Gyunggoo Cho

Relative apparent diffusion coefficient: Determination of reference site and validation of benefit for detecting metastatic lymph nodes in uterine cervical cancer

To determine the reference site for relative apparent diffusion coefficient (rADC) and to evaluate the benefit of rADC for detecting metastatic lymph nodes in uterine cervical cancer.

Prostate Cancer Detection on Dynamic Contrast-Enhanced MRI: Computer-Aided Diagnosis Versus Single Perfusion Parameter Maps

OBJECTIVE The purpose of this article is to assess the value of computer-aided diagnosis (CAD) for prostate cancer detection on dynamic contrast-enhanced MRI (DCE-MRI). MATERIALS AND METHODS DCE-MRI examinations of 42 patients with prostate cancer were used to generate perfusion parameters, including baseline and peak signal intensities, initial slope, maximum slope within the initial 50 seconds after the contrast injection (slope(50)), wash-in rate, washout rate, time to peak, percentage of relative enhancement, percentage enhancement ratio, time of arrival, efflux rate constant from the extravascular extracellular space to the blood plasma (k(ep)), first-order rate constant for eliminating gadopentetate dimeglumine from the blood plasma (k(el)), and constant depending on the properties of the tissue and represented by the size of the extravascular extracellular space (A(H)). CAD for cancer detection was established by comprehensive evaluation of parameters using a support vector machine. The diagnostic accuracy of single perfusion parameters was estimated using receiver operating characteristic analysis, which determined threshold and parametric maps for cancer detection. The diagnostic performance of CAD for cancer detection was compared with those of T2-weighted imaging (T2WI) and single perfusion parameter maps, using histologic results as the reference standard. RESULTS The accuracy, sensitivity, and specificity of CAD were 83%, 77%, and 77%, respectively, in the entire prostate; 77%, 91%, and 64%, respectively, in the transitional zone; and 89%, 89%, and 89%, respectively, in the peripheral zone. Values for k(ep), k(el), initial slope, slope(50), wash-in rate, washout rate, and time to peak showed greater area under the curve values (0.803-0.888) than did the other parameters (0.545-0.665) (p < 0.01) and were compared with values for CAD. In the entire prostate, accuracy was greater for CAD than for all perfusion parameters or T2WI (63-77%); sensitivity was greater for CAD than for T2WI, initial slope, wash-in rate, slope(50), and washout rate (38-77%); and specificity was greater for CAD than for T2WI, k(ep), k(el), and time to peak (59-68%) (p < 0.05). CONCLUSION CAD can improve the diagnostic performance of DCE-MRI in prostate cancer detection, which may vary according to zonal anatomy.

Sex differences in amygdala subregions: evidence from subregional shape analysis.

Each subregion of the amygdala is characterized by a distinct cytoarchitecture and function. However, most previous studies on sexual dimorphism and aging have assessed differences in the structure of the amygdala at the level of the amygdala in its entirety rather than at the subregional level. Using an amygdala subregional shape analysis, we investigated the effects of sex, age, and the sex × age interaction on the subregion after controlling for intracranial volume. We found the main effect of age in the subregions and the effect of sex in the superficial nucleus, which showed that men had a larger mean radius than women. We also found a sex × age interaction in the centromedial nucleus, in that the radius of the centromedial nucleus showed a steeper decline with age in women compared with men. Regarding the amygdala volume as a whole, we found only an age effect and did not find any other significant difference between genders. The sex difference in the amygdala subregion and its relevance to the circulating gonadal hormone were discussed.

MDCT-based scoring system for differentiating angiomyolipoma with minimal fat from renal cell carcinoma.

Background Subtype-related various computed tomography (CT) features of renal cell carcinoma (RCC) are a confusing factor in differentiating angiomyolipoma with minimal fat (AMLmf) from RCC. To overcome RCC heterogeneity, a scoring system, which integrates multiple discrimitive parameters can be helpful for differentiating AMLmf from RCC. Purpose To develop a MDCT-based scoring system for differentiating AMLmf from RCC. Material and Methods In 407 patients with pathologically confirmed 48 AMLmfs and 359 RCCs (247 clear cell RCCs, 67 papillary RCCs, and 45 chromophobe RCCs), MDCT features (ratio of long-to-short diameter, enhancement characteristics, tumor attenuation on unenhanced scan, tumor margin, calcification), age, and sex were compared between AMLmf and RCCs. Based on logistic regression, a scoring system for diagnosing AMLmf over RCC was built, and its diagnostic accuracy was evaluated. Results Scores suggesting AMLmf, i.e. the logit function as used in logistic regression analysis, were calculated as follows: Score = e 6 . 16 . A - 0 . 003 . B + 1 . 20 . C + 0 . 97 . D + 2 . 13 . E - 0 . 05 . F 1 + e 6 . 16 . A - 0 . 003 . B + 1 . 20 . C + 0 . 97 . D + 2 . 13 . E - 0 . 05 . F , where A = ratio of long-to-short diameter, B = enhancement amount in early excretory phase, C = homogeneous enhancement, D = tumor attenuation on unenhanced scan, E = sex, and F = age. Area under receiver-operating characteristics curve of scoring system was 0.919. With a score of 0.204 or higher, the scoring system yielded greatest accuracy (90%, 368/407) for diagnosing AMLmf over RCC, which was greater than that of any single MDCT or clinical parameter (53–85%) (P < 0.05). With a score of 0.317 or higher, sensitivity and specificity were 68% (32/48) and 95% (340/359). Conclusion MDCT-based scoring system can improve diagnostic performance of MDCT in differentiating AMLmf from RCC and help patients with AMLmf to avoid unnecessary surgery with high specificity.

Electrochemical property of surface modified polypyrrole film with heteropoly anions

Summary form only given. Preparation of heteropoly anion modified polypyrrole on glassy carbon and their electrochemical properties were studied. Keggin-type heteropolymolybdate and heteropolytungstate were chosen in this study because of their distinct catalytic activity towards the reduction of oxygen and nitrite in the solution. Electrochemical polymerization and incorporation of poly-anions were performed in solution containing both chemicals. The first scan of cyclic voltammogram showed the polymer film grew via nucleation and growth mechanism. Electrochemical peaks from the film were from polymer itself and from the incorporated poly anions. They were similar to those obtained from the solution and were stable under pH value of 4.5. The peak potential due to polypyrrole shifted to cathodic direction by about 40 mV/pH, while those of poly anions peak exhibited cathodic shift of about 60 mV/pH. As the thickness of the film changed the charge transport mechanism also changed and the redox peaks shifted to cathodic direction. The amount of incorporated anions determined by electrochemical method linearly depended on the charge passed in the polymerization process. The apparent diffusion coefficient of incorporated poly-anions in the polymer film was determined to be in the order of 10/sup -9/ to 10/sup -10/ cm/sup 2//sec. Electrochemical quartz crystal microbalance technique provided some insight of the film formation and the incorporation of poly anion. Also the catalytic activity towards the reduction of oxygen and hydrogen peroxide will be discussed.

Associations between anterior cingulate cortex glutamate and γ-aminobutyric acid concentrations and the harm avoidance temperament

Converging lines of evidence have suggested that the personality traits might have neurobiological underpinnings. The anterior cingulate cortex (ACC) has been implicated to play an important role in the human fear and anxiety. Functional and structural characteristics of ACC have been suggested to be associated with the harm avoidance (HA) temperament, one of the important temperament dimensions. Therefore, we aimed to investigate correlations between neurometabolite concentrations in ACC, specifically glutamate and gamma-aminobutyric acid (GABA), which are major excitatory and inhibitory neurotransmitters, respectively, and HA scores. Neurometabolite concentrations were measured using high resolution single voxel proton magnetic resonance spectroscopy ((1)H-MRS), and the HA temperament was evaluated using the Temperament and Character Inventory (TCI). Correlations between HA scores from 37 participants (21 men/16 women, age of 30.3+/-7.0) and glutamate and GABA concentrations in the mid-ACC region were evaluated. HA scores correlated negatively with glutamate concentrations in ACC (partial correlation, R=-0.54, df=33, P=0.001) and positively with GABA concentrations in ACC (partial correlation, R=0.48, df=30, P=0.005). These findings suggest that glutamate and GABA concentrations in ACC are closely related to levels of the HA temperament in healthy subjects.

Evaluation of MRI resolution affecting trabecular bone parameters: Determination of acceptable resolution

The objective of this study is to evaluate the effect of MR image resolution on trabecular bone parameters and to determine the acceptable resolution that can be accurately analyzed to assess structural parameters. Ten distal femoral condyle specimens of 1 × 1 × 1 cm3 were scanned with a 4.7‐T Bruker BioSpec MRI scanner using a three‐dimensional fast large‐angle spin‐echo sequence with various iso‐cubic voxels sizes (65, 130, 160, 196, 230, and 260 μm). Otsu thresholding was applied to identify voxels containing bone. Conventional bone parameters, structural bone parameters, and skeleton‐based local trabecular thickness (slTB.Th) were evaluated. The Bland–Altman method and correlation indicated that the conventional and structural bone parameters were preserved with an iso‐cubic voxel size up to 230 μm (r > 0.932 and r > 0.843, respectively). In addition, slTB.Th derived from the highest resolution images (65 μm iso‐cubic voxel size), correlated well (r > 0.833) with the values computed from lower resolution images, up to 230 μm, which is twice typical human trabecular thickness range (100–150 μm). The outcome of this study suggests that the various bone parameters were well preserved up to 230 μm images. Magn Reson Med, 2011.

The use of the fusion protein RGD-HSA-TIMP2 as a tumor targeting imaging probe for SPECT and PET.

The human serum albumin tissue inhibitor of metalloproteinase 2 (HSA-TIMP2) is known to possess antitumor activity, which has been attributed to its ability to inhibit endothelial cell proliferation by binding to integrin receptors. In this study, a fusion protein, cyclic arginine-glycine-aspartate (RGD)-HSA-TIMP2, formed by conjugating HSA-TIMP2 with a RGD peptide, and its (123)I- and (68)Ga-labeled compounds, were synthesized and evaluated with in vivo tumor imaging using single photon emission computed tomography (SPECT) and positron emission tomography (PET). RGD-HSA-TIMP2 was synthesized by covalent bonding of the RGD peptide to the side chain amino groups of HSA-TIMP2 from a two-step reaction involving from activation with N-succinimidyl iodoacetate. This conjugation improved the anticancer effect of HSA-TIMP2 in cancer cells. The (123)I- and (68)Ga-labeled fusion proteins were prepared and subsequently injected into the tail veins of mice bearing human glioblastoma cancer U87MG xenografts for SPECT and PET imaging and biodistribution studies. Tumor uptake of radioligand was high in both the PET images and in the biodistribution studies at 3 h after injection. These studies demonstrated that the new fusion protein has potential not only as an anticancer agent but also as a radioligand for the diagnosis of tumors.

Robust MR assessment of cerebral blood volume and mean vessel size using SPION-enhanced ultrashort echo acquisition.

Intravascular superparamagnetic iron oxide nanoparticles (SPION)-enhanced MR transverse relaxation rates (∆R2(⁎) and ∆R2) are widely used to investigate in vivo vascular parameters, such as the cerebral blood volume (CBV), microvascular volume (MVV), and mean vessel size index (mVSI, ∆R2(⁎)/∆R2). Although highly efficient, regional comparison of vascular parameters acquired using gradient-echo based ∆R2(⁎) is hampered by its high sensitivity to magnetic field perturbations arising from air-tissue interfaces and large vessels. To minimize such demerits, we took advantage of the dual contrast property of SPION and both theoretically and experimentally verified the direct benefit of replacing gradient-echo based ∆R2(⁎) measurement with ultra-short echo time (UTE)-based ∆R1 contrast to generate the robust CBV and mVSI maps. The UTE acquisition minimized the local measurement errors from susceptibility perturbations and enabled dose-independent CBV measurement using the vessel/tissue ∆R1 ratio, while independent spin-echo acquisition enabled simultaneous ∆R2 measurement and mVSI calculation of the cortex, cerebellum, and olfactory bulb, which are animal brain regions typified by significant susceptibility-associated measurement errors.

Feasibility of FAIR imaging for evaluating tumor perfusion

To evaluate the feasibility of flow‐sensitive alternating inversion recovery (FAIR) for measuring blood flow in tumor models.