Clinical Scenarios Where SUV Values Remain Low or Decrease

Treatment Response and Disease Resolution

Successful therapy leads to decreased SUV values, which indicates positive treatment response rather than therapy failure 1
In multiple myeloma, complete metabolic response is defined when uptake in previous hot focal lesions decreases to less than liver uptake or becomes unmeasurable 2
Greater than 25% reduction in tracer uptake corresponds to therapeutic response in meningiomas treated with peptide receptor radionuclide therapy 1
In oncology, diminishing uptake indicates positive response to treatment, while increasing intensity suggests therapy failure 1

Treatment-related changes such as radionecrosis and scar tissue demonstrate low or absent FDG uptake, allowing differentiation from recurrent disease 1
Necrotic tumor tissue lacks metabolic activity and therefore shows no increased SUV, even when viable tumor is present elsewhere 3
Post-radiation changes typically show minimal to no tracer uptake compared to active recurrent disease 1

Rare meningioma cases present with low uptake (SUV < 2.3 or SUVRSSS < 3) despite being malignant, though this excludes meningioma with high probability 1
Low-grade tumors may demonstrate SUV values below diagnostic thresholds, making them difficult to distinguish from benign processes 3

Healthy brain parenchyma in the contralateral hemisphere shows consistently low baseline uptake, serving as reference tissue for tumor-to-background ratios 1, 3
Normal liver uptake remains stable and serves as a reference standard for determining pathological uptake in various malignancies 1, 2
Mediastinal blood pool maintains consistent low uptake, used as a comparator for defining pathological bone marrow involvement 2

SUV accuracy depends critically on proper timing, with standardized protocols requiring approximately 60 minutes post-injection before scanning 4, 5
Partial volume effects cause underestimation of SUV in lesions smaller than 2.5-3 cm, where background tissue dilutes the signal 6
Improper normalization to body mass can mask true metabolic activity, particularly when total body mass is used instead of lean body mass 4, 5

Different reconstruction algorithms and scanner settings can suppress apparent SUV values, though standardization protocols minimize this effect 7
Test-retest variability can reach ±30-40% in multicenter studies, meaning apparent lack of SUV increase may reflect measurement error rather than true biology 6
Gibbs artifacts from point-spread-function reconstructions can create quantitative errors that vary with tumor size and scanner model 3

Iodine contrast administration suppresses radioiodine uptake in thyroid tissue, preventing SUV increase in I-131 studies when contrast timing is inappropriate 8
Brown adipose tissue activation requires specific cold exposure protocols; without proper activation, SUV remains at baseline despite tissue presence 4, 5
Shivering within 60 minutes before or after tracer injection can alter biodistribution, preventing expected SUV increases in target tissues 4, 5

Visual assessment alone can be misleading—semi-quantitative analysis with SUV or tumor-to-background ratios is essential for accurate interpretation 3, 7
Heterogeneous uptake patterns may show areas of high and low SUV within the same lesion, requiring careful region-of-interest placement to avoid sampling error 3
Mixed responses can occur where some lesions show increased SUV while others decrease, complicating overall treatment assessment 7

SUV thresholds vary by tumor type and tracer used: meningiomas use 2.3 for [68Ga]Ga-DOTATATE 1
Reference tissue selection critically affects interpretation—brain tumors should not use contralateral brain for meningiomas but should for metastases 1, 3
Timing of assessment matters: early post-treatment scans may not yet show SUV decrease despite effective therapy 1