==== Front Cureus Cureus 2168-8184 Cureus 2168-8184 Cureus Palo Alto (CA) 10.7759/cureus.11520 Radiology Infectious Disease Effective Use of F-18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography to Rule Out Prosthetic Aortic Valve as the Source of Infection Muacevic Alexander Adler John R Agrawal Pooja 1 Roberts James T 1 Bezold Samuel 1 Villanueva-Meyer Javier 1 Nguyen Quan D 1 1 Radiology, University of Texas Medical Branch, Galveston, USA Quan D. Nguyen qunguyen@utmb.edu 17 11 2020 11 2020 12 11 e1152017 11 2020 Copyright © 2020, Agrawal et al.2020Agrawal et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.This article is available from https://www.cureus.com/articles/41235-effective-use-of-f-18-fluorodeoxyglucose-positron-emission-tomographycomputed-tomography-to-rule-out-prosthetic-aortic-valve-as-the-source-of-infectionSeveral nuclear imaging techniques can be used to diagnose infectious and inflammatory processes. F-18-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is a useful diagnostic technique to detect inflammation and infection quickly and accurately. We report the case of a patient with end-stage renal disease (ESRD) and recurrent bacterial infections where FDG PET/CT was used to identify the source of infection as sternal osteomyelitis and rule out suspected infection of the aortic valve prosthesis.  site of infectionpet scansct (computed tomography) imagingnuclear medicine imagingaortic valveThe content published in Cureus is the result of clinical experience and/or research by independent individuals or organizations. Cureus is not responsible for the scientific accuracy or reliability of data or conclusions published herein. All content published within Cureus is intended only for educational, research and reference purposes. Additionally, articles published within Cureus should not be deemed a suitable substitute for the advice of a qualified health care professional. Do not disregard or avoid professional medical advice due to content published within Cureus. ==== Body Introduction Infection and inflammation can be detected with various nuclear medicine imaging techniques. For example, imaging with technetium 99m (99mTc) methylene diphosphonate, gallium 67 (67Ga) citrate, indium 111 (111In)-oxine autologous labeled leukocytes, and 99mTc hexylmethylpropylene amineoxime autologous labeled leukocytes can provide diagnostic information; however, each has limitations [1,2]. F-18-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is a useful method to detect inflammation and infection quickly and with high sensitivity [3]. FDG PET/CT measures metabolic tissue activity. The uptake of FDG is increased in tissues with increased glucose consumption, such as sites of increased inflammation [4-6]. Inflammatory cells, such as neutrophils and macrophages, have increased glucose transporters [4,6]. Thus, sites of infection can be visualized using FDG PET/CT. Previous research has found that FDG PET/CT is useful in identifying fevers of undetermined origin (FUO) [7], focal infection [8], and osteomyelitis [9]. Here, we present the case of a patient with suspected infection of a prosthetic aortic valve, and the usefulness of FDG PET/CT in ruling out infection of the valve. Case presentation A man with a past medical history of end-stage renal disease (ESRD) on hemodialysis, aortic dissection, bioprosthetic valve, and recurrent bacteremia was admitted as a transfer for line exchange after he was found to have methicillin-resistant Staphylococcus aureus (MRSA) bacteremia and symptoms of fevers, night sweats, and chills. The patient received vancomycin and subsequent cultures were negative for MRSA, however, repeat blood cultures grew Proteus mirabilis. Multiple sources of recurrent infection were possible, including his permanent dialysis catheter, bioprosthetic aortic valve, or aortic root graft, but the most likely source was thought to be the dialysis catheter. Interventional radiology performed removal of the permanent catheter. Blood cultures and catheter tip cultures were drawn following removal. The catheter tip did not have bacterial growth, however, blood cultures were positive for MRSA and the patient was given appropriate antibiotics. Given the patient’s history of recurrent infections, the attending team needed to identify the source and discuss its replacement. The attending team discussed whether a gallium scan or tagged WBC scan would be helpful in identifying the source of the infection with the nuclear medicine team. Attending radiologists recommended a PET scan to evaluate prosthesis. The scan revealed hypermetabolism in the upper sternal body, suspicious for osteomyelitis (Figures 1, 2). The bone in the region of hypermetabolism was abnormal. The sternotomy was unfused and showed no signs of healing. The margins of the upper sternotomy, which is the region of osseous hypermetabolism, were irregular with areas of erosion. More inferiorly, the sternotomy showed callus formation, no erosions, and no hypermetabolism. An additional crescentic collection was found along the right aspect of the ascending aortic arch, however, it did not extend along with the valve. The collection was most likely a hematoma, measuring above fluid attenuation by CT. Whether there was infection superimposed upon the hematoma is unknown, though possible. While the collection abutted the prosthetic valve, there was no other uptake around the valve to suggest infection of the prosthesis. Thus, the source of infection was likely from the sternum and aortic arch and not from the aortic valve prosthesis. Figure 1 F-18-Fluorodeoxyglucose Positron Emission Tomography Scan A diagnostic FDG PET scan found moderate to marked hypermetabolism within the sternotomy line with maximum standard uptake value (SUV) 4.6. FDG PET: F-18-fluorodeoxyglucose positron emission tomography Figure 2 F-18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Scan FDG PET/CT scan revealed hypermetabolism in the upper sternal body with adjacent soft tissue in the anterior mediastinum, suspicious for osteomyelitis. An additional crescentic collection was found along the right aspect of the ascending aortic arch that did not extend along with the prosthetic valve. The scan includes axial (A), sagittal (B), and coronal (C) views. The red circles denote sites of increased FDG uptake. FDG PET/CT: F-18-fluorodeoxyglucose positron emission tomography/computed tomography The patient’s antibiotic therapy was extended. A second PET scan confirmed the infection was not from the aortic valve prosthesis. The patient underwent AV fistula creation for permanent dialysis access. Discussion A variety of nuclear imaging studies can aid in the diagnosis of infection, particularly in complex cases of recurrent bacteremia, such as the case presented above. MRI is used often in infection imaging but has prolonged acquisition times and may have inconclusive results in certain infectious processes [10,11]. White blood cell imaging is another technique that may be used, but it exhibits a low range of sensitivity in chronic infection, such as chronic osteomyelitis [10]. FDG PET/CT is a particularly useful diagnostic technique to identify the source of infection. FDG PET/CT also shows increased uptake in bone lesions, such as brown tumors. Advantages include short acquisition time, high-resolution, and increased sensitivity in chronic and spinal infection [10]. FDG PET has been shown to have value in the diagnosis of chronic limb osteomyelitis, where it has high rates of specificity and sensitivity [12,13]. For example, the sensitivity and specificity of FDG PET were found to have sensitivity and specificity over 95% in the diagnosis of osteomyelitis [13]. Three-phase bone scintigraphy and labeled white cell scintigraphy have comparatively lower rates of sensitivity and specificity [12]. The infection of a prosthetic aortic valve is associated with high rates of morbidity and mortality [14]. This is partly due to a delay in diagnosing infection and identifying the source [15]. Patients may also present with a wide range of symptoms, delaying accurate diagnosis and treatment [15]. Thus, it is imperative to quickly identify the source of infection to result in improved outcomes. Further, if the infection of a prosthetic aortic valve is suspected, accurate diagnosis is vital, given the high rates of mortality associated with valve replacement [16]. In this setting of a patient with recurrent bacteremia, FDG PET/CT was helpful in ruling out infection of aortic valve prosthesis (and thus avoiding high-risk surgery) and diagnosing osteomyelitis. Conclusions FDG PET/CT can be used to identify the source of infection or exclude certain infectious processes with high sensitivity. FDG PET/CT ruled out infection of the aortic valve prosthesis in this patient with recurrent bacteremia. Given its increasing availability, as well as rapidness and relatively lower cost compared to labeled WBC scan, FDG PET/CT should be considered in the diagnosis of infectious processes. The authors have declared that no competing interests exist. Human Ethics Consent was obtained by all participants in this study ==== Refs References 1 The molecular imaging approach to image infections and inflammation by nuclear medicine techniques Ann Nucl Med Signore A Glaudemans AW 681 700 25 2011 21837469 2 Labeled leukocyte imaging: current status and future directions Q J Nucl Med Mol Imaging Palestro C Love C Bhargava K 105 123 53 2009 https://search.proquest.com/docview/214574862?accountid=6724 19182734 3 Nuclear medicine and the infected joint replacement Sem Nucl Med Love C Marwin SE Palestro CJ 66 78 39 2009 4 Intratumoral distribution of fluorine-18-fluorodeoxyglucose in vivo: high accumulation in macrophages and granulation tissues studied by microautoradiography J Nucl Med Kubota R Yamada S Kubota K Ishiwata K Tamahashi N Ido T 1972 1980 33 1992 http://jnm.snmjournals.org/content/33/11/1972.short 1432158 5 18-Fluorodeoxyglucose positron emission tomographic imaging in the detection and monitoring of infection and inflammation Semin Nucl Med Zhuang H Alavi A 47 59 32 2002 11839069 6 FDG uptake and glucose transporter subtype expressions in experimental tumor and inflammation models J Nucl Med Mochizuki T Tsukamoto E Kuge Y 1551 1555 42 2001 http://jnm.snmjournals.org/content/42/10/1551.short 11585872 7 Clinical value of [18F] fluoro-deoxyglucose positron emission tomography for patients with fever of unknown origin Arch Clin Infect Dis Blockmans D Knockaert D Maes A De Caestecker J Stroobants S Bobbaers H Mortelmans L 191 196 32 2001 8 Clinical value of FDG PET in patients with fever of unknown origin and patients suspected of focal infection or inflammation Eur J Nucl Med Mol Imaging Bleeker-Rovers CP de Kleijn EM Corstens FH van der Meer JW Oyen WJ 29 37 31 2004 14551752 9 Diagnostic value of 18 F-FDG PET/CT in trauma patients with suspected chronic osteomyelitis Eur J Nucl Med Mol Imaging Hartmann A Eid K Dora C Trentz O von Schulthess GK Stumpe KD 704 714 34 2007 17136411 10 FDG PET/CT in infection and inflammation—current and emerging clinical applications Clin Radiol Vaidyanathan S Patel C Scarsbrook A Chowdhury F 787 800 70 2015 25917543 11 Evolving role of positron emission tomography in the management of patients with inflammatory and other benign disorders Semin Nucl Med El-Haddad G Zhuang H Gupta N Alavi A 313 329 34 2004 15493008 12 The accuracy of diagnostic imaging for the assessment of chronic osteomyelitis: a systematic review and meta-analysis J Bone Joint Surg Am Termaat M Raijmakers P Scholten H Bakker F Patka P Haarman H 2464 2471 87 2005 16264122 13 PET and SPECT in osteomyelitis and prosthetic bone and joint infections: a systematic review Semin Nucl Med van der Bruggen W Bleeker-Rovers CP Boerman OC Gotthardt M Oyen WJ 3 15 40 2010 19958846 14 Aortic valve infection: risk factors for death and recurrent endocarditis after aortic valve replacement J Thorac Cardiovasc Surg McGiffin DC Galbraith AJ McLachlan GJ 511 520 104 1992 1495318 15 Management of infective endocarditis: challenges and perspectives Lancet Thuny F Grisoli D Collart F Habib G Raoult D 965 975 379 2012 22317840 16 Staphylococcus aureus bacteremia in patients with prosthetic devices: costs and outcomes Am J Med Chu VH Crosslin DR Friedman JY 1416 118 2005