Fig 1.
Frequency analysis of a bSSFP.
A 50° flip angle indicating a perfusion related peak in the vessel (a) and in the parenchyma (b) ROI at the heart frequency close to 1 Hz (red triangles).
Table 1.
SNR and perfusion contrast of the bSSFP (a) and the FLASH (b) sequences.
Varying slice thickness and flip angle in grey matter and white matter ROIs in a 30-year-old healthy volunteer at 1.5T and 3T. Regional correlation and spatial Dice overlap towards pCASL-MRI in 25 healthy individuals (c).
Fig 2.
Perfusion-weighted FREE maps of a healthy 30-year-old male participant with 50° (a) and 70° (b) flip angle, 15 mm slice thickness, 128 x 128 matrix size interpolated to 256 x 256, 250 x 250 mm FOV, 321 ms acquisition time for 1 image, 1 ms TE at 1.5T. The grey matter and white matter ROIs in the morphology map (c) (green and red boxes) showed a SNR of 167.80 and 138.02 and a perfusion contrast of 3.27 and 1.74 at 50° flip angle and a SNR of 160.27 and 130.83 and a perfusion contrast of 3.70 and 1.76 at 70° flip angle.
Fig 3.
Dice overlap of pCASL and FREE MRI.
Images of a 31-year-old healthy male proband. pCASL and FREE images are transformed into binary maps using the 40th percentile of its perfusion values as a threshold before calculating the grey and white matter overlap.
Fig 4.
T1 post-contrast and perfusion-weighted images with the resulting Dice maps of three male patients with brain metastases of a malignant melanoma (a and b) and a pulmonary adenocarcinoma (c). Notice the differing perfusion contrast after radiation of the right frontal lobe in (b).
Fig 5.
CT and MRI images of a 78-year-old male patient with an acute M1 infarct of his left hemisphere. MRI was performed due to the unknown time window, while another emergency patient was treated. Afterwards this patient had thrombectomy, but showed a demarcated infarction as already visible on the previous CT and MRI. The demarcation is already visible on the native CT (a) and MRI fluid attenuated inversion recovery (FLAIR) (d) images (see red marking). CTA shows the occluded left middle cerebral artery (b) (see red triangle). Diffusion restriction is detected at the diffusion-weighted imaging (DWI) sequence (c). The CT perfusion (e) and the FREE perfusion-weighted (f) images present large Dice matching areas of 78% for the stroke area and 94% for the healthy brain area with delayed perfusion within the territory of the left middle cerebral artery (g).
Table 2.
MRI brain perfusion techniques in comparison.