3D MRI‐based tumor delineation of ocular melanoma and its comparison with conventional techniques

Abstract

The aim of this study is to (1) compare the delineation of the tumor volume for ocular melanoma on high‐resolution three‐dimensional (3D) T2‐weighted fast spin echo magnetic resonance imaging (MRI) images with conventional techniques of A‐ and B‐scan ultrasound, transcleral illumination, and placement of tantalum markers around tumor base and (2) to evaluate whether the surgically placed marker ring tumor delineation can be replaced by 3D MRI based tumor delineation. High‐resolution 3D T2‐weighted fast spin echo (3D FSE) MRI scans were obtained for 60 consecutive ocular melanoma patients using a 1.5 T MRI (GE Medical Systems, Milwaukee, WI), in a standard head coil. These patients were subsequently treated with proton beam therapy at the UC Davis Cyclotron, Davis, CA. The tumor was delineated by placement of tantalum rings (radio‐opaque markers) around the tumor periphery as defined by pupillary transillumination during surgery. A point light source, placed against the sclera, was also used to confirm ring agreement with indirect ophthalmoscopy. When necessary, intraoperative ultrasound was also performed. The patients were planned using EYEPLAN software and the tumor volumes were obtained. For analysis, the tumors were divided into four categories based on tumor height and basal diameter. In order to assess the impact of high‐resolution 3D T2 FSE MRI, the tumor volumes were outlined on the MRI scans by two independent observers and the tumor volumes calculated for each patient. Six (10%) of 60 patients had tumors, which were not visible on 3D MRI images. These six patients had tumors with tumor heights ⩽3mm. A small intraobserver variation with a mean of (−0.22±4)% was seen in tumor volumes delineated by 3D T2 FSE MR images. The ratio of tumor volumes measured on MRI to EYEPLAN for the largest to the smallest tumor volumes varied between 0.993 and 1.02 for 54 patients. The tumor volumes measured directly on 3D T2 FSE MRI ranged from 4.03 to 0.075cm3. with a mean of 0.87±0.84cm3. The tumor shapes obtained from 3D T2 FSE MR images were comparable to the tumor shapes obtained using EYEPLAN software. The demonstration of intraocular tumor volumes with the high‐resolution 3D fast spin echo T2 weighted MRI is excellent and provides additional information on tumor shape. We found a high degree of accuracy for tumor volumes with direct MRI volumetric measurements in uveal melanoma patients. In some patients with extra large tumors, the tumor base and shape was modified, because of the additional information obtained from 3D T2 FSE MR images.

Fundus image fusion in EYEPLAN software: An evaluation of a novel technique for ocular melanoma radiation treatment planning

“…Daftari et al 19 compared 3D MRI-based tumor delineation of ocular melanoma with EYEPLAN planning techniques for 60 consecutive patients with ocular melanoma. The tumor volumes obtained with 3D MRI were comparable to tumor volumes obtained from EYEPLAN software.…”

“…18 In these lesions, additional information from 3D T2 FSE MRI images is helpful in delineating the tumor. 19 At the time of treatment planning two orthogonal x rays are taken either digitally or as a hard copy to delineate the exact location of the radio-opaque clips. EYEPLAN software relies on eye length, measured by ultrasonography.…”

Diffusion-Weighted Imaging of Malignant Ocular Masses: Initial Results and Directions for Further Study

“…Since the initial descriptions of the MR imaging appearance of various ocular masses, continued technical advances in MR imaging have allowed higher resolution imaging and enhanced characterization of lesions. [1][2][3][4][5] Despite high spatial resolution, MR imaging by using routine sequences is sometimes unable to distinguish different ocular masses and may be limited in its ability to detect ocular masses in the presence of hemorrhagic/exudative retinal detachments, due to suboptimal tissue contrast. Thus, it would be helpful to evaluate additional MR imaging techniques capable of providing different forms of tissue contrast that may aid in the detection and further characterization of ocular masses.…”

Proton Therapy of Uveal Melanomas

“…With their physical properties (finite range in tissue, sharp lateral penumbra), protons are suited for covering the target volume without delivering a significant dose to critical structures nearby (e.g., optic disk, lens, ciliary body, and macula). This advantage of proton beams is also used for the treatment of other tumor entities [5,25,33,36].Proton therapy of the uveal melanoma has been performed in more than 10,000 patients worldwide. 5-year local tumor control rates range from 89% to 98% with eye retention rates between 75% and 93% [2, 4, 7, 10-12, 15, 17, 37].…”