Intraoperative x-ray to measure distance between DBS leads: A reliability study.
BACKGROUND
Many factors can jeopardize the accuracy of deep brain stimulation (DBS) lead placement. Confirmation of lead placement while the patient is still in the operating room would be advantageous. Intraoperative MRI or CT can identify placement errors, but these modalities can be cost- or time prohibitive. Intraoperative fluoroscopy may give information on the accuracy of the Y coordinate, but the accuracy of the X coordinate usually cannot be confirmed. When an object of known dimensions is present in the brain, such as a unilateral DBS lead, its dimensions can be used to calculate unknown distances. The objective of this study was to determine if intraoperative AP skull x-ray accurately predicts the distance between DBS electrodes using postoperative MRI as the gold standard.


METHODS
The distance between 32 pairs of DBS leads was measured by 2 independent raters under blinded conditions on intraoperative AP x-ray and postoperative axial and coronal MRI. Variable x-ray magnification was accounted for using the formula: actual distance between 2 leads = (measured distance between DBS leads)/(average measured length of electrodes) × 7.5 mm.


RESULTS
The mean (± SD) distance on x-ray was 22.62 ± 2.23 mm, on axial MRI 22.78 ± 1.90 mm, and on coronal MRI 22.79 ± 2.00 mm. ANOVA revealed no difference based on method (P = .887) or raters (P = .940). The intraclass correlation coefficient showed excellent interrater reliability,


CONCLUSIONS
Intraoperative AP x-ray accurately predicts the distance between DBS leads. The technique is especially useful when the location of the first DBS lead relative to the midline is known, such as during staged bilateral procedures or lead replacement procedures.
Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612, USA. lverhage@rush.edu
Leo
L
Verhagen Metman
Julie G
JG
Pilitsis
Glenn T
GT
Stebbins
Maarten
M
Bot
Roy A E
RA
Bakay
D000704:Analysis of Variance; D001921:Brain / Q000000981:diagnostic imaging*; D046690:Deep Brain Stimulation / Q000379:methods*; D004567:Electrodes, Implanted; D005240:Feasibility Studies; D006801:Humans; D007432:Intraoperative Period; D008279:Magnetic Resonance Imaging; D015588:Observer Variation; D010300:Parkinson Disease / Q000628:therapy; D011184:Postoperative Period; D011859:Radiography; D015203:Reproducibility of Results; D012886:Skull / Q000000981:diagnostic imaging