Comparison of Amino Acid PET to Advanced and Emerging MRI Techniques for Neurooncology Imaging: A Systematic Review of the Recent Studies

Figure 8

FDOPA PET combined with MRS in diffuse midline glioma (DMG). ¹⁸F-DOPA PET and MR images of H3K27M-mutant and wild-type DMG. Upper row: DMG, H3K27M-mutant, and WHO grade IV; ¹⁸F-DOPA PET shows an area of markedly increased uptake within the lesion (tumor/normal [T/N] ratio: 2.80; tumor/striatum [T/S] ratio: 1.80). ADC demonstrates a focal area with mildly reduced diffusivity (rADC min: 0.95) on the left side of the lesion corresponding to the ¹⁸F-DOPA PET hot spot region. ASL shows increased perfusion (rCBF max: 1.90). Contrast-enhanced (CE) T1-weighted MR image does not show contrast enhancement. ¹H-MRS demonstrates marked increase of Cho/NAA (7.15) and mild increase of Cho/Cr (1.39) ratios. Middle row: diffuse intrinsic pontine glioma, H3K27M-wild type, and WHO grade III; ¹⁸F-DOPA PET shows absence of tracer uptake in the lesion (T/N: 1.00; T/S: 0.60). ADC demonstrates increased diffusion (rADC min: 1.42). ASL shows low perfusion (rCBF max: 0.80). CE T1-weighted MR image does not show contrast enhancement. ¹H-MRS demonstrates normal Cho/NAA (0.80) and mild increase of Cho/Cr (1.54) ratios. Of note, this was the only histologically defined high-grade glioma which demonstrated lack of increased ¹⁸F-DOPA uptake. Lower row: Diffuse intrinsic pontine glioma, H3K27M-wild type, and WHO grade II. ¹⁸F-DOPA PET shows absence of tracer uptake in the lesion (T/N: 0.95; T/S: 0.45). ADC and ASL images demonstrate increased diffusion (rADC min: 1.26) and low perfusion (rCBF max: 0.78). CE T1-weighted MR image does not show contrast enhancement. ¹H-MRS demonstrates normal Cho/NAA (0.93) and Cho/Cr (1.08) peak area ratios. Note: the box on T2-weighted images indicates the region of interest from which the spectra were acquired. Reproduced with permission from Figure 1 of Piccardo et al. [54].