Single-Shot Turbo Spin-Echo Diffusion-Weighted Imaging for Retinoblastoma: Initial Experience

BACKGROUND AND PURPOSE: Retinoblastoma may exhibit variable hyperintensities on DWI, resulting in different values in the ADC maps, depending on their histology and cellularity. However, EP-based DWI has susceptibility artifacts and image distortions, which make DWI of the orbit a challenging technique. The aim of this study was to investigate the feasibility of single-shot turbo spin-echo (HASTE) DWI in the evaluation of children with retinoblastoma and to assess the value of ADC maps in differentiating viable and necrotic tumor tissue. MATERIALS AND METHODS: Two radiologists assessed conventional MR images, DWI, and ADC maps of 17 patients with retinoblastoma (n = 17 eyes). Non-EP DWI was performed by using a HASTE sequence with b-values of 0 and 1000 s/mm2. ADC values were measured for enhancing and nonenhancing tumor tissue. ADC maps were compared with histopathologic findings regarding tumor differentiation and viability. RESULTS: On DWI, vital tumor tissue showed hyperintensity with negligible intensity of surrounding vitreous. The difference in mean (range) ADC values between enhancing (1.03 [0.72–1.22] × 10−3 mm2 s−1) and nonenhancing (1.47 [0.99–1.80] × 10−3 mm2 s−1) parts of retinoblastoma was statistically significant (P < .0005). Nonenhancing tumor parts showed a significantly lower ADC compared with vitreous (2.67 [2.24–3.20]×10−3 mm2 s−1) (P < .0005) and subretinal fluid (2.20 [1.76–2.96] × 10−3 mm2 s−1) (P < .0005). Histopathologically, low ADC values (enhancing tumor part) correlated to viable tumor tissue, whereas intermediate ADC values (nonenhancing tumor parts) correlated to necrotic tumor tissue. CONCLUSIONS: HASTE DWI allowed adequate characterization of retinoblastoma, and ADC is a helpful tool to differentiate viable and necrotic tumor tissue and might be valuable in monitoring the response to eye-preserving therapies.