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Linear.prc

PalmOS PDA Applications: Linear

A popular basis for brachytherapy QA are the Paterson-Parker implant tables. These tables were originally designed for radium implants according to the Manchester system (Meredith WJ, ed. Radium dosage. The Manchester System. Edinburgh: Livingston 1967). The data in the original tables gave the number of mg hours required to deliver an exposure of 1000 roentgens (mg-h/1000R). These data were based on a value of 0.84 for the exposure rate constant (Γ) for radium. It is common for the original tables to be modified to yield mg-h/10Gy by multiplying the original values by the factor C = 0.84 / (0.825 * 0.957) = 1.064 which corrects for the alteration of Γ for radium and converts exposure to dose to tissue. The tables can be adapted for HDR use by converting the original values to a more convenient form for Ir-192 (Γ = 0.469) HDR by multiplying the original values by C and then again by H = (0.001 * 3600) * (0.825 / 0.469) = 6.333 to yield mCi-sec/cGy. The HDR dwell time in seconds is calculated by multiplying the tabulated mCi-sec/cGy values by the prescribed dose (in cGy) and dividing by the current activity of the source (in mCi).

Click here to download the .zip archive: Linear 1.0.0 (20K), last updated 9/8/03.

Download: Linear.prc.zip (16K)
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The total HDR dwell time is displayed in the bezel at the top of the form. Input fields for prescribed dose (in cGy) and source activity (in mCi) are just below the bezel. The source activity is automatically decayed to the current date whenever you enter this form, but can be changed if necessary. The current date (9/7/03 in this example) and the source calibration date (9/1/03 in this case) are displayed to the left of these fields. Buttons for treatment distance "h" (0.5 to 3.0 cm) lie just below the activity field. A scrollable version of the modified Paterson-Parker linear source table occupies the bottom half of the form.

To use the program, simply tap any cell in the row of the table which corresponds to the active source length (L).

HDR source calibration data is maintained from the Physics form.

Other information about this program is found in the Options menu.



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