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

Real-world assessment of the clinical utility of whole body 18F-FDG PET/CT in the diagnosis of infection

Few studies have aimed to capture the full spectrum of 18fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG PET/CT) use for evaluation of infections in a real-world context. We performed a retrospective chart review of hospitalized patients who underwent 18F-FDG PET/CT for the workup of infection between April, 2013 and September, 2019. The clinical indications for and impact of 18F-FDG PET/CT on diagnostic and antimicrobial management were evaluated across different infectious indications. Sixty-one patients met the inclusion criteria. The most common indication was identifying a source of a known infection (46%), followed by fever of unknown etiology (FUE)/fever of unknown origin (FUO) (38%), and other (16%). 18F-FDG PET/CT was determined to have had a diagnostic or management clinical impact for a total of 22 patients (36%) including 12/28 (43%) of patients with known infection, 7/23 (30%) of patients with FUE/FUO, and 3/10 (30%) of patients with other indications. 18F-FDG PET/CT confirmed suspected prosthetic endovascular infection for 6/16 (38%) patients. In this study,18F-FDG PET/CT led to a clinical impact on diagnostic and treatment management of hospitalized patients across a variety of syndromes and particularly for source identification in the setting of known infection.

Diagnostic performance of 18F-FDG PET/CT in patients with spinal infection: a systematic review and a bivariate meta-analysis

PURPOSE

Diagnosis of spinal infection (SI) is challenging and usually requires multiple tests. We aimed to perform a systematic review and a bivariate meta-analysis on the diagnostic role of ¹⁸F-FDG PET/CT in patients with SI.

METHODS

A comprehensive literature search of studies published through February 2019 in PubMed/MEDLINE and Cochrane library databases was carried out. Studies investigating the diagnostic performance of ¹⁸F-FDG PET/CT in patients with SI were eligible for inclusion in the qualitative analysis. For the quantitative analysis, pooled sensitivity, specificity, positive and negative likelihood ratio (LR+ and LR-) and diagnostic odds ratio (DOR) of ¹⁸F-FDG PET/CT in patients with suspected SI were calculated on a per examination-based analysis. Pooled data were presented with 95% confidence intervals (95% CI).

RESULTS

Twenty-six articles (833 patients) using ¹⁸F-FDG PET/CT were eligible for the qualitative analysis. Twelve studies (396 patients) were selected for the meta-analysis. Overall, ¹⁸F-FDG PET/CT demonstrated a very good diagnostic performance in patients with SI and several studies underlined the value of ¹⁸F-FDG PET/CT in assessing the response to treatment. The bivariate meta-analysis on ¹⁸F-FDG PET/CT in patients with suspected SI provided the following results: sensitivity 94.8% (95% CI 88.9-97.6%) and specificity 91.4% (95% CI 78.2-96.9%). The pooled LR+, LR- and DOR were 4.7 (95% CI 2.9-7.7), 0.11 (95% CI 0.07-0.16) and 63.4 (95% CI 28.9-139), respectively. No significant heterogeneity or publication bias was found.

CONCLUSION

¹⁸F-FDG PET/CT demonstrated a very good diagnostic performance in patients with SI and can be used in patients in which MRI cannot be performed or is non-diagnostic or inconclusive. Several studies underlined the value of ¹⁸F-FDG PET/CT in assessing the response to treatment in patients with SI. Overall, larger multicentre and prospective studies and cost-effectiveness analyses are warranted.

Joint EANM/ESNR and ESCMID-endorsed consensus document for the diagnosis of spine infection (spondylodiscitis) in adults

PURPOSE

Diagnosis of spondylodiscitis (SD) may be challenging due to the nonspecific clinical and laboratory findings and the need to perform various diagnostic tests including serologic, imaging, and microbiological examinations. Homogeneous management of SD diagnosis through international, multidisciplinary guidance would improve the sensitivity of diagnosis and lead to better patient outcome.

METHODS

An expert specialist team, comprising nuclear medicine physicians appointed by the European Association of Nuclear Medicine (EANM), neuroradiologists appointed by the European Society of Neuroradiology (ESNR), and infectious diseases specialists appointed by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID), reviewed the literature from January 2006 to December 2015 and proposed 20 consensus statements in answer to clinical questions regarding SD diagnosis. The statements were graded by level of evidence level according to the 2011 Oxford Centre for Evidence-based Medicine criteria and included in this consensus document for the diagnosis of SD in adults. The consensus statements are the result of literature review according to PICO (P:population/patients, I:intervention/indicator, C:comparator/control, O:outcome) criteria. Evidence-based recommendations on the management of adult patients with SD, with particular attention to radiologic and nuclear medicine diagnosis, were proposed after a systematic review of the literature in the areas of nuclear medicine, radiology, infectious diseases, and microbiology.

RESULTS

A diagnostic flow chart was developed based on the 20 consensus statements, scored by level of evidence according to the Oxford Centre for Evidence-based Medicine criteria.

CONCLUSIONS

This consensus document was developed with a final diagnostic flow chart for SD diagnosis as an aid for professionals in many fields, especially nuclear medicine physicians, radiologists, and orthopaedic and infectious diseases specialists.

FDG-PET/CT for diagnosis and follow-up of necrotizing (malignant) external otitis

OBJECTIVE

Imaging is important for the diagnosis and follow-up of necrotizing external otitis (NEO). The best imaging modality is controversy. To suggest 2-deoxy-2-[fluorine-18] fluoro-D-glucose-positron emission tomography/computed tomography (18F-FDG-PET/CT) as an alternative to technetium-99m and gallium-67 scans for diagnosis and assessment of response to treatment for patients with NEO.

STUDY DESIGN

Case series.

METHODS

Tertiary referral center. From 2013 through 2017, 12 patients were diagnosed with NEO based on clinical features and positive FDG uptake within the temporal bone on PET/CT. Mean age was 74 ± 11.5; 83% of the patients were male; and 83% had diabetes.

RESULTS

PET/CT scans were reviewed independently by two nuclear medicine specialists. Imaging located osteomyelitis in external ear canal, mastoid, temporomandibular joint, and nasopharyngeal region (100%, 50%, 16%, 8%, respectively). Mean follow-up was 16 months. Eight patients (67%) underwent a second PET/CT scan after active otitis resolved and after at least 6 weeks of antibiotic treatment. The scan demonstrated no or substantially reduced FDG uptake and treatment was stopped. The patients had no NEO symptoms at the end of follow-up. One patient had significant uptake, and antibiotic treatment was continued until a third scan demonstrated no FDG uptake. Two patients died before the second PET/CT, and two were lost to follow-up.

CONCLUSION

18F-FDG-PET/CT is a reliable imaging modality for diagnosis, disease localization, and decision making regarding treatment cessation. 18F-FDG-PET/CT should be considered as the imaging modality of choice for initial diagnosis and follow-up in NEO patients. Larger, controlled studies are warranted.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:961-966, 2019.

In Vivo Molecular Imaging of Musculoskeletal Inflammation and Infection

In vivo molecular imaging detects biologic processes at molecular level and provides diagnostic information at an earlier time point during disease onset or repair. It offers definite advantage over anatomic imaging in terms of improved sensitivity and ability to quantify. Radionuclide molecular imaging has been widely used in clinical practice. This article discusses the role of radionuclide imaging in various infective and inflammatory diseases affecting musculoskeletal system with a focus on PET. It appears that, as more data become available, combined PET/MR imaging could emerge as a front runner in the imaging of musculoskeletal infection and inflammation.

Anatomo-radiological correlation using 18-FDG-PET in abdominal sepsis model in rats. A preliminary study

Purpose:

To examine a correlation of micro-PET images with photographic images of the digestive organs in abdominal sepsis model.

Methods:

Male Wistar rats weighing 265±18g were used. Abdominal sepsis was induced by ligature and cecal puncture. Micro-PET Images from abdominal cavity septic foci were obtained using 18-Fluoro-deoxyglucose, looking for a correlation with photographic images of abdominal cavity organs. Pearson's correlation test was used.

Results:

The mean standard uptake values (SUV) and lesion areas were 2.58±0.63SUVbwg/ml and 546.87±300.95mm2, respectively. There was a strong positive correlation between the two variables (r=0.863, p=0.137), which resulted in a coefficient of determination r2?0.75, meaning that 75% of SUV variation is explained by the lesion areas of digestive organs.

Conclusion:

Micro-PET allows high throughput assessment of lesion count and volume in pre-clinical rat model of CPL abdominal sepsis.

Febrile syndrome of unknown origin: Indications for 18F-FDG PET/CT in inflammatory and infectious processes

Fever of unknown origin is defined as a body temperature greater than 38.3°C lasting more than three weeks for which the cause could not be found within one week of hospital admission. More than 200 causes have been reported, and these can be classified into four categories: infections, inflammatory diseases, oncologic processes, and miscellaneous conditions. Noninvasive diagnostic techniques are used in 69.2% of cases and invasive techniques in 30.8%. Structural imaging techniques show the morphological changes from infectious, inflammatory, and tumor-related processes, but they do not allow the detection of the early changes brought about by these processes. The metabolic information provided by ¹⁸F-FDG PET/CT has a promising role in these patients. ¹⁸F-FDG uptake is based on the cells' use of glucose as a source of energy, so it can be observed in infectious, inflammatory, and tumor-related processes. The established non-oncologic indications for ¹⁸F-FDG PET/CT are sarcoidosis, osteomyelitis, spondylodiscitis, fever of unknown origin, and vasculitis, which together account for more than 85% of studies.

Assessment of Therapy Response by FDG PET in Infection and Inflammation

Positron emission tomography (PET) is a well-known imaging modality in assessing the treatment response to chemotherapy or radiotherapy in various malignancies. A systematic review of the literature reveals a few publications reporting evaluation of the treatment response in benign conditions using PET/computed tomography. PET holds a promising future role in the follow-up of inflammatory or infectious diseases. In this article, [(18)F]Fluorodeoxyglucose PET as a tool in the evaluation, treatment, and follow-up of infectious and inflammatory diseases is discussed.

Diagnostic value of F-18 FDG PET/CT in patients with spondylodiscitis: Is dual time point imaging time worthy?

PURPOSE

In this retrospective study, we aimed to investigate the value of FDG-PET/CT in the diagnosis of spondylodiscitis (SD), the significance of dual time point imaging (DTPI) for SD diagnosis and the worth of SUVmax data for distinguishing tuberculous vs. non-tuberculous SD.

MATERIALS AND METHODS

32 patients with suspected SD were scanned with FDG-PET/CT. For quantitative analysis maximum standardized uptake value (SUVmax) of the lesion area was measured. Nineteen patients had DTPI of FDG-PET/CT. The final diagnoses were achieved by histopathological, microbiological, and clinical results.

RESULTS

Specific pathogens were isolated in 21 patients; other patients were accepted as nonspecific bacterial SD. In all patients, FDG-PET/CT results were compatible with SD diagnosis. The SUVmax data for tuberculous and non-tuberculous SD and DTPI results were statistically insignificant.

CONCLUSION

FDG-PET/CT is a successful modality for SD diagnosis; additionally, DTPI protocol for FDG-PET/CT in SD diagnosis and SUVmax data for differentiation between non-tbc SD and tbc SD are useless.

Imaging for infection: from visualization of inflammation to visualization of microbes

BACKGROUND

With the development of high-resolution cross-sectional imaging, anatomic identification of most areas of infection has become routine. Imaging a site of infection allows for diagnosis and treatment. In the past, molecular imaging for infection involved mainly the use of radiolabeled leukocytes for functional targeting at infection sites. With the recent development of functional nuclear imaging, bacterial and viral metabolism can also be imaged directly for potential identification of early infection.

METHODS

Review of pertinent English-language literature.

RESULTS

Cross-sectional imaging is used routinely to identify and treat sources of infection in patients with fever, leukocytosis, or unexplained hemodynamic instability. Although ultrasound is preferred for the identification of biliary or hepatic sepsis, computed tomography (CT) has proved to be accurate for the identification and treatment of intra-abdominal fluid collections and abscesses. Biologic imaging is a non-invasive technique that identifies sites of infection in cases in which no definite abnormality is identified via cross-sectional imaging. This is made possible by imaging the accumulation of radioisotopes that have been attached to white blood cells or glucose. Biologic imaging is useful for the identification of anatomic sites where there is inflammation or high metabolic demand. However, a drawback of biologic imaging is that it is not specific for infection. Techniques that image microbes directly increase the specificity of imaging results significantly and can be used to quantify and track infectious processes. For example, radiolabeling of antimicrobial proteins and antibiotics is one technique that has been demonstrated to identify areas of infection accurately in animals but is not currently being used clinically in humans. With the advent of gene therapy, many researchers are inserting the herpes viral thymidine kinase gene into both viruses and bacteria. This allows for tracking of the infectious process by imaging the accumulation of radiolabeled thymidine analogues.

CONCLUSION

This review summarizes standard imaging for infection as it is currently practiced clinically. We will also explore the promising new methods of microbial imaging that are likely to become standards in clinical care in the near future.

Positron emission tomography in spinal infections

Magnetic resonance imaging is the imaging method of choice for diagnosing infection of the spine in unoperated cases. 2-[(18)F]-fluoro-2deoxy-d-glucose positron emission tomography/computed tomography study is recommended to distinguish between spinal infection and common Modic change in patients with metallic implants and prosthetic replacements and for differentiating tuberculous from pyogenic spondylitis in ambiguous cases, reflecting the activity of the infection. Also, it seems to have a strong clinical impact in more than half of patients with infectious spondylitis, while it is superior to other imaging techniques in revealing residual disease after treatment and early response to therapy. New tracers as well as new hybrid modalities are under investigation.

Prospective comparison of whole-body (18)F-FDG PET/CT and MRI of the spine in the diagnosis of haematogenous spondylodiscitis

PURPOSE

To prospectively compare (18)F-FDG PET/CT and MRI in the diagnosis of haematogenous spondylodiscitis

METHODS

The study included 26 patients (12 women, 14 men; mean age 59 ± 17 years) with clinical symptoms of infection of the spine. Patients who had had prior spinal surgery or any type of antibiotic therapy in the previous 3 months were excluded from the study. Whole-body PET/CT 60 min after injection of 4.07 MBq/kg of (18)F-FDG and an MRI scan of the spine was performed in all patients. SUVmax in an area surrounding the lesions with the suspicion of infection as well as a background SUVmean in a preserved area of the spine were calculated for quantification. Infection was diagnosed by microbiological documentation in cultures of image-guided spinal puncture fluid or blood. Infection was excluded if symptoms were absent without antimicrobial therapy during a follow-up of at least 6 months.

RESULTS

Spondylodiscitis was confirmed in 18 of the 26 patients. Staphylococcus aureus was found in 8 patients, Mycobacterium tuberculosis in 4, Escherichia coli in 2 and other pathogens in 4. Of the remaining 8 patients, the diagnoses were degenerative spondyloarthropathy in 5 and vertebral fracture in 3. The sensitivity, specificity, and positive and negative predictive value were 83%, 88%, 94% and 70% for (18)F-FDG PET/CT, and 94%, 38%, 77% and 75% for MRI, respectively. The accuracies of (18)F-FDG PET/CT and MRI were similar (84% and 81%, respectively). The combination of (18)F-FDG PET/CT and MRI detected the infection in 100% of the patients with spondylodiscitis. (18)F-FDG uptake, quantified in terms of SUVmax corrected by the background SUVmean, was significantly higher in patients with spondylodiscitis than in those without infection (p < 0.001).

CONCLUSION

Due to its high specificity, (18)F-FDG PET/CT should be considered as a first-line imaging procedure in the diagnosis of spondylodiscitis. Quantification of uptake in terms of SUVmax was able to discriminate infection of the spine from other processes in this series of patients.

18F-fluorodeoxyglucose uptake pattern in patients with suspected spondylodiscitis

BACKGROUND

Infections of the spine are rare and often discovered late, but they can have a severe outcome with hospital case fatality rates of up to 17%. Efficient and early diagnosis is important, because early diagnosis and therapy improve outcome. The aim of the current study was to evaluate the clinical value of F-fluorodeoxyglucose (18F-FDG) uptake pattern in PET as a diagnostic modality for the detection of spondylodiscitis.

MATERIALS AND METHODS

18F-FDG-PET examinations of the spine were performed in 42 patients with suspected spondylodiscitis. Of these 42 patients, 13 had already undergone spinal surgery in the past, making initial definition of the test group difficult and complex. Qualitative analysis was based on 18F-FDG uptake patterns, and quantitative maximal standard uptake value measurements were ascertained. PET findings were verified by comparing them with combined information from intraoperative findings, blood results, microbiological investigations, histopathology, and clinical examination.

RESULTS

Evidence of spondylodiscitis was correctly determined in 95% of patients and absence of spondylodiscitis in 86% of patients using 18F-FDG-PET. The detection of spondylodiscitis by 18F-FDG-PET had a sensitivity of 86% and a specificity of 95%. Three patients had false-negative and one patient a false-positive finding on 18F-FDG-PET.

CONCLUSION

The application of 18F-FDG uptake patterns in 18F-FDG-PET helps to predict or exclude spondylodiscitis. Differentiation between inflammatory and degenerative changes in the vertebral body endplates is possible. Owing to the high specificity of this method, a negative PET result in the setting of a diagnostically unclear case diminishes the need for surgical intervention. 18F-FDG-PET is therefore an important tool in inflammation imaging and can be used in the diagnostic cascade of difficult cases with suspected spondylodiscitis. In contrast, a positive PET result does not always clearly establish the cause of increased 18F-FDG uptake.

The use of (18)F-FDG-PET/CT for diagnosis and treatment monitoring of inflammatory and infectious diseases

FDG-PET, combined with CT, is nowadays getting more and more relevant for the diagnosis of several infectious and inflammatory diseases and particularly for therapy monitoring. Thus, this paper gives special attention to the role of FDG-PET/CT in the diagnosis and therapy monitoring of infectious and inflammatory diseases. Enough evidence in the literature already exists about the usefulness of FDG-PET/CT in the diagnosis, management, and followup of patients with sarcoidosis, spondylodiscitis, and vasculitis. For other diseases, such as inflammatory bowel diseases, rheumatoid arthritis, autoimmune pancreatitis, and fungal infections, hard evidence is lacking, but studies also point out that FDG-PET/CT could be useful. It is of invaluable importance to have large prospective multicenter studies in this field to provide clear answers, not only for the status of nuclear medicine in general but also to reduce high costs of treatment.

Fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography scan contributes to the diagnosis and management of brucellar spondylodiskitis

Background

Limited data suggest that fluorine-18 fluoro-2-deoxy-D-glucose (F-18 FDG) positron emission tomography combined with computed tomography (PET/CT) scan may be useful for diagnosing infections of the spine. Brucellar spondylodiskitis might be devastating and current imaging techniques lack sensitivity and specificity. The aim of this prospective study was to determine the role of F-18 FDG PET/CT scan in the diagnosis of brucellar spondylodiskitis and in monitoring the efficacy of its treatment.

Methods

Ten consecutive patients with brucellar spondylitis were prospectively evaluated with PET/CT. Baseline evaluation included also magnetic resonance imaging (MRI) of the affected spine, indices of inflammation, the slide agglutination test (SAT), and the standard hematology and biochemistry. All cases were treated with suitable antibiotics until resolution or significant improvement of clinical and radiological (MRI) findings. Upon completion of treatment, they were re-evaluated with follow-up PET/CT scan. The maximum standardized uptake values (SUV) were measured and compared with SAT.

Results

In all patients there was an increased F-18 FDG activity in the infected spine region detected by the initial MRI. F-18 FDG PET/CT provided additional information, compared to MRI, in 4 (40%) patients. More specifically it revealed additional spine lesions (in 3 patients), lymphadenitis, arthritis, organomegaly, as well as new paravertebral soft tissue involvement and epidural masses. This additional information had an impact on the duration of treatment in these patients. At the end of treatment all patients had a complete clinical response; 5 patients had positive serology, 6 patients had residual MRI findings, while 9 had a positive PET/CT but with significantly decreased FDG uptake compared to baseline (median 2.6, range 1.4 – 4.4 vs. median 5.5, range 2.8 – 9.4, p = 0.005). During the follow up period (median 12.5 months) no relapses have been observed. No significant association was observed between the SUV and SAT.

Conclusions

Our study suggests that in patients with brucellar spondylodiskitis F-18 FDG PET/CT scan can provide additional information on the spread of the infection, compared to MRI. Successful treatment is associated with a significant decrease in SUVmax values; thus, PET/CT scan may be a complementary method for determining the efficacy of treatment.

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.