Association between preoperative cortical magnetic susceptibility and postoperative changes in the cerebral blood flow on cognitive improvement following carotid endarterectomy.

INTRODUCTION: While patients who experience improved cognition following carotid endarterectomy (CEA) typically demonstrate restored brain perfusion after the procedure, it is worth noting that less than 50% of patients in whom postoperative cerebral blood flow (CBF) restoration is achieved actually show improved cognition after postoperatively. This suggests that factors beyond the mere restoration of CBF may play a role in postoperative cognitive improvement. Increased iron deposition in the cerebral cortex may cause neural damage, and quantitative susceptibility mapping (QSM) obtained using magnetic resonance imaging (MRI) quantifies magnetic susceptibility in the cerebral cortex, allowing for the assessment of iron deposition in vivo. The purpose of the present study was to determine whether preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA. METHODS: Brain MRI with a three-dimensional gradient echo sequence was preoperatively performed in 53 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), and QSM with brain surface correction and vein removal was obtained. Cortical magnetic susceptibility was measured in the cerebral hemisphere ipsilateral to surgery on QSM. Preoperatively and at two months after the surgery, brain perfusion single-photon emission computed tomography (SPECT) and neuropsychological assessments were conducted. Using these collected data, we evaluated alterations in CBF within the affected hemisphere and assessed cognitive improvements following the operation. RESULTS: A logistic regression analysis showed that a postoperative greater increase in CBF (95% confidence interval [CI], 1.06-1.90; p = 0.0186) and preoperative lower cortical magnetic susceptibility (95% CI, 0.03-0.74; p = 0.0201) were significantly associated with postoperatively improved cognition. Although sensitivity, specificity, and positive- and negative-predictive values with the cutoff value lying closest to the upper left corner of a receiver operating characteristic curve for the prediction of postoperatively improved cognition did not differ between postoperative changes in CBF and preoperative cortical magnetic susceptibility, the specificity and the positive-predictive value were significantly greater for the combination of postoperative changes in CBF and preoperative cortical magnetic susceptibility (specificity, 95% CI, 93-100%; positive-predictive value 95% CI, 68-100%) than for the former parameter alone (specificity, 95% CI, 63-88%; positive-predictive value 95% CI, 20-64%). CONCLUSION: Preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA.

[Imaging Techniques to Assess Cerebral Perfusion and Metabolism in Chronic Cerebral Ischemia].

The assessment of cerebral perfusion and metabolism is crucial in evaluating the indications for bypass surgery and other revascularization procedures in patients with chronic hemodynamic cerebral ischemia. In particular, it is necessary to detect misery perfusion(Powers' stage II), which is defined as an increased oxygen extraction fraction and increased cerebral blood volume or impaired cerebrovascular reactivity, with a constant cerebral metabolic rate of oxygen. Among the imaging techniques available for this purpose, 15O-positron emission tomography(PET)and acetazolamide-challenge single-photon emission computed tomography(SPECT)remain the de facto standards; however, these have substantial limitations such as invasiveness and the risk of severe adverse effects. Recently, several less invasive, easy-to-use techniques, such as perfusion computed tomography and magnetic resonance(MR)imaging, arterial spin labeling, quantitative susceptibility mapping, intravoxel incoherent motion, MR spectroscopy, and single-slab MR angiography, have also been introduced. These techniques may serve as alternatives to PET or SPECT if validation studies are successful and standardization among vendors is achieved.

Quantitative clinical and radiological recovery in post-operative patients with superficial siderosis by an iron chelator.

BACKGROUND: Superficial siderosis is a rare neurodegenerative disease caused by hemosiderin deposition on the brain surface. Although the efficacy of the iron chelator-deferiprone-in superficial siderosis has recently been documented, a comparative study of patients who underwent surgical ablation of their bleeding source and subsequently received treatment with or without deferiprone has not yet been conducted. METHODS: Fifteen postoperative patients with superficial siderosis were recruited, and seven patients were administered deferiprone (combination therapy group). Quantitative changes in the hypointense signals on T2*-weighted magnetic resonance images were acquired; additionally, cerebellar ataxia was assessed (International Cooperative Ataxia Rating Scale score and Scale for the Assessment and Rating of Ataxia). Audiometry was performed and the results were compared with those of patients who did not receive deferiprone (surgical treatment group; controls). RESULTS: Significant improvements in signal contrast ratios were noted in the lateral orbitofrontal gyrus, superior temporal lobe, insular lobe, brainstem, lingual gyrus, and cerebellar lobe in the combination therapy group. The scores of patients in the combination therapy group on the cerebellar ataxia scales significantly improved. The degree of signal improvement in the cerebellar lobe correlated with the improvement of cerebellar ataxia scores. Early deferiprone administration after disease onset and long-term administration were correlated with greater signal improvements on magnetic resonance imaging. No adverse effects were observed in the clinical or laboratory parameters. CONCLUSIONS: Deferiprone administration significantly improved radiological and clinical outcomes in patients with postoperative superficial siderosis. Earlier and longer courses of deferiprone could result in better patient prognosis.

Predicting the consistency of intracranial meningiomas using apparent diffusion coefficient maps derived from preoperative diffusion-weighted imaging.

OBJECTIVE: The consistency of meningiomas is a critical factor affecting the difficulty of resection, operative complications, and operative time. The apparent diffusion coefficient (ADC) is derived from diffusion-weighted imaging (DWI) and is calculated using two optimized b values. While the results of comparisons between the standard ADC and the consistency of meningiomas vary, the shifted ADC has been reported to be strongly correlated with liver stiffness. The purpose of the present prospective cohort study was to determine whether preoperative standard and shifted ADC maps predict the consistency of intracranial meningiomas. METHODS: Standard (b values 0 and 1000 sec/mm2) and shifted (b values 200 and 1500 sec/mm2) ADC maps were calculated using preoperative DWI in patients undergoing resection of intracranial meningiomas. Regions of interest (ROIs) were placed within the tumor on standard and shifted ADC maps and registered on the navigation system. Tumor tissue located at the registered ROI was resected through craniotomy, and its stiffness was measured using a durometer. The cutoff point lying closest to the upper left corner of a receiver operating characteristic (ROC) curve was determined for the detection of tumor stiffness such that an ultrasonic aspirator or scissors was always required for resection. Each tumor tissue sample with stiffness greater than or equal to or less than this cutoff point was defined as hard or soft tumor, respectively. RESULTS: For 76 ROIs obtained from 25 patients studied, significant negative correlations were observed between stiffness and the standard ADC (ρ = -0.465, p < 0.01) and the shifted ADC (ρ = -0.490, p < 0.01). The area under the ROC curve for detecting hard tumor (stiffness ≥ 20.8 kPa) did not differ between the standard ADC (0.820) and the shifted ADC (0.847) (p = 0.39). The positive predictive value (PPV) for the combination of a low standard ADC and a low shifted ADC for detecting hard tumor was 89%. The PPV for the combination of a high standard ADC and a high shifted ADC for detecting soft tumor (stiffness < 20.8 kPa) was 81%. CONCLUSIONS: A combination of standard and shifted ADC maps derived from preoperative DWI can be used to predict the consistency of intracranial meningiomas.

High Prevalence of Cerebral Small Vessel Disease on 7T Magnetic Resonance Imaging in Familial Hypercholesterolemia.

AIM: It remains unclear whether elevated low-density lipoprotein cholesterol (LDL-C) is a risk factor for cerebral vascular disease. Familial hypercholesterolemia (FH) is the most appropriate model for understanding the effects of excess LDL-C because affected individuals have inherently high levels of circulating LDL-C. To clarify the effects of hypercholesterolemia on cerebral small vessel disease (SVD), we investigated cerebrovascular damage in detail due to elevated LDL-C using high resolution brain magnetic resonance imaging (MRI) in patients with FH. METHODS: Twenty-eight patients with FH and 35 healthy controls underwent 7T brain MRI. The prevalence of SVD and arterial structural changes were determined in each group. RESULTS: The prevalence of periventricular hyperintensity (PVH) was significantly higher (control, 0% vs. FH, 14.2%, p=0.021) and deep white matter intensity tended to be more frequent in FH patients than in controls. The prevalence of SVD in patients with forms of cerebral damage, such as lacunar infarction, PVH, deep white matter hyperintensities (DWMH), microbleeding, and brain atrophy, was significantly higher among FH patients (control, n=2, 5.7% vs. FH, n=7, 25.0%, p＜0.001, chi-square test). The tortuosity of major intracranial arteries and the signal intensity of lenticulostriate arteries were similar in the two groups. In FH patients, as the grade of PVH progressed, several atherosclerosis risk factors, such as body mass index, blood pressure, and triglyceride level, showed ever worsening values. CONCLUSION: These results obtained from FH patients revealed that persistently elevated LDL-C leads to cerebral PVH. It is necessary in the management of FH to pay attention not only to the development of coronary heart disease but also to the presence of cerebral SVD.

Comparison of Different Post-Processing Algorithms for Dynamic Susceptibility Contrast Perfusion Imaging of Cerebral Gliomas.

PURPOSE: The purpose of the present study was to compare different software algorithms for processing DSC perfusion images of cerebral tumors with respect to i) the relative CBV (rCBV) calculated, ii) the cutoff value for discriminating low- and high-grade gliomas, and iii) the diagnostic performance for differentiating these tumors. METHODS: Following approval of institutional review board, informed consent was obtained from all patients. Thirty-five patients with primary glioma (grade II, 9; grade III, 8; and grade IV, 18 patients) were included. DSC perfusion imaging was performed with 3-Tesla MRI scanner. CBV maps were generated by using 11 different algorithms of four commercially available software and one academic program. rCBV of each tumor compared to normal white matter was calculated by ROI measurements. Differences in rCBV value were compared between algorithms for each tumor grade. Receiver operator characteristics analysis was conducted for the evaluation of diagnostic performance of different algorithms for differentiating between different grades. RESULTS: Several algorithms showed significant differences in rCBV, especially for grade IV tumors. When differentiating between low- (II) and high-grade (III/IV) tumors, the area under the ROC curve (Az) was similar (range 0.85-0.87), and there were no significant differences in Az between any pair of algorithms. In contrast, the optimal cutoff values varied between algorithms (range 4.18-6.53). CONCLUSIONS: rCBV values of tumor and cutoff values for discriminating low- and high-grade gliomas differed between software packages, suggesting that optimal software-specific cutoff values should be used for diagnosis of high-grade gliomas.

Narrow safety range of intraoperative rectal irradiation exposure volume for avoiding bleeding after seed implant brachytherapy.

BACKGROUND & PURPOSE: Rectal toxicity is less common after 125I seed implant brachytherapy for prostate cancer, and intraoperative rectal dose-volume constraints (the constraint) is still undetermined in pioneering studies. As our constraint failed to prevent grade 2 or 3 rectal bleeding (bled-pts) in 5.1% of patients, we retrospectively explored another constraint for the prevention of rectal bleeding. MATERIALS AND METHODS: The study population consisted of 197 patients treated with the brachytherapy as monotherapy using real-time intraoperative transrectal ultrasound (US)-guided treatment at a prescribed dose of 145 Gy. Post-implant dosimetry was performed on Day 1 and Day 30 after implantation using computed tomography (CT) imaging. Rectal bleeding toxicity was classified by CTC-AE ver. 3.0 during a mean 29-month (range, 12-48 months) period after implantation. The differences in rV100s were compared among intraoperative, Day 1 and Day 30 dosimetry, and between that of patients with grade 2 or 3 rectal bleeding (the bled-pts) and of the others (the spared-pts). All patients were divided into groups based on provisional rV100s that were increased stepwise in 0.1-cc increments from 0 to 1.0 cc. The difference in the ratios of the bled-pts to the spared-pts was tested by chi-square tests, and their odds ratios were calculated (bled-OR). All statistical analyses were performed by t-tests. RESULTS: The mean values of rV100us, rV100CT_1, and rV100CT_30 were 0.31 ± 0.43, 0.22 ± 0.36, and 0.59 ± 0.68 cc, respectively. These values temporarily decreased (p = 0.020) on Day 1 and increased (p = 0.000) on Day 30. There was no significant difference in rV100s between the bled-pts and spared-pts at any time of dosimetry. The maximum bled-OR was identified among patients with an rV100us value above 0.1 cc (p = 0.025; OR = 7.8; 95% CI, 1.4-145.8); an rV100CT_1 value above 0.3 cc (p = 0.014; OR = 16.2; 95% CI, 3.9-110.7), and an rV100CT_30 value above 0.5 cc (p = 0.019; OR = 6.3; 95% CI, 1.5-42.3). CONCLUSION: By retrospective analysis exploring rV100 as intraoperative rectal dose-volume thresholds in 125I seed implant brachytherapy for prostate cancer, it is proved that rV100 should be less than 0.1 cc for preventing rectal bleeding.

CT and MR perfusion can discriminate severe cerebral hypoperfusion from perfusion absence: evaluation of different commercial software packages by using digital phantoms.

INTRODUCTION: Computed tomography perfusion (CTP) and magnetic resonance perfusion (MRP) are expected to be usable for ancillary tests of brain death by detection of complete absence of cerebral perfusion; however, the detection limit of hypoperfusion has not been determined. Hence, we examined whether commercial software can visualize very low cerebral blood flow (CBF) and cerebral blood volume (CBV) by creating and using digital phantoms. METHODS: Digital phantoms simulating 0-4% of normal CBF (60 mL/100 g/min) and CBV (4 mL/100 g/min) were analyzed by ten software packages of CT and MRI manufacturers. Region-of-interest measurements were performed to determine whether there was a significant difference between areas of 0% and areas of 1-4% of normal flow. RESULTS: The CTP software detected hypoperfusion down to 2-3% in CBF and 2% in CBV, while the MRP software detected that of 1-3% in CBF and 1-4% in CBV, although the lower limits varied among software packages. CONCLUSION: CTP and MRP can detect the difference between profound hypoperfusion of <5% from that of 0% in digital phantoms, suggesting their potential efficacy for assessing brain death.

Computer-assisted identification of the central sulcus in patients with brain tumors using MRI.

PURPOSE: To develop computer-assisted image processing to identify the central sulcus from the MRI data sets in patients with brain tumors. MATERIALS AND METHODS: All MR images were acquired with a 3.0 Tesla scanner by three-dimensional (3D) spoiled gradient recalled acquisition using the steady state (SPGR) gradient-echo sequence and short inversion time inversion-recovery fast spin-echo sequence. The sulci were extracted automatically from reconstructed two-dimensional images of the cortical surface of 30 patients with brain tumors, and the extracted sulci were scored according to matching of the accepted anatomical features of the central sulcus. The candidates with the three highest scores were then superimposed on the 3D images. The correct position of the central sulcus was agreed by two senior neurosurgeons and one neuroradiologist. RESULTS: One of the three candidates corresponded to the central sulcus identified by the manual segmentation method for all 60 affected and unaffected hemispheres in the 30 patients. The candidate with the highest score coincided with the central sulcus in 26 of the 28 unaffected hemispheres and in 28 of the 32 affected hemispheres. CONCLUSION: The proposed method of computer-assisted image processing can provide accurate guidance to identifying the central sulcus in patients with brain tumors.