Adrien Peters

Quantification of right to left shunt at rest and during exercise in patients with pulmonary arteriovenous malformations.

BACKGROUND: Current treatment of patients with pulmonary arteriovenous malformations requires serial embolisations by means of steel coils or balloons. Measurement of right to left shunt is the most specific index of response to treatment. A new method of measuring shunt has been developed that is less invasive than traditional methods. METHODS: Right to left pulmonary shunt (expressed as percentage of cardiac output) was measured at rest in 19 patients with pulmonary arteriovenous malformations and six normal subjects by using intravenously injected albumin microspheres labelled with technetium-99m. The technique was compared with a simultaneous shunt measurement in subjects breathing 100% oxygen while they rested. The microsphere technique was adapted to measure the right to left shunt during exercise in 12 patients and five normal subjects with a new method of quantification. RESULTS: The mean (SD) shunt at rest as measured by the microsphere method was 23.2% (15.6%) in the patients and 2.7% (1.2%) in the normal subjects. When these values were compared with those of the 100% oxygen method the difference in mean values was 1% and the limits of agreement between the two methods -32% to +45%. The microsphere method is less invasive (arterial blood gas sampling is not required), quicker, and more comfortable for patients than the 100% oxygen method. In five of the normal subjects the mean (SD) 99mTc microsphere shunt increased from 2.9% (1.3%) at rest to 5.1% (2.9%) during exercise. In the 12 patients studied during exercise the shunt increased from 33.7% (12.7%) at rest to 41.7% (13.3%) during exercise in eight but decreased from 22.6% (2.4%) at rest to 17.6% (2.2%) during exercise in four. Arterial desaturation during exercise correlated with change in the size of the right to left shunt during exercise (r = +0.80). CONCLUSIONS: The microsphere method allows measurement of right to left shunt at rest and during exercise. Serial measurements at rest provide a simple, safe assessment of the physiological response to embolisation in patients with pulmonary arteriovenous malformations.

Lymphatic dysfunction in the apparently clinically normal contralateral limbs of patients with unilateral lower limb swelling.

Purpose: To determine how often lymphatic dysfunction is bilateral when, clinically, lymphedema appears unilateral. Methods: Lymphoscintigraphy was performed after subcutaneous Tc-99m-nanocolloid injection in the first webspaces of both feet. The percentage of injected radioactivity accumulating in the ilioinguinal regions was recorded in dedicated images separately acquired at 60 and 180 minutes after injection. Results: Within a consecutive series of 204 patients, 74 had unilateral clinical lymphedema of whom 68 had abnormal scintigraphy. Of these 68 patients, 46 had unilateral abnormal scintigraphy affecting the clinically abnormal limb, but 20 patients had bilateral abnormal scintigraphy and 2 had unilateral abnormal scintigraphy in the clinically unaffected limb. Thus, 32% (22/68) of patients in whom clinical lymphedema appeared to be unilateral, nevertheless, had abnormal scintigraphy in the clinically normal limb. Twenty-nine patients had no clinical evidence of lymphedema in either limb and were scintigraphically normal bilaterally. Mean ilioinguinal nodal accumulation at 180 minutes in the 44 limbs of 22 of these clinically and scintigraphically normal patients (dedicated ilioinguinal imaging was not performed in all patients) was 13.1% (standard deviation, 8.8%), higher (P = 0.02) than the mean value of 9.3% (standard deviation, 5.0%) in the clinically and scintigraphically normal contralateral limbs of 39 patients with unilateral clinical lymphedema. Conclusions: In the presence of unilateral lymphedema, the contralateral limb is often also abnormal. On lymphoscintigraphy, therefore, care should be taken before diagnosing unilateral lymphatic dysfunction. Quantification should be included in routine lymphoscintigraphy, as reduced ilioinguinal nodal accumulation may be the only apparent abnormality.

Accumulation of (18)F-FDG in the liver in hepatic steatosis.

OBJECTIVE Nonalcoholic fatty liver disease is associated with hepatic inflammation. An emerging technique to image inflammation is PET using the glucose tracer, (18)F-FDG. The purpose of this study was to determine whether in hepatic steatosis the liver accumulates FDG in excess of FDG physiologically exchanging between blood and hepatocyte. MATERIALS AND METHODS Hepatic FDG uptake, as SUV = [voxel counts / administered activity] × body weight), and CT density were measured in a liver region in images obtained 60 minutes after injection of FDG in 304 patients referred for routine PET/CT. Maximum SUV (region voxel with the highest count rate, SUVmax) and average SUV ( SUVave) were measured. Blood FDG concentration was measured as the maximum SUV over the left ventricular cavity (SUVLV). SUVave was adjusted for hepatic fat using a formula equating percentage fat to CT density. Patients were divided in subgroups on the basis of blood glucose (< 4, 4 to < 5, 5 to < 6, 6 to < 8, 8 to < 10, and > 10 mmol/L). Hepatic steatosis was defined as CT density less than 40 HU (n = 71). RESULTS The percentage of hepatic fat increased exponentially with blood glucose. SUVmax / SUVLV and fat-adjusted SUVave / SUVLV but not SUVave / SUVLV correlated with blood glucose. Fat-adjusted SUVave was higher in patients with hepatic steatosis (p < 0.001) by ~0.4 in all blood glucose groups. There was a similar difference (~0.3) in SUVmax (p < 0.005) but no difference in SUVave. SUVmax / SUVLV and fat-adjusted SUVave / SUVLV correlated with blood glucose in patients with hepatic steatosis but not in those without. SUVave / SUVLV correlated with blood glucose in neither group. CONCLUSION FDG uptake is increased in hepatic steatosis, probably resulting from irreversible uptake in inflammatory cells superimposed on reversible hepatocyte uptake.

Use of technetium-99m-labeled eosinophils to detect active eosinophilic inflammation in humans.

To the Editor: The diagnosis of focal eosinophilic inflammation is notoriously difficult. Here we describe a novel technique using technetium-99m–labeled autologous eosinophils to image eosinophilic vasculitis affecting the lung and skin in a patient with granulomatosis with polyangiitis. Our patient, a 48-year-old male, presented with cough, purulent sputum, hemoptysis, lethargy, and painful ulcers affecting his hands and feet. His thoracic computed tomography (CT) showed bilateral upper zone nodules with cavity formation. Previously he had experienced recurrent anterior uveitis and small joint polyarthropathy. His medications were hydroxychloroquine and etodolac, which he took intermittently. Examination revealed periungual erythema and multiple deep ulcers affecting his fingers and right ankle (Figure 1A). His blood eosinophil count was 0.76 × 109/L, with normal renal and liver function and normal antinuclear antibody and rheumatoid factor. His antineutrophil cytoplasmic antibody (ANCA) immunofluorescence was positive with a (PR3) ANCA of 25 IU/ml (normal range < 0.2 IU/ml). He also had evidence of IgG4-related disease associated with his ANCA-positive vasculitis with a serum IgG4 of 4.1 g/L. Surgical lung biopsy revealed dense fibrosis, with scattered noncaseating granulomas, heavy eosinophil infiltration, a medium-small vessel vasculitis, and IgG4-staining plasma cells. Similar findings were observed in the skin (Figure 1B). Figure 1. Technetium-99m–labeled eosinophil scanning in granulomatosis with polyangiitis. (A) Photograph of vasculitic ulcers affecting the patient’s right ankle. (B) The corresponding histology (×20 magnification) shows active vasculitis ... Technetium-99m–labeled eosinophils (98.5% pure) were prepared using clinical grade anti-CD16 immuno-magnetic beads as described (1) and 16 × 106 cells (187 MBq) reinjected. Dynamic images were taken for 40 minutes (1) followed by single-photon emission CT (SPECT-CT) images at 45 minutes and 2, 4, and 6 hours. His legs were imaged using a γ camera (Figure 1C). The intravascular residence time (1.5 h) of the technetium-99m–labeled eosinophils was much shorter than that observed in healthy subjects (1) with only 4.9% of the injected cells remaining in the circulation at 30 minutes. This compares to an intravascular residence time of indium-111–labeled eosinophils in healthy volunteers of 28.1 ± 1.7 hours (mean ± SEM), with 14.5 ± 2.5% of radiolabeled cells remaining in the circulation at 30 minutes (1). Although the technetium-99m–labeled eosinophils accumulated as expected in the liver, spleen, and bone marrow (Figure 1D), SPECT-CT revealed additional uptake in some but not all of his lung nodules (Figures 1E–1G). Although radiolabeled leukocyte scanning is used routinely for localizing occult infection, this approach has not been used previously to demonstrate focal eosinophilic inflammation. Advances in immuno-magnetic bead technology have permitted the isolation of ultra-pure nonactivated eosinophils from blood, which are amenable to radiolabeling and behave physiologically when reinjected in healthy subjects (1). Alternative, indirect methods of detecting eosinophilic inflammation in humans, such as exhaled nitric oxide and analysis of breath condensates, are nonspecific and can only assess the inflammatory burden in the respiratory tract. In contrast, technetium-99m–labeled eosinophils plus SPECT-CT can localize focal eosinophilic inflammation directly in vivo. Furthermore, this technique is less invasive than performing bronchoscopy and transbronchial biopsy, which may be contraindicated in some patients and carry significant risk. This novel approach therefore offers the prospect of a noninvasive method to aid in the diagnosis, localization, and assessment of disease activity.

Hepatic glucose utilisation in hepatic steatosis and obesity

Hepatic steatosis is associated with obesity and insulin resistance. Whether hepatic glucose utilization rate (glucose phosphorylation rate; MRglu) is increased in steatosis and/or obesity is uncertain. Our aim was to determine the separate relationships of steatosis and obesity with MRglu. Sixty patients referred for routine PET/CT had dynamic PET imaging over the abdomen for 30 min post-injection of F-18-fluorodeoxyglucose (FDG), followed by Patlak–Rutland graphical analysis of the liver using abdominal aorta for arterial input signal. The plot gradient was divided by the intercept to give hepatic FDG clearance normalized to hepatic FDG distribution volume (ml/min per 100 ml) and multiplied by blood glucose to give hepatic MRglu (μmol/min per 100 ml). Hepatic steatosis was defined as CT density of ≤40 HU measured from the 60 min whole body routine PET/CT and obesity as body mass index of ≥30 kg/m2. Hepatic MRglu was higher in patients with steatosis (3.3±1.3 μmol/min per 100 ml) than those without (1.7±1.2 μmol/min per 100 ml; P<0.001) but there was no significant difference between obese (2.5±1.6 μmol/min per 100 ml) and non-obese patients (2.1±1.3 μmol/min per 100 ml). MRglu was increased in obese patients only if they had steatosis. Non-obese patients with steatosis still had increased MRglu. There was no association between MRglu and chemotherapy history. We conclude that MRglu is increased in hepatic steatosis probably through insulin resistance, hyperinsulinaemia and up-regulation of hepatic hexokinase, irrespective of obesity.

Lymph proteins may access peripheral blood without entering thoracic duct in patients with lymphatic dysfunction.

OBJECTIVE The objective was to investigate the hypothesis that lymphovenous communications, which allow lymph proteins to access peripheral blood without first entering the thoracic duct, open in patients with abnormal lymphatic function. METHODS Routine lymphoscintigraphy of 182 patients, including 27 without clinical evidence of lymphedema (controls), was performed immediately and 45 and 150 minutes after subcutaneous injection of technetium Tc 99m nanocolloid into both feet. Counts per pixel in a region of interest over the liver (L) were divided by total counts in bilateral ilioinguinal nodes (N) at 45 minutes (L/N45) and 150 minutes (L/N150). If all activity leaving ilioinguinal lymph nodes entered the thoracic duct, these L/N ratios would be similar from patient to patient. RESULTS Eight patients were excluded because of immediate liver activity suggesting inadvertent intravascular injection of tracer. In controls (group 1), L/N150 displayed a normal distribution with mean (± standard deviation) of 0.16 (0.09) × 10(-4) pixels(-1). Patients with L/N150 >0.34 × 10(-4) pixels(-1) (ie, 0.16 + 2 standard deviations) were assumed to have lymphovenous communications. Of 34 patients with clinical evidence of lymphedema but with normal findings on lymphoscintigraphy (group 2), 3 (9%) had lymphovenous communications; of 114 with abnormalities on lymphoscintigraphy (group 3), 43 (38%) had lymphovenous communications (P = .001). N45/150 was significantly higher than L45/150 in all four groups, indicating arrival of activity in nodes before the liver. Abnormal features of lymphoscintigraphy-lymph transport delay, popliteal node visualization, and diversion of lymph through the skin-showed no association with L/N ratios. CONCLUSIONS Lymphovenous communications exist in about one-third of patients with abnormalities detected on lymphoscintigraphy. The timings of tracer arrival in the liver and lymph nodes is consistent with lymphovenous communication within lymph nodes themselves.

FAMILIAL COMBINED HYPERLIPIDEMIA IS CHARACTERIZED BY HIGHER HEPATIC FDG UPTAKE AND VISCERAL ADIPOSE TISSUE VOLUME COMPARED TO HETEROZYGOUS FAMILIAL HYPERCHOLESTEROLAEMIA

Familial combined hyperlipidaemia (FCH) phenotype is associated with increased prevalence of non-alcoholic fatty liver disease and obesity. No data exists regarding the impact of heterozygous familial hypercholesterolaemia (heFH), another type of familial dyslipidaemia, on liver function and

S65 Quantification of ‘whole lung’ pulmonary eosinophilic inflammation using radiolabelled autologous human eosinophils

Background Eosinophils are key mediators of allergic inflammation. The ability to localise and quantify eosinophilic inflammation in vivo would facilitate patient endotyping and evaluation of eosinophil-targeted therapeutics. We aimed to quantify eosinophil distribution and organ-specific uptake in healthy subjects, asthmatics, and patients with focal pulmonary eosinophilic inflammation. Methods We injected autologous radiolabelled eosinophils into 8 healthy volunteers, 15 asthmatics (7 obese and 7 non-obese), and 3 patients with focal eosinophilic inflammation and monitored eosinophil distribution (planar imaging, single photon emission computed tomography – SPECT)/CT). Lung accumulation of technetium-99 m-labelled eosinophils was quantified (Patlak-Rutland analysis). Whole body indium-111-labelled eosinophil distribution and loss were further assessed in 5 healthy volunteers and 7 asthmatics using a whole body counter. Findings Pulmonary eosinophil clearance was increased in patients with focal eosinophilia (0·0033 ml/min/ml; 95% CI −0·005–0·011; p=0.02) compared to asthmatics (0·0007 ml/min/ml; 95% CI 0·0003–0·0010; p=0.14) and controls (0·0003 ml/min/ml; 95% CI −7·5 × 10–5–0·0008). Absolute lung eosinophil migration was elevated in patients with focal inflammation (5932 eosinophils/min/ml; 95% CI −14351–26215, p=0.01) and asthma (364 eosinophils/min/ml; 95% CI 38–689; p=0.03) versus healthy volunteers (38 eosinophils/min/ml; 95% CI −11–87). Stratification of asthmatics based on BMI revealed increased pulmonary eosinophil clearance in obese (0·001 ml/min/ml; 95% CI 0·0007–0·001; p=0.02) versus non-obese asthmatics (0·0003 ml/min/ml; 95% CI −0·0002–0·0009). Interpretation Eosinophil radiolabelling can quantify pulmonary eosinophilic inflammation, with the potential for patient endotyping and testing eosinophil-targeted treatments. Funding Medical Research Council, Wellcome Trust, Asthma UK, Cambridge NIHR Biomedical Research Centre.

Circulating granulocyte lifespan in compensated alcohol-related cirrhosis: a pilot study

Although granulocyte dysfunction is known to occur in cirrhosis, in vivo studies of granulocyte lifespan have not previously been performed. The normal circulating granulocyte survival half‐time (G − t½), determined using indium‐111 (111In)‐radiolabeled granulocytes, is ~7 h. In this pilot study, we aimed to measure the in vivo G − t½ in compensated alcohol‐related cirrhosis. Sequential venous blood samples were obtained in abstinent subjects with alcohol‐related cirrhosis over 24 h post injection (PI) of minimally manipulated 111In‐radiolabeled autologous mixed leukocytes. Purified granulocytes were isolated from each sample using a magnetic microbead‐antibody technique positively selecting for the marker CD15. Granulocyte‐associated radioactivity was expressed relative to peak activity, plotted over time, and G − t½ estimated from data up to 12 h PI. This was compared with normal neutrophil half‐time (N − t½), determined using a similar method specifically selecting neutrophils in healthy controls at a collaborating center. Seven patients with cirrhosis (six male, aged 57.8 ± 9.4 years, all Child‐Pugh class A) and seven normal controls (three male, 64.4 ± 5.6 years) were studied. Peripheral blood neutrophil counts were similar in both groups (4.6 (3.5 − 5.5) × 109/L vs. 2.8 (2.7 − 4.4) × 109/L, respectively, P = 0.277). G − t½ in cirrhosis was significantly lower than N − t½ in controls (2.7 ± 0.5 h vs. 4.4 ± 1.0 h, P = 0.007). Transient rises in granulocyte and neutrophil‐associated activities occurred in four patients from each group, typically earlier in cirrhosis (4–6 h PI) than in controls (8–10 h), suggesting recirculation of radiolabeled cells released from an unidentified focus. Reduced in vivo granulocyte survival in compensated alcohol‐related cirrhosis is a novel finding and potentially another mechanism for immune dysfunction in chronic liver disease. Larger studies are needed to corroborate these pilot data and assess intravascular neutrophil residency in other disease etiologies.