Davidson Melanie T M, Batchelar Deidre L, Velupillai Sujeevan, Denstedt John D, Cunningham Ian A
Imaging Research Laboratories, Robarts Research Institute, London, Ontario, N6A 5K8, Canada.
Phys Med Biol. 2005 Aug 21;50(16):3907-25. doi: 10.1088/0031-9155/50/16/017. Epub 2005 Aug 2.
Knowledge of urinary stone composition and structure provides important insights in guiding treatment and preventing recurrence. No current method can successfully provide information relating structure and composition of intact stones. We are developing a tomographic technique that uses measures of coherently scattered diagnostic x-rays to yield stone composition. Coherent-scatter (CS) properties depend on molecular structure and are, therefore, sensitive to material composition. Powdered, amorphous or polycrystalline materials with no significant orientation produce circularly symmetric CS patterns. However, in materials with preferred crystallite orientation, like urinary stones, bright spots in CS patterns are observed. This compromises a composition analysis based on comparing CS measurements from calculi to a library of CS signatures from powdered chemicals. We show that a computed tomographic reconstruction of CS measurements using filtered backprojection (CSCT) effectively eliminates bright spots and yields CS patterns equivalent to powdered materials. This allows for direct comparison with a powdered chemical reference library to establish composition. Validation is achieved through a tomographic CS analysis of an aluminium (Al) rod phantom. Much like calculi, CS patterns from a solid polycrystalline Al rod exhibit diffraction spots, absent in the ring-like Al powder CS pattern. We show that the reconstructed Al CS cross-section is equivalent to its powdered counterpart and results in clearly defined composition images. The potential of CSCT to identify stone composition is demonstrated through images of intact stones deemed chemically pure by infrared spectroscopy. Computed tomographic reconstruction of CS signals allowed the generation of composition maps, showing the distribution of stone components. These images provide strong evidence that current laboratory techniques risk missing critical stone components due to inadequate sampling. This is of particular importance since follow-up treatments are based on these composition analyses. CS analysis can distinguish common stone components and can provide topographic composition maps of intact stones. Such details offer invaluable clinical information regarding stone formation, treatment and follow-up, and thus support the development of CS analysis as a laboratory stone analysis technique.
了解尿石的成分和结构对于指导治疗和预防复发具有重要意义。目前尚无任何方法能够成功提供完整结石的结构和成分信息。我们正在开发一种断层扫描技术，该技术利用相干散射诊断X射线的测量结果来确定结石成分。相干散射（CS）特性取决于分子结构，因此对材料成分敏感。无明显取向的粉末状、非晶态或多晶材料会产生圆对称的CS图案。然而，在具有择优微晶取向的材料（如尿石）中，会观察到CS图案中的亮点。这使得基于将结石的CS测量结果与粉末状化学物质的CS特征库进行比较的成分分析变得复杂。我们表明，使用滤波反投影法对CS测量进行计算机断层扫描重建（CSCT）可有效消除亮点，并产生与粉末状材料等效的CS图案。这使得能够直接与粉末状化学参考库进行比较以确定成分。通过对铝（Al）棒体模进行断层CS分析实现了验证。与结石非常相似，实心多晶Al棒的CS图案显示出衍射斑点，而在环状Al粉末CS图案中则不存在。我们表明，重建的Al CS横截面与其粉末状对应物等效，并能生成清晰定义的成分图像通过红外光谱法被认为化学纯的完整结石图像证明了CSCT识别结石成分的潜力。CS信号的计算机断层扫描重建允许生成成分图，显示结石成分的分布。这些图像有力地证明，由于采样不足，当前实验室技术可能会遗漏关键的结石成分。这一点尤为重要，因为后续治疗是基于这些成分分析的。CS分析可以区分常见的结石成分，并能提供完整结石的地形成分图。这些细节提供了有关结石形成、治疗和随访的宝贵临床信息，从而支持将CS分析发展成为一种实验室结石分析技术。
