A Ventilation/Perfusion scan (V/Q scan) is a non-invasive medical imaging test that uses a small amount of radioactive material to evaluate the flow of air and blood within the lungs. The “V” (ventilation) checks how well air moves into the lungs, and the “Q” (perfusion) measures how effectively blood circulates through the lung tissue. This two-part study is most frequently performed to determine the likelihood of a pulmonary embolism, which is a blood clot in the lungs.
Breaking Down the V/Q Scan Timeline
The total time a patient spends at the facility for a V/Q scan appointment can range from approximately 90 minutes up to three hours, depending on the clinic’s workflow and scheduling. This overall duration encompasses administrative tasks, patient preparation, the two distinct imaging phases, and any necessary waiting periods. The time the patient is actively lying under the camera, however, is much shorter, typically lasting between 30 and 60 minutes for both parts combined.
The procedure begins with the Ventilation (V) phase. This phase involves the patient inhaling a slightly radioactive gas or aerosol, such as Technetium-99m DTPA, through a mouthpiece or a mask. Imaging of the lungs then commences, with the patient lying still while a gamma camera captures pictures of the tracer distribution. This initial imaging sequence usually takes about 15 to 30 minutes to complete.
Once the ventilation images are acquired, the Perfusion (Q) phase immediately follows. A different radioactive tracer, typically Technetium-99m macro aggregated albumin (MAA), is injected intravenously into a vein in the arm. This tracer travels through the bloodstream and becomes temporarily lodged in the small capillaries of the lungs, allowing the camera to track blood circulation.
The imaging portion of the perfusion phase generally requires about 5 to 10 minutes of active scanning time. Both studies involve the gamma camera rotating or moving around the chest to capture views from multiple angles. While the scan itself may be completed within an hour, additional time is needed for the technologist to review the images to ensure the quality is sufficient before the patient is released.
Patient Experience During the Procedure
The V/Q scan is a straightforward procedure. During the ventilation phase, the technologist guides the patient to breathe in the radioactive tracer through a specialized device. The patient may be asked to hold their breath briefly while the camera captures static images, ensuring the tracer remains distributed throughout the air passages.
For the perfusion phase, the patient is prepared for the intravenous injection of the second tracer. Once the tracer is administered, the patient is positioned on the imaging table, typically lying on their back with their arms placed above their head to allow the gamma camera an unobstructed view of the chest. This positioning is maintained throughout the imaging sequences.
The patient must remain completely motionless while the gamma camera is operating around the chest. Movement can blur the images, which may necessitate repeating portions of the scan and extending the total procedure time. Although the camera may appear large as it moves close to the body, it does not make physical contact with the patient. The patient is able to breathe normally throughout the perfusion imaging process.
Preparation and Post Scan Logistics
Preparing for a V/Q scan is minimal; there is no requirement for fasting, and patients can take their regular medications as scheduled. Patients are advised to wear loose, comfortable clothing and should remove any metal objects, such as jewelry, from around the chest area. Many facilities require a recent chest X-ray, sometimes taken within 24 hours of the scan, to provide the interpreting physician with supplementary information for the diagnosis.
Following the completion of the imaging, the radioactive tracers naturally leave the body over the next few days, primarily through urine. Patients are typically instructed to drink extra fluids in the hours after the scan to help flush the remaining tracer from their system. Because trace amounts of radiation are temporarily present, a common precaution is to limit prolonged, close contact with infants, young children, and pregnant women for the first 24 hours after the injection.
If a mother is breastfeeding, she will need to stop for a set period, often between 12 and 24 hours, and discard any milk expressed during that time to prevent the infant from ingesting the tracer. The final images are analyzed by a specialized physician, a radiologist, who generates a report. This report is sent directly to the ordering physician, and the patient should expect to discuss the results with their provider, often within a week of the procedure.