Lateral Position With Gantry Tilt Further Improves Computed Tomography Image Quality Reconstructed Using Single-Energy Metal Artifact Reduction Algorithm in the Oral Cavity.

OBJECTIVE: To assess the limitations of single-energy metal artifact reduction algorithm in the oral cavity and evaluate the availability of a solution by setting the patient in a lateral position (LP) with the use of a gantry tilt (GT). METHODS: We analyzed 88 patients with dental metals retrospectively in study 1, and 74 patients prospectively in study 2. Patients were classified: metal I with dental metals in 1 region, metal II in 2 regions, and metal III in 3 regions. Patients underwent neck computed tomography examinations in a supine position (SP) in study 1, and 2 positions, an LP with a GT and an SP, in study 2. All images were reconstructed with this algorithm. Image quality was scored using a 4-point scale: 1 = severe artifact, 2 = moderate artifact, 3 = slight artifact, 4 = no artifact. The scores were compared between metal I, metal II, and metal III using the Mann-Whitney U test in study 1, and between an LP with a GT and an SP using the Wilcoxon signed ranks test in study 2. RESULTS: The scores outside the dental arch were significantly higher in metal I than in metal II and metal III (3.0 ± 0.6 vs 2.3 ± 0.5 vs 2.2 ± 0.4; P < 0.0001 for metal I vs metal II and for metal I vs metal III) and significantly higher in an LP with a GT than an SP (3.2 ± 0.4 vs 2.3 ± 0.4; P < 0.0001). CONCLUSIONS: Single-energy metal artifact reduction algorithm could reduce metal artifacts adequately in patients with dental metals in 1 region, but not in 2 or more regions. However, even for the latter, combination of this algorithm and an LP with a GT could further improve the image quality.

[Evaluation of Improvement of Tissue Contrast and Reduction of Imaging Time by Shortening TR in Brain T2 FLAIR Using MTC Pulse].

T2 fluid-attenuated inversion recovery (FLAIR) using inversion recovery pulse to suppress cerebrospinal fluid signal needs adequate T1 recovery time after data acquisition, otherwise, the T2-weighted contrast in brain tissue will get lower. Over 10000 ms of repetition time (TR) is recommended for the 1.5 T MR scanner, so it is difficult to shorten the imaging time. We verified whether T2 FLAIR combined with the magnetization transfer contrast (MTC) pulse shows better gray-to-white matter (GM/WM) and lesion-to-normal tissue contrasts even when the TR is shortened compared to the conventional T2 FLAIR. Optimal parameters of the MTC pulse were determined with a self-produced phantom, which modeled on cerebral cortical gray and white matters. GM/WM contrasts of the phantom were measured in T2 FLAIR with the MTC pulse while decreasing TR gradually from 10000 ms to 6500 ms. Although GM/WM contrast of the phantom in T2 FLAIR with the MTC pulse gradually decreased as the TR got shortened, the T2 FLAIR with the MTC pulse of 6500 ms of TR still showed 27% higher contrast than the conventional T2 FLAIR (TR 10000 ms). GM/WM contrast in T2 FLAIR with the MTC pulse was improved also in healthy volunteers, but improvement in thalamo-medullary contrast was less than that of cerebral cortico-medullary and putamino-medullary contrasts. It seems to be because thalamus, which is a deep gray matter, shows a higher MTC effect than other gray matters. Thus, it is necessary to note that the tissue contrast might differ between T2 FLAIR with the MTC pulse and the conventional T2 FLAIR. Because general lesions with an elongated T2 value show lower MTC effect compared to the normal brain tissue, a clinical case with thalamic lesion showed that the lesion-to-normal tissue contrast improved in T2 FLAIR with the MTC pulse of 6500 ms of TR. Although it is necessary to note the difference in contrast between some tissues, T2 FLAIR with the MTC pulse improves GM/WM and lesion-to-normal tissue contrasts even when the TR is shortened compared to the conventional T2 FLAIR, and it enables to shorten the imaging time.

The signal intensity ratio of the optic nerve to ipsilateral frontal white matter is of value in the diagnosis of acute optic neuritis.

OBJECTIVES: To evaluate the usefulness of the signal intensity ratio (SIR) of the optic nerve to the white matter (WM) on short tau inversion recovery (STIR) images to diagnose acute optic neuritis (AON). METHODS: The 405 consecutive patients with suspected orbital diseases underwent orbital magnetic resonance imaging (MRI) using a 3-T scanner between June 2008 and August 2011. Among them, 108 optic nerves (33 AON and 75 control) were retrospectively analysed. The averaged SIR (SIRave) and maximum SIR (SIRmax) were defined as the averaged signal intensity (SI) of the optic nerve divided by that of WM, and the maximum SI of the optic nerve divided by averaged SI of WM, respectively. These values were compared between AON and control using the Mann-Whitney U test. A P < 0.05 was considered statistically significant. RESULTS: SIRave and SIRmax were significantly (P < 0.001) higher in the AON compared to the control. At a cut-off SIRave value of 1.119, the sensitivity, specificity and accuracy were 0.939, 0.840, and 0.870; and at a cut-off SIRmax value of 1.281, these were 1.000, 0.720 and 0.806, respectively. CONCLUSION: The SIR of the optic nerve to WM on STIR images is of value in diagnosing AON. KEY POINTS: • We propose a method of diagnosing acute optic neuritis using 3-T MRI. • Our method is simple and objective and requires no novel imaging techniques. • Our method shows high diagnostic accuracy.

[Evaluation of prototype for additional pad packing (polystyrene ball bullet) for homogenously fat suppressed magnetic resonance imaging].

PURPOSE: Homogeneity of static magnetic field (B(0)) is unstable for head and neck magnetic resonance (MR) examination; consequently, chemical shift selective fat suppression becomes inhomogeneous. There is a commercially available additional pad to attenuate the B(0) inhomogeneity, but it is expensive. It has been reported that uncooked rice can be used as a material in the pad, but it has hygienic and weight problems. We searched for a material which can replace the uncooked rice, and evaluated its performance. METHOD: After filling various materials into the cylindrical phantom, each material was evaluated by image distortion of gradient filed echo and spin echo single-shot echo planar images. A prototype additional pad was made with a material which showed less image distortion in the phantom experiment and is easily available in clinical examination. For comparison, an uncooked rice pad with the same volume was also prepared. Fat suppressed head and neck magnetic resonance imaging (MRI) of normal volunteers were visually compared when the three additional pads, including the commercial product, were used or not. RESULT: The polystyrene ball bullet (BB bullet) was adopted as a material for the additional pad. The improvement of the fat suppression in the head and neck MRI was almost the same between the three additional pads. BB bullet pad was the lightest. CONCLUSION: BB bullet can be used as a material of additional pad attenuating the B(0) inhomogeneity instead of uncooked rice.

Comprehensive analysis of perforator territory infarction on postoperative diffusion-weighted imaging in patients with surgically treated unruptured intracranial saccular aneurysms.

OBJECTIVE: Perforator territory infarction (PTI) is still a major problem needing to be solved to achieve good outcomes in aneurysm surgery. However, details and risk factors of PTI diagnosed on postoperative MRI remain unknown. The authors aimed to investigate the details of PTI on postoperative diffusion-weighted imaging (DWI) in patients with surgically treated unruptured intracranial saccular aneurysms (UISAs). METHODS: The data of 848 patients with 1047 UISAs were retrospectively evaluated. PTI was diagnosed on DWI, which was performed the day after aneurysm surgery. Clinical and radiological characteristics were compared between UISAs with and without PTI. Poor outcome was defined as an increase in 1 or more modified Rankin Scale scores at 12 months after aneurysm surgery. RESULTS: Postoperative DWI was performed in all cases, and it revealed PTI in 56 UISA cases (5.3%). Forty-three PTIs occurred without direct injury and occlusion of perforators (43 of 56, 77%). Poor outcome was more frequently observed in the PTI group (17 of 56, 30%) than the non-PTI group (57 of 1047, 5.4%) (p < 0.0001). Thalamotuberal arteries (p < 0.01), lateral striate arteries (p < 0.01), Heubner's artery (p < 0.01), anterior median commissural artery (p < 0.05), terminal internal carotid artery perforators (p < 0 0.01), and basilar artery perforator (p < 0 0.01) infarctions were related to poor outcome by adjusted residual analysis. On multivariate analysis, statin use (OR 10, 95% CI, 3.3-31; p < 0.0001), specific aneurysm locations (posterior communicating artery [OR 4.1, 95% CI 2.1-8.1; p < 0.0001] and basilar artery [OR 3.1, 95% CI 1.1-8.9; p = 0.031]), larger aneurysm size (OR 1.1, 95% CI 1.1-1.2; p = 0.043), and permanent decrease of motor evoked potential (OR 38, 95% CI 3.1-468; p = 0.0045) were related to PTI. CONCLUSIONS: Despite efforts to avoid PTI, it occurred even without direct injury, occlusion of perforators, or evoked potential abnormality. Therefore, surgical treatment of UISAs, especially with the aforementioned risk factors of PTI, should be more carefully considered. The evaluation of PTI in the territory of the above-mentioned perforators could be useful in helping predict the clinical course in patients after aneurysm surgery.

Thick Clot in the Inferior Limiting Sulcus on Computed Tomography Image as an Indicator of Sylvian Subpial Hematoma in Patients with Aneurysmal Subarachnoid Hemorrhage.

OBJECTIVE: Sylvian subpial hematoma (SSH) is occasionally observed in aneurysm subarachnoid hemorrhage (aSAH) when accompanied with the thick clot in the inferior limiting sulcus (ILS). We aimed to determine whether the thickness of the clot in the ILS (TCILS) was an indicator of SSH. METHODS: Data from 150 consecutive patients with aSAH were retrospectively analyzed. The relationship between TCILS on axial computed tomography (CT) image and intraoperatively confirmed SSH was reviewed. In patients without SSH, the average of the clot thickness in the bilateral ILS was used. The primary outcome was SSH. RESULTS: The median TCILS of the SSH group (n = 18, 12%) was larger than that of the non-SSH group (n = 132, 88%) (21 vs. 2.1 mm, respectively; P < 0.001). The intraclass correlation coefficients for clot thickness in the right and left ILS between 2 observers were 0.97 (P < 0.001) and 0.85 (P < 0.001). The TCILS threshold of ≥6.0 mm was associated with SSH, with a sensitivity of 89% and specificity of 99%. The unadjusted and adjusted odds ratios of the SSH of clot thickness in the affected ILS ≥6 mm relative to clot thickness in the affected ILS <6 mm were 263 (95% confidence interval [CI], 46-5063) and 137 (95% CI, 19-3029), respectively. CONCLUSIONS: The clot thickness in the ILS on CT image was easily measured and could be a marker of SSH. SSH assessment could be useful in helping us predict the clinical course in patients with aSAH.

Embryological basilar apex disposition as a risk factor of basilar apex aneurysm.

The pathogenesis of basilar apex aneurysm (BAA) are still poorly understood. Embryologically, basilar apex anatomical disposition is formed by the fusion of both caudal internal carotid divisions on the midline. To compare basilar apex morphology by embryological classification among patients with BAAs, anterior circulation aneurysms (ACAs), and controls. Prospectively collected data of 47 consecutive patients with unruptured BAAs (42 females and five males), age- and gender-matched 47 patients with unruptured ACAs, and 47 controls without any aneurysms were analyzed. Based on embryology, basilar apex morphology was classified into symmetric cranial fusion (SCrF), symmetric caudal fusion, and asymmetric fusion type. Posterior communicating artery (Pcom) was classified into hypoplastic, adult, or fetal type. The asymmetrical Pcom was defined as bilaterally different type Pcom. The ACAs located at the anterior communicating artery (n = 18), paraclinoid portion (n = 12), middle cerebral artery (n = 8), anterior cerebral artery (n = 5), the top of internal carotid artery (n = 2), and anterior choroidal artery (n = 2). Compared with the ACA group and controls, smoking, asymmetrical Pcom (fetal and adult type), and SCrF type were more prevalent in patients with BAAs by residual analysis. The multinomial logistic regression comparative analysis demonstrated that SCrF type was associated with BAAs (vs. ACA group; odds ratio, 13; 95% confidence interval, 3.8-41 and vs. controls; odds ratio, 25; 95% confidence interval, 5.4-121). The assessment of basilar apex morphology may aid in the understanding of the pathogenesis of BAA and the prediction of BAA formation.

Morphological parameters as factors of 12-month neurological worsening in surgical treatment of patients with unruptured saccular intracranial aneurysms: importance of size ratio.

OBJECTIVE: It is well known that larger aneurysm size is a risk factor for poor outcome after surgical treatment of unruptured saccular intracranial aneurysms (USIAs). However, the authors have occasionally observed poor outcome in the surgical treatment of small USIAs and hypothesized that size ratio has a negative impact on outcome. The aim of this paper was to investigate the influence of size ratio on outcome in the surgical treatment of USIAs. METHODS: Prospectively collected clinical and radiological data of 683 consecutive patients harboring 683 surgically treated USIAs were evaluated. Dome-to-neck ratio was defined as the ratio of the maximum width of the aneurysm to the average neck diameter. The aspect ratio was defined as the ratio of the maximum perpendicular height of the aneurysm to the average neck diameter of the aneurysm. The size ratio was calculated by dividing the maximum aneurysm diameter (height or width, mm) by the average parent artery diameter (mm). Neurological worsening was defined as an increase in modified Rankin Scale score of 1 or more points at 12 months. Clinical and radiological variables were compared between patients with and without neurological worsening. RESULTS: The median patient age was 64 years (IQR 56-71 years), and 528 (77%) patients were female. The median maximum size, dome-to-neck ratio, aspect ratio, and size ratio were 4.7 mm (IQR 3.6-6.7 mm), 1.2 (IQR 1.0-1.4), 1.0 (IQR 0.76-1.3), and 1.9 (IQR 1.4-2.8), respectively. The size ratio was significantly correlated with maximum size (r = 0.83, p < 0.0001), dome-to-neck ratio (r = 0.69, p < 0.0001), and aspect ratio (r = 0.74, p < 0.0001). Multivariate logistic regression analysis showed that the specific USIA location (paraclinoid segment of the internal carotid artery: OR 6.2, 95% CI 2.6-15, p < 0.0001; and basilar artery: OR 8.4, 95% CI 2.8-25, p < 0.0001), size ratio (OR 1.3, 95% CI 1.1-1.6, p = 0.021), and postoperative ischemic lesion (OR 9.4, 95% CI 4.4-19, p < 0.0001) were associated with neurological worsening (n = 52, 7.6%), and other characteristics showed no significant differences. CONCLUSIONS: The present study showed that size ratio, and not other morphological parameters, was a risk factor for 12-month neurological worsening in surgically treated patients with USIAs. The size ratio should be further studied in a large, prospective observational cohort to predict neurological worsening in the surgical treatment of USIAs.

Analysis for risk factors of 12-month neurological worsening in patients with surgically treated small-to-moderate size unruptured intracranial aneurysms.

The risk associated with surgical treatment for small-to-moderate size unruptured intracranial aneurysms (SMUIAs, defined as <15 mm) has not been well characterized. Authors aimed to investigate risk factors for poor outcome in surgical treatment of SMUIAs. The data of prospectively collected 801 consecutive patients harboring 971 surgically treated SMUIAs was evaluated. Neurological worsening (NW) was defined as an increase in 1 or more modified Rankin Scale at 12-month. Clinical and radiological characteristics were compared. Neurological worsening was observed in 45 (4.6%). In multivariate analysis, only perforator territory infarction (PTI) on postoperative diffusion-weighted imaging (odds ratio (OR), 13; 95% confidence interval (CI), 4.9-32, p < 0.0001), and aneurysm locations (paraclinoid (OR, 6.9; 95% CI, 3.1-15, p < 0.0001), basilar artery (OR, 4.5; 95% CI, 1.5-14, p = 0.008), vertebral artery (OR, 11; 95% CI, 3.3-34, p < 0.0001)) were related to neurological worsening. Multivariate analysis showed that statin use (OR, 12; 95% CI, 3.8-39, p < 0.0001) and aneurysm locations (internal carotid artery-posterior communicating artery (OR, 3.9; 95% CI, 1.8-8.2, p < 0.0001) and basilar artery (OR, 6.3; 95% CI, 2.3-17, p = 0.008)), and aneurysm size >10 mm (OR, 5.3; 95% CI, 1.8-15, p = 0.003) were related to PTI. Although all SMUIAs should be carefully considered whether to be treated, those with statins, specific locations, and larger sizes should perhaps be more meticulously contemplated, and neurosurgeons should continue to avoid PTI.

Surgical Treatment of Middle Cerebral Artery Aneurysms: Aneurysm Location and Size Ratio as Risk Factors for Neurologic Worsening and Ischemic Complications.

BACKGROUND: Regardless of acceptable surgical results of middle cerebral artery aneurysms (MCAs), MCA territory infarction (MCATI) remains a major obstacle to achieving a good outcome. We investigated the MCATI in patients with surgically treated MCA aneurysms. METHODS: The data of 286 consecutive patients with 322 MCA aneurysms were evaluated retrospectively. The aneurysm location was classified as early frontal cortical branch (EFCB), early temporal cortical branch (ETCB), bifurcation or trifurcation (M1-2), and distal aneurysms on the insular, opercular, or cortical segments of the MCA (distal MCA). Neurologic worsening was defined as an increase in 1 or more modified Rankin Scale (mRS) scores. RESULTS: Multivariate analysis identified EFCB location as the sole risk factor for MCATI (odds ratio [OR], 3.8; 95% confidence interval [CI], 1.2-12; P = 0.021) and MCATI (OR, 18; 95% CI, 2.8-117; P = 0.002) and a larger size ratio (OR, 1.4; 95% CI, 1.1-1.8; P = 0.019) were related to 12-month neurologic worsening (n = 6; 1.9%). During follow-up (median, 885 days; interquartile range, 485-1229 days), posttreatment rupture and aneurysm recurrence were not observed. CONCLUSIONS: In the present study, compared with M1-2 aneurysms, MCATIs were observed more frequently in EFCB aneurysms, and the presence of MCATI and a larger size ratio were related to 12-month neurologic worsening in patients with surgically treated MCA aneurysms.

MRI of Perfusion: Principles and Clinical Applications.

The principle and clinical application of measurement of cerebral blood perfusion (CBP) using MRI are described. Purposes of measuring CBP using MRI are wide-ranging. Generally, it is used to diagnose cerebro-vascular disorders or brain tumors. There are two types of measuring methods. One is dynamic susceptibility contrast (DSC) method using a contrast agent as a tracer. Another is an arterial spin labeling (ASL) method using protons in arterial blood as an endogenous tracer, instead of bio-exogenous tracer. Basic theory of ASL method was published in the 1990s, recently, its clinical application has been spreading rapidly by the technological innovations. ASL method is attractive as a way to measure CBP because of its non-invasiveness (no radiation-exposure, not need intravenous injection or blood sampling), and the imaging time is about 5 minutes, thereby the measurement can be repeated. The analysis of DSC method has not been standardized, though various valuable parameters are provided. And the prerequisite of DSC method is uncertain in vivo. On the other hand, the result of ASL is affected by the post labeling delay, and limited to the arterial information.

Comparison of magnetic resonance imaging sequences for depicting the subthalamic nucleus for deep brain stimulation.

Electrodes are surgically implanted into the subthalamic nucleus (STN) of Parkinson's disease patients to provide deep brain stimulation. For ensuring correct positioning, the anatomic location of the STN must be determined preoperatively. Magnetic resonance imaging has been used for pinpointing the location of the STN. To identify the optimal imaging sequence for identifying the STN, we compared images produced with T2 star-weighted angiography (SWAN), gradient echo T2*-weighted imaging, and fast spin echo T2-weighted imaging in 6 healthy volunteers. Our comparison involved measurement of the contrast-to-noise ratio (CNR) for the STN and substantia nigra and a radiologist's interpretations of the images. Of the sequences examined, the CNR and qualitative scores were significantly higher on SWAN images than on other images (p < 0.01) for STN visualization. Kappa value (0.74) on SWAN images was the highest in three sequences for visualizing the STN. SWAN is the sequence best suited for identifying the STN at the present time.

[CT perfusion abnormalities in a case of non-herpetic acute limbic encephalitis].

We report a 42-year-old woman of non-herpetic acute limbic encephalitis (NHALE) whose CT perfusion (CTP) images revealed abnormalities of the limbic system at the early stage. The patient had high fever, convulsion and memory disturbance soon after having caught a common cold, and was admitted to a hospital where she developed progressive disturbance of consciousness. She was then transferred to our hospital 7 days after the initial manifestations. Although enhanced CT images of the brain failed to find any lesion, CTP images revealed a focal increase in the cerebral blood flow and shortening of mean transit time in the bilateral hippocampi and amygdalae. MRI of the subsequent day showed high signal intensity lesions on diffusion, T2-weighted and FLAIR images at the same area. Her consciousness improved by intravenous administration of high-dose methylprednisolone together with other combination therapies. Her CTP images apparently improved by 5 weeks after the onset, but she was left with mild memory disturbance, amenorrhea secondary to hypothalamic failure, hyperosmia, and hypogeusia. In conclusion, CTP is sensitive enough to detect the lesions of the limbic system even in the early stage of NHALE.

Delineation of the safe zone in surgery of sylvian insular triangle: morphometric analysis and magnetic resonance imaging study.

BACKGROUND: Surgery within the insula carries significant risk of morbidity, particularly hemiparesis, because of the difficulty in detecting the internal capsule boundaries. OBJECTIVE: We analyzed the anatomy of the insula and identified landmarks anticipated to facilitate surgery for intrinsic insular lesions. METHODS: Insular region anatomy was studied in 11 cadaveric brains harvested within 72 hours postmortem. MRI of the specimens was acquired using 3.0 T with T2-weighting and 25 directions of diffusion tensor imaging. Landmarks easily recognizable during surgery were identified on the surface of the insula. The interrelationships between surface landmarks and critical structures were analyzed. RESULTS: The posterior inferior insular point (PIIP) and the upper central insular point (UCIP) were newly established as landmarks on the insula. The PIIP corresponded to the obvious bend in the posterior long insular gyrus. The UCIP is the meeting point between the central insular sulcus and superior peri-insular sulcus. The corticospinal tract was identified as a high-intensity area in the posterior limb of the internal capsule on T2-weighted imaging and its course confirmed with diffusion tensor imaging tractography. The corticospinal tract took a course deep to the posterosuperior insula on T2-weighted imaging, 4.8 mm from the UCIP and 6.2 mm from the PIIP. CONCLUSION: The posterosuperior part of the insula forms the region at greatest risk to corticospinal tract injury. The PIIP and UCIP are crucial to understanding the relationship of the insula with the posterior limb of the internal capsule including the corticospinal tract.

Improved arterial visibility using short-tau inversion-recovery (STIR) fat suppression in non-contrast-enhanced time-spatial labeling inversion pulse (Time-SLIP) renal MR angiography (MRA).

PURPOSE: To evaluate whether short-tau inversion-recovery (STIR) fat suppression is worthwhile in non-contrast-enhanced respiration-triggered free-breathing time-spatial labeling inversion pulse (Time-SLIP) renal magnetic resonance angiography (MRA) compared with chemical shift selective (CHESS) fat suppression. MATERIALS AND METHODS: Simulation-based analyses of inversion time (TI) for spatial-selective inversion-recovery (ssIR) pulse and breathing rate were performed, and confirmed on a phantom and in human subjects using a three-dimensional (3D) coherent steady-state free precession (SSFP) sequence on a 1.5T Toshiba scanner. RESULTS: The STIR fat suppression successfully suppressed signals from the intestines and parenchymous organs and provided better contrast between the arteries and the background, although an extension of TI was required for the ssIR pulse when a patient's respiration was extremely slow. CONCLUSION: STIR fat suppression provides better renal artery contrast than CHESS fat suppression in non-contrast free-breathing Time-SLIP MRA; it is also an effective screening tool for renal artery stenosis because of the lack of interference from intestinal signals. However, close attention is needed if the patient has slow respiration. As the TI for the ssIR pulse decreases, the STIR method requires faster-paced respiration.

Improvement of vessel visibility in time-of-flight MR angiography of the brain.

PURPOSE: To improve vessel visibility in time-of-flight MR angiography (TOF-MRA) by careful consideration of coil choice, coil position, and frequency offset and profile of the nonspatially selective chemical shift selective (CHESS) presaturation pulse. MATERIALS AND METHODS: The effects of both the CHESS and the excitation radiofrequency (RF) pulses on flow signal and signals from stationary substances were evaluated by changing the spatial area where RF pulses were applied to upstream flow in a flow phantom and in human subjects. The difference between the eight-channel phased-array receive-only coil and the transmit-receive coil was evaluated. RESULTS: The CHESS pulse suppresses the flow signal over a wider frequency range than the signals from stationary substances, especially when using the body coil for transmission. Even without presaturation pulse, the excitation pulse slightly suppressed the flow signal. Adjusting the position of the transmit-receive coil relative to the head improved these TOF-MRA images. The results were better than those obtained with the eight-channel coil. CONCLUSION: The excitation and the nonspatially selective CHESS pulses degraded the flow signal. Our results suggest that reduced spatial extent of RF pulse application to upstream flow can improve image quality of TOF-MRA. This result can be implemented on conventional scanners.

Double-subtraction maximum intensity projection MR angiography for detecting the artery of Adamkiewicz and differentiating it from the drainage vein.

PURPOSE: To evaluate the efficacy of double-subtraction magnetic resonance angiography (MRA) (subtraction of the subtracted venous phase image from the subtracted arterial dominant phase image) for depicting the artery of Adamkiewicz and differentiating it from the drainage vein. MATERIALS AND METHODS: A total of 170 patients (123 men, 47 women; aged 17-84 years, mean = 67 years), with a thoracoabdominal vascular lesion underwent MRA for detection of the artery of Adamkiewicz. MRA was performed as a five-phase dynamic-enhanced three-dimensional (3D) fast spoiled gradient recalled acquisition in steady state (GRASS) sequence on a 1.5-T system, with double-dose bolus contrast and saline injection. The levels at which the artery of Adamkiewicz and drainage vein originated were determined. Signal intensities of the two vessels were measured with source images to assess the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and necessity of the double-subtraction technique. RESULTS: The artery of Adamkiewicz was detected in 140 patients (82.4%). Branching occurred at levels T8-T12 on the left and T8-T11 on the right. An additional anterior radiculomedullary artery was detected in 18 patients. The drainage vein was detected in 133 patients (78.2%). It merged at the T9-L2 level on both sides. In six of the 133 patients (4.5%), the drainage vein branched upwardly. Neither SNR nor CNR differed significantly between the artery of Adamkiewicz and the drainage vein in the arterial phase; but on the subtraction image, signal intensity of the artery was higher than that of the drainage vein (P < 0.05). CONCLUSION: Double-subtraction MRA is useful for detecting the artery of Adamkiewicz when it is necessary to differentiate it from the drainage vein.

Novel magnetic resonance angiography stage grading for moyamoya disease.

BACKGROUND: Magnetic resonance angiography (MRA) has been acknowledged as a noninvasive diagnostic modality for moyamoya disease. However, in terms of staging of moyamoya disease, conventional angiography is still the gold standard. Therefore, the purpose of this study was to establish MRA grades for moyamoya disease as an alternative to conventional angiography. METHODS: Twenty-two patients (44 sides) with moyamoya disease diagnosed by conventional angiography were evaluated by MRA during the past 5 years. MRA scores were assigned based on the severity of occlusive changes of the internal carotid artery, the horizontal portion of the middle cerebral artery, the anterior and the posterior cerebral arteries and the signals of the distal branches of these arteries. Total points ranged from 0 (normal) to 10 (most severe). RESULTS: MRA scores (0-10) were significantly consistent with the conventional angiographic staging. Four grades based on this novel MRA scores correlated well with Suzuki's stages, with high sensitivity and specificity. CONCLUSIONS: These novel MRA grades can be a reliable alternative to conventional staging. By employing these novel MRA grades, the use of conventional angiography can be avoided for the purpose of evaluation of the stages of moyamoya disease.