Monitoring Near-Field Heating - Profound Sonalleve MR-HIFU Instructions For Use Manual

4. Treatment methods > 4.5. Temperature monitoring
The Sonalleve Software calculates the thermal dose from temperature maps. As the volume
outside the intended heating location is not expected to warm up, thermal dose is not calculated
there. Therefore, any potential temperature artefacts outside the intended heating location will not
produce any graphical depiction of dose.
Thermal dose is not calculated for scans started from the Scan tab. Thermal dose is only
calculated for sonications, including temperature maps acquired before and after the actual
sonication.
Thermal dose gives an estimate of expected tissue damage. It does not measure the actual
outcome of the treatment. Use other methods to evaluate whether the treatment was successful.
The typical method to determine the outcome of the treatment is to observe non-perfused volumes,
using non-contrast and contrast MR images of the treated volumes after the Sonalleve treatment.
See 10.3. Comparing thermal dose volumes and non-perfused volumes.

4.5.3. Monitoring near-field heating

When a target volume is sonicated, some heating occurs in all the tissue layers through which the
ultrasound beam travels, both in the near field and in the far field. This is a property of all
ultrasound therapy systems and cannot be avoided. The amount of heating in the near field
tissues, such as the skin and the subcutaneous fat layer, is considerably lower than the heating at
the target. The deposited heat energy is carried away by the active cooling mechanisms of the
body (blood flow) and passive diffusion to surrounding tissues and to the Table Top. A cool-down
period is needed between sonications to avoid dangerous temperature build-up (cumulative
heating).
Cumulative heating is a particular concern in the patient's skin and subcutaneous fat layer, and
may potentially lead to severe skin burns. To assist the user in preventing skin burns, Sonalleve
Software uses information about sonication parameters and data from post-sonication fat-
monitoring scans (if available) to estimate the temperature at the patient's skin and subcutaneous
fat layer. The software estimates the heat that has been produced in near-field tissue during the
entire treatment and displays these estimated skin and fat temperatures to the user. If the estimate
suggests that the currently selected sonication would cause the temperature of the near-field
tissues to rise too high, the software does not allow sonication to start. If the sonication is
estimated to induce heat close to the risk level, the software displays a warning (see the following
figure), and the user is asked to confirm the start of the sonication.
Instructions for Use
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