Keita Kuya

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.

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

IntroductionNeuromelanin-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 123I-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.MethodsTwenty-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.ResultsThe 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).ConclusionsDecrease 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.

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

IntroductionThe 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).MethodsWe 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.ResultsThe 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).ConclusionEffective Z maps generated by GSI can detect vulnerable carotid plaque materials.

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.

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

IntroductionAcute 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.MethodsWe 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).ResultsEight 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.ConclusionR2* 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.

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

IntroductionFollow-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.MethodsIn 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.ResultsIn 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.ConclusionMBIR 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.

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.

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.

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

OBJECTIVE To investigate the usefulness of magnetic resonance imaging (MRI) including three-dimensional (3D) sequences in the differentiation between Bells 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 Intracranial Subependymoma: Histopathological Confirmation of Ring-shaped Lateral Ventricular Nodule

Ring-shaped lateral ventricular nodules (RSLVNs) were first described by Shimono et al. in 2009.1 They reported the MRI features of these incidentally discovered lesions and reported a prevalence of only about 0.023%. Subsequently, Nakajima et al. reported a 0.45% prevalence of RSLVNs.2 Although they noted RSLVNs might be benign lesions without rapid growth, histopathological confirmation has not been described. We report a case of RSLVN with histopathological examination of surgical specimens. A 68-year-old man with obstructive hydrocephalus caused by a metastatic lesion in the pineal region secondary to renal cell carcinoma was referred to our institution for endoscopic third ventriculostomy. On preoperative brain MRI, a ring-shaped nodule of 5 mm in diameter was incidentally found to be projecting in the frontal horn of the right lateral ventricle. The nodule showed isointensity relative to the white matter, and the core portion demonstrated isointensity relative to the cerebrospinal fluid (CSF) on T2-weighted and T1-weighted images. It showed no contrast enhancement on gadolinium-enhanced T1-weighted images (Fig. 1). Neither the size nor the signal intensity of this nodule had changed in comparison with MRI findings from 32 months prior (not shown). These findings corresponded well with the MRI features of RSLVNs. During ventriculoscopy, a well-defined, solid, white mass protruded into the right lateral ventricle, and tumorectomy was performed to exclude disseminated carcinoma. Histopathologically, clusters of oval-shaped cells lacking atypia were embedded in the fine fibrillary background accompanied by microcystic formations, and the specimen was diagnosed as subependymoma (Fig. 2). Shimono et al. described that RSLVNs are similar in nature to subependymoma.1 Subependymoma is often incidentally found in the lateral ventricle as a well-defined, nonenhancing tumor on MRI, especially in middle-aged and elderly adults.3 Nakajima et al. also proposed that RSLVN may be a precursor to or variant of subependymoma because of the similar radiological and clinical findings.2 Multiple RSLVNs also will not inconsistent with subependymoma, because a case of multiple subependymoma was reported previously.3 However, a definitive conclusion has been difficult because subependymoma has not been described as having a ring-shaped appearance. In our case, the CSF signal in the core portion of the ring-shaped nodule on MRI might have been caused by microcystic formations, in comparison with the histopathological findings. On microscopic evaluation of histopathological specimen sections, microcystic formations were prominent centrally, and the marginal region was occupied by fibrillary stroma and lacked microcystic formations. These histopathological findings might give a thick-walled, ring shape on MRI. It has been suggested that the main component of subependymoma is fibrous stroma when it is small. Then microcystic formations expand from the center to the marginal regions as the tumor increases in size. Therefore, the MRI appearance of subependymoma is ring-shaped when it is small, but not when it is large enough to be resected. This report demonstrates the surgical and histopathological findings of RSLVN. In our case, RSLVN was subependymoma with centrally predominant microcystic change. RSLVNs are considered to be small subependymomas, and follow-up observation is sufficient management, as has been described previously.