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311Development of medical imaging and patient doses In Germany the x rays were discovered by Wilhelm Roentgen in 1895 and in 1905 he was awarded the Nobel Prize in recognition of his contributions to physics After this discovery the new x ray technology was rapidly applied in clinical medicine There is no published information documenting the starting use of ionizing radiation in diagnosis in Saudi Arabia but in 1950 it began to pay attention to safety health and established the first Public Health Department in Makah This was followed by establishing the first hospital of King Saud in Riyadh as early as 1956 1 Since 1896 the x ray in the United States was rapidly applied in clinical medicine and the number of radiologic examinations increased about tenfold between 1980 and 2006 2 The availability of x ray technology and the volume of medical imaging can vary extensively from country to country however in Saudi Arabia the growing of x ray technology was increased and potentially increase the radiation dose received by the patients and this has concerned physicians and radiation physicists as well as regulatory bodies such as the National Center for Radiation Protection SNCRP in King Abdul Aziz City for Science and Technology KACST
The relation between the growing of x ray technology and increasing the dose have also intensified the question of justification and knowledge of physicians about patient dose during radiological examinations To name a few the study in Swedish evaluated that 20 of all multi slice CT performed in Sweden may not be justified 3 On the other hand two studies estimating the awareness of physicians and they have revealed a lack of knowledge about the hazards of radiological examinations on their health and on their patients 4 5 Increasing the dose for patients with the growing of x ray technology prompted the International Commission on Radiological Protection ICRP in 1990 to mention using of diagnostic reference levels DRLs as benchmarks for radiation protection and optimization of patient imaging 6 performed in the local area country or region where they are applied DRLs should be set the median doses representing typical practice for a patient group for a specific type of examination In 1996 the ICRP defined two principles govern the professional use radiation sources optimization and justification of radiology examinations Optimization implies that the exposure of the individuals and of the population should preserve as low as reasonably achievable ALARA On the other hand Justification implies that every human activity involving patient exposure should be justified by the advantages that can give 7 1 2 Risk and Radiation biology Radiation that causes cancer depends on sex and age and its effect can be divided into deterministic and stochastic effects
Moreover Eisenberg et al 11 reported significant relation between radiation doses and risk of cancer to cardiac patients Rebecca et al 12 found a dose dependent association between radiation exposure from CT procedures and risk of cancer Looking at about 870 patients undergoing CT examinations Rebecca et al estimated 0 37 n 270 of women and 0 16 n 600 of men who went to coronary angiography CT at age 40 will develop cancer from that CT The research program of the Life Span Study LSS which investigating the lifelong health effects based on epidemiologic studies showed increased of cancer risk in the nuclear industry for the worker exposed to a lower mean dose of 20 mSv 13 The radiation dose for patient per imaging procedure can vary extensively from one hospital to another because of the difference in the equipment status protocol and image quality standards The average dose of radiation from Posteroanterior chest radiography skull radiography mammography pelvic radiography abdominal radiography lung perfusion scintigraphy 99mTc MMA CT brain Intravenous urography bone isotope scintigraphy 99mTc MDP CT chest CT abdomen and Barium enema are 0 02 0 1 0 4 0 6 0 7 2 2 3 6 3 7 8 8 mSv respectively 14 In 1990 the Committee on the Biological Effects of Ionizing Radiations BEIR 15 reported that the Radon is the largest source of radiation and the medical imaging is the second source of radiation and in 2009 an average American is exposed to about 5 6 mSv