Clinical Implications of Virtual versus Anatomical Isocenter Selection in Intensity- Modulated Radiotherapy Treatment Planning
Year: 2026
Type: article
Abstract: A BSTRACT Purpose: Iso-center placement is a key determinant of dosimetric accuracy and workflow efficiency in intensity-modulated radiotherapy (IMRT). While the anatomical iso-center (AIP) is conventionally used, high-volume centers increasingly consider the virtual iso-center (VIP) defined during CT simulation to streamline patient setup. This study evaluates the dosimetric impact and workflow benefits of VIP relative to AIP in IMRT planning. Materials and Methods: A retrospective planning analysis was performed for 40 IMRT patients. For each case, two plans were generated: one centered on the AIP and the other on the VIP. Dosimetric indices, including conformity index (CI), homogeneity index (HI), target coverage, organ-at-risk (OAR) doses, monitor units (MUs), and iso-center displacement were compared. Workflow efficiency was assessed by estimating setup time saved through omission of couch shifts. Results: VIP-based plans demonstrated a statistically significant increase in MUs (mean + 4.4%, P < 0.001), strongly correlated with iso-center displacement ( r = 0.82). CI, HI, and OAR doses showed no significant differences between AIP and VIP plans ( P > 0.15). The VIP approach eliminated couch shifts, reducing average setup time by approximately 4.2 min per patient, translating into the potential to treat 5–6 additional patients per month. Larger displacements (>6 cm) were associated with greater MU penalties. Conclusions: VIP planning enhances workflow efficiency without compromising target coverage or OAR sparing. However, the consistent MU increase, particularly with large displacements, supports selective use and vigilant quality assurance.
Institution: Sher-i-Kashmir Institute of Medical Sciences
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W7160128663