IMRT optimization including random and systematic geometric errors based on the expectation of TCP and NTCP.

The purpose of this work was the development of a probabilistic planning method with biological cost functions that does not require the definition of margins. Geometrical uncertainties were integrated in tumor control probability (TCP) and normal tissue complication probability (NTCP) objective functions for inverse planning. For efficiency reasons random errors were included by blurring the dose distribution and systematic errors by shifting structures with respect to the dose.

Impact of geometrical uncertainties on 3D CRT and IMRT dose distributions for lung cancer treatment.

Purpose: To quantify the effect of set-up errors and respiratory motion on dose distributions for non-small cell lung cancer (NSCLC) treatment.

Methods And Materials: Irradiations of 5 NSCLC patients were planned with 3 techniques, two (conformal radiation therapy (CRT) and intensity modulated radiation therapy (IMRT1)) with a homogeneous dose in the planning target volume (PTV) and a third (IMRT2) with dose heterogeneity. Set-up errors were simulated for gross target volume (GTV) and organs at risk (OARs).

The sensitivity of dose distributions for organ motion and set-up uncertainties in prostate IMRT.

Background And Purpose: To determine the effect of organ motion and set-up uncertainties on IMRT dose distributions for prostate.

Methods: For five patients, IMRT techniques were designed to irradiate the CTV (prostate plus seminal vesicles). Technique I delivered 78 Gy to PTV1 (CTV+10 mm margin).

The effects of target size and tissue density on the minimum margin required for random errors.

The minimum margins required to compensate for random geometric uncertainties in the delivery of radiotherapy treatment were determined for a spherical Clinical Target Volume, using an analytic model for the cumulative dose. Margins were calculated such that the minimum dose in the target would be no less than 95% of the prescribed dose for 90% of the patients. The dose distribution model incorporated two Gaussians, and could accurately represent realistic dose profiles for various target sizes in lung and water.

Biologic and physical fractionation effects of random geometric errors.

Purpose: We are developing a system to model the effect of random and systematic geometric errors on radiotherapy delivery. The purpose of this study was to investigate biologic and physical fractionation effects of random geometric errors and respiration motion and compare the resulting dose distributions with Gaussian blurring of the planned dose.

Materials And Methods: A hypothetical dose distribution with Gaussian penumbra was used.