Objective: To describe the principal medical applications of spectral imaging.

Medical applications of spectral imaging in computed tomography (CT) rely on the basic principle that this technique allows a more precise material differentiation[1]. It is helpful in metal artifacts reduction or bone removal. Another use is renal stone composition determination [2].

Monoenergetic images at low keV provide enhanced density and reduced noise; hence, CNR and SNR are higher, with the additional advantage to decrease further more contrast medium doses and radiation exposure; at high keV, blooming artifacts are reduced, improving stenosis assessment in highly calcified patients in coronary CT angiography for instance. Moreover, atherosclerotic plaques composition becomes achievable, with the hope to identify vulnerable plaques[3].

The other main advantage is establishment of iodine maps. This can be used to generate virtual noncontrast images from enhanced images, i.e. with a reduction in radiation exposure; determining iodine concentration within an organ improves both sensibility and specificity of enhancements detection, for instance to distinguish between a tumor and a thrombus, between hemorrhage and enhancement, to detect endoleaks, or to follow-up on antiangiogenic therapies[4-6]. It is also key for a more robust perfusion quantification, leading towards functional CT imaging, in lungs for pulmonary embolism diagnosis, brain for stroke, cardiac for ischemia detection, or “body” in oncologic applications [7-10].

References:

1. McCollough CH, Leng S, Yu L, Fletcher JG. Dual- and Multi-Energy CT: Principles, Technical Approaches, and Clinical Applications. Radiology 2015;276:637–53.

2. Kulkarni NM, Eisner BH, Pinho DF, Joshi MC, Kambadakone AR, Sahani DV. Determination of renal stone composition in phantom and patients using single-source dual-energy computed tomography. J Comput Assist Tomogr 2013;37:37–45.

3. Danad I, Fayad ZA, Willemink MJ, Min JK. New Applications of Cardiac Computed Tomography: Dual-Energy, Spectral, and Molecular CT Imaging. JACC Cardiovasc Imaging 2015;8:710–23.

4. Kaza RK, Caoili EM, Cohan RH, Platt JF. Distinguishing Enhancing From Nonenhancing Renal Lesions With Fast Kilovoltage-Switching Dual-Energy CT. AJR Am J Roentgenol 2011;197:1375–81.

5. Hong YJ, Hur J, Kim YJ, Lee H-J, Hong SR, Suh YJ, et al. Dual-energy cardiac computed tomography for differentiating cardiac myxoma from thrombus. Int J Cardiovasc Imaging 2014;30:121–8.

6. Müller-Wille R, Borgmann T, Wohlgemuth WA, Zeman F, Pfister K, Jung EM, et al. Dual-energy computed tomography after endovascular aortic aneurysm repair: The role of hard plaque imaging for endoleak detection. Eur Radiol 2014;24:2449–57.

7. Thieme SF, Becker CR, Hacker M, Nikolaou K, Reiser MF, Johnson TRC. Dual energy CT for the assessment of lung perfusion—Correlation to scintigraphy. Eur J Radiol 2008;68:369–74.

8. So A, Hsieh J, Narayanan S, Thibault J-B, Imai Y, Dutta S, et al. Dual-energy CT and its potential use for quantitative myocardial CT perfusion. Journal of Cardiovascular Computed Tomography 2012;6:308–17.

9. Postma AA, Das M, Stadler AAR, Wildberger JE. Dual-Energy CT: What the Neuroradiologist Should Know. Curr Radiol Rep 2015;3:16–6.

10. Agrawal MD, Pinho DF, Kulkarni NM, Hahn PF, Guimaraes AR, Sahani DV. Oncologic Applications of Dual-Energy CT in the Abdomen. Radiographics 2014;34:589–612.