What Is A VQ Scan For Lungs? - Information For The Layman

What is a VQ Scan for Lungs a.k.a. Lung VQ, Lung VP.

From the desk of Marcus R Hall - Retired Nuclear Medicine Technologist

A VQ scan for the lungs is a Nuclear Medicine Procedure whose purpose is to detect and diagnose a blood clot in the lungs, evaluating chronic vs. acute PE, and or staging COPD.

                                                              VP Comparison Depicting PE

Some of the clinical indicators to warrant a Nuclear Medicine Lung VQ Scan include:

• shortness of breath (developed after a long period of being stationary ie; long plane, train, train, or automobile trips.
• a history of COPD (asthma, emphysema)
• a history of pulmonary emboli (blood clots in the lungs).
• a drop in oxygen saturation levels following surgery.

What to expect.

The patient reports to the imaging center. The technologist will explain the above information to the patient. Techniques and protocols may vary between imaging centers; but, will be similar with the same data collection at the end.  This data may be manipulated by the Nuclear Medicine Technologist based on the Physicians Orders, Suspected Diagnosis, etc.

Phase One The Ventilation Portion (V) of the exam may be done with a radioactive Xenon Gas which the patient breathes in and out while images are taken with a Nuclear Medicine Camera. This data may be used to determine wash in, equilibrium, and washout timing images as well as any obstructions of the lungs.

A DTPA-Tc99m aerosol may be used for the ventilation, it depends on which protocol the facility is licensed to perform, and equipment on hand.

A Xenon Washin-Equalibrium-Wash Out

Ventilation Image                                                               A Tc99m-DTPA Ventilation Image

Phase Two - Quantification and/or Perfusion Portion of the Exam.

A Tc99m-DTPA Perfusion Image

In a Quantification Study the data collected is manipulated to determine the sectional function and perfusion of the lungs for patient's facing the removal of a portion or an entire lung. 

In a Perfusion Study the Technologist will acquire and manipulate the data to evaluate for a pulmonary emboli, a.k.a.

For the Perfusion Portion of the Nuclear Medicine VQ scan the patient is injected with a radioactive pharmaceutical that localizes in the lungs relative to blood flow.

Blood clots in the lungs are evident as segmental or sub-segmental defects in the lung images as shown in the image below.

The Patient will lay or sit in the Nuclear Medicine camera while images are taken of the lungs.

The entire procedure will take as long as 30 minutes to one hour, dependent on the patients condition.

Upon completion, the Radiologist will interpret the results of the exam, and report them to the requesting Physician.