A novel method for interactive multi-objective dose-guided patient positioning

Abstract

In intensity-modulated radiation therapy (IMRT), 3D in-room imaging data is typically utilized for accurate patient alignment on the basis of anatomical landmarks. In the presence of non-rigid anatomical changes, it is often not obvious which patient position is most suitable. Thus, dose-guided patient alignment is an interesting approach to use available in-room imaging data for up-to-date dose calculation, aimed at finding the position that yields the optimal dose distribution. This contribution presents the first implementation of dose-guided patient alignment as multi-criteria optimization problem. User-defined clinical objectives are employed for setting up a multi-objective problem. Using pre-calculated dose distributions at a limited number of patient shifts and dose interpolation, a continuous space of Pareto-efficient patient shifts becomes accessible. Pareto sliders facilitate interactive browsing of the possible shifts with real-time dose display to the user. Dose interpolation accuracy is validated and the potential of multi-objective dose-guided positioning demonstrated for three head and neck (H&N) and three prostate cancer patients. Dose-guided positioning is compared to replanning for all cases. A delineated replanning CT served as surrogate for in-room imaging data. Dose interpolation accuracy was high. Using a [Formula: see text] dose difference criterion, a median pass-rate of 95.7% for H&N and 99.6% for prostate cases was determined in a comparison to exact dose calculations. For all patients, dose-guided positioning allowed to find a clinically preferable dose distribution compared to bony anatomy based alignment. For all H&N cases, mean dose to the spared parotid glands was below [Formula: see text] (up to [Formula: see text] with bony alignment) and clinical target volume (CTV) [Formula: see text] above 99.1% (compared to 95.1%). For all prostate patients, CTV [Formula: see text] was above 98.9% (compared to 88.5%) and [Formula: see text] to the rectum below [Formula: see text] (compared to 56.1%). Replanning yielded improved results for the H&N cases. For the prostate cases, differences to dose-guided positioning were minor.

Current state and future applications of radiological image guidance for particle therapy

“…An interesting alternative approach to re‐planning is dose‐guided positioning where treatment plan adaptation is emulated by optimizing the patient positioning to yield an optimal dose distribution in terms of target coverage and organ at risk sparing, potentially reducing the quality assurance workload associated with the creation of a new treatment plan. The necessary data for this procedure are the SPR distribution corresponding to the anatomy of the day as well an updated structure set.…”

On-line dose-guidance to account for inter-fractional motion during proton therapy

“…It took approximately three minutes to calculate 36 DGPT dose distributions; however with a modern processor a 1.5x speed-up could possibly be achieved. Pareto sliders are also a possibility, which have been implemented and investigated by Haehnle et al [20], who concluded that an optimised dose-guidance workflow can be performed in minutes.…”

“…The concept of dose-guided RT (DGRT) was proposed as an alternative to image-guidance based on reference anatomy by Cheung et al [19]. Haehnle et al later explored DGRT using pareto fronts for selection of the most beneficial isocenter positioning in treatment of prostate as well as head and neck cancer [20]. Cheung et al [21] further applied dose-guidance to PT (DGPT) exploring pre-calculated isocenter shifts to account for anatomical changes in lung cancer patients and found that dose-based isocenter adjustments of passive scattering proton fields was able to improve the dose distributions compared to IGPT.…”