Even experienced physicians make errors when interpreting nuclear medicine scans. Most of the time, the issue is not knowledge but interpretation. You can know the radiopharmaceuticals, physics, and protocols thoroughly, yet one missed clue or overlooked clinical detail can lead to the wrong conclusion.
These are the ten mistakes most often seen in clinical practice and resident training, and how to avoid them.
1. Ignoring Clinical Correlation
Too many reports sound like machine output, with pure description and no context.
A nuclear medicine report should always answer why the scan was done. Before reviewing images, read the request form, check recent labs, and see if the patient had surgery, biopsy, or therapy.
Context changes everything. A mild focal FDG uptake in a post-radiation site is inflammation, not recurrence. Always review the full clinical picture from hospital records, prior CT or MRI, and oncology notes before finalizing the report.
2. Misjudging Normal Variants
Not every focus of activity represents disease. Physiologic uptake can mimic pathology.
Common examples include:
• Bowel activity from swallowed secretions.
• Thymic uptake in young adults mistaken for mediastinal disease.
• Brown fat activation mimicking nodal metastases in cold environments.
Always consider patient preparation, including blood glucose, temperature, anxiety, or muscle activity.
For quick refreshers, review normal PET variants on SNMMI Teaching Cases or Radiopaedia.
3. Overlooking Motion or Attenuation Artifacts
Artifacts quietly sabotage accuracy. Motion, respiration, or metal implants can distort activity distribution.
Always inspect raw data and non-attenuation-corrected images. If uptake disappears there, it is an artifact.
Ten seconds of checking raw data can prevent a serious reporting error.
4. Misregistration Between PET and CT
This is one of the most common and costly errors. If the patient’s arms were moved or the table flexed between acquisitions, PET and CT may misalign.
A benign lung-base uptake may appear in the liver, or a lesion may shift across organs.
Always verify localization using both fused and separate PET and CT datasets.
5. Using the Wrong Window or Color Scale
Display settings can easily deceive you.
Oversaturated hot scales make mild findings look intense, while grayscale can hide them completely.
Your department should standardize windowing and color scales based on SUV or relative activity.
Interpretation should be reproducible and never based on visual preference.
6. Missing Extravasation or Injection Site Activity
Tracer infiltration is more common than many realize. When activity leaks subcutaneously, distribution changes, creating false negatives or false positives.
Start from the periphery. Check the injection site before calling “unilateral axillary uptake” pathological.
Always document extravasation because it affects SUV accuracy.
7. Misinterpreting Post-Therapy Changes as Recurrence
Post-surgical or post-radiation inflammation often lights up for weeks, mimicking recurrence.
Timing and morphology matter. Fibrosis has low metabolic activity and stable size, while tumor recurrence shows rising uptake and enlarging volume.
If you are unsure, suggest short-interval follow-up instead of labeling recurrence prematurely.
8. Ignoring Physiologic Uptake Patterns
Every tracer has a signature distribution.
FDG normally accumulates in the brain, myocardium, kidneys, and bladder.
Bone agents highlight growth plates and degenerative joints.
Thyroid agents show gastric or salivary activity from swallowed secretions.
If uptake is symmetric, bilateral, and physiologic, do not overcall it.
For quick reference, see my earlier article, Normal Biodistribution of Common Radiopharmaceuticals.
It includes detailed tables summarizing normal tracer uptake patterns for Tc-99m, In-111, Ga-67, Tl-201, and F-18 agents, based on SNMMI Procedure Standards.
9. Neglecting Dosimetry or Scan Timing
Dose and timing errors can completely alter the appearance of a scan.
Acquire too early and you will see low uptake. Acquire too late and background noise increases.
In bone scans, imaging before soft-tissue clearance can mimic metastasis.
Always verify that the injection-to-scan interval follows protocol, and mention deviations in the report.
10. Failing to Communicate Clearly
Even the best analysis is wasted if the report confuses the clinician.
Avoid vague terms such as “cannot rule out” or “likely.” Physicians need clarity, not hedging.
Use a three-part structure:
Findings – concise and factual.
Interpretation – meaning in context.
Recommendation – a clear next step.
Example:
“Focal FDG uptake in the right lung apex corresponds to post-surgical scarring. No new hypermetabolic lesions. Follow-up PET in 6 months recommended.”
Precise. Actionable. Useful.
Final Thoughts
Interpretation is not image reading alone; it is clinical reasoning supported by data.
It requires pattern recognition, physiologic knowledge, and clear communication.
Before signing any report, ask yourself:
• Does this fit the clinical story?
• Could this be artifact or normal variation?
• Did I review all planes and raw data?
• Is my conclusion clear and defensible?
If you can answer “yes” to all, you are practicing at consultant level.
Suggested Resources
• SNMMI Procedure Standards – normal biodistribution and imaging protocols
• Radiopaedia PET/CT Cases – normal variants and artifacts
• ESMIT eLearning Modules – interactive scan interpretation training
• Masters of Nuclear Medicine, Volumes 1–3 – system-based MCQs and board-level reasoning practice
Sharpen Your Interpretation Skills
If you want to refine your reporting and diagnostic confidence, explore the Masters of Nuclear Medicine series.
Each volume builds your clinical reasoning, integrates tracer mechanisms, and strengthens your decision-making for high-stakes exams and daily practice.
See patterns others miss and avoid the mistakes most doctors make every day.
