Optimizing MRI based Optimizing MRI based direct visualization of direct visualization of

the Subthalamic nucleus the Subthalamic nucleus on 1.5 T systems on 1.5 T systems

Navneet Sharma, Dr. Curtis Sutton

Dr. Erich O. Richter

ObjectivesObjectivesDetermine protocol parameters

that enhance visualization of the Subthalamic nucleus (STN) using MRI (1.5T)

Check if these parameters need to be changed or not for each individual

Compare and contrast the parameter values between normal and Parkinson's patients

DBS research over the DBS research over the yearsyears Source: Web of ScienceSource: Web of Science

What kind of magnets are we What kind of magnets are we using?using?Source: Web of ScienceSource: Web of Science

ComplicationsComplicationsCurrently the MRI techniques

using the 1.5 T magnet only gives a vague outline of the STN’s location

localized during the procedure using microelectrode recording

RICHTER, ET AL. Determining the position and size of the subthalamic nucleus based on magnetic resonance imaging results in patients with advanced Parkinson disease. J Neurosurg 100:541–546, 2004

MethodsMethodsT1 volumetric and T2 weighted MRIs were

taken from 3 different volunteersControlled various variables to assess

quality of the images◦ Time Echo (TE)◦ Time Repetition (TR)◦ Bandwidth◦ Slice Thickness

3D reconstructions of the STN were generated using BrainLAB 2.6 software

Subsequently, the parameters from the normal MRI scans was compared to those of Parkinson’s patients

ResultsResults

These values help differentiate Fe containing structures from non-Fe containing structures in the

Basal Ganglia*switch to in-patient procedure to accommodate the increased scan time

Variable Optimal ValueTE 144 msecTR 4000 msec

Bandwidth 100 KHzSlice Thickness 1 mm

NEX 2Scan Time 13 - 17 mins*

  Normal ParkinsonTR (msec) 4000 5459.3 ± 348.3 TE (msec) 144 103.4 ± 6.3

The reduced TE associated with PD is indicative of increased free iron levels in PD compared to normal

This leads to highly neurotoxic states which cause neurodengeneration in the STN

Based on literature review, the pars compacta of the SN shows significant increase in free iron accumulation

compared to the STN associated with PD. We observed the opposite to be true in our normal controls. Wypijewska, et al Iron and reactive oxygen species activity in parkinsonian substantia nigra Parkinsonism Relat Disord. 2010 Jun;16(5):329-33. Epub

2010 Mar 9.

TE = 108

TE = 126

TE = 153

TE = 144

TR = 3000

TR = 8000TR = 6000

TR = 5000

BW = 31.25

BW = 166.67BW = 100.00

BW = 62.50

3D recontruction vs Atlas3D recontruction vs Atlas

3D recontruction vs Atlas3D recontruction vs Atlas

ConclusionConclusionOptimizing the right parameters can help

directly visualize the subthalamic and surrounding nuclei with a 1.5T MRI

These parameters work equally well for different individuals in normal individuals

Further improvements in treatment of PD patients can be achieved through a combinatorial imaging approach

Addition of DT images to delineate the white matter shell around the STN

T1 based grey-white matter differentiation

Future DirectionFuture Direction