The role of molecular imaging in detecting fibrosis in Crohn’s disease

Figures & data

Table 2. Overview of the selected studies on the role of molecular imaging in diagnosing fibrosis CD.

Ref.	N of pt. Type of study	Indication	Imaging technique	Gold standard	Conclusion
Pellino et al. [34]	35 Prospective	To compare the accuracy and clinical impact of hybrid [PET_MRE and PET CTE in CD patients	PET/CTE PET/MRE	Histopathology (resection)	The PET-MRE approach was able to effectively discriminate between fibrotic and non-fibrotic strictures, exhibiting a sensitivity of 66.7%, specificity of 88%, and an AUC of 0.77.
Lenze et al. [73]	30 Prospective	To identify strictures in CD patients and to distinguish between those caused by inflammatory processes versus fibrosis	18F-FDG-PET/CT and MR enteroclysis, Trans-abdominal ultrasound	Histology and endoscopy	All three techniques investigated in this study demonstrated high rates of stricture detection when compared to the gold standard. However, none of the techniques were able to accurately differentiate between the nature of the strictures. Nevertheless, the use of a combination of these methods enabled the identification of all strictures that required surgical intervention.
Catalano et al. [43]	19	To distinguish fibrotic from inflammatory structures in CD patients	18F-FDG-PET/MRE	Post-surgical histology	The utilization of 18 F-FDG-PET/MRE provides credible biomarkers for the assessment of strictures. In CD patients, PET/MRE differentiated purely fibrotic strictures from inflammatory or mixed strictures.
Scharitzer et al. [72]	14 prospective single-center study	To assess the potential usefulness 68 (68Ga)- (FAPI) PET/MRE as a predictive tool for evaluating bowel wall fibrosis in CD.	68Ga-FAPI PET/MRE	Histopathology (Surgical resection)	A statistically significant positive correlation was found between higher SUVmax values and the presence of fibrosis in pathological specimens. There was a positive correlation observed between increasing SUVmax values and the severity of fibrosis identified in resected specimens.

Table 1. Shows the current applications for nuclear medicine imaging in different diseases.

Modality	Description	Radiotracers	Indications/Examples	Advantages
Gamma camera	Planar whole body and spot imaging, flow/cine.	Gamma-emitting radionuclides (^99mTc, ^81Tl, ^111In, ^131I, ^123I, etc.).	Main traditional nuclear medicine modality with broad spectrum of indications.	Functional imaging as opposite to traditional anatomic data provided by CT and radiography.
SPECT/CT	Tomographic reconstruction algorithm produces 3-D data. Multiplanar reformats can be created.	Gamma-emitting radionuclides can be simply added to planar imaging as needed.	Myocardial perfusion imaging, VQ scan, parathyroid localization	Improved accuracy and lesion localization compared with planar images.
PET/CT	Currently almost always in conjunction with CT for attenuation correction and lesion localization	^18FDG—nonspecific Multiple newer tracers	Oncologic imaging. Infection/inflammation (FUO, sarcoidosis including cardiac). Detection of active sites of CD within the small bowel and colon	Metabolism evaluation (FDG). Targeted molecular imaging (newer tracers). Higher resolution than SPECT.
MRI (PET/MR)	Magnetic Resonance Imaging used in conjunction with PET	PET tracers Gadolinium-based contrast. Ultrasmall superparamagnetic iron oxide particles (USPIOs).	Oncologic imaging, most commonly pelvic malignancies (cervical cancer, prostate cancer), hepatocellular carcinoma.	Superb soft tissue characterization, complimentary anatomic and functional information.
PET-MRE (and PET-CTE)		Assessment of the maximum standard uptake value of the tracer (SUVs)		Successful differentiation of fibrotic from nonfibrotic stricture
Optical imaging	Fluorescence	Fluorophores and quantum dots.	Preclinical	Limited depth (< 1–2 cm
	Bioluminescence	Luciferase enzyme.

Pellino G, Nicolai E, Catalano OA, et al. PET/MR versus PET/CT imaging: impact on the clinical management of small-bowel crohn’s disease. J Crohns Colitis. 2016;10(3):277–285. doi: 10.1093/ecco-jcc/jjv207.

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Lenze F, Wessling J, Bremer J, et al. Detection and differentiation of inflammatory versus fibromatous Crohn’s disease strictures: prospective comparison of 18F-FDG-PET/CT, MR-enteroclysis, and transabdominal ultrasound versus endoscopic/histologic evaluation. Inflamm Bowel Dis. 2012;18(12):2252–2260. doi: 10.1002/ibd.22930.

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Catalano OA, Gee MS, Nicolai E, et al. Evaluation of quantitative PET/MR enterography biomarkers for discrimination of inflammatory strictures from fibrotic strictures in Crohn disease. Radiology. 2016;278(3):792–800. doi: 10.1148/radiol.2015150566.

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Scharitzer M, Macher-Beer A, Mang T, et al. Evaluation of intestinal fibrosis with 68Ga-FAPI PET/MR enterography in Crohn disease. Radiology. 2023;307(3):e222389. doi: 10.1148/radiol.222389.

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Data availability statement

The data that support the findings of this study are available from the corresponding author, [Dr Alyami], upon reasonable request.

Table 1. Shows the current applications for nuclear medicine imaging in different diseases.

Modality	Description	Radiotracers	Indications/Examples	Advantages
Gamma camera	Planar whole body and spot imaging, flow/cine.	Gamma-emitting radionuclides (^99mTc, ^81Tl, ^111In, ^131I, ^123I, etc.).	Main traditional nuclear medicine modality with broad spectrum of indications.	Functional imaging as opposite to traditional anatomic data provided by CT and radiography.
SPECT/CT	Tomographic reconstruction algorithm produces 3-D data. Multiplanar reformats can be created.	Gamma-emitting radionuclides can be simply added to planar imaging as needed.	Myocardial perfusion imaging, VQ scan, parathyroid localization	Improved accuracy and lesion localization compared with planar images.
PET/CT	Currently almost always in conjunction with CT for attenuation correction and lesion localization	^18FDG—nonspecific Multiple newer tracers	Oncologic imaging. Infection/inflammation (FUO, sarcoidosis including cardiac). Detection of active sites of CD within the small bowel and colon	Metabolism evaluation (FDG). Targeted molecular imaging (newer tracers). Higher resolution than SPECT.
MRI (PET/MR)	Magnetic Resonance Imaging used in conjunction with PET	PET tracers Gadolinium-based contrast. Ultrasmall superparamagnetic iron oxide particles (USPIOs).	Oncologic imaging, most commonly pelvic malignancies (cervical cancer, prostate cancer), hepatocellular carcinoma.	Superb soft tissue characterization, complimentary anatomic and functional information.
PET-MRE (and PET-CTE)		Assessment of the maximum standard uptake value of the tracer (SUVs)		Successful differentiation of fibrotic from nonfibrotic stricture
Optical imaging	Fluorescence	Fluorophores and quantum dots.	Preclinical	Limited depth (< 1–2 cm
	Bioluminescence	Luciferase enzyme.