Comparison between Tc-HMPAO labelled white cells and Tc LeukoScan in the investigation of inflammatory bowel disease

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.

Assessing the interactions between radiotherapy and antitumour immunity

Immunotherapy, specifically the introduction of immune checkpoint inhibitors, has transformed the treatment of cancer, enabling long-term tumour control even in individuals with advanced-stage disease. Unfortunately, only a small subset of patients show a response to currently available immunotherapies. Despite a growing consensus that combining immune checkpoint inhibitors with radiotherapy can increase response rates, this approach might be limited by the development of persistent radiation-induced immunosuppression. The ultimate goal of combining immunotherapy with radiotherapy is to induce a shift from an ineffective, pre-existing immune response to a long-lasting, therapy-induced immune response at all sites of disease. To achieve this goal and enable the adaptation and monitoring of individualized treatment approaches, assessment of the dynamic changes in the immune system at the patient level is essential. In this Review, we summarize the available clinical data, including forthcoming methods to assess the immune response to radiotherapy at the patient level, ranging from serum biomarkers to imaging techniques that enable investigation of immune cell dynamics in patients. Furthermore, we discuss modelling approaches that have been developed to predict the interaction of immunotherapy with radiotherapy, and highlight how they could be combined with biomarkers of antitumour immunity to optimize radiotherapy regimens and maximize their synergy with immunotherapy.

Performance of Common Disease Activity Markers as a Reflection of Inflammatory Burden in Ulcerative Colitis

BACKGROUND

The inflammatory burden influences therapeutic decisions in patients with ulcerative colitis (UC). We aimed to study which commonly used markers of disease activity correlate best with inflammatory burden in patients with UC using leukocyte scintigraphy (single-photon emission computed tomography [SPECT-CT]) as the gold standard.

METHODS

Patients with different severity of UC underwent colonoscopy with biopsies and leukocyte SPECT-CT scintigraphy. Serum C-reactive protein (CRP), fecal calprotectin, and clinical questionnaires were collected. The maximum uptake of technetium-labeled leukocytes was calculated as a SPECT score for each colon segment and a summed activity score for 5 colonic segments combined.

RESULTS

Thirty patients with UC were included; 14 of 30 (47%) had left-sided colitis, and 16 of 30 (53%) had pancolitis. One patient (3%) had inactive UC, 5 of 30 (17%) had mild, 11 of 30 (37%) had moderate, and 13 of 30 (43%) had severe disease activity based on the endoscopic Mayo score. The endoscopic Mayo score correlated better with the SPECT score than with the ulcerative colitis endoscopic index of severity (UCEIS) (r = 0.50; P < 0.01 and r = 0.32; P = 0.08, respectively). The Geboes UC histologic score correlated equally well as the Mayo score (r = 0.50; P < 0.01). We found a significant correlation between scintigraphy and fecal calprotectin (r = 0.44; P = 0.02) but not with serum CRP (r = 0.25; P = 0.18). Fecal calprotectin reflected inflammatory burden significantly better in left-sided colitis (r = 0.80; P = 0.001) than in pancolitis (r = 0.22; P = 0.41).

CONCLUSIONS

The inflammatory burden in patients with UC, measured by SPECT-CT, is better reflected by the endoscopic Mayo score and the Geboes histologic score than by the UCEIS. Fecal calprotectin is a more accurate inflammatory marker than CRP, predominantly in patients with left-sided colitis.

REGISTRATION

This study was approved by the Ethics Committee Review at October 22, 2012 and, in accordance with Dutch legislation, prospectively registered at the CCMO (Dutch central commission for human research) https://www.toetsingonline.nl with NL39801.018.12.

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.

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.

Role of scintigraphy in inflammatory bowel disease

The diagnosis of inflammatory bowel disease (IBD) depends on direct endoscopic visualization of the colonic and ileal mucosa and the histological study of the obtained samples. Radiological and scintigraphic methods are mainly used as an adjunct to endoscopy. In this review, we focus on the diagnostic potential of nuclear medicine procedures. The value of all radiotracers is described with special reference to those with greater experience and more satisfactory results. Tc-99m hexamethylpropylene amine oxime white blood cells remain a widely acceptable scintigraphic method for the diagnosis of IBD, as well as for the evaluation of disease extension and severity. Recently, pentavalent Tc-99m dimercaptosuccinic acid has been recommended as an accurate variant and a complementary technique to endoscopy for the follow-up and assessment of disease activity. Positron emission tomography alone or with computed tomography using fluorine-18 fluorodeoxyglucose appears to be a promising method of measuring inflammation in IBD patients.

(99m)Tc-Fab' fragments (sulesomab) for imaging septically loosened total knee arthroplasty

The diagnostic accuracy of infection scintigraphy with (99m)Tc-labelled monoclonal antibody Fab' fragments (sulesomab) was studied in patients with suspected total knee arthroplasty (TKA) infection. Images from 26 patients were evaluated by two independent readers and compared with a quantitative interpretation of time-activity courses. Microbiological examinations and joint aspiration results were used as reference standards. Histologically, aseptic TKA loosening occurred in two patients and severe, moderate or mild septic loosening in four, nine and 11 patients, respectively. Diagnostic accuracy for severe infection was 100% for both readers, whereas for moderate infection accuracy decreased by 12% and 12% for readers one and two, respectively. For mild infection a further decrease of approximately 61% and 52% occurred for readers one and two, respectively. Quantitative evaluation gave significantly better results over visual interpretation with a diagnostic accuracy of 100% for severe infection and decreased by only 10% and 15% in patients with moderate and mild infection, respectively. Quantitative evaluation of (99m)Tc-Fab' fragments is highly sensitive and specific for diagnostic imaging of infection in patients with septically-loosened TKA.