CT-DCG Guided Stereotactic Navigation in Lacrimal Surgery

Hello. My name is Mohammad Javed Ali. And today we will discuss CT dacryocystography as a base imaging modality during stereotactic lacrimal surgeries for certain complex secondary acquired lacrimal duct obstructions.

A brief about myself. I head the Govindram Seksaria Institute of Dacryology and the LV Prasad Eye Institute in India. And I exclusively practice the lacrimal drainage sciences both as a clinician and as a basic science scientist.

The outline of the talk would be briefly take you through the stereotactic modality of operating certain lacrimal drainage disorders. And then we will discuss the utility of CT-DCG for stereotactic guidance. And we’ll exemplify it using a post-maxillectomy secondly acquired lacrimal duct obstruction.

Now if you look, navigation or stereotactic guidance is not only important for intraoperative localization of anatomical landmarks, but it is also very useful for geometric localization of certain targets. In this case, lacrimal sac, for example.

Now there are two modes of performing stereotactic guidance. One is through electromagnetic mode the first picture on the left that you see. Or the central picture that shows an optical mode of performing navigation, which is a little less cumbersome. The image on the right, extreme right actually, shows a tracker.

Now following whichever imaging modality, in this case, CT-DCG, those images are then uploaded into the navigation machine using softwares. And then this is followed by probe registration and confirmation of certain known anatomical landmarks. And once we do that, we are set for going ahead with the stereotactic [AUDIO OUT].

And this is how an intraoperative image would look. Now here, if you see the right lower one is an endoscopic image of the left nasal cavity where the surgeon is trying to assess the inferior extent of the osteotomy.

And then in the radiological images of coronal cuts, the green line that you see are called as crosshairs. And the intersection of this crosshair actually reflects the tip of the probe and where it is located.

CT-DCG is a well-known modality to not only delineate the lacrimal drainage system, but also to delineate pathologies mostly of anatomical nature.

Now here you can see the radiological image on the left side shows a left-sided, dilated lacrimal sac, very well delineated without any subsequent flow downwards. And in the example on the right side, you see that the left nasolacrimal duct demonstrate the dye, whereas the right nasolacrimal duct is not demonstrating any dye.

Not only 2D but also 3D images can be obtained with the 3D volume reconstructions from the CT images. An example here is a right-sided lacrimal obstruction at the level of inferior portion of the lacrimal sac. Whereas the left side shows a patent lacrimal drainage system.

To exemplify, we will be discussing about one surgery where a 67-year-old female who had a maxillary carcinoma presented following a complete maxillectomy with complaints of a different discharge. And the surgery had happened three years back. And there was no evidence of any recurrence.

Well, if you look at the image of the endoscopy on the left side, there is no discernible anatomical landmarks that one can see. So in such situation, where would one go about localizing or performing a DCR? And that is stereotactic guidance helps.

The image on the right shows a three dimensional reconstruction of a CT-DCG which we will employ in this particular case. And there you can see that the right side the entire maxilla is not there. And there is a dilated sac with an abrupt ending at its lower part, obviously because of an iatrogenic excision of the nasolacrimal duct along with the maxilla.

Using the 3D CT-DCG, we can also reconstruct the same patient as a virtual model using navigation software like the one that you see here, the right-sided dilated lacrimal sac whereas the left side is patent and the dye has flowed into the inferior meatus.

Intraoperatively, actively using the virtual mode– this is a combination of a CT-DCG and virtual model in the same patient. Where you can see that, in the right lower column, the blue is a probe. And the red one is a delineated lacrimal sac, and where one is touching the lacrimal sac at that point.

And that can be confirmed by the coronal, sagittal, and axial sections where the crosshair intersection is at a nice dilated lacrimal sac.

So I hope and I’m very sure that this modality of management is here to stay and experienced lacrimal surgeons who deal with lot of challenges would find this very interesting. And I hope it is useful for everyone. Thank you.