Eun-jung Kong, Presenter: Nothing to Disclose

Ihn-Ho Cho, Abstract Co-Author: Nothing to Disclose

Dixon MRI sequence is acquired for attenuation correction (AC) of the PET data in the integrated PET/MR. But, we sometimes failed to create umap because some beds were wrongly assigned of fat and water. Then, we investigated its clinical effects and related factors.

48 oncological patients(pt) [19 males, mean age: 59±11 y-o] underwent a single-FDG injection/dual-imaging protocol on a PET/CT- and subsequently a PET/MR-scanner (Biograph mMR) from 07. 12. 2012-08.13.2012. We compared their body mass index (BMI), lean body mass, fasting duration, volume of hydration and age of group A(pt had some wrong assign bed) and group B (right umap). And we also analyzed their SUV changes on wrong assign bed and correct assign bed by comparing with SUV on PET/CT.

All pt were scanned in 4 bed positions on PET/MR. The number of Group A is 10; 5 pt showed wrong assign in 1 bed (4 head and 1 abdomen), 3 pt had 3 beds (head-thorax-abdomen) and 2 pt had partial bed in neck. Group A and group B showed no statistically significant differences in their BMI, lean body mass, fasting duration and age then, the hydration was 260mL in group A and 448mL in group B(p>o.o5). In group A, we analyzed the ratio of SUV(Dixon AC)/SUV(CT AC) in 17 wrong assign region and 16 correct assign region. The ratio was 0.81 in wrong assign and 1.0 in correct assign (p=0.03)

Wrong assign was observed in approximately 21% of all pt. There is no software to correct this error after PET/MR acquisition and still no known cause for it. It is necessary to check the Dixon AC images before interpreting the results. The wrong assign does not change the presence of FDG uptake but it can make significant decrease of SUV in a wrong assign bed.

(dealing with integrated PET/MR) "dixon based MR attenuation correction could make error, It is necessary to check the Dixon AC images before interpreting.. The wrong assign does not change the presence of FDG uptake but it can make significant decrease of SUV in a wrong assign bed.  

Kong, E, Cho, I, Clinical Issue in Dixon—based PET/MR Attenuation Correction.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14019455.html