Vitamin E capsules can effectively serve as low-cost fiducial markers for image-guided neurosurgery. By marking the tips of the capsules instead of the scalp, registration accuracy of under 1.5 mm was achieved. This is improved over conventional fiducials due to decreased scalp movement. Using vitamin E capsules saves over 99% of the cost of proprietary fiducials, while still providing sufficient contrast and accuracy for image guidance. The study demonstrates successful indigenization of affordable fiducial markers for neurosurgery in India.

1. Fiducials: Achilles heel of image guided neurosurgery An attempt at indigenization & improvement Dr Deepak Agrawal

2. Background Image-guided neurosurgery is becoming more popular It increases accuracy and … Improves the quality of neurosurgical output in a centre A step towards consistency in surgical results (References to be put)

3. Limitations High initial purchase cost Learning curve Cost of disposables (fiducials) and MR/CT

4. High Initial purchase cost Initial systems cost 2-4 crores AIIMS was the first centre to have IG system (Stealthstation) in India ?1999 Now a image guidance system can be purchased for RS 80 lakhs

5. Learning curve Systems are getting more user friendly Initially added 2-3hrs to the operating time With experience, only 15-20 minutes are needed to set up the system

6. Cost of diposables Propriety item. In stealthstation 10 disposable fiducials are used Literature shows less tha 8-10 fiducials may cause Incr errors Set of 10 fiducials costs $100 (approx Rs 4000)

7. Disposable fiducials can be reused upto a max of 2-3 times Problems may arise in registration due to movement of scalp

8. Process of image guided surgery Fiducials are applied to the patients scalp Ideally should be around the site of pathology May need to shave the hair

9. Thin Slice CT/MRI is done with the fiducials in place according to prtocol 1mm slices starting from the hard palate in Read

10. The CT/MRI may be contrast or plain depending on the pathology The images are saved on a CD in the standard DICOM format CD loaded on the stealthstation wokstation (inside the OT, just prior to surgery)

11. Loaded images checked for orientation & windowing The fiducials are marked visually

12. Following intubation, the patient is positioned & head fixed rigidly on mayfield clamp The actual fiducials are then matched with those marked on the MR/CT images This gives a 3D localisation of any point in space in the patients brain

13. Sources of error Wrong marking on CT/MR Errors during reg due to movement of scalp & affixed fiducial Head fixation not rigid

14. Aim of this study: To indigenize the fiducials for use in image-guided neurosurgery To improve upon the accuracy obtained using conventional fiducials

15. Prerequisites for a potential fiducial Cheap and easily available Can be used with both CT/MRI Good contrast ratio with scalp Easy & good fixation to scalp Easy to register with stealthstation Should allow mm accuracy during registration

16. Copper sulphate paste Filled into syringe and applied wet to the scalp Allowed to dry

17. Rubber caps from vials filled with copper sulphate Poor contrast ratio with surroundings Difficult to stick to scalp

18. Vitamin E capsules Good contrast ratio (?Fat content) Potential problem: Being curved,no identifiable point to register Tried making a hole in it-vitamin leaked out

19. Vitamin E capsule Easier to fix to scalp Cleaned the area with Tinc Benzoin Put the capsule & taped it with leukoplast/dynapore Being compact, whole head shave not required

20. Vitamin E (Registration) As expected, registration difficult on scalp as no identifiable point present.

21. For want of a nail the shoe was lost, For want of a shoe the horse was lost, For want of a horse the rider was lost, For want of a rider the battle was lost, For want of a battle the Kingdom was lost, And all for the want of a horseshoe nail. Attributed to Benjamin Franklin

22. Vitamin E (Registration) Decided to mark the tips of the capsule instead of a point on the scalp

23. Registration using this method yielded overall accuracy < 1.5 mm Improved accuracy could be attributed to decreased scalp movement

24. Only 5 capsules were required (each tip on either end serves as a fiducial) Total cost comes to Rs 5 As a backup measure 5 additional capsules may be applied

25. Conclusions Vitamin E capsules serve as excellent fiducials for image guided neurosurgery Save more than 99% costs on the disposables Improve accuracy of the procedure as scalp movement is diminshed

26. Representative cases (1-2)

27. Indigenization of fiducials in Image-guided neurosurgery