Dose Delivery Accuracy of Therapeutic Photon and Electron Beams at Low Monitor Unit Settings

Abstract

The dose delivery accuracy at LMU settings has to be ascertained before implementing conformal and IMRT (intensity- modulated radiotherapy) techniques. When there is dose nonlinearity, the treatment delivered with multiple small MU settings can result in significant error in dose delivery.

Multisegmented Tangential Breast Fields: a Rational Way to Treat Breast Cancer

“…Planning time was ~10-20 min. To avoid delivery dose-MU fluctuations [28,31], all segments were > 2 MU and were treated after the open segments, during the 5-10 min of delivery.…”

Linearity of the Dose Monitor System at Low Monitor Units

“…The available results show drastic variations: whereas Hansen et al [11] report minor changes of the order of 1-2% of the relative dose at low MU, very recently Ravikumar et al [18] have measured relative doses which are increased by about 20-40% at low MU.…”

“…This problem has been noticed and a number of publications are available [1,2,4,5,10,11,13,17,18,20,22] which analyze the linearity of the dose monitor system of medical electron linear accelerators (linac) down to 1 MU which is the lowest MU setting which can be used at most linacs. The available results show drastic variations: whereas Hansen et al [11] report minor changes of the order of 1-2% of the relative dose at low MU, very recently Ravikumar et al [18] have measured relative doses which are increased by about 20-40% at low MU.…”

The Effect of a Carbon-Fiber Couch on the Depth-Dose Curves and Transmission Properties for Megavoltage Photon Beams

“…Treatment techniques like IMRT (intensity-modulated radiotherapy) have become more popular in modern radiotherapy [2,[15][16][17][18]22]. Carbon-fiber tabletops are an important tool for the delivery of these techniques [3,7,13].…”