Combined role of lymphoscintigraphy, x-ray computed tomography, magnetic resonance imaging, and positron emission tomography in the management of lymphedematous disease

Abstract

Various imaging options exist for the evaluation of lymphedematous diseases. Although each imaging technique can be considered separately according to its principles and technical methodologies, the interface among these techniques has become indistinct in practice. Indeed, most of the apparatuses used today for lymphoscintigraphic (LySc) investigations utilize a combination of single photon emission computed tomography dual-headed devices (SPECT) with an X-ray computed tomography machine (CT or SPECT-CT). When positron emission tomography (PET) systems are considered, these are nearly always combined with CT devices. Although these CT scans may not conform to high radiological diagnostic standards, they allow easy fusion of the SPECT or PET images with other high-quality and high-resolution X-ray CT or magnetic resonance images, thus providing additional diagnostic data. The techniques can then be used in an orderly fashion: The interface among imaging techniques of lymphedema has become indistinct in clinical practice. Lymphoscintigraphy and/or SPECT-CT lymphoscintigraphy can be used and interpreted by taking into account the origin of the lymphedema and the clinical stage of the disease. SPECT-CT lymphoscintigraphy (after conventional three-phase planar acquisitions) is particularly useful in patients with chylous reflux or/and leakage. For the evaluation of lymphangiomas, lymphoscintigraphy is clinically useful in order to demonstrate the exact anatomical connections and the relationships among the lymphatic structures. In the management of secondary upper and/or lower lymphedemas, PET-CT can be useful when serum tumor markers are increasing or when the lymphedema becomes treatment-resistant. Heavily T2-weighted magnetic resonance imaging may have greater sensitivity, and the MRL image may have enhanced legibility for the detection of pathologically modified lymphatic vessels and accompanying complications. Magnetic resonance imaging also permits visualization of deep-lying, ordinarily inaccessible lymphatic vessels, such as those of the retroperitoneum in chylous reflux syndromes. MRI techniques offer good anatomical resolution, but are more expensive and have been used in only relatively small series of patients. The potential renal toxicity of the imaging contrast agent must be considered. On the other hand, lymphoscintigraphic techniques have been evaluated in very large series of patients and are relatively less expensive, but require radiation exposure and offer reduced anatomical resolution. Because MRI lymphangiography requires intradermal injections, its functional contributions may be considered to be lower than those of the lymphoscintigraphic techniques where the tracer is injected subcutaneously.