Abstract
Magnetic resonance imaging (MRI) of pulmonary emboli obtained ex vivo, verified by immunohistochemistry, showed that platelet layers display brighter signal intensity than areas containing predominantly red blood cells (RBC) in T 1-weighted MRI. These results were surprising since platelets do not contain paramagnetic haemoglobin that would enhance magnetic relaxation. Our assumption was that the fibrin meshwork areas with entrapped RBC retain abundant extracellular space filled with serum, whereas platelets regroup into tight aggregates lacking serum, essentially mimicking solid tissue structure, rich with cellular proteins that enhance T 1-relaxation. Our hypothesis was examined by MRI and NMR relaxometry of in vitro RBC suspensions and sedimented platelets, as well as by MRI of model clots and pulmonary emboli obtained ex vivo. Pure sedimented platelets exhibited shorter proton spin lattice relaxation times (T 1 = 874 ± 310 ms) than those of venous blood of a healthy male with 40% haematocrit (T 1 = 1277 ± 66 ms). T 1-values of RBC samples containing high haematocrit (≥80%) resembled T 1 of platelet samples. In T 1-weighted spin-echo MRI echo time and repetition time (TE/TR = 10/120 ms) the ratio of signal intensities between a non-retracted whole blood clot (with a haematocrit of 35%) and a pure platelet clot was 3.0, and the ratio between a retracted whole blood clot with an estimated haematocrit of about 58% and a pure platelet clot was 2.6. We conclude that T 1-weighted MRI can discriminate between platelet layers of thrombi and RBC-rich areas of thrombi that are not compacted to a haematocrit level of ≥80%.
Similar content being viewed by others
Abbreviations
- RBC:
-
Red blood cell
- Ht:
-
Haematocrit
- MR:
-
Magnetic resonance
- MRI:
-
Magnetic resonance imaging
References
Blackmore CC, Francis CW, Bryant RG, Brenner B, Marder VJ (1990) Magnetic resonance imaging of blood and clots in vitro. Invest Radiol 25:1316–1324
Blinc A, Lahajnar G, Blinc R, Zidansek A, Sepe A (1990) Proton NMR study of the state of water in fibrin gels, plasma, and blood clots. Magn Reson Med 14:105–122
Blinc A, Keber D, Lahajnar G, Zupancic I, Zorec-Karlovsek M, Demsar F (1992) Magnetic resonance imaging of retracted and nonretracted blood clots during fibrinolysis in vitro. Haemostasis 22:195–201
Francis CW, Totterman S (1995) Magnetic resonance imaging of deep vein thrombi correlates with response to thrombolytic therapy. Thromb Haemost 73:386–391
Gupta RK (1987) NMR spectroscopy of cells and organisms. CRC Press, Boca Raton
Kozak M, Mikac U, Blinc A, Sersa I (2005) Lysability of arterial thrombi assessed by magnetic resonance imaging. Vasa 34:262–265
Meiboom S, Gill D (1958) Modified spin-echo method for measuring nuclear relaxation times. Rev Sci Instrum 29:688–691
Ruggeri ZM (1997) Mechanisms initiating platelet thrombus formation. Thromb Haemost 78:611–616
Savage B, Cattaneo M, Ruggeri ZM (2001) Mechanisms of platelet aggregation. Curr Opin Hematol 8:270–276
Stump DC, Mann KG (1988) Mechanisms of thrombus formation and lysis. Ann Emerg Med 17:1138–1147
Tratar G, Blinc A, Strukelj M, Mikac U, Sersa I (2004) Turbulent axially directed flow of plasma containing rt-PA promotes thrombolysis of non-occlusive whole blood clots in vitro. Thromb Haemost 91:487–496
Tratar G, Blinc A, Podbregar M, Kralj E, Balazic J, Sabovic M, Sersa I (2007) Characterization of pulmonary emboli ex vivo by magnetic resonance imaging and ultrasound. Thromb Res 120:763–771
Viereck J, Ruberg FL, Qiao Y, Perez AS, Detwiller K, Johnstone M, Hamilton JA (2005) MRI of atherothrombosis associated with plaque rupture. Arterioscler Thromb Vasc Biol 25:240–245
Weisel JW (2007) Structure of fibrin: impact on clot stability. J Thromb Haemost 5(Suppl 1):116–124
Acknowledgments
We thank Dr Dragoslav Domanovič from the Blood Transfusion Centre of the Republic of Slovenia for providing human plasma and platelet concentrate.
Author information
Authors and Affiliations
Corresponding author
Additional information
Regional Biophysics Conference of the National Biophysical Societies of Austria, Croatia, Hungary, Italy, Serbia, and Slovenia.
Rights and permissions
About this article
Cite this article
Vidmar, J., Serša, I., Kralj, E. et al. Discrimination between red blood cell and platelet components of blood clots by MR microscopy. Eur Biophys J 37, 1235–1240 (2008). https://doi.org/10.1007/s00249-008-0336-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00249-008-0336-6