Combined spin- and gradient-echo perfusion-weighted imaging.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Neuroimaging
• Medical Physics

Background:

• Dynamic susceptibility-contrast (DSC) MRI is crucial for assessing brain perfusion.
• Traditional DSC techniques often rely on relative signal changes, limiting quantitative accuracy.
• Spin-echo (SE) and gradient-echo (GE) EPI sequences offer complementary information but are typically acquired separately.

Purpose of the Study:

• To introduce and validate a novel MRI pulse sequence, SAGE EPI, for simultaneous DSC perfusion and vessel size imaging.
• To demonstrate the T(1)-independent nature of SAGE EPI by using absolute R2* and R(2) estimates.
• To evaluate the performance of SAGE EPI in preclinical stroke and tumor models.

Main Methods:

• Development of a SAGE EPI pulse sequence acquiring five readout trains with echo times < 100 ms.
• Quantification of contrast agent concentration using absolute R2* and R(2) values.
• Simultaneous estimation of R2* and R(2) for vessel size imaging.
• Application of SAGE EPI in imaging studies of stroke and tumor models.

Main Results:

• SAGE EPI successfully acquired simultaneous gradient-echo and spin-echo DSC perfusion data.
• The method provided T(1)-independent perfusion quantification.
• Vessel size imaging was achieved without extending acquisition time.
• Demonstrated utility in stroke and tumor imaging scenarios.

Conclusions:

• SAGE EPI offers a powerful, time-efficient approach for advanced brain perfusion and microvasculature assessment.
• This technique combines the sensitivity of GE-DSC with the microvascular selectivity of SE-DSC.
• SAGE EPI holds significant potential for improved diagnosis and monitoring of cerebrovascular diseases and brain tumors.