Abstract
Many efforts have been made to standardize the interpretation of 18F-FDG PET/CT in multiple myeloma (MM) with qualitative visual analysis or with quantitative metabolic parameters using various methods for lesion segmentation of PET images. The aim of this study was to propose a quantitative method for bone and bone marrow evaluation of 18F-FDG PET/CT considering the extent and intensity of bone 18F-FDG uptake: Intensity of Bone Involvement (IBI). Whole body 18F-FDG PET/CT of 59 consecutive MM patients were evaluated. Compact bone tissue was segmented in PET images using a global threshold for HU of the registered CT image. A whole skeleton mask was created and the percentage of its volume with 18F-FDG uptake above hepatic uptake was calculated (Percentage of Bone Involvement - PBI). IBI was defined by multiplying PBI by mean SUV above hepatic uptake. IBI was compared with visual analysis performed by two experienced nuclear medicine physicians. IBI calculation was feasible in all images (range:0.00–1.35). Visual analysis categorized PET exams into three groups (negative/mild, moderate and marked bone involvement), that had different ranges of IBI (multi comparison analysis, p < 0.0001). There was an inverse correlation between the patients’ hemoglobin values and IBI (r = −0.248;p = 0.02). IBI score is an objective measure of bone and bone marrow involvement in MM, allowing the categorization of patients in different degrees of aggressiveness of the bone disease. The next step is to validate IBI in a larger group of patients, before and after treatment and in a multicentre setting.
Highlights
Lytic bone lesions are reported in approximately 80% of myeloma multiple (MM) patients[1,2]
Many efforts have been attempted to standardize the interpretation of 18F-FDG PET/CT in MM, using qualitative visual analysis or quantitative metabolic parameters, such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG)[6,7,8,9]
Intensity of Bone Involvement (IBI) calculation was feasible in all 59 18F-FDG PET/CT images and ranged from 0.00 to 1.35 (Fig. 2)
Summary
Lytic bone lesions are reported in approximately 80% of myeloma multiple (MM) patients[1,2]. Hybrid image of positron emission tomography with 18F-fluordeoxyglucose and computed tomography (18F-FDG PET/CT) is one of the main methods for the evaluation of MM patients. It allows whole-body images, intra and extramedullary lesion detection, distinction between active lesions and scar or necrotic tissue and has been more sensitive than MRI in treatment assessment[3,4,5]. Many efforts have been attempted to standardize the interpretation of 18F-FDG PET/CT in MM, using qualitative visual analysis or quantitative metabolic parameters, such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG)[6,7,8,9]. CT-based bone segmentation is critical to obtain a standardized and reproducible quantitative assessment of bone 18F-FDG uptake, since the direct segmentation of PET images is difficult to standardize, especially in cases of diffuse involvement
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