Utility of intravoxel incoherent motion magnetic resonance imaging and arterial spin labeling for recurrent glioma after bevacizumab treatment.

Background Detecting recurrence of glioma on magnetic resonance imaging (MRI) is getting more and more important, especially after administration of new anti-tumor agent. However, it is still hard to identify. Purpose To examine the utility of intravoxel incoherent motion (IVIM) MRI and arterial spin labeling-cerebral blood flow (ASL-CBF) for recurrent glioma after initiation of bevacizumab (BEV) treatment. Material and Methods Thirteen patients (7 men, 6 women; age range = 41-82 years) with glioma (high grade, n = 11; low grade, n = 2) were enrolled in the study. IVIM parameters including apparent diffusion coefficient (ADC), true diffusion coefficient (D), and perfusion fraction (f) were obtained with 14 different b-values. We identified tumor progression during BEV therapy by MRI monitoring consisting of diffusion-weighted imaging (DWI), fluid-attenuated inversion recovery (FLAIR) imaging, and contrast-enhanced T1-weighted (CE-T1W) imaging by measuring tumor area. We also measured each parameter of IVIM and ASL-CBF, and calculated relative ADC (rADC), relative D (rD), relative f (rf), and relative CBF (rCBF) by obtaining the ratio between each area and the contralateral cerebral white matter. We calculated the rate of change (Δ) by subtracting values from those from the preceding MRI study, and obtained Spearman's rank correlation coefficient (rs). Results Tumor progression was identified in nine patients (high grade, n = 7; low grade, n = 2). Negative correlations were identified between ΔrD and ΔDWI area (rs = -0.583), and between ΔrD and ΔCE-T1W imaging area (rs = -0.605). Conclusion Tumor progression after BEV treatment can be identified by decreasing rD.

Evaluation of Parkinson's disease by neuromelanin-sensitive magnetic resonance imaging and 123I-FP-CIT SPECT.

Background Both neuromelanin-sensitive magnetic resonance imaging (NmMRI) and 123I-FP-CIT single photon emission computed tomography (SPECT) (DaTSCAN) assist the diagnosis of Parkinson's disease (PD). However, there have been few studies investigating a correlation between them. Purpose To correlate the utility of NmMRI and DaTSCAN and to evaluate the relationship between both imaging findings and the Unified PD rating scale part III (UPDRS III) score for the diagnosis and management of PD. Material and Methods Seventeen patients with PD who underwent both NmMRI and DaTSCAN were included. We measured the volume of the neuromelanin-positive substantia nigra pars compacta (SNc volume) on NmMRI and measured the specific binding ratio (SBR) on DaTSCAN. The asymmetry index (AI) of the SNc volume and SBR were also calculated. We evaluated the relationship between the UPDRS III score and the SNc volume and SBR, respectively. Results The SNc volume showed a significant correlation with the SBR. The AIs of them also showed a significant correlation. Both the mean of the bilateral SBR and the mean of the bilateral SNc volume showed significant negative correlations with the UPDRS III score. However, the correlation between the SBR and the UPDRS III score was stronger than that between the SNc volume and the UPDRS III score. Conclusion Both NmMRI and DaTSCAN are helpful for PD diagnosis. However, we conclude that DaTSCAN is more suitable for the evaluation of the clinical motor severity and would be more useful for the management of PD patients than NmMRI.

Reduction of metal artifacts due to dental hardware in computed tomography angiography: assessment of the utility of model-based iterative reconstruction.

PURPOSE: The aim of this study is to assess the value of adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) for reduction of metal artifacts due to dental hardware in carotid CT angiography (CTA). METHODS: Thirty-seven patients with dental hardware who underwent carotid CTA were included. CTA was performed with a GE Discovery CT750 HD scanner and reconstructed with filtered back projection (FBP), ASIR, and MBIR. We measured the standard deviation at the cervical segment of the internal carotid artery that was affected most by dental metal artifacts (SD1) and the standard deviation at the common carotid artery that was not affected by the artifact (SD2). We calculated the artifact index (AI) as follows: AI = [(SD1)2 - (SD2)2]1/2 and compared each AI for FBP, ASIR, and MBIR. Visual assessment of the internal carotid artery was also performed by two neuroradiologists using a five-point scale for each axial and reconstructed sagittal image. The inter-observer agreement was analyzed using weighted kappa analysis. RESULTS: MBIR significantly improved AI compared with FBP and ASIR (p < 0.001, each). We found no significant difference in AI between FBP and ASIR (p = 0.502). The visual score of MBIR was significantly better than those of FBP and ASIR (p < 0.001, each), whereas the scores of ASIR were the same as those of FBP. Kappa values indicated good inter-observer agreements in all reconstructed images (0.747-0.778). CONCLUSIONS: MBIR resulted in a significant reduction in artifact from dental hardware in carotid CTA.

Proximal Bright Vessel Sign on Arterial Spin Labeling Magnetic Resonance Imaging in Acute Cardioembolic Cerebral Infarction.

BACKGROUND: The congestion of spin-labeled blood at large-vessel occlusion can present as hyperintense signals on perfusion magnetic resonance imaging with 3-dimensional pseudo-continuous arterial spin labeling (proximal bright vessel sign). The purpose of this study was to clarify the difference between proximal bright vessel sign and susceptibility vessel sign in acute cardioembolic cerebral infarction. METHODS: Forty-two patients with cardioembolic cerebral infarction in the anterior circulation territory underwent magnetic resonance imaging including diffusion-weighted imaging, 3-dimensional pseudo-continuous arterial spin labeling perfusion magnetic resonance imaging, T2*-weighted imaging, and 3-dimensional time-of-flight magnetic resonance angiography using a 3-T magnetic resonance scanner. Visual assessments of proximal bright vessel sign and the susceptibility vessel sign were performed by consensus of 2 experienced neuroradiologists. The relationship between these signs and the occlusion site of magnetic resonance angiography was also investigated. RESULTS: Among 42 patients with cardioembolic cerebral infarction, 24 patients showed proximal bright vessel sign (57.1%) and 25 showed susceptibility vessel sign (59.5%). There were 19 cases of proximal bright vessel sign and susceptibility vessel sign-clear, 12 cases of proximal bright vessel sign and susceptibility vessel sign-unclear, and 11 mismatched cases. Four out of 6 patients with proximal bright vessel sign-unclear and susceptibility vessel sign-clear showed distal middle cerebral artery occlusion, and 2 out of 5 patients with proximal bright vessel sign-clear and susceptibility vessel sign-unclear showed no occlusion on magnetic resonance angiography. CONCLUSIONS: Proximal bright vessel sign is almost compatible with susceptibility vessel sign in patients with cardioembolic cerebral infarction.

Carotid Plaque Evaluation Using Gemstone Spectral Imaging: Comparison with Magnetic Resonance Angiography.

BACKGROUND: The present study compared the applicability of computed tomography carotid plaque imaging using effective Z maps with gemstone spectral imaging (GSI) to that of magnetic resonance plaque imaging using 3-dimensional time-of-flight magnetic resonance angiography. METHODS: Stenosis was assessed in 18 carotid arteries of 14 patients, and the effective Z values of noncalcified carotid plaques were compared with the signal intensities of magnetic resonance angiography. RESULTS: It was found that the effective Z value of noncalcified carotid plaques was significantly lower for a group with high signal intensity than for a group with low signal intensity on magnetic resonance angiography (P <.001). The area under the receiver operating characteristic curve of effective Z values was .975, and the presumed cutoff effective Z value required to discriminate low and high intensity plaques on magnetic resonance angiography was 7.83. CONCLUSIONS: The effective Z value generated by GSI is a useful parameter to detect vulnerable carotid plaque materials.

Correlation between neuromelanin-sensitive MR imaging and (123)I-FP-CIT SPECT in patients with parkinsonism.

INTRODUCTION: Neuromelanin-sensitive MR imaging (MRI) can visualize neuromelanin-containing neurons in the substantia nigra pars compacta (SNc), and its utility has been reported in the evaluation of parkinsonism. Conversely, dopamine transporter imaging by (123)I-N-v-fluoropropyl-2b-carbomethoxy-3b-(4-iodophenyl)nortropane (FP-CIT) SPECT (DaTSCAN) is now an established method for evaluating parkinsonism, detecting presynaptic dopamine neuronal dysfunction. Both methods can assist differentiating neurodegenerative and other forms of parkinsonism. However, to our knowledge, there have been no studies concerning a correlation between the two methods. The aim of this study was to assess the utility of neuromelanin-sensitive MRI for diagnosing parkinsonism by examining a correlation with DaTSCAN. METHODS: Twenty-three patients with parkinsonism who underwent both neuromelanin-sensitive MRI and DaTSCAN were included. We measured the neuromelanin-positive SNc region volume by manually contouring the high signal intensity region of the SNc on neuromelanin-sensitive MRI and measured the specific binding ratio (SBR) on DaTSCAN. The asymmetry index of neuromelanin-positive SNc volume and the asymmetry index of SBR were also calculated. RESULTS: The volume of the neuromelanin-positive SNc region showed significant correlation with specific binding ratio (SBR) (right P < .001, ρ = 0.78, left P < .001, ρ = 0.86). The asymmetry index of neuromelanin-positive SNc volume also showed significant correlations with the asymmetry index of SBR (P < .001, ρ = 0.73). CONCLUSIONS: Decrease of the high signal intensity region of the SNc on neuromelanin-sensitive MRI would indicate damage to the nigrostriatal dopaminergic function as well as loss of dopaminergic neurons. We conclude that neuromelanin-sensitive MRI is a useful diagnostic biomarker for parkinsonism.

Usefulness of R2* maps generated by iterative decomposition of water and fat with echo asymmetry and least-squares estimation quantitation sequence for cerebral artery dissection.

INTRODUCTION: Acute intramural hematoma resulting from cerebral artery dissection is usually visualized as a region of intermediate signal intensity on T1-weighted images (WI). This often causes problems with distinguishing acute atheromatous lesions from surrounding parenchyma and dissection. The present study aimed to determine whether or not R2* maps generated by the iterative decomposition of water and fat with echo asymmetry and least-squares estimation quantitation sequence (IDEAL IQ) can distinguish cerebral artery dissection more effectively than three-dimensional variable refocusing flip angle TSE T1WI (T1-CUBE) and T2*WI. METHODS: We reviewed data from nine patients with arterial dissection who were assessed by MR images including R2* maps, T2*WI, T1-CUBE, and 3D time-of-flight (TOF)-MRA. We visually assessed intramural hematomas in each patient as positive (clearly visible susceptibility effect reflecting intramural hematoma as hyperintensity on R2* map and hypointensity on T2*WI), negative (absent intramural hematoma), equivocal (difficult to distinguish between intramural hematoma and other paramagnetic substances such as veins, vessel wall calcification, or hemorrhage) and not evaluable (difficult to determine intramural hematoma due to susceptibility artifacts arising from skull base). RESULTS: Eight of nine patients were assessed during the acute phase. Lesions in all eight patients were positive for intramural hematoma corresponding to dissection sites on R2* maps, while two lesions were positive on T2*WI and three lesions showed high-intensity on T1-CUBE reflected intramural hematoma during the acute phase. CONCLUSION: R2* maps generated using IDEAL IQ can detect acute intramural hematoma associated with cerebral artery dissection more effectively than T2*WI and earlier than T1-CUBE.

Assessment of carotid plaque composition using fast-kV switching dual-energy CT with gemstone detector: comparison with extracorporeal and virtual histology-intravascular ultrasound.

INTRODUCTION: The present study compares the applicability of CT carotid plaque imaging using effective Z maps using gemstone spectral imaging (GSI) with that of conventional extracorporeal carotid ultrasound (US) and virtual histology-intravascular ultrasound (VH-IVUS). METHODS: We assessed stenosis in 31 carotid arteries of 30 patients. All patients underwent carotid CTA using GSI (Discovery CT750 HD, GE Healthcare). US and IVUS were examined with 25 and 8 vessels, respectively. We compared the effective Z values at noncalcified carotid plaque with the plaque components identified by US. We defined the plaque with low or low to iso intensity on US as vulnerable plaque and the plaque with iso, iso to high, and high intensity on US as stable plaque. We also performed visual assessment of color-coded effective Z maps in comparison with VH-IVUS and compared effective Z values with plaque components generated by VH-IVUS. RESULTS: The effective Z values at noncalcified carotid plaque were significantly lower for a group with vulnerable plaque, than with stable plaque on US (p < 0.05). Receiver operating curve analysis showed that AUC of effective Z values was 0.882 concerning the differentiation of these two groups on US. The interpretation of color-coded effective Z maps was essentially compatible with that of VH-IVUS for carotid plaque in all vessels. Effective Z values at noncalcified plaque showed significant negative correlation with the areas of fibro-fatty components generated by VH-IVUS (ρ = -0.874, p < 0.05). CONCLUSION: Effective Z maps generated by GSI can detect vulnerable carotid plaque materials.

CT angiography after carotid artery stenting: assessment of the utility of adaptive statistical iterative reconstruction and model-based iterative reconstruction.

INTRODUCTION: Follow-up CT angiography (CTA) is routinely performed for post-procedure management after carotid artery stenting (CAS). However, the stent lumen tends to be underestimated because of stent artifacts on CTA reconstructed with the filtered back projection (FBP) technique. We assessed the utility of new iterative reconstruction techniques, such as adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR), for CTA after CAS in comparison with FBP. METHODS: In a phantom study, we evaluated the differences among the three reconstruction techniques with regard to the relationship between the stent luminal diameter and the degree of underestimation of stent luminal diameter. In a clinical study, 34 patients who underwent follow-up CTA after CAS were included. We compared the stent luminal diameters among FBP, ASIR, and MBIR, and performed visual assessment of low attenuation area (LAA) in the stent lumen using a three-point scale. RESULTS: In the phantom study, stent luminal diameter was increasingly underestimated as luminal diameter became smaller in all CTA images. Stent luminal diameter was larger with MBIR than with the other reconstruction techniques. Similarly, in the clinical study, stent luminal diameter was larger with MBIR than with the other reconstruction techniques. LAA detectability scores of MBIR were greater than or equal to those of FBP and ASIR in all cases. CONCLUSION: MBIR improved the accuracy of assessment of stent luminal diameter and LAA detectability in the stent lumen when compared with FBP and ASIR. We conclude that MBIR is a useful reconstruction technique for CTA after CAS.

Usefulness of monochromatic imaging with metal artifact reduction software for computed tomography angiography after intracranial aneurysm coil embolization.

BACKGROUND: Recently, a newly developed fast-kV switching dual energy CT scanner with a gemstone detector generates virtual high keV images as monochromatic imaging (MI). Each MI can be reconstructed by metal artifact reduction software (MARS) to reduce metal artifact. PURPOSE: To evaluate the degree of metal artifacts reduction and vessel visualization around the platinum coils using dual energy CT with MARS. MATERIAL AND METHODS: Dual energy CT was performed using a Discovery CT750 HD scanner (GE Healthcare, Milwaukee, WI, USA). In a phantom study, we measured the mean standard deviation within regions of interest around a 10-mm-diameter platinum coil mass on MI with and without MARS. Thirteen patients who underwent CTA after endovascular embolization for cerebral aneurysm with platinum coils were included in a clinical study. We visually assessed the arteries around the platinum coil mass on MI with and without MARS. RESULTS: Each standard deviation near the coil mass on MI with MARS was significantly lower than that without MARS in a phantom study. On CTA of a clinical study, better visibility of neighboring arteries was obtained in 11 of 13 patients on MI with MARS compared to without MARS due to metal artifact reduction. CONCLUSION: Dual energy CT with MARS reduces metal artifact of platinum coils, resulting in favorable vessel visualization around the coil mass on CTA after embolization.

Usefulness of deep learning-assisted identification of hyperdense MCA sign in acute ischemic stroke: comparison with readers' performance.

PURPOSE: To evaluate the usefulness of deep learning-assisted diagnosis for identifying hyperdense middle cerebral artery sign (HMCAS) on non-contrast computed tomography in comparison with the diagnostic performance of neuroradiologists. MATERIALS AND METHODS: We obtained 46 HMCAS-positive and 52 HMCAS-negative test samples extracted using 50-pixel-diameter circular regions of interest. Five neuroradiologists undertook an initial diagnostic performance test by describing the HMCAS-positive prediction rate in each sample. Their diagnostic performance was compared with that of a deep convolutional neural network (DCNN) model that had been trained using another dataset in our previous study. In the second test, readers could reference the prediction rate of the DCNN model in each sample. RESULTS: The diagnostic performance of the DCNN for HMCAS showed an accuracy of 81.6% and area under the receiver-operating characteristic curve (AUC) of 0.869, whereas the initial diagnostic performance of neuroradiologists showed an accuracy of 78.8% and AUC of 0.882. The second diagnostic test of neuroradiologists with reference to the results of the DCNN model showed an accuracy of 84.7% and AUC of 0.932. In all readers, AUC values were higher in the second test than the initial test. CONCLUSION: The ability of DCNN to identify HMCAS is comparable with the diagnostic performance of neuroradiologists.

Role of Neuroimaging on Differentiation of Parkinson's Disease and Its Related Diseases.

An accurate diagnosis of Parkinson's disease (PD) is a prerequisite for therapeutic management. In spite of recent advances in the diagnosis of parkinsonian disorders, PD is misdiagnosed in between 6 and 25% of patients, even in specialized movement disorder centers. Although the gold standard for the diagnosis of PD is a neuropathological assessment, neuroimaging has been playing an important role in the differential diagnosis of PD and is used for clinical diagnostic criteria. In clinical practice, differential diagnoses of PD include atypical parkinsonian syndromes such as dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, caused by a striatal dopamine deficiency following nigrostrial degeneration. PD may also be mimicked by syndromes not associated with a striatal dopamine deficiency such as essential tremor, drug-induced parkinsonism, and vascular parkinsonism. Moreover, difficulties are associated with the clinical differentiation of patients with parkinsonism from those with Alzheimer's disease. In this review, we summarize the typical imaging findings of PD and its related diseases described above using morphological imaging modalities (conventional MR imaging and neuromelanin MR imaging) and functional imaging modalities (99mTc-ethyl cysteinate dimer perfusion single photon emission computed tomography, 123I-metaiodobenzylguanidine myocardial scintigraphy, and 123I-FP-CIT dopamine transporter single photon emission computed tomography) that are clinically available in most hospitals. We also attempt to provide a diagnostic approach for the differential diagnosis of PD and its related diseases in clinical practice.

Usefulness of High-Resolution 3D Multi-Sequences for Peripheral Facial Palsy: Differentiation Between Bell's Palsy and Ramsay Hunt Syndrome.

OBJECTIVE: To investigate the usefulness of magnetic resonance imaging (MRI) including three-dimensional (3D) sequences in the differentiation between Bell's palsy (BP) and Ramsay Hunt syndrome (RHS). STUDY DESIGN: A prospective study. SETTING: Tertiary care center. PATIENTS: Twenty patients: 15 patients with BP and five patients with RHS. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURE: Clinical diagnosis (BP or RHS). RESULTS: The presence of hyperintensity on 3D-fluid-attenuated inversion recovery sequence (3D-FLAIR) and enhancement on gadolinium-enhanced (CE)-3D-FLAIR and CE-3D-T1-weighted image (3D-T1WI) along the internal auditory canal (IAC) wall were significantly associated with RHS (p < 0.05). Hyperintensity in the inner ear was observed on pre- and postcontrast 3D-FLAIR, and enhancement of the cranial nerve (CN)-VIII was observed only on CE-3D-FLAIR. The presence of these findings also showed significant relationships with RHS (p < 0.05). Moreover, thickening of the CN-VII in the fundus of the IAC in 3D-constructive interference on steady state sequence (3D-CISS) also showed a significant association with RHS (p < 0.05). In contrast, the presence of hyperintensity of the CN-VII in the fundus of the IAC on 3D-FLAIR did not demonstrate a significant relationship (p = 0.95), and enhancement in this region was observed in all cases on CE-3D-FLAIR and gadolinium-enhanced-three-dimensional-T1-weighted gradient echo sequence (CE-3D-T1WI). CONCLUSIONS: 3D MRI sequences are useful for differentiating RHS from BP. In particular, the enhancement in the CN-VIII and/or along the IAC wall are valuable findings, and CE-3D-FLAIR is the most useful sequence to evaluate these findings. Thickening of the CN-VII on 3D-CISS is also an important finding.

A case of acute encephalopathy with biphasic seizures and late reduced diffusion: Utility of arterial spin labeling sequence.

A 1-year-old boy was admitted because of febrile status epilepticus (FSE). A secondary cluster of seizures was seen on day 5 after onset, and the patient eventually displayed developmental delay. Conventional magnetic resonance imaging (MRI) showed no abnormal findings on day 1 after onset, but showed reduced diffusion in the subcortical regions of bilateral frontal lobes on day 5 after onset. Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) was diagnosed. Arterial spin labeling (ASL) revealed reduced cerebral blood flow (CBF) in bilateral frontal lobes on day 1 after onset and showed increased CBF in the corresponding region in the subacute phase. Outcomes after prolonged febrile seizures are usually good, but mental deficit and/or epilepsy often remain in AESD. Discriminating between these syndromes is difficult, because no useful biomarkers have been identified. Reduced CBF in bilateral frontal lobes was observed on ASL on day 1 of FSE in the present case, and this finding may be predictive of developing AESD.