Clinical value of FDG PET in patients with fever of unknown origin and patients suspected of focal infection or inflammation

Diagnostic utility of fluorodeoxyglucose positron emission tomography/computed tomography in pyrexia of unknown origin

PURPOSE OF THE STUDY

The present study was undertaken to evaluate the diagnostic utility of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in patients presenting as pyrexia of unknown origin (PUO).

MATERIALS AND METHODS

Forty-seven patients (31 males and 16 females; mean age of 42.7 ± 19.96 years) presenting as PUO to the Department of Medicine at the All India Institute of Medical Sciences, New Delhi over a period of 2 years underwent F-18 FDG PET/CT. PET ⁄ CT was considered supportive when its results correlated with the final definitive diagnosis. Final diagnosis was made on the basis of combined evaluation of history, clinical findings, investigations, and response to treatment.

RESULTS

Thirty-five PET/CT studies (74.5%) were positive. However, only 18 (38.3%) were supportive of the final diagnosis. In three patients (6.4%), PET/CT was considered diagnostic as none of the other investigations including contrast-enhanced computed tomography of chest and abdomen, and directed tissue sampling could lead to the final diagnosis. All these three patients were diagnosed as aortoarteritis.

CONCLUSION

Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography is an important emerging modality in the workup of PUO. It supported the final diagnosis in 38% of our patients and was diagnostic in 6.4% of patients. Thus, PET/CT should only be considered as second-line investigation for the diagnostic evaluation of PUO; especially in suspected noninfectious inflammatory disorders.

The diagnostic role of (18)F fluorodeoxyglucose positron emission tomography in patients with fever of unknown origin

BACKGROUND

Identification of aetiology for fever of unknown origin (FUO) is challenging, due to the high rates of undiagnosed cases. The current diagnostic approach includes initially first-line procedures such as general examination and various laboratory tests and basic imaging techniques followed by second-line tests such as more advanced imaging techniques including (18)F fluorodeoxyglucose positron emission tomography (FDG PET) and tissue biopsies. If no diagnosis is obtained, more invasive measures may be in order such as liver biopsy and exploratory laparotomy.

MATERIALS AND METHODS

This review article is based on the relative published material found on MEDLINE and PubMed up to August 2014. We looked for the terms 'fever of unknown origin, FDG PET' in combination with 'cancer, infection and autoimmune disease'.

RESULTS

Several clinical studies have investigated the utility of the FDG PET during the diagnostic approach of FUO. Recent evidence suggests that FDG PET has the advantage of total body imaging and may depict all common causes of FUO such as infections, noninfectious inflammatory causes and tumours because they all exhibit glucose hypermetabolism. Depiction of an abnormal lesion on FDG PET could guide clinicians to the next diagnostic procedure (another imaging method, culture, biopsy or surgery) to establish the diagnosis.

CONCLUSIONS

Emerging evidence suggests that FDG PET, when available, may provide critical diagnostic information early during evaluation of FUO.

FDG PET/CT in infection and inflammation--current and emerging clinical applications

Integrated positron emission tomography/computed tomography (PET/CT) with the glucose analogue, 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG), is an evolving hybrid imaging technique in the evaluation of an important and diverse group of pathological conditions, which are characterised by infection and aseptic inflammation. With a rapidly expanding body of evidence, it is being increasingly recognised that, in addition to its established role in oncological imaging, FDG PET/CT also has clinical utility in suspected infection and inflammation. The technique can identify the source of infection or inflammation in a timely fashion ahead of morphological changes on conventional anatomical imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), map the extent and severity of disease, identify sites for tissue sampling, and assess therapy response. FDG PET/CT exhibits distinct advantages over traditional radionuclide imaging techniques in terms of shorter duration of examination, higher spatial resolution, non-invasive nature of acquisition, ability to perform quantitative analyses, and the provision of a synergistic combination of functional and anatomical imaging. With the use of illustrative clinico-radiological cases, this article discusses the current and emerging evidence for the use of FDG PET/CT in a broad spectrum of disorders, such as fever of unknown origin, sarcoidosis, large vessel vasculitis, musculoskeletal infections, joint prosthesis or implant-related complications, human immunodeficiency virus (HIV)-related infections, and miscellaneous indications, such as IgG4-related systemic disease. It will also briefly summarise the role of more novel tracers such as FDG-labelled leukocytes and gallium-68 PET tracers in this arena.

[18F]FDG-PET/CT for the diagnosis of patients with fever of unknown origin

BACKGROUND AND AIMS

The diagnosis of patients with fever of unknown origin (FUO) remains a challenging medical problem. We aimed to assess the diagnostic contribution of 18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET)/computed tomography (CT) for the evaluation of FUO.

METHODS

We performed a 4-year retrospective single-center study of all hospitalized patients that underwent FDG-PET/CT for evaluation of FUO. The final diagnosis of the febrile disease was based on clinical, microbiological, radiological and pathological data available at the final follow-up. Predictors for a contributory exam were sought.

RESULTS

One hundred and twelve patients underwent FDG-PET/CT for the investigation of FUO in the years 2008-2012 and were included in the study. A final diagnosis was determined in 83 patients (74%) and included: infectious disease in 49 patients (43%), non-infectious inflammatory disease in 17 patients (16%), malignancies in 15 patients (14%), other diagnoses in 2 patients (1.7%), FUO resolved with no diagnosis and no evidence of disease during a 6-month follow-up in 23 patients (20%), and death with fever and with no diagnosis in 6 patients (5%). Seventy-four FDG-PET/CT studies (66%) were considered clinically helpful and contributory to diagnosis (46% positive contributory value and 20.5% contributory to exclusion of diagnosis). PET/CT had a sensitivity of 72.2%, a specificity of 57.5%, a positive predictive value (PPV) of 74.2% and a negative predictive value (NPV) of 53.5%. On multivariable analysis, significant predictors of a positive PET/CT contributory to diagnosis were a short duration of fever and male gender.

CONCLUSIONS

PET/CT is an important diagnostic tool for patients with FUO.

Inflammation

Inflammation was described as early as 3000 BC in an Egyptian papyrus [1] and is still a common problem despite continuous advancements in prevention and treatment methods. The delineation of the site and extent of inflammation are crucial to the clinical management of infection and for monitoring the response to therapy [2].

Clinical utility of indium 111-labeled white blood cell scintigraphy for evaluation of suspected infection

We assessed the clinical utility of indium 111–labeled white blood cell scans at our tertiary referral center from 2005 to 2011. Overall, scans meaningfully impacted clinical care <50% of the time. Scan utility was greater for suspected vascular graft infections or osteomyelitis.

Background

 We sought to characterize the clinical utility of indium 111 (¹¹¹In)–labeled white blood cell (WBC) scans by indication, to identify patient populations who might benefit most from this imaging modality.

Methods

 Medical records for all patients who underwent ¹¹¹In-labeled WBC scans at our tertiary referral center from 2005 to 2011 were reviewed. Scan indication, results, and final diagnosis were assessed independently by 2 infectious disease physicians. Reviewers also categorized the clinical utility of each scan as helpful vs not helpful with diagnosis and/or management according to prespecified criteria. Cases for which clinical utility could not be determined were excluded from the utility assessment.

Results

 One hundred thirty-seven scans were included in this analysis; clinical utility could be determined in 132 (96%) cases. The annual number of scans decreased throughout the study period, from 26 in 2005 to 13 in 2011. Forty-one (30%) scans were positive, and 85 (62%) patients were ultimately determined to have an infection. Of the evaluable scans, 63 (48%) scans were deemed clinically useful. Clinical utility varied by scan indication: ¹¹¹In-labeled WBC scans were more helpful for indications of osteomyelitis (35/50, 70% useful) or vascular access infection (10/15, 67% useful), and less helpful for evaluation of fever of unknown origin (12/35, 34% useful).

Conclusions

 ¹¹¹In-labeled WBC scans were useful for patient care less than half of the time at our center. Targeted ordering of these scans for indications in which they have greater utility, such as suspected osteomyelitis and vascular access infections, may optimize test utilization.

Diagnostic value of FDG-PET/(CT) in children with fever of unknown origin and unexplained fever during immune suppression

PURPOSE

Fever of unknown origin (FUO) and unexplained fever during immune suppression in children are challenging medical problems. The aim of this study is to investigate the diagnostic value of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and FDG-PET combined with computed tomography (FDG-PET/CT) in children with FUO and in children with unexplained fever during immune suppression.

METHODS

All FDG-PET/(CT) scans performed in the Radboud university medical center for the evaluation of FUO or unexplained fever during immune suppression in the last 10 years were reviewed. Results were compared with the final clinical diagnosis.

RESULTS

FDG-PET/(CT) scans were performed in 31 children with FUO. A final diagnosis was established in 16 cases (52 %). Of the total number of scans, 32 % were clinically helpful. The sensitivity and specificity of FDG-PET/CT in these patients was 80 % and 78 %, respectively. FDG-PET/(CT) scans were performed in 12 children with unexplained fever during immune suppression. A final diagnosis was established in nine patients (75 %). Of the total number of these scans, 58 % were clinically helpful. The sensitivity and specificity of FDG-PET/CT in children with unexplained fever during immune suppression was 78 % and 67 %, respectively.

CONCLUSIONS

FDG-PET/CT appears a valuable imaging technique in the evaluation of children with FUO and in the diagnostic process of children with unexplained fever during immune suppression. Prospective studies of FDG-PET/CT as part of a structured diagnostic protocol are warranted to assess the additional diagnostic value.

Clinical impact of 18F-FDG-PET/CT in the extra cardiac work-up of patients with infective endocarditis

OBJECTIVE

The purpose of this study was to assess the clinical importance of 18F-FDG-PET/CT used in the extra cardiac work-up of patients with infective endocarditis (IE).

BACKGROUND

IE is a serious condition with a significant mortality. Besides the degree of valvular involvement, the prognosis relies crucially on the presence of systemic infectious embolism.

METHODS

Seventy-two patients (71% males and mean age 63 ± 17 years) with IE were evaluated with 18F-FDG-PET/CT in addition to standard work-up including patient history, physical examination, conventional imaging modalities, and weekly interdisciplinary conferences. When previous unknown lesions detected by 18F-FDG-PET/CT were confirmed by succeeding examinations, they were considered true positive new findings and were further assessed for their clinical importance. Number needed to investigate was calculated as the number of patients who needed to undergo 18F-FDG-PET/CT to find at least one clinical important true positive new finding, not identified by standard work-up prior to 18F-FDG-PET/CT.

RESULTS

18F-FDG-PET/CT detected 114 lesions and 64 were true positive, of which 25 were new findings and detected in 17 patients. In 11 patients, the lesions were considered to have a clinical importance; osteomyelitis (n = 7), iliopsoas abscess (n = 1), gastrointestinal lesions (n = 2), and vascular prosthetic graft (n = 1). Number needed to investigate was 7 (11 of 72 patients).

CONCLUSIONS

18F-FDG-PET/CT detected lesions of clinical importance in one of seven IE patients and may be a substantial imaging technique for tracing peripheral infectious embolism due to IE. Thus, 18F-FDG-PET/CT may help to guide adequate therapy and thereby improve the prognosis of patients with IE.

Utility of fluorodeoxyglucose positron emission tomography/computed tomography in patients with fever of unknown origin diagnosed as lymphoma

OBJECTIVE

To assess the efficacy of fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET)/computed tomography (CT) in the diagnosis of patients with fever of unknown origin (FUO), who were finally diagnosed as lymphoma.

SUBJECTS AND METHODS

A retrospective study was performed in the First Affiliated Hospital, School of Medicine of Zhejiang University, China, from March 2009 to March 2012. The PET/CT images of consecutive patients with FUO were analyzed. Within 1 week of PET/CT scanning, additional histological tests were also performed if clinically needed.

RESULTS

A total of 73 consecutive patients were included. Of these, 34 (47%) had a PET/CT finding suggestive of the presence of lymphoma and 29 (85%) had a diagnosis of confirmed lymphoma; 39 (53%) had a PET/CT result revealing the absence of lymphoma and 4 (10%) were diagnosed by biopsy as having lymphoma, . The most frequent lymphoma diagnosis was peripheral T cell lymphoma (n = 16; 55%), followed by diffuse large B cell lymphoma (n = 9; 31%). The accuracy of PET/CT was 88%.

CONCLUSION

In this study, PET/CT had high diagnostic accuracy in patients with FUO resulting from lymphoma, which indicated that PET/CT scanning was a valuable diagnostic tool for these groups of patients with FUO.

Radionuclide imaging of inflammation and infection in the acute care setting

Although infection may be suggested by signs and symptoms such as fever, pain, general malaise, and abnormal laboratory results, imaging tests often are used to confirm its presence. Morphologic imaging tests identify structural alterations of tissues or organs that result from a combination of microbial invasion and the inflammatory response of the host. Functional imaging studies use minute quantities of radioactive material, which are taken up directly by cells, tissues, and organs, or are attached to substances that subsequently migrate to the region of interest. Bone scintigraphy is extremely sensitive and can be positive within 2 days after the onset of symptoms. With an accuracy of more than 90%, 3-phase bone scintigraphy is the radionuclide procedure of choice for diagnosing osteomyelitis in unviolated bone. In patients with acute renal failure, gallium imaging facilitates the differentiation of acute interstitial nephritis from acute tubular necrosis. Gallium imaging also is useful in the evaluation of pulmonary infections and inflammation. Many opportunistic infections affect the lungs, and a normal gallium scan of the chest excludes infection with a high degree of certainty, especially when the chest x-ray is negative. In the human immunodeficiency virus positive patient, lymph node uptake usually is associated with mycobacterial disease or lymphoma. Focal pulmonary parenchymal uptake suggests bacterial pneumonia. Diffuse pulmonary uptake suggests an opportunistic pneumonia. Gallium imaging provides useful information about other acute respiratory conditions, including radiation pneumonitis and hypersensitivity pneumonitis. In vitro labeled leukocyte imaging with indium-111 and technetium-99m labeled leukocytes is useful in various acute care situations. The test facilitates the differentiation of normal postoperative changes from infection and is useful for diagnosing prosthetic vascular graft infection. In inflammatory bowel disease, labeled leukocyte imaging is useful for initial screening, monitoring treatment response, detecting recurrent disease, and evaluating patients with discordant physical presentation and laboratory test results. Labeled leukocyte imaging, combined with bone marrow scintigraphy accurately diagnoses complicating osteomyelitis. Fluorine-18-fluorodeoxyglucose, imaging is rapidly completed and provides high-resolution images. This test is especially valuable in patients with fever of unknown origin, patients in septic shock, and mechanically ventilated patients suspected of harboring infection. Fluorine-18-fluorodeoxyglucose imaging also shows promise in inflammatory bowel disease.

Infectious and inflammatory complications of surgical management of cancer patients imaged with 18F-FDG PET/CT: a pictorial essay

The aim of this pictorial essay was to highlight the usefulness of fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in evaluating incidental infection or inflammation in cancer patients, related to surgical management. A retrospective review of 10,985 consecutive oncologic PET/CTs was done, and nine cases with suspected FDG positive infectious or inflammatory processes were selected for further review. PET/CT helped identify infections and inflammatory processes related to surgical management of cancer patients, define the extent of infection or inflammation, guide the management and, in some cases, evaluate response to therapy.

A Rationale for the Use of F18-FDG PET/CT in Fever and Inflammation of Unknown Origin

This review focuses on the diagnostic value of hybrid F18-FDG Positron Emission Tomography/Computerized tomography (PET/CT) in fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Due to the wide range of possible causes both FUO and IUO remain a clinical challenge for both patients and physicians. In addition, the aetiology of IUO shows the same variation in diseases as the FUO spectrum and probably requires the same diagnostic approach as FUO. There are numerous historically used diagnostic approaches incorporating invasive and non-invasive, and imaging techniques, all with relative high specificity but limited sensitivity. This hampers the generalization of these diagnostic approaches. However, recently published reports show that F18-FDG PET/CT in FUO and IUO has a high sensitivity and a relative non-specificity for malignancy, infection and inflammation. This makes F18-FDG PET/CT an ideal diagnostic tool to start the diagnostic process and to guide subsequent focused diagnostic approaches with higher specificity. In addition, F18-FDG PET/CT has a relative high negative predictive value. Therefore F18 FDG PET/CT should be incorporated in the routine diagnostic work-up of patients with FUO and IUO, preferably at an early stage in the diagnostic process.

Mesenchymal bone marrow cell therapy in a mouse model of chagas disease. Where do the cells go?

BACKGROUND

Chagas disease, resulting from infection with the parasite Trypanosoma cruzi (T. cruzi), is a major cause of cardiomyopathy in Latin America. Drug therapy for acute and chronic disease is limited. Stem cell therapy with bone marrow mesenchymal cells (MSCs) has emerged as a novel therapeutic option for cell death-related heart diseases, but efficacy of MSC has not been tested in Chagas disease.

METHODS AND RESULTS

We now report the use of cell-tracking strategies with nanoparticle labeled MSC to investigate migration of transplanted MSC in a murine model of Chagas disease, and correlate MSC biodistribution with glucose metabolism and morphology of heart in chagasic mice by small animal positron emission tomography (microPET). Mice were infected intraperitoneally with trypomastigotes of the Brazil strain of T. cruzi and treated by tail vein injection with MSC one month after infection. MSCs were labeled with near infrared fluorescent nanoparticles and tracked by an in vivo imaging system (IVIS). Our IVIS results two days after transplant revealed that a small, but significant, number of cells migrated to chagasic hearts when compared with control animals, whereas the vast majority of labeled MSC migrated to liver, lungs and spleen. Additionally, the microPET technique demonstrated that therapy with MSC reduced right ventricular dilation, a phenotype of the chagasic mouse model.

CONCLUSIONS

We conclude that the beneficial effects of MSC therapy in chagasic mice arise from an indirect action of the cells in the heart rather than a direct action due to incorporation of large numbers of transplanted MSC into working myocardium.

The role of 18F-FDG PET or PET/CT in the detection of fever of unknown origin

Even with the recent advance in diagnostic tools and techniques, fever of unknown origin (FUO) remains a clinical challenge. A wide range of diseases, mainly infections, autoimmune conditions (inflammatory diseases), malignancies and miscellaneous can cause FUO. Positron emission tomography (PET) or positron emission tomography/computed tomography (PET/CT) scanning makes a great contribution to the diagnosis and differential diagnosis of FUO due to the high sensitivity of pathological accumulation of 18F-FDG. The diagnostic yield of PET/CT is higher than traditional radiographic imaging and other nuclear medicine scanning. Owing to the numerous advantages of PET/CT including high sensitivity and the ability to perform whole-body scans, many rare diseases presenting with FUO can be detected and the spectrum of diseases that can exhibit FUO has been increasing. Recent studies utilizing FUO are discussed in this paper. However, there are limited data available about the role of 18F-FDG PET or PET/CT in evaluation of FUO.

[Isolated tracheobronchial involvement by atrophic polychondritis: role of PET scanning]

INTRODUCTION

Atrophic polychondritis is a rare and serious disease characterised by multifocal inflammatory lesions of cartilage. The diagnosis, though urgent, is difficult when there is isolated tracheal involvement.

CASE REPORT

We report the case of a woman of 55 with recent, non-infectious febrile episodes accompanied by a steroid sensitive inflammatory syndrome. Auscultation, lung function tests and a thoracic CT scan suggested tracheobronchomalacia. Atrophic polychondritis was suspected without being confirmed on the basis of histological or biological tests; particularly as no other cartilaginous involvement was discovered. Laryngeal and tracheal hypermetabolism on a PET scan, performed in the absence of corticosteroid treatment, was also in favour of this diagnosis. One month after resumption of steroid treatment at increased dosage, this examination was normal. Secondarily, after careful reduction of steroids, the patient developed nasal chondritis, confirming the diagnosis of atrophic polychondritis.

CONCLUSION

The PET scanner could be useful in the diagnosis of atrophic polychondritis in its isolated tracheobronchial form. Its place in the follow-up of this disease remains to be evaluated and should take account of the irradiation dose of this examination.

[The role of FDG PET/CT for detecting the cause of fever of unknown origin in a clinical case]

The fever of unknown origin from time to time constitutes a serious clinical problem and nearly all diagnostic methods are involved to discover urgently its cause. According to literature data (18)F-fluoro-deoxyglucose PET/CT was successful in 25-70% of cases even in patients without any positive findings with conventional diagnostic techniques. The Hungarian National Health Fund does not include fever of unknown origin in the list of reimbursed (18)F-fluoro-deoxyglucose PET/CT indications. The authors try to illustrate the clinical problem with this case report. Fever of unknown origin persisted in a patient for a year, but conventional diagnostic procedures were unsuccessful to find the cause of the fever. Finally, (18)F-fluoro-deoxyglucose PET/CT indicated a metabolically active focus between the pancreas tail and the spleen. After a long-lasting antibiotic therapy the patient became symptomfree.

PET scanning in plastic and reconstructive surgery

In this report we highlight the use of PET scan in plastic and reconstructive surgery. PET scanning is a very important tool in plastic surgery oncology (melanoma, soft-tissue sarcomas and bone sarcomas, head and neck cancer, peripheral nerve sheath tumors of the extremities and breast cancer after breast esthetic surgery), as diagnosis, staging, treatment planning and follow-up of cancer patients is based on imaging. PET scanning seems also to be useful as a flap monitoring system as well as an infection's imaging tool, for example in the management of diabetic foot ulcer. PET also contributes to the understanding of pathophysiology of keloids which remain a therapeutic challenge.

Clinical features of 66 lymphoma patients presenting with a fever of unknown origin

OBJECTIVE

To investigate the clinical characteristics, diagnostic approaches, short-term efficacy of treatment and prognosis of lymphoma patients presenting with a fever of unknown origin (FUO).

METHODS

We reviewed the records of 132 patients finally diagnosed with lymphoma in Huashan Hospital, half of whom initially presented with a FUO. The other 66 lymphoma patients without a history of FUO were diagnosed within a month when several patients in the FUO group were also diagnosed.

RESULTS

The patients presenting with a FUO were predominantly young men (71.21%, p=0.35) characterized by a temperature ≥ 39°C (55/66, 83.33%). Compared with the non-FUO group, patients in the FUO group more often had pancytopenia and hypohepatia, 61.54% with hypoalbuminemia (p<0.0001), 15.50% with significantly elevated lactate dehydrogenase (LDH) (p<0.0001), 92.45% with elevated serum β(2) microglobulin (p=0.017), 93.48% with elevated urine β(2) microglobulin (p=0.002) and 30.77% with elevated alkaline phosphatase (p=0.001). Ninety-four percent of the FUO patients had aggressive lymphomas (p=0.012), with a poor performance status (96.97%, p=0.003), stage III/IV disease (96.97%, p<0.0001), night sweats (21.21%, p=0.026), unexplained weight loss (46.97%, p=0.002) and more than one extranodal site involved (65.15%, p=0.002). The patients in the FUO group also showed poor prognoses, and most of them were in the high-intermediate or high risk classification of the disease (96.61%, p<0.0001), with a low complete remission (CR) rate (61.11% vs. 93.75%, p=0.043). Twenty-one (15.91%) of all the patients were diagnosed based on the finding of lesion sites by Positron Emission Tomography/Computed Tomography (PET/CT) scanning, which had not been detected by conventional scans.

CONCLUSION

Lymphoma presenting as FUO has a rapid progression and poor prognosis, and is difficult to diagnose. PET/CT scans can provide complementary information for an etiological diagnosis of a FUO and biopsy examinations are significant to establish an early diagnosis for patients presenting with a FUO.

A positron emission tomography/computed tomography (PET/CT) evaluation of asymptomatic abdominal aortic aneurysms: another point of view

BACKGROUND

To assess the prevalence of increased (18)F-fluorodeoxyglucose (FDG) uptake in aneurysmal walls, adopting a case-control approach in a population of asymptomatic patients with abdominal aortic aneurysm (AAA).

METHODS

This study included 40 males (mean age: 74 years, range: 59-93 years), consecutive, white Caucasian patients, with asymptomatic infrarenal AAA. The mean diameter of AAA was 4.9 cm (range: 4.8-5.4 cm), detected by computed tomography (CT) scan. Control Subjects: 44 age-matched controls subjects (mean age: 71 years, range: 59-85 years, 24 males, 20 females) who were selected according to a case-control criterion among a population of patients without any clinical evidence of atherosclerotic disease. Patients and controls underwent simultaneous FDG-positron emission tomography (PET) and CT imaging from the skull base to the femoral neck by using an integrated PET/CT scanner. PET/CT studies were analysed both visually and quantitatively. For quantitative analysis, circular CT-based regions of interest (ROIs) were drawn on the AAA, on all the aortic segments, and on the large vessel included in the study (carotid, subclavian, and iliac arteries). FDG uptake was quantified by calculating the mean and maximum standardized uptake values (SUVs) within each ROI and normalizing for the blood-pool SUV to obtain the final target-to-background ratio. Arterial calcium load was graded according to a semiquantitative five-point scale based on calcification of the arterial ring.

RESULTS

Metabolic activity in the aneurysmal aortic segment was even lower with respect to both the adjacent--nonaneurysmal--samples of patient group and the corresponding arterial segments of control subjects (P < 0.001 and P < 0.01, respectively). In visual analysis, no patients showed an increased focal uptake of degree adequate to identify the aneurysmal arterial wall. AAA patients showed significantly higher values of total calcium load (ACL) than controls in ascending aorta and subclavian and iliac arteries (P < 0.01), and only in AAA patient group, a significant correlation was present between values of ACL in both iliac arteries and abdominal aorta on one side and wall metabolic activity in the same arteries on the other (P < 0.05).

CONCLUSIONS

In conclusion, our results suggest that FDG hot spot, as well an increased diffuse uptake of FDG, in PET/CT studies is an extremely rare finding in patients with AAA of diameter close to surgical indications.

[Analysis of cost-effectiveness in the diagnosis of fever of unknown origin and the role of (18)F-FDG PET-CT: a proposal of diagnostic algorithm]

AIM

To analyze the costs of Fever of Unknown Origin (FUO) prior to the PET-CT study. To determine the effectiveness of PET-CT in the diagnosis of FUO. A proposal of diagnostic algorithm.

MATERIAL AND METHODS

A retrospective study was performed that included 20 patients who had been studied between January 2007 and January 2011, with a mean age of 57.75 years and FUO diagnosis. All underwent a PET-CT study with (18)F-FDG. Individual and mean costs of FUO in these patients were assessed, including hospitalization days and complementary tests prior to the PET-CT study. The effectiveness of the PET-CT study in the diagnosis of FUO was analyzed. Costs of the FUO process were determined, including those of the PET-CT study, and if it had been done earlier in the diagnostic process.

RESULTS

Mean hospital stay per patient until the PET-CT study was 28 days. The cost per hospitalization day was 342 €. Average cost per patient in complementary tests was 1395 €. Total cost of the FUO process until the PET-CT study was around 11167 € per patient. The PET-CT study showed a 78% sensitivity, 83% specificity, 92% PPV and 62% NPV. If PET-CT had been performed earlier in the FUO process, assuming the same effectiveness, 5471 € per patient would have been saved.

CONCLUSION

The PET-CT study could be cost-effective in the FUO process if used at an early stage, helping to establish an early diagnosis, reducing hospitalization days due to diagnostic purposes and the repetition of unnecessary tests.

18F-FDG PET/CT for diagnosing infectious complications in patients with severe neutropenia after intensive chemotherapy for haematological malignancy or stem cell transplantation

Purpose

Between 30 and 50% of febrile neutropenic episodes are accounted for by infection. C-reactive protein (CRP) is a nonspecific parameter for infection and inflammation but might be employed as a trigger for diagnosis. The aim of the study was to evaluate whether ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT can be used to detect inflammatory foci in neutropenic patients with elevated CRP and whether it helps to direct treatment.

Methods

Twenty-eight consecutive patients with neutropenia as a result of intensive chemotherapy for haematological malignancies or myeloablative therapy for haematopoietic stem cell transplantation were prospectively included. ¹⁸F-FDG PET/CT was added to the regular diagnostic workup once the CRP level rose above 50 mg/l.

Results

Pathological FDG uptake was found in 26 of 28 cases despite peripheral neutrophil counts less than 0.1 × 10⁻⁹/l in 26 patients: in the digestive tract in 18 cases, around the tract of the central venous catheter (CVC) in 9 and in the lungs in 7 cases. FDG uptake in the CVC tract was associated with coagulase-negative staphylococcal bacteraemia (p < 0.001) and deep venous thrombosis (p = 0.002). The number of patients having Streptococcus mitis bacteraemia appeared to be higher in patients with grade 3 oesophageal FDG uptake (p = 0.08). Pulmonary FDG uptake was associated with the presence of invasive fungal disease (p = 0.04).

Conclusion

¹⁸F-FDG PET/CT scanning during chemotherapy-induced febrile neutropenia and increased CRP is able to detect localized foci of infection and inflammation despite the absence of circulating neutrophils. Besides its potential role in detecting CVC-related infection during febrile neutropenia, the high negative predictive value of ¹⁸F-FDG PET/CT is important for avoiding unnecessary diagnostic tests and therapy.

PET/CT imaging in infectious conditions

New aggressive pathogens are responsible for the increasing incidence and difficult management of infections. Modern epidemics such as diabetes are frequently complicated by severe infections with subsequent high morbidity. Diagnosis (essentially early detection of infection) and also management decision making pose clinical challenges. Many resources are invested in developing precise, noninvasive diagnostic tests and efficient therapies for infectious processes. Nuclear medicine procedures are part of the evaluation armamentarium of patients with suspected or confirmed infection. Their strength relies on the fact that they are noninvasive tests that provide both functional as well as metabolic information early in the course of disease. Their limitations relate to the need for specific radiotracers and the rather low resolution of images. These limitations have been largely overcome by the hybrid PET/CT and SPECT/CT technology. PET/CT, primarily using FDG, is redefining the diagnostic work up and is currently leading to changes in the management of patients with suspected or known infections. The main indications for FDG PET/CT in infection, as well as updated literature results, are presented in the following review.

The molecular imaging approach to image infections and inflammation by nuclear medicine techniques

Inflammatory and infectious diseases are a heterogeneous class of diseases that may be divided into infections, acute inflammation and chronic inflammation. Radiological imaging techniques have, with the exception of functional MRI, high sensitivity but lack in specificity. Nuclear medicine techniques, by contrast, allow the in vivo detection in humans of different physiologic and pathologic phenomena and offer noninvasive tools to detect early pathophysiological changes before anatomical changes occur. In this review, we highlight the role of nuclear medicine in inflammation/infection with emphasis on molecular imaging for in vivo histological characterization of affected tissues for diagnostic purposes and follow-up of therapies. We also describe the clinical indications of all available radiopharmaceuticals in the light of the newly available guidelines.

Necrotizing Cervical Lymphadenitis Caused by Mycobacterium simiae in an HIV-Positive Patient: Imaging with (18)F-FDG PET/CT

Mycobacterium simiae (M. simiae) is an opportunistic pathogen rarely associated with human disease, although in recent years M. simiae has been detected with increasing frequency in human immunodeficiency virus (HIV)-infected patients, usually causing disseminated infection with fever, diarrhea and weight loss. We report the case of an HIV-positive man, who was referred for an (18)F-FDG PET/CT to evaluate a solitary pulmonary nodule. The PET/CT showed incidental large necrotic cervical lymph nodes, compatible with necrotizing cervical lymphadenitis. Biopsy and culture of one of the affected lymph nodes were positive for M. simiae. We present the first report of (18)F-FDG PET/CT imaging of an infectious process caused by M. simiae in humans.

The Diagnostic Role of FDG PET/CT in Patients with Fever of Unknown Origin

Objective: Fever of unknown origin (FUO) is a challenge for the physician and needs use of clinical, laboratory, and imaging studies and also invasive and/or non-invasive interventions to detect the etiology. The aim of present study was to assess the role of FDG PET/CT in determining the etiology in patients with FUO.

Material and Methods: Twenty-four patients (median age 52, range 5-77 years, 6 female, 18 male) who were diagnosed with FUO were retrospectively analyzed in this study. Before the FDG PET/CT studies, none of them had a definitive reason for their diseases investigated by conventional radiological or scintigraphic methods, clinical and laboratory observations.

Results: The positive result was achieved in 19 (79.2%) of 24 patients as findings of the FDG PET/CT. However, FDG PET/CT was useful for definitive diagnosis in 12 (63.2%) of 19 positive patients. Malignant diseases were determined to be the underlying cause of FUO in 5 (41.6%) of 12 patients. Noninfectious inflammatory causes were detected in 2 (16.7%) patients, infections were exhibited in 3 (25%) patients, and miscellaneous diseases demonstrated in 2 (16.7%) patients. In 7 patients the detected pathological uptakes on FDG PET/CT were not helpful for the definitive diagnosis. In remaining 5 patients who showed no pathological uptake in the FDG PET/CT, diagnosis could not be established by other methods, as well. The sensitivity, specificity, and positive and negative predictive values for the determination of FUO etiology were 92.3%, 45.4%, 63.1%, and 100% for FDG PET/CT.

Conclusion: Our results demonstrate that FDG PET/CT seems to have considerable contribution to reveal the reason of undiagnosed patients with FUO investigated by conventional diagnostic methods, clinical and laboratory observations.

Conflict of interest:None declared.

FDG-PET or PET/CT in Fever of Unknown Origin: The Diagnostic Role of Underlying Primary Disease

Fever of unknown origin (FUO) is generally defined as a fever greater than 38.3°C on several occasions during a period longer than 3 weeks for which the etiology behind cannot be diagnosed at the end of at least 1 week hospital stay. Conventional diagnostic methods are still not adequate to reveal underlying reason in approximately 50% of patients with FUO. In patients with certain diagnosis, three major categories are infections, malignancies, and noninfectious inflammatory diseases. Fluoro-18-fluoro-2-deoxy-D-glucose (FDG) is a structural analog of 2-deoxyglucose and accumulates in malignant tissues but also at sites of infection and inflammation. For this reason, FDG PET or PET/CT has great advantage in understanding of underlying pathology in assessment of FUO. However, till today, there are limited studies about the role of FDG PET or PET/CT in evaluation of FUO. In this paper, the impact of FDG PET or PET/CT in the diagnostic work-up of FUO is described by data obtained from literature review.

Diagnostic value of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography in patients with fever of unknown origin

BACKGROUND

While fever of unknown origin (FUO) remains a challenging problem in clinical practice, fluorine-18 fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) has been considered helpful in diagnosing its cause. The present study is set to evaluate the diagnostic value of PET/CT for patients with FUO.

METHODS

We analyzed the records of 48 patients with FUO (34 men and 14 women; mean age of 57-year-old with a range between 24- and 82-year-old). The patients were examined by (18)F-FDG PET/CT and the results were compared to a final diagnosis that was established by additional procedures.

RESULTS

A final diagnosis was established for 36 patients (75%). Among them, 15 patients had infectious diseases, 12 patients had malignancies, and 9 patients had non-infectious inflammatory diseases. Thirty-two abnormal PET/CT results correctly revealed the source of fever (true-positives). Abnormal PET/CT results were considered false-positives for 8 patients without diagnoses. Normal PET/CT results in 4 patients with no diagnoses were classified as true-negatives. Four patients with normal PET/CT results with diagnosed cause for FUO were considered false-negatives. Therefore, PET/CT had a positive predictive value of 80%, a negative predictive value of 50%, a sensitivity of 89%, and a specificity of 33% in patients with FUO.

CONCLUSIONS

Our study demonstrated that FDG-PET/CT is a valuable imaging tool for the identification of the etiology in patients with FUO. The results suggest that this procedure may be considered as a second-line test, especially when conventional structural imaging was normal or unable to distinguish lesions from benign and malignant.

Clinical impact of (18)F-FDG PET/CT on the management and diagnosis of infectious spondylitis

OBJECTIVE

The aim of this study was to evaluate the impact of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) on the management of patients with infectious spondylitis.

MATERIALS AND METHODS

Twenty-nine patients with infectious spondylitis (9 with tuberculous spondylitis and 20 with pyogenic spondylitis) who had undergone an (18)F-FDG PET/CT examination were retrospectively evaluated; 42 lesions were detected. A useful impact on the clinical management of infection therapy (start or longer duration of antibiotic therapy, or surgical intervention, etc) was defined as a strong impact, whereas gaining new information not affecting the clinical management of infection therapy from (18)F-FDG PET/CT was defined as a weak impact. No impact was defined as not obtaining any new information influencing infection therapy.

RESULTS

(18)F-FDG PET/CT had a strong impact on the clinical management of 52% (15 of 29) of the patients. (18)F-FDG PET/CT detected 10 cases of spondylitis and one artificial graft infection that the clinician had not recognized, and the therapeutic period was extended in these patients. In five patients with tuberculous spondylitis, the (18)F-FDG PET/CT images were used to decide the biopsy sites in three patients and to determine which lesions required surgery in two patients.

CONCLUSION

(18)F-FDG PET/CT is useful for detecting infectious spondylitis.