Tomoko Ochi

Time Course of Axial and Radial Diffusion Kurtosis of White Matter Infarctions: Period of Pseudonormalization

BACKGROUND AND PURPOSE: Diffusion kurtosis is a statistical measure for quantifying the deviation of the water diffusion profile from a Gaussian distribution. The current study evaluated the time course of diffusion kurtosis in patients with cerebral infarctions, including perforator, white matter, cortical, and watershed infarctions. MATERIALS AND METHODS: Subjects were 31 patients, representing 52 observations of lesions. The duration between the onset and imaging ranged from 3 hours to 122 days. Lesions were categorized into 4 groups listed above. Diffusion kurtosis images were acquired with b-values of 0, 1000, and 2000 s/mm2 applied in 30 directions; variables including DWI signal, ADC, fractional anisotropy, radial diffusivity, axial diffusivity, radial kurtosis, and axial kurtosis, were obtained. The time courses of the relative values (lesion versus contralateral) for these variables were evaluated, and the pseudonormalization period was calculated. RESULTS: Diffusion kurtosis was highest immediately after the onset of infarction. Trend curves showed that kurtosis decreased with time after onset. Pseudonormalization for radial/axial kurtosis occurred at 13.2/59.9 days for perforator infarctions, 33.1/40.6 days for white matter infarctions, 34.8/35.9 days for cortical infarctions, and 34.1/28.2 days after watershed infarctions. For perforator infarctions, pseudonormalization occurred in the following order: radial kurtosis, ADC, axial kurtosis, and DWI. CONCLUSIONS: Diffusion kurtosis variables in lesions increased early after infarction and decreased with time. Information provided by diffusion kurtosis imaging, including axial and radial kurtosis, seems helpful in conducting a detailed evaluation of the age of infarction, in combination with T2WI, DWI, and ADC.

Application of susceptibility weighted imaging (SWI) for evaluation of draining veins of arteriovenous malformation: utility of magnitude images.

IntroductionThe current study evaluated the signal characteristics of susceptibility weighted imaging (SWI) of arteriovenous malformation (AVM), especially for draining veins. For this purpose, we identified the draining veins of the AVM on angiography and evaluated the signal on magnitude image for SWI (SWI-mag) and minimum intensity projection image (SWI-minIP).MethodsSubjects were 14 cases with angiographically proven AVM. SWI-mag, SWI-minIP, and time-of-flight (TOF) magnetic resonance angiography were acquired. For the draining veins of the AVM identified on angiography, we analyzed signal intensity on the images listed above, and classified it into hyperintensity (hyper), mixed intensity (mixed), hypointensity (hypo), and no visualization.ResultsOn the analysis of 27 angiographically proven draining veins, 19 draining veins were classified as hyper, 3 as mixed, 0 as hypo, and 6 as no visualization on SWI-mag. On TOF images, 21 draining veins were classified as hyper, 2 as mixed, 0 as hypo, and 4 as no visualization, while 6 draining veins did not show hyperintensity on TOF, and SWI-mag visualized 3 of these 6 veins as hyper.ConclusionSWI-mag depicted most draining veins of AVM as hyperintensity. We speculate that this is mainly due to the higher concentration of oxygenated hemoglobin (oxy-Hb) and inflow effect of the draining vein. SWI-mag seems to be useful in the analysis and follow-up for AVM as the signal on the image may reflect physiological status.

Transient hyperintensity in the subthalamic nucleus and globus pallidus of newborns on T1-weighted images.

In newborns, high signal intensity in the subthalamic nuclei may be indicative of cerebral ischemia, particularly in combination with high signal in the posterior putamen. This article describes transient and normal high signal intensity in the subthalamic nuclei and globi pallidus. Seventy-nine neonates who had normal examinations 2 years later were included in the study. The authors performed qualitative and quantitative evaluations of these 2 regions on T1- and T2-weighted images and correlated their results with postnatal and gestational ages. With increasing postnatal age at examination, the high signal intensity on the T1-weighted images for both subthalamic and globi pallidus diminished. Although the disappearance of this hyperintensity was well correlated with the postnatal age at examination for both the qualitative and quantitative studies, there was no correlation with gestational age at examination. For the T2 images, there was no correlation with either the postnatal age or gestational age at examination. BACKGROUND AND PURPOSE: In the brains of newborns, changes in signal intensity in most structures can be explained by the development of myelination. However, there are some structures for which signal intensity changes cannot be accounted for by myelination alone. We examined the STN and globus pallidus signal intensities and tried to determine whether a relationship exists between the signal intensity and the postnatal age or the gestational age at the examination. MATERIALS AND METHODS: We examined T1WI and T2WI obtained from 79 neonates who showed normal development at their 2-year follow-up examinations. We performed both qualitative and quantitative (signal intensity ratio to the thalamus) evaluation of the STN and globus pallidus signals, and we examined the correlation between signal intensity changes and the age of neonates. RESULTS: With increasing postnatal age at examination, the high signal intensity on the T1WI for both STN and globus pallidus diminished. Although the disappearance of this hyperintensity was well correlated with the postnatal age at examination for both the qualitative and quantitative studies, there was no correlation with gestational age at examination. For the T2WI, there was no correlation with either the postnatal age or the gestational age at examination. CONCLUSIONS: Signal intensity on T1WI in the STN and globus pallidus is not related to the gestational age at examination; instead, signal intensities on T1WI seem to be more dependent upon the postnatal age at examination.

Dural Thickening of the Internal Auditory Canal in Patients With Spontaneous Intracranial Hypotension Syndrome.

Objective This study aimed to assess the utility of dural thickening of the internal auditory canal (IAC) in patients with spontaneous intracranial hypotension (SIH) syndrome and determined the sensitivity and specificity of this image finding. Methods Magnetic resonance images were evaluated for 22 cases of definite SIH and 16 cases of unlikely SIH. On contrast-enhanced magnetic resonance imaging, pachymeningeal enhancement and dural thickening of the IAC were assessed. Results Pachymeningeal enhancement was observed in 21 of 22 patients in the definite SIH group and 1 of 16 patients in the unlikely SIH group (sensitivity, 95.5%; specificity, 93.8%). Dural thickening of the IAC was observed in 15 of 22 patients in the definite SIH group and 0 of 16 patients in the unlikely SIH group (sensitivity, 68.2%; specificity, 100%). Conclusions Dural thickening of the IAC showed 100% specificity for SIH syndrome and can increase the accuracy of diagnosis of SIH syndrome.

Safety and feasibility for single-incision laparoscopic cholecystectomy in local community hospital: a retrospective comparison with conventional 4-port laparoscopic cholecystectomy.

Background: The aim of this study was to evaluate the safety and feasibility for single-incision laparoscopic cholecystectomy (SILC) by retrospective comparison with conventional laparoscopic cholecystectomy (CLC) in a local community hospital. Methods: SILC was introduced and performed in 57 patients for benign gallbladder diseases. Their clinical data were compared with those of 62 patients treated with CLC. They included patient demographic data and operative outcomes. Results: SILC was attempted in 57 patients and 52 cases (91.2%) were successfully completed. There were no statistical differences between the 2 groups in terms of operative time, blood loss, and postoperative complications. The length of hospital stay in the SILC group was significantly shorter compared with CLC (P<0.0001). Conclusions: SILC has been successfully introduced in a local community hospital. The safety and feasibility was also confirmed. The SILC procedure may become 1 standard option for the treatment of benign gallbladder diseases.

“Cerebellar peduncle quarter notes” formed by the superior and middle cerebellar peduncles: comparison with a diffusion tensor study of spinocerebellar degeneration

PurposeTo investigate morphological changes of the superior and middle cerebellar peduncles (SCP, MCP) in spinocerebellar degeneration (SCD) by observing “cerebellar peduncle quarter notes”.Materials and MethodsWe examined 21 patients with SCD, including nine patients with multiple system atrophy cerebellar type (MSA-C), and 24 controls. We measured SCP angle and performed diffusion tensor analysis to quantify the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) of the MCP. We quantified the relationship between SCP angle and the ADC and FA of the MCP, and compared these variables between MSA-C patients and controls.ResultsThere was statistically significant negative correlation between SCP angle and FA of the MCP, and a positive correlation between SCP angle and the ADC of the MCP. Mean SCP angle was larger among MSA-C patients than among normal controls.ConclusionsSCP angle tended to be larger among patients with severe degeneration of the MCP. The SCP angle, quantified by observing “cerebellar peduncle quarter notes”, may be a simple index for evaluation of degeneration of the MCP.

Comparison between Two Separate Injections and a Single Injection of Double-dose Contrast Medium for Contrast-enhanced MR Imaging of Metastatic Brain Tumors.

PURPOSE As stereotactic radiotherapy (SRT) becomes widespread, precise information including number, location, and margin of lesions is required when magnetic resonance (MR) imaging of brain metastasis is performed. We compare methods using 2 separate injections and a single injection for the administration of a double dose of contrast medium for contrastenhanced MR imaging. MATERIALS AND METHODS We divided 40 patients with brain metastasis into 2 groups of 20 patients. Group A received 2 separate injections (0.2 + 0.2 mL/kg) of contrast medium (gadoteridol); Group B received a single injection of the same total dose (0.4 mL/kg). Group A underwent spin echo (SE) T1-weighted imaging (T1WI) and magnetization prepared rapid acquisition with gradient echo sequence (MPRAGE) after each injection, and Group B underwent the same MR studies at the same timing as Group A. We evaluated the number, signal-to-noise ratio (SNR), diameter, margin delineation, and volume of lesions and compared them between early and delayed studies by the 2 methods. RESULTS The number of detected lesions was largest in delayed studies of MPRAGE in both groups. The SNR of the lesions was statistically lower in early studies of Group A than other studies. Delayed studies of Group B showed statistically better margin delineation than other studies on both SE-T1WI and MPRAGE studies. Diameter and enhanced volume were statistically significantly larger on delayed phase than early phase in both groups. CONCLUSION Use of a single injection of double-dose contrast medium and longer delay time may improve margin delineation of lesions for the study of brain metastasis. Enhanced volume was larger on delayed phase, and it may influence selection of therapeutic strategy.

Structures Showing Negative Correlations of Signal Intensity with Postnatal Age on T1-weighted Imaging of the Brain of Newborns and Infants.

Purpose: Although the neonatal and infantile brain typically shows sequential T1 shortening according to gestational age as a result of myelination, several structures do not follow this rule. We evaluated the relationship between the signal intensity of various structures in the neonatal and infantile brain on T1-weighted imaging (T1WI) and either postnatal or gestational age. Materials and Methods: We examined magnetic resonance images from 120 newborns and infants without any abnormalities in the central nervous system. Written informed consent was obtained from all parents and the institutional review board approved the study. Gestational age at examination ranged from 35 weeks, 3 days to 46 weeks, 6 days, and postnatal age ranged from 7 days to 127 days. Signal intensity on T1WI was evaluated on a scale from Grade 1 (indistinguishable from surrounding structures) to Grade 4 (higher than cortex and close to fat). We evaluated relationships between the T1 signal grades of various structures in the neonatal brain and postnatal or gestational age using Spearman’s correlation analysis. Results: Significant positive correlations were identified between T1 signal grade and gestational age in the pyramidal tract (P < 0.001). Conversely, significant negative correlations were evident between T1 signal grade and postnatal age (P < 0.001), in structures including the stria medullaris thalami, fornix cerebellar vermis, dentate nucleus and anterior pituitary gland. Conclusion: Significant negative correlations exist between signal intensity on T1WI and postnatal age in some structures of the neonatal and infantile brain. Some mechanisms other than myelination might play roles in the course of signal appearance.