ACR Radiology Coding Source™ May-June 2003
Computed tomographic angiography (CTA), a less-invasive technique for imaging vessels (both arteries and veins), has gained widespread usage in clinical practice. Prior to the introduction of this new technique, vascular evaluation was performed primarily by invasive catheter angiography. CTA offers important advantages over conventional angiography, which only depicts the vascular lumen. With CTA, additional information is provided, including vessel wall thickness, relationship to adjacent structures, enhanced depiction of the venous anatomy, and parenchymal information about the target organ and other structures within the scan range and field of view.
Description of Procedure
The acquisition of CTA image data includes skeletal anatomy, soft tissues and vessels. In CTA, a few unenhanced (without contrast) images are typically taken to calibrate the scanner and identify the anatomic region to be evaluated during the contrast-enhanced scan. Then the patient gets a rapid injection of intravenous contrast via power injector to enhance the blood vessels. A full set of enhanced CT data is then obtained, which includes all of the anatomy in the area to be examined; an enhanced CT of that region and field-of-view is included in the CTA. Following the imaging, 2-D or 3-D reformatted (reconstruction) images are typically performed. The 2-D reformatted images can be created in multiple planes, then interpreted, annotated and archived as hard copy, electronic files or both. The 3-D or volume-rendered reconstructions are typically evaluated in multiple projections. The work of 3-D reformatting is quite extensive and is usually performed on a separate workstation. Vessels are highlighted and featured for viewing, and the noncritical areas, such as bony structure and surrounding soft tissues, are eliminated in order to provide a focused evaluation of the vasculature. It is this entire process—which includes the acquisition of localizing (without contrast) and contrast-enhanced (with contrast) images, the reformatting of those images, and the interpretation of both the source images and the reconstructions—that constitutes the work of the CTA study included in the respective CPT® codes.
Imaging of the vessels is not necessarily CTA. The key distinction between CTA and CT is that CTA includes reconstruction post-processing of angiographic images of the vessels and interpretation. If reconstruction post-processing is not done, it is not a CTA study.
The following eight codes were developed in 2001 to describe CTA:
70496 CTA, Head
70498 CTA, Neck
71275 CTA, Chest
72191 CTA, Pelvis
73206 CTA, Upper Extremity
73706 CTA, Lower Extremity
74175 CTA, Abdomen
75635 CTA, Abdominal Aorta and Bilateral Iliofemoral Lower Extremity Runoff
The descriptors for the above codes all specify "without contrast material(s), followed by contrast material(s) and further sections, including image post-processing." 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. The phrase "imaging post-processing" in the descriptor refers to the 2-D and 3-D reconstructions performed. Therefore, CPT® code 76375 (coronal, sagittal, multiplanar, oblique, three-dimensional and/or holographic reconstruction of computerized tomography, magnetic resonance imaging or other tomographic modality) should not be coded separately for CTA studies, since imaging post-processing is included in the descriptor.
Injection of contrast material is part of the "with contrast" CTA procedure; therefore, it is not appropriate to separately report the code for the administration of contrast. The supply of low osmolar contrast, however, may be reported separately with CPT® code 99070 [Supplies and materials provided by the physician over and above those usually included with the office visit or other services rendered (list drugs, trays, supplies or materials provided)] or with the appropriate HCPCS Level II code for the contrast material used. Low osmolar contrast is always used for CTA, because CTA is always performed with a power injector. Note that Medicare pays only if certain criteria are met.
It should be noted that code 75635 was developed to appropriately identify an abdominal aorta with bilateral iliofemoral runoff CTA. Therefore, although the distal abdominal aorta and iliofemoral vessels are in the pelvis, it would not be appropriate to code a CTA of the pelvis when the procedure is performed as a runoff study. The cross-references under CTA CPT® codes 72191 (pelvis), 73706 (lower extremity), and 74175 (abdomen) specify that 75635 should be used for CTA aorto-iliofemoral runoff. If a complete CTA study of the abdomen and a complete CTA study of the pelvis from the diaphragm to the symphysis pubis are performed, without a runoff examination, it would be appropriate to code for both a CTA abdomen and CTA pelvis.
If CT venography is performed, the CTA procedure code would be the appropriate code to assign. Angiography refers to coding of the vasculature, which includes both arteries and veins.
CT in Conjunction with CTA
Relative to the total number of procedures performed, the performance of separate CT and CTA examinations of the same anatomy-specific region on the same day would be infrequent. There may be instances, however, when findings on an anatomic CT will raise clinical questions that require performance of a CTA on the same day in order to answer. For example, a patient who is experiencing continuous or severe abdominal pain is referred to radiology for an abdominal CT scan. The CT study demonstrates a tumor in the head of the pancreas. Based on this finding, it is determined that a CTA should be performed as soon as possible to evaluate the vascular invasion by the tumor. A subsequent CTA, involving a new data acquisition, is performed and demonstrates the tumor encasing the pancreaticoduodenal artery and invading the portal vein, rendering the tumor inoperable. In this scenario, although both procedures are performed during the same session or on the same day, the CT and CTA are separate and distinct procedures that use separate data sets and, therefore, are coded separately.