Insulinoma MRI

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Amandeep Singh M.D.[2]

Overview

MRI has better sensitivity than CT scan. It is still considered as the second line of investigation due to cost and availability. Insulinoma shows low intensity on T1 weighted and high intensity on T2 weighted signals, having better visualization on T1 and T2 weighted images with fat suppression. They exhibit typically homogenous enhancement when small and ring enhancement when more than 2 cm. A similar pattern is seen in metastatic lesion as of primary tumor.

MRI

MRI is superior in detecting insulinoma in that it has greater sensitivity of approximately 85%. In a study of 21 insulinomas by Owen et al, the sensitivity was noted to be 94%.(19/21 cases). The 2 cases were of 5 and 7 mm size and in the pancreatic tail.[1][2]

MRI Insulinoma- Case courtesy of Dr Andrew Dixon, Radiopaedia.org, rID: 10407
  • Abdominal MRI may be helpful in the diagnosis of insulinoma. Findings on MRI suggestive of Insulinoma include:[4][3]
    • Low in signal intensity on fat-suppressed T1-weighted images.
    • High on intensity on fat-suppressed T2-weighted images independent of lesion size.
    • Enhancement patterns are due to hypervascularity. Homogeneous enhancement is exhibited commonly in insulinoma, ring enhancement if they are larger than 2 cm.
    • Same pattern can be seen in metastatic lymph node as of the primary; homogeneous when small and ring enhancement if the tumor is more than 2 cm.
  • Modern MRI has rapid tri-phasic, breath held T1 rapid gadolinium-enhanced sequences which help to reduce artifacts produced by motion.[1][3]
  • MRI enables accurate location of the tumor in terms of resectability and involvement of vessels.[1][3]

References

  1. 1.0 1.1 1.2 Owen NJ, Sohaib SA, Peppercorn PD, Monson JP, Grossman AB, Besser GM; et al. (2001). "MRI of pancreatic neuroendocrine tumours". Br J Radiol. 74 (886): 968–73. doi:10.1259/bjr.74.886.740968. PMID 11675319.
  2. Thoeni RF, Mueller-Lisse UG, Chan R, Do NK, Shyn PB (2000). "Detection of small, functional islet cell tumors in the pancreas: selection of MR imaging sequences for optimal sensitivity". Radiology. 214 (2): 483–90. doi:10.1148/radiology.214.2.r00fe32483. PMID 10671597.
  3. 3.0 3.1 3.2 3.3 McAuley G, Delaney H, Colville J, Lyburn I, Worsley D, Govender P; et al. (2005). "Multimodality preoperative imaging of pancreatic insulinomas". Clin Radiol. 60 (10): 1039–50. doi:10.1016/j.crad.2005.06.005. PMID 16179163.
  4. Noone TC, Hosey J, Firat Z, Semelka RC (2005). "Imaging and localization of islet-cell tumors of the pancreas on CT and MRI". Best Pract Res Clin Endocrinol Metab. 19 (2): 195–211. doi:10.1016/j.beem.2004.11.013. PMID 15763695.

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