Figure 3: A 41-year-old patient with a mass lesion (invasive ductal cancer) in the left breast. From (a) to (d), the maximum intensity projection (MIP) images of pretreatment, F/U-1, F/U-2, and F/U-3 MRI are shown. The tumor size is 4.0 cm before treatment, which shrinks down to 2.7 cm in F/U-1 (32% reduction), 1.2 cm in F/U-2, and reaches a complete response in F/U-3 after completing NAC. This patient is confirmed as pCR in post-NAC pathological examination. The total choline concentration measured by MRS is [tCho] = 2.33 ± 0.54 mmol/kg before therapy, which decreases to 1.15 ± 0.25 mmol/kg in F/U-1, showing 51% reduction. Tumor size is too small in F/U-2 and F/U-3 for MRS measurements. For this pCR case, the tumor size reduction is 32% at F/U-1, and [tCho] reduction is greater at 51%.