[Novel Application of Post-contrast T1map for Detection of Subendocardial Infarction].

In cardiac magnetic resonance (CMR) for myocardial infarction, there have been quite a few cases of obscure image contrast between subendocardial lesion and left ventricular (LV) blood pool on late gadolinium enhancement (LGE) images. This study was motivated by confirmation of usefulness of post-contrast T1map for detection of subendocardial infarction. From June 2017 to May 2018, forty-eight consecutive patients who underwent contrast-enhanced CMR to assess myocardial infarction were reviewed. We measured the contrast ratio (CR) between the infarcted myocardium and LV blood pool on LGE and on post-contrast T1map images, and compared them. The CR (mean±standard deviation) was -0.04±0.11 for LGE images and 0.02±0.04 for post-contrast T1map images (P<0.05). These results suggest that the post-contrast T1map, which uses the difference in T1 value as image contrast rather than magnitude image, can clearly depict the boundary between the infarcted myocardium and LV blood pool. The addition of post-contrast T1map to image interpretation might provide valuable information in the evaluation of subendocardial infarction.

Clinical significance of gadobutrol in magnetic resonance imaging for the detection of myocardial infarction: matched-pair cohort study to compare with gadopentetate dimeglumine at standard dose.

We aimed to confirm whether gadobutrol is more useful for late gadolinium enhancement (LGE) imaging than gadopentetate dimeglumine (Gd-DTPA) at the standard dose. Patients who underwent LGE imaging to assess myocardial infarction were retrospectively enrolled: gadobutrol, 51 cases; Gd-DTPA, 49 cases. Contrast ratios of infarcted lesion to remote myocardium (CRremote) and to left ventricular blood (CRblood) were compared. Patient characteristics that might affect image contrast did not differ between groups. CRremote (median, (interquartile range)) at 10 and 15 min after administration was 0.79 (0.08) and 0.70 (0.09) for gadobutrol, and 0.74 (0.13) and 0.65 (0.16) for Gd-DTPA (P < 0.05 and < 0.05), respectively. CRblood was - 0.05 (0.17) and - 0.002 (0.15) for gadobutrol, and - 0.05 (0.18) and 0.01 (0.16) for Gd-DTPA (P = 0.29 and = 0.22), respectively. Gadobutrol provided significantly better delineation of infarcted from normal myocardium than Gd-DTPA. Meanwhile, there was no difference in image contrast between infarcted myocardium and left ventricular blood.

[Clinical Usefulness of Ultra-short TE MRA for Follow-up Imaging after Cerebral Aneurysm Clipping].

The aims of this study were to elucidate signal pattern of cerebral aneurysm clip in brain magnetic resonance angiography (MRA) using non-contrast enhanced ultra-short echo time (UTE) sequence and to explore effective utilization of this novel technique for patients, who underwent cerebral aneurysm clipping. The clip was embedded in homemade phantom and scanned using UTE sequence. We investigated characteristic features of the artifacts derived from the clip. Besides, we compared the volume of signal loss between conventional time-of-flight (TOF) and UTE-MRA in 50 patients with the cerebral aneurysm clip. In phantom study, the clip was delineated as signal void area fully surrounded by high signal on original images. On reconstructed short-axial views for the clip, four-leaf clover pattern of artifact was observed when clip was arranged orthogonal to the static magnetic field. On the other hand, this artifact disappeared when the clip was arranged in parallel with the static magnetic field. The volume of signal loss in clinical cases was significantly reduced in UTE-MRA (P < 0.05): 1.30, 0.52-2.77 cm3 for TOF; 0.84, 0.28-1.74 cm3 for UTE (median, range). The scan time for UTE-MRA was 2 minutes and 52 seconds. To understand the characteristic feature of the artifacts from the clip could contribute to define vascular structure in image interpretation. Adding UTE-MRA to routine protocol is useful approach for follow-up imaging after cerebral aneurysm clipping with clinically acceptable prolongation of the scan time.

Quantification of the radiation dose to the pyramidal tract using tractography in treatment planning for stereotactic radiosurgery.

In stereotactic radiosurgery for intracranial lesions, optimization of the dose to the at-risk organs is important to avoid neurological complications. We aimed to quantify the dose to the pyramidal tract (PT) and improve treatment planning for gamma knife radiosurgery by combining tractography. Pyramidal tractography images were depicted in 23 patients with lesions adjacent to the PT and fused with stereotactic magnetic resonance images. We regarded the PT as an at-risk organ and performed dose planning. To assess the efficacy of this process, we compared clinical parameters between plans with and without tractography. In the plans with tractography, the maximum PT dose was significantly reduced, although the irradiation time was prolonged by 3.5 min. There was no significant difference in the dose covering 95% of the lesion volume (D95). This result suggests that the PT dose can be reduced while maintaining the D95 with clinically acceptable prolongation of the irradiation time.