Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands.
Br J Radiol. 2012 Sep;85(1017):e616-21. doi: 10.1259/bjr/29602784.
Sutures with polytetrafluorethylene (PTFE) felt pledgets are commonly used in prosthetic heart valve (PHV) implantation. Paravalvular leakage can be difficult to distinguish from PTFE felt pledgets on multislice CT because both present as hyperdense structures. We assessed whether pledgets can be discriminated from contrast-enhanced solutions (blood/saline) on CT images based on attenuation difference in an ex vivo experiment and under in vivo conditions.
PTFE felt pledgets were sutured to the suture ring of a mechanical PHV and porcine aortic annulus, and immersed and scanned in four different contrast-enhanced (Ultravist®; 300 mg jopromide ml(-1)) saline concentrations (10.0, 12.0, 13.6 and 15.0 mg ml(-1)). Scanning was performed on a 256-slice scanner with eight different scan protocols with various tube voltage (100 kV, 120 kV) and tube current (400 mAs, 600 mAs, 800 mAs, 1000 mAs) settings. Attenuation of the pledgets and surrounding contrast-enhanced saline were measured. Additionally, the attenuation of pledgets and contrast-enhanced blood was measured on electrocardiography (ECG)-gated CTA scans of 19 patients with 22 PHVs.
Ex vivo CT attenuation differences between the pledgets and contrast-enhanced solutions were larger by using higher tube voltages. CT attenuation values of the pledgets were higher than contrast-enhanced blood in patients: 420±26 Hounsfield units (mean±SD, range 383-494) and 288±41 Hounsfield units (range 202-367), respectively.
PTFE felt pledgets have consistently higher attenuation than surrounding contrast-enhanced blood. CT attenuation measurements therefore may help to differentiate pledgets from paravalvular leakage, and detect paravalvular leakage in patients with suspected PHV dysfunction.
在人工心脏瓣膜（PHV）植入术中，常使用聚四氟乙烯（PTFE）毡垫缝线。由于在多层 CT 上两者均表现为高密度结构，瓣周漏与 PTFE 毡垫很难区分。我们通过离体实验和体内条件评估了在 CT 图像上基于衰减差异，能否区分毡垫与增强对比剂溶液（血液/盐水）。
PTFE 毡垫缝合到机械 PHV 缝线环和猪主动脉瓣环上，然后浸入并扫描四种不同增强（Ultravist®；300mg 钆喷替酸葡甲胺 ml(-1))盐水浓度（10.0、12.0、13.6 和 15.0mg ml(-1))。在 256 层扫描仪上使用八种不同的扫描方案进行扫描，具有不同的管电压（100kV、120kV）和管电流（400mAs、600mAs、800mAs、1000mAs）设置。测量毡垫和周围增强盐水的衰减。此外，在 19 例 22 个 PHV 患者的心电图（ECG）门控 CTA 扫描上测量了毡垫和增强血液的衰减。
使用更高的管电压时，毡垫与增强溶液之间的 CT 衰减差异更大。患者中毡垫的 CT 衰减值高于增强血液：420±26 亨氏单位（均值±标准差，范围 383-494）和 288±41 亨氏单位（范围 202-367）。
PTFE 毡垫的衰减始终高于周围增强血液。因此，CT 衰减测量值可能有助于区分瓣周漏与毡垫，并在怀疑 PHV 功能障碍的患者中检测瓣周漏。
