FDG Distribution Pattern Research Articles

The Diagnostic Value of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography for the Detection of Surgical Site Infection after Spine Surgery.

Retrospective case series. The purpose of this study was to assess the diagnostic yield of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) for surgical site infection (SSI) after spine surgery. Diagnosis of SSI in the spine based on F-18 FDG PET/CT requires experienced nuclear medical physicians for a detailed analysis of F-18 FDG distribution pattern. It has also been reported that increases in the maximal standardized uptake values of F-18 FDG (SUVmax) closely correlated with SSI, suggesting potential of more objective and quantitative diagnosis. We assessed the diagnostic yield of F-18 FDG PET/CT (pattern-based diagnosis by nuclear medical physicians and SUVmax-based diagnosis) for SSI in 52 subjects who underwent spine surgery. The 52 subjects included 11 nonimplant and 41 implant cases. F-18 FDG PET/CT was performed in 33 and 19 cases in early (≤12 weeks after the surgery) and late (>12 weeks) phases, respectively. The final diagnosis of SSI was based on the results of pathogen identification, plain radiography, and CT and/or magnetic resonance imaging or response to antibiotics and/or reoperation. SUVmax-based diagnosis was performed with a cut off value of 5.0 as determined by receiver operating characteristic analysis. Both pattern-based and SUVmax-based diagnoses demonstrated excellent diagnostic yields with high sensitivity (97% and 90%), specificity (100% and 100%), and accuracy (98% and 94%). High diagnostic yields (accuracy of ≥90%) were consistently observed irrespective of presence or absence of implantation or interval between surgery and F-18 FDG PET/CT. F-18 FDG PET/CT can be the procedure of choice for investigation of SSI in the spine when other imaging fails to provide a definitive diagnosis.Level of Evidence: 4.

Accuracy of PET/CT in the Diagnosis of Vascular Graft Infections

Introduction - Vascular graft infections (VGI) have an incidence of 1 to 6 %. Positron emission tomography/computed tomography with 18F-fluorodeoxyglucose (FDG-PET/CT) has emerged as a new tool to replace nuclear scintigraphy. However, its clinical reliability is still unknown. The aim of this study was to evaluate the diagnostic accuracy of FDG-PET/CT in a population with suspected VGI and to validate the quantitative value of diagnostic parameters. Methods - This is a retrospective cohort study. FDG-PET/CT was performed in 37 patients with suspected VGI between 2013 and 2017. A reliable culture was obtained in 25 of them and were finally included in the study. VGI was considered proven only in case of a positive culture (blood, peri-graft collections or graft samples. Diagnostic accuracy was assessed comparing culture results (gold standard) with FDG-PET/CT values. We assessed maximal standardized uptake value (SUVmax), tissue-to-background ratio (TBR), and visual parameters (FDG distribution patterns and visual grading scale) in the final confirmation of the diagnosis of AGI. Receiver operating characteristics (ROC) curves were used to assess the ability of SUVmax and TBR to identify the presence and absence of VGI. Results - The mean age was 64.32 ± 16.75 years, 72% were males. Cultures were positive in 20/25 patients. FDG-PET/CT was considered positive in 19/25 patients. Surgery was performed in 13/25 patients. Mortality was 24% (6/25 patients). The most frequent microorganism was Staphylococcus aureus (9/13 patients). All these patients were followed with long-term antibiotic treatment until negativization of tests including FDG-PET / CT. Mean SUVmax was 6.4 ± 3.41 and TBR 2.14 ± 0.5 in all cases. For positives cultures the mean SUVmax was 7.34 ± 3.3 with a TBR 3.73 ±1.7. In the ROC analysis, the area under the curve for SUVmax was 0.56 (95% CI: 0.30-0.84) and for TBR was 0.53 (95% CI:0.27-0.78). A SUVmax cut off point of 4.5 yielded a 91,7% Sensitivity (Sens) and 50% Specificity (Spec). A TBR cut off point of 2.9 yielded 58% Sens and a 60% Spec with a positive predictive value of 73.68% and negative predictive value of 83.33%. Conclusion - FDG-PET/CT may be a useful tool in the diagnosis and surveillance of VGI. Nevertheless, the accuracy of quantitative parameters is jeopardized by the uncertainty of gold standard based on microbiology data. Further and larger registers with standardized measurements are needed to establish a more reliably parameters, necessary to take difficult decisions in this kind of patients. References-Sah BR, Husmann L, Mayer D, Scherrer A, Rancic Z, Puippe G, Weber R, Hasse B; VASGRA Cohort. Diagnostic performance of 18F-FDG-PET/CT in vascular graft infections. Eur J Vasc Endovasc Surg. 2015 Apr;49(4):455-64.-Saleem BR, Berger P, Vaartjes I, de Keizer B, Vonken EJ, Slart RH, de Borst GJ, Zeebregts CJ. Modest utility of quantitative measures in (18)F-fluorodeoxyglucose positron emission tomography scanning for the diagnosis of aortic prosthetic graft infection. J Vasc Surg. 2015 Apr;61(4):965-71.

Morpho-metabolic post-surgical patterns of non-infected prosthetic heart valves by [18F]FDG PET/CTA: "normality" is a possible diagnosis.

To define characteristic PET/CTA patterns of FDG uptake and anatomic changes following prosthetic heart valves (PVs) implantation over time, to help not to misdiagnose post-operative inflammation and avoid false-positive cases. Prospective evaluation of 37 post-operative patients without suspected infection that underwent serial cardiac PET/CTA examinations at 1, 6, and 12 months after surgery, in which metabolic features (FDG uptake distribution pattern and intensity) and anatomic changes were evaluated. Standardized uptake values (SUVs) were obtained and a new measure, the valve uptake index (VUI), (SUVmax-SUVmean)/SUVmax, was tested to homogenize SUV results.In total, 111 PET/CTA scans were performed in 37 patients (19 aortic and 18 mitral valves). FDG uptake was visually detectable in 79.3% of patients and showed a diffuse, homogeneous distribution pattern in 93%. Quantitative analysis yielded a mean maximum standardized uptake value (SUVmax) of 4.46 ± 1.50 and VUI of 0.35 ± 0.10. There were no significant differences in FDG distribution or uptake values between 1, 6, or 12 months. No abnormal anatomic changes or endocarditis lesions were detected in any patient during follow-up. FDG uptake, often seen in recently implanted PVs, shows a characteristic pattern of post-operative inflammation and, in the absence of associated anatomic lesions, could be considered a normal finding. These features remain stable for at least 1 year after surgery, so questioning the recommended 3-month safety period. A new measure, the VUI, can be useful for evaluating the FDG distribution pattern.

Comment on Minamimoto: incidental focal FDG uptake in heart is a lighthouse for considering cardiac screening

Dear Sir,An interesting article has recently been published [1] on theclinical significance of focal cardiac FDG uptake inpatients with unknown cardiac disease studied for unre-lated purposes. The topic is of great interest because thepossibility to identify unexpected cardiac disease duringPET studies could allow an early diagnosis and reduceunfavorable events. The paper suggests a correlationbetween focal cardiac FDG uptake and the likelihood ofcoronary artery disease (CAD) in patients without cardiacsymptoms and unknown cardiac disease. Apart from theinteresting analysis and the effort to identify the clinicalsignificance of focal uptakes, we agree and highlight theremarks and concerns reported by the authors in the paper.The myocardium derives energy from many sources suchas free fatty acid (FFAs), glucose, pyruvate, ketone bodies,lactate, and amino acids [2–4]. In fasting and resting con-dition, heart metabolism is mainly based on FFAs oxida-tion, the myocardial FDG uptake should be negligible,glycolysis contributes only about 30 % of substrate butdietary and hormonal conditions can modify this situation[5]. In the fasting state, the rate of myocardial FFAs oxi-dation is high, inhibiting glycolysis and glucose oxidationwith consequently low levels of glucose and insulin, while,after glucose load or during hyperglycemic condition,plasma concentrations of glucose and insulin rise reducingperipheral lipolysis, lowering plasma concentrations ofFFAs and hence reducing their availability to the myo-cardium. Glucose then becomes the dominant substrate formyocardial energy production [5, 6]. However, the myo-cardial FDG uptake in the fasting healthy subjects variesunder the clinical fasting conditions [7, 8] and increasedFDG uptake in the myocardium does not significantlycorrelate with the blood glucose level, age, or duration offasting in non-diabetic patients [7, 9]. Only in the uncon-trolled diabetic patients with high levels of blood glucosethere is absent or faint myocardial FDG uptake. Myocardialischemia strikingly alters myocardial substrate metabolism[5]. As blood flow and oxygen supply decline, oxidativemetabolism decreases but still remains the dominant sourceof residual ATP production accounting for more than 90 %[10]. Ischemia is also associated with increased glycolysisbut becomes uncoupled from glucose oxidation with excessproduction of pyruvate and lactate which impair glycolysis[4, 11]. In the normal myocardium FDG distribution pat-terns could be classified into three types (absent to faintuptake; regional uptake; diffuse uptake), but they couldhave no specific meaning [7]. Moreover, even in the sameindividual and under similar fasting conditions, the myo-cardial FDG uptake is neither stable nor reproducible andthe transition from the intense FDG uptake of a dominantlyglycolytic myocardial metabolism to the absent FDGuptake of a dominantly FFAs metabolism is not entirelyuniform either temporally or regionally [6]. In daily clini-cal practise, despite adequate fasting period, the pattern ofmyocardial FDG heart uptake varies a lot, making difficultthe differential diagnosis between physiological and path-ological uptakes. For these reasons the results of

PET/MR imaging of the pelvis in the presence of endoprostheses: reducing image artifacts and increasing accuracy through inpainting

In combined whole-body PET/MR, attenuation correction (AC) is performed indirectly using the available MR image information and subsequent segmentation. Implant-induced susceptibility artifacts and subsequent signal voids may challenge MR-based AC (MR-AC). We evaluated the accuracy of MR-AC in PET/MR in patients with metallic endoprostheses, and propose a clinically feasible correction method. We selected patients with uni- or bilateral endoprostheses from 61 consecutive referrals for whole-body PET/MR imaging (mMR; Siemens Healthcare). Simultaneous whole-body PET/MR imaging was performed at 120min after injection of about 300MBq [(18)F]FDG. MR-AC was performed using (1) original MR images and subsequent Dixon water-fat segmentation, (2) as method 1 with implant-induced signal voids filled with soft tissue, (3) as method 2 with superimposed coregistered endoprostheses from the CT scan, and (4) as method 1 with implant-induced signal voids filled with metal. Following MR-AC (methods 1-4) PET emission images were reconstructed on 344 × 344 matrices using attenuation-weighted OSEM (three iterations, 21 subsets, 4mm gaussian). Maximum body-weight normalized standardized uptake values (SUVmax) were obtained for both hips. Mean SUV (SUVmean) in homogeneous reference regions in the gluteal muscle and bladder following MR-AC (methods 1-4) are also reported. In total, four patients presented with endoprostheses, unilateral in two and bilateral in two. The fraction of voxels in MR images affected by the implant was at least twice that of the voxels representing the actual implants. MR-AC using methods 2 and 3 recovered the FDG distribution pattern compared to uncorrected PET images and method 1, while method 4 resulted in severe overestimation of FDG uptake (>460% SUVmax). When compared to method 1, relative changes in SUVmean in the reference regions from method 2 and 3 were generally small albeit not correlated with the fraction of the attenuation image affected by implant-induced artifacts. Endoprostheses cause PET/MR artifacts that exceed the volume occupied by the implants, and bias PET quantification. Artifacts and bias can be corrected by semiautomated inpainting with soft tissue with a single composition prior to MR-AC, thus restoring quantitative activity distribution.

Apport de deux techniques d’analyse automatisées des examens [ 18F] FDG TEP dans la discrimination des patients déments frontotemporaux et malades d’Alzheimer

Introduction In younger patients, the in vivo clinical diagnosis of Alzheimer's disease (AD) and of the frontotemporal type (FTD) may be cumbersome. The gold standard diagnostic proof is currently still based upon pathology examination. It is crucial to find reliable techniques to make an accurate in vivo diagnosis and to differentiate the etiology of the dementia. Patients and method Twenty-four patients bearing clinically diagnosed AD ( n = 16) and FTD ( n = 8) underwent [ 18F] FDG-PET/CT brain scan. Four nuclear medicine physicians with varying expertise in neuroimaging read each scan according to: visual analysis; automated analysis computed by BRASS ® Hermes ® software; automated analysis computed by Cortex ID ® General Electric ® software. Interpretation aimed at assessing the global scan aspect, the cerebral metabolism per hemisphere (in five relevant regions) and the diagnostic degree of confidence. Diagnostic interpretations derived from visual and automated analyses were compared to clinical diagnosis. Inter-observer agreement and Kappa scores were calculated. Results Kappa analyses showed a gain in diagnostic accuracy for a nonexpert physician, a gain in diagnostic confidence with Cortex ID ® and a gain in interobserver diagnostic agreement with BRASS ®. Conclusion Using automated software such as Cortex ID ® or BRASS ® helps standardizing the interpretation of [ 18F] FDG distribution pattern in AD or FTD.

Influence of mild hyperglycemia on cerebral FDG distribution patterns calculated by statistical parametric mapping

In clinical cerebral 2-[(18)F]fluoro-2-deoxy-D: -glucose positron emission tomography (FDG-PET) studies, we sometimes encounter hyperglycemic patients with diabetes mellitus or patients who have not adhered to the fasting requirement. The objective of this study was to investigate the influence of mild hyperglycemia (plasma glucose range 110-160 mg/dl) on the cerebral FDG distribution patterns calculated by statistical parametric mapping (SPM). We studied 19 healthy subjects (mean age 66.2 years). First, all the subjects underwent FDG-PET scans in the fasting condition. Then, 9 of the 19 subjects (mean age 64.3 years) underwent the second FDG-PET scans in the mild hyperglycemic condition. The alterations in the FDG-PET scans were investigated using SPM-and region of interest (ROI)-based analyses. We used three reference regions: (1) SPM global brain (SPMgb) used for SPM global mean calculation, (2) the gray and white matter region computed from magnetic resonance image (MRIgw), and (3) the cerebellar cortex (Cbll). The FDG uptake calculated as the standardized uptake value (average) in SPMgb, MRIgw, and Cbll regions in the mild hyperglycemic condition was 42.7%, 41.3%, and 40.0%, respectively, of that observed in the fasting condition. In SPM analysis, the mild hyperglycemia was found to affect the cerebral distribution patterns of FDG. The FDG uptake was relatively decreased in the gray matter, mainly in the frontal, temporal, and parietal association cortices, posterior cingulate, and precuneus in both SPMgb-and MRIgw-reference-based analyses. When Cbll was adopted as the reference region, those decrease patterns disappeared. The FDG uptake was relatively increased in the white matter, mainly in the centrum semiovale in all the reference-based analyses. It is noteworthy that the FDG distribution patterns were altered under mild hyperglycemia in SPM analysis. The decreased uptake patterns in SPMgb-(SPM default) and MRIgw-reference-based analyses resembled those observed in Alzheimer's disease. Under mild hyperglycemia, we can recommend Cbll as the reference region to detect decreased uptake patterns. We should pay special attention to controlling the diet condition, monitoring hyperglycemia, and optimizing the reference region in SPM analysis, particularly in the diagnosis of early Alzheimer's disease in clinical FDG-PET.

Potenciales fuentes de error diagnóstico y variantes de la FDG-PET/TAC

Oncological FDG PET show variants and findings that may lead to a diagnostic error and that may be clarified by the morfofunctional imaging from PET/CT. In this article we show the experience acquired since a Siemens PET/CT Biograph LSO Pico3D was applied in our centre. We describe some representative examples of FDG distribution patterns which may lead to erroneous interpretations of the clinical studies when they refer to specific clinical situations. The examples included are classified into two main groups according to the cause: Technical and biological, and the latter into physiological and non-physiological (pathophysiological). Patterns are described within the biological group showing changes of the FDG biodistribution that may reduce the uptake in tumoural lesions, the physiological variants that may be interpreted as pathology, the effects of previous treatment and uptakes related to benign diseases. We consider that knowledge of these variants and findings to be crucial in order to obtain optimal performance of PET/CT and to overcome the PET limitations.

Characteristics of myocardial 18F-fluorodeoxyglucose positron emission computed tomography in dilated cardiomyopathy and ischemic cardiomyopathy.

Myocardial 18F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has been used to assess myocardial ischemia and viability, but few studies have conducted on FDG-PET for dilated cardiomyopathy (DCM). We investigated myocardial FDG uptake in patients with DCM in comparison with ischemic cardiomyopathy (ICM). Twenty-four patients with heart failure were included in this study. Fourteen of them were diagnosed as DCM and the other 10 were ICM. All of them underwent myocardial FDG-PET at fasting and after glucose loading the same day. FDG uptake was quantified by the ratio of the counts at the heart to those at the liver (H/L ratio). Left ventricular (LV) function was measured by echocardiography. We classified FDG distribution patterns in the myocardium in the fasting state into 3 types (faint uptake, regional uptake and diffuse uptake). In DCM patients, 5 had faint uptake, 7 had regional uptake, and the other 2 had diffuse uptake. On the other hand, all ICM patient had regional uptake (p < 0.05). In DCM, there were no significant relationships between the patterns and LV functions. On the other hand, there were close correlation between the H/L ratio after glucose loading and the left ventricular ejection fraction (r = 0.680, p < 0.01). The changes in PET images caused by glucose loading were classified into 2 types (non-reversing and reversing patterns). DCM significantly showed a non-reversing pattern (86%, 12 of 14 patients) whereas ICM showed mainly a reversing pattern (70%, 7 of 10 patients; p < 0.05). In conclusion, myocardial FDG uptake after glucose loading may indicate a myocardial viable mass although FDG uptake at fasting was not evidently related to LV function. The change in the pattern of the FDG image from fasting to glucose loading may be useful in differentiating DCM from ICM.