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W Sewchand

Publications and source records attributed to W Sewchand.

11 recordsLinked to original sources
PubMed1989

Technical aids for the flexible use of the Leksell stereotactic system.

As part of a multimodality therapy program for intracranial tumours, 105 stereotactic and implant procedures have been carried out utilizing the CT-compatible Leksell stereotactic system. In the iridium implant series, 86 catheters have been implanted for an average of 3.6 targets per patient. There have been no deaths or missed targets and only two incidential haemorrhages detected. In order to facilitate the reliability, safety and speed of multiple catheter insertion, several techniques have been developed including: (a) a standardized single-length catheter and flange system; (b) a ceramic catheter for microwave hyperthermia; (c) a mnemonic card for ease of calculation; (d) a radiation shield for nursing; (e) a stereotactic drill and surgical approaches to far lateral and posterior fossa targets. Principles for the use of these technical aids are discussed.

Brain Neoplasms↗
PubMed1989

Alumina ceramic as a biomaterial for use in afterloading radiation catheters for hyperthermia.

A major technical challenge to the use of interstitial hyperthermia in malignant brain tumors is the production of a well-defined, uniform hyperthermal field. In theory, A 915-MHz microwave antenna should allow fewer antennas to be used and cause less mechanical brain damage; however, standard radiation afterloading catheters require antennas to be 12 cm long; this is clearly impractical for intracranial use. Since alumina ceramic (Al2O3) catheters permit short microwave antennas (3-5 cm in length) to function properly in neural tissue, it is important to test the biocompatibility of alumina for use in combined interstitial microwave hyperthermia and brachytherapy. A 5-mm length of alumina catheter was implanted into the brains of 15 white rats. The animals were killed at 3, 7, 14, 28, and 56 days. Histological examination revealed only minor mechanical damage and no encapsulation until 1 month; even then, the glial wall was only a few cell layers thick. Five animals received implants and were killed at similar intervals for x-ray microanalysis with the scanning electron microscope. No migration of aluminum into the brain was detected when compared with two control animals that did not receive implants and an alumina blank. Although we measured 50% attenuation of the radiation from iridium-192 sources in alumina catheters as compared with conventional ones, alumina catheters can still be used for interstitial radiation by increasing either the activity of the seeds or the duration of treatment.

Aluminum↗
PubMed1988

Once-a-week vs conventional daily radiation treatment for lung cancer: final report.

This is the final report of a prospective randomized clinical trial which began in 1982 and explored once-a-week hypofractionation in lung cancer patients with unresectable, non-metastatic, measurable, loco-regionally advanced disease. Stratification to this protocol has been done by histology, stage, and performance status categories. Patients with ipsilateral supraclavicular and/or brain metastases as the only evidence of distant spread, have been included in the study, but were stratified and analyzed separately. The two protocol arms were: (I) Conventional daily radiation [5 x W]-5 daily fractions of 2 Gy each to a total dose of 60 Gy in 6 weeks, protecting the spinal (SC) at 45 Gy and (II) Once-a-week radiation [1 x W]-one weekly fraction of 5 Gy each to a total tumor dose of 60 Gy in 12 weeks protecting the SC at 30 Gy. A total of 150 patients have been entered. Of these, 30 pts. are inevaluable, but the reasons of non-compliance, progression of disease or death due to intercurrent disease were of equal incidence in both groups. Of the 120 evaluable patients, 63 were treated 5 x W and 57 with 1 x W therapy. Complete tumor responses are similar in both arms with 1 x W pts demonstrating a numerical advantage (26% vs 17%). The average follow-up of the entire series is 3 yrs with a range of 12-66 months. Survival data is comparable in both groups with the 12 and 24 month actuarial survival of 49% and 23% for the 5 x W arm and 59% and 29% for the 1 x W arm. 1 x W patients continue to show a better tolerance than 5 x W pts. There are sufficient long-term survivors in both arms to assess chronic toxicity. The number of patients alive at 12, 18, and 24 months were 25, 11, and 5 for the 5 x W arm and 29, 16, and 7 for the 1 x W arm. No significant differences in late reactions have been noted. The longest surviving patient in the 1 x W arm is now 48 months after treatment.

Adenocarcinoma↗
PubMed1987

Neuro-oncology update: radiation safety and nursing care during interstitial brachytherapy.

Radiation control and safety are major considerations for nursing personnel during the care of patients receiving brachytherapy. Since the theory and practice of radiation applications are not part of the routine curriculum of nursing programs, the education of nurses and other health care professionals in radiation safety procedures is important. Regulatory agencies recommend that an annual safety course be given to all persons frequenting, using, or associated with patients containing radioactive materials. This article presents pertinent aspects of the principles and procedures of radiation safety, the role of personnel dose-monitoring devices, and the value of additional radiation control features, such as a lead cubicle, during interstitial brain implants. One institution's protocol and procedures for the care of high-intensity iridium-192 brain implants are discussed. Preoperative teaching guidelines and nursing interventions included in the protocol focus on radiation control principles.

Astrocytoma↗
PubMed1985

Palliative half-body irradiation. Single and fractionated doses.

Systemic half-body irradiation (HBI) has been used extensively for the palliation of cancer pain. It has also been tried as an adjuvant therapy in patients with advanced locoregional tumors with a high propensity to disseminate and as consolidation therapy after primary systemic treatment. The limitations and toxicity of this technique have been studied extensively. Single doses of 600 rad to the upper half-body (UHB) and 800 rad to the lower half-body (LBH) have been found to achieve excellent palliative responses with an acceptable rate of complications. In order to determine the feasibility of increasing the dose of radiation delivered, a pilot study was conducted at the University of Maryland. Forty-four patients received palliative HBI. Of these, the first 36 patients received single doses to the UHB, mid-body (MB), or LHB using doses of 600 rad to the UHB and 800 rad to MB and LHB. The last consecutive eight patients received two fractions of 400 rad each, given 2-3 weeks apart. The pain response achieved by each group is similar; single dose achieved 84% complete and partial responses vs. the fractionated group, which achieved 87% complete and partial responses. The main difference between the two groups was the time necessary to achieve a response. The single dose group achieved improvement of their symptoms in 24-48 hours in approximately 70% of the patients who responded. The fractionated group achieved symptomatic response after the second dose of irradiation was given. The toxicity of both groups was similar. The acute radiation syndrome after half-body irradiation was controlled with a premedication program. Hematological toxicity was similar in both groups, and no cases of fatal radiation pneumonitis were seen. At the present time, it seems feasible to proceed with other fractionation schemes in order to try to increase the total dose delivered.

Female↗
PubMed1979

Total-body superficial electron-beam therapy using a multiple-field pendulum-arc technique.

A technique using pendulum-arc rotation is presented for electron-beam treatment of generalized superficial malignancies. The technique consists of six arcing fields symmetrically dispersed around the body surface for circumferential coverage. The arc angle is selected to scan the height of the body fully. Beam uniformity within 10% over a height of 180 cm is achieved at a treatment distance of 385 cm. Randophantom dosimetry, using an 8 MeV electron beam degraded by 3/8 in. Plexiglas, indicates a surface dose uniformity within +/- 7% over most of the body surface. Underdosages occur at regions obstructed by adjacent body parts.

Abdomen↗
PubMed1978

CT determination of parameters for inhomogeneity corrections in radiation therapy of the esophagus.

Accurate dose prediction for megavoltage photon therapy of carcinoma of the esophagus requires information on tumor depth, lung thickness, and lung density. The authors found that CT localization of internal and external contours is accurate within +/- 1 mm. Lung density can be measured with an error of less than 0.02 g/cm3 in the range 0.25-1.00 g/cm3. Variance between predicted and measured dosage was less than 3% in all patients and in most RANDO phantom measurements. Accurate radiation therapy planning is possible with CT information from a commercial scanner.

Computers↗
PubMed1978

Effect of air space and depth dose in electron beam therapy.

In electron beam therapy, alterations in dosimetry occur as a result of air space between the end-of-treatment cone and the skin surface. A large air gap may be introduced in order to obtain a field size larger than that available at the cone end. Needed dosimetry corrections related to these air space problems are discussed, along with a proposed method of measuring effective source-to-cone end distance. Data presented show the modifications of a dosimetric field which occur with an increase in the air space below the treatment cone.

Electrons↗
PubMed1978

Variations in depth-dose data between open and wedge fields for 4-MV X-rays.

Central-axis depth-dose data for 4-MV x rays, including tissue-maximum ratios, were measured for wedge fields. Comparison with corresponding open-field data revealed differences in magnitude which increased with depth, field size, and wedge thickness. However, phantom scatter correction factors for the wedge fields differed less than 1% from corresponding open-field factors. The differences in central-axis per cent depth doses between the two types of fields indicate beam hardening by the wedge filter. This study also implies that the derivation of tissue-maximum ratios from central-axis per cent depth is as valid for wedge as for open fields.

Humans↗
PubMed1977

Total-body irradiation with a high-dose-rate linear accelerator for bone-marrow transplantation in aplastic anemia and neoplastic disease.

Nine children with various hematologic disorders underwent bone-marrow transplantation following total-body irradiation with 750 rads at a rate of 26 rads/min. from a 13-MeV linear accelerator in conjunction with cytotoxic drugs. This treatment was tolerated reasonably well, with acceptable side effects. Three patients were alive and well at 18, 11, and 7 months post-transplantation at the time this paper was written.

Anemia, Aplastic↗