094701-1 We have studied the various conditions and limitations for achieving compact fixed-field alternatinggradient (FFAG) accelerators to be widely used in heavy-ion cancer therapy. For the case of a normalconducting FFAG accelerator, our linear calculation indicates 12-cell radial sectors with a field index of 10.5 as a suitable configuration. We found that its ring circumference can be as small as 70 m and that triple-cascade rings are needed to accelerate a carbon beam from 40 keV=u to 400 MeV=u. In this paper, we report a systematic analysis based on a linear optical model, a comparison of various types of FFAG, and a design example with some technical concerns. An important result is that viable radialsector designs are possible with circumference factor C significantly lower than the value 4.45 previously quoted.