In PET/CT, quantitative evaluation of tumour metabolic activity is possible through standardized uptake values, usually normalized for body weight (BW) or lean body mass (LBM). Patient-specific LBM can be estimated from whole-body (WB) CT images. As most clinical indications only warrant PET/CT examinations covering head to midthigh, the aim of this study was to develop a simple and reliable method to estimate LBM from limited-coverage (LC) CT images and test its validity.
Head-to-toe PET/CT examinations were retrospectively retrieved and semiautomatically segmented into tissue types based on thresholding of CT Hounsfield units. LC was obtained by omitting image slices. Image segmentation was validated on the WB CT examinations by comparing CT-estimated BW with actual BW, and LBM estimated from LC images were compared with LBM estimated from WB images. A direct method and an indirect method were developed and validated on an independent data set.
Comparing LBM estimated from LC examinations with estimates from WB examinations (LBMWB) showed a significant but limited bias of 1.2 kg (direct method) and nonsignificant bias of 0.05 kg (indirect method).
This study demonstrates that LBM can be estimated from LC CT images with no significant difference from LBMWB.
aDepartment of Public Health and Primary Care, KU Leuven Kulak
bDepartment of Nuclear Medicine, AZ Groeninge, Kortrijk, Belgium
Correspondence to Hans Pottel, PhD, Department of Public Health and Primary Care, KU Leuven Kulak, Etienne Sabbelaan 53, 8500 Kortrijk, Belgium Tel: +32 562 46022; fax: +32 562 46999; e-mail: firstname.lastname@example.org
Received January 19, 2018
Received in revised form March 20, 2018
Accepted March 22, 2018