Diagnostic performance of ultrasound hepatorenal index for the diagnosis of hepatic steatosis in children.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is increasing in prevalence and is the most common cause of pediatric chronic liver disease. Objective US-based measures of hepatic steatosis are an unmet clinical need. OBJECTIVE: To evaluate the diagnostic performance of quantitative measurement of liver echogenicity (hepatorenal index, or HRI) for hepatic steatosis in a pediatric cohort. MATERIALS AND METHODS: We identified pediatric patients (≤18 years old) who underwent both clinically indicated abdominal US and MRI with liver proton-density fat fraction (PDFF) within the 3-month period during the timeframe of July 2015-April 2020 (n=69). Using ImageJ, we drew small circular regions of interest (ROIs) and large freehand ROIs in the liver and right kidney on single longitudinal and transverse images to measure echogenicity (arbitrary units). We calculated four HRIs (liver-to-kidney ratio) as well as liver histogram features. Five pediatric radiologists independently reported the qualitative presence/absence of hepatic steatosis. We used Pearson correlation (r) to assess associations and receiver operating characteristic (ROC) curve analyses to evaluate diagnostic performance. Multivariable logistic regression was used to further assess relationships. RESULTS: Mean patient age was 11.6 (standard deviation [SD] 4.7, range 0.3-18) years; 27/69 (39.1%) were female. Mean PDFF was 12.5% (SD 13.1%, range 1-48%); 34/69 (49.3%) patients were classified as having hepatic steatosis by MRI (PDFF ≥6%). There were significant, positive correlations between all four US HRI methods and PDFF (r=0.51-0.61); longitudinal freehand ROIs exhibited the strongest correlation (r=0.61; P<0.0001). Longitudinal freehand ROI HRI had moderate diagnostic performance for the binary presence of steatosis (area under the curve [AUC]=0.80, P<0.0001), with an optimal cut-off value >1.75 (sensitivity=70.6%, specificity=77.1%). Radiologists' sensitivity for detecting hepatic steatosis ranged from 79.4% to 97.1%, and specificity ranged from 91.2% to 100%. Significant multivariable predictors of PDFF ≥6% included HRI (P=0.002; odds ratio [OR]=34.2), body mass index (BMI) percentile (P=0.005; OR=1.06), and liver gray-scale echogenicity standard deviation (P=0.02; OR=0.79) (receiver operating characteristic AUC = 0.92). CONCLUSION: Quantitative US HRI has moderate diagnostic performance for detecting liver fat in children and positively correlates with MRI PDFF. Incorporation of BMI-percentile and gray-scale echogenicity standard deviation improved diagnostic performance.

PET measurement of cyclooxygenase-2 using a novel radioligand: upregulation in primate neuroinflammation and first-in-human study.

BACKGROUND: Cyclooxygenase-2 (COX-2), which is rapidly upregulated by inflammation, is a key enzyme catalyzing the rate-limiting step in the synthesis of several inflammatory prostanoids. Successful positron emission tomography (PET) radioligand imaging of COX-2 in vivo could be a potentially powerful tool for assessing inflammatory response in the brain and periphery. To date, however, the development of PET radioligands for COX-2 has had limited success. METHODS: The novel PET tracer [11C]MC1 was used to examine COX-2 expression [1] in the brains of four rhesus macaques at baseline and after injection of the inflammogen lipopolysaccharide (LPS) into the right putamen, and [2] in the joints of two human participants with rheumatoid arthritis and two healthy individuals. In the primate study, two monkeys had one LPS injection, and two monkeys had a second injection 33 and 44 days, respectively, after the first LPS injection. As a comparator, COX-1 expression was measured using [11C]PS13. RESULTS: COX-2 binding, expressed as the ratio of specific to nondisplaceable uptake (BPND) of [11C]MC1, increased on day 1 post-LPS injection; no such increase in COX-1 expression, measured using [11C]PS13, was observed. The day after the second LPS injection, a brain lesion (~ 0.5 cm in diameter) with high COX-2 density and high BPND (1.8) was observed. Postmortem brain analysis at the gene transcript or protein level confirmed in vivo PET results. An incidental finding in an unrelated monkey found a line of COX-2 positivity along an incision in skull muscle, demonstrating that [11C]MC1 can localize inflammation peripheral to the brain. In patients with rheumatoid arthritis, [11C]MC1 successfully imaged upregulated COX-2 in the arthritic hand and shoulder and apparently in the brain. Uptake was blocked by celecoxib, a COX-2 preferential inhibitor. CONCLUSIONS: Taken together, these results indicate that [11C]MC1 can image and quantify COX-2 upregulation in both monkey brain after LPS-induced neuroinflammation and in human peripheral tissue with inflammation. TRIAL REGISTRATION: ClinicalTrials.gov NCT03912428. Registered April 11, 2019.

First-in-human evaluation of [11C]PS13, a novel PET radioligand, to quantify cyclooxygenase-1 in the brain.

PURPOSE: This study assessed whether the newly developed PET radioligand [11C]PS13, which has shown excellent in vivo selectivity in previous animal studies, could be used to quantify constitutive levels of cyclooxygenase-1 (COX-1) in healthy human brain. METHODS: Brain test-retest scans with concurrent arterial blood samples were obtained in 10 healthy individuals. The one- and unconstrained two-tissue compartment models, as well as the Logan graphical analysis were compared, and test-retest reliability and time-stability of total distribution volume (VT) were assessed. Correlation analyses were conducted between brain regional VT and COX-1 transcript levels provided in the Allen Human Brain Atlas. RESULTS: In the brain, [11C]PS13 showed highest uptake in the hippocampus and occipital cortex. The pericentral cortex also showed relatively higher uptake compared with adjacent neocortices. The two-tissue compartment model showed the best fit in all the brain regions, and the results from the Logan graphical analysis were consistent with those from the two-tissue compartment model. VT values showed excellent test-retest variability (range 6.0-8.5%) and good reliability (intraclass correlation coefficient range 0.74-0.87). VT values also showed excellent time-stability in all brain regions, confirming that there was no radiometabolite accumulation and that shorter scans were still able to reliably measure VT. Significant correlation was observed between VT and COX-1 transcript levels (r = 0.82, P = 0.007), indicating that [11C]PS13 binding reflects actual COX-1 density in the human brain. CONCLUSIONS: These results from the first-in-human evaluation of the ability of [11C]PS13 to image COX-1 in the brain justifies extending the study to disease populations with neuroinflammation. CLINICAL TRIAL REGISTRATION: NCT03324646 at https://clinicaltrials.gov/ . Registered October 30, 2017. Retrospectively registered.

Single Quantum Dot Tracking Illuminates Neuroscience at the Nanoscale.

The use of nanometer-sized semiconductor crystals, known as quantum dots, allows us to directly observe individual biomolecular transactions through a fluorescence microscope. Here, we review the evolution of single quantum dot tracking over the past two decades, highlight key biophysical discoveries facilitated by quantum dots, briefly discuss biochemical and optical implementation strategies for a single quantum dot tracking experiment, and report recent accomplishments of our group at the interface of molecular neuroscience and nanoscience.

[O-methyl-11C]N-(4-(4-(3-Chloro-2-methoxyphenyl)-piperazin-1-yl)butyl)-1H-indole-2-carboxamide ([11C]BAK4-51) Is an Efflux Transporter Substrate and Ineffective for PET Imaging of Brain D3 Receptors in Rodents and Monkey.

Selective high-affinity antagonists for the dopamine D3 receptor (D3R) are sought for treating substance use disorders. Positron emission tomography (PET) with an effective D3R radioligand could be a useful tool for the development of such therapeutics by elucidating pharmacological specificity and target engagement in vivo. Currently, a D3R-selective radioligand does not exist. The D3R ligand, N-(4-(4-(3-chloro-2-methoxyphenyl)piperazin-1-yl)butyl)-1H-indole-2-carboxamide (BAK4-51, 1), has attractive properties for PET radioligand development, including full antagonist activity, very high D3R affinity, D3R selectivity, and moderate lipophilicity. We labeled 1 with the positron-emitter carbon-11 (t1/2 = 20.4 min) in the methoxy group for evaluation as a radioligand in animals with PET. However, [11C]1 was found to be an avid substrate for brain efflux transporters and lacked D3R-specific signal in rodent and monkey brain in vivo.

Evaluation of 11C-NR2B-SMe and Its Enantiomers as PET Radioligands for Imaging the NR2B Subunit Within the NMDA Receptor Complex in Rats.

[S-methyl-11C](±)-7-methoxy-3-(4-(4-(methylthio)phenyl)butyl)-2,3,4,5-tetrahydro-1H-benzo[d]azepin-1-ol (11C-NR2B-SMe) and its enantiomers were synthesized as candidates for imaging the NR2B subunit within the N-methyl-d-aspartate receptor with PET. Methods: Brains were scanned with PET for 90 min after intravenous injection of one of the candidate radioligands into rats. To detect any NR2B-specific binding of radioligand in brain, various preblocking or displacing agents were evaluated for their impact on the PET brain imaging data. Radiometabolites from brain and other tissues were measured ex vivo and in vitro. Results: Each radioligand gave high early whole-brain uptake of radioactivity, followed by a brief fast decline and then a slow final decline. 11C-(S)-NR2B-SMe was studied extensively. Ex vivo measurements showed that radioactivity in rat brain at 30 min after radioligand injection was virtually unchanged radioligand. Only less lipophilic radiometabolites appeared in plasma. High-affinity NR2B ligands, Ro-25-6981, ifenprodil, and CO101244, showed increasing preblocking of whole-brain radioactivity retention with increasing dose (0.01-3.00 mg/kg, intravenously). Five σ1 antagonists (FTC146, BD1407, F3, F4, and NE100) and 4 σ1 agonists ((+)-pentazocine, (±)-PPCC, PRE-084, and (+)-SKF10047) were ineffective preblocking agents, except FTC146 and F4 at a high dose. Two potent σ1 receptor agonists, TC1 and SA4503, showed dose-dependent preblocking effects in the presence or absence of pharmacologic σ1 receptor blockade with FTC146. Conclusion:11C-(S)-NR2B-SMe has adequate NR2B-specific PET signal in rat brain to warrant further evaluation in higher species. TC1 and SA4503 likely have off-target binding to NR2B in vivo.

Synthesis and evaluation of two new candidate high-affinity full agonist PET radioligands for imaging 5-HT1B receptors.

INTRODUCTION: The serotonin 1B receptor subtype is of interest in the pathophysiology and treatment of depression, anxiety, and migraine. Over recent years 5-HT1B receptor binding in human brain has been examined with PET using radioligands that are partial but not full agonists. To explore how the intrinsic activity of a PET radioligand may affect imaging performance, two high-affinity full 5-HT1B receptor agonists (AZ11136118, 4; and AZ11895987, 5) were selected from a large compound library and radiolabeled for PET examination in non-human primates. METHODS: [11C]4 was obtained through Pd(0)-mediated insertion of [11C]carbon monoxide between prepared iodoarene and homochiral amine precursors. [11C]5 was obtained through N-11C-methylation of N-desmethyl precursor 6 with [11C]methyl triflate. [11C]4 and [11C]5 were studied with PET in rhesus or cynomolgus monkey. [11C]4 was studied with PET in mice and rats to measure brain uptake and specific binding. Ex-vivo experiments in rats were performed to identify whether there were radiometabolites in brain. Physiochemical parameters for [11C]4 (pKa, logD and conformational energetics) were evaluated. RESULTS: Both [11C]4 and [11C]5 were successfully produced in high radiochemical purity and in adequate amounts for PET experiments. After intravenous injection of [11C]4, brain radioactivity peaked at a low level (0.2 SUV). Pretreatment with tariquidar, an inhibitor of the brain P-gp efflux transporter, increased brain exposure four-fold whereas pretreatment with a high pharmacological dose of the 5-HT1B antagonist, AR-A000002, had no effect on the binding. Ex-vivo experiments in rats showed no radiometabolites entering brain. [11C]5 also failed to enter monkey brain under baseline conditions. CONCLUSIONS: [11C]4 and [11C]5 show too low brain uptake and specific binding to be useful PET radioligands. Low brain uptake is partly ascribed to efflux transporter action as well as unfavorable conformations.

Evaluation of a PET Radioligand to Image O-GlcNAcase in Brain and Periphery of Rhesus Monkey and Knock-Out Mouse.

Accumulation of hyperphosphorylated tau, a microtubule-associated protein, plays an important role in the progression of Alzheimer disease. Animal studies suggest that one strategy for treating Alzheimer disease and related tauopathies may be inhibition of O-GlcNAcase (OGA), which may subsequently decrease pathologic tau phosphorylation. Here, we report the pharmacokinetics of a novel PET radioligand, 18F-LSN3316612, which binds with high affinity and selectivity to OGA. Methods: PET imaging was performed on rhesus monkeys at baseline and after administration of either thiamet-G, a potent OGA inhibitor, or nonradioactive LSN3316612. The density of the enzyme was calculated as distribution volume using a 2-tissue-compartment model and serial concentrations of parent radioligand in arterial plasma. The radiation burden for future studies was based on whole-body imaging of monkeys. Oga∆Br, a mouse brain-specific knockout of Oga, was also scanned to assess the specificity of the radioligand for its target enzyme. Results: Uptake of radioactivity in monkey brain was high (∼5 SUV) and followed by slow washout. The highest uptake was in the amygdala, followed by striatum and hippocampus. Pretreatment with thiamet-G or nonradioactive LSN3316612 reduced brain uptake to a low and uniform concentration in all regions, corresponding to an approximately 90% decrease in distribution volume. Whole-body imaging of rhesus monkeys showed high uptake in kidney, spleen, liver, and testes. In Oga∆Br mice, brain uptake of 18F-LSN3316612 was reduced by 82% compared with control mice. Peripheral organs were unaffected in Oga∆Br mice, consistent with loss of OGA expression exclusively in the brain. The effective dose of 18F-LSN3316612 in humans was calculated to be 22 µSv/MBq, which is typical for 18F-labeled radioligands. Conclusion: These results show that 18F-LSN3316612 is an excellent radioligand for imaging and quantifying OGA in rhesus monkeys and mice. On the basis of these data, 18F-LSN3316612 merits evaluation in humans.

Assessing the inter-observer variability of Computer-Aided Nodule Assessment and Risk Yield (CANARY) to characterize lung adenocarcinomas.

Lung adenocarcinoma (ADC), the most common lung cancer type, is recognized increasingly as a disease spectrum. To guide individualized patient care, a non-invasive means of distinguishing indolent from aggressive ADC subtypes is needed urgently. Computer-Aided Nodule Assessment and Risk Yield (CANARY) is a novel computed tomography (CT) tool that characterizes early ADCs by detecting nine distinct CT voxel classes, representing a spectrum of lepidic to invasive growth, within an ADC. CANARY characterization has been shown to correlate with ADC histology and patient outcomes. This study evaluated the inter-observer variability of CANARY analysis. Three novice observers segmented and analyzed independently 95 biopsy-confirmed lung ADCs from Vanderbilt University Medical Center/Nashville Veterans Administration Tennessee Valley Healthcare system (VUMC/TVHS) and the Mayo Clinic (Mayo). Inter-observer variability was measured using intra-class correlation coefficient (ICC). The average ICC for all CANARY classes was 0.828 (95% CI 0.76, 0.895) for the VUMC/TVHS cohort, and 0.852 (95% CI 0.804, 0.901) for the Mayo cohort. The most invasive voxel classes had the highest ICC values. To determine whether nodule size influenced inter-observer variability, an additional cohort of 49 sub-centimeter nodules from Mayo were also segmented by three observers, with similar ICC results. Our study demonstrates that CANARY ADC classification between novice CANARY users has an acceptably low degree of variability, and supports the further development of CANARY for clinical application.

Dynamic left ventricular outflow obstruction during lumbar laminectomy as an unexpected cause of intraoperative hypotension.

We present a case of previously undiagnosed hypertrophic obstructive cardiomyopathy (HOCM) with left ventricular outflow obstruction in a woman anesthetized for lumbar hemilaminectomy and diskectomy. The treatment of her sudden unexplained hypotension was initially confounded by a diagnosis of compensated congestive heart failure and diuretic therapy. Swift intervention with transesophageal echocardiography revealed the tru pathology altering her intraoperative treatment and her subsequent chronic treatment for her heart condition.

Factors associated with successful tracheal intubation of children with sevoflurane and no muscle relaxant.

UNLABELLED: Better definition of end points required to achieve successful tracheal intubation after induction with sevoflurane could improve patient care. The authors therefore designed a study that could determine, with meaningful confidence intervals, the time required to successfully intubate 80% of children by using 8% inspired sevoflurane and no muscle relaxant. We hypothesized that the time required could vary by age or body mass index. One-hundred fifty-three ASA physical status I or II patients received induction with 8% sevoflurane in 60% nitrous oxide with discontinuation of nitrous oxide 1 min after the start of the induction. The time until laryngoscopy remained close to the time required to achieve 80% successful intubation by varying induction time according to the success rate in each group of five patients. A probit model of induction time and age found that both were predictive of successful intubation (P values of 0.006 and 0.02, respectively). The induction times needed to achieve 80% successful intubation were 137 s (95% confidence interval, 94.6-159 s) and 187 s (153-230 s) for ages 1-4 yr and 4-8 yr, respectively. The persistence of spontaneous ventilation at the time of laryngoscopy, despite attempts to control ventilation, was associated with poor intubation conditions (P < 0.001). IMPLICATIONS: To successfully intubate 80% of children by using sevoflurane and no muscle relaxant, induction times of 137 and 187 s were needed in children of 1-4 yr and 4-8 yr, respectively.