Registration of dynamic contrast-enhanced MRI of the common carotid artery using a fixed-frame template-based squared-difference method

PURPOSE

This study examines template-based squared-difference registration for motion correction in dynamic contrast-enhanced (DCE) MRI studies of the carotid artery wall and compares the results of fixed-frame template-based registration with a previously proposed consecutive-frame registration method.

MATERIALS AND METHODS

Ten T1-weighted black-blood, turbo spin-echo DCE-MRI studies of the carotid artery wall were used to test template-based squared-difference registration. An intermediate image from each series was selected as the fixed-frame template for registration. Squared-difference minimization was used to align each image and template. Time-intensity curves generated from data aligned with template-based squared-difference registration were compared with gold standard curves created by drawing regions of interest on each image in the series. The results were also compared with unregistered data and data after consecutive-frame squared-difference registration.

RESULTS

An analysis of variance test of root mean-square error values between gold standard curve and curves from unregistered data and data registered with consecutive-frame and fixed-frame template-based methods was significant (P < 0.005) with template-based squared-difference registration producing curves that most closely matched the gold standard.

CONCLUSION

A fixed-frame template-based squared-difference registration method was proposed and validated for alignment of DCE-MRI of carotid arteries.

Heat stress and reduced plane of nutrition decreases intestinal integrity and function in pigs

Heat stress can compromise intestinal integrity and induce leaky gut in a variety of species. Therefore, the objectives of this study were to determine if heat stress (HS) directly or indirectly (via reduced feed intake) increases intestinal permeability in growing pigs. We hypothesized that an increased heat-load causes physiological alterations to the intestinal epithelium, resulting in compromised barrier integrity and altered intestinal function that contributes to the overall severity of HS-related illness. Crossbred gilts (n=48, 43±4 kg BW) were housed in constant climate controlled rooms in individual pens and exposed to 1) thermal neutral (TN) conditions (20°C, 35-50% humidity) with ad libitum intake, 2) HS conditions (35°C, 20-35% humidity) with ad libitum feed intake, or 3) pair-fed in TN conditions (PFTN) to eliminate confounding effects of dissimilar feed intake. Pigs were sacrificed at 1, 3, or 7 d of environmental exposure and jejunum samples were mounted into modified Ussing chambers for assessment of transepithelial electrical resistance (TER) and intestinal fluorescein isothiocyanate (FITC)-labeled lipopolysaccharide (LPS) permeability (expressed as apparent permeability coefficient, APP). Further, gene and protein markers of intestinal integrity and stress were assessed. Irrespective of d of HS exposure, plasma endotoxin levels increased 45% (P<0.05) in HS compared with TN pigs, while jejunum TER decreased 30% (P<0.05) and LPS APP increased 2-fold (P<0.01). Furthermore, d 7 HS pigs tended (P=0.06) to have increased LPS APP (41%) compared with PFTN controls. Lysozyme and alkaline phosphatase activity decreased (46 and 59%, respectively; P<0.05) over time in HS pigs, while the immune cell marker, myeloperoxidase activity, was increased (P<0.05) in the jejunum at d 3 and 7. These results indicate that both HS and reduced feed intake decrease intestinal integrity and increase endotoxin permeability. We hypothesize that these events may lead to increased inflammation, which might contribute to reduced pig performance during warm summer months.

The complementary roles of dynamic contrast-enhanced MRI and 18F-fluorodeoxyglucose PET/CT for imaging of carotid atherosclerosis

PURPOSE

Inflammation and neovascularization in vulnerable atherosclerotic plaques are key features for severe clinical events. Dynamic contrast-enhanced (DCE) MRI and FDG PET are two noninvasive imaging techniques capable of quantifying plaque neovascularization and inflammatory infiltrate, respectively. However, their mutual role in defining plaque vulnerability and their possible overlap has not been thoroughly investigated. We studied the relationship between DCE-MRI and (18)F-FDG PET data from the carotid arteries of 40 subjects with coronary heart disease (CHD) or CHD risk equivalent, as a substudy of the dal-PLAQUE trial (NCT00655473).

METHODS

The dal-PLAQUE trial was a multicenter study that evaluated dalcetrapib, a cholesteryl ester transfer protein modulator. Subjects underwent anatomical MRI, DCE-MRI and (18)F-FDG PET. Only baseline imaging and biomarker data (before randomization) from dal-PLAQUE were used as part of this substudy. Our primary goal was to evaluate the relationship between DCE-MRI and (18)F-FDG PET data. As secondary endpoints, we evaluated the relationship between (a) PET data and whole-vessel anatomical MRI data, and (b) DCE-MRI and matching anatomical MRI data. All correlations were estimated using a mixed linear model.

RESULTS

We found a significant inverse relationship between several perfusion indices by DCE-MRI and (18)F-FDG uptake by PET. Regarding our secondary endpoints, there was a significant relationship between plaque burden measured by anatomical MRI with several perfusion indices by DCE-MRI and (18)F-FDG uptake by PET. No relationship was found between plaque composition by anatomical MRI and DCE-MRI or (18)F-FDG PET metrics.

CONCLUSION

In this study we observed a significant, weak inverse relationship between inflammation measured as (18)F-FDG uptake by PET and plaque perfusion by DCE-MRI. Our findings suggest that there may be a complex relationship between plaque inflammation and microvascularization during the different stages of plaque development. (18)F-FDG PET and DCE-MRI may have complementary roles in future clinical practice in identifying subjects at high risk of cardiovascular events.

Heat stress reduces intestinal barrier integrity and favors intestinal glucose transport in growing pigs

Excessive heat exposure reduces intestinal integrity and post-absorptive energetics that can inhibit wellbeing and be fatal. Therefore, our objectives were to examine how acute heat stress (HS) alters intestinal integrity and metabolism in growing pigs. Animals were exposed to either thermal neutral (TN, 21°C; 35–50% humidity; n = 8) or HS conditions (35°C; 24–43% humidity; n = 8) for 24 h. Compared to TN, rectal temperatures in HS pigs increased by 1.6°C and respiration rates by 2-fold (P<0.05). As expected, HS decreased feed intake by 53% (P<0.05) and body weight (P<0.05) compared to TN pigs. Ileum heat shock protein 70 expression increased (P<0.05), while intestinal integrity was compromised in the HS pigs (ileum and colon TER decreased; P<0.05). Furthermore, HS increased serum endotoxin concentrations (P = 0.05). Intestinal permeability was accompanied by an increase in protein expression of myosin light chain kinase (P<0.05) and casein kinase II-α (P = 0.06). Protein expression of tight junction (TJ) proteins in the ileum revealed claudin 3 and occludin expression to be increased overall due to HS (P<0.05), while there were no differences in claudin 1 expression. Intestinal glucose transport and blood glucose were elevated due to HS (P<0.05). This was supported by increased ileum Na⁺/K⁺ ATPase activity in HS pigs. SGLT-1 protein expression was unaltered; however, HS increased ileal GLUT-2 protein expression (P = 0.06). Altogether, these data indicate that HS reduce intestinal integrity and increase intestinal stress and glucose transport.

Heat stress reduces barrier function and alters intestinal metabolism in growing pigs

High ambient temperature exposure can cause major reductions in intestinal function, pig performance, and, if severe enough, mortality. Therefore, our objective was to examine how acute heat stress (HS) alters growing pig intestinal integrity and metabolism. Individually penned crossbred gilts and barrows (46 ± 6 kg BW) were exposed to either thermal neutral (TN; 21°C; 35 to 50% humidity; n = 8) or HS conditions (35°C; 24 to 43% humidity; n = 8) for 24 h. All pigs had ad libitum access to feed and water. Rectal temperature (Tr), respiration rates (RR), BW, and feed intake (FI) were measured. Pigs were killed after 24 h of environmental exposure and freshly isolated ileum and colon samples were mounted into modified Ussing chambers. Segments were analyzed for glucose and glutamine nutrient transport and barrier integrity [transepithelial electrical resistance (TER) and fluorescein isothiocyanate-labeled dextran transport]. As expected, pigs exposed to HS had an increase in Tr (39.3 vs. 40.9°C; P < 0.01) and RR (52 vs. 119 breaths per minute; P < 0.05). Heat stress decreased FI (53%; P < 0.05) and BW (-2.2 kg; P < 0.05) compared to TN pigs. Compared to TN pigs, mucosal heat shock protein 70 increased (101%; P < 0.05) whereas intestinal integrity was compromised in the HS pigs (ileum and colon TER decreased 52 and 24%, respectively; P < 0.05). Furthermore, serum endotoxin concentrations increased 200% due to HS (P = 0.05). Intestinal glucose transport and blood glucose were elevated due to HS (P < 0.05). However, ileal sucrase and maltase activities decreased in HS pigs (30 and 24%, respectively; P < 0.05). Altogether, these data indicate that high ambient heat loads reduce intestinal integrity and increase circulating endotoxin and stress in pigs. Furthermore, glucose transport and digestive capacity are altered during acute HS.

SHILO, a novel dual imaging approach for simultaneous HI-/LOw temporal (Low-/Hi-spatial) resolution imaging for vascular dynamic contrast enhanced cardiovascular magnetic resonance: numerical simulations and feasibility in the carotid arteries

BACKGROUND

Dynamic contrast enhanced (DCE) cardiovascular magnetic resonance (CMR) is increasingly used to quantify microvessels and permeability in atherosclerosis. Accurate quantification depends on reliable sampling of both vessel wall (VW) uptake and contrast agent dynamic in the blood plasma (the so called arterial input function, AIF). This poses specific challenges in terms of spatial/temporal resolution and matched dynamic MR signal range, which are suboptimal in current vascular DCE-CMR protocols. In this study we describe a novel dual-imaging approach, which allows acquiring simultaneously AIF and VW images using different spatial/temporal resolution and optimizes imaging parameters for the two compartments. We refer to this new acquisition as SHILO, Simultaneous HI-/LOw-temporal (low-/hi-spatial) resolution DCE-imaging.

METHODS

In SHILO, the acquisition of low spatial resolution single-shot AIF images is interleaved with segments of higher spatial resolution images of the VW. This allows sampling the AIF and VW with different spatial/temporal resolution and acquisition parameters, at independent spatial locations. We show the adequacy of this temporal sampling scheme by using numerical simulations. Following, we validate the MR signal of SHILO against a standard 2D spoiled gradient recalled echo (SPGR) acquisition with in vitro and in vivo experiments. Finally, we show feasibility of using SHILO imaging in subjects with carotid atherosclerosis.

RESULTS

Our simulations confirmed the superiority of the SHILO temporal sampling scheme over conventional strategies that sample AIF and tissue curves at the same time resolution. Both the median relative errors and standard deviation of absolute parameter values were lower for the SHILO than for conventional sampling schemes. We showed equivalency of the SHILO signal and conventional 2D SPGR imaging, using both in vitro phantom experiments (R2 =0.99) and in vivo acquisitions (R2 =0.95). Finally, we showed feasibility of using the newly developed SHILO sequence to acquire DCE-CMR data in subjects with carotid atherosclerosis to calculate plaque perfusion indices.

CONCLUSIONS

We successfully demonstrate the feasibility of using the newly developed SHILO dual-imaging technique for simultaneous AIF and VW imaging in DCE-CMR of atherosclerosis. Our initial results are promising and warrant further investigation of this technique in wider studies measuring kinetic parameters of plaque neovascularization with validation against gold standard techniques.

Intestinal integrity, endotoxin transport and detoxification in pigs divergently selected for residual feed intake

Microbes and microbial components potentially impact the performance of pigs through immune stimulation and altered metabolism. These immune modulating factors can include endotoxin from gram negative bacterial outer membrane component, commonly referred to as lipopolysaccharide (LPS). In this study, our objective was to examine the relationship between intestinal barrier integrity, endotoxin and inflammation with feed efficiency (FE), using pig lines divergently selected for residual feed intake (RFI) as a model. Twelve gilts (62 ± 3 kg BW) from the low RFI (LRFI, more efficient) and 12 from the high RFI (HRFI, less efficient) were used. Individual performance data was recorded for 5 wk. At the end of the experimental period, ADFI of LRFI pigs was less (P < 0.001), ADG not different between the 2 lines (P = 0.72) but the G:F of LRFI pigs was greater than for HRFI pigs (P = 0.019). Serum endotoxin concentration (P < 0.01) and the acute phase protein haptoglobin (P < 0.05) were greater in HRFI pigs. Transepithelial resistance of the ileum, transport of fluorescein isothiocyanate labeled-Dextran and-LPS in ileum and colon, as well as tight junction protein mRNA expression in ileum, did not differ between the lines, indicating the 2 lines did not differ in transport characteristics at the intestinal level. Ileum inflammatory markers, myeloperoxidase (P < 0.05) and IL-8 (P < 0.10), were found to be greater in HRFI pigs. Alkaline phosphatase (ALP) activity was significantly increased in the LRFI pigs in ileum and liver tissues and negatively correlated with blood endotoxin (P < 0.05). Lysozyme activity in the liver was not different between the lines; however, the LRFI pigs had a twofold greater lysozyme activity in ileum (P < 0.05). Despite the difference in their activity, ALP or lysozyme mRNA expression was not different between the lines in either tissue. Decreased endotoxin and inflammatory markers and the enhanced activities of antimicrobial enzymes in the LRFI line may not fully explain the difference in the FE between the lines, but they have the potential to prevent the growth potential in HRFI pigs. Further studies are needed to identify the other mechanisms that may contribute to the greater endotoxin and acute phase proteins in the HRFI pigs and the greater FE in the LRFI pigs.

Dietary oil composition differentially modulates intestinal endotoxin transport and postprandial endotoxemia

BACKGROUND

Intestinal derived endotoxin and the subsequent endotoxemia can be considered major predisposing factors for diseases such as atherosclerosis, sepsis, obesity and diabetes. Dietary fat has been shown to increase postprandial endotoxemia. Therefore, the aim of this study was to assess the effects of different dietary oils on intestinal endotoxin transport and postprandial endotoxemia using swine as a model. We hypothesized that oils rich in saturated fatty acids (SFA) would augment, while oils rich in n-3 polyunsaturated fatty acids (PUFA) would attenuate intestinal endotoxin transport and circulating concentrations.

METHODS

Postprandial endotoxemia was measured in twenty four pigs following a porridge meal made with either water (Control), fish oil (FO), vegetable oil (VO) or coconut oil (CO). Blood was collected at 0, 1, 2, 3 and 5 hours postprandial and measured for endotoxin. Furthermore, ex vivo ileum endotoxin transport was assessed using modified Ussing chambers and intestines were treated with either no oil or 12.5% (v/v) VO, FO, cod liver oil (CLO), CO or olive oil (OO). Ex vivo mucosal to serosal endotoxin transport permeability (Papp) was then measured by the addition of fluorescent labeled-lipopolysaccharide.

RESULTS

Postprandial serum endotoxin concentrations were increased after a meal rich in saturated fatty acids and decreased with higher n-3 PUFA intake. Compared to the no oil control, fish oil and CLO which are rich in n-3 fatty acids reduced ex vivo endotoxin Papp by 50% (P < 0.05). Contrarily, saturated fatty acids increased the Papp by 60% (P = 0.008). Olive and vegetable oils did not alter intestinal endotoxin Papp.

CONCLUSION

Overall, these results indicate that saturated and n-3 PUFA differentially regulate intestinal epithelial endotoxin transport. This may be associated with fatty acid regulation of intestinal membrane lipid raft mediated permeability.

Effect of vitamin E supplementation on mRNA expression of superoxide dismutase and interleukin-2 in arsenic exposed goat leukocytes

The aim of this study was to quantify the expression level of genes involved in antioxidant defenses during inorganic arsenic (iAs) exposure in the blood of goats and to evaluate the regulative activity on these genes of antioxidant vitamin E in the diet. Twenty-four crossbred lactating goats (Alpine × Beetal) were distributed randomly into four equal groups (Control, T(1), T(2) and T(3)) of six in each, on the basis of average body weight (36.10 ± 0.11 kg) and milk yield (1.61 ± 0.004 kg/day). The animals in T(1), T(2) and T(3) were given 50 mg/kg dry matter arsenic daily, while in T(2) and T(3), vitamin E @100 IU and 150 IU/kg dry matter, respectively, was also supplemented additionally for the period of 12 months. Blood was sampled at 0 day then at 3 months interval and analyzed for the expression level of superoxide dismutase (Cu/Zn SOD) and interleukin-2 (IL-2) using real-time PCR technique. Initially there was no difference (p > 0.05) in relative expression of the two genes. But, at 3 months, relative expression of Cu/Zn SOD increased (p < 0.05) in T(1) groups then, at 6 and 9 months expression was decreased (p < 0.05) in all the iAs treated groups whereas at 12 months, vitamin E supplementation increased (p < 0.05) the expression which is comparable to control groups. IL-2 mRNA expression was decreased (p < 0.05) at 6 months in all iAs treated groups, at 9 months there was decline trend but not significantly different whereas at 12 months decline trend was less (p < 0.05) in vitamin E supplemented groups. The result suggests that vitamin E may have a controlling effect on oxidative stress through modulation of SOD and IL-2 expression.

Feasibility of [18F]-2-Fluoro-A85380-PET imaging of human vascular nicotinic acetylcholine receptors in vivo

OBJECTIVES

The aim of this feasibility study was to evaluate [(18)F]-2-Fluoro-A85380 for in vivo imaging of arterial nicotinic acetylcholine receptors (nAChRs) in humans. Furthermore, potentially different vascular uptake patterns of this new tracer were evaluated in healthy volunteers and in patients with neurodegenerative disorders.

BACKGROUND

[(18)F]-2-Fluoro-A85380 was developed for in vivo positron emission tomography (PET) imaging of nAChR subunits in the human brain. These nAChRs are also found in arteries and seem to mediate the deleterious effects of nicotine as a part of tobacco smoke in the vasculature. It has been previously shown that uptake patterns of the radiotracer in the brain differs in patients with neurodegenerative disorders compared with healthy controls.

METHODS

[(18)F]-2-Fluoro-A85380 uptake was quantified in the ascending and descending aorta, the aortic arch, and the carotids in 5 healthy volunteers and in 6 patients with either Parkinson's disease or multiple system atrophy, respectively, as the maximum target-to-background ratio. The maximal standardized uptake value values, the single hottest segment, and the percent active segments of the [(18)F]-2-Fluoro-A85380 uptake in the arteries were also assessed.

RESULTS

[(18)F]-2-Fluoro-A85380 uptake was clearly visualized and maximum target-to-background ratio uptake values corrected for the background activity of the tracer showed specific tracer uptake in the arterial walls. Significantly higher uptake values were found in the descending aorta. Comparison between volunteers and patients revealed significant differences, with lower [(18)F]-2-Fluoro-A85380 uptake in the patient group when comparing single arterial territories but not when all arterial territories were pooled together.

CONCLUSIONS

[(18)F]-2-Fluoro-A85380 can provide specific information on the nAChR distribution in human arteries. Vascular nAChR density seems to be lower in patients with Parkinson's disease or multiple system atrophy. Once confirmed in larger study populations and in the experimental setting, this approach might provide insights into the pathogenic role of nAChRs in the human vasculature.

Impact of noninsulin-dependent type 2 diabetes on carotid wall 18F-fluorodeoxyglucose positron emission tomography uptake

OBJECTIVES

In this study, the impact of noninsulin-dependent type 2 diabetes mellitus on carotid wall (18)F-fluorodeoxyglucose (FDG) uptake in patients with documented or suspected cardiovascular disease was evaluated.

BACKGROUND

Inflammation is a pivotal process in the progression of atherosclerosis, which can be noninvasively imaged by FDG positron emission tomography (FDG-PET).

METHODS

Carotid artery wall FDG uptake was quantified in 134 patients (age 60.2 ± 9.7 years; diabetic subjects, n = 43). The pre-scan glucose (gluc) level corrected mean of the maximum standardized uptake value (SUV) values ((mean)SUV(gluc)), mean of the maximum target-to-background ratio ((mean)TBR(gluc)), and single hottest segment (SHS(gluc)) of FDG uptake in the artery wall were calculated. Associations between FDG uptake, the presence of risk factors for atherosclerosis, and diabetes were then assessed by multiple regression analysis with backward elimination.

RESULTS

The study demonstrated a significant association between diabetes and FDG uptake in the arterial wall (diabetes (mean)SUV(gluc) β = 0.324, (mean)TBR(gluc) β = 0.317, and SHS(gluc) β = 0.298; for all, p < 0.0001). In addition, in diabetic patients, both body mass index ≥ 30 kg/m(2) ((mean)SUV(gluc) β = 0.4, (mean)TBR(gluc) β = 0.357, and SHS(gluc) β = 0.388; for all, p < 0.015) and smoking ((mean)TBR(gluc), β = 0.312; SHS(gluc), β = 0.324; for all, p < 0.04) were significantly associated with FDG uptake.

CONCLUSIONS

Type 2 diabetes was significantly associated with carotid wall FDG uptake in patients with known or suspected cardiovascular disease. In diabetic patients, obesity and smoking add to the risk of increased FDG uptake values.

Errors during the preparation of drug infusions: a randomized controlled trial

BACKGROUND

We investigated the extent and frequency of dose errors and treatment delays made as a consequence of preparing drug infusions at the bedside, rather than using pre-filled syringes.

METHODS

Forty-eight nurses with critical care experience volunteered to take part in this randomized, blinded, controlled study conducted in the simulation centre of an urban hospital. They assisted in the management of a simulated patient with septic shock. Vasopressor infusions were prepared either by diluting concentrated drugs from ampoules or were provided in syringes pre-filled beforehand by an intensive care unit resident.

RESULTS

The time taken for the infusion to be started and the final concentration of the drugs were measured. We also measured the concentration of infusions prepared by a pharmacist and a pharmaceutical company. Nurses took 156 s to start infusions when using pre-filled syringes compared with 276 s when preparing them de novo, a mean delay of 106 s [95% confidence interval (CI) 73-140 s, P<0.0001]. One infusion prepared from ampoules contained one-fifth of the expected concentration of epinephrine; another contained none at all. Medication errors were 17.0 times less likely when pre-filled syringes were used (95% CI 5.2-55.5), and infusions prepared by pharmacy and industry were significantly more likely to contain the expected concentration (P<0.001 for norepinephrine and P=0.001 for epinephrine).

CONCLUSIONS

Providing drug infusions in syringes pre-filled by pharmacists or pharmaceutical companies would reduce medication errors and treatment delays, and improve patient safety. However, this approach would have substantial financial implications for healthcare providers, especially in less developed countries.

Effect of vitamin E supplementation on arsenic induced oxidative stress in goats

The present study was designed to assess whether supplementation of different levels of vitamin E to long-term arsenic exposed goats affords protection against the oxidative stress caused by the metalloid. Twenty-four crossbred lactating goats were distributed randomly into four groups (control, T(1), T(2) and T(3)) of six in each. The animals in T(1), T(2) and T(3) were given 50 mg/kg DM arsenic daily, while in T(2) and T(3), vitamin E @100 IU and 150 IU/kg DM, respectively, was also supplemented additionally for the period of 12 months. Compared to control, significant (p < 0.05) decline in SOD (45 %), CAT activities of erythrocytes (63 %), plasma total Ig (22 %) and total antioxidant activity (24 %) was observed in only arsenic treated groups and vitamin E supplementation in both doses produced partial mitigation effect against SOD (23 %, 20 %) and CAT (39 %, 48 %) while complete mitigation against total Ig (16 %, 7 %) and antioxidant activity (10 %, 8 %) was found. Average lymphocyte stimulation index at the end of experiment was (p < 0.05) lower in arsenic exposed groups (1.003 ± 0.01) and significant (p < 0.05) recovery was observed in response of vitamin E supplementation at higher doses (1.138 ± 0.03). So, vitamin E is helpful in reducing the burden of arsenic induced oxidative stress and activities of antioxidant enzymes in goats.

Prevalence and risk factors of carotid vessel wall inflammation in coronary artery disease patients: FDG-PET and CT imaging study

OBJECTIVES

We investigated the prevalence and clinical risk factors of carotid vessel wall inflammation by means of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in a population consisting of coronary artery disease (CAD) patients.

BACKGROUND

The atherosclerotic disease process is characterized by infiltration and retention of oxidized lipids in the artery wall, triggering a disproportionate inflammatory response. Efforts have been made to use noninvasive imaging to quantify this inflammatory response in the vessel wall. Recently, carotid FDG-PET has been shown to reflect the metabolic rate of glucose, a process known to be enhanced in inflamed tissue.

METHODS

Carotid inflammation was quantified in 82 CAD patients (age 62 ± 10 years) as the maximum target-to-background ratio ((wholevessel)TBR(max)). Furthermore, we assessed the maximal standardized uptake value values ((wholevessel)SUV(max)), the single hottest segment (SHS), and the percent active segments (PAS) of the FDG uptake in the artery wall, measured by FDG-PET.

RESULTS

Whole-vessel TBR(max) >1.8 was present in 67%, >2.0 in 39%, >2.2 in 23%, and >2.4 in 12% of the population. Multiple linear regression analysis with backward elimination revealed that body mass index (BMI) ≥30 kg/m2 (p < 0.0001), age >65 years (p = 0.01), smoking (p = 0.02), and hypertension (p = 0.01) were associated with (wholevessel)TBR(max). The number of components of the metabolic syndrome was also associated with (wholevessel)TBR(max) (p = 0.02). In similar analyses, (wholevessel)SUV(max) was associated with BMI ≥30 kg/m2 (p < 0.0001), age >65 years (p = 0.004), male gender (p = 0.02), and hypertension (p = 0.04); SHS with BMI ≥30 kg/m2 (p < 0.0001), age >65 years (p = 0.02), smoking (p = 0.04), and hypertension (p = 0.05); PAS with BMI ≥30 kg/m2 (p = 0.001), smoking (p = 0.03), and hypertension (p = 0.01).

CONCLUSIONS

Carotid inflammation as revealed by FDG-PET is highly prevalent in the CAD population and is associated with obesity, age over 65 years, history of hypertension, smoking, and male gender. Artery wall FDG uptake increased when components of the metabolic syndrome clustered.

MRI-based motion correction of thoracic PET: initial comparison of acquisition protocols and correction strategies suitable for simultaneous PET/MRI systems

OBJECTIVES

Magnetic resonance imaging (MRI) acquired on equipment capable of simultaneous MRI and positron emission tomography (PET) could potentially provide the gold standard method for motion correction of PET. To assess the latter, in this study we compared fast 2D and 3D MRI of the torso and used deformation parameters from real MRI data to correct simulated PET data for respiratory motion.

METHODS

PET sinogram data were simulated using SimSET from a 4D pseudo-PET image series created by segmenting MR images acquired over a respiratory cycle. Motion-corrected PET images were produced using post-reconstruction registration (PRR) and motion-compensated image reconstruction (MCIR).

RESULTS

MRI-based motion correction improved PET image quality at the lung-liver and lung-spleen boundaries and in the heart but little improvement was obtained where MRI contrast was low. The root mean square error in SUV units per voxel compared to a motion-free image was reduced from 0.0271 (no motion correction) to 0.0264 (PRR) and 0.0250 (MCIR).

CONCLUSIONS

Motion correction using MRI can improve thoracic PET images but there are limitations due to the quality of fast MRI.

Growth and Development Symposium: Endotoxin, inflammation, and intestinal function in livestock

Endotoxin, also referred to as lipopolysaccharide (LPS), can stimulate localized or systemic inflammation via the activation of pattern recognition receptors. Additionally, endotoxin and inflammation can regulate intestinal epithelial function by altering integrity, nutrient transport, and utilization. The gastrointestinal tract is a large reservoir of both gram-positive and gram-negative bacteria, of which the gram-negative bacteria serve as a source of endotoxin. Luminal endotoxin can enter circulation via two routes: 1) nonspecific paracellular transport through epithelial cell tight junctions, and 2) transcellular transport through lipid raft membrane domains involving receptor-mediated endocytosis. Paracellular transport of endotoxin occurs through dissociation of tight junction protein complexes resulting in reduced intestinal barrier integrity, which can be a result of enteric disease, inflammation, or environmental and metabolic stress. Transcellular transport, via specialized membrane regions rich in glycolipids, sphingolipids, cholesterol, and saturated fatty acids, is a result of raft recruitment of endotoxin-related signaling proteins leading to endotoxin signaling and endocytosis. Both transport routes and sensitivity to endotoxin may be altered by diet and environmental and metabolic stresses. Intestinal-derived endotoxin and inflammation result in suppressed appetite, activation of the immune system, and partitioning of energy and nutrients away from growth toward supporting the immune system requirements. In livestock, this leads to the suppression of growth, particularly suppression of lean tissue accretion. In this paper, we summarize the evidence that intestinal transport of endotoxin and the subsequent inflammation leads to decrease in the production performance of agricultural animals and we present an overview of endotoxin detoxification mechanisms in livestock.

Safety and efficacy of dalcetrapib on atherosclerotic disease using novel non-invasive multimodality imaging (dal-PLAQUE): a randomised clinical trial

BACKGROUND

Dalcetrapib modulates cholesteryl ester transfer protein (CETP) activity to raise high-density lipoprotein cholesterol (HDL-C). After the failure of torcetrapib it was unknown if HDL produced by interaction with CETP had pro-atherogenic or pro-inflammatory properties. dal-PLAQUE is the first multicentre study using novel non-invasive multimodality imaging to assess structural and inflammatory indices of atherosclerosis as primary endpoints.

METHODS

In this phase 2b, double-blind, multicentre trial, patients (aged 18-75 years) with, or with high risk of, coronary heart disease were randomly assigned (1:1) to dalcetrapib 600 mg/day or placebo for 24 months. Randomisation was done with a computer-generated randomisation code and was stratified by centre. Patients and investigators were masked to treatment. Coprimary endpoints were MRI-assessed indices (total vessel area, wall area, wall thickness, and normalised wall index [average carotid]) after 24 months and (18)F-fluorodeoxyglucose ((18)F-FDG) PET/CT assessment of arterial inflammation within an index vessel (right carotid, left carotid, or ascending thoracic aorta) after 6 months, with no-harm boundaries established before unblinding of the trial. Analysis was by intention to treat. This trial is registered at ClinicalTrials.gov, NCT00655473.

FINDINGS

189 patients were screened and 130 randomly assigned to placebo (66 patients) or dalcetrapib (64 patients). For the coprimary MRI and PET/CT endpoints, CIs were below the no-harm boundary or the adverse change was numerically lower in the dalcetrapib group than in the placebo group. MRI-derived change in total vessel area was reduced in patients given dalcetrapib compared with those given placebo after 24 months; absolute change from baseline relative to placebo was -4·01 mm(2) (90% CI -7·23 to -0·80; nominal p=0·04). The PET/CT measure of index vessel most-diseased-segment target-to-background ratio (TBR) was not different between groups, but carotid artery analysis showed a 7% reduction in most-diseased-segment TBR in the dalcetrapib group compared with the placebo group (-7·3 [90% CI -13·5 to -0·8]; nominal p=0·07). Dalcetrapib did not increase office blood pressure and the frequency of adverse events was similar between groups.

INTERPRETATION

Dalcetrapib showed no evidence of a pathological effect related to the arterial wall over 24 months. Moreover, this trial suggests possible beneficial vascular effects of dalcetrapib, including the reduction in total vessel enlargement over 24 months, but long-term safety and clinical outcomes efficacy of dalcetrapib need to be analysed.

FUNDING

F Hoffmann-La Roche Ltd.

Rationale and design of dal-PLAQUE: a study assessing efficacy and safety of dalcetrapib on progression or regression of atherosclerosis using magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography/computed tomography

dal-PLAQUE is a placebo-controlled multicenter study designed to assess the effect of dalcetrapib on imaging measures of plaque inflammation and plaque burden. dal-PLAQUE is a multimodality imaging study in the context of the large dal-HEART Program. Decreased high-density lipoprotein cholesterol is linked to increased risk of coronary heart disease (CHD). Dalcetrapib, a compound that increases high-density lipoprotein cholesterol by modulating cholesteryl ester transfer protein, is being studied to assess if it can reduce the progression of atherosclerotic disease and thereby decrease cardiovascular morbidity and mortality. Patients with CHD or CHD-risk equivalents were randomized to receive 600 mg dalcetrapib or placebo daily for 24 months, in addition to conventional lipid-lowering medication and other medications for cardiovascular risk factors. The primary outcomes are the effect of dalcetrapib on 18F-fluorodeoxyglucose positron emission tomography target-to-background ratio after 6 months and magnetic resonance imaging (MRI) plaque burden (wall area, wall thickness, total vessel area, and wall area/total vessel area ratio) after 12 months. Secondary objectives include positron emission tomography target-to-background ratio at 3 months and MRI plaque burden at 6 and 24 months; plaque composition at 6, 12, and 24 months; and aortic compliance at 6 months. A tertiary objective is to examine the dynamic contrast-enhanced MRI parameters of plaque neovascularization. In total, 189 subjects entered screening, and 130 were randomized. dal-PLAQUE will provide important information on the effects of dalcetrapib on markers of inflammation and atherosclerotic plaque burden and, thereby, on the safety of cholesteryl ester transfer protein modulation with dalcetrapib. Results are expected in 2011.

Multifunctional nanoemulsion platform for imaging guided therapy evaluated in experimental cancer

Nanoparticle applications in medicine have seen a tremendous growth in the past decade. In addition to their drug targeting application and their ability to improve bioavailability of drugs, nanoparticles can be designed to allow their detection with a variety of imaging methodologies. In the current study, we developed a multimodal nanoparticle platform to enable imaging guided therapy, which was evaluated in a colon cancer mouse model. This "theranostic" platform is based on oil-in-water nanoemulsions and carries iron oxide nanocrystals for MRI, the fluorescent dye Cy7 for NIRF imaging, and the hydrophobic glucocorticoid prednisolone acetate valerate (PAV) for therapeutic purposes. Angiogenesis-targeted nanoemulsions functionalized with αvβ(3)-specific RGD peptides were evaluated, as well. When subcutaneous tumors were palpable, the nanoemulsions were administered at a dose of 30 mg of FeO/kg and 10 mg of PAV/kg. MRI and NIRF imaging showed significant nanoparticle accumulation in the tumors, while tumor growth profiles revealed a potent inhibitory effect in all of the PAV nanoemulsion-treated animals as compared to the ones treated with control nanoemulsions, the free drug, or saline. This study demonstrated that our nanoemulsions, when loaded with PAV, iron oxide nanocrystals, and Cy7, represent a flexible and unique theranostic nanoparticle platform that can be applied for imaging guided therapy of cancer.