## 1 Introduction  
Oncological patients may require a number of computed tomography (CT) scans based on stand-alone techniques or in combination with integrated positron emission tomography (PET)/CT for diagnosis, staging and disease monitoring. Thus, there is an increasing interest in obtaining as much data as possible from each diagnostic procedure. Moreover, for patients with high probability of long-term survival, it is very important to assess cardiovascular risk, as oncological patients, in particular those undergoing radiotherapy and/or chemotherapy, are at high risk of cardiovascular events [1]. In the past, this risk was less evident because of the too short life expectancy of patients with already advanced disease at diagnosis [1]. However, with spread of early diagnosis and more efficient therapies, cardiotoxicity of cancer therapy and cardiac comorbidity are pivotal issues. Coronary artery calcification (CAC) and muscle mass evaluation have shown diagnostic and prognostic power in this context [2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21].  
Coronary artery calcification (CAC) has emerged as a predictive single cardiovascular risk marker in asymptomatic persons, adding cost effectiveness information beyond traditional cardiovascular risk factors. Therefore, CAC testing represents a reasonable option to risk-stratify cardiovascular impairment without increased costs [2; 3; 4; 5; 6; 7]. Because cardiovascular disease and cancer are leading causes of death, the evaluation for both with one procedure may improve the standard assessment of patients with malignancy without any additional exposure and cost.  
It has been also demonstrated that patients with advanced cancer and sarcopenia, defined by severe lowering of skeletal muscle mass, are more prone to experiencing adverse oncologic, surgical, and overall survival outcomes [8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21]. Hence, quantifying abdominal muscle mass in clinical practice is important in predicting clinical outcome, as enlightened by multiple studies [22; 23; 24; 25; 26; 27; 28]. Sarcopenia has a role in cancer as well as in non-malignant conditions. Several imaging modalities, including dual-energy X-ray absorptiometry, CT, magnetic resonance, and ultrasound, can be used to evaluate muscle mass and quality, providing data that may help in reaching the diagnosis of sarcopenia [29]. Muscle mass can be measured on unenhanced CT scan drawing regions of interest (ROIs) and using standardized Hounsfield unit (HU) thresholds (\(-\)29/+150) to obtain the cross-sectional area of the muscle [30].  
Two semiautomatic free independent software programs, Horos (Horos Medical Image software, version 3.3; [[https://horosproject.org](https://horosproject.org)]([https://horosproject.org](https://horosproject.org)); Horos Project, accessed on 26 January 2022) and LIFEx (www.lifexsoft.org, accessed on 27 January 2022), can be applied to an image set generated from any scanner to measure both CAC score and muscle mass, obtaining from a single examination different parameters in addition to those regarding the main indication. Horos is based upon OsiriXTM and other open source medical imaging libraries and is made available under the GNU Lesser General Public License, Version 3 (LGPL-3.0) [31; 32]. LIFEx is a freeware for radiomic feature calculation in multimodality imaging used to characterize tumor heterogeneity [30]. LIFEx is usable on operative systems Linux, Windows, and MacOS and is applied for its native use in texture analysis [33; 34; 35; 36], while Horos may be used in a generalized way. While this software may contribute to refining and personalizing treatment strategies, the agreement of CAC and muscle mass measurement performed via these two methods has not been previously evaluated. In this study, we compared these two approaches for the assessment of CAC score and muscle mass in patients undergoing whole-body PET/CT.