Impact of Different Independent Dose Verification Software Programs for Secondary Check

A multi-institutional study was performed to identify the impact of different independent dose verification programs on independent dose verification software program.

Data for 1,543 treatment fields were collected in three institutions. RADCALC and Simple MU Analysis (Simple MU) using the Clarkson-based algorithm were used. RADCALC needs the input of radiological path length (RPL) from radiotherapy treatment planning systems (RTPSs) (Eclipse or Pinnacle³). The Simple MU computes the RPL using CT images independently from the RTPSs. Ion-chamber measurements were performed for commissioning the two programs and the RTPSs. Next, the results of the two programs were compared to the RTPSs obtained in the clinically-approved plans in all three institutions.

The commissioning results showed ±1.5% variation in the ion-chamber measurements and there was slight difference between the institutions. The RADCALC (0.9±2.2%) and the Simple MU (1.7±2.1%) results showed a slight systematic difference. Pinnacle³ computed longer RPLs because it used CT-physical density tables. Thus, there was an impact on the accuracy in the treatment plans involving bone and other high-density materials.

Dose calculation algorithms in different dose verification programs provided similar results. However, care must be taken because different RPL calculation methods in the RTPSs may affect dose difference between different independent dose verification programs by 1%.