Beeldvorming bij long transplantatie en Restrictive Allograft Syndrome: nieuwe radiologische inzichten

Long-term survival after lung transplantation remains poor compared with other solid organ transplants, with a five-year survival rate of only 54%. This limited survival is largely attributable to the development of chronic lung allograft dysfunction (CLAD), also referred to as chronic lung rejection, which affects approximately 50% of patients within five years after transplantation. CLAD comprises of two main subtypes: bronchiolitis obliterans syndrome (BOS), characterized by an obstructive decline in pulmonary function, and restrictive allograft syndrome (RAS), which presents with a restrictive pulmonary function pattern. Annual follow-up with computed tomography (CT), preferably high-resolution CT (HRCT), is essential for the early detection and differentiation of CLAD subtypes, particularly RAS. In RAS, the transplanted lungs progressively develop fibrotic changes, predominantly involving the upper lobes. The first research chapter focuses on the application of photon-counting CT (PCCT) in the follow-up of lung transplant recipients. This patient population may particularly benefit from the superior spatial resolution of PCCT, as well as its potential for substantial radiation dose reduction. We compared subjective image quality between conventional energy-integrating detector CT (EIDCT) and PCCT using two PCCT protocols: a standard-dose protocol with optimal image quality (IQ100) and a low-dose protocol with significantly reduced radiation exposure (IQ40). This analysis was performed in a cohort of 100 lung transplant patients undergoing routine follow-up imaging. Prior to this PhD, we performed a study on the onset and progression of RAS on CT imaging and identified two distinct radiological subtypes: a typical upper-lobe-predominant fibrosis associated with characteristic pleural thickening, and a diffuse consolidation pattern that rapidly progresses to widespread fibrosis. Survival outcomes differed markedly between these subtypes, with a significantly poorer prognosis observed in the diffuse consolidation group. In patients with the upper-lobe fibrosis subtype, subtle reticulations were often detectable on imaging before the clinical diagnosis of RAS was established. In the second research chapter, we further expand the HRCT analysis in a cohort of 100 patients diagnosed with RAS, incorporating clinical and histopathological data. Previous studies have described specific histopathological patterns in RAS. In this large cohort study, we comprehensively assess HRCT features at disease onset and during progression, correlate imaging findings with clinical diagnosis and survival, and examine their relationship with established histopathological patterns.