ABSTRACT
Various researchers who have carried out national and international surveys have reported wide variations in patient dose arising from specific X-ray examinations. This study intends to quantify and evaluate, by means of thermo luminescence dosimeter (TLD) chips, the average radiation dose to the patients undergoing pelvic x-ray examinations. ESD (entrance surface doses) to patients’ pelvic will be measured with thermo luminescence dosimeter (TLD) chips, also the exit dose will be measured using TLD chips. The absorbed dose is thus gotten by subtracting the exit dose from the entrance surface dose.The study group will consist of 30 patients who were referred for pelvic X-ray examinations to the two selected hospitals in Enugu State, UNTH and NOHE. The risks associated with pelvic examinations for patients are negligible if the suitable radiation dose is applied. The exposure of patients to unsuitable/ very high levels of radiation during x-ray examination of the pelvis imposes both short-term and long-term health hazards to the patient. The importance of good regulatory activities and trained personnel will be stressed in this work. Apart from the fact that the data provided in this work will be useful for the formulation of national guidance levels, they will also provide patient dosimetry information on healthcare level IV countries where Nigeria is categorized.The results of this study will provide baseline data to establish reference dose levels for pelvic examination in patients.
INTRODUCTION
Ionizing radiation is used daily in hospitals and clinics to perform diagnostic procedures. The most commonly mentioned forms of ionizing radiation are x-rays and gamma rays.1
Medical uses of radiation have grown very rapidly over the past decade, and as of 2007, medical uses represent the largest source of exposure to the U.S. population. Most physicians have difficulty assessing the magnitude of exposure or potential risk. Effective dose provides an approximate indicator of potential detriment from ionizing radiation and should be used as one parameter in evaluating the appropriateness of examinations involving ionizing radiation.2
When a person is exposed to radiation, energy is deposited in the tissues of the body. The amount of energy deposited per unit of weight of human tissue is called the absorbed dose. Absorbed dose is measured using the conventional rad or the SI unit Gy (gray). The rad, which stands for radiation absorbed dose, was the conventional unit of measurement, but it has been replaced by the Gy. One Gy is equal to 100 rad.3
A person’s biological risk (that is, the risk that a person will suffer health effects from an exposure to radiation) is measured using the conventional unit rem or the SI unit Sv (sieverts). One Sv is equal to 100 rem.3
A thermo luminescent dosimeter (TLD) is a type of radiation dosimeter that measures ionizing radiation exposure by measuring the amount of visible light emitted from a crystal in the detector when the crystal is heated. The amount of light emitted is dependent upon the radiation exposure.4
The physical principle of TLD is concerned with electrons being trapped within the atomic structure of the material, but essentially it amounts to this: the energy deposited by the ionising radiation is stored until the material is heated, when it is released in the form of light. Hence, “thermo” – it’s heated up; “luminescence” – it glows.5
There are a number of different TLD materials, and a number of different means of heating them. Heating is carried out by playing a jet of hot nitrogen gas onto the TLD. Light collection is always carried out by a device known as a photomultiplier tube, which turns the light into an electrical signal by means of the photo-electric effect. The read-out temperature depends on the material used.5
Material exhibiting thermo luminescence in response to ionizing radiation include but are not limited to calcium fluoride, lithium fluoride, calcium sulphate, lithium borate, calcium borate, potassium bromide and feldspar. The two most common types of thermo luminescent dosimeters are calcium fluoride and lithium fluoride.4
In both developed and developing countries, the number and range of X-ray facilities and X-ray equipment is increasing rapidly. Although alternative modalities for diagnosis of diseases and injury, such as ultrasound and MRI are becoming increasingly available, steady improvement in the quality of X-ray images and patient protection have ensured that diagnostic X-rays remain the most used tool in diagnosis and hence make a major contribution to man's exposure to ionizing radiation from artificial sources6.
In recent years, health physicists have devoted much effort to the minimization of patients' doses in diagnostic radiology. Through these efforts, substantial reductions in radiation doses to patients resulting from radiographic procedures have been achieved in many countries. A useful background for such efforts is the knowledge of radiation doses to patients. This has led to surveys of patients' doses in diagnostic radiology in many countries. Many researchers who have carried out national and international surveys on appropriate radiation dose have reported wide variations in patient dose arising from specific X-ray examinations due to a combination of factors such as age of patient, type of ailment, position, organ or part of the body involved etc.6
A pelvis X-ray is a safe and painless test that uses a small amount of radiation to take a picture of the pelvic bones, which surround the hip area. During the examination, an X-ray machine sends a beam of radiation through the pelvis and an image is recorded on special film or a computer. This image shows the bones of the pelvis, which include the two hip bones, plus the sacrum and the coccyx (tailbone). The X-ray image is black and white. Dense body parts that block the passage of the X-ray beam through the body, such as bones, appear white on the X-ray image. Softer body tissues, such as muscles and fat, allow the X-ray beams to pass through them and appear darker.7
Radiological examination of the pelvis is a common investigation we see in the radiology department, in which a large portion of the trunk is irradiated. The tissues exposed to radiation contain many of the most sensitive organs.8The dangers associated with unsuitable dose in pelvic examinations using x-ray are diverse and pose numerous health problems to patients. For low levels of radiation, the biological effects are so small that they may not be detected in epidemiological studies, because the body repairs many types of radiation and chemical damage. But Biological effects of radiation on living tissue may result in a variety of outcomes, including: Cells experience DNA damage and are able to detect and repair the damage; Cells experience DNA damage and are unable to repair the damage. These cells may go through the process of programmed cell death, or apoptosis, thus eliminating the potential genetic damage from the larger tissue. Cells experience a nonlethal DNA mutation that is passed on to larger tissue. Cells experience a nonlethal DNA mutation that is passed onto subsequent cell divisions. This mutation may contribute to the formation of a cancer. Cells experience “Irreparable DNA Damage.” Low level ionizing radiation may induce “Irreparable DNA Damage” (leading to replication and transcriptional errors needed for neoplasia or may trigger viral interactions) leading to pre-mature aging and cancer.9