Educational Effects of Radiation Reduction During Fluoroscopic Examination of the Adult Gastrointestinal Tract

Comparison of the Medical Uses and Cellular Effects of High and Low Linear Energy Transfer Radiation

Exposure to ionizing radiation can occur during medical treatments, from naturally occurring sources in the environment, or as the result of a nuclear accident or thermonuclear war. The severity of cellular damage from ionizing radiation exposure is dependent upon a number of factors including the absorbed radiation dose of the exposure (energy absorbed per unit mass of the exposure), dose rate, area and volume of tissue exposed, type of radiation (e.g., X-rays, high-energy gamma rays, protons, or neutrons) and linear energy transfer. While the dose, the dose rate, and dose distribution in tissue are aspects of a radiation exposure that can be varied experimentally or in medical treatments, the LET and eV are inherent characteristics of the type of radiation. High-LET radiation deposits a higher concentration of energy in a shorter distance when traversing tissue compared with low-LET radiation. The different biological effects of high and low LET with similar energies have been documented in vivo in animal models and in cultured cells. High-LET results in intense macromolecular damage and more cell death. Findings indicate that while both low- and high-LET radiation activate non-homologous end-joining DNA repair activity, efficient repair of high-LET radiation requires the homologous recombination repair pathway. Low- and high-LET radiation activate p53 transcription factor activity in most cells, but high LET activates NF-kB transcription factor at lower radiation doses than low-LET radiation. Here we review the development, uses, and current understanding of the cellular effects of low- and high-LET radiation exposure.

Defecating proctography: A pictorial essay

OBJECTIVES

To provide an illustrative description of the technique and spectrum of findings in defecating proctography.

KEY FINDINGS

Important findings on defecating proctography include rectocoele, enterocoele, sigmoidocoele, cystocoele, intussusception, rectal prolapse, descending perineum, incomplete emptying, anismus, and faecal incontinence. This review article illustrates these key findings with examples.

CONCLUSION

Defecating proctography is a well-established and cost-effective method of assessing disordered defecation. In conjunction with clinical information and other diagnostic tests, findings on defecating proctography can guide appropriate multidisciplinary management and may lead to improvement in embarrassing and debilitating symptoms in many patients.

IMPLICATIONS FOR PRACTICE

This review article provides a suggested technique and covers the spectrum of findings on defecating proctography.