[IGSTK-Users] Which kind of fiducials are best for image registration in IGSTK?

[Yaniv, Ziv]

Hi Alejandro,

Practical answer:

The markers you have chosen may work for you, but we haven’t used spherical markers for this form of registration (see theoretical answer for reasoning).

Try the doughnut fiducials from IZI (http://www.izimed.com/catalog.shtml?&Vl=6&Tp=2) or the conical fiducials from Beekley (http://www.beekley.com/MultiModality/index.asp).

We have used both and they worked well for us. You can request a sample from these companies and they will send you several markers. There’s nothing like trying it out for yourself.

Theoretical answer (fiducial choice in general):

What you want from a fiducial is that the SAME point be easily and accurately localized in the volume (CT/MR) AND in the physical world. This means that you need to think about the fiducial attachment (implanted or skin adhesive), and shape (sphere, doughnut, conical).

Ideally you would use bone implanted fiducials, but skin adhesive fiducials are the most popular. The reason for this choice is that there is no additional trauma, but on the other hand they will often fall off.

The fiducial you chose, spherical, is easily localized in the volume both manually or automatically. You get the center of the sphere. In the physical world to accurately digitize the center of the sphere you need a tracked and calibrated tool that has a cup with a specific diameter that fits the sphere. I used this approach in the past with a customized tool for registration so it is doable. Usually you will have a pointer tool and not a cup tool so your localization in the physical world will be less accurate.  [The reason most labs have a pointer tool readily available is that most tracking systems provide such a tool when you buy the system].

The conical and doughnut shaped fiducials may be less accurately localized in the image but this depends on your localization approach, manual or automatic. They are localized relatively accurately in the physical world using a standard pointer tool, hence our choice to use these markers.

                regards
                   Ziv

--
Ziv Yaniv, PhD.,
Principal Investigator,
The Sheikh Zayed Institute for Pediatric Surgical Innovation
Children's National Medical Center
6th Floor Main Hospital, Room M7740
111 Michigan Ave., N.W
Washington, D.C 20010

Phone: 202-476-1288
email: zyaniv at childrensnational.org
web: http://yanivresearch.info



From: igstk-users-bounces at public.kitware.com [mailto:igstk-users-bounces at public.kitware.com] On Behalf Of Alejandro De León Cuevas
Sent: Wednesday, October 16, 2013 9:03 PM
To: igstk-developers-request at public.kitware.com; igstk-users at public.kitware.com
Subject: [IGSTK-Users] Which kind of fiducials are best for image registration in IGSTK?

Hi everybody, I have a question that I hope somebody there can answer. I want to know what kind of fiducials are best for image registration, I will use it on an artificial skull and make the registration procedure using ​​IGSTK with DICOM images (CT) of the skull. I found skin markers as shown in this link:

http://www.pdchealthcare.com/en-us/products/SDM-CT1.html

but I don’t know if they are optimal. Thank you for your attention.
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