Radiation exposure and computed tomography.

Computed Tomography (CT) is recognised as a relatively high-dose diagnostic procedure. There is some obscurity in the literature about the doses due t o conventional CT, spiral CT and High Resolution Computed Tomography (HRCT) of the chest. Conventional chest CT results in a radiation close approxima tely 100 rimes that of a standard chest film and 10 times that of a mammogr aphy; on the other hand conventional chest CT is safe for the lens and the pelvis ( ovaries, testes and uterus). Radiation dose associated with helica l CT is potentially lower than the dose associated with conventional CT. HR CT, consisting of 1- to 2- mm thick-sections performed at 10 mm intervals, has an effective radiation close lower than that of conventional CT, even w ith high-dose techniques (400 mAs). HRCT scans obtained at reduced milliamp erage (40-80 mAs) the so-called "low-dose HRCT technique", may provide sati sfactory visualization of lung parenchyma in the majority of cases and is r ecommended in patients in whom radiation dose is a major concern (pediatric population or young women in order to minimize breast irradiation). The aw areness of radiation dose will become increasingly important far both refer ring physicians and radiologists when determining indications and deciding which types of imaging procedures and specific protocols should be used.