Study of ExacTrac X‐ray 6D IGRT setup uncertainty for marker‐based prostate IMRT treatment

Abstract

Novalis Tx ExacTrac X‐ray system has the 6D adjustment ability for patient setup. Limited studies exist about the setup uncertainty with ExacTrac X‐ray system for IMRT prostate treatment with fiducial markers implanted. The purpose of this study is to investigate the marker‐based prostate IMRT treatment setup uncertainty using ExacTrac 6D IGRT ability for patient setup. Forty‐three patients with prostate cancers and markers implanted have been treated on the Novalis Tx machine. The ExacTrac X‐ray system has been used for the patient pretreatment setup and intratreatment verification. In total, the shifts data for 1261 fractions and 3504 correction times (the numbers of X‐ray images were taken from tube 1 and tube 2) have been analyzed. The setup uncertainty has been separated into uncertainties in 6D. Marker matching uncertainty was also analyzed. Correction frequency probability density function was plotted, and the radiation dose for imaging was calculated. The minimum, average, and maximum translation shifts were: −5.12±3.89 mm, 0.20±2.21 mm, and 6.07±4.44 mm, respectively, in the lateral direction; −6.80±3.21 mm, −1.09±2.21 mm, and 3.12±2.62 mm, respectively, in the longitudinal direction; and −7.33±3.46 mm, −0.93±2.70 mm, and 5.93±4.85 mm, respectively, in the vertical direction. The minimum, average, and maximum rotation shifts were: −1.23° ± 1.95°, −0.25° ± 1.30°, and −2.38° ± 2.91°, respectively, along lateral direction; −0.67° ± 0.91°, −0.10° ± 0.61°, and −1.51° ± 2.04°, respectively, along longitudinal direction; and −0.75° ± 1.01°, −0.02° ± 0.50°, and −0.82° ± 1.13°, respectively, along vertical direction. On average, each patient had three correction times during one fraction treatment. The radiation dose is about 3 mSv per fraction. With the ExacTrac 6D X‐ray system, the prostate IMRT treatment with marker implanted can achieve less than 2 mm setup uncertainty in translations, and less than 0.25° in rotations as overall interfraction mean error. The imaging dose is less than kV (CBCT) for setup verification.PACS number: 87.55.km, 87.55.Qr, 87.56.bd

Adaptive optimization by 6 DOF robotic couch in prostate volumetric IMRT treatment: rototranslational shift and dosimetric consequences

“…This is the first geometrical and dosimetric analysis on prostate VMAT treatment plan using Protura Robotic Patient Positioning System, reconstructing and not simulating prostate delivered dose through the real daily deviations. Our geometric results (translational shift $<5\text{mm}$ in 81% of patients and rotational shift $<2^{\circ }$ in 93% of cases) are comparable with those reported by other authors 14 , 15 , 33 with a larger translational SD or random errors, possibly related to patient's compliance or organ motion. Regarding rotational displacement, the mean systematic errors, ranging from 0.1° to 0.3°, and the random error, ranging from 0.7° and 1.1°, compare respectively with those reported by Guckenberger et al (14) and Van Herten et al (34) Also in our experience, no correlation was seen between the magnitude of the translational and rotational shift.…”

Simultaneous MV‐kV imaging for intrafractional motion management during volumetric‐modulated arc therapy delivery*

“…(5–14) For the most part, image-based intratreatment motion detection has been studied using MV or on-board (i.e., gantry-mounted) kilovoltage (kV) single-source systems (6,9,11) or external (i.e., room-mounted) dual-kV source systems. (5,13,14) Although kV systems provide high-quality images, current capabilities related to image acquisition frequency and directionality of the images can limit three-dimensional motion detection, either because the imaging system consists of a single kV source orthogonal to the MV beam direction (as is the case for accelerator on-board systems) or because the patient field of view may periodically be occluded by the accelerator itself (for external dual-source systems). Motion detection in two dimensions with gantry-mounted kV systems is often less than ideal since the detected motion in the transverse direction of the image is typically along the direction of the MV beam and, therefore, of limited dosimetric usefulness.…”

Fiducial marker guided prostate radiotherapy: a review

“…Using the ExacTrac® 6D IGRT system (Brainlab AG, Feldkirchen, Germany), Shi et al 60 In a series of 40 patients, Fuller et al 61 compared treatment setup errors derived from in-room TAUS imaging of the prostate with those from kV SC images of prostate FMs for radiotherapy verification. As in Barney et al, the purpose of this comparison study was not to establish which modality was superior, although treatment was corrected and treated according to SC FM position.…”