V/Q Lung Scan — Dictation, Appropriateness, and Dose for Residents

1. The V/Q Scan: Your Go-To for Pulmonary Embolism When CT Isn’t an Option

It’s a busy afternoon shift. You get a call from the ED about a 32-year-old pregnant patient at 30 weeks gestation with acute shortness of breath and pleuritic chest pain. Her D-dimer is elevated, and they’re worried about a pulmonary embolism (PE). A CT pulmonary angiogram (CTPA) is off the table due to fetal radiation dose concerns. The next study up is the V/Q scan. Your attending wants a definitive PIOPED probability, not a hedge. You need to nail the interpretation of mismatched defects and put a confident, clear impression in the report.

This is a classic scenario where knowing the ins and outs of the V/Q scan makes you look sharp. It’s not just for pregnancy; it’s a critical tool for patients with severe renal failure or a life-threatening contrast allergy. As a resident, I remember the pressure of trying to recall the exact PIOPED criteria on the fly. This guide is designed to be the reference I wish I had—a practical template and clinical refresher to help you dictate V/Q scans with confidence. For more tools like this, check out the residents and fellows resource hub we’ve put together.

2. What a NM Ventilation-Perfusion (V/Q) Lung Scan Covers and What Attendings Look For

The Nuclear Medicine Ventilation-Perfusion (V/Q) scan is a functional study that evaluates the distribution of blood flow (perfusion) and air (ventilation) in the lungs. Its primary purpose is to diagnose pulmonary embolism by identifying areas of the lung that are ventilated but not perfused—the classic “mismatched” defect. Beyond PE, it’s the first-line imaging for screening for chronic thromboembolic pulmonary hypertension (CTEPH) and can be used for quantitative lung function assessment before surgery or to detect right-to-left shunts.

Your attending expects a report that clearly answers the clinical question. For a PE study, this means a definitive probability assessment based on established criteria. Your report should systematically address:

• Technique: Mention the radiotracers used (e.g., Tc-99m DTPA and Tc-99m MAA) and the imaging method (planar or SPECT/CT).
• Correlation: Always reference the recent chest radiograph, as underlying parenchymal disease is a major factor in interpretation.
• Ventilation Findings: Describe the distribution of the inhaled radiotracer.
• Perfusion Findings: Describe the distribution of the injected radiotracer, specifically noting the location, size (small, moderate, large), and shape (segmental, non-segmental, wedge-shaped) of any defects.
• V/Q Comparison: State whether perfusion defects correspond to ventilation defects (matched), radiographic abnormalities (triple-matched), or normal ventilation (mismatched).
• Impression: Provide a final probability of pulmonary embolism (e.g., high, intermediate, low, or very low probability) based on PIOPED criteria.

3. Radiology Report Template for a NM Ventilation-Perfusion (V/Q) Lung Scan

Here is a solid, structured template you can load into your dictation system. The key principles before the impression are your mental checklist for interpretation.

Technique

A ventilation-perfusion lung scan was performed following the intravenous administration of [4.0] mCi of Tc-99m MAA and inhalation of [30] mCi of Tc-99m DTPA aerosol. Planar images of the lungs were obtained in the anterior, posterior, right and left anterior oblique, and right and left posterior oblique projections. SPECT/CT was also performed for improved localization.

Comparison is made to a chest radiograph from [DATE].

Findings

Ventilation: The inhaled radiotracer is homogeneously distributed throughout both lungs, with no significant ventilation defects identified.

Perfusion: The perfusion images demonstrate [multiple large, wedge-shaped, peripherally-based perfusion defects in the right upper lobe, right middle lobe, and left lower lobe]. The remainder of the lungs are homogeneously perfused.

V/Q Comparison: The perfusion defects noted above are not matched by corresponding ventilation or radiographic abnormalities (mismatched defects).

Incidental Findings: [e.g., Activity is noted within the visualized kidneys and brain, consistent with a right-to-left shunt, calculated at approximately X%.]

Key Principles for Your Impression:

• Mismatch: Ventilated but not perfused = PE pattern.
• Match: Both ventilation and perfusion are abnormal = parenchymal disease (e.g., COPD, pneumonia).
• Reverse Mismatch: Perfused but not ventilated = airway obstruction (e.g., mucus plug).
• High Probability (PIOPED): Requires ≥2 large mismatched segmental defects (or equivalent). This carries an >80% likelihood of PE.
• Intermediate Probability: A single mismatched segment or numerous small mismatches. This is often indeterminate and may require further imaging like CTPA if clinically feasible.
• Low Probability: Small or non-segmental mismatches.
• Pregnancy Protocol: If you do perfusion-only first and it’s completely normal, the study is over. No PE. This saves the ventilation dose.

Impression

High probability of pulmonary embolism.

Findings are consistent with multiple mismatched segmental perfusion defects, as described above. Per modified PIOPED II criteria, these findings indicate a high probability (>80%) of pulmonary embolism.

4. Free Template Sources from the Radiology Community

Building a personal library of templates is a rite of passage in residency. But you don’t have to start from scratch. Before you build your own, it’s worth checking the excellent free repositories maintained by the radiology community. They are a great starting point and often have templates for studies you don’t see every day.

Two of the best free repositories are:

• RadReport.org: Curated by the RSNA, this is a comprehensive library with a huge number of templates covering nearly every modality and subspecialty.
• Radiology Templates (AU): An excellent, well-organized resource maintained by Australian radiologists with clean, practical templates.

5. The Next-Level Move: From Free-Form Dictation to Structured Reports

Templates are great, but they can feel rigid. The real goal is to dictate your positive findings naturally and have the report structure itself correctly. This is where AI-powered tools can significantly streamline your workflow. Instead of navigating a complex template, you can simply dictate, “There are multiple large mismatched perfusion defects in the right upper lobe and left lower lobe,” and let the software build the structured report for you.

GigHz Precision AI is designed for this exact workflow. You dictate the key findings in free form, and the AI engine generates a complete, structured report using pre-loaded templates from governing bodies like the ACR and SIR. While this V/Q scan template doesn’t have a specific Clinical Decision Support (CDS) popup, for many other studies (like those requiring LI-RADS, Bosniak, or Lung-RADS classifications), the system automatically fires the appropriate CDS to guide you through the scoring. This approach helps ensure your reports are not only fast but also consistently accurate and complete. You can learn more about how the AI-powered reporting assistant works here.

6. When Should You Order a NM Ventilation-Perfusion (V/Q) Lung Scan? ACR Appropriateness Criteria

The decision to order a V/Q scan versus a CTPA is a common clinical question. The American College of Radiology (ACR) provides clear guidance on this. According to the ACR Appropriateness Criteria for Acute Pulmonary Embolus, the V/Q scan is a cornerstone of diagnosis in specific patient populations.

For patients with suspected acute PE who have a contraindication to iodinated contrast—such as severe chronic kidney disease or a history of anaphylaxis to contrast—a V/Q scan is rated “Usually Appropriate.” Similarly, in pregnant patients, a V/Q scan is also “Usually Appropriate” and is often preferred over CTPA to minimize radiation dose to the fetus. If a perfusion-only scan is normal in a pregnant patient, PE can be excluded, and the ventilation portion (and its associated dose) can be omitted entirely.

However, for the general population of hemodynamically stable patients without these contraindications, CTPA remains the first-line imaging modality and is rated “Usually Appropriate.” A V/Q scan is less ideal for patients with significant underlying lung disease (like severe COPD) on their chest X-ray, as this can lead to a high number of indeterminate results. In hemodynamically unstable patients, CTPA is strongly preferred as it can also provide crucial information about right ventricular strain.

7. How Much Radiation Does a NM Ventilation-Perfusion (V/Q) Lung Scan Deliver?

Patients, especially expectant mothers, are often concerned about radiation. Being able to contextualize the dose is a key part of your job. A combined ventilation and perfusion (V/Q) scan delivers an estimated effective dose of 1.5 to 2.5 mSv.

This dose places the V/Q scan in the low-to-moderate radiation tier, comparable to a few months to a few years of natural background radiation that we all receive just by living on Earth. This is significantly lower than a conventional CTPA, which typically delivers a higher dose. Dose-reduction techniques are standard, especially in pregnancy, where the injected activity of Tc-99m MAA is often reduced to 1-2 mCi. As mentioned, performing the perfusion scan first and stopping if it’s normal is the most effective dose-reduction strategy in this population.

The table below helps put the dose into perspective.

Source: Protocol data curated by practicing interventional radiologists and cross-referenced with ACR RRL guidelines.

8. NM Ventilation-Perfusion (V/Q) Lung Scan Imaging Protocol

The V/Q scan is a two-part study. Understanding the sequence and the agents involved is crucial for troubleshooting or discussing the protocol with a technologist. The goal is to create two sets of images—one showing where air goes, the other showing where blood flows—and compare them directly.

The protocol typically involves an inhaled agent for ventilation followed by an intravenous agent for perfusion, with identical views acquired for both phases to allow for direct comparison. SPECT or SPECT/CT is increasingly used to improve sensitivity and specificity by providing 3D localization of defects.

Common protocol pitfalls: A key decision point is the ventilation agent. Tc-99m DTPA aerosol is generally easier to handle and more widely available. Xenon-133 is a true gas and can provide additional information during washout, but it requires specialized negative-pressure rooms. Another common practice, especially in pregnancy, is the “perfusion-first” approach. If the perfusion images are entirely normal, PE is ruled out, and the study can be stopped, saving the patient the radiation dose from the ventilation phase.

9. The 3-Months-Free Offer for Radiology Residents and Fellows

Look like a rockstar on your reports — get 3+ months of GigHz Precision AI free.

We want to help you produce high-quality, attending-ready reports faster. The best way to do that is to let you use the tool without friction during your training. Dictate your positive findings in free form, and watch the AI generate a perfectly structured report using ACR and SIR templates. For relevant studies, the appropriate Clinical Decision Support (CDS) for frameworks like LI-RADS, Bosniak, and TI-RADS fires automatically to guide your classification.

All we ask in return is your feedback so we can keep improving the product for trainees. The signup process is simple, with no credit card and no long forms. To get started, just reply to the application with three items:

1. Your PGY year (e.g., PGY-2, PGY-4)
2. Your training type (radiology residency or fellowship specialty)
3. Your training program / hospital name

Ready to give it a try? Apply for the residents free-access program and see how it fits into your workflow.

10. Frequently Asked Questions (FAQ)

Is GigHz Precision AI HIPAA-compliant?

Yes. The platform is designed for de-identified workflows by default. No Protected Health Information (PHI) is required to generate a structured report from your dictated findings. It operates securely within compliance frameworks.

Do I need my hospital’s IT department to set it up?

No. GigHz Precision AI is browser-based and requires no local software installation or special permissions from your IT department. It works on any modern web browser, including the one on your call-room computer or personal iPad.

How does this work with PowerScribe or other dictation systems?

It works alongside your existing dictation system, not as a replacement. You can dictate your findings into the GigHz web interface, let the AI generate the structured report, and then simply copy and paste the final, clean text into your PACS/RIS dictation window. This workflow is fast and requires no complex integration.

Can I use this on my phone or iPad?

Yes, the platform is fully responsive and designed to work on desktops, tablets, and mobile devices. This is perfect for reviewing a template or using a CDS calculator on the go or in the reading room.

Can I customize the templates?

Yes. While the system comes pre-loaded with official templates from bodies like the ACR and SIR, you can create, modify, and save your own templates to match your personal or institutional preferences.

What happens after my residency or fellowship ends?

We offer straightforward conversion paths for trainees who want to continue using the platform in their post-training practice. We provide details on individual and group practice plans as you approach graduation.