Motion adaptive x-ray therapy: a feasibility study

Abstract

Intrafraction motion caused by breathing requires increased treatment margins for chest and abdominal radiotherapy and may lead to 'motion artefacts' in dose distributions during intensity modulated radiotherapy (IMRT). Technologies such as gated radiotherapy may significantly increase the treatment time, while breath-hold techniques may be poorly tolerated by pulmonarily compromised patients. A solution that allows reduced margins and dose distribution artefacts, without compromising delivery time, is to synchronously follow the target motion by adapting the x-ray beam using a dynamic multileaf collimator (MLC), i.e. motion adaptive x-ray therapy, or MAX-T for short. Though the target is moving with time, in the MAX-T beam view the target is static. The MAX-T method superimposes the target motion due to respiration onto the beam originally planned for delivery. Thus during beam delivery the beam is dynamically changing position with respect to the isocentre using a dynamic MLC, the leaf positions of which are dependent upon the target position. Synchronization of the MLC motion and target motion occurs using respiration gated radiotherapy equipment. The concept and feasibility of MAX-T and the capability of the treatment machine to deliver such a treatment were investigated by performing measurements for uniform and IMRT fields using a mechanical sinusoidal oscillator to simulate target motion. Target dose measurements obtained using MAX-T for a moving target were found to be equivalent to those delivered to a static target by a static beam.

A Respiratory Motion Prediction Based on Time-Variant Seasonal Autoregressive Model for Real-Time Image-Guided Radiotherapy

“…Note that, the constant reference interval shown by (17) corresponds to that used in the general SARIMA equations of (7) and (8).…”

“…An ideal irradiation to the moving target is to continuously irradiate a sufficient dose to the tumor which can be achieved by controlling the radiation beam to chase the moving target [8]. Such real-time tumor following (or chasing) irradiation yields an ideal therapeutic effect and can shorten the treatment duration.…”

Real‐time 4D dose reconstruction for tracked dynamic MLC deliveries for lung SBRT

“…Tracking was proposed to manage intrafractional motion as an alternative to breath‐hold and gating techniques 7 . It does not affect patient comfort and has a minimal impact on treatment delivery time.…”

“…Both machines are intentionally designed for tumor tracking by either allowing for moving the whole beam using a robotic arm or panning and tilting the beam utilizing gimbals. Alternatively, multileaf collimator (MLC) tracking was proposed as a tracking solution for conventional linacs 7 , 12 . The currently established method is centroid tracking, which aims at dynamically reshaping the treatment field in the beam's‐eye‐view according to the actual recorded target motion.…”

Development and performance evaluation of a high‐speed multileaf collimator

“…Among them, MLC tracking is realized through dynamically adapting the aperture to the moving target, which does not rely on margin enlargement or beam hold‐offs (unless large position error occurs) in contrast to the first two. Previous studies have applied MLC tracking to dealing with different forms of target motion: one‐dimensional (1D) translation,3, 4, 5, 6 two‐dimensional (2D) translation,7, 8, 9 three‐dimensional (3D) translation,10 rotational motion11 and deformation 12…”