Review of ultrasound image guidance in external beam radiotherapy: I. Treatment planning and inter-fraction motion management

Abstract

In modern radiotherapy, verification of the treatment to ensure the target receives the prescribed dose and normal tissues are optimally spared has become essential. Several forms of image guidance are available for this purpose. The most commonly used forms of image guidance are based on kilovolt or megavolt x-ray imaging. Image guidance can also be performed with non-harmful ultrasound (US) waves. This increasingly used technique has the potential to offer both anatomical and functional information.This review presents an overview of the historical and current use of two-dimensional and three-dimensional US imaging for treatment verification in radiotherapy. The US technology and the implementation in the radiotherapy workflow are described. The use of US guidance in the treatment planning process is discussed. The role of US technology in inter-fraction motion monitoring and management is explained, and clinical studies of applications in areas such as the pelvis, abdomen and breast are reviewed. A companion review paper (O'Shea et al 2015 Phys. Med. Biol. submitted) will extensively discuss the use of US imaging for intra-fraction motion quantification and novel applications of US technology to RT.

Initial results for patient setup verification using transperineal ultrasound and cone beam CT in external beam radiation therapy of prostate cancer

“…CBCT based systems enable a reliable detection of interfractional target organ movements, however with the disadvantage of additional radiation exposure to the patient. Non-radiation based systems use ultrasound [4], optical surface detection [5], electromagnetic tracking [6] or MRI [7, 8]. Optical systems are suitable in situations where an external surface may act as a reliable surrogate for internal position or motion.…”

“…To date, no reports on transperineal US scanning for prostate localization are available. However, there is an ongoing controversial discussion on the precision of existing US systems [4]. …”

Evaluation of uterine ultrasound imaging in cervical radiotherapy; a comparison of autoscan and conventional probe

“…7 There is limited literature on gynaecological ultrasound scan, but many articles on prostate ultrasound scanning. Some studies have claimed that prostate displacement might occur owing to probe pressure, [8][9][10][11] while others have speculated that the impact on uterus displacement is less significant. 12 The conventional ultrasound (C-US) probe is a frequently used ultrasound IGRT system.…”

Temporal regularization of ultrasound-based liver motion estimation for image-guided radiation therapy

“…Imaging‐based respiratory motion compensation strategies generally use kilo‐voltage x‐rays and often assume correlation between external surrogates and internal motion 3 , 4 . Ultrasound has been explored for use in both inter‐ and intra‐fraction motion compensation strategies and its use in RT has recently been reviewed 5 . Benefits of ultrasound‐based image‐guided RT (IGRT) include (i) no ionizing radiation, 6 (ii) no implantation of fiducial markers, and (iii) potential for high volumetric imaging rate (∼kHz for matrix transducer technology 7 ).…”