The Apparent Diffusion Coefficient in the Diagnosis of Metastatic Lesions of Skeletal Bones

Aim: To evaluate the possibilities of absolute and relative values of the apparent diffusion coefficient (ADC) in the diagnosis of metastatic lesions of skeletal bones.

Material and methods: The study included 12 patients with metastatic bone lesions, before any treatment was applied. The age of the patients ranged from 38 to 73 years, 3 men, 9 women. Among the morphological forms of tumors were presented: cancers of the breast (3), prostate (1) glands, colon (1), lung (2), body (1) and cervix (1) uterus, thyroid (1) and pancreas (2). The detected changes were classified on the basis of Bone scan, SPECT/CT and standard MRI. The ADC values of unchanged bone marrow (n=360), divided by anatomical zones, metastatic foci (n=117), as well as benign changes of various nature (n=19) were analyzed. The ratio of the ADC values of each of the metastatic and benign focal formations to the normal values for each of the localizations was calculated.

Results: Unchanged bone marrow, depending on anatomical localization (cervical, thoracic, lumbar spine, pelvic bones, shoulder blades, collarbones, sternum, ribs, proximal humerus and femur bones) from the point of view of ADC, showed statistically significant heterogeneity. Statistical analysis has shown that there is no connection between the groups of ADC indicators in the foci of metastatic lesions, combined depending on the anatomical localization. With a similar comparison, but by belonging to the primary tumor, an even greater intergroup difference was found. ADC values in the foci of metastatic lesions turned out to be dependent on the morphological type of the primary tumor and significantly differ both from metastases of other morphological affiliation and from normal red bone marrow parameters. The use of relative values allowed to increase the specificity from 15 to 19 %.

Conclusion: This study showed that knowledge of the range of reference ADC values for unchanged red bone marrow and anomalies of various genesis is important in differential diagnosis. The differentiation of the skeleton into separate anatomical zones probably makes it possible to increase the effectiveness of the isolated application of the technique when it comes to absolute values. The morphological affiliation of metastatic foci is important in the formation of ADC values, rather than the bone marrow microenvironment, which is also supported by the low efficiency of the use of relative values.