Aims and objectives
Thermoablation of ventral intermediate thalamic nucleus by magnetic resonance-guided focused ultrasounds is a non-invasive interventional procedure in the treatment of tremors,
particularly essential tremor and Parkinson-related.
Ultrasound administration is performed by a variable number of controlled deliveries called "sonications".
When setting sonications up,
to obtain an oprtimal result many factors are to be taken in account; they include fixed,
non-modifiable indexes,
and modifiable physical parameters:
energy delivered,
expressed in Joule;
sonication power,
expressed in Watt
sonication effective time,
in seconds;
target temperature reached,
in Celsius...
Methods and materials
We performed a linear regression analysis with robust standard error between the aforementioned parameters and indexes.
Physical values were taken in account if the sonication reached at least 55°C in the target.
76 sets of parameters were included in the analysis,
belonging to 20 patients.
Values and indexes were calculated with the MRGFUs planning and treatment tool by INSIGHTEC Ltd,
1999,
Tirat Carmel,
Israel.
Linear regression was performed using a dedicated software (STATA,
StataCorp LLC,
1985).
Results
Most relevant correlations were as follows:
energy-SS,
negative.
This indicates that patients with a lower skull score,
i.e.
lower skull density ratio,
need to be delivered more energy in order to obtain optimal results.
Time-temperature,
negative.
Time-SS,
negative.
In patients with lower skull density ratio,
more time must be allowed to the machine for energy supply in order to obtain an optimal result.
Time-elements,
negative.
If few tranducers are available (e.g.,
if there are many intracranial calcifications,
or if the helmet in angled in certain...
Conclusion
Conclusion: The study describes issues performing MRGFUs: difficulty when treating patients with low SS,
needing higher energy deliveries; the need to quickly deliver energy,
to reach higher ablation temperatures; the importance of including the highest number of sonication elements,
to reduce time and increase temperatures; the role of skull area in including more elements.
References
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Magnetic resonance-guided focused ultrasound thalamotomy for tremor: a report of 30 Parkinson's disease and essential tremor cases.
Zaaroor M,...