Comparison of 18F-fluoro-deoxy-glucose, 18F-fluoro-methyl-choline, and 18F-DPA714 for positron-emission tomography imaging of leukocyte accumulation in the aortic wall of experimental abdominal aneurysms

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a frequent form of atherothrombotic disease, whose natural history is to enlarge and rupture. Indicators other than AAA diameter would be useful for preventive surgery decision-making, including positron-emission tomography (PET) methods permitting visualization of aortic wall leukocyte activation relevant to prognostic AAA evaluation. In this study, we compare three PET tracers of activated leukocytes, 18F-fluoro-deoxy-glucose (FDG), 18F-fluoro-methyl-choline (FCH), and 18F-DPA714 (a peripheral benzodiazepine receptor antagonist) for in vivo PET quantification of aortic wall inflammation in rat experimental AAAs, in correlation with histopathological studies of lesions.

METHODS

AAAs were induced by orthotopic implantation of decellularized guinea pig abdominal aorta in 46 Lewis rats. FDG-PET (n = 20), FCH-PET (n = 8), or both (n = 12) were performed 2 weeks to 4 months after the graft, 1 hour after tracer injection (30 MBq). Six rats (one of which had FDG-PET) underwent 18F-DPA714-PET. Rats were sacrificed after imaging; AAAs and normal thoracic aortas were cut into axial sections for quantitative autoradiography and histologic studies, including ED1 (macrophages) and CD8 T lymphocyte immunostaining. Ex vivo staining of AAAs and thoracic aortas with 18F-DPA714 and unlabeled competitors was performed.

RESULTS

AAAs developed in 35 out of 46 cases. FCH uptake in AAAs was lower than that of FDG in all cases on imaging, with lower AAA-to-background maximal standardized uptake value (SUV(max)) ratios (1.78 ± 0.40 vs 2.71 ± 0.54; P < .01 for SUV(max) ratios), and lower AAA-to-normal aorta activity ratios on autoradiography (3.52 ± 1.26 vs 8.55 ± 4.23; P < .005). FDG AAA-to-background SUV(max) ratios correlated with the intensity of CD8 + ED1 staining (r = .76; P < .03). FCH AAA-to-background SUV(max) ratios correlated with the intensity of ED1 staining (r = .80; P < .03). 18F-DPA714 uptake was similar in AAAs and in normal aortas, both in vivo and ex vivo.

CONCLUSIONS

In rat experimental AAA, characterized by an important aortic wall leukocytes activity, FDG-PET showed higher sensitivity than FCH-PET and 18F-DPA714-PET to detect activated leukocytes. This enhances potential interest of this tracer for prognostic evaluation of AAA in patients.

Detection of 18fluoride sodium accumulation by positron emission tomography in calcified stenotic aortic valves

Aortic valve stenosis progression rate is highly variable among patients and to date remains unpredictable. Evaluation of osteoblastic activity inside aortic valves may help identify patients with fast aortic stenosis progression rates and worse prognoses. Fluoride-18 sodium (FNa) is a clinically approved positron emission tomographic (PET) radiotracer with high and rapid bone uptake. The aim of this study was to test whether FNa accumulates in degenerative aortic valves and can be detected with PET imaging. Five patients with severe aortic stenosis and 10 patients free of aortic valvular calcium on computed tomography underwent PET imaging 40 minutes after the injection of 4 MBq/kg of FNa for oncologic or rheumatologic purposes. Maximal standard uptake values (SUVs) were measured retrospectively in aortic valves using PET imaging. Tissue-to-background ratios were calculated for each patient by dividing the maximal SUV measured in aortic valves by the mean SUV of blood. In patients with severe aortic stenosis, an intense accumulation of FNa was detected in aortic valve region on PET imaging, whereas only low activity was found in patients free of valvular calcification (median maximal SUV 2.6 g/ml/kg [interquartile range (IQR) 2.3 to 3.6] vs 2.0 g/ml/kg [IQR 1.7 to 2.2] and median tissue-to-background ratio 2.2 [IQR 2.0 to 2.7] vs 1.5 [IQR 1.5 to 1.7], respectively, p = 0.008 for both). Intraobserver variability for maximal SUV and tissue-to-background ratio in aortic valves was measured at 0.99 and interobserver variability at 0.98 and 0.97, respectively. In conclusion, in this pilot study, FNa accumulated in patients with severe aortic stenosis and could be quantified on PET imaging with good reproducibility. FNa PET imaging represents a promising imaging modality to evaluate osteoblastic activity inside calcified aortic valves.

Melorheostosis associated with peripheral form spondyloarthropathy: new image with 18-fluoride positron emission tomoscintigraphy coupled to computed tomography

Melorheostosis is a rare benign bone pathology which can be responsible for incapacitating pain and bone deformations. Its imaging abnormalities are often typical. We describe here the case of a patient with melorheostosis involving the lower limbs, associated with a peripheral form of inflammatory spondyloarthropathy, who underwent ¹⁸FNa positron emission tomography coupled to a computed tomography scan. Our objective is to present this new image, to show the value of this new modality and emphasize its advantages compared to the ^99mTechnetium bone scan.

Radiolabeled fucoidan as a p-selectin targeting agent for in vivo imaging of platelet-rich thrombus and endothelial activation

P-selectin expression is involved in the pathophysiology of biologically active arterial thrombus and endothelial activation after a transient ischemic event. Fucoidan is a polysaccharidic ligand of P-selectin, with a nanomolar affinity. In the present study, we propose a new approach of P-selectin molecular imaging based on radiolabeled fucoidan.

METHODS

Two kinds of experimental models were selected to evaluate the ability of radiolabeled fucoidan to detect P-selectin expression: platelet-rich arterial thrombi (vegetations of infective endocarditis and arterial mural thrombus) and myocardial ischemia-reperfusion. These 2 settings were chosen because they were clinically relevant, and both were associated with an important overexpression of platelet and endothelial P-selectin, respectively.

RESULTS

(99m)Tc-fucoidan SPECT was able to detect the presence of platelet-rich arterial thrombi in all animals, with a median target-to-background ratio of 5.2 in vegetations of endocarditis and 3.6 in mural aneurysmal thrombus, and to detect a persistent endothelial activation at 2 h after reperfusion. In this latter model, the magnitude of the signal was correlated with the extent of myocardium that underwent transient ischemia. The sensitivity of selectivity of the uptake and retention of (99m)Tc-fucoidan in both settings was excellent.

CONCLUSION

This study supports (99m)Tc-fucoidan as a relevant imaging agent for in vivo detection of biologic activities associated with P-selectin overexpression, such as arterial thrombus and ischemic memory. Given the reported wide availability at a low cost, and its low toxicity, fucoidan seems to overcome some of the limitations of previous P-selectin-targeted imaging agents.

Fetal exposure to maternal type 1 diabetes is associated with renal dysfunction at adult age

OBJECTIVE

In animal studies, hyperglycemia during fetal development reduces nephron numbers. We tested whether this observation translates into renal dysfunction in humans by studying renal functional reserve in adult offspring exposed in utero to maternal type 1 diabetes.

RESEARCH DESIGN AND METHODS

We compared 19 nondiabetic offspring of type 1 diabetic mothers with 18 offspring of type 1 diabetic fathers (control subjects). Glomerular filtration rate ((51)Cr-EDTA clearance), effective renal plasma flow ((123)I-hippurate clearance), mean arterial pressure, and renal vascular resistances were measured at baseline and during amino acid infusion, which mobilizes renal functional reserve.

RESULTS

Offspring of type 1 diabetic mothers were similar to control subjects for age (median 27, range 18-41, years), sex, BMI (23.1 ± 3.7 kg/m(2)), and birth weight (3,288 ± 550 vs. 3,440 ± 489 g). During amino acid infusion, glomerular filtration rate and effective renal plasma flow increased less in offspring of type 1 diabetic mothers than in control subjects: from 103 ± 14 to 111 ± 17 ml/min (8 ± 13%) vs. from 108 ± 17 to 128 ± 23 ml/min (19 ± 7%, P = 0.009) and from 509 ± 58 to 536 ± 80 ml/min (5 ± 9%) vs. from 536 ± 114 to 620 ± 140 ml/min (16 ± 11%, P = 0.0035). Mean arterial pressure and renal vascular resistances declined less than in control subjects: 2 ± 5 vs. -2 ± 3% (P = 0.019) and 3 ± 9 vs. -14 ± 8% (P = 0.001).

CONCLUSIONS

Reduced functional reserve may reflect a reduced number of nephrons undergoing individual hyperfiltration. If so, offspring of type 1 diabetic mothers may be predisposed to glomerular and vascular diseases.

Non-invasive molecular imaging of fibrosis using a collagen-targeted peptidomimetic of the platelet collagen receptor glycoprotein VI

BACKGROUND

Fibrosis, which is characterized by the pathological accumulation of collagen, is recognized as an important feature of many chronic diseases, and as such, constitutes an enormous health burden. We need non-invasive specific methods for the early diagnosis and follow-up of fibrosis in various disorders. Collagen targeting molecules are therefore of interest for potential in vivo imaging of fibrosis. In this study, we developed a collagen-specific probe using a new approach that takes advantage of the inherent specificity of Glycoprotein VI (GPVI), the main platelet receptor for collagens I and III.

METHODOLOGY/PRINCIPAL FINDINGS

An anti-GPVI antibody that neutralizes collagen-binding was used to screen a bacterial random peptide library. A cyclic motif was identified, and the corresponding peptide (designated collagelin) was synthesized. Solid-phase binding assays and histochemical analysis showed that collagelin specifically bound to collagen (Kd 10(-7) M) in vitro, and labelled collagen fibers ex vivo on sections of rat aorta and rat tail. Collagelin is therefore a new specific probe for collagen. The suitability of collagelin as an in vivo probe was tested in a rat model of healed myocardial infarctions (MI). Injecting Tc-99m-labelled collagelin and scintigraphic imaging showed that uptake of the probe occurred in the cardiac area of rats with MI, but not in controls. Post mortem autoradiography and histological analysis of heart sections showed that the labeled areas coincided with fibrosis. Scintigraphic molecular imaging with collagelin provides high resolution, and good contrast between the fibrotic scars and healthy tissues. The capacity of collagelin to image fibrosis in vivo was confirmed in a mouse model of lung fibrosis.

CONCLUSION/SIGNIFICANCE

Collagelin is a new collagen-targeting agent which may be useful for non-invasive detection of fibrosis in a broad spectrum of diseases.

Myocardial uptake of 99mTc-annexin-V and 111In-antimyosin-antibodies after ischemia-reperfusion in rats

OBJECTIVES

Phosphatidylserin exposure on cell surfaces occurs early during apoptosis and is detected in vivo by using (99m)Tc-annexin-V (ANX). Cardiomyocyte membrane disruption is detected in vivo by using (111)In-antimyosin-antibodies (AM). We aimed to determine if ANX and AM allow evaluation of the time-course of these two distinct cell death events after myocardial ischemia-reperfusion.

METHODS

Coronary tying (20 min) followed by reperfusion (IR) was performed in 31 rats. Twelve of the rats were injected with ANX, 11 with AM, and eight with both tracers. Myocardial uptake of tracers was studied 1-2 h, 4 h, or 24 h after IR by scintigraphy (ANX, n = 14) and autoradiography (all cases), and compared to histology and Apostain staining.

RESULTS

Scintigraphy was positive in all rats 2 h after IR and in three of five rats at 24 h. On autoradiography, ANX activity was intense in myocardial lesions as early as 1 h post-IR, whereas AM activity was mild at 2 h then increased at 4 h post-IR. ANX and AM uptakes evolved from mid-myocardium to endocardial and epicardial regions from 2 h to 24 h post-IR. Apostain staining was significant in myocardial lesions (p < 10(6) compared to six sham-operated rats). On histology, myocardial lesion was characterized by interstitial oedema, myocytes necrosis, and dramatic thinning at 24 h.

CONCLUSION

These data suggest that ANX and AM allow temporal and regional evaluations of PS exposure and membrane disruption, respectively, during myocytes death after 20-min myocardial ischemia followed by reperfusion. Also, (i) apoptosis starts very early in injured myocardium, (ii) myocyte necrosis occurs later (3-4 h post-reperfusion), and (iii) most dead cells are removed from mid-myocardium between 6 h and 24 h after reperfusion.

Diagnosis of diffuse and localized arrhythmogenic right ventricular dysplasia by gated blood-pool SPECT

This study aimed to assess the ability of global and local systolic parameters measured with gated blood-pool SPECT (GBPS) to diagnose and characterize the severity of diffuse or localized arrhythmogenic right ventricular dysplasia (ARVD).

METHODS

Fifty-nine subjects with symptomatic ventricular arrhythmias were prospectively included in the study. With the International Society and Federation of Cardiology criteria for ARVD as a gold standard, these subjects were classified as subjects without ARVD (21 control subjects) and patients with localized ARVD (16 patients) or diffuse ARVD (22 patients). Right ventricular volumes, right ventricular ejection fractions (EF), the SD of local EF (sigma-EF), and the SD of the local times of end systole (sigma-TES) were computed from GBPS data and compared among the groups in the study population.

RESULTS

sigma-EF did not differ between control subjects and patients with diffuse or localized ARVD. Right ventricular EF and volumes differed between patients with diffuse ARVD and control subjects, with similar areas under the receiver-operating-characteristic curves, but right ventricular EF and volumes failed to differentiate patients with localized ARVD. In contrast, sigma-TES differed between patients with diffuse or localized ARVD and control subjects. Regression analysis showed that the systolic parameter most strongly associated with the diagnosis of ARVD was sigma-TES. The probabilities of a randomly chosen patient in the diffuse ARVD group and of a randomly chosen patient in the localized ARVD group having sigma-TES values greater than that of a randomly chosen control subject were 98.5% and 96.7%, respectively. For the diagnosis of localized ARVD, a threshold of 80 ms for sigma-TES corresponded to sensitivity, specificity, and positive and negative predictive values of 100%, 81%, 80%, and 100%, respectively.

CONCLUSION

With GBPS, both diffuse ARVD and localized ARVD can be accurately diagnosed by computing sigma-TES for all of the pixels on the surface of the right ventricle.

Evaluation of 99mTc-UBI 29-41 scintigraphy for specific detection of experimental Staphylococcus aureus prosthetic joint infections

PURPOSE

(99m)Tc-UBI 29-41 (UBI), an antimicrobial peptide, specifically targets bacteria. We tested the ability of UBI to discriminate between infected and uninfected prosthetic joints using a rabbit model previously validated.

METHODS

Left knee arthroplasty was performed on 20 New Zealand rabbits, then 10(7) cfu of S. aureus (n = 12) or sterile saline (n = 8) was injected into the joint. On days 9 and 20 after surgery, planar UBI scintigraphy was performed in six infected and four uninfected rabbits, 1 h and 4 h p.i. (150 MBq), on a gamma camera. Operated-to-normal knee activity ratio (ONKR) was calculated on each scintigram. Then, after sacrifice, tissue samples of both knees were counted in a gamma counter.

RESULTS

One rabbit injected with sterile saline had cutaneous infection at sacrifice and was excluded from analysis. ONKR was higher in infected than in uninfected animals 4 h p.i. 20 days after surgery: 1.75 +/- 0.48 vs 1.13 +/- 0.11, p = 0.04. From 1 h to 4 h p.i., ONKR increased in 9/12 infected and 0/7 uninfected animals. According to UBI uptake intensity and kinetics, scintigraphy was truly positive in all infected cases on day 9 and in four of six infected cases on day 20. It was truly negative in two of three sterile inflamed prosthetic knees on day 9, and in all cases on day 20. Biodistribution studies revealed increased UBI uptake in periprosthetic tissues in all animals 9 days after surgery, and only in infected animals on day 20.

CONCLUSION

In this experimental study, (99m)Tc-UBI 29-41 scintigraphy permitted the early detection of acute prosthetic joint infection, and exclusion of infection in chronic sterile prosthetic joint inflammation.

Alveolar edema dispersion and alveolar protein permeability during high volume ventilation: effect of positive end-expiratory pressure

OBJECTIVES

To evaluate whether PEEP affects intrapulmonary alveolar edema liquid movement and alveolar permeability to proteins during high volume ventilation.

DESIGN AND SETTING

Experimental study in an animal research laboratory.

SUBJECTS

46 male Wistar rats.

INTERVENTIONS

A (99m)Tc-labeled albumin solution was instilled in a distal airway to produce a zone of alveolar flooding. Conventional ventilation (CV) was applied for 30 min followed by various ventilation strategies for 3 h: CV, spontaneous breathing, and high volume ventilation with different PEEP levels (0, 6, and 8 cmH(2)O) and different tidal volumes. Dispersion of the instilled liquid and systemic leakage of (99m)Tc-albumin from the lungs were studied by scintigraphy.

MEASUREMENTS AND RESULTS

The instillation protocol produced a zone of alveolar flooding that stayed localized during CV or spontaneous breathing. High volume ventilation dispersed alveolar liquid in the lungs. This dispersion was prevented by PEEP even when tidal volume was the same and thus end-inspiratory pressure higher. High volume ventilation resulted in the leakage of instilled (99m)Tc-albumin from the lungs. This increase in alveolar albumin permeability was reduced by PEEP. Albumin permeability was more affected by the amplitude of tidal excursions than by overall lung distension.

CONCLUSIONS

PEEP prevents the dispersion of alveolar edema liquid in the lungs and lessens the increase in alveolar albumin permeability due to high volume ventilation.

99m Tc-Annexin-V Functional Imaging of Luminal Thrombus Activity in Abdominal Aortic Aneurysms

Background— The mural thrombus of abdominal aortic aneurysms (AAA) is involved in aneurysm progression via several interdependent biological processes including platelet activation. 99m Tc-annexin V (ANX) is a scintigraphic tracer that binds to phosphatidylserine exposed on activated platelets and apoptotic cells. Here, we evaluated the potential of ANX imaging to assess mural thrombus biological activity in an experimental AAA model. The clinical applicability was further tested ex vivo on human samples of excised AAA thrombi.

Methods and Results— Experimental AAA was created by infusing elastase into infrarenal abdominal aorta in 17 rats, and 6 sham-operated rats were used as controls. Abdominal ANX scintigraphy was performed 2 weeks later followed by quantitative autoradiography and histological studies. Among the 13 rats which developed AAA, 11 displayed intense ANX uptake within AAA by scintigraphy. ANX uptake in the aneurysms on planar and single-photon emission computed tomography (SPECT) imaging was higher than that observed in infrarenal aorta of sham-operated controls (target/background ratio: 5.7±0.9 versus 1.33±0.21; P <0.005 for SPECT). Aneurysm-to-background activity ratios obtained by scintigraphy correlated with ANX activity in corresponding autoradiograms ( R =0.69; P <0.02). This activity was located in the thrombus area where activated platelets and polymorphonuclear leukocytes accumulated. Similar patterns were also found in all of the 7 human AAA thrombi harvested during surgery.

Conclusions— ANX imaging may assess mural thrombus renewal activity linked to permanent flowing blood interface.

Increased uptake of 111In-octreotide in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by an uncontrolled accumulation and activation of lung fibroblasts. A modulation of fibroblast activation has been observed in various systems with octreotide, a synthetic somatostatin analog with strong affinity for the somatostatin receptor subtype 2 (sst2). One aim of our study was to evaluate the expression of somatostatin receptors in the lungs of patients with IPF. A second aim was to evaluate the relationship between 111In-octreotide uptake and the effect of pulmonary fibrosis as assessed by lung function tests and parameters and by radiologic findings.

METHODS

We investigated 11 patients with IPF, 6 patients with pulmonary fibrosis associated with systemic sclerosis (SSc), and 19 patients with disease not of the lung (control patients). The expression of somatostatin receptors was evaluated in vivo using 111In-octreotide scintigraphy. We evaluated the relationship between 111In-octreotide uptake and the activity of pulmonary fibrosis as assessed by lung function tests, bronchoalveolar lavage (BAL) cellularity, and high-resolution CT (HRCT) of the chest. Planar images and thoracic SPECT (24 h) were performed after injection of 222 MBq of 111In-octreotide. Lung uptake was quantified using the lung-to-background ratio (L/B). In addition, the expression of sst2 was evaluated in vitro, in frozen lung-tissue samples using autoradiography, and in human cultures of lung fibroblasts using a ligand-binding assay.

RESULTS

Compared with lung uptake in control patients (median L/B, 1.25; range, 1.14-1.49), lung uptake was increased in all 11 IPF patients (median L/B, 2.63; range, 1.59-3.13; P < 0.001) and in 4 of 6 SSc patients (median L/B, 1.68; range, 1.42-2.16). The L/B was lower in SSc patients than in IPF patients (P = 0.011). Increased uptake correlated with the alteration of lung function (carbon monoxide diffusing capacity [rho = -0.655; P = 0.038], diffusing capacity for carbon monoxide and alveolar volume ratio [rho = -0.627; P = 0.047], vital capacity [rho = -0.609; P = 0.054], and total lung capacity [rho = -0.598; P = 0.058]) and with the intensity of alveolitis (total BAL cellularity [rho = 0.756; P = 0.045], neutrophil counts [rho = 0.738; P = 0.05]), and HRCT fibrosis score (rho = 0.673; P = 0.007). Autoradiography suggested that vascular structures were a prominent binding site. Lung fibroblasts expressed somatostatin receptors in vitro as measured by binding assay.

CONCLUSION

Our preliminary results identified an increased expression of sst2 in (mainly idiopathic) pulmonary fibrosis. Lung uptake correlates with the alteration of lung function and with the intensity of alveolitis.

Impact of liver transplantation on cardiac autonomic denervation in familial amyloid polyneuropathy

Familial amyloid polyneuropathy (FAP) is a rare and severe hereditary form of amyloidosis, due to the deposition of a genetic variant transthyretin essentially produced by the liver, and characterized by both sensorimotor and autonomic neuropathy. Liver transplantation (LT) is the most effective treatment to stop the progression of the disease. Cardiac amyloid infiltration is usually associated with cardiac denervation, restrictive cardiomyopathy, conduction disturbances, and sometimes sudden death. Whether the cardiac involvement related to amyloid deposition may be altered after LT remains unclear. We conducted the present study to define the outcome of cardiac involvement after LT in 31 patients with FAP (age, 39 +/- 12 yr). Patients were evaluated before and after LT (24 +/- 15 mo). Cardiac sympathetic denervation was assessed by both iodine-123 metaiodobenzylguanidine (MIBG) scintigraphy and heart rate variability (HRV) analysis. The scintigraphic importance of sympathetic denervation was evaluated globally on planar imaging using heart-to-mediastinum activity ratio (H/M) measured 4 hours after injection, and regionally using single-photon emission tomography (SPET) imaging. Amyloid myocardial infiltration was assessed by echocardiography. Diffuse sympathetic denervation was found when using cardiac MIBG planar imaging in patients evaluated before LT and compared with 12 control subjects (H/M: 1.45 +/- 0.29 vs. 1.98 +/- 0.35, p < 0.001). On SPET images, defects were diffuse in 12 patients and focal in 19 patients, with predominance at the inferior and apical segments. No change in sympathetic innervation was found in patients after LT as assessed either with planar imaging (H/M after LT: 1.46 +/- 0.28, p = not significant vs. H/M before LT) or with SPET imaging. HRV nonspectral indexes showed that the standard deviation of all cycles was significantly lower in patients compared with control subjects, and remained unchanged after LT. Conduction disturbances and ventricular arrhythmias were associated with low cardiac MIBG uptake, and progressed after LT. The left ventricular wall was slightly thickened in patients, and a further increase was observed after LT (posterior wall from 9.2 +/- 1.8 to 10.1 +/- 2.3 mm, p = 0.02; septal wall from 10.6 +/- 2.7 to 12.1 +/- 4, p = 0.046). Neurologic status stabilized in 26 patients, but worsened in the 5 patients who had the most severe cardiac sympathetic denervation before LT as measured by MIBG imaging. The magnitude of the cardiac sympathetic denervation remained stable 2 years after LT in patients with FAP, whereas the cardiac amyloid infiltration progressed. The importance of cardiac sympathetic denervation found in FAP patients before LT was associated with a neurologic worsening after LT.

(99m)Tc-annexin V and (111)In-antimyosin antibody uptake in experimental myocardial infarction in rats

PURPOSE

(99m)Tc-annexin V (ANX) allows scintigraphic detection of apoptotic cells via specific binding to exposed phosphatidylserine. In myocardial infarction, apoptosis of myocytes is variable and depends especially on the presence or absence of coronary reperfusion. In this study, ANX uptake in non-reperfused experimental myocardial infarcts was compared with uptake of a marker of myocyte necrosis ((111)In-antimyosin antibodies, AM) and an immunohistochemical marker of apoptosis (Apostain).

METHODS

The left anterior coronary artery was ligated in 47 Wistar rats, which were then injected with ANX (n=20), AM (n=21) or both (n=6). Myocardial uptake of ANX and AM was determined at 2 h (n=14), 4 h (n=14) and 24 h (n=19) after coronary ligation (CL), by quantitative autoradiography with (n=23) or without (n=24) gamma imaging. Heart-to-lung ratios (HLRs) and infarct-to-remote myocardium activity ratios (INRs) were calculated on the scintigrams and autoradiograms respectively. Cardiac sections were stained with haematoxylin-eosin and Apostain. The above studies were repeated in 12 normal rats.

RESULTS

All rats with CL showed increased ANX and AM uptake in cardiac areas on scintigrams 24 h after CL, with HLRs higher than in controls: 3.1+/-0.6 versus 1.5+/-0.3 (p=0.001) for ANX and 1.99+/-0.44 versus 1.01+/-0.05 (p<0.0005) for AM. Autoradiography showed intense ANX and AM uptake in infarcts, with comparable topography and INRs at 2 h, 4 h and 24 h after CL (4.6+/-0.9 versus 5.0+/-1.8 at 24 h), while Apostain staining was very low (0.06+/-0.06% of cells).

CONCLUSION

In this model of persistent CL, we observed increased ANX uptake in injured myocardium, comparable in intensity, topography and kinetics to that of AM. There was only minimal Apostain staining in the same areas.

Effects of carvedilol on myocardial sympathetic innervation in patients with chronic heart failure

Carvedilol is a beta-blocking agent with antioxidant properties that has been shown to improve survival in chronic heart failure (CHF). Previous open-label studies have suggested that its use may have positive effects on the abnormalities of cardiac sympathetic innervation integrity and functioning. The present study aimed to test the hypothesis that carvedilol exerts its beneficial effects on hemodynamics in parallel with an action on myocardial sympathetic activity and with its antioxidant property.

METHODS

A randomized, multicenter, double-blind, placebo-controlled study of carvedilol was conducted on 64 CHF patients. Patients underwent-before and after 6 mo of therapy with either carvedilol or placebo-measurements of cardiac sympathetic activity, circulating catecholamine level, and hemodynamic indices. Myocardial meta-(123)I-iodobenzylguanidine ((123)I-MIBG) uptake was used to assess the changes in myocardial sympathetic activity. The antioxidant properties of the plasma were assessed by measuring the percentage of nonhemolyzed erythrocytes and the volume of plasma capable of inhibiting 50% of hemolysis after an oxidative stress. Echographic left ventricular (LV) diameters, radionuclide LV ejection fraction (LVEF), and exercise cardiopulmonary capacity were measured to evaluate the hemodynamic response.

RESULTS

End-diastolic and end-systolic LV diameters decreased (both P < 0.05) and LVEF increased (P = 0.03) in the carvedilol group, whereas these parameters remained unchanged in the placebo group. Carvedilol did not alter the submaximal exercise cardiopulmonary capacity or the circulating catecholamine level. The beneficial hemodynamic effects in the carvedilol group were associated with an increase in myocardial (123)I-MIBG uptake as assessed by both planar and tomographic imaging (P < 0.01). Carvedilol had no detectable effect on antioxidant properties of the plasma.

CONCLUSION

The benefits of carvedilol on resting hemodynamics appear to be associated with a partial recovery of cardiac adrenergic innervation functioning without detectable antioxidant effect in the plasma.

Noninvasive evaluation of acute capillary permeability changes during high-volume ventilation in rats with and without hypercapnic acidosis

OBJECTIVE

To evaluate whether hypercapnic acidosis attenuates acute alterations of pulmonary capillary permeability due to high lung stretch in rats using a simple, noninvasive, scintigraphic method.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Male adult Wistar rats weighing 291 +/- 7.5 g.

INTERVENTIONS

Three groups of rats were studied: controls ventilated with a low (6 mL/kg body weight) tidal volume and rats ventilated with a high (38 mL/kg body weight) tidal volume under normocapnic (Paco(2) = 35.2 +/- 1.65 mm Hg) or hypercapnic (Paco(2) = 102.5 +/- 5.63 mm Hg) conditions.

MEASUREMENTS AND MAIN RESULTS

Pulmonary capillary permeability alterations were assessed by monitoring the rate of (111)In-transferrin accumulation in lung tissue. Respiratory system pressure-volume curves were registered and analyzed. High tidal volume ventilation increased In-transferrin plasma to lung flux in such a way that I(111)In-transferrin behaved like a marker of water. The rate of initial (first 30 mins of high tidal volume ventilation) lung transferrin accumulation measured by scintigraphy (standardized lung/heart ratio) was steady, correlated with the percent decrease in respiratory system compliance (a marker of edema progression), and did not differ between normocapnic and hypercapnic groups (18.9 +/- 3.97 vs. 14.2 +/- 2.89%/hr, not significant). However, lung In-tranferrin accumulation rate was highly scattered due to variable interindividual mechanical properties of the respiratory system. This rate was correlated with initial values of volume of the upper inflection point of the pressure-volume curve (r = -.53, p < .001) and end-inspiratory pressure (r = .54, p < .001). Mechanical properties were similar in normocapnic and hypercapnic rats. There was no difference between In-transferrin accumulation rates in these rats when a stringent selection was made based on end-inspiratory pressure (28-32 cm H(2)O) or body weight (330-360 g).

CONCLUSIONS

Hypercapnic acidosis does not influence in vivo the acute increase in pulmonary capillary permeability due to high-volume ventilation.

Imaging apoptosis with (99m)Tc-annexin-V in experimental subacute myocarditis

99mTc-Annexin-V (ANX), which allows in vivo detection of apoptotic cells, is potentially a promising noninvasive tool to diagnose myocarditis. To test this assumption, we compared the myocardial uptake of ANX (imaging and quantitative autoradiography) in experimental subacute myocarditis (Wistar Bonn/Kobori rats [WBN/Kob]) and in normal Wistar rats. WBN/Kob is an inbred strain of Wistar rat in which myocardial injury mimicking subacute catecholamine-induced myocarditis spontaneously develops (course duration, 18 mo). The apoptotic myocardial rates were determined by immunohistochemical studies.

METHODS

Fourteen WBN/Kob rats (8-10 mo old) and 12 control rats were injected with ANX (7.4 MBq/100 g). Ten-minute anterior planar thoracic images (matrix, 128 x 128) were obtained using a pinhole collimator, 1 and 4 h after injection. Heart-to-lung activity ratios were calculated on the scintigrams. Four hours after ANX injection, quantitative autoradiography of myocardial slices was performed, as well as histologic studies with hematoxylin-eosin and with a staining assay specific for apoptotic cells.

RESULTS

Heart-to-lung activity ratios were higher in WBN/Kob rats than in control rats on 4-h images (2.07 +/- 0.07 vs. 1.66 +/- 0.06, P = 0.0007). Autoradiographic studies showed moderate diffuse, homogeneous myocardial ANX uptake significantly higher in WBN/Kob rats than in control rats: 54 +/- 4 versus 37 +/- 3 counts/mm(2) (P < 0.007). The apoptotic rate, evaluated with an apoptotic cell-staining assay, was 0.51% +/- 0.14% of cells in WBN/Kob rats versus 0.0042% +/- 0.0008% in control rats (P < 0.008).

CONCLUSION

Compared with control rats, rats with subacute myocarditis mimicking catecholamine-induced myocarditis showed increased ANX myocardial uptake. This suggests a potential role for ANX imaging in the diagnosis of myocarditis.

Automatic quantification of right ventricular function with gated blood pool SPECT

BACKGROUND

Quantification of right ventricular (RV) function is clinically relevant for the risk stratification and follow-up of patients with a wide spectrum of disease. This can be achieved with electrocardiography-gated blood pool single photon emission computed tomography (GBPS). We aimed to evaluate the accuracy of the completely automatic QBS GBPS processing software as compared with equilibrium planar radionuclide angiography (RNA) and with a GBPS manual segmentation method (GBPS(35%)) for the measurement of global RV ejection fraction (EF), taking the first-pass RNA (FP-RNA) as the gold standard. In parallel, we compared the RVEF, RV end-diastolic volume (EDV), and RV end-systolic volume (ESV) provided by QBS and GBPS(35%).

METHODS AND RESULTS

The population included 85 patients with chronic post-embolic pulmonary hypertension. Twenty-one patients were excluded because of unsuccessful FP-RNA. Intraobserver and interobserver RVEF, RVEDV, and RVESV reproducibilities encountered with planar RNA, QBS, and GBPS(35%) were similar and compared favorably with those calculated with FP-RNA for RVEF. Mean RVEF was different between all methods. RVEF calculated with FP-RNA was better correlated to QBS (r = 0.68) and GBPS(35%) (r = 0.70) than to planar RNA (r = 0.59). RVEDV and RVESV with QBS were lower than with GBPS(35%), by 29% +/- 14% and 36% +/- 13%, respectively. RVEDV and RVESV with QBS were highly correlated to corresponding GBPS(35%) values: r = 0.88 and r = 0.91, respectively.

CONCLUSION

As opposed to FP-RNA, GBPS is highly successful for the quantification of RV function. Both QBS and GBPS(35%) provide RVEF values similarly well correlated to FP-RNA and performed better than planar RNA. RVEF, RVEDV, and RVESV provided by QBS and GBPS(35%) are highly correlated. All of these RV functional measurements require further validation versus a better gold standard before their accuracy can be established.

Discordance between exercise SPECT lung Tl-201 uptake and left ventricular transient ischemic dilation in patients with CAD

BACKGROUND

In patients with coronary artery disease (CAD), the characteristics of those with discordant exercise thallium 201 single photon emission computed tomography (SPECT) lung uptake (lung-to-heart [L/H] ratio) and left ventricular (LV) transient ischemic dilation (LVTID) are not well defined.

METHODS AND RESULTS

The population included 310 patients having exercise Tl-201 SPECT and coronary angiography. The population was subclassified into 4 subgroups: increased L/H ratio only, increased LVTID only, both, and neither. The L/H ratio was weakly correlated to LVTID (r = 0.18). The L/H ratio was correlated to the summed difference score (r = 0.26), summed rest score (r = 0.31), summed stress score (r = 0.5), and rest and stress LV volume (r = 0.5 and r = 0.54, respectively). LVTID was only correlated to the summed difference score (r = 0.32) and stress LV volume (r = 0.17). Increased LVTID only was associated with more frequent ischemia and patients with it tended to be more extensively ischemic, as compared with patients with increased L/H ratio only, but had a similar angiographic extent of CAD. These results were independent of prior myocardial infarction variable.

CONCLUSIONS

As compared with patients with increased L/H ratio alone, patients with increased LVTID alone are more frequently ischemic but have a similar angiographic extent of CAD. Increased L/H ratio was correlated to both rest and postexercise LV volume, whereas increased LVTID was correlated only to postexercise LV volume.

Optimisation of the OS-EM algorithm and comparison with FBP for image reconstruction on a dual-head camera: a phantom and a clinical 18F-FDG study

Iterative reconstruction algorithms, such as the ordered subsets expectation maximisation (OS-EM), are a promising alternative to filtered backprojection (FBP). The aims of this study were first to optimise the OS-EM algorithm in terms of iteration number and to study the usefulness of post-filtering, and second to compare OS-EM and FBP for image reconstruction on a fluorine-18 fluorodeoxyglucose ((18)F-FDG) dual-head camera (DHC). These two goals were addressed using phantom acquisitions. The performances of these algorithms were also studied in patient acquisitions performed on a DHC and a PET on the same day. Phantom experiments were performed on a DHC using a Jaszczak phantom containing six spheres filled with (18)F-FDG, two background levels (0.95, 6.80 kBq/ml) and three object contrasts (5.9, 3.7, 2.7). The reconstruction algorithms were FBP with a Gaussian filter (FWHM 0.5-2 pixel width) and OS-EM using 8-128 equivalent iterations (equivalent to the ML-EM algorithm) with and without Gaussian post-filtering [OS-EM (iterations, pixel width)]. Contrast recovery coefficient (CRC) and noise characteristics were assessed. Twenty-two patients (21 male, one female; age 55+/-15 years) with lung cancer underwent, on the same day, PET (1 h post injection of 37 MBq/kg (18)F-FDG) and DHC acquisitions (3 h post injection). DHC data were reconstructed using six methods: FBP (1), OS-EM (16), (40), (40,1), (64) and (64,1). These sets were evaluated by two observers and compared to PET reconstructed with OS-EM (16). The number of detected lesions and the visual quality were assessed. A marked improvement in CRC was observed with OS-EM as compared with FBP when more than 24 iterations were used. The CRC increased markedly from 8 to 40 iterations and then reached a plateau. The noise was stable until 40 iterations and then increased. The best compromise was obtained for OS-EM (32) and OS-EM (40,1). For the patient study, OS-EM provided images of better visual quality, but with no significant difference in detection sensitivity. OS-EM was superior to FBP in terms of contrast recovery and noise level. The optimal compromise between contrast recovery and noise was obtained for OS-EM (32) and (40,1) on the phantom study. The clinical study showed that OS-EM yielded images of better visual quality but with no improvement in terms of detection of lung cancer.

Incomplete resolution of ST-segment elevation is a marker of transient microcirculatory dysfunction after stenting for acute myocardial infarction

BACKGROUND

Incomplete ST-segment resolution (STR) after successful primary angioplasty for acute myocardial infarction (AMI) is associated with a poor prognosis. We used intracoronary Doppler velocimetry to investigate whether incomplete STR after primary angioplasty is a marker of severe microcirculatory dysfunction.

METHODS AND RESULTS

Fifty patients with < or =12-hour AMI underwent successful primary angioplasty and systematic stenting with a Doppler guidewire. Patients with incomplete (<50%) STR 60 minutes after TIMI 3 flow was restored had flow velocity features suggestive of severe microcirculatory dysfunction, including a higher incidence of early systolic retrograde flow (41% versus 9%, P=0.007) and lower coronary flow velocity reserve (CVR, 1.3 versus 1.6, P<0.001). CVR improved immediately after stenting in patients with > or =50% STR but not in patients with <50% STR. There was a significant correlation between STR and poststent CVR. At 3 months, CVR was similar in patients with <50% and > or =50% STR. However, left ventriculography indicated lower global (42% versus 55%, P=0.001) and regional (16% versus 20%, P=0.03) left ventricular ejection fractions and 201Tl rest-redistribution scintigraphy indicated a larger infarct size (34% versus 16% 201Tl defect, P=0.007) in patients with <50% STR.

CONCLUSIONS

After successful primary angioplasty with systematic stenting, <50% STR is a marker of severe albeit transient microcirculatory dysfunction in patients with AMI and is associated with more extensive myocardial damage.

Comparative value of ECG-gated blood pool SPET and ECG-gated myocardial perfusion SPET in the assessment of global systolic left ventricular function

Both electrocardiographically (ECG) gated blood pool SPET (GBPS) and ECG-gated myocardial perfusion SPET (GSPET) are currently used for the measurement of global systolic left ventricular (LV) function. In this study, we aimed to compare the value of GSPET and GBPS for this purpose. The population included 65 patients who underwent rest thallium-201 GSPET imaging at 15 min after (201)Tl injection followed by planar (planar(RNA)) and GBPS equilibrium radionuclide angiography immediately after 4-h redistribution myocardial perfusion SPET imaging. Thirty-five patients also underwent LV conventional contrast angiography (X-rays). LV ejection fraction (EF) and LV volume [end-diastolic (EDV) and end-systolic (ESV) volumes] were calculated with GBPS and GSPET and compared with the gold standard methods (planar(RNA) LVEF and X-ray based calculation of LV volume). For both LVEF and LV volume, the inter-observer variability was lower with GBPS than with GSPET. GBPS LVEF was higher than planar(RNA) (P<0.01) and GSPET LVEF (P<0.01). Planar(RNA) LVEF showed a slightly better correlation with GBPS LVEF than with GSPET LVEF: r=0.87 and r=0.83 respectively. GSPET LV volume was lower than that obtained using X-rays and GBPS (P<0.01 for both). LV volume calculated using X-rays showed a slightly better correlation with GBPS LV volume than with GSPET LV volume: r=0.88 and r=0.83 respectively. On stepwise regression analysis, the accuracy of GSPET for the measurement of LVEF and LV volume was correlated with a number of factors, including planar(RNA) LVEF, signal to noise ratio, LV volume calculated using X-rays, summed rest score and acquisition scan distance (i.e. the radius of rotation). The accuracy of GBPS for the measurement of LVEF and LV volume was correlated only with the signal level, the signal to noise ratio and the acquisition scan distance. Both GSPET and GBPS provide reliable estimation of global systolic LV function. The better reliability of GBPS and in particular its lower sensitivity to different variables as compared with GSPET favours its use when precise assessment of global systolic LV function is clinically indicated.

Inability of 99mTc-ciprofloxacin scintigraphy to discriminate between septic and sterile osteoarticular diseases

Ciprofloxacin labeled with (99m)Tc specifically binds to various bacteria. Thus, it potentially constitutes a specific marker allowing discrimination between septic arthritis/osteomyelitis and aseptic osteoarticular diseases. The aim of this prospective study was to evaluate such properties in patients with skeletal diseases.

METHODS

We prospectively investigated 2 groups of patients: patients with suspected osteoarticular infections (G1, n = 16) and a control group of patients with a presentation of osteoarticular diseases and no sign suggestive of infection (G2, n = 11). All had clinical, biologic, and radiologic evaluations and had 1-, 4-, and 24-h images from (99m)Tc-ciprofloxacin scintigraphy (370 MBq) before planned biopsy or surgery. For 23 patients, the scintigraphic results were compared with histologic and bacteriologic analyses of biopsy tissue samples; for 4 patients, the scintigraphic results were compared with the findings from 23 +/- 5 mo of follow-up.

RESULTS

In G1, (99m)Tc-ciprofloxacin findings were true-positive in all 11 infected sites, true-negative in 2 cases, and false-positive in 3. In G2, (99m)Tc-ciprofloxacin was true-negative in 4 cases and false-positive in 7. Neither the location of (99m)Tc-ciprofloxacin activity nor its intensity or kinetics between 1, 4, and 24 h allowed discrimination between infection and aseptic diseases (sterile loosened joint replacement, pseudoarthrosis, or arthrosis). Sensitivity, specificity, and accuracy were 100%, 37.5%, and 63%.

CONCLUSION

(99m)Tc-Ciprofloxacin scintigraphy showed good sensitivity and a high negative predictive value for the detection of bone and joint infection, but it did not discriminate between infected and aseptic osteoarticular diseases in symptomatic patients referred for surgery.

Performance of OSEM and depth-dependent resolution recovery algorithms for the evaluation of global left ventricular function in 201Tl gated myocardial perfusion SPECT

It is unknown whether the use of ordered-subsets expectation maximization (OSEM) and depth-dependent resolution recovery (RR) will increase the accuracy of (201)Tl electrocardiogram-gated SPECT (GSPECT) for the measurement of global left ventricular (LV) function.

METHODS

Fifty-six patients having both rest (201)Tl GSPECT and planar equilibrium radionuclide angiography (planar(RNA)) on the same day were studied. Twenty-nine patients also had LV conventional contrast angiography (Rx). LV ejection fraction (LVEF), end-diastolic volume (EDV), and end-systolic volume (ESV) were calculated with the quantitative gated SPECT software (QGS) using 4 different processing methods: filtered backprojection (FBP), OSEM, RR + FBP, and RR + OSEM. LVEF calculated with planar(RNA) and LV EDV and ESV calculated with Rx were considered gold standards. LVEF and volumes provided with the GSPECT methods were compared with the gold standard methods.

RESULTS

LVEF calculated with GSPECT methods (FBP, OSEM, RR + FBP, and RR + OSEM) were similar (not statistically significant) and correlated well with planar(RNA). On Bland-Altman analysis, the mean +/- SD of absolute difference in LVEF with GSPECT FBP, OSEM, RR + FBP, and RR + OSEM methods versus planar(RNA) were similar, with relatively large limits of agreement. LV volumes calculated with the 4 GSPECT methods were significantly lower but correlated well with Rx LV volumes. LV volumes calculated with FBP and OSEM were lower than those calculated with RR + FBP and RR + OSEM (P < 0.01). On Bland-Altman analysis, the mean +/- SD of absolute difference in LV volumes with FBP, OSEM, RR + FBP, and RR + OSEM versus Rx was, respectively, 56 +/- 45 mL (P < 0.01 vs. the other 3 methods), 57 +/- 45 mL (P < 0.01 vs. the other 3 methods), 43 +/- 48 mL, and 46 +/- 47 mL, with correspondingly large limits of agreement. The variance of random error did not differ between FBP, OSEM, RR + FBP, and RR + OSEM for either LVEF or volumes.

CONCLUSION

OSEM and FBP presented similar accuracy for LVEF and volume measured with the QGS software. Their combination with depth-dependent RR provided similar LVEF but more accurate LV volumes.

Activity and diffusion of tigecycline (GAR-936) in experimental enterococcal endocarditis

The activity of tigecycline (GAR-936), a novel glycylcycline, was investigated in vitro and in experimental endocarditis due to the susceptible Enterococcus faecalis JH2-2 strain, its VanA type transconjugant BM4316, and a clinical VanA type strain, E. faecium HB217 resistant to tetracycline. MICs of GAR-936 were 0.06 micro g/ml for the three strains. In vitro pharmacodynamic studies demonstrated a bacteriostatic effect of GAR-936 that was not enhanced by increasing concentrations to more than 1 micro g/ml and a postantibiotic effect ranging from 1 to 4.5 h for concentrations of 1- to 20-fold the MIC. Intravenous injection of [(14)C]GAR-936 to five rabbits with enterococcal endocarditis sacrificed 30 min, 4 h, or 12 h after the end of the infusion evidenced a lower clearance of GAR-936 from aortic vegetations than from serum and a homogeneous diffusion of GAR-936 into the vegetations. In rabbits with endocarditis, GAR-936 (14 mg/kg of body weight twice a day [b.i.d.]) given intravenously for 5 days was bacteriostatic against both strains of E. faecalis. Against E. faecium HB217, bacterial counts in vegetations significantly decreased during therapy (P < 0.01), and the effect was similar with GAR-936 at 14 mg/kg b.i.d., 14 mg/kg once a day (o.d.), and 7 mg/kg o.d., which provided concentrations in serum constantly above the MIC. Mean serum elimination half-life ranged from 3.3 to 3.6 h. No GAR-936-resistant mutants were selected in vivo with any regimen. We concluded that the combination of prolonged half-life, significant postantibiotic effect, and good and homogeneous diffusion into the vegetations may account for the in vivo activity of GAR-936 against enterococci susceptible or resistant to glycopeptides and tetracyclines, even when using a o.d. regimen in rabbits.

Detection of neuroendocrine tumors: 99mTc-P829 scintigraphy compared with 111In-pentetreotide scintigraphy

The aim of this study was to evaluate the diagnostic value of a new somatostatin analog, 99mTc-P829, compared with that of 111In-pentetreotide.

METHODS

Forty-three patients (32 men, 11 women; age range, 24-78 y; mean age, 56 y) with biologically or histologically proven neuroendocrine tumors were prospectively included: 11 patients with Zollinger-Ellison syndrome, 16 patients with carcinoid tumors, and 16 patients with other types of functioning (n = 6) or nonfunctioning (n = 10) endocrine tumors. 111In-Pentetreotide planar images (head, chest, abdomen, and pelvis) were obtained 4 and 24 h after injection of 10 microg somatostatin analog labeled with 148 +/- 17 MBq 111In, and SPECT was performed 24 h after injection. Similar (99m)Tc-P829 planar images were obtained at 1, 4-6, and 24 h after injection of 50 microg peptide labeled with 991.6 +/- 187.59 MBq 99mTc. Abdominal SPECT was performed 4-6 h after injection.

RESULTS

111In-Pentetreotide detected 203 tumoral sites in 39 (91%) of 43 patients, whereas 99mTc-P829 detected 77 sites in 28 (65%) of 43 patients (P < 0.005). In the liver, 129 sites (in 24 patients) were detected by 111In-pentetreotide scintigraphy and 34 sites (in 10 patients) were detected by 99mTc-P829 scintigraphy.

CONCLUSION

In patients with endocrine tumors, the detection rate of 99mTc-P829 scintigraphy was lower than that of 111In-pentetreotide scintigraphy, which appeared to be more sensitive, especially for liver metastases.

Identification of extensive coronary artery disease: incremental value of exercise Tl-201 SPECT to clinical and stress test variables

BACKGROUND

The ability of the size of a total myocardial perfusion defect (MPD) to detect extensive coronary artery disease (CAD) is currently suboptimal with exercise thallium 201 single photon emission computed tomography (SPECT). To improve its performance, exercise electrocardiography and indirect scintigraphic markers of extensive CAD were proposed (increased right ventricular Tl-201 uptake, lung-to-heart [L/H] ratio, and left ventricular transient ischemic dilation ratio). We aimed to determine the additive value of these criteria for the detection of extensive CAD.

METHODS AND RESULTS

The population included 338 patients who underwent exercise Tl-201 SPECT and coronary angiography. Patients were classified as having extensive CAD (left main, multivessel, or 1-vessel proximal left anterior descending CAD) or limited CAD (1-vessel disease other than proximal left anterior descending CAD or no CAD). First, Tl-201 SPECT provided higher diagnostic value than exercise electrocardiography. Second, age, percent target heart rate achieved, total MPD, and L/H ratio were independent predictors of extensive CAD. Third, visually estimated abnormal right ventricular Tl-201 uptake did not present additional information. Fourth, L/H ratio presented a higher diagnostic accuracy than left ventricular transient ischemic dilation ratio.

CONCLUSIONS

With exercise Tl-201 SPECT, age, percent target heart rate achieved, total MPD, and L/H ratio were independent predictors of extensive CAD.

Evaluation of (99m)Tc-ciprofloxacin scintigraphy in a rabbit model of Staphylococcus aureus prosthetic joint infection

Ciprofloxacin, a quinolone antibiotic drug, binds to DNA topoisomerase IV and DNA gyrase of various bacteria. Thus ciprofloxacin labeled with (99m)Tc could potentially act as a specific marker allowing discrimination between infection and sterile inflammation. We evaluated these properties on a rabbit model of prosthetic joint infection previously validated. We compared the images obtained in 2 groups of animals: rabbits with infected (G1; n = 6) and uninfected (G2; n = 7) prosthesis.

METHODS

Partial right-knee arthroplasty was performed on 13 New Zealand White female rabbits, with a tibial silicone-elastomer implant fitting into the intramedullary canal of the tibia. After the surgical wound was closed, 10(7) cfu of a clinical strain of methicillin-susceptible Staphylococcus aureus were injected into the joint in G1 rabbits. G2 rabbits were injected with sterile saline. No antibiotic therapy was given to the animals. (99m)Tc-ciprofloxacin planar imaging was performed on days 5, 12, and 19 after surgery, and after 3 mo in 1 uninfected rabbit. Images were obtained 1, 4, and 24 h after injection (147 +/- 13 MBq).

RESULTS

In G1, increased right knee (99m)Tc-ciprofloxacin uptake was observed in 3 of 5 rabbits on day 5, and in all cases on days 12 and 19. Killing of the animals revealed purulent arthritis, osteitis, and tibial myelitis. In G2, significant right-knee uptake was found on days 12 and 19 in 5 of 6 rabbits, and after 3 mo in 1; all sets of images were negative in 1 animal. Bacteriologic studies after the animals were killed were negative in G2. Mean right/left knee uptake ratios on day 19 (4-h images) were 1.8 +/- 0.4 in G1 versus 1.4 +/- 0.3 in G2 (not significant). Late images did not discriminate between infected and uninfected arthroplasty.

CONCLUSION

Results of (99m)Tc-ciprofloxacin imaging in rabbits with infected/uninfected knee prosthesis suggest good sensitivity but lack of specificity for the detection of S. aureus infection.

Determination of left ventricular cardiac volume by simultaneous radionuclide angiography and measurement of oxygen consumption at rest and during maximal exercise: a comparison of two non-invasive isotopic procedures

The investigation of left ventricular contractile reserve usually requires the determination of left ventricular volume, but its measurement with radionuclide angiography is difficult. The aim of this study was to determine left ventricular volume directly during exercise by the simultaneous measurement of peak exercise left ventricular ejection fraction (LVEF) and oxygen consumption (VO2max) and to compare the results with another geometric method. In the absence of lung disease, the systemic arteriovenous oxygen difference (DAVmax) during maximal exercise converges to 0.13-0.14 ml O2 per ml blood. The measurement of VO2max allows maximal cardiac output (COmax) to be calculated as VO2max = COmax. DAVmax. By simultaneously determining LVEFex, exercise end-diastolic volume (EDVex) can then be expressed as a linear function of VO2max, maximal heart rate (HRmax), DAVmax and LVEFex. Then, the relationship between end-diastolic counts and true volume can be derived at rest. The two methods were closely correlated (r = 0.91, P < 0.001), despite the geometric method being less accurate when applied to low counting statistic acquisitions. We conclude that rest and exercise left ventricular volume can be determined non-invasively by the simultaneous measurement of VO2max and LVEFex. Furthermore, this method provides additional prognostic information which is clinically relevant in the staging of patients with heart failure.