Software-controlled, highly automated intrafraction prostate motion correction with intrafraction stereographic targeting: System description and clinical results.

Purpose: A new system for software-controlled, highly automated correction of intrafraction prostate motion," intrafraction stereographic targeting" (iSGT), is described and evaluated.

Methods: At our institute, daily prostate positioning is routinely performed at the start of treatment beam using stereographic targeting (SGT). iSGT was implemented by extension of the SGT software to facilitate fast and accurate intrafraction motion corrections with minimal user interaction.

Day-to-day reproducibility of prostate intrafraction motion assessed by multiple kV and MV imaging of implanted markers during treatment.

Purpose: When one is performing online setup correction for prostate positioning displacements prior to daily dose delivery, intrafraction motion can become a limiting factor to prostate targeting accuracy. The aim of this study was to quantify and characterize prostate intrafraction motion assessed by multiple kilovoltage (kV) and megavoltage (MV) imaging of implanted markers during treatment in a large patient group.

Methods And Materials: Intrafraction motion in the sagittal plane was studied by retrospective analysis of displacements of implanted gold markers on (nearly) lateral kV and MV images obtained at various time points during the treatment fractions (mean, 27 per patient) in 108 consecutive patients.

A population-based model to describe geometrical uncertainties in radiotherapy: applied to prostate cases.

Local motions and deformations of organs between treatment fractions introduce geometrical uncertainties into radiotherapy. These uncertainties are generally taken into account in the treatment planning by enlarging the radiation target by a margin around the clinical target volume. However, a practical method to fully include these uncertainties is still lacking.

Margin evaluation in the presence of deformation, rotation, and translation in prostate and entire seminal vesicle irradiation with daily marker-based setup corrections.

Purpose: To develop a method for margin evaluation accounting for all measured displacements during treatment of prostate cancer.

Methods And Materials: For 21 patients treated with stereographic targeting marker-based online translation corrections, dose distributions with varying margins and gradients were created. Sets of possible cumulative delivered dose distributions were simulated by moving voxels and accumulating dose per voxel.

Deformation of prostate and seminal vesicles relative to intraprostatic fiducial markers.

Purpose: To quantify the residual geometric uncertainties after on-line corrections with intraprostatic fiducial markers, this study analyzed the deformation of the prostate and, in particular, the seminal vesicles relative to such markers.

Patients And Methods: A planning computed tomography (CT) scan and three repeat CT scans were obtained for 21 prostate cancer patients who had had three to four cylindrical gold markers placed. The prostate and whole seminal vesicles (clinical target volume [CTV]) were delineated on each scan at a slice thickness of 1.