Real-time motion-adaptive delivery (MAD) using binary MLC: II. Rotational beam (tomotherapy) delivery

Abstract

TomoTherapy delivery is controlled by a planned, projection-wised leaf sequence (sinogram) that is optimized during treatment planning. In this paper, we developed a software solution for real-time motion compensation that delivers helical TomoTherapy plans without modifying the hardware and workflow of the TomoTherapy delivery system. Unlike the dynamic MLCbased method, our technique only requires instantaneous tumor positions, which greatly simplifies its implementation. This technique re-uses the planned sinogram by shuffling its projections and leaf sequences. In order to compensate for longitudinal tumor motion in real-time, instead of sequential execution of the planned sinogram, the projections are executed out of order. That is, we may choose a past or future projection of the planned sinogram rather than the current projection depending on tumor motion, so that the planned radiation source position of the chosen projection is the same as the radiation source position at the current delivery time in the tumor reference frame. The transverse tumor motion is further compensated for by shifting and scaling the leaf open time of the chosen projection. We tested different planned sinograms that were optimized using various synthetic tumor/OAR configurations, as well as planned sinogram of a lung cancer patient, all with zero motion margins. Various TomoTherapy machine parameters and both regular and irregular respiratory traces were used in calculations. By applying the motionadaptive delivery (MAD) technique, the delivered dose matched the planned dose very well in both DVH and dose profiles. As for the regular and minor irregular respiration, the dose errors were well below 3 mm and 3% criteria. No hot and cold spots were noticeable. For irregular respiration with some missing breathing cycles, this method demonstrates the capability for motion margin reduction.

Ensemble framework based real-time respiratory motion prediction for adaptive radiotherapy applications

“…(3 samples), 154ms (4 samples) and 308ms (8 samples). These lengths were selected considering the typical latencies of commercial robotic radiotherapy systems: ∼ 77ms in VERO systems [2], ∼ 115ms in CyberKnife [13], ∼ 170ms in Tomotherapy [38] and latencies up to several hundred milliseconds for typical couch or multi-leaf collimator (MLC) tracking devices [13,9]. A comparative analysis was then carried out among 1) no prediction, Figure 5.…”

Application of Extremely Thin ZrN Film as Diffusion Barrier between Cu and SiOC

“…Thus, although our study provides a simple and clear rule to translate longitudinal motion into dosimetric error, interrupting the treatment is still clearly not a desired option. Other investigators have proposed motion adaptive TomoTherapy that (Lu 2008, Zhang et al 2007, 2004 modifies beam modulation and shuffles the dose delivery sequence to compensate for the intrafractional motion, but these methods were designed for cyclic breathing motion and were not tested for non-cyclic random motion.…”

“…However, although the patients can be set up accurately initially, because of the prolonged treatment time in SBRT and its frameless nature, intrafractional motion can occur and affect the dose. The interplay between breathing motion and HT delivery was studied (Kissick et al 2005, 2008, Kanagaki et al 2007, and it was demonstrated that regular periodic motion in that direction only blurs the dose slightly and minimally affects the quality of treatment delivery (Kissick et al 2005, Kanagaki et al 2007. However, it was also shown that if the breathing motion is not completely regular but involves random baseline drifting, then undesired significant dose deviation can occur, and this is attributed to the similarity of time scales between the random baseline drifting and the time to deliver dose to a slice by HT (Kissick et al 2008).…”

Study on Motion Management of Helical Tomotherapy Specially Lung Cancer

“…Lung cancer has been the leading cancer diagnosed and cause of cancer death for many years in China, with a rapidly increasing trend during the past several decades [1,2] The incidence rate of lung cancer in China is relatively high, but is increasing at a more rapid rate than in Western countries. Many risk factors, such as cigarette smoking and air pollution, have been proven as risk factors of the disease [3][4][5][6].…”