Blood pool agent

Blood pool agents (BPAs) are a class of magnetic resonance angiography contrast agents.[1] [2] Blood pool agents (also known as intravascular contrast agents) are differentiated from other contrast agents due to their high molecular weight and higher relaxivities.[3] Their large size prevents diffusion through the vascular epithelium and leakage into the interstitial space, and because of this they stay in the vascular system for a longer time period. Most contrast agents, leave the vascular system within a few minutes, however blood pool agents remain in the circulation for up to an hour, extending the window available for imaging. Longer image acquisition times allow better signal-to-noise ratio and improved image resolution.

Roles of blood pool agents

Due to their extended time in the circulatory system, blood pool agents can be used for delayed steady-state imaging, and additionally these results can be combined with first pass arterial imaging.[2][3] Their extended circulation time means that they are able to be used for both arterial and venous mapping. Additional uses include: detection of gastrointestinal bleeding; visualization of the vasculature associated with certain tumors; measuring tissue blood volume and perfusion; and detection of endovascular leaks (such as following stent-graft repair of an aortic aneurysm).

Classes of blood pool agents

Albumin-binding gadolinium complexes

This class of BPAs is based on the noncovalent binding of low molecular weight Gd3+-based complexes to human serum albumin. The first commercial agent to be approved in this class is gadofosveset trisodium[4] (also known as Vasovist®[5] or Ablavar®,[6] and previously known as MS-325[7]). Many clinical and case studies documenting the use of this BPA have been published,[8][9][10][11][12][13][14] and its efficacy in enhancing blood vessels visibility has been demonstrated.[15]

Gadocoletic acid[16] (Bracco SpA), also known as B-22956 and B22956/1, is a Gd-DTPA derivative that is currently in development, but has not yet been approved for clinical use.

Gadobenic acid (MultiHance®[17]) is sometimes categorized as a BPA; however, as it only binds weakly to albumin and because hepatobiliary uptake of this compound occurs, this contrast agent should not be classified as a BPA.

Polymeric gadolinium complexes

Polymeric Gd3+ chelates are large in size, which prevents leakage into the interstitial space, and provides long imaging windows. Several polymeric gadolinium-based BPAs are currently in development but have not yet been approved for clinical use: Gadomelitol[18] (Guerbet, France), also known as Vistarem® and P792 Gadomer-17[19] (Schering AG, Berlin, Germany) also known as Gd-DTPA-17, SH L 643 A.

References

  1. ↑ "MR Contrast Agents". 2014.
  2. 1 2 Blood Pool Agents
  3. 1 2 Geraldes CF, Laurent S, Classification and basic properties of contrast agents for magnetic resonance imaging, Contrast Media Mol Imaging, 2009;4:1-23.
  4. ↑ Ablavar (gadofosveset trisodium) injection
  5. ↑ VASOVIST (gadofosveset trisodium)
  6. ↑ Ablavar®
  7. ↑ MS-325. Magnetic Resonance - Technology Information Portal
  8. ↑ Wolf F, Plank C, Beitzke D, et al., Prospective evaluation of high-resolution MRI using gadofosveset for stent-graft planning: comparison with CT angiography in 30 patients, AJR Am J Roentgenol, 2011;197:1251-7
  9. ↑ Partovi S, Aschwanden M, Staub D, et al., Gadofosveset enhanced MR phlebography for detecting pelvic and deep vein leg thrombosis, Vasa, 2011;40:315-9
  10. ↑ Haneder S, Attenberger UI, Biffar A, et al., Gadofosveset: parameter optimization for steady-state imaging of the thoracic and abdominal vasculature, Invest Radiol, 2011;46:678-85
  11. ↑ Pfeil A, Betge S, Poehlmann G, et al., Magnetic resonance VIBE venography using the blood pool contrast agent gadofosveset trisodium-An interrater reliability study, Eur J Radiol, 2011;81:547-52
  12. ↑ Pedersen SF, Thrysoe SA, Paaske WP, et al., CMR assessment of endothelial damage and angiogenesis in porcine coronary arteries using gadofosveset, J Cardiovasc Magn Reson, 2011;13:10
  13. ↑ Yamashita T, Takahara T, Kwee TC, et al., Diffusion magnetic resonance imaging with gadofosveset trisodium as a negative contrast agent for lymph node metastases assessment, Jpn J Radiol, 2011;29:25-32
  14. ↑ Lambregts DM, Beets GL, Maas M, et al., Accuracy of gadofosveset-enhanced MRI for nodal staging and restaging in rectal cancer, Ann Surg, 2011;253:539-45
  15. ↑ McGregor R, Vymazal J, Martinez-Lopez M, et al., A multi-center, comparative, phase 3 study to determine the efficacy of gadofosveset-enhanced magnetic resonance angiography for evaluation of renal artery disease, Eur J Radiol, 2008;65:316-25
  16. ↑ Gadocoletic acid
  17. ↑ MultiHance®
  18. ↑ Gadomelitol
  19. ↑ Gadomer-17
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