Evaluation of Whole Body Diffusion- Weighted Imaging in the Staging and Treatment Response of Lymphoma Compared With Fluoride-Oxyglucose (FDG) PET/CT as a Reference Standard

Abstract

Introduction: Positron emission tomography/computed tomography (PET/CT) is currently considered
standard of practice for the management of lymphoma with sensitivity and specificity
approaching 100%. However, it is expensive, time-consuming and requires exposure to ionizing
radiation. Whole body-diffusion weighted imaging (WB-DWI), does not involve exposure
to ionizing radiation, is more widely available and can be performed within an acceptable time
frame. PET/CT will be used as a reference standard in the evaluation of the value of WB-DWI
in the initial staging and treatment response in patients with lymphoma.
Methods: Nine patients with newly diagnosed lymphoma and a pre-treatment PET/CT were
prospectively recruited. Patients were analyzed with both imaging modalities before treatment
initiation and at four-weeks post-completion of chemotherapy. The presence or absence of nodal
and extra-nodal involvement was independently assessed by two radiologists blinded to the
PET/CT findings. The PET/CT images were assessed by a single nuclear medicine physician.
Results: Compared to PET/CT, the overall sensitivity, specificity and accuracy of WB-DWI in
staging were 62%, 98% and 87% respectively and the overall specificity and accuracy for treatment
response were both 99%. Majority of false negative findings were a result of small nodes
which showed uptake on PET/CT but were either not identified or did not show restricted diffusion.
Further false negative and positive findings were due to reduced spatial resolution and
increased motion and susceptibility artefact on magnetic resonance imaging (MRI).
Conclusion: WB-DWI may be a viable alternative to PET/CT in the treatment response of
lymphoma. However, in terms of staging, PET/CT probably remains the imaging modality of
choice.