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Role of computed tomography angiography

In the article, David et al. (2015) outline the role of computed tomography angiography in small bowel carcinoid tumors detection and staging. Small bowel carcinoid tumors mainly occur in the form of either tracheobronchial or gastrointestinal carcinoid and arise from cells of the neuroendocrine system. Despite being generally rare, carcinoids form the most common primary small bowel malignancy at a percentage of between 20 and 30. The article is primarily focused with the imaging and evaluation of carcinoid tumors including the jejuna, ileal and duodenal tumors and their resultant diseases.

Among gastrointestinal carcinoids, carcinoid tumors involving small bowel are most prevalent at above 40% that is about 70% of all neuroendocrine tumors. To overlook the nature and occurrence of these tumors would be an injustice both to the medical field and the human health realms. It is in this regard that the article primarily focuses on the early detection and staging of these tumors and the ways in which this can be achieved. Ideally, computed tomography angiography is one of the most effective methods in achieving this detection

The imaging of the carcinoid tumors is dependent on certain stringent parameters that include high tube voltage and an equally effective tube current. In addition, the beam pitch and table speed must be adjusted to reflect the proposed levels per gantry rotation. Optimal patient preparation is a necessary step before CT enterography and should be coupled with neutral endoluminal contrast.  Barium sulfate suspension is used for this step by being administered to the patients orally. A dual-phase examination is then conducted to confidently detect the manifestation of small bowel carcinoids diseases. In this regard, and arterial CT angiography is done using delays of 30 seconds from the intravenous injection time.

In the interpretation stage, images from the CTA examination are thoroughly reviewed for small lesions. Ordinarily, the primary tumors are not well differentiated and therefore appear smaller on the bowel wall. In order to make sure that the small masses of primary tumors are not missed out, the images are correlated to multiplanar and 3D analysis. The analysis enhances the imaging review process by utilizing volume rendered technique and 3D mapping techniques. The surface shading technique employed in 3D analysis is of particular importance in depicting the high contrast structures including vessels. The use of volume rendered technique is also helpful in discerning the relationship between vessels and masses.

The study presents the imaging findings of carcinoid tumors in 14 challenging cases which are grouped into four (duodenal, periampullary, ileal, and jejuna carcinoids). Eventually, recurrent tumors and especially those that have been treated are observed for their imaging appearance. Although primary tumors are usually solitary and difficult to identify, they are not uncommonly small as to not be seen using computed tomography angiography. The presence of small bowel obstruction is an impediment to the proper distention through bowel preparation. In such cases, an evaluation of the primary tumor’s location is often necessary.

The protocol involved in the scanning of carcinoid tumors requires a volume acquisition with thin collimation for all the phases. The voltage of the tube should be set at 120 kVp and the effective current between 120 to 160 effective mAs. However, the current can be adjusted by the automatic tube current modulation in real time.  The gentry rotation time and the beam pitch should also be set at 0.5 s and 1.2 respectively with a table speed of 46 mm per gantry rotation. The isotropic dataset that results from these parameters is suitable for 3D analysis and multiplanar reformations of the highest standards.

The ability of future scanners to detect even smaller lesions is also explored due to the increased quality from emerging 3D techniques. In addition, the article finds that CT enterography protocol achieved higher comfort and good bowel distention among patients during the study. The study underlines the improvement in accurately diagnosing carcinoid tumors if the criteria proposed in the procedure are met.

 

References

Bonekamp, D., Raman, S. P., Horton, K. M., & Fishman, E. K. (2015). Role of computed tomography angiography in detection and staging of small bowel carcinoid tumors. World journal of radiology, 7(9), 220.