Biomedical subjects

M J Chung

Publications and source records attributed to M J Chung.

7 recordsLinked to original sources

PubMed1997

Functioning islet cell tumor of the pancreas. Localization with dynamic spiral CT.

PURPOSE: The purpose of this study was to evaluate the usefulness of dynamic spiral CT, including multidimensional reformation, in the detection and localization of islet cell tumors of the pancreas. MATERIAL AND METHODS: Seven patients with histopathologically proven functioning islet cell tumors of the pancreas were studied with 2-phase contrast-enhanced spiral CT. Scanning of the arterial phase and late phase was started 30 s and 180 s, respectively, after injection of 100 ml of contrast medium at a rate of 3 ml/s. RESULTS: Axial images in the arterial phase depicted the lesions in 5 patients, but in the late phase in only one patient. Multiplanar reformatted images of the arterial phase depicted the lesions in all 7 patients. Maximal intensity projection images demonstrated all lesions with information of their relationship to the vascular structure. CONCLUSION: Dynamic spiral CT with scanning during the arterial phase and retrospective multidimensional reformation is useful for preoperative detection and localization of small islet cell tumors of the pancreas.

Adenoma, Islet Cell↗

PubMed1997

Pericaval fat collection that mimics thrombosis of the inferior vena cava: demonstration with use of multi-directional reformation CT.

PURPOSE: To evaluate the causes for localized fat collection that seemed to be within the subdiaphragmatic inferior vena cava (IVC) on axial computed tomographic (CT) scans. MATERIALS AND METHODS: Six consecutive patients with presumed intracaval fat collection at routine abdominal CT (n = 2) or thin-section CT of the lung (n = 4) were studied prospectively with helical CT. Three patients had chronic liver diseases. Multi-directional, two-dimensional, reformatted images were obtained from the helical CT data for identification of the relation between the IVC and fat collection. Six patients without intracaval fat collection were studied as control subjects. RESULTS: On axial CT scans, the fat collection had a round or oval shape (in four of six patients) and was located posteromedial to the IVC (in four of six patients). On coronal reformatted images, the fat collection was outside the IVC between the diaphragm and subdiaphragmatic IVC, which was contiguous to the fat around the subdiaphragmatic esophagus. In the fat collection group, the IVC angled toward the right and narrowed to half in diameter as it passed down to the diaphragm. In the control group, the IVC was straight, although the diameter decreased similarly. CONCLUSION: A localized fat collection adjacent to the subdiaphragmatic IVC that mimics intracaval fat on axial CT scans is due to acute angulation of the IVC, which is probably a result of anatomic variation, chronic liver disease, or both.

Adipose Tissue↗

PubMed1996

Spiral CT angiography of the thoracic aorta.

Computed tomographic (CT) angiography is a new minimally invasive vascular imaging modality. FOr its clinical use to increase, the advantages and potential applications of this modality must be understood. The clinical applications of CT angiography in the thoracic aorta and its branches include evaluation of congenital aortic anomalies, aortic aneurysm, aortic dissection, Takayasu arteritis, penetrating aortic atherosclerotic ulcer, traumatic aortic injury, the postoperative aorta, arch vessels, and pulmonary sequestration. The advantages of CT angiography over conventional angiography are as follows: (a) high-quality, thin axial sections that demonstrate mural changes, extraluminal pathologic conditions, and spatial relationships with adjacent organs; (b) high contrast resolution and high sensitivity for detecting calcified lesions; (c) angiographic or three-dimensional display of vascular structures and adjacent organs in any projection with a single spiral acquisition; and (d) demonstration of extrinsic causes of vascular compromise. CT angiography has the potential to replace conventional catheter angiography in the diagnosis of many pathologic conditions of the thoracic aorta.

Aortic Dissection↗

PubMed1994

Multiple sequence alignment using simulated annealing.

Multiple sequence alignment is a useful technique for studying molecular evolution and analyzing structure-sequence relationships. Dynamic programming of multiple sequence alignment has been widely used to find an optimal alignment. However, dynamic programming does not allow for certain types of gap costs, and it limits the number of sequences that can be aligned due to its high computational complexity. The focus of this paper is to use simulated annealing as the basis for developing an efficient multiple sequence alignment algorithm. An algorithm called Multiple Sequence Alignment using Simulated Annealing (MSASA) has been developed. The computational complexity of MSASA is significantly reduced by replacing the high-temperature phase of the annealing process by a fast heuristic algorithm. This heuristic algorithm facilitates in minimizing the solution set of the low-temperature phase of the annealing process. Compared to the dynamic programming approach, MSASA can (i) use natural gap costs which can generate better solution, (ii) align more sequences and (iii) take less computation time.

Algorithms↗

PubMedDate not supplied

Helical CT anatomy of pancreatic arteries.

BACKGROUND: To assess the frequency of visualization of pancreatic arteries in the arterial phase of helical computed tomography (CT). METHODS: The visibility of pancreatic and peripancreatic arteries in helical CT images was evaluated in 20 consecutive patients who had no evidence of pancreatic disease. CT examinations were performed by using a continuously rotating CT scanner and intravenous injection of contrast media. The scans were taken 35 s after the start of injection and with a table speed of 3 mm/s. Images were reconstructed in 3-mm section increments. RESULTS: Frequently visualized arteries were the gastroduodenal, anterior and posterior superior pancreaticoduodenal, and right gastroepiploic arteries. Infrequently visualized arteries were the dorsal pancreatic, pancreatica magna, caudal pancreatic, transverse pancreatic, and common, anterior, and posterior inferior pancreaticoduodenal arteries. CONCLUSION: Helical CT enabled us to recognize small pancreatic arteries, and the evaluation of these arteries should be considered in the staging of pancreatic carcinoma.

Arteries↗

PubMedDate not supplied

Detection of pancreatic adenocarcinoma: relative value of arterial and late phases of spiral CT.

BACKGROUND: Spiral computed tomography (CT) allows the pancreas to be imaged during peak contrast levels owing to the capability of fast data acquisition. The objective of this study was to evaluate the relative value of the arterial and late phases of spiral CT for detecting pancreatic adenocarcinomas. METHODS: Twenty-two patients with pathologically proved pancreatic adenocarcinomas underwent two-phase spiral CT. The CT scans were performed with 5 mm collimation and 5 mm/s table speed. Images during the arterial and late phases were obtained at 30- and 180-second delays, respectively. The images of the arterial phase were compared with those of the late phase in terms of tumor conspicuity from surrounding pancreatic parenchyma and tumor detectability by means of a 3-point grading system: 1 (poor), 2 (fair), and 3 (good). RESULTS: In terms of tumor conspicuity from surrounding pancreatic parenchyma, 16 lesions (73%) were good, 5 lesions (23%) were fair, and 1 lesion (4%) was poor during the arterial phase, whereas 6 lesions (27%) were good, 9 lesions (41%) were fair, and 7 lesions (32%) were poor during the late phase (p = 0.0007). The arterial phase was superior to the late phase in 16 patients (73%) and equal in 6 patients (27%). For tumor detectability, 18 lesions (82%) were good, 3 lesions (14%) were fair, and 1 lesion (4%) was poor during the arterial phase, whereas 10 lesions (45%) were good, 7 lesions (32%) were fair, and 5 lesions (23%) were poor during the late phase (p = 0.0033). For detectability, the arterial phase was superior to the late phase in 14 patients (64%) and equal in 8 patients (36%). CONCLUSION: The arterial phase of spiral CT is superior to the late phase, which is equivalent to conventional CT for detecting pancreatic adenocarcinoma.

Adenocarcinoma↗

PubMedDate not supplied

Lobular low attenuation of the lung parenchyma on CT: evaluation of forty-eight patients.

PURPOSE: Our goal was to analyze patients with pulmonary lobular low attenuation (LLA) on thin section CT with regard to the underlying pulmonary diseases and the dynamic changes occurring in the low attenuation regions during respiration. METHOD: Forty-eight consecutive patients with LLA on thin section CT were analyzed retrospectively. Forty-six patients (95%) had symptoms related to respiratory disease, such as productive cough (n = 25) and hemoptysis (n = 18). Only two patients, one with chronic pulmonary embolism and one with Takayasu arteritis combined with bronchiectasis, had pulmonary vascular disease. Six patients, four with bronchiectasis and two with vascular disease, were studied with dynamic CT during forced vital capacity maneuver. Attenuation values for LLA areas and adjacent lung were measured and time-density curves were plotted. RESULTS: Forty-one (85%) patients had bronchiectasis, typically in other than the regions of the LLA. Areas with proximal bronchiectasis showed low attenuation but without notable lobular distribution. Pulmonary vessels in the LLA areas were smaller than those of adjacent normal lung (n = 45). Of 22 patients who underwent pulmonary function tests, 15 had obstructive pattern of impairment. Respiratory dynamic CT showed expiratory air trapping in LLA areas in all six patients. The mean attenuation values of LLA areas were lower than those of the adjacent normal lung by 67 HU at end-inspiration and by 165 HU at end-expiration (p = 0.002). CONCLUSION: The majority of the patients with LLA shown by thin section CT had bronchiectasis elsewhere in the lung, and evidence of air trapping in the LLA was clearly demonstrated. Bronchiolar obstruction may be the most prevalent cause for the development of LLA.

Adult↗