Masatoshi Yamane

Objectives: This study evaluated the utility of adaptive complex signal average (ACSA) diffusion-weighted imaging (DWI) specifically in breath-hold (BH) liver imaging, with a focus on signal intensity (SI) improvement, intrahepatic signal homogeneity, and apparent diffusion coefficient (ADC) behavior, and compared these findings with conventional non-ACSA DWI and free-breathing (FB) ACSA DWI. Methods: This retrospective study included 62 patients (mean age, 67.8 ± 13.6 years; 27 women) who underwent liver MRI with both FB and BH DWI on a 3-T system. Non-ACSA images were generated using conventional magnitude reconstruction, and ACSA images were reconstructed from identical raw data. SI, signal-to-noise ratio (SNR) and ADC were measured in the left lateral segment and right hepatic lobe. The signal intensity difference ratio (SIDR) between ACSA and non-ACSA, signal intensity ratio (SIR) and ADC ratio between right lobe and lateral segment were calculated. Results: In both FB and BH imaging, SI and SNR in both liver regions were significantly higher on ACSA DWI than on non-ACSA DWI (p < 0.01). ADC values were significantly lower with ACSA. SIDR was significantly higher in the left lateral segment (p < 0.01), indicating greater SI improvement in motion-prone regions. SIR and ADC ratios between lobes were significantly smaller with ACSA in both respiratory conditions (p < 0.01). FB-ACSA showed smaller SIR than BH-ACSA, while ADC ratios did not differ. Conclusions: ACSA DWI significantly improves SI, intrahepatic uniformity, and ADC reliability even under BH liver imaging. BH ACSA DWI may represent a potentially useful application complementary to FB ACSA DWI, supporting its consideration as a post-processing strategy for improving qualitative and quantitative liver DWI in future investigations.

BACKGROUND: The clinical relevance of glymphatic dysfunction in patients with subarachnoid hemorrhage (SAH) remains unclear. This study aimed to evaluate glymphatic system function in patients with aneurysmal SAH using the diffusion tensor imaging–based analysis along the perivascular space (ALPS) index and to investigate its association with the development of hydrocephalus and clinical outcomes. In particular, we explored whether hydrocephalus could act as a potential mediator of the relationship between glymphatic dysfunction and poor functional outcome. METHODS: We retrospectively analyzed 60 patients with aneurysmal SAH who underwent magnetic resonance imaging, including diffusion tensor imaging, at a median of 18 days after onset. The ALPS index was calculated from directional diffusivity values in the deep white matter, and its relationship with 3-month functional outcomes (modified Rankin Scale) and shunt-dependent hydrocephalus was examined. A logistic regression–based causal mediation analysis was performed to assess whether hydrocephalus statistically mediated the association between a low ALPS index (P =0.0002). Shunt-dependent hydrocephalus occurred more frequently in the poor outcome group and was associated with a markedly reduced ALPS index (median, 0.99). Mediation analysis with covariates including age and World Federation of Neurosurgical Societies grade revealed that the total effect of a low ALPS index on poor outcome was significant (odds ratio, 7.98 [95% CI, 1.12–56.79]), and this effect was largely mediated by hydrocephalus development (indirect effect odds ratio, 3.11 [95% CI, 1.23–7.89]; proportion mediated=0.78). CONCLUSIONS: Reduced ALPS index, which may reflect impaired glymphatic transport, was associated with poor functional outcomes in patients with aneurysmal SAH. This relationship appeared to be largely mediated by the presence of shunt-dependent hydrocephalus. Although causality cannot be established in this observational study, these findings suggest that glymphatic dysfunction may play a clinically relevant role in the pathophysiology of SAH-related hydrocephalus and outcome.

Focal cerebral arteriopathy (FCA) is a clinically important disease that often causes progressive arteriopathy. We report a case of FCA with progressive arteriopathy due to arterial shrinkage of the outer diameter found on T2-weighted three-dimensional sampling perfection with application optimized contrasts using different flip angle evolutions (3D-SPACE) imaging. The patient was a 9-year-old girl who developed right hemiparesis. Acute infarction was detected in the basal ganglia. Vascular images revealed stenosis from the distal internal carotid artery (ICA) to the middle cerebral artery (MCA). Intravenous heparin was administered for 8 days, and the symptoms improved. However, 29 days after onset, right hemiparesis transiently developed again and magnetic resonance angiography (MRA) showed progressive stenosis from the ICA to MCA, while 3D-SPACE showed similar shrinkage of the outer diameter. Aspirin was started, and there was no subsequent recurrence. After 12 months, MRA and 3D-SPACE showed improvement of stenosis and arterial shrinkage. Given the time course, the change in the outer diameter was thought to be vasospasm. Thus, vasospasm may be one of the causes of progressive arteriopathy in FCA.