1394 Fig. 4 Björk-Shiley tilting disc in aortic position. This PHV type and the periprosthetic anatomy are not suitable for MDCT diagnostic assessment due to severe artefacts have significantly lower image quality than other PHVs and demonstrate severe artefacts which preclude diagnostic assessment. TTE, TEE and fluoroscopy are the primary imaging modalities used for PHV assessment [1]. Echocardiography provides both anatomical and functional information. Fluoroscopy provides information on the leaflet motion in patients with a mechanical PHV only. These imaging techniques are suitable to detect PHV dysfunction, but may fail to detect the pathologic anatomical substrate, especially if this is pannus tissue [2]. Girard et al. [2] evaluated a total of 92 patients that underwent reoperation for prosthetic aortic valve obstruction: 49 mechanical and 43 biological PHVs. In the mechanical PHV group, the mechanism of obstruction (pannus, thrombosis and PPM) was correctly identified by TTE and TEE in 5/49 (10%) and 17/35 (49%) of cases, respectively. In the biological PHV group, the mechanism of aortic valve obstruction was correctly diag- nosed in 27/43 63% (TTE) and 21/26 81% (TEE) of the cases, respectively. These findings illustrate that a conven- tional work-up of PHV dysfunction with echocardiography fails to detect the cause of dysfunction in upto 51% of mechanical PHVs. MDCT is emerging as a new diagnostic modality to evaluate PHV dysfunction. Figure 7 illustrates the potential diagnostic potential of MDCT in visualizing PHV dysfunction. Fig. 5 Carbomedics mechanical PHV in aortic position Eur Radiol (2011) 21:1390–1396 We previously reported our findings in 13 patients with 15 mechanical heart valves. MDCT imaging provided additional diagnostic findings to echocardiography and fluoroscopy in 9 of 13 patients (69%) [4]. MDCT is especially suitable to visualize pannus formation [5]. Our findings are supported by other groups. Tsai et al. [6] reported on 25 patients with 31 PHVs evaluated by TTE and MDCT. In 6 patients who underwent reoperation, MDCT findings were confirmed by intraoperative surgical findings. The image quality of PHVs was good, except for one Björk-Shiley tilting disc valve. In this prospective study diagnostic evaluation with TEE and fluoroscopy were lacking. Because some PHV types present with severe artefacts on CT, it is important to determine which PHV types are suitable for CT assessment. Data concerning the CT compatibility of PHV are scarce. Konen et al. [3] assessed leaflet motion in 20 patients with 23 PHVs using a 40- or 64-MDCT. This study included 18 bileaflet and 5 tilting disc valves. The image quality of the bileaflet mechanical valves was good to excellent whereas the image quality of the tilting disc valves (Björk-Shiley and Sorin monoleaflet PHVs) was significantly lower. In only two out of the five tilting disc valves the opening and closing angles could be measured. Tsai et al.[6] evaluated two tilting disc valves (Medtronic Hall and Björk-Shiley tilting disc) and found severe artefacts in the Björk-Shiley valve precluding diagnostic assessment. In our article titled “Multidetector-row computed tomography imaging charac- teristics of mechanical prosthetic valves” accepted for publication in the Journal of Heart Valve Disease, we examined the CT imaging characteristics of 5 different PHV types in a strictly controlled in vitro test set-up with valve leaflet motion but no annular motion. In this study modern PHVs manufactured of carbon and titanium (St Jude, ON-X, Medtronic Hall, Carbomedics) showed a good image quality. The Björk-Shiley valve, made of a cobalt chrome alloy, exhibited severe artefacts. Within the carbon titanium group, the Carbomedics and ON-X valve scored better than the St Jude and Medtronic Hall valves. These differences were attributed to valve design. Although this study demonstrated the suitability of CT for the assess- ment of PHV, the clinical application of CT could well