In which size of tumor is PVE (Partial Volume Effect) more prominent?

For understanding the partial volume effect (PVE) in positron emission tomography (PET), it's essential to recognize that this phenomenon occurs primarily in small structures due to the limited spatial resolution of the imaging modality. In the context of tumors, when a tumor is small relative to the spatial resolution of the scanner, the PVE becomes significant because the detected signal is an average of the tumor and surrounding tissue.

In small tumors, the PET imaging system may not have adequate resolution to distinguish between the radioactivity originating from the tumor and that from surrounding tissues. Consequently, this can lead to an underestimation of the true tumor activity because the measured signal is diluted by the contribution from adjacent non-tumor tissue.

As tumor size increases, the effects of PVE become less pronounced because larger tumors can produce a stronger and more concentrated signal that can be more easily distinguished from surrounding tissues, allowing for more accurate measurements. Thus, small tumors experience PVE more significantly than medium or large tumors due to their smaller size relative to the imaging resolution, which complicates accurate quantification of their metabolic activity.

This foundational understanding of PVE highlights the importance of tumor size in PET imaging and the challenges faced in assessing small tumors effectively.