Department of Radiology, Dr. Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital, Istanbul, Turkey.
Heart Lung Circ. 2010 Apr;19(4):228-33. doi: 10.1016/j.hlc.2009.11.009. Epub 2010 Feb 7.
Tilting of the Günther-Tulip filter may be responsible for failure or difficulty to retrieve. Assessment of the filter tilt can be difficult when only AP imaging is available. This study is performed in vitro to develop a simple method to assess the Günther-Tulip filter for tilting.
A model consisting of a plastic tube was used to simulate vena cava. A Günther-Tulip filter was placed centred or tilted within the tube at various positions and radiograms were taken in AP, lateral, and craniocaudally angled projections. The images were analysed to determine the actual degree of tilt, the distance between the limb hooks on AP radiograms and the craniocaudal angulation degree needed to align the limb hooks linearly.
When the filter was centred or tilted laterally, all limb hooks of the filter were aligned linearly on AP radiograms. When the filter was tilted in AP or oblique direction, linear alignment of the limb hooks was lost and the ventral and dorsal limb hooks showed separation on AP projection. The amount of separation and the craniocaudal angles to align the filter hooks corresponded to actual tilt angles.
Loss of linear alignment of limb hooks in AP radiograms may suggest the presence of tilt in the AP plane. Significant separation of limb hooks should be alarming for significant filter tilt, and further evaluation of the filter position by CT scan or lateral cavogram should be obtained prior to planning of the retrieval.
Günther-Tulip 过滤器的倾斜可能是导致其失败或难以取出的原因。当仅可获得前后位成像时，评估过滤器的倾斜度可能较为困难。本研究旨在体外开发一种简单的方法来评估 Günther-Tulip 过滤器的倾斜度。
使用一个由塑料管制成的模型来模拟腔静脉。将 Günther-Tulip 过滤器放置在管内的中心或不同位置处，以倾斜状态进行模拟，并在前后位、侧位和头足位斜位拍摄放射片。对图像进行分析，以确定实际的倾斜角度、前后位放射片中肢钩之间的距离以及需要将肢钩线性对齐的头足向倾斜角度。
当过滤器处于中心位置或向侧面倾斜时，过滤器的所有肢钩在前后位放射片中均呈线性对齐。当过滤器在前后位或斜位倾斜时，肢钩的线性对齐会丢失，并且在前后位投影中，腹侧和背侧肢钩会出现分离。分离的程度和将过滤器肢钩对齐所需的头足向角度与实际的倾斜角度相对应。
在前后位放射片中肢钩失去线性对齐可能提示存在 AP 平面内的倾斜。肢钩的明显分离应该引起对过滤器明显倾斜的警惕，并且在计划取出之前，应通过 CT 扫描或侧腔静脉造影进一步评估过滤器的位置。
