RT Journal Article
SR Electronic
T1 Uptake quantification in the presence of attenuation correction defects due to MR coils
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 337
OP 337
VO 54
IS supplement 2
A1 Mark Ahlman
A1 Roberto Maass-Moreno
A1 Songtao Liu
A1 David Bluemke
YR 2013
UL http://jnm.snmjournals.org/content/54/supplement_2/337.abstract
AB 337 Objectives Attenuation correction (AC) may be problematic with PET-MR due to overlying MR coils, which are not represented in the µ-map. Our aim was to find and validate a procedure to recover quantitative accuracy in artery inflammation imaging. Methods Two cylindrical phantoms 12cm and 21cm in diameter containing 18FDG solution and a 68Ge solid mix (each 10 kBq/ml) were scanned (Siemens Biograph 16 PET/CT) at a single bed for 20 min without coils (control) followed by two different MR coils: a Siemens, mMR Body A-Tim, low attenuating coil (LAC) and a Siemens carotid coil (CC) of unknown attenuation. All images were reconstructed (Siemens TrueXTM, 3 iterations, 24 subsets, 256 matrix) using the µ-map from the control. Regions of interest (ROI) were placed where coil artifacts (CA) were most conspicuous and at the approximate anatomic depth of the human carotid a. and the nearby jugular v. to create carotid/jugular ratios (CJ). Compared to control, average% differences(±SD) in CA were obtained for LAC and CC. Compared to the ideal ratio of 1.0, %errors in the CJ were described (mean±SD). Results For the Large phantom, VAD %errors in the LAC and CC compared to control were 14.0%(2.0) and 6.5%(4.9). By contrast, the CJ ratios for the LAC and CC for the large phantom compared to control were 2.6%(0.35) and 2.4%(0.75). With no significant CA for the small phantom, CJ for LAC and CC had 1.0%(0.7) and 1.1%(0.9) error. Conclusions Both LAC and CC coil attenuation had significant effects on absolute quantification when their attenuation is not accounted for. Surprisingly; the effect of the PET-ready coils (LAC) was larger. Normalizing the carotid a. uptake using CJ resulted in deviations of less than 3% in the presence of coils. For quantification of arterial inflammation, these results suggest that trading absolute quantification for the described normalization procedure provides acceptably accurate quantification when AC is in question. Research Support Supported by the NIH intramural research program and the Imaging Sciences Training Program (ISTP).