Laxative-free CT colonography

Using naso- and oro-intestinal catheters in physiological research for intestinal delivery and sampling in vivo: practical and technical aspects to be considered

Intestinal catheters have been used for decades in human nutrition, physiology, pharmacokinetics, and gut microbiome research, facilitating the delivery of compounds directly into the intestinal lumen or the aspiration of intestinal fluids in human subjects. Such research provides insights about (local) dynamic metabolic and other intestinal luminal processes, but working with catheters might pose challenges to biomedical researchers and clinicians. Here, we provide an overview of practical and technical aspects of applying naso- and oro-intestinal catheters for delivery of compounds and sampling luminal fluids from the jejunum, ileum, and colon in vivo. The recent literature was extensively reviewed, and combined with experiences and insights we gained through our own clinical trials. We included 60 studies that involved a total of 720 healthy subjects and 42 patients. Most of the studies investigated multiple intestinal regions (24 studies), followed by studies investigating only the jejunum (21 studies), ileum (13 studies), or colon (2 studies). The ileum and colon used to be relatively inaccessible regions in vivo. Custom-made state-of-the-art catheters are available with numerous options for the design, such as multiple lumina, side holes, and inflatable balloons for catheter progression or isolation of intestinal segments. These allow for multiple controlled sampling and compound delivery options in different intestinal regions. Intestinal catheters were often used for delivery (23 studies), sampling (10 studies), or both (27 studies). Sampling speed decreased with increasing distance from the sampling syringe to the specific intestinal segment (i.e., speed highest in duodenum, lowest in ileum/colon). No serious adverse events were reported in the literature, and a dropout rate of around 10% was found for these types of studies. This review is highly relevant for researchers who are active in various research areas and want to expand their research with the use of intestinal catheters in humans in vivo.

Contrast enhanced oesophageal avoidance for stereotactic body radiotherapy: Barium vs. Gastrografin

INTRODUCTION

SABR may facilitate treatment in a greater proportion of locally-advanced NSCLC patients, just as it has for early-stage disease. The oesophagus is one of the key dose-limiting organs and visualization during IGRT would better ensure toxicity is avoided. As the oesophagus is poorly seen on CBCT, we assessed the extent to which this is improved using two oral contrast agents.

MATERIALS & METHODS

Six patients receiving radiotherapy for Stage I-III NSCLC were assigned to receive 50 mL Gastrografin or 50 mL barium sulphate prior to simulation and pre-treatment CBCTs. Three additional patients who did not receive contrast were included as a control group. Oesophageal visibility was determined by assessing concordance between six experienced observers in contouring the organ. 36 datasets and 216 contours were analysed. A STAPLE contour was created and compared to each individual contour. Descriptive statistics were used and a Kappa statistic, Dice Coefficient and Hausdorff distance were calculated and compared using a t-test. Contrast-induced artefact was assessed by observer scoring.

RESULTS

Both contrast agents significantly improved the consistency of oesophagus localisation on CBCT across all comparison metrics compared to CBCTs without contrast. Barium performed significantly better than Gastrografin with improved kappa statistics (p = 0.007), dice coefficients (p < 0.001) and Hausdorff distances (p = 0.002), although at a cost of increased image artefact.

DISCUSSION

Barium produced lower delineation uncertainties but more image artefact, compared to Gastrografin and no contrast. It is feasible to use oral contrast as a tool in IGRT to help guide clinicians and therapists with online matching and monitoring of the oesophageal position.

Model-based vs hybrid iterative reconstruction technique in ultralow-dose submillisievert CT colonography

OBJECTIVE

To compare image quality of different reconstruction techniques in submillisievert ultralow-dose CT colonography (CTC) and to correlate colonic findings with subsequent optical colonoscopy.

METHODS

58 patients underwent ultralow-dose CTC. The images were reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR) or model-based iterative reconstruction (MBIR) techniques. In each segment, endoluminal noise (expressed as standard deviation of endoluminal density) was measured and image quality was rated on a five-point Likert scale by two independent readers. Colonic lesions were evaluated in consensus and correlated with subsequent optical colonoscopy where possible.

RESULTS

The estimated radiation dose was 0.41 ± 0.05 mSv for the supine and 0.42 ± 0.04 mSv for the prone acquisitions. In the endoluminal view, the image quality was rated better in HIR, whereas better scores were obtained in MBIR in the cross-sectional view, where the endoluminal noise was the lowest (p < 0.0001). Five (26%) polyps were not identified using both computer-aided detection and endoluminal inspection in FBP images vs only one (5%) in MBIR and none in HIR images.

CONCLUSION

This study showed that in submillisievert ultralow-dose CTC, the image quality for the endoluminal view is better when HIR is used, whereas MBIR yields superior images for the cross-sectional view. The inferior quality of images reconstructed with FBP may result in decreased detection of colonic lesions.

ADVANCES IN KNOWLEDGE

Radiation dose from CTC can be safely reduced <1 mSv for both positions when iterative reconstruction is used. MBIR provides better image quality in the cross-sectional view and HIR in the endoluminal view.