From the Guidelines
Red marrow related changes in the pelvic bone on MRI are characterized by intermediate to low signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted images, and can be distinguished from pathologic processes by careful evaluation of signal characteristics, distribution patterns, and clinical context 1. The distribution of red marrow in the pelvis follows a predictable pattern, with conversion from red to yellow (fatty) marrow occurring in a centrifugal fashion from the appendicular to the axial skeleton throughout life.
- Key factors that can affect this conversion include:
- Physical activity
- Smoking
- Certain medical conditions In children and young adults, the pelvis contains predominantly red marrow, which gradually converts to yellow marrow with aging. However, red marrow reconversion, where yellow marrow reverts to red marrow, can occur in response to increased hematopoietic demand such as in anemia, obesity, smoking, or endurance training 1. The use of in-phase and out-of-phase MRI sequences can help differentiate benign stress fractures from pathologic fractures, as normal marrow has both fat and water in the same voxel, resulting in suppression of signal intensity on opposed-phase images 1. It is essential to consider the clinical context and signal characteristics when evaluating red marrow related changes in the pelvic bone on MRI to avoid misdiagnosis of stress fractures as more aggressive lesions 1.
From the Research
Red Marrow Related Changes in Pelvic Bone by MRI
- Red marrow is a dynamic organ with variable composition in relation to age or pathophysiological changes, and MRI is the technique of choice to assess its different components 2
- MRI features of normal developmental red marrow-to-yellow-conversion, reconversion, and physiologic conditions can be evaluated using T1-weighted, T2-weighted, Dixon chemical shift imaging, and diffusion-weighted imaging, as well as dynamic contrast-enhanced (DCE) MRI 2
- Fat-saturation pulse sequences, such as short-TI inversion recovery (STIR) and fat-saturation T2-weighted imaging, offer important potential advantages for depiction of bone marrow lesions on MR images, including those in the pelvis 3
- Incidental musculoskeletal findings, including normal and abnormal bone marrow, can be identified on MRI of the pelvis, and abdominal radiologists should be familiar with their appearance and diagnostic considerations 4
- Bone marrow edema (BME) is defined as an excess of fluids that builds up in the bone marrow, and MRI is the only method that highlights its presence, which can be associated with various diseases, including hematological malignancies 5
- Advanced MR imaging of bone marrow, including quantification of signal alterations on T1-weighted Dixon and T2-weighted Dixon sequences, can help differentiate between yellow marrow, red marrow, and osseous lesions, both benign and malignant 6
MRI Sequences for Evaluating Red Marrow
- T1-weighted imaging: essential for evaluating bone marrow morphology and detecting lesions 2, 3, 6
- T2-weighted imaging: helpful for detecting bone marrow edema and lesions, especially when combined with fat suppression 3, 5, 6
- Dixon chemical shift imaging: useful for differentiating between yellow marrow, red marrow, and osseous lesions 2, 6
- Diffusion-weighted imaging: can help evaluate bone marrow pathology, including infiltration and proliferation 2
- Dynamic contrast-enhanced (DCE) MRI: can help evaluate bone marrow perfusion and vascularization 2
Clinical Implications
- Accurate diagnosis and evaluation of bone marrow lesions, including those in the pelvis, are crucial for effective management and treatment 2, 3, 4, 5, 6
- MRI is a valuable tool for monitoring disease progression and treatment response in patients with malignant hemopathies 5
- Advanced MR imaging techniques, including quantification of signal alterations on T1-weighted Dixon and T2-weighted Dixon sequences, can improve diagnostic accuracy and help guide clinical decision-making 6