In a modern editorial in Chest.

In a modern editorial in Chest,[1] DiMarco and Briones questioned whether thoracic CT is being overutilized. Despite acknowledging a part for CT in evaluating the mediastinum, nodules, interstitial lung disease, and bronchiectasis, these authors state that in their wisdom specific indications for the use of CT remain "vague" and the utility of CT in enhancing patient-care decisions is "unclear."

These observations ignore more than a decade's worth of research documenting the clinical value of thoracic CT[23] This research has clearly demonstrated CT to have a lively impact on diagnosis and patient management. Comput tomography has prov especially helpful when question s are identified but unresolved on plain films. Specific indications for the use of CT in this setting include evaluation of abnormal mediastinal contours, in particular to differentiate normal variants from pathologic entities, including the two benign and malignant disease; to further define and characterize solitary or focal parenchymal abnormalities, including the use of CT densitometry to determine the air of calcification within solitary pulmonary nodules, and to evaluate involved pleural and parenchymal pathology, especially to differentiate lung abscesses from an empyema.[4-6] More not long ago high-resolution CT has emerged as a revolutionary arrangement with well defined indications in the evaluation of diffuse infiltrative lung disease.[7]

Comput tomography has also been shown to be efficacious in evaluating patients suspected of having latent intrathoracic pathologic condition, such as thymoma in patients with myasthenia gravis. Additional general indications in this category include suspected metastatic disease, including abstruse mediastinal disease, as well as lymphangitic carcinoma, agitation of unknown origin, especially in the immunocompromised population, and unexplained symptoms like as dyspnea or hemoptysis.[8-10]

DiMarco and Briones[1] also raise questions concerning the risk of ionizing radiation. It is axiomatic that the indications for the use of ionizing radiation always ne to be weighed against the potential risks of exposure[1112] This determination, however, requires informed and responsible evaluation. in the greatest degree important, it is necessary to differentiate between the powers of radiation limited to a single part of the material part from the effects of whole-body radiation. unruffled if one accepts the estimates propos by way of Beir V (and these remain controversial), the data cited on DiMarco and Briones reflect the forces of whole-body radiation.[13,14] Radiation risk is considerably greater, by unit dose, for whole visible form [i]or[/i] frame exposure than when only a part of the visible form [i]or[/i] frame is exposed. Radiation risk in the chest is further reduc because there is little active marrow in the adult bony thorax, and lung tissue is relatively insensitive to radiation-induced carcinogenic transformation. Similarly, comparisons between the consequences of ionizing radiation and those resulting from radiation exposing to uranium, as suggested, are also misleading. Uranium is deposited directly into the lung has radiations other than photons, and localizes to small portions of the lung which are continuously radiated.

DiMarco and Briones'[1] suggestion that the dose for high-resolution CT may be equivalent to 500 chest radiographs is misguided.[15-17] This determination is based exclusively onward theoretical calculations extrapolated from a single phantom reflection based on the maximal dose a patient could theoretically receive.[16] What is the radiation dose resulting from routine clinical thoracic CT? The effective radiation dose of conventional CT of the chest, using 10-mm-thick sections performed at 10 mm intervals, is approximately 7 mSv[17] High-resolution CT consisting of 1-to 2-mm-thick sections performed at 10 mm intervals, has an effective radiation dose solitary 10 to 20 percent that of conventional CT[16] at comparison, the combined effective radiation dose of a posteroanterior (PA) and lateral chest radiograph is 015 mSv[1819] This means that the effective radiation dose of conventional CT is approximately equal to 50 PA and lateral radiographs, while a high-resolution CT cogitation is equivalent to only 5 to 10 PA and lateral radiographs (not 500!) More freshly it has been shown that the dose level of a standard 10-mm-thick CT cogitation can be reduced approximately tenfold through reducing the mAs without sacrificing lung parenchymal detail.[11] Placed in perspective, the effective radiation dose of high-resolution CT of the chest is les than 30 percent of the average annual effective dose that all individuals receive to be paid to natural radiation in North America.[13,19] Although more difficult to calculate, it also should be taken into account that CT many times obviates more traditional methods of diagnosis associated with ionizing radiation, including whole lung and 55 [degrees] oblique tomography, as well as fluoroscopy associated with angiography, bronchography, and calm bronchoscopy.

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