CT-on-Rails versus in-Room CBCT for Online Daily Adaptive Proton Therapy of Head-and-Neck Cancers

Purpose: To compare the efficacy of CT-on-rails versus in-room CBCT for daily adaptive proton therapy. Methods: We analyzed a cohort of ten head-and-neck patients with daily CBCT and corresponding virtual CT images. The necessity of moving the patient after a CT scan is the most significant difference in the adaptation workflow, leading to an increased treatment execution uncertainty σ. It is a combination of the isocenter-matching σi and random patient movements induced by the couch motion σm. The former is assumed to never exceed 1 mm. For the latter, we studied three different scenarios with σm = 1, 2, and 3 mm. Accordingly, to mimic the adaptation workflow with CT-on-rails, we introduced random offsets after Monte-Carlo-based adaptation but before delivery of the adapted plan. Results: There were no significant differences in accumulated dose-volume histograms and dose distributions for σm = 1 and 2 mm. Offsets with σm = 3 mm resulted in underdosage to CTV and hot spots of considerable volume. Conclusion: Since σm typically does not exceed 2 mm for in-room CT, there is no clinically significant dosimetric difference between the two modalities for online adaptive therapy of head-and-neck patients. Therefore, in-room CT-on-rails can be considered a good alternative to CBCT for adaptive proton therapy.

VIRTUAL CT COLONOSCOPY: METHODOLOGY FOR CONDUCTING RESEARCH AND INTERPRETATION

Virtual CT colonoscopy is an accurate, highly informative, and less invasive method of examining the colon. The predominant and additional positive ability of virtual CT colonoscopy is the ability to detect non-intestinal pathologies. Based on the high sensitivity and specificity of the method to the developmental abnormalities of the colon, diverticula, polyps, cancer and other volumetric formations, we can conclude that virtual CT colonoscopy is one of the main methods of diagnosis and screening for diseases of the colon.

Optimization of preoperative verification of isolated middle ear abnormalities using virtual ct endoscopy

Isolated anomalies of the middle ear are one of the most difficult areas of practical otorhinolaryngology. Its relevance is due to the rare occurrence, high technical complexity of performing surgical treatment, and the high frequency of unsatisfactory results of surgical interventions. One of the most important factors determining the success of medical actions is high-quality X-ray imaging at the diagnostic stage. It allows you to correctly assess the anatomical features of the temporal bone and plan the tactics of the surgeon. Over the past few years, new technological possibilities have been introduced for the imaging of the ear. Over the past several decades, multispiral computed tomography has been the gold standard of radiation research used in otosurgery. This study has established itself as an informative method for diagnosing middle ear pathology and should be used before planning surgical interventions, as well as a monitoring tool in the postoperative period and for assessing the course of middle ear diseases. With the development of computer-mathematical technologies, over time, it became possible to model the result in three-dimensional space on the basis of axial projection, which led to the emergence of a branch of radiation diagnostics, called virtual CT endoscopy. The work evaluates the specificity of virtual CT endoscopy performed at the preoperative stage in patients with isolated anomalies of the ossicle chain with intact stapes, in terms of diagnosing the continuity of the ossicle chain, changes in their configuration and adhesions with the surrounding bone structures. A comparative analysis of the specificity of standard two-dimensional computed tomography and virtual CT endoscopy was performed, where explorative tympanotomy was used as test results in 43 patients. The advantages of virtual CT endoscopy in visualization of minor defects in the structures of the tympanic cavity were revealed. The importance of virtual CT endoscopy in measuring the tympanic cavity in arbitrary planes was determined. In addition to the above, virtual endoscopy opens up new possibilities for measuring the anatomical structures of the middle ear in arbitrary planes, which makes it possible, for example, to calculate the length of the prosthesis intended for use as plasty of the ossicular chain before surgery.