Imaging Anatomic Study Of Carpal Tunnel:DCET Evaluation In Normal Adult

Purpose: To explore the anatomical features of normal carpal tunnel on adult through DECT(Dual Energy Computed Tomography). Seeking the optimum keV energy values of the carpal tunnel structures, and use the keV getting the best quality images of the carpal tunnel structures,further understanding the anatomical characteristics and trends of median nerve, tendon and flexor retinaculum, as well as the bone structures.Meanwhile, studying the anatomical correlations between the bony structures and soft tissue in carpal tunnel, providing more abundant information for diagnosis of carpal tunnel disease.Materials and Methods: 15 normal adult wrist joints scanned with DECT were enrolled, using monoenergetic technology for postprocessing,seeking the optimum keV energy value of the carpal tunnel structures, on the basis of the best quality images, mapping and calculating the cross-sectional area at the level of distal radio-ulnar joint, middle os pisiformis, hook of hamate, proximal metacarpal bone, as well as the long axis and short axis of median nerve, the cross-sectional area of median nerve, flattening swelling ratio of median nerve, the CT value(Hu) of median nerve, tendon and flexor retinaculum at the four levels. Mappingthe palmar bowing of retinaculum at the level of Hook of hamate.Measuring the width, height and product of bone structures at the level of middle os pisiformis, hook of hamate, proximal metacarpal bone.Analyzing the datas above through ANOVA of single factor, P<0.05 was statistically significant. At the same time, Correlative analysis between the bony structures and soft tissue measurements, P<0.05 was statistically significant.Results: The mean value of optimized image quality keV of the carpal tunnel structures was 61.867±0.915. The mean value of palmar bowing of retinaculum was 1.041±1.718 mm. The mean flattening ratio of median nerve was 1.419±0.558. With distal radio-ulnar joint as a starting point, from proximal to distal as middle os pisiform, hook of hamate,proximal metacarpal bone of three level of carpal tunnel, the median nerve long axis trends as follow: increasing, no obvious change, no obvious change, the min median nerve long axis at at the level of distal radio-ulnar joint. The median nerve short axis trends as follow: increasing,decreasing, no obvious change, the max median nerve short axis at the level of middle os pisiformis. The cross-sectional area of median nerve trends as follow: increasing, decreasing, increasing, the min cross-sectional area of median nerve at the level of hook of hamate.Flattening ratio of median nerve trends as follow: increasing, increasing,no obvious change, the min flattening ratio at the level of distalradio-ulnar joint. The cross-sectional area of carpal tunnel trends as follow: increasing, decreasing, increasing, the min cross-sectional area of median nerve at the level of hook of hamate. The CT value(Hu) of palmar bowing of retinaculum trends as follow: increasing, increasing, no obvious change, the min palmar bowing of retinaculum at the level of distal radio-ulnar joint. The CT value(Hu) of median nerve and tendon showed no significant differences. With middle os pisiform as a starting point, from proximal to distal as hook of hamate, proximal metacarpal bone of two level of carpal tunnel, the width of bone structures trends as follow: decreasing, increasing, the min width of bone structures at the level of hook of hamate. The height of bone structures trends as follow:no obvious change, decreasing, the min height of bone structures at the level of proximal metacarpal bone. The product of bone structures trends as follow: decreasing, no obvious change, the max product of bone structures at the level of middle os pisiformis. The width of bony structures and the soft tissue in carpal tunnel at the three levels were not correlated(P>0.05). The height of bony structures and the cross-sectional area of carpal tunnel at the three levels were correlated(P<0.05). The product of bony structures and the cross-sectional area of carpal tunnel at the level of hook of hamate were correlated(P<0.05).Conclusion: The optimum keV energy values of the carpal tunnel structures is 62 keV on DECT. DECT can clearly display the carpal tunnel,possessing the potential on providing carpal tunnel information. DECT inherits the advantages of SECT(Single Energy Computed Tomography),having unique advantages on displaying the bony structures, the changes of soft tissue structures in carpal tunnel and the bony structures correlated.