MRI-guided lung SBRT: Present and future developments

Abstract

Stereotactic body radiotherapy (SBRT) is rapidly becoming an alternative to surgery for the treatment of early-stage non-small cell lung cancer patients. Lung SBRT is administered in a hypo-fractionated, conformal manner, delivering high doses to the target. To avoid normal-tissue toxicity, it is crucial to limit the exposure of nearby healthy organs-at-risk (OAR). Current image-guided radiotherapy strategies for lung SBRT are mostly based on X-ray imaging modalities. Although still in its infancy, magnetic resonance imaging (MRI) guidance for lung SBRT is not exposure-limited and MRI promises to improve crucial soft-tissue contrast. Looking beyond anatomical imaging, functional MRI is expected to inform treatment decisions and adaptations in the future. This review summarises and discusses how MRI could be advantageous to the different links of the radiotherapy treatment chain for lung SBRT: diagnosis and staging, tumour and OAR delineation, treatment planning, and inter-or intrafractional motion management. Special emphasis is placed on a new generation of hybrid MRI treatment devices and their potential for real-time adaptive radiotherapy.

First online real‐time evaluation of motion‐induced 4D dose errors during radiotherapy delivery

“…While not utilized here, extension to nonisocentric and noncoplanar treatments, including 4 π treatments, would be straightforward by inclusion of additional time‐resolved variables, that is, couch translation and rotation and collimator rotations. Furthermore, the current motion‐including dose reconstruction can easily, and without further computational cost, be extended from translational shifts to rotations and deformations when such information is available during treatment, for example, by MR imaging or 6 degree‐of‐freedom motion monitoring by KIM or COSMIK . It is important to stress that DoseTracker works equally well for tracking and conventional nontracking treatments.…”

“…This study helps in bringing independent plan QA into the real-time era by exploiting the growing possibilities of real-time motion monitoring [3][4][5][6][7][8][9]28,[31][32][33] to follow the dose as it gradually builds up during the treatment delivery. The real-time dose reconstruction by DoseTracker provides a seamless form of QA similar to the time-consuming QA presently being used for tumor tracking in the clinic 20 and could help pave the way for broader clinical use of tumor tracking.…”

CAMPEP graduate program standards should require a dedicated course in Magnetic Resonance Imaging physics

“…Recent advances in MRI for radiation therapy applications have triggered a burst of research developments and discussions on the related topics,1, 4, 5, 6, 7 sending a strong signal that MRI physics may require more in‐depth training in order to prepare medical physicists for the upcoming challenges. While I generally agree that MR physics education should be enhanced, I do not believe that it should be achieved by requiring CAMPEP graduate program standards to have dedicated courses in MR physics.…”

“…However, the clinical popularity of MRI‐guided radiation therapy is unclear and debatable. Many questions have been raised regarding the added value of MRI‐guided radiation therapy over current IGRT, for example, what are the relative merits of tumor tracking using cine MRI in different clinical situations vs simple breath‐hold?4 Ultimately, the additional financial burden of an add‐on MRI for radiotherapy has to be justified by proving whether these conceptual advantages can translate to any measurable increase in patient survival or reduction in treatment toxicities 5…”

Real‐time 4DMRI‐based internal target volume definition for moving lung tumors

“…1 This motion can be substantial, is patient-specific, difficult to predict, can be irregular and change from one day to another. [2][3][4][5][6][7][8] Intrafractional motion, defined as any motion induced by physiological processes occurring within a treatment session such as breathing, and interfractional changes occurring between treatment sessions need to be accounted for in the planning and delivery process. 9 To address intrafractional changes, passive and active motion management techniques have been developed over the last decades.…”