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Objective: Tissue uptake of 2-deoxy-2-fluorine-18 fludeoxyglucose (18F-FDG) is routinely quantified as standardized uptake value (SUV), which in general is the fraction (F) of administered activity per millilitre of tissue multiplied by an index of body size, usually weight (W), i.e. F/ml × W = SUV or F/ml = SUV × (1/W). Other indices have been suggested as preferable to W, especially lean body mass (LBM) and body surface area (BSA), The second equation mentioned above shows that the reciprocal of the ideal index should correlate closely with F/ml and give a regression line through the origin. The purpose of this study was to determine which of these three indices best meets these criteria. Methods: Data were evaluated from 49 males and 51 females undergoing routine 18F-FDG positron emission tomography/CT. A 3 cm diameter region of interest was drawn over the liver and F/ml recorded. LBM and BSA were estimated from height and weight. Results: Based on all patients, the reciprocals of the three indices gave similar correlation coefficients with F/ml, but only 1/LBM gave regressions close to the origin. Intercepts were significantly higher for females for 1/W and 1/BSA, consistent with females having more body fat, but there was no significant difference with 1/LBM. Conclusion: LBM is the best index on which to base SUV because adipose tissue accumulates less 18F-FDG than other soft tissues. Advances in knowledge: The value of this study lies in its use of a novel, more rational approach than previously to confirm that SUV should be based on LBM. [ABSTRACT FROM AUTHOR]

Competing Interests: DECLARATION OF COMPETING INTEREST The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kevin Cheng reports a relationship with British Heart Foundation that includes: funding grants. Ranil de Silva reports a relationship with British Heart Foundation that includes: funding grants. Ranil de Silva reports a relationship with Neovasc Inc that includes: consulting or advisory, funding grants, and speaking and lecture fees. Ranil de Silva reports a relationship with Shockwave Medical Inc that includes: consulting or advisory, funding grants, and speaking and lecture fees. Ranil de Silva reports a relationship with Abbott Vascular Inc that includes: consulting or advisory, funding grants, and speaking and lecture fees. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Background: Refractory angina leads to a poor quality of life and increased healthcare resource utilization. In this growing population of patients, multiple mechanism(s) of ischaemia may co-exist, including functional disorders of the coronary microcirculation. There are few evidence-based effective therapies resulting in a large unmet clinical need., Case Summary: A 38-year-old woman with refractory angina was referred with daily chest pain despite multiple anti-anginal medications and previous percutaneous coronary intervention. Cardiac magnetic resonance imaging demonstrated apical hypertrophic cardiomyopathy (HCM). Rubidium-82 positron emission tomography (PET) with regadenoson stress confirmed significant myocardial ischaemia in the apex and apical regions (16% of total myocardium) with a global myocardial perfusion reserve (MPR) of 1.23. Coronary angiography confirmed patent stents and no epicardial coronary artery disease. Therefore, the mechanism of ischaemia was thought attributable to coronary microvascular dysfunction (CMD) in the context of HCM. In view of her significant symptoms and large burden of left-sided myocardial ischaemia, a Coronary Sinus Reducer (CSR) was implanted. Repeat PET imaging at 6 months showed a marked reduction in ischaemia (<5% burden), improvement in global MPR (1.58), symptoms, and quality of life., Conclusion: In refractory angina, ischaemia may be due to disorders of both the epicardial and coronary microcirculations. The CSR is a potential therapy for these patients, but its mechanism of action has not been confirmed. This report suggests that CSR implantation may reduce myocardial ischaemia and improve symptoms by acting on the coronary microcirculation. The efficacy of CSR in patients with CMD and its mechanism of action on the coronary microcirculation warrant further investigation., Competing Interests: Conflict of interest: None declared., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Objective: Myocardial blood flow (MBF) is measured with 82 Rb using non-linear, least-squares computerised modelling. The study aim was to explore the feasibility of Gjedde-Patlak-Rutland (GPR) graphical analysis as a simpler method for measuring MBF., Methods: Patients had myocardial perfusion imaging using adenosine (n = 45) or regadenoson (n = 33) for stressing. Blood 82 Rb clearance into myocytes (K 1 ) was measured from Cedar-Sinai QPET software using the modified Crone-Renkin equation of Lortie et al. (K 1  = [1-0.77 × e -B/MBF ] × MBF) to convert K 1 to MBF (ml/min/100 ml), where B (63 ml/min/100 ml) is myocardial permeability-surface area product. Using aorta or left ventricular cavity (LV) to measure arterial blood 82 Rb concentration, blood 82 Rb clearance into myocardium (Z) was measured from GPR analysis based on data acquired between 1 and 3 min post-injection. As units of K 1 and Z are, respectively, ml/min/ml intracellular space and ml/min/ml total tissue including extracellular space, myocardial extracellular fluid volume (ECV) is 1 - [Z/K 1 ]. Using Z/K 1 (see Results) to modify its index, the Lortie equation was changed to Z = (1-0.77 × [Formula: see text]e -B Z /MBF Z )*MBF Z , following which MBF Z was calculated from Z. In GPR analysis, spillover of activity from LV to myocardium conveniently 'drops out' in the intercept of the plot., Results: Both agents increased myocardial blood flow almost equally. ECV was ~ 35 ml/100 ml at rest, increasing to ~ 40 ml/100 ml after stress. Z/K 1 , averaged between stress, rest, stressing agents and arterial ROI, was 0.62, so B Z was taken as 39 (i.e. 0.62 × 63) ml/min/100 ml. Based on LV, MBF Z (y) correlated with MBF (x): y = 0.43x + 22 ml/min/100 ml; r = 0.84; n = 156). Their respective stress/rest ratios showed a moderate correlation (r = 0.64; n = 78)., Conclusions: GPR analysis offers promise as a valid and analytically simpler technique for measuring myocardial blood flow, which, as with any clearance measured from GPR analysis, has units of ml/min/ml total tissue volume, and merits development as a polar map display.

Aim: The study aim was to compare the kinetics of the potassium analogue, 82 Rb, between spleen, liver and kidney., Methods: Patients had myocardial stress/rest perfusion imaging using adenosine (n = 45) or regadenoson (n = 33) for stressing. Hepatic arterial (HAP), splenic (SP) and renal (RP) perfusions were measured from first-pass and blood 82 Rb clearances (Ki) from Gjedde-Patlak-Rutland graphical analysis of data between 1 and 2 min postinjection, using regions of interest over left ventricular cavity or abdominal aorta to monitor arterial concentration. Tissue 82 Rb extraction efficiency (E) was calculated as [Ki/perfusion]*100. Tissue extracellular fluid volume (ECV) was derived from the GPR plot intercept., Results: SP (24%) and RP (23%) increased after regadenoson but decreased (-41% and -19%) after adenosine. HAP increased after adenosine (91%) and regadenoson (68%). Resting E was high in kidney (69%) and low in spleen (26%). After adenosine, it increased to 91% in kidney and 49% in spleen. Assuming an arterial contribution of 25% to hepatic blood flow, resting E in liver was estimated as 23%. Relationships between Ki and perfusion in spleen and kidney were consistent with the Crone-Renkin equation (Ki = [1 - A.e -B/perfusion ]*perfusion), with respective values of A of 0.95 and 0.94 and B of 31 and 186 ml/min/100 ml. Splenic ECV decreased following adenosine from 62 to 39 ml/100 ml and showed a logarithmic correlation with SP., Conclusion: Kidney, spleen and liver display contrasting tissue kinetics. E is high in kidney and low in spleen and liver. Spleen is erectile, collapsing when perfusion decreases., (© 2021 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.)

Objectives: The hepatic arterial buffer response is a mechanism mediated by adenosine whereby hepatic arterial perfusion (HAP) increases when portal flow decreases, and is implicated in liver disease. The first study aim was to measure HAP in patients undergoing myocardial perfusion imaging (MPI), thus developing hepatic arterial rest/stress perfusion imaging (HAPI). The second aim was to compare adenosine-induced changes in splenic perfusion (SP) and HAP with corresponding changes in myocardial blood flow (MBF)., Methods: Patients had MPI with 82 Rb PET/CT using adenosine (n = 45) or regadenoson (n = 33) for stressing. SP and HAP were measured using a first-pass technique that gives HAP rather than total hepatic perfusion. Renal perfusion (RP) was also measured., Results: Mean MBF and HAP increased after both adenosine ([stress-rest]/rest 1.1 and 0.8) and regadenoson (1.4 and 0.6), but the respective changes did not correlate. After adenosine, SP (- 0.48) and RP (- 0.26) both decreased. The change in SP correlated positively with the change in MBF (r = 0.36; p = 0.015) but did not correlate with change in HAP. After regadenoson, SP (0.2) and RP (0.2) both increased. The changes in SP correlated with the changes in MBF (r = 0.39; p = 0.025) and HAP (r = 0.39; p = 0.02). Changes in RP correlated with changes in HAP (r = 0.51; p = 0.0008) but not MBF. Resting SP (r = 0.32; p = 0.004), but not resting HAP, correlated with hepatic fat burden. Adenosine-induced change in HAP also correlated with hepatic fat (r = 0.29; p = 0.05)., Conclusion: HAPI could be a useful new hepatic function test. Neither splenic 'switch-off' nor hepatic arterial 'switch-on' identifies adequacy of stress in MPI., Key Points: • This article describes a new method for assessing arterial perfusion of the liver and its capacity to respond to an infusion of adenosine, a substance that normally 'drives' hepatic arterial flow. • Hepatic arterial flow increased in response to adenosine, sometimes dramatically. Adenosine is already used clinically to stimulate myocardial blood flow in patients with suspected coronary disease, but the increase in flow did not correlate with the corresponding increase in hepatic arterial flow. • Analogous to the use of adenosine in the myocardium, the increase in hepatic arterial flow in response to adenosine has the potential to be a new clinically useful method for the evaluation of hepatic arterial haemodynamics in liver disease.

The aim of the present study is to evaluate the intra- and inter-observer agreement in assessing the renal function by means of 99m Tc-MAG3 diuretic renography. One hundred and twenty adults were enrolled in the study. One experienced and one junior radiographer processed the renograms twice by assigning manual and semi-automated regions of interest. The differential renal function (DRF, %), time to maximum counts for the right and left kidney (T maxR -T maxL , min) and time to half-peak counts (T 1/2 , min) were calculated. The Bland-Altman analysis (bias±95% limits of agreement), Lin's concordance correlation coefficient and weighted Fleiss' kappa coefficient were used to assess agreement. Based on the Bland-Altman analysis, the intra-observer repeatability results for the experienced radiographer using the manual and the semi-automated techniques were 0.2 ± 2.6% and 0.3 ± 6.4% (DRF), respectively, -0.01 ± 0.24 and 0.00 ± 0.34 (T maxR ), respectively, and 0.00 ± 0.26 and 0.00 ± 0.33 (T maxL ), respectively. For the junior radiographer, the respective results were 0.5 ± 5.0% and 0.8 ± 9.4% (DRF), 0.00 ± 0.44 and 0.01 ± 0.28 (T maxR ), and 0.01 ± 0.28 and -0.02 ± 0.44 (T maxL ). The inter-observer repeatability for the manual method was 0.6 ± 5.0% (DRF), -0.10 ± 0.42 (T maxR ) and -0.05 ± 0.38 (T maxL ), and for the semi-automated method -0.2 ± 9.1% (DRF), 0.00 ± 0.31 (T maxR ) and -0.05 ± 0.40 (T maxL ). The weighted Fleiss' kappa coefficient for the T 1/2 assessments ranged between 0.85-0.97 for both intra- and inter-observer repeatability with both methods. These findings suggest a very good repeatability in DRF assessment with the manual method-especially for the experienced observer-but a less good repeatability with the semi-automated approach. The calculation of T max was also operator-dependent. We conclude that reader experience is important in the calculation of renal parameters. We therefore encourage reader training in renal scintigraphy. Moreover, the manual tool seems to perform better than the semi-automated tool. Thus, we encourage cautious use of automated tools and adjunct validation by manual methods where possible.

Because of obesity, non-alcoholic fatty liver disease (NAFLD) is becoming increasingly important. 10% of NAFLD patients develop non-alcoholic steatohepatitis (NASH), which may progress to cirrhosis and is now the leading indication for liver transplantation in the Western world. Prefibrotic NASH can only be reliably diagnosed by biopsy. However, given its success in other inflammatory diseases, PET/CT with 18 F-fluorodeoxyglucose (FDG), although non-specific, may offer a promising approach to diagnosing not only NASH but also other inflammatory liver conditions. In addition, FDG PET has generated pathophysiological information on hepatic glucose metabolism and, diagnostically, used liver for quantification of tumour FDG accumulation (e.g. Deauville scoring). A review of hepatic FDG PET is therefore timely. There are two general approaches to the quantification of hepatic FDG accumulation: firstly, standard uptake value (SUV) and secondly dynamic PET. SUV is a poor index of hepatic metabolic function because most hepatic FDG (~75%) is un-phosphorylated 60-min postinjection. Hepatic fat is increased in NAFLD but accumulates negligible FDG. Because fat distribution is heterogeneous, maximum pixel SUV is therefore preferred to mean pixel SUV. Computer modelling of dynamic PET dissects the transport constants governing hepatic FDG kinetics but is challenged by the liver's dual blood supply. Graphical analysis is less informative but more robust and will be the preferred clinical approach to measurement of hepatic FDG phosphorylation. Previous dynamic PET studies have ignored hepatic fat and therefore potentially underestimated glucose accumulation in patients with hepatic steatosis. Future work should use graphical analysis of dynamic PET and correction for hepatic fat., (© 2020 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.)

Competing Interests: There are no conflicts of interest.

Aim: The study aim was to investigate the relationships of blood glucose level (BGL) with hepatic and splenic blood FDG clearances (Ki) in patients with diabetes mellitus (DM) and/or hepatic steatosis (HS)., Methods: This was a retrospective study of 238 patients, including 92 with type 2 DM (DM2) and 11 with type 1 DM (DM1), having routine whole body FDG PET/CT. Patients with lymphoma were excluded. Patients were divided into the following groups: HS-DM-, HS-DM2+, HS+DM-, HS+DM2+ and 2 DM1 groups (hypoglycaemic and hyperglycaemic). ROI were placed over liver and spleen for measurement of SUV max , and left ventricular cavity (LV) for measurement of SUV mean . Tissue SUV max was divided by LV SUV mean . This division, giving Z, eliminates bias from the whole body metric used to calculate SUV and renders SUV max a closer surrogate of Ki. HS was diagnosed when hepatic unenhanced CT was ≤40 HU., Results: In all patients, individual hepatic Z and individual splenic Z correlated significantly with individual BGL. Highest mean hepatic Z and highest mean BGL were recorded in HS+ DM2+ group and lowest in hypoglycaemic DM1 group. Patients with DM1 and hyperglycaemia showed low hepatic Z in relation to BGL. Hepatic and splenic Z correlated inversely with CT density in patients without DM but not in those with DM2., Conclusion: As BGL increases, hepatocyte glucokinase is up-regulated. This includes patients with HS and DM2 but not DM1. We speculate that in HS and DM2, up-regulation results from insulin resistance and hyperinsulinaemia. The data also support a hepato-splenic metabolic axis., (© 2019 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.)

We aimed to use simple physiological equations to show similarities and differences in blood fluorine-18-fluorodeoxyglucose (F-FDG) clearance in the liver (Ki) and distribution volume (V0) in the liver, respectively, generated from nonlinear least squares computer modelling and Gjedde-Patlak-Rutland graphical analysis of dynamic F-FDG PET. We show theoretically that when, as is usually the case, vascular fraction (fraction of liver occupied by blood, Vb) is included as a parameter in modelling but ignored in graphical analysis, the ratio of Ki values, respectively, generated by graphical anlaysis (Ki) and by modelling (Ki) is equal to 1-Vb. This theoretical prediction was then confirmed from dynamic PET data acquired in a clinical population of patients undergoing routine F-FDG PET/computed tomography and from a review of the literature in which it can be seen that Ki/Ki ranges from 0.47 to 0.98. When Vb is not included as a parameter in modelling, Ki is theoretically equal to Ki and to V0·k3, and V0 is equal to V0. There are several attractions to normalising Ki to V0 with respect to liver. Thus, first, there is no need to correct imaging for photon attenuation. Second, it makes no difference whether uptake constant is expressed as blood or plasma clearance. Third, it circumvents the effects of hepatic fat, which, because it accumulates negligible F-FDG, physically dilutes the F-FDG signal and reduces both uptake constant and distribution volume.

The numerator and denominator of the left-hand side of the Gjedde-Patlak-Rutland (GPR) equation for measurement of blood fluorine-18 fluorodeoxyglucose (F-FDG) clearance into tissue (Ki) are the standardized uptake values (SUVs) of tissue and blood, respectively. The extent to which normalized time (NT) in the GPR equation exceeds real time depends on half-time of clearance of F-FDG from blood. A literature review shows that NT is fairly constant, about 100 min at 60 min postinjection of F-FDG, in keeping with our own finding of no significant difference in maximum SUV in blood 60 min postinjection of F-FDG between 39 patients with F-FDG-avid malignancy on routine PET/CT (1.74±0.31) and 21 patients with normal PET/CT (1.79±0.32), and similar blood glucose levels (BGLs). Volume of distribution (V0) in the GPR equation is ∼0.4 ml/ml for brain and ∼0.9 ml/ml for lean liver. Using these values of V0 and an NT of 100 min, we used the GPR equation to calculate Ki from our own published values of SUVliver/SUVblood and SUVbrain/SUVblood at 60 min postinjection, obtaining 0.0045 ml/min/ml for liver and 0.036 ml/min/ml for brain at BGL of 5 mmol/l. These values for Ki at this BGL are close to literature values of Ki, which for liver and brain are ∼0.0033 and ∼0.035 ml/min/ml, respectively. We conclude, therefore, that following division with blood pool SUV, tissue SUV becomes a closer surrogate of Ki. This division also eliminates the controversy over which whole body metric to use in the calculation of SUV.

Aim: Hepatic steatosis is associated with insulin resistance and hyperinsulinaemia. Insulin stimulates hepatic glucokinase, even in insulin resistance, so hepatic glucose uptake is increased in hepatic steatosis. The study hypothesis was that hepatic glucose uptake is also influenced locally by fat, the hepatic distribution of which is heterogeneous., Patients and Methods: Sixty patients undergoing PET/CT using fluorine-18-fluorodeoxyglucose (F-FDG) had dynamic imaging of the liver for 30 min after injection before undergoing whole-body PET/CT at 60 min after injection. Hepatic F-FDG uptake was measured using Gjedde-Patlak-Rutland graphical analysis. Plot gradient (Ki), which represents hepatic blood clearance of F-FDG to phosphorylation, was normalized to intercept [V(0)], which represents the hepatic F-FDG distribution volume. The 60 min computed tomography (CT) was co-registered on to each of the 30 dynamic PET frames. This failed in 20 patients. A further seven patients with lymphoma and three with hepatic metastases were excluded. Within transaxial sections, the liver was divided into small regions of interest (ROIs) of 5×5 pixels each in sections of 5 mm (range: 118-586 ROIs/liver). CT density and Ki/V(0) were measured in each ROI., Results: Throughout the 25-pixel ROIs in the individual liver, CT density and Ki/V(0) showed a significant negative correlation in 15/30 patients. It was significantly positive in only three (P=0.01). In some patients, parametric imaging showed regional concordance between Ki/V(0) and hepatic fat, identified as reduced CT density., Conclusion: In addition to systemic influences, hepatic glucose uptake is regionally linked to the distribution of hepatic fat. Increased metabolism could be the cause or result of local fat deposition.

Objectives: To evaluate the effect of pre-scan blood glucose levels (BGL) on standardized uptake value (SUV) in 18 F-FDG-PET scan., Methods: A literature review was performed in the MEDLINE, Embase, and Cochrane library databases. Multivariate regression analysis was performed on individual datum to investigate the correlation of BGL with SUV max and SUV mean adjusting for sex, age, body mass index (BMI), diabetes mellitus diagnosis, 18 F-FDG injected dose, and time interval. The ANOVA test was done to evaluate differences in SUV max or SUV mean among five different BGL groups (< 110, 110-125, 125-150, 150-200, and > 200 mg/dl)., Results: Individual data for a total of 20,807 SUV max and SUV mean measurements from 29 studies with 8380 patients was included in the analysis. Increased BGL is significantly correlated with decreased SUV max and SUV mean in brain (p < 0.001, p < 0.001,) and muscle (p < 0.001, p < 0.001) and increased SUV max and SUV mean in liver (p = 0.001, p = 0004) and blood pool (p = 0.008, p < 0.001). No significant correlation was found between BGL and SUV max or SUV mean in tumors. In the ANOVA test, all hyperglycemic groups had significantly lower SUVs compared with the euglycemic group in brain and muscle, and significantly higher SUVs in liver and blood pool. However, in tumors only the hyperglycemic group with BGL of > 200 mg/dl had significantly lower SUV max ., Conclusion: If BGL is lower than 200 mg/dl no interventions are needed for lowering BGL, unless the liver is the organ of interest. Future studies are needed to evaluate sensitivity and specificity of FDG-PET scan in diagnosis of malignant lesions in hyperglycemia.

Aim: To compare weight, lean body mass and body surface area for calculation of standardised uptake value (SUV) in fluorine-18-fluorodeoxyglucose PET/computed tomography, taking sex into account., Patients and Methods: This was a retrospective study of 161 (97 men) patients. Maximum standardised uptake value (SUVmax) and mean standardised uptake value (SUVmean) were obtained from a 3-cm region of interest over the right lobe of the liver and scaled to weight, scaled to lean body mass (SUL) and scaled to body surface area (SUA). Mean hepatic computed tomography density was used to adjust SUVmean for hepatic fat (SUVFA). Hepatic SUV indices were divided by SUV from left ventricular cavity, thereby, eliminating whole body metric, to obtain a surrogate of blood fluorine-18-fluorodeoxyglucose clearance into liver, and multiplied by blood glucose to give a surrogate of hepatic glucose uptake rate (mSUV)., Results: SULmax, SUAmax and all scaled to weight indices correlated strongly with weight. SULmean, SULFA, SUAmean and SUAFA, however, correlated weakly or not at all with weight, nor with their corresponding whole body metric in men or women, but correlated strongly when the sexes were combined into one group. This was the result of sex differences in SUL (greater in men) and SUA (greater in women). There was, however, no sex difference in mSUV., Conclusion: Weight is unsuitable for calculating SUV. SUL and SUA are also inappropriate as maxima but appropriate as mean and fat-adjusted values. However, SUL is recommended for both sexes because SUA is influenced by both body fat and weight. Sex differences in SUL and SUA give rise to misleading correlations when sexes are combined into one group.

Background Following convection from blood capillaries, plasma proteins are transported to loco-regional lymph nodes in two stages: first, uptake into peripheral lymphatics, and second, transport to nodes. Purpose To introduce a new parameter of lymphatic function that quantifies stage 2 - lymphatic drainage efficiency (LDE). Material and Methods Percentage injected activity (IIQ) in ilio-inguinal nodes 150 min following subcutaneous foot web-space injection of Tc-99 m-nanocolloid was measured in 102 patients undergoing lymphoscintigraphy using a method in which a standard is placed by image guidance over the nodes. Percentage activity leaving the injection depot by 150 min ( k) was measured in 60/102 patients. LDE (%) = 100 × (IIQ/ k). Abnormal lymphoscintigraphy was defined qualitatively as: (i) no activity in ilio-inguinal nodes at 45 min or negligible activity at 150 min (delay); (ii) lymph diversion through skin and/or deep system; and (iii) focal tracer accumulation suggesting cellulitis. Results Scintigraphy was bilaterally normal in 82 limbs, unilaterally normal in 40 limbs and abnormal in 82 limbs. IIQ correlated with k in bilaterally normal (r = 0.86; n = 52), unilaterally normal (r = 0.67; n = 27), and abnormal (r = 0.82; n = 41) limbs. IIQ, k, and LDE were significantly lower in unilaterally normal (9.3 ± 5.4%, 13.8 ± 7.1%, and 65 ± 30%) compared with bilaterally normal limbs (15.4 ± 8.4% [ P > 0.0001], 18.3 ± 8.9% [ P = 0.025], and 84 ± 30% [ P = 0.01]). LDE was lower in limbs displaying skin diversion and/or delay. Conclusion LDE is a new quantitative index that has potential value in clinical research but requires further clinical evaluation. Abnormal quantitative indices indicate that limbs unilaterally normal on lymphoscintigraphy are not functionally normal.

The concept of a hepato-splenic axis has recently been put forward. We aimed to investigate whether hepatic and splenic metabolic activities are linked, and if splenic metabolic activity is increased in non-alcoholic fatty liver disease (NAFLD). Blood clearance rates of phosphorylated 18 F-fluorodeoxyglucose were measured in the spleen and liver from dynamic PET using Gjedde-Patlak-Rutland graphical analysis and abdominal aorta for input function in 59 patients undergoing routine PET/CT. Plot gradient (Ki), which represents blood clearance, was divided by intercept (V(0)), which represents tissue FDG distribution volume, and multiplied by blood glucose to give glucose uptake rate per unit tracer distribution volume (MRglu). In addition, liver-to-spleen raw count rate ratio was plotted against time, and gradient (b) divided by intercept (A) to obtain hepatic-to-splenic blood clearance ratio independent of aortic input function. Hepatic steatosis was inferred when hepatic CT density was ≤40 HU. There was no difference in splenic MRglu between 8 patients with inactive lympho-proliferative disease (LPD) as identified by negative PET/CT, 25 with non-haematological malignancy and 13 with normal PET/CT. It was significantly increased in 13 with active LPD, who were therefore excluded, along with 3 more with type-2 diabetes mellitus. Splenic MRglu was higher in patients with hepatic steatosis (4.0±1.6; n = 12) than without (2.6±1.7 μmol/min/100 ml; P = 0.02) and correlated inversely with hepatic CT density (r = -0.49; P<0.001). Hepatic and splenic Ki/V(0) correlated (r = 0.52; P<0.01) in 22 patients in whom the correlation coefficient between b/A and hepatic-to-splenic Ki/V(0) ratio was 0.99 and in whom, therefore, input function errors in graphical analysis could be discounted. In men, splenic longitudinal diameter correlated significantly with hepatic CT density (r = -0.35; P = 0.046), hepatic MRglu (r = 0.44; P = 0.005) and splenic MRglu (r = 0.35; P = 0.046). Splenic Ki/V(0) correlated positively with blood glucose, suggesting sensitivity to insulin. We conclude that hepatic and splenic metabolic activities are linked and that a speculative mechanism, which deserves further investigation, is shared insulin sensitivity. Splenic MRglu and spleen size are increased in NAFLD., Competing Interests: None.

Background: Familial dyslipidemias of either heterozygous (heFH) or combined (FCH) type lead to accelerated atherogenesis and increased cardiovascular risk., Objective: The aim of this study was to investigate in statin-naïve adult patients with familial dyslipidemias whether inflammatory activation and liver, spleen and bone marrow metabolic activity differ compared with normolipidemic subjects and between dyslipidemic groups., Methods: Fourteen patients with FCH, 14 with heFH, and 14 normolipidemic individuals were enrolled. Serum lipids, high-sensitivity C-reactive protein, and fibrinogen levels were measured, followed by 18 F-fluorodeoxyglucose positron-emission tomography/computed tomography imaging. Radiotracer uptake in the aortic wall, spleen, bone marrow, and liver was quantified as tissue-to-background ratio (TBR)., Results: Patients with heFH had significantly higher low-density lipoprotein levels compared with those with FCH and controls (P < .001). However, aortic TBRs were higher in FCH compared with heFH patients and controls (P = .02 and P < .001, respectively). FCH patients exhibited higher FDG uptake in the spleen compared with controls (P = .05). In addition, FCH exhibited higher bone marrow FDG uptake compared with heFH patients and controls (P = .03 and P = .02, respectively). FCH had higher liver uptake compared with heFH patients and controls (P < .001 for both). Significant correlations were observed between inflammatory biomarkers and imaging indices as well as between aortic TBR and FDG uptake of hematopoietic organs and liver., Conclusions: Systemic, as well as vascular inflammation and spleen, bone marrow, and hepatic metabolic activity are increased in patients with FCH despite lower levels of low-density lipoprotein., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Purpose: In FDG PET/CT, standardized uptake value (SUV) is used to measure metabolic activity but detects un-phosphorylated FDG as well as phosphorylated FDG (FDG6P). Our aim was to determine the proportions of intrahepatic and intrasplenic FDG that are phosphorylated after FDG injection and compare them with SUVs., Methods: Sixty patients undergoing whole-body PET/CT 60 min post-injection of FDG first had dynamic PET imaging for 30 min with measurement of hepatic and splenic FDG clearances using Patlak-Rutland analysis. The gradient of the Patlak-Rutland plot, which is proportional to clearance (Ki), was normalized to the intercept, which is proportional to FDG distribution volume (V(0)) with the same proportionality constant. Using measured values of Ki/V(0), FDG6P/FDG ratios as functions of time in the two organs were measured for assumed FDG blood disappearance half-times of 40, 50 and 60 min. Hepatic and splenic SUVs were measured from whole-body PET/CT., Results: The mean (SD) Ki/V(0) was 0.0036 (0.0021) and 0.0060 (0.0041) ml/min/ml for the liver and spleen, respectively, but the hepatic SUV was 1.36-fold higher than the splenic SUV. This discrepancy was explained by the hepatic V(0) being 1.6-fold higher than the splenic V(0). The percentages of FDG phosphorylated 60 min post-injection were 27, 25 and 23% for the liver and 39, 36 and 34% for the spleen, for blood clearance half-times of 40, 50 and 60 min, respectively. SUV indices correlated poorly with Ki/V(0) for both organs., Conclusions: SUV is largely determined by un-phosphorylated FDG in dynamic exchange with blood FDG, explaining the poor correlations between SUV indices and Ki/V(0).

Objective: In fluorine-18 fludeoxyglucose positron emission tomography/CT, hepatic standardized uptake value (SUV) is reduced through "signal dilution" by hepatic fat. The maximum SUV (SUV max ) is less affected than the mean SUV (SUV mean ), therefore SUV max /SUV mean correlates with hepatic fat. The SUV can be corrected for signal dilution using an equation relating CT density (CTD) to %fat. The objective was to exploit the relationship between SUV indices and CTD to assess the validity of two previously published equations (one linear and one sigmoid) for estimating %fat from CTD and two new exponential equations., Methods: Study population comprised 465 patients having routine fluorine-18 fludeoxyglucose positron emission tomography/CT. The SUV max , SUV mean and CTD were measured from a 3-cm-diameter region of interest over the liver. The exponential equations assumed that 100% fat corresponds to CTD of -50 or -100 HU. The proportion of liver occupied by fat (P F ) was estimated from all four equations. Then fat-corrected SUV mean is SUV mean /(1 - P F ). The ideal equation should give SUV mean approaching but not exceeding SUV max and give fat-corrected SUV mean /SUV max that shows no correlation with CTD., Results: The linear equation failed at CTD values exceeding 55.8 HU because it gave negative P F values. Moreover, fat-corrected SUV mean /SUV max still correlated with CTD. The sigmoid equation grossly overcorrected SUV mean at low CTD. The exponential equations abolished the correlation between fat-corrected SUV mean /SUV max and CTD., Conclusion: The sigmoid equation is unsuitable for estimating %fat from CTD. The linear equation performed well, but the exponential equation assuming that 100% fat corresponds to -50 HU performed best. Advances in knowledge: Improved (exponential) equations to estimate hepatic fat from hepatic CTD.

Differences in glucose metabolism between men and women have previously been reported. Our purpose was to determine if there is a gender difference in fasting hepatic glucose uptake (MRglu). Fifty-five patients (44 men, 11 women) referred for routine PET/CT using the glucose tracer 2-deoxy-2-[F-18]fluoro-D-glucose (FDG), mainly for cancer, had dynamic imaging for 30 min immediately following injection. Hepatic FDG clearance (mL/min/100 mL) was measured as gradient divided by intercept from Patlak-Rutland graphical analysis using a volume of interest over the abdominal aorta to record input function. Hepatic MRglu was obtained by multiplication of clearance by blood glucose concentration. Hepatic steatosis was diagnosed as CT density ≤40 HU Mean (standard deviation) hepatic MRglu in 44 men was 2.30 (1.14) μ mol/min/100 mL, significantly higher than in 11 women in whom it was 1.07 (1.35) μ mol/min/100 mL ( P  = 0.003). CT density was 52 (12) HU in women compared with 45 (9) HU in men ( P  = 0.04), but there was no significant difference in blood glucose, BMI, or prevalence of recent chemotherapy (within 6 months preceding PET/CT). When patients were subdivided into those without hepatic steatosis (31 men/9 women), those without evidence of FDG-avid malignancy on PET/CT (15/6), and those without either (11/5), gender differences in hepatic MRglu remained highly significant, but there were no significant differences in CT density, blood glucose, BMI, or recent chemotherapy history. Despite this being a population of clinically referred patients, the results strongly suggest that fasting hepatic MRglu is higher in men than in women., (© 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

Aims: The aims of this study were to improve the quantification of lower extremity lymphoscintigraphy, determine its value and lower limit of normal, and determine whether intermediate postinjection time imaging is necessary., Patients and Methods: This was a study of 102 consecutive patients undergoing routine lower extremity lymphoscintigraphy using subcutaneous Tc-99m-nanocolloid with imaging at 5, 45 and 150 min after injection. Abnormal imaging criteria were delay (no activity in ilio-inguinal nodes at 45 min or negligible activity at 150 min), lymph diversion (through skin or deep system) and focal accumulation suggesting cellulitis. Lymphatic function was quantified as % injected activity in ilio-inguinal nodes at 150 min (IIQ) using a standard placed, by image guidance, exactly over the nodes., Results: Forty-one patients had bilateral normal scintigraphy. IIQ was normally distributed in 15 limbs, with IIQ of 1-7.5%. In contrast, it was log-normally distributed in 68 limbs, with IIQ of at least 7.5%, suggesting 8% as the lower limit of normal. In 57 limbs, delay was the only scintigraphic abnormality at 45 min. Of these, 33 were abnormal at 150 min. Of the remaining 24 limbs, 17 had reduced IIQ; thus, 50 of these 57 (88%) limbs had lymphatic dysfunction. The seven limbs that remained normal at 150 min were in six patients. The contralateral limb was abnormal in five of these six patients; hence, lymphatic dysfunction would have been missed in only one patient without 45 min imaging., Conclusion: IIQ is strongly recommended. Isolated delay at 45 min is abnormal. However, 45 min imaging is not necessary if IIQ is performed.

Splenic pathophysiology has been relatively unstudied, but recently, the spleen has received more attention as a result of the discovery of the 'cardiosplenic axis'. This term describes a role that the spleen plays in the progression of atherosclerosis following acute myocardial infarction. Human studies of this axis have largely used fluorine-18-fluorodeoxyglucose (F-FDG) PET/CT to quantify peri-infarction inflammation, arterial wall inflammation and splenic metabolic activity. Most of these studies have quantified arterial wall inflammation and splenic metabolic activity using the standardized uptake value, but this is a semiquantitative measurement with several drawbacks, including overestimation of metabolic activity in overweight individuals and a dependence on blood glucose levels. A better approach to the measurement of metabolic activity using F-FDG is to measure tissue F-FDG clearance from dynamic imaging and Patlak-Rutland graphical analysis. This is the preferred approach for future human studies of the cardiosplenic axis that will be required to better define the nature of the spleen's role.

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/m 2 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., (© 2016 The Author(s).)

Objectives: Hepatic steatosis is common but less is known of the heterogeneity of hepatic fat distribution and its clinical significance. Our objective was to measure the regional variabilities within the liver of standardised uptake values (SUV) as potential markers of hepatic fat distribution heterogeneity., Methods: Twenty-four patients having routine, clinically indicated PET/CT with (18)F-FDG and a wide range of fatty liver severity were selected. Maximum SUV (SUVmax), average SUV (SUVave), both calculated using lean body mass, and CT density were measured in 12 × 2-cm diameter ROIs in each patient. SUVave was also measured over the left ventricular cavity (SUVLV). Mean values of SUV indices, their ratios with SUVLV, and CT density in the 12 ROIs were calculated. Regional variabilities of SUV indices were expressed as coefficients of variation (CV; standard deviation/mean). Body mass index (BMI) was estimated from height and body weight, and %body fat and lean body mass from height, weight and gender., Results: Mean SUVmax/SUVave correlated significantly with mean CT density (r = -0.51; p < 0.02). In contrast, mean SUVmax, mean SUVave and their ratios with SUVLV showed no correlation with CT density. Mean CT density correlated with weight (r = -0.59; p < 0.005), BMI (r = -0.57; p < 0.01) and %body fat (r = -0.49; p < 0.02). Corresponding correlation coefficients for mean SUVmax/SUVave were 0.74 (p < 0.001), 0.65 (p < 0.001) and 0.46 (p < 0.03). In contrast, mean SUVmax, mean SUVave and their ratios with SUVLV showed no correlation with BMI, weight and %body fat. The CV of SUVmax/SUVave (r = -0.67; p < 0.001), but not the CVs of SUVmax or SUVave, correlated with mean CT density., Conclusions: SUVmax/SUVave and CT density are markers of hepatic steatosis. The regional variability of SUVmax/SUVave may be a marker of hepatic fat distribution heterogeneity. The novel concept is introduced that hepatic fat distribution heterogeneity may be a marker of hepatic pathology and of clinical value, and deserves further exploration with texture analysis.

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., (Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Purpose: To compare normalisation to blood glucose (BG) with scaling to hepatic uptake for quantification of tumour (18) F-FDG uptake using the brain as a surrogate for tumours., Methods: Standardised uptake value (SUV) was measured over the liver, cerebellum, basal ganglia, and frontal cortex in 304 patients undergoing (18) F-FDG PET/CT. The relationship between brain FDG clearance and SUV was theoretically defined., Results: Brain SUV decreased exponentially with BG, with similar constants between cerebellum, basal ganglia, and frontal cortex (0.099-0.119 mmol/l(-1)) and similar to values for tumours estimated from the literature. Liver SUV, however, correlated positively with BG. Brain-to-liver SUV ratio therefore showed an inverse correlation with BG, well-fitted with a hyperbolic function (R = 0.83), as theoretically predicted. Brain SUV normalised to BG (nSUV) displayed a nonlinear correlation with BG (R = 0.55); however, as theoretically predicted, brain nSUV/liver SUV showed almost no correlation with BG. Correction of brain SUV using BG raised to an exponential power of 0.099 mmol/l(-1) also eliminated the correlation between brain SUV and BG., Conclusion: Brain SUV continues to correlate with BG after normalisation to BG. Likewise, liver SUV is unsuitable as a reference for tumour FDG uptake. Brain SUV divided by liver SUV, however, shows minimal dependence on BG., Key Points: • FDG standard uptake value in tumours helps clinicians assess response to treatment. • SUV is influenced by blood glucose; normalisation to blood glucose is recommended. • An alternative approach is to scale tumour SUV to liver SUV. • The brain used as a tumour surrogate shows that neither approach is valid. • Applying both approaches, however, appropriately corrects for blood glucose.

To understand pitfalls and limitations in adult renography, it is necessary to understand firstly the physiology of the kidney, especially the magnitude and control of renal blood flow, glomerular filtration rate and tubular fluid flow rate, and secondly the pharmacokinetics and renal handling of the three most often used tracers, Tc-99m-mercaptoacetyltriglycine (MAG3), Tc-99m-diethylene triamine pentaacetic acid (DTPA) and Tc-99m-dimercaptosuccinic acid (DMSA). The kidneys may be imaged dynamically with Tc-99m-MAG3 or Tc-99m-DTPA, with or without diuretic challenge, or by static imaging with Tc-99m-DMSA. Protocols are different according to whether the kidney is native or transplanted. Quantitative analysis of dynamic data includes measurement of renal vascularity (important for the transplanted kidney), absolute tracer clearance rates, differential renal function (DRF) and response to diuretic challenge. Static image reveals functional renal parenchymal damage, both focal and global, is useful in the clinical management of obstructive uropathy, renal stone disease and hypertension (under angiotensin converting enzyme inhibition), and is the preferred technique for determining DRF. Diagnosis based on morphological appearances is important in transplant management. Even though nuclear medicine is now in the era of hybrid imaging, renal imaging remains an important subspecialty in nuclear medicine and requires a sound basing in applied physiology, the classical supporting discipline of nuclear medicine., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: Systemic inflammation impairs brain function and is increasingly implicated in the etiology of common mental illnesses, particularly depression and Alzheimer's disease. Immunotherapies selectively targeting proinflammatory cytokines demonstrate efficacy in a subset of patients with depression. However, efforts to identify patients most vulnerable to the central effects of inflammation are hindered by insensitivity of conventional structural magnetic resonance imaging., Methods: We used quantitative magnetization transfer (qMT) imaging, a magnetic resonance imaging technique that enables quantification of changes in brain macromolecular density, together with experimentally induced inflammation to investigate effects of systemic inflammatory challenge on human brain microstructure. Imaging with qMT was performed in 20 healthy participants after typhoid vaccination and saline control injection. An additional 20 participants underwent fluorodeoxyglucose positron emission tomography following the same inflammatory challenge., Results: The qMT data demonstrated that inflammation induced a rapid change in brain microstructure, reflected in increased magnetization exchange from free (water) to macromolecular-bound protons, within a discrete region of insular cortex implicated in representing internal physiologic states including inflammation. The functional significance of this change in insular microstructure was demonstrated by correlation with inflammation-induced fatigue and fluorodeoxyglucose positron emission tomography imaging, which revealed increased resting glucose metabolism within this region following the same inflammatory challenge., Conclusions: Together these observations highlight a novel structural biomarker of the central physiologic and behavioral effects of mild systemic inflammation. The widespread clinical availability of magnetic resonance imaging supports the viability of qMT imaging as a clinical biomarker in trials of immunotherapeutics, both to identify patients vulnerable to the effects of systemic inflammation and to monitor neurobiological responses., (Copyright © 2015 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

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.

Lymphoscintigraphy following subcutaneous injection of a radiolabeled macromolecule, such as Tc-99m-nanocolloid, is used to investigate limb swelling, usually to confirm lymphedema. A well-known abnormal finding is dermal backflow, which occurs a result of diversion of lymph into skin lymphatic vessels. We describe a case in which this important sign was partially obscured by a stocking. The case also illustrates, first, the frequent though poorly recognized occurrence of lymphatic dysfunction in the clinically normal contralateral limb of a patient with unilateral swelling, and second, the principle underlying treatment with compression hosiery. Stockings should be removed before injection and all subsequent imaging.

Objective: The use of liver as a reference tissue for semi-quantification of tumour FDG uptake may not be valid in hepatic steatosis (HS). Previous studies on the relation between liver FDG uptake and HS have been contradictory probably because they ignored blood glucose (BG). Because hepatocyte and blood FDG concentrations equalize, liver FDG uptake parallels BG, which must therefore be considered when studying hepatic FDG uptake. We therefore re-examined the relation between HS and liver uptake taking BG into account., Methods: This was a retrospective study of 304 patients undergoing routine PET/CT with imaging 60min post-FDG. Average standard uptake value (SUVave), maximum SUV (SUVmax) and CT density (index of HS) were measured in a liver ROI. Blood pool SUV was based on the left ventricular cavity (SUVLV). Correlations were assessed using least squares fitting of continuous data. Patients were also divided into BG subgroups (<4, 4-5, 5-6, 6-8, 8-10 and 10+mmol/l)., Results: SUVave, SUVmax and SUVLV displayed similar relations with BG. SUVmax/SUVLV, but not SUVave/SUVLV, correlated significantly with BG. SUVmax, but not SUVave, correlated inversely with CT density before and after adjusting for BG. SUVmax/SUVave correlated more strongly with CT density than SUVmax. CT density correlated inversely with SUVmax/SUVLV but positively with SUVave/SUVLV., Conclusions: Hepatic SUV is more influenced by BG than by HS. Its relation with BG renders it unsuitable as a reference tissue. Nevertheless, hepatic fat does correlate positively with liver SUV, although this is seen only with SUVmax because SUVave is 'diluted' by hepatic fat., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

This is a case of a 54 years old woman with fever of unknown origin. Physical examination showed nothing remarkable. Chest radiographs, abdominal ultrasound examination (US) and chest-abdominal-pelvic CT, showed segmental thickening of the wall of the aorta. On admission, the C-reactive protein level and the erythrocyte sedimentation rate were elevated. (18)Fluoro-fluorodeoxyglucose-positron emission tomography ((18)F-FDG-PET/CT) showed increased uptake of the aorta wall and its main branches that could be indicative of arteritis. The temporal artery biopsy was negative for giant-cell arteritis. The patient responded well to prednisolone treatment. A second (18)F-FDG-PET/CT scan showed great improvement. (18)F-FDG-PET/CT scan early indicates arteritis of the great vessels that in this case was considered to be TA and contributes in monitoring disease activity.