## 1 Introduction  
Transcatheter pulmonary valve replacement (TPVR) is a well-established alternative therapeutic approach for patients with right ventricular outflow tract (RVOT) dysfunction, the majority of whom are young and suffer from congenital heart defects or have had multiple previous cardiac surgeries [1, 2]. Recent studies show that, in terms of survival and freedom from reintervention or surgery, the outcomes of TPVR are comparable with those of surgical conduit/valve replacement to manage RVOT dysfunction across a wide age range [3, 4]. Similar to transcatheter aortic valve replacement (TAVR), cardiac computedtomography angiography (C-CTA) plays a crucial role in the characterization of the morphology, distensibility, and compliance of the RVOT prior to TPVR, since inaccurate sizing can complicate the procedure and cause device-related complications, such as embolization and paravalvular leak (PVL) [5, 6]. Technological developments in three-dimensional (3D) and four-dimensional (4D) C CTA have opened the door to a novel method for the personalized planning of transcatheter heart valve implantation for patients with structural heart valve diseases [7, 8, 9]. Cross-sectional imaging with 3D and 4D C-CTA is critical to determine patients' suitability for TPVR; knowledge of RVOT anatomy, the proximity of the left coronary artery to the native pulmonary root, and the distensibility of the RVOT are indispensable for TPVR [10, 11]. In addition to this, 3D and 4D C-CTA can support the identification of candidate percutaneous access routes, including the transfemoral, transjugular, and subclavian routes, and answer key anatomical questions. Furthermore, the landing zone--the ideal implantation site for TPVR--can protect the stented pulmonary valve (PV) from PVL, migration, and coronary compression. To create an accurate 4D segmentation of the landing zone anatomy at the RVOT, CT datasets should undergo segmentation where the personalized CT data are assigned to a region of interest to generate the 4D structures in synchronization with the heart rate. A previous study showed that the RVOT's morphology and size can vary significantly throughout the entire cardiac cycle, and so perimeter- and cross-sectional area-based measurements have proven more reliable than PV annulus diameters alone [12]. Additionally, the necessity of 4D C-CTA is emphasized by [PERSON] and colleagues, who encourage taking measurements for the landing zone both during end-systole and end-diastole phases [13]. However, in current traditional clinical and preclinical settings, the resulting 4D CT data are frequently transformed into 3D data for manual quantification and visual evaluation, which can only show static information. Furthermore, anatomical 4D segmentations are unable to fully depict the characteristics of the RVOT adjacent to the aortic root during the course of the cardiac cycle, even with 4D information. Yet, the 4D dynamic volumes of the right ventricle, implanted stent, and landing zone, which are crucial for the quantitative interpretation of TPVR, are only partially illustrated by the available data. In addition to the 4D anatomical segmentation, the angle between the RVOT and the main pulmonary artery can cause the measuring lines to not fully align with the landing zone planes (e.g., the annular plane or sinothular junction plane), which can result in incorrect landing zone measurements. The 2D properties of the STJ plane, the sinus plane and the pulmonary valve annular plane, are defined by three points at each level--the three commissures, the petaline peak of the sinuses, and the nadir of the pulmonary valve--instead of 3D properties, which could lead to inaccurate landing zone measurements. Multi-planar measurements are often employed in clinical practice to assess the RVOT before TPVR, but due to their 3D properties, planes may be positioned incorrectly in anatomical segmentations.