FDG PET/CT in Crohn’s disease: correlation of quantitative FDG PET/CT parameters with clinical and endoscopic surrogate markers of disease activity. Eur J Nucl Med Mol Imaging. 2014;41:605-614. [PMID: 24253895 DOI: 10.1007/s00259-013-2625-2]

Role of Total Body PET/CT in Inflammatory Disorders

Inflammatory disorders historically have been difficult to monitor with conventional PET imaging due to limitations including radiation exposure, lack of validated imaging biomarkers, low spatial resolution, and long acquisition durations. However, the recent development of long-axial field-of-view (LAFOV) PET/CT scanners may allow utilization of novel noninvasive biomarkers to diagnose, predict outcomes, and monitor therapeutic response of inflammatory conditions. LAFOV PET scanners can image most of the human body (if not the entire body) simultaneously in one bed position, with improved signal collection efficiency compared to conventional PET scanners. This allows for imaging with shorter acquisition durations, decreased injected radiotracer dose, prolonged uptake times, or a combination of any of these. In addition, LAFOV PET scanners enable whole-body dynamic imaging. Altogether, these intrinsically superior capabilities in assessing both local and systemic diseases, have allowed these scanners to make increasingly significant contributions to the assessment of inflammatory conditions. This review aims to further explore the role and benefits of LAFOV scanners for imaging various inflammatory conditions while addressing future developments and challenges faced by this technology.

18F-FDG-PET and other imaging modalities in the diagnosis and management of inflammatory bowel disease

Inflammatory bowel disease (IBD), which encompasses ulcerative colitis (UC) and Crohn's disease (CD), is a chronic inflammatory condition of the gastrointestinal (GI) tract that presents complex diagnostic and management challenges. Early detection and treatment of IBD is paramount, as IBD can present with serious complications, including bowel perforation, arthritis, and colorectal cancer. Most forms of diagnosis and therapeutic management, like ileocolonoscopy and upper endoscopy are highly invasive and require extensive preparation at great discomfort to patients. 18F-fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) imaging can be a potential solution to the current limitations in imaging for IBD. This review explores the utility and limitations of various imaging modalities used to detect and manage IBD including ileocolonoscopy, magnetic resonance enterography (MRE), gastrointestinal ultrasound (IUS), and 18F-FDG-PET/computed tomography (18F-FDG-PET/CT) and magnetic resonance imaging (18F-FDG-PET/MR). This review has an emphasis on PET imaging and highlights its benefits in detection, management, and monitoring therapeutic response of UC and CD.

Granzyme B PET Imaging for Assessment of Disease Activity in Inflammatory Bowel Disease

Developing a noninvasive imaging method to detect immune system activation with a high temporal resolution is key to improving inflammatory bowel disease (IBD) management. In this study, granzyme B (GZMB), typically released from cytotoxic T and natural killer cells, was targeted using PET with 68Ga-NOTA-GZP (where GZP is β-Ala-Gly-Gly-Ile-Glu-Phe-Asp-CHO) to detect early intestinal inflammation in murine models of colitis. Methods: Bioinformatic analysis was used to assess the potential of GZMB as a biomarker for detecting IBD and predicting response to treatment. Human active and quiescent Crohn disease and ulcerative colitis tissues were stained for GZMB. We used IL-10-/- mice treated with dextran sulfate sodium (DSS) as an IBD model, wild-type C57BL/6J mice as a control, and anti-tumor necrosis factor as therapy. We used a murine GZMB-binding peptide conjugated to a NOTA chelator (NOTA-GZP) labeled with 68Ga as the PET tracer. PET imaging was conducted at 1, 3, and 4 wk after colitis induction to evaluate temporal changes. Results: Bioinformatic analysis showed that GZMB gene expression is significantly upregulated in human ulcerative colitis and Crohn disease compared with the noninflamed bowel by 2.98-fold and 1.92-fold, respectively; its expression is lower by 2.16-fold in treatment responders than in nonresponders. Immunofluorescence staining of human tissues demonstrated a significantly higher GZMB in patients with active than with quiescent IBD (P = 0.032).68Ga-NOTA-GZP PET imaging showed significantly increased bowel uptake in IL-10-/- mice with DSS-induced colitis compared with vehicle-treated IL-10-/- mice (SUVmean, 0.75 vs. 0.24; P < 0.001) and both vehicle- and DSS-treated wild-type mice (SUVmean, 0.26 and 0.37; P < 0.001). In the IL-10-/- DSS-induced colitis model, the bowel PET probe uptake decreased in response to treatment with tumor necrosis factor-α (SUVmean, 0.32; P < 0.001). There was a 4-fold increase in colonic uptake of 68Ga-NOTA-GZP in the colitis model compared with the control 1 wk after colitis induction. The uptake gradually decreased to approximately 2-fold by 4 wk after IBD induction; however, the inflamed bowel uptake remained significantly higher than control at all time points (week 4 SUVmean, 0.23 vs. 0.08; P = 0.001). Conclusion: GZMB is a promising biomarker to detect active IBD and predict response to treatment. This study provides compelling evidence to translate GZMB PET for imaging IBD activity in clinical settings.

Unanticipated pathological clearance in two cases of clinical T4b dMMR/MSI-h advanced colorectal cancer: the potential of immune checkpoint inhibitors despite positive positron-emission tomography results

BACKGROUND

The standard treatment for colorectal cancer consists of surgery and chemotherapy, which can be combined to improve outcomes. Immune checkpoint inhibitors (ICI) are a significant advancement in the standard treatment of metastatic, unresectable colorectal cancer with deficient mismatch repair (dMMR). However, limited data are available about the use of ICI in the neoadjuvant and conversion settings. Here, we present two cases treated with ICI.

CASE PRESENTATION

Case 1: A 75-year-old male with a large, borderline resectable rectal cancer diagnosed as cT4bN1bM0 who underwent neoadjuvant chemotherapy, followed by combination ICI consisting of ipilimumab and nivolumab. After four courses of ICI, the tumor significantly shrank, but positron emission tomography still showed a positive result and R0 resection was performed. Pathological analysis revealed no residual cancer cells. The patient has been monitored without adjuvant chemotherapy, and no recurrences have occurred after one year. Case 2: A 60-year-old male with locally advanced sigmoid colon cancer who received neoadjuvant treatment with pembrolizumab. The tumor partially shrank after three courses, and continued pembrolizumab monotherapy resulted in further tumor shrinkage which still showed positive positron emission tomography. Curative sigmoidectomy with partial resection of the ileum and bladder was performed, and the pathological outcome was pCR. There was no viable tumor in the specimen. The patient has been monitored without adjuvant chemotherapy for six months, and no recurrence has been observed.

CONCLUSIONS

The present study reports two cases, including a large, borderline resectable rectal cancer after failure of chemotherapy followed by combination treatment with nivolumab and ipilimumab and one case of sigmoid colon cancer after pembrolizumab treatment, which resulted in pathological complete response. However, it remains unknown whether ICI therapy can replace surgery or diminish the optimal extent of resection, or whether adjuvant chemotherapy is needed after surgery in the case of achieving pCR after ICI therapy. Overall, this case report suggests that ICI before colorectal surgery can be effective and potentially a 'watch-and-wait" strategy could be used for cases in which ICI is effective.

PET/MR enterography in inflammatory bowel disease: A review of applications and technical considerations

Positron emission tomography (PET) magnetic resonance (MR) enterography is a novel hybrid imaging technique that is gaining popularity in the study of complex inflammatory disorders of the gastrointestinal system, such as inflammatory bowel disease (IBD). This imaging technique combines the metabolic information of PET imaging with the spatial resolution and soft tissue contrast of MR imaging. Several studies have suggested potential roles for PET/MR imaging in determining the activity status of IBD, evaluating treatment response, stratifying risk, and predicting long-term clinical outcomes. However, there are challenges in generalizing findings due to limited studies, technical aspects of hybrid MR/PET imaging, and clinical indications of this imaging modality. This review aims to further elucidate the possible role of PET/MR in IBD, highlight important technical aspects of imaging, and address potential pitfalls and prospects of this modality in IBDs.

The value of FDG-PET/CT imaging in the assessment, monitoring, and management of COVID-19

The pathogenesis of Coronavirus Disease 2019 (COVID-19) involves cytokine-driven recruitment and accumulation of inflammatory cells at sites of infection. These activated neutrophils, monocytes, and effector T cells are highly glycolytic and thus appear as [18]F-labeled fluorodeoxyglucose (FDG) avid sites on positron emission tomography (PET) imaging. FDG-PET-computed tomography (FDG-PET/CT) is a highly sensitive modality for the detection, monitoring, and assessing response related to COVID-19 disease activity that holds significant clinical relevance. To date, concerns over cost, access, and undue radiation exposure have limited the use of FDG-PET/CT in COVID-19 to a small number of individuals where PET-based interventions were already indicated. In this review, we summarize the existing literature on the use of FDG-PET in the detection and monitoring of COVID-19 with particular focus on several areas of clinical relevance that warrant future research: (1) incidental early detection of subclinical COVID-19 in patients who have undergone FDG-PET for other underlying diseases, (2) standardized quantitative assessment of COVID-19 disease burden at specific points in time, and (3) analysis of FDG-PET/CT data leading to better characterization of COVID-19 pathogenesis. Employing FDG-PET/CT for these purposes may allow for the earliest detection of COVID-19-associated venous thromboembolism (VTE), standardized monitoring of disease progression and response to treatment, and better characterization of the acute and chronic complications of this disease.

The role of PET imaging in inflammatory bowel diseases: state-of-the-art review

Inflammatory bowel diseases (IBD), i.e. Crohn disease and ulcerative colitis, are autoimmune processes of undetermined origin characterized by the chronic inflammation of the digestive tract. There is no single gold-standard to diagnose IBD which is therefore carried out through the combination of endoscopy, biopsy, radiological and biological investigations; and the development of non-invasive technique allowing the assessment and monitoring of these diseases is necessary. In this state-of-the-art review of the literature, we present the results of PET imaging studies for the diagnosis and staging of IBD (suspected or known), response evaluation to treatment and evaluation of one the main complication, i.e. strictures; explain the reasons why this examination is currently not considered in the IBD guidelines, e.g. radiation exposure, lack of standardization and not validated performances; and finally discuss the perspectives that could possibly allow it to find a place in the future, e.g. digital PET-CT, dynamic PET images acquisition, new radiopharmaceuticals, use of radiomics and use of artificial intelligence for automatically characterize and quantify digestive [¹⁸F]FDG uptake.

Immuno-PET Imaging of TNF-α in Colitis Using 89Zr-DFO-infliximab

Tumor necrosis factor-alpha (TNF-α) neutralization has become increasingly important in the treatment of inflammatory bowel diseases (IBD). A series of monoclonal antibodies were approved in the clinic for anti-TNF-α therapy. However, a comprehensive assessment of TNF-α levels throughout the colon, which facilitates the diagnosis of IBD and predicts anti-TNF-α efficacy, remains challenging. Here, we radiolabeled infliximab with long-lived radionuclides ⁸⁹Zr for immuno-positron emission tomography (PET) imaging of TNF-α in vivo. The increased TNF-α level was detected in the inflammatory colon of the dextran sodium sulfate-induced colitis mice. The immuno-PET imaging of ⁸⁹Zr-desferrioxamine-infliximab reveals a high uptake (7.1 ± 0.3%ID/g) in the inflammatory colon, which is significantly higher than in the healthy control and blocked groups. The colon-to-muscle ratio reached more than 10 and was maintained at a high level for 10 h after injection. The ex vivo biodistribution study also verified the superior uptake in the inflammatory colon. This study provides an in vivo immune-PET approach to molecular imaging of the pro-inflammatory cytokine TNF-α. It is promising in diagnosing and predicting efficacy in both IBD and other autoimmune diseases.

Investigating the attenuating effect of telmisartan against radiation-induced intestinal injury using 18F-FDG micro-PET imaging

BACKGROUND AND OBJECTIVE

This study was aimed to investigate the ability of ¹⁸F-Fluro-deoxy-glucose (¹⁸F-FDG)-based micro-positron emission tomography (microPET) imaging to evaluate the efficacy of telmisartan, a highly selective angiotensin II receptor antagonist (ARA), in intestinal tissue recovery process after in vivo irradiation.

METHODS

Male Balb/c mice were randomly divided into four groups of control, telmisartan, irradiation, and telmisartan + irradiation. A solution of telmisartan in phosphate-buffered saline (PBS) was administered orally at 12 mg/kg body weight for seven consecutive days prior to whole body exposing to a single sub-lethal dose of 5 Gy X-rays. The mice were imaged using ¹⁸F-FDG microPET at 9 and 30 days post-irradiation. The ¹⁸F-FDG uptake in jejunum was determined according to the mean standardized uptake value (SUVmean) index. Tissues were also processed in similar time points for histological analysis.

RESULTS

The ¹⁸F-FDG microPET imaging confirmed the efficacy of telmisartan as a potent attenuating agent for ionizing radiation-induced injury of intestine in mice model. The results were also in line with the histological analysis indicating that pretreatment with telmisartan reduced damage to the villi, crypts, and intestinal mucosa compared with irradiated and non-treated group from day 9 to 30 after irradiation.

CONCLUSION

The results revealed that ¹⁸F-FDG microPET imaging could be a good candidate to replace time-consuming and invasive biological techniques for screening of radioprotective agents. These findings were also confirmed by histological examinations which indicated that telmisartan can effectively attenuates radiation injury caused by ionizing-irradiation.

PET-CTBased Quantitative Parameters for Assessment of Treatment Response and Disease Activity in Cancer and Noncancerous Disorders

The various semiquantitative and quantitative PET-CT parameters provide measurement of disease activity and assessment of treatment response in the PET-CT studies. These include standardized uptake value (SUV), metabolic tumor volume (MTV) and total lesion glycolysis (TLG), and total metabolic tumor volume (TMTV). Thresholding and adaptive thresholding methods are commonly used algorithms for the evaluation of global disease activity. Readily available commercial software frequently in-built with the current generation PET-CT scanners for providing easy, less time consuming, highly reproducible, and more accurate measurement of global disease activity on PET-CT imaging in evaluation of malignant as well as benign disorders.

Potential and Most Relevant Applications of Total Body PET/CT Imaging

ABSTRACT

The introduction of total body (TB) PET/CT instruments over the past 2 years has initiated a new and exciting era in medical imaging. These instruments have substantially higher sensitivity (up to 68 times) than conventional modalities and therefore allow imaging the entire body over a short period. However, we need to further refine the imaging protocols of this instrument for different indications. Total body PET will allow accurate assessment of the extent of disease, particularly, including the entire axial and appendicular skeleton. Furthermore, delayed imaging with this instrument may enhance the sensitivity of PET for some types of cancer. Also, this modality may improve the detection of venous thrombosis, a common complication of cancer and chemotherapy, in the extremities and help prevent pulmonary embolism. Total body PET allows assessment of atherosclerotic plaques throughout the body as a systematic disease. Similarly, patients with widespread musculoskeletal disorders including both oncologic and nononcologic entities, such as degenerative joint disease, rheumatoid arthritis, and osteoporosis, may benefit from the use of TB-PET. Finally, quantitative global disease assessment provided by this approach will be superior to conventional measurements, which do not reflect overall disease activity. In conclusion, TB-PET imaging may have a revolutionary impact on day-to-day practice of medicine and may become the leading imaging modality in the future.

Artificial Intelligence in Lymphoma PET Imaging:: A Scoping Review (Current Trends and Future Directions)

Malignant lymphomas are a family of heterogenous disorders caused by clonal proliferation of lymphocytes. 18F-FDG-PET has proven to provide essential information for accurate quantification of disease burden, treatment response evaluation, and prognostication. However, manual delineation of hypermetabolic lesions is often a time-consuming and impractical task. Applications of artificial intelligence (AI) may provide solutions to overcome this challenge. Beyond segmentation and detection of lesions, AI could enhance tumor characterization and heterogeneity quantification, as well as treatment response prediction and recurrence risk stratification. In this scoping review, we have systematically mapped and discussed the current applications of AI (such as detection, classification, segmentation as well as the prediction and prognostication) in lymphoma PET.

Unparalleled and revolutionary impact of PET imaging on research and day to day practice of medicine

Positron emission tomography (PET) imaging is the most quantitative modality for assessing disease activity at the molecular and cellular levels, and therefore, it allows monitoring its course and determining the efficacy of various therapeutic interventions. In this scientific communication, we describe the unparalleled and revolutionary impact of PET imaging on research and day to day practice of medicine. We emphasize the critical importance of the development and synthesis of novel radiotracers (starting from the enormous impact of F-Fluorodeouxyglucose (FDG) introduced by investigators at the University of Pennsylvania (PENN)) and PET instrumentation. These innovations have led to the total-body PET systems enabling dynamic and parametric molecular imaging of all organs in the body simultaneously. We also present our perspectives for future development of molecular imaging by multiphoton PET systems that will enable users to extract substantial information (owing to the evolving role of positronium imaging) about the related molecular and biological bases of various disorders, which are unachievable by the current PET imaging techniques.

Current noninvasive modalities in Crohn's disease monitoring

Crohn’s disease (CD) is characterized by a remitting and relapsing course. Longstanding active CD may result in accumulating intestinal damage and disease-related complications. In contrast, mucosal healing is associated with significant improvement in the health-related quality of life, longer periods of disease remission and lower risk of disease progression, complications, hospitalizations, intestinal surgeries, as well as a lower risk of developing colorectal cancer. Mucosal healing, the new treatment endpoint in CD, made necessary the development of noninvasive, accurate, objective and reliable tools for the evaluation of CD activity. Ileocolonoscopy with biopsies remains the reference standard method for the evaluation of the colonic and terminal ileal mucosa. However, it is an invasive procedure with a low risk of complications, allowing the investigation of only a small part of the small bowel mucosa without being able to assess transmural inflammation. These disadvantages limit its role in the frequent follow up of CD patients. In this review, we present the currently available biomarkers and imaging modalities for the noninvasive assessment of CD activity.

Fluorodeoxyglucose PET/CT of Arthritis in Rheumatic Diseases: A Pictorial Review

Rheumatic diseases are various painful conditions that affect joints, bones, cartilage, tendons, ligaments, and muscles. Arthritis is a typical condition of rheumatic disease. Although rheumatoid arthritis is a representative rheumatic disease, various diseases other than rheumatoid arthritis can also affect joints, and differential diagnosis of rheumatic diseases is often difficult owing to the similar clinical manifestations. However, accurate diagnosis is crucial for an appropriate treatment strategy. The utility of fluorine 18 fluorodeoxyglucose (FDG) PET/CT has been established, and it is widely used for assessing malignancies. In addition to accumulating in tumor cells, FDG also accumulates in inflammatory tissue, allowing FDG PET/CT to demonstrate arthritis. PET/CT allows evaluation of whole-body articular and extra-articular lesions in one examination, representing a key advantage over US and MRI, which allow assessment of only a few regions because of their limited field of view. Although FDG PET/CT is sensitive for detecting inflammatory lesions, the uptake itself is nonspecific; therefore, knowledge of characteristic uptake patterns is necessary to narrow the differential diagnosis in rheumatic disease. Furthermore, pathognomonic extra-articular findings such as vasculitis, skin lesions, lymphadenopathy, and chondritis play an important role in achieving accurate diagnosis. The authors present the FDG PET/CT appearances of (a) rheumatoid arthritis and allied disorders (polymyalgia rheumatica, remitting seronegative symmetrical synovitis with pitting edema, adult-onset Still disease), (b) spondyloarthritis (ankylosing spondylitis, psoriatic arthritis, reactive arthritis, inflammatory bowel disease arthritis, SAPHO [synovitis, acne, pustulosis, hyperostosis, and osteitis] syndrome, chronic recurrent multifocal osteomyelitis), and (c) miscellaneous systemic disorders with arthropathy (relapsing polychondritis, multicentric reticulohistiocytosis, amyloidosis, sarcoidosis, hemophilia). ^©RSNA, 2020.

Characterization of activation induced [18]F-FDG uptake in Dendritic Cells

AIM

 Activation of immune cells leads to enhanced glucose uptake that can be visualized by [¹⁸]F-Fluorodeoxyglucose ([¹⁸]F-FDG) positron emission tomography/computed tomography (PET/CT). Dendritic cells (DC) are essential for the function of the adaptive immune system. In contrast to other immune cells metabolic changes leading to an increase of [¹⁸]F-FDG uptake are poorly investigated. Here, we analysed the impact of different DC activation pathways on their [¹⁸]F-FDG uptake. This effect was then used to radiolabel DC with [¹⁸]F-FDG and track their migration in vivo.

METHODS

 DC were generated from bone marrow progenitors (BMDC) or isolated from spleens (SPDC) of C57BL/6 mice. After stimulation with the TLR ligands LPS and CpG or anti-CD40 antibody for up to 72 hours activation markers and glucose transporters (GLUTs) were measured by flow cytometry. Uptake of [¹⁸]F-FDG was measured by gamma-counting. DC lysates were analysed for expression of glycolysis relevant proteins by mass spectrometry (MS). [¹⁸]F-FDG-labeled DC were injected into footpads of mice to image DC migration.

RESULTS

 BMDC and SPDC showed strong upregulation of activation markers predominantly 24 hours after TLR stimulation followed by higher uptake of [¹⁸]F-FDG. In line with this, the expression of GLUTs was upregulated during the course of activation. Furthermore, MS analyses of DC lysates revealed differential regulation of glycolysis relevant proteins according to the stimulatory pathway. As a proof of principle, DC were labeled with [¹⁸]F-FDG upon activation to follow their migration in vivo via PET/MRI.

CONCLUSION

 Immune stimulation of DC leads to enhanced [¹⁸]F-FDG uptake into DC, representing the typical shift to aerobic glycolysis in immune cells after activation.

FDG-PET/CT in Inflammatory Bowel Disease: Is There a Future?

FDG-PET/CT has potential in inflammatory bowel disease. The literature generally presents good sensitivity and specificity in various settings. At present, the most promising roles are assessment of early treatment response and stricture characterization, whereas general use in the initial diagnostic workup should be reserved for equivocal cases for the time being. However, it is challenging to image the moving and physiologically active bowel with FDG, and available literature is far from ideal. Thus, several issues remain unclarified, and further data are needed to make firm conclusions on the role of FDG and PET/CT in inflammatory bowel disease.

Reinventing Molecular Imaging with Total-Body PET, Part II: Clinical Applications

Total-body PET scans will initiate a new era for the PET clinic. The benefits of 40-fold effective sensitivity improvement provide new capabilities to image with lower radiation dose, perform delayed imaging, and achieve improved temporal resolution. These technical features are detailed in the first of this 2-part series. In this part, the clinical impacts of the novel features of total-body PET scans are further explored. Applications of total-body PET scans focus on the real-time interrogation of systemic disease manifestations in a variety of practical clinical contexts. Total-body PET scans make clinical systems biology imaging a reality.

Toward Molecular Imaging of Intestinal Pathology

Inflammatory bowel disease (IBD) is defined by a chronic relapsing and remitting inflammation of the gastrointestinal tract, with intestinal fibrosis being a major complication. The etiology of IBD remains unknown, but it is thought to arise from a dysregulated and excessive immune response to gut luminal microbes triggered by genetic and environmental factors. To date, IBD has no cure, and treatments are currently directed at relieving symptoms and treating inflammation. The current diagnostic of IBD relies on endoscopy, which is invasive and does not provide information on the presence of extraluminal complications and molecular aspect of the disease. Cross-sectional imaging modalities such as computed tomography enterography (CTE), magnetic resonance enterography (MRE), positron emission tomography (PET), single photon emission computed tomography (SPECT), and hybrid modalities have demonstrated high accuracy for the diagnosis of IBD and can provide both functional and morphological information when combined with the use of molecular imaging probes. This review presents the state-of-the-art imaging techniques and molecular imaging approaches in the field of IBD and points out future directions that could help improve our understanding of IBD pathological processes, along with the development of efficient treatments.

Potential Applications of PET-Based Novel Quantitative Techniques in Pediatric Diseases and Disorders

The progress made in hybrid PET imaging during the past decades has significantly expanded the role of this modality in both clinical and research applications. Semi-quantitative PET/CT has been the workhorse of clinical PET/CT due to its simplicity and availability. In addition to semi-quantitative PET/CT, volumetric PET and global metabolic activity have recently shown promise in a more accurate assessment of various diseases. PET/CT has been widely used in pediatric oncologic and non-oncologic diseases. Here we have highlighted few of the pitfalls in the quantitative PET/CT and their potential remedies which have potential in PET/CT evaluation of pediatric diseases.

ACR Appropriateness Criteria® Crohn Disease

Three common clinical scenarios involving use of imaging in Crohn disease are covered. These include the initial evaluation of Crohn disease when the diagnosis has not been previously established, the evaluation for anticipated exacerbation of known disease, and the evaluation of disease activity during therapy monitoring. The appropriateness of a given imaging modality for each scenario is rated as one of three categories (usually appropriate, may be appropriate, usually not appropriate) to help guide evaluation. Pediatric presentation of Crohn disease and the appropriateness of imaging are not covered in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Noninvasive Multimodal Methods to Differentiate Inflamed vs Fibrotic Strictures in Patients With Crohn's Disease

Fibrotic strictures occur in 30% of patients with Crohn's disease (CD). However, there are no therapeutic agents that prevent or reverse fibrotic strictures. Strictures are treated by endoscopic dilatation procedures and surgical procedures, but there are high rates of recurrence. Two antifibrotic agents (nintedanib and pirfenidone) recently were approved for the treatment of idiopathic pulmonary fibrosis and inhibitors of Rho-associated protein kinases 1 and 2 reversed fibrosis in mice with chronic intestinal inflammation. Cross-sectional imaging techniques, such as magnetic resonance (MR) enterography, computed tomography enterography, and bowel ultrasound, are used to assess small-bowel and CD-related complications, including strictures. It is important to be able to determine the degree of inflammation and fibrosis in strictures to select the best therapy; this can be a challenge because inflammation and fibrosis co-exist to varying degrees in a damaged bowel segment. Delayed gadolinium enhancement, magnetization transfer MR imaging, and ultrasound elastography seem to be promising tools for assessing fibrosis in patients with CD. We review noninvasive techniques for fibrosis assessment, including analyses of genetic, epigenetic, and protein markers. We discuss the potential of imaging techniques such as diffusion-weighted and magnetization transfer MR imaging, strain elastography, shear-wave imaging, and positron emission tomography to guide therapeutic decisions for patients with stricturing CD.

Idiopathic chronic diarrhea associated with dysbiosis in a captive cynomolgus macaque (Macaca fascicularis)

Chronic inflammatory enteric diseases occur commonly in humans and animals, especially in captive bred macaques. However, information about the etiology of idiopathic chronic inflammatory diarrhea in cynomolgus monkeys is limited. In this paper, we reported the unusual case of idiopathic chronic diarrhea in a captive cynomolgus monkey based on microbial, imaging, and microbiome examinations.

Axillary lymph-node metabolic activity assessment on 18F-FDG-PET/CT in rheumatoid arthritis patients treated with biologic therapies

Objective: Recent studies have provided new insights into the role of lymph nodes (LNs) in rheumatoid arthritis (RA). The aim of this study was to evaluate the metabolic activity of the axillary LNs in relation to that of the upper limb joints and the clinical assessment of disease activity in RA patients treated with biologic therapies.Method: ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) scans were acquired for 64 patients with RA at baseline and after 6 months of biologic therapy, and the patients' clinical status was evaluated. The maximum standardized uptake value (SUV_max), metabolic active volume, and total lesion glycolysis (TLG) were used to assess glucose metabolism in the LNs and 12 joints. Clinical evaluations included serum markers and the Disease Activity Score based on 28-joint count-erythrocyte sedimentation rate (DAS28-ESR).Results: Changes in the SUV_max and TLG for the axillary LNs correlated significantly with those of the ipsilateral wrist joints. There was a positive correlation between the changes in the three metabolic parameters of the axillary LNs and the changes in disease activity after treatment. After 6 months of biologic therapy, all metabolic parameters for the axillary LNs in patients with a DAS28-ESR < 3.2 were significantly lower than those of patients with a DAS28-ESR ≥ 3.2.Conclusion: A relationship between the glucose metabolism of the axillary LNs and the ipsilateral wrist joints was demonstrated by the ¹⁸F-FDG-PET/CT parameters. The metabolic activity and active volume of axillary LNs may reflect the therapeutic response to the biologic treatment of RA.

Assessment of Ileocolonic Inflammation in Crohn's Disease: Which Surrogate Marker Is Better-MaRIA, Clermont, or PET/MR Index? Initial Results of a Feasibility Trial

Our objective was to define an ¹⁸F-FDG PET/MR enterography index as a hybrid surrogate marker for active ileocolonic inflammation in Crohn's disease (CD) and assess its diagnostic performance in comparison to validated MR indices (MR index of activity [MaRIA], Clermont score). Methods: Fifty-two CD patients with recurrent symptoms underwent ileocolonoscopy and ¹⁸F-FDG PET/MR enterography. Three hundred three ileocolonic segments were assessed for inflammation using MaRIA and the Clermont score as well as the newly defined PET/MR index. On the basis of tobit regression, the PET/MR index was defined as (0.87 × wall thickness) + (1.97 × edema) + (0.83 × ulceration) + (0.55 × SUVmax ratio) + 1.14. The endoscopic activity of inflammation was determined by the simplified endoscopic activity score for CD (SES-CD). Receiver-operating-characteristic curves for each surrogate marker were created and tested against each other using the DeLong test, and diagnostic accuracies were compared using the McNemar test. Correlations between surrogate markers and SES-CD were tested with the Spearman rank correlation test. Results: The PET/MR index showed a comparable sensitivity but a significantly higher specificity and accuracy than MaRIA and the Clermont score in predicting both active and severe inflammation (active inflammation: specificities of 0.933, 0.711, and 0.707 and accuracies of 0.921, 0.739, and 0.736, P < 0.001; severe inflammation: specificities of 0.91, 0.81, and 0.785 and accuracies of 0.914, 0.818, and 0.795, P < 0.01, respectively). All surrogate markers correlated moderately with SES-CD on a segmental basis and a global level (0.5 < ρ < 0.7, all P < 0.001). Conclusion: As a hybrid surrogate marker comprising MR parameters and the PET component, the PET/MR index yielded significantly improved specificity and diagnostic accuracy compared with conventional MR indices (MaRIA and the Clermont score), demonstrating its high potential for noninvasive assessment of CD.

Novel Quantitative PET Techniques for Clinical Decision Support in Oncology

Quantitative image analysis has deep roots in the usage of positron emission tomography (PET) in clinical and research settings to address a wide variety of diseases. It has been extensively employed to assess molecular and physiological biomarkers in vivo in healthy and disease states, in oncology, cardiology, neurology, and psychiatry. Quantitative PET allows relating the time-varying activity concentration in tissues/organs of interest and the basic functional parameters governing the biological processes being studied. Yet, quantitative PET is challenged by a number of degrading physical factors related to the physics of PET imaging, the limitations of the instrumentation used, and the physiological status of the patient. Moreover, there is no consensus on the most reliable and robust image-derived PET metric(s) that can be used with confidence in clinical oncology owing to the discrepancies between the conclusions reported in the literature. There is also increasing interest in the use of artificial intelligence based techniques, particularly machine learning and deep learning techniques in a variety of applications to extract quantitative features (radiomics) from PET including image segmentation and outcome prediction in clinical oncology. These novel techniques are revolutionizing clinical practice and are now offering unique capabilities to the clinical molecular imaging community and biomedical researchers at large. In this report, we summarize recent developments and future tendencies in quantitative PET imaging and present example applications in clinical decision support to illustrate its potential in the context of clinical oncology.

Lower Gastrointestinal Tract Applications of PET/Computed Tomography and PET/MR Imaging

This article discusses the role of PET/CT and PET/MR imaging in the evaluation of inflammatory and malignant disorders of the lower gastrointestinal tract. This includes a review of the current literature and a discussion of new and emerging research.

A novel method to assess subchondral bone formation using [18F]NaF-PET in the evaluation of knee degeneration

PURPOSE

Fluorine-18-sodium fluoride-PET ([F]NaF-PET) facilitates direct assessment of subchondral bone formation to evaluate degeneration in articulating joints. No standards exist for the quantification of joint activity using [F]NaF-PET, and many techniques rely on focal uptake to characterize an entire region of interest. This study proposes a novel method of quantitative global knee analysis to assess regions of expected bone remodeling in the evaluation of knee degeneration.

PATIENTS AND METHODS

The study population consisted of 18 patients with rheumatoid arthritis who underwent [F]NaF-PET/computed tomography imaging. The maximum standardized uptake value (knee SUVmax) in addition to a target-to-background ratio (TBR) that represents global knee activity adjusted for systemic bone formation measured at the lateral femoral neck (global knee TBR) were calculated. A radiologist scored standard radiographs of the knee in nine patients using the Kellgren-Lawrence grading system.

RESULTS

Patients with greater [F]NaF uptake demonstrated greater knee deterioration, which was corroborated by the radiograph findings. Average Kellgren-Lawrence grading was strongly associated with both global knee TBR (Spearman ρ=0.69, P=0.04) and knee SUVmax scores (Spearman ρ=0.93, P=0.0003).

CONCLUSION

Assessment of global activity within the joint is a feasible and clinically useful technique for characterizing disease activity with a single value. Furthermore, a ratio based on systemic bone turnover in a nonarticulating, weight-bearing site adjusts for differences in bone formation related to bodyweight or metabolic bone diseases. We hypothesize that a global knee TBR score may be more sensitive at detecting changes in disease progression, as new spatially distinct lesions with a lower SUV that develop within an region of interest would not be detected by the SUVmax methodology. Longitudinal studies assessing sensitivity with larger patient cohorts are needed to further validate this methodology.

Role of Positron Emission Tomography in Assessing Disease Activity in Ulcerative Colitis: Comparison with Biomarkers

BACKGROUND

Disease activity in ulcerative colitis (UC) is best assessed clinically by Mayo score. 18-Fluorodeoxyglucose positron emission tomography-computerized tomography (FDG PET-CT) is a noninvasive imaging technique to assess extent, disease activity and response to treatment of UC, especially in high risk population or patients unwilling for endoscopy.

AIMS

We conducted a prospective observational study with the aim of assessing and correlating UC disease activity by clinical criteria, endoscopy, histology, serum and fecal biomarkers, and FDG PET-CT.

METHODS

Sixty eligible patients of UC were enrolled into three groups (26 remission, 24 moderate and 10 severe activity) as per Mayo score and FDG PET-CT was performed within 72 h of colonoscopy. ESR, CRP, and fecal calprotectin (FC) levels were determined for all patients.

RESULTS

Of 60 enrolled patients, 10% patients had proctitis, 43.3% left-sided colitis, and 46.7% extensive colitis. ESR, CRP, FC levels, and rectal PET activity were significantly higher in groups with moderate and severe disease activity. Rectal PET activity showed a significant correlation with the Mayo score (k = 0.465, p < 0.001), endoscopic subscore (k = 0.526, p < 0.001), histological score (k = 0.496, p < 0.001), and FC (k = 0.279, p = 0.031). Extent evaluation by FDG PET-CT and colonoscopy showed a significant correlation (k = 0.582, p < 0.001). Besides, FDG PET-CT identified sacroiliitis in one patient and adenocarcinoma in one patient.

CONCLUSION

FDG PET-CT is a reliable noninvasive tool for detection of disease activity, extent in UC with good correlation with Mayo score, histology and fecal biomarkers and accurate predictor of disease remission.

The potential role of FDG PET-CT in the characterization of the activity of Crohn's disease, staging follow-up and prognosis estimation: a pilot study

OBJECTIVES

FDG PET-CT is a global, noninvasive, sensitive method to determine the location and activity of inflammatory lesions. Segmental FDG uptake is proportional with immune cell infiltration of bowel. Our aim was to evaluate prospectively the role of PET in patients with active Crohn's disease (CD) before and after one year's biological therapy, and to compare simple endoscopic score for CD (SES-CD), CD activity index (CDAI) and global PET scores. We also analyzed the prognostic value of initial PET scores.

PATIENTS

Twelve patients were selected: six male/six female, ages between 18 and 39, average: 24 years, with CDAI values >300.

METHODS

We scored the FDG uptake in the small intestine and the four colon segments (on a scale 0-3 for each), and summed them thus forming a global PET score. The scoring was based on the maximal standardized uptake value of the intestinal segment, related to the SUVmax of the liver (as a reference for normal tissue activity). The SES-CD, CDAI and global PET scores before and after treatment were statistically compared.

RESULTS

There were significant changes in CDAI and SES-CD after therapy, PET scores improved only in patients' subgroup with high (>4) initial PET score, indicating good prognosis of biological treatment. In active disease, PET was more informative than endoscopy to access the extent of the inflammation, and small intestine involvement.

CONCLUSIONS

FDG PET-CT score is a promising, noninvasive complementary method in the staging, treatment planning and follow-up of CD. Limitation of the study is the small number of patients.

Optimization of Pediatric PET/CT

PET/CT, the most common form of hybrid imaging, has transformed oncologic imaging and is increasingly being used for nononcologic applications as well. Performing PET/CT in children poses unique challenges. Not only are children more sensitive to the effects of radiation than adults but, following radiation exposure, children have a longer postexposure life expectancy in which to exhibit adverse radiation effects. Both the PET and CT components of the study contribute to the total patient radiation dose, which is one of the most important risks of the study in this population. Another risk in children, not typically encountered in adults, is potential neurotoxicity related to the frequent need for general anesthesia in this patient population. Optimizing pediatric PET/CT requires making improvements to both the PET and the CT components of the procedure while decreasing the potential for risk. This can be accomplished through judicious performance of imaging, the use of recommended pediatric ¹⁸fluorine-2-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) administered activities, thoughtful selection of pediatric-specific CT imaging parameters, careful patient preparation, and use of appropriate patient immobilization. In this article, we will review a variety of strategies for radiation dose optimization in pediatric ¹⁸F-FDG-PET/CT focusing on these processes. Awareness of and careful selection of pediatric-specific CT imaging parameters designed for appropriate diagnostic, localization, or attenuation correction only CT, in conjunction with the use of recommended radiotracer administered activities, will help to ensure image quality while limiting patient radiation exposure. Patient preparation, an important determinant of image quality, is another focus of this review. Appropriate preparative measures are even more crucial in children in whom there is a higher incidence of brown fat, which can interfere with study interpretation. Finally, we will discuss measures to improve the patient experience, the resource use, the departmental workflow, and the diagnostic performance of the study through the use of appropriate technology, all in the context of minimizing procedure-related risks.

Nuclear Medicine Imaging in Pediatric Infection or Chronic Inflammatory Diseases

In this review article, we focus on the most recent applications of nuclear medicine techniques (mainly ^99mTc/¹¹¹In white blood cells (WBC) scan, [¹⁸F]-FDG-PET/CT, [¹⁸F]-FDG-PET/MRI, and ^99mTc-IL-2 scintigraphy) in the study of children affected by peripheral bone osteomyelitis, fungal infections, inflammatory bowel diseases, and type 1 diabetes, owing to recent important published evidences of their role in the management of these diseases. For osteomyelitis in children, both bone scintigraphy and [¹⁸F]-FDG-PET have a major advantage of assessing the whole body in one imaging session to confirm or exclude multifocal involvement, whereas WBC scan has a limited role. In children with fungal infections, [¹⁸F]-FDG-PET can help in defining the best location for biopsy and can help in evaluating the extent of the infection and organs involved (also sites that were not yet clinically apparent), although its main role is for therapy monitoring. In inflammatory bowel diseases, and Crohn disease in particular, WBC scan has been successfully used for many years, but it is now used only in case of doubtful magnetic resonance (MR) or when MR cannot be performed and endoscopy is inconclusive. By contrast, there is an accumulating evidence of the role of [¹⁸F]-FDG-PET in management of children with Crohn disease, and PET/MR could be a versatile and innovative hybrid imaging technique that combines the metabolic information of PET with the high soft tissue resolution of MR, particularly for distinguishing fibrotic from active strictures. Finally, there are several new radiopharmaceuticals that specifically target inflammatory cells involved in the pathogenesis of insulitis aiming at developing new specific immunotherapies and to select children candidates to these treatments for improving their quality of life.

Role of 18F-fluorodeoxyglucose Positron Emission Tomography in the Monitoring of Inflammatory Activity in Crohn's Disease

BACKGROUND

Fluorine-fluorodeoxyglucose positron emission tomography (F-FDG PET) has recently attracted interest for the measurement of disease activity in Crohn's disease (CD). The aim of this study was to assess the utility of FDG-PET as a marker of progression of inflammatory activity and its response to treatment in patients with CD.

METHODS

Twenty-two patients with active CD were recruited prospectively to undergo FDG-PET scanning at 2 time points. All 22 index scans were used to assess sensitivity and specificity against a reference standard magnetic resonance imaging measure. Correlations with clinicopathological markers of severity (Harvey-Bradshaw Index, C-reactive protein, and calprotectin) were also performed. Of note, 17/22 patients participated in the longitudinal component and underwent scanning before and 12 weeks after the initiation of anti-tumor necrosis factor alpha therapy. Patients were subcategorized on the basis of a clinically significant response, and responsiveness of the PET measures was assessed using previously described indices. Of note, 5/22 patients took part in the test-retest component of the study and underwent scanning twice within a target interval of 1 week, to assess the reproducibility of the PET measures.

RESULTS

The sensitivity and specificity of F-FDG PET were 88% and 70%, respectively. Standardized uptake value (SUV)-related PET measures correlated significantly both with C-reactive protein and Harvey-Bradshaw Index in cross-sectional and longitudinal analyses. (G)SUVMAX and (G)SUVMEAN demonstrated favorable responsiveness and reliability characteristics (responsiveness ratio of Guyatt >0.80 and % variability <20%) compared with volume-dependent FDG-PET measures. A proportion of the FDG signal (10%-30%) was found to originate from the lumen of diseased segments.

CONCLUSIONS

F-FDG PET may be useful for longitudinal monitoring of inflammatory activity in CD.

Role of molecular imaging in the management of patients affected by inflammatory bowel disease: State-of-the-art

AIM

To present the current state-of-the art of molecular imaging in the management of patients affected by inflammatory bowel disease (IBD).

METHODS

A systematic review of the literature was performed in order to find important original articles on the role of molecular imaging in the management of patients affected by IBD. The search was updated until February 2016 and limited to articles in English.

RESULTS

Fifty-five original articles were included in this review, highlighting the role of single photon emission tomography and positron emission tomography.

CONCLUSION

To date, molecular imaging represents a useful tool to detect active disease in IBD. However, the available data need to be validated in prospective multicenter studies on larger patient samples.

Advanced multimodality imaging of inflammatory bowel disease in 2015: An update

The diagnosis and effective management of inflammatory bowel disease (IBD) requires a combination clinical, endoscopic, histological, biological, and imaging data. While endoscopy and biopsy remains the gold standard for diagnosis of IBD, imaging plays a central role in the assessment of extra mural disease, in disease surveillance and in the assessment of response to medical treatments, which are often expensive. Imaging is also vital in the detection and diagnosis of disease related complications, both acute and chronic. In this review, we will describe, with illustrative images, the imaging features of IBD in adults, with emphasis on up-to-date imaging techniques focusing predominantly on cross sectional imaging and new magnetic resonance imaging techniques.

The utility of PET/CT with (68)Ga-DOTATOC in sarcoidosis: comparison with (67)Ga-scintigraphy

OBJECTIVE

This study was designed to compare the clinical efficacy of (68)Ga-DOTA-Tyr-octreotide (DOTATOC)-positron emission tomography (PET)/computed tomography (CT) with that of conventional (67)Ga-scintigraphy (GS), and to correlate quantitative parameters on DOTATOC-PET/CT with clinical data, in patients with sarcoidosis.

METHODS

Twenty patients who were histologically and/or clinically diagnosed with sarcoidosis and underwent both DOTATOC-PET/CT and GS were analyzed in this study. The numbers of patients with positive findings for each organ were determined. The total numbers of involved nodal areas in the chest, as determined by DOTATOC-PET and gallium single-photon emission tomography (Ga-SPECT), were compared. The correlations between quantitative parameters on PET and clinical laboratory data were evaluated.

RESULTS

DOTATOC-PET/CT was positive in 19 patients, being negative in only one patient with chronic inactive sarcoidosis, whereas GS was positive in 17 patients. DOTATOC-PET/CT visualized more lesions in lymph nodes, uvea, and muscles than did Ga-scintigraphy and identified more involved areas than did GS-SPECT (p < 0.0001). Whole-body active lesion volume showed a significant, but moderate correlation with angiotensin-converting enzyme level (ρ = 0.64, p = 0.0044).

CONCLUSIONS

PET/CT with DOTATOC may be superior to conventional GS in detecting sarcoidosis lesions, especially in lymph nodes, uvea, and muscles. Volumetric parameters in DOTATOC-PET/CT may be helpful in estimating the activity of sarcoidosis.

The Role of MR Enterography in Assessing Crohn's Disease Activity and Treatment Response

MR enterography (MRE) has become the primary imaging modality in the assessment of Crohn's disease (CD) in both children and adults at many institutions in the United States and worldwide, primarily due to its noninvasiveness, superior soft tissue contrast, and lack of ionizing radiation. MRE technique includes distention of the small bowel with oral contrast media with the acquisition of T2-weighted, balanced steady-state free precession, and multiphase T1-weighted fat suppressed gadolinium contrast-enhanced sequences. With the introduction of molecule-targeted biologic agents into the clinical setting for CD and their potential to reverse the inflammatory process, MRE is increasingly utilized to evaluate disease activity and response to therapy as an imaging complement to clinical indices or optical endoscopy. New and emerging MRE techniques, such as diffusion-weighted imaging (DWI), magnetization transfer, ultrasmall superparamagnetic iron oxide- (USPIO-) enhanced MRI, and PET-MR, offer the potential for an expanded role of MRI in detecting occult disease activity, evaluating early treatment response/resistance, and differentiating inflammatory from fibrotic strictures. Familiarity with MR enterography is essential for radiologists and gastroenterologists as the technique evolves and is further incorporated into the clinical management of CD.

Application of partial volume effect correction and 4D PET in the quantification of FDG avid lung lesions

PURPOSE

The aim of this study is to assess a software-based method with semiautomated correction for partial volume effect (PVE) to quantify the metabolic activity of pulmonary malignancies in patients who underwent non-gated and respiratory-gated 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG)-positron emission tomography (PET)/x-ray computed tomography(CT).

PROCEDURES

The study included 106 lesions of 55 lung cancer patients who underwent respiratory-gated FDG-PET/CT for radiation therapy treatment planning. Volumetric PET/CT parameters were determined by using 4D PET/CT and non-gated PET/CT images. We used a semiautomated program employing an adaptive contrast-oriented thresholding algorithm for lesion delineation as well as a lesion-based partial volume effect correction algorithm. We compared respiratory-gated parameters with non-gated parameters by using pairwise comparison and interclass correlation coefficient assessment. In a multivariable regression analysis, we also examined factors, which can affect quantification accuracy, including the size of lesion and the location of tumor.

RESULTS

This study showed that quantification of volumetric parameters of 4D PET/CT images using an adaptive contrast-oriented thresholding algorithm and 3D lesion-based partial volume correction is feasible. We observed slight increase in FDG uptake by using PET/CT volumetric parameters in comparison of highest respiratory-gated values with non-gated values. After correction for partial volume effect, the mean standardized uptake value (SUVmean) and total lesion glycolysis (TLG) increased substantially (p value <0.001). However, we did not observe a clinically significant difference between partial volume corrected parameters of respiratory-gated and non-gated PET/CT scans. Regression analysis showed that tumor volume was the main predictor of quantification inaccuracy caused by partial volume effect.

CONCLUSIONS

Based on this study, assessment of volumetric PET/CT parameters and partial volume effect correction for accurate quantification of lung malignant lesions by using respiratory non-gated PET images are feasible and it is comparable to gated measurements. Partial volume correction increased both the respiratory-gated and non-gated values significantly and appears to be the dominant source of quantification error of lung lesions.

Dual-time-point Imaging and Delayed-time-point Fluorodeoxyglucose-PET/Computed Tomography Imaging in Various Clinical Settings

The techniques of dual-time-point imaging (DTPI) and delayed-time-point imaging, which are mostly being used for distinction between inflammatory and malignant diseases, has increased the specificity of fluorodeoxyglucose (FDG)-PET for diagnosis and prognosis of certain diseases. A gradually increasing trend of FDG uptake over time has been shown in malignant cells, and a decreasing or constant trend has been shown in inflammatory/infectious processes. Tumor heterogeneity can be assessed by using early and delayed imaging because differences between primary versus metastatic sites become more detectable compared with single time points. This article discusses the applications of DTPI and delayed-time-point imaging.

Small bowel imaging of inflammatory bowel disease

The study of the small bowel (SB) has always been challenging both for clinicians and radiologist. It is a long and tortuous tube that can be affected by various pathologies whose signs and symptoms are usually non specific and can mimic other acute abdominal disorders. For these reasons, imaging plays a central role in the diagnosis of the different pathological conditions that can occur. They are important also in the management and follow up of chronic diseases. We expose and evaluate all the radiological methods that are now available for the study of the SB with particular emphasis on the technological improvement of cross-sectional imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI). These techniques have, infact, highly improved in terms of execution times (fast acquisitions images), patients discomfort and radiation dose, for CT, with consequent reduced biological risks. Moreover, the new post-processing options with multiplanar reconstruction and isotropic images have made significant changes in the evaluation of the exams. Especially MRI scans have been improved by the advent of new sequences, such as diffusion weighted imaging and cine-MRI, parallel imaging and breath-hold sequences and can provide excellent soft-tissue contrast without the use of ionizing radiations.