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Biomedical subjects

C C Ma

Publications and source records attributed to C C Ma.

16 recordsLinked to original sources
PubMed2006

The short-to-midterm results of endovascular stent grafting for acute thoracic aortic diseases in Chinese patients.

OBJECTIVE: To review the results of endovascular treatment of acute thoracic aortic diseases in a group of Chinese patients. DESIGN: Retrospective study. SETTING: A tertiary referral hospital with a cardiothoracic surgery service. PATIENTS: All 15 patients presenting with acute thoracic aortic diseases between September 2001 and October 2005 inclusive, of whom eight had traumatic rupture, four had complicated acute dissections, two had mycotic aneurysms, and one an aneurysm with an aortobronchial fistula. INTERVENTIONS: Thoracic aortic stent grafting. MAIN OUTCOME MEASURES: Immediate success, 6-month and 1-year survival rates. RESULTS: The median follow-up period was 20.6 months (range, 0-50.1 months). Stent grafts were deployed with immediate success in all patients. Two patients had ancillary bypass surgery for the supra-aortic branches. There were two in-hospital deaths. Four sustained access artery injury and needed graft repair. Computed tomography at 1 month showed complete thrombosis of the aneurysmal lumen or the thoracic aortic false lumen in 12 of 13 survivors. Computed tomography at 6 months showed complete thrombosis of the aneurysmal lumen or the false lumen in nine of 10 patients due for follow-up. Both 6-month and 1-year survival rates were 87%. CONCLUSIONS: Thoracic aortic stent grafting for acute thoracic aortic disease is feasible and has a high success rate, with good short-to-midterm results. However, the large size of the stent graft introducer set imposes a high risk of access artery injury, for which further improvements are necessary.

Aortic Dissection↗
PubMed2005

Benign metastasising leiomyoma: a rare but possible cause of bilateral pulmonary nodules in Chinese patients.

We report three cases of benign metastasising leiomyoma, which is a rare cause of multiple lung nodules, in three Hong Kong Chinese females. One patient presented with pleuritic chest pain, another was asymptomatic, while the last presented with haemoptysis. All three patients had previously undergone surgical resection of uterine leiomyomas. Multiple lung nodules mimicking lung metastases were demonstrated on chest radiographs, and all three diagnoses were obtained from lung biopsies. Hormonal therapy was given to two patients with variable responses. To the best of our knowledge, this is the first report of benign metastasising leiomyoma in Hong Kong Chinese population. It highlights the importance of considering this rare and benign disease in premenopausal females presenting with multiple lung nodules.

Adult↗
PubMed2001

The investigation of three-dimensional vibration for piezoelectric rectangular parallelepipeds using the AF-ESPI method.

Electronic speckle pattern interferometry (ESPI) is a powerful tool for the full-field measurement of a deformed body. In this paper, a three-dimensional vibrating block that couples the out-of-plane and in-plane motions is investigated using the amplitude-fluctuation ESPI (AF-ESPI). This method demonstrates the advantages of combining high processing speed, such as in the subtraction method, with high fringe sensitivity, such as in the time-averaged method. The optical system for AF-ESPI is then employed to analyze the volume vibration of piezoelectric material for a rectangular parallelepiped configuration. Based on the fact that fringe patterns measured by the AF-ESPI method appear as a clear picture only at the resonant frequency, both the natural frequencies and the out-of-plane and in-plane vibration mode shapes are successfully obtained in this study. Finally, the impedance analysis as well as the finite element method (FEM) with three-dimensional model are also conducted to compare with the result obtained by AF-ESPI. It is shown that the numerical calculation and the experimental result agree fairly well for both the resonant frequency and the mode shape in three-dimensional configurations.

Journal Article↗
PubMed2001

Vibration characteristics of composite piezoceramic plates at resonant frequencies: experiments and numerical calculations.

The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. In this paper, we employ an optical interferometry method called the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) to investigate the vibration characteristics of piezoceramic/aluminum laminated plates. The AF-ESPI is a powerful tool for the full-field, noncontact, and real-time measurement method of surface displacement for vibrating bodies. As compared with the conventional film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Because the clear fringe patterns measured by the AF-ESPI method will be shown only at resonant frequencies, both the resonant frequencies and corresponding vibration mode shapes are obtained experimentally at the same time. Excellent quality of the interferometric fringe patterns for both the in-plane and out-of-plane vibration mode shapes are demonstrated. Two different configurations of piezoceramic/aluminum laminated plates, which exhibit different vibration characteristics because of the polarization direction, are investigated in detail. From experimental results, we find that some of the out-of-plane vibration modes (Type A) with lower resonant frequencies cannot be measured by the impedance analysis; however, all of the vibration modes of piezoceramic/aluminum laminated plates can be obtained by the AF-ESPI method. Finally, the numerical finite element calculations are also performed, and the results are compared with the experimental measurements. Excellent agreements of the resonant frequencies and mode shapes are obtained for both results.

Letter↗
PubMed2001

Experimental and numerical investigations of resonant vibration characteristics for piezoceramic plates.

Electronic speckle pattern interferometry (ESPI) is a full field, non-contact technique for measuring the surface displacement of a structure subjected to static loading or, especially, to dynamic vibration. In this article we employ an optical system called the amplitude-fluctuation ESPI with out-of-plane and in-plane measurements to investigate the vibration characteristics of piezoceramic plates. Two different configurations of piezoceramic plates, namely the rectangular and the circular plates, are discussed in detail. As compared with the film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Because the clear fringe patterns will be shown only at resonant frequencies, both the resonant frequencies and the corresponding mode shapes are obtained experimentally at the same time by the proposed AF-ESPI method. Excellent quality of the interferometric fringe patterns for both the in-plane and out-of-plane vibration mode shapes is demonstrated. The resonant frequencies of the piezoceramic plates are also measured by the conventional impedance analysis. From experimental results, we find that the out-of-plane vibration modes (type A) with lower resonant frequencies cannot be measured by the impedance analysis and only the in-plane vibration modes (type B) will be shown. However, both the out-of-plane (bending) and in-plane (extensional) vibration modes of piezoceramic plates are obtained by the AF-ESPI method. Finally, the numerical finite element calculations are also performed, and the results are compared with the experimental measurements. It is shown that the numerical calculations and the experimental results agree fairly well for both the resonant frequencies and the mode shapes.

Journal Article↗
PubMed2000

A pharmacodynamic assessment of the impact of antihypertensive non-adherence on blood pressure control.

OBJECTIVES: To evaluate if antihypertensive regimens that conform to present FDA guidelines by maintaining > or = 50% of their peak effect at the end of the dosing interval protect patients during sporadic lapses in adherence. METHODS: 169 patients on monotherapy for high blood pressure underwent electronic adherence monitoring for 3 months. Blood pressures were measured during non-study office visits and were retrieved from automated medical records. Questionnaires were used to obtain other covariate information. The ratio of the dosing interval to the half-life of drug activity (I') was used to capture conformity with FDA guidelines. Data analysis focused on the interaction between I' and the impact on blood pressure of delayed dosing. RESULTS: The average (+/- standard deviation) blood pressure during the study was 139.0(+/- 12.0)/85.0(+/- 6.9) mm Hg. Lisinopril followed by sustained-release verapamil, atenolol, and hydrochlorothiazide were the most frequently prescribed agents. The majority of regimens (99%) conformed to FDA dosing guidelines. Of the patients 23% missed a dose before their blood pressure check. Non-adherence, however, did not have a direct impact on blood pressure, and no interaction with I' of was detected. CONCLUSIONS: Among patients with relatively mild hypertension on single-drug therapy, regimens that conform to current FDA dosing guidelines may prevent losses of blood pressure control during episodic lapses of adherence. These findings should be replicated in other patient populations with standardized blood pressure measurement to confirm their validity.

Adult↗
PubMed1998

Thoracoscopic major lung resections: an Asian perspective.

The application of video-assisted thoracic surgery (VATS) for major lung resection is controversial. We review our combined experience from three centers in Asia. From June 1993 through June 1997, 214 patients underwent VATS major resections (2 segmentectomies, 203 lobectomies, 6 bilobectomies, 3 pneumonectomies), mostly for primary malignancy. Stringent selection criteria were used to choose patients for this approach. We prefer a technique of not spreading ribs, using conventional thoracic instrument for dissection and routine use of wound protector for specimen retrieval. There was one postoperative surgical death and 47 non-fatal complications, which compare favorably with published series on open technique. Of the primary lung cancer patients, 93% are still alive after a mean follow-up of 26 months. We conclude that VATS major lung resection is technically feasible in selected patients and associated with favorable intermediate-term results.

Asia↗
PubMed1996

Video-assisted thoracoscopic anatomic lung resections. The initial Hong Kong experience.

We report our combined experience on video-assisted thoracoscopic (VAT) anatomic lung resections from two major hospitals in Hong Kong over a 17-month period. From August 1993 to December 1994, 82 cases of major lung resections were attempted using the VATS approach, of which 60 were successfully completed (55 lobectomies, 2 bilobectomies, 2 pneumonectomies, and 1 segmentectomy). Of these 60 cases, there were 43 men and 17 women with a mean age of 66 years (range, 37 to 85 years). The final pathologies were 52 primary lung cancers (37 adenocarcinoma, 11 squamous cell carcinoma, 2 bronchoalveolar carcinoma, 1 adenosquamous carcinoma, and 1 undifferentiated carcinoma); 1 pulmonary metastasis (from nasopharyngeal carcinoma); and 7 benign lesions (3 tuberculosis, 1 bronchiectasis, 1 sclerosing hemangioma, 2 organizing pneumonia). There was one postoperative death (mortality rate, 1.8%). Complications include persistent air leak over 10 days (four), wound infection (two), supraventricular tachycardia (three), and recurrence of tumor over the utility thoracotomy scar (one). All the patients were followed up from 8 weeks to 19 months (mean, 10 months). The mean duration of chest drainage was 5.4 days (range, 2 to 25 days). The mean hospital stay was 7.2 days (range, 4 to 35 days). The average postoperative parenteral narcotic (meperidine hydrochloride [Pethidine]) requirement by patient-controlled analgesia was 275 mg (range, 75 to 800 mg). This compared favorably with an age- and sex-matched historic group of patients who underwent posterolateral thoracotomy and had a hospital stay of 10.4 days (statistically non-significant) and narcotic requirement of 950 mg (statistically significant by paired t test). We conclude that VAT anatomic lung resection is technically feasible. However, there are some specific complications associated with major lung resection through minimal access. Refinement of our present technique and attention to details are important to improve our results.

Adenocarcinoma↗
PubMed1996

Thoracoscopic lobectomy for benign diseases.

The few reports in the literature on thoracoscopic anatomic lung resections were almost exclusively for early primary lung cancers. We report our combined experience on video-assisted thoracoscopic (VAT) lobectomy for benign diseases from two major hospitals in Hong Kong over a 20-month period. From August 1993 to March 1995, 66 VAT lobectomies were performed; of this number, 10 cases (15%) were for benign diseases (5 tuberculosis, 2 organized pneumonia, 1 bronchiectasis, 1 sclerosing hemangioma, 1 infected bronchogenic cyst). There was no mortality or incidence of intraoperative complications. Postoperative complications occurred in one patient with tuberculosis and consisted of persistent air leak and subsequent wound infection. There were no long-term complications after a mean follow-up of 11 months. The mean duration of chest tube drainage was 6.7 days and that of hospital stay was 9.8 days. These results were not statistically different from those achieved in VAT lobectomies performed for malignant tumors (5.0 days for drainage and 6.8 days for hospital stay) despite the fact that hilar dissection was sometimes more difficult in the former because of inflammatory changes. We conclude that VAT lobectomy for benign diseases is technically feasible even though its role in thoracic surgery remains to be defined.

Adult↗
PubMed1995

Distinct mutational spectrum of the p53 gene in lung cancers from Chinese women in Hong Kong.

Accumulating evidence suggests that the p53 gene is a good target for molecular epidemiological studies to search for risk factors in carcinogenic events. The lung cancer incidence for females in Hong Kong is unusually high, ranking among the highest in the world despite a low percentage with a history of smoking. To gain insights into possible etiological risk factors responsible for this high incidence, we examined p53 mutations in 35 lung cancer specimens from Chinese females living in Hong Kong and compared them with 35 matched cases from Japanese women as well as previously reported p53 mutations in the world literature. p53 mutations in exons 5-8 were present in 20 and 31% of the Hong Kong and Japanese cases, respectively. Notably, single-base deletions within runs of identical bases were observed in 3 (43%) of the 7 mutations in the Hong Kong cases, in contrast to the absence of such mutations in the controls and the extreme scarcity in the literature, suggesting that distinct environmental and/or genetic factor(s) might be involved. Although the frequent occurrence of characteristic single-base deletions could be a reflection of mutator mutations leading to inefficient mismatch repair of slipped strand mispairings, none of the lung cancer specimens exhibited such microsatellite instabilities.

Adult↗
PubMed1995

Primary lymphoepithelioma-like carcinoma of the lung. A clinicopathologic study of 11 cases.

BACKGROUND: Lymphoepithelioma-like carcinoma (LELC), best known to occur in the nasopharynx, can arise in a variety of sites, such as the salivary gland, thymus, lung, stomach, and skin. Primary LELC of the lung is very rare, with only limited information in the literature. METHODS: The clinicopathologic features of 11 patients with pulmonary LELC collected from two regional hospitals in Hong Kong are described. RESULTS: The patients, all Chinese, were aged 38 to 73 years (median, 54 years), with equal sex incidence. Two of the 8 patients were smokers. Four presented with coin lesions incidentally discovered on chest X-ray, five with cough and blood-stained sputum, and two with pleural effusion. The tumor formed a discrete (9 patients) or an ill-defined (1 patient) nodule in the lung, or, rarely, showed extensive bilateral pulmonary involvement (1 patient). The major bronchi were not involved except in 1 patient. Three patients had lymph node metastasis at presentation; two of them had bone metastasis, one at presentation and one after 9 months. The tumors had pushing margins, and grew in the form of anastomosing islands and sheets, comprising syncytial-appearing large cells with vesicular nuclei and prominent nucleoli. They were infiltrated by an appreciable number of small lymphocytes and plasma cells. Intratumoral amyloid globules were found in one tumor. In five patients, the tumor showed intraepithelial growth within the small bronchi; this could represent either the in-situ phase of the tumor or pagetoid spread into the bronchial epithelium. The neoplastic cells of all patients harbored Epstein-Barr virus (EBV) as demonstrated by in situ hybridization for EBV-encoded small nuclear RNAs. All eight Asian patients with pulmonary LELC previously reported in the literature similarly have been EBV-positive, whereas the four reported Caucasian patients all have been EBV-negative. CONCLUSION: Lymphoepithelioma-like carcinoma of lung occurring in Asians is an EBV-associated neoplasm; it also appears to occur at a higher frequency in Asians than Caucasians. It usually presents as a solitary subpleural nodule, and there is no strong association with cigarette smoking. Most patients have early stage disease at presentation. From the limited available data, the behavior of LELC of lung is highly variable, ranging from apparent curability by excision (particularly for localized disease) to highly aggressive, extensive disease at presentation.

Adult↗
PubMed1990

[The efficacy of sonic and ultrasonic appliances on root canal debridement].

The purpose of this study was to compare the debridement efficacy of hand, sonic (MM-3000), and ultrasonic (Cavi-Endo) appliances, utilizing the same K-type files and a constant flow irrigation system, in the mesial root canals of extracted human mandibular 1st and 2nd molars. Only those roots with a canal curvature of between 10 and 30 degrees, by Schneider's method, were used in this study. The instrumentation time per mesial root canal for each treatment group was also evaluated. Following canal preparation and histological processing, the middle and apical cross-sections were examined to determine the percentage of canal and isthmus cleanliness, and the percentage of planed canal walls in the main canal area. Statistical analysis indicated no significant difference in canal and isthmus cleanliness at the middle and apical levels. All techniques achieved a high level of canal cleanliness. However, step-back hand instrumentation had the greatest percentage of planed canal walls in the main canal area at every portion of the root. Sonic instrumentation, in this study, was significantly faster than hand instrumentation in preparing the root canal system.

Analysis of Variance↗