PubMed Health⌕ Search

Biomedical subjects

E K Osei

Publications and source records attributed to E K Osei.

7 recordsLinked to original sources
PubMed2003

Software for the estimation of foetal radiation dose to patients and staff in diagnostic radiology.

Occasionally, it is clinically necessary to perform a radiological examination(s) on a woman who is known to be pregnant or an examination is performed on a woman who subsequently discovers that she was pregnant at the time. In radiological examinations, especially of the lower abdomen and pelvis area, the foetus is directly irradiated. It is therefore important to be able to determine the absorbed dose to the foetus in diagnostic radiology for pregnant patients as well as the foetal dose from occupational exposure of the pregnant worker. The determination of the absorbed dose to the unborn child in diagnostic radiology is of interest as a basis for risk estimates from medical exposure of the pregnant patient and occupational exposure of the pregnant worker. In this paper we describe a simple computer program, FetDose, which calculates the dose to the foetus from both medical and occupational exposures of the pregnant woman. It also calculates the risks of in utero exposure, compares calculated doses with published data in the literature and provides information on the natural spontaneous risks. The program will be a useful tool for the medical and paramedical personnel who are involved with foetal dose (and hence risks) calculations and counselling of pregnant women who may be concerned about in utero exposure of their foetuses.

Algorithms↗
PubMed2003

Stereotactic radiotherapy in the treatment of ocular melanoma: a noninvasive eye fixation aid and tracking system.

Ocular melanoma is frequently treated using brachytherapy implants (such as 125I and 60Co plaques or 184Ta wire), surgery, or external beam radiotherapy using small 60Co beams, high energy x-rays, or proton therapy. The last technique, though very expensive, provides improved dose distributions and dose localizations in the treatment of tumours adjacent to critical normal tissues. The technique of fractionated stereotactic radiotherapy is now being used at an increasingly large number of centers in the treatment of lesions in the brain, and the head and neck. This article describes the successful extension of the stereotactic technique to the treatment of ocular melanoma: an eye fixation aid is attached to a noninvasive, relocatable Gill-Thomas-Cosman head frame together with a simple eye-movement tracking system.

Dose Fractionation, Radiation↗
PubMed2001

Equivalent dose to the fetus from occupational exposure of pregnant staff in diagnostic radiology.

The protection of the unborn children of pregnant women from ionizing radiations is very important because the fetus is particularly vulnerable to the effects of ionizing radiation. From the radiation protection perspective, the International Commission on Radiological Protection regards the unborn child as a member of the public when considering the occupational exposure of pregnant workers. The determination of the equivalent dose to the unborn child in diagnostic radiology is of interest as a basis for risk estimates from occupational exposures of the pregnant worker. In this paper, coefficients for converting dosemeter readings to equivalent dose to the fetus have been calculated using Monte Carlo simulation. X-ray transport was simulated by tracing individual photons through soft tissue phantoms. Equivalent dose to the uterus was used to simulate the equivalent dose to the fetus during the first 2 months of pregnancy. The Monte Carlo model was validated experimentally by direct measurements made in an Alderson female Rando phantom for a range of irradiation conditions. The two sets of data indicated good agreement with the Monte Carlo results, being relatively greater than the experimental results to a maximum of about 15%.

Computer Simulation↗
PubMed1999

Fetal position and size data for dose estimation.

In order to establish both positional and size data for estimation of fetal absorbed dose from radiological examinations, the depth from the mother's anterior surface to the mid-line of the fetal head and abdomen were measured from ultrasound scans in 215 pregnant women. Depths were measured along a ray path projected in the anteroposterior (AP) direction from the mother's abdomen. The fetal size was estimated from measurements of the fetal abdominal and head circumference, femur length and the biparietal diameter. The effects of fetal presentation, maternal bladder volume, placenta location, gestational age and maternal AP thickness on fetal depth and size were analysed. The fetal position from the anterior surface of the mother's abdomen is shorter for posterior placenta and empty bladder volume, but longer for anterior placenta and full bladder volume. Mean fetal depth (MFD) observed for all bladder volumes, fetal presentations and placenta locations increased from 6.5 +/- 0.5 cm to 10.2 +/- 0.7 cm over the duration of pregnancy. Similarly, mean fetal skull depth (FSD) increased from 6.6 +/- 0.6 cm to 9.8 +/- 0.6 cm over the period of pregnancy, but only from about 6.6 cm to 7.8 cm over the period (8-25 weeks) when damage to the developing brain has been observed to result in mental retardation. Using the range of mean fetal depth (4.7-13.9 cm) observed in this study and depth dose data at 75 kVp and 3.0 mmAl half value thickness (HVT), fetal absorbed dose would be overestimated by up to 66% or underestimated by up to 77% if the mean value of MFD (8.1 cm) is used rather than actual individual values. These errors increase with lower tube potential and filtration up to over 90% overestimation and up to 100% underestimation at 60 kVp and 1.0 mmAl filtration.

Anthropometry↗
PubMed1999

Fetal doses from radiological examinations.

There has been growing concern about radiation exposures in the case of pregnant women who undergo radiological examinations of the lower abdomen and pelvis, when the embryo/fetus is near or included in the X-ray field. This paper describes a retrospective study of 50 pregnant women accrued over a period of 10 years. Most of these women were not aware of pregnancy at the time of their radiological examinations. They subsequently discovered that they were pregnant and sought advice from their physicians on fetal dose and risk. They were then referred to a Radiation Protection Advisor for an estimation of the fetal dose. Radiation absorbed dose to the embryo/fetus was estimated from a knowledge of technique factors and examination details using normalized uterine doses published by the National Radiological Protection Board (NRPB). Doses to the embryo/fetus varied between less than 0.01 microGy and 117 mGy, depending on the examination. Gestational ages ranged between 2 and 24 weeks.

Abnormalities, Radiation-Induced↗
PubMed1997

Risk ranking by perception.

The study of people's perception and acceptability of risk is important in understanding the public reaction to technology and its environmental and health impact. The perception of risk depends on several factors, including early experiences, education, controllability of the risk, the type of consequence, and the type of person(s) who makes the judgment. This paper reviews some of the main factors influencing people's perception and acceptability of risk. Knowledge about which factors influence the perception of risk may enhance the understanding of different points of view brought into risk controversies, improve risk communication, and facilitate policy making. Results from a risk ranking by perception survey conducted in Ghana are also presented.

Environmental Health↗