Towards real-time VMAT verification using a prototype, high-speed CMOS active pixel sensor

Abstract

This work investigates the feasibility of using a prototype complementary metal oxide semiconductor active pixel sensor (CMOS APS) for real-time verification of volumetric modulated arc therapy (VMAT) treatment. The prototype CMOS APS used region of interest read out on the chip to allow fast imaging of up to 403.6 frames per second (f/s). The sensor was made larger (5.4 cm × 5.4 cm) using recent advances in photolithographic technique but retains fast imaging speed with the sensor's regional read out. There is a paradigm shift in radiotherapy treatment verification with the advent of advanced treatment techniques such as VMAT. This work has demonstrated that the APS can track multi leaf collimator (MLC) leaves moving at 18 mm s(-1) with an automatic edge tracking algorithm at accuracy better than 1.0 mm even at the fastest imaging speed. Evaluation of the measured fluence distribution for an example VMAT delivery sampled at 50.4 f/s was shown to agree well with the planned fluence distribution, with an average gamma pass rate of 96% at 3%/3 mm. The MLC leaves motion and linac pulse rate variation delivered throughout the VMAT treatment can also be measured. The results demonstrate the potential of CMOS APS technology as a real-time radiotherapy dosimeter for delivery of complex treatments such as VMAT.

An independent system for real-time dynamic multileaf collimation trajectory verification using EPID

“…Zin et al investigated the use of a prototype complementary metal oxide semiconductor active pixel sensor (CMOS APS) as a real-time verification tool. The acquisition rate of this device is approximately 21 fps, which was shown to increase the accuracy of the DMLC detection (Zin et al 2013). However, the CMOS APS EPID is still in the prototype stage, and is not used clinically.…”

Fiducial marker and marker‐less soft‐tissue detection using fast MV fluoroscopy on a new generation EPID: Investigating the influence of pulsing artifacts and artifact suppression techniques

“…Based on testing of VMAT verification with a highspeed CMOS active pixel sensor (400 Hz), it was found that a synchronization with beam pulses was required for accurate dose rate verification. 33 Furthermore, combined W-FFT filtering was resulting in an additional computation time with respect to a synchronized MV readout. Such an additional delay could be disadvantageous for real-time applications of soft-tissue or marker detection on MV images acquired during treatment.…”

Upstream Dosimetry using a Monolithic Active Pixel Sensor (MAPS)

“…To minimise this further a Monolithic Active Pixel Sensor (MAPS) was used to build a prototype, this was based on the initial work described here [8], which also resulted in intellectual property being generated [9]. The trend in treatments to be more dynamic also motivates MAPS technology, with good S/N and fast frame rates making real-time monitoring and verification a very real possibility [10] [11].…”