PET/MR in children. Initial clinical experience in paediatric oncology using an integrated PET/MR scanner

Abstract

Use of PET/MR in children has not previously been reported, to the best of our knowledge. Children with systemic malignancies may benefit from the reduced radiation exposure offered by PET/MR. We report our initial experience with PET/MR hybrid imaging and our current established sequence protocol after 21 PET/MR studies in 15 children with multifocal malignant diseases. The effective dose of a PET/MR scan was only about 20% that of the equivalent PET/CT examination. Simultaneous acquisition of PET and MR data combines the advantages of the two previously separate modalities. Furthermore, the technique also enables whole-body diffusion-weighted imaging (DWI) and statements to be made about the biological cellularity and nuclear/cytoplasmic ratio of tumours. Combined PET/MR saves time and resources. One disadvantage of PET/MR is that in order to have an effect, a significantly longer examination time is needed than with PET/CT. In our initial experience, PET/MR has turned out to be an unexpectedly stable and reliable hybrid imaging modality, which generates a complementary diagnostic study of great additional value.

Potential Pediatric Applications of PET/MR

“…Because ALARA (as low as reasonably achievable) principles should be considered for all imaging studies, one of the most important reasons for establishing PET/MR in pediatric patients is that PET/MR has a lower radiation burden than PET/CT (1,7,8). This fact may be especially significant for pediatric cancer patients, who may need to undergo repeated diagnostic imaging sessions.…”

“…A recommendation for a child-specific sequence protocol for PET/MR imaging, involving a combination of whole-body imaging to determine the spread of cancer and additional dedicated local sequences to provide a more detailed visualization in the region of the primary tumor, was made by Hirsch et al (8). On the basis of our experience with pediatric whole-body MR, a water-sensitive fast inversion recovery sequence is used for whole-body imaging, and T1-weighted gradient-echo sequences are used in the abdominal region because of a preferred shorter acquisition time.…”

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

“…The effective dose from PET/MR examination was about 20∼50 % that of PET/CT examinations [72][73][74]. Despite the SUV decrease in bone marrow in PET with MRbased attenuation correction method, lesion detection performance of PET/MR showed comparable to that of PET/CT (61 focal uptakes among 62 focal uptakes on PET/CT) [73].…”

Potential of PET-MRI for imaging of non-oncologic musculoskeletal disease

“…Minimizing radiation exposure to patients is critical to widespread application of nuclear medicine techniques to musculoskeletal imaging. As MRI does not produce any ionizing radiation, replacing CT with MRI can reduce the radiation dose to patients undergoing hybrid PET imaging by up to 80% (31). Further, MRI protocols (20-60 minutes) are often longer than the data collection time in one patient bed position in clinical PET-CT (3-5 minutes).…”