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== MRI ==
== MRI ==
* MRI scan is helpful in the diagnosis of insulinoma in the case of failed CT.
* [[Magnetic resonance imaging|MRI]] scan is helpful in the diagnosis of [[insulinoma]] in the case of failed [[Computed tomography|CT.]]
* '''T1 C''' typically shows enhancement, although contrast enhancement may not improve [[tumor]] visualization.<ref name="pmid23590041">{{cite journal| author=Pongprasobchai S, Lertwattanarak R, Pausawasdi N, Prachayakul V| title=Diagnosis and localization of insulinoma in Thai patients: performance of endoscopic ultrasonography compared to computed tomography and magnetic resonance imaging. | journal=J Med Assoc Thai | year= 2013 | volume= 96 Suppl 2 | issue=  | pages= S187-93 | pmid=23590041 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23590041  }}</ref>


* MRI is superior in detecting insulinoma in that it has greater sensitivity currently ~85%. In a study of 21 insulinomas by Owen et al,the sensitivity was noted to be 94%.(19/21 cases).
* MRI is superior in detecting [[insulinoma]] and has greater [[Sensitivity (tests)|sensitivity]]. The sensitivity has increased to 94%.
* The 2 cases were of 5 and 7 mm size and in pancreatic tail.[1][2]
* Findings of [[Magnetic resonance imaging|MRI]] suggestive of [[insulinoma]] include:
* T1 and T2 relaxation times for islet cell tumor like insulinoma has lower protein and proton concentration time.[3] Abdominal MRI may be helpful in the diagnosis of insulinoma. Findings on MRI suggestive of Insulinoma include[4][3]:
* T1 typically shows enhancement, although contrast enhancement may not improve [[tumor]] visualization.<ref name="pmid23590041">{{cite journal| author=Pongprasobchai S, Lertwattanarak R, Pausawasdi N, Prachayakul V| title=Diagnosis and localization of insulinoma in Thai patients: performance of endoscopic ultrasonography compared to computed tomography and magnetic resonance imaging. | journal=J Med Assoc Thai | year= 2013 | volume= 96 Suppl 2 | issue=  | pages= S187-93 | pmid=23590041 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23590041  }}</ref>
* Low in signal intensity on fat suppressed T1-weighted images High on intensity on fat suppressed T2-weighted images independent of lesion size
* T1 and T2 relaxation times for [[Islet cell|islet-cell]] tumor-like [[insulinoma]] has lower protein and proton concentration time.
* Enhancement patterns are due to hypervascularity. Homogeneous enhancement is exhibited commonly in insulinoma, ring enhancement if they are larger than 2 cm.
* Homogeneous enhancement is exhibited commonly in insulinoma. Enhancement patterns are due to hypervascularity.
* 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]
* [[Metastasis|Metastatic]] lesions in [[lymph nodes]] are homogeneous when small and show ring enhancement if the [[tumor]] is more than 2 cm.
* MRI enables accurate location of the tumor in terms of resectability and involvement of vessels.[1][3]
[[File:Metastatic insulinomaGIF.gif|center|300px|thumb|MRI showing metastatic insulinoma, source: Case courtesy of Dr Maxime St-Amant, Radiopaedia.org, rID: 19080]]
[[File:Metastatic insulinomaGIF.gif|center|300px|thumb|MRI showing metastatic insulinoma, source: Case courtesy of Dr Maxime St-Amant, Radiopaedia.org, rID: 19080]]



Revision as of 15:01, 22 September 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];{AE}} Mohammed Abdelwahed M.D[2]

Overview

MRI scan is helpful in the diagnosis of insulinoma in the case of failed CT. It shows enhancement. 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 and has greater sensitivity. The sensitivity has increased to 94%.
  • Findings of MRI suggestive of insulinoma include:
  • T1 typically shows enhancement, although contrast enhancement may not improve tumor visualization.[1]
  • T1 and T2 relaxation times for islet-cell tumor-like insulinoma has lower protein and proton concentration time.
  • Homogeneous enhancement is exhibited commonly in insulinoma. Enhancement patterns are due to hypervascularity.
  • Metastatic lesions in lymph nodes are homogeneous when small and show ring enhancement if the tumor is more than 2 cm.
MRI showing metastatic insulinoma, source: Case courtesy of Dr Maxime St-Amant, Radiopaedia.org, rID: 19080


References

  1. Pongprasobchai S, Lertwattanarak R, Pausawasdi N, Prachayakul V (2013). "Diagnosis and localization of insulinoma in Thai patients: performance of endoscopic ultrasonography compared to computed tomography and magnetic resonance imaging". J Med Assoc Thai. 96 Suppl 2: S187–93. PMID 23590041.