PET/MRI for the Evaluation of Patients With Lymphoma: Initial Observations

Abstract

OBJECTIVE The objective of our study was to assess the role of recently introduced hybrid PET/MRI in the evaluation of lymphoma patients using PET/CT as a reference standard. SUBJECTS AND METHODS In this prospective study 28 consecutive lymphoma patients (18 men, 10 women; mean age, 53.6 years) undergoing clinically indicated PET/ CT were subsequently imaged with PET/MRI using residual FDG activity from the PET/ CT study. Blinded readers evaluated PET/CT (reference standard), PET/MRI, and diffusion-weighted imaging (DWI) studies separately; for each study, they assessed nodal and extranodal involvement. Each FDG-avid nodal station was marked and compared on DWI, PET/MRI, and PET/CT. Modified Ann Arbor staging was performed and compared between PET/MRI and PET/CT. The maximum standardized uptake value (SUVmax) on PET/MRI for FDG-avid nodal lesions was compared with the SUVmax on PET/CT. The apparent diffusion coefficient (ADC) for FDG-avid nodal lesions was compared to SUVmax on PET/MRI. RESULTS Fifty-one FDG-avid nodal groups were identified on PET/CT in 13 patients. PET/MRI identified 51 of these nodal groups with a sensitivity of 100%. DWI identified 32 nodal groups for a sensitivity of 62.7%. PET/MRI staging and PET/CT staging were concordant in 96.4% of patients. For the one patient with discordant staging results, disease was correctly upstaged to stage IV on the basis of the PET/MRI finding of bone marrow involvement, which was missed on PET/CT. DWI staging was concordant with PET/CT staging in 64.3% of the patients. The increased staging accuracy of PET/MRI relative to DWI was significant (p = 0.004). SUVmax measured on PET/MRI and PET/CT showed excellent statistically significant correlation (r = 0.98, p < 0.001). There was a poor negative correlation between ADC and SUVmax (r = −0.036, p = 0.847). CONCLUSION PET/MRI can be used to assess disease burden in lymphoma with sensitivity similar to PET/CT and can be a viable alternative for lymphoma staging and follow-up.

Potential Role of PET/MRI for Imaging Metastatic Lymph Nodes in Head and Neck Cancer

“…Heacock et al [42] showed that ADC is not correlated with SUV in lymphoma, supporting the idea that ADC represents additional independent information. Recently, Rakheja et al [89] reported that patients with progressive metastatic cancers have a higher ratio of SUV to ADC than do those with a partial treatment response.…”

“…It has been shown that the PET system integrated with the MRI scanner performs the same as the PET portion of a PET/CT for various cancers [40, 41]. For lymphoma, Heacock et al [42] found a strong correlation ( r = 0.98; p < 0 0.001) between the maximum standardized uptake value (SUV) measured on a hybrid PET/MRI scanner and those measured on PET/CT. Platzek et al [43] performed PET/MRI in the head and neck for initial staging after the clinical PET/CT without additional FDG injection and found that PET/MRI was able to detect 64% more metastatic lymph nodes, partly because of the increased uptake time.…”

Current Status of Hybrid PET/MRI in Oncologic Imaging

“…One study reported a head-to-head comparison of PET/MRI and PET/CT in 28 consecutive patients with lymphoma [73]. PET/MRI identified the same 51 FDG-avid nodal groups as PET/CT with 100% sensitivity and concordant staging in all cases, aside from one patient who was accurately upstaged on MRI due to bone marrow involvement identified on DWI and subsequently confirmed by biopsy that was not seen on PET/CT.…”

“…The available data show strong concordance between PET/CT and PET/MRI for lesion localization [73] (Melsaether et al, 2014 ISMRM annual meeting) and suggest that PET/MRI achieves improved T categorization for primary bone, head and neck, and soft-tissue tumors and a higher accuracy for metastatic lesion detection in the brain, liver, and bone [73–75]. One of the most promising applications of hybrid PET/MRI is for radiation treatment planning and differentiation of posttreatment changes from viable tumor in patients with brain tumors [76].…”

FDG Whole-Body PET/MRI in Oncology: a Systematic Review

“…One study reported that the sensitivity and specificity of PET/MR were 93.8 and 99.4 % based on the standard of reference [75]. Simultaneous PET/MR imaging identified nodal involvement of lymphoma with higher sensitivity than that of DWI (100 % vs. 62.7 %) and correctly diagnosed bone marrow involvement which was missed by PET/CT scan [76].…”