Background: In radiotherapy, various imaging modalities are utilized to delineate the tumor region and assess its size. However, it is crucial to acknowledge the current limitations inherent in these imaging techniques. These limitations include marker displacement, increased radiation exposure, and lack of volumetric data in X-ray imaging; failure to obtain information in CBCT due to patient movement during treatment; and severe distortions and inability to produce volumetric images in MRI. Consequently, the need for alternative methods or enhancements to current imaging techniques has become apparent. Ultrasound imaging devices offer real-time volumetric imaging with excellent contrast and no additional radiation exposure. However, they are prone to systematic errors due to probe pressure. This article will evaluate the performance of ultrasound imaging devices, including BAT, SonArray, and Clarity Autoscan, in the context of radiotherapy. Materials and Methods: Recently, inter-fractional and intra-fractional ultrasound imaging devices, as well as tissue tracking systems, have emerged as alternatives to traditional imaging modalities. The pioneering devices for inter-fractional imaging included BAT, SonArray, and Clarity, with BAT demonstrating improved positioning accuracy over CBCT. The Clarity device enables volumetric ultrasound imaging before or after a CT scan, providing superior patient positioning compared to BAT and SonArray. Clarity Autoscan was the first device to facilitate intra-fractional imaging, allowing sonographers to leave the treatment room while the probe remained in place, thereby enabling the commencement of radiotherapy. Robotic devices are also used for intra-fractional imaging, offering advantages over static imaging systems, though they remain in development. Tissue tracking devices encompass both ۲D and ۳D/۴D systems. While ۳D/۴D devices offer more comprehensive data, they are limited by lower frame rates and increased processing times. These systems are essential for real-time tracking of tissue movement, enhancing the accuracy and effectiveness of radiotherapy treatments. Conclusion: Ultrasound imaging demonstrates a positive impact on cancer treatment by decreasing side effects and enhancing the precision of radiation dose delivery. This technology significantly improves treatment planning and minimizes systematic errors through real-time imaging and precise tumor localization. Moreover, recent advancements in robotics and tissue tracking software have further bolstered the accuracy and efficiency of ultrasound, paving the way for future innovations in this field.
