Usefulness of T2 star-weighted imaging in ovarian cysts and tumors.

AIM: The aim of this study was to investigate the prevalence of hypointensity on T2 star-weighted imaging (T2*WI), which is useful for detecting hemosiderin, in endometriomas and other ovarian tumors. The efficacy of detecting adhesions around ovarian tumors was also investigated. METHODS: Pelvic magnetic resonance (MR) examinations, including T2*WI, were carried out. The inclusion criteria were female patients with ovarian surgical treatments. One hundred seventeen patients with a total of 147 lesions were enrolled. Two radiologists retrospectively evaluated MR imaging (MRI) to predict ovarian pathology and the presence of adhesions. T2*WI hypointensity of the inside and outside along ovarian cysts/tumors was utilized to predict pathological diagnoses and the presence of adhesions, respectively. The kappa scores were calculated to measure interobserver agreement on MRI findings. The MRI interpretations were compared with the results of pathological investigation and surgical observations. RESULTS: Hypointensity inside along the cyst walls on T2*WI was observed in 100 out of 106 lesions of endometriomas (94.3%), and three out of 41 non-endometrial ovarian cysts/tumors (7.3%). Four different patterns of T2*WI were observed in ovarian cysts/tumors. The kappa score regarding T2*WI hypointensity inside along the cyst walls was 0.633. Using conventional routine pelvic MRI, the sensitivity for detecting adhesions around ovarian cysts was 84.5%. By adding T2*WI, the sensitivity improved to 91.4% (P < 0.01). With conventional methods to predict adhesions, the kappa score was 0.660. After adding T2*WI to the conventional methods, the kappa score was 0.767. CONCLUSION: Hypointensity on T2*WI was observed frequently in endometrioma. T2*WI also improved the sensitivity for detecting adhesions around ovarian cysts/tumors.

Relationship between MRI T1 rho value and histological findings of intact and radially incised menisci in microminipigs.

PURPOSE: To examine whether the T1 rho value reflects histological changes in menisci we analyzed the relationship between T1 rho value and histological findings in intact and radially incised menisci of pigs. MATERIALS AND METHODS: Seven microminipigs were used for this experiment. A radial incision was created and repaired in the medial meniscus, which was evaluated 4 weeks after surgery. Sagittal T1 rho mapping images were taken by 3.0T magnetic resonance imaging (MRI). The region of interest was set by dividing the meniscus into six zones (from zone 1 to zone 6). For histological evaluation of intact menisci, characteristics of each zone were determined. In incised menisci, a histological score was used to evaluate pathological change. RESULTS: In intact lateral menisci, the zone where histological findings indicated fibrocartilage showed a lower T1 rho value (34.2 ± 2.3 msec) than hyaline-like cartilage (38.2 ± 2.5 msec) or fibrous tissue (37.2 ± 2.0 msec). In incised medial menisci, T1 rho values increased (about 50-90 msec) in the zone where histological findings indicated that synovial ingrowth, scar tissue formation, and degenerative changes had occurred. There were correlations between T1 rho values and histological scores in all zones (r = 0.62-0.92, P = 0.001-0.026). CONCLUSION: Zonal variations of the T1 rho value were observed in intact menisci due to varying structure in each zone. T1 rho values were correlated with histological changes such as collagen fiber organization and safranin-o stainability in incised menisci. This study supports T1 rho mapping as useful for evaluating ultrastructural composition in menisci.

The superior ophthalmic vein: delineation with high-resolution magnetic resonance imaging.

OBJECTIVE: To delineate the superior ophthalmic vein (SOV) with high-resolution magnetic resonance (MR) imaging. METHODS: This retrospective study enrolled 302 consecutive outpatients, 101 patients, 51 males and 50 females, who underwent coronal T2-weighted imaging and 201 patients, 99 males and 102 females, who underwent three-dimensional (3D) phase-contrast (PC) MR angiography. RESULTS: Coronal T2-weighted imaging clearly delineated the intraorbital course of SOV on serial images in all 101 subjects. The SOV could be topographically divided into three segments in relation to the superior rectus muscle. The SOV crossed over the optic nerve at the level of the anterior ethmoidal foramina in 87% of right orbits and 71% of left orbits. The mean outer diameter of the SOV at the crossing point was 1.7 mm on both sides, but the SOVs were asymmetric in the same individual in 75% of the subjects. 3D PC MR angiography showed that the bilateral SOVs were symmetrical in 16% of subjects, larger in the right orbit in 18%, and larger in the left orbit in 13%, and were unidentified in 52%. The SOV showed a consistent lateral course to the ophthalmic artery. CONCLUSIONS: The SOV consistently courses lateral to the ophthalmic artery, but tends to show bilateral asymmetry in the outer diameter. The superior rectus muscle, anterior ethmoidal foramen, and anterior ethmoidal artery are valuable landmarks to identify the SOV during transcranial orbital surgery. Combination of high-resolution MR imaging and 3D PC MR angiography is useful for delineating the SOV.

Cervical spondylosis: Evaluation of microstructural changes in spinal cord white matter and gray matter by diffusional kurtosis imaging.

INTRODUCTION: We investigated microstructural changes in the spinal cord, separately for white matter and gray matter, in patients with cervical spondylosis by using diffusional kurtosis imaging (DKI). METHODS: We studied 13 consecutive patients with cervical myelopathy (15 affected sides and 11 unaffected sides). After conventional magnetic resonance (MR) imaging, DKI data were acquired by using a 3T MR imaging scanner. Values for fractional anisotropy (FA), apparent diffusion coefficient (ADC), and mean diffusional kurtosis (MK) were calculated and compared between unaffected and affected spinal cords, separately for white matter and gray matter. RESULTS: Tract-specific analysis of white matter in the lateral funiculus showed no statistical differences between the affected and unaffected sides. In gray matter, only MK was significantly lower in the affected spinal cords than in unaffected spinal cords (0.60±0.18 vs. 0.73±0.13, P=0.0005, Wilcoxon's signed rank test). CONCLUSIONS: MK values in the spinal cord may reflect microstructural changes and gray matter damage and can potentially provide more information beyond that obtained with conventional diffusion metrics.

Improvement of T1 contrast in whole-brain black-blood imaging using motion-sensitized driven-equilibrium prepared 3D turbo spin echo (3D MSDE-TSE).

We demonstrated a new scheme for performing the T1-enhanced whole-brain black-blood imaging pulse sequence using motion-sensitized driven-equilibrium prepared 3-dimensional (3D) turbo spin echo (MSDE-TSE) with anti-driven-equilibrium post pulse. The use of an anti-driven-equilibrium pulse considerably improved the T1 contrast of MSDE-TSE black-blood images. This sequence can be used for whole-brain 3D volumetric T1-weighted black-blood imaging and may improve the accuracy of anatomical localization for certain brain lesions.

Whole-brain black-blood imaging with magnetization-transfer prepared spin echo-like contrast: a novel sequence for contrast-enhanced brain metastasis screening at 3T.

In contrast-enhanced (CE) brain metastasis screening, coexistence of enhanced blood vessel suppression and higher tumor-to-parenchyma contrast may improve radiologists' performances in detecting brain metastases compared with conventional sequences. In this study, we propose a new scheme, allowing both suppression of blood signals and improvement of tumor-to-parenchyma contrast, using motion-sensitized driven equilibrium prepared 3D low-refocusing flip-angle turbo spin echo (TSE) ("magnetization transfer prepared spin echo"-like contrast volume examination: MATLVE) for brain metastasis screening at 3.0 T, and we compare MATLVE to conventional three-dimensional (3D)-gradient recalled echo (GRE) and 3D-TSE sequences. With the use of MATLVE, the signal intensity of CE blood decreased substantially. Furthermore, the contrast ratio of tumor-to-white matter was significantly higher than in either conventional 3D-GRE or 3D-TSE. MATLVE can be used for 3D volumetric post-CE black-blood imaging, and it may be effective in detecting small brain metastases by selectively enhancing tumor signals while suppressing blood signals.

Rapid high resolution MR neurography with a diffusion-weighted pre-pulse.

PURPOSE: To introduce, optimize, and assess the feasibility of a new scheme to rapidly acquire high-resolution volumetric neurographic images using a three-dimensional turbo spin-echo sequence combined with a diffusion-weighted pre-pulse called improved motion-sensitized driven equilibrium (iMSDE): Diffusion-prepared MR Neurography (D-prep MRN). METHODS: In order to optimize the signal suppression of blood vessels and muscle at D-prep MRN, coronal lumbosacral plexus images were acquired in five volunteers at 3T, and the following parameters were examined: iMSDE gradient-strength (b-value) of 0, 2 and 10 s/mm² (with the aim to suppress blood vessels) and iMSDE preparation duration (iMSDEprep-time) of 18, 50 and 100 ms (with the aim to suppress muscle signal). Subsequently, the feasibility of the optimized D-prep MRN sequence in visualizing the brachial plexus, lumbosacral plexus, and cranial nerves was evaluated in 5 healthy volunteers. RESULTS: A higher b-value of 10 s/mm² was better in signal suppression of blood vessels, whereas an intermediate iMSDEprep-time of 50 ms provided the best compromise between suppression of muscle signal and minimization of signal loss of nerves. With these parameters, the normal nerve structures showed high signal intensity, while the blood vessels and muscles were effectively suppressed. The optimized D-prep MRN sequence clearly showed the three-dimensional trajectory of the brachial plexus, lumbosacral plexus, and cranial nerves. CONCLUSION: D-prep MRN was introduced and optimized, and clearly showed detailed anatomy of the brachial plexus, lumbosacral plexus, and cranial nerves. These results suggest that the D-prep MRN can be used for fast, high-resolution, volumetric imaging of the peripheral nervous system.

Calvarial diploic venous channels: an anatomic study using high-resolution magnetic resonance imaging.

BACKGROUND: The calvarial diploic venous channels (CDVCs) are well-known intraosseous structures, but their distribution and anatomofunctional implications are not fully understood. OBJECTIVE: To investigate the architecture of CDVCs using high-resolution magnetic resonance (MR) imaging. METHOD: This prospective study enrolled 43 male and 37 female outpatients who underwent a 3.0-T MR imaging equipped by a 32-channel head coil. T1-weighted imaging covering the whole cranial vault was performed after gadolinium injection. In addition, one-piece orbitozygomatic craniotomy was performed in three cadaveric heads to observe the interruption of the CDVCs. RESULTS: The CDVCs showed irregular contours and peculiar branching patterns with four common major pathways: the pteriofrontparietal (PFP), frontoorbital (FO), occipitoparietal (OP), and occipitocervical (OC) routes. The proximal PFP coursed as a single trunk and divided into several branches at the level of the frontal eminence. The orbital part of the FO continued to the subcutaneous vein via the supraorbital rim. The PFP and the pterional part of the FO fused proximally with the sphenoparietal sinus and descended as the middle meningeal vein. The OP coursed in the superoinferior direction and connected the junction part of the transverse-sigmoid sinus to the parietal superior sagittal sinus. The OC occurred as a single trunk in the median occipital bone, drained extracranially, and joined the suboccipital venous channels. CONCLUSIONS: The CDVCs seem to be a relatively consistent network functioning not only as conduits connecting the intracranial dural sinuses but also as pathways to the extracranial venous systems. High-resolution MR imaging is useful for investigating the CDVCs.

Vessel-selective, non-contrast enhanced, time-resolved MR angiography with vessel-selective arterial spin labeling technique (CINEMA-SELECT) in intracranial arteries.

We demonstrate the feasibility of the vessel-selective, non-contrast, time-resolved magnetic resonance angiography (MRA) technique, "contrast inherent inflow enhanced multi-phase angiography combining vessel-selective arterial spin labeling technique (CINEMA-SELECT)". This sequence consists of two major techniques: pulsed star labeling of arterial regions (PULSAR) and Look-Locker sampling. We hypothesize that this technique allows selective labeling of single intracranial arteries, consisting of high-resolution four-dimensional data with a wide coverage of the brain. In this study, a new vessel-selective, time-resolved angiographic technique is demonstrated that can produce individual angiograms non-invasively by labeling the principal arterial vessels proximal to the circle of Willis. Clear vessel delineation is achieved, and the separation of the three vessels is evident in healthy volunteers. This technique could play an important role in the assessment of the structure and hemodynamics of intracranial arteries without the use of contrast agents.

Reevaluation of T2-weighted fast field echo (T2FFE): application to rapid volumetric black-blood imaging.

T2-fast field echo (T2FFE) sequence is a rapid T2-weighted steady state free precession sequence, but has not become a widely utilized MR-imaging strategy because of its low signal-to-noise ratio and high sensitivity to motion. These effects have seriously limited the clinical use of T2FFE and therefore T2FFE has not been used for routine clinical studies. Nevertheless, in this study, we have investigated the possibility of clinical application by re-optimization of the T2FFE on the current MRI systems. Our purpose in this study was to explore the sensitivity of T2FFE to flow spins using a flow phantom and a contrast optimization/comparison with 2D turbo spin-echo (TSE) T2-weighted images, and to evaluate its feasibility in volunteers and patients. This study demonstrated that the T2FFE sequence achieves rapid 3D T2-weighted black-blood imaging while minimizing the impact of motion using a low flip angle under the shortest repetition time and the shortest echo time conditions. Furthermore, 3D T2FFE with use of an optimal flip angle (30°-40°) can provide contrast equivalent to that of 2D TSE T2-weighted images. This proposed T2FFE sequence might be promising for numerous clinical applications.

An anatomic study of the inferior oblique nerve with high-resolution magnetic resonance imaging.

OBJECTIVE: To investigate anatomic features of the inferior oblique nerve (IObN) by high-resolution magnetic resonance (MR) imaging and cadaveric dissection. METHODS: This study enrolled 100 consecutive outpatients, who underwent 3.0 T MR imaging equipped by the 32-channel head coil. The T2-weighted imaging data of IObN were extracted for analysis and compared with the findings of microsurgical dissection in 14 orbits. RESULTS: 50 male and 50 female subjects allotted to the imaging study were aged from 11 to 78 years. In 94 % sides, the IObN was found to separate from the inferior rectus muscle (IRM) at the level just behind to the posterior pole of the bulb. At the midpoint of the IObN part coursing along the orbital floor and above or adjacent to the infraorbital nerve and artery complex, the mean distance from the lateral margin of the IRM was 1.0 mm on the right and 0.9 mm on the left. The IObN showed upward direction change just below the belly of the inferior oblique muscle and innervated to it at the equator level in 78 sides on the right and 89 on the left. Dissected specimens revealed the consistent morphological findings of the IObN. CONCLUSIONS: The IObN seems to be a relatively consistent structure. Anatomic information on the IObN and surrounding structures that are provided by high-resolution MR imaging can be a help for safe surgery.

Venous lacunae presenting with unusual upward protrusion: an anatomic study using high-resolution magnetic resonance imaging.

PURPOSE: This study aims to investigate the distribution and anatomic features of venous lacuna presenting with unusual upward protrusion (VLUUP) using high-resolution magnetic resonance (MR) imaging. METHODS: This retrospective study included 59 consecutive outpatients who underwent MR imaging with gadolinium. Acquired imaging data were transferred to a workstation for analysis. RESULTS: The 30 male and 29 female subjects were aged from 10 to 76 years. A total of 46 VLUUPs located parasagittally were identified in 36 of the 59 patients, 24 on the right, and 22 on the left; 29 patients had one VLUUP, 4 patients had two, and 3 patients had three. Most VLUUPs (93 %) were distributed in the posterior third of the frontal region and the remainder (7 %) in the middle third. There were no VLUUP found in the anterior third of the frontal region or the parietal or occipital regions. The mean longitudinal and lateral dimensions of the VLUUPs and distance from the midline to the medial margin of the VLUUP were 9.7 mm (3.1-27.6), 6.9 mm (3.1-11.5), and 14.3 mm (1.6-43.5), respectively. CONCLUSIONS: The VLUUPs carry a higher risk of injury when making a bony window in or involving the parasagittal posterior frontal region. High-resolution MR imaging is useful for delineating the VLUUPs.

[Non-contrast time-resolved magnetic resonance angiography combining high resolution multiple phase echo planar imaging based signal targeting and alternating radiofrequency contrast inherent inflow enhanced multi phase angiography combining spatial resolution echo planar imaging based signal targeting and alternating radiofrequency in intracranial arteries].

Detailed information on anatomy and hemodynamics in cerebrovascular disorders such as AVM and Moyamoya disease is mandatory for defined diagnosis and treatment planning. Arterial spin labeling technique has come to be applied to magnetic resonance angiography (MRA) and perfusion imaging in recent years. However, those non-contrast techniques are mostly limited to single frame images. Recently we have proposed a non-contrast time-resolved MRA technique termed contrast inherent inflow enhanced multi phase angiography combining spatial resolution echo planar imaging based signal targeting and alternating radiofrequency (CINEMA-STAR). CINEMA-STAR can extract the blood flow in the major intracranial arteries at an interval of 70 ms and thus permits us to observe vascular construction in full by preparing MIP images of axial acquisitions with high spatial resolution. This preliminary study demonstrates the usefulness of the CINEMA-STAR technique in evaluating the cerebral vasculature.

Optimization of 3D-variable refocusing flip angle RARE imaging for high-resolution volumetric black-blood angiography.

3D rapid acquisition with relaxation enhancement or turbo spin-echo sequence is promising for black-blood angiography. In this paper, we propose a new scheme of sequence parameter optimization for "flow-void enhanced" volumetric black-blood angiography. Although black-blood imaging has numerous applications, we focused on the carotid artery in this study. All experiments were performed on a 3.0-T imager. The methods used were a flow phantom study and a volunteer study. From the results, the optimal parameters for black-blood angiography were the use of very-low refocusing flip angles, use of a "90° + α/2" refocusing flip angle sweep, and "flow sensitization" at the "in-plane flow" situational imaging plane. This sequence can be used for 3D volumetric black-blood angiography and vessel wall imaging.

Visualization of the ophthalmic artery by phase-contrast magnetic resonance angiography: a pilot study.

OBJECTIVE: This study aimed at investigating whether phase-contrast (PC) magnetic resonance (MR) angiography is useful for visualizing the ophthalmic artery (OA). METHODS: This prospective study enrolled 196 consecutive outpatients who underwent three-dimensional PC MR angiography. The basal image parallel to the anteroposterior dimension of the OA was extracted for analysis from the imaging data. RESULTS: The 99 male and 97 female subjects were aged from 10 years to 80 years (mean 47.9 years). The OAs were supplied only by the external carotid system or in combination with the internal carotid artery (ICA) in 18 subjects (9.2%). The bilateral OAs were symmetrical in 12%, asymmetrical in 87%, and unidentified in 1%. The contour of the proximal segment of the OAs could be classified into straight, curved, and tortuous types. The ICA-OA angle defined by the angle between the approximate line of the proximal OA and the vertical line was also variable. The first bend of the OA corresponded to the anastomosis site with the external carotid system. The proximal medial bend was the origin of the posterior ethmoidal artery, and the distal medial bend was the origin of the anterior ethmoidal artery. CONCLUSIONS: According to the results the OA not only possesses three characteristic bends, but also shows prominent individual variability and commonly shows bilateral asymmetry. The contour of the OA may be regulated by the anchor effect at the bend sites. PC MR Angiography is useful for visualizing the main trunk of the OA.

The Virchow-Robin spaces: delineation by magnetic resonance imaging with considerations on anatomofunctional implications.

INTRODUCTION: The Virchow-Robin spaces (V-R spaces) are well-known, but not systematically understood fluid-filled perivascular spaces that allow the convexity and basal perforating vessels to penetrate deep into the cerebral parenchyma. OBJECTIVE: This study aims to delineate anatomical characteristics of the normal V-R spaces by MR imaging with considerations on clinical and anatomofunctional implications of the V-R spaces. METHODS: In this prospective study with 3T magnetic resonance (MR) imaging, the whole extent of the intracranial V-R spaces was classified into basal, cortical, subcortical, paraventricular, and brainstem segments, on the basis of the topological difference in 105 control subjects. Morphological characteristics in each segment of the V-R spaces are described. For comparison with the neuroimaging appearance, V-R spaces were histologically examined in cadaveric human brains. The physiological functions of the V-R spaces and pathognomonic implications of unusually dilated, but asymptomatic, V-R spaces encountered in five subjects are discussed. RESULTS: The V-R spaces were found to form a complicated, while anatomically highly consistent, intraparenchymal canal network distributed over the whole cerebral hemispheres and connect the cerebral convexity, basal cistern, and ventricular system. CONCLUSION: The V-R spaces may be essential for drainage routes of cerebral metabolites, additional buoyancy for the brain, and maintenance of homogenous intracranial pressure. MR imaging may be more advantageous in depicting the V-R spaces than histological examination.

Intradiscal transplantation of synovial mesenchymal stem cells prevents intervertebral disc degeneration through suppression of matrix metalloproteinase-related genes in nucleus pulposus cells in rabbits.

INTRODUCTION: Synovial mesenchymal stem cells (MSCs) have high proliferative and chondrogenic potentials, and MSCs transplanted into the articular cartilage defect produce abundant extracellular matrix. Because of similarities between the articular cartilage and the intervertebral disc cartilage, synovial MSCs are a potential cell source for disc regeneration. Here, we examined the effect of intradiscal transplantation of synovial MSCs after aspiration of nucleus pulposus in rabbits. METHODS: The nucleus pulposus tissues of rabbit's intervertebral discs were aspirated to induce disc degeneration, and allogenic synovial MSCs were transplanted. At 2, 4, 6, 8, 16, 24 weeks postoperatively, we evaluated with imaging analyses such as X-ray and magnetic resonance imaging (MRI), and histological analysis. To investigate interaction between synovial MSCs and nucleus pulposus cells, human synovial MSCs and rat nucleus pulposus cells were co-cultured, and species specific microarray were performed. RESULTS: The existence of transplanted cells labeled with DiI or derived from green fluorescent protein (GFP)-expressing transgenic rabbits was confirmed up until 24 weeks. X-ray analyses demonstrated that intervertebral disc height in the MSC group remained higher than that in the degeneration group. T2 weighted MR imaging showed higher signal intensity of nucleus pulposus in the MSC group. Immunohistological analyses revealed higher expression of type II collagen around nucleus pulposus cells in the MSC group compared with even that of the normal group. In co-culture of rat nucleus pulposus cells and human synovial MSCs, species specific microarray revealed that gene profiles of nucleus pulposus were altered markedly with suppression of genes relating matrix degradative enzymes and inflammatory cytokines. CONCLUSIONS: Synovial MSCs injected into the nucleus pulposus space promoted synthesis of the remaining nucleus pulposus cells to type II collagen and inhibition of expressions of degradative enzymes and inflammatory cytokines, resulting in maintaining the structure of the intervertebral disc being maintained.

Quantification of left ventricular volumes from cardiac cine MRI using active contour model combined with gradient vector flow.

We investigated the feasibility of combining the active contour model with gradient vector flow (Snakes-GVF) to estimate left ventricular (LV) volumes from cardiac cine magnetic resonance imaging (MRI). MRI data were acquired from 27 patients, including 14 adults (9 men, 5 women, 55.0+/-23.3 years) and 13 children (10 boys, 3 girls, 2.7+/-2.1 years) using Gyroscan Intera (1.5 Tesla, Philips Medical Systems). LV volumes were calculated by adding the areas surrounded by the contour extracted by Snakes-GVF and compared with volumes estimated by manual tracing. Those estimated by Snakes-GVF [y (mL)] correlated well with those estimated by manual tracing [x (mL)]. In adult cases, the regression equation and correlation coefficient were y=1.008x - 0.517 and 0.996, respectively. In pediatric cases, they were y=1.174x - 2.542 and 0.992, respectively. In conclusion, Snakes-GVF is a powerful and useful tool for quantifying LV volumes using cardiac MRI.