Chun-Sing Wong

Correlations between microstructural alterations and severity of cognitive deficiency in Alzheimer's disease and mild cognitive impairment: a diffusional kurtosis imaging study

OBJECT Diffusional kurtosis imaging (DKI), a natural extension of diffusion tensor imaging (DTI), can characterize non-Gaussian diffusion in the brain. We investigated the capability of DKI parameters for detecting microstructural changes in both gray matter (GM) and white matter (WM) in patients with mild cognitive impairment (MCI) and Alzheimers disease (AD) and sought to determine whether these DKI parameters could serve as imaging biomarkers to indicate the severity of cognitive deficiency. MATERIALS AND METHODS DKI was performed on 18AD patients and 12 MCI patients. Fractional anisotropy, kurtosis and diffusivity parameters in the temporal, parietal, frontal and occipital lobes were compared between the two groups using Mann-Whitney U test. The correlations between regional DKI parameters and mini-mental state examination (MMSE) score were tested using Pearsons correlation. RESULTS In ADs, significantly increased diffusivity and decreased kurtosis parameters were observed in both the GM and WM of the parietal and occipital lobes as compared to MCIs. Significantly decreased fractional anisotropy was also observed in the WM of these lobes in ADs. With the exception of fractional anisotropy and radial kurtosis, all the five other DKI parameters exhibited significant correlations with MMSE score in both GM and WM. CONCLUSION Bearing additional information, the DKI model can provide sensitive imaging biomarkers for assessing the severity of cognitive deficiency in reference to MMSE score and potentially improve early detection and progression monitoring of AD based on characterizing microstructures in both the WM and especially the GM.

Imaging biomarker with T1ρ and T2 mappings in osteoarthritis - in vivo human articular cartilage study.

INTRODUCTION Osteoarthritis (OA) of the knee is a common and disabling disease worldwide. Its prevalence is increasing in view of the aging population. Changes in collagen content, its orientation and GAG content in the articular cartilage with age are the major features in knee osteoarthritis. These changes in collagen and GAG contents show no manifestation in plain radiography and conventional magnetic resonance imaging (MRI). Nevertheless, early diagnosis of the knee osteoarthritis is of paramount importance clinically in view of the evolution of putative interventions in its early stage. The aim of this project is to identify the relationships between the two imaging biomarkers (i.e. T1ρ and T2 mappings) and the GAG concentration in living human symptomatic cartilage. METHODOLOGY 28 patients with clinical diagnosis of knee osteoarthritis were enrolled. 7 males and 16 females were recruited and their mean age was 68.1 (ranges from 53 to 84). Conventional PD sequence, T1ρ and T2 mappings were performed for each subject within 1 week before total knee arthroplasty. Articular cartilage from the lateral tibial plateau was harvested and the GAG content in cartilage was determined by using dimethylmethylene blue method. T1ρ mean and T2 values were calculated and correlate with GAG concentration statistically. RESULTS The mean value T1ρ was 40.3±13.5ms, ranging from 15.3 to 69.3ms and the mean value T2 was 31.0±10.5ms, ranging from 16.1 to 46.9ms. The mean value of GAG content was 80.1±33.3mg, ranging from 24.9 to 166.0mg while the mean value of GAG concentration was 267.4±165.9mg/cm(3), ranging from 91.3 to 760.5mg/cm(3). T2 values were inversely correlated with GAG concentration with R(2)=0.375, p=0.001 while T1ρ values were also inversely correlated with GAG concentration with R(2)=0.200, p=0.025. CONCLUSION This in vivo study confirmed that T1ρ and T2 values correlate with the GAG concentration in living human knee cartilages which corroborate with the previous works. The later (T2 values) is found more reliable in our study and less controversial in literatures. We postulate that T2 values can serve as a non-invasive imaging biomarker in the progress of knee osteoarthritis in terms of both disease diagnosis and treatment response monitoring.

Prevalence and extent of subclinical atherosclerosis in patients with psoriasis

Patients with psoriasis are prone to premature atherosclerosis and increased risk of cardiovascular disease events. However, the prevalence and extent of atherosclerosis in patients with psoriasis are unknown.

Aging in Deep Gray Matter and White Matter Revealed by Diffusional Kurtosis Imaging

Diffusion tensor imaging has already been extensively used to probe microstructural alterations in white matter tracts, and scarcely, in deep gray matter. However, results in literature regarding age-related degenerative mechanisms in white matter tracts and parametric changes in the putamen are inconsistent. Diffusional kurtosis imaging is a mathematical extension of diffusion tensor imaging, which could more comprehensively mirror microstructure, particularly in isotropic tissues such as gray matter. In this study, we used the diffusional kurtosis imaging method and a white-matter model that provided metrics of explicit neurobiological interpretations in healthy participants (58 in total, aged from 25 to 84 years). Tract-based whole-brain analyses and regions-of-interest (anterior and posterior limbs of the internal capsule, cerebral peduncle, fornix, genu and splenium of corpus callosum, globus pallidus, substantia nigra, red nucleus, putamen, caudate nucleus, and thalamus) analyses were performed to examine parametric differences across regions and correlations with age. In white matter tracts, evidence was found supportive for anterior-posterior gradient and not completely supportive for retrogenesis theory. Age-related degenerations appeared to be broadly driven by axonal loss. Demyelination may also be a major driving mechanism, although confined to the anterior brain. In terms of deep gray matter, higher mean kurtosis and fractional anisotropy in the globus pallidus, substantia nigra, and red nucleus reflected higher microstructural complexity and directionality compared with the putamen, caudate nucleus, and thalamus. In particular, the unique age-related positive correlations for fractional anisotropy, mean kurtosis, and radial kurtosis in the putamen opposite to those in other regions call for further investigation of exact underlying mechanisms. In summary, the results suggested that diffusional kurtosis can provide measurements in a new dimension that were complementary to diffusivity metrics. Kurtosis together with diffusivity can more comprehensively characterize microstructural compositions and age-related changes than diffusivity alone. Combined with proper model, it may also assist in providing neurobiological interpretations of the identified alterations.

Treatment response monitoring in patients with gastrointestinal stromal tumor using diffusion-weighted imaging: preliminary results in comparison with positron emission tomography/computed tomography

We compared the parameters derived from diffusion‐weighted imaging (DWI) and positron emission tomography/computed tomography (PET/CT) for treatment response evaluation and response prediction in patients with gastrointestinal stromal tumor (GIST). Seven patients with histologically proven metastatic disease were enrolled. DWI and PET/CT data were collected from all patients at diagnosis and from six at follow‐up. All 37 lesions were identifiable in DWI with a sensitivity of 100%. To achieve higher accuracy, we used the apparent diffusion coefficient (ADC) of liver and background noise as thresholds for the measurement of the ADCs of lesions. Significant inverse correlations were found between ADCmean_thr (ADCmean with thresholds) and SUVmean (mean standardized uptake value) (R2 = 0.523, p < 0.001 at diagnosis, and R2 = 0.916, p < 0.001 at follow‐up), between ADCmean_thr and SUVmax (maximum SUV) (R2 = 0.529, p < 0.001 at diagnosis, and R2 = 0.761, p < 0.001 at follow‐up), between ΔADCmean_thr (percentage change in ADCmean_thr) and ΔSUVmean (percentage change in SUVmean) (R2 = 0.384, p < 0.001), and between ΔADCmean_thr and ΔSUVmax (percentage change in SUVmax) (R2 = 0.500, p < 0.001). In lesion‐based analysis, pre‐treatment ADCmean_thr outperformed SUVmean and SUVmax in treatment response prediction, with an area under the receiver operating characteristic curve of 0.706. These results show that DWI can provide a quantitative assessment comparable with PET/CT in GIST lesion characterization, treatment response evaluation and response prediction. Copyright

Assessing local patients' knowledge and awareness of radiation dose and risks associated with medical imaging: A questionnaire study

To assess the awareness of radiation dose and associated risks caused by radiological procedures among local patients.

Hepatocellular carcinoma with extrahepatic collateral arterial supply.

Haepatocellular carcinoma (HCC) is the most common primary liver malignancy, representing the fifth most common cancer in the world. Without treatment, the median survival of HCC patients has been reported to be 8 weeks from symptomatic presentation. Transarterial chemoembolisation is widely used to manage unresectable HCCs. However, when a tumour is large or locates near the liver capsule, it may receive supplies from vessels other than hepatic arteries. In this paper, we discuss the anatomy of possible extrahepatic collateral arterial supplies of HCCs.

The use of FDG-PET/CT in extranodal Rosai–Dorfman disease of bone

We report the case of a 41-year-old man with extranodal Rosai–Dorfman disease (RDD), presenting with clinically detectable bone involvement only. The use of FDG-PET/CT in the diagnosis of RDD is discussed.

Increasing the Accuracy of Volume and ADC Delineation for Heterogeneous Tumor on Diffusion-Weighted MRI: Correlation with PET/CT

PURPOSE To improve the accuracy of volume and apparent diffusion coefficient (ADC) measurements in diffusion-weighted magnetic resonance imaging (MRI), we proposed a method based on thresholding both the b0 images and the ADC maps. METHODS AND MATERIALS In 21 heterogeneous lesions from patients with metastatic gastrointestinal stromal tumors (GIST), gross lesion were manually contoured, and corresponding volumes and ADCs were denoted as gross tumor volume (GTV) and gross ADC (ADC(g)), respectively. Using a k-means clustering algorithm, the probable high-cellularity tumor tissues were selected based on b0 images and ADC maps. ADC and volume of the tissues selected using the proposed method were denoted as thresholded ADC (ADC(thr)) and high-cellularity tumor volume (HCTV), respectively. The metabolic tumor volume (MTV) in positron emission tomography (PET)/computed tomography (CT) was measured using 40% maximum standard uptake value (SUV(max)) as the lower threshold, and corresponding mean SUV (SUV(mean)) was also measured. RESULTS HCTV had excellent concordance with MTV according to Pearsons correlation (r=0.984, P<.001) and linear regression (slope = 1.085, intercept = -4.731). In contrast, GTV overestimated the volume and differed significantly from MTV (P=.005). ADC(thr) correlated significantly and strongly with SUV(mean) (r=-0.807, P<.001) and SUV(max) (r=-0.843, P<.001); both were stronger than those of ADC(g). CONCLUSIONS The proposed lesion-adaptive semiautomatic method can help segment high-cellularity tissues that match hypermetabolic tissues in PET/CT and enables more accurate volume and ADC delineation on diffusion-weighted MR images of GIST.

Hemisphere, gender and age‐related effects on iron deposition in deep gray matter revealed by quantitative susceptibility mapping

The purpose of this work was to investigate the effects of hemispheric location, gender and age on susceptibility value, as well as the association between susceptibility value and diffusional metrics, in deep gray matter.