Revisiting oral barium sulfate contrast agents

Bismuth drug-inspired ultra-small dextran coated bismuth oxide nanoparticles for targeted computed tomography imaging of inflammatory bowel disease

Bismuth (Bi)-based computed tomography (CT) imaging contrast agents (CAs) hold significant promise for diagnosing gastrointestinal diseases due to their cost-effectiveness, heightened sensitivity, and commendable biocompatibility. Nevertheless, substantial challenges persist in achieving an easy synthesis process, remarkable water solubility, and effective targeting ability for the potential clinical transformation of Bi-based CAs. Herein, we show Bi drug-inspired ultra-small dextran coated bismuth oxide nanoparticles (Bi2O3-Dex NPs) for targeted CT imaging of inflammatory bowel disease (IBD). Bi2O3-Dex NPs are synthesized through a simple alkaline precipitation reaction using bismuth salts and dextran as the template. The Bi2O3-Dex NPs exhibit ultra-small size (3.4 nm), exceptional water solubility (over 200 mg mL-1), high Bi content (19.75 %), excellent biocompatibility and demonstrate higher X-ray attenuation capacity compared to clinical iohexol. Bi2O3-Dex NPs not only enable clear visualization of the GI tract outline and intestinal loop structures in CT imaging but also specifically target and accumulate at the inflammatory site in colitis mice after oral administration, facilitating a precise diagnosis and enabling targeted CT imaging of IBD. Our study introduces a novel and clinically promising strategy for synthesizing high-performance Bi2O3-Dex NPs for diagnosing gastrointestinal diseases.

Targeted Computed Tomography Visualization and Healing of Inflammatory Bowel Disease by Orally Delivered Bacterial-Flagella-Inspired Polydiiododiacetylene Nanofibers

Accurate diagnosis and timely therapeutic intervention of inflammatory bowel disease (IBD) is essential in preventing the progression of the disease, although it still represents an insurmountable challenge. Here we report the design of bacterial-flagella-inspired polydiiododiacetylene (PIDA) nanofibers and its performance in targeted computed tomography (CT) imaging and on-demand therapeutic intervention of IBD. With a morphology mimicking bacterial flagella, PIDA nanofibers attach on the mucus layer of the gastrointestinal (GI) tract after oral administration, evenly distributing on the GI surface to portray the GI lining under CT scan within 2 h. PIDA can retain for a longer time in the damaged mucosa at the inflamed lesions than in normal GI tissues to enable the targeted CT visualization of IBD. PIDA also scavenges reactive oxygen species and ameliorates gut dysbiosis attributed to its iodine-substituted polydiacetylene structure, so that the enriched PIDA nanofibers at the targeted IBD lesions can alleviate the inflammation while maintaining the gut microbiota homeostasis, thus promoting the rebalance of GI microenvironment and the mucosal healing.

Polymer-coated BiOCl nanosheets for safe and regioselective gastrointestinal X-ray imaging

Bismuth-based compounds are considered to be the best candidates for computed tomography (CT) imaging of gastrointestinal (GI) tract due to high X-ray absorption. Here, we report the introduction of polymer-coated bismuth oxychloride (BiOCl) nanosheets for highly efficient CT imaging in healthy mice and animal with colitis. We demonstrate simple, low cost and fast aqueous synthesis protocol which provides gram-quantity yield of chemically stable BiOCl nanosheets. The developed contrast gives 2.55-fold better CT enhancement compared to conventional contrast with negligible in vivo toxicity. As a major finding we report a regioselective CT imaging of GI tract by using nanoparticles coated with differentially charged polymers. Coating of nanoparticles with a positively charged polymer leads to their fast accumulation in small intestine, while the coating with negatively charged polymers stimulates prolonged stomach retention. We propose that this effect may be explained by a pH-controlled aggregation of nanoparticles in stomach. This feature may become the basis for advancement in clinical diagnosis of entire GI tract.

Hypersensitivity Reactions to Iodinated Contrast Media

At present, iodinated contrast media (ICM) are mostly non-ionic, have low osmolality, and are safe. Even if adverse drug reactions (ADRs) occur, most are chemo-toxic symptoms and require only observation or H1 antihistamines. However, rare, unpredictable, and even life-threatening hypersensitivity can still occur. The aim of this review is to summarize the issues that all relevant staff need to know about and be able to respond to. The most significant risk factor for ICM hypersensitivity is a history of ICM hypersensitivity. For high-risk populations, we must cautiously weigh the advantages and disadvantages of premedication and be aware that breakthrough reactions may still occur. The best policy for patients with a history of severe ICM hypersensitivity is to avoid the same ICM. If ICM are inevitable, skin tests, in vitro tests, and drug provocation tests may help to find a feasible alternative that is safer. The severity of the hypersensitivity is correlated with the positivity rate of these tests, so there is no need for further investigations for patients with only mild reactions. We should also keep in mind that even excipients in ICM may induce hypersensitivity. Detailed, standardized documentation is essential for correct diagnosis and the prevention of future occurrence.

Injectable Biodegradable Multimodal Mammography Marker

Introducing temporary markers for imaging studies is an idea, which in the proper clinical settings can be advantageous for patient compliance and in selected cases where a permanent marker is nondesirable. Hence, we developed injectable marker formulation using a biodegradable "pasty polymer" of poly(ricinoleic acid-co-sebacic acid) (PSA:RA) containing iodixanol and iron oxide as contrast agents that can serve as a visual marker for the region suspected to have tumor growth. The goal of this work is to noninvasively evaluate the visibility, shape, and degradation of the injectable PSA:RA formulation using magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound (US). Prescreening of the marker formulation was performed under MRI and CT scanning using agar gel phantom models with poly(l-lactide-co-ε-caprolactone) (PCL:LA) solid inserts (clips) that contained varying combinations of the contrast agents. The contrast agent combination with the PCL:LA clip that had the best visibility in both MRI and CT was selected and additionally tested as in PSA:RA formulation. Further, we evaluated the PSA:RA marker placement in bovine liver and poultry muscles. The PSA:RA formulation is predictable with good MRI, CT, and US visibility and shows no in vivo systemic toxicity symptoms when implanted subcutaneously in mice. Further, the advantage of PSA:RA formulation is its undefined shape and ease of injecting through a small gauge needle, making it possible to reach into the regions of the body.

In vivo evaluation of targeted delivery of biological agents using barium sulfate

This study was aimed to monitor the transit through the intestine by X-ray imaging using barium sulfate (BS) as tracer. The in vitro features of monolithic tablets were correlated with their in vivo behavior in order to provide a tool for the development of targeted formulations containing macromolecular bioactive agents. The impact of BS on various matrices (neutral, ionic) was studied in simulated fluids using the disintegration time (DT) as main parameter. Dry tablets were characterized by spectroscopic methods (X-ray diffraction and Infra-Red) and scanning electron microscopy (SEM). The selected formulations were followed in a beagle dog model. The in vivo and in vitro DT of tablets formulated with BS were compared. Results: anionic excipients carboxymethylcellulose (CMC) and carboxymethylstarch (CMS) protected the active ingredient from the gastric acidity, ensuring its targeted delivery in the intestine. The SEM analysis, before and after transit in simulated fluids, showed that BS remained in the tablets allowing their good follow-up in vivo. The incorporation of 30% protein in tablets with 40% BS had no impact on their behavior. In conclusion, BS and X-ray imagery could be a good alternative to scintigraphy for development of targeted formulations containing high molecular weight bioactive agents.

Novel contrast media based on the liquid metal gallium for in vivo digestive tract radiography: a feasibility study

The barium sulfate has been playing an important role as the contrast medium in gastrointestinal radiography and disease diagnosis. However, its application has been gradually reduced due to the limitation of its imaging effect and the progress of other imaging techniques. Here, the liquid metal gallium was proposed as an improved contrast agent, which was applied in the in vivo digestive tract radiography of the mice for the first time. Under the CT scanning, the gallium produced excellent contrast effect intuitively. According to the records of discharge time, the tissue sections of organs, the survival state and body weight, the liquid metal was proven to be capable and safe for gastrointestinal radiography. Further, the mixture of the gallium and the barium sulfate has been tested, which showed better performance in both contrast and detail. Therefore, with the characteristics of better imaging contrast effect and acceptable safety, the gallium and its mixture with the barium sulfate might be useful as potential candidates for digestive tract contrast agent in animal experiments, even possibly as alternative contrast agents for clinical use.

The Association Between Barium Examination and Subsequent Appendicitis: A Nationwide Population-Based Study

OBJECTIVE

The incidence and association between appendicitis and barium examination (BE) remain unclear. Such potential risk may be omitted. We conducted a longitudinal, nationwide, population-based cohort study to investigate the association between BE and appendicitis risk.

METHODS

From the Taiwan National Health Insurance Research Database, a total of 24,885 patients who underwent BE between January 1, 2000 and December 31, 2010 were enrolled in a BE cohort; an additional 98,384 subjects without BE exposure were selected as a non-BE cohort, matched by age, sex, and index date. The cumulative incidences of subsequent appendicitis in the BE and non-BE cohorts were assessed using the Kaplan-Meier curves and log-rank test. Cox proportional hazards regression analyses were employed to calculate the appendicitis risk between the groups.

RESULTS

The cumulative incidence of appendicitis was higher in the BE cohort than in the non-BE cohort (P = .001). The overall incidence rates of appendicitis for the BE and non-BE cohorts were 1.19 and 0.80 per 1000 person-years, respectively. After adjustment for sex, age, and comorbidities, the risk of appendicitis was higher in the BE cohort (adjusted hazard ratio = 1.46, 95% confidence interval = 1.23-1.73) compared with the non-BE cohort, especially in the first 2 months (adjusted hazard ratio = 9.72, 95% confidence interval = 4.65-20.3).

CONCLUSIONS

BE was associated with an increased, time-dependent appendicitis risk. Clinicians should be aware of this potential risk to avoid delayed diagnoses.

Colorectal Findings at Repeat CT Colonography Screening after Initial CT Colonography Screening Negative for Polyps Larger than 5 mm

Purpose To determine the rate and types of polyps detected at repeat computed tomographic (CT) colonography screening after initial negative findings at CT colonography screening. Materials and Methods Among 5640 negative CT colonography screenings (no polyps ≥ 6 mm) performed before 2010 at one medical center, 1429 (25.3%; mean age, 61.4 years; 736 women, 693 men) patients have returned for repeat CT colonography screening (mean interval, 5.7 years ± 0.9; range, 4.5-10.7 years). Positive rates and histologic findings of initial and repeat screening were compared in this HIPAA-compliant, institutional review board-approved study. For all patients with positive findings at repeat CT colonography, the findings were directly compared against the initial CT colonography findings. Fisher exact, Pearson χ², and Student t tests were applied as indicated. Results Repeat CT colonography screening was positive for lesions 6 mm or larger in 173 (12.1%) adults (compared with 14.3% at initial CT colonography screening, P = .29). In the 173 patients, 29.5% (61 of 207) of nondiminutive polyps could be identified as diminutive at the initial CT colonography and 12.6% (26 of 207) were missed. Large polyps, advanced neoplasia (advanced adenomas and cancer), and invasive cancer were seen in 3.8% (55 of 1429), 2.8% (40 of 1429), and 0.14% (two of 1429), respectively, at follow-up, compared with 5.2% (P = .02), 3.2% (P = .52), and 0.45% (P = .17), respectively, at initial screening. Of 42 advanced lesions in 40 follow-up screenings, 33 (78.6%) were right sided and 22 (52.4%) were flat, compared with 45.4% (P < .001) and 11.3% (P < .001), respectively, at initial screening. Large right-sided serrated lesions were confirmed in 20 individuals (1.4%), compared with 0.5% (P < .001) confirmed at initial screening. Conclusion Positive rates for large polyps at repeat CT colonography screening (3.7%) were lower compared with those at initial screening (5.2%). However, more advanced right-sided lesions were detected at follow-up CT colonography, many of which were flat, serrated lesions. The cumulative findings support both the nonreporting of diminutive lesions and a 5-10-year screening interval. ^© RSNA, 2016 An earlier incorrect version of this article appeared online. This article was corrected on August 30, 2016.

Abdominal and pelvic CT: is positive enteric contrast still necessary? Results of a retrospective observational study

PURPOSE

Evaluation of diagnostic accuracy of abdominal CT depending on the type of enteric contrast agent.

METHODS AND MATERIALS

Multislice CTs of 2,008 patients with different types of oral preparation (positive with barium, n = 576; neutral with water, n = 716; and no enteric contrast, n = 716) were retrospectively evaluated by two radiologists including delineation of intestinal segments and influence on diagnosis and diagnostic reliability exerted by the enteric contrast, using a three-point scale. Furthermore, diagnostic reliability of the delineation of selected enteric pathologies was noted. CT data were assigned into groups: oncology, inflammation, vascular, pathology, trauma and gastrointestinal pathology.

RESULTS

Delineation of the bowel was clearly practicable across all segments irrespective of the type of enteric contrast, though a slight impairment was observed without enteric contrast. Although delineation of intestinal pathologies was mostly classified "clearly delimitable" more difficulties occurred without oral contrast (neutral/positive/no contrast, 0.8 %/3.8 %/6.5 %). Compared to examinations without enteric contrast, there was a significant improvement in diagnosis that was even increased regarding the reader's diagnostic reliability. Positive opacification impaired detection of mucosal enhancement or intestinal bleeding.

CONCLUSION

Water can replace positive enteric contrast agents in abdominal CTs. However, selected clinical questions require individual enteric contrast preparations. Pathology detection is noticeably impaired without any enteric contrast.

Utilization of nanoparticles as X-ray contrast agents for diagnostic imaging applications

Among all the diagnostic imaging modalities, X-ray imaging techniques are the most commonly used owing to their high resolution and low cost. The improvement of these techniques relies heavily on the development of novel X-ray contrast agents, which are molecules that enhance the visibility of internal structures within the body in X-ray imaging. To date, clinically used X-ray contrast agents consist mainly of small iodinated molecules that might cause severe adverse effects (e.g. allergies, cardiovascular diseases and nephrotoxicity) in some patients owing to the large and repeated doses that are required to achieve good contrast. For this reason, there is an increasing interest in the development of alternative X-ray contrast agents utilizing elements with high atomic numbers (e.g. gold, bismuth, ytterbium and tantalum), which are well known for exhibiting high absorption of X-rays. Nanoparticles (NPs) made from these elements have been reported to have better imaging properties, longer blood circulation times and lower toxicity than conventional iodinated X-ray contrast agents. Additionally, the combination of two or more of these elements into a single carrier allows for the development of multimodal and hybrid contrast agents. Herein, the limitations of iodinated X-ray contrast agents are discussed and the parameters that influence the efficacy of X-ray contrast agents are summarized. Several examples of the design and production of both iodinated and iodine-free NP-based X-ray contrast agents are then provided, emphasizing the studies performed to evaluate their X-ray attenuation capabilities and their toxicity in vitro and in vivo.

Current techniques in the performance, interpretation, and reporting of CT colonography

The technical objective of computed tomographic colonography (CTC) is to acquire high-quality computed tomography images of the cleansed, well-distended colon for polyp detection. In this article the authors provide an overview of the technical components of CTC, from preparation of the patient to acquisition of the imaging data and basic methods of interpretation. In each section, the best evidence for current practices and recommendations is reviewed. Each of the technical components must be optimized to achieve high sensitivity in polyp detection.

Comparison study of different bowel preparation regimens and different fecal-tagging agents on tagging efficacy, patients' compliance, and diagnostic performance of computed tomographic colonography: preliminary study

PURPOSE

To compare and find the optimal combination of bowel preparation regimens and different concentrations of barium-based fecal-tagging agents on computed tomographic colonography in terms of tagging efficacy, patients' compliance, and diagnostic performance.

MATERIALS AND METHODS

Sixty-nine consecutive patients were prospectively enrolled and randomly divided into 4 groups according to a combination of bowel preparation regimens (sodium phosphate [Colclean] vs magnesium citrate [LoSoPrep]) and different concentrations of barium-based fecal-tagging agents (Tagitol V [thick, 40% wt/vol] 60 mL vs EasyCT [thin, 4.6% wt/vol] 600 mL). Patients who received Colclean and EasyCT were designated as group 1; Colclean and Tagitol V as group 2; LoSoPrep and EasyCT, group 3; and LoSoPrep and Tagitol V, group 4. For objective analysis, the volume of tagged feces and fluid was semiautomatically calculated using a threshold of 150 Hounsfield units. The volume of untagged feces and fluid was also calculated using the seeded region-growing method. The tagging efficacy was then calculated and compared using the analysis of variance test. For subjective analysis, 2 radiologists visually determined the overall tagging efficacy on a segmental basis. The numbers of homogeneously tagged, heterogeneously tagged, heterogeneously untagged, and homogeneously untagged feces greater than or equal to 6 mm and fluid were counted in each segment. The rates of homogeneously tagged stool and fluid were compared between the groups using the chi test. Patients' compliance for taking the regimens was recorded and compared using the Kruskal-Wallis test. Per-polyp and per-patient sensitivity for polyps greater than or equal to 6 mm were analyzed and compared using the chi or Fisher exact test.

RESULTS

Objective analysis showed that tagging efficacy was significantly lower in group 1 than in the other 3 groups. In a subjective analysis, overall tagging efficacy was significantly higher in group 4 than in the other groups. The rate of homogeneously tagged fluid was significantly higher in group 4 than in the other groups. The rate of homogeneously tagged feces was significantly higher in the thick barium group than in the thin barium group. Patients' compliance was significantly worse in group 1 than in the other 3 groups. Per-polyp and per-patient sensitivities for polyps greater than or equal to 6 mm were not significantly different among all groups. However, per-patient specificity for lesions greater than or equal to 10 mm was significantly lower in group 2 than in the other groups.

CONCLUSIONS

With better tagging efficacy and compliance while maintaining comparable diagnostic performance, it is our belief that the best combination of bowel preparation and fecal-tagging regimen is a combination of magnesium citrate and a high concentration of a barium tagging agent.