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71.
Victor Arni D P Sicam Joris J Snellenburg Rob G L van der Heijde Ivo H M van Stokkum 《Optometry and vision science》2007,84(9):915-923
PURPOSE: A pseudo forward ray-tracing (PFRT) algorithm is developed to evaluate surface reconstruction in corneal topography. The method can be applied to topographers where one-to-one correspondence between mire and image points can be established. METHODS: The PFRT algorithm was applied on a corneal topographer designed and constructed at the VU University Medical Center, Amsterdam, The Netherlands. Performance of the algorithm was evaluated using artificial test surfaces and two sample eyes. The residual output of the PFRT algorithm is displayed as pixel displacements of actual feature points on the corneal image. Displacement of 1 pixel indicates submicrometer corneal height accuracy. RESULTS: PFRT residual increases with complexity of the measured surface. Using Zernike radial order 6, the mean residual for the artificial surfaces is subpixel. The mean residual for the regular cornea and the irregular cornea is 1.16 and 2.94 respectively. To some extent, increasing the Zernike radial order improves the accuracy. The improvement from order 6 to 20 is factor 2.3 for the irregular cornea. Using the residuals to further improve the accuracy brought local changes as high as 0.28 D in some areas of the reconstructed corneal power map. CONCLUSION: PFRT can be used to evaluate how close a reconstructed corneal surface is to the actual one. The residue information obtained from this algorithm can be displayed simultaneously with the corneal image. This provides accurate information about the corneal shape that is useful for application in laser refractive surgery. 相似文献
72.
73.
Microneurographic measurements of muscle sympathetic nerve activity (SNA) have suggested that, during static exercise, central command is much less important than skeletal muscle afferents in causing sympathetic neural activation. The possibility remains, however, that the sympathetic discharge produced by central command is targeted mainly to tissues other than skeletal muscle. To examine this possibility, we recorded SNA with microelectrodes placed selectively in skin, as well as in muscle, nerve fascicles of the peroneal nerve during static handgrip maneuvers designed to separate the effects of central command from those of muscle afferents. To study the relative effects of cutaneous sympathetic activation on sudomotor versus vasomotor function, we simultaneously estimated changes in skin blood flow (laser Doppler velocimetry) and in sudomotor (electrodermal) activation in the region of skin innervated by the impaled nerve fascicle. Two minutes of static handgrip at 10%, 20%, and 30% of maximal voluntary contraction caused large and intensity-dependent increases in skin SNA. These increases in SNA immediately preceded the onset of muscle tension, accelerated progressively during sustained handgrip, and resolved promptly with the cessation of motor effort. The handgrip-induced increases in skin SNA were not maintained when handgrip was followed by arrest of the forearm circulation, a maneuver that maintains the stimulation of chemically sensitive muscle afferents while eliminating the influences of central command and mechanically sensitive muscle afferents. During normothermia, static handgrip at 30% maximal voluntary contraction caused sustained increases in skin SNA (+400 +/- 83%, mean +/- SEM, p less than 0.05) and in electrodermal activity (+276 +/- 56%, p less than 0.05) but only transient increases in estimated skin vascular resistance (+11 +/- 2%, p less than 0.05). When skin temperature was increased or decreased to a new stable baseline level, subsequent increases in skin SNA during handgrip were accompanied by sustained but directionally opposite changes in estimated skin vascular resistance, with exercise-induced vasodilation during hyperthermia but exercise-induced vasoconstriction during hypothermia. From these observations, we conclude the following: 1) static exercise markedly increases sympathetic outflow to skin as well as to skeletal muscle; 2) the increases in skin SNA, unlike muscle SNA, appear to be caused mainly by central command rather than by muscle afferent reflexes; and 3) this cutaneous sympathetic activation appears to be targeted both to sweat glands and to vascular smooth muscle, with the relative targeting being temperature dependent.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
74.
Kambiz Dowlatshahi M. D. Ming Fan M. D. Mahsa Shekarloo B. A. Kenneth J. Bloom M. D. Victor E. Gould M. D. 《The breast journal》1996,2(5):304-311
Abstract: Coagulation leading to fibrosis of mammo-graphically detected breast cancers by interstitial laser therapy was tested as an alternative to surgical removal. Availability of computerized stereotaxic digital imaging allows the precise placement of laser and thermal needles into the target tumor and its controlled ablation by heat. The methodology of interstitial laser therapy (ILT), evolution of the subsequently removed tumors, and their histologic appearance are outlined.
Eight patients with mammographically well-defined tumors were selected. Definitive diagnosis and receptor evaluation were made on core biopsies. Under local anesthesia, stereotaxically guided diode laser energy at 5–10 w was delivered via a 400 xm fiber in a 19-gauge needle placed into the center of the tumor until the peripheral temperature exceeded 60°C. Patients experienced transient pain and pyrexia. Subsequent to ILT, seven invasive carcinomas were excised while one case of multiple papillomas was kept under surveillance. Histologic study revealed central necrosis but some peripheral residual tumor in the first five cases. In the last two, central necrosis surrounded by concentrically arranged, recognizable but severely injured, focally "windswept" and "ghostlike" tumor and granulation tissue were noted. The multiple papillomas showed radiologic shrinkage at 5 months and extensive fibrosis on needle biopsy.
ILT is an attractive new method of treating small, well-defined breast tumors and offers a potentially significant alternative to surgical removal; further exploration is warranted. 相似文献
Eight patients with mammographically well-defined tumors were selected. Definitive diagnosis and receptor evaluation were made on core biopsies. Under local anesthesia, stereotaxically guided diode laser energy at 5–10 w was delivered via a 400 xm fiber in a 19-gauge needle placed into the center of the tumor until the peripheral temperature exceeded 60°C. Patients experienced transient pain and pyrexia. Subsequent to ILT, seven invasive carcinomas were excised while one case of multiple papillomas was kept under surveillance. Histologic study revealed central necrosis but some peripheral residual tumor in the first five cases. In the last two, central necrosis surrounded by concentrically arranged, recognizable but severely injured, focally "windswept" and "ghostlike" tumor and granulation tissue were noted. The multiple papillomas showed radiologic shrinkage at 5 months and extensive fibrosis on needle biopsy.
ILT is an attractive new method of treating small, well-defined breast tumors and offers a potentially significant alternative to surgical removal; further exploration is warranted. 相似文献
75.
Victor Y. Fujimoto MD J.Heath Miller MD Nancy A. Klein MD Michael R. Soules MD 《American journal of obstetrics and gynecology》1997,177(6):1419-1425
OBJECTIVE: Our aim was to evaluate the clinical course and management of congenital cervical atresia. STUDY DESIGN: This retrospective analysis included 7 patients referred to our clinic and a review of the medical literature. RESULTS: Including this case series, 58 cases of congenital cervical atresia have been reported in the literature. Forty-eight percent of patients had isolated congenital cervical atresia with a normal vagina whereas the remainder had either complete or partial vaginal atresia (“shortened blind vaginal pouches”). Surgical management has included abdominal hysterectomy or uterovaginal cannulation with or without vaginoplasty. In 59% of patients who underwent uterovaginal canalization procedures (23/39), normal menstrual bleeding was achieved. Four of these patients subsequently became pregnant and were delivered at term. CONCLUSION: Surgical canalization in selected patients with congenital cervical atresia can be successfully performed to provide patients an opportunity for conservative management, resulting in normal menstrual bleeding, resolution of cyclic pelvic pain, and some potential (albeit limited) for fertility.(Am J Obstet Gynecol 1997;177:25) 相似文献
76.
Dr. Hershel Jick M.D. Dr. Laura E. Derby D.Sc. Dr. Victor Gurewich M.D. Mr. Catherine Vasilakis M.P.H. 《Pharmacotherapy》1996,16(3):321-326
We conducted a case-control study based on computer-recorded information accrued in the United Kingdom General Practice Research Database to assess and compare the relation between different antihypertensive drug therapies and myocardial infarction in patients with no known clinical or laboratory risk factors for myocardial infarction other than hypertension. Cases were treated hypertensive patients with no other known risk factors who developed a first acute myocardial infarction between January 1, 1993, and October 31, 1994. They were ascertained from a review of the clinical record together with a questionnaire filled out by the attending general practitioner. Controls were matched to each case for age, sex, general practice, and index date. Antihypertensive therapy was derived from the computerized patient record. The study consisted of 210 cases and 793 controls. Compared with users of β-blockers alone, the adjusted relative risk (RR) estimates for all other treatment regimens were close to 1.0. A comparison of users of calcium channel blockers alone with users of β-blockers alone yielded a RR estimate of 0.9 (95% CI 0.5, 1.7). We conclude that the risk of acute myocardial infarction in otherwise healthy, treated hypertensive patients is not materially associated with the particular drug they receive. 相似文献
77.
Victor L. Roggli Philip C. Pratt Arnold R. Brody 《American journal of industrial medicine》1993,23(4):605-614
Although the association between asbestos exposure and malignant mesothelioma is indisputable, controversy continues regarding the relative contribution of the various types of asbestos fibers to the development of mesothelioma. We examined the types of asbestos fibers recovered from lung parenchyma in more than 90 cases of malignant mesothelioma from the United States, using an analytical scanning electron microscope. Almost half of the patients were former asbestos insulators or shipyard workers. The fibers were recovered from lung tissues obtained at autopsy or surgical resection by means of a sodium hypochlorite digestion procedure. Amosite absestos was identified in 81% of the cases and accounted for 58% of all fibers 5 μm or greater in length. Tremolite/actinolite/anthophyllite were identified in 55% of the cases and accounted for 10% of all fiber types. Chrysotile was identified in 21% of the cases and accounted for 3% of fibers exceeding 5 μm in length. Crocidolite was found in 16% of the cases and accounted for 3% of fibers exceeding 5 μm in length. Nonasbestos mineral fibers (commonly found in the lungs of the general population) were observed in 71% of the cases and accounted for 25% of all fibers 5 μm or greater in length. The findings in this study are at odds with the assertion that crocidolite asbestos is responsible for most mesotheliomas in the United States. © 1993 Wiley-Liss, Inc. 相似文献
78.
Lee V. Leak Victor J. Ferrans Steven R. Cohen Elling E. Eidbo Michael Jones 《Developmental dynamics》1987,180(4):373-390
To study the evolution of pericardial inflammation, we have developed a model of pericarditis in sheep by surgically injecting heat-killed staphy-lococci and Freund's adjuvant into the pericardial cavity under sterile conditions. The pericarditis evolved through the following phases: (1) inflammatory response, (2) mesothelial cell injury and desquamation, and (3) fibrotic phase. At 3–24 hr there was increased microvascular permeability, which resulted in the exudation of fluid, neutrophils, macrophages, ami fibrin into the pericardial cavity and the pericardial intersti-tium. By 72 hr, large numbers of inflammatory cells were aggregated on the mesothelial surfaces and dispersed throughout the pericardial cavity, either as free-floating cells or located between strands of fibrin. At 6 days, fibrinolysis was apparent along the mesothelial surfaces; and newly formed collagen fibrils were deposited throughout the interstitial spaces and among the aggregated cells. These fibrils provided a matrix for the growth of new blood and lymphatic vessels into new connective tissue on both parietal and visceral pericardial surfaces. At 2 weeks, intrapericardial fibrosis had produced focal adhesions between the pericardial surfaces. By 1 month, extensive areas of the pericardial cavity were obliterated. By 9 months, there was a marked reduction in the numbers of cells and blood vessels and increased deposition of collagen and elastic fibers. The intrapericardial injection of heat-killed staphylococci and adjuvant provides a reproducible animal model to study the time course of pericardial inflammation. 相似文献
79.
Retrohepatic cavoatrial bypass for coarctation of inferior vena cava with a polytetrafluoroethylene graft 总被引:1,自引:0,他引:1
S Victor V Jayanthi I Kandasamy A Ratnasabapathy N Madanagopalan 《The Journal of thoracic and cardiovascular surgery》1986,91(1):99-105
Eight patients with chronic Budd-Chiari syndrome resulting from coarctation of the inferior vena cava underwent operation. Transatrial dilatation was of no avail in the first case. The obstructed segment was directly visualized in the subsequent seven cases by a transthoracic, transdiaphragmatic, retroperitoneal approach. In these latter seven cases, severe hourglass constriction of the inferior vena cava was observed just above the right hepatic vein. There was no evidence of inflammation, extrinsic compression, or thrombosis. Retrohepatic cavoatrial bypass with an antibiotic-sterilized aortic homograft was unsuccessful in three patients. Five patients including one with homograft failure underwent successful retrohepatic cavoatrial bypass with a polytetrafluoroethylene graft (20 mm plain in four cases and 16 mm ringed graft in one case). These patients have been followed up for 21 months to 6 years with no recurrence of symptoms. The term coarctation of the inferior vena cava appears more appropriate than membranous obstruction of the inferior vena cava because of the operative findings in the present series. 相似文献
80.
L. Guillermo Palacio Ivan Jimnez H. Hugo Garcia Marta E. Jimnez Jorge L. Snchez John Noh IlLisa Ahn Ofelia Mora Margarita Giraldo Victor C. W. Tsang 《Epilepsia》1998,39(12):1334-1339
Summary: Purpose: A prospective series of 643 persons with epilepsy attending a reference neurologic center in Medellin, Colombia, was examined by computed tomography (CT scan) or serology or both with the enzyme-linked immunoelectrotransfer blot assay (EITB) to assess the prevalence of Taenia solium cysticercosis. Methods: All presenting patients were consecutively enrolled in the study. Five hundred forty-six persons underwent cerebral CT scans; 376 of them also had serum EITB performed. Results: Prevalence of neurocys@ercosis by CT scan was 13.92%. Overall prevalence of T. solium antibodies with EITB was 9.82%, but for those with late-onset epilepsy (onset after age 30 years), prevalence increased to 17.5% and 19% for those who originated from outside urban Medellin. Seroprevalence in individuals with mixed lesions (cysts and calcifications) was 88.2% and 64.10% in those with live cysts. Conversely, only 2.72% of persons with CT findings not related to neurocysticercosis had positive EITB tests. Conclusions: Our study shows that an important proportion of individuals with epilepsy have radiologic or serologic evidence of T. solium infection, suggesting that neurocysticercosis is an important etiology for epilepsy in Colombia. 相似文献