Dear Editors,<\/p>\n
We read with a great interest the recent study by Jessica M. Winfield et al (2017) in which they investigated the role of Apparent Diffusion Coefficient (ADC) values in distinguishing haemangiomas from malignant vertebral lesions [1]. In this study, the authors identified ADC values for typical haemangiomas in the spine and compared them with active malignant focal lesions. It has been found that ADC values of classical vertebral hemangiomas are significantly higher than malign focal deposits in this study and that high ADC of vertebral hemangiomas can be visually and quantitatively distinguished from active disease, which showed restricted diffusion.<\/p>\n
We would like to discuss a couple of points about the patient characteristics included in the study and the treatment status at the time of imaging. First, this study did not state clearly the treatment status prior to MR imaging. There are many causes of bone marrow hypercellularity and hypocellularity observed in cancer patients. Common causes of bone marrow atrophy include chemotherapy and radiation treatment. Successful therapy increases the ADC values and decreases te signal intensity consistent with decreasing cellularity. Also, granulocyte colony stimulating factor (G-CSF) administration during chemotherapy results in increased signal intensity on DWI, due to increase in bone marrow cellularity and water. Therefore, benign red marrow reconversion changes related to G-CSF could potentially be mistaken for malignant vertebral lesions in whole-body diffusion-weighted MRI. Thus, the ADC values of treated lesions may be misinterpreted [2]. Second, we feel that there is not enough description of the study population regarding the types of the underlying metastatic disease. Unlike the inverse correlations between ADC and cell density seen in many soft tissue tumours, ADC alterations in bone marrow as a consequence of metastatic disease are not inverse. Bone marrow cell density, the relative proportions of fat and marrow cells, water content and bone marrow perfusion are different in osteolytic and osteoblastic metastasis. Therefore, lytic bony metastases are always better seen than pure sclerotic metastases on Diffusion-Weighted MRI. ADC values of these lesions might be changed depends on whether the lesion is osteolytic and osteoblastic [2]. Thus, in this study, malignant vertebral lesions were not differentiated as osteolytic and osteoblastic.<\/p>\n
In order to avoid misinterpretations arising from ADC values alone, it is necessary to know patients traetment status and correlate signal intensity assessments taking into account morphologic features on other MRI sequences.<\/p>\n