Fusion and subtraction post-processing in body MRI

Fused high b-value diffusion weighted and T2-weighted MR images in staging of pediatric Hodgkin's lymphoma: A pilot study

PURPOSE

To evaluate the value of fused high b-value diffusion weighted and T2-weighted MRI compared to T1-weighted imaging, T2-weighted imaging and DWI for staging pediatric Hodgkin's lymphoma.

METHOD

21 consecutive pediatric patients who underwent whole-body MRI at Hodgkin's lymphoma staging were included. Fused, colorized DWI/T2-weighted images were created. Image sets consisting of (a) T1-weighted, T2-weighted and DWI images and (b) T1-weighted, T2-weighted, DWI and DWI/T2-weighted fused images were reviewed by a radiologist using a cross-over design with blinding and randomization. Scoring was performed using a standardized form, based on detection, characterization and reading time, using a FDG-PET/CT based reference standard. Test characteristics, test agreement to a FDG-PET/CT based reference standard and reading times were calculated.

RESULTS

Agreement for whole-body MRI without fused images and FDG-PET/CT was very good for nodal staging (κ = 0.86, 95% CI 0.78-0.93) and extra-nodal staging (κ = 0.90, 95% CI 0.71-1.09). Agreement improved with the addition of the fused DWI/T2-weighted images (κ = 0.92 95% CI 0.87-0.97 (nodal staging), κ = 0.92 95% CI 0.76-1.08 (extra-nodal staging). Sensitivity and specificity for staging nodal disease were 99 % and 95% respectively for whole-body MRI including DWI/T2-weighted fused images (versus 88 % and 97 % without fused images) and 100 % and 99 % for extra-nodal disease (83 % and 100 % without fused images). Disease stage for MRI including fused DWI/T2-weighted images agreed with the reference standard in 18 out of 21 patients.

CONCLUSIONS

The addition of DWI/T2-weighted fusion images to T1-weighted, T2-weighted and DWI whole-body MRI might shorten reading times and might improve the diagnostic performance of whole-body MRI in staging pediatric Hodgkin's lymphoma.

Is MRI imaging in pediatric age totally safe? A critical reprisal

Current radiological literature is strongly focussed on radiation imaging risks. Indeed, given there is a small but actual augment in cancer risk from exposure to ionizing radiation in children, it is important to understand what the risk of alternative techniques could be. We retrospectively review literature data concerning possible MR imaging risks, focussing on the biological effects of MR, sedation and gadolinium compound risks when dealing with infant patients. The main concerns can be summarized in: (1) Biological effects of non-ionizing electromagnetic fields (EMF) employed-whose mechanisms of interaction with human tissues are polarization, induced current, and thermal heating, respectively. (2) Risks associated with noises produced during MRI examinations. (3) Hazards from ferromagnetic external and/or implanted devices-whose risk of being unintentionally brought inside MR room is higher in children than in adults. (4) Risks associated with sedation or general anaesthesia, essential problem in performing MR in very young patients, due to the exam long-lasting. (5) Risks related to gadolinium-based contrast agents, especially considering the newly reported brain deposition.

Imaging of Soft-Tissue Musculoskeletal Masses: Fundamental Concepts

Radiologic evaluation of musculoskeletal soft-tissue masses has changed dramatically with the continued improvements in imaging technology. The integration of advanced imaging has provided the radiologist with a wide range of assessment tools, but as with all powerful arsenals, selection and application of the appropriate imaging method can be problematic. Although the choices available for imaging evaluation of musculoskeletal masses have changed dramatically, the basic objectives of this assessment have remained constant: diagnosis and staging. The basic principles for evaluating musculoskeletal soft-tissue masses and achieving these objectives have not changed. This article addresses application of the current imaging methods to assessment of soft-tissue musculoskeletal masses, emphasizing fundamental concepts. We do not intend to provide a comprehensive review of imaging techniques, but rather to provide a useful review of the concepts needed to select the appropriate initial imaging method, magnetic resonance (MR) imaging field of view, MR imaging sequences, contrast material requirements, and rapid image acquisition techniques. We also address use of the new quantitative techniques of chemical shift and diffusion-weighted imaging. Finally, we review the current uses of computed tomography and ultrasonography. Although the choices available for imaging evaluation of musculoskeletal masses have changed dramatically within the past decade, appropriate application of the fundamental concepts of imaging will maximize the diagnostic utility of imaging examinations. ^©RSNA, 2016.