Irradiation-induced modulation of T₂ relaxation times in sucrose solutions: a novel externally controlled design strategy for quantitative magnetic resonance imaging phantoms

This study investigated whether irradiation-induced chemical changes in sucrose solutions could be utilized to control magnetic resonance imaging (MRI) relaxation properties and to propose a novel design strategy for quantitative MRI phantoms. Aqueous sucrose solutions at concentrations of 5–40% (w/w) containing 3.6 g/L NaCl were irradiated with 6 MV photons at doses of 0–20,000 monitor units. T₁ and T₂ relaxation times were measured at 1.5 T. Hydrogen peroxide (H₂O₂) and glucose concentrations were quantified to assess the radiolytic products. Linear regression and Type III ANOVA were used to evaluate the effects of sucrose concentration and irradiation dose. The T₂ relaxation times increased with increasing irradiation dose (p < 0.001), with a significant interaction between sucrose concentration and dose (p < 0.001). The slope of T₂ monotonically decreased with increasing sucrose concentration. R₂ (defined as 1/T₂) showed a significant linear dose-dependence at all concentrations, with the absolute magnitude of the negative regression coefficients increasing at higher sucrose concentrations, which was consistent with the reciprocal relationship between T₂ and R₂. In contrast, both T₁ and R₁ (defined as 1/T₁) exhibited minimal dose-dependence. The H₂O₂ concentration increased stepwise with the dose and demonstrated a strong positive correlation with T₂ (Spearman’s ρ = 1.00), whereas glucose showed no consistent dose-dependence. Irradiation enabled concentration-dependent modulation of T₂ relaxation in sucrose solutions without altering the initial composition. This externally controllable approach provides a simple and flexible framework for designing quantitative MRI phantoms with tunable relaxation properties and offers a new paradigm beyond conventional composition-based phantom fabrication.