Treatment precision of image-guided liver SBRT using implanted fiducial markers depends on marker–tumour distance

Abstract

The purpose of this study is to assess the accuracy of day-to-day predictions of liver tumour position using implanted gold markers as surrogates and to compare the method with alternative set-up strategies, i.e. no correction, vertebrae and 3D diaphragm-based set-up. Twenty patients undergoing stereotactic body radiation therapy (SBRT) with abdominal compression for primary or metastatic liver cancer were analysed. We determined the day-to-day correlation between gold marker and tumour positions in contrast-enhanced CT scans acquired at treatment preparation and before each treatment session. The influence of marker-tumour distance on the accuracy of prediction was estimated by introducing a method extension of the set-up error paradigm. The distance between gold markers and the centre of the tumour varied between 5 and 96 mm. Marker-guidance was superior to guiding treatment using other surrogates, although both the random and systematic components of the prediction error SD depended on the tumour-marker distance. For a marker-tumour distance of 4 cm, we observed σ = 1.3 mm and Σ = 1.6 mm. The 3D position of the diaphragm dome was the second best predictor. In conclusion, the tumour position can be predicted accurately using implanted markers, but marker-guided set-up accuracy decreases with increasing distance between implanted markers and the tumour.

Evaluation of reproducibility of tumor repositioning during multiple breathing cycles for liver stereotactic body radiotherapy treatment

“…Many studies on liver motion characterization using markers have been published. 12,16,19 Seppenwoolde et al showed that the tumor position can be accurately predicted using implanted markers considering that there is a real influence of the marker-tumor distance on the set-up accuracy. They also showed that the diaphragm dome was the second best predictor of tumor motion and that it could be used as a surrogate for tumor located close to it.…”

“…They also showed that the diaphragm dome was the second best predictor of tumor motion and that it could be used as a surrogate for tumor located close to it. 19 Park et al studied the liver motion characteristics based on fiducial markers tracked with the X-rays projections of the CBCT scans. Their results showed large variations in liver motion and their conclusion was similar to those of Seppenwoolde et al, mainly that the distance between the markers and the tumor was a major element to track.…”

Evaluation of the intra‐ and interfractional tumor motion and variability by fiducial‐based real‐time tracking in liver stereotactic body radiation therapy

“…All patients were implanted with 2–4 fiducials near the tumor under CT guidance 11. Simulation was typically administered 7–10 days after the implantation, which can minimize the risk of marker migration.…”

Institutional experience in the treatment of colorectal liver metastases with stereotactic body radiation therapy

“…Initially the motion was measured with video fluoroscopy registrations and later on with a reconstruction of 4DCT registrations. 14,15 No margin between gross target volume and clinical target volume was used. Planning target volume (PTV) margins were initially based on the Karolinska experience.…”

“…tracking or non-tracking), the amplitude of the respiratory-induced motion, and the distance between the center-off-mass of the marker configuration and the center of the tumor. 15 For conventional linac based treatments the personalized margins that were applied clinically ranged between 8-10 mm superior-inferior, and 5-7 mm left-right and anterior-posterior. For CyberKnife treatments the personalized margins ranged between 5 and 7 mm in all directions.…”