Shuang Xia

Decreased oxygen saturation in asymmetrically prominent cortical veins in patients with cerebral ischemic stroke

Decreased oxygen saturation in asymmetrically prominent cortical veins (APCV) seen in ischemic stroke has been hypothesized to correlate with an increase of de-oxygenated hemoglobin. Our goal is to quantify magnetic susceptibility to define APCV by establishing a cutoff above which the deoxyhemoglobin levels are considered abnormal. A retrospective study was conducted on 26 patients with acute ischemic stroke in one cerebral hemisphere that exhibited APCV with 30 age- and sex-matched healthy controls. Quantitative susceptibility mapping (QSM) was used to calculate the magnetic susceptibility of the cortical veins. A paired t-test was used to compare the susceptibility of the cortical veins in the left and right hemispheres for healthy controls as well as in the contralateral hemisphere for stroke patients with APCV. The change in oxygen saturation in the APCV relative to the contralateral side was calculated after thresholding the susceptibility using the mean plus two standard deviations of the contralateral side for each individual. The thresholded susceptibility value of the APCVs in the stroke hemisphere was 254±48 ppb which was significantly higher (p<0.05) than that in the contralateral hemisphere (123±12 ppb) and in healthy controls (125±8 ppb). There was a decrease of oxygen saturation in the APCV ranging from 16% to 44% relative to the veins of the contralateral hemisphere. In conclusion, APCV seen in SWI correspond to reduced levels of oxygen saturation and these abnormal veins can be identified using a susceptibility threshold on the QSM data.

Susceptibility-weighted imaging: current status and future directions

Susceptibility‐weighted imaging (SWI) is a method that uses the intrinsic nature of local magnetic fields to enhance image contrast in order to improve the visibility of various susceptibility sources and to facilitate diagnostic interpretation. It is also the precursor to the concept of the use of phase for quantitative susceptibility mapping (QSM). Nowadays, SWI has become a widely used clinical tool to image deoxyhemoglobin in veins, iron deposition in the brain, hemorrhages, microbleeds and calcification. In this article, we review the basics of SWI, including data acquisition, data reconstruction and post‐processing. In particular, the source of cusp artifacts in phase images is investigated in detail and an improved multi‐channel phase data combination algorithm is provided. In addition, we show a few clinical applications of SWI for the imaging of stroke, traumatic brain injury, carotid vessel wall, siderotic nodules in cirrhotic liver, prostate cancer, prostatic calcification, spinal cord injury and intervertebral disc degeneration. As the clinical applications of SWI continue to expand both in and outside the brain, the improvement of SWI in conjunction with QSM is an important future direction of this technology. Copyright

Patterns of chronic venous insufficiency in the dural sinuses and extracranial draining veins and their relationship with white matter hyperintensities for patients with Parkinson's disease

BACKGROUND Idiopathic Parkinsons disease (IPD) remains one of those neurodegenerative diseases for which the cause remains unknown. Many clinically diagnosed cases of IPD are associated with cerebrovascular disease and white matter hyperintensities (WMHs). The purpose of this study was to investigate the presence of transverse sinus and extracranial venous abnormalities in IPD patients and their relationship with brain WMHs. METHODS Twenty-three IPD patients and 23 age-matched normal controls were recruited in this study. They had conventional neurologic magnetic resonance structural and angiographic scans and, for blood flow, quantification of the extracranial vessels. Venous structures were evaluated with two-dimensional time of flight; flow was evaluated with two-dimensional phase contrast; and WMH volume was quantified with T2-weighted fluid-attenuated inversion recovery. The IPD and normal subjects were classified by both the magnetic resonance time-of-flight and phase contrast images into four categories: (1) complete or local missing transverse sinus and internal jugular veins on the time-of-flight images; (2) low flow in the transverse sinus and stenotic internal jugular veins; (3) reduced flow in the internal jugular veins; and (4) normal flow and no stenosis. RESULTS Broken into the four categories with categories 1 to 3 combined, a significant difference in the distribution of the IPD patients and normal controls (χ(2) = 7.7; P < .01) was observed. Venous abnormalities (categories 1, 2, and 3) were seen in 57% of IPD subjects and in only 30% of controls. In IPD subjects, category type correlated with both flow abnormalities and WMHs. CONCLUSIONS From this preliminary study, we conclude that a major fraction of IPD patients appear to have abnormal venous anatomy and flow on the left side of the brain and neck and that the flow abnormalities appear to correlate with WMH volume. Studies with a larger sample size are still needed to confirm these findings.

Quantitative measurements of brain iron deposition in cirrhotic patients using susceptibility mapping

Background Susceptibility-weighted imaging (SWI) has been used to detect micro-bleeds and iron deposits in the brain. However, no reports have been published on the application of SWI in studying iron changes in the brain of cirrhotic patients. Purpose To compare the susceptibility of different brain structures in cirrhotic patients with that in healthy controls and to evaluate susceptibility as a potential biomarker and correlate the measured susceptibility and cadaveric brain iron concentration for a variety of brain structures. Material and Methods Forty-three cirrhotic patients (27 men, 16 women; mean age, 50 ± 9 years) and 34 age- and sex-matched healthy controls (22 men, 12 women; mean age, 47 ± 7 years) were included in this retrospective study. Susceptibility was measured in the frontal white matter, basal ganglia, midbrain, and dentate nucleus and compared with results gathered from two postmortem brain studies. Correlation between susceptibility and clinical biomarkers and neuropsychiatric tests scores was calculated. Results In cirrhotic patients, the susceptibility of left frontal white matter, bilateral caudate head, and right substantia nigra was higher than that in healthy controls (P < 0.05). There was a positive correlation between susceptibility and iron concentration from one postmortem brain study (r = 0.835, P = 0.01) in eight deep grey matter structures and another in five brain structures (r = 0.900, P = 0.03). The susceptibility of right caudate head (r = 0.402) and left caudate head (r = 0.408) correlated with neuropsychological test scores (both P < 0.05). Conclusion Abnormal iron deposits occur in cirrhotic patients and abnormal susceptibility of some brain regions appears to reflect neurocognitive changes.

Increased brain iron deposition is a risk factor for brain atrophy in patients with haemodialysis: a combined study of quantitative susceptibility mapping and whole brain volume analysis

To explore the correlation between increased brain iron deposition and brain atrophy in patients with haemodialysis and their correlation with clinical biomarkers and neuropsychological test. Forty two patients with haemodialysis and forty one age- and gender-matched healthy controls were recruited in this prospective study. 3D whole brain high resolution T1WI and susceptibility weighted imaging were scanned on a 3 T MRI system. The brain volume was analyzed using voxel-based morphometry (VBM) in patients and to compare with that of healthy controls. Quantitative susceptibility mapping was used to measure and compare the susceptibility of different structures between patients and healthy controls. Correlation analysis was used to investigate the relationship between the brain volume, iron deposition and neuropsychological scores. Stepwise multiple regression analysis was used to explore the effect of clinical biomarkers on the brain volumes in patients. Compared with healthy controls, patients with haemodialysis showed decreased volume of bilateral putamen and left insular lobe (All P < 0.05). Susceptibilities of bilateral caudate head, putamen, substantia nigra, red nucleus and dentate nucleus were significantly higher (All P < 0.05). The increased brain iron deposition is negatively correlated with the decreased volume of bilateral putamen (P < 0.01). Neuropsychological scores positively correlated with decreased volume of left insular lobe (P < 0.05). Dialysis duration was negatively associated with decreased volume of bilateral putamen (P < 0.05). Our study indicated increased brain iron deposition and dialysis duration was risk factors for brain atrophy in patients with haemodialysis. The decreased gray matter volume of the left insular lobe was correlated with neurocognitive impairment.

Quantitative measurement of brain iron deposition in patients with haemodialysis using susceptibility mapping

To compare the susceptibility of different brain structures in patients with haemodialysis with that in healthy controls using susceptibility mapping and explore the correlations with neuropsychiatric tests and clinical parameters. Fifty three patients with haemodialysis and forty-five age-and sex-matched healthy controls were recruited in this prospective study. Susceptibility maps (SM) were reconstructed from original phase data and used to compare the susceptibility of different brain structures between patients and healthy controls. The SM was compared with iron predictions from a classic cadaver brain study. Spearman’s correlation and stepwise multiple regression analysis between susceptibility and neuropsychiatric tests and clinical parameters were calculated. In patients with haemodialysis, the susceptibility of the bilateral caudate head, putamen, substantia nigra, red nucleus and dentate nucleus were significantly higher than those in healthy controls (P < 0.01). There was positive correlation between susceptibility both from normal controls and patients and iron concentration from a classic post-mortem brain study (both r = 0.900, both P = 0.037). In patients with haemodialysis, the susceptibility of the left putamen (r = 0.944), right putamen (r = 0.882) and right thalamus (r = 0.852) were correlated to dialysis duration (all P < 0.05). The susceptibility of the left caudate head (r = −0.415) and right caudate head (r = −0.311) were mildly negatively correlated with neuropsychiatric test scores (all P < 0.05). In summary, our findings indicated that increased brain iron deposition does occur in patients with haemodialysis and correlated with duration of dialysis.

Characterization of cervical lymph nodes using DCE-MRI: Differentiation between metastases from SCC of head and neck and benign lymph nodes

PURPOSES To compare the characteristics of DCE-MRI between metastatic and benign lymph nodes (LNs). To explore the effect of sizes of LNs on the value of Ktrans, Ve and iAUC. MATERIALS AND METHODS Metastatic and benign LNs were retrospectively analyzed. Chi-square test and two sample t-test were applied to TICs and parameters. One factor covariance analysis was used to explore the effect of diameters on the value of Ktrans, Ve and iAUC. RESULTS The value of Ktrans, Ve and iAUC of metastatic LNs were statistically higher (all p < 0.001) than those of benign LNs. The short-axis diameters had no influence on parameters. CONCLUSIONS DCE-MRI is useful to differentiate the metastatic LNs from benign LNs. Sizes of LNs has no effect on parameters.

Increased Number and Distribution of Cerebral Microbleeds Is a Risk Factor for Cognitive Dysfunction in Hemodialysis Patients: A Longitudinal Study.

AbstractThe aim of this study was to explore the risk factors associated with longitudinal changes in hemodialysis patients including the correlation between number and distribution of cerebral microbleeds (CMBs).Sixty-one hemodialysis patients were enrolled in this prospective study. Twenty-eight patients had follow-up examinations with a mean interval of 24.79 ± 5.17 months. The number of CMBs was manually counted on susceptibility-weighted imaging. Subjects were divided into 2 groups with and without CMBs. In the CMB group, 8 of 33 patients did not have a mini-mental state examination (MMSE) because of blurred vision. Multiple logistic regression was used to investigate the risk factors for CMBs. Partial correlation was used to explore the correlation between the increased number of CMBs and the change of MMSE scores.CMBs were seen in 33 (54%) hemodialysis patients. Both age and pre/postdialysis systolic blood pressure (SBP) positively correlated with CMBs. Serum iron (SI), and high-density lipoprotein cholesterol (HDL-c) negatively correlated with CMBs (all P < 0.05). Among 25 patients with CMBs and MMSE, 9 patients had scores <27, which was considered as subnormal and most CMBs in these patients were located in the brainstem and basal ganglia. Considering age and follow-up time as the co-confounding factors, the number of new CMBs over the 2 imaging time points negatively correlated with the change of MMSE scores (r = −0.673, P = 0.023).The presence of new CMBs was a risk factor for cognitive dysfunction and the location of CMBs may be correlated with cognitive impairment. Both SI and HDL-c were protective factors for the CMBs. The risk factors for CMBs included age, pre- and postdialysis SBP.

Radiological Findings of Malignant Tumors of External Auditory Canal: A Cross-Sectional Study Between Squamous Cell Carcinoma and Adenocarcinoma.

AbstractThe primary malignant tumors of external auditory canal (EAC) are rare. The purpose of this study is to compare the imaging features of growth and recurrence pattern between 2 most common carcinomas namely squamous cell carcinoma (SCC) and adenocarcinoma of the EAC.This is a retrospective study involving 41 patients with primary EAC carcinomas of which 22 are SCC and 19 are adenocarcinoma. They were all scanned with high resolution computer tomography (HRCT) and magnetic resonance imaging. Follow-up clinical and imaging studies have also been collected and compared with a median follow-up time of 43 months (range 5–192 months). Necrosis was presented as hypodensity on computed tomography images, hyper-intense on T2WI and heterogeneous enhancement.Eighteen patients were diagnosed to be in T1 and T2 stage, it was found that SCC involved both the cartilaginous part and the bony part of the EAC (11/12), whereas adenocarcinoma involved only the cartilaginous part (6/6) (P < 0.01). Twenty-three patients were diagnosed to be in T3 and T4 stage showed bony involvement and adjacent tissue involvement for both SCC and adenocarcinoma. Parapharyngeal space involvement is much more common in recurrent SCC (P = 0.02). Lymph node metastasis was seen in 6 out of 22 patients with SCC, while 5 out of 19 patients of adenocarcinoma had lung metastasis, even at early stage (1/6; 1/5). Necrosis is more likely to occur in the patients with SCC (9/10) than that of adenocarcinoma (3/13) (P = 0.02).SCC and adenocarcinoma is seen to have different growth pattern at early stage but share similar patterns in the advanced stage. Lymph node metastasis is commonly seen in patients with SCC while adenocarcinoma shows lung metastasis even at early stage.

Recent advances in magnetic resonance imaging for stroke diagnosis

In stroke, diagnosis and identification of the infarct core and the penumbra is integral to therapeutic determination. With advances in magnetic resonance imaging (MRI) technology, stroke visualization has been radically altered. MRI allows for better visualization of factors such as cerebral microbleeds (CMBs), lesion and penumbra size and location, and thrombus identification; these factors help determine which treatments, ranging from tissue plasminogen activator (tPA), anti-platelet therapy, or even surgery, are appropriate. Current stroke diagnosis standards use several MRI modalities in conjunction, with T2- or T2FNx01- weighted MRI to rule out intracerebral hemorrhage (ICH), magnetic resonance angiography (MRA) for thrombus identification, and the diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) mismatch for penumbral identification and therapeutic determination. However, to better clarify the neurological environment, susceptibility-weighted imaging (SWI) for assessing oxygen saturation and the presence of CMBs as well as additional modalities, such as amide proton transfer (APT) imaging for pH mapping, have emerged to offer more insight into anatomical and biological conditions during stroke. Further research has unveiled potential for alternative contrasts to gadolinium for PWI as well, as the contrast has contraindications for patients with renal disease. Superparamagnetic iron oxide nanoparticles (SPIONs) as an exogenous contrast and arterial spin labeling (ASL) as an endogenous contrast offer innovative alternatives. Thus, emerging MRI modalities are enhancing the diagnostic capabilities of MRI in stroke and provide more guidance for patient outcome by offering increased accessibility, accuracy, and information.