Today, I review, link to and embed Appendix S3 Terminology of Cross-sectional Imaging Techniques Used in Imaging GI Bleeding from The Role of Imaging for GI Bleeding: ACG and SAR Consensus Recommendations [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. Radiology. 2024 Mar;310(3):e232298. doi: 10.1148/radiol.232298.
All that follows is from the above resource.
Appendix S3 Terminology of Cross-sectional Imaging Techniques Used in Imaging GI Bleeding
CTA
CTA is a type of CT where images are acquired while the IV contrast is within the arteries (arterial phase) and postprocessed images are generated to better demonstrate the arterial anatomy. In most cases, images are also acquired during an additional phase such as the portal venous or delayed phase (multiphase).
CTE
CTE is a type of CT where a large volume (1350–1500 mL) of oral contrast is administered to optimize evaluation of the small bowel (8,9). The increased small bowel distension improves
visualization of abnormalities. The oral contrast agent has attenuation near water density which improves conspicuity of hyperenhancing lesions which cause GI bleeding. The majority of CTE examinations performed for inflammatory conditions are performed during a single phase.When evaluating for suspected occult small bowel bleeding, many institutions perform a variation of the routine CTE examination and acquire images during multiple phases
(multiphase) (10). The term for this specialized CTE varies by institution and includes multiphase CTE (mpCTE), CT Angiogram Enterography, CT for occult GI bleeding, CT for
Obscure GI Bleeding, and Suspected Small-Bowel Bleeding CTE Protocol (7). To reduce confusion and develop consistency in reporting, this panel recommends using the term
multiphase CTE (mpCTE).Tables 1* and 2* show more information on CT technique, scan timing and utility of the individual phases for evaluating GI bleeding.
*From The Role of Imaging for GI Bleeding: ACG and SAR Consensus Recommendations [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. Radiology. 2024 Mar;310(3):e232298. doi: 10.1148/radiol.232298.
MR Angiography (MRA)
MRA is a type of MR where images are acquired while the IV contrast is within the arteries, similar to CTA. An advantage of MR is the lack of ionizing radiation and therefore multiple phases can be acquired. Because CTA has higher spatial and temporal resolution, MRA is generally not used in the setting of overt bleeding, and only performed in certain scenarios which will be discussed in subsequent sections.
MRE
MRE is a type of MR where a large volume (1350–1500 mL) of oral contrast is administered to optimize evaluation of the small bowel, similar to CTE. Most institutions administer the same
oral contrast and drinking algorithm for both MRE and CTE. Because of the lack of ionizing radiation, multiple phases are routinely acquired after the administration of IV contrast compared with the single-phase examination performed for routine CTE. Additional pulse sequences are also routinely performed which aid in characterizing abnormalities. MRE has similar performance to CTE for inflammatory conditions (11,12) however, because of the inferior temporal and spatial resolution and artifacts which commonly occur on MR, CT techniques are recommended for evaluating the majority of the other noninflammatory causes (vascular lesions,
masses) of small bowel bleeding.Individual techniques will be described in greater detail in the pertinent sections of the
manuscript.
