Time-dependent low-field MRI characteristics of canine blood: an in vitro study

Abstract

This study was conducted to assess time-sensitive magnetic resonance (MR) changes in canine blood using low-field MR. Arterial and venous blood samples were collected from eight healthy beagle dogs. Samples were placed in 5-mL tubes and imaged within 3 hours of collection at 1 day intervals from day 1 to day 30. The following sequences were used: T1-weighted (T1W), T2-weighted (T2W), fluid-attenuated inversion recovery (FLAIR), short tau inversion recovery (STIR), and T2-star gradient-echo (T2(*)-GRE). Visual comparison of the images revealed that four relatively homogenous blood clots and twelve heterogeneous blood clots developed. The margination of the clot and plasma changed significantly on day 2 and day 13. On day 2, heterogeneous blood clots were differentiated into 2 to 3 signal layers in the T2W, T1W, and especially the STIR images. Hypointense signal layers were also detected in the blood clots in STIR images, which have T2 hypo, FLAIR hypo, and T1 hyper intense signals. In all images, these signal layers remained relatively unchanged until day 13. Overall, the results suggest that hematomas are complex on low-field MRI. Accordingly, it may not be feasible to accurately characterize hemorrhages and predict clot age based on low-field MRI.

Keywords: blood; canine; in vitro; low field; magnetic resonance.

Fig. 1. (A) Blood filled sample tube. (B) Phantom sample container surrounded by agarose bath (asterisk) to avoid ghost artifact. (C) 0.25 T MR system and a solenoid Knee coil.

Fig. 2. Dog 1 arterial blood sample at day 1. (A) Transverse T2-weighted. (B) T1-weighted. (C) Fluid attenuated inversion recovery (FLAIR). (D) Short tau inversion recovery (STIR). (E) T2-star gradient-echo (T2^*-GRE). Note the partial development of hypo to null intensity (asterisk) in STIR images.

Fig. 3. Dog 1 venous blood sample at day 1. (A) Transverse T2-weighted. (B) T1-weighted. (C) FLAIR. (D) STIR. (E) T2^*-GRE.

Fig. 4. Transverse T1-wegithed images of dog 5 arterial blood sample with time. Note the developing partial hyperintensity in the blood clot at day 3.

Fig. 5. Transverse STIR images of dog 5 arterial blood sample with time. Note the developing partial hypo to null intensity in the blood clot at day 3.

Fig. 6. Transverse T2-weighted images of dog 2 venous blood sample with time.

Fig. 7. Transverse FLAIR images of dog 2 venous blood sample with time.

Fig. 8. Transverse STIR images of dog 3 (A, arterial; D, venous), 4 (B, arterial; E, venous), 5 (C, arterial; F, venous) blood sample with time. Note the difference in the degree of developed hypo to null intensity (asterisk) between arterial and venous blood samples.

Fig. 9. Transverse T2^*-GRE images of dog 1 to 8 arterial blood samples at day 3. There is no significant susceptibility artifact visible in any samples.