PET/MRI as Effective as PET/CT for Pediatric Tumors

Positron emission tomography plus MRI provide equivalent lesion detection rates to PET/CT in pediatric patients with solid tumors, according to an article published in the journal Radiology.

Researchers from Germany performed a prospective study to compare the use of PET/MRI and PET/CT for lesion detection and interpretation, quantification of fluorine 18 (18F) fluorodeoxyglucose (FDG) uptake, and accuracy of MR-based PET attenuation correction among this population.

Nine boys and nine girls (median age 14) participated in the study. The 18F-FDG PET/CT and 18F-FDG PET/MR data were acquired sequentially on the same day for all patients, and 20 examinations were performed overall.[[{"type":"media","view_mode":"media_crop","fid":"28269","attributes":{"alt":"","class":"media-image media-image-right","id":"media_crop_1434702196071","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"2850","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 253px; width: 250px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"A–D, Images depict bone marrow infiltration in an 11-year-old female patient with neuroblastoma. C, Coronal STIR image shows bone marrow infiltration of the left femur (arrows) not visible at, A, CT. B, PET/CT and, D, PET/MR images show a relatively decreased FDG uptake in the involved area (arrows) compared with the adjacent physiologically activated bone marrow. Image courtesy of Radiology. ©RSNA, 2014.","typeof":"foaf:Image"}}]]

The researchers measured PET standardized uptake values (SUVs), which were quantified with volume of interest measurements in lesions and healthy tissues. The MR-based PET attenuation correction was compared with CT-derived attenuation maps (µ-maps). Lesion detection was assessed with separate reading of PET/CT and PET/MR data. Estimates of radiation dose were derived from the applied doses of 18F-FDG and CT protocol parameters.

The results showed that both PET/MRI and PET/CT provided similar lesion detection rates, and PET/MRI offered a significant radiation dose reduction (73%) over PET/CT. “Apart from drawbacks of MR-based PET attenuation correction in osseous structures and lungs, similar SUVs were found on PET images corrected with CT-based µ-maps (13.1% deviation of SUVs for bone marrow and less than 5% deviation for other tissues),” wrote the authors. There were 61 areas of focal uptake on PET/MRI versus 62 areas on PET/CT images. The advantages were particularly seen in the soft-tissue regions.

The researchers concluded that use of PET/MRI was feasible among pediatric oncology patients, and provided equivalent lesion detection rates, along with lower radiation exposure.