Clinical diagnosis
Case 173
【Progress】
She got non-steroid anti-inflammatory drug (RILICA). It made her soothing pain.
【Discussion】
At birth, bone marrow is fulfilled with red marrow. Bone marrow converts red marrow into yellow marrow with age. Red marrow contains 40% fat, 40% water and 20% protein, while yellow marrow contains 80% fat 15% water and 5% protein (1). Yellow marrow begins at pharynx bone and tarsal bone followed by proximal bone of extremity bones, and ends vertebra. In a long bone, yellow marrow begins at epiphysis followed by diaphysis and eventually ends at metaphysis (1, 2).
Meanwhile, reconversion from yellow marrow to red marrow can occur in various situations; smoking which comes out CO in blood, inducing to produce red blood cells as carrier of O2; Respiratory disease; Anemia; Sports; Obesity; Treated with hematopoietic growth factors. Because bone marrow conversion is most delayed at metaphysis, metaphysis often remains red marrow. Reconversion of bone marrow occurs most at diaphysis of vertebra, long bone and pelvis. It does not occur beyond growth line, which indicates that reconversion of bone marrow rarely occurs at epiphysis (1-4).
MRI with T1WI is sensitive to fat component and shows mild to hyperintense in normal vertebra dependent on fat concentration. Namely, hyperintense of bone marrow on T1WI indicates benign such as yellow bone marrow and hemangioma except melanoma metastasis. Low intense on T1WI categorizes into three types; inflammation and injury; neoplasm such as myeloma or metastatic tumors: reconversion to red marrow (5).
Meanwhile, MRI with T2WI is sensitive to fat as well as water, inducing hyperintense. Fat is more hyperintense than water on T2WI. In general, inflammation, injury and edema associated malignant tumor appears low signal intensity on T1WI and hyperintensity on T2WI. However, when these lesions occur in bone marrow, they can appear relatively low signal intensity rather than bone marrow on T2WI because fat is more hyperintense than water (5, 6).
What hypointense lesion both on T2WI and on T1WI indicates fibrosis, calc, dense cell population such as red marrow, myeloma, leukemia, lymphoma or diffuse metastatic tumor. To differentiate benign lesion from malignant lesion with both of hypointense on T1WI and T2WI, diffusion WI and ADC values are useful: ADC value of 1.1 or less is reported to occur in malignant neoplasm (6-8). Further, we should notice that lipid is far less diffusion, ADC value is approximately 0.3 (9). That is why a diffusion weighted image is created in a situation of fat suppression.
In our case, lumbar vertebra appeared in both hypointense lesion on T1WI and T2WI. Laboratory test revealed increase of Ig G, indicating mononuclear gammopathy, which can progress to myeloma or leukemia. It is reported that hypointense of vertebra on T1WI and on T2WI precedes emergence of leukemia cells in laboratory test. Then, the follow up of this case is crucial.
【Summary】
We present an eighty one-year-old female suffering from lumbago. Spine MRI showed lumbar vertebrae body with diffuse low signal intensity both on T1WI and T2WI. It is borne in mind that red bone marrow contains 40% fat and yellow bone marrow contains 80% fat. Fat is more hyperintense than water on T2WI. Then, when injury or inflammation occurs on bone marrow, it can be found to be a hypointense lesion in bone marrow on T2WI. Further, fat is diffusion far repressive, inducing ADC value approximately 0.3 so that an diffusion weighted image is taken in fat repression state. Bone marrow conversion from red marrow to yellow bone marrow begins at peripheral bones and advances extremity bone and ends at the vertebra. Reconversion from yellow marrow to red marrow occurs at diaphysis and usually does not extend to epiphysis. What hypointense lesion both on T2WI and on T1WI indicates fibrosis, calc, dense cell population such as red marrow, myeloma, leukemia, lymphoma or diffuse metastatic tumor. To differentiate benign lesion from malignant lesion with both of hypointense on T1WI and T2WI, diffusion WI and ADC values are useful: ADC value of 1.1 or less is reported to occur in malignant neoplasm.
【References】
1.Małkiewicz, A et al. Bone marrow reconversion – imaging of physiological changes in bone marrow. Pol J Radiol. 2012 Oct-Dec; 77(4): 45–50.
2.Grande FD, et al. Bone marrow lesions: A systematic diagnostic approach. Indian J Radiol Imaging. 2014 Jul-Sep; 24(3): 279–287.
3.Kane EV, et al.: Tabacco and the risk of acute leukemia in adults. Br J Cancer 81: 1228-1233, 1998
4.Parker AS, et al.: Smoking and risk of non-Hodgkin lymphoma in a cohort of old women. Leukemia Lymphoma 37: 341349, 2000
5.Hanrahan CJ, et al. MRI of Spinal Bone Marrow: Part 2, T1-Weighted Imaging-Based Differential Diagnosis. American Journal of Roentgenology. 2011;197: 1309-1321
6.Paterson SC, et.al. MRI Changes associated with Bone Marrow Reconversion can Mimic Infiltration with Multiple Myeloma. J Leuk 2013; 1: 125.
7.Shigematsu Y et. al. Distinguishing Imaging Features between Spinal Hyperplastic Hematopoietic Bone Marrow and Bone Metastasis Am J Neuroradiol 35:2013-20 Oct 2014
8.Silva J, et al. MRI of bone marrow abnormalities in hematological malignancies. Diagnostic and Interventional Radiology. 2013;19(5):393–399.
9.Kim SE, et al. In Vivo and Ex Vivo Measurements of the Mean ADC Values of Lipid Necrotic Core and Hemorrhage Obtained From Diffusion Weighted Imaging in Human Atherosclerotic Plaques. Journal of Magnetic Resonance Imaging 2011; 34:1167-75
2019.12.11