Maximum-likelihood estimation in Optical Coherence Tomography in the context of the tear film dynamics

Understanding tear film dynamics is a prerequisite for advancing the management of Dry Eye Disease (DED). In this paper, we discuss the use of optical coherence tomography (OCT) and statistical decision theory to analyze the tear film dynamics of a digital phantom. We implement a maximum-likelihood (ML) estimator to interpret OCT data based on mathematical models of Fourier-Domain OCT and the tear film. With the methodology of task-based assessment, we quantify the tradeoffs among key imaging system parameters. We find, on the assumption that the broadband light source is characterized by circular Gaussian statistics, ML estimates of 40 nm +/− 4 nm for an axial resolution of 1 μm and an integration time of 5 μs. Finally, the estimator is validated with a digital phantom of tear film dynamics, which reveals estimates of nanometer precision.OCIS codes: (030.0030) Coherence and statistical optics, (110.3000) Image quality assessment     

Pharmacokinetics and protein binding of intravenous ibuprofen in the premature newborn infant

The elimination, disposition and protein binding of ibuprofen (IBU) in premature infants were studied for use in the prevention of intraventricular hemorrhage and closure of patent ductus arteriosus. The kinetic profile of i.v. IBU lysine (10 mg/kg bolus) given within the first 3 h after birth was studied in 21 premature neonates (mean birthweight = 944.7 g, range: 575–1450 g; gestational age: 26.8 weeks, range: 22–31 weeks). Blood samples (0.3 ml/sample) were obtained at time 0 and at 1, 3, 6, 12, 24, 48, and 72 h post-dose for IBU by high-performance liquid chromatography (HPLC). Kinetic analyses assumed applicability of one open-compartment model and calculations from the model-independent areas under the time concentration curve (AUC). Data (mean ± SEM) show that apparent volume of distribution (AVd) was 62.1 ± 3.9 ml/kg, plasma t _1/2 beta was 30.5 ± 4.2 h, elimination rate constant (k_el) was 0.032 ± 0.004 h^-1plasma clearance was 2.06 ± 0.33 ml/kg/h and plasma concentration (Cp) at 1 h was 180.6 ±11.1 mg/1. Gestational age and birthweight were not related to drug elimination. In 10 neonates, IBU maintenance dose of 5 mg/kg once daily on days 2 and 3 generated mean Cp of 116.6 ± 54.5 mg/1 and 113.6 ± 58.2mg/1, respectively. Protein binding by ultrafiltration and capillary electrophoresis showed that the percentage bound IBU was significantly lower in full term cord plasma (94.98 ± 0.39%, n = 26) compared to adult plasma protein (mean ± SE = 98.73 ± 0.31%, n = 8, p < 0.0001). Compared to data from adults and older children, IBU elimination is markedly prolonged in neonates and protein binding is slightly lower. Thus, investigational and clinical therapeutic regimens should be adjusted to account for decreased drug disposition to ensure safe and effective therapy.     

Meniscal tears of the knee: accuracy of MR imaging

Before surgery, 277 menisci in 144 knees were examined with magnetic resonance (MR) imaging. They were then examined directly with arthroscopy or arthrotomy. Menisci were graded on a scale of 1-3 according to the character of the intrameniscal MR imaging signal. At surgery, 137 of 154 (89%) menisci exhibiting only grade 1 or grade 2 signal were found to be normal. One hundred sixteen of 123 (94%) menisci exhibiting intrameniscal signal communicating with a meniscal articular surface (grade 3 signal) had tears. If only a grade 3 signal is considered consistent with meniscal tears, then MR findings and surgical findings agreed in 91.3% of menisci. MR imaging can separate surgically significant from nonsignificant meniscal lesions and is useful in the noninvasive preoperative screening of suspected meniscal tears.     

Blood donor-, apheresis-, and transfusion-related activities: results of the 1991 American Association of Blood Banks Institutional Membership Questionnaire

Approximately 2154 regional blood centers and hospital-based blood banks and transfusion services responded to the 1991 American Association of Blood Banks Institutional Membership Questionnaire that elicited data from 1990. Information from 2144 institutions was considered valid. Questionnaire topics were donor blood collections, hemapheresis, perioperative cell salvage, component usage, and transfusion-associated diseases. Institutional members reported collecting 9.3 million units, of which 90.9 percent were for allogeneic use in the community, 6.0 percent were for autologous use, and 3.1 percent were directed donations. The percentage of directed-donor units that were crossed over for allogeneic use (51%) was greater than the percentage of units transfused to the designated patient (49%). Only 12.5 percent of institutions reported obtaining specific consent for transfusion. Of the 15.4 million transfused blood components, 8.5 million were red cells, 4.1 million were platelets, 1.8 million were fresh-frozen plasma, and 0.9 million were cryoprecipitate. There were 1263 reported cases of transfusion-associated hepatitis. Approximately 44 percent of the patients who were tested proved positive for hepatitis B surface antigen, and 80 percent of the patients who were tested proved positive for antibody to hepatitis C. The questionnaire's aggregate results can be used to assess current patterns of blood donation and transfusion activities.     

Effect of collagen shields on corneal epithelialization following penetrating keratoplasty

To evaluate the effects of collagen shields on corneal epithelial healing following keratoplasty, we conducted a prospective study of 89 consecutive penetrating keratoplasty patients over a 9-month period, applying collagen shields in alternate cases. Eyes were evaluated on the first and on the eighth postoperative day. The appearance of the epithelium was graded on a scale from 0 to 4. Independent variables, such as donor age, patient age, patient and donor sex, death to preservation time, and donor time in K-Sol media prior to surgery, were also evaluated. Donor corneas treated with collagen demonstrated less epithelial staining and smaller epithelial defects on the first day following surgery. The results were evaluated with a Student's t test and were found to be significant (P less than 0.001). We conclude that the application of porcine collagen shields following keratoplasty is an effective means of encouraging reepithelialization of the graft.     

Cephalosporium endophthalmitis following penetrating keratoplasty.

A 69-year-old male with chronic herpes simplex keratitis underwent penetrating keratoplasty, using cryopreserved tissue. Seven weeks postoperatively the patient developed cephalosporium endophthalmitis. Intensive medical and surgical therapy was unsuccessful and the eye had to be enucleated within three weeks. Cephalosporium species are isolated more often in intraocular infection than from corneal ulceration. Although favorable response to Amphotericin-B and Primaricin has been reported, the final outcome has been unfavorable in most of these cases.