Table of Contents
Advertisement
4. Treatment methods > 4.6. Motion detection
WARNING
Always leave sufficient cooling intervals between sonications.
Failure to do so may cause heat buildup in the near field or far field, leading to skin burn or
other unwanted tissue damage.
A diminishing progress bar labeled Cooling and a count-down timer in the System Status Display
indicate the system-recommended cooling time. The part of cooling time that cannot be overridden
is displayed in red. The recommended cooling time is displayed in two shades of orange, with the
brighter color corresponding to higher risk.
Fig. 20: Three examples of cooling time in the System Status Display. Left:
Almost one third of the remaining system-recommended cooling time is
mandatory and cannot be overridden. Middle: The cooling period can be
overridden because there is no mandatory cooling time, but the system
indicates a high risk of internal burn. Right: Recommended cooling time still
remaining, but it is possible to use the override and start sonication.
4.5.5. Temperature limits
The Sonalleve MR-HIFU system imposes the following temperature limits to prevent overheating of
tissue:
Warning zone heating limit: 47 °C (116.6 °F). If the system detects this temperature inside the
beam path in the near-field monitor slice or inside a user-defined Freehand Warning ROI, it
generates a warning message and the user must decide whether to continue or stop the
sonication.
System safety limit: The highest temperature that is allowed in a treatment cell during
sonication is 85 °C (185 °F). If this temperature is reached within the treatment cell, the system
issues a warning and automatically stops the sonication.
4.6. Motion detection
Patient motion may result in misplaced heating. Observe carefully that vulnerable structures such
as neurovascular bundles have not moved into the beam path.
As a safety measure, the system detects unintended patient movement during treatment and
issues a warning if it is detected. If the movement is significant, the system issues a more severe
warning.
If the patient moves during treatment, a spatial variation of the measured temperature outside the
heated region occurs. Carefully monitor the temperature maps during therapy.
Additionally, if you suspect the patient has moved, scan a fast scan with markers and compare the
images. If you see significant movement in the images, scan the planning images again and verify
the validity of the treatment planning. An alternative is to use registration tool. Registration is a
feature that can perform the necessary corrections if any patient or organ movement is observed
during the treatment. See 6.8.8. Registration.
In addition, the Sonalleve software provides graphical tools, such as markers, that can be used for
detecting movement of visible anatomical landmarks. For more information, see 6.6.6.1. How to
use markers and why ?.
Instructions for Use
109745C2 / 02-2022
54 (192)
Advertisement
Table of Contents
