Real-to-virtual domain transfer-based depth estimation for real-time 3D annotation in transnasal surgery: a study of annotation accuracy and stability

PURPOSE

Surgical annotation promotes effective communication between medical personnel during surgical procedures. However, existing approaches to 2D annotations are mostly static with respect to a display. In this work, we propose a method to achieve 3D annotations that anchor rigidly and stably to target structures upon camera movement in a transnasal endoscopic surgery setting.

METHODS

This is accomplished through intra-operative endoscope tracking and monocular depth estimation. A virtual endoscopic environment is utilized to train a supervised depth estimation network. An adversarial network transfers the style from the real endoscopic view to a synthetic-like view for input into the depth estimation network, wherein framewise depth can be obtained in real time.

RESULTS

(1) Accuracy: Framewise depth was predicted from images captured from within a nasal airway phantom and compared with ground truth, achieving a SSIM value of 0.8310 ± 0.0655. (2) Stability: mean absolute error (MAE) between reference and predicted depth of a target point was 1.1330 ± 0.9957 mm.

CONCLUSION

Both the accuracy and stability evaluations demonstrated the feasibility and practicality of our proposed method for achieving 3D annotations.

The nose lid for the endoscopic endonasal procedures during COVID-19 era: technical note

Background

COVID-19 pandemic has disrupted the global health systems worldwide. According to the tremendous rate of interhuman transmission via aerosols and respiratory droplets, severe measures have been required to contain contagion spread. Accordingly, medical and surgical maneuvers involving the respiratory mucosa and, among them, transnasal transsphenoidal surgery have been charged of maximum risk of spread and contagion, above all for healthcare professionals.

Method

Our department, according to the actual COVID-19 protocol national guidelines, has suspended elective procedures and, in the last month, only three patients underwent to endoscopic endonasal procedures, due to urgent conditions (a pituitary apoplexy, a chondrosarcoma causing cavernous sinus syndrome, and a pituitary macroadenoma determining chiasm compression). We describe peculiar surgical technique modifications and the use of an endonasal face mask, i.e., the nose lid, to be applied to the patient during transnasal procedures for skull base pathologies as a further possible COVID-19 mitigation strategy.

Results

The nose lid is cheap, promptly available, and can be easily assembled with the use of few tools available in the OR; this mask allows to both operating surgeon and his assistant to perform wider surgical maneuvers throughout the slits, without ripping it, while limiting the nostril airflow.

Conclusions

Transnasal surgery, transgressing respiratory mucosa, can definitely increase the risk of virus transmission: we find that adopting further precautions, above all limiting high-speed drill can help preventing or at least reducing aerosol/droplets. The creation of a non-rigid face mask, i.e., the nose lid, allows the comfortable introduction of instruments through one or both nostrils and, at the same time, minimizes the release of droplets from the patient’s nasal cavity.

A case of acute unilateral maxillary atelectasis following endoscopic pituitary surgery

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Maxillary atelectasis has traditionally been described as a chronic, progressive pathology.

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This case report challenges the traditional definition of maxillary atelectasis.

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Atelectasis developed acutely following endoscopic transnasal transsphenoidal pituitary surgery.

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Combined with other cases of maxillary atelectasis developing acutely the potential pathophysiology of the disease is challenged.

Introduction

Chronic maxillary atelectasis (CMA) is traditionally described as a rare, acquired condition of persistent and progressive antral wall collapse causing a reduction in maxillary sinus volume. In a handful of cases, CMA has been identified in patients with previously normal computed tomography (CT) imaging. However, maxillary atelectasis occurring rapidly after pituitary surgery, despite a normal pre-operative CT scan, has not previously been described in the literature.

Presentation of case

A 29-year-old male presented two months post endoscopic transnasal, transsphenoidal excision of a Rathke’s cleft cyst with facial pain and pressure, unresponsive to medical treatment. CT of the paranasal sinuses at five months post-operatively demonstrated evidence of a left CMA, which was not present on pre-operative imaging. He underwent endoscopic uncinectomy and middle meatal antrostomy with complete resolution of symptoms.

Discussion

To our knowledge, this is the first case in the literature describing acute development of maxillary atelectasis. While lateralisation of the middle turbinate causing ostiomeatal obstruction may lead to sinus atelectasis, it is typically a slow process and often seen in the context of chronic disease. Review of the literature demonstrates six cases of documented rapid-onset atelectasis of maxillary sinuses. Four of these cases were post-operative, with one involving direct surgery on the affected sinus.

Conclusion

This case represents the first in the literature of acute, post-operative unilateral maxillary atelectasis following pituitary surgery, where the affected sinus was not directly involved in the initial operation. Consideration should be made to incorporate acute cases into the current classification system.

A multi-subject accuracy study on granular jamming for non-invasive attachment of fiducial markers to patients

PURPOSE

This short communication describes experimental evaluation of a new granular jamming cap (GJC) recently introduced in Wellborn et al. (Int J Comput Assist Radiol Surg 12(6):1069-1077, 2017). The contributions beyond [8] are (1) to evaluate accuracy across multiple human subjects, and (2) to determine how much of the accuracy improvement is attributable to improved fiducial marker arrangement alone, and how much is due to granular jamming. The motivation for this GJC is to improve the accuracy of image-guidance interfaces in transnasal skull base surgery. Accuracy depends on a rigid connection between tracked fiducial markers and the patient. By molding itself to the unique contours of the individual patient's head and then solidifying, the GJC can firmly attach fiducial markers to a patient, increasing accuracy in the presence of disturbances.

METHODS

A multi-subject study ([Formula: see text]) was performed to evaluate the accuracy of the GJC compared to a clinically used headband-based fixation device, in the presence of simulated accidental bumping (light force and impact events) that could occur in a real-world operating room.

RESULTS

The GJC reduced the average target registration error at the pituitary gland by 66% in our force experiments and 78% in our impact experiments, which were statistically significant reductions ([Formula: see text]). Maximum target registration error was similarly reduced by 55% and 78% in the same two perturbation tests.

CONCLUSION

The GJC increases the accuracy of transnasal image-guidance under force and impact perturbations by more firmly, yet non-invasively, attaching fiducial markers to the patient. We find that granular jamming provides accuracy improvement beyond that associated with improved fiducial marker arrangement.