Impact of hybrid molecular imaging in retroperitoneal fibrosis: a systematic review

18F-FDG PET/CT in Inflammation and Infection: Procedural Guideline by the Korean Society of Nuclear Medicine

Abstract

This guideline outlines the use of 18F-fluoro-2-deoxyglucose positron emission tomography / computed tomography for the diagnosis and management of infectious and inflammatory diseases. It provides detailed recommendations for healthcare providers on patient preparation, imaging procedures, and the interpretation of results. Adapted from international standards and tailored to local clinical practices, the guideline emphasizes safety, quality control, and effective use of the technology in various conditions, including spinal infections, diabetic foot, osteomyelitis, vasculitis, and cardiac inflammation. The aim is to assist nuclear medicine professionals in delivering accurate diagnoses and improving patient outcomes while allowing flexibility to adapt to individual patient needs, technological advancements, and evolving medical knowledge. This document is a comprehensive resource for enhancing the quality and safety of 18F-fluoro-2-deoxyglucose positron emission tomography / computed tomography for the evaluation of infectious and inflammatory diseases.

Preamble

The Korean Society of Nuclear Medicine (KSNM) was established in 1961 to promote the clinical and technological advancement of nuclear medicine in South Korea, with members that include nuclear medicine physicians and associated scientists. The KSNM regularly formulates and revises procedural guidelines for nuclear medicine examinations to enhance the field and improve the quality of patient care. These guidelines are designed to support healthcare professionals in providing appropriate medical care to patients. However, they are not immutable rules or mandatory requirements for conducting examinations.Therefore, KSNM states that these guidelines should not be used in legal actions challenging a healthcare professional's medical decisions. The ultimate judgment regarding specific procedures or appropriate measures should be made by nuclear medicine physicians, considering the unique circumstances of each case. Deviation from these guidelines does not imply substandard medical practice. Rather, reasonable judgments differing from the guidelines can be made based on the patient's condition, available resources, and advancements in knowledge or technology. Due to the diversity and complexity of patients, it is often challenging to predict the most appropriate diagnostic and accurate therapeutic responses. Thus, adherence to these guidelines does not always guarantee an exact diagnosis or successful outcomes.The purpose of this guideline is to assist healthcare providers in making reasonable decisions and conducting effective and safe examinations based on current medical knowledge, available resources, and patient needs when performing 18F-fluoro-2-deoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) examinations for infectious/inflammatory diseases.

EANM/SNMMI guideline/procedure standard for [18F]FDG hybrid PET use in infection and inflammation in adults v2.0

INTRODUCTION

Hybrid [18F]FDG PET imaging is currently the method of choice for a wide variety of infectious and inflammatory disorders and was recently adopted in several clinical guidelines. A large amount of evidence-based articles, guidelines and appropriate use criteria have been published since the first version of this guideline in 2013.

PURPOSE

To provide updated evidence-based information to assist physicians in recommending, performing and interpreting hybrid [18F]FDG PET examinations for infectious and inflammatory disorders in the adult population.

METHODS

A systematic literature search of evidence-based articles using whole-body [18F]FDG hybrid imaging on the indications covered within this guideline was performed. All systematic reviews and meta-analyses published within the last 10 years until January 2023 were identified in PubMed/Medline or Cochrane. For each indication covered in this manuscript, diagnostic performance was provided based on meta-analyses or systematic reviews. If not available, results from prospective or retrospective studies were considered based on predefined selection criteria. RESULTS AND CONCLUSIONS: Hybrid [18F]FDG PET is extremely useful in the work-up and management of adults with infectious and inflammatory diseases, as supported by extensive and rapidly growing evidence-based literature and adoption in clinical guidelines. Practical recommendations are provided describing evidence-based indications as well as interpretation criteria and pitfalls. Monitoring treatment response is the most challenging but insufficiently studied potential application in infection and inflammation imaging.

Роль позитронно-емісійної томографії при інфекційних та запальних захворюваннях (огляд літератури)

Мета. Дослідити клінічну роль методів гібридної променевої візуалізації, зокрема позитронно-емісійної томографії (ПЕТ) у діагностиці та лікуванні пацієнтів із запальними та інфекційними захворюваннями. Матеріали та методи. Матеріалом для дослідження були наукові результати публікацій фахових наукових видань провідних країн світу  наукової та клінічної діяльності за останні 10 років щодо клінічного значення методів гібридної променевої візуалізації у діагностиці та лікуванні пацієнтів із запальними та інфекційними захворюваннями. Методи дослідження передбачали застосування методів променевої візуалізації ПЕТ при інфекційних та запальних захворюваннях. Результати. Показана ефективність ПЕТ у випадках, коли інші звичайні дослідження є неможливими через високий ризик ускладнень. В роботі розглянуто  корисність методу при діагностиці станів, які виникають як ускладнення після протезування: при ендокардитах протезованого клапану; інфекції  імплантованих електронних пристроїв; протезованих суглобів та імплантантів для фіксації переломів.  ПЕТ в таких випадках дозволяє провести диференційну діагностику між асептичним та інфекційним запаленням, особливо за наявності спричинених  металевими елементами артефактів, які можуть  обмежують дослідження за допомогою комп’ютерної томографії  або магнітно-резонансної томографії. Висновки. Позитронно-емісійна томографія у пацієнтів із запальними або інфекційними захворюваннями є ефективним допоміжним додатковим методом променевої візуалізації. ПЕТ знаходить своє ефективне застосування на різних етапах лікування, а також є корисним методом променевої візуалізації для моніторингу терапевтичної відповіді на лікування.

A role of FDG PET/CT for Response Assessment in Large Vessel Disease?

Currently, a large amount of evidence-based data clearly demonstrates the usefulness of [¹⁸F]FDG PET/CT in the diagnosis of several infectious and inflammatory diseases, including those related to the large vessels. The aim of this article is to clarify whether, beyond initial diagnosis, [¹⁸F]FDG PET/CT may have a role in treatment response assessment in inflammatory or infectious diseases of the large vessels, including large vessel vasculitis, vascular graft infection, retroperitoneal fibrosis/chronic periaortitis and infective native aortic aneurysms. Rapidly accumulating data suggest that [¹⁸F]FDG PET/CT could be a valuable imaging method for therapy monitoring in some infectious and inflammatory diseases of large vessels. The available data, albeit preliminary, indicate that [¹⁸F]FDG PET/CT could even play a pivotal role in the management of these diseases, leading to better drug dosage, confirmation of the usefulness of the treatment, and early modification of the therapeutic strategy. However, to date, the role of [¹⁸F]FDG PET/CT for treatment assessment in large vessel diseases, in particular large vessel vasculitis, is not clearly defined and well-designed prospective studies are needed to confirm its possible role in treatment monitoring and treatment guidance.

Retroperitoneal fibrosis masquerading as pelvi-ureteric junction obstruction - Laparoscopic management

Introduction

Retroperitoneal fibrosis (RPF) is a rare fibro-inflammatory condition which is characterized by development of extensive fibrosis throughout the retroperitoneum. It is classically centred over the anterior surface of the fourth and fifth lumbar vertebrae. It results in entrapment and extrinsic compression of retroperitoneal structures.

Presentation of the case

We present the case of a 69 years old man who was reported to have right pelvi - ureteric junction obstruction on computed tomography, but turned out to have RPF.

Discussion

Retroperitoneal fibrosis commonly causes obstructive uropathy (either unilateral, bilateral or progressing from unilateral to bilateral) and if untreated, renal failure. It has high response/remission rates to glucocorticoid therapy. However, relapse rates are also high. Hence, close surveillance with serial laboratory and imaging investigations, after achieving remission, is key to long term disease control.

Conclusion

Although classical imaging findings, supportive laboratory markers and suggestive/diagnostic histopathology appearances for RPF are well documented, its accurate preoperative diagnosis is not always an assured certainty.

•

This case is unique in that the original plan to perform a laparoscopic pyeloplasty, purportedly for right pelvi-ureteric junction obstruction; was aborted ‘on table’ and a laparoscopic ureterolysis performed, instead.

•

Though ureteral involvement is bilateral in most cases of retroperitoneal fibrosis, this case is rare and unique in that the patient had unilateral involvement of his ureter (right sided).

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Periaortic fibro-inflammatory mass at the level of the lumbar vertebrae is the hallmark of primary / idiopathic retroperitoneal fibrosis. However in this case, no such imaging finding was noted. Instead, the patient had just obvious unilateral (ride sided) disease on pre-operative imaging.

State of the art of 18F-FDG PET/CT application in inflammation and infection: a guide for image acquisition and interpretation

AIM

The diagnosis, severity and extent of a sterile inflammation or a septic infection could be challenging since there is not one single test able to achieve an accurate diagnosis. The clinical use of 18F-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) imaging in the assessment of inflammation and infection is increasing worldwide. The purpose of this paper is to achieve an Italian consensus document on [18F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases, such as osteomyelitis (OM), prosthetic joint infections (PJI), infective endocarditis (IE), prosthetic valve endocarditis (PVE), cardiac implantable electronic device infections (CIEDI), systemic and cardiac sarcoidosis (SS/CS), diabetic foot (DF), fungal infections (FI), tuberculosis (TBC), fever and inflammation of unknown origin (FUO/IUO), pediatric infections (PI), inflammatory bowel diseases (IBD), spine infections (SI), vascular graft infections (VGI), large vessel vasculitis (LVV), retroperitoneal fibrosis (RF) and COVID-19 infections.

METHODS

In September 2020, the inflammatory and infectious diseases focus group (IIFG) of the Italian Association of Nuclear Medicine (AIMN) proposed to realize a procedural paper about the clinical applications of [18F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases. The project was carried out thanks to the collaboration of 13 Italian nuclear medicine centers, with a consolidate experience in this field. With the endorsement of AIMN, IIFG contacted each center, and the pediatric diseases focus group (PDFC). IIFG provided for each team involved, a draft with essential information regarding the execution of [18F]FDG PET/CT or PET/MRI scan (i.e., indications, patient preparation, standard or specific acquisition modalities, interpretation criteria, reporting methods, pitfalls and artifacts), by limiting the literature research to the last 20 years. Moreover, some clinical cases were required from each center, to underline the teaching points. Time for the collection of each report was from October to December 2020.

RESULTS

Overall, we summarized 291 scientific papers and guidelines published between 1998 and 2021. Papers were divided in several sub-topics and summarized in the following paragraphs: clinical indications, image interpretation criteria, future perspectivess and new trends (for each single disease), while patient preparation, image acquisition, possible pitfalls and reporting modalities were described afterwards. Moreover, a specific section was dedicated to pediatric and PET/MRI indications. A collection of images was described for each indication.

CONCLUSIONS

Currently, [18F]FDG PET/CT in oncology is globally accepted and standardized in main diagnostic algorithms for neoplasms. In recent years, the ever-closer collaboration among different European associations has tried to overcome the absence of a standardization also in the field of inflammation and infections. The collaboration of several nuclear medicine centers with a long experience in this field, as well as among different AIMN focus groups represents a further attempt in this direction. We hope that this document will be the basis for a "common nuclear physicians' language" throughout all the country.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40336-021-00445-w.

Hybrid imaging of the abdomen and pelvis

Accurate imaging is crucial for lesion detection in abdominal organs, for the noninvasive characterization of focal and diffuse abnormalities, and for surgical planning. To accomplish these tasks, several imaging modalities such as multidetector computer tomography (MDCT), magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) are used for abdominal imaging, providing important morphological, functional or metabolic information. More recently, PET/MRI has been gaining attention due to the possibility of combining high-resolution imaging with metabolic imaging. PET/MRI is a novel hybrid imaging technology that in the near future might play a pivotal role in the clinical management of oncologic and inflammatory abdominopelvic diseases. Despite the still limited number of published clinical studies, PET/MRI has been proven to be at least equivalent to PET/CT and to standalone MRI in a variety of oncologic disease. Moreover, in selected and focused clinical studies, it has been proven to outperform current standard of care imaging, for example, in evaluating cholangiocarcinomas, liver metastases, untreated and treated rectal cancer. This has also had an impact on therapeuticmanagement in some studies. Therefore in some institutions, including those of the authors, PET/MRI is becoming the new standard imaging modality in staging treatment-naïve intrahepatic massforming cholangiocarcinomas and prior to complicated hepatic surgery.

Hybrid Imaging in Evaluation of Abdominal Sarcoidosis

OBJECTIVE

To determine the prevalence of abdominal involvement, distribution pattern and evaluate role of hybrid molecular imaging in patients with abdominal sarcoidosis.

METHODS

Between January 2010 and December 2011, 98 patients with chronic sarcoidosis and presence of prolonged symptoms or other findings suggestive of active disease were referred to FDG PET/CT examination. Active disease was found in 82 patients, and they all were screened for the presence of abdominal sarcoidosis on FDG PET/CT. All patients also underwent MDCT and assessment of serum ACE level. Follow up FDG PET/CT examination was done 12.3±5.4 months after the baseline.

RESULTS

Abdominal sarcoidosis was present in 31/82 patients with active sarcoidosis. FDG uptake was present in: retroperitoneal lymph nodes (77%), liver (26%), spleen (23%), adrenal gland (3%). Majority of patients had more than two locations of disease. Usually thoracic disease was spread into the extrathoracic localizations, while isolated abdominal sarcoidosis was present in 10% of patients. After first FDG PET/CT examination therapy was changed in all patients. Eleven patients came to the follow up examination where SUVmax significantly decreased in the majority of them. Three patients had total remission, three had absence of abdominal disease but discrete findings in thorax and others had less spread disease. ACE levels did not correlate with SUVmax level.

CONCLUSION

FDG PET/CT can be a useful tool for detection of abdominal sarcoidosis and in the evaluation of therapy response in these patients. Awareness of the presence of intra-abdominal sarcoidosis is important in order to prevent long-standing unrecognized disease.

[Hybrid imaging of the abdomen and pelvis. German version]

Accurate imaging is crucial for lesion detection in abdominal organs, for the noninvasive characterization of focal and diffuse abnormalities, and for surgical planning. To accomplish these tasks, several imaging modalities such as multidetector computer tomography (MDCT), magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) are used for abdominal imaging, providing important morphological, functional or metabolic information. More recently, PET/MRI has been gaining attention due to the possibility of combining high-resolution imaging with metabolic imaging. PET/MRI is a novel hybrid imaging technology that in the near future might play a pivotal role in the clinical management of oncologic and inflammatory abdominopelvic diseases. Despite the still limited number of published clinical studies, PET/MRI has been proven to be at least equivalent to PET/CT and to stand-alone MRI in a variety of oncologic disease. Moreover, in selected and focused clinical studies, it has been proven to outperform current standard of care imaging, for example, in evaluating cholangiocarcinomas, liver metastases, untreated and treated rectal cancer. This has also had an impact on therapeutic management in some studies. Therefore in some institutions, including those of the authors, PET/MRI is becoming the new standard imaging modality in staging treatment-naïve intrahepatic mass-forming cholangiocarcinomas and prior to complicated hepatic surgery.

[18F-FDG positron emission tomography in non-oncological renal pathology: Current indications and perspectives]

Positron emission tomography combined with computed tomography (PET/CT) is a nuclear imaging technique which provides anatomical and functional information. PET/CT is increasingly used in non-oncological nephrology since conventional radiological approaches after injection of contrast agents are relatively contra-indicated in patients with chronic kidney disease (CKD). PET/CT after i.v. injection of ¹⁸F-fluoro-deoxy-glucose (FDG) is not toxic and is characterized by a high sensitivity. The level of irradiation (∼5mSv) is acceptable. CKD does not significantly influence tissue uptake of ¹⁸F-FDG. The purpose of the present review aims at detailing the non-oncological indications of ¹⁸F-FDG PET/CT in general nephrology and after kidney transplantation. Particularly, ¹⁸F-FDG PET/CT appears useful in the diagnosis of cyst infection in patients with autosomal dominant polycystic kidney disease, as well as in the characterization of retroperitoneal fibrosis. In kidney transplant recipients, ¹⁸F-FDG PET/CT may help in the diagnostic work-up of suspected acute rejection, thereby eventually avoiding unnecessary kidney transplant biopsy. Perspectives in ¹⁸F-FDG PET/CT imaging are discussed, including innovative approaches of image analysis.