Two-dimensional modulation transfer functions for rotational panoramic radiography

The two-dimensional modulation transfer function (MTF) provides a method for describing resolution in panoramic x-ray systems where the process of image formation differs in the horizontal and vertical dimensions. As an example, two-dimensional MTFs for the Philips OrthOralix SD machine were calculated from point spread functions (PSF) describing the various sources of unsharpness within the system. The PSF for the focal spot was measured using a pinhole camera. The PSF for the screen-film combination was calculated from data supplied by the manufacturer. The PSF for the motion blurring that is inherent in rotational panoramic radiography was derived from standard mathematical models. The three functions were convolved together to obtain the PSF of the entire system and the two-dimensional MTF was derived from the system PSF by Fourier transformation. The two-dimensional MTF provides a tool which should be useful in the future for the evaluation of existing systems, for the design of improved equipment, and for the implementation of image processing algorithms.     

Point spread functions for rotational panoramic radiography: An experimental test

Point spread functions for rotational panoramic radiography were determined experimentally. The results were compared with theoretically functions calculated from known system parameters. There was a satisfactory agreement between theoretically and experimentally obtained data. It is concluded that theoretically calculated point spread functions and their blurring effects in panoramic radiography give reliable results.     

Tracheal replacements: Part 2

In this review, we summarize the history of tracheal reconstruction and replacement as well as progress in current tracheal substitutes. In Part 1, we covered the historical highlights of grafts, flaps, tube construction, and tissue transplants and addressed the progress made in tracheal stenting as a means of temporary tracheal support. In Part 2 we analyze solid and porous tracheal prostheses in experimental and clinical trials and provide a summary of efforts aimed at generating a bioengineered trachea. In both parts, we provide an algorithm on the spectrum of options available for tracheal replacement.     

A matched case-control study: investigating the relationship between youth assets and sexual intercourse among 13- to 14-year-olds

BACKGROUND: The number of teenagers engaging in sexual intercourse has consistently changed over the past several years. This can become a major challenge when trying to determine why teens continue to have sex. The purpose of this paper was to investigate the relationship between youth assets and sexual intercourse among 13- to 14-year-olds. METHODS: Cross-sectional data were collected using in-person at-home interviews from a random sample of inner-city neighbourhood 13- to 14-year-old teenagers (n = 64 matched pairs; 36% 13-year-olds, 53% female, 45% white, 28% African-American, 16% Hispanic and 11% Native American). Nine individual youth assets were analysed using conditional logistic regression (matching for several demographic variables) to assess the association between assets and abstinence in younger teens. RESULTS: Conditional logistic regression analyses showed that two assets, positive Peer Role Models [odds ratios (OR) = 4.67, 95% confidence intervals (CI) = 1.93, 11.27] and Use of Time (Religion) (OR = 2.20, 95% CI = 1.04, 4.65), were significantly related (P < 0.05) to younger teens never having engaged in sexual activity. CONCLUSION: These findings suggest, when considering abstinence behaviour, involvement in religious activities and having positive peer role models appear to be protective factors related to delaying sexual intercourse among teens aged 13-14 years.     

Highly heterogeneous nature of delta-aminolevulinate dehydratase (ALAD) deficiencies in ALAD porphyria

The properties of 9 delta-aminolevulinate dehydratase (ALAD) mutants from patients with ALAD porphyria (ADP) were examined by bacterial expression of their complementary DNAs and by enzymologic and immunologic assays. ALADs were expressed as glutathione-S-transferase (GST) fusion proteins in Escherichia coli and purified by glutathione-affinity column chromatography. The GST-ALAD fusion proteins were recognized by anti-ALAD antibodies and were enzymatically active as ALAD. The enzymatic activities of 3 ALAD mutants, K59N, A274T, and V153M, were 69.9%, 19.3%, and 41.0% of that of the wild-type ALAD, respectively, whereas 6 mutants, G133R, K59N/G133R, F12L, R240W, V275M, and delTC, showed little activity (< 8%). These variations generally reflect the phenotype of ALAD in vivo in patients with ADP and indicate that GST-ALAD fusion protein is indeed useful for predicting of the phenotype of ALAD mutants. The location of F12L mutation in the enzyme's molecular structure indicates that its disturbance of the quaternary contact of the ALAD dimer appears to have a significant influence on the enzymatic activity. Mouse monoclonal antibodies to human ALAD were developed that specifically recognized a carboxy terminal portion of ALAD, or other regions in the enzyme. This study represents the first complete analysis of 9 mutants of ALAD identified in ADP and indicates the highly heterogeneous nature of mutations in this disorder.     

Laboratory and field evaluation of Teknar HP-D, a biolarvicidal formulation of Bacillus thuringiensis ssp. israelensis, against mosquito vectors

Larvicidal efficacy of Teknar HP-D, an improved biolarvicidal formulation of Bacillus thuringiensis ssp. israelensis (Bti), against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti was determined in the laboratory, and in field the efficacy of the formulation was tested against Cx. quinquefasciatus breeding in cesspits, unused wells and drains. The toxicity of the formulation to Gambusia affinis (larvivorous fish), Notonecta sp. and Diplonychus indicus (water bugs) was also evaluated in the laboratory. Teknar HP-D was field tested at three recommended dosages, 1, 1.5 and 2l/ha, selecting five habitats for each dosage. Another five habitats were kept untreated as controls. Ae. aegypti showed greatest susceptibility to the Bti toxin in the laboratory. In cesspits, all the three dosages caused >80% reduction of pupal recruitment up to day 6 post-treatment, indicating that a weekly application at the lowest would be necessary for sustained control. The residual activity of the formulation was longer in unused wells, causing >80% reduction of pupal recruitment for 17 days from the day of treatment. In controlling pupal recruitment the three dosages produced equal effect. Application of Teknar HP-D at 1 l/ha once in three weeks is therefore recommended to control Cx. quinquefasciatus in unused wells. However, in drains, >80% reduction of pupal recruitment was observed for only 3 days and hence, application of Teknar HP-D at 2 l/ha that caused significantly higher level of reduction twice in a week at 3-day interval is necessary. At dosages from 0.032 to 3.2 mg/l (ppm), Teknar HP-D was non-toxic to Gambusia fish. The two predatory water bugs, Notonecta sp. and Diplonychus indicus that fed on the surviving larvae of Cx. quinquefasciatus exposed to the sub-lethal doses (LC(50) and LC(80)) of Teknar HP-D were safe with out having any mortality.     

Sutured coronary artery grafting utilizing the Heartflo anastomosis device--first clinical experiences

BACKGROUND: The Heartflo device was developed to facilitate consistency in distal coronary anastomosis quality. The device automates the suturing process during the anastomosis procedure via simultaneous delivery of ten standard 7-0 polypropylene sutures through the graft and the coronary vessel wall. METHODS: In 30 elective coronary artery bypass patients, one distal anastomosis was intentionally performed with the anastomosis device. Device success was stated if a patent anastomosis with a minimal flow of 50 ml/min resulted, additional stitches were counted if bleeding occurred. RESULTS: 4 cases of device failure occurred in the first 5 patients. The subsequent patients were operated without any mechanical problems. In 16 patients (53 %), a patent anastomosis with a mean flow of 75 +/- 6 ml/min using 1.7 +/- 0.3 additional stitches was achieved. Anastomoses were completed in 19.0 +/- 0.7 min; postoperative course was uneventful in all patients. CONCLUSIONS: We have shown that coronary anastomoses are feasible using the Heartflo device, representing a promising step on the way to automated coronary anastomoses. Its application is still limited by the size and tissue quality of the target vessel and difficult suture management during the anastomosis procedure.