Comparison of PET-CT and magnetic resonance diffusion weighted imaging with body suppression (DWIBS) for initial staging of malignant lymphomas
Introduction
Hodgkin and non-Hodgkin lymphoma are the most common primary hematopoietic malignancies. Contrast-enhanced multidetector computed tomography (MDCT is the imaging technique most commonly used for staging patients in a prognostic group and for evaluating the follow-up. Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-d-glucose (FDG) (FDG) is highly sensitive and specific, and integrated PET/CT is now widely used in staging and evaluating treatment response [1]. However, there exist some limitations to the technique: (1) Cerebral lymphoma and some false hot intestinal spots are sometimes difficult to characterize due to physiologic accumulation of FDG; (2) PET/CT shows not only tumor-specific uptake, but also increased accumulation through various benign conditions such as inflammation or red cell regeneration; (3) The method is irradiant even if it is widely accepted that the benefits of proper staging using PET/CT outweigh its disadvantages [2].
Diffusion-weighted magnetic resonance imaging noninvasively probes random microscopic motion of water molecules in the body. Because of their high cellularity and elevated nuclear-to-cytoplasm ratio, lymphomas have relatively high signal intensity on DWI compared to normal tissues [3]. Lymphomas also have lower apparent diffusion coefficients (ADC) than other tumor types in different body regions [4]. Associated with background body signal suppression, diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) provides homogeneous fat suppression and thereby helps to visualize the spread of the disease at first glance [5]. In addition, the high signal-to-noise ratio obtained allows high b value, which enhances specificity in detection of high cellularity. However, to date there are very few reports on the possible interest of DWIBS in cases of lymphoma [6], [7], [8].
In this prospective study, we wish to compare the performance of DWIBS and PET/CT for evaluation of lymphomas in pre-therapeutic staging.
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Patients
All patients with aggressive lymphoma newly diagnosed between June 2008 and October 2009 were eligible for this prospective study provided that they were adults with histological proven malignant lymphoma requiring pre-treatment staging. Exclusion criteria were applied to patients with other malignancies or hematological disorders and contraindications to MRI, such as claustrophobia and implanted pacemakers or neurostimulators.
The study was approved by the Ethics Committee of our hospital and
Results
345 lymph node regions (15 regions per patient) were evaluated. With combined size and ADC analysis, DWIBS and PET/CT results in 333 regions showed excellent agreement (κ = 0.97, P < 0.0001). Sensitivity compared to PET/CT was 95% and specificity was 97% (Table 2). On DWIBS, seven false-positive regions (2 cervical, 2 axillary, 2 iliac and 1 femoral nodes) and five false negative regions (2 mediatinal and 3 pulmonary hilary nodes) were observed. Therefore, positive and negative predictive value
Discussion
This study shows that whole-body DWIBS can be used to stage patients with malignant lymphoma. From size-based analysis of lymph node and ADC measurement, our results show excellent agreement between DWIBS and PET/CT as regards both lymph node and organ involvements. DWIBS reflects tissue structure and cellularity, and may be complementary to FDG-PET, which indicates glucose metabolic activity and disease aggressiveness but this relationship must be evaluated in further studies.
Several works
Conflicts on interest
The authors have no conflicts of interest.
Acknowledgements
The authors would like to thank Philips Health Care for their technical supports for using the whole body diffusion sequence and the Pr Catherine Cheze le Rest and the Dr Francois Salmon for their help in the reviewing procedure.
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