Perihematomal Cerebral Tissue Iron Quantification on MRI Following Intracerebral Hemorrhage in Two Human Subjects: Proof of Principle

MR Imaging-based Biomarker Development in Hemorrhagic Stroke Patients Including Brain Iron Quantification, Diffusion Tensor Imaging, and Phenomenon of Ultra-early Erythrolysis

This review article discusses the role of MR imaging-based biomarkers in understanding and managing hemorrhagic strokes, focusing on intracerebral hemorrhage (ICH) and aneurysmal subarachnoid hemorrhage. ICH is a severe type of stroke with high mortality and morbidity rates, primarily caused by the rupture of small blood vessels in the brain, resulting in hematoma formation. MR imaging-based biomarkers, including brain iron quantification, ultra-early erythrolysis detection, and diffusion tensor imaging, offer valuable insights for hemorrhagic stroke management. These biomarkers could improve early diagnosis, risk stratification, treatment monitoring, and patient outcomes in the future, revolutionizing our approach to hemorrhagic strokes.

Assessing early erythrolysis and the relationship to perihematomal iron overload and white matter survival in human intracerebral hemorrhage

AIMS

Iron released from lysed red blood cells within the hematoma plays a role in intracerebral hemorrhage (ICH)-related neurotoxicity. This study utilizes magnetic resonance imaging (MRI) to examine the time course, extent of erythrolysis, and its correlation with perihematomal iron accumulation and white matter loss.

METHODS

The feasibility of assessing proportional erythrolysis using T2* MRI was examined using pig blood phantoms with specified degrees of erythrolysis. Fifteen prospectively enrolled ICH patients had MRIs (3-Tesla) at days 1-3, 14, and 30 (termed early, subacute, and late periods, respectively). Measurement was performed on T2*, 1/T2*, and fractional anisotropy (FA) maps.

RESULTS

Pig blood phantoms showed a linear relationship between 1/T2* signal and percent erythrolysis. MRI on patients showed an increase in erythrolysis within the hematoma between the early and subacute phases after ICH, almost completing by day 14. Although perihematomal iron overload (IO) correlated with the erythrolysis extent and hematoma volume at days 14 and 30, perihematomal white matter (WM) loss significantly correlated with both, only at day 14.

CONCLUSION

MRI may reliably assess the portion of the hematoma that lyses over time after ICH. Perihematomal IO and WM loss correlate with both the erythrolysis extent and hematoma volume in the early and subacute periods following ICH.

Perihematomal brain tissue iron concentration measurement by MRI in patients with intracerebral hemorrhage

Aims

Over the past two decades, animal intracerebral hemorrhage (ICH) model studies have indicated that iron, released after hemoglobin degradation, is neurotoxic. Iron phantom and animal experiments have shown that magnetic resonance imaging (MRI) relaxivity maps correlate with iron concentration. This study expands this into patients.

Methods

Eighteen human subjects with ICH underwent MRI at 3, 14, and 30 days. R2* relaxivity maps were used to calculate perihematomal iron concentrations and T2 imaging to determine hematoma and edema volumes.

Results

Perihematomal iron concentrations were increased at all three time points and decreased with distance from the hematoma. While perihematomal iron concentrations did not vary with hematoma size, the total iron overload (increased iron concentration x volume of affected tissue) did. Total iron overload correlated with edema volume.

Conclusions

These results demonstrate the feasibility of measuring perihematomal iron in ICH patients which may be important for monitoring treatment strategies and assessing efficacy noninvasively.

High signal-intensity abnormalities in susceptibility-weighted imaging for primary intracerebral hemorrhage

Purpose: To identify the regularity of signal evolution of intracerebral hemorrhage on susceptibility-weighted imaging (SWI) at different stages compared with T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI). Methods: We retrospectively evaluated a series of 365 patients who underwent T1WI, T2WI, and SWI examination simultaneously or sequentially in our hospital from January 2015 to May 2017. Two neuroradiologists assessed the images and discrepancies between their interpretations were resolved by consensus. Statistical analysis was performed using Chi-squared and Kappa tests. Results: Of the 365 patients on SWI sequence, 94 were enrolled. SWI detected the cases at different stages; T1WI detected 89 cases and T2WI detected 91 cases. The signal intensity of intracerebral hemorrhage on SWI was significantly associated with T1WI imaging and T2WI (χ² = 4.651; p < 0.05; χ² = 26.396; p < 0.01, respectively), especially at the late subacute stage. There was moderate consistency between the signal intensity of intracerebral hemorrhage on T2WI and SWI (Kappa coefficient = 0.530). Conclusion: Intracerebral hemorrhage has a varied appearance on SWI, and the evolution of signal of intracerebral hemorrhage on SWI sequence is influenced by T1WI and T2WI. Hematoma detection should be closely combined with clinical manifestation.

Complement Inhibition Attenuates Early Erythrolysis in the Hematoma and Brain Injury in Aged Rats

Background and Purpose- Early erythrolysis in the hematoma contributes to brain injury after intracerebral hemorrhage (ICH). This study investigated the effects of N-acetylheparin, a complement inhibitor, and aurin tricarboxylic acid, a membrane attack complex inhibitor, on early erythrolysis, brain iron deposition, and brain injury in aged rats. Methods- There were 3 parts in the study. First, aged (18 months old) male Fischer 344 rats had an ICH. The time course of erythrolysis in the hematoma was determined by T2* weighted magnetic resonance imaging, and the expression of CD163 was examined. Second, aged rats had an ICH with N-acetylheparin or vehicle. Rats were euthanized at days 1, 3, and 28 after magnetic resonance imaging (T2-, T2*-weighted, and T2* array) and behavioral tests. Brains were used for immunohistochemistry. Third, aged rats had an ICH with avaurin tricarboxylic acid or vehicle. The rats had magnetic resonance imaging and behavioral tests and were euthanized at day 3. Brains were used for immunohistochemistry. Results- Early erythrolysis occurred within the clot in aged F344 rats. There were increased numbers of CD163-positive cells after ICH. Almost all perihematomal CD163-positive cells were microglia/macrophages, while positive neurons were found more distant from the hematoma. Coinjection of N-acetylheparin attenuated erythrolysis, iron accumulation, CD163 expression, microglia activation, brain swelling, and neuronal death in the acute phase, as well as reducing brain atrophy and neurological deficits in the chronic phase. Coinjection of aurin tricarboxylic acid also reduced erythrolysis and ICH-induced brain injury. Conclusions- Inhibiting complement activation resulted in less erythrolysis and brain injury after ICH.

Brain tissue iron quantification by MRI in intracerebral hemorrhage: Current translational evidence and pitfalls

Intracerebral hemorrhage (ICH) is a common subtype of hemorrhagic stroke with devastating consequences with no specific treatment. There is, however, substantial evidence for iron-mediated neurotoxicity in animal ICH models. Non-invasive quantification of the peri-hematomal tissue iron based on MRI has shown some promise in animal models and is being validated for clinical translation. This commentary reviews evidence for this approach and discusses potential pitfalls.

The Involvement of Iron in Traumatic Brain Injury and Neurodegenerative Disease

Traumatic brain injury (TBI) consists of acute and long-term pathophysiological sequelae that ultimately lead to cognitive and motor function deficits, with age being a critical risk factor for poorer prognosis. TBI has been recently linked to the development of neurodegenerative diseases later in life including Alzheimer’s disease, Parkinson’s disease, chronic traumatic encephalopathy, and multiple sclerosis. The accumulation of iron in the brain has been documented in a number of neurodegenerative diseases, and also in normal aging, and can contribute to neurotoxicity through a variety of mechanisms including the production of free radicals leading to oxidative stress, excitotoxicity and by promoting inflammatory reactions. A growing body of evidence similarly supports a deleterious role of iron in the pathogenesis of TBI. Iron deposition in the injured brain can occur via hemorrhage/microhemorrhages (heme-bound iron) or independently as labile iron (non-heme bound), which is considered to be more damaging to the brain. This review focusses on the role of iron in potentiating neurodegeneration in TBI, with insight into the intersection with neurodegenerative conditions. An important implication of this work is the potential for therapeutic approaches that target iron to attenuate the neuropathology/phenotype related to TBI and to also reduce the associated risk of developing neurodegenerative disease.

Minocycline Effects on Intracerebral Hemorrhage-Induced Iron Overload in Aged Rats: Brain Iron Quantification With Magnetic Resonance Imaging

BACKGROUND AND PURPOSE

Brain iron overload is a key factor causing brain injury after intracerebral hemorrhage (ICH). This study quantified brain iron levels after ICH with magnetic resonance imaging R2* mapping. The effect of minocycline on iron overload and ICH-induced brain injury in aged rats was also determined.

METHODS

Aged (18 months old) male Fischer 344 rats had an intracerebral injection of autologous blood or saline, and brain iron levels were measured by magnetic resonance imaging R2* mapping. Some ICH rats were treated with minocycline or vehicle. The rats were euthanized at days 7 and 28 after ICH, and brains were used for immunohistochemistry and Western blot analyses. Magnetic resonance imaging (T2-weighted, T2* gradient-echo, and R2* mapping) sequences were performed at different time points.

RESULTS

ICH-induced brain iron overload in the perihematomal area could be quantified by R2* mapping. Minocycline treatment reduced brain iron accumulation, T2* lesion volume, iron-handling protein upregulation, neuronal cell death, and neurological deficits (P<0.05).

CONCLUSIONS

Magnetic resonance imaging R2* mapping is a reliable and noninvasive method, which can quantitatively measure brain iron levels after ICH. Minocycline reduced ICH-related perihematomal iron accumulation and brain injury in aged rats.