Use of T₁ relaxation time in rotating frame (T₁ ρ) and apparent diffusion coefficient to estimate cerebral stroke evolution

Background: The major factor for the appropriate treatment strategies for ischemia patients is its onset timing.

Purpose/hypothesis: To study to evaluate the diagnostic accuracy of T₁ relaxation time in a rotating frame (T₁ ρ) and apparent diffusion coefficient (ADC) from MRI to estimate ischemia stages.

Study type: Prospective.

Population/subjects/phantom/specimen/animal model: In all, 73 patients (49 males, aged 29-78 years and 24 females, aged 22-94 years) with ischemia were prospectively imaged with T₁ ρ and diffusion MRI during the postischemic period.

Field strength/sequence: 3T/T₁ ρ and diffusion-weighted imaging (DWI).

Assessment: Ischemic parenchyma included tissue with elevated signal areas on DWI and correlative hypointense areas on ADC maps.

Statistical tests: The sensitivity of variables to ischemia time was quantified by analyzing the respective correlations of these values with onset time.

Results: ΔT₁ ρ (ipsilateral-contralateral differences in T₁ ρ) (R² = 0.956) and T₁ ρ_ipsi (ipsilateral ischemia T₁ ρ values) (R² = 0.941) were elevated in all ischemic lesions; these values increased linearly as a function of time, unlike ΔADC (ipsilateral-contralateral differences in ADC) (R² = -0.410) and ADC_ipsi (ipsilateral ischemia ADC values) (R² = 0.550). ΔT₁ ρ and T₁ ρ_ipsi were significantly different between all stages (P < 0.01), except the acute and hyperacute stages (P = 0.589 for ΔT₁ ρ, P = 0.290 for T₁ ρ_ipsi , respectively), but ΔADC and ADC_ipsi only between the late subacute and early subacute stages (P < 0.01) and the late subacute and chronic stages (P < 0.01).

Data conclusion: These data suggest that T₁ ρ can provide estimates for the ischemic time in patients. T₁ ρ has the potential to outperform diffusion for single-timepoint examination because the T₁ ρ change during strokes is positive and linear. If patients with suspected stroke are scanned by MRI within the appropriate timeframe, T₁ ρ may provide tools for evaluating stroke onset, potentially aiding in treatment strategies.

Level of evidence: 4 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1247-1254.