Every earlier MRI encoding lesson in this book (chapters one and six) fixed the gyromagnetic ratio at 4 Hz/T and only ever scanned base field or gradient. This scan holds base field (1 T) and gradient (1 T/m) fixed and checks three gyromagnetic ratios instead: ratio 2 Hz/T gives frequencies 2, 4, 6 Hz; ratio 4 Hz/T gives 4, 8, 12 Hz, exactly matching chapter one's own checked example; ratio 6 Hz/T gives 6, 12, 18 Hz. The ratio rescales the entire checked frequency ladder together, not just one address.
Every earlier MRI encoding row fixed the gyromagnetic ratio and scanned base field or gradient; this scan holds those fixed and scans the ratio itself. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Every earlier MRI row fixed the gyromagnetic ratio at four
Chapters one and six both kept the gyromagnetic ratio at 4 hertz per tesla and only ever varied base field or gradient. Here base field stays 1 tesla and gradient stays 1 tesla per metre, but the ratio itself drops to 2, giving frequencies 2, 4, 6 hertz at positions 0, 1, 2 metres.
f=2(Bbase+Gx)=2,4,6
The gyromagnetic ratio rescales the whole frequency ladder
Base field and gradient never change across these rows. The gyromagnetic ratio alone stretches or compresses the three checked frequencies together.
f0=γ⋅1,f1=γ⋅2,f2=γ⋅3
A higher gyromagnetic ratio spreads the addresses further
At ratio 6 hertz per tesla, the same three fields 1, 2, 3 tesla give frequencies 6, 12, 18 hertz.