Pediatric oncologic PET/MR shows promise

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Images are shown that were interpreted at PET as being negative for paravertebral metastasis in a 17-year-old female patient with hepatocellular carcinoma. PET fusion images are shown on the right-hand side.
Source: Radiology: 13173210.1148/radiol.14131732

Pediatric oncologic PET/MR is a promising modality for the clinical work-up of pediatric malignancies as it performs comparably to PET/CT and provides significantly reduced radiation exposure, according to a study published online May 31 by Radiology.

While 18 (18F) fluorodeoxyglucose (FDG) PET/CT is useful in staging and stratifying pretreatment risk of solid tumors in pediatric patients, whole-body MRI has demonstrated utility in accomplishing the same tasks through radiation-less means. The advent of PET/MR imaging calls for evaluation of the modality in the context of diagnostic accuracy for children by directly comparing the technology with PET/CT. Lead author Jürgen F. Schäfer, MD, of Eberhard-Karls-University Tübingen in Germany, and colleagues compared the two in terms of lesion detection and interpretation, quantification of 18F-FDG uptake and accuracy of MR-based PET attenuation correction in pediatric patients with solid tumors.

The prospective study included 20 whole-body 18F-FDG PET/CT and 18F-FDG PET/MR exams that were performed in 18 pediatric patients between the ages of 11 and 17. The researchers quantified PET standardized uptake values (SUVs) with volume of interest measurements in lesions and healthy tissues. MR-based PET attenuation correction was compared with CT-derived attenuation maps (µ-maps) and lesion detection was assessed with separate readings of PET/CT and PET/MR data.

PET SUVs showcased strong correlations between PET of PET/CT and PET of PET/MR. Although there were drawbacks associated with MR-based PET attenuation correction in osseous structures and lungs, similar SUVs were discovered on PET images correct with CT-based µ-maps, with a 13.1 percent deviation of SUVs for bone marrow and less than five percent deviation for other tissues.

The lesion detection rate with PET/MR imaging was equal to that with PET/CT, as there were 61 areas of focal uptake on PET/MR images and 62 areas on PET/CT images. Schäfer and colleagues found PET/MR’s advantages especially evident in soft-tissue regions. Additionally, PET/MR had a 73 percent dose reduction in comparison to PET/CT.

“As expected, additional diagnostic information was obtained with MR imaging data in areas of soft tissue,” wrote Schäfer and colleagues. “Furthermore, our results imply reliable PET quantification in PET/MR imaging, apart from the described drawbacks of MR-based attenuation correction. Taken together, our results suggest that PET/MR imaging is a promising modality for pediatric oncology with intrinsically lower radiation exposure than PET/CT and should be considered for juvenile patients wherever available.”