PET/CT in the evaluation of inflammatory bowel disease: studies in patients before and after treatment

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.

Clinical utility of positron emission tomography/computed tomography in inflammatory bowel disease

PURPOSE

The clinical utility of positron emission tomography/computed tomography (PET/CT) in comparison to standard workup in patients with known or suspected inflammatory bowel disease (IBD) is unknown.

PROCEDURES

Clinical data were collected on seven patients with known or suspected IBD undergoing PET/CT. Standard workup included history, physical exam, laboratory tests, colonoscopy and/or cross-sectional imaging. We divided the intestine into five regions [small bowel and four colon (ascending, transverse, descending and rectosigmoid)] and graded relative standard uptake values 0, 1, 2 or 3 by comparison to the liver, using a region-of-interest analysis (0 = no activity, 1 = liver, 2 and 3 = significant inflammation).

RESULTS

In patients 1 and 2, PET/CT demonstrated more activity than we thought clinically present. The other patients avoided unnecessary escalation or initiation of IBD therapy based on PET/CT results. Compared with standard workup, all seven patients had superior results when therapeutic decisions were based on PET/CT.

CONCLUSIONS

We found PET/CT to be very useful in diagnosis and management in patients with known or suspected IBD.

F-18 FDG-PET/CT in aseptic abscesses with recurrent febrile abdominal pain

OBJECTIVE

Mendelian and complex autoinflammatory disorders frequently manifest as recurrent abdominal pain and fever. Diagnosis may be difficult and scant data are available about the interest of 2-deoxy-2-[18F]fluoro-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) in such conditions, particularly aseptic abscesses (AA).

MATERIAL AND METHODS

We analyzed five cases of AA in which FDG-PET/CT was performed at diagnosis (n = 2) and after a suspected relapse (n = 5). Follow-up FDG-PET/CT was performed in two patients 9 days and 6 weeks after the initiation of oral corticosteroids.

RESULTS

FDG-PET/CT showed intense uptake foci in the abdominal lymph nodes (n = 4), liver (n = 2) and spleen (n = 4) before treatment. A marked metabolic response was observed while patients were being treated. In a relapsing patient with abdominal pain but no raised CRP, although CT scan was unchanged, abnormal uptake of FDG was observed. By contrast, some lesions previously observed on CT scan displayed no fixation on new FDG-PET/CT and were suggestive of sequelae in three patients.

CONCLUSION

Although nonspecific, FDG-PET/CT may be an interesting tool for the diagnosis and management of recurrent and febrile abdominal pain in AA. At the time of relapse, it can differentiate between a sequela of previous flares and a new localization. It can be used for whole-body screening to look for other asymptomatic disease localizations.

Nuclear imaging of autoimmunity: focus on IBD and RA

There is a need for methods to improve the diagnosis, patient staging and evaluation of therapeutic response in patients with autoimmune conditions to improve patient care. Inflammatory bowel disease (IBD) and rheumatoid arthritis (RA) are two inflammatory diseases characterized by involvement of innate and adaptive immune components that change the metabolic state of their respective target tissues, thus providing an opportunity for molecular imaging probes to detect such changes. Optimally, such probes and the imaging methods employed would be non-invasive, robust and reproducible, give a quantitative result, report on the status of the affected tissue(s) and respond to the effects of a therapeutic molecule. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are nuclear imaging approaches that have the potential to satisfy such requirements. In this review, the work to date and the potential of PET and SPECT imaging probes in these two inflammatory conditions, IBD and RA, are discussed.

Noninvasive assessment of pediatric inflammatory bowel disease with ¹⁸F-fluorodeoxyglucose-positron emission tomography and computed tomography

OBJECTIVES

¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) is a less invasive diagnostic tool and promising in detecting gastrointestinal lesions of pediatric inflammatory bowel disease (IBD) patients. Co-registration of low-dose computed tomography (CT) could lead to improvements in the assessment of disease. Therefore, this retrospective study evaluates the value of PET±CT in pediatric IBD patients.

PATIENTS AND METHODS

We analyzed ¹⁸F-FDG-PET scans without (n=24) or with combined (n=21) low-dose CT in children (18 females, 27 males, age: 3.7-16.7 years, median 13.2 years) who presented with the diagnosis of IBD (n=45). Results of PET±CT scans and conventional diagnostic procedures (endoscopy, histology, and ultrasound) were compared by a segment-based analysis.

RESULTS

Overall, 253 segments of the gastrointestinal tract (GIT) were explored by endoscopy/histology and ¹⁸F-FDG-PET±CT. Twenty-five additional small bowel segments were assessed by abdominal ultrasound and further 152 GIT segments not reached during endoscopy were evaluated by PET±CT. PET±CT revealed a segment-based sensitivity, specificity, positive predictive value, negative predictive value, and an accuracy for the detection of GIT lesions of 82, 97, 96, 88, and 91%, respectively. The patient-based sensitivity and specificity was 97 and 100%, respectively. Interestingly, the co-registration of CT did not improve the diagnostic informative value.

CONCLUSION

FDG-PET±CT is especially suitable for the assessment of IBD in children. The radiation exposure of 3-7 mSv is justified by the accuracy of this approach. FDG-PET seems to be a reliable tool for detecting inflamed gut segments in IBD with high sensitivity and specificity. The co-registration of CT had no additional benefit.

Low-dose 18F-FDG PET/CT enterography: improving on CT enterography assessment of patients with Crohn disease

The purpose of this study was to evaluate the diagnostic efficacy of low-dose, combined (18)F-FDG PET/CT enterography (PET/CTE), compared with CT enterography (CTE) alone, in the assessment of patients with Crohn disease.

METHODS

Thirteen patients with Crohn disease were prospectively enrolled in this pilot study and underwent abdominal-pelvic (18)F-FDG PET/CTE using neutral oral and intravenous contrast medium. The effective dose from PET/CTE was 17.7 mSv for the first 4 patients and 8.31 mSv for the last 9 patients. Six patients underwent surgical resection of the bowel, and 7 patients underwent colonoscopy with biopsies within 27 d (mean, 12 d) of PET/CTE. PET/CTE and CTE images were each visually assessed for Crohn disease involvement in 54 bowel segments with pathology correlation. Extraintestinal findings were recorded. A CTE severity score, maximum standardized uptake value (SUVmax), SUVmax ratio, simplified endoscopic score, and clinical parameters were correlated with pathology inflammation grade, on a per-patient basis and on a per-bowel-segment basis, using Spearman correlation.

RESULTS

In 3 (23.1%) of 13 patients, (18)F-FDG uptake using PET/CTE revealed active inflammation in a bowel segment not evident using CTE (n = 2) or revealed an enterocolic fistula missed with CTE (n = 1). Visual interpretation of both PET/CTE and CTE images detected the presence of disease in all bowel segments with more than mild inflammation (sensitivity, 100%; specificity, 89.7%; positive predictive value, 78.9%; and negative predictive value, 100%). Correlation to inflammation grade per patient was the strongest for the SUVmax ratio (0.735, P = 0.004) and SUVmax (0.67, P = 0.013), as compared with the CTE score (0.62, P = 0.024). Correlation with inflammation per bowel segment was higher for the CTE score (0.79, P < 0.0001) than the SUVmax ratio (0.62, P < 0.0001) or SUVmax (0.48, P < 0.0001). SUVmax correlated strongly with serum C-reactive protein (0.82, P = 0.023), but CTE score did not.

CONCLUSION

Low-dose (18)F-FDG PET/CTE, compared with CTE, may improve the detection and grading of active inflammation in patients with Crohn disease. PET/CTE also may reveal clinically significant findings, such as enterocolic fistula, not evident on PET or CTE alone.

Imaging of cell trafficking in Crohn's disease

Inflammatory bowel diseases are represented by ulcerative colitis and Crohn's disease, both consisting of a chronic, uncontrolled inflammation of the intestinal mucosa of any part of the gastrointestinal tract with patchy or continuous inflammation. Ileo-colonoscopy is considered the current gold standard imaging technique for the diagnosis. However, as the majority of patients need a long-term follow-up it would be ideal to rely on a non-invasive technique with good compliance. This review focuses on nuclear medicine imaging techniques in Crohn's disease. Different scintigraphic methods of imaging cells involved in the pathogenesis are described. The radiopharmaceuticals can be divided into non-specific radiopharmaceuticals for inflammation and specific radiopharmaceuticals that directly image lymphocytes involved in the process. This non-invasive molecular imaging approach can be useful also because it images the small bowel or other areas--where colonoscopy is not useful-and that it may play a role for constant follow-up, because relapses are frequent. Finally, an update on other imaging modalities, and particularly MRI, in the evaluation of Crohn's disease activity, is provided. Although MRI cannot directly detect inflammatory cells, it has shown a high sensitivity in detecting the macroscopic signs of inflammation at the level of the intestinal wall affected by Crohn's disease and Ulcerative colitis. The current diagnostic value of MRI in the detection of inflamed bowel segment and in the assessment of CD activity, as well the potentials MR spectroscopy, MR diffusion imaging and MR molecular imaging, is briefly discussed.