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Biomedical subjects

Richard E Davis

Publications and source records attributed to Richard E Davis.

26 records · Page 2Linked to original sources
PubMed2002

Assessment of the Wiener-Retinex process.

We assess the performance of the Retinex transformation, the Wiener restoration, and the combined Wiener-Retinex process in the context of the end-to-end model of color visual-communication channels for near-surface acquisition. We extend the formulations of panchromatic imaging for the nonlinear Retinex transformation and the linear Wiener and Wiener-Retinex restoration filters to color imaging. We further assess the accuracy by which colors are restored in the cases of uniform and spatially varying irradiance levels, and the shadow depth for which color consistency is still possible with reasonable accuracy. Finally, we assess the sensitivity of these processes to perturbations in the visual channel, including the image-gathering design and the spatial support of the Retinex transformation.

Journal Article↗
PubMed2002

Effects of folic acid.

Explore the source record for details and available documents.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

Expression of endothelin 1 in rat random-pattern skin flaps treated with topical nifedipine.

OBJECTIVE: To evaluate the relative tissue concentrations of the endogenous vasoactive peptide endothelin 1 (ET-1) in random-pattern skin flaps (RPSF) treated with either topical anti-ischemic drug therapy (nifedipine) or placebo. DESIGN: Prospective, randomized, placebo-controlled therapeutic trial. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTION: Experimental subjects underwent caudally based RPSFs using the modified McFarlane technique. Subjects received either topical anti-ischemic drug therapy (nifedipine; n = 6) or inert carrier ointment (placebo; n = 6). Treatment was initiated immediately following flap closure and continued every 6 hours for 5 days. At the end of the treatment period, the animals were killed and the concentration of ET-1 was determined using enzyme-linked immunosorbent assay. Representative tissues from nifedipine- and placebo-treated skin flaps were also analyzed for ET-1 using immunohistochemical stains. RESULTS: The ET-1 levels in the distal (necrotic) flap segments were increased by 4.53 pg/mL over baseline (nonnecrotic) flaps in the placebo-treated animals and decreased by 4.70 pg/mL below baseline in the nifedipine-treated group (P =.03). CONCLUSIONS: The correlation between tissue levels of ET-1 and the severity of tissue necrosis suggests that ET-1 may play a pivotal role in ischemic injury of RPSFs. Moreover, treatment with topical nifedipine may antagonize the vasoconstrictive effects of ET-1. Although immunohistochemical analysis revealed ET-1 staining within the flap microvasculature, no quantitative differences were detected between the nifedipine- and placebo-treated flaps. Further studies are needed to define the role of ET-1 in RPSF necrosis.

Administration, Topical↗
PubMedDate not supplied

Powered instrumentation for nasal bone reduction: advantages and indications.

OBJECTIVE: To evaluate power-assisted bone removal in cosmetic rhinoplasty. DESIGN: Nonrandomized, nonblinded, retrospective evaluation of consecutive case series. SETTING: Academic facial plastic surgery practice. INTERVENTIONS: Power-assisted bone removal in 105 consecutive rhinoplasties requiring nasal bone reduction. MAIN OUTCOME MEASURES: Subjective evaluation by patient and surgeon. RESULTS: Of the 105 patients undergoing power-assisted bone removal, 102 obtained satisfactory refinement of the nasal dorsum after 1 operation. Three patients required surgical revision of the nasal dorsum following power-assisted bony hump reduction. Of these, 2 required surgical revision for delayed bone regrowth, while the remaining patient required surgical treatment of a persistent bony hump. Ultimately, all 105 patients achieved satisfactory surgical results. No other surgical complications were observed. CONCLUSIONS: Power-assisted bone removal is a useful adjunct for bone removal in cosmetic rhinoplasty. This study confirms the previously reported advantages of powered instrumentation for patients with small bony humps or modest bony asymmetries. Moreover, because powered instrumentation is comparatively atraumatic, it may be preferable for use in nasal bones previously weakened by trauma, aging, or prior nasal surgery. Finally, because the powered nasal rasp permits rounding of the bone edges, the characteristic widening associated with flat hump reduction is reduced, and the need for aggressive sidewall infracture is diminished. Complications associated with power-assisted bone removal were rare.

Adult↗
PubMedDate not supplied

Rhinoplasty and the nasal SMAS augmentation graft: advantages and indications.

We evaluated the nasal superficial musculoaponeurotic system (SMAS) as an autologous augmentation graft material in the thick-skinned patient undergoing cosmetic rhinoplasty using a retrospective review. Representative case reports demonstrated preliminary long-term results after augmentation with the nasal SMAS graft in an academic rhinoplasty practice. En bloc excision of the nasal SMAS in thick-skinned patients produced uniformly favorable improvements in nasal tip definition without adverse sequelae. Moreover, in 10 patients, the harvested material was also used for volume augmentation at various adjacent nasal sites, including the radix, nasal sidewall, and nasal dorsum. Long-term follow-up ranging from 1 to 3 years suggests stable volume augmentation in this initial patient series. No donor morbidity was observed in properly selected patients, and enhancements in nasal tip definition were uniformly favorable. Additional studies are needed to more accurately characterize long-term nasal SMAS graft survival in all patients.

Adolescent↗
PubMedDate not supplied

Diagnosis and surgical management of the caudal excess nasal deformity.

Surgical correction of the overgrown columella-labial junction remains a controversial and neglected aspect of cosmetic rhinoplasty. Failure to reduce an obtuse nasolabial angle resulting from overgrowth of the septum and/or nasal spine may adversely affect the otherwise satisfactory cosmetic result. I review the historical considerations regarding caudal overgrowth and discuss its relevance to contemporary rhinoplasty. Case studies are presented to illustrate surgical treatment options for various overgrowth deformities.

Adult↗
PubMedDate not supplied

A long-term comparison of plication configurations for endoluminal gastroplication: circumferential versus helical.

GOALS: To determine the long-term efficacy of endoluminal gastroplication (ELGP) and the most effective plication configuration. BACKGROUND: Endoluminal gastroplication is an intriguing therapy for gastroesophageal reflux disease. We conducted a retrospective review of a prospective experience of patient cohorts comparing outcomes of the circumferential and helical plication patterns. STUDY: Twenty patients underwent ELGP, with 9 receiving the circumferential (Group 1) and 11 the helical pattern (Group 2). Manometry, endoscopy, and 24-hour pH monitoring were performed at baseline and at 6 months. Symptom scores and medication usage were assessed at baseline, 1, 3, 6, 12, and 18 months. RESULTS: Both groups did not differ significantly from each other with respect to symptom improvement, medication usage, or other variables measured. At 6 months, symptom scores, histamine-2 receptor antagonist (H2RA), proton pump inhibitor usage, and hernia size decreased significantly. No other parameter showed a significant change. At the 18-month follow-up, symptom scores and H2RA usage decreased significantly. CONCLUSION: ELGP improves heartburn and regurgitation scores at 18 months. Our study suggests that there is no benefit to additional plications when using the helical pattern.

Adult↗