Radial Imaging Research Articles

Self-gated cardiac Cine MRI of the rat on a clinical 3 T MRI system.

The ability to perform small animal functional cardiac imaging on clinical MRI scanners may be of particular value in cases in which the availability of a dedicated high field animal MRI scanner is limited. Here, we propose radial MR cardiac imaging in the rat on a whole-body clinical 3 T scanner in combination with interspersed projection navigators for self-gating without any additional external triggering requirements for electrocardiogram (ECG) and respiration. Single navigator readouts were interspersed using the same TR and a high navigator frequency of 54 Hz into a radial golden-angle acquisition. The extracted navigator function was thresholded to exclude data for reconstruction from inhalation phases during the breathing cycle, enabling free breathing acquisition. To minimize flow artifacts in the dynamic cine images a center-out half echo radial acquisition scheme with ramp sampling was used. Navigator functions were derived from the corresponding projection navigator data from which both respiration and cardiac cycles were extracted. Self-gated cine acquisition resulted in high-quality cardiac images which were free of major artifacts with spatial resolution of up to 0.21 × 0.21 × 1.00 mm(3) and a contrast-to-noise ratio (CNR) of 21 ± 3 between the myocardium and left ventricle. Self-gated golden ratio based radial acquisition successfully acquired cine images of the rat heart on a clinical MRI system without the need for dedicated animal ECG equipment.

Isotropic diffusion weighting for measurement of a high-resolution apparent diffusion coefficient map using a single radial scan in MRI

This work proposes an isotropic diffusion weighting method for a high-resolution diffusion-weighted image and for a high-resolution apparent diffusion coefficient (ADC) map using a single radial scan in MRI. By using a conventional radial imaging technique, a high-resolution diffusion-weighted (DW) image can be obtained at the cost of a long imaging time. To reduce the imaging time, the proposed method acquires a DW image by altering the diffusion gradient directions for each radial spoke. The acquisition order and directions of the diffusion gradients for an accurate DW image and an ADC map are also proposed by modifying the golden angle ratio in 3D space. In addition, an individual-direction diffusion-weighted (id-DW) image can also be obtained by a diffusion gradient direction, which is one of the multiple directions used in isotropic diffusion weighting. Computer simulations and experiment results show that the proposed method is more accurate and faster than the conventional radial diffusion-weighted imaging. This study suggests that the proposed isotropic diffusion-weighted imaging can be used to obtain a DW image and a high-resolution ADC map accurately in a single radial scan, while reducing the artifacts caused by the diffusion anisotropy, compared to the diffusion-weighted echo-planar-imaging.

100% Efficient three-dimensional coronary MR angiography with two-dimensional beat-to-beat translational and bin-to-bin affine motion correction.

To develop a flexible image navigator for 3D coronary MR angiography that allows respiratory motion of variable complexity to be compensated for on different temporal scales. A two-dimensional (2D) golden radial image navigator is proposed; translational motion is compensated for on a beat-to-beat basis, and residual affine motion is compensated for on a bin-to-bin basis in a two-step procedure. The method does not use a respiratory gating window and therefore achieves 100% scan efficiency and a predictable scan time. The proposed method was tested in 11 healthy volunteers and compared against a navigator-gated and tracked acquisition. The proposed method achieved comparable quantitative and qualitative image quality to a 6-mm navigator-gated and tracked scan while reducing the scan time by a factor of approximately 2. Combined motion correction using image navigators improved visualization of the coronary arteries in four of 11 subjects in comparison with translational correction only, and image quality was maintained in the remaining cases. In one case, visualization of the left anterior descending coronary artery was degraded using combined correction compared with translation correction only. The feasibility of correcting for 2D translational motion on a beat-to-beat basis as well as affine motion on a bin-to-bin basis has been demonstrated.

Free-breathing, zero-TE MR lung imaging.

The investigation of three-dimensional radial, zero-echo time (TE) imaging for high-resolution, free-breathing magnetic resonance (MR) lung imaging using prospective and retrospective motion correction. Zero-TE was implemented similarly to the rotating-ultra-fast-imaging-sequence, providing 3D, isotropic, radial imaging with proton density contrast. Respiratory motion was addressed using prospective triggering (PT), prospective gating (PG) and retrospective gating (RG) with physiological signals obtained from a respiratory belt and interleaved pencil beam and DC navigators. The methods were demonstrated on four healthy volunteers at 3T. 3D, radial zero-TE imaging with high imaging bandwidth and nominally zero echo-time enables efficient capture of short-lived signals from the lung parenchyma and the vessels. Compared to Cartesian encoding, unaccounted for free-breathing respiration resulted in only benign blurring artifacts confined to the origin of motion. Breath holding froze respiration but achieved only limited image resolution (~1.8 mm, 30 s). PT and PG obtained similar quality expiratory-phase images at 1.2 mm resolution in ~6 min scan time. RG allowed multi-phase imaging in ~15 min, derived from eight individually stored averages. Zero-TE appears to be an attractive pulse sequence for 3D isotropic lung imaging. Prospective and retrospective approaches provide high-quality, free-breathing MR lung imaging within reasonable scan time.

The Relationship Between Cam Lesion and Physis in Skeletally Immature Patients

Although it has been postulated that injury to the proximal femoral physis results in the formation of a cam lesion, a clear causal association has not been established. The purpose of this study was to investigate the relationship between the physis and the cam lesion. Our hypotheses were that (1) the location of the cam lesion would coincide with the growth plate and (2) the distance between the cam lesion and the physis would vary as a function of skeletal maturity. A retrospective review of the charts and magnetic resonance images of adolescent patients with femoroacetabular impingement (FAI) was performed. Data collected included the alpha angle, the distance between the cam lesion and physis, and physeal status. Linear mixed models were used to describe the association between the distance to the cam lesion and physeal status. Twenty-four hips in 17 patients were included. The average alpha angles were 50.7, 63.2, 64.4, and 63.9 degrees for the anterior, anterosuperior, superoanterior, and superior radial magnetic resonance imaging sections. The average distance from the cam lesion to the physis was 0.07 cm. There was a significant association between physeal status and the distance of the cam lesion to the physis. The location of the cam lesion occurs at the level of the physis. In skeletally mature adolescents, the cam lesion is located further from the physis than it is in patients whose growth plates remain widely open. This suggests a possible causal relationship between physeal injury and the development of the cam deformity in patients with femoroacetabular impingement. Level IV-retrospective case series.

Acceleration and motion‐correction techniques for high‐resolution intravascular MRI

High-resolution intravascular (IV) MRI is susceptible to degradation from physiological motion and requires high frame-rates for true endoscopy. Traditional cardiac-gating techniques compromise efficiency by reducing the effective scan rate. Here we test whether compressed sensing (CS) reconstruction and ungated motion-compensation using projection shifting, could provide faster motion-suppressed, IVMRI. CS reconstruction is developed for undersampled Cartesian and radial imaging using a new IVMRI-specific cost function to effectively increase imaging speed. A new motion correction method is presented wherein individual IVMRI projections are shifted based on the IVMRI detector's intrinsic amplitude and phase properties. The methods are tested at 3 Tesla (T) in fruit, human vessel specimens, and a rabbit aorta in vivo. Images are compared using structural-similarity and "spokal variation" indices. Although some residual artifacts persisted, CS acceleration and radial motion compensation strategies reduced motion artifact in vitro and in vivo, allowing effective accelerations of up to eight-fold at 200-300 µm resolution. The 3T IVMRI detectors are well-suited to CS and motion correction strategies based on their intrinsic radially-sparse sensitivity profiles and high signal-to-noise ratios.

Balanced UTE-SSFP for 19F MR imaging of complex spectra.

A novel technique for highly sensitive detection of multiresonant fluorine imaging agents was designed and tested with the use of dual-frequency 19F/1H ultrashort echo times (UTE) sampled with a balanced steady-state free precession (SSFP) pulse sequence and three-dimensional (3D) radial readout. Feasibility of 3D radial balanced UTE-SSFP imaging was demonstrated for a phantom comprising liquid perfluorooctyl bromide (PFOB). Sensitivity of the pulse sequence was measured and compared with other sequences imaging the PFOB (CF2 )6 line group including UTE radial gradient-echo (GRE) at α = 30°, as well as Cartesian GRE, balanced SSFP, and fast spin-echo (FSE). The PFOB CF3 peak was also sampled with FSE. The proposed balanced UTE-SSFP technique exhibited a relative detection sensitivity of 51 μmolPFOB(-1) min(-1/2) (α = 30°), at least twice that of other sequence types with either 3D radial (UTE GRE: 20 μmolPFOB(-1) min(-1/2) ) or Cartesian k-space filling (GRE: 12 μmolPFOB(-1) min(-1/2) ; FSE: 16 μmolPFOB(-1) min(-1/2) ; balanced SSFP: 23 μmolPFOB(-1) min(-1/2) ). In vivo imaging of angiogenesis-targeted PFOB nanoparticles was demonstrated in a rabbit model of cancer on a clinical 3 Tesla scanner. A new dual 19F/1H balanced UTE-SSFP sequence manifests high SNR, with detection sensitivity more than two-fold better than traditional techniques, and alleviates imaging problems caused by dephasing in complex spectra.

Projective Texturing Uncertain Geometry: silhouette-aware box-filtered blending using integral radial images

Abstract. Projective texturing is a commonly used image based rendering technique that enables the synthesis of novel views from the blended reprojection of nearby views on a coarse geometry proxy approximating the scene. When scene geometry is inexact, aliasing artefacts occur. This introduces disturbing artefacts in applications such as street-level immersive navigation in mobile mapping imagery, since a pixel-accurate modelling of the scene geometry and all its details is most of the time out of question. The filtered blending approach applies the necessary 1D low-pass filtering on the projective texture to trade out the aliasing artefacts at the cost of some radial blurring. This paper proposes extensions of the filtered blending approach. Firstly, we introduce Integral Radial Images that enable constant time radial box filtering and show how they can be used to apply box-filtered blending in constant time independently of the amount of depth uncertainty. Secondly, we show a very efficient application of filtered blending where the scene geometry is only given by a loose depth interval prior rather than an actual geometry proxy. Thirdly, we propose a silhouette-aware extension of the box-filtered blending that not only account for uncertain depth along the viewing ray but also for uncertain silhouettes that have to be blurred as well.

The conceptual design of an electron cyclotron emission imaging system for studying ITER-like high temperature plasmas

The design of an electron cyclotron emission imaging (ECEI) system for two-dimensional (2D) observation of the magnetohydrodynamical modes in high temperature ITER (from ‘International Thermonuclear Experimental Reactor’) H-mode-like plasmas (5.3 T and 25 keV) based on fundamental ordinary mode (O1-mode) and second-harmonic extraordinary mode (X2-mode) measurements is explored conceptually. For studying the spatial resolution in high temperature plasmas, the relativistic broadening and inward shift of the emission layer in the mid-plane are calculated. The radial spatial resolution is significantly degraded in the range R < 5.1 m for the O1-mode and in the range R < 6.9 m for the X2-mode. The region with R < 6.5 m is inaccessible for X2-mode study. The emission layer width is enlarged in a narrow region of the pedestal due to the magnetic field being modified by the large pressure gradient. The broadening and shift in the poloidal plane are also calculated, to investigate their effects on 2D measurements. The frequency range of electron cyclotron emission measurements is selected to protect the system from stray radiations of the 170 GHz electron cyclotron resonance heating source and to avoid harmonic overlap. The frequency ranges of 115–160 GHz for the O1-mode and 230–320 GHz for the X2-mode provide radial coverage of 5.9 < R < 8.2 m or −0.15 < r/a < 1.The ECEI system utilizes a dual-array detection technique which provides a simultaneous measurement at two radial positions, and each array has 8 by 16 (radial by vertical) channels. The radial image size with 8 channels is ∼41–76 cm for the O1-mode and ∼19–36 cm for the X2-mode, with sufficient resolution. The front-end optics, which focuses the electron cyclotron emission to the low loss corrugated transmission waveguides, is designed with two flat mirrors and two focusing mini-lens arrays. The vertical image size with 16 channels is ∼150 cm and the spot size of each channel is 8–15 cm in the plasma region, taking into account the sensitivity pattern of the waveguide. The refraction effect due to inhomogeneous plasma enlarges the vertical image size up to 20% and 5% for the O1-mode and X2-mode cases, respectively. The horizontal distortion due to the relativistic inwards shift is reduced by the increased toroidal field in the core region.

Oxygen-enhanced 3D radial ultrashort echo time magnetic resonance imaging in the healthy human lung.

The purpose of this work was to use 3D radial ultrashort echo time (UTE) MRI to perform whole-lung oxygen-enhanced (OE) imaging in humans. Eight healthy human subjects underwent two 3D radial UTE MRI acquisitions (TE = 0.08 ms): one while breathing 21% O2 and the other while breathing 100% O2. Scans were each performed over 5 min of free breathing, using prospective respiratory gating. For comparison purposes, conventional echo time (TE = 2.1 ms) images were acquired simultaneously during each acquisition using a radial " outward-inward" k-space trajectory. 3D percent OE maps were generated from these images. 3D OE maps showing lung signal enhancement were generated successfully in seven subjects (technical failure in one subject). Mean percent signal enhancement was 6.6% ± 1.8%, near the value predicted by theory of 6.3%. No significant enhancement was seen using the conventional echo time data, confirming the importance of UTE for this acquisition strategy. 3D radial UTE MRI shows promise as a method for OE MRI that enables whole-lung coverage and isotropic spatial resolution, in comparison to existing 2D OE methods, which rely on a less time-efficient inversion recovery pulse sequence. These qualities may help OE MRI become a viable low-cost method for 3D imaging of lung function in human subjects.

Diagnostic accuracy of magnetic resonance imaging for subscapularis tendon tears using radial-slice magnetic resonance images

Magnetic resonance imaging has low diagnostic accuracy for subscapularis tendon tears. This study investigated the utility of radial-slice magnetic resonance images for diagnosing subscapularis tendon tears. We investigated 55 shoulders in 54 patients with rotator cuff tears evident during arthroscopic shoulder surgery. The intraoperative finding of a subscapularis tendon tear was compared with the identification of a subscapularis tendon tear on preoperative radial, transverse, and oblique sagittal images using a 3.0-T system. The sensitivity and specificity of diagnostic images generated using different imaging methods for subscapularis tendon tears were investigated. A subscapularis tendon tear was present in 38 shoulders (69.1%). When the diagnostic accuracy of the magnetic resonance images was compared with the arthroscopic findings, the radial images had 94.7% sensitivity and 82.4% specificity, the transverse images had 57.9% sensitivity and 100% specificity, and the oblique sagittal images had 60.5% sensitivity and 100% specificity. Radial-slice magnetic resonance images have high sensitivity for subscapularis tendon tears and are useful for diagnosing these lesions. In particular, the sensitivity for tears in the superior part of the subscapularis tendon is higher than that of conventional methods.

SU‐F‐18C‐03: Loss of Image Sharpness in CT Bone Imaging Due to Positioning Within the Scan Field of View – Possible Solutions

Purpose:To demonstrate how both the positioning of an object in the scan field of view (SFOV) and the size of the reconstructed field of view (RFOV) can both significantly affect and degrade the image sharpness.Methods:Clinical CT scans of the shoulders and elbows were inspected for image sharpness. GE scanners were used for the imaging with a “Bone Plus” reconstruction algorithm. In all scans the anatomy of interest was significantly displaced from the center of the SFOV (away from the scanner iso‐center). Radial and azimuthal image sharpness measurements using the Modulation Transfer Function (MTF) were made using the same RFOV at the center of the SFOV and at varying distances from the center. These MTF measurements were also made with varying values of the RFOV.Results:Clinical images with the bone anatomy of interest positioned farther from the center of the SFOV showed increasing image softness occasionally to the point of being non‐diagnostic. The MTF measurements showed that the resolution degraded significantly, by more than a factor of 2, moving from the center toward the periphery of the SFOV: from 12 cycles/cm to less than 6 cycles/cm at distances of 15 cm or more from the center of the SFOV. Increasing the RFOV beyond 20 cm also degraded the resolution, though less significantly.Conclusion:When preservation of bone detail is important one must not only use the proper bone reconstruction algorithm, but also must keep the body part as close to the center of the SFOV as possible. Though this may be difficult with some imaging tasks, such as imaging of the shoulder and elbow, every effort should be made to this end. For the best resolution, the RFOV should also be kept small, ideally to 20 cm or less.Partial research funding from GE HealthCare.

Frequency of anatomic variations of radial artery in patients undergoing transradial heart catheterisation

Over the last ten years, transradial cardiac catheterisation has been increasingly applied, primarily because of its lower incidence of complications compared to the femoral approach. However, one of the greatest flaws of the transradial approach is a relatively high incidence of catheterisation failure (1-5%). Anatomic variations of the radial artery are ranked second among the reasons for this. Previous studies have not provided unambiguous data on the frequency of them. It is therefore the aim of this study to determine the frequency of anatomic variations using routine angiographies of the radial artery (RA) during the left heart catheterisation at the Interventional Cardiology Unit of the University Hospital Centre Zagreb in 2013. Seven hundred and fortynine such cardiac catheterisations were carried out during the studied period. All the images were examined and, after selection, 602 remained for further research. The process of selection required all patients to be of age and to have an accurate image of radial artery angiography. Correctly performed radial artery imaging involved the imaging of the division of the brachial artery into the ulnar and radial arteries. It also implied the visibility of at least half of the radial and half of the brachial artery. Anatomic variations are classified in accordance with the classification provided by Burzotta et al. Of the total of 602 patients, 414 (68.8%) were men and 188 were women. The youngest patient was 18 and the oldest one was 87 (mean±SD; 64±10.78), with a normal distribution of subjects across the age groups. In 538 (89.4%) of patients, cardiac catheterisation was performed through the right arm. The frequency of anatomic variations of RA was 8.8%, exclusive of tortuosities whose frequency was 12.7%. The most frequent anatomic variation was the high origin of the radial artery, found in a total of 31 (5.1%) subjects. Radioulnar loops, being one of potential contraindications for the procedure, were reported in 2% of the cases. Regression analysis revealed that age (p<0.001), female sex (p=0.015) and high origin (p=0.034) statistically significantly contributed to the development of tortuosity. The results indicate that the incidence of tortuosity increases linearly with age. Although this is not a contraindication for continuing with the procedure, we recommend that elderly patients should have angiography performed at the beginning of the procedure due to a higher frequency of tortuosity.

Using self-consistency for an iterative trajectory adjustment (SCITA).

To iteratively correct for deviations in radial trajectories with no need of additionally performed calibration scans. Radially acquired data sets-even when undersampled to a certain extend-inherently feature an oversampled area in the center of k-space. Thus, for a perfectly measured trajectory and neglecting noise, information is consistent between multiple measurements gridded to the same Cartesian position within this region. In the case of erroneous coordinates, this accordance-and therefore a correction of the trajectory-can be enforced by an algorithm iteratively shifting the projections with respect to each other by applying the GRAPPA operator. The method was validated in numerical simulations, as well as in radial acquisitions of a phantom and in vivo images at 3T. The results of the correction were compared to a previously proposed correction method. The newly introduced technique allowed for a reliable trajectory correction in each of the presented examples. The method was able to remove artifacts as effectively as methods that are based on data from additional calibration scans. The iterative technique introduced in this paper allows for a correction of trajectory errors in radial imaging with no need for additional calibration data.

CT assessment of asymptomatic hip joints for the background of femoroacetabular impingement morphology

The purposes of this study were to assess the presence of cam and pincer morphology in asymptomatic individuals with a negative femoroacetabular impingement test, and to determine and compare the ranges of alpha angle using two measurement methods. In total, 68 consecutive patients who underwent abdominopelvic computed tomography (CT) for reasons other than hip problems were the patient population. Patients who had a positive femoroacetabular impingement test were excluded. Alpha angle measurements from axial oblique (AN) and radial reformat-based images (AR) from the anterior through the superior portion of the femoral head-neck junction, as well as femoral head-neck offset, center-edge angle, acetabular version angle measurements, and acetabular crossover sign assessment, were made. Overall prevalences of cam (increased alpha angle, decreased femoral head-neck offset) and pincer morphology (increased center-edge angle, decreased acetabular version) were 20.0%, 26.8%, 25.8%, and 10.2% of the hips, respectively. The mean AR ranged from 41.64° ± 4.23° to 48.13° ± 4.63°, whereas AN was 41.10° ± 4.44°. The values of AR were higher than AN, and the difference was statistically significant (P <0.001). The highest AR values were measured on images from the anterosuperior section of femoral head-neck junction. In asymptomatic subjects, higher alpha angle values were obtained from radial reformatted images, specifically from the anterosuperior portion of the femoral head-neck junction compared with the axial oblique CT images. Other measurements used for the assessment of cam and pincer morphology can also be beyond the ranges that are considered normal in the general population.

Radial modulation contrast imaging using a 20-mhz single-element intravascular ultrasound catheter

Contrast-enhanced intravascular ultrasound imaging is a promising tool for the characterization of coronary vasa vasorum proliferation, which has been identified as a marker of, and possible etiologic factor in, the development of high-risk atherosclerotic plaques. Resonance-based nonlinear detection methods have required the development of prototype catheters which are not commercially available, thus limiting clinical translation. In this study, we investigated the performances of a radial modulation imaging approach (25/3 MHz combination) using simulations, implemented it on a clinical 20-MHz rotating catheter, and tested it in a wall-less tissue-mimicking flow phantom perfused with lipid-encapsulated microbubbles (MBs). The effects of the phase lag, low-frequency pressure, and MB concentration on the envelope subtracted radial modulation signals were investigated as a function of depth. Our dual-pulse dual-frequency approach produced contrast-specific images with contrast-to-tissue improvements over B-mode of 15.1 ± 2.1 dB at 2 mm and 6.8 ± 0.1 dB at 4 mm depths. Using this imaging strategy, 200 μm-diameter cellulose tubing perfused with MBs could be resolved while surrounding tissue scattering was suppressed. These results raise promise for the detection of coronary vasa vasorum and may ultimately facilitate the detection of plaque at risk for rupture.

Influence of asynchronous actuation of the Angara-5-1 facility modules on the penetration of the magnetic field inside a wire array

The influence of asynchronous actuation of the Angara-5-1 facility modules on the implosion symmetry of the wire array plasma in the Z-pinch mode is studied. It is shown that an increase in the r.m.s. jitter in the start times of the modules leads to an appreciable azimuthal asymmetry of magnetic field penetration inside the wire array and, as a consequence, to an increase in the duration of the soft X-ray pulse, a decrease in its power, and a shift of the Z-pinch with respect to the array axis. Necessary conditions for axisymmetric pinch implosion are determined. Experimental data on the magnitude and azimuthal distribution of the current (magnetic field) inside the wire array were obtained from magnetic probe measurements. The position of the Z-pinch with respect to the wire array axis was determined from two-dimensional X-ray images and radial optical streak images.

Radial modulation contrast imaging using a 20-MHz single-element intravascular ultrasound catheter.

Contrast-enhanced intravascular ultrasound imaging is a promising tool for the characterization of coronary vasa vasorum proliferation, which has been identified as a marker of, and possible etiologic factor in, the development of high-risk atherosclerotic plaques. Resonance-based nonlinear detection methods have required the development of prototype catheters which are not commercially available, thus limiting clinical translation. In this study, we investigated the performances of a radial modulation imaging approach (25/3 MHz combination) using simulations, implemented it on a clinical 20-MHz rotating catheter, and tested it in a wall-less tissue-mimicking flow phantom perfused with lipid-encapsulated microbubbles (MBs). The effects of the phase lag, low-frequency pressure, and MB concentration on the envelope subtracted radial modulation signals were investigated as a function of depth. Our dual-pulse dual-frequency approach produced contrast- specific images with contrast-to-tissue improvements over B-mode of 15.1 ± 2.1 dB at 2 mm and 6.8 ± 0.1 dB at 4 mm depths. Using this imaging strategy, 200-μm-diameter cellulose tubing perfused with MBs could be resolved while surrounding tissue scattering was suppressed. These results raise promise for the detection of coronary vasa vasorum and may ultimately facilitate the detection of plaque at risk for rupture.

Recent Structural Alteration of the Peripheral Lamina Cribrosa Near the Location of Disc Hemorrhage in Glaucoma

We investigated whether disc hemorrhage (DH) is associated with the recent structural alteration of the peripheral lamina cribrosa (LC) as assessed by enhanced depth imaging (EDI) spectral-domain optical coherence tomography (SD-OCT). Serial horizontal B-scan images were obtained by EDI SD-OCT from primary open-angle glaucoma (POAG) patients before and after the detection of DH (DH group, n = 45), and those who had no DH during the 1-year scan interval (non-DH group, n = 36). The images were processed using compensation and contrast enhancement. Then, 11 radial OCT images centered on the optic disc were generated from the 3-dimensionally reconstructed volume image. A recent structural alteration of the LC was defined when either the outward deformation of the anterior LC surface or radial disruption of the LC was identified in the temporal periphery. A recent structural alteration of the LC was found in 40 (88.9%) eyes in the DH group versus 4 (11.1%) eyes in the non-DH group. The amount of maximum outward deformation (55.82 ± 34.60 vs. 20.15 ± 4.28 μm) and radial disruption (69.87 ± 46.74 vs. 18.31 ± 1.17 μm) was larger in the DH group than in the non-DH group. The maximum LC alteration was observed within 1 clock-hour distance from the location of DH in all 40 eyes. The peripheral LC exhibited a recent alteration in eyes with DH. The alteration was correlated spatially with the location of the DH. These findings suggest that DH may result from microvascular damage incurred from alteration of the LC near its insertion.

Diffusion tensor imaging analysis of optic radiation using readout-segmented echo-planar imaging.

To investigate the diffusion tensor imaging parameters of the optic radiation and surrounding structures using the high-resolution readout-segmented diffusion tensor imaging method. Coronal readout-segmented diffusion tensor images were acquired in 15 healthy volunteers. On three slices of each image, eigenvalue 1, fractional anisotropy, radial diffusivity, apparent diffusion coefficient, and signal intensity on T2-weighted images were measured in the lateral inferior longitudinal fasciculus, external and internal layers of the optic radiation, and the tapetum within regions of interest delineated by two independent observers. Profile curve analysis of regions of interest across the optic radiation and surrounding structures was performed for a representative typical case. Significant differences in fractional anisotropy, radial diffusivity and apparent diffusion coefficient were observed between external and internal layers of the optic radiation, while there was no significant difference in eigenvalue 1. In fractional anisotropy maps, two low signal bands were observed between the inferior longitudinal fasciculus, the optic radiation and the tapetum. Profile curve analysis showed a minimum on the fractional anisotropy and eigenvalue 1 images and a maximum in the radial diffusivity image. Readout-segmented diffusion tensor imaging revealed significant differences in the diffusion tensor imaging parameters between internal and external layers of the optic radiation.