Tomoelastography

Tomoelastography of the abdomen of a healthy volunteer and a patient
Tomoelastography of the abdomen; upper a healthy state, lower with malignancy.

Tomoelastography (from ancient Greek τόμος tomos, “slice” and elastography – imaging of viscoelastic properties) is a medical imaging technique that provides quantitative maps of the mechanical properties of biological soft tissues with high spatial resolution (called elastograms). It is an advancement of elastography[1][2] in that it generates unmasked maps of stiffness and viscosity across the entire field of view that can be captured with a given imaging modality. Medical ultrasound and magnetic resonance imaging (MRI) are the most commonly used imaging modalities for elastography. Classical elastography only measures stiffness in a limited region, such as at a depth of 6 cm in the liver or in a selected liver lobe, and thus cannot provide an overview of the adjacent tissues or organs. Tomoelastography, on the other hand, is a radiological imaging method that allows estimation of quantitative mechanical parameters of all organs and structures in the field of view.[3] Moreover, tomoelastography does not rely on a single, specific imaging modality. While it has been introduced and is mostly performed using magnetic resonance elastography (MRE),[2] tomoelastography can be extended to other imaging techniques as well.

Tomoelastography requires external driver systems, which can efficiently generate shear waves throughout the entire field of view including tissues deep within the body. Multiple drivers can be combined such that waves propagate from the surface into the body from different directions to enable full illumination of larger regions with shear waves. Tomoelastography often employs mechanical vibrations at several driving frequencies for multifrequency wave analysis in order to stabilize inverse problem solutions for viscoelasticity reconstructions. A standard way of multifrequency viscoelasticity reconstruction is based on phase gradient analysis of plane waves[4] whereas other methods employ solutions of the Helmholtz equation.[5][6][7] The feasibility of tomoelastography was first demonstrated in the human abdomen using multifrequency MRE, where it was possible for the first time to display stiffness values (quantified as shear wave speed in m/s) across the entire axial MRI slice.[4] Although the elastograms are quantitative maps, tomoelastography images, like other radiological images, are often presented in standard gray-scale which gives more perceptual contrast to the subtle nuances than the color-scale.

Applications

Currently, most applications of tomoelastography are based on MRI, which is why tomoelastography is often referred to as an advanced MRE technique. Multifrequency-MRE based tomoelastography has been used for the diagnosis of diffuse liver disease,[8][9][10] renal diseases such as renal allograft dysfunction,[11] lupus nephritis,[12] and immunoglobulin A nephropathy (IgAN).[13] In addition, tomoelastography has been used for cancer imaging. In the liver, viscoelastic parameters of lesions less than 1 cm in diameter could be quantified for diagnostic purposes.[14] Pancreatic cancer has been shown to be abnormally stiff compared to surrounding tissue, resulting in a large tumor contrast in elastograms.[15][16] In the prostate, tomoelastography has been able to distinguish cancer from benign lesions.[17]

References

  1. ↑ Lerner RM, Huang SR, Parker KJ (1990). ""Sonoelasticity" images derived from ultrasound signals in mechanically vibrated tissues". Ultrasound Med Biol. 16 (3): 231–9. doi:10.1016/0301-5629(90)90002-t. PMID 1694603.
  2. 1 2 Muthupillai R, Ehman RL (May 1996). "Magnetic resonance elastography". Nat Med. 2 (5): 601–3. doi:10.1038/nm0596-601. PMID 8616724. S2CID 5140184.
  3. ↑ Sack, Ingolf (2016). Principles and Applications of Magnetic Resonance Elastography. Somerset: John Wiley & Sons, Incorporated. ISBN 978-3-527-34008-8. OCLC 965775099.
  4. 1 2 Tzschätzsch H, Guo J, Dittmann F, Hirsch S, Barnhill E, Jöhrens K, Braun J, Sack I (May 2016). "Tomoelastography by multifrequency wave number recovery from time-harmonic propagating shear waves". Med Image Anal. 30: 1–10. doi:10.1016/j.media.2016.01.001. PMID 26845371.
  5. ↑ Papazoglou S, Hirsch S, Braun J, Sack I (April 2012). "Multifrequency inversion in magnetic resonance elastography". Phys Med Biol. 57 (8): 2329–46. doi:10.1088/0031-9155/57/8/2329. PMID 22460134.
  6. ↑ Honarvar M, Sahebjavaher R, Sinkus R, Rohling R, Salcudean SE (December 2013). "Curl-Based Finite Element Reconstruction of the Shear Modulus Without Assuming Local Homogeneity: Time Harmonic Case". IEEE Trans Med Imaging. 32 (12): 2189–99. doi:10.1109/TMI.2013.2276060. PMID 23925367. S2CID 5807358.
  7. ↑ Barnhill E, Davies PJ, Ariyurek C, Fehlner A, Braun J, Sack I (May 2018). "Heterogeneous Multifrequency Direct Inversion (HMDI) for magnetic resonance elastography with application to a clinical brain exam". Med Image Anal. 46: 180–188. doi:10.1016/j.media.2018.03.003. hdl:11693/49924. PMID 29574398. S2CID 4964009.
  8. ↑ Reiter R, Tzschätzsch H, Schwahofer F, Haas M, Bayerl C, Muche M, Klatt D, Majumdar S, Uyanik M, Hamm B, Braun J, Sack I, Asbach P (March 2020). "Diagnostic performance of tomoelastography of the liver and spleen for staging hepatic fibrosis". Eur Radiol. 30 (3): 1719–1729. doi:10.1007/s00330-019-06471-7. PMC 7033143. PMID 31712963.
  9. ↑ Marticorena Garcia SR, Althoff CE, Dürr M, Halleck F, Budde K, Grittner U, Burkhardt C, Jöhrens K, Braun J, Fischer T, Hamm B, Sack I, Guo J (February 2021). "Tomoelastography for Longitudinal Monitoring of Viscoelasticity Changes in the Liver and in Renal Allografts after Direct-Acting Antiviral Treatment in 15 Kidney Transplant Recipients with Chronic HCV Infection". J Clin Med. 10 (3): 510. doi:10.3390/jcm10030510. PMC 7867050. PMID 33535495.
  10. ↑ Hudert CA, Tzschätzsch H, Rudolph B, Bläker H, Loddenkemper C, Müller HP, Henning S, Bufler P, Hamm B, Braun J, Holzhütter HG, Wiegand S, Sack I, Guo J (April 2019). "Tomoelastography for the Evaluation of Pediatric Nonalcoholic Fatty Liver Disease". Invest Radiol. 54 (4): 198–203. doi:10.1097/RLI.0000000000000529. PMID 30444796. S2CID 53568878.
  11. ↑ Marticorena Garcia SR, Fischer T, Dürr M, Gültekin E, Braun J, Sack I, Guo J (September 2016). "Multifrequency Magnetic Resonance Elastography for the Assessment of Renal Allograft Function". Invest Radiol. 51 (9): 591–5. doi:10.1097/RLI.0000000000000271. PMID 27504796. S2CID 34327744.
  12. ↑ Marticorena Garcia SR, Grossmann M, Bruns A, Dürr M, Tzschätzsch H, Hamm B, Braun J, Sack I, Guo J (February 2019). "Tomoelastography Paired With T2* Magnetic Resonance Imaging Detects Lupus Nephritis With Normal Renal Function". Invest Radiol. 54 (2): 89–97. doi:10.1097/RLI.0000000000000511. PMID 30222647. S2CID 52286012.
  13. ↑ Lang ST, Guo J, Bruns A, Dürr M, Braun J, Hamm B, Sack I, Marticorena Garcia SR (October 2019). "Multiparametric Quantitative MRI for the Detection of IgA Nephropathy Using Tomoelastography, DWI, and BOLD Imaging". Invest Radiol. 54 (10): 669–674. doi:10.1097/RLI.0000000000000585. PMID 31261295. S2CID 195772720.
  14. ↑ Shahryari M, Tzschätzsch H, Guo J, Marticorena Garcia SR, Böning G, Fehrenbach U, Stencel L, Asbach P, Hamm B, Käs JA, Braun J, Denecke T, Sack I (November 2019). "Tomoelastography Distinguishes Noninvasively between Benign and Malignant Liver Lesions". Cancer Res. 79 (22): 5704–5710. doi:10.1158/0008-5472.CAN-19-2150. PMID 31551364.
  15. ↑ Marticorena Garcia SR, Zhu L, Gültekin E, Schmuck R, Burkhardt C, Bahra M, Geisel D, Shahryari M, Braun J, Hamm B, Jin ZY, Sack I, Guo J (December 2020). "Tomoelastography for Measurement of Tumor Volume Related to Tissue Stiffness in Pancreatic Ductal Adenocarcinomas". Invest Radiol. 55 (12): 769–774. doi:10.1097/RLI.0000000000000704. PMID 32796197. S2CID 221133340.
  16. ↑ Zhu L, Guo J, Jin Z, Xue H, Dai M, Zhang W, Sun Z, Xu J, Marticorena Garcia SR, Asbach P, Hamm B, Sack I (May 2021). "Distinguishing pancreatic cancer and autoimmune pancreatitis with in vivo tomoelastography". Eur Radiol. 31 (5): 3366–3374. doi:10.1007/s00330-020-07420-5. PMID 33125553. S2CID 225994738.
  17. ↑ Li M, Guo J, Hu P, Jiang H, Chen J, Hu J, Asbach P, Sack I, Li W (May 2021). "Tomoelastography Based on Multifrequency MR Elastography for Prostate Cancer Detection: Comparison with Multiparametric MRI". Radiology. 299 (2): 362–370. doi:10.1148/radiol.2021201852. PMID 33687285.
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