Adaptive planning strategy for high dose rate prostate brachytherapy—a simulation study on needle positioning errors

Abstract

The development of magnetic resonance (MR) guided high dose rate (HDR) brachytherapy for prostate cancer has gained increasing interest for delivering a high tumor dose safely in a single fraction. To support needle placement in the limited workspace inside the closed-bore MRI, a single-needle MR-compatible robot is currently under development at the University Medical Center Utrecht (UMCU). This robotic device taps the needle in a divergent way from a single rotation point into the prostate. With this setup, it is warranted to deliver the irradiation dose by successive insertions of the needle. Although robot-assisted needle placement is expected to be more accurate than manual template-guided insertion, needle positioning errors may occur and are likely to modify the pre-planned dose distribution.In this paper, we propose a dose plan adaptation strategy for HDR prostate brachytherapy with feedback on the needle position: a dose plan is made at the beginning of the interventional procedure and updated after each needle insertion in order to compensate for possible needle positioning errors. The introduced procedure can be used with the single needle MR-compatible robot developed at the UMCU. The proposed feedback strategy was tested by simulating complete HDR procedures with and without feedback on eight patients with different numbers of needle insertions (varying from 4 to 12). In of the cases tested, the number of clinically acceptable plans obtained at the end of the procedure was larger with feedback compared to the situation without feedback. Furthermore, the computation time of the feedback between each insertion was below 100 s which makes it eligible for intra-operative use.

Development of patient and catheter specific error thresholds for high dose rate prostate brachytherapy

“…The potential for real-time adaptation involves constantly optimizing the dose distribution after each catheter is either inserted (pre-treatment adaptation) or retrospectively delivered, by accounting for the new source positions measured by an IVST or IVD system (realtime in-vivo adaptive HDRPBT). 31,32 Although Borot de Battisti et al 32 showed an increase in clinically acceptable plans after adaptation during the catheter insertion phase of treatment, real-time in-vivo adaptive HDRPBT introduced by Koprivec et al 31 showed there was only a benefit for prostate coverage recovery, but was unable to account for excess dose delivered to OARs during the delivery phase of treatment. Therefore, there also needs to be a solution for when to interrupt treatment if errors occur between the catheter insertion phase and delivery phases of treatment.…”

“…A recent study identified a potential method for amending/adapting the treatment in real‐time. The potential for real‐time adaptation involves constantly optimizing the dose distribution after each catheter is either inserted (pre‐treatment adaptation) or retrospectively delivered, by accounting for the new source positions measured by an IVST or IVD system (real‐time in‐vivo adaptive HDRPBT) 31,32 . Although Borot de Battisti et al 32 .…”

“…The potential for real‐time adaptation involves constantly optimizing the dose distribution after each catheter is either inserted (pre‐treatment adaptation) or retrospectively delivered, by accounting for the new source positions measured by an IVST or IVD system (real‐time in‐vivo adaptive HDRPBT) 31,32 . Although Borot de Battisti et al 32 . showed an increase in clinically acceptable plans after adaptation during the catheter insertion phase of treatment, real‐time in‐vivo adaptive HDRPBT introduced by Koprivec et al 31 .…”

Fiber Bragg gratings‐based sensing for real‐time needle tracking during MR‐guided brachytherapy

“…Those events can lead to uncertainties and errors in the delivered dose to the planning target volume (PTV) and organs at risk (OARs). 11 To reduce those uncertainties, two methods are possible: (1) restraining at maximum the needle positioning errors and (2) dynamically updating the dose plan with feedback on the actual catheter locations as shown by Borot de Battisti et al 12 For that, the real-time determination of the needle position (consisting of tracking the needle during insertion and reconstructing the needle after insertion) is warranted.…”