Noninvasive inter- and intrafractional motion control in ultrahypofractionated radiation therapy of prostate cancer using RayPilot HypoCath™-a substitute for gold fiducial-based IGRT?

PURPOSE: In ultrahypofractionated radiation concepts, managing of intrafractional motion is mandatory because tighter margins are used and random errors resulting from prostate movement are not averaged out over a large number of fractions. Noninvasive live monitoring of prostate movement is a desirable asset for LINAC-based prostate stereotactic body radiation therapy (SBRT). METHODS: We prospectively analyzed a novel live tracking device (RayPilot HypoCath™; Micropos Medical AB, Gothenburg, Sweden) where a transmitter is noninvasively positioned in the prostatic urethra using a Foley catheter in 12 patients undergoing ultrahypofractionated intensity-modulated radiation therapy (IMRT) of the prostate. Gold fiducials (Innovative Technology Völp, Innsbruck, Austria) were implanted to allow comparison of accuracy and positional stability of the HypoCath system and its ability to be used as a standalone IGRT method. Spatial stability of the transponder was assessed by analyzing transmitter movement in relation to gold markers (GM) in superimposed kV image pairs. Inter- and intrafractional prostate movement and the impact of its correction were analyzed. RESULTS: A total of 64 fractions were analyzed. The average resulting deviation vector compared to the GM-based position was 1.2 mm and 0.7 mm for inter- and intrafractional motion, respectively. The mean intrafractional displacement vector of the prostate was 1.9 mm. Table readjustment due to exceeding the threshold of 3 mm was required in 18.8% of fractions. Repositioning reduced the time spent outside the 3­mm margin from 7.9% to 3.8% of beam-on time. However, for individual patients, the time spent outside the 3­mm margin was reduced from to 49% to 19%. CONCLUSION: the HypoCath system allows highly accurate and robust intrafractional motion monitoring. In conjunction with cone beam CT (CBCT) for initial patient setup, it could be used as a standalone image-guided radiation therapy (IGRT) system.

Noninvasive Tracking of Every Individual in Unmarked Mouse Groups Using Multi-Camera Fusion and Deep Learning.

Accurate and efficient methods for identifying and tracking each animal in a group are needed to study complex behaviors and social interactions. Traditional tracking methods (e.g., marking each animal with dye or surgically implanting microchips) can be invasive and may have an impact on the social behavior being measured. To overcome these shortcomings, video-based methods for tracking unmarked animals, such as fruit flies and zebrafish, have been developed. However, tracking individual mice in a group remains a challenging problem because of their flexible body and complicated interaction patterns. In this study, we report the development of a multi-object tracker for mice that uses the Faster region-based convolutional neural network (R-CNN) deep learning algorithm with geometric transformations in combination with multi-camera/multi-image fusion technology. The system successfully tracked every individual in groups of unmarked mice and was applied to investigate chasing behavior. The proposed system constitutes a step forward in the noninvasive tracking of individual mice engaged in social behavior.

Noninvasive Tracking of Alginate-Microencapsulated Cells.

This chapter presents a description of standardized techniques used routinely in our laboratory to encapsulate different cell types using the alginate-PLL-alginate immunoisolation system. Given the importance of noninvasive tracking of encapsulated cell transplants, we present a detailed guidance to achieve maximum efficiency and functionality of the capsule preparations for optimal tracking posttransplantation. The provided protocols cover tracking of encapsulated cells using magnetic resonance (MR), X-ray, computed tomography (CT), and ultrasound (US) imaging. Practical suggestions to optimize each method with specific references to recommended suppliers are included.