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Determine the difference between CT and CTA

Radiology Administrator's Compliance and Reimbursement Insider, August 1, 2007

by Melody W. Mulaik, MSHS, CPC, CPC-H, RCC

CTA has become a hot topic for radiology during the past few years. CTA reimbursement, equipment requirements, and joint venture relationships between cardiologists and radiologists for the interpretation of CTA have generated much discussion in the radiology community.  

Coders find it difficult to assign a CTA procedure code that accurately represents the service that the radiologist performed according to the standard definition of CTA procedures. 

By definition, all CTA procedure codes, except the category III cardiac codes, include the following verbiage: “without contrast material(s), followed by contrast material(s) and further sections, including image postprocessing.”

Coding by definition 

According to the AHA Coding Clinic for HCPCS (volume five, number one, first quarter 2005), “the portion of the CTA exam referred to as ‘without contrast material(s)’ represents the images taken to calibrate the scanner and to identify the anatomic region to be evaluated during the ‘with contrast’ portion of the study.”  New CT scanners have more advanced technology that has nearly eliminated the need for calibration images.  

Clinical Examples in Radiology (volume one, issue three, summer 2005) also states, “When a localizer image is not obtained, it is still appropriate to report the CTA procedure codes. In such circumstances, a reduced service modifier is not required.” This clarification is important, because many organizations have expressed concern that the “without contrast” portion actually refers to diagnostic images, contrary to the Coding Clinic definition. The bottom line—if the exam occurs without initial noncontrast images, this does not change the code assignment.

Determining postprocessing

Radiology coders and administrators face another challenge, as well. Despite the fact that the radiologist, or radiology technologist, documents the procedure in the report, the administrator or coder must ensure that the required “postprocessing” was performed and -properly documented in that report. 

Imaging postprocessing refers to two-dimensional (2-D) and/or three-dimensional (3-D) reconstruction(s) of the CT data set acquired during the imaging process. The 2-D reformatted images can be created in multiple planes (e.g., sagittal), then interpreted, annotated, and archived as hard-copy and/or electronic files. The radiologist typically evaluates 3-D or volume-rendered reconstructions in multiple projections. The 3-D reformatting requires extensive effort from the radiologist, who typically performs the processing on a separate workstation. The CPT Manual lists separate procedure codes for 3-D rendering (76376 and 76377); however, do not assign these in addition to the CTA codes, because the CTA procedure codes already include the work that these codes define.

CT imaging of an anatomic region is not always considered CT angiography, even if the primary concern involves the blood vessels. The key distinction between CT and CTA is that CTA includes image postprocessing, such as maximum-intensity profile or 3-D renderings. A CTA study includes: