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Introduction Interstitial lung disease (ILD) in systemic sclerosis (SSc) is the leading cause of morbidity and mortality, yet on CT it remains challenging to distinguish active inflammation (ground-glass) from established fibrosis, but Photon-counting CT (PC-CT), a novel imaging technology with higher spatial resolution and reduced radiation exposure, may improve this discrimination. Primary cardiac involvement, is also common but often underdiagnosed, as cardiac magnetic resonance (CMR), is not routinely performed. Consequently, the interplay between pulmonary and cardiac manifestations remains poorly defined.Material and Methods We aimed (1) to evaluate concomitant lung and heart involvement in systemic sclerosis through a comprehensive multimodal imaging approach, and (2) to compare photon-counting CT (PC-CT) with standard-of-care high-resolution CT (HRCT) in the quantification of ILD. In this prospective study, all enrolled patients underwent PC-CT, HRCT, cardiac magnetic resonance (CMR), coronary CT, and pulmonary function tests (PFTs). Descriptive analyses and Spearman’s correlations were performed.Results We enrolled 30 patients with defined SSc, 16 with limited cutaneous (lcSSc, 53%) and 14 with diffuse cutaneous disease (dcSSc, 47%). Autoantibody analysis showed anti-Scl70 in 70%, anticentromere in 13%, and rarer specificities (RNAP III, fibrillarin, PM/Scl) in 3% each. Regarding objective 1, there was a high prevalence of concomitant abnormalities: most patients demonstrated both ILD changes on CT and evidence of primary myocardial involvement on CMR. Specifically, increased extracellular volume (ECV) was observed in 96% (diffuse interstitial fibrosis), prolonged T1 mapping in 32% (early fibrotic remodeling), elevated T2 mapping in 68% and STIR hyperintensity (myocardial edema/inflammation), and late gadolinium enhancement (LGE) in 50% (focal replacement fibrosis). RV dilation (EDV/BSA >69 ml/m 2) occurred in 86%, while reduced LVEF and RVEF were each observed in 7%. Larger RV volumes and augmented myocardial tissue markers (ECV, T2 mapping) were associated with loss of normal parenchyma, while RV dilation is also linked to increased ground-glass and fibrosis burden (tab 1 and 2). Regarding objective 2, PC-CT consistently measured lower lung volumes compared with HRCT but globally detected slightly less fibrosis (3.0% vs 3.5%, p<0.001) and relatively more ground-glass. This trend was most evident in patients with shorter disease duration, suggesting greater sensitivity to early inflammatory changes (tab3).Conclusions In SSc-ILD, combined imaging showed that primary cardiac involvement is frequent and closely linked to parenchymal loss and fibrotic burden. Importantly, RV dilation—an established negative prognostic marker—was associated with both lung and myocardial alterations. PC-CT, with reduced radiation dose and higher resolution, may complement HRCT by highlighting inflammatory versus fibrotic components.Abstract P.114 Table 2Abstract P.114 Table 1Abstract P.114 Table 3