A brief review of diagnostic properties of point-of-care ultrasound for adult bowel intussusception: Making the case for ultrasound.

Undifferentiated abdominal pain in adults is a common chief complaint in acute care clinics and emergency departments worldwide, representing up to 10% of visits to emergency departments. Many patients have a non-specific presentation and an initial workup with labwork, urine analysis or X-ray might not reveal a specific diagnosis. Although bowel intussusception is a primarily pediatric disease, adult intussusception is a recognized but rare cause of bowel obstruction often requiring surgical intervention. However, recent data from advanced multi-detector computed tomography imaging shows that milder or recurring cases in adults have been underrecognized. Multi-detector computed tomography is still the imaging gold standard for detecting intussusception in adults, but new data showed that sonographers with basic training using the point-of-care ultrasound approach have a reasonable accuracy in detecting this pathology. As the point-of-care ultrasound for undifferentiated abdominal pain is an emerging core skill in the acute care setting, knowledge of sonographic signs of intestinal intussusception should be included in the skill set of physicians. Sonographic findings in adults mimic pediatric cases, but different location patterns and higher malignancy rates exist in adults. In this manuscript, we will review the current literature on adult intussusception and summarize key knowledge of intestinal intussusception in adults. We will present four adult patients diagnosed with different types of adult acute bowel intussusception using the point-of-care ultrasound and describe a focused scanning approach with typical sonographic findings.

On the Inclusion of Short-distance Bystander Effects into a Logistic Tumor Control Probability Model.

Currently, interactions between voxels are neglected in the tumor control probability (TCP) models used in biologically-driven intensity-modulated radiotherapy treatment planning. However, experimental data suggests that this may not always be justified when bystander effects are important. We propose a model inspired by the Ising model, a short-range interaction model, to investigate if and when it is important to include voxel to voxel interactions in biologically-driven treatment planning. This Ising-like model for TCP is derived by first showing that the logistic model of tumor control is mathematically equivalent to a non-interacting Ising model. Using this correspondence, the parameters of the logistic model are mapped to the parameters of an Ising-like model and bystander interactions are introduced as a short-range interaction as is the case for the Ising model. As an example, we apply the model to study the effect of bystander interactions in the case of radiation therapy for prostate cancer. The model shows that it is adequate to neglect bystander interactions for dose distributions that completely cover the treatment target and yield TCP estimates that lie in the shoulder of the dose response curve. However, for dose distributions that yield TCP estimates that lie on the steep part of the dose response curve or for inhomogeneous dose distributions having significant hot and/or cold regions, bystander effects may be important. Furthermore, the proposed model highlights a previously unexplored and potentially fruitful connection between the fields of statistical mechanics and tumor control probability/normal tissue complication probability modeling.