Simultaneous multi-slice (SMS) imaging with short repetition time (TR) accelerates diffusion tensor imaging (DTI) acquisitions. However, its impact when combined with readout-segmented echo planar imaging (RESOLVE) on the cranial nerves given the challenging skull base/posterior fossa terrain is unexplored. We evaluated the reliability of trigeminal nerve DTI metrics using SMS with RESOLVE-DTI. Eight healthy controls and six patients with unilateral trigeminal neuralgia (TN) underwent brain MRI scan. Three different RESOLVE-DTI protocols were performed on a 3-T MRI system: non-SMS (TR = 4330 ms), SMS with identical TR (4330 ms), and SMS with short TR (2400 ms). Pontine signal-to-noise ratio (SNR) and DTI metrics of the trigeminal nerve streamlines tracked by two independent raters using deterministic tractography and standardized tracking protocol were obtained. These were statistically analyzed and compared across the three protocols using intra-rater and inter-rater intraclass correlation coefficients (ICCs), one-way analysis of variance (ANOVA), post hoc analysis, and linear regression. On visual screening, there were no artifacts across the trigeminal nerves. All data also cleared objective image quality assurance analysis. Pontine SNR was similar for the two SMS protocols and higher for the non-SMS RESOLVE-DTI (F(2,36) = 4.40, p = 0.02). Intra-rater and inter-rater ICCs were very good (> 0.85). Trigeminal nerve DTI metrics were consistently measured by the three protocols, revealing significant linear relationships between non-SMS- and SMS-derived DTI metrics. SMS RESOLVE-DTI enables fast and reliable evaluation of microstructural integrity of the trigeminal nerve, with potential application in the clinical management of TN. • Readout-segmented diffusion-weighted echo planar imaging (RESOLVE-DTI) reduces image distortion artifacts in the posterior fossa but its long acquisition time limits clinical utility. • Simultaneous multi-slice (SMS) imaging combined with RESOLVE-DTI provides reliable trigeminal nerve tractography with potential applications in trigeminal neuralgia. • Two-fold-accelerated RESOLVE-DTI yields comparable trigeminal nerve streamlines and DTI metrics while near-halving acquisition time.

Purpose To assess the difference in optic nerve tortuosity during eye movements and globe proptosis between primary open angle glaucoma and normal subjects using orbital magnetic resonance imaging. Methods 10 Chinese subjects matched for age, ethnicity and refractive errors were recruited, including five normal controls and five patients with primary open angle glaucoma. All subjects underwent magnetic resonance imaging to assess their optic nerves and globes for three eye positions: primary gaze, adduction and abduction. Optic nerve tortuosity (optic nerve length divided by the distance between two ends) and globe proptosis (maximum distance between cornea and interzygomatic line) were measured from magnetic resonance imaging images. Results In adduction, the tortuosity of normal eyes was significantly larger than that of the glaucomatous eyes. Optic nerve tortuosity in adduction in the control and glaucoma groups were 1.004±0.003 (mean ± standard deviation) and 1.001±0.001, respectively (p=0.037). Globe proptosis (primary gaze) in glaucoma subjects (19.14±2.11 mm) was significantly higher than that in control subjects (15.32±2.79 mm; p = 0.046). Conclusions In this sample, subjects with glaucoma exhibited more taut optic nerves and more protruding eye globes compared to normal eyes. This may impact optic nerve head deformations in anatomically predisposed patients. Précis Eyes with glaucoma have tauter optic nerves compared with normal eyes, which may exert more force on the optic nerve head tissues during eye movements.

Introduction: To assess if parameters in intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) can be used to evaluate early renal fibrosis in a mouse model of diabetic nephropathy.Materials & methods: In a population of 38 male CD1 mice (8 weeks old, 20-30 g), streptozotocin induced diabetes was created in 20 mice via a single intraperitoneal injection of streptozotocin at 150 mg/kg, while 18 mice served as control group. IVIM parameters were acquired at 0,12 and 24 weeks after injection of streptozotocin using a range of b values from 0 to 1200 s/mm(2). DTI parameters were obtained using 12 diffusion directions and lower b values of 0, 100 and 400 s/mm2. DTI and IVIM parameters were obtained using region of interests drawn over the renal parenchyma. Histopathological analysis of the right kidney was performed in all mice. Results were analyzed using an unpaired t-test with P < 0.05 considered statistically significant.Results: Renal cortex fractional anisotropy (FA) was significantly lower in the diabetes group at week 12 as compared with the control group. Renal cortex apparent diffusion coefficient and tissue diffusivity were significantly higher in the diabetes group at week 12 compared with the control group at 12 weeks. Blood flow was significantly decreased at the renal medulla at 24 weeks. Histopathological analysis confirmed fibrosis in the diabetes group at 24 weeks.Conclusion: FA is significantly reduced in diabetic nephropathy. FA might serve a potential role in the detection and therapy monitoring of early diabetic nephropathy. (C) 2016 Elsevier Inc. All rights reserved.

PURPOSE We combined finite element (FE) analysis and dynamic magnetic resonance imaging (MRI) to estimate optic nerve head (ONH) strains during horizontal eye movements, and identified factors influencing such strains. We also compared ONH strains (prelamina, lamina cribrosa, and retrolamina strains) induced by eye movements to those induced by IOP. METHODS The ocular globes and orbits of a healthy subject were visualized during horizontal eye movements (up to 13°), using dynamic MRI. A baseline FE model of one eye was reconstructed in the primary gaze position, including details from the orbital and ONH tissues. Finite element-derived ONH strains induced by eye movements were compared to those resulting from an IOP of 50 mm Hg. Finally, a FE sensitivity study was performed, in which we varied the stiffness of all ONH connective tissues, to understand their influence on ONH strains. RESULTS Our models predicted that, during horizontal eye movements, the optic nerve pulled the ONH posteriorly. Optic nerve head strains following a lateral eye movement of 13° were large and higher than those resulting from an IOP of 50 mm Hg. These results held true even with variations in connective tissue stiffness. We also found that stiff sclerae reduced lamina cribrosa and prelamina strains during eye movements, but stiff optic nerve sheaths significantly increased those strains. CONCLUSIONS Our models predicted high ONH strains during eye movements, which were aggravated with stiffer optic nerve sheaths. Further studies are needed to explore links between ONH strains induced by eye movements and axonal loss in glaucoma.

Diffusion tensor imaging (DTI) is an increasingly used noninvasive imaging tool. However its long-term clinical utility is unclear. Parkinson's disease (PD) is a common neurodegenerative disease.We prospectively examined a cohort of 46 Parkinson's disease (PD) patients who underwent diffusion tensor imaging (DTI) of the brain at baseline and 6 years later on a 1.5 Tesla scanner using a standardized protocol. DTI parameters of mean diffusivity (MD) and fractional anisotrophy (FA) were extracted using regions-of-interest (ROIs) analysis from various brain regions.Compared to the baseline scan, MD increased in all brain regions (P < 0.0001). FA increased in the substantia nigra and posterior putamen, but decreased in the frontal white matter (P < 0.0001). Linear regression analysis demonstrated that the MD in the anterior putamen increased 11.6 units (95% CI = [4.71, 18.43]) (P = 0.0003) for every unit increase of United PD Rating Scale (UPDRS).Our 6-year prospective longitudinal study demonstrated increased diffusivity in all brain regions and that in the anterior putamen correlated with disease progression. Serial diffusion data may be useful as an additional objective in vivo biomarker for motor progression in PD.

Susceptibility-weighted MRI (SWI) is sensitive to T2 effects and mineralization.We investigated differences in the extrapyramidal brain structures on SWI between Parkinson disease (PD) and postural instability gait disorder (PIGD) patients and correlated the SWI values with the degree of gait dysfunction.Forty patients diagnosed with PD and PIGD underwent 3 Tesla magnetic resonance imaging (MRI) brain study. An SWI sequence (TE/TR/FA 20/33/15) was used. Ten regions of interest were placed in the midbrain and basal ganglia by 2 independent raters blinded to subject data and quantitatively evaluated.The inter-rater reliability between the raters was excellent (interclass correlation coefficient >0.8). The SWI intensity values in all regions were on average lower in PIGD than in PD patients, with the lowest results found in globus pallidus.Multivariate analysis showed a lower SWI hypointensity in the putamen and globus pallidus in PIGD compared with PD patients, with a similar trend for the other basal ganglia nuclei. Pearson correlation analysis showed a statistically significant positive correlation between SWI putaminal hypointensity and the Tinetti total score (r = 0.39, P = 0.01) in both PD and PIGD.SWI putaminal hypointensity may be a useful imaging marker in prospective evaluation for clinical progression for Parkinsonian disorders.

PurposeTo evaluate non-invasive imaging biomarkers for assessing renal fibrosis. DWI is used to assess renal function; intravoxel incoherent motion (IVIM) provides additional measures of perfusion-related diffusion (D*, blood flow; f, perfusion fraction). We aim to determine if reduced ADC seen in renal fibrosis is attributable to perfusion-related diffusion changes or to known reduction in tissue diffusivity (D).Materials and methodsUnilateral ureteral obstruction (UUO) was created in six mice to induce renal fibrosis. DWI was performed the day before and 7 days post-UUO. A range of b-values from 0 to 1200 s/mm2 were used. IVIM parameters were obtained using region of interests drawn over the renal parenchyma. Histopathological analysis of both kidneys was performed in all mice. Results were analyzed using the paired t-test with P<0.05 considered statistically significant.ResultsD and f were significantly lower in the ligated kidneys at Day 7 compared to before ligation and no significant difference was found for D*. Comparing non-ligated and ligated kidneys within the same mouse at Day 7, significantly lower D values were observed in the ligated kidneys, while no significant difference was found for f and D*, although the values of f were generally lower. Histopathological analysis confirmed development of fibrosis and reduction in glomeruli in all the ligated kidneys at Day 7.ConclusionOur study shows that the reduction in ADC seen in renal fibrosis is attributable not only to reduced D as previously encountered but also a decrease in vascularity as assessed by f. Reduction in f is possibly related to a reduction in glomeruli.

Objectives: There is much interest in evaluating diffusion tensor imaging (DTI) as an accessible disease biomarker of Parkinson's Disease (PD). Whilst there are multiple cross-sectional studies in PD, there is little information on longitudinal DTI data. The objective of this study is to study changes of DTI metrics of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) over a six-year longitudinal follow-up of PD patients.

We hypothesized that deterministic tractography is practical and sensitive to changes in the complex nigrostriatal and nigropallidal pathway (NSP) in Parkinson's disease (PD). Using diffusion tensor imaging (DTI) tractography, we investigated the NSP to evaluate differences between PD patients and controls, and examined their clinico-radiologic correlation. Structural and DTI brain scans were obtained in 40 subjects (21 PD patients and 19 healthy controls). We isolated the NSP using a user-friendly DTI toolkit based on deterministic brute-force tractography. DTI parameters of fractional anisotropy (FA), mean, axial, and radial diffusivity, and streamline count of the NSP were measured. Average FA (p < 0.01) and streamline count (p < 0.001) were significantly lower in the PD compared to control group. Mean diffusivity and radial diffusivity were significantly higher in the PD group (p < 0.05). Average streamline count correlated with the United Parkinson's Disease Rating Scale motor score (p < 0.05). Point-to-point FA profiles of the tract demonstrated peak divergence between PD and control towards the tract midpoint rather than the distal grey matter. Our findings demonstrated a clinically and radiologically practical application of DTI tractography to the NSP in PD, without requiring complex imaging sequences for anatomical localization or segmentation software.

Background: Magnetic drug targeting (MDT) uses magnetic fields to localize magnetic nanoparticles (MNP) to tumor. Once localized, applying an alternating magnetic field (AMF) to the MNPs generates heat energy. Poly-N-isopropylacrylamide (PNIPA) is a thermosensitive polymer that contracts when heated, releasing any drugs which are bound to it. Utilizing these properties, MNP coated with PNIPA polymer on to which doxorubicin is loaded can be localized to hepatocellular carcinoma (HCC) with an external magnetic field. Application of an AMF will then generate localized magnetic hyperthermia (MH) within the tumor, thus releasing bound doxorubicin. This study explores this novel drug delivery model which can be used for targeted dual therapy (MDT and MH) of HCC. Aim: To demonstrate that doxorubicin-loaded-PNIPA-coated-MNP can be delivered intra-arterially to target HCC in a rat model and that heat is generated and doxorubicin is released when an AMF is applied. Methods: Morris hepatoma cells are implanted into the livers of buffalo rats. HCC development is confirmed on MRI using a specially-constructed rat-MRI coil. 0.5 ml of doxorubicin-loaded-PNIPA-coated-MNP solution is injected into the hepatic artery and localization of MNP in HCC is confirmed with MRI. Rats are sacrificed for histology of liver and other organs. AMF is applied to doxorubicin-loaded-PNIPA-coated-MNP solution and the temperature measured to demonstrate local hyperthermia in vitro. The amount of doxorubicin released is measured by spectrophotometry. Results: Successful intra-arterial delivery of MNP was confirmed on post-injection MRI. On histology, iron particles were seen in HCC but not in normal liver or other organs. When AMF was applied, temperature of the suspension reached the target temperature of 42°C within 5 minutes and remained within hyperthermia range(42°C-48°C) for 15 minutes. During this period of hyperthermia, 4.7% (~71 μg) of loaded doxorubicin was released. Conclusions: We have demonstrated in a rat model the feasibility of intra-arterial doxorubicin-loaded-PNIPA-coated-MNP for synergistic dual therapy of HCC using targeted hyperthermia and doxorubicin.

The past decade has seen a vast number of new MRI sequences and a great deal of development of protocols, so that we are left with the question: Does the MRI terrain lend itself to complexity? The answer is no. MRI sequences are made of modules on image contrast and image acquisition. The purpose of this short reprise is to compile the well-established methods based on this modular approach together with recent advances in MRI. This will take away the mystery of seemingly complex MRI sequences. An MRI sequence can be expressed as a series of time events. For instance, in conventional imaging, a Spin Echo sequence refers to a timed series comprising excitation – refocussing – readout and a Gradient Echo sequence refers to a timed series of excitation – dephasing – readout. These sequences are then repeated along the phase encoding direction. In a more generalised term this comprises the steps of excitation – phase encoding – frequency encoding. The image contrast relies mainly on TR and TE in a conventional sense. Fast imaging is achieved through a transformation of this sequence. The sequence is now an ordered list of events: Preparation – evolution – detection, this initial idea dating back to 1990 by Haase et al. [1]. The first part of such a sequence prepares for image contrast whilst the second creates the contrast, and these evolve over time. This is followed by a detection part, which can yield the spatial resolution in one go, or even over a time course. In the last decade, ‘The many combinations of MRI’ [2] for structural and functional images rich in contrast have entered clinical routine. In this article, we attempt a classification of these MR techniques based on the concept of preparation – evolution – detection with the following subcategories of: • Inversion Recovery prepared sequences • Spin Echo / Gradient Echo prepared sequences • Subtraction imaging • Double preparation-evolution approaches as shown in Table 1. Contrast: Preparation – Evolution The term ‘Preparation’ refers to preparation for T1, T2, and T2* contrast. ‘Evolution’ over time allows the spin system to change. • T1 effects are achieved by inversion of the longitudinal magnetization, which can be in a non-selective manner, spatially-selective, or frequency-selective. The time to inversion recovery of T1 is used for nulling either lipid (STIR/SPAIR), CSF (FLAIR) or background signal in non-contrast MR angiography. Note that in the frequency-selective mode (SPAIR), only the signal-of-interest, e.g. lipid or silicone, follows this scheme of inversion recovery, hence leaving the water signal undisturbed for optimal signal-to-noise ratio. Other applications of TI effects include enhancement in contrast differentiation between grey matter and white matter (MPRAGE, MP2RAGE) or in-flow time in ASL. • T2 contrast is generated by a Spin Echo preparation module. Its TE period can be used for T2 contrast preparation or encoding of diffusion (diffusion-weighted imaging). • T2* weighting during a Gradient Echo sequence serves as a contact time for water in blood to exchange with deoxyor meth-haemoglobin/ hemosiderin deposits, to detect haemorrhagic lesions, or with oxy/ deoxy-haemoglobin to produce BOLD contrast in fMRI, or to assess liver and cardiac iron overload. • No contrast preparation: The FLASH sequence can produce PD/T1/T2*weighted tissue contrast depending on the acquisition parameters, whilst TrueFISP exhibits an intrinsic T1/T2 contrast. How-I-do-it 82 MAGNETOM Flash | 5/2014 | www.siemens.com/magnetom-world

BACKGROUND:There have been no previous diffusion tensor imaging (DTI) studies comparing Parkinson's disease (PD) with postural instability and gait disorder (PIGD) parkinsonism.OBJECTIVE:Utilizing DTI with 2-region tractography, we conducted a case control study to determine if different brain regions representing the neural network of the motor system are differentially affected in PIGD compared to PD and controls.METHODS:On a 3 T MR machine, using manual ROI (regions of interest) we determined the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values on DTI in anatomical brain regions representing the extrapyramidal, pyramidal, and transcallosal tracts, aided by 2-region tractography. FA and ADC were correlated with the Tinetti score (measure of gait and balance).RESULTS:Sixty-five subjects (21 PD, 25 PIGD, 19 controls) were included in the analysis. We demonstrated greater ADC abnormalities in the extrapyramidal, pyramidal and transcallosal motor systems in PIGD compared to controls. Multivariate analysis taking into consideration various clinical variables showed that the FA (p = 0.02) and ADC (p = 0.001) values in the corpus callosum body differentiated PIGD from PD. PIGD with low Tinetti score had a lower FA (p = 0.02) and a higher ADC value (corpus callosum body) (p = 0.03) compared to those with a high score.CONCLUSIONS:We demonstrated for the first time that DTI abnormalities along the transcallosal motor tract in the body of the corpus callosum, but not the substantia nigra, differentiated PIGD from PD, and the degree of corpus callosum body abnormality correlated with the Tinetti score (a measure of risk of falls).

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FazitDie kombinierte ADC-MRS-Analyse mit residualer Lipidfraktion als Zusatzinformation kann sich bei leichten Traumata zur Differenzierung von benignen und metastatischen Wirbelfrakturen als hilfreich erweisen. Die Differenzierung gelang in dieser Gruppe am zuverlässigsten, wenn die Lipidfraktion vernachlässigbar war.

This paper describes a novel microbend fiber optic sensor system for respiratory monitoring and respiratory gating in the MRI environment. The system enables the noninvasive real-time monitoring and measurement of breathing rate and respiratory/body movement pattern of healthy subjects inside the MRI gantry, and has potential application in respiratory-gated image acquisition based on respiratory cues. The working principle behind this sensor is based on the microbending effect of an optical fiber on light transmission. The sensor system comprises of a 1.0-mm-thin graded-index multimode optical fiber-embedded plastic sensor mat, a photoelectronic transceiver, and a computer with a digital signal processing algorithm. In vitro testing showed that our sensor has a typical signal-to-noise ratio better than 28 dB. Clinical MRI trials conducted on 20 healthy human subjects showed good and comparable breathing rate detection (with an accuracy of ±2 bpm) and respiratory-gated image quality produced using the sensor system, with reference to current predicate hospital device/system. The MRI safe, ease of operation characteristics, low fabrication cost, and extra patient comfort offered by this system suggest its good potential in replacing predicate device/system and serve as a dual function in real-time respiratory monitoring and respiratory-gated image acquisition at the same time during MRI.