Real-time methods and systems for mapping a target region in the brain during surgery
A real-time method and system to accurately demarcate sub-territories of the subthalamic nucleus area in the brain during surgery, based on microelectrode recordings and a Hidden Markov Model. Root mean square and power spectral density of the microelectrode recordings are used to train and test Hidden Markov Model in identifying the dorsolateral oscillatory region and non-oscillatory sub-territories within the subthalamic nucleus. After the dorsolateral oscillatory region in the subthalamic nucleus is mapped, the microelectrodes are removed, and a macroelectrode is inserted in the mapped dorsolateral oscillatory region for producing deep brain simulation for treatment of Parkinson's disease.
1. A method for real-time mapping during surgery of subterritories of the subthalamic nucleus (STN) in the brain, the method comprising the steps of:
(i) inserting one or more electrodes into the brain according to a predetermined insertion trajectory;
(ii) advancing said one or more electrodes towards the estimated location of a dorsolateral oscillatory region (DLOR) of the STN;
(iii) recording beta oscillatory activity by said one or more electrodes along the insertion trajectory;
(iv) calculating power spectral analysis values for the beta oscillatory activity recorded along the insertion trajectory; and
(v) using a Hidden Markov Model (HMM) based on part or all of the calculated power spectral analysis values along the insertion trajectory for detecting the borders of said DLOR and assigning to each selected point along the insertion trajectory one of the following regions with the highest probability value: 1. the DLOR of the STN; 2. the region in the insertion trajectory before the STN; 3. the region inside the non-oscillatory STN; or 4. the region in the insertion trajectory after the STN, thereby detecting borders of said subterritories of the STN in the brain.
2. A method according to claim 1 , further comprising the step of removing said one or more electrodes and inserting a macroelectrode in the identified DLOR of the STN for producing deep brain simulation for treatment of Parkinson's disease.
3. A method according to claim 1 , wherein said one or more electrodes are microelectrodes, macroelectrodes or both.
4. A method according to claim 1 , wherein said one or more electrodes are advanced towards the estimated location of said DLOR of the STN continuously; in small discrete steps of equal size; in small discrete steps of variable size; or any combination thereof.
5. A method according to claim 1 , wherein the power spectral analysis values are obtained by using power spectral density (PSD) calculations.
6. A method according to claim 1 , further comprising the step of calculating normalized Root mean square (NRMS) values for the recorded beta oscillatory activity.
7. A method according to claim 6 , wherein root mean square (RMS) values for the beta oscillatory activity recorded along the insertion trajectory are calculated by applying the formula
RMS
(
X
_
)
=
∑
i
=
1
n
(
X
i
-
μ
)
2
n
-
1
where X is the vector of a sampled analog signal with mean μ, Xi is each sample, and n is the number of samples, and the RMS values are then normalized to obtain NRMS values.
8. A method according to claim 1 , further comprising an initial step of training the HMM by providing reference data of a statistically-significant number of insertion trajectories wherein points along each insertion trajectory are assigned by an expert to one of the following regions: 1. the DLOR of the STN; 2. the region in the insertion trajectory before the STN; 3. the region inside the nonoscillatory STN; or 4. the region in the insertion trajectory after the STN.
9. A system for real-time mapping during surgery of subterritories of the subthalamic nucleus (STN) in the brain, the system comprising:
(i) one or more electrodes configured to be inserted into the brain according to a predetermined insertion trajectory;
(ii) advancing means for advancing said one or more electrodes towards the estimated location of a dorsolateral oscillatory region (DLOR) of the STN;
(iii) a recording unit for recording beta oscillatory activity by said one or more electrodes along the insertion trajectory;
(iv) first data processing means for calculating power spectral analysis values for the beta oscillatory activity recorded along the insertion trajectory; and
(v) second data processing means for using a Hidden Markov Model (HMM) based on part or all of the calculated power spectral analysis values along the insertion trajectory for detecting the borders of said DLOR and assigning to each selected point along the insertion trajectory one of the following regions with the highest probability value: 1. the DLOR of the STN; 2. the region in the insertion trajectory before the STN; 3. the region inside the nonoscillatory STN; or 4. the region in the insertion trajectory after the STN, thereby detecting borders of said subterritories of the STN in the brain.