Ultrafast cervcial spine MRI protocol using deep learning-based reconstruction: Diagnostic equivalence to a conventional protocol.

PURPOSE: A major drawback of magnetic resonance imaging (MRI) is its limited imaging speed. This study proposed an ultrafast cervical spine MRI protocol (2 min 57 s) using deep learning-based reconstruction (DLR) and compared the diagnostic results to those of conventional MRI protocols (12 min 54 s). METHODS: Fifty patients who underwent cervical spine MRI using both conventional and ultrafast protocols, including sagittal T1-weighted, T2-weighted, short-TI inversion recovery, and axial T2*-weighted imaging were included in this study. The ultrafast protocol shortened the acquisition time to approximately-one-fourth of that of the conventional protocol by reducing the phase matrix, oversampling rate, and number of excitations, and by applying compressed sensing. To compensate for the decreased signal-to-noise ratio caused by acceleration, noise reduction using DLR was performed. For image interpretation, three neuroradiologists graded or classified degenerative changes, including central canal stenosis, foraminal stenosis, endplate degeneration, disc degeneration, and disc hernia. The presence of other pathologies was also recorded. Given the absence of a reference standard, we tested the interchangeability of the two protocols by calculating the 95% confidence interval (CI) of the individual equivalence index. We also assessed the inter-protocol intra-reader agreement using kappa statistics. RESULTS: Except for endplate degeneration, the 95 % CI of the individual equivalence index for all variables did not exceed 5 %, indicating interchangeability between the two protocols. The kappa values ranged from 0.600 to 0.977, indicating substantial to almost perfect agreement. CONCLUSIONS: The proposed ultrafast MRI protocol yielded almost equivalent diagnostic results compared as the conventional protocol.

MR imaging features of mammary analogue secretory carcinoma and acinic cell carcinoma of the salivary gland: a preliminary report.

OBJECTIVES: To report MR imaging features of mammary analogue secretory carcinoma (MASC) and acinic cell carcinoma (AciCC) of the salivary gland based on the latest version of the World Health Organization (WHO) 2017 classification of head and neck tumours. METHODS: MR images in 4 patients with MASC and 4 with AciCC were reviewed for margin characteristics, the presence of pathological cervical nodes, the presence of a cystic component and interface between cystic and solid component, signal intensity of the cystic components on T1 weighted images, and signal intensity of the solid component on T1 and T2 weighted images. RESULTS: All the MASCs and AciCCs had well-defined boundaries, and 1 AciCC had pathological nodes. All 4 MASCs presented as predominantly cystic tumours with papillary projection of the solid component. All 4 AciCCs presented as solid tumours. The signal intensity of the cystic components on T1 weighted images was entirely hyperintense in 2, and partly hyperintense demonstrating fluid-fluid level in 2. In all the MASCs, the signal intensity of the solid components on T1 weighted images was intermediate. In the AciCCs, the signal intensity of the solid components on T1 weighted images was high in 2 tumours and intermediate in 2. The signal intensity of the solid components on T2 weighted images varied from low to high in both MSACs and AciCCs. CONCLUSIONS: All 4 MASCs had a large cystic component, including areas of high signal intensity on T1 weighted images. The solid component appeared as a papillary projection into the cystic component. All 4 AciCCs presented as solid tumours, 2 of which showed high signal intensity on T1 weighted images.

Reduction of misregistration on cerebral four-dimensional computed tomography angiography images using advanced patient motion correction reconstruction.

PURPOSE: The aim of this study was to evaluate whether advanced patient motion correction (APMC) can reduce the misregistration of pixels between the different X-ray tube positions in four-dimensional CT angiography (4D-CTA). MATERIALS AND METHODS: Eight patients with intracranial aneurysms were included in this retrospective study. We compared the CTA images with APMC reconstruction and half-scan reconstruction with regard to the following 3 items: (1) bone misalignment area; (2) image noise; and (3) aneurysm volume change. RESULTS: The bone misalignment area and image noise were significantly reduced in the APMC images, as compared to that in the half-scan reconstruction images (bone misalignment area: 33.0 ± 18.1 cm(3) vs 152.0 ± 72.2 cm(3), respectively; p < 0.001) (image noise at pons: 9.70 ± 2.58 vs 15.16 ± 5.02, respectively, p < 0.001). The aneurysm volume and volume variance were significantly smaller in the APMC reconstruction than those in the half-scan reconstruction (volume: 1107.2 ± 1813.8 mm(3) vs 1135.1 ± 1853.8 mm(3); p < 0.05; coefficient of variation: 0.0291 ± 0.014 vs 0.0463 ± 0.026, p < 0.05, respectively). CONCLUSION: Our results show that APMC reduces the reconstruction related misregistration between the cardiac phases compared to half-scan reconstruction.

Model-based iterative reconstruction for detection of subtle hypoattenuation in early cerebral infarction: a phantom study.

PURPOSE: Model-based iterative reconstruction (MBIR) was recently shown to enable dose reduction in computed tomography (CT). The detectability of low-contrast lesions was assessed on CT images reconstructed with MBIR compared with the conventional filtered back-projection (FBP) method. MATERIALS AND METHODS: A phantom simulating brain gray matter containing small lesions mimicking early cerebral infarctions was scanned at tube currents of 50, 100, 200, and 400 mA. Images were reconstructed by use of both methods. Round regions were cropped from the reconstructed images, half with a lesion, the other half without. Eight radiologists reviewed the images and scored the certainty of lesion detection on a 5-point scale. Overall performance was analyzed by use of a receiver operating characteristic curve. RESULTS: For the tube currents investigated, the analysis showed that the mean areas under the curves for the reviewers were 0.65, 0.70, 0.82, and 0.83 for FBP and 0.70, 0.76, 0.78, and 0.90 for MBIR. For each current, there was no significant difference between the areas under the curves for the different reconstruction methods (p = 0.32, 0.24, 0.49, and 0.17). CONCLUSION: For the small, low-contrast lesions in the phantom model used in this study, no significant difference between detectability was observed for MBIR and FBP.

Prevalence and diagnostic performance of computed tomography angiography spot sign for intracerebral hematoma expansion depend on scan timing.

INTRODUCTION: The computed tomography angiography (CTA) spot sign correlates with intracerebral hemorrhage (ICH) expansion; however, various diagnostic performances for hematoma expansion, especially in sensitivity, have been reported. We aimed to assess the impact of scan timing of CTA on the diagnostic performance of the CTA spot sign for ICH expansion in two different arterial phases within patients. METHODS: Eighty-three consecutive patients with primary ICH who received two sequential CTAs were recruited. Two neuroradiologists reviewed CTAs for CTA spot signs, while one reviewed initial and follow-up non-contrast CT for measuring ICH volume. The time interval between two phases was then calculated, and the diagnostic performance of CTA spot sign in each phase was evaluated. RESULTS: CTA spot signs were observed in 20/83 (24.1 %) patients in the early phase and 44/83 (53.0%) patients in the late phase. The mean time interval between the two phases was 12.7 s. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for hematoma progression of CTA spot sign were 48.1, 87.5, 65.0, 77.8, and 74.7%, respectively, in early phase and 92.6, 66.1, 56.8, 94.9, and 74.7%, respectively, in late phase. The CTA spot sign was significantly associated with ICH expansion in early (P < 0.001) and late (P < 0.00001) phases (Pearson's chi-square test). CONCLUSION: A mere 10-s difference in scan timing could make a difference on prevalence and diagnostic performance of the CTA spot sign, suggesting a need for the standardization of the CTA protocol to generalize the approach for effective clinical application.

Neuromelanin magnetic resonance imaging reveals increased dopaminergic neuron activity in the substantia nigra of patients with schizophrenia.

PURPOSE: The dopamine hypothesis suggests that excessive dopamine release results in the symptoms of schizophrenia. The purpose of this study was to elucidate the dopaminergic and noradrenergic neurons using 3-T neuromelanin magnetic resonance imaging (MRI) in patients with schizophrenia and healthy control subjects. METHODS: We prospectively examined 52 patients with schizophrenia (M: F = 27∶25, mean age, 35 years) and age- and sex-matched healthy controls. Using a 3T MRI unit, we obtained oblique T1-weighted axial images perpendicular to the brainstem. We measured the signal intensity and area for the substantia nigra (SNc), midbrain tegmentum, locus ceruleus (LC), and pons. We then calculated the contrast ratios (CR) for the SNc (CRSN) and LC (CRLC), which were compared between patients and healthy controls using unpaired t-tests. RESULTS: The SNc and LC were readily identified in both patients and healthy controls as areas with high signal intensities in the posterior part of the cerebral peduncle and in the upper pontine tegmentum. The CRSN values in patients were significantly higher than those in healthy controls (10.89±2.37 vs. 9.6±2.36, p<0.01). We observed no difference in the CRLC values between the patients and healthy controls (14.21±3.5 vs. 13.44±3.37, p = 0.25). Furthermore, there was no difference in area of the SNc and LC between schizophrenia patients and controls. CONCLUSIONS: Neuromelanin MRI might reveal increased signal intensity in the SNc of patients with schizophrenia. Our results indicate the presence of excessive dopamine products in the SNc of these patients.

Dual-energy CT for detection of contrast enhancement or leakage within high-density haematomas in patients with intracranial haemorrhage.

INTRODUCTION: Our study aimed to elucidate the diagnostic performance of dual-energy CT (DECT) in the detection of contrast enhancement in intracranial haematomas (ICrH) with early phase dual-energy computed tomography angiography (CTA) and compare the results with those obtained by delayed CT enhancement. METHODS: Thirty-six patients with ICrH were retrospectively included in this study. All patients had undergone single-energy non-contrast CT and contrast-enhanced dual-source DECT. DECT images were post-processed with commercial software, followed by obtaining iodine images and virtual non-contrast images and generating combined images that created the impression of 120-kVp images. Two neuroradiologists, blinded to the patients' data, reviewed two reading sessions: session A (non-contrast CT and combined CT) and session B (non-contrast CT, combined CT, and iodine images) for detection of contrast enhancement in the haematomas. RESULTS: Contrast leakage or enhancement was detected in 23 (57.5 %) out of 40 haemorrhagic lesions in 36 patients on delayed CT. Three enhanced lesions were depicted only in the DECT iodine images. The sensitivity, specificity, positive predictive value, and negative predictive value of session A were 82.6, 94.1, 95.0, and 80.0 %, respectively, and those of session B were 95.7, 94.1, 95.7, and 94.1 %, respectively. CONCLUSION: DECT emphasised the iodine enhancement and facilitated the detection of contrast enhancement or leakage.