Bom-yi Kim

Magnetic resonance imaging and diffusion-weighted imaging changes after hypoglycemic coma.

The authors report a case of severe hypoglycemic encephalopathy in an elderly patient. The magnetic resonance images showed bilateral cortical signal changes and basal ganglia lesions, which spared the thalami. The lesions were bright on fluid‐attenuated inversion recovery and diffusion‐weighted images and dark on the apparent diffusion coefficient map, being more conspicuous on the diffusion‐weighted images than on the fluid‐attenuated inversion recovery images. A literature review of the imaging features and pathophysiological mechanism in comparison with those of hypoxic ischemic injury is discussed.

DCE and DSC MR perfusion imaging in the differentiation of recurrent tumour from treatment-related changes in patients with glioma.

AIM To retrospectively compare the utility of perfusion magnetic resonance imaging (MRI) in distinguishing treatment-related changes from recurrent disease in glioma patients. MATERIALS AND METHODS Thirty-one patients with histologically diagnosed gliomas and increased enhancement after or during concurrent (chemo-) radiation therapy were enrolled. They underwent dynamic contrast-enhanced (DCE) permeability MRI followed by dynamic susceptibility contrast (DSC) perfusion MRI. The vascular transfer constant (rK(trans)) and initial areas under the concentration curve (riAUC) were obtained from DCE MRI, and cerebral blood volume (rCBV) was obtained from DSC MRI. Patients were classified as having treatment-related changes or recurrent tumours based on clinicoradiological results or pathological results from surgery. RESULTS Nineteen patients were diagnosed as having recurrences and 12 patients as having treatment-related changes. The rK(trans), riAUC, and rCBV values in the recurrent group were significantly higher than the values in the group with treatment-related changes (p < 0.05). For all 31 patients, there was no significant difference between DSC MRI and DCE MRI for the differentiating power between recurrence and treatment-related changes (p = 0.7227). However, when including only the 24 patients with concordant values of rK(trans) and riAUC, DCE MRI showed a significant AUC value of 0.786 in the receiver operating characteristic (ROC) curve analysis (p = 0.003), whereas DSC MRI did not (AUC = 0.643, p = 0.229). CONCLUSION MRI perfusion images appear to show promise in distinguishing treatment-related changes from recurrent tumours. When both rK(trans) and riAUC show concordant values, DCE MRI seems to be more powerful than DSC MRI in the differentiation of recurrence from treatment-related changes.

Supra-aortic low-dose contrast-enhanced time-resolved magnetic resonance (MR) angiography at 3 T: comparison with time-of-flight MR angiography and high-resolution contrast-enhanced MR angiography

Background Low-dose, time-resolved, contrast-enhanced, magnetic resonance angiography (TR-CEMRA) has been described previously; however, a comparative study between low dose TR-CEMRA and time-of-flight MRA (TOF-MRA) in the diagnosis of supra-aortic arterial stenosis has not yet been published. Purpose To demonstrate the feasibility and effectiveness of low-dose TR-CEMRA compared with TOF-MRA, using high-resolution contrast-enhanced MRA (HR-CEMRA) as the reference standard. Material and Methods This prospective study consisted of 30 consecutive patients. All patients underwent TOF-MRA of the neck and circle of Willis and supra-aortic HR-CEMRA, followed by supra-aortic low-dose TR-CEMRA. Gadoterate meglumine (Gd-DOTA, Dotarem®, Guerbet, Roissy CdG Cedex, France) was injected at a dose of 0.1 mmol/kg for HR-CEMRA, followed by a 0.03 mmol/kg bolus for low-dose TR-CEMRA. Three readers evaluated the assessibility and image quality, and then two readers classified each stenosis into the following categories: normal (0–30%), mild stenosis (31–50%), moderate (51–70%), severe (71–99%), and occlusion. Results TR-CEMRA and HR-CEMRA showed a greater number of assessable arterial segments than TOF-MRA (P < 0.01). For TR-CEMRA, 29 cases showed within or better than the diagnostic range, whereas all 30 cases were in the diagnostic range for TOF-MRA and HR-CEMRA. For evaluation of stenosis in a total of 743 arterial segments, both TR-CEMRA and TOF-MRA results agreed with those of HR-CEMRA in 729 segments (98.1%), with excellent inter-observer agreement of TR-CEMRA; stenosis was overestimated in nine segments (1.2%) and underestimated in five segments (0.7%). For diagnosis of stenosis using 30% as the cut-off value on HR-CEMRA, the sensitivity and specificity were 88.2% and 99.3%, respectively, for the TR-CEMRA procedure, versus 94.1% and 99.6%, respectively, for TOF-MRA. Conclusion Low-dose TR-CEMRA is feasible and effective in the diagnosis of supra-aortic arterial stenosis, and could be more useful option than TOF-MRA.

Subtraction MR Venography Acquired from Time-Resolved Contrast-Enhanced MR Angiography: Comparison with Phase-Contrast MR Venography and Single-Phase Contrast-Enhanced MR Venography

Objective To evaluate the image characteristics of subtraction magnetic resonance venography (SMRV) from time-resolved contrast-enhanced MR angiography (TRMRA) compared with phase-contrast MR venography (PCMRV) and single-phase contrast-enhanced MR venography (CEMRV). Materials and Methods Twenty-one patients who underwent brain MR venography (MRV) using standard protocols (PCMRV, CEMRV, and TRMRA) were included. SMRV was made by subtracting the arterial phase data from the venous phase data in TRMRA. Co-registration and subtraction of the two volume data was done using commercially available software. Image quality and the degree of arterial contamination of the three MRVs were compared. In the three MRVs, 19 pre-defined venous structures (14 dural sinuses and 5 cerebral veins) were evaluated. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the three MRVs were also compared. Results Single-phase contrast-enhanced MR venography showed better image quality (median score 4 in both reviewers) than did the other two MRVs (p < 0.001), whereas SMRV (median score 3 in both reviewers) and PCMRV (median score 3 in both reviewers) had similar image quality (p ≥ 0.951). SMRV (median score 0 in both reviewers) suppressed arterial signal better than did the other MRVs (median score 1 in CEMRV, median score 2 in PCMRV, both reviewers) (p < 0.001). The dural sinus score of SMRV (median and interquartile range [IQR] 48, 43-50 for reviewer 1, 47, 43-49 for reviewer 2) was significantly higher than for PCMRV (median and IQR 31, 25-34 for reviewer 1, 30, 23-32 for reviewer 2) (p < 0.01) and did not differ from that of CEMRV (median and IQR 50, 47-52 for reviewer 1, 49, 45-51 for reviewer 2) (p = 0.146 in reviewer 1 and 0.123 in reviewer 2). The SNR and CNR of SMRV (median and IQR 104.5, 83.1-121.2 and 104.1, 74.9-120.5, respectively) were between those of CEMRV (median and IQR 150.3, 111-182.6 and 148.4, 108-178.2) and PCMRV (median and IQR 59.4, 49.2-74.9 and 53.6, 43.8-69.2). Conclusion Subtraction magnetic resonance venography is a promising MRV method, with acceptable image quality and good arterial suppression.

The usefulness of diffusion-weighted readout-segmented EPI and fast spin echo with BLADEPROPELLER k-space sampling: A comparison with single-shot EPI for diffusion-weighted imaging in ischemic stroke patients

We evaluated the value of diffusion‐weighted readout‐segmented EPI (DW rs‐EPI) and diffusion‐weighted fast spin echo images with BLADE (PROPELLER) k‐space sampling (DW BLADE) in patients with ischemic stroke through intra‐individual comparisons with diffusion‐weighted single‐shot EPI (DW ss‐EPI). Forty‐four patients with acute ischemic stroke who had undergone three different types of diffusion weighted imaging (DWI) (b = 1000 s/mm2) were included. Two reviewers assessed the three types of DWI for diagnostic confidence based on a five‐point confidence score (CS). The inter‐ and intra‐observer agreements for the CS were assessed. The DWI signal ratio to the contralateral normal area and the apparent diffusion coefficient (ADC) of DWI lesions were compared. The CSs of the three DWI methods were significantly different (P < 0.001). A post hoc analysis showed a significantly higher CS with DW rs‐EPI than with DW ss‐EPI (P = 0.022). There were significant increases in the CSs for DW rs‐EPI compared to DW ss‐EPI, for patients who underwent DWI within 24 h of symptom onset, and for patients with DWI lesions ≤ 50 mm2. The inter‐observer and intra‐observer agreements of the CS were good. DW rs‐EPI increased the diagnostic confidence of ischemic stroke compared to DW ss‐EPI, particularly for patients with small lesions and for those who underwent DWI within 24 h of symptom onset. DW BLADE showed a similar level of diagnostic confidence to DW ss‐EPI.

Pituitary Infarct Masquerading as a Pituitary Abscess

A 64-year-old woman presented with headache for a week. Contrast-enhanced T1-weighted sellar magnetic resonance imaging showed an ovoid intrasellar nonenhancing lesion with peripheral enhancement (Figure 1). The lesion showed intermediate to high signal intensity on diffusion-weighted imaging and restricted diffusion on apparent diffusion coefficient map (Figure 2). Initial differential diagnosis included pituitary abscess and infected Rathke’s cleft cyst. Initially, partial removal of the pituitary gland was performed via the transsphenoidal approach. The result of the frozen biopsy was pituitary infarct; thus, the operation was finished. The final pathological diagnosis was also pituitary infarct. Pituitary lesions with intermediate to high signal on diffusion-weighted imaging include pituitary abscess and pituitary infarct. A pituitary infarct should be considered as a differential diagnosis in the case of pituitary apoplexy.