Optimized whole-body positron emission tomography magnetic resonance imaging sequence workflow in pediatric Hodgkin lymphoma patients

Abstract

Rationale: Fluorodeoxyglucose positron emission tomography (PET)/ magnetic resonance imaging (MRI) might be the diagnostic method of choice for Hodgkin lymphoma patients, as it combines significant metabolic information provided by PET with excellent soft tissue contrast in MRI and avoids radiation exposure from computed tomography (CT). However, a major issue are longer examination times compared to PET/CT, especially for younger children needing anesthesia. Thus, a targeted selection of suitable whole-body MRI sequences is important to optimize the PET/MRI workflow. Methods: Initial PET/MRI scans of 84 EuroNet-PHL-C2 study patients from 13 international PET centers were evaluated. In each available MRI sequence, a total of five PET-positive lymph nodes were assessed. If extranodal involvement occurred, two splenic lesions, two skeletal lesions and two lung lesions were also assessed. A detection rate was calculated dividing the number of visible, anatomically assignable and measurable lesions in the respective MRI sequence by the number of all lesions. Results: Transverse relaxation time-weighted (T2w) transverse sequences with fat saturation (fs) yielded the best result with detection rates of 95% for nodal lesions, 62% for splenic lesions, 94% for skeletal lesions and 83% for lung lesions, followed by T2w transverse sequences without fs (86%, 49%, 16% and 59%, respectively) and longitudinal relaxation time-weighted (T1w) contrast-enhanced transverse sequences with fs (74%, 35%, 57% and 55%, respectively). Conclusion: T2w transverse sequences with fs yielded the highest detection rates and are well-suited for accurate whole-body PET/MRI in lymphoma patients. There is no evidence to recommend the use of contrast agents.