Clinical diagnosis
Case 255
【Discussion】
Hematoma is a hemorrhagic mass that composes of red blood cells most. Red blood cells contain hemoglobin. Hemoglobin coming out from vessels turn from oxyhemoglobin which bind to oxygen such as in arterial blood, into various steps until its breaking: deoxyhemoglobin, intra red blood cell methemoglobin, extra blood cell methemoglobin, and finally hemosiderin. Deoxyhemoglobin indicates oxygen separate from oxyhemoglobin such as in venous blood. It takes 1 or 2 days from oxyhemoglobin to deoxyhemoglobin from hemorrhage. It takes 2 to 7 days from deoxyhemoglobin to intra red cell methemoglobin and further 7 to 28 days from intra red cell met hemoglobin to extra red cell methemoglobin (1- 4). Thereafter, extra methemoglobin changes into hemosiderin as time progress. The various period of transformation probably depends on hepatoma sizes. These changes affect MRI magnification field because hemoglobin include iron ion. Further, extracellular methemoglobin indicates methemoglobin exists in more free water than intracellular methemoglobin, which affect T2 time elongation, implying elevation of high signal intensity on T2WI. In other words, T1WI and T2WI images are influenced by hemoglobin changes and volume of free water. Oxyhemoglobin is diamagnetic which does not affect magnetic field while methemoglobin is paramagnetic and hemosiderin is super paramagnetic which both affect magnetic field. Hemosiderin affects magnetic field most which indicates hemosiderin affect more than free water, implying low signal intensity on both of T1WI and T2WI.
There is a period when hematoma appeared high signal intensity on T1WI. This is time of existence of methemoglobin, irrespective of intracellular or extracellular: although deoxyhemoglobin causes high signal intensity on T1WI, time of staying deoxyhemoglobin is a short period within a week as described above. There is a period when hematoma appeared on low signal intensity on T2WI. This is time of least free water. Hematoma is a mass of blood cells with least free water of extracellular fluids. As time progress, hemolysis occurs which indicate the increase of free water. As free water increases, signal intensity on T2WI elevates higher.
Then, it comes a period when hematoma appears high signal intensity on both T1WI and T2WI. This is time of extra cellular methemoglobin with paramagnetic. This implies that T1WI is influenced by paramagnetic effect of methemoglobin than free water, while T2WI is influenced by free water than paramagnetic effect of methemoglobin. Fat tissues appear high signal intensity on T1WI and T2WI, indicating that fat tissue is paramagnetic and also it contains free water, extracellular water.
Hemosiderin which is appeared low signal intensity on both T1WI and T2WI, indicating superparamagnetic of hemosiderin affect more than free water. Hemosiderin become to move to the surroundings microglia or macrophages phagocyte hemosiderin as foreign body in the process of absorption.
In our case, laboratory test revealed no elevation of white blood cells and LDH, CPK which indicate neither evidence of abscess, muscle necrosis nor infarction but hematoma. There are two lesions of hematoma on MRI; small one with high signal intensity on both T1WI and T2WI, indicating paramagnetic of extracellular methemoglobin: another large one with mixed signal intensity on both T1WI and T2WI. The area on mixed signal intensity on T1WI indicate it includes methemoglobin plus deoxyhemoglobin. The area on mixed signal intensity on T2WI indicate methemoglobin of both intracellular and extracellular.
The small hematoma traces the homogeneous breakdown process of hematoma while the large hematoma traces the inhomogeneous breakdown.
【Summary】
We presented a sixty nine-year-old male with swollen left leg emerged after working to stand for long and running around for road security. Three days after, laboratory test revealed no elevation of white blood cells and LDH, CPK but a little elevation of CRP and anemia. Leg MRI depicted two lesions; small one with high signal intensity on both T1WI and T2WI: large one with mixed signal intensity on mixed signal intensity. It was borne in mind that the area with high signal intensity on T1WI indicates it includes paramagnetic substance such as methemoglobin or lipid, while the area with low signal intensity on T2WI indicates that it includes least free water area. The small lesion with high signal intensity on both T1WI and T2WI implies it includes para magnetic such as extracellular methemoglobin. Meanwhile, the large lesion with mixed signal intensity on T1WI indicates weak paramagnetic of deoxyhemoglobin and usual paramagnetic of methemoglobin, one with mixed signal intensity on T2WI indicates extracellular free water plus intracellular water.
【References】
1.Flores DV, et al. MR Imaging of Muscle Trauma: Anatomy, Biomechanics, Pathophysiology, and Imaging Appearance. Radiographics 2018;38(1):124-148
2.Aoki S et al. Diffusion MRI 3rd edition. Syujunnsha 2013 (Japanese)
3.Kang B, Na D, Ryoo J, Byun H, Roh H, Pyeun Y. Diffusion-Weighted MR Imaging of Intracerebral Hemorrhage. Korean J Radiol. 2001; 2:183-191.
4.Kita M. Personal communication in Fuchu Hospital, Osaka, Japan
2022.1.21