Page 14 - ARNM-3-3

Advances in Radiotherapy
& Nuclear Medicine Review of image-guided adaptive radiotherapy

Figure 3. Workflow of the three-mode ART approach
Abbreviations: ART: Adaptive radiotherapy; CBCT: Cone-beam computed tomography; CT: Computed tomography; MRI: Magnetic resonance imaging;
OAR: Organ at risk.

Table 1. Three distinct image guidance techniques in ART
Characteristics CBCT CT MRI
Platform system Varian Medical Systems (Palo Alto, California, CT on rails Elekta Unity 1.5 T MRI: 7 MV FFF LINAC
®
USA) Ethos 6MV FFF uRT-506c ViewRay MRIdian (legacy system): 6MV FFF
0.35 T MRI
Working mode Choose between the adaptive plan and the Choose between the adaptive plan UNITY: adapt to position and adapt to shape
radiotherapy plan and the radiotherapy plan MRIdian: Choose between the adaptive plan
and the radiotherapy plan
Advantage • Fast scanning speed, HyperSight™ • Fast scanning speed • High soft tissue resolution
• High‑throughput scan • High‑throughput scan • Radiation‑free, providing image support for
• Easier to operate • High image quality real-time ART
• Develop treatment plans directly in the • Functional imaging and metabolic imaging
HyperSight
Disadvantage • Limited soft‑tissue contrast • Long scanning time • Expensive
• Additional radiation • Additional radiation • The scanning time is long, and the output flux
• No functional imaging • No functional imaging of the scanned image is low
• Electronic density information is required for
planning: MRIdian: DIR; UNITY: Electron
density
• Metals are incompatible
Clinical application • Pelvic cavity • Abdominal cavity • Abdominal cavity
• Head and neck • Pelvic cavity • Pelvic cavity
• Breast • Head and neck
• Lung • Breast
• Lung
Abbreviations: ART: Adaptive radiotherapy; CBCT: Cone-beam computed tomography; CT: Computed tomography; DIR: Deformable image
registration; MRI: Magnetic resonance imaging.

®
no or only minor modifications. Similarly, for patients demonstrated that following treatment using the Ethos
undergoing radical RT for cervical cancer, a similarly high platform, there was a 2.9% ± 5.3% increase in the dose
level of accuracy was achieved, in which 92.1% (387/420) received by 98% of the CTV (D98%), while the bladder
of anatomical structure contours and 91.4% (384/420) of and rectum experienced respective decreases of 13.1%
CTV contours were accurately delineated. ± 1.0% and 6.5% ± 7.3% in volume receiving 90% of the

®
Moreover, the Ethos platform exhibited exceptional dose (V90%). These findings indicate that the contours
®
performance in online ART for prostate cancer. It was automatically generated by the Ethos ART consistently
44
Volume 3 Issue 3 (2025) 6 doi: 10.36922/ARNM025110012