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Biomedical subjects

S C Sharma

Publications and source records attributed to S C Sharma.

At least 415 records · Page 23Linked to original sources
PubMedDate not supplied

Systemic absorption and toxicity from topically administered lidocaine during transesophageal echocardiography.

This report describes the cases of three patients who had central nervous system toxicity from locally administered lidocaine during transesophageal echocardiography. Parenteral sedation was not employed. Serum levels of lidocaine were obtained after the procedure in all three patients, who recovered spontaneously and suffered no permanent ill effects. Medical conditions such as congestive heart failure and diminished hepatic function or concomitant use of lidocaine analogs may predispose patients to the toxic side effects of locally administered lidocaine. Extreme care and close monitoring of patients are warranted when topical lidocaine anesthetic is employed in the setting of delayed lidocaine clearance.

Administration, Topical↗
PubMedDate not supplied

Expansion of visual receptive fields in experimental glaucoma.

Glaucoma is a major cause of blindness and is characterized by death of retinal ganglion cells. In a rat model of glaucoma in which intraocular pressure is raised by cautery of episcleral veins, the somata and dendritic arbors of surviving retinal ganglion cells expand. To assess physiological consequences of this change, we have measured visual receptive-field size in a primary retinal target, the superior colliculus. Using multiunit recording, receptive-field sizes were measured for glaucomatous eyes and compared to both those measured for contralateral control eyes and to homolateral eyes of unoperated animals. Episcleral vein occlusion increased intraocular pressure. This was accompanied by a significant increase in receptive-field size across the superior colliculus. The expansion of receptive fields was proportional to both degree and duration of the increase of intraocular pressure. We suggest that this increase in the size of receptive fields of glaucomatous eyes may be related to the increase in the size of dendritic arbors of the surviving ganglion cells in retina.

Animals↗
PubMedDate not supplied

Rabbit as an animal model of paranasal sinus mycoses.

Paranasal sinus mycoses are endemic in rural populations of northern India. To study host-parasite interactions, we developed an animal model of paranasal sinus mycoses. After failure in small animals such as mice and rats, we used New Zealand white rabbits weighing 2.5-3 kg. Inoculum sizes consisted of 0.75-1.0 x 10(8), 0.75-1.0 x 10(7), 0.75-1.0 x 10(6) conidia of a clinical isolate of Aspergillus flavus. The inoculum was injected at a spot 0.5 cm in front of the alveolar process of the maxilla and 0.5 cm below the maxillary process of frontal bone and vertically to a depth of 0.5 cm across the bone directly into the nasal sinus. Paranasal sinus mycoses proven by culture and histopathology developed in 67% of animals injected with 0.75-1.0 x 10(8) conidia and 17% of animals with 0.75 x 10(7) conidia. No lesions were found in the group injected with 0.75-1.0 x 10(6) conidia. Precipitating antibody against culture filtrate antigen was found in rabbits with paranasal sinus mycoses. Therefore, rabbits can be used as an animal model to study paranasal sinus mycoses.

Animals↗
PubMedDate not supplied

Paranasal sinus mycoses in north India.

Recognizing the high incidence of paranasal sinus mycoses in north India, we analysed retrospectively the clinical, mycological and management aspects of 178 patients with proven disease attending our institute. On the basis of clinical, radiological, histopathological and mycological findings, the patients could be categorized into those with allergic (8), non-invasive (92) and invasive (78) disease types. Bony erosion without mucosal invasion by fungi was seen in 16 patients with non-invasive disease. Young men from rural areas were the most commonly affected. Rhinorrhoea with nasal polyposis (45.8%) and proptosis (46.4%) was the most common presentation. Concurrent involvement of the maxillary and ethmoid sinuses was common in these patients, whereas isolated sphenoid and frontal sinuses were involved in the invasive variety only. Orbital and intracranial extensions were detected in 100% and 13.2%, respectively, of patients with the invasive type of disease. Aspergillus flavus (79.7%) was the most common isolate. Surgical debridement and sinus ventilation were adequate for the effective management of the non-invasive disease. However, adjuvant medical therapy was included in treatment of the semi-invasive and invasive varieties of the disease. Itraconazole was found to be most useful in prevention of recurrence in the invasive type. Mortality was highest (33.3%) among patients with zygomycotic infection. Invasive fungal granuloma with orbital and intra-cranial invasion is a distinct entity in terms of its clinical course and treatment compared with non-invasive fungal sinusitis, and it needs to be treated aggressively with surgical excision and postoperative itraconazole.

Adolescent↗
PubMedDate not supplied

Results of radiotherapy alone in the treatment of carcinoma of uterine cervix: a retrospective analysis of 1069 patients.

Carcinoma of the uterine cervix is the most common malignancy affecting women in developing countries like India. This retrospective study was made to analyze our results of radiotherapy alone in the treatment of carcinoma cervix. Between January 1996 and December 2001, 1069 patients of carcinoma cervix were treated at our center with external beam radiotherapy (EBRT) and intracavitary radiotherapy (871) or EBRT alone (198). The median dose to point A was 81 Gy. Overall survival (OS), disease-free survival (DFS), and pelvic control at 5 years were 51.8%, 49.4%, and 63.9%, respectively. For the patients who could receive intracavitary radiotherapy (871), the OS, DFS, and pelvic control rates were 60.7%, 58.6%, and 73.5%, respectively. On multivariate analysis, bulk, overall treatment time (OTT) and response to EBRT were found to affect OS and DFS independently. Similarly, OTT, response to EBRT, stage, and age were the factors that influenced pelvic control. Incidence of severe late toxicities (grade 3/4) in the rectum, bladder, small intestine, and skin were 1.1%, 1.2%, 0.2%, and 1.2%, respectively. In developing countries like India, where chemoradiation can be afforded by a minority only, judicious use of radiotherapy still produces satisfactory results with acceptable toxicity. The addition of chemotherapy may be beneficial in patients with adverse prognostic factors.

Adult↗
PubMedDate not supplied

Film dosimetry of megavoltage photon beams: a practical method of isodensity-to-isodose curve conversion.

The central problems of photon beam film dosimetry are the dependence of film response upon photon energy, processing conditions, and film plane orientation. We have overcome these problems by accurately fitting the depth-dependent sensitometric curve of Kodak XV-2 film (exposed parallel to beam axis) to the equation OD(D,d) = ODs(1 - exp [- alpha 0[1 + beta(d-dm)]D]) where OD(D,d) is the optical density for dose D at depth d. ODs, alpha 0, and beta are constants characteristic of the film and beam energy but are independent of field size. Only central axis depth dose data for a single field are required to determine their values. A computer program based upon this equation has been written which successfully generates single field isodose curves from film data for a variety of field sizes (including wedged fields) with an accuracy of +/- 3%. Data are presented for 60Co, and 4 and 10 MV x rays.

Film Dosimetry↗
PubMedDate not supplied

Variation of output with atmospheric pressure and ambient temperature for Therac-20 linear accelerator.

The Therac-20 (a linear accelerator manufactured by the Atomic Energy of Canada, Ltd.) employs an unsealed monitor chamber to control the dose output. Daily fluctuations in machine output for both x rays and electron beams were observed to vary with ambient temperature and atmospheric pressure. These variations were not related to any other machine parameters. Variations as large as 3.5% were seen by monitoring 18-MV x-ray output over several months. We recommend that the manufacturers take steps to eliminate the atmospheric dependence of dose rate.

Atmospheric Pressure↗
PubMedDate not supplied

Dosimetry of small fields for Therac 20 electron beams.

The Therac 20 medical linear accelerator produces electron beams of 6, 9, 13, 17, and 20 MeV. We measured depth dose, isodose curves, and output factors for small electron fields using an ionization chamber, film, and thermoluminescent dosimeters. Tables and graphs were generated from these measurements for accurate treatment planning of various blocked and open fields.

Electrons↗
PubMedDate not supplied

Depth dose characteristics of elongated fields for electron beams from a 20-MeV accelerator.

In a Therac-20 linear accelerator, 6-20 MeV electron beams are normally produced by shaping a scanned electron beam through primary x-ray collimators and secondary electron trimmers. The collimator settings range continuously from 2 to 30 cm. Depth dose and field flatness parameters were measured for small elongated fields of the various electron energies. Depth dose of narrow fields defined either by the machine's collimator or lead cutouts agreed with data predicted from small square fields using the "square-root" method.

Biophysical Phenomena↗
PubMedDate not supplied

Dosimetric study of total skin irradiation with a scanning beam electron accelerator.

The Therac 20 6-MeV scanned electron beam may be used for partial or total skin therapy. The maximum field size at 1 m is 30 X 30 cm defined by a set of primary photon collimators in conjunction with secondary trimmers. We have studied electron beam profiles with and without trimmers at the nominal source-skin distance of 1 m versus extended distances of 3-5 m. We find that the trimmers limit the field size and add little to the beam uniformity at extended distances. Beam energy, dose distributions, and output factors at extended distances were measured for single and multiple field arrangements with and without trimmers. Beam parameters were measured after introducing a degrader that lowered the energy to 3.7 MeV.

Humans↗
PubMedDate not supplied

Evaluation of a photon and an electron beam of a 6-MV linear accelerator.

The first Mitsubishi medical linear accelerator in the United States was commissioned in April 1985. This unit EXL-8 (marketed by Mitsubishi International Corporation) produces 8-MeV electron beams in addition to 6-MV x rays. It is a 100-cm source-axis distance isocentric machine. Acceptance testing and performance evaluation of this accelerator were completed. Our measurements included beam characteristics and dosimetry parameters for both modalities. Central axis % depth dose (% DD), tissue-maximum ratio, field size output factors, wedge factors, etc., for this Linac 6-MV beam, are reported. Characteristics of the 8-MeV electron beam, namely % DD data, isodose curves, and cone ratios for various electron applicators are presented.

Electrons↗
PubMedDate not supplied

Surface dose perturbation due to air gap between patient and bolus for electron beams.

The effect of air gaps under bolus material on the surface dose for electron beams is investigated. Dose measurements were performed for air gaps from 0.0 to 3.0 cm and bolus thicknesses of 0.5 and 1.0 cm using the various electron energies and cone sizes available on an electron linear accelerator. Our results show that the surface dose decreases for lower electron energies, smaller field sizes, thicker boluses, and larger air gaps.

Electrons↗
PubMedDate not supplied

Management of mediastinal compression due to bronchogenic carcinoma.

Fifty-six cases of bronchogenic carcinoma with mediastinal compression were analyzed retrospectively. Microscopic confirmation was obtained in 23 patients and small cell carcinoma was most frequent. Radiation treatment gave complete remission in about 70 per cent when the total tumour dose exceeded 35 Gy fractionated during 3 weeks. Addition of cyclophosphamide marginally increased the remission rate to about 85 per cent. Total tumour doses of less than 35 Gy gave obviously poorer results. The response rate was highest in small cell carcinoma.

Carcinoma, Bronchogenic↗
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Prostaglandin Falpha, progesterone and oestrogens in relation to parturition in sheep.

Six hourly blood samples were collected from either the uterine vein or posterior vena cava of 8 conscious ewes over a period of about 1 week prior to and 2 days after parturition. In addition blood was also collected simultaneously from the jugular vein. Using sensitive radioimmunoassay techniques, these samples were analyzed for PGF2 alpha, progesterone and oestrogens. The results indicate that concentrations of PGF2 alpha in sheep blood started to rise before a fall in progesterone concentrations. A rise in total oestrogens also preceded the fall in progesterone concentrations. It was however not possible to show a temporal relationship between the rises in oesterogens and PGF2 alpha concentrations.

Animals↗
PubMedDate not supplied

Adjuvant interstitial brachytherapy in a case of anorectal melanoma.

PURPOSE: A locally resectable case of anorectal melanoma is reported. In order to prevent local recurrence, interstitial brachytherapy was used. METHOD: A 45 years old emaciated female presented with a 8 x 6 x 6 cm, hard, mobile, intraluminal mass in the anal canal and rectum, biopsy revealed malignant melanoma. As the mass was locally resectable, wide local excision of the tumour was carried out. She was subsequently given interstitial brachytherapy with Caesium--137 implants at tumour bed, not described so far in literature. Six months later her general condition had improved but abdomino-perineal resection was necessitated due to presence of extra-rectal metastasis. RESULTS: Patient is in our follow-up for 36 months now and doing well. CONCLUSION: Supplementation of interstitial brachytherapy after local resection of ano-rectal melanoma may help to prevent local recurrence.

Anus Neoplasms↗