How to Read Your FDG PET Radiology Report: A Patient's Glossary

A PET-CT report can be intimidating. Numbers like "SUVmax 6.2" sit beside phrases like "intense uptake in the right paratracheal station," and a patient often does not know whether to be relieved or alarmed. This guide breaks the report into its sections, explains the key numbers, and shows what should prompt a follow-up appointment.

Sections of a PET-CT Report

A standard PET-CT report follows this structure:

1. Patient and study identifiers
2. Indication — clinical reason for the scan (initial staging of lymphoma, restaging after chemotherapy, etc.)
3. Technique — tracer (FDG), injected dose, fasting status, blood glucose at injection, time from injection to scan
4. Comparison — date of any prior PET or CT used as reference
5. Findings — anatomical region by region, with SUV values where relevant
6. Impression — synthesis and clinical recommendation

The impression is the most important section. The clinician synthesizes the findings into a concise interpretation and often suggests next steps.

SUVmax, SUVmean, SUV-Lean: What Each Means

The numbers a radiologist reports:

• SUVmax — the highest single-pixel SUV in the lesion. Most commonly cited. Sensitive but susceptible to noise.
• SUVmean — the average SUV across a defined region of interest. Smoother, less prone to noise.
• SUVpeak — the average of the highest 1 mL volume. Compromise between max and mean.
• SUV-Lean (SUL) — SUV corrected for lean body mass rather than total weight. More reliable in obese patients.

For most clinical purposes, SUVmax is the working number. A liver SUVmax of 6.5 in a normal liver would be unusual; a lung mass SUVmax of 8 is suspicious.

Physiologic vs Pathologic Uptake

The radiologist distinguishes normal high-uptake areas from disease. Areas of expected uptake in a healthy person:

Site	Expected SUV range	Why
Brain (cortex)	6–14	High glucose use
Heart	0–25 (variable)	Depends on fasting state
Liver	2.5–3.5	Baseline reference
Spleen	1.5–2.5	Slightly lower than liver
Kidneys, ureters, bladder	High	FDG excreted in urine
Brown adipose tissue	Variable	Active in cold patients
Gastrointestinal tract	2–5 (variable)	Intermittent activity
Skeletal muscle	<2	Higher with recent exercise
Bone marrow	2–3	Background
Thymus (young adult)	2–4	Normal involution age-dependent

These are normal patterns. A skilled radiologist mentally subtracts these from the findings and reports only what is abnormal.

Quantifying Uptake Intensity

The qualitative descriptors used in reports:

• "No abnormal FDG uptake" — best news; no concerning hotspots
• "Mild uptake, likely physiologic" — within normal patterns
• "Moderate focal uptake, indeterminate" — needs further evaluation or follow-up
• "Intense focal uptake, concerning for [pathology]" — high suspicion; biopsy or treatment may be needed
• "Markedly increased FDG-avid mass" — aggressive disease

The Deauville 5-point score (used in lymphoma) converts these descriptions into numbers. For non-lymphoma cancers, narrative description is more common.

Comparison with Prior Studies

When a prior PET exists:

• "Decreased compared to prior" — treatment response (good)
• "Stable compared to prior" — disease unchanged; depends on context
• "Increased compared to prior" — disease progression or new inflammation
• "New uptake at [site] not seen previously" — new lesion; requires workup
• "Resolution of prior uptake at [site]" — treatment success at that site

A 30% drop in SUVmax is the threshold for "response" in PERCIST criteria (PET response criteria for solid tumors).

Impression Section: Red Flags

Words and phrases in the impression that should prompt action:

• "Suspicious for malignancy" or "compatible with" — explicit cancer concern
• "Concerning for" — strong suspicion
• "Differential diagnosis includes" — multiple possibilities, including disease
• "Recommend biopsy" or "recommend additional imaging" — explicit next step
• "Concerning for metastatic disease" — staged upward
• "Indeterminate" — needs clarification, often with follow-up PET in 3 months or correlation with anatomic imaging

Phrases that are reassuring:

• "No FDG-avid disease" — no concerning hotspots anywhere
• "Complete metabolic response" — best news in oncology
• "Stable disease, no progression" — good news in monitoring
• "Physiologic uptake only" — nothing pathological

For interpretation of an ambiguous PET impression, our team can help.

Asking Your Doctor the Right Questions

When discussing your PET report with your physician:

1. "What is the SUVmax of the highest-uptake lesion compared to the liver?" — provides relative context
2. "Is this physiologic uptake or pathologic?" — helps separate normal background from disease
3. "Has it changed from my previous scan?" — trend matters more than absolute values
4. "What are the alternatives if it isn't cancer?" — inflammation, infection, post-treatment changes
5. "What is the next step?" — biopsy, repeat imaging, treatment, observation
6. "How confident is the radiologist?" — language like "highly suspicious" vs "indeterminate" tells you the certainty level

A 15-minute conversation with your physician can convert an alarming report into a manageable plan. Most uncertainty in PET reports is resolved by clinical context.

Second-Opinion Reads from International Centers

Teleradiology second opinions on PET-CT are common and inexpensive:

• US (cash): $300–800 for a formal second read
• UK (private): £200–400
• Mainland China (top centers): ¥1,000–2,500 with English written report
• Turnaround: 24–72 business hours

To request a second opinion:

1. Export the original DICOM PET-CT data (not just the JPEG report) from your imaging center
2. Send via secure upload to the second-opinion radiologist
3. Provide clinical context: indication, recent treatment, prior scans
4. Receive a written re-read

Top Chinese centers offering this service include Sun Yat-sen Cancer Center, PUMC Beijing, Fudan SCC, and Ruijin Shanghai.

Frequently Asked Questions

My SUVmax is 6.2 in a lymph node. Is that cancer?
SUVmax alone doesn't diagnose cancer. A 6.2 lymph node is suspicious — most reactive nodes have SUV under 4. But infections, sarcoidosis, and recent vaccinations can also produce SUV in this range. Biopsy or close follow-up is typical.

The report says "indeterminate." Why can't they decide?
Indeterminate means the finding doesn't fit cleanly into "benign" or "malignant" patterns. Causes: borderline SUV, unusual location, post-treatment context. The standard resolution is a follow-up scan in 3 months — if the finding shrinks or disappears, it was inflammation; if it grows, it was disease.

Why does my SUVmax differ from my last scan when I haven't been treated?
Day-to-day SUV variation of 15–25% is normal — depends on blood glucose, body weight, scanner calibration, and timing post-injection. Differences of <30% are usually noise, not real change.

Should I request a different tracer if FDG is negative?
For most common cancers (lung, lymphoma, colon, head and neck), FDG is appropriate. For prostate, renal, mucinous, or well-differentiated NET, a specialized tracer (PSMA, DOTATATE, choline) may be more sensitive. Discuss with your oncologist.

Is the SUV measurement accurate enough to track tiny changes?
For volumes under 1 cm, SUV is unreliable due to partial volume effects. For larger lesions, 30%+ changes are considered real treatment effects (PERCIST criteria).

Why does my report include the CT findings?
PET-CT is a combined modality. The CT portion provides anatomical localization for the metabolic findings. A "PET-positive" finding is always interpreted in conjunction with what the CT shows at the same location.

Need Help Booking?

SinoCareLink can arrange teleradiology second-opinion reads, in-person specialist consultations, or repeat PET-CT at a top Chinese hospital, translate reports into English, and coordinate everything from your home country. Contact us for a free consultation.