Energy is transferred (336) to cause a mechanical property of biological tissue to change, as in ablation. An effect of the transferring is examined in more than one spatial dimension to, for example, make an ablation halting decision for a treatment region, i.e., line (312) or layer (314), or for a location (316) within the region. Halting decisions can be based on lesion-central and/or lesion-peripheral longitudinal displacement of treated tissue evaluated in real time against a characteristic curve. Steering in the azimuthal and/or elevation direction is afforded by, for example, linear, or 2D, multi-channel ultrasound arrays for therapy and imaging. Protocols includable are region-wide scanning (SI 010) and location-by-location completion for both (HIFU) therapy and tracking (acoustic-radiation-forced-based) displacement of treated tissue. Fine, location- to-location monitoring can be used for relatively inhomogeneous tissue； whereas, quicker, sparser and more generalized monitoring (1 100, 1200) can be employed for relatively homogeneous tissue.
