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후두와 혈관아세포종의 방사선학적 소견: MR 소견을 중심으로
김선교 대한영상의학회 1995 대한영상의학회지 Vol.32 No.3
Purpose: To review MR findings of the posterior fossa hemangioblastomas and to evaluate diagnostic value of MRI correlated with CT and angiographic findings. Materials and Methods: The MR findings in twelve patients with surgically proven posterior fossa hemangioblastomas including one case of von Hippel- Lindau disease were retrospectively analyzed and correlated with CT (7 patients) and angiographic findings (9 patients). Results: On MRI, five hemangioblastomas were located in the cerebellar hemisphere and seven in the vermis. The masses appeared to be solid in 3 cases(25%), solid tumors with central cyst in 2 cases(17%), and cyst with mural nodules in 7cases(58%). Abnormal tumor vessels represented by characteristic signal voids on MRI were observed in 9 cases(75%) and were not seen in 3 cases(25%) with mural nodule below 1.5 cm in diameter. On pre-contrast CT, hemangioblastomas appeared poorly marginated slightly hyperdense masses in solid tumors, and hypodense cystic masses in cysts. After contrast enhancement, solid tumors were markedly enhanced, but it was difficult to differentiate hemangioblastomas from other tumors. In nine patients, angiograms demonstrated hypervascular blush corresponding to the solid component of the tumors. Conclusion: MRI was superior to CT in evaluating the characteristic of abnormal tumor vessels and mural nodules, delineation of tumor margin and tumor extent. Angiography was useful in the diagnosis of cystic hemangioblastomas which contain small mural nodule (less than1.5 cm in diameter) without definite vascular signal voids on MRI. MRI demonstrated solid or cystic tumor with small mural nodule and abnormal vascular signal voids in the posterior fossa should suggest hemangioblastoma.
Counting Process of MAP(3)s and Moment Fittings
김선교,Kim, Sunkyo The Korean Operations Research and Management Scie 2017 한국경영과학회지 Vol.3 No.1
Moments of stationary intervals and those of the counting process can be used for moment fittings of the point processes. As for the Markovian arrival processes, the moments of stationary intervals are given as a polynomial function of parameters whereas the moments of the counting process involve exponential terms. Therefore, moment fittings are more complicated with the counting process than with stationary intervals. However, in queueing network analysis, cross-correlation between point processes can be modeled more conveniently with counting processes than with stationary intervals. A Laplace-Stieltjies transform of the stationary intervals of MAP (3)s is recently proposed in minimal number of parameters. We extend the results and present the Laplace transform of the counting process of MAP (3)s. We also show how moments of the counting process such as index of dispersions for counts, IDC, and limiting IDC can be used for moment fittings. Examples of exact MAP (3) moment fittings are also presented on the basis of moments of stationary intervals and those of the counting process.