Overall image effect of the sellar tumor model
For all models, multiple anatomical structures were constructed successfully. The integration effects between sequences were good, and the three-dimensional displays of the skin soft tissue, sellar bone mass, paranasal sinuses, optic nerve and chiasm, optic canal, ICA, circle of Willis and its branches, brain tissue, ventricular system and configuration of the tumor and its spatial relationship were clear.
Application of the digital sellar tumor model in surgical planning
The images of the planes containing the surgical approach-related anatomical structures were extracted from the model and displayed simultaneously in the VR environment. According to the perspective of the surgical approach, the anatomical structures and key points for the operation were analyzed. Virtual instruments were used to simulate the operating process based on the actual surgical requirement for the instruments, and individualized surgical plans were developed. The surgical results showed that good operative field and exposure were obtained during the surgeries conducted according to the surgical plan, and the intraoperative findings were consistent with the results of the preoperative simulation. Thirty-one surgeries via the transmononasal sphenoid sinus approach, 25 surgeries via the transpterional approach, 3 surgeries via the interhemispheric approach, and 1 surgery via the subfrontal approach were performed. Total resection of the tumor was performed in 50 patients and subtotal resection (≥90%) was performed in 10 patients. There were no intraoperative deaths or severe postoperative complications (Table
Transmononasal sphenoid sinus approach
For the pituitary adenomas that were mainly located at the sphenoid sinus or within the sellar region, we successfully simulated surgery via the transmononasal sphenoid sinus approach. The structures, including the soft tissue in the nasal cavity, sellar bone mass, sphenoid sinus, ethmoid sinus, ICA, optic nerve, and hypothalamus, were extracted separately and were displayed in different colors. The configuration of the anatomical markers, including the nasal septum, turbinate, posterior nare, sphenoid sinus openings, sphenoidal crest, sphenoid sinus cavity, and sellar floor, were observed for intraoperative localization.
The surgery was completed under a microscope in all patients. The intraoperative anatomy was consistent with the results of the surgery simulation (Figure
). It is worth noting that some fine structures were difficult to show in the models including the sphenopalatine artery, pituitary and the pituitary stalk, and dura mater on the sellar floor, as was the intraoperative shift of the structures and sinking of the tumor.
Figure 1 Simulation of the transmononasal sphenoid sinus approach (large pituitary adenoma model). (a and b) Exploration and exposure of the sphenoid sinus opening; the "boat head" sign was seen, which was consistent with the intraoperative finding. (c and d) (more ...)
For tumors that mainly expanded toward the suprasellar, anterior sellar, parasellar, and posterior sellar regions, including giant pituitary adenoma, sphenoid ridge medial meningioma, tuberculum sellae meningioma, and craniopharyngioma, surgery via the transpterional approach was successfully simulated. The tumor growth, size, nature, and the surrounding involvement were assessed through three-dimensional rotation to determine whether the tumor wrapped around or had any adhesions with the optic chiasm, hypothalamus, and and and its branches. For the tumors that invaded the branches of the anterior and middle cerebral artery, the blood supply was assessed, and a decision was made whether preoperative embolization was necessary and what the embolization range would be. According to the observations, the size and location of the bone window was determined (Figure
) to allow full exposure of the tumor. The gaps I, II, and III and the gap above the ICA in the sellar region were measured, and the operation space and precautions were identified. The volume of the tumor part in the optic canal or at the anterior skull base was measured so that the grinding degree of the anterior clinoid process and the optic canal was determined. The rationality of each exposure approach was assessed and injury to the ICA and optic nerve was prevented.
Figure 2 Simulation of the transpterional approach (tuberculum sellae meningioma model). (a and b) Development of the bone fenestration plan. (c and d) Simulation of the intraoperative traction of the frontotemporal lobe (1: Tumor; 2: Optic nerve; VR: Blue – (more ...)
In this group of patients, to simulate the frontal and temporal lobe traction for the tumor exposure during actual surgery, some part of the frontal and temporal lobe was grinded off; the simulation results were consistent with the intraoperative findings (Figure
). Some subtle anatomical structures such as the pituitary stalk and circle of Willis could not be shown in the model as well as the shift of tissues during the actual surgery.
For special tumors in the suprasellar region, preconstruction of the structures including the tumors, bone mass in the sellar region, optic nerve, ICA, circle of Willis and its branches, brainstem, and ventricles could be performed. The final surgical approach could be chosen based on the observations and assessment results. For example, a craniopharyngioma was mainly located in the third ventricle in a patient, and the assessment showed that with the transpterional approach it is difficult to expost the whole tumor and easy to injure the optic chiasm, hypothalamus, and pituitary stalk. Therefore, we chose the anterior interhemispheric approach because it was reasonable and we were acquainted with it (Figure
). Structures including the vertex, anterior interhemispheric fissure, corpus callosum, bilateral ventricles, and interventricular foramen were extracted and surgery via the anterior interhemispheric approach was simulated. Actual surgery was performed according to the simulated surgical plan (Figure
Figure 3 Simulation of the anterior interhemispheric-lamina terminalis approach (craniopharyngioma model). The structures adjacent to the tumor were observed and the advantages and disadvantages of the transpterional approach (a) and interhemispheric approach (more ...)
When the tumor model with intracavernous invasion was used to simulate the surgical approach, the display resolution of some fine structures including the dura mater in the cavernous sinus, oculomotor nerve, trochlear nerve, and trigeminal nerve was poor in two-dimensional cross-sections and they could not be reconstructed in VR. The surrounding structures of the tumor could be assessed using two-dimensional cross-sectional images to determine the surgical approach. In VR, with the in situ display of the bone mass, lobes, and brainstem, the visual field via the subtemporal approach with a lower border as low as the middle cranial fossa bottom basically could be simulated. The exposure extent of the tumor, ICA, and cavernous sinus could be assessed; however, the results of the simulation were poor. Preoperative simulation based on a model of cavernous hemangioma within the cavernous sinus (Figure
) showed that tumor expanded toward the right suprasellar region could not be resected completly via the subtemporal approach and total resection required the transpterional approach.
Figure 4 Preoperative simulation of a model of cavernous hemangioma in the cavernous sinus. (a) In the left anterior view, the tumor was closely related to the cavernous sinus. (b) In the coronal view, the tumor expanded toward the right suprasellar region. ( (more ...)
Due to the tumor characteristics and the surgeon's personal preferences, the constructed models in this study were applied in surgical planning for other approaches such as the expanded transnasal approach and supraorbital keyhole approach.
The specific postoperative complications in 30 patients with pituitary adenomas were described. Changes in hormone levels and vision and visual field were improved. However, cerebrospinal fluid leakage occurred in one patient which was cured after absolute bed rest. One patient experienced diabetes insipidus, which was alleviated after administration of desmopressin and was cured at 3 months follow-up. One patient had severe diabetes insipidus, which was cured after pituitrin treatment. Transient diabetes insipidus occurred in two patients.
Thirty cases of pituitary adenoma models were researched in detail based on the sellar tumor models.
Thirty patients were randomly selected from the 60 patients. There were 14 male and 16 female patients; their ages ranged from 17–73 years (average: 47.7 years). The clinical characteristics and anatomical measurements of these patients are presented in Table
Clinical characteristics and anatomical measurements of 30 patients with sellar tumors
Eleven surgeons who used this VR tool completed a survey questionnaire. Their perceptions on the relationship between the model and actual surgery were as follows: no difference (n=0); some differences are present, but the model still helps with understanding the anatomy (n=10); differences are significant and the model is not conducive to observing the anatomical structures (n=1); no similarities (n=0). Their perceptions about the advantages of the model compared with conventional two-dimensional images that benefit surgery were the following: no other images are needed (n=0); superior to other images, but the use of other images needs to be combined (n=9); same as other images, the model is optional (n=2); the model was of no help (n=0).