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Imaging


some extent longitudinal assessment of disease activity. Major downsides of whole-body CT are its availability, higher costs and radiation exposure compared with X-ray films. Limited soft tissue contrast and detection of extramedullary lesions are drawbacks compared with magnetic resonance imaging (MRI). Furthermore, the application of iodine- based contrast agents to increase sensitivity should not be considered in MM patients because of the increased risk of renal failure. However, given the many advantages, low-dose whole-body CT has replaced skeletal survey in our clinical practice and in most European, and some Northern American, centres.


PET/CT


Application of radiotracers such as 18F-fluorodeoxyglucose (FDG) to visualise increased glucose metabolism in MM cells increases sensitivity and specificity of CT images when combined with modern hybrid techniques such as PET/CT.5


In addition to conventional


morphological imaging, the information about tumour cell viability improves detection of bone lesions and has prognostic implications: increasing numbers of FDG-avid focal lesions are


MRI


Although mineralised bone cannot be visualised on MRI, its role for imaging MM has increased over recent years. Due to superior soft tissue contrast compared


"Skeletal survey has largely been replaced by computed tomography"


associated with shortened progression- free and overall survival. Furthermore, detection of residual disease activity after therapy in longitudinally performed PET/ CT translates into adverse outcome.11 Because methods to monitor residual disease after primary therapy gained importance over the last years, advanced imaging modalities such as FDG-PET/CT might contribute to risk-adapted therapy in MM as it has in other diseases, such as Hodgkin’s lymphoma.12


However, data on


PET/CT in MM are still limited and there is no widespread availability of hybrid scanners, at least in European countries. We therefore endorse the inclusion of patients in PET/CT studies to clarify its role in MM.


with X-ray and CT, MRI has the highest sensitivity for detection of intra- and extramedullary growth,4


without


Pathological patterns of bone marrow involvement that can be found in different frequencies among all stages of MM13


additional radiation exposure. Typical changes in signal intensity upon malignant plasma cell infiltration are signal decay in T1-weighted images and signal increase in T2-weighted sequences.9


include diffuse infiltration and focal lesions. The presence of diffuse marrow infiltration and focal lesions is associated with adverse outcome in patients with symptomatic disease.14,15


The underlying


biological mechanisms that lead to such pathological MRI patterns in some MM patients remains to be clarified. However, studies have correlated findings from MRI to the presence of adverse cytogenetic abnormalities15


and there are


efforts to combine data from gene- expression profiling with MRI.16


Because


MRI enables the assessment of bone marrow infiltration before bone destruction has occurred, it holds promise for imaging patients with asymptomatic plasma cell disease such as MGUS17 SMM.18


and


For both precursor diseases, the presence of more than a single focal


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