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Transsplenic Portal Scintigraphy Mebrofenin vs. 99m TcO 4 -

Transsplenic Portal Scintigraphy Mebrofenin vs. 99m TcO 4 -. James Montgomery March 29, 2010. Transsplenic Portal Scintigraphy. Two common radiopharmaceuticals for this procedure Na 99m TcO 4 99m Tc-Mebrofenin Dose 0.5 – 2.0 mCi in 0.2 – 0.5 mL volume

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Transsplenic Portal Scintigraphy Mebrofenin vs. 99m TcO 4 -

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  1. Transsplenic Portal ScintigraphyMebrofenin vs. 99mTcO4- James Montgomery March 29, 2010

  2. Transsplenic Portal Scintigraphy • Two common radiopharmaceuticals for this procedure • Na99mTcO4 • 99mTc-Mebrofenin • Dose • 0.5 – 2.0 mCi in 0.2 – 0.5 mL volume • Much smaller dose than PRPS (5 – 20 mCi)

  3. Transsplenic Portal Scintigraphy • Normal • Radioactivity travels from spleen and then seen in liver before the heart • 127461 • PSS • See the radioactive isotope travel from the spleen through the shunt vessel to the vena cava • Activity in the heart before the liver • 125132

  4. Technetium-99m • The first man-made element • Produced by atomic bombardment of Mo in 1937 • Principal mode of decay • Isometric transition – gamma ray emitter • Physical T1/2 • 6.02 hours • Principal photon energy • 140 keV • Production method • Generator (Mo-99)

  5. 99mTc-Mebrofenin • Lidocaine analog • Liver is the primary site of uptake and metabolism of lidocaine • High first pass extraction by the liver

  6. Advantages of Mebrofenin • Gives excellent images of the portal vein just like 99mTcO4- but gives additional information…hepatic function • High first pass extraction by the liver • >90% removed from blood pool on first pass • Will not pass through the liver to the heart • Retained in the liver and gradually cleared into the biliary system • Half-time clearance rate of 19 minutes • Dogs with PSS have a conspicuously different pattern from normal dogs

  7. Advantages of Mebrofenin • Evaluate size and morphology of the liver • Also evaluate function • In a normal dog, a static image at 5 minutes should have no activity anywhere except the liver and some residual in the spleen • Releasable at 1 hr

  8. Comparison

  9. TSPS - Mebrofenin

  10. Hepatic Morphology

  11. Sensitivity/Specificity • Additionally, able to accurately determine shunt termination 97% of the time • vs. 46% with PRPS • Able to accurately determine number of shunt vessels 91% of the time • vs. 71% with PRPS • Cannot diagnose Microvascular Dysplasia

  12. Portoazygous shunt

  13. Portocaval or Splenocaval

  14. Multiple acquired shunts

  15. UT • Do all of their TSPS with mebrofenin • $120 • Hardly ever do US shunt hunts • Only for resident practice • $210 • CT those that are questionable with scintigraphy • Go to surgery based on scitigraphic results

  16. NCSU • Abdominal US • $262 • Abdominal CT • $537 • TSPS – pertechnetate • $163 • TSPS – mebrofenin • $220

  17. Should we change our protocol?

  18. References • Nuclear Medicine Short Course Notes • Morandi F, et al. Transsplenic portal scintigraphy using 99mTc-Mebrofenin in normal dogs. Veterinary Radiology & Ultrasound 2007(48):286-91.

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