MRI of bone marrow abnormalities in hematological malignancies

Abstract

Magnetic resonance imaging (MRI) is essential for evaluating bone marrow. Bone marrow undergoes constant modification and its appearance on MRI changes in response. Knowledge of the types of changes and their origins is essential for analysis of MRI findings of bone marrow infiltration with hematological malignancies. This pictorial review describes the MRI pulse sequences used for imaging of bone marrow, and illustrates bone marrow changes due hematological malignancies, including changes following treatment. Magnetic resonance imaging (MRI) is the only imaging method that enables direct visualization of the bone marrow with high anatomical resolution and excellent soft tissue contrast. The MRI appearance of bone marrow depends on the amounts and proportions of yellow and red marrow, which change with age and environmental factors. Red marrow contains about 40% fat, 40% water, and 20% proteins, and a proportion of 60% hematopoietic cells to 40% fat cells (1). Yellow marrow has a sparse vascular supply, and contains mainly fat (80%) and a small proportion of water (15%), with 95% fat cells. Conversion from red to yellow marrow is generally completed by 25-30 years of age. In adults, red marrow represents only half the marrow content and it is located predominantly in the axial skeleton and proximal limbs (2). MRI sequences used for bone marrow imaging T1-weighted imagingT1-weighted spin-echo sequences are the most useful for evaluating bone marrow. Lipid protons have short T1 relaxation times, so the fatty marrow appears hyperintense on T1-weighted images, similar to subcutaneous fat. Red marrow has an intermediate T1 relaxation time, with a lower signal than subcutaneous fat, but a higher one than intervertebral disc or muscle (1). T2-weighted imaging with fat suppressionT2-weighted fast spin-echo sequences can also be used to evaluate bone marrow and are the sequences used most commonly in a clinical setting. Fat suppression is required to differentiate red and yellow marrow. On fat-suppressed T2-weighted fast spin-echo sequences, the signal intensity of red marrow is higher than that of yellow marrow (1), giving better bone marrow contrast than non-fat-suppressed sequences. Short tau inversion recovery (STIR) sequenceThis technique is used to cancel the fat signal of the marrow with a 180° inversion pulse and yields high tissue contrast. The STIR sequence generally produces more homogeneous fat suppression than T2-weighted fast spin-echo sequences, but the main drawback of this sequence is that it cancels every signal close to that of fat. Gadolinium-enhanced T1-weighted imagingGadolinium-enhanced T1-weighted images might be helpful for detecting some marrow lesions. Gadolinium enhancement of the normal bone marrow in adults is generally imperceptible on T1-weighted spinFrom the Department of Radiology

Quantitative MRI and spectroscopy of bone marrow

“…For the detection of bone marrow infiltration, before bone destruction has occurred, MRI remains the most sensitive imaging modality . Conventional T 1 ‐weighted spin‐echo sequences have been considered to be the most useful tool for the evaluation of the infiltration of bone marrow in clinical routine along with short tau inversion recovery (STIR), yet there is evidence that the detection rate of bone marrow abnormalities and therapy response using MRI can be enhanced by applying techniques such as DWI and DCE‐MRI …”

The Usefulness of T1-Weighted Magnetic Resonance Images for Diagnosis of Acute Leukemia Manifesting Musculoskeletal Symptoms prior to Appearance of Peripheral Blood Abnormalities

“…MRI is a relatively noninvasive and useful modality for visualizing the bone marrow composition and condition, as well as the joints, with high anatomical resolution and excellent soft tissue contrast [7, 8]. In this context, T1WI of bone marrow gives us valuable information to suspect the presence of insidious leukemia.…”

“…Diffuse low signal intensity of bone marrow on T1WI is not specific for acute leukemia and can be seen in other conditions, including myelodysplastic and myeloproliferative syndromes, metastasis of lymphoma, and certain solid tumors [7, 8]. Daldrup-Link et al [10] reported that bone marrow with decreased cellularity and subsequent fatty conversion after chemotherapy exhibited an increase in signal intensity on T1WI.…”

“…It is also the best imaging modality that can directly depict the bone marrow condition and marrow infiltration in malignant diseases, including acute leukemia, with high anatomical resolution and excellent soft tissue contrast [7, 8]. Kato et al [9] demonstrated that MRI is useful for diagnosing pediatric acute leukemia presenting with prolonged bone pain and without peripheral blood abnormality.…”

Kraniyal Kemik İliği Metastazlarında Difüzyon Ağırlıklı MR Görüntüleme

“…The best imaging modality to evaluate bone marrow is MR imaging due to its high resolution 3 . Normal fatty bone marrow in the adult population is hyperintense on T1-weighted images.…”