Radiology Coding Alert

The first code in the nuclear medicine "Respiratory System" section is 78580 (Pulmonary perfusion imaging, particulate). This is the only code in the section specific to perfusion alone.

Perfusion essentially tells the physician if there are any blood flow restrictions in the lungs, confirms Stacy Gregory, CPC, CCC, RCC, of Gregory Medical Consulting Services in Tacoma, Wash. For perfusion, the provider injects protein particles tagged with a radioactive material that travel through the vascular system. The pulmonary circulatory system's small arterioles (small diameter blood vessels) trap the relatively large particles. The provider takes a series of images to assess lung perfusion (blood flow). Radioactivity won't be visible in the non-perfused areas, so the radiologist can spot where the blood flow problems are.

Recognize perfusion: The other type of lung scan is ventilation (described in the next section), so you have to be able to differentiate between perfusion and ventilation to choose the proper CPT code.

The quickest route is to look for the injection of the radioisotope, which is unique to perfusion. Ventilation studies require inhalation rather than injection.

Hint: Look for references to macroaggregated albumin in the report. This is the radiopharmaceutical injected for perfusion imaging. You may see it documented as Tc-99m-MAA, MAA, or Technetium MAA. The term "macrospheres" -- referencing the macroaggregated albumin -- also can narrow your choice to a perfusion study.

If you see documentation that the patient inhaled the radioactive substance for a lung scan -- instead of having it injected -- you will need to choose among several ventilation study codes:

• 78586 -- Pulmonary ventilation imaging, aerosol;single projection

• 78587 -- ... multiple projections (e.g., anterior,posterior, lateral views)

• 78591 -- Pulmonary ventilation imaging, gaseous,single breath, single projection

• 78593 -- Pulmonary ventilation imaging, gaseous, with rebreathing and washout with or without single breath; single projection

• 78594 -- ... multiple projections (e.g., anterior,posterior, lateral views).

For ventilation, the provider places a mask over the patient's mouth and nose so he breathes in the radioactive material while images are taken to measure air flow in and out of the lungs.

One of the main distinguishing factors among the ventilation codes is whether the study was aerosol (78586,78587) or gaseous (78591, 78593, 78594).

Aerosol: Aerosol tests involve the patient inhaling nebulized (reduced to a fine spray) aerosol agents with radioactive particles. The key term to look for indicating aerosol is "DTPA," the radioactive aerosol the provider has the patient inhale, says Becki Garaud, CPC, CPCE/M, RCC, compliance education and coding trainer for the University of Washington Physicians and Children's University Medical Group Compliance Program.

Other terms you might see indicating aerosol include Technetium DTPA, particulate, and mist.

Gaseous: You may identify gaseous ventilation studies from references to the gas used, typically Xenon gas (such as Xenon-133 or Xe 133), says Garaud.

Another possibility is Krypton gas (Krypton-81 or Kr 81), although you may not see this much in practice.

CPT further distinguishes gaseous ventilation studies by whether the patient takes only a single breath or the patient does rebreathing and washout with plain oxygen.

"Rebreathing" is inhalation of the gasses previously exhaled. "Washout" is the elimination of the radioisotope from the lungs. The xenon gas exams typically consist of three phases:

1. a single breath -- the patient takes a single deep inhalation

2. rebreathing -- the patient takes normal breaths while rebreathing a mix of oxygen and xenon

3. washout -- the patient breathes room air while exhaling the xenon, clearing the lungs of the radioactive gas.

The physician will usually mention "air trapping," "gas trapping," or "clearance" when a washout has been part of the exam.

Other terms you might see indicating rebreathing and washout include the following:

• "equilibrium" (or "EQ") because the patient breathes a mixture of the xenon gas and oxygen to create xenon equilibirum in the airways;

• "wash-in" because following rebreathing, the provider takes one or more wash-in images to see the total ventilated lung volume.

Note that the rebreathing and washout codes (78593,78594) indicate "with or without single breath."

Translation: If the provider doesn't take an image of the first inhalation (single breath), that will not prevent you from using these codes.

The ventilation code choices also vary by whether the provider took one projection (an image in just one plane,such as AP) or multiple projections (or planes).

Single projection codes include 78586, 78591, and 78593. Multiple projection codes include 78587 and 78594.

Stay tuned: Next month, learn about how to report combined studies, the diagnosis codes and HCPCS codes you may use most often with lung scans, as well as proper use of 78596 (Pulmonary quantitative differential function [ventilation/perfusion] study).