High-resolution MR imaging of the elbow using a microscopy surface coil and a clinical 1.5 T MR machine: preliminary results

Objective To obtain high-resolution MR images of the elbow using a microscopy surface coil with a 1.5 T clinical machine and to evaluate the feasibility of its use for elbow injuries.Design and patients Five asymptomatic normal volunteers and 13 patients with elbow pain were prospectively studied with MR imaging using a microscopy surface coil 47 mm in diameter. High-resolution MR images using a microscopy coil were obtained with fast spin echo (FSE) proton density-weighted sequence, gradient recalled echo (GRE) T2*-weighted sequence, and short tau inversion recovery (STIR) sequence, with a 1–2 mm slice thickness, a 50–70 mm field of view, an imaging matrix of 140–224×512 using zero fill interpolation, and 2–6 excitations.Results High-resolution MR images of normal volunteers using a microscopy coil clearly showed each structure of the medial and lateral collateral ligaments on GRE T2*-weighted images and FSE proton-density weighted images. Partial medial collateral ligament injury, a small avulsion of the medial epicondyle, and osteochondritis dissecans were well demonstrated on high-resolution MR images.Conclusion High-resolution MR imaging of the elbow using a microscopy surface coil with a 1.5 T clinical machine is a promising method for accurately characterizing the normal anatomy of the elbow and depicting its lesions in detail.     

Intraindividual comparison of myocardial delayed enhancement MR imaging using gadobenate dimeglumine at 1.5 T and 3 T

For contrast-enhanced imaging techniques relying on strong T1 weighting, 3 T provides increased contrast compared with 1.5 T. The aim of our study was the intraindividual comparison of delayed enhancement MR imaging at 1.5 T and at 3 T. Twenty patients with myocardial infarction were examined at 1.5 T and 3 T. Fifteen minutes after injection of contrast agent (0.1 mmol gadobenate dimeglumine per kg body weight), inversion recovery gradient recalled echo (IR-GRE) sequences were acquired (1.5 T/3 T: TR 11.0/9.9 ms, TE 4.4/4.9 ms, flip 30°/30°, slice thickness 6/6 mm) to assess myocardial viability. Two observers rated image quality (Wilcoxon signed rank test). Quantification of hyperenhanced myocardium and standardized SNR/CNR measurements were performed (Student’s t test). There was no significant difference with respect to image quality (1.5 T/3 T: 3.5/3.3, p = 0.34, reader 1; 2.4/2.7, p = 0.12, reader 2) and infarction size (760 ± 566/828 ± 677 mm² at 1.5 T, 808 ± 639/826 ± 726 mm² at 3 T, reader 1/reader 2, p > 0.05). Mean SNR in hyperenhanced/normal myocardium was 19.2/6.2 at 1.5 T and 29.5/8.8 at 3 T (p < 0.05). Mean CNR was 14.3 at 1.5 T and 26.0 at 3 T (p < 0.05). Delayed enhancement MR imaging at 3 T is a robust procedure yielding superior tissue contrast at 3 T compared with 1.5 T which is, however, not reflected by increased image quality.     

Endometrial cancer: preoperative staging using three-dimensional T2-weighted turbo spin-echo and diffusion-weighted MR imaging at 3.0 T: a prospective comparative study

Objectives

To prospectively assess the efficacy of 3-T magnetic resonance (MR) imaging using the three-dimensional turbo spin-echo T2-weighted and diffusion-weighted technique (3D-TSE/DW) compared with that of conventional imaging using the two-dimensional turbo spin-echo T2-weighted and dynamic contrast-enhanced technique (2D-TSE/DCE) for the preoperative staging of endometrial cancer, with pathological analysis as the reference standard.

Methods

Seventy-one women with endometrial cancer underwent MR imaging using 3D-TSE/DW (b?=?1,000 s/mm²) and 2D-TSE/DCE. Two radiologists independently assessed the two imaging sets. Accuracy, sensitivity, and specificity for staging were analysed with the McNemar test; the areas under the receiver operating characteristic curve (Az) were compared with a univariate z-score test.

Results

The results for assessing deep myometrial invasion, accuracy, sensitivity, specificity and Az, respectively, were as follows: 3D-TSE/DW—observer 1, 87 %, 95 %, 85 % and 0.96; observer 2, 92 %, 84 %, 94 % and 0.95; 2D-TSE/DCE—observer 1, 80 %, 79 %, 81 % and 0.89; observer 2, 86 %, 84 %, 87 % and 0.86. Most of the values were higher with 3D-TSE/DW without significant differences (P?>?0.12). For assessing cervical stromal invasion, there were no significant differences in those values for both observers (P?>?0.6).

Conclusions

Accuracy of 3D-TSE/DW was at least equivalent to that of the conventional technique for the preoperative assessment of endometrial cancer.

Key Points

? New techniques in MR imaging help assess patients with endometrial cancer. ? A 3D T2-weighted TSE sequence seems equally as accurate as conventional techniques. ? Three-dimensional TSE/DW imaging does not require intravenous contrast material and is relatively quick. ? Tumour extent of endometrial cancer can be clearly shown on diffusion-weighted images. ? Junctional zone can be visualised well on 3D-TSE T2-weighted images.     

Comparison of left ventricular function assessment using phonocardiogram- and electrocardiogram-triggered 2D SSFP CINE MR imaging at 1.5 T and 3.0 T

Objective

As high-field cardiac MRI (CMR) becomes more widespread the propensity of ECG to interference from electromagnetic fields (EMF) and to magneto-hydrodynamic (MHD) effects increases and with it the motivation for a CMR triggering alternative. This study explores the suitability of acoustic cardiac triggering (ACT) for left ventricular (LV) function assessment in healthy subjects (n?=?14).

Methods

Quantitative analysis of 2D CINE steady-state free precession (SSFP) images was conducted to compare ACT’s performance with vector ECG (VCG). Endocardial border sharpness (EBS) was examined paralleled by quantitative LV function assessment.

Results

Unlike VCG, ACT provided signal traces free of interference from EMF or MHD effects. In the case of correct R-wave recognition, VCG-triggered 2D CINE SSFP was immune to cardiac motion effects—even at 3.0 T. However, VCG-triggered 2D SSFP CINE imaging was prone to cardiac motion and EBS degradation if R-wave misregistration occurred. ACT-triggered acquisitions yielded LV parameters (end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF) and left ventricular mass (LVM)) comparable with those derived from VCG-triggered acquisitions (1.5 T: ESV_VCG?=?(56?±?17) ml, EDV_VCG?=?(151?±?32) ml, LVM_VCG?=?(97?±?27) g, SV_VCG?=?(94?±?19) ml, EF_VCG?=?(63?±?5)% cf. ESV_ACT?=?(56?±?18) ml, EDV_ACT?=?(147?±?36) ml, LVM_ACT?=?(102?±?29) g, SV_ACT?=?(91?±?22) ml, EF_ACT?=?(62?±?6)%; 3.0 T: ESV_VCG?=?(55?±?21) ml, EDV_VCG?=?(151?±?32) ml, LVM_VCG?=?(101?±?27) g, SV_VCG?=?(96?±?15) ml, EF_VCG?=?(65?±?7)% cf. ESV_ACT?=?(54?±?20) ml, EDV_ACT?=?(146?±?35) ml, LVM_ACT?=?(101?±?30) g, SV_ACT?=?(92?±?17) ml, EF_ACT?=?(64?±?6)%).

Conclusions

ACT’s intrinsic insensitivity to interference from electromagnetic fields renders it suitable for clinical CMR.     

High-resolution myocardial perfusion imaging at 3 T: comparison to 1.5 T in healthy volunteers

The purpose of this study was to evaluate high-resolution (HR) myocardial first-pass perfusion in healthy volunteers at 3 T compared to a typical clinical imaging protocol at 1.5 T, with respect to overall image quality and the presence of subendocardial dark rim artifacts. Myocardial first-pass rest perfusion studies were performed at both field strengths using a T1-weighted saturation-recovery segmented k-space gradient-echo sequence combined with parallel imaging (Gd-DTPA 0.05 mmol/kg). Twenty-six healthy volunteers underwent (1) a HR perfusion scan at 3 T(pixel size 3.78 mm²) and (2) a standard perfusion approach at 1.5 T(pixel size 9.86 mm²). The contrast enhancement ratio (CER) and overall image quality (4-point grading scale: 4: excellent; 1: non-diagnostic) were assessed, and a semiquantitative analysis of dark rim artifacts was performed for all studies. CER was slightly higher (1.31 ± 0.32 vs. 1.14 ± 0.34; p<0.01), overall image quality was significantly improved (3.03 ± 0.43 vs. 2.37 ± 0.39; p<0.01), and the number of dark rim artifacts (139 ± 2.09 vs. 243 ± 2.33; p<0.01) was significantly reduced for HR perfusion imaging at 3 T compared to the standard approach at 1.5 T. HR myocardial rest perfusion at 3 T is superior to the typical clinical perfusion protocol performed at 1.5 T with respect to the overall image quality and presence of subendocardial dark rim artifacts.     

Multiparametric MR imaging of the prostate at 1.5-T without endorectal coil using an 8 channel pelvic phased array: Is it still a viable option?

IntroductionThe purpose of our work was to evaluate the feasibility of prostate multiparametric MR imaging at 1.5-T without endorectal coil using an 8 channel pelvic phased array coil.Material and methodsA total of 154 patients who underwent mp-MRI were retrospectively included. Patients received a standardized mp-MRI, compliant with 2012 European Society of Uro-Radiology guidelines, with 1·5 T magnetic field strength and an 8 channel pelvic phased-array coil.Two blinded readers graded the image quality of mp-MRI on a three-point scale and they scored the prostate lesions according to PI-RADS v2. All PI-RADS of 4 or 5 underwent biopsy. A third radiologist and a pathologist verified the correspondence between the MRI images and the results of the biopsy.Results64 (41.6%) patients showed a Pi-rads of 4 or 5. At biopsy, 79.7% showed a Gleason score ≥7, 12.5% showed a Gleason score of 6 and 7.8% showed a negative biopsy. In the group of Pi-rads ≤ 3, 12 patients underwent a biopsy with the following results: negative biopsy in 33.3%, atypical Small Acinar Proliferation in 16.7%, prostatic intraepithelial neoplasia in 25% and indolent PCa 25%. Mp-MRI in the identification of clinically significant cancer provided a low percentage of false positive (7.8%) while in 79.7% of cases it was capable to detect clinically significant prostate cancer. In 92.2% of patients mp-MRI identified a prostate cancer with a Gleason score ≥6. The inter-reader agreement was excellent in defining both the quality of the examination and the PI-RADS category (k = 0.83 and k = 0.70, respectively).Conclusionsmp-MRI at 1.5-T without endorectal coil using an 8 channel phased array is an appropriate tool for early detection of clinically significant prostate cancer.Implications for practice8 channel pelvic phased array is still an appropriate tool for early detection of clinically significant prostate cancer and for obtaining a reduction in overdiagnosis of indolent PCa.     

MR imaging of recent non-traumatic intracranial hemorrhage: early experience at 3 T

Magnetic resonance imaging (MRI) using 3.0 T scanners in the clinical environment is in its infancy and is only available at a limited number of sites worldwide. There is great interest amongst radiologists about the perceived benefits of clinical imaging at 3.0 T; however, it remains to be seen whether the theoretical advantages will bring real gains. MRI in patients with non-traumatic intracranial hemorrhage (ICH) is difficult, yet, these patients benefit from non-invasive angiography. Conventional catheter angiography (CCA) remains the reference standard for excluding/confirming the presence of intracranial vascular abnormalities, but MR angiography at 3.0 T may offer opportunities for significant changes in patient management. We present our experiences of using 3.0 T MR angiography in 27 patients with acute or early subacute ICH.     

Optimization of diffusion-tensor MR imaging data acquisition parameters for brain fiber tracking using parallel imaging at 3 T

The purpose of this study was to optimize the parameters of diffusion-tensor magnetic resonance imaging (DT MRI) for brain fiber tracking using a slice thickness of 2 mm, a resolution advantage allowed by the high signal-to-noise ratio at 3 T, combined with an 8-channel phased-array head coil. The b-factor, number of motion probing gradient (MPG) directions, and number of averages were varied, and the results of brain fiber tracking for the pyramidal tract and trigeminal nerve were compared qualitatively and quantitatively. The DT MRI data sufficient for brain fiber tracking in healthy subjects can be obtained in <2 min with a 2-mm slice thickness, 700-s/mm² b-factor, 6 MPG directions, and no averaging (number of averages=1).     

MR imaging and proton MR spectroscopic studies in Sjögren-Larsson syndrome: characterization of the leukoencephalopathy

BACKGROUND AND PURPOSE: Sj?gren-Larsson syndrome (SLS) is a neurocutaneous syndrome caused by a genetic enzyme deficiency in lipid metabolism. Our purpose was to characterize the nature of the cerebral involvement in SLS. METHODS: MR imaging was performed in 18 patients (aged 5 months to 45 years) and repeated in 14. Single-voxel proton MR spectra were acquired from cerebral white matter and gray matter in 16 patients, with follow-up studies in 11. LCModel fits were used to determine brain metabolite levels. RESULTS: MR imaging showed retardation of myelination and a mild persistent myelin deficit. A zone of increased signal intensity was seen in the periventricular white matter on T2-weighted images. Proton MR spectroscopy of white matter revealed a prominent peak at 1.3 ppm, normal levels of N-acetylaspartate, and elevated levels of creatine (+14%), choline (+18%), and myo-inositol (+54%). MR imaging and proton MR spectroscopy of gray matter were normal. In the two patients examined during the first years of life, abnormalities on MR imaging and proton MR spectroscopy gradually emerged and then stabilized, as in all other patients. CONCLUSION: Abnormalities on MR imaging and proton MR spectroscopy emerge during the first years of life and are similar in all patients with SLS, but the severity varies. The changes are confined to cerebral white matter and suggest an accumulation of lipids, periventricular gliosis, delayed myelination, and a mild permanent myelin deficit.     

What is the optimal b value in diffusion-weighted MR imaging to depict prostate cancer at 3T?

Objective  

To determine an optimal b value to visualise prostate cancer using diffusion-weighted magnetic resonance imaging at 3 T.     

Optimization of scanning parameters for MR elastography at 3.0 T clinical unit: volunteer study

Purpose

We sought to optimize scanning parameters for MR elastography at 3.0 T clinical unit.

Materials and methods

10 volunteers were scanned with various magnetization encoding gradient (MEG) frequencies from 60 to 120 Hz at every 10 Hz, with otherwise fixed parameters (external driver frequency/amplitude = 60 Hz/50 %, 10 mm slice thickness, etc.). Images were qualitatively assessed for the degree of image defects, and also quantitatively for the areas without cross-hatching. After determining optimal MEG frequency, external driver amplitudes of 70 % (vs 50 %) and slice thickness of 8 mm (vs 10 mm) were also tested. With the optimized parameters, scans were repeated 1 week after the initial scan, and the repeatability of the liver stiffness measurement was validated.

Results

80 or 90 Hz was shown to be the best MEG frequency. There were no significant differences in the qualitative and quantitative assessment between the two amplitudes and two slice thicknesses; however, 70 % amplitude resulted in discomfort at the chest wall beneath the external acoustic driver. Thus, MEG 80 (or 90) Hz, amplitude 50 %, and thickness 10 (or 8) mm were considered optimal. Repeatability of the liver stiffness measurement was ±10 % (95 % confidence interval).

Conclusions

With the optimized parameters, repeatability of ±10 % in liver stiffness measurement was obtained.     

Diffusion-weighted and T2-weighted MR imaging for colorectal liver metastases detection in a rat model at 7 T: a comparative study using histological examination as reference

Objectives

To compare diffusion-weighted (DW) and T2-weighted MR imaging in detecting colorectal liver metastases in a rat model, using histological examination as a reference method.

Methods

Eighteen rats had four liver injections of colon cancer cells. MR examinations at 7 T included FSE-T2-weighted imaging and SE-DW MR imaging (b?=?0, 20 and 150 s/mm²) and were analysed by two independent readers. Histological examination was performed on 0.4-mm slices. McNemar’s test was used to compare the sensitivities and the Wilcoxon matched pairs test to compare the average number of false-positives per rat.

Results

One hundred and sixty-six liver metastases were identified on histological examination. The sensitivity in detecting liver metastases was significantly higher on DW MR than on T2-weighted images (99/166 (60 %) (reader 1) and 92/166 (55 %) (reader 2) versus 77/166 (46 %), P?≤?0.001), without an increase in false-positives per rat (P?=?0.773/P?=?0.850). After stratification according to metastasis diameter, DW MR imaging had a significantly higher sensitivity than T2-weighted imaging only for metastases with a diameter (0.6–1.2 mm) similar to that of the spatial resolution of MR imaging in the current study.

Conclusions

This MR study with histological correlations shows the higher sensitivity of DW relative to T2-weighted imaging at 7 T for detecting liver metastases, especially small ones.

Key Points

? Diffusion weighted (DW) sequences are increasingly used in magnetic resonance imaging (MRI). ? DW has higher sensitivity for liver metastases than T2-weighted imaging at 7 T. ? This increase in sensitivity is especially marked for small liver metastasis detection. ? This higher sensitivity is confirmed in an animal model with histological correlation. ? DW imaging has the potential for earlier diagnosis of small liver metastases.     

Specificity of choline metabolites for in vivo diagnosis of breast cancer using 1H MRS at 1.5 T

The purpose was to determine if in vivo proton magnetic resonance spectroscopy (¹H MRS) at 1.5 T can accurately provide the correct pathology of breast disease. Forty-three asymptomatic volunteers including three lactating mothers were examined and compared with 21 breast cancer patients. Examinations were undertaken at 1.5 T using a purpose-built transmit-receive single breast coil. Single voxel spectroscopy was undertaken using echo times of 135 and 350 ms. The broad composite resonance at 3.2 ppm, which includes contributions from choline, phosphocholine (PC), glycerophosphocholine (GPC), myo-inositol and taurine, was found not to be a unique marker for malignancy providing a diagnostic sensitivity and specificity of 80.0 and 86.0%, respectively. This was due to three of the asymptomatic volunteers and all of the lactating mothers also generating the broad composite resonance at 3.2 ppm. Optimised post-acquisitional processing of the spectra resolved a resonance at 3.22 ppm, consistent with PC, in patients with cancer. In contrast the spectra recorded for three false-positive volunteers, and the three lactating mothers had a resonance centred at 3.28 ppm (possibly taurine, myo-inositol or GPC). This improved the specificity of the test to 100%. Careful referencing of the spectra and post-acquisitional processing intended to optimise spectral resolution of in vivo MR proton spectra from human breast tissue resolves the composite choline resonance. This allows the distinction of patients with malignant disease from volunteers with a sensitivity of 80% and specificity of 100%. Therefore, resolution of the composite choline resonance into its constituent components improves the specificity of the in vivo ¹H MRS method, but does not overcome the problem of 20% false-negatives.     

Extracardiac findings at cardiac MR imaging: a single-centre retrospective study over 14 years

Objectives

To determine the prevalence and significance of extracardiac findings (ECF) in a large set of cardiac magnetic resonance (MR) imaging examinations.

Methods

The institutional review board (IRB) of the Charité approved this retrospective, single-centre study. A total of 4376 cardiac MR imaging reports of 3553 patients (age 37.4 ± 20 years, 60.8 % male) examined from 2000 to 2014 were included. Findings with a recommendation for follow-up were considered “major ECF”. To analyse the association of indication, age and gender with ECF, Poisson regression and computed incidence rate ratios (IRR) were evaluated.

Results

The overall prevalence of ECF was 34% (95% confidence interval [CI] 32.5–35.6%). Major ECF were present in 3.4% (95% CI 2.9–4.1%) while findings that changed patient management were found in 0.9% (95% CI 0.7–1.3%). In the cases of congenital heart disease, ECF prevalence was higher compared to myocarditis (IRR, 6.0; 95% CI 5.1–7.1%; p < 0.001), while the prevalence of major ECF was lower (IRR, 0.2; 95% CI 0.02–0.51%; p < 0.05). Older patient age was associated with more nonvascular ECF (p < 0.001). Female patients had the same probability of having an ECF as male patients (IRR, 1.04; 95% CI 0.95–1.1%; p = 0.43).

Conclusion

ECF in cardiac MR imaging are present in about every third patient while relevant ECF that change patient management can be found in about one out of 100 patients. Our data suggest that it is important to involve well-trained radiologists in reading cardiac MR images, which often reveal ECF if congenital heart disease is the clinical indication.

Key Points

? Extracardiac findings are present in about every third patient.? Relevant ECF changing patient management are found in one out of 100 findings.? Chance of ECF is high in patients with CHD and vascular indications.

     

Efficacy of magnetic resonance imaging at 3 T compared with 1.5 T in small pituitary tumors for stereotactic radiosurgery planning

Purpose

The objective of this study was to determine the value of high-field magnetic resonance imaging and to clarify the characteristics of each image among three-dimensional gradient echo (3D-GRE), two-dimensional spin echo (2D-SE) and inversion recovery (2D-IR) sequences used as contrast-enhanced T1-weighted images for stereotactic irradiation treatment planning of sellar lesions.

Materials and methods

Pulse sequences of 2D-SE and 3D-spoiled gradient recalled acquisition in the steady state (3D-SPGR) using GRE at 1.5 T and 2D-IR and 3D-fast SPGR (3D-FSPGR) at 3 T after injection of contrast material were acquired for 14 small pituitary tumors. As quantitative methods, signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were evaluated using a region-of-interest analysis.

Results

There was no significant difference in SNR between 1.5-T SPGR and 3-T FSPGR, while 3-T IR was superior to 1.5-T SE. The 2D-SE and -IR provided significantly better CNR than 3D-GRE between tumor and normal structures.

Conclusions

Three Tesla was found to be superior to 1.5 T in distinguishing tumors from the normal sellar structure. Optimal dose planning will utilize each advantage of imaging; 3D-GRE allows high-resolution acquisition and 2D-SE and -IR can offer better tissue contrast.     

Gray matter-white matter contrast on spin-echo T1-weighted images at 3 T and 1.5 T: a quantitative comparison study

Discrepancies exist in the literature regarding contrast between gray and white matter on spin-echo (SE) T1-weighted MR imaging at 3 T. The present study quantitatively assessed differences in gray matter-white matter contrast on both single- and multi-slice SE T1-weighted imaging between 3 and 1.5 T. SE T1-weighted sequences with the same parameters at both 3 and 1.5 T were used. Contrast-to-noise ratio (CNR) between gray and white matter (CNR_GM-WM) was evaluated for both frontal lobes. To assess the effects of interslice gap, multi-slice images were obtained with both 0 and 25% interslice gap. Single-slice CNR_GM-WM was higher at 3 T (17.66 ± 2.68) than at 1.5 T (13.09 ± 2.35; P < 0.001). No significant difference in CNR_GM-WM of multi-slice images with 0% gap was noted between 3 and 1.5 T (3T, 8.61 ± 2.55; 1.5T, 7.43 ± 1.20; P > 0.05). Multi-slice CNR_GM-WM with 25% gap was higher at 3T (12.47 ± 3.31) than at 1.5 T (9.73 ± 1.37; P < 0.001). CNR_GM-WM reduction rate of multi-slice images with 0% gap compared with single-slice images was higher at 3T (0.47 ± 0.13) than at 1.5 T (0.38 ± 0.09; P = 0.02). CNR_GM-WM on single-slice SE T1-weighted imaging and CNR_GM-WM on multi-slice images with 25% interslice gap were better at 3 T than at 1.5 T. The influence of multi-slice imaging on CNR_GM-WM was significantly larger at 3T than at 1.5 T. This study was supported in part by a Health and Labour Sciences Research Grant of Japan Yasutaka Fushimi and Yukio Miki equally contributed to the study.     

In vitro comparison of different carotid artery stents: a pixel-by-pixel analysis using CT angiography and contrast-enhanced MR angiography at 1.5 and 3 T

Introduction  

CT angiography (CTA) and MR angiography (MRA) are increasingly used methods for evaluation of stented vessel segments. The purpose of this study was to compare CTA, contrast-enhanced MRA (CEMRA) at 1.5 T, and CEMRA at 3 T for the visualization of carotid artery stents and to define the best noninvasive imaging technique for each stent.