PMC5766057_01
GK-SRS treatment procedure. Images of a 57-year old female patient with a right eye stage IIA choroidal melanoma. (A) Eyeball fixation. The treated eye was fixed with retrobulbar anesthesia, and two extraocular muscles were sutured. (B) Stereotactic frame fixation. The Leksell G frame was fixed to the patient's head with four pins placed into the skull and the sutured muscles were fixed to the frame.
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Subsequently, the threads of the two sutured muscles were fixed to the stereotactic frame to immobilize the eye throughout the procedure (Fig. 1).
GK-SRS and verification procedure. Head frame coordinate indicators were used for (A) CT simulation and (B) MRI study. (C) CT-1 was performed immediately following the patient undergoing eye fixation and stereotactic frame immobilization. (D) MRI scans were loaded into the GK treatment planning system for dose planning. (E) To determine the precision of the eye fixation, CT-2 was performed following the treatment plan was completed, but prior to the start of the GK-SRS procedure. (F) CT-2 and the MRI scans were fused and evaluated across the axial, sagittal and coronal planes to analyze the reproducibility of the eye position. (G) The final GK treatment plan was approved and used for radiosurgery treatment. (H) CT-3 was performed immediately following GK-SRS. GK-SRS, gamma knife stereotactic radiosurgery; CT, computed tomography; MRI, magnetic resonance imaging.
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CT images were acquired using a Philips 16-slice CT scanner (Brilliance Big Bore; Philips Healthcare, Cleveland, OH, USA) with a 1-mm slice thickness (Fig. 2). The dose to the tumor margin was 30 Gy at the 55% isodose line (Figs. 2D and 3). During the treatment, the patient was maintained in a supine position, instead of the traditional prone position (Fig. 2G). The second CT scan (CT-2) was performed following completion of the treatment planning, but prior to the GK-SRS procedure (Fig. 2E). The third CT scan (CT-3) was performed immediately following the completion of the GK-SRS procedure (Fig. 2H).
Eye movement analysis. The tumor was contoured in the 3 sets of CT images on the GK treatment planning system and exported to the CERR software. (A) The MRI scans with the GK-SRS treatment planning dose distribution were fused with different CT sets, on the basis of the localizer position. (B) The dose volume histogram of the tumor for the 3 sets of CT scans was evaluated. GK-SRS, gamma knife stereotactic radiosurgery; CT, computed tomography; MRI, magnetic resonance imaging; CERR, Computational Environment for Radiotherapy Research.
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The dose to the tumor margin was 30 Gy at the 55% isodose line (Figs. 2D and 3). The fused images (Fig. 3A) and the raw data were exported from GK-SRS to the Computational Environment for Radiotherapy Research (CERR) treatment planning software, to compare the positioning error, dose volume histogram of the tumor and critical organs (Fig. 3B).
Fundoscopic views of the choroidal melanoma. (A) At diagnosis; (B) 4 months after GK-SRS; (C) 3 months after trans pars plana vitrectomy and endo diode laser thermotherapy (oculus dexter); and (D) 20 months after GK-SRS, following the resolution of the serous retinal detachment, tumor surface hyperpigmentation, tumor margin distinct borders and tumor shrinkage. GK-SRS, gamma knife stereotactic radiosurgery.
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The follow-up fundoscopic examination, performed 1 month after GK-SRS, revealed hyperpigmentation of the tumor surface, distinct borders of the tumor margins and tumor shrinkage (Fig. 4).
Cytology findings. Vitreous fluid cytology (oculus dexter) revealed sparse malignant cell nests with rich melanin-pigment compatible with malignant melanoma. Immunostaining revealed (A) HMB45 (+) and (B) Ki-67 (+ for some cells) (magnification, x400).
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An Olympus BX41 light microscope (Olympus Corporation, Tokyo, Japan) was used to visualize results at a magnification of x400 (Fig. 5), demonstrated sparse malignant cell nests with rich melanin-pigment compatible with malignant melanoma.
MRI images of a patient with choroidal melanoma. (A) Prior to treatment; and (B) 38 months after GK-SRS; the images revealed tumor shrinkage and a decrease in thickness. Left, coronal short tau inversion recovery image; middle, axial T1 image; and right, sagittal T1 image. MRI, magnetic resonance imaging; GK-SRS, gamma knife stereotactic radiosurgery.
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At 37 months after LGK-SRS and 32 months after vitrectomy, follow-up MRI scans revealed tumor shrinkage (9.5x8.9 to 7.2x6.4 mm) and a decrease in tumor thickness (4.1-3.0 mm) (Fig. 6).