Fig. 12. Placement of iodine-125 radiation plaque. Transverse B-scan demonstrates a dome-shaped intraocular lesion with a concave radiation plaque behind the lesion and adjacent to the sclera. The highly reflective linear points within the plaque correspond to the I-125 seeds (arrow heads). Note that the margins of the tumor (arrows) are well within the margins of the plaque (lines).

diagnosis of diffuse melanoma includes metastatic carcinoma, diffuse choroidal hemangioma, uveal lymphoid hyperplasia, diffuse choroidal nevus, and Vog-Koyanagi-Harada syndrome.

Tumor biometry

Ultrasonography plays a critical role in managing and monitoring uveal melanoma by providing accurate measurements of tumor dimensions. Apical height of uveal melanomas can be determined using the A- or B-scan. In small tumors (less than 1.5 mm), A-scan measurements can be challenging, and B-scan is recommended. The measurements obtained with these two methods should be within 0.2 to 0.3 mm for medium tumors and 0.5 mm for large tumors. When the retina is attached to the apex of the lesion, the tumor surface spike on the A-scan may appear thick, because it includes both the retina and tumor surface. In these cases, measurements should be obtained from the retinal portion of the surface spike. When the retina is detached, measurements should be taken from the tumor surface and not the retinal detachment. Basal diameter of

a uveal melanoma is determined with the transverse and longitudinal approaches of the B-scan. The transverse approach measures the circumferential diameter, while the longitudinal approach evaluates the radial diameter.

Intraoperative confirmation of plaque placement

Ultrasonagraphy is used commonly to assess proper placement of radioactive material in radiation therapy and evaluate the effectiveness of various treatments. In brachytherapy, localization of a plaque can be performed in the operating room under sterile conditions or postoperatively. It is particularly helpful in posterior tumors, where transillumination cannot indicate the tumor margins adequately. The iodine-125 plaque produces an echolucent pattern with marked shadowing of the orbital tissues (Fig. 12).

Response to radiation therapy

After radiation treatment, uveal melanoma becomes more irregular and reflective as necrosis

occurs. The tumor loses its internal vascularity and decreases in size, indicating effective treatment (Fig. 13). Some lesions initially enlarge as a result of edema, but most eventually reduce in size. Continued enlargement may signify true tumor growth. Additionally, long-term follow-up is recommended even in lesions with significant initial regression, as tumor growth has been reported in these cases.26,27

Differential Diagnosis of Choroidal Melanoma

Several pigmented and nonpigmented lesions can resemble choroidal melanoma. Ultrasonography can be valuable to diagnose and differentiate the more common simulating lesions (Table 2).

Circumscribed choroidal hemangioma

Uveal hemangioma most frequently affects the choroid and presents as a circumscribed or diffuse orange-red, mildly elevated lesion. Circumscribed tumors are sporadic, usually located in the posterior pole, and dome-shaped with a thickness less

Fig. 16. Leiomyoma. High-frequency ultrasound scan demonstrating ciliary body leiomyoma resembling a melanoma. (From Rundle P, Mudhar HS, Parsons MA, et al. Uveal myogenic, fibrous, and histiocytic tumors. In: Singh AD, Damato BE, Pe’er J, et al, editors. Clinical Ophthalmic Oncology. Philadelphia: Saunders-Elsevier; 2007. p. 312; with permission.)

Fig. 17. Disciform lesion. Longitudinal B-scan demonstrating an irregularly shaped and structured lesion in the macula.