Assessment of a one-week ketogenic diet on brain glycolytic metabolism and on the status epilepticus stage of a lithium-pilocarpine rat model.

The ketogenic diet (KD) has been shown to be effective in refractory epilepsy after long-term administration. However, its interference with short-term brain metabolism and its involvement in the early process leading to epilepsy remain poorly understood. This study aimed to assess the effect of a short-term ketogenic diet on cerebral glucose metabolic changes, before and after status epilepticus (SE) in rats, by using [18F]-FDG PET. Thirty-nine rats were subjected to a one-week KD (KD-rats, n = 24) or to a standard diet (SD-rats, n = 15) before the induction of a status epilepticus (SE) by lithium-pilocarpine administrations. Brain [18F]-FDG PET scans were performed before and 4 h after this induction. Morphological MRIs were acquired and used to spatially normalize the PET images which were then analyzed voxel-wisely using a statistical parametric-based method. Twenty-six rats were analyzed (KD-rats, n = 15; SD-rats, n = 11). The 7 days of the KD were associated with significant increases in the plasma ß-hydroxybutyrate level, but with an unchanged glycemia. The PET images, recorded after the KD and before SE induction, showed an increased metabolism within sites involved in the appetitive behaviors: hypothalamic areas and periaqueductal gray, whereas no area of decreased metabolism was observed. At the 4th hour following the SE induction, large metabolism increases were observed in the KD- and SD-rats in areas known to be involved in the epileptogenesis process late-i.e., the hippocampus, parahippocampic, thalamic and hypothalamic areas, the periaqueductal gray, and the limbic structures (and in the motor cortex for the KD-rats only). However, no statistically significant difference was observed when comparing SD and KD groups at the 4th hour following the SE induction. A one-week ketogenic diet does not prevent the status epilepticus (SE) and associated metabolic brain abnormalities in the lithium-pilocarpine rat model. Further explorations are needed to determine whether a significant prevention could be achieved by more prolonged ketogenic diets and by testing this diet in less severe experimental models, and moreover, to analyze the diet effects on the later and chronic stages leading to epileptogenesis.

Aortic regurgitation: multimodal assessment of quantification and impact.

BACKGROUND: The assessment of severity of aortic regurgitation (AR) by transthoracic echocardiography (TTE) remains challenging in routine practice. Contemporary guidelines recommend cardiovascular magnetic resonance imaging (CMR) in patients with significant disease and suboptimal TTE images. The objective of this study was to assess the role of CMR in the evaluation of severity of AR and to compare both modalities in the quantification of regurgitation and left ventricular volumes. METHODS: Fifty consecutive patients who had isolated chronic AR and who underwent TTE and CMR within an interval of less than three months between May 2009 and June 2020 were included. The main indication for CMR was difficulties in quantifying AR, either because of lack of multiparametric analysis (only one method possible) or because of discrepancies in the different methods by TTE. RESULTS: In 25 patients, precise grading of AR was not possible by echocardiography. Among them, CMR finally detected seven patients with mild AR, 11 with moderate AR and seven with severe AR. For the 25 patients who had AR quantification by TTE, there was concordance between TTE and CMR in only seven patients (28%), and the AR was re-graded by CMR in 18 patients, including eight patients with severe AR by TTE and moderate AR by CMR. The concordance between TTE and CMR was weakly significant (intraclass correlation coefficient = 0.39, 95% confidence interval: 0.003-0.67, p = 0.02). There was a moderate correlation between left ventricular volumes measured by TTE and by CMR (left ventricular end-diastolic volume: r = 0.57; p = 0.01; left ventricular end-systolic volume: r = 0.47, p = 0.01) but regurgitant volumes were not correlated (r = 0.04; p = 0.8). No TTE parameter of quantification was correlated with regurgitant volume measured by CMR. CONCLUSIONS: The concordance of AR quantification by CMR and TTE was weak. CMR re-graded some patients with severe AR by TTE into moderate AR. This should motivate practitioners to systematically assess all significant AR by CMR in order to improve quantification and optimise clinical management.

Assessment of the routine reporting of very low-dose exercise-first myocardial perfusion SPECT from a large-scale real-world cohort and correlation with the subsequent reporting of coronary stenosis at angiography.

PURPOSE: Our study assesses the routine reporting of exercise ischemia using very low-dose exercise-first myocardial perfusion SPECT in a large number of patients and under real-life conditions, by evaluating correlations with the subsequent routine reporting of coronary stenosis by angiography and with factors that predict ischemia. METHODS: Data from 13,126 routine exercise MPI reports, from 11,952 patients (31% women), using very low doses of sestamibi and a high-sensitivity cardiac CZT camera, were extracted to assess the reporting of significant MPI-ischemia (> 1 left ventricular segment), to determine the MPI normalcy rate in a group with < 5% pretest probability of coronary artery disease (CAD) (n = 378), and to assess the ability of MPI to predict a > 50% coronary stenosis in patients with available coronary angiography reports in the 3 months after the MPI (n = 713). RESULTS: The median effective patient dose was 2.51 [IQR: 1.00-4.71] mSv. The normalcy rate was 98%, and the MPI-ischemia rate was independently predicted by a known CAD, the male gender, obesity, and a < 50% LV ejection fraction, ranging from 29.5% with all these risk factors represented to 1.5% when there were no risk factors. A > 50% coronary stenosis was significantly predicted by MPI-ischemia, less significantly for mild (odds ratio [95% confidence interval]: 1.61 [1.26-1.96]) than for moderate-to-severe MPI-ischemia (4.05 [3.53-4.57]) and was also impacted by having a known CAD (2.17 [1.83-2.51]), by a submaximal exercise test (1.48 [1.15-1.81]) and being ≥ 65 years of age (1.43 [1.11-1.76]). CONCLUSION: Ischemia detected using a very low-dose exercise-first MPI protocol in a large-scale clinical cohort and under real-life routine conditions is a highly significant predictor for the subsequent reporting of coronary stenosis, although this prediction is enhanced by other variables. This weakly irradiating approach is amenable to being repeated at shorter time intervals, in target patient groups with a high probability of MPI-ischemia.

Monte Carlo simulation of digital photon counting PET.

A GATE Monte Carlo model of the Philips Vereos digital photon counting PET imaging system using silicon photo-multiplier detectors was proposed. It was evaluated against experimental data in accordance with NEMA guidelines. Comparisons were performed using listmode data in order to remain independent of image reconstruction algorithms. An original line of response-based method is proposed to estimate intrinsic spatial resolution without reconstruction. Four sets of experiments were performed: (1) count rates and scatter fraction, (2) energy and timing resolutions, (3) sensitivity, and (4) intrinsic spatial resolution. Experimental and simulated data were found to be in good agreement, with overall differences lower than 10% for activity concentrations used in most standard clinical applications. Illustrative image reconstructions were provided. In conclusion, the proposed Monte Carlo model was validated and can be used for numerous studies such as optimizing acquisition parameters or reconstruction algorithms.

Assessment of 18F-Florbetaben Amyloid PET Imaging in Patients with Suspected Alzheimer's Disease and Isolated Increase in Cerebrospinal Fluid Tau Proteins.

BACKGROUND/OBJECTIVE: The aim of this study was to assess, in routine, the rates with which an amyloid deposition was documented by 18F-florbetaben PET in patients with suspected Alzheimer's disease (AD) but with isolated increases in cerebrospinal fluid (CSF) tau-protein concentrations, and the subsequent impact of these PET results on medical management. METHODS: This prospective study included 34 patients with mild neurocognitive disorders (MND) and suspected AD (73±9 years, 16 women) and with abnormal CSF concentrations in total-tau (T-tau) and/or phosphorylated-tau (P-tau) proteins but normal Aß42 concentration and Aß42/Aß40 ratio. These patients were referred to 8F-florbetaben PET from which the PET-related changes in the confidence for AD diagnosis (low, intermediate, or high) and treatments were reported. RESULTS: The PET examinations were positive for amyloid deposition (brain amyloid plaque load, BAPL score >1) in none of the 9 patients with an increase in only T-tau proteins and in 8 among the 25 (32%) with an increase in P-tau proteins (one BAPL score of 2 and seven BAPL scores of 3). Knowledge of the PET results was associated with subsequent changes in diagnostic confidence in 44% of patients (15/34) and in the intention-to-treat with a cholinesterase inhibitor drug in 18% (6/34). CONCLUSION: In patients with suspected AD and isolated increase in CSF tau protein concentrations, an amyloid deposition is documented by 18F-florbetaben PET in as much as one third of cases when the concentration of P-tau is abnormal, and PET results are associated with significant further changes in medical management.

Assessment of Myocardial CZT SPECT Recording in a Forward-Leaning Bikerlike Position.

This prospective randomized study assessed myocardial perfusion imaging with the high-sensitivity D.SPECT cadmium-zinc-telluride camera in a forward-leaning bikerlike position, which may potentially lower diaphragmatic attenuation and reduce breathing-related cardiac motion, in a manner comparable to the prone position proposed with other SPECT cameras. Methods: Patients referred for a stress-rest 99mTc-sestamibi protocol and positioned in the biker position, with the chest leaning forward on the D.SPECT camera-head at 35° from vertical, had an additional resting D.SPECT recording in the supine position (n = 40) or in the sitting position with the back rearward at 30° from vertical (n = 40). Segments with attenuation artifacts were defined as those with less than 65% uptake but with strictly normal contractility at gated SPECT and no defect reversibility from stress images. Results: The biker position was associated with lower heart-to-detector distances than the supine or sitting positions (both P < 0.001); lower cardiac motion amplitudes, assessed on panograms, than the supine position (P < 0.001); and fewer segments with attenuation artifacts than the supine position (on average, 1.10 ± 1.01 vs. 1.90 ± 1.74, P = 0.010) or the sitting position (0.75 ± 0.93 vs. 1.38 ± 1.60, P = 0.011). Conclusion: Myocardial perfusion images from D.SPECT are enhanced for patients positioned in a forward-leaning bikerlike position comparatively to sitting or supine positions, with a notably lower rate of attenuation artifacts.

Three-Dimensional Echocardiography for the Assessment of Right Ventriculo-Arterial Coupling.

BACKGROUND: The analysis of right ventriculo-arterial coupling (RVAC) from pressure-volume loops is not routinely performed. RVAC may be approached by the combination of right heart catheterization (RHC) pressure data and cardiac magnetic resonance (CMR)-derived right ventricular (RV) volumetric data. RV pressure and volume measurements by Doppler and three-dimensional echocardiography (3DE) allows another way to approach RVAC. METHODS: Ninety patients suspected of having pulmonary hypertension underwent RHC, 3DE, and CMR (RHC mean pulmonary artery pressure [mPAP] 37.9 ± 11.3 mm Hg; range, 15-66 mm Hg). Three-dimensional (3D) echocardiography was performed in 30 normal patients (echocardiographic mPAP 18.4 ± 3.1 mm Hg). Pulmonary artery (PA) effective elastance (Ea), RV maximal end-systolic elastance (Emax), and RVAC (PA Ea/RV Emax) were calculated from RHC combined with CMR and from 3DE using simplified formulas including mPAP, stroke volume, and end-systolic volume. RESULTS: Three-dimensional echocardiographic and RHC-CMR measures for PA Ea (3DE, 1.27 ± 0.94; RHC-CMR, 0.71 ± 0.52; r = 0.806, P < .001), RV Emax (3DE, 0.72 ± 0.37; RHC-CMR, 0.38 ± 0.19; r = 0.798, P < .001), and RVAC (3DE, 2.01 ± 1.28; RHC-CMR, 2.32 ± 1.77; r = 0.826, P < .001) were well correlated despite a systematic overestimation of 3DE elastance parameters. Among the whole population, 3D echocardiographic PA Ea and 3D echocardiographic RVAC but not 3D echocardiographic RV Emax were significantly lower in patients with mPAP < 25 mm Hg (n = 41) than in others (n = 79). Among the 90 patients who underwent RHC, 3D echocardiographic PA Ea and 3D echocardiographic RVAC but not 3D echocardiographic RV Emax increased significantly with increasing levels of pulmonary vascular resistance. CONCLUSIONS: Three-dimensional echocardiography-derived PA Ea, RV Emax, and RVAC correlated well with the reference RHC-CMR measurements. Ea and RVAC but not Emax were significantly different between patients with different levels of afterload, suggesting failure of the right ventricle to maintain coupling in severe pulmonary hypertension.

Assessment of Left Ventricular Ejection Fraction Calculation on Long-axis Views From Cardiac Magnetic Resonance Imaging in Patients With Acute Myocardial Infarction.

To assess left ventricular ejection fraction (LVEF) accurately, cardiac magnetic resonance (CMR) can be indicated and lays on the evaluation of multiple slices of the left ventricle in short axis (CMRSAX). The objective of this study was to assess another method consisting of the evaluation of 2 long-axis slices (CMRLAX) for LVEF determination in acute myocardial infarction.One hundred patients underwent CMR 2 to 4 days after acute myocardial infarction. LVEF was computed by the area-length method on horizontal and vertical CMRLAX images. Those results were compared to reference values obtained on contiguous CMRSAX images in one hand, and to values obtained from transthoracic echocardiography (TTE) in the other hand. For CMRSAX and TTE, LVEF was computed with Simpson method. Reproducibility of LVEF measurements was additionally determined. The accuracy of volume measurements was assessed against reference aortic stroke volumes obtained by phase-contrast MR imaging.LVEF from CMRLAX had a mean value of 47 ±â€Š8% and were on average 5% higher than reference LVEF from CMRSAX (42 ±â€Š8%), closer to routine values from TTELAX (49 ±â€Š8%), much better correlated with the reference LVEF from CMRSAX (R = 0.88) than that from TTE (R = 0.58), obtained with a higher reproducibility than with the 2 other techniques (% of interobserver variability: CMRLAX 5%, CMRSAX 11%, and TTE 13%), and obtained with 4-fold lower recording and calculation times than for CMRSAX. Apart from this, CMRLAX stroke volume was well correlated with phase-contrast values (R = 0.81).In patients with predominantly regional contractility abnormalities, the determination of LVEF by CMRLAX is twice more reproducible than the reference CMRSAX method, even though the LVEF is consistently overestimated compared with CMRSAX. However, the CMRLAX LVEF determination provides values closer to TTE measurements, the most available and commonly used method in clinical practice, clinical trials, and guidelines in ischemic cardiomyopathy. Moreover, LVEF determination by CMRLAX allows a 63% gain of acquisition/reading time compared with CMRSAX. Thus, despite the fact that LVEF obtained from CMRSAX remains the gold standard, CMRLAX should be considered to shorten the overall imaging acquisition and reading time as a putative replacement.

Usefulness of Speckle-Tracking Imaging for Right Ventricular Assessment after Acute Myocardial Infarction: A Magnetic Resonance Imaging/Echocardiographic Comparison within the Relation between Aldosterone and Cardiac Remodeling after Myocardial Infarction Study.

BACKGROUND: Right ventricular (RV) dysfunction after acute myocardial infarction (AMI) is frequent and associated with poor prognosis. The complex anatomy of the right ventricle makes its echocardiographic assessment challenging. Quantification of RV deformation by speckle-tracking echocardiography is a widely available and reproducible technique that readily provides an integrated analysis of all segments of the right ventricle. The aim of this study was to investigate the accuracy of conventional echocardiographic parameters and speckle-tracking echocardiographic strain parameters in assessing RV function after AMI, in comparison with cardiac magnetic resonance imaging (CMR). METHODS: A total of 135 patients admitted for AMI (73 anterior, 62 inferior) were prospectively studied. Right ventricular function was assessed by echocardiography and CMR within 2 to 4 days of hospital admission. Right ventricular dysfunction was defined as CMR RV ejection fraction < 50%. Right ventricular global peak longitudinal systolic strain (GLPSS) was calculated by averaging the strain values of the septal, lateral, and inferior walls. RESULTS: Right ventricular dysfunction was documented in 20 patients. Right ventricular GLPSS was the best echographic correlate of CMR RV ejection fraction (r = -0.459, P < .0001) and possessed good diagnostic value for RV dysfunction (area under the receiver operating characteristic curve [AUROC], 0.724; 95% CI, 0.590-0.857), which was comparable with that of RV fractional area change (AUROC, 0.756; 95% CI, 0.647-0.866). In patients with inferior myocardial infarctions, the AUROCs for RV GLPSS (0.822) and inferolateral strain (0.877) were greater than that observed for RV fractional area change (0.760) Other conventional echocardiographic parameters performed poorly (all AUROCs < 0.700). CONCLUSIONS: After AMI, RV GLPSS is the best correlate of CMR RV ejection fraction. In patients with inferior AMIs, RV GLPSS displays even higher diagnostic value than conventional echocardiographic parameters.

Effect of chronic left ventricular unloading on myocardial remodeling: Multimodal assessment of two heterotopic heart transplantation techniques.

BACKGROUND: Cardiac recovery is possible by means of mechanical unloading yet remains rare. Excessive unloading-associated myocardial atrophy and fibrosis may adversely affect the process of reverse remodeling. In this study, we sought to evaluate the effect of different intensities of chronic left ventricular (LV) unloading on myocardial remodeling. METHODS: Twenty-five isogenic Lewis rats underwent complete LV unloading (CU, n = 15) induced by heterotopic heart transplantation or partial LV unloading (PU, n = 10) by heterotopic heart-lung transplantation. Information obtained from serial echocardiography, 2-deoxy-2[(18)F]fluoro-d-glucose ((18)F-FDG)-positron emission tomography, and an LV pressure-volume catheter were used to evaluate the morphology, glucose metabolism, and hemodynamic performance of the orthotopic hearts and heterotopic transplants over 4 weeks. Cell size, collagen content, tissue cytokines (interleukin [IL]-1α, IL-2, IL-6, IL-10, tumor necrosis factor-α, and vascular endothelial growth factor), and matrix metalloproteinase-2 and -9 were also determined. The recorded parameters included LV end-systolic dimension, LV end-diastolic dimension, posterior wall thickness, diastolic interventricular septum thickness, LV fractional shortening, and LV ejection fraction. RESULTS: We demonstrated an LV load-dependent relationship using echo-based structural (left posterior wall thickness, diastolic interventricular septum thickness, and left ventricular end-diastolic dimension) and functional (LV fractional shortening and LV ejection fraction) parameters, as well as an (18)F-FDG uptake (all p < 0.05). This load-dependent relationship was also evidenced in measurements from the pressure-volume conductance catheter (stroke volume, stroke work, cardiac output, dP/dTmax, and -dP/dTmin; all p < 0.05). Significant myocardial atrophy and fibrosis were observed in unloaded hearts, whereas concentrations of cytokines and matrix metalloproteinases were comparable in both unloading conditions. CONCLUSIONS: Partial and complete unloading affected the remodeling of non-failing hearts in a rodent model to different extents on myocardial atrophy, fibrosis, glucose metabolism, and mechanical work. Cardiac atrophy is the prominent change after mechanical unloading, which exaggerates the proportion of total collagen that is responsible for diastolic dysfunction.

Assessment of a Monte-Carlo simulation of SPECT recordings from a new-generation heart-centric semiconductor camera: from point sources to human images.

Geant4 application for tomographic emission (GATE), a Monte-Carlo simulation platform, has previously been used for optimizing tomoscintigraphic images recorded with scintillation Anger cameras but not with the new-generation heart-centric cadmium-zinc-telluride (CZT) cameras. Using the GATE platform, this study aimed at simulating the SPECT recordings from one of these new CZT cameras and to assess this simulation by direct comparison between simulated and actual recorded data, ranging from point sources to human images. Geometry and movement of detectors, as well as their respective energy responses, were modeled for the CZT 'D.SPECT' camera in the GATE platform. Both simulated and actual recorded data were obtained from: (1) point and linear sources of (99m)Tc for compared assessments of detection sensitivity and spatial resolution, (2) a cardiac insert filled with a (99m)Tc solution for compared assessments of contrast-to-noise ratio and sharpness of myocardial borders and (3) in a patient with myocardial infarction using segmented cardiac magnetic resonance imaging images. Most of the data from the simulated images exhibited high concordance with the results of actual images with relative differences of only: (1) 0.5% for detection sensitivity, (2) 6.7% for spatial resolution, (3) 2.6% for contrast-to-noise ratio and 5.0% for sharpness index on the cardiac insert placed in a diffusing environment. There was also good concordance between actual and simulated gated-SPECT patient images for the delineation of the myocardial infarction area, although the quality of the simulated images was clearly superior with increases around 50% for both contrast-to-noise ratio and sharpness index. SPECT recordings from a new heart-centric CZT camera can be simulated with the GATE software with high concordance relative to the actual physical properties of this camera. These simulations may be conducted up to the stage of human SPECT-images even if further refinement is needed in this setting.

Assessment of right ventricular functional recovery after acute myocardial infarction by 2D speckle-tracking echocardiography.

To assess the pattern of right ventricular (RV) functional recovery in a cohort of patients with successful reperfusion of a first episode of acute myocardial infarction (AMI) with 2D speckle-tracking echocardiography and cardiac magnetic resonance imaging (CMR). Ninety-five revascularized AMI patients were prospectively included (56.8 ± 11.1 years, 48 inferior, 47 anterior). RV function was assessed by echocardiography and CMR within the initial 72 h and 6 months later. A RV global strain was calculated while averaging strain values from septal, lateral and inferior walls. At the acute phase, RVEFCMR was lower in inferior than in anterior AMI patients (52.5 ± 6.8 vs. 56.0 ± 4.8, p = 0.006). Similarly, RV global, inferior and lateral strains were lower in inferior MI patients (p < 0.001 for all) whereas septal strain was not significantly different across groups. At 6 months, RVEFCMR and all strain parameters improved compared to baseline. Improvements were more substantial for patients with inferior than with anterior MI. RV parameters ultimately reached similar levels in the two groups at 6 months except for inferior strain which remained lower in patients with inferior MI (-24.5 ± 6.5 vs. -27.5 ± 5.4, p = 0.03). In low risk patients after AMI, RV function ultimately recovered over the 6 months of follow up. Higher levels of both initial impairment and subsequent recovery were observed for inferior MI. Although RV function was relatively preserved in these patients, RV strain analysis revealed a persistent impairment of RV inferior strain in patients with inferior MI, which may not be identified by RVEFCMR or conventional echocardiographic parameters.

Assessment of right ventricle volumes and function by cardiac MRI: quantification of the regional and global interobserver variability.

Reproducibility of the manual assessment of right ventricle volumes by short-axis cine-MRI remains low and is often attributed to the difficulty in separating the right atrium from the ventricle. This study was designed to evaluate the regional interobserver variability of the right ventricle volume assessment to identify segmentation zones with the highest interobserver variability. Short-axis views of 90 right ventricles (30 hypertrophic, 30 dilated, and 30 normal) were acquired with 2D steady-state free precession sequences at 1.5 T and were manually segmented by two observers. The two segmentations were compared and the variations were quantified with a variation score based on the Hausdorff distance between the two segmentations and the interobserver 95% limits of concordance of the global volumes. The right ventricles were semiautomatically split into four subregions: apex, mid-ventricle, tricuspid zone, and infundibulum. These four subregions represented 11%, 34%, 36%, and 19% of the volume but, respectively, yielded variation scores of 8%, 16%, 42%, and 34%. The infundibulum yielded the highest interobserver regional variability although its variation score remained comparable to the tricuspid zone due to its lower volume. These results emphasize the importance of standardizing the segmentation of the infundibulum and the tricuspid zone to improve reproducibility.

Posterior glucose hypometabolism in Lafora disease: early and late FDG-PET assessment.

Establishing an early diagnosis of Lafora disease (LD) is often challenging. We describe two cases of LD presenting as myoclonus and tonic-clonic seizures, initially suggesting idiopathic generalized epilepsy. The subsequent course of the disease was characterized by drug-resistant myoclonic epilepsy, cognitive decline, and visual symptoms, which oriented the diagnosis toward progressive myoclonic epilepsy and, more specifically, LD. Early in the evolution in the first case, and before histopathologic and genetic confirmation of LD in both cases, [18]Fluorodeoxyglucose positron emission tomography (FDG-PET) revealed posterior hypometabolism, consistent with the well-known posterior impairment in this disease. This suggests that FDG-PET could help to differentiate LD in early stages from other progressive myoclonic epilepsies, but confirmation is required by a longitudinal study of FDG-PET in progressive myoclonic epilepsy.

Re-assessment of chronic radio-induced tissue damage in a rat hindlimb model.

Radiotherapy is successfully used to treat neoplastic lesions, but may adversely affect normal tissues within the irradiated volume. However, additional clinical and para-clinical data are required for a comprehensive understanding of the pathogenesis of this damage. We assessed a rat model using clinical records and medical imaging to gain a better understanding of irradiation-induced tissue damage. The hindlimbs of the rats in this model were irradiated with a single dose of 30 or 50 Gy. Sequential analysis was based on observation records of stage and planar scintigraphy. Additional radiography, radiohistology and histology studies were performed to detect histological alterations. All animals developed acute and late effects, with an increased severity after a dose of 50 Gy. The bone uptake of (99m)Tc-HDP was significantly decreased in a dose- and time-dependent manner. Histologically, significant tissue damage was observed. After the 50 Gy irradiation, the animals developed lesions characteristic of osteoradionecrosis (ORN). Radiographic and histological studies provided evidence of lytic bone lesions. Our rat model developed tissue damage characteristic of radiation injury after a single 30 Gy irradiation and tissue degeneration similar to that which occurs during human ORN after a 50 Gy irradiation. The development of this animal model is an essential step in exploring the pathogenesis of irradiation-induced tissue damage, and may be used to test the efficacy of new treatments.

Pulse wave velocity assessment by external noninvasive devices and phase-contrast magnetic resonance imaging in the obese.

Carotid-femoral pulse wave velocity (PWV) is considered the gold-standard measurement of arterial stiffness. Obesity, however, can render inaccurate the measurement of PWV by external noninvasive devices. Phase-contrast MRI allows the determination of aortic PWV in multiple aortic locations with intra-arterial distance measurements, as well as the assessment of aortic mechanical properties. The purpose of this study was to assess the reliability of external carotid-femoral PWV values measured by well-validated external devices in comparison with MRI acquisitions of PWV and aortic mechanical properties in a population of obese subjects. PWV was measured with PulsePen and Complior II devices in 32 volunteers (18 men and 14 women), aged 46 to 65 years (mean: 55.7+/-5.1 years), presenting with isolated abdominal obesity, with a waist circumference >102 cm for men and >88 cm for women, and a body mass index between 27 and 35. These results were then compared with MRI PWV values and cross-sectional MRI thoracic aorta distensibility values. MRI PWV values were positively correlated with PWV measured by both PulsePen (r=0.47; P=0.005) and Complior (r=0.43; P=0.01). Aortic cross-sectional stiffness was positively correlated with PulsePen PWV (r=0.42; P=0.02). The same trend was also observed with Complior PWV (r=0.33; P=0.06). This is the first study comparing transcutaneous PWV measurements with MRI aortic elastic properties in obese subjects. Our results indicate that, for body mass index values < or =35 kg m(-2), PWV measured externally with Complior or PulsePen validly reflect values obtained directly in the thoracic aorta through MRI.