Whole-body magnetic resonance imaging: technique, guidelines and key applications

Abstract

Whole-body magnetic resonance imaging (WB-MRI) is an imaging method without ionising radiation that can provide WB coverage with a core protocol of essential imaging contrasts in less than 40 minutes, and it can be complemented with sequences to evaluate specific body regions as needed. In many cases, WB-MRI surpasses bone scintigraphy and computed tomography in detecting and characterising lesions, evaluating their response to therapy and in screening of high-risk patients. Consequently, international guidelines now recommend the use of WB-MRI in the management of patients with multiple myeloma, prostate cancer, melanoma and individuals with certain cancer predisposition syndromes. The use of WB-MRI is also growing for metastatic breast cancer, ovarian cancer and lymphoma as well as for cancer screening amongst the general population. In light of the increasing interest from clinicians and patients in WB-MRI as a radiation-free technique for guiding the management of cancer and for cancer screening, we review its technical basis, current international guidelines for its use and key applications.

Keywords: diffusion-weighted imaging; magnetic resonance imaging; oncology; whole-body.

Figure/Video 1.. Illustration of the quantitative analysis of ADC via semi-automated segmentation in a patient with metastatic PC. To view this video, click here https://ecancer.org/journal/14/1064-whole-body-magnetic-resonance-imaging-technique-guidelines-and-key-applications. Male with hormone-sensitive metastatic PC seen at (a): baseline, (b): 4 month follow-up and (c): 8 month follow-up examinations during hormonal therapy. Overlaid on inverted grey-scale MIPs from b-900 diffusion weighted images are colours representing three ranges of ADC values. Based on MET-RADS-P guidelines [13], the user-defined thresholds (1,000 and 1,400 μm²/s) define ranges corresponding to: active disease (red) < 1,000 μm²/s < normal bone/responding lesion (yellow) < 1,400 μm²/s < treated disease/necrotic tissue (green) measured in the bone metastases. These ranges also serve to define the coloured backdrop to comparisons of ADC histograms between successive examinations in (d) and (e). (d): The peak of the (blue) histogram at baseline falls in the active disease range (red band), while the (orange) histogram at first follow-up shows two peaks. The right-most peak, falling in the likely-response range (yellow band) indicating according to the MET-RADS-P guidelines [13], together with a reduction in PSA, this could suggest a positive therapeutic response, but the left-hand peak indicates a residual component of disease is still active. At the second follow-up (yellow histogram), (e): the distribution has returned to the active disease range (red band) and the PSA having increased, is compatible with a predominance of active metastatic disease.

Figure 2.. Metastatic PC staging with WB-MRI. A 70-year-old male with high-risk PC (PSA 28 ng/mL, Gleason score (GS) 4+4) seen in (a): coronal inverted grey-scale MIP of b-900 diffusion-weighted images and (b–d): axial b-900 diffusion-weighted images b-900 images from WB-MRI performed for staging. In the ‘at-a-glance’ disease assessment facilitated by the MIP, WB-MRI shows a clinical pattern of type N1 M1b, involving (b): regional lymph node metastasis (c): a non-regional lymph node metastasis and (d): bone marrow disease.

Figure 3.. Bone lesions in lymphoma. A 51-year-old male with follicular lymphoma (G1-G2). (a): ¹⁸FDG-PET for distant staging to have a single bone metastasis of the T10 vertebra (white arrowhead). At WB-MRI 1 month later, oligometastatic disease with multiple bone lesions was evident in (b): the inverted grey scale MIP of the b-900 diffusion weighted images; with corresponding hyperintensities being seen in the axial source images (c–e). In addition to the T10 metastasis (white arrowhead in a and b), a sternal metastasis (smaller white arrow in b and c), a second thoracic vertebral lesion (longer white arrow in b and d) and an iliac lesion (black arrow in b and e). Metastasis in the right iliac bone was confirmed by CT-guided biopsy (f).