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Additional Findings
V/PSPECT allows diagnosis of several other diseases which have different scintigraphic appearances to PE, as detailed below [2, 3, 37].
Chronic Obstructive Pulmonary Disease (COPD)
In COPD matched areas with defects in ventilation and perfusion are observed. Ventilation defects are commonly more prominent than those of perfusion which leads to a pattern called reverse mismatch [19]. V/P SPECT frequently provides the first indication of COPD. Notably, V/P SPECT allows the diagnosis of PE even in the presence of COPD [32, 37], Figure 4 (click to enlarge).
Heart Failure
In left heart failure, redistribution of perfusion towards upper lung regions is well recognised since long [38]. Ventilation is usually not affected to the same degree as perfusion, which leads to a mismatch pattern. Importantly, this pattern does not conform to segmental anatomy of pulmonary arteries and it is not of a segmental character. Among patients referred for suspected PE, redistribution of perfusion to upper ventral regions indicated heart failure in 15% of cases [39]. The positive predictive value of the referred V/P SPECT pattern was 88%. Figure 5 shows V/P SPECT before and after treatment for heart failure (click to enlarge).
Pneumonia
Pneumonic regions lack ventilation while perfusion may partly be upheld. The most frequent finding is a matched defect [40]. In case of partly preserved perfusion ,reversed mismatch is observed [40, 41]. Preserved perfusion along the pleural border leads to a "stripe sign" [42, 43]. V/P SPECT frequently shows this sign because no overlaying structures obscure the images, Figure 6 (click to enlarge).The combination of PE and pneumonia is common [32]. Suspicion or knowledge that a patient has pneumonia does not contraindicate V/P SPECT. On the contrary, V/P SPECT may be life-saving in the most complex cases [44].
References
[2] M. Bajc, J.B.Neilly, M.Miniati, C. Schuemichen, M.Meignan, and B. Jonson, "EANM guidelines for ventilation/perfusion scintigraphy: part 2. Algorithms and clinical considerations for diagnosis of pulmonary emboli with V/P SPECT and MDCT," European Journal of Nuclear Medicine and Molecular Imaging, vol. 36, no. 9, pp. 1528-1538, 2009.
[3] M. Bajc, J. B. Neilly, M. Miniati, C. Schuemichen, M.Meignan, and B. Jonson, "EANM guidelines for ventilation/perfusion scintigraphy: part 1. Pulmonary imaging with ventilation/perfusion single photon emission tomography," European Journal of Nuclear Medicine and Molecular Imaging, vol. 36, no. 8, pp. 1356-1370, 2009.
[19] J. J¨ogi, B. Jonson, M. Ekberg, and M. Bajc, "Ventilation perfusion SPECT with 99mTc-DTPA versus Technegas: a head-to-head study in obstructive and nonobstructive disease," Journal of Nuclear Medicine, vol. 51, no. 5, pp. 735-741, 2010.
[32] M. Bajc, B. Olsson, J. Palmer, and B. Jonson, "Ventilation/Perfusion SPECT for diagnostics of pulmonary embolismin clinical practice," Journal of Internal Medicine, vol. 264, no.4, pp. 379-387, 2008.
[37] M. Bajc and B. Jonson, "Lung," in Clinical Nuclear Medicine, H. J. Biersack and L. Freeman, Eds., pp. 118-137, Springer, Berlin, Germany, 2007.
[38] W. F. Friedman and E. Braunwald, "Alterations in regional pulmonary blood flow in mitral valve disease studied by radioisotope scanning. A simple nontraumatic technique for estimation of left atrial pressure," Circulation, vol. 34, no. 3, pp. 363-376, 1966.
[39] J. Jögi, J. Palmer, B. Jonson, and M. Bajc, "Heart failure diagnostics based on ventilation/perfusion single photon emission computed tomography pattern and quantitative perfusion gradients," Nuclear Medicine Communications, vol.29, no. 8, pp. 666-673, 2008.
[40] D. J. Li, I. Stewart, K. A. Miles, and E. P. Wraight, "Scintigraphic appearances in patients with pulmonary infection and lung scintigrams of intermediate or low probability for pulmonary embolism," Clinical Nuclear Medicine, vol. 19, no.12, pp. 1091-1093, 1994.
[41] P. Carvalho and J. P. Lavender, "The incidence and etiology of the ventilation/perfusion reverse mismatch defect," Clinical Nuclear Medicine, vol. 14, no. 8, pp. 571-576, 1989.
[42] H. D. Sostman and A. Gottschalk, "The stripe sign: a new sign for diagnosis of nonembolic defects on pulmonary perfusion scintigraphy," Radiology, vol. 142, no. 3, pp. 737-741, 1982.
[43] H. D. Sostman and A. Gottschalk, "Prospective validation of the stripe sign in ventilation-perfusion scintigraphy," Radiology, vol. 184, no. 2, pp. 455-459, 1992.
[44] C. G. Olsson, M. Bajc, B. Jonson, and U. Albrechtsson, "Value of ventilation/perfusion SPECT detecting extensive pulmonary embolism in a patient with pneumonia," Thrombosis and Haemostasis, vol. 93, no. 5, pp. 993-994, 2005
