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Biomedical subjects

M Greenspan

Publications and source records attributed to M Greenspan.

At least 19 recordsLinked to original sources
PubMed2005

An estimation/correction algorithm for detecting bone edges in CT images.

The normal direction of the bone contour in computed tomography (CT) images provides important anatomical information and can guide segmentation algorithms. Since various bones in CT images have different sizes, and the intensity values of bone pixels are generally nonuniform and noisy, estimation of the normal direction using a single scale is not reliable. We propose a multiscale approach to estimate the normal direction of bone edges. The reliability of the estimation is calculated from the estimated results and, after re-scaling, the reliability is used to further correct the normal direction. The optimal scale at each point is obtained while estimating the normal direction; this scale is then used in a simple edge detector. Our experimental results have shown that use of this estimated/corrected normal direction improves the segmentation quality by decreasing the number of unexpected edges and discontinuities (gaps) of real contours. The corrected normal direction could also be used in postprocessing to delete false edges. Our segmentation algorithm is automatic, and its performance is evaluated on CT images of the human pelvis, leg, and wrist.

Algorithms↗
PubMed2000

Percutaneous microdecompressive endoscopic cervical discectomy with laser thermodiskoplasty.

OBJECTIVE: To study the surgical outcome of outpatient percutaneous microdecompressive endoscopic cervical discectomy with lower energy laser for shrinkage of disc material (thermodiskoplasty). METHOD: Since 1994, 200 patients with herniated cervical discs have presented at the authors' clinic, with unilateral radicular pain. The diagnosis was confirmed by MRI or CT, and EMG. RESULTS: At an average follow-up of 25 months, 94.5% of the cases had good-to-excellent results. Eleven patients (5.5%) remained symptomatic, with persistent neck and upper extremity pain associated with paresthesias. There were no significant postoperative complications. Average time before returning to work was 10 days. CONCLUSIONS: Percutaneous microdecompressive endoscopic cervical discectomy with laser thermodiskoplasty has proven to be a safe and efficacious minimally invasive procedure.

Adult↗
PubMed1999

Microdecompressive percutaneous endoscopy: spinal discectomy with new laser thermodiskoplasty for non-extruded herniated nucleosus pulposus.

Open spinal discectomy, at times with spinal fusion, is associated with significant local morbidity and long-term convalescence, requires general anesthesia, and involves dissection of muscle, removal of bone, ligament and disc, which are all at greater financial cost. Therefore, the search for a less traumatic spinal discectomy began, including micro-discectomy, and percutaneous techniques and endoscopic discectomy. Lyman Smith reported intradiscal injection of chymopapain in 1964. Onik et al. developed the automated percutaneous discectomy device for continuous aspiration/irrigation of disc tissue in 1985. Hijikata et al also described nucleotomy independently in 1985. In 1986, Ascher and Choy first reported laser discectomy to decrease intradiscal pressure.

Journal Article↗
PubMed1997

Percutaneous (endoscopic) decompression discectomy for non-extruded cervical herniated nucleus pulposus.

In 1838, Key described the pathological findings of two cases of cord compression by "intervertebral substance." In the 1800s and early 1900s many cases of chondromas of the cervical spine were reported. In 1928 Stookey, described the clinical symptoms and anatomic location of cervical disk herniation. In 1934, Mixter and Barr documented four cervical disc protrusions. Before 1950, the standard approach to discs in this region was posteriorly with laminectomy. In the 1950s Bailey, Badgley, Cloward, Smith and Robinson popularized the anterior approach with interbody fusion. Hirsch in 1960, then Robertson in 1973, recommended cervical discectomy without fusion. Similar results were noted.

Journal Article↗
PubMed1991

Aspects of psychology in sports medicine.

Psychology's impact as an ergogenic aid across sports and competitive levels has been well documented. In addition, exercise can play a major role in disease prevention and health enhancement while also enhancing psychological well-being. In addition to its preventive value, exercise is being recognized as a valuable therapeutic tool. Like most therapeutic modalities, however, exercise also has some potentially negative qualities.

Athletic Injuries↗
PubMed1986

Regulation of rat liver 3-hydroxy-3-methylglutaryl coenzyme A synthase and the chromosomal localization of the human gene.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase was purified to homogeneity from rat liver cytoplasm. The active enzyme is a dimer composed of identical subunits of Mr = 53,000. The amino acid composition and the NH2-terminal sequence are presented. Partial cDNA clones for the enzyme were isolated by screening of a rat liver lambda gt11 expression library with antibodies raised against the purified protein. The identity of the clones was confirmed by hybrid selection and translation. When rats were fed diets supplemented with cholesterol, cholestyramine, or cholestyramine plus mevinolin, the hepatic protein mass of cytoplasmic synthase, as determined by immunoblotting, was 25, 160, and 1100%, respectively, of the mass observed in rats fed normal chow. Comparable changes in enzyme activity were observed. Approximately 9-fold increases in both HMG-CoA synthase mRNA mass and synthase mRNA activity were observed when control diets were supplemented with cholestyramine and mevinolin. When rats were fed these two drugs and then given mevalonolactone by stomach intubation, there was a 5-fold decrease of synthase mRNA within 3 h. These results indicate that cytoplasmic synthase regulation occurs primarily at the level of mRNA. This regulation is rapid and coordinate with that observed for HMG-CoA reductase. The chromosomal localization of human HMG-CoA synthase was determined by examining a panel of human-mouse somatic cell hybrids with the rat cDNA probe. Interestingly, the synthase gene resides on human chromosome 5, which has previously been shown to contain the gene for HMG-CoA reductase. Regional mapping, performed by examination of a series of chromosome 5 deletion mutants and by in situ hybridization to human chromosomes indicates that the two genes are not tightly clustered.

Amino Acid Sequence↗
PubMed1983

Ventricular ectopic beats with exit block: a retrospective Holter monitor study.

A retrospective study was conducted to define the incidence of ventricular ectopic beats with exit block (concealed extrasystoles). Of 904 Holter recordings, 92 were admitted for study on the basis of sufficient ventricular ectopic beats on rhythm strips. Concealed bigeminy conforming to the equation of S = 2n - 1 (where S = the interectopic sinus beat and N = any interger) was the most common and occurred in 42 of 92 (46%) Holters included in this study. Concealed trigeminy was observed in 12 of 92 (13%) studies. These Holters also showed ventricular ectopic beats strongly suggestive of parasystole with entrainment. Of 53 Holters reviewed for parasystole 12 were suggestive of, and five indicated this dysrhythmia. We conclude that: 1. Concealed extrasystoles are more common than previously appreciated. 2. Concealed bigeminy and trigeminy appear together and conversion may not always be associated with a change in heart rate. 3. Recognition of this dysrhythmia is uncommon mostly because of inadequate lengths of rhythm strips. 4. Parasystole with entrainment is suggested as a common dysrhythmia when frequent extrasystoles are present.

Cardiac Complexes, Premature↗
PubMed1981

Concealed junctional bigeminy inducing pseudo 2:1 AV block.

This case report describes the electrocardiographic features of concealed junctional premature beats. When the junctional premature beats occurred in a bigeminal fashion, pseudo 2:1 AV block occurred. The presence of 2:1 AV block was related to the prematurity (H1-H2) of the junctional extrasystoles, in which coupling intervals less than 425 msec were concealed and those greater than 425 msec were manifest. This report is unusual in that persistent long runs of pseudo 2:1 AV conduction were established. In addition, the extrasystolic beats demonstrated exit block and the interectopic sinus beats (n) followed the formula 2n-1.

Aged↗
PubMed1980

Myocardial bridging of the left anterior descending artery: evaluation using exercise thallium-201 myocardial scintigraphy.

Seven patients with myocardial bridging of the left anterior descending coronary artery were evaluated by mens of thallium-201 exercise scintigraphy. The degree of systolic narrowing was 60-70% in five patients and 75-80% in two patients. All patients had presented with chest pain. The resting electrocardiogram was normal in six patients; there were ST segment and T-wave abnormalities in one patient. No patient complained of chest pain during exercise. The exercise electrocardiogram was negative in six patients and inconclusive in one patient. Exercise myocardial scans were negative in all seven patients. We conclude that no evidence of ischemia was demonstrated in patients with myocardial bridging of the left anterior descending coronary artery as determined by exercise electrocardiography and stress thallium-201 scintigraphy.

Adult↗
PubMed1980

Exercise myocardial scintigraphy with 201-thallium. Use in patients with mitral valve prolapse without associated coronary artery disease.

Thirty patients with angiographically documented mitral valve prolapse but without associated coronary artery disease, underwent exercise 201thallium myocardial scintigraphy. The resting ECG demonstrated ST segment abnormalities in 15 patients (50 percent). The exercise ECGs were abnormal in two patients (6.7 percent), normal in four (13.3 percent), and inconclusive in 24 patients (80 percent). Two patients (6.7 percent) had abnormal exercise myocardial scintigraphy (both patients had abnormal exercise ECGs). Two additional patients (6.7 percent) had perfusion abnormalities in the rest images that did not change with exercise. Twenty-six patients (86.4 percent) had normal scans. We conclude that the majority of patients with mitral valve prolapse have normal exercise 201thallium images in the absence of associated coronary artery disease and exercise electrocardiography is of limited value in patients with mitral valve prolapse because the results are frequently (80 percent) inconclusive.

Adult↗
PubMed1979

Complete occlusion of the left main coronary artery.

In this report, we describe the clinical, hemodynamic, and angiographic findings in three patients with atherosclerotic complete occlusion of the left main coronary artery. This rare entity was only seen in three out of 7,000 coronary angiograms. The three patients had extensive right-to-left collateralization. Two patients underwent saphenous vein bypass surgery and are asymptomatic, while the third patient died awaiting surgery. We suggest that patients with complete left main occlusion must undergo surgery as soon as possible.

Adult↗
PubMed1979

The significance of exercise-induced Q waves.

The significance of transient exercise-induced Q waves present during treadmill testing was prospectively evaluated and correlated with the findings at cardiac catheterization. Exercise-induced Q waves were present in 14 of 560 patients (2.5 per cent) undergoing treadmill exercise testing. Thirteen patients had Q waves in leads V1 through V3 and one patient had Q waves in leads II, III and aVF. Ten patients underwent cardiac catheterization; six did not have coronary artery disease as determined by angiography. Two patients had a documented anterior myocardial infarction and did not undergo cardiac catheterization. Exercise myocardial perfusion imaging was performed in 10 patients. Six patients without coronary artery disease had no evidence of exercise perfusion defects. In the four patients with coronary artery disease, three patients had an abnormal resting perfusion study without change with exercise and one patient had a new exercise myocardial perfusion defect. We conclude that exercise-induced transient Q waves are not diagnostic of underlying coronary disease. In patients without coronary artery disease the mechanism of exercise-induced Q waves is as yet unclear. In patients with coronary artery disease, the mechanism may also be undefined or secondary to myocardial ischemia.

Adult↗