**4. Stereotactic radiosurgery for intraocular tumors**

Stereotactic radiosurgery was initially developed in 1949 by Lars Leksell, the Swedish neurosurgeon, who treated small targets of tumors located in the brain. It was a new step in radiotherapy methods. Nowadays, the stereotactic radiosurgery (or external beam irradiation with protons or helium ions) is a regularly used option in the treatment of mainly medium-sized choroidal melanomas. In many cases, it has been applied for larger tumors. Eye globe and orbit scanning by CT or MRI is necessary for verifying of extraocular extension. It is necessary to use these techniques to differentiate between choroidal tumor and primary versus secondary retinal detachment. Every patient with a medium-sized melanoma is sent to chest X-ray, liver ultrasound, and general examination but also to PET/CT to detect possible metastases.

Methods like MRI, CT and also digital subtraction angiography (DSA) are included in imaging equipment. Structures of the eye globe and lesions are defined, visualized and localized. Software for target verification, which is used in conjunction with stereotactic frame system and imaging (CT, MRI) modalities, is used to determine the coordinates of the lesion (tumor) target into the stereotactic frame reference system.

Each patient's record includes the tumor size, tumor volume, the maximum height of the tumor, age and gender, the presence and the extent of secondary retinal detachment, and the possible signs of extrascleral extension. The very important step of SRS is tumor volume calculation in each patient directly by results of CT and MRI examination. It is the basic step

3D Printing Planning Stereotactic Radiosurgery in Uveal Melanoma Patients

http://dx.doi.org/10.5772/intechopen.79032

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Immobilization of the affected eye globe for stereotactic irradiation is achieved by mechanical fixation of the sutures to the Leibinger stereotactic frame. Vicryl sutures from four extraocular muscles (m. rect. sup., m. rect. inf, m. medialis and m. temp.) are placed through the conjunctiva and the lids. The stereotactic frame is fixed to the head, and the sutures are tied to the stereotactic frame. The day after stereotactic irradiation is the patient examined by an ophthalmologist (the slit lamp examination, ophthalmoscopy, and intraocular pressure measuring) and is released for home treatment, he gets antibiotic and corticosteroid eye drops.

In software for data segmentation (3D Slicer, freeware version 4.5.0+), virtual 3D models of the eye globe were created. Imported data set came from CT (computer tomography) with accuracy 1 mm scan thickness. Visualized and created model has basic anatomical structures like globe, corneal segment, lens, optic nerve and tumor mass inside the created 3D model of eye globe. Extraocular muscles and vitreous body are not included in the model. Eye globe anatomical structures—lens and optic nerve—are very important for orientation. They are necessary visible points at the small printed 3D model because the model itself has the same size as the normal human eye globe—from anterior to posterior part is 24 mm. Virtual 3D model of the eye globe is then sliced. Additional support is calculated. The next step can be model preparing for printing in 3D printing slicing software Simplify3D. After creating and refining our models, for process of 3D printing, we used fused deposition modeling (FDM) technology. The 3D models in our study are printed on ZYYX 3D Printer by Magicfirm LLC using one extruder heated to 215–230°C. Chosen material is polylactic acid (PLA) with low deformability during rapid temperature changes and contributing high accuracy of the model. One layer of the model thickness of in vertical line is 100 μm. This provided an ideal proportion of a ratio between accuracy and velocity of a printing process. Estimated time of printing process in 3D printer is usually from 15 to 30 min per one model (**Figures 2** and **3**).

**Figure 2.** 3D printed model of the eye globe with intraocular tumor—arrow shows the tumor mass (melanoma).

involved to the stereotactic planning scheme.

The radiosurgical treatment is calculated by physicist by planning system for treatment (TPS) with the 3-D dose distribution. The result is superimposed onto the certain patient's anatomical status to get an appropriate radiation dose for tumor and also for risk structures (optic nerve, lens, chism, etc.) and radiosurgical procedure [12–14].
