Potential of advanced MR imaging techniques in the differential diagnosis of parkinsonism.

The clinical differentiation of parkinsonian syndromes remains challenging not only for neurologists but also for movement disorder specialists. Conventional magnetic resonance imaging (cMRI) with the visual assessment of T2- and T1-weighted imaging as well as different advanced MRI techniques offer objective measures, which may be a useful tool in the diagnostic work-up of Parkinson's disease and atypical parkinsonian disorders (APDs). In clinical practice, cMRI is a well-established method for the exclusion of symptomatic parkinsonism due to other pathologies. Over the past two decades, abnormalities in the basal ganglia and infratentorial structures have been shown especially in APDs not only by cMRI but also by different advanced MRI techniques, including methods to assess regional cerebral atrophy quantitatively such as magnetic resonance volumetry, proton magnetic resonance spectroscopy, diffusion-weighted imaging, and magnetization transfer imaging. This article aims to review recent research findings on the role of advanced MRI techniques in the differential diagnosis of neurodegenerative parkinsonian disorders.

Phosphorus-31 two-dimensional chemical shift imaging in the myocardium of patients with late onset of Friedreich ataxia.

PURPOSE: Friedreich ataxia (FRDA) is characterized by GAA expansions in the intron 1 of the frataxin gene correlating with disease onset and progression as well as cardiac affection. Accordingly, FRDA patients with early disease onset show a clear impairment of mitochondrial function in the myocardium. The purpose of this study was to investigate cardiac function and high-energy phosphate metabolism in FRDA patients with late disease onset. PROCEDURES: Using a 1.5 T magnetic resonance scanner, cardiac phosphorus-31 two-dimensional chemical shift imaging was performed in ten patients (seven male, three female) with a late onset of FRDA and in 35 healthy, male controls. Ejection faction (EF) and interventricular septum thickness (IST) were determined by echocardiography. RESULTS: The differences in left ventricular phosphocreatine (PCr) to beta-adenosine triphosphate (beta-ATP) ratios between both groups were not significant. FRDA patients had increased ISTs (10.8+/-1.6 vs. 9.7+/-0.9 mm; p=0.048), which correlated significantly with the left ventricular PCr to beta-ATP ratios (r= -0.644; p=0.04), and decreased EFs (52.24+/-7.72% vs. 64.09+/-4.25%; p=0.001) compared to normal controls. CONCLUSIONS: In contrast to FRDA patients with early disease onset, our patients collective exhibited a normal, probably compensated cardiac mitochondrial function, whereby IST and EF were mildly altered.

Quantification of blood flow velocity in stenosed arteries by the use of finite elements: an observer-independent noninvasive method.

Interventions for peripheral arterial disease should be designed to treat a physiological rather than an anatomic defect. Thus, for vascular surgeons, functional information about stenoses is as important as the anatomic one. In case of finding a stenosis by the use of magnetic resonance angiography, it would be a matter of particular interest to derive automatically and directly objective information about the hemodynamic influence on blood flow, caused by patient-specific stenoses. We developed a methodology to noninvasively perform numerical simulations of a patient's hemodynamic state on the basis of magnetic resonance images and by the means of the finite element method. We performed patient-specific three-dimensional simulation studies of the increase in systolic blood flow velocity due to stenoses using the commercial computational fluid dynamic software package FIDAP 8.52. The generation of a mesh defining the flow domain with a stenosis and some simulation results are shown.

Topography of dopamine transporter availability in progressive supranuclear palsy: a voxelwise [123I]beta-CIT SPECT analysis.

BACKGROUND: Dopaminergic loss can be visualized by means of iodine I 123-labeled 2beta-carbomethoxy-3beta-(4-iodophenyl)tropane ([(123)I]beta-CIT) single-photon emission computed tomography (SPECT) in several neurodegenerative parkinsonian disorders. Most previous SPECT studies have adopted region-of-interest methods for analysis, which are subjective and operator dependent. OBJECTIVE: To objectively localize the cerebral dopamine transporter status in the early stages of progressive supranuclear palsy (PSP). DESIGN: Prospective study. SETTING: Parkinson disease outpatient clinic. PATIENTS: Fourteen patients with PSP, 17 with Parkinson disease (PD), 15 with Parkinson-variant multiple-system atrophy (MSA-P), and 13 healthy control subjects, matched for age and disease duration. INTERVENTIONS: Statistical parametric mapping applied to [(123)I]beta-CIT SPECT. MAIN OUTCOME MEASURES: Differences in [(123)I]beta-CIT uptake. RESULTS: All patients with the different parkinsonian disorders showed a significant decrease in striatal [(123)I]beta-CIT uptake without any overlap with the control group. In patients with MSA-P and PSP, an additional reduction in brainstem [(123)I]beta-CIT signal compared with controls and patients with PD was identified with statistical parametric mapping. Midbrain [(123)I]beta-CIT uptake discriminated atypical parkinsonian disorders from PD with an overall correct classification of 91.3%. On the other hand, [(123)I]beta-CIT SPECT failed to discriminate PSP and MSA-P. CONCLUSION: By applying statistical parametric mapping to [(123)I]beta-CIT SPECT images of patients with PSP, a widespread decline of monoaminergic transporter availability including the striatum and brainstem was localized in PSP, discriminating patients with PSP from patients with PD, but not from those with MSA-P. Quantification of midbrain dopamine transporter signal may therefore enhance the utility of SPECT imaging in the differential diagnosis of patients with parkinsonism.

High-energy phosphate metabolism during calf ergometry in patients with isolated aorto-iliac artery stenoses.

OBJECTIVES: Patients with peripheral arterial disease (PAD) and aorto-iliac atherosclerotic lesions suffer from a broad range of complaints, such as pain at the hip, the thigh, and calf claudication. The purpose of this study was to investigate the high-energy metabolism in the calf muscle of patients with PAD with isolated aorto-iliac stenoses during incremental plantar flexion exercise. MATERIALS AND METHODS: Using a 1.5 T whole-body magnetic resonance (MR) scanner, 12 patients with PAD with uni- or bilateral aorto-iliac atherosclerotic lesions and 10 healthy male controls underwent serial phosphor-31 MR spectroscopy during incremental exercise at 2, 3, 4, and 5 W. The phosphocreatine (PCr) time constants were calculated for each increment and recovery using a monoexponential model. In the patient group, the run-off resistance was determined on MR angiograms. In both the patients and the controls, the ankle brachial pressure index was measured. RESULTS: The diseased legs exhibited significantly increased PCr time constants during the second and the third workload increment at 3 and 4 W, but not during the first increment at 2 W and recovery compared with normal controls. Only 3 diseased legs succeeded the last increment at 5 W. We detected significant correlations between the ankle brachial pressure index scores and the PCr time constants when including both the diseased and the control legs. The diseased legs showed a significant correlation with the run-off resistance only during the first increment. CONCLUSIONS: Our study shows that the impairment of muscle metabolism, expressed by prolonged PCr time constants, occurs with greater work intensities in patients with aorto-iliac disease compared with patients with multisegmental PAD, as recently published, whereas our patients collective exhibited normal PCr recovery time constants. Our findings may help to understand variability of clinical symptoms in aorto-iliac PAD.

High-energy phosphate metabolism during incremental calf exercise in humans measured by 31 phosphorus magnetic resonance spectroscopy (31P MRS).

Several previous 31 phosphorus magnetic resonance spectroscopy ((31)P MRS) studies performing incremental or progressive muscle exercises have observed that a decrease in pH is accompanied with an acceleration in phosphocreatine (PCr) hydrolysis. The purpose of this study was to investigate the relationship between PCr breakdown and pH during isotonic, exhaustive, incremental plantar flexion exercises. We included eight healthy, male volunteers into this study. Using a 1.5 Tesla MR scanner and a self-built exercise bench, we performed serial free induction decay (FID) (31)P MRS measurements with a time resolution of 1 min at rest, isotonic calf muscle exercise, and recovery. The exercise protocol consisted of 5-min intervals with 4.5, 6, 7.5, and 9 W workload followed by 9-min recovery. Changes in PCr and inorganic phosphate (Pi) were determined as percent changes in comparison to the baseline. In addition, pH values were calculated. This study obtained significant decreases in PCr corresponding to the gradual increases in workload. In each workload level that was succeeded by all volunteers, PCr hydrolysis passed into a steady state. After an early biphasic response, we detected a significant decrease in pH from the first to the second minute of the 6-W workload level followed by a further continuous decrease in pH up to the second minute of the recovery phase. The decrease in pH was not accompanied by acceleration in PCr hydrolysis. In conclusion, this study shows that PCr hydrolysis during incremental plantar flexion exercises passes into a steady state at different workload levels. The observed decrease in pH does not result in acceleration of PCr hydrolysis.

Cardiac phosphorus-31 two-dimensional chemical shift imaging in patients with hereditary hemochromatosis.

Hemochromatosis is a hereditary iron overload syndrome characterized by increased iron storage, followed by liver cirrhosis and is often associated with restrictive cardiomyopathy. The purpose of this study was to detect alterations of cardiac high-energy phosphate metabolism in patients with hereditary hemochromatosis (HHC) prior to the development of structural heart diseases. Therefore cardiac phosphorus-31 two-dimensional chemical shift imaging ((31)P 2D CSI) was employed. Twenty-four male patients (mean age 47.2 +/- 12 years) homozygous for the C282Y mutation in the hemochromatosis associated HFE gene and twenty-four male healthy volunteers (mean age 47 +/- 11 years) as age-matched controls were included in this study. Using a 1.5-Tesla whole-body magnetic resonance scanner, electrocardiograph-triggered transversal 31P 2D CSI was performed. Left ventricle mean phosphocreatine (PCr) to beta-adenosine triphosphate (beta-ATP) ratios of patients with HHC (1.60 +/- 0.41) were significantly decreased in comparison to healthy volunteers (1.93 +/- 0.36; p = 0.004). Furthermore, we detected moderate, negative correlations between left ventricular PCr to beta-ATP ratios and transferrin saturation, cholesterol, low-density lipoprotein as well as triglyceride. This study shows that 31P 2D CSI permits the detection of alterations of cardiac high-energy phosphate metabolism in patients with HHC, but without any evidence for heart disease. The decreased PCr to beta-ATP ratios in HHC might be caused by mitochondrial impairment due to cardiac iron overload.

Impact of aging on cardiac high-energy phosphate metabolism determined by phosphorus-31 2-dimensional chemical shift imaging (31P 2D CSI).

Previous echocardiographic and experimental animal studies have shown that cardiac function, structure, and metabolism change with age. The aim of this study was to evaluate the impact of age on left ventricular high-energy phosphate metabolism. Using a 1.5 Tesla whole-body MR scanner 31P 2D CSI (8 x 8 phase encoding steps, 320 mm field of view) was performed in 76 healthy male volunteers (41.7 +/- 13 years) without any history of coronary heart disease. Fourier interpolation, corrections for T1 saturation effects, the nucleus Overhauser effect, and the blood contamination were applied to the spectroscopic data. The volunteers were divided into two groups, younger (n = 37) and older (n = 39) than 41.7 years. In all volunteers, laboratory specimen were sampled, and transthoracal echocardiography was carried out. Significant differences in left ventricular phosphocreatine (PCr) to beta-adenosine-triphosphate (beta-ATP) ratios (2.16 vs. 1.83, p < 0.001), fasting serum glucose levels (83.3 vs. 98.7 mg/dl, p < 0.001), E/A (1.51 vs. 1.14 p < 0.001), and ejection fraction (EF, 65.3 vs. 59.9%, p = 0.005) were detected between the two groups of volunteers, younger and older than 41.7 years. Moreover, age correlated moderately to well with left ventricular PCr to beta-ATP ratios (r = -0.44), fasting serum glucose levels (r = 0.4), E/A (r = -0.7), left ventricular myocardial mass (r = -0.41), and EF (r = -0.55). In conclusion, our study shows that left ventricular PCr to beta-ATP ratios decrease moderately with age, as suggested by previous experimental animal studies. Additionally, age correlates negatively with E/A, left ventricular myocardial mass, and EF, as reported by previous echocardiography studies. The present study is the first to show the impact of age on left ventricular PCr to beta-ATP values in humans.

Cardiac high-energy phosphate metabolism alters with age as studied in 196 healthy males with the help of 31-phosphorus 2-dimensional chemical shift imaging.

Recently published studies have elucidated alterations of mitochondrial oxidative metabolism during ageing. The intention of the present study was to evaluate the impact of ageing on cardiac high-energy phosphate metabolism and cardiac function in healthy humans. 31-phosphorus 2-dimensional chemical shift imaging (31P 2D CSI) and echocardiography were performed in 196 healthy male volunteers divided into groups of 20 to 40 years (I, n = 43), 40 to 60 years (II, n = 123) and >60 years (III, n = 27) of age. Left ventricular PCr/ß-ATP ratio, myocardial mass (MM), ejection fraction and E/A ratio were assessed. Mean PCr/ß-ATP ratios were significantly different among the three groups of volunteers (I, 2.10 ± 0.37; II, 1.77 ± 0.37; III, 1.45 ± 0.28; all p<0.001). PCr/ß-ATP ratios were inversely related to age (r(2)  =  -0.25; p<0.001) with a decrease from 2.65 by 0.02 per year of ageing. PCr/ß-ATP ratios further correlated with MM (r =  -0.371; p<0.001) and E/A ratios (r = 0.213; p<0.02). Moreover, E/A ratios (r =  -0.502, p<0.001), MM (r = 0.304, p<0.001), glucose-levels (r = 0.157, p<0.05) and systolic blood pressure (r = 0.224, p<0.005) showed significant correlations with age. The ejection fraction did not significantly differ between the groups. This study shows that cardiac PCr/ß-ATP ratios decrease moderately with age indicating an impairment of mitochondrial oxidative metabolism due to age. Furthermore, MM increases, and E/A ratio decreases with age. Both correlate with left-ventricular PCr/ß-ATP ratios. The findings of the present study confirm numerous experimental studies showing an impairment of cardiac mitochondrial function with age.

Inter- and intra-rater reproducibility of semiautomatic determination of volume parameters in cardiac magnetic resonance imaging.

PURPOSE: The purpose of this study was to evaluate inter- and intra-rater reproducibility in volume assessment using cardiac magnetic resonance imaging (CMRI). METHODS: Twenty-five healthy volunteers and 106 patients were included into this retrospective study and received CMRI. The patients were divided in three groups (group I, 80 patients with arrhythmia; group II, 20 patients with cardiomyopathy; group III, 6 patients after correction of septum defects). Therefore, the images were semiautomatically segmented by an experienced and an unexperienced radiologists. The analysis of end-diastolic volume (EDV), end-systolic volume (ESV) and stroke volume (SV) as well as ejection fraction (EF) and myocardial mass (MM) were performed twice by an experienced and an unexperienced radiologists. The intra-class correlation coefficients (ICC) were determined for the evaluation of inter- and intra-rater variance. RESULTS: The intra-rater reproducibility for determination of EF, ESV, EDV and MM was excellent with ICCs ranging from 0.88 to 0.99 (all p<0.001). The inter-observer reproducibility for these parameters was also excellent with ICCs ranging from 0.91 to 0.98 (all p<0.001). The assessment of the SV showed an excellent intra-rater agreement with ICCs of 0.96 and 0.92 (both p<0.001), but only a moderate ICC for the inter-rater reproducibility (0.54, p<0.001). CONCLUSIONS: Our study shows that assessment of cardiac volumes can be performed on CMRIs with an excellent reproducibility by both experienced and unexperienced investigators.

High-energy phosphate metabolism in the calf muscle of healthy humans during incremental calf exercise with and without moderate cuff stenosis.

It is known that the relevance of a peripheral stenosis for muscle function increases with exercise. Our intention was to investigate the impact of a moderate cuff stenosis (CS) at 120 mmHg of the superficial femoral artery on high-energy phosphate (HEP) metabolism during isotonic, incremental calf exercise. Serial phosphorus 31 magnetic resonance spectroscopy (31P MRS) and velocity-encoded phase-contrast MR imaging (VEPC MRI) were carried out in each leg of ten healthy male volunteers. Each leg underwent four increments of calf exercise (2, 3, 4 and 5 W) followed by recovery during separate exercise sessions with and without a CS at 120 mmHg. The serial 31P MRS measurements had a time resolution of 10 s. VEPC MRI was performed at the end of each increment during separate sessions. During all increments, we detected significant differences (P < 0.05) in the phosphocreatine (PCr) time constants and the amount of PCr hydrolysis between the sessions without and with CS. Regarding the time courses of the PCr, inorganic phosphate (Pi) and pH level, we observed significant differences (P < 0.002) during exercise and recovery. During both conditions, the end-increment PCr levels as well as blood flow correlated significantly with the mechanical power. The PCr time constants during exercise significantly correlated with the intramuscular pH, but not with blood flow or mechanical power. However, the PCr recovery time constants correlated significantly with blood flow and end-exercise pH. Our study shows that reduction of blood flow due to a peripheral stenosis results in a prolongation of PCr time constants, decreased PCr and pH level as well as increased Pi level during exercise. We believe that 31P MRS during incremental exercise might provide additional information for assessing the relevance of a peripheral stenosis and its impact on muscle function.

High-energy phosphate metabolism during incremental calf exercise in patients with unilaterally symptomatic peripheral arterial disease measured by phosphor 31 magnetic resonance spectroscopy.

BACKGROUND: The treadmill exercise test is the most important examination of the functional ability of patients with intermittent claudication or leg pain during exercise, but it does not provide any metabolic information in the calf muscle. The purpose of this study was to investigate the high-energy metabolism in the calf muscle during incremental progressive plantar flexion exercise of a selected peripheral arterial disease (PAD) patient group. METHODS: Using a 1.5-T whole-body magnetic resonance scanner, 17 male patients with PAD who had 1 symptomatic and 1 asymptomatic leg and 9 healthy male controls underwent serial phosphor 31 (31P) magnetic resonance spectroscopy during incremental exercise at 2, 3, 4, and 5 W. Furthermore, magnetic resonance angiography was performed, and the ankle-brachial pressure index was determined in the patient group. The runoff resistance (ROR) was separately assessed in each patient's leg. RESULTS: The symptomatic legs exhibited significantly increased phosphocreatine (PCr) time constants during the first three workload increments (2-4 W) and the recovery phase compared with the asymptomatic legs and the normal controls. Only two symptomatic legs reached the last increment at 5 W. Compared with the normal controls, the asymptomatic legs showed significantly increased PCr time constants only at 5 W. In the patient group, we detected significant correlations between the PCr time constants and the ROR, as well as the ankle-brachial pressure index. Moreover, the symptomatic legs presented significantly lower PCr levels and pH values at the end of exercise compared with the asymptomatic and control legs. CONCLUSIONS: Our study shows that muscle function in PAD patients can be objectively quantified with the help of 31P magnetic resonance spectroscopy and correlates significantly with hemodynamic parameters such as ROR and ankle-brachial pressure index. Consequently, 31P magnetic resonance spectroscopy seems to be a useful method to monitor the muscle function of PAD patients for evaluation of established therapies or new therapeutic strategies during research trials.

Topography of putaminal degeneration in multiple system atrophy: a diffusion magnetic resonance study.

There is neuropathologic evidence that, in early stages of the Parkinson variant of multiple system atrophy (MSA-P), the putamen shows a distinct topographical pathology affecting predominantly the dorsolateral and caudal regions while leaving the rostral to midparts almost intact. We investigated the topographic profile of putaminal degeneration in MSA-P patients in vivo by means of diffusion-weighted imaging (DWI), which has been shown to reveal abnormalities in the basal ganglia of patients with MSA-P compared to patients with PD and healthy controls. For this purpose, regional trace of the diffusion tensor (rTrace(D)) values were determined in the entire, anterior, and posterior putamen in 15 patients with probable MSA-P, in 20 patients with PD, and in 11 healthy volunteers matched for age and disease duration. MSA-P patients had significantly higher rTrace(D) values in entire, anterior, and posterior putamen compared to both controls and PD patients. Trace(D) values were significantly higher in the posterior compared to the anterior putamen in the MSA-P group. There were no significant differences between posterior and anterior putamen in both the control and PD group. Our study demonstrates prominent involvement of the posterior putamen in early disease stages of MSA-P in vivo by assessing putaminal diffusivity with the help of DWI.

Progression of putaminal degeneration in multiple system atrophy: a serial diffusion MR study.

By using diffusion-weighted imaging (DWI), we have recently shown abnormal diffusivity in the putamen of patients with the Parkinson variant of multiple system atrophy (MSA-P) which also correlated with disease severity, indicating the capability of putaminal diffusivity to serve as a marker for disease progression. We therefore performed a serial DWI study in 10 patients with MSA-P compared to 10 patients with Parkinson's disease (PD) to evaluate the dynamic evolution of diffusion properties in the basal ganglia including putamen, caudate nucleus and globus pallidum by means of the trace of the diffusion tensor (Trace(D)). For comparison, we have also analyzed the frequency and semiquantitative grading of MSA-P-related structural changes on conventional MRI including putaminal atrophy, lateral hyperintense margination of the putamen and putaminal signal hypointensity relative to the globus pallidum on T2 MR images. None of the Trace(D) values in the basal ganglia regions in the PD group changed significantly at follow-up compared to baseline. In MSA-P, a significant increase of the Trace(D) was found in the putamen, which correlated with motor progression as assessed by the Unified Parkinson's Disease Rating Scale (UPDRS). No significant change of any of the abnormal putaminal findings on routine MRI was obtained. We suggest that abnormal diffusivity in the putamen is sensitive to change over time in MSA-P and correlates with motor progression indicating that DWI may serve to monitor disease progression in MSA-P in an objective and quantitative manner.

Diffusion-weighted imaging in Huntington's disease.

Huntington's disease (HD) is an autosomal dominant progressive neurodegenerative disorder that results from an expanded trinucleotide (CAG) repeat on the huntingtin gene. Neurodegeneration in HD affects most prominently the basal ganglia. Therefore, diffusivity was obtained in the basal ganglia and thalamus of 29 patients with early HD and 27 healthy volunteers by means of the trace of the diffusion tensor (Trace(D)). Putaminal, caudate, pallidal, and thalamic Trace(D) values were increased in patients with HD compared with controls. Increased diffusivity in the putamen and caudate nucleus correlated with global functional impairment, CAG repeat length, as well as bicaudate ratio. Diffusion-weighted imaging appears to be a promising surrogate marker for disease severity in HD. Sensitivity to change remains to be established longitudinally.

An update on conventional and advanced magnetic resonance imaging techniques in the differential diagnosis of neurodegenerative parkinsonism.

PURPOSE OF REVIEW: The clinical differentiation between Parkinson's disease and atypical parkinsonian disorders (APD) remains a challenge for every neurologist. Conventional magnetic resonance imaging (MRI) and different advanced MRI techniques offer the potential for objective criteria in the differential diagnosis of neurodegenerative parkinsonism. The aim of this article is to review the recent literature on the role of conventional and advanced MRI techniques in the differential diagnosis of neurodegenerative parkinsonian disorders. RECENT FINDINGS: An important role of MRI is the exclusion of symptomatic parkinsonism due to other pathologies. Over the past two decades, conventional MRI and different advanced MRI techniques, including proton magnetic resonance spectroscopy (1H-MRS), diffusion-weighted imaging (DWI), magnetization transfer imaging (MTI) and magnetic resonance volumetry (MRV) have been found to show abnormalities in the substantia nigra and basal ganglia, especially in APD. Recent studies using MRV, MTI, DWI and 1H-MRS to discriminate Parkinson's disease from APD are discussed extensively. SUMMARY: Research findings suggest that novel MRI techniques such as MTI, DWI and MRV have superior sensitivity compared to conventional MRI in detecting abnormal features in neurodegenerative parkinsonian disorders. Whether these techniques will emerge as standard investigations in the work-up of patients presenting with parkinsonism requires further prospective magnetic resonance studies during early disease stages.

Does stent overlap influence the patency rate of aortoiliac kissing stents?

PURPOSE: To determine if the position of kissing stents in the distal aorta has any influence on the patency rate. METHODS: A retrospective review was conducted of 41 patients (22 men; median age 60.8 years, range 44-86) electively treated for atherosclerotic aortoiliac occlusive disease with angioplasty and kissing stents between January 1997 and January 2005. Two patient groups were defined by reviewing postinterventional anteroposterior radiograms: (1) patients in whom the proximal end of the kissing stents overlapped more than half of their angiographic width within the aorta ("crossing" group) and (2) patients in whom the proximal ends of the stents overlapped half of their width or less ("non-crossing" group). RESULTS: At 2 years, the primary and assisted primary patency rates by life-table analysis were 60.8% and 69.4%, respectively, for the 35 patients included in the life-table analysis. There was no significant difference between the 16-patient "crossing" group and the 19-patient "non-crossing" group in terms of the baseline demographic, morphological, and procedural variables. The primary and assisted primary patency rates at 2 years for the "non-crossing" group were significantly higher (94.1% and 100%, respectively) compared to 33.2% and 45.3%, respectively, for the "crossing" group (p=0.01). CONCLUSIONS: Failure of kissing stents in the aortic bifurcation may be significantly increased by the overlap of the free proximal stent ends in the distal aorta.

High-energy phosphate metabolism during two bouts of progressive calf exercise in humans measured by phosphorus-31 magnetic resonance spectroscopy.

According to the literature the steady-state level of phosphocreatine (PCr) has a linear relationship to the workload during muscle exercise intensities below the lactate threshold, whereas this linearity is impaired during exercise intensities above the lactate threshold. The purpose of this study was to investigate the linearity between PCr kinetics and workload during two bouts of isotonic incremental calf exercise with transitions from moderate- to high-intensity as well as from high- to moderate-intensity work rates. Using a whole-body 1.5 T MR scanner and a self-built exercise bench, we performed serial phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) with a time resolution of 30 s in nine healthy male volunteers. Changes in PCr, inorganic phosphate (Pi) and pH were statistically evaluated in comparison to the baseline. The exercise protocol started with a 4.5 W interval of 6 min followed by two bouts of 1.5 W increments. The workload was increased in 2-min intervals up to 9 W during the first bout and up to 7.5 W during the second bout. The second bout was preceded by a 4.5 W interval of 2 min and followed by a 4.5 W interval of 4 min. PCr hydrolysis achieved a steady state during each increment and was highly linear to the work rate (r (2), -0.796; P <0.001). Pi accumulated during each bout, whereas the pH decreased continuously during the first bout and did not exhibit any substantial decrease during the second bout. The metabolite levels and pH were expressed as the median value and the range. Our study confirms that steady-state PCr levels also have a linear relationship to work intensities above the lactate threshold, while pH changes do not have any impact on PCr degradation. The lack of substantial changes in pH during the second exercise bout indicates that prior high-intensity exercise leads to an activation of oxidative phosphorylation.

High-energy phosphate metabolism in the calf muscle during moderate isotonic exercise under different degrees of cuff compression: a phosphorus 31 magnetic resonance spectroscopy study.

BACKGROUND: The purpose of this study was to investigate phosphocreatine (PCr) and inorganic phosphate levels as well as pH changes in exercising muscle at a workload of 4.5 W under progressive cuff stenoses, whereby the flow reduction due to cuff compression was quantified by flow-sensitive magnetic resonance imaging. METHODS: By using a whole-body 1.5-T magnetic resonance scanner and an exercise bench, serial phosphorus 31 (31P) magnetic resonance spectroscopy with a time resolution of 30 seconds was performed in 10 healthy men. Percentage changes in PCr, inorganic phosphate (Pi), and pH were statistically evaluated in comparison with baseline. The exercise protocol was characterized by a constant workload level of 4.5 W. Ischemic conditions were achieved by a cuff that was placed at the upper leg. Consecutively, increments of 0, 60, 90, 120, and 150 mm Hg were applied. Each increment lasted for 3 minutes. The following rest period was 10 minutes. RESULTS: Blood flow increased significantly immediately after the onset of muscle exercise. No significant changes in blood flow were detected as long as the air pressure of the pneumatic cuff was 60 to 90 mm Hg. Significant reductions in blood flow were observed immediately after inflation of the cuff to 120 and 150 mm Hg. PCr passed into a steady state during the first increment with 0 mm Hg and showed no substantial changes during the increment with 60, 90, and 120 mm Hg. PCr hydrolysis seemed progressive during the 150-mm Hg increment. Pi passed into a plateau level at the onset of exercise and increased significantly at the increment of 150 mm Hg. The pH turned into a steady state with no significant changes during the increments up to 120 mm Hg. At 150 mm Hg, pH decreased progressively. PCr levels at the end of the 150-mm Hg increment correlated significantly and moderately with the reduction in blood flow. CONCLUSIONS: Our study shows that the ischemic condition during constant muscle exercise is clearly characterized by PCr and Pi kinetics, as well as by pH changes. The correlation between the degree of blood flow reduction and PCr levels in the exercising muscle groups, which are supplied by the stenosed arteries, is the first essential of using 31P magnetic resonance spectroscopy in the assessment of the effect of arterial stenoses on muscle function in claudicants.

Decreased high-energy phosphate ratios in the myocardium of men with diabetes mellitus type I.

AIMS/HYPOTHESIS: To investigate whether alterations in high-energy phosphates occur in the myocardium of persons with diabetes mellitus type I. Microvascular abnormalities and dysfunction via thickening of the basement membrane are known to occur in diabetic patients. Myocardial high-energy phosphates have been shown to be reduced by ischemia, and alterations of the cardiac metabolism are the primary consequence of myocardial ischemia. METHODS: The present study involved 34 male patients (mean age 35.5 +/- 10.1) with diabetes mellitus type I and 35 healthy male volunteers (mean age 36 +/- 8.6) as age-matched controls. Phosphorus-31 magnetic resonance spectroscopic imaging of the heart was performed in all subjects using a 1.5-T whole-body magnetic resonance scanner. The ratios of phosphocreatine (PCr) to beta-adenosinetriphosphate (beta-ATP) were calculated. Moreover, echocardiographic evaluation and stress tests were performed in all individuals. RESULTS: The myocardium of patients with diabetes mellitus type I showed significantly decreased ratios of PCr to beta-ATP compared with healthy controls in the left ventricle (1.90 +/- 0.4 vs. 2.15 +/- 0.3, p < 0.05). We found a moderate negative correlation between the ratio of PCr to beta-ATP in the left ventricle and both, the diastolic left ventricular function (E/A; r = -0.41) and the glycohemoglobin A1c (GHbA1c; r = -0.42). CONCLUSION: This study demonstrates for the first time a decreased ratio of PCr to beta-ATP in the myocardium of persons with diabetes mellitus type I without a known history of coronary heart disease.