Application of tissue-air ratios for patient dosage in diagnostic radiology

A method for calculating organ dose form radiographic procedures which utilizes the concept of tissue-air ratio (TAR) is described. TAR's were measured for 70-120 kVp x-rays filtered by a total of 2.5 and 3.5 mm Al under conditions which simulate those in radiography. The output of the x-ray tube tube, in terms of mR/mAs at 40 inches (101.6 cm) was also measured, and these are compared with previously published data. A step-by-step procedure for calculating organ dose is described and an example given to illustrate the magnitude of the dose delivered by a typical radiographic procedure.