UC San Diego

Essentials The best imaging modality for joint blood detection in hemophilia is unknown. Blood appearance and detection thresholds were studied with ultrasound and conventional MRI. Ultrasound is sensitive to low volume and concentration of blood, whereas conventional MRI is not. The findings establish the validity of ultrasound for rapid bleed detection in hemophilia care. SUMMARY:Background There is increasing demand for musculoskeletal ultrasound (MSKUS) to detect hemophilic joint bleeding, but there is uncertainty regarding blood detection concentration thresholds or if magnetic resonance imaging (MRI) is more accurate. Aims Compare the sensitivity of blood detection by MSKUS and MRI. Methods Increasing blood concentrations in plasma were imaged with MSKUS and MRI 1-2 h, 3-4 days and 7 days after blood withdrawal in vitro, and after injection into cadaveric pig joints. Additionally, effusions in the joints of two patients with hemophilia joints were imaged, followed by aspiration. MSKUS was performed using an 8-18-MHz linear transducer; MRI was performed at 3T using T1-weighted and T2-weighted fat-suppressed sequences. Images were reviewed by a hematologist certified in MSKUS and a musculoskeletal radiologist. Results MSKUS permitted the detection of blood in vitro and in pig joint spaces at concentrations as low as 5%, demonstrated by the presence of echogenic signals that were absent with plasma alone. In contrast, no differences between fluids were discernible on the T1-weighted or T2-weighted MRI images. Results were confirmed in the two patients with hemophilia. Blood clots demonstrated varying and dynamic echogenicity patterns over time and, using MRI, were visualized best with T2 sequences. Conclusion MSKUS is extremely sensitive in detecting low concentrations of intra-articular blood and in discriminating between bloody and non-bloody fluid, whereas conventional MRI is not. These observations demonstrate the advantages of MSKUS over MRI in detecting intra-articular blood, and show that MSKUS is ideal for rapid bleed detection in the clinic.