The Production of Isodose Curves and the Calculation of Energy Absorption from Standard Depth Dose Data

Determination of Integral Absorbed Dose from Exposure Measurements

“…MEREDITH and NEARY (1944) have proposed a method of constructing isodose curves which makes it possible to extrapolate depth doses to infinite field areas. The method has only been applied for radiation qualities used in conventional roentgen therapy, and data are lacking for its application with radiation qualities common in diagnostic radiology.…”

The Effect of Source Size upon Integral Dose in Teletherapy Units

“…For a given set of conditions the following procedure may be adopted. Using published data on depth doses and backscatter the integral dose per 100 r on the skin is calculated by the method of MERE-DITH and NEARY (9) for the roentgen set and the teletherapy unit assuming point sources in both cases. These are then converted to integral doses per 100 r at the tumor, and the value for the roentgen set is multiplied by the appropriate value of R. One can then obtain a value of R for the teletherapy unit that will give the same integral dose as the roentgen set, and hence obtain a permissible value of source radius, s,.…”

“…The actual values of the parameters were: s = a = 2.5 cm, f = 2d = 16 cm, and z = 7.5 cm in a phantom of total depth 15 cm. The contribution to the integral dose due to scattered radiation was calculated by the method of MEREDITH and NEARY (9), and the absorption of the primary beam allowed for using an absorption coefficient of 0 . 1 0 6 cm-1.…”

Calculation of Tissue Doses and Data for the Production of Isodose Charts, Using Standard Depth-Dose Tables

“…It was thought that another function might better represent the data, but though a number were tried, none proved to be as satisfactory as that originally used. For fuller details concerning this, the reader is referred to the original paper of Meredith and Neary (6). The developments to be set forth here are based on their function, and on the depthdose data in Physical Foundations of Radiology, except for the values of the primary radiation.…”

“…This is not entirely satisfactory, since it is seldom possible to obtain curves for all field shapes and radiation qualities desired, and adaptation is rather hazardous. On the other hand, the calculation of such data from available central-axis depth-dose tables is practicable, and several methods have been developed for the procedure (1,4,(6)(7)(8)(9)(10). None of these has been widely employed in the United States, either because of lack of familiarity with them, or because the work involved seemed too great.…”