Piezoelectric crystals convert electrical energy into mechanical energy. When an alternating electrical signal is applied, the crystal rapidly deforms, producing mechanical vibrations that travel as sound or ultrasonic waves. This is why the primary energy conversion is electrical energy to mechanical (acoustic) energy. Magnetic energy and chemical energy aren’t generated by this effect, and electrical energy is the input, not the output.

The main point here is that a dosimetric plan should state what results you expect to achieve and how you’ll measure success. Describing the expected outcomes sets the goals of the plan—things like achieving adequate target coverage, meeting dose constraints for healthy tissues, and anticipating tumor response or symptom relief. These anticipated results guide how the dose is prescribed, optimized, and evaluated. The other elements—where electrodes are placed, how long the treatment lasts, or which modality is used—are about how the therapy is delivered. They influence the results, but they don’t define the outcomes themselves; they are means to reach those planned results.

MIST therapy delivers ultrasound energy in a non-contact way, using a fine saline mist as the coupling medium to carry low-frequency energy to the wound bed. The energy is typically around 30–40 kHz and is applied without touching the wound, so it mechanically stimulates cells in and underneath the wound bed without the heating or direct contact associated with conventional ultrasound. This non-contact, low-frequency approach helps promote cellular activity, granulation, and healing while minimizing disruption of the wound surface. That’s why this option is the best fit: it describes non-contact delivery through a saline mist at a low frequency, rather than direct-contact high-frequency ultrasound, laser-based therapy, or standard contact ultrasound.

When frequency rises, tissue attenuates and absorbs energy more rapidly. In soft tissue, the attenuation coefficient increases with frequency, so a 3 MHz wave loses energy per unit depth faster than a 1 MHz wave. This means the rate at which tissue absorbs energy—and thus heats up—is higher at 3 MHz, approximately three times greater if other factors are equal. The side effect is shallower penetration, but the heating occurs more quickly near the surface. So the correct idea is that the tissue absorbs the energy faster at 3 MHz.