over怎么理解？什么东西在“上方”？

Biopsy of the parietal pleura should be performed over a rib to avoid the neurovascular bundle. The forceps frst probes for the rib followed by grasping the abnormal pleura and stripped by tearing rather than “grab and pull” motion. The specimens are not only larger than those with Abram’s or Cope needle; importantly, they are visually guided. Biopsies with the fexible forceps are limited by the size of forceps which may lack the mechanical strength in obtaining pleural specimens of suffcient depth if fbrotic pleura is encountered. This can be overcome by taking multiple biopsies (5–10) as well as several “bites” of the same area to obtain tissue of suffcient depth. Comparative studies show no difference in diagnostic yield between biopsies using fexible and rigid forceps even in mesothelioma [55, 56]. Fullthickness parietal pleural biopsies can be achieved using the insulated tip (IT) diathermic knife during fex-rigid pleuroscopy. In one study, the reported diagnostic yields were 85% with IT knife and 60% with fexible forceps. The IT knife was notably useful when smooth, thickened lesions were encountered, of which nearly half were malignant mesothelioma [57]. Cryobiopsy is another method that achieves bigger specimens and better preserved cellular architecture and tissue integrity

为避开神经血管束，应在肋骨上方行壁层胸膜活检。首先用钳子探查肋骨，然后钳夹异常胸膜，通过撕裂而不是“抓拽”动作剥离胸膜。这样获取的标本不仅比使用Abram针或Cope针取的标本大，重要的是，它们是直视下引导的。若胸膜纤维化，软性钳因尺寸大小也缺乏机械强度，获取深部胸膜标本受限，需要多次活检（5-10次）和“钳咬”来获得深度组织标本。对照研究表明，即使间皮瘤中，使用软性钳和硬性钳活检的诊断率也无差异^[55,56]。全壁层胸膜活检可在可弯曲硬胸膜腔镜下使用绝缘尖端（insulated tip，IT）刀进行。一项研究报道，使用IT刀的诊断率为85%，使用软性钳的诊断率为60%。当遇到光滑、增厚的病变时（近一半是恶性间皮瘤），IT刀尤其有用^[57]。冷冻活检是另一种获得更大样本并更好地保存细胞结构和组织的完整性的方法^[58]（表13.2）。

over怎么理解？什么东西在“上方”？“胸膜”总是在“肋骨”下方吧？