Radiology Coding Alert

Question: Does 3D postprocessing need to be documented on a magnetic resonance angiography (MRA) the same way as it does a computed tomography angiography (CTA)?

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Answer: As multiple authoritative guidelines point out, three-dimensional (3D) postprocessing is a necessary prerequisite in order to report a CTA scan code, such as 71275 (Computed tomographic angiography, chest (noncoronary), with contrast material(s), including noncontrast images, if performed, and image postprocessing). CPT^® Assistant (January 2007; Volume 17: Issue 1) further explains that “the key distinction between CTA and computed tomography (CT) is that CTA includes reconstruction postprocessing of angiographic images and interpretation. If reconstruction postprocessing is not done, it is not a CTA study.”

On the other hand, the same rules do not apply to MRA scan coding. By definition, 3D postprocessing is one of the primary features that distinguishes a CT from a CTA. An MRA will instead utilize either 2D or 3D time-of-flight (TOF) methods depending on anatomy of the imaged vessels. For instance, 2D TOF is reserved for imaging of longer vascular pathways, whereas 3D TOF is better utilized for shorter, more compact vascular segments.