To assess agreement between 123I-metaiodobenzylguanidine (MIBG) and diffusion-weighted whole-body imaging with background body signal suppression (MR-DWIBS) in Neuroblastoma (NB), a retrospective review was performed on MIBG and MR-DWIBS paired scans acquired at our institutions in patients affected by pathologically proven NB (12 High Risk IV; 8 Low/intermediate Risk).
A total of 55 paired scans were acquired for 20 patients (7 girls and 13 boys; mean age at diagnosis 3 years, median 2 years, range 3 months -12 years).
Scans were obtained between 06/2009 and 07/2014 and paired scans were acquired within 30 days of each other without intercurrent therapy . All MIBG scans were acquired using 123I-MIBG with administered activities of 5.18 MBq/kg (0.14 mCi/kg), with a maximum dose of 370 MBq (10 mCi). All 55 123I-MIBG scans included 24-h whole-body and SPECT images according EANM GL (Eur J Nucl Med Mol Imaging 2010 37:2436–2446). MRI-Diffusion-weighted whole-body imaging with background body signal suppression (MR-DWIBS)were acquired. Semi-quantitative scoring systems for neuroblastoma described with the body divided into 12 sections to evaluate disease extent (Decarolis B, J Clin ONCol 31:944-951, March 2013) was applied to MIBG and MR scans. We also evaluated specificity, sensibility, overall accuracy, VPP and VPN of MR respect MIBG considered as gold standard.
MR DWIBS and MIBG results were congruent in 660 body regions on the 802 areas analyzed, with agreement in 701 areas (=0.663, P<0.0001). From 213 MIBG positive results analyzed disease was detected in 148 areas on DWIBS and from DWIBS 184 positive results MIBG agreed on 148 (Chi2355, P<0.0001). Negative concordant areas were 553. MR overall accuracy respect MIBG was 87 %; sensibility 70 %; specificity 94%; VPP 80%; VPN 89%. Siopen Semi-quantitative scoring systems for NB in both tests resulted superimposable (Rho of Spearman = 0,87, p< 0,0001).
DWIBS and 123I-MIBG results showed a high congruence. 123I-MIBG sensitivity is overall superior in the evaluation of NB lesions on the other hand MR shows very high specificity and VPN, therefore RM might provide important information in patients with tumors that weakly accumulate 123I-MIBG.

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