Pech P, Bergström K, Rauschning W, Haughton V M
Department of Diagnostic Radiology, Akademiska Sjukhuset, University of Uppsala, Sweden.
Acta Radiol. 1987 Nov-Dec;28(6):779-82.
Freezing of animal and human tissue may change their shape, size and other physical properties such as attenuation of roentgen rays. In correlative radiologic-anatomic studies such artifacts are potential sources of inaccuracy. In fluid phantoms changes of computed tomography (CT) numbers and volume were measured before and after freezing. Frozen saline decreased in attenuation by 80 Hounsfield units (HU) and increased in volume by 9 per cent. Pure soy oil increased in attenuation by 40 HU after freezing and shrank in volume by 4 per cent. Emulsions of 10, 20 and 30 per cent lipid expanded in inverse relationship to the changes in attenuation. In animal and human tissue, changes in CT number of -80 to +55 HU were measured and changes in volume of -6 to +9 per cent were calculated. The attenuation of the vitreous body in the eye decreased by 80 HU and its volume was calculated to increase by 8 to 9 per cent. In the muscle and spinal cord the attenuation decreased by 40 to 60 HU, corresponding to the increase in volume of 4 to 6 per cent. Attenuation of fat was increased by 55 HU after freezing and a decrease in volume of 5 to 6 per cent was calculated. Deformation of soft tissue and herniation of the cerebellar tonsils into the foramen magnum were observed. Most anatomic, freezing artifacts can be avoided by careful preparation.
动物和人体组织的冷冻可能会改变其形状、大小以及其他物理特性，如X射线衰减。在相关的放射解剖学研究中，这些伪像可能是误差的潜在来源。在液体模型中，测量了冷冻前后计算机断层扫描（CT）数值和体积的变化。冷冻后的生理盐水衰减降低了80亨氏单位（HU），体积增加了9%。纯大豆油冷冻后衰减增加了40 HU，体积缩小了4%。10%、20%和30%脂质的乳剂体积膨胀与衰减变化呈反比关系。在动物和人体组织中，测量到CT数值变化为-80至+55 HU，并计算出体积变化为-6至+9%。眼部玻璃体的衰减降低了80 HU，其体积经计算增加了8至9%。肌肉和脊髓的衰减降低了40至60 HU，相应地体积增加了4至6%。冷冻后脂肪的衰减增加了55 HU，经计算体积减少了5至6%。观察到软组织变形以及小脑扁桃体疝入枕骨大孔。通过仔细准备，大多数解剖学上的冷冻伪像可以避免。
