Reporting Nuclear Medicine Studies
Structures nuclear medicine and PET/CT interpretation with SUV measurement and staging correlation.
Why This Skill Exists
Nuclear medicine studies provide unique functional and metabolic information that complements anatomic imaging. PET/CT with 18F-FDG is the cornerstone of oncologic staging, treatment response assessment, and surveillance. Other nuclear medicine studies — bone scans, thyroid scans, V/Q scans, hepatobiliary scans, renal scans — each have specific interpretation criteria, quantitative thresholds, and reporting standards. Misinterpreting physiologic radiotracer uptake as pathology, failing to correlate PET findings with CT anatomy, or omitting SUV measurements undermines the clinical utility of these studies.
The ACR-SNMMI Practice Parameter for PET/CT and general nuclear medicine mandates structured reporting with quantitative measurements, clinical correlation, and explicit comparison with prior studies. The Deauville 5-point scale is the international standard for interim PET response in lymphoma, and the Lugano classification integrates PET findings into lymphoma staging. For PE evaluation, the PIOPED II criteria and modified PIOPED criteria define V/Q interpretation standards. This skill provides the systematic framework for interpreting and reporting nuclear medicine studies across all major exam types.
Checkpoint A: Pre-Draft Intake (Mandatory)
- What nuclear medicine study is being interpreted? (Default: Identify — PET/CT, bone scan, thyroid scan, V/Q scan, renal scan, HIDA/hepatobiliary, MUGA, etc.)
- What radiotracer was used? (Default: 18F-FDG for PET/CT — specify for other studies)
- What is the clinical indication? (Default: Staging, restaging, treatment response, surveillance — obtain specific clinical question)
- Are prior nuclear medicine studies available? (Default: No — obtain for comparison)
- Is the patient's blood glucose level documented? (Default: Required for FDG PET — must be <200 mg/dL)
- What is the patient's oncologic history/staging? (Default: Obtain cancer type, treatment history, current staging)
- Was diagnostic CT performed concurrently or is this a low-dose attenuation-correction CT only? (Default: Verify CT technique)
Documents to Request
- Nuclear medicine images (all standard views and reconstructions)
- Blood glucose level at time of FDG injection
- Radiotracer type, dose, injection-to-scan time
- Prior nuclear medicine studies for comparison
- Recent cross-sectional imaging (CT, MRI) for correlation
- Oncologic staging history and treatment timeline
- Relevant tumor markers and clinical notes
Step 1: Technical Assessment
FDG PET/CT Technical Quality
| Parameter |
Standard |
Impact if Suboptimal |
| Blood glucose |
<200 mg/dL (ideally <150) |
Elevated glucose competes with FDG; decreases tumor uptake, increases muscle uptake |
| Uptake time |
60 ± 10 minutes |
Inconsistent uptake times affect SUV comparability between studies |
| Patient fasting |
≥4–6 hours |
Non-fasting increases physiologic GI and muscle uptake |
| CT technique |
Diagnostic vs. low-dose AC only |
Low-dose CT limits anatomic correlation; document limitation |
| Misregistration |
PET-CT alignment |
Respiratory motion causes misregistration at diaphragm; note if findings are affected |
| Injection quality |
Extravasation check |
Extravasation at injection site reduces circulating activity; document and note impact |
Other Nuclear Medicine Technical Factors
| Study |
Key Technical Factor |
| Bone scan |
2–3 hour delay post-injection; adequate hydration and voiding |
| V/Q scan |
Adequate Tc-99m MAA particles (200,000–700,000); Xe-133 or Tc-99m DTPA for ventilation |
| Thyroid scan |
TSH level (elevated for whole-body I-131); iodine-free diet if I-131 |
| Renal scan (MAG3) |
Adequate hydration; Lasix timing for diuretic renogram |
| HIDA |
Fasting ≥4 hours; morphine augmentation if needed |
Step 2: PET/CT Interpretation — Systematic Approach
SUV Measurement Technique
| Metric |
Definition |
Clinical Use |
| SUVmax |
Maximum SUV within a VOI |
Most commonly reported; highest single-voxel value |
| SUVpeak |
Average SUV in a 1 cm³ sphere centered on hottest voxel |
Less susceptible to noise than SUVmax |
| SUVmean |
Average SUV across the entire VOI |
Used in research; less common clinically |
| SULpeak |
Lean-body-mass-corrected SUVpeak |
Recommended for treatment response; normalizes for body composition |
| MTV |
Metabolic tumor volume |
Total volume of metabolically active tumor |
| TLG |
Total lesion glycolysis (SUVmean × MTV) |
Quantifies total metabolic burden |
Physiologic FDG Uptake (Normal — Do Not Misinterpret)
| Location |
Pattern |
Mimics |
| Brain |
Intense cortical uptake |
— (baseline reference) |
| Tonsillar/Waldeyer ring |
Symmetric ring of uptake |
Lymphoma (asymmetric = suspicious) |
| Vocal cords |
Bilateral, symmetric, post-vocalization |
Laryngeal tumor (unilateral = suspicious) |
| Myocardium |
Variable (fasting state reduces) |
Cardiac tumor (focal = suspicious) |
| GI tract (stomach, colon) |
Variable physiologic; peristaltic pattern |
GI malignancy (focal, intense = suspicious) |
| Urinary tract |
Excreted FDG in collecting system, bladder |
Urothelial tumor (wall-based uptake) |
| Bone marrow |
Diffuse after chemotherapy or G-CSF |
Marrow involvement (focal = suspicious) |
| Brown fat |
Bilateral symmetric neck/supraclavicular |
Lymphadenopathy (correlate with CT) |
PET/CT Report Structure — Organ-System Review
- Head/Neck: Brain, cervical lymph nodes, thyroid, salivary glands
- Chest: Lungs, mediastinal/hilar lymph nodes, pleura, chest wall
- Abdomen/Pelvis: Liver, spleen, adrenals, kidneys, GI tract, mesenteric/retroperitoneal lymph nodes, pelvis
- Musculoskeletal: Bones (focal vs. diffuse uptake), joints (degenerative vs. inflammatory)
- Skin/Subcutaneous: Injection site, skin metastases
Step 3: Disease-Specific Reporting Criteria
Lymphoma — Deauville 5-Point Scale (Lugano Classification)
| Score |
Uptake Level |
Interpretation |
| 1 |
No uptake |
Complete metabolic response (CMR) |
| 2 |
Uptake ≤ mediastinal blood pool |
CMR |
| 3 |
Uptake > mediastinal blood pool but ≤ liver |
CMR (for most aggressive lymphomas) |
| 4 |
Uptake moderately > liver |
Partial metabolic response or progressive disease (context-dependent) |
| 5 |
Uptake markedly > liver and/or new lesions |
Progressive metabolic disease |
| X |
New areas of uptake unlikely related to lymphoma |
Document separately |
Reference structures: Measure mediastinal blood pool SUV (aortic arch) and liver SUV (right lobe, avoiding vessels) as internal references at every timepoint.
Bone Scan Interpretation
| Finding |
Description |
Significance |
| Focal increased uptake |
Single or multiple discrete foci |
Metastasis, fracture, infection, degenerative (correlate with history and location) |
| Superscan |
Diffusely increased skeletal uptake with absent renal activity |
Diffuse skeletal metastases (prostate, breast) |
| Flare response |
Increased uptake on post-treatment scan → improves on subsequent scan |
Healing response; not progression |
| Photopenic lesion |
Cold defect |
Purely lytic metastasis (myeloma, renal cell), avascular necrosis, radiation |
V/Q Scan — Modified PIOPED II Criteria
| Category |
Criteria |
PE Probability |
| Normal |
No perfusion defects |
<5% |
| Very low |
Non-segmental perfusion defects; match defects with normal CXR |
<10% |
| Low |
Small subsegmental V/Q mismatch |
10–30% |
| Intermediate |
Difficult to categorize |
30–70% |
| High |
≥2 large segmental mismatched perfusion defects |
>80% |
Step 4: Report Structure
Standard Nuclear Medicine Report Format
Header: Patient demographics, study type, radiotracer, dose, injection-to-scan time, blood glucose (PET)
Clinical Indication: Specific clinical question with relevant history
Comparison: Prior studies with dates and modality
Technique: Radiotracer, dose, route, uptake time, CT parameters (diagnostic vs. low-dose), fasting status
Findings: Organ-system review with SUV measurements for significant findings; comparison with prior SUV values when available
Impression:
- Most clinically significant finding addressing the clinical question
- Disease-specific classification (Deauville score, Lugano response category)
- Incidental findings with recommendations
- Comparison summary with prior study
Step 5: Treatment Response Assessment
PET Response Criteria — PERCIST 1.0
| Category |
Criteria |
| CMR (Complete) |
Complete resolution of FDG uptake in all lesions; no new FDG-avid lesions |
| PMR (Partial) |
≥30% decrease in SULpeak of target lesion |
| SMD (Stable) |
Does not meet CMR, PMR, or PMD criteria |
| PMD (Progressive) |
≥30% increase in SULpeak or new FDG-avid lesions |
Checkpoint B: Post-Draft Alignment (Mandatory)
- Is the radiotracer and technical quality documented (glucose, uptake time)?
- Are SUV measurements provided for all significant findings?
- Is physiologic uptake distinguished from pathology?
- Is the appropriate disease-specific classification applied (Deauville, PERCIST)?
- Are prior studies compared with SUV trending?
Quality Audit
Guidelines
- Always document blood glucose level for FDG PET — studies performed with glucose >200 mg/dL have reduced sensitivity and should prompt consideration of rescanning.
- Report SUVmax for all significant lesions; use SULpeak when applying PERCIST criteria for treatment response.
- Correlate every PET finding with the CT component — FDG-avid findings without a CT correlate require further investigation, not dismissal.
- Apply the Deauville 5-point scale for lymphoma interim and end-of-treatment PET; always report mediastinal blood pool and liver reference SUVs.
- Recognize physiologic variants (brown fat, post-G-CSF marrow activation, GI peristalsis) to avoid false-positive interpretations.
- For V/Q scans, use the modified PIOPED II criteria and provide a probability category — vague interpretations like "indeterminate" should prompt recommendation for CTA.
- Compare uptake-time-matched studies when trending SUV; a 90-minute uptake-time PET is not directly comparable to a 60-minute study.
1---2name: reporting-nuclear-medicine-studies3description: Structures nuclear medicine and PET/CT interpretation with SUV measurement and staging correlation. Use when reading nuclear medicine studies, interpreting PET findings, or documenting radiotracer uptake.4---5
6# Reporting Nuclear Medicine Studies
7
8Structures nuclear medicine and PET/CT interpretation with SUV measurement and staging correlation.
9
10## Why This Skill Exists
11
12Nuclear medicine studies provide unique functional and metabolic information that complements anatomic imaging. PET/CT with 18F-FDG is the cornerstone of oncologic staging, treatment response assessment, and surveillance. Other nuclear medicine studies — bone scans, thyroid scans, V/Q scans, hepatobiliary scans, renal scans — each have specific interpretation criteria, quantitative thresholds, and reporting standards. Misinterpreting physiologic radiotracer uptake as pathology, failing to correlate PET findings with CT anatomy, or omitting SUV measurements undermines the clinical utility of these studies.
13
14The ACR-SNMMI Practice Parameter for PET/CT and general nuclear medicine mandates structured reporting with quantitative measurements, clinical correlation, and explicit comparison with prior studies. The Deauville 5-point scale is the international standard for interim PET response in lymphoma, and the Lugano classification integrates PET findings into lymphoma staging. For PE evaluation, the PIOPED II criteria and modified PIOPED criteria define V/Q interpretation standards. This skill provides the systematic framework for interpreting and reporting nuclear medicine studies across all major exam types.
15
16---
17
18## Checkpoint A: Pre-Draft Intake (Mandatory)
19
201. **What nuclear medicine study is being interpreted?** (Default: Identify — PET/CT, bone scan, thyroid scan, V/Q scan, renal scan, HIDA/hepatobiliary, MUGA, etc.)
212. **What radiotracer was used?** (Default: 18F-FDG for PET/CT — specify for other studies)
223. **What is the clinical indication?** (Default: Staging, restaging, treatment response, surveillance — obtain specific clinical question)
234. **Are prior nuclear medicine studies available?** (Default: No — obtain for comparison)
245. **Is the patient's blood glucose level documented?** (Default: Required for FDG PET — must be <200 mg/dL)
256. **What is the patient's oncologic history/staging?** (Default: Obtain cancer type, treatment history, current staging)
267. **Was diagnostic CT performed concurrently or is this a low-dose attenuation-correction CT only?** (Default: Verify CT technique)
27
28### Documents to Request
29
30- Nuclear medicine images (all standard views and reconstructions)
31- Blood glucose level at time of FDG injection
32- Radiotracer type, dose, injection-to-scan time
33- Prior nuclear medicine studies for comparison
34- Recent cross-sectional imaging (CT, MRI) for correlation
35- Oncologic staging history and treatment timeline
36- Relevant tumor markers and clinical notes
37
38---
39
40## Step 1: Technical Assessment
41
42### FDG PET/CT Technical Quality
43
44| Parameter | Standard | Impact if Suboptimal |
45|-----------|---------|---------------------|
46| Blood glucose | <200 mg/dL (ideally <150) | Elevated glucose competes with FDG; decreases tumor uptake, increases muscle uptake |
47| Uptake time | 60 ± 10 minutes | Inconsistent uptake times affect SUV comparability between studies |
48| Patient fasting | ≥4–6 hours | Non-fasting increases physiologic GI and muscle uptake |
49| CT technique | Diagnostic vs. low-dose AC only | Low-dose CT limits anatomic correlation; document limitation |
50| Misregistration | PET-CT alignment | Respiratory motion causes misregistration at diaphragm; note if findings are affected |
51| Injection quality | Extravasation check | Extravasation at injection site reduces circulating activity; document and note impact |
52
53### Other Nuclear Medicine Technical Factors
54
55| Study | Key Technical Factor |
56|-------|---------------------|
57| Bone scan | 2–3 hour delay post-injection; adequate hydration and voiding |
58| V/Q scan | Adequate Tc-99m MAA particles (200,000–700,000); Xe-133 or Tc-99m DTPA for ventilation |
59| Thyroid scan | TSH level (elevated for whole-body I-131); iodine-free diet if I-131 |
60| Renal scan (MAG3) | Adequate hydration; Lasix timing for diuretic renogram |
61| HIDA | Fasting ≥4 hours; morphine augmentation if needed |
62
63---
64
65## Step 2: PET/CT Interpretation — Systematic Approach
66
67### SUV Measurement Technique
68
69| Metric | Definition | Clinical Use |
70|--------|-----------|-------------|
71| SUVmax | Maximum SUV within a VOI | Most commonly reported; highest single-voxel value |
72| SUVpeak | Average SUV in a 1 cm³ sphere centered on hottest voxel | Less susceptible to noise than SUVmax |
73| SUVmean | Average SUV across the entire VOI | Used in research; less common clinically |
74| SULpeak | Lean-body-mass-corrected SUVpeak | Recommended for treatment response; normalizes for body composition |
75| MTV | Metabolic tumor volume | Total volume of metabolically active tumor |
76| TLG | Total lesion glycolysis (SUVmean × MTV) | Quantifies total metabolic burden |
77
78### Physiologic FDG Uptake (Normal — Do Not Misinterpret)
79
80| Location | Pattern | Mimics |
81|----------|---------|--------|
82| Brain | Intense cortical uptake | — (baseline reference) |
83| Tonsillar/Waldeyer ring | Symmetric ring of uptake | Lymphoma (asymmetric = suspicious) |
84| Vocal cords | Bilateral, symmetric, post-vocalization | Laryngeal tumor (unilateral = suspicious) |
85| Myocardium | Variable (fasting state reduces) | Cardiac tumor (focal = suspicious) |
86| GI tract (stomach, colon) | Variable physiologic; peristaltic pattern | GI malignancy (focal, intense = suspicious) |
87| Urinary tract | Excreted FDG in collecting system, bladder | Urothelial tumor (wall-based uptake) |
88| Bone marrow | Diffuse after chemotherapy or G-CSF | Marrow involvement (focal = suspicious) |
89| Brown fat | Bilateral symmetric neck/supraclavicular | Lymphadenopathy (correlate with CT) |
90
91### PET/CT Report Structure — Organ-System Review
921. **Head/Neck**: Brain, cervical lymph nodes, thyroid, salivary glands
932. **Chest**: Lungs, mediastinal/hilar lymph nodes, pleura, chest wall
943. **Abdomen/Pelvis**: Liver, spleen, adrenals, kidneys, GI tract, mesenteric/retroperitoneal lymph nodes, pelvis
954. **Musculoskeletal**: Bones (focal vs. diffuse uptake), joints (degenerative vs. inflammatory)
965. **Skin/Subcutaneous**: Injection site, skin metastases
97
98---
99
100## Step 3: Disease-Specific Reporting Criteria
101
102### Lymphoma — Deauville 5-Point Scale (Lugano Classification)
103
104| Score | Uptake Level | Interpretation |
105|-------|-------------|---------------|
106| 1 | No uptake | Complete metabolic response (CMR) |
107| 2 | Uptake ≤ mediastinal blood pool | CMR |
108| 3 | Uptake > mediastinal blood pool but ≤ liver | CMR (for most aggressive lymphomas) |
109| 4 | Uptake moderately > liver | Partial metabolic response or progressive disease (context-dependent) |
110| 5 | Uptake markedly > liver and/or new lesions | Progressive metabolic disease |
111| X | New areas of uptake unlikely related to lymphoma | Document separately |
112
113**Reference structures**: Measure mediastinal blood pool SUV (aortic arch) and liver SUV (right lobe, avoiding vessels) as internal references at every timepoint.
114
115### Bone Scan Interpretation
116
117| Finding | Description | Significance |
118|---------|------------|-------------|
119| Focal increased uptake | Single or multiple discrete foci | Metastasis, fracture, infection, degenerative (correlate with history and location) |
120| Superscan | Diffusely increased skeletal uptake with absent renal activity | Diffuse skeletal metastases (prostate, breast) |
121| Flare response | Increased uptake on post-treatment scan → improves on subsequent scan | Healing response; not progression |
122| Photopenic lesion | Cold defect | Purely lytic metastasis (myeloma, renal cell), avascular necrosis, radiation |
123
124### V/Q Scan — Modified PIOPED II Criteria
125
126| Category | Criteria | PE Probability |
127|----------|---------|---------------|
128| Normal | No perfusion defects | <5% |
129| Very low | Non-segmental perfusion defects; match defects with normal CXR | <10% |
130| Low | Small subsegmental V/Q mismatch | 10–30% |
131| Intermediate | Difficult to categorize | 30–70% |
132| High | ≥2 large segmental mismatched perfusion defects | >80% |
133
134---
135
136## Step 4: Report Structure
137
138### Standard Nuclear Medicine Report Format
139
140**Header**: Patient demographics, study type, radiotracer, dose, injection-to-scan time, blood glucose (PET)
141
142**Clinical Indication**: Specific clinical question with relevant history
143
144**Comparison**: Prior studies with dates and modality
145
146**Technique**: Radiotracer, dose, route, uptake time, CT parameters (diagnostic vs. low-dose), fasting status
147
148**Findings**: Organ-system review with SUV measurements for significant findings; comparison with prior SUV values when available
149
150**Impression**:
1511. Most clinically significant finding addressing the clinical question
1522. Disease-specific classification (Deauville score, Lugano response category)
1533. Incidental findings with recommendations
1544. Comparison summary with prior study
155
156---
157
158## Step 5: Treatment Response Assessment
159
160### PET Response Criteria — PERCIST 1.0
161
162| Category | Criteria |
163|----------|---------|
164| CMR (Complete) | Complete resolution of FDG uptake in all lesions; no new FDG-avid lesions |
165| PMR (Partial) | ≥30% decrease in SULpeak of target lesion |
166| SMD (Stable) | Does not meet CMR, PMR, or PMD criteria |
167| PMD (Progressive) | ≥30% increase in SULpeak or new FDG-avid lesions |
168
169---
170
171## Checkpoint B: Post-Draft Alignment (Mandatory)
172
1731. Is the radiotracer and technical quality documented (glucose, uptake time)?
1742. Are SUV measurements provided for all significant findings?
1753. Is physiologic uptake distinguished from pathology?
1764. Is the appropriate disease-specific classification applied (Deauville, PERCIST)?
1775. Are prior studies compared with SUV trending?
178
179---
180
181## Quality Audit
182
183- [ ] Radiotracer, dose, and injection-to-scan time are documented
184- [ ] Blood glucose level is recorded for FDG PET studies
185- [ ] CT technique (diagnostic vs. low-dose) is specified
186- [ ] SUVmax is reported for all significant lesions
187- [ ] Physiologic uptake is recognized and not over-interpreted
188- [ ] Disease-specific scoring is applied (Deauville, PERCIST, modified PIOPED)
189- [ ] Reference structure SUVs (mediastinal blood pool, liver) are documented for lymphoma
190- [ ] Comparison with prior PET studies includes SUV trending
191- [ ] New lesions are explicitly identified and flagged
192- [ ] Incidental findings are managed per ACR recommendations
193- [ ] Report addresses the specific clinical question in the impression
194- [ ] Technical limitations (misregistration, extravasation, elevated glucose) are noted
195- [ ] Bone scan flare response is considered in post-treatment context
196
197---
198
199## Guidelines
200
2011. Always document blood glucose level for FDG PET — studies performed with glucose >200 mg/dL have reduced sensitivity and should prompt consideration of rescanning.
2022. Report SUVmax for all significant lesions; use SULpeak when applying PERCIST criteria for treatment response.
2033. Correlate every PET finding with the CT component — FDG-avid findings without a CT correlate require further investigation, not dismissal.
2044. Apply the Deauville 5-point scale for lymphoma interim and end-of-treatment PET; always report mediastinal blood pool and liver reference SUVs.
2055. Recognize physiologic variants (brown fat, post-G-CSF marrow activation, GI peristalsis) to avoid false-positive interpretations.
2066. For V/Q scans, use the modified PIOPED II criteria and provide a probability category — vague interpretations like "indeterminate" should prompt recommendation for CTA.
2077. Compare uptake-time-matched studies when trending SUV; a 90-minute uptake-time PET is not directly comparable to a 60-minute study.
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