Outcomes of patients admitted with high-sensitive cardiac troponin T levels meeting the new rule out criteria for myocardial infarction

Background

The 2020 ESC non-ST-elevation (NSTE) acute coronary syndromes (ACS) guidelines have adopted the paradigm that patients presenting with suspected NSTE-ACS and high-sensitive cardiac troponin T (hs-cTnT) values <99th percentile in a single test or small increment within 1/2 hours have a high negative predictive value for myocardial infarction (MI). Their management remains controversial.

Purpose

We examined the clinical outcomes and resource utilization of suspected NSTE-ACS patients who presented with hs-cTnT values meeting the early rule out criteria, but were nevertheless admitted.

Methods

Our single center retrospective cohort study included 4,263 visits for suspected NSTE-ACS triaged in the Emergency Room (ER), had hs-cTnT values that met the early rule-out criteria, and were admitted (Figure 1).

Routine quality control and dedicated tests proved a coefficient of variance of <10% for hs-cTnT values <99th percentile (14 ng/L).

Results

There were no deaths in-hospital and at 30 days. Discharge diagnosis of MI was documented in 10 patients (∼0.2%). Median ER stay and hospital stay were 6 hours and 3 days, respectively. In hospital evaluation included 844 gated cardiac CT angiography (CTA), 580 SPECT heart scans, 101 ECG-exercise tests, and 178 coronary angiography, of which 70 (∼1.6% of cohort) culminated in percutaneous/surgical intervention.

Conclusion

Our findings highlight the high negative predictive value for MI applying the early rule out algorithm and supports a policy of ER discharge for further evaluation, sparing unnecessary and resource-consuming hospital admissions.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Outcomes of patients admitted with limit of blank high-sensitive cardiac troponin T levels versus those with levels under the limit of detection

Background

Patients with suspected non-ST-elevation acute coronary syndrome (NSTE-ACS) and high-sensitive cardiac troponin T (hs-cTnT) values below the level of detection (5 ng/L) in a single test have a high negative predictive value for myocardial infarction (MI).

Purpose

We compared the clinical outcomes and resource utilization of suspected NSTE-ACS patients who were admitted despite hs-cTnT values below the limit of detection (5 ng/L) versus those with values ≤ the limit of blank (3 ng/L).

Methods

This single center retrospective cohort analysis included 2,081 emergency room (ER) visits for suspected NSTE-ACS that manifested single hs-cTnT value <5 ng/L (limit of detection) - 624 with single hs-cTnT ≤3 ng/L (limit of blank) and 1,457 with single hs-cTnT values >3 ng/L and <5 ng/L, and yet were admitted (Figure 1).

Routine quality control and dedicated tests proved a coefficient of variance of <10% for hs-cTnT values <99th percentile (14 ng/L).

Results

There were no in-hospital or 30-day deaths in both groups. Discharge diagnosis of MI was documented only in the 3–5 ng/L hs-cTnT group – 3 cases (∼0.2%). Median ER stay were 5 and 6 hours for ≤3 ng/L and 3–5 ng/L groups, respectively. Median hospital stay was 3 days for both groups. Coronary angiographies culminating in interventions were documented in 1 case (∼0.2%) and 24 cases (∼1.6%) for ≤3 ng/L and 3–5 ng/L groups, respectively.

Conclusion

Suspected NSTE-ACS patients with hs-cTnT values ≤ the limit of blank are at very low risk and may not need any further evaluation.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Accelerations from wearable accelerometers reflect knee loading during running after anterior cruciate ligament reconstruction

BACKGROUND

Following anterior cruciate ligament reconstruction, individuals exhibit sagittal plane knee loading deficits as they underload their injured limb during running. These between-limb biomechanical differences are difficult to clinically detect. Wearable accelerometers may aid in the development of early rehabilitation programs to improve symmetrical loading. This study aimed to identify whether segment accelerations from wearable accelerometers can predict knee loading asymmetry in an anterior cruciate ligament reconstructed population.

METHODS

14 individuals 5-months post-anterior cruciate ligament reconstruction performed self-selected speed running. Data were collected concurrently using a marker-based motion system and accelerometers positioned on participants' shanks and thighs. Stepwise linear regression was used to determine predictive value of accelerometer data on biomechanical variables.

FINDING

Shank acceleration was not predictive of any biomechanical variable. Between-limb differences in thigh axial acceleration explained 30% of the variance in between-limb differences in knee power absorption (p = 0.045), suggesting that accelerometers placed on proximal joint segments may provide information regarding knee loading asymmetry. Between-limb differences in thigh axial acceleration also explained 38% of the variance in between-limb differences in ground reaction force (p = 0.002).

INTERPRETATION

These relationships indicate that accelerations from wearable accelerometers may provide some useful information regarding knee loading during running in individuals following anterior cruciate ligament reconstruction.

Parasitism by Monogenoidea in Piaractus mesopotamicus (Characiformes, Characidae) cultivated in Paraná River (Brazil)

This study investigated the occurrence, prevalence, mean abundance and mean intensity of monogenoidean parasites in Piaractus mesopotamicus farmed in cages in the reservoir of the Itaipu Hydroelectric Power Station, Paraná River, Brazil. The parasite distribution pattern and the correlation of prevalence and abundance with the total length of hosts were also investigated. Four monogenoidean species were collected: Anacanthorus penilabiatus, A. toledoensis, Mymarothecium ianwhitingtoni and M. viatorum. All the parasites collected in P. mesopotamicus showed the typical aggregated distribution pattern, and the abundance and the prevalence did not shown any correlation with the total length of hosts.

Ultrastructure of the tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955 (Monogenea, Microcotylidae)

The ultrastructure of the body tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955, parasite of Mugil liza from Brazil, was studied by transmission electron microscopy. The body tegument is composed of an external syncytial layer, musculature, and an inner layer containing tegumental cells. The syncytium consists of a matrix containing three types of body inclusions and mitochondria. The musculature is constituted of several layers of longitudinal and circular muscle fibers. The tegumental cells present a well-developed nucleus, cytoplasm filled with ribosomes, rough endoplasmatic reticulum and mitochondria, and characteristic organelles of tegumental cells.

Report on two species of Digenea from marine fishes in Brazil

Two species of Digenea were recorded for the first time in South America and in new hosts: Acanthostomum spiniceps (Looss, 1896) (Cryptogonimidae) was reported from Astroscopus sexspinosus (Steindachner, 1877) (Uranoscopidae) and Diplomonorchis sphaerovarium Nahhas & Cable, 1964 (Monorchiidae) from Ophichthus gomesi (Castelnau, 1855) (Ophichthidae). From the latter, Heliconema heliconema Travassos, 1919 (Nematoda, Physalopteridae), was also recovered representing also a new host for this nematode species.

Dietary exposures to mineral hydrocarbons from food-use applications in the United States

Food-use applications of mineral hydrocarbons (MHC) derived from petroleum sources result in dietary exposure to these compounds by consumers. Food applications of MHC, including white mineral oils, paraffin waxes, microcrystalline waxes and petrolatum, include both direct-additive uses in which the MHC is intentionally applied to the food and indirect-additive uses in which the MHC become components of the food due to migration from food-contact surfaces. A key consideration in evaluating the safety of these uses of MHC is the level of exposure that results. We estimated exposures to MHC in the US from food applications based primarily on a food-consumption approach, in which MHC concentrations in foods were multiplied by the amount of these foods consumed. This was a conservative estimate, because it assumes that all foods that might contain MHC in fact do so at maximum possible concentrations. A "poundage approach", in which the amount of MHC used in food applications was divided by the US population to determine maximum potential per capita exposures, was used to validate the consumption-based estimates. Exposures to MHC from food-packaging applications were estimated using the FDA's food-factor approach, which takes into account the volume and kinds of food packaged with specific types of materials. A conservative estimate of mean exposure to all MHC types combined is 0.875 mg/kg BW/day. Half of this, 0.427 mg/kg BW/day, is white mineral oils used as pan-release lubricants in baking, for de-dusting of stored grain, in confectioneries, and in coatings for fruits and vegetables. Nearly all of the remainder, 0.404 mg/kg BW/day, is petrolatum, primarily from its use as trough grease in bakery applications. Exposure to paraffin and microcrystalline waxes combined is only 0.044 mg/kg BW/day.

Paranaella luquei gen. et sp. n. (Monogenea: Microcotylidae), a new parasite of Brazilian catfishes

Paranaella, a new microcotyline monotypic genus, is erected to accommodate Paranaella liquei sp. n., parasite of gill filaments from Hypostomus sp., Hypostomus regani (Ihering) and Rhinelepis aspera Spix et Agassiz (Loricariidae) from the Parani River, Brazil. The new genus is most closely related to Microcotyle Van Beneden et Hesse, 1863, Diplostamenides Unnithan. 1971 and Solostamenides Unnithan, 1971. From Microcotyle it differs mainly by having the genital atrium formed by a muscular ring with a concentric row of numerous elongate and straight spines; from Diplostamenides it can be distinguished by the unarmed and not differentiated cirrus and from Solostamenides it differs by the single vaginal pore and absence of larval hooks.

Scanning and transmission electron microscopy of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000 (Microcotylidae, Monogenea), parasite of a Brazilian catfish, Hypostomus regani

The surface topography and ultrastructure of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000, a microcotylid monogenean parasite from the gills of Hypostomus regani (Ihering, 1905) (Loricariidae) was studied by scanning (SEM) and transmission electron microscopy (TEM). By SEM, it was observed that the tegument presents transversal ridges, forming folds in the ventral and dorsal surfaces and microvillous-like tegumental projections in the anterior and median regions of body. These projections were also observed by TEM. The tegument is made up of a syncytium delimited by apical and basal plasma membranes, containing inclusion bodies and mitochondria, connected to the nucleated region by means of cytoplasmatic processes. The tegumental cells present a well developed nucleus and cytoplasm containing inclusion bodies, similar to those found on the external layer, mitochondria, rough endoplasmatic reticulum and free ribossomes.

Ultrastructure of the tegument of Saccocoelioides godoyi

The tegument of adult Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea: Haploporidae), specimens of which were collected from the intestine of the freshwater fish, Leporinus friderici (Bloch, 1794) (Anostomidae) from the reservoir of Itaipu Hydroelectric Power Station, Parana State, Brazil, was studied by transmission electron microscopy. The tegument comprises an external anucleate layer, covered by a surface plasma membrane and associated glycocalyx. The surface layer is bound by the basal plasma membrane and contains spines, two types of inclusion bodies and mitochondria. Tegumental cell bodies are located beneath the surface musculature and contain a single nucleus, cytoplasm with rough endoplasmic reticulum, mitochondria, ribosomes, and inclusion bodies similar to those found in the external layer. Cytoplasmic strands connect the cell bodies to the external surface layer, suggesting that the inclusion bodies are produced in these cells and pass up into the syncytium, as is known for other digeneans from experimental evidence.

Ultrastructure of spermatogenesis and sperm development in Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea, Haploporidae)

Ultrastructural observations of spermatogenesis and sperm development of Saccocoelioides godoyi, an intestinal parasite of Leporinus friderici (Bloch, 1794) are described. The irregular-shaped spermatogonia form a peripheral layer, and show a prominent nucleus. Spermatocytes are larger than spermatogonia, and in the early stage present synaptonemal complex. Spermatids show nuclei smaller than the spermatocytes. Spermiogenesis is characterized by outgrowth of the zone of differentiation, presenting basal bodies, separated by an intercentriolar body. At the end of this process, the spermatozoa are released into the residual cytoplasmic mass. The spermatozoa of S. godoyi are elongate, similar to the pattern described for other Digenea, showing nuclei, mitochondria and two axonemes with the 9+1 configuration. The peripheral cortical microtubules on the dorsal and ventral faces are laterally interrupted.

Relationships between radiographic alveolar bone height and probing attachment level: data from healthy post-menopausal women

OBJECTIVE

To determine the cross-sectional and longitudinal relationships between radiographic alveolar bone height and probing attachment level in a population of healthy postmenopausal women.

MATERIALS AND METHODS

The 81 patients in this report were part of a prospective estrogen replacement interventional study. All patients were in good oral health at entry and received annual oral prophylaxis as part of the study. Standard probing measurements were made with a pressure sensitive probe at 6 sites on each tooth. Vertical bitewing radiographs were digitized, and 6 linear measurements corresponding to probing-site measurements were made from the cementoenamel junction to the alveolar crest. These procedures were performed at baseline and at annual intervals for three years. Data were analyzed both by site and by patient.

RESULTS

Moderately strong correlations were found between cross-sectional measurements of probing attachment height and radiographic bone height. Correlations were stronger for patient data (r=0.44-0.61) than for site data (r=0.19-0.36). No relationships were found between longitudinal changes in alveolar bone height and attachment level in either the site data (r=-0.10-0.04). or the patient data (r=-0.005-0.10).

CONCLUSION

Healthy patients may experience sporadic, temporary changes in attachment level or alveolar bone height which are resolved without one affecting the other.

Spermatogenesis and spermiogenesis in Microcotyle sp. (Microcotylidae, Monogenea)

Ultrastructural observations of spermatogenesis and spermiogenesis in Microcotyle sp. a microcotylid monogenean parasite from the gills of Hypostomus sp., are described. The spermatogonia were irregularly shaped, forming a peripheral layer of cells; spermatocytes were larger than spermatogonia and a nuclear synaptonemal complex was observed; young spermatids were joined by a central cytophore forming rosettes. Spermiogenesis was characterized by the outgrowth of a cytoplasmic protuberance, the zone of differentiation, containing the basal bodies, separated by an intercentriolar body, from which flagella grow out and fuse posteriorly with the median process. Cross sections of the anterior and the middle regions of spermatozoa revealed nuclei, mitochondria, peripheral microtubules, and paired axonemes each with a 9+1 pattern.

Relationships between longitudinal changes in radiographic alveolar bone height and probing depth measurements: data from postmenopausal women

BACKGROUND

The relationship between loss of radiographic alveolar bone height and probing attachment loss has been studied by a number of investigators, with mixed results. Recent studies have found weak correlations and have suggested that the relationship between bone loss and attachment loss is complex, perhaps because changes in bone height and attachment level are separated in time.

METHODS

The 85 patients in this report were part of a prospective estrogen replacement interventional study. All patients were in good oral health at entry and received annual oral prophylaxis as part of the study. Standard probing measurements were made with a pressure-sensitive probe at 6 sites on each tooth. Vertical bite-wing radiographs were taken of each patient, radiographs were digitized, and 6 linear measurements (corresponding to probing site measurements) were made from the cemento-enamel junction to the alveolar crest. These procedures were performed at baseline and at annual intervals; this study reports results after 2 years. Data were analyzed both by individual site and by averaging identical sites from all measured teeth for each patient.

RESULTS

Very weak direct relationships between change in alveolar bone height and change in attachment level were found in both the site data (r2=0.0022; P = 0.189) and the patient average data (r2=0.031; P= 0.104).

CONCLUSIONS

The changes in these patients were probably due to systemic changes in bone health rather than to periodontal disease. However, the weak correlations between changes in attachment level and bone height are similar to recent studies of periodontal disease. Our results support suggestions in the literature that the link between changes in attachment and alveolar bone height is complex, perhaps because changes in the 2 tissue types are separated by a considerable time delay.

South American Monogenea--list of species, hosts and geographical distribution

Five-hundred and twenty-three species of monogeneans have been recorded in South America: 43 from Argentina, one from Bolivia, 252 from Brazil, 29 from Chile, 15 from Colombia, eight from Ecuador, 26 from Falkland and Patagonian regions, four from French Guyana, 11 from Galapagos, two from Guiana, four from Paraguay, 92 from Peru, 16 from Uruguay and 20 from Venezuela. A list of these species with hosts and geographical distribution is presented.

Scanning electron microscopic study of Prosorhynchoides arcuatus (Linton, 1990) (Bucephalidae: Digenea)

Prosorhynchoides arcuatus (Linton, 1900) from the intestine of Pomatomus saltator (L.) from the Atlantic coast of the State of Rio de Janeiro is studied by scanning electron microscopy, with detailed description of tegumental spines. Comments on the synonymy of this species with Bucephalopsis callicotyle Kohn, 1962 are made. The tegument of adult P. arcuatus presents scale like and serrated spines and uniciliated sensory papillae, distributed over the body surface and is compared with other digenetic trematodes.

AIDS education and a volunteer training program for medical students

The process of AIDS education poses exceptional challenges for teachers and students. Medical students are in a unique position in the health care system. They are young enough to be ideal role models for high school and college students. They are mature enough to be responsible educators. We describe a special program designed and implemented by a medical student to train other medical students to become AIDS educators. This student-run program provides education for student volunteers who are able to educate other students and members of the community. The program is designed to educate a generation of physicians who will be well-equipped to combat the HIV epidemic and who can serve the community as AIDS educators while still in medical school.

Use of mycobacterial smears in the diagnosis of pulmonary tuberculosis in AIDS/ARC patients

Pulmonary tuberculosis in AIDS/ARC patients is an increasing problem. To assess the utility of acid-fast smears of pulmonary secretions in this patient population, we evaluated 38 AIDS/ARC patients with culture-positive pulmonary infection. A control group consisted of 57 non-AIDS/ARC patients, who also did not belong to an AIDS risk group, diagnosed during the same period. The number of culture-positive sputum samples evaluated per patient was similar in both groups (3.82 +/- 3.11 AIDS/ARC vs 4.47 +/- 2.83 control group). Significantly fewer AIDS/ARC patients, 45 percent, however, had a positive acid-fast smear compared with the control group, 81 percent (p less than 0.001). The initial sputum smear submitted was positive in only 29 percent of the AIDS/ARC group compared with 61 percent of control subjects (p less than 0.01). Further, greater than or equal to 5 negative smears were found in 60 percent of the evaluable AIDS/ARC patients compared with just 13 percent of control subjects (p less than 0.01). More extensive findings on chest roentgenograms were not associated with a significantly higher yield of smear positivity in the AIDS/ARC group. We conclude that acid-fast smears on sputum specimens are a relatively insensitive test for pulmonary tuberculosis in AIDS/ARC patients.

Endodontics and litigation: an American perspective

Dentists can reduce the risk of legal entanglements following endodontic treatment. Dentists should not fail to meet the standard of care required at one or more of the several stages in endodontic treatment: at diagnosis, in record keeping, by accidentally treating the wrong tooth, by not using rubber dam, by breaking endodontic instruments in the root canal, by using inappropriate endodontic implants, by creating root perforations, by failing to give adequate instructions for home care and by not providing emergency care. Recognition of problems likely to rise to litigation and the methods to be used in their avoidance are emphasized.

Cisplatin-induced gastric paresis

A 27 year old male with metastatic testicular carcinoma was treated with cisplatin, vinblastine, and bleomycin (PVB) chemotherapy. After receiving a cumulative dose of 500 mg/m2 of cisplatin, he developed severe nausea and vomiting and had clinical evidence of a cisplatin-induced peripheral neuropathy. His vomiting resolved five weeks after discontinuation of cisplatin. We believe this case represents the first report of gastric autonomic neuropathy induced by cisplatin.

Magnetic-induction hyperthermia. Results of a 5-year multi-institutional national cooperative trial in advanced cancer patients

Nine US institutions performed 14,807 Phase I-II treatments of magnetic-induction (Magnetrode [Henry Medical Electronics, Inc., Los Angeles, CA]) hyperthermia in 1170 adults. All had advanced tumors: 20% had untreated inoperable cancer or disease progression despite surgery (10%), radiation therapy (XRT) (3%), chemotherapy (27%), or combinations (40%); 67% had pain; and 79% had reduced activity. Eighteen percent were advanced primaries, 26% were recurrent, and 56% metastatic tumors in the head and neck (7%), body wall (7%), extremity (4%), abdominal cavity (17%), pelvis (17%), lung (15%), or liver (30%); 36% were less than 5 cm and 64% greater than or equal to 5 cm. Treatments were to safe tolerance for 30 to 60 minutes for five or more treatments. Results in 960 evaluable patients were complete response 9% (1-34 months; median, 7 months), partial response 18% (1-39 months; median, 4 months), minimal response 10% (1-15 months; median, 3 months), and no change 33% (1-32 months; median, 3 months), with decreased pain in 30% and improved activity in 21%, independent of histologic type or site. Regression was dependent on treatment type and minimum temperature: heat only, 23%; heat + XRT, 60%; heat + less-than-standard XRT because of prior XRT failure, 39%, heat + intravenous (IV) chemotherapy, 28%; heat + same previously failed IV chemotherapy, 20%; heat + intraarterial (IA) chemotherapy, 28%; heat + same previously failed IA chemotherapy, 15%; heat + standard XRT + chemotherapy, 58%; heat + less-than-standard XRT + chemotherapy, 47%; less than 40 degrees C, 31%; 40 to 40.9 degrees C, 45%; 41 to 41.9 degrees C, 54%; 42 to 42.9 degrees C, 47%; 43 to 43.9 degrees C, 40%; 44 to 44.9 degrees C, 33%; 45 to 45.9 degrees C, 55%; 46 to 46.9 degrees C, 63%; greater than 47 degrees C, 100%. There were 49 (0.33%) skin burns and 2 systemic injuries (stomach ulcer at 1 month; lung fibrosis at 9 months). This trial indicates that localized hyperthermia has a significant role in palliation of human advanced solid cancer.

Megestrol acetate therapy for advanced breast cancer

One hundred twenty-four patients with metastatic breast cancer were treated with 40 mg of megestrol acetate four times daily. Complete responses (CR) or partial responses (PR) were seen in 29 patients (23%). CR, PR, or stable disease (S) was seen in 80 patients (65%). The median duration of response was 22 months for CR and PR and ten months for S. A significantly higher response rate (CR + PR) was seen in estrogen-receptor-positive (ER-positive) patients (26%) and in patients who had not received prior therapy (39%). A significant relationship to response could not be established for menopausal status, progesterone-receptor (PrR) status, dominant site of disease, or prior administration of chemotherapy. Median survival was 66+ months for responders, 35 months for patients with stable disease, and 9 months for nonresponders. These differences are all statistically significant (P less than .001). Toxicity was minimal, and side effects consisted primarily of weight gain, which was seen in 18 patients (14.5%). Megestrol acetate can provide effective palliation in patients with advanced breast cancer.

Effects of cyclophosphamide and adriamycin on the healing of surgical wounds in mice

Administration of therapeutic dose levels of cyclophosphamide as a single dose or as daily treatments for 5 days during the perisurgical period resulted in a significant decrease in the strength of surgical skin wounds in mice as measured 21 days after surgery. Administration of a single dose of 200 mg/kg either at the time of surgery or up to 4 days prior to or after surgery impaired 21-day wound strength, with the most extensive depression observed when the drug was given 1 or 2 days after surgery. Earlier stages of wound healing (day 3 or day 7) were not as sensitive to cyclophosphamide. Adriamycin in the therapeutic dosage range for mice did not significantly impair wound healing. This drug had an effect only at the LD10 dosage level. Combination treatment with cyclophosphamide plus adriamycin at the time of surgery impaired 21-day wound strength to a greater degree than observed with either agent alone, but did not significantly depress wound strength 3 or 7 days after surgery. These studies indicate that dosage level, the time of drug administration relative to surgery, and the time at which wound strength measurements are made are important parameters in determination of the effects of antineoplastic agents on wound healing.

Effects of antineoplastic agents on wound healing in mice

The influence of antineoplastic agents on wound healing was evaluated in an experimental model employing surgical incisions in the skin of mice. A single injection in the therapeutic dose range of various clinically active antitumor agents was administered immediately following operation and the breaking strength of skin wounds was measured 3, 7, and 21 days later. Vincristine and methotrexate decreased wound strength at 3 days but not on days 7 or 21. Actinomycin D interfered with early phases of wound healing and had less effect on later phases. Treatment with bleomycin had no effect on wound strength at days 3 or 21 but prevented an increase in wound strength from day 3 to day 7; 1,3-bis(2-choroethyl)-1-nitrosurea (BCNU) decreased wound strength at all time points after operation, whereas 5-Fluorouracil had no significant effect at any time. The presence of a large tumor mass had no direct effect on wound strength nor did it modify the effect on wound strength of an antineoplastic agent, cyclophosphamide. These findings are discussed, taking into account the experimental and clinical literature on the effects of antitumor drugs on wound healing.

Heterodyne detection: phase front alignment, beam spot size, and detector uniformity

We consider the effects of signal and local oscillator phase front misalignment, beam spot sizes, and electric field distributions on heterodyne detection. The signal and local oscillator fields that we consider are various combinations of Airy, Gaussian, and uniform distributions. We show that the values of the beam radii that maximize the heterodyne SNR are sensitive to phase front misalignment and that the degradation with misalignment angle is somewhat less severe for Airy received signals than for uniform. We also prove that for small optical spot sizes and perfect alignment, the optimal ratio of local oscillator Gaussian l/e field radius to signal Airy F number is approximately 0.7lambda. We next consider the effects of nonuniform detector quantum efficiency. Simple examples show that quantum efficiencies averaged over the detector surface give only crude estimates of the sensitivity of a heterodyne system. For accurate estimates full account must be made of the electric field parameters and the detector re ponse at each point on its photosurface.

Fourier spectrum of a chopped bivariate normal intensity distribution

Theoretical and experimental results are presented for chopping or mechanically modulating a bivarate normal intensity distribution. This distribution is a useful approximation in many optical situations. The present analysis is an extension of that due to McQuistan and Julich. The chopped intensity distribution is expanded in a Fourier series with the coefficients calculated numerically by computer. Coefficients are determined for various beam to chopper width ratios and for several levels of approximation to the intensity distribution. Experimental verification is provided by spectral analysis of the detected signal from a chopped laser beam.