Environmental temperature effects on adipose tissue growth in a hibernator

Obligate hibernators express circannual patterns of body mass and hibernation, which persist under constant laboratory conditions. Brown Adipose Tissue (BAT) is important for thermogenesis during arousals from hibernation, whereas White Adipose Tissue (WAT) serves as energy storage and thermal insulation. The goal of this study was to investigate the effects of environmental temperature on BAT and WAT. We hypothesized that changes to environmental temperature would not influence the pattern of mass gain or BAT and WAT volume in the thirteen-lined ground squirrel (Ictidomys tridecemlineatus). To test this, we housed animals thermoneutral 25°C (warm-housed) or 5°C (cold-housed), with the same photoperiod (12 h light:12 h dark) over an entire year. Throughout the year we measured the volume and water-fat ratio of WAT and BAT using magnetic resonance imaging (MRI). We found no evidence of torpor in the warm-housed animals, indicating that this species might not be an obligate hibernator, as previously assumed. Regardless of ambient temperature BAT volume increased prior to winter, then decreased in late winter with no change in water-fat ratio. By contrast both body mass and WAT volume of cold-housed animals declined throughout the winter and recovered after hibernation, but thermoneutral housing produced no circannual pattern in body mass, even though WAT volume declined in late winter. Cold exposure appears to be a primary regulator for WAT but BAT may exhibit an endogenous circannual rhythm in terms of depot volume.

Water-fat MRI in a hibernator reveals seasonal growth of white and brown adipose tissue without cold exposure

Obligate hibernators, such as ground squirrels, display circannual patterns which persist even under constant laboratory conditions, suggesting that they are regulated by endogenous rhythms. Brown adipose tissue (BAT) is important for thermogenesis during periodic arousals from hibernation when core body temperature rises spontaneously from 5 to 37 °C. In most small eutherians BAT growth requires several weeks of cold exposure. We hypothesized that in the thirteen-lined ground squirrel (Ictidomys tridecemlineatus), a hibernator, BAT growth is regulated, in part, by an endogenous rhythm and we predicted that this growth would precede the hibernation season without cold exposure. We tested this prediction using repeated water-fat magnetic resonance imaging over a year, including the hibernation season. Thoracic BAT depots increased in volume from spring through autumn even though animals were housed at ~22 °C. Subsequent cold exposure (5 °C) enlarged the thoracic BAT further. The fat fraction of this tissue fell significantly during the period of peak growth, indicating relative increases in non-triglyceride components, perhaps mitochondria or vasculature. We also found that the proportion of the body consisting of white adipose tissue (WAT) increased steadily from spring through autumn, and fell throughout hibernation, mirroring changes in body mass. Unlike BAT, WAT fat fractions remained constant (near 90%) throughout the year. Future studies will evaluate the significance of photoperiod and cold exposure on the growth of these tissues. We also found tissue with a fat fraction characteristic of BAT in the head near the eyes, a potentially novel discovery that requires further confirmation.

Sitagliptin in patients with non-alcoholic steatohepatitis: A randomized, placebo-controlled trial

AIM

To evaluate the effect of sitagliptin vs placebo on histologic and non-histologic parameters of non-alcoholic steatohepatitis (NASH).

METHODS

Twelve patients with biopsy-proven NASH were randomized to sitagliptin (100 mg daily) (n = 6) or placebo (n = 6) for 24 wk. The primary outcome was improvement in liver fibrosis after 24 wk. Secondary outcomes included evaluation of changes in NAFLD activity score (NAS), individual components of NAS (hepatocyte ballooning, lobular inflammation, and steatosis), glycemic control and insulin resistance [including measurements of glycated hemoglobin (HbA1C) and adipocytokines], lipid profile including free fatty acids, adipose distribution measured using magnetic resonance imaging (MRI), and thrombosis markers (platelet aggregation and plasminogen activator inhibitor 1 levels). We also sought to determine the correlation between changes in hepatic fat fraction (%) [as measured using the Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation (IDEAL) MRI technique] and changes in hepatic steatosis on liver biopsy.

RESULTS

Sitagliptin was not significantly better than placebo at reducing liver fibrosis score as measured on liver biopsy (mean difference between sitagliptin and placebo arms, 0.40, P = 0.82). There were no significant improvements evident with the use of sitagliptin vs placebo for the secondary histologic outcomes of NAS total score as well as for the individual components of NAS. Compared to baseline, those patients who received sitagliptin demonstrated improved HbA1C (6.7% ± 0.4% vs 7.9% ± 1.0%, P = 0.02), and trended towards improved adiponectin levels (4.7 ± 3.5 μg/mL vs 3.9 ± 2.7 μg/mL, P = 0.06) and triglyceride levels (1.26 ± 0.43 mmol/L vs 2.80 ± 1.64 mmol/L, P = 0.08). However, when compared with placebo, sitagliptin did not cause a statistically significant improvement in HbA1C (mean difference, -0.7%, P = 0.19) nor triglyceride levels (mean difference -1.10 mmol/L, P = 0.19) but did trend towards improved adiponectin levels only (mean difference, 0.60 μg/mL, P = 0.095). No significant changes in anthropometrics, liver enzymes, other adipocytokines, lipid profile, thrombosis parameters, or adipose distribution were demonstrated. The MRI IDEAL procedure correlated well with steatosis scores obtained on liver biopsy in both groups at baseline and post-treatment, and the Spearman correlation coefficients ranged from r = 0.819 (baseline) to r = 0.878 (post-treatment), P = 0.002.

CONCLUSION

Sitagliptin does not improve fibrosis score or NAS after 24 wk of therapy. The MRI IDEAL technique may be useful for non-invasive measurement of hepatic steatosis.

On the accurate analysis of vibroacoustics in head insert gradient coils

PURPOSE

To accurately analyze vibroacoustics in MR head gradient coils.

THEORY AND METHODS

A detailed theoretical model for gradient coil vibroacoustics, including the first description and modeling of Lorentz damping, is introduced and implemented in a multiphysics software package. Numerical finite-element method simulations were used to establish a highly accurate vibroacoustic model in head gradient coils in detail, including the newly introduced Lorentz damping effect. Vibroacoustic coupling was examined through an additional modal analysis. Thorough experimental studies were used to validate simulations.

RESULTS

Average experimental sound pressure levels (SPLs) and accelerations over the 0-3000 Hz frequency range were 97.6 dB, 98.7 dB, and 95.4 dB, as well as 20.6 g, 8.7 g, and 15.6 g for the X-, Y-, and Z-gradients, respectively. A reasonable agreement between simulations and measurements was achieved. Vibroacoustic coupling showed a coupled resonance at 2300 Hz for the Z-gradient that is responsible for a sharp peak and the highest SPL value in the acoustic spectrum.

CONCLUSION

We have developed and used more realistic multiphysics simulation methods to gain novel insights into the underlying concepts for vibroacoustics in head gradient coils, which will permit improved analyses of existing gradient coils and novel SPL reduction strategies for future gradient coil designs. Magn Reson Med 78:1635-1645, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Flip angle mapping with the accelerated 3D look-locker sequence

PURPOSE

A new approach to mapping the flip angle quickly and efficiently in 3D based on the Look-Locker technique is presented.

METHODS

We modified the accelerated 3D Look-Locker T1 measurement technique to allow rapid measurement of flip angle. By removing the inversion pulses and interleaving two radio frequency pulses with different amplitude, it is possible to fit directly for the true flip angle using a reduced number of parameters. This technique, non-inverted Double Angle Look-Locker, allows quick and efficient mapping of the flip angle in 3D.

RESULTS

non-inverted Double Angle Look-Locker is validated in vitro against the actual flip angle imaging technique for a range of flip angles and T1 values. Flip angle maps produced with non-inverted Double Angle Look-Locker can be acquired in approximately 1 min, and are accurate to within 10% of the actual flip angle imaging measurement. It is shown to accurately measure the excited slab profile of several different pulses. An application to correcting in vivo DESPOT T1 data is presented.

CONCLUSION

The presented technique is a rapid method for mapping flip angles across a 3D volume, capable of producing a flip angle map in approximately 1 min.

R2*-corrected water-fat imaging using compressed sensing and parallel imaging

PURPOSE

To demonstrate an approach to water-fat separation with R2* correction using compressed sensing and parallel imaging.

METHODS

Acquisition times for chemical shift based water-fat separation imaging are lengthy, and many applications rely on image acceleration techniques. In this study, we present an integrated compressed sensing, parallel imaging, R2* corrected water-fat separation technique for water-fat imaging of highly accelerated acquisitions. Reconstruction times are reduced using coil compression.

RESULTS

The proposed technique is demonstrated using a customized IDEAL-SPGR pulse sequence to acquire retrospectively and prospectively undersampled datasets of the liver, calf, knee, and abdominal cavity. This technique is shown to offer comparable image quality relative to fully sampled reference images for a range of acceleration factors. At high acceleration factors, this technique is shown to offer improved image quality over parallel imaging.

CONCLUSION

A technique is described that uses compressed sensing and parallel imaging to reconstruct R2*-corrected water and fat images from accelerated datasets. Acceleration factors as high as 7.0 are shown with excellent image quality. These high acceleration factors enable water-fat separation with higher resolution or greater anatomical coverage in breath-hold applications.

Hyperpolarized [1-(13) C]pyruvate MRI for noninvasive examination of placental metabolism and nutrient transport: A feasibility study in pregnant guinea pigs

PURPOSE

To test the feasibility of hyperpolarized [1-(13) C]pyruvate magnetic resonance imaging (MRI) for noninvasive examination of guinea pig fetoplacental metabolism and nutrient transport.

MATERIALS AND METHODS

Seven pregnant guinea pigs with a total of 30 placentae and fetuses were anesthetized and scanned at 3T. T1 -weighted (1) H images were obtained from the maternal abdomen. An 80 mM solution of hyperpolarized [1-(13) C]pyruvate (hereafter referred to as pyruvate) was injected into a vein in the maternal foot. Time-resolved 3D (13) C images were acquired starting 10 seconds after the beginning of bolus injection and every 10 seconds after to 50 seconds. The pregnant guinea pigs were recovered after imaging. Regions of interest (ROIs) were drawn around the maternal heart and each placenta and fetal liver in all slices in the (1) H images. These ROIs were copied to the (13) C images and were used to calculate the sum of the pyruvate and lactate signal intensities for each organ. The signal intensities were normalized by the volume of the organ and the maximum signal in the maternal heart.

RESULTS

No adverse events were observed in the pregnant guinea pigs and natural pupping occurred at term (∼68 days). Pyruvate signal was observed in all 30 placentae, and lactate, a by-product of pyruvate metabolism, was also observed in all placentae. The maximum pyruvate and lactate signals in placentae occurred at 20 seconds. In addition to the observation of pyruvate and lactate signals in the placentae, both pyruvate and lactate signals were observed in all fetal livers. The maximum pyruvate and lactate signals in the fetal livers occurred at 10 seconds and 20 seconds, respectively.

CONCLUSION

This work demonstrates the feasibility of using hyperpolarized [1-(13) C]pyruvate MRI to noninvasively examine fetoplacental metabolism and transport of pyruvate in guinea pigs. Hyperpolarized (13) C MRI may provide a novel method for longitudinal studies of fetoplacental abnormalities.

Pharmacist's review and outcomes: Treatment-enhancing contributions tallied, evaluated, and documented (PROTECTED-UK)

PURPOSE

The purpose was to describe clinical pharmacist interventions across a range of critical care units (CCUs) throughout the United Kingdom, to identify CCU medication error rate and prescription optimization, and to identify the type and impact of each intervention in the prevention of harm and improvement of patient therapy.

MATERIALS AND METHODS

A prospective observational study was undertaken in 21 UK CCUs from November 5 to 18, 2012. A data collection web portal was designed where the specialist critical care pharmacist reported all interventions at their site. Each intervention was classified as medication error, optimization, or consult. In addition, a clinical impact scale was used to code the interventions. Interventions were scored as low impact, moderate impact, high impact, and life saving. The final coding was moderated by blinded independent multidisciplinary trialists.

RESULTS

A total of 20517 prescriptions were reviewed with 3294 interventions recorded during the weekdays. This resulted in an overall intervention rate of 16.1%: 6.8% were classified as medication errors, 8.3% optimizations, and 1.0% consults. The interventions were classified as low impact (34.0%), moderate impact (46.7%), and high impact (19.3%); and 1 case was life saving. Almost three quarters of interventions were to optimize the effectiveness of and improve safety of pharmacotherapy.

CONCLUSIONS

This observational study demonstrated that both medication error resolution and pharmacist-led optimization rates were substantial. Almost 1 in 6 prescriptions required an intervention from the clinical pharmacist. The error rate was slightly lower than an earlier UK prescribing error study (EQUIP). Two thirds of the interventions were of moderate to high impact.

Chemical shift encoded imaging of hyperpolarized (13) C pyruvate

PURPOSE

To demonstrate a reconstruction technique for separating signal from different hyperpolarized carbon-13 metabolites.

METHODS

A reconstruction method is described for chemical shift encoded separation of the signal from pyruvate and its downstream metabolites. This method uses consistency of the data with the signal model rather than an additional free-induction decay (FID) acquisition to estimate the B0 offset. Compressed sensing was also integrated into the reconstruction allowing reconstruction of metabolite images from undersampled datasets. The performance of the reconstruction was assessed using thermal phantoms, digital phantoms, and in vivo hyperpolarized [1-(13) C] pyruvate experiments.

RESULTS

Thermal and digital phantoms indicate that metabolite separation is feasible given Signal-to-noise ratio > 5 and an initial B0 offset estimate within -105 Hz to 90 Hz of the actual B0 offset. In vivo comparisons to an existing FID calibrated reconstruction show improved fidelity in regions with significant field map inhomogeneity provided that these field map variations are accounted for using an additional proton acquisition. Prospectively and retrospectively undersampled studies show acceleration factors of 2 are feasible using compressed sensing.

CONCLUSION

A reconstruction framework for the separation of signal from pyruvate and its downstream metabolites is shown. This reconstruction eliminates the need to acquire additional calibration FID acquisition and allows acceleration through compressed sensing.

Direct enzyme-substrate affinity determination by real-time hyperpolarized (13)C-MRS

A specialized kinetic analysis of real-time hyperpolarized [1,1,2,2-D4, 1-(13)C]choline (13)C-magnetic resonance spectroscopy enabled the determination of initial rates of metabolic enzyme activity (choline oxidase), enzyme-substrate affinity (Km), and inhibition. In a clinical MRI scanner, metabolite levels lower than 16 μM were detected at a temporal resolution of 1 s.

Hyperpolarized choline as an MR imaging molecular probe: feasibility of in vivo imaging in a rat model

PURPOSE

To assess the feasibility of choline MRI using a new choline molecular probe for dynamic nuclear polarization (DNP) hyperpolarized MRI.

MATERIALS AND METHODS

Male Sprague-Dawley rats with an average weight of 400 ± 20 g (n = 5), were anesthetized and injection tubing was placed in the tail vein. [1,1,2,2-D4 , 1-(13) C]choline chloride (CMP1) was hyperpolarized by DNP and injected into rats at doses ranging from 12.6 to 50.0 mg/kg. Coronal projection (13) C imaging was performed on a 3 Tesla clinical MRI scanner (bore size 60 cm) using a variable flip angle gradient echo sequence. Images were acquired 15 to 45 s after the start of bolus injection. Signal intensities in regions of interest were determined at each time point and compared.

RESULTS

(13) C MRI images of hyperpolarized CMP1 at a 50 mg/kg dose showed time-dependent organ distribution patterns. At 15 s, high intensities were observed in the inferior vena cava, heart, aorta, and kidneys. At 30 s, most of the signal intensity was localized to the kidneys. These distribution patterns were reproduced using 12.6 and 25 mg/kg doses. At 45 s, only signal in the kidneys was detected.

CONCLUSION

Hyperpolarized choline imaging with MRI is feasible using a stable-isotope labeled choline analog (CMP1). Nonradioactive imaging of choline accumulation may provide a new investigatory dimension for kidney physiology. J. Magn. Reson. Imaging 2015;41:917-923. © 2014 Wiley Periodicals, Inc.

Max-IDEAL: a max-flow based approach for IDEAL water/fat separation

PURPOSE

To propose a novel approach to water/fat separation using a unique smoothness constraint.

THEORY AND METHODS

Chemical-shift based water/fat separation is an established noninvasive imaging tool for the visualization of body fat in various anatomies. Nevertheless, B0 magnetic field inhomogeneities can hamper the water/fat separation process. In this work, B0 variations are mapped using a convex-relaxed labeling model which produces a coarse estimate of the field map, while considering T2* decay during the labeling process. Fat and water components are subsequently resolved using T2*-IDEAL. An adaptive spatial filtering (ASF) was introduced to improve the robustness of the estimate. The method was tested on cardiac and abdominal datasets from healthy volunteers and nonalcoholic fatty liver disease (NAFLD) patients.

RESULTS

Out of 168 cardiac and abdominal images, only 1 case has shown water/fat swaps that can hinder the clinical interpretation of the underlying anatomy.

CONCLUSION

This work demonstrates a new water/fat separation approach that prevents the occurrence of water/fat swaps, by means of a unique smoothness constraint. Incorporating T2* effect in the labeling procedure and including the ASF processing enhance the robustness of the proposed approach and permit the procedure to handle abrupt B0 variations within the field of view.

Fat fraction bias correction using T1 estimates and flip angle mapping

PURPOSE

To develop a new method of reducing T1 bias in proton density fat fraction (PDFF) measured with iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL).

MATERIALS AND METHODS

PDFF maps reconstructed from high flip angle IDEAL measurements were simulated and acquired from phantoms and volunteer L4 vertebrae. T1 bias was corrected using a priori T1 values for water and fat, both with and without flip angle correction. Signal-to-noise ratio (SNR) maps were used to measure precision of the reconstructed PDFF maps. PDFF measurements acquired using small flip angles were then compared to both sets of corrected large flip angle measurements for accuracy and precision.

RESULTS

Simulations show similar results in PDFF error between small flip angle measurements and corrected large flip angle measurements as long as T1 estimates were within one standard deviation from the true value. Compared to low flip angle measurements, phantom and in vivo measurements demonstrate better precision and accuracy in PDFF measurements if images were acquired at a high flip angle, with T1 bias corrected using T1 estimates and flip angle mapping.

CONCLUSION

T1 bias correction of large flip angle acquisitions using estimated T1 values with flip angle mapping yields fat fraction measurements of similar accuracy and superior precision compared to low flip angle acquisitions.

Prevalence of overweight and obesity among children six to ten years of age in the north-east health region of Jamaica

OBJECTIVE

To estimate the prevalence and correlates of overweight and obesity among children six to ten years old in the North-East Health Region (NEHR) ofJamaica.

METHODS

Weights and heights were measured in a representative sample of 5710 children between the ages of six and ten years in 34 schools between October 2008 and March 2009. Overweight and obesity were defined as body mass index (BMI) Z-score > 1SD and >2SD, respectively based on the World Health Organization (WHO)-endorsed age and gender-specific growth standards for children. Point prevalence estimates of overweight and obesity were calculated. Odds ratios (OR) and 95% confidence intervals (CI) were used to estimate associations between overweight and obesity and age, gender and school location.

RESULTS

Overweight and obesity prevalence among children six to ten years old in NEHR, Jamaica, was 10.6% and 7.1%, respectively. Overweight (OR = 1.11, 95% CI: 1.04, 1.18) and obesity (OR = 1.17, 95% CI: 1.08, 1.26) prevalence increased significantly with age. Overweight (OR = 1.51, 95% CI: 1.27, 1.80) and obesity (OR = 1.36, 95% CI: 1.11, 1.67) prevalence was significantly higher among girls than boys. Children attending rural-public schools had less risk of being overweight (OR = 0.57, 95% CI: 0.46, 0.70) and obese (OR = 0.35, 95% CI: 0.28, 0.44) when compared with urban-public schools and private schools. Both overweight (OR = 2.11, 95% CI: 1.60, 2.78) and obesity (OR = 1.68, 95% CI: 1.24, 2.28) were significantly more common among children attending private schools. After adjusting for age and gender the results still remained statistically significant.

CONCLUSIONS

Overweight/obesity prevalence among children six to ten years old in NEHR of Jamaica is 17.7% with older children and girls having higher rates. Children attending urban-public and private schools have higher prevalence than those attending rural schools. Appropriately targeted interventions are needed to combat this problem.

Optimisation of dynamic nuclear polarisation of [1-(13)C] pyruvate by addition of gadolinium-based contrast agents

Dynamic nuclear polarisation (DNP) of carbon-13 ((13)C) enriched endogenous compounds provides a novel means for magnetic resonance imaging and spectroscopy of biological processes. Adding small amounts of gadolinium-based contrast agents (GBCAs) to the (13)C-enriched substrate matrix increases the amount of hyperpolarisation that can be achieved, but also may decrease the longitudinal relaxation time (T(1)) of the (13)C nucleus in solution. This study examined the effects of five different GBCA at concentrations of 0.5, 1, 2, and 3 mM on [1-(13)C]-enriched pyruvic acid. It was found that contrast agents with an open chain structure (Gadobenate dimeglumine, Gadopentetate dimeglumine, Gadodiamide) caused the largest enhancement (up to 82%) in solid state polarisation relative to solutions without GBCA. In the liquid state, T(1) of pyruvate decreased by as much as 62% and polarisation was much lower (70%) relative to solutions without GBCA added. Conversely, for GBCA with macrocyclic structures (Gadoterate meglumine, Gadoteridol), the solid state polarisation enhancement was only slightly less than the open chain GBCA, but enhanced polarisation was retained much better in the liquid state with minimal decrease in T(1) (25% at the highest GBCA concentrations). Near maximum polarisation in the solid state was obtained at a GBCA concentration of 2 mM, with a higher concentration of 3 mM producing minimal improvement. These results indicate that the macrocyclic contrast agents provide the best combination of high solid state and liquid state polarisations with minimal loss of T(1) in experiments with hyperpolarised (13)C-enriched pyruvate. This suggests that macrocyclic contrast agents should be the GBCA of choice for maximising signal in experiments with hyperpolarised (13)C-enriched pyruvate, particularly for in vivo measurements where shortened substrate T(1) is especially problematic.

Sex differences in quadriceps strength in OA

The purposes of this study were to determine 1) whether sex differences in quadriceps torque and isotonic power persist when controlling for muscle volume (i. e., torque/muscle volume and power/muscle volume) in participants with knee osteoarthritis (OA) and 2) the factors responsible for potential sex differences. Isometric torque, isotonic power (the product of torque and velocity, measured at 10, 20, 30, 40 and 50% maximal voluntary contraction; MVC) and maximal unloaded velocity were assessed in men (n=16, mean age=62.1 ± 7.2) and women (n=17, mean age=60.4 ± 4.3) with knee OA. Torque and power were normalized to muscle volume. The interpolated twitch technique was used to measure voluntary activation (VA) and evoked twitch and torque-frequency characteristics were measured to obtain information about muscle fibre distribution. Torque and power at all loads were significantly lower in women (p<0.05). Sex differences in power were reduced by 50% when controlling for muscle volume but were still significant at 10-40% MVC (p<0.05). No differences in VA, torque-frequency properties or time-to-peak tension of the evoked twitch were observed (p>0.05). These results suggest that only minor sex differences in torque and power persist when controlling for muscle volume. As VA and contractile property differences were not observed, other factors seem to be responsible.

Safety of nicotine replacement therapy in critically ill smokers: a retrospective cohort study

PURPOSE

Nicotine replacement therapy (NRT) has been used to ameliorate nicotine withdrawal in the intensive care unit (ICU). Previous cohort studies have suggested an increased mortality with NRT use: methodological problems may call into question the validity of these findings. We undertook a retrospective cohort study to determine if NRT use was associated with adverse outcomes.

METHODS

This retrospective cohort study was conducted in a 30-bed, university affiliated, teaching hospital ICU.

RESULTS

We identified 423 smokers admitted over 2 years, of whom 73 received transdermal NRT. Cox proportional hazard regression models, with NRT modelled as a time-varying covariate, were used to test the hypothesis that NRT was associated with an altered ICU or hospital mortality. A second analysis utilized propensity scores. The unadjusted ICU and hospital mortalities were lower for the NRT group; although both differences were non-significant. The Cox models showed that, after adjustment for APACHE risk, age, sex and alcohol use, risk associated with NRT administration was not statistically different than non-administration for both ICU (hazard ratio 0.50, [95 % CI 0.20-1.24], p = 0.14) and hospital (hazard ratio 0.95, [95 % CI 0.52-1.75], p = 0.88) mortality. Similar findings occurred with the propensity matched analysis.

CONCLUSION

We were unable to demonstrate any harm associated with NRT, with the ICU model actually trending towards benefit. We conclude that a randomised, blinded, placebo controlled trial is required to assess adequately the safety and efficacy of NRT as a treatment in critically ill smokers.

Quadriceps neuromuscular function and self-reported functional ability in knee osteoarthritis

The purposes of this study were to determine 1) the relationships of self-reported function scores in patients with knee osteoarthritis (OA) to both maximal isometric torque and to isotonic power at a variety of loads, and 2) the degree to which muscle volume (MV) or voluntary activation (VA) are associated with torque and power measures in this population. Isometric maximal voluntary contraction (MVC) torque and isotonic power [performed at loads corresponding to 10, 20, 30, 40, and 50% MVC, and a minimal load ("Zero Load")] were measured in 40 participants with knee OA. Functional ability was measured with the Western Ontario and McMaster Osteoarthritis Index (WOMAC) function subscale. MV was determined with magnetic resonance imaging, and VA was measured with the interpolated twitch technique. In general, power measured at lower loads (Zero Load and 10-30% MVC, r(2) = 0.21-0.28, P < 0.05) predicted a greater proportion of the variance in function than MVC torque (r(2) = 0.18, P < 0.05), with power measured at Zero Load showing the strongest association (r(2) = 0. 28, P < 0.05). MV was the strongest predictor of MVC torque and power measures in multiple regression models (r(2) = 0.42-0.72). VA explained only 6% of the variance in MVC torque and was not significantly associated with power at any load (P > 0.05). Quadriceps MVC torque and power are associated with self-reported function in knee OA, but muscle power at lower loads is more predictive of function than MVC torque. The variance in MVC torque and power between participants is due predominantly to differences in MV and has little to do with deficits in VA.

Prostate: registration of digital histopathologic images to in vivo MR images acquired by using endorectal receive coil

PURPOSE

To develop and evaluate a technique for the registration of in vivo prostate magnetic resonance (MR) images to digital histopathologic images by using image-guided specimen slicing based on strand-shaped fiducial markers relating specimen imaging to histopathologic examination.

MATERIALS AND METHODS

The study was approved by the institutional review board (the University of Western Ontario Health Sciences Research Ethics Board, London, Ontario, Canada), and written informed consent was obtained from all patients. This work proposed and evaluated a technique utilizing developed fiducial markers and real-time three-dimensional visualization in support of image guidance for ex vivo prostate specimen slicing parallel to the MR imaging planes prior to digitization, simplifying the registration process. Means, standard deviations, root-mean-square errors, and 95% confidence intervals are reported for all evaluated measurements.

RESULTS

The slicing error was within the 2.2 mm thickness of the diagnostic-quality MR imaging sections, with a tissue block thickness standard deviation of 0.2 mm. Rigid registration provided negligible postregistration overlap of the smallest clinically important tumors (0.2 cm(3)) at histologic examination and MR imaging, whereas the tested nonrigid registration method yielded a mean target registration error of 1.1 mm and provided useful coregistration of such tumors.

CONCLUSION

This method for the registration of prostate digital histopathologic images to in vivo MR images acquired by using an endorectal receive coil was sufficiently accurate for coregistering the smallest clinically important lesions with 95% confidence.