostium was visually absent (Fig. 2B). Magnetic resonance imaging was subsequently performed, which showed blunting of the endometrium within the left cornua at the level of the uterotubal junction. There was no evidence of a kidney in the left renal fossa or within the pelvis (Fig. 2C). These findings indicated the congenital absence of the left fallopian tube and kidney. The patient underwent ovulation induction with intrauterine insemination and conceived in her second cycle. Fig. 2(A) Diagnostic hysteroscopy confirming the presence of the right ostium (white arrow). (B) Hysteroscopy indicating the absence of the left ostium (white X). (C) Single-shot fast spin echo magnetic resonance imaging confirming the presence of the right kidney (dotted white circle) in a coronal section. The same section shows an absent left kidney (white X). View Large Image Figure Viewer Download Hi-res image

Diagnostic performance of wrist magnetic resonance (MR) arthrography: comparison of three-dimensional isotropic T1 weighted fast spin-echo MR arthrography and two-dimensional MR arthrography.

To compare the diagnostic performance of direct wrist MR arthrography (D-MRA) with two-dimensional (2D) T1 weighted fast spin-echo (FSE) and three-dimensional (3D) isotropic T1 weighted FSE sequences for detecting triangular fibrocartilage (TFC) central perforations and scapholunate ligament (SLL) and lunotriquetral ligament (LTL) tears. 26 patients who had undergone pre-operative wrist D-MRA with 2D and 3D isotropic T1 weighted FSE sequences and subsequent arthroscopic surgeries were included. Each MRI sequence was independently evaluated and scored by two readers retrospectively for the presence of TFC central perforations and SLL and LTL tears. Arthroscopic findings were used as the reference standard. Diagnostic performance was evaluated by using the area under the receiver operating characteristic curve. The sensitivity, specificity and accuracy of both sequences for diagnosing the injuries were calculated. Arthroscopic surgery revealed 21 TFC central perforations, 7 SLL tears and 3 LTL tears. The area under the receiver operating characteristic curve value of 2D and 3D for central perforations in TFC and tears in SLL and LTL was identical or similar (0.667-0.947). The sensitivity, specificity and accuracy of both sequences for diagnosing the injury of each structure were not significantly different (TFC, 90.5/80/88.5% for both readers/sequences; SLL, 100/89.5/92.3% for both readers' 2D and Reader A's 3D, and 85.7/89.5/88.5% for Reader B's 3D; LTL, 66.7/100/96.2% for both readers' 2D and 33.3/100/92.3% for both readers' 3D). Interobserver agreements were substantial to excellent. In wrist D-MRA, the diagnostic performances of 3D isotropic and 2D T1 weighted FSE sequences are comparable for TFC central perforations and SLL and LTL tears. Advances in knowledge: The diagnostic performance of 3D isotropic T1 weighted FSE D-MRA and that of 2D T1 weighted FSE D-MRA were not significantly different in the diagnosis of central perforations in the TFC and tears in the SLL and LTL. 3D isotropic T1 weighted FSE D-MRA has potential for substituting 2D imaging.

9.4T MR microscopy of the substantia nigra with pathological validation in controls and disease.

BackgroundThe anatomy of the substantia nigra on conventional MRI is controversial. Even using histological techniques it is difficult to delineate with certainty from surrounding structures. We sought to define the anatomy of the SN using high field spin-echo MRI of pathological material in which we could study the anatomy in detail to corroborate our MRI findings in controls and Parkinson's disease and progressive supranuclear palsy.Methods23 brains were selected from the Queen Square Brain Bank (10 controls, 8 progressive supranuclear palsy, 5 Parkinson's disease) and imaged using high field 9.4 Tesla spin-echo MRI. Subsequently brains were cut and stained with Luxol fast blue, Perls stain, and immunohistochemistry for substance P and calbindin. Once the anatomy was defined on histology the dimensions and volume of the substantia nigra were determined on high field magnetic resonance images.ResultsThe anterior border of the substantia nigra was defined by the crus cerebri. In the medial half it was less distinct due to the deposition of iron and the interdigitation of white matter and the substantia nigra. The posterior border was flanked by white matter bridging the red nucleus and substantia nigra and seen as hypointense on spin-echo magnetic resonance images. Within the substantia nigra high signal structures corresponded to confirmed nigrosomes. These were still evident in Parkinson's disease but not in progressive supranuclear palsy. The volume and dimensions of the substantia nigra were similar in Parkinson's disease and controls, but reduced in progressive supranuclear palsy.ConclusionsWe present a histologically validated anatomical description of the substantia nigra on high field spin-echo high resolution magnetic resonance images and were able to delineate all five nigrosomes. In accordance with the pathological literature we did not observe changes in the nigrosome structure as manifest by volume or signal characteristics within the substantia nigra in Parkinson's disease whereas in progressive supranuclear palsy there was microarchitectural destruction.

Safety of dorsal wrist arthroscopy portals: A magnetic resonance study

In wrist arthroscopy, the standard dorsal portals are the most commonly used. However, their placement can be associated with injuries to the neurovascular structures of the radiocarpal joint. The present study assessed and compared the distance of commonly used dorsal portals to radial and ulnar neurovascular structures.Forty patients (20 males, 20 females) were evaluated with T1-weighted spin-echo (SE) magnetic resonance (MR) sequences. We measured the distance between 1–2 and 3–4 portals and radial vascular bundle and the nearest branch of the superficial branch of radial nerve (SBRN). We also measured the distance between 4 and 5, 6/U and 6/R and ulnar vascular bundle and the nearest branch of the dorsal ulnar nerve (DUN).The median age of patients was 39 years (95% IC 36.97–43.32 years). The 3–4 portal was farther away from the vascular structure than the 1–2 portal (P < 0.0001), 4–5 portal (P = 0.008), 6/R (P < 0.0001), and 6/U portals (P < 0.0001). Moreover, the 3–4 portal was farther away from the nerve branch than the 1–2 portal (P < 0.0001), 4–5 portal (P < 0.0001), 6/R (P < 0.0001), and 6/U portals (P < 0.0001). No statistical significant differences were found between the two genders.The 3–4 and 4–5 portals are the farthest away from the neurovascular structures, and likely reduce the risk to damage these structures. On the other hand, the 1–2 and 6/U portals likely increase the risk of neurovascular damage, because of their proximity to neurovascular structures.Level of evidence: Diagnostic study; Level III.

Cross-sectional and longitudinal associations between serum inflammatory cytokines and knee bone marrow lesions in patients with knee osteoarthritis.

To describe cross-sectional and longitudinal associations between serum levels of interleukin (IL) - 6, IL-17A, IL-17F, IL-23 and knee bone marrow lesions (BMLs) in patients with knee osteoarthritis (OA). Patients (n=192) with symptomatic knee OA (mean 63 years, range 50-79, female 53%) were assessed at baseline and after 24 months. At each time point, serum IL-6, IL-17A, IL-17F and IL-23 were measured using Bio-Plex® Multiplex Immunoassays with Luminex xMAP technology. Knee BMLs were scored using the modified whole organ MRI score (WORMS) from T2 weighted fat-suppressed fast spin echo magnetic resonance imaging (MRI). Multivariable linear regression and log binominal regression were used to determine the associations between cytokines and BMLs. Baseline IL-6 (quarters) were significantly associated with total knee BMLs (P<0.01 for the trend) as well as associated with an increase in BML score (P=0.05 for the trend), after adjustment for confounders. Baseline IL-17F and IL-23 (highest quarters vs others) was associated with an increase in BML score in females (P=0.04 for IL-17F; P=0.01 for IL-23), but not in males, in multivariable analyses. In contrast, IL-17A was not significantly associated with BMLs in either females or males. IL-6 is associated with increased knee BMLs in both females and males with OA. Serum IL-17F and IL-23 predicted increased knee BML scores in females only, suggesting that inflammation is involved in BML pathogenesis in knee OA, especially in women. ClinicalTrials.gov identifier: NCT01176344; Australian New Zealand Clinical Trials Registry: ACTRN12610000495022.

Spin-echo Echo-planar Imaging MR Elastography versus Gradient-echo MR Elastography for Assessment of Liver Stiffness in Children and Young Adults Suspected of Having Liver Disease.

Purpose To compare two-dimensional (2D) gradient-recalled echo (GRE) and 2D spin-echo (SE) echo-planar imaging (EPI) magnetic resonance (MR) elastography for measurement of hepatic stiffness in pediatric and young adult patients suspected of having liver disease. Materials and Methods In this institutional review board-approved, HIPAA-compliant study, 58 patients underwent both 2D GRE and 2D SE-EPI MR elastography at 1.5 T during separate breath holds. Liver stiffness (mean of means; in kilopascals) was measured by five blinded reviewers. Pooled mean liver stiffness and region-of-interest (ROI) size were compared by using paired t tests. Intraclass correlation coefficients (ICCs) were used to assess agreement between techniques. Respiratory motion artifacts were compared across sequences by using the Fisher exact test. Results Mean patient age was 14.7 years ± 5.2 (standard deviation; age range, 0.7-20.5 years), and 55.2% (32 of 58) of patients were male. Mean liver stiffness was 2.92 kPa ± 1.29 measured at GRE MR elastography and 2.76 kPa ± 1.39 at SE-EPI MR elastography (n = 290; P = .15). Mean ROI sizes were 8495 mm2 ± 4482 for 2D GRE MR elastography and 15 176 mm2 ± 7609 for 2D SE-EPI MR elastography (n = 290; P < .001). Agreement was excellent for measured stiffness between five reviewers for both 2D GRE (ICC, 0.97; 95% confidence interval: 0.95, 0.98) and 2D SE-EPI (ICC, 0.98; 95% confidence interval: 0.96, 0.99). Mean ICC (n = 5) for agreement between 2D GRE and 2D SE-EPI MR elastography was 0.93 (range, 0.91-0.95). Moderate or severe breathing artifacts were observed on 27.5% (16 of 58) of 2D GRE images versus 0% 2D SE-EPI images (P < .001). Conclusion There is excellent agreement on measured hepatic stiffness between 2D GRE and 2D SE-EPI MR elastography across multiple reviewers. SE-EPI MR elastography allowed for stiffness measurement across larger areas of the liver and can be performed in a single breath hold. © RSNA, 2016.

Application of Modified Spin-Echo–based Sequences for Hepatic MR Elastography: Evaluation, Comparison with the Conventional Gradient-Echo Sequence, and Preliminary Clinical Experience

Purpose To (a) evaluate modified spin-echo (SE) magnetic resonance (MR) elastographic sequences for acquiring MR images with improved signal-to-noise ratio (SNR) in patients in whom the standard gradient-echo (GRE) MR elastographic sequence yields low hepatic signal intensity and (b) compare the stiffness values obtained with these sequences with those obtained with the conventional GRE sequence. Materials and Methods This HIPAA-compliant retrospective study was approved by the institutional review board; the requirement to obtain informed consent was waived. Data obtained with modified SE and SE echo-planar imaging (EPI) MR elastographic pulse sequences with short echo times were compared with those obtained with the conventional GRE MR elastographic sequence in two patient cohorts, one that exhibited adequate liver signal intensity and one that exhibited low liver signal intensity. Shear stiffness values obtained with the three sequences in 130 patients with successful GRE-based examinations were retrospectively tested for statistical equivalence by using a 5% margin. In 47 patients in whom GRE examinations were considered to have failed because of low SNR, the SNR and confidence level with the SE-based sequences were compared with those with the GRE sequence. Results The results of this study helped confirm the equivalence of SE MR elastography and SE-EPI MR elastography to GRE MR elastography (P = .0212 and P = .0001, respectively). The SE and SE-EPI MR elastographic sequences provided substantially improved SNR and stiffness inversion confidence level in 47 patients in whom GRE MR elastography had failed. Conclusion Modified SE-based MR elastographic sequences provide higher SNR MR elastographic data and reliable stiffness measurements; thus, they enable quantification of stiffness in patients in whom the conventional GRE MR elastographic sequence failed owing to low signal intensity. The equivalence of the three sequences indicates that the current diagnostic thresholds are applicable to SE MR elastographic sequences for assessing liver fibrosis. © RSNA, 2016.

Breath-hold spin echosequence for assessing liver iron content

ObjectiveTo compare a multiple breath-hold, multiecho, multiplanar spin-echo (BHMEMPSE) magnetic resonance (MR) sequence with a TR of 300ms with a traditional multiecho, multiplanar spin-echo (MEMPSE) MR sequence for assessing liver iron content. Materials and methodsThis study was approved by the institutional review board; informed consent was waived. Liver R2 measurement was derived from the mono-exponential model by BHMEMPSE and MEMPSE MR sequences of a 1.5T MR machine in 30 thalassemia patients (9men, 21women, aged 27.7±6.8years). Hepatic iron contents were estimated using Ferriscan in all patients. The inter- and intra-observer agreement of the 2 MR sequences was also evaluated. ResultsMEMPSE R2 values significantly correlated with Ferriscan iron content values (r=0.895, p<0.001) and serum ferritin concentration (r=0.661, p<0.001). BHMEMPSE R2 values significantly correlated with Ferriscan values (r=0.914, p<0.001) and serum ferritin concentration (r=0.608, p<0.001). The distribution of MEMPSE R2 values against BHMEMPSE R2 values revealed an excellent linear relationship (r=0.978, p<0.001). The inter- and intra-observer agreement of the 2 MR sequences was excellent, with an interclass correlation coefficient exceeding 0.9. The distribution of Ferriscan against BHMEMPSE R2 values revealed a curvilinear relationship (r=0.935, p<0.001). ConclusionsThe BHMEMPSE sequence exhibited comparable estimation for assessing liver iron content, comparable repeatability and a shorter acquisition time compared with the MEMPSE sequence. The BHMEMPSE sequence can serve as an adjunctive sequence to assess liver iron content.

Confidence in Assessment of Lumbar Spondylolysis Using Three-Dimensional Volumetric T2-Weighted MRI Compared With Limited Field of View, Decreased-Dose CT.

Background:Limited z-axis–coverage computed tomography (CT) to evaluate for pediatric lumbar spondylolysis, altering the technique such that the dose to the patient is comparable or lower than radiographs, is currently used at our institution. The objective of the study was to determine whether volumetric 3-dimensional fast spin echo magnetic resonance imaging (3D MRI) can provide equal or greater diagnostic accuracy compared with limited CT in the diagnosis of pediatric lumbar spondylolysis without ionizing radiation.Hypothesis:Volumetric 3D MRI can provide equal or greater diagnostic accuracy compared with low-dose CT for pediatric lumbar spondylolysis without ionizing radiation.Study Design:Clinical review.Level of Evidence:Level 2.Methods:Three pediatric neuroradiologists evaluated 2-dimensional (2D) MRI, 2D + 3D MRI, and limited CT examinations in 42 pediatric patients who obtained imaging for low back pain and suspected spondylolysis. As there is no gold standard for the diagnosis of spondylolysis besides surgery, interobserver agreement and degree of confidence were compared to determine which modality is preferable.Results:Decreased-dose CT provided a greater level of agreement than 2D MRI and 2D + 3D MRI. The kappa for rater agreement with 2D MRI, 2D + 3D MRI, and CT was 0.19, 0.32, and 1.0, respectively. All raters agreed in 31%, 40%, and 100% of cases with 2D MRI, 2D + 3D MRI, and CT. Lack of confidence was significantly lower with CT (0%) than with 2D MRI (30%) and 2D + 3D MRI (25%).Conclusion:For diagnosing spondylolysis, radiologist agreement and confidence trended toward improvement with the addition of a volumetric 3D MRI sequence to standard 2D MRI sequences compared with 2D MRI alone; however, agreement and confidence remain significantly greater using decreased-dose CT when compared with either MRI acquisition.Clinical Relevance:Decreased-dose CT of the lumbar spine remains the optimal examination to confirm a high suspicion of spondylolysis, with dose essentially equivalent to radiographs. If clinical symptoms are not classic for spondylolysis, 2D MRI is still very good at detecting spondylolysis while remaining sensitive for detection of alternative diagnoses such as disc abnormalities and pars stress reaction. The data suggest that standard 2D MRI sequences should not be entirely replaced by a volumetric T2-weighted 3D sequence (despite promising features of rapid acquisition time, increased spatial resolution, and reconstruction capability).

Can Signal Abnormalities Detected with MR Imaging in Knee Articular Cartilage Be Used to Predict Development of Morphologic Cartilage Defects? 48-Month Data from the Osteoarthritis Initiative.

Purpose To determine the incidence with which morphologic articular cartilage defects develop over 48 months in cartilage with signal abnormalities at baseline magnetic resonance (MR) imaging in comparison with the incidence in articular cartilage without signal abnormalities at baseline. Materials and Methods The institutional review boards of all participating centers approved this HIPAA-compliant study. Right knees of 90 subjects from the Osteoarthritis Initiative (mean age, 55 years ± 8 [standard deviation]; 51% women) with cartilage signal abnormalities but without morphologic cartilage defects at 3.0-T MR imaging and without radiographic osteoarthritis (Kellgren-Lawrence score, 0-1) were frequency matched for age, sex, Kellgren-Lawrence score, and body mass index with right knees in 90 subjects without any signal abnormalities or morphologic defects in the articular cartilage (mean age, 54 years ± 5; 51% women). Individual signal abnormalities (n = 126) on intermediate-weighted fast spin-echo MR images were categorized into four subgrades: subgrade A, hypointense; subgrade B, inhomogeneous; subgrade C, hyperintense; and subgrade D, hyperintense with swelling. The development of morphologic articular cartilage defects (Whole-Organ MR Imaging Score ≥2) at 48 months was analyzed on a compartment level and was compared between groups by using generalized estimating equation logistic regression models. Results Cartilage signal abnormalities were more frequent in the patellofemoral joint than in the tibiofemoral joint (59.5% vs 39.5%). Subgrade A was seen more frequently than were subgrades C and D (36% vs 22%). Incidence of morphologic cartilage defects at 48 months was 57% in cartilage with baseline signal abnormalities, while only 4% of compartments without baseline signal abnormalities developed morphologic defects at 48 months (all compartments combined and each compartment separately, P < .01). The development of morphologic defects was not significantly more likely in any of the subgrades (P = .98) and was significantly associated with progression of bone marrow abnormalities (P = .002). Conclusion Knee cartilage signal abnormalities detected with MR imaging are precursors of morphologic defects with osteoarthritis and may serve as imaging biomarkers with which to assess risk for cartilage degeneration. (©) RSNA, 2016.